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Proceedings Paper

Contact performance with an attenuated phase shift reticle and variable partial coherence
Author(s): William L. Krisa; Cesar M. Garza; Robert D. Bennett
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Paper Abstract

The application of optical enhancement techniques on high numerical aperture i-line steppers along with attenuated phase shift reticles have enabled contact processing to 0.35 micrometers and below. Previous work has shown that a high numerical aperture and low partial coherence improve contact printing capabilities. This paper focuses on a detailed evaluation of the effect of partial coherence on subhalf micron contact performance using both attenuated phase shift and binary reticles. The initial characterization of contact performance for contact sizes ranging from 0.3 micrometers to 0.45 micrometers confirms previous results that a 10% attenuated phase-shift provides the largest focus latitude when compared with a 6% attenuated reticle and a binary reticle. In extending previous work to 0.3 micrometers , it was confirmed that a larger focus latitude is achieved for a reduced partial coherence and high numerical aperture. Cross section micrographs presented confirm the improvement in profile and focus latitude by reducing the partial coherence. Cross section micrographs also demonstrate the capability with attenuated phase-shift to print 0.3 micrometers contacts at a pitch of 2.5 times the contact width. The pitch does not effect the contact focus latitude until it falls below 2.5 times the contact width. Uniformity (3(sigma) ) across the exposure field is reduced from 0.035 micrometers to 0.021 micrometers as the partial coherence is reduced from 0.6 to 0.3. The uniformity (3(sigma) ) across the wafer is reduced from 0.056 micrometers to 0.023 micrometers for the same reduction in partial coherence. Application of the best case process conditions also produced a focus latitude of 0.75 micrometers for 0.25 micrometers contacts. The results of this study show that i-line processing can be extended to 0.3 micrometers contact processing on random logic devices.

Paper Details

Date Published: 26 May 1995
PDF: 8 pages
Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); doi: 10.1117/12.209282
Show Author Affiliations
William L. Krisa, Texas Instruments Inc. (United States)
Cesar M. Garza, Texas Instruments Inc. (United States)
Robert D. Bennett, Texas Instruments Inc. (United States)

Published in SPIE Proceedings Vol. 2440:
Optical/Laser Microlithography VIII
Timothy A. Brunner, Editor(s)

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