Development And Fabrication Of Polyimide Integrated Temperature, Humidity And Pressure Sensor

Detection of temperature, humidity and pressure is not only closely related to daily life, but also wide applied in industrial manufacturing, weather forecast, climate analysis, environment monitoring and aviation. Integrated temperature, humidity and pressure sensors with small size, low power consumption and cost can satisfy the demand of large amount and disposal use, especially in weather forecast application.MEMS based polyimide\ integrated temperature; humidity and pressure sensors are fabricated and tested. Pt thin film resistor is used to measure temperature as well as to realize compensation for humidity and pressure detection. Polyimide capacitive structure is used for humidity detection. The lower electrodes are in the form of plates or interdigital structure while the upper electrode is a plate with slot or grid. Both-side strain gauges on polyimide deformable membrane are used to detect pressure. Symmetric Wheatstone bridge is used to eliminate temperature effect. To simplify the fabrication, the encapsulation is carried out under constant pressure.It is illuminated that grid Au upper electrode has more uniform electric field, and slot electrode has larger interface with environment, consequently larger sensitivity. For polyimide has small Yang's Module, pressure membrane has good flexibility. Both side strain gauges have improved the pressure linearity. The integrated sensor has good temperature linearity from -20℃ to 100℃ and a sensitivity of 1.1 mV/℃. With slot upper electrodes, sensitivity for humidity detection is 3.314pF/%RH in the range of 20~90%RH. Pressure sensor achieves a sensitivity of 0.17mV/kPa and the linear error is only 0.06kPa in the range of-40-0kpa differential pressure.Integrated temperature, humidity and pressure sensor based on polyimide sensing material is realized and the structure is improved. The performance of the integrated sensor has achieved the design target approximately.