Thin film bulk acoustic resonator based on size effect and applications thereof

Abstract

The application discloses a film bulk acoustic resonator based on size effect and application thereof. The film bulk acoustic resonator based on size effect comprises a first electrode and a second electrode which are sequentially stacked on a resonant cavity, and a piezoelectric layer is arranged between the first electrode and the second electrode; and a nanoscale-thickness insertion layer is further arranged between the first electrode and the second electrode. The FBAR temperature sensor provided by the embodiment of the application inserts a nanoscale-thickness insertion layer in the FBAR, thereby greatly improving the detection sensitivity of the FBAR temperature sensor without obviously reducing the resonant frequency of the device.

Description

TECHNICAL FIELD

[0001] The application relates to a temperature sensor, in particular to a thin film bulk acoustic resonator based on a size effect and application thereof, and belongs to the technical field of sensors. BACKGROUND

[0002] Temperature is an important technical parameter in scientific research and industrial production, and the continuous development of modern industry puts forward higher requirements for temperature control. For implantable and high-temperature harsh application occasions, wireless and passive temperature sensors have obvious advantages because they do not need other electronic components. At present, there have been many related researches, such as wireless temperature sensors based on SAW devices, micro antennas and super surface antennas.

[0003] The film bulk acoustic resonator (FBAR) has the advantages of small size, high working frequency and higher quality factor, can greatly reduce the size of the antenna, and can also be used to prepare wireless sensors. In addition, the output of the FBAR-based temperature sensor is in the form of frequency, which can be easily converted into digital and is not easily affected by circuit noise, and has unique advantages.

[0004] The FBAR is an acoustoelectric transducer, and the working mechanism is the piezoelectric effect of the piezoelectric film. Among them, common piezoelectric materials include AlN, PZT, ZnO and LiNbO3. The temperature coefficient of Young's modulus (TCE) of most materials is negative, and the longitudinal wave speed will decrease when the temperature rises, which will further cause the resonant frequency of the FBAR device to decrease. Using materials with large TCE or increasing their thickness ratio in the device can improve the temperature sensitivity of the device.

[0005] Taking an AlN FBAR device as an example, the intrinsic frequency temperature coefficient (TCF) is about -25ppm / ℃, and the TCE of most electrode metals is larger than that. In 2009, Kao et al. improved the thickness ratio of Al electrode in AlN FBAR to increase the TCF to -34.5ppm / ℃, and the corresponding temperature sensitivity is 82.8kHz / ℃. The TCE temperature sensitivity of AlN can be improved by doping Sc in AlN, which can also be used to improve the temperature sensitivity of the sensor. In 2021, WANG et al. prepared an AlN FBAR temperature sensor based on AlN doped with Sc, and the temperature sensitivity of the sensor is 1.2kHz / ℃. 0.7 Sc 0.3The FBAR of N has a working frequency of 2.8 GHz, a TCF of -39.6 ppm / ℃, and a temperature sensitivity of 111 kHz / ℃. However, compared with the micro antenna (580 kHz / ℃), the sensitivity of the FBAR temperature sensor is much lower, which limits its application scenarios. Although the sensitivity of the FBAR temperature sensor can be improved by further increasing the thickness of the high-TCE thin film, it is difficult to achieve a large range of improvement, and increasing the thickness of the resonant zone thin film will cause the working frequency of the device to decrease, thereby reducing the sensitivity of the device. SUMMARY

[0006] The main purpose of the present application is to provide a thin film bulk acoustic resonator based on size effect and its application, so as to overcome the shortcomings in the prior art.

[0007] To achieve the above-mentioned purposes, the technical solutions adopted by the present application include:

[0008] The embodiment of the present application provides a thin film bulk acoustic resonator based on size effect, which comprises a first electrode and a second electrode which are sequentially stacked on a resonant cavity, and a piezoelectric layer is arranged between the first electrode and the second electrode; a nanoscale thickness insertion layer is further arranged between the first electrode and the second electrode.

[0009] Further, the thickness of the insertion layer is 10-40 nm.

[0010] Further, the material of the insertion layer includes Ti, Ni, Cu, W, Al or Si, but is not limited thereto.

[0011] Further, the insertion layer is arranged in a large stress area inside the thin film bulk acoustic resonator.

[0012] Further, the insertion layer is stacked between the piezoelectric layer and any one of the first electrode and the second electrode.

