Single-crystal production equipment and single-crystal production method

Abstract

Produced is a large single crystal with no crystal grain boundary, which is a high-quality single crystal that has a uniform composition in both the vertical and horizontal directions at an optimum dopant concentration and contains only a small number of negative crystals and exsolution lamellae. A single-crystal production equipment includes at least: a quartz crucible in which a seed crystal is placed on its bottom; a powder raw material supply apparatus which supplies a powder raw material into the quartz crucible; and an infrared ray irradiation apparatus which applies an infrared ray to the powder raw material supplied into the quartz crucible from the powder raw material supply apparatus.

Claims

1. A single-crystal production equipment comprising, at least: a quartz crucible in which a seed crystal is placed on its bottom; a powder raw material supply apparatus which supplies a powder raw material into said quartz crucible; an infrared ray irradiation apparatus positioned to irradiate said powder raw material supplied into said quartz crucible from said powder raw material supply apparatus with an infrared ray; and an infrared ray local irradiation apparatus which is separate from said infrared ray irradiation apparatus, said single-crystal production equipment being configured to produce a single crystal in said quartz crucible by applying said infrared ray into said quartz crucible from said infrared ray irradiation apparatus and thereby melting and solidifying said powder raw material, wherein said single-crystal production equipment is configured such that: said supplied powder raw material is irradiated with said infrared ray by said infrared ray irradiation apparatus while being supplied into said quartz crucible from said powder raw material supply apparatus, said powder raw material supply apparatus continuously supplies said powder raw material into said quartz crucible in accordance with an amount of melted powder raw material being solidified, and said infrared ray local irradiation apparatus is positioned to apply an infrared ray only to a periphery of a melt formed in said quartz crucible and thereby increases a temperature in a vicinity of the periphery of said melt formed in said quartz crucible to be higher than a temperature of an entirety of said melt in said quartz crucible.

2. The single-crystal production equipment according to claim 1, wherein an auxiliary heating apparatus is arranged on an outer surface of the bottom and of a vertical wall section of said quartz crucible.

3. The single-crystal production equipment according to claim 1, wherein said powder raw material supply apparatus comprises: a hopper which stores said powder raw material; a supply adjustment unit which supplies a prescribed amount of said powder raw material stored in said hopper to a prescribed position in said quartz crucible; and a supply pipe which is arranged on a lower end of said supply adjustment unit and through which said powder raw material is supplied into said quartz crucible.

4. The single-crystal production equipment according to claim 3, wherein said supply adjustment unit comprises a supply rate adjustment apparatus which adjusts a rate at which said powder raw material is supplied into said quartz crucible.

5. The single-crystal production equipment according to claim 3, wherein said supply adjustment unit comprises a supply position adjustment apparatus which moves said supply pipe laterally from a central position above said quartz crucible to a position above an outer periphery of the quartz crucible.

6. The single-crystal production equipment according to claim 3, wherein said hopper is configured such that a powder raw material container, which stores said powder raw material, is detachably attached thereto.

7. The single-crystal production equipment according to claim 3, wherein said hopper is constituted by: a hopper for crystal base material powder, which stores a crystal base material powder; and a hopper for dopant doped powder, which stores a dopant doped powder.

8. The single-crystal production equipment according to claim 3, wherein said hopper is a hopper for mixed powder, which stores a mixed powder obtained by mixing a crystal base material powder and a dopant doped powder.

9. The single-crystal production equipment according to claim 3, wherein said hopper comprises: a hopper for crystal base material powder, which stores a crystal base material powder; and a hopper for mixed powder, which stores a mixed powder obtained by mixing said crystal base material powder and a dopant doped powder.

10. The single-crystal production equipment according to claim 7, wherein said crystal base material powder is a silicon powder.

11. The single-crystal production equipment according to claim 1, wherein a recess is formed in a vicinity of a center on the bottom of said quartz crucible, and said seed crystal is placed in said recess.

12. The single-crystal production equipment according to claim 1, wherein a slope inclined toward the center is formed on the bottom of said quartz crucible, and said slope is inclined at an angle in a range of 3 to 60 degrees.

13. The single-crystal production equipment according to claim 1, wherein said quartz crucible is housed inside a carbon crucible.

