Assembly and packaging technologies for high-temperature and high-power GaN HEMTs

摘要

In this work, assembly and packaging technologies for high-temperature high-power GaN high electron mobility transistors (HEMTs) are presented. GaN HEMTs with epitaxial growth on Silicon substrates were used during these experiments. Both die-attachment and interconnection techniques were investigated and a performance comparison is given before and after the assembly process. State-of-the-art silver sintering and transient liquid phase bonding were used as die-attachment methods [2], [3]. For the die-attach material, various characterizations such as shear strength, Energy Dispersive X-ray (EDX) spectroscopy and Differential Scanning Calorimetery (DSC) were performed to characterize the operation up to 500 °C. An estimation of the thermal behavior of the sintered and TLP-bonded GaN HEMTs is performed. For interconnection, gold- and palladium-based materials were investigated for wire-bonding. The complete bonding process was characterized. Estimations about the current carrying capabilities are made for both materials. Passive temperature cycling from −40 to +150 °C was performed as an indication of initial reliability for both die-attachments and interconnections. A systematic electrical characterization of HEMTs is performed starting from the on-wafer measurements up to the final assembly process. The influence of thermal effects on the electrical properties, such as on-state resistance at higher power levels, i.e., 350 W were studied before and after the assembly process. A combination of sintered device with the gold wire bonds is considered as the optimum packaging of GaN HEMTs.