Thin film bulk acoustic resonator and method of manufacturing the same, filter

Abstract

The application provides a film bulk acoustic resonator and a preparation method thereof and a filter. The film bulk acoustic resonator comprises a substrate and a piezoelectric oscillation structure. The piezoelectric oscillation structure comprises a bottom electrode, a piezoelectric film layer and a top electrode which are sequentially formed on a top surface of the substrate. The bottom electrode is covered by the piezoelectric film layer. The piezoelectric film layer is provided with a through hole. The bottom electrode is led to the piezoelectric film layer away from the top surface of the substrate through a conductor in the through hole. The top surface of the substrate is provided with a groove. The groove is filled with a conductive block. The conductive block is in contact with the bottom electrode. The orthographic projection of the through hole on the substrate is located within the range of the area where the groove is located. The bottom electrode at least partially covers the groove. The film bulk acoustic resonator provided by the application can have higher reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communications, and in particular to a film bulk acoustic resonator, a filter comprising the film bulk acoustic resonator, and a method for manufacturing the film bulk acoustic resonator. BACKGROUND

[0002] With the development of communication technology, the requirements for core communication devices used to support information transmission in communication technology are becoming higher and higher. As a core device for realizing signal transmission, a radio frequency module usually needs to have performance parameters such as high frequency, large bandwidth, and low loss. In the radio frequency module, devices that play an important role include filters. In the prior art, a film bulk acoustic resonator (FBAR) based on acoustic resonance plays an extremely important role in wireless communication technology due to its excellent performance and operability.

[0003] In a typical FBAR structure, an electrode layer, a piezoelectric film layer, and an electrode layer are usually deposited on a substrate in sequence, that is, the piezoelectric film layer is sandwiched between the two electrodes to form a "sandwich" structure. In this structure, the piezoelectric film layer usually needs to be etched to lead the bottom electrode on the substrate side to the other side of the piezoelectric film layer. In addition, in order to improve the resonant frequency of the FBAR, the bottom electrode is usually made as thin as possible. However, in the process of etching the piezoelectric film material, the material of the bottom electrode will not have infinite selectivity to the etchant, so part of the material of the bottom electrode will be consumed. When the bottom electrode is thin, this will cause the bottom electrode to be etched through or the remaining material of the bottom electrode to be insufficient, thereby causing poor contact of the FBAR and greatly reducing the reliability of the FBAR. Therefore, how to maintain sufficient material of the bottom electrode and improve the reliability of the FBAR becomes a problem. SUMMARY

[0004] The film bulk acoustic resonator, the method for manufacturing the film bulk acoustic resonator, and the filter comprising the film bulk acoustic resonator provided by the present application can maintain sufficient material of the bottom electrode of the FBAR, reduce poor contact of the FBAR, and thus improve the reliability of the FBAR.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] In a first aspect, the embodiments of the present application provide a thin film bulk acoustic resonator, which is a cavity structure. The thin film bulk acoustic resonator comprises a substrate and a piezoelectric oscillation structure. The piezoelectric oscillation structure comprises a bottom electrode, a piezoelectric thin film layer and a top electrode formed in sequence on a top surface of the substrate. The bottom electrode is covered by the piezoelectric thin film layer. The piezoelectric thin film layer is provided with a through hole. The bottom electrode is connected to the piezoelectric thin film layer away from the top surface of the substrate through a conductor in the through hole. The top surface of the substrate is provided with a groove. The groove is filled with a conductive block. The conductive block is in contact with the bottom electrode. A projection of the through hole on the substrate is located in a range of an area where the groove is located. The bottom electrode at least partially covers the groove.

[0007] In a second aspect, the embodiments of the present application provide a thin film bulk acoustic resonator, which is a Bragg reflection structure. The thin film bulk acoustic resonator comprises a substrate, a Bragg reflector and a piezoelectric oscillation structure. The Bragg reflector comprises a plurality of layers stacked in sequence on a top surface of the substrate. The plurality of layers at least comprises a top layer and a lower layer. The top layer is a layer close to the substrate. The lower layer is a layer away from the substrate. The piezoelectric oscillation structure comprises a bottom electrode, a piezoelectric thin film layer and a top electrode formed in sequence on the top layer of the Bragg reflector. The bottom electrode is covered by the piezoelectric thin film layer. The piezoelectric thin film layer is provided with a through hole. The bottom electrode is connected to the piezoelectric thin film layer away from the top surface of the substrate through a conductor in the through hole. The top layer of the Bragg reflector is provided with a groove on a side in contact with the bottom electrode. The groove is filled with a conductive block. The conductive block is in contact with the bottom electrode. A projection of the through hole on the substrate is located in a range of an area where the groove is located. The bottom electrode at least partially covers the groove.

[0008] The thin film bulk acoustic resonator provided by the present application can increase the thickness of the contact part of the top electrode and the through hole, avoid consuming part of the bottom electrode material in the process of etching the through hole, or etching the bottom electrode through, and also avoid the unevenness of the bottom electrode, to provide a relatively smooth plane for the deposition of the piezoelectric thin film layer. Thus, the thin film bulk acoustic resonator with the cavity structure or the Bragg reflection structure provided by the present application can improve the reliability of the thin film bulk acoustic resonator.

