METHOD FOR PRODUCING DIRECTIONALLY SOLIDIFIED SILICON INGOTS

摘要

The present invention relates to a method for the production of directionally solidified Czochralski, float zone or multicrystalline silicon ingots or thin sheets or ribbon for making wafers for solar cells from silicon feedstock initially containing between 0.2 ppma and 10 ppma boron and between 0.1 ppma and 10 ppma phosphorous. If the boron content in the silicon feedstock is higher than the phosphorous content, the boron content in the molten silicon is kept higher than the phosphorous content during the directional solidification process by adding boron to the molten silicon in order to extend the part of the directionally solidified ingot or the thin sheet or ribbon solidifying as p-type material. If the content of phosphorous in the silicon feedstock is higher than the boron content, the phosphorous content in the molten silicon is kept higher than the boron content during the directional solidification process by adding phosphorous to the molten silicon in order to extend the part of the ingot or the thin sheet or ribbon solidifying as n-type material.