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|Packaging Technology for High Temperature Silicon-on-Insulator Electronics|
|Keywords: High temperature, Packaging, SOI|
|Silicon-on-insulator (SOI) integrated circuits have been demonstrated for use at temperatures up to 300oC. However, to build functional electronics, multiple devices must be interconnected to provide the desired functionality. A system-in-package (SiP) approach has been developed using thick film technology on Si3N4 ceramic substrates. Si3N4 has a near coefficient of thermal expansion (CTE) match to Si, and higher thermal conductivity and flexural modulus than Al2O3, which is commonly used for thick film applications. The conductor metallization is Au. For 325oC operation, eutectic Au-Ge die attach was used with a Ti/Ti:W/Au backside die metallization. After 3000 hours at 325oC, the average die shear strength had decreased from 3.96kg/mm2 to 3.33kg/mm2, a decrease of only 16%. SOI die typically have Al wire bond pads that are not compatible with Au thermosonic wire bonding for high temperature applications. An electroless Ni/electroless Pd/Immersion Au plating process was used to provide a barrier layer (Ni) and a wire bondable finish (PdAu) over the Al wire bond pads. After 500 hours at 320oC, the ball shear strength has remained constant, the wire pull strength has decreased ~10% due to annealing of the Au wire and the daisy chain resistance decreased slightly. The results of ongoing tests and failure analysis will be presented.|
|R. Wayne Johnson, Professor