US20050224179A1

US20050224179A1 - Baffle plate and plasma etching device having same

Info

Publication number: US20050224179A1
Application number: US10/514,844
Authority: US
Inventors: Young Moon; Jeung Lee; Moon Kim
Original assignee: Tokyo Electron Korea Ltd
Current assignee: Tokyo Electron Korea Ltd
Priority date: 2002-05-22
Filing date: 2003-05-22
Publication date: 2005-10-13
Also published as: KR20030090305A; WO2003098669A1; KR20050007405A; AU2003232645A1; JP2005526395A; KR100627324B1; TW200403961A

Abstract

A plasma etching device includes a baffle plate having a plurality of slots for preventing leakage of plasma gas generated during a plasma generating process while discharging other materials such as exhaust gas, residual products and particles generated during the process. The slots, each of which extends in the form of a curve from an inner circumference of the baffle plate to an outer circumference thereof, expedites the discharge of the exhaust gas and residual products. Therefore, the plasma generating progresses more smoothly and, further, an amount of discharged exhaust gas is increased.

Description

TECHNICAL FIELD

The present invention relates to a plasma generating device; and, more particularly, to a plasma etching device including a baffle plate for preventing leakage of plasma while efficiently discharging such other materials as exhaust gas, residual products and particles, wherein the baffle plate is connected to an inner wall of a plasma processing chamber in such a manner as to surround a lower electrode installed within the chamber.

