Using multiple focal planes to enhance depth of focus

Chris A. Spence; Daniel C. Cole; Barbara Peck

doi:10.1117/12.130328

1 June 1992 Using multiple focal planes to enhance depth of focus

Chris A. Spence, Daniel C. Cole, Barbara Peck

Proceedings Volume 1674, Optical/Laser Microlithography V; (1992) https://doi.org/10.1117/12.130328
Event: Microlithography '92, 1992, San Jose, CA, United States

Abstract

The technique of exposing chips several times, changing the focal plane of the stepper between exposures, has been proposed by others as a way of improving the depth of focus when printing contact holes. We have investigated this technique with aerial image simulation, using criteria based on exposure and defocus latitudes. In addition, we have performed experiments using an i-line stepper to establish the correlation between simulation and what is achievable when printing images in resist. In this paper we investigate the following questions: (i) what is the optimum number of focal planes; (ii) what is the best separation of these planes; (iii) what is the effect on exposure dose; and (iv) what is the net process improvement?

Citation Download Citation

Chris A. Spence, Daniel C. Cole, and Barbara Peck "Using multiple focal planes to enhance depth of focus", Proc. SPIE 1674, Optical/Laser Microlithography V, (1 June 1992); https://doi.org/10.1117/12.130328

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