Claudio Falco

High-Sensitivity Single Thermopile SOI CMOS MEMS Thermal Wall Shear Stress Sensor

In this paper, we present a novel silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) microelectromechanical-system thermal wall shear stress sensor based on a tungsten hot-wire and a single thermopile. Devices were fabricated using a commercial 1-

A thermopile based SOI CMOS MEMS wall shear stress sensor

\mu \text{m}

Diode-based CMOS MEMS thermal flow sensors

SOI-CMOS process followed by a deep reactive ion etching back-etch step to release a silicon dioxide membrane, which mechanically supports and thermally isolates heating and sensing elements. The sensors show an electrothermal transduction efficiency of

On the Seebeck Coefficient and Its Temperature Dependence for Standard CMOS Materials

50~\mu \text{W}

SOI CMOS humidity sensor based on MWCNTs/MMA composite films. On the necessary verification of fabrication stages

/°C, and a very small zero flow offset. Calibration for wall shear stress measurement in air in the range of 0-0.48 Pa was performed using a suction type, 2-D flow wind tunnel. The sensors were found to be extremely sensitive, up to 4 V/Pa for low wall shear stress values. Furthermore, we demonstrate the superior signal-to-noise ratio (up to five times higher) of a single thermopile readout configuration compared with a double thermopile readout configuration (embedded for comparison purposes within the same device). Finally, we verify that the output of the sensor is proportional to the cube root of the wall shear stress and we propose an accurate semiempirical formula for its modeling.

3D modelling of a thermopile-based SOI CMOS thermal wall shear stress sensor

In this paper we present for the first time, a novel silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal wall shear stress sensor based on a tungsten hot-film and three thermopiles. These devices have been fabricated using a commercial 1 μm SOI-CMOS process followed by a deep reactive ion etch (DRIE) back-etch step to create silicon oxide membranes under the hot-film for effective thermal isolation. The sensors show an excellent repeatability of electro-thermal characteristics and can be used to measure wall shear stress in both constant current anemometric as well as calorimetric modes. The sensors have been calibrated for wall shear stress measurement of air in the range of 0-0.48 Pa using a suction type, 2-D flow wind tunnel. The calibration results show that the sensors have a higher sensitivity (up to four times) in calorimetric mode compared to anemometric mode for wall shear stress lower than 0.3 Pa.

3D Multiphysics Modelling of an SOI CMOS MEMS Thermal Wall Shear Stress Sensor

This paper reports on the intrinsic advantages of thermoelectronic flow sensors in comparison to their thermoresistive and thermoelectric counterparts. Hereafter, we will numerically and experimentally show that thermoelectronic flow sensors (i.e. thermal flow sensors employing p-n junction based devices as temperature sensors) benefit from the possibility of having the temperature sensor located in the hottest area of the heating element for enhanced convective effects and thus improved sensor sensitivity (Average Sensitivity +42%). Further improvements can be achieved by putting more diodes in series (Average Sensitivity +380%). A multidirectional thermoelectronic flow sensor is also reported.

On the application of a numerical model to improve the accuracy of the seebeck coefficient in CMOS materials

This paper presents an extensive experimental study of the Seebeck coefficients in several conductive materials offered by standard CMOS technology when subject to a high temperature gradient. The measurements have been carried out on specific devices designed and fabricated in high-temperature SOI technology, comprising: one heating element, several thermopiles with different combinations of materials, and two highly sensitive, low leakage SOI diodes used to calibrate the absolute temperature in different points of the structure. To increase the accuracy, the chip characterization is performed in a controlled temperature chamber, with different values of the environmental temperature in the range 20 °C to 40 °C. This analysis leads to the extraction of the relative Seebeck coefficients for all thermocouples made with specific CMOS materials and, from that, the absolute values for the various materials at high temperature.

Geometrical Optimisation of Diode-Based Calorimetric Thermal Flow Sensors through Multiphysics Finite Element Modelling

A humidity sensor, which is part of an air quality sensor system, based on MWCNTs/MMA composite doped with KOH has been studied. A standard SOI CMOS process, with only one post-processing step for the membrane etching, was used to fabricate the sensor presented. In order to have a homogeneous distribution of the CNTs in the solution, the tip sonication method was employed. The current voltage and resistance voltage characteristics have been investigated.

On the necessary verification of fabrication stages for SOI CMOS humidity sensors

This paper presents a multiphysic 3-D model of an SOI CMOS MEMS thermal wall shear stress sensor obtained using “Comsol Multiphysics”. It includes all the physical domains involved and their interaction. After a brief introduction, the device is presented and its working principle explained. The numerical model and the validation process are then described.