Increasing The Registration Accuracy Of Step And Repeat Systems Through Software Improvement

Abstract

A new software option was developed for GCA wafer steppers which enables the site -by -site alignment system to be used as an automatic tool for stepper self -calibration and grid-matching. This software, called grid standardization, permits the use of ideal wafers to self -tune the stepper grid to a standard via site -by -site alignment prior to stepping product wafers. In this paper, the potential of this improved method of global alignment for use in VLSI circuit production is assessed by analyzing its various sources of misregistration.A mathematical model is developed which allows registration accuracy to be predicted for a given set of processing conditions.