Thermal oxide growth kinetics

This completes our development of the thick-film parabolic growth law. This particular theory has been presented in some detail because it is an extremely important domain of metal oxidation. In addition, it provides an excellent example of the way the coupled-currents approach [10,11] can be used to obtain oxide growth kinetics and built-in voltages in thermal oxidation. 

Supported model catalysts are frequently prepared by thermally evaporating metal atoms onto a planar oxide surface in UHV. The morphology and growth of supported metal clusters depend on a number of factors such as substrate morphology, the deposition rate, and the surface temperature. For a controlled synthesis of supported model catalysts, it is necessary to monitor the growth kinetics of supported metal... 

There are many types of silicon oxides such as thermal oxide, CVD oxide, native oxide, and anodized oxide. Only native oxide and anodic oxide are directly relevant in the context of this book. Anodic oxide film, which is involved in most of the electrochemical processes on silicon electrodes, has not been systematically understood, partly due to its lack of application in mainstream electronic device fabrication, and partly due to the great diversity of conditions under which anodic oxide can be formed. On the other hand, thermal oxide, due to its importance in silicon technology, has been investigated in extremely fine detail. This chapter will cover some aspects of thermal oxide such as growth kinetics and physical, electrical, and chemical properties. The data on anodic oxide will then be described relative to those of thermal oxide. 

While the thermal oxidation of a compact metal surface is usually limited to the growth of an oxide layer with a thickness of a few of nanometers, bulk metal nanostmctures can be fully converted into the corresponding oxide or chalcogenide. Again the relative diffusion rate of metal atoms and the oxidation agent in the oxide determine the oxidation kinetics and structure formation. A topographic transformation to a metal oxide nanostructure is observed when the mobility of the oxidation agent exceeds the one of the metal atoms. When this is not the case, the so-called nanoscale Kirkendall effect (NKE) responsible for the formation of sophisticated hollow nanostructures, such as nanospheres, nanotubes, and nanopeapods, proceeds [2-5]. 

Nuclear reaction analysis has mostly been applied to problems in material science, where the use of isotopically enriched compounds allows the profile of a specific element to be targeted by ion beam reactions with its isotopes. For example, in the thermal oxidation of silicon, the growth kinetics and diffusion of oxygen across the Si/Si02 interface region has been studied using sequential oxidations in natural and 0 enriched oxygen gas. The differentiation between possible pathways is due to the isotopic specificity of the NRA technique. 

Thermal oxidation is a common technique to manipulate macropore shape and realize a variety of novel structures in silicon. The stress and deformation induced by such oxidation, kinetics of oxide growth, and its anisotropy are reviewed. Uniform arrays of both silicon and silica microstructures such as needles and tubules have been realized via thermal oxidation. 

For the anodic growth of films under high-field conditions in an electrolyte such as purified boric acid ( 0 logarithmic kinetics common to those for dry oxidation in the temperature range below 300°C are observed. At temperatures between 300 " and 425 "C thermal oxidation of aluminum obeys classic parabolic-diffusion-controlled kinetics ... 

Zinc acetylacetonate [Zn(acac)2] has also been used by several groups as the source for zinc in thermal MOCVD [212-219]. The only kinetic investigation was carried out by Kamata et al. [218] and their results are listed in Table 3-11. They found an unusual behavior of the deposition rate with respect to the substrate temperature. The growth rate is constant in the temperature range of 400-550 °C, then increases rapidly from about 120 to 220 nm/min and remains constant above 600 °C. They explain the abrupt increase by a vigorous oxidation reaction on the substrate. Another explanation could be the transition from surface to gas phase reaction. 

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