A stacked crystal filter and a duplexer

Abstract

This application relates to the technical field of stacked crystal filters, and specifically provides a stacked crystal filter and a duplexer. The filter includes: 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 connected in sequence from top to bottom; when the intermediate electrode and the first bottom electrode are commonly grounded, the intermediate electrode is connected to the first bottom electrode, and the edge of the projection of the connection point 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 intermediate electrode and the first top electrode are commonly grounded, the intermediate electrode is connected to the first top electrode, and the edge of the projection of the connection point 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; this filter can effectively solve the problem that due to the need for three electrodes to extend outward in the stacked crystal filter, there are too many spurious modes generated, and the performance of the stacked crystal filter is significantly weakened.

Description

Technical Field

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

[0002] Related stacked crystal filters include a substrate, a bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer, and a top electrode that are sequentially connected from bottom to top. The intermediate electrode is grounded. When the bottom electrode is connected to the signal input terminal, the top electrode is connected to the signal output terminal. 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 art needs to extend an electrode of the bottom electrode, the intermediate electrode, and the top electrode to an area outside the acoustic mirror, that is, the related stacked crystal filter needs to extend three electrodes outward. And since the electrodes extending outside the acoustic mirror will inevitably generate spurious modes (clutter) under the action of an electrical signal, there is a problem in the related art that too many spurious modes are generated due to the need for the stacked crystal filter to extend three electrodes outward, and the performance of the stacked crystal filter is significantly weakened.

[0003] In view of the above problems, there is currently no effective technical solution. It should be noted that the above information disclosed in this part is only used to understand the background of the inventive concept of the present invention, and therefore may include information that does not constitute the prior art. Summary of the Invention

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

[0005] In a first aspect, this application provides a stacked crystal filter, which includes:

[0006] A first substrate, a first bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer, and a first top electrode that are sequentially connected from top to bottom. A first acoustic mirror is provided on the first substrate. The intermediate electrode and the first bottom electrode are commonly grounded, or the intermediate electrode and the first top electrode are commonly grounded;

[0007] When the intermediate electrode and the first bottom electrode are commonly grounded, the first top electrode is externally connected, the intermediate electrode or the first bottom electrode is connected to the ground terminal, the intermediate 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 intermediate electrode and the first top electrode are commonly grounded, the first bottom electrode is externally connected, the intermediate electrode or the first top electrode is connected to the ground terminal, the intermediate 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.

[0008] A stacked crystal filter provided by the present application can effectively reduce the size of the electrodes extending outward when the first bottom electrode, the intermediate electrode, and the first top electrode are externally connected by connecting the intermediate electrode to the first bottom electrode or the first top electrode. That is, the present application can achieve the external connection of the first bottom electrode, the intermediate electrode, and the first top electrode without extending the three electrodes outward. Since, compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the intermediate electrode, and the top electrode are externally connected, and the size of the electrodes extending outward is positively correlated with the generation amount of spurious modes, therefore, compared with the prior art, the present application can effectively reduce the generation amount of spurious modes, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to excessive spurious modes generated when the stacked crystal filter needs to extend three electrodes outward. That is, the present application can effectively improve the performance of the stacked crystal filter.

[0009] Optionally, when the intermediate electrode and the first bottom electrode are commonly grounded, the first bottom electrode is connected to the ground terminal, and the edge of the projection of the connection between the intermediate electrode and the first bottom electrode in the top view direction does not exceed the edge of the projection of the first acoustic mirror in the top view direction.

[0010] Since when the intermediate electrode and the first bottom electrode are commonly grounded, one side of the first bottom electrode is connected to the ground terminal, that is, one side of the first bottom electrode extends outside the first acoustic mirror, and the edge of the projection of the connection between the intermediate electrode and the first bottom electrode in the top view direction does not exceed the edge of the projection of the first acoustic mirror in the top view direction. That is, when the intermediate electrode and the first bottom electrode are commonly grounded, the first bottom electrode extends one electrode outward and the intermediate electrode does not extend outward. Therefore, this technical solution is equivalent to reducing the number of electrodes extending outward when the bottom electrode, the intermediate 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 intermediate electrode, and the top electrode are externally connected, thereby minimizing the generation amount of spurious modes and optimizing the performance of the stacked crystal filter.

