JP2019160460A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

To provide a plasma processing apparatus and a plasma processing method, capable of suppressing deterioration of a seal member interposed between a chamber wall and a microwave transmission window.SOLUTION: A plasma processing apparatus comprises: a chamber wall to be grounded while having a fitting grove 11G; a microwave transmission window 21 opposite to the chamber wall; and a seal member 20 interposed between the chamber wall and the microwave transmission window 21. The seal member 20 is fitted to the fitting grove 11G, and defines a gap between the chamber wall and the microwave transmission window 21 to a generation space 20S and an outer space. The fitting grove 11G comprises: a first groove side surface 11G1 on the generation space 20S side and a second side surface 11G2 on the outer space side. The first groove side surface 11G1 comprises a seal portion having a form separated from the generation space 20S as closer to the microwave transmission window 21 in a portion, and contacted to the seal member 20 between a groove bottom part and a groove opening. A distance H between the groove opening and the seal portion is less than a sheath length of a plasma generated in the generation space 20S.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for processing an object using microwave plasma.

  The above-described plasma processing apparatus generates microwave plasma by irradiating a microwave output from a microwave source to supply radicals contained in the microwave plasma mainly to a processing target. The plasma processing apparatus includes a generation space that generates microwave plasma and a processing space that communicates with the generation space and accommodates a processing target. The generation space is partitioned by a microwave transmission window that transmits microwaves, and the output port of the waveguide is connected to the microwave transmission window. Then, the plasma processing apparatus supplies gas to the generation space, and transmits the microwave propagated through the waveguide through the microwave transmission window into the generation space to generate microwave plasma in the generation space ( For example, see Patent Document 1).

JP 2011-29559 A

  By the way, the chamber wall that defines the generation space includes an opening that opens toward the output port of the waveguide, an annular fitting groove that surrounds the opening, and a seal member that is fitted in the fitting groove. The microwave transmitting window is pressed against the seal member to close the opening from outside the chamber wall. On the other hand, the gas supplied to the generation space may stay in a slight gap between the chamber wall and the microwave transmission window to generate microwave plasma. In particular, the gap between the fitting groove and the microwave transmission window is larger than the other part by the groove depth, and microwave plasma is easily generated. As a result, a part of the seal member continues to be exposed to the microwave plasma, causing cracks and progress of curing. In the field of the above-described plasma processing, since the output of microwaves is increasing in order to increase the processing efficiency, suppression of deterioration in the seal member has become a more serious problem.

  An object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of suppressing deterioration of a seal member interposed between a chamber wall and a microwave transmission window.

  A plasma processing apparatus for solving the above problems includes a chamber wall provided with a fitting groove and grounded, a microwave transmission window facing the chamber wall, and the chamber wall and the microwave transmission window. And an intervening seal member. The seal member is fitted in the fitting groove, and divides a gap between the chamber wall and the microwave transmission window into a generation space and an external space. The fitting groove includes a first groove side surface on the generation space side and a second groove side surface on the external space side, and the first groove side surface is inclined with respect to a groove depth direction, and the microwave A portion closer to the transmission window has a shape that is separated from the generation space, and a seal portion that contacts the seal member is provided between the groove bottom and the groove opening. The distance between the groove opening and the seal portion is less than the sheath length of the plasma generated in the generation space.

  A plasma processing method for solving the above-described problem includes a seal member interposed between a chamber wall grounded with a fitting groove and a microwave transmitting window facing the chamber wall, and the seal member It is a plasma processing method using a plasma processing apparatus that is fitted in the fitting groove and divides a gap between the chamber wall and the microwave transmission window into a generation space and an external space. The fitting groove includes a first groove side surface on the generation space side and a second groove side surface on the external space side, and the first groove side surface is inclined with respect to a groove depth direction, and the microwave A portion closer to the transmission window has a shape that is separated from the generation space, and a seal portion that contacts the seal member is provided between the groove bottom and the groove opening. Then, a gas is supplied to the generation space so that a distance between the groove opening and the seal location is less than a sheath length in the generation space, and a microwave is supplied from the microwave transmission window to the generation space. To propagate.

