Relevance of remote scattering in gate to channel mobility of thin-oxide CMOS devices

Coulomb drag between electrons in the channel, and electrons in the gate was measured for the first time on silicon MOSFETs having different gate oxide thicknesses and poly-silicon doping levels. These measurements were augmented by mobility measurements in both the channel and the gate. The drag results showed current transfer ratios between channel and gate of ∼ 2×10^-4, and not to be a strong function of oxide thickness in the 1.9-2.8 nm range. The derived transfer mobility between channel and gate is ∼1.5×10⁴ cm²/V-s, too large to significantly affect channel current. We show also that neither drag nor remote impurity scattering can account for mobility degradation observed on our thinner oxide samples.