Patent ID: 7046361

Claim:
A method of positioning a first element with respect to a second element, said method comprising: providing an alignment target on said first element and said second element, said alignment target having at least two locations having a periodic pattern on said first element and a periodic pattern on said second element that overlap and have the same pitch, at least one of said locations has a designed in offset between said periodic pattern on said first element and said periodic pattern on said second element such that when said first element and said second element are aligned said periodic pattern on said first element and said periodic pattern on said second element are offset; illuminating said at least two locations on said alignment target with incident radiation; detecting the radiation from said at least two locations after interacting with said alignment target; comparing the detected radiation from said at least two locations to determine the alignment of said first element with respect to said second element; and moving said first element with respect to said second element.