Nanofabricated Concentric Ring Structures by Templated Self-Assembly of a Diblock Copolymer

Abstract

The formation of well-controlled circular patterns on the nanoscale is important for the fabrication of a range of devices such as sensors, memories, lasers, transistors, and quantum devices. Concentric, smooth ring patterns with tunable dimensions have been formed from a cylinder-forming poly(styrene- b-dimethylsiloxane) (PS-PDMS) diblock copolymer under confinement in shallow circular trenches. The high etch selectivity between PS and PDMS facilitates pattern transfer, illustrated by the fabrication of arrays of ferromagnetic cobalt rings with a density of 1.1 x 10 (9)/cm (2). The effects of confinement diameter and commensurability on the diameter and period of the concentric rings are analyzed using a free energy model that includes interfacial, strain, and bending energies. This work provides a simple process for the fabrication of nanoscale circular patterns with very narrow line width using a much coarser-scale template, and may facilitate the miniaturization of a variety of microelectronic devices.

A Path to Ultranarrow Patterns Using Self-Assembled Lithography

“…Spin-coating a film of the block copolymer onto a smooth substrate, then solvent-annealing and etching [25][26][27] (see Supplementary Information for methods) yields oxidized PDMS cylinders with a natural period L o of $35 nm and with varying in-plane orientations as shown in Fig. 1.…”

“…The HSQ posts and native oxide on the silicon wafers were chemically functionalized with a brush layer of PDMS to ensure that the posts had an affinity for the PDMS block of the block copolymer and to improve annealing kinetics. Thin PDMS layers formed at the air and substrate interfaces 3,[25][26][27] .…”

“…The final complex patterns can then be transferred into metal using previously demonstrated techniques 27 . The major advantage of this templated self-assembly technique is that the post array requires much less time to write than the entire layout.…”

Enhancing the Potential of Block Copolymer Lithography with Polymer Self-Consistent Field Theory Simulations

“…4 We previously reported that poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymers with a large FloryHuggins interaction parameter can generate sub-15-nm wide patterns of 32-40 nm period with excellent long-range ordering and reliability. [12][13][14][15] Our prior work also showed that oxidized PDMS patterns obtained from the BCP can be used as a robust etch mask to pattern soft polymeric films such as a conducting polymer using an oxygen etch 15 and for patterning metal films into dot, ring, line, and antidot arrays. 16,17 (Figures S1 and S2 in the Supporting Information show another example of pattern transfer into a polymer resin.)…”

“…12-15 Our prior work also showed that oxidized PDMS patterns obtained from the BCP can be used as a robust etch mask to pattern soft polymeric films such as a conducting polymer using an oxygen etch 15 and for patterning metal films into dot, ring, line, and antidot arrays. 16,17 (Figures S1 and S2 in the Supporting Information show another example of pattern transfer into a polymer resin.) In this Letter, we demonstrate transfer of high-quality linear patterns into a variety of metals,…”