Atomic Layer Deposition of Aluminum Phosphate Using AlMe3, PO(OMe)3, and O2 Plasma: Film Growth and Surface Reactions

High purity, uniform, and conformal aluminum phosphate (AlxPOy) thin films were deposited by atomic layer deposition (ALD) between 25 and 300 °C using super-cycles consisting of (i) PO(OMe)3 dosing combined with O2 plasma exposure and (ii) AlMe3 dosing followed by O2 plasma exposure. In situ spectroscopic ellipsometry and mass spectrometry were applied to demonstrate the ALD self-limiting behavior and to gain insight into the surface reactions during the precursor and co-reactant exposures, respectively. Compared to earlier reported AlxPOy ALD studies using H2O and O3 as co-reactants, the use of an oxygen plasma generally leads to higher growth per cycle values and promotes phosphorus incorporation in the film. Specifically, when using a 1:1 POx:Al2O3 cycle ratio and a substrate temperature of 150 °C, the growth per super-cycle is found to be 1.8 A. The [P]:[Al] atomic ratio for this process is approximately 0.5 (~ Al2PO6) and can be tailored by changing the ratio between the two cycles or the substrate t...