JP7047803B2 - Single crystal pulling device - Google Patents

Description

The present invention relates to a single crystal pulling device by the Czochralski method (CZ method).

In the production of a semiconductor crystal by the CZ method, a raw material melt is generated in a quartz crucible in a furnace, a seed crystal is deposited, and a single crystal is pulled up. At this time, oxygen dissolves from the inner surface of the quartz crucible into the raw material melt, which reacts with the raw material melt to generate silicon oxide (SiO and SiO ₂ ). In addition, CO and CO ₂ are generated from graphite members such as heaters. Silicon oxide is sublimable, and when the temperature drops in the furnace, it becomes a solid and falls into the raw material melt, causing dislocations during single crystal growth. CO and CO ₂ are incorporated into the raw material melt and cause carbon contamination of the crystals. Therefore, in order to discharge these harmful gases, while an inert gas such as Ar gas is circulated in the furnace, the inside of the furnace is kept at a predetermined vacuum degree.

Silicon oxide solidifies into powder at low temperatures, but when it comes into contact with a solid such as a structure and has a temperature below the sublimation point, it adheres to it and becomes lumpy. In the case of the silicon single crystal pulling device by the CZ method, the position where such a tendency is likely to occur is often in the vicinity of the pipe for discharging the exhaust gas from the chamber, and in many cases, in the exhaust gas pipe.

In the pipe that discharges the exhaust gas containing the oxide discharged from the silicon single crystal pulling device by the CZ method, the oxide and silicon are deposited from the pulling machine outlet portion to the inside of the exhaust gas pipe. The deposition of oxides and silicon in the exhaust gas pipe system has a different progress rate depending on the temperature of the exhaust gas pipe system, and progresses remarkably at a specific place.

The deposition at this specific location progresses as the operating time elapses, and the progress of the deposition causes problems in controlling the flow rate and vacuum degree of the inert gas flowing into the furnace. If the flow rate of the inert gas or the degree of vacuum control is disturbed, there is a problem that the quality of the crystal being manufactured is not desired.

In order to prevent this, it is necessary to terminate the operation and remove the sediment before the vacuum degree control is hindered. Furthermore, in operations where it is necessary to dope the dopant at a high concentration, the amount of oxide evaporation increases, the deposition of oxide and silicon progresses in the exhaust gas pipe system in a short time, and the flow rate and vacuum are earlier than planned. It is easy for problems to occur in which the control of the degree is hindered and the operation must be interrupted.

Therefore, in order to solve such a problem, it has been proposed, for example, as shown in Patent Document 1, that a large number of outlets are provided and the shape of the outlets is devised to make it difficult to block. There is.

Japanese Unexamined Patent Publication No. 2002-97098

However, the method shown in Patent Document 1 alone has the effect of prolonging the time until a defect occurs in the vacuum degree control by dispersing the easily blocked portions in a plurality of places, but a significant prolongation effect cannot be expected, and the effect of prolonging the vacuum degree control cannot be expected. It is not possible to prevent a sudden defect in vacuum degree control when the dopant is doped at a high concentration. In addition, there is a problem that the effect of the device by changing the shape is sharply reduced when the exhaust gas temperature changes due to the change of the operating conditions.

On the other hand, in order to prevent the place where oxides and silicon are likely to be deposited in the exhaust gas pipe, it is conceivable to lower the temperature of the exhaust gas to a temperature lower than the sublimation point before entering the exhaust gas pipe. In this case, it is necessary to lower the temperature inside the furnace in the path through which the exhaust gas in the furnace passes. However, the HZ (hot zone) type, which has strengthened the heat insulation inside the furnace through recent efforts to improve energy efficiency, and the HZ type, which has a larger quartz rut pot diameter than the size of the furnace body in order to improve productivity, are single. In the crystal pulling device, it is difficult to achieve both the characteristics of the HZ type and the technique of lowering the temperature in the furnace of the path through which the exhaust gas passes.

As described above, with the conventional technology, it is difficult to prevent the formation of places where oxides and silicon are likely to accumulate in the exhaust gas pipe, and in order to perform stable operation, the operation time is shortened and the exhaust gas is exhausted. It was necessary to clean the pipe system frequently, and a solution to this was desired.

