A method is provided to improve the adhesion between bonding pads and ball portions
of gold wires to improve the reliability of a semiconductor device. About 1 wt.
% of Pd is contained in gold wires for connection between electrode pads formed
on a wiring substrate and electrode pads (exposed areas of a top layer wiring formed
mainly of Al) formed on a semiconductor chip. In bonded portions between the electrode
and ball portions of the gold wires, an interdiffusion of Au and Al is suppressed
to prevent the formation of Au4Al after PCT (Pressure Cooker Test).
Thus, a desired bonding strength is obtained even when the pitch of the electrode
pads is smaller than 65 m and the diameter of the ball portion is smaller
than 55 m or the diameter of the wire portion of each gold wire is not larger
than 25 m.
