JP2002217166A - Cleaning method of gas processing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively clean a stacked material in a circulation path in a gas processing equipment in which gas is circulated and recycled. SOLUTION: A cleaning method is provided for cleaning the gas processing equipment which comprises a processing unit 11 for carrying out a fixed process by introducing a process gas, a first exhaust unit 22, a secondary exhaust unit 23, first piping 25 and 28 for supplying a portion of an exhausted gas from the first exhaust unit and a secondary piping 27 branched from a first piping and connected to a secondary exhaust unit. The equipment has a gas circulation function of carrying out a fixed process to circulate a process gas from the gas exhaust unit of the processing unit to the gas inlet part of the processing unit through the first exhaust unit and the first piping. In the cleaning method of the gas processing equipment, times required for carrying out a fixed process by circulating the process gas in the circulation path are added up and the stacked material stacked at least in the circulation path is removed by a dry cleaning process at a stage when the added up time approaches a fixed time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a gas processing apparatus in which a gas is circulated and reused.

[0002]

2. Description of the Related Art In recent years, there has been proposed a method of circulating and reusing a processing gas in a plasma etching apparatus or the like in order to reduce the amount of processing gas used or discharged (for example, Japanese Patent Application Laid-Open No. 9-251981). No.).

For example, in an RIE process for an oxide film, PFC (Per-Fluoro Compound) is used as a processing gas. However, if a long-time etching process is performed using PFC, a thick fluorocarbon film is formed in a chamber (processing chamber). accumulate. When the thickness of the deposited film becomes a certain value or more, the film is peeled off, causing dust. Normally, when the integrated time of the discharge in the etching process reaches a certain time, the deposits accumulated in the chamber are wiped and cleaned to prevent generation of dust.

On the other hand, a fluorocarbon film is deposited in the processing gas circulation system by a long-time treatment, and the deposited film may be peeled off and introduced into the chamber to cause dust. Further, since the gas circulation increases the use efficiency of the processing gas higher than usual, the concentration of the etching product (such as SiF ₄ ) in the exhaust gas is higher than usual, and the deposited film containing Si or SiO ₂ circulates. It may cause clogging of pumps and valves installed in the system. Unlike a chamber that is originally assumed to be periodically cleaned and can be easily opened, the piping and the like of the circulation system have a fixed structure, and the internal structure is also complicated. For this reason, it is not easy to confirm the state of film deposition inside as well as cleaning.

[0005]

As described above, in the gas processing apparatus that circulates and reuses gas, sufficient consideration is not given to cleaning of deposits in the circulation path, and a large cause of dust and the like is not considered. Had become.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. In a gas processing apparatus that circulates and reuses gas, a cleaning method capable of effectively cleaning deposits in a circulation path. It is intended to provide a way.

[0007]

According to the present invention, there is provided a cleaning method for a gas processing apparatus, comprising: a processing section for performing a predetermined process by introducing a processing gas; and a first exhaust section for exhausting the gas from the processing section. A second exhaust unit that exhausts gas from the first exhaust unit to the outside, and a first piping unit that supplies a part of the gas exhausted from the first exhaust unit to the processing unit. ,
A second pipe section branched from the first pipe section and connected to the second exhaust section, and a gas exhaust section of the processing section is provided through the first exhaust section and the first pipe section. A method of cleaning a gas processing apparatus having a gas circulation function of performing a predetermined process by circulating a processing gas through a circulation path leading to a gas introduction unit of the processing unit, wherein the processing gas is circulated through the circulation path. The time during which the predetermined process is performed is accumulated, and at the stage when the accumulated time reaches the predetermined time, at least deposits accumulated in the circulation path by the dry cleaning process are removed.

The cleaning method for a gas processing apparatus according to the present invention includes a processing section for performing a predetermined process by introducing a processing gas; a first exhaust section for exhausting gas from the processing section; The second to exhaust the gas from the exhaust section to the outside
An exhaust unit, a first piping unit that supplies a part of the gas exhausted from the first exhaust unit to the processing unit, and a branch from the first piping unit to the second exhaust unit. A second piping section connected to the first section and a first section from the gas discharge section of the processing section.
A method of cleaning a gas processing apparatus having a gas circulation function of performing a predetermined process by circulating a processing gas through a circulation path leading to a gas introduction unit of the processing unit via the exhaust unit and the first piping unit. Circulating the process gas through the circulation path to perform the predetermined process, and detecting a deposition state of deposits deposited at a predetermined location of the first pipe portion or the second pipe portion by the process; At the stage when it is detected that the deposition state has reached a predetermined state, at least deposits deposited on the circulation path are removed by dry cleaning processing.

