State various Chemical Vapor Deposition Techniques. Explain in brief any one of the techniques of Chemical Vapor Deposition for MEMS device fabrication.
1 Answer

Chemical – Vapor deposition (CVD) works on the principle of initiating a surface chemical reaction in a controlled atmosphere resulting in the deposition of a reacted specific on a heated substrate.

In contrast to sputtering, CVD is a high tensile process, usually performed above 3000 C.

Common thin film deposited by CVD include polysilicon, silicon oxides and nitrides, tungsten titanium and tantalum as well as their nitride copper and low- permittivity dielectric insulator (€r<3)

Chemical vapor deposition processes are categorize as atmospheric pressure (as APCVD) or low pressure (LPCVD) or plasma – enhanced which also has- density plasma (HPD-CVD)

APCVD and LPCVD methods operate at rather high temp(4000 - 8000).

In PECVD and HDP-CVD, the substrate temp. is typically near 3000 , though the plasma deposition of silicon nitride (SiN3) at room temp. is feasible.

Substrate temp, gas flows, presence of dopants and pressure are important process variables for all types of CVD. Power and plasma are important for PECVD.

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