Metal and organic nanostructure fabrication by electron beam lithography and dry liftoff

Liftoff and direct etch are the two most popular pattern transfer methods used for nanofabrication. The latter is limited by the etching rate selectivity between the resist and the substrate material, which is usually on the order of unity for dry plasma etching. Moreover, some metals including most noble metals cannot be dry etched. Thus liftoff is often the preferred pattern transfer method. Liftoff is typically carried out using a solvent that dissolves the resist. A strong solvent aided by ultrasonic agitation and/or heating is sometimes needed if the resist is difficult to dissolve due to, for example, cross-linking by exposure to electron beam or plasma. Another serious issue with conventional liftoff process is that the metal debris may stay at the active device area after drying. To avoid the above issues, dry liftoff using mechanical approach may be utilized. Here we report a simple dry liftoff technique using a scotch tape to peel off the resist film coated with the material to lift off. We obtained high resolution (down to 50 nm) liftoff of metal and organic materials polystyrene and Alq3, with PMMA as electron beam resist coated on a substrate treated with a low energy surfactant.