Oxidation thermal oxide

Sihcon dioxide layers can be formed using any of several techniques, including thermal oxidation of siUcon, wet anodization, CVD, or plasma oxidation. Thermal oxidation is the dominant procedure used in IC fabrication. The oxidation process selected depends on the thickness and properties of the desired oxide layer. Thin oxides are formed in dry oxygen, whereas thick (>0.5 jim) oxide layers are formed in a water vapor atmosphere (13). 

The performance of thermal oxidizers usually gives destruction efficiency greater than 98%. When designed to do so, destruction efficiency can be virtually 100% (depending on temperature, residence time and mixing in the thermal oxidizer). Thermal oxidizers can be designed to handle minor fluctuations but are not suitable for large fluctuations in flowrate. 

Gravity separation Centrifugal separation Filtration Membrane filtration Coalescence Centrifugal separation Flotation Wet oxidation Thermal oxidation Biological oxidation (aerobic, anaerobic, reed beds) Chemical oxidation Activated carbon Wet oxidation Thermal oxidation... 

The in situ nature of this treatment also minimizes potential exposure to humans and the environment. Ex situ options like excavation require repeated worker handhng of the contaminated soil and increased opportunity for volatilization of contaminants (leading to off-site contamination). The off-gas stream generated as part of the SPSH process can be treated using conventional off-gas treatment technologies such as catalytic oxidation, thermal oxidation, condensation, and granular activated carbon (GAC). 

Figure 5.21 Polish rate vs. a) pressure and b) velocity for BPSG oxide, thermal oxide, and PECVD oxide. (From Ref. (17).)...

Oxidative stability of edible oils depends primarily on their fatty acid composition and, to a lesser extent, in the stereospecific distribution of fatty acids in the triacyl-glycerol molecules. The presence of minor components in the oils also affects their oxidative stability. A detailed discussion of oxidative processes in fats and oils is provided elsewhere in this series. Oxidation may occur via different routes and includes autoxidation, photo-oxidation, thermal oxidation, and hydrolytic processes, all of which lead to production of undesirable flavor and products harmful to health. Flavor and odor defects may be detected by sensory analysis or by chemical and instrumental methods. However, chemical and instrumental procedures are often employed in the processing and during usage of edible oils. Indicators of oxidation are those that measure the primary or secondary products of oxidation as well as those from hydrolytic processes or from thermal oxidation, including polymers and polar components (15). 

Thermal oxidation of silicon can be achieved under dry or wet oxidation condition. In dry oxidation, oxygen is the oxidant whereas in wet oxidation, water molecule is the oxidant. Thermal oxidation is often carried out at elevated temperatures, such as 600-1250°C. The oxide growth rate is generally faster in wet oxidation compared to dry oxidation. Also, the growth rate of the oxide depends on the crystallographic orientation of the silicon, that is, the linear oxidation rate of silicon qualitatively is [110] > [111] > z[100]. However, crossover in growth rate is possible for instance, the oxide growth rate at 700-1000°C, [111] > [110], but not at 1100°C. 

Oxidizers. Thermal oxidizers rely on high temperature combustion of VOC/HAP species to reduce emissions levels. Although often expensive, they provide high destruction efficiencies, often >99.8%. Hence, they often prove a useful asset with high measurable return. 

Table 5.5.1 shows typical stress data for selected types of oxide. Thermal oxide layers are very stable in terms of stress, similar to TEOS-deposited oxides, and their stress is nearly uninfluenced by deposition parameters. However, depending on the deposition parameters, the stress in PECVD oxide can vary significantly as shown below. The reasons for the large variations in stress in PECVD oxides are manifold. 

Deposited oxide/thermal oxide composite Oxide charges comparable to thermal oxide [5,6]... 

With its high surface area and reactive Si-H and Si-Si moieties, porous Si is particularly susceptible to air, water, or chemical oxidation. Thermal oxidation is employed by the microelectronic industry to produce high-quality oxides on silicon, and this approach also works with porous Si. However, the extent of oxidation of a porous Si sample can be significantly greater than with flat silicon due to the small features in the porous nanostructure. For example, 1 nm of oxide on the surface of a flat Si wafer is considered a minor degree of oxidation, whereas 1 nm of oxide on a microporous Si sample that consists of 2 nm features is essentially completely oxidized. Thus it is important to know not only time and temperature but also feature size in the micro-, meso-, or macroporous structure to understand the oxidation process in porous Si (see chapters Oxidation of Macroporous Silicon, Oxidation of Mesoporous Silicon ). 

Thermal-oxidative Aging, see Aging, thermal-oxidative Thermal-oxidative Stabilization, see Antioxidants Thermogravimetric analysis 158 Thermoplastic elastomers 6... 

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