Evolution of crystallographic ordering in Hf1-xAlxOy high-k dielectric deposited by atomic layer deposition

The evolution of the morphology and of the crystallographic ordering of hafnium aluminates deposited by atomic layer deposition has been investigated. Annealing at temperatures as high as 900 °C in N2 or O2 atmosphere is found to promote crystallization of the high-k layer, together with the growth of an interfacial low-k oxide. The crystallographic phase has been identified by indexation of transmission electron microscopy selected area diffraction patterns and by Rietveld refinement of grazing incidence x-ray diffractograms. The high k is found to crystallize in an orthorhombic ternary Hf12xAlxO2 phase even for an Al content as high as x50.74. The temperature of crystallization is higher for the Al-richer alloy. The thickness and the electronic density of the interfacial layer are evaluated by combining cross-sectional transmission electron microscopy and x-ray reflectivity analysis