The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a bonding pad for preventing a pad peeling and method for fabricating the same.
Generally, in a process for fabricating semiconductor devices, particularly in a package process (in a wire bonding process), a metal pad of a bonding pad unit disposed in a chip is electrically connected to an external device through a leadframe. For instance, when performing the wire bonding, a ball bonding is performed over the metal pad. The bonding pad unit where the ball bonding is performed includes an insulation layer among a plurality of metal layers.
FIG. 1 is a cross-sectional view of a typical bonding pad.
FIG. 2 is microscopic pictures showing limitations generated when performing a typical wire bonding.
Referring to FIG. 1, a typical bonding pad includes first to third metal layers 11, 13 and 15. A first insulation layer 12 is formed between the first metal layer 11 and the second metal layer 15. A second insulation layer 14 is formed between the second metal layer 13 and the third metal layer 15. A passivation layer 16 is formed over the third metal layer 15 to expose a portion of the third metal layer 15 where the bonding is performed.
Referring to FIG. 2, when performing the wire bonding, the bonding pad, i.e., the third metal layer 15, may be peeled off and even the second insulation layer 14 may be peeled off together. That is, a pad peeling occurs. The pad peeling of the second insulation layer 14 is generated because of the third metal layer 15 being damaged when the passivation layer 16 for exposing the third metal layer 15 is etched to thereby decrease a thickness of the third metal layer 15. More specifically, the third metal layer 15 with the decreased thickness is not capable of standing against power or stress applied thereto during a subsequent wire bonding process. Thus, the third metal layer 15 is cracked to thereby cause the pad peeling. Furthermore, the crack in the third metal layer 15 is transmitted to the second insulation layer 14 to deteriorate the second insulation layer 14. As a result, the pad peeling grows even worse. The pad peeling causes a bonding failure to thereby drop throughput of the semiconductor devices.