Chapter 12 - Time-resolved scanning nonlinear dielectric microscopy

Abstract

Monitoring variations in capacitance over time is potentially an extremely helpful means of characterizing semiconductor defects. This chapter describes time-resolved nanoscale capacitance analyses using scanning nonlinear dielectric microscopy (SNDM). Specifically, the ability to detect the transient capacitance of a SiO2/4H-SiC interface resulting from 3ns voltage pulses is discussed, demonstrating the use of this method to provide exceptional temporal resolution. Using this approach, both the activation energy and density of defects at this interface were determined, which confirms the high sensitivity and capacity for quantitative analysis of this technique. Inhomogeneous contrast on the nanoscale in two-dimensional maps of interface states suggests that these defects originate from microscopic clusters. High-resolution observation of the density of interface states (Dit) at SiO2/4H-SiC interfaces was also performed by local deep-level transient spectroscopy (DLTS) based on time-resolved SNDM (tr-SNDM). The resulting Dit maps exhibit inhomogeneous contrasts with sizes on the order of tens of nanometers. Simulated tr-SNDM results indicate that the spatial resolution provided by this method is approximately equivalent to the radius of the cantilever tip employed during the measurement process, and can be less than the distance over which the depletion layer widens in the lateral direction.