A surface acoustic wave temperature sensor based on ring interdigital electrodes

Abstract

The application discloses a surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode. The sensor is a resonant type surface acoustic wave sensor, comprising a metal film layer and a piezoelectric substrate. The metal film layer comprises a ring-shaped interdigital electrode, a ring-shaped reflection grating, a bus bar and a pad, wherein the ring-shaped interdigital electrode extends to both sides along the circumferential direction from the opposite bus bars on the same straight line, and the ring-shaped reflection grating is arranged at the periphery of the ring-shaped interdigital electrode. The metal film layer is prepared by metal patterning on the surface of the substrate through a micro-nano processing technology. The sensor can convert the ambient temperature into the surface acoustic wave resonant frequency of the sensor, and the change of the sensor frequency is read by using a sweep frequency electric signal to perceive the change of the external temperature. The sensor has the advantages of high temperature resistance, large range, high signal-to-noise ratio, high accuracy, easy processing and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature sensors, in particular to a surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode. BACKGROUND

[0002] High-temperature sensing technology is very important for the fine control and green and efficient operation of high-end industrial equipment such as metallurgical furnaces, power generation equipment, aerospace engines, etc. Through sensing technology, various indicators and equipment operating conditions in the industrial production process are monitored in real time to provide accurate data support for production control and optimization, thereby improving production efficiency and ensuring equipment and production safety. However, the industrial process generally has adverse environmental conditions such as closed high temperature, multiphase and multi-field, numerous disturbances, and dusty shielding, which are not conducive to sensing and monitoring. Therefore, high-temperature sensors are required to have high sensitivity, high precision, strong anti-interference ability, and wireless and passive characteristics. Although existing surface acoustic wave sensors have shown good application prospects in high-temperature process monitoring of power plants, industrial furnaces, gas turbines, aerospace engines, chemical processing, and other manufacturing facilities, the non-uniqueness of the surface acoustic wave propagation mode, scattering phenomena, and the existence of other transverse modes have a negligible negative impact on the performance of the device. In particular, in high-temperature wide temperature range measurement, existing surface acoustic wave sensors face the problems of insufficient frequency selection characteristics, low quality factor, poor transverse mode and stray suppression performance, etc. These challenges limit their performance and reliability in extreme industrial environments.

[0003] It should be noted that the information disclosed in the above background section is only for understanding the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0004] The main purpose of the present application is to overcome the defects in the background art, and to provide a surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode, comprising:

[0007] a double-layer structure formed by a metal thin film layer and a piezoelectric substrate;

[0008] The metal thin film layer is located on the piezoelectric substrate and includes a ring-shaped interdigital electrode, a ring-shaped reflective grid, a bus bar, and a pad;

[0009] The ring-shaped interdigital electrode extends to both sides along the circumferential direction from the opposite bus bars on the same straight line, and the sum of the electrode line width and the pitch is half the surface acoustic wave wavelength;

[0010] The ring-shaped reflector is arranged outside the ring-shaped interdigital electrode, and the sum of the line width and the pitch of the reflector is half of the wavelength of the surface acoustic wave;

[0011] The piezoelectric substrate can convert the external temperature into the surface acoustic wave resonance frequency, and the resonance is initiated by inputting the frequency sweeping electric signal into the metal electrode and the reflector, and the corresponding resonance frequency is read to sense the external temperature.

[0012] Further, the metal thin film layer comprises a metal adhesion layer adhered to the piezoelectric substrate and a high-temperature-resistant metal conductive layer attached to the metal adhesion layer.

[0013] Further, the material of the metal adhesion layer comprises chromium or titanium.

[0014] Further, the material of the high-temperature-resistant metal conductive layer comprises platinum or gold.

[0015] Further, the thickness of the metal adhesion layer is 5-15 nm.

[0016] Further, the thickness of the high-temperature-resistant metal conductive layer is 80-300 nm.

[0017] Further, the piezoelectric substrate is a piezoelectric crystal, a piezoelectric ceramic or a piezoelectric film, and when the piezoelectric substrate is a piezoelectric film, the piezoelectric film is attached to a high-temperature-resistant substrate.

[0018] Further, the thickness of the piezoelectric crystal or the piezoelectric ceramic is 300-1000 microns.

[0019] Further, the thickness of the piezoelectric film is 1-2 wavelengths of the surface acoustic wave, and the high-temperature-resistant substrate to which the piezoelectric film is attached is 300-1000 microns.

[0020] The present application has the following advantages:

[0021] The present application provides a surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode, which has good stray and transverse mode suppression performance, is high-temperature-resistant, has a large range, high signal-to-noise ratio, high accuracy and is easy to process.

