Direct nanoimprint lithography of Al₂O₃ using a chelated monomer-based precursor.
Nanostructuring of Al₂O₃ is predominantly achieved by the anodization of aluminum film and is limited to obtaining porous anodized aluminum oxide (AAO). One of the main restrictions in developing approaches for direct fabrication of various types of Al₂O₃ patterns, such as lines, pillars, holes, etc, is the lack of a processable aluminum-containing resist. In this paper, we demonstrate a stable precursor prepared by reacting aluminum tri-sec-butoxide with 2-(methacryloyloxy)ethyl acetoacetate, a chelating monomer, which can be used for large area direct nanoimprint lithography of Al₂O₃. Chelation in the precursor makes it stable against hydrolysis whilst the presence of a reactive methacrylate group renders it polymerizable. The precursor was mixed with a cross-linker and their in situ thermal free-radical co-polymerization during nanoimprinting rigidly shaped the patterns, trapped the metal atoms, reduced the surface energy and strengthened the structures, thereby giving a ~100% yield after demolding. The imprinted structures were heat-treated, leading to the loss of organics and their subsequent shrinkage. Amorphous Al₂O₃ patterns with line-widths as small as 17 nm were obtained. Our process utilizes the advantages of sol-gel and methacrylate routes for imprinting and at the same time alleviates the disadvantages associated with both these methods. With these benefits, the chelating monomer route may be the harbinger of the universal scheme for direct nanoimprinting of metal oxides.
Institute of Materials Research and Engineering, A*STAR-Agency for Science, Technology and Research, 3 Research Link, Singapore 117602, Republic of Singapore. ram.ganesan@bits-hyderabad.ac.in
Ramakrishnan
R
Ganesan
Saman Safari
SS
Dinachali
Su Hui
SH
Lim
M S M
MS
Saifullah
Wee Tit
WT
Chong
Andrew H H
AH
Lim
Jin Jie
JJ
Yong
Eng San
ES
Thian
Chaobin
C
He
Hong Yee
HY
Low