JP2010251064A - Plasma generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma generator for preventing damage on an O-ring which is air-tightly held between a transmissive window and a chamber. <P>SOLUTION: An annular conductive film 25 is formed in a region positioned in a part which is an outer circumference part of a lower surface 20a of a microwave transmissive window 20 and is connected to an upper surface 15a of a cylindrical body 15, and a microwave transmitting through an outer circumferential part of the microwave transmissive window 20 is shielded by the conductive film 25 and is prevented from transmitting to a top plate side. Thus, an interval holding plate 23 prevents the microwave from being introduced in a clearance D between the lower surface 20a of the microwave transmissive window 20 and the upper surface 15a of the cylindrical body 15 generated on an inside of the O-ring 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma generator.

  2. Description of the Related Art Plasma generators that generate plasma by introducing a reactive gas and high frequency or microwave into a chamber are known. Plasma generators are widely used in various technical fields. For example, plasma processing apparatuses that perform dry etching, surface modification, ashing, etc. on a semiconductor substrate by exposing the semiconductor device to generated plasma are known. (For example, Patent Document 1).

  In this type of plasma processing apparatus, for example, in an ashing processing apparatus for ashing (ashing) a resist film formed on a semiconductor substrate using a plasma of a reactive gas, a plasma generation chamber is provided on the upper side of the chamber, A stage on which a semiconductor substrate is placed is provided on the lower side. The plasma generated in the plasma generation chamber is led out toward a stage provided below. The semiconductor substrate placed on the stage is ashed by being exposed to plasma derived from the plasma generation chamber.

  By the way, the plasma generation chamber provided in the chamber is provided with an opening in the top plate of the chamber, and is closed with a microwave transmission window above the opening, and the lower side of the opening is closed with a lower lid, It is formed in a space surrounded by a top plate, a microwave transmission window, and a lower lid. Then, a waveguide is connected to the microwave transmission window, the microwave propagated through the waveguide is introduced into the plasma generation chamber, and a gas introduction passage formed between the top plate and the lower lid A reactive gas (for example, oxygen, nitrogen, carbon tetrafluoride) is introduced into the plasma generation chamber via Thereby, plasma is generated in the plasma generation chamber by the microwave and the reaction gas introduced into the plasma generation chamber.

  And the plasma produced | generated in the plasma production | generation chamber is derived | led-out to the stage provided below from the extraction hole formed in the center position of a lower cover. A semiconductor substrate is placed on the stage, and the surface of the semiconductor substrate is subjected to ashing by being exposed to plasma derived from the plasma generation chamber.

JP 2005-122939 A

  By the way, the microwave transmission window that closes the opening formed in the top plate of the chamber is connected and fixed to the top plate with an O-ring interposed between the microwave transmission window and the top plate. Thereby, the airtight state between the top plate and the microwave transmission window is maintained. When this O-ring is interposed between the microwave transmission window and the top plate, a slight gap is formed between the top plate and the microwave transmission window inside and outside the O-ring.

There is no problem with the gap formed outside the O-ring, but there is a problem with the gap formed inside the O-ring (on the plasma generation chamber side).
That is, the reaction gas introduced into the plasma generation chamber enters the gap formed inside the O-ring (plasma generation chamber side), and the reaction gas and the microwave transmitted through the microwave transmission window Plasma is generated in the gap. At this time, there has been a problem that the inside of the O-ring is deteriorated by being exposed to plasma generated in this gap.

  Therefore, it is conceivable that the top plate and the microwave transmission window are firmly connected and fixed so that the reaction gas does not enter, and the top plate and the microwave transmission window are brought into close contact with each other. However, the top plate and the microwave transmission window are repeatedly expanded and contracted due to temperature fluctuations caused by the light emission heat of the plasma generated in the plasma generation chamber. As a result, when the top plate and the microwave transmission window that are firmly fixed are brought into close contact with each other, there is a problem that due to the difference in the linear expansion coefficient, the friction is caused by direct friction and wear, and the contact portion is deteriorated and particles are generated. Arise.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a plasma generator capable of preventing damage to an O-ring that is hermetically held between a transmission window and a chamber. is there.

