WO2009008555A1

WO2009008555A1 - Method for production of purified silicon

Info

Publication number: WO2009008555A1
Application number: PCT/JP2008/062972
Authority: WO
Inventors: Tomohiro Megumi; Hiroshi Tabuchi
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2007-07-12
Filing date: 2008-07-11
Publication date: 2009-01-15

Abstract

A standard temperature gradient (T0) and a standard solidification rate (R0) which meet the formula (1) are determined in advance based on C10max and Y0. k = [K1×Ln(R0)+K2]×[K3×exp[K4×R0×(K5×C2+K6)]]×[K7×T0+K8]-K9 (1) wherein k represents a coefficient selected from a range from 0.9 time to 1.1 times an aluminum effective distribution coefficient (k') so measured as to meet the formula (2): C10max = k'×C2×(1-Y0)k'-1 (2) wherein k' represents analuminum effective distribution coefficient; C2 represents the concentration of aluminum in a silicon molten solution raw material.

Description

Description Manufacturing method of purified silicon Technical field

The present invention relates to a method for producing purified silicon, and more specifically, a so-called directional solidification, in which a raw material silicon melt containing aluminum is solidified by cooling in a vertical shape with a temperature gradient provided in one direction. The present invention relates to a method for producing purified silicon. Background art

As shown in Fig. 1, the raw silicon melt in the vertical mold (3) is used as a method for producing purified silicon (1) by removing aluminum from the raw silicon melt (2) containing aluminum. A so-called directional solidification method is known in which (2) is solidified by cooling with a temperature gradient (T) provided in one direction. According to such a method, the raw material silicon melt (2) solidifies while prejudice aluminum from the low temperature side (21) to the high temperature side (22) of the temperature gradient (T), and the silicon direction solidified material (4) and Therefore, this silicon direction solidified product (4) is on the low temperature side (21) of the temperature gradient (T) during solidification, and the purified silicon region (41) with a relatively low aluminum concentration (C), and the temperature gradient It consists of two regions, a crude silicon region (45) on the high temperature side (22) of (T) and a relatively high aluminum concentration (C). Of these, the target silicon (1) is obtained as a purified silicon region (41) having a relatively low aluminum concentration (C) by cutting the crude silicon region (45) from the silicon direction solidified material (4). [Publication of Japanese Patent Laid-Open No. 2000-0 1 9 6 5 7 7].

In this directional solidification method, the larger the temperature gradient (T) and the slower the solidification rate (R), the more aluminum is segregated on the high temperature side (22). It is known that more silicon (1) can be obtained, but the installation of a large temperature gradient (T) requires a large amount of equipment, and slowing the solidification rate (R) is in terms of production rate. It is disadvantageous. Because of this, purified silicon The target maximum aluminum concentration (C,. _Max) of (1) and the ratio (M of the mass of the mass of the raw material silicon melt using (2) the purified silicon to (M ₂₎ (1) (M,), / The target purified silicon (1) is manufactured by adjusting the temperature gradient (Τ) and solidification rate (R) according to the target yield rate (Y.) indicated by M ₂ ). Disclosure of the invention

However, the relationship between the temperature gradient (Τ) and solidification rate (R) and the yield (Υ) and maximum aluminum concentration (C _lmax ) of the resulting purified silicon (1) has not been clear.

Therefore, in order to obtain purified silicon (1) with a target yield rate (Y .;) and an aluminum concentration (C) lower than the target maximum aluminum concentration (〇1 ( _{) 11} „) Through repeated mistakes, the optimum temperature gradient (T) and the optimum solidification rate (R) have been obtained, and the present inventor has obtained the target yield rate (Y ₀ ) without much trial and error. Thus, as a result of intensive studies to develop a method capable of producing purified silicon (1) having an aluminum concentration (C) equal to or less than a target maximum aluminum concentration (C _{1 () raax} ), the present invention has been achieved.

