Patent ID: 8184897

Claim:
A method for determining a parameter for a photolithography process, the method comprising: receiving a layout; determining a resist critical-dimension value by measuring a critical dimension of an iso-focal pattern as printed on a wafer, wherein the critical dimension is substantially insensitive to focus variations; determining an optical critical-dimension value by: determining multiple aerial-image-intensity values in proximity to the iso-focal pattern by convolving the layout with multiple optical models, wherein the multiple optical models model the photolithography process's optical system under different focus conditions; determining a first location in proximity to the iso-focal pattern where the aerial-image-intensity values are substantially insensitive to focus variations; and determining the optical critical-dimension value by determining a distance between the first location and a reference location; determining a resist bias for the photolithography process by determining a difference between the resist critical-dimension value and the optical critical-dimension value; and storing the resist bias.