High power impulse magnetron sputtering is characterized by discharge pulses whose target power density exceeds conventional sputtering power densities by two orders of magnitude or more; the goal is to provide a large flux of ionized sputtered material. The processes of pulse evolution are briefly reviewed, including secondary electron emission, self-sputtering, and rarefaction. Using a pulse power supply capable of providing constant voltage for target peak power densities up to 5 kW/cm2, the evolution of the current-voltage characteristics was investigated for copper and titanium. It is shown that the characteristic cannot be reduced to value pairs. Rather, a strong but reproducible development exists. The details depend on the argon pressure and applied voltage. Each target material exhibits a distinct and sharp transition to a high current regime that appears to be dominated by metal plasma. Despite the higher sputter yields for copper, the transition to the high current regime occurs much earlier and stronger for titanium, which may be attributed to a higher secondary electron yield and hence a higher density of electrons confined in the magnetron structure. At high currents, the closed-drift Hall current generates a magnetic field that weakens plasma confinement, thereby enabling large ion currents to reach a biased substrate.
BT - ISSP2007: The 9th International Symposium on Sputtering & Plasma Processes C1 -Windows and Daylighting Group
C2 - LBNL-62147 CN - LBNL-62147 LA - eng N2 -High power impulse magnetron sputtering is characterized by discharge pulses whose target power density exceeds conventional sputtering power densities by two orders of magnitude or more; the goal is to provide a large flux of ionized sputtered material. The processes of pulse evolution are briefly reviewed, including secondary electron emission, self-sputtering, and rarefaction. Using a pulse power supply capable of providing constant voltage for target peak power densities up to 5 kW/cm2, the evolution of the current-voltage characteristics was investigated for copper and titanium. It is shown that the characteristic cannot be reduced to value pairs. Rather, a strong but reproducible development exists. The details depend on the argon pressure and applied voltage. Each target material exhibits a distinct and sharp transition to a high current regime that appears to be dominated by metal plasma. Despite the higher sputter yields for copper, the transition to the high current regime occurs much earlier and stronger for titanium, which may be attributed to a higher secondary electron yield and hence a higher density of electrons confined in the magnetron structure. At high currents, the closed-drift Hall current generates a magnetic field that weakens plasma confinement, thereby enabling large ion currents to reach a biased substrate.
PY - 2007 T2 - ISSP2007: The 9th International Symposium on Sputtering & Plasma Processes T3 - ISSP2007: The 9th International Symposium on Sputtering & Plasma Processes TI - Physics of High Power Impulse Magnetron Sputtering ER -