14. The single-crystal production equipment according to claim 1, wherein said infrared ray irradiation apparatus comprises: an elliptical reflector whose inner surface is used as a reflection surface; and an infrared lamp which is arranged at a first focus position on the bottom side of said elliptical reflector.

15. The single-crystal production equipment according to claim 14, wherein said infrared lamp is a halogen lamp or a xenon lamp.

16. The single-crystal production equipment according to claim 1, wherein said infrared ray irradiation apparatus is a semiconductor laser module which applies a laser beam of said infrared ray.

17. The single-crystal production equipment according to claim 1, wherein a plurality of said infrared ray irradiation apparatus is arranged.

18. The single-crystal production equipment according to claim 1, wherein an infrared ray transmission window, which transmits said infrared ray applied from said infrared ray irradiation apparatus and/or said infrared ray local irradiation apparatus, is arranged between said infrared ray irradiation apparatus and said quartz crucible.

19. The single-crystal production equipment according to claim 18, wherein an evaporant adhesion-inhibiting apparatus is arranged on a crucible-side outer periphery of said infrared ray transmission window.

20. The single-crystal production equipment according to claim 1, wherein said quartz crucible is configured to be rotatable.

21. The single-crystal production equipment according to claim 1, wherein said quartz crucible is configured to be movable in a vertical direction at a prescribed speed.

22. The single-crystal production equipment according to claim 2, wherein said quartz crucible and said auxiliary heating apparatus are housed in a vacuum-evacuable closed chamber.

23. The single-crystal production equipment according to claim 22, wherein said closed chamber is a water-cooling structure.

24. The single-crystal production equipment according to claim 22, wherein said closed chamber is configured to be movable in a vertical direction together with said infrared ray irradiation apparatus arranged outside said closed chamber.

25. The single-crystal production equipment according to claim 1, wherein said dopant doped powder is phosphorus or boron.

26. The single-crystal production equipment according to claim 1, wherein an inner wall of the quartz crucible has a release agent part that coats the inner wall with a releasing agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic cross-sectional view showing a single-crystal production equipment according to one Example of the present invention.

(2) FIG. 2 is a drawing of the single-crystal production equipment shown in FIG. 1 as viewed from the above and is used for explaining the movement of a supply pipe of a powder raw material.

(3) FIGS. 3(a)-(g) are a process chart showing the steps of producing a single crystal using the single-crystal production equipment of the present invention in one Example of the present invention.

DETAILED DESCRIPTION AND BEST MODE FOR CARRYING OUT THE INVENTION

(4) Embodiments (Examples) of the present invention will now be described in more detail based on the drawings.

(5) The single-crystal production equipment and single-crystal production method according to the present invention are used for highly efficiently producing a large single crystal of, for example, 800 to 1,000 mm or larger in diameter, while homogenizing its composition to be optimum.

(6) The term seed crystal used herein refers to an initial form of a crystal in the production of a large-diameter single crystal using a single-crystal production equipment, and a single crystal is used. A crystal which is grown from this seed crystal and maintains the same orientation in its entirety is referred to as single crystal. In contrast, an aggregate of single crystals each having a different orientation is referred to as polycrystal.

(7) In the case of a polycrystal, individual single crystals have different crystal orientations at their boundaries, and this leads to disadvantages such as reduction in the power generation efficiency. Therefore, a high-performance silicon substrate is desired to be a single crystal which entirely has the same orientation and thus does not contain such crystal grain boundaries.

(8) <Single Crystal Production Equipment 2>

(9) As shown in FIG. 1, in a single-crystal production equipment 2 of the present Example, a lower table 7 and a pedestal 8, which constitute a driving unit 6, are arranged on the bottom of a closed chamber 4 whose inside can be vacuum-evacuated and which can retain an inert gas atmosphere such as argon gas. On the pedestal 8, a quartz crucible 10 having a substantially cylindrical cross-section is set via a carbon crucible 22 which also has a substantially cylindrical cross-section. The closed chamber 4 is a water-cooling structure which is capable of efficiently adjusting its internal temperature.

(10) Meanwhile, above the closed chamber 4, an infrared ray irradiation apparatus 30 is arranged via a mirror stage 48 at a position away from the axis of a rotating shaft 12 of the driving unit 6, and the mirror stage 48 is configured such that it can be moved in the vertical direction by a mirror stage-operating apparatus 54.

