JP2006086156A - Method for removing product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing a product by which a product can be removed in a shorter time than the conventional method and an end point can be detected accurately. <P>SOLUTION: This method is used to remove a product in a reaction vessel 101 or a piping 108 communicated with the reaction vessel 101 through chemical reaction. It includes a step to flow a gas for removing a product into the reaction vessel 101, and a step where temperature on at least one or more wall surfaces of the reaction vessel 101 or the piping 108 is measures. When the measured temperature reaches a specified value, a condition of the chemical reaction is changed to that for promoting the chemical reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for removing a product deposited in a reaction vessel or a pipe communicating with the reaction vessel.

  In semiconductor processes using silicon-containing gases such as silane, it is an important technical issue to increase the deposition rate and to produce high-quality films in order to reduce production costs and increase production volumes. . In high-frequency plasma CVD, as means for solving the above-mentioned problem, it is disclosed that the plasma density is increased, the source gas is supplied so as not to be exhausted, and the pressure is set to a relatively high region condition ( Patent Document 1).

  The semiconductor process under the above conditions is an excellent means for forming a high-quality film at a high speed, but when film formation is performed continuously for a long time, it is mainly in the semiconductor formation container and the exhaust pipe. Generation of a product such as polysilane is induced in a place where the flow rate changes (particularly, a place where the flow rate decreases or a place where gas stays). And if excessive products accumulate in the semiconductor formation vessel and the exhaust pipe, they are released as dust into the plasma space and taken into the film, or cause changes in the plasma discharge conditions. This is a factor that deteriorates the film quality. In addition, when deposited on the high frequency input electrode, the effective power input to the plasma is reduced, making it difficult to maintain desired plasma conditions. Furthermore, clogging of the exhaust system piping and malfunction of the pressure control valve are induced, and it becomes difficult to maintain the semiconductor process under a desired constant condition. From the above, it is necessary to periodically remove the product.

When the removal method is carried out by using physical means after opening the reaction vessel or piping to the atmosphere, the product has active physical properties, and therefore causes a cause of ignition due to factors such as friction. Become. In addition, since the atoms contained in the semiconductor gas used in the semiconductor process and adsorbed on the product are released to the atmosphere, there is a problem in terms of workability and safety. Therefore, as a method for removing the product, while maintaining a sealed state, the product is gasified by a chemical reaction to be removed from the pipe, and detoxified using a gas scrubber such as a scrubber installed downstream. The method of performing is preferable. In particular, a cleaning method that does not depend on plasma discharge is particularly excellent as a means for removing products outside the plasma region, such as in the exhaust pipe, in a safe and efficient manner. As a means for that purpose, a method is known in which a product removal gas such as ClF ₃ gas is flowed to a region where the product is deposited, and the product is gasified and removed by a chemical reaction (Patent Document 2,). Patent Document 3).

The step of removing the product in the film formation apparatus is preferably completed in as short a time as possible in view of the utilization efficiency of the apparatus. For this purpose, it is necessary to remove the product as quickly as possible, and to accurately detect the end point of the removal of the product. Regarding the method for detecting the end point of product removal, Patent Document 4 discloses a method for detecting the end point from the change in the opening of the pressure control valve while maintaining the pressure in the reaction chamber at a predetermined value. . As another method, utilizing the fact that the reaction in which the product is gasified by ClF ₃ gas is an exothermic reaction, the temperature of the piping is measured, and the temperature has reached the convergence point to the set temperature. A method for detecting the end point of the product removal is disclosed in Patent Document 5.

JP 2002-134774 A Japanese Patent Laid-Open No. 2-77579 JP 2001-189277 A Japanese Patent Application Laid-Open No. 7-211163 JP-A-8-306628

  As described above, the product removal method already disclosed is an excellent method. However, in the method of Patent Document 4, a system having a large reaction vessel volume, a system having a complicated pipe shape, or a pipe When the product is locally present in a long system, it is difficult to detect the local reaction sensitively with the pressure fluctuation of the entire system or the valve opening position. There was a problem in implementing good end point detection. Further, in the method of detecting the end point by measuring the temperature of the pipe or the like while continuously flowing the product removal gas under the same conditions, a region where the product is present in a large amount or a region where the product is present as a lump However, it has been found that the reaction rate decreases with time even though the product removal is not completed. Therefore, if the product removal gas is kept flowing under the same conditions, it takes a lot of time to remove the product, and furthermore, since the temperature gradually decreases, the end point of product removal is clear. However, there was a problem that the accuracy of end point detection was poor. If the end point detection accuracy is poor and the processing time is too short, the resulting product removal is incomplete and the purpose of product removal cannot be achieved. Problems such as reduction or consumption of product removal gas more than necessary, and damage caused by overetching of reaction vessels and piping, etc., occur.

