Highly sensitive 3C-SiC on glass based thermal flow sensor realized using MEMS technology

• Published in: Sensors and actuators. A. Physical. Vol. 279; pp. 293 - 305
• Main Authors: Balakrishnan, Vivekananthan, Dinh, Toan, Phan, Hoang-Phuong, Dao, Dzung Viet, Nguyen, Nam-Trung
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.08.2018; Elsevier BV
• Subjects: Aerodynamics; Air flow; Ambient temperature; Flow velocity; Fluid dynamics; Glass; Glass substrates; Microelectromechanical systems; Power consumption; Sensitivity; Sensitivity analysis; Sensors; SiC flow sensor; Silicon carbide; Temperature sensors; Thermoresistive effect; Turbulent flow; Two dimensional flow; Air flow; Sensitivity; Thermoresistive effect; SiC flow sensor; Glass
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2018.06.025

•The NTC characteristics observed in 3C-SiC/glass sensor leads to an increasing signal with increasing flow velocity.•The relationship among various SiC heater geometries indicates that a larger heater is highly sensitive to flow.•Influence of flow direction on the sensor performance was studied. Downstream sensor is more sensitive.•A simple, low power consuming, highly sensitive and full dynamic range thermal flow sensor was developed. This paper presents a silicon carbide (SiC) based thermal flow sensor on a transparent and electrically insulating glass substrate via anodic bonding process. The paper elaborates on the fabrication steps of the thermal flow sensor. Three resistive heater size configurations of dimensions 100 μm × 100 μm, 300 μm × 300 μm, and 1000 μm × 1000 μm were fabricated. The thermoresistive properties of 3C-SiC on glass were investigated from ambient temperature to 443 K. The characterization of the SiC heater and temperature sensors revealed a high thermoresistive effect with a temperature coefficient of resistance (TCR) of approximately −20,716 ppm/K at ambient temperature(298 K) and −9367 ppm/K at 443 K respectively. The performance of the sensors was evaluated based on the sensitivity of the flow sensor. For a turbulent flow velocity of 7.4 m/s, the sensitivity of the sensor operating in the constant -voltage mode is 0.091 s/m with a power consumption of 133.50 mW for the 1000 μm × 1000 μm heater. Finally, a study on the flow direction was conducted to confirm the operation of 2-D direction independent hot-film flow sensor. Results indicated that the performance of the sensor remained the same when the flow direction was perpendicular to SiC heater and sensor respectively. However, the best sensitivity was achieved by passing air flow perpendicular to the sensing elements. The high TCR of the single crystalline 3C-SiC material, the relatively low power consumption on the order of milliwatts and the high sensitivity of our sensor demonstrates its potential use for high temperature flow sensing applications.