Hochschulschrift:
Freiburg i. Br., Univ., Diss., 2015
Anmerkungen:
Beschreibung:
Zusammenfassung: This thesis work is aimed at investigating the assembly and packaging technologies for GaN and SiC based high-power and high-temperature electronic devices. The die-attachment and interconnection methods have been in the focus of investigations. For mounting SiC and GaN devices, Ag-sintering and foil-based Transient Liquid Phase (TLP) bonding were selected as die-attachment techniques. For TLP bonding process, the TLP-interlayer material was produced in the form of electroplated multilayer foils, which were based on Ag-Sn and Ag-In binary systems. Two design variants of multilayer foils, consisting of a 3-layer sandwich structure and a 9-layer structure, were successfully produced. The 9-layer structure provided the benefit of avoiding the post-bonding annealing step. The novel multi-layer foil can be utilized as a commercial product for TLP-interlayer material. For both Ag-sintering and foil-based TLP bonding, a complete process parameter optimization was performed. Various characterizations methods such as Differential Scanning Calorimetry (DSC), Energy Dispersive X-ray (EDX) Spectroscopy, Infrared (IR) Thermography, Digital Image Correlation (DIC) and Die-Shear Tests were used to determine the properties of the die-attachments. Subsequently, electrical, thermal and mechanical properties of both die-attachment types were compared to the current state-of-the-art high-temperature die-attachments such as Au80Sn20, Au88Ge12 etc. It was found that both Ag-sintering and TLP bonding exhibited better thermal and electrical properties. The thermo-mechanical stresses in Ag-sintered and TLP bonded joints were considerably low in a wide range of temperatures i.e. 30 – 400 ºC. The GaN-on-Si High Electron Mobility Transistors (HEMTs) from Fraunhofer IAF Freiburg, were used during the investigations. These devices feature high breakdown-voltages, lower specific on-state resistances and achieve higher performances on smaller area as compared to their Si counterpart. A systematic electrical characterization of GaN-on-Si HEMTs was performed from on-wafer devices to the final assembly. The objective was to investigate the assembly-related thermal and thermo-mechanical influences on the electrical characteristics of the devices. A major emphasis was given to the thermal characterization of the GaN assemblies. The surface temperatures of the devices were measured using IR-thermography and surface-mounted Pt-1000 temperature sensors. The actual channel tem ...