Stacked crystal filter and duplexer

Abstract

The invention relates to the technical field of stacked crystal filters, and particularly provides a stacked crystal filter and a duplexer, and the filter comprises a first substrate, a first bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer and a first top electrode which are sequentially connected from top to bottom; when the middle electrode and the first bottom electrode are grounded together, the middle electrode is connected with the first bottom electrode, and the edge of the projection of the connection position in the overlook direction is located in the edge of the projection of the electrode connected with the grounding end in the overlook direction. The middle electrode is connected with the first top electrode, and the edge of the projection of the joint in the overlook direction is located in the edge of the projection of the electrode connected with the grounding end in the overlook direction; the filter can effectively solve the problems that due to the fact that a stacked crystal filter needs to extend outwards to form three electrodes, too many stray modes are generated, and the performance of the stacked crystal filter is obviously weakened.

Description

Technical Field

[0001] The present application relates to the technical field of stacked crystal filters, and in particular to a stacked crystal filter and a duplexer. Background Art

[0002] The related stacked crystal filter includes a substrate, a bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer and a top electrode connected in sequence from bottom to top, the intermediate electrode is grounded, and when the bottom electrode is connected to the signal input terminal, the top electrode is connected to the signal output terminal, and when the bottom electrode is connected to the signal output terminal, the top electrode is connected to the signal input terminal. Since the connection objects of the bottom electrode, the intermediate electrode and the top electrode are different, the related technology requires that the bottom electrode, the intermediate electrode and the top electrode all extend one electrode to the area outside the acoustic reflector, that is, the related stacked crystal filter needs to extend three electrodes outward, and since the electrodes extending outside the acoustic reflector will inevitably generate spurious modes (clutter) under the action of electrical signals, the related technology has the problem that too many spurious modes are generated due to the need to extend three electrodes outward from the stacked crystal filter, and the performance of the stacked crystal filter is significantly weakened.

[0003] There is no effective technical solution to the above problems. It should be noted that the above information disclosed in this section is only used to understand the background of the present invention, and therefore may contain information that does not constitute prior art. Summary of the invention

[0004] The purpose of the present application is to provide a stacked crystal filter and a duplexer, which can effectively solve the problem that the performance of the stacked crystal filter is significantly weakened due to excessive spurious modes generated by the need to extend three electrodes outward from the stacked crystal filter.

[0005] In a first aspect, the present application provides a stacked crystal filter, comprising: A first substrate, a first bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer and a first top electrode are connected in sequence from top to bottom, a first acoustic reflector is provided on the first substrate, and the intermediate electrode and the first bottom electrode are grounded together, or the intermediate electrode and the first top electrode are grounded together; When the middle electrode and the first bottom electrode are grounded together, the first top electrode is externally connected, the middle electrode or the first bottom electrode is connected to the ground terminal, the middle electrode is connected to the first bottom electrode, and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal in the top-view direction. When the middle electrode and the first top electrode are grounded together, the first bottom electrode is externally connected, the middle electrode or the first top electrode is connected to the ground terminal, the middle electrode is connected to the first top electrode, and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal in the top-view direction.

[0006] The present application provides a stacked crystal filter, which can effectively reduce the size of the electrode extending outward when the first bottom electrode, the middle electrode and the first top electrode are externally connected by connecting the middle electrode to the first bottom electrode or the first top electrode, that is, the present application can realize the external connection of the first bottom electrode, the middle electrode and the first top electrode without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrode extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected, and the size of the electrode extending outward is positively correlated with the amount of stray modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of stray modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to the excessive stray modes generated due to the need to extend three electrodes outward, that is, the present application can effectively improve the performance of the stacked crystal filter.

[0007] Optionally, when the middle electrode and the first bottom electrode are grounded together, the first bottom electrode is connected to the ground terminal, and the edge of the projection of the connection between the middle electrode and the first bottom electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction.

[0008] Because when the middle electrode and the first bottom electrode are grounded together, one side of the first bottom electrode is connected to the ground end, that is, one side of the first bottom electrode extends outside the first acoustic reflector, and the edge of the projection of the connection between the middle electrode and the first bottom electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction, that is, when the middle electrode and the first bottom electrode are grounded together, the first bottom electrode extends outward by one electrode, and the middle electrode does not extend outward. Therefore, this technical solution is equivalent to reducing the number of electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected from three to two, so as to minimize the size of the electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected, thereby minimizing the generation of spurious modes and optimizing the performance of the stacked crystal filter.

[0009] Optionally, when the middle electrode and the first top electrode are grounded together, the middle electrode is connected to the ground terminal, and the edge of the projection of the connection between the first top electrode and the middle electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction.

