INTERFACIAL SLIDING IN CU TA/POLYIMIDE HIGH-DENSITY INTERCONNECTS AS A RESULT OF THERMAL CYCLING/

A scanning probe microscope was used to observe thermally induced defo rmation of 1 mu m thick Cu/Ta/polyimide test structures on Si. Relativ e height changes in arrays of parallel Cu and polyimide lines of vario us aspect ratios were examined in air at room temperature before and a fter a 25-350-25 degrees C thermal cycle conducted in gettered nitroge n. Grain elevation and hillock formation at grain boundaries were obse rved on the Cu surface as a result of the thermal cycling. It was also observed that significant sliding occurs at the Cu/Ta interface with 1 mu m wide Cu lines. Less or no sliding was observed at the interface with 10 mu m wide Cu lines.