Mapping of electrically active defects in silicon by optical-beam-induced reflectance

Abstract

The mapping of electrically active defects in silicon is of interest in the semiconductor industry. Non-destructive approaches with high spatial resolution allow material to be screened for micro-defects, and then submitted for processing. The non-contact optical beam-induced reflectance (OBIR) technique employs a pump/probe laser configuration to reveal micrometer sized, electrically active features near the surface of silicon wafers. The system combines the spatial resolution possible with visible light with the sensitivity to carrier concentration exhibited by IR radiation. This paper presents a two-dimensional model of the photoexcited carrier and temperature distributions. The results indicate that the OBIR signal is dominated by carrier density, and that carrier diffusion does not prevent high spatial resolution. Spatial scans exhibiting metallic precipitates and epitaxial stacking faults are also presented.