Gettering Technology Based on Porous Silicon

This paper briefly reviews a gettering technology based on porous silicon (PS). PS layers shown to have effective gettering properties for fast-diffusing impurities. Samples saturated with Au or Cu on which the PS layer made on the wafer backside, increases the generation lifetime of minority carriers from 0.05 - 0.1 mus to - 0.5 mus. The PS getter is demonstrated to be located either on the wafer backside or on the front side underneath an epitaxial layer. When formed on the wafer backside, the PS getter may be readily removed together with the absorbed impurities after the gettering process. When fabricated on the wafer front side underneath the epitaxial layer, the getter is brought closer to the wafer working regions as much as possible to provide the most effective gettering effect. At the same time, the epitaxial layer protects chemically active PS against all chemical attacks during the device manufacturing. The buried PS getter may be designed as either a continuous or discontinuous layer configured as, for example, a pattern of isolating regions in VLSI. When property adapted to the produced device conditions, the buried PS getter is shown to withstand successfully the whole VLSI production run providing advanced gain characteristics.