Annealing Effects on the Chemical Configuration of Uncapped and (Poly-Si)-Capped HfO x N y Films Deposited on Si(001)

We use spatially resolved spectroscopy in a scanning transmission electron microscope to study the thermal stability of the HfOxNy∕Si(001) system with and without an in situ capping layer of silicon. The films were deposited by metallorganic chemical vapor deposition using the amide precursor tetrakis(diethylamido)hafnium with NO as the oxidant. A SiOxNy interfacial layer (∼1.8nm) is observed at the HfOxNy∕substrate interface for films directly exposed to air. In addition, the N loss in the HfOxNy film for the uncapped sample is significant. In contrast, in situ capping is found to reduce the thickness of the interfacial layer and to keep the N content in the final dielectric film high. The capped HfOxNy films are quasi-amorphous, whereas uncapped films are polycrystalline following exposure to air. Oxinitridation at both interfaces is observed following a rapid thermal annealing process ( 900°C in N2 for 30s ) of the capped HfOxNy film. However, the interfacial layers remain thin (∼1nm) and a significant amount of N is present in the HfOxNy film. The rapid thermal annealing leads to the partial crystallization of the HfOxNy film and the Si capping layer. No Hf silicate is detected on a scale of ∼6Å in the electron energy loss spectroscopy analysis.