Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering in Ar–O2 mixture

The structure, composition, and temperature coefficient of resistance of tantalum films sputtered in Ar–O2 mixture were studied as a function of deposition parameters and substrates temperature. As the sputtering power increased from 25 to 100 W, the samples deposited at 300 °C only consisted of the β phase, the preferred-growth orientation of films changed from (2 0 0) to (2 0 2) and the temperature coefficient of resistance reduced from −289.8 to −116.7 ppm/°C. The decrease of the oxygen and other impurity in the films was observed as the increase of the sputtering power. In addition, the O/Ta ratio decrease and grain size reduction in the films related to a change of electrical resistivity were observed at substrate temperatures in the range of 300–500 °C. These results suggested that the electrical properties were due to the oxygen and other impurity content and grain size in the films rather than to growth orientation. At 650 °C, the deposited films contained both partial stable body-centered-cubic α phase with low resistivity and tetragonal β phase of Ta. The presence of α phase of Ta causes a sharp decrease of the electrical resistivity and a significant change in the microstructure of the samples.