Strategies for Increasing the Rate of Defect Annihilation in the Directed Self-Assembly of High-χ Block Copolymers

Abstract

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.

Thermodynamics and ordering kinetics in asymmetric PS-b-PMMA block copolymer thin films

“…29 Moreover, measuring the correlation length of unguided self-assembled BCP thin films, Ellison et al demonstrated that it is possible to directly predict the density of kinetically trapped defects in BCP thin films deposited on a fixed chemical pattern and self-assembled under the same process conditions. 31 Therefore, the understanding of the selfassembling process for a BCP deposited on an unpatterned substrate is fundamental for the development of any directed self-assembly based nanolithograpic application. 25,26,31…”

“…31 Therefore, the understanding of the selfassembling process for a BCP deposited on an unpatterned substrate is fundamental for the development of any directed self-assembly based nanolithograpic application. 25,26,31…”

“…24 Moreover, reduced L 0 and effective ordering are crucial for the exploitation of BCPs as a valuable technological platform for the fabrication of dense and ordered nanostructures. [25][26][27][28][29][30][31] All these fundamental and practical characteristics make such a system very interesting to investigate.…”

Directed Self-Assembly of Block Copolymers for the Fabrication of Functional Devices

“…Additionally, recent research on DSA has also been greatly focused on the study, understanding and mitigation of defects [ 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 ]. Minimization of defects is crucial for the incorporation of DSA into high-volume manufacturing, either as a primary patterning option or in combination with already established techniques like DUV or EUV.…”

Solvent Vapor Annealing, Defect Analysis, and Optimization of Self-Assembly of Block Copolymers Using Machine Learning Approaches

“…The self-assembly of a monolayer of a given BCP on a flat, featureless surface results in a polycrystalline morphology with uncorrelated nano- to micron-sized domains, with a significant concentration of defects . The ITRS (now IDRS roadmap) has specified a target of a maximum defectivity of ∼1 per 100 cm –2 , − which is several orders of magnitude lower than that quantified in patterns derived from these monolayers of self-assembled BCPs on substrates lacking guiding patterns. Some kinetically trapped nonequilibrium metastable configurations in the free energy landscape persist even through long annealing times, which is an issue for high volume manufacturing on 300 mm wafers. ,,, In an attempt to minimize defect formation during the course of self-assembly, much effort has been directed toward the optimization of annealing of the spin-coated BCP films, including solvent vapor, − thermal (including microwave irradiation), − a combination of solvent and thermal (solvothermal), , laser annealing, , shear flow, , and annealing within an electric field .…”