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

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Abstract
Achieving the theoretical performance of 2D molybdenum disulfide (MoS 2 ) 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 MoS 2 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 MoS 2 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 × 10 6 Ω·µm to 2.58 × 10 5 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.

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