The optimization of an optical metrology model for use in measuring a
wafer structure is evaluated. An optical metrology model having metrology
model variables, which includes profile model parameters of a profile
model, is developed. One or more goals for metrology model optimization
are selected. One or more profile model parameters to be used in
evaluating the one or more selected goals are selected. One or more
metrology model variables to be set to fixed values are selected. One or
more selected metrology model variables are set to fixed values. One or
more termination criteria for the one or more selected goals are set. The
optical metrology model is optimized using the fixed values for the one
or more selected metrology model variables. Measurements for the one or
more selected profile model parameters are obtained using the optimized
optical metrology model. A determination is then made as to whether the
one or more termination criteria are met by the obtained measurements.