CN110578167A

CN110578167A - Charging method for protecting crucible side wall coating

Info

Publication number: CN110578167A
Application number: CN201910976835.3A
Authority: CN
Inventors: 徐�明; 孟涛; 张志强; 周鹤军
Original assignee: Baotou Meike Silicon Energy Co Ltd
Current assignee: Baotou Meike Silicon Energy Co Ltd
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2019-12-17

Abstract

The invention discloses a charging method for protecting a crucible side wall coating, which comprises the following steps: firstly, uniformly paving small blocks of silicon materials at the bottom of a crucible; then square reclaimed materials are laid on the small silicon materials in a uniform arrangement mode, and then crystal brick reclaimed materials or stacked square reclaimed materials are placed at the four corners of the crucible; then, the flaw-piece recycled materials lean against the side wall of the crucible in an inclined mode, the side walls of the four sides of the crucible are guaranteed not to be exposed, the flaw-piece recycled materials are in linear contact with the side wall of the crucible, and an included angle is formed between the flaw-piece recycled materials and the side wall of the crucible; and finally, charging silicon raw materials and doping agents to finish charging. The charging method can reduce the possibility that the coating is scraped by the silicon material due to expansion extrusion, and can also reduce the possibility that the crucible is damaged by the silicon material due to thermal expansion extrusion in the process of casting the polycrystalline silicon ingot so as to overflow.

Description

Charging method for protecting crucible side wall coating

Technical Field

The invention belongs to the technical field of polycrystalline ingots, and particularly relates to a charging method for protecting a coating on the side wall of a crucible.

Background

in the existing full-melting ingot casting process, silicon materials expand when heated and melted after being charged, the expansion extrusion among the silicon materials can damage the coating on the inner wall of the crucible, and melt silicon can contact the crucible body from the damaged coating to generate Si + SiO₂Reaction of → SiO, and the gaseous SiO further destroys the silicon nitride powder coating. After the ingot is demolded, punctiform crucible sticking phenomena known as "white spots" occur at these damaged locations, which affect the oxygen content of the ingot. For the B-doped P-type polycrystalline silicon wafer, the higher the oxygen content is, the higher the light-induced attenuation of the silicon wafer after the silicon wafer is made into a cell due to the recombination of boron and oxygen is, which can seriously affect the photoelectric conversion efficiency and the service life of the cell. The traditional method is to obtain a harder coating by adding a binder, so as to reduce the damage of the silicon material to the coating. However, the method of adding the PVA-based binder has the following drawbacks: 1. the viscosity of the slurry for crucible spraying is greatly increased, a spraying gun is easy to block and wear, and the service life of the spraying equipment is greatly shortened; 2. the protective effect is poor, and for the full-melting ingot casting process that the ingot casting temperature rises and is accelerated and the silicon material expands rapidly, the coating added with the adhesive cannot be completely prevented from being penetrated.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a charging method for protecting a coating on the side wall of a crucible, which can reduce the possibility of scraping the coating by expanding and extruding silicon materials and can also reduce the possibility of overflow caused by damage to the crucible by the silicon materials due to heated expanding and extruding in the process of casting a polycrystalline silicon ingot.

The invention is realized by the following technical scheme:

a charging method for protecting a coating on a sidewall of a crucible, comprising the steps of:

Step 1) uniformly paving small blocks of silicon materials with the length size of 3-12 mm at the bottom of a crucible;

step 2) paving square reclaimed materials on the small silicon materials in a uniform arrangement mode, and then placing crystal brick reclaimed materials or stacked square reclaimed materials at four corners of the crucible;

Step 3) obliquely leaning the flaw-piece reclaimed materials on the side wall of the crucible to ensure that the side walls of the four sides of the crucible are not exposed, wherein the flaw-piece reclaimed materials are in linear contact with the side wall of the crucible, and an included angle formed between the flaw-piece reclaimed materials and the side wall of the crucible is less than 10 degrees;

and 4) charging silicon raw materials and doping agents to finish charging.

Preferably, the reclaimed materials are silicon raw materials reclaimed in a polycrystalline ingot casting process.

Preferably, the distance between the recycled crystal brick material or the stacked square recycled material in the step 2) and the side wall of the crucible is more than or equal to 1 cm.

The invention has the following beneficial effects:

according to the charging method, the silicon material of the edge protector is replaced by the wide strip-shaped edge protector, the edge protector is obliquely placed, and the traditional surface contact edge protector is changed into line contact, so that the contact area of the coating on the inner wall of the crucible and the silicon material is greatly reduced, and the possibility that the coating is scraped by the silicon material due to expansion extrusion is reduced. The silicon nitride coating on the inner wall of the crucible is protected, the probability of contact between the silicon melt and the crucible body in the ingot casting process is reduced, and finally the oxygen content of the polycrystalline silicon ingot can be reduced by 0.5-1 ppm (after the silicon ingot produced by the method is used for cutting, the oxygen content at the bottom of a large ingot center crystal brick is detected to be about 7.5ppm on average and is 1ppm lower than the normal 8.5ppm of the same production line, so that the improvement effect is obvious). Meanwhile, due to the fact that enough gaps are reserved, the possibility of overflow caused by the fact that the crucible is damaged by the fact that silicon materials are heated, expanded and extruded in the polycrystalline silicon ingot casting process can be reduced.

drawings

FIG. 1 is a schematic diagram of a charging method for protecting a coating on a side wall of a crucible;

FIG. 2 is a top view of the crucible after the protective measures have been taken.

In the figure: 1. a crucible; 2. small silicon material; 3. square reclaimed materials; 4. recovering the crystal brick; 5. recycling the flaw-piece; 6. a side wall.

Detailed Description

the invention is further explained below with reference to the drawings and the examples.

Example 1

A charging method for protecting the coating of the side wall of a crucible, as shown in fig. 1 and 2, comprises the following steps:

(1) Small blocks of silicon materials 2 with the length size of 3-12 mm are uniformly paved at the bottom of the crucible 1, and a coating at the bottom of the crucible is not exposed outside.

(2) Square reclaimed materials 3 are laid on the small silicon materials 2 in a uniform arrangement mode, and then crystal brick reclaimed materials 4 or stacked square reclaimed materials 3 are placed at the four corners of the crucible 1.

Wherein, the distance between the crystal brick reclaimed material 4 or the stacked square reclaimed material 3 and the crucible side wall 6 is more than or equal to 1 cm.

(3) And the flaw-piece reclaimed materials 5 lean against the side wall 6 of the crucible in an inclined way, so that the side walls 6 on the four sides of the crucible are ensured not to be exposed, the flaw-piece reclaimed materials 5 and the side wall 6 of the crucible are in linear contact, and an included angle formed between the flaw-piece reclaimed materials and the side wall 6 of the crucible is less than 10 degrees. Instead of using surface contact or irregular polycrystalline blocks directly contacting the crucible coating as in conventional charging methods.

(4) And charging the remaining silicon raw material and the dopant to complete charging.

The reclaimed materials in the steps are all silicon raw materials reclaimed in the polycrystalline ingot casting process.

Claims

1. a charging method for protecting a coating on the side wall of a crucible, comprising the steps of:

and 4) charging silicon raw materials and doping agents to finish charging.

2. The charging method for protecting the coating on the side wall of the crucible as claimed in claim 1, wherein the reclaimed materials are silicon raw materials reclaimed in the process of polycrystal ingot casting.

3. The charging method for protecting the coating on the side wall of the crucible as claimed in claim 1, wherein the distance between the recycled crystal brick material or the stacked square recycled material in the step 2) and the side wall of the crucible is not less than 1 cm.