阅读说明：本技术 全熔高效多晶生长用坩埚底部涂层及其喷涂工艺和应用 (Crucible bottom coating for full-melting efficient polycrystalline growth and spraying process and application thereof ) 是由 严东 王艺澄 于 2020-04-27 设计创作，主要内容包括：本发明公开了一种全熔高效多晶生长用坩埚底部涂层及其喷涂工艺和应用,该涂层覆于坩埚底部表面,包括浆料A涂层和浆料B涂层,其中：浆料A涂层的材料为氮化硅粉、超纯水及硅溶胶的混合物,按质量比计氮化硅粉:超纯水:硅溶胶=2.5-3:8-10:1；浆料B涂层的材料为氮化硅粉、超纯水、硅溶胶及混合粉末α的混合物,按质量比计氮化硅粉:超纯水:硅溶胶:混合粉末α的质量比例为2.5-3:8-10:1:0.3-0.5,混合粉末α由200-300目的硅粉和二氧化硅粉末混合制成,该涂层材料纯度高,杂质少,形成的涂层致密性高,阻隔作用好,喷涂工艺简单易行。(The invention discloses a crucible bottom coating for full-melting efficient polycrystalline growth, a spraying process and application thereof, wherein the coating is coated on the surface of the bottom of a crucible and comprises a slurry A coating and a slurry B coating, wherein: the coating of the slurry A is made of a mixture of silicon nitride powder, ultrapure water and silica sol, wherein the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol is =2.5-3:8-10: 1; the coating of the slurry B is made of a mixture of silicon nitride powder, ultrapure water, silica sol and mixed powder alpha, the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol to the mixed powder alpha is 2.5-3:8-10:1:0.3-0.5, the mixed powder alpha is prepared by mixing 200-mesh and 300-mesh silicon powder and silicon dioxide powder, the coating material is high in purity and less in impurities, the formed coating is high in compactness and good in blocking effect, and the spraying process is simple and easy to implement.)

1. The crucible bottom coating for the full-melting high-efficiency polycrystalline growth is characterized in that the coating covers the bottom surface of a crucible and comprises a slurry A coating and a slurry B coating, wherein:

the coating of the slurry A is prepared by spraying the slurry A, the slurry A is a mixture of silicon nitride powder, ultrapure water and silica sol, and the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol is =2.5-3:8-10: 1;

the coating of the slurry B is prepared by spraying the slurry B, the slurry B is a mixture of silicon nitride powder, ultrapure water, silica sol and mixed powder alpha, the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol to the mixed powder alpha is 2.5-3:8-10:1:0.3-0.5, and the mixed powder alpha is prepared by mixing 200-mesh 300-mesh silicon powder and silicon dioxide powder.

2. The crucible bottom coating for all-molten high-efficiency polycrystalline growth according to claim 1, wherein: the mixed powder alpha contains 1-10% of silicon dioxide powder by mass ratio.

3. The crucible bottom coating for all-molten high-efficiency polycrystalline growth according to claim 1, wherein: the purity of the silicon powder and the silicon dioxide powder is more than 99.99 percent.

4. The spray coating process of the crucible bottom coating for the all-molten high-efficiency polycrystalline growth according to claim 1, characterized in that: the method specifically comprises the following steps:

(1) setting spray gun atomization pressure to 4-4.5kgf/cm, and setting mist pressure to 4-4.5 kgf/cm;

(2) the spraying starting point and the spraying finishing point are arranged on the edge line of the crucible, the interval of each gun is 8-11cm, six temperature measuring points are selected on the surface of the crucible, one temperature measuring point is arranged on each of the four side walls of the crucible, the temperature of the two temperature measuring points at the bottom of the crucible reaches 60-90 ℃, and the bottom of the crucible is sprayed by using the slurry A;

(3) adding the slurry B when the slurry A is left at 200-.

5. The spray coating process of the crucible bottom coating for the all-molten high-efficiency polycrystalline growth according to claim 4, characterized in that: slurry A and slurry B used in the spraying process are calculated according to the mass ratio: slurry B =1-1.4: 1-0.6.

6. The use of a bottom coating for a crucible for all-molten high efficiency polycrystalline growth according to claim 1, wherein: charging materials into a crucible for forming a coating, casting ingots, reducing the surface temperature of the ingot to below 50 ℃ after discharging, and discharging the ingot.

Technical Field

The invention relates to a technology for coating the bottom of a high-efficiency polycrystalline crucible, in particular to a crucible bottom coating for full-melting high-efficiency polycrystalline growth, and belongs to the field of photovoltaic ingot polycrystalline growth.

Background

With the comprehensive popularization of diamond wire slicing and the large-scale application of new battery technologies such as PERC, HIT and the like, the efficiency and the cost of monocrystalline silicon wafers and polycrystalline silicon wafers are gradually increased, so that the improvement of the cost and the quality of the existing polycrystalline ingot casting technology is particularly important.

At present, polycrystal ingot casting technologies mainly comprise a semi-melting technology and a full-melting technology, and compared with the semi-melting technology, the full-melting technology has the advantages of being few in head-tail cutoff, high in effective utilization rate, short in ingot casting time consumption, low in unit water and electricity consumption and the like, but one of the cost advantages (few in tail cutoff) brings the defect that the number of silicon wafer black edges is slightly large, and the control difficulty of key points of the full-melting technology is high. The 3-5mm crystal flower proportion of the crystal ingot is easily reduced due to slight negligence of production control or quality control, the bottom of the crystal ingot is stuck to a crucible, even the whole ingot is scrapped, the problem of batch efficiency of silicon wafers occurs, and most enterprises in the industry adopt a semi-melting process with higher cost.

