TW201435160A - Polycrystalline germanium ingot manufacturing device and manufacturing method thereof - Google Patents

Abstract

The present invention provides a polycrystalline germanium ingot manufacturing apparatus, comprising: a crucible capable of accommodating a crucible raw material; a heater disposed around the crucible; a thermal conductor disposed under the crucible; and a cooling unit cooling the thermal conductor; In the polycrystalline germanium ingot manufacturing apparatus, the heat conductor is formed with a bottomed cylindrical body that is opened downward, and a bottom outer surface of the heat conductor is disposed to face the outer surface of the bottom of the crucible, and the cooling unit is provided by the cooling unit. The vicinity of the opening end of the heat conductor is cooled.

Description

Polycrystalline germanium ingot manufacturing device and manufacturing method thereof

The present invention relates to a manufacturing apparatus for manufacturing a polycrystalline germanium ingot and a method for producing a polycrystalline germanium ingot.

Multi-crystalline silicon is mainly used as a substrate material for solar cells. A polycrystalline silicon used for a solar cell or the like is usually produced by cutting a polycrystalline germanium ingot into an arbitrary size and shape. A polycrystalline germanium ingot is usually produced by accommodating a tantalum raw material in a crucible, heating the crucible to obtain a molten crucible, and then cooling the crucible from the bottom thereof to solidify the crucible (refer to Patent Document 1 and Patent) Literature 2). In recent years, in order to obtain a large-diameter polycrystalline germanium wafer, it is required to manufacture a larger polycrystalline germanium ingot. In order to manufacture a large polycrystalline niobium ingot, it is necessary to control the amount of heat dissipated from the bottom of the crucible to appropriately control the solidification speed of the crucible. However, the control of the solidification rate of the crucible requires extremely delicate and precise control of the amount of heat dissipation, which is extremely difficult (Patent Document 3). For example, in the solidification process of the molten crucible, the heat dissipation from the bottom of the crucible tends to be large due to the previous heat dissipation method, so the temperature of the melting crucible must be melted. The melt temperature is maintained at a temperature sufficiently higher than the solidification temperature of the crucible (1410 ° C) (for example, 1440 to 1460 ° C) to prevent solidification from rapidly proceeding from the initial stage of solidification to the middle of solidification. The ruthenium crystal obtained under these conditions has many lattice defects, and when processed into a substrate for a solar cell, there is a problem in quality such as a decrease in energy conversion efficiency. Further, in order to appropriately control the solidification speed of the crucible, a method of controlling the position of the crucible in the apparatus to control the amount of heat radiation (Patent Document 3), a method of controlling the temperature distribution in the crucible, and the like have been known. However, in the method, it is difficult to completely control the amount of heat dissipation from the crucible.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. SHO 60-103017

[Patent Document 2] Japanese Patent Laid-Open Publication No. SHO 63-166711

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-308616

An object of the present invention is to provide a manufacturing apparatus for manufacturing a polycrystalline germanium ingot which can appropriately control the amount of heat radiation from the crucible.

Further, it is an object of the present invention to provide a method for producing a good polycrystalline germanium ingot by appropriately controlling the amount of heat released from the crucible.

In particular, it is an object of the present invention to produce polycrystalline ruthenium ingots of various sizes by using the above-described manufacturing apparatus and manufacturing method, and to obtain a polycrystalline yttrium ingot having excellent crystal quality in all height directions of the polycrystalline yttrium ingot. Upper crystal defect Very few.

The present invention has been completed based on the following findings: when manufacturing a polycrystalline germanium ingot, a heat conductor disposed under the crucible for cooling the crucible is used, the thermal conductor is set to a specific shape, and an appropriate thermal body cooling method is employed. Thereby, the amount of heat dissipation of the crucible can be appropriately controlled.

In particular, the invention may include the following.

A polycrystalline germanium ingot manufacturing apparatus comprising: a crucible capable of accommodating a crucible raw material; a heater disposed around the crucible; a thermal conductor disposed under the crucible; and a cooling unit cooling the thermal conductor; the polycrystalline crucible In the bismuth ingot manufacturing apparatus, the heat conductor is formed with a bottomed cylindrical body that is opened downward, and an outer surface of the bottom surface of the heat conductor is disposed to face the outer surface of the bottom surface of the crucible, and an open end of the heat conductor is disposed. The area of the opening near the portion is arbitrarily changed across the entire solidification period, and is cooled by the cooling unit.

The above thermal conductor is measured at 25 ° C according to the flash method of JIS R1611 and has 30 W / m. K~150W/m. The thermal conductivity of K.

The above thermal conductor is made of black lead.

The polycrystalline germanium ingot manufacturing apparatus further includes an induction heating coil that heats the heat conductor.

The polycrystalline germanium ingot manufacturing apparatus further includes a heat insulating material covering at least a part of the crucible, the heater, and the heat conductor.

The polycrystalline germanium ingot manufacturing device further comprises: a cover covering the above-mentioned crucible An open end; and a nozzle for injecting an inert gas into the interior of the crucible.

