Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1996-10-04
1998-04-07
McGraw, Vincent P.
Optics: measuring and testing
For optical fiber or waveguide inspection
356237, G01N 2188
Patent
active
057370729
ABSTRACT:
A method and apparatus for inspecting patterned transmissive substrates, such as photomasks, for unwanted particles and features occurring on the transmissive, opaque portions and at the transition regions of the opaque and transmissive portions of the substrate. A transmissive substrate is illuminated by a laser through an optical system comprised of a laser scanning system, individual transmitted and reflected light collection optics and detectors collect and generate signals representative of the light transmitted and reflected by the substrate as the substrate is scanned repeatedly in one axis in a serpentine pattern by a laser beam which is focused on the patterned substrate surface. The defect identification of the substrate is performed using only those transmitted and reflected light signals, and other signals derived from them, such as the second derivative of each of them. The actual defect identification is then performed by comparing combinations of at least two of those measured and derived signals. Simultaneously, defect and particle inspection using the same measured transmitted and reflected light signals. Additionally, phase shift and line widths on the substrate can also be performed simultaneously using the same transmitted light signal that is collected for defect analysis.
REFERENCES:
patent: 4468120 (1984-08-01), Tanimoto et al.
patent: 4610541 (1986-09-01), Tanimoto et al.
patent: 4669885 (1987-06-01), Ina
patent: 5363187 (1994-11-01), Hagiwara et al.
Emery David Garth
Fein Michael E.
Fu Tao-Yi
Kvamme Damon F.
Saidin Zain Kahuna
Jones Allston L.
KLA Instruments Corporation
McGraw Vincent P.
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