Ion Implantation and Synthesis of Materials - Studium

15.2 Implanters Used in CMOS Processing 219Fig. 15.2. A 300 mm high current implanter showing (left to right) gas delivery system, ionsource, analyzer magnet, process chamber, and wafer handling systemFollowing this parallelizing element, the beam may also be electrostaticallydeflected once more to provide energy filtering. This filtering removes ions ofunwanted energy that may have had coincidental paths through the beamline.Acceleration of the beam to its final energy (which may be as high as severalhundred keV for multiply charged ions) may occur before or after the scanningand parallelizing stages. Schematically, a typical medium current beamline withelectric scanning and electrostatic parallelizing is shown in Fig. 15.3. Given thatthe beam is scanned in one dimension, there is only a need for one dimension ofmechanical wafer scanning. For this reason, medium current beamlinearchitectures are almost exclusively coupled with single-wafer processingchambers.High Energy BeamlinesHigh energy implanters are designed to deliver up to hundreds of µA beams atenergies up to several MeV. There are two fundamental beamline approaches toachieving this. Most commercial high energy systems today use an RF linearaccelerator (referred to as a linac) to deliver the MeV range of energies. Thecommercial RF linac beamline relies on a conventional ion source and analyzermagnet similar to those found in a high current beamline, to produce a DC beamof up to several mA at ~80 keV. This DC beam is then injected into a series of 8–12