阅读说明：本技术 一种多晶硅坩埚涂层及其制备方法 (Polycrystalline silicon crucible coating and preparation method thereof ) 是由 曾磊 张乃文 张玉玉 纪杨 于 2019-09-11 设计创作，主要内容包括：本发明公开了一种多晶硅坩埚涂层及其制备方法,包括,氮化硅重量百分比为15-25％,氧化剂重量百分比为5-15％,粘合剂重量百分比为5-20％,分散剂重量百分比为60-70％。按比例称取氮化硅粉末、氧化剂、粘合剂和分散剂混合搅拌成均匀的混合液；混合液通过喷涂设备进行二次喷涂,均匀喷涂于坩埚内壁后低温烘干；低温烘干结束后,将坩埚放入烧结炉内900-1000℃烧结2-3小时,烧结完成后在1小时内降至室温25℃。所得氮化硅涂层与坩埚具有极佳的粘结力,附着牢固,不易脱落；氮化硅涂层厚度为200μm-600μm,可以完全阻隔硅液与二氧化硅以及其他杂质发生反应,有效避免了坩埚及杂质对硅的污染。(The invention discloses a polysilicon crucible coating and a preparation method thereof, comprising 15-25% of silicon nitride, 5-15% of oxidant, 5-20% of adhesive and 60-70% of dispersant by weight percentage. Weighing silicon nitride powder, an oxidant, a binder and a dispersant according to a proportion, mixing and stirring to obtain a uniform mixed solution; the mixed solution is sprayed for the second time by a spraying device, and is evenly sprayed on the inner wall of the crucible and then dried at low temperature; after the low-temperature drying is finished, the crucible is placed into a sintering furnace for sintering at the temperature of 900-1000 ℃ for 2-3 hours, and the temperature is reduced to 25 ℃ within 1 hour after the sintering is finished. The obtained silicon nitride coating has excellent binding power with the crucible, is firmly attached and is not easy to fall off; the thickness of the silicon nitride coating is 200-600 μm, which can completely prevent the silicon liquid from reacting with silicon dioxide and other impurities, and effectively avoid the pollution of the crucible and the impurities to silicon.)

1. A polycrystalline silicon crucible coating, comprising: silicon nitride, oxidant, adhesive and dispersant, and is characterized in that: 15-25% of silicon nitride, 5-15% of oxidant, 5-20% of adhesive and 60-70% of dispersant.

2. The polysilicon crucible coating of claim 1, wherein: the dispersant is one or two of water and ethanol.

3. The polysilicon crucible coating of claim 1, wherein: the adhesive is one or two of paraffin and polyvinyl alcohol.

4. The polysilicon crucible coating of claim 1, wherein: the oxidant is any one of hydrogen peroxide, potassium permanganate and potassium chromate.

5. the polysilicon crucible coating of claim 1, wherein: the particle size of the silicon nitride powder particles is 50nm-1 μm.

6. The polysilicon crucible coating of claim 1, wherein: the particle size of the silicon nitride powder particles is the mixture of particles with the particle size of less than 50nm and particles with the particle size of 50nm-1 mu m, wherein the silicon nitride powder particles with the particle size of less than 50nm account for 10-50%.

7. the polysilicon crucible coating of claim 1, wherein: the thickness of the silicon nitride coating is 200-600 μm.

8. A preparation method of a polycrystalline silicon crucible coating is characterized by comprising the following steps: weighing silicon nitride powder, an oxidant, a binder and a dispersant according to a proportion, mixing and stirring to obtain a uniform mixed solution; uniformly spraying the mixed solution on the inner wall of the crucible by using spraying equipment, drying the mixed solution at the low temperature of 70-90 ℃ for 1 hour, then performing secondary spraying, and continuously drying the mixed solution at the low temperature of 70-90 ℃ for 5 hours after the secondary spraying; after the low-temperature drying is finished, the crucible is placed into a sintering furnace for sintering at the temperature of 900-1000 ℃ for 2-3 hours, and the temperature is reduced to 25 ℃ within 1 hour after the sintering is finished.

Technical Field

The invention relates to the field of crucible coatings of polycrystalline silicon ingot furnaces, in particular to a polycrystalline silicon crucible coating and a preparation method thereof.