[0022] The surface acoustic wave sensor based on the ring-shaped interdigital electrode of the present application can suppress the transverse mode and the stray of the surface acoustic wave. The direction of the ring-shaped interdigital electrode of the sensor extends along both sides of the same bus bar, so that the interdigital electrodes on the same bus bar are subjected to opposite forces, resulting in suppression of the transverse mode vibration of the electrodes. The surface acoustic wave generated by the ring-shaped interdigital electrode can only propagate in the radial direction, and the rest of the directions are suppressed due to the unequal electrode spacing in the propagation path, hindering the propagation of scattered waves. The significant advantages of the sensor include good stray and transverse mode suppression performance, high-temperature resistance, large range, high signal-to-noise ratio, high accuracy, easy processing and the like.

[0023] Other advantages of embodiments of the present application will be described in further detail below. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of an embodiment of a surface acoustic wave sensor based on a ring-shaped interdigital electrode according to the present application;

[0025] Figure 2 is a structural schematic diagram of a metal thin film layer of an embodiment of a surface acoustic wave sensor based on a ring-shaped interdigital electrode according to the present application;

[0026] Figure 3 is an A-A sectional view of Figure 1 ;

[0027] Figure 4 is a performance diagram of a surface acoustic wave temperature sensor according to the prior art;

[0028] Figure 5 is a performance diagram of a surface acoustic wave temperature sensor based on a ring-shaped interdigital electrode according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The embodiments of the present application will be described in detail below. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present application and its applications.

[0030] It should be noted that when an element is referred to as being "fixed" or "attached" to another element, it can be directly on the other element or indirectly on the other element, with one or more intervening elements. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or indirectly connected or coupled to the other element, with one or more intervening elements. Further, the connection can be fixed or it can be moveable or releasable.

[0031] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, as used herein, are intended to refer to the orientation or position of the device or element as shown in the drawings, and are merely used for convenience in describing the present application and its application, and are not intended to indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present application.

[0032] In addition, the terms "first", "second", "third", etc. are used only for the purpose of description and are not to be interpreted as indicating or implying relative importance or a number of limitations. Thus, features with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of embodiments of the present application, the meaning of "a plurality" is two or more, unless otherwise explicitly specified.

[0033] Referring to Figures 1 to 3 The embodiments of the present application provide a surface acoustic wave temperature sensor based on a ring-shaped interdigital transducer 2, comprising a double-layer structure formed by a metal thin film layer and a piezoelectric substrate 1; the metal thin film layer is located on the piezoelectric substrate 1 and includes a ring-shaped interdigital transducer 2, a ring-shaped reflector 3, a bus bar 4 and a pad 5; the ring-shaped interdigital transducer 2 extends to both sides along the circumferential direction from the opposite bus bars 4 on the same straight line, and the sum of the electrode line width and the interval is half of the surface acoustic wave wavelength; the ring-shaped reflector 3 is arranged at the periphery of the ring-shaped interdigital transducer 2, and the sum of the reflector line width and the interval is half of the surface acoustic wave wavelength; wherein the piezoelectric substrate 1 can convert the external temperature into the surface acoustic wave resonance frequency, and the resonance is triggered by inputting a frequency sweeping electrical signal to the metal electrode and the reflector, and the corresponding resonance frequency is read to perceive the external temperature. As a resonant surface acoustic wave sensor, the sensor can convert the environmental temperature into the surface acoustic wave resonance frequency of the sensor during operation, and the change of the sensor frequency is read by using the frequency sweeping electrical signal to perceive the change of the external temperature.

[0034] In some embodiments, the metal thin film layer includes a metal adhesion layer adhered to the piezoelectric substrate 1 and a high-temperature-resistant metal conductive layer attached to the metal adhesion layer.

[0035] In some embodiments, the material of the metal adhesion layer can be chromium or titanium. The material of the high-temperature-resistant metal conductive layer can be platinum or gold. Preferably, the thickness of the metal adhesion layer is 5-15 nm. Preferably, the thickness of the high-temperature-resistant metal conductive layer is 80-300 nm. The metal thin film layer can be prepared by metal patterning on the surface of the substrate through micro-nano processing technology.

[0036] In preferred embodiments, the piezoelectric substrate 1 is a piezoelectric crystal, a piezoelectric ceramic or a piezoelectric film, and when the piezoelectric substrate 1 is a piezoelectric film, the piezoelectric film is attached to a high-temperature-resistant substrate. Preferably, the thickness of the piezoelectric crystal or the piezoelectric ceramic is 300-1000 μm. Preferably, the thickness of the piezoelectric film is 1-2 surface acoustic wave wavelengths, and the high-temperature-resistant substrate to which the piezoelectric film is attached is 300-1000 μm.

