Tungsten (W)

Tungsten (W) is a refractory metal with the highest melting point of any element, remarkable density, hardness, and outstanding resistance to radiation and corrosion, making it indispensable in semiconductor, optical, and harsh‑environment technologies. Thin films are produced primarily by magnetron sputtering or e-beam evaporation, yielding dense, low-resistivity body-centered-cubic α-W when pressure, substrate temperature, and energy are adequately controlled. Within semiconductor process flows, α‑W serves as a robust diffusion‑barrier/liner, gate or contact metal, and reliable via/plug fill for logic, memory, and power devices operating at elevated temperatures. In optics, the metal’s high atomic number and thermal stability underpin multilayer W/Si or W/C stacks used in X‑ray mirrors—such as Göbel mirrors, Kirkpatrick–Baez optics, synchrotron beamline monochromators, and space‑borne telescope coatings—delivering high reflectivity and power‑handling in the soft-to-hard-X-ray range. α‑W also supports high‑temperature plasmonic and thermally emissive coatings, mid‑IR absorbers, and durable metamaterial surfaces that endure far greater power densities than noble metals. Beyond electronics and photonics, tungsten’s mechanical strength and radiation tolerance enable MEMS springs, X‑ray/EUV shielding, high‑temperature sensors, and dense protective components; moreover, α‑W becomes superconducting at millikelvin temperatures, allowing niche low‑loss microwave resonators and detector elements where extreme stability is required.

Tungsten deposition

Tungsten (W) can be deposited by e-beam evaporation and sputtering. However, in the case of evaporation, the process generates a lot of heat, so it is not easy to deposit films much thicker than 50-60 nm. Sputtering can be used without any particular issues. In the chart below, you can compare the deposition equipment.

Evaporation of W

E-beam evaporation of Tungsten in the Temescal

Sputtering of W

	E-beam evaporation (Temescal)	Sputter-system (Lesker)	Sputter deposition ((Sputter-system Metal-Oxide (PC1) and Sputter-system Metal-Nitride (PC3)) )	Sputter coater (Sputter coater 03)
General description	E-beam evaporation of W	DC Sputtering of W	DC and HiPIMS Sputtering of W	DC Sputtering of W
Pre-clean	Ar ion beam	None	RF bias on a substrate	None
Layer thickness	10Å to 20nm*	10Å to 600nm	10Å to 600nm	10Å to 250nm
Deposition rate	0.5 Å/s to 1 Å/s	about 1 Å/s	about 1 Å/s	configuration dependent
Batch size	Up to 4x6" wafers Up to 3x8" wafers (ask for holder) small pieces	Up to 1x4" wafers Up to 1x6" wafer small pieces	Up to 10x4" wafers Up to 10x6" wafer small pieces	Up to 1x4" wafers small pieces
Allowed materials	Silicon Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals
Comments	Substrate gets hot during deposition (for a 60 nm film it rose above 123 C) Wait for low base pressure before start (3-5 10^-7 Torr)	Deposition rate is 0.107 nm/s for 150W and 3mTorr (Src3, DC)	Deposition rate is 0.124 nm/s for 140W and 3mTorr (PC3, Src3 DC), (0.04 nm/s using HiPIMS - PC3, Src3)	Note! Bad uniformity. Deposition rate is 0.03 nm/s using big glass chamber. Deposition rate is 0.2-0.9 nm/s (current dependent) using small glass chamber.

* For thicknesses above 20 nm talk to staff (write to thinfilm@nanolab.dtu.dk), as the heat and subsequent pressure rise means the deposition needs to be carried out in steps.