JP4855799B2 - Method for producing granular silicon crystal - Google Patents

Description

  The present invention relates to a method for producing granular silicon crystals, and more particularly to a method for producing granular silicon crystals suitable for obtaining granular silicon crystals used in a photoelectric conversion device.

  Conventionally, a solar cell having high photoelectric conversion efficiency (hereinafter also referred to as conversion efficiency) using a crystalline silicon wafer has been put into practical use. This crystalline silicon wafer is manufactured by cutting from a large single crystal or polycrystalline silicon ingot having good crystallinity, low impurities, and no uneven distribution. However, large single crystal or polycrystalline silicon ingots take a long time to produce and thus have low productivity. Therefore, wafers cut from these ingots are expensive. Therefore, the advent of next-generation solar cells that do not require large single crystal or polycrystalline silicon ingots and that have low photoelectric conversion efficiency and high cost is strongly desired.

  Therefore, as one of promising photoelectric conversion devices in the future market, a photoelectric conversion device using granular silicon crystals as a constituent element of photoelectric conversion means has attracted attention.

  At present, as raw materials for producing granular silicon crystals, fine silicon particles generated as a result of pulverizing a single crystal silicon material, high-purity silicon synthesized in a gas phase by a fluidized bed method, and the like are used. As a method for producing granular silicon crystals, after separating the above raw materials by size or weight, they are melted in a container by infrared irradiation or high-frequency induction heating, and this melt can be freely used as droplets (granular melt). A method of solidifying while dropping (for example, see Patent Document 1) or a method of making it spherical by high-frequency plasma heating and melting (for example, see Patent Document 2) is used.

International Publication No. WO99 / 22048 pamphlet U.S. Pat. No. 4,188,177

  However, the conventional method for producing granular silicon crystals has a problem of low productivity because it is difficult to make the weight of silicon microparticles as a raw material uniform. Since the variation in the weight of the silicon microparticles of the raw material is reflected in the size of the granular silicon crystal produced therefrom, a raw material composed of microparticles having a uniform weight is required. However, it is difficult for silicon to efficiently obtain the fine particles of the raw material by a method such as pulverization or classification so that the particle diameter is 100 to 1000 μm and the dispersion of the particle diameter becomes small.

  Further, when silicon fine particles are obtained by pulverization, contamination (contamination) from the pulverization media occurs, so that there is a problem that impurities cannot be avoided.

  Furthermore, a high-frequency plasma heating and melting apparatus for obtaining granular silicon crystals requires a very large power source and the like, has a problem that the apparatus cost is high and the power consumption is large, resulting in an increase in production cost.

  In addition, in a method for producing granular silicon crystals in which a silicon melt (silicon melt) is solidly dropped as liquid droplets (granular melt), the silicon melt is melted from a nozzle portion of a crucible containing the silicon melt. Is discharged and dripped. However, there is a problem in that silicon in the silicon melt reacts with carbon and nitrogen, which are materials of the nozzle portion made of silicon carbide or silicon nitride, and the nozzle hole of the nozzle portion becomes large. In this case, the size of the droplets of the silicon melt changes in a short period (one to two times of use), and it becomes impossible to produce granular silicon crystals having a uniform particle size with high productivity. there were. In addition, since the nozzle hole of the nozzle portion is deformed and cannot be used in a short period of time, it is necessary to frequently replace the nozzle portion, which has been an obstacle to reducing the manufacturing cost.

As described above, the conventional method for producing a granular silicon crystal has problems that the productivity of the granular silicon crystal is low, the particle size variation of the produced granular silicon crystal is large, and the production cost is high. It was.
It is an object of the present invention to provide a granular silicon crystal in which a granular silicon crystal can be produced with high reproducibility, with high productivity of the granular silicon crystal, small variation in particle diameter of the produced granular silicon crystal, and high reproducibility. It is to provide a manufacturing method.

  As a result of intensive studies to solve the above problems, the inventors of the present invention discharged the silicon melt in the crucible in a granular form from a nozzle portion made of silicon carbide or silicon nitride and dropped it. In the method for producing granular silicon crystals by cooling and solidifying the liquid while dropping, the silicon melt in the crucible is carbonized when the nozzle portion is made of silicon carbide, and the nozzle portion is nitrided. In the case of silicon, by adding a nitrogen source, melt droplets of uniform size can be generated, and granular silicon crystals with small particle size variations can be produced with high productivity and good reproducibility. As a result, the present invention has been completed.

That is, the manufacturing method of the granular silicon crystal of this invention has the following structures.
(1) The silicon melt in the crucible is discharged in a granular form from a nozzle portion made of silicon carbide or silicon nitride and dropped, and the granular silicon crystal is cooled and solidified by dropping the granular silicon melt. In the method for producing granular silicon crystals to be produced, the silicon melt in the crucible is supplied with a carbon source when the nozzle portion is made of silicon carbide, and with a nitrogen source when the nozzle portion is made of silicon nitride. A method for producing granular silicon crystals, characterized by comprising adding.
(2) When the carbon source is a gas containing carbon, the nitrogen source is a gas containing nitrogen, and the nozzle portion is made of silicon carbide, carbon is added to the atmosphere gas in the crucible containing silicon melt. The method for producing granular silicon crystals according to (1), wherein a gas containing nitrogen is added when the nozzle portion is made of silicon nitride.
(3) When the nozzle part is made of silicon carbide, the carbon-containing gas is carbon monoxide gas or carbon dioxide gas.
(4) When the nozzle portion is made of silicon carbide, carbon in an amount of 1 × 10 ¹⁷ atoms / cm ³ to 1 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. (2) The manufacturing method of the granular silicon crystal as described in (2).
(5) The method for producing granular silicon crystals according to (2), wherein when the nozzle portion is made of silicon nitride, the gas containing nitrogen is nitrogen gas.
(6) When the nozzle portion is made of silicon nitride, nitrogen is added to the silicon melt in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon. (2) The manufacturing method of the granular silicon crystal as described in (2).
(7) The atmosphere gas in the crucible containing the silicon melt contains a gas containing carbon when the nozzle portion is made of silicon carbide, and a gas containing nitrogen when the nozzle portion is made of silicon nitride. After adding, the pressure of the atmospheric gas in the said crucible is made higher than the pressure before addition of the said gas, The manufacturing method of the granular silicon crystal as described in (2) characterized by the above-mentioned.
(8) The gas introduction pipe for adding a gas containing carbon or nitrogen to the silicon melt is characterized in that the gas outlet is located 10 to 300 mm above the silicon melt surface (2) The manufacturing method of the granular silicon crystal of description.
(9) The method for producing granular silicon crystals according to (1), wherein the carbon source is silicon carbide powder and the nitrogen source is silicon nitride powder.
(10) The silicon of the silicon melt is silicon obtained by forming a silicon carbide film as the carbon source on the surface of a silicon raw material by carbonization when the nozzle portion is made of silicon carbide. 2. The method for producing granular silicon crystals according to claim 1, wherein the silicon nitride is silicon in which the silicon nitride film as the nitrogen source is formed on the surface of the silicon raw material by nitriding.
(11) When the carbon source is an inorganic solid member containing carbon, the nitrogen source is an inorganic solid member containing nitrogen, and the nozzle part is made of silicon carbide, the inorganic solid member containing carbon is used as the nozzle part. In the case where is made of silicon nitride, the inorganic solid member containing nitrogen is introduced into the silicon melt in the crucible, and the method for producing granular silicon crystals according to (1).
(12) The method for producing granular silicon crystals according to (11), wherein the inorganic solid member containing carbon is made of graphite or silicon carbide.
(13) When the nozzle portion is made of silicon carbide, carbon in an amount of 1 × 10 ¹⁷ atoms / cm ³ to 1 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. (11) The manufacturing method of the granular silicon crystal as described in (11).
(14) The method for producing granular silicon crystals according to (11), wherein the inorganic solid member containing nitrogen is made of silicon nitride.
(15) When the nozzle portion is made of silicon nitride, nitrogen in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. (11) The manufacturing method of the granular silicon crystal as described in (11).
(16) The inorganic solid member containing carbon is installed so as to cover the upper part of the nozzle hole of the nozzle part, and a large number of through holes that do not pass silicon carbide particles generated in the silicon melt are formed. (14) The method for producing granular silicon crystals according to (11).
(17) The method for producing a granular silicon crystal according to (16), wherein the diameter of the through hole is 80 to 200 μm.
(18) The nitrogen-containing inorganic solid member is installed so as to cover the upper part of the nozzle hole of the nozzle part, and a large number of through holes that do not allow the silicon nitride particles generated in the silicon melt to pass therethrough are formed. (14) The method for producing granular silicon crystals according to (11).
(19) The method for producing a granular silicon crystal according to (18), wherein the diameter of the through hole is 80 to 200 μm.

  According to the method for producing a granular silicon crystal of the present invention, according to the above (1) and (2), when the nozzle portion is made of silicon carbide, the atmosphere gas in the crucible is carbonized, and the nozzle portion is nitrided. In the case of silicon, by adding a nitrogen-containing gas, a slight amount of carbon or nitrogen in the atmosphere gas enters the silicon melt, so that the reaction between the nozzle material and the silicon melt is suppressed, and the nozzle portion It is possible to suppress changes in the shape of the. As a result, melt droplets of uniform size are generated, and granular silicon crystals with small particle size variations can be manufactured with high productivity and good reproducibility. In addition, since the grain size variation of the granular silicon crystal is small, uniform crystal growth can be realized, so that a granular silicon crystal with small variation in crystal quality can be manufactured.

  According to the above (3) and (4), when the nozzle portion is made of silicon carbide, the gas containing carbon is carbon monoxide gas or carbon dioxide gas. It has an effect that it can be easily dissolved in carbon and can be easily added with carbon.

  According to the above (5) and (6), when the nozzle portion is made of silicon nitride, the gas containing nitrogen is nitrogen gas, so that the nitrogen gas does not contain oxygen, so that the oxygen concentration of the silicon melt is increased. There is an effect that it can be suppressed.

  According to the above (7) and (8), when the nozzle part is made of silicon carbide, the atmosphere gas in the crucible containing the silicon melt contains carbon-containing gas, and when the nozzle part is made of silicon nitride. After adding the gas containing nitrogen, the pressure of the atmospheric gas in the crucible is made higher than the pressure before the addition of the gas, and the lower end which is the discharge port of the gas introduction pipe is the silicon melt surface. Since it is located at a higher position, carbon or nitrogen in the atmospheric gas can efficiently enter the silicon melt.

  According to the above (9), since the carbon source is silicon carbide powder and the nitrogen source is silicon nitride powder, the addition method of the carbon source or the nitrogen source is simple, and the adjustment of the addition amount is easy. There is an effect that can be done.

    According to the above (10), silicon having a silicon carbide film formed on the surface of the silicon raw material by carbonization treatment is used as the carbon source, or the silicon nitride film formed on the surface of the silicon raw material by nitriding treatment is used as the nitrogen source. Since silicon is used, there are effects that contamination of impurities can be reduced and the amount of carbon or nitrogen added can be easily adjusted.

  According to the method for producing granular silicon crystals of the present invention, according to the above (11), the silicon melt is discharged in a granular form from the nozzle portion made of silicon carbide or silicon nitride in the crucible and dropped. A granular silicon crystal manufacturing method for manufacturing granular silicon crystals by cooling and solidifying a silicon melt while falling, and when the nozzle portion is made of silicon carbide, an inorganic solid member containing carbon is used for the nozzle portion. When silicon is made of silicon nitride, since an inorganic solid member containing nitrogen is introduced into the silicon melt in the crucible, carbon or nitrogen of the inorganic solid member enters the silicon melt in a trace amount and at a saturation concentration. Most of the silicon in the melt does not react with the nozzle part but reacts with carbon or nitrogen derived from the inorganic solid member, and the reacted silicon carbide or silicon nitride Morphology will be present in the silicon melt, that silicon in the silicon melt reacts with the carbon and silicon which is the material of the nozzle portion can be significantly suppressed.

  As a result, it is possible to suppress changes in the shape of the nozzle portion, and to produce melt droplets of a uniform size over a long period of time, and to produce granular silicon crystals with small particle size variations with high productivity and high reproducibility. be able to. In addition, since the grain size variation of the granular silicon crystal is small, uniform crystal growth can be realized, so that a granular silicon crystal with small variation in crystal quality can be manufactured.

  According to the above (12) and (13), the inorganic solid member containing carbon is made of graphite or silicon carbide, so that the carbon or silicon carbide of the inorganic solid member dissolves in the highly reactive silicon melt and easily Carbon is added to near the solid solution limit (saturation concentration), and as a result, there is an effect that most of the silicon reacts in the silicon melt to form silicon carbide.