BACKGROUND ART

As well known in the art, plasma refers to a state of matter electrically neutral and highly ionized with ions (+) and electrons (−) of a same density. A device using plasma is, for example, a discharge tube.
In the course of manufacturing a semiconductor or TFT LCD integration circuit, a metal layer is formed in a metalization step for the wiring of devices formed on a silicon substrate and a contact hole is formed at an insulation layer below the metal layer to electrically connect the devices on the silicon substrate to the metal layer. In general, the contact hole is formed by performing a dry etching on the insulation layer, for example, an oxide layer, by using plasma.
Referring to FIG. 1, there is provided a conventional plasma etching device 100. A lower electrode 102 for accommodating thereon an object to be etched, e.g., a wafer, is installed within a chamber 101 and an upper electrode 103 is installed above the lower electrode 102 with a predetermined distance maintained therebetween. Formed at the upper electrode 103 is a plurality of process gas inlets 104 through which a process gas (e.g., C₄F₈, C₃F₈, C₅F₈, CF₄, CHF₃, CH₂F₂, CO, Ar, O₂, N₂and/or H₂) is introduced into the chamber 101. The process gas introduced into the chamber 101 is converted into a plasma-state gas (i.e., gas composed of radicals, ions, electrons, etc.) by a RF voltage applied between the upper electrode 103 and the lower electrode 102 to be used for the processing of the wafer. Further, prepared at a lower part of the chamber 101 is an exhaust system 105 for discharging an exhaust gas or residual products generated during the conversion of the process gas into the plasma-state gas. The exhaust system 105 is, for example, a turbo molecular pump (TMP). A baffle plate 10 is connected to an inner wall of the chamber 101 in such a manner as to surround the lower electrode 102 to thereby confine a plasma generation space 110, i.e., a space between the upper electrode 103 and the lower electrode 102, and prevent leakage of plasma generated in the plasma generation space 110. Formed at the baffle plate 10 is a plurality of openings or slots sized to be adequate for discharging the residual products or exhaust gas while preventing leakage of the plasma. The baffle plate 10 is connected to an upper bellows cover 130 by driving a screw into the upper bellows cover 103 through a screw hole 150 (shown in FIG. 2).
FIG. 2 provides a perspective view of a prior art baffle plate 120. The baffle plate 120 is of a donut shape having a circular opening 122 formed at the center thereof. A plurality of long slots 121, each of which is linearly extended from an inner circumference of the baffle plate 120 to an outer circumference thereof in a radial direction, is arranged along the circumference of the baffle plate 120. Exhaust gas or residual products (e.g., impurities, electrons, ions, radicals, etc.) generated during the plasma processing flow into the lower portion of a chamber through the slots 121 of the baffle plate 120 and then is discharged to the outside of the chamber by an exhaust system. FIGS. 3A and 3B respectively depict an enlarged perspective view and a plane view of a portion A in FIG. 2.
As shown in FIGS. 3A and 3B, the plurality of slots 121, each of which has a predetermined width Ts, is linearly extended on the baffle plate 120 in a radial direction. In general, the width Ts of each of the slots 121 is defined as about 1 mm to prevent leakage of the plasma through the slots 121. Accordingly, a distance T2 between end portions of slots 121 around the inner circumference of the baffle plate 120 is found to be different from a distance T1 between the other end portions of the slots 121 around the outer circumference of the baffle plate 120. That is, T1 is larger than T2. Therefore, a dead area incapable of discharging exhaust gas or residual products is large in the conventional baffle plate 120, so that the processing efficiency of the plasma etching device is reduced, resulting in an increase in the manufacturing cost of the semiconductor or the integrated circuit. In order to reduce such dead area, attempts have been made to increase the entire width of each of the slots 121 or increase it gradually as it goes toward the outer circumference of the baffle plate 120 while maintaining the width of each of the slots 121 to be about 1 mm at its one end portion around the inner circumference of the baffle plate. However, it is inevitable in both cases that plasma leakage is increased, thereby lowering plasma etching efficiency.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide a plasma generating device, particularly a plasma etching device, using a baffle plate having slots adequate for preventing leakage of plasma while efficiently discharging exhaust gas and residual products.
In accordance with a preferred embodiment of the present invention, there is provided a plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas or residual products, wherein the plurality of slots are extended from an inner circumference of the baffle plate to an outer circumference thereof in the form of a curve.
Each of the plurality of slots has preferably a predetermined width. A distance between first end portions of the neighboring slots may be identical to a distance between second end portions thereof.
It is preferable that each of the plurality of slots has a cross section in which an upper width is larger than a lower width. Preferably, the upper width of each slot is about 1.6 to 1.8 mm while the lower width thereof is about 1.0 mm.
A portion on the baffle plate in which the plurality of slots are formed (hereinafter referred to as a slot formation portion) may be bent upward or downward in a predetermined angle. Preferably, the slot formation portion of the baffle plate is bent upward or downward within an angular range of about 0 to 45°.
The slot formation portion of the baffle plate may be bent upward or downward in the form of an arc.
The slot formation portion of the baffle plate may be bent upward or downward two or more times in a predetermined angle.
The plasma generating device may be a plasma etching device.
In accordance with another preferred embodiment of the present invention, there is provided a plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas or residual products, wherein the plurality of slots are extended linearly from an inner circumference of the baffle plate to an outer circumference thereof diagonally to a radial direction.
