Bulk acoustic wave filter and multiplexer

Abstract

The invention discloses a bulk acoustic wave filter and a multiplexer. The bulk acoustic wave filter comprises an input terminal, an output terminal, a plurality of series resonators and a plurality of parallel resonators, the series resonator is connected in series between the input terminal and the output terminal, and the parallel resonator is connected between one end of the series resonator and the ground terminal; the plurality of series resonators comprise at least one first series resonator and at least one second series resonator; the plurality of parallel resonators comprise at least one first parallel resonator and at least one second parallel resonator; the thermal conductivity of the piezoelectric layer in the first series resonator is smaller than the thermal conductivity of the piezoelectric layers in the second series resonator and the second parallel resonator, and the thermal conductivity of the piezoelectric layer in the first parallel resonator is smaller than the thermal conductivity of the piezoelectric layers in the second series resonator and the second parallel resonator. According to the invention, the heat dissipation capability of the resonator close to the input terminal in the bulk acoustic wave filter can be improved.

Description

Technical Field

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

[0002] Currently, bulk acoustic wave filters have been widely used in 5G filters.

[0003] In order to improve the electromechanical coupling coefficient of a bulk acoustic wave filter, the prior art generally improves the electromechanical coupling coefficient by doping a single element metal in the piezoelectric film of the resonator.

[0004] However, the thermal conductivity of the piezoelectric film doped with a single metal will decrease, which will cause the heat in the active area of ​​the resonator in the BAW filter to be unable to be transferred to the substrate and dissipated in time. Especially for the resonator close to the input terminal of the BAW filter, where the active area of ​​the resonator has more heat, the lower thermal conductivity of the piezoelectric film doped with a single metal will have a greater impact on the resonator here, and the resonator here is prone to damage due to the inability to dissipate the heat in time. Summary of the invention

[0005] The present invention provides a bulk acoustic wave filter and a multiplexer to solve the problem that the resonator near the input terminal of the existing bulk acoustic wave filter has poor heat dissipation capability and is easy to be damaged.

[0006] In a first aspect, an embodiment of the present invention provides a bulk acoustic wave filter, including an input terminal, an output terminal, a plurality of series resonators, and a plurality of parallel resonators;

[0007] The series resonator is connected in series between the input terminal and the output terminal, and the parallel resonator is connected between one end of the series resonator and a ground terminal;

[0008] The plurality of series resonators include at least one first series resonator and at least one second series resonator; the plurality of parallel resonators include at least one first parallel resonator and at least one second parallel resonator;

[0009] A distance between the first series resonator and the input terminal is smaller than a distance between the second series resonator and the input terminal; a distance between the first parallel resonator and the input terminal is smaller than a distance between the second parallel resonator and the input terminal;

[0010] The thermal conductivity of the piezoelectric layer in the first series resonator is greater than the thermal conductivity of the piezoelectric layer in the second series resonator and the second parallel resonator; the thermal conductivity of the piezoelectric layer in the first parallel resonator is greater than the thermal conductivity of the piezoelectric layer in the second series resonator and the second parallel resonator.

[0011] Optionally, the relative dielectric constant of the piezoelectric layer in the first series resonator is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator and the second parallel resonator; the relative dielectric constant of the piezoelectric layer in the first parallel resonator is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator and the second parallel resonator.

[0012] Optionally, an area of ​​an active region of the first series resonator is greater than an area of ​​an active region of the second series resonator and the second parallel resonator; an area of ​​an active region of the first parallel resonator is greater than an area of ​​an active region of the second series resonator and the second parallel resonator.

[0013] Optionally, the scandium content of the piezoelectric layer in the first series resonator is less than the scandium content of the piezoelectric layer in the second series resonator and the second parallel resonator; the scandium content of the piezoelectric layer in the first parallel resonator is less than the scandium content of the piezoelectric layer in the second series resonator and the second parallel resonator.

[0014] Optionally, the scandium content C1 of the piezoelectric layer in the first series resonator satisfies 0≤C1≤9.5%;

[0015] The scandium content C2 of the piezoelectric layer in the second series resonator satisfies 9.5%<C2≤40%;

[0016] The scandium content C3 of the piezoelectric layer in the first parallel resonator satisfies 0≤C3≤9.5%;

[0017] The scandium content C4 of the piezoelectric layer in the second parallel resonator satisfies 9.5%<C4≤40%.

