A process step in fabricating a structure on a wafer in a wafer
application having one or more process steps and one or more process
parameters is controlled by determining a correlation between a set of
profile models and one or more key profile shape variables. Each profile
model is defined using a set of profile parameters to characterize the
shape of the structure. Different sets of profile parameters define the
profile models in the set. The one or more key profile shape variables
include one or more profile parameters or one or more process parameters.
One profile model is selected from the set of profile models based on the
correlation and a value of at least one key profile shape variable of the
process of the wafer application to be used in fabricating the structure.
The structure is fabricated in a first fabrication process cluster using
the process step and the value of the at least one key profile shape
variable. A measured diffraction signal is obtained off the structure.
One or more profile parameters of the structure are determined based on
the measured diffraction signal and the selected profile model. The one
or more determined profile parameters are transmitted to the first
fabrication process cluster or a second fabrication process cluster.