JPH07169592A - Discharge tube cooling mechanism for plasma processing device - Google Patents

Abstract

PURPOSE:To enable long hour and stable operation of a plasma processing device by arranging a cooling mechanism, restraining a temperature rise in a discharge tube, and maintaining high sealing performance of a vacuum sealing member. CONSTITUTION:In a cooling mechanism 5, as a heat conductive sheet 60, a sheet obtained by impregnating boron nitride into an alumina mesh is wound a semicircle by a semicircle round the outer periphery of a discharge tube 20 from above and below, and aluminum blocks 51 and 52 are fixed to these surfaces by interposingly pressing the surfaces between them from above and below by a clamp. This sheet is deformed by flexibility so as not to leave the void between both when being pressed between the tube 20 and the blocks 51 and 51, and thermally brings both into close contact with each other. Through holes 54 and 56 are arranged inside of the blocks 51 and 52, and tubular screw members 59 to connect tubes 53, 55 and 57 to each other are fixed to the respective opening ends, and box nuts 58 of tube terminals are screw-fitted to these, and a cooling water passage to communicate the blocks 51 and 52 with each other is formed, and the blocks 51 and 52 are cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling mechanism for a discharge tube used in a plasma processing apparatus.

[0002]

2. Description of the Related Art In a plasma processing apparatus such as a plasma ashing apparatus, a plasma etching apparatus and a plasma CVD apparatus, a microwave or RF high frequency is applied to generate plasma in a discharge tube. It is widely used in the manufacture of LSI and other semiconductor products.
Here, the technology and problems of the plasma ashing apparatus using microwaves will be described as a conventional example.

FIG. 8 is a side sectional view showing an outline of a plasma ashing apparatus 1'using microwaves. In general,
A process chamber 10 for accommodating a wafer substrate 17 to be ashed (resist film ashing process), an oxygen gas supply end 25 for generating plasma to be introduced into the process chamber 10 and a discharge tube 20, and the discharge tube 20. It is composed of a power supply 31 for applying a microwave and a waveguide 30.

Protrusions 14a and 14b facing the inner wall of the process chamber 10 are provided, and a gas rectifier 15 is installed so as to be supported by them. A support 16 is provided below the gas rectifier 15, and a wafer substrate 17 whose resist film is to be ashed and removed is placed on the support 16. Further, an insertion fixing portion 18 for inserting the end portion of the discharge tube 20 is provided on the side wall of the process chamber 10, and a vacuum pump 13 is connected to an exhaust port 11 provided on the bottom wall via a vacuum valve 12. There is.

The discharge tube 20 is inserted through the waveguide 30 with a clearance 34. One end of the discharge tube 20 is inserted into the insertion fixing portion 18 of the process chamber 10 as described above, but an O-ring is provided between the two. It is vacuum-sealed at 22b, and the discharge tube 2
The other end of 0 is inserted into the oxygen gas supply end 25, and a vacuum seal is provided between the two by an O-ring 22a.
Further, cooling gas nozzles 23a and 23b for spraying a cooling gas are arranged on the O-rings 22a and 22b, respectively, with their tips close to the O-rings 22a and 22b. The discharge tube 20 is made of an insulating material such as quartz glass, sapphire, or alumina.

The waveguide 30 has a microwave power source 3 at its starting end.
1, a stub tuner 32 that penetrates the tube wall of the waveguide 30 is provided below the discharge tube 20, and a terminal matching unit 33 that matches microwaves is provided at the terminal end.

The plasma ashing apparatus 1'according to the conventional example is constructed as described above, and its operation will be described below.

With reference to FIG. 6, a wafer substrate 17 on which the resist film used for fine processing remains is placed on the support 16. The vacuum valve 12 is opened and the process chamber 10 is evacuated by the vacuum pump 13. On the other hand, oxygen gas from a cylinder (not shown) is introduced into the discharge tube 20 from the supply end 25. At the same time, cooling gas is ejected from the cooling gas nozzles 23a and 23b to cool the O-rings 22a and 22b and the vicinity of the O-rings 22a and 22b of the discharge tube 20a. The microwave power supply 31 is switched on to generate microwaves having a frequency of 2.45 GHz, and the discharge tube 2
When microwaves are applied to 0 and discharged, the stub tuner 32 and the terminal matching box 33 of the waveguide 30 are adjusted in advance, so that the plasma 21 of oxygen gas is generated in the discharge tube 20. If necessary, the stub tuner 32 is further adjusted to match the microwaves so that the reflected waves are minimized.

As described above, the oxygen gas introduced into the discharge tube 20 becomes plasma 21, that is, highly reactive oxygen radicals, and is introduced into the process chamber 10. The oxygen radicals are rectified via the gas rectifier 15 and uniformly transported to the lower wafer substrate 17, and react with the resist film to ash and remove it.

