Wafer-scale mapping of carrier density and mobility with terahertz time-domain ellipsometry
Verdad C. Agulto, Toshiyuki Iwamoto, Zixi Zhao, Shuang Liu, Kosaku Kato, Makoto Nakajima
Abstract
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.