Effect of post metallization annealing on structural and electrical properties of Ge metal-oxide-semiconductor (MOS) capacitors with Pt/HfO ₂ gate stack

We fabricated Ge metal-oxide-semiconductor (MOS) capacitors with Pt/HfO₂ gate stack and demonstrated the effects of post metallization annealing on their structural and electrical properties. Post metallization annealing was carried out at the temperatures of 500 and 600 °C for 30 min in oxygen (O₂) ambient. Post metallization annealing at both temperatures led to the reduction of the interface traps density (D _it) with a decrease in accumulation capacitance. By considering the presence of interfacial layer (IL) in-between HfO₂ and Ge, the effective work function (Φ_m,eff) values of Pt gate electrode after annealing at 500 and 600 °C, extracted from the relations of equivalent oxide thickness (EOT) versus flatband voltages (V_FB), were determined to be ∼4.05 and ∼5.43 eV, respectively. The presence of positive charge at the interface between HfO₂ and IL produced by the formation of oxygen-rich HfO₂/IL interface resulted in the minimization of Fermi level pinning in Ge, which could be responsible for relatively high Φ_m,eff value of Pt gate electrode in Ge MOS capacitor with O₂ post metallization annealing at 600 °C.