Reaction mechanism of a lanthanum precursor in liquid source metalorganic chemical vapor deposition

The reaction mechanism of a lanthanum precursor, tris(dipivaloylmethanato)lanthanum (La(DPM)3), was investigated in liquid source metalorganic chemical vapor deposition (MOCVD) of lanthanum oxide films. The behavior of La(DPM)3 in the gas phase was analyzed under actual CVD conditions by in situ infrared absorption spectroscopy. The infrared band identification was performed using density functional theory calculations. We confirmed that the liquid source delivery using tetrahydrofuran as a solvent supplies a La(DPM)3 molecule maintaining almost the whole molecular structure. The spectroscopic data on the gas-phase reactions were correlated with the characteristics of the deposited oxide films. The temperature dependence of the infrared absorption suggests that the thermal decomposition of La(DPM)3 in the gas phase may trigger the film deposition. La(DPM)3 was only partially decomposed in the gas phase under the actual deposition conditions, which indicates that surface reactions rather than gas-phase reactions control dominantly the film deposition.