Preferably, each of the plurality of slots, which are linearly extended from the inner circumference of the baffle plate to the outer circumference thereof diagonally to the radial direction, is bent at least one time.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a conventional plasma etching device;
FIG. 2 provides a perspective view of a prior art baffle plate;
FIGS. 3A and 3B respectively provide an enlarged perspective view and a plan view of a portion A in FIG. 2;
FIG. 4 depicts a perspective view of a baffle plate in accordance with a first preferred embodiment of the present invention;
FIGS. 5A and 5B respectively set forth an enlarged perspective view and a plan view of a portion B in FIG. 4;
FIGS. 6A and 6B offer cross-sectional views taken by a line C-C′ shown in FIG. 5A;
FIGS. 7A to 7D illustrate various modifications of the baffle plate in accordance with the present invention;
FIGS. 8A and 8B respectively show a partial perspective view of a baffle plate in accordance with a second embodiment of the present invention; and
FIGS. 9A and 9B respectively provide a partial perspective view and a plan view of an exemplified modification of the baffle plate in accordance with the second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, there is provided a plasma etching device having a baffle plate in accordance with a first preferred embodiment of the present invention. An upper electrode 103 and a lower electrode 102 are installed opposite to each other within a chamber 101. The lower electrode 102 accommodates thereon an object to be processed (i.e., an object to be etched), e.g., a wafer. Formed at the upper electrode 103 is a plurality of process gas inlets 104 through which process gas (e.g., C₄F₈, C₃F₈, C₅F₈, CF₄, CHF₃, CH₂F₂, CO, Ar, O₂, N₂and/or H₂) is introduced into the chamber 101. The process gas introduced into the chamber 101 is converted into plasma-state gas by a RF voltage applied between the upper electrode 103 and the lower electrode 102 to be used to process (etch) the wafer. During the conversion of the process gas into the plasma-state gas, there are generated residual products such as impurities, electrons, ions and radicals. Thus, an exhaust system 105 for discharging such residual products and exhaust gas is prepared at a lower part of the chamber 101. The exhaust system 105 may be, for example, a turbo molecular pump (TMP).
Further, a baffle plate 10 is installed within the chamber 101. Specifically, the baffle plate 10 is connected to an upper bellows cover 130 by driving a screw into the upper bellows cover 103 through a screw hole 150 (shown in FIG. 4). At this time, the baffle plate 10 is installed in such a manner that an inner circumference thereof surrounds the lower electrode 102 while an outer circumference thereof is connected to an inner wall of the chamber 101 to thereby prevent leakage of plasma generated in a plasma generation space 110 (i.e., a space formed between the upper electrode 103 and the lower electrode 102). Formed at the baffle plate 10 is a plurality of openings or slots having a size adequate for discharging the residual products and the exhaust gas while preventing leakage of the plasma.
FIG. 4 provides a perspective view of the baffle plate 10 in accordance with a first preferred embodiment of the present invention. The baffle plate 10 is of a donut shape having an inner diameter of, e.g., about 250 mm and an outer diameter of, e.g., about 366 mm. The inner circumference of the baffle plate 10 surrounds the lower electrode 102 while the outer circumference thereof is fixed at the upper bellows cover 130 to be brought into tight contact with the inner wall of the chamber 101. The baffle plate 10 serves to confine the plasma generation area. Though the baffle plate 10 has the donut shape in accordance with the first preferred embodiment of the present invention, it is preferable to modify the shape of the baffle plate 10 depending on the shape of the chamber 101. For example, the baffle plate may have a shape of a rectangular plate. Formed at the baffle plate 10 is a plurality of long slots 11 for use in discharging exhaust gas or residual products as fast as possible while preventing leakage of plasma process gas.
Each of the slots 11 has a predetermined width (about 1 mm) and is extended from the inner circumference of the baffle plate 10 to the outer circumference thereof. At this time, each of the slots 11 is extended in the form of a curve. Thus, if the inner diameter and the outer diameter of the baffle plate 10 are identical with those of the conventional baffle plate as described before with reference to FIG. 2 and FIGS. 3A and 3B, the length of each of the slots 11 is found to be larger than that of each slot in the conventional baffle plate in which slots are extended linearly in a radial direction. Accordingly, an open area is enlarged and, as a result, a larger amount of exhaust gas or residual products can be discharged out through the slots 11.
Referring to FIGS. 5A and 5B, there are provided an enlarged perspective view and a plan view of a portion B in FIG. 4. As shown, the slots 11 are formed at the baffle plate 10 in a manner that a distance T3 between first end portions of the neighboring slots 11 is identical to a distance T4 between second end portions of the slots 11. Herein, T3 and T4 can have the same value since the slots 11 are extended from the inner circumference of the baffle plate 10 to the outer circumference of the baffle plate 10 in the form of a curve.
For example, assume that there is a donut-shaped baffle plate having an inner diameter of about 250 mm and an outer diameter of about 366 mm. If 360 slots respectively having a width of about 1 mm and a length of about 40 mm are formed at the baffle plate linearly in a radial direction in accordance with prior art, the total area of open portions formed by the slots is calculated as about 14400 mm².
On the other hand, if slots having a width of about 1 mm are formed at the same baffle plate in the form of a curve in accordance with the present invention, each the slots can be formed to have a curvilinear length of about 45 mm. If the number of the slots formed at the baffle plate is 360, the total area of open portions formed by the slots is calculated to be about 16200 mm². Thus, the total area of the open portions in the baffle plate having the slots formed in accordance with the present invention increases by about 12.5% of that of the baffle plate having the slots formed in accordance with the prior art.
