US20060151115A1

US20060151115A1 - Dry stripping equipment comprising plasma distribution shower head

Info

Publication number: US20060151115A1
Application number: US11/316,879
Authority: US
Inventors: Hoon-Ho Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2005-01-11
Filing date: 2005-12-27
Publication date: 2006-07-13
Also published as: KR100610019B1; KR20060082090A

Abstract

A plasma distribution device for supplying plasma onto an object in a chamber is provided. The device includes a tube for supplying the plasma into the chamber, and a baffle installed under the tube for controlling flow of the plasma supplied from the tube. The baffle includes an upper shower head and a lower shower head, the upper shower head having a center portion for reflecting the plasma supplied from the tube, and a plurality of holes spaced apart from each other around the center portion for uniformly distributing the plasma.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a semiconductor fabricating apparatus. More particularly, the present invention relates to dry stripping equipment using plasma for removing photoresist from a wafer.
2. Description of the Related Art
In general, a semiconductor device is fabricated by carrying out a plurality of unit processes in succession. More specifically, a typical semiconductor device is fabricated by subjecting a wafer to photolithographic, diffusion, etching, and deposition processes. Plasma is usually employed in the deposition process to deposit material onto the wafer and in the etching process to etch material on the wafer. A deposition process employing such plasma is referred to as chemical vapor deposition. The etching processes that employ plasma include sputtering and reactive ion etching processes. Plasma is also employed in a dry stripping process to remove photoresist deposited on the wafer in the photolithographic process and cured as the result of the etching process.
The chemical vapor deposition process is advantageous in that it can produce a thin film that is more uniform and provides better step coverage than thin films produced by other existing deposition processes. In addition, the deposition rate is higher. Hence, chemical vapor deposition is widely utilized to form thin films in the fabricating of semiconductor devices.
With respect to dry etching, such as sputter etching and reactive ion etching, a wafer having an insulation film or metal layer thereon, and a photoresist pattern (mask) exposing select portions of the insulation film or metal layer, is loaded into an airtight process chamber. Gas is introduced into the chamber, and a high frequency or microwave power is applied to the chamber to transform the gas into a plasma that etches the exposed portions of the insulation film or metal layer. Dry etching is characterized in that a cleaning process is not required after the etching process, and the insulation film or metal layer is etched anisotropically. Hence, dry etching is simpler to carry out than wet etching, and dry etching can form fine patterns of a highly integrated circuit which are superior to those which can be formed by wet etching.
Meanwhile, after the etching process has been completed, the wafer is subjected to a stripping process for removing the photoresist from the wafer. As compared to a wet stripping process, the dry stripping process is advantageous in that it does not require the handling of batches of liquid chemicals, it does not present the concerns that are present when a wet etching bath or a hood is employed, and the wafer is not exposed to chemicals or a cleaning solution.
In dry stripping, the etched wafer which is transferred onto a support in a chamber. The chamber is sealed once the wafer is seated on the support. Subsequently, the interior of the chamber is evacuated by a vacuum pump until a high degree of vacuum is produced in the chamber. Next, plasma produced by a generator is supplied into the chamber through a tube installed on a lid of the chamber. The plasma is reflected by a reflector installed on a central portion of an upper surface of a plate, which together constitute an upper shower head. The reflected plasma is diffused, and propagates downwardly through a plurality of holes in the plate and a plurality of holes of a lower shower head. Hence, the plasma is uniformly distributed over the wafer seated on the support, and the photoresist is stripped off of the wafer by the plasma.
FIG. 1 illustrates an upper shower head of the conventional stripping equipment. A reflector 45 is disposed on a central portion of an upper surface of a plate 40 and is fixed thereto by fixing pins 47. The reflector 45, the fixing pins 47, and the upper shower head 40 are made of quartz, and the reflector 45 and the plate 40 are coated with sapphire to prevent the reflector and plate from being etched by the plasma. The fixing pins 47 are not coated with sapphire due to technical reasons. Accordingly, the fixing pins 47 are etched by the plasma, as shown in FIG. 2.
