Film bulk acoustic resonator and filter

Abstract

The invention discloses a film bulk acoustic resonator and a filter. The film bulk acoustic resonator comprises a substrate; a cavity is formed in the top of the substrate; a first electrode located at the top of the substrate; a first piezoelectric layer on the top of the first electrode; the second electrode is positioned at the top of the first piezoelectric layer; the device further comprises at least one functional structure. The functional structure is positioned from the bottom of the first piezoelectric layer to the upper part of the second electrode; the orthographic projection of the functional structure on the substrate falls into the cavity, and the area of the orthographic projection of the functional structure on the substrate is smaller than the area of the cavity. According to the technical scheme provided by the invention, the filter formed by the resonator realizes multi-passband filter response, so that the multiplexer only comprises one filter, the miniaturization of the multiplexer is realized, and meanwhile, the heat dissipation capability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a thin film bulk acoustic wave resonator and a filter. Background Art

[0002] RF multiplexers, such as duplexers or quadplexers, play a key role in modern communication devices by isolating transmit and receive signals.

[0003] However, traditional multiplexers use filter technologies such as ceramic, surface acoustic wave and bulk acoustic wave, so that one duplexer contains two filters and one quadplexer contains four filters, resulting in low integration and large size of the multiplexer. In a multi-band multi-mode system, different frequency bands require multiple duplexers in parallel to meet the needs, which makes the multiplexer occupy a large space on the circuit board, thus affecting the compactness and design flexibility of the system.

[0004] Secondly, in order to achieve high-performance isolation and low insertion loss, the RF duplexer needs to be precisely matched with other RF devices, such as power amplifiers and low-noise amplifiers. During the system integration process, it is easily affected by factors such as packaging materials and device spacing, resulting in a complex and time-consuming design process. In addition, in order to adapt to the application requirements of 5G and higher frequencies in the future, the size and integration difficulty of the duplexer have been further increased.

[0005] In addition, the size and integration limitations of multiplexers also have an adverse effect on the heat dissipation and power consumption management of the device. Although highly integrated multiplexers are conducive to improving the portability of the device, their high density increases heat accumulation, leading to signal attenuation and affecting the stability of device performance.

[0006] Therefore, in the design of the multiplexer, not only the miniaturization of the device needs to be considered, but also the heat dissipation capacity of the device needs to be guaranteed to ensure the stability and reliability of the device when working at high frequencies. Summary of the invention

[0007] The present invention provides a thin film bulk acoustic wave resonator and a filter to solve the problems existing in the prior art, realize the miniaturization of the multiplexer and improve the heat dissipation capacity.

[0008] In a first aspect, the present invention provides a thin film bulk acoustic wave resonator, comprising:

[0009] A substrate; a cavity is provided on the top of the substrate;

[0010] a first electrode located on top of the substrate;

[0011] a first piezoelectric layer located on top of the first electrode;

[0012] a second electrode located on top of the first piezoelectric layer;

[0013] It also includes: at least one functional structure; the functional structure is located from the bottom of the first piezoelectric layer to above the second electrode; the orthographic projection of the functional structure on the substrate falls into the cavity, and the area of ​​the orthographic projection of the functional structure on the substrate is smaller than the area of ​​the cavity.

[0014] Optionally, the functional structure includes a temperature compensation layer structure; and the temperature compensation layer structure is located above the first piezoelectric layer or the second electrode.

[0015] Optionally, the functional structure further includes a third electrode;

[0016] The third electrode is located above the second electrode, and the orthographic projection of the third electrode on the substrate covers the orthographic projection of the temperature compensation layer structure on the substrate.

[0017] Optionally, the density of the third electrode is greater than the density of the second electrode.

[0018] Optionally, the functional structure further includes a second piezoelectric layer structure;

[0019] The second piezoelectric layer structure is located in the first piezoelectric layer or above the first piezoelectric layer, and the orthographic projection of the second piezoelectric layer structure on the substrate covers the orthographic projection of the temperature compensation layer structure on the substrate.

[0020] Optionally, the c-axis of the second piezoelectric layer and the c-axis of the first piezoelectric layer are oriented in the same direction.

[0021] Optionally, the functional structure includes N sub-functional structures; each of the sub-functional structures has a different thickness;

[0022] Wherein, N is an integer greater than or equal to 1.

[0023] Optionally, when the functional structure includes one sub-functional structure, the area of ​​the cavity is S1, the area of ​​the orthographic projection of the functional structure on the substrate is S2, and the value range of S2 is: 1 / 3S1≤S2≤2 / 3S1.

