WO1997021986A1

WO1997021986A1 - Microsensors with silicon membranes and method of manufacturing such sensors

Info

Publication number: WO1997021986A1
Application number: PCT/CH1996/000396
Authority: WO
Inventors: Stephan Trautweiler; Jürg Stahl
Original assignee: Micronas Semiconductor S.A.
Priority date: 1995-12-08
Filing date: 1996-11-11
Publication date: 1997-06-19

Abstract

The invention concerns a method of manufacturing a microsensor from a single-crystal silicon wafer (1) and a substrate (11), the method consisting of the following steps: electronic functional units (3) are mounted on the inside surface (2) of the wafer (1); spacers (10) are produced, for instance by making recesses (13) in the substrate (11); holes (14) are made in the substrate (11); the wafer (1) is connected to the substrate (11) so that the inside surface (2) of the wafer faces towards the substrate; the wafer (1) is reduced in thickness from the outside (4), thus forming a thin silicon membrane (6); the individual sensors thus produced are separated from each other; these sensors are mounted on fixed components (7); electrical connection means (8) are applied through the holes (14). A microsensor manufactured in this way makes optimum use of the sensor surface since almost the whole detector surface is available for the silicon membrane (6). In addition, it meets the two following requirements: separation of the processed inside surface (2) of the membrane from the test medium and flush mounting of the sensor.

Description

MICROSENSORS WITH SILICONE MEMBRANES AND METHOD FOR THE PRODUCTION THEREOF

The invention relates to a method for producing microsensors, which are each provided with at least one silicon membrane, and to a microsensor provided with a silicon membrane.

A large number of microsensors, which are provided with micromechanically manufactured silicon membranes, are successfully used today to measure gas concentration, flow, viscosity, air humidity, pressure, sound and more. The function of the silicon membrane is firstly to reduce heat losses via the contact points to a substrate of a heating element located on the silicon membrane and secondly to reduce the mechanical rigidity of the transducer, both with the aim of optimizing the sensitivity of the sensor. A substrate serves as a support for the silicon membrane and thus significantly influences the mechanical stability and the sensitivity of the sensor to mechanical stresses, which often occur when the sensor is installed in its measurement environment. Another function of the substrate is to electrically or thermally isolate the silicon membrane or to contact the surroundings. , 9 -

A frequently used method for producing sensors with thin silicon membranes is anisotropic etching from single-crystalline silicon wafers. Single-crystalline silicon has excellent mechanical properties and can be anisotropically etched using suitable etching agents, for example potassium hydroxide or ethylenediamine pyrocatechol. As a result, thin, very precisely reproducible, mechanically resilient silicon membranes can be mass-produced. A disadvantage of this method is the poor utilization of the sensor area. When anisotropically etching a (100) -oriented silicon substrate, an etching pit is formed, which is delimited by oblique (1 reoriented walls. Thus, only a fraction of the sensor surface that decreases with increasing silicon substrate thickness can be used for the silicon membrane Thicker silicon wafers are also used, this problem becomes more and more important, although the thickness of the silicon wafers before anisotropic etching can be reduced by chemical or mechanical processes, but this creates difficulties in "wafer handling" and leads to increased production costs.

Another problem arises when an anisotropically etched silicon membrane structure is used for determining a flow rate of fluids. With this use, on the one hand, it should be ensured that the (processed) side of the silicon membrane provided with electronic functional units is separated from the possibly corrosive fluid. It follows that the fluid has to flow over the unprocessed side of the silicon membrane. On the other hand, the sensor should have as few unevenness as possible with respect to the wall of the flow channel during installation, in order not to disturb the flow and to avoid eddies. As already mentioned, in the production of silicon membranes by anisotropic etching, an etching groove is formed on the unprocessed side of the silicon membrane, which would strongly disrupt the flow. This means that The flush installation only applies to the processed side of the silicon membrane, which, however, contradicts the first requirement.

The invention is based on the object of specifying a method for producing a microsensor provided with a silicon membrane and the microsensor which can be produced using the method, the sensor surface of which is optimally used and the silicon membrane exterior to be exposed to the measurement signal does not contain any delicate electronic functional units and is at the same time flat .

The invention solves the problem by the method and the microsensor as defined in the corresponding independent claims. A further independent patent claim relates to an intermediate sensor product that can be produced using the method according to the invention.

The basic idea of the method according to the invention is to apply a silicon wafer to a substrate in such a way that its processed side faces the substrate and is therefore protected. The thickness of the silicon wafer can then be reduced from the outside to a small silicon membrane thickness.

