A chemical mechanism for nitrogen incorporation into HfO2 ALD films using ammonia and alkylamide as precursors

An atomistic mechanism for the incorporation of nitrogen into HfO2 ALD films grown using Hf[N(CH3)2]4 and NH3 was investigated using density functional theory. We find a ligand-exchange mechanism similar to those thought to occur in the ALD of other metal oxide films. Both half-reactions form intermediates that are more stable than the products, have larger barriers than for reaction between H2O and Hf[N(CH3)2]x∗ and will thus be significantly slower at ALD temperatures. Therefore water must be purged from the chamber when depositing Hf nitrides or incorporating N into HfO2 using this chemistry. These results indicate that NH3 and Hf[N(CH3)2]4 can be used to either incorporate N into HfO2 ALD films or grow hafnium nitride.