| 摘要 |
PURPOSE:To restain the dielectric breakdown of a wafer from occurring, by installing an electron shower consisting of a metallic target, which receiving a primary electron to be emitted out of an electron gun in a direction orthogonal with an ion beam and with the impact, generates a secondary electron in the opposite direction of a beam flow. CONSTITUTION:An aluminum target 7, for example, is installed in a position to be opposed to an electron gun 6 as holding an ion beam 5 in between. At the time of ion implantation, a disc 1 rotates at high speed while reciprocates up and down, and a positive ion beam 5 is irradiated to a wafer 3 part on the disc 1. And, an electron is emitted out of a target 7 of an electron shower toward the upstream of a beam flow. At this time, a partial electron is caught in the beam flow and moves in the reverse direction, that is, toward the wafer 3 together with the positive ion, and thereupon this positive ion is neutralized. The electron not caught in the ion beam flow passes through the ion beam 5 and quenched by a metallic plate. Wafer voltage comes down with an increase in a primary current, but it is in no case dropped up to the negative side so suddenly, thus no dielectric breakdown happens.
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