A thin copper layer (35 nm) deposited on SiO2 has been subjected to ion-beam mixing with 80 keV Ar+ at room temperature, 550 and 650 K. Interfacial properties of irradiated samples were investigated using Rutherford backscattering spectroscopy, grazing-angle X-ray diffraction, X-ray photo-electron spectroscopy and scratch testing. The adhesion of the copper film was improved by a factor of three at a dose of 1.5 x 10(16) Ar+ cm-2 by the ion-beam mixing at room temperature, while the high-temperature ion-beam mixing enhanced the adhesion by a factor of five. Ballistic mixing plays a role in the improvement of adhesion for the room-temperature ion mixing, and the creation Of Cu2O phase induced by ion-beam mixing contributes to the enhancement of adhesion at high temperature.