Method of increasing field inversion threshold voltage and reducing leakage current and electrical noise in semiconductor devices

TLDR: In this article, an annealing cycle stabilizes the semiconductor device by allowing an oxide-semiconductor interface region of the wafer to attain a minimum energy configuration, thereby reducing the surface-state charge density.

Abstract: A method for processing a semiconductor wafer to reduce electrical noise, to reduce the surface component of junction leakage current, to increase junction reverse breakdown voltage, and to increase field inversion voltage. Subsequent to last high temperature processing to which the semiconductor wafer is exposed in course of its manufacture, the semiconductor wafer is subjected to an annealing cycle in an inert ambient at a temperature in the range of 600 to 950 degrees Centigrade. At this point the semiconductor wafer has a field oxide thereon produced by prior processing operations. The annealing cycle stabilizes the semiconductor device by allowing an oxide-semiconductor interface region of the wafer to attain a minimum energy configuration, thereby reducing the surface-state charge density. The semiconductor wafer is then exposed to an oxidizing ambient for a short time to increase the oxide charge. At the end of the oxidizing procedure, the wafer is quenched to prevent reduction of the oxide charge by diffusion of the oxidizing species which create the oxide charge. The increased oxide charge increases the field inversion voltage. The semiconductor wafer is thus again subjected to an inert ambient, for restabilization. The semiconductor wafer is then subjected to a low temperature annealing cycle in a hydrogen ambient at a temperature in the range from 300 to 500 degrees Centigrade. The low temperature annealing step reduces the surface-state charge density without substantially decreasing the density of the oxide charge trapped in the field oxide, and therefore does not substantially lower the field inversion voltage.