JP2006008423A - Silicon manufacturing method and silicon manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently grasp polycrystalline silicon efficiently by indirectly grasping the amount of deposited silicon, the deposited state, the melted-down state, etc. even in a silicon production apparatus in which the deposited state of silicon cannot be visually monitored, and the method To provide a silicon manufacturing apparatus used for manufacturing.
A method for producing silicon according to the present invention supplies chlorosilanes and hydrogen into a heated carbon cylindrical reaction vessel, deposits silicon on the inner surface of the cylindrical reaction vessel, and deposits silicon. When silicon is dropped or recovered from the cylindrical reaction vessel by melting a part or all of it, the amount of silicon attached to the cylindrical reaction vessel is monitored by measuring the weight of the cylindrical reaction vessel alone. The operation condition is controlled based on the silicon adhesion amount.
[Selection] Figure 1

Description

  The present invention relates to a silicon manufacturing method and a silicon manufacturing apparatus. More specifically, the present invention relates to a silicon manufacturing method characterized by controlling operating conditions while monitoring the amount of silicon deposited in a cylindrical reaction vessel, and a silicon manufacturing apparatus suitably used for the manufacturing method.

  Polycrystalline silicon is currently used as a raw material for semiconductors and solar power generation batteries, which are currently used in various fields and are expected to develop and demand in the future. Efficiently produce high-purity polycrystalline silicon. Is required.

As a conventional method for producing polycrystalline silicon, for example, the surface of a silicon rod arranged inside a bell jar is heated, and trichlorosilane (SiHCl ₃ ; hereinafter also referred to as TCS) or monosilane (SiH ₄ ) is used. Examples thereof include a Siemens method in which polycrystalline silicon is deposited by bringing a silicon deposition source gas containing chlorosilanes and a reducing gas such as hydrogen into contact therewith.

  The Siemens method is characterized in that high-purity silicon can be obtained, and is currently implemented as the most common method. However, since precipitation is batch-type, it is necessary to install a silicon rod as a seed, and to heat the current. There is a problem that extremely complicated procedures such as precipitation, cooling, taking out, and cleaning of the bell jar must be performed.

  In order to solve such problems, the present applicant, as a method and apparatus capable of efficiently producing silicon, has introduced a silicon deposition source gas into a cylindrical reaction vessel heated to a temperature below the melting point of silicon. After supplying and precipitating silicon, the inner surface of the cylindrical reaction vessel is heated to a temperature equal to or higher than the melting point of silicon to melt part or all of the precipitated silicon, thereby dropping the precipitated silicon. A method of manufacturing polycrystalline silicon to be recovered and a silicon manufacturing apparatus used in the method have been proposed (see Patent Document 1).

  However, since the cylindrical reaction vessel used in the silicon production method as described above is usually made of a base material that does not transmit visible light, such as a carbon material, the internal deposition state cannot be visually observed. Therefore, the amount of silicon actually deposited in the reaction vessel and the state of precipitation cannot be accurately grasped, and the amount of precipitation may be excessive or excessive.

  Thus, when the amount of silicon deposited becomes excessive, not only the fixed part of the reaction vessel is easily damaged by receiving an excessive load, but also when the silicon deposited excessively is melted and dropped, There is also a risk that more than the accepted amount of silicon may fall and overflow from the collection container.

  On the other hand, if the amount of silicon deposited becomes too small, there is a problem in terms of productivity and economics. Also, if there is a deposition failure due to an abnormality in the equipment, it will not be possible to detect it early and will react. If continued, the situation could be further exacerbated, leading to major troubles.

The trouble caused by the amount of deposited silicon as described above can be grasped to some extent by measuring the gas composition of the reaction exhaust gas by gas chromatography or the like and calculating the mass balance in the normal state. However, since this method is an indirect method,
When there is an abnormal situation such as the amount of by-products that cannot be measured by gas chromatography or the occurrence of silicon deposition outside the reaction vessel, it is difficult to accurately grasp the silicon deposition amount. Furthermore, the melted and dropped state of the deposited silicon cannot be grasped at all by gas chromatography.

