Reliable low-temperature die attach process using Ag/Sn/Ag sandwich structure for high-temperature semiconductor devices

A low-cost and eco-friendly die attach process for high temperatures should be developed owing to the expansion of the field of high-temperature applications, such as high-power and high-frequency semiconductors. Pb-based and Au-based systems have been used as conventional die attach materials for high-temperature devices. However, these materials exhibit environmental problems and are expensive. Here, we show that the die attach process using the backside metal of the Ag/Sn/Ag sandwich structure is successfully developed for the mass production of Si devices. It has a low-temperature bonding process (235 °C), a high remelting temperature (above 400 °C), and rapid bonding time (20 ms). In addition, it exhibits better properties than Au-12Ge and Pb-10Sn backside metals, which are conventional materials for the high-temperature die attach process. After the die bonding process, various reliability tests of Si devices with the Ag/Sn/Ag backside metal structure were performed.