Effect of NH3 plasma treatment on the interfacial property between ultrathin HfO2 and strained Si0.65Ge0.35 substrate

摘要

The effect of NH3 plasma treatment on the interfacial property between ultrathin HfO2 and strained Si0.65Ge0.35 substrate has been investigated by high-resolution cross-sectional transmission electron micrographs, x-ray photoelectron spectroscopy, VBS, capacitance-voltage (C-V), and current density-voltage (J-V). TEM and XPS results confirm that interfacial layer with N–Hf and N–Si/O-N-Si bonds acts as a barrier layer against interdiffusions during annealing in some degree. The valence-band offsets ΔEV of HfO2/SiGe interfaces with and without nitridation are determined to be 3.02 ± 0.05 eV and 2.91 ± 0.05, respectively while the conduction-band offsets ΔEC are found to be 1.79 ± 0.05 and 1.90 ± 0.05 eV. The largest total dielectric constant (k) of 15.0 and smallest equivalent oxide thickness of 0.78 nm has been calculated from the accumulation capacitance of the capacitor with NH3 nitridation before post-deposition annealing (PDA). Moreover, the nitrided capacitor after PDA shows a small C-V hysteresis loop of ∼239 mV and low leakage current density (J) of ∼6.53 × 10-7 A/cm2 at a gate bias of Vg = -2.0 V.