Ellipsometric Characterization of Si Surface Damage Induced by Sputter Etching

Abstract

Surface characterization using spectroscopic ellipsometry is applied to sputter etched Si surfaces. It is elucidated by spectrum measurement that broadening of the refractive index spectrum occurs due to crystal damage induced by sputter etching. As more damage is introduced by increasing the rf power, the spectrum peaks in and are broadened, and especially for the extinction coefficient . Thus, the extinction value can be a measure of the degree of damage. For crystal damage evaluation, ellipsometric measurement at a wavelength of 4200–4500Å is effective and reasonable. Comparing the results of ellipsometry with those of RHEED patterns and electrical properties, it is verified that the degree of broadening is compatible with that of blurring in RHEED patterns and increase in leakage current in Schottky type diodes constructed on the etched surfaces. It is concluded that surface quality can be assessed numerically by measuring the change in refractive index.