[0010] Because when the middle electrode and the first top electrode are grounded together, one side of the middle electrode is connected to the ground end, that is, one side of the middle electrode extends outside the first acoustic reflector, and the edge of the projection of the connection between the first top electrode and the middle electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction, that is, when the middle electrode and the first top electrode are grounded together, the middle electrode extends outward by one electrode, and the first top electrode does not extend outward. Therefore, this technical solution is equivalent to reducing the number of electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected from three to two, so as to minimize the size of the electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected, thereby minimizing the generation of spurious modes and optimizing the performance of the stacked crystal filter.

[0011] Optionally, when the middle electrode and the first bottom electrode are grounded together, the first top electrode is connected to an electrode other than the first top electrode in another stacked crystal filter or an external device through a conductive structure penetrating the first piezoelectric layer and the second piezoelectric layer.

[0012] Optionally, a ratio of a thickness of the first piezoelectric layer to a thickness of the middle electrode is 1.2:1-2.5:1, and a ratio of a thickness of the second piezoelectric layer to a thickness of the middle electrode is 1.2:1-2.5:1.

[0013] This technical solution can suppress the generation of spurious modes and optimize the energy conversion efficiency and frequency response characteristics of the stacked crystal filter by setting the ratio of the thickness of the first piezoelectric layer to the thickness of the middle electrode and the ratio of the thickness of the second piezoelectric layer to the thickness of the middle electrode to 1.2:1-2.5:1. Therefore, this technical solution can effectively improve the performance indicators of the stacked crystal filter.

[0014] Optionally, the first acoustic reflection mirror is an air cavity or a plurality of Bragg reflection layers.

[0015] In a second aspect, the present application also provides a duplexer, which includes a transmitting filter, a receiving filter and the stacked crystal filter provided in the first aspect above, wherein the stacked crystal filter is arranged between the transmitting filter and the receiving filter and is connected in parallel with the transmitting filter and the receiving filter.

[0016] A duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the first bottom electrode, the middle electrode and the first top electrode are externally connected by connecting the middle electrode to the first bottom electrode or the first top electrode, that is, the present application can realize the external connection of the first bottom electrode, the middle electrode and the first top electrode without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected, and the size of the electrodes extending outward is positively correlated with the amount of stray modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of stray modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to the excessive stray modes generated due to the need to extend three electrodes outward. That is, the present application can effectively improve the performance of the stacked crystal filter.

[0017] Optionally, the first top electrode and the middle electrode of the stacked crystal filter are grounded together, and the first bottom electrode is connected to the antenna terminal.

[0018] Optionally, the transmitting filter includes two first series filters and several first parallel filters, the first series filter and the first parallel filter each include a second substrate, a second bottom electrode, a third piezoelectric layer and a second top electrode connected in sequence from bottom to top, a second acoustic reflector is provided on the second substrate, the second top electrodes of the two first series filters are interconnected, the second bottom electrode of one of the first series filters is connected to the antenna end, the second top electrode of the first parallel filter is connected to the second top electrode of any first series filter, the second bottom electrode of the first parallel filter is connected to the ground, and when the number of first parallel filters is multiple, the multiple first parallel filters are connected in parallel.

[0019] Since the second top electrodes of the two first series filters of the technical solution are interconnected, the second top electrode of the first parallel filter of the technical solution is connected to the second top electrode of the first series filter, and the height of the second top electrode of the first series filter is consistent with the height of the second top electrode of the first parallel filter, the second top electrodes of the transmitting filter of the technical solution can be interconnected by extending outward without using a conductive structure that passes through the third piezoelectric layer for interconnection, that is, the technical solution is equivalent to minimizing the number of conductive structures required when the second top electrode is externally connected, and since the conductive structure needs to occupy an arrangement area and is made using an additional preparation process, the technical solution can minimize the size of the transmitting filter and reduce the production cost of the transmitting filter, thereby effectively reducing the size and production cost of the duplexer.

[0020] Optionally, the receiving filter includes two second series filters and several second parallel filters, the second series filters and the second parallel filters each include a third substrate, a third bottom electrode, a fourth piezoelectric layer and a third top electrode connected in sequence from bottom to top, a third acoustic reflector is provided on the third substrate, the third top electrodes of the two second series filters are interconnected, the third bottom electrode of one of the second series filters is connected to the antenna end, the third top electrode of the second parallel filter is connected to the third top electrode of any second series filter, and the third bottom electrode of the second parallel filter is grounded. When the number of second parallel filters is multiple, multiple second parallel filters are connected in parallel.

