Effect of post metallization annealing on structural and electrical properties of Ge metal-oxide-semiconductor (MOS) capacitors with Pt/HfO2 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 (Dit) with a decrease in accumulation capacitance. By considering the presence of interfacial layer (IL) in-between HfO2 and Ge, the effective work function (Φm,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 (VFB), 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 Φm,eff value of Pt gate electrode in Ge MOS capacitor with O2 post metallization annealing at 600 °C.

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► O2 post metallization annealing leads to the improvement of HfO2 interfacial quality.
► The incorporation of Ge atoms in HfO2 film causes the decrease in the accumulation capacitance.
► Negative charge on Ge induced by annealing at 600 °C leads to the increase in Φm,eff of Pt electrode.