  The region facing the above-described microwave transmission window is a region irradiated with the microwave transmitted through the microwave transmission window. The chamber wall is located in a region facing the microwave transmission window, and forms a slight gap between the chamber wall and the microwave transmission window. The distance between the fitting groove and the microwave transmission window is larger than the other parts by the depth of the fitting groove in the gap between the chamber wall and the microwave transmission window. In this regard, in each configuration described above, since the distance between the groove opening and the seal portion is less than the sheath length in the generation space, a space sufficient to form a sheath between the groove opening and the seal portion. Is hard to exist. For this reason, generation of microwave plasma in the fitting groove can be suppressed. As a result, it is possible to suppress the deterioration of the seal member interposed between the chamber wall and the microwave transmission window.

  The plasma processing apparatus further includes a waveguide that guides the microwave to the microwave transmission window along the traveling direction. The microwave transmitting window extends in a planar shape including the traveling direction, the chamber wall is connected to the fitting groove, has a depth equal to or greater than the groove depth of the fitting groove, and A circular hole having a diameter of the same size as the groove width of the fitting groove is further provided. A straight line extending in the traveling direction through the center of the microwave transmission window as viewed from the direction facing the microwave transmission window is a center line, and the circular hole is located at a position other than the center line. May be.

  A plasma processing apparatus for solving the above problems includes a chamber wall provided with a fitting groove and grounded, a microwave transmission window facing the chamber wall, and the chamber wall and the microwave transmission window. An intervening seal member, and a waveguide section for guiding the microwave to the microwave transmission window along the traveling direction. The seal member is fitted in the fitting groove to partition a gap between the chamber wall and the microwave transmission window into a generation space and an external space, and the microwave transmission window is a plane including the traveling direction. The chamber wall has a circular hole connected to the fitting groove, having a depth equal to or greater than the groove depth of the fitting groove, and having a groove width of the fitting groove as a diameter. Further prepare. A straight line extending in the traveling direction through the center of the microwave transmission window as viewed from the direction facing the microwave transmission window is a center line, and the circular hole is located at a position other than the center line. To do.

  In the plasma processing apparatus, a range in which a central angle around the center with respect to the center line is −60 ° or more and 60 ° or less is a high irradiation region, and the circular hole is other than the high irradiation region. May be located.

  In the method of forming the fitting groove described above, for example, the chamber wall is processed using a drill whose diameter is increased toward the tip so as to form a dovetail groove. At this time, a circular hole formed at the tip of the drill is formed in the chamber wall before the formation of the fitting groove, and then the fitting groove is formed so as to extend in the radial direction from the inner peripheral surface of the circular hole. It begins to be done. Accordingly, the circular hole described above is connected to the fitting groove, has a depth equal to or greater than the groove depth of the fitting groove, and has the groove width of the fitting groove as a diameter.

  Here, the inner peripheral surface of the circular hole does not include the first groove side surface described above, and is difficult to come into contact with the seal member. And the location which contacts a sealing member in a circular hole becomes a groove bottom part instead of the internal peripheral surface of a circular hole. As a result, the distance between the location in contact with the seal member and the groove opening may be longer than the sheath length of the plasma generated in the generation space in the circular hole. In this regard, in the above-described configurations, the circular holes are arranged avoiding a region where microwave irradiation is relatively high. Therefore, deterioration of the seal member due to the presence of the circular hole can be suppressed.

  In the plasma processing apparatus, the fitting groove may be a dovetail groove. According to this configuration, it is possible to suppress deterioration of the seal member and to prevent the seal member fitted in the fitting groove from coming off from the fitting groove.

  In the plasma processing apparatus, the second groove side surface may extend in the groove depth direction. According to this configuration, it is possible to reduce the fitting load of the seal member with respect to the fitting groove, to prevent the sealing member fitted in the fitting groove from coming off from the fitting groove, and to balance these. Become.

The apparatus figure which shows the apparatus structure of one Embodiment of a plasma processing apparatus. Sectional drawing which shows the 1st example of the seal structure in one Embodiment. Sectional drawing which shows the 2nd example of the seal structure in one Embodiment. The top view which shows arrangement | positioning of the circular hole in one Embodiment.

