Complex impedance versus frequency analysis of Al:SiC:Al metal–insulator–metal structures

Abstract

Metal–insulator–metal (MIM) structures have been fabricated by sputter depositing SiC on Al substrates, using a single SiC target, and evaporating Al contacts on the front surface. The resulting MIM structures were investigated by measuring the complex impedance of the samples as a function of frequency (5 Hz–13 MHz) under varying conditions of bias and temperature. An electrically equivalent model of the MIM structure can be developed by analyzing the plots of various parameters derived from the impedance versus frequency tests. The model consists of an RC network where each element represents a particular physical phenomenon. By fitting the test data curves to curves of the appropriate RC network, element values can be estimated and the characteristics of the film and its contact regions can be quantified. A system has been assembled that will automatically perform the tests and then allow the researcher to interactively develop models based on a curve fit to the test data. Algorithms have been developed that help determine the model configuration and estimate the element values from visual inspection of the various impedance parameter curves. The ac analysis of the films indicates that Schottky barrier contacts with depletion widths in the range of 300 to 600 Å are forming at the metal–insulator interfaces.