Multichip Module Technologies:Conductor Metallization

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Conductor Metallization

In MCM, fabrication materials chosen will depend on the design, electrical requirements, and process chosen to fabricate the MCM. It is important to note that the most critical requirements for conductor metallization are conductivity and reliability.

Aluminum

Aluminum is a low-cost material that has adequate conductivity and can be deposited and patterned by typical IC techniques. It is resistant to oxidation. It can be sputtered or evaporated, but cannot be electroplated.

Copper

Copper has significant conductivity over aluminum and is more electromigration-resistant. It can be deposited by sputtering, evaporation, electroplating, or electroless plating. Copper rapidly oxidizes, forming a variety of oxides that can have poor adhesion to polymer dielectrics and copper itself.

Gold

Gold is used in thin-film structures to minimize via contact resistance problems caused by oxidation of Cu and Al. Gold can be deposited by sputtering, evaporation, electroplating, or electroless plating. Cost is high with excellent resistivity characteristic. Adhesion is poor and so it requires a layer (50 to 200 nm) of Ti or Ti/W.

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