A method for producing a polycrystalline ruthenium ingot, comprising the steps of: (1) accommodating a ruthenium raw material in a temperature-adjustable crucible; and (2) heating the niobium raw material in the crucible to a temperature higher than a melting point of niobium to make the niobium raw material And (3) cooling the molten crucible in the crucible via a heat conductor disposed under the crucible to obtain a polycrystalline ingot; the polycrystalline ingot manufacturing method is characterized in that the thermal conductor forms a lower opening The bottomed cylindrical body is disposed such that a bottom outer surface of the heat conductor is opposed to a bottom outer surface of the crucible, and the vicinity of an opening end portion of the heat conductor is cooled by the cooling unit.

The cooling is performed under the following conditions, that is, the temperature (Tg) (° C.) of the outer surface of the bottom surface of the heat conductor is set to the following linear approximation equation: Tg=a-bt

(In the formula, a is 1,250 to 1,400, and b is 10 to 35, and t is an elapsed time (hour) from the start of cooling).

The heating is performed by a heater and the heat conductor, and the heater is disposed around the crucible, and the heat conductor is heated by an induction heating coil.

The heating step and the cooling step are carried out under an inert gas atmosphere.

According to the present invention, a manufacturing apparatus for manufacturing a polycrystalline germanium ingot can be provided It can properly control the amount of heat dissipation from the self. In particular, heat can be appropriately dissipated by a special-shaped heat conductor disposed under the crucible. Moreover, according to the present invention, it is possible to provide a method for producing a crystallized polycrystalline germanium ingot having a good quality by appropriately controlling the amount of heat released from the crucible. In particular, the cooling conditions are focused on the temperature of the heat conductor close to the crucible without relying on the upper temperature of the previous crucible or the cooling condition of the crucible itself to control the cooling of the crucible, thereby allowing the crucible to be cooled at an appropriate temperature. Without overcooling. In particular, the superheat degree of the molten crucible (the melt temperature of the molten crucible - the solidification temperature of the crucible) is maintained below 40 ° C, preferably below 10 ° C, and more preferably by the entire solidification time range of the crucible. At 2 ° C to 5 ° C, high quality polycrystalline germanium with few crystal defects can be obtained.

1‧‧‧Bottom outer surface

2‧‧‧ bottom inner surface

3‧‧‧ wall

4‧‧‧ bottom outer dimensions

5‧‧‧ bottom size

6‧‧‧ thickness at the bottom

7‧‧‧ Height of the wall

8‧‧‧ Thickness of the wall

9‧‧‧Open end

101‧‧‧Polysilicon manufacturing equipment

102‧‧‧矽Materials

103‧‧‧坩埚

104‧‧‧heater

105‧‧‧ upper room

106‧‧‧ Thermal Conductor

107‧‧‧Cooling unit

108‧‧‧low room

109‧‧‧Cover

110‧‧‧Support board

111‧‧‧Nozzles

112‧‧‧Upper insulation

113‧‧‧Induction heating coil

114‧‧‧Bottom insulation

115‧‧‧ cylinder

116‧‧‧ gap

117‧‧‧temperature sensor

Temperature of Ts‧‧‧ melting enthalpy

Tx‧‧‧坩埚The temperature inside the bottom of the bottom

Temperature of the outer surface of the bottom of the Tg‧‧‧ thermal conductor

1(a) to 1(c) are schematic views of a heat conductor of the present invention.

2(a) to 2(f) are longitudinal cross-sectional views of the heat conductor of the present invention.

Fig. 3 (a) is a cross-sectional view showing the polycrystalline germanium ingot manufacturing apparatus of the present invention in the step of heating the crucible.

Fig. 3 (b) is a cross-sectional view showing the polycrystalline germanium ingot manufacturing apparatus of the present invention in the step of cooling the crucible.

4 is a time change of the temperature Ts (° C.) of the molten crucible in the first embodiment, the temperature Tx (° C.) inside the crucible bottom, and the temperature Tg (° C.) of the outer surface of the bottom surface of the heat conductor from the start of solidification to the end of solidification.

Figure 5 is a temperature Ts (°C) of the molten crucible in Example 2, and inside the bottom of the crucible The temperature Tx (° C.) and the temperature Tg (° C.) of the outer surface of the bottom portion of the heat conductor change from the start of solidification to the end of solidification.

6 is a temperature Ts (° C.) of the molten crucible in Comparative Example 1, and a temperature Tg (° C.) of the bottom outer surface of the water-cooled copper cooling chiller (black lead supporting plate that is in contact with the bottom of the crucible). The time from the start of solidification to the end of solidification.

Fig. 7 is a graph showing changes in time of solidification rate (mm/min) from the start of solidification to the end of solidification in Example 1, Example 2, and Comparative Example 1.

[A] Polycrystalline germanium manufacturing device

Hereinafter, the polycrystalline germanium ingot manufacturing apparatus of the present invention will be described in detail.

