D.C. measurement of the space charge capacitance and impurity profile beneath the gate of an MOST

Abstract

An analysis of the MOS Transistor with bias between the source and substrate has shown that when the surface is weakly inverted, the silicon space charge capacitance over a wide range of temperature and bias can be obtained from the change in gate voltage required to maintain a constant channel current. The substrate impurity profile beneath the gate oxide can then be calculated from capacitance-bias measurements. Measurements made on n-channell and p-channel transistors following the growth of a thick gate oxide indicate a segregation coefficient of ⋍ 0·3 and ⋍ 100 for boron and phosphorus respectively.