Temperature-Oriented Mobility Measurement and Simulation to Assess Surface Roughness in Ultrathin-Gate-Oxide ( $sim$1 nm) nMOSFETs and Its TEM Evidence

摘要

On a 1.27-nm gate-oxide nMOSFET, we make a comprehensive study of $ hbox{SiO}_{2}hbox{/Si}$ interface roughness by combining temperature-dependent electron mobility measurement, sophisticated mobility simulation, and high-resolution transmission electron microscopy (TEM) measurement. Mobility measurement and simulation adequately extract the correlation length $lambda$ and roughness rms height $Delta$ of the sample, taking into account the Coulomb-drag-limited mobilities in the literature. The TEM measurement yields the apparent correlation length $ lambda_{m}$ and roughness rms height $Delta_{m}$ . It is found that the following hold: 1) $lambda approx lambda_{m}$ for both the Gaussian and exponential models, validating the temperature-oriented extraction process; 2) the extracted $Delta$ ($sim !!hbox{1.3} hbox{rm{AA}}$ for the Gaussian model and 1.0 $hbox{rm{AA}}$ for the exponential one) is close to that $( sim!! hbox{1.2} hbox{rm{AA}})$ of $Delta_{m}$, all far less than the conventional values $(sim!hbox{3} hbox{ rm{AA}})$ in thick-gate-oxide case; and 3) the TEM 2-D projection correction coefficient $Delta_{m}/Delta$ is approximately 1.0, which cannot be elucidated with the current thick-gate-oxide-based knowledge.