Dislocation formation related with high oxygen dose implantation on silicon

Abstract

The generation of dislocations in silicon implanted by oxygen (SIMOX) is studied by transmission electron microscopy. In an effort to separate the effects of displacement damage caused by ion implantation from the dynamic structural transformation which occurs due to the insertion of oxygen into the lattice, two special experiments were designed. The first consisted of a series of low dose oxygen implantations in which the energy was either ramped up or down in small steps. This served to expand the region in which oxygen was implanted, permitting a more detailed study of the defects. The second experiment involved the implantation of oxygen into a (111) wafer in order to study the influence of the crystallographic orientation on the generation of dislocations. Both experiments reveal the important role of the surface in the generation of dislocations. It is concluded that most of the threading dislocations are formed during the high-temperature anneal and have their origin in a defect-rich zone near the surface. These defects are attributed to Si-interstitial migration to the surface which results from the formation of SiO2. Consequently, epitaxial growth takes place on the surface and due to the growth defects generated there, dislocations are extended to the Si overlayer during the high-temperature annealing. Dislocations are also formed in the Si overlayer near the interface with the SiO2 buried layer. These dislocations are pinned by the SiO2 precipitates and are either consumed or dragged by them to the oxide interface during subsequent high-temperature annealing. The effect of surface contamination on the generation of dislocations in the early stage of implantation is discussed and factors which yield a better quality SIMOX material are presented.