Nanoscale rings from silicon-containing triblock terpolymers.

Nanoscopic ring arrays of various materials show promise for both technological applications and fundamental studies. In this work we report the preparation of sub-50 nm diameter ring arrays from metallic thin films using a block polymer lithographic pattern transfer approach. We prepared a triblock terpolymer that adopts a core-shell cylindrical morphology where the shell is an oxidizable polydimethylsiloxane block. Solvent annealed thin films of this terpolymer produce cylindrical features oriented perpendicular to the substrate surface. The polydimethylsiloxane shell is then converted into SiOx rings by an oxygen reactive ion etch. The resultant hard mask pattern is then transferred into Au, Ni80Fe20, and Ni80Cr20 thin films via Ar ion beam milling, demonstrating the generality of the approach.

Non-lift-off block copolymer lithography of 25 nm magnetic nanodot arrays.

Although nanolithographic techniques based on self-assembled block copolymer templates offer tremendous potential for fabrication of large-area nanostructure arrays, significant difficulties arise with both the lift-off and etch processes typically used for pattern transfer. These become progressively more important in the limit of extreme feature sizes. The few techniques that have been developed to avoid these issues are quite complex. Here, we demonstrate successful execution of a nanolithographic process based on solvent annealed, cylinder-forming, easily degradable, polystyrene-b-polylactide block copolymer films that completely avoids lift-off in addition to the most challenging aspects of etching. We report a "Damascene-type" process that overfills the polystyrene template with magnetic metal, employs ion beam milling to planarize the metal surface down to the underlying polystyrene template, then exploits the large etch rate contrast between polystyrene and typical metals to generate pattern reversal of the original template into the magnetic metal. The process is demonstrated via formation of a large-area array of 25 nm diameter ferromagnetic Ni(80)Fe(20) nanodots with hexagonally close-packed order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation. We argue that the approach is generalizable to a wide variety of materials, is scalable to smaller feature sizes, and critically, minimizes etch damage, thus preserving the essential functionality of the patterned material.

Polylactide-poly(dimethylsiloxane)-polylactide triblock copolymers as multifunctional materials for nanolithographic applications.

Highly immiscible block copolymers are attractive materials for applications in nanolithography due to their ability to self-assemble on length scales that are difficult to access by conventional lithography. The incorporation of inorganic domains into such block copolymers provides etch contrast that can potentially reduce processing times and costs in nanolithographic applications. We explored thin films of polylactide-poly(dimethylsiloxane)-polylactide (PLA-PDMS-PLA) triblock copolymers as multifunctional nanolithographic templates. We demonstrate the formation of well-ordered arrays of hexagonally packed PDMS cylinders oriented normal to the substrate, the orthogonal etchability of these cylinders and the PLA matrix, and the formation of etch-resistant domains that can be used as pattern transfer masks.