JP5076164B2 - Cleaning method for semiconductor manufacturing equipment - Google Patents

Description

  The present invention relates to a method for cleaning a semiconductor manufacturing apparatus.

Conventionally, when a photoresist film formed on a semiconductor wafer is peeled off, SPM (Sulfuric acid), which is a chemical solution in which hydrogen peroxide (H ₂ O ₂ ) and sulfuric acid (H ₂ SO ₄ ) are mixed, is used. -Hydrogen Peroxide Mixture) solution is widely used (see Patent Document 1).

Sulfuric acid alone has a cleaning effect, but when mixed with hydrogen peroxide, the following reaction occurs, and as a result, CARO acid (H ₂ SO ₅ ) is generated and a strong cleaning effect can be obtained.

2H ₂ SO ₄ + H ₂ O ₂ → H ₂ SO ₄ + H ₂ SO ₅ + H ₂ O
CARO acid (H ₂ SO ₅ ) produced by this reaction is a compound having a very strong oxidizing power. By the action of this CARO acid, the resist is peeled off from the wafer surface and simultaneously decomposed into carbon dioxide (CO ₂ ) and escapes from the SPM solution. This process is called resist stripping process.

However, when the concentration of CARO acid is low, there is a problem that the resist peeled off from the wafer remains in the SPM solution without being decomposed by CARO acid and adheres to the wafer surface to be processed next as particles (residual foreign matter). It was. Although the particles adhering to the wafer surface are as small as about several tens of nanometers, in recent years, the semiconductor manufacturing process has been refined, which may affect the quality of the element. For example, depending on the processing step, it may become an etching inhibitor or cause swelling during film growth, which may cause defects that affect the product yield.
U.S. Pat. No. 3,900,367

  A system in which a plurality of wafers are processed together by a single resist stripping process is called a batch processing system. In this batch processing method, the SPM liquid in the processing tank is usually replaced after being used a plurality of times. The reason is that there are many SPM liquids used for one resist peeling process. Another reason is that the SPM solution takes a long time for the drainage process, and if the SPM solution is replaced every time it is used, the processing capacity of the apparatus is reduced.

For this reason, the SPM liquid is usually replaced after being used a plurality of times. However, as the number of times the SPM liquid is used increases, there is a problem that residual foreign matter in the tank gradually accumulates and cannot be ignored. FIG. 5 is a graph showing the relationship between the number of times the SPM liquid is used and the number of particles. The horizontal axis indicates the number of times the SPM liquid is used, that is, the number of resist stripping processes performed using the same SPM liquid. The vertical axis represents the ratio of the number of particles when the number of particles when the number of times the SPM liquid is used is 1 is 1. FIG. 5 shows a wafer removal process using an APM (Ammonia-Hydrogen Peroxide Mixture) solution, which is a chemical solution obtained by mixing ammonia (NH ₃ ), hydrogen peroxide solution, and water after resist stripping with an SPM solution. This is obtained by cleaning and obtaining the number of particles adhering to the cleaned wafer. As can be seen from FIG. 5, the number of particles increases as the number of times the SPM liquid is used. In addition, there has been a problem that residual foreign matters when the SPM liquid is used a plurality of times are gradually accumulated not only in the tank but also in the circulation system of the apparatus and are difficult to remove.

  An object of the present invention is to provide a method for cleaning a semiconductor manufacturing apparatus that can keep the inside of the semiconductor manufacturing apparatus clean.

According to one aspect of the present invention, there is provided a semiconductor manufacturing apparatus cleaning method for cleaning a semiconductor manufacturing apparatus that performs a resist stripping process on a substrate a plurality of times using a resist stripping chemical solution in which sulfuric acid and hydrogen peroxide are mixed. there, after the resist stripping treatment is performed, before the next of the resist stripping process is performed, the hydrogen peroxide solution was added to the resist stripping liquid chemical used in the resist stripping process, the peroxide Using the resist stripping chemical solution to which hydrogen water has been added, removing foreign matter generated by the resist stripping process, and discharging the resist stripping chemical solution used for removing the foreign matter from the semiconductor manufacturing apparatus. A cleaning method for a semiconductor manufacturing apparatus is provided.

