Effect of arc suppression on the physical properties of low temperature dc magnetron sputtered tantalum thin films

Abstract

Arcing is a common phenomenon in the sputtering process. Arcs and glow discharges emit electrons which may influence the physical properties of films. This article reports the properties of tantalum (Ta) thin films prepared by continuous dc magnetron sputtering in normal and arc-suppression modes. The substrate temperature was varied in the range of 300–673K. The tantalum films were ∼1.8μm thick and have good adherence to 316 stainless steel and single-crystal silicon substrates. The phase of the Ta thin film determines the electrical and tribological properties. The films deposited at 300K using both methods were crystallized in a tetragonal structure (β phase) with a smooth surface (grain size of ∼10nm) and exhibited an electrical resistivity of ∼194μΩcm and a hardness of ∼20GPa. When the substrate temperature was 473K and higher, the arc-suppression mode appears to influence the films to crystallize in the α phase with a grain size of ∼40nm, whereas the normal power mode gave mixed phases β and α beyond 473K, the arc-suppression mode yields larger grain sizes in the Ta thin films and the hardness decreases. These changes in the physical properties in arc-suppression mode are attributed to either the change in plasma characteristics or the energetic particle bombardment onto the substrate, or both.