  If the amount of silicon falling cannot be grasped during the melting and dropping operation of the deposited silicon, the following problems occur. For example, if the deposited silicon does not fall sufficiently and the silicon deposition operation is repeated while the deposit remains in the reaction vessel, the remaining precipitate may accumulate and normal deposition may be difficult. Further, the residual precipitates may cause abnormal gas convection in the reaction vessel and increase by-products. Furthermore, if the melted and dropped operation (heating operation) of the deposited silicon is performed excessively, the reaction vessel becomes excessively hot and by-products are increased, and the load applied to the reaction vessel is increased, resulting in an increase in the life of the reaction vessel. May decrease.

  The above problems are problems that have not been observed in the Siemens method using a conventional bell jar container. Because, in the Siemens method, silicon is deposited on the silicon filament, so even if it is a metal bell jar container, it is possible to visually confirm the state of the deposit by installing a viewing window or the like in the container. It is because the trouble at the time of precipitation was able to be grasped at any time. In addition, the Siemens method was a batch type in which the entire amount of precipitated silicon was cut off and a new silicon filament was re-installed to start precipitation. Therefore, an abnormality due to the recovered state such as residual precipitates could not occur.

Therefore, the problem as described above is caused by depositing silicon in a cylindrical reaction vessel as described in Patent Document 1 and melting part or all of the deposited silicon to drop and recover the deposited silicon. In this method, a new problem has arisen, and it is required to solve the above problem in order to increase the production efficiency of polycrystalline silicon.
WO02 / 100777

  An object of the present invention is to provide a method for efficiently producing polycrystalline silicon by indirectly grasping the amount of deposited silicon, the deposited state, the melted-down state, etc. even in a silicon production apparatus in which the deposited state of silicon cannot be visually monitored. Another object of the present invention is to provide a silicon manufacturing apparatus used in the method.

  As a result of intensive studies in view of the above problems, the present inventors can accurately monitor the amount of silicon deposited by measuring the weight of a single cylindrical reaction vessel on which silicon is deposited, and based on this result. It has been found that polycrystalline silicon can be produced efficiently by adjusting the operating conditions.

  That is, in the method for producing silicon according to the present invention, chlorosilanes and hydrogen are supplied into a heated carbon cylindrical reaction vessel, silicon is deposited on the inner surface of the cylindrical reaction vessel, and a part of the deposited silicon is obtained. Alternatively, when silicon is dropped and recovered from the cylindrical reaction vessel by melting the whole, the amount of silicon attached to the cylindrical reaction vessel is monitored by measuring the weight of the cylindrical reaction vessel alone, The operation condition is controlled based on the silicon adhesion amount.

  In the method for producing silicon according to the present invention, it is preferable that the weight of the cylindrical reaction vessel alone is directly measured by a load cell.

  The silicon production apparatus of the present invention used for the silicon production method as described above is a carbon cylindrical reaction vessel in which silicon is deposited on the inner surface by reacting chlorosilanes and hydrogen in a metal sealed vessel, A support structure for supporting the cylindrical reaction vessel, a heating means for heating the inner surface of the cylindrical reaction vessel to a melting point of silicon or higher, a load cell for measuring the weight of the cylindrical reaction vessel, and a precipitation And a silicon recovery container for recovering silicon dropped from the cylindrical reaction container by melting part or all of the silicon.

  In the silicon manufacturing apparatus, it is preferable that an upper end of the cylindrical reaction vessel has a flange shape, and the cylindrical reaction vessel is suspended by being supported by the support structure at the flange portion.

  Moreover, it is desirable that the cylindrical reaction vessel is supported by the support structure via the load cell.

