Radiant energy – Invisible radiant energy responsive electric signalling – With means to inspect passive solid objects
Patent
1985-08-02
1987-03-24
Howell, Janice A.
Radiant energy
Invisible radiant energy responsive electric signalling
With means to inspect passive solid objects
250338, 250341, 2503581, G01N 2188
Patent
active
046527575
ABSTRACT:
Individual defects in or near the surface of a silicon wafer (16) are detected by directing a time-modulated laser beam (44), having an energy level above the bandgap energy of the silicon material, towards the wafer. The beam (44) is focused to a one to two micron spot (48) on the wafer surface to photoexcite (i.e., pump) a high density of electrons and holes which changes the infrared reflectance in the area of the pumped spot. A probe beam (34) of infrared radiation is directed at the surface (0.126 square mm in area) of the substrate (16) and at a small angle thereto and the reflection thereof monitored by a detector (54). The pumped spot (48) is raster scanned within the area of the probe beam spot (38). The detector (54) detects only that portion of the intensity of reflected probe beam (34) that is modulated by the pump beam frequency to create a video display having a high spatial resolution showing individual defects.
REFERENCES:
patent: 3355980 (1967-12-01), Mathias
patent: 4211488 (1980-07-01), Kleinknecht
patent: 4352016 (1982-09-01), Duffy et al.
patent: 4352017 (1982-09-01), Duffy et al.
Robert E. McMahon, "A Laser Scanner for Integrated Circuit Testing", Proceedings of the 10th Annual Conference on Reliability Physics, Las Vegas, Nevada (Apr. 1972) pp. 23-25.
I. Nagata, R. J. Galagali, S. Horiguchi, T. Sakai and T. Nakaya, "Optical Constants of Germanium Crystal Under Giant-Pulse Irradiation", Journal of Physics D: Applied Physics, vol. 3, No. 9 (Sep. 1970) pp. 1305-1313.
AT&T - Technologies, Inc.
Hannaher Constantine
Howell Janice A.
Kirk D. J.
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