Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1996-11-15
1998-09-22
Font, Frank G.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356432, 356433, G01N 200
Patent
active
058122591
ABSTRACT:
A photomask defect inspection method is provided by which defects of pin holes with the diameter equal to or less than 0.35 .mu.m can be detected with certainty. According to the inspection method, a pattern whose image is projected onto an imaging position by the use of illumination light (P1) for exposure consists of light transmitting portions (41) formed on a glass base (2) and light intercepting portions (42) which transmit part of the illumination light (P1) in such a way that a phase of the part of the illumination light (P1) passing through the light intercepting portions (42) is delayed with respect to a phase of the illumination light (P1) passing through the light transmitting portions (41). Slight defects in the photomask pattern are detected on the basis of a signal obtained by illuminating the pattern with inspection light having an inspection wavelength in which the transmittance (T) of the light intercepting portions (42) is defined in the following formula on the basis of a signal detection limit (Thr). When the signal detection limit (Thr) of an inspection circuit is calculated on the supposition that a signal level of the inspection light passing through the light transmitting portions (41) is equal to 1, the relational expression is T.gtoreq.(Thr-0.01).sup.1/1,8.
REFERENCES:
patent: 3658420 (1972-04-01), Axelrod
patent: 5172000 (1992-12-01), Scheff
"Mask Defect Inspection Method by Database Comparison with 0.25-0.35 .mu.m Sensitivity," Jpn. J. Appl. Phys. vol. 33 (1994) pp. 7156-7162.
Sekine Akihiko
Tabata Mitsuo
Tojo Toru
Yoshino Hisakazu
Font Frank G.
Kabushiki Kaisha Topcon
Kabushiki Kaisha Toshiba
Ratliff Reginald A.
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