  According to the first aspect of the present invention, an opening is provided in a chamber into which a reaction gas is introduced, the opening is closed with a dielectric transmission window, and a high-frequency or micro wave is introduced into the chamber through the dielectric transmission window. A plasma generation apparatus that introduces wave electromagnetic waves and generates plasma with the electromagnetic waves and the reactive gas, and is at least in close contact with a region located in a portion connected to the chamber of the dielectric transmission window A conductive film that shields the transmitted electromagnetic waves was formed inside the O-ring.

  According to the first aspect of the present invention, an electromagnetic wave is transmitted by the conductive film between the dielectric transmission window and the chamber, which is a connecting portion of the dielectric transmission window and the chamber and is inside the O-ring. Absent. Accordingly, plasma is not generated by the electromagnetic wave from the reaction gas that has entered between the dielectric transmission window inside the O-ring and the chamber. As a result, there is no possibility that the O-ring located near the gap is exposed to plasma and damaged.

According to a second aspect of the present invention, in the plasma generator according to the first aspect, a gap is formed between the dielectric transmission window inside the O-ring and the chamber.
According to the first aspect of the present invention, even if a gap is provided in a portion where the dielectric transmission window inside the O-ring is connected to the chamber, plasma is not generated in the gap. In addition, by providing the gap, even if the dielectric transmission window and the chamber expand and contract by the plasma emission heat generated in the chamber, the dielectric transmission window and the top plate are directly rubbed and worn. Is prevented.

  According to a third aspect of the present invention, in the plasma generating apparatus according to the second aspect, the gap is configured such that a gap maintaining plate is interposed between the dielectric transmission window outside the O-ring and the chamber. Formed by.

According to the third aspect of the present invention, it is possible to easily form a desired gap between the dielectric transmission window and the chamber without forming the chamber by the spacing plate.
According to a fourth aspect of the present invention, in the plasma generator according to the third aspect, the gap has a stepped surface that is lower on the surface of the chamber inside the O-ring than on the surface of the chamber outside the O-ring. Formed.

According to the fourth aspect of the present invention, it is possible to easily form a gap between the dielectric transmission window and the chamber by simply forming the chamber without increasing the number of parts.
According to a fifth aspect of the present invention, in the plasma generating device according to any one of the first to fourth aspects, the conductive film is made of aluminum.

According to the invention described in claim 5, since aluminum is a conductive metal, it reliably shields electromagnetic waves such as high-frequency waves or microwaves.
A sixth aspect of the present invention is the plasma generator according to the fifth aspect, wherein the conductive film formed of aluminum is subjected to alumite treatment or ceramic spray treatment on the surface thereof.

  According to the sixth aspect of the invention, since the conductive film made of aluminum is prevented from being directly exposed to plasma, aluminum metal is released from the conductive film by being directly exposed to plasma. Absent.

  According to the present invention, it is possible to prevent damage to the O-ring that is kept airtight between the transmission window and the chamber.

The schematic sectional drawing of the plasma ashing apparatus of embodiment. Sectional drawing for demonstrating a top plate and a microwave permeation | transmission window. The disassembled perspective view for demonstrating a microwave permeation | transmission window. The disassembled perspective view for demonstrating a top plate and a lower cover. Sectional drawing for demonstrating the top plate and microwave transmission window for demonstrating another example. Similarly, sectional drawing for demonstrating the top plate and microwave transmission window for demonstrating another example.

Hereinafter, an embodiment in which a plasma generator of the present invention is embodied in a plasma ashing apparatus which is one of plasma processing apparatuses will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a plasma ashing device 10 as a plasma generator. The chamber 11 of the plasma ashing apparatus 10 has a rectangular parallelepiped shape and is made of aluminum (Al). A stage 13 is disposed and fixed to the inner bottom surface 11 a of the chamber 11 via a leg portion 12. The stage 13 has a mounting surface 13a on the upper surface of which the semiconductor substrate W as a processing target is mounted.

  The top plate 14 that forms the chamber 11 has a cylindrical body 15 projecting upward from the outer side thereof, and a through hole 18 serving as an opening that penetrates the outer side and the inner side of the chamber 11 at a central position of the cylindrical body 15. Is formed.

