Dynamic Film Composition Transition Phenomena in the Copper Oxide Metal Organic Chemical Vapor Deposition (MOCVD) Studied by Scanning Electron Microscopy (Sem)

Abstract

ABSTRACTIn this report, the impact of deposition temperature variation on the evolution of film morphology and microstructure was studied. In the copper oxide metal organic chemical vapor deposition (MOCVD) process, a temperature gradient was created on the substrate surface. By using a specific design of the heating susceptor, the local temperature of the leading edge (upstream) on the substrate surface was maintained at 70°C lower than the temperature of the ending (downstream) edge. The evolution of local composition and microstructure in deposited films were analyzed by X-ray diffraction (XRD), transmission Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and SEM. From XPS and XRD results, Cu2O rich phase was deposited at the low temperature area, while CuO rich phase was deposited at the high temperature area. These two areas were divided by a phase intermixing (transition) zone of 40–100 ums wide. The temperature of this abrupt Cu2O->CuO deposition product transition was determined to be 390°C -400°C. As indicated by SEM results, the low temperature favorite Cu2O continuous phase, collapsed into coarse grains (with the scale of 10 urn) first, then became fine grains among channels of CuO phase, and finally diminished into the high temperature favorite CuO continuous phase. Spatially resolved XPS results also indicated that the film composition changed abruptly through the transition zone. A nucleation-growth competition mechanism, between the Cu2O rich phase and the CuO rich phase, was suggested to occur in this zone. In this model, this dynamic deposition product transition is interpreted by the temperature dependency of nucleation rates for the specific CuO phase or Cu2O phase.