O-2 PLASMA OXIDATION OF SPUTTER-DEPOSITED CU THIN-FILM DURING PHOTO RESIST ASHING

O-2 plasma oxidation of sputter-deposited copper thin film during phot oresist ashing has been investigated by X-ray diffraction (XRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The copper thin film was oxidi zed by O-2 plasma under a typical condition to remove photoresist. O-2 pressure was 700 mTorr and 500 W radio frequency power was supplied. Substrate was held at room temperature before plasma generation and it was not heated additionally during plasma treatment. After O-2, plasm a treatment, a new surface oxide layer was formed on copper film. It w as found from electron diffraction and Auger electron depth profiling that the plasma-induced oxide had an oxygen deficient Cu2O1-x structur e compared to the conventional thermal oxide. The oxide layer was comp osed of very small and relatively tightly packed grains typically 25 n m in diameter and with random orientation on large grains of copper. T he topography of plasma-induced oxide layer was close to that of therm al oxide formed at a low temperature, but the oxidation rate of plasma oxidation was relatively high and seemed to follow an oxidation law a t relatively high temperature. (C) 1998 Elsevier Science B.V. All righ ts reserved.