Surface acoustic wave wireless passive temperature sensor and monitoring system
By designing the empty cavity structure and grooves in the sound surface wave temperature sensor, and using thermal sensitive materials and solid -state conductive metal materials, the problem of insufficient sensitivity of the sensor and the damage of the line achieves the temperature detection of high accuracy and rapid response.
Patent Information
- Application Number
- CN202411379997.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-01-24
AI Technical Summary
The existing surface acoustic wave temperature sensors are difficult to improve their sensitivity due to the temperature coefficient limitation of the material itself. In high-temperature and high-speed motion scenarios, traditional wired temperature sensors have problems with line melting and knotting.
Design a kind of sound surface wave wireless passive temperature sensor that forms an empty cavity structure between the substrate and the voltage layer, and set the groove on the piezoelectric layer, combined with the thermal sensitive materials and the solid conductive metal material to enhance the sensor to enhance the sensor to enhance the sensor The precision and sensitivity of temperature detection.
It achieves high-precision temperature detection in high-temperature and high-speed motion scenarios, improves the temperature sensitivity and response speed of the sensor, and avoids the problem of line damage.
Smart Images
Figure CN119354363A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of surface acoustic wave sensors, and in particular to a surface acoustic wave wireless passive temperature sensor and a monitoring system. Background Art
[0002] As one of the most commonly used sensing technologies, temperature sensing is widely used in various fields such as new energy vehicle power battery temperature monitoring, industrial automation control, smart home and biopharmaceuticals. At present, the commonly used temperature sensors on the market mainly include thermocouples, thermistors and resistance temperature detectors. These sensors have their own advantages and disadvantages: thermocouple sensors require cold compensation and have low accuracy; thermistor sensors are easily affected by the environment; resistance temperature sensors are expensive and have a limited temperature range. In addition, the above-mentioned sensors have some limitations in data acquisition, energy supply and wireless signal transmission. In some special applications such as ultra-high temperature monitoring and high-speed motion scenarios, excessively high temperatures will cause the lines to melt, and high-speed motion will cause the lines to tangle. In these scenarios, wired temperature sensing will be severely limited by wiring.
[0003] In comparison, temperature sensors based on surface acoustic waves (SAW) have gradually become mainstream due to their small size and ability to achieve wireless passive detection. However, the temperature sensitivity of this type of sensor is easily limited by the material's own frequency temperature coefficient. The temperature drift characteristics of surface acoustic wave temperature sensors mainly come from two aspects: one is the material's own temperature coefficient. Temperature changes will affect the elastic coefficient and density of the piezoelectric material, thereby changing the transmission speed of the surface acoustic wave; the other is that the structure expands due to heat, causing the period of the interdigital transducer to change, thereby changing the operating frequency. The former is related to the material properties, and the sensitivity can be improved by replacing the material; the latter can increase the deformation after heating through the structural design of the device, thereby improving the temperature sensitivity.
[0004] However, the overall temperature-frequency coefficient of the existing surface acoustic wave resonator mainly depends on the temperature-frequency coefficient of the piezoelectric layer of the surface acoustic wave resonator, and due to the limitation of piezoelectric materials, it is not conducive to improving the sensitivity of the surface acoustic wave temperature sensor. Therefore, based on the existing piezoelectric materials, it is necessary to design a specific structure to increase the sensitivity of the sensor. Summary of the invention
[0005] In order to solve the problems existing in the prior art, the present invention provides a surface acoustic wave wireless passive temperature sensor, which includes a substrate, a piezoelectric layer, and a top electrode structure from bottom to top. The substrate has a groove and forms a cavity structure with the piezoelectric layer.
[0006] Furthermore, the piezoelectric layer is provided with a groove, and the depth of the groove is 0.01-0.9 times the thickness of the piezoelectric layer.
[0007] Furthermore, the cavity structure is filled with a heat-sensitive material.
[0008] Furthermore, the heat sensitive material includes at least one of polycrystalline silicon, high temperature co-fired ceramics, and aluminum nitride ceramics. Further, the top electrode structure includes interdigitated electrodes and a reflective grid; The material of the interdigital electrodes and the reflective grid is solid conductive metal.
[0009] Furthermore, a bottom electrode layer is provided between the piezoelectric layer and the substrate, and the material of the bottom electrode layer is solid conductive metal.
