Effect of different ALD Al2O3 oxidants on the surface passivation of black silicon

We study how different oxidants in atomic layer deposition of aluminium oxide (ALD Al2O3) affect the surface passivation of black silicon. Here we show that processes using ozone cause higher fixed charge but surprisingly lead to lower lifetimes in black silicon samples as compared to water-based samples. In planar samples however, the best surface passivation is reached with O3-based processes. In case of water as oxidant, the planar wafers suffer from severe blistering and poorer surface passivation, while this seems to be the best process for black silicon. To find a reason for the lifetime differences we also study different Al2O3 stacks where both H2O and O3 are used as oxidants. In conclusion, surface texture seems to affect the optimal oxidant in the ALD process.