Thin-Film Multichip Packaging for High-Temperature Geothermal Application

A thin-film multichip module substrate technology has been developed and evaluated for packaging high-temperature (300 °C) geothermal well instrumentation. The base substrate technology selected was AlN to minimize the difference in the coefficient of thermal expansion between the substrate and the SiC digital die. The conductor was vacuum deposited Ti/Ti:W/Au followed by an electroplated Au. A plasma-enhanced chemical vapor-deposited silicon nitride was used for the interlayer dielectric. The substrate was characterized as a function of temperature and after aging at 300 °C. The electrical properties and adhesion remained stable after 2000 h at 300 °C.