Directed self-assembly of block copolymers is a bottom-up approach to nanofabrication that has attracted high interest in recent years due to its inherent simplicity, high throughput, low cost and potential for sub-10 nm resolution. In this paper, we review the main principles of directed self-assembly of block copolymers and give a brief overview of some of the most extended applications. We present a novel fabrication route based on the introduction of directed self-assembly of block copolymers as a patterning option for the fabrication of nanoelectromechanical systems. As a proof of concept, we demonstrate the fabrication of suspended silicon membranes clamped by dense arrays of single-crystal silicon nanowires of sub-10 nm diameter. Resulting devices can be further developed for building up high-sensitive mass sensors based on nanomechanical resonators.
An accurate knowledge of the parameters governing the kinetics of block copolymer self-assembly is crucial to model the time- and temperature-dependent evolution of pattern formation during annealing as well as to predict the most efficient conditions for the formation of defect-free patterns. Here, the self-assembly kinetics of a lamellar PS-b-PMMA block copolymer under both isothermal and non-isothermal annealing conditions are investigated by combining grazing-incidence small-angle X-ray scattering (GISAXS) experiments with a novel modelling methodology that accounts for the annealing history of the block copolymer film before it reaches the isothermal regime. Such a model allows conventional studies in isothermal annealing conditions to be extended to the more realistic case of non-isothermal annealing and prediction of the accuracy in the determination of the relevant parameters, namely the correlation length and the growth exponent, which define the kinetics of the self-assembly.
Synchrotron radiation offers great opportunities to improve the understanding of block copolymer morphology and self-assembly processes. In particular, GISAXS characterization is an interesting complementary method to analyze with sub-nanometer resolution the patterns that block copolymer thin films form, in addition to chemical composition. Most of the synchrotron radiation techniques are compatible with block copolymer processes, allowing for an in-situ and real time analysis of the self-assembly processes, what is very important for the analysis of process kinetics. In this contribution, we present the analysis of the self-assembly process of lamellar PS-b-PMMA block copolymer submitted to thermal annealing. The analysis of the 2D-GISAXS patterns allows the evaluation of the block copolymer morphology on formed nanopatterns and about the block copolymer kinetics.
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