That is, the present invention

By cooling the raw material silicon melt containing aluminum (2) in the vertical mold (3) with the temperature gradient (T) provided in one direction, the aluminum concentration (C) becomes the target maximum aluminum concentration. (C x (p pm)) to obtain a silicon direction solidified material (4) including a purified silicon region (41) below and a crude silicon region (45) exceeding the target maximum aluminum concentration (C _{1 Cmax} ),

Crude silicon region (45) is excised from the obtained silicon directional solidified material (4), and purified silicon with aluminum concentration (C _(ppm )) below target maximum aluminum concentration (C _{1 () Biax} ) (1) Is a way to get

The target maximum aluminum concentration (C, _{Q ra ax)} and the ratio of the mass of the mass of the raw material silicon melt using (2) the purified silicon to _{(M 2) (1) (} M ,;) (M, / M 2 ), The reference temperature gradient (T „C / mm) that satisfies the following equation (1) and the reference solidification rate (R. (mmZ min)) The reference temperature gradient (T.) ± 0 With the temperature gradient (T) in the range of 1 ° CZmm, the raw material silicon melt is solidified at the solidification rate (R) in the range of the reference solidification rate (R.) ± 0.01 mm / min. The present invention provides a method for producing purified silicon (1) characterized by cooling (2). k = {K, XL n (R ₀ ) + K _Z }

X {Κ ₃ e χ ρ [K ₄ XR. X (K ₅ XC. + K ₆ )]}

X {Κ ₇ ΧΤ. + Κ ₈ } —K _g (1)

[Where k is the formula (2)

_{_{C 10max = k 'XC 2 X}} (1- Y.) k' - 1 (2)

(Where C, _max is the target maximum aluminum concentration (p pm) of purified silicon, k 'is the effective aluminum distribution coefficient, C ₂ is the aluminum concentration (ppm) of the raw silicon melt, and Y „is the step. Indicates the target value of the retention rate.)

Is a coefficient selected from the range of 0.9 times to 1.1 times the effective aluminum distribution coefficient k ′ determined to satisfy

Is, 1. 1 X 1 0 - a constant selected from a range of ^{^{3 ± 0. 1 X 1 0- 3}} , κ 2 is, 4. 2 X 1 0 - from a range of ^³ ± 0. 1 X 1 CT ³ Κ ₃ is a constant selected from the range of 1.2 ± 0.1.

κ ₄ is a constant selected from the range of 2.2 ± 0.1.

kappa ₅ is -. 1 0 X 1 0 one ³ ± 0. 1 X 1 0- been Bareru constants obtained from ³ range, kappa ₆ is a constant selected from 1. 0 ± 0 1 range.

κ ₇ is a constant selected from the range of 0.4 ± 0.1,

κ ₈ is a constant selected from the range of 1. 36 ± 0.01

9 is a constant selected from the range of 2.0 X 1 0 _ ⁴ ± 1. 0 X 1 0,

R _c is the standard solidification rate (mmZ min),

T ₀ indicates a reference temperature gradient (° CZmm). ]

According to the production method of the present invention, purified silicon having a target yield (γ) and an aluminum concentration (C) equal to or lower than a target maximum aluminum concentration (C a _χ ) from a raw material silicon melt (2) containing aluminum. Since the reference temperature gradient (T _Q ) and the reference solidification rate (R.) for producing (1) can be obtained, the temperature gradient (T) and solidification rate (R ) Cool the raw silicon melt (2) so that it solidifies Thus, it is possible to produce purified silicon (1) having a target aluminum yield (C) with a target maximum aluminum concentration (c,) at a target yield (Y.).

FIG. 1 is a cross-sectional view schematically showing a process of obtaining a silicon direction solidified material from a raw silicon melt by a direction solidification method.

FIG. 2 is a cross-sectional view schematically showing the process of obtaining purified silicon from silicon direction solidified material.

Explanation of symbols

1: Purified silicon

2: Raw material silicon melt 21: Low temperature side of temperature gradient 22: High temperature side of temperature gradient

24: Solid phase 25: Liquid phase

26: Interface

3: vertical

4: Silicon direction solidified material 41: Refined silicon region

45: Crude silicon area

5: Crude silicon 6: Heater 7: Furnace

8: Water-cooled plate T: Temperature gradient Y. : Target yield rate Mode for carrying out the invention

Hereinafter, the manufacturing method of the present invention will be described with reference to FIG.

The raw material silicon melt (2) used in the production method of the present invention is silicon that is in a molten state by heating, and its temperature exceeds the melting point of silicon (about 1414 ° C), usually from 1420 ° C to 1 58 0 ° C.