[0024] In a second aspect, the present invention further provides a filter comprising an input port, an output port and the thin film bulk acoustic wave resonator described in any one of the above items.

[0025] Optionally, the plurality of thin film bulk acoustic wave resonators include a plurality of series resonators and a plurality of parallel resonators;

[0026] The thickness of the first piezoelectric layer of the series resonator is smaller than the thickness of the first piezoelectric layer of the parallel resonator.

[0027] The technical solution of the present invention is to make a thin film bulk acoustic wave resonator include a substrate provided with a cavity, a first electrode, a first piezoelectric layer, and a second electrode, and a functional structure located from the bottom of the first piezoelectric layer to the top of the second electrode in sequence, and the orthographic projection of the functional structure on the substrate falls into the cavity, and the area of ​​the orthographic projection of the functional structure on the substrate is smaller than the area of ​​the cavity, so that when a voltage is applied to the first electrode and the second electrode of the resonator, due to the existence of the inverse piezoelectric effect, the resonator generates a variety of resonant frequencies, so that the filter formed by the resonator realizes a multi-passband filter response, and further enables the multiplexer to include only one filter, thereby realizing the miniaturization of the multiplexer and improving the heat dissipation capacity.

[0028] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic structural diagram of a thin film bulk acoustic resonator provided by an embodiment of the present invention;

[0031] Figure 2 A schematic structural diagram of another thin film bulk acoustic resonator provided by an embodiment of the present invention;

[0032] Figure 3 A schematic structural diagram of another thin film bulk acoustic resonator provided by an embodiment of the present invention;

[0033] Figure 4 A schematic structural diagram of another thin film bulk acoustic resonator provided by an embodiment of the present invention;

[0034] Figure 5 A schematic structural diagram of another thin film bulk acoustic resonator provided by an embodiment of the present invention;

[0035] Figure 6 A schematic diagram of the structure of a filter provided in this embodiment;

[0036] Figure 7-Figure 14 A schematic diagram of the structure of the process of a method for preparing an acoustic wave filter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0039] It should be noted that the “top” of each structure mentioned in this embodiment should be understood as the side pointed to by the top of the film bulk acoustic wave resonator in each structure, and the “bottom” of each structure mentioned in this embodiment should be understood as the side pointed to by the bottom of the film bulk acoustic wave resonator in each structure.

[0040] This embodiment provides a thin film bulk acoustic resonator. Figure 1 A schematic diagram of the structure of a thin film bulk acoustic wave resonator provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the film bulk acoustic wave resonator 1 includes: a substrate 101, a first electrode 103 located on the top of the substrate 101, a first piezoelectric layer 104 located on the top of the first electrode 103, and a second electrode 105 located on the top of the first piezoelectric layer 104, wherein a cavity 102 is provided on the top of the substrate 101. The film bulk acoustic wave resonator 1 also includes: a functional structure 10, which is located from the bottom of the first piezoelectric layer 104 to above the second electrode 105; the orthographic projection of the functional structure 10 on the substrate 101 falls into the cavity 102, and the area of ​​the orthographic projection of the functional structure 10 on the substrate 101 is smaller than the area of ​​the cavity 102.

[0041] The cavity 102, the first electrode 103, the first piezoelectric layer 104 and the second electrode 105 are sequentially arranged on the substrate 101, and the orthographic projections of the first electrode 103, the first piezoelectric layer 104 and the second electrode 105 on the substrate 101 all fall into the cavity 102, so that resonance is generated when a voltage is applied between the first electrode 103 and the second electrode 105. In an optional embodiment, the first electrode 103 and the second electrode 105 are made of the same material.

[0042] In an optional embodiment, a seed layer 111 is further disposed between the substrate 101 and the first electrode 103 , so that the lattice of the first electrode 103 matches that of the substrate 101 .

[0043] In an optional embodiment, a passivation layer 108 and a metal layer 109 are sequentially disposed above the second electrode 105. The metal layer 109 includes a first extraction electrode 1091 and a second extraction electrode 1092, wherein the first extraction electrode 1091 is electrically connected to the first electrode 103, and the second extraction electrode 1092 is electrically connected to the second electrode 105, and the first extraction electrode 1091 and the second extraction electrode 1092 are not connected to each other. By applying different voltages to the first extraction electrode 1091 and the second extraction electrode 1092, a voltage difference is generated between the first electrode 103 and the second electrode 105.