(11) This infrared ray irradiation apparatus 30 is configured such that an infrared ray 34 emitted from an infrared lamp 32 is reflected by the inner surface of an elliptical reflector 36 and the reflected light heats the inside of the quartz crucible 10.

(12) As the infrared lamp 32, a halogen lamp, a xenon lamp or the like can be used. The number of the infrared ray irradiation apparatuses 30 is not restricted to one, and a plurality of the infrared ray irradiation apparatuses 30 may be arranged.

(13) Alternatively to the case where the infrared ray irradiation apparatus 30 is constituted by the infrared lamp 32 and the elliptical reflector 36, the infrared ray irradiation apparatus 30 may be a semiconductor laser module (not shown).

(14) Further, separately from the infrared ray irradiation apparatus 30, it is preferred that the vicinity of a vertical wall section 11 of the quartz crucible 10 be irradiated by an infrared ray local irradiation apparatus 33, which can irradiate the infrared ray 34 over an irradiation range of 5 to 10 mm or so. By this infrared ray local irradiation apparatus 33, the vicinity of the periphery of a melt formed in the quartz crucible 10 is irradiated with the infrared ray 34, so that the temperature in the vicinity of the periphery of the melt formed in the quartz crucible 10 can be increased to be higher than the temperature of the melt in the entire quartz crucible 10. The temperature in the vicinity of the periphery of the melt formed in the quartz crucible 10, which is increased by the infrared ray local irradiation apparatus 33, is preferably at least 3 C. higher than that of the whole quartz crucible 10.

(15) Such infrared ray local irradiation apparatus 33 is, in the same manner as the infrared ray irradiation apparatus 30, arranged on the mirror stage 48 and configured such that it can be moved in the vertical direction by moving the mirror stage 48. As the infrared ray local irradiation apparatus 33, a semiconductor laser module (not shown) is preferably used; however, the infrared ray local irradiation apparatus 33 may also be such an infrared lamp as described above.

(16) Above the closed chamber 4, a powder raw material supply apparatus 68 is further arranged, and this powder raw material supply apparatus 68 comprises: a hopper 66, which stores a powder raw material 24; a supply adjustment unit 64, which supplies a prescribed amount of the powder raw material 24 stored in the hopper 66 to a prescribed position in the quartz crucible 10; and a supply pipe 72, which is arranged on the lower end of the supply adjustment unit 64 and through which the powder raw material 24 is supplied into the quartz crucible 10.

(17) The supply adjustment unit 64 comprises: a supply rate adjustment apparatus 62 which adjusts the rate of supplying the powder raw material 24 into the quartz crucible 10; and a supply position adjustment apparatus 60 which adjusts the supply position, and this configuration enables to adjust the supply of the powder raw material 24 in accordance with the growth state of a single crystal.

(18) The hopper 66 in this embodiment is a hopper for mixed powder, which stores a mixed powder obtained by mixing a crystal base material powder (silicon powder) and a dopant doped powder, and this enables to surely maintain the composition ratio of the powder raw material 24 constant.

(19) In this case, however, the dopant concentration of a melt phase initially formed on a seed crystal 18 is required to be higher than that of the powder raw material 24 at a ratio defined by distribution coefficient. Therefore, a solid in an amount corresponding to the required amount of a solvent phase is separately prepared at a high concentration and placed on the seed crystal 18 in advance, and this solid is melted first to form a solvent phase and the powder raw material 24 starts to be supplied thereafter, whereby a single crystal having a uniform composition in its entirety can be produced.

(20) In this embodiment, a hopper for mixed powder is used as the hopper 66; however, the hopper 66 is not restricted thereto and, for example, the hopper 66 may be constituted by both a hopper for crystal base material powder (a hopper for silicon powder) which stores the crystal base material powder (silicon powder) and a hopper for dopant doped powder which stores the dopant doped powder.

(21) By using both a hopper for crystal base material powder (a hopper for silicon powder) and a hopper for dopant doped powder in this manner, a desired composition ratio can be easily achieved in the supply adjustment unit 64.

(22) For example, when growing a phosphorus-doped N-type silicon single crystal, the powder raw material 24 to be supplied first is adjusted to have a phosphorus concentration that is three times higher than that of an optimum-concentration composition, and this powder raw material 24 is supplied in the same amount as that of a melt phase formed in a steady state, after which the powder raw material 24 having the optimum-concentration composition is supplied in an amount controlled to be the same as that of the material being solidified, whereby the resulting single crystal is allowed to have a composition that roughly conforms to the optimum-concentration composition from the beginning, so that the good-quality product yield as a whole can be improved.