Specifically, the fixing pins 47 are gradually etched by the plasma as the dry stripping progresses. After a period of time, the fixing pins 47 no longer can secure the reflector 45 to the upper surface of the plate 40 in the upper shower head. In this case, the reflector 45 is moved from the central portion of the plate 40 by the operation of the vacuum pump or by the plasma. Thus, the reflector 45 stops up some of the holes 43 in the plate 40. Accordingly, the plasma does not pass through the stopped up holes 43. As a result, the plasma is not uniformly distributed over the lower shower head and hence, the plasma is not uniformly distributed over the wafer such that a processing defect is produced on the wafer.
When the above-described problem occurs in the equipment, a considerable time is required to repair the equipment. This detracts from the productivity in the overall process of fabricating the semiconductor device.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide plasma dry stripping equipment capable of preventing plasma from being non-uniformly distributed over an object to be processed.
In accordance with one aspect of the present invention, the plasma dry stripping equipment comprises: a process chamber, a tube for supplying plasma into the chamber, and a baffle for distributing the plasma supplied from the tube, wherein the baffle includes an upper shower head and a lower shower head, and the upper shower comprises a plate having a central portion that reflects the plasma supplied from the tube, and a plurality of holes spaced apart from each other around the central portion for uniformly distributing the plasma.
That is, the central portion of the upper surface of the plate is disposed directly across from and is exposed to the end of the tube from which plasma issues into the chamber. The holes in the plate are only present in the plate outside the central portion of the plate and are spaced apart from each other beginning at the periphery of the central portion of the plate. Also, the upper shower head and the lower shower head extend across the chamber so as to divide the chamber into a first space located between the plate of the upper shower head and the end of the tube, a second space located between the plate of the upper shower head and the lower shower head, and a third space located between the lower shower head and the support. Thus, the plasma introduced into the chamber through the tube directly impinges and is reflected from the central portion of the plate so as to diffuse throughout the first space. Then, the plasma is distributed by the plate of the upper shower head to the lower shower head. From there, the plasma is distributed by the lower shower head into the third space in which the object to be processed is supported.
Basically, the upper shower head consists of the plate that has the plasma distribution holes therein. In other words, the upper shower head does not include a reflector that is discrete from the plate having the plasma distribution holes. Thus, the present invention obviates the problems associated with keeping such a reflector secured to the plate. Moreover, the entire upper surface of the plate is exposed, i.e., all of the holes in the plate are unobstructed. Accordingly, plasma is distributed uniformly.
Also, the plate of the upper shower head and the lower shower head are coated with sapphire, so that the shower heads are not etched by the plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by referring to the detailed description of the preferred embodiments thereof made with reference to the attached drawings in which:
FIG. 1 is a perspective view of an upper shower head of conventional dry stripping equipment;
FIG. 2 is a similar perspective view but showing a case in which fixing pins of the upper shower head are etched by plasma;
FIG. 3 is a schematic longitudinal sectional view of dry stripping equipment according to the present invention;
FIG. 4 is a perspective view of an upper shower head of the dry stripping equipment according to the present invention; and
FIG. 5 shows data of the rate and uniformity of a photoresist stripping process according to the present invention and of a photoresist stripping process according to the prior art; and
FIG. 6 shows data of particles present on wafers after performing the stripping process according to the present invention and after performing a stripping process according to the prior art.

