Current-Voltage Testing of Candidate Dielectric Materials for 500 °C SiC Integrated Circuits

High temperature operation (500 °C and higher) of integrated circuits offers important benefits to harsh environment applications such as aerospace, aeronautics, and energy production. SiC-based electronics are a promising solution to this need for high temperature operation. However, thermally activated degradation of materials used in conjunction with SiC (such as interconnect metals and insulators) are a limiting factor in the longterm operation of SiC integrated circuits. In particular, dielectric material properties degrade with increased operating temperature but are nevertheless critical in the ability to demonstrate long-term integrated circuits with multiple layers of interconnect. We fabricated and tested capacitors using several different dielectric thin films to initially compare their potential suitability for use in high temperature (500 °C and above) SiC integrated circuit applications. We conducted current versus voltage testing (up to hundreds of volts) at 25, 300, and 500 °C on capacitors made from reactively sputtered silicon nitride, silicon nitride deposited by plasma enhanced chemical vapor deposition (PECVD), silicon dioxide deposited from tetra-ethyl-ortho-silicate (TEOS) by PECVD, and amorphous SiC deposited by ion-beam assisted sputtering. The I-V characteristics of the 0.7-μm-thick amorphousSiC capacitors were unacceptably leaky (> 0.6 A/cm at 0.4 MV/cm at room temperature). As-deposited 0.7-μmthick PECVD TEOS silicon dioxide (deposited at 400 °C) demonstrated the best insulating performance with a leakage current density of less than 1 μA/cm for an electric field of 0.7 MV/cm (50 V) at 500 °C. These initial I-V measurements at elevated temperatures will be used to down-select dielectrics for prolonged electrical stress testing at 500 °C.