Thin film self-assembly of poly(trimethylsilylstyrene-b-d, l-lactide) with sub-10 nm domains

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-b-dimethylsiloxane) (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.