Also found in: Dictionary, Acronyms, Wikipedia.
ion implantation[′ī‚än ‚im‚plan′tā·shən]
(also called ion alloying), the implantation of extrinsic atoms in a solid by bombarding its surface with ions. The greater the energy of the ions, the greater will be the average depth to which ions penetrate into the target (ions with energies of ~ 10–100 kilo electron volts penetrate to a depth of 0.01–1.0 micron). On bombardment of single crystals the depth of penetration of particles in certain crystallographic directions increases sharply.
During intensive bombardment ion implantation is affected by cathode sputtering of the target, the diffusion of the implanted ions, and their explusion from the surface. Maximum possible concentration of implanted ions depends on the type of ion and target and on the temperature of the target.
Ion implantation is used most widely to implant impurities in semiconductor single crystals in order to create the required impurity electrical conductivity of the semiconductor. The subsequent annealing is used to eliminate the crystal defects that form and also to ensure that the implanted ions occupy certain positions at points of the crystal lattice. Ion implantation makes possible the introduction of precisely measured quantities of almost any chemical elements into various semiconductor materials. The distribution of implanted ions with respect to depth may be controlled by modifying the energy of the ions and the intensity and direction of the ion beam with respect to the crystallographic axes. Ion implantation makes it possible to create in a semiconductor crystal a p-n transition at shallow depth, which increases, for example, the maximum frequency of transistors.
REFERENCESMayer, J., A. Erikssen, and J. Davies. Ionnoe legirovanie poluprovodnikov (kremnii, germanii).Moscow [in press]. (Translated from English.)
Legirovanie poluprovodnikov ionnym vnedreniem. Moscow, 1971. (Translated from English.)
IU. V. MARTYNENKO
A process that utilizes accelerated ions to penetrate a solid surface. The implanted ions can be used to modify the surface composition, structure, or property of the solid material. This surface modification depends on the ion species, energy, and flux. The penetration depth can be controlled by adjusting the ion energy and the type of ions used. The total number of ions incorporated into the solid is determined by the ion flux and the duration of implantation. This technique allows for the precise placement of ions in a solid at low temperatures. It is used for many applications such as modifying the electrical properties of semiconductors and improving the mechanical or chemical properties of alloys, metals, and dielectrics. See Alloy, Dielectric materials, Metal, Semiconductor
Wide ranges of ion energy and dose are applied. For ion energy ranging from 1 keV to 10 MeV, the ion penetration depth varies from 10 nanometers to 50 micrometers. In general, it is difficult to get deeper penetration since extremely high energy ions are required. As such, ion implantation is a surface modification technique and not suitable for changing the entire bulk property of a solid. Ion dosage also varies depending on the applications. Doses ranging from 1010 to 1018 ions/cm2 are typically applied. For high-dose applications, ion sources providing high ion currents are needed to keep the implantation time reasonable for production purposes.
Ion implantation is used extensively in the semiconductor industry. The fabrication of integrated circuits in silicon often requires many steps of ion implantation with different ion species and energies. The implanted ions serve as dopants in semiconductors, changing their conductivity by more than a factor of 108. See Integrated circuits
Ion implantation is also used to change the surface properties of metals and alloys. It has been applied successfully to improve wear resistance, fatigue life, corrosion protection, and chemical resistance of different materials. Even though the ion projected range is less than 1 μm, surface treatment by ion implantation can extend the lives of metal or ceramic tools by 80 times or more. Ion implantation can form new compounds such as nitrides on the surface, and the implanted ions can be found at much greater depths than the projected range due to diffusion or mechanical mixing. See Ceramics