Science Fair Project Encyclopedia
An ion beam is a stream of charged particles, which has many uses in electronics manufacturing and other industries. Today's ion beam sources are typically derived from the mercury vapor thrusters developed by NASA in the 1960s.
One type of ion beam source, the duoplasmatron operates as follows: a cathode filament emits electrons into a vacuum chamber. A gas such as Argon is introduced in very small quantities into the chamber, where it becomes charged or ionized through interactions with the free electrons from the cathode, forming a plasma. The plasma is then accellerated through a series of at least two highly charged grids, and becomes an ion beam, moving at fairly high speed from the aperature of the device.
Ion beams can be used for sputtering, and for ion beam etching.
Ion beam etching
In a typical use in semiconductor manufacturing, a mask is used to expose a layer of photoresist on a substrate such as a silicon dioxide or gallium arsenide wafer. The photoresist is developed, and the unexposed portions are removed in a chemical process, leaving a pattern on the surface of the wafer. The wafer is then placed in a vacuum chamber, and exposed to the ion beam. The impact of the ions erodes the target, abrading away the areas not covered by the photoresist.
Ion beams are also used in materials science to thin samples or specific regions of samples for transmission electron microscope analysis.
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