Impacts of a polycrystalline-silicon buffer layer on the performance and reliability of strained n-channel metal-oxide-semiconductor field-effect transistors with SiN capping

Abstract

Characteristics of n-channel metal-oxide-semiconductor field-effect transistors with SiN capping were investigated in this work. Although the SiN capping could dramatically enhance the carrier mobility and thus the device drive current, the resistance to hot-carrier degradation is compromised as well, owing to the large amount of hydrogen contained in the SiN layer which may diffuse into the channel region during the process. To eliminate this shortcoming, the insertion of an ultrathin (10nm) polycrystalline-silicon buffer layer between the gate and the SiN capping was proposed and demonstrated to restore the hot-carrier reliability of the devices without compromising the current enhancement due to the SiN capping.