THE CHARGING MECHANISM OF INSULATED ELECTRODE IN NEGATIVE-ION IMPLANTATION

The wafer charging during ion implantation is a serious problem with g reater levels of circuit integration in semiconductor device fabricati ons. Positive charges are accumulated on insulated electrodes or insul ators and cause dielectric breakdown if there is no compensation of ch arging. Ion implantation with negative ions is one of the hopeful tech niques to solve this problem. Since an incident ion is a negative char ge, an incoming negative charge and an outgoing negative charge of sec ondary electrons will achieve electrical equilibrium on the insulated electrode. Therefore the charging voltage is extremely low because of this electrical equilibrium. We have measured the charging voltage at several energies of negative ions and also simulated the charging volt age with varying secondary-electron emission factor. We have found tha t the charging voltage depends on the secondary-electron emission fact or.