Experimental and Numerical Study on Uniaxial-Stress Effects of N-Type Metal-Oxide-Semiconductor Field Effect Transistors

In this study, the effects of uniaxial stress on n-type metal-oxide-semiconductor field effect transistors are investigated by experiments and numerical simulations. In the numerical evaluation, mechanical stress simulation and drift-diffusion device simulation are conducted to consider the impact of stress distribution in the device. The device simulation incorporates an electron mobility model by considering the effects of stress on the following: 1) change in relative population, 2) momentum relaxation time and 3) effective mass of electrons in conduction-band valleys. The variations in the dc characteristics (i.e., drain current and transconductance) of n-type metal-oxide-semiconductor field effect transistors with a gate length of 12μm are evaluated under (nominal) uniaxial stress applied to the device parallel (0°), 45° and perpendicular (90°) to the current flow direction. The results of device simulation are in good qualitative agreement with the experimental results; the device simulation including the present electron mobility model can determine the uniaxial-load-direction dependence of the stress sensitivity of the change in transconductance.