<title>Proposed methodology for characterization of microroughness-induced optical scatter instrumentation</title>

Abstract

Measurements of optical scatter are often employed in production line diagnostics for surface roughness of silicon wafers. However, the geometry of the optical scatter instrumentation lacks universal standardization, making it difficult to compare values obtained by instruments made by different manufacturers. The bidirectional reflectance distribution function, on the other hand, is a well-defined quantity, and under conditions usually met with bare silicon wafers, can be related to the power spectral density of the surface roughness. In this paper, we present an approach for characterizing low level optical scatter instrumentation using a spatial frequency response function. Methods for calculating or measuring the response function are presented. Limitations to the validity of the spatial frequency response function are also discussed.