Atomic layer deposition of tin oxide films using tetrakis(dimethylamino) tin

The authors present a new method for preparing thin films of SnO2 by atomic layer deposition (ALD) using alternating exposures to tetrakis(dimethylamino) tin and hydrogen peroxide. This method avoids problems of corrosion and agglomeration associated with the halogenated compound, SnCl4. Tin oxide films were successfully deposited on a variety of substrates using deposition temperatures of 50–300°C at an average growth rate of 1.2Å∕cycle. They use in situ quartz crystal microbalance and quadrupole mass spectrometry measurements to explore the mechanism for SnO2 ALD. Scanning electron microscopy of SnO2 films deposited on Si(100) show that the SnO2 films are smooth, conformal, and nearly featureless, while atomic force microscopy yields a surface roughness of only 0.84nm for a film with a thickness of 92nm. X-ray diffraction reveals that the SnO2 films are amorphous. Films deposited on glass yielded a resistivity of ∼0.3Ωcm and an optical transmission of 94% for a film thickness of 140nm. X-ray photoelectron spectroscopy measurements were consistent with residual dimethylamine ligands remaining in the film at deposition temperatures below 150°C. This method allows, for the first time, low temperature (50°C) growth of SnO2 films by ALD. Additionally, they show that this process is suitable for conformally coating high aspect ratio anodic alumina membranes.