Abstract
The objective of this study is twofold: to design reticle patterns with desirable alignment properties; to build an automatic alignment system using these patterns. We design such reticle patterns via a synthetic approach; the resultant patterns, so-called pseudonoise arrays, are binary and their autocorrelation functions are bilevel. Both properties are desirable in optical alignment. Besides, these arrays have attractive signal-to-noise ratio performance when employed in alignment. We implement the pseudonoise array as a 2-D cross-grating structure of which the grating period is much less than the wavelength of impinging light used for alignment. The short grating period feature, together with the use of polarized light, enables us to perform essentially 2-D optical alignment in one dimension. This alignment separability allows us to build a system that performs alignment automatically according to a simple 1-D algorithm.
© 1988 Optical Society of America
Full Article | PDF ArticleMore Like This
Yajun Li
Appl. Opt. 27(12) 2612-2620 (1988)
Joseph N. Mait and Karl-Heinz Brenner
Appl. Opt. 27(9) 1692-1700 (1988)
Brian Robertson, David Kabal, Guillaume C. Boisset, Yongsheng Liu, William M. Robertson, Mohammad R. Taghizadeh, and David V. Plant
Appl. Opt. 37(23) 5368-5376 (1998)