  According to the present invention, even in a manufacturing apparatus in which the deposition state of silicon and the like cannot be visually monitored, the amount of silicon deposited in the reaction vessel can be accurately grasped, so that an abnormality in the precipitation reaction is detected early and dealt with. In addition, the production efficiency of polycrystalline silicon can be improved.

  Hereinafter, a silicon manufacturing method and a silicon manufacturing apparatus suitably used for the manufacturing method according to the present invention will be described in detail.

<Silicon manufacturing method>
In the method for producing silicon according to the present invention, a chlorosilane and hydrogen are supplied into a cylindrical reaction vessel made of carbon heated to a temperature lower than the melting point temperature of silicon to deposit silicon, and then the inside of the cylindrical reaction vessel When the silicon is dropped from the cylindrical reaction vessel and recovered by heating the surface above the melting point temperature of silicon and melting part or all of the deposited silicon, the weight of the cylindrical reaction vessel alone And measuring the operating conditions, for example, the heating temperature of the cylindrical reaction vessel, while monitoring the silicon adhesion amount in the cylindrical reaction vessel.

  In general, the method of controlling the process by measuring the weight of the entire device, the weight of the entire device is more than 100 times heavier than the deposited amount of silicon. However, it is difficult to accurately determine the weight of silicon adhering to the reaction container and the weight of silicon recovered in the silicon recovery container. Therefore, in the method of measuring the weight of the entire apparatus, it is practically impossible to grasp the silicon residual amount in the reaction vessel during the melting and dropping operation.

  However, by measuring the weight of the reaction vessel alone as in the present invention, the measurement error can be reduced, and the weight of silicon adhering to the reaction vessel and the weight of the dropped silicon, that is, silicon recovery It is possible to accurately grasp the weight of silicon collected in the container. In addition, as a method for measuring the weight of the reaction vessel alone, a method of directly measuring using a load cell is preferable because it can be measured with a high response speed with high accuracy over time.

Measure the weight of the reaction vessel alone as described above, monitor the amount of silicon adhered to the reaction vessel, confirm that a certain amount of deposited silicon has adhered, and make the inner surface of the reaction vessel above the melting point temperature of silicon. By heating to, silicon can be dropped and recovered. Furthermore, since the weight of the silicon recovered by dropping can be easily grasped, it is possible to prevent the silicon recovered from the silicon recovery container from overflowing.

  In addition, by monitoring the weight of the reaction vessel alone, it is possible to prevent the heating from continuing even after the silicon that has deposited and adhered to the reaction vessel has completely dropped. Time and heating costs can be reduced. In this way, polycrystalline silicon can be produced efficiently and economically by measuring the weight of the reaction vessel alone to monitor the silicon adhesion amount and controlling the operating conditions based on the result.

  The operating condition control method based on the silicon adhesion amount includes a method of adjusting the output of the heating means, a method of adjusting the heating output balance of the heating means which can be divided and controlled independently, a method of adjusting the feed gas supply amount, Examples thereof include a method for adjusting the gas temperature and a method for appropriately combining these plural methods.

  By controlling the temperature and temperature distribution of the reaction vessel to a desired state while monitoring the weight of the cylindrical reaction vessel in this manner, the silicon production amount can be maximized during the silicon deposition operation. In addition, during the melting and dropping operation, it is possible to prevent the deterioration of the material of the reaction vessel due to excessive temperature rise, and to effectively prevent the residual silicon due to insufficient melting and the elimination of the clogging. When controlling the heating temperature, it is a more preferable aspect to measure the temperature in the outer peripheral portion of the cylindrical reaction vessel at several locations with a radiation thermometer, a thermocouple, etc. and monitor the heating control state. .

  In addition, by measuring the weight of the reaction vessel alone as described above, even when a precipitation reaction or an abnormality of the apparatus occurs, the amount of silicon deposited relative to the reaction time is compared with the amount deposited at the time of stability. An abnormality can be detected at an early stage, and a large trouble can be prevented beforehand if an appropriate countermeasure is taken against the abnormality that has occurred.

