Bonding Degradation in the Tantalum Nitride-Chromium-Gold Metallization System

Thermocompression bondability in the tantalum nitride-chromium-goald metallization system is degraded because of diffusion and oxidation of chromiium resulting from a 300°C 2-hour air bake used to stabilize the tantalum nitride resistor network. Bondability can be restored by chemically removing the contaminant with either a gold etch treatment using potassium iodide and iodine or a chromium oxide etch treatment using ceric ammonium nitrate before thermocompression bonding. The integrity of bonds made to restored films is not degraded in tests at temperatures between -50° and 350°C for up to 200 hours. Delamination at the gold-chromium interface ciould not be induced by extended etching in ceric ammonium nitrate for as long as 96 hours.