Investigation on mechanisms for ion Beam Induced Degradation of Polyimide

Three types of ions with different atomic masses (B , Ar and As ) were chosen to irradiate polyimide films in similar conditions in order to check mechanisms of the formation of ion beam induced damage in polyimide. A four-point probe technique was used to measure sheet resistivities of implanted films. An ion mass effect on conductivity of ion irradiated polyimide film was discovered. The ion mass effect on ion beam induced change of conductivity and on the energy loss process of the ions in polyimide suggest that the electronic energy loss of incident ions is an important factor for the increase of conductivity of implanted polyimide, and the contributions of recoil ionization are restricted by the grave damages as a result of nuclear energy loss process of ions in targets. Our hypothesis is supported by automatic spreading resistance measurement of B implanted polyimide film coated on silicon substrate. The results of this work have been compared with the hypothesis of degradation through direct knock on of atoms in polyimide, proposed by D.Fink et al [Nucl. Instr. and Meths B32 (1988) 125]