An embodiment of a plasma processing apparatus and a plasma processing method will be described.
[Plasma processing equipment]
As shown in FIG. 1, the plasma processing apparatus includes a chamber 11, a partition member 13, a diffusion member 14, and a seal member 20. Further, the plasma processing apparatus includes a microwave transmission window 21, a waveguide 22, and a microwave source 23.

  The chamber 11 has, for example, an aluminum box shape and partitions the processing space 11S. The chamber 11 is grounded and includes an upper wall of the chamber 11 as an example of a chamber wall. The upper wall of the chamber 11 includes a partition hole 12 penetrating upward.

  The partition hole 12 is a hole for partitioning the generation space 20S above the processing space 11S. The partition hole 12 has, for example, a two-stage circular hole shape whose diameter is reduced upward. The partition hole 12 communicates with the gas port 11H.

  The gas port 11H is a gas G passage for generating microwave plasma. The gas G supplied from the gas port 11H is at least one selected from the group consisting of an oxidizing gas such as oxygen and ozone, a nitriding gas such as nitrogen and ammonia, and a rare gas such as helium and argon.

  The partition member 13 is a member for partitioning the generation space 20 </ b> S in the partition hole 12. The partition member 13 has, for example, a two-stage disk shape made of aluminum that has a diameter reduced upward. The partition member 13 includes an outer surface that follows the inner surface of the partition hole 12.

  The small diameter portion of the partition member 13 is connected to the small diameter portion of the partition hole 12. The upper end surface of the partition member 13 is positioned below the upper end portion of the partition hole 12 and partitions the lower end of the generation space 20S. The large diameter portion of the partition member 13 faces the outlet of the gas port 11H.

  The large diameter portion of the partition member 13 guides the gas G exiting from the gas port 11H into the small diameter portion of the partition member 13. The small-diameter portion of the partition member 13 includes a hole opened in the upper end surface of the partition member 13, and the gas G guided to the small-diameter portion of the partition member 13 is above the upper end surface of the partition member 13 (generation space 20S). Derived toward.

  The microwave transmission window 21 is a member for partitioning the generation space 20 </ b> S in the partition hole 12. The microwave transmission window 21 is a member that transmits microwaves, and has, for example, a disk shape made of quartz or aluminum oxide.

  The microwave transmission window 21 has a larger diameter than the small diameter portion of the partition hole 12. The microwave transmission window 21 is located immediately above the partition hole 12 and partitions the upper end of the generation space 20S. The lower surface of the microwave transmission window 21 and the upper end surface of the partition member 13 sandwich the upper end portion of the partition hole 12 in the vertical direction, thereby partitioning the generation space 20S in the partition hole 12. The generation space 20 </ b> S is surrounded by the inner surface of the partition hole 12, the upper end surface of the partition member 13, and the lower surface of the microwave transmission window 21.

The partition member 13 includes a lead-out hole 13 </ b> H at the center of the partition member 13. The lead-out hole 13H communicates the processing space 11S and the generation space 20S. The diffusion member 14 is connected to the lower surface of the partition member 13 via a leg and faces the outlet of the outlet hole 13H.
The diffusion member 14 receives the plasma derived from the outlet hole 13H and diffuses the plasma throughout the processing space 11S.

  The waveguide 22 propagates the microwave output from the microwave source 23 to the waveguide space 22 </ b> S defined by the waveguide 22. The microwave transmission window 21 is connected to the output port of the waveguide 22. When viewed from the direction facing the microwave transmission window 21, the size of the output port of the waveguide 22 is wider than the small diameter portion (generation space 20 </ b> S) of the partition hole 12.

  The waveguide 22 propagates the microwave output from the microwave source 23 in the traveling direction, and propagates the microwave to almost the entire microwave transmission window 21. The microwave transmission window 21 extends in a planar shape including the traveling direction of microwaves (the direction from the left to the right in the drawing). The frequency of the microwave output from the microwave source 23 is 860 MHz, 2.45 GHz, 8.35 GHz, 5.8 GHz, 1.98 GHz, or the like.

