A seed crystal laying method for producing low dislocation density cast single crystal ingot or polycrystalline silicon ingot

Abstract

The patent of the present invention discloses a seed crystal laying method for producing low dislocation density cast single crystal ingots or polycrystalline silicon ingots, which includes the following steps: S1, straight pulling the single crystal round rod to remove the edge skin to obtain a single crystal square rod without rounded corners ; S2, cutting the single crystal square rod into large seed crystal blocks; S3, cutting the large seed crystal block into small seed crystal blocks or seed crystal strips again; S4, cutting the small seed crystal block or seed crystal Lay strips on the bottom of the crucible to form a complete seed crystal layer; S5, place primary polysilicon material and circulating materials such as head and tail edges on the seed crystal layer; S6, put the crucible filled with polysilicon material into an ingot casting furnace In the process, a cast monocrystalline silicon ingot or a polycrystalline silicon ingot is obtained by adopting a semi-melting process; S7, the silicon ingot is squared, and a small square ingot is obtained after square cutting; S8, a cast single crystal silicon ingot is obtained after slicing the small square ingot Silicon wafer or polycrystalline silicon wafer; high seed crystals and short seed crystals are alternately matched when laying, so that the sides of the high seed crystals and short seed crystals are in contact with each other perfectly, reducing the probability of dislocations.

Description

technical field [0001] The invention relates to the technical field of photovoltaic manufacturing, in particular to a method for laying seed crystals when producing low dislocation density cast single crystal ingots or polycrystalline silicon ingots. Background technique [0002] At present, the general steps of producing cast single crystal are as follows: Lay a layer of single crystal seed crystal on the bottom of the crucible, install the head material, tail material, side skin and primary polysilicon material of the normal ingot on the single crystal seed crystal, and use the semi-melting process to obtain Cast single crystal. figure 1 Schematic diagram of seed laying for the production of conventional cast single crystals, figure 2 It is a schematic diagram of the square root when producing a conventional cast single crystal, image 3 Schematic diagram of a conventional cast single crystal silicon wafer. It can be seen that the size of the seed block is the same as t...

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Problems solved by technology

figure 1 Schematic diagram of seed laying for the production of conventional cast single crystals, figure 2 It is a schematic diagram of the square root when producing a conventional cast single crystal, image 3 Schematic diagram of a conventional cast single crystal silicon wafer. It can be seen that the size of the seed block is the same as the size of the silicon wafer. There are few grain boundaries in the cast single crystal silicon wafer. The internal growth of the silicon ingot reduces the single crystal area; due to the lack of grain boundaries, impurities such as carbon, nitrogen, and metals are easy to gather, precipitate, and nucleate locally in the cast single crystal silicon ingot, forming a non-(100) crystal growth direction. The crystal grains reduce the single crystal area; because there are few grain boundaries, there is no grain boundary to block the dislocation crystal, and dislocations are easy to proliferate in large quantities during the crystal growth process, which reduces the crystal quality of cast single crystal silicon

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