(23) As an alternative to the above-described combination of a hopper for crystal base material powder (a hopper for silicon powder) and a hopper for dopant doped powder, a combination of a hopper for crystal base material powder (a hopper for silicon powder) and a hopper for mixed powder, which stores a mixed powder obtained by mixing a crystal base material powder (silicon powder) and a dopant doped powder, may be used as well.

(24) The upper end of such hopper 66 is configured such that a powder raw material container 70, which stores the powder raw material 24, can be attached to and detached from as desired. (FIG. 1 shows a state where the powder raw material container 70 is detached).

(25) By using such powder raw material container 70, the powder raw material 24 can be freshly supplied even in the midst of operating the single-crystal production equipment 2 to produce a single crystal, and this enables to continuously supply a required amount of the powder raw material 24 into the quartz crucible 10 at all times without having to hold an extremely large powder raw material container 70 over the hopper 66, so that an increase in the size of the single crystal production equipment 2 can be avoided.

(26) The powder raw material container 70 is preferably configured in conformity with the specifications of the hopper 66. For example, as in this embodiment, when the hopper 66 is a hopper for mixed powder which stores a mixed powder obtained by mixing a silicon powder and a dopant doped powder, it is preferred that the powder raw material container 70 be configured to store the mixed powder.

(27) Meanwhile, when the hopper 66 is constituted by a combination of a hopper for crystal base material powder (a hopper for silicon powder) and a hopper for dopant doped powder, the powder raw material container 70 may be a combination of a container for crystal base material powder (container for silicon powder) and a container for dopant doped powder.

(28) The supply pipe 72 of the powder raw material 24 is configured such that a prescribed amount of the powder raw material 24 is supplied therethrough to a prescribed position on the seed crystal 18 contained in the quartz crucible 10 by the supply adjustment unit 64 arranged above the supply pipe 72.

(29) As shown in FIG. 2, the supply pipe 72 is arranged above the seed crystal 18 placed in the quartz crucible 10 and configured such that it can be moved between a central position above the seed crystal 18 and a position of the vertical wall section 11.

(30) As for the position and amount at which the powder raw material 24 is supplied through the supply pipe 72, they are desirably determined using the supply position adjustment apparatus 60 and the supply rate adjustment apparatus 62 of the supply adjustment unit 64, respectively.

(31) For example, by reducing the supply amount of the powder raw material 24 in the vicinity of the center of the quartz crucible 10 and increasing the supply amount toward the vertical wall section 11 of the quartz crucible 10, the powder raw material 24 is evenly supplied at all positions in the quartz crucible 10 and can thus be surely melted, and a single crystal having a uniform composition in both the vertical and horizontal directions at an optimum additive concentration can be produced.

(32) The material of such supply pipe 72 is preferably quartz. Since quartz does not absorb the infrared ray 34, it does not cause a temperature increase by absorbing stray light from the infrared source and, since quartz has a smooth surface, the amount of the powder raw material 24 retained thereon can be reduced, which are preferred.

(33) The driving unit 6 transmits a rotational force via a belt 14 to the rotating shaft 12 which supports the lower table 7 arranged in the closed chamber 4, and the quartz crucible 10 placed on the pedestal 8 rotates at a prescribed speed by receiving the force from the belt 14.

(34) Therefore, at the time of melting, the powder raw material 24 supplied to the quartz crucible 10 can be heated evenly.

(35) On the bottom of the quartz crucible 10, a slope (inclination angle=) which is inclined toward the center at an angle of 3 to 60 degrees, preferably 5 to 30 degrees, is formed. The smaller this slope (inclination angle=), the more likely it is that other crystal starts to grow in the middle. Meanwhile, when the inclination angle is excessively large, the product obtained between the center and the vertical wall section 11 of the quartz crucible 10 has a non-standard size, so that the product yield is deteriorated.

(36) In the vicinity of the center on the bottom of the quartz crucible 10, a cylindrical recess 16 is arranged. This recess 16 has, for example, an inner diameter of 5 cm and a height of 10 cm. By forming such a recess 16, for example, the silicon seed crystal 18 can be placed in an upright position and, by reducing the gap between the recess 16 and the seed crystal 18 as much as possible, generation of a new coarse microcrystal from a site other than the seed crystal 18 can be inhibited.

