Topcoat‐Assisted Perpendicular and Straightly Parallel Coexisting Orientations of Block Copolymer Films

Abstract

Highly ordered perpendicular orientation and straightly parallel orientation coexisting polystyrene-block-polydimethylsiloxane (PS-b-PDMS) cylindrical microdomains with 10 nm width can be realized by using polyvinyl acetate as a partially dewetted topcoat and solvent annealing with acetone vapor. During solvent annealing, the swelled topcoat begins to dewet and the dewetting rim sweeps the surface of the block copolymer films to align the cylindrical microdomains with the direction of dewetting propagation. However, the wetted region of the topcoat/PS-b-PDMS film forms with a perpendicular orientation due to reduced surface tension and sufficient concentration gradient in the solvent evaporation step. The orientational changes (perpendicular/straightly parallel orientation) in the dewetted/wetted area are also investigated according to the vapor pressure of solvent annealing. The degree of directionality of the swept PS-b-PDMS films according to the distance from the dewetting front, which is equivalent with time after sweeping, is examined. To control the direction of dewetting and complex structures within a specific area, an imprinting process is introduced to form topographical line-space patterns in the topcoat and perpendicular/parallel orientation of BCP patterns in the line-space patterns, respectively.

In situ GISAXS study of a Si-containing block copolymer under solvent vapor annealing: Effects of molecular weight and solvent vapor composition

“…The perpendicular cylinder orientation was assumed to be caused by the solvent concentration gradient during swelling. 6,[47][48][49] Between 2 min and 15 min, the fraction of in-plane cylinders increased from 8% to 80% for Process (i), and from 8% to 90% for Process (ii), and remained at that value throughout the anneal. During drying there was a slight decrease of the fraction of in-plane cylinders.…”

Technological strategies for self-assembly of PS-b-PDMS in cylindrical sub-10 nm nanostructures for lithographic applications

“…For Wsc [86], Microwave [85], PdMs pad [88], and idsA [87] M n = 16 (kg mol −1 ). For svA [64,77,83,84,89], the M n = 16 (kg mol −1 ) and 28 (kg mol −1 ). The resulting cylindrical PdMs nanostructures is comparable for all the annealing methods, around 8-9 nm.…”

“…[82]. Top-view seM images of cylindrical Ps-b-PdMs obtained by means of (c) 4 h of svA at room temperature, adapted from [64], (d) 15 min of svA with PvA topcoat at room temperature, adapted from [83], and (e) 5 min of svA at 85 °c in trances, adapted from [77].…”

“…Jeong et al obtained highly ordered sub-10 nm cylindrical nanostructures in only 15 min by static SVA performed at room temperature in acetone vapor, exploiting the dewetting property of a poly(vinyl alcohol) PVA topcoat deposited onto the PS-b-PDMS film, [83] (Figure 5(d)). Conversely, Park et al introduced a preheating step of the chamber to speed up the kinetic of the ordering process.…”

Rapid shear alignment of sub-10 nm cylinder-forming block copolymer films based on thermal expansion mismatch

“…Shear can also be produced by swelling a top PDMS pad with solvent vapor [19,20,28,29] or by scanning a laser to locally heat substrates or PDMS top coats [18,30]-in both cases, the expansion/contraction of the PDMS or substrate translates a shear stress to the adjacent BCP film. Other reports have observed shear-induced alignment during: viscous flow of BCP films [31,32], specifically during nanoimprint lithography [33]; dewetting of a top coat poly(vinyl alcohol) pad [34,35]; or scanned zone heating [16,17,36]. Chaikin et al have investigated shear alignment extensively via rheological measurements for both sphere and cylinder forming BCPs [11-13, 22, 24-27, 37, 38].…”