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In wafer fabrication,
photoresist is used to transfer a circuit pattern onto the wafer. Once a
pattern is transferred, the remaining photoresist must be removed from
the wafer before it can move to the next processing step. Plasma systems
are effective for stripping thick layers of photoresist, as well as
descumming, etching, and removing organics.
Plasma is an ionized gas capable of conducting electricity and absorbing
energy from an electrical supply. (Lightning and the Aurora Borealis are
naturally occurring examples of plasma). Manmade plasma is generally
created in a low-pressure environment.
In an inert gas, such as Argon, the excited ions can bombard a surface
("sandblast") and remove a small amount of material. In the case of an
active gas such as Oxygen, ion bombardment as well as chemical reactions
occur. As a result, organic compounds and residues volatilize and are
removed. |
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