Impacts of nonrectangular fin cross section on the electrical characteristics of FinFET

The effects of nonrectangular fin cross section of double-gate FinFETs are studied. For a given top-fin width, which is defined by the photolithography step, the short-channel effect immunity is degraded by the inclination of the sidewalls. The nonrectangular fin geometry also leads to nonuniform current flow and current crowding in the vertical direction. Together with the nonuniform series resistance along the height of the fin, a nonlinear dependence of on-current with fin heights (which have been regarded as the Ws in planar MOSFET) is observed. The impacts of nonvertical sidewall have been characterized according to the inclination angle in this work. Under different inclination angles as dictated by the processing technology, the device performances at various fin heights are characterized. A new design constraint that limits the choice of fin height for a given technology is also discussed.