A Temperature-Insensitive Resonant Low-Pressure Microsensor Based on Au–Si Eutectic Wafer Bonding

This article shows a temperature-insensitive resonant low-pressure microsensor based on Au–Si eutectic wafer bonding. The microsensor comprised an silicon-on-insulator (SOI) wafer as the sensitive part, and a silicon cap packaging the SOI wafer in vacuum through Au–Si eutectic bonding to lower the thermal stresses and reduce the temperature sensitivity as no coefficient of thermal expansion mismatch exists between the SOI wafer and the silicon cap. Meanwhile, the silicon cap can counterbalance the thermal stresses induced by Au layer and Ti getter, lowering the temperature sensitivity of the microsensor from 7 to 2 Hz/°C with the thickness increasing from 300 to $1500 \,\mu \text{m}$ based on numerical simulation. Characterization results showed that the low-pressure sensitivities of the microsensors were about ±6 Hz/Pa, and the temperature sensitivities were about 5 Hz/°C, indicating the microsensor was insensitive to temperature based on Au–Si eutectic wafer bonding. Furthermore, high accuracies (measurement errors within ±3.5 Pa) and satisfactory long-term stability (measurement errors within ±3 Pa after one month) were obtained under the low pressures from 0.1 to 1 kPa and temperature from −40 °C to 80 °C, indicating the better performances than previous works for the low-pressure microsensors.