Heavy copper wire-bonding on silicon chips with aluminum-passivated Cu bond-pads

• Thin Al-capping of thick electroplated Cu pads prevents Cu oxidation.
• Electroplated Cu pads allow for heavy Cu wire-bonding.
• Oxidized Cu pads prevent heavy Cu wire-bonding.
• Thin Al-capped Cu pads can be directly bonded without de-oxidation.

Thick electroplated Cu bond-pads have recently been shown to allow for heavy Cu wire-bonding on silicon power devices. The Cu surface oxides present on these pads are a major concern for the bonding process and for a sufficiently stable bond formation. They currently have to be removed after the die-attach and prior to wire-bonding. To avoid such removal, the application of a thin Al coating on the Cu bond-pads is investigated for its passivating ability and its suitability for the bonding process.

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