Atomic layer deposition of noble metals: Exploration of the low limit of the deposition temperature

摘要

The low limit of the deposition temperature for atomic layer deposition (ALD) of noble metals has been studied. Two approaches were taken; using pure oxygen instead of air and using a noble metal starting surface instead of A1_2O_3. Platinum thin films were obtained by ALD from MeCpPtMe_3 and pure oxygen at deposition temperature as low as 200 deg C, which is significantly lower than the low-temperature limit of 300 deg C previously reported for the platinum ALD process in which air was used as the oxygen source. The platinum films grown in this study had smooth surfaces, adhered well to the substrate, and had low impurity contents. ALD of ruthenium, on the other hand, took place at lower deposition temperatures on an iridium seed layer than on an A1_2O_3 layer. On iridium surface, ruthenium films were obtained from RuCp_2 and oxygen at 225 deg C and from Ru(thd)_3 and oxygen at 250 deg C, whereas no films were obtained on A1_2O_3 at temperatures lower than 275 and 325 deg C, respectively. The crystal orientation of the ruthenium films was found to depend on the precursor. ALD of palladium from a palladium delta-ketoiminate precursor and oxygen at 250 and 275 deg C was also studied. However, the film-growth rate did not saturate to a constant level when the precursor pulse times were increased.