  According to the above (14) and (15), the inorganic solid member containing nitrogen is made of silicon nitride, so that nitrogen or silicon nitride of the inorganic solid member dissolves in the highly reactive silicon melt and easily dissolves. Nitrogen is added to near the limit, and as a result, most of the silicon melt reacts with silicon to form silicon nitride.

  According to the above (16) and (17), the carbon-containing inorganic solid member is installed so as to cover the upper part of the nozzle hole of the nozzle part, and does not pass silicon carbide particles generated in the silicon melt. Since a large number of through-holes are formed, it is possible to prevent most of the large silicon carbide particles present in the silicon melt from reaching the nozzle portion, so the nozzle of the nozzle portion that discharges the silicon melt Stable production is possible by suppressing clogging of holes.

  According to the above (18) and (19), the inorganic solid member containing nitrogen is installed so as to cover the upper part of the nozzle hole of the nozzle part, and the silicon nitride particles generated in the silicon melt are removed. Since a large number of through-holes that do not pass are formed, it is possible to prevent most of the large silicon nitride particles present in the silicon melt from reaching the nozzle portion side, so that the nozzle portion that discharges the silicon melt Stable production is possible by suppressing clogging of the nozzle holes.

  Embodiments of the method for producing granular silicon crystals of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a manufacturing apparatus in an example of an embodiment of a method for manufacturing a granular silicon crystal of the present invention. In FIG. 1, 1 is a crucible, 1 a is a nozzle part provided at the bottom of the crucible 1, 2 is a tube arranged below the crucible 1 so that the longitudinal direction is the vertical direction, and 3 is a quartz provided in the crucible 1. Etc., 4 is a granular silicon melt, and 5 is a granular silicon crystal.

(crucible)
The crucible 1 is a container for heating and melting silicon particles as a raw material to form a silicon melt and discharging it from the nozzle portion 1a at the bottom as a granular silicon melt 4. The silicon melt heated and melted in the crucible 1 is discharged from the nozzle portion 1 a into the tube 2, and becomes a granular silicon melt 4 that falls inside the tube 2. The crucible 1 is made of a material having a melting point higher than that of silicon. The crucible 1 is preferably made of a material having low reactivity with the silicon melt, and when the reaction with the silicon melt is large, the material of the crucible 1 is mixed in the granular silicon crystal 5 as impurities. Therefore, it is not preferable.

  For example, the material of the crucible 1 is carbon, silicon carbide sintered body, silicon carbide crystal, boron nitride sintered body, silicon oxynitride sintered body, quartz, crystal, silicon nitride sintered body, oxidation Aluminum sintered bodies, sapphire, magnesium oxide sintered bodies and the like are preferable. Moreover, the composite of these materials, a mixture, or a combination may be sufficient. Further, a silicon carbide film, a silicon nitride film, or a silicon oxide film may be coated on the surface of the base made of the above material. Moreover, as a heating method for heating the raw material to the melting point or more in the crucible 1, electromagnetic induction heating, resistance heating, or the like is suitable.

  The nozzle portion 1a is made of silicon carbide (silicon carbide crystal or silicon carbide sintered body) or silicon nitride (silicon nitride sintered body). The nozzle hole formed in the nozzle part 1a is good in the column shape which has a diameter of 80-200 micrometers and a length of 0.5-2 mm. Further, the shape of the nozzle hole may be substantially conical as long as the cross section of the discharge port has a substantially circular shape, and is not particularly limited.

(Carbon source)
When the material of the nozzle portion 1a is silicon carbide (silicon carbide crystal or silicon carbide sintered body), a gas containing carbon is mixed into the atmospheric gas in the crucible 1 and added. When carbon is not added to the atmospheric gas, a small amount of carbon does not enter the silicon melt from the atmospheric gas, so that the reaction between the silicon melt not containing carbon and the nozzle portion 1a increases, and the shape of the nozzle portion 1a is Change. As a result, for example, the nozzle hole of the nozzle portion 1a becomes large, the size of the granular silicon melt 4 increases with time, and it becomes difficult to obtain the granular silicon crystal 5 having a required particle size. Further, when the nozzle hole is enlarged, the granular silicon melt 4 reaches the bottom of the tube 2 before solidifying and cannot be obtained as the granular silicon crystal 5.

  At this time, the gas containing carbon as a carbon supply source to the silicon melt is preferably a gas such as carbon dioxide gas, carbon monoxide gas, methane gas, acetylene gas, methylene gas, methanol gas, and ethanol gas. . In particular, carbon monoxide gas or carbon dioxide gas is preferable, and these gases have an advantage that they can be easily dissolved in a highly reducible silicon melt.

  A gas containing carbon is mixed and added to an argon gas as an atmospheric gas supplied into the crucible 1. That is, carbon is mixed as an impurity in an amount that greatly reduces the crystal quality of the granular silicon crystal 5 by being added to the atmospheric gas in the crucible 1 through the gas introduction pipe 3 and entering the silicon melt from the atmospheric gas in a small amount. It is possible to allow a small amount of carbon to enter the silicon melt. As a result, enlargement of the nozzle holes can be suppressed, and high-quality and high-quality granular silicon crystals 5 can be obtained.

When introducing a small amount of carbon from the atmospheric gas into the silicon melt, it is preferable to add carbon in an amount of 1 × 10 ¹⁷ atoms / cm ³ to 1 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon. If it is less than 1 × 10 ¹⁷ atoms / cm ³ , silicon carbide in the nozzle hole is eluted in the silicon melt, and the nozzle hole diameter is likely to be increased. If it exceeds 1 × 10 ¹⁹ atoms / cm ³ , Silicon carbide particles are likely to precipitate and aggregate to block the nozzle holes. In order to add carbon within the above range to the silicon melt, the amount of carbon in the melt is adjusted by controlling the amount of gas containing carbon added to the argon gas.

  Moreover, it is preferable that the gas inlet tube 3 for adding carbon to a silicon melt has a lower end which is a gas discharge port located 10 to 300 mm above the silicon melt surface. If the thickness is less than 10 mm, the material of the gas introduction tube 3 is eluted by direct contact with the silicon melt due to the vibration of the surface of the silicon melt. If the thickness exceeds 300 mm, the gas for adding carbon reaches the surface of the silicon melt. Not enough carbon is added.

(Nitrogen source)
When the nozzle 1a is made of a silicon nitride sintered body, a small amount of nitrogen is introduced into the silicon melt by adding a gas containing nitrogen to the atmospheric gas in the crucible 1. When a small amount of nitrogen is not allowed to enter the silicon melt, the shape of the nozzle portion 1a changes because the reaction between silicon and the nozzle portion 1a is large. As a result, the nozzle hole of the nozzle portion 1a becomes large, the size of the granular silicon melt 4 increases with time, and it becomes difficult to obtain the granular silicon crystal 5 having a required particle size. Further, when the nozzle hole is enlarged, the granular silicon melt 4 reaches the bottom of the tube 2 before solidifying and cannot be obtained as the granular silicon crystal 5.

  At this time, the gas containing nitrogen as a nitrogen supply source to the silicon melt is preferably a gas such as nitrogen gas, nitrogen oxide gas, or ammonia gas. Nitrogen gas is particularly good, and nitrogen gas has the advantage that an increase in the oxygen concentration of the silicon melt can be suppressed.

  Nitrogen-containing gas is added to the argon gas as the atmospheric gas supplied in the crucible 1 and added. That is, by adding a gas containing nitrogen from the gas introduction pipe 3 to the atmospheric gas in the crucible 1 and causing a slight amount of nitrogen in the atmospheric gas to enter the silicon melt, it is possible to suppress the expansion of the nozzle hole of the nozzle portion 1a. it can. As a result, since a small amount of nitrogen can be introduced into the silicon melt without mixing nitrogen as an amount of impurities that greatly reduces the crystal quality of the granular silicon crystal 5, high-quality and high-quality granular silicon crystal 5 Can be obtained.

When introducing a slight amount of nitrogen from the atmospheric gas into the silicon melt, it is preferable to add nitrogen in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon. Is less than ^{2 × 10 17 atoms / cm 3} , the silicon nitride of the nozzle hole is eluted into the silicon melt, easily expanded nozzle hole diameter is more than ^{2 × 10 19 atoms / cm 3} , the silicon of the nozzle portion 1a Silicon nitride particles are deposited on the melt side, and the nozzle holes are easily blocked. In order to add nitrogen within the above range to the silicon melt, the amount of nitrogen in the melt is adjusted by controlling the amount of nitrogen-containing gas added to the argon gas.

  Moreover, it is preferable that the gas introduction pipe | tube 3 for adding nitrogen to a silicon melt has the lower end which is a gas discharge port located 10-300 mm above the liquid level of a silicon melt. If the thickness is less than 10 mm, the silicon melt and the lower end of the gas introduction pipe 3 are in direct contact with each other due to the peristaltic movement of the silicon melt, and the material of the gas introduction pipe 3 is eluted. Nitrogen addition gas does not reach the liquid surface, and nitrogen tends to be insufficiently added.

In the present invention, the atmospheric gas in the crucible 1 containing the silicon melt contains a gas containing carbon when the nozzle portion 1a is made of silicon carbide, and a nitrogen containing gas when the nozzle portion 1a is made of silicon nitride. After adding, it is preferable to make the pressure of the atmospheric gas in the crucible 1 higher than the pressure before the addition of the gas. In this case, carbon or nitrogen in the atmospheric gas efficiently enters the silicon melt. In this case, when the pressure of the atmospheric gas in the crucible 1 is compared with the pressure in the quartz tube 2, the pressure in the tube 2 is preferably about 0.01 to 0.1 MPa higher, If it is less than 0.01 MPa, it becomes difficult to efficiently enter carbon or nitrogen in the atmosphere gas into the silicon melt, and if it exceeds 0.1 MPa, the carbon or nitrogen deteriorates the crystal quality in the silicon melt. It will enter as an amount of impurities.
The pressure of the atmospheric gas can be changed using a hydraulic or electric piston and cylinder, a compression pump, or the like.

(tube)
Further, in the present invention, the pipe 2 arranged so that the longitudinal direction extends vertically from the nozzle portion 1a of the crucible 1 drops the granular silicon melt 4 discharged from the nozzle portion 1a. It is a container that cools and solidifies. The inside of the tube 2 is controlled to a desired pressure with a desired atmospheric gas. The desired atmospheric gas is preferably helium gas or argon gas. The helium gas or argon gas is an inert gas, and can prevent impurities from being mixed into the granular silicon melt 4 from the atmospheric gas. Furthermore, helium gas or argon gas has low reactivity with the silicon melt 4 and can suppress the formation of a reaction layer on the surface of the melt 4 that hinders the solid silicon melt 4 from solidifying and crystallizing. preferable. The pressure of helium gas or argon gas can be controlled by adjusting the gas inflow and gas discharge.

  The tube 2 is preferably made of a material having a melting point higher than that of silicon, or preferably has a cooling structure (not shown) for cooling the tube 2 itself.

  When the material of the tube 2 has a melting point higher than that of silicon, even if the granular silicon melt 4 is discharged obliquely and collides with the inner wall of the tube 3, the tube 2 is made of the material. It is not heated above its melting point, and is not mixed as impurities into the granular silicon melt 4 collided with the material of the tube 2.

  When the melting point of the material of the tube 2 is lower than the melting point of silicon, when the granular silicon melt 4 is discharged in an oblique direction and collides with the inner wall of the tube 2, the tube 2 is heated above the melting point of the material. However, the material of the tube 2 may be mixed as impurities into the collapsible granular silicon melt 4. However, in this case, a cooling structure for cooling the tube 2 itself is added to the tube 2. Thus, the collision of the melt 4 can prevent the tube 2 from being heated above the melting point of the material, and it is possible to avoid contamination of the melt 4 with impurities.

  As the material of the tube 2, when it has a melting point higher than that of silicon, carbon, silicon carbide sintered body, silicon carbide crystal, boron nitride sintered body, silicon oxynitride sintered body, quartz, crystal, A silicon nitride sintered body, an aluminum oxide sintered body, sapphire, a magnesium oxide sintered body and the like are preferable. Moreover, the composite of these materials, a mixture, or a combination may be sufficient. In addition, a silicon carbide film, a silicon nitride film, or a silicon oxide film may be coated on the surface of the substrate made of the above material.

  When the material of the tube 2 is a material having a lower melting point than that of silicon such as stainless steel or aluminum, it is preferable that the tube 2 is water-cooled with a double tube structure or a water-cooling jacket.

  Note that silicon carbide or silicon nitride powder can be added in place of the gas containing carbon or nitrogen as a supply source of carbon or nitrogen to the silicon melt. In this case, the powder may be added directly to the silicon melt, or a material obtained by adding the powder to a silicon raw material in advance may be put in the crucible 1 and melted. When adding the powder to the silicon raw material or silicon melt, the amount of each powder added is adjusted so as to be equal to or lower than the saturation concentration, and the powder is molded and enlarged (for example, the particle size is 500 μm or more), and the nozzle It is necessary to cover the hole with a member made of mesh-like silicon carbide or silicon nitride. In this case, the mesh-shaped hole is preferably 80 to 200 μm. As a result, the powder added to the silicon melt is discharged without being melted and mixed into the product, thereby preventing deterioration of characteristics.

