Stability and Failure Analysis of a W-Based Microhotplate

In this paper, we present the stability and failure of a tungsten-based microhotplate (W-MHP) fabricated with 0.5-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> standard CMOS technology. Resistance measurements and three-dimensional optical profilometer results combined with scanning electron microscopy observations were used to analyze the failure mechanisms of the W-MHP at operation temperatures up to 1000 °C. The electro-stress migration of the W film, recrystallization of the polycrystal W thin film, and breakage of the dielectric membrane were the dominant stability-failure mechanisms observed. The W-MHP had recoverable deformation and no evident resistance drift when the working temperature was below 450 °C. Correspondingly, at the operating temperature range of 500 °C–<inline-formula> <tex-math notation="LaTeX">$850~^{\circ }\text{C}$ </tex-math></inline-formula>, the W-MHP showed unrecoverable deformation and regular resistance drift caused by the electro-stress migration of the W heater and the interdiffusion of atoms between the W, Ti/TiN and SiO2. At temperatures higher than <inline-formula> <tex-math notation="LaTeX">$1000~^{\circ }\text{C}$ </tex-math></inline-formula>, the recrystallization of the polycrystalline W film caused a sharp drop in resistance. In addition, sudden and large heat pulses were more likely to cause the suspended membrane to rupture, which resulted from the rapid accumulation of internal thermal stress and lack of time to release, indicating that the operating temperature of the MHP should slowly increase or decrease. One million cycles of thermal pulse between <inline-formula> <tex-math notation="LaTeX">$25~^{\circ }\text{C}$ </tex-math></inline-formula> and 300 °C did not cause performance degradation of the device. Self-heating high-temperature rapid thermal annealing significantly improved the high-temperature stability of the MHP. [2022-0135]