WO2023000228A1

WO2023000228A1 - Radio frequency filter and electronic device

Info

Publication number: WO2023000228A1
Application number: PCT/CN2021/107703
Authority: WO
Inventors: 侯航天; 罗天成; 孙成亮; 高宗智
Original assignee: 华为技术有限公司
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2023-01-26
Also published as: CN117178481A

Abstract

The present application relates to the technical field of communications and provides a radio frequency filter and an electronic device, for improving the frequency of a radio frequency filter. The radio frequency filter has an input terminal and an output terminal, and comprises a first bulk acoustic wave resonator connected in series between the input terminal and a first node, and a second bulk acoustic wave resonator connected in parallel between the first node and a ground terminal, and the first node is coupled to the output terminal, wherein the first bulk acoustic wave resonator comprises a substrate, a bottom electrode, a first piezoelectric structure layer and a top electrode which are sequentially stacked, the first piezoelectric structure layer comprises at least two piezoelectric layers which are stacked, and an intermediate electrode is disposed between any two adjacent piezoelectric layers in the at least two piezoelectric layers; the second bulk acoustic wave resonator comprises a substrate, a bottom electrode, a second piezoelectric structure layer and a top electrode which are sequentially stacked, and the second piezoelectric structure layer comprises at least one piezoelectric layer. The number of the piezoelectric layers comprised in the first piezoelectric structure layer is different from the number of piezoelectric layers comprised in the second piezoelectric structure layer.

Description

A radio frequency filter and electronic equipment

technical field

The present application relates to the technical field of communication, in particular to a radio frequency filter and electronic equipment.

Background technique

RF filters play an extremely important role in the communication field. In order to meet the growing communication needs, RF filters must meet the requirements of high frequency, integration, miniaturization, low power consumption, high performance, and low cost. Resonators are the main components of radio frequency filters, usually including bulk acoustic wave resonators (bulk acoustic wave resonators, BAWR) and surface acoustic wave resonators (surface acoustic wave resonators, SAWR), bulk acoustic wave resonators compared with surface acoustic wave resonators It has excellent properties such as small size, high process compatibility and is conducive to the development of miniaturization, so it is widely used in the high frequency field. With the commercialization of the fifth-generation mobile communication, when BAW resonators work in higher frequency bands, higher requirements are put forward for the performance of BAW resonators and filters. Therefore, a new method is needed to improve the performance of RF filters.

Contents of the invention

Embodiments of the present application provide a radio frequency filter and electronic equipment, which are used to improve the performance of the radio frequency filter.

In order to achieve the above object, the embodiments of the present application adopt the following technical solutions:

The first aspect provides a radio frequency filter, the radio frequency filter has an input end and an output end, the radio frequency filter includes: a first bulk acoustic wave resonator connected in series between the input end and the first node, and a first bulk acoustic wave resonator connected in parallel between the input end and the first node The second bulk acoustic wave resonator between the first node and the ground terminal, the first node is coupled to the output end; wherein, the first bulk acoustic wave resonator includes a substrate, a bottom electrode, a first piezoelectric A structural layer and a top electrode, the first piezoelectric structural layer includes at least two piezoelectric layers stacked, and an intermediate electrode is arranged between any adjacent two piezoelectric layers in the at least two piezoelectric layers; the second piezoelectric layer The two-body acoustic wave resonator comprises a substrate, a bottom electrode, a second piezoelectric structure layer and a top electrode stacked in sequence, the second piezoelectric structure layer comprises at least one piezoelectric layer; the first piezoelectric structure layer comprises The number of piezoelectric layers is different from the number of piezoelectric layers included in the second piezoelectric structural layer.

In the above technical solution, the frequency of the radio frequency filter depends on the frequencies of the first BAW resonator and the second BAW resonator, since the frequencies of the first BAW resonator and the second BAW resonator depend on the first pressure The number of piezoelectric layers and intermediate electrodes in the electrical structure layer and the second piezoelectric structure layer, the more the number of piezoelectric layers and intermediate electrodes, the higher the frequency of the first BAW resonator and the second BAW resonator. Under the premise of not reducing the thickness of the piezoelectric layer, bottom electrode, middle electrode and top electrode, the frequency differential adjustment of the first bulk acoustic wave and the second resonator bulk acoustic wave is realized by introducing different quantities of piezoelectric layers, and then The performance of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator is guaranteed, therefore, using the radio frequency filter formed by the first bulk acoustic wave resonator and the second bulk acoustic wave resonator, the radio frequency filter is improved. performance.

In a possible implementation manner of the first aspect, the number of piezoelectric layers included in the first piezoelectric structure layer is greater than the number of piezoelectric layers included in the second piezoelectric structure layer. In the above possible implementation manner, the frequency of the first BAW resonator is greater than the frequency of the second BAW resonator without changing the thicknesses of the piezoelectric layer, the bottom electrode, the middle electrode and the top electrode.

In a possible implementation manner of the first aspect, a groove is provided on a side of the substrate close to the bottom electrode, so that an air cavity is formed when the bottom electrode is stacked on the substrate. In the above possible implementation manner, during the resonant process of the first BAW resonator and the second BAW resonator, due to the existence of the air cavity, the energy cannot leak in the substrate, but is confined in the piezoelectric layer , thereby forming the first BAW resonator and the second BAW resonator with a high quality factor.

In a possible implementation manner of the first aspect, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator further include: an acoustic reflection layer stacked between the substrate and the bottom electrode between. In the above possible implementation, due to the existence of the acoustic reflection layer, the energy cannot leak in the substrate, but is confined in the piezoelectric layer, thereby forming the first BAW resonator and the second BAW resonator with high quality factor .

In a possible implementation manner of the first aspect, the at least two piezoelectric layers include three piezoelectric layers or four piezoelectric layers. In the above possible implementation manner, when the at least two piezoelectric layers include three or four piezoelectric layers, each adjacent two piezoelectric layers in the three or four piezoelectric layers are provided with The middle electrode is the common electrode of the adjacent two piezoelectric layers. At this time, the resonance effective area includes three or four resonance effective areas, which is equivalent to each resonance effective area including one piezoelectric layer and The four-thirds layer of electrodes or each resonance effective area includes one piezoelectric layer and five-quarters of layers of electrodes. Compared with a bulk acoustic wave resonator composed of one piezoelectric layer and two layers of electrodes, the resonance effective area is thinner, thereby increasing the frequencies of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator.

In a possible implementation manner of the first aspect, when the at least one piezoelectric layer includes two or more piezoelectric layers stacked, any of the two or more piezoelectric layers An intermediate electrode is arranged between two adjacent piezoelectric layers. In the above possible implementation mode, an intermediate electrode is arranged between any two adjacent piezoelectric layers in the two or more piezoelectric layers, and the intermediate electrode is a common electrode of the two adjacent piezoelectric layers. , at this time, the resonance effective area includes two or more resonance effective areas, which is equivalent to each resonance effective area including one piezoelectric layer and one-half layer of electrodes or one piezoelectric layer and less electrode. Compared with a bulk acoustic wave resonator composed of one piezoelectric layer and two layers of electrodes, the resonance effective area is thinner, thereby increasing the frequencies of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator.

