Twenty‐five nm features patterned with trilevel e‐beam resist

We describe a trilevel e‐beam resist process based on the high resolution resist PMMA. This process has been used to form metal features 25 nm wide on thick Si substrates by liftoff. Ni–Cr films patterned in this way have been used as masks for reactive ion etching of Si. The resulting structures were arrays of fins ∠ 30 nm wide and 330 nm high on 95 nm centers with a total length of 3 μm. We also discuss the resolution improvement obtained in a trilevel process based on a higher speed resist, P (MMA/MAA).