Patent ID: 7160654
Filing Date: 2007-01-09
Classification: G03F

Abstract:
1. A method for overlaying a second layer pattern on a substrate having a first layer pattern, comprising: (a) providing a substrate having a first photoresist layer formed thereon and patterning said first photoresist layer by a patternwise exposure through a first layer mask comprised of an inner pattern area and an outer region, and a plurality of first reference marks formed within the inner pattern area and on the outer region; (b) transferring the first layer pattern into said substrate and removing said first photoresist layer to form a first layer pattern in said substrate wherein the first layer pattern includes first reference marks each having a center point; (c) forming a second photoresist layer on the first layer pattern and patternwise exposing said second photoresist layer through a second layer mask comprised of an inner pattern area, an outer region, and a plurality of second reference marks formed within the inner pattern area and on the outer region wherein each second reference mark is matched with a first reference mark at a similar location on the first layer mask, said second photoresist layer is developed to form a second layer pattern with second reference marks each having a center point; (d) determining the offset values of the center points for each matched pair of first and second reference marks formed in the first layer pattern and in the second layer pattern; (e) inputting the offset values into an error table and applying a correction algorithm to the data in the error table which calculates adjustments in the exposure tool settings for subsequent exposures with the second layer mask of a second photoresist layer on a first layer pattern; and (f) removing the second reference marks in the second layer pattern by exposing said second photoresist layer comprised of the second layer pattern with a third mask having clear regions that are located at the same locations as the second reference marks in the second layer mask and then developing said second photoresist layer.