Novel humidity sensing method based on the transient response of a micro-heater
Novel humidity sensing method based on the transient response of a micro-heater
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DOI：
10.1016/j.sna.2012.10.018
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发表时间：
2013-04
影响因子：
4.6
通讯作者：
O. Legendre;H. Bertin;H. Mathias;F. Mailly;S. Megherbi
中科院分区：
文献类型：
--
作者：
O. Legendre;H. Bertin;H. Mathias;F. Mailly;S. Megherbi
介绍了一种新颖的湿度传感方法。它基本上是基于测量的加热时间的热致动的微线周围的湿空气，这是取决于热物理性质的湿空气。这是基于这种传感器的稳态响应的相关方法的改进，并且具有较低的加热温度、增加的灵敏度以及改进的分辨率的益处，因为它强烈地降低了由于体运动对流热传递引起的低频噪声。传感部分是一个1 mm长，4kΩ的电阻性微导线，由多晶硅制成，并涂有氮化硅，一种众所周知的防水屏障。其制造依赖于完全标准化的CMOS类工业工艺以及在后处理中通过TMAH各向异性湿法蚀刻的单步FSBM，以便从硅块体释放微线，这是众所周知的非常有竞争力的制造策略。测量本身依赖于1位ADC（即单个电压比较器），传感器响应的数字化通过数字时钟实现，如果与传感器单片集成，则在额外功耗、硅面积和设计时间方面非常有效。这些特征加起来是相关方法的已经建立的益处，其是CMOS兼容的、不存在水反应材料、最快的响应时间、最低的长期漂移、非常低的滞后、最快的设计时间和生产成本。在其原型形式中，这里介绍的CMOS兼容传感器具有在20°C下0.497μs/%RH灵敏度，在60%RH下最大非线性为3%RH，在10%RH-80%RH范围内具有±1.5%RH分辨率，以及1.58mW功耗，单次测量的积分时间小于2 ms。鉴于这项工作的概念性质证明，这些结果非常令人鼓舞。
This paper introduces a novel method for sensing humidity. It is fundamentally based on the measurement of the heating time of a thermally actuated micro-wire surrounded by humid air, which is dependent upon the thermophysical properties of humid air. It is an improvement of related methods based on the steady state response of such a sensor and benefits of a lower heating temperature, increased sensitivity, as well as improved resolution since it strongly reduces low frequency noise due to bulk motion convective heat transfer. The sensing part is a 1mm long, 4kΩ resistive micro-wire made of polysilicon and coated with silicon nitride, a well known water resistant barrier. Its fabrication relies on a fully standardized CMOS-like industrial process as well as on a single-step FSBM in post-process by means of TMAH anisotropic wet etching in order to release the micro-wire from the silicon bulk, which is well known to be a very competitive fabrication strategy. The measurement itself relies on a 1-bit ADC (i.e. a single voltage comparator), and the digitalization of the sensor's response is achieved by a digital clock, which is very effective in terms of extra-power consumption, silicon area and design time, if monolithically integrated with the sensor. These features add up to already established benefits of related methods, which are CMOS compatible, absence of water reacting material, fastest response time, lowest long term drift, very low hysteresis, fastest design time and production cost. In its prototyping form, the here presented CMOS-compatible sensor features, at 20°C, 0.497μs/%RH sensitivity, with a maximal nonlinearity of 3%RH at 60%RH, with a ±1.5%RH resolution in the 10%RH–80%RH range as well as 1.58mW power consumption integrated within less than 2ms for a single measurement. These results are very encouraging given the proof of concept nature of this work.