[0044] It can be understood that, as a device for controlling the frequency by thickness, the thickness of the first piezoelectric layer 104 and the second electrode 105 of the FBAR 1 plays a decisive role in the frequency of the FBAR 1. The greater the thickness of the first piezoelectric layer 104 and the second electrode 105, the greater the mass of the first piezoelectric layer 104 and the second electrode 105 per unit area, and thus the smaller the resonance frequency generated.

[0045] The functional structure 10 is located from the bottom of the first piezoelectric layer 104 to the top of the second electrode 105. The orthographic projection of the functional structure 10 on the substrate 101 falls into the cavity 102, and the area of ​​the orthographic projection of the functional structure 10 on the substrate 101 is smaller than the area of ​​the cavity 102, so that the thickness of part of the first piezoelectric layer 104 to the second electrode 105 changes, that is, the first piezoelectric layer 104 to the second electrode 105 has a variety of thicknesses, so that the resonator can generate a variety of resonant frequencies.

[0046] In an optional embodiment, the functional structure 10 includes N sub-functional structures 010, each of which has a different thickness, so that the first piezoelectric layer 104 and the second electrode 105 of the resonator have N+1 thicknesses, so that the resonator can generate N+1 resonance frequencies.

[0047] Wherein, N is an integer greater than or equal to 1.

[0048] In an exemplary embodiment, Figure 1For example, the functional structure 10 includes one sub-functional structure 010, the thickness of the first piezoelectric layer 104 and the second electrode 105 in the region above the cavity 102 with the functional structure 10 is taken as the first thickness, and the thickness of the first piezoelectric layer 104 and the second electrode 105 in the region above the cavity 102 without the functional structure 10 is taken as the second thickness, the resonance frequency generated by the first thickness is the first resonance frequency f1, and the resonance frequency generated by the second thickness is the second resonance frequency f2. In this way, when the functional structure 10 includes one sub-functional structure 010, the resonator generates two resonance frequencies.

[0049] In an optional embodiment, when the functional structure 10 includes one sub-functional structure 010, the area of ​​the cavity 102 is S1, the area of ​​the orthographic projection of the functional structure 10 on the substrate 101 is S2, and the value range of S2 is: 1 / 3S1≤S2≤2 / 3S1.

[0050] It can be understood that the larger the area S2 of the positive projection of the functional structure 10 on the substrate 101, the greater the intensity of the first resonance frequency f1, and the smaller the intensity of the second resonance frequency. By making the value range of S2 1 / 3S1≤S2≤2 / 3S1, the intensity of the first resonance frequency f1 and the intensity of the second resonance frequency f2 are equal, so that the resonator produces a stable double-peak response.

[0051] It should be noted that Figure 1 The example only shows that the functional structure 10 includes one sub-functional structure 010, and does not limit the number of sub-functional structures 010. In this embodiment, the number of sub-functional structures 010 can be set according to actual needs.

[0052] In an exemplary embodiment, Figure 2 A schematic diagram of another thin film bulk acoustic resonator provided in an embodiment of the present invention, referring to Figure 2 As shown, the functional structure 10 includes three sub-functional structures 010, and the thickness of each sub-functional structure 010 is different, so that the first piezoelectric layer 104 and the second electrode 105 of the resonator have four thicknesses, so that the resonator can generate four resonance frequencies.

[0053] In the present embodiment, the thin film bulk acoustic wave resonator includes, in sequence, a substrate provided with a cavity, a first electrode, a first piezoelectric layer, and a second electrode, and a functional structure located from the bottom of the first piezoelectric layer to the top of the second electrode, the orthographic projection of the functional structure on the substrate falls into the cavity, and the area of ​​the orthographic projection of the functional structure on the substrate is smaller than the area of ​​the cavity, so that when a voltage is applied to the first electrode and the second electrode of the resonator, the resonator generates a plurality of resonant frequencies due to the inverse piezoelectric effect, so that the filter formed by the resonator realizes a multi-passband filter response, and further enables the multiplexer to include only one filter, thereby realizing the miniaturization of the multiplexer and improving the heat dissipation capability.

[0054] Optional, combined with reference Figure 1 and Figure 2 As shown, the functional structure 10 includes a temperature compensation layer structure 106 , and the temperature compensation layer structure 106 is located above the first piezoelectric layer 104 or the second electrode 105 .