[0009] In combination with the first aspect or the second aspect, in a possible implementation manner, a top surface of the piezoelectric thin film layer is provided with a conductive plate. The conductive plate is provided in the same layer as the top electrode and is insulated from each other. The bottom electrode is connected to the conductive plate through the conductor in the through hole.

[0010] By placing a conductive plate on the top surface of the piezoelectric thin film layer, the area of ​​the lead-out terminals of the thin film bulk acoustic resonator can be increased, avoiding poor contact due to excessively small lead-out terminal area, thereby improving the reliability of the resonator.

[0011] In conjunction with the first or second aspect, in one possible implementation, the material forming the conductive block within the groove is the same as the material forming the bottom electrode.

[0012] This implementation method allows the conductive block and the bottom electrode to be formed in the same process step, thereby simplifying the process steps.

[0013] In conjunction with the first or second aspect, in one possible implementation, the material forming the top electrode is the same as the material forming the conductor within the through hole.

[0014] This implementation allows the top electrode and the conductor inside the through-hole to be formed in the same process step, thereby simplifying the process.

[0015] In conjunction with the first or second aspect, in one possible implementation, the material forming the top electrode is the same as the material forming the conductive plate.

[0016] This implementation method allows the top electrode and the conductive plate to be formed in the same process step, thereby simplifying the process steps.

[0017] Thirdly, embodiments of this application provide a filter that includes at least one thin-film bulk acoustic resonator as described in the first aspect.

[0018] Fourthly, embodiments of this application provide a filter that includes at least one diaphragm bulk acoustic resonator as described in the second aspect.

[0019] Fifthly, embodiments of this application provide a filter comprising at least one thin-film bulk acoustic resonator as described in the first aspect and at least one thin-film bulk acoustic resonator as described in the second aspect.

[0020] In a sixth aspect, the embodiments of the present application provide a method for manufacturing a film bulk acoustic resonator. The film bulk acoustic resonator manufactured by the method is a cavity structure. The method comprises the following steps: providing a substrate, etching a top surface of the substrate to form a groove, filling a first conductive material in the groove to form a conductive block, so that a top surface of the conductive block is at the same level as a top surface of the substrate, depositing a second conductive material on the top surface of the substrate to form a first conductive layer, and patterning the first conductive layer to form a bottom electrode, depositing a piezoelectric thin film material on the top surface of the substrate and a surface of the bottom electrode away from the substrate to form a piezoelectric thin film layer, etching the piezoelectric thin film layer in a region formed by a normal projection of the groove to the piezoelectric thin film layer to form at least one through hole penetrating through a top surface and a bottom surface of the piezoelectric thin film layer, wherein the bottom electrode is in contact with the conductive block filled in the groove, and the bottom electrode at least partially covers the groove.

[0021] In a seventh aspect, the embodiments of the present application provide a method for manufacturing a film bulk acoustic resonator. The film bulk acoustic resonator manufactured by the method is a Bragg reflection structure. The method comprises the following steps: providing a substrate, depositing a Bragg reflector on a top surface of the substrate, wherein the Bragg reflector comprises a plurality of layers, the plurality of layers at least include a top layer and a bottom layer, the top layer is a layer close to the substrate, and the bottom layer is a layer away from the substrate, etching the top layer of the Bragg reflector to form a groove, filling a first conductive material in the groove to form a conductive block, so that a top surface of the conductive block is at the same level as a top surface of the top layer of the Bragg reflector, depositing a second conductive material on the top surface of the top layer of the Bragg reflector to form a first conductive layer, and patterning the first conductive layer to form a bottom electrode, depositing a piezoelectric thin film material on the top surface of the top layer of the Bragg reflector and a surface of the bottom electrode away from the substrate to form a piezoelectric thin film layer, etching the piezoelectric thin film layer in a region formed by a normal projection of the groove to the piezoelectric thin film layer to form at least one through hole penetrating through a top surface and a bottom surface of the piezoelectric thin film layer, wherein the bottom electrode is in contact with the conductive block filled in the groove, and the bottom electrode covers the groove.

[0022] In combination with the sixth aspect or the seventh aspect, in a possible implementation manner, the method further comprises the following steps: depositing a third conductive material on a surface of the piezoelectric thin film layer away from the top surface of the substrate to form a second conductive layer and a conductor flowing into the through hole and in contact with the bottom electrode, patterning the second conductive layer to form a top electrode and a conductive plate, wherein the top electrode and the conductive plate are insulated, and the conductive plate at least partially covers the through hole; and the bottom electrode is connected to the conductive plate through the conductor in the through hole. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0024] Figure 1 is a schematic diagram of an application scenario of a film bulk acoustic resonator provided by the embodiments of the present application;

[0025] Figure 2 is a structural schematic diagram of a filter provided by the embodiments of the present application;

[0026] Figure 3 is a top view of a film bulk acoustic resonator provided by the embodiments of the present application;

