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Forming electronic devices on a wafer involves a long series of highly
precise processes. Many of these operations consist of depositing and then
patterning layers. Depositing a layer is generally done by one of the following
processes:
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Spin-on deposition (SOD)
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Physical vapor deposition (PVD; evaporation or sputtering)
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Chemical vapor deposition (CVD)
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"Grown" films (e.g., SiO2 grown from oxidation of silicon
substrate)
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Deposited films
The discussion below will focus on deposited films via CVD.
The basic process uses one or more gas or liquid precursor materials (in our
case, a precursor would be a silicon source) carried by an inert gas stream
into a deposition chamber containing the wafers. The precursors react (often by
using additional energy from heat or plasma) and attach themselves to the wafer
surface, gradually building a layer of the desired composition. Any byproducts
are then swept away in the gas stream. This continues until the desired
thickness of the new thin film has been achieved.
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