The method according to the invention is explained in more detail below. The starting material for the silicon membrane is - as in the known methods - a single-crystalline silicon wafer. On the at least one side, the required electronic functional units are first integrated using known processes. Spacers are attached to one side of a substrate and / or one side of the silicon wafer to be protected. brings or molded out of substrate and / or silicon membrane. The silicon wafer and the substrate are then joined together in such a way that the at least one side of the silicon wafer provided with electronic functional units, hereinafter referred to as the “inner side”, faces the substrate. The spacers ensure that voids are created between the substrate and the silicon wafer. The thickness of the entire silicon wafer can then be reduced from the outside to a small silicon membrane thickness, so that a silicon membrane is formed from the silicon wafer. Finally, the individual sensors can be separated from one another, housed in fixed assemblies and provided with electrical connecting means using known methods.

A first advantage of the method according to the invention is the optimal use of the sensor surface. Virtually the entire sensor area can be used for the silicon membrane because the substrate does not have to have high, oblique etching walls. A second advantage of the method according to the invention results in particular when it is used for the production of microsensors which measure the properties of fluids. The microsensors according to the invention combine the two requirements of separating the processed silicon membrane inside from the fluid and flush installation. The silicon membrane outside has no etching pits and is flat. The fluid can therefore flow over the silicon membrane outside without being disturbed by it, and at the same time the processed silicon membrane inside is also protected.

In the method according to the invention, the substrate has holes at most locally; it is not necessary to remove all of the material underneath the silicon membrane. This gives the substrate increased mechanical strength and thus it is less susceptible to parasitic voltages which occur, for example, when gluing - a problem that plays an important role, especially with pressure sensors. The possibility of using a glass substrate with the method according to the invention opens up further advantages over conventionally anisotropically etched silicon substrates: glass is a good thermal and electrical insulator, which has a positive effect particularly in the case of thermal sensors.

Different variants of the method according to the invention and for comparison also the prior art are described in detail with reference to the figures. Show it:

Fig. 1 shows a schematic cross section through a conventional

Processed microsensor according to the prior art,

2-8 schematic cross sections through starting, intermediate and end products after various steps of the method according to the invention,

9 shows a schematic cross section through a piezoresistive pressure sensor according to the invention,

10-13 schematic cross sections through further embodiments of sensor sensors manufactured according to the method of the invention.

Intermediate products,

14 shows a schematic plan view of the silicon membrane inside of a flow sensor according to the invention and 15 is a perspective, partially disclosed schematic view of a flow sensor according to the invention installed in a flow channel.

In Figures 1-13 and 15, the heights of the individual elements are not necessarily in the correct relationship to one another for reasons of illustration; the ratio of the heights to the lengths does not always correspond to the actual conditions.

FIG. 1 illustrates the state of the art with a cross section through a schematically illustrated microsensor produced by known methods. A single-crystal (100) -oriented silicon wafer 1 is typically used as the starting material for such a sensor. In one side 2, hereinafter referred to as the "inside", the electronic function units 3 required for supply, conversion, signal processing and output are first integrated; This is done by processes such as epitaxy, oxidation, photolithography, diffusion, ion implantation, metallization, etc., which are common in microelectronics. The silicon wafer is then, from the other side 4, hereinafter referred to as "outside", at certain points 5 anisotropically etched down to a desired thickness t (typically a few to a few tens of micrometers), for example with potassium hydroxide (KOH) or ethylenediamine pyrocatechol (EDP). This results in silicon membranes 6 with electronic functional units 3 on the inner sides 2. (The electronic functional units 3 and the silicon membrane 6 are drawn in excessive thickness in all figures for didactic reasons in relation to the other elements.) Special materials may also have to be used Exercise or strengthen the actual converter function, are applied to the inside 2. Finally, the silicon wafer 1 is divided into the individual sensors; these are then converted into suitable ones fixed modules 7 housed and provided with electrical connecting means 8.