(1) The polycrystalline germanium ingot manufacturing apparatus of the present invention comprises: a crucible capable of accommodating a crucible raw material; a heater disposed around the crucible; a thermal conductor disposed under the crucible; and a cooling unit cooling the thermal conductor . Further, the polycrystalline germanium ingot manufacturing apparatus of the present invention arbitrarily includes an induction heating coil, a heat insulating material, a lid, a nozzle for injecting an inert gas, and the like. Hereinafter, each member will be described.

. crucible

The crucible is used for accommodating a crucible raw material, heating the crucible raw material to obtain a molten crucible, and further cooling to produce a polycrystalline antimony ingot. The shape of the crucible is preferably a bottomed cylindrical body having an open upper end, and more preferably a flat bottom. The bottom portion may be a polygon other than a circle or a triangle, but is preferably a circle or a quadrangle. The size of the crucible also depends on the size of the polycrystalline silicon produced, for example, when the crucible is a bottomed cylinder with a square bottom. The outer dimension of the bottom is, for example, suitably 300 mm to 1500 mm square, preferably 500 mm to 1200 mm square, more preferably 670 mm to 1000 mm square, and the thickness of the bottom is suitably 1 mm to 50 mm, preferably 5 mm to 30 mm, more preferably 10mm~25mm. The height of the crucible is, for example, suitably from 100 mm to 1000 mm, preferably from 200 mm to 800 mm, more preferably from 300 mm to 700 mm. For example, when the crucible is a bottomed cylindrical shape, the bottom portion is suitably a circle having a radius of 150 mm to 750 mm, preferably a circle having a radius of 250 mm to 600 mm, more preferably a circle having a radius of 335 mm to 500 mm, and a bottom portion. The thickness is suitably, for example, 1 mm to 100 mm, preferably 5 mm to 70 mm, more preferably 10 mm to 50 mm. The height of the crucible is, for example, suitably from 100 mm to 1000 mm, preferably from 200 mm to 800 mm, more preferably from 300 mm to 500 mm. Further, the thickness of the wall portion of the crucible is, for example, suitably 1 mm to 50 mm, preferably 5 mm to 30 mm, more preferably 10 mm to 25 mm. The thermal conductivity of ruthenium is measured at 25 ° C according to the flash method of JIS R1611, and is suitably 1.2 W/m, for example. K~11.6W/m. K, preferably 1.7 W/m. K~5.8W/m. K, more preferably 2.3W/m. K~4.7W/m. K.

On the upper part of the crucible, a cover can be provided.

The crucible and the lid are not particularly limited, and a known crucible and a lid used in a conventional polycrystalline ingot manufacturing apparatus can be used. For example, ruthenium is preferably opaque quartz, and as a cover, black lead is preferred. The wall surface of the crucible is preferably coated with tantalum nitride, for example, containing 1% by mass to 10% by mass of silica, preferably containing 3% by mass to 7% by mass of dioxide. Oh, better for the package Containing 4% by mass to 6% by mass of cerium oxide.

. nozzle

A nozzle may also be provided, from which an inert gas is injected into the crucible for injecting an inert gas into the crucible during the manufacturing process of the polycrystalline ingot, particularly when heating and cooling the crucible material. . As the inert gas, a rare gas is preferable, and for example, helium gas, argon gas or the like is preferable. In addition to the inert gas, a gas such as a carbon monoxide gas which lowers or controls the oxygen concentration may be added. When carbon monoxide gas is added to argon gas, the concentration of carbon monoxide gas is, for example, suitably from 600 ppmm to 1400 ppmm, preferably from 800 ppmm to 1200 ppm, more preferably from 1000 ppmm to 1100 ppm.

.矽 raw materials

The tantalum raw material accommodated in the crucible is suitably polycrystalline germanium, and the polycrystalline germanium has a purity of, for example, 6-N or more, preferably has a purity of 7-N or more, more preferably 9-N or more (that is, 99.9999999%). Purity) purity.

. Heater

The heater is disposed around the crucible, that is, disposed above the crucible and/or at least in a direction, preferably disposed above the crucible. As the heater, a known heater can be used as long as it is a temperature-adjustable heater. For example, black lead or carbon fiber (carbon ceramic matrix (CCM) composition, etc., such as isotropic black lead or the like can be used. A resistance heating heater or an induction heating heater for a heating element.