In a possible implementation manner of the first aspect, the at least one piezoelectric layer includes two piezoelectric layers or three piezoelectric layers. In the above possible implementation manner, an intermediate electrode is arranged between any adjacent two piezoelectric layers of the two piezoelectric layers or three piezoelectric layers, and the intermediate electrode is a common electrode of the two adjacent piezoelectric layers. electrode, at this time, the resonance effective area includes two or three resonance effective areas, which is equivalent to each resonance effective area including 1 layer of piezoelectric layer and 1/2 layer of electrode or 1 layer of piezoelectric layer and 4/3 the electrodes. Compared with a bulk acoustic wave resonator composed of one piezoelectric layer and two layers of electrodes, the resonance effective area is thinner, thereby increasing the frequencies of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator.

In a possible implementation manner of the first aspect, the piezoelectric layers in the first piezoelectric structure layer and the second piezoelectric structure layer have the same thickness. In the above possible implementation manners, the same thickness of the piezoelectric layer reduces the difficulty of integrated processing of the filter.

In a possible implementation manner of the first aspect, the radio frequency filter further includes: a third BAW resonator connected in series between the first node and the output terminal, and a third BAW resonator connected in parallel between the output terminal and the ground terminal The fourth BAW resonator between them; the third BAW resonator includes a substrate, a bottom electrode, a third piezoelectric structure layer and a top electrode stacked in sequence, and the third piezoelectric structure layer includes at least Two piezoelectric layers, an intermediate electrode is arranged between any adjacent two piezoelectric layers in the at least two piezoelectric layers; the fourth bulk acoustic wave resonator includes a substrate, a bottom electrode, and a fourth bulk acoustic wave resonator stacked in sequence. A piezoelectric structural layer and a top electrode, the fourth piezoelectric structural layer includes at least one piezoelectric layer; the number of piezoelectric layers included in the third piezoelectric structural layer is the same as the number of piezoelectric layers included in the fourth piezoelectric structural layer The number is different. In the foregoing possible implementation manner, the frequency of the filter is further increased by adding a third BAW resonator connected in series and a fourth BAW resonator connected in parallel.

In a possible implementation manner of the first aspect, the number of piezoelectric layers included in the third piezoelectric structure layer is greater than the number of piezoelectric layers included in the fourth piezoelectric structure layer. In the foregoing possible implementation manner, it is ensured that the frequency of the third BAW resonator is higher than the frequency of the fourth BAW resonator.

In a possible implementation manner of the first aspect, the thickness of the piezoelectric layer in the third piezoelectric structure layer and the fourth piezoelectric structure layer is different from the thickness of the piezoelectric layer included in the first piezoelectric structure layer same. In the above possible implementation manner, the frequencies of the third BAW resonator and the fourth BAW resonator are increased by increasing the number of piezoelectric layers in the third piezoelectric structure layer and the fourth piezoelectric structure layer , the more the number of piezoelectric layers in the third piezoelectric structure layer and the fourth piezoelectric structure layer, the higher the frequency of the third bulk acoustic resonator and the fourth bulk acoustic wave resonator, and on this basis The thickness of the piezoelectric layer is not reduced, thereby ensuring the performance of the third BAW resonator and the fourth BAW resonator, thereby ensuring the performance of the filter.

In a possible implementation manner of the first aspect, the material of the substrate is any one of silicon, silicon carbide, aluminum oxide, or silicon-on-insulator (SOI). In the above possible implementation manners, different materials have different properties, and thus the properties of the substrates formed by them are also different. For example, silicon is a good conductor of heat, so the silicon substrate has good thermal conductivity; silicon carbide has good electrical and thermal conductivity, so the substrate has good electrical and thermal conductivity; aluminum oxide has good stability, High mechanical strength, easy to handle and clean and can be used in high temperature growth process, so the quality of alumina substrate is high and the production technology of alumina substrate is mature.

In a possible implementation manner of the first aspect, the piezoelectric layer is made of one or more combinations of aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate, and barium sodium niobate. In the above possible implementation manners, the diversity and flexibility of selection are improved, and different materials can be selected according to actual needs in practical applications.

In a possible implementation of the first aspect, the material of any one of the bottom electrode, the middle electrode and the top electrode is molybdenum, platinum, gold, silver, aluminum, tungsten, titanium, copper, ruthenium and chromium One or more combinations of them. In the above possible implementation manners, the diversity and flexibility of selection are improved.

In a possible implementation manner of the first aspect, the acoustic reflective layer is alternately composed of high acoustic impedance materials and low acoustic impedance materials. In the above possible implementation manner, during the resonant process of the first BAW resonator and the second BAW resonator, due to the presence of acoustic reflection layers alternately composed of high acoustic impedance materials and low acoustic impedance materials, the energy Cannot leak in the substrate, but is confined in the piezoelectric layer, thereby forming the first BAW resonator and the second BAW resonator with a high quality factor.

In a possible implementation manner of the first aspect, the high acoustic impedance material includes one or more combinations of tungsten, molybdenum, and tantalum pentoxide. In the above possible implementation manners, the diversity and flexibility of selection are improved.

In a possible implementation manner of the first aspect, the low acoustic impedance material includes one or more combinations of silicon dioxide and silicon nitride. In the above possible implementation manners, the diversity and flexibility of selection are improved.

In a second aspect, an electronic device is provided, the electronic device includes a processor, a radio frequency circuit and an antenna coupled in sequence, the radio frequency circuit can be used to receive or send a signal through the antenna, and the processor can be used to process the signal of the radio frequency circuit; Wherein, the radio frequency circuit includes a radio frequency filter, and the radio frequency filter is the radio frequency filter provided in the first aspect or any possible implementation manner of the first aspect.

It can be understood that any of the devices provided above can be used to implement the corresponding method provided above, therefore, the beneficial effects it can achieve can refer to the beneficial effects in the corresponding method provided above, here No longer.

Description of drawings

FIG. 1 is a schematic structural diagram of a surface acoustic wave resonator and a bulk acoustic wave resonator provided in an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a bulk acoustic wave resonator provided in the prior art;

FIG. 3 is a schematic structural diagram of an electronic device provided in an embodiment of the present application;

FIG. 4 is a schematic structural diagram of a radio frequency filter provided in an embodiment of the present application;

FIG. 5 is a schematic structural diagram of another radio frequency filter provided by an embodiment of the present application;

FIG. 6 is a schematic structural diagram of an acoustic reflection layer provided in an embodiment of the present application;

FIG. 7 is a schematic structural diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;

FIG. 8 is a schematic structural diagram of another bulk acoustic wave resonator provided in an embodiment of the present application;

FIG. 9 is a schematic structural diagram of another bulk acoustic wave resonator provided in an embodiment of the present application;

FIG. 10 is a schematic diagram of an amplitude trend of a resonant frequency provided by an embodiment of the present application;

Fig. 11 is a schematic diagram of the amplitude trend of quality factor, frequency and piezoelectric coupling coefficient provided by the embodiment of the present application;

FIG. 12 is a schematic structural diagram of a radio frequency filter provided in an embodiment of the present application;

FIG. 13 is a schematic structural diagram of another radio frequency filter provided by the embodiment of the present application;

FIG. 14 is a schematic structural diagram of another radio frequency filter provided in the embodiment of the present application;

Fig. 15 is a schematic diagram of an electrode shape provided by an embodiment of the present application;

Fig. 16 is a schematic flowchart of a method for manufacturing a bulk acoustic wave resonator provided in an embodiment of the present application.

detailed description

In this application, "at least one" means one or more, and "multiple" means two or more. "And/or" describes the association relationship of associated objects, indicating that there can be three types of relationships, for example, "A and/or B", which can indicate: A exists alone, A and B exist simultaneously, and B exists alone, among which A, B can be singular or plural. The character "/" generally indicates that the contextual objects are an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one item (piece) of a, b, or c can represent: a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, c can be single or multiple .

