Self‐Assembled Nanoscale Ring Arrays from a Polystyrene‐b‐polyferrocenylsilane‐b‐poly(2‐vinylpyridine)Triblock Terpolymer Thin Film

Abstract

Block copolymers can microphase-separate into periodic nanoscale structures with well-defined geometries and length scales, making them attractive materials for self-assembled nanolithography. [1][2][3][4] Ordered arrays of block copolymer spheres, cylinders, or lamellae have been used to pattern features in functional materials with sizes of $10-50 nm. The fabrication of a range of devices, such as silicon capacitors and transistors, discrete magnetic storage media, and photonic crystals, [5][6][7][8] have been demonstrated using block copolymer lithography.Previous work has mainly focused on diblock copolymers, with the study of triblock or multiblock copolymers being less actively pursued, largely due to the increased level of synthetic difficulty. However, these materials offer a wider range of geometries than the line and dot patterns available from diblock copolymers, making them potentially valuable for nanolithography applications. In particular, triblock terpolymers can form ring shaped features, which are useful in the fabrication of memories or sensors, [9][10][11] and quantum devices. [12][13][14] Ring-shaped structures have been formed previously from thin films of core/shell structured linear ABC triblock terpolymers, [15][16][17] in which the cylinders are oriented perpendicular to the film plane during the anneal process. However, this work, as well as work on thin film triblock terpolymers of other morphologies, [18] has focused on materials in which all three blocks consist of organic segments. This can limit the utility of these materials in nanoscale lithography because the etch selectivity between the blocks, and their etch resistance for subsequent pattern transfer steps, is typically low. It is therefore interesting to examine thin film triblock terpolymers in which one of the blocks contains inorganic components which impart high etch selectivity and etch resistance.Triblock copolymers containing inorganic blocks such as polyphosphazenes, [19,20] polysilanes [21,22] and polysulfides [23] have been prepared previously. However, these are symmetrical ABA type triblock copolymers, which phase separate on the nanoscale into morphologies comparable to diblock copolymers.There have been several studies on bulk ABC triblock terpolymers with an inorganic polydimethylsiloxane (PDMS) block, [24][25][26] such as polyisoprene-b-polystyrene-b-poly(dimethyl siloxane) [24,25] and poly(ethyleneoxide)-b-poly(dimethyl siloxane)-b-poly(methyl oxazoline). [26] Polyferrocenylsilane (PFS) is a metal-containing polymer with iron and silicon in the polymer backbone.[27] Synthesis of PFS with controlled molecular weights and narrow polydispersities is achieved by a living anionic mechanism. [28,29] PFS has also been incorporated into multiblock copolymers with a variety of organic and inorganic coblocks. [28][29][30][31][32][33][34] These block copolymers microphase-separate to give ordered arrays of iron and silicon containing nanostructures, which have already been used in lithographic applications. [35][36][37]...

Polyferrocenylsilanes: synthesis, properties, and applications

“…Self-assembly of linear PFS triblock terpolymers to form phase-separated materials. 230 Thin films of a polyisoprene-block-polysyrene-block-polyferrocenylethylmethylsilane 201,204,279,280 By increasing the complexity of the system used, for example by using ABC triblock terpolymers or miktoarm star polymers, a host of previously unattainable morphologies become available with a diverse range of possible geometries and applications.…”

Strategies for Inorganic Incorporation using Neat Block Copolymer Thin Films for Etch Mask Function and Nanotechnological Application

“…In 2009, the synthesis and self-assembly of a new tri-BTP was described for developing nanoscale ring patterns. [ 205 ] After solvent vapor annealing of a PS-bpoly(ferrocenylsilane)-b -P2VP (PS-b -PFS-b -P2VP) BTP, a PS core and PFS shell in a P2VP matrix was developed. PFS, an iron and silicon containing moiety, is particularly useful as a BCP component due to its resistance to dry etching as detailed earlier.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…229 These are of particular interest in the fabrication of memories or sensors and in quantum devices. Spin-coating and annealing of the material gave a PS core/PFEMS shell cylinder morphology in a P2VP matrix perpendicular to the film substrate with a period of 50 nm, as shown in Figure 31.…”