High-power pulsed magnetron sputtering of copper and titanium films was systematically investigated. The depositions were performed using a strongly unbalanced magnetron system with a target of 100mm in diameter. The repetition frequency of the pulsed dc power supply (with a maximum voltage and current of 1kV and 120A, respectively) was 1kHz at a 20% duty cycle and an argon pressure of 0.5Pa.
Time evolutions of the magnetron voltage, the target current density (up to 1.5 A/cm2) and the ion current density on the substrate (up to 0.45A/cm2) were measured to provide information on absorption of energy in the discharge plasma and on transfer of arising ions to the substrate at a target power density in a pulse up to 950W/cm2. The deposition rate and the substrate ion current density per average target power density were determined to investigate efficiency of magnetron sputtering, and formation and transfer of ions to the substrate, respectively. Time-averaged mass spectroscopy was performed at the substrate position to characterize ion energy distributions and composition of total ion fluxes to the substrate.
A different trend in measured values of the deposition rate per average target power density obtained for these two technologically interesting materials and the same trend in their values of the ionized fraction of sputtered atoms in the flux onto the substrate (up to 56% for copper and 81% for titanium) were explained on the basis of model predictions. We present a qualitative model based on that developed recently by Christie (2005). The effects of self-sputtering of target material, losses of the target material ions during transport to the substrate and additional ionization of sputtered atoms in a plasma bulk on the deposition rate per average target power density and on the ionized fraction of sputtered atoms in the flux onto the substrate are shown.
References:
[1] J. Vlèek, P. Kudláèek, K. Burcalová and J. Musil, J. Vac. Sci. Technol. A 25 (2007) 42.
[2] J. Vlèek, P. Kudláèek, K. Burcalová and J. Musil, Europhys. Lett. 77 (2007) 45002. |