[0021] Since the third top electrodes of the two second series filters of the technical solution are interconnected, the third top electrode of the second parallel filter of the technical solution is connected to the third top electrode of the second series filter, and the height of the third top electrode of the second series filter is consistent with the height of the third top electrode of the second parallel filter, the third top electrode of the receiving filter of the technical solution can be interconnected by extending outward without the need to use a conductive structure that passes through the fourth piezoelectric layer for interconnection, that is, the technical solution is equivalent to minimizing the number of conductive structures required when the third top electrode is externally connected, and since the conductive structure needs to occupy an arrangement area and is made using an additional preparation process, the technical solution can minimize the size of the receiving filter and reduce the production cost of the receiving filter, thereby effectively reducing the size and production cost of the duplexer.

[0022] From the above, it can be seen that the stacked crystal filter and duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the first bottom electrode, the middle electrode and the first top electrode are externally connected by connecting the middle electrode to the first bottom electrode or the first top electrode, that is, the present application can realize the external connection of the first bottom electrode, the middle electrode and the first top electrode without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the middle electrode and the top electrode are externally connected, and the size of the electrodes extending outward is positively correlated with the amount of spurious modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of spurious modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to the excessive spurious modes generated due to the need to extend three electrodes outward in the stacked crystal filter, that is, the present application can effectively improve the performance of the stacked crystal filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic cross-sectional structural diagram of a stacked crystal filter when the middle electrode and the first bottom electrode provided in an embodiment of the present application are grounded together.

[0024] Figure 2This is a schematic cross-sectional structural diagram of a stacked crystal filter when the middle electrode and the first top electrode provided in an embodiment of the present application are grounded together.

[0025] Figure 3 This is a schematic cross-sectional structural diagram of an embodiment of the present application in which the intermediate electrode and the first bottom electrode are grounded together and the first top electrode is externally connected through a conductive structure.

[0026] Figure 4 A schematic diagram of the electrical symbols of the stacked crystal filter provided in an embodiment of the present application.

[0027] Figure 5 A schematic diagram of the relationship between output and frequency of a stacked crystal filter provided in an embodiment of the present application.

[0028] Figure 6 A schematic diagram of the structure of a duplexer provided in an embodiment of the present application.

[0029] Figure numerals: 1. first substrate; 2. first bottom electrode; 3. first piezoelectric layer; 4. middle electrode; 5. second piezoelectric layer; 6. first top electrode; 7. first acoustic reflector; 8. conductive structure; 9. transmitting filter; 91. first series filter; 92. first parallel filter; 10. receiving filter; 101. second series filter; 102. second parallel filter; 11. stacked crystal filter; BE2. second bottom electrode; TE2. second top electrode; BE3. third bottom electrode; TE3. third top electrode; ANT. antenna terminal; GND. ground terminal. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0031] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0032] First, as Figure 1-Figure 5 As shown, the present application provides a stacked crystal filter, which includes: A first substrate 1, a first bottom electrode 2, a first piezoelectric layer 3, an intermediate electrode 4, a second piezoelectric layer 5 and a first top electrode 6 are connected in sequence from top to bottom. A first acoustic reflector 7 is provided on the first substrate 1. The intermediate electrode 4 and the first bottom electrode 2 are grounded together, or the intermediate electrode 4 and the first top electrode 6 are grounded together. When the middle electrode 4 and the first bottom electrode 2 are grounded together, the first top electrode 6 is externally connected, the middle electrode 4 or the first bottom electrode 2 is connected to the ground terminal GND, the middle electrode 4 is connected to the first bottom electrode 2 and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top-view direction; when the middle electrode 4 and the first top electrode 6 are grounded together, the first bottom electrode 2 is externally connected, the middle electrode 4 or the first top electrode 6 is connected to the ground terminal GND, the middle electrode 4 is connected to the first top electrode 6 and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top-view direction.

