Silicon Surface Passivation by Mixed Aluminum Precursors in Al2O3 Atomic Layer Deposition

Dimethylaluminum chloride (DMACl) is a cost-effective aluminium precursor alternative to conventional trimethylaluminium (TMA) for Atomic Layer Deposited (ALD) Al2O3. The DMACl water process shows better passivation after high temperature firing when compared with conventional TMA water process. However, after low-temperature post-anneal its passivation quality is slightly worse than with TMA. Here we show that a mixed use of TMA and DMACl precursors in the ALD process results in better surface passivation both after 400 °C post-anneal and after an 800 °C firing step. The high-quality passivation results from the low interface defect density and high negative charge at the surface. Specifically, we investigate the role of chlorine in the ALD Al2O3 passivation by varying the TMA and DMACl pulse proportions.