Patent ID: 6788405
Filing Date: 2004-09-07
Classification: G01N

Abstract:
A nonlinear optical system for sensing the presence of contamination on a semiconductor wafer, comprising:a) a first optical source for providing a first laser input directable to a location on a semiconductor wafer to be interrogated; b) a second optical source for providing a second laser input directable to said semiconductor wafer location to be interrogated, said first and second laser inputs being alignable so that their surface locations of optical illumination overlap on said interrogated location; c) a first surface optical signal analyzer for receiving a first light signal at a first second-harmonic wavelength generated by said first laser input on the semiconductor wafer to be interrogated, said first surface optical signal analyzer for converting said first light signal at the first second-harmonic wavelength to a first electronic signal, thus monitoring the intensity of said first second-harmonic wavelength, as a function of semiconductor wafer contamination; d) a second surface optical signal analyzer for receiving a second light signal at a second second-harmonic wavelength generated by said second laser input on the semiconductor wafer to be interrogated, said second surface optical signal analyzer for converting said second light signal at the second second-harmonic wavelength to a second electronic signal, thus monitoring the intensity of said second second-harmonic wavelength, as a function of semiconductor wafer contamination; e) a third surface optical signal analyzer for receiving a third light signal at a sum-frequency wavelength generated by said first laser input and said second laser input on the semiconductor wafer to be interrogated, said third surface optical signal analyzer for converting said third light signal at said sum-frequency wavelength to a third electronic signal, thus monitoring the intensity of said sum-frequency wavelength, as a function of semiconductor wafer contamination; and, f) an electronic signal analyzer for comparing said first, second and third electronic signals for determining the level of semiconductor wafer contamination.