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Proceedings Paper

Combined mask and illumination scheme optimization for robust contact patterning on 45nm technology node flash memory devices
Author(s): Alessandro Vaglio Pret; Gianfranco Capetti; Maddalena Bollin; Gina Cotti; Danilo De Simone; Pietro Cantù; Alessandro Vaccaro; Laura Soma
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Paper Abstract

Immersion Lithography is the most important technique for extending optical lithography's capabilities and meeting the requirements of Semiconductor Roadmap. The introduction of immersion tools has recently allowed the development of 45nm technology node in single exposure. Nevertheless the usage of hyper-high NA scanners (NA > 1), some levels still remain very critical to be imaged with sufficient process performances. For memory devices, contact mask is for sure the most challenging layer. Aim of this paper is to present the lithographic assessment of 193nm contact holes process, with k1 value of ~0.30 using NA 1.20 immersion lithography (minimum pitch is 100nm). Different issues will be reported, related to mask choices (Binary or Attenuated Phase Shift) and illuminator configurations. First phase of the work will be dedicated to a preliminary experimental screening on a simple test case in order to reduce the variables in the following optimization sections. Based on this analysis we will discard X-Y symmetrical illuminators (Annular, C-Quad) due to poor contrast. Second phase will be dedicated to a full simulation assessment. Different illuminators will be compared, with both mask type and several mask biases. From this study, we will identify some general trends of lithography performances that can be used for the fine tuning of the RET settings. The last phase of the work will be dedicated to find the sensitivity trends for one of the analyzed illuminators. In particular we study the effect of Numerical Aperture, mask bias in both X and Y direction and poles sigma ring-width and centre.

Paper Details

Date Published: 1 April 2008
PDF: 12 pages
Proc. SPIE 6924, Optical Microlithography XXI, 69243B (1 April 2008); doi: 10.1117/12.772676
Show Author Affiliations
Alessandro Vaglio Pret, STMicroelectronics (Italy)
Gianfranco Capetti, STMicroelectronics (Italy)
Maddalena Bollin, STMicroelectronics (Italy)
Gina Cotti, STMicroelectronics (Italy)
Danilo De Simone, STMicroelectronics (Italy)
Pietro Cantù, STMicroelectronics (Italy)
Alessandro Vaccaro, STMicroelectronics (Italy)
Laura Soma, STMicroelectronics (Italy)

Published in SPIE Proceedings Vol. 6924:
Optical Microlithography XXI
Harry J. Levinson; Mircea V. Dusa, Editor(s)

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