CMUT for gas sensing and preparation method thereof

A gas sensing and mixed gas technology, applied in the analysis of fluids using sound waves/ultrasonic waves/infrasonic waves, the use of sound waves/ultrasonic waves/infrasonic waves for material analysis, measuring devices, etc. The influence of the transmission spectrum cannot be detected, the detection system is complex and huge, etc., to achieve the effect of broadening the detection range, improving the success rate and stability, and improving the detection efficiency

Active Publication Date: 2019-07-26
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] 1. The detection system often requires ultrasonic transmitters of different frequencies, and multiple ultrasonic probes make the detection system complex and huge
[0008] 2. When the content of a certain component in the mixed gas is much smaller than that of other components, the influence on the sound transmi

Method used

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  • CMUT for gas sensing and preparation method thereof
  • CMUT for gas sensing and preparation method thereof
  • CMUT for gas sensing and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0054] An embodiment of the present invention provides a capacitive ultrasonic sensor (CMUT), which is composed of several array elements, and each array element is composed of several sensitive units, see figure 1 , the structure of the single sensitive unit consists of an upper electrode 1 , a vibrating membrane 2 , an air or vacuum chamber 3 , a lower electrode 4 and a glass substrate 5 from top to bottom.

[0055] Air or vacuum cavity 3 is sandwiched between the vibrating film 2 and the glass substrate 5 to form a capacitor, and a DC voltage is applied to the electrodes at both ends of the CMUT in advance, so that an electrostatic field is formed between the upper electrode 1 and the lower electrode 4, and the vibrating film 2 Deformation occurs under the action of the electric field force, thereby forming a pre-tightening force in the vibrating membrane 2, and the vibrating membrane 2 is in a stable equilibrium state.

[0056] When the upper electrode 1 is grounded and an...

Embodiment 2

[0069] see image 3 , the embodiment of the present invention provides a method for preparing a CMUT applied to mixed gas analysis based on two types of sensing technologies, the preparation method comprising:

[0070] The SOI wafer and BF33 glass bonding technology used in the embodiment of the present invention overcomes the defect of through holes on the diaphragm caused by the surface silicon process for releasing the sacrificial layer, and at the same time avoids the problems caused by the whole piece of low-resistance silicon as the lower electrode. The parasitic capacitance, and the processing reliability of this process is high.

[0071] The process flow of SOI wafer and BF33 glass bonding is as follows:

[0072] Referring to Figure (A), the glass substrate 5 is prepared, and the glass substrate 5 is made of Schott glass BF33 specially used for anodic bonding, so as to form a high-strength bond with the device layer of the SOI wafer;

[0073] Referring to Figure (B),...

Embodiment 3

[0080] The resonance frequency of a single vibrating membrane 2 in the CMUT is:

[0081]

[0082] Among them, t is the thickness, r is the radius, E is the equivalent Young's modulus, m is the equivalent mass, and v is the equivalent Poisson's ratio.

[0083] When gas molecules with a mass of Δm are adsorbed on the surface of the vibrating membrane 2, the equivalent mass m of the vibrating membrane 2 e =m+Δm, resulting in a decrease in the resonant frequency. Adsorb and desorb a certain concentration of gas within a specific period of time. By detecting the change of the resonance frequency of each array element in the first working area in real time, collect and record the resonance peak pattern, and save it as a database after signal processing and algorithm processing, so as to realize Subsequent rapid identification of unknown gas mixtures.

[0084] The sensitivity of a single diaphragm 2 to mass is:

[0085]

[0086] Among them, ρ is the equivalent density of the...

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Abstract

The invention discloses a CMUT for gas sensing and preparation method thereof. All vibration films in a single working area are connected in parallel in an electrode connection mode, and the connection line of an upper electrode and the connection line of a lower electrode are distributed in a 90-degree manner, so that the signal intensity is increased, and the parasitic capacitance is reduced. When low-concentration gas is detected, only the first working area works in a resonator mode; and when the gas concentration is increased to exceed the adsorption saturation concentration of the sensitive material, the second working area cooperates with the first working area to work in an ultrasonic transducer mode. The sensor has a calibration compensation area, so that the detection reliabilityis improved. The preparation method comprises the following steps: sputtering a layer of lower electrode in a cavity and a channel of the etched glass substrate by adopting a mode of bonding the glass substrate and the SOI wafer, and grounding the lower electrode to be used as a lower electrode of a parallel capacitor. The vibration film is a composite film consisting of a monocrystalline siliconvibration film and a buried oxide layer.

Description

technical field [0001] The invention relates to the field of ultrasonic transducers, in particular to a design, preparation method and working principle of a capacitive micro-machined ultrasonic transducer (CMUT) based on the two principles of resonance mass sensing and ultrasonic propagation spectrum. Background technique [0002] The capacitive micro-ultrasonic sensor (CMUT) is manufactured by MEMS (micro-electro-mechanical system). Its sensitive unit size can be micron-level, with wide bandwidth, high sensitivity, good electromechanical conversion efficiency, and easy to manufacture various array shapes. With the advantages of circuit integration and other advantages, it has gradually become a candidate to replace traditional ultrasound sensors, and has been widely studied in the fields of intravascular ultrasound imaging systems, smart microfluidics and sensors, and air-coupled ultrasound. [0003] With the rapid development of science and technology, material civilizati...

Claims

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Application Information

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IPC IPC(8): G01N29/02G01N29/036
CPCG01N29/022G01N29/036
Inventor 张慧于露梁冬梅
Owner TIANJIN UNIV
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