CONTROL OF ION-BEAM CURRENT-DENSITY AND PROFILE FOR HIGH-CURRENT ION-IMPLANTATION SYSTEMS

One solution for the problems of the local temperature increase and the charge-up of a wafer during high current ion implantation is to decrease the beam current density while maintaining the total beam current necessary on the wafer. To solve these problems, a method, that maintains the beam spatial profile on a wafer by controlling the normalized perveance and the pole face angle of the analyzing magnet for various beam currents, has been developed experimentally. As a result, under the experimental conditions of 1 to 8 mA of 35 keV As+, the beam uniformity, defined as [average current density]/[maximum current density], became more than 0.2 and the beam profile on the wafer was maintained by using a suitable value of the perveance.