Oxidation processing of electronic materials

To date. Si is still the backbone of the modem semiconductor industry. Its dominant role is the result of its fundamental advantages over its competitors (i) availability in a wide variety of sizes and shapes (ii) mature material preparation and property control (iii) native oxide films on its surface and (iv) compatibility to planar integrated circuit technology. In 2004 a grand total of about 4,000,000m of polished Si wafers was produced, equivalent to about 1.25 xlO 200 mm wafers. This gives us a rough idea how big the industry is. 

Si02 films could be applied onto the Si surface with many techniques to fulfil the surface electronic passivation purpose. However, a comparison of the different ways to prepare Si02 on Si (CVD, PVD and thermal oxidation) 

Si02 films with different thicknesses are produced by oxidation (dry or wet) for different applications. Thick oxide films (0.1 to 1 pm), normally grown by wet oxidation, are used for device isolation and as masking layers thin oxide layers ( lOOnm) are finding applications as gate dielectrics, flash memory tunnel oxides and dynamic random access memory (DRAM) capacitor oxides. For reasons of space, only the literature on the fabrication of ultra-thin oxide films and the oxidation behaviour of low-dimensional Si nanostructures will be summarized in this chapter. Detailed discussions on the oxidation mechanisms and modelling of Si oxidation have been the subject of several excellent reviews [20-26]. 

Oxidation at low temperatures is another way to synthesize thin or ultra-thin Si02 films since it can reduce the interface thickness and achieve a more precise process. However, in this case the oxidation process becomes too slow. Recently, it has been shown that oxidation of Si at low temperatures ( 500°C) could be enhanced by UV or vacuum UV (VUV) radiation [40,46-49]. It was believed that if the photons released by the lamp have a higher energy than the bond energy of O2,02 will be readily dissociated to generate excited state oxygen atoms which can react with Si to form Si02 at low temperatures. Tinoco etal. employed plasma oxidation to produce ultra-thin 

The deformation of oxide scale is also related to the temperature. At higher temperatures, the oxide can have a greater viscous relaxation, leading to a reduced stress for the same radius of curvature. This stress-related self-limiting oxidation can be used to prepare Si nanowires down to 5 nm in diameter with high reproducibility. 

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This is a preliminary approach to the use of a new generation of solid-state sensors based on the capacity of the sensor element to catalyze the photodegradation of various kinds of organic compounds and to recognize their structure on the basis of the type of process catalyzed. The electron holes present in the Ti02 structure are able to promote the oxidative process of substances present in the environment, in particular the ones easily adsorbed on it. Titanium dioxide is a well-known photocatalyst [5-13]. Less famous are its characteristics as sensor material [14-18] of the ability of the organic molecules to be completely degraded, that is mineralized. 

Electrode processes are a class of heterogeneous chemical reaction that involves the transfer of charge across the interface between a solid and an adjacent solution phase, either in equilibrium or under partial or total kinetic control. A simple type of electrode reaction involves electron transfer between an inert metal electrode and an ion or molecule in solution. Oxidation of an electroactive species corresponds to the transfer of electrons from the solution phase to the electrode (anodic), whereas electron transfer in the opposite direction results in the reduction of the species (cathodic). Electron transfer is only possible when the electroactive material is within molecular distances of the electrode surface thus for a simple electrode reaction involving solution species of the fonn... 

The electrons undergo the equivalent of a partial oxidation process ia a dark reaction to a positive potential of +0.4 V, and Photosystem I then raises the potential of the electrons to as high as —0.7 V. Under normal photosynthesis conditions, these electrons reduce tryphosphopyridine-nucleotide (TPN) to TPNH, which reduces carbon dioxide to organic plant material. In the biophotolysis of water, these electrons are diverted from carbon dioxide to a microbial hydrogenase for reduction of protons to hydrogen ... 

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