[0055] The temperature compensation layer structure 106 is used to improve the temperature drift characteristics of the resonator, thereby improving the stability of the resonator at a high temperature operating frequency.

[0056] Optional, continue to refer to Figure 1 and Figure 2 As shown, the functional structure 10 further includes a third electrode 107 , which is located above the second electrode 105 , and the orthographic projection of the third electrode 107 on the substrate 101 covers the orthographic projection of the temperature compensation layer structure 106 on the substrate 101 .

[0057] The material constituting the third electrode 107 may be the same as or different from the material constituting the second electrode 105. In an optional embodiment, the material constituting the third electrode 107 is different from the material constituting the second electrode 105, and the density of the third electrode 107 is greater than the density of the second electrode 105, so that the mass of the functional structure 10 per unit area is increased, and the mass of the first piezoelectric layer 104 and the second electrode 105 in the area above the cavity 102 with the functional structure 10 is further increased, so that the resonant frequency generated in the area above the cavity 102 with the functional structure 10 can be further reduced.

[0058] In an exemplary embodiment, Figure 1 and Figure 2 For example, the temperature compensating layer structure 106 and the third electrode 107 are both located above the second electrode 105, and the third electrode 107 wraps the temperature compensating layer structure 106, thereby further improving the integration of the resonator.

[0059] It should be noted that Figure 1 and Figure 2The situation that the temperature compensating layer structure 106 and the third electrode 107 are located above the second electrode 105 is only exemplified, and the positions of the temperature compensating layer structure 106 and the third electrode 107 are not limited. In this embodiment, the positions of the temperature compensating layer structure 106 and the third electrode 107 are not limited thereto, and can be set according to actual needs under the premise of achieving the core invention point.

[0060] In an exemplary embodiment, Figure 3 A schematic diagram of a thin film bulk acoustic resonator according to an embodiment of the present invention is shown in FIG. Figure 3 As shown, the temperature compensation layer structure 106 is located on the first piezoelectric layer 104, and the third electrode 107 is located above the second electrode 105, which is beneficial to reducing the effective electromechanical coupling coefficient of the resonator, thereby meeting the ultra-narrowband application requirements of communication radars or satellites.

[0061] Optional, Figure 4 A schematic diagram of a thin film bulk acoustic resonator according to an embodiment of the present invention is shown in FIG. Figure 4 As shown, the functional structure 10 also includes a second piezoelectric layer structure 110, which is located in the first piezoelectric layer 104 or above the first piezoelectric layer 104, and the orthographic projection of the second piezoelectric layer structure 110 on the substrate 101 covers the orthographic projection of the temperature compensation layer structure 106 on the substrate 101, so that the first piezoelectric layer 104 combined with the second piezoelectric layer structure 110 can adjust the effective electromechanical coupling coefficient of the resonator, thereby meeting the relative bandwidth requirements of the multiplexer passband.

[0062] In this embodiment, the c-axis of the second piezoelectric layer and the c-axis of the first piezoelectric layer 104 are oriented in the same direction, and the substrate 101 and the seed layer 111 of the resonator match the lattice of the first piezoelectric layer 104 and the second piezoelectric layer to achieve the purpose of adjusting the effective electromechanical coupling coefficient of the resonator.

[0063] It should be noted that Figure 4 The second piezoelectric layer structure 110 is only exemplarily shown as being located on the first piezoelectric layer 104, and the position of the second piezoelectric layer structure 110 is not limited. Figure 5 As shown, the second piezoelectric layer may also be disposed above the first piezoelectric layer 104 , so that the resonator has a variety of different thicknesses through the first piezoelectric layer 104 and the second piezoelectric layer structure 110 , thereby causing the resonator to generate a variety of resonance frequencies.

[0064] Based on the same concept, an embodiment of the present invention further provides a filter. Figure 6 A schematic diagram of the structure of a filter provided in this embodiment, referring to Figure 6 As shown, the filter includes an input port, an output port and a plurality of thin film bulk acoustic wave resonators 1 provided by any embodiment of the present invention.

[0065] In this embodiment, since the filter includes the thin film bulk acoustic wave resonator provided by any embodiment of the present invention, the filter can achieve multi-band filter response, and thus the multiplexer can include only one filter, thereby achieving miniaturization of the multiplexer and improving heat dissipation capability.