[0010] The materials of the substrate, bottom electrode, piezoelectric layer, interdigital electrode, and reflective grid used in the present invention do not need to be strictly limited, and are conventional materials used in the art. For example, the substrate can be Si, SiC, silicon on insulator (SOI), sapphire, etc.; the materials of the bottom electrode and the top electrode can be conductive metals such as Mo, Au, Al, Ti, Pt, and W; the material of the piezoelectric layer can be AlN, ScAlN, GaN, GaO, MoS2, ZnO, lithium niobate, lithium tantalate, lanthanum gallium silicate, etc.
[0011] In the present invention, the shape of the substrate groove does not need to be strictly determined, and can be circular, elliptical, polygonal or other shapes.
[0012] The present invention also provides a temperature monitoring system, comprising the above-mentioned sensor, and also comprising a sensing antenna, a matching circuit, a wireless transceiver and a signal processing component; The sensor is connected to the sensing antenna via the matching circuit; The sensing antenna is used to receive the excitation signal sent by the wireless transceiver and signal processing component.
[0013] Furthermore, the wireless transceiver and signal processing component includes a transceiver antenna, a low noise amplifier, a mixer, a filter, a detector, a microprocessor, a power amplifier and a radio frequency switch connected in sequence.
[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts piezoelectric material as temperature sensitive material and uses the principle of surface acoustic wave for detection, which can be applied to special passive wireless scenarios. At the same time, a cavity structure is formed between the substrate and the piezoelectric layer, which improves the temperature detection range and accuracy of the temperature sensor. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0016] Figure 1 A schematic cross-sectional view of the surface acoustic wave wireless passive temperature sensor of Example 1 is shown; Figure 2 A top view of the surface acoustic wave wireless passive temperature sensor of Example 1 is shown; Figure 3 The frequency response curves of the surface acoustic wave wireless passive temperature sensor of Example 1 at different temperatures are shown; Figure 4 A schematic cross-sectional view of a surface acoustic wave wireless passive temperature sensor according to Embodiment 2 is shown; Figure 5 A schematic cross-sectional view of a surface acoustic wave wireless passive temperature sensor according to Embodiment 3 is shown; Figure 6 A cross-sectional schematic diagram of a surface acoustic wave wireless passive temperature sensor according to Embodiment 4 is shown; Figure 7 A schematic cross-sectional view of a surface acoustic wave wireless passive temperature sensor according to Embodiment 5 is shown; Figure 8 A schematic cross-sectional view of the surface acoustic wave wireless passive temperature sensor of Comparative Example 1 is shown; Fig. 9 The temperature-frequency deviation diagram obtained by simulating the surface acoustic wave wireless passive temperature sensor of Example 1 is shown; Fig.10 The temperature frequency deviation diagram obtained by simulating the surface acoustic wave wireless passive temperature sensor of comparative example 1 is shown. Fig.11 A cross-sectional schematic diagram of a surface acoustic wave wireless passive temperature sensor of Comparative Example 2 is shown; Fig.12 A schematic diagram of the structure of the temperature monitoring system of Example 6 is shown; Fig.13 The frequency spectrum of the excitation signal and the response signal of the temperature monitoring system of Example 5 is shown; Fig.14 The temperature monitoring of Example 5 is actually used for monitoring at different temperatures; Description of reference numerals: 1. Substrate; 2. Piezoelectric layer; 201. Through groove; 202. Groove; 3. Top electrode structure; 301. Reflection grid; 302. Interdigital electrode; 4. Cavity structure; 5. Bottom electrode layer; 6. Thermal sensitive material. DETAILED DESCRIPTION
[0017] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0018] Example 1 like Figure 1 As shown, a surface acoustic wave wireless passive temperature sensor includes a substrate 1, a piezoelectric layer 2, and a top electrode structure 3 from bottom to top; the substrate 1 has a groove and forms a cavity structure 4 with the piezoelectric layer 2; the top electrode structure 3 includes an interdigitated electrode 302 and a reflection grating 301. According to the arrangement of the reflection grating 301, the temperature sensor can be designed as a resonant type and a delay line type, wherein the reflection grating 301 of the resonant type sensor is symmetrical; the reflection grating 301 of the delay line type sensor is asymmetrical, and the reflection grating 301 may not be arranged.
