Topographical surface patterning with block copolymer stamps

Abstract

We explore the potential of stamps of the block copolymer (BCP) polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP) for the parallel lithographic generation of topographic surface patterns taking advantage of the specific BCP properties. A first example includes additive surface manufacturing by decal transfer microcontact lithography with PS-b-P2VP breath figure (BF) arrays. Suppression of entanglements at the internal BCP domain interfaces and the BF array morphology facilitate rupture of the thinnest wall segments in the BF arrays. The uppermost PS-b-P2VP BF array layers with heights of nearly 1 µm thus remained attached to counterpart substrates. Treatment with solvents selective to PS or P2VP enabled wettability switching of thus-functionalized surfaces. A second example includes subtractive surface manufacturing. We deposited holey films or stripe patterns of the perfluorinated alkylphosphonic acid F21-DDPA on glass substrates using PS-b-P2VP stamps penetrated by spongy mesopore systems generated by swelling-induced pore formation. The use of spongy-mesoporous stamps allows carrying out succesive stamping steps without ink replenishment. Subsequently, we topographically patterned the glass substrates by etching the parts of the glass substrates not protected by F21-DDPA with hydrofluoric acid (HF) solution. Within certain limitations, shape, area and depth of the topographic patterns may be adjusted by the etching durations. Circular PS-b-P2VP films were selectively deposited into hexagonal microwells and subjected to swelling-induced pore formation. Moreover, F21-DDPA-patterned glass substrates can be used to template the dewetting of polystyrene (PS). Arrays of PS droplets obtained in this way were in turn used as etch resists to produce arrays of glass nanoneedles. Hence, BCP stamps may be exploited to produce topographically patterned surfaces with different architectures for wettability management or graphoepitaxy.