The embodiments of the present application use words such as "first" and "second" to distinguish the same or similar items with basically the same function and effect. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their sequence is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order.

It should be noted that, in this application, words such as "exemplary" or "for example" are used as examples, illustrations or illustrations. Any embodiment or design described herein as "exemplary" or "for example" is not to be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete manner.

RF filters play an extremely important role in the communication field. In order to meet the growing communication needs, RF filters must meet the requirements of high frequency, integration, miniaturization, low power consumption, high performance, and low cost. Resonators are the main components of RF filters, usually including surface acoustic wave resonators (SAWR) and bulk acoustic wave resonators (BAWR). FIG. 1 is a schematic structural diagram of a surface acoustic wave resonator and a bulk acoustic wave resonator provided in an embodiment of the present application. As shown in (a) of FIG. 1 , the surface acoustic wave resonator includes a substrate 101 , a piezoelectric layer 102 and a plurality of electrodes 103 disposed on the side of the piezoelectric layer 102 away from the substrate 101 . As shown in (b) in Figure 1, the bulk acoustic wave resonator includes a silicon substrate 101, a bottom electrode 103, a piezoelectric layer 104, and a top electrode 105 that are stacked in sequence, and the side of the silicon substrate 101 that is close to the bottom electrode 103 Grooves are provided to form an air cavity 102 when the bottom electrode 103 is stacked on the silicon substrate 101 . Among them, the surface acoustic wave resonator has a simple process and mature production, but due to the limitation of the lithography machine process, it is difficult to reach a frequency above 2.5 gigahertz (GHz), and due to its own structural characteristics, it is different from the bulk acoustic wave resonator. Compared with the large size, it is not compatible with the integrated circuit (integrated circuit, IC) process, which is not conducive to the development of miniaturization. The bulk acoustic wave resonator has excellent performances such as small size, high process compatibility, easy realization of high frequency, and favorable miniaturization development, so it is widely used in the communication field.

The prior art provides a bulk acoustic wave resonator, usually by reducing the thickness of the electrodes and piezoelectric layers to increase the frequency of the bulk acoustic wave resonator, as shown in Figure 2, the bulk acoustic wave resonator includes substrates 201 stacked in sequence , a bottom electrode 203 , a piezoelectric layer 204 and a top electrode 205 , a groove is provided on a side of the substrate 201 close to the bottom electrode 203 , so that an air cavity 202 is formed when the bottom electrode 203 is stacked on the substrate 201 . The frequency of the bulk acoustic wave resonator is increased by reducing the thickness of the bottom electrode 203, top electrode 205 and piezoelectric layer 204, when the thickness of the bottom electrode 203, top electrode 205 and piezoelectric layer 204 is reduced, the frequency of the bulk acoustic wave resonator improve.

However, while reducing the thickness of the bottom electrode 203 and the top electrode 205, the resistivity of the electrodes will also be increased, thereby increasing the resistance of the BAW resonator, resulting in an increase in the insertion loss of the BAW resonator. In addition, reducing the thickness of the piezoelectric layer 204 increases the difficulty of manufacturing the piezoelectric layer and reduces the quality of the piezoelectric layer crystal, thereby affecting the piezoelectric coupling coefficient and quality factor of the bulk acoustic wave resonator, thereby reducing the bulk acoustic resonance. device performance.

Based on this, the present application provides a radio frequency filter, which can be used to increase frequency. The radio frequency filter can be applied in electronic equipment. The electronic devices may include, but are not limited to, personal computers, server computers, mobile devices (such as mobile phones, tablet computers, media players, etc.), wearable devices, vehicle-mounted devices, consumer electronics devices, mobile robots, and drones. The specific structure of the electronic device will be described below.

FIG. 3 is a schematic structural diagram of an electronic device provided in an embodiment of the present application, and the electronic device is described by taking a mobile device as an example. As shown in FIG. 3 , the electronic device may include: a memory 301 , a processor 302 , a radio frequency circuit 303 , an antenna 304 and an input/output interface 305 .

Among them, the memory 301 can be used to store data, software programs and software modules; mainly includes a program storage area and a data storage area, wherein the program storage area can store the operating system and at least one application program required by a function, such as a sound playback function or an image playback function, etc.; the storage data area can store data created according to the use of the electronic device, such as audio data, image data, and the like. In addition, the electronic device may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage devices.

The processor 302 is the control center of the electronic device, which uses various interfaces and lines to connect various parts of the entire device, runs or executes the software program and/or software module stored in the memory 301, and calls the data stored in the memory 301 , to perform various functions of the electronic equipment and process data, so as to monitor the electronic equipment as a whole. Optionally, the processor 302 may include one or more processing units, for example, the processor 302 may include a central processing unit (central processing unit, CPU), an application processor (application processor, AP), a modem processor , graphics processing unit (graphics processing unit, GPU), image signal processor (image signal processor, ISP), controller, video codec, digital signal processor (digital signal processor, DSP), baseband processor and/or Neural-network processing unit (NPU), etc. Wherein, different processing units may be independent devices, or may be integrated in one or more processors.

The radio frequency circuit 303 is mainly used for converting baseband signals and radio frequency signals and processing radio frequency signals. In the embodiment of the present application, the radio frequency circuit 303 may include the radio frequency filter provided herein, and the radio frequency filter may be used to effectively filter the frequency point of a specific frequency in the radio frequency circuit 303 or frequencies other than the frequency point, to obtain A baseband or radio frequency signal of a specific frequency.

The antenna 304 is mainly used for sending and receiving radio frequency signals in the form of electromagnetic waves. The integration of the antenna 304 and the radio frequency circuit 303 may also be called a transceiver.

The input/output interface 305 provides an interface between the processor 302 and a peripheral interface module. For example, the peripheral interface module can be a keyboard, a mouse, or a universal serial bus (universal serial bus, USB) device, etc.

The working process of each part of the above-mentioned electronic device is described in detail by taking the mobile device as an example. When the mobile device is started, the processor 302 can read the software program in the memory 301, interpret and execute the instructions of the software program, and process the data of the software program. When it is necessary to transmit data wirelessly, the processor 302 performs baseband processing on the data to be transmitted, and then outputs the baseband signal to the radio frequency circuit 303, and the radio frequency circuit 303 performs radio frequency processing on the baseband signal, and sends the radio frequency signal outward in the form of electromagnetic waves through the antenna 304. send. When data is sent to the mobile device, the radio frequency circuit 303 receives the radio frequency signal through the antenna 304, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor 302, and the processor 302 converts the baseband signal into data and converts the baseband signal to the The data is processed and stored in memory 301 .

It should be noted that FIG. 3 only shows one memory and one processor. In an actual electronic device, there may be multiple processors and multiple memories, and the memories may also be called storage media or storage devices. This embodiment of the present application does not limit it.

FIG. 4 is a schematic structural diagram of a radio frequency filter provided by an embodiment of the present application. The radio frequency filter has an input terminal and an output terminal. The radio frequency filter includes: a first node connected in series between the input terminal and the first node P1 A bulk acoustic wave resonator, and a second bulk acoustic wave resonator connected in parallel between the first node P1 and the ground terminal, the first node P1 is coupled to the output terminal. In FIG. 4, the radio frequency filter includes a first BAW resonator and a second BAW resonator as an example for illustration.

