Reactive d.c. magnetron sputtering of the oxides of Ti, Zr, and Hf

Abstract

Conventional direct current (dc) magnetron sputtering of nonconducting oxide films via reactive sputtering is extremely difficult. Without good separation of the oxygen from the target, the surface of the target rapidly becomes covered with an oxide film or “poisoned” when there is a high enough partial pressure of the reactive gas to form the desired film composition on the substrate. Breakdown of the oxide film on the target surface leads to arcing, which can damage the power supply and which can also eject droplets into the growing film. Depending on the application, these droplets can degrade performance of the oxide film. Recent advances in power supply technology with the introduction of pulsed d.c. power has overcome many of the problems in using d.c. power for the reactive sputtering of oxide films. In this study, a d.c. power supply was used along with an arc suppression unit to provide pulsed d.c. power for the reactive sputter deposition of the oxides of Ti, Zr, and Hf. As long as partial pressure control of the reactive gas was used along with the pulsed d.c. power, crystalline TiO 2, ZrO 2, and HfO 2 and suboxides of these materials were deposited in a well-controlled manner. Arcing on the sputtering target was virtually eliminated, and there were no forbidden composition zones. Details of the deposition process are provided along with the hysteresis curves and deposition data for the oxide systems.