Effect of DC bias voltage on the deposition rate for Ni thin films by RF–DC coupled unbalanced-magnetron sputtering

The article reports on sputtering of Ni films using a modified unbalanced magnetron equipped with Ni target (200 mm φ, 5 mm thick) and supplied simultaneously with RF (13.56 MHz) and DC power. A DC power supply was connected to the Ni target through a low pass filter. This makes it possible to control the incident Ar+ ion energy on the target. The deposition rate of Ni films increases linearly with the target DC bias voltage at a proper choice of the RF power. The film growth coefficient (deposition rate/ion current density) of Ni films can be controlled by the target DC bias voltage. The Ni films deposited at a target DC bias voltage of −300 V exhibit the Ni (111) reflection and contain grains with an average size of approximately 80 nm. The electrical resistivity of Ni films deposited at a target DC bias voltage of −300 V is approximately 7.1 μΩ cm. It was also found that the magnetron discharge produced by an unbalanced magnetron with external magnets located above the target can be sustained at lower Ar gas pressures, down to 6.7×10−2 Pa.