. Thermal conductor

The heat conductor is disposed below the crucible. One or more crucibles may be disposed on one thermal conductor. Moreover, the heat conductor and the crucible may be in close contact or separated from each other. Further, a support plate may be included between the heat conductor and the crucible, and the support plate is used to support the crucible. The heat conductor is disposed such that the outer surface of the bottom of the heat conductor faces the outer surface of the bottom of the crucible. By disposing as described above, the crucible is efficiently cooled by the heat conductor, and is sometimes heated efficiently by the heat conductor. Fig. 1 shows an example of the outer shape of a heat conductor. Fig. 1(a) is a cylindrical body having a rectangular or square bottom. Fig. 1(b) is a cylindrical body having a shape in which the bottom is rectangular or square, and the bottom protrudes from the wall portion of the side wall to a fixed length. Fig. 1(c) is a cylindrical body having a circular bottom. The length of the bottom of the cylindrical body of Fig. 1(b) protruding from the side wall is, for example, 70 mm to 220 mm, preferably 60 mm to 120 mm, more preferably 50 mm to 100 mm, or 1% of the outer dimension of the wall portion of the protruding side wall. ~30%, preferably 5% to 20% of the outer dimension of the wall portion of the protruding side wall. As the shape of the heat conductor, a cylindrical body having an open end and a bottomed bottom is preferably a square. The shape of the longitudinal cross section of the heat conductor is preferably concave (see Fig. 1 (a) or Fig. 1 (c)), π type (or Π type, see Fig. 1 (b)), and particularly preferably concave. Fig. 2(a) is a longitudinal sectional view showing a concave heat conductor. The heat conductor is formed with a bottomed cylindrical body that is open on the side opposite to the side on which the crucible is disposed, that is, is opened below, and is formed in a shape in which the inside of the heat conductor is hollowed out. The inner portion of the heat conductor, that is, the longitudinal cross-section of the hollow portion may have a triangular shape (see FIGS. 2(b), 2(c)) and a quadrangle (see FIG. 2(d)), and a semicircle. shape (Refer to Fig. 2(e)) and other curved shapes.

Further, as shown in Fig. 2(a), the longitudinal end shape of the open end portion (Fig. 2(a) 9) may be a rectangle having a constant thickness of the wall portion, or may be a wall portion as shown in Fig. 2(f). The thickness is one step or two steps. For example, when the height of the wall portion (Fig. 2(a) 7) is 500 mm to 1000 mm and the thickness of the wall portion is 60 mm to 180 mm, it is appropriate that the height of the open end portion (Fig. 2 (f) 9) is 50 mm to 200 mm. (5% to 20% of the height of the wall), and the thickness of the opening end is about 30 mm to 100 mm (30 to 60% of the thickness of the wall).

The thermal conductor is a solid as follows, that is, when the thermal conductivity is measured at room temperature (25 ° C) (refer to JIS R1611 flash method) is 30 W / m. K~150W/m. K, preferably 40 W/m. K~120W/m. K, more preferably 50W/m. K~100W/m. K, any material can be used, but it is preferably black lead. As a particularly preferable black lead which can be used as a heat conductor, isotropic black lead G535, G330, G320, G347, etc. by Tokai Carbon Co., Ltd. are mentioned. The support plate is also preferably a solid having the same thermal conductivity as the heat conductor, more preferably the same black lead as the heat conductor.

In order to maintain the control accuracy of the solidification, it is important that the heat capacity of the heat conductor is equal to or less than the total heat capacity of the heat of the crucible at the start of solidification and the heat capacity of the raw material crucible and the latent heat of solidification of the raw material crucible, for example, 90% of the total. Hereinafter, it is preferably from 1% to 80% of the total, and more preferably from 10% to 60% of the total. For example, when the heat conductor is bottomed and the bottom (ie, the bottom of the inner side of the cylindrical body (FIG. 2(a) 2)) is a square cylindrical shape, the outer dimension of the bottom (FIG. 2(a) 4) is, for example, Appropriate is waiting The outer dimensions of the crucible (the sum of the outer dimensions of the crucibles when a plurality of crucibles are arranged) ±400 mm, preferably equal to the outer dimension of the bottom of the crucible ±200 mm, more preferably equal to the outer dimension of the crucible 50mm size. Specifically, the outer dimension of the bottom portion of the heat conductor is, for example, suitably from 100 mm to 4000 mm square, preferably from 200 mm to 2000 mm square, more preferably from 300 mm to 1500 mm square. Further, the thickness of the bottom portion (Fig. 2(a) 6) is, for example, 5 mm to 200 mm, preferably 20 mm to 100 mm, more preferably 30 mm to 60 mm. Further, the height of the cylindrical wall portion (Fig. 2(a) 7) is, for example, suitably 250 mm to 2000 mm, preferably 400 mm to 1500 mm, more preferably 500 mm to 1000 mm. The thickness of the cylindrical wall portion (Fig. 2(a) 8) is, for example, 20 mm to 300 mm, preferably 40 mm to 250 mm, more preferably 60 mm to 180 mm.

For example, when the heat conductor is a bottomed cylindrical shape, the radius of the bottom portion is suitably, for example, a radius of the crucible of ±200 mm, preferably a radius of the crucible of ±100 mm, more preferably a radius of the crucible of ±50 mm. Specifically, the radius of the bottom portion is, for example, suitably from 100 mm to 1000 mm, preferably from 150 mm to 800 mm, more preferably from 200 mm to 500 mm. Further, the thickness of the bottom portion is, for example, 5 mm to 200 mm, preferably 20 mm to 100 mm, more preferably 30 mm to 60 mm. The thickness of the cylindrical wall portion is, for example, 20 mm to 100 mm, preferably 30 mm to 70 mm, more preferably 40 mm to 50 mm, and the height of the cylindrical wall portion is, for example, 250 mm to 700 mm, preferably 350 mm to 550 mm, more preferably 400mm~500mm. The thickness of the support plate is, for example, suitably 5 mm to 100 mm, preferably 10 mm to 60 mm, more preferably 20 mm to 50 mm.

