Study of silicon-treated and silicon-containing block copolymers for patterning of $SiO_2$ nanostructures

Abstract

$\Bf{ Silicon-Treated Block Copolymers for $SiO_2$ Nanostructures}$ Surfaces patterned with regularly sized and spaced features at the nanoscopic level have attracted much interest over the last decade. The inherent variety of block copolymers makes their self-assembly an attractive means of creating such surfaces and they have been used as effective and versatile templates for many inorganic materials. Silicon oxide ($SiO_2$) in particular has demonstrated tremendous promise in applications ranging from microelectronics to photonic devices. First, highly dense $SiO_2$ nanodot arrays were fabricated via a selective chemical reaction with a functionalized block copolymer template. Polystyrene-$\It{b}-poly(acrylic acid/acrylic anhydride) (PS-$\It{b}-PAA/AN) thin films on an SU-8 photoresist, generated from polystyrene-$\It{b}-poly($\It{tert}-butylacrylate) (PS-$\It{b}-PtBA) by acid-catalyzed thermal deprotection, were used as templates. Due to the presence of PAA/AN nanodomains with carboxylic acids cross-linked by anhydride linkages, these templates acted as robust and versatile scaffolds with excellent solvent and thermal resistance. Hexamethyldisilazane (HMDS) was spin-sprayed uniformly over the entire surface of the self-assembled PS-$\It{b}-PAA/AN film and reacted selectively with carboxylic acids in the spherical domains of PAA/AN. RIE in an $O_2/Ar$ atmosphere removed all organic components, resulting in arrays of free-standing silica nanostructures over a wide area of the substrate. Secondly, the self-assembly of an amine-terminated polydimethylsiloxane (PDMS) via the noncovelent interactions onto the functionalized block copolymer template was used to silicon oxide nanodot arrays. This method could make a possible not only to increase contents of silicon but also to simplify a whole process. PS-$\It{b}-PAA/AN thin films on an SU-8 photoresist were dipped on the amine-terminated PDMS solution and PDMS was self-assembled selectively onto the spheric...