Bulk acoustic wave resonator and preparation method therefor, and electronic device

Abstract

The present disclosure belongs to the technical field of communications, and provides a bulk acoustic wave resonator and an electronic device. The bulk acoustic wave resonator comprises a base substrate, a first electrode, a piezoelectric layer and a second electrode, wherein the first electrode is arranged on the base substrate; the second electrode is arranged on the side of the first electrode facing away from the base substrate; the piezoelectric layer is arranged between the first electrode and the second electrode; and the orthographic projections of any two of the first electrode, the piezoelectric layer and the second electrode on the base substrate at least partially overlap. The thermal conductivity of the piezoelectric layer is greater than the thermal conductivity of at least one of the first electrode and the second electrode.

Description

Bulk acoustic wave resonator, preparation method thereof, and electronic device Technical Field

[0001] The present disclosure belongs to the field of communication technology, and particularly relates to a bulk acoustic wave resonator, a preparation method thereof, and an electronic device. Background Art

[0002] In the field of mobile communications, because the total available frequency range is relatively narrow and there are many frequency bands used for mobile communications, the spacing between adjacent frequency bands is very narrow (approximately a few MHz to tens of MHz), and the bandwidth of a single frequency band is very narrow (tens of MHz), the filters used in mobile phones must have the performance characteristics of small in-band ripple, large out-of-band suppression, and good rectangularity. Conventional microstrip filters are large in size, have insufficient out-of-band suppression, and poor rectangularity, making them unsuitable. Cavity filters are also large in size and cannot be matched. Dielectric filters have large in-band insertion loss and poor rectangularity, making them unsuitable. IPD filters have large in-band ripple and poor rectangularity, making them unsuitable.

[0003] BAW resonators, the basic structural unit of BAW filters, currently use a silicon wafer as the substrate material. A sandwich structure is formed from the bottom up, with a first electrode, a piezoelectric layer, and a second electrode. The first and second electrodes are metal electrodes, while the piezoelectric layer is made of piezoelectric material.

[0004] The working principle of a bulk acoustic wave resonator is as follows: an RF signal is transmitted from the electrode at one end of the resonator and then converted into a mechanical vibration acoustic wave signal through the inverse piezoelectric effect at the interface between the piezoelectric material and the metal electrode. This acoustic wave signal forms a resonant standing wave with a certain frequency in the sandwich structure of the first electrode, the piezoelectric layer, and the second electrode. The frequency of the RF signal is equal to the resonant frequency of the resonator. The acoustic wave signal is transmitted to the electrode at the other end of the resonator and is converted into an RF signal through the piezoelectric effect at the interface between the metal electrode and the piezoelectric material. The resonator has a fixed resonant frequency. When the frequency of the RF signal is equal to the resonant frequency of the resonator, the conversion efficiency of RF signal → acoustic wave signal → RF signal is high. When the frequency of the RF signal is not equal to the resonant frequency of the resonator, the conversion efficiency of RF signal → acoustic wave signal → RF signal is very low, and most RF signals cannot be transmitted from the resonator. In other words, the resonator functions as a filter, filtering the RF signal. In order to reduce the insertion loss during the filtering process, the acoustic wave signal needs to be confined as much as possible inside the piezoelectric material to prevent the acoustic wave signal from spreading outward. Therefore, acoustic wave reflectors are usually constructed on the upper and lower surfaces of the resonator.

[0005] Summary of the Invention

[0006] The present disclosure provides a bulk acoustic wave resonator, a preparation method thereof, and an electronic device.

[0007] In a first aspect, the present disclosure provides a bulk acoustic wave resonator, comprising: a substrate, a first electrode, a piezoelectric layer, and a second electrode; the first electrode is arranged on the substrate, the second electrode is arranged on a side of the first electrode facing away from the substrate, the piezoelectric layer is arranged between the first electrode and the second electrode, and the orthographic projections of any two of the first electrode, the piezoelectric layer, and the second electrode on the substrate at least partially overlap; wherein the thermal conductivity of the piezoelectric layer is greater than the thermal conductivity of at least one of the first electrode and the second electrode.

[0008] In some embodiments, the base substrate has a first cavity extending through the base substrate along its thickness direction.

[0009] In some embodiments, the base substrate has a first groove portion penetrating a portion of the base substrate along a thickness direction thereof, and an opening of the first groove portion faces the first electrode.

[0010] In some embodiments, the first electrode is bonded to the base substrate.

[0011] In some embodiments, the BAW resonator further includes: a support layer disposed between the base substrate and the first electrode, wherein the support layer is bonded to the base substrate.

[0012] In some embodiments, the bulk acoustic wave resonator also includes at least one acoustic reflector structure arranged between the substrate and the first electrode, the acoustic reflector structure is bonded to the first electrode, and includes a first substructure layer and a second substructure layer arranged in sequence along a direction away from the substrate, and the acoustic impedance of the material of the first substructure layer is greater than the acoustic impedance of the material of the second substructure layer.

[0013] In some embodiments, the BAW resonator further includes a mass loading layer disposed on a side of the second electrode facing away from the substrate.

[0014] In some embodiments, the material of the piezoelectric layer includes at least one of single crystal AlN and single crystal BN.

[0015] In some embodiments, the materials of the first electrode and the second electrode each include at least one of Mo, Al, Cu, Co, Ag, Ti, Pt, Ru, W, and Au.

[0016] In a second aspect, the present disclosure further provides a method for preparing a bulk acoustic wave resonator, comprising:

[0017] providing a substrate;

[0018] A first electrode, a piezoelectric layer, and a second electrode are respectively formed on one side of the substrate, wherein the second electrode is formed on a side of the first electrode facing away from the substrate, the piezoelectric layer is formed between the first electrode and the second electrode, and the orthographic projections of any two of the first electrode, the piezoelectric layer, and the second electrode on the substrate at least partially overlap; wherein the thermal conductivity of the piezoelectric layer is greater than the thermal conductivity of at least one of the first electrode and the second electrode.

[0019] In some embodiments, the steps of forming a first electrode, a piezoelectric layer, and a second electrode on one side of the substrate include:

[0020] performing ion implantation on the piezoelectric substrate;

[0021] forming a first structure to be bonded on one side of the piezoelectric substrate, wherein the first structure to be bonded includes at least the first electrode;

[0022] Arranging the piezoelectric substrate having the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded and the second structure to be bonded to form a bonded assembly; the second structure to be bonded at least includes the substrate;

[0023] Annealing the bonding assembly to diffuse the ions implanted in the piezoelectric substrate and aggregate into a gas, thereby separating the piezoelectric substrate into the piezoelectric layer and the redundant portion;

[0024] A second electrode is formed on a side of the piezoelectric material layer away from the base substrate.

[0025] In some embodiments, in the step of implanting ions into the piezoelectric substrate, the implanted ions include hydrogen ions or helium ions.

[0026] In some embodiments, the material of the piezoelectric substrate includes at least one of single crystal AlN and single crystal BN.

[0027] In some embodiments, the first structure to be bonded further includes a support layer located on a side of the first electrode away from the piezoelectric substrate.

[0028] In some embodiments, the second structure to be bonded further includes at least one acoustic reflector structure located on one side of the substrate; the acoustic reflector structure includes a first substructure layer and a second substructure layer sequentially arranged in a direction away from the substrate, and the acoustic impedance of the material of the first substructure layer is greater than the acoustic impedance of the material of the second substructure layer;

[0029] In the bonding assembly, the first electrode material layer is bonded to the acoustic reflector structure.

[0030] In some embodiments, the preparation method further comprises:

[0031] A mass loading layer is formed on a side of the second electrode facing away from the substrate.

[0032] In some embodiments, the preparation method further comprises:

[0033] The base substrate is processed to form a first cavity penetrating along a thickness direction of the base substrate.

[0034] In some embodiments, the preparation method further comprises:

[0035] Before forming the first electrode, the base substrate is processed to form a first groove portion penetrating a portion of the base substrate; wherein the opening of the first groove portion faces the first electrode.

[0036] In a third aspect, the present disclosure further provides an electronic device comprising the above-mentioned bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0038] FIG1 is a schematic diagram of a first exemplary bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0039] FIG2 is a schematic diagram of a preparation process of a first example of a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0040] FIG3 is a schematic diagram of a second example of a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0041] FIG4 is a schematic diagram of a preparation process of a second example of a BAW resonator according to an embodiment of the present disclosure.

[0042] FIG5 is a schematic diagram of a third exemplary BAW resonator according to an embodiment of the present disclosure.

