A dual-mode surface acoustic wave pressure sensor and methods of use and manufacture

Abstract

The application relates to a bimodal surface acoustic wave pressure sensor and a use and preparation method, which comprises a substrate, a pressure-sensitive cavity is arranged in the substrate; a lower electrode, the lower electrode is configured as grounding; a piezoelectric layer, the piezoelectric layer is made of vanadium-doped zinc oxide film, a through hole is arranged on the piezoelectric layer, the through hole is connected with the lower electrode to realize grounding; an upper electrode, the upper electrode is configured to convert an alternating current signal into a periodic electromagnetic field and load the periodic electromagnetic field into the piezoelectric layer; the lower electrode, the piezoelectric layer and the upper electrode jointly form a surface acoustic wave excitation unit, two modes of surface acoustic waves can be obtained from the surface acoustic wave excitation unit, the resonance frequencies and working frequency bands of the two modes of surface acoustic waves are different and are sensitive to pressure and temperature changes. Through mutual calculation of the resonance frequency changes under the two working modes, single-chip temperature compensation and pressure measurement are realized, and the measurement accuracy and sensitivity are improved.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and relates to a dual-mode surface acoustic wave pressure sensor and its use and preparation method. Background Technology

[0002] During high-speed driving, both excessively high and low tire pressure can cause sudden traffic accidents. Therefore, it is necessary to monitor tire pressure in real time to ensure the vehicle operates at the correct pressure. Tire pressure monitoring systems (TPMS) can monitor tire pressure in real time, and the most commonly used TPMS is the direct type. Direct monitoring primarily uses a sensor module and a receiving and processing module to monitor tire pressure. A sensor chip is installed inside the tire to obtain information such as internal tire pressure and temperature. However, direct monitoring also has some drawbacks. The biggest drawback is that the sensor requires a battery, making maintenance inconvenient, and it is not suitable for engineering transport vehicles operating in flammable and explosive extreme environments such as coal mines and oil fields.

[0003] Surface acoustic wave (SAW) devices, with their wireless and passive nature, can achieve high-precision, high-stability, and high-sensitivity tire pressure measurement, overcoming the drawback of existing direct sensors that require batteries. They also have unique application trends in extreme and harsh environments such as flammable and explosive environments. However, the center frequency of SAW devices is affected not only by pressure but also by changes in the ambient temperature, thus necessitating temperature compensation for pressure sensors. Summary of the Invention

[0004] Technical problems to be solved

[0005] To avoid the shortcomings of existing technologies, this invention proposes a dual-mode surface acoustic wave pressure sensor and its application and preparation method, which solves the problems of temperature compensation and sensitivity improvement in tire pressure monitoring systems.

[0006] Technical solution

[0007] A dual-mode surface acoustic wave (SAW) pressure sensor is characterized by comprising, from bottom to top, a substrate 1, a lower electrode 2, a piezoelectric layer 3, and an upper electrode 4. The substrate 1 comprises two layers: an upper substrate 12 and a lower substrate 13, with a pressure-sensitive cavity 11 for measuring pressure between the two substrate layers. The lower electrode 2 is mounted on the upper substrate 12, followed by the piezoelectric layer 3, which has through-holes 32 electrically connected to the lower electrode 2. The upper electrode 4 is mounted on the piezoelectric layer 3, and includes interdigitated electrodes 41, signal pads 42, ground pads 43, and a Bragg reflector grating 44. The upper electrode 4 can load a periodic electromagnetic field into the piezoelectric layer 3. The lower electrode 2, the piezoelectric layer 3, and the upper electrode 4 together constitute a SAW excitation unit, in which ultrasonic waves are continuously reflected and superimposed for interference, thus obtaining two modes of SAW: Rayleigh waves and Lamb waves.

[0008] The pressure-sensitive cavity 11 is a blind groove provided on the surface where the upper substrate 12 and the lower substrate 13 are connected.