The raw material silicon melt (2) contains aluminum. Aluminum concentration in the raw material silicon melt ₍₂₎ (C 2) is usually 1 0 p pm~ 1 000 p pm , preferably 1 5 p pm or less. If the aluminum concentration (C ₂ ) of the raw material silicon melt is less than 10 p pm, it will be difficult to remove aluminum. If it exceeds l OOO p pm, it will be too large to obtain purified silicon (1). Requires temperature gradient (T) and solidification rate (R) It is not practical.

In addition to aluminum, the raw material silicon melt (2) may contain other impurity elements other than silicon and aluminum as long as it is a small amount, specifically a total of 1 ppm or less. In particular, purified silicon (1 ) Is obtained with the target yield rate (Y .;), the lower the content of boron, phosphorus, etc., the more preferable. Is preferably 0.1 ppm or less.

In the production method of the present invention, the raw silicon melt (2) is cooled in the saddle mold (3) as in the normal directional solidification method. The vertical type (3) is usually inert and heat resistant to the raw material silicon melt (2). Specifically, carbon such as graphite, carbon carbide, nitrogen carbide, alumina ( Aluminum oxide) and silica (quarium oxide) such as quartz are used.

The cooling is performed with the temperature gradient (T) provided in one direction in the raw material silicon melt (2). The temperature gradient (T) only needs to be provided in one direction. It is provided in the horizontal direction, and the low temperature side (21) and the high temperature side (22) may be the same height, or provided in the direction of gravity. It may be installed so that the low temperature side (21) is on the top and the high temperature side (22) is on the bottom, but usually the low temperature side (21) is on the bottom, as shown in Figure 1. The temperature gradient (T) is provided in the direction of gravity so that the high temperature side (32) is on the top. The temperature gradient (T) is usually 0.2 ° CZmm to l.5 ° CZmm, preferably 0.4 to 11111 to 0.9 °, in that it does not require excessive equipment and is practical. C / mm, more preferably 0.7 ° C Zmm or more. For example, the temperature gradient (T) is provided in the furnace (7) provided with a heater (6), and the lower side is open to the atmosphere. It can be provided by the method of cooling the lower part of the saddle shape under (7). In order to cool the lower part of the vertical mold (3), it is possible to cool it in the atmosphere. However, depending on the temperature gradient (T), for example, a water cooling plate (8) is installed under the furnace (7). You may cool with this water cooling plate (8).

The raw silicon melt (2) can be cooled, for example, by moving the saddle mold (3) containing it downward and guiding it out of the furnace (7) from below. By cooling the raw material silicon melt (2) in this way, the raw material silicon melt (2) solidifies while forming a solid phase (24) from the low temperature side (21), and the silicon direction solidified material (4) It becomes. The solidification rate (R) is the moving speed of the interface (26) between the solid phase (24) formed from the low temperature side (21) by cooling and the liquid phase (25) not yet solidified on the high temperature side (22). It can be adjusted by the moving speed of the vertical mold (3) when moving the vertical mold (3) out of the furnace (7).

In the process of solidifying the raw silicon melt (2) by cooling in this way, the aluminum contained in the raw silicon melt (2) is segregated to the high temperature side (22). For this reason, the solidified silicon direction (4) after solidification has an aluminum content (C) that increases in one direction from the low temperature side (21) to the high temperature side (22) of the temperature gradient [T]. Become. Of this solid material (4), the region on the low temperature side (21) of the temperature gradient (Τ) during the cooling process becomes the purified silicon region (41) with a low aluminum content, and on the high temperature side (22). The region was a crude silicon region (45) containing a large amount of segregated aluminum. In such a silicon direction solidified material (4), the target purified silicon (1) can be obtained by cutting out the rough silicon region (45). The method of cutting the rough silicon region (45) is not particularly limited, and the rough silicon region (45) may be cut by a normal method using, for example, a diamond cutter.

In the production method of the present invention, the temperature gradient (Τ) is in the range of the reference temperature gradient (T _Q ) ± 0.l ° CZmm, preferably the reference temperature gradient [Ding. ] ± 0. 0 5 ° C / mm, solidification rate (R) is standard solidification rate (R.) within ± 0.O lmmZ, preferably standard solidification rate (R.) ± 0 . 00 The range is 5 mmZ.

The reference temperature gradient (T.) and the reference solidification rate (R.) are obtained by the above equation (1). The effective aluminum distribution coefficient k in equation (1) is determined so as to satisfy the above equation (2).

