Development of copper wire bonding application technology

The continuous forming of oxide-free, stable, spherical copper balls which has been realized by blowing a reducing gas over the copper wire during copper ball formation (sparkling) is described. The prevention of chip damage resulting from hard copper wire, including underpad cracking and silicon cratering, by the double-load wire bonding technology is discussed; this technology can minimize chip damage from wire bonding stress because the bonding load is decreased during ultrasonic power oscillation. It was confirmed that copper wires have a reliability equivalent to that of gold wires. The double-load wire bonding technology makes it possible to use copper wires in MOS LSI devices on a commercial basis.>