Chemical vapor deposition (CVD) is a process that uses a reactive gas chamber to synthesize high-purity solid materials, such as electronic components. It involves depositing materials at high temperatures and low pressures. CVD products include silicon, carbon fiber, and diamond, but the process can be expensive due to power requirements. There are several classification schemes based on pressure, vapor characteristics, and plasma processing.
Chemical vapor deposition (CVD) is a chemical process that uses a reactive gas chamber to synthesize high-purity, high-performance solid materials, such as electronic components. Some integrated circuit components require electronic components made of the materials polysilicon, silicon dioxide, and silicon nitride. An example of a chemical vapor deposition process is the synthesis of polycrystalline silicon from silane (SiH4), using this reaction:
SiH4 -> Si + 2H2
In the silane reaction, the medium would be pure silane gas or silane with 70-80% nitrogen. Using a temperature between 600 and 650 °C (1100 – 1200 °F) and a pressure between 25 and 150 Pa – less than a thousandth of an atmosphere – pure silicon can be deposited at a rate between 10 and 20 nm per minute, perfect for many printed circuit components, whose thickness is measured in microns. In general, the temperatures inside a temperature chemical vapor deposition machine are high, while the pressures are very low. The lowest pressures, below 10-6 pascals, are called ultrahigh vacuum. This is different from the use of the term “ultra high vacuum” in other fields, where it usually refers instead to a pressure below 10-7 pascals.
Some chemical vapor deposition products include silicon, carbon fiber, carbon nanofibers, filaments, carbon nanotubes, silicon dioxide, silicon germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, and diamond. Mass-producing materials using chemical vapor deposition can get very expensive due to the power requirements of the process, which in part account for the extremely high cost (hundreds of millions of dollars) of semiconductor factories. Chemical vapor deposition reactions often leave behind by-products, which must be removed by a continuous flow of gas.
There are several main classification schemes for chemical vapor deposition processes. These include classification based on pressure (atmospheric, low pressure or ultrahigh vacuum), vapor characteristics (direct injection of liquids or aerosols), or type of plasma processing (microwave plasma-assisted deposition, plasma-enhanced deposition , remote plasma-enhanced deposition).
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