Photocopying – Projection printing and copying cameras – Focus or magnification control
Patent
1997-08-08
2000-05-02
Mathews, Alan A.
Photocopying
Projection printing and copying cameras
Focus or magnification control
355 53, 356372, 356401, 250548, 430 5, G03B 2742, G03B 2752, G01B 1100
Patent
active
060579080
ABSTRACT:
Disclosed is a method to measure the actual exposure image of an evaluation pattern on a reticle with increased the accuracy to determine the best focus position. An evaluation mark is formed on a reticle. The evaluation mark is comprised of an arrangement in a lattice form (regular geometric arrangement) in the measurement direction, of multiple basic marks formed by the arrangement in the non-measurement direction of multiple wedge-shaped marks, which are pointed in the measurement direction. While the focus position of the wafer is changed and while the wafer is laterally shifted, the image of the evaluation mark is transferred onto the wafer. After the wafer is developed, the position of the image of the evaluation mark is measured by means of an alignment sensor. The center position of the image of the evaluation mark shifts towards the point of the wedge-shaped marks the closer the surface of the wafer comes to the best focus position. Therefore the focus position when the center of the image of the evaluation mark is positioned closest to the point of the wedge-shaped marks is made the best focus position.
REFERENCES:
patent: 4908656 (1990-03-01), Suwa et al.
patent: 5475490 (1995-12-01), Hirukawa et al.
Mathews Alan A.
Nikon Corporation
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