In the embodiment of the present application, the first bulk acoustic wave resonator may include a substrate 40, a bottom electrode 42, a first piezoelectric structure layer 43, and a top electrode 44 that are sequentially stacked, and the first piezoelectric structure layer 43 includes a stack At least two piezoelectric layers are provided, and an intermediate electrode is arranged between any two adjacent piezoelectric layers in the at least two piezoelectric layers. Wherein, the at least two piezoelectric layers may include two piezoelectric layers, three piezoelectric layers, four piezoelectric layers, or more than four piezoelectric layers. Exemplarily, as shown in FIG. 4, the at least two piezoelectric layers include two piezoelectric layers, the two piezoelectric layers are a first piezoelectric layer 431 and a second piezoelectric layer 433, and the first piezoelectric layer An intermediate electrode 432 is arranged between the layer 431 and the second piezoelectric layer 433 .

The second BAW resonator may include a substrate 50 , a bottom electrode 52 , a second piezoelectric structure layer 53 and a top electrode 54 which are stacked in sequence, and the second piezoelectric structure layer 53 includes at least one piezoelectric layer. Wherein, the at least one piezoelectric layer may include one piezoelectric layer or two or more than two piezoelectric layers stacked, when the at least one piezoelectric layer includes two or more than two piezoelectric layers In the case of a piezoelectric layer, an intermediate electrode is arranged between any two adjacent piezoelectric layers of the two piezoelectric layers or more than two piezoelectric layers. Exemplarily, as shown in FIG. 4 , the at least one piezoelectric layer includes one piezoelectric layer, and the piezoelectric layer is a third piezoelectric layer 531 .

In the embodiment of the present application, for the first piezoelectric structural layer 43 and the second piezoelectric structural layer 53 in the above-mentioned first bulk acoustic resonator and second bulk acoustic resonator, the first piezoelectric structural layer 43 The number of piezoelectric layers included is different from the number of piezoelectric layers included in the second piezoelectric structure layer 53 . Optionally, the number of piezoelectric layers included in the first piezoelectric structure layer 43 may be greater than the number of piezoelectric layers included in the second piezoelectric structure layer 53 . Exemplarily, the number of piezoelectric layers included in the first piezoelectric structure layer 43 is A, and the number of piezoelectric layers included in the second piezoelectric structure layer 53 is B, where A is different from B, for example, A greater than B.

In addition, the piezoelectric layers in the first piezoelectric structure layer 43 and the second piezoelectric structure layer 53 have the same thickness. Exemplarily, the first piezoelectric layer 43 includes a first piezoelectric layer 431 and the second piezoelectric layer 433, the second piezoelectric layer 53 includes a third piezoelectric layer 531, and the first piezoelectric layer 431 The thickness of the second piezoelectric layer 433 is the same as L1, and the thickness of the third piezoelectric layer 531 is also L1.

In a possible embodiment, as shown in FIG. 4, in the first BAW resonator, a groove is provided on the side of the substrate 40 close to the bottom electrode 42, so that the bottom electrode 42 is stacked on the substrate. An air cavity 41 is formed when the bottom 40 is on. Similarly, in the second BAW resonator, a groove is provided on a side of the substrate 50 close to the bottom electrode 52 , so that an air cavity 51 is formed when the bottom electrode 52 is stacked on the substrate 50 .

Or, in another possible embodiment, as shown in FIG. 5 , the above-mentioned first BAW resonator further includes an acoustic reflection layer 41, and the acoustic reflection layer 41 is stacked between the substrate 40 and the bottom electrode 42. between. Similarly, the second BAW resonator further includes an acoustic reflection layer 51 stacked between the substrate 50 and the bottom electrode 52 . The acoustic reflective layer 41 and the acoustic reflective layer 51 may be alternately composed of high acoustic impedance materials and low acoustic impedance materials. Wherein, the acoustic reflection layer may also be called a Bragg reflection layer or a phonon crystal structure, and the phonon crystal structure may be a structure that satisfies the elastic constant and density periodic distribution. In Fig. 5, the radio frequency filter includes a first bulk acoustic wave resonator and a second bulk acoustic wave resonator, the first bulk acoustic wave resonator includes two piezoelectric layers stacked, and the second bulk acoustic wave resonator A piezoelectric layer is included as an example for illustration.

In the following, the acoustic reflection layer 41 and the acoustic reflection layer 51 in the first bulk acoustic wave resonator and the second bulk acoustic wave resonator both include four layers for illustration. Exemplarily, as shown in FIG. 6 , the acoustic reflection layer The reflective layer includes a first layer, a second layer, a third layer and a fourth layer stacked in sequence; wherein, the first layer and the third layer are high acoustic impedance materials, and the second layer and the fourth layer are A low acoustic impedance material; or, the first layer and the third layer are low acoustic impedance materials, and the second layer and the fourth layer are high acoustic impedance materials. It should be noted that the acoustic reflective layer 42 and the acoustic reflective layer 52 may include four layers but are not limited to four layers, and the specific number of layers may be set according to actual needs or the experience of relevant technical personnel, and this embodiment of the present application does not make specific limit

Both the first piezoelectric structural layer 43 of the first bulk acoustic resonator and the second piezoelectric structural layer 53 of the second bulk acoustic resonator may include different numbers of piezoelectric layers. 43 includes two piezoelectric layers, three piezoelectric layers and four piezoelectric layers stacked as examples for detailed description. The structure of the second piezoelectric structure layer 53 is similar to that of the first piezoelectric structure layer 43 , for details, please refer to the relevant description of the first piezoelectric structure layer 43 , which will not be repeated in this embodiment of the present application.

In the first embodiment, the first piezoelectric structure layer 43 includes two piezoelectric layers stacked. As shown in FIG. 7 , the first BAW resonator includes a substrate 40 , a bottom electrode 42 , a first piezoelectric layer 431 , a middle electrode 432 , a second piezoelectric layer 433 and a top electrode 44 which are stacked in sequence. Wherein, the side of the substrate 40 close to the bottom electrode 42 is provided with a groove, so that an air cavity 41 is formed when the bottom electrode 42 is stacked on the substrate 40 .

In this embodiment, an intermediate electrode 432 is provided between the first piezoelectric layer 431 and the second piezoelectric layer 433, and the intermediate electrode 432 is the connection between the first piezoelectric layer 431 and the second piezoelectric layer 433. Common electrodes, at this time, the first BAW resonator includes two effective resonant regions. Wherein, the first effective resonant region includes the bottom electrode 42, the first piezoelectric layer 431 and one-half of the middle electrode 432, and the second effective resonant region includes one-half of the middle electrode 432, the second piezoelectric layer 433 and The top electrode 44 , which is equivalent to each effective resonance area, includes one piezoelectric layer and three-half layers of electrodes. Compared with the BAW resonator shown in (b) in FIG. 1 , the resonance effective region is thinned, thereby increasing the frequency of the first BAW resonator.

In the second embodiment, the first piezoelectric structure layer 43 includes three piezoelectric layers stacked. As shown in FIG. 8, the first BAW resonator includes a substrate 40, a bottom electrode 42, a first piezoelectric layer 431, a first intermediate electrode 432, a second piezoelectric layer 433, and a second intermediate electrode stacked in sequence. 434 , the third piezoelectric layer 435 and the top electrode 44 . Wherein, the side of the substrate 40 close to the bottom electrode 42 is provided with a groove, so that an air cavity 41 is formed when the bottom electrode 42 is stacked on the substrate 40 .

