7 March 2008 Double patterning down to k1=0.15 with bilayer resist
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Abstract
Double patterning based on litho-etch-litho-etch techniques requires the fabrication of small lines or of small spaces after first patterning. If spacer techniques are used for pitch fragmentation small lines are needed as carrier in dense arrays. In any case the CD control is crucial. Focus of this paper is the patterning of small lines with bilayer resist in comparison with single layer resist as pre-requisite for both methods, for various litho conditions. The basic suitability of a bilayer patterning has been demonstrated at k1=0.146 at half pitch of 37.5nm with a sufficient process window and a good CD uniformity after litho and after etch. Single layer resists suffer from pattern collapse and resist thickness loss at defocus if a CD trim by litho "overexposure" is applied. This results in deficiency of masking during etch, although the resist profiles and litho process windows look perfect. If a CD trim is achieved by an etch process the CDU is diminished and the minimum patterned space is enlarged compared to bilayer, due the widening by trim etch. The bilayer resist for 193nm dry lithography showed convincing overall performance. First results with 193nm immersion bilayer look also promising but shows grass formation.
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Christoph Noelscher, Franck Jauzion-Graverolle, Marcel Heller, Matthias Markert, Bee-Kim Hong, Ulrich Egger, Dietmar Temmler, "Double patterning down to k1=0.15 with bilayer resist", Proc. SPIE 6924, Optical Microlithography XXI, 69240Q (7 March 2008); doi: 10.1117/12.772750; https://doi.org/10.1117/12.772750
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