Photopatternable Interfaces for Block Copolymer Lithography

Abstract

Directly photopatternable interfaces are introduced that facilitate two-dimensional spatial control of block copolymer (BCP) orientation in thin films. Copolymers containing an acid labile monomer were synthesized, formulated with a photoacid generator (PAG), and coated to create grafted surface treatments (GSTs). These as-cast GST films are either inherently neutral or preferential (but not both) to lamella-forming poly(styrene-block-trimethylsilylstyrene) (PS-b-PTMSS). Subsequent contact printing and baking produced GSTs with submicron chemically patterned gratings. The catalytic reaction of the photoacid generated in the UV-exposed regions of the GSTs changed the interfacial interactions between the BCP and the GST in one of two ways: from neutral to preferential (“N2P”) or preferential to neutral (“P2N”). When PS-b-PTMSS was thermally annealed between a chemically patterned GST and a top coat, alternating regions of perpendicular and parallel BCP lamellae were formed.

Interfacial Layers with Photoswitching Surface Energy for Block Copolymer Alignment and Directed Self-Assembly

“…Alternating areas of parallel and perpendicular domains, 200 nm in width, were observed. The interface between perpendicular domains and parallel domains are much sharper than previously reported because the exposure tool is much more sophisticated [17]. The fact that the areas are well defined is encouraging for device patterning applications.…”

“…The photopatternable interfaces were fully characterized in previous work [17]. Characterization of the top coats can be found in other manuscripts [7,8].…”

“…Samples were prepared by grafting the photopatternable polymers to the surface of a silicon wafer previously modified with aminopropyltriethoxysilane (APTES) and the methods were the same as previously reported [17] except for the following modifications: During the underlayer grafting procedure, each polymer film contained 10 wt% triphenylsulfonium nonaflate (relative to the polymer mass). Samples were exposed with a dose of approximately 1-5 mJ/cm 2 .…”

Spatial arrangement of block copolymer nanopatterns using a photoactive homopolymer substrate

“…The resulting self-assembled nanostructures have been applied in a range of areas including in nanolithography, 2 electronic devices 7 and biomaterials. 6,8 In particular, owing to the ability to form sub-20 nm nanopatterns, [9][10][11][12][13][14][15] block copolymer selfassembly has emerged as a viable alternative approach to conventional photolithography with high potential for gaining industrial relevance. Compared to other high resolution lithography techniques such as extreme ultraviolet 16 and electron beam lithography, 17 block copolymer lithography has advantages of potentially high throughput and low cost, and has become one of the most important alternative next-generation lithography techniques.…”

Orthogonally Spin-Coated Bilayer Films for Photochemical Immobilization and Patterning of Sub-10-Nanometer Polymer Monolayers

“…35,36 Spatial control of surface energy by grafted polymers is critical to controlling microdomain orientation and alignment over multiple length scales, which is a requirement of very specific potential end uses like surface plasmonics, 20,37,38 microprocessor transistors, 39 and hard-disk memory. 31,40 Due to processing considerations, poly(styrene-block-methyl methacrylate) (PS-b-PMMA) is a model material for block copolymer lithography, and it is produced commercially at pilot scale for this application. 41 Therefore, we chose PS homopolymer, PMMA homopolymer, and the copolymers thereof to study as overlayers immobilized by grafting to PSSMA.…”