[0009] The blind groove is etched into the lower surface of the upper substrate 12 using an etching method to form a cuboid or cylindrical blind groove.

[0010] The piezoelectric layer 31 is a patterned piezoelectric layer.

[0011] The upper electrode 4 has an interdigitated electrode 41 between the two pads. Bragg reflector grids 44 are distributed on both sides of the interdigitated electrode 41. The signal terminal interdigitated electrode 411 is connected to the signal terminal pad 42, and the ground terminal interdigitated electrode 412 is connected to the ground terminal pad 43.

[0012] The signal end interdigitated electrode 411 and the ground end interdigitated electrode 412 are located directly above the pressure-sensitive cavity of the piezoelectric layer 3, which is the center of the surface acoustic wave excitation unit.

[0013] The piezoelectric layer is a vanadium-doped zinc oxide thin film, and the thickness of the piezoelectric layer is configured to not exceed the wavelength of the surface acoustic wave propagating therein.

[0014] A method for achieving single-chip temperature compensation and pressure measurement using the aforementioned dual-modal surface acoustic wave pressure sensor, characterized in that:

[0015] First, the pressure-frequency response of the first and second modes at temperature T0 is calibrated to obtain the first mode frequency-pressure coefficient α1 and the second mode frequency-pressure coefficient α2.

[0016] Then, the temperature-frequency response of the first and second modes under P0 pressure was calibrated to obtain the first mode frequency-temperature coefficient β1 and the second mode frequency-temperature coefficient β2.

[0017] Substitute the measured f1(P,T), f2(P,T), α1, α2, β1, and β2 into the pressure calculation and temperature compensation formula:

[0018] f1(P,T)=f1(P0,T0)[1-α1(P-P0)-β1(T-T0)]

[0019] f2(P,T)=f2(P0,T0)[1-α2(P-P0)-β2(T-T0)]

[0020] Eliminate the (T-T0) term to obtain the measured pressure change (P-P0).

[0021] A method for fabricating the dual-modal surface acoustic wave pressure sensor, characterized in that:

[0022] A lower electrode is prepared by DC magnetron sputtering gold deposition on the upper surface of the upper substrate of the substrate layer; a photoresist mask is prepared on the lower surface, and the photoresist mask is patterned into a blind trench. A blind trench is obtained on the lower surface of the upper substrate by reactive ion etching. The lower substrate and the lower surface of the upper substrate are pressed together to obtain a pressure-sensitive cavity.

[0023] A piezoelectric layer was prepared on the lower electrode by zinc oxide deposition via radio frequency magnetron sputtering.

[0024] Gold thin films were prepared on piezoelectric layers by DC magnetron sputtering.

[0025] A photoresist mask is prepared on the upper surface of a gold thin film. The photoresist mask is patterned and then the upper electrode is obtained by dry etching. The pattern has an interdigitated electrode in the middle, Bragg reflector gates on the left and right sides of the interdigitated electrode, and signal pads and ground pads on the upper and lower sides of the interdigitated electrode.

[0026] A photoresist mask is prepared on the surface of the upper electrode at the via design location in the piezoelectric layer. The via is patterned on the photoresist mask, and the via is obtained in the piezoelectric layer by wet etching with dilute hydrochloric acid.

[0027] Gold wires are soldered to the grounding pad of the upper electrode, and the gold wires are soldered to the surface of the lower electrode through the piezoelectric layer vias.

[0028] On the surface of the grounding pad of the upper electrode, a gold wire is welded using an ultrasonic wire bonding machine; the other end of the gold wire is welded to the surface of the lower electrode through the through-hole of the piezoelectric layer, so that it is electrically connected to the grounding pad of the upper electrode.

[0029] Two gold wires are welded between the grounding pad of the upper electrode and the lower electrode.

