Mechanistic Investigation and Prevention of Al Bond Pad Corrosion in Cu Wire-Bonded Device Assembly

Heavy corrosion on Aluminum (Al) bond pad, with a "mud-crack" appearance, in a Copper (Cu) wire-bonded assembly can be a critical failure mode, especially under harsh conditions such as in automotive environments. Such corrosion can be associated with the presence of contaminants such as chloride ions (Cl-). However, the exact corrosion activation mechanism remains unclear and hence the effective corrosion prevention cannot be achieved. In this paper, a novel immersion corrosion screening metrology was utilized as an in situ characterization tool to establish the corrosion mechanism directly relevant to Cu wire-bonded devices. With this improved understanding of Al bond pad corrosion mechanism, significant progress has been made toward developing effective corrosion prevention strategies to improve and ensure the overall packaging reliability.