Production process of high-purity spray-free crucible

Abstract

The invention discloses a production process of a high-purity free-spraying crucible. The production process comprises the following steps of: (1) preparing silicon nitride slurry, and painting the silicon nitride slurry on the inner surface of a common quartz crucible; and (2) drying the painted crucible at 130-200 DEG C so as to obtain the high-purity free-spraying crucible which has a silicon nitride coating on the inner surface, wherein the silicon nitride slurry comprises, in percent by weight, 30-44% of silicon oxide powder with an alpha phase content of 90% or above, 15-22% of silica sol and 41-48% of deionized water. By introducing the silica sol with high-temperature viscosity into the silicon nitride slurry, the content of silicon nitride in the silicon nitride coating is reduced, and the diffusion amount of nitrogen to the surface of silicon melt is reduced; and meanwhile, the strength and density of the silicon nitride coating and adhesion of the silicon nitride coating tothe surface of the common quartz crucible are increased, and probability of adhesion and falling off of the silicon nitride coating on the surface of a silicon ingot is reduced after demoulding is conducted.

Description

technical field [0001] The invention relates to the technical field of crucible production, in particular to a production process of a high-purity spray-free crucible. Background technique [0002] During high temperature production process, molten Si and crucible raw material SiO 2 The reaction product is gaseous SiO, which escapes and reacts with graphite products placed in the crucible to form CO gas. CO is easy to enter the silicon melt, and carbon and oxygen are introduced into the silicon. The increase of C in the silicon melt will increase the formation of needles in polysilicon. The amount of formed SiC crystals, especially in the uppermost area of ​​the ingot is more, which will cause a short circuit in the solar cells made, and the efficiency of the cells will decrease sharply. In addition, boron and phosphorus, common impurities in crucible raw materials, will also be transferred to silicon ingots, so that the resistivity of silicon ingots cannot meet the require...

AI Technical Summary

Problems solved by technology

In actual production, the above-mentioned spraying of silicon nitride slurry has the following technical defects: spraying needs to be heated, the spraying temperature in the above-mentioned literature is 55-65°C, and the commonly used temperature in actual production is 80-120°C, and the temperature is not enough There will be sagging phenomenon; the spraying pipeline is prone to blockage; the mechanical strength and adhesion of the silicon nitride coating are insufficient, and it is easy to cause excessive wettability between the silicon melt and the silicon nitride coating, resulting in sticking phenomenon

The diffusion coefficient of oxygen in the silicon melt is large, and the silicon nitride coating has a certain barrier effect on the diffusion of impurity oxygen, boron, and carbon, but in actual production, the surface of the silicon ingot is enriched with impurity element precipitation and the width of the red zone It is still about 10mm, and the above-mentioned red zone needs to be sawn off before the silicon wafer is manufactured, resulting in a waste of silicon raw materials

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