[0030] Beneficial effects

[0031] This invention proposes a dual-mode surface acoustic wave (SAW) pressure sensor, along with its application and fabrication method. Unlike other SAW resonators, this sensor exhibits two operating modes. The sensor comprises: a substrate with a pressure-sensitive cavity; a lower electrode configured for grounding; a piezoelectric layer made of vanadium-doped zinc oxide thin film with through-holes connecting to the lower electrode for grounding; and an upper electrode configured to convert AC signals into a periodic electromagnetic field and apply it to the piezoelectric layer. The lower electrode, piezoelectric layer, and upper electrode together constitute a SAW excitation unit, from which two modes of SAW can be obtained. The resonant frequencies and operating frequency bands of the SAW in the two modes are different, and both are sensitive to pressure and temperature changes. By mutually calculating the resonant frequency changes in the two operating modes, single-chip temperature compensation and pressure measurement are achieved, improving measurement accuracy and sensitivity.

[0032] The sensor surface acoustic wave excitation unit of this invention can acquire two modes of surface acoustic waves. By mutually calculating the resonant frequency changes under the two modes, single-chip temperature compensation and high-precision pressure measurement are achieved. The dual-mode surface acoustic wave pressure sensor proposed in this invention has a higher sensitivity to pressure and temperature changes, thus improving the measurement sensitivity. The piezoelectric layer of the dual-mode surface acoustic wave pressure sensor proposed in this invention is a vanadium-doped zinc oxide thin film, which has a higher piezoelectric coefficient and lower dielectric loss, further improving the measurement sensitivity. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a dual-mode surface acoustic wave pressure sensor provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a substrate structure provided in an embodiment of the present invention;

[0035] Figure 3 for Figure 2 Cross-sectional view along the AA direction;

[0036] Figure 4 A schematic diagram of a piezoelectric layer structure provided in an embodiment of the present invention;

[0037] Figure 5 This is a schematic diagram of an upper electrode structure provided in an embodiment of the present invention;

[0038] Figure 6 The spectrum of the reflection coefficient of the first mode, as measured by a network analyzer;

[0039] Figure 7 The spectrum of the reflection coefficient of the second mode, measured by a network analyzer;

[0040] Figure 8 This is a flowchart illustrating a method for fabricating a dual-mode surface acoustic wave pressure sensor according to an embodiment of the present invention.

[0041] In the figure, 1 is the substrate, 11 is the pressure-sensitive cavity, 12 is the upper substrate, and 13 is the lower substrate; 2 is the lower electrode; 3 is the piezoelectric layer, 31 is the patterned piezoelectric layer, and 32 is the via; 4 is the upper electrode, 41 is the interdigitated electrode, 411 is the signal interdigitated electrode, 412 is the ground interdigitated electrode, 42 is the signal pad, 43 is the ground pad, and 44 is the Bragg reflector. Detailed Implementation

[0042] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0047] In the following description, suffixes such as “module,” “part,” or “unit” used to denote elements are used only for the purposes of this application and have no specific meaning in themselves.

[0048] like Figure 1 The diagram shows a schematic of a dual-mode surface acoustic wave pressure sensor according to an embodiment of the present invention. The pressure sensor includes: a substrate 1, comprising an upper substrate 12 and a lower substrate 13, wherein a pressure-sensitive cavity 11 is provided in both the upper substrate 12 and the lower substrate 13 for measuring tire pressure; a lower electrode 2 disposed on the substrate 1, configured to be grounded; and a piezoelectric layer 3 disposed on the lower electrode 2, the piezoelectric layer 3 including a patterned piezoelectric layer 31 and a through-hole 32. The patterned piezoelectric layer 31 is subjected to... After being loaded with an electromagnetic field, surface acoustic waves (SAWs) can be generated. The through-hole 32 connects to the lower electrode 2, enabling it to be grounded. An upper electrode 4 is disposed on the piezoelectric layer 3. The upper electrode 4 is configured to convert the AC signal into a periodic electromagnetic field and load the periodic electromagnetic field into the patterned piezoelectric layer 31. The lower electrode 2, the piezoelectric layer 3, and the upper electrode 4 together constitute a SAW excitation unit (not shown in the figure). The SAW excitation unit can obtain two modes of SAWs, and the resonant frequency and operating frequency band of the SAWs are different in the two modes.

