Low temperature Au-Au bonding using Ag nanoparticles as intermediate for die attachment in power device packaging

Low temperature and environmental-economic friendly die attachment processing technology is essential for power device packaging. In this paper, a novel die attachment strategy of power devices is proposed, which is Au-Au bonding strategy utilizing Ag NPs as a surface modification layer deposited by high-pressure magnetron sputtering method. To explore underlying bonding mechanisms, the Ag NPs morphology is observed by TEM at different temperatures from 27 °C to 200 °C under ambient atmosphere without pressure for 3 mins. Also, the robustness and fracture modes of the chips bonded at different parameters are investigated by die shear strength test and SEM along with EDS analysis. Additionally, the morphology and microstructures of the bonding interface are observed by TEM. The experimental results demonstrate that a robust and reliable low-temperature Au-Ag NPs-Au bonding is realized at the temperature of 200 °C for 3 mins under the pressure of 20 MPa without annealing. The bonding strategy illustrated here can provide a fresh understanding on low-temperature and time-saving thermo-compression bonding.