DETAILED DESCRITPION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will now be described with reference to the FIGS. 3-6. Like reference numbers designate like elements throughout the drawings.
Referring first to FIGS. 3 and 4, the dry plasma equipment according to the present invention includes a chamber, a tube 115 for supplying plasma into the chamber, a baffle 130, and a slit valve 129. The plasma is produced by a remote plasma generator (not shown) disposed on the outside of the chamber. The interior of the chamber is defined by a chamber lid 110 and a body 120. The tube 115 extends through the chamber lid 110.
The baffle 130 is installed in the chamber lid 110 under the tube 115 to control the diffusion of the plasma. The baffle 130 includes an upper shower head 140 and a lower shower head 150.
The upper shower head 140 consists of a plate having a central portion 147 for reflecting the plasma supplied from the tube 115, and a plurality of holes 143 spaced apart from each other around the central portion 147 for uniformly distributing the plasma. The entire upper surface of the plate is exposed with the central portion of the plate being disposed directly across from the end of the tube 115 in the direction in which plasma is introduced into the chamber. The plate constituting the upper shower head 140 is coated with sapphire to prevent the upper shower head from being etched by the plasma supplied from the tube 115.
The lower shower head 150 is disposed under the upper shower head 140. The lower shower head 150 comprises a plate having a plurality of holes 153 spaced apart from each other to uniformly distribute the plasma supplied through the upper shower head 140. The lower shower head 150 is also coated with sapphire to prevent the lower shower head 150 from being etched by the plasma.
The baffle 130 extends across the chamber so as to divide the chamber into a first space located between the plate of the upper shower head 140 and the end of the tube 115, a second space located between the plate of the upper shower head 140 and the lower shower head 150, and a third space located between the lower shower head 150 and the support 125.
A support 125 on which the wafer 10 to be processed is seated under the lower shower head 150 is disposed in the third space at the bottom of the body 120 of the chamber. One side of the body 120 has an opening 127 through which the wafer 10 can pass. A slit valve 129 is disposed on the outer side of the body 120 over the opening 127 and is operable to open and close over the opening 127.
A dry stripping process performed by the dry etching equipment will now be described in more detail.
Initially, the interior of the chamber is maintained at atmospheric pressure. Then, the slit valve 129 uncovers the opening 127 in the body 120, and the wafer 10 is transferred onto the support 125 through the opening 127. The transfer of the wafer 10 is achieved by transfer means (not shown) such as a robot. Once the wafer 10 is seated on the support 125, the slit valve 129 closes over the opening 127, and the interior of the chamber is evacuated by a vacuum pump (not shown) until a high degree of vacuum prevails inside the chamber.
Next, the tube 115 supplies plasma produced by the remote plasma generator onto the central portion 147 of the plate constituting the shower head 140, whereupon the plasma is reflected by the central portion 147. The plasma diffuses throughout the entire space above the shower head 140 because the space is maintained in a high vacuum state. That is, the plasma is uniformly distributed in the first space.
The plasma propagates downwardly through the holes 43 in the plate and the holes 153 in the lower shower head 150. Hence, the plasma is uniformly distributed on the wafer 10 seated on the support 25. Accordingly, a dry stripping process is carried out by the plasma.
Once the dry stripping process is completed, the interior of the chamber is vented so that atmospheric pressure prevails in the chamber. At this time, the slot valve 129 is opened to uncover the opening 127, the processed wafer 10 is withdrawn from the chamber by the transfer means, and a new wafer is loaded into the chamber. The above-described process is then carried out on the new wafer.
FIGS. 5 and 6 illustrate results of stripping processes according to the present invention and according to the prior art. In particular, FIG. 5 shows comparative data of the rate and uniformity of the stripping processes, and FIG. 6 shows comparative data of the production of particles after the stripping processes.
In general, a stripping process is deemed satisfactory when the rate at which the photoresist removed is 53000 Å/min to 65000 Å/min and the uniformity of the process is about 10%. FIG. 5 shows that photoresist was removed at rates of 57582 Å/min and 53373 Å/min by two pieces of conventional plasma stripping equipment, respectively, each having an upper shower head comprising a plate and a reflector covering the central portion of the upper surface of the plate. Both pieces of the conventional stripping equipment were also able to execute dry stripping processes having a uniformity of about 10%.
As is also shown in FIG. 5, photoresist was removed at rates of 61562 Å/min, and 60517 Å/min by two pieces of plasma stripping equipment, respectively, according to the present invention. Both pieces of the plasma stripping equipment according to the present invention were also able to execute dry stripping processes having a uniformity of about 10%.
The abovementioned data thus shows that the rate at which photoresist is removed and the uniformity of the stripping process are within what are deemed normal operating parameters of photoresist dry stripping equipment. Therefore, it is clear from the data that plasma is adequately reflected from the upper shower head of the present invention, which consists of a plate having plasma distribution holes therethrough.
Moreover, no more than 30 particles should be produced as the result of a dry stripping process.
FIG. 6 shows particles distributed on wafers after two stripping processes performed using conventional dry stripping equipment and dry stripping equipment according to the present invention. Note, most of the particles shown on the wafers were produced prior to the stripping process. The difference in the number of particles counted pre- and post-stripping, i.e., the number of particles produced as the result of the stripping process is listed at the top of each drawing in the figure.
The results show that one particle was produced as the result of a stripping process performed in the P/C (process chamber) of one piece of the conventional dry stripping equipment, and no particles were produced as the result of a stripping process performed in the other piece of conventional dry stripping equipment. The results also show that three particles were produced as the result of a stripping process performed in the P/C of one piece of the dry stripping equipment according to the present invention, and no particles were produced as the result of a stripping process performed in the other piece of dry stripping equipment according to the present invention. Thus, the abovementioned data shows that the number of particles produced when the photoresist is removed by the present invention is within an allowable range.
In short, the present invention is able to perform at nearly the same level as the conventional dry stripping equipment even though the upper shower head of the dry stripping equipment of the present invention is not provided with a discrete reflector for reflecting the plasma.
According to the present invention as described above, the plasma is always uniformly distributed over an object to be processed because there is no discrete reflector that could potentially block the holes in the upper shower head.
That is, the dry stripping equipment of the present invention is less likely to fail than the conventional equipment. Thus, the present invention requires less maintenance and repair. Accordingly, the productivity of the dry stripping equipment according to the present invention is relatively high, thereby making it more economical to manufacture a semiconductor device.
In addition, the dry stripping equipment of the present invention is less costly to fabricate than the prior art because the present invention does not require a reflector that is discrete from the plate constituting the upper shower head.
Finally, although the present invention has been described above in connection with the preferred embodiments thereof, the scope of the invention is not limited to the disclosed embodiments. Rather, various modifications of the preferred embodiments will become apparent to those skilled in the art. Accordingly, the true spirit and scope of the invention is not defined by the detailed description of the preferred embodiments but by the appended claims.