[0049] Specifically, in this embodiment, such as Figure 2-3 As shown, Figure 2 This is a schematic diagram of the structure of a substrate provided in an embodiment of the present invention. Figure 3 for Figure 2 A cross-sectional view along the AA direction shows that the base 1 includes an upper base 12 and a lower base 13. A pressure-sensitive cavity 11 is arranged tangentially along the upper base 12 and the lower base 13. Optionally, the pressure-sensitive cavity 11 can be a cylinder or a cuboid. Figure 4 The diagram shows a piezoelectric layer structure according to an embodiment of the present invention. The piezoelectric layer 3 includes a patterned piezoelectric layer 31 and a through-hole 32. The patterned piezoelectric layer 31 covers the lower electrode 2, isolating other parts of the lower electrode 2 from the upper electrode 4. The patterned piezoelectric layer 31 can generate surface acoustic waves after being subjected to an electromagnetic field. The through-hole 32 directly connects the lower electrode 2 and the upper electrode 4, grounding the lower electrode 2. Figure 5The diagram shows a schematic of an upper electrode structure according to an embodiment of the present invention. The upper electrode 4 includes: an interdigitated electrode 41 located at the center of the surface acoustic wave excitation unit (not shown in the figure), directly above the pressure-sensitive cavity 11; the interdigitated electrode 41 including a signal end interdigitated electrode 411 and a ground end interdigitated electrode 412; a signal end pad 42 connected to one end of the signal end interdigitated electrode 411; a ground end pad 43 connected to one end of the ground end interdigitated electrode 412 and connected to the lower electrode 2 through the through hole 32. In this embodiment of the invention, an ultrasonic wire bonding machine can be used to pass wires through the through hole 32 to achieve electrical connection between the ground end pad 42 and the lower electrode 2; and a Bragg reflector grating 44 located on both sides of the interdigitated electrode 41.

[0050] Furthermore, cuboid or cylindrical blind grooves are etched on the lower surface of the upper substrate 12, and bond formation is induced and sealed under preset pressure and temperature conditions to obtain the pressure-sensitive cavity 11. Ambient pressure applies stress above the substrate 1, changing the wavelength of the surface acoustic wave (SAW) and shifting its resonant frequency. At a certain temperature, the SAW resonant frequency output by the pressure-sensitive cavity 11 decreases linearly with increasing pressure. Because ambient temperature changes the stiffness and density of the substrate 1, causing thermal expansion of the structure, temperature drift is introduced into the pressure sensing signal. Under a certain pressure, the SAW resonant frequency output by the pressure-sensitive cavity 11 decreases linearly with increasing temperature.

[0051] Furthermore, when the dual-mode surface acoustic wave (SAW) pressure sensor measures tire pressure, an AC signal is input to the upper electrode 4 and the lower electrode 2. The interdigital electrode 41 converts the received AC signal into a periodic electromagnetic field and applies the converted periodic electromagnetic field to the piezoelectric layer 3. Excited by the electromagnetic field, the piezoelectric layer 3 generates a surface acoustic wave. The Bragg reflector grating 44 reflects the generated SAW, and the interdigital electrode 41 converts the reflected SAW back into an electrical signal for transmission, thereby obtaining the resonant frequency. The signal; specifically, when the thickness of the piezoelectric layer 3 is properly configured, surface acoustic waves (SAWs) will be reflected when they propagate to the interface between the piezoelectric layer 3 and the lower electrode 2. The reflected SAWs and the incident SAWs couple in the piezoelectric layer 3, generating SAWs of various modes. Different modes of SAWs have different resonant frequencies and different degrees of frequency shift to pressure and temperature changes. SAWs are highly sensitive to disturbances on the waveguide surface; changes in elastic modulus, density, and strain will cause shifts in the frequency, amplitude, and phase of the sound waves. Compared with capacitive and inductive sensors, SAW sensors have advantages such as high quality factor, long communication distance, and small size.