[0018] Optionally, an area of ​​the first series resonator is smaller than an area of ​​the second series resonator.

[0019] Optionally, along the thickness direction of the BAW filter, the first series resonator, the second series resonator, the first parallel resonator and the second parallel resonator are arranged in the same layer.

[0020] Optionally, along the thickness direction of the BAW filter, the first series resonator and the first parallel resonator are arranged in the same layer, and the second series resonator and the second parallel resonator are arranged in the same layer;

[0021] Along the thickness direction of the BAW filter, the first series resonator overlaps with the second series resonator or the second parallel resonator;

[0022] The first parallel resonator overlaps with the second series resonator or the second parallel resonator along a thickness direction of the BAW filter.

[0023] Optionally, the BAW filter further includes a first inductor, a second inductor and a plurality of third inductors;

[0024] The first inductor is connected between the input terminal and the series resonator;

[0025] The second inductor is connected between the series resonator and the output terminal;

[0026] The third inductor is connected between the parallel resonator and the ground terminal.

[0027] In a second aspect, an embodiment of the present invention provides a multiplexer, including an antenna, at least one receiving unit and at least one transmitting unit;

[0028] The antenna is communicatively connected to the receiving unit and the sending unit respectively;

[0029] At least one of the receiving unit and the transmitting unit comprises a bulk acoustic wave filter as described in the first aspect.

[0030] The technical solution of the embodiment of the present invention can improve the heat dissipation capacity of the resonator close to the input terminal by setting the thermal conductivity of the first series resonator and the first parallel resonator close to the input terminal to be greater than the thermal conductivity of other resonators, thereby solving the problem of poor heat dissipation capacity and easy damage of the resonator close to the input terminal in the existing bulk acoustic wave filter.

[0031] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic circuit diagram of a bulk acoustic wave filter provided by an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a bulk acoustic wave filter provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the structure of another bulk acoustic wave filter provided by an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of the structure of another bulk acoustic wave filter provided by an embodiment of the present invention;

[0037] Figure 5 A circuit diagram of another bulk acoustic wave filter provided by an embodiment of the present invention;

[0038] Figure 6 A circuit diagram of a multiplexer provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only used to illustrate the relative positional relationship between the components or components, and does not particularly limit the specific installation orientation of the components or components.

[0041] Figure 1 A schematic diagram of a bulk acoustic wave filter circuit according to an embodiment of the present invention is provided. Figure 1The bulk acoustic wave filter 100 in the embodiment of the present invention includes an input terminal in, an output terminal out, a plurality of series resonators 10 and a plurality of parallel resonators 20. The series resonator 10 is connected in series between the input terminal in and the output terminal out, and the parallel resonator 20 is connected between one end of the series resonator 10 and the ground terminal. The plurality of series resonators 10 include at least one first series resonator 11 and at least one second series resonator 12. The plurality of parallel resonators 20 include at least one first parallel resonator 21 and at least one second parallel resonator 22.

[0042] There is a distance between the first series resonator 11 and the input terminal in that is smaller than a distance between the second series resonator 12 and the input terminal in. There is a distance between the first parallel resonator 21 and the input terminal in that is smaller than a distance between the second parallel resonator 22 and the input terminal in.

[0043] The thermal conductivity of the piezoelectric layer in the first series resonator 11 is greater than that in the second series resonator 12 and the second parallel resonator 22. The thermal conductivity of the piezoelectric layer in the first parallel resonator 21 is greater than that in the second series resonator 12 and the second parallel resonator 22.

[0044] It should be noted that the resonator in the bulk acoustic wave filter 100 includes a substrate, a first electrode, a piezoelectric layer, a second electrode and a cavity stacked along the thickness direction of the resonator. The substrate is provided to provide physical support for the entire resonator. The first electrode and the second electrode are respectively located on both sides of the piezoelectric layer. Based on the inverse piezoelectric effect of the piezoelectric material in the piezoelectric layer, the piezoelectric layer can be deformed by applying a voltage to the two electrodes. This deformation vibrates rapidly with the change of the electric field, thereby forming a sound wave. In order to improve the performance of the resonator, a cavity is usually set on one side of the first electrode or the second electrode. The cavity overlaps with the active area of ​​the resonator, which can reduce the energy loss of the sound wave during propagation, thereby improving the quality factor (Q value) and frequency stability of the resonator. The active area of ​​the resonator refers to the area where the two electrodes of the resonator overlap with the piezoelectric layer along the thickness direction of the resonator.

