AZO deposition

Aluminum‑doped zinc oxide (AZO) is a degenerate n‑type transparent conducting oxide that pairs high visible transparency with tunable electrical conductivity, offering an abundant, low‑cost, and non‑toxic alternative to ITO. It can be deposited by sputtering for scalable, large-area films and by atomic layer deposition (ALD) for conformal, ultra-uniform coatings at relatively low temperatures, which suits complex or temperature-sensitive substrates. AZO serves widely as a transparent electrode in photovoltaics, LEDs, displays, and touch panels, where it enables efficient light coupling while providing adequate sheet resistance. In optics and photonics, its carrier-driven refractive-index control and epsilon-near-zero behavior in the near-IR support plasmonics, compact modulators, waveguides, and tunable anti-reflective coatings. Beyond semiconductors and optics, AZO films are utilized in UV and gas sensors, SAW/acoustoelectronic devices, transparent heaters, low-emissivity and EMI-shielding coatings, and energy-saving window stacks. The material offers good thermal and mechanical robustness; when even lower resistance is needed, AZO is often paired with ultrathin metals in hybrid multilayers while retaining high transparency.

Atomic Layer deposition of AZO

Atomic Layer deposition of AZO is a well-known method, where high uniformity coverage (aspect ratio over 100) can be achieved.

ALD deposition of AZO

Sputtering of AZO

AZO can be deposited by RF, reactive RF, reactive DC, or reactive p-DC sputtering or atomic layer deposition (ALD). In the sputter deposition of AZO, an AZO target is used that may be RF-sputtered with or without adding additional oxygen, or reactively DC- or p-DC-sputtered. Elevated temperatures of 200 °C are typically employed. You can also co-deposit Al and ZnO, although it is usually not the most recommended approach. Note that in multipurpose sputter systems, such as ours, it may be challenging to achieve sufficiently low contamination for high-quality AZO. Contact Nanolab staff or your colleagues if you would like to locate a sputter system dedicated to AZO deposition.

In the chart below, you can compare the different deposition equipment available here at Nanolab:

	Sputter deposition Sputter-system Metal-Oxide(PC1)	Sputter deposition (Sputter-System(Lesker))	Atomic layer deposition (ALD Picosun R200)
General description	Reactive DC sputtering pulsed DC sputtering RF sputtering Reactive HiPIMS (high-power impulse magnetron sputtering)	Reactive DC sputtering RF sputtering	Atomic layer deposition of AZO
Pre-clean	RF Ar clean	RF Ar clean
Layer thickness	few nm to ? hundreds of nm*	10Å to 5000Å*	0 to 1000 Å
Deposition rate	Depending on process parameters.	Depending on process parameters, e.g., 0.3 Å/s reactive DC-sputtering (see process log for details)	Depending on temperature
Batch size	Many smaller samples Up to 10x4" or 6" wafers (Cassette load in the LL)	Pieces or 1x4" wafer or 1x6" wafer	Pieces or 1x4" wafer or 1x6" wafer or 1x8" wafer
Allowed materials	Almost any that do not outgas and are not very toxic See cross-contamination sheet	Silicon Silicon oxide Silicon nitride Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals Carbon	Silicon Silicon oxide, silicon nitride Quartz/fused silica Al, Al₂O₃ Ti, TiO₂ Other metals (use dedicated carrier wafer) III-V materials (use dedicated carrier wafer) Polymers (depending on the melting point/deposition temperature, use carrier wafer)
Comment	Uses 3" target Substrate rotation Substrate RF bias option	Uses 2" target Substrate rotation Substrate RF Bias (optional)

* For thicknesses above 200 nm permission is required. Write to thinfilm@nanolab.dtu.dk.