  In addition, carbon or nitrogen as a carbon or nitrogen supply source to the silicon melt described above, after previously forming a silicon carbide film or silicon nitride film on the silicon raw material surface and adding them as a carbon source or nitrogen source, The silicon raw material may be put in the crucible 1 and melted. The silicon carbide film formed on the surface of the silicon raw material can be formed by thermal carbonization. In addition, the silicon nitride film can be formed by thermally nitriding a silicon raw material on the surface thereof. A CVD method or a sputtering method may be used for forming the silicon carbide film and the silicon nitride film. In addition, when adding carbon or nitrogen by forming a silicon carbide film or a silicon nitride film, the amount of each film formation is adjusted to be equal to or lower than a saturated concentration, and the nozzle is added in the same manner as in the case of adding the powder. It is preferable to cover the holes with mesh-like silicon carbide or silicon nitride. In this case, the mesh-shaped holes are preferably 80 to 200 μm. Accordingly, the film formation is not melted in the silicon melt and is discharged in the form of particles and is not mixed into the product, thereby preventing deterioration of characteristics.

<Other embodiments>
FIG. 2 is a cross-sectional view of a manufacturing apparatus used in a method for manufacturing granular silicon crystals according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same component as FIG. 1, and description is abbreviate | omitted. 6 shows an inorganic solid member.

  The method for producing granular silicon crystal 5 according to another embodiment of the present invention is to discharge the silicon melt in a granular form from nozzle portion 1a made of silicon carbide or silicon nitride in crucible 1 and drop the granular silicon crystal. A method for producing a granular silicon crystal 5 in which the melt is cooled and solidified while falling, and when the nozzle portion 1a is made of silicon carbide, an inorganic solid member 6 containing carbon is used. When the nozzle portion 1a is made of silicon nitride, the inorganic solid member 6 containing nitrogen is introduced into the silicon melt in the crucible 1.

(Inorganic solid member: carbon source)
When the material of the nozzle portion 1a is silicon carbide (silicon carbide crystal or silicon carbide sintered body), the inorganic solid member 6 containing carbon is introduced into the silicon melt in the crucible 1. The shape may be a simple piece, but it is necessary to arrange the nozzle portion 1a so as not to block the nozzle hole. For example, the inorganic solid member 6 can be arranged in a ring shape so as to surround the nozzle hole of the nozzle portion 1a. In addition, the inorganic solid member 6 may be formed into a disk shape or a disk shape in which a concave portion is formed above the nozzle hole of the nozzle portion 1a. The inorganic solid member 6 may be spherical.

  Further, as shown in FIG. 2, the inorganic solid member 6 has a cylindrical shape in which the inside is hollowed out leaving the upper bottom portion, and the upper bottom portion has the same degree as the nozzle hole of the nozzle portion 1a. A shape in which a large number of through-holes having a diameter of about 100 to 150 μm are formed. In this case, a large number of through holes have a function of preventing reaching to the nozzle portion 1a without passing through the large silicon carbide particles and silicon nitride particles generated in the silicon melt. Since the absolute amount of silicon carbide particles and silicon nitride particles generated in the member 6 is small, there is almost no influence on the nozzle portion 1a.

  In the case where the inorganic solid member 6 containing carbon is not introduced, carbon does not elute from the inorganic solid member 6 containing carbon into the silicon melt, so that silicon in the silicon melt not containing carbon and the nozzle portion 1a The reaction with the material (carbon) increases, and the shape of the nozzle portion 1a changes. As a result, for example, the nozzle hole of the nozzle portion 1a becomes large, the size of the granular silicon melt 4 increases with time, and it becomes difficult to obtain the granular silicon crystal 5 having a required particle size. Further, when the nozzle hole is enlarged, the granular silicon melt 4 reaches the bottom of the tube 2 before solidifying and cannot be obtained as the granular silicon crystal 5.

  In the present invention, the inorganic solid member 6 containing carbon as a carbon supply source to the silicon melt is preferably made of graphite and silicon carbide having high purity (purity of about 99.99 to 99.999% by weight). The shape of the inorganic solid member 6 is preferably spherical in that it has a large surface area and a large amount of elution, but it may be a cube or columnar rounded corner (corner), in which case the carbon is eluted. It becomes easy to control the elution amount of carbon by rounding a corner portion (corner portion) having a large amount.

  An inorganic solid member 6 containing carbon is introduced into the crucible 1 and immersed in the silicon melt. That is, by introducing a small amount of carbon from the inorganic solid member 6 containing carbon into the silicon melt and about a saturated concentration, carbon is not mixed as an impurity in an amount that greatly reduces the crystal quality of the granular silicon crystal 5. Carbon can be introduced into the silicon melt. As a result, enlargement of the nozzle holes can be suppressed, and high-quality and high-quality granular silicon crystals 5 can be obtained.

In caused to enter the carbon in the silicon melt from inorganic solid member 6, is to such an amount of carbon in the silicon 1 cm ³ per ^{1 × 10 17 atomsatoms / cm 3} ~1 × 10 19 atoms / cm 3 is added Good. If it is less than 1 × 10 ¹⁷ atoms / cm ³ , silicon carbide in the nozzle hole is eluted in the silicon melt, and the nozzle hole diameter is likely to be increased. If it exceeds 1 × 10 ¹⁹ atoms / cm ³ , Silicon carbide particles are likely to precipitate and aggregate to block the nozzle holes. In order to add carbon within the above range to the silicon melt, the amount of carbon in the melt is adjusted by controlling the amount of the inorganic solid member 6 containing carbon to be added.

  In addition, the silicon melt into which the inorganic solid member 6 for adding carbon is introduced is discharged after a sufficient amount of carbon is eluted from the inorganic solid member 6 by allowing a certain period of time after the silicon is melted. It is preferable to do. If the silicon melt is discharged immediately after melting the silicon, the diffusion of the eluted carbon into the entire silicon melt becomes insufficient, resulting in enlargement of the nozzle holes.

