Thermal stability of atomic-layer-deposited HfO2 thin films on the SiNx-passivated Si substrate

HfO2 thin films were deposited on SiNx-passivated Si wafers at 300 and 400 degreesC using an atomic-layer-deposition technique. The SiNx films were deposited by another atomic-layer-deposition process at 595 degreesC. The SiNx films worked well as barriers to both Si and O diffusion, resulting in a small decrease in the capacitance density even after post-annealing at temperatures up to 1000 degreesC, compared either to the HfO2 film deposited directly on Si or an Al2O3-barrier-layer/Si substrate. The decrease in the capacitance density after post-annealing, although relatively small, was due to Hf and O diffusion into the interface layer. Interestingly, post-annealing under an atmosphere containing small amount of oxygen (similar to1%) decreased the capacitance density to a smaller degree. However, the interface and bulk capturing of the carrier was serious, resulting in a rather large hysteresis (similar to100 mV) voltage in the capacitance-voltage measurements even after post-annealing. (C) 2002 American Institute of Physics.