Patent ID: 7734437

Claim:
An apparatus for designing an optical metrology system, the optical metrology system measuring structures on a workpiece, the optical metrology system configured to meet one or more signal criteria, the apparatus comprising: an optical metrology signal model for an optical metrology system, the optical metrology system designed to measure structures on a workpiece and having an optical path including optical components, the optical metrology signal model configured based on an initial design of the optical metrology system, the initial design based on a range of determined capabilities of the optical metrology system, and configured to store for each optical component in the optical path a corresponding function that determines output signal characteristics based on input signal characteristics; an operating data collector configured to collect signal data from input sources and associate the collected signal data to a criterion of the one or more signal criteria; and a model analyzer configured to develop and store an initial design of the optical metrology system, compare calculated one or more signal criteria using the collected signal data with one or more signal criteria set from input sources, and if the calculated one or more signal criteria do not match the set one or more signal criteria, to determine and implement design modifications of the optical metrology system, and iterate an operation for updating the optical metrology signal model with the design modifications, collecting signal data with the operating data collector, and performing the comparison of collected signal data to the set one or more signal criteria until the calculated one or more signal criteria match the set one or more signal criteria.