<Silicon manufacturing equipment>
A silicon manufacturing apparatus used in the above-described silicon manufacturing method of the present invention will be described with reference to schematic views of the apparatus structure illustrated in FIGS. In addition, the silicon manufacturing apparatus of this invention is not limited to the aspect shown in FIG. 1 and FIG.

  The silicon production apparatus of the present invention is covered with a metal sealed container 1. Here, sealing means that process gas (such as silicon deposition raw material gas) is in circulation but is shut off from the external atmosphere.

  In addition, the silicon production apparatus of the present invention has a carbon cylindrical reaction vessel 2 for precipitating silicon in the sealed vessel 1, and a silicon deposition raw material containing chlorosilanes and hydrogen gas in the reaction vessel. A source gas supply pipe 3 for supplying gas is provided. Here, examples of the chlorosilanes used as the source gas include various known chlorosilanes. Specific examples include monosilane, dichlorosilane (DCS), trichlorosilane (TCS), and silicon tetrachloride (STC). It is done. Among these, monosilane or TCS is preferable because industrially high-purity products can be obtained in large quantities.

Furthermore, the silicon production apparatus of the present invention is provided in the closed vessel 1 for heating the support structure 4 supporting the cylindrical reaction vessel 2 and the inner surface of the reaction vessel 2 to a melting point or higher of silicon. Heating means 5, a heat insulating material 6 provided between the heating means 5 and the reaction vessel 2, a load cell 7 for measuring the weight of the reaction vessel 2, and gas discharge for discharging reaction exhaust gas A tube 8 and a silicon recovery container 9 for recovering silicon dropped from the reaction container 2 by melting part or all of the deposited silicon are provided.

  Note that a seal gas supply pipe (not shown) is provided in the gap formed by the outer wall of the reaction vessel 2 and the inner wall of the sealed vessel 1 to supply a seal gas such as nitrogen, hydrogen, or argon. Good.

  The cylindrical reaction vessel 2 has an opening 10 at the lower end, from which silicon deposited in the inside and partially or wholly melted by heating can fall by natural flow. Moreover, it is preferable that the upper end of the reaction vessel 2 has a flange shape. By supporting the support structure 4 with the flange portion, the reaction vessel 2 can be suspended. The reaction vessel 2 is preferably supported by the support structure 4 via the load cell 7. The cross-sectional shape of the reaction vessel 2 and the shape of the opening 10 are not particularly limited as long as the production efficiency of silicon is not hindered.

  As described above, the upper end of the reaction vessel 2 is formed into a flange shape, and the flange portion is supported by the support structure 4 via the load cell 7 so that the outer reaction vessel 2 is suspended. A single weight can be directly measured with high accuracy by the load cell 7, and a change in weight due to deposition and dropping of silicon can be measured at a high response speed.

  In order to prevent the raw material gas from leaking into the gap between the reaction vessel 2 and the closed vessel 1, the silicon production apparatus of the present invention has a portion where the cylindrical reaction vessel 2 is fixedly installed, for example, the load cell 6 and the support. As shown in FIG. 2, sealing members 11 and 12 may be provided between the structure 4 or between the upper end of the reaction vessel 2 and the metal closed vessel 1 to form an airtight structure. The airtight structure can be formed by a sealing method such as a face seal, a gasket, or an O-ring.

  The heating means 5 is not particularly limited as long as the inner wall of the reaction vessel 2 can be heated to a melting point temperature of silicon (approximately 1410 to 1430 ° C.) or higher. It is preferable to use it.

  The gas exhaust pipe 8 is for exhausting the reaction exhaust gas out of the system. Even if the gas composition of the reaction exhaust gas is measured by connecting an analyzer such as gas chromatography to the gas exhaust pipe 8. Good. Thus, by measuring the gas composition of the reaction exhaust gas and calculating the mass balance, the state of the precipitation reaction, the reaction efficiency, etc. can be grasped in more detail.

