Polyimide (C22H10N2O5)(n) films were irradiated at room temperature by 200, and 300 keV Yb+ and 400 keV Er+. The dose was 1 x 10(15) ions/cm(2). The Rutherford backscattering technique has been used to study the diffusion behavior and the depth distribution of implanted Yb+ and Er+ in polyimide (C22H10N2O5)n The results show that (1) for the sample annealed at lower temperature, the migration of Yb+ and Er+ into the overlying polyimide is faster than into the undamaged polyimide, but there is a significant non-Fickian tail extending deep into the undamaged polyimide film, (2) oxygen loss was observed, and (3) the depth distributions of "as implanted" Yb+ and Er+ were nearly Gaussian in all cases. The x-ray photoelectron spectroscopy was used to study the structural modification. After ion implantation, the binding energy of carbon 1s, nitrogen 1s and oxygen 1s in polyimide was decreased.