Ellipsometry measurement and analysis

An instrument for performing a measurement of properties of a sample, the instrument comprising:

• a first beam source for directing a first beam of light at a first wavelength and having a first energy at the sample for a first length of time, where a combination of the first wavelength, the first energy, and the first length of time is sufficient to cause a temporary damage to the sample, the damage including at least one of atomic changes and molecular changes to the sample,
• a stage for holding the sample, the sample thereby reflecting the first beam of light to create a first reflected beam having properties indicative of the properties of the sample,
• a first sensor for sensing the properties of the first reflected beam to create a first electrical signal indicative of the properties of the sample,
• means for waiting a length of time sufficient for the a temporary damage to the sample to substantially heal,
• a second beam source for directing a second beam of light at a second wavelength and having a second energy at the sample for a second length of time, where a combination of the second wavelength, the second energy, and the second length of time is sufficient to cause a temporary damage to the sample, the damage including at least one of atomic changes and molecular changes to the sample,
• the stage for holding the sample, the sample thereby reflecting the second beam of light to create a second reflected beam having properties indicative of the properties of the sample,
• a second sensor for sensing the properties of the second reflected beam to create a second electrical signal indicative of the properties of the sample, and
• an analyzer for analyzing the first and second electrical signals to determine the properties of the sample.