JPH1054356A - Deposit removing trap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a life and reliability of operation in a vacuum pump and an exhaust gas processing device, by protecting the vacuum pump and the exhaust gas processing device from deposition of a reaction byproduct in a process. SOLUTION: This trap is constituted so as to provide an air-tight chamber, trap vessel 102 provided in a vacuum exhaust system having a vacuum pump for forming a vacuum in this air-tight chamber, baffle plate 106 formed with a non-linear flow path in the trap vessel and a pulse tube refrigerator 134 cooling the baffle plate 106. Here, the baffle plate 106 is thermally connected to a cold head 137 of the pulse tube refrigerator 134.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in a vacuum exhaust system for evacuating a vacuum chamber for semiconductor production.

[0002]

2. Description of the Related Art A conventional vacuum pumping system will be described with reference to FIG. The vacuum chamber 10 is a process chamber of a semiconductor manufacturing apparatus such as an etching apparatus and a chemical vapor deposition apparatus (CVD).
The pipe 14 is connected to the vacuum pump 12. The vacuum pump 12 is for raising the pressure of the process exhaust gas from the vacuum chamber 10 to the atmospheric pressure. Conventionally, an oil rotary pump is used, and at present, a dry pump is mainly used.

The degree of vacuum required by the vacuum chamber 10 is as follows:
When the degree of vacuum is higher than the ultimate vacuum of the dry pump 12, an ultra-high vacuum pump such as a turbo molecular pump may be further provided upstream of the dry pump. Exhaust gas from the process is toxic or explosive depending on the type of process and cannot be released to the atmosphere as it is. Therefore, the vacuum pump 1
An exhaust gas treatment device 26 is provided downstream of the apparatus 2. Among the exhaust gas of the process whose pressure has been increased to the atmospheric pressure, those which cannot be released to the atmosphere as described above are subjected to treatment such as adsorption, decomposition, absorption and the like, and only harmless gas is released to the atmosphere. The pipe 14 is provided with a valve at an appropriate position as needed.

[0004]

In the conventional vacuum evacuation system as described above, when a substance having a high sublimation temperature is present in a reaction by-product, the gas is exhausted by a vacuum pump. There is a disadvantage that the gas solidifies and precipitates in the vacuum pump, which causes a failure of the vacuum pump.

For example, when BCl ₃ or Cl ₂ which is a representative process gas is used for etching aluminum, the remaining gas of the process gas of BCl ₃ or Cl ₂ reacts with AlCl ₃ from the process chamber. The product is evacuated by the vacuum pump 12.

This AlCl ₃ does not precipitate on the suction side of the vacuum pump due to its low partial pressure, but the partial pressure rises during pressurization and exhaust, and precipitates in the vacuum pump, causing a failure of the vacuum pump. . The same applies to the case of a reaction by-product such as (NH ₄ ) ₂ SiF ₆ or NH ₄ Cl generated from a CVD apparatus for forming a SiN film.

Conventionally, to solve this problem, (1) a vacuum pump is heated so that solidified substances do not precipitate inside the vacuum pump, and the gas is passed through the vacuum pump. (2) Provide a water-cooled cooler upstream (intake side) of the vacuum pump to trap precipitates. And other measures have been taken.

[0008] However, the measure (1) is effective for a vacuum pump, but as a result, solids precipitate in an exhaust gas treatment device provided downstream of the vacuum pump, and the packed bed is formed. There is a problem that causes clogging.
In the measure (2), since the water-cooled cooler is provided on the suction side of the vacuum pump, the partial pressure of the precipitate is low, and the precipitate cannot be sufficiently trapped due to the saturated vapor pressure. I couldn't say I was working.

