The Electrical Properties of MOS Transistors Fabricated with Direct Ion Beam Nitridation

Direct ion beam nitridation was used to form a thin masking layer in the field oxide growth step. The resulting field oxide encroachment per device edge was reduced from 1.0 µm found in LOCOS devices to 0.33 µm. However, the transistors fabricated with the ion beam nitridation step displayed poor device characteristics. We found that with the growth of 50 nm of sacrificial oxide at 950°C and then subsequent removal of the oxide before the gate oxide growth, the adverse side effects, such as; low electron field effect mobility, high junction leakage current and low gate oxide breakdown strength can be drastically improved.