Method and apparatus for inspecting a substrate using a plurality of inspection wavelength regimes

A method of inspecting a surface, the method comprising:

• a) illuminating the surface with:
• i) light in a first wavelength range selected such that the surface is opaque to the light of the first wavelength range, thereby producing a first resultant optical signal that is predominated by diffractive and scattering properties of the surface, wherein the light in the first wavelength range is further selected such that the light in the first wavelength range is optimal for detecting a defect on the surface;
• and
• ii) light in a second wavelength range selected such that the surface is at least partially transmissive to the light in the second wavelength range, thereby producing a second resultant optical signal that is predominated by thin film optical properties of the surface, wherein the light in the second wavelength range is further selected such that the light in the second wavelength range is optimal for detecting the defect on the surface, and wherein the light in the second wavelength range comprises light having a band of wavelengths;
• b) detecting the first and second resultant optical signals and generating associated electronic signals;
• and
• c) processing the electronic signals using a non-defect signal to detect defects and process variations in the surface.

An apparatus for detecting defects in an inspected surface, the apparatus comprising:

• an illumination element for illuminating a surface, the illumination element having two operative modes,
• a first mode for producing first wavelengths of light selected for inspection of the surface in a first optical regime where the surface is opaque to the first wavelengths of light, thereby producing a first resultant optical signal that is predominated by diffractive and scattering properties of the surface, wherein the first wavelengths of light are further selected such that the first wavelengths of light are optimal for detecting a defect on the surface;
• and
• a second mode for producing second wavelengths of light selected for inspection of the surface in a second optical regime where the surface is at least partially transmissive to the second wavelengths of light, thereby producing a second resultant optical signal that is predominated by thin film optical properties of the surface, wherein the second wavelengths of light are further selected such that the second wavelengths of light are optimal for detecting the defect on the surface, and wherein the light of the second wavelengths comprises light having a band of wavelengths;
• an optical system for receiving the first and second resultant optical signals from the inspected surface and producing associated electronic signals;
• a scanning element that enables the apparatus to scan desired portions of the inspected surface;
• and
• electronic circuitry for processing the electronic signals using a non-defect signal to detect defects and process variations in the inspected surface.