[0043] FIG6 is a schematic diagram of a preparation process of a third example BAW resonator according to an embodiment of the present disclosure.

[0044] Figure 7 is a schematic diagram of a fourth example of a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0045] FIG8 is a schematic diagram of a preparation process of a fourth example of a BAW resonator according to an embodiment of the present disclosure.

[0046] FIG9 is a schematic diagram of a fifth exemplary BAW resonator according to an embodiment of the present disclosure.

[0047] FIG10 is a schematic diagram of a preparation process of a fifth example of a BAW resonator according to an embodiment of the present disclosure.

[0048] FIG. 11 is a schematic diagram of a sixth example of a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0049] FIG12 is a schematic diagram of a preparation process of a sixth example of a BAW resonator according to an embodiment of the present disclosure.

[0050] FIG. 13 is a schematic diagram of a seventh example of a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0051] FIG14 is a schematic diagram of a preparation process of a seventh example of a BAW resonator according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0052] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0053] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0054] Unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should have the usual meanings understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0055] As used herein, "parallel" and "perpendicular" include the conditions described and conditions similar to the conditions described, and the range of the similar conditions is within an acceptable deviation range, wherein the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range for approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range for approximate perpendicularity can also be, for example, a deviation within 5°.

[0056] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0057] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0058] The inventors have discovered that the current power tolerance of a typical BAW resonator is generally less than or equal to 33dBm. When the power is higher than 33dBm, due to the certain insertion loss of the BAW resonator itself, part of the electromagnetic wave energy will be converted into heat, causing the temperature of the device to rise sharply, causing the BAW resonator's filtering curve to drift and the BAW resonator's performance to deteriorate; when the temperature rises to close to the melting point of certain materials that make up the BAW resonator, the device will fail, lose its filtering function, or directly cause the link to be disconnected.

[0059] In response to the above problems, the embodiments of the present disclosure provide a bulk acoustic wave resonator, in which the piezoelectric layer adopts a material with higher thermal conductivity, so that the heat generated by the piezoelectric layer can be promptly conducted to other membrane layers (such as the substrate). Without affecting the RF performance of the resonator, its heat dissipation capacity is greatly improved, reducing or preventing the failure of the resonator due to a sharp rise in temperature, and can cope with high-power application scenarios at the base station end.

[0060] The BAW resonator and the manufacturing method thereof according to the embodiment of the present disclosure are described below by using specific examples.

[0061] First example:

[0062] Figure 1 is a schematic diagram of a first example of a bulk acoustic wave resonator according to an embodiment of the present disclosure. As shown in Figure 1 , the bulk acoustic wave resonator includes: a substrate 10, a first electrode 11, a piezoelectric layer 13, and a second electrode 12; the first electrode 11 is arranged on the substrate 10, the second electrode 12 is arranged on a side of the first electrode 11 facing away from the substrate 10, the piezoelectric layer 13 is arranged between the first electrode 11 and the second electrode 12, and the orthographic projections of any two of the first electrode 11, the piezoelectric layer 13, and the second electrode 12 on the substrate 10 at least partially overlap.

[0063] In some examples, the material of the substrate 10 can be Si, or can also be selected from materials such as glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, GaO, SOI (silicon on insulator), PI, PET, etc. The thickness of the substrate 10 ranges from about 0.1 μm to 10 mm. To improve the heat dissipation effect of the BAW resonator, the substrate 10 can be made of Si or SiC, which can quickly conduct heat to the driver circuit board bonded to the substrate 10, and then dissipate the heat to the outside through the driver circuit board.

[0064] In some examples, the material of the first electrode 11 is a metal material, such as Mo. The material of the first electrode 11 may also be Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. The material may also be an alloy material formed by any combination of the above metals, or a stacked structure formed by the above metals. The thickness of the first electrode 11 ranges from 1 nm to 10 μm.

[0065] In some examples, the second electrode 12 is made of a metal, such as Mo. Alternatively, the second electrode 12 may be made of Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. Alternatively, the second electrode 12 may be made of any combination of the above metals, or a laminated structure of the above metals. The thickness of the second electrode 12 may range from 1 nm to 10 μm.

[0066] In some examples, the material of the piezoelectric layer 13 is a piezoelectric material, such as AlN or doped AlN, where doped AlN includes, for example, Al (1-x) Sc x N, Al (1-x) Cr x N, Al (1-x) Yx N, Al (1-x) Ti x N, Al (1-x) Zr x N, Al (1-x) Hf x N, Al (1-x) Yb x N, Al (1-x) Ta x N, Mg 0.5x Nb 0.5x Al (1-x) N, Mg 0.5x Ti 0.5x Al (1-x) N, Mg 0.5x Zr 0.5x A l(1-x) N, Mg 0.5x Hf 0.5x Al (1-x) N, Mg 0.5x Si 0.5x Al (1-x) N, Zn 0.25 Ti0. 25Al0.5 N, Zn 0.25 Zr 0.25 Al 0.5 N, Zn 0.25 Hf 0.25 Al 0.5 N. The material of the piezoelectric layer 13 can also be selected from BN, ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF, etc. The piezoelectric layer 13 can be composed of a single layer of piezoelectric material or a stack of the above piezoelectric materials. The thickness of the piezoelectric layer 13 ranges from 10 nm to 100 μm.

[0067] Preferably, the thermal conductivity of the piezoelectric layer 13 is greater than the thermal conductivity of at least one of the first electrode 11 and the second electrode 12, thereby enabling the piezoelectric layer 13 to have a better heat dissipation effect and promptly dissipate the generated heat. For example, the material of the piezoelectric layer 13 includes single-crystal AlN or single-crystal BN, or it can be a laminate of the two materials. In this case, the piezoelectric layer 13 itself has few defects and thus very low losses, thus generating very little heat and a small temperature rise. In addition, the undoped single-crystal AlN or single-crystal BN material has strong thermal conductivity, which can quickly conduct the small amount of heat generated from the piezoelectric layer 13.

[0068] For example, the materials of the first electrode 11 and the second electrode 12 both include metal Mo, so that the lattice size of the first electrode 11 and the second electrode 12 can be very close to the lattice size in the piezoelectric layer 13 .

[0069] In some examples, the base substrate 10 has a first groove 101 that penetrates a portion of the base substrate 10 along its thickness direction. The opening of the first groove 101 faces the first electrode 11, so that the base substrate 10 and the first electrode 11 define an air cavity. After the radio frequency signal is transmitted into the resonator, it is converted into an acoustic wave signal through the inverse piezoelectric effect at the interface between the second electrode 12 (or the first electrode 11) and the piezoelectric layer 13, and propagates longitudinally in the piezoelectric layer 13. When it reaches the interface between the first electrode 11 (or the second electrode 12) and the piezoelectric layer 13, it is converted into a radio frequency signal through the piezoelectric effect, and finally transmits out of the resonator. The air cavity below and the air layer above act as acoustic reflectors, and their function is to confine the acoustic signal to the resonator structure instead of dissipating it, which can reduce the loss of the resonator.

[0070] In some examples, an encapsulation layer may be further provided on the side of the second electrode 12 facing away from the base substrate 10 to isolate water vapor and oxygen to prevent device damage.

[0071] The following describes a method for preparing a bulk acoustic wave resonator in the first example. As shown in FIG2 , the method includes the following steps:

[0072] S10 , providing a base substrate 10 , wherein the base substrate 10 may be a silicon substrate. At this time, the base substrate 10 may be cleaned by standard RCA cleaning and then dried by air knife.

[0073] S11 , forming a first groove 101 on the base substrate 10 .

[0074] In some examples, step S11 may specifically include: preparing a mask pattern on the base substrate 10 (the material of the mask pattern can be selected from photoresist, inorganic mask material, or metal mask material), and performing a photolithography process, including resist coating (or spraying), pre-baking, exposure, development, and post-baking. Then, an etching process is performed to form the first groove portion 101. The etching process can be either wet etching or dry etching, with wet etching being preferred. Finally, a resist stripping process is performed to complete the preparation of the first groove portion 101.

[0075] Then, a first electrode 11, a piezoelectric layer 13, and a second electrode 12 are formed on one side of the base substrate 10, respectively, wherein the opening of the first groove 101 faces the first electrode 11. In some examples, the steps of forming the first electrode 11, the piezoelectric layer 13, and the second electrode 12 on the base substrate 10 specifically include the following steps S12 to S18.

[0076] S12, providing a piezoelectric substrate 131, cleaning the piezoelectric substrate 131, and then drying it with an air knife.

[0077] S13 , performing ion implantation on the piezoelectric substrate 131 .

