Patent ID: 7523439
Filing Date: 2009-04-21
Classification: G03F

Abstract:
1. A method of determining position accuracy of double exposure lithography using optical metrology, the method comprising: a) exposing a mask to form a first set of repeating patterns on a wafer, wherein the repeating patterns of the first set have a first pitch; b) after a), exposing the mask to form a shifted second set of repeating patterns on the wafer, wherein the repeating patterns of the second set of repeating patterns interleave with the repeating patterns of the first set of repeating patterns; c) after b), developing the wafer to form a first set of repeating structures from the first set of repeating patterns and a second set of repeating structures from the second set of repeating patterns; d) measuring a first diffraction signal of a first repeating structure from the first set of repeating structures and a second repeating structure from the second set of repeating structures, wherein the first repeating structure is adjacent to the second repeating structure; e) determining a second pitch between the first repeating structure and the second repeating structure using the first measured diffraction signal; and f) determining position accuracy of the mask used to form the second set of repeating patterns based on the determined second pitch and the first pitch, wherein the position of the mask is determined to have been misaligned if the second pitch is not half of the first pitch, and wherein the position of the mask is determined to have been aligned properly if the second pitch is half of the first pitch.