Focused ion beam (FIB) systems are used for deposition, ablation of materials, and site-specific analysis. It closely resembles a scanning electron microscope, but while the SEM used a focused electron beam to image the chamber sample, an FIB system uses a focused beam of gallium ions to get the job done.
The finely focused beam of gallium ions is rastered on the surface of the analyzed material. It traces over the surface, sputtering a small amount of the material from the surface. This dislodged material will be in the form of secondary ions, atoms, and electrons. These are collected and analyzed in order to create an image on a screen while the primary beams scan the surface of the material. This process allows for high magnification of microscopy and is an excellent method of image forming.
Gallium is used for a focused ion beam because of the simplicity it takes to build a liquid metal ion source from that element. The gallium metal is heated and placed in contact with a tungsten needle, wetting the latter element. An electric field of 108 volts per centimeter or greater generates ionization and the gallium atoms experience field emission.
FIB systems have several uses. It is commonly used as a micro-machining tool due to its sputtering capability, in order to modify materials at the nanoscale. It can also be used for depositing materials through the use of ion beam induced deposition. This is referred to as FIB-assisted chemical vapor deposition. It is most often, however, used in the semiconductor industry in order to patch or modify a semiconductor device, such as an integrated circuit with unwanted electrical connections.
Focused ion beam systems can also be set up to bombard an area of the die with gases in order to perform primary beam sputtering. Based on the gas used, the gases can react either with the primary beam or the deposit material on the surface.