[0011] Optionally, when the intermediate electrode and the first top electrode are grounded together, the intermediate electrode is connected to the ground terminal, and the edge of the projection of the connection between the first top electrode and the intermediate electrode in the top view direction does not extend beyond the edge of the projection of the first acoustic mirror in the top view direction.

[0012] Since when the intermediate electrode and the first top electrode are grounded together, one side of the intermediate electrode is connected to the ground terminal, that is, one side of the intermediate electrode extends outside the first acoustic mirror, and the edge of the projection of the connection between the first top electrode and the intermediate electrode in the top view direction does not extend beyond the edge of the projection of the first acoustic mirror in the top view direction. That is, when the intermediate electrode and the first top electrode are grounded together, the intermediate electrode extends out an electrode, and the first top electrode does not extend outwards. Therefore, this technical solution is equivalent to reducing the number of electrodes extending outwards when the bottom electrode, the intermediate electrode, and the top electrode are externally connected from three to two, so that the size of the electrodes extending outwards when the bottom electrode, the intermediate electrode, and the top electrode are externally connected reaches the minimum, thereby minimizing the generation of spurious modes and optimizing the performance of the stacked crystal filter.

[0013] Optionally, when the intermediate electrode and the first bottom electrode are grounded together, the first top electrode is connected to an electrode other than the first top electrode or an external device in another stacked crystal filter through a conductive structure penetrating the first piezoelectric layer and the second piezoelectric layer.

[0014] Optionally, the ratio of the thickness of the first piezoelectric layer to the thickness of the intermediate electrode is 1.2:1 - 2.5:1, and the ratio of the thickness of the second piezoelectric layer to the thickness of the intermediate electrode is 1.2:1 - 2.5:1.

[0015] 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 intermediate electrode and the ratio of the thickness of the second piezoelectric layer to the thickness of the intermediate electrode to 1.2:1 - 2.5:1. Therefore, this technical solution can effectively improve the performance index of the stacked crystal filter.

[0016] Optionally, the first acoustic mirror is an air cavity or several layers of Bragg reflection layers.

[0017] In a second aspect, the present application further provides a duplexer, which includes a transmit filter, a receive filter, and the stacked crystal filter provided in the first aspect above. The stacked crystal filter is disposed between the transmit filter and the receive filter and is connected in parallel with the transmit filter and the receive filter.

[0018] A duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the middle electrode is connected to the first bottom electrode or the first top electrode, that is, the present application can achieve the external connection of the first bottom electrode, the middle electrode, and the first top electrode without extending the three electrodes outward. Since 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 generation amount of spurious modes. Therefore, compared with the prior art, the present application can effectively reduce the generation amount of spurious modes, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to the excessive generation of spurious modes caused by 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.

[0019] Optionally, the first top electrode and the middle electrode of the stacked crystal filter are commonly grounded, and the first bottom electrode is connected to the antenna terminal.

[0020] Optionally, the transmit 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 mirror 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 terminal. The second top electrode of the first parallel filter is connected to the second top electrode of any one of the first series filters. The second bottom electrode of the first parallel filter is grounded. When the number of the first parallel filters is multiple, the multiple first parallel filters are connected in parallel.

[0021] Since the second top electrodes of the two first series filters of this technical solution are interconnected, and the second top electrode of the first parallel filter of this 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 the same as the height of the second top electrode of the first parallel filter, the second top electrodes of the transmit filter of this technical solution can be interconnected by extending outward without using a conductive structure penetrating the third piezoelectric layer. That is, this technical solution is equivalent to minimizing the number of conductive structures required when the second top electrode is externally connected. Since the conductive structure needs to occupy layout area and is made by using additional manufacturing processes, this technical solution can minimize the size of the transmit filter and reduce the production cost of the transmit filter, thereby effectively reducing the size and production cost of the duplexer.

[0022] Optionally, the receiving filter includes two second series filters and a plurality of 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 that are connected in sequence from bottom to top. A third acoustic mirror 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 terminal. The third top electrode of the second parallel filter is connected to the third top electrode of any one of the second series filters. The third bottom electrode of the second parallel filter is grounded. When the number of the second parallel filters is multiple, the multiple second parallel filters are connected in parallel.

[0023] Since the third top electrodes of the two second series filters of this technical solution are interconnected, the third top electrode of the second parallel filter of this 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 the same as the height of the third top electrode of the second parallel filter. Therefore, the third top electrodes of the receiving filter of this technical solution can be interconnected by extending outward, without using a conductive structure that penetrates the fourth piezoelectric layer for interconnection. That is, this technical solution is equivalent to minimizing the number of conductive structures required when the third top electrode is externally connected. Since the conductive structure needs to occupy layout area and is made by using an additional manufacturing process, this 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.

