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Failure analysis of discolored and nonstick Al bondpad during wafer sorting process

In this paper, a discolored and nonstick bondpad case due to Si dust contamination is discussed. It was found that discoloration surrounded the probe mark area, resulting in nonstick 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.