Interfacial reactions and phase equilibria in the Al-Cu/Ta systems

Abstract

Thermal inkjet technology is in widespread use for color printers. In the roofshooter thermal inkjet printhead, tantalum is often used as the diffusion barrier between the gold and the conduction layers, Al, Cu, and Al-Cu. This study investigated the contact stabilities of Al/Ta, Cu/Ta, and Al-Cu/Ta systems using the reaction couple technique. The couples were annealed in af urnace at 600°C, 750°C, 900°C, 1000°C, and 1200°C for various lengths of time. One reaction layer, the Al 3 Ta phase, was formed at the interface in the Al/Ta and Al-Cu/Ta couples heat treated at 750°C, 900°C, and 1000°C. No Cu is observed in the Al 3 Ta phase even in the Al-Cu/Ta couples; however, the reaction couples with Al-Cu have slower reaction rates. For the Al/Ta reaction couples annealed at 600°C and Cu/Ta couples annealed at 750°C, 900°C, 1000°C, and 1200°C, no noticeable interfacial reaction was observed. It was concluded that the contacts were very stable and Ta was av ery good barrier layer. In addition, phase equilibria studies of the Al-Ta system were carried out. The experimental results indicate that the Al 2 Ta phase was not stable at 850°C and higher. A revised Al-Ta phase diagram was proposed in this study.