This equation (2) indicates the proportion of the raw material silicon melt (2) used that solidifies in the process of solidifying the raw material silicon melt (2) by cooling into a solid phase (23). Equation (2-1) showing the relationship between the rate (f) and the aluminum concentration (C) in the part that immediately became the solid phase (23)

C = k 'XC ₂ X (1 1 f) ^k '-'( ^2-1 )

[Where C is the aluminum concentration (p pm) in the liquid phase, k 'is the effective aluminum distribution coefficient, C ₂ is the aluminum concentration (p pm) of the raw silicon melt used (2) Where f is the solidification rate. ]

Is derived from This formula (2-1) is a relational expression that is generally called the Seil's formula ["solidification of metal" (published on Mar. 25, 1 February 1965) 1 2 1 Pages 1 to 3 4].

Equation (1) is an equation showing the relationship between the aluminum effective partition coefficient (k), the solidification rate, and the temperature gradient, and was first discovered by the present inventors. The production method of the present invention is based on the reference temperature gradient (T _Q ) and the reference solidification rate (R.) satisfying the equation (1), and the temperature gradient (in the range specified by the present invention) The raw material silicon melt (2) is solidified so as to solidify at T) and a solidification rate (R).

The silicon direction solidified material (4) obtained by solidifying the raw material silicon melt (2) by the method of the present invention has a low temperature side (21) of the temperature gradient (T) in the cooling process (41) in the purified silicon region (41). The high temperature side (22) is the crude silicon region (45). In addition, since the ratio of the refined silicon region (41) in the silicon direction solidified material (4) is the same as the target yield (Y.), in the portion corresponding to this target yield (Υ). By cutting the silicon direction solidified material (4), the crude silicon region (45) can be removed, and thus the desired purified silicon (1) can be obtained.

The obtained purified silicon (1) may be further purified by a method such as pickling. As acids used for pickling, mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid are usually used, and those with few metal impurities are usually used from the viewpoint of preventing contamination. The purified silicon (1) thus obtained is heated and melted and used as the raw material silicon melt (2) in the production method of the present invention, so that purified silicon having a lower aluminum content can be obtained. Silicon (5) can be heated and melted together with silicon having a lower aluminum content and used again as the raw silicon melt (2) of the present invention.

The purified silicon (1) obtained by the production method of the present invention can be suitably used as a raw material for solar cells, for example. Example

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example. Reference Example 1 [Derivation of Equation (1)]

Experiment 1

Using the apparatus shown in Fig. 1, a silicon melt (2) with an aluminum concentration (C ₂ ) of 1000 ppm was added to a temperature gradient (T) (0.9 ° C) in a bowl (3). / mm) was provided to cool so as to solidify at a solidification rate (R) of 0.4 mm, and a silicon direction solidified product (4) was obtained. In the obtained silicon directional solidified product (4), the aluminum concentration (C) in the portion where the solidification rate (f) was 0.18 and 0.38 during the cooling process was measured using ICP (inductively coupled plasma) emission spectrometry. And 4.0 p pm (f = 0.18) and 4.9 ppm (ί = 0.38), as determined by the method or ICP mass spectrometry. From the solidification rate (ί) and the aluminum concentration (C), the effective aluminum distribution coefficient (k) satisfying the formula (2-1) was determined and found to be 3.1 × 10. The results are summarized in Table 1.

Experiment 2 and Experiment 3

Instead of the raw material aluminum melt (2) used in Experiment 1, the raw material silicon melt (2) with the aluminum concentration (C ₂ ) shown in Table 1 was provided with the temperature gradient (T) shown in Table 1. In the state, it was cooled to solidify at the solidification rate (R) shown in Table 1, and in the obtained silicon direction solidified product (4), the solidification rate (ί) in the cooling process is shown in Table 1 respectively. Except for determining the aluminum concentration (C) in the part that was the value, the same procedure as in Experiment 1 was performed to determine the aluminum effective distribution coefficient (k). The results are shown in Table 1. Table 1 Bell C ₂ τ R f C k

ΡΡΐη ° c / 匪 mm / min ppm

1 1000 0.9 0.4 0. 18 4.0 3. 1X10— 3

0. 38 4.9

2 1000 0.9 0.2 0. 17 2.8 2. 5X10 " ³

0. 38 4.2

3 1000 0.9 0.05 0. 32 1.2 0.

