US20050183950A1

US20050183950A1 - Fluid actuating apparatus and method for manufacturing a fluid actuating apparatus, and electrostatically-actuated fluid discharge apparatus and process for producing an electrostatically-actuated fluid discharge apparatus

Info

Publication number: US20050183950A1
Application number: US11/063,816
Authority: US
Inventors: Masanari Yamaguchi
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2004-02-25
Filing date: 2005-02-23
Publication date: 2005-08-25
Also published as: CN1660691A; KR20060043164A; CN1660691B; JP2005238540A

Abstract

A fluid actuating apparatus is proposed, which includes: a diaphragm for providing a pressure change in fluid; a diaphragm-side electrode, formed for the diaphragm, for actuating the diaphragm; a substrate-side electrode formed so that it faces the diaphragm-side electrode; a space formed between the diaphragm-side electrode and the substrate-side electrode; and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space. where the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present invention contains subject mater related to Japanese Patent Application JP2004-049131 filed in the Japanese Patent Office on Feb. 25, 2004, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a fluid actuating apparatus, which can prevent a stress from concentrating on a portion between an electrode and a support post wherein the stress is caused due to deformation of a diaphragm when a voltage is applied to the electrode for vibrating the diaphragm, while securing repulsion force of the diaphragm, and a method for manufacturing the fluid actuating apparatus, and an electrostatically-actuated fluid discharge apparatus using the fluid actuating apparatus and a method for manufacturing the electrostatically-actuated fluid discharge apparatus.
2. Description of Related Art
In a printer which meets the demands of printing images having quality as high as photography at high speed and with high resolution, an ink-jet printer head for discharging an ink in a very small volume at a level of pl (picolitter) is widely used. For meeting the demands of printing higher-quality images at high speed and with high resolution, it is desired that nozzles are arranged with higher density in future without increasing the power consumption and without sacrificing the discharge performance.
Conventionally, the method for actuating a chemical agent in a very small volume employed in the ink-jet printer head includes, in respect of a fluid in a very small volume (ink in a very small volume) held in an ink holding space (so-called cavity), a resistance heating method and a diaphragm method. The resistance heating method is a method in which a fluid in a cavity is discharged through a nozzle by gas (bubbles) generated by resistance heating. The diaphragm method is a method in which a fluid is discharged through a nozzle by a pressure application means (so-called diaphragm) using a piezoelectric element or the like.
The resistance heating method can be prepared by a semiconductor process and hence the cost is low, and a resistance heating element having a very small size can be produced, and therefore nozzles with high density are advantageously formed, but the use of Joule heat generated by an electric current increases both the number of nozzles and the power consumption, and further the resistance heating element must be cooled, making it difficult to increase the discharge frequency.
On the other hand, the diaphragm method using a piezoelectric effect is classified into a laminate piezoelectric type and a single-layer piezoelectric type, and, in the laminate piezoelectric type, a piezoelectric actuator and a diaphragm are laminated together and then subjected to isolation by cutting, and therefore a semiconductor process cannot be used, and the process for fabrication is complicated, thus increasing the cost. In addition, the actuation distance is small, and hence there is a need to increase the actuation area to a length at a level of millimeter (mm) to secure the actuation capacity, thus making it difficult to increase the density. Further, there is a problem in that a change of the design is not easy.
The ink-jet head using a conventional electrostatic actuation method is prepared by forming a diaphragm from a Si substrate which is shaped to be thin by etching, and laminating together the diaphragm and a substrate of glass or the like having a lower electrode formed thereon. In this method, it is difficult to control the thickness of the diaphragm and its uniformity. In addition, the diaphragm is formed from a Si substrate by etching and hence almost all the thickness of the Si substrate is removed, and therefore the productivity is poor, and a diaphragm having a uniform thickness as small as several μm or less cannot be formed and therefore, for achieving actuation with a low voltage, the short side of the diaphragm is required to be longer, thus making it difficult to increase the density. Further, in lamination of the substrates, the joint surface is required to be smooth with high precision to secure a joint area for the lamination, and a lamination accuracy of ±several μm is needed, thus making it impossible to increase the density. Furthermore, there is a problem in that handling of a substrate having a thickness of about 0.1 to 0.2 mm is not easy.
For this reason, there is desired a fluid actuating apparatus using an electrostatic method, which is advantageous in that the diaphragm is formed by a semiconductor fabrication process and hence the thickness of the diaphragm can be easily controlled, no lamination of substrates is required, the density of the actuating portions can be increased, high fluid actuating force can be obtained, and the yield is high and a change of the design is easy, thus improving the productivity.
In the single-layer piezoelectric type, a semiconductor process can be almost always used, and the cost is low, as compared to that for the laminate type, and the power consumption can be lowered. However, warpage is caused during the sintering of the piezoelectric element, and it is difficult to prepare a large-size head having an increased number of nozzles. On the other hand, in the diaphragm method using electrostatic actuation, the power consumption is very low, as compared to that for the resistance heating method and the piezoelectric method, and high-speed actuation is possible (see, for example, patent documents 1 and 2).
[Patent document 1] Unexamined Japanese Patent Application Publication No. Hei 10-86362
[Patent document 2] Japanese Domestic Re-Publication of PCT International Patent Application No. WO99/34979

