MOSFET's on Au-diffused high-resistivity Si substrates

Si MOSFET's on Au-diffused high-resistivity substrates were fabricated and their electrical properties were investigated. At 80 K, the current leakage between the source and drain of both n- and p-channel devices decreased below 10-10A, and the devices exhibited normally-off behaviors. Au concentrations (N) in Si substrates as a function of diffusion temperature Tdiffwas determined from the change in the threshold voltage.Nversus Tdiffthus obtained is in fairly good agreement with that obtained by other methods. Dependence of effective mobility on Tdiffwas investigated in the form of a MOS device. The effective mobility decreased with increasing Tdiff, and it became clear that the diffusion temperature must be lower than about 700°C to obtain semi-insulating substrates with reasonably high carrier mobility. A C-MOS inverter was fabricated using an Au-diffused Si substrate, where no isolation wells were needed, in operation at low temperatures.