Electrical enhancement and higher-k engineering in ultra-thin atomic layer deposited Hf_1-xAl_xO_y films

Abstract

We have successfully deposited Hf1-xAlxOy with Al/(Al+Hf)% ranging from 0 to 25% using an atomic layer deposition (ALD) process which incorporates a sequential metal precursor pulse method. The dielectric crystal phase was confirmed to be a mixed phase of tetragonal and monoclinic using a combination of synchrotron measurement techniques consisting of grazing incidence X-ray diffraction, and grazing incidence extended X-ray absorption fine structure. The crystallization temperature as a function of Al incorporation was assessed by synchrotron X-ray diffraction with in-situ ramp annealing. In metal-oxide-semiconductor (MOS) capacitors we observed an equivalent oxide thickness (EOT) reduction of ∼2 Å compared to HfO2 for Hf1-xAlxOy with Al/(Al+Hf)% ≤ 6% annealed near the crystallization temperature of the Hf1-xAlxOy films. In addition, the leakage current was also reduced by a factor of 10 while maintaining a flatband voltage that is comparable to post deposition annealed (PDA) HfO2 films processed under identical conditions. This study highlights the importance of understanding the crystallization temperature and its relationship to electrical performance for higher-k phase stabilized Hf1-xAlxOy films.