Claims

1. Dry stripping equipment comprising:

a chamber in which a plasma stripping process is carried out;

a support disposed in the chamber, and on which an object to be processed in the chamber is to be seated;

a tube having an end at which the tube opens into the chamber and through which plasma is introduced into the chamber in a given direction; and

a baffle disposed in the chamber as interposed between the tube and the support,

the baffle including an upper shower head and a lower shower head, the upper shower head comprising a plate having a central portion, an upper surface and a lower surface, the upper surface at the central portion of the plate being disposed directly across from and exposed to said end of the tube in the direction in which plasma is introduced into the chamber, and the plate having a plurality of holes extending from the top surface to the bottom surface thereof and which holes are only present in the plate outside the central portion of the plate and are spaced apart from each other beginning at the periphery of the central portion of the plate, and the upper shower head and the lower shower head extending across the chamber so as to divide the chamber into a first space located between the plate of the upper shower head and the end of the tube, a second space located between the plate of the upper shower head and the lower shower head, and a third space located between the lower shower head and the support, whereby the plasma introduced into the chamber through the tube directly impinges and is reflected from the central portion of the plate in said first space so as to diffuse throughout said first space, is distributed by the plate of the upper shower head into said second space to the lower shower head, and is distributed by the lower shower head into said third space.

2. The dry stripping equipment according to claim 1, wherein the plate of the upper shower head and the lower shower head each have an outer coating of sapphire.

3. Dry stripping equipment comprising:

a chamber in which a plasma stripping process is carried out;

the baffle including an upper shower head and a lower shower head, the upper shower head consisting of a plate having a central portion, an upper surface and a lower surface, and the plate having a plurality of holes extending from the top surface to the bottom surface thereof and which holes are only present in the plate outside the central portion of the plate and are spaced apart from each other beginning at the periphery of the central portion of the plate, and the plate and the lower shower head extending across the chamber so as to divide the chamber into a first space located between the plate and the end of the tube, a second located between the plate and the lower shower head, and a third space located between the lower shower head and the support, and the entire upper surface of the plate being exposed to said first space with the central portion of the plate at said upper surface thereof being disposed directly across from said end of the tube in the direction in which plasma is introduced into the chamber, whereby the plasma introduced into the chamber through the tube directly impinges and is reflected from the central portion of the plate in said first space so as to diffuse throughout said first space, is distributed through all of the holes in the plate to the lower shower head, and is distributed by the lower shower head into said third space.

4. The dry stripping equipment according to claim 3, wherein the plate and the lower shower head each have an outer coating of sapphire.