[0078] In some examples, the implanted ions 13c can diffuse and aggregate into gas after subsequent annealing. Preferably, the implanted ions 13c are hydrogen ions (H + ) or helium ions (He + ). In addition, ion implantation is performed by a small-angle ion implantation method to ensure the ion implantation effect. For example, the implantation angle is about 7°.

[0079] In some examples, the energy range of the implanted ions is 50 KeV to 500 KeV, and the peak depth range of the implanted ions can be adjusted along with the implantation energy range, generally between 100 nm and 10 μm.

[0080] S14 , forming a first structure to be bonded on one side of the piezoelectric substrate 131 , where the first structure to be bonded includes at least a first electrode 11 .

[0081] For the bulk acoustic wave resonator shown in FIG1 , the first structure to be bonded may include only the first electrode 11. In this case, step S14 may include: forming a first electrode material layer on one side of the piezoelectric substrate 131. The first electrode material layer may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the first electrode 11 is formed by a patterning process. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed. A wet etching process is preferably used, but a dry etching process may also be selected.

[0082] S15. Arrange the piezoelectric substrate 131 with the first structure to be bonded opposite to the second structure to be bonded, and bond the first structure to be bonded to the second structure to be bonded to form a bonding assembly; the second structure to be bonded includes at least a base substrate 10, and the opening of the first groove 101 faces the first structure to be bonded.

[0083] For the BAW resonator shown in FIG1 , the second structure to be bonded may include only the base substrate 10 . In this case, step S15 is to flip the piezoelectric substrate 131 , place it opposite to the base substrate 10 , and bond the first electrode 11 to the base substrate 10 .

[0084] During bonding, a low-temperature bonding process under vacuum conditions can be used to form strong chemical bonds between atoms on both sides of the interface between the first electrode 11 and the base substrate 10. The bonding temperature range is 100°C to 250°C, and the bonding pressure range is 10 MPa to 10,000 GPa.

[0085] S16 , annealing the bonded assembly to diffuse the ions 13 c implanted in the piezoelectric substrate 131 and aggregate into a gas, thereby separating the piezoelectric substrate 131 into the piezoelectric material layer 13 a and the redundant portion.

[0086] The thickness of the piezoelectric material layer 13a is related to the peak implantation depth in the ion implantation step, for example, between 100 nm and 10 μm. The annealing temperature ranges from 600° C. to 1000° C., and the annealing time ranges from 30 seconds to 30 minutes.

[0087] Afterwards, an electrochemical mechanical polishing (CMP) process is performed on the surface of the piezoelectric material layer 13a facing away from the base substrate 10 to eliminate various defects in the surface layer and polish the surface.

[0088] S17: The polished piezoelectric material layer 13a is patterned to form the piezoelectric layer 13. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be selected.

[0089] S18 . Form a second electrode 12 on a side of the piezoelectric layer 13 away from the base substrate 10 .

[0090] Specifically, S18 may include first forming a second electrode material layer, which may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (or RF magnetron sputtering), and may also be pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. Thereafter, the second electrode 12 is formed by patterning the second electrode material layer. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, and a dry etching process may also be selected.

[0091] It should be noted that FIG2 illustrates an example in which the piezoelectric layer 13 is a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a that has fallen off the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the heat dissipation effect of the device is better.

[0092] Afterwards, an encapsulation layer can be formed on the side of the second electrode 12 facing away from the base substrate 10. The material of the encapsulation layer is preferably an organic compound that can isolate water vapor and oxygen, such as polyimide, epoxy resin, etc., or an inorganic material such as SiNx, Al2O3, etc. The encapsulation layer can be a single layer of a single material, or a stacked configuration of multiple materials. The encapsulation process can first perform a cutting process, and then use a standard semiconductor chip packaging process to encapsulate the resonator. There are many packaging forms, which are not specifically limited in this disclosure.

[0093] It should be noted that the above-described fabrication process is described by first forming a pattern of the first electrode 11 on the piezoelectric substrate 131, then bonding the first electrode 11 to the base substrate 10, and then sequentially forming the piezoelectric layer 13 and the second electrode 12. In other embodiments, a first electrode material layer may be first formed on the piezoelectric substrate 131, followed by the bonding step. After the piezoelectric material layer is formed, a second electrode material layer may be formed, and then the second electrode material layer, the piezoelectric material layer, and the first electrode material layer may be patterned.

[0094] Second example:

[0095] FIG3 is a schematic diagram of a second example BAW resonator of an embodiment of the present disclosure. As shown in FIG3 , the structure of the BAW resonator is similar to the structure shown in FIG1 , with the only difference being that, in FIG3 , the BAW resonator further includes: a mass load layer 14 , which is located on a side of the second electrode 12 away from the substrate 10 .

[0096] The mass load layer 14 can be a single layer of a single material or a stack of multiple materials. Its functions are: (1) to isolate water vapor and oxygen, act as a package, and prevent the resonator performance from deteriorating over time; and (2) to adjust and correct the resonator frequency to the ideal value by performing localized plasma etching on the mass load layer 14 when the resonator frequency shifts.

[0097] The mass-load layer 14 is preferably electrically insulating SiO2, but may also be made of materials such as Si3N4, Al2O3, AlN, and BN. Conductive metal materials such as Mo, Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, and Au may also be used. The mass-load layer 14 may be a single layer or a stack or alloy of the above materials. The thickness of the mass-load layer 14 ranges from 1 nm to 10 μm.

[0098] In one example, the mass loading layer 14 may be a planar film layer.

[0099] FIG4 is a schematic diagram of the preparation process of a BAW resonator according to a second example of an embodiment of the present disclosure. The preparation process in the second example is similar to the preparation process in FIG2 . In the preparation process shown in FIG4 , steps S20 to S28 are respectively the same as steps S10 to S18 in FIG2 . The following only describes the differences between the two preparation processes. After step S28, the following steps are also included:

[0100] S29 , forming a mass load layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0101] Specifically, the mass load layer 14 can be an insulating material. In this case, radio frequency measurement and control sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD) and the like can be used to deposit the load material layer. Alternatively, the load layer 14 is a metal material. In this case, a DC magnetron sputtering method is preferred (radio frequency magnetron sputtering is also possible), and pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation and the like can also be selected to deposit the load material layer. Afterwards, the load material layer is subjected to a patterning process to form the load layer 14. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, or a dry etching process can be selected.

[0102] Afterwards, an encapsulation layer can be formed on the side of the mass-load layer 14 facing away from the base substrate 10. The encapsulation layer is preferably made of an organic compound that can isolate water vapor and oxygen, such as polyimide or epoxy resin. Inorganic materials such as SiNx and Al2O3 can also be used. The encapsulation layer can be a single layer of a single material or a stacked configuration of multiple materials. The encapsulation process can begin with a dicing process, followed by standard semiconductor chip packaging techniques for resonator packaging. Various packaging formats are available.

[0103] It should be noted that in the fabrication process of FIG. 4 , the piezoelectric layer 13 is illustrated as a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a detached from the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the heat dissipation effect of the device is better.

[0104] 4 illustrates an example in which a pattern of the first electrode 11 is first formed on the piezoelectric substrate 131, the first electrode 11 is bonded to the base substrate 10, and the piezoelectric layer 13, the second electrode 12, and the load layer 14 are sequentially formed. In other embodiments, a first electrode material layer may be first formed on the piezoelectric substrate 131, followed by bonding. After the piezoelectric material layer is formed, a second electrode material layer and a load material layer are formed, and then the load material layer, the second electrode material layer, the piezoelectric material layer, and the first electrode material layer are patterned.

[0105] The third example:

[0106] Figure 5 is a schematic diagram of a third example BAW resonator according to an embodiment of the present disclosure. The structure of the BAW resonator in Figure 5 is similar to that in Figure 3 , differing only in that mass-load layer 14 is a patterned layer rather than a continuous planar film. When the resonator frequency shifts, localized plasma etching of mass-load layer 14 is performed to adjust and correct the resonator frequency to the desired value.

[0107] In FIG5 , mass-load layer 14 is preferably electrically insulating SiO 2 , but may also be made of materials such as Si 3 N 4 , Al 2 O 3 , AlN, or BN. Conductive metal materials such as Mo, Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, and Au may also be used. The mass-load layer 14 may be a single layer or a stack or alloy of the above materials. The thickness of mass-load layer 14 ranges from 1 nm to 10 μm.

