Patent ID: 6043864
Filing Date: 2000-03-28
Classification: G03F

Abstract:
A method of aligning a mask to a wafer, comprising:providing a number of wafers wherein each of said wafers has a physical alignment feature and a unique wafer identification code formed thereon;providing a memory unit, wherein said memory unit has alignment data for each of said number of said wafers stored therein;providing a mask image projection system;providing a wafer holder;providing a mechanical controller, having data inputs, wherein said mechanical controller controls the position of said wafer holder relative to the position of said mask image projection system and said position of said wafer holder relative to the position of said mask image projection system is determined by data fed to said data inputs of said mechanical controller;providing a detector which can detect each said unique wafer identification code;providing a data processing unit connected to said detector, said memory unit, and data inputs of said mechanical controller, wherein said data processing unit selects alignment data for a wafer identified by said unique wafer identification code from said memory unit and provides said alignment data to said data inputs of said mechanical controller;selecting one of said wafers;placing said selected wafer in said wafer holder using said physical alignment features;determining said unique wafer identification code for said selected wafer using said detector;using said mechanical controller to align the position of said wafer holder relative to the position of said mask image projection system for said selected wafer using said data processing unit and said alignment data for said selected wafer in said memory unit to control said mechanical controller; andprojecting said mask image on said selected wafer using said mask image projection system.