The plasma processing apparatus propagates the microwave output from the microwave source 23 to the generation space 20 </ b> S through the microwave transmission window 21. The microwave propagated to the generation space 20S generates an electrodeless plasma in the generation space 20S. At this time, the control unit of the plasma processing apparatus adjusts the flow rate of the gas G supplied to the generation space 20S and the microwave power output to the microwave source 23 so that the plasma density in the generation space 20S is 10 ⁹ cm. ³ or more and 10 ¹¹ cm ³ or less. In the plasma processing apparatus, the sheath length in the plasma generated in the generation space 20S is set to 0.8 mm or more and 1.0 mm or less. The microwave plasma generated in the generation space 20S is supplied to the processing space 11S while being diffused by the diffusion member 14 through the outlet hole 13H.

[Seal structure]
FIG. 2 shows an example of a seal structure between the upper wall of the chamber 11 and the microwave transmission window 21, and FIG. 3 shows another example of the seal structure. 2 and 3, for convenience of explaining the gap between the upper wall of the chamber 11 and the microwave transmission window 21 and the gas G staying there, the upper wall of the chamber 11 and the microwave are not shown. The size of the gap with the transmission window 21 is exaggerated.

  As shown in FIG. 2, in the first example of the seal structure, the upper wall of the chamber 11 includes a fitting groove 11G. The fitting groove 11 </ b> G is an annular groove over the entire circumference of the microwave transmission window 21. The seal member 20 is an O-ring made of an insulating resin such as fluorine rubber or silicone rubber.

  The seal member 20 is fitted in the fitting groove 11G, and divides the gap between the upper wall of the chamber 11 and the microwave transmission window 21 into a generation space 20S and an external space (atmospheric space). The seal member 20 suppresses the gas G supplied to the generation space 20S from leaking into the atmospheric space.

  The fitting groove 11G is a dovetail groove having two groove side surfaces 11G1 and 11G2. The two groove side surfaces include a first groove side surface 11G1 on the generation space 20S side and a second groove side surface 11G2 on the external space side. The distance between the first groove side surface 11G1 and the second groove side surface 11G2 gradually decreases from the groove bottom toward the groove opening.

  The first groove side surface 11G1 has an inclination of, for example, 25 ° with respect to the groove depth direction, and a portion closer to the microwave transmission window 21 has a shape farther from the generation space 20S. Further, the first groove side surface 11G1 includes a seal portion P that contacts the seal member 20 in the middle of the groove depth direction. The distance H between the groove opening and the seal location P is less than the sheath length of the plasma generated in the generation space 20S.

  The second groove side surface 11G2 has an inclination of, for example, 25 ° with respect to the groove depth direction, and a portion closer to the microwave transmission window 21 has a shape closer to the generation space 20S. The second groove side surface 11G2 also includes a seal portion that comes into contact with the seal member 20 in the middle of the groove depth direction. That is, the seal member 20 is separated from the groove opening of the fitting groove 11G.

  The upper wall of the chamber 11 is located in a region facing the microwave transmission window 21, and a slight gap is formed between the microwave transmission window 21 and the seal member 20. The distance between the fitting groove 11G and the microwave transmission window 21 is larger than the other parts in the gap between the upper wall of the chamber 11 and the microwave transmission window 21 by the depth of the fitting groove 11G. large. These regions facing the microwave transmission window 21 are regions irradiated with the microwave transmitted through the microwave transmission window 21.

  Here, since the distance H between the groove opening and the seal portion P is less than the sheath length in the generation space 20S, it is difficult for a space sufficient to form a sheath to exist between the groove opening and the seal portion P. . Therefore, even if the microwave is irradiated toward the fitting groove 11G, generation of microwave plasma in the fitting groove 11G can be suppressed. As a result, deterioration of the seal member 20 can be suppressed.

  As shown in FIG. 3, in the second example of the seal structure, the upper wall of the chamber 11 includes a fitting groove 11G. The fitting groove 11 </ b> G is an annular groove over the entire circumference of the microwave transmission window 21. As in the first example, the first groove side surface 11G1 of the fitting groove 11G has an inclination with respect to the groove depth direction, and a portion closer to the microwave transmission window 21 has a shape that is farther from the generation space 20S. Also in the first groove side surface 11G1, the distance H between the groove opening and the seal portion P is less than the sheath length of the plasma generated in the generation space 20S.