[0045] The two electrodes in the resonator are usually made of metal materials, such as gold (Au), aluminum (Al), etc. When a voltage is applied to the two electrodes through the input terminal in of the bulk acoustic wave filter 100, a current will pass through the electrodes. Since the electrodes have resistance, Joule heat will be generated when the current passes through the electrodes. This heat is one of the main sources of heat in the resonator. The heat dissipation mainly depends on the piezoelectric layer that is in contact with both the electrode and the substrate. The piezoelectric layer can transfer the heat generated by the electrode to the substrate, and finally dissipate it to the outside air through the substrate. It can be understood that the electrode in the resonator closest to the input terminal in is subjected to the largest voltage and generates more heat than other resonators.

[0046] Figure 1 The bulk acoustic wave filter 100 shown includes one first series resonator 11 and three second series resonators 12. The above-mentioned one first series resonator 11 and three second series resonators 12 are connected in series between the input terminal in and the output terminal out in sequence. The first series resonator 11 is closest to the input terminal in compared to the other second series resonators 12, and generates more heat. Its piezoelectric layer needs a larger thermal conductivity so that the heat generated by its electrode can be conducted to its substrate through the piezoelectric layer and dissipated. Figure 1 The bulk acoustic wave filter 100 shown also includes a first parallel resonator 11 and three second parallel resonators 12, one end of the first parallel resonator 21 is electrically connected to the end of the first series resonator 11 away from the input terminal in, the other end of the first parallel resonator 11 is electrically connected to the ground terminal and grounded through the ground terminal, one end of the three second parallel resonators is respectively electrically connected to the ends of the three second series resonators 12 away from the input terminal in, the other ends of the three second parallel resonators are respectively electrically connected to the ground terminal and grounded through the ground terminal, the first parallel resonator 21 is closest to the input terminal in compared to the other second parallel resonators 22, and generates more heat, and its piezoelectric layer needs a larger thermal conductivity, so that the heat generated by its electrode can be conducted to its substrate through the piezoelectric layer and dissipated.

[0047] It should be noted that the embodiment of the present invention does not limit the number of first series resonators 11 and first parallel resonators 21 included in the bulk acoustic wave filter 100. The bulk acoustic wave filter 100 can also have two first series resonators 11 and two first parallel resonators 21. The two first series resonators 11 can be the two series resonators 10 closest to the input terminal in among all the series resonators 10, and the two first parallel resonators 21 can be the two parallel resonators 20 closest to the input terminal in among all the parallel resonators 20.

[0048] The embodiment of the present invention improves the heat dissipation capacity of the resonator near the input terminal in by setting the thermal conductivity of the first series resonator 11 and the first parallel resonator 21 near the input terminal in to be greater than the thermal conductivity of other resonators, thereby solving the problem of poor heat dissipation capacity and easy damage of the resonator near the input terminal in the existing bulk acoustic wave filter 100.

[0049] As a feasible implementation, the scandium content of the piezoelectric layer in the first series resonator 11 is less than the scandium content of the piezoelectric layer in the second series resonator 12 and the second parallel resonator 22. The scandium content of the piezoelectric layer in the first parallel resonator 21 is less than the scandium content of the piezoelectric layer in the second series resonator 12 and the second parallel resonator 22.

[0050] Exemplarily, in order to improve the electromechanical coupling coefficient of the resonator in the bulk acoustic wave filter 100, the piezoelectric layer of the resonator in the embodiment of the present invention can be made of an aluminum nitride (AlN) film containing scandium (Sc), that is, an aluminum scandium nitride (AlScN) film. It can be understood that the higher the scandium content in the aluminum scandium nitride film, the higher the thermal conductivity of the aluminum scandium nitride film. In order to improve the thermal conductivity of the piezoelectric layer of the first series resonator 11 and the first parallel resonator 21 close to the input terminal in, the embodiment of the present invention can be achieved by reducing the scandium content of the piezoelectric layer (aluminum scandium nitride film) of the first series resonator 11 and the first parallel resonator 21. Moreover, the embodiment of the present invention only reduces the scandium content of the piezoelectric layer (aluminum scandium nitride film) of the first series resonator 11 and the first parallel resonator 21, and does not reduce the scandium content of the piezoelectric layer (aluminum scandium nitride film) of other resonators (the second series resonator 12 and the second parallel resonator 22). It will not have a significant impact on the electromechanical coupling coefficients of other resonators, thereby ensuring that the bulk acoustic wave filter 100 still has a relatively high performance.