SUMMARY OF THE INVENTION

With respect to the diaphragm method using electrostatic actuation, the present inventors have proposed a fluid actuating apparatus which includes a diaphragm for providing a pressure change in fluid, a diaphragm-side electrode, formed for the diaphragm through an insulating film, for actuating the diaphragm, a substrate-side electrode formed so that it faces the diaphragm-side electrode through a space, and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space.
In the electrostatically-actuated fluid discharge apparatus, the strength (repulsion force) of the diaphragm and the power consumption are important factors. For example, with respect to the diaphragm method using electrostatic actuation, the present inventors have proposed a fluid actuating apparatus which includes a diaphragm for providing a pressure change in fluid, a diaphragm-side electrode, formed for the diaphragm through an insulating film, for actuating the diaphragm, a substrate-side electrode formed so that it faces the diaphragm-side electrode through a space, and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space. In this fluid actuating apparatus having a construction in which the diaphragm-side electrode separately formed has a rectangular form having such a size that the diaphragm-side electrode does not extend to the support post, when a voltage is applied, a stress due to deformation of the diaphragm concentrates on a portion between the electrode and the support post to weaken the diaphragm, leading to a problem in that there is a lack of the repulsion force.
According to an embodiment of the present invention, there is provided a fluid actuating apparatus which includes a diaphragm for providing a pressure change in fluid; a diaphragm-side electrode, formed for the diaphragm, for actuating the diaphragm; a substrate-side electrode formed so that it faces the diaphragm-side electrode; a space formed between the diaphragm-side electrode and the substrate-side electrode; and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space, wherein the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post.
According to another embodiment of the present invention, there is provided a fluid actuating apparatus which includes: a diaphragm for providing a pressure change in a fluid; a diaphragm-side electrode, formed for the diaphragm, for actuating the diaphragm; a substrate-side electrode formed so that it faces the diaphragm-side electrode; a space formed between the diaphragm-side electrode and the substrate-side electrode; and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space, wherein the diaphragm-side electrode is formed so that it extends from the support post to another.
According to further another embodiment of the present invention, there is provided a method for manufacturing a fluid actuating apparatus, which method includes the steps of forming a substrate-side electrode on a substrate; forming a first insulating film on the substrate-side electrode; forming a sacrifice layer pattern for forming a space in a region above the first insulating film, excluding a support post-forming region; forming a second insulating film for covering the sacrifice layer pattern; forming a diaphragm-side electrode through the second insulating film on the upper surface of the sacrifice layer pattern, the sidewall of the sacrifice layer pattern, and part of the bottom of the support post-forming region; forming a third insulating film for covering the diaphragm-side electrode; forming, on the third insulating film, a diaphragm for providing a pressure change in fluid; and removing the sacrifice layer pattern to form a space in a region formed by removing the sacrifice layer pattern, and further forming, in the support post-forming region formed at the side portion of the space, a support post from the second insulating film, the diaphragm-side electrode, the third insulating film, and the diaphragm.
According to further another embodiment of the present invention, there is provided a method for manufacturing a fluid actuating apparatus, which method includes the steps of: forming a substrate-side electrode on a substrate; forming a first insulating film on the substrate-side electrode; forming a sacrifice layer pattern for forming a space in a region above the first insulating film, excluding a support post-forming region; forming a second insulating film for covering the sacrifice layer pattern; forming a diaphragm-side electrode through the second insulating film on the sacrifice layer pattern including a portion between the support post-forming regions; forming a third insulating film for covering the diaphragm-side electrode; forming, on the third insulating film, a diaphragm for providing a pressure change in fluid; and removing the sacrifice layer pattern to form a space in a region formed by removing the sacrifice layer pattern, and further forming, in the support post-forming region formed at the side portion of the space, a support post from the second insulating film, the third insulating film, and the diaphragm.
According to further another embodiment of the present invention, there is provided an electrostatically-actuated fluid discharge apparatus, which includes: a diaphragm for providing a pressure change in fluid; a diaphragm-side electrode, formed for the diaphragm, for actuating the diaphragm; a substrate-side electrode formed so that it faces the diaphragm-side electrode; a space formed between the diaphragm-side electrode and the substrate-side electrode; and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space, wherein the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post, wherein the diaphragm has formed thereon a pressure chamber having a fluid feed section and a fluid discharge section.
According to further another embodiment of the present invention, there is provided an electrostatically-actuated fluid discharge apparatus which includes: a diaphragm for providing a pressure change in fluid; a diaphragm-side electrode, formed for the diaphragm through an insulating film, for actuating the diaphragm; a substrate-side electrode formed so that it faces the diaphragm-side electrode; a space formed between the diaphragm-side electrode and the substrate-side electrode; and a support post, formed on the substrate-side electrode, for supporting the diaphragm-side electrode through the space, wherein the diaphragm-side electrode is formed so that it extends from the support post to another, wherein the diaphragm has formed thereon a pressure chamber having a fluid feed section and a fluid discharge section.
According to further another embodiment of the present invention, there is provided a method for manufacturing an electrostatically-actuated fluid discharge apparatus, which method includes the steps of: forming a substrate-side electrode on a substrate; forming a first insulating film on the substrate-side electrode; forming a sacrifice layer pattern for forming a space in a region above the first insulating film, excluding a support post-forming region; forming a second insulating film for covering the sacrifice layer pattern; forming a diaphragm-side electrode through the second insulating film on the upper surface of the sacrifice layer pattern, the sidewall of the sacrifice layer pattern, and part of the bottom of the support post-forming region; forming a third insulating film for covering the diaphragm-side electrode; forming, on the third insulating film, a diaphragm for providing a pressure change in fluid; removing the sacrifice layer pattern to form a space in a region formed by removing the sacrifice layer pattern, and further forming, in the support post-forming region formed at the side portion of the space, a support post from the second insulating film, the diaphragm-side electrode, the third insulating film, and the diaphragm; and forming, on the diaphragm through the third insulating film, a pressure chamber having a fluid feed section and a fluid discharge section.
According to further another embodiment of the present invention, there is provided a method for manufacturing an electrostatically-actuated fluid discharge apparatus, which method includes the steps of: forming a substrate-side electrode on a substrate; forming a first insulating film on the substrate-side electrode; forming a sacrifice layer pattern for forming a space in a region above the first insulating film, excluding a support post-forming region; forming a second insulating film for covering the sacrifice layer pattern; forming a diaphragm-side electrode through the second insulating film on the sacrifice layer pattern including a portion between the support post-forming regions; forming a third insulating film for covering the diaphragm-side electrode; forming, on the third insulating film, a diaphragm for providing a pressure change in fluid; removing the sacrifice layer pattern to form a space in a region formed by removing the sacrifice layer pattern, and further forming, in the support post-forming region formed at the side portion of the space, a support post from the second insulating film, the third insulating film, and the diaphragm; and forming, on the diaphragm through the third insulating film, a pressure chamber having a fluid feed section and a fluid discharge section.
In the fluid actuating apparatus according to an embodiment of the present invention, the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post, or it extends from the support post to another, and therefore, as compared to the construction in which the diaphragm-side electrode is formed so that it covers the whole of the bottom of the support post, the amount of the charge, which does not contribute to deformation of the diaphragm and which is stored on the bottom of the support post, is small, thus suppressing a waste of the power consumption. In addition, in the construction in which the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post, with respect to the strength of the diaphragm, there is an advantage in that the support post has a larger thickness by the thickness of the diaphragm-side electrode than that in the construction in which the diaphragm-side electrode is formed so that it does not extend to the support post, and thus the support post gets stronger.
The method for manufacturing a fluid actuating apparatus according to another embodiment of the present invention, includes the step for forming a diaphragm-side electrode through the second insulating film on the upper surface of the sacrifice layer pattern, the sidewall of the sacrifice layer pattern, and part of the bottom of the support post-forming region, and hence the diaphragm-side electrode is formed so that it passes through the support post and extends to and covers part of the bottom of the support post. Therefore, there can be produced a fluid actuating apparatus having a construction such that, as compared to the construction in which the diaphragm -side electrode is formed so that it covers the whole of the bottom of the support post, the amount of the charge, which does not contribute to deformation of the diaphragm and which is stored on the bottom of the support post, is small, thus suppressing a waste of the power consumption. In addition, with respect to the strength of the diaphragm, there is an advantage in that the fluid actuating apparatus can be produced so that the support post has a larger thickness by the thickness of the diaphragm-side electrode than that in the construction in which the diaphragm-side electrode is formed so that it does not extend to the support post, and thus the support post is stronger.
The method for manufacturing a fluid actuating apparatus according to an embodiment of the present invention includes the steps of forming a diaphragm-side electrode through the second insulating film on the sacrifice layer pattern including a portion between the support post-forming regions. Therefore, there can be produced a fluid actuating apparatus having a construction such that, as compared to the construction in which the diaphragm-side electrode is formed so that it covers the whole of the bottom of the support post, the amount of the charge, which does not contribute to deformation of the diaphragm and which is stored on the bottom of the support post, is small, thus suppressing a waste of the power consumption.
The electrostatically-actuated fluid discharge apparatus according to an embodiment of the present invention includes the fluid actuating apparatus according to an embodiment of the present invention, and therefore has not only the above-mentioned advantages obtained by the fluid actuating apparatus according to an embodiment of the present invention, but also an advantage in that there can be provided the electrostatically-actuated fluid discharge apparatus having high fluid actuating force and having an increased density of fluid discharge sections, e.g., nozzles for liquid, or discharge outlets for gas.
The method for manufacturing an electrostatically-actuated fluid discharge apparatus according to an embodiment of the present invention includes the method for manufacturing a fluid actuating apparatus according to an embodiment of the present invention, and therefore has not only the above-mentioned advantages obtained by the method for manufacturing a fluid actuating apparatus according to an embodiment of the present invention, but also an advantage in that the electrostatically-actuated fluid discharge apparatus can be produced easily with high precision. Further, there is an advantage in that the electrostatically-actuated fluid discharge apparatus, for example, an ink-jet printer head having a diaphragm, a pressure chamber, a discharge section (nozzle or discharge outlet), and the like can be produced by, e.g., surface micromachining without using lamination.
A task of reducing a waste of the power consumption to suppress the power consumption while achieving a diaphragm having satisfactory repulsion force for actuation of a fluid, and preventing the stress concentration on the diaphragm-side electrode and the support post is achieved by employing a structure in which the diaphragm-side electrode is formed so that it extends to and passes through the support post or a structure in which the diaphragm-side electrode is formed so that it extends from the support post to another without complicating the process for production.
The fluid actuating apparatus and the method for manufacturing a fluid actuating apparatus, and the electrostatically-actuated fluid discharge apparatus and the method for manufacturing an electrostatically-actuated fluid discharge apparatus according to the embodiments of the present invention can be generally applied to the uses in which liquid in a very small volume (volume with a unit of picolitter or smaller) is fed or discharged. For example, in the civil use, for example, an ink-jet printer head, and, in the commercial use, for example, a high molecular-weight or low molecular-weight organic material coating apparatus for organic EL or the like, a printing apparatus for printed wiring board, a printing apparatus for solder bump, a three-dimensional modeling apparatus, and a μTAS (micro total analysis system), the present invention can be applied to a feed head for feeding a chemical agent or another liquid with a unit as small as pl (picolitter) or less while controlling it with high accuracy and a feed head for feeding gas in a very small volume while controlling it with high accuracy. Further, the fluid actuating apparatus 10 can be applied to an actuator of, for example, a fluid pump for use in cooling a central processing unit (CPU) in a computer.
Further features of the invention, and the advantages offered thereby, are explained in detail hereinafter, in reference to specific embodiments of the invention illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are views showing the fluid actuating apparatus according to the first embodiment of the present invention, wherein FIG. 1A is a plan view of the layout, FIG. 1B shows a diagrammatic cross-sectional structure taken along the line A-A of FIG. 1A, and FIG. 1C shows a diagrammatic cross-sectional structure taken along the line B-B of FIG. 1A;
FIGS. 2A-2B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 3A-3B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 4A-4C are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 5A-5B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 6A-6B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 7A-7B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 8A-8B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 9A-9B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 10A-10B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 11A-11B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIGS. 12A-12B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the first embodiment of the present invention;
FIG. 13 are diagrammatic perspective view showing the construction of the electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention;
FIGS. 14A-14B are diagrammatic cross-sectional views showing the construction of the electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention;
FIGS. 15A-15B are views for explaining the operation of the electrostatically-actuated fluid discharge apparatus;
FIGS. 16A-16B are views showing the steps in the method for manufacturing an electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention;
FIGS. 17A-17B are views showing the steps in the method for manufacturing an electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention;
FIGS. 18A-18D are views showing the electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention;
FIG. 19 are plan view showing one form of opening sections formed when removing the sacrifice layer pattern;
FIGS. 20A-20C are views showing the fluid actuating apparatus according to the second embodiment of the present invention, wherein FIG. 20A is a plan view of the layout, FIG. 20B shows a diagrammatic cross-sectional structure taken along the line A-A of FIG. 20A, and FIG. 20C shows a diagrammatic cross-sectional structure taken along the line B-B of FIG. 20A;
FIGS. 21A-21B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 22A-22B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 23A-23C are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 24A-24B are views showing the steps in the method for manufacturing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 25A-25B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 26A-26B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 27A-27B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 28A-28B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 29A-29B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 30A-30B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIGS. 31A-31B are views showing the steps in the method for producing a fluid actuating apparatus according to the second embodiment of the present invention;
FIG. 32 are diagrammatic perspective view showing the construction of the electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention;
FIGS. 33A-33B are diagrammatic cross-sectional views showing the construction of the electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention;
FIGS. 34A-34B are views showing the steps in the method for producing an electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention; and
FIGS. 35A-35B are views showing the steps in the method for producing an electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