  Therefore, by combining the monitoring of the weight of the reaction vessel with the load cell described above and the analysis with gas chromatography etc., the operating conditions such as the reaction temperature and the gas supply amount can be controlled to a higher degree. In addition to improving the production efficiency of polycrystalline silicon, abnormalities can be detected at an early stage to prevent major troubles.

  The silicon recovery container 9 is a container for storing and cooling the silicon melt falling from the reaction container 2 or partially melted solid silicon. Such a silicon recovery container is not particularly limited as long as the recovery operation is not deteriorated, and a conventionally used recovery container can be used.

By having the structure as described above, the process gas can be circulated in the cylindrical reaction vessel while measuring the weight of the reaction vessel alone with the load cell, and polycrystalline silicon is produced by the above-described silicon production method according to the present invention. Can be produced efficiently and economically. In addition, in the silicon manufacturing apparatus of the present invention, improvement measures that have been performed in the conventional silicon manufacturing apparatus, for example, means for providing protrusions on the inner surface of the reaction vessel in order to increase the reaction efficiency by promoting stirring of the source gas Etc. may be appropriately applied within a range not impairing the object of the present invention.

〔Example〕
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
Hereinafter, description will be made with reference to the schematic diagram of FIG.

  As the cylindrical reaction vessel 2, a cylindrical vessel made of isotropic graphite (inner diameter: 210 mm, barrel thickness: 25 mm, flange thickness: 55 mm, total length: 4000 mm) having a flanged upper part was used. The cylindrical reaction vessel 2 was installed on the support structure 4 in the metal hermetic vessel 1 via a fiber-reinforced resin sealing material 11 and a load cell 7. A sealing material 12 made of Teflon (registered trademark) was also installed between the upper part of the cylindrical reaction vessel 2 and the metal closed vessel 1. Furthermore, a gas-tight paste was applied to each contact portion of the metal sealed container 1, the sealing materials 11 and 12, the load cell 7 and the cylindrical reaction container 2.

  On the inner surface of the cylindrical reaction vessel 2, an orifice-shaped protrusion (not shown) having a triangular cross section in the vertical direction and a height of 70 mm in order to promote gas stirring and increase the reaction efficiency and silicon yield. 6 were installed at equal intervals. Moreover, as the heating means 5, the high frequency heating means 5 of 5 kHz which can control independently the auxiliary reaction part of the cylindrical reaction container 2 upper part and the main reaction part below it was installed. Further, a carbon fiber heat insulating material 6 was installed between the cylindrical reaction vessel 2 and the heating means 5.

The heating output of the heating means 5 of the main reaction part and the auxiliary reaction part is controlled so that the inner surface temperature of the main reaction part of the cylindrical reaction vessel 2 becomes 1200 to 1400 ° C., and 1000 Nm of hydrogen is supplied from the source gas supply pipe 3 ^The reaction was started by supplying a mixed gas of ³ / H and 600 kg / H of trichlorosilane, and solid silicon was deposited on the inner surface of the cylindrical reaction vessel 2. The reaction pressure at this time was about 50 kPaG.

  After the reaction for 2 hours under the above conditions, the supply of trichlorosilane is stopped, the supply amount of hydrogen is halved, and the heating output of the heating means 5 of the main reaction part and the auxiliary reaction part is increased and the tubular reaction By heating and controlling the silicon precipitation part of the container 2 to 1450-1700 ° C. for 30 minutes, the silicon deposited in the cylindrical reaction container 2 was melted and dropped. When the operation was continued in such a cycle of precipitation (2 hours) -melting drop (30 minutes), the weight value indicated by the load cell 7 gradually increased.