The conventional microwave plasma ashing apparatus 1'is constructed and operates as described above, but in the actual manufacturing process of semiconductor products, in order to increase the ashing rate, microwave power of 1 KW or more is used. Is applied, and the cycle of insertion, ashing, and removal of the wafer substrate 17 is repeated to operate for a long time semicontinuously, so that part of the energy of the plasma 21 becomes heat and the temperature of the discharge tube 20 is changed. The temperature is raised to reach a temperature of 200 ° C. or higher in the vicinity of the O-rings 22a and 22b for vacuum sealing.

Although the O-rings 22a and 22b are made of silicone rubber or fluororubber having good heat resistance as the material, they are thermally deteriorated at a temperature of 200 ° C. or higher to maintain the vacuum sealing property. Can no longer plasma
There was a problem that the ashing device failed. Of course,
Cooling gas is sprayed from the cooling gas nozzles 23a and 23b onto the surfaces of the O-rings 22a and 22b themselves and the discharge tube 20 in the vicinity thereof to cool them.
It was not enough to cool the O-rings 22a and 22b to a temperature below the temperature at which the vacuum sealability was not lost.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and suppresses the temperature rise of the discharge tube and maintains the vacuum sealability of the vacuum seal member, thereby stabilizing the plasma processing apparatus for a long time. To enable various operations,
An object is to provide a discharge tube cooling mechanism in a plasma processing apparatus.

[0013]

The above object is that a cooling body is pressed against the outer periphery of the discharge tube of the plasma processing apparatus in the vicinity of the vacuum seal member provided on the discharge tube via a heat conductive sheet. And a discharge tube cooling mechanism in a plasma processing apparatus.

[0014]

With the cooling body pressed against the outer circumference of the discharge tube near the vacuum seal member via the heat conductive sheet, the temperature rise of the discharge tube is suppressed and the vacuum sealability of the vacuum seal member is maintained for a long time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A discharge tube cooling mechanism in a plasma ashing apparatus 1 according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of the plasma ashing apparatus 1 of the embodiment, and the same parts as those of the apparatus 1'of the conventional example are designated by the same reference numerals, and the detailed description thereof will be omitted. The device 1 of the embodiment is different from the device 1'of the conventional example in that the discharge tubes 20 are provided with new cooling mechanisms 5 and 5 '.

The cooling mechanism 5'is inside the O-ring 22a,
The cooling mechanism 5 is provided inside the O-ring 22b and on the outer circumference of the discharge tube 20, but both are configured in exactly the same manner, and the respective members are, for example, one aluminum block 51 and the other one. Like reference numeral 51 ′, a dash is added to the same reference numeral, so that only the cooling mechanism 5 will be described below.

Details of the cooling mechanism 5 are shown in FIGS.
2 is a cooling mechanism 5 shown in a sectional view taken along line [2]-[2] in FIG. 1, and FIG. 3 is a perspective view of the cooling mechanism 5.

Referring to FIGS. 2 and 3, the cooling mechanism 5 is O-
A "BN sheet" (trade name, Denki Kagaku Kogyo Co., Ltd.), which is a sheet obtained by impregnating alumina mesh with boron nitride, is wound around the outer circumference of the discharge tube 20 in the vicinity of the ring 22b as a half turn from the top and bottom. Aluminum blocks 51, 52 are attached to the surfaces of the aluminum blocks 5 and the aluminum blocks 5 are clamped by an unillustrated clamp.
It is fixed by pinching 1, 52 from above and below. In addition,
Due to its flexibility, the "BN sheet" is deformed so as not to leave a gap between the discharge tube 20 and the aluminum blocks 51, 52 when pressed, and thermally adheres them to each other. .

Further, aluminum blocks 51, 52
Are provided with through holes 54, 56 inside thereof, and tubular screw members 59 for connecting the tubes 53, 55, 57 are fixed to the respective open ends, and the cap nuts 58 of the tube ends are fixed to the tubular screw members 59. A passage for cooling water is formed by being screwed to connect the aluminum blocks 51 and 52. Cooling water is flowed in the direction indicated by the arrow to cool the aluminum blocks 51, 52.

The discharge tube cooling mechanism in the plasma ashing apparatus 1 according to the embodiment of the present invention is constructed as described above. Next, its operation will be described.