The crucible used in the existing full-melting process is a high-efficiency crucible which is manufactured by a crucible manufacturer by taking 'sand (quartz sand particles)' as a seeding layer at the bottom of a common crucible in advance as shown in figure 1, and an ingot manufacturer sprays a silicon nitride powder coating on the bottom high-efficiency layer by adopting a full-melting spraying process, wherein the silicon nitride powder coating has the same effect of protecting the crucible from being adhered to the crucible as the coating of the semi-melting spraying process, and silicon liquid and the quartz sand particles are required to be properly corroded. However, the spraying cannot be guaranteed to be completely uniform, the center and the edge of a thermal field of the ingot furnace are different, and the nucleation seeding effect at the bottom of the crucible in the full-melting process is not completely uniform, so that the process window for good nucleation seeding is relatively narrow, which is a main factor with high control difficulty of key points of the full-melting process.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and provides a crucible bottom coating for full-melting efficient polycrystalline growth and a spraying process and application thereof.

In order to solve the technical problems, the invention provides a crucible bottom coating for full-melting efficient polycrystalline growth, which is coated on the bottom surface of a crucible and comprises a slurry A coating and a slurry B coating, wherein:

the coating of the slurry A is prepared by spraying the slurry A, wherein the slurry A is a mixture of silicon nitride powder, ultrapure water and silica sol, and the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol is =2.5-3:8-10: 1;

the coating of the slurry B is prepared by spraying the slurry B, the slurry B is a mixture of silicon nitride powder, ultrapure water, silica sol and mixed powder alpha, the mass ratio of the silicon nitride powder to the ultrapure water to the silica sol to the mixed powder alpha is 2.5-3:8-10:1:0.3-0.5, and the mixed powder alpha is prepared by mixing 200-mesh and 300-mesh silicon powder and silicon dioxide powder.

The technical scheme of the invention is further defined as follows:

further, in the bottom coating of the crucible for full-melting high-efficiency polycrystalline growth, the silicon dioxide powder accounts for 1-10% of the mixed powder alpha by mass ratio.

In the crucible bottom coating for the full-melting efficient polycrystalline growth, the purity of the silicon powder and the silicon dioxide powder is more than 99.99 percent.

The method has the advantages that the adopted material has high purity and few impurities, the formed coating has high compactness, and the method can play a role in blocking the impurity diffusion at the bottom.

The invention also relates to a spraying process of the crucible bottom coating for full-melting efficient polycrystalline growth, which specifically comprises the following steps:

(1) setting spray gun atomization pressure to 4-4.5kgf/cm, and setting mist pressure to 4-4.5 kgf/cm;

(2) the spraying starting point and the spraying finishing point are arranged on the edge line of the crucible, the interval of each gun is 8-11cm, six temperature measuring points are selected on the surface of the crucible, one temperature measuring point is arranged on each of the four side walls of the crucible, the temperature of the two temperature measuring points at the bottom of the crucible reaches 60-90 ℃, and the bottom of the crucible is sprayed by using the slurry A;

(3) adding the slurry B when the slurry A is left at 200-.

In the spraying process of the crucible bottom coating for the full-melting efficient polycrystalline growth, the spraying process is characterized in that: slurry A and slurry B used in the spraying process are calculated according to the mass ratio: slurry B =1-1.4: 1-0.6.

The invention also relates to the application of the bottom coating of the crucible for full-melting efficient polycrystalline growth, the crucible with the coating is filled with materials, ingot casting is carried out, the surface temperature of the ingot after discharging is reduced to below 50 ℃, and the ingot is unloaded.

The invention has the beneficial effects that:

according to the invention, due to the reasons of material and particle size, nucleation and seeding conditions of quartz sand particles are different, and silicon dioxide particles in the coating play a role in auxiliary seeding at the position with poor seeding of the quartz sand particles, so that a process window is enlarged, and the ratio of crystal flowers with the diameter of 3-5mm at the bottom of a crystal ingot is increased; meanwhile, the coating main body material has high purity and less impurities, and the formed coating has high compactness and can play a role in blocking the impurity diffusion at the bottom.

The invention improves the aspects of spraying materials and spraying process, and improves the quality of the silicon wafer as follows:

(1) the area proportion of the crystal boule at the bottom of the crystal ingot with the diameter of 3-5mm is increased by 3-9%, and the silicon wafer batch verification conversion efficiency is improved by 0.02%.

(2) The red area of the ingot is reduced by 1.6mm, the corresponding black edge of the silicon wafer is reduced by 10%, and the larger the size of the silicon wafer is, the more the corresponding black edge is reduced.

Drawings

FIG. 1 is a schematic structural view of a crucible in the prior art without a sprayed coating;

FIG. 2 is a schematic structural view of a crucible after being sprayed with a coating according to an embodiment of the present invention;

in the figure: 1-crucible substrate, 2-quartz sand particles, 3, slurry A coating and 4-slurry B coating.

Detailed Description