Patent ID: 6275621
Filing Date: 2001-08-14
Classification: G01B,H01L

Abstract:
A method of measuring misalignment which comprises the steps of:(a) providing a first grating pattern on a first layer, wherein said first grating pattern comprises a first group of plural sets of lines, each of said lines of each of said sets being parallel to each other and extending across first imaginary straight lines, a second group of plural sets of lines, each of the lines of each set of lines of the second group being parallel to each other and each extending across a second imaginary straight line, each said second imaginary line being parallel to a different one of said first imaginary lines;(b) providing a second grating pattern on a second layer capable of providing Moire fringes when disposed over said first grating pattern; said second grating pattern being substantially identical to that of the first layer with the imaginary lines overlapping except that overlapping sets of lines are at an angle to each other different from being parallel;(c) placing said second grating pattern over said first grating pattern whereby said first and second grating patterns are capable of providing Moire fringes; and(d) measuring misalignment of said first layer relative to said second layer from the position of the Moire fringe provided by said first and second grating patterns.