Silicon nitride powder, mold release agent for polycrystalline silicon ingots, and method for producing polycrystalline silicon ingots

A technology of silicon nitride powder and silicon nitride, which is applied in the field of silicon nitride powder, can solve the problems of adhesion and poor mold release of polysilicon ingots, and achieve the effect of improving mold release performance.

Inactive Publication Date: 2019-07-23
UBE IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In this case, there may be problems such as that the release property of the polysilicon ingot deteriorates at the upper part of the mold at high temperature, or the release layer peels off from the mold and adheres to the polysilicon ingot, etc.

Method used

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  • Silicon nitride powder, mold release agent for polycrystalline silicon ingots, and method for producing polycrystalline silicon ingots
  • Silicon nitride powder, mold release agent for polycrystalline silicon ingots, and method for producing polycrystalline silicon ingots
  • Silicon nitride powder, mold release agent for polycrystalline silicon ingots, and method for producing polycrystalline silicon ingots

Examples

Experimental program
Comparison scheme
Effect test

preparation example Construction

[0046]

[0047] First, silicon powder is mixed with silicon nitride powder as a diluent to prepare mixed raw material powder. Since the combustion synthesis reaction is at a high temperature of 1800° C. or higher, melting / welding of silicon may occur in a portion where the combustion reaction occurs. For the purpose of suppressing this, it is preferable to add silicon nitride powder as a diluent to the raw material powder within the range that does not hinder the self-propagation of the combustion reaction. The addition rate of the diluent is usually 10 to 50% by mass (the mass ratio of silicon:silicon nitride is 90:10 to 50:50), and further 15 to 40% by mass. In addition, on the basis of adjusting the proportion of β-type silicon nitride in the combustion product obtained in the combustion synthesis reaction, NH 4 Cl, NaCl, etc. These additives have the effect of lowering the reaction temperature through sensible heat, latent heat, and endothermic reactions. Here, the Fe...

Embodiment 1-1

[0085] D50 is 4.0μm, bulk density is 0.40g / cm 3 , the content ratio of Fe is 3ppm, the content ratio of Al is 4ppm, and the content ratio of metal impurities other than Fe and Al is 3ppm, the addition ratio of silicon nitride is 20% by mass (silicon: silicon nitride Silicon nitride powder (manufactured by Ube Industries, Ltd., product name "SN-E10" (Fe content ratio: 9ppm, Al content ratio: 2ppm, except The content rate of metal impurities other than Fe and Al: 4 ppm)) was used as a raw material powder. The above-mentioned raw material powder was accommodated in a nylon cylinder filled with silicon nitride balls and the inner wall surface was lined with urethane, and mixed for 0.5 hours at a vibration frequency of 1200 cpm and an amplitude of 8 mm using a batch vibrating mill to obtain a mixed raw material. powder.

[0086] figure 1 The combustion synthesis reaction apparatus 1 used for the combustion synthesis reaction of silicon in this example is shown in . The mixed r...

Embodiment 1-2～1-6

[0102] The time of the fine pulverization of Examples 1-2 to 1-6 is sequentially set to 0.30 hours, 1.50 hours, 2.50 hours, 4.00 hours, and 6.00 hours from Example 1-2. In addition, the same as Example 1-1 The same operation was performed to obtain the silicon nitride powders of Examples 1-2 to 1-6. Then, using the silicon nitride powder obtained in each of the examples as a mold release agent, two molds for casting polycrystalline silicon ingots were produced in the same manner as in Example 1-1. In each embodiment, use these molds, utilize the same method as embodiment 1-1 to carry out the unidirectional solidification experiment under the same two furnace temperatures as embodiment 1-1, utilize the same method as embodiment 1-1 Methods Evaluation of molds for polysilicon ingot casting.

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Abstract

The purpose of the present invention is to provide a silicon nitride powder that can be advantageously used as a mold release agent for polycrystalline silicon ingots and that exhibits an excellent mold releasability for polycrystalline silicon ingots even when, during unidirectional solidification, the melting temperature of the silicon is increased or the melting time for the silicon is lengthened. The silicon nitride powder is characterized by having a specific surface area of 2 m2 / g to 13 m2 / g, a [beta]-silicon nitride percentage of at least 50 mass%, a [beta]-silicon nitride crystallite diameter DC of at least 150 nm, and a ratio between the specific surface area-equivalent diameter DBET and DC, i.e., DBET / DC (nm / nm), of not more than 3, and having two peaks in the frequency distribution curve yielded by measurement of the particle size distribution, wherein the peak tops of these peaks are in the range from 0.5 to 2 [mum and in the range from 6 to 30 [mu]m and the ratio of the frequencies for these peak tops is 0.1 to 1.

Description

technical field [0001] The present invention relates to a silicon nitride powder capable of forming a mold release layer in a mold with good adhesion to the mold and good mold release properties, and in particular to a silicon nitride powder suitable as a mold release agent for polycrystalline silicon ingots. Background technique [0002] A polycrystalline silicon substrate used in a solar cell is generally obtained from a polycrystalline silicon ingot produced by unidirectionally solidifying molten silicon using a vertical Britzmann furnace. Higher performance and lower cost are required for polycrystalline silicon substrates. To meet this requirement, it is important to suppress the incorporation of impurities into polycrystalline silicon ingots during unidirectional solidification of molten silicon and to improve the yield of polycrystalline silicon ingots. In the unidirectional solidification of molten silicon by the vertical Britzmann method, a casting mold made of quar...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B21/068C01B33/02
CPCC01B21/068C01B33/02
Inventor 王丸卓司柴田耕司山尾猛山田哲夫
Owner UBE IND LTD
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