Sputtered Pt electrode structures with smoothly tapered edges by bi-layer resist lift-off

• Ti–Pt electrode structures were prepared using sputtering bi-layer-resist lift-off.
• Prepared lift-off electrodes can be used for good overgrowth of thin films.
• Ultra-smoothly tapered edges were controlled by the process parameters.
• Simulations using a geometric shadowing model confirm our experimental results.

A lift-off process using a bi-layer resist consisting of an image reversal resist on top and a lift-off resist at the bottom was used to structure Ti–Pt thin films. DC magnetron sputtered metal films patterned by this process show ultra smooth edges, ideal for applications such as interdigitated electrodes in resistive gas sensors including thin-film based sensitive coatings with thicknesses below 100 nm. Profiles of processed structures were analyzed by scanning electron microscopy and surface profilometer. The thickness profile and structure width were controlled by using different resist thicknesses and undercut lengths. Results were compared with iterative simulations by a geometric shadowing model, predicting undersputtering length and profile structure of the experimentally manufactured samples in good agreement. Target-to-substrate distance variation was found to have only a minor influence on the sputtering result.