FIG. 7A exemplifies a modification of the baffle plate 10 in accordance with the first preferred embodiment of the present invention. If a slot formation portion (meaning a portion on which slots are formed) of the baffle plate having an inner diameter of about 250 mm and an outer diameter of about 350 mm is bent downward by a predetermined angle ( 0 ), e.g., about 22°, the length of each slot is increased to about 53 mm. If 360 slots are formed, the area of open portions of the baffle plate formed by the slots amounts to about 19080 mm². Thus, by forming the slots in the form of a curve and bending the slot formation portions as described above, the area of the slots can be increased, resulting in increase of the total area of open portions of the baffle plate.
FIGS. 6A and 6B are cross-sectional views taken by a line C-C′ in FIG. 5A. In FIG. 6A, an upper width P1 of each of the slots 11 in the baffle plate 10 is greater than a lower width P2 thereof. Thus, it can be prevented that materials generated during a plasma process, e.g., polymer, get stuck to walls of the slots 11 to thereby clog the slots 11, which frequently happens during a plasma process using a conventional baffle plate. Preferably, the upper width P1 is about 1.6 to 1.8 mm while the lower width P2 is about 1 mm.
Further, as shown in FIG. 6B, each of the slots 11 can have a cross-section of a sand watch shape. At this time, it is preferable to define the upper width P1 as about 1.6 to 1.8 mm, the lower width P2 as about 1.1 to 1.5 mm and a middle width P3 as about 1 mm. Further, if the thickness H of the baffle plate 10 is about 3 mm, a distance H1 from an upper surface of the baffle plate 10 to the middle width P3 is preferably about 1.8 mm. More preferably, the upper width P1, the lower width P2 and the middle width P3 of each of the slots 11 are about 1.6 mm, 1.2 mm and 1 mm, respectively.
FIGS. 7A to 7D exemplify various modifications of the shape of the baffle plate in accordance with the present invention, in which slot formation portions on baffle plates 20 and 30 are modified in various ways in order to increase the length of slots formed thereon in the form of a curve.
As shown in FIGS. 7A and 7B, the slot formation portions of the baffle plates 20 and 30 are bent downward (FIG. 7A) or upward (FIG. 7B) by a predetermined angle φ while an outer circumference of each of the baffle plates 20 and 30 is maintained at a certain value. At this time, the angle φ is determined so as not to interfere with the plasma process. Preferably, the angle φ is determined within an angular range of 0° to 45° and, more preferably, it is 22°.
Further, as shown in FIG. 7C, a slot formation portion on the baffle plate 40 can be bent downward in an arch, if necessary. It is also possible that the slot formation portion is bent upward in the form of an arc though it is not shown in the drawing (not illustrated).
Still further, a slot formation portion on the baffle plate 50 can be bent downward two times, i.e. in the form of a stair, as shown in FIG. 7D. At this time, the slot formation portion can be bent upward two times as well though it is not illustrated in the drawing.
Still further, a slot formation portion can be bent three or more times though it is not illustrated herein.
Referring to FIGS. 8A and 8B, there are respectively provided a partial enlarged perspective view and a plan view of a baffle plate 10 a in accordance with a second preferred embodiment of the present invention. The baffle plate 10 a has a donut shape with an inner diameter of, e.g., about 250 mm and an outer circumference of, e.g., about 366 mm. The baffle plate 10 a is connected to an upper bellow cover 130 in a manner that its inner circumference surrounds a lower electrode while an outer circumference thereof is in tight contact with an inner wall of the chamber 101. The baffle plate 10 a serves to confine a plasma generation space. Though the baffle plate 10 a has a donut shape in accordance with the present invention, it is also preferable that it has another shape, e.g., the shape of a square plate, depending on the shape of the chamber 101. Formed at the baffle plate 10 a is a plurality of long slots 11 a for discharging an exhaust gas or residual products while preventing leakage of a plasma process gas.
In the second preferred embodiment, each of the slots 11 a has a predetermined width (about 1 mm) and is linearly extended from the inner circumference to the outer circumference of the baffle plate 10 a diagonally to a radial direction. Thus, if the inner diameter and the outer diameter of the baffle plate 10 a are identical with those of the conventional baffle plate as described before, the length of each of the slots 11 a is found to be larger than that of each slot in the conventional baffle plate in which slots are extended linearly in a radial direction. Accordingly, an open area is enlarged and, as a result, a larger amount of exhaust gas or residual products can be discharged out through the slots 11.
FIGS. 9A and 9B respectively depict a partial enlarged perspective view and a plan view of a baffle plate 10 b as a modification of the baffle plate 10 a in accordance with the second preferred embodiment of the present invention. As shown, the slots 11 b in the baffle plate 10 b are bent one time when they are linearly extended from an inner circumference to an outer circumference of the baffle plate 10 b diagonally to a radius direction. Thus, the length of each of the slots 11 b can be further lengthened. As a result, a greater amount of an exhaust gas and residual products can be discharged out through the slots 11 b. Though the slots 11 b are bent one time in the description, the slots 11 b can be bent two or more times if required.
In the above-described baffle plates in accordance with the present invention, the length of each slot is increased while the width thereof is maintained as about 1 mm. Accordingly, the open area is increased, allowing a greater amount of exhaust gas or residual products to be discharged while preventing leakage of plasma during a plasma process. As a result, manufacturing costs of semiconductors or integrated circuits can be reduced.
As described above, by forming slots in the form of a curve or linearly extending the slots diagonally to a radial direction and/or by modifying a slot formation portion in various ways while maintaining a current outer diameter of the baffle plate, exhaust gas or residual products generated during a plasma process can be effectively discharged out. Accordingly, the performance of the plasma process can be improved and a larger amount of process gas can be flowed into the chamber. As a result, the efficiency of the plasma process is greatly increased and manufacturing costs can be reduced.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

