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Apparatus and method for generating low energy, high intensity ion beams. A Hall current ion source is provided to conduct many integrated circuit fabrication processes which require low energy ion bombardment such as surface cleaning. Ion sources are provided which have tapered magnetic pole pieces

Apparatus and method for generating low energy, high intensity ion beams. A Hall current ion source is provided to conduct many integrated circuit fabrication processes which require low energy ion bombardment such as surface cleaning. Ion sources are provided which have tapered magnetic pole pieces for controlling the dispersion pattern of the ion beam.

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1. In a system for working the surface of electronic circuit substrates, a low energy, high intensity ion source comprising: a plasma chamber receiving at one end thereof a gas for ionizing, and open at another end to deliver ions; said chamber including an anode, and an external electron emittin

1. In a system for working the surface of electronic circuit substrates, a low energy, high intensity ion source comprising: a plasma chamber receiving at one end thereof a gas for ionizing, and open at another end to deliver ions; said chamber including an anode, and an external electron emitting cathode adjacent said open end exterior to said chamber for receiving a voltage potential, whereby a current flow of electrons between said cathode and anode is generated; a first magnetic pole piece having an interior surface forming an interior circumferential surface of said chamber; and a second magnetic pole piece extending along a longitudinal axis of said plasma chamber, said pole pieces forming an interior magnetic field for increasing the production of ions within said chamber, said first magnetic pole piece forming an interior angle with said second pole piece, said magnetic pole pieces producing an arcuate fringe field at said open end, said anode and cathode forming an accelerating electrostatic field therebetween along an axis of said plasma chamber to said open end, whereby ions exiting said plasma generator are formed in a predetermined beam pattern determined by said angle as a result of said electrostatic field and magnetic field. 2. In a system for working substrates of an electronic component, a low energy, high intensity ion source comprising: a plasma chamber receiving at one end thereof a gas for producing ions, and having an exit aperture for emitting ions; first and second electrodes, one of said electrodes located within said chamber, the remaining of said electrodes located external of said chamber for emitting electrons which migrate to said one electrode, said electrodes receiving a voltage potential for producing a plasma within said chamber; said plasma chamber including a central longitudinal extending pole piece and a circumferentially extending pole piece, said circumferentially extending pole piece forming an acute angle with said central pole piece, said pole pieces extending from said one end to said exit aperture in said plasma chamber, said electrodes forming an electrostatic accelerating field therebetween for accelerating ions through said exit aperture and magnetic field, said electrostatic field and magnetic field cooperating to produce a stream of ions having a beam pattern substantially controlled by said acute angle. 3. The ion source of claim 2, wherein a third electrode is included in said plasma chamber. 4. The ion source of claim 3, wherein said third electrode comprises a cathode for connection with a source of voltage potential. 5. The ion source of claim 2 wherein said pole pieces diverge towards said open end forming a diverging ion beam. 6. The ion source of claim 2 wherein said pole pieces converge towards said open end forming a focussed ion beam. 7. In a system for working the surface of an electronic component substrate, a low energy, high intensity ion source comprising: a plasma chamber having an outer circumferential housing comprising a first magnetic pole piece tapered from a first closed end towards an opposite open end for emitting a beam of ions, said plasma chamber including an opening for receiving an ionizing gas; an anode adjacent said first closed end and said gas emitting opening; at least one electron emitting cathode located adjacent said opposite end external to said chamber for producing a plasma in response to a voltage potential between said anode and cathode, said cathode and anode producing an accelerating electrostatic field extending therebetween through said open end; a second magnetic pole piece extending along said plasma chamber for establishing a magnetic field with said first pole piece for enhancing ion production by increasing the path length for electrons emitted by said cathode, said second pole piece being centrally located, with magnetic field lines between the pole pieces forming substantially equal potential contours substantially normal to said accelerating electrostatic field, whereby ions leaving said plasma chamber through said opposite end are formed in a beam having a dimension controlled by said housing taper. 8. The ion source of claim 7 further including second and third cathode elements located within said magnetic pole pieces. 9. In a system for working the surface of an electronic component substrate, a low energy, high intensity ion source comprising: a plasma chamber having a magnetic circumferential pole piece diverging from a first closed end towards a second, ion emitting end, said first end including a gas emitting aperture; a second tapered magnetic pole piece located along the axis of said circumferential pole piece, said pole piece having a narrower end adjacent said second ion emitting end, and a wider end adjacent said first end; an anode located adjacent said first end; and, at least one electron emitting cathode located outside of said ion emitting second end; said anode and cathodes adapted to receive a voltage potential producing a current flow from said cathode to said anode, whereby an electrostatic acceleration field extending between said anode and cathode is produced extending through said ion emitting second end; said pole pieces diverging away from each other towards said second ion emitting end, forming a magnetic field of substantially equal potential contours substantially normal to said acceleration field, whereby ions formed within said chamber form a diverging ion beam exiting from said second ion emitting end. 10. The ion source of claim 9 further including a second cathode element located within said chamber. 11. The ion source of claim 9 wherein said anode element circumferentially encloses said first magnetic pole piece adjacent said first end. 12. In a system for working the surface of electronic circuit substrates, low energy, high intensity ion source comprising: a plasma chamber for receiving an ionizing gas, said chamber including a circumferentially extending first pole piece, open at one end, said pole piece being tapered between said one end and a remaining closed end; a second longitudinal pole piece extending along the central axis of said first pole piece; an anode element located between said pole pieces; an electron emitting cathode element located adjacent said first pole piece open end, whereby said gas is ionized in response to a voltage difference between said anode and cathode, and an accelerating electrostatic field extending between said anode and cathode is formed extending through the plasma chamber open end, said pole pieces forming arcuate magnetic lines of force in said accelerating electrostatic field, whereby an ion beam exits said plasma chamber open end forming a beam pattern determined by the taper of said first pole piece. 13. The Hall current ion source of claim 12 further comprising a circumferential electrode spaced apart and concentric to said first pole piece, said electrode reducing the ion collisions with said first pole piece. 14. The Hall current ion source of claim 12 comprising a second electrode for enclosing a portion of said second pole piece wherein ion collisions with said second pole piece are reduced.