Particle detection method and apparatus

A method for detecting particles on a surface of a semiconductor wafer, said surface having repetitive patterns, the method comprising:

• a. illuminating an area on said surface with a beam of polarized light,
• b. collecting light scattered from said area and for forming a Fourier diffraction pattern of said light collected,
• c. removing from said Fourier diffraction pattern light whose intensity is above a predetermined level indicative of background information and leaving in areas whose intensity is below said threshold level indicative of particle information using a spatial light modulator which is optically addressable and a polarization discrimination, and
• d. recording an image of light collected by said optical means and not removed by said Fourier mask.

Apparatus for detecting particles on a surface of a semiconductor wafer, said surface having repetitive patterns, the apparatus comprising:

• a. means for illuminating an area on said surface with a beam of polarized light,
• b. optical means for collecting light scattered from said area, said optical means forming a Fourier diffraction pattern of light scattered from said area illuminated,
• c. a Fourier mask for blocking light in said Fourier diffraction pattern where the intensity is above a predetermined level indicative of background information and leaving in areas where the intensity is below said predetermined level indicative of particle information, the Fourier mask including an optically addressable spatial light modulator and a polarization discriminator, said optically addressable spatial light modulator including a photoconductive layer and a liquid crystal, and
• d. a detector for detecting light collected by said optical means and not blocked by said Fourier mask.

Apparatus for detecting particles on a surface of a semiconductor wafer, said surface having repetitive patterns, the apparatus comprising:

• a. means for illuminating an area on said surface with a beam of polarized light,
• b. optical means for collecting light scattered from said area, said optical means forming a Fourier diffraction pattern of light scattered from said area illuminated,
• c. a Fourier mask for blocking light in said Fourier diffraction pattern where the intensity is above a predetermined level indicative of background information and leaving in areas where the intensity is below said predetermined level indicative of particle information, the Fourier mask including a spatial light modulator and a polarization discriminator,
• d. said spatial light modulator being constructed to receive a read and write beam, said scattered light collected by said optical means being used to provide said read beam and said write beam, and
• e. a detector for detecting light collected by said optical means and not blocked by said Fourier mask.

Apparatus for detecting particles on a surface of a semiconductor wafer, said surface having repetitive patterns, the apparatus comprising:

• a. means for illuminating an area on said surface with a beam of polarized light,
• b. optical means for collecting light scattered from said area, said optical means forming a Fourier diffraction pattern of light scattered from said area illuminated,
• c. a Fourier mask for blocking light in said Fourier diffraction pattern where the intensity is above a predetermined level indicative of background information and leaving in areas where the intensity is below said predetermined level indicative of particle information, the Fourier mask including a spatial light modulator and a polarization discriminator,
• d. said spatial light modulator being addressed using light collected by said optical means, and
• e. a detector for detecting light collected by said optical means and not blocked by said Fourier mask.