[0027] Figure 4 is a sectional view of the film bulk acoustic resonator shown in FIG. 8 along AA'; Figure 4

[0028] Figure 5 is a structural schematic diagram of a film bulk acoustic resonator in the prior art;

[0029] Figure 6 is a top view of another film bulk acoustic resonator provided by the embodiments of the present application;

[0030] Figure 7 is another sectional view of the film bulk acoustic resonator shown in FIG. 10 along AA'; Figure 6 DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] The "first", "second", and similar words mentioned herein do not represent any order, quantity, or importance, but are only used to distinguish different components. Similarly, "one" or "a" and similar words do not represent a quantity limit, but represent the existence of at least one. The "connection" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. ​​

[0033] The "unit" mentioned in the present document generally refers to a logically divided functional structure, which can be implemented by pure hardware or a combination of hardware and software.

[0034] In the present document, the relationship between the associated objects described by "and / or" represents that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone.

[0035] In the present document, the words such as "exemplary" or "for example" are used to represent an example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present document should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the words such as "exemplary" or "for example" are intended to present the relevant concept in a specific manner.

[0036] In the description of the embodiments of the present document, unless otherwise specified, the meaning of "a plurality of" is two or more. For example, a plurality of film bulk acoustic resonators refers to two or more film bulk acoustic resonators.

[0037] Please refer to Figure 1 which shows an application scenario of the film bulk acoustic resonator provided by the embodiments of the present document.

[0038] In Figure 1The application scenario diagram shown includes a network device 11 and a terminal device 12. The network device 11 can be configured to communicate with the terminal device 12. The network device 11 can also be referred to as an access network device or a radio access network device, and can be an evolved NodeB (eNB or eNodeB) in an LTE system, a radio controller in a cloud radio access network (CRAN) scenario, a gNB in a new radio (NR) system, or the like, and the embodiments of the present application are not limited thereto. The network device 11 generally includes a processor and a transceiver to receive various signals from the terminal device 12 or transmit signals to the terminal 12 and process the signals. The processor can be a CPU, a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The transceiver generally includes a receiver and a transmitter. The transmitter processes (for example, analog conversion, filtering, amplification, and up-conversion) output samples and generates a downlink signal, which can be transmitted to the terminal device 12 via an antenna. On the uplink, the antenna receives an uplink signal transmitted by the terminal device 12. The receiver processes (for example, filtering, amplification, down-conversion, and digitization) the signal received from the antenna and provides input samples. In the transceiver, a radio frequency module is generally included for transmitting and receiving the downlink signal and the uplink signal. Specifically, the radio frequency module generally includes a signal amplifier, a mixer, a power divider, an attenuator, a filter, a frequency multiplier, a frequency divider, and the like. The film bulk acoustic resonator shown in the embodiments of the present application can be disposed in the filter of the radio frequency module.

[0039] It should be noted that in some application scenarios, the processor and the transceiver in the network device 11 are the same module, and are not distinguished, and can be referred to as a processor. At this time, the radio frequency module including the film bulk acoustic resonator described above can also be disposed in the processor.

[0040] The terminal device 12 in the embodiments of the present application can also be referred to as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), an access terminal, a subscriber unit, a subscriber station, a mobile station, a mobile terminal, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device, and the like.

[0041] The terminal device 12 can be a device that provides voice / data connectivity to a user, such as a handheld device with wireless connectivity, a vehicle-mounted device, and the like. Examples of the terminal device include a mobile phone, a tablet computer, a notebook computer, a palm computer, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal device in a future 5G network, or a terminal device in a future evolved public land mobile network (PLMN), and the like. The embodiments of the present application are not limited thereto.

[0042] Figure 1The terminal device 12 shown can include a processor and a transceiver. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic components, discrete hardware components, and the like, without limitation. The transceiver generally includes a receiver and a transmitter. The transmitter processes (for example, analog conversion, filtering, amplification, and up-conversion, and the like) output samples and generates an uplink signal, which is transmitted to the network device 11 via an antenna. On the downlink, the antenna receives a downlink signal transmitted by the network device 11. The receiver processes (for example, filtering, amplification, down-conversion, and digitization, and the like) the signal received from the antenna and provides input samples. In the transceiver, a radio frequency module is generally included for transmitting and receiving the above-mentioned downlink signal and uplink signal. Specifically, the radio frequency module generally includes signal amplifiers, mixers, power dividers, attenuators, filters, frequency multipliers, frequency dividers, and the like. The film bulk acoustic resonator shown in the embodiments of the present application can also be provided in the filter of the radio frequency module.

[0043] It should be noted that in some application scenarios, the processor and the transceiver in the terminal device 12 are the same module, and are not distinguished, and can both be referred to as a processor. At this time, the radio frequency module including the film bulk acoustic resonator can also be provided in the processor.

[0044] Please continue to refer to Figure 2 which shows a structural schematic diagram of a filter 20 provided by the present application. Among them, Figure 2 The filter 20 shown can be applied to Figure 1 The radio frequency module of the network device 11 shown, and can also be applied to Figure 1 The radio frequency module of the terminal device 12 shown.

