Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

Abstract

We report a method for the directed self-assembly (DSA) of block copolymers (BCPs) in which a first BCP film deploys homopolymer brushes, or “inks”, that sequentially graft onto the substrate’s surface via the interpenetration of polymer molecules during the thermal annealing of the polymer film on top of existing polymer brushes. By selecting polymer “inks” with the desired chemistry and appropriate relative molecular weights, it is possible to use brush interpenetration as a powerful technique to generate self-registered chemical contrast patterns at the same frequency as that of the domains of the BCP. The result is a process with a higher tolerance to dimensional and chemical imperfections in the guiding patterns, which we showcase by implementing DSA using homopolymer brushes for the guiding features as opposed to more robust cross-linkable mats. We find that the use of “inks” does not compromise the line width roughness, and the quality of the DSA as a lithographic mask is verified by implementing a robust “dry lift-off” pattern transfer.

Nanopatterned Monolayers of Bioinspired, Sequence-Defined Polypeptoid Brushes for Semiconductor/Bio Interfaces

“…The compatibility with lithographic patterning of the polypeptoid brush monolayers is an important attribute of this class of bioinspired, sequence-defined polymers as surface modification materials as it will enable the generation of chemical contrast nanopatterns by design with monomer-level control. The lithographic patterning workflow adopted in this study follows a typical strategy of patterning surface modification layers on Si substrates. ,,, As shown in Figure a, it involves the following steps: (i) spin coating an ∼40 nm PMMA resist on top of the polypeptoid brush monolayer for electron-beam lithography, with a subsequent development step; (ii) reactive ion etching with oxygen plasma to transfer the pattern of the PMMA resist layer into the underlying polypeptoid brush monolayer; (iii) stripping the PMMA resist and reannealing the polypeptoid brush to obtain a nanopatterned polypeptoid brush monolayer on Si substrates. AFM height profiles show that the generated line-space patterns are well-defined with sharp edges and reveal that the polypeptoid brush monolayers are ∼1 nm in thickness (Figure b).…”

“…Generation of robust, well-defined chemical contrast patterns at desired resolution is of critical importance for applications such as biological assays for sensing and diagnostics, , surfaces for cell adhesion and growth, , directed self-assembly of block copolymers, ,,, and site-specific immobilization of nanoscale objects such as DNA origami nanostructures and gold nanoparticles. ,− In particular, leveraging different polymer brushes to modify the corresponding lithographically defined regions is a common strategy to generate chemical contrast nanopatterns, where the effects from potential brush interpenetration could be minimized by molecular weight engineering per specific application requirements. − With a sequence-defined polymer brush platform, the parameter space of chemical contrast nanopatterns can be further expanded with precise, monomer-level engineering of the chemical functionalities.…”

Revealing the Kinetic Phase Behavior of Block Copolymer Complexes Using Solvent Vapor Absorption–Desorption Isotherms

“…The self-assembly of block copolymers (BCPs) has been widely studied 1 as a templating material for a plethora of nanotechnological applications such as nanomembranes, 2 nanolithography, 3,4 and nanocomposites. 5,6 The self-assembly of BCPs occurs from the microphase separation of chemically incompatible blocks.…”

“…The self-assembly of block copolymers (BCPs) has been widely studied as a templating material for a plethora of nanotechnological applications such as nanomembranes, nanolithography, , and nanocomposites. , The self-assembly of BCPs occurs from the microphase separation of chemically incompatible blocks . The BCP adopts lattice structures that minimize the interfacial area between blocks and maximize the conformational entropy of the polymer chains.…”

Processive Pathways to Metastability in Block Copolymer Thin Films

“…There is no doubt that current BCP architectures are incomparable to biopolymers (i.e., proteins and DNA), however, they provide the necessary building blocks for us to comprehend (and appreciate) the complexity and hierarchical nature of the molecular machines. From inception as surfactants [ 1 ] research in BCPs have evolved into more advanced areas, including battery electrolyte membranes [ 2 , 3 ], advanced lithography [ 2 , 4 , 5 , 6 , 7 ], nanocomposites [ 8 , 9 , 10 , 11 ], ion-exchange membranes [ 12 , 13 ], nanopore templates [ 14 ], and patterned surfaces [ 15 , 16 ].…”