  The present invention has been made in view of such circumstances, and provides a product removal method capable of removing a product in a shorter time than a conventional method and capable of detecting an end point with higher accuracy. The purpose is to do.

  In order to achieve the above object, the present invention is a method for removing a product in a reaction vessel or a pipe communicating with the reaction vessel by a chemical reaction, the step of flowing a product removal gas in the reaction vessel And measuring the temperature of at least one wall surface of the reaction vessel or pipe, and when the temperature reaches a predetermined value, the condition of the chemical reaction is changed to a condition that promotes the chemical reaction. It is characterized by including the process to make.

The method for removing the product of the present invention is as follows.
“Measurement of the temperature of the wall surface is performed at a plurality of locations, and when the temperature at the highest temperature of the plurality of locations reaches a predetermined value, the condition of the chemical reaction is more Including the process of changing to promoted conditions ",
“After the change to a condition that promotes the chemical reaction, the end point of product removal is detected by preventing the temperature from increasing.”
“The condition under which the chemical reaction is further promoted is to increase the partial pressure of the product removing gas”,
“The condition under which the chemical reaction is further promoted is to increase the flow rate of the product removing gas”,
"The product removal gas contains a gas containing fluorine atoms, and a chemical reaction with the product is performed without plasma",
“The product removing gas is ClF ₃ gas or F ₂ gas”,
"The product contains a fluorine atom",
Is included as a preferred embodiment thereof.

  According to the product removal method of the present invention, when the temperature of a certain region reaches a predetermined value due to a chemical reaction between the product removal gas and the product, the product removal gas and the product By changing the conditions of the chemical reaction to conditions that promote the chemical reaction and introducing a process that further promotes the removal of the remaining product, the product can be produced in a shorter time than the conventional method. The end point can be detected with higher accuracy.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to such embodiments.

  FIG. 1 is a schematic view showing a reaction vessel and piping communicating with the reaction vessel for explaining the operation of the present invention. A supply gas pipe 103 is connected to the reaction vessel 101 that can be kept in vacuum via a supply valve 102, and gas can be introduced into the reaction vessel. The exhaust valve 107 is opened and the vacuum exhaust pipe 108 is opened. And is discharged to the exhaust pipe 110 by the vacuum pump 109. In this case, for example, by using means such as a valve whose opening degree can be adjusted as the exhaust valve 107 or a vacuum pump 109 having a function capable of adjusting the motor rotation speed, a desired pressure can be set in the container or the exhaust pipe. It is possible to maintain the adjustment.

A high-frequency application electrode 106 connected to a high-frequency power source (not shown) is installed in the reaction vessel 101 so that plasma discharge can be performed in a space between the substrate holder / counter electrode 104 capable of holding the substrate 105. Yes. For example, the gas flow rate is adjusted using a mixing device or the like configured with a mass flow controller (not shown), and silane gas, SiF ₄ gas, and hydrogen gas are respectively 400 cm ³ / min (normal), 200 cm ³ / min (normal), Mixing while flowing 10,000 cm ³ / min (normal), flowing into the container through the supply gas pipe 103, adjusting the pressure in the container to 500 Pa using the exhaust valve 107, and applying VHF (60 MHz) power to the high frequency application electrode 106. 3 kW was applied to generate plasma, and a glass plate was used as the substrate 105 to form a microcrystalline silicon thin film on the surface. After such a thin film forming process is continued for 50 hours, products mainly composed of polysilane adhere to and deposit on the inner wall of the reaction vessel 101 and the inner walls of the exhaust valve 107 and the vacuum exhaust pipe 108. A large amount of polysilane was deposited in bulk. Then, since deposition of polysilane in the vicinity of the exhaust valve 107 has progressed, it has become difficult to maintain the internal pressure of the container at 500 Pa even if the opening degree of the exhaust valve 107 is adjusted.