[0033] The stacked crystal filter 11 of this embodiment belongs to a bulk acoustic wave filter. The material of the first substrate 1 of this embodiment is preferably silicon material. The material of the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 of this embodiment is preferably a metal material with high conductivity, large acoustic impedance and large Young's modulus (for example, any one or more of gold, molybdenum, ruthenium and platinum). The material of the first bottom electrode 2, the material of the middle electrode 4 and the material of the first top electrode 6 of this embodiment are preferably the same. The material of the first piezoelectric layer 3 and the second piezoelectric layer 5 of this embodiment is preferably aluminum nitride. Specifically, when the first top electrode 6 or the first bottom electrode 2 is externally connected to a signal source (equivalent to applying a voltage signal or an electric signal to the first top electrode 6 or the first bottom electrode 2), both ends of the first piezoelectric layer 3 and the second piezoelectric layer 5 form an electric field to excite bulk acoustic waves (equivalent to exciting the first piezoelectric layer 3 and the second piezoelectric layer 5 to generate longitudinal waves), thereby realizing the mutual conversion of electrical energy and mechanical energy and the frequency selection of the stacked crystal filter 11. A first acoustic reflector 7 is provided on the first substrate 1 of this embodiment, and the first acoustic reflector 7 is preferably located on the top surface of the first substrate 1. The intermediate electrode 4 of this embodiment can be grounded together with the first bottom electrode 2 or the first top electrode 6. Specifically, when the intermediate electrode 4 and the first bottom electrode 2 are grounded together, the first top electrode 6 is connected to an external circuit, the intermediate electrode 4 or the first bottom electrode 2 is connected to the ground terminal GND, the intermediate electrode 4 is connected to the first bottom electrode 2 and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top-view direction. When the intermediate electrode 4 and the first top electrode 6 are grounded together, the first bottom electrode 2 is connected to an external circuit, the intermediate electrode 4 or the first top electrode 6 is connected to the ground terminal GND, the intermediate electrode 4 is connected to the first top electrode 6 and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top-view direction.It should be understood that, since the middle electrode 4 of this embodiment is connected to the first bottom electrode 2 or the first top electrode 6, and when the first top electrode 6 and the middle electrode 4 are grounded together, this embodiment can choose to extend the middle electrode 4 or the first top electrode 6 outward by one electrode, and the middle electrode 4 is connected to the first top electrode 6 and the edge of the projection of the connection in the top view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top view direction, that is, when the first top electrode 6 and the middle electrode 4 are grounded together, this embodiment does not need to extend two electrodes outward to achieve the external connection of the first top electrode 6 and the middle electrode 4, and when the first bottom electrode 2 and the middle electrode 4 are grounded together, the first bottom electrode 6 is connected to the first top electrode 6. The first bottom electrode 2 or the middle electrode 4 extends an electrode outward, and the middle electrode 4 is connected to the first bottom electrode 2, and the edge of the projection of the connection in the top view direction is located within the edge of the projection of the electrode connected to the ground terminal GND in the top view direction, that is, when the first bottom electrode 2 and the middle electrode 4 are grounded together, this embodiment can realize the external connection of the first bottom electrode 2 and the middle electrode 4 without extending two electrodes outward, so the present application can effectively reduce the size of the electrode extended outward when the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 are externally connected, that is, the present application can realize the external connection of the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 without extending three electrodes outward. It should also be understood that this embodiment can adjust the performance indicators such as the center frequency, bandwidth and passband ripple of the stacked crystal filter 11 by adjusting the size and material parameters of each layer structure, and the present application can make the stacked crystal filter 11 have two transmission zeros (reference) by connecting the middle electrode 4 to the first bottom electrode 2 or the first top electrode 6. Figure 4 F2 and F4 in the figure are equivalent to the parallel resonant frequency point. At a certain frequency, the output corresponding to the transmission zero is 0) and the two transmission poles (refer to Figure 4 F1 and F3 in the figure are equivalent to the series resonant frequency point), so the stacked crystal filter 11 of the present application can be connected as a parallel filter in the parallel circuit of the ladder structure filter.

[0034] The present application provides a stacked crystal filter, which can effectively reduce the size of the electrode extending outward when the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 are externally connected by connecting the middle electrode 4 to the first bottom electrode 2 or the first top electrode 6, that is, the present application can realize the external connection of the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrode extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, and the size of the electrode extending outward is positively correlated with the amount of stray modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of stray modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter 11 is significantly weakened due to the excessive stray modes generated due to the need to extend three electrodes outward, that is, the present application can effectively improve the performance of the stacked crystal filter 11. It should be understood that since the purpose of this embodiment is to reduce the size of the electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, this embodiment can achieve this purpose only by making the edge of the projection of the connection point of the two electrodes grounded together in the top view direction located within the edge of the projection of the electrode connected to the ground terminal GND in the top view direction, that is, even if the electrode that is not connected to the ground terminal GND of the two electrodes grounded together extends part of the electrode outward (the electrode extension amount is less than that of one electrode), this purpose can be achieved. Therefore, when the middle electrode 4 is grounded together with the first bottom electrode 2 and the middle electrode 4 is connected to the ground terminal GND, the first bottom electrode 2 can extend part of the electrode outward, and when the middle electrode 4 is grounded together with the first bottom electrode 2 and the first bottom electrode 2 is connected to the ground terminal GND, the middle electrode 4 can extend part of the electrode outward (refer to Figure 3 ), when the middle electrode 4 and the first top electrode 6 are grounded together and the middle electrode 4 is connected to the ground terminal GND, the first top electrode 6 can extend part of the electrode outward. When the middle electrode 4 and the first top electrode 6 are grounded together and the first top electrode 6 is connected to the ground terminal GND, the middle electrode 4 can extend part of the electrode outward.