[0024] As can be seen from the above, a stacked crystal filter and a duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the intermediate electrode is connected 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 intermediate electrode, and the first top electrode without extending the three electrodes outward. Since compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the intermediate electrode, and the top electrode are externally connected, and the size of the electrodes extending outward is positively correlated with the generation amount of spurious modes. Therefore, compared with the prior art, the present application can effectively reduce the generation amount of spurious modes, thereby effectively solving the problem that the performance of the stacked crystal filter is significantly weakened due to excessive spurious modes generated when the stacked crystal filter needs to extend three electrodes outward, that is, the present application can effectively improve the performance of the stacked crystal filter. Description of the Drawings

[0025] Figure 1 It is a schematic cross-sectional structure diagram of the stacked crystal filter when the intermediate electrode and the first bottom electrode are commonly grounded provided by an embodiment of the present application.

[0026] Figure 2Schematic cross-sectional structure diagram of the stacked crystal filter when the intermediate electrode and the first top electrode are commonly grounded provided by the embodiment of the present application.

[0027] Figure 3 Schematic cross-sectional structure diagram of the stacked crystal filter when the intermediate electrode and the first bottom electrode are commonly grounded and the first top electrode is externally connected through a conductive structure provided by the embodiment of the present application.

[0028] Figure 4 Schematic diagram of the electrical symbol of the stacked crystal filter provided by the embodiment of the present application.

[0029] Figure 5 Schematic diagram of the relationship between the output and frequency of the stacked crystal filter provided by the embodiment of the present application.

[0030] Figure 6 Schematic structure diagram of the duplexer provided by the embodiment of the present application.

[0031] Reference numerals: 1, first substrate; 2, first bottom electrode; 3, first piezoelectric layer; 4, intermediate electrode; 5, second piezoelectric layer; 6, first top electrode; 7, first acoustic mirror; 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 implementation manners

[0032] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying 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 the embodiments. Usually, the components of the embodiments of the present application described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application to be protected, but only represents the selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0033] It should be noted that: similar reference numerals and letters represent similar items in the following drawings. Therefore, 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 the present application, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0034] In the first aspect, asFigures 1-5 As shown, the present application provides a stacked crystal filter, which includes:

[0035] 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 connected in sequence from top to bottom. A first acoustic mirror 7 is provided on the first substrate 1. The intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, or the intermediate electrode 4 and the first top electrode 6 are commonly grounded;

[0036] When the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, the first top electrode 6 is externally connected, the intermediate electrode 4 or 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 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 commonly grounded, the first bottom electrode 2 is externally connected, the intermediate electrode 4 or the first top electrode 6 is connected to the ground terminal GND, and the edge of the projection of the connection between the intermediate electrode 4 and the first top electrode 6 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.

