A review on the copper bond pad application in wire bond technique

Aluminum (Al) has been used as an interconnection material for the last 40 years. As the ultra-large-scale integrated devices become more and more smaller, low junction capacitance and higher drive current are measures to improve the performance of semiconductor gate. One attempt is to replace the conventional Al interconnection with copper (Cu), as Cu possesses improved electromigration resistance, lower electrical resistivity and higher thermal conductivity. The front-end change, however, brings concerns to back-end process, probe and later wire bond process on a readily oxidized Cu surface. Questions like the Cu pad oxidation during handling, wafer dicing, die attach and thermosonic bonding are concerns. This review summarizes the current literature on Cu pad, including its manufacturing methods, advantages, disadvantages, oxidation prevention measures, wire bond process and wire bond reliability. It will provide guidance for the work relevant to Cu pad.