Investigation of Bond-Pad Etching Chemistries for Determination of Probe/Bonding Related Sub-Pad Cracks

Bond-pad integrity directly affects the performance of microelectronic devices. Bond-pad cracking and the related sub-pad cracking of Inter-Metal Dielectric (IMD) may introduce a high reliability risk and cause units to fail at environmental stress. Bond-pad cracks may be initiated by probing during wafer sort and the wire bonding process during assembly. This paper presents a comparative analysis of the various chemistries used for exposure and decoration of pad cracks. The investigation showed that a tri-iodine etch provides clean and artifact-free exposure of the TiN barrier layer of the pad and is the best (of the methods tried herein) for pad crack observation.