Island-edge effects in C-MOS/SOS transistors

The physical and electrical properties of C-MOS/SOS silicon island edges are investigated. Roughness of etched surfaces, nonuniform crystalline quality, and doping concentration along island-edge surfaces, and the formation of "V"-shaped grooves after thermal oxidation of silicon islands are related to leakage currents and other undesirable electrical characteristics. The interaction of oxide charges at the edge and the top surfaces, body doping level, and body bias effects due to the floating substrate are analyzed with respect to early turn-on of the edge channel in n-channel transistors. Finally, SOS transistors with various edge configurations (e.g., conventional island, oxide-backfilled, edge-channel-stopped, and edgeless) are studied to confirm the analysis experimentally.