Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Patent
1991-05-15
1993-01-12
McGraw, Vincent P.
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
250572, G01N 2188
Patent
active
051794225
ABSTRACT:
A system for detecting minute amounts of water contaminant in semi-conductor microelectronic integrated circuits (MIC) includes two lasers 11,12 producing electromagnetic radiation at two discrete wavelengths. Each laser beam being sent through a chopper 13 and 14 respectively and combined via mirror 16 and beam splitter 17 to form a single two part beam along optical axis 22. The beam passes through a reflective beam splitter 26, a quarter wave plate 28 and lens 29 to be directed to a MIC 31 that is mounted onto drive mechanisms 31 and 32. Diffuse reflections from the bottom of the MIC or specular reflections from metallization layers pass back through MIC 31, lens 29, quarter wave plate 28, beam splitter 27 and through lens 48 to detector 47 which compares the intensity of the radiation at the two wavelengths with the intensities of the wavelengths as detected by detector 21 through a lock-in amplifier 49.
REFERENCES:
patent: 4689491 (1987-08-01), Lindow et al.
patent: 4764676 (1988-08-01), Doyle
patent: 5002391 (1991-03-01), Wolfrum et al.
patent: 5017787 (1991-05-01), Sato et al.
Article by Beyer and Garbuny in Applied Optics, Jul. 1973, vol. 12, No. 7, p. 1496, entitled "Pollutant Detection by Absorption Using Mie Scattering and Topographic Targets as Retroreflectors".
Environmental research Institute of Michigan
McGraw Vincent P.
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