Effect of Post Metallization Annealing for Alternative Gate Stack Devices

The effect of the post-metallization annealing of devices having HfO 2 , La 2 O 3 , or Y 2 O 3 dielectrics and poly-Si or TaN gate electrodes was studied. Forming gas (10% H 2 /90% N 2 ) annealing at 400°C enhanced drive current and channel mobility of devices having 1.2 nm HfO 2 gate dielectrics, by eliminating interface states. Post-metal annealing in 10% D 2 for 1.2 nm HfO 2 gate dielectrics resulted in larger enhancements in drive current and device channel mobility than forming gas annealing. Similar enhancements of the device characteristics were observed in La 2 O 3 (300 mV shift in both flatband and threshold voltage) and Y 2 O 3 (200 mV shift only in threshold voltage) materials. Annealing in pure nitrogen was found to degrade the dielectric quality of HfO 2 , including a decrease in device current and 50% lower capacitance.