In the above invention, the first piping portion and the second piping portion include, in addition to the piping itself, valves and the like when the piping and the like are provided in the middle of the piping.

Further, in the above invention, the circulation path (particularly, the first piping section) is formed by the dry cleaning process.
In addition to the above, it is preferable to further remove deposits deposited on the second pipe portion.

As described above, according to the present invention, the processing gas is circulated to accumulate the time during which a predetermined process such as an etching process is performed, or the accumulation of deposits deposited at a predetermined location by the predetermined process such as an etching process. The state is detected, and when the accumulated time reaches a predetermined time or when the deposition state reaches a predetermined state, the deposits deposited on the circulation path and the like by the dry cleaning process are removed, so that it is efficient at an optimal time. It is possible to clean deposits. Therefore, it is possible to reduce the dust caused by the deposits in the circulation path without lowering the operation rate of the apparatus and increasing the maintenance cost, and it is possible to improve the yield of semiconductor devices and the like. .

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a gas circulation system according to an embodiment of the present invention. Hereinafter, a cleaning process in a parallel plate type RIE apparatus for etching a silicon oxide film or the like will be described as an example.

In a chamber (processing chamber) 11, an upper electrode 12 and a lower electrode 13 serving as electrodes for applying a high frequency are arranged to face each other. The upper electrode 12 is provided with a shower head 14, and the lower electrode 13 is provided with a matching device 15.
The high frequency power supply 16 is connected via the. Upper electrode 1
A high-frequency discharge is generated between the lower electrode 1 and the lower electrode 13 to activate a source gas for etching.
In addition to performing etching on the sample (semiconductor wafer or the like) 17 placed on 3 and cleaning the circulation system,
The cleaning source gas can be activated by high-frequency discharge and supplied to the circulation system.

A variable valve 21 for adjusting pressure is connected to the chamber 11, and the pressure in the chamber 11 can be kept constant by adjusting the opening of the valve 21.

An exhaust device 22 for gas circulation is connected to the gas exhaust side of the chamber 11, and an exhaust device 23 for exhausting a gas to the outside through a pipe or the like described later is connected to the exhaust device 22. Is connected. Exhaust device 22
For example, a turbo molecular pump or a Roots type pump can be used, and for the exhaust device 23, for example, a dry pump can be used.

Between the exhaust device 22 and the exhaust device 23,
A variable valve 24 for adjusting the back pressure of the exhaust device 22 is provided. Also, a pipe 25 on the gas exhaust side of the exhaust device 22
Is branched into a pipe 27 toward the exhaust device 23 and a pipe 28 for gas circulation at a branch point 26, and the gas circulation rate can be adjusted by adjusting the opening of the variable valve 24 for adjusting the back pressure. Is possible.

A pipe 31 for introducing a source gas for etching or a source gas for cleaning into the chamber 11 is connected to the chamber 11. The source gas for the etching process is supplied from a gas source 32 composed of a gas cylinder or the like to a mass flow controller 3.
3 and a valve 34, the source gas for the cleaning process is supplied from a gas source 35 such as a gas cylinder.
From the mass flow controller 36 and the valve 37. By changing the processing conditions of the etching process and the cleaning process, it is also possible to share the source gas for the etching process or the source gas for the cleaning process. It is also possible to make them common.

The above-described components are controlled by a control device 41. In addition, the control device 41 integrates the time spent in the etching process (the time during which etching was performed without performing gas circulation, the time during which etching was performed while performing gas circulation, and the total time of both).
A function is provided for making a predetermined notification when the accumulated time reaches a predetermined time. In addition, piping 25,
Based on the detection result by the predetermined detecting means, it is determined that the deposited state of the deposit deposited on the predetermined position of the pipe 27, the pipe 28, or a valve (for example, the valve 24) disposed in the pipe system has reached a predetermined state. May be provided.

Next, an example of a specific process when the cleaning process is performed using the system shown in FIG. 1 will be described.