The present invention has been made to solve the above problems, and to provide a single crystal pulling device provided with means for removing deposits such as oxides and silicon deposited in an exhaust gas pipe while continuing operation. The purpose.

In order to achieve the above object, the present invention is a single crystal pulling device by the CZ method including a main chamber and an exhaust gas pipe for discharging gas in the main chamber, and deposits in the exhaust gas pipe during operation. Provided is a single crystal pulling device characterized by having a deposit removing mechanism capable of removing an object.

According to such a silicon single crystal pulling device, the deposits adhering to the inside of the exhaust gas pipe can be removed by the deposit removing mechanism during the operation, so that the continuous operation time can be stably extended and the device can be downed. Time loss can be reduced.

It is preferable that the deposit removing mechanism is installed at a place where the deposit is deposited during the operation and is automatically operated at a predetermined timing while continuing the production of the single crystal.

In this case, since the deposits in the exhaust gas pipe can be removed without interrupting the production of the single crystal, the continuous operation time can be stably extended and the downtime loss can be reduced.

It is preferable that the predetermined timing is set at a predetermined time other than the period during which the single crystal is pulled up, or before the pressure adjusting valve for controlling the degree of vacuum of the main chamber is fully opened.

In this way, if the predetermined timing is set to a period other than the period during which the single crystal is pulled up, even if the resistance to the flow of the exhaust gas changes due to the operation of removing the deposit, the quality of the single crystal in which the single crystal is grown will be improved. It has no effect. Further, if the predetermined timing is set before the pressure adjustment valve that controls the vacuum degree of the main chamber is fully opened, the deposits in the exhaust gas pipe are removed before the pressure adjustment valve cannot control the vacuum degree. Can be done.

It is preferable that the deposit removing mechanism has a scraping portion for removing the deposit by moving in the exhaust gas pipe while rotating.

In this case, since the deposits in the exhaust gas pipe can be reliably removed, the continuous operation time can be stably extended while maintaining the quality of the grown single crystal.

It is preferable that the exhaust gas pipe locally has a portion where the temperature is equal to or lower than the sublimation point of the deposit so that the deposit is selectively deposited.

As described above, by intentionally providing a place where deposits such as oxides and silicon are likely to be deposited, the deposits adhering to the place can be easily removed by the deposit removing mechanism.

The deposit is silicon oxide.

That is, for example, when growing a silicon single crystal, silicon oxide gas that causes dislocation of the single crystal is generated in the main chamber. Therefore, if the silicon oxide gas is discharged from the main chamber, deposits (silicon oxide) caused by the silicon oxide gas are intentionally deposited at the above-mentioned location in the exhaust gas pipe, and the deposits are removed by the deposit removal mechanism, the deposits can be removed. It is possible to stably grow high-quality silicon single crystals for a long period of time.

As described above, according to the present invention, the problem that deposits are accumulated in the exhaust gas pipe and the progress thereof interferes with the control of the vacuum degree of the main chamber is effective in the operation of the deposit removal mechanism. Can be suppressed. Therefore, the continuous operation time can be stably extended, and the downtime loss of the device can be reduced.

In addition, in the operation of producing a single crystal that requires high-concentration doping of a dopant whose deposition rate of deposits such as oxides and silicon is fast in the exhaust gas pipe, it is assumed that the operation status varies and the inside of the exhaust gas pipe is earlier than planned. Even if the sediment is clogged, it is effective to detect the situation before the control of the vacuum degree of the main chamber is disturbed and to remove the sediment by the operation of the sediment removal mechanism. It is possible to prevent interruption of operations and avoid loss of raw materials and quality defects.

It is sectional drawing which shows the example of the single crystal pulling apparatus of this invention. It is a schematic diagram which shows the example of the scraping part which removes a deposit. It is sectional drawing which shows the single crystal pulling apparatus of a comparative example. It is a figure explaining the effect with respect to the extension of a continuous operation time (Example 1, comparative example 1). It is a figure explaining the effect with respect to the extension of a continuous operation time (Example 2, comparative example 2).