(37) Alternatively to directly arranging the recess 16 on the quartz crucible 10 as shown in FIG. 1, the recess 16 may also be formed by, for example, making a hole in the center on the bottom of the quartz crucible 10 and then fitting a separately-produced quartz concave member having a truncated conical shape into the hole, although this is not shown in the drawing.

(38) In this case, particularly by tapering the margin of the hole and also tapering the periphery of the concave member in substantially the same manner, a gap created between these members can be eliminated as much as possible. As a result, leakage of the melt from this junction can be inhibited.

(39) On the outer surface of the bottom and vertical wall section 11 of the quartz crucible 10, a carbon heater 20 is arranged as an auxiliary heating apparatus. This carbon heater 20 is preferably arranged away from the wall surface of the recess 16 such that the silicon seed crystal 18 inside the quartz crucible 10 is not directly heated.

(40) Meanwhile, between the quartz crucible 10 and the infrared ray irradiation apparatus 30, an infrared ray transmission window 46 is arranged. The infrared ray transmission window 46 may be arranged on the path of the infrared rays 34 emitted from the infrared ray irradiation apparatus 30 and the infrared ray local irradiation apparatus 33. The material of the infrared ray transmission window 46 is not particularly restricted as long as it can transmit the infrared rays 34; however, the infrared ray transmission window 46 is preferably made of, for example, quartz.

(41) It is preferred that the quartz crucible 10 be movable in the vertical direction at a prescribed speed in accordance with the growth rate of a single crystal such that the infrared rays 34 from the infrared ray irradiation apparatus 30 and the infrared ray local irradiation apparatus 33 be constantly irradiated into the quartz crucible 10 through the infrared ray transmission window 46.

(42) In the same manner, it is also preferred that the closed chamber 4 be configured to be movable in the vertical direction along with the infrared ray irradiation apparatus 30 arranged outside the closed chamber 4.

(43) In this case, the driving unit 6 may be imparted with a function of vertically moving the quartz crucible 10 and a function of vertically moving the closed chamber 4.

(44) Since evaporants in the quartz crucible 10 are likely to adhere to the inner surface of the infrared ray transmission window 46, it is preferred that an evaporant adhesion-inhibiting apparatus 44 be arranged on the crucible-side outer periphery of the infrared ray transmission window 46.

(45) As the evaporant adhesion-inhibiting apparatus 44, a gas-blowing apparatus, which is configured to blow argon gas or the like against the infrared ray transmission window 46, is arranged on the periphery of the infrared ray transmission window 46.

(46) The single-crystal production equipment 2 according to one Example of the present invention is configured as described above, and a single-crystal production method using the single-crystal production equipment 2 will now be described. It is noted here that, in FIG. 3, the powder raw material 24 is depicted to have an elliptical shape for the sake of convenience in making the drawings; however, the diameter, shape and size of the particles are not restricted.

(47) <Single Crystal Production Method>

(48) First, as shown in FIG. 3(a), the silicon seed crystal 18 is placed in the recess 16 arranged in the vicinity of the center on the bottom of the quartz crucible 10.

(49) Then, the closed chamber 4 is hermetically sealed, and the atmosphere inside the closed chamber 4 is vacuum-evacuated by an exhaust apparatus (not shown). Further, from the gas-blowing apparatus which also has the function of the evaporant adhesion-inhibiting apparatus 44, an inert atmosphere such as argon gas is introduced into the closed chamber 4.

(50) Meanwhile, operation of the carbon heater 20 arranged the outer surface of the bottom and vertical wall section 11 of the quartz crucible 10 is initiated, as a result of which the lower side of the quartz crucible 10 is heated to about 1,300 C. In this process, since the carbon heater 20 is arranged away from the recess 16 of the quartz crucible 10, the seed crystal 18 is not subjected to a large amount of heat.

(51) It is preferred that the inner surface of the quartz crucible 10 be coated with a release agent composed of silicon nitride. This enables to easily remove a silicon single crystal, which is to be eventually produced, from the quartz crucible 10.

(52) Next, from the powder raw material supply apparatus 68, a mixed powder (powder raw material 24) in which a silicon powder and a dopant doped powder are mixed at a prescribed composition ratio in advance is supplied into the quartz crucible 10.

