Interfacial properties of thin film hetero-structure: copper-oxides of hafnium-silicon
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This dissertation focuses on the properties of Cu / high-k oxide and high-k / Si (100) interfaces using surface analysis tools such as X-ray photoelectron spectroscopy (XPS), low-energy ion scattering (LEIS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). In the first study, the growth and thermal annealing of Cu on HfO2 surface were investigated using physical vapor deposition (PVD), in-situ XPS, in-situ LEIS, and ex-situ TEM. Growth of Cu on HfO2 at 300 K involves initial formation of three-dimensional clusters without Cu oxidation. After thermal annealing at 673 K for 10 min, the Cu cluster size increases but there was no diffusion of Cu into the HfO2 layer. STEM shows uniform Cu clusters (~11 nm diameter) after thermal annealing. The uniformity was attributed to self-limiting growth. In the second study, the growth and thermal annealing of Cu on HfSiO4 were studied using PVD, in-situ XPS, in-situ LEIS, and ex-situ AFM. Like Cu/HfO2, the growth mode of Cu on HfSiO4 at 300 K is three-dimensional. Using a CO2 laser, the change of Cu morphology was monitored during thermal annealing by LEIS. During thermal annealing, Cu cluster size increased by combining small ones and Cu may diffuse into HfSiO4 layer, although we do not have any evidence for the latter. AFM images of annealed samples show uniform diameter of Cu clusters. In the third study, various compositions of hafnium silicide and hafnium silicate were formed on a Cu substrate, and the growth and thermal annealing of HfO2 on Si (100) were studied using PVD, in-situ XPS and in-situ LEIS. At 300 K, there is no evidence for the formation of hafnium silicide at the interface between HfO2 and Si (100). At 823 K, HfO2 is thermodynamically stable upon contact with nonstoichiometric silicon oxide.