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Proceedings Paper

Resolution improvement of isolated line pattern in quarter-micrometer level by layout-optimized assistant pattern method
Author(s): Keiichiro Tounai; Naoaki Aizaki
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Paper Abstract

In the previous report, we showed the optimized results of off-axis illumination (OAI) for 0.25 micrometers resist patterning. Wide DOF was obtained for dense patterns like 1:1 L and S pattern, however, DOF was small for the sparse patterns. In order to widen the DOF for isolated line patterns under the OAI, we have examined the assistant pattern method, which needs the only unresolved additional patterns beside the isolated pattern. Optimization has been carried out by light intensity simulation under the following criteria; CD variation within plus or minus 10 percent, resist thickness loss of 10 percent and unresolved assistant patterns. CD value has been defined by the threshold method of aerial images. The evaluation method by aerial image is useful for rough estimate because the calculation is very rapid. However, the difference from the experimental results cannot be ignored in some cases, especially, in important CD- focus characteristics. For more accurate evaluation, we also investigated the result difference using a simplified resist development model. This model is useful for rapid calculation as light intensity calculation. From the evaluation of the exposure dose and focus latitude (EFL), the optimal layout must be decided considering exposure dose latitude decrease by resist development process. We have additionally investigated the combination effect of assistant pattern and halftone phase-shifting under OAI. EFL was improved a little by halftone phase- shifting mask without assistant patterns, on the other hand, EFL was improved by combination of HPSM and assistant patterns.

Paper Details

Date Published: 7 June 1996
PDF: 6 pages
Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996); doi: 10.1117/12.240952
Show Author Affiliations
Keiichiro Tounai, NEC Corp. (Japan)
Naoaki Aizaki, NEC Corp. (Japan)


Published in SPIE Proceedings Vol. 2726:
Optical Microlithography IX
Gene E. Fuller, Editor(s)

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