EXAMPLE 1

The fluid actuating apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1A-1C. FIG. 1A shows part of a plan view of the layout, FIG. 1B shows a diagrammatic cross-sectional structure taken along the line A-A of FIG. 1A, and FIG. 1C shows a diagrammatic cross-sectional structure taken along the line B-B of FIG. 1A. The scale of FIG. 1A and that of FIG. 1B, FIG. 1C are not the same. Fluid actuating apparatuses are actually arranged in a line, but the figures show a single fluid actuating apparatus, which is described below.
As shown in FIGS. 1A-1C, a substrate-side electrode 12, which includes a conductor thin film and which is common to another fluid actuating apparatus (not shown), is formed on a substrate 11 having at least a surface formed from an insulating layer. A first insulating film 13 is formed on the substrate-side electrode 12. A second insulating film 14 is formed on the first insulating film 13 so that a space 31 is formed. Accordingly, the space 31 is a substantially rectangular parallelepiped space defined by the two-dimensional first insulating film and the three-dimensional second insulating film 14, and a support post 21 including the second insulating film 14 is formed so that the support post intrudes into the side portion of the space 31 and has a comb teeth-like form. The first insulating film 13 and the second insulating film 14 are insulating films for preventing the below-described diaphragm-side electrode from being brought into contact with the substrate-side electrode 12 when the diaphragm-side electrode is deflected.
On the second insulating film 14 is formed a diaphragm-side electrode 15 which is independently actuated with respect to the space 31 through the second insulating film 14. The diaphragm-side electrode 15 is rectangular (square or rectangular) as viewed from the top (as viewed from the top of the plan view of the layout) and, in the support post-forming region, the diaphragm-side electrode is formed along the sidewall of the comb teeth-like form support post 21 formed along the sidewall of the space, and may be formed so that it extends to and covers part of the bottom of the support post 21, but it is not preferred that the diaphragm-side electrode is formed so as to cover the whole of the bottom of the support post 21 since an increase of the electrostatic capacity is caused to increase the power consumption. Thus, the diaphragm-side electrode 15 is basically a rectangular electrode, and formed so that it extends into the comb teeth-like form support post formed along the side portion of the space 31. For preventing the occurrence of leakage between the adjacent diaphragm-side electrodes 15, the diaphragm-side electrodes 15 are formed independently of each other.
A third insulating film 16 for covering the diaphragm-side electrode 15 is formed on the second insulating film 14. Further, on the third insulating film 16, a plurality of diaphragms 17 for providing a pressure change in fluid, integrally having the diaphragm-side electrode 15 actuated independently, are arranged in a line, and the support post 21 is formed on the substrate 11, substantially on the first insulating film 13 in such a way that the support post supports the individual diaphragms 17 on both sides by a beam. Further, a fourth insulating film 18 is formed on the third insulating film 16 so as to cover the diaphragm 17. The third insulating film 16 is formed for the purpose of relaxing the stress applied to the diaphragm-side electrode 15 by the diaphragm 17, and, when the stress relaxation is not required, it can be omitted. As described above, in the support post-forming region which is formed so that it intrudes into the side portion of the space 31 and has a comb teeth-like form, the support post 21 is formed from the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
The diaphragm 17 formed in the example shown in the figures has a strip form, and a plurality of support posts 21 are formed along the side portion of the diaphragm 17 at predetermined intervals (pitch between the support posts). The predetermined interval (pitch between the support posts) is preferably 2 to 10 μm, most preferably 5 μm. The adjacent diaphragms 17 are formed continuously through the support post 21, and the support post 21 including the diaphragm 17 is formed. Therefore, the space 31 defined by the diaphragm 17 and the substrate-side electrode 12 forms a hollow portion between a plurality of diaphragms 17 arranged in a line. The space 31 forming a hollow portion between the diaphragms 17 is formed so that it is an enclosed space as a whole.
Near the support post 21 of each diaphragm 17, in the present Example, between the support posts 21 along the side portion of the single diaphragm 17, an opening section (not shown) for introducing gas or liquid used for removing a sacrifice layer by etching in the production process described below is formed. After removing the sacrifice layer by etching, the opening section is sealed up by a predetermined member.
As the substrate 11, a semiconductor substrate comprised of silicon (Si), gallium arsenide (GaAs), or the like, which has an insulating film (not shown) formed thereon, can be used. Therefore, as the substrate 11, an insulating substrate, such as a glass substrate including a quartz substrate, can be used. In this case, there is no need to form an insulating film on the surface of the substrate. In the present Example, as the substrate 11, a silicon substrate having an insulating film comprised of, e.g., a silicon oxide film formed on the surface is used.
The substrate-side electrode 12 is formed from an impurity-doped polycrystalline silicon film, metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. An n⁺ diffused layer electrode can be formed by a method in which a substrate-side electrode pattern is formed by selective oxidation, and then implanted with B⁺, P⁺, and B⁺, and a channel stopper layer is formed on the p-Well, followed by arsenic (As) implantation. Similarly, a p⁺ diffused layer electrode can be formed on the n-Well. In the present Example, the substrate-side electrode 12 is formed from an impurity -doped polycrystalline silicon film.
The diaphragm-side electrode 15 can be formed from a material similar to the material for the substrate-side electrode 12 by a method similar to the method for forming the substrate-side electrode 12. Specifically, the diaphragm-side electrode 15 can be formed from an impurity-doped polycrystalline silicon film, metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. In the present Example, the diaphragm-side electrode 15 is formed from an impurity-doped polycrystalline silicon film.
The diaphragm-side electrode 15 is connected to the diaphragm 17 through the third insulating film 16, and formed so that it is inserted into the lower surface concave portion formed by the bent diaphragm 17 and extends to the side of the sidewall of the space 31. The diaphragm 17 is formed from, for example, an insulating film, especially preferably a silicon nitride film (SiN film) which generates a tension stress and high repulsion force as a diaphragm. A fourth insulating film 18 is formed on the upper surface of the diaphragm 17, and the fourth insulating film 18 is formed from, e.g., a silicon oxide film. Each of the second insulating film 14 and the third insulating film 16 can be formed from, e.g., a silicon oxide film. Therefore, in the present Example, the diaphragm is comprised of substantially the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
The fluid actuating apparatus 1 having the above construction vibrates the diaphragm 17 by applying a voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 to change a fluid on the diaphragm 17 in pressure, allowing the fluid to move.
In the fluid actuating apparatus 1 of the present invention, the diaphragm-side electrode 15 is formed so that it passes through the support post 21 and extends to and covers part of the bottom of the support post 21, and therefore, as compared to the construction in which the diaphragm-side electrode 15 is formed so that it covers the whole of the bottom of the support post 21, the amount of the charge, which does not contribute to deformation of the diaphragm 17 and which is stored on the bottom of the support post 21, is small, thus suppressing a waste of the power consumption. In addition, with respect to the strength of the diaphragm 17, there is an advantage in that the support post 21 has a larger thickness by the thickness of the diaphragm-side electrode 15 than that in the construction in which the diaphragm-side electrode 15 is formed so that it does not extend to the support post 21, and thus the support post 21 is stronger. The charge density was measured when 30 V was applied to the electrode of the fluid actuating apparatus 1 having the above construction, and the deflection was measured when a distribution load of 61 kPa was applied. As a result, the charge density was 4.4 fF, and the deflection was 13 nm. On the other hand, in the conventional construction in which the diaphragm-side electrode is formed outside of the support post, the charge density was as small as 1.7 fF, but the deflection was as very large as 186 nm, and hence the diaphragm was too soft and the repulsion force was unsatisfactory. Further, in the construction in which the diaphragm-side electrode is formed so that it extends to and covers the whole of the bottom of the support post, the charge density was as very large as 5.1 fF to cause a waste of the power consumption, but the deflection was as small as 13 nm. Thus, in the fluid actuating apparatus 1 of the present invention, small deflection could be achieved without considerably increasing the charge density.

