Graphoepitaxial Directed Self‐Assembly of Polystyrene‐Block‐Polydimethylsiloxane Block Copolymer on Substrates Functionalized with Hexamethyldisilazane to Fabricate Nanoscale Silicon Patterns

Abstract

In block copolymer (BCP) nanolithography, microphase separated polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) thin films are particularly attractive as they can form small features and the two blocks can be readily differentiated during pattern transfer. However, PS‐b‐PDMS is challenging because the chemical differences in the blocks can result in poor surface‐wetting, poor pattern orientation control and structural instabilities. Usually the interfacial energies at substrate surface are engineered with the use of a hydroxyl‐terminated polydimethylsiloxane (PDMS‐OH) homopolymer brush. Herein, we report a facile, rapid and tuneable molecular functionalization approach using hexamethyldisilazane (HMDS). The work is applied to both planar and topographically patterned substrates and investigation of graphoepitaxial methods for directed self‐assembly and long‐range translational alignment of BCP domains is reported. The hexagonally arranged in‐plane and out‐of‐plane PDMS cylinders structures formed by microphase separation were successfully used as on‐chip etch masks for pattern transfer to the underlying silicon substrate. The molecular approach developed here affords significant advantages when compared to the more usual PDMS‐OH brushes used.

Aligned silicon nanofins via the directed self-assembly of PS-b-P4VP block copolymer and metal oxide enhanced pattern transfer

“…These systems extend the work on PS-block-polydimethylsiloxane (PSb-PDMS, χ = 0.26) which combines both high χ and the presence of a Si backbone that enhances etch contrast and facile pattern transfer when used as an on-chip etch mask. 21,22 Other notable commercially available high χ BCP materials for etch mask applications include poly-2-vinylpyridine (P2VP)b-PDMS (χ ∼ 1.06), 23 PS-b-P2VP (χ ∼ 0.18) 24 and PS-b-PLA (χ ∼ 0.23). [25][26][27] However to date, successful pattern transfer for high χ BCPs (other than PS-b-PDMS) 22,28 has been limited.…”

“…21,22 Other notable commercially available high χ BCP materials for etch mask applications include poly-2-vinylpyridine (P2VP)b-PDMS (χ ∼ 1.06), 23 PS-b-P2VP (χ ∼ 0.18) 24 and PS-b-PLA (χ ∼ 0.23). [25][26][27] However to date, successful pattern transfer for high χ BCPs (other than PS-b-PDMS) 22,28 has been limited. PS-b-PVP BCPs may be particularly attractive for nanolithography due to their high χ and a reactive PVP group that can enable inclusion of etch contrast agents.…”

Self-Assembled Nanofeatures in Complex Three-Dimensional Topographies via Nanoimprint and Block Copolymer Lithography Methods

“…To date, DSA demonstration has primarily used either topographical (graphoepitaxy) or chemical (chemoepitaxy) prepatterns to guide BCP features. − More recently, synergistic approaches that combine NIL and BCP lithography have shown significant promise for DSA. Here, the guiding topography is created using reusable NIL stamps to replicate features.…”

Solvent Vapor Annealing of Block Copolymers in Confined Topographies: Commensurability Considerations for Nanolithography

“…BCP self‐assembly can be directed via prepatterned chemical patterns (chemoepitaxy) or using topographical patterns (graphoepitaxy) . Graphoepitaxy has been exploited in many BCP systems such as PS‐ b ‐PMMA (PS‐ b ‐polymethyl methacrylate), PS‐ b ‐PDMS (PS‐ b ‐polydimethylsiloxane), and PS‐ b ‐PVP . DSA of BCP thin films through both thermal annealing and solvent vapor annealing (SVA) has been studied extensively and attention is being given to the selective removal of block components or the inclusion of etch contrast agents to facilitate pattern transfer …”