(Inorganic solid member: Nitrogen source)
When the nozzle part 1a is made of silicon nitride (silicon nitride-based sintered body), a small amount of nitrogen is saturated in the silicon melt by introducing the inorganic solid member 6 containing nitrogen into the silicon melt in the crucible 1. It is possible to get into the concentration. When a very small amount of nitrogen is not allowed to enter the silicon melt, since the reaction between the silicon in the silicon melt and the material (nitrogen) of the nozzle portion 1a is large, the shape of the nozzle portion 1a changes. As a result, the nozzle hole of the nozzle portion 1a becomes large, the size of the granular silicon melt 4 increases with time, and it becomes difficult to obtain the granular silicon crystal 5 having a required particle size. Further, when the nozzle hole is enlarged, the granular silicon melt 4 reaches the bottom of the tube 2 before solidifying and cannot be obtained as the granular silicon crystal 5.

  At this time, the inorganic solid member 6 containing nitrogen as a nitrogen supply source to the silicon melt is preferably high-purity silicon nitride (purity of about 99.5 to 99.99% by weight). When the nitrogen element is eluted, there is an advantage that an increase in the oxygen concentration of the silicon melt can be suppressed.

  Nitrogen is eluted from the inorganic solid member 6 and is allowed to enter the silicon melt into a trace amount and a saturated concentration, thereby suppressing expansion of the nozzle hole of the nozzle portion 1a. As a result, since nitrogen can be introduced into the silicon melt without mixing nitrogen as an amount of impurities that greatly reduces the crystal quality of the granular silicon crystal 5, the high-purity and high-quality granular silicon crystal 5 Can be obtained.

When introducing nitrogen from the inorganic solid member 6 into the silicon melt, it is preferable to add nitrogen in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon. . Is less than ^{2 × 10 17 atoms / cm 3} , the silicon nitride of the nozzle hole is eluted into the silicon melt, easily expanded nozzle hole diameter is more than ^{2 × 10 19 atoms / cm 3} , the silicon of the nozzle portion 1a Silicon nitride particles are deposited on the melt side, and the nozzle holes are easily blocked. In order to add nitrogen within the above range to the silicon melt, the amount of nitrogen in the melt is adjusted by controlling the amount of the inorganic solid member 6 containing nitrogen to be added.

  In the present invention, when the nozzle part 1a is made of silicon carbide in the silicon melt in the crucible 1 containing the silicon melt, the inorganic solid member 6 containing carbon is used, and the nozzle part 1a is made of silicon nitride. By introducing the inorganic solid member 6 containing nitrogen, it is possible to suppress the expansion of the nozzle hole that occurs when the discharged silicon melt dissolves the material of the nozzle portion 1a. Thereby, the shape of the silicon melt droplet discharged and formed from the nozzle portion 1a is stabilized, and the productivity can be improved.

  Preferably, in the present invention, the carbon-containing inorganic solid member 6 is installed so as to cover the upper portion of the nozzle hole of the nozzle portion 1a, and a large number of silicon carbide particles generated in the silicon melt are not passed. A through hole is preferably formed. Preferably, the inorganic solid member 6 containing nitrogen is installed so as to cover the upper part of the nozzle hole of the nozzle portion 1a, and has a large number of through holes that do not allow the silicon nitride particles generated in the silicon melt to pass therethrough. Is preferably formed. As a result, it is possible to prevent large silicon carbide particles and silicon nitride particles present in the silicon melt from reaching the nozzle portion 1a side, so that the nozzle hole for discharging the silicon melt is prevented from being clogged and more stable. Production becomes possible.

  This is also effective for removing silicon carbide particles floating in the silicon melt by forming and growing silicon carbide fine particles in the silicon melt that has reached the saturation concentration of carbon. The same applies to nitrogen.

  In this case, the through-hole formed in the inorganic solid member 6 should just have a diameter of about 80-200 micrometers. If the diameter of the through hole is less than 80 μm, most of the silicon carbide particles and silicon nitride particles having a size of less than 80 μm that have passed through the through hole pass through the nozzle hole having a diameter of about 150 μm as they are. If the diameter of the through hole exceeds 200 μm, silicon carbide fine particles and silicon nitride particles larger than the nozzle hole having a diameter of about 150 μm pass through the through hole and block the nozzle hole.

  EXAMPLES Hereinafter, although the manufacturing method of the granular silicon crystal of this invention is demonstrated in detail, giving an Example and a comparative example, this invention is not limited only to a following example.

  An embodiment of the method for producing granular silicon crystals of the present invention will be described below based on the example shown in FIG.

First, 5000 g of silicon added with 1 × 10 ¹⁶ atoms / cm ^{3 of} p-type dopant B (boron) as a material of the granular silicon crystal 5 is put into a crucible 1 made of graphite, and the crucible 1 is heated by electromagnetic induction. did. The nozzle portion 1a is formed by forming a nozzle hole (through hole) on a flat plate made of silicon carbide crystal, the diameter of the nozzle hole having a circular cross section is 100 μm, and the length (thickness) of the nozzle portion 1a. Was 1 mm.

  A mixed gas of argon gas and carbon dioxide gas was introduced into the crucible 1 through the gas introduction pipe 3 as the atmospheric gas. The mixing ratio of argon gas and carbon dioxide gas was 1000: 10 in volume ratio.

Thereafter, the pressure of the atmospheric gas in the crucible 1 is increased from 0.1 MPa to 0.3 MPa, which is the pressure in the tube 2 before the addition of carbon dioxide gas, and pressure is applied to the surface of the silicon melt. Then, the silicon melt was discharged from the nozzle portion 1 a to the inside of the tube 2, and the granular silicon melt 4 was cooled and solidified while dropping inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle diameter of 700 μm, a standard deviation of particle diameter of 100 μm, and a recovery rate of 95%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. Further, the obtained granular silicon crystal 5 contained carbon as a trace component of about 1 × 10 ¹⁸ atoms / cm ³ .
The particle size of the granular silicon particles was measured using a laser diffraction / scattering type measuring device (manufactured by Nikkiso Co., Ltd.). In the cumulative particle size curve, the average particle size is Q% = in the cumulative particle size curve in which the horizontal axis is the particle size D (μm) and the vertical axis is Q% (the ratio of particles below the particle size is the unit is the volume% of the particles). The value of the particle diameter D ₅₀ corresponding to 50% was taken. The concentration of impurities such as carbon contained in the silicon crystal was measured using an ICP-MS (Inductively Coupled Plasma Mass Spectrometer) apparatus (manufactured by Micromass). The same applies to the embodiments described below.

