A method for monitoring overlay alignment on a wafer that includes identifying
a target machine, identifying a target process, identifying a plurality of critical
layers, obtaining a plurality of overlay data from at least one of designated registration
patterns on the wafer as baseline data, providing a plurality of reference overlay
data, correlating the plurality of the reference overlay data with the baseline
data to obtain overlay error, comparing the overlay error with specifications of
the target machine, accepting the baseline data when the overlay error is within
the specifications, and performing overlay alignment monitoring with the baseline data.