Method and system for measuring patterned structures

A method for use in evaluating the geometry of a patterned structure formed on a sample, the method comprising:

• focusing a probe beam of broad wavelength illumination light to a spot on the sample surface in a manner providing that the spot size on the sample is larger than a spacing between features of the periodic pattern in the structure so that the probe beam is diffracted at the patterned structure;
• monitoring light of the probe beam diffracted from the patterned structure, generating a plurality of independent output signals corresponding to a plurality of different angles of incidence and spectral intensities, and evaluating the geometry of the patterned structure on the sample based on the output signals.

A method for use in monitoring the processing of semiconductor wafers, wherein the processing creates one or more geometrical features on the surface of the wafer having at least one sub-micron dimension, said method comprising:

• focusing a probe beam of broad wavelength illumination light to a spot on the wafer surface in a manner that the spot size on the wafer is larger than a spacing between the features of the periodic pattern on the wafer so that the probe beam is diffracted at the wafer;
• monitoring the light of the probe beam diffracted from the pattern on the wafer, generating a plurality of independent output signals corresponding to a plurality of different angles of incidence and spectral intensities, evaluating the geometry of the patterned structure of the sample based on the output signals and comparing the output signals to an expected set of signals to determine whether the process being monitored is within a specified tolerance.