[0013] Further, the insertion layer is arranged between the piezoelectric layer and the second electrode, and the thickness d t of the second electrode t is greater than 1 / 2 of the wavelength of the acoustic wave in the second electrode. b , and the thickness d b of the first electrode t is greater than 1 / 2 of the wavelength of the acoustic wave in the first electrode. b , and the thickness d t of the first electrode b is greater than 1 / 2 of the wavelength of the acoustic wave in the first electrode.

[0014] Further, the crystal form of the insertion layer is amorphous or preferentially oriented.

[0015] Further, the insertion layer is arranged between the piezoelectric layer and the second electrode, and a grain size of the second electrode is larger than a grain size of the insertion layer.

[0016] Further, the first electrode, the piezoelectric layer and the second electrode are sequentially arranged on the substrate, and the resonant cavity is formed in the substrate.

[0017] Further, the resonant cavity is formed on a first surface of the substrate, and the first electrode, the piezoelectric layer and the second electrode are sequentially arranged on the first surface of the substrate; or the resonant cavity is formed on a second surface of the substrate, and the first electrode, the piezoelectric layer and the second electrode are sequentially arranged on the first surface of the substrate, the first surface being opposite to the second surface.

[0018] Further, the first electrode, the piezoelectric layer and the second electrode are sequentially arranged on the substrate, and at least a partial region of the first electrode is concave in a direction away from the substrate to form the resonant cavity.

[0019] Further, the piezoelectric layer is made of any one or a combination of two or more of AlN, ZnO, PZT and LiNbO3, but is not limited thereto.

[0020] Further, the piezoelectric layer has a thickness of 50nm-5000nm.

[0021] Further, the first electrode is made of any one or a combination of two or more of Mo, Al, Pt and W, but is not limited thereto.

[0022] Further, the second electrode is made of any one or a combination of two or more of Mo, Al, Pt, W, Ni, Au, FeGa, FeNi and FeGaB, but is not limited thereto.

[0023] Further, the first electrode has a thickness of 50nm-2000nm.

[0024] Further, the second electrode has a thickness of 50nm-2000nm.

[0025] The embodiment of the present application further provides a temperature sensor comprising the FBAR.

[0026] The embodiment of the present application further provides a use of the FBAR or the temperature sensor in temperature detection.

[0027] Compared with the prior art, the FBAR temperature sensor provided by the embodiment of the present application inserts an insertion layer with a nanoscale thickness in the FBAR, thereby greatly improving the detection sensitivity of the FBAR temperature sensor without significantly reducing the resonant frequency of the device. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an FBAR temperature sensor according to Embodiment 1 of the present invention;

[0029] Figure 2a This is a microstructure diagram of an FBAR temperature sensor according to Embodiment 1 of the present invention;

[0030] Figure 2b This is a flowchart illustrating the fabrication process of an FBAR temperature sensor according to Embodiment 1 of the present invention.

[0031] Figure 3a This is a diagram showing the correspondence between S11 and temperature in an FBAR temperature sensor according to Embodiment 1 of the present invention.

[0032] Figure 3b This is a graph showing the relationship between the resonant frequency and temperature of an FBAR temperature sensor according to Embodiment 1 of the present invention.

[0033] Figure 4 A graph showing the relationship between the sensitivity of the FBAR temperature sensor prepared in Example 1 of this invention and the thickness of the Ti insertion layer;

[0034] Figure 5a This is a schematic diagram of the structure of an FBAR temperature sensor according to Embodiment 2 of the present invention;

[0035] Figure 5b This is a flowchart illustrating the fabrication process of an FBAR temperature sensor according to Embodiment 2 of the present invention.

[0036] Figure 5c This is a graph showing the relationship between the sensitivity of the FBAR temperature sensor prepared in Embodiment 2 of the present invention and the thickness of the Si insertion layer.

[0037] Figure 5d This is the temperature characteristic curve of the FBAR temperature sensor when the thickness of the Si insertion layer is 23 nm in Embodiment 2 of the present invention.

[0038] Figure 6a This is a schematic diagram of the structure of an FBAR temperature sensor according to Embodiment 3 of the present invention;

[0039] Figure 6b This is a flowchart illustrating the fabrication process of an FBAR temperature sensor according to Embodiment 3 of the present invention.

[0040] Figure 7 This is a flowchart illustrating the fabrication process of an FBAR temperature sensor according to Embodiment 4 of the present invention. Detailed Implementation

[0041] In view of the deficiencies in the prior art, the present inventors have obtained the technical solutions of the present application through long-term research and a large number of practices. The technical solutions, implementation processes and principles thereof will be further explained in combination with the accompanying drawings and specific implementation cases. Unless otherwise specified, the structure growth processes of the devices in the embodiments of the present application, such as sputtering, etching, epitaxy and the like, can be known to those skilled in the art.

