Contrast reversal in scanning capacitance microscopy imaging

We have investigated the quantification properties of scanning capacitance microscopy (SCM) by using two dedicated test structures and highlight the response of SCM to changes in dopant density. Our results indicate that contrast reversal occurs and that the SCM output is not always a monotonically increasing signal with decreasing dopant density. Two epitaxially grown staircase structures covering the doping ranges 10(14)-10(20) cm(-3) p type and 5 x 10(14)-5 x 10(19) cm(-3) n type were produced for this study as the turning point in the response function typically occurs at a doping level of around 10(17) cm(-3). Through the use of a simple simulation model we see that contrast reversal is expected due to a relative shift between the dC/dV curves for different doping levels. The onset of contrast reversal can be adjusted by changing the dc sample bias leading to a shift in the operating position of the SCM, and the significance of this point will be discussed here. (C) 1998 American Institute of Physics. [S0003-6951(98)03844-3].