Apparatus and method for inspection of a film on a substrate

A method of inspecting an oxide layer comprising:

• determining a reference spectrum of light reflected from a surface of a first sample of a first material having an oxide film thereon over a wavelength range encompassed by the reflected light, wherein the first sample does not include a predetermined defect;
• selecting an illumination source that outputs light encompassing at least part of the wavelength range;
• illuminating at least a portion of a second sample of a second material having an oxide layer with the light from the selected illumination source, wherein the light reflected from the first material and light from the selected illumination source reflected from the second material have respective spectral responses over the wavelength range that have a predetermined relationship;
• receiving the light output from the illumination source that has reflected from the second sample, including the oxide layer of the second sample;
• acquiring a measurement spectrum from the light received at the receiving step over at least part of the wavelength range that is encompassed by the light output from the illumination source;
• comparing at least one characteristic of the measurement spectrum to the same at least one characteristic of the reference spectrum, wherein the at least one characteristic varies in a predetermined manner depending upon whether a material and oxide film from which received light reflects contains the predetermined defect;
• and
• determining whether the material and oxide film of the second sample contain the predetermined defect based upon the comparison of the at least one characteristic of the measurement spectrum to the same at least one characteristic of the reference spectrum.