Fluorine Plasma Corrosion Resistance of Anodic Oxide Film Depending on Electrolyte Temperature

Samples of anodic oxide film used in semiconductor and display manufacturing processes were prepared at different electrolyte temperatures to investigate the corrosion resistance. The anodic oxide film was grown on aluminum alloy 6061 by using a sulfuric acid (H2SO4) electrolyte of 1.5 M at 0 C, 5C, 10C, 15C, and 20C. The insulating properties of the samples were evaluated by measuring the breakdown voltage, which gradually increased from 0.43 kV (0C) to 0.52 kV (5C), 1.02 kV (10C), and 1.46 kV (15C) as the electrolyte temperature was increased from 0C to 15C, but then decreased to 1.24 kV (20C). To evaluate the erosion of the film by fluorine plasma, the plasma erosion and the contamination particles were measured. The plasma erosion was evaluated by measuring the breakdown voltage after exposing the film to CF4/O2/Ar and NF3/O2/Ar plasmas. With exposure to CF4/O2/Ar plasma, the breakdown voltage of the film slightly decreased at 0C, by 0.41 kV; however, the breakdown voltage significantly decreased at 20C, by 0.83 kV. With exposure to NF3/O2/Ar plasma, the breakdown voltage of the film slightly decreased at 0C, by 0.38 kV; however, the breakdown voltage significantly decreased at 20C, by 0. 77 kV. In addition, for the entire temperature range, the breakdown voltage decreased more when sample was exposed to NF3/O2/Ar plasma than to CF4/O2/Ar plasma. The decrease of the breakdown voltage was lower in the anodic oxide film samples that were grown slowly at lower temperatures. The rate of breakdown voltage decrease after exposure to fluorine plasma was highest at 20C, indicating that the anodic oxide film was most vulnerable to erosion by fluorine plasma at that temperature. Contamination particles generated by exposure to the CF4/O2/Ar and NF3/O2/Ar plasmas were measured on a real-time basis. The number of contamination particles generated after the exposure to the respective plasmas was lower at 5C and higher at 0C. In particular, for the entire temperature range, about five times more contamination particles were generated with exposure to NF3/O2/Ar plasma than for exposure to CF4/O2/Ar plasma. Observation of the surface of the anodic oxide film showed that the pore size and density of the non-treated film sample increased with the increase of the temperature. The change of the surface after exposure to fluorine plasma was greatest at 0C. The generation of contamination particles by fluorine plasma exposure for the anodic oxide film prepared in the present study was different from that of previous aluminum anodic oxide films.