Ion implantation device

Herein disclosed is an ion implantation device which completely captures secondary electrons produced by the ionic bombardment of a semiconductor specimen. The device comprises an ion source for producing and accelerating ions, a semi-conductor base for supporting and positioning the specimen in the ion beam path, a circular first electrode held at a positive potential and positioned in the vicinity of the base so that the bombarding ions pass centrally therethrough, a circular secondary electrode held at a negative potential and positioned in the vicinity of the first electrode so as to be coaxially aligned therewith, and an ammeter tied between the base, the first electrode and ground for measuring the rate of ion flow. Secondary electrons which are produced at the specimen surface and scattered by ionic bombardment during the implantation operation are, to a large extent, captured by the positive first electrode. Secondary electrons escaping this initial capture are deflected by the negative second electrode back toward the first electrode for eventual capture. Secondary electrons thus removed do not collide with the specimen and react with suspended organic molecules to produce the undesired formation of a hard film on the specimen surface due to polymerization cross-linking. (K.J. Owens)