In this embodiment, the etching process is performed in the normal mode in which the gas is not circulated in the process in which the etching time is less than 15 seconds, and in the gas circulation mode in which the gas is circulated in the process in which the etching time is 15 seconds or more. Was. This is because it has been confirmed that the gas circulation mode is advantageous in the process of about 15 seconds or more in consideration of the reduction of the supply and discharge of the PFC gas and the throughput of the apparatus.

For example, in the contact etching step in which the etching time is 30 seconds, the gas circulation mode is used, and a gas introduction system including a gas source 32, a mass flow controller 33, a valve 34, and a pipe 31 is supplied to the chamber 11.
CF ₄ / O ₂ / Ar was introduced at a flow rate of 16/2/40 sccm as a raw material gas for etching, a high frequency power of 1200 W and a chamber pressure of 40 mTorr were used.
The oxide film formed on the semiconductor wafer was etched. At this time, the opening degree of the variable valve 24 is adjusted so that the pressure in the circulation pipe becomes 5 Torr, and the gas circulation rate (Q2 / (Q1 + Q2)) is adjusted so that the total gas flow rate into the chamber 11 becomes 290 sccm. ) 80% treatment.

In another process having an etching time of 12 seconds, the etching process was performed in a normal mode without gas circulation. At this time, the amount of the raw material gas CF ₄ / O ₂ / Ar introduced into the chamber from the gas introduction system is 80/10 /
It was 200 sccm.

As described above, while the etching process is performed in the normal mode or the gas circulation mode, the control device 4
In step 1, the integrated time of the etching process in each of the normal mode and the gas circulation mode was managed.

When the sum of the integrated times of the etching process in the normal mode and the etching process in the gas circulation mode has reached 70 hours, a predetermined message indicating this fact is sent from the control device 41. At this stage, the inside of the chamber 11 was opened to the atmosphere, and a cleaning process of a deposited film such as a fluorocarbon film deposited in the chamber 11 was performed.

When the integrated time of the etching process in the gas circulation mode reached 200 hours, the circulating system was dry-cleaned as follows.

First, the raw material gas for cleaning SF ₆ /
The O ₂ gas flow rate was 200/20 sccm, and the gas was introduced into the chamber 11 from the gas introduction system. The pressure in the chamber 11 was controlled at 500 mTorr, and plasma discharge was performed with high frequency power of 800 W. At this time, the opening of the variable valve 24 was controlled so that the pressure in the circulation pipe became 5 Torr. By the action of the fluorine radical (F ^* ) generated by the high-frequency discharge, the chamber 11, the valve 21,
Exhaust device 22, pipes 25, 27 and 28, variable valve 2
The deposited film mainly composed of Si such as Si or SiO adhered to the inside of the substrate ₄ was removed by etching by the reaction of Si + 4F ^* → SiF ₄ , thereby preventing problems such as film peeling and clogging in advance.

Next, the raw material gas for cleaning CF ₄ /
The O ₂ gas flow rate was set to 5/200 sccm, and the gas was introduced into the chamber 11 from the gas introduction system. The pressure in the chamber 11 was controlled to 500 mTorr, and plasma discharge was performed at a high frequency power of 1200 W. At this time, the opening of the variable valve 24 is controlled so that the pressure in the circulation pipe becomes 1 Torr,
The oxygen radicals (O ^* ) generated by the high-frequency discharge in the chamber 11 were made to reach as far as possible without being deactivated. Due to the action of oxygen radicals generated by the high-frequency discharge, the deposited film mainly composed of C adhered to the inside of the chamber 11, the valve 21, the exhaust device 22, the pipes 25, 27 and 28, and the variable valve 24, becomes C + O ^* → C
It was removed by etching by the reaction of O, C + O ₂ → CO ₂ , and problems such as film peeling and clogging could be prevented in advance.

As described above, by performing dry cleaning of the circulation system at the stage when the integrated time of the etching process in the gas circulation mode has reached the predetermined time, a decrease in the yield of semiconductor devices due to dust generated due to film peeling or the like can be prevented. In addition to being prevented, maintenance of pipes, valves, pumps, and the like can be performed efficiently.

When performing the cleaning process, it is preferable that a new reaction product (SiF ₄ ) is not generated as much as possible from inside the chamber. Therefore, it is preferable to use a wafer on which a film not containing Si and having a low etching rate is formed as a wafer placed on the lower electrode to protect the lower electrode. In addition, when a wafer having a silicon oxide film formed thereon is used, it is preferable that the discharge conditions be such that ion energy is suppressed as much as possible.

