Patent ID: 8149384

Claim:
A method for monitoring a photolithography system, comprising: defining a model of the photolithography system for modeling top and bottom critical dimension data associated with features formed by the photolithography system as a function of dose and focus; generating a library of model inversions of the model for different combinations of top and bottom critical dimension values, each entry in the library specifying a dose value and a focus value associated with a particular combination of top and bottom critical dimension values; receiving by a computing device a top critical dimension measurement and a bottom critical dimension measurement of a feature formed by the photolithography system using a commanded dose parameter and a commanded focus parameter; accessing the library using the top and bottom critical dimension measurements to generate values for a received dose parameter and a received focus parameter in the computing device by: identifying a set of entries in the library having top and bottom critical dimension values closer to the top and bottom critical dimension measurements than the other entries in the library; selecting the entry in the set having associated dose and focus values closest to the commanded dose and focus parameters; and providing the dose and focus values associated with the selected entry as the received dose and focus parameters; and comparing, by the computing device, the received dose and focus parameters to the commanded dose and focus parameters to characterize the photolithography system.