  A waveguide 19 is connected and fixed to the upper surface 15 a of the cylindrical body 15. The waveguide 19 has a connection hole 19 a formed at a position corresponding to the through hole 18, and a microwave transmission window 20 as a disk-shaped dielectric transmission window is formed in the connection hole 19 a. It arrange | positions so that an upper side opening part may be obstruct | occluded. A microwave from a microwave oscillator (not shown) provided upstream of the waveguide 19 propagates through the waveguide 19 and is introduced into the through hole 18 through the microwave transmission window 20.

The disk-shaped microwave transmission window 20 is a dielectric transmission window made of ceramics, quartz, or the like, and is tightly fixed to the upper surface 15 a of the cylindrical body 15 via an O-ring 21.
Specifically, as shown in FIG. 2, an annular groove 22 is formed on the upper surface 15 a of the cylindrical body 15 and on the outer periphery of the upper opening of the through hole 18. An O-ring 21 is disposed in the annular groove 22 so that the upper side protrudes from the upper surface 15a. An annular spacing plate 23 is disposed on the upper surface 15 a of the cylindrical body 15 and outside the annular groove 22. The spacing plate 23 is made of metal, and the thickness thereof is such that the upper part of the O-ring 21 disposed in the annular groove 22 protrudes from the upper surface 23 a of the spacing plate 23.

  The microwave transmitting window 20 is connected and fixed to the upper surface 15 a of the columnar body 15 via the annular spacing plate 23 at the outer peripheral portion of the lower surface 20 a. At this time, the lower surface 20a of the microwave transmission window 20 is pressure-bonded to the O-ring 21, and the microwave transmission window 20 and the cylindrical body 15 are held and connected in an airtight state. As shown in FIG. 3, a gap D is generated between the microwave transmission window 20 and the cylindrical body 15 inside the O-ring 21 by the thickness of the interval holding plate 23.

  An annular conductive film 25 is formed in a region located on the outer peripheral portion of the lower surface 20 a of the microwave transmission window 20 and connected to the upper surface 15 a of the cylindrical body 15. More specifically, the radial width of the annular conductive film 25 is such that its inner peripheral edge faces the opening edge of the through hole 18 and its outer peripheral edge faces the outer peripheral edge of the spacing plate 23. . In the present embodiment, the conductive film 25 is a metal film made of aluminum (Al), and is formed by metal vapor deposition. The conductive film 25 is grounded by being electrically connected to the upper surface 15 a (chamber 11) of the cylindrical body 15 via the spacing plate 23.

  Therefore, among the microwaves transmitted through the microwave transmission window 20, the microwaves transmitted through the outer peripheral portion of the microwave transmission window 20 are shielded by the annular conductive film 25 formed on the lower surface 20 a of the microwave transmission window 20. And is not transmitted to the top plate 14 side. That is, the microwave is not introduced into the gap D between the lower surface 20a of the microwave transmission window 20 and the upper surface 15a of the cylindrical body 15 generated inside the O-ring 21 by the spacing plate 23.

  As shown in FIG. 4, the lower opening of the through hole 18 is formed with a fitting recess 30 that is widened to an inner diameter larger than the inner diameter of the through hole 18. Four female screw holes 31 are formed. A gas introduction path 32 is formed through the inner circumferential surface 18 a of the through hole 18 adjacent to the fitting recess 30 so as to communicate with the outer circumferential surface of the cylindrical body 15. The gas introduction path 32 forms a passage for introducing a plasma forming gas supplied from a gas supply means (not shown) provided upstream to the through hole 18.

  The lower opening of the through hole 18 in which the fitting recess 30 is formed is closed by a disk-shaped lower lid 33. The lower lid 33 has a disc-shaped lower lid body 34 formed through the lead-out hole 33a in the center, and a flange portion 35 formed to extend to the lower outer peripheral surface of the lower lid body 34. In the lower lid 33, the lower lid body 34 is inserted into the through hole 18, and the flange portion 35 is fitted into the fitting recess 30. At this time, a cushioning sheet 36 is disposed between the flange portion 35 and the inner surface 30 a of the fitting recess 30. The cushion sheet 36 is worn by rubbing directly between the upper surface 35a of the flange portion 35 and the inner surface 30a of the fitting recess 30 as the upper surface 35a of the flange portion 35 and the inner surface 30a of the fitting recess 30 expand and contract. To prevent it.

