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IMPROVING BEAM NEUTRALIZATION IN LOW-ENERGY HIGH-CURRENT RIBBON-BEAM IMPLANTERS
IMPROVING BEAM NEUTRALIZATION IN LOW-ENERGY HIGH-CURRENT RIBBON-BEAM IMPLANTERS
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机译：在低能量高电流色带束注入器中改善束中和性
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摘要
The fabrication of modern semiconducting integrated circuits often requires implantation steps that involve high currents of low-energy charged dopant atoms. When employing such beams, the addition of electrons or negative ions for neutralizing the effects of space charge is often crucial for achieving success. Without this supplement, ion beams can 'blow-up' causing loss of intensity and disruption of beam focusing. In the present disclosure, methods are presented for introducing and constraining neutralizing low-energy electrons and negative ions within the boundaries of ribbon beams within regions of magnetic field deflection. Apparatus is described for maintaining neutralization based upon a reduction of electron losses, plasma bridge connections and secondary electron production. As part of plasma introduction to the deflection region a novel cryogenic pumping apparatus selectively removes neutral atoms from a plasma stream. Described herein is a magnetic pole of a deflection magnet. Although those skilled in the art will recognize that the pole surface (101) may actually be part of the underlying magnetic return yoke (102) in the preferred embodiment the surfaces of the poles (103) are located within the vacuum chamber (104) rather than outside it. The magnetic field is produced by the coils (112). This allows the magnetic poles to be as close as needed to the trajectories of the ion beam (105) without wasting distance for a wide vacuum envelope that needs thick walls to withstand atmospheric forces.
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