Accurate determination of flat band voltage in advanced MOS structure

This study concerns the accurate and automatic extraction of the flat band voltage (Vfb) from CV measurements in MOS structures. By comparison to Quantum CV simulator, it focalizes on the experimental conditions needed for an accurate determination of Vfb with various analytical methods. First, we demonstrate that an accurate determination of substrate doping level is crucial. Second, the so called Maserjian’s method appears to be more reliable when the maximum measurable capacitance is reduced; it is also less sensitive to variations of the depletion bias used for extraction of substrate doping level. Third, with non-constant substrate doping profile, significant source of error can be induced by uncertainty on the effective doping level at flat band conditions. A simple rule between doping gradient and surface doping level is proposed to ensure reliable extraction.