Background

The solar material is widely applied to civil and national defense construction due to the excellent characteristics of green, environmental protection, high efficiency and the like. Polycrystalline silicon is an important component of a solar material, and the quality of the polycrystalline silicon plays a decisive role in the performance of the solar material. At present, the main process technology for producing polycrystalline silicon at home and abroad is 'Siemens improvement method', purified high-purity trichlorosilane and hydrogen are mixed in proportion, then the mixture is introduced into a polycrystalline silicon reduction furnace at a certain temperature and pressure, and deposition reaction is carried out on electrified high-temperature silicon cores to generate polycrystalline silicon, and finally rod-shaped polycrystalline silicon products are generated. And (4) collecting the rod-shaped polycrystalline silicon products, feeding the collected rod-shaped polycrystalline silicon products into an ingot furnace, casting the rod-shaped polycrystalline silicon products into polycrystalline silicon ingots, and then further cutting and processing the polycrystalline silicon ingots. The polysilicon ingot is processed and formed in a crucible of an ingot furnace, and at present, the crucible for ingot casting is mainly made of a quartz ceramic crucible, which is called a high-purity fused quartz ceramic crucible (the content of silicon dioxide is more than or equal to 99.9%). The ceramic crucible is made of high-purity fused quartz. Generally, the shape thereof is mainly square and cylindrical. The square high-purity quartz crucible is used in a polycrystalline silicon ingot casting link and serves as a container for melting and growing polycrystalline silicon; the round high-purity quartz crucible is used in the link of pulling single crystal in monocrystalline silicon. The quartz ceramic crucible has the characteristics of fine structure, low thermal conductivity, small thermal expansion coefficient, high dimensional precision of a finished product, no deformation at high temperature, good thermal shock stability, good electrical property, good chemical erosion resistance and the like, but has some defects in the polycrystalline silicon ingot casting process. As is well known, in the production process of polysilicon ingots, a ceramic crucible is mainly used for containing molten silicon, and the main chemical component of the ceramic crucible is silicon dioxide, and the molten silicon can react with the ceramic crucible which is contacted with the ceramic crucible. The silicon liquid reacts with the silicon dioxide to generate silicon monoxide, thereby introducing oxygen to pollute the silicon liquid. Meanwhile, the silicon monoxide has volatility and can react with a graphite component in the polycrystalline silicon ingot furnace to generate silicon carbide and carbon monoxide. The carbon monoxide will react with the silicon liquid to produce more volatile substances or impurities, such as silicon monoxide, carbon, silicon carbide, metal trace substances or carbides and oxides of additives. In addition, the silicon liquid reacts with various impurities in the ceramic crucible, such as iron, boron, aluminum, and the like.

The reaction between the silica and the silicon liquid promotes the adhesion of silicon to the crucible, and due to the difference in thermal expansion coefficient between the two materials, silica and silicon, if the silicon material and the ceramic crucible wall are tightly bonded, it is likely that the crystalline silicon or the ceramic crucible will crack when the crystal cools. The prolonged contact between the silicon melt and the ceramic crucible can also cause corrosion of the ceramic crucible and even breakage of the crucible, resulting in overflow of the silicon melt.

In order to solve the problems, materials such as silicon nitride and the like are generally adopted in the process as coatings to be coated on the inner wall of the ceramic crucible, so that the direct contact between the silicon melt and the ceramic crucible is isolated, the reaction of the molten silicon and silicon dioxide can be prevented or reduced, and the pollution and cracking of the polycrystalline silicon ingot are avoided or reduced. To achieve this effect, the silicon nitride coating must be of sufficient thickness to prevent the silicon liquid from reacting with the silicon dioxide, and the silicon nitride coating itself does not allow the introduction of new impurities to contaminate the silicon.

However, the ceramic crucible using the silicon nitride coating at present has two serious disadvantages, on one hand, the ceramic crucible using the silicon nitride coating is not firmly bonded, and is easy to fall off or peel off during use or even before use, and can not completely prevent the phenomena that silicon liquid reacts with silicon dioxide, the crucible is easy to be bonded, an ingot is cracked and the like; on the other hand, the thickness of the silicon nitride coating is not enough, the thickness of the silicon nitride coating is at least more than 200 μm generally, so that the silicon liquid can be effectively prevented from reacting with the ceramic crucible, and the coating is too thin, so that the pollution of impurities in the crucible to the silicon ingot can not be effectively prevented, and the quality of the silicon ingot is influenced.

Disclosure of Invention

The invention provides a polycrystalline silicon crucible coating and a preparation method thereof, which can obtain a coating with the thickness of 200-600 mu m, and the coating is firmly bonded with a ceramic crucible and is not easy to fall off.

the specific technical scheme is that the polycrystalline silicon crucible coating comprises: silicon nitride, oxidant, adhesive and dispersant, and is characterized in that: 15-25% of silicon nitride, 5-15% of oxidant, 5-20% of adhesive and 60-70% of dispersant.

Further, the dispersant is one or two of water and ethanol.

Further, the adhesive is one or two of paraffin and polyvinyl alcohol.

Further, the oxidant is any one of hydrogen peroxide, potassium permanganate and potassium chromate.

Furthermore, the particle diameter of the silicon nitride powder particles is 50nm-1 μm.

Furthermore, the particle size of the silicon nitride powder particles is a mixture of particles with the particle size of less than 50nm and particles with the particle size of 50nm-1 mu m, wherein the silicon nitride powder particles with the particle size of less than 50nm account for 10-50%.

Further, the thickness of the silicon nitride coating is 200-600 μm.

Further, the preparation method of the polycrystalline silicon crucible coating comprises the following steps: weighing silicon nitride powder, an oxidant, a binder and a dispersant according to a proportion, mixing and stirring to obtain a uniform mixed solution; uniformly spraying the mixed solution on the inner wall of the crucible by using spraying equipment, drying the mixed solution at the low temperature of 70-90 ℃ for 1 hour, then performing secondary spraying, and continuously drying the mixed solution at the low temperature of 70-90 ℃ for 5 hours after the secondary spraying; after the low-temperature drying is finished, the crucible is placed into a sintering furnace for sintering at the temperature of 900-1000 ℃ for 2-3 hours, and the temperature is reduced to 25 ℃ within 1 hour after the sintering is finished.

Compared with the prior art, the invention has the following advantages:

The silicon nitride coating prepared by the invention has excellent binding power with the crucible, is firmly attached and is not easy to fall off; the thickness of the silicon nitride coating obtained by the secondary spraying method is 200-600 mu m, so that the silicon liquid can be completely prevented from reacting with silicon dioxide and other impurities, and the pollution of a crucible and the impurities to silicon is effectively avoided.

Detailed Description