[0051] Specifically, the scandium content C1 of the piezoelectric layer in the first series resonator 11 satisfies 0≤C1≤9.5%. The scandium content C2 of the piezoelectric layer in the second series resonator 12 satisfies 9.5%<C2≤40%. The scandium content C3 of the piezoelectric layer in the first parallel resonator 21 satisfies 0≤C3≤9.5%. The scandium content C4 of the piezoelectric layer in the second parallel resonator 22 satisfies 9.5%<C4≤40%.

[0052] Further, the relative dielectric constant of the piezoelectric layer in the first series resonator 11 is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator 12 and the second parallel resonator 22. The relative dielectric constant of the piezoelectric layer in the first parallel resonator 21 is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator 12 and the second parallel resonator 22.

[0053] Further, the active area of ​​the first series resonator 11 is larger than the active area of ​​the second series resonator 12 and the second parallel resonator 22. The active area of ​​the first parallel resonator 21 is larger than the active area of ​​the second series resonator 12 and the second parallel resonator 22.

[0054] It can be understood that the higher the scandium content in the piezoelectric layer (aluminum scandium nitride film), the smaller the relative dielectric constant of the piezoelectric layer (aluminum scandium nitride film). The smaller the relative dielectric constant of the piezoelectric layer (aluminum scandium nitride film), the larger the area of ​​the active region of the resonator under the same impedance. The larger the area of ​​the active region of the resonator, the higher the power capacity of the filter. Therefore, by setting the scandium content of the piezoelectric layer (aluminum scandium nitride film) of the first series resonator 11 and the first parallel resonator 21 to be smaller than the scandium content of other resonators (the second series resonator 12 and the second parallel resonator 22), the relative dielectric constant of the piezoelectric layer in the first series resonator 11 and the first parallel resonator 21 can be made smaller than the relative dielectric constant of the piezoelectric layer in the other resonators, thereby making the area of ​​the active region in the first series resonator 11 and the first parallel resonator 21 larger than the area of ​​the active region in the other resonators.

[0055] In the embodiment of the present invention, the scandium content of the piezoelectric layer (aluminum scandium nitride film) of the first series resonator 11 and the first parallel resonator 21 is set to be smaller than the scandium content of other resonators (the second series resonator 12 and the second parallel resonator 22), thereby making the area of ​​the active region in the first series resonator 11 and the first parallel resonator 21 larger than the area of ​​the active region in other resonators, thereby improving the power capacity and roll-off of the bulk acoustic wave filter 100.

[0056] In other possible implementations, the area of ​​the first series resonator 11 is smaller than the area of ​​the second series resonator 12 .

[0057] It can be understood that the smaller the area of ​​the resonator, the smaller its heat dissipation capacity. In order to prevent the smallest series resonator 10 from being damaged due to poor heat dissipation capacity, the embodiment of the present invention also sets the thermal conductivity of the piezoelectric layer of the smallest series resonator among all series resonators 10 to be smaller than the thermal conductivity of the piezoelectric layers of other series resonators 10. It should be noted that the first series resonator 11 with the smallest area may be the first series resonator 11 closest to the input terminal in, or may not be the first series resonator 11 closest to the input terminal in, and the embodiment of the present invention does not limit this.

[0058] As a feasible implementation method, Figure 2 A schematic diagram of the structure of a bulk acoustic wave filter provided by an embodiment of the present invention, referring to Figure 2 Along the thickness direction Z of the BAW filter 100 , the first series resonator 11 , the second series resonator 12 , the first parallel resonator 21 , and the second parallel resonator 22 are arranged in the same layer.

[0059] It should be noted that Figure 2The embodiment shown only shows the first series resonator 11 and the second series resonator 12 arranged in the same layer, and does not show the first parallel resonator 21 and the second parallel resonator 22 arranged in the same layer as the first series resonator 11 and the second series resonator 12. However, those skilled in the art will understand from Figure 2 It can be clearly known that the specific manner in which the first series resonator 11, the second series resonator 12, the first parallel resonator 21 and the second parallel resonator are arranged in the same layer.

