Ion Implantation systems

Ion implanters are usually specified in terms of two key parameters; the ion energy which determines the penetration depth and the ion current which decides the dose. The basic building blocks of an implanter are ion sources, ion extractors, accelerators to high energies and beam manipulators as shown in Fig.3.51. Ions are produced by passing the gas vapour through a discharge chamber. The electrons are accelerated towards an anode which is typically at 100V. A magnetic field is provided to force electrons into a spiral trajectory and this will enhance the ionisation efficiency. The positive ions are moved out of the discharge chamber by means of another anode biased at 15-20 kV. The pressure in the remaining part of the system is kept below 10 ^-6 Torr to minimize the ion scattering.