Referring to FIG. 1, the ashing action of oxygen radicals of the plasma ashing apparatus 1 is basically the same as that of the conventional plasma ashing apparatus 1 ',
The only difference is that the discharge tube 20 is forcibly cooled by the cooling mechanism 5, 5 '. That is, the process chamber 10 is exhausted, and oxygen gas is introduced into the discharge tube 20 from the supply end 25. At the same time, referring to FIG. 2 and FIG.
Tap water from a faucet (not shown) serves as cooling water for the cooling mechanism 5.
Is introduced into the tube 53 and discharged from the tube 57, and the aluminum blocks 51 and 52 on the way are cooled. This also applies to the cooling mechanism 5 '.
Further, the air ejected from the cooling gas nozzles 23a and 23b causes the O-rings 22a and 22b and the O of the discharge tube 20 to become O.
-The vicinity of the rings 22a, 22b is cooled.

Next, the microwave power source 31 is switched on, and microwaves having a frequency of 2.45 GHz are applied.
When discharged, the oxygen gas in the discharge tube 20 becomes plasma 21.
Then, the generated highly reactive oxygen radicals are introduced into the process chamber 10 to ash the resist film remaining on the surface of the contained wafer substrate 17.

In order to monitor the temperature of the discharge tube 20 at this time, a connection point of the thermocouple 70 is attached to the surface of the discharge tube 20 in the immediate vicinity of the O-ring 22b (see FIGS. 1 and 3) to obtain the temperature. FIG. 5 shows the relationship between the elapsed time after the start of discharge and the temperature of the discharge tube 20. In FIG. 5, when the microwave power is set to 1 KW and 2 KW, the abscissa indicates the elapsed time from power-on to after power-off, and the ordinate indicates the observed temperature of the discharge tube 20. Although the temperature of the discharge tube 20 rises after power-on, the temperature rises slowly, and the temperature at power-off is about 100 ° C. even in the case of 2 kW. It was also confirmed that the O-rings 22a and 22b maintained the vacuum sealing property even in the continuous discharge test for 6 hours at 2 kW.

On the other hand, in the plasma ashing apparatus 1'of the conventional example, the microwave power is similarly 1K.
The results of monitoring the temperature of the discharge tube 20 when applied as W and 2 KW are shown in FIG. At 2 kW, the temperature rises sharply, and in addition, the temperature rise is large even when the power discharge exceeds 1 KW, and the vacuum sealability of the O-rings 22a and 22b is impaired.

FIG. 7 shows the relationship between the flow rate of air when the air is ejected from the cooling gas nozzle 23b to cool it and the temperature of the discharge tube. When the flow rate of the cooling gas is increased, the discharge tube 20 is accordingly cooled. The temperature is also lowered, which indicates that the water-cooled aluminum blocks 51 and 52 assist the cooling of the discharge tube 20.

As the heat conductive sheet 60, instead of the "BN sheet" used in the embodiment, as shown in FIG.
When an aluminum foil 62 was wound around the outer circumference of the discharge tube 20 and a "BN sheet" 61 was laminated on the aluminum foil 62 to form a two-layer structure, the cooling characteristics of the discharge tube 20 were almost the same as those of the example. The boron nitride was prevented from sticking and hardening on the surface of the discharge tube 20, and the “BN sheet” could be reused. Discharge tube 2 with aluminum foil only
0 is insufficient in thermal contact with the aluminum blocks 51 and 52, and it is effective to have a two-layer structure with "BN sheet".

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in the embodiment, the cooling of the vacuum seal portion of the discharge tube, which is used in the conventional example, is also used, but this cooling can be omitted.

In the examples, the "BN sheet" in which the mesh of alumina is impregnated with boron nitride having a good thermal conductivity is used as the heat conducting sheet, but the boron nitride is replaced with a good thermal conductivity. Carbon, such as graphite,
A sheet impregnated with beryllium oxide or other metals may be used.

Further, in the embodiment, the aluminum foil is used as one layer of the heat conducting sheet having two layers, but this may be other metal foil such as tin foil or silver foil.

Although water-cooled aluminum blocks are used as cooling bodies in the embodiments, alcoholic refrigerants or fluorocarbon-based heat mediums may be used instead of water. Further, a copper block may be used instead of the aluminum block. Further, instead of the aluminum block, a box made of an aluminum plate having a similar shape may be used. In addition, various conventionally known cooling bodies may be used.

In the embodiment, the frequency is 2.45 GH.
The discharge tube for applying the microwave of z has been described,
High-frequency discharge tubes other than this, for example, 100 kHz to 400 kHz, 13.56 MHz, 27.12 MHz
The cooling mechanism of the present invention can also be applied to the discharge tube of the plasma processing apparatus that applies the high frequency.

In the embodiment, the cooling of the cylindrical discharge tube has been described, but the present invention can be applied to cooling the bell jar when the bell jar is used for discharging.

