Evaluation of GaAs Wafer Using Noncontact Capacitance/Voltage Measurement

Abstract

A new noncontact capacitance/voltage ( C–V ) measurement technique which enables the application of semiconductor materials without insulator film on the surface is introduced. The applicability of this technique has been verified by measuring oxidized silicon wafers whose characteristics were well investigated. Based on the general theory of metal-oxide-silicon (MOS) system, the derivation of ideal C–V curves under various conditions was discussed for the analysis of the measured C–V curves. Then, GaAs wafers subjected to various processing steps were evaluated. The behaviors of the measured C–V curves not only agreed with the results reported earlier but led to detection of the thermal annealing effect of the interface traps at low temperature. Furthermore, the ionized impurity concentration was determined from the (1/C)2 plots and the inversion capacitance, and it was found that the difference between their determined values was related to the density of the bulk traps.