Studies of block copolymer (BCP) materials and their phase separation in bulk and thin-film forms have exploded over the last decades, due to the wide range of accessible morphologies (e.g. spheres, cylinders, gyroid, and lamellae) and sizes (5-200 nm) of features. The phase separation of a BCP is governed by three factors which include the relative volume fraction (f) of the blocks A and B (fA = 1 – fB), the degree of polymerization (N), and the Flory-Huggins interaction parameter (χ). The basic BCP self-assembly principles have enabled the BCP community to control the morphology as well as to tune the domain size and have driven the community to target smaller sizes by synthesizing BCPs with high interaction parameter. Accessing sub-5 nm feature size is no longer a challenge utilizing BCP self-assembly. However, transferring the self-assembled BCP features to a substrate over a large area with high fidelity presents additional challenges, especially at the 10 nm length scale. In this work, the highly polar, functional and hydrophilic poly(3-hydroxystyrene) (P3HS) is incorporated with the acid sensitive poly(dimethylsiloxane) (PDMS). A tetrahydroxydropyranyloxy protecting group which requires mild deprotection condition is introduced to the system and hence PDMS block remains intact after deprotection. We explore both P3HS/PDMS-based diblocks and triblocks synthesized by sequential living anionic polymerization and atom transfer radical polymerization, respectively. P3HS-b-PDMS shows well-ordered lamellae or hexagonally packed cylinders with characteristic dimensions ranging from 7.4 to 17.7 nm. Mean-field theory analysis of the temperature-dependent correlation-hole scattering derived from a disordered symmetric P3HS-b-PDMS gives χ(T) = 33.491/T + 0.3126, which is more than 4-fold increase over PS-b-PDMS. Etching study indicates that the etch contrast between P3HS and PDMS is 15:1 under oxygen plasma treatment. Inorganic precursors such as trimethylaluminium can selectively penetrate into P3HS domain which can be further converted into alumina mask for pattern transfer. These new BCPs not only exhibit high interaction parameter to achieve sub-10 nm feature size, but also present high etch contrast and versatile etch selectivity to facilitate the pattern transfer.

Ultrahigh-χ block copolymer materials with versatile etch selectivity for sub-10 nm pattern transfer

ACS Fall 2020 Virtual Meeting

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