There an old saying that goes
"Garbage in – garbage out."
So it is with your metrology, any attempt to control a process or exposure tool will fail unless the metrology is providing stable and precise data.
TEA Systems products all support active validation of metrology through their unique proprietary modeling engines that intelligently control data integrity. All TEA Systems products also support data culling through automated, manual and mouse-interactive features.
Optical CD tools, and all Rigorously Coupled Wave Analysis (RCWA) based metrology, require model library and algorithm development. TEA Systems products can use the quality variables of these models, such as "Goodness of Fit" (GOF) and "Alarm", to provide data point culling.
The engineer can also use the precision, covariance and variable spatial mapping functions to characterize the performance and valid range of the RCWA model to speed-up the model and library development cycle times.
The Weir PW software is unique in it’s special features for evaluation of the metrology tool and the algorithms used to calculate the variables.