Comparison of hafnium oxide films grown by atomic layer deposition from iodide and chloride precursors

Stoichiometric HfO2 films were atomic layer deposited from HfI4 and HfCl4 at 300 deg. C on p-Si(1 0 0) substrates. Water was in both cases used as an oxygen precursor. The films consisted dominantly of monoclinic HfO2 phase. Additional tetragonal HfO2 could be detected only in the films grown from HfCl4. Effective permittivities were frequency-independent and varied in the range of 12-14, without clear dependence on the precursor used. Oxide rechargeable trap densities were relatively high for the films grown from HfCl4. The films grown from HfI4 were more resistant against breakdown. The films grown from either precursor contained 0.4 at.% of halide residues and 1.0-1.5 at.% hydrogen. Annealing in forming gas at 400 deg. C did not affect the film composition. The growth rate was somewhat more stable in the HfI4 based process