This paper discusses the reliability characterization of thermal micro-structures implemented on industrial 0.8 m CMOS chips. Various degradation and failure mechanisms are identified and evaluated under high temperature operation. At high temperatures the mechanisms are many and varied, and co-incidental thermally-induced mechanical defects are found in both the poly-Si heater and the poly-Si temperature sensor, along with temperature- and current-enhanced interlayer diffusion degradation of the heater contacts. Local reduction in the device thermal capacity by using silicon micro-machining can be expected to hold the promise of a number of significant advantages, especially for limiting current stressing of the contact regions. The results can be used to optimize the design of thermally based micro-sensors on CMOS chips, such as CMOS compatible chemoresistive gas sensors.
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