[0045] As Figure 2 shown, the filter 20 includes an input end 21 for receiving an input signal and an output end 22 for outputting a filtered output signal. The filter 20 further includes at least one film bulk acoustic resonator according to any embodiment described herein. As Figure 2As shown, one or more thin-film bulk acoustic wave resonators 200a, 200b, ..., 200n are used to filter the input signal. When multiple thin-film bulk acoustic wave resonators 200a, 200b, ..., 200n are used to filter the input signal, these multiple thin-film bulk acoustic wave resonators can be connected in series, in parallel, or in a series-parallel configuration, depending on the application scenario.

[0046] The following is combined Figure 3 , Figure 4 , Figure 6 , Figure 7 For example Figure 2 The structure of the thin-film bulk acoustic wave resonator shown is described in detail. First, it should be noted that, in order to describe the features and elements of the thin-film bulk acoustic wave resonator of the present invention, the relative positions and orientations of the various components of the thin-film bulk acoustic wave resonator will be described with reference to the x, y, and z directions in a Cartesian coordinate system. However, as those skilled in the art will understand, the relative positions and orientations of the various components may not be perfectly aligned with, parallel to, or perpendicular to one of these axes. For example, when the layers are formed in the thin-film bulk acoustic wave resonator device, the top and bottom surfaces of these layers may not be perfectly flat surfaces, and they may not be perfectly parallel to each other. Similarly, the sidewalls of layers or other components such as through-holes may not be perfectly perpendicular to their top and bottom surfaces, and may not be perfectly parallel. Likewise, the components may have slightly inclined walls or surfaces, but for ease of illustration, they are described as straight or planar. Therefore, it is to be understood by those skilled in the art that references to the x, y, and z directions are intended to provide a general understanding of the orientation and position of the components relative to each other, and should not be construed as limiting.

[0047] Please refer to Figure 3 , Figure 4 , Figure 3 A top view of a thin-film bulk acoustic resonator provided in an embodiment of this application is shown. Figure 4 It shows Figure 3 A cross-sectional view of a thin-film bulk acoustic resonator along the AA' direction.

[0048] Along the z-axis, the thin-film bulk acoustic resonator 200 sequentially includes a substrate 201, a bottom electrode 202 formed on the top surface of the substrate 201, and a top electrode 204 formed on the top surface of a piezoelectric thin film layer 203. The bottom electrode 202 is in contact with the substrate 201, i.e., deposited on the substrate 201. A piezoelectric thin film layer 203 is formed on the bottom electrode 202, completely covering the bottom electrode 202. That is, the piezoelectric thin film layer 203 is in partial contact with the top surface of the substrate 201. Here, the material forming the piezoelectric thin film layer 203 may include, but is not limited to, aluminum nitride, scandium aluminum nitride, zinc oxide, etc.

[0049] Through holes 205 penetrating the upper and lower surfaces of the piezoelectric thin film layer 203 are formed on the piezoelectric thin film layer 203. Multiple through holes 205 may be included. Figure 3 Four are schematically shown. It is understood that this application does not limit the number of through holes 205, and can set them according to the needs of the scenario. For example... Figure 3 As shown, the pattern formed by the orthographic projection of the through hole 205 onto the substrate 201 can be a circle, or it can be a square, pentagon, or other shapes.

[0050] In this embodiment, the through-hole 205 may be filled with a conductive material to form a conductor. This conductive material may be the same as the material forming the bottom electrode 202 or the same as the material forming the top electrode 204. The conductive material may include, but is not limited to, tungsten, molybdenum, aluminum, gold, platinum, or an alloy material formed from two or more of the above materials. Figure 4 As shown, the conductive material filling the through-hole 205 is in contact with the bottom electrode 202. Therefore, the bottom electrode 202 can be led through the conductor in the through-hole 205 to the side of the piezoelectric thin film layer 203 away from the substrate 201, i.e., the top surface. Figure 3 or Figure 4 In this process, a conductive plate 206 is also formed on the top surface of the piezoelectric thin film layer 203. The conductive plate 206 is connected to the bottom electrode 202 through a conductor in the through hole 205. Thus, two ports are led out from the conductive plate 206 and the top electrode 204 respectively to receive externally applied voltage or to be connected in series or in parallel with other thin film bulk acoustic resonators.

[0051] like Figure 4 As shown, a groove 207 is formed on the top surface of the substrate 201, and the groove 207 is filled with a conductive material to form a metal block. Along the x-axis and y-axis, the bottom electrode 202 may partially or completely cover the groove 207; the figure schematically shows the case where the bottom electrode 202 completely covers the groove 207. Along the z-axis, the height of the conductive material filling the groove 207 is flush with the top surface of the substrate 201, or in other words, the top surface of the conductive block formed by the conductive material in the groove 207 is flush with the top surface of the substrate 201. This means that the surface formed by the filled conductive material is located in the same horizontal plane as the top surface of the substrate 201, thereby making the top surface of the substrate 201 smoother. The conductive material filling the groove 207 can be the same as or different from the material of the bottom electrode 202. Preferably, the conductive material filling the groove 207 is the same as the material of the bottom electrode 202. Here, the conductive material filling the groove 207 includes, but is not limited to, tungsten, molybdenum, aluminum, gold, platinum, or an alloy material formed from two or more of the above materials.

