Using a slit doser to probe gas dynamics during Al2O3 atomic layer deposition and to fabricate laterally graded Al2O3 layers

A special slit doser is used to form near unit steps in the spatial profile of an Al2O3 ALD film thickness. The unit step is formed as the Al2O3 ALD occurs mainly downstream from the slit doser because the trimethylaluminum and H2O reactants are entrained in a viscous flow carrier gas. Spectroscopic ellipsometry measurements yielded thickness profiles of Al2O3 ALD on samples placed at different locations relative to the exit of the slit doser and the ALD growth zone. The effects of carrier gas flow rate, reactor pressure, and reactant dose and purge times on the Al2O3 ALD film profile provided details about the gas dynamics around the slit doser. Experimental indications of gas turbulence were observed at the exit of the slit doser. Lateral gradients in the Al2O3 ALD film thickness were also formed by linear translation of the sample relative to the slit doser during ALD. Lateral gradients of various desired pitches ranging from 119 Å/in to 444 Å/in were achieved as a result of accurate control of the Al2O3 ALD film thickness and small sample translation steps relative to the slit doser.