Method of forming circuit patterns on semiconductor wafers using two optical steppers having nonaligned imaging systems

摘要

A method of forming circuit patterns on a semiconductor wafer using two different image steppers having nonaligned optical image systems achieves optical alignment of multiple overlays with high accuracy. A first alignment mark is imaged by the first stepper onto a material layer deposited on the wafer, and a second alignment mark is imaged onto a subsequently deposited material layer using the second stepper. Alignment of the two marks, and thus of successively imaged, overlying circuit patterns, is achieved by translating the optical coordinates of the second alignment system into the those of the first alignment system, and then making corresponding two dimensional adjustment of the wafer position relative to the second stepper.