[0108] FIG6 is a schematic diagram of the preparation process of a BAW resonator according to a third example of an embodiment of the present disclosure. The preparation process in the third example is similar to the preparation process in FIG2 . In the preparation process shown in FIG6 , steps S31 to S38 are respectively the same as steps S10 to S18 in FIG4 . The following only describes the differences between the two preparation processes. After step S18, the following steps are also included:

[0109] S39 , forming a supporting layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0110] Specifically, a support material layer can be formed first, and then patterned to form the desired patterned mass support layer 14. The patterning process for the intermediate support pattern includes resist coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be used.

[0111] Afterwards, an encapsulation layer can be formed on the side of the mass-load layer 14 facing away from the base substrate 10. The encapsulation layer is preferably made of an organic compound that can isolate water vapor and oxygen, such as polyimide or epoxy resin. Inorganic materials such as SiNx and Al2O3 can also be used. The encapsulation layer can be a single layer of a single material or a stacked configuration of multiple materials. The encapsulation process can begin with a dicing process, followed by standard semiconductor chip packaging techniques for resonator packaging. Various packaging formats are available.

[0112] It should be noted that the above-described fabrication process is described using the piezoelectric layer 13 as a patterned structure as an example. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a detached from the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the device exhibits better heat dissipation.

[0113] 6 illustrates an example in which a pattern of the first electrode 11 is first formed on the piezoelectric substrate 131, the first electrode 11 is then bonded to the base substrate 10, and the piezoelectric layer 13, the second electrode 12, and the load layer 14 are sequentially formed. In other embodiments, a first electrode material layer may be first formed on the piezoelectric substrate 131, followed by bonding. After the piezoelectric material layer is formed, a second electrode material layer and a load material layer are formed, and then the load material layer, the second electrode material layer, the piezoelectric material layer, and the first electrode material layer are patterned.

[0114] Fourth example:

[0115] FIG7 is a schematic diagram of a fourth example of a BAW resonator according to an embodiment of the present disclosure. The structure of the BAW resonator in FIG7 is similar to that in FIG3 , except that the BAW resonator shown in FIG7 may further include a support layer 15, which is located between the base substrate 10 and the first electrode 11. The support layer 15 may be bonded to the base substrate 10. By providing the support layer 15, the first electrode 11, the second electrode 12 and the piezoelectric layer 13 may be supported. In addition, the support layer 15 may be made of an electrically insulating material, thereby effectively avoiding the leakage of electromagnetic wave signals and reducing insertion loss.

[0116] In some examples, the material of the support layer 15 is preferably Si3N4, and materials such as SiO2, Al2O3, and their combinations can also be selected. The thickness of the support layer 15 ranges from about 1 nm to 100 μm.

[0117] In addition, the BAW resonator shown in FIG7 may further include a mass-load layer 14, which is located on the side of the second electrode 12 away from the substrate 10. Mass-load layer 14 is preferably electrically insulating SiO2, but may also be made of materials such as Si3N4, Al2O3, AlN, and BN. Alternatively, conductive metal materials such as Mo, Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, and Au may also be selected. The mass-load layer 14 may be a single layer or a stack or alloy of the above materials. The thickness of mass-load layer 14 ranges from 1 nm to 10 μm.

[0118] FIG. 7 illustrates an example in which the mass-loading layer 14 is a planar film layer. Of course, the mass-loading layer 14 may also be a patterned film layer.

[0119] In the BAW resonator shown in Figure 7, after an RF signal is transmitted into the resonator, it is converted into an acoustic wave signal through the inverse piezoelectric effect at the interface between second electrode 12 (or first electrode 11) and piezoelectric layer 13. This acoustic wave then propagates longitudinally through piezoelectric layer 13. Upon reaching the interface between first electrode 11 (or second electrode 12) and piezoelectric layer 13, it is converted back into an RF signal through the piezoelectric effect and finally exits the resonator. The air cavity below and the air layer above act as acoustic reflectors, confining the acoustic signal within the resonator structure rather than dissipating it, thereby reducing resonator losses.

[0120] The following describes a method for preparing a BAW resonator in the fourth example. As shown in FIG8 , the method includes the following steps:

[0121] S40 , providing a base substrate 10 .

[0122] The material of the substrate 10 can be Si, glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, GaO, SOI (silicon on insulator), PI, PET, and other materials. The thickness of the substrate 1010 ranges from approximately 0.1 μm to 10 mm. To improve the heat dissipation of the BAW resonator, the substrate 10 can be made of Si or SiC. For example, if the substrate 10 is a silicon substrate, the substrate 10 can be cleaned using standard RCA cleaning and then dried with an air knife.

[0123] S41 , forming a first groove 101 on the base substrate 10 .

[0124] In some examples, step S41 may specifically include: preparing a mask pattern on the base substrate 10 (the material of the mask pattern can be selected from photoresist, inorganic mask material, or metal mask material), and performing a photolithography process, including resist coating (or spraying), pre-baking, exposure, development, and post-baking. An etching process is then performed to form the first groove 101. The etching process can be either wet etching or dry etching, with wet etching being preferred. Finally, a resist stripping process is performed to complete the preparation of the first groove 101.

[0125] Then, a first electrode 11, a piezoelectric layer 13, and a second electrode 12 are formed on one side of the base substrate 10, wherein the opening of the first groove 101 faces the first electrode 11. In some examples, the steps of forming the first electrode 11, the piezoelectric layer 13, and the second electrode 12 on the base substrate 10 specifically include the following steps S42 to S49.

[0126] S42 , providing a piezoelectric substrate 131 , cleaning the piezoelectric substrate 131 , and then drying it with an air knife.

[0127] The material of the piezoelectric substrate 131 is a piezoelectric material, such as AlN or doped AlN. The doped AlN includes, for example, Al (1-x) Sc x N, Al (1-x) Cr x N, Al (1-x) Y x N, Al (1-x) Ti x N, Al (1-x) Zr x N, Al (1-x) Hf x N, Al (1-x) Yb x N, Al (1-x) Ta x N, Mg 0.5x Nb 0.5x Al (1-x) N, Mg0.5x Ti 0.5x Al (1-x) N, Mg 0.5x Zr 0.5x A l(1-x) N, Mg 0.5x Hf 0.5x Al (1-x) N, Mg 0.5x Si 0.5x Al (1-x) N, Zn 0.25 Ti0. 25Al0.5 N, Zn 0.25 Zr 0.25 Al 0.5 N, Zn 0.25 Hf 0.25 Al 0.5 N. The material of the piezoelectric layer 13 can also be selected from BN, ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF and other materials.

[0128] Preferably, the thermal conductivity of the piezoelectric substrate 131 is greater than the thermal conductivity of at least one of the first electrode 11 and the second electrode 12. This allows the subsequently formed piezoelectric layer 13 to have a good heat dissipation effect and promptly dissipate the generated heat. For example, the material of the piezoelectric substrate 131 includes at least one of single crystal AlN and single crystal BN.

[0129] S43 , performing ion implantation on the piezoelectric substrate 131 .

[0130] In some examples, the implanted ions 13c can diffuse and aggregate into gas after subsequent annealing. Preferably, the implanted ions 13c are hydrogen ions (H + ) or helium ions (He + ). In addition, ion implantation is performed by a small-angle ion implantation method to ensure the ion implantation effect. For example, the implantation angle is about 7°.

[0131] In some examples, the energy range of the implanted ions is 50 KeV to 500 KeV, and the peak depth range of the implanted ions can be adjusted along with the implantation energy range, generally between 100 nm and 10 μm.

[0132] S44. Form a first structure to be bonded on one side of the piezoelectric substrate 131. The first structure to be bonded includes at least the first electrode 11. Furthermore, when the preparation method is used to prepare the bulk acoustic wave resonator shown in FIG7 , the first structure to be bonded may further include a support layer 15. The support layer 15 is located on a side of the first electrode 11 away from the piezoelectric substrate 131. The opening of the first groove 101 faces the first electrode 11.

[0133] The first electrode 11 can be formed by metal thin film deposition, preferably DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, and the like can be used. The support layer 15 is made of an electrically insulating material and can be deposited using processes such as RF magnetron sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), and low-pressure chemical vapor deposition (LPCVD). The support layer 15 can be a solid layer or a patterned structure.

[0134] The material of the first electrode 11 is, for example, metallic Mo. Alternatively, materials such as Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au may be used. Alternatively, an alloy material formed by any combination of the above metals may be used, or a laminated structure formed by the above metals may be used. The thickness of the first electrode 11 ranges from 1 nm to 10 μm.

[0135] S45 , arranging the piezoelectric substrate 131 with the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded and the second structure to be bonded to form a bonded assembly; the second structure to be bonded at least includes the base substrate 10 .

