A surface of polytetrafluoroethylene (PTFE) was modified with changing ion doses by 1 keVAr+ion irradiation and Cu films with a 5000 Å were deposited on the modified PTFE. The scanning electron microscopy study showed that the surface texture of modified PTFE was in the form of filaments whose height increased depending on ion doses. Through x-ray photoelectron spectroscopy spectra, it was found that the intensity ofF 1speaks decreased with ion doses by preferential sputtering of F atoms and the C–C and/or C–F chains were formed by the crosslinking in the newly unstable chains. Cu films were deposited uniformly along the filaments formed on the modified PTFE. In x-ray diffraction spectra of deposited Cu films on modified PTFE, a preferred orientation along (111) and (200) planes was found and a relative intensity of(111)/(200)orientation increased as surface roughness of modified PTFE increased. The resistivity of Cu films was changed from 2.7 μΩ cm of unmodified PTFE to 4.3 μΩ cm of modified PTFE at an ion dose of1×1016/cm2and the abrupt increase of resistivity in the modified PTFE at an ion dose of1×1017/cm2was due to being cut off the film which resulted from the increased surface roughness.