Silicon nitride
The chemical formula is: The chemical formula of urea is as follows:
3Si(s) + 2N2(g) -Si3N4(s)
This can be done with diimine.
SiCl4(l) + 6NH3(g) -Si(NH)2(s) + 4NH4Cl(s) (at 0 degC)
3Si(NH)2(s) -Si3N4(s) +N2(g) + 3H2(g) (at 1000 degC)
Use the carbothermal reduction to synthesize at 1400-1450degC in an atmosphere of nitrogen:
3SiO2(s) + 6 C(s) + 2N2(g) -Si3N4(s) + 6 CO(g)
In the 1950s the method of nitriding a silicon elemental powder was discovered. This method is also the only one that allows for mass production. The silicon nitride powder will be impure if the quality of the raw silicon material is poor.
It’s important to note that the diamine method of silicon nitride production is only relevant in terms of commercial production. Currently, the diamine-decomposition method has only a limited importance. The commercial production method for silicon nitride comes second after the nitriding process.
The most cost-effective and easiest way of manufacturing silicon nitride is through the carbothermal reaction.
Electronic grade
silicon nitride
The film is made by either chemical vapor deposited or plasma enhanced chemical-vapor deposition:
3SiH4(g) + 4NH3(g) -Si3N4(s) + 12H2(g) 3SiCl4(g) + 4NH3(g) -Si3N4(s) + 12 HCl(g) 3SiCl2H2(g) + 4NH3(g) -Si3N4 (s) + 6 HCl(g) + 6H2(g)
Two methods are available to deposit Silicon Nitride on a Semiconductor Substrate:
1. Use a tube furnace vertically or horizontally to use low-pressure, chemical vaporization technology at relatively high temperatures.
2. The plasma-enhanced deposition of chemical vapors is done under vacuum conditions at low temperatures.
The unit cell parameter of silicon nitride is different than that of elemental Silicon. Dependant on the deposition technique, the silicon nitride generated film can either generate tension, or stress. Adjusting the deposition parameter is a great way to reduce tension, especially when using plasma enhanced chemical vapor technology.
To obtain silicon nitride, the first step is to prepare silica using the sol-gel process. Next, the silica containing ultrafine carbon particles will be processed with the carbothermal method of reduction, followed by nitridation. The ultrafine carbon particles are formed by the decomposition glucose at temperatures between 1200 and 1350degC. The reactions which are part of the synthesis can be:
SiO2(s), C(s), SiO(g), CO(g), SiO(g), 2N2 (g), CO(g), Si3N4 (s), + 3CO2(g), or Si3N4 (+ 3CO2(g), or Si3N4+ 3CO2(g),
Processing silicon nitride block
Silicon nitride
As a granular product, it is difficult to work with. It can’t be heated higher than its melting point (1850degC) because silicon nitride would decompose to silicon and nitrogen. Hot press sintering is no longer acceptable. By adding sintering or binding aids, the powdered silicon nitride can be bonded to form a solid material. Due to the necessity of adding binders or other sintering aids to the material, impurities will be introduced. Another method to produce purer bulk material is spark plasma sintering. The compacted powder will be pulsed within a short period of time (a few seconds). This method works at temperatures between 1500degC and 1700degC. The temperature at which you want to obtain compact and dense lumps of silicon nitride.
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silicon nitride
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