Cast single crystal seed crystal laying method with short bottom red area and few native dislocations

Abstract

The invention discloses a cast single crystal seed crystal laying method with a short bottom red area and few native dislocations, which comprises the following steps: removing the head, tail and edgeskins of a Czochralski silicon rod, carrying out linear cutting to obtain cast single crystal seed crystals, and carrying out sand blasting treatment on the surfaces of the cast single crystal seed crystals to increase the surface roughness of the cast single crystal seed crystals; cutting the polycrystalline silicon block or the monocrystalline silicon block to obtain a thick sheet, and carryingout sand blasting on the surface of the thick sheet to increase the surface roughness of the thick sheet; laying a first thick sheet layer at the bottom of the crucible; spreading casting single crystal seed crystals on the first thick sheet layer, and reserving a gap between the side faces of every two adjacent casting single crystal seed crystals; spreading a second thick sheet layer in the center of the upper surface of each cast single crystal seed crystal; paving a thick sheet on the second thick sheet layer, tightly attaching the side wall of the thick sheet to form a third thick sheetlayer, placing a raw silicon material, a recycled silicon material and the like on the third thick sheet layer, manufacturing a temperature gradient in the vertical direction when the silicon materialis melted to 1 / 2 position of the cast single crystal seed crystal layer, and gradually solidifying from bottom to top to obtain a cast single crystal silicon ingot.

Description

technical field [0001] The invention relates to the field of photovoltaic manufacturing, in particular to a method for laying cast single-crystal seed crystals with a short red zone at the bottom and few primary dislocations. Background technique [0002] At present, the general steps of producing cast single crystal are as follows: lay one or several layers of silicon wafers or no silicon wafer on the bottom of the crucible, lay cast single crystal seed crystals on the silicon wafer, and leave space between the sides of adjacent cast single crystal seed crystals. There is a gap of a certain distance, and the head material, tail material, side skin and primary polysilicon material of the normal casting ingot are placed on the cast single crystal seed crystal, and the cast single crystal silicon ingot is obtained by the semi-melting process. Among them, the surface roughness of the cast single crystal seed crystal is small after cleaning, and the surface roughness of the sili...

AI Technical Summary

Problems solved by technology

Among them, the surface roughness of the cast single crystal seed crystal is small after cleaning, and the surface roughness of the silicon wafer is also small. The cast single crystal seed crystal is directly spread on the bottom of the crucible or on the silicon wafer at the bottom of the crucible. There are point or line contacts between the cast single crystal seeds, between the cast single crystal seeds and the silicon material, these positions will generate stress concentration, and it is easy to generate native dislocations

The diffusion speed of impurities on the free surface>grain boundary>inside the crystal, so a layer of silicon wafers or several layers of silicon wafers are laid on the bottom of the crucible (several layers of silicon wafers cannot be completely bonded), so that the impurities at the bottom of the crucible can easily diffuse to Cast single crystal seed crystals and inside cast single crystal silicon ingots, these impurities lead to the length of the red area at the bottom of the cast single crystal silicon ingots, and impurities can also easily cause lattice distortion of silicon crystals, thereby generating dislocation sources and reducing crystal quality

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