Apparatus and method for detecting a dust particle having high p

Details Apparatus and method for detecting a dust particle having high p Apparatus and method for detecting a dust particle having high p

1995-03-29

1996-11-12

Le, Que T.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

2505594, 356237, G01V 904

Patent

active

055742769

ABSTRACT:
There is provided a dust particle inspection apparatus which comprises a laser beam source for emitting a laser beam having a coherence distance longer than 1 km; a scanner for scanning the surface of an article, which is to be inspected, with the emitted laser beam; an optical detector for detecting the laser beam reflected and diffracted on the surface of the article being inspected; a stage for setting the article thereon and displacing the same in a predetermined direction; and a gas supply means for surrounding the article with a high-purity inert gas atmosphere. There is also provided a dust particle inspection method which comprises the steps of surrounding the article under inspection with a high-impurity inert gas atmosphere; while displacing the article in a predetermined direction, scanning the surface of the article with a laser beam having a wavelength .lambda. and a coherence distance longer than 1 km; and detecting the laser beam reflected and diffracted on the surface of the article to thereby detect any dust particle or the like with high precision and certainty on the surface of the article such as a reticle.

REFERENCES:
patent: 5214486 (1993-05-01), DeWitt
patent: 5317380 (1994-05-01), Allemand
patent: 5416594 (1995-05-01), Gross et al.

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