Sub-quarter-micrometer n-channel MOSFET´s fabricated with direct ion-beam Nitridation

N-channel MOSFET´s with physical gate lengths as short as 0.19 µm were fabricated with direct e-beam writing and high resolution pattern transfer techniques. The gate oxide thickness was 8.3 nm with a channel doping level of 1 × 10¹⁸cm^-3. An ion beam nitridized film was used as a selective oxidation mask during the growth of the field oxide. The resulting lateral encroachment of the field oxide was 0.25 µm per device edge which was much less than that of the conventional LOCOS process. The transport mechanism in the 0.19 µm gate length transistor was limited by the electron drift velocity saturation. The rough surface created by the ion beam nitridation step limited the value of the saturation velocity. Intrinsic transconductance of 140 mS/ram was measured. The oxide fields needed to produce 10^-6A/cm²leakage current through the gate oxide was about 7 MV/cm for the positively biased gate and 8.8 MV/cm for the negatively biased gate.