Device Fabrication Using Block Copolymer Lithography

Block copolymers can be used to make a variety of functional electronic or magnetic devices. We have developed pattern transfer processes to produce metal, silicon, oxide, or polymer patterns using a mask made from a PS-PDMS (polystyrene-polydimethylsiloxane) block copolymer.

Metal films are patterned using a “damacene” process in which a metal film is deposited over a pattern made from the oxidized PDMS microdomains. Reactive ion etching planarizes and slowly removes the metal until the oxidized PDMS is exposed. The oxidized PDMS etches much faster than the metal, and termination of the etch process at this point leaves a metal pattern that is the reverse contrast of the block copolymer pattern. This process has been used to make magnetic nanostructures such as dot, line, and antidot arrays, as well as narrow metallization lines.

We have also deposited films of block copolymers on top of materials such as conductive polymers or graphene, and then used the block copolymer pattern as an etch mask to form structures such as arrays of conducting polymer nanowires or graphene nanoribbons. Other pattern transfer includes the formation of high aspect silicon nanowires by catalytic etching of a Si wafer using a BCP-patterned gold catalyst and the formation of inverted pyramid arrays by anisotropic etching of silicon through a block copolymer mask.