[0136] For the BAW resonator shown in FIG. 7 , the second structure to be bonded may include only the base substrate 10 . In this case, step S45 is to flip the piezoelectric substrate 131 , place it opposite to the base substrate 10 , and bond the support layer 15 to the base substrate 10 .

[0137] During bonding, a low-temperature bonding process under vacuum conditions can be used to form strong chemical bonds between atoms on both sides of the interface between the support layer 15 and the base substrate 10. The bonding temperature range is 100°C to 250°C, and the bonding pressure range is 10 MPa to 10,000 GPa.

[0138] S46: Annealing the bonded assembly to diffuse and aggregate the ions 13c implanted in the piezoelectric substrate 131 into a gas, thereby separating the piezoelectric substrate 131 into the piezoelectric material layer 13a and the redundant portion. Subsequently, electrochemical mechanical polishing (CMP) is performed on the surface of the piezoelectric material layer 13a facing away from the base substrate 10 to eliminate various surface defects and polish the surface.

[0139] The thickness of the piezoelectric material layer 13a is related to the peak implantation depth in the ion implantation step, for example, between 100 nm and 10 μm. The annealing temperature ranges from 600° C. to 1000° C., and the annealing time ranges from 30 seconds to 30 minutes.

[0140] S47: Patterning the piezoelectric material layer 13a to form the piezoelectric layer 13. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be selected.

[0141] S48 , forming a second electrode 12 on a side of the piezoelectric layer 13 away from the base substrate 10 .

[0142] Specifically, S48 may include first forming a second electrode material layer. The second electrode material layer may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the second electrode material layer is patterned to form the second electrode 12. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, but a dry etching process may also be selected.

[0143] The material of the second electrode 12 is, for example, metallic Mo. Alternatively, materials such as Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au may be selected. Alternatively, an alloy material formed by any combination of the above metals may be used, or a laminated structure formed by the above metals may be used. The thickness of the second electrode 12 ranges from 1 nm to 10 μm.

[0144] In one example, the material of the first electrode 11 and the second electrode 12 is metal Mo, so that the lattice size of the first electrode 11 and the second electrode 12 can be very close to the lattice size in the piezoelectric layer 13 .

[0145] S49 , forming a mass load layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0146] Specifically, the mass-load layer 14 can be made of an insulating material. In this case, the load material layer can be deposited by methods such as radio frequency controlled sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), and low-pressure chemical vapor deposition (LPCVD). Alternatively, the load material layer can be made of a metallic material. In this case, DC magnetron sputtering is preferred (radio frequency magnetron sputtering is also acceptable). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, and electron beam evaporation can be used to deposit the load material layer, which is then patterned to form the mass-load layer 14.

[0147] Afterwards, an encapsulation layer can be formed on the side of the mass-load layer 14 facing away from the base substrate 10. The encapsulation layer is preferably made of an organic compound that can isolate water vapor and oxygen, such as polyimide or epoxy resin. Inorganic materials such as SiNx and Al2O3 can also be used. The encapsulation layer can be a single layer of a single material or a stacked configuration of multiple materials. The encapsulation process can begin with a dicing process, followed by standard semiconductor chip packaging techniques for resonator packaging. Various packaging formats are available.

[0148] It should be noted that the above-described fabrication process is described using the piezoelectric layer 13 as a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a that has fallen off the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the device exhibits better heat dissipation. Furthermore, the above-described process is described using an example in which the first electrode 11 and the support layer 15 are first patterned on the piezoelectric substrate 131, the support layer 15 is then bonded to the base substrate 10, and the piezoelectric layer 13, the second electrode 12, and the mass-load layer 14 are subsequently formed. In other embodiments, the support material layer and the first electrode material layer may be first formed on the piezoelectric substrate 131, followed by the bonding step. After the piezoelectric material layer is formed, the second electrode material layer may be formed, and then the second electrode material layer, the piezoelectric material layer, the first electrode material layer, and the support material layer may be patterned. Of course, in other embodiments, the support layer 15 may not be patterned, but may be a single film layer.

[0149] The fifth example:

[0150] FIG9 is a schematic diagram of a fifth example BAW resonator according to an embodiment of the present disclosure. The BAW resonator in FIG5 is similar to that in FIG3 , differing only in the structure of the substrate 10. In FIG5 , the substrate 10 does not have a first groove 101, but instead has a first cavity 102 extending through the substrate 10 along its thickness.

[0151] In Figure 9, first cavity 102 forms an acoustic reflection layer. After an RF signal is transmitted into the resonator, it is converted into an acoustic wave signal through the inverse piezoelectric effect at the interface between second electrode 12 (or first electrode 11) and piezoelectric layer 13. This acoustic wave propagates longitudinally through piezoelectric layer 13, and upon reaching the interface between first electrode 11 (or second electrode 12) and piezoelectric layer 13, it is converted back into an RF signal through the piezoelectric effect before finally exiting the resonator. The air cavity below the resonator and the air layer above it act as acoustic reflectors, confining the acoustic signal within the resonator structure rather than dissipating it, thereby reducing resonator losses.

[0152] The following describes a method for preparing a BAW resonator in the fifth example. As shown in FIG10 , the method includes the following steps:

[0153] S50 , providing a base substrate 10 .

[0154] The material of the substrate 10 can be Si, glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, GaO, SOI (silicon on insulator), PI, PET, and other materials. The thickness of the substrate 1010 ranges from approximately 0.1 μm to 10 mm. To improve the heat dissipation of the BAW resonator, the substrate 10 can be made of Si or SiC. For example, if the substrate 10 is a silicon substrate, the substrate 10 can be cleaned using standard RCA cleaning and then dried with an air knife.

[0155] Afterwards, the first electrode 11, the piezoelectric layer 13 and the second electrode 12 are formed on the base substrate 10 respectively. The process specifically includes the following steps S51 to S58:

[0156] S51 , providing a piezoelectric substrate 131 , cleaning the piezoelectric substrate 131 , and then drying it with an air knife.

[0157] The material of the piezoelectric substrate 131 is a piezoelectric material, such as AlN or doped AlN. The doped AlN includes, for example, Al (1-x) Sc x N, Al (1-x) Cr x N, Al (1-x) Y x N, Al (1-x) Ti x N, Al (1-x) Zr x N, Al (1-x) Hf x N, Al (1-x) Yb x N, Al (1-x) Ta x N, Mg 0.5x Nb0.5x Al (1-x) N, Mg 0.5x Ti 0.5x Al (1-x) N, Mg 0.5x Zr 0.5x A l(1-x) N, Mg 0.5x Hf 0.5x Al (1-x) N, Mg 0.5x Si 0.5x Al (1-x) N, Zn 0.25 Ti0. 25Al0.5 N, Zn 0.25 Zr 0.25 Al 0.5 N, Zn 0.25 Hf 0.25 Al 0.5 N. The material of the piezoelectric layer 13 can also be selected from ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF and other materials.

[0158] Preferably, the thermal conductivity of the piezoelectric substrate 131 is greater than the thermal conductivity of at least one of the first electrode 11 and the second electrode 12. This allows the subsequently formed piezoelectric layer 13 to have a good heat dissipation effect and promptly dissipate the generated heat. For example, the material of the piezoelectric substrate 131 includes at least one of single crystal AlN and single crystal BN.

[0159] S52 , performing ion implantation on the piezoelectric substrate 131 .

[0160] In some examples, the implanted ions 13c can diffuse and aggregate into gas after subsequent annealing. Preferably, the implanted ions 13c are hydrogen ions (H + ) or helium ions (He + ). In addition, ion implantation is performed by a small-angle ion implantation method to ensure the ion implantation effect. For example, the implantation angle is about 7°.

[0161] In some examples, the energy range of the implanted ions is 50 KeV to 500 KeV, and the peak depth range of the implanted ions can be adjusted along with the implantation energy range, generally between 100 nm and 10 μm.

[0162] S53 , forming a first structure to be bonded on one side of the piezoelectric substrate 131 , where the first structure to be bonded includes at least a first electrode 11 .

[0163] For the bulk acoustic wave resonator in FIG9 , the first structure to be bonded may include only the first electrode 11. In this case, step S53 may include: forming a first electrode material layer on one side of the piezoelectric substrate 131. The first electrode material layer may be formed by metal thin film deposition, preferably by DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the first electrode 11 is formed by a patterning process, which includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably by wet etching, but dry etching may also be selected.

[0164] The material of the first electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or a laminated structure formed by the above metals. The thickness of the first electrode material layer ranges from 1 nm to 10 μm.