  The second groove side surface 11G2 extends in the groove depth direction (vertical direction) and is substantially orthogonal to the upper end surface of the upper wall of the chamber 11 and the lower end surface of the microwave transmission window 21. The groove opening of the fitting groove 11G is narrower than the width (groove width) of the groove bottom portion, and the distance between the first groove side surface 11G1 and the second groove side surface 11G2 gradually decreases from the groove bottom portion toward the groove opening. The second groove side surface 11G2 is separated from the seal member 20, and a gap is formed between the second groove side surface 11G2 and the seal member 20.

  Also here, since the distance H between the groove opening and the seal portion P is less than the sheath length in the generation space 20S, there is hardly enough space between the groove opening and the seal portion P to form a sheath. . Therefore, generation of microwave plasma in the fitting groove 11G can be suppressed, so that deterioration of the seal member 20 can be suppressed.

[Fitting groove]
As shown in FIG. 4, the waveguide 22, which is an example of a waveguide unit, is microwaved to the microwave transmission window 21 along one direction (traveling direction) from the microwave source 23 toward the microwave transmission window 21. Lead. The microwave transmission window 21 extends in a planar shape including the traveling direction.

  A straight line extending in the traveling direction through the center C of the microwave transmission window 21 when viewed from the direction facing the microwave transmission window 21 is a center line. The range in which the central angle θ around the center C with respect to the center line is −60 ° or more and 60 ° or less is a high irradiation region in which the intensity of microwave irradiation is higher than other portions.

  The upper wall of the chamber 11 includes a circular hole 11G3 connected to the fitting groove 11G. The circular hole 11G3 has a depth equal to or greater than the groove depth of the fitting groove 11G, and has a diameter of the same size as the width (groove width) of the groove bottom of the fitting groove 11G. In FIG. 4, the groove opening of the fitting groove 11G is indicated by a thick solid line, and the groove width of the fitting groove 11G has the same size as the diameter of the circular hole 11G3. The circular hole 11G3 is located other than on the center line. The circular hole 11G3 is preferably located outside the high irradiation region.

  In order to form the fitting groove 11G of the first example, for example, the upper wall of the chamber 11 is processed using a drill whose diameter is increased toward the tip. At this time, the circular hole 11G3 is first formed on the upper wall of the chamber 11 by cutting using the tip of the drill, and then the drill moves so as to draw the fitting groove 11G from the circular hole 11G3. The fitting groove 11G is formed.

  The inner peripheral surface of the circular hole 11G3 does not easily form a portion that contacts the seal member 20, and the portion that contacts the seal member 20 in the circular hole 11G3 is a groove bottom of the circular hole 11G3. As a result, in the circular hole 11G3, the distance between the location in contact with the seal member 20 and the groove opening may be longer than the sheath length of the plasma generated in the generation space 20S. That is, microwave plasma is more easily generated in the circular hole 11G3 than in the fitting groove 11G.

  In this regard, if the circular hole 11G3 is located at a position other than the center line, and particularly located outside the high irradiation area, the circular hole 11G3 is arranged while avoiding a relatively high microwave irradiation area. Therefore, deterioration of the seal member 20 due to the presence of the circular hole 11G3 can be suppressed.

As mentioned above, according to the said embodiment, the effect enumerated below is acquired.
(1) Since the distance between the groove opening and the seal location P is less than the sheath length in the generation space 20S, a space sufficient to form a sheath is unlikely to exist between the groove opening and the seal location P. Therefore, generation of microwave plasma in the fitting groove 11G can be suppressed. As a result, deterioration of the seal member 20 interposed between the chamber 11 and the microwave transmission window 21 can be suppressed.

  (2) The circular hole 11G3 that does not include the first groove side surface 11G1 is disposed to avoid a region where microwave irradiation is relatively high. Therefore, deterioration of the seal member 20 due to the presence of the circular hole 11G3 can be suppressed.

  (3) When the fitting groove 11G is a dovetail groove having the first groove side surface 11G1, the deterioration of the seal member 20 is suppressed, and the seal member 20 fitted in the fitting groove 11G is fitted into the fitting groove. It is possible to suppress the deviation from 11G.

  (4) When the second groove side surface 11G2 of the fitting groove 11G extends in the groove depth direction, the fitting load of the sealing member 20 on the fitting groove 11G is reduced, and the sealing member fitted in the fitting groove 11G It is also possible to suppress the separation of 20 from the fitting groove 11G and to balance these.

