Stability of advanced gate stack devices

The stability of poly-Si gated HfO2 (similar to1.2 nm equivalent oxide thickness, EOT) and Y2O3 (similar to3.1 nm EOT) n-channel metal oxide semiconductor field effect transistor devices were assessed after constant current stressing of the gate. The changes in threshold voltage and transconductance were measured as a function of stress time and stress current over the range of 10(-3) to 10(5) C of injected charge per square centimeter. With forming gas annealed HfO2, positive shifts in the threshold voltage exhibited a power-law dependence. Under high stressing conditions, a power- law dependence of degradation of threshold voltage on the injected charge (similar toQ(0.1)) was observed. Stressing at high current was seen to generate traps. Stressing at low current revealed a saturation of the threshold voltage after modest stressing times. Stressing on deuterium annealed sample showed less V-t and g(m) shift (under high injection conditions), which is attributed to the effectiveness of heavier D-2 in preventing trap generation under high stressing conditions. With Y2O3, stressed at similar electric fields, the threshold voltage shifted negatively and the transconductance increased. (C) 2004 The Electrochemical Society.