Variable axis immersion lens electron beam projection system

An electron beam projection system comprising:

• electron beam producing means for producing an electron beam;
• deflection means for deflecting said electron beam;
• magnetic immersion lens means for producing a magnetic field to focus the deflected electron beam, said magnetic immersion lens means including an upper pole piece having a predetermined bore, a lower pole piece having a non-zero bore section and a zero bore section, and means for inserting a target between said upper pole piece and said lower pole piece zero bore section;
• and
• magnetic compensation means for producing a magnetic compensation field between said magnetic immersion lens means upper and lower pole pieces, said magnetic compensation field being proportional to the first derivative of the axial magnetic projection field to thereby cause the electron optical axis of said magnetic immersion lens means to shift to the position of the deflected electron beam, and being approximately zero in the vicinity of said lower pole piece to thereby eliminate stray magnetic fields in the vicinity of said lower pole piece zero bore section.

An electron beam projection system comprising:

• electron beam producing means for producing an electron beam;
• deflection means for deflecting said electron beam;
• and,
• a variable axis immersion lens, having upper and lower pole pieces and means for inserting a target therebetween, for producing an axial magnetic projection field having zero first derivative in the vicinity of said lower pole piece, and for producing a magnetic compensation field which is proportional to the first derivative of said axial magnetic projection field, to thereby focus the deflected electron beam and shift the electron optical axis to coincide with the deflected electron beam and eliminate stray magnetic fields in the vicinity of said lower pole piece.