Subsequently, a product removal step was performed. Adjust the gas flow rate using a mixing device or the like configured with a mass flow controller (not shown), use ClF ₃ gas as a product removal gas, flow into the container through the supply gas pipe 103 while diluting with nitrogen gas, The exhaust valve 107 is fully opened, and the internal pressure of the container and the pressure of the vacuum exhaust pipe are adjusted to 13.3 kPa or more by adjusting the number of rotations of the vacuum pump 109 using an inverter (not shown), and left while flowing the mixed gas. Then, cleaning was performed without plasma. The flow rates of ClF ₃ gas and nitrogen gas were 2,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal), respectively. In the above description, ClF ₃ is exemplified as a gas for removing the product without plasma, but a method using a gas highly reactive with polysilane such as F ₂ gas may be used. In addition, if the reactivity between the product and the product removal gas is too intense, the amount of heat generation becomes too large and damages the reaction vessel and the piping part. When a liquefied gas such as ClF ₃ is used, the supply pipe is used. For the purpose of improving the convenience of handling such as preventing reliquefaction inside, it is preferable to use an inert gas added as a diluent gas to the product removing gas. When ClF ₃ gas is used as the product removal gas, it is preferably used at a concentration of 50% or less.

Since the reaction for gasifying the product with the product removal gas such as ClF ₃ gas is an exothermic reaction, the degree of progress of the product removal or the judgment of the end is determined by piping in the region where the product is accumulated, etc. The temperature can be measured, and the change in temperature can be observed as a guide. The temperature measurement may be performed on at least one wall surface of the reaction vessel or piping. However, when a region where the product is likely to be deposited is known in advance, a temperature measurement point 200 is set in the vicinity thereof, A method such as making a thermocouple contact the side wall of the pipe and continuously monitoring the temperature, a method of measuring continuously or intermittently using a contact or non-contact temperature measuring instrument, etc. Appropriate selection and implementation can also be mentioned as a preferred mode.

  However, in the region where the product is present in a large amount as described above or in the region where the product is present in a lump shape, the reaction rate decreases with time even though the product removal is not completed. It has been found that the phenomenon of going on occurs. For this reason, although the temperature of the piping and the like is lowered even though the product removal is not completed, it is difficult to accurately detect the end point of the product removal. The details of why the phenomenon of the reaction rate decreasing with time even though the product removal has not been completed are unclear, but as the product reaction progresses, for example, the surface shape of the product This is not because the contact area between the product removal gas and the product is reduced due to the change, the composition near the surface of the product is changed, or the surface is solidified. I guess.

  In the product removal method of the present invention, the end point detection of product removal in a region where a large amount of product exists or a region where the product exists in a lump is detected when the temperature of the region decreases to a predetermined value. In addition, the process of changing the condition of the chemical reaction between the product removal gas and the product to a condition that promotes the chemical reaction is introduced at least once to further promote the removal of the remaining product. By performing such a process, the product can be removed in a shorter time. That is, when the product is still remaining and is changed to a condition that promotes the chemical reaction, the product removal reaction is promoted again. Shows an upward trend. On the other hand, when the removal of the product is completed, the temperature does not increase. For this reason, the end point detection method used as the end point of product removal by confirming that the said temperature does not rise by the said method is preferable in order to be able to detect more accurately.

  In the present invention, in order to promote the chemical reaction between the product and the product removing gas, it is effective to increase the contact frequency between the product and the product removing gas. Specific methods for achieving this include increasing the flow rate of the product removal gas introduced into the reaction vessel, increasing the concentration of the product removal gas, and increasing the pressure in the reaction vessel and piping. A method of increasing the partial pressure of the product removal gas in the vicinity of the product removal gas removal atmosphere is preferable.

  In carrying out product removal, when the step of changing the condition of the chemical reaction to a condition that promotes the chemical reaction is performed a plurality of times when the temperature reaches a predetermined value, This value may be carried out at the same temperature for all steps, or may be changed for each step.

  Also, depending on conditions such as the shape of the pipe, the amount of product, the pressure in the pipe, etc., the place where the product is deposited is separated, or there are areas where the amount of deposition is large and areas where there is little In some cases, the regions are spaced apart. In such a case, since the removal of the product is sequentially performed from the upstream side to the downstream side of the gas flow, after the removal of one product or one region with a large amount of deposition is completed, Return the product removal condition to the initial condition, proceed to the removal of the next product, and change to a condition that promotes the chemical reaction again when the temperature reaches a predetermined value during the process. It is also preferable to repeat the process of. In this case, the predetermined value in the removal of each product or each region with a large amount of deposition may be performed at the same temperature, or may be a method of changing each process.