As described above, in the exhaust gas pipe that discharges the exhaust gas containing the oxide and silicon discharged from the single crystal pulling device by the CZ method, deposits composed of the oxide and the silicon are deposited. In this way, when deposits of oxides, silicon, etc. are deposited in the exhaust gas pipe system, the flow rate of the inert gas flowing into the main chamber and the control of the vacuum degree of the main chamber are hindered, and the desired crystal quality is obtained. I can't do it. In order to prevent this, it is necessary to stop the operation and perform cleaning within the operating time within the range where the control of the degree of vacuum is not hindered, resulting in a decrease in productivity and yield.

In addition, in the operation of producing a single crystal that requires a high concentration of dopant, the deposition progress rate of deposits such as oxides and silicon in the exhaust gas pipe system is fast, and the operation status varies, so it is faster than planned. , The exhaust gas pipe system may be clogged, which may interfere with the control of the vacuum degree of the main chamber. In such a case, the operation is frequently interrupted and the exhaust gas pipe system is obliged to be cleaned, resulting in raw material loss and poor quality.

For these reasons, there has been a demand for the development of a method for improving productivity by reducing the downtime of the equipment by reducing the frequency of cleaning the exhaust gas pipe system and stably extending the continuous operation time.

As a result of diligent studies on the above-mentioned problems, the present inventors have provided a sediment removal mechanism having a structure that can be operated without stopping the operation at a position where the exhaust gas pipe system is likely to be clogged, and an inert gas during the operation. By operating the sediment removal mechanism under conditions that do not interfere with the control of the flow rate and the degree of vacuum, and removing the clogging of the exhaust gas pipe, the clogging of the exhaust gas pipe system and the control of the degree of vacuum are not hindered. We have found that the continuous operation time can be stably extended, and completed the present invention.

That is, the present invention is a single crystal pulling device by the CZ method including a main chamber and an exhaust gas pipe for discharging gas in the main chamber, and deposits capable of removing deposits in the exhaust gas pipe during operation. It is a single crystal pulling device characterized by being provided with an object removing mechanism.

The deposit removal mechanism for removing the deposits in the exhaust gas pipe has a structure capable of removing the deposits in the exhaust gas pipe while the raw material melt is in the main chamber (furnace), specifically, mechanically. It is preferable to use a method of scraping off the deposit. Further, it is preferable to have a structure in which the flow of exhaust gas from the furnace is not impaired even during the operation of removing deposits. In addition, when the mechanism is installed in the main chamber provided with multiple exhaust gas outlets, the operation timing is staggered so that one or more exhaust gas paths can always be prepared during operation at one location. Even if the flow of the exhaust gas is blocked and the deposit is removed, the exhaust gas may be discharged from another place so as not to hinder the operation.

In addition, the sediment removal mechanism that removes the deposits in the exhaust gas pipe does not necessarily have to be operated all the time, and the deposits cause resistance to the flow of exhaust gas, causing problems in controlling the degree of vacuum in the furnace. You can do it intermittently before you do. For example, during the operation of the mechanism, the mechanism portion that mechanically scrapes off the deposit may move in the exhaust gas pipe and change the resistance to the flow of the exhaust gas in the exhaust gas pipe. Therefore, the operation timing of the mechanism is not in the middle of single crystal growth that requires precise vacuum degree control, but in a process other than single crystal production, for example, when the raw material is melted, that does not require precise vacuum degree control. Is preferable.

Further, it is preferable that the operation cycle of the deposit removing mechanism for removing the deposits in the exhaust gas pipe is carried out based on the time until the vacuum degree control becomes defective due to the deposits in the exhaust gas pipe obtained empirically. .. In addition, in operations such as manufacturing single crystals that require high-concentration doping of dopants, deposits of oxides, silicon, and other deposits progress in the exhaust gas pipe system in a short time, so the operation cycle is determined by time management. There are things that cannot be done. In such a case, whether or not to detect the resistance generated in the flow of the exhaust gas by the deposits of the exhaust gas pipe and operate the mechanism for removing the deposits of the exhaust gas pipe based on the sensed resistance. You may decide.