[0052] When the thickness of the bottom electrode 202 along the z-axis is thin (e.g., less than 100 nm), during the etching of the piezoelectric thin film layer 203 to form the via 205, some material of the bottom electrode 202 is usually consumed, or the bottom electrode 202 is easily etched through. This can easily lead to poor contact of the bottom electrode 202 of the thin-film bulk acoustic wave resonator, reducing the reliability of the thin-film bulk acoustic wave resonator. In related technologies, a conductive layer 211 of a different material than the bottom electrode 202 is usually placed between the via 205 and the bottom electrode 202, so that the etching material stops at the conductive layer 211, preventing the etching material from continuing to etch and protecting the bottom electrode 202. Its structure is as follows: Figure 5 As shown. This structure typically results in unevenness at the contact point between the bottom electrode 202 and the via 205, affecting the deposition of the piezoelectric thin film layer 203 and consequently the performance of the thin-film bulk acoustic resonator. In this embodiment, by etching a groove 207 on the substrate 201 and depositing conductive material in the groove 207 to form a conductive block, and with the surface of the conductive block lying in the same plane as the top surface of the substrate 202, the thickness of the contact point between the top electrode 202 and the via 205 can be increased. This avoids consuming some of the bottom electrode material or piercing the bottom electrode 202 during the etching of the via 205. Furthermore, it avoids unevenness at the bottom electrode, providing a smoother surface for the deposition of the piezoelectric thin film layer, thereby improving the reliability of the thin-film bulk acoustic resonator.

[0053] In this embodiment, the orthographic projection of the through-hole 205 onto the substrate 201 lies within the region of the groove 207. That is, the opening of the groove 207 is located directly below the through-hole 205, and the shadow area formed by the orthographic projection of the through-hole 205 onto the substrate falls precisely within the region of the groove 207 on the substrate 201. This ensures that the portion of the through-hole 205 that contacts the bottom electrode 202 has sufficient thickness along the z-axis, improving the reliability of the thin-film bulk acoustic resonator 200.

[0054] In this embodiment, as Figure 3 and Figure 4 The thin-film bulk acoustic resonator 200 shown has a cavity structure. The orthographic projection of the top electrode 204 onto the substrate overlaps with the cavity 208 in the x-axis and y-axis directions, as shown. Figure 3 As shown, along the z-axis, the top electrode 204, the cavity 208, and the piezoelectric thin film layer 203 aligned with it in the x-axis and y-axis directions, and the bottom electrode 202 form the resonator operating region.

[0055] In practice, a voltage is applied to the top electrode 204 and the conductive plate 206 of the thin-film bulk acoustic resonator 200, generating an electric field between the top electrode 204 and the bottom electrode 202. The piezoelectric thin film layer 203 converts some of the electrical energy into mechanical energy in the form of sound waves. The sound waves propagate in the same direction as the electric field, that is, along the Z-axis inside the piezoelectric thin film layer 203. The sound waves with amplitude and phase differences inside the thin-film bulk acoustic resonator 200 are then converted into proportional electrical signals by the piezoelectric thin film layer 203. To prevent sound wave energy from leaking through the substrate 201, the sound wave energy is confined within the cavity 208.

[0056] Combination Figure 3 and Figure 4 The specific process for forming the thin-film bulk acoustic resonator 200 is described.

[0057] First, a substrate 201 is provided, and its top surface is etched to form a cavity. The substrate 201 can be made of monocrystalline silicon, polycrystalline silicon, silicon oxide, etc. In specific implementations, polycrystalline silicon can be used to improve the impedance of the substrate 201. The position of the cavity in the substrate 201, its area along the x-axis and y-axis, and its thickness along the z-axis can be set based on parameters such as the resonant frequency of the required resonator 200, which will not be elaborated here.

[0058] Second, a semiconductor material is deposited on the top surface of the substrate 201 to fill the cavity and cover the top surface of the substrate 201. In a specific implementation, the semiconductor material can be silicon dioxide.

[0059] Third, the semiconductor material located on the top surface of the substrate 201 outside the etching cavity is etched, exposing the top surface of the substrate 201. In a specific implementation, chemical mechanical polishing (CMP) can be used to etch the semiconductor material on the top surface of the substrate 201.

[0060] Fourth, the top surface of the substrate 201 is etched to form a groove 207.

[0061] Fifth, a first conductive layer is deposited on the top surface of the substrate 201 using a metal deposition process, thereby filling the groove 207 with conductive material. The conductive material here is a metallic material.

[0062] Sixth, etch the first conductive layer on the top surface of the substrate 201 to expose the top surface of the substrate 201.

[0063] Seventh, a second conductive layer is deposited on the top surface of the substrate 201 using a metal deposition process.

