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 degrees C for 30 min in oxygen (O-2) 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 (Phi(m,eff)) values of Pt gate electrode after annealing at 500 and 600 degrees C, extracted from the relations of equivalent oxide thickness (EOT) versus flatband voltages (V-FB), were determined to be similar to 4.05 and similar to 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 Phi(m,eff) value of Pt gate electrode in Ge MOS capacitor with O-2 post metallization annealing at 600 degrees C. (C) 2011 Elsevier B.V. All rights reserved.