Reducing space charge effects in ion beams using cusp-type magnetic fields

摘要

Ion implantation apparatus for generating a low energy ion beam with increased beam current, comprising an ion beam line including a vacuum chamber 46 extending from an ion source 41 for generating ions, to a process chamber 45 in which is disposed a substrate 44. The ion beam line includes extraction electrodes 42, a mass analysis magnet apparatus 47 for generating a magnetic field M2 for mass analysing the extracted ions, and a mass analysis slit 43, the ions passed through said slit 43 being implanted into the substrate 44. The ion beam line further comprises a magnet assembly comprising a plurality of permanent magnets 48 for generating cusp magnetic fields M1 within the vacuum chamber 46. The generated multicusp field M2 confines electrons and negative ions in the vicinity of the ion beam, thereby further neutralising the space charge effect, and reducing beam divergence.