[0064] Eighth, photoresist is deposited on the second conductive layer, and a mask is used to mask the second conductive layer to etch away excess material, forming the bottom electrode 202.

[0065] Ninth, a piezoelectric thin film layer 203 is deposited on the top surface of the bottom electrode 202 and in the area of ​​the top surface of the substrate 201 not covered by the bottom electrode 202.

[0066] Tenth, within the projection area formed by the orthogonal projection of the groove 207 onto the piezoelectric thin film layer 203, the piezoelectric thin film layer 203 is etched to form a through hole 205 penetrating the top and bottom surfaces of the piezoelectric thin film layer 203.

[0067] Tenth, a third conductive layer is deposited on the side of the piezoelectric thin film layer 203 away from the substrate. At this time, conductive material can be injected into the wall of the via 205 and make contact with the bottom electrode 202.

[0068] Eleventh, photoresist is deposited on the third conductive layer. A mask is used to mask the third conductive layer, and excess material is etched away to form the top electrode 204 and the conductive plate 206. The top electrode 204 and the conductive plate 206 are mutually insulated. The conductive plate 206 can be formed within the projection area formed by the orthogonal projection of the groove 207 onto the piezoelectric thin film layer 203. Thus, the conductive plate 206 is connected to the bottom electrode 202 through the conductive material in the through-hole 205. That is, the conductive plate 206, the top electrode 204, and the conductive material poured into the through-hole 205 can be integrally formed. Therefore, the conductive plate 206, the top electrode 204, and the conductive material poured into the through-hole 205 can be the same material, simplifying the manufacturing process.

[0069] The materials of the first conductive layer, the second conductive layer, and the third conductive layer can be metallic materials or other known or unknown conductive materials. The materials used for the first conductive layer, the second conductive layer, and the third conductive layer can be the same or different.

[0070] Twelfth, the piezoelectric thin film layer 203 is etched in the non-active region (i.e., the region where the bottom electrode 202 and the top electrode 204 are not deposited) to form multiple vias 209.

[0071] Thirteenth, etching solution or etching gas is released through through-hole 209 to etch the semiconductor material in the cavity, thereby forming cavity 208. It should be noted that when etching the semiconductor material in the cavity, to avoid consuming the bottom electrode 202, the etching solution or etching gas used can corrode the semiconductor material but cannot corrode the metal material. Figure 3 As can be seen, since it is necessary to set the via 209 in the non-active region, the region of the cavity 208 along the x-axis and y-axis is usually set to be slightly larger than the region of the top electrode 204, so that the via 209 can connect to the cavity to etch the semiconductor material in the cavity.

[0072] In some implementations, when the material deposited in the groove 207 is the same as the material forming the bottom electrode 202, steps six and seven mentioned above are unnecessary. That is, the deposited first conductive layer can be directly masked, allowing the deposition of the conductive material in the groove 207 and the formation of the bottom electrode 202 to be completed in one step. This further simplifies the fabrication process of the thin-film bulk acoustic resonator 200.

[0073] By using the above-described manufacturing process to create a cavity-type thin-film bulk acoustic resonator 200, the thickness of the contact portion between the top electrode 202 and the through hole 205 can be increased, avoiding the consumption of some bottom electrode material or the etching of the bottom electrode 202 during the etching process of the through hole 205, thereby improving the reliability of the thin-film bulk acoustic resonator.

[0074] The structure of the thin-film bulk acoustic resonator 200 can also be a Bragg reflection structure. For example... Figure 6 and Figure 7 As shown, it illustrates a schematic diagram of the thin-film bulk acoustic resonator 200 when its structure is a Bragg reflection structure. Wherein, Figure 6 This is a top view of a thin-film bulk acoustic resonator; Figure 7 For along Figure 6 The cross-sectional view of AA' of the thin-film bulk acoustic resonator shown.

[0075] like Figure 6 , Figure 7 As shown, the thin-film bulk acoustic resonator 200 includes a substrate 201, a Bragg reflector 210 formed on the top surface of the substrate 201, a bottom electrode 202 formed on the top surface of the Bragg reflector 210, a piezoelectric thin film layer 203 covering the top surface of the bottom electrode 202 and part of the top surface of the Bragg reflector 210, and a top electrode 204 formed on the top surface of the piezoelectric thin film layer 203. Along the z-axis, the Bragg reflector 210 includes multiple stacked layers. These multiple layers may include at least one L1 layer and at least one L2 layer, wherein the L1 layer may be formed of a low acoustic impedance material (e.g., silicon dioxide), and the L2 layer may be formed of a high acoustic impedance material (e.g., tungsten). The L1 and L2 layers are stacked alternately. Figure 7 The diagram schematically illustrates the structure of the Bragg reflector 210, which includes two L1 layers and two L2 layers. Here, the L1 and L2 layers can have the same thickness or different thicknesses along the z-axis; furthermore, the materials forming each L1 layer can be the same or different, and the materials forming each L2 layer can be the same or different, depending on the application requirements.