[0037] Among them, 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 a silicon material. The materials of the first bottom electrode 2, the intermediate electrode 4, and the first top electrode 6 of this embodiment are preferably metal materials with high conductivity, large acoustic impedance, and large Young's modulus (such as any one or more of gold, molybdenum, ruthenium, and platinum). The materials of the first bottom electrode 2, the intermediate electrode 4, and the first top electrode 6 of this embodiment are preferably the same. The materials of the first piezoelectric layer 3 and the second piezoelectric layer 5 of this embodiment are preferably aluminum nitride. Specifically, when a signal source is externally connected to the first top electrode 6 or the first bottom electrode 2 (equivalent to applying a voltage signal or an electrical signal to the first top electrode 6 or the first bottom electrode 2), electric fields are formed at both ends of the first piezoelectric layer 3 and the second piezoelectric layer 5 to excite bulk acoustic waves (equivalent to exciting longitudinal waves in the first piezoelectric layer 3 and the second piezoelectric layer 5), thereby realizing the mutual conversion of electrical energy and mechanical energy and the frequency selection of the stacked crystal filter 11. A first acoustic mirror 7 is provided on the first substrate 1 of this embodiment, and the first acoustic mirror 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 externally connected to an external circuit, the intermediate electrode 4 or the first bottom electrode 2 is connected to the ground terminal GND, and the connection between the intermediate electrode 4 and the first bottom electrode 2 and the edge of the projection of the connection in the top view direction are 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 externally connected to an external circuit, the intermediate electrode 4 or the first top electrode 6 is connected to the ground terminal GND, and the connection between the intermediate electrode 4 and the first top electrode 6 and the edge of the projection of the connection in the top view direction are 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 intermediate electrode 4 of this embodiment is connected to the first bottom electrode 2 or the first top electrode 6, when the first top electrode 6 and the intermediate electrode 4 are grounded together, this embodiment can choose to extend one electrode outward from the intermediate electrode 4 or the first top electrode 6, and the connection between the intermediate electrode 4 and the first top electrode 6 is such that the edge of the projection 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 intermediate electrode 4 are grounded together, this embodiment can achieve the external connection of the first top electrode 6 and the intermediate electrode 4 without extending two electrodes outward. When the first bottom electrode 2 and the intermediate electrode 4 are grounded together, the first bottom electrode 2 or the intermediate electrode 4 extends one electrode outward, and the connection between the intermediate electrode 4 and the first bottom electrode 2 is such that the edge of the projection 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 intermediate electrode 4 are grounded together, this embodiment can achieve the external connection of the first bottom electrode 2 and the intermediate electrode 4 without extending two electrodes outward. Therefore, the present application can effectively reduce the size of the electrodes extended outward when externally connecting the first bottom electrode 2, the intermediate electrode 4, and the first top electrode 6. That is, the present application can achieve the external connection of the first bottom electrode 2, the intermediate electrode 4, and the first top electrode 6 without extending three electrodes outward. It should also be understood that this embodiment can adjust performance indicators such as the center frequency, bandwidth, and passband ripple of the stacked crystal filter 11 by adjusting the dimensions and material parameters of each layer structure, and the present application can make the stacked crystal filter 11 have two transmission zeros (refer to Figure 4 F2 and F4 in, which are equivalent to the parallel resonance frequency points. At a certain frequency, the output corresponding to the transmission zero is 0) and two transmission poles (refer to Figure 4 F1 and F3 in, which are equivalent to the series resonance frequency points). Therefore, the stacked crystal filter 11 of the present application can be connected as a parallel filter in the parallel line of the ladder structure filter.

[0038] A stacked crystal filter provided by the present application can effectively reduce the size of the electrodes extending outward when the middle electrode 4 is connected to the first bottom electrode 2 or the first top electrode 6, that is, the present application can achieve 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. Since, 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 generation amount of spurious modes, therefore, compared with the prior art, the present application can effectively reduce the generation amount of spurious modes, thereby effectively solving the problem that the performance of the stacked crystal filter 11 is significantly weakened due to excessive spurious modes generated when the stacked crystal filter 11 needs 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, and this embodiment only needs to make the edge of the projection of the connection of the two electrodes with a common ground in the top view direction be located within the edge of the projection of the electrode connected to the ground terminal GND in the top view direction to achieve this purpose, that is, even if the electrode that is not connected to the ground terminal GND in the two electrodes with a common ground extends a partial electrode (the electrode extension amount is less than one electrode), this purpose can also be achieved. Therefore, when the middle electrode 4 and the first bottom electrode 2 have a common ground and the middle electrode 4 is connected to the ground terminal GND, the first bottom electrode 2 can extend a partial electrode. When the middle electrode 4 and the first bottom electrode 2 have a common ground and the first bottom electrode 2 is connected to the ground terminal GND, the middle electrode 4 can extend a partial electrode (refer to Figure 3 ), when the middle electrode 4 and the first top electrode 6 have a common ground and the middle electrode 4 is connected to the ground terminal GND, the first top electrode 6 can extend a partial electrode. When the middle electrode 4 and the first top electrode 6 have a common ground and the first top electrode 6 is connected to the ground terminal GND, the middle electrode 4 can extend a partial electrode.

