Composite carbon barrier coating for polysilicon ingot furnace and preparation method, graphite guard plate, polysilicon ingot furnace

Abstract

The invention discloses a composite carbon barrier coating for a polycrystalline silicon ingot furnace, which is used to coat the surface of a carbon material device in the ingot furnace to prevent carbon pollution, and is characterized in that: the composite carbon barrier coating includes coating A first coating composed of metal tungsten or metal molybdenum coated on the surface of the device, and a second coating coated on the first coating, the second coating is a silicon nitride layer or a silicon nitride layer In the laminated layer formed with the silicon oxide layer, the thickness of the first coating is 0.02-300 microns, and the thickness of the second coating is 0.02-300 microns. The invention also discloses a method for preparing the composite carbon barrier coating; at the same time, the invention also discloses a graphite guard plate and a polysilicon ingot furnace comprising the composite carbon barrier coating. The present invention eliminates the generation of carbon monoxide by coating the composite carbon barrier layer on the surface of the carbon material device in the polycrystalline ingot furnace, thereby reducing the impurities in the ingot polysilicon and the dislocations derived from the impurities, improving the crystal quality, and further Improve the conversion efficiency of solar cells.

Description

technical field [0001] The present invention relates to a composite carbon-barrier coating for a polysilicon ingot casting furnace and a preparation method thereof. At the same time, the present invention also relates to a graphite guard plate and a polysilicon ingot casting furnace containing the composite carbon-barrier coating, which are mainly suitable for photovoltaic Reduction of carbon impurities in the field of ingot polysilicon production. Background technique [0002] At present, polycrystalline silicon photovoltaic cells occupy the mainstream position in the silicon-based photovoltaic market due to their low cost. On the premise of maintaining low cost, continuously improving the quality of silicon crystals is one of the main development directions of the industry. [0003] Ingot polycrystalline has an unparalleled cost advantage over CZ single crystal, but the crystal quality is slightly inferior. Therefore, continuously improving the crystal quality of ingot po...

AI Technical Summary

Problems solved by technology

[0004] The impurity in polysilicon is mainly caused by the segregation of carbon content in the silicon melt exceeding the solid solubility (6.6ppma) to produce silicon carbide, and the source of carbon is mainly the chemical reaction between the silicon melt and the oxygen in the quartz crucible at high temperature to produce a Silicon oxide gas, silicon monoxide reacts with the graphite thermal field to produce carbon monoxide, while the flow rate of the argon protective atmosphere in the ingot furnace is small (generally 30L / min), the space between the cover plate and the melt is large, and the exhaust on the guard plate The gas port is large, so the generated carbon monoxide gas is easy to contact with the surface of the silicon melt through convection and diffusion, thus causing carbon pollution

[0005] For this reason, people have carried out various attempts and improvements, such as CN201110242948.4 in the patent number, the Chinese invention patent document titled "Anti-Carbon Pollution Coating of Carbon Materials for Polysilicon Ingot Furnace and Its Preparation Process" discloses a way to reduce the pollution of carbon to crystals by in-situ producing silicon carbide crystal coatings on the surface of carbon-carbon materials. This technology changes the contact reaction between carbon and silicon monoxide into the contact reaction between silicon carbide and silicon monoxide. The reaction rate of the latter is significantly lower than that of the former, which solves the problem of carbon pollution in ingot polysilicon to a certain extent. However, this solution cannot fundamentally eliminate the generation of carbon monoxide, so it cannot fundamentally solve the problem of carbon pollution.

[0006] In addition, a Chinese utility model patent document with the patent number CN201220218492.8 titled "An Ingot Casting Furnace for Preparing Low-Carbon and Low-Oxygen Polysilicon Equipped with a New Guard Plate" discloses a metal molybdenum sheet isolation technology , can prevent the production of carbon monoxide, but silicon monoxide gas is prone to disproportionation reaction to produce silicon and silicon dioxide, and silicon will react with molybdenum to produce molybdenum disilicide, which will corrode the molybdenum plate, especially when the molybdenum plate is used on the inner surface of the cover plate as a separator When the carbon layer is formed, the generated molybdenum disilicide is easily peeled off from the substrate and falls into the silicon melt, resulting in metal molybdenum contamination

[0007] In addition, there are still some improved technologies for the flow of argon in the polycrystalline furnace. Due to the limitation of the furnace body structure, it is difficult to fundamentally eliminate the generation of carbon monoxide.

Images