Optical characterization of silicon and sapphire surfaces as related to SOS discrete device performance

Abstract

Specular reflectance measurements were used in the quantitative characterization of sapphire and silicon film surfaces. Residual polishing damage in sapphire surfaces can be readily detected by infrared multiple reflectance measurements in the lattice-band region of sapphire at about 600 cm -1. Specular reflectance measurements in the ultraviolet, at a photon energy of about 4.3 eV (corresponding to the X 4− X 1 silicon transition), were used for the surface characterization of silicon films on sapphire. The reflectance methods were applied to the characterization of variously polished sapphire surfaces and to the characterization of heteroepitaxial silicon films grown on the substrates. The results of these measurements were correlated with various parameters of silicon-on-sapphire (SOS) devices fabricated in the silicon films. Measured device parameters include drain current, extrapolated threshold voltage, leakage current, and drain breakdown voltage. Most device data were automatically recorded on test patterns and statistical data were computed for the various device parameters.