0. 72 2.6

X From the results of Experiment 1 to Experiment 3, the relationship between the solidification rate (R) and the effective aluminum distribution coefficient (k) was determined.

k = {K, 'XL n (R) + Κ ₂ '} (1— 1)

[In the formula, k represents the effective aluminum distribution coefficient, and R represents the solidification rate (mm / min). ] Was obtained. In the formula (1 1), 1 ^ '1. a 1 X 1 0- ^3, kappa _2' is 4. a 2 X 10- 3.

The temperature gradient (Τ), solidification rate (R), and effective aluminum distribution coefficient (k) in Experiment 1 to Experiment 3 satisfy Eq. (1 1 1).

Experiment 4 to Experiment 6

Although the temperature gradient (T) of the raw material silicon melt (2) matches that of Experiment 1 to Experiment 3 above, Experiment 4 to Experiment 6 were performed with different aluminum concentrations (C ₂ ) in the raw material silicon melt (2). The Table 2 shows the aluminum concentration (C ₂ ), temperature gradient (T), and solidification rate (R) of the raw aluminum melt (2). In the obtained silicon direction solidified material (4), the aluminum concentration (C) in the part where the solidification rate (f) in the cooling process was the value shown in Table 2 was obtained, respectively. Table 2 shows the effective aluminum distribution coefficient (k). Table 2 Experiment 2 TR f C k

ppm / mm mm / min pm

4 100 0.9 0.2 0. 17 0.4 4. 1X10- ³

0. 45 1.1

5 10 0.9 0.4 0. 32 0.1 9. 0X10 " ³

0. 72 0.3

6 10 0.9 0.2 0. 20 0.05 4. 2X10 " ³

0. 52 0.17 This experiment 4 to experiment 6 is similar to experiment 1 to experiment 3 in that the temperature gradient (T) of the raw silicon melt (2) matches, but the aluminum concentration of the raw silicon melt (2) (C ₂ ) is different. The effective aluminum distribution coefficient (k) obtained in Experiment 4 to Experiment 6 does not satisfy the above equation (1-1).

Equation (1) is an equation that satisfies the effective aluminum distribution coefficient (k) obtained in Experiment 1 to Experiment 3 and also satisfies the effective aluminum distribution coefficient (k) obtained in Experiments 4 to 6. — 2)

k = {K, 'XL n (R) + Κ ₂ '}

X {Κ ₃ 'X exp [K XRX (Κ ₅ ' XC ₂ + Κ ₆ ')]} (1-2) [where k, R, K,' and Κ ₂ 'have the same meaning as above. Show. C ₂ represents an aluminum concentration _(p pm) of the raw material aluminum melt. ]

Got. In the formula (1-2), Κ ₃ 'is 1.2, Κ ₄ ' is 2.2, Κ ₅ 'is one 1.0 X 1 0- 3, and Κ ₆ ' is 1. 0.

The temperature gradient (Τ), solidification rate (R), aluminum concentration (C ₂ ) of the raw aluminum melt used (C ₂ ), and aluminum effective partition coefficient (k) in Experiment 1 to Experiment 3 and Experiment 4 to Experiment 6 are And satisfies the equation (1 1 2).

Experiment 7 1 Experiment 7 was conducted, although the aluminum concentration (C ₂ ) of the raw silicon melt (2) matches the experiment 2, but the temperature gradient (T) was different. Table 1 shows the aluminum concentration (C ₂ ), temperature gradient (T), and solidification rate (R) of the raw aluminum melt (2). In the obtained silicon directional solidified product (4), the aluminum concentration (C) in the portion where the solidification rate (f) in the cooling process was the value shown in Table 3 was obtained, and the same procedure as in Experiment 1 was performed. Table 3 shows the effective aluminum distribution coefficient (k).

Table 3 Experiment C ₂ TR f C

ppm / dragon mm / min ppm

7 1000 0.4 0. 0.17 3.1 3.0X 10 " ³

0.52 6.7 This experiment 7 differs from experiment 2 in the aluminum concentration (C ₂ ) of the raw silicon melt (2), but the temperature gradient (T) is different. For this reason, the effective aluminum distribution coefficient (k) obtained in Experiment 7 does not satisfy the above formulas (1-1) and (1-12).

