Equilibrium and metastable structures of Nickel/Silicon Dioxide/Silicon and Nickel/Silicon interfaces.

摘要

Solid-state dewetting occurs in thin continuous metal films when capillary instabilities drive the nucleation and growth of holes. Dewetting of thick (>100nm) metals films has extensively been studied and is well understood, however the dewetting of ultra-thin films is not well understood. Recent studies have shown that Ni films less than 5nm thick do not dewet at the same temperatures as thicker Ni films, however it is not well understood why. A fundamental understanding of the dewetting behavior of ultra-thin metal films has key relevance in applications such as catalysis and complimentary metal-oxide semiconductor (CMOS) transistors. Self-assembly of metal islands can be created through the solid-state dewetting of thin metal films on a support substrate. These metal islands are used as catalyst to grow arrays of nanotubes and nanowires. Solid-state dewetting degrades the functional properties of NiSi films, which are used as contacts to the source and drain in CMOS transistors. Once the transistors are processed above 650°C the NiSi film will agglomerate, degrading the contacts to the source and drain. Alloying NiSi with refractory metals increases the dewetting temperature to over 900°C. The effect of Pt on the NiSi/Si interface structure and how the interface structure changes the functional properties of the interface is not understood. In this thesis Transmission Electron Microscopy (TEM) and aberration corrected Scanning TEM (STEM) are used to study the interface structure of ultra-thin films. In-Situ annealing, inside the TEM is used to observe morphological changes in ultra-thin Ni films sputtered onto SiO2/Si substrates. A new Aduro Double tilt heating holder, made by Protochips Inc., is implemented for studying solid-state dewetting, in situ. The Aduro heating holder is based off a Microelectromechanical systems (MEMS) design, where ultra-fast and controlled heating rates are obtained by resistively heating a SiC membrane with a low thermal mass. Advantages and limitations of the Aduro holder, and how to overcome them, are discussed. STEM, TEM, and Electron Energy Loss Spectroscopy (EELS) are used to study the Ni/SiO2/Si interface structure before and after the Ni film has dewetted. Aberration corrected STEM and EELS are used to study the Ni1-xPtxSi /Si interface structure, and how the pre-silicide layer differs from the previously observed diffusion layer. The effect of the Ni1-xPtxSi /Si interface structure on the Schottky barrier height is then discussed based off of the measured Schottky barrier heights.