1. A plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas or residual products, wherein the plurality of slots are extended from an inner circumference of the baffle plate to an outer circumference thereof in the form of a curve.

2. The device of claim 1, wherein each of the plurality of slots has a predetermined width.

3. The device of claim 1, wherein the distance between first end portions of two neighboring slots is identical to the distance between second end portions thereof.

4. The device of claim 1, wherein each of the plurality of slots has a cross section in which an upper width thereof is larger than a lower width thereof.

5. The device of claim 4, wherein the upper width of each slot ranges from about 1.6 to 1.8 mm while the lower width thereof is about 1.0 mm.

6. The device of claim 1, wherein a portion on the baffle plate in which the plurality of slots are formed is bent upward or downward in a predetermined angle.

7. The device of claim 6, wherein the slot formation portion of the baffle plate is bent upward or downward within an angular range of about 0 to 45°.

8. The device of claim 1, wherein the slot formation portion of the baffle plate is bent upward or downward in the form of an arc.

9. The device of claim 1, wherein the slot formation portion of the baffle plate is bent upward or downward two or more times in a predetermined angle.

10. The device of claim 1 or 9, wherein the plasma generating device is a plasma etching device.

11. A plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots, wherein the plurality of slots is extended from an inner circumference of the baffle plate to an outer circumference thereof in the form of a curve.

12. The device of claim 11, wherein each of the plurality of slots has a predetermined width.

13. The device of claim 11 or 12, wherein a distance between first end portions of the neighboring slots is identical to a distance between second end portions thereof.

14. The device of claim 11 or 12, wherein each of the plurality of slots has a cross section in which an upper width thereof is larger than a lower width thereof.

15. The device of claim 14, wherein the upper width of each slot ranges from about 1.6 to 1.8 mm while the lower width thereof is about 1.0 mm.

16. The device of claim 11 or 12, wherein a portion on the baffle plate in which the plurality of slots are formed is bent upward or downward in a predetermined angle.

17. The device of claim 16, wherein the slot formation portion of the baffle plate is bent upward or downward within an angular range from 0 to 45°.

18. The device of claim 11 or 12, wherein the slot formation portion of the baffle plate is bent upward or downward in the form of an arc.

19. The device of claim 11 or 12, wherein the slot formation portion of the baffle plate is bent upward or downward two or more times in a predetermined angle.

20. A plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas or residual products, wherein the plurality of slots are extended linearly from an inner circumference of the baffle plate to an outer circumference thereof diagonally in a radial direction.

21. The device of claim 20, wherein each of the plurality of slots, which are linearly extended from the inner circumference of the baffle plate to the outer circumference thereof diagonally to the radial direction, is bent at least one time.

22. The device of claim 1, wherein each of the plurality of slots has a cross-section of a sand watch shape in which an upper width is larger than a lower width and a middle width is smaller than the lower width.

23. The device of claim 22, wherein the upper width of each slot ranges from about 1.6 to 1.8 mm, the lower width ranges from about 1.1 to 1.5 mm and the middle width is about 1.0 mm.

24. A plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas, residual products, and the like, wherein a portion on the baffle plate in which the plurality of slots are formed (hereinafter referred to as a slot formation portion) is bent upward or downward in a predetermined angle.

25. The device of claim 24, wherein the slot formation portion of the baffle plate is bent upward or downward at least two times.

26. A plasma generating device installed within a plasma generating chamber and including a baffle plate having a plurality of slots for discharging exhaust gas, residual products, and the like, wherein a portion on the baffle plate in which the plurality of slots are formed (hereinafter, a slot formation portion) is bent upward or downward in the form of an arc.

27. The device of claim 11, wherein each of the plurality of slots has a cross-section of a sand watch shape in which an upper width thereof is larger than a lower width thereof and a middle width thereof is smaller than the lower width.

28. The device of claim 27, wherein the upper width of each slot ranges from about 1.6 to 1.8 mm, the upper width is about 1.1 to 1.5 mm and the middle width ranges from about 1.0 mm.