EPITAXIAL-GROWTH ON POROUS SI FOR A NEW BOND AND ETCHBACK SILICON-ON-INSULATOR

A new bond and etchback silicon-on-insulator (SOI) has been proposed and demonstrated, in which epitaxial layers on porous Si are transferred by bonding and etching back porous Si. The key processes are epitaxial growth on porous Si and selective removal of porous Si. In the epitaxial layers over porous Si, the major defects are stacking faults, which can be reduced to 10(3) to 10(4)/cm(2) by raising the H-2 prebake temperature and lengthening the immersion time in diluted HF prior to the prebake. Bondable smooth surfaces were formed at growth temperatures below 900 degrees C. A highly selective etchant of HF-H2O2 was discovered and enabled us to etch off porous Si with a selectivity of 10(5), leaving behind epitaxial layers on the oxidized handle wafers. The rough as-etched SOI surface was smooth comparable to that of the commercially available bulk-polished wafer, and boron concentration in the SOI-Si layer was simultaneously decreased to similar to 1 x 10(16)/cm(3), by H-2 annealing. Finally, a uniform SOI layer of 507 nm +/-3% across a 5 in. wafer was achieved by this method.