Mechanical Reliability of Thick Films for High-Temperature Packaging

High-temperature electronics are required to reliably operate at 300 °C in gas and oil exploration and downhole drilling for geothermal energy applications. Advances in SiC and GaN devices enabled these applications. Reliable interconnect materials and technology are necessary to build functional circuits in high-temperature packaging. This paper investigated the mechanical reliability of two thick-film conductors (PtPdAu and Au) and two dielectrics at 300 °C with bias. Test vehicles (TVs) were fabricated with thick films as capacitors and aged at 300 °C with a 100-V bias. For the TVs fabricated with PtPdAu and thin dielectrics, adhesion degradation was first observed after 100-h aging with positive bias voltage applied on the top electrode. The adhesion remained relatively constant when vehicles were aged with positive bias voltage applied on the bottom electrode. Increasing the dielectric thickness or reducing the Bi concentration in PtPdAu delayed the first observed adhesion degradation from 100 to 500 h. Aging with alternating polarities also resulted in adhesion degradation. In all tests, no adhesion degradation was observed with the thick-film Au, which did not contain Bi.