Nanometer measurement of silicon wafer surface texture based on Fraunhofer diffraction pattern

Abstract A new optical measuring method which can be applied to in-process measurement of surface defects as well as microroughness of ultra-fine finished surfaces with an accuracy of nanometer order is presented in this paper. The principle of our method is based on the Fraunhofer diffraction theory taking account of Gaussian laser beam propagation. The feasibility of the proposed optical method is verified by measurements of the ultra-fine polished silicon wafer surfaces. Consequently, the Fraunhofer diffraction method makes it possible to not only measure microroughness of less than 1nm Rrms, but also detect distinctively micro-scratches, pinholes and particles.