2-DIMENSIONAL IMAGING OF CHARGE-CARRIER PROFILES USING LOCAL METAL-SEMICONDUCTOR CAPACITANCE-VOLTAGE MEASUREMENT

We will report a variation of the scanning capacitance microscopy for two-dimensional delineation of semiconductor charge carrier profiles b ased on the measurement of the local Schottky contact capacitance. Whe n a metal probe is brought into contact with a semiconductor, a space- charged depletion region and therefore a capacitor is formed at the ju nction. By applying a small ac voltage, the voltage derivative of the contact capacitance can be measured with a lock-in amplifier. The ampl itude of the derivative signal is a function of the carrier concentrat ion, and the sign gives the type of carrier. We have carried out the l ocal contact capacitance-voltage measurements on standard doping conce ntration samples and two-dimensional (2D) carrier concentration profil ing on device structures. The results demonstrate that the contact cap acitance measurement is capable of quantitative 2D characterization of semiconductor devices. These preliminary results also demonstrate tha t this technique, when used as a method for carrier profiling, is rela tively insensitive to the sample surface condition. (C) 1998 American Vacuum Society.