(53) Consequently, as shown in FIG. 3(b), the powder raw material 24 is accumulated on the bottom of the quartz crucible 10.

(54) Further, the powder raw material 24 is melted by irradiating the infrared ray 34 into the quartz crucible 10 from the infrared lamp 32 of the infrared ray irradiation apparatus 30 positioned above the quartz crucible 10. It is noted here that this melting process is carried out while rotating the quartz crucible 10.

(55) The powder raw material 24 continues to be supplied from the powder raw material supply apparatus 68 for a while after the start of the melting.

(56) When the powder raw material 24 is melted and liquefied in the upper side of the quartz crucible 10 by irradiation with the infrared ray 34 emitted from the infrared ray irradiation apparatus 30 and unmelted powder raw material 24 is supplied thereto, this powder raw material 24 floats on a liquefied raw material melt 50. Then, by further melting the powder raw material 24 floating on the liquefied raw material melt 50, the surface of the melt is slowly raised, whereby the melted raw material melt 50 is gradually accumulated in the quartz crucible 10 as shown in FIG. 3(c).

(57) Once the thickness of the raw material melt 50 reaches, for example, 10 mm, since the infrared ray 34 no longer reaches therebelow, the temperature of the raw material melt 50 decreases, as a result of which, as shown in FIG. 3(d), solidification starts from the upper side of the seed crystal 18 placed on the center of the quartz crucible 10.

(58) In this state, as shown in FIG. 3(e), the powder raw material 24 composed of a silicon powder raw material and a dopant doped powder continues to be supplied, melted and solidified in the lower part and, once it reaches the vertical wall section 11 of the quartz crucible 10, solidification continues in the upward direction. At this point, the infrared ray local irradiation apparatus 33 is put into operation so as to maintain the temperature of the vertical wall section 11 of the quartz crucible 10 at a few degrees higher than the surrounding.

(59) Once the supply of a prescribed amount of the powder raw material 24 is completed and the powder raw material 24 is completely melted as shown in FIG. 3(f), the lamp power of the infrared ray irradiation apparatus 30 and that of the infrared ray local irradiation apparatus 33 are slowly lowered.

(60) Thereafter, as shown in FIG. 3 (g), the whole melt is made into a solidified product 52 (single crystal).

(61) Once the solidification of the whole melt is completed, the temperature is slowly lowered and the closed chamber 4 is cooled to room temperature and opened, after which the solidified product 52 (single crystal) in the quartz crucible 10 is taken out.

(62) In this Example, the irradiation dose distribution of the infrared ray 34 is designed such that the surface of the solidified product 52 can be maintained as flat as possible throughout the production process. At the same time, it is preferred to delay the crystallization from the surface of the quartz crucible 10 by irradiating the part of the melt that is in contact with the quartz crucible 10 (the vicinity of the wall section 11) using the infrared ray local irradiation apparatus 33 at an irradiation does of about 2 to 7% higher, preferably about 2 to 5% higher, than that of the infrared ray irradiation apparatus 30 which heats the whole quartz crucible 10 and thereby increasing the temperature in the vicinity of the vertical wall section 11 of the quartz crucible 10 to be not less than 3 C. higher, preferably not less than 5 C. higher, than the temperature of the whole quartz crucible 10.

(63) By this, even if new microcrystals start to grow from this part, since the growth of a large single crystal proceeds on the inner side, the growth of the large single crystal on the inner side can be prevented from being adversely affected by the microcrystals formed afterwards.

(64) As described above, in the single-crystal production equipment 2 and single-crystal production method according to the present invention, the supply of the powder raw material 24 composed of a silicon powder raw material and a dopant doped powder into the quartz crucible 10 and the melting and solidification of the powder raw material 24 are continuously carried out. That is, since a single crystal is produced while continuously supplying the powder raw material 24 to the quartz crucible 10 in the same amount as that of the material being solidified, the composition of the resulting crystal can be made uniform.

(65) This enables to produce a high-quality single crystal having a uniform composition at a dopant concentration that allows the single crystal to realize the highest conversion efficiency when used for photovoltaic power generation. A single crystal having an optimum composition can thus be produced with good yield, and this consequently contributes to a reduction of the production cost.

