Method for controlling resistivity in ingots made of compensated feedstock silicon

摘要

Techniques for controlling resistivity in the formation of a silicon ingot from compensated feedstock silicon material prepares a compensated, upgraded metallurgical silicon feedstock for being melted to form a silicon melt. The compensated, upgraded metallurgical silicon feedstock provides a predominantly p-type semiconductor for which the process assesses the concentrations of boron and phosphorus and adds a predetermined amount of aluminum or/and gallium. The process further melts the silicon feedstock together with a predetermined amount of aluminum or/and gallium to form a molten silicon solution from which to perform directional solidification and, by virtue of adding aluminum or/and gallium, maintains the homogeneity the resistivity of the silicon ingot throughout the silicon ingot. In the case of feedstock silicon leading to low resistivity in respective ingots, typically below 0.4 Ωcm, a balanced amount of phosphorus can be optionally added to aluminum or/and gallium. Adding phosphorus becomes mandatory at very low resistivity, typically close to 0.2 Ωcm and slightly below.