Failure Mechanisms in MEMS Based Silicon Carbide High Temperature Pressure Sensors

Abstract

The paper reports recent results of the long term reliability evaluation of single crystal silicon carbide (SiC) piezoresistive pressure sensors operated up to 500 degC. In-depth failure analysis was performed to identify the mechanisms responsible for their failures. Accelerated stress test (AST) that was developed specifically for high temperature operating devices was initially performed to extract the stable operating parameters of the transducers, which allowed for extracting the operating parameters. After the AST that included several hours of cyclic pressure and temperature excursions, the recorded maximum drift of the zero pressure offset voltage at room temperature, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OZ</sub> (25 degC), was 1.9 mV, while the maximum drift at 500 degC was 2.0 mV. The maximum recorded drift of the full-scale pressure sensitivity after ten hours of thermal cycling at 500 degC was plusmn1 muV/V/psi. In all cases, the observed failures during field validation were associated with the detachment of the Au die-attach from the sensor bondpads.