Additional peaks in mass spectra due to charge exchange events and dissociation of molecular ions during extraction

It is well-known that charge exchange events and dissociation of molecular ions after extraction and prior to mass analysis result in changes to a so-called apparent mass of the ion and increase the possibility of energetic contamination in ion implantation. It was found that if charge exchange events and dissociation of molecular ions already take place during extraction, additional peaks occur in a mass spectrum. They were observed for all of the used source feed materials, such as AsH3, BF3, and argon. In this paper, the origin of these peaks is discussed and a model that calculates the apparent mass as a function of the extraction voltage is presented.