Patent ID: 7663766

Claim:
A method, comprising: collecting optical data from an unpatterned region including a first process layer; determining at least one optical parameter of the first process layer based on the optical data associated with the unpatterned region by: modeling a film stack including a plurality of layers, at least one of the layers comprising the first process layer; predicting reflection data for the film stack based on a set of properties associated with the film stack; comparing the predicted reflection data to the optical data associated with the unpatterned region; and iteratively modifying the set of properties, predicting the reflection data, and comparing the predicted reflection data to the optical data associated with the unpatterned region to determine the set of properties yielding the closest matching predicted reflection data; collecting optical data from a patterned region including a second process layer; and determining with a processing unit at least one characteristic of the patterned region based on the optical data associated with the patterned region and the at least one optical parameter.