Analysis of electron mobility in 7-level stacked nanosheet GAA nMOSFETs

In this study, an experimental assessment of transport parameters in 7-level stacked nanosheet GAA nMOSFETs is conducted, employing the Y-Function methodology to extract carrier mobility. Specifically, the contribution of horizontal and vertical conduction planes to mobility and degradation factors is investigated for transistors with varying channel lengths and nanosheet widths. The findings reveal that while overall low-field mobility demonstrates weak dependency on nanosheet width, it suffers some reduction in short-channel transistors. Furthermore, the mobility degradation was analyzed, and the results indicate that overall mobility degradation coefficients depend on the nanosheet width, as the balance between horizontal and vertical contributions varies. Notably, while the linear degradation factor dominates the mobility degradation at horizontal planes, vertical planes exhibit a dominant quadratic degradation factor. This suggests larger surface roughness scattering at sidewalls compared to horizontal planes.