[0165] S54 , arranging the piezoelectric substrate 131 with the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded and the second structure to be bonded to form a bonded assembly; the second structure to be bonded at least includes the base substrate 10 .

[0166] For the BAW resonator shown in FIG9 , the second structure to be bonded may include only the base substrate 10 . In this case, step S54 is to flip the piezoelectric substrate 131 , place it opposite to the base substrate 10 , and bond the first electrode 11 to the base substrate 10 .

[0167] During bonding, a low-temperature bonding process under vacuum conditions can be used to form strong chemical bonds between atoms on both sides of the interface between the first electrode 11 and the base substrate 10. The bonding temperature range is 100°C to 250°C, and the bonding pressure range is 10 MPa to 10,000 GPa.

[0168] S55: Anneal the bonded assembly to diffuse and aggregate the ions 13c implanted in the piezoelectric substrate 131 into a gas, thereby separating the piezoelectric substrate 131 into the piezoelectric material layer 13a and the redundant portion. Subsequently, perform an electrochemical mechanical polishing (CMP) process on the surface of the piezoelectric material layer 13a facing away from the base substrate 10 to eliminate various surface defects and polish the surface.

[0169] The thickness of the piezoelectric material layer 13a is related to the peak implantation depth in the ion implantation step, for example, between 100 nm and 10 μm. The annealing temperature ranges from 600° C. to 1000° C., and the annealing time ranges from 30 seconds to 30 minutes.

[0170] S56: Patterning the piezoelectric material layer 13a to form the piezoelectric layer 13. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be selected.

[0171] S57 , forming a second electrode 12 on a side of the piezoelectric layer 13 away from the base substrate 10 .

[0172] Specifically, S57 may include first forming a second electrode material layer. The second electrode material layer may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the second electrode material layer is subjected to a patterning process to form the second electrode 12. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, but a dry etching process may also be selected.

[0173] The material of the second electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or it may be a laminated structure formed by the above metals. The thickness of the second electrode material layer ranges from 1 nm to 10 μm.

[0174] In one example, in order to make the lattice size of the first electrode material layer and the second electrode material layer close to the lattice size of the piezoelectric layer 13 , both the first electrode material layer and the second metal material layer can be made of metal Mo.

[0175] S58 , forming a mass load layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0176] Specifically, the mass-load layer 14 can be made of an insulating material. In this case, the mass-load layer 14 can be deposited by methods such as radio frequency controlled sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), and low-pressure chemical vapor deposition (LPCVD). Alternatively, the mass-load layer 14 can be made of a metallic material. In this case, DC magnetron sputtering is preferred (radio frequency magnetron sputtering is also acceptable). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, and electron beam evaporation can be used to deposit the mass-load layer 14.

[0177] S59: Turn over the base substrate 10 and process it to form a first cavity 102 penetrating along the thickness direction of the base substrate 10. The base substrate 10 can be hollowed out to the first electrode 11 by wet etching or dry etching.

[0178] Afterwards, an encapsulation layer can be formed on the side of the mass-load layer 14 facing away from the base substrate 10. The encapsulation layer is preferably made of an organic compound that can isolate water vapor and oxygen, such as polyimide or epoxy resin. Inorganic materials such as SiNx and Al2O3 can also be used. The encapsulation layer can be a single layer of a single material or a stacked configuration of multiple materials. The encapsulation process can begin with a dicing process, followed by standard semiconductor chip packaging techniques for resonator packaging. Various packaging formats are available.

[0179] It should be noted that, in the above-mentioned manufacturing process, the piezoelectric layer 13 is illustrated as a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a that has fallen off the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the heat dissipation effect of the device is better. In addition, in the above-mentioned process, the pattern of the first electrode 11 is first formed on the piezoelectric substrate 131, and then the first electrode 11 is bonded to the base substrate 10, and then the piezoelectric layer 13, the second electrode 12 and the mass load layer 14 are formed in sequence. In other embodiments, the first electrode material layer may be first formed on the piezoelectric substrate 131, and then the bonding step may be performed. After the piezoelectric material layer is formed, the second electrode material layer may be formed, and then the second electrode material layer, the piezoelectric material layer and the first electrode material layer may be patterned.

[0180] The sixth example:

[0181] FIG11 is a schematic diagram of a sixth example of a bulk acoustic wave resonator according to an embodiment of the present disclosure. The bulk acoustic wave resonator in FIG11 is similar to that in FIG9 , except that the bulk acoustic wave resonator in FIG11 further includes a support layer 15, which is located between the base substrate 10 and the first electrode 11. The support layer 15 can be bonded to the base substrate 10. By providing the support layer 15, the first electrode 11, the second electrode 12 and the piezoelectric layer 13 can be supported. In addition, the support layer 15 can be made of an electrically insulating material, thereby effectively avoiding the leakage of electromagnetic wave signals and reducing insertion loss.

[0182] In some examples, the material of the support layer 15 is preferably Si3N4, and materials such as SiO2, Al2O3, and their combinations can also be selected. The thickness of the support layer 15 ranges from about 1 nm to 100 μm.

[0183] The following describes a method for preparing a BAW resonator in the sixth example. As shown in FIG12 , the method includes the following steps:

[0184] S61 , providing a base substrate 10 .

[0185] The material of the substrate 10 can be Si, glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, GaO, SOI (silicon on insulator), PI, PET, and other materials. The thickness of the substrate 1010 ranges from approximately 0.1 μm to 10 mm. To improve the heat dissipation of the BAW resonator, the substrate 10 can be made of Si or SiC. For example, if the substrate 10 is a silicon substrate, the substrate 10 can be cleaned using standard RCA cleaning and then dried with an air knife.

[0186] Afterwards, the first electrode 11, the piezoelectric layer 13 and the second electrode 12 are formed on the base substrate 10 respectively. The process specifically includes the following steps S61 to S69:

[0187] S61 , providing a piezoelectric substrate 131 , cleaning the piezoelectric substrate 131 , and then drying it with an air knife.

[0188] The material of the piezoelectric substrate 131 is a piezoelectric material, such as AlN or doped AlN. The doped AlN includes, for example, Al (1-x) Sc x N, Al (1-x) Cr x N, Al (1-x) Y x N, Al (1-x) Ti x N, Al (1-x) Zr x N, Al(1-x) Hf x N, Al (1-x) Yb x N, Al (1-x) Ta x N, Mg 0.5x Nb 0.5x Al (1-x) N, Mg 0.5x Ti 0.5x Al (1-x) N, Mg 0.5x Zr 0.5x A l(1-x) N, Mg 0.5x Hf 0.5x Al (1-x) N, Mg 0.5x Si 0.5x Al (1-x) N, Zn 0.25 Ti0. 25Al0.5 N, Zn 0.25 Zr 0.25 Al 0.5 N, Zn 0.25 Hf 0.25 Al 0.5 N. The material of the piezoelectric layer 13 can also be selected from ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF and other materials.

[0189] Preferably, the thermal conductivity of the piezoelectric substrate 131 is greater than the thermal conductivity of at least one of the first electrode 11 and the second electrode 12. This allows the subsequently formed piezoelectric layer 13 to have a good heat dissipation effect and promptly dissipate the generated heat. For example, the material of the piezoelectric substrate 131 includes at least one of single crystal AlN and single crystal BN.

[0190] S62 , performing ion implantation on the piezoelectric substrate 131 .

[0191] In some examples, the implanted ions 13c can diffuse and aggregate into gas after subsequent annealing. Preferably, the implanted ions 13c are hydrogen ions (H + ) or helium ions (He + ). In addition, ion implantation is performed by a small-angle ion implantation method to ensure the ion implantation effect. For example, the implantation angle is about 7°.

[0192] In some examples, the energy range of the implanted ions is 50 KeV to 500 KeV, and the peak depth range of the implanted ions can be adjusted along with the implantation energy range, generally between 100 nm and 10 μm.

[0193] S63 , forming a first structure to be bonded on one side of the piezoelectric substrate 131 , the first structure to be bonded comprising a first electrode 11 and a support layer 15 . The support layer 15 is located on a side of the first electrode 11 away from the piezoelectric substrate 131 .

[0194] Step S63 may include forming a first electrode material layer on one side of the piezoelectric substrate 131 and patterning the first electrode material to form a first electrode. The first electrode material layer may be formed by metal thin film deposition, preferably by DC magnetron sputtering (which may also be RF magnetron sputtering), or by pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, or the like. A support material layer is then formed, and the support material layer is patterned to form a support layer 15. Of course, the support material layer may also be directly used as the support layer 15, i.e., the support material layer is not patterned.