[0037] The surface acoustic wave sensor based on the ring-shaped interdigital electrode can effectively suppress the transverse mode and stray of the surface acoustic wave. Since the ring-shaped interdigital electrode extends along the same bus bar on both sides, the interdigital electrodes on the same bus bar are subjected to opposite forces, resulting in suppression of the transverse mode vibration of the electrode. At the same time, the surface acoustic wave generated by the ring-shaped interdigital electrode can only propagate in the radial direction, and the rest of the directions are suppressed due to the unequal electrode spacing in the propagation path, hindering the propagation of scattered waves. Through the above innovative design, the surface acoustic wave temperature sensor has better performance and reliability in a high-temperature environment, has the advantages of high-temperature resistance, large range, high signal-to-noise ratio, high accuracy, easy processing, etc., and can well meet the needs of high-end industrial equipment for high-temperature sensors.

[0038] The specific embodiments and experimental verification of the present application are further described below.

[0039] As shown in Figure 1 , the surface acoustic wave temperature sensor based on the ring-shaped interdigital electrode includes a metal film layer and a piezoelectric substrate 1. The metal film layer is located on the piezoelectric substrate 1, forming a double-layer structure. The piezoelectric substrate 1 can convert the external temperature into a surface acoustic wave resonance frequency and input a frequency sweeping electrical signal into the metal electrode to induce resonance with the reflection grid, read the corresponding resonance frequency, and thus sense the external temperature.

[0040] Further referring to Figure 2 and Figure 3 , the metal film layer includes a ring-shaped interdigital electrode 2, a ring-shaped reflection grid 3, a bus bar 4, and a solder pad 5. The ring-shaped interdigital electrode 2 extends to both sides along the circumferential direction from the opposite bus bars on the same straight line, and the sum of the electrode line width and the spacing is half the surface acoustic wave wavelength. The ring-shaped reflection grid 3 is arranged at the periphery of the ring-shaped interdigital electrode, and the sum of the reflection grid line width and the spacing is half the surface acoustic wave wavelength.

[0041] In a preferred embodiment, the metal film layer includes a metal adhesion layer (such as chromium (Cr), titanium (Ti), etc.) adhered to the piezoelectric substrate 1 and a high-temperature-resistant metal conductive layer (such as platinum (Pt), gold (Au), etc.) attached to the metal adhesion layer. The metal adhesion layer is required to enhance the adhesion of the high-temperature-resistant metal conductive layer and the piezoelectric substrate to improve the reliability of the metal film layer. The high-temperature-resistant metal conductive layer is required to have high-temperature stability and good conductivity at high temperatures.

[0042] In a further preferred embodiment, the thickness of the metal adhesion layer is 5-15 nm, and the thickness of the high-temperature-resistant metal conductive layer is 80-300 nm.

[0043] In a further preferred embodiment, the piezoelectric substrate 1 can be a piezoelectric crystal, a piezoelectric ceramic, or a piezoelectric film. The piezoelectric film needs to be attached to a high-temperature-resistant substrate, and the piezoelectric substrate is required to have a high Curie temperature and maintain good piezoelectric properties at high temperatures.

[0044] In a further preferred embodiment, the thickness of the piezoelectric crystal or piezoelectric ceramic is 300 μm-1000 μm, the thickness of the piezoelectric film is 1-2 surface acoustic wave wavelengths, and the high temperature resistant substrate to which the piezoelectric film is attached is 300 μm-1000 μm.

[0045] Example 1

[0046] Surface acoustic wave temperature sensors based on annular interdigital electrodes such as Figure 1 As shown in the figure, a Y-cut 128° lithium niobate single crystal is used as the piezoelectric substrate 1. A metal thin film layer is deposited on the lithium niobate wafer. Ring-shaped interdigitated electrodes 2, ring-shaped reflective gratings 3, busbars 4, and pads 5 are obtained through photolithography, evaporation, and lift-off processes. The metal adhesion layer is a chromium (Cr) layer, and the high-temperature resistant metal conductive layer is a platinum (Pt) layer.

[0047] In the prepared surface acoustic wave temperature sensor based on annular interdigital electrodes, the surface acoustic wave design wavelength is 12 μm, the annular interdigital electrodes 2 have a line width of 3 μm and a spacing of 3 μm, and the annular reflective grating 3 has a line width of 3 μm and a spacing of 3 μm.

[0048] In the prepared surface acoustic wave temperature sensor based on annular interdigital electrodes, the piezoelectric substrate is 500 μm thick, the chromium layer in the metal film layer is 10 nm thick, and the platinum layer is 100 nm thick.