  The predetermined value differs depending on the device configuration, the shape of the piping part, the heat resistance of the member used, etc., and thus cannot be determined unconditionally, but the maximum temperature limited by the heat resistant temperature of the member used and the room temperature It is set between and. From the viewpoint of reducing the time taken to remove the product, the predetermined value is more preferably 5 ° C. or more than room temperature.

  Here, the chemical reaction for product removal proceeds sequentially from the upstream side to the downstream side of the gas flow. Therefore, the decision to change to a condition that facilitates the removal of the product is the most active removal of the product at that time, that is, when measuring the temperature of multiple locations It is more preferable to pay attention to the temperature at the highest temperature and change the condition to a condition that facilitates the removal of the product when the temperature reaches a predetermined value.

  In particular, when the product contains fluorine atoms, the reason is not clear, but the reaction rate of the product and the product removal gas decreases with time. The phenomenon may increase. Therefore, it can be said that using the above method is a more effective method for removing the product in a shorter time. In addition, if the product contains fluorine atoms, the end point detection of the product removal is not performed correctly, and if the product remains, the piping etc. is opened to the atmosphere. As a result, the fluorine atom is diffused into the atmosphere as a compound such as HF, which causes a problem regarding work safety. Therefore, it can be said that it is preferable from the viewpoint of safety that the accuracy of the end detection of product removal is improved by the above method.

In the following examples, the present invention is specifically described by taking as an example a method in which a product in a pipe communicating with a reaction vessel when using a plasma CVD method is removed using ClF ₃ as a product removal gas. However, these examples do not limit the contents of the present invention.

Example 1
After forming a thin film on the substrate 105 for 50 hours using the reaction vessel 101 shown in FIG. 1 in the same manner as in the previous embodiment, ClF ₃ gas and nitrogen gas were respectively added in the same manner as before. The product removal was started by flowing 20,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal). Temperature measurement points were set at four locations (200-1 to 200-4) as shown in FIG.

After starting the removal of the product, first, the temperature at the temperature measurement point 200-1 began to rise, reached 95 ° C., and then gradually decreased. When the temperature of the temperature measurement point 200-1 decreased to 45 ° C., the flow rates of ClF ₃ gas and nitrogen gas were changed to 3,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal), respectively. However, the temperature of the temperature measurement point 200-1 started to rise again, and after reaching 55 ° C., the temperature gradually decreased. When the temperature of the temperature measurement point 200-1 is lowered to 45 ° C again, the flow rates of ClF ₃ gas and nitrogen gas are changed to 4,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal), respectively. As a result, the temperature at the temperature measurement point 200-1 did not rise again. During this step, the temperature at the temperature measurement point 200-2 gradually increased from room temperature to 40 degrees, and the temperature at the temperature measurement point 200-3 did not vary from room temperature.

Next, the flow rate of ClF ₃ gas and nitrogen gas was returned to the initial values of 2,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal), respectively, and the flow was continued. The temperature of No. 2 started to rise while being higher than the other points, and after reaching 90 ° C., the temperature gradually decreased. Thereafter, similarly to the temperature measurement point 200-1, when the temperature at the temperature measurement point 200-2 reached 45 ° C., the process of monitoring the temperature while increasing the concentration of ClF ₃ was continued. Even with increasing concentrations of ClF ₃ when it is no longer the temperature of the temperature measurement point 200-2 increases, subsequently, as 200-3 temperature measurement point of interest, the temperature rise was observed even by increasing the concentration of ClF ₃ The product removal step was completed when the temperature dropped to room temperature.

The time required from the start of flowing ClF ₃ gas and nitrogen gas to the removal of the product was 250 minutes. Then, after sufficiently replacing the piping portion with an inert gas, the piping portion was removed and the inside was visually observed. As a result, it was confirmed that the product was removed cleanly.

