Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering

The structure, composition, and temperature coefficient of resistance of tantalum films were studied as a function of deposition parameters and substrate temperature. As the sputtering power increases from 25 to 100 W, tantalum films deposited at 300 degrees C consisting of the beta phase, the preferred-growth orientation changes from (200) to (202) and the temperature coefficient of resistance reduces from -289.79 to -116.65 ppm/degrees C. The decrease in oxygen and other impurity content in the films was observed when the deposition power was increased. The O/Ta ratio decrease and grain size reduction, which were related to a change in electrical resistivity, were also observed as substrate temperature was varied from 300 to 500 degrees C. These results indicated that the electrical properties were related to the oxygen and other impurity content and grain size in the films rather than to growth orientation. At 650 degrees C, the metastable beta-Ta phase was partially transformed into the stable alpha-Ta phase which leads to a sharp decrease in the electrical resistivity and a significant change in the microstructure of the tantalum films.