To follow the SIA roadmap, lithographers must deal everyday with the bad effects of a low-kl lithography transfer process. One of the ways to reduce the pressure associated with such low-kl values is to use Alternating Phase Shift Masks (henceforth “Alt-PSM”). Unfortunately, Alt-PSM also has some drawbacks, such as transmission imbalance between the phase shifted and non-phase shifted areas, and aspect ratio phase etch depth variation resulting from the mask etching process. Moreover, fast two-dimensional simulators that are commonly used in resolution enhancement simulation are unable to directly predict these inherently three-dimensional effects. We demonstrate a general approach to simulate and correct these effects in large circuit designs by combining accurate mask representation with Optical and Process Correction (“OPC”). Using a DRC tool, geometry in the input circuit design is partitioned based on size and shape. Guided by accurate three-dimensional simulations or empirical data, these partitions may be classified and assigned different phases and transmission values to more realistically simulate the mask. By using this more accurate mask representation in our integrated OPC tool, Calibre OPCPro, we are able to correct designs for these three-dimensional mask effects as well as for conventional proximity effects.

Date Published: 22 January 2001
PDF: 7 pages
Proc. SPIE 4186, 20th Annual BACUS Symposium on Photomask Technology, (22 January 2001); doi: 10.1117/12.410769

Published in SPIE Proceedings Vol. 4186:
20th Annual BACUS Symposium on Photomask Technology
Brian J. Grenon; Giang T. Dao, Editor(s)