[0052] Specifically, in this embodiment, the upper substrate 12 is an SOI wafer with a diameter of 4 inches and a thickness of 400 μm, and the device layer thickness is 50 μm; the lower substrate 13 is BF33 glass with a diameter of 4 inches and a thickness of 500 μm.

[0053] Specifically, in this embodiment, the surface acoustic wave excitation unit (not shown in the figure) can acquire two modes of surface acoustic waves. The first mode has a resonant frequency of 312.45MHz and an operating frequency band of 310-315MHz. The second mode has a resonant frequency of 453.6MHz and an operating frequency band of 450-455MHz. The second mode of surface acoustic waves is more sensitive to changes in pressure and temperature.

[0054] Specifically, in this embodiment, the piezoelectric layer 3 is a vanadium-doped zinc oxide thin film oriented along the c-axis (002) and is prepared by radio frequency measurement and control sputtering: a two-inch vanadium-doped zinc oxide ceramic target is used, the sputtering power is 70W, the sputtering pressure is 0.7Pa, the argon-oxygen atmosphere ratio is 40:12, and the vanadium doping concentration is 1%. The final piezoelectric layer 3 has a thickness of 1μm. This thickness of the piezoelectric layer 3 can ensure that the surface acoustic wave can propagate from the upper surface of the piezoelectric layer 3 to the interface between the piezoelectric layer 3 and the lower electrode 2 without attenuation, and can effectively couple the reflected surface acoustic wave and the incident surface acoustic wave in the piezoelectric layer 3, thereby generating two new modes of surface acoustic waves.

[0055] Furthermore, in this embodiment, the piezoelectric layer 3 was tested, and its longitudinal piezoelectric strain constant d... 33 The piezoelectric layer 3 has a piezoelectric response of 85 pm / V and a dielectric constant of 14.8, indicating that it has good piezoelectric response and low dielectric loss, thus ensuring that the dual-mode surface acoustic wave pressure sensor has good sensitivity.

[0056] Specifically, in this embodiment, the pressure calculation and temperature compensation formulas for the dual-mode surface acoustic wave pressure sensor are as follows:

[0057] f1(P,T)=f1(P0,T0)[1-α1(P-P0)-β1(T-T0)]

[0058] f2(P,T)=f2(P0,T0)[1-α2(P-P0)-β2(T-T0)]

[0059] In the formula, f1(P0,T0) and f2(P0,T0) are the first and second mode resonant frequencies, respectively; α1 is the first mode frequency-pressure coefficient; β1 is the first mode frequency-temperature coefficient; α2 is the second mode frequency-pressure coefficient; β2 is the second mode frequency-temperature coefficient; f1(P,T) and f2(P,T) are the first and second mode resonant frequencies under the conditions of temperature T and pressure P, respectively. In this embodiment, during measurement, the pressure-frequency response of the first and second modes at temperature T0 can be calibrated first to obtain α1 and α2; then the temperature-frequency response of the first and second modes under pressure P0 can be calibrated to obtain β1 and β2; by substituting the measured f1(P,T), f2(P,T), α1, α2, β1, and β2 into the pressure calculation and temperature compensation formula and eliminating the (T-T0) term, the measured pressure change (P-P0) can be obtained.

