Unique Selected Area Deposition o Copper Onto Aluminum for Multichip Module Applications

The inability to deposit copper directly onto aluminum is a longstanding problem in microelectronic manufacturing. Presently, aluminum must be coated with a barrier layer such as TiN to promote copper adhesion and provide good electrical contact between the two metals. This work will demonstrate a nonaqueous galvanic process for selectively depositing a highly adherent copper coating directly onto aluminum device structures. The coating, which forms spontaneously at ambient temperature via direct displacement of aluminum, will serve as a base for further copper deposition by sputtering or electroless methods.The direct displacement copper coating process potentially offer a lower cost-of-ownership than sputtered or CVD barrier layer processes since no specialized equipment would be required. Moreover, application from a liquid bath should improve the ability to deposit copper into deep contact holes and trenches where sputtering or CVD processes often fail. The required chemicals should pose no exceptional disposal problems within a fab environment and, in principle, should be recyclable to allow further cost savings.The proposed program will be conducted in conjunction with the University of Missouri-rolla where the nonaqueous direct displacement process was initially developed to supplement solvent extraction techniques for the reclamation of heavy metals.