In this case, it is conceivable to trap the precipitate by using a means for generating an extremely low temperature as a cooler. As such a method, a method using a liquefied gas such as liquid nitrogen or a method using a Gifford McMahon refrigerator used in a cryopump or the like can be considered. Therefore, there is a disadvantage that it is difficult to use as a cooling means for capturing various solidified substances having different solidification temperatures. In addition, facilities and construction work for storing and supplying cryogenic liquefied gas are expensive and difficult. With respect to (2), there is a vibrating portion having a seal called a displacer on the principle of refrigeration generation, so that the problems of seal durability and vibration cannot be avoided. For this reason, no effective means has been hitherto provided for the problem of precipitation of solidified substances during evacuation.

The present invention has been made in view of the above circumstances, and protects a vacuum pump and an exhaust gas treatment device from the deposition of reaction by-products in the process, prolongs the life of the vacuum pump and the exhaust gas treatment device, and provides reliable operation. It is an object of the present invention to provide a trap for removing precipitates capable of improving the performance.

[0011]

Means for solving the above-mentioned problems in the present invention is to provide a baffle in which a cold head of a pulse tube refrigerator is thermally connected in the middle of an evacuation system for evacuating a vacuum chamber. That is, a trap for removing precipitates is provided.

In the present invention, by using a pulse tube refrigerator, the temperature of the cold head can be varied to solve the above problems, and the performance is good and stable over a wide range. Further, in terms of facilities, installation (construction) is easy because only a compressor for operating the refrigerator and a normal-temperature pipe for working gas, which have a high degree of freedom in installation, are provided. As for the pulse tube refrigerator, the cold head has no moving parts, and thus has the advantage of no vibration and a long maintenance interval.

In addition, during regeneration of the trap, in the Gifford McMahon refrigerator, since the displacer is made of resin, for example, if the solidified substance is NH ₄ Cl, the cold head is heated to the sublimation temperature of 188 ° C. Although it is impossible to perform sublimation regeneration by using a pulse tube refrigerator, there is also an advantage that heating and sublimation regeneration can be performed since there is no displacer.

When a pulse tube refrigerator having such advantages is thermally connected to a baffle arranged in a trap for removing precipitates, the baffle is cooled to an extremely low temperature, so that the baffle is formed in the trap. The gas molecules of the solidified component passing through the existing gas channel are solidified by contacting the baffle and can be captured and removed.

As shown in FIG. 1, the pulse tube refrigerator 134 is a refrigerator using gas as a working medium, and includes a compressor 140, a high / low pressure switching device 139, a cold storage tube 136 filled with a cold storage material, and a low-temperature extraction. The cold tube 137 as a part and the pulse tube 13 as a gas expansion space
8. When extremely low temperature is required, helium is generally used as the working gas, but other gases such as nitrogen and dry air may be used.

When helium gas is used as the working medium for the purpose of cryogenic temperature, the compressor 140 is operated to periodically switch the high / low pressure switching device 139 to supply gas into the pulse tube 138 through the regenerator tube 136. And when exhausted, the adiabatic expansion of the gas continuously
8 and a low temperature of about −140 ° C. is generated in the cold head 137.

Normally, in order to efficiently generate adiabatic expansion of gas in the pulse tube 138 and generate a lower temperature, as shown in FIG. 2, an orifice 133 or a needle valve is provided at the tip of the pulse tube 138. Buffer tank 142 via a mechanism for regulating the gas flow such as 135
Is provided. With this mechanism, it is possible to generate an extremely low temperature of about -220 ° C. Further, as shown in FIG.
May be provided via a mechanism for adjusting a gas flow such as an orifice or a needle valve.

FIG. 4 shows an example of the performance of the pulse tube refrigerator. The vertical axis represents the refrigerating capacity (watts) of the cold head, and the horizontal axis represents the temperature (° C.) of the cold head at that time.
Is shown. In the example of FIG. 4, the temperature reached by the cold head when the refrigerating capacity is zero is −213 ° C., and the refrigerating capacity increases as the temperature of the cold head increases. As a feature, it has an almost linear refrigerating capacity over a wide temperature range, so that even if the required temperature level changes, it can easily be changed by using a pulse tube refrigerator. Can respond.

