SiC Die Attach Metallurgy and Processes for Applications up to 500 $^{\circ}{\rm C}$

The challenges of packaging SiC-based electronics for high-temperature applications include their high operating temperatures, wide thermal cycle ranges, and, sometimes, high currents and high voltages. As a result, the selection of metallurgy for high-temperature SiC die attach is crucial to a successful package design, which involves chip metallization, substrate metallization, and die attach alloy. This paper examines off-eutectic Au-Sn as the die attach alloy with a PtAu thick film metallization on AlN substrates. A pure Au thick film layer was printed over the PtAu thick film layer. AlN substrates metalized with refractory MoMn and electroplated Ni/Au were also used. Two different die attach approaches have been investigated, using Sn-Au-Sn off-eutectic thick foil and limited-volume eutectic AuSn (80/20 wt.%) preform. The SiC backside metallizations evaluated were Ti/TaSi₂/Pt/Au and Cr/NiCr/Au. Die shear tests were performed after aging at 500°C and after thermal cycling. The shear test results and failure surface analysis are discussed.