Composition and bonding structure of plasma-assisted ALD Al2O3 films

A systematic study on the composition and bonding structure of plasma-assisted ALD Al2O3 films deposited at substrate temperatures between 25 and 400 °C is presented. The composition of the films is determined with Rutherford back scattering (RBS) and elastic recoil detection (ERD). The O/Al atom ratio in the films changes from 2.0 to 1.5 and the mass density increases from 2.6 to 3.1 g/cm3 when increasing the substrate temperature. The hydrogen content decreases with substrate temperature from 13 at.% at 50 °C to less than 1 at.% at 400 °C. Fourier transform infrared spectroscopy shows that the H atoms are predominantly bonded to O atoms, and that the H atoms are effectively removed after annealing at 400 °C. Depth resolved XPS measurements reveal that the atomic concentrations remains constant after annealing. The O1s and Al2p XPS peak positions show that film has different bonding structure at the interface. compared to the bulk. After annealing the bulk of the film shows indications of relaxation whereas the interface is unchanged

Atomic layer deposition (ALD) for crystalline Si photovoltaics: surface passivation by Al2O3

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