Effects of the magnetic field strength on the modulated pulsed power magnetron sputtering of metallic films

The influence of the magnetic field strength (B) on the deposition rate and plasma properties for Ta, Cr, Ti, Al, Cu materials using the modulated pulsed power (MPP) magnetron sputtering technique in a closed field unbalanced magnetron sputtering system was investigated. The MPP deposition rates were compared to those obtained from the films deposited by direct current magnetron sputtering (DCMS) under similar experimental conditions. The time averaged ion energy and mass distributions of positive ions in the MPP plasmas at different magnetic field strengths were compared, using a Hiden electrostatic quadrupole plasma mass spectrometer. The effects of the repetition frequency and pulse length on the MPP deposition rate were investigated. For a given target power, the MPP deposition rate increased when the repetition frequency was increased. It also increased as the pulse length was increased at a constant repetition frequency and target power. The MPP deposition rate is strongly material dependent. The MPP deposition rate increased as B decreased for a given target power. For a B of 550 G, the R-MPP/R-DCMS ratio for Cu was in a range of 0.81-1.02, for Al it was 0.84-1.01, for Cr it was 0.64-1.01, for Ti it was 0.52-0.89, and for Ta it was 0.47-0.84. For a B of 350 G, the R-MPP/R-DCMS ratio for Cu was increased to 1.03-1.07, for Al it was 0.94-1.04, for Cr it was 0.8-1.03, for Ti it was 0.79-0.94, and for Ta it was 0.72-0.88. However, a decrease in the ionization of metal and gas species was observed as B was decreased, which affected the microstructure and mechanical properties of the deposited Cr films. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3645612]