Optical Imaging Method for Investigation of Surface Irregularity
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
A simple optical imaging method is described for quick evaluation of irregularities on silicon wafer surfaces. The experimental set-up of this method is shown schematically in Fig. 1. A highly collimated beam is used as a light source. The beam is projected onto a wafer surface. The beam reflects back at an angle about 12 degrees horizontally and nearly zero degree vertically. The reflected beam forms an image of the wafer surface on a matt-glass screen. The image on the screen can be examined and recorded for surface irregularities. A square grid is used for quantitative measurements of image distortion which is related to wafer warpage. For investigation of surface irregularities, the square grid is omitted.