. Cooling unit

The heat conductor is cooled by the cooling unit in the vicinity of the opening end (Fig. 2 (a) 9) of the heat conductor. As described above, only the vicinity of the open end portion is cooled, whereby heat is directly transmitted inside the heat conductor at the bottom of the heat conductor close to the open end portion, thereby cooling the bottom portion (heat conduction). Further, at the bottom of the heat conductor remote from the end of the opening, heat is transmitted to the vicinity of the opening end by radiation at the opening of the heat conductor, thereby cooling the bottom portion (heat radiation). As described above, the heat conductor of the present invention can uniformly cool the bottom of the heat conductor by having the opening and cooling the vicinity of the opening end of the heat conductor by the cooling unit.

The cooling unit includes a cooling portion such as an induction heating coil cooled by a refrigerant for cooling the wall and the coil portion of the lower chamber that has been cooled inside. By arranging the cooling portion toward the open end of the heat conductor, the radiant heat transfer from the open end surface of the heat conductor to the cooling portion can be performed without being in contact with the open end of the heat conductor. . For the cooling of the cooling portion, a gas medium method such as a liquid medium method such as a water cooling method, an inert gas or an air cooling method can be used. The radiant heat transfer amount (Q) and the fourth power of the surface temperature (T1) of the open end of the heat conductor are proportional to the fourth power difference of the surface temperature (T2) of the cooling portion (Q=A×B×k×(T1) ^{4 -} T2 ⁴ ), where A is the surface area of the open end of the heat conductor, B is the form factor, and k is the Boltzmann factor, so that the surface of the cooling portion can be used with a temperature sensor The temperature was measured, and the surface area (A) of the opening of the open end of the heat conductor was arbitrarily adjusted to control the amount of heat radiation.

The vicinity of the opening end portion of the heat conductor cooled by the cooling unit is not particularly limited. However, when the height of the heat conductor tubular wall is 100%, it means 1% to 70% from the opening end. The height region is preferably a region having a height of 1% to 50% from the open end portion, and more preferably a region having a height of 1% to 40% from the open end portion. The open end itself may also be included near the open end. Specifically, the gap with the cooling unit provided around the opening end portion of the heat conductor is, for example, suitably larger than 0 mm and 400 mm or less, preferably 1 mm to 300 mm, and more preferably 10 mm to 200 mm.

. Insulation materials

When the crucible raw material in the crucible is heated by the heater, it is preferable that the entire polycrystalline silicon manufacturing apparatus of the present invention is thermally insulated from the outside, in particular, the entire crucible and the thermal conductor are thermally insulated from the outside. Therefore, in the heating process, it is preferable to insulate the heat conductor and the cooling unit. As a method of performing heat insulation, for example, a mounting table for a heat conductor is adhered to a heat insulating material covering the heat sink and the heat conductor. On the other hand, in the cooling process, for example, the lower heat insulating material in the vicinity of the opening end portion of the heat conductor is lowered by the cylinder for raising and lowering the heat insulating material, and a gap is formed in the vicinity of the opening end portion of the heat conductor. . The gap is not in contact with the heat transfer body such as the wall of the lower chamber or the induction heating coil, but is cooled by heat transfer to the cooling portion disposed on the outer peripheral portion. The amount of radiation heat transfer can be arbitrarily controlled by changing the area of the opening of the open end of the heat conductor according to the temperature of the surface of the open end of the heat conductor and the surface temperature of the cooling portion. Here, the insulating material can cover the above-mentioned crucible and heater The back side and at least a portion of the heat conductor. The heat insulating material is preferably a heat insulating material having a heat resistance of at least 2000 ° C or higher, and preferably having a heat resistance of 2500 ° C or higher. As the heat insulating material, a carbon fiber forming heat insulating material or the like is preferable. As an example of a preferable heat insulating material, DONACARBO (DON-1000, DON-2000, DON-3000, DON-4000) by Osaka Gas Chemicals Co., Ltd. is mentioned, for example.

. Induction heating coil

The heat conductor is heated by the induction heating coil, and can also be used as a heater that can be heated by the lower portion of the crucible. Since the induction heating coil can be disposed apart from the heat conductor, the heat conductor can be heated from the outside of the heat insulating material even when the heat conductor is covered by the heat insulating material. Further, the induction heating coil can not only heat the surface of the heat conductor but also heat the inside of the heat conductor, so that it has the advantage of uniformly heating the bottom of the heat conductor. The induction heating coil is preferably provided with a temperature sensor for temperature adjustment. The induction coil is controlled, for example, at a frequency of 1 Hz to 500 Hz, preferably at a frequency of 10 Hz to 300 Hz, and more preferably at a frequency of 30 Hz to 100 Hz.

[B] Polycrystalline germanium ingot manufacturing method

The polycrystalline silicon crucible manufacturing method of the present invention is carried out using the polycrystalline germanium ingot manufacturing apparatus, and includes the steps of: (1) storing the tantalum raw material in a temperature-adjustable crucible; and (2) heating the crucible raw material in the crucible to The temperature above the melting point of the crucible The crucible raw material is melted; and (3) the molten crucible in the crucible is cooled by a heat conductor disposed under the crucible to obtain polycrystalline germanium.