  Accordingly, while monitoring the weight value by the load cell 7 five days after the start of operation, the heating output, the balance of the heating output of the main reaction part and the auxiliary reaction part, the gas supply amount and the melting and dropping time are appropriately controlled to clean the reaction vessel. Driving was performed. As a result, by further reducing the gas supply amount, the weight of the tubular reaction vessel 2 could be returned to the original value while keeping the maximum temperature of the tubular reaction vessel 2 within 1800 ° C. After that, even if it returned to the original driving cycle, it was possible to continue the operation without any problem, and it was possible to continuously operate for 30 days or more by appropriately performing the cleaning operation.

  Thus, since the load cell 7 was able to grasp the residual state of the deposits, it was possible to set appropriate cleaning operation conditions while confirming the effect of the cleaning operation. That is, it was confirmed that the silicon manufacturing apparatus and the silicon manufacturing method using the apparatus according to the present invention contribute to the improvement of the productivity of polycrystalline silicon and the protection of the devices.

[Comparative Example 1]
A polycrystalline silicon production operation was carried out under the same reactor and operating conditions as in Example 1 except that no load cell was installed.

  The amount of silicon fine powder, which is a by-product, gradually increased from about the seventh day of operation, and the differential pressure in the reactor also increased. Thereafter, the operation was continued under the same conditions, but on the 10th day, the reaction vessel cleaning operation was performed because the inlet pressure of the reactor rose to the limit pressure of the gas supply facility. The cleaning operation was performed by monitoring the differential pressure and controlling the heating output, the heating output balance, and the gas supply amount while suppressing the maximum temperature to 1800 ° C. As a result, the differential pressure almost recovered and normal operation was resumed, but the amount of silicon fine powder by-produced did not decrease much.

  Therefore, when the operation was stopped, the apparatus was opened, and the cylindrical reaction vessel was cut and observed, the inside of the cylindrical reaction vessel was slightly above the auxiliary reaction unit and near the tip of the orifice located above. Solid silicon remained.

  Thus, in the differential pressure measurement, the residual state of silicon deposits that adversely affect the reaction state could not be sufficiently grasped, so that it was not possible to set appropriate operating conditions for the cleaning operation. As a result, productivity decreased.

It is the schematic which shows the structural example of the silicon manufacturing apparatus which concerns on this invention. It is the schematic which shows the structural example (airtight structure) of the silicon manufacturing apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Metal sealed container 2 ... Cylindrical reaction container 3 ... Raw material gas supply pipe 4 ... Support structure 5 ... Heating means 6 ... Heat insulating material 7 ... Load cell 8. ..Gas discharge pipe 9 ... silicon recovery container 10 ... opening 11 ... seal material 12 ... seal material

Claims (5)

Supplying chlorosilanes and hydrogen into a heated carbon cylindrical reaction vessel, precipitating silicon on the inner surface of the cylindrical reaction vessel, and melting part or all of the deposited silicon, the cylindrical reaction When collecting silicon by dropping it from the container,
A method for producing silicon, characterized in that the amount of silicon attached to the cylindrical reaction vessel is monitored by measuring the weight of the cylindrical reaction vessel alone, and the operating conditions are controlled based on the amount of silicon attached.   The method for producing silicon according to claim 1, wherein the weight of the cylindrical reaction vessel alone is directly measured by a load cell. In a metal sealed container,
A carbon cylindrical reaction vessel in which chlorosilanes and hydrogen are reacted to deposit silicon on the inner surface;
A support structure for supporting the cylindrical reaction vessel;
Heating means for heating the inner surface of the cylindrical reaction vessel to a temperature equal to or higher than the melting point of silicon;
A load cell for measuring the weight of the cylindrical reaction vessel;
A silicon production apparatus comprising: a silicon collection container for collecting a part or all of the deposited silicon and collecting silicon dropped from the cylindrical reaction container.   4. The silicon according to claim 3, wherein an upper end of the cylindrical reaction vessel has a flange shape, and the cylindrical reaction vessel is suspended by being supported by the support structure at the flange portion. Manufacturing equipment.   The silicon manufacturing apparatus according to claim 3 or 4, wherein the cylindrical reaction vessel is supported by the support structure via the load cell.

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