Failure analysis based on dummy TIVA spot

Several lots suffer from electrical monitor structure fail, which failed the wafer center contact chain high resistance. EFA was performed on the failed unit. Compared with good unit, high resistance contact chain was found by I-V curve tracing, but the high resistance curve is a non-linear I-V curve. TIVA was employed to do electrical fault isolation and several series connected TIVA hotspot was observed on the contact chain. TEM cutting on the hotspot location found nothing abnormal. Even though TIVA spot is a dummy spot or induced spot, it is still useful. Combining dummy TIVA spot, electrical measurement and actual monitor structure property, detailed and in-depth electrical analysis was performed. According to the deep-dive electrical and logical analysis, the defect location is theoretically suspected on the contact that is nearby the last hotspot. In order to verify our hypothesis, further advance electrical analysis was performed by the AFP nanoprobing. The result confirms our analysis. Further physical FA, TEM cut found the open contact at our suspected location. Detailed failure mechanism and electrical analysis was described in the paper. it is a good reference for this kind of dummy spot related failure analysis.