Wafer-scale mapping of carrier density and mobility with terahertz time-domain ellipsometry

Terahertz (THz) measurements are increasingly valued for nondestructive testing of materials in power devices and other applications. Hence, there is a growing demand for highly accurate characterization methods in the THz range. Here we demonstrate the application of THz time-domain ellipsometry (THz-TDE) to large-scale, quantitative mapping of semiconductor wafers. While THz-TDE is an established technique, its application in wafer-scale mapping, which is an important process in the semiconductor industry, has not yet been demonstrated. In this work, we highlight the effectiveness of THz-TDE by mapping the electrical properties of a widely used semiconductor, silicon carbide (SiC). Spatial distribution maps of conductivity, carrier density, and mobility of a commercial 4-in. SiC wafer are derived using the measured ellipsometric parameters. THz-TDE mapping offers a nondestructive, contactless testing method to evaluate semiconductor quality and electrical homogeneity and is notably suitable for doped semiconductors characterized by high THz absorption.