Advanced Contactless Analysis of Plasma-Induced Damage on Si by Temperature-Controlled Photoreflectance Spectroscopy

Abstract

We propose an advanced photoreflectance (PR) spectroscopy technique, for use as a method for the contactless analysis of plasma-induced damage (physical damage) on Si. Si wafers damaged by Ar plasma were placed on a measurement stage capable of sample cooling by liquid nitrogen. In comparison to the spectra at 300 K, the signal intensity at 90 K was increased by cooling. A spectral peak of a heavily-damaged sample was identified at 90 K, which was difficult at 300 K. Changes in the surface potential induced by plasma exposure (ΔVs) were calculated by analyzing the spectral parameters. Areal densities of trapped charges were estimated from ΔVs. The temperature dependence of the PR spectra was discussed, and the primary cause of the increase in signal intensity was attributed to the reduced electron–phonon interactions in a lower temperature range. The proposed technique expands the applicable range of PR-based damage analysis.