In addition, the said embodiment can be changed and implemented suitably as follows.
In the first example of the seal structure, it is also possible to further include a backup ring that is in close contact with the second groove side surface 11G2 between the second groove side surface 11G2 of the fitting groove 11G and the seal member 20.
The plasma processing apparatus can further include a slot antenna having conductivity on the side opposite to the generation space 20 </ b> S with respect to the microwave transmission window 21.

θ ... center angle, C ... center, H ... distance, P ... seal location, 11 ... chamber, 11G ... fitting groove, 11G1 ... first groove side, 11G2 ... second groove side, 11G3 ... circular hole, 11H ... gas Port, 11S ... processing space, 12 ... partition hole, 13 ... partition member, 13H ... lead-out hole, 14 ... diffusion member, 20 ... seal member, 20S ... generation space, 21 ... microwave transmission window, 22 ... waveguide, 22S ... guide space, 23 ... microwave source.

Claims (7)

A chamber wall grounded with a fitting groove;
A microwave transmitting window facing the chamber wall;
A seal member interposed between the chamber wall and the microwave transmission window,
The seal member is fitted in the fitting groove, and divides a gap between the chamber wall and the microwave transmission window into a generation space and an external space,
The fitting groove includes a first groove side surface on the generation space side and a second groove side surface on the external space side,
The first groove side surface is inclined with respect to the groove depth direction, has a shape that is closer to the microwave transmission window, and away from the generation space, and the seal is provided between the groove bottom and the groove opening. It has a sealing part that contacts the member,
The distance between the groove opening and the seal portion is less than the sheath length of the plasma generated in the generation space. Further comprising a waveguide section for guiding the microwave along the traveling direction to the microwave transmission window,
The microwave transmission window extends in a plane including the traveling direction,
The chamber wall is connected to the fitting groove and has a circular hole having a depth equal to or greater than the groove depth of the fitting groove and having a diameter of the same size as the groove width of the fitting groove. In addition,
Seen from the direction facing the microwave transmission window,
A straight line extending in the traveling direction through the center of the microwave transmitting window is a center line,
The plasma processing apparatus according to claim 1, wherein the circular hole is positioned other than on the center line. The plasma processing apparatus according to claim 1, wherein the fitting groove is a dovetail groove. The plasma processing apparatus according to claim 1, wherein the second groove side surface extends in the groove depth direction. A chamber wall grounded with a fitting groove;
A microwave transmitting window facing the chamber wall;
A seal member interposed between the chamber wall and the microwave transmitting window;
A waveguide section for guiding the microwave along the traveling direction to the microwave transmission window,
The seal member is fitted in the fitting groove, and divides a gap between the chamber wall and the microwave transmission window into a generation space and an external space,
The microwave transmission window extends in a plane including the traveling direction,
The chamber wall is further connected to the fitting groove, has a depth greater than or equal to the groove depth of the fitting groove, and further includes a circular hole having a groove width of the fitting groove as a diameter,
Seen from the direction facing the microwave transmission window,
A straight line extending in the traveling direction through the center of the microwave transmitting window is a center line,
The circular hole is located at a position other than the center line. A range in which a central angle around the center with respect to the center line is −60 ° or more and 60 ° or less is a high irradiation region,
The plasma processing apparatus according to claim 5, wherein the circular hole is located outside the high irradiation region. A sealing member interposed between a chamber wall grounded with a fitting groove and a microwave transmitting window facing the chamber wall, the sealing member being fitted into the fitting groove, A plasma processing method using a plasma processing apparatus that partitions a gap with the microwave transmission window into a generation space and an external space,
The fitting groove includes a first groove side surface on the generation space side and a second groove side surface on the external space side,
The first groove side surface is inclined with respect to the groove depth direction, has a shape that is closer to the microwave transmission window, and away from the generation space, and the seal is provided between the groove bottom and the groove opening. It has a sealing part that contacts the member,
Gas is supplied to the generation space so that the distance between the groove opening and the seal location is less than the sheath length in the generation space, and the microwave is propagated from the microwave transmission window to the generation space. Plasma processing method.

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