Gettering of Impurities

Abstract

Since the early 1960s gettering has been a common method to reduce unintentional metal impurities in the electrically-active zones of semiconductor devices. Starting with the extrinsic gettering by means of phosphorus diffusion [8.1] various alternative methods were developed, mostly by utilizing a trial-and-error technique. The effectiveness of a gettering process was usually estimated from improved reverse current-voltage characteristics, from increased minority-carrier lifetimes, or from increased yields in device production. Since that time various gettering processes were developed and applied in device production such as boron or gallium diffusion [8.2], lattice distortion on the reverse side of the wafer by lapping [8.3], grinding [8.4], scratching [8.5], sand-blasting, sound stressing [8.6], laser irradiation [8.7,8], and ion implantation of various elements [8.9].