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

Abstract

We use spatially resolved spectroscopy in a scanning transmissionelectron microscope to study the thermal stability of the HfOxNy/Si(001)system with and without an in situ capping layer of silicon. The filmswere deposited by metallorganic chemical vapor deposition using theamide precursor tetrakis(diethylamido)hafnium with NO as the oxidant. ASiOxNy interfacial layer (similar to 1.8 nm) is observed at theHfOxNy/substrate interface for films directly exposed to air. Inaddition, the N loss in the HfOxNy film for the uncapped sample issignificant. In contrast, in situ capping is found to reduce thethickness of the interfacial layer and to keep the N content in thefinal 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 thermalannealing process (900 degrees C in N-2 for 30 s) of the capped HfOxNyfilm. However, the interfacial layers remain thin (similar to 1 nm) anda significant amount of N is present in the HfOxNy film. The rapidthermal annealing leads to the partial crystallization of the HfOxNyfilm and the Si capping layer. No Hf silicate is detected on a scale ofsimilar to 6 angstrom the electron energy loss spectroscopy analysis.(c) 2005 The Electrochemical Society. All rights reserved.