[0035] In some preferred embodiments, when the intermediate electrode 4 and the first bottom electrode 2 are grounded together, the first bottom electrode 2 is connected to the ground terminal GND, and the edge of the projection of the connection between the intermediate electrode 4 and the first bottom electrode 2 in the top-view direction does not exceed the edge of the projection of the first acoustic reflector 7 in the top-view direction. Preferably, when the intermediate electrode 4 and the first bottom electrode 2 are grounded together, the edge of the projection of the connection between the intermediate electrode 4 and the first bottom electrode 2 in the top-view direction of this embodiment coincides with the edge of the projection of the first acoustic reflector 7 in the top-view direction, so as to ensure the performance of the intermediate electrode 4. Since when the middle electrode 4 and the first bottom electrode 2 are grounded together, one side of the first bottom electrode 2 is connected to the ground terminal GND, that is, one side of the first bottom electrode 2 extends to the outside of the first acoustic reflector 7, the edge of the projection of the connection between the middle electrode 4 and the first bottom electrode 2 in the top-view direction does not exceed the edge of the projection of the first acoustic reflector 7 in the top-view direction, that is, when the middle electrode 4 and the first bottom electrode 2 are grounded together, the first bottom electrode 2 extends one electrode outward, and the middle electrode 4 does not extend outward. Therefore, this embodiment is equivalent to reducing the number of electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected from three to two, so as to minimize the size of the electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, thereby minimizing the generation of spurious modes and optimizing the performance of the stacked crystal filter 11.

[0036] In some preferred embodiments, when the middle electrode 4 and the first top electrode 6 are grounded together, the middle electrode 4 is connected to the ground terminal GND, and the edge of the projection of the connection between the first top electrode 6 and the middle electrode 4 in the top-view direction does not exceed the edge of the projection of the first acoustic reflector 7 in the top-view direction. Since when the middle electrode 4 and the first top electrode 6 are grounded together, one side of the middle electrode 4 is connected to the ground terminal GND, that is, one side of the middle electrode 4 extends outside the first acoustic reflector 7, and the edge of the projection of the connection between the first top electrode 6 and the middle electrode 4 in the top-view direction does not exceed the edge of the projection of the first acoustic reflector 7 in the top-view direction, that is, when the middle electrode 4 and the first top electrode 6 are grounded together, the middle electrode 4 extends outward by one electrode, and the first top electrode 6 does not extend outward, so this embodiment is equivalent to reducing the number of electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected from three to two, so as to minimize the size of the electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, thereby minimizing the amount of spurious modes generated and optimizing the performance of the stacked crystal filter 11. It should be understood that the middle electrode 4 of this embodiment can be connected to the ground terminal GND only through the conductive structure 8 penetrating the first piezoelectric layer 3 .

[0037] In some preferred embodiments, Figure 3As shown, when the middle electrode 4 and the first bottom electrode 2 are grounded together, the first top electrode 6 is connected to an electrode or an external device other than the first top electrode 6 in another stacked crystal filter 11 through a conductive structure 8 penetrating the first piezoelectric layer 3 and the second piezoelectric layer 5. When the first top electrode 6 is connected to the first top electrode 6 of another stacked crystal filter 11, since the heights of the two are the same, this embodiment only needs to extend the first top electrode 6 outward by one electrode to achieve the connection between the first top electrode 6 of the current stacked crystal filter and the first top electrode 6 of another stacked crystal filter 11. Since the height of the first top electrode 6 is different from the height of the electrode other than the first top electrode 6 in another stacked crystal filter 11 (the first bottom electrode 2 or the middle electrode 4 in another stacked crystal filter 11) or the external device, this embodiment needs to pass through the conductive structure 8 of the first piezoelectric layer 3 and the second piezoelectric layer 5 to achieve the connection between the first top electrode 6 and the electrode other than the first top electrode 6 in another stacked crystal filter 11 or the external device. It should be understood that the external device can be a device with a different height from the first top electrode 6, such as the ground terminal GND or the antenna terminal ANT.