[0076] In such Figure 7 In the thin-film bulk acoustic resonator 200 shown, on the top surface of the Bragg reflector 210, that is, the layer in contact with the bottom electrode 202 ( Figure 7The diagram shows an L2 layer with a groove 207 filled with a conductive material. Along the x and y axes, the bottom electrode 202 can completely or partially cover the groove 207; along the z-axis, the height of the conductive material filling the groove 207 is flush with the top surface of the Bragg reflector 210. That is, the top surface of the conductive block formed by the conductive material filling the groove 207 is on the same horizontal plane as the top surface of the Bragg reflector 210, thus making the top surface of the Bragg reflector 210 smoother. Figure 7 As shown, a conductive plate 206 is formed on the top surface of the piezoelectric thin film layer 203. A through-hole 205 is formed on the piezoelectric thin film layer 203, penetrating both the top and bottom surfaces. The conductive plate 206 is connected to the bottom electrode 202 through the through-hole 205. The relative positions of the conductive plate 206, the through-hole 205, and the bottom electrode 202 are... Figure 3 , Figure 4 The thin-film bulk acoustic resonator 200 shown is the same; for a detailed description, please refer to [reference needed]. Figure 3 , Figure 4 The description of the embodiments shown will not be repeated here.

[0077] like Figure 7 The thin-film bulk acoustic resonator 200 shown illustrates the sound wave generation method and the electric field-sound wave-electric field conversion method. Figure 3 , Figure 4 The thin-film bulk acoustic resonator 200 shown is the same and will not be described again here. Figure 3 , Figure 4 The cavity structure of the thin-film bulk acoustic resonator 200 shown is different. Figure 7 In the Bragg reflection structure shown, in order to prevent energy leakage through the substrate 201, the Bragg reflector reflects the acoustic wave energy to the piezoelectric thin film layer 203 as much as possible.

[0078] Combination Figure 6 and Figure 7 The specific process for forming the thin-film bulk acoustic resonator 200 is described.

[0079] First, a substrate 201 is provided, and a Bragg reflector 210 is deposited on the top surface of the substrate 201. The Bragg reflector is formed by stacking L1 layers and L2 layers.

[0080] Second, the top surface of the L2 layer in the Bragg reflector 210, which is far from the substrate 201, is etched to form a groove 207.

[0081] Third, a first conductive layer is deposited in the L2 layer of the Bragg reflector 210 using a metal deposition process, thereby filling the groove 207 with conductive material. This conductive material can be a metallic material. It should be noted that, for ease of description, the L2 layer mentioned below refers to the L2 layer in the Bragg reflector 210 that is furthest from the substrate 201 and in contact with the bottom electrode 202.

[0082] Fourth, etch the first conductive layer deposited on the top surface of the L2 layer to expose the top surface of the L2 layer.

[0083] Fifth, a second conductive layer is deposited on the top surface of the L2 layer using a metal deposition process.

[0084] Sixth, photoresist is deposited on the second conductive layer, and a mask is used to mask the second conductive layer to etch away excess metal and form the bottom electrode 202.

[0085] Seventh, a piezoelectric thin film layer 203 is deposited in the area of ​​the bottom electrode 202 and the L2 layer that is not covered by the second electrode.

[0086] Eighth, in the projection area formed by the orthogonal projection of the groove 207 onto the piezoelectric thin film layer 203, the piezoelectric thin film layer 203 is etched to form a through hole 205 penetrating the top and bottom surfaces of the piezoelectric thin film layer 203.

[0087] Ninth, a third conductive layer is deposited on the top surface of the piezoelectric thin film layer 203. At this time, conductive material can be injected into the hole wall of the through hole 205 and make contact with the bottom electrode 202.

[0088] Tenth, photoresist is deposited on the third conductive layer. A mask is used to mask the third conductive layer, and excess material is etched away to form the top electrode 204 and the conductive plate 206. The top electrode 204 and the conductive plate 206 are mutually insulated. The conductive plate 206 is formed within the projection area formed by the orthogonal projection of the groove 207 onto the piezoelectric thin film layer 203. Thus, the conductive plate 206 is connected to the bottom electrode 202 through a through-hole.

[0089] The materials of the first conductive layer, the second conductive layer, and the third conductive layer can be metallic materials or other known or unknown conductive materials. The materials used for the first conductive layer, the second conductive layer, and the third conductive layer can be the same or different.

[0090] In some implementations, when the material deposited in the groove 207 is the same as the material forming the bottom electrode 202, steps four and five mentioned above are unnecessary. That is, the deposited first conductive layer can be directly masked, allowing the deposition of the conductive material in the groove 207 and the formation of the bottom electrode 202 to be completed in one step. This further simplifies the fabrication process of the thin-film bulk acoustic resonator 200.

[0091] By using the above-described manufacturing process to fabricate a Bragg reflector type thin-film bulk acoustic resonator 200, the thickness of the contact portion between the top electrode 202 and the through hole 205 can be increased, avoiding the consumption of some bottom electrode material or the etching of the bottom electrode 202 during the etching process of the through hole 205, thereby improving the reliability of the thin-film bulk acoustic resonator.