When anisotropically etching a (100) -oriented silicon wafer, an etching pit 5 is formed, which is delimited by oblique (1 reoriented walls 9; its angle of inclination to the horizontal is arctan / 2 = 54.7 °. Thus, for a given thickness T, the silicon wafer can only a part of the surface can be used for the silicon membrane 6. For example, in the case of a square sensor of side length L with a silicon membrane length of 1 = 2 mm, an initial thickness of T = 0.6 mm and a silicon membrane thickness t <<T, there is only the fraction

1 ² / L ² = 1 ² / (1 + 2T / V2) ² = 0.49, ie less than half of the sensor area, is available for the actual silicon membrane 6. This disadvantage of microsensors produced by conventional methods is illustrated in FIG. 1. A further disadvantage can also be seen from FIG. 1. If the silicon membrane structure is used, for example, for determining the flow rate of a fluid, the possibly corrosive fluid can attack the electronic functional units 3 and electrical connection means 8 on the inside of the silicon membrane 2 and destroy the sensor. If the fluid is allowed to flow over the outer side 4 in order to avoid this disadvantage, a new problem appears: the etching pit 5 on the outer side 3 disturbs the fluid flow and leads to eddies which can severely impair the sensor function.

The method according to the invention eliminates the disadvantages described above. FIGS. 2-8 each show in cross section the manufacture of a microsensor according to the invention in a preferred variant of the method according to the invention. In this example, the process consists of seven steps. These are only the first three steps for the inventive one Procedure necessary; the other procedural steps are optional. In the example dealt with here, the manufacture of two identical sensors is shown. However, with modern integration methods known from microelectronics, it is possible to manufacture many sensors at the same time; typical length dimension L of microsensors today is in the millimeter range and could be reduced in the future.

A single-crystalline silicon wafer 1 is used as the starting material for the sensor membranes. In a first method step, one side 2, hereinafter referred to as "inside", integrates the electronic functional units 3 required for supply, conversion, signal processing and output; this is done by processes customary in microelectronics, such as epitaxy, oxidation, photolithography, diffusion, ion implantation, metallization, etc. The inside 2 is the side which is to be protected from possibly corrosive fluids when the microsensor is subsequently used. FIG. 2 shows an exemplary embodiment of the silicon wafer 1 or a part thereof after the first method step. The electronic functional units 3 are, for example, diffusion layers 3.1, metal layers 3.2, oxide layers 3.3, silicon nitride layers 3.4, etc .; for didactic reasons they are drawn exaggeratedly thick in relation to the silicon membrane in all figures. The silicon wafer 1 can additionally be preconditioned for a special sensor function in this method step. If desired, additional special materials which exercise or reinforce the actual converter function are applied to the inside 2 in this method step.

In a second method step (which is temporally independent of the first), spacers 10 are attached to one side 13 of a substrate and / or the inside 2 of the silicon wafer 1 or from substrate 11 and / - or silicon membrane 6 molded out. Firstly, these ensure that the silicon wafer 1 does not touch a substrate 11 at the intended locations, and secondly, they provide contact areas for joining the silicon wafer 1 and substrate 11 together. The spacers 10 can, for example, as shown in FIG. 3, be molded out of the substrate 11 by providing one side 12 of the substrate with depressions 13 of depth d (typically a few to a few hundred micrometers). The recesses 13 will form cavities between the silicon membrane and the substrate after the silicon wafer 1 and substrate 11 have been joined together (third method step). Through holes 14 can also be made in the substrate 11 at the same time as the depressions 13. These serve, for example, to accommodate electrical connecting means. The position and size of the depressions 13 and holes 14 on the substrate 11 must be matched to the electronic functional units 3 on the silicon wafer 1.

The substrate 11 can preferably consist of glass or ceramic, silicon or another material. Glass as a substrate material has the advantage that it is a good thermal and electrical insulator, which has a positive effect especially with thermal sensors. The recesses 13 and holes 14 are made by chemical or mechanical ablation processes such as isotropic etching with hydrofluoric acid (HF, BHF) or drilling in the Subsrat. With these processing methods it is possible to obtain almost vertical walls in suitable materials and to optimally utilize practically the entire sensor surface. Because the substrate 11 only has holes 14 locally and not all of the material underneath the silicon wafer 1 is removed, the substrate is given increased mechanical strength and is therefore less susceptible to parasitic mechanical stresses which occur, for example, when bonding in the sixth process step ¬ kicking - a problem that is particularly important with pressure sensors. In a third method step, the silicon wafer 1 and the substrate 11 are joined to one another and fixed, that is to say connected to one another, so that the spacers 10 lie between the silicon wafer and the substrate and cavities 13 of thickness d are formed between the silicon wafer and the substrate. It is crucial that the inside 2 of the silicon wafer 1 to be protected faces the substrate, as shown in FIG. 4; Thereby the protection of the electronic functional units 3 against a possibly corrosive fluid is achieved. Care must be taken that the silicon wafer 1 and substrate 11 are positioned on one another with respect to displacement and rotation; this can be accomplished, for example, with a wafer stepper with an accuracy in the order of magnitude of micrometers or better. In the exemplary embodiment of the sensor shown in FIG. 4, silicon wafer 1 and substrate 11 only adhere to one another at the edge of each sensor. The remaining parts of the silicon wafer 1 hang over the cavities 13.

