(111)硅片的高性能热堆式气体流量传感器及其封装技术研究

High-performance p^(+)Si/Au Thermopile-based Gas Flow Sensor in (111) Silicon and Its Packaging Technology

流量测控在生物医疗、农业监测、汽车电子等方面具有举足轻重的作用。针对现有热堆式气体流量传感器普遍存在着器件尺寸大、灵敏度低、成本高等不足,基于(111)硅片的单面微机械加工工艺设计了一款p^(+)Si/Au热电堆式气体流量传感器。采用高塞贝克系数的p^(+)Si/Au材料制作热电偶,结合“鱼骨状”隔热薄膜和嵌入式隔热腔体结构,最大程度增大了器件的热阻,降低了热损耗,提升了器件的灵敏度。同时,热电偶冷端与单晶硅衬底之间采用高导热的复合金属相连,不仅增大了热电偶冷热端之间的温度差,而且简化了工艺的复杂度。得益于单面微机械加工工艺,传感器尺寸仅有0.65 mm×0.65 mm。在此基础上,基于气体流道封装以及信号处理电路,设计了集传感器芯片,气流流道以及处理电路于一体的气体流量检测模块。测试结果表明,在320倍电压放大及1.0 V的电压偏置下,该器件的归一化灵敏度约为5.4 mV/sccm/mW,响应时间为1.44 ms。

Flow measurement and control plays an important part in biomedicine, agricultural monitoring, automotive electronics, etc.Aim at the shortcoming of the large-size, low-sensitivity and high-fabrication cost of the most of the previously reported thermopile-based gas flow sensor, a front-sided micromachined p^(+)Si/Au thermopile-based gas flow sensor is designed, fabricated and characterized. P^(+)Si/Au materials with high Seebeck coefficient are employed to construct the thermocouple, combined with the "fishbone" thermal insulation membrane and the embedded isolation cavity structure, which maximizes the thermal resistance of the sensor, reduces the heat loss, and improves the sensitivity. At the same time, high heat-conductivity Au-film is used to connect the cold-junction of the thermocouple and silicon-substrate to not only realize the high temperature difference between the hot-junction and cold-junction, but also simplify the complexity of the process. Thanks to the front-side microfabrication process, the size of sensor is as small as 0.65 mm×0.65 mm. In addition, based on the design of gas flow channel packaging and signal processing circuit, a gas flow detection module integrating sensor chip, air flow channel and processing circuit is completed. With 320 times amplification and 1.0 V voltage bias, tested results show that the sensor has a normalized sensitivity of 5.4 mV/sccm/mW and a quick response time of 1.44 ms.