EXAMPLE 2

The method for producing a fluid actuating apparatus according to the first embodiment of the present invention will be described with reference to the views of FIGS. 2A to 12B showing the steps in the production process. The views of FIGS. 2A to 12B showing the steps in the production process mainly show cross-sectional structures at positions similar to the positions of the cross-section taken along the line A-A and the cross-section taken along the line B-B shown in the plan view of the layout of FIG. 1A. In FIGS. 4A-4C, a plan view of the layout of the sacrifice layer pattern is also shown.
As shown in FIGS. 2A-2B, a substrate 11 having at least an insulating surface is prepared. As the substrate 11, for example, in the present Example, a substrate comprising an insulating film, e.g., a silicon oxide film formed on a silicon substrate is used. A common substrate-side electrode 12 is formed on the substrate 11. In the present Example, the substrate-side electrode 12 is formed as follows. An amorphous silicon film is deposited by, e.g., a chemical vapor deposition (CVD) method, and then doped with an impurity, e.g., phosphorus (P). Then, the impurity as dopant is activated by a heat treatment so that the electrode has conduction properties, thus forming the substrate-side electrode 12 comprised of polycrystalline silicon.
The substrate-side electrode 12 is formed from an impurity-doped polycrystalline silicon film, but it can be also formed from an impurity-doped metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. An n⁺ diffused layer electrode can be formed by a method in which a substrate-side electrode pattern is formed by selective oxidation, and then implanted with B⁺, P⁺, and B⁺, and a channel stopper layer is formed on the p-Well, followed by arsenic (As) implantation. Similarly, a p⁺ diffused layer electrode can be formed on the n-Well.
Next, as shown in FIGS. 3A-3B, a first insulating film 13 is formed on the surface of the substrate-side electrode 12. The first insulating film 13 can be formed by a reduced pressure CVD method at a temperature as high as, e.g., about 1,000° C. or a thermal oxidation method. The first insulating film 13 is required to be a protective film for the substrate-side electrode 12 and to be a film having a resistance to the etching liquid or etching gas used for etching the below-mentioned sacrifice layer, and further required to prevent discharge caused when the diaphragm and the substrate-side electrode are close to each other and to prevent short-circuiting caused when the diaphragm is in contact with the substrate-side electrode 12. As the first insulating film 13, a silicon oxide (SiO₂) film can be used when using etching gas comprised of, e.g., sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂), or a silicon nitride (SiN) film can be used when using etching liquid comprised of, e.g., hydrofluoric acid. Subsequently, a sacrifice layer 41 is formed on the entire surface of the first insulating film 13. In the present Example, as the sacrifice layer 41, a polycrystalline silicon film is deposited by a CVD method.
Then, as shown in FIGS. 4A-4C, using general lithography technique and etching technique, the sacrifice layer 41 in the portion, in which a support post (so-called anchor) to be formed later for supporting the diaphragm is formed (when a not shown auxiliary support post is formed, a portion corresponding to the auxiliary support post is included), is selectively removed by etching to form an opening section 42, thus forming a sacrifice layer pattern 43. That is, the single sacrifice layer pattern 43 is basically formed in a rectangular parallelepiped form, the region in which the support post is formed is removed to have a comb teeth-like form, the removed portion constitutes the opening section 42, and the region in communication with the sacrifice layer pattern 43 for forming the space in the adjacent fluid actuating apparatus has a comb teeth-like form by the sacrifice layer 41. The etching for the sacrifice layer 41 is preferably dry etching by which processing with high precision can be achieved since there is a portion which must be processed into a comb teeth-like form.
Then, as shown in FIGS. 5A-5B, a second insulating film 14 for covering the surface of the sacrifice layer pattern 43 is formed on the first insulating film 13. Like the first insulating film 13, the second insulating film 14 is formed from a film having a resistance to the etching liquid or etching gas used for etching the sacrifice layer 41. In the present Example, the sacrifice layer 41 comprised of a polycrystalline silicon film is removed by etching using, e.g., sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂), and therefore the second insulating film 14 is formed from a silicon oxide film (SiO₂film) by thermal oxidation or CVD. Each of the first and second insulating films 13, 14 is required to protect the diaphragm-side electrode, and to prevent discharge caused when the diaphragm and the substrate-side electrode 12 are close to each other and to prevent short-circuiting caused when the diaphragm is in contact with the substrate-side electrode 12. When the substrate-side electrode is not etched by the etchant for the sacrifice layer, e.g., hydrofluoric acid used for etching the silicon oxide (SiO₂film) sacrifice layer, and further a satisfactory pressure resistance can be secured only by the second insulating film 14, the first insulating film can be omitted.
Next, as shown in FIGS. 6A-6B, an independent diaphragm-side electrode 15 is formed on the second insulating film 14. In the present Example, the diaphragm-side electrode 15 is formed as follows. An amorphous silicon film is deposited by, e.g., a chemical vapor deposition (CVD) method, and then doped with an impurity, e.g., phosphorus (P). Then, the impurity as dopant is activated by a heat treatment so that the electrode has conduction properties, thus forming the diaphragm-side electrode 15 comprised of polycrystalline silicon. The diaphragm-side electrode 15 is formed in the support post, and hence formed through the second insulating film 14 on the upper surface of the sacrifice layer pattern 43, the sidewall of the sacrifice layer pattern 43, and part of the bottom of the support post-forming region. In the present Example, the diaphragm-side electrode 15 is formed so that it extends to part of the bottom of the support post, but it may be formed so that it extends to only the sidewall portion.
The diaphragm-side electrode 15 is formed from an impurity-doped polycrystalline silicon film, but it can be also formed from an impurity-doped metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used.
Next, as shown in FIGS. 7A-7B, a third insulating film 16 for covering the diaphragm-side electrode 15 is formed. The third insulating film 16 may be formed from either a silicon oxide (SiO₂) film obtained by, for example, subjecting the surface of the diaphragm-side electrode 15 to thermal oxidation, or silicon oxide deposited by a chemical vapor deposition (CVD) method or the like. The third insulating film 16 is formed for the purpose of relaxing the stress applied to the diaphragm-side electrode 15 by a diaphragm 17 to be formed later, and, when the stress relaxation is not required, it can be omitted.
Then, as shown in FIGS. 8A-8B, a diaphragm 17 for providing a pressure change in fluid is formed on the entire surface of the third insulating film 16. The diaphragm 17 is formed from, for example, an insulating film, especially preferably formed from a silicon nitride film (SiN film) which generates a tension stress and high repulsion force as a diaphragm. As an example of a method for forming the film, there can be mentioned a reduced pressure CVD method. When the diaphragm 17 is formed from a silicon nitride film (SiN film) as mentioned above, the diaphragm 17 has a tension stress and high repulsion force which are advantageous to the diaphragm.
Next, as shown in FIGS. 9A-9B, a fourth insulating film 18 for covering the diaphragm 17 is formed. The fourth insulating film 18 is formed from, e.g., a silicon oxide film. With respect to the insulating film 18, for example, when an ink, a chemical agent, or another liquid is used as a fluid, the hydrophilic insulating film 18 is formed as the liquid contacting surface. When gas is used as a fluid, the insulating film 18 having a resistance to the gas is formed. When sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas is used for etching of the sacrifice layer pattern 43, it is preferred that the insulating film 18 is formed from an oxide film (e.g., silicon oxide film) having a resistance to the etching gas.
The diaphragm 17 comprised of a silicon nitride film has a construction such that it is disposed between the third insulating film 16 and the fourth insulating film 18, and this construction is effective in preventing warpage of the diaphragm when a stacked structure of the silicon nitride film having a tension stress and the silicon oxide film having a compression stress is formed. In the stacked structure of the silicon nitride film and the silicon oxide film, the diaphragm is markedly bent downwards due to the synergetic effect of the tension stress and the compression stress, lacking in the deflection of the diaphragm. By covering the both sides of the silicon nitride film with a silicon oxide film, the warpage can be relaxed. Therefore, in the present Example, the diaphragm is comprised of substantially the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
In the support post-forming region which is formed so that it intrudes into the side portion of the sacrifice layer pattern 43 and has a comb teeth-like form, the support post 21 is formed from the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
Next, as shown in FIGS. 10A-10B, near the support post 21, an opening section 44 which penetrates the fourth insulating film 18, the diaphragm 17, the third insulating film 16, the second insulating film 14, and the like is formed so that the sacrifice layer pattern 43 is exposed. The opening section 44 serves as a vent hole in the removal of the sacrifice layer pattern 43 by etching, and it can be formed by anisotropic dry etching, e.g., reactive ion etching (RIE). The opening section may have a size as small as 2 μm square or less, and, the smaller the size of the opening section, the more easily the opening section can be sealed up. It has been confirmed that a 0.5 μm square of the opening section is satisfactory in dry etching for the sacrifice layer. Further, in the present Example, when the diaphragm 17 used is thin, for improving the repulsion force of the diaphragm 17 itself, an auxiliary support post (so-called post)(not shown) can be formed immediately under the middle of the diaphragm 17 simultaneously with the support post 21.
Then, as shown in FIGS. 11A-11B, etching liquid or etching gas is introduced through the opening section 44. In the present Example, sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas is introduced and the sacrifice layer pattern 43 (see FIG. 10) is removed by etching to form a space 31 between the diaphragm 17 and the substrate-side electrode 12 integrally having the diaphragm-side electrode 15. In this case, a plurality of opening sections 44 are formed along the long side of the diaphragm 17 and etching proceeds in the direction along the short side of the diaphragm 17 through the opening sections 44, so that the etching can be done in a short time. When silicon, such as polycrystalline silicon, is used in the sacrifice layer pattern 43, it can be removed by etching using sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas. When a silicon oxide film (SiO₂film) is used in the sacrifice layer pattern 43, it can be removed by etching using etching liquid comprised of hydrofluoric acid. When the sacrifice layer pattern 43 is removed using etching liquid, a drying treatment is carried out. Thus, the space 31 is formed in a region formed by removing the sacrifice layer pattern 43, and further, in the support post-forming region formed at the side portion of the space 31, the support post 21 is formed from the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
Next, as shown in FIGS. 12A-12B, the opening section 44 is sealed up with a sealing member 45. The sealing can be made by a metal sputtering method of aluminum (Al) or the like, but the space 31 as a vibration chamber is under a reduced pressure and hence the diaphragm 17 is bent downwards, so that a stress is always applied to the vicinity of the support post 21 (or auxiliary support post) of the diaphragm 17. In addition, when the diaphragm 17 is bent downwards, the deformable range of the diaphragm 17 is narrow. Considering this point, a method can be employed in which, for example, a boron phosphorus silicate glass (BPSG) film is formed, followed by reflow, to seal the opening section 44 up. By conducting the reflow in an atmosphere of nitrogen gas (N₂) under pressure, the pressure of the space 31 as a vibration chamber can be controlled to be a desired value. Alternatively, the opening section 44 can be sealed up utilizing the viscosity of the member forming the below-mentioned pressure chamber. Thus, the fluid actuating apparatus 1 is produced.
The method for producing the fluid actuating apparatus 1 of the present invention comprises the step for forming the diaphragm-side electrode 15 through the second insulating film 14 on the upper surface of the sacrifice layer pattern 43, the sidewall of the sacrifice layer pattern 43, and part of the bottom of the support post-forming region, and hence the diaphragm-side electrode 15 is formed so that it passes through the support post 21 and extends to and covers part of the bottom of the support post 21. Therefore, there can be produced a fluid actuating apparatus having a construction such that, as compared to the construction in which the diaphragm-side electrode is formed so that it covers the whole of the bottom of the support post 21, the amount of the charge, which does not contribute to deformation of the diaphragm 17 and which is stored on the bottom of the support post 21, is small, thus suppressing a waste of the power consumption. In addition, with respect to the strength of the diaphragm 17, there is an advantage in that the fluid actuating apparatus can be produced so that the support post 21 has a larger thickness by the thickness of the diaphragm-side electrode 15 than that in the construction in which the diaphragm -side electrode is formed so that it does not extend to the support post 21, and thus the support post 21 is stronger.

EXAMPLE 3

Next, the electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention will be described with reference to the diagrammatic perspective view of FIG. 13 and the diagrammatic cross-sectional views of FIGS. 14A-14B. In this Example, an electrostatic head is described as an example of the electrostatically-actuated fluid discharge apparatus using the fluid actuating apparatus of the present invention.
First, as shown in FIG. 13, an electrostatically-actuated fluid discharge apparatus (electrostatic head) 1 according to the present embodiment comprises a fluid actuating apparatus 2 comprising a plurality of diaphragms 17 actuated (vibrated) by electrostatic force, which diaphragms are arranged in a line with high density, and a so-called fluid feed zone 55 comprising a partition structure 54 which is disposed above the diaphragms 17 at the corresponding position, and which has formed therein a pressure chamber (so-called cavity) 51 for storing a fluid 61 (indicated by an arrow) and a discharge section 53 for discharging the fluid 61, a nozzle in the present Example (since liquid is used as a fluid). The figure shows a construction in which auxiliary support posts (posts) 23 are formed between the support posts (anchors) 21.
As shown in FIGS. 14A-14B, in the fluid actuating apparatus 1 of the present invention is formed a partition structure having the pressure chamber 51 and the nozzle 53 so that a partition 52 of the fluid feed zone 55 is formed at the position corresponding to the support post 21 for supporting the diaphragm 17. That is, the fluid feed zone 55 is arranged. The pressure chamber 51 is in communication with a fluid feed channel (not shown).
Next, the operation of the electrostatically-actuated fluid discharge apparatus 2is described with reference to FIGS. 15A-15B. In the following description of FIGS. 15A-15B and in FIGS. 1A-1C, FIG. 13, and FIGS. 14A-14B, like parts or portions are indicated by like reference numerals.
As shown in FIG. 15A, in the fluid actuating apparatus 1, when a predetermined voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is applied, electrostatic attraction force is generated, so that the diaphragm 17 having the diaphragm-side electrode 15 is deflected to the side of the substrate-side electrode 12. Conversely, when the application of the voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is removed, as shown in FIG. 15B, the diaphragm 17 is released from the electrostatic force and undergoes damping vibration by its restoring force. The up-and-down motion of the diaphragm 17 changes the capacity of the pressure chamber 51, so that the fluid 61 contained in the pressure chamber 51 is discharged through the nozzle 53, or the fluid 61 is fed to the pressure chamber 51. When the diaphragm 17 is deflected to the side of the substrate-side electrode 12 and the space 31 is a closed space, air between the diaphragm 17 and the substrate-side electrode 12 is compressed to prevent the diaphragm 17 from being deflected, but the support structure comprised of the support post 21 (auxiliary support post 23) permits the compressed air to escape to the space 31 under the adjacent diaphragm 17, so that the diaphragm 17 can be satisfactorily deflected.

