Gas-free & Nano Al2O3-coated Ag Bonding Wire for Replacing Au Wire

Ag and Cu wires require forming gas environment during wire bonding contrary to Au wires due to surface oxidation at high temperature. Au is the only noble metal not requiring passivation against oxidation, being most expensive metal. H2 gas in forming gases is hazardous and expensive. For replacing Au wire and forming gas, we propose a passivation solution using the application of a ceramic (Al2O3) coating at nanometer scales on Ag bonding wires. We used ALD (Atomic Layer Deposition) methods to apply Al2O3 coating on Ag metal wires with diameters ranging from 0.7 to 1.0 mils. We present bondability and reliability data followed by workability test at 200,000 continuous bondings. Al2O3 coated Ag wire satisfied all of the package level requirements from camera module manufacturers.