  According to the present invention, an SPM solution in which hydrogen peroxide solution is sufficiently mixed with sulfuric acid, that is, a cleaning chemical solution having a high CARO acid concentration is used to clean the SPM tank and the piping through which the SPM solution circulates. Can be sufficiently decomposed and removed. Moreover, according to the present invention, the SPM liquid immediately before draining, that is, the SPM liquid having a sufficiently high CARO acid concentration by adding hydrogen peroxide water sufficiently to the SPM liquid that has been subjected to the resist stripping treatment a plurality of times. Since the liquid is generated and the chemical liquid is used for cleaning, the particles can be frequently decomposed and removed. Therefore, according to the present invention, the semiconductor manufacturing apparatus that performs the resist stripping process using the SPM liquid can be kept extremely clean.

[One Embodiment]
A semiconductor manufacturing apparatus cleaning method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic view showing a tank configuration of the semiconductor manufacturing apparatus according to the present embodiment. FIG. 2 is a flowchart showing the cleaning method of the semiconductor manufacturing apparatus according to the present embodiment.

  First, the tank configuration of the semiconductor manufacturing apparatus according to the present embodiment will be described with reference to FIG.

  The semiconductor manufacturing apparatus according to the present embodiment is provided with an inner tank 10 that performs a resist stripping process on a wafer and an outer tank 12 that stores SPM liquid overflowing from the inner tank 10.

  Further, a preliminary temperature adjustment tank 14 for temporarily storing sulfuric acid supplied to the inner tank 10 is provided. A pipe 16 is provided between the preliminary temperature control tank 14 and the inner tank 10. The pipe 16 is provided with a valve 18.

  A pipe 20 is provided between the sulfuric acid supply port and the preliminary temperature control tank 14. The pipe 20 is provided with a valve 22.

  The inner tank 10 is provided with a pipe 24 for supplying hydrogen peroxide water. The pipe 24 is provided with a valve 26.

  This pipe 24 is provided with a pipe 28 branched in the middle, and this pipe 28 is provided to the outer tank 12. The pipe 28 is provided with a valve 30.

  Further, the outer tank 12 is provided with a pipe 32 for replenishing sulfuric acid. The pipe 32 is provided with a valve 34.

  A draining pipe 36 is connected to the inner tank 10. Further, a drain pipe 38 is connected to the outer tub 12.

  The pipe 36 is provided with a valve 40 for draining the solution in the inner tank 10. The pipe 38 is provided with a valve 42 for discharging the solution in the outer tub 12.

  The pipe 36 and the pipe 38 are combined to form a pipe 44. The piping 44 is provided with a circulation pump 46, a valve 45, and a filter 48. The SPM liquid is returned to the inner tank 10 through the filter 48 by the circulation pump 46. The valve 45 causes the solution to reach the inner tank 10 via the filter 48 when the solution in the inner tank 10 or the outer tank 12 is drained via the pipe 50 using the circulation pump 46. It is for preventing.

  A pipe 50 for drainage branches from the pipe 44. The pipe 50 is provided with a valve 52.

  Next, the cleaning method of the semiconductor manufacturing apparatus according to the present embodiment will be explained with reference to the flowchart of FIG.

  First, although not shown in the flowchart, sulfuric acid is stored in the preliminary temperature control tank 14 in advance. The valve 22 is opened and sulfuric acid is stored in the preliminary temperature control tank 14 via the pipe 20.

  Next, the valve 26 is opened, and hydrogen peroxide solution is injected into the inner tank 10 through the pipe 24 (step S10).

  Next, the sulfuric acid stored in the preliminary temperature control tank 14 is dropped into the inner tank 10 through the pipe 16 by opening the valve 18 (step S11).

  In this manner, an SPM solution (resist stripping solution) that is a solution obtained by mixing hydrogen peroxide and sulfuric acid is generated in the inner tank 10.

  Using this SPM solution, the resist is removed from the wafer (step S12). This process is a batch process in which a plurality of wafers are processed simultaneously by a single resist stripping process. The wafer is immersed in the SPM liquid in the inner tank 10 to remove the resist attached to the surface of the wafer. The SPM liquid overflowing from the inner tank 10 during the processing is accumulated in the outer tank 12. The SPM liquid collected in the outer tub 12 is discharged from the pipe 38 with the valve 42 opened. The SPM liquid discharged from the outer tank 12 is sent to the pipe 44 by the circulation pump 46, and is returned to the inner tank 10 again through the valve 45 and the filter 48 in the opened state.

