Thin film optical measurement system and method with calibrating ellipsometer

An optical measurement system for evaluating a reference sample that has at least a partially known composition, comprising:

• at least one non-contact optical measurement device that includes:
• a first light generator that generates a first beam of light that is directed to interact with the reference sample,
• a first detector that measures the intensity of the first beam of light after the interaction with the reference sample, and
• a processor that determines an optical parameter of the reference sample from the intensity measured by the first detector;
• and
• a reference ellipsometer that includes:
• a second light generator that generates a second beam of quasi-monochromatic light having a known wavelength and a known polarization for interacting with the reference sample, the second beam directed at a non-normal angle of incidence relative to the reference sample to interact with the reference sample;
• an analyzer that creates interference between S and P polarized components in the second light beam after the second light beam has interacted with reference sample;
• and
• a second detector that measures the intensity of the second light after the second beam has passed through the analyzer;
• and
• wherein the processor determines the polarization state of the second light beam entering the analyzer from the intensity measured by the second detector, and determines an optical property of the reference sample based upon the determined polarization state, the known wavelength of light from the second light generator and the at least partially known composition of the reference sample;
• and
• wherein the processor calibrates the optical measurement device by comparing the optical parameter of the reference sample determined from the first detector to the optical property of the reference sample determined from the second detector.

A method for calibrating an optical measurement device using a reference sample having at least a partially known composition, comprising the steps of:

• optically probing the reference sample with an off-axis ellipsometer that includes:
• a light generator that generates a quasi-monochromatic beam of light having a known wavelength and a known polarization for interacting with the reference sample, the beam directed at a non-normal angle of incidence relative to the reference sample to interact with the reference sample,
• an analyzer that creates interference between S and P polarized components in the light beam after the light beam has interacted with reference sample, and
• a detector that measures the intensity of the light after the beam has passed through the analyzer;
• determining an optical property of the reference sample based upon the intensity measured by the detector, the known wavelength of light from the light generator and the at least partially known composition of the reference sample;
• measuring an optical parameter of the reference sample using the optical measurement device;
• and
• calibrating the optical measurement device by comparing the optical parameter measured by the optical measurement device to the determined optical property of the reference sample.