Patent ID: 6452197
Filing Date: 2002-09-17
Classification: H01J

Abstract:
Ion implantation apparatus having an evacuated housing and, contained in said housing,a) a holder for holding a substrate for implantation; b) a source of positive ions for implanting in said substrate; c) a beam of said ions being formed which is directed at said substrate; d) an electron flood source to supply low energy electrons to the beam in front of said substrate for neutralizing positive charge build up on said substrate; e) a magnetic filter located adjacent to said substrate holder between said substrate holder and said electron flood source providing a magnetic field extending across the beam immediately in front of said substrate, said field having a strength selected to deflect out of the region containing the beam secondary electrons emitted from the substrate with energies above 15 eV, but to allow lower energy electrons including those supplied by said flood source to diffuse across said field without being deflected out of said beam region; and f) a conductive element located out of said beam region to be impacted by and absorb said deflected secondary electrons; said magnetic filter being located substantially at a substrate end of the conductive element.