Vision Algorithms For VLSI Wafer Probing

This paper deals with an important problem encountered in automating VLSI wafer probing. In this automation, vision is used for accurately guiding and lowering a probe to make contact with the wafer. In this paper, we discuss various algorithms used in measurement of the distance of the micro-manipulator from the wafer surface. In particular, we describe algorithms for alignment of consecutive frames of the wafer, separation of probe and wafer regions, and getting a clean image of the probe by eliminating traces of the background patterns. We also describe a three-level procedure for obtaining the proximity of the probe from the wafer. These algorithms are verified with the experimental data.