Technique to form ultrathin buried oxides in Si by O/sup +/-implantation

High-dose implantation of oxygen into Si to form a buried oxide (BOX) is used commercially to synthesize a silicon-on-insulator (SOI) material. This SOI is projected for use as the starting substrate of future generations of integrated circuits but is costly and suffers from residual defects in the top layer of Si. Both of these issues relate to the magnitude of the implantation dose and can be substantially overcome by simply utilizing a smaller dose. However, acceptance of this approach is problematic since a straight-forward application by simply reducing the implantation dose leads to a disastrous result; a low-dose O/sup +/-implant fails to coalesce into a continuous layer during post-implantation annealing and, thus, does not provide electrical isolation of the superficial Si. A technique involving a two-step implantation scheme was developed to overcome this problem.