We measured the energy distributions of negative ions during reactive
sputtering of silicon in oxygen. Various oxygen containing negative io
ns are formed in the cathode sheath or directly at the sputter target,
respectively. These negative ions are accelerated away from the catho
de by the electrical field, and can be detected using a mass spectrome
ter facing the sputter magnetron. The origin of each ion can be determ
ined from peak structures in the energy distribution. Additionally the
flux of different negative ions provides information on poisoning of
the target by oxide films. (C) 1998 American Institute of Physics.