Extending the scope of poly(styrene)-block-poly(methyl methacrylate) for directed self assembly. Thomas Bennett, a,b Kevin Pei, a Han Hao Cheng, c Kristofer J. Thurecht, a,b Kevin S. Jack, d and Idriss Blakey a,b* * a The University of Queensland, Australian Institute for Bioengineering and Nanotecnhology, Brisbane Qld Australia 4072; b The University of Queensland, Centre for Advanced Imaging, Brisbane Qld Australia 4072; c The University of Queensland, , Australian National Fabrication Facility, QLD Node, Brisbane Qld Australia 4072; d The University of Queensland Centre for Microscopy and Microanalysis, Brisbane Qld Australia 4072 ABSTRACT Directed self-assembly (DSA) is a promising technique for extending conventional lithographic techniques by being able to print features with critical dimensions under 10 nm. The most widely studied block copolymer system is polystyrene- block-polymethyl methacrylate (PS-b-PMMA). The system is well understood in terms of its synthesis, properties and performance in DSA. However, PS-b-PMMA also has a number of limitations that impact on its performance and hence scope of application. The primary limitation is the low Flory-Huggins polymer-polymer interaction parameter (χ), which limits the size of features that can be printed by DSA. Another issue with block copolymers in general is that specific molecular weights need to be synthesized to achieve desired morphologies and feature sizes. We are exploring blending ionic liquid additiveswithPS-b-PMMAto increase the χ parameter. This allows smaller feature sizes to be accessed by PS-b-PMMA. Depending on the amount of additive it is also possible to tune the domain size and the morphology of the systems. These findings may expand the scope of PS-b-PMMA for DSA. Keywords: ionic liquids, block copolymer, PS-b-PMMA, Chi parameter, Flory Huggins polymer-polymer interaction parameter 1. INTRODUCTION Three key parameters that are used to measure the performance of photoresists are resolution, line edge roughness (LER) and sensitivity. It is well known that these three performance criteria are linked and thisrelationship is often described as the resolution-line edge roughness-sensitivity (RLS) trade-off. A key aim for the development of photoresists and associated processes is to simultaneously improve RLS. Many gains can be made by optimisation of resist formulations, although more disruptive technologies include the redesign of the resists and such approaches include: polymer bound PAG resists, [1-7] molecular glass resists [8-16] and chain scissioning resists. [17-26] In particular, polymer bound PAG resists have achieved a great deal of success as EUVL platforms, although improvements are still required for achieving the ITRS goals. Healing of LER following development is another approach that has led to significant improvements in LER. [27, 28] On the other hand, directed self assembly (DSA) of block copolymers is a technique that has demonstrated significant promise for achieving high resolution. DSA is a technique that brings together lithography (top-down) to fabricate patterns that guide the self assembly of diblock copolymers (bottom-up). The end result is ordered features with sub-lithographic resolution. [29-39] Block copolymers are made up of least two chemically-distinct polymer chains which are covalently linked. When the respective blocks are immiscible, arrays of highly-ordered nanostructures can form. The final morphology depends on the relative volume fraction of each block, the total molecular weight (N) and degree of immisciblity, i.e. the Flory-Huggins polymer-polymer interaction parameter, (χ). There are two main techniques for i.blakey@uq.edu.au; www.aibn.uq.edu.au/a-prof-idriss-blakey Alternative Lithographic Technologies VI, edited by Douglas J. Resnick, Christopher Bencher, Proc. of SPIE Vol. 9049, 90490R · © 2014 SPIE · CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2046296 Proc. of SPIE Vol. 9049 90490R-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 12/14/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx