Charging measurement and control in high current implanters

Data on beam potential measurements and gate oxide yield studies a high current implanter are presented. The beam potential measurements were made using a test structure on a silicon wafer with a time resolved in situ data gathering system in the mechanically scanned implanter. The yield studies used specially designed test devices with oxide breakdown measurements before and after a high dose implant. Data for different conditions in the implanter show that the voltage of the beam is forced on the surface exposed to the ion beam. This voltage can be effectively controlled by the use of electron injection from an electron shower as currently practiced. Preliminary results from the yield studies show very good yields over a wide range of conditions. Analysis of the results in terms of a theoretical model suggests that charge induced breakdown of very thin gate oxides in ion implantation will not become an insuperable obstacle in the foreseeable future.<
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