Abstract
The measurement of charged particle energies has been a key technique used in fundamental investigations of wafer surface charging phenomena and ion beam propagation at Applied Materials. A previous paper described the use of a spectrometer incorporating hemispherical energy analysers which was used for the measurement of potentials present inside ion beams from the spectroscopy of “slow ions” emitted from the beams, and the determination of relatively high potentials on surfaces from the energy spectra of sputtered ons. Extension of this work to measure low surface voltages induced on an oxide wafer during implantation has given experimental confirmation that beam potentials influence surface potentials. Other spectrometer types have also been used. Cylindrical mirror analysers, having the advantages of simplicity and compactness, have been used for ion spectroscopy inside Precision Implant 9500 systems. These have given valuable insight into the effects of ion source tuning on beam potential and, in particular, the correlation between beam quality and device yield. Retarding field analysers have also been used for ion energy measurements, but their main application has been for electron spectroscopy due to their immunity from the problems of internally reflected electrons experienced by other spectrometer types. This paper will discuss the operation of these various spectrometers and review some results relevant to ion beam tuning and wafer surface charge control phenomena.