Signal process method and apparatus for defect inspection

Details Signal process method and apparatus for defect inspection Signal process method and apparatus for defect inspection

1997-02-12

1998-08-18

Epps, Georgia Y.

Optics: measuring and testing

Inspection of flaws or impurities

Having predetermined light transmission regions

356431, 25055945, G01N 2188

Patent

active

057964750

ABSTRACT:
A signal processing method and an improved defect detecting apparatus which scans a circuit substrate with a laser beam is provided to enable a distinction between a circuit pattern signal and a defect signal. A laser beam is scanned across the surface of a substrate with the reflected light picked up by a photodetector. The photodetector provides an output signal that can comprise both a pattern signal and a defect signal. This output signal is applied to a first signal processing line having a low-pass filter characteristic and a second signal processing line without a low-pass filter characteristic. The signals can be appropriately amplified and/or delayed and are finally submitted to a subtraction circuit so that the resulting output signal enables a ready determination of a defect apart from the existence of any pattern signal.

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