Patent ID: 7301156

Claim:
An apparatus for variable focusing of charged particles used for implanting a plurality of charged particles into semiconductor materials thereby modifying properties of said semiconductor materials, said apparatus comprising: an upper magnetic core member; a lower magnetic core member spaced apart from said upper core member, said lower core member being oriented with its axis substantially parallel to the axis of said upper core member; a plurality of focusing coil units distributed along said upper core member and corresponding focusing coil units distributed along said lower core member, each said focusing coil unit comprising a single continuous electrical circuit that surrounds an individual core member; and a current controller configured to excite said plurality of focusing coil units distributed along said upper core member and said corresponding focusing coil units distributed along said lower core member such that the direction of the current in each of said plurality of excited focusing coil unit distributed along said upper core member is the opposite of the direction of the current in said corresponding focusing coil unit distributed along said lower core member when viewed from one end of the upper and lower core members.