Thermosonic Bonding of Gold Wire onto a Copper Pad with Titanium Thin-Film Deposition

A thermosonic (TS) bonding process for gold wire bonded onto chips with copper interconnects was developed by depositing a thin, titanium passivation layer on a copper pad. The copper pad oxidized easily at elevated temperature during TS wire bonding. It was shown that the bonding strength did not degrade after prolonged storage at elevated temperature. The results show that this process could be applied to chips with copper interconnect packaging in the TS wire-bonding process.