According to the above-described means, since the solidified substance can be captured and removed in the trap having the baffle cooled to an extremely low temperature, the trap is installed in a place where the solidified substance is deposited and exerts an adverse effect. By doing
The vacuum pump and the exhaust gas treatment device can be protected from deposits.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 shows a basic embodiment of the present invention, in which a pipe 14 connecting a vacuum chamber 10 and a vacuum pump 12 is provided.
A trap 16 for removing precipitates is arranged via valves 20 and 22. An exhaust gas treatment device 26 is provided downstream of the vacuum pump 12.

The precipitate removing trap 16 is, for example, as shown in FIG.
As shown in FIG. 7, the shaft comprises a shaft body 112 to which a tubular trap container 102 and a baffle 106 are attached, and a pulse tube refrigerator 134. The baffle 106 and the shaft 112 are formed of a material having good heat conductivity such as metal, and the cold head 1 of the pulse tube refrigerator 134 is formed.
37 is thermally coupled.

The baffle 106 is provided with a large number of holes, for example, to form a gas flow path. Since the deposited substance is easily captured by the baffle near the gas inlet 110, the diameter of the hole formed in the baffle is gradually reduced from upstream to downstream in order to use the entire baffle effectively, and the baffle is It is preferable to gradually narrow the interval provided on the shaft body 112 from upstream to downstream. Also, in order to increase the trapping rate, the relative positional relationship of the holes between the baffles is shifted so that the gas flow path 10 in which the gas flows in a zigzag pattern.
9 may be formed. In this embodiment, the baffle 106 has a large number of holes. However, the same effect can be obtained in any form as long as the baffle is formed so that the gas flow becomes non-linear.

If the buffer tank 142 attached to the pulse tube refrigerator 134 is formed integrally with the trap container 102, space may be saved. Further, as shown in FIG. 6, it is more preferable to mount the refrigerator such that the cold head 137 of the pulse tube refrigerator 134 faces downward, because it is possible to prevent a decrease in performance due to heat convection of the gas in the pulse tube 138. . Further, in order to prevent heat from entering the baffle cooled to a low temperature from the outside of the trap container 102, the outside of the trap container 102 is covered with a heat insulating material, or a vacuum heat insulating layer is provided with a double structure of the trap container, It may be possible to insulate heat from the outside.

Using the trap 16 for removing precipitates having the above structure, the silicon nitride (Si--N)
A case where the process chamber of a low pressure chemical vapor deposition (CVD) apparatus for forming a film is evacuated will be described. Silicon nitride (S
In a low pressure CVD process for forming a film of i-N), Si is used.
H ₂ Cl ₂ and NH ₃ are introduced as process gases, and SiH _2, which is the remaining gas of the process gas, is introduced from the vacuum chamber 10.
Cl ₂ , NH ₃ and reaction by-products Si ₃ N ₄ , NH ₄
Cl is discharged. Among them, Si ₃ N ₄ and NH ₄ Cl have a high freezing point, and thus precipitate before or inside the vacuum pump 12. However, since NH ₄ Cl is generated in a large amount, it has been a problem in the past. Here, in this embodiment,
A trap 16 is provided in front of the vacuum pump 12 so that NH ₄ Cl
To solve the problem.

When the pulse tube refrigerator 134 is operated, the baffle 106 and the shaft 11
2 is cooled. As a result, NH ₄ Cl gas molecules precipitate on the baffle 106 or the shaft 112, so that they can be captured and removed upstream of the vacuum pump 12. The set temperature of the baffle 106 is determined by the trap 16
Is set at an extremely low temperature, for example, about -150 ° C. in order to increase the trapping rate from the relationship between the partial pressure of NH ₄ Cl gas and the saturated vapor pressure.