[0066] Optional, continue to refer to Figure 6 As shown, the plurality of FBAW resonators 1 include a plurality of series resonators 100 and a plurality of parallel resonators 200; the thickness of the first piezoelectric layer 104 of the series resonator 100 is smaller than the thickness of the first piezoelectric layer 104 of the parallel resonator 200, thereby reducing the overall resonance frequency of the filter.

[0067] It should be noted that Figure 6 The filter includes four series resonators 100 and four parallel resonators 200, but does not limit the number of series resonators 100 and parallel resonators 200 in the filter. The structure of the filter in this embodiment is not limited to this, as long as the core invention of this embodiment can be achieved.

[0068] The technical solution of the present invention is described below with specific embodiments:

[0069] Example 1

[0070] refer to Figure 1 As shown, the thin film bulk acoustic wave resonator 1 includes a substrate 101 with a cavity 102 on the top, a first electrode 103, a second electrode 105, a temperature compensation layer structure 106, a third electrode 107, a passivation layer 108 and a metal layer 109 in sequence, the temperature compensation layer structure 106 and the third electrode 107 constitute a functional structure 10, the third electrode 107 wraps the temperature compensation layer structure 106, the orthographic projection of the functional structure 10 on the substrate 101 falls into the cavity 102, and the area S2 of the orthographic projection of the functional structure 10 on the substrate 101 has a value range of 1 / 3S1≤S2≤2 / 3S1, where S1 is the area of ​​the cavity 102.

[0071] In this embodiment, the temperature compensation layer structure 106 can improve the temperature drift characteristics of the resonator, thereby improving the stability of the resonator at high temperature operating frequency. The existence of the functional structure 10 changes the thickness of part of the first piezoelectric layer 104 to the second electrode 105, so that the resonator can generate two resonant frequencies.

[0072] Figure 7-Figure 14 The process structure diagram of the method for preparing an acoustic wave filter provided by an embodiment of the present invention is as follows:

[0073] S1 . Form a sacrificial layer on the top of the silicon substrate 101 .

[0074] like Figure 7 shown.

[0075] S2 . Form a seed layer 111 and a first electrode 103 on the top of the substrate 101 .

[0076] like Figure 8 shown.

[0077] Exemplarily, a seed layer 111 and a first electrode layer are formed in sequence on the top of the substrate 101 , and then the first electrode layer is etched to obtain the first electrode 103 .

[0078] S3 . Form a piezoelectric layer above the seed layer 111 and the first electrode 103 , and etch the first piezoelectric layer 104 to expose a portion of the first electrode 103 .

[0079] like Fig. 9 shown.

[0080] Exemplarily, the first piezoelectric layer 104 is formed above the seed layer 111 and the first electrode 103 , and then the first piezoelectric layer 104 is etched to expose a portion of the first electrode 103 , so that the first extraction electrode 1091 can be formed in a subsequent step.

[0081] S4. Form a second electrode 105 on the first piezoelectric layer 104.

[0082] like Fig.10 shown.

[0083] Exemplarily, a second electrode layer is formed on the first piezoelectric layer 104 , and then the second electrode layer is etched to obtain the second electrode 105 .

[0084] S5 . Form a temperature compensation layer structure 106 on the second electrode 105 .

[0085] like Fig.11 shown.

[0086] Exemplarily, a temperature compensation layer is formed on the second electrode 105 , and then the temperature compensation layer is etched to obtain the temperature compensation layer structure 106 .

[0087] S6. Forming a third electrode 107 on the temperature compensation layer.

[0088] like Fig.12 shown.

[0089] Exemplarily, a third electrode layer is formed above the second electrode 105 and the temperature compensation layer structure 106, and then the third electrode layer is etched to obtain a third electrode 107.

[0090] S7 . Form a passivation layer 108 on the second electrode 105 and the third electrode 107 , and etch the passivation layer 108 to expose the first electrode 103 and the second electrode 105 .

[0091] like Fig.13 shown.

[0092] S8, forming a metal layer 109 on the passivation layer 108, and etching the metal layer 109 to form a first extraction electrode 1091 and a second extraction electrode 1092; at the same time, drilling a hole above the sacrificial layer, and introducing a corrosive gas to form a cavity 102.

[0093] like Fig.14 shown.

[0094] It can be understood that when preparing the thin film bulk acoustic wave resonator provided in the following embodiments, only some steps are adjusted in sequence, so the preparation process of the thin film bulk acoustic wave resonator is not described again.