EXAMPLE 4

Next, the method for producing an electrostatically-actuated fluid discharge apparatus according to the first embodiment of the present invention will be described with reference to the views of FIGS. 16A to 17B showing the steps in the production process. The views of FIGS. 16A to 17B showing the steps in the production process show cross-sectional structures at positions similar to the positions of the cross-section taken along the line A-A and the cross-section taken along the line B-B shown in the plan view of the layout of FIG. 1A.
A fluid actuating apparatus 1 is produced by the process described above with reference to FIGS. 2A to 12B, and then, as shown in FIGS. 16A-16B, a partition-forming film is deposited on the fluid actuating apparatus 1. The partition-forming film can be formed from, e.g., a photo-curing resin material, such as an epoxy resin material having photosensitive properties. Then, the partition-forming film is patterned using a lithography technique and an etching technique to form a partition 52 (52A) constituting a pressure chamber (so-called chamber) 51 for storing a fluid and a fluid feed channel (not shown) in communication with the pressure chamber 51. Specifically, the pressure chamber 51 is formed on the diaphragm 17, and the partition 52 constituting the pressure chamber 51 is formed, for example, on and between the support posts 21 of the adjacent fluid actuating apparatus 1.
Then, as shown in FIGS. 17A-17B, the partition 52 (52B) having a discharge section (e.g., nozzle) 53 is joined or bonded to the upper edge faces of the partition 52A so that each pressure chamber 51 is closed at the upper portion. The partition 52B is comprised of, for example, a sheet material (so-called a nozzle sheet), and can be formed from a predetermined material, e.g., a metal, such as nickel or stainless steel, or a Si wafer. The electrostatically-actuated fluid discharge apparatus 2 of the present invention is obtained through the steps described above.
The opening section 44 in the diaphragm 17 described above with reference to FIGS. 12A-12B can be sealed up not by forming a sealing member 45 by metal sputtering but by forming the sealing member 45 using a photo-curing resin and controlling the viscosity of the photo-curing resin.
In the fluid actuating apparatus 1 in the present Example, the diaphragm 17 is deflected by electrostatic force and the restoring force is used as actuating force, and therefore a fluid in a very small volume can be fed while controlling it with high precision. By forming an auxiliary support post 23 immediately under the middle of the diaphragm 17, even when the diaphragm 17 is thin or the short side width of the diaphragm 17 is long, the length of the diaphragm 17 between the support posts 21 appears to be short, so that the repulsion force of the diaphragm 17 can be increased, thus obtaining required actuating force.
By virtue of the construction in which the diaphragm 17 is supported by a plurality of support posts 21 which are integrated with the diaphragm, and the opening section 44 for introducing an etchant used for etching of the sacrifice layer pattern 43 is formed near the support post 21, with respect to the formation of the space 31 between the diaphragm 17 having a long side of about 0.5 to 3 mm and a short side of about 15 to 100 μm and the substrate-side electrode 12, the space 31 to be formed by removing the sacrifice layer pattern 43 under the diaphragm 17 can be formed by performing etching in the direction of the short side, and hence, not only can the etching be done in a short time, but also the space 31 under the adjacent diaphragm 17 can be simultaneously formed with high precision. Therefore, there can be provided the fluid actuating apparatus 1 which can secure actuating force for the fluid and achieve high density.
When the substrate-side electrode 12 on the lower side is formed as a common electrode and the diaphragm-side electrode 15 on the upper side is formed in the form of a plurality of independent electrodes, the lower surface of the diaphragm 17 can be flattened. When the substrate-side electrode 12 on the lower side is in a separate form, the step due to the thickness of the electrode appears as a step of the diaphragm 17, and hence the tension stress of the diaphragm 17 is relaxed by the step, so that the tension stress does not effectively act. On the other hand, the diaphragm 17 comprised of a silicon nitride (SiN) film and the diaphragm-side electrode 15 comprised of polycrystalline silicon (Si) are disposed so that the diaphragm-side electrode 15 closely adheres to the side of the lower surface of the diaphragm 17 formed by the step portion through the third insulating film 16, and therefore, even when the diaphragm 17 has a step portion, the tension of the diaphragm 17 is not absorbed by the step portion.
When the positions of the diaphragm 17 comprised of a silicon nitride (SiN) film and the diaphragm-side electrode 15 comprised of polycrystalline silicon (Si) are switched, that is, when the diaphragm 17 comprised of a silicon nitride film is first formed and the diaphragm-side electrode 15 comprised of polycrystalline silicon is formed on the diaphragm, the diaphragm 17 can be flattened, but the voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is also distributed to the SiN film having a higher specific permittivity, and therefore the effective voltage applied to the space 31 between the lower surface of the diaphragm 17 and the upper surface of the substrate-side electrode 12 is lowered and thus the electrostatic attraction force is lowered, so that the deflection of the diaphragm 17 is reduced, which is disadvantageous to the actuation with low power consumption.
When the fluid 61 fed to the pressure chamber 51 is liquid and the portion in contact with the liquid is comprised of a conductor, air bubbles may be formed in the liquid 61 at the conductor surface or the conductor surface may suffer corrosion, but, in the present Example, the diaphragm 17 is disposed on the diaphragm-side electrode 15 and the surface of the diaphragm 17 is covered with the fourth insulating film 18, and hence the above problem does not occur.
When the fluid 61 is liquid, by forming on the surface of the diaphragm 17 the fourth insulating film 18 from a hydrophilic film, flowing of the liquid 61 into the pressure chamber 51 can be facilitated. On the other hand, when the fluid 61 is gas, by forming on the surface of the diaphragm 17 the fourth insulating film 18 having a resistance to the gas, the diaphragm 17 is prevented from suffering corrosion due to the gas.
In the method for producing the fluid actuating apparatus 1 in the present Example, when the sacrifice layer 41 and the diaphragm 17 are formed by vapor deposition, the following effects can be obtained. The interval between the electrodes and the thickness of the diaphragm 17 are uniform, so that the dispersion of the actuation voltage between the diaphragms 17 is reduced. The flatness of the surface of the diaphragm 17 is improved. The control of the electrode interval and the thickness of the diaphragm 17 is easy, and hence the diaphragm 17 having a desired thickness can be easily formed by controlling the time or temperature for deposition. The sacrifice layer and diaphragm can be easily formed by a general semiconductor process, which is advantageous to mass production.
The opening section 44 is formed near the support post 21 and the sacrifice layer pattern 43 is removed by etching through the opening section 44, and therefore the space 31 between the diaphragm 17 and the substrate-side electrode 12 can be formed with high precision. A plurality of opening sections 44 are formed along the longitudinal direction of the diaphragm 17, and hence etching of the sacrifice layer pattern 43 proceeds in the direction of the short side of the diaphragm 17, thus making it possible to reduce the time for the etching.
In the electrostatically-actuated fluid discharge apparatus 2 in the present Example, by virtue of having the above-described fluid actuating apparatus 1, not only can the discharge sections 53 for the fluid 61, nozzles in the present Example be arranged with high density, but also the fluid 61 in a very small volume can be fed by high actuating force while controlling it with high accuracy.
The electrostatically-actuated fluid discharge apparatus 2 involves an apparatus having a construction such that the pressure chamber 51 is comprised of a plurality of high pressure chamber, intermediate pressure chamber, and low pressure chamber and the pressure chambers 51 are connected to one another, and a back-flow valve is disposed between the pressure chambers 51 and a pressure difference is utilized to permit the fluid to flow. One example is described with reference to FIGS. 18A-18D. In FIGS. 18A-18D, FIG. 18A shows a plan view, FIG. 18B shows a cross-sectional view, and FIGS. 18C and 18D show cross-sectional views for explaining the operation.
As shown in FIGS. 18A and 18B, the electrostatically-actuated fluid discharge apparatus 2 comprises the fluid actuating apparatus 1 of the present invention, and the pressure chamber 51 is formed above the fluid actuating apparatus 1 and a plurality of sets of them are formed. The pressure chamber 51 is comprised of, for example a high pressure chamber, an intermediate pressure chamber, and a low pressure chamber, and the individual pressure chambers 51 are connected to one another through flow channels 71, 72, and back- flow valves 75, 76 are disposed between the pressure chambers 51. The back- flow valves 75, 76 are opened or closed based on the downstream side. Arrows in the figures indicate the direction of the flow of the fluid.
In the electrostatically-actuated fluid discharge apparatus 2, as shown in FIG. 18C, in the fluid actuating apparatus 1, when a predetermined voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is applied, electrostatic attraction force is generated, so that the diaphragm 17 having the diaphragm-side electrode 15 is deflected to the side of the substrate-side electrode 12. Conversely, when the application of the voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is removed, as shown in FIG. 18D, the diaphragm 17 is released from the electrostatic force and undergoes damping vibration by its restoring force. The up-and-down motion of the diaphragm 17 changes the capacity of the pressure chamber 51. As shown in FIG. 18C, when the capacity of the pressure chamber 51 is increased, the pressure chamber 51 is under a reduced pressure and hence under a lower pressure relative to the downstream side, so that the back-flow valve 75 is opened. On the other hand, the pressure chamber is under a lower pressure relative to the upstream side, so that the back-flow valve 76 is closed. Then, as shown in FIG. 18D, when the capacity of the pressure chamber 51 is reduced, the pressure chamber 51 is under pressure and hence under a higher pressure relative to the downstream side, so that the back-flow valve 75 is closed. On the other hand, the pressure chamber is under a higher pressure relative to the upstream side, so that the back-flow valve 76 is opened. By causing a pressure difference between before and after the pressure chamber 51 in this way, the fluid 61 can be fed in the direction indicated by an arrow.
When gas is used as a fluid, the electrostatically-actuated fluid discharge apparatus 2 can be produced so that a not shown valve is basically provided at the discharge outlet of the pressure chamber 51.
In the present invention, the electrostatically-actuated fluid discharge apparatus 2 comprising the fluid actuating apparatus 1 including the diaphragm 17, and the partition structure 54 having the pressure chamber 51 and the discharge section (e.g., nozzle) 53 for a fluid can be produced by surface micromachining without using lamination. In the step for removing by etching the sacrifice layer pattern 43 through the opening section 44 formed near the support post 21 and other steps, a generally used semiconductor process can be utilized, thus lowering the cost for the fluid actuating apparatus 1 and the electrostatically-actuated fluid discharge apparatus 2.
The electrostatically-actuated fluid discharge apparatus 2 can also be produced by stacking on the fluid actuating apparatus 1 the separately formed partition structure 54 having the discharge section (e.g., nozzle) 53, the pressure chamber 51, and a fluid feed channel (not shown). Further, for example, as shown in FIG. 19, a plurality of opening sections 44 can be formed near the single support post 21. In the figure, two opening sections are formed respectively on the both sides of the support post 21 as viewed in the longitudinal direction of the support post, and one opening section is formed respectively on the both sides as viewed in the lateral direction of the support post, but the number of the opening sections can be appropriately selected. In addition, the positions of the opening sections to be formed can be appropriately selected. The support post 21 and the auxiliary support post 23 can be formed from part of the materials constituting the diaphragm 17, the diaphragm-side electrode 15, the second insulating film 14, the third insulating film 16, and the fourth insulating film 18.

