New Findings on Coulomb Scattering Mobility in Strained-Si nFETs and its Physical Understanding

In this paper, the impact of strain on the electron mobility limited by Coulomb scattering (interface states Nit and substrate impurities N
_A
), is experimentally examined for the first time. Compared to Si devices, the mobility limited by N
_A
is enhanced in strained Si whereas the mobility limited by N
_it
is degraded. These new findings are explained through valleys population and scattering rate considerations. It is also found that the interface state generation in strained Si is smaller than in Si. This fact is beneficial to the device performance as well as the MOS device reliability.