[0039] In some preferred embodiments, when the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, 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 extend beyond the edge of the projection of the first acoustic mirror 7 in the top view direction. Preferably, when the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, the edge of the projection of the connection between the intermediate electrode 4 and the first bottom electrode 2 in the top view direction coincides with the edge of the projection of the first acoustic mirror 7 in the top view direction to ensure the performance of the intermediate electrode 4. Since when the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, 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 outside the first acoustic mirror 7, 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 extend beyond the edge of the projection of the first acoustic mirror 7 in the top view direction, that is, when the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, the first bottom electrode 2 extends out one electrode, and the intermediate electrode 4 does not extend out. Therefore, this embodiment is equivalent to reducing the number of electrodes extending out when the bottom electrode, the intermediate electrode 4, and the top electrode are externally connected from three to two, so that the size of the electrodes extending out when the bottom electrode, the intermediate electrode 4, and the top electrode are externally connected reaches the minimum, thereby minimizing the generation amount of spurious modes and optimizing the performance of the stacked crystal filter 11.

[0040] In some preferred embodiments, when the intermediate electrode 4 and the first top electrode 6 are commonly grounded, the intermediate 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 intermediate electrode 4 in the top view direction does not extend beyond the edge of the projection of the first acoustic mirror 7 in the top view direction. Since when the intermediate electrode 4 and the first top electrode 6 are commonly grounded, one side of the intermediate electrode 4 is connected to the ground terminal GND, that is, one side of the intermediate electrode 4 extends outside the first acoustic mirror 7, and the edge of the projection of the connection between the first top electrode 6 and the intermediate electrode 4 in the top view direction does not extend beyond the edge of the projection of the first acoustic mirror 7 in the top view direction, that is, when the intermediate electrode 4 and the first top electrode 6 are commonly grounded, the intermediate electrode 4 extends out one electrode, and the first top electrode 6 does not extend out. Therefore, this embodiment is equivalent to reducing the number of electrodes extending out when the bottom electrode, the intermediate electrode 4, and the top electrode are externally connected from three to two, so that the size of the electrodes extending out when the bottom electrode, the intermediate electrode 4, and the top electrode are externally connected reaches the minimum, thereby minimizing the generation amount of spurious modes and optimizing the performance of the stacked crystal filter 11. It should be understood that the intermediate electrode 4 of this embodiment needs to be connected to the ground terminal GND through the conductive structure 8 penetrating the first piezoelectric layer 3.

[0041] In some preferred embodiments, such as Figure 3As shown, when the intermediate electrode 4 and the first bottom electrode 2 are commonly grounded, the first top electrode 6 is connected to an electrode other than the first top electrode 6 in another stacked crystal filter 11 or an external device through a conductive structure 8 penetrating through 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 their heights are the same, in this embodiment, only by extending the first top electrode 6 outward by one electrode can the first top electrode 6 of the current stacked crystal filter be connected to the first top electrode 6 of another stacked crystal filter 11. However, since the height of the first top electrode 6 is different from the height of an electrode other than the first top electrode 6 in another stacked crystal filter 11 (the first bottom electrode 2 or the intermediate electrode 4 in another stacked crystal filter 11) or an external device, in this embodiment, the connection between the first top electrode 6 and an electrode other than the first top electrode 6 in another stacked crystal filter 11 or an external device can be achieved only through the conductive structure 8 penetrating through the first piezoelectric layer 3 and the second piezoelectric layer 5. It should be understood that the external device can be a device with a different height from the first top electrode 6, such as a ground terminal GND or an antenna terminal ANT.

[0042] 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. Therefore, this embodiment can effectively improve the performance index of the stacked crystal filter 11.

[0043] In some preferred embodiments, the first acoustic mirror 7 is an air cavity or several layers of Bragg reflection layers. The first acoustic mirror 7 in this embodiment can be an air cavity or several layers of Bragg reflection layers, and each layer of Bragg reflection layer is composed of a low acoustic impedance layer and a high acoustic impedance layer. This embodiment can form an air cavity on the first substrate 1 to form the first acoustic mirror 7 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 the first bottom electrode 2, the first piezoelectric layer 3, the intermediate electrode 4, the second piezoelectric layer 5, and the first top electrode 6 on the first substrate 1, and finally removing the sacrificial layer based on a wet etching process. This embodiment can also form an acoustic mirror 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 reflection layers in the groove based on the existing Bragg reflection layer forming process.

[0044] As can be seen from the above, a stacked crystal filter provided by the present application can effectively reduce the size of the electrodes extending outward when the middle electrode 4 is connected to the first bottom electrode 2 or the first top electrode 6, that is, the present application can achieve 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. Since 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 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 11 is significantly weakened due to the excessive spurious modes generated by the need to extend three electrodes outward for the stacked crystal filter 11, that is, the present application can effectively improve the performance of the stacked crystal filter 11.

