Optimizing efficiency of Ti ionized deposition in HIPIMS

The evolution of plasma composition, electron temperature and deposition rates of high-power impulse magnetron sputtering (HIPIMS) of a titanium target have been studied by optical emission spectroscopy and deposition on a crystal oscillator, for pulse lengths of 50 µs and 100 µs over a range of voltages. The observations indicate a strong power dependence of the populations of Ti1+ ions with respect to the Ti neutrals. A clear saturation point for Ti1+ is seen, while the more highly ionized species increase, even at a constant electron temperature. The creation of the more highly ionized species follows the current, increasing throughout the pulse, and is attributed to ionization by collisions with energetic secondary electrons. Within the HIPIMS regime, deposition energy efficiency correlates positively with the emission from Ti1+ ions and negatively with emission from more highly ionized species.