In this paper, a discolored and nonstick bondpad case due to Si dust contamination will be discussed. It was found that discoloration surrounded the probe mark area, resulting in non-stick bondpad issue at the assembly house. SEM, EDX and Auger analysis techniques were used to identify the root cause. After performing FA and investigations, the discoloration was concluded to be due to Si dust corrosion, which was introduced during wafer die-saw process. However, the root cause for Si dust corrosion was NaOH contamination during wafer sorting process. In this case, Si dust corrosion had made it difficult to clean away Si dust during wafer die-saw process. In this paper, an electrochemical mechanism on Si dust corrosion on Al bondpads is proposed and discussed.
A bondpad peeling case due to passivation residue is presented for 0.13 um copper process in wafer fabrication (fab). It was reported that some dies from two lots of wafers failed die-pull and die shear test at the assembly house. SEM, Auger and TEM techniques were used to identify the root cause. Based on failure analysis and wafer fab investigation results, it is concluded that the peeling occurred between the barrier metal Ta and Cu layers. The root cause of the metal peeling was due to an extra thin Si3N4 layer between the barrier Ta and Cu layers, which could be due to passivation underetch or Nitrogen flow issue during passivation layer deposition.
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