Development of an intra-level mix-and-match lithography process using negative-tone photoresist AR-N 4400-10 S4 to combine i-line stepper and electron beam exposure

We present an approach to combine EBL and i-line wafer stepper exposure in a single resist layer, without the need for intermediate development steps. The chemically amplified negative tone photoresist AR-N 4400-10 S4 by Allresist GmbH is sensitive to both UV light and electron beam exposure, which is prerequisite to perform an intra-level mix-and-match (ILM&M) process. This approach takes advantage of the key benefits of both exposure strategies, EBL’s extreme resolution and the high throughput of a wafer stepper, while reducing the number of processing steps and time. To find an overlapping process window, at first both exposure types have been analyzed independently. The resist was spun on at 4000 rpm, resulting in a thickness of 480 nm. Studies with varying exposure doses, post-exposure bakes (PEB) and developments were conducted consecutively for i-line stepper and electron beam exposure. Analysis of these experiments yielded a set of process parameters suitable for an ILM&M approach: e-Beam exposure doses of <80 μC/cm² and i-line doses of around 100 mJ/cm², followed by a PEB at 100 °C for 120 s and subsequent development in a 2:1 diluted solution of AR 300-44 and deionized, resulted in good quality resist structures on the wafer.