In this embodiment, the first intermediate electrode 432 is the common electrode of the first piezoelectric layer 431 and the second piezoelectric layer 433, and the second intermediate electrode 434 is the common electrode of the second piezoelectric layer 433 and the third piezoelectric layer 433. The common electrode of layer 435. At this time, the first BAW resonator includes three resonance effective regions. Wherein, the first effective resonance area includes the bottom electrode 42, the first piezoelectric layer 431 and one third of the first intermediate electrode 432; the second effective area of resonance includes two thirds of the first intermediate electrode 432, the second piezoelectric layer Electric layer 433 and two-thirds of the second middle electrode 434; the third resonance effective region includes one-third of the second middle electrode 434, the third piezoelectric layer 435 and the top electrode 44, which is equivalent to each resonance The active area includes 1 piezoelectric layer and 4/3 layers of electrodes. Each resonance effective region is thinned compared to the first BAW resonator provided in FIG. 7 so that the frequency of the first BAW resonator is higher than that of the first BAW resonator provided in FIG. 7 described above.

In the third embodiment, the first piezoelectric structure layer 43 includes four piezoelectric layers stacked. As shown in FIG. 9, the first BAW resonator includes a substrate 40, a bottom electrode 42, a first piezoelectric layer 431, a first intermediate electrode 432, a second piezoelectric layer 433, and a second intermediate electrode stacked in sequence. 434 , the third piezoelectric layer 435 , the third middle electrode 436 , the fourth piezoelectric layer 437 and the top electrode 44 . Wherein, the side of the substrate 40 close to the bottom electrode 42 is provided with a groove, so that an air cavity 41 is formed when the bottom electrode 42 is stacked on the substrate 40 .

In this embodiment, the first intermediate electrode 432 is the common electrode of the first piezoelectric layer 431 and the second piezoelectric layer 433, and the second intermediate electrode 434 is the common electrode of the second piezoelectric layer 433 and the third piezoelectric layer 433. The common electrode of the layer 435 and the third intermediate electrode 436 are the common electrodes of the third piezoelectric layer 435 and the fourth piezoelectric layer 437, and at this time, the first BAW resonator includes four effective resonant regions. Wherein, the first effective resonance area includes the bottom electrode 42, the first piezoelectric layer 431 and a quarter of the first intermediate electrode 432; the second effective area of resonance includes three quarters of the first intermediate electrode 432, the second piezoelectric layer The electric layer 433 and two quarters of the second intermediate electrode 434; the third effective region of resonance includes two quarters of the second intermediate electrode 434, the third piezoelectric layer 435 and three quarters of the third intermediate electrode 436; the third The four resonance effective regions include one quarter of the third middle electrode 436 , the fourth piezoelectric layer 437 and the top electrode 44 , which is equivalent to each resonance effective region including one piezoelectric layer and five quarters of electrodes. Each resonance effective region is thinned compared to the first BAW resonator provided in FIG. 8 so that the frequency of the first BAW resonator is higher than that of the first BAW resonator provided in FIG. 8 .

The bulk acoustic wave resonator provided by the embodiment of the present application (including the first bulk acoustic wave resonator and the second bulk acoustic wave resonator) can increase the resonance frequency while ensuring the performance of the bulk acoustic wave resonator. When the piezoelectric structural layers (including the first piezoelectric structural layer 43 and the second piezoelectric structural layer 53) of the bulk acoustic wave resonator include different numbers of piezoelectric layers and intermediate electrodes through FIG. 10 and FIG. 11 respectively, The amplitude trends of the corresponding frequency, quality factor and piezoelectric coupling coefficient are illustrated.

Fig. 10 shows a schematic diagram of the amplitude trend of the resonant frequency of the bulk acoustic wave resonator when the piezoelectric structure layer includes different numbers of piezoelectric layers. In Fig. 10, the curve S01 represents the amplitude trend of the resonant frequency when the piezoelectric structure layer includes one piezoelectric layer, and the resonant frequency of the BAW resonator is 3*10 ⁹ (Hz); the curve S02 represents the piezoelectric The amplitude trend of the resonant frequency when the electrical structural layer includes 2 piezoelectric layers and 1 intermediate electrode. At this time, the resonant frequency of the BAW resonator is 3.4*10 ⁹ (Hz); Curve S03 indicates that the piezoelectric structural layer includes 3 The amplitude trend of the resonant frequency when there are two piezoelectric layers and two intermediate electrodes. At this time, the resonant frequency of the BAW resonator is 3.7*10 ⁹ (Hz); the curve S04 indicates that the piezoelectric structure layer includes four piezoelectric layers and The amplitude trend of the resonant frequency when there are 3 middle electrodes. At this time, the resonant frequency of the bulk acoustic wave resonator is 3.8*10 ⁹ (Hz); the curve S05 indicates that the piezoelectric structure layer includes 5 piezoelectric layers and 4 middle electrodes. The amplitude trend of the resonant frequency, at this time, the resonant frequency of the BAW resonator is 3.9*10 ⁹ (Hz). It can be seen that the resonant frequency of the bulk acoustic wave resonator increases with the increase of the piezoelectric layer and the number of intermediate electrodes in the piezoelectric structure layer. When the bulk acoustic wave resonator has 4 piezoelectric layers, the stray mode (the The stray mode means that other modes except the required resonance mode) are very small, so that the performance of the bulk acoustic wave resonator is guaranteed while increasing the resonance frequency of the bulk acoustic wave resonator.

Fig. 11 shows a schematic diagram of the amplitude trend of quality factor, resonance frequency, anti-resonance frequency and piezoelectric coupling coefficient of the bulk acoustic wave resonator when the piezoelectric structure layer includes different numbers of piezoelectric layers and intermediate electrodes. In Fig. 11, the curve S01 indicates that when the piezoelectric structure layer includes one piezoelectric layer, the amplitude trend of the piezoelectric coupling coefficient; the curve S02 indicates that when the piezoelectric structure layer includes two piezoelectric layers and one intermediate electrode, The amplitude trend of the resonance quality factor; the curve S03 indicates the amplitude trend of the anti-resonance quality factor when the piezoelectric structure layer includes 3 piezoelectric layers and 2 intermediate electrodes; the curve S04 indicates that the piezoelectric structure layer includes 4 piezoelectric layers and 3 intermediate electrodes, the amplitude trend of the anti-resonant frequency; the curve S05 indicates the amplitude trend of the resonant frequency when the piezoelectric structure layer includes 5 piezoelectric layers and 4 intermediate electrodes. It can be seen that when the number of piezoelectric layers in the piezoelectric structure layer increases from 1 to 4, and the number of intermediate electrodes increases from 0 to 3, the performance indicators of the BAW resonator do not change significantly. In the piezoelectric structure layer, when the number of piezoelectric layers is 5 and the number of intermediate electrodes is 4, other forms of stray modes become stronger and affect the quality factor of the resonator. With the increase of the number of piezoelectric layers, the efficiency of relative resonant frequency improvement decreases, and the performance of the resonator and the difficulty of manufacturing process also increase accordingly.

Further, the radio frequency filter may further include: a third BAW resonator connected in series between the first node and the output terminal, and a fourth BAW resonator connected in parallel between the output terminal and the ground terminal . Wherein, the third BAW resonator includes a substrate, a bottom electrode, a third piezoelectric structure layer and a top electrode stacked in sequence, the third piezoelectric structure layer includes at least two piezoelectric layers stacked, and the at least two An intermediate electrode is arranged between any two adjacent piezoelectric layers in the laminated piezoelectric layer. The fourth bulk acoustic wave resonator includes a substrate, a bottom electrode, a fourth piezoelectric structure layer and a top electrode stacked in sequence, and the fourth piezoelectric structure layer includes at least one piezoelectric layer. The number of piezoelectric layers included in the third piezoelectric structure layer is different from the number of piezoelectric layers included in the fourth piezoelectric structure layer.

