Automatic Mask Alignment for Optical Lithography Using GA- and PSO-Based Image Registration Technique

Abstract

Mask Alignment is a very important part of modern day VLSI fabrication process. To replicate the desired structure on the mask to the wafer, it is necessary to have some degree of accurate mask alignment procedure. However, present day mask alignment process is operated by manual inspection and hence may produce significant human errors. The objective of this work is to develop a novel mask alignment procedure based on image registration technique which is independent of manual inspection. For this purpose only requirement is a standard webcam to capture the images of mask and wafer to be registered. It is well known that registration is a technique by which one object is aligned geometrically with respect to other. Present study shows that genetic algorithm/particle swarm optimization based mask registration technique produces satisfactory results in a reasonable time. First section of this work describes the registration technique of mask and wafer images in details and following this registration values second part is hardware implementation of mask alignment procedure.