  In this embodiment, the SPM solution is used a plurality of times in batch processing and then replaced with a new SPM solution.

  For this reason, every time the resist stripping process is completed, it is determined whether or not the SPM liquid needs to be replaced. First, it is set in advance how many times the same SPM liquid is used, and the liquid exchange is performed. Then, the number of times the SPM liquid has been used so far is compared with the number of times of replacement use (step S13).

  As a result, if the number of times of use of the SPM liquid has not reached the number of times of replacement use, the process returns to step S12 and a resist stripping process is performed on a new wafer using the same SPM liquid. On the other hand, when the number of times of use of the SPM liquid has reached the number of times of replacement use, the SPM liquid is drained and replaced.

  When the resist stripping process is repeated with the SPM liquid, minute foreign matters (particles) accumulate in the SPM tank, the circulation pipe, and the filter portion. However, it is not always possible to sufficiently remove these minute foreign substances only by replacing the SPM liquid. Therefore, in the present embodiment, a treatment for decomposing and removing foreign matters is added by increasing the concentration of CARO acid in the SPM liquid by supplementing the SPM liquid before replacement with hydrogen peroxide. The purpose of this process is to remove foreign substances accumulated in the tank and maintain the cleanliness of the tank, and therefore it is not always necessary to perform this process every time the SPM liquid is replaced.

  Therefore, it is set in advance how many times the liquid exchange is performed and the tank is cleaned, and this is set as the number of times of cleaning replacement. Then, the number of times the SPM liquid has been replaced so far is compared with the number of times the cleaning has been replaced (Step S14).

  As a result, if the number of replacements of the SPM liquid does not reach the number of replacements for cleaning, the SPM liquid is discharged to perform only normal liquid replacement (step S15). The valve 40 is opened, and the SPM liquid in the inner tank 10 is discharged to the pipe 36. Similarly, the valve 42 is opened and the SPM liquid in the outer tub 12 is discharged to the pipe 38. The two pipes 36 and 38 are coupled to the pipe 44. When draining the SPM liquid, the pump 46 is operated. The pump 46 is operated in a state where the valve 45 is closed so that the SPM liquid does not return into the inner tank 10 through the filter 48. Then, the valve 52 is opened and the SPM liquid is drained through the pipe 50. And it returns to step S10 and produces | generates a new SPM liquid.

  On the other hand, when the number of replacements of the SPM liquid reaches the number of replacements for cleaning, a cleaning process is performed using the SPM liquid before replacement.

  First, the valve 42 is opened, and a certain amount of SPM liquid is discharged from the outer tank 12 to the pipe 38. Then, the valve 52 is opened, and a certain amount of SPM liquid is drained through the pipe 50 (step S16).

  Next, the valve 30 is opened, and hydrogen peroxide solution is replenished to the outer tank 12 by a certain amount via the pipe 28 (step S17). At this time, if hydrogen peroxide solution is replenished at a time, there is a risk of sudden reaction with sulfuric acid and bumping, so a small amount of hydrogen peroxide solution is replenished to the outer tank 12 by a certain amount.

  Then, it is determined whether or not the total amount of the hydrogen peroxide solution replenished in the outer tub 12 has reached the amount of the SPM liquid drained in step S16 (step S18).

  As a result, if the total amount of the hydrogen peroxide solution replenished to the outer tank 12 does not reach the amount of the SPM liquid drained in step S16, the process returns to step S17 and the hydrogen peroxide solution is replenished to the outer tank 12 again. .

  On the other hand, when the total amount of the hydrogen peroxide solution replenished to the outer tank 12 reaches the amount of the SPM solution drained in step S16, the valve 30 is closed to complete the replenishment of the hydrogen peroxide solution, and the SPM solution is circulated. The apparatus is cleaned (step S19). First, the valve 42 is opened, and the SPM liquid in the outer tank 12 supplemented with hydrogen peroxide is discharged to the pipe 38. Then, the SPM liquid supplemented with the hydrogen peroxide solution is sent to the pipe 44 by the circulation pump 46, and sent to the inner tank 10 through the valve 45 and the filter 48 in the opened state. In this way, the SPM liquid supplemented with the hydrogen peroxide solution is supplied to the inner tank 10. Then, the SPM liquid is discharged to the pipe 36 by opening the valve 40 and merges again into the pipe 38 connected to the outer tank 12.