[0049] As an example, the existing surface acoustic wave temperature sensor is compared with the surface acoustic wave temperature sensor based on the ring-shaped interdigital electrode of the present invention. The comparison results are as follows: Figure 4 and Figure 5 As shown, Figure 4 The performance graphs of a common surface acoustic wave temperature sensor using existing interdigital electrodes at 50°C, 250°C, 450°C, and 650°C are shown below. Figure 5 The performance diagram of the surface acoustic wave temperature sensor using the ring-shaped interdigital electrode of the present invention at 50℃, 250℃, 450℃ and 650℃. Figure 4 and Figure 5 It can be seen from the comparison that the stray peaks of the surface acoustic wave temperature sensor based on the annular interdigital electrode are almost invisible, which effectively suppresses the stray and transverse modes and significantly improves the performance of the sensor.

[0050] In summary, the surface acoustic wave temperature sensor based on the ring-shaped interdigital electrode of the application realizes the accurate conversion and reading of the surface acoustic wave resonance frequency through the unique double-layer structure of the metal thin film layer and the piezoelectric substrate, so as to accurately perceive the external temperature change. The main technical advantages include excellent stray and transverse mode suppression performance, which is due to the special design of the ring-shaped interdigital electrode, so that the interdigital electrode is stressed in opposite directions, effectively suppressing the transverse mode vibration, and only allowing the surface acoustic wave to propagate in the radial direction, thereby hindering the propagation of scattered waves. It has the advantages of high temperature resistance, large range, high signal-to-noise ratio, high accuracy, easy processing and the like.

[0051] The above is a further detailed description of the application in combination with specific / preferred embodiments, and cannot be considered as limiting the specific implementation of the application to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, without departing from the concept of the application, they can make several alternatives or modifications to the described embodiments, and these alternatives or modifications shall be considered as belonging to the protection scope of the application. In the description of the specification, the description of the terms "an embodiment", "some embodiments", "preferred embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In the case of no mutual contradiction, the skilled person in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples. Although the embodiments of the application and their advantages have been described in detail, it should be understood that various changes, replacements and modifications can be made herein without departing from the protection scope of the patent application.

Claims

1. A surface acoustic wave temperature sensor based on an annular interdigital electrode, characterized in that: include: A double-layer structure formed by a metal film layer and a piezoelectric substrate; The metal film layer is located on the piezoelectric substrate and includes an annular interdigitated electrode, an annular reflective grid, a bus bar and a pad; The annular interdigitated electrodes extend from opposite bus bars on the same straight line to both sides along the circumferential direction, and the sum of the electrode line width and the spacing is half the wavelength of the surface acoustic wave; The annular reflection grating is arranged on the periphery of the annular interdigitated electrode, and the sum of the line width and spacing of the reflection grating is half the wavelength of the surface acoustic wave; The piezoelectric substrate can convert the external temperature into the surface acoustic wave resonant frequency. By inputting a frequency-sweeping electrical signal into the annular interdigitated electrode, resonance is induced with the reflective grating, and the corresponding resonant frequency is read to sense the external temperature.

2. The surface acoustic wave temperature sensor based on an annular interdigital electrode according to claim 1, characterized in that: The metal film layer includes a metal adhesion layer adhered to the piezoelectric substrate and a high-temperature resistant metal conductive layer adhered to the metal adhesion layer.

3. The surface acoustic wave temperature sensor based on annular interdigital electrodes according to claim 2, characterized in that: The material of the metal adhesion layer includes chromium or titanium.

4. The surface acoustic wave temperature sensor based on an annular interdigital electrode according to claim 2 or 3, characterized in that: The material of the high temperature resistant metal conductive layer includes platinum or gold.

5. The surface acoustic wave temperature sensor based on an annular interdigital electrode according to any one of claims 2 to 3, characterized in that: The thickness of the metal adhesion layer is 5nm-15nm.

6. The surface acoustic wave temperature sensor based on an annular interdigital electrode according to any one of claims 2 to 3, characterized in that: The thickness of the high-temperature resistant metal conductive layer is 80nm-300nm.

7. The surface acoustic wave temperature sensor based on an annular interdigital electrode according to any one of claims 1 to 3, characterized in that: The piezoelectric substrate is a piezoelectric crystal, a piezoelectric ceramic or a piezoelectric film. When the piezoelectric substrate is a piezoelectric film, the piezoelectric film is attached to a high temperature resistant substrate.

8. The surface acoustic wave temperature sensor based on annular interdigital electrodes according to claim 7, characterized in that: The piezoelectric crystal or piezoelectric ceramic has a thickness of 300 μm-1000 μm.

9. The surface acoustic wave temperature sensor based on annular interdigital electrodes according to claim 7, characterized in that: The thickness of the piezoelectric film is 1-2 wavelengths of surface acoustic waves, and the high-temperature resistant substrate to which the piezoelectric film is attached is 300 μm-1000 μm.

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