[0195] The material of the first electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or a laminated structure formed by the above metals. The thickness of the first electrode material layer ranges from 1 nm to 10 μm.

[0196] S64 , arranging the piezoelectric substrate 131 with the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded and the second structure to be bonded to form a bonded assembly; the second structure to be bonded at least includes a base substrate 10 .

[0197] For the BAW resonator shown in FIG11 , the second structure to be bonded may include only the base substrate 10 . In this case, step S64 is to flip the piezoelectric substrate 131 , place it opposite to the base substrate 10 , and bond the support layer 15 to the base substrate 10 .

[0198] During bonding, a low-temperature bonding process under vacuum conditions can be used to form strong chemical bonds between atoms on both sides of the interface between the first electrode 11 and the base substrate 10. The bonding temperature range is 100°C to 250°C, and the bonding pressure range is 10 MPa to 10,000 GPa.

[0199] S65 , annealing the bonded assembly to diffuse the ions 13 c implanted in the piezoelectric substrate 131 and aggregate into a gas, thereby separating the piezoelectric substrate 131 into the piezoelectric material layer 13 a and the redundant portion.

[0200] The thickness of the piezoelectric material layer 13a is related to the peak implantation depth in the ion implantation step, for example, between 100 nm and 10 μm. The annealing temperature ranges from 600° C. to 1000° C., and the annealing time ranges from 30 seconds to 30 minutes.

[0201] S66 , performing an electrochemical mechanical polishing (CMP) process on the surface of the piezoelectric material layer 13 a facing away from the base substrate 10 to eliminate various defects in the surface layer and polish the surface.

[0202] S67: Patterning the piezoelectric material layer 13a to form the piezoelectric layer 13. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be selected.

[0203] S68 , forming a second electrode 12 on a side of the piezoelectric layer 13 away from the base substrate 10 .

[0204] Specifically, S68 may include first forming a second electrode material layer. The second electrode material layer may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (which may also be radio frequency magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the second electrode material layer is patterned to form the second electrode 12. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, but a dry etching process may also be selected.

[0205] The material of the second electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or it may be a laminated structure formed by the above metals. The thickness of the second electrode material layer ranges from 1 nm to 10 μm.

[0206] In one example, in order to make the lattice size of the first electrode 11 and the second electrode 12 close to the lattice size of the piezoelectric layer 13 , both the first electrode material layer 11 and the second metal 12 can be made of metal Mo.

[0207] S69 , forming a mass load layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0208] Specifically, the mass load layer 14 can be made of an insulating material. In this case, the mass load layer 14 can be deposited by methods such as radio frequency controlled sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), and low pressure chemical vapor deposition (LPCVD). Alternatively, the mass load layer 14 can be made of a metal material. In this case, DC magnetron sputtering is preferred (radio frequency magnetron sputtering is also acceptable). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, and electron beam evaporation can be used to deposit the mass load layer 14.

[0209] S691: Turn over the base substrate 10 and process it to form a first cavity 102 penetrating along the thickness direction of the base substrate 10. The base substrate 10 can be hollowed out to the support layer 15 by wet etching or dry etching.

[0210] Afterwards, an encapsulation layer can be formed on the side of the mass-load layer 14 facing away from the base substrate 10. The encapsulation layer is preferably made of an organic compound that can isolate water vapor and oxygen, such as polyimide or epoxy resin. Inorganic materials such as SiNx and Al2O3 can also be used. The encapsulation layer can be a single layer of a single material or a stacked configuration of multiple materials. The encapsulation process can begin with a dicing process, followed by standard semiconductor chip packaging techniques for resonator packaging. Various packaging formats are available.

[0211] It should be noted that the above-described fabrication process is described using the piezoelectric layer 13 as a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a that has fallen off the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the device exhibits better heat dissipation. Furthermore, the above-described process is described using an example in which the first electrode 11 and the support layer 15 are first patterned on the piezoelectric substrate 131, the support layer 15 is then bonded to the base substrate 10, and the piezoelectric layer 13, the second electrode 12, and the mass-load layer 14 are subsequently formed. In other embodiments, the support material layer and the first electrode material layer may be first formed on the piezoelectric substrate 131, followed by the bonding step. After the piezoelectric material layer is formed, the second electrode material layer may be formed, and then the second electrode material layer, the piezoelectric material layer, the first electrode material layer, and the support material layer may be patterned. Of course, in other embodiments, the support layer 15 may not be patterned, but may be a single film layer.

[0212] The seventh example:

[0213] FIG13 is a schematic diagram of a BAW resonator according to a seventh example of an embodiment of the present disclosure. The BAW resonator in FIG13 is similar to that in FIG9 , and only the differences between FIG13 and FIG9 are described below. In FIG13 , the substrate 10 does not have the first cavity 102 or the first groove 101. Furthermore, in FIG13 , the BAW resonator further includes at least one acoustic reflector structure 16 located between the substrate 10 and the first electrode 11.

[0214] After the RF signal enters the resonator, it is converted into an acoustic wave signal through the inverse piezoelectric effect at the interface between the second electrode 12 (or first electrode 11) and the piezoelectric layer 13. The acoustic wave propagates longitudinally through the piezoelectric layer 13, and then, upon reaching the interface between the first electrode 11 (or second electrode 12) and the piezoelectric layer 13, is converted back into an RF signal through the piezoelectric effect before finally exiting the resonator. The acoustic reflector structure 16 below the resonator and the air layer above it act as acoustic reflectors, confining the acoustic signal within the resonator structure rather than dissipating it, thereby reducing resonator losses.

[0215] The acoustic reflector structure 16 includes a first substructure and a second substructure disposed sequentially in a direction away from the substrate 10. The acoustic impedance of the material of the first substructure is greater than that of the material of the second substructure. For ease of description and understanding, the first substructure is referred to as the high acoustic impedance layer 161, and the second substructure is referred to as the low acoustic impedance layer 162.

[0216] The acoustic impedance of a material is equal to the speed of sound waves propagating through it multiplied by its density. Theoretically, when the thickness of high-impedance layer 161 is equal to one-quarter the wavelength of sound waves at the resonant frequency of the bulk acoustic wave resonator propagating through high-impedance layer 161, and the thickness of low-impedance layer 162 is equal to one-quarter the wavelength of sound waves at the resonant frequency of the bulk acoustic wave resonator propagating through low-impedance layer 162, the alternating arrangement of high and low-impedance layers 162 (high / low / high / low, or low / high / low / high, etc.) creates an acoustic mirror, reflecting back sound signals leaking from above. A high-impedance layer 161 and a low-impedance layer 162 form a group. Generally, three to four groups are required to achieve good acoustic reflection. Of course, more groups are better, but this increases cost. The disclosed embodiments do not limit the number of groups; specifically, it can be between 1 and 100. There is also no restriction on whether the thickness of high-impedance layer 161 and low-impedance layer 162 is equal to one-quarter the wavelength; any thickness is acceptable. The material of high acoustic impedance layer 161 may be W, Ir, Pt, Ru, Au, Mo, Ta, Ti, Cu, Ni, Zn, Al, Al2O3, Ag, etc. The material of low acoustic impedance layer 162 may be SiO2, Si3N4, Mg, rubber, nylon, polyimide, polyethylene, polystyrene, Teflon, etc. Depending on the different resonant frequencies and the different sound velocities of different materials, the thickness of each high acoustic impedance layer 161 and each low acoustic impedance layer 162 may range from 1 nm to 10 μm.

[0217] The following describes a method for preparing a BAW resonator in the seventh example. As shown in FIG14 , the method includes the following steps:

[0218] S70 , providing a base substrate 10 .

[0219] The material of the substrate 10 can be Si, glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, GaO, SOI (silicon on insulator), PI, PET, and other materials. The thickness of the substrate 1010 ranges from approximately 0.1 μm to 10 mm. To improve the heat dissipation of the BAW resonator, the substrate 10 can be made of Si or SiC. For example, if the substrate 10 is a silicon substrate, the substrate 10 can be cleaned using standard RCA cleaning and then dried with an air knife.

[0220] S71 , forming at least one layer of acoustic reflector structure 16 on the base substrate 10 .

[0221] Specifically, (a) first deposit the thin film material of the high acoustic impedance layer 161, preferably by direct current magnetron sputtering. Of course, it can also be radio frequency magnetron sputtering, or pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc.; (b) then deposit the thin film material of the low acoustic impedance layer 162, and the deposition method can be radio frequency measurement and control sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), organic material spin coating or spray coating followed by post-annealing, etc. After steps (a) and (b), the production of the acoustic reflector structure 16 is completed. When it is necessary to form a multi-layer acoustic reflector structure 16, steps (a) and (b) are repeated until an acoustic reflector structure 16 having the required number of layers is obtained.

