Combined ultraviolet- and electron-beam lithography with Micro-Resist-Technology GmbH ma-N1400 resist

Abstract

We present a “mix-and-match” process to create large structures with submicrometer features by combining UV contact lithography and 100 kV electron-beam lithography in a single layer of negative-tone resist: Micro-Resist-Technology ma-N1405. The resist is successfully applied for the fabrication of an on-chip terahertz spectrometer, where the design requires 450 nm wide lines and 300 nm wide trenches in a 150 nm thick niobium-titanium-nitride layer, tolerating errors of [Formula: see text] nm. We use a resist thickness of 500 nm, optimized to allow reliable SF[Formula: see text]/O[Formula: see text]-based reactive ion etching of structures with 30 nm accuracy. We find that resist requires an electron-beam cross-linking dose of 1100 [Formula: see text] for an acceleration voltage of 100 kV in combination with a 180 s 100 [Formula: see text]C bake on a hot plate and 45 s development. The smallest resist bars made with our dedicated recipe are 100 nm wide, with the smallest gaps about 300 nm. The difference between the designed and realized feature size is between 2 and 30 nm for structures up to 700 nm wide. The optical exposure dose is 300 [Formula: see text] for the same development time and is optimized to produce a positive sloped edge profile allowing good step coverage for subsequent layers. The resist can be applied, shipped, and processed in a time span of a couple of days without notable deterioration of patterning quality.