[0038] In some preferred embodiments, the ratio of the thickness of the first piezoelectric layer 3 to the thickness of the intermediate electrode 4 is 1.2:1-2.5:1, and the ratio of the thickness of the second piezoelectric layer 5 to the thickness of the intermediate electrode 4 is 1.2:1-2.5:1. This embodiment can suppress the generation of spurious modes and optimize the energy conversion efficiency and frequency response characteristics of the stacked crystal filter 11 by setting the ratio of the thickness of the first piezoelectric layer 3 to the thickness of the intermediate electrode 4 and the ratio of the thickness of the second piezoelectric layer 5 to the thickness of the intermediate electrode 4 to 1.2:1-2.5:1, so this embodiment can effectively improve the performance indicators of the stacked crystal filter 11.

[0039] In some preferred embodiments, the first acoustic reflector 7 is an air cavity or several layers of Bragg reflective layers. The first acoustic reflector 7 of this embodiment can be an air cavity or several layers of Bragg reflective layers, each of which is composed of a low acoustic impedance layer and a high acoustic impedance layer. This embodiment can be formed by first etching the first substrate 1 to form a groove on the first substrate 1, then depositing a sacrificial layer in the groove, and sequentially forming a first bottom electrode 2, a first piezoelectric layer 3, an intermediate electrode 4, a second piezoelectric layer 5 and a first top electrode 6 on the first substrate 1, and finally forming an air cavity on the first substrate 1 by removing the sacrificial layer based on a wet etching process, so as to form the first acoustic reflector 7 on the first substrate 1. This embodiment can also form an acoustic reflector on the first substrate 1 by first etching the first substrate 1 to form a groove on the first substrate 1, and then forming several layers of Bragg reflective layers in the groove based on the existing Bragg reflective layer formation process.

[0040] From the above, it can be seen that a stacked crystal filter provided by the present application can effectively reduce the size of the electrode extending outward when the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 are externally connected by connecting the middle electrode 4 to the first bottom electrode 2 or the first top electrode 6, that is, the present application can realize the external connection of the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrode extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, and the size of the electrode extending outward is positively correlated with the amount of stray modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of stray modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter 11 is significantly weakened due to the excessive stray modes generated due to the need to extend three electrodes outward, that is, the present application can effectively improve the performance of the stacked crystal filter 11.

[0041] Second, as Figure 6 As shown, the present application also provides a duplexer, which includes a transmitting filter 9, a receiving filter 10 and the stacked crystal filter 11 provided in the first aspect above, and the stacked crystal filter 11 is arranged between the transmitting filter 9 and the receiving filter 10 and is connected in parallel with the transmitting filter 9 and the receiving filter 10.

[0042] A duplexer provided in the present application includes a transmitting filter 9, a receiving filter 10 and a stacked crystal filter 11 provided in the first aspect above. The working principle of a duplexer provided in an embodiment of the present application is the same as the principle of a stacked crystal filter 11 provided in the first aspect above, and will not be discussed in detail here. Since the present application can adjust the performance index of the stacked crystal filter 11 by adjusting the size of each layer structure of the stacked crystal filter 11, this embodiment can adjust the thickness of any one or more of the first bottom electrode 2, the first piezoelectric layer 3, the middle electrode 4, the second piezoelectric layer 5 and the first top electrode 6 so that the difference between one of the transmission poles of the stacked crystal filter 11 and the transmission pole of the transmitting filter 9 is less than a preset difference, the difference between one of the transmission zero points of the stacked crystal filter 11 and the transmission zero point of the transmitting filter 9 is less than a preset difference, and the difference between another transmission pole of the stacked crystal filter 11 and the transmission pole of the receiving filter 10 is less than The preset difference and the difference between the other transmission zero point of the stacked crystal filter 11 and the transmission zero point of the receiving filter 10 are made smaller than the preset difference. Therefore, this embodiment can replace a parallel filter in the transmitting filter 9 and a parallel filter in the receiving filter 10 by setting a stacked crystal filter 11 in parallel with the transmitting filter 9 and the receiving filter 10 between the transmitting filter 9 and the receiving filter 10. That is, this embodiment is equivalent to replacing two parallel filters with the stacked crystal filter 11, thereby achieving the goal of enhancing the out-of-band suppression capability of the duplexer while reducing the number of parallel filters used in the duplexer, so as to reduce the size and production cost of the duplexer.

[0043] In some preferred embodiments, the first top electrode 6 and the middle electrode 4 of the stacked crystal filter 11 are grounded together, and the first bottom electrode 2 is connected to the antenna terminal ANT. The middle electrode 4 of this embodiment needs to be connected to the ground terminal GND through the conductive structure 8 that penetrates the first piezoelectric layer 3.

