Effects of Pretreatments of PET Substrate on the Adhesion of Copper Films Prepared by a Room Temperature ECR-MOCVD Method

Abstract

Effects of various pretreatments on the adhesion of copper-coated polymer films were investigated. Copper-coated polymer films were prepared by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) coupled with a DC bias system at room temperature. PET(polyethylene terephthalate) film was employed as a substrate material and it was pretreated by industrially feasible methods such as chromic acid, sand-blasting, oxygen plasma and ion-implantation treatment. Surface characterization of the copper-coated polymer film was carried out by AFM(Atomic Force Microscopy) and FESEM(Field Emission Scanning Electron Microscopy). Surface energy was calculated by based on the value of the contact angle measured. The adhesion of copper/PET films was determined by a pull-off test according to ASTM D-5179. It was found that suitable pretreatment of the PET substrate was required for obtaining good adhesion property between copper films and the substrate. In this study the highest adhesion was observed in sand-blasting, and then followed by those of acid and oxygen plasma treatment. However, the effect of surface energy was insignificant in our experimental range. This is probably due to compensating the difference in surface energy from various pretreatments by exposing substrate to ECR plasma for 5 min or longer at the early stage of the copper deposition. Therefore, it can be concluded that surface roughness of the polymer substrate plays an important role to determine the adhesion of copper-coated polymer for the deposition of copper by ECR-MOCVD.