Oxides silicon

The processing sequence for silicon dioxide (SiOi) depends on its specific use. For example, silica for use as inter-metallization insulation the order is deposition, densi-fication by annealing, and etching to the correct configuration. CVD processes for Si02 films can be characterized by chemical reaction type, the growth pressure, or deposition temperature. The choice of route is often dictated by requirements of the thermal stability of the substrate or the conformality. Table 5-4 summarizes selected 

Ikble 5-3. Physical properties of common metal-organic precursor sources for CVD of dielectric materials. 

Compound Formula M.p.t. [°C] B.p.t. [°C] Oxygen sensitivity Vapor pressure Comments 

The most widely used method for Si02 thin film CVD is the oxidation of silane (SiH4), first developed in 1967 for APCVD [13]. Nonetheless, LPCVD systems have since become increasingly employed [14, 15], and exceptionally high growth rates (30000 Amin ) have been obtained by the use of rapid thermal CVD [16]. 

The chemical reaction for Si02 deposition from SiH4 is shown in Eq. 5.1, however, some water is formed at high oxygen partial pressures (Eq. 5.2). 

Dechlorination of chlorofluorocarbons adsorbed to dry desert sand has been reported by Bahadir et al. (1978). As much as 71% of adsorbed CCI2F2 was observed to react in this system. No input of external heat or light energy was required. Sunlight has also been observed to promote oxidation of organic matter in the presence of sand or silica gel (see Section 6.E.3a). The mechanisms of these reactions 

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Thin oxide films may be prepared by substrate oxidation or by vapour deposition onto a suitable substrate. An example of the fomrer method is the preparation of silicon oxide thin-films by oxidation of a silicon wafer. In general, however, the thickness and stoichiometry of a film prepared by this method are difficult to control. 

Figure C2.4.11. The fonnation of SAMs from OTS on a silicon oxide substrate.

Sellaite, see Magnesium fluoride Senarmontite, see Antimony(III) oxide Siderite, see Iron(II) carbonate Siderotil, see Iron(II) sulfate 5-water Silica, see Silicon dioxide Silicotungstic acid, see Silicon oxide—tungsten oxide—water (1/12/26)... 

Sillimanite, see Aluminum silicon oxide (1/1) Smithsonite, see Zinc carbonate Soda ash, see Sodium carbonate Spelter, see Zinc metal Sphalerite, see Zinc sulflde Spherocobaltite, see Cobalt(II) carbonate Spinel, see Magnesium aluminate(2—)... 

Zircon is synthesized by heating a mixture of zirconium oxide and silicon oxide to 1500°C for several hours (163). The corresponding hafnium silicate, hafnon, has been synthesized also. Zircon can be dissociated into the respective oxides by heating above 1540°C and rapidly quenching to prevent recombination. Commercially, this is done bypassing closely sized zircon through a streaming arc plasma (38). 

Figure 4 SFM image of an integrated circuit (a) and close-up of silicon oxide on its surface (b).

Anhydrous hydrogen fluoride and hydrofluoric acid react with substances containing silica and silicon oxide to form silicon tetrafluoridc and fluorosilic acid. SiF, a colorless gas at ambient temperature, is liighly toxic. An equilibrium mixture of SiF in the presence of moisture also contains hydrogen fluoride and hydrofluoric acid. 

This test indicates the amount of metallic constituents in a crude oil. The ash left after completely burning an oil sample usually consists of stable metallic salts, metal oxides, and silicon oxide. The ash could be further analyzed for individual elements using spectroscopic techniques. 

Conventional electronic devices are made on silicon wafers. The fabrication of a silicon MISFET starts with the diffusion (or implantation) of the source and drain, followed by the growing of the insulating layer, usually thermally grown silicon oxide, and ends with the deposition of the metal electrodes. In TFTs, the semiconductor is not a bulk material, but a thin film, so that the device presents an inverted architecture. It is built on an appropriate substrate and the deposition of the semiconductor constitutes the last step of the process. TFT structures can be divided into two families (Fig. 14-12). In coplanar devices, all layers are on the same side of the semiconductor. Conversely, in staggered structures gate and source-drain stand on opposing sides of the semiconductor layer. 

Interesting results have also been obtained with light-induced oscillations of silicon in contact with ammonium fluoride solutions. The quantum efficiency was found to oscillate complementarity with the PMC signal. The calculated surface recombination rate also oscillated comple-mentarily with the charge transfer rate.27,28 The explanation was a periodically oscillating silicon oxide surface layer. Because of a periodically changing space charge layer, the situation turned out to be nevertheless relatively complicated. 

Fujimo, K., Nishimoto, Y., Tokumasu, N., andMaeda, K., Doped Silicon Oxide Deposition by Atmospheric Pressure and Low Temperature CVD using Tetraethoxysilane and Ozone, J. Electrochem. Soc., 138(10) (Oct. 1991)... 

Fluorinated Silicon Oxide. The introduction of fluorine in the ratio of 2 to 14 at.% lowers the dielectric constant, which is reported as low as 3.0. This is a major factor in the design of dielctric films. The CVD of these fluorinated compounds is accomplished by plasma-CVD and usually with Sip4 as a fluorine source. Also available are fluorinated compounds, such as fluorotriethoxysilane (FTES), l,2bis(methyldifluorosilyl)ethane, and 2,5disilahexane.P2]... 

Insulator (dielectrics) Alumina Silicon oxide Silicon nitride Glass Bound to nucleus 1012 to 1022... 

CVD plays an increasingly important part in the design and processing of advanced electronic conductors and insulators as well as related structures, such as diffusion barriers and high thermal-conductivity substrates (heat-sinks). In these areas, materials such as titanium nitride, silicon nitride, silicon oxide, diamond, and aluminum nitride are of particular importance. These compounds are all produced by CVD. 1 1 PI... 

Thin films of electrical insulators are essential elements in the design and fabrication of electronic components. The most widely used insulator materials (dielectrics) are silicon oxide (Si02) and silicon nitride (Si3N4). These materials are extensively produced by CVD. 

Ryen, C. M. andZhu, X. Y., "Two-Step Approach to the Formation of Organic Monolayers on the Silicon Oxide Surface, Langmuir,Vol. 17,2001,pp- 5576-5580. 

FIG. 4 FTIR-ATR spectra of ethanol on a silicon oxide surface in ethanol-cyclohexane binary liquids at various ethanol concentrations 0.0, 0.1, 0.3, 0.5, 1.0, and 2.0 mol%. 

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