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Proceedings Paper

Through-pitch low-k1 contact hole imaging with CPL technology
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Paper Abstract

Chromeless-Phase Lithography (CPL) combined with IML (Interference Mapping Lithography) technology is experimentally demonstrated as a viable resolution enhancement technique (RET) to pattern low-k1 (0.39) contact holes (CHs) from dense through sparse pitches. Both the process latitude and the MEEF values are measured. The most promising single exposure techniques combine off-axis-illumination (OAI) with the use of non-printing assist features, as in the case of CPL with IML. Contrary to other RETs, CPL does not use sub-resolution assist features but non-printing assist slots with a well-chosen phase (180° or 0°) and transmission (0% or 100%) assignment. The optimization and the positioning of assist features result of IML, based on a mapping of the field intensity at the wafer level: the assist features interfere to enhance the image at the contact hole location. The experimental layout optimization is discussed, showing how the process is maximized together with the dose-margin before any side-lobe printing. Using ArF immersion lithography at 0.75 NA with Quasar 20° σout=0.92 / σin=0.72, the CPL printing performance of 100 nm contact holes, from 200 nm pitch through isolated, is measured. The Depth-Of-Focus at 8% Exposure Latitude (DOF @ 8% EL) remains above 0.4 μm through pitch, with 0.43 μm DOF @ 8% EL at the difficult 300 nm pitch. The MEEF becomes a multi-dimensional metric on CPL masks. The wafer CD uniformity depends not only on the size variation of the CH on the reticle, but also on the size variations at the two reticle write steps, i.e. the assist slots opening and the Cr removal. The MEEF metrics related to the CH and slot sizes appear as the most critical ones. For each of those parameters, measured MEEF is always below 3.

Paper Details

Date Published: 20 August 2004
PDF: 10 pages
Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); doi: 10.1117/12.557803
Show Author Affiliations
Vincent Wiaux, IMEC (Belgium)
Joost Bekaert, IMEC (Belgium)
J. Fung Chen, ASML MaskTools, Inc. (United States)
Stephen D. Hsu, ASML MaskTools, Inc. (United States)
Kurt G. Ronse, IMEC (Belgium)
Robert John Socha, ASML Technology Development Ctr. (United States)
Geert Vandenberghe, IMEC (Belgium)
Douglas J. Van Den Broeke, ASML MaskTools, Inc. (United States)

Published in SPIE Proceedings Vol. 5446:
Photomask and Next-Generation Lithography Mask Technology XI
Hiroyoshi Tanabe, Editor(s)

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