Reduction of crystalline defects to 50/cm/sup 2/ in epitaxial layers over porous silicon for ELTRAN/sup R/ process

As the design rules of large scale integrated circuits (LSIs) progress, excellent gate oxide integrity (GOI) is demanded despite the requirement for thinner gate oxides. Crystal originated particles (COPs) are currently reported as killer defects for GOI on Czochralski-silicon (CZ-Si) wafers; however, an epitaxial layer on the CZ substrate gives quite good GOI characteristics because of the significantly small amount of COPs in it. It is expected that the epitaxial layer would be used in silicon-on-insulator (SOI), which is one of the candidates for high speed and low power consumption LSIs. We have already reported the epitaxial layer transfer (ELTRAN) method (Yonehara et al, 1994, and Sato et al, 1995), in which the epitaxial layer on porous Si was transferred on to a handle wafer to form an SOI wafer by bonding and etching back of porous Si with extremely high etching selectivity. In this paper, it is reported that the density of stacking faults, which is the major defect in these wafers, is significantly reduced to 50/cm/sup 2/ by controlling both the porous structure and the prebaking step before growth.