(1) Steps of accommodating 矽 raw materials

First, the raw material is stored in a crucible. The details of the raw materials and bismuth are as described above.

(2) Steps of heating the crucible

Next, the niobium raw material in the crucible is heated to a temperature equal to or higher than the melting point of niobium to melt the niobium raw material. Heating is performed by a heater disposed around the crucible, preferably above the crucible. The details of the heater are as described above.

Since the melting point of cerium is about 1410 ° C, heating is performed in such a manner that the temperature of the molten cerium raw material in the crucible reaches a temperature sufficiently higher than the melting point, for example, a temperature of 1450 ° C or higher, preferably The temperature of 1450 ° C ~ 1600 ° C, more preferably reaches the temperature of about 1500 ° C ~ 1550 ° C.

Further, heating may be performed by a combination of the heater and the heat conductor which is heated by the induction heating coil. By heating by the heater and the heat conductor, it is possible to heat the upper and lower sides of the crucible, which is efficient. The details of the induction heating coil are as described above.

(3) Steps for cooling the crucible

Melting enthalpy in the above crucible via a heat conductor disposed under the crucible Cool down. In order to produce a homogeneous polycrystalline crucible, it is particularly preferable to cool while maintaining the temperature of the outer surface of the bottom portion of the heat conductor (the side close to the outer surface of the bottom surface of the crucible). Further, when the temperature of the outer surface of the bottom portion of the heat conductor is Tg (° C.), it is preferred to lower the temperature under the condition that Tg satisfies the following general formula (linear approximation equation): Tg=a-bt.

In the formula, a is 1,250~1,400 (°C), preferably 1,290~1,380 (°C), more preferably 1,300~1,360 (°C), b is 10~35, preferably 15~33, more preferably 17~ 30, t is the elapsed time (hours) from the start of cooling. In other words, it is preferred to lower the Tg in a substantially linear manner at a rate of from 10 ° C / hour to 35 ° C / hour, preferably from 15 ° C / hour to 33 ° C / hour, more preferably 17 ° C / Hour ~ 30 ° C / hour speed.

Further, the temperature Tx of the portion where the molten crucible is in contact with the bottom of the crucible is suitably 40 ° C to 200 ° C higher than Tg, preferably 50 ° C to 150 ° C higher, more preferably 60 ° C to 120 ° C higher. Here, the solidification rate of the molten crucible is, for example, suitably 0.1 mm/min to 1.5 mm/min, preferably 0.2 mm/min to 1.0 mm/min, more preferably 0.3 mm/min to 0.5 mm/min. The degree of superheat of the molten crucible (the temperature of the melting crucible - the solidification temperature of the crucible) is suitably in the range of the entire solidification time, for example, kept below 40 ° C, preferably below 10 ° C, more preferably maintained at 2 ° C ~ 5 °C.

[C] illustrates a polysilicon manufacturing device by a schematic diagram

Hereinafter, the polycrystalline silicon manufacturing apparatus of the present invention will be described with reference to the drawings.

Fig. 3 (a) is a cross-sectional view showing the apparatus for producing a polycrystalline silicon of the present invention in the step of heating the crucible. Fig. 3 (b) is a cross-sectional view showing the apparatus for producing a polycrystalline silicon of the present invention in the step of cooling the crucible.

As shown in FIGS. 3(a) and 3(b), the polysilicon manufacturing apparatus (101) of the present invention includes an upper chamber (105) and a lower chamber (108), and the upper chamber (105) includes a raw material ( a crucible (103) of 102), and a heater (104) disposed above the crucible (103), the lower chamber (108) including a heat conductor (106) disposed under the crucible (103), and A cooling unit (107) and a cooling portion (108, 113) for cooling the heat conductor (106). The inside of the lower chamber (108) serving as the cooling portion and the inside of the induction heating coil (113) are cooled by a liquid medium method such as a liquid cooling method such as a water cooling method or an inert gas or air cooling method. A cover (109) may be provided on the upper portion of the crucible (103), and a support plate (110) for supporting the crucible (103) may be provided in the lower portion of the crucible. A nozzle (111) may be provided in the crucible (103), and an inert gas or the like is injected from the nozzle (111). The crucible (103), the heater (104), and the heat conductor (106) are covered by a heat insulating material (112) and a heat insulating material (114). In Fig. 3(a), since the lower heat insulating material (114) constituting the cooling unit (107) is in contact with the upper heat insulating material (112), the space (116) which is a part of the cooling unit (107) is similarly referred to (refer to Figure 3 (b)) is closed. The heat conductor (106) is heated by an induction heating coil (113) disposed outside the heat insulating material (112). Therefore, the cooling unit (107) It does not work in Figure 3(a). On the other hand, as shown in FIG. 3(b), in the step of cooling the crucible (103), the lower heat insulating material (114) is dropped by the cylinder (115), thereby providing a void (116). Thereby, the vicinity of the opening end portion of the heat conductor (106) that is in contact with the gap (116) is cooled. Furthermore, the temperature of the bottom of the heater (104), the heat conductor (106), the surface temperature of the open end, the temperature of the front side of the induction heating coil (113), and the inner surface of the wall of the lower chamber can be respectively sensed by temperature. The device (117) performs the measurement.