[0060] like Figure 8 The diagram shown is a flowchart illustrating a method for fabricating a dual-mode surface acoustic wave pressure sensor according to an embodiment of the present invention. The method includes:

[0061] Step S1: Sputtering, a lower electrode is prepared on the upper substrate by DC magnetron sputtering gold deposition; a piezoelectric layer is prepared on the lower electrode by radio frequency magnetron sputtering zinc oxide deposition; a thin film is prepared on the piezoelectric layer by DC magnetron sputtering gold deposition; specifically, the thickness of the lower electrode and the gold thin film is controlled at 100 nm, and the thickness of the piezoelectric layer is controlled at 1 μm.

[0062] Step S2: Patterning of the upper electrode. A photoresist mask is prepared on the upper surface of the gold thin film, and the photoresist mask is patterned. The pattern is transferred to the gold thin film by etching with an argon ion beam, and the photoresist is removed to obtain the upper electrode. Specifically, the photoresist thickness can be 2 μm. The pattern is transferred to the gold thin film by etching with an argon ion beam. The photoresist mask is removed using an organic solvent. Step S3: Patterning of the piezoelectric layer. A photoresist mask is prepared on the surface of the upper electrode, and the photoresist mask is patterned. Through-holes are obtained in the piezoelectric layer by wet etching with dilute hydrochloric acid. The through-holes are connected to the lower electrode, and the photoresist is removed. Specifically, the photoresist thickness can be 2 μm. The piezoelectric layer is wet etched with dilute hydrochloric acid at a volume ratio of 0.02% to obtain the through-holes. The photoresist mask is removed using an organic solvent.

[0063] Step S4: Obtain the pressure-sensitive cavity. Prepare a photoresist mask on the lower surface of the upper substrate and pattern the photoresist mask. Obtain a blind trench on the lower surface of the upper substrate by reactive ion etching. Remove the photoresist and press the lower substrate and the upper substrate together with a preset pressure. After maintaining the pressing for a preset time threshold, keep the pressed lower substrate and the upper substrate at a set temperature for a preset time and then cool them to form the pressure-sensitive cavity.

[0064] Step S5: Wire bonding. Using an ultrasonic wire bonding machine, gold wires are bonded to the surface of the grounding pad of the upper electrode. The other end of the gold wire is bonded to the surface of the lower electrode through the piezoelectric layer via, thus achieving an electrical connection with the grounding pad of the upper electrode. Specifically, to ensure reliable electrical connection, this embodiment bonds two gold wires between the grounding pad of the upper electrode and the lower electrode. One bonding location is on the surface of the grounding pad of the upper electrode, and the other bonding location is on the exposed surface of the lower electrode at the via.

[0065] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-mode surface acoustic wave pressure sensor, characterized in that... The structure, from bottom to top, consists of a substrate (1), a lower electrode (2), a piezoelectric layer (3), and an upper electrode (4). The substrate (1) comprises two layers: an upper substrate (12) and a lower substrate (13), with a pressure-sensitive cavity (11) for measuring pressure between the two substrate layers. The lower electrode (2) is located on the upper substrate (12), followed by the piezoelectric layer (3), which has a through-hole (32) electrically connected to the lower electrode (2). The upper electrode (4) is located on the piezoelectric layer (3). The upper electrode (4) includes an interdigitated electrode (41), a signal pad (42), a ground pad (43), and a Bragg reflector (44). The upper electrode (4) can load a periodic electromagnetic field into the piezoelectric layer (3). The lower electrode (2), the piezoelectric layer (3), and the upper electrode (4) together constitute a surface acoustic wave excitation unit. In the surface acoustic wave excitation unit, ultrasonic waves can be continuously reflected and superimposed for interference, and two modes of surface acoustic waves can be obtained: Rayleigh waves and Lamb waves.

2. The dual-mode surface acoustic wave pressure sensor according to claim 1, characterized in that: The pressure-sensitive cavity (11) is a blind groove provided on the surface where the upper substrate (12) and the lower substrate (13) are connected.

3. The dual-mode surface acoustic wave pressure sensor according to claim 2, characterized in that: The blind groove is formed by etching a cuboid or cylindrical blind groove on the lower surface of the upper substrate (12) using an etching method.

