Browsing by Subject "Top coats"

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Advanced materials for block copolymer lithography
(2013-05) Bates, Christopher Martin; Willson, C. G. (C. Grant), 1939-
The multi-billion dollar per year lithography industry relies on the fusion of chemistry, materials science, and engineering to produce technological innovations that enable continual improvements in the speed and storage density of microelectronic devices. A critical prerequisite to improving the computers of today relies on the ability to economically and controllably form thin film structures with dimensions on the order of tens of nanometers. One class of materials that potentially meets these requirements is block copolymers since they can self-assemble into structures with characteristic dimensions circa three to hundreds of nanometers. The different aspects of the block copolymer lithographic process are the subject of this dissertation. A variety of interrelated material requirements virtually necessitate the synthesis of block copolymers specifically designed for lithographic applications. Key properties for the ideal block copolymer include etch resistance to facilitate thin film processing, a large interaction parameter to enable the formation of high resolution structures, and thin film orientation control. The unifying theme for the materials synthesized herein is the presence of silicon in one block, which imparts oxygen etch resistance to just that domain. A collection of silicon-containing block copolymers was synthesized and characterized, many of which readily form features on approximately the length scale required for next-generation microelectronic devices. The most important thin film processing step biases the orientation of block copolymer domains perpendicular to the substrate by control of interfacial interactions. Both solvent and thermal annealing techniques were extensively studied to achieve orientation control. Ultimately, a dual top and bottom surface functionalization strategy was developed that utilizes a new class of "top coats" and cross-linkable substrate surface treatments. Perpendicular block copolymer features can now be produced quickly with a process amenable to existing manufacturing technology, which was previously impossible. The development of etching recipes and pattern transfer processes confirmed the through-film nature of the features and the efficacy of both the block copolymer design and the top coat process.
Design, synthesis, and engineering of advanced materials for block copolymer lithography
(2015-05) Durand, William John; Willson, C. G. (C. Grant), 1939-; Ellison, Christopher J.; Bonnecaze, Roger T; Truskett, Thomas M; Akinwande, Deji
Block copolymers (BCPs) are an attractive alternative for patterning applications used to produce next-generation microelectronic devices. Advancements require the development of high interaction parameter χ BCPs that enable patterning at the sub-10 nm length scale. Several organosilicon BCPs were designed to both enhance χ and impart an inherent etch selectivity that facilitates pattern transfer processes. Increasing the BCP silicon content both increases χ and bolsters the etch resistance, providing a pathway to designing new high-χ materials. Unfortunately, the BCPs investigated are not amenable to thermal annealing because the organosilicon block preferentially segregates to an air/vacuum interface and drives orientation parallel to the surface. A series of spin-coatable, polarity-switching top coats (as well as other strategies) were developed to provide a “neutral” top interface and promote the perpendicular orientation of BCP domains. In addition, a methodology for evaluating the neutral condition, relying on thickness quantization and the corresponding wetting behavior (i.e. island/hole topography) of lamellae. The top coat strategy was demonstrated for several BCP systems, and perpendicular structures can successfully be etched on commercial tools and be transferred into underlying substrates. The interaction parameter χ was evaluated using two methods to compare the performance of several BCPs: the order-disorder transition (ODT) of symmetric diblock copolymers, and the absolute scattering profile of a disordered BCP melt. Both methods, while severely limited for quantitative comparison, indicate trends towards higher χ with additional appended polar and organosilicon functional groups. Furthermore, the pattern fidelity is shown to be a function of the overall BCP segregation strength. The free energy of confined lamella was modeled algebraically to produce response surface plots capable of identifying process conditions favorable for perpendicular orientation. Thickness independent perpendicular orientation is only favorable using two neutral interfaces. Incommensurate film thicknesses are the most favorable, with commensurability conditions dependent on the wetting behavior at each interface. The modeling was supplemented with an extensive body of thin film experimental work that qualitatively agrees well with the above conclusions.