ESD protection under wire bonding pads

We have developed a configuration for diode-based electrostatic discharge structures that can be reliably placed under the metal stack of an integrated circuit wire-bonding pad, thereby reducing the die area consumed for ESD. Prototype structures from both three- and four-level CMOS processes were assembled using gold ball and aluminum wedge bonding, respectively. Visual inspections after bonding found nothing that would compromise the integrity of the structure. Electrical tests found no failures from the ESD structure placement under the pad for over 8000 pads in the three-level metal and over 7000 pads for the four-level metal process. Structures under the pads pass full product-level qualification procedures.