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Silicon Nitride |
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Silicon nitride (Si3N4) is a hard,
solid substance, that can be obtained by direct reaction between
silicon and nitrogen at high temperatures. Silicon nitride is the
main component in silicon nitride ceramics, which have relatively
good shock resistance compared to other ceramics. Rollers made of silicon nitride ceramic are
sometimes used in high-end skateboard bearings, due to the
material's shock and heat-resistant characteristics. It is also used
as an ignition source for domestic gas appliances, hot surface
ignition. In microelectronics, silicon nitride is usually
formed using chemical vapor deposition (CVD) method, or one of its
variants, such as plasma-enhanced chemical vapor deposition (PECVD).
It is usually used either as an insulator layer to electrically
isolate different structures or as an etch mask in bulk
micromachining. As a passivation layer for microchips, it is
superior to silicon dioxide, as it is a significantly better
diffusion barrier against water molecules and sodium ions, two major
sources of corrosion and instability in microelectronics. It is also
used as a dielectric between
polysilicon layers in capacitors in analog chips. Bulk, monolithic silicon nitride is used as a
material for cutting tools, due to its hardness, thermal stability,
and resistance to wear. It is especially recommended for high speed
machining of cast iron. For machining of steel, it is usually coated
by titanium nitride (usually by
CVD) for increased chemical resistance. Natural existence of silicon nitride is
restricted to meteorites, where it very rarely occurs as mineral
nierite. Typical applications: electronic components; heat sinks; and turbine blades.
See also Aluminium Nitride and Boron Nitride |
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