[0092] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A film bulk acoustic resonator, characterized by, The film bulk acoustic resonator comprises a substrate, a Bragg reflector and a piezoelectric oscillation structure. The piezoelectric oscillation structure comprises a bottom electrode, a piezoelectric film layer and a top electrode formed in sequence on the top surface of the Bragg reflector, wherein the bottom electrode is covered by the piezoelectric film layer, the piezoelectric film layer is provided with a through hole, and the bottom electrode is connected to the piezoelectric film layer away from the top surface of the substrate through a conductor in the through hole. The top surface of the substrate is provided with a groove, and the groove is filled with a conductive block in contact with the bottom electrode, wherein the through hole is projected onto the area where the groove is located, and the bottom electrode at least partially covers the groove.

2. A film bulk acoustic resonator, characterized by, The film bulk acoustic resonator comprises a substrate, a Bragg reflector and a piezoelectric oscillation structure. The Bragg reflector comprises a plurality of layers stacked in sequence on the top surface of the substrate, and the plurality of layers at least comprises a top layer and a low layer, wherein the top layer is the layer close to the substrate, and the low layer is the layer away from the substrate. The piezoelectric oscillation structure comprises a bottom electrode, a piezoelectric film layer and a top electrode formed in sequence on the top layer of the Bragg reflector, wherein the bottom electrode is covered by the piezoelectric film layer, the piezoelectric film layer is provided with a through hole, and the bottom electrode is connected to the piezoelectric film layer away from the top surface of the substrate through a conductor in the through hole. The top layer of the Bragg reflector is provided with a groove on the side in contact with the bottom electrode, and the groove is filled with a conductive block in contact with the bottom electrode, wherein the through hole is projected onto the area where the groove is located, and the bottom electrode at least partially covers the groove.

3. The film bulk acoustic resonator of claim 1 or 2, wherein, The top surface of the piezoelectric film layer is provided with a conductive plate, and the conductive plate is provided in the same layer with the top electrode and is insulated from each other, and the bottom electrode is connected to the conductive plate through the conductor in the through hole.

4. The film bulk acoustic resonator of claim 1 or 2, wherein, The material forming the conductive block in the groove is the same as the material forming the bottom electrode.

5. The film bulk acoustic resonator of claim 1 or 2, wherein, The material forming the top electrode is the same as the material forming the conductor in the through hole.

6. The film bulk acoustic resonator of claim 3, wherein, The material forming the top electrode is the same as the material forming the conductive plate.

7. The film bulk acoustic resonator of claim 1, wherein, The film bulk acoustic resonator is a cavity structure.

8. A filter comprising at least one film bulk acoustic resonator according to any one of claims 1-7.

9. A method of fabricating a film bulk acoustic resonator, the method comprising: The preparation method comprises: providing a substrate, etching the top surface of the substrate to form a groove; filling the first conductive material in the groove to form a conductive block, so that the top surface of the conductive block is at the same level with the top surface of the substrate; depositing the second conductive material on the top surface of the substrate to form a first conductive layer, and patterning the first conductive layer to form a bottom electrode; depositing the piezoelectric film material on the top surface of the substrate and the surface of the bottom electrode away from the substrate to form a piezoelectric film layer; etching the piezoelectric film layer in the area formed by the projection of the groove to the piezoelectric film layer to form at least one through hole penetrating through the top surface and the bottom surface of the piezoelectric film layer; The bottom electrode is in contact with the conductive block filled in the groove, and the bottom electrode at least partially covers the groove.

10. A method of fabricating a film bulk acoustic resonator, characterized by, The preparation method comprises: providing a substrate, depositing a Bragg reflector on the top surface of the substrate, wherein the Bragg reflector comprises a plurality of layers, and the plurality of layers at least comprises a top layer and a low layer, the top layer is a layer close to the substrate, and the low layer is a layer away from the substrate; etching the top layer of the Bragg reflector to form a groove; filling a first conductive material in the groove to form a conductive block, so that the top surface of the conductive block is at the same horizontal plane with the top surface of the top layer of the Bragg reflector; depositing a second conductive material on the top surface of the top layer of the Bragg reflector to form a first conductive layer, and patterning the first conductive layer to form a bottom electrode; depositing a piezoelectric thin film material on the top surface of the top layer of the Bragg reflector and the surface of the bottom electrode away from the substrate to form a piezoelectric thin film layer; etching the piezoelectric thin film layer in the area formed by the orthographic projection of the groove to the piezoelectric thin film layer to form at least one through hole penetrating through the top surface and the bottom surface of the piezoelectric thin film layer; The bottom electrode is in contact with the conductive block filled in the groove, and the bottom electrode at least partially covers the groove.

11. The production method according to claim 9 or 10, characterized by, The preparation method further comprises: depositing a third conductive material on the top surface of the piezoelectric thin film layer away from the substrate to form a second conductive layer and a conductor flowing into the through hole and in contact with the bottom electrode; patterning the second conductive layer to form a top electrode and a conductive plate, wherein the top electrode and the conductive plate are insulated, and the conductive plate at least partially covers the through hole; The bottom electrode is connected with the conductive plate through the conductor in the through hole.

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