(Comparative Example 1)
Argon gas alone is introduced into the crucible 1 from the gas introduction tube 3 as an atmospheric gas, pressure is applied to the surface of the silicon melt in the crucible 1 in the same manner as in the first embodiment, and the inside of the tube 2 from the nozzle portion 1a. The silicon melt was discharged, and the granular silicon melt 4 was cooled and solidified while dropping the inside of the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle diameter of 1200 μm, a standard deviation of particle diameter of 400 μm, and a recovery rate of 10%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. The obtained granular silicon crystal 5 contained carbon as a trace component of about 3 × 10 ¹⁶ atoms / cm ³ .

  As a nozzle portion 1a having a diameter of 100 μm and a length (thickness) of the nozzle portion 1a of 1 mm, the nozzle portion (through hole) is formed on a flat plate made of a silicon nitride sintered body. Using.

  A mixed gas of argon gas and nitrogen gas was introduced into the crucible 1 from the gas introduction tube 3 as the atmospheric gas. The mixing ratio of argon gas and nitrogen gas was 1000: 50 in volume ratio.

Thereafter, the pressure of the atmospheric gas in the crucible 1 is increased from 0.1 MPa, which is the pressure before the addition of nitrogen gas, and the pressure in the tube 2 to 0.3 MPa, so that the silicon melt liquid level in the crucible 1 is reached. Pressure was applied, the silicon melt was discharged from the nozzle part 1 a to the inside of the tube 2, and the granular silicon melt 4 was cooled and solidified while dropping inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle diameter of 700 μm, a standard deviation of particle diameter of 90 μm, and a recovery rate of 97%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. Further, the obtained granular silicon crystal 5 contained nitrogen as a trace component of about 5 × 10 ¹⁷ atoms / cm ³ .

(Comparative Example 2)
Argon gas alone is introduced into the crucible 1 from the gas introduction tube 3 as an atmospheric gas, and pressure is applied to the surface of the silicon melt in the crucible 1 in the same manner as in the second embodiment. The silicon melt was discharged, and the granular silicon melt 4 was cooled and solidified while dropping inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle diameter of 1400 μm, a standard deviation of particle diameter of 450 μm, and a recovery rate of 15%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of a desired particle size (−400 μm to +400 μm) with respect to the average particle size by the total input weight. The obtained granular silicon crystal 5 contained nitrogen as a trace component of about 1 × 10 ¹⁶ atoms / cm ³ .

  As the nozzle portion 1a, a flat plate made of silicon carbide crystal is used to form nozzle holes (through holes). The diameter of the nozzle hole having a circular cross section is 100 μm, and the length of the nozzle portion 1a ( The thickness was 1 mm. An inorganic solid member 6 made of silicon carbide was placed in the crucible 1. As shown in FIG. 2, the inorganic solid member 6 has a cylindrical shape with a diameter of about 10 mm and a height of about 3 mm, and has a structure in which the inside is hollowed out, leaving an upper bottom portion. Many through holes having the same diameter as the nozzle holes of the nozzle portion 1a are formed. The inorganic solid member 6 was rounded at the corners in order to suppress excessive elution of carbon from the corners.

Next, 5000 g of silicon added with 1 × 10 ¹⁶ atoms / cm ^{3 of} p-type dopant B (boron) as a material of the granular silicon crystal 5 is put into the crucible 1 made of graphite, and the crucible 1 is electromagnetically placed. Heated by induction.

  Argon gas was used as the atmospheric gas and circulated in the crucible 1 to exclude exhaust gas such as silicon monoxide formed based on the silicon melt in the crucible 1.

Thereafter, the pressure of the atmospheric gas in the crucible 1 is increased from 0.1 MPa to 0.3 MPa, which is the pressure in the tube 2, and pressure is applied to the liquid surface of the silicon melt. Then, the molten silicon 4 was cooled and solidified while dropping the granular silicon melt 4 inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle diameter of 450 μm, a standard deviation of particle diameter of 70 μm, and a recovery rate of 96%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. Further, the obtained granular silicon crystal 5 contained carbon as a trace component of about 1 × 10 ¹⁸ atoms / cm ³ .

  After repeating the discharge of the silicon melt many times, the nozzle hole was examined. As a result, the hole diameter was not enlarged and was maintained at about 100 μm. Further, particles such as slag formed in the silicon melt did not pass through the through holes of the inorganic solid member 6 and were filtered, and the nozzle holes were not clogged.

(Comparative Example 3)
Without introducing the inorganic solid member 6 into the silicon melt in the crucible 1, pressure is applied to the surface of the silicon melt in the crucible 1 in the same manner as in Example 1 above, and from the nozzle portion 1 a to the inside of the tube 2. The silicon melt was discharged, and the granular silicon melt 4 was cooled and solidified while dropping inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle size of 800 μm, a standard deviation of particle size of 200 μm, and a recovery rate of 10%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. The obtained granular silicon crystal 5 contained carbon as a trace component of about 2 × 10 ¹⁶ atoms / cm ³ .

  As the nozzle portion 1a, a nozzle hole (through hole) is formed in a flat plate made of a silicon nitride sintered body as the nozzle portion 1a having a nozzle hole diameter of 100 μm and a length (thickness) of the nozzle portion 1a of 1 mm. I used the following. The periphery of the nozzle hole protruded from the upper surface of the nozzle portion 1a, and ten spherical inorganic solid members 6 made of silicon nitride and having a diameter of about 5 mm were introduced into the crucible 1.

  Argon gas was introduced into the crucible 1 from the gas introduction tube 3 as the atmospheric gas.

Into the crucible 1 made of graphite, 5000 g of silicon added with 1 × 10 ¹⁶ atoms / cm ^{3 of} p-type dopant B (boron) as a material of the granular silicon crystal 5 is put, and the crucible 1 is heated by electromagnetic induction. did.

Thereafter, the pressure of the atmospheric gas in the crucible 1 is increased from 0.1 MPa, which is the pressure in the tube 2, to 0.3 MPa, the pressure is applied to the liquid surface of the silicon melt in the crucible 1, and the tube 2 from the nozzle portion 1a. The silicon melt was discharged to the inside, and the granular silicon melt 4 was cooled and solidified while dropping inside the tube 2 to obtain a granular silicon crystal 5. The obtained granular silicon crystal 5 had an average particle size of 480 μm, a standard deviation of particle size of 70 μm, and a recovery rate of 97%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of the desired particle size (−300 μm to +300 μm) with respect to the average particle size by the total input weight. The obtained granular silicon crystal 5 contained nitrogen as a trace component of about 7 × 10 ¹⁷ atoms / cm ³ .

