Long-term temperature resistance stability of gold-based multilayer electrodes for gas sensors

The long-term stability of resistive gas sensor microheaters was investigated. The microheaters were created as multilayered metallizations on a silicon oxide membrane. The behavior of Cr/Au/Cr and Cr/Ni/Au stacks was studied. The resistance of the Cr/Ni/Au stack stabilized after 15 hours of exposure due to gold burning into the chromium-nickel sublayer. Resistance drift is less than 7% after 48 hours of continuous operation at 350 °C and 12% at 500 °C. However, Cr/Au/Cr metallization cannot be used in high-temperature sensors because it degrades significantly at temperatures as low as 300 °C. Stack capping with SiO₂ layer has low influence on initial forming stage and improves long-term stability.