[0222] Afterwards, a first electrode 11, a piezoelectric layer 13, and a second electrode 12 are formed on the side of the acoustic reflector structure 16 facing away from the substrate 10. The process specifically includes the following steps S72 to S78:

[0223] S72, providing a piezoelectric substrate 131, cleaning the piezoelectric substrate 131, and then drying it with an air knife.

[0224] The material of the piezoelectric substrate 131 is a piezoelectric material, such as AlN or doped AlN. The doped AlN includes, for example, Al (1-x) Sc x N, Al (1-x) Cr x N, Al (1-x) Y x N, Al (1-x) Ti x N, Al (1-x) Zr x N, Al (1-x) Hf x N, Al (1-x) Yb x N, Al (1-x) Ta x N, Mg 0.5x Nb 0.5x Al (1-x) N, Mg 0.5x Ti 0.5x Al (1-x) N, Mg 0.5x Zr 0.5x A l(1-x) N, Mg 0.5x Hf 0.5x Al (1-x) N, Mg 0.5x Si 0.5x Al (1-x)N, Zn 0.25 Ti0. 25Al0.5 N, Zn 0.25 Zr 0.25 Al 0.5 N, Zn 0.25 Hf 0.25 Al 0.5 N. The material of the piezoelectric layer 13 can also be selected from ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF and other materials.

[0225] Preferably, the thermal conductivity of the piezoelectric substrate 131 is greater than the thermal conductivity of at least one of the first electrode 11 and the second electrode 12. This allows the subsequently formed piezoelectric layer 13 to have a good heat dissipation effect and promptly dissipate the generated heat. For example, the material of the piezoelectric substrate 131 includes at least one of single crystal AlN and single crystal BN.

[0226] S73 , perform ion implantation on the piezoelectric substrate 131 .

[0227] In some examples, the implanted ions 13c can diffuse and aggregate into gas after subsequent annealing. Preferably, the implanted ions 13c are hydrogen ions (H + ) or helium ions (He + ). In addition, ion implantation is performed by a small-angle ion implantation method to ensure the ion implantation effect. For example, the implantation angle is about 7°.

[0228] In some examples, the energy range of the implanted ions is 50 KeV to 500 KeV, and the peak depth range of the implanted ions can be adjusted along with the implantation energy range, generally between 100 nm and 10 μm.

[0229] S74. Form a first structure to be bonded on one side of the piezoelectric substrate 131, the first structure to be bonded including at least a first electrode 11. For the bulk acoustic wave resonator in FIG13 , the first structure to be bonded may include only the first electrode 11. In this case, step S74 may include: forming a first electrode material layer on one side of the piezoelectric substrate 131, the first electrode material layer may be formed by depositing a metal thin film, preferably by DC magnetron sputtering (or radio frequency magnetron sputtering), or by pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, or the like.

[0230] The material of the first electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or a laminated structure formed by the above metals. The thickness of the first electrode material layer ranges from 1 nm to 10 μm.

[0231] S75 , arranging the piezoelectric substrate 131 formed with the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded to the second structure to be bonded to form a bonded assembly.

[0232] For the bulk acoustic wave resonator in Figure 13, the second structure to be bonded may include a base substrate 10 and an acoustic reflector structure 16 located on the base substrate 10. In this case, step S75 is to invert the piezoelectric substrate 131 and set it opposite to the acoustic reflector structure 16, and bond the first electrode 11 to the acoustic reflector.

[0233] S76: Anneal the bonded assembly to diffuse and aggregate the ions 13c implanted in the piezoelectric substrate 131 into a gas, thereby separating the piezoelectric substrate 131 into the piezoelectric material layer 13a and the redundant portion. Then, perform an electrochemical mechanical polishing (CMP) process on the surface of the piezoelectric material layer 13a facing away from the base substrate 10 to eliminate various surface defects and polish the surface.

[0234] The thickness of the piezoelectric material layer 13a is related to the peak implantation depth in the ion implantation step, for example, between 100 nm and 10 μm. The annealing temperature ranges from 600° C. to 1000° C., and the annealing time ranges from 30 seconds to 30 minutes.

[0235] S77: Patterning the piezoelectric material layer 13a to form the piezoelectric layer 13. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process can also be selected.

[0236] S78 . Form a second electrode 12 on a side of the piezoelectric layer 13 away from the base substrate 10 .

[0237] Specifically, S78 may include first forming a second electrode material layer. The second electrode material layer may be formed by metal thin film deposition. The deposition method is preferably DC magnetron sputtering (which may also be RF magnetron sputtering). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. may be selected. Subsequently, the second electrode material layer is patterned to form the second electrode 12. The patterning process includes coating (or spraying), pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably a wet etching process, but a dry etching process may also be selected.

[0238] The material of the second electrode material layer is, for example, metal Mo, but may also be selected from Al, Cu, Co, Ag, Ti, Ni, Cr, Fe, Sn, Mn, Zn, Mg, Cd, V, Pb, Li, Be, Ca, K, Li, Na, Ta, Pd, Pt, Ru, W, or Au. It may also be an alloy material formed by any combination of the above metals, or it may be a laminated structure formed by the above metals. The thickness of the second electrode material layer ranges from 1 nm to 10 μm.

[0239] In one example, in order to make the lattice size of the first electrode 11 and the second electrode 12 close to the lattice size in the piezoelectric material layer 13 a , the first electrode 11 and the second electrode 12 may both be made of metal Mo.

[0240] S79 , forming a mass load layer 14 on a side of the second electrode 12 away from the base substrate 10 .

[0241] Specifically, the mass-load layer 14 can be made of an insulating material. In this case, the mass-load layer 14 can be deposited by methods such as radio frequency controlled sputtering, pulsed laser sputtering (PLD), atomic layer deposition (ALD), plasma chemical vapor deposition (PECVD), and low-pressure chemical vapor deposition (LPCVD). Alternatively, the mass-load layer 14 can be made of a metallic material. In this case, DC magnetron sputtering is preferred (radio frequency magnetron sputtering is also acceptable). Alternatively, pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, and electron beam evaporation can be used to deposit the mass-load layer 14.

[0242] Afterwards, an encapsulation layer can be formed on the side of the mass load layer 14 facing away from the base substrate 10. The material of the encapsulation layer is preferably an organic compound that can isolate water vapor and oxygen, such as polyimide, epoxy resin, etc., or an inorganic material such as SiNx, Al2O3, etc. can also be selected. The encapsulation layer can be a single layer of a single material, or a stacked configuration of multiple materials. Taking the encapsulation layer as an example of an organic compound material, the steps of forming the encapsulation layer can specifically include first applying an organic material liquid, which can be specifically done by spin coating, spraying, inkjet printing, transfer printing, etc., and then heating and curing to form a pattern of the encapsulation layer.

[0243] It should be noted that, in the above-mentioned manufacturing process, the piezoelectric layer 13 is described as a patterned structure. In other examples, the piezoelectric material layer 13a may not be patterned, that is, the piezoelectric material layer 13a that has fallen off the piezoelectric substrate 13 may be directly used as the piezoelectric layer 13. When the piezoelectric material layer 13a is not patterned, the heat dissipation effect of the device is better. In addition, the above-mentioned process is described as an example of first forming a pattern of the first electrode 11 on the piezoelectric substrate 131, then bonding the first electrode 11 to the base substrate 10, and then sequentially forming the piezoelectric layer 13, the second electrode 12 and the load layer 14. In other embodiments, the first electrode material layer may be formed on the piezoelectric substrate 131 first, and then the bonding step may be performed. After the piezoelectric material layer is formed, the second electrode material layer and the load material layer may be formed, and then the load material layer, the second electrode material layer, the piezoelectric material layer and the first electrode material layer may be patterned.

[0244] An embodiment of the present disclosure further provides an electronic device, which may include any of the above-mentioned bulk acoustic wave resonators.

[0245] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A bulk acoustic wave resonator, comprising: a substrate, a first electrode, a piezoelectric layer, and a second electrode; The first electrode is arranged on the base substrate, the second electrode is arranged on the side of the first electrode facing away from the base substrate, the piezoelectric layer is arranged between the first electrode and the second electrode, and the orthographic projections of any two of the first electrode, the piezoelectric layer and the second electrode on the base substrate at least partially overlap; wherein the thermal conductