Block Co-Polymers for Nanolithography: Rapid Microwave Annealing for Pattern Formation on Substrates

Nature, 2003

Microwave annealing is an emerging technique for achieving ordered patterns of block copolymer films on substrates. Little is understood about the mechanisms of microphase separation during the microwave annealing process and how it promotes the microphase separation of the blocks. Here, we use controlled power microwave irradiation in the presence of tetrahydrofuran (THF) solvent, to achieve lateral microphase separation in high-χ lamellar-forming poly(styrene-b-lactic acid) PS-b-PLA. A highly ordered line pattern was formed within seconds on silicon, germanium and silicon on insulator (SOI) substrates. In-situ temperature measurement of the silicon substrate coupled to condition changes during “solvomicrowave” annealing allowed understanding of the processes to be attained. Our results suggest that the substrate has little effect on the ordering process and is essentially microwave transparent but rather, it is direct heating of the polar THF molecules that causes microphase separation. It is postulated that the rapid interaction of THF with microwaves and the resultant temperature increase to 55 °C within seconds causes an increase of the vapor pressure of the solvent from 19.8 to 70 kPa. This enriched vapor environment increases the plasticity of both PS and PLA chains and leads to the fast self-assembly kinetics. Comparing the patterns formed on silicon, germanium and silicon on insulator (SOI) and also an in situ temperature measurement of silicon in the oven confirms the significance of the solvent over the role of substrate heating during “solvo-microwave” annealing. Besides the short annealing time which has technological importance, the coherence length is on a micron scale and dewetting is not observed after annealing. The etched pattern (PLA was removed by an Ar/O2 reactive ion etch) was transferred to the underlying silicon substrate fabricating sub-20 nm silicon nanowires over large areas demonstrating that the morphology is consistent both across and through the film.

ACS Nano, 2007

Thermal scanning probe lithography (t-SPL) is applied to the fabrication of chemical guiding patterns for directed self-assembly (DSA) of block copolymers (BCP). The two key steps of the overall process are the accurate patterning of a poly(phthalaldehyde) resist layer of only 3.5 nm thickness, and the subsequent oxygen-plasma functionalization of an underlying neutral poly(styrene-random-methyl methacrylate) brush layer. We demonstrate that this method allows one to obtain aligned line/space patterns of poly(styrene-block-methyl methacrylate) BCP of 18.5 and 11.7 nm half-pitch. Defect-free alignment has been demonstrated over areas of tens of square micrometres. The main advantages of t-SPL are the absence of proximity effects, which enables the realization of patterns with 10 nm resolution, and its compatibility with standard DSA methods. In the brush activation step by oxygen-plasma exposure, we observe swelling of the brush. This effect is discussed in terms of the chemical reactions occurring in the exposed areas. Our results show that t-SPL can be a suitable method for research activities in the field of DSA,in particular for low-pitch, high-χ BCP to achieve sub-10 nm line/space patterns.

Colloids and Interface Science Communications, 2014

Advanced Materials, 2008

Journal of Photopolymer Science and Technology, 2010

International Journal of Old Uyghur Studies, 2023

Tuvan belongs to -d- “adak” group or Northern Siberian subgroups in classification studies on Turkic languages. It was first noticed by the German geographer Anton Friedrich Büsching in the eighteenth century and attracted attention with its similarity to Tofa. Matthias Castrén also visited the Tunka Soyots during his trip to the Buryat Republic in the nineteenth century and noticed the same similarity. Thanks to Wilhelm Radloff's compilation of language examples in Altai and Western Siberia since 1860 and the language materials collected by Katanov during his 1889 trip to Tuva, we have a wide range of folkloric and literature material belonging to Tuvan today. In this study, the vocabulary of Tuvan and Old Turkish was examined and compared by making use of the compilations. / Özet Tuvaca, Türk dilleri üzerine yapılan tasnif çalışmalarında -d- “adak” grubu veya Kuzey Sibirya dilleri arasına girmektedir. İlk olarak 18. yüzyılda Alman coğrafyacı Anton Friedrich Büsching tarafından fark edilmiş ve Tofaca ile benzerliği dikkat çekmiştir. Matthias Castrén de on dokuzuncu yüzyılda Buryat Cumhuriyeti'ne yaptığı bir gezi sırasında Tunka Soyotlarını ziyaret etmiş ve aynı benzerliği fark etmiştir. Wilhelm Radloff’un 1860 yılından itibaren Altay ve Batı Sibirya'da dil örneklerini derlemesi ve N.F. Katanov’un 1889 yılında Tuva’ya yapmış olduğu gezide topladığı dil malzemeleri Tuvacaya ait geniş bir folklorik ve literatür malzemesini bugün elimizde bulundurmaktadır. Bu çalışmada, yapılan derlemelerden yararlanılarak Tuvaca ve Eski Türkçeye ait söz varlığı incelenmiş ve karşılaştırılmıştır.

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