Light scattering particle detector for wafer processing equipment
AssigneeHigh Yield Technology
InventorPeter Borden
Life of this patent
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Abstract
A particle detector includes a laser, a beam shaping lens, and a pair of mirrors which reflect the shaped laser beam back and forth between the mirrors a selected number of times in order to create a sheet of light or light net between the mirrors. The path of the beam is terminated by a beam stop which contains a photodiode to monitor beam intensity and thereby system alignment. Light scattered by a particle falling through the sheet of light is gathered and transmitted to a photodiode. A peak detector provides a measure of the peak intensity of light scattered by such a particle to a microprocessor, which counts the number of particles falling through the light net in a selected time interval. The microprocessor also uses the peak intensity to estimate the size of the particle.
Claims20
Apparatus for detecting particles in a vacuum, or air or fluid environment comprising:
- means for providing a light beam having a defined access;
- lens means for shaping said light beam to provide a collimated beam having a predetermined width and height;
- first mirror means having a first surface for providing multiple reflections of said light beam, the angle of incidence of each of said reflections of said light beam being less than 90.degree.;
- second mirror means having a second surface for providing multiple reflections of said light beam that is reflected from said first surface, the angle of incidence of each of said reflections of said second surface being less than 90.degree.;
- said first and second surfaces of said first and second mirror means respectively being substantially parallel and spaced from each other so that the distance between adjacent points of reflection on each surface is substantially the dimension of the width of said light beam;
- photodiode means for detecting light that is scattered by particles that traverse said beam, said photodiodes being spaced at a distance from each other greater than the distance between said first and second reflecting surfaces.
Dependencies are inferred from the claim text.