[D] Evaluation of polycrystalline germanium

The characteristics of the polycrystalline germanium ingot produced by the above method can be evaluated by measuring the energy conversion efficiency as a solar cell. The energy conversion efficiency is usually evaluated by using a solar simulator manufactured by Solar Light Co., Ltd., etc., according to STC (Standard Test Cell conditions). Further, the STC is a solar simulator having a solar radiation intensity of 1.0 kW/m ² and an air mass of AM = 1.5 as a light source, and is evaluated based on the maximum output power of the solar cell measured at a solar cell temperature of 25 °C. As the sample, a solar cell produced by cutting out a tantalum wafer from the obtained polycrystalline germanium ingot can be used.

Hereinafter, the invention of the present application will be described in more detail by way of examples and comparative examples, but the examples are examples of the invention and are not intended to limit the scope of the invention.

[Examples]

Embodiment 1 and Embodiment 2

Polycrystalline is produced using a polysilicon manufacturing apparatus as shown in Figs. 3(a) and 3(b) Hey. However, in the examples and comparative examples, the support plate (110) was not used.

As a crucible, a bottomed cylindrical crucible having a square bottom of 1000 mm square and a height of 650 mm is used. The thermal conductivity of tantalum is 4.5W/m. K (measurement temperature 950 ° C). The thickness of the crucible is 25 mm. The crucible was made of opaque quartz, and a coating of tantalum nitride to which 5 mass% of ceria was added was applied to the inner surface of the crucible. As the heat conductor, an isotropic black lead heat conductor G535 made of Tokai Carbon Co., Ltd. having a concave profile in a longitudinal section is used. The heat conductor is a bottomed cylindrical shape having a square outer outer dimension of 1100 mm square, and the height of the wall portion (Fig. 2(a) 7) is 500 mm (refer to Fig. 1 and embodiment 2) (refer to Fig. 1 (a), Figure 2 (a)). The thickness of the bottom and wall portions of the heat conductor (Figs. 2(a) 6 and 8) was 150 mm (Examples 1 and 2). The thermal conductivity of the thermal conductor is 81W/m. K (measured at room temperature (refer to JIS R1611 flash method)). The gap of the cooling unit provided around the open end of the heat conductor is adjusted within a range of more than 0 mm and 200 mm or less.

As the niobium raw material accommodated in the crucible, a polycrystalline crucible (manufactured by Wacker Co., Ltd.) having a purity of 99.9999999% or more is used.

As the heater, an isotropic black lead G535 manufactured by Tokai Carbon Co., Ltd. was used, and as the induction heating coil, a low-frequency induction heating device (output: 50 kW) manufactured by Fuji Electric Furnace Co., Ltd. was used. Further, as a heat insulating material in the apparatus, DONACARBO (DON-1000) manufactured by Osaka Gas Chemical Co., Ltd. was used.

First, the crucible is heated by the heater and the heat conductor above the crucible. The temperature of the molten crucible was brought to 1550 ° C, and the heat conductor was heated by an induction heating coil (50 Hz).

After all the raw materials of the crucible are melted, the heating of the thermal conductor is stopped, the lower heat insulating material for the thermal conductor is lowered, and a gap is provided near the open end of the thermal conductor to start cooling of the thermal conductor. The temperature profile of the temperature Tg (° C.) of the bottom outer surface of the heat conductor can be expressed by the following linear approximation equation: Tg=a-bt.

Here, a and b in the formula are as shown in the following Table 1, and t is an elapsed time (hour) from the start of cooling. Further, in Example 1 and Example 2, the height of the crucible added to the crucible was 300 mm, and the temperature Ts of the surface of the molten crucible during solidification was maintained at a state 2 ° C higher than the melting point of 1410 ° C (superheat = 2 ° C, Ts = 1412 ° C). Regarding the solidification rate Vs, the target of Example 1 was 0.3 mm/min, and the target of Example 2 was 0.5 mm/min. 4, 5, and 7 are graphs showing changes in Ts (°C), Tx (°C), Tg (°C), and solidification speed in Examples 1 and 2, respectively. Further, in the final stage of solidification, in order to solidify the molten crucible, the heater output level above the crucible is maintained constant.

Comparative example 1

In place of the heat conductor of the present invention, as a conventional method, a water-cooled copper refrigerator (a commercially available deoxidized copper, a 1,000 mm square, a box type cooling structure, a cooling plate portion thickness: 12 mm, a cooling water: purified water) is disposed facing the bottom of the crucible. , the amount of water 50l / min), and A polycrystalline germanium ingot was produced in the same manner as in Example 1 except that the crucible ingot was solidified in a crucible having a height of 250 mm. Fig. 6 and Fig. 7 show changes in the temperature Tg (°C) of the molten tantalum surface temperature T° (°C) and the bottom outer surface (the side in contact with the bottom of the crucible) of the water-cooled copper cooling refrigerator, and the solidification rate.