  This circulation is repeated for a certain time to clean the SPM tank and the piping through which the SPM liquid circulates.

  When the apparatus is cleaned with the SPM liquid supplemented with hydrogen peroxide, the valves 40, 42 and 52 are opened to drain the SPM liquid (step S20).

  By this cleaning treatment, foreign substances (particles) accumulated in the SPM tank and the circulation system in which the resist is repeatedly peeled can be decomposed. However, in such a cleaning process, all foreign matters accumulated in the apparatus cannot be decomposed. Therefore, in the present embodiment, a process for decomposing and removing foreign substances accumulated in the apparatus is added by increasing the concentration of hydrogen peroxide water and circulating a chemical solution in which the CARO acid concentration in the SPM solution is set sufficiently high. To do.

  As a result of the cleaning process performed in step S19, when the foreign matter in the apparatus is not sufficiently removed and remains in the apparatus, the apparatus is cleaned with a chemical solution having a sufficiently high CARO acid concentration in the SPM solution.

  Therefore, first, the amount of foreign matter (particles) remaining in the apparatus is measured. More specifically, the amount of foreign matter in the SPM liquid is measured. Then, it is compared with a reference value (predetermined value) set in advance, and it is determined whether or not cleaning with a chemical solution is performed (step S21).

  As a result, if it is determined that the amount of foreign matter remaining in the apparatus is equal to or less than the reference value and it is not necessary to perform the cleaning process with the chemical liquid, the process returns to step S10 to generate a new SPM liquid.

  On the other hand, if the amount of foreign matter remaining in the apparatus exceeds the reference value, the apparatus is cleaned by circulating a chemical solution having a sufficiently high concentration of CARO acid in the SPM solution.

  Foreign substances accumulated in the SPM tank and circulation system where resist stripping has been repeated can be decomposed by increasing the concentration of the hydrogen peroxide solution and circulating a chemical solution with a sufficiently high CARO acid concentration in the SPM solution. it can.

  First, sulfuric acid and hydrogen peroxide solution are respectively injected into the inner tank 10 and the outer tank 12 (step S22). The ratio of sulfuric acid and hydrogen peroxide solution injected into the inner tank 10 and the outer tank 12 is, for example, 4: 1. As a result, an SPM solution (cleaning chemical solution) in which 20% of hydrogen peroxide is mixed is generated. In this way, a cleaning SPM liquid (cleaning chemical) having a sufficiently high CARO acid concentration is obtained.

  Since hydrogen peroxide gradually evaporates from the SPM liquid, the concentration of hydrogen peroxide in the SPM liquid gradually decreases. For this reason, even if 20% of hydrogen peroxide is mixed when generating the SPM liquid, the concentration of hydrogen peroxide in the SPM liquid is not maintained at 20% for a long time. The SPM liquid in which 20% hydrogen peroxide water is mixed means that the mixing ratio of the hydrogen peroxide water in generating the SPM liquid is 20%.

  Then, this cleaning chemical is circulated to clean the inside of the apparatus (step S23). The valve 40 is opened and the cleaning chemical in the inner tank 10 is discharged to the pipe 36. Next, the valve 42 is opened, and the cleaning chemical in the outer tub 12 is discharged to the pipe 38. The two pipes 36 and 38 are coupled to the pipe 44. Then, the cleaning chemical is sent to the filter 48 by the circulation pump 46 through the valve 45 in the opened state, and is sent to the inner tank 10 again.

  This circulation is repeated for a certain time to clean the SPM tank and the piping through which the SPM liquid circulates.

  Then, when the cleaning of the apparatus with the SPM liquid (cleaning chemical liquid) in which the CARO acid concentration is set to be sufficiently high is completed, the valves 40, 42 and 52 are opened to drain the cleaning chemical liquid (step S24).