[0060] Specifically, the first series resonator 11 includes a substrate 111 stacked along the thickness direction of the bulk acoustic wave, an acoustic reflector 112 formed by alternating at least one layer of high acoustic impedance material and at least one layer of low acoustic impedance material, a first electrode 113, a piezoelectric layer 114, and a second electrode 115. The second series resonator 12 includes a substrate 121 stacked along the thickness direction of the bulk acoustic wave, an acoustic reflector 122 formed by alternating at least one layer of high acoustic impedance material and at least one layer of low acoustic impedance material, a first electrode 123, a piezoelectric layer 124, and a second electrode 125. The substrate 111 of the first series resonator 11 and the substrate 121 of the second series resonator 12 are arranged in the same layer and can be prepared together. The acoustic reflector 112 of the first series resonator 11 and the acoustic reflector 122 of the second series resonator 12 are arranged in the same layer and can be prepared together. The first electrode 113 of the first series resonator 11 and the first electrode 123 of the second series resonator 12 are arranged in the same layer and can be prepared together. The piezoelectric layer 114 of the first series resonator 11 and the piezoelectric layer 124 of the second series resonator 12 are disposed in the same layer and can be manufactured together. The second electrode 115 of the first series resonator 11 and the second electrode 125 of the second series resonator 12 are disposed in the same layer and can be manufactured together.

[0061] Since the scandium content of the piezoelectric layer (aluminum scandium nitride film) of the first series resonator 11 and the first parallel resonator 21 is less than the scandium content of other resonators (the second series resonator 12 and the second parallel resonator 22), there are some differences in the preparation process of the bulk acoustic wave filter 100 from the preparation process of the existing bulk acoustic wave filter 100. Specifically, when preparing the piezoelectric layer of the bulk acoustic wave resonator, that is, preparing the piezoelectric layer of each resonator, first prepare a whole layer of aluminum scandium nitride film with a high scandium content, then pattern the aluminum scandium nitride film, etch away the aluminum scandium nitride film with a high scandium content at the first series resonator 11 and the first parallel resonator 21, and then fill the etched grooves with aluminum scandium nitride film with a low scandium content. Alternatively, a whole layer of aluminum scandium nitride film with a low scandium content is prepared first, and then the aluminum scandium nitride film is patterned, and the aluminum scandium nitride film with a low scandium content at the second series resonator 12 and the second parallel resonator 22 is etched away, and then the aluminum scandium nitride film with a high scandium content is filled in the etched grooves.

[0062] As another possible implementation, Figure 3 A schematic diagram of the structure of another bulk acoustic wave filter provided by an embodiment of the present invention, Figure 4 A schematic diagram of the structure of another bulk acoustic wave filter provided in an embodiment of the present invention, referring to Figure 3 and Figure 4 , along the thickness direction Z of the BAW filter 100, the first series resonator 11 and the first parallel resonator 21 are arranged in the same layer, and the second series resonator 12 and the second parallel resonator are arranged in the same layer. Along the thickness direction Z of the BAW filter 100, the first series resonator 11 overlaps with the second series resonator 12 or the second parallel resonator 22. Along the thickness direction Z of the BAW filter 100, the first parallel resonator 21 overlaps with the second series resonator 12 or the second parallel resonator 22.

[0063] Figure 3 and Figure 4 The embodiment shown only shows the first series resonator 11 and the second series resonator 12 arranged in an overlapping manner along the thickness direction Z of the bulk acoustic wave filter 100, and does not show other overlapping arrangements and arrangements in the same layer, but those skilled in the art will understand from the following. Figure 2 It can be clearly known that the first series resonator 11 and the first parallel resonator 21 are arranged on the same layer, and the second series resonator 12 and the second parallel resonator are arranged on the same layer. Figure 3 and Figure 4 It can be clearly known that the first series resonator 11 overlaps with the second parallel resonator 22 , and the specific manner in which the first parallel resonator 21 overlaps with the second series resonator 12 or the second parallel resonator 22 .

[0064] For example, in Figure 3 In the illustrated embodiment, the first series resonator 11 includes a bonding layer 116 arranged in a Z-stacked manner along the thickness direction of the bulk acoustic wave, a second electrode 115, a piezoelectric layer 114, a first electrode 113, an acoustic reflector 112 formed by alternating at least one layer of high acoustic impedance material and at least one layer of low acoustic impedance material, and a substrate 111. The second series resonator 12 includes a substrate 121 arranged in a Z-stacked manner along the thickness direction of the bulk acoustic wave, an acoustic reflector 122 formed by alternating at least one layer of high acoustic impedance material and at least one layer of low acoustic impedance material, a first electrode 123, a piezoelectric layer 124, a second electrode 125, and a bonding layer 126.