As a method of sensing the resistance generated in the flow of exhaust gas due to the deposit of the exhaust gas pipe, for example, a method based on the valve opening of the pressure adjustment valve that controls the pressure (vacuum degree) in the main chamber is adopted. Can be done. That is, when resistance is generated in the flow of exhaust gas due to the deposits in the exhaust gas pipe, a valve operation is performed in order to maintain the pressure in the main chamber at the target value, and the valve opening degree of the pressure adjusting valve changes. This is because before the valve opening of the pressure adjusting valve is fully opened, the pressure in the main chamber is set to the target value by increasing the opening of the pressure adjusting valve even if deposits are accumulated in the exhaust gas pipe. Means that it can be maintained.

Therefore, if the mechanism for removing the deposits of the exhaust gas pipe is activated before the valve opening of the pressure adjusting valve is fully opened, that is, when it is detected that the valve opening reaches a certain value or more. Substantially, it is synonymous with operating the mechanism when the resistance generated in the flow of the exhaust gas due to the deposit of the exhaust gas pipe is accumulated to the extent that the vacuum degree control is defective.

As described above, by setting the operation timing of the mechanism for removing the deposits in the exhaust gas pipe, in the exhaust gas pipe in the continuous operation for a long time or in the operation of manufacturing a single crystal requiring high concentration doping of the dopant. The deposits cause resistance to the flow of exhaust gas, and the deposits can be removed before the problem that the degree of vacuum in the furnace deviates from the target value occurs, and stable operation can be continued. It will be possible.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 shows an example of the single crystal pulling device of the present invention.
A quartz crucible 3a and an outer crucible 3b made of a material such as graphite that holds the quartz crucible 3a are arranged in the main chamber 1, and the crucible drive unit 15 drives the rotation and elevating of the crucible 3b via a rotation support (crucible shaft) 14. conduct. The raw material melt 13 is placed in a quartz crucible 3a and heated by a heater 5 kept warm by a heat insulating cylinder 4.

In the production of a single crystal, a seed crystal (not shown) attached to the seed wire 11 lowered from the pull chamber 2 is landed on the raw material melt 13, and the electric power of the heater 5 is controlled to grow the single crystal 12. From the liquid surface of the raw material melt 13, silicon oxide gas such as oxides and silicon generated by the reaction between the quartz crucible 3a and the raw material melt 13 is generated. This silicon oxide gas becomes silicon oxide gas containing oxides, silicon, etc. when the inert gas (for example, Ar gas) introduced into the main chamber 1 from the gas introduction pipe 17 passes through the surface of the raw material melt. The exhaust gas pipes 6a and 6b provided at the two locations are discharged to the outside of the main chamber 1 as exhaust gas. That is, the silicon oxide gas is discharged by the vacuum pump 10 via the exhaust gas pipes 6a and 6b and the pressure adjusting valve 9 that controls the degree of vacuum in the main chamber 1.

Here, the exhaust gas that has entered the exhaust port provided at the upper end of the exhaust gas pipes 6a and 6b is oxidized (for example, oxidized) at the locations 6a'and 6b'where the deposits in the exhaust gas pipes 6a and 6b are likely to be deposited. (Silver mass, etc.) 16 is generated. The locations 6a'and 6b'where deposits are likely to be deposited are locations where the temperature is equal to or lower than the sublimation point of the element or compound contained in the exhaust gas. For example, when the single crystal 12 to be pulled up is a silicon single crystal, the locations 6a'and 6b'are locations where the temperature is equal to or lower than the sublimation point of silicon oxide, and in this case, the exhaust gas is directed to the location. The deposit 16 gives rise to a mass of silicon oxide.

The locations 6a'and 6b'where deposits are likely to accumulate are, specifically, at locations where the temperature of the exhaust gas naturally drops, such as the outlet of the main chamber 1 (exhaust gas outlet), or water cooling or air cooling. It does not matter whether it is a place where cooling is forcibly performed by a predetermined cooling mechanism such as.

In the example shown in the figure, the places where the exhaust gas pipes 6a and 6b exit from the main chamber 1 are the places 6a'and 6b' where deposits are likely to accumulate. This is because the bottom of the main chamber 1 is cooled, so that it can be set as locations 6a'and 6b' where deposits are likely to accumulate. That is, by cooling the main chamber 1, the exhaust gas pipes 6a and 6b can be easily set to a temperature equal to or lower than the sublimation point of silicon oxide, for example. If the easy points 6a'and 6b' are set, the points 6a'and 6b' can be set without major changes in the device.