[0044] In some preferred embodiments, the transmitting filter 9 includes two first series filters 91 and several first parallel filters 92. The first series filter 91 and the first parallel filter 92 both include a second substrate (not shown in the figure), a second bottom electrode BE2, a third piezoelectric layer (not shown in the figure) and a second top electrode TE2 connected in sequence from bottom to top. A second acoustic reflector (not shown in the figure) is provided on the second substrate. The second top electrodes TE2 of the two first series filters 91 are interconnected, the second bottom electrode BE2 of one of the first series filters 91 is connected to the antenna terminal ANT, the second top electrode TE2 of the first parallel filter 92 is connected to the second top electrode TE2 of any first series filter 91, and the second bottom electrode BE2 of the first parallel filter 92 is grounded. When the number of first parallel filters 92 is multiple, multiple first parallel filters 92 are connected in parallel. Since the second top electrodes TE2 of the two first series filters 91 of this embodiment are interconnected, the second top electrode TE2 of the first parallel filter 92 of this embodiment is connected to the second top electrode TE2 of the first series filter 91, and the height of the second top electrode TE2 of the first series filter 91 is consistent with the height of the second top electrode TE2 of the first parallel filter 92, the second top electrode TE2 of the transmitting filter 9 of this embodiment can be interconnected by extending outward without using the conductive structure 8 that passes through the third piezoelectric layer for interconnection, that is, this embodiment is equivalent to minimizing the number of conductive structures 8 required when the second top electrode TE2 is externally connected, and since the conductive structure 8 needs to occupy an arrangement area and is made using an additional preparation process, this embodiment can minimize the size of the transmitting filter 9 and reduce the production cost of the transmitting filter 9, thereby effectively reducing the size and production cost of the duplexer.

[0045] In some preferred embodiments, the receiving filter 10 includes two second series filters 101 and several second parallel filters 102, the second series filters 101 and the second parallel filters 102 each include a third substrate (not shown in the figure), a third bottom electrode BE3, a fourth piezoelectric layer (not shown in the figure) and a third top electrode TE3 connected in sequence from bottom to top, a third acoustic reflector (not shown in the figure) is provided on the third substrate, the third top electrodes TE3 of the two second series filters 101 are interconnected, the third bottom electrode BE3 of one of the second series filters 101 is connected to the antenna terminal ANT, the third top electrode TE3 of the second parallel filter 102 is connected to the third top electrode TE3 of any second series filter 101, the third bottom electrode BE3 of the second parallel filter 102 is grounded, and when the number of second parallel filters 102 is multiple, the multiple second parallel filters 102 are connected in parallel. Since the third top electrodes TE3 of the two second series filters 101 of this embodiment are interconnected, the third top electrode TE3 of the second parallel filter 102 of this embodiment is connected to the third top electrode TE3 of the second series filter 101, and the height of the third top electrode TE3 of the second series filter 101 is consistent with the height of the third top electrode TE3 of the second parallel filter 102, the third top electrode TE3 of the receiving filter 10 of this embodiment can be interconnected by extending outward without using the conductive structure 8 that passes through the fourth piezoelectric layer for interconnection, that is, this embodiment is equivalent to minimizing the number of conductive structures 8 required when the third top electrode TE3 is externally connected, and since the conductive structure 8 needs to occupy an arrangement area and is made using an additional preparation process, this embodiment can minimize the size of the receiving filter 10 and reduce the production cost of the receiving filter 10, thereby effectively reducing the size and production cost of the duplexer.

[0046] Preferably, if Figure 6As shown, the first top electrode 6 and the middle electrode 4 of the stacked crystal filter 11 are grounded together, the first bottom electrode 2 is connected to the antenna terminal ANT, the second top electrodes TE2 of the two first series filters 91 are interconnected, the second bottom electrode BE2 of one of the first series filters 91 is connected to the antenna terminal ANT, the second top electrode TE2 of the first parallel filter 92 is connected to the second top electrode TE2 of the first series filter 91, the second bottom electrode BE2 of the first parallel filter 92 is grounded, and the third top electrodes TE3 of the two second series filters 101 are interconnected, the third bottom electrode BE3 of one of the second series filters 101 is connected to the antenna terminal ANT, the third top electrode TE3 of the second parallel filter 102 is connected to the third top electrode TE3 of the second series filter 101, and the third bottom electrode BE3 of the second parallel filter 102 is grounded. Since this embodiment only needs to use one conductive structure 8 to realize the external connection of the duplexer, that is, this embodiment is equivalent to minimizing the number of conductive structures 8 required when the duplexer is externally connected, so this embodiment can minimize the size of the duplexer and minimize the production cost of the duplexer.

