Templated Self-Assembly of Square Symmetry Arrays from an ABC Triblock Terpolymer

Abstract

Self-assembly provides the ability to create well-controlled nanostructures with electronic or chemical functionality and enables the synthesis of a wide range of useful devices. Diblock copolymers self-assemble into periodic arrays of microdomains with feature sizes of typically 10-50 nm, and have been used to make a wide range of devices such as silicon capacitors and transistors, photonic crystals, and patterned magnetic media(1-3). However, the cylindrical or spherical microdomains in diblock copolymers generally form close-packed structures with hexagonal symmetry, limiting their device applications. Here we demonstrate self-assembly of square-symmetry patterns from a triblock terpolymer in which one organometallic block imparts high etch selectivity and etch resistance. Long-range order is imposed on the microdomain arrays by self-assembly on topographical substrates, and the orientation of both square lattices and in-plane cylinders is controlled by the substrate chemistry. Pattern transfer is demonstrated by making an array of square-packed 30 nm tall, 20 nm diameter silica pillars. Templated self-assembly of triblock terpolymers can generate nanostructures with geometries that are unattainable from diblock copolymers, significantly enhancing the capabilities of block copolymer lithography.

Block Copolymer Nanostructures for Technology

“…Only a few polymer blocks have shown promising etch resistance, and most pattern transfer processes following BCP lithography necessitate a hard mask. Polymer blocks containing metals such as polyferrocenylsilanes (PFS) [49][50][51][52] or silicon such as PDMS [53][54][55] have enhanced resistance to plasma etching, and therefore a large etch contrast relative to organic blocks. However, since iron degrades transistor performance, its presence in semiconductor processing is generally undesirable, especially for front-end processes where the high-resolution capability of BCP lithography is most relevant.…”

Versatile and controlled functionalization of polyferrocenylsilane‐b‐polyvinylsiloxane block copolymers using a N‐hydroxysuccinimidyl ester strategy

“…The reaction was stirred at room temperature for 16 h, then precipitated three times into methanol and dried in vacuo to afford the pure BCP 4a (19 Figure S3). …”

“…14,15 Polyferrocenylsilane block copolymers have attracted widespread attention with respect to their self-assembly in the solid state to form metal-rich nanodomains. [16][17][18][19][20][21][22][23] In addition, solution self-assembly of BCPs containing a solvophobic poly(ferrocenyldimethylsilane) (PFS) block have also been well-studied and have been found to favour the formation of morphologies with low interfacial curvature such as cylinders and platelets due to core crystallization. [24][25][26] Significantly, the core termini of the micelles remain active to further growth on addition of further molecularly dissolved BCP.…”

Pattern transfer using block copolymers

“…This novel structure enables the fabrication of inorganic ring arrays after removal of PS and P2VP. Chuang et al [131] reported the formation of arrays of PFS domains with square symmetry after solvent annealing of thin films of polyisoprene-b-polystyrene-b-polyferrocenylsilane (PIb-PS-b-PFS) triblock copolymers with volume fractions of 25%, 65% and 10%, respectively, and a subsequent transfer of the PFS pattern to a silica substrate by using RIE ( figure 16). Moreover, the DSA of triblock copolymers was demonstrated by using e-beam patterned hydrogen silsesquioxane (HSQ) pillars [132].…”