Thermal Atomic Layer Deposition of Aluminum–Molybdenum Oxide Films Using Trimethylaluminum, Molybdenum Dichloride Dioxide and Water

Abstract

In the present work thermal atomic layer deposition (ALD) of aluminum-molybdenum oxide films (Al_xMo_yO_z) using trimethylaluminum (TMA, Al(CH₃)₃), molybdenum dichloride dioxide (MoO₂Cl₂) and water was studied. The possibility of ALD molybdenum oxide (MoO₃) film using MoO₂Cl₂ and water was also examined. The film growth process was studied in situ using a quartz crystal microbalance (QCM) technique and ex situ using various spectroscopic methods. ALD of Al_xMo_yO_z was carried out using supercycles consisting of TMA/H₂O and MoO₂Cl₂/H₂O subcycles. The subcycle ratios were 1 : 1 and 1 : 7, which are designated as 1Al1MoO and 1Al7MoO, respectively. At 150°C, film growth is linear with a growth rate of 5.39 and 7.62 Å per supercycle for 1Al1MoO and 1Al7MoO, respectively. The density of the films were 3.44 and 3.80 g/cm³ for 1Al1MoO and 1Al7MoO, respectively. The 1Al1MoO film with a thickness of 215.8 Å had a roughness of 10–12 Å, and the film obtained from the 1Al7MoO process with a thickness of 228.7 Å had a roughness of 16–18 Å. The synthesized thin films were characterized with XPS, XRR, SE, and XRD. The oxidation state of molybdenum in the Al_xMo_yO_z films is +6, +5, and +4. X-ray diffraction analysis showed that the films had an amorphous structure.