  Then, the male screw 38 is passed through the insertion hole 37 formed in the flange portion 35 corresponding to the female screw hole 31 of the fitting recess 30, and the male screw 38 is screwed into the female screw hole 31. 35 is fastened and fixed to the top plate 14 (the back surface 30a of the fitting recess 30).

As a result, the plasma generation chamber S is partitioned and formed in a space where the upper and lower openings of the through hole 18 formed in the cylindrical body 15 are closed by the microwave transmitting window 20 and the lower lid 33.
An annular annular groove 41 is formed on the outer peripheral surface of the lower lid body 34, and an annular passage is formed by the annular groove 41 and the inner peripheral surface 18 a of the through hole 18 that closes the annular groove 41. The annular groove 41 is formed at a position facing the opening of the gas introduction path 32 formed in the inner peripheral surface 18 a of the through hole 18, and the plasma forming gas introduced from the gas introduction path 32 is an annular path (annular passage). It is introduced into the groove 41).

  Four cut grooves 42 communicating with the plasma generation chamber S and the annular groove 41 (annular passage) are formed in the outer peripheral edge of the upper surface of the lower lid body 34 by notching at equal intervals (90 degrees). Then, the plasma forming gas introduced into the annular groove 41 is introduced into the plasma generation chamber S through the kerf 42.

  The plasma forming gas introduced into the plasma generation chamber S is excited by microwaves that are also introduced through the microwave transmission window 20 to become plasma. Then, the plasma generated in the plasma generation chamber S is led out toward the semiconductor substrate W placed on the lower stage 13 through a lead-out hole 33 a formed in the lower lid 33.

  A diffusion plate 43 is disposed below the lower lid main body 34 and at a position facing the opening of the lead-out hole 33a. The diffusion plate 43 is made of aluminum (Al), and is connected and fixed to the lower lid main body 34 with a bolt 45 via a spacing member 44. The diffusion plate 43 diffuses the plasma derived from the outlet hole 33a of the lower lid main body 34 and uniformly exposes it to the semiconductor substrate W. Then, the resist film formed on the semiconductor substrate W is ashed by plasma on the semiconductor substrate W placed on the stage 13.

As described above, according to the present embodiment, the following effects can be obtained.
(1) According to the present embodiment, the annular conductive film 25 is formed in the region located on the outer peripheral portion of the lower surface 20a of the microwave transmission window 20 and connected to the upper surface 15a of the cylindrical body 15, The microwaves that permeate the outer periphery of the microwave transmission window 20 are shielded by the conductive film 25 so as not to be transmitted to the top plate 14 side. In other words, microwaves are prevented from being introduced into the gap D between the lower surface 20 a of the microwave transmitting window 20 and the upper surface 15 a of the cylindrical body 15 generated inside the O-ring 21 by the spacing plate 23.

  Therefore, in the gap D formed inside the O-ring 21, the reaction gas introduced into the plasma generation chamber S enters, and plasma is generated by the reaction gas and the microwave transmitted through the microwave transmission window 20. Never do. As a result, the O-ring 21 is not deteriorated by plasma.

  (2) According to the present embodiment, the gap D is formed inside the O-ring 21 by the spacing plate 23. Therefore, even if expansion and contraction are repeated due to temperature fluctuations caused by the light emission heat of the plasma generated in the plasma generation chamber S, the upper surface 15a of the cylindrical body 15 (top plate 14) and the lower surface 20a of the microwave transmission window 20 remain. There is no direct frictional contact. As a result, the upper surface 15a of the cylindrical body 15 (top plate 14) and the lower surface 20a of the microwave transmission window 20 are not worn, and no particles are generated.

  In the above embodiment, the microwave transmission window 20 as the dielectric transmission window is formed of aluminum nitride (AlN). However, the present invention is not limited to this. For example, the microwave transmission window 20 is made of another dielectric member such as quartz. A window may be formed.