[0047] From the above, it can be seen that the stacked crystal filter and duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 are externally connected by connecting the middle electrode 4 to the first bottom electrode 2 or the first top electrode 6, that is, the present application can realize the external connection of the first bottom electrode 2, the middle electrode 4 and the first top electrode 6 without extending the three electrodes outward. Compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the middle electrode 4 and the top electrode are externally connected, and the size of the electrodes extending outward is positively correlated with the amount of stray modes generated. Therefore, compared with the prior art, the present application can effectively reduce the amount of stray modes generated, thereby effectively solving the problem that the performance of the stacked crystal filter 11 is significantly weakened due to the excessive stray modes generated due to the need to extend three electrodes outward of the stacked crystal filter 11, that is, the present application can effectively improve the performance of the stacked crystal filter 11.

[0048] In the embodiments provided in the present application, it should be understood that, herein, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0049] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A stacked crystal filter, characterized in that: The stacked crystal filter comprises: A first substrate, a first bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer and a first top electrode are connected in sequence from top to bottom, wherein a first acoustic reflector is provided on the first substrate, and the intermediate electrode and the first bottom electrode are grounded together, or the intermediate electrode and the first top electrode are grounded together; When the middle electrode and the first bottom electrode are grounded together, the first top electrode is externally connected, the middle electrode or the first bottom electrode is connected to the ground terminal, the middle electrode is connected to the first bottom electrode, and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal in the top-view direction. When the middle electrode and the first top electrode are grounded together, the first bottom electrode is externally connected, the middle electrode or the first top electrode is connected to the ground terminal, the middle electrode is connected to the first top electrode, and the edge of the projection of the connection in the top-view direction is located within the edge of the projection of the electrode connected to the ground terminal in the top-view direction.

2. The stacked crystal filter according to claim 1, characterized in that: When the middle electrode and the first bottom electrode are grounded together, one side of the first bottom electrode is connected to the grounding end, and the edge of the projection of the connection between the middle electrode and the first bottom electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction.

3. The stacked crystal filter according to claim 1, characterized in that: When the middle electrode and the first top electrode are grounded together, one side of the middle electrode is connected to the ground end, and the edge of the projection of the connection between the first top electrode and the middle electrode in the top-view direction does not exceed the edge of the projection of the first acoustic reflector in the top-view direction.

4. The stacked crystal filter according to claim 1, characterized in that: When the middle electrode and the first bottom electrode are grounded together, the first top electrode is connected to an electrode or an external device other than the first top electrode in another stacked crystal filter through a conductive structure penetrating the first piezoelectric layer and the second piezoelectric layer.

5. The stacked crystal filter according to claim 1, characterized in that: The ratio of the thickness of the first piezoelectric layer to the thickness of the middle electrode is 1.2:1-2.5:1, and the ratio of the thickness of the second piezoelectric layer to the thickness of the middle electrode is 1.2:1-2.5:

1.

6. The stacked crystal filter according to claim 1, characterized in that: The first acoustic reflection mirror is an air cavity or a plurality of Bragg reflection layers.

7. A duplexer, characterized in that: The duplexer includes a transmit filter, a receive filter, and a stacked crystal filter as claimed in any one of claims 1 to 6, wherein the stacked crystal filter is arranged between the transmit filter and the receive filter and is connected in parallel with the transmit filter and the receive filter.

8. The duplexer according to claim 7, characterized in that: The first top electrode and the middle electrode of the stacked crystal filter are grounded together, and the first bottom electrode is connected to the antenna terminal.

9. The duplexer according to claim 7, characterized in that: The transmitting filter includes two first series filters and several first parallel filters, the first series filters and the first parallel filters each include a second substrate, a second bottom electrode, a third piezoelectric layer and a second top electrode connected in sequence from bottom to top, a second acoustic reflector is provided on the second substrate, the second top electrodes of the two first series filters are interconnected, the second bottom electrode of one of the first series filters is connected to the antenna end, the second top electrode of the first parallel filter is connected to the second top electrode of any of the first series filters, the second bottom electrode of the first parallel filter is grounded, and when the number of the first parallel filters is multiple, multiple first parallel filters are connected in parallel.

10. The duplexer according to claim 7, characterized in that: The receiving filter includes two second series filters and several second parallel filters, the second series filters and the second parallel filters each include a third substrate, a third bottom electrode, a fourth piezoelectric layer and a third top electrode connected in sequence from bottom to top, a third acoustic reflector is provided on the third substrate, the third top electrodes of two second series filters are interconnected, the third bottom electrode of one of the second series filters is connected to the antenna end, the third top electrode of the second parallel filter is connected to the third top electrode of any of the second series filters, the third bottom electrode of the second parallel filter is grounded, and when the number of the second parallel filters is multiple, multiple second parallel filters are connected in parallel.

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