Wafer bonding by low-temperature soldering

Recently. wafer level packaging received lots of attention in microsystems because it shows the potential to reduce the packaging cost, while the yield of devices after dicing and packaging can be increased. However, there is a limitation of commercialized wafer bonding technology. i.e., the high process temperature, such as 1000 degrees C of silicon fusion bonding, and 450 degrees C of anodic bonding. A novel tow-temperature wafer bonding with process temperature lower than 160 degrees C is proposed, it applies the In-Sn alloy to form the interface of wafer bonding. The experiment results show helium leak test of 6 x 10(-9) Torr 1/s, and a tensile strength as high as 200 kg/cm(2). Reliability test after 1500 temperature cycles between -10 degrees C and 80 degrees C also shows no trace of degradation compared to the initial quality of the samples. This low-temperature soldering process demonstrates its promising potential at the wafer level packaging in industrial production. (C) 2000 Elsevier Science. S.A. All rights reserved.