[0065] As a feasible implementation, the first series resonator 11 and the second series resonator 12 may be prepared separately, and finally the first series resonator 11 and the second series resonator 12 may be overlapped and arranged together by bonding the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12 .

[0066] Specifically, the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12 can both be made of silicon dioxide, and the bonding of the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12 can be achieved by directly bonding silicon dioxide to silicon dioxide (i.e., forming a covalent bond).

[0067] It should be noted that the first series resonator 11 and the first parallel resonator 21 are arranged in the same layer, and when the first series resonator 11 is prepared, the first parallel resonator 21 having the same structural material as the first series resonator 11 is also prepared. The second series resonator 12 and the second parallel resonator 22 are arranged in the same layer, and when the second series resonator 12 is prepared, the second parallel resonator 22 having the same structural material as the second series resonator 12 is also prepared.

[0068] For example, in Figure 4 In the illustrated embodiment, the first series resonator 11 includes a bonding layer 116, a second electrode 115, a piezoelectric layer 114, a first electrode 113, an acoustic reflector 112 formed by alternating at least one layer of high acoustic impedance material and at least one layer of low acoustic impedance material, and a substrate 111. The second series resonator 12 includes a substrate 121, a first electrode 123, a piezoelectric layer 124, a second electrode 125, and a bonding layer 126, which are stacked in a Z-direction of the thickness of the bulk acoustic wave.

[0069] As a feasible implementation, the first series resonator 11 and the second series resonator 12 composed of the substrate 121, the piezoelectric layer 124, the second electrode 125 and the bonding layer 126 can be prepared separately, and then the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12 are bonded to overlap the first series resonator 11 and the second series resonator 12, and finally the substrate 121 of the second series resonator 12 is etched and the first electrode 123 is deposited to form a series resonator 11. Figure 4 A bulk acoustic wave filter 100 is shown.

[0070] The specific bonding method of the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12 in the embodiment of the present invention can be referred to the above description, which will not be repeated here.

[0071] It should be noted that the first series resonator 11 and the first parallel resonator 21 are arranged in the same layer. When preparing the first series resonator 11, the first parallel resonator 21 with the same structural material as the first series resonator 11 is also prepared. The second series resonator 12 and the second parallel resonator 22 are arranged in the same layer. When preparing the second series resonator 12, the second parallel resonator 22 with the same structural material as the second series resonator 12 is also prepared. Finally, the first series resonator 11 and the second series resonator 12 can be overlapped and arranged together by bonding the bonding layer 116 of the first series resonator 11 and the bonding layer 126 of the second series resonator 12.

[0072] It should also be noted that the connection between the first series resonator 11 and the second series resonator 12 or the second parallel resonator 22, and the connection between the first parallel resonator 21 and the second series resonator 12 or the second parallel resonator 22 can be connected by vias ( Figure 3 and Figure 4 not shown).

[0073] In the embodiment of the present invention, along the thickness direction Z of the bulk acoustic wave filter 100, the first series resonator 11 and the first parallel resonator 21 are arranged on the same layer, the second series resonator 12 and the second parallel resonator are arranged on the same layer, the first series resonator 11 overlaps with the second series resonator 12 or the second parallel resonator 22, and the first parallel resonator 21 overlaps with the second series resonator 12 or the second parallel resonator 22, thereby effectively reducing the area of ​​the bulk acoustic wave filter 100 and achieving miniaturization.

[0074] Optional, Figure 5 A circuit diagram of another bulk acoustic wave filter provided by an embodiment of the present invention, referring to Figure 5 The bulk acoustic wave filter 100 further includes a first inductor L1, a second inductor L2 and a plurality of third inductors L3. The first inductor L1 is connected between the input terminal in and the series resonator 10. The second inductor L2 is connected between the series resonator 10 and the output terminal out. The third inductor L3 is connected between the parallel resonator 20 and the ground terminal.

[0075] The arrangement of the first inductor L1 , the second inductor L2 and the plurality of third inductors L3 can effectively suppress high-frequency interference, retain low-frequency signals, suppress power pulsation, filter out high-frequency noise, etc., thereby improving the stability and reliability of the BAW filter 100 .