In one embodiment, the number of piezoelectric layers included in the third piezoelectric structure layer is greater than the number of piezoelectric layers included in the fourth piezoelectric structure layer.

In one embodiment, the thickness of the piezoelectric layer in the third piezoelectric structure layer and the fourth piezoelectric structure layer is the same as the thickness of the piezoelectric layer included in the first piezoelectric structure layer and the first piezoelectric structure The piezoelectric layers included in the layers have the same thickness, that is, the piezoelectric layers included in the piezoelectric structure layers in the four bulk acoustic wave resonators all have the same thickness.

It should be noted that the structure of the third BAW resonator is similar to that of the above-mentioned first BAW resonator (the number of piezoelectric layers included may be the same or different), and the fourth BAW resonator is similar to the above-mentioned second BAW resonator. The structures are similar (the number of piezoelectric layers included may be the same or different). For specific descriptions, refer to the descriptions of the first BAW resonator and the second BAW resonator above, which will not be repeated here in the embodiments of the present application.

In a possible embodiment, the structures of the first BAW resonator and the third BAW resonator may be the same or different, when the structures of the first BAW resonator and the third BAW resonator When different, it specifically means that the number of piezoelectric layers included in the first BAW resonator and the third BAW resonator are different; the structure of the second BAW resonator and the fourth BAW resonator can be the same or Can be different, when the structure of the second bulk acoustic wave resonator and the fourth bulk acoustic wave resonator are different, it specifically means that the number of piezoelectric layers included in the second bulk acoustic wave resonator and the fourth bulk acoustic wave resonator is different .

Further, in the radio frequency filter, when the radio frequency filter includes a plurality of bulk acoustic wave resonators in series (the plurality of bulk acoustic wave resonators may include the first bulk acoustic wave resonator and the third bulk acoustic wave resonator above, as For convenience of description, hereinafter collectively referred to as a plurality of BAW resonators A), and a plurality of BAW resonators connected in parallel (the plurality of BAW resonators may include the second BAW resonator and the fourth BAW resonator above, for For convenience of description, when collectively referred to as a plurality of BAW resonators B below), the number of piezoelectric layers included in the piezoelectric structural layers in the plurality of BAW resonators A may be the same or different, and the number of piezoelectric layers in the plurality of BAW resonators B The number of piezoelectric layers included in the piezoelectric structure layer may also be the same or different. The radio frequency filter includes three bulk acoustic wave resonators A and three bulk acoustic wave resonators B, and the number of piezoelectric layers in each bulk acoustic wave resonator is illustrated through the following three embodiments.

In the first embodiment, as shown in FIG. 12, the radio frequency filter includes 3 bulk acoustic wave resonators A and can be represented as B1 to B3, and 3 bulk acoustic wave resonators B and can be represented as C1 to C3, B1 to B3 Each includes two piezoelectric layers, C1 to C3 each include a piezoelectric layer, B1 to B3 are connected in series between the input and output ends of the RF filter, and the point where B1 and B2 are connected in series is the first node The point where P1, B2 and B3 are connected in series is the second node P2, C1 is connected between the first node P1 and the ground terminal (GND), and C2 is connected between the second node P2 and the ground terminal (GND). , C3 is connected in parallel between the output terminal and the ground terminal (GND).

In the second embodiment, as shown in FIG. 13, the radio frequency filter includes 3 bulk acoustic wave resonators A and can be represented as B1 to B3, and 3 bulk acoustic wave resonators B and can be represented as C1 to C3, B1 to B3 All include three piezoelectric layers, C1 to C3 each include two piezoelectric layers, B1 to B3 are connected in series between the input and output ends of the RF filter, and the point where B1 and B2 are connected in series is the first node The point where P1, B2 and B3 are connected in series is the second node P2, C1 is connected between the first node P1 and the ground terminal (GND), and C2 is connected between the second node P2 and the ground terminal (GND). , C3 is connected in parallel between the output terminal and the ground terminal (GND).

In the third embodiment, as shown in FIG. 14, the radio frequency filter includes 3 bulk acoustic wave resonators A and can be represented as B1 to B3, and 3 bulk acoustic wave resonators B and can be represented as C1 to C3, B1 and B3 Both include three piezoelectric layers, B2 includes four piezoelectric layers, C1 and C2 include two piezoelectric layers, C3 includes one piezoelectric layer, and B1 to B3 are connected in series between the input end of the RF filter and Between the output terminals, the point where B1 and B2 are connected in series is the first node P1, the point where B2 and B3 are connected in series is the second node P2, and C1 is connected between the first node P1 and the ground terminal (GND), and C2 and connected between the second node P2 and the ground terminal (GND), and C3 is connected between the output terminal and the ground terminal (GND).

The substrate, acoustic reflection layer, bottom electrode, piezoelectric The materials of the layers, the middle electrode and the top electrode meet the following requirements.

Wherein, the material of the substrate can adopt different materials. For example, the material of the substrate may be any one of silicon, silicon carbide, aluminum oxide, or silicon on insulator (SOI). Among them, different materials have different properties, and thus the properties of the substrates formed by them are also different. For example, silicon is a good conductor of heat, so the silicon substrate has good thermal conductivity; compared with silicon, silicon carbide has better thermal conductivity. Alumina has the characteristics of good stability, high mechanical strength, and good insulation.

In addition, different materials can be used for the piezoelectric layer. For example, the piezoelectric layer can be made of one or more combinations of materials such as aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate, and barium sodium niobate. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Furthermore, different materials can be used for the bottom electrode, the middle electrode and the top electrode. For example, the material of any one of the bottom electrode, the middle electrode, and the top electrode can be one or more combinations of materials such as molybdenum, platinum, gold, silver, aluminum, tungsten, titanium, copper, ruthenium, and chromium. . Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Wherein, the size of the bottom electrode, the middle electrode and the top electrode can be the same or different, and the specific size can be set according to actual needs or the experience of relevant technical personnel, which is not specifically limited in the embodiment of the present application. Optionally, the shapes of the bottom electrode, the middle electrode and the top electrode may be regular or irregular. For example, when the shape of the bottom electrode, the middle electrode and the top electrode is a regular figure, as shown in (a) and (b) in Figure 15, the bottom electrode, the middle electrode and the top electrode can be circular shape or ellipse; when the shapes of the bottom electrode, the middle electrode and the top electrode are irregular figures, as shown in (c) and (d) in Figure 15, the bottom electrode, the middle electrode and the top electrode The electrodes can be any polygon or interdigitated made of multiple metal strips. The specific shape may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Furthermore, in the acoustic reflection layer, the high acoustic impedance material may comprise different materials. For example, the high acoustic impedance material may include one or more combinations of materials such as tungsten, molybdenum, and tantalum pentoxide. The low acoustic impedance material may comprise different materials. For example, the low acoustic impedance material may include one or more combinations of materials such as silicon dioxide and silicon nitride. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

