Patent ID: 7636649

Claim:
A method of automated process control of a fabrication tool used to fabricate structures on semiconductor wafers, the method comprising: obtaining an optical metrology model for the structure, the optical metrology model comprising one or more profile parameters, which characterize one or more geometric characteristics of the structure, one or more process parameters, which characterize one or more process conditions for fabricating the structure, a dispersion, which characterizes optical properties of a material of the structure; obtaining a dispersion function that relates the dispersion to at least one of the one or more process parameters; generating a simulated diffraction signal using the optical metrology model and a value for the at least one of the process parameters and a value for the dispersion, wherein the value for the dispersion is calculated using the value for the at least one of the process parameter and the dispersion function; obtaining a measured diffraction signal of the structure using an optical metrology tool, wherein the measured diffraction signal was measured off a structure fabricated on a semiconductor wafer using the fabrication tool; comparing the measured diffraction signal to the simulated diffraction signal; determining one or more profile parameters of the structure based on the comparison of the measured diffraction signal to the simulated diffraction signal; and controlling the fabrication tool based on the determined one or more profile parameters of the structure.