(66) The single-crystal production equipment 2 of the present invention and a single-crystal production method using the single-crystal production equipment 2 have been described thus far; however, the present invention is not restricted to the above-described embodiments.

(67) For instance, in the above-described Example, the carbon heater 20 is arranged on the lower surface of the quartz crucible 10 as an auxiliary heating apparatus; however, the auxiliary heating apparatus is not restricted to the carbon heater 20 by any means. An auxiliary heating apparatus other than the carbon heater 20 can also be used to heat a portion of the outer surface of the quartz crucible 10.

(68) Further, although the quartz crucible 10 is described above to have a substantially cylindrical shape, this is also not restricted, and the quartz crucible 10 may have a substantially tetragonal columnar shape. A variety of modifications can be made within the scope of the objects of the present invention.

(69) Moreover, in the above-described Example, the powder raw material 24 is prepared by incorporating phosphorus as a dopant doped powder into a silicon powder raw material for the production of an N-type semiconductor, or by incorporating boron as a dopant doped powder into a silicon powder raw material for the production of a P-type semiconductor. When a silicon powder raw material and a dopant doped powder of phosphorus, boron or the like are separately supplied, there is an advantage that the dopant concentration can be changed as appropriate. However, in most cases, since the optimum concentration is known, it is efficient to prepare a powder raw material (silicon powder raw material+dopant doped powder) 24 that has a composition ratio conforming to the optimum concentration and to supply this powder raw material 24 at once.

(70) It is efficient to supply the powder raw material 24, in which a silicon powder raw material and a dopant doped powder are mixed in advance, at once in this manner, and the productivity is thereby improved.

(71) Further, in the above-described Example, no particular mention is made on the particle size of the powder raw material 24 and the like; however, when the particle size is excessively large, it takes time to melt the particles, and the particles, upon falling into the quartz crucible 10, may sink through the melt phase and reach the surface of the solidified product 52 below. If the powder raw material 24 and the like reach the surface of the solidified product 52, they are incorporated into the solidified product 52, and the growth of other crystals tends to start therefrom.

(72) Meanwhile, if the powder raw material 24 and the like have an excessively small particle size, since the powder raw material 24 and the like are scattered in the surrounding when they are allowed to fall toward the quartz crucible 10, the controllability is impaired. Accordingly, the particles of the pre-mixed powder raw material 24 preferably have a size of 0.1 to 0.5 mm or so in diameter.

(73) Moreover, when supplying the powder raw material 24 into the quartz crucible 10, it is necessary to supply the powder raw material 24 evenly from the center to the outer periphery of a circle with respect to the circular plane of the quartz crucible 10, although this is not explained in detail in the above-described Example.

(74) Accordingly, as shown in FIG. 2, for example, while rotating the circular quartz crucible 10, by controlling the moving speed of the supply pipe 72 of the powder raw material supply apparatus 68 such that the supply pipe 72 moves faster in the vicinity of the center of the quartz crucible 10 and slows down as it approaches the vertical wall section 11, the powder raw material (crystal base material powder+dopant doped powder) 24 can be evenly supplied to the entire surface of the quartz crucible 10.

(75) Furthermore, in the above-described embodiment, a case where a silicon powder is used as the crystal base material powder was described as an example, the crystal base material powder is not restricted thereto, and any powder prepared in accordance with the substance to be produced can be used.

(76) In the above-described manner, a variety of modifications can be made in the single-crystal production equipment 2 of the present invention within the scope of the objects of the present invention.

DESCRIPTION OF SYMBOLS

(77) 2: single-crystal production equipment 4: closed chamber 6: driving unit 7: lower table 8: pedestal 10: quartz crucible 11: vertical wall section 12: rotating shaft 14: belt 16: recess 18: seed crystal 20: carbon heater 22: carbon crucible 24: powder raw material 30: infrared ray irradiation apparatus 32: infrared lamp 33: infrared ray local irradiation apparatus 34: infrared ray 36: elliptical reflector 44: evaporant adhesion-inhibiting apparatus 46: infrared ray transmission window 48: mirror stage 50: raw material melt 52: solidified product 54: mirror stage-operating apparatus 60: supply position adjustment apparatus 62: supply rate adjustment apparatus 64: supply adjustment unit 66: hopper 68: powder raw material supply apparatus 70: powder raw material container 72: supply pipe : inclination angle