Substrate current enhancement in 65 nm metal-oxide-silicon field-effect transistor under external mechanical stress

An approach to get uniaxial tensile stress from the channel by using strained silicon to enhance drain current and mobility was developed. A 65 nm metal-oxide-semiconductor field-effect transistor (MOSFET) was bent by applying external mechanical stress. The drain current and transconductance of the transistor were found to increase 15% and 20%, respectively. In this paper, the behaviors of the substrate current and the impact ionization rate are also investigated. It was found that the substrate current and gate voltage corresponding to the maximum impact ionization current have significantly increased by increasing external mechanical stress. According to the relationship to the strain-induced mobility enhancement, the increase in impact ionization efficiency resulted from the decrease in threshold energy for impact ionization which was due to the narrowing of the bandgap.