Experimental investigation and CFD-based analysis of an ALD reactor depositing alumina from TMA and water

Numerous experiments of alumina deposition using trimethyl aluminum (TMA, Al(CH3)3) and water vapor (H2O) as precursors and argon as inert gas have been performed in a commercial Cambridge Nanotech® ALD reactor. As illustrated in Fig. 1, they show that even for established recipes, the thickness variation of the deposit reaches 2.5 to 3% on a 8’ silicon wafer substrate after 500 ALD cycles, and a clear influence of the reactor geometry appears, in particular for the loading door. The influence of the loading door is due to an argon flow inlet suggested as presumably optimized by the manufacturer of the machine. A three-dimensional Computational Fluid Dynamics (CFD) model is developed, in order to investigate the various phenomena involved and aiming at improving the deposit uniformity. The model comprises two sub-models: one for the precursor feeding system, to compensate for the lack of measurements of the reactants inlet flows into the reactor; the other for treating the reactant pulses of the ALD cycle in the reactor