Crystallisation and Tetragonal-Monoclinic Transformation in ZrO_2 and HfO_2 Dielectric Thin Films

摘要

The crystallisation and the tetragonal-to-monoclinic phase transformation in ZrO_2 and HfO_2 thin films prepared by atomic layer chemical vapour deposition (ALCVD) are studied using high-temperature grazing-incidence X-ray diffraction (HT-XRD). These films are developed for applications as high-k dielectric gate in CMOS transistors. HT-XRD shows that all the tested samples have a crystallisation onset temperature below 600°C. The crystallisation onset temperature depends not only on the material, but also on the film thickness. The thinner a film is, the higher is the crystallisation onset temperature. For a film with the same thickness, HfO_2 crystallises at a higher temperature than ZrO_2. The phase composition of the crystallised films depends also on the material and film thickness. In ZrO_2, the tetragonal phase is more stable than in HfO_2. The t-m transformation during annealing has been observed.