The Structural Investigation of Alumina and Aluminum Nitride Mixed Thin Films Prepared by D.C. Plasma Processes Under Different Conditions

Composite films of aluminum nitride and alumina were fabricated on 6061 aluminum alloys in a d.c. plasma chamber. Samples were treated by three main processes. They were 1) Ar plasma etching, 2) NH3/Ar plasma with low pressure and low current density, and 3) NH3 plasma with high pressure and high current density. The oxygen-free Al surface was obtained after 10 min. 2.8 keV Ar+ sputtering in a UHV analysis chamber after the sample was treated by processes 1 and 2. Composite films of aluminum nitride and alumina were obtained on samples treated by processes 1, 2, and 3. The surface compositions and bonding environments of the composite films were characterized by AES and XPS. Composite films containing Al-N, Al-O and Al-Al bonds were formed but no nitrogen-oxygen bonds were observed. The thicknesses of the films were estimated by argon sputtering in the UHV chamber. The surface morphologies of samples after fabrication processes in d.c. plasma were investigated by SEM. A possible formation mechanism of the composite film in the ammonia plasma is proposed.