Thomas N. Adam, Stephen W. Bedell, et al.
ECS Transactions
HfO2 layers, 25-Å thick, were grown by cyclic Hf sputter deposition and room temperature oxidation steps on chemically oxidized Si(001). Subsequent in situ annealing and TiN deposition yield a high-κ gate-stack for which the original 8-Å-thick SiO2 layer is eliminated, as confirmed by transmission electron microscopy. Transistors fabricated with this gate-stack achieve an equivalent oxide thickness in inversion Tinv =9.7Å, with a gate leakage Jg =0.8 A/cm2. Devices fabricated without in situ annealing of the HfO2 layer yield a Tinv which increases from 10.8 to 11.2 Å as the oxidation time during each HfO2 growth cycle increases from 10 to 120 s, also causing a decrease in Jg from 0.95 to 0.60 A/cm2, and an increase in the transistor threshold voltage from 272 to 294 mV. The annealing step reduces Tinv by 1.5 Å (10%) but also increases the gate leakage by 0.1 A/cm2 (30%), and causes a 61 mV reduction in Vt. These effects are primarily attributed to the oxygen-deficiency of the as-deposited HfO2, which facilitates both the reduction of an interfacial SiO2 layer and a partial phase transition to a high-κ cubic or tetragonal HfO2 phase.
Thomas N. Adam, Stephen W. Bedell, et al.
ECS Transactions
Ruqiang Bao, Reinaldo A. Vega, et al.
IEDM 2019
Lin Dong, Steven Hung, et al.
VLSI Technology 2021
Thomas N. Adam, Stephen W. Bedell, et al.
Journal of Crystal Growth