A stable, permanent adhesion between the silicon wafer 1 and a substrate 11 made of glass is achieved, for example, by the known technique of "anodic bonding". If the substrate 11 consists of silicon, the known technique of "silicon fusion bonding" can be used for fixing. Another possibility of fixing silicon wafer 1 and substrate 11 to one another is to use soldering methods. Silicon wafer 1 and substrate 11 can optionally be joined together in air, another atmosphere or in a vacuum; the corresponding gas or vacuum will remain in the cavities 13 between the silicon wafer and the substrate if the cavities are closed. An interesting way of influencing the mechanical tension of the silicon membrane 6 (formed in the fifth method step) is to use a glass substrate 11 with a thermal expansion coefficient that differs from that of silicon. Since the anodic bonding process is free of mechanical stresses at a temperature of approximately 300 ° C., a mechanical stress is generated in the cooled state, which can be used to, for example, relate to original mechanical stresses in the silicon wafer 1 or in the subsequent silicon membrane 6 to compensate.

In a fourth method step, the thickness of the entire silicon wafer 1 is reduced from the outside 4 to a desired thickness t (from typically a few to a few tens of micrometers), as shown in FIG. 5. The silicon wafer 1 thus becomes a thin silicon membrane 6, the processed inner side 2 of which faces the substrate 11. (For functional reasons, the electronic functional units 3 and the silicon membrane 6 are drawn in excessively thick relation to the other elements.) The silicon membrane 6 is partially supported and fastened on the spacers 10. If the cavities 13 between the silicon membrane 6 and the substrate 11 are thin enough, they also serve as stoppers and can prevent the silicon membrane from breaking if the excess pressure on the outside 4 is too high.

Etching methods, for example anisotropic etching in potassium hydroxide (KOH), in ethylenediamine pyrocatechol (EDP) or plasma etching, are preferably used to reduce the thickness of the silicon wafer 1. In this case, the silicon membrane thickness t can be controlled by known etching stop methods, for KOH, for example, the electrochemical etching stop method. Another option for reducing the thickness is mechanical Processes, for example grinding or polishing. The thickness reduction, ie the fourth method step, can be dispensed with if a sufficiently thin silicon wafer 1 is used from the start. In this case, electronic functional units 3 can be applied to both sides 2, 4 of the silicon wafer 1.

The individual independent units 15, consisting of at least one processed silicon membrane 6 and a substrate 11, which are adhered to one another via spacers 10, are referred to below as "sensor intermediate products". In a fifth method step, the individual intermediate sensor products 15 are separated from one another and from any remaining pieces 16. Figure 6 shows two separate sensor intermediate products 15. The separation is accomplished, for example, with special saws or by breaking.

In a sixth process step, the individual intermediate sensor products 15 are accommodated in fixed assemblies 7. These assemblies 7 give the sensors mechanical stability and protect them from undesired environmental influences; at the same time, however, they must ensure that the input signal to be measured really reaches the sensor converter. The solid assemblies can be, for example, ceramic substrates to which the sensor intermediate products 15 are glued. In Figure 7, only one glued on sensor intermediate 15 is shown; the same procedure is followed with all other sensor intermediate products.

In a seventh, last method step, the silicon membranes 6 are electrically contacted and provided with electrical connecting means 8.

This is done, for example, by manufacturing in the first process step Electrical contacts 17 on the silicon membrane inner sides 2 are connected to the fixed assemblies 7 by the known technique of "wire bonding". FIG. 8 shows a finished sensor produced by the method according to the invention. Electrical connection means 8, for example contact wires, can run outwards from the silicon membrane inside 2 through the holes 14 in the substrate 11 and through holes 18 in the fixed assembly 7. When designing the masks for silicon wafer 1 and substrate 11, it must of course be ensured that the positions of the contact points 17 and the holes 14 are coordinated with one another so that they come to lie one above the other.

