Alignment system and method

Details Alignment system and method Alignment system and method

2008-01-15

2008-01-15

Mathews, Alan (Department: 2851)

Photocopying

Projection printing and copying cameras

Step and repeat

C355S071000, C356S400000, C356S401000, C356S508000, C356S509000, C430S022000

Reexamination Certificate

active

07319506

ABSTRACT:
An alignment system uses a self-referencing interferometer that produces two overlapping and relatively rotated images of an alignment marker. Detectors detect intensities in a pupil plane where Fourier transforms of the images are caused to interfere. The positional information is derived from the phase difference between diffraction orders of the two images which manifests as intensity variations in the interfered orders. Asymmetry can also be measured by measuring intensities at two positions either side of a diffraction order.

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Moel et al., “Novel on-axis interferometric alignment method with sub-10 nm precision,”J. Vac. Sci. Technol. B. 11(6):2191-2194 (1993).
Ota et al., “New Alignment Sensors for Wafer Stepper,”SPIE Optical/Laser Microlithography IV: 1463:304-314 (1991).
T. Omatsu et al., “Time-resolved measurement of spatial coherence of a copper vapor laser beam using a reversal shear interferometer”, Optics Communications, vol. 87, No. 5/6, pp. 278-286 (Feb. 15, 1992).
European Search Report issued in EP 03253494.3-2222 dated Mar. 3, 2006.

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