Measuring methods and measuring circuit for the simultaneous measurement of the frequency-dependent small-signal capacity of test - and components structures for two frequencies

摘要

One capacitance is measured for one frequency and a capacitance difference is measured directly and simultaneously for both frequencies using a special measurement circuit. A bridge circuit is operated with the sum of high and low frequency small signal a.c. voltages. A bridge arm contg. the series circuit of a voltage controlled amplifier and a capacitor is automatically controlled using the amplified and phase sensitively rectified high frequency (HF) bridge voltage so that the bridge is balanced for the HF current. The amplifier transfer factor is directly proportional to HF capacitance and the low frequency bridge current is directly proportional to capacitance difference. USE/ADVANTAGE - Esp. for measurement of boundary surface state densities in MIS structures. Cable and stray capacitances can be measured without calibration and state density measurements can be extended to smaller value ranges.