Patent ID: 7444198

Claim:
A method of determining a physical property of a substrate, the method comprising: recording a first spectrum obtained from a substrate, the first spectrum being obtained during a polishing process that alters a physical property of the substrate; identifying, in a database, at least one of multiple previously recorded spectra that is similar to the recorded first spectrum, each of the spectra in the database having a physical property value associated therewith; generating a signal indicating that a first value of the physical property is associated with the first spectrum, the first value being determined using the physical property value associated with the identified previously recorded spectrum in the database; and establishing the database before the steps of recording, identifying and generating are performed, wherein establishing the database comprises: performing a first measurement of a physical property of a substrate specimen before it is polished, the physical property being measured in multiple predefined zones on the substrate specimen: polishing the substrate specimen after measuring the physical property, the polishing being done in multiple rotations; and collecting spectra from the substrate specimen while it is being polished.