Patent ID: 7359577
Filing Date: 2008-04-15
Classification: G03F

Abstract:
1. A method for aligning two selected layers of two or more layers of a semiconductor wafer, a first layer of said two selected layers defining a first mark of at least one mark of said first layer, said first mark having a pitch grating d 1 , a second layer of said two selected layers defining a second mark of at least one mark of said second layer, said second mark having a pitch grating d 2 , said first mark and said second mark overlapping each other, the method comprising steps of: directing light from at least one light source to at least one first portion and at least one second portion of each of said first and second marks; receiving at least one first signal from said light directed at said at least one first portion of each of said first and second marks; receiving at least one second signal from said light directed at said at least one second portion of said first and second marks; comparing said at least one first signal and said at least one second signal to determine an overlaid image distribution shift Δx; determining an actual lay shift Δs =Δx(d adjusting said two selected layers of said semiconductor wafer by said Δs relative to each other to thereby align said two selected layers of said semiconductor wafer with each other.