[0019] As an implementation method, Figure 2 As shown, in this embodiment, the temperature sensor is a resonant type, and the steps for preparing the sensor are described in detail below: S1, obtaining a substrate 1 with a groove, and etching silicon to obtain a silicon substrate 1 with a groove; S2, depositing a sacrificial material on the groove surface of the silicon substrate 1 with the groove to fill the groove, and chemically mechanically polishing the upper surface of the silicon substrate 1 so that the height of the sacrificial material is flush with the top of the silicon substrate 1; S3, depositing aluminum nitride to form a piezoelectric layer 2; S4, depositing molybdenum on the piezoelectric layer 2 and patterning it to obtain a top electrode structure 3, wherein the top electrode structure 3 includes interdigitated electrodes 302 and a reflective grid 301; S5. Etch the piezoelectric material layer outside the interdigital electrode 302 of the product obtained in S4 to form a through groove 201 that directly reaches the sacrificial material in the groove, and introduce etching gas into the through groove 201 to remove the sacrificial material in the groove, so that a cavity structure 4 is formed between the substrate 1 and the piezoelectric layer 2.
[0020] The surface acoustic wave wireless passive temperature sensor is prepared through the above steps.
[0021] like Figure 3As shown, the frequency response curves of the sensor of this embodiment at different temperatures obtained by finite element simulation show that the resonant frequency gradually decreases as the temperature increases, which indicates that the sensor has good temperature sensitivity.
[0022] Example 2 like Figure 4 As shown, compared with Example 1, the difference is that a bottom electrode 5 layer is further arranged between the piezoelectric layer 2 and the substrate 1, and the material of the bottom electrode 5 layer is molybdenum.
[0023] The steps for preparing the sensor are: S1, obtaining a substrate 1 with a groove, and etching silicon to obtain a silicon substrate 1 with a groove; S2, depositing a sacrificial material on the groove surface of the silicon substrate 1 with the groove to fill the groove, and chemically mechanically polishing the upper surface of the silicon substrate 1 so that the height of the sacrificial material is flush with the top of the silicon substrate 1; S3, depositing molybdenum and aluminum nitride in sequence to form a bottom electrode layer 5 and a piezoelectric layer 2; S4, depositing molybdenum on the piezoelectric layer 2 and patterning it to obtain a top electrode structure 3, wherein the top electrode structure 3 includes interdigitated electrodes 302 and a reflective grid 301; S5. Etch the piezoelectric material layer outside the interdigital electrode 302 of the product obtained in S4 to form a through groove 201 that directly reaches the sacrificial material in the groove, and introduce etching gas into the through groove 201 to remove the sacrificial material in the groove, so that a cavity structure 4 is formed between the substrate 1 and the piezoelectric layer 2.
[0024] Example 3 like Figure 5 As shown, compared with Example 2, the difference is that a groove 202 is provided on the piezoelectric layer 2 at the upper part of the cavity structure 4, and the depth of the groove 202 is 0.5 times the thickness of the piezoelectric layer 2. By etching part of the piezoelectric layer 2 material, the deformation of the sensor during thermal expansion can be increased, thereby increasing the temperature offset of the device.
[0025] The steps for preparing the sensor are: S1, obtaining a substrate 1 with a groove, and etching silicon to obtain a silicon substrate 1 with a groove; S2, depositing a sacrificial material on the groove surface of the silicon substrate 1 with the groove to fill the groove, and chemically mechanically polishing the upper surface of the silicon substrate 1 so that the height of the sacrificial material is flush with the top of the silicon substrate 1; S3, depositing molybdenum and aluminum nitride in sequence to form a bottom electrode layer 5 and a piezoelectric layer 2; S4, depositing molybdenum on the piezoelectric layer 2 and patterning it to obtain a top electrode structure 3, wherein the top electrode structure 3 includes interdigitated electrodes 302 and a reflective grid 301; S5, etching the piezoelectric layer 2 at the upper part of the cavity structure 4 and the inner side of the interdigital electrode 302 of the product obtained in S4, and forming a groove 202 on the surface of the piezoelectric layer 2; S6. Etch the outer side of the interdigital electrode 302 of the product obtained in S5 to form a through groove 201 that directly reaches the sacrificial material in the groove, and introduce etching gas into the through groove 201 to remove the sacrificial material in the groove, so that a cavity structure 4 is formed between the substrate 1 and the piezoelectric layer 2.
