CD metrology method
AssigneeTherma-Wave, Inc.
InventorKenneth C. Johnson
Life of this patent
Estimating the term…
Abstract
A method for rapidly analyzing data gathered during scatterometry and related methods uses a combination of database lookup, database interpolation and theoretical model evaluation. Database lookup is used to provide an initial mapping between a measured optical response and a set of associated measurement parameters. Interpolation is then used to refine the optical response and parameters beyond the accuracy provided by the database. A theoretical model is then repeatedly evaluated to refine the optical response and parameters beyond the accuracy provided by interpolation. In this way, the present invention avoids the inaccuracies associated with traditional interpolation-based analysis and without incurring the computational complexity associated with real-time database supplementation.
Claims18
A method for optically inspecting a sample, the method comprising:
- illuminating the sample with an incident field;
- measuring the resulting output field to determine an optical response of the sample;
- generating measurement parameters that correspond to the measured optical response by performing the following operations:
- a) searching a database to locate a pre-computed optical response and associated measurement parameters,
- b) interpolating between pre-computed responses in the database to generate an interpolated optical response and associated measurement parameters, and
- c) iteratively evaluating a theoretical model to generate a theoretical optical response and associated measurement parameters.
A device for optically inspecting a sample, the device comprising:
- a measurement system for illuminating the sample with an incident field and measuring the resulting output field to determine an optical response of the sample;
- a processor for generating measurement parameters that correspond to the measured optical response, the processor configured to include:
- a database searching module for searching a database to locate a pre-computed optical response and associated measurement parameters
- a interpolated refinement module for interpolating between pre-computed responses in the database to generate an interpolated optical response and associated measurement parameters;
- and
- a theoretical refinement module for iteratively evaluating a theoretical model to generate a theoretical optical response and associated measurement parameters.
A method of evaluating a sample comprising the steps of:
- creating a database of pre-computed optical responses and associated measurement parameters of the sample;
- optically inspecting the sample to generate an empirical optical response;
- comparing the empirical optical response to the theoretical optical responses stored in the database and selecting the closest match;
- using the closest match, interpolating between pre-computed responses in the database to generate an interpolated optical response and associated measurement parameters;
- and
- using the interpolated optical response and associated measurement parameters as a starting point, iteratively evaluating a theoretical model corresponding to the sample to minimize the difference between theoretically generated optical responses and the empirical optical response to produce a best fit for the actual measurement parameters of the sample.
Dependencies are inferred from the claim text.