Directed Self-Assembly of Block Copolymers for lithographic applications : from materials design to pattern transfer demonstration

Perfectly ordered microstructures with nanometrically defined periodicity offer promising opportunities in microelectronic applications and nanotechnologies for the production of advanced CMOS digital logic circuits wherein the pitch reduction and the component density increase are two of the main challenges. To produce long-range ordered two-dimensional arrays inherent to such technologies, the combination of the « bottom-up » self-assembly with « top-down » guiding patterned templates has been successfully introduced leading to new technological breakthroughs wherein self-assembling materials (and particularly block copolymers) are the cornerstone of the « bottom-up » nanofabrication processes through their self-assembly in periodic mesostructures. Well-ordered 2D-arrays of block copolymers can be produced by solvent or thermal annealing thin films cast onto grooved substrates when the block copolymer equilibrium period is commensurate with the dimension of the guiding template. Consequently, density multiplication of patterned templates by directed self-assembly (DSA) of block copolymers stands out as a promising methodology to supplement conventional lithography. We have developed a first generation of lithographic materials based on the DSA of PMMA-b-PS and PMMA-s-PS copolymers following the International Technology Roadmap for Semiconductors for the 22 nm node. Results summarizing this approach will be exposed during this talk. Besides, as the understanding of « bottom up »-type approaches is constantly improving, progress with « top-down »-type techniques is stagnating, since they have been already quite well developed and understood for many years. Methods used to fabricate the topographic surface patterns over large areas needed for the guidance of the block copolymer DSA present some technological limitations. Thus a novel set of methodologies in order to guide the block copolymer DSA into 2D crystal arrays over large flexible area was developed and will be presented.1 By applying this novel topographical methodology to control the DSA of block copolymers into highly-ordered 2D arrays, block copolymer -2D crystal- array were obtained as shown in Figure 1.

{Figure 1: (2 x 2 µm) AFM phase image of a solvent annealed film with highly ordered PEO cylindrical microdomains. Inset: 2D-FFT showing multiple higher-order interferences characteristic of the long-range ordering of the cylindrical nanodomain array.}

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1. K. Aissou, J. Shaver, G. Fleury, G. Pécastaings, C. Brochon, C. Navarro, S. Grauby, J.-M. Rampnoux, S. Dilhaire, G. Hadziioannou, Adv Mater 25, 213-7 (2013)