Study On Low Power Consumption And Array Of MEMS MOS Gas Sensor

Gas sensors are widely used in industrial production,environmental monitoring,food safety,aerospace,and biomedical fields.With the development of the Internet of Things,the application fields of gas sensors have gradually expanded to our daily lives,and the demand for gas sensors in consumer market is increasing.MEMS MOS gas sensors have huge market potential because of their low power consumption,low cost,high sensitivity,extensive material system,and easy integration with CMOS circuits.Low power consumption,array and intelligence are the development trend of gas sensors in the future.However,the existing gas sensors are still difficult to meet the increasing application requirements,especially for smart applications such as portable and wearable devices.The main work of this thesis is to use MEMS technology to design new low power gas sensors and new array structures of gas sensor,aiming at the application requirements of low power consumption and array.An ultra-low power single-cantilever MOS gas sensor has been proposed.A low-power suspended-bridge gas sensor with stronger structural strength has been further designed and manufactured.Besides,a new concept of gas sensor cell that is more integreated has been proposed for the first time,and a four-channel single-cantilever gas sensor cell and a regular polygon gas sensor cell have been designed and verified on basis of the single-cantilever structure and the bridge structure,respectively.A single-cantilever gas sensor with ultra-low power consumption was successfully designed and fabricated.The sensor is designed on a slender cantilever beam,eliminating the heating wire winding and interdigital electrode structure of the traditional membrane type gas sensors.The structure is the very simple,and about 10 sensors can be integrated in die of 1 mm2.The sensor was fabricated by using standard MEMS technology,and can reach a working temperature of 400? at about 3 m W with a heating-up time of just 260?s.The sensor achieved 0-100 ppm ethanol detection with a detection resolution of 10%.Compared with the existing technology,the power consumption of the single-cantilever gas sensor has been reduced by an order of magnitude,while the heating-up speed and integration has been increased by an order of magnitude.Based on the single-cantilever structure,a suspended-bridge gas sensor with fixed ends has been proposed,and the mechanical structure is verified by the finite element method(FEM).Compared with the single-cantilever gas sensor,the bridge-type gas sensor has stronger anti-deformation ability and more stable structure beside low power consumption.A layer of sputtered SnO2 film serves as the gas sensing material.The sensor realizes the response to ethanol under the heating input of 0.7-1.15 V,and the working temperature covers the best working temperature of the SnO2.The power consumption of the sensor is only 5.12 mW at 0.7 V.For the first time,a new array method has been proposed and the concept of gas sensor cell has been introduced.Different from the traditional sensor array,the gas sensor cell is an independent device with multiple detection channels,rather than a combination of multiple gas sensors,and each channel in the gas sensor cell is inseparable.A low power four-channel single-cantilever gas sensor cell was designed and manufactured based on the single-cantilever structure combined with the concept of the gas sensor cell.On the one hand,the heat generated by the heater on the cantilever is more fully utilized and the average power consumption of the sensor is reduced.On the other hand,the working temperature of each channel is different because of the natural temperature gradient on the single-cantilever beam.The sensor cell realizes four-channel ethanol real-time detection with a low power consumption of 8.55 mW.Besides,the responses of each channel to ethanol,H2 and NH3 are different,providing a new idea for low power gas recognition.Futhermore,combining the bridge structure and sensor cell concept,we propose a regular polygonal gas sensor cell,in which several sensing channels are made on a polygonal frame structure made up by a same number of bridges and share a common polygonal heater.The polygon sensor cell has high structural strength,low power consumption,as well as multi-channel detection capabilities.The number of detection channels of the sensor cell is highly expandable.It's easy to obtain a polygon sensor unit with different numbers of sensing channels by increasing or decreasing the number of sensing edges and supporting beams.The multi-channel detection capability of the sensor cell was verified by ethanol,and the average power consumption of each channel is about 6 mW.