[0035]

As described above, according to the discharge tube cooling mechanism in the plasma processing apparatus of the present invention, the temperature rise of the discharge tube is suppressed and the vacuum sealing property of the vacuum sealing member is maintained for a long time. The plasma processing apparatus can be stably operated for a long time.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a discharge tube cooling mechanism in a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line [2]-[2] in FIG. 1, showing a main part of the cooling mechanism.

FIG. 3 is a perspective view of the cooling mechanism.

FIG. 4 is a perspective view of a heat conductive sheet having a two-layer structure.

FIG. 5 is a diagram showing the relationship between the time after microwave application and the temperature of the discharge tube in the plasma ashing apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a time after microwave application and a temperature of a discharge tube in a plasma ashing device according to a conventional example.

FIG. 7 is a diagram showing a relationship between a flow rate of a cooling gas and a temperature of a discharge tube when a vacuum seal portion formed by an O-ring is cooled by a cooling gas.

FIG. 8 is a side sectional view of a conventional plasma ashing device.

[Explanation of symbols]

 20 Discharge Tube 51 Aluminum Block 52 Aluminum Block 53 Tube 54 Through Hole 55 Tube 56 Through Hole 57 Tube 58 Cap Nut 59 Tubular Screw Member 60 Heat Conduction Sheet

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 26, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Referring to FIGS. 2 and 3, the cooling mechanism 5 is O
In the vicinity of the ring 22b, a sheet obtained by impregnating alumina mesh with boron nitride is wound around the outer circumference of the discharge tube 20 half a turn from the top and bottom, and aluminum blocks 51 and 52 are applied to the surfaces thereof. The aluminum block 5 with a clamp (not shown)
It is fixed by pinching 1, 52 from above and below. Incidentally,
Due to its flexibility, the port 60 is deformed so as not to leave a space between the discharge tube 20 and the aluminum blocks 51 and 52 when pressed, and thermally adheres them.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

Further, as a heat conduction sheet, instead of the sheet 60 used in the embodiment, as shown in FIG. 4, an aluminum foil 62 is wrapped around the outer periphery of the discharge tube 20 and then the aluminum foil 62 is wound on the aluminum foil 62.
When a sheet 61 similar to the sheet 60 is stacked to have a two-layer structure, the cooling characteristics of the discharge tube 20 are almost the same as those of the embodiment, and boron nitride is used.
It was possible to prevent the sheet 61 from being fixed and hardened, and to reuse the sheet 61 . Discharge tube 2 with aluminum foil only
0 is insufficient in thermal contact between the aluminum blocks 51 and 52, and it is effective to have a two-layer structure with the sheet 61 .

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Further, in the examples, as the heat conductive sheet, a sheet obtained by impregnating alumina mesh with boron nitride having good thermal conductivity was used, but carbon having good thermal conductivity, for example, is used instead of boron nitride. A sheet impregnated with graphite, beryllium oxide or other metals may be used. Also, alumina fibers and carbon fibers are woven alternately.
The same effect can be obtained by using a different sheet. Or
Reconstituted rubber impregnated with boron nitride, which has good thermal conductivity
Sheets may be used.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Nakamura 3313 Ueno, Yokogawa-cho, Aira-gun, Kagoshima Aruba Kyushu Co., Ltd.

Claims (7)

[Claims] 1. A discharge in a plasma processing apparatus, characterized in that, in the vicinity of a vacuum seal member provided in the discharge tube of the plasma processing apparatus, a cooling body is pressed against the outer circumference of the discharge tube via a heat conductive sheet. Tube cooling mechanism. 2. A discharge tube cooling mechanism in a plasma processing apparatus according to claim 1, wherein a vacuum-sealed portion of said vacuum-sealing member of said discharge tube is cooled by the blown gas. 3. The discharge tube cooling mechanism in the plasma processing apparatus according to claim 1, wherein the heat conductive sheet is a sheet obtained by impregnating an alumina mesh with boron nitride. 4. The heat conductive sheet is a sheet obtained by impregnating an alumina mesh with carbon.
A discharge tube cooling mechanism in the plasma processing apparatus according to. 5. The heat conducting sheet is a two-layer sheet having an aluminum foil as a side in contact with the discharge tube and an alumina mesh impregnated with boron nitride as a side in contact with the cooling body. A discharge tube cooling mechanism in the plasma processing apparatus according to claim 1 or 2. 6. The heat conductive sheet is a two-layer sheet having an aluminum foil as a side in contact with the discharge tube and an alumina mesh sheet impregnated with carbon as a side in contact with the cooling body. The discharge tube cooling mechanism in the plasma processing apparatus according to claim 1 or 2. 7. The cooling body is water-cooled aluminum.
The discharge tube cooling mechanism in the plasma processing apparatus according to any one of claims 1 to 6, which is a block.