EXAMPLE 5

Next, the fluid actuating apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 20A-20C. The fluid actuating apparatus according to the second embodiment has substantially the same construction as that of the above-described fluid actuating apparatus according to the first embodiment, except for the construction in connection with the diaphragm-side electrode. Therefore, in the following description and in the first embodiment, like parts or portions are indicated by like reference numerals. FIG. 20A shows part of a plan view of the layout, FIG. 20B shows a diagrammatic cross-sectional structure taken along the line A-A of FIG. 20A, and FIG. 20C shows a diagrammatic cross-sectional structure taken along the line B-B of FIG. 20A. The scale of FIG. 20A and that of FIGS. 20B-20C are not the same. Fluid actuating apparatuses are actually arranged in a line, but the figures show a single fluid actuating apparatus, which is described below.
As shown in FIGS. 20A-20C, a substrate-side electrode 12, which is comprised of a conductor thin film and which is common to another fluid actuating apparatus (not shown), is formed on a substrate 11 having at least a surface formed from an insulating layer. A first insulating film 13 is formed on the substrate-side electrode 12. A second insulating film 14 is formed on the first insulating film 13 so that a space 31 is formed. Accordingly, the space 31 is a substantially rectangular parallelepiped space defined by the two-dimensional first insulating film and the three-dimensional second insulating film 14, and a support post 21 including the second insulating film 14 is formed so that the support post intrudes into the side portion of the space 31 and has a comb teeth-like form. The first insulating film 13 and the second insulating film 14 are insulating films for preventing the below-described diaphragm-side electrode from being brought into contact with the substrate-side electrode 12 when the diaphragm-side electrode is deflected.
On the second insulating film 14 is formed a diaphragm-side electrode 15 which is independently actuated with respect to the space 31 through the second insulating film 14. The diaphragm-side electrode 15 is rectangular (square or rectangular) as viewed from the top (as viewed from the top of the plan view of the layout), and is formed so that it extends from a support post-forming region to another. That is, the diaphragm-side electrode 15 is formed between support post-forming regions so as to have a comb teeth-like form. Thus, the diaphragm-side electrode 15 is basically a rectangular electrode, and is formed so that it extends from a support post-forming region to another and has a comb teeth-like form. For preventing the occurrence of leakage between the adjacent diaphragm-side electrodes 15, the diaphragm-side electrodes 15 are formed independently of each other.
A third insulating film 16 for covering the diaphragm-side electrode 15 is formed on the second insulating film 14. Further, on the third insulating film 16, a plurality of diaphragms 17 for providing a pressure change in fluid, integrally having the diaphragm-side electrode 15 actuated independently, are arranged in a line, and the support post 21 is formed on the substrate 11, substantially on the first insulating film 13 in such a way that the support post supports the individual diaphragms 17 on both sides by a beam. Further, a fourth insulating film 18 is formed on the third insulating film 16 so as to cover the diaphragm 17. The third insulating film 16 is formed for the purpose of relaxing the stress applied to the diaphragm-side electrode 15 by the diaphragm 17, and, when the stress relaxation is not required, it can be omitted. As described above, in the support post-forming region which is formed so that it intrudes into the side portion of the space 31 and has a comb teeth-like form, the support post 21 is formed from the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
The diaphragm 17 formed in the example shown in the figures has a strip form, and a plurality of support posts 21 are formed along the side portion of the diaphragm 17 at predetermined intervals (pitch between the support posts). The predetermined interval (pitch between the support posts) is preferably 2 to 10 μm, most preferably 5 μm. The adjacent diaphragms 17 are formed continuously through the support post 21, and the support post 21 including the diaphragm 17 is formed. Therefore, the space 31 defined by the diaphragm 17 and the substrate-side electrode 12 forms a hollow portion between a plurality of diaphragms 17 arranged in a line. The space 31 forming a hollow portion between the diaphragms 17 is formed so that it is an enclosed space as a whole.
Near the support post 21 of each diaphragm 17, in the present Example, between the support posts 21 along the side portion of the single diaphragm 17, an opening section (not shown) for introducing gas or liquid used for removing a sacrifice layer by etching in the production process described below is formed. After removing the sacrifice layer by etching, the opening section is sealed up by a predetermined member.
As the substrate 11, a semiconductor substrate comprised of silicon (Si), gallium arsenide (GaAs), or the like, which has an insulating film (not shown) formed thereon, can be used. Therefore, as the substrate 11, an insulating substrate, such as a glass substrate including a quartz substrate, can be used. In this case, there is no need to form an insulating film on the surface of the substrate. In the present Example, as the substrate 11, a silicon substrate having an insulating film comprised of, e.g., a silicon oxide film formed on the surface is used.
The substrate-side electrode 12 is formed from an impurity-doped polycrystalline silicon film, metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. An n⁺ diffused layer electrode can be formed by a method in which a substrate-side electrode pattern is formed by selective oxidation, and then implanted with B⁺, P⁺, and B⁺, and a channel stopper layer is formed on the p-Well, followed by arsenic (As) implantation. Similarly, a p⁺ diffused layer electrode can be formed on the n-Well. In the present Example, the substrate-side electrode 12 is formed from an impurity-doped polycrystalline silicon film.
The diaphragm-side electrode 15 can be formed from a material similar to the material for the substrate-side electrode 12 by a method similar to the method for forming the substrate-side electrode 12. Specifically, the diaphragm-side electrode 15 can be formed from an impurity-doped polycrystalline silicon film, metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. In the present Example, the diaphragm-side electrode 15 is formed from an impurity-doped polycrystalline silicon film.
The diaphragm-side electrode 15 is connected to the diaphragm 17 through the third insulating film 16, and formed so that it is inserted into the lower surface concave portion formed by the bent diaphragm 17 and extends to the side of the sidewall of the space 31. The diaphragm 17 is formed from, for example, an insulating film, especially preferably a silicon nitride film (SiN film) which generates a tension stress and high repulsion force as a diaphragm. A fourth insulating film 18 is formed on the upper surface of the diaphragm 17, and the fourth insulating film 18 is formed from, e.g., a silicon oxide film. Each of the second insulating film 14 and the third insulating film 16 can be formed from, e.g., a silicon oxide film. Therefore, in the present Example, the diaphragm is comprised of substantially the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
The fluid actuating apparatus 3 having the above construction vibrates the diaphragm 17 by applying a voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 to change a fluid on the diaphragm 17 in pressure, allowing the fluid to move.
In the fluid actuating apparatus 3 of the present invention, the diaphragm-side electrode 15 is formed so that it passes through the support post 21 and extends to and covers part of the bottom of the support post 21, and therefore, as compared to the construction in which the diaphragm-side electrode 15 is formed so that it covers the whole of the bottom of the support post 21, the amount of the charge, which does not contribute to deformation of the diaphragm 17 and which is stored on the bottom of the support post 21, is small, thus suppressing a waste of the power consumption. In addition, there is an advantage in that the strength of the diaphragm 17 is larger than that in the construction in which the diaphragm-side electrode is formed so that it does not extend to the support post 21. Further, the charge density was measured when 30 V was applied to the electrode of the fluid actuating apparatus 3 having the above construction, and the deflection was measured when a distribution load of 61 kPa was applied. As a result, the charge density was 2.7 fF, and the deflection was 88 nm. On the other hand, in a conventional structure such that the diaphragm-side electrode was not formed in the support post, the charge density was as small as 1.7 fF, but the deflection was as very large as 186 nm, and hence the diaphragm was in contact with the surface beneath the diaphragm when the diaphragm was vibrated, so that the vibration did not smoothly proceed. Thus, in the fluid actuating apparatus 3 of the present invention, small deflection could be achieved without considerably increasing the charge density.