As shown in the figure, it is preferable that the locations 6a'and 6b'where deposits are likely to be deposited are sections extending from the inside to the outside of the main chamber 1.

Here, when the deposit 16 grows and the mass of the deposit 16 becomes large at the locations 6a'and 6b' where the deposit is likely to be deposited, the flow of the exhaust gas is obstructed and the pressure adjusting valve 9 is pressed. Even if it is used, the desired degree of vacuum cannot be obtained, and problems will occur.

In order to prevent this, a sediment removal mechanism 8a, 8b capable of removing the sediment in the exhaust gas pipes 6a, 6b was provided during the operation. The deposit removal mechanisms 8a and 8b are provided corresponding to the exhaust gas pipes 6a and 6b. In the example of the figure, since there are two systems of exhaust gas pipes 6a and 6b, two deposit removal mechanisms 8a and 8b are provided correspondingly. However, the number of the exhaust gas pipes 6a and 6b and the deposit removing mechanisms 8a and 8b is not limited to this, and may be one or more.

The deposit removing mechanism 8a, 8b has scraping portions 7a, 7b for removing the deposit 16 by moving in the exhaust gas pipes 6a, 6b while rotating.

An example of the scraping portions 7a and 7b for removing the deposit is shown in FIG.
The scraping portions 7a and 7b are plate-shaped members attached to the columns 18, and can rotate around the columns 18 as a rotation axis. Then, by using a drive device (not shown) in the deposit removal mechanisms 8a and 8b to control the elevating operation (up and down operation shown in A of FIG. 1) and the rotational operation of the support column 18, scraping is performed. One side 19 parallel to the column 18 of the portions 7a and 7b can be moved spirally, that is, as shown in B of FIG. 2, along the inner surface of the exhaust gas pipes 6a and 6b.

By forming the scraping portions 7a and 7b in the shape as shown in FIG. 2 in this way, the deposit 16 can be reliably removed, and the scraping portions 7a and 7b are rotationally driven in the exhaust gas pipes 6a and 6b. Even in this case, the resistance to the flow of the exhaust gas can be reduced, and the deposit removal mechanisms 8a and 8b can be operated even during the production of the single crystal. The shapes of the scraped portions 7a and 7b are not limited to the plate-shaped members as shown in FIG. 2, and may be any shape as long as the deposits can be removed. For example, the shape of the scraping portions 7a and 7b may be a brush-like shape. Further, the material of the scraping portions 7a and 7b can be, for example, stainless steel.

When the scraping portions 7a and 7b are not operated, it is preferable that the scraping portions 7a and 7b are made to stand by by a standby portion provided at a position that does not obstruct the exhaust gas flow. In the example of FIG. 1, the scraping portion 7a that can move in the exhaust gas pipe 6a on the right side is located in the standby portion of the exhaust gas pipe 6a. It is preferable that the standby portion is provided at a position of the exhaust gas pipe 6a extending in the vertical direction below the branch point where the exhaust gas pipe 6a is bent in the vertical direction to the horizontal direction.

Then, when the operation of removing the deposit is performed, the scraping portions 7a and 7b are fed out to the upper part of the exhaust gas pipes 6a and 6b by using the drive device (not shown) of the deposit removal mechanism 8a and 8b and rotated. By repeating the ascending / descending operation while performing the operation, the deposit 16 in the exhaust gas pipes 6a and 6b is scraped off. In the example of FIG. 1, the scraping portion 7b that can move in the exhaust gas pipe 6b on the left side scrapes the deposit 16 in the exhaust gas pipe 6b.

The deposit 16 scraped by the scraping portions 7a and 7b naturally falls due to gravity and is housed in, for example, a storage portion (not shown) provided in the deposit removing mechanisms 8a and 8b. Therefore, the scraped deposit 16 is not deposited again in the pressure adjusting valve 9, the inside of the vacuum pump 10, or the like, and causes inconvenience such as clogging. Further, if the accommodating portion has a detachable structure, the deposits accommodating in the accommodating portion can be easily recovered.

After the operation of removing the deposit 16 is completed, the scraping portion 7b is located at a position below the branch point where the exhaust gas pipe 6b is bent from the vertical direction to the horizontal direction among the exhaust gas pipes 6b extending in the vertical direction. It is arranged in the standby part provided in.

