Electron and hole surface roughness scattering-limited mobilities in oxygen-inserted (OI) Si channel

The electron and hole surface roughness scattering (SRS)-limited mobilities, deconvolved from 4.2 K measurements, were compared between oxygen-inserted (OI) and control Si channel for n- and pMOSFETs. It was found that electron SRS-limited mobility in the OI-Si channel is 55% higher, whereas hole SRS-limited mobility is comparable to the control. To elucidate the difference, the Si/SiO2 interface roughness and the nanoscale thickness variation of the gate oxide were analyzed in detail, via high-resolution transmission electron microscopy images, and fed into numerical calculation of the SRS-limited mobility. The power spectral densities (PSDs) based on the Yule–Walker autoregressive model revealed that the OI-Si has a smaller surface roughness at low-frequency components, corresponding to the electron Fermi surface energy level. In contrast, surface roughness improvement was found to be less at a higher frequency region of the PSDs corresponding to the hole Fermi surface energy level. Furthermore, an oxygen tracer experiment identified a dynamic exchange process between the Si/SiO2 interface and the OI-Si layer, suggesting an opportunity for improving hole SRS-limited mobility in the OI-Si channel via tuning post-oxidation thermal process steps.