Comparative In Situ Study of the Initial Growth Trends of Atomic Layer-Deposited Al2O3 Films

In this work, we compare the initial growth trends of atomic layer-deposited aluminum oxide (Al2O3) using three different Al precursors and H2Oasthe oxygen source on hydroxyl-terminated silicon (Si-OH) and hydrogen-terminated silicon (Si-H) surfaces. Trimethylaluminum (TMA), triethylaluminum(TEA), and dimethylaluminum chloride (DMAC) are chosen as the Al precursorsdue to comparable variations between their structures. Thickness evolutionobtained fromin situellipsometry exhibits similar behavior for all three precursorswith initially accelerated growth during thefirst cycle on the Si-OH startingsurface, which then proceeds in a steady manner characteristic of atomic layerdeposition (ALD).In situFourier transform infrared spectroscopy (FTIR) showsthat at 200 degrees C both TEA and TMA react with above 85% of-OH ligands presenton the initial Si-OH substrate and the subsequent H2O dose reacts with only similar to 50% of the surface C-H groups, indicating incomplete removal of the methyl or ethyl ligands on the surface. Al2O3growth on theSi-H surface exhibits a delay due to the lack of surface hydroxyl groups, leading to formation of Si-Me or Si-Et groups. A lowerreactivity of DMAC compared to TMA and TEA results in a lower initial selectivity fraction. The results provide vital insight into theimportance of precursor selection for area-selective ALD applications and open a pathway for realizing selective Al2O3depositionbased on inherent substrate selectivity