[0076] Based on the same inventive concept, an embodiment of the present invention provides a multiplexer 200, Figure 6A circuit diagram of a multiplexer provided in an embodiment of the present invention includes an antenna 201, at least one receiving unit 202 and at least one transmitting unit 203. The antenna 201 is connected to the receiving unit 202 and the transmitting unit 203 for communication. At least one of the receiving unit 202 and the transmitting unit 203 includes the bulk acoustic wave filter 100 provided in any of the above embodiments. Therefore, the multiplexer includes the technical features of the bulk acoustic wave filter 100 and has the beneficial effects of the bulk acoustic wave filter 100. The same as that of the bulk acoustic wave filter 100 can be referred to the above description.

[0077] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A bulk acoustic wave filter, characterized in that: comprising an input terminal, an output terminal, a plurality of series resonators and a plurality of parallel resonators; The series resonator is connected in series between the input terminal and the output terminal, and the parallel resonator is connected between one end of the series resonator and a ground terminal; The plurality of series resonators include at least one first series resonator and at least one second series resonator; the plurality of parallel resonators include at least one first parallel resonator and at least one second parallel resonator; There is a distance between the first series resonator and the input terminal that is smaller than a distance between the second series resonator and the input terminal; There is a distance between the first parallel resonator and the input terminal that is smaller than a distance between the second parallel resonator and the input terminal; The thermal conductivity of the piezoelectric layer in the first series resonator is greater than the thermal conductivity of the piezoelectric layer in the second series resonator and the second parallel resonator; The thermal conductivity of the piezoelectric layer in the first parallel resonator is greater than the thermal conductivity of the piezoelectric layer in the second series resonator and the second parallel resonator.

2. The bulk acoustic wave filter according to claim 1, characterized in that The relative dielectric constant of the piezoelectric layer in the first series resonator is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator and the second parallel resonator; the relative dielectric constant of the piezoelectric layer in the first parallel resonator is smaller than the relative dielectric constant of the piezoelectric layer in the second series resonator and the second parallel resonator.

3. The bulk acoustic wave filter according to claim 1, wherein: An area of ​​the active region of the first series resonator is greater than an area of ​​the active region of the second series resonator and the second parallel resonator; an area of ​​the active region of the first parallel resonator is greater than an area of ​​the active region of the second series resonator and the second parallel resonator.

4. The bulk acoustic wave filter according to claim 1, wherein: The scandium content of the piezoelectric layer in the first series resonator is less than the scandium content of the piezoelectric layer in the second series resonator and the second parallel resonator; the scandium content of the piezoelectric layer in the first parallel resonator is less than the scandium content of the piezoelectric layer in the second series resonator and the second parallel resonator.

5. The bulk acoustic wave filter according to claim 4, characterized in that The scandium content C1 of the piezoelectric layer in the first series resonator satisfies 0≤C1≤9.5%; The scandium content C2 of the piezoelectric layer in the second series resonator satisfies 9.5%<C2≤40%; The scandium content C3 of the piezoelectric layer in the first parallel resonator satisfies 0≤C3≤9.5%; The scandium content C4 of the piezoelectric layer in the second parallel resonator satisfies 9.5%<C4≤40%.

6. The bulk acoustic wave filter according to claim 1, wherein: There is an area of ​​the first series resonator that is smaller than an area of ​​the second series resonator.

7. The bulk acoustic wave filter according to claim 1, wherein: Along the thickness direction of the BAW filter, the first series resonator, the second series resonator, the first parallel resonator, and the second parallel resonator are arranged in the same layer.

8. The bulk acoustic wave filter according to claim 1, wherein: Along the thickness direction of the BAW filter, the first series resonator and the first parallel resonator are arranged in the same layer, and the second series resonator and the second parallel resonator are arranged in the same layer; Along the thickness direction of the BAW filter, the first series resonator overlaps with the second series resonator or the second parallel resonator; The first parallel resonator overlaps with the second series resonator or the second parallel resonator along a thickness direction of the BAW filter.

9. The bulk acoustic wave filter according to claim 1, wherein: The BAW filter further includes a first inductor, a second inductor and a plurality of third inductors; The first inductor is connected between the input terminal and the series resonator; The second inductor is connected between the series resonator and the output terminal; The third inductor is connected between the parallel resonator and the ground terminal.

10. A multiplexer, characterized in that: comprising an antenna, at least one receiving unit and at least one transmitting unit; The antenna is communicatively connected to the receiving unit and the sending unit respectively; At least one of the receiving unit and the transmitting unit comprises a bulk acoustic wave filter as claimed in any one of claims 1 to 9.

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