Adhesion and delamination of tantalum and chromium films on glass

Abstract

The adhesion and delamination behavior of sputtered Ta and Cr films on barium boroaluminosilicate glass were investigated. The locus of delamination was determined by XPS analysis of peeled film strips to be at the film-glass interface. We found a strong correlation between the intensity and thickness of the metal suboxide interphase layer formed and resistance to film delamination. For Ta, we found that the presence of a sufficiently thick TaOx layer at the glass-film interface effectively prevented debonding of the film from the glass substrate. The role of oxygen in metal-glass bonding chemistry was explored by sputter deposition of metal films with in situ oxygen or air dosing. SIMS sputter-depth composition profiles confirmed the presence of a Ta-oxide phase (20-90 nm, depending on the dosing conditions) at the film-glass interface. We found that the delamination mechanism was prevented by in situ oxygen doping of the glass surface during film deposition. The cleanliness of the glass surface prior to sputtering, the ability to provide surface oxygen, and the film deposition conditions were found to be critical in avoiding delamination of the films from the glass. Although other factors may be involved in the mechanism of adhesion of Ta, the ability of the glass surface to provide oxygen for bonding is the overriding one, as shown in this work. Thus, oxide formation and chemical bonding at the metal-glass interface are more important than surface topography in the bonding of oxygen-active transition metals, such as Ta and Cr, to glass.