(Comparative Example 1)
Next, after thin film formation similar to that in Example 1 was performed for 50 hours, the flow rates of ClF ₃ gas and nitrogen gas were set to initial values of 2,000 cm ³ / min (normal) and 20,000 cm ³ / min, respectively. (Normal) is maintained and the product removal step is performed. After 250 minutes, the temperature at the temperature measurement point 200-3 has not yet returned to room temperature, and the removal of the product has been completed. There wasn't. Furthermore, when the product removal process was continued, it was determined that the temperature at the temperature measurement point 200-3 continued to decrease gradually and returned to about room temperature after 450 minutes. Then, after sufficiently replacing the piping part with an inert gas, the piping part was removed and the inside was visually observed, and it was confirmed that the product remained in a part of the piping.

  As is apparent from the results of Example 1 and Comparative Example 1, it can be seen that the method for removing a product of the present invention is excellent.

(Example 2)
In the product removal process, instead of increasing the flow rate of ClF ₃ when the temperature at the temperature measurement point reaches a predetermined value, the internal pressure of the vacuum exhaust pipe is reduced by decreasing the rotation speed of the vacuum pump 109. The product was removed after forming a microcrystalline silicon thin film on the substrate in the same manner as in Example 1 except that the chemical reaction was promoted by increasing the.

First, the product removal was started with the flow rates of ClF ₃ gas and nitrogen gas being 2,000 cm ³ / min (normal) and 20,000 cm ³ / min (normal), respectively. After the temperature of the temperature measurement point 200-1 reaches 95 ° C., the temperature gradually decreases, and when the temperature reaches 45 ° C., the rotation speed of the vacuum pump 109 is reduced to the initial 90%. The temperature of 200-1 began to rise. Thereafter, the temperature at the temperature measurement point 200-1 gradually decreased after reaching 60 ° C. When the temperature of the temperature measurement point 200-1 again decreased to 45 ° C., the number of rotations of the vacuum pump 109 was reduced to the initial 85%. This time, the temperature of the temperature measurement point 200-1 increased again. There wasn't. Thereafter, the rotation speed of the vacuum pump 109 is returned to the initial value, and the temperature measurement point 200 is repeated while repeating the operation of the rotation speed of the vacuum pump 109 for the temperature measurement points 202-2 and 202-3 as in the first embodiment. The product was removed until a temperature increase of −3 was not observed even when the rotation speed of the vacuum pump 109 was decreased. As a result, the time required from the start of flowing ClF ₃ gas and nitrogen gas to the removal of the product was 270 minutes. Then, after sufficiently replacing the piping part with an inert gas, the piping part was removed and the inside was visually observed. As in Example 1, it was confirmed that the product was removed cleanly.

It is a schematic diagram which shows schematic structure of the reaction apparatus which has the reaction container which implemented the removal method of the product of this invention, and piping connected with this reaction container.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Reaction container 102 Supply valve 103 Supply gas piping 104 Counter electrode 105 Substrate 106 High frequency application electrode 107 Exhaust valve 108 Vacuum exhaust piping 109 Vacuum pump 110 Exhaust piping 112 Deposition location 200 Temperature measurement point

Claims (8)

  A method of removing a product in a reaction vessel or a pipe communicating with the reaction vessel by a chemical reaction, a step of flowing a product removing gas in the reaction vessel, and at least one or more locations of the reaction vessel or the pipe Measuring the temperature of the wall surface of the product, and changing the condition of the chemical reaction to a condition that promotes the chemical reaction when the temperature reaches a predetermined value. Removal method.   The temperature of the wall surface is measured at a plurality of locations, and when the temperature at the highest temperature of the plurality of locations reaches a predetermined value, the chemical reaction further promotes the conditions of the chemical reaction. The method for removing a product according to claim 1, further comprising a step of changing to a predetermined condition.   The method for removing a product according to claim 1 or 2, wherein the end point of product removal is detected when the temperature does not rise after the chemical reaction is changed to a more accelerated condition. .   The method for removing a product according to any one of claims 1 to 3, wherein the condition for further promoting the chemical reaction is to increase a partial pressure of the product removing gas.   The method for removing a product according to any one of claims 1 to 3, wherein the condition for further promoting the chemical reaction is to increase a flow rate of the product removing gas.   The said product removal gas contains the gas containing a fluorine atom, and the chemical reaction with the said product is performed plasmaless, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. Product removal method. The method for removing a product according to claim 6, wherein the product removing gas is ClF ₃ gas or F ₂ gas.   The method for removing a product according to any one of claims 1 to 7, wherein the product contains a fluorine atom.

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