The frequency of the radio frequency filter provided by the embodiment of the present application depends on the frequency of the first bulk acoustic resonator and the second bulk acoustic wave resonator. and the frequency of the second bulk acoustic wave resonator depends on the number of piezoelectric layers and intermediate electrodes in the first piezoelectric structural layer and the second piezoelectric structural layer, the more the number of piezoelectric layers and intermediate electrodes, the first bulk acoustic wave The higher the frequency of the resonator and the second BAW resonator. Since the first piezoelectric structural layer may include at least two piezoelectric layers stacked, each of the second piezoelectric structural layers may include at least one piezoelectric layer, and the adjacent two layers of the at least two piezoelectric layers are laminated. An intermediate electrode is arranged between the electric layers, and the intermediate electrode is a common electrode of two adjacent piezoelectric layers. When the first BAW resonator and the second BAW resonator are in resonance, the middle electrode can be equivalently split into two adjacent piezoelectric layers, which is equivalent to the thinning of the effective resonance area, The frequencies of the first BAW resonator and the second BAW resonator are thereby increased. For example, the at least two piezoelectric layers include a stacked first piezoelectric layer, an intermediate electrode, and a second piezoelectric layer, and the intermediate electrode is a common electrode of the first piezoelectric layer and the second piezoelectric layer. In this case, the effective resonance area includes a first effective resonance area and a second effective resonance area. Wherein, the first effective resonant region includes a bottom electrode, the first piezoelectric layer and half of the middle electrode, and the second effective resonant region includes half of the middle electrode, the second piezoelectric layer and the top electrode, That is to say, each effective resonance area includes one piezoelectric layer and three-half layers of electrodes. Compared with the first bulk acoustic wave resonator and the second bulk acoustic wave resonator, the resonance effective area of the bulk acoustic wave resonator shown in (b) in Fig. 1 comprises 1 piezoelectric layer and 2 layers of electrodes, the resonance effective area Thinning, thereby increasing the frequency of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator, on this basis, the thickness of the piezoelectric layer, bottom electrode, middle electrode and top electrode is not reduced, thereby ensuring the Properties of the first BAW resonator and the second BAW resonator. Therefore, while increasing the frequency of the radio frequency filter, the performance of the radio frequency filter is also guaranteed.

Fig. 16 is a schematic flowchart of a method for manufacturing a bulk acoustic wave resonator provided in an embodiment of the present application. The bulk acoustic wave resonator may be the first bulk acoustic wave resonator, the second bulk acoustic wave resonator, the third bulk acoustic wave resonator described above For a BAW resonator or a fourth BAW resonator, the method may include the following steps.

S161: Fabricate a substrate.

Wherein, the material of the substrate can adopt different materials. For example, the material of the substrate may be any one of silicon, silicon carbide, aluminum oxide or SOI. Among them, different materials have different properties, and the properties of substrates made of different materials are also different. For example, silicon is a good conductor of heat, so the silicon substrate has good thermal conductivity; compared with silicon, silicon carbide has better thermal conductivity. Alumina has the characteristics of good stability, high mechanical strength, and good insulation.

Exemplarily, the description of the fabrication process is performed with the substrate being a silicon substrate. The manufacturing process of silicon substrate mainly consists of three main processes: cutting silicon single crystal rod (slicing process), grinding silicon single wafer (grinding process) and polishing silicon single wafer (polishing process).

S162: Stack and arrange an acoustic reflection layer on one side of the substrate.

Wherein, the acoustic reflective layer may be alternately composed of high acoustic impedance materials and low acoustic impedance materials. Wherein, the acoustic reflection layer may also be called a Bragg reflection layer, or a phonon crystal structure.

The following description will be made by taking the acoustic reflective layer comprising four layers as an example. Specifically, the acoustic reflection layer includes a first layer, a second layer, a third layer and a fourth layer stacked in sequence, the first layer and the third layer are high acoustic impedance materials, and the second layer and the first layer The four layers are low acoustic impedance materials, or, the first layer and the third layer are low acoustic impedance materials, and the second layer and the fourth layer are high acoustic impedance materials. It should be noted that the acoustic reflection layer may include but is not limited to 4 layers, and the specific number of layers may be set according to actual needs or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

The process flow will be described below by taking the acoustic reflection layer comprising four layers and the material of the first layer being a high acoustic impedance material as an example. growing a high acoustic impedance material on the substrate to form a first layer, depositing a first low acoustic impedance material on a high acoustic impedance material to form a second layer, depositing a high acoustic impedance material on a low acoustic impedance material to form a third layer, A fourth layer is formed by depositing a low acoustic impedance material on the first layer to obtain a reflective layer.

Further, the high acoustic impedance material may comprise different materials. For example, the high acoustic impedance material may include one or more combinations of materials such as tungsten, molybdenum, and tantalum pentoxide. The low acoustic impedance material may comprise different materials. For example, the low acoustic impedance material may include one or more combinations of materials such as silicon dioxide and silicon nitride. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Optionally, when the BAW resonator includes an air cavity, the above step S162 may be: forming a groove on one side of the substrate. For example, a groove is formed by etching on one side of the substrate, so that an air cavity is formed between the bottom electrode and the substrate when the bottom electrode is formed in the following step S163.

S163: Stack and arrange a bottom electrode on a side of the acoustic reflection layer away from the substrate.

Specifically, it will be described by taking the acoustic reflection layer including 4 layers as an example. A metal layer is deposited on the fourth layer to form the bottom electrode.

Further, different materials can be used for the bottom electrode. For example, the material of the bottom electrode may be one or more combinations of materials such as molybdenum, platinum, gold, silver, aluminum, tungsten, titanium, copper, ruthenium and chromium. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

S164: Stack and arrange piezoelectric structure layers on a side of the bottom electrode away from the substrate, where the piezoelectric structure layers include at least one piezoelectric layer.

Wherein, when the bulk acoustic resonator is the first bulk acoustic resonator (or the third bulk acoustic resonator) described above, the piezoelectric structure layer is the first piezoelectric structure layer (or the third piezoelectric structure layer) and includes at least two piezoelectric layers; when the BAW resonator is the second BAW resonator (or the fourth BAW resonator) described above, the piezoelectric structural layer is the second piezoelectric The structural layer (or the fourth piezoelectric structural layer) includes at least one piezoelectric layer.

In the following, the process flow will be described in detail by taking the piezoelectric structure layer including two piezoelectric layers as an example. Specifically, a first piezoelectric thin film material is deposited on the bottom electrode to form a first piezoelectric layer; a metal material is deposited on the first piezoelectric thin film to form an intermediate electrode; a second piezoelectric thin film material is deposited on the intermediate electrode to form a piezoelectric layer. The second piezoelectric layer is formed to obtain the piezoelectric structural layer. It should be noted that, when the first piezoelectric structure layer includes 3 or 4 piezoelectric layers, the process flow is similar to that when the piezoelectric structure layer includes 2 piezoelectric layers, and will not be repeated here.

Wherein, the size of the intermediate electrode and the piezoelectric layer may be the same or different, and the specific size may be set according to actual requirements or the experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Further, different materials can be used for the piezoelectric layer. For example, the piezoelectric layer can be made of one or more combinations of materials such as aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate, and barium sodium niobate. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

The material of the intermediate electrode can adopt different materials. For example, the material of the bottom electrode may be one or more combinations of materials such as molybdenum, platinum, gold, silver, aluminum, tungsten, titanium, copper, ruthenium and chromium. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

S165: Stack and arrange a top electrode on a side of the piezoelectric structure layer away from the bottom electrode to form a bulk acoustic wave resonator.

Specifically, the piezoelectric structure layer includes two piezoelectric layers as an example for illustration, and a metal material is deposited on the second piezoelectric layer of the piezoelectric structure layer to form a top electrode.

Further, different materials can be used for the top electrode. For example, the material of the bottom electrode may be one or more combinations of materials such as molybdenum, platinum, gold, silver, aluminum, tungsten, titanium, copper, ruthenium and chromium. Specific materials may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

Wherein, the size of the bottom electrode, the middle electrode and the top electrode can be the same or different, and the specific size can be set according to actual needs or the experience of relevant technical personnel, which is not specifically limited in the embodiment of the present application.

