Apparatus to characterize substrates and films

A method for measuring a thickness of a substrate, the method comprising:

• setting a polarization state of a light source, the polarization state substantially matching an eigenmode of the substrate;
• selecting at least one wavelength from the light source;
• setting an analyzer component based on a returned light signal from the substrate;
• impinging a beam of light from the light source substantially orthogonally onto the substrate;
• and
• calculating a thickness of the substrate based on the returned light signal from the substrate.

A metrology apparatus to measure a thickness of a substrate having chiral properties, the apparatus comprising:

• an illumination source directed substantially orthogonally to an upper surface of the substrate, wherein the illumination source is configured to be rotated to a polarization state to match an eigenmode of the substrate;
• a polarizer coupled between the illumination source and the substrate, the substrate to receive light from the illumination source after the light passes through the polarizer in a pre-determined plane of polarization;
• an optical detector to receive light returned from the substrate, the optical detector arranged substantially orthogonally to the upper surface of the substrate;
• an analyzer coupled between the substrate and the optical detector, the analyzer to determine an angle in the plane of polarization to which the light received from the substrate has been rotated due to the chiral properties of the substrate, each of the polarizer and the analyzer being located in a common optical path;
• and
• at least one optical compensator to determine an optical path difference between the illumination source and the received light returned back from the substrate.