Patent ID: 6621570
Filing Date: 2003-09-16
Classification: G01N,H01L

Abstract:
An apparatus for detecting the presence of contaminant particles on a semiconductor wafer having repetitive patterns, said apparatus comprising:(a) means for producing a first beam of light and a second beam of light, (b) first optical means for illuminating an area on the semiconductor wafer with said first beam of light, (c) second optical means for illuminating said same area on the semiconductor wafer with said second beam of light, (d) said first beam of light striking the semiconductor wafer at a first approach angle which is angularly adjustable and a first angle of incidence which is angularly adjustable, (e) said second beam of light striking the semiconductor wafer at a second approach angle which is angularly adjustable and a second angle of incidence which is angularly adjustable, (f) said first approach angle and said first angle of incidence being adjustable independent of said second approach angle and said second angle of incidence, respectively, (g) an imaging detector disposed above the semiconductor wafer for detecting light scattered from the area illuminated but not specularly reflected light, (h) an imaging lens for imaging said area illuminated on said imaging detector, and (i) a spatial filter in the Fourier plane of the imaging lens for masking off the diffraction pattern produced by the background on the semiconductor wafer from each one of the two illuminating beams of light.