Preventing Plasma-Induced Resist Hardening in Molybdenum Disulfide Transistors via Sacrificial Metal Mask Lithography

Achieving the theoretical performance of 2D molybdenum disulfide (MoS₂) electronics is currently bottlenecked by interfacial contamination derived from lithographic processing. A critical, yet often overlooked, mechanism is the interaction between photoresist (PR) and plasma, which chemically alters the interface. In this work, we elucidate the atomistic origin of this degradation: theoretical calculations based on molecular dynamics (MD) and density functional theory (DFT) reveal that plasma exposure functionalizes the PR with oxygen, drastically increasing its adsorption energy on the MoS₂ surface from -1.15 to -2.36 eV. This doubling of adsorption energy creates thermodynamically stable, hardened residues that resist conventional removal methods. To overcome this fundamental limitation, we introduce a universal prevention-first strategy: Sacrificial Metal Mask Lithography. By utilizing a sacrificial layer to physically isolate the channel, we shield the MoS₂ from reactive plasma species, preventing the formation of hardened residue entirely. This strategy results in a ten-fold reduction in contact resistance (R_C) from 2.59 × 10⁶ Ω·µm to 2.58 × 10⁵ Ω·µm and an order-of-magnitude enhancement in on-current. Crucially, we demonstrate the universality of this method by successfully applying it to top-gated transistor arrays, electron-beam lithography (EBL), and atomic layer deposition (ALD)-synthesized films.