Effects of Cu/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability

Copper wire bonding is an alternative interconnection technology to serve as a viable, and cost saving alternative to gold wire bonding. Its excellent mechanical and electrical characteristics attract the high-speed, power management devices and fine-pitch applications. The copper wire bonding will be an important interconnection technology along with a flip chip technology. However, the growth of Cu/Al IMC (intermetallic compound) at the copper wire and aluminum interface can induce a mechanical failure and increase a potential contact resistance. In this study, the copper wire bonded chip samples were annealed at the temperature range from 150°C to 300°C for 2 to 250 hours, respectively. The formation of Cu/Al IMC was observed and the activation energy of Cu/Al IMC growth was obtained from an Arrhenius plot (In (growth rate) vs. 1/T). The obtained activation energy was 26 Kcal/mol. And the behavior of IMC growth was very sensitive to the annealing temperature