Thermal stability of Cu/Ta/GaAs multilayers

Copper metallization for GaAs was evaluated by using Cu/Ta/GaAs multilayers for its thermal stability. A thin Ta layer of 40 nm was sputtered on the GaAs substrate as the diffusion barrier before copper film metallization. As judged from sheet resistance, x-ray diffraction, Auger electron spectroscopy and transmission electron microscopy, the Cu/Ta films with GaAs were very stable up to 500 degreesC without migration into GaAs. After 550 degreesC annealing, the interfacial mixing of Ta with GaAs substrate occurred, resulting in the formation of TaAs2. At 600 degreesC annealing, the reaction GaAs with Ta and Cu formed TaAs, TaAs2, and Cu3Ga, resulting from Cu migration and interfacial instability. (C) 2000 American Institute of Physics. [S0003-6951(00)03047-3].