Patent ID: 7175951
Filing Date: 2007-02-13
Classification: G03F

Abstract:
1. A method of checking mask overlay accuracy, comprising: providing a stepper, wherein said stepper is a photolithographic alignment and exposure system; providing a first mask having a first overlay pattern; providing a second mask having a second overlay pattern; providing a wafer having a layer of photosensitive material formed thereon; placing said first mask and said wafer in said stepper; aligning said first mask to said wafer and exposing said first pattern in said layer of photosensitive material using said stepper, after placing said first mask and said wafer in said stepper; removing said first mask from said stepper and placing said second mask in said stepper without removing said wafer from said stepper, after exposing said first pattern in said layer of photosensitive material; aligning said second mask to said wafer and exposing said second pattern in said layer of photosensitive material using said stepper, after placing said second mask in said stepper; developing said layer of photosensitive material, after exposing said first pattern and said second pattern in said layer of photosensitive material, thereby forming said first pattern and said second pattern in said developed layer of photosensitive material; and analyzing said first pattern and said second pattern formed in said developed layer of photosensitive material, thereby determining the alignment accuracy between said first mask, said second mask, and said wafer.