Electrical properties of Ag/Ta and Ag/TaN thin-films

• Silver shows promise for interconnections at high temperatures.
• Metal stacks, consisting of silver on either Ta or TaN were investigated up to 800 °C.
• Both systems showed stable performance up to 600 °C.
• At 700 °C Ag/Ta is more stable than Ag/TaN.

Although wide band gap devices (WBG, e.g. GaN and SiC) are eminently suitable for high temperatures and harsh environments, these properties cannot be fully taken advantage of without an appropriate interconnect metallization. In this context, silver shows promise for interconnections at high temperatures. In this work, the thermal stability of Ag with two barrier metals – Ta and TaN – was therefore investigated. Metal stacks, consisting of 100 nm of silver on 45 nm of either Ta or TaN were sputter-deposited on the substrate. Each metal system was annealed in vacuum for one hour at temperatures up to 800 °C. Both systems showed stable performance up to 600 °C. The system with Ta as a barrier metal was found to be more stable than the TaN system. Above 700 °C, silver agglomeration led to degradation of electrical performance.

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