IME develops low temperature die-to-wafer bonding technology for MEMS and heterogeneous integration. Heterogeneous integration of multi-functional devices is an emerging key technology for the multifunctional electronics products. Several approaches have been evaluated for heterogeneous integrations via die-to-die, die-to-wafer and wafer-to-wafer bonding. For the divergent devices integration having different die size, yield, functions and process requirement, die-to-wafer bonding could be the best approach to achieve the flexible heterogeneous integration. Die-to-wafer bonding allows for the usage of know good dice (KGD) and after dicing the device wafer , which is difficult for wafer-to-wafer. Bonding of MEMS die to ASIC wafer is a good example for the die-to-wafer application, since there have been many issues on the low yield in MEMS device bonding and assemblies to ASIC devices. Die to wafer bonding enables to provide low cost and high yield solutions to MEMS die to ASIC wafer assembly.

At IME, die-to-wafer assembly has been developed with a low temperature bonding technology. As some MEMS devices are sensitive to the high temperature which could degrade device performances, low temperature bonding technology can reduce the thermal issues when attaching each MEMS die to the ASIC wafer. The whole processes can be performed below 200oC. The electrical interconnection was established by forming AuInSnCu intermetallic compound (IMC) phases. The MEMS die was hermetically packaged by CuInSn IMC sealing ring. The images below show an 8” ASIC wafer assembled with the 5 x 5 mm2 MEMS dice by low temperature bonding. The bonding shear strength after die-to-wafer bonding was ~ 10MPa. The He (helium) leakage rate of individual die was measured to be lower than 10-8 atm cc/sec. These packages were confirmed to be robust up to 400oC.

FMEMS Dice on ASIC Wafer by D2W with Low Temperature Bonding