The effective aluminum distribution coefficient obtained in Experiment 1 to Experiment 3 and Experiment 4 to Experiment 6 (satisfying l and the aluminum effective distribution coefficient (k) obtained in Experiment 7 is -3)

k = {K, 'XL n (R) + Κ ₂ '}

X {Κ ₃ 'X exp [Κ ₄ ' XR X (Κ ₅ 'XC ₂ + Κ ₆ ')]}

X {Κ, 'XT + K _g '} -Κ ₉ '(1— 3)

[Wherein k, R, C ₂ , K, ′, K ₂ ′, K ₃ ′, K ₄ ′, K ₅ ′, and K ₆ ′ have the same meaning as described above. Τ indicates a temperature gradient (° C / mm). ]

Got. In equation (1-3), K ₇ 'is 0.4, Κ ₈ ' is 1.36, and Κ ₉ 'is 2.0 X 1 0-4.

Temperature gradient (Τ), solidification speed in Experiment 1 to Experiment 3, Experiment 4 to Experiment 6 and Experiment 7 The degree (R), the aluminum concentration (C ₂ ) and the aluminum effective distribution coefficient (k) of the raw aluminum melt used (2) satisfy Eq. (11-3).

Substituting the reference temperature gradient (T .;) and the reference solidification rate (R .;) in place of the temperature gradient (T) and solidification rate (R) in the formula (1-3) obtained above, Based on the value of Κ ₉ ', if the values of 1 ^ to 1 ^ ₉ are respectively expressed by the above equation (1), the above equation (1) is obtained. Example 1 1 1

The aluminum concentration (C ₂ ) of the raw material silicon melt (2) is 1 000 p pm, the target maximum aluminum concentration (C _{1 Qmax} ) is 4.0 p pm, and the target value of the yield rate [target yield rate] ( Y ₀ ) is assumed to be 0.1 8 and the formula (1) [However,! ^ ~! Each value of ^! ^ ~~! Same value as ^. ], The standard temperature gradient (T) and the standard solidification rate (R) are 0.9 ° CZmm and the standard solidification rate (R .;) is 0.4 mm. Minutes.

Using the equipment shown in Fig. 1, a silicon melt (2) with an aluminum concentration (C ₂ ) of 10 ° 0 ppm is heated in a bowl (3) with a temperature gradient (T) of 0.9 ° CZmm. In this state, cooling to solidify at a solidification rate (R) of 0.4 mmZ gives a silicon direction solidified material (4) as shown in Fig. 2.

As shown in Fig. 2, the resulting silicon directional solidified product (4) was cut at the part where the solidification rate (f) in the cooling process was 0.18, and the high temperature side of the temperature gradient (T) ( Purified silicon (1) is obtained by removing the region (45) in 22). The obtained purified _silicon (1) has a maximum aluminum concentration (C _lmax ) of 4. O p pm. Examples 1 1 2 and Examples 2 to 7

_{Except that} the aluminum concentration (C ₂ ), the target maximum aluminum concentration (C _10llax ), and the target yield (Y.) of the raw silicon melt (2) are as shown in Table 4, the same as in Example 1 To obtain the reference temperature gradient (Τ.) And the reference solidification rate (R .;), and the same temperature gradient (Τ) as the obtained reference temperature gradient (Τ.), The same as the obtained reference solidification rate (R _D ) Except for the solidification rate (R), the silicon direction solidified material (4) obtained by the same operation as in Example 1 was used. 3. Obtain purified silicon (1) by cutting at the part where the solidification rate (f) in the cooling process is the same as the target solidification rate (Y). Table 4 shows the maximum aluminum concentration (C _{l fflax} ) of this purified silicon (1). Table 4 Example C ₂ 10 max Yo T „TR flm,

