Experimental Study of Uniaxial-Stress Effects on DC Characteristics of nMOSFETs

Stress-induced shifts of the direct current characteristics on n-type metal oxide semiconductor field effect transistors (nMOSFETs) were investigated experimentally. The stress sensitivities of nMOSFET characteristics were measured by the 4-point bending method, and the gate-length dependence of transconductance shifts caused by uniaxial stress was evaluated. As a result, it is shown that the gate-length dependence of transconductance shifts is attributed to parasitic resistance of the nMOSFETs. Also, this paper verified the electron-mobility model proposed in the previous study that includes stress effects in comparison with the experimental results. As a result, several improvements for the electron-mobility model are proposed in this paper. We describe the change of the conduction-band energy induced by the shear deformation of silicon. The shear deformation with a uniaxial stress along the direction of silicon should be considered in the change of the conduction-band energy.