Magnetic tunnel junctions (MTJs) are among the most promising building blocks for unconventional computing, offering non-volatile multi-state resistance with fast, low-energy switching [1]. Multi-level MTJs (M2TJs) can exhibit multiple discrete resistance states accessible via spin-orbit torques (SOTs), making them attractive for neuromorphic and multi-level magnetic memory applications [2]. Realizing this potential at 150mm wafer-scale requires precise fabrication of sub-micron lateral pillar dimensions, while defining in the same level micro-scale electrode structures for electrical integration — a dual-scale patterning challenge that conventional, time-consuming single-tool electron beam (e-beam) nanolithography addresses inefficiently.

We present an intra-level mix-and-match (ILM&M) UV/e-beam lithographic approach using a negative-tone resist, to resolve the severe writing-time bottleneck in combined nano and micro-features patterning in 150mm wafers. The ILM&M strategy — combining two exposure technologies on the same resist layer followed by a single development step, thereby reducing process steps and total exposure time [3,4,5] — exploits the dual sensitivity of the negative-tone novolac resists AR-N 7520.18 and AR-N 7520.17 (AllResist GmbH) to both ultraviolet (UV) light and e-beam. Within a single lithographic level, e-beam lithography (RAITH150, ~30 nm resolution) writes the nanoscale elliptical M2TJ pillars — where nanopattern fidelity is important as shape anisotropy controls the multi-state switching field distribution — while UV lithography (Karl Suss MA/BA6, hard-contact mode at λ = 365 nm, ~1 µm resolution) defines the micron-scale protection pads required for subsequent ion beam etching of the multi-layer stack. As our e-beam lithography of the full pattern was already optimized for these resists, UV lithography process was systematically optimized for AR-N 7520.17 and AR-N 7520.18 resists at 500 and 200 nm thicknesses, in 150mm silicon wafers, using an in-house fabricated hard mask. UV exposure dose and development conditions were optimized based on pattern fidelity, sidewalls profile and resist thickness. Optimal UV conditions of 20s exposure and 150s development were identified for 500nm AR-N 7520.17, yielding well-defined structures down to 1 µm with a retained resist thickness of ~490 nm.

By offloading the large-area pad patterning from e-beam to UV lithography within the same resist layer, the e-beam bottleneck is confined exclusively to the critical nanoscale features, reducing the total lithographic exposure time for a full 150-mm wafer by more than an order of magnitude compared to an all e-beam approach. This optimized ILM&M methodology using AR-N 7520.17 resist establishes a scalable, high-throughput framework for the prototyping of multi-state spintronic components beyond the throughput limits of single-tool e-beam nanofabrication.