4. The dual-mode surface acoustic wave pressure sensor according to claim 1, characterized in that: The piezoelectric layer (31) is a patterned piezoelectric layer.

5. The dual-mode surface acoustic wave pressure sensor according to claim 1, characterized in that: The upper electrode (4) has an interdigitated electrode (41) between the two pads. Bragg reflector grids (44) are distributed on both sides of the interdigitated electrode (41). The signal end interdigitated electrode (411) is connected to the signal end pad (42), and the ground end interdigitated electrode (412) is connected to the ground end pad (43).

6. The dual-mode surface acoustic wave pressure sensor according to claim 5, characterized in that: The signal end interdigitated electrode (411) and the ground end interdigitated electrode (412) are located directly above the pressure-sensitive cavity of the piezoelectric layer 3, which is the center of the surface acoustic wave excitation unit.

7. The dual-mode surface acoustic wave pressure sensor according to claim 1 or 4, characterized in that: The piezoelectric layer is a vanadium-doped zinc oxide thin film, and the thickness of the piezoelectric layer is configured to not exceed the wavelength of the surface acoustic wave propagating therein.

8. A method for realizing single-chip temperature compensation and pressure measurement using the dual-mode surface acoustic wave pressure sensor according to any one of claims 1 to 7, characterized in that: First, the pressure-frequency response of the first and second modes at temperature T0 is calibrated to obtain the first mode frequency-pressure coefficient α1 and the second mode frequency-pressure coefficient α2. Then, the temperature-frequency response of the first and second modes under P0 pressure was calibrated to obtain the first mode frequency-temperature coefficient β1 and the second mode frequency-temperature coefficient β2. Substitute the measured f1(P,T), f2(P,T), α1, α2, β1, and β2 into the pressure calculation and temperature compensation formula: f1(P,T)=f1(P0,T0)[1-α1(P-P0)-β1(T-T0)] f2(P,T)=f2(P0,T0)[1-α2(P-P0)-β2(T-T0)] Eliminate the (T-T0) term to obtain the measured pressure change (P-P0).

9. A method for fabricating a dual-mode surface acoustic wave pressure sensor according to any one of claims 1 to 7, characterized in that: A lower electrode is prepared by DC magnetron sputtering gold deposition on the upper surface of the upper substrate of the substrate layer; a photoresist mask is prepared on the lower surface, and the photoresist mask is patterned into a blind trench. A blind trench is obtained on the lower surface of the upper substrate by reactive ion etching. The lower substrate and the lower surface of the upper substrate are pressed together to obtain a pressure-sensitive cavity. A piezoelectric layer was prepared on the lower electrode by zinc oxide deposition via radio frequency magnetron sputtering. Gold thin films were prepared on piezoelectric layers by DC magnetron sputtering. A photoresist mask is prepared on the upper surface of a gold thin film. The photoresist mask is patterned and then the upper electrode is obtained by dry etching. The pattern has an interdigitated electrode in the middle, Bragg reflector gates on the left and right sides of the interdigitated electrode, and signal pads and ground pads on the upper and lower sides of the interdigitated electrode. A photoresist mask is prepared on the surface of the upper electrode at the via design location in the piezoelectric layer. The via is patterned on the photoresist mask, and the via is obtained in the piezoelectric layer by wet etching with dilute hydrochloric acid. Gold wires are soldered to the grounding pad of the upper electrode, and the gold wires are soldered to the surface of the lower electrode through the piezoelectric layer vias. On the surface of the grounding pad of the upper electrode, a gold wire is welded using an ultrasonic wire bonding machine; the other end of the gold wire is welded to the surface of the lower electrode through the through-hole of the piezoelectric layer, so that it is electrically connected to the grounding pad of the upper electrode.

10. The method according to claim 9, characterized in that: Two gold wires are welded between the grounding pad of the upper electrode and the lower electrode.

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