Quantum II™ : low energy beamline innovations for increased manufacturing productivity

An investigation into the processes that limit the performance of ion implanters at low energies (≤10keV) is described. Experimental results, obtained using an indirectly-heated cathode (IHC) ion source and tetrode extraction system are used to illustrate how the transmission of low energy ions can be optimised by matching the beam emittance produced by a specific beamline element to the acceptance of the subsequent beamline component. Emittance measurements on a 5keV B
_x
F
_y
(i.e. B, F, BF, BF
₂
) beam immediately downstream of the extraction electrodes demonstrated that, for a standard source, the beam quality deteriorates dramatically when the it is tuned to maximise the cracking of molecular feed gases. Incorporation of a slotted cathode was shown to overcome this problem and resulted in enhanced beam transmission through the extraction lens. Quality measurements on a set of 1keV B
_x
F
_y
beams were also undertaken to investigate the effects of extraction lens voltages and electrode position on their current density profiles. A 100μm slit was used to section the beams and the transmitted beamlets were profiled to identify aberrations introduced by the extraction lens. By distorting the emittance diagram these aberrations lead to the requirement of a larger acceptance in the subsequent beamline and resulted in increased beam loss. Based on these finding a series of design modifications were made to Applied Material's Quantum
_LEAP
^™
implant system. Performance statistics from the resulting Quantum II™ ion implanter show a 30-50% improvement over its predecessor in beam transmission efficiency and, as a result, low energy ion currents.