A modified expression of the flat‐band voltage due to the fixed surface charge density of a MOS configuration

摘要

By considering the finite distance of the semiconductor space‐charge center away from the Si‐SiO2 interface, a modified expression of the flat‐band voltage (VFB) due to the surface charge density (Qss) is derived. For the accumulation and strong inversion cases, the conventional expression Qss/Co, is valid, however, under the depletion condition the modified expression will be used. The VFB is found to be nonlinearly related to Qss, and the expression may be deduced to the conventional form only in the limit that the Qss is low, the semiconductor is heavily doped, and the oxide thickness is large.