EXAMPLE 6

The method for producing a fluid actuating apparatus according to the second embodiment of the present invention will be described with reference to the views of FIGS. 21 to 31 showing the steps in the production process. The views of FIGS. 21 to 31 showing the steps in the production process mainly show cross-sectional structures at positions similar to the positions of the cross-section taken along the line A-A and the cross-section taken along the line B-B shown in the plan view of the layout of FIG. 20A. In FIGS. 23A-23C, a plan view of the layout of the sacrifice layer pattern is also shown.
As shown in FIGS. 21A-21B, a substrate 11 having at least an insulating surface is prepared. As the substrate 11, for example, in the present Example, a substrate comprising an insulating film, e.g., a silicon oxide film formed on a silicon substrate is used. A common substrate-side electrode 12 is formed on the substrate 11. In the present Example, the substrate-side electrode 12 is formed as follows. An amorphous silicon film is deposited by, e.g., a chemical vapor deposition (CVD) method, and then doped with an impurity, e.g., phosphorus (P). Then, the impurity as dopant is activated by a heat treatment so that the electrode has conduction properties, thus forming the substrate-side electrode 12 comprised of polycrystalline silicon.
The substrate-side electrode 12 is formed from an impurity-doped polycrystalline silicon film, but it can be also formed from an impurity-doped metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used. An n⁺ diffused layer electrode can be formed by a method in which a substrate-side electrode pattern is formed by selective oxidation, and then implanted with B⁺, P⁺, and B⁺, and a channel stopper layer is formed on the p-Well, followed by arsenic (As) implantation. Similarly, a p⁺ diffused layer electrode can be formed on the n-Well.
Next, as shown in FIGS. 22A-22B, a first insulating film 13 is formed on the surface of the substrate-side electrode 12. The first insulating film 13 can be formed by a reduced pressure CVD method at a temperature as high as, e.g., about 1,000° C. or a thermal oxidation method. The first insulating film 13 is required to be a protective film for the substrate-side electrode 12 and to be a film having a resistance to the etching liquid or etching gas used for etching the below-mentioned sacrifice layer, and further required to prevent discharge caused when the diaphragm and the substrate-side electrode are close to each other and to prevent short-circuiting caused when the diaphragm is in contact with the substrate-side electrode 12. As the first insulating film 13, a silicon oxide (SiO₂) film can be used when using etching gas comprised of, e.g., sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂), or a silicon nitride (SiN) film can be used when using etching liquid comprised of, e.g., hydrofluoric acid. Subsequently, a sacrifice layer 41 is formed on the entire surface of the first insulating film 13. In the present Example, as the sacrifice layer 41, a polycrystalline silicon film is deposited by a CVD method.
Then, as shown in FIGS. 23A-23C, using general lithography technique and etching technique, the sacrifice layer 41 in the portion, in which a support post (so-called anchor) to be formed later for supporting the diaphragm is formed (when a not shown auxiliary support post is formed, a portion corresponding to the auxiliary support post is included), is selectively removed by etching to form an opening section 42, thus forming a sacrifice layer pattern 43. That is, the single sacrifice layer pattern 43 is basically formed in a rectangular parallelepiped form, the region in which the support post is formed is removed to have a comb teeth-like form, the removed portion constitutes the opening section 42, and the region in communication with the sacrifice layer pattern 43 for forming the space in the adjacent fluid actuating apparatus has a comb teeth-like form by the sacrifice layer 41. The etching for the sacrifice layer 41 is preferably dry etching by which processing with high precision can be achieved since there is a portion which must be processed into a comb teeth-like form.
Then, as shown in FIGS. 24A-24B, a second insulating film 14 for covering the surface of the sacrifice layer pattern 43 is formed on the first insulating film 13. Like the first insulating film 13, the second insulating film 14 is formed from a film having a resistance to the etching liquid or etching gas used for etching the sacrifice layer 41. In the present Example, the sacrifice layer 41 comprised of a polycrystalline silicon film is removed by etching using, e.g., sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂), and therefore the second insulating film 14 is formed from a silicon oxide film (SiO₂film) by, e.g., thermal oxidation or CVD so that the second insulating film serves as an etching stopper. In addition, the second insulating film 14 is required to protect the diaphragm-side electrode, and to prevent discharge caused when the diaphragm and the substrate-side electrode 12 are close to each other and to prevent short-circuiting caused when the diaphragm is in contact with the substrate-side electrode 12. When the substrate-side electrode is not etched by the etchant for the sacrifice layer, e.g., hydrofluoric acid used for etching the silicon oxide (SiO₂film) sacrifice layer, and further a satisfactory pressure resistance can be secured only by the second insulating film 14, the first insulating film can be omitted.
Next, as shown in FIGS. 25A-25B, an independent diaphragm-side electrode 15 is formed on the second insulating film 14. In the present Example, the diaphragm-side electrode 15 is formed as follows. An amorphous silicon film is deposited by, e.g., a chemical vapor deposition (CVD) method, and then doped with an impurity, e.g., phosphorus (P). Then, the impurity as dopant is activated by a heat treatment so that the electrode has conduction properties, thus forming the diaphragm-side electrode 15 comprised of polycrystalline silicon. The diaphragm-side electrode 15 is formed through the second insulating film 14 on the sacrifice layer pattern 43 including a portion between the support post-forming regions.
The diaphragm-side electrode 15 is formed from an impurity-doped polycrystalline silicon film, but it can be also formed from an impurity-doped metal film {e.g., platinum (Pt), titanium (Ti), aluminum (Al), gold (Au), chromium (Cr), nickel (Ni), or copper (Cu)}, ITO (indium tin oxide) film, or the like. As a method for forming the film, various film formation methods, such as an evaporation method, a vapor deposition method, and a sputtering method, can be used.
Next, as shown in FIGS. 26A-26B, a third insulating film 16 for covering the diaphragm-side electrode 15 is formed. The third insulating film 16 may be formed from either a silicon oxide (SiO₂) film obtained by, for example, subjecting the surface of the diaphragm-side electrode 15 to thermal oxidation, or silicon oxide deposited by a chemical vapor deposition (CVD) method or the like. The third insulating film 16 is formed for the purpose of relaxing the stress applied to the diaphragm-side electrode 15 by a diaphragm 17, and, when the stress relaxation is not required, it can be omitted.
Then, as shown in FIGS. 27A-27B, a diaphragm 17 for providing a pressure change in fluid is formed on the entire surface of the third insulating film 16. The diaphragm 17 is formed from, for example, an insulating film, especially preferably formed from a silicon nitride film (SiN film) which generates a tension stress and high repulsion force as a diaphragm. As an example of a method for forming the film, there can be mentioned a reduced pressure CVD method. When the diaphragm 17 is formed from a silicon nitride film (SiN film) as mentioned above, the diaphragm 17 has a tension stress and high repulsion force which are advantageous to the diaphragm.
Next, as shown in FIGS. 28A-28B, a fourth insulating film 18 for covering the diaphragm 17 is formed. The fourth insulating film 18 is formed from, e.g., a silicon oxide film. With respect to the insulating film 18, for example, when an ink, a chemical agent, or another liquid is used as a fluid, the hydrophilic insulating film 18 is formed as the liquid contacting surface. When gas is used as a fluid, the insulating film 18 having a resistance to the gas is formed. When sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas is used for etching of the sacrifice layer pattern 43, it is preferred that the insulating film 18 is formed from an oxide film (e.g., silicon oxide film) having a resistance to the etching gas.
The diaphragm 17 comprised of a silicon nitride film has a construction such that it is disposed between the third insulating film 16 and the fourth insulating film 18, and this construction is effective in preventing warpage of the diaphragm when a stacked structure of the silicon nitride film having a tension stress and the silicon oxide film having a compression stress is formed. In the stacked structure of the silicon nitride film and the silicon oxide film, the diaphragm is markedly bent downwards due to the synergetic effect of the tension stress and the compression stress, lacking in the deflection of the diaphragm. By covering the both sides of the silicon nitride film with a silicon oxide film, the warpage can be relaxed. Therefore, in the present Example, the diaphragm is comprised of substantially the second insulating film 14, the diaphragm-side electrode 15, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
In the support post-forming region which is formed so that it intrudes into the side portion of the sacrifice layer pattern 43 and has a comb teeth-like form, the support post 21 is formed from the second insulating film 14, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
Next, as shown in FIGS. 29A-29B, near the support post 21, an opening section 44 which penetrates the fourth insulating film 18, the diaphragm 17, the third insulating film 16, the second insulating film 14, and the like is formed so that the sacrifice layer pattern 43 is exposed. The opening section 44 serves as a vent hole in the removal of the sacrifice layer pattern 43 by etching, and it can be formed by anisotropic dry etching, e.g., reactive ion etching (RIE). The opening section may have a size as small as 2 μm square or less, and, the smaller the size of the opening section, the more easily the opening section can be sealed up. It has been confirmed that a 0.5 μm square of the opening section is satisfactory in dry etching for the sacrifice layer. Further, in the present Example, when the diaphragm 17 used is thin, for improving the repulsion force of the diaphragm 17 itself, an auxiliary support post (so-called post)(not shown) can be formed immediately under the middle of the diaphragm 17 simultaneously with the support post 21.
Then, as shown in FIGS. 30A-30B, etching liquid or etching gas is introduced through the opening section 44. In the present Example, sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas is introduced and the sacrifice layer pattern 43 (see FIGS. 29A-29B) is removed by etching to form a space 31 between the diaphragm 17 and the substrate-side electrode 12 integrally having the diaphragm-side electrode 15. In this case, a plurality of opening sections 44 are formed along the long side of the diaphragm 17 and etching proceeds in the direction along the short side of the diaphragm 17 through the opening sections 44, so that the etching can be done in a short time. When silicon, such as polycrystalline silicon, is used in the sacrifice layer pattern 43, it can be removed by etching using sulfur hexafluoride (SF₆), carbon tetrafluoride (CF₄), or xenon difluoride (XeF₂) gas. When a silicon oxide film (SiO₂film) is used in the sacrifice layer pattern 43, it can be removed by etching using etching liquid comprised of hydrofluoric acid. When the sacrifice layer pattern 43 is removed using etching liquid, a drying treatment is carried out. Thus, the space 31 is formed in a region formed by removing the sacrifice layer pattern 43, and further, in the support post-forming region formed at the side portion of the space 31, the support post 21 is formed from the second insulating film 14, the third insulating film 16, the diaphragm 17, and the fourth insulating film 18.
Next, as shown in FIGS. 31A-31B, the opening section 44 is sealed up with a sealing member 45. The sealing can be made by a metal sputtering method of aluminum (Al) or the like, but the space 31 as a vibration chamber is under a reduced pressure and hence the diaphragm 17 is bent downwards, so that a stress is always applied to the vicinity of the support post 21 (or auxiliary support post) of the diaphragm 17. In addition, when the diaphragm 17 is bent downwards, the deformable range of the diaphragm 17 is narrow. Considering this point, a method can be employed in which, for example, a boron phosphorus silicate glass (BPSG) film is formed, followed by reflow, to seal the opening section 44 up. By conducting the reflow in an atmosphere of nitrogen gas (N₂) under pressure, the pressure of the space 31 as a vibration chamber can be controlled to be a desired value. Alternatively, the opening section 44 can be sealed up utilizing the viscosity of the member forming the below-mentioned pressure chamber. Thus, the fluid actuating apparatus 3 is produced.
The method for producing the fluid actuating apparatus 3 of the present invention comprises the step for forming the diaphragm-side electrode 15 through the second insulating film 14 on the sacrifice layer pattern 43 including a portion between the support post-forming regions, and therefore, there can be produced a fluid actuating apparatus having a construction such that, as compared to the construction in which the diaphragm-side electrode is formed so that it covers the whole of the bottom of the support post 21, the amount of the charge, which does not contribute to deformation of the diaphragm 17 and which is stored on the bottom of the support post 21, is small, thus suppressing a waste of the power consumption. In addition, there is an advantage in that the strength of the diaphragm 17 is larger than that in the construction in which the diaphragm-side electrode is formed so that it does not extend to the support post 21.

EXAMPLE 7

Next, the electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention will be described with reference to the diagrammatic perspective view of FIG. 32 and the diagrammatic cross-sectional views of FIGS. 33A-33B. In this Example, an electrostatic head is described as an example of the electrostatically-actuated fluid discharge apparatus using the fluid actuating apparatus of the present invention.
First, as shown in FIG. 32, an electrostatically-actuated fluid discharge apparatus (electrostatic head) 4 according to the present embodiment comprises a fluid actuating apparatus 3 comprising a plurality of diaphragms 17 actuated (vibrated) by electrostatic force, which diaphragms are arranged in a line with high density, and a so-called fluid feed zone 55 comprising a partition structure 54 which is disposed above the diaphragms 17 at the corresponding position, and which has formed therein a pressure chamber (so-called cavity) 51 for storing a fluid 61 (indicated by an arrow) and a discharge section 53 for discharging the fluid 61, a nozzle in the present Example (since liquid is used as a fluid). The figure shows a construction in which auxiliary support posts (posts) 23 are formed between the support posts (anchors) 21.
As shown in FIGS. 33A-33B, in the fluid actuating apparatus 3 of the present invention is formed a partition structure having the pressure chamber 51 and the nozzle 53 so that a partition 52 of the fluid feed zone 55 is formed at the position corresponding to the support post 21 for supporting the diaphragm 17. That is, the fluid feed zone 55 is arranged. The pressure chamber 51 is in communication with a fluid feed channel (not shown).
The operation of the electrostatically-actuated fluid discharge apparatus 4 is similar to the above-described operation of the electrostatically-actuated fluid discharge apparatus 2.

