Two-dimensional imaging of charge carrier profiles using local metal–semiconductor capacitance–voltage measurement

Abstract

We will report a variation of the scanning capacitance microscopy for two-dimensional delineation of semiconductor charge carrier profiles based on the measurement of the local Schottky contact capacitance. When a metal probe is brought into contact with a semiconductor, a space-charged depletion region and therefore a capacitor is formed at the junction. By applying a small ac voltage, the voltage derivative of the contact capacitance can be measured with a lock-in amplifier. The amplitude of the derivative signal is a function of the carrier concentration, and the sign gives the type of carrier. We have carried out the local contact capacitance–voltage measurements on standard doping concentration samples and two-dimensional (2D) carrier concentration profiling on device structures. The results demonstrate that the contact capacitance measurement is capable of quantitative 2D characterization of semiconductor devices. These preliminary results also demonstrate that this technique, when used as a method for carrier profiling, is relatively insensitive to the sample surface condition.