Investigation of scattering mechanisms for scaled mosfets

The scattering mechanisms are investigated for MOSFETs with gate length varying from 1000 nm to 32 nm in this paper. Although the carrier mobility should theoretically be independent on the gate length, using the universal mobility model it is found that as the gate length reduces the Coulombic scattering decreases while the phonon scattering and the surface roughness scattering increase with a decreasing effective mobility. It is revealed that the decreasing effective substrate doping concentration N_a related to the reduced threshold voltage V_t is the dominant reason. However, the dominant mechanism varies from the Coulombic scattering for the long gate length to the phonon scattering for the short gate length at medium effective field (about 1 MV/cm).