Broad ion beam mass filters working by a mass dependent radio-frequency acceleration of ions are a new approach to generate mass filtered broad ion beams with diameters of about 300 mm in the future. The ions are extracted from an ion source by a two grid extraction system with holes of 2.5 mm diameter followed by seven hole grids with the radio-frequency mass separator. A basic question for future successful use of this system for ion implantation is the impurity generation by sputtering of ions on the walls of the hole grids. Therefore the amount of neutral and charged impurities in the ion beam was investigated by mass spectroscopic beam analysis. It is shown that the relative amount of charged impurities in the ion beam is less than5×10−4,and the amount of neutral impurities from sputtering is smaller than impurities created by ion-molecule interactions of the ion beam with the residual gas (basic pressure10−8 mbar). ©1998 American Institute of Physics.