Patent ID: 6327513
Filing Date: 2001-12-04
Classification: G03F,H01L

Abstract:
A method of calculating alignment of layers during semiconductor processing comprising:forming a first alignment target over a substrate, the first alignment target having a pair of first alignment target edges;forming a second alignment target over the first alignment target, the second alignment target having a pair of second alignment target edges, the second alignment target defining a point of reference;measuring a first distance between one of the first alignment target edges and one of the second alignment target edges as a first function of the distance from the point of reference; andmeasuring a second distance between the other of the first alignment target edges and the other of the second alignment target edges as a second function of the distance from the point of reference;forming a third alignment target over the substrate, the third alignment target having a pair of third alignment target edges;forming a fourth alignment target over the third alignment target, the fourth alignment target having a pair of fourth alignment target edges, the fourth alignment target defining a different point of reference;measuring a third distance between one of the third alignment target edges and one of the fourth alignment target edges as a third function of the distance from the different point of reference;measuring a fourth distance between the other of the third alignment target edges and the other of the fourth alignment target edges as a function of the distance from the different point of reference;differencing the first and second functions to define a linear equation having a slope and a first intercept, the first intercept containing offset components in the x and y directions;differencing the third and fourth functions to define a linear equation having a slope and a second intercept, the second intercept containing offset components in the x and y directions; andusing the first and second intercepts, calculating values for the offset in the x and y directions, wherein:the forming of the first and third alignment targets comprises forming individual non-right angle parallelograms at a common substrate elevation; andthe forming of the second and fourth alignment targets comprises forming individual rectangles at common substrate elevations.