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Proceedings Paper

Analysis of the combined impact of the laser spectrum, illuminator miscalibrations, and lens aberrations on the 90nm technology node imaging with off-axis illuminations
Author(s): Sara Loi; Umberto Iessi; Robert Chung
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Paper Abstract

To meet lithographic requirements for the 100 nm generation, the influence of laser spectrum bandwidth, illuminator miscalibrations, and lens aberrations on printing of specific patterns by specific customized illuminations has to be investigated. The contribution to critical dimension (CD) dispersion and pattern shift due to lens aberrations of an exposure tool has become an important issue in the production of semiconductor devices. Current 90nm NVM design introduces critical points from the imaging point of view in many layers such as active, poly, contacts and first metallization. The selection of strong off axis illumination shapes and phase shift masks to enhance lithographic resolution and improve process window of such a critical layers may result in a huge impact of lens aberrations. Lens aberrations have a specific impact on the defined layout of the lithographic layer to be printed. An effect similar to the impact of lens aberration can also be induced by illuminator miscalibration and can be enhanced depending on the characteristics of the laser spectrum. The goal of this work is to analyse, for a critical pattern, the contribution to CD dispersion and distortion arising from combined effects of illuminator miscalibration and lens aberrations, depending on laser spectrum characteristics. For this purpose the real pupil shapes through the exposure field and the lens aberrations have been characterized by Litel Instruments HA-SMI and HA-ISI source and aberrations measuring tools to allow reliable optical simulations. Therefore a comparison between simulations and experimental results will be reported for imaging of an NVM critical pattern.

Paper Details

Date Published: 20 March 2006
PDF: 11 pages
Proc. SPIE 6154, Optical Microlithography XIX, 615434 (20 March 2006); doi: 10.1117/12.655567
Show Author Affiliations
Sara Loi, STMicroelectronics (Italy)
Umberto Iessi, STMicroelectronics (Italy)
Robert Chung, Litel Instruments (United States)


Published in SPIE Proceedings Vol. 6154:
Optical Microlithography XIX
Donis G. Flagello, Editor(s)

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