Study of die bond voids on memory semiconductor devices in 24-L cerquad packages

Abstract

Die bond voids were encountered in the eutectic die-attachment of memory products. The failures observed were characterized by the depletion of the Au layer of the base substrate thus exposing the underlying bare ceramic. An evaluation carried out showed that the voids encountered were not related to the Au thickness of the base substrate. Instead, the quality of the Au layer would affect eutectic wettability and percentage of die bond voids over the intended contact area under the die. Subsequent study identified oxide contaminant to be the cause of the die bond voids and showed that units with dice that had been chemically treated to remove the oxide layer were free of die bond voids. Units with untreated die backside were found to have a higher percentage of Si in the Au-Si bond while units with treated backside were found to have a Au-Si com-position closer to the eutectic point. To prevent oxide growth during high temperature exposure, a Au-Si alloying process in a N₂/H₂ reducing gas ambient was investigated. The results showed that no die bond voids were encountered in the die bonding process under this condition.