Investigation of the defect density in ultra-thin Al2O3 films grown using atomic layer deposition

The film perfection in terms of pinhole defect densities of ultra-thin Al2O3 grown by atomic layer deposition (ALD) has been quantitatively characterized. A significant defect density reduction from ~ 1.2 × 105/cm2 to ~ 90/cm2 was demonstrated for 2 nm-thick Al2O3 by using an ALD tungsten (W) buffer layer on the nickel (Ni) substrate. The reason for the defect reduction was attributed to efficient nucleation of ALD Al2O3 on ALD W. The effect of the buffer layer becomes less essential as the Al2O3 thickness increases, where the substrate surface physical conditions such as particle contamination become the main cause for defects.