Influence of peak current on substrate plasma sheath properties of Ti films deposited by high-power pulsed magnetron sputtering

Abstract

For film deposition, the substrate sheath properties, such as the plasma density, ion-to-atom ratios around the substrate, are more important for the film structure. In this paper, titanium thin films were deposited on grounded substrates by high-power pulsed magnetron sputtering (HPPMS) with the peak current in the range of 113–185 A. A simple and new equivalent circuit model of the sheath was established to study the plasma density around the substrate sheath. The Ti ion-to-atom ratios near substrate were studied by optical emission spectroscopy (OES), and the film structure was detected by transmission electron microscopy (TEM). The results showed that the calculated plasma density was from 0.8 × 10[Formula: see text] to 1.4 × 10[Formula: see text] m[Formula: see text] at different peak current. These were consistent with the results measured by a modified one-grid ion collector using saturation current probe method, which proved our proposed equivalent circuit model was correct. The Ti ion-to-atom ratios around the substrate were estimated at about 24%–62%. The plasma density and ion to atom ratio around the substrate increased with the peak current, and this could lead to a higher film crystallization and preference growth on Ti (101) and (100).