[0045] In a second aspect, as Figure 6 shown, the present application further 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. The stacked crystal filter 11 is disposed 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.

[0046] A duplexer provided by the present application includes a transmit filter 9, a receive filter 10, and the stacked crystal filter 11 provided in the first aspect above. The working principle of the duplexer provided in the embodiment of the present application is the same as that of the stacked crystal filter 11 provided in the first aspect above, and will not be elaborated in detail here. Since the present application can adjust the performance indexes of the stacked crystal filter 11 by adjusting the sizes of the structures of each layer of the stacked crystal filter 11, in this embodiment, the difference between one transmission pole of the stacked crystal filter 11 and the transmission pole of the transmit filter 9 can be made less than a preset difference, the difference between one transmission zero of the stacked crystal filter 11 and the transmission zero of the transmit filter 9 can be made less than a preset difference, the difference between the other transmission pole of the stacked crystal filter 11 and the transmission pole of the receive filter 10 can be made less than a preset difference, and the difference between the other transmission zero of the stacked crystal filter 11 and the transmission zero of the receive filter 10 can be made less than a preset difference by adjusting the thickness of any one or more of the first bottom electrode 2, the first piezoelectric layer 3, the intermediate electrode 4, the second piezoelectric layer 5, and the first top electrode 6. Therefore, in this embodiment, a stacked crystal filter 11 connected in parallel with the transmit filter 9 and the receive filter 10 can be arranged between the transmit filter 9 and the receive filter 10 to replace one parallel filter in the transmit filter 9 and one parallel filter in the receive filter 10. That is, this embodiment is equivalent to using the stacked crystal filter 11 to replace two parallel filters, so as to reduce the number of parallel filters used in the duplexer while enhancing the out-of-band rejection ability of the duplexer, thereby reducing the size and production cost of the duplexer.

[0047] In some preferred embodiments, the first top electrode 6 and the intermediate electrode 4 of the stacked crystal filter 11 are commonly grounded, and the first bottom electrode 2 is connected to the antenna terminal ANT. The intermediate electrode 4 in this embodiment needs to be connected to the ground terminal GND through the conductive structure 8 that penetrates the first piezoelectric layer 3.

[0048] In some preferred embodiments, the transmit filter 9 includes two first series filters 91 and a plurality of first parallel filters 92. Both the first series filter 91 and the first parallel filter 92 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, which are connected in sequence from bottom to top. A second acoustic mirror (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 one of the first series filters 91. The second bottom electrode BE2 of the first parallel filter 92 is grounded. When the number of the first parallel filters 92 is multiple, the multiple first parallel filters 92 are connected in parallel. Since the second top electrodes TE2 of the two first series filters 91 in this embodiment are interconnected, and the second top electrode TE2 of the first parallel filter 92 in 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 the same as the height of the second top electrode TE2 of the first parallel filter 92, the second top electrodes TE2 of the transmit filter 9 in this embodiment can be interconnected by extending outward, without using the conductive structure 8 that penetrates the third piezoelectric layer for interconnection. That is, this embodiment is equivalent to minimizing the number of the conductive structures 8 required when the second top electrode TE2 is externally connected. Since the conductive structure 8 needs to occupy layout area and is made by using an additional manufacturing process, this embodiment can minimize the size of the transmit filter 9 and reduce the production cost of the transmit filter 9, thereby effectively reducing the size and production cost of the duplexer.

[0049] In some preferred embodiments, the receiving filter 10 includes two second series filters 101 and a plurality of second parallel filters 102. Both the second series filter 101 and the second parallel filter 102 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, which are connected in sequence from bottom to top. A third acoustic mirror (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 one of the second series filters 101. The third bottom electrode BE3 of the second parallel filter 102 is grounded. When the number of the 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 in this embodiment are interconnected, and the third top electrode TE3 of the second parallel filter 102 in 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 the same as the height of the third top electrode TE3 of the second parallel filter 102, the third top electrodes TE3 of the receiving filter 10 in this embodiment can be interconnected by extending outward, without using the conductive structure 8 that penetrates the fourth piezoelectric layer for interconnection. That is, this embodiment is equivalent to minimizing the number of the conductive structures 8 required when the third top electrode TE3 is externally connected. Since the conductive structure 8 needs to occupy layout area and is made by using an additional manufacturing 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.