When a certain amount or more of NH ₄ Cl is trapped in the trap 1
When captured at 6, regeneration is required. Fig. 6
In the above, the temperature is measured by attaching the temperature sensor 120 to the baffle 106, and when the temperature rises above a preset value, it can be known by judging that NH ₄ Cl has adhered and the thermal load has increased. Alternatively, pressure sensors 12 may be provided at the entrance and exit of trap 16.
2, 124 may be provided to measure the differential pressure, and the determination may be made based on the measured differential pressure. In addition, reproduction may be performed at regular intervals.

If it is determined that the regeneration time is reached, the valves 20 and 22 before and after the trap 16 are closed to disconnect the trap 16 from the evacuation system.
Regeneration can be performed by introducing nitrogen gas heated to about 200 ° C. higher than the sublimation temperature of H ₄ Cl, exhausting the gas from the regeneration gas exhaust port 118, and treating it with a scrubber 128 or the like. At the same time, it is preferable to provide a heater 126 on the baffle 106 or the shaft body 112 for heating, thereby promoting the regeneration and shortening the time required for the regeneration. At this time, the pulse tube refrigerator can be heated to a high temperature because there is no resin expander or the like inside.

FIG. 7 shows another embodiment of the present invention.
When the vacuum chamber of the plasma CVD apparatus for forming a silicon nitride (Si-N) film is evacuated, the precipitate removing trap 16 according to the present invention is provided with a multistage structure of a former stage 30 and a latter stage 32 of a vacuum pump. The case where it is provided in between is described.

[0029] Silicon nitride (Si-
The deposition process of N), by introducing SiH _4, NH ₃ as a process gas, which is, SiH _4, NH _3, and reaction by-products is a residual gas of the process gas from the vacuum chamber 10 (NH _{4) 2} SiF ₆ and H ₂ are discharged. Among them, (NH ₄ ) ₂ SiF ₆ has a high freezing point of 270 ° C., so that it exceeds the saturation pressure inside the vacuum pump in the middle of evacuation and precipitates.
This caused the vacuum pump to fail. Therefore, in the present embodiment, the trap removal trap 16 is provided between the former stage 30 and the latter stage 32 during the pressure increase of the vacuum pump (NH
₄ ) The problem is solved by capturing and removing ₂ SiF ₆ gas molecules.

At the position of the trap 16 shown in this embodiment,
Although the partial pressure of (NH ₄ ) ₂ SiF ₆ is close to the saturated vapor pressure, the temperature of the baffle 106 may be set to, for example, about −100 ° C. in order to increase the trapping rate.

FIG. 8 shows another embodiment of the present invention.
In the case where the vacuum chamber of the etching apparatus for etching aluminum is evacuated, a case where the precipitate removal trap 16 of the present invention is provided between the vacuum pump 12 and the exhaust gas treatment apparatus 26 will be described.

In the process of etching aluminum, Cl ₂ and BCl ₃ are introduced as process gases, and the remaining gas Cl
₂ , BCl ₃ and AlCl _{3 as} a reaction by-product are discharged. Among them, since AlCl ₃ has a high sublimation temperature of 180 ° C., it exceeds the saturation pressure inside the vacuum pump on the way of evacuation and precipitates, causing a failure of the vacuum pump. Conventionally in order to deal with this problem, AlCl ₃ and the vacuum pump
Heated to about 200 ° C higher than the sublimation temperature of AlCl
₃ passed through the inside of the vacuum pump. As another method, a roots type is usually used for a dry vacuum pump, but since this type has a structure that is weak against precipitates in terms of clearance, a screw type having a structure strong against precipitates is used. To avoid the problem by passing AlCl ₃ precipitated inside the pump. However, in the method of coping with passing through AlCl ₃ , the exhaust gas treatment device 26 connected downstream of the vacuum pump 12 is provided with AlC 3.
l ₃ is in that adversely affect problem precipitated had not been resolved.

Therefore, in this embodiment, a trap 16 for removing precipitates is provided between the vacuum pump 12 and the exhaust gas treatment device 26, and AlCl ₃ passing through the vacuum pump 12 is captured and removed to solve the problem. ing. At the position of the trap 16 shown in this embodiment, the gas discharged from the vacuum chamber is pressurized to the atmospheric pressure by the vacuum pump 12, so that
Although Cl ₃ precipitates even at room temperature, the baffle 106 may be set to, for example, about −20 ° C. in order to increase the capture rate.