The exhaust gas pipes 6a and 6b and the deposit removal mechanisms 8a and 8b provided at the two locations are, for example, staggered from each other in operation timing, that is, after one scraping operation is completed, the other scraping operation is completed. Or, when one of them is performing the scraping operation, the other may stop the scraping operation and perform an operation of discharging the exhaust gas from the main chamber 1.

Further, the removal of the deposit 16 deposited on the exhaust gas pipes 6a and 6b is performed not during the growth of the single crystal 12, but before the seed crystal is landed on the raw material melt 13, for example, other than the single crystal manufacturing process. It is preferable to do so. Further, the progress of clogging in the exhaust gas pipes 6a and 6b during the growth of the single crystal 12 can be checked by electrically acquiring the valve opening information of the pressure adjusting valve 9 that controls the degree of vacuum in the main chamber 1. It is possible to detect. That is, the deposit removal mechanisms 8a and 8b are operated at a predetermined time point before the pressure adjusting valve 9 is fully opened, for example, before the growth of the single crystal 12 is started, and the oxides deposited on the exhaust gas pipes 6a and 6b are generated. The deposit 16 such as silicon can be removed.

By doing so, it becomes possible to start the growth of the single crystal 12 in a state where the deposit 16 deposited on the exhaust gas pipes 6a and 6b is removed, and the exhaust gas pipes 6a and 6b can be started during the growth of the single crystal 12. It is possible to effectively suppress the occurrence of a defect in the degree of vacuum control due to the clogging of the deposit 16 in the above. Further, even if the deposit 16 is deposited on the exhaust gas pipes 6a and 6b earlier than expected, the deposit 16 deposited on the exhaust gas pipes 6a and 6b is removed before the vacuum degree control becomes defective, so that the vacuum is obtained. The occurrence of quality defects in the single crystal 12 due to a defect in degree control is suppressed.

As described above, according to the present invention, the problem that the deposit 16 is deposited on the exhaust gas pipes 6a and 6b and the progress thereof interferes with the control of the vacuum degree of the main chamber 1 is solved. It can be effectively suppressed by the operation of the mechanisms 8a and 8b. Therefore, the continuous operation time can be stably extended, and the downtime loss of the device can be reduced.

Further, in the operation of manufacturing the single crystal 12 which requires a high concentration doping of the dopant whose deposition progress rate of the deposit 16 in the exhaust gas pipes 6a and 6b is fast, it is assumed that the exhaust gas pipe is earlier than planned due to the variation of the operation situation. Even if the deposits 16 cause clogging in 6a and 6b, the situation is detected before the control of the degree of vacuum of the main chamber 1 is hindered, and the sediment removal mechanisms 8a and 8b operate. By removing the deposit 16, it is possible to effectively prevent the interruption of the operation, and it is possible to avoid the loss of raw materials and the quality defect.

Hereinafter, the present invention will be described in detail with reference to examples of the present invention, but these are not intended to limit the present invention.

(Example 1)
In Example 1, the single crystal pulling device of FIG. 1 is used to repeatedly manufacture a single crystal while removing the deposits adhering to the exhaust gas pipes 6a and 6b by the deposit removing mechanisms 8a and 8b under the following conditions. , The relationship between the number of repetitions and the degree of vacuum in the main chamber 1 was verified.

As shown in FIG. 1, the single crystal pulling device has two systems of exhaust gas pipes 6a and 6b at the bottom of the main chamber 1, and the single crystal produced by the single crystal pulling device is a silicon single crystal. Then, the exhaust gas pipes 6a and 6b are provided with locations 6a'and 6b' whose temperature is below the sublimation point of the oxide (silicon oxide gas) contained in the gas in the main chamber 1. The upper ends of the locations 6a'and 6b'are 4 cm above (inside the furnace) from the bottom of the water-cooled main chamber 1 (positions where they come into contact with the exhaust gas pipes 6a and 6b), and the lower end thereof is from the bottom. It was set to 10 cm on the lower (outside the furnace) side. That is, the locations 6a'and 6b'where the oxide is deposited are 14 cm sections extending from the inside to the outside of the main chamber 1.