  Thereafter, the process returns to step S10, a new SPM solution is generated, and a resist stripping process is appropriately performed.

  FIG. 3 is a graph showing the effect of the cleaning process using the cleaning chemical. In FIG. 3, “before cleaning” indicates the number of particles observed when resist stripping is performed using a semiconductor manufacturing apparatus before cleaning with a cleaning chemical, and “after cleaning” indicates cleaning chemical. The number of particles observed when the resist stripping process is performed using the semiconductor manufacturing apparatus after performing the cleaning by the above is shown. The vertical axis represents the ratio of the number of particles when the number of particles observed when the resist is peeled off using the semiconductor manufacturing apparatus before cleaning with the cleaning chemical is 1. FIG. 3 is obtained by cleaning the wafer with the APM solution after performing the resist stripping process with the SPM solution and determining the number of particles adhering to the cleaned wafer.

  As can be seen from FIG. 3, the particles are sufficiently decomposed and removed by washing with an SPM solution in which hydrogen peroxide is sufficiently mixed with sulfuric acid, that is, a cleaning chemical solution having a sufficiently high CARO acid concentration. Is possible.

  FIG. 4 is a graph showing the effect of combining a cleaning process using hydrogen peroxide added to an SPM liquid immediately before drainage and a cleaning process using a cleaning chemical. In FIG. 4, the comparative example shows a case where the resist stripping process is performed using a semiconductor manufacturing apparatus in which only a cleaning process using a cleaning chemical solution is performed. In the case of this embodiment, the example is performed by combining the cleaning process using hydrogen peroxide added to the SPM liquid immediately before drainage and the cleaning process using the cleaning chemical as described above. Shows the case. FIG. 4 is obtained by performing the resist stripping process with the SPM liquid, cleaning the wafer with the APM liquid, and determining the number of particles adhering to the cleaned wafer.

  As can be seen from FIG. 4, according to the present embodiment, not only the cleaning chemical solution having a sufficiently high CARO acid concentration is used, but also hydrogen peroxide is added to the SPM solution immediately before draining. Therefore, the semiconductor manufacturing apparatus can be kept extremely clean.

  Thus, according to this embodiment, the SPM tank, the piping through which the SPM liquid circulates, etc. using the SPM liquid in which hydrogen peroxide solution is sufficiently mixed with sulfuric acid, that is, the cleaning chemical liquid having a high CARO acid concentration is used. Since the particles are washed, the particles can be sufficiently decomposed and removed. Moreover, according to the present embodiment, the CARO acid concentration is sufficiently high by sufficiently adding hydrogen peroxide to the SPM liquid immediately before draining, that is, the SPM liquid that has been subjected to the resist stripping process a plurality of times. Since the SPM liquid is generated and the chemical liquid is used for cleaning, the particles can be frequently decomposed and removed. Therefore, according to the present embodiment, the semiconductor manufacturing apparatus that performs the resist stripping process using the SPM liquid can be kept extremely clean.

[Modified Embodiment]
The present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above-described embodiment, the case where cleaning is performed using an SPM solution (cleaning chemical solution) in which 20% or more of hydrogen peroxide solution is mixed has been described. However, the hydrogen peroxide solution mixed in the cleaning chemical solution Is not limited to 20% or more. If an SPM liquid (cleaning chemical) in which hydrogen peroxide is sufficiently mixed is used, the CARO acid concentration in the cleaning chemical can be set sufficiently high, and particles can be sufficiently decomposed and removed. For example, if an SPM solution (cleaning chemical solution) in which hydrogen peroxide is mixed at 15% or more is used, the CARO acid concentration in the cleaning chemical solution can be set sufficiently high, and particles are sufficiently decomposed and removed. It is possible. Note that the SPM liquid (cleaning chemical liquid) mixed with 15% hydrogen peroxide water means that the mixing ratio of the hydrogen peroxide water when the SPM liquid is generated is 15%.

  Moreover, in the said embodiment, the washing | cleaning process using what added hydrogen peroxide to the SPM liquid just before drainage, and the washing process using the SPM liquid (cleaning chemical | medical solution) which set CARO acid density | concentration high enough, However, it is not necessary to perform the cleaning process using the SPM solution (cleaning chemical solution) in which the CARO acid concentration is set sufficiently high. The number of particles can be suppressed to some extent only by performing a cleaning process using an SPM solution immediately before drainage to which hydrogen peroxide is added.

