Investigating the plasma parameters of an Ar/O2 discharge during the sputtering of Al targets in an inverted cylindrical magnetron

Abstract

The plasma parameters and reaction kinetics in an inverted cylindrical magnetron chamber have been studied with an energy resolved mass spectrometer during the sputtering of aluminum targets in an Ar/O2 discharge. Mixtures of argon and oxygen were studied as a function of oxygen percentage (0%–90%) in the discharge. The plasma was powered at 4 kW and 40 kHz at a process pressure of 5 mTorr. Al+, Al, AlO, AlO+, O2+, O+, Al2O+, and Ar+ were among the species detected in the discharge. The deposition rate of the deposited thin film decreased with increasing oxygen percentage in the discharge and results indicated that the pure gamma-alumina was obtained when the percentage of oxygen was approximately 70%. The linear plot of energy distributions of the positively charged film forming species changed from a single peak to a bimodal distribution as the percentage of oxygen exceeds 65%. In a log plot, however, the distributions showed multiple peaks ranging from 2 eV to 78 eV. Fluctuations of about 1 eV in peak energies were observed.