Polysilicon ingot casting method with low defect and high output and thermal field structure thereof

Abstract

The invention relates to a polysilicon ingot casting method with low defect and high output and a thermal field structure thereof. The thermal field structure comprises a thermal insulation cover system, a crucible system, split resistance heaters, a support part and a cooling device, wherein the three heaters are independently and separably controlled to lower energy consumption to the maximum degree and bring convenience for regulating a crystal growth interface, thereby obtaining an evener crystal growth interface, improving crystal quality and solving the later-stage cooling problem of the crystal growth because of the increase of the height of the ingot casting. A support block with the unique design and a cooling device are combined to realize the purpose of local cooling, so that the local position on the bottom of a crucible generates cold spots at the early stage of the crystal growth; nucleation is carried out firstly to reduce nucleation spots, and lateral temperature gradient is obtained to provide the necessary condition for the lateral growth of the crystal nucleus; crystalline grains are enlarged to reduce a crystal boundary to the large extent; and microdefects, such as dislocation and the like, are lowered.

Description

technical field [0001] The invention belongs to the technical field of solar cell ingot casting, and relates to a low-defect high-yield polycrystalline silicon ingot casting method and a thermal field structure thereof. Background technique [0002] In the field of solar photovoltaics, the method of directional solidification to produce polysilicon ingots is a commonly used method. The basic principle is: place the polysilicon raw material in a quartz ceramic crucible, place it in a specific thermal field system, and heat it until it is completely melted; The bottom of the crucible begins to cool, and the silicon solution begins to crystallize at the bottom of the crucible and gradually grows (solidifies); The consumption is around 3800 degrees. The high energy consumption is mainly due to the fact that the heater is located in the upper half of the entire thermal field structure. The heater is located at the top and upper side of the thermal field. In order to maintain the...

AI Technical Summary

Problems solved by technology

The high energy consumption is mainly due to the position of the heater in the upper half of the entire thermal field structure. The heater is located on the top and upper side of the thermal field. In order to maintain the temperature gradient of crystal growth, more energy is lost.

At present, the 450kg polycrystalline ingot furnace type is generally used in the industry. Due to the problem of production capacity or the load of the slicer, the actual feeding amount is generally 390-420kg. With the development of the industry, the competition is becoming more and more fierce, and the solar cell manufacturers are getting more and more More and more attention is paid to cost control. In order to increase production capacity and reduce energy costs, various new equipment are constantly being developed. The polycrystalline furnace has a larger furnace type (800kg) successfully developed, and these large furnace types are developing horizontally. , that is, the original 450kg polycrystalline ingot furnace type can cut 25 small pieces of 156mm×156mm×250mm, and the 800kg furnace type can cut 36 such small pieces, but the large-scale crucible production process is not yet mature. , and require a larger square cutting machine, the original square cutting machine is too narrow to continue to use, so its cost advantage is not obvious

In order to improve the output, on the basis of the original 450kg furnace type, the charging amount is directly increased. With the increase of the charging amount, it is difficult to dissipate heat in the later stage of crystal growth, the crystal growth time is greatly prolonged, and the energy consumption is increased.

At the same time, due to the problem of the growth method of the polysilicon ingot, the bottom of the quartz ceramic crucible starts to dissipate heat first, and the heat dissipation intensity of the entire plane is basically the same. Many nucleation points are generated at the bottom of the crucible, and the resulting grains are small, and the density of grain boundaries and dislocation defects Higher, so compared with single crystal, the solar cell efficiency will be lower by 1% to 2%

Images