FIG. 9 shows another embodiment of the present invention. The trap 16 for removing precipitates according to the present invention
6 downstream. Depending on the process performed in the vacuum chamber 10, solidified substances may precipitate on the pipe 14 downstream of the exhaust gas treatment device 26, which may have an adverse effect. In such a case, if the trap 16 of the present invention is provided immediately after the exhaust gas treatment device 26,
The solidified substance that has passed through is solidified and deposited on the baffle 106 cooled by the pulse tube refrigerator, so that the solidified substance can be removed before depositing on the pipe 14 for exhausting to the atmosphere. can do.

[0035]

As described above, according to the present invention, since the baffle of the trap container is cooled to a very low temperature by the pulse tube refrigerator, it passes through the gas passage formed by the baffle in the trap container. The gas molecules of the solidified component are solidified and captured by contacting the baffle. Therefore, it is possible to remove deposits of solidified components which are deposited in the vacuum pump to damage the sliding portion or accumulate in the packed bed of the exhaust gas treatment device and cause adverse effects such as clogging. The pump and the exhaust gas treatment device can be protected. Since this trap device uses a pulse tube refrigerator as a cooling device, the temperature of the cold head can be varied, the performance becomes stable over a wide range, and since there are no moving parts in the cold head, there is no vibration and the maintenance interval is reduced. Therefore, the service life of the vacuum pump and the exhaust gas treatment device can be extended, the operation reliability can be improved, and maintenance and inspection can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a pulse tube refrigerator.

FIG. 2 is a diagram showing another configuration of the pulse tube refrigerator.

FIG. 3 is a diagram showing still another configuration of the pulse tube refrigerator.

FIG. 4 is a graph showing the performance of a pulse tube refrigerator.

FIG. 5 is a diagram showing the overall configuration of the trap according to the first embodiment of the present invention.

6 is a diagram showing a specific configuration of the trap of the embodiment in FIG.

FIG. 7 is a diagram showing an overall configuration of a trap according to a second embodiment of the present invention.

FIG. 8 is a diagram showing an overall configuration of a trap according to a third embodiment of the present invention.

FIG. 9 is a diagram showing an overall configuration of a trap according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing an entire configuration of a conventional trap.

[Explanation of symbols]

 Reference Signs List 10 vacuum chamber 12 vacuum pump 26 exhaust gas treatment device 102 trap container 106 baffle 134 pulse tube refrigerator 137 cold head

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiro Fukasaku 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside Ebara Research Institute Co., Ltd.

Claims (8)

[Claims] An airtight chamber, a trap container provided in a vacuum evacuation system having a vacuum pump for evacuating the chamber, a baffle plate forming a non-linear flow path in the trap container, A pulse tube refrigerator for cooling the baffle plate, wherein the baffle plate is thermally coupled to a cold head of the pulse tube refrigerator. 2. The trap for removing precipitates according to claim 1, wherein the vacuum exhaust system has an exhaust gas treatment device. 3. The trap for removing precipitates according to claim 1, wherein said chamber is a process chamber of a semiconductor manufacturing apparatus. 4. The trap according to claim 1, wherein the vacuum pump is a dry pump that does not use a lubricating oil in an exhaust path. 5. The trap according to claim 1, wherein the trap container is disposed between a chamber in the evacuation system and a vacuum pump. 6. The vacuum pump is of a multi-stage boost type,
2. The trap for removing precipitates according to claim 1, wherein the trap container is arranged between the plurality of vacuum pumps. 7. The trap for removing precipitates according to claim 2, wherein the trap container is disposed between the vacuum pump and the exhaust gas treatment device. 8. The trap for removing precipitates according to claim 2, wherein the trap container is disposed downstream of the exhaust gas treatment device.