阅读说明：本技术 一种保护坩埚侧壁涂层的装料方法 (Charging method for protecting crucible side wall coating ) 是由 徐�明 孟涛 张志强 周鹤军 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种保护坩埚侧壁涂层的装料方法,该装料方法具体为：首先在坩埚底部均匀地铺满小块硅料；然后在所述小块硅料之上采用均匀排列的方式铺设方形回收料,之后再在所述坩埚的四角位置放置晶砖回收料或堆叠的方形回收料；再将边皮回收料斜靠在所述坩埚的侧壁上,保证坩埚四面的侧壁不被露出,所述边皮回收料与坩埚侧壁之间呈线性接触,两者之间形成夹角；最后装入硅原料以及掺杂剂,完成装料。本发明的装料方法能够减少硅料由于膨胀挤压刮坏涂层的可能,同时能够降低多晶硅铸锭过程中由于硅料受热膨胀挤压破坏坩埚而发生溢流的可能性。(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.)

1. a charging method for protecting a coating on the side wall 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.

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.

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.