Patent ID: 7352456

Claim:
A method of inspecting a surface, the method comprising: providing a substrate characterized by an opacity transition wavelength configured such that when the surface is illuminated with wavelengths of light in an opaque regime of light having wavelengths shorter than the opacity transition wavelength a first resultant optical signal is produced that is predominated by diffractive and scattering properties of the surface and configured such that when the surface is illuminated with wavelengths of light in a transmissive regime of light having wavelengths longer than the opacity transition wavelength a second resultant optical signal is produced that is predominated by thin film optical properties of the surface; determining a first optimal inspection wavelength band selected from the wavelengths in the opaque regime defined by the wavelengths shorter than the opacity transition wavelength of the substrate such that the first optimal inspection wavelength band is optimal for detecting a defect on the substrate; determining a second optimal inspection wavelength band selected from the wavelengths in the transmissive regime defined by the wavelengths longer than the opacity transition wavelength of the substrate such that the second optimal inspection wavelength band is optimal for detecting the defect on the substrate; illuminating the substrate with light in the first and second optimal inspection wavelength bands, wherein the light in the second optimal inspection wavelength band comprises light having a band of wavelengths; detecting the first and second resultant optical signals produced by the illumination and generating associated electronic signals; and processing the electronic signals using a non-defect signal to detect defects and process variations in the surface.