Direct silicon-silicon bonding by electromagnetic induction heating

A novel heating technique, electromagnetic induction heating (EMIH), uses electromagnetic radiation, ranging in frequency from a few megahertz to tens of gigahertz, to volumetrically heat silicon above 1000°C in only a few seconds. Typical power requirements fall between 900 to 1300 W for silicon wafers 75 to 100 mm in diameter. This technique has successfully produced direct silicon wafer-to-wafer bonds without the use of an intermediate glue layer. Infrared images indicate void free bonds that could not be delaminated with knife-edge tests. In addition, four pairs of stacked wafers were bonded simultaneously in 5 min, demonstrating the potential for multiwafer bonds and high-throughput batch processing.