[0042] Specifically, when the thickness of the thin film is less than several tens of nanometers, the change rule of the Young's modulus (E) of the thin film with temperature is directly related to the thickness of the thin film, and the size effect is exhibited. When the thickness of the thin film becomes thinner, the cohesive energy decreases, the bonding strength between atoms weakens, and the thermal expansion coefficient increases. Under the same temperature difference, the thin film with nanoscale thickness exhibits a greater temperature coefficient of Young's modulus (TCE) than the bulk material. Further, the present inventors have unexpectedly found that inserting a thin film with nanoscale thickness (10-40 nm) in a film bulk acoustic resonator (FBAR) can greatly improve the detection sensitivity of the temperature sensor of the FBAR without significantly reducing the resonant frequency of the device.

[0043] Taking Ti as an example, it has the advantages of high Young's modulus and high sound speed, and the Young's modulus of Ti is very sensitive to temperature. Inserting a Ti thin film with nanoscale thickness in an FBAR can greatly improve the detection sensitivity of the temperature sensor of the FBAR without significantly reducing the resonant frequency of the device.

[0044] Specifically, the influence of temperature on the modulus of copper thin film is simulated by using molecular dynamics method, and the results show that the elastic modulus of the copper thin film decreases with the increase of temperature, and the rate of modulus decrease increases with the decrease of the thickness of the thin film. The simulation results show that the same rule also applies to Ni, W, Al and silicon. Based on this, the present inventors have found that, in addition to Ti, Ni, Cu, W, Al and Si are also suitable for the present application.

[0045] The working mechanism of the FBAR temperature sensor provided by the embodiments of the present application at least lies in that the resonant frequency of the device changes with the test temperature, and when the temperature being tested changes, the Young's modulus of the nanoscale thickness insertion layer changes dramatically, thereby causing the sound speed and acoustic impedance of the thin film to change dramatically, and finally causing the resonant frequency of the FBAR to shift.

[0046] The mechanism of the FBAR temperature sensor provided by the embodiments of the present application is bulk acoustic wave resonance, and the material in the large stress region in the device has a greater impact on the temperature sensitivity of the device. The present application can set the insertion layer in the large stress region inside the device by adjusting the thickness ratio of the upper and lower electrodes.

[0047] The inventors have found that the change of the Young's modulus of the nanoscale thickness of the insertion layer increases the influence on the sensitivity of the device, which is conducive to obtaining greater temperature sensitivity. The material in the large stress area of the device has a greater influence on the temperature characteristics of the device, and the speed and thickness of the film acoustic velocity determine the stress distribution in the device. In the embodiments of the present application, the thickness dt of the upper electrode is set to be greater than (V t / V b )×d b , where d t , d b are the thicknesses of the upper and lower electrodes, respectively, and V t , V b are the propagation speeds of the acoustic wave in the upper and lower electrodes, respectively.

[0048] The technical solutions, implementation processes and principles will be further explained in combination with the accompanying drawings and specific implementation cases. The following embodiments only give the case that the insertion layer is arranged between the piezoelectric layer and any one of the first electrode and the second electrode. Of course, the insertion layer can also be arranged inside the piezoelectric layer. It should be noted that the embodiments only illustrate how to use the content of the present application, but cannot be implemented in this way only.

[0049] Embodiment 1

[0050] In this embodiment, Mo film is used as the lower electrode (i.e. the first electrode mentioned above, the same below) of the FBAR, AlN film is used as the piezoelectric resonant layer (i.e. the piezoelectric layer mentioned above, the same below), and FeGa / Au film is used as the upper electrode (i.e. the second electrode mentioned above, the same below).

[0051] Please refer to Figure 1 and Figure 2a , a FBAR temperature sensor includes a Mo lower electrode, an AlN piezoelectric layer, a Ti insertion layer and a FeGa / Au upper electrode which are sequentially stacked on the first surface of a silicon substrate, the second surface of the silicon substrate is provided with a resonant cavity, and the Mo lower electrode, the AlN piezoelectric layer, the Ti insertion layer and the FeGa / Au upper electrode are arranged in a resonant area corresponding to the resonant cavity, wherein the thickness of the Ti insertion layer is 20 nm.

