Novel Hf and La Formamidinates for ALD Application

Abstract

HfO2 is a promising dielectric for alternative high-k gate dielectrics and DRAM capacitor applications because of its high dielectric constant, excellent thermal stability and compatibility with Si processing. Particularly atomic layer deposition (ALD) is suitable as a deposition tool for gate dielectrics as well as capacitor dielectrics due to its excellent conformity and precise thickness control. In order to achieve ideal ALD performance, it is critical to have appropriate precursors. In order to achieve ideal ALD performance, it is critical to use appropriate enabling precursors. So far, Tetrakisethylmethylamidohafnium (TEMAHf) has been considered as one of the most promising precursors due to its good physical properties. However, this precursor has relatively low thermal stability, which has often become a drawback to ALD process for HfO2. To circumvent the decomposition issues of TEMAHf during ALD deposition, often low process temperatures have been used that lead to less dense films and high level of carbon contamination. In order to overcome these challenges, the novel hafnium formamidinate (Hf-FAMD) precursor is developed as an alternate Hf source at Dow Electronic Materials. Following our success with formamidinate platform in previously reported novel lanthanum formamidinate (La-FAMD) source, this new precursor also exhibits high thermal stability and high reactivity towards water and ozone. In this work, we report, for the first time, comparative studies with TEMAHf and novel Hf-FAMD source, e.g. Hf-FAMD exhibits acceptable vapor pressure (> 0.1 Torr at 100 °C) similar to that of TEMAHf, and higher thermal stability than TEMAHf, thus leading to high quality ALD films. We also present the crystal structure of La-FAMD, elucidated by X-Ray Crystallography, and physical properties of novel Hf-FAMD relevant to ALD.