ppm ppm ° C / mm 匪 / min ° C / mm mm / min ppm

1-1 1000 4.0 0.18 0.9 0.4 0.9 0.4 0. 18 4.0

1-2 4.9 0.38 0. 38 4.9

2-1 1000 2.8 0.17 0.9 0.2 0.9 0.2 0. 17 2.8

2-2 4.2 0.38 0. 38 4.2

3-1 1000 1.2 0.32 0.9 0.05 0.9 0.05 0. 32 1.2

3-2 2.6 0.72 0. 72 2.6

4- 1 100 0.4 0.17 0.9 0.2 0.9 0.2 0. 17 0.4

4-2 1.1 0.45 0. 45 1.1

5-1 10 0.1 0.32 0.9 0.4 0.9 0.4 0. 32 0.1

5-2 0.3 0.72 0. 72 0.3

6-1 10 0.05 0.20 0.9 0.2 0.9 0.2 0. 20 0.05

6-2 0.17 0.52 0. 52 0.17

7-1 1000 3.1 0.17 0.4 0.2 0.4 0.2 0. 17 3.1

7-2 6.7 0.52 0. 52 6.7

Industrial applicability

According to the production method of the present invention, from the raw silicon melt containing aluminum (2), the target yield (YQ) and the aluminum concentration (C) are equal to or lower than the target maximum aluminum concentration (C _{10 NI A} _x ). Reference temperature gradient (T \) and reference solidification rate for producing purified silicon (1) Degree (R.) can be obtained, and by cooling the raw material silicon melt (2) so that it solidifies at the temperature gradient (T) and solidification rate (R) in the above range based on these. Purified silicon (1) having an aluminum concentration (C) of not more than the target maximum aluminum concentration can be produced with a target yield (Y „).

Claims

The scope of the claims

By cooling the raw material silicon melt containing aluminum (2) in the vertical mold (3) with the temperature gradient (T) provided in one direction, the aluminum concentration (C) becomes the target maximum aluminum concentration. (C _{1 () Diax} (ppm)) or less refined silicon region (41), and a silicon directional solidified material (4) containing a crude silicon region (45) exceeding the target maximum aluminum concentration (C _{1 () nax} ) (4 )

Crude silicon region (45) is excised from the obtained silicon directional solidified material (4) and refined silicon (1) with aluminum concentration (C _(ppm )) below target maximum aluminum concentration (C1 _{() Iiax} ) Is a way to get

The target maximum concentration (C, Q _{ra ax} ) and the ratio of the mass (Μ,) of the purified silicon (1) to the mass (M ₂ ) of the raw material silicon melt (2) (indicated by Μ, ΖΜ The reference temperature gradient (T _Q (° C Zmm)) and reference solidification rate (R. (mm / min)) satisfying the following equation (1) are obtained in advance from the target yield rate (Υ ₀ ). The reference temperature gradient (T.) With a temperature gradient (Τ) in the range of ± 0-l ° CZmm, the solidification rate (R „) in the range of ± 0.0 ImmZ The raw material silicon melt (2) is cooled so that it solidifies in (1).

k = {K, XL n (R ₀ ) + K ₂ }

X {K ₃ X exp [K ₄ XR ₀ X (K ₅ XC ₂ + K ₆ )]}

X {K ₇ XT ₀ + K ₈ } 1 Κ ₉ (1)

[Where k is the formula (2)

C ₁₀ » _a x = k 'XC ₂ X (1-Y.)- ¹ (2)

( _Where C _{1 Qraax} is the target maximum aluminum concentration (p pm) of purified silicon, k 'is the effective aluminum distribution coefficient, C ₂ is the aluminum concentration (ppm) of the raw silicon melt, and Y is the yield. Indicates the target value for each rate.)

Is a constant selected from the range 1. 1 Χ 1 0— ³ ± 0. 1 X 1 0— 3. κ ₂ is a constant selected from the range 4.2 X 1 0-3 ± 0. 1 X 1 0,

3 is a constant selected from the range of 1.2 Sat 0 • 1.

κ ₄ is a constant selected from the range of 2.2 Sat 0 1

5, the resulting Bareru constant from a 1. 0 X 1 0 one ³ ± 0. 1 range of X 1 0- ^3, 6 is a 1. 0 ± 0 • constant selected from 1, and

κ ₇ is a constant selected from the range of-0. 4 Sat 0 • 1.

8 is a constant selected from the range 1.36 ± 0 • 01,

kappa ₉ is, 2 0 X 1 0 - a 4 ± 1. constant selected from 0 X 1 0- ⁴ range.

Ro is the standard solidification rate (mmZ min),

T. Indicates the reference temperature gradient (° CZmm). ]

2.

2. The manufacturing method according to claim 1, wherein a target value (Y .;) of the yield rate is 0.9 or less.

3.

The target maximum aluminum concentration (C _1Qnax ) is 1 to ₁₀₀₀ times to 3 to 100 times the aluminum concentration (C ₂ ) of the raw silicon melt (2). Production method.