[0026] Example 4 like Figure 6 As shown, compared with Example 1, the difference is that there are multiple cavity structures 4, which form an array structure and are filled with a thermally sensitive material 6, and the material of the thermally sensitive material 6 is polycrystalline silicon. Filling the cavity structure with a thermally sensitive material having a large thermal expansion coefficient helps to increase the thermal strain at the interdigital electrodes, thereby increasing the temperature sensitivity of the sensor.
[0027] The steps for preparing the sensor are: S1, obtaining a substrate 1 with grooves, and etching silicon to obtain a silicon substrate 1 with multiple grooves; S2, depositing polysilicon on the groove surface of the silicon substrate 1 with the groove to fill the groove, and chemically and mechanically polishing the upper surface of the silicon substrate 1 so that the height of the polysilicon is flush with the top of the silicon substrate 1; S3, depositing aluminum nitride to form a piezoelectric layer 2; S4 , depositing molybdenum on the piezoelectric layer 2 and performing patterning to obtain a top electrode structure 3 , wherein the top electrode structure 3 includes interdigitated electrodes 302 and a reflective grating 301 .
[0028] Example 5 like Figure 7 As shown, compared with Example 4, the difference is that a groove 202 is provided on the piezoelectric layer 2 at the upper part of the cavity structure 4, and the depth of the groove 202 is 0.5 times the thickness of the piezoelectric layer 2. By etching part of the piezoelectric layer 2 material, the deformation of the sensor when it expands due to heat can be increased, thereby increasing the temperature deviation of the device.
[0029] The steps for preparing the sensor are: S1, obtaining a substrate 1 with grooves, and etching silicon to obtain a silicon substrate 1 with multiple grooves; S2, depositing polysilicon on the groove surface of the silicon substrate 1 with the groove to fill the groove, and chemically and mechanically polishing the upper surface of the silicon substrate 1 so that the height of the polysilicon is flush with the top of the silicon substrate 1; S3, depositing aluminum nitride to form a piezoelectric layer 2; S4, depositing molybdenum on the piezoelectric layer 2 and patterning it to obtain a top electrode structure 3, wherein the top electrode structure 3 includes interdigitated electrodes 302 and a reflective grid 301; S5 , etching the upper part of the cavity structure 6 and the piezoelectric layer 2 at the inner side of the interdigital electrode 302 of the product obtained in S4 , and forming a groove 202 on the surface of the piezoelectric layer 2 .
[0030] Comparative Example 1 like Figure 8 As shown, that is, a traditional sensor structure, compared with Example 1, the difference is that there is no cavity structure 4 between the substrate 1 and the piezoelectric layer 2.
[0031] The steps for preparing the sensor are: S1, depositing aluminum nitride on a silicon substrate 1 to form a piezoelectric layer 2; S2 . After attaching a mask on the piezoelectric layer 2 , deposit molybdenum to obtain a top electrode structure 3 . The top electrode structure 3 includes interdigitated electrodes 302 and a reflective grating 301 .
[0032] The sensors of Example 1 and Comparative Example 2 are simulated to obtain their frequency temperature coefficients TCF, which are specifically calculated by the following formula: ; in, f s is the frequency, T For temperature.
[0033] like Fig. 9 and Fig.10 As shown, the frequency temperature coefficients of the sensors of Example 1 and Comparative Example 1 are 24.52 ppm / °C and 20.96 ppm / °C, respectively. This is because the presence of the cavity structure increases the temperature thermal strain of the device and thus increases the temperature coefficient, thereby improving the temperature sensitivity.
[0034] Comparative Example 2 like Fig.11 As shown, compared with embodiment 3, the difference is that there is no cavity structure 4 between the substrate 1 and the bottom electrode layer 2 .
[0035] Example 6 A temperature monitoring system, such as Fig.12 As shown, it includes the sensor prepared in Example 1, and also includes a sensor antenna, a matching circuit, and a wireless transceiver and signal processing component, wherein the sensor is connected to the sensor antenna through a matching circuit; the sensor antenna receives an excitation signal sent by the wireless transceiver and signal processing component; the wireless transceiver and signal processing component includes a transceiver antenna, a low-noise amplifier, a mixer, a filter, a detector, a microprocessor, a power amplifier and a radio frequency switch connected in sequence.
