The quality of HfO2 dielectric layers was systematically evaluated by using wet etching monitored by open-circuit potential analysis. Scanning electron microscopy imaging was used to observe changes in the topography after etching. The results showed that surface pre-treatment before high-k deposition, as well as post-deposition treatment, had an effect upon the quality of the high-k material; as seen from the etching behavior of these materials. Wet-etching defect monitoring was then used to improve the quality of the high-k films. As-deposited films could have a defect density of 109/cm2. However, after suitable post-deposition annealing, high-k layers with a reduced defect density could be obtained. A lower defect density could also be related to improved electrical properties of the high-k layer. The presence of defects was suggested to be due to crystallization effects and/or an O-deficient HfO2 film; as seen by Si/SiO up-diffusion during heat treatment.

Effect of Post-Deposition Annealing Conditions on Defect Density of HfO2 Layers Measured by Wet Etching. M.Claes, S.De Gendt, T.Witters, V.Kaushik, T.Conard, C.Zhao, Y.Manabe, A.Delabie, E.Rohr, J.Chen, W.Tsai, M.M.Heynsa: Journal of the Electrochemical Society, 2004, 151[11], F269-75