Crystallisation and tetragonal-monoclinic transformation in ZrO2 and HfO2 dielectric thin films

The crystallisation and the tetragonal-to-monoclinic phase transformation in ZrO2 and HfO2 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 degreesC, 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, HfO2 crystallises at a higher temperature than ZrO2. The phase composition of the crystallised films depends also on the material and film thickness. In ZrO2, the tetragonal phase is more stable than in HfO2. The t-m transformation during annealing has been observed.