thumb|A small ion beam rocket being tested by NASA.
An ion beam is a beam of ions, a type of charged particle beam. Ion beams have many uses in electronics manufacturing (principally ion implantation) and other industries. There are many ion beam sources, some derived from the mercury vapor thrusters developed by NASA in the 1960s. The most widely used ion beams are of singly-charged ions.
Units
Ion current density is typically measured in mA/cm<sup>2</sup>, and ion energy in electronvolts (eV). The use of eV is convenient for converting between voltage and energy, especially when dealing with singly charged ion beams.
Broad-beam ion sources
Most commercial applications use two popular types of ion source, gridded and gridless, which differ in current and power characteristics and the ability to control ion trajectories.
Another common use of FIB instruments is for design verification and/or failure analysis of semiconductor devices. Design verification combines selective material removal with gas-assisted material deposition of conductive, dielectric, or insulating materials. Engineering prototype devices may be modified using the ion beam in combination with gas-assisted material deposition in order to rewire an integrated circuit's conductive pathways. The techniques are effectively used to verify the correlation between the CAD design and the actual functional prototype circuit, thereby avoiding the creation of a new mask for the purpose of testing design changes.
Ions beams are also used for analysis purposes in Materials science. For example sputtering techniques can be used for surface analysis or depth profiling by performing secondary ion mass spectrometry. It is also possible to gain information from the spectroscopy of transmitted or backscattered primary ions, e.g. depth profiles can be obtained from Rutherford backscattering (RBS) spectra.