Evaluation

The lower end of the bismuth ingot of the examples and the comparative examples produced as described above was cut into 20 mm, the upper end was 10 mm, and the side portion was 20 mm, and 36 pieces of 150 mm □ blocks were cut out from the remaining bismuth ingots. A solar cell having a cross-sectional dimension of 150 mm and a thickness of 200 μm was cut out from 36 blocks. The energy conversion efficiency of the solar cell was measured under the above-described STC conditions using a solar simulator (16S-300-002) manufactured by Sunlight Co., Ltd. The distribution of the energy conversion efficiencies of each of all the wafers corresponding to the bismuth ingots obtained in Example 1, Example 2, and Comparative Example is collectively shown in Table 2.

* The numerical values of Example 1, Example 2, and Comparative Example 1 are ratios (%) of the number of wafers showing the conversion efficiency that meets the conditions in all wafers.

As shown in the above-mentioned Table 2, in the first embodiment and the second embodiment, the number of blocks of the germanium wafer having a relatively high energy conversion efficiency of 17% or more is 70% or more of the total, and in contrast, In the prior method, the number of blocks of the germanium wafer is 20% of the whole, and the yield is less than one third.

As a result of the above, the polycrystalline germanium ingot manufacturing apparatus of the present invention can maintain the melting enthalpy temperature at a temperature slightly higher than the melting point across the entire solidification range, and maintain the solidification speed lower and constant across the entire solidification range. The polycrystalline germanium produced from the obtained polycrystalline germanium ingot has superior energy conversion efficiency as compared with the comparative example.

101‧‧‧Polysilicon manufacturing equipment

102‧‧‧矽Materials

103‧‧‧坩埚

104‧‧‧heater

105‧‧‧ upper room

106‧‧‧ Thermal Conductor

108‧‧‧low room

109‧‧‧Cover

110‧‧‧Support board

111‧‧‧Nozzles

112‧‧‧Upper insulation

113‧‧‧Induction heating coil

114‧‧‧Bottom insulation

115‧‧‧ cylinder

117‧‧‧temperature sensor

Claims (10)

A polycrystalline germanium ingot manufacturing apparatus comprising: a crucible capable of accommodating a crucible raw material; a heater disposed around the crucible; a thermal conductor disposed under the crucible; and a cooling unit cooling the thermal conductor; the polycrystalline crucible In the bismuth ingot manufacturing apparatus, the heat conductor is formed with a bottomed cylindrical body that is opened downward, and the bottom outer surface of the heat conductor is disposed to face the outer surface of the bottom of the crucible, and the cooling unit is configured to The vicinity of the open end of the heat conductor is cooled. The polycrystalline germanium ingot manufacturing apparatus according to claim 1, wherein the heat conductor is measured at 25 ° C according to the flash method of JIS R1611 and has 30 W/m. K~150W/m. The thermal conductivity of K. The polycrystalline germanium ingot manufacturing apparatus according to the first or second aspect of the invention, wherein the heat conductor is made of black lead. The polycrystalline germanium ingot manufacturing apparatus according to any one of claims 1 to 3, further comprising an induction heating coil, wherein the induction heating coil heats the heat conductor. The polycrystalline germanium ingot manufacturing apparatus according to any one of claims 1 to 4, further comprising a heat insulating material covering at least a part of the crucible, the heater, and the heat conductor. Polycrystalline germanium as described in any one of claims 1 to 5 The ingot manufacturing apparatus further includes: a cover covering the open end of the crucible; and a nozzle for injecting an inert gas into the crucible. A method for producing a polycrystalline ruthenium ingot, comprising the steps of: (1) accommodating a ruthenium raw material in a temperature-adjustable crucible; and (2) heating the niobium raw material in the crucible to a temperature higher than a melting point of niobium to make the niobium raw material And (3) cooling the molten crucible in the crucible via a heat conductor disposed under the crucible to obtain a polycrystalline ingot; the polycrystalline ingot manufacturing method is characterized in that the thermal conductor forms a lower opening The bottomed cylindrical body is disposed such that a bottom outer surface of the heat conductor is opposed to a bottom outer surface of the crucible, and the vicinity of an opening end portion of the heat conductor is cooled by the cooling unit. The method for producing a polycrystalline germanium ingot according to claim 7, wherein the cooling is performed under the following conditions, that is, the temperature (Tg) (° C.) of the outer surface of the bottom surface of the heat conductor is set to the following linear approximation equation. :Tg=a-bt, where a is 1,250~1,400, b is 10~35, and t is the elapsed time (hours) from the start of cooling. The manufacturer of polycrystalline germanium ingots as described in claim 7 or 8 In the method, the heating is performed by a heater and the heat conductor, and the heater is disposed around the crucible, and the heat conductor is heated by an induction heating coil. The method for producing a polycrystalline germanium ingot according to any one of claims 7 to 9, wherein the heating step and the cooling step are carried out under an inert gas atmosphere.