[0052] Specifically, please refer to Figure 2b , the steps for preparing the temperature sensor by using the MEMS process are as follows:

[0053] 1) A sputtering table is used to sequentially deposit an AlN buffer layer with a thickness of 30 nm and a Mo lower electrode with a thickness of 200 nm on the front surface of a (100) high-resistance Si wafer. The AlN buffer layer can improve the (110) preferred orientation of the metal Mo, which is conducive to promoting the (002) preferred orientation degree of the AlN piezoelectric layer;

[0054] 2) sputtering platform to form AlN piezoelectric layer with thickness of 1000 nm, 20 nm Ti insertion layer, 200 nm FeGa / 20 nm Au upper electrode on Mo electrode in sequence; wherein, Au is used to prevent FeGa material from oxidation;

[0055] 3) IBE and ICP etching machines are respectively used to perform pattern processing on FeGa / Au upper electrode and AlN piezoelectric layer, Mo lower electrode, PECVD equipment is used to form Si3N4 insulating layer with thickness of 400 nm on the surface of the device, and RIE etching machine is used to perform pattern processing on the Si3N4 insulating layer, and then a stripping process is used to prepare Ni / Au coplanar waveguide electrode with thickness of 20 nm / 200 nm;

[0056] 4) the high-resistance Si wafer is thinned to 200 μm, and a deep silicon etching equipment is used to process a patterned cavity on the back surface of the high-resistance Si wafer, thereby forming the FBAR temperature sensor.

[0057] A network analyzer and a temperature control platform are used to test the change of the resonant frequency of the FBAR temperature sensor with temperature, and the temperature sensitivity of the FBAR temperature sensor is calculated, and the test results are shown in Figure 3a 、 Figure 3b 、 Figure 4 , Figure 3a is a typical relationship diagram of S11 of the FBAR temperature sensor and temperature, Figure 3b is a relationship diagram of the resonant frequency of the FBAR temperature sensor and temperature, it can be seen that the resonant frequency of the device decreases by 28.3 MHz as the temperature rises from 30℃ to 80℃. The sensitivity of temperature detection is about 546 kHz / ℃ through linear fitting, and the linearity between frequency and temperature is 0.9965.

[0058] Specifically, in addition to the 20 nm Ti insertion layer, the inventors of the present application also prepared sensors containing 10 nm, 40 nm, 50 nm and 100 nm Ti insertion layers during the research process. Figure 4 shows the relationship between the sensitivity of the sensor and the thickness of the Ti insertion layer, Figure 4 also gives the calculation results based on the Mason model and the experimental test data provided by the inventors of the present application, wherein the Mason data is calculated by using the parameters in Table 1, and the TCE parameters of Ti are the data reported in the literature (Bottoni G., Candolfo D, Cecchetti A., Giarda L., and Masoli F. 2010 Phys Status Solidi 143K75).

[0059] Table 1 Material parameters used in Mason model

[0060]

[0061] According to the Mason model, it is learned that as the thickness of Ti increases from 10 nm to 700 nm, the sensitivity of the sensor gradually increases, and the maximum value is 315 kHz / ℃, because Ti is a negative TCE material, and its contribution to the temperature sensitivity of the device will increase as the thickness increases; and when the thickness continues to increase from 700 nm to 1000 nm, the sensitivity gradually decreases, because the thickness of Ti is too thick, which will cause the resonant frequency to gradually decrease, and eventually lead to the decrease of the sensitivity.

[0062] The experimental results show that when the thickness of Ti is 50 nm and 100 nm, the experimental results of the sensitivity are similar to the prediction of the Mason model, and the change trend is consistent, but the inventors of the present application unexpectedly found that when the thickness of Ti is less than or equal to 40 nm, the sensor shows abnormally high sensitivity; when the thickness of Ti is 20 nm, the sensitivity reaches 546 kHz / ℃, which is an abnormal phenomenon related to the thickness scale effect compared with the calculated result (147 kHz / ℃). When the thickness of Ti is thinned to 10 nm, the phenomenon still exists, but the sensitivity is slightly smaller than that when the thickness of Ti is 20 nm, that is, when the thickness of Ti is 20 nm, the sensitivity of the corresponding device reaches the maximum value.

[0063] It is found through experiments that increasing and decreasing the thickness of Ti can improve the sensitivity of the sensor, but compared with the two, the method based on the thickness scale effect is more obvious. The experimental results show that Al, Pt and W also have excellent acoustic characteristics and can be used as the lower electrode of the FBAR filter, so the lower electrode Mo in the embodiment can also be replaced by Al, Pt and W.