  Moreover, in the said embodiment, the washing | cleaning process using what added hydrogen peroxide to the SPM liquid just before drainage, and the washing process using the SPM liquid (cleaning chemical | medical solution) which set CARO acid density | concentration high enough, However, it is not necessary to perform the cleaning process using the SPM liquid immediately before drainage added with hydrogen peroxide. The number of particles can be suppressed to some extent only by performing a cleaning process using an SPM liquid (cleaning chemical) with a sufficiently high CARO acid concentration.

It is the schematic which shows the tank structure of the semiconductor manufacturing apparatus by one Embodiment of this invention. 5 is a flowchart illustrating a method for cleaning a semiconductor manufacturing apparatus according to an embodiment of the present invention. It is a graph which shows the effect of the washing process using the chemical | medical solution for washing | cleaning. It is a graph which shows the effect of combining the cleaning process using what added hydrogen peroxide to the SPM liquid just before drainage, and the cleaning process using a chemical for cleaning. It is a graph which shows the relationship between the frequency | count of use of SPM liquid, and the number of particles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inner tank 12 ... Outer tank 14 ... Preliminary temperature control tank 16 ... Pipe 18 ... Valve 20 ... Pipe 22 ... Valve 24 ... Pipe 26 ... Valve 28 ... Pipe 30 ... Valve 32 ... Pipe 34 ... Valve 36 ... Pipe 38 ... Pipe 40 ... Valve 42 ... Valve 44 ... Piping 45 ... Valve 46 ... Circulation pump 48 ... Filter 50 ... Piping 52 ... Valve

Claims (6)

A method for cleaning a semiconductor manufacturing apparatus for cleaning a semiconductor manufacturing apparatus that performs a resist stripping process on a substrate a plurality of times using a resist stripping chemical solution in which sulfuric acid and hydrogen peroxide are mixed.
After the resist stripping process is performed and before the next resist stripping process is performed , hydrogen peroxide water is added to the resist stripping chemical solution used in the resist stripping process, Using the added resist stripping chemical, foreign matter generated by the resist stripping process is removed, and the resist stripping chemical used for removing the foreign matter is discharged from the semiconductor manufacturing apparatus. Cleaning method for semiconductor manufacturing equipment. In the cleaning method of a semiconductor manufacturing apparatus according to claim 1 Symbol placement,
After the resist stripping process is performed and before the next resist stripping process is performed , the amount of foreign matter in the resist stripping chemical is measured, and the amount of the foreign matter in the resist stripping chemical is a predetermined value. The cleaning method for a semiconductor manufacturing apparatus is characterized by removing the foreign matter generated by the resist stripping process using a cleaning chemical solution in which sulfuric acid and hydrogen peroxide water are mixed. In the cleaning method of the semiconductor manufacturing apparatus according to claim 1 or 2 ,
In the semiconductor manufacturing apparatus, the resist removing chemical solution to which the hydrogen peroxide solution has been added is circulated in a pipe of the semiconductor manufacturing apparatus to remove the foreign matter generated by the resist stripping process. Cleaning method. In the washing | cleaning method of the semiconductor manufacturing apparatus of any one of Claims 1 thru | or 3,
In the semiconductor manufacturing apparatus, the resist stripping chemical used for removing the foreign matter has a higher mixing ratio of the hydrogen peroxide solution than the resist stripping chemical used in the resist stripping process . Cleaning method. In the washing | cleaning method of the semiconductor manufacturing apparatus of any one of Claims 1 thru | or 4,
A cleaning method for a semiconductor manufacturing apparatus, wherein foreign substances generated by the resist stripping treatment are removed using the resist stripping chemical solution having a mixing ratio of 15% or more of the hydrogen peroxide solution . The semiconductor manufacturing apparatus cleaning method according to claim 5,
A cleaning method of a semiconductor manufacturing apparatus , wherein foreign substances generated by the resist stripping treatment are removed using the resist stripping chemical solution having a mixing ratio of 20% or more of the hydrogen peroxide solution .

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