Abstract
Recently, the use of reactive gases in ion milling equipment has received increasing attention. We have characterized the operation of a Kaufman‐type ion source for use with 
, by mass spectrometric measurements of both ionic and neutral components of the beam. Fragmentation of the parent gas to 
ions and 
neutrals is found to be extensive. Fragmentation is also strongly dependent on gas pressure and on confinement of the discharge in the source due to the axial magnetic field. Previously reported dependence of 
etch rate on 
background gas pressure is examined in more detail. It is concluded that variation of ion composition does effect etch rate, but ion‐induced reaction of adsorbed neutral species is occurring. A simple mass transport model that considers adsorption and desorption processes of reagent and product species is adequate to explain the major features of the data.