Further, deposit removal mechanisms 8a and 8b having scraping portions 7a and 7b for removing deposits were attached directly under the exhaust gas pipes 6a and 6b, respectively. The deposit removal mechanism 8a, 8b has an exhaust gas pipe for the scraping portions 7a, 7b so that the scraping portions 7a, 7b cover at least the locations 6a', 6b'where the deposits are deposited. It was made possible to move within 6a and 6b. In this example, the upper ends of the sediment scraping portions 7a and 7b are 5 cm from the bottom of the water-cooled main chamber 1 from a position below the position where the exhaust gas pipes 6a and 6b are bent from the vertical direction to the horizontal direction. Made it possible to move the section up to the top. Further, the scraping portions 7a and 7b are made of a stainless steel material and have a structure as shown in FIG. 2, and the scraping portions 7a and 7b are moved (elevated) according to the movement (elevation) of the scraping portions 7a and 7b. The 7b is configured to rotate around the support column (rotational shaft) 18 at a predetermined rotation speed.

Further, the timing of operating the deposit removal mechanisms 8a and 8b, that is, the timing of removing the deposits deposited in the exhaust gas pipes 6a and 6b was carried out at the timing when the melting of the polysilicon in the quartz crucible 3a was completed. .. Under the above conditions, the section from the exhaust gas pipes 6a and 6b extending in the lateral direction, that is, the section from the position where the exhaust gas pipes 6a and 6b are bent in the vertical direction to the vacuum pump is not cleaned. The production of P-type (boron-doped) and N-type (phosphorus-doped) silicon single crystals having normal resistivity was repeated, and the relationship between the number of repetitions and the degree of vacuum in the main chamber 1 was verified.

Further, after manufacturing each silicon single crystal, Ar gas was introduced into the main chamber 1 at a flow rate of 100 L / min, and the degree of vacuum in the main chamber 1 was measured with the pressure adjusting valve 9 fully open. The degree of clogging of the entire exhaust gas pipes 6a and 6b of each system was confirmed.

(Comparative Example 1)
In Comparative Example 1, the single crystal pulling device of FIG. 3 is used to repeatedly produce a single crystal under the same conditions as in Example 1 (however, the operation of removing deposits during operation is not performed), and the process is repeated. The relationship between the number of times and the degree of vacuum in the main chamber 1 was verified. In the single crystal pulling device of FIG. 3, the same components as the components of the single crystal pulling device of FIG. 1 are designated by the same reference numerals.

The measurement results of Example 1 and Comparative Example 1 are summarized in FIG.
It is assumed that the upper limit of the degree of vacuum (pressure in the main chamber 1) of the main chamber 1 required for producing a high-quality silicon single crystal is 50 hPa.

As is clear from the figure, the number of repetitions of silicon single crystal production until the pressure in the main chamber 1 reaches the upper limit value (50 hPa) was 5 times in Comparative Example 1, but 40 times in Example 1. However, the upper limit was never reached. That is, in Example 1, the continuous operation time could be extended by 8 times or more as compared with Comparative Example 1. This means that in Example 1, cleaning of the exhaust gas pipe system (work of stopping the operation and removing the deposits in the exhaust gas pipe) is not required for a period of 8 times or more as compared with Comparative Example 1. do.

Regarding the degree of clogging of the exhaust gas pipes 6a and 6b of each system as a whole, in Example 1, the state where the amount of deposits was small was stably maintained regardless of the number of repetitions of silicon single crystal production. In Comparative Example 1, it was confirmed that the deposits increased rapidly in proportion to the number of repetitions.

(Example 2)
In Example 2, the single crystal pulling device of FIG. 1 was used to remove deposits under the same conditions as in Example 1 above (however, the single crystal to be grown was a silicon single crystal doped with a high concentration of phosphorus). The single crystal was repeatedly produced while removing the deposits adhering to the exhaust gas pipes 6a and 6b by the mechanisms 8a and 8b, and the relationship between the number of repetitions and the degree of vacuum in the main chamber 1 was verified. Further, as in Example 1, after manufacturing each silicon single crystal, the degree of clogging of the entire exhaust gas pipes 6a and 6b of each system was confirmed.

