Nano/microlevel surface roughness measurement of polycrystalline silicon solar wafer with the laser speckle technique

Abstract

Proposed herein is a simple laser speckle technique to measure the surface roughness of polycrystalline silicon solar wafer in the submicron range. When an optically rough surface of a polycrystalline silicon solar wafer is illuminated by a diode laser beam, a speckle pattern is formed due to the scattering effect. The objective type of the speckle pattern is captured by a high resolution charge-coupled device (CCD) camera. From this pattern, the surface roughness of the polycrystalline silicon solar wafer is determined by fractal box analysis with the help of B/D pixels. Stylus profilometer results were used for verification and were found to agree well with the laser speckle technique.