Ion Energy Distributions in Magnetron Sputtering of Zinc Aluminium Oxide

Ion energy distributions have been measured with an energy-dispersive mass spectrometer during magnetron sputtering of Al doped ZnO. A d.c. and a pulsed d.c. discharge have been investigated. Different positive ions from the target material have been observed with low energies in d.c. and a second energy peak of about 30 eV in pulsed d.c. with only weak additional energy due to the sputter process. Negative ions are mainly O− with energies corresponding to the target voltage of several 100 eV. They originate from the target and barely from the (O2) gas and hit the substrate opposite the race track. In pulsed d.c., due to the varying target voltage, energies of up to 500 eV have been observed. With increasing pressure, negative ions at the substrate are reduced exponentially in their density but not in their energy.