9 shows a piezoresistive pressure sensor as an example of the use of a microsensor according to the invention. In the vicinity of the spacers 10, piezoresistive strain gauges 3.1, 3.1 'are integrated in the silicon membrane 6; the silicon membrane 6 can consist, for example, of n-type silicon and the strain gauges 3.1, 3.1 'of p-type silicon. Due to an external pressure p, the silicon membrane 6 experiences the schematically represented deformation, which leads to a change in the length of the strain gauges 3.1, 3.1 '. This change in length is converted by means of the piezoresistive effect into an electrical output signal, which is a measure of the pressure p. The output signal is conducted to the outside with electrical connection means 8 through a through hole 14. Electrical connecting means 8 and through hole 14 are shown only for a strain gauge 3.1; for the other strain gauge 3.1 ', they can lie in a different sectional plane. Of course, more than two strain gauges can be integrated on the silicon membrane 6. Some variants of the method according to the invention are shown below with reference to FIGS. 10-13. Only the intermediate sensor products 15 are drawn after the fifth method step; the fixed assemblies 7 and the electrical connection means 8 are omitted in these figures.

In the examples discussed so far, the spacers 10 were made along the edges 19 of the sensors. FIG. 10, on the other hand, shows an intermediate sensor product 15 with an additional spacer 10 ', which is located inside the sensor, i. H. is not located on a sensor edge 19. This spacer 10 ′ supports the silicon membrane 6 and gives it additional mechanical strength, which could be desirable, for example, in the vicinity of the electrical contacts 17. All spacers 10, 10 'can be produced, for example, in the second method step by suitable structuring of the substrate 11. They can be designed as "blocks" extended in two dimensions, as "walls" extended in one dimension or as thin "columns".

The spacers 10, 10 'shown in FIG. 11 have the same function as the spacers in FIG. 9. The spacers 10, 10' in FIG. 10 were, however, simultaneously with the first method step, by applying and structuring an additional layer on the inside 2 the silicon wafer 1 manufactured. This additional layer can consist, for example, of an oxide, a metal or polycrystalline or monocrystalline silicon. Spacers 10, 10 'produced in this way can also be applied to the substrate 11 instead of to the silicon wafer 1. In a further variant of the method according to the invention, spacers 10, 10 ′ can be applied both to the silicon wafer 1 and to the substrate 11. The production of spacers 10, 10 'from an additional Layer has the advantage that it saves the production of depressions 13 in the substrate 11.

For certain uses of microsensors, it is desirable to measure changes Δd in the distance d between silicon membrane 6 and substrate 11. For this purpose, means for measuring the distance are attached to the silicon wafer 1 and / or the substrate 11 before the third method step in the method according to the invention. As an example, FIG. 12 shows an arrangement for the capacitive measurement of distance changes Δd. The means for measuring changes in distance Δd are electrodes 20 on the substrate 11 and counter electrodes 20 'on the silicon membrane 6. The electrodes 20 of any shape are applied to the flat substrate surface 12 and are electrically contacted outside the silicon membrane 6. The counter electrodes 20 'are produced in the first process step. The microsensor shown in FIG. 12 can be used, for example, as a capacitive pressure sensor for measuring changes Δp in pressure p or as a condenser microphone. The distance changes Δd (Δp) can be linearized by a suitable choice of the electrode shape. In Fig. 12, two holes 14, 14 'are made in the substrate 11 as an example; the holes allow the air to flow out of the cavity 13 and increase the flexibility of the silicon membrane 6 and shorten the reaction time of the pressure sensor.

Another option (not shown in the drawing) for measuring distance changes Δd is provided by the tunnel effect. In order to realize this possibility, at least one ultra-fine tip is produced in the first and / or second method step on the side 2 of the silicon wafer 1 provided with the electronic functional units 3 and / or on a side 12 of the substrate 11. In operation, an electrical voltage between the Tip and the opposite part (silicon membrane 6 or substrate 11) created. The tunnel current is a measure of the distance between the tip and the opposite part 6 or 11.

In the exemplary embodiment of FIG. 13, the substrate 11 consists only of spacers 10 in the form of walls along the sensor edges 19. The through hole 14 in the substrate 11 is thus large and is not only located under the electrical contacts 17 on the inside of the silicon membrane 2 , but under the entire silicon membrane 6. This embodiment can also be viewed as a borderline case in FIG. 6, in which the depth d of the recess 13 is equal to the substrate thickness T. The measures for this variant are taken in the second process step.

FIGS. 14 and 15 finally show, as a further example, a microsensor according to the invention, which is used as a flow sensor.