In a system in which SF ₆ is not supplied as described above, if it is desired to reduce the cost of supplying SF ₆ exclusively for etching, it is possible to substitute SF ₆ with CF ₄ .

Further, according to the components of the deposited film which change depending on the operation of the system, the time distribution of the cleaning process mainly comprising fluorine radicals and the cleaning process mainly comprising oxygen radicals are optimized, and the respective cleaning processes are alternately performed. It may be performed a plurality of times.

Next, another example of the specific processing when the cleaning processing is performed using the system shown in FIG. 1 will be described.

In the above-described example, the cleaning timing of the circulation system is determined based on an empirical cleaning cycle. In this example, the state of film deposition at a location that limits the cleaning cycle is monitored. Thus, the cleaning time is determined. The location to be monitored is preferably a location where film deposition is easy, that is, a location where pressure is high. Specifically, it is preferable to monitor the state of film deposition on the downstream side of the exhaust device 22, that is, at predetermined locations of the pipes 25, 27 and 28 or at the variable valve 24.

In one system, it was found that the rate at which the cleaning cycle was controlled was determined by the fact that the deposited film in the variable valve 24 shown in FIG. In this variable valve 24, when the deposited film becomes thicker, the conductance changes in a state where the valve is almost fully closed. Therefore, the film deposition state was monitored as follows.

Periodically, for example, once a week, the circulating gas flow rate becomes a specified flow rate under high circulation rate conditions.
The opening of the variable valve 24 was controlled and monitored. Specifically, N ₂ gas is supplied from the pipe 31 to the chamber 1.
20 is introduced into the chamber 1 and the opening of the variable valve 24 is adjusted so that the circulation rate becomes 95%.
When the opening of No. 4 became plus 10% with respect to the opening immediately after cleaning of the circulating system, dry cleaning of the circulating system was performed.

If the film deposition near the outlet of the compressed gas (point A in FIG. 1) on the downstream side of the exhaust device 22 composed of a turbo molecular pump limits the cleaning cycle, the film at this location is determined. Monitoring the state of deposition is effective. In particular, when the deposited film affects the rotation performance of the pump, it is possible to monitor the film deposition state by monitoring the rotation speed of the pump or the current supplied to the pump.

Further, the pipe 25, the pipe 27 or the pipe 28
It is also possible to monitor the state of film deposition by monitoring the film thickness of the deposited film inside by optical means. An example is shown in FIG. In this example, an optical means is provided at the point A of the pipe 25. That is, transparent glass windows 51 and 52 are provided facing the pipe 25, and light from the light source 53 provided in the glass window 51 is received by the light receiving element 54. The inner wall of the pipe 25, that is, the glass window 51
The thickness of the deposited film can be detected by utilizing the fact that the amount of light received by the light receiving element 54 changes in accordance with the thickness of the deposited film adhered to the inner wall of the first and second layers 52.

As described above, in this embodiment, by monitoring the deposited state of the deposited film, such as the thickness of the deposited film, the circulating system can be operated even if the operation of the etching process is changed in the middle such as when the product is changed. It is possible to accurately ascertain the time for performing the dry cleaning.

In the above-described embodiment, an example has been described in which dry cleaning is performed by fluorine radicals or oxygen radicals generated by high-frequency discharge. However, even if the dry cleaning is not activated by high-frequency discharge, a deposit containing silicon can be removed by the gas itself. A gas that can be dry-etched may be used.

For example, when cleaning a silicon oxide film-based deposited film, it is effective to use HF gas. With HF gas, the etching rate of a silicon oxide film can be obtained about 10 to 100 times, and since there is no need to perform discharge in the chamber, the silicon wafer placed on the lower electrode is not etched, and SiF
₄ is never generated. In this case, HF gas may be introduced from the pipe 31 into the chamber 11 and circulated, but may be circulated in the gas circulation path, for example, the exhaust device 22.
Alternatively, a pipe 29 may be connected to the downstream side, and HF gas may be introduced from the pipe 29.

The gas capable of etching the deposit containing silicon without being activated by the discharge is H.
In addition to F gas, F ₂ gas or ClF ₃ gas can be used.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the gist thereof. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent elements. For example, even if some constituent elements are deleted from the disclosed constituent elements, they can be extracted as an invention as long as a predetermined effect can be obtained.