  In the above embodiment, the gap D is formed inside the O-ring 21 by the spacing plate 23. As shown in FIG. 5, the spacing plate 23 is omitted, and the upper surface 15 a of the cylindrical body 15 on the inner side of the annular groove 22 is made lower than the upper surface 15 a outside the annular groove 22. Alternatively, the stepped surface 15b may be formed by notching, and the gap D may be formed.

  In the above embodiment, the conductive film 25 made of aluminum is formed on the lower surface 20 a of the microwave transmission window 20. As shown in FIG. 6, the oxide film 50 may be formed by alumite treatment on the surface of the annular conductive film 25 and inside the O-ring 21. Accordingly, it is possible to prevent aluminum metal from being released from the conductive film 25 when the conductive film 25 made of aluminum is directly exposed to plasma. Further, a similar protective film may be formed on the inner surface of the O-ring 21 by ceramic spraying.

  In the above embodiment, the conductive film 25 is formed in a region located on the outer peripheral portion of the lower surface 20 a of the microwave transmission window 20 and connected to the upper surface 15 a of the cylindrical body 15. This may be carried out by forming the inner region from the O-ring 21. Also in this case, the microwave is not transmitted through the gap D between the lower surface 20a of the microwave transmitting window 20 and the upper surface 15a of the cylindrical body 15 generated inside the O-ring 21.

  In the above embodiment, the conductive film 25 is formed on the lower surface 20 a of the microwave transmission window 20. You may form this in the outer peripheral part on the upper surface of the microwave transmission window 20. FIG. Also in this case, it is possible to prevent the microwave from being transmitted through the gap D between the lower surface 20a of the microwave transmission window 20 generated inside the O-ring 21 and the upper surface 15a of the cylindrical body 15.

  In the above embodiment, the plasma generation apparatus is embodied in the plasma ashing apparatus 10 which is one of the plasma processing apparatuses. However, the plasma generation apparatus can be applied to a plasma processing apparatus that performs dry etching on a semiconductor substrate using plasma, You may apply to the plasma processing apparatus which performs surface modification. Moreover, you may apply to plasma generators other than a plasma processing apparatus.

  DESCRIPTION OF SYMBOLS 10 ... Plasma ashing apparatus, 11 ... Chamber, 13 ... Stage, 14 ... Top plate, 15 ... Cylindrical body, 15a ... Upper surface, 15b ... Step surface, 18 ... Through-hole, 18a ... Inner peripheral surface, 19 ... Waveguide, 19a ... Connecting hole, 20 ... Microwave transmission window, 20a ... Lower surface, 21 ... O-ring, 22 ... Annular groove, 23 ... Spacing plate, 23a ... Upper surface, 25 ... Conductive film, 30 ... Fitting recess, 30a ... Back surface: 32 ... gas introduction path, 33 ... lower lid, 33a ... outlet hole, 34 ... lower lid body, 35 ... flange portion, 41 ... annular groove, 42 ... cut groove, D ... gap, S ... plasma generation chamber, W: Semiconductor substrate.

Claims (6)

An opening is provided in the chamber into which the reaction gas is introduced, the opening is closed with a dielectric transmission window, and a high frequency or microwave electromagnetic wave is introduced into the chamber through the dielectric transmission window. And a plasma generator for generating plasma with the reaction gas,
A plasma generating apparatus, wherein a conductive film that shields the transmitted electromagnetic wave is formed at least inside an O-ring that is in close contact with a region located in a portion of the dielectric transmission window that is connected to the chamber. In the plasma generator of Claim 1,
A plasma generating apparatus, wherein a gap is formed between the dielectric transmission window inside the O-ring and the chamber. The plasma generator according to claim 2, wherein
The plasma generator according to claim 1, wherein the gap is formed by interposing a spacing plate between the dielectric transmission window outside the O-ring and the chamber. In the plasma generator of Claim 3,
The plasma generating apparatus according to claim 1, wherein the gap is formed such that a surface of the chamber inside the O-ring is a stepped surface lower than a surface of the chamber outside the O-ring. In the plasma generator of any one of Claims 1-4,
The plasma generating apparatus, wherein the conductive film is made of aluminum. In the plasma generator of Claim 5,
The plasma generating apparatus, wherein the conductive film formed of aluminum is subjected to alumite treatment or ceramic spraying treatment on the surface thereof.

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