(Comparative Example 2)
In Comparative Example 2, the single crystal pulling device of FIG. 3 is used to repeatedly produce a single crystal under the same conditions as in Example 2 above (however, the operation of removing deposits during operation is not performed), and the process is repeated. The relationship between the number of times and the degree of vacuum in the main chamber 1 was verified.

The measurement results of Example 2 and Comparative Example 2 are summarized in FIG.
It is assumed that the upper limit of the degree of vacuum (pressure in the main chamber 1) of the main chamber 1 required for producing a high-quality silicon single crystal is 100 hPa.

As is clear from the figure, the number of repetitions of silicon single crystal production until the pressure in the main chamber 1 reaches the upper limit value (100 hPa) was 2 times in Comparative Example 2, but 7 times in Example 2. Met. That is, in Example 2, the continuous operation time could be extended 3.5 times as compared with Comparative Example 2. This means that in Example 2, cleaning of the exhaust gas pipe system is unnecessary for a period of 3.5 times that of Comparative Example 2.

Regarding the degree of clogging of the exhaust gas pipes 6a and 6b of each system as a whole, in Example 2, the ratio of the increase in sediment to the increase in the number of repetitions was gradual, whereas in Comparative Example 2, the repetition was repeated. It was confirmed that the ratio of the increase in sediment to the increase in the number of times was rapid.

As can be seen from the above results, in Example 1 and Example 2, the cleaning interval of the exhaust gas pipe system could be extended as compared with Comparative Example 1 and Comparative Example 2, respectively. That is, in Example 1 and Example 2, it was proved that the continuous operation time can be stably extended.

As described above, according to the present invention, the problem that oxides are deposited on the exhaust gas pipe and the progress of the oxides interferes with the control of the vacuum degree of the main chamber is effective in the operation of the deposit removal mechanism. Can be suppressed. Therefore, the continuous operation time can be stably extended, and the downtime loss can be reduced.

In addition, in the operation of producing a single crystal that requires high-concentration doping of a dopant whose deposition rate of deposits such as oxides and silicon is fast in the exhaust gas pipe, it is assumed that the operation status varies and the inside of the exhaust gas pipe is earlier than planned. Even if the sediment is clogged, it is effective to detect the situation before the control of the vacuum degree of the main chamber is disturbed and to remove the sediment by the operation of the sediment removal mechanism. It is possible to prevent interruption of operations and avoid loss of raw materials and quality defects.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and the present invention can be anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same function and effect. Is included in the technical scope of.

1 ... main chamber, 2 ... pull chamber, 3a ... quartz pump, 3b ... outer pump, 4 ... heat insulation tube, 5 ... heater, 6a, 6b ... exhaust pipe, 6a', 6b' ... where deposits are likely to accumulate, 7a, 7b ... scraping part, 8a, 8b ... deposit removal mechanism, 9 ... pressure adjustment valve, 10 ... vacuum pump, 11 ... seed wire, 12 ... single crystal, 13 ... raw material melt, 14 ... rotary support ( Rutsubo shaft), 15 ... Rutsubo drive unit, 16 ... Sediment, 17 ... Gas introduction pipe, 18 ... Strut (rotary shaft), 19 ... One side of scraping part 7a, 7b.

Claims (5)

A single crystal pulling device by the CZ method including a main chamber and an exhaust gas pipe for discharging gas in the main chamber.
The single crystal pulling device is equipped with a deposit removing mechanism.
The sediment removal mechanism is used to continue the production of the single crystal, but at a time other than the period during which the single crystal is being pulled up, or before the pressure adjusting valve for controlling the degree of vacuum in the main chamber is fully opened, the exhaust gas is discharged. A single crystal pulling device characterized in that deposits in a tube can be removed. The single crystal pulling device according to claim 1 , wherein the deposit removing mechanism is installed at a place where the deposit is deposited and is automatically operated. The single crystal pulling mechanism according to claim 1 or 2, wherein the deposit removing mechanism has a scraping portion for removing the deposit by moving in the exhaust gas pipe while rotating. Device. Any one of claims 1 to 3 , wherein the exhaust gas pipe locally has a portion having a temperature equal to or lower than the sublimation point of the deposit so that the deposit is selectively deposited. The single crystal pulling device according to the section. The single crystal pulling device according to any one of claims 1 to 4 , wherein the deposit is silicon oxide.

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