  Moreover, when the nozzle hole after repeating discharge | emission of silicon melt many times was investigated, the hole diameter was not expanded.

(Comparative Example 4)
Except for introducing argon gas as an atmospheric gas into the crucible 1 through the gas introduction tube 3 and not using the solid member 6 made of silicon nitride in the crucible 1, the silicon melt in the crucible 1 is the same as in Example 4 above. Pressure is applied to the liquid surface, the silicon melt is discharged from the nozzle portion 1a to the inside of the tube 2, and the granular silicon melt 4 is cooled and solidified while falling inside the tube 2 to form a granular silicon crystal. 5 was obtained. The obtained granular silicon crystal 5 had an average particle size of 900 μm, a standard deviation of particle size of 220 μm, and a recovery rate of 15%. The recovery rate was obtained by dividing the weight recovered as the granular silicon crystal 5 within the range of a desired particle size (−400 μm to +400 μm) with respect to the average particle size by the total input weight. The obtained granular silicon crystal 5 contained nitrogen as a trace component of about 1 × 10 ¹⁶ atoms / cm ³ .

  From the above results, the granular silicon crystal obtained by the example of the present invention has a smaller particle size variation and a larger recovery amount than the granular silicon crystal obtained by the comparative example. This indicates that the method for producing granular silicon crystals of the present invention can obtain granular silicon crystals having small particle size variations with high productivity and good reproducibility.

  The present invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from the scope of the present invention.

It is sectional drawing of the basic composition which shows an example of embodiment about the manufacturing apparatus concerning the manufacturing method of the granular silicon crystal of this invention. It is sectional drawing of the basic composition about the manufacturing apparatus used for the manufacturing method of the granular silicon crystal which concerns on other embodiment of this invention.

Explanation of symbols

1: crucible 1a: nozzle part 2: pipe 3: gas introduction pipe 4: granular silicon melt 5: granular silicon crystal 6: inorganic solid member

Claims (19)

  Granules for producing granular silicon crystals by discharging and dropping the silicon melt in the crucible in a granular form from a nozzle portion made of silicon carbide or silicon nitride, and cooling and solidifying the granular silicon melt during the dropping. A silicon crystal manufacturing method, wherein a carbon source is added to the silicon melt in the crucible when the nozzle portion is made of silicon carbide, and a nitrogen source is added when the nozzle portion is made of silicon nitride. The manufacturing method of the granular silicon crystal characterized by these.   The carbon source is a gas containing carbon, the nitrogen source is a gas containing nitrogen, and the atmosphere gas in the crucible containing a silicon melt contains a gas containing carbon when the nozzle portion is made of silicon carbide. The method for producing granular silicon crystals according to claim 1, wherein when the nozzle portion is made of silicon nitride, a gas containing nitrogen is added.   3. The method for producing granular silicon crystals according to claim 2, wherein when the nozzle portion is made of silicon carbide, the gas containing carbon is carbon monoxide gas or carbon dioxide gas. When the nozzle part is made of silicon carbide, carbon in an amount of 1 × 10 ¹⁷ atoms / cm ³ to 1 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. Item 3. A method for producing a granular silicon crystal according to Item 2.   3. The method for producing granular silicon crystals according to claim 2, wherein when the nozzle portion is made of silicon nitride, the gas containing nitrogen is nitrogen gas. When the nozzle portion is made of silicon nitride, nitrogen in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. Item 3. A method for producing a granular silicon crystal according to Item 2.   After adding a gas containing carbon when the nozzle part is made of silicon carbide, or a gas containing nitrogen when the nozzle part is made of silicon nitride to the atmosphere gas in the crucible containing the silicon melt The method for producing granular silicon crystals according to claim 2, wherein the pressure of the atmospheric gas in the crucible is made higher than the pressure before the addition of the gas.   3. The granular silicon according to claim 2, wherein the gas introduction pipe for adding a gas containing carbon or nitrogen to the silicon melt has a gas outlet located 10 to 300 mm above the silicon melt surface. Crystal production method.   2. The method for producing granular silicon crystals according to claim 1, wherein the carbon source is silicon carbide powder and the nitrogen source is silicon nitride powder.   When the nozzle portion is made of silicon carbide, silicon in the silicon melt is silicon in which a silicon carbide film as the carbon source is formed on the surface of a silicon raw material by carbonization, and the nozzle portion is made of silicon nitride. 2. The method for producing granular silicon crystals according to claim 1, wherein the silicon nitride film is formed by forming a silicon nitride film as the nitrogen source on the surface of a silicon raw material by nitriding.   When the carbon source is an inorganic solid member containing carbon, the nitrogen source is an inorganic solid member containing nitrogen, and the nozzle part is made of silicon carbide, the inorganic solid member containing carbon is used, and the nozzle part is silicon nitride. 2. The method for producing granular silicon crystals according to claim 1, wherein the inorganic solid member containing nitrogen is introduced into the silicon melt in the crucible.   12. The method for producing granular silicon crystals according to claim 11, wherein the inorganic solid member containing carbon is made of graphite or silicon carbide. When the nozzle part is made of silicon carbide, carbon in an amount of 1 × 10 ¹⁷ atoms / cm ³ to 1 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. Item 12. A method for producing a granular silicon crystal according to Item 11.   12. The method for producing granular silicon crystals according to claim 11, wherein the inorganic solid member containing nitrogen is made of silicon nitride. When the nozzle portion is made of silicon nitride, nitrogen in an amount of 2 × 10 ¹⁷ atoms / cm ³ to 2 × 10 ¹⁹ atoms / cm ³ per 1 cm ^{3 of} silicon is added to the silicon melt. Item 12. A method for producing a granular silicon crystal according to Item 11.   The carbon-containing inorganic solid member is installed so as to cover the upper part of the nozzle hole of the nozzle part, and a plurality of through holes that do not allow the silicon carbide particles generated in the silicon melt to pass therethrough are formed. The method for producing granular silicon crystals according to claim 11.   The diameter of the said through-hole is 80-200 micrometers, The manufacturing method of the granular silicon crystal of Claim 16 characterized by the above-mentioned.   The inorganic solid member containing nitrogen is installed so as to cover the upper part of the nozzle hole of the nozzle part, and a large number of through holes that do not allow the silicon nitride particles generated in the silicon melt to pass therethrough are formed. The method for producing granular silicon crystals according to claim 11. The diameter of the said through-hole is 80-200 micrometers, The manufacturing method of the granular silicon crystal of Claim 18 characterized by the above-mentioned.

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