EXAMPLE 8

Next, the method for producing an electrostatically-actuated fluid discharge apparatus according to the second embodiment of the present invention will be described with reference to the views of FIGS. 34 and 35 showing the steps in the production process. The views of FIGS. 34 and 35 showing the steps in the production process show cross-sectional structures at positions similar to the positions of the cross-section taken along the line A-A and the cross-section taken along the line B-B shown in the plan view of the layout of FIG. 20A.
A fluid actuating apparatus 3 is produced by the process described above with reference to FIGS. 21 to 31, and then, as shown in FIGS. 35A-35B, a partition-forming film is deposited on the fluid actuating apparatus 3. The partition-forming film can be formed from, e.g., a photo-curing resin material, such as an epoxy resin material having photosensitive properties. Then, the partition-forming film is patterned using a lithography technique and an etching technique to form a partition 52 (52A) constituting a pressure chamber (so-called chamber) 51 for storing a fluid and a fluid feed channel (not shown) in communication with the pressure chamber 51. Specifically, the pressure chamber 51 is formed on the diaphragm 17, and the partition 52 constituting the pressure chamber 51 is formed, for example, on and between the support posts 21 of the adjacent fluid actuating apparatus 3.
Then, as shown in FIGS. 35A-35B, the partition 52 (52B) having a discharge section (e.g., nozzle) 53 is joined or bonded to the upper edge faces of the partition 52A so that each pressure chamber 51 is closed at the upper portion. The partition 52B is comprised of, for example, a sheet material (so-called a nozzle sheet), and can be formed from a predetermined material, e.g., a metal, such as nickel or stainless steel, or a Si wafer. The electrostatically-actuated fluid discharge apparatus 4 of the present invention is obtained through the steps described above.
The opening section 44 in the diaphragm 17 described above with reference to FIGS. 31A-31B can be sealed up not by forming a sealing member 45 by metal sputtering but by forming the sealing member 45 using a photo-curing resin and controlling the viscosity of the photo-curing resin.
In the fluid actuating apparatus 3 in the present Example, the diaphragm 17 is deflected by electrostatic force and the restoring force is used as actuating force, and therefore a fluid in a very small volume can be fed while controlling it with high precision. By forming an auxiliary support post 23 immediately under the middle of the diaphragm 17, even when the diaphragm 17 is thin or the short side width of the diaphragm 17 is long, the length of the diaphragm 17 between the support posts 21 appears to be short, so that the repulsion force of the diaphragm 17 can be increased, thus obtaining required actuating force.
By virtue of the construction in which the diaphragm 17 is supported by a plurality of support posts 21 which are integrated with the diaphragm, and the opening section 44 for introducing an etchant used for etching of the sacrifice layer pattern 43 is formed near the support post 21, with respect to the formation of the space 31 between the diaphragm 17 having a long side of about 0.5 to 3 mm and a short side of about 15 to 100 μm and the substrate-side electrode 12, the space 31 to be formed by removing the sacrifice layer pattern 43 under the diaphragm 17 can be formed by performing etching in the direction of the short side, and hence, not only can the etching be done in a short time, but also the space 31 under the adjacent diaphragm 17 can be simultaneously formed with high precision. Therefore, there can be provided the fluid actuating apparatus 3 which can secure actuating force for the fluid and achieve high density.
When the substrate-side electrode 12 on the lower side is formed as a common electrode and the diaphragm-side electrode 15 on the upper side is formed in the form of a plurality of independent electrodes, the lower surface of the diaphragm 17 can be flattened. When the substrate-side electrode 12 on the lower side is in a separate form, the step due to the thickness of the electrode appears as a step of the diaphragm 17, and hence the tension stress of the diaphragm 17 is relaxed by the step, so that the tension stress does not effectively act. On the other hand, the diaphragm 17 comprised of a silicon nitride (SiN) film and the diaphragm-side electrode 15 comprised of polycrystalline silicon (Si) are disposed so that the diaphragm-side electrode 15 closely adheres to the side of the lower surface of the diaphragm 17 formed by the step portion through the third insulating film 16, and therefore, even when the diaphragm 17 has a step portion, the tension of the diaphragm 17 is not absorbed by the step portion.
When the positions of the diaphragm 17 comprised of a silicon nitride (SiN) film and the diaphragm-side electrode 15 comprised of polycrystalline silicon (Si) are switched, that is, when the diaphragm 17 comprised of a silicon nitride film is first formed and the diaphragm-side electrode 15 comprised of polycrystalline silicon is formed on the diaphragm, the diaphragm 17 can be flattened, but the voltage between the substrate-side electrode 12 and the diaphragm-side electrode 15 is also distributed to the SiN film having a higher specific permittivity, and therefore the effective voltage applied to the space 31 between the lower surface of the diaphragm 17 and the upper surface of the substrate-side electrode 12 is lowered and thus the electrostatic attraction force is lowered, so that the deflection of the diaphragm 17 is reduced, which is disadvantageous to the actuation with low power consumption.
When the fluid 61 fed to the pressure chamber 51 is liquid and the portion in contact with the liquid is comprised of a conductor, air bubbles may be formed in the liquid 61 at the conductor surface or the conductor surface may suffer corrosion, but, in the present Example, the diaphragm 17 is disposed on the diaphragm-side electrode 15 and the surface of the diaphragm 17 is covered with the fourth insulating film 18, and hence the above problem does not occur.
When the fluid 61 is liquid, by forming on the surface of the diaphragm 17 the fourth insulating film 18 from a hydrophilic film, flowing of the liquid 61 into the pressure chamber 51 can be facilitated. On the other hand, when the fluid 61 is gas, by forming on the surface of the diaphragm 17 the fourth insulating film 18 having a resistance to the gas, the diaphragm 17 is prevented from suffering corrosion due to the gas.
In the method for producing the fluid actuating apparatus 3 in the present Example, when the sacrifice layer 41 and the diaphragm 17 are formed by vapor deposition, the following effects can be obtained. The interval between the electrodes and the thickness of the diaphragm 17 are uniform, so that the dispersion of the actuation voltage between the diaphragms 17 is reduced. The flatness of the surface of the diaphragm 17 is improved. The control of the electrode interval and the thickness of the diaphragm 17 is easy, and hence the diaphragm 17 having a desired thickness can be easily formed by controlling the time or temperature for deposition. The sacrifice layer and diaphragm can be easily formed by a general semiconductor process, which is advantageous to mass production.
The opening section 44 is formed near the support post 21 and the sacrifice layer pattern 43 is removed by etching through the opening section 44, and therefore the space 31 between the diaphragm 17 and the substrate-side electrode 12 can be formed with high precision. A plurality of opening sections 44 are formed along the longitudinal direction of the diaphragm 17, and hence etching of the sacrifice layer pattern 43 proceeds in the direction of the short side of the diaphragm 17, thus making it possible to reduce the time for the etching.
In the electrostatically-actuated fluid discharge apparatus 4 in the present Example, by virtue of having the above-described fluid actuating apparatus 3, not only can the discharge sections 53 for the fluid 61, nozzles in the present Example be arranged with high density, but also the fluid in a very small volume can be fed by high actuating force while controlling it with high accuracy.
The electrostatically-actuated fluid discharge apparatus 4 involves an apparatus having a construction such that the pressure chamber 51 is comprised of a plurality of high pressure chamber, intermediate pressure chamber, and low pressure chamber and the pressure chambers 51 are connected to one another, and a back-flow valve is disposed between the pressure chambers 51 and a pressure difference is utilized to permit the fluid to flow. As an example, there can be mentioned an apparatus having a construction similar to that of the electrostatically-actuated fluid discharge apparatus 1 described above with reference to FIG. 18.
When gas is used as a fluid, the electrostatically-actuated fluid discharge apparatus 4 can be produced so that a not shown valve is basically provided at the discharge outlet of the pressure chamber 51.
In the present invention, the electrostatically-actuated fluid discharge apparatus 4 comprising the fluid actuating apparatus 3 including the diaphragm 17, and the partition structure 54 having the pressure chamber 51 and the discharge section (e.g., nozzle) 53 for a fluid can be produced by surface micromachining without using lamination. In the step for removing by etching the sacrifice layer pattern 43 through the opening section 44 formed near the support post 21 and other steps, a generally used semiconductor process can be utilized, thus lowering the cost for the fluid actuating apparatus 3 and the electrostatically-actuated fluid discharge apparatus 4.
The electrostatically-actuated fluid discharge apparatus 4 can also be produced by stacking on the fluid actuating apparatus 3 the separately formed partition structure 54 having the discharge section (e.g., nozzle) 53, the pressure chamber 51, and a fluid feed channel (not shown). Further, for example, as described above with reference to FIG. 19, a plurality of opening sections 44 can be formed near the single support post 21.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

Claims

1. A fluid actuating apparatus comprising:

a diaphragm for providing a pressure change in fluid;

a diaphragm-side electrode, formed for said diaphragm, for actuating said diaphragm;

a substrate-side electrode formed so that it faces said diaphragm-side electrode;

a space formed between said diaphragm-side electrode and said substrate-side electrode; and

a support post, formed on said substrate-side electrode, for supporting said diaphragm-side electrode through said space;

wherein said diaphragm-side electrode is formed so that it passes through said support post and extends to and covers part of the bottom of said support post.

2. A method for manufacturing a fluid actuating apparatus, said method comprising the steps of:

forming a substrate-side electrode on a substrate;

forming a first insulating film on said substrate-side electrode;

forming a sacrifice layer pattern for forming a space in a region above said first insulating film, excluding a support post-forming region;

forming a second insulating film for covering said sacrifice layer pattern;

forming a diaphragm-side electrode through said second insulating film on the upper surface of said sacrifice layer pattern, the sidewall of said sacrifice layer pattern, and part of the bottom of said support post-forming region;

forming a third insulating film for covering said diaphragm-side electrode;

forming, on said third insulating film, a diaphragm for providing a pressure change in fluid; and

removing said sacrifice layer pattern to form a space in a region formed by removing said sacrifice layer pattern, and further forming, in said support post-forming region formed at the side portion of said space, a support post from said second insulating film, said diaphragm-side electrode, said third insulating film, and said diaphragm.

3. An electrostatically-actuated fluid discharge apparatus comprising:

a diaphragm for providing a pressure change in fluid;

wherein said diaphragm-side electrode is formed so that it passes through said support post and extends to and covers part of the bottom of said support post, and said diaphragm has formed thereon a pressure chamber having a fluid feed section and a fluid discharge section.

4. A method for manufacturing an electrostatically-actuated fluid discharge apparatus, said method comprising the steps of:

forming a substrate-side electrode on a substrate;

forming a first insulating film on said substrate-side electrode;

forming a second insulating film for covering said sacrifice layer pattern;

forming a third insulating film for covering said diaphragm-side electrode;

forming, on said third insulating film, a diaphragm for providing a pressure change in fluid;

removing said sacrifice layer pattern to form a space in a region formed by removing said sacrifice layer pattern, and further forming, in said support post-forming region formed at the side portion of said space, a support post from said second insulating film, said diaphragm-side electrode, said third insulating film, and said diaphragm; and

forming, on said diaphragm through said third insulating film, a pressure chamber having a fluid feed section and a fluid discharge section.

5. A fluid actuating apparatus comprising:

a diaphragm for providing a pressure change in a fluid;

wherein said diaphragm-side electrode is formed so that it extends from said support post to another.

6. A method for manufacturing a fluid actuating apparatus, said method comprising the steps of:

forming a substrate-side electrode on a substrate;

forming a first insulating film on said substrate-side electrode;

forming a second insulating film for covering said sacrifice layer pattern;

forming a diaphragm-side electrode through said second insulating film on said sacrifice layer pattern including a portion between said support post-forming regions;

forming a third insulating film for covering said diaphragm-side electrode;

removing said sacrifice layer pattern to form a space in a region formed by removing said sacrifice layer pattern, and further forming, in said support post-forming region formed at the side portion of said space, a support post from said second insulating film, said third insulating film, and said diaphragm.

7. An electrostatically-actuated fluid discharge apparatus comprising:

a diaphragm for providing a pressure change in fluid;

a diaphragm-side electrode, formed for said diaphragm through an insulating film, for actuating said diaphragm;

a support post, formed on said substrate-side electrode, for supporting said diaphragm-side electrode through said space,

wherein said diaphragm-side electrode is formed so that it extends from said support post to another, and said diaphragm has formed thereon a pressure chamber having a fluid feed section and a fluid discharge section.

8. A method for manufacturing an electrostatically-actuated fluid discharge apparatus, said method comprising the steps of:

forming a substrate-side electrode on a substrate;

forming a first insulating film on said substrate-side electrode;

forming a second insulating film for covering said sacrifice layer pattern;

forming a third insulating film for covering said diaphragm-side electrode;

removing said sacrifice layer pattern to form a space in a region formed by removing said sacrifice layer pattern, and further forming, in said support post-forming region formed at the side portion of said space, a support post from said second insulating film, said third insulating film, and said diaphragm; and