Structure and thermal stability of MOCVD ZrO2 films on Si (1 0 0)

The structure and thermal stability of ZrO2 films grown on Si (100) substrates by metalorganic chemical vapor deposition have been studied by high-resolution transmission electron microscopy, selected area electron diffraction and X-ray energy dispersive spectroscopy. As-deposited films consist of tetragonal ZrO2 nanocrystallites and an amorphous Zr silicate interfacial layer. After annealing at 850°C, some monoclinic phase is formed, and the grain size is increased. Annealing a ∼6nm thick film at 850°C in O2 revealed that the growth of the interfacial layer is at the expense of the ZrO2 layer. In a 3.0nm thick Zr silicate interfacial layer, there is a 0.9nm Zr-free SiO2 region right above the Si substrate. These observations suggest that oxygen reacted with the Si substrate to grow SiO2, and SiO2 reacted with ZrO2 to form a Zr silicate interfacial layer during the deposition and annealing. Oxygen diffusion through the tetragonal ZrO2 phase was found to be relatively easier than through the monoclinic phase.