Block copolymers demonstrate potential for use in next-generation lithography due to their ability to self-assemble into well-ordered periodic arrays on the 3-100 nm length scale. The successful lithographic application of block copolymers relies on three critical conditions being met: high Flory-Huggins interaction parameters (χ), which enable formation of <10 nm features, etch selectivity between blocks for facile pattern transfer, and thin film self-assembly control. The present paper describes the synthesis and self-assembly of block copolymers composed of naturally derived oligosaccharides coupled to a silicon-containing polystyrene derivative synthesized by activators regenerated by electron transfer atom transfer radical polymerization. The block copolymers have a large χ and a low degree of polymerization (N) enabling formation of 5 nm feature diameters, incorporate silicon in one block for oxygen reactive ion etch contrast, and exhibit bulk and thin film self-assembly of hexagonally packed cylinders facilitated by a combination of spin coating and solvent annealing techniques. As observed by small angle X-ray scattering and atomic force microscopy, these materials exhibit some of the smallest block copolymer features in the bulk and in thin films reported to date.

Integrating block copolymer self-assembly with existing lithography processes to enhance their patterning capability is a promising approach for manufacturing a variety of semiconductor devices and next-generation magnetic storage media. Sub-10 nm block copolymer domains are specifically targeted in many of these applications, yet there are relatively few block copolymers that can achieve these dimensions. Here the synthesis and self-assembly characteristics of a new block copolymer poly(trimethylsilylstyrene-b-D,L-lactide) (PTMSS-b-PLA) capable of forming domains as small as ∼5 nm are described. Several lamellar and cylinder forming diblocks were synthesized with bulk domain periodicities of 12−15 nm which are among the smallest domains yet reported for any neat block copolymer. Such small domains are possible because this new material has a large segment−segment interaction parameter which is an order of magnitude higher than poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and twice as large as poly(styrene-bdimethylsiloxane) (PS-b-PDMS), two commonly studied polymers for these applications. Furthermore, the PTMSS-b-PLA blocks have glass transitions well above room temperature with a large reactive ion etch rate contrast between them (∼28) which is at least 4 times greater than PS-b-PMMA due to incorporation of a trimethylsilyl group into the styrene monomer.