Silicon Dioxide and Doped Glasses Film Properties and Applications Silane/Oxygen Thermal CVDTEOS/Oxygen Thermal CVDTEOS/Ozone Thermal CVDSilane/N2O PECVDTEOS/O2 PECVDHigh-Density Plasma CVDSilicon Nitride Film Properties and Applications Silicon Nitride Thermal CVDSilicon Nitride Plasma CVDLow-K and High-K Dielectrics Fluorine and Methyl in Silica Tantalum Oxide Barium Strontium Titanate Metals Tungsten and Tungsten Silicide Titanium Nitride and Barriers Silicon dioxide (silica) is one of the most commonly encountered substances in both daily life and in electronics manufacturing.Crystalline silicon dioxide (in several forms: quartz, cristobalite, tridymite) is an important constituent of a great many minerals and gemstones, both in pure form and mixed with related oxides. The working of silica into glass (usually by the addition of natron -- sodium oxide -- to lower the melting point) has been known since antiquity, with polished glass lenses in eyeglasses and optical instruments dating back more than 5 centuries.
(Arsenic is also occasionally employed as a dopant.)Phosphosilicate glass (PSG) flows readily at 1000 °C for 6-8 weight% P in the alloy.("Devitrification" -- that is, crystallization -- of quartz furnace tubes used for high-temperature oxidation is sometimes observed after thousands of hours of use at temperatures exceeding 1200 °C.) The amorphous structure is tends to be very "open": even in thermally-grown oxides, channels exist through which small positive ions such as Na can readily migrate.These ions can move under the influence of electric fields within the gate oxides of MOS transistors, causing shifts in the voltage at which the transistor turns on ("threshold shifts").It is the oxygen "bridge" bonds between silicon atoms that give Si O2 many of its unique properties.
The bond angle Si-O-Si is nominally about 145 degrees, but can vary from about 100 to 170 degrees with very little change in bond energy.
Some important reactions are: The first reaction has little change in enthalpy and is nearly reversible; locally strained bonds, with reduced bond energy, are particularly vulnerable to attack by water (hydrolysis).