Si MOSFET fabrication using focused ion beams

Submicrometer focused ion beams have been used both for the maskless ion implantation of p-channel depletion-mode Si MOSFETs and for the gate lithography of n-channel enhancement-mode Si MOSFETs. B-Pt and Au-Si liquid-metal-alloy ion sources were utilized in a single-lens focusing column for the implantation and lithography steps, respectively. An 800-Å-thick Al stopping layer was used at the target to separate the lighter ions from the heavier ion species in the beams. Reasonable dc electrical characteristics were measured for the chosen device process parameters.