利用含矽化嵌段共聚物聚苯乙烯-聚二甲基矽氧烷製備奈米圖案

Nanopatterning from Silicon-containing PS-PDMS Block Copolymers

趙家崢(Chia-Cheng Chao)

指導教授 ： 何榮銘

國立清華大學/工學院/奈米工程與微系統研究所/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00034

摘要

Nanopatterning, the fabrication of patterns with nanoscale features, has drawn great attention during the last decade. To create well-defined nanopatterns over large areas, a variety of patterning technologies (including top-down and bottom-up methods) have been developed. Nanopatterning based on bottom-up method has been considered as a candidate to substitute or improve top-down method so as to enable a variety of nanotechnologies. Among the bottom-up methods, self-assembled block copolymers (BCPs) driven by the immiscibility between the constituted blocks own inherently various nanostructures. For BCPs containing silicon atoms, the self-assembled nanostructures give rise to appealing applications in nanopatterning because of their capability to form inorganic oxide under oxygen plasma treatment. In this study, a series of silicon-containing BCPs, polystyrene-b- polydimethylsiloxane (PS-PDMS), has been synthesized for nanopatterning.
We aim to use a one-step oxidation process in PDMS-rich PS-PDMS BCP thin films to simultaneously etch the minor PS component into thru-pore nanochannels and to convert the PDMS matrix into a robust inorganic film. Well-defined ultra-thin freestanding nanoporous films with hexagonally packed nanochannels can be identified by transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM). To further examine the chemical nature of the oxidized PS-PDMS thin-film, X-ray photoelectron spectroscopy (XPS) was carried out to investigate the conversion of PDMS block and the removal of PS block. From the XPS results, we suggest that the PS-PDMS thin film is oxidized to form SiOC after oxygen plasma treatment. By taking advantage of the robust property and high etching selectivity of the SiOC thin films under oxygen reactive ion etching (RIE), this nanoporous thin film can be used as an etch-resistant and reusable mask for the pattern transfer to various polymeric materials. Consequently, topographic nanopatterns of PS, PMMA and PC can be obtained.
Considering the geometries of nanostructures for potential applications, the self-assembled diblock copolymer nanostructures typically include dots, layers and pillars but ring-shaped nanostructure is not common. One way to create the ring-shaped nanostructure is to employ the self-assembly of triblock terpolymers for the formation of core-shell cylinder thin film with low aspect-ratio cylinders perpendicular to the substrate so as to use it as a nanoring template. In contrast to the approach by using triblock terpolymers that requires a complete synthetic process, we aim to create SiOC nanoring arrays from PS-PDMS BCP. Perpendicular PDMS cylinders in the PS-rich PS-PDMS thin film can be obtained by solvent annealing. The PS-PDMS thin film was immersed into a selective solvent for the PDMS to create nanoporous arrays after surface reconstruction. Subsequently, the core-shell cylinder thin film with hexagonally packed can be obtained by CF4 RIE. These core-shell cylinder thin-film samples can be used as a template to fabricate SiOC nanoring arrays through oxygen plasma treatment. This method provides a convenience way to create silicon oxy carbide nanoring arrays from diblock copolymers.
Among all of the nanostructures from the self-assembly of BCPs, gyroid is one of the most appealing nanostructured phase for practical applications because of the unique texture with a matrix and bi-continuous networks in three-dimensional space. To acquire the formation of gyroid phase, we aim to study the phase transition of solution-cast bulk samples of PS-rich PS-PDMS samples. Different selective solvents for PS with different evaporation rates were employed. For PS-PDMS samples with lamellae-forming stable phase, by controlling the solvent evaporation for solution-casting, cylinder and gyroid phases can be obtained. Conversely, the formation of metastable phase can be kinetically controlled through solution-casting by using solvents with different evaporation rates. For practical applications, we are interested in the formation of thin-film samples with bi-continuous networks. Similar to the results of phase transition behavior in bulk, thin films with bi-continuous networks can be formed through solution-casting. As a result, PS-PDMS thin-film samples can be used as a template to fabricate SiOC thin-film samples with bi-continuous networks through one-step oxidation. This approach suggests an easy way to create inorganic oxide thin films with bi-continuous networks that can provide large specific surface area for practical applications.

關鍵字

奈米圖案 ； 自組裝

並列摘要

無資料

並列關鍵字

Nanopattern ； Self-assembly

參考文獻

1. Lehn, J. -M. Science 1985, 227, 849.

4. Whiteside, G. M.; Grzybowski, B. Science 2002, 295, 2418.

5. Hatzakis, M. J. Electrochem. Soc. 1969, 116, 1033.

7. Rai-Choudhury, P. Handbook of microlithography, micromachining, and microfabrication SPIE Optical Engineering Press, 1997.

10. Xia, Y.; Whitesides, G. M. Angew. Chem. Int. Ed. 1998, 37, 550.