[0050] Preferably, as Figure 6As shown, the first top electrode 6 of the stacked crystal filter 11 and the intermediate electrode 4 are commonly grounded, 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, 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 only one conductive structure 8 is required in this embodiment to realize the external connection of the duplexer, that is, this embodiment is equivalent to minimizing the number of conductive structures 8 required for the external connection of the duplexer, so this embodiment can minimize the size of the duplexer and minimize the production cost of the duplexer.

[0051] As can be seen from the above, a stacked crystal filter and a duplexer provided by the present application can effectively reduce the size of the electrodes extending outward when the intermediate electrode 4 is connected 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 intermediate electrode 4, and the first top electrode 6 without extending three electrodes outward. Since, compared with the prior art, the present application can effectively reduce the size of the electrodes extending outward when the bottom electrode, the intermediate electrode 4, 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, so compared with the prior art, the present application can effectively reduce the amount of spurious modes generated, thereby effectively solving the problem that too many spurious modes are generated due to the need for the stacked crystal filter 11 to extend three electrodes outward, and the performance of the stacked crystal filter 11 is significantly weakened, that is, the present application can effectively improve the performance of the stacked crystal filter 11.

[0052] In the embodiments provided by the present application, it should be understood that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0053] The above description is only for the embodiments 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 can have various changes and modifications. 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 includes: A first substrate, a first bottom electrode, a first piezoelectric layer, an intermediate electrode, a second piezoelectric layer, and a first top electrode connected in sequence from bottom to top. A first acoustic mirror is provided on the first substrate. The intermediate electrode and the first bottom electrode are commonly grounded, or the intermediate electrode and the first top electrode are commonly grounded; When the intermediate electrode and the first bottom electrode are commonly grounded, the first top electrode is externally connected, the intermediate electrode or the first bottom electrode is connected to the ground terminal, the connection between the intermediate electrode and the first bottom electrode and the edge of the projection in the top view direction are located within the edge of the projection of the electrode connected to the ground terminal in the top view direction. When the intermediate electrode and the first top electrode are commonly grounded, the first bottom electrode is externally connected, the intermediate electrode or the first top electrode is connected to the ground terminal, the connection between the intermediate electrode and the first top electrode and the edge of the projection in the top view direction are 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, wherein, When the intermediate electrode and the first bottom electrode are commonly grounded, one side of the first bottom electrode is connected to the ground terminal, and the edge of the projection of the connection between the intermediate electrode and the first bottom electrode in the top view direction does not exceed the edge of the projection of the first acoustic mirror in the top view direction.

3. The stacked crystal filter according to claim 1, wherein When the intermediate electrode and the first top electrode are commonly grounded, one side of the intermediate electrode is connected to the ground terminal, and the edge of the projection of the connection between the first top electrode and the intermediate electrode in the top view direction does not exceed the edge of the projection of the first acoustic mirror in the top view direction.

4. The stacked crystal filter according to claim 1, wherein When the intermediate electrode and the first bottom electrode are commonly grounded, the first top electrode is connected to an electrode other than the first top electrode or an external device in another stacked crystal filter through a conductive structure passing through the first piezoelectric layer and the second piezoelectric layer.

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

1.

6. The stacked crystal filter according to claim 1, wherein The first acoustic mirror is an air cavity or several layers of Bragg reflection layers.

7. A duplexer, characterized in that, The duplexer includes a transmit filter, a receive filter, and the stacked crystal filter according to any one of claims 1 - 6. The stacked crystal filter is disposed 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, wherein The first top electrode of the stacked crystal filter and the intermediate electrode are commonly grounded, and the first bottom electrode is connected to the antenna terminal.

9. The duplexer according to claim 7, wherein The transmitting filter includes two first series filters and a plurality of 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 that are connected in sequence from bottom to top. A second acoustic mirror 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 terminal. The second top electrode of the first parallel filter is connected to the second top electrode of any one of the first series filters. The second bottom electrode of the first parallel filter is grounded. When the number of the first parallel filters is multiple, the multiple first parallel filters are connected in parallel.

10. The duplexer according to claim 7, wherein The receiving filter includes two second series filters and a plurality of 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 that are connected in sequence from bottom to top. A third acoustic mirror 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 terminal. The third top electrode of the second parallel filter is connected to the third top electrode of any one of the second series filters. The third bottom electrode of the second parallel filter is grounded. When the number of the second parallel filters is multiple, the multiple second parallel filters are connected in parallel.

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