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Proceedings Paper

Mutually optimizing resolution enhancement techniques: illumination, APSM, assist feature OPC, and gray bars
Author(s): Bruce W. Smith
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Paper Abstract

As sub-half wavelength optical lithography is pursued, the variety of imaging requirements increases. This can result in complex combinations of various resolution enhancement techniques. Optimization based on simple standards or rules is not possible. Although the goal is to design processes so that enhancement approaches work cooperatively as manufacturable solutions, it is often an overwhelming task. Problems often arise as analysis is carried out in a spatial domain, where mask and image properties are evaluated using sizing or dimensional evaluation. A more appropriate perspective for image optimization is that of the lens pupil, in a spatial frequency domain. In this paper, we describe the common characteristics of resolution enhancement, beyond the historical comparisons of alternating PSM and strong OAI. Enhancement techniques including assist feature OPC, custom illumination, attenuated PSM, and pupil filtering are described from a spatial frequency standpoint where each can be utilized to take advantage of strengths and avoid weaknesses. As a result of this type of analysis, we will also describe an alternative OPC method where assist features of varying tone, referred to as Gray Bars, provide for significant image improvement.

Paper Details

Date Published: 14 September 2001
PDF: 15 pages
Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); doi: 10.1117/12.435747
Show Author Affiliations
Bruce W. Smith, Rochester Institute of Technology (United States)

Published in SPIE Proceedings Vol. 4346:
Optical Microlithography XIV
Christopher J. Progler, Editor(s)

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