Specific Process Knowledge/Thin film deposition/Deposition of Tungsten Nitride

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Tungsten Nitride (WN_x)

Tungsten nitride (WNₓ, commonly W₂N or δ‑WN) is a refractory ceramic that combines very high melting temperature, extreme hardness, chemical inertness, and good electrical conductivity in a composition‑tunable, CMOS‑compatible matrix. Thin films are produced chiefly by reactive magnetron sputtering, where nitrogen flow and substrate temperature set stoichiometry and phase, yielding dense layers with controllable resistivity and stress. In semiconductor process flows, WNₓ acts as a robust Cu diffusion barrier/liner, hard mask, gate or contact material, and precision thin‑film resistor; its high absorption coefficient also makes it the standard absorber layer in EUV lithography photomasks and a candidate for x‑ray mask blanks. Optically, WN-based stacks offer durable, high-temperature plasmonic and thermally emissive coatings, mid-IR absorbers, and multilayer structures for soft-x-ray mirrors and synchrotron beamline optics, delivering stability far beyond noble metals under extreme photon flux. Beyond electronics and photonics, the material’s wear and oxidation resistance support MEMS springs, high‑temperature sensors, and corrosion‑resistant coatings, while select WN phases become superconducting below roughly 3–5 K, enabling niche low‑loss microwave resonators and detector elements that benefit from its mechanical robustness and diffusion‑barrier capability.

Deposition of Tungsten Nitride

Deposition of WN_x can only be done by reactive sputtering using W target.

The tool of choice for this application is the Cluster-based multi-chamber high vacuum sputtering deposition system, commonly referred to as the "Cluster Lesker." The operating process is described in detail.:

• Deposition of Tungsten Nitride (WN) using reactive sputtering in Sputter-System Metal-Nitride(PC3) Source 2 (3-inch target)

At the moment (July 2025) we have a 3-inch W target (0.125" thick, bonded to Cu) for PC3 or PC1.

Comparison of sputter systems for reactive deposition

	Sputter-System Metal-Nitride(PC3)	Lesker sputter system
Generel description	reactive DC/Pulsed DC reactive HIPIMS (high-power impulse magnetron sputtering)	reactive DC sputtering (not tested)
Stoichiometry	Tunable	Tunable
Film thickness	Limited by process time. Deposition rate (0.2 nm/s) is likely faster than Sputter-System (Lesker)	Limited by process time. Deposition rate unknown
Process temperature	Up to 600 °C	Up to 400 °C (Room temperature from 2021)
Step coverage	Some step coverage possible	Some step coverage possible but amount unknown
Film quality	Deposition on one side of the substrate Properties including tunable stoichiometry (requires process development)	Deposition on one side of the substrate Unknown quality Likely O-contamination
Batch size	Many smaller samples Up to 10*100 mm or 150 mm wafers	Several smaller samples 1-several 50 mm wafers 1*100 mm wafers 1*150 mm wafer
Allowed materials	Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets	Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets