(Invited) Developments of ALD Processes: Experiments and Thermodynamic Evaluations

The most commonly use for gaseous precursors in CVD and ALD processes are organometallic molecules. These ones are generally thermally unstable at low temperatures (100 - 300{degree sign}C) and requires an understanding of its gas-phase chemical behavior. The thermal cracking of the gaseous precursor PDMAT has been studied by Mass Spectrometry. Ta[N(CH3)2]5(g), Ta[N(CH3)2]4(g), N(CH3)2(g) together with TaO[N(CH3)2]4(g) have been found to be the main molecules observed in the vapor phase originated from the PDMAT vaporization. The thermodynamic data of the O-free molecules have been evaluated from literature and statistical calculations. Comparison between experiments and thermodynamic simulations performed at different temperatures and pressures, evidenced kinetic limitations in the decomposition processes: ligand rupture and ligand decomposition. Furthermore, the experimental gas-phase study confirms the presence of oxygen containing molecules in the PDMAT cracking gaseous phase which explains the presence of oxygen in the deposited ALD TaN films. Thermodynamic simulations were also used to evaluate the use of hydrogen addition to the process.