A general 1-D model was presented to predict the characteristics of CMOS thermoresistive micro calorimetric flow (TMCF) sensor with two types of packaging, i.e., open-space type and channel type, for both gases and liquids. The 1-D model was first validated by a numerical computational fluid dynamics (CFD) model and was subsequently normalized for different fluids flow. Notably, the model proposed by Nguyen and Dötzel is a special case of our 1-D model. The normalized output of TMCF sensor is a function of normalized input parameters of Reynolds number Re and Prandtl number Pr. The scaling analysis of the sensor output, sensitivity, and power consumption was performed to optimize the design of TMCF sensors in terms of key design parameters, including the thin film thickness, the height of bottom cavity, and so on. Accordingly, three pairs of TMCF sensors were designed and fabricated by using a 0.35 μm 2P4M CMOS microelectromechanical systems technology. The fabricated sensors showed a normalized sensitivity of 230 mV/(m/s)/mW for nitrogen gas flow, which was two orders of magnitude higher than the previous CMOS flow sensors. Therefore, the proposed 1-D model is a promising tool for the sensor's system-level design with the on-chip microelectronics for the Internet of Things.

In this paper, we propose a new 1D thermoresistive micro calorimetric flow (TMCF) sensor model for moist airflow with the temperature-dependent thermophysical properties. The 1D model and the corresponding proposed equivalent circuit model enable rapid design optimization of an ambient temperature-compensated TMCF (T²MCF) sensor integrated with the interface circuit by using a commercial 0.35-μm 2P4M CMOS MEMS technology. The fabricated sensor shows a prominent sensitivity of 0.543 V/(m/s) and a low power consumption of less than 2.8 mW. Moreover, in comparison with the large drifting of 49% for the uncompensated TMCF sensor, the T²MCF sensor's output has an ultralow drifting of 0.5% with the ambient temperature variation of 22°C~48°C. Therefore, this robust T²MCF sensor can be a promising Internet of Things (IoT) for smart energy-efficient buildings. [2018-0241]

This paper presents a 10-bit SAR ADC operating at a supply voltage (VDD) from 0.200 to 0.250 V. In the proposed ADC structure, the positive input of the comparator is fixed at VDD to bias the comparator's input transistor pair with a sufficient gate-to-source voltage at such a low VDD. We propose an ultra-low VDD temperature-compensated bias generator to bias the comparator for addressing the severe temperature-dependent issue of the MOSFETs in the comparator, which operate in the deep subthreshold region. Detailed circuit analysis and derivation of design requirements are presented. A double-boosted and low-leakage sampling switch is also proposed to alleviate the severe leakage issue at low sampling rates. A test chip has been designed and fabricated in 180-nm CMOS. The ADC core occupies only 0.024 mm². Measurement results show that the ADC achieves stable performance in the VDD range. At 0.225 V, the DNL and INL are within +1.04/-0.66 and +0.97/-1.04 LSB in the rail-to-rail input range, respectively. The measured peak SNDR at the Nyquist input frequency is 49.2 dB at 450 S/s. The whole ADC totally consumes 0.85 nW at 0.225 V including circuit leakages. The sub-nW power consumption makes it well suited for self-sustainable Internet-of-Things applications.

The knife-edge method is a commonly used technique to characterize the optical profiles of laser beams or focused spots. In this paper, we present a micro knife-edge scanner fabricated in a silicon-on-insulator substrate using the micro-electromechanical-system technology. A photo detector can be fabricated in the device to allow further integration with on-chip signal conditioning circuitry. A novel backside deep reactive ion etching process is proposed to solve the residual stress effect due to the buried oxide layer. Focused optical spot profile measurement is demonstrated.

In this paper, a thin film based Thermoresistive Micro Calorimetric Flow (TMCF) sensor by using a 0.35 µm 2P4M CMOS MEMS technology is designed, fabricated and tested. The developed 1.6 µm thick thin film CMOS TMCF sensor shows a maximum normalized sensitivity of 103 mV/(m/s)/mW with respect to the input heating power and a wide dynamic flow range of 0 ∼ 19.4 m/s. The high sensitivity and wide dynamic range achieved by our CMOS MEMS flow sensor enable its deployment as a promising sensing node for HVAC application in the smart energy-efficient building (EeB). Moreover, a new one-dimensional (1D) analytical sensor model that considers the three-dimensional (3D) heat loss via the end of the thin film is proposed. The new 1D model can successfully capture the thin film based TMCF sensor’s response, and its prediction results show a good agreement with the experimental study. Therefore, this new 1D model will be a useful design tool for the development of a high-performance TMCF sensor with a greatly reduced footprint.