Optionally, the shapes of the bottom electrode, the middle electrode and the top electrode may be regular or irregular. For example, when the shapes of the bottom electrode, the middle electrode and the top electrode are regular patterns, the bottom electrode, the middle electrode and the top electrode can be circular or oval; when the bottom electrode, the middle electrode and the top electrode When the shape of the top electrode is an irregular pattern, the bottom electrode, the middle electrode and the top electrode may be in the shape of any polygon or an interdigitated shape composed of a plurality of metal strips. The specific shape may be set according to actual requirements or experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

The manufacturing method provided by the embodiment of the present application can be applied to the manufacturing of the first BAW resonator and the second BAW resonator, and the frequencies of the first BAW resonator and the second BAW resonator depend on the first The higher the number of piezoelectric layers and intermediate electrodes in the piezoelectric structure layer and the second piezoelectric structure layer, the higher the frequency. Since the first piezoelectric structural layer may include at least two piezoelectric layers stacked, each of the second piezoelectric structural layers may include at least one piezoelectric layer, and the adjacent two layers of the at least two piezoelectric layers An intermediate electrode is arranged between the piezoelectric layers, and the intermediate electrode is a common electrode of two adjacent piezoelectric layers. When the first BAW resonator and the second BAW resonator are resonating, the middle electrode is equivalently split into two adjacent piezoelectric layers, which is equivalent to the thinning of the effective resonance area, thereby The frequencies of the first BAW resonator and the second BAW resonator are increased. On this basis, the thicknesses of the piezoelectric layer, the bottom electrode, the middle electrode and the top electrode are not reduced, thereby ensuring the performance of the first BAW resonator and the second BAW resonator. Therefore, while increasing the frequency of the radio frequency filter, the performance of the radio frequency filter is also guaranteed.

The embodiment of the application also provides an electronic device, the electronic device includes a sequentially coupled processor, a radio frequency circuit and an antenna, the radio frequency circuit can be used to receive or send a signal through the antenna, and the processor can be used to process the signal of the radio frequency circuit ; Wherein, the radio frequency circuit includes a radio frequency filter, and the radio frequency filter may be the radio frequency filter provided above. In addition, the electronic device also includes a memory and an input/output interface, the memory is used to store data, and the specific structure is shown in 3.

It should be noted that, for related descriptions about the radio frequency filter, reference may be made to the related description of the radio frequency filter provided above, which will not be repeated in this embodiment of the present application.

Finally, it should be noted that: the above is only a specific implementation of the application, but the scope of protection of the application is not limited thereto, and any changes or replacements within the technical scope disclosed in the application shall be covered by this application. within the scope of the application. Therefore, the protection scope of the present application should be determined by the protection scope of the claims.

Claims

A radio frequency filter, characterized in that the radio frequency filter has an input end and an output end,

The radio frequency filter includes: a first BAW resonator connected in series between the input terminal and a first node, and a second BAW resonator connected in parallel between the first node and a ground terminal, the A first node is coupled to the output; wherein,

The first bulk acoustic resonator includes a substrate, a bottom electrode, a first piezoelectric structure layer and a top electrode stacked in sequence, the first piezoelectric structure layer includes at least two piezoelectric layers stacked, the An intermediate electrode is arranged between any two adjacent piezoelectric layers in at least two piezoelectric layers;

The second bulk acoustic resonator includes a substrate, a bottom electrode, a second piezoelectric structure layer, and a top electrode stacked in sequence, and the second piezoelectric structure layer includes at least one piezoelectric layer;

The number of piezoelectric layers included in the first piezoelectric structure layer is different from the number of piezoelectric layers included in the second piezoelectric structure layer.
The radio frequency filter according to claim 1, wherein the number of piezoelectric layers included in the first piezoelectric structure layer is greater than the number of piezoelectric layers included in the second piezoelectric structure layer.
The radio frequency filter according to claim 1 or 2, wherein a groove is provided on a side of the substrate close to the bottom electrode, so that air is formed when the bottom electrode is stacked on the substrate. cavity.
The radio frequency filter according to claim 1 or 2, wherein the first BAW resonator or the second BAW resonator further comprises: an acoustic reflection layer, and the acoustic reflection layer is stacked on the between the substrate and the bottom electrode.
The radio frequency filter according to any one of claims 1-4, wherein the at least two piezoelectric layers include three piezoelectric layers or four piezoelectric layers.
The radio frequency filter according to any one of claims 1-5, wherein when the at least one piezoelectric layer includes two or more than two piezoelectric layers stacked, the two layers or An intermediate electrode is arranged between any two adjacent piezoelectric layers among the more than two piezoelectric layers.
The radio frequency filter according to claim 6, wherein the at least one piezoelectric layer comprises two piezoelectric layers or three piezoelectric layers.
The radio frequency filter according to any one of claims 1-7, characterized in that the piezoelectric layers in the first piezoelectric structure layer and the second piezoelectric structure layer have the same thickness.
The radio frequency filter according to any one of claims 1-8, wherein the radio frequency filter further comprises: a third BAW resonator connected in series between the first node and the output end, and a fourth BAW resonator connected in parallel between the output terminal and the ground terminal;

The third bulk acoustic resonator includes a substrate, a bottom electrode, a third piezoelectric structural layer, and a top electrode stacked in sequence, the third piezoelectric structural layer includes at least two piezoelectric layers stacked, the An intermediate electrode is arranged between any two adjacent piezoelectric layers in at least two piezoelectric layers;

The fourth BAW resonator includes a substrate, a bottom electrode, a fourth piezoelectric structure layer, and a top electrode stacked in sequence, and the fourth piezoelectric structure layer includes at least one piezoelectric layer;

The number of piezoelectric layers included in the third piezoelectric structure layer is different from the number of piezoelectric layers included in the fourth piezoelectric structure layer.
The radio frequency filter according to claim 9, wherein the number of piezoelectric layers included in the third piezoelectric structure layer is greater than the number of piezoelectric layers included in the fourth piezoelectric structure layer.
The radio frequency filter according to claim 9 or 10, wherein the thickness of the piezoelectric layer in the third piezoelectric structural layer and the fourth piezoelectric structural layer is the same as that of the first piezoelectric structural layer The included piezoelectric layers have the same thickness.
The radio frequency filter according to any one of claims 1-11, characterized in that the material of the substrate is any one of silicon, silicon carbide, aluminum oxide or silicon on insulating substrate (SOI).
The radio frequency filter according to any one of claims 1-12, characterized in that, the material of the piezoelectric layer is aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate and barium sodium niobate One or more combinations.
The radio frequency filter according to any one of claims 1-13, wherein the material of any one of the bottom electrode, the middle electrode and the top electrode is molybdenum, platinum, gold, silver, aluminum , tungsten, titanium, copper, ruthenium and chromium in one or more combinations.
The radio frequency filter according to any one of claims 4-14, characterized in that, the acoustic reflection layer is alternately composed of high acoustic impedance materials and low acoustic impedance materials.
The radio frequency filter according to claim 15, wherein the high acoustic impedance material comprises one or more combinations of tungsten, molybdenum and tantalum pentoxide.
The radio frequency filter according to claim 15 or 16, wherein the low acoustic impedance material comprises one or more combinations of silicon dioxide and silicon nitride.
An electronic device, characterized in that the electronic device includes a memory, a processor, a radio frequency circuit, an antenna, and an input and output interface, wherein the radio frequency circuit includes the radio frequency filter according to any one of claims 1-17 .