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Proceedings Paper

Experimental evaluation of Bulls-Eye illumination for assist-free random contact printing at sub-65nm node
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Paper Abstract

Patterning of random CH for the 65nm node and below has proven to be a very difficult task. As a rule of thumb, difficulties in contact patterning are driven by the low depth of focus towards isolated contacts and/or the lower contrast combined with higher mask error factor (MEEF) for denser contact arrays. In this work, we experimentally investigate the use of illumination modes consisting of the combination of annular plus conventional illumination, so-called "Bulls-Eye" illumination. This study is a search for the optimal sigma settings for the annular and conventional parts, with respect to process window and MEEF through pitch. Also, the extend to which the Bulls-Eye is advantageous is demonstrated by means of experimental comparison to wafer prints by conventional illumination. Besides regular grid CH arrays, the Bulls-Eye performance is evaluated for different 2D contact patterns. Experimental results are obtained on ASML ArF scanners at various NAs up to 0.93. Additionally, immersion lithography and Focus Drilling are considered at given exposure setting as techniques to increase the focal depth. The experiments show promising results, printing contacts from k1 = 0.40 onwards with acceptable process, MEEF, and proximity through pitch, and this without side-lobe printing.

Paper Details

Date Published: 15 March 2006
PDF: 12 pages
Proc. SPIE 6154, Optical Microlithography XIX, 615412 (15 March 2006); doi: 10.1117/12.659420
Show Author Affiliations
Jo Finders, ASML (Netherlands)
Andre Engelen, ASML (Netherlands)
Geert Vandenberghe, IMEC (Belgium)
Joost Bekaert, IMEC (Belgium)
Tim Chen, ASML Masktools (United States)


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

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