[0064] Embodiment 2

[0065] In this embodiment, Mo thin film is used as the lower electrode (i.e. the first electrode mentioned above, the same below) of the FBAR, AlN thin film is used as the piezoelectric resonant layer (i.e. the piezoelectric layer mentioned above, the same below), and Ni / Au is used as the upper electrode (i.e. the second electrode mentioned above, the same below).

[0066] Please refer to Figure 5a A FBAR temperature sensor includes a Mo lower electrode, an AlN piezoelectric layer, a Si insertion layer and a Ni / Au upper electrode which are sequentially stacked on a first surface of a silicon substrate, the first surface of the silicon substrate is provided with a resonant cavity, and the Mo lower electrode, the AlN piezoelectric layer, the Si insertion layer and the Ni / Au upper electrode are arranged in a resonant region corresponding to the resonant cavity, wherein the thickness of the Si insertion layer is 10 nm.

[0067] Specifically, please refer to Figure 5bThe steps for preparing the temperature sensor by using the MEMS process are as follows:

[0068] 1) Form a patterned cavity on the front surface of a high-resistance Si wafer by using ICP etching, then grow a sacrifice layer PSG by using PECVD, and then remove the excess PSG film on the surface by using the CMP process;

[0069] 2) Form a 30 nm-thick AlN buffer layer and a 200 nm-thick Mo lower electrode on the front surface of the high-resistance Si wafer by using a sputtering station, the AlN buffer layer can improve the (110) preferred orientation of the metal Mo, and then facilitate the (002) preferred orientation degree of the AlN piezoelectric layer; form a 1080 nm-thick AlN piezoelectric layer on the Mo lower electrode by using a sputtering station, prepare a nanometer-thick Si insertion layer by using a chemical vapor deposition method, and prepare a 200 nm Ni / 30 nm Au upper electrode by using a sputtering station; wherein the thickness of the Si insertion layer is 10 nm, and Au is used to prevent the Ni film from being oxidized;

[0070] 3) Perform patterned processing on the Ni / Au upper electrode and the AlN piezoelectric layer and the Mo lower electrode by using IBE and ICP etching machines respectively, form a 400 nm-thick Si3N4 insulating layer on the surface of the device by using a PECVD device, and perform patterned processing on the Si3N4 insulating layer by using a RIE etching machine, and then prepare a 20 nm / 200 nm-thick Ni / Au coplanar waveguide electrode by using a stripping process,

[0071] 4) Form a release hole by using ICP etching, and release the sacrifice layer PSG in the cavity by using HF or VHF, thereby forming an FBAR temperature sensor.

[0072] The network analyzer and the temperature control platform are used to test the change of the resonant frequency of the FBAR temperature sensor with temperature, and the temperature sensitivity of the FBAR temperature sensor is calculated. In addition to the 10 nm-thick silicon insertion layer, FBAR temperature sensors based on 15 nm, 23 nm, 34 nm, 65 nm, 104 nm, 140 nm and 190 nm-thick silicon insertion layers are also prepared in the experiment. The FBAR temperature sensors obtained in the experiment are tested, and the test results are shown in Figure 5c 、 Figure 5d The experimental results show that when the thickness of the Si insertion layer is 10 nm-65 nm, the FBAR temperature sensor has a high temperature sensitivity.

[0073] The experimental results show that Al, Pt and W have excellent acoustic characteristics and can also be used for FBAR filters. Therefore, the lower electrode Mo in the embodiment can also be replaced by Al, Pt and W.

[0074] Embodiment 3

[0075] Referring to Figure 6a and 6b A FBAR temperature sensor comprises a Pt lower electrode, a PZT piezoelectric layer, a Ni interlayer and a W upper electrode which are sequentially stacked on a first surface of a silicon substrate, a partial region of the Pt lower electrode is recessed in a direction away from the silicon substrate to form a resonance cavity, and the Pt lower electrode, the PZT piezoelectric layer, the Ni interlayer and the W upper electrode are arranged in a resonance region corresponding to the resonance cavity, wherein the thickness of the Ni interlayer is 30 nm.

[0076] The manufacturing process of the FBAR temperature sensor in the embodiment is basically the same as that in Embodiment 2.

[0077] Embodiment 4

[0078] The structure and manufacturing process of the FBAR temperature sensor in the embodiment are basically the same as those in Embodiment 3, except that a Pt thin film is used as the lower electrode (i.e., the first electrode, the same below) of the FBAR, a PZT thin film is used as the piezoelectric resonance layer (i.e., the piezoelectric layer, the same below), and a W thin film is used as the upper electrode (i.e., the second electrode, the same below).

[0079] Referring to Figure 7 A FBAR temperature sensor comprises a Pt lower electrode, a PZT piezoelectric layer, a Ni interlayer and a W upper electrode which are sequentially stacked on a first surface of a silicon substrate, a partial region of the Pt lower electrode is recessed in a direction away from the silicon substrate to form a resonance cavity, and the Pt lower electrode, the PZT piezoelectric layer, the Ni interlayer and the W upper electrode are arranged in a resonance region corresponding to the resonance cavity, wherein the thickness of the Ni interlayer is 30 nm.

[0080] It should be noted that the embodiment only illustrates how to use the content of the application, but it is not the only way to implement the application. The application can adjust the thickness ratio of the upper and lower electrodes, and set the interlayer in a large stress area inside the device. The influence of the Young's modulus change of the nanoscale thickness interlayer on the sensitivity of the device will increase, which is beneficial to obtain greater temperature sensitivity.

[0081] The FBAR temperature sensor provided by the embodiment of the application inserts a nanoscale thickness interlayer in the FBAR, which greatly improves the detection sensitivity of the FBAR temperature sensor without significantly reducing the resonance frequency of the device.

[0082] It should be understood that the above-described embodiments are merely intended to illustrate the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A size effect based film bulk acoustic resonator comprising a first electrode and a second electrode sequentially stacked on a resonant cavity, a piezoelectric layer being disposed between the first electrode and the second electrode; characterized in that: The first electrode and the second electrode are further provided with an interposed layer with nanometer thickness, the interposed layer is arranged between the piezoelectric layer and the second electrode, the interposed layer is arranged in a large stress area inside the film bulk acoustic resonator, and the thickness d t > (V t / b ) × d b , wherein d t , d b are thicknesses of the second electrode and the first electrode respectively, V t , V b are propagation speeds of acoustic waves in the second electrode and the first electrode respectively, the thickness of the interposed layer is 10-40 nm, and the material of the interposed layer comprises Ti, Ni, Cu, W, Al or Si.

2. The film bulk acoustic resonator of claim 1, wherein: The crystal form of the insertion layer is amorphous or preferentially oriented.

3. The film bulk acoustic resonator of claim 2, wherein: The insertion layer is arranged between the piezoelectric layer and the second electrode, and the grain size of the second electrode is larger than the grain size of the insertion layer.

4. The film bulk acoustic resonator of claim 1, wherein: The first electrode, the piezoelectric layer and the second electrode are sequentially stacked on the substrate, and the resonant cavity is formed in the substrate.

5. The film bulk acoustic resonator of claim 4, wherein: The resonant cavity is formed on the first surface of the substrate, and the first electrode, the piezoelectric layer and the second electrode are sequentially stacked on the first surface of the substrate; or the resonant cavity is formed on the second surface of the substrate, and the first electrode, the piezoelectric layer and the second electrode are sequentially stacked on the first surface of the substrate, the first surface being opposite to the second surface.

6. The film bulk acoustic resonator of claim 1, wherein: The first electrode, the piezoelectric layer and the second electrode are sequentially stacked on the substrate, and at least a partial region of the first electrode is recessed in a direction away from the substrate to form the resonant cavity.

7. The film bulk acoustic resonator of claim 1, wherein: The material of the piezoelectric layer comprises any one or a combination of two or more of AlN, ZnO, PZT and LiNbO3.

8. The film bulk acoustic resonator of claim 1, wherein: The thickness of the piezoelectric layer is 50-5000 nm.

9. The film bulk acoustic resonator of claim 1, wherein: The material of the first electrode comprises any one or a combination of two or more of Mo, Al, Pt and W.

10. The film bulk acoustic resonator of claim 1, wherein: The material of the second electrode comprises any one or a combination of two or more of Mo, Al, Pt, W, Ni, Au, FeGa, FeNi and FeGaB.

11. The film bulk acoustic resonator of claim 1, wherein: The thickness of the first electrode is 50-2000 nm.

12. The film bulk acoustic resonator of claim 1, wherein: The thickness of the second electrode is 50-2000 nm.

13. A temperature sensor characterized by The film bulk acoustic resonator of any one of claims 1-12.

14. Use of the film bulk acoustic resonator of any one of claims 1-12 or the temperature sensor of claim 13 in temperature detection.

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