LAUSR

Abstract In this paper, we present comprehensive results on Al-postmetallization annealing (Al-PMA) effect for the SiO 2 /GeO 2 gate stack on a Ge substrate, which were fabricated by a physical vapor deposition method. The effective oxide thickness of metal-oxide-semiconductor (MOS) capacitor (CAP) was ~7 nm, and the Al-PMA was performed at a temperature in the range of 300–400 °C. The flat band voltage ( V FB ), the hysteresis (HT), the interfacial states density ( D it ), and the border traps density ( D bt ) for MOSCAPs were characterized by a capacitance–voltage method and a constant-temperature deep-level transient spectroscopy method. The MOSCAP without Al-PMA had an electrical dipole of ~−0.8 eV at a SiO 2 /GeO 2 interface, which was disappeared after Al-PMA at 300 °C. The HT, D it , and D bt were decreased after Al-PMA at 300 °C and were maintained in the temperature range of 300–400 °C. On the other hand, the V FB was monotonically shifted in the positive direction with an increase in PMA temperature, suggesting the generation of negatively charged atoms. Structural analyses for MOSCAPs without and with Al-PMA were performed by a time-of-flight secondary ion mass spectroscopy method and an X-ray photoelectron spectroscopy method. It was confirmed that Al atoms diffused from an Al electrode to a SiO 2 film and reacted with GeO 2 . The dipole disappearance after Al-PMA at 300 °C is likely to be associated with the structural change at the SiO 2 /GeO 2 interface. We also present the device performances of Al-gated p-channel MOS field-effect transistors (FET) with PMA treatments, which were fabricated using PtGe/Ge contacts as source/drain. The peak field-effect mobility ( μ h ) of the p-MOSFET was reached a value of 468 cm 2 /Vs after Al-PMA at 325 °C. The μ h enhancement was explained by a decrease in the total charge densities at/near the GeO 2 /Ge interface.