Electromigration and electrochemical reaction mixed failure mechanism in gold interconnection system

Power bipolar devices with gold metallization experience high failure rates. The failures are characterized as shorts, detected during LSI testing at burn-in. Many of these shorted locations in the chip are the same for the failed devices. From a statistical analysis for wafer lots, it is found that the short failure rate is higher for the lots with thinner SiON interlayer dielectric films. Cracks are commonly observed in the SiON films at step edge portions of the device. The SiON film is locally turned to Au–Si eutectic at short positions by the reaction of Au with the SiON film and the reaction is only generated at specific step edge portions, i.e., at step edge on emitter electrodes in driver transistors and/or at cross-points of power lines. Based upon these results, a new electromigration and electrochemical reaction mixed failure mechanism is proposed for the failure.