Effect of Process Parameters on Remote PEALD for HighlyTransparent ZnO Film Growth

From Precursor Chemistry to Gas Sensors: Plasma‐Enhanced Atomic Layer Deposition Process Engineering for Zinc Oxide Layers from a Nonpyrophoric Zinc Precursor for Gas Barrier and Sensor Applications

“…Above λ ≥ 580 nm, the transparency is even higher with transmittance ≥98%. These values are slightly better than for those reported for ZnO thin films deposited via PEALD at deposition temperatures below T dep = 100 °C, [ 34,41 ] confirming the high quality of our films. While the ZnO thin film has a high transparency in the visible spectrum, it shows a strong absorption band at λ = 350–380 nm which is known to be the characteristic band‐to‐band transition in ZnO.…”

“…Furthermore, DEZ was used in plasma‐enhanced (PE)ALD processes with oxygen or water plasma, especially for very low deposition temperatures down to room temperature. [ 40–47 ] ALD processes employing DEZ/water as precursors are predominantly described as “true” ALD processes in the individual publications, showing the typical ALD characteristics saturation, linearity and a defined ALD window. However, what is most striking from reported reviews is that the ALD window spreads over a broad range of possible ALD deposition temperatures (25–300 °C) and is, therefore, not as consistent as is often described.…”

Highly Tunable Electrical Properties in Undoped ZnO Grown by Plasma Enhanced Thermal-Atomic Layer Deposition

“…It should be noted that other PE-ALD studies of ZnO have typically found higher growth rates than those observed here, possibly due to the use of a “direct plasma”. ,, In the direct plasma configuration, the substrate rests on one of the electrodes used to create the plasma, often producing a plasma very near the growing film surface rather than remotely as in our process. Nevertheless, in some reports of PE-ALD ZnO using a remote plasma, the observed growth rate was also significantly higher. , This suggests exact reactor designs and growth conditions can lead to distinctions in ALD processes involving a plasma. As a further comparison, another ZnO thin film was deposited in which a 15 s O 2 plasma served as the initial oxidation, followed by the normal H 2 O pulse and purge after the plasma to complete the growth cycle.…”

“…Nevertheless, in some reports of PE-ALD ZnO using a remote plasma, the observed growth rate was also significantly higher. 15,30 This suggests exact reactor designs and growth conditions can lead to distinctions in ALD processes involving a plasma. As a further comparison, another ZnO thin film was deposited in which a 15 s O 2 plasma served as the initial oxidation, followed by the normal H 2 O pulse and purge after the plasma to complete the growth cycle.…”

The carbon and hydrogen contents in ALD-grown ZnO films define a narrow ALD temperature window

“…Kwon et.al. defined a higher ALD window for ZnO with temperature ranging from 150 to 200℃ [25], whilst Tapily et.al. and Illiberi et.al.…”