FIG. 14 shows the inside 2 of the silicon membrane 6 of the flow sensor. The silicon membrane 6, for example made of n-type silicon, essentially contains three elements: two heating resistors 21, 21 'and a thermopile 22. The heating resistors 21 consist, for example, of p-type silicon, the thermopile 22, for example, of strips of p- conductive silicon 3.1 and aluminum 3.2. Contact surfaces 23 made of aluminum are used to contact these elements. In sensor operation, the fluid to be measured should flow in the direction indicated by the arrows 24 over the outside of the silicon membrane (not shown); the silicon membrane should be thin in order to ensure optimal heat transfer between the fluid and the silicon membrane inside 2. The sensor works as follows: the heating resistors 21, 21 'are heated with the same heating currents and the output signal of the thermopile 22 is read out. If the flow 24 is equal to zero, the temperature difference measured by the thermopile 22 is also zero. If a fluid flows over the outside of the silicon membrane, part of the heat is transferred from the silicon membrane 6 to the fluid on its way between the heating resistors 21 and 21 '. This creates a temperature difference between the two heating resistors 21, 21 ', which is measured by the thermopile 22 by means of the thermoelectric effect. The amount of this temperature difference is a measure of the flow rate 24, its sign indicates the direction of flow.

FIG. 15 shows the perspective, partially disclosed view of the flow sensor according to the invention. It is installed in a flow channel 25 and measures, for example, the flow rate of a fluid through the channel, represented by the arrows 24. Two advantages of the flow sensor according to the invention are clearly evident from FIG. 15: the sensor membrane 6 is flush with the flow channel 21 installed and does not disturb the flow 22 through the flow channel, and at the same time its electronics on the inside of the silicon membrane 2 are protected from the possibly corrosive fluid.

The method according to the invention can also be used to produce a sensor for different sizes, for example for flow and pressure. For this purpose, the silicon membrane can be divided into several sub-membranes, for example by spacers 10 '; each sub-membrane can measure a different size using a suitable transducer principle. The electronics required for signal processing can also be integrated on the same silicon membrane 6. In summary, the method according to the invention is used to manufacture microsensors, each with a sensor surface that is partially formed by outer sides 4 of at least one silicon membrane 6; the silicon membrane 6 carries electronic functional units 3, electrical connecting means 8 being created for the electrical connection of the electronic functional units 3. For each microsensor, a silicon wafer 1 provided with electronic functional units 3 on at least one inner side 2 is connected to a substrate 11. The inside 2 of the silicon wafer 1 faces the substrate 11, and spacers 10, 10 ′ are provided between the substrate and the silicon wafer in such a way that cavities 13 are formed between the substrate 11 and the silicon wafer. The silicon wafer 1 either has the thickness t of a silicon membrane 6 or is thicker than a silicon membrane 6 and is reduced to the silicon membrane thickness t after being joined to the substrate 11.

A microsensor obtainable by the method according to the invention has a sensor surface, which is partially formed by the outside of at least one silicon membrane 6, and electrical connection means 8. The silicon membrane 6 has at least on its inside 2 electronic function units 3. The silicon membrane 6 is applied to a substrate 11, spacers 10, 10 'being positioned between the silicon membrane 6 and the substrate 11 such that there are cavities 13 between the silicon membrane 6 and the substrate 11.

An intermediate sensor product according to the invention has a silicon wafer 1 applied to a substrate 11 with electronic functional units 3 at least on its inside 2 facing the substrate 11 and with cavities 13 and spacers 10, 10 'between the silicon wafer 1 and the substrate 11. The silicon wafer 1 and the substrate 11 together form a plurality of microsensors without electrical connection means 8.

Claims

PATENT CLAIMS

1. A method for producing microsensors, each with a sensor surface, which is partially formed by the outer sides (4) of at least one silicon membrane (6), which silicon membrane (6) carries electronic functional units (3), for the electrical connection of the electronic functional units ( 3) electrical connection means (8) are created, characterized in that for each microsensor a silicon disk (1) provided with electronic functional units (3) at least on one inside (2) is connected to a substrate (11), the inside (2 ) the silicon wafer (1) faces the substrate (11) and spacers (10, 10') are provided between the substrate and the silicon wafer in such a way that cavities (13) are created between the substrate (11) and the silicon wafer (1), and wherein the silicon wafer (1) either has the thickness (t) of a silicon membrane (6) or is thicker than a silicon membrane (6) and is reduced to the silicon membrane thickness (t) after being joined to the substrate (11).

2. The method according to claim 1, characterized in that the silicon wafer (1) is preconditioned for a special sensor function.

3. The method according to claim 1 or 2, characterized in that the spacers (10, 10 ') are formed from the substrate (11) and / or the silicon wafer (1) using chemical or mechanical removal processes.

4. The method according to claim 1 or 2, characterized in that the spacers (10, 10 ') are attached by applying and structuring at least one additional layer on the substrate (11) and / or on the silicon wafer (1). .

5. Method according to one of claims 1-4, characterized in that the silicon wafer (1) and the substrate (11) are connected to one another by anodic bonding.

6. Method according to one of claims 1-4, characterized in that the silicon wafer (1) and the substrate (11) are connected to one another by a soldering process.

7. The method according to any one of claims 1-6, characterized in that the thickness of the silicon wafer (1) is reduced by an etching process, the thickness (t) of the silicon membrane (6) being controlled by an etching stop process.

8. The method according to any one of claims 1-6, characterized in that the thickness of the silicon wafer (1) is reduced by a mechanical process.

9. Method according to one of claims 1-8, characterized in that the microsensor is accommodated in a fixed assembly (7).

10. The method according to claim 9, characterized in that a ceramic substrate is used as the fixed assembly (7) and the microsensor is glued onto it.

11. The method according to any one of claims 1-10, characterized in that the electrical connection means (8) are attached by means of “wire bonding”.

12. The method according to any one of claims 1-11, characterized in that through holes (14, 14 ') are made in the substrate (1) using chemical or mechanical removal processes.

13. The method according to any one of claims 1-12, characterized in that a plurality of microsensors are produced simultaneously by a silicon wafer (1) with an area which essentially corresponds to the sum of the sensor areas, and a corresponding substrate (11 ) can be used and by connecting the sensors after assembling

Silicon wafer (1) and substrate (11) are separated from each other or after reducing the silicon wafer thickness.

14. The method according to claim 13, characterized in that the sensor intermediate products (15) are separated from one another and from any remaining pieces (16) by sawing.

15. Microsensor, obtainable by the method according to one of claims 1-14, with a sensor surface that is partially at least through the outside a silicon membrane (6) is formed, and with electrical connecting means (8), characterized in that the silicon membrane (6) is connected to a substrate (11), with spacers (10) between the silicon membrane (6) and the substrate (11). , 10 ') are positioned in such a way that there are cavities (13) between the silicon membrane (6) and the substrate (11), and that the silicon membrane (6) has electronic functional units at least on its inside (2) facing the substrate (11). (3).

16. Microsensor according to claim 15, characterized in that it is housed in a fixed assembly (7).

17. Microsensor according to claim 16, characterized in that the fixed assembly (7) is a ceramic substrate.

18. Microsensor according to one of claims 15-17, characterized in that the substrate (11) has at least one through hole (14, 14 ').

19. Microsensor according to claim 18, characterized in that the electrical connecting means (8) through at least one through hole

(14) are guided in the substrate (1).

20. Microsensor according to claim 18 or 19, characterized in that the at least one through hole (14, 14 ') covers the entire surface (12) of the

Substrate (11) with the exception of the spacers (10, 10 '). 21. Microsensor according to one of claims 15-20, characterized in that the inside (2) of the membrane (6) has heating elements (21,

21') and temperature measuring elements (22).

22. Microsensor according to one of claims 15-20, characterized in that it has means for measuring the distance between the silicon membrane (6) and the substrate (11).

23. Microsensor according to claim 22, characterized in that as a means for capacitive measurement of the distance between the silicon membrane (6) and the substrate (11) there is at least one electrode (20) on the substrate (11) and at least one counter electrode ( 20') are located on the silicon wafer (1).

24. Microsensor according to one of claims 15-23, characterized in that the substrate (11) consists of glass.

25. Use of the microsensors according to one of claims 15-24 for measuring gas concentration, flow, viscosity, air humidity, pressure or sound pressure.

26. Sensor intermediate product of the method according to one of claims 1-14, characterized by a silicon wafer (1) applied to a substrate (11) with electronic functional units (3) at least on its inside (2) facing the substrate (11) and with cavities (13) and spacer hooks (10, 10') between the silicon wafer (1) and substrate (11), which silicon wafer (1) and substrate (11) together form a plurality of microsensors without electrical connecting means (8).

CHANGED REQUIREMENTS

[received by the International Bureau on April 7, 1997 (04/07/97); Original claims 1-26 replaced by amended claims 1-25 (6 pages)]

1. A method for producing microsensors, each with a sensor surface, which is at least partially formed by a first side (4) of at least one silicon membrane (6), which silicon membrane (6) carries electronic functional units (3), characterized in that a silicon wafer (1) provided on a second side (2) with electronic functional units (3) is connected to a substrate (11), the second side (2) of the silicon wafer (1) facing the substrate (11) and between Substrate (11) and silicon wafer (1) spacers (10, 10') are provided in such a way that between the substrate (11) and silicon wafer (1) there is at least one chamber (13) that can be optionally involved in the measurement for receiving and contacting The result of the electronic functional units (3) is that the silicon wafer (1) is reduced to the silicon membrane thickness (t) from the first side (4) after being joined to the substrate (11) and that electrical connections are made the electronic functional units (3) are created by attaching the electrical connecting means (8) in through holes (14, 14 ') in the substrate (11) and making electrical contact with the electronic functional units (3) in the at least one chamber (13). - the.

