Comparison between thermal and plasma enhanced atomic layer deposition processes for the growth of HfO2 dielectric layers

In this work, hafnium oxide (HfO2) thin films have been grown on (0 0 1)Si substrates by two different Atomic Layer Deposition (ALD) methods, namely thermal and plasma-enhanced modes. Films have been deposited using tetrakis-dimethylamino hafnium as metal precursor, while water vapor was used as an oxygen reactant in the case of the thermal ALD (T-ALD) process, and oxygen plasma was used as oxidant during the plasma enhanced ALD (PE-ALD) process. A systematic study by varying the deposition temperature (200 °C <= Tdep <= 300 °C) and number of cycles (i.e. film thickness in the 10-100 nm range) has been carried out for both ALD methods, and the influence on their physical properties has been evaluated. In particular, the comparison of the growth rates and refractive indexes has been carried out by spectroscopic ellipsometry. All the collected results provided data to identify the best suited deposition process.