MOSFETs Fabricated in {100} single crystal silicon-on-oxide obtained by a laser-induced lateral seeding technique

By using a modified LOCOS oxidation process, a 1 µm thick layer of SiO 2 was grown on selected areas of a {100} silicon wafer such that the resulting oxide surface was level with the original silicon surface. A 0.5 µm thick LPCVD polysilicon layer was deposited over the surface of the entire wafer. By focusing a laser beam at the polysilicon-on-silicon region, liquid phase epitaxial regrowth was induced in the polysilicon layer. By scanning the laser beam from the epitaxial region to the polysilicon-on-oxide region, {100} single crystal silicon was formed on the oxide by a melting and recrystallization process, using the previously formed epitaxial layer as the seed. The single crystal growth extended into the oxide region by as much as 80 µm, providing a sufficiently large single crystal SOI region for device fabrication. MOSFET devices fabricated in this material exhibited a surface electron mobility of 540 cm 2 /V-sec and a subthreshold current of 0. 1 nA per micron channel width with 5 V between the source and the drain, and -5 volts at the gate.