[0036] Matching circuit: used to optimize the energy transmission efficiency between the surface acoustic wave resonator and the RF antenna to ensure the stable transmission of the sensing signal. Transceiver antenna: used to receive and transmit wireless signals, and transmit the temperature information measured by the sensor to the wireless transceiver and signal processing components. Microprocessor: The microprocessor is responsible for processing and decoding the received signal to extract the temperature information. The microprocessor can generate a high-frequency signal source and a high-frequency local oscillator signal source to excite the sensor to generate a sensing signal with temperature information. Power amplifier: The transmitting end power amplifier amplifies the high-frequency local oscillator signal so that it can be transmitted over a long distance and stimulate the sensor to generate a response signal. RF switch: used to control the transmission path of the signal to achieve the sending and receiving functions. Low noise amplifier: used to enhance the received signal to improve the transmission distance, sensitivity and strength of the sensing signal of the system, and reduce noise interference. Mixer, filter and detector: modulate, filter and demodulate the received sensing signal to restore the original temperature information.
[0037] The entire sensing process consists of two stages: the excitation radio transmission stage and the response radio reception stage. The microprocessor generates a signal source that transmits an excitation signal to the sensor through the RF switch via the antenna, and then the microprocessor controls the RF switch to enter the receiving stage. The transmitted signal is connected to the sensor through the receiving end sensor antenna. The sensor resonates after being excited. The temperature changes the material properties of the piezoelectric material, thereby changing the resonant frequency of the sensor. The sensor signal with temperature information is then transmitted to the processor through the antenna. The microprocessor modulates the received sensor signal to read the current temperature information and realize wireless passive monitoring. Fig.13 The excitation signal and response signal of the sensing process are shown. Before 0μs, the signal generator mainly generates the excitation signal. At 0μs, the signal generator stops and the sensor generates the response signal. The time from the stop of the excitation radio signal to the direct response of the wireless sensor is about 78ns, and the effective signal duration is 5μs. This result shows that the temperature monitoring system of this embodiment can perform corresponding temperature monitoring according to the excitation signal very quickly.
[0038] The temperature monitoring system of this embodiment is also applied to actual temperature monitoring, such as Fig.14 As shown, it can be seen that when the temperature is increased or decreased in the temperature range of 30-100°C, the resonant frequency of the sensor has a good linear relationship with the temperature. After obtaining its specific resonant frequency, the corresponding temperature can be known, and finally the temperature measurement can be achieved.
[0039] In general, the temperature sensor and monitoring system constructed by the present invention have good temperature sensitivity and extremely fast responsiveness, can realize wireless passive measurement, and have more application scenarios.
[0040] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A surface acoustic wave wireless passive temperature sensor, comprising from bottom to top a substrate, a piezoelectric layer, and a top electrode structure, characterized in that: The substrate has a groove and forms a cavity structure with the piezoelectric layer.
2. The sensor according to claim 1, characterized in that The piezoelectric layer is provided with a groove, and the depth of the groove is 0.01-0.9 times the thickness of the piezoelectric layer.
3. The sensor according to claim 1, characterized in that The cavity structure is filled with a heat-sensitive material.
4. The sensor according to claim 3, characterized in that The heat sensitive material includes at least one of polycrystalline silicon, high temperature co-fired ceramics, and aluminum nitride ceramics.
5. The sensor according to claim 1, characterized in that The top electrode structure includes interdigitated electrodes and a reflective grid; The interdigital electrodes and the reflective grid are made of solid conductive metal.
6. The sensor according to any one of claims 1 to 5, characterized in that: A bottom electrode layer is also arranged between the piezoelectric layer and the substrate, and the material of the bottom electrode layer is solid conductive metal.
7. A temperature monitoring system, characterized in that: A sensor comprising any one of claims 1 to 5, further comprising a sensor antenna, a matching circuit, a wireless transceiver and a signal processing component; The sensor is connected to the sensing antenna via the matching circuit; The sensing antenna is used to receive the excitation signal sent by the wireless transceiver and signal processing component.
8. The temperature monitoring system according to claim 7, characterized in that: The wireless transceiver and signal processing component includes a transceiver antenna, a low noise amplifier, a mixer, a filter, a detector, a microprocessor, a power amplifier and a radio frequency switch which are connected in sequence.