Comprehensive understanding of surface roughness limited mobility in unstrained- and strained-Si MOSFETs by novel characterization scheme of Si/SiO2 interface roughness

In this paper, a novel method to determine the surface roughness-limited mobilities (mu_sr) of electrons and holes in MOSFETs directly from experimental data of MOS interface roughness is proposed and compared with experimental mu_sr with and without bi-axial tensile strain. This method includes the direct evaluation of the scattering potential from the power spectra of Si/SiO₂ interface roughness data, which are taken through high resolution advanced TEM measurements, without assuming any autocorrelation function form like Gaussian or exponential. It is found, for the first time, that, by employing the present method, the amount of the calculated electron and hole mu_sr and the strain dependencies are in a systematic agreement with the experimental ones. As a result, the difference in the strain dependence between electrons and holes is found to be attributed to the change in spatial waveform of the roughness by oxidizing Si surfaces with tensile strain.