Patent ID: 6944578

Claim:
A method of controlling tilt of a photolithographic exposure tool comprising: a) making measurements of three dimensional feature changes in a photosensitive resist by exposing a focus expose matrix wafer at varying exposure levels and focus conditions wherein said feature measurements include a plurality of edge width vs. focus data points for any one of said exposure levels; b) generating a function which defines a relationship between said measurements of three dimensional features changes and a focus of said photolithographic exposure tool; c) making a plurality of edge width measurements at multiple points in x and y directions across an exposure field for a specific feature type; d) processing said edge width measurements obtained at specific locations of said exposure field to obtain edge width deltas in both x and y directions; and, e) computing from said edge width deltas and said generated function average focus values at specific locations of said exposure field from which both x and y focus tilt angle values may be derived, wherein said x and y focus tilt angle values are used for controlling said photolithographic exposure tool.