Patent ID: 6768117
Filing Date: 2004-07-27
Classification: H01J

Abstract:
A variable axis immersion lens assembly for use with a charged particle beam, where the electron optical axis of the charged particle beam is shifted to be coincident at all times with a downstream deflected electron beam emanating from the immersion lens, said variable axis immersion lens comprising:at least two optical axis deflection coils located coaxial to the charged particle beam, which optical axis deflection coils are used to shift the optical axis of the charged particle beam to be coincident with a downstream deflected electron beam; an excitation coil located coaxial with respect to the optical axis deflection coils; a magnetic field deflector coil used to coincide a magnetic axis of a magnetic field generated by the excitation coil with the shifted optical axis of the charged particle beam; a first pole piece located coaxial to the excitation coil, the first pole piece extending at least partly around the excitation coil; a magnetically floating field shield located coaxial to and downstream from the magnetic field deflection coil with regard to propagation of the charged particle beam from the magnetic field deflection coil; a support for a target of the charged particle beam, which support is downstream with regard to propagation of the deflected charged particle beam from the magnetic field shield, wherein the magnetic field shield is located intermediate the magnetic field deflection coil and the support, thereby limiting a magnetic field generated by the magnetic field deflection coil from radiating downstream into areas protected by the magnetic field shield.