Mechanism of silicon exfoliation induced by hydrogen/helium co-implantation

Infrared spectroscopy and secondary ion mass spectrometry are used to eluci date the mechanism by which co-implantation of He with H facilitates the sh earing of crystalline Si. By studying different implant conditions, we can separate the relative contributions of damage, internal pressure generation , and chemical passivation to the enhanced exfoliation process. We find tha t the He acts physically as a source of internal pressure but also in an in direct chemical sense, leading to the reconversion of molecular H-2 to boun d Si-H in "VH2-like" defects. We postulate that it is the formation of thes e hydrogenated defects at the advancing front of the expanding microcavitie s that enhances the exfoliation process. [S0003-6951(98)01851-8].