Highly ordered nanopatterns are obtained at sub‐5 nm periodicities by the graphoepitaxial directed self‐assembly of monodisperse, oligo(dimethylsiloxane) liquid crystals. These hybrid organic/inorganic liquid crystals are of high interest for nanopatterning applications due to the combination of their ultrasmall feature sizes and their ability to be directed into highly ordered domains without additional annealing.
Directed self-assembly (DSA) of high-χ block copolymer
thin
films is a promising approach for nanofabrication of features with
length scale below 10 nm. Recent work has highlighted that kinetics
are of crucial importance in determining whether a block copolymer
film can self-assemble into a defect-free ordered state. In this work,
different strategies for improving the rate of defect annihilation
in the DSA of a silicon-containing, high-χ block copolymer film
were explored. Chemo-epitaxial DSA of poly(4-methoxystyrene-block-4-trimethylsilylstyrene) with 5× density multiplication
was implemented on 300 mm wafers by using production level nanofabrication
tools, and the influence of different processes and material parameters
on dislocation defect density was studied. It was observed that only
at sufficiently low χN can the block copolymer
assemble into well-aligned patterns within a practical time frame.
In addition, there is a clear correlation between the rate of the
lamellar grain coarsening in unguided self-assembly and the rate of
dislocation annihilation in DSA. For a fixed chemical pattern, the
density of kinetically trapped dislocation defects can be predicted
by measuring the correlation length of the unguided self-assembly
under the same process conditions. This learning enables more efficient
screening of block copolymers and annealing conditions by rapid analysis
of block copolymer films that were allowed to self-assemble into unguided
(commonly termed fingerprint) patterns.
A graphoepitaxy directed self-assembly process using cylindrical phase block copolymers is regarded as a promising approach for patterning irregularly distributed contact holes in future integrated circuits. However, control over cylinder profile and open hole rate, among others, needs to be proven before this technique can be implemented in device fabrication. Computational simulation studies predict that selective control over the surface energy of the template bottom and sidewall is crucial for achieving perpendicular cylinders in an adequate range of template dimensions and block copolymer fill levels. This work offers an experimental investigation of the influence of the surface energy on the morphology of the assembly inside the template. For this study, a dedicated surface energy modification is implemented in our process flow. Selective control over the surface energy of the template bottom and sidewall is achieved by using random copolymer brushes. The optimization of surface energy prior to the directed self-assembly allows an improvement of the three-dimensional morphology of the assembly as well as larger process windows in terms of template dimensions and template fill. In addition, a sidewall that has an affinity for the majority block allows for smaller prepattern templates.
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