[0095] Example 2

[0096] refer to Figure 2 As shown, based on Example 1, this embodiment enables the functional structure 10 to include three temperature compensation layer structures 106 with different thicknesses, so that the first piezoelectric layer 104 and the second electrode 105 of the resonator have four thicknesses, so that the resonator can generate four resonance frequencies.

[0097] Example 3

[0098] refer to Figure 3 As shown, based on Example 1, this embodiment buries the temperature compensation layer structure 106 in the first piezoelectric layer 104, thereby reducing the effective electromechanical coupling coefficient of the resonator and meeting the ultra-narrowband application requirements of communication radars and satellites.

[0099] Example 4

[0100] refer to Figure 4 As shown, in this embodiment, based on embodiment 1, a second piezoelectric layer is added to the first piezoelectric layer 104, the c-axis orientation of the second piezoelectric layer is the same as the c-axis orientation of the first piezoelectric layer 104, and the substrate 101 and the seed layer 111 of the resonator match the lattice of the first piezoelectric layer 104 and the second piezoelectric layer, so that the first piezoelectric layer 104 combined with the second piezoelectric layer can adjust the effective electromechanical coupling coefficient of the resonator, thereby meeting the relative bandwidth requirement of the multiplexer passband.

[0101] Example 5

[0102] refer to Figure 5As shown, in this embodiment, the temperature compensating layer structure 106 is arranged on the first piezoelectric layer 104, and the second piezoelectric layer wraps the temperature compensating layer structure 106, wherein the orthographic projection of the second piezoelectric layer structure 110 on the substrate 101 covers the orthographic projection of the temperature compensating layer structure 106 on the substrate 101, and the area of ​​the orthographic projection of the second piezoelectric layer structure 110 on the substrate 101 is smaller than the area of ​​the cavity 102, and the rest of the structures are the same as those in Example 1.

[0103] In this embodiment, the first piezoelectric layer 104 and the second piezoelectric layer structure 110 are used to make the resonator have two different thicknesses, so that the resonator generates two resonance frequencies.

[0104] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thin film bulk acoustic resonator, characterized in that: include: A substrate; a cavity is provided on the top of the substrate; a first electrode located on top of the substrate; a first piezoelectric layer located on top of the first electrode; a second electrode located on top of the first piezoelectric layer; It also includes: at least one functional structure; the functional structure is located from the bottom of the first piezoelectric layer to above the second electrode; the orthographic projection of the functional structure on the substrate falls into the cavity, and the area of ​​the orthographic projection of the functional structure on the substrate is smaller than the area of ​​the cavity.

2. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The functional structure includes a temperature compensation layer structure; the temperature compensation layer structure is located above the first piezoelectric layer or the second electrode.

3. The thin film bulk acoustic wave resonator according to claim 2, characterized in that: The functional structure further includes a third electrode; The third electrode is located above the second electrode, and the orthographic projection of the third electrode on the substrate covers the orthographic projection of the temperature compensation layer structure on the substrate.

4. The thin film bulk acoustic wave resonator according to claim 3, characterized in that: The density of the third electrodes is greater than the density of the second electrodes.

5. The thin film bulk acoustic wave resonator according to claim 2, characterized in that: The functional structure also includes a second piezoelectric layer structure; The second piezoelectric layer structure is located in the first piezoelectric layer or above the first piezoelectric layer, and the orthographic projection of the second piezoelectric layer structure on the substrate covers the orthographic projection of the temperature compensation layer structure on the substrate.

6. The thin film bulk acoustic wave resonator according to claim 5, characterized in that: The c-axis of the second piezoelectric layer and the c-axis of the first piezoelectric layer are oriented in the same direction.

7. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The functional structure includes N sub-functional structures; each of the sub-functional structures has a different thickness; Wherein, N is an integer greater than or equal to 1.

8. The thin film bulk acoustic wave resonator according to claim 7, characterized in that: When the functional structure includes one sub-functional structure, the area of ​​the cavity is S1, the area of ​​the orthographic projection of the functional structure on the substrate is S2, and the value range of S2 is: 1 / 3S1≤S2≤2 / 3S1.

9. A filter, characterized in that: The device comprises an input port, an output port and a plurality of film bulk acoustic wave resonators according to any one of claims 1 to 8.

10. The filter according to claim 9, characterized in that The plurality of thin film bulk acoustic wave resonators include a plurality of series resonators and a plurality of parallel resonators; The thickness of the first piezoelectric layer of the series resonator is smaller than the thickness of the first piezoelectric layer of the parallel resonator.

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