Calculating the surface topography of integrated circuit wafers from SEM images

The ability to make three-dimensional measurements of surface topography is important to the control of quality in the fabrication ofIC wafers. We describe a technique usingshape from shadingto produce a dense depth map from ICs imaged in the scanning electron microscope. The method minimises error terms to ensure the resultant surface is everywhere continuous and accurately explains the observed image intensities. We describe how this method is extended when stereo images are available and how the extra information in stereo could be used to derive properties of the reflectance Junction.