[0044]

According to the present invention, deposits can be efficiently cleaned at an appropriate time, and the generation of dust due to deposits in the circulation path can be effectively prevented. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a gas circulation system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example in which the thickness of a deposited film is monitored by optical means in the gas circulation system shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Chamber 12 ... Upper electrode 13 ... Lower electrode 14 ... Shower head 15 ... Matching device 16 ... High frequency power supply 17 ... Semiconductor wafer 21, 24, 34, 37 ... Valve 22, 23 ... Exhaust device 25, 27, 28, 29, DESCRIPTION OF SYMBOLS 31 ... Piping 26 ... Branch point 32,35 ... Gas source 33,36 ... Mass flow controller 41 ... Control device 51,52 ... Glass window 53 ... Light source 54 ... Light receiving element

Claims (10)

[Claims] A processing unit that performs a predetermined process by introducing a processing gas; a first exhaust unit that exhausts gas from the processing unit; and a gas that exhausts the gas from the first exhaust unit to the outside. A second exhaust unit; a first piping unit that supplies a part of the gas exhausted from the first exhaust unit to the processing unit; and a second exhaust unit that branches off from the first piping unit. A second piping section connected to the processing section, wherein a processing gas is provided in a circulation path from a gas discharge section of the processing section to a gas introduction section of the processing section via the first exhaust section and the first piping section. A method of cleaning a gas processing apparatus having a gas circulation function of circulating gas and performing the predetermined processing, wherein the processing gas is circulated through the circulation path to accumulate a time during which the predetermined processing is performed, and the integration is performed. When the time reaches the specified time, dry cleaning The cleaning method of the gas processing device characterized by removing at least the deposits deposited on the circulating path. 2. A processing section for performing a predetermined process by introducing a processing gas, a first exhaust section for exhausting gas from the processing section, and exhausting gas from the first exhaust section to the outside. A second exhaust unit; a first piping unit that supplies a part of the gas exhausted from the first exhaust unit to the processing unit; and a second exhaust unit that branches off from the first piping unit. A second piping section connected to the processing section, wherein a processing gas is provided in a circulation path from a gas discharge section of the processing section to a gas introduction section of the processing section via the first exhaust section and the first piping section. A cleaning method for a gas processing apparatus having a gas circulation function of performing the predetermined processing by circulating the processing gas, wherein the processing gas is circulated through the circulation path to perform the predetermined processing, and the processing performs the first processing. Deposits of deposits deposited at predetermined locations in the pipe section or the second pipe section Detects, at the stage where the deposition condition is detected that reaches a predetermined state, the cleaning method of the gas processing device characterized by removing at least said deposited circulation path Deposits by dry cleaning process. 3. The deposit state of the deposit is detected based on a film thickness of the deposit at a predetermined location in the first piping section or the second piping section. A cleaning method for a gas processing apparatus according to the above. 4. A variable valve for adjusting a back pressure of the first exhaust unit is provided in the second piping unit, and a predetermined flow rate of gas is supplied to the circulation path in the circulation path. The method for cleaning a gas processing apparatus according to claim 2, wherein the detection is performed based on the opening when the opening of the variable valve is adjusted so as to flow. 5. The dry cleaning process is performed by at least one of a gas containing fluorine capable of etching a deposit containing silicon and a gas containing oxygen capable of etching a deposit containing carbon. Item 3. The method for cleaning a gas processing apparatus according to Item 1 or 2. 6. The gas processing apparatus according to claim 5, wherein the dry cleaning process is performed by alternately flowing the gas containing fluorine and the gas containing oxygen through the circulation path at least once or more. Cleaning method. 7. The method according to claim 1, wherein the gas containing fluorine is a gas containing active species of fluorine generated by discharge, and the gas containing oxygen is a gas containing active species of oxygen generated by discharge. The method for cleaning a gas processing apparatus according to claim 5, wherein 8. The cleaning method for a gas processing apparatus according to claim 5, wherein the gas containing fluorine is a gas capable of etching a deposit containing silicon without being activated by electric discharge. 9. A gas capable of etching a deposit containing silicon without being activated by the discharge is HF or F _2.
9. The method for cleaning a gas processing apparatus according to claim 8, wherein the cleaning method is ClF ₃ . 10. A cleaning method for a gas processing apparatus according to claim 8, wherein a gas capable of etching a deposit containing silicon without being activated by said discharge is introduced from a predetermined portion of said circulation path. .