Low-Frequency Noise Characterization of Ultra-Low Equivalent-Oxide-Thickness Thulium Silicate Interfacial Layer nMOSFETs

Low-frequency noise measurements were performed on n-channel MOSFETs with a novel ultra-low 0.3-nm equivalent-oxide-thickness (EOT) interfacial layer (TmSiO) and two different bulk high- $k$ dielectrics (Tm2O3 and HfO2). The MOSFETs were fabricated in a gate-last process and the total gate-stack EOT was 1.2 and 0.65 nm for the Tm2O3 and HfO2 samples, respectively. In general, both gate-stacks resulted in 1/ $f$ type of noise spectra and noise levels comparable with the conventional SiO2/HfO2 devices with similar EOTs. The extracted average effective oxide trap density was $2.5\times 10^{17}$ and $1.5\times 10^{17}$ cm $^{\mathrm {-3}}$ eV $^{\mathrm {-1}}$ for TmSiO/HfO2 and TmSiO/Tm2O3, respectively. Therefore, the best noise performance was observed for the gate-stack with Tm2O3 bulk high- $k$ layer and we suggest that the interface free single-layer atomic layer deposition (ALD) fabrication scheme could explain this.