Method according to claim 1, characterized in that the silicon wafer (1) is preconditioned for a special sensor function.

AMENDED SHEET (ARTICLE 19) 3. The method according to claim 1 or 2, characterized in that the spacers (10, 10 ') are formed from the substrate (11) and / or the silicon wafer (1) using chemical or mechanical removal processes.

8. The method according to any one of claims 1-6, characterized in that the thickness of the silicon wafer (1) is reduced by a mechanical process. Method according to one of claims 1-8, characterized in that the microsensor is accommodated in a fixed assembly (7).

Method according to claim 9, characterized in that a ceramic substrate is used as the fixed assembly (7) and the microsensor is glued onto it

Method according to one of claims 1-10, characterized in that the electrical connection means (8) are attached by means of “wire bonding”.

Method according to one of claims 1-11, characterized in that through openings (14, 14') are made in the substrate (1) using chemical or mechanical removal processes.

Method according to one of claims 1-12, characterized in that a plurality of microsensors are produced simultaneously by using a silicon wafer (1) with an area that essentially corresponds to the sum of the sensor areas and a corresponding substrate (11). - and by separating the sensors from each other after reducing the thickness of the silicon pane.

Method according to claim 13, characterized in that the separation of the sensor intermediate products (15) from each other and from any

Remaining pieces (16) are done by saying. 15 Microsensor, obtainable by the method according to one of claims 1-14, with a sensor surface which is at least partially formed by a first side (4) of at least one sealing membrane (6), and with electrical connecting means (8), characterized that the silicon membrane (6) is connected to a substrate (11), the substrate (11) serving as a support for the silicon membrane (6), that the silicon membrane (6) is on its substrate (11 ) facing the second side (2) has electromic functional units (3) that spacers (10, 10 ') are arranged between the silicon membrane (6) and substrate (11) in such a way that between the silicon membrane (6) and substrate (11 ) at least one chamber (13) that can be optionally involved in the measurement is formed for receiving and contacting the electronic functional units (3), and that at least one continuous opening (14, 14 ') in the substrate (11) to at least one chamber (13 ), whereby the electrical connecting means (8) are passed through the at least one opening (14, 14') and are electrically contacted with the electronic functional units (3) in the at least one chamber (13).

16 Microsensor according to claim 15, characterized in that the first side (4) of the silicon membrane (6) is flat.

17 Microsensor according to claim 15 or 16, characterized in that it is housed in a fixed assembly (7).

18. Microsensor according to claim 17, characterized in that the fixed assembly (7) is a ceramic substrate. 19. Microsensor according to one of claims 15-18, characterized in that the at least one through hole (14, 14 ') occupies the entire surface (12) of the substrate (11) with the exception of the spacers (10, 10'). .

20. Microsensor according to one of claims 15-19, characterized in that the second side (2) of the membrane (6) has heating elements (21, 21 ') and temperature measuring elements (22).

21. Microsensor according to one of claims 15-19, characterized in that it has means for measuring the distance between the silicon membrane (6) and the substrate (11).

->- ^* > Microsensor according to claim 21, characterized in that as a means for capacitive measurement of the distance between the silicon membrane (6) and the substrate (11) there is at least one electrode (20) on the substrate (11) and at least a counter electrode (20') is located on the silicon wafer (1).

23. Microsensor according to one of claims 15-22, characterized in that the substrate (11) consists of glass.

24. Use of the microsensors according to one of claims 15-23 for measuring gas concentration, flow, viscosity, air humidity, pressure or sound pressure. 25. Sensor intermediate product of the method according to one of claims 1-14, characterized by a silicon wafer (1) applied to a substrate (11), electronic functional units (3) being arranged on its second side (2) facing the substrate (11). are, through chambers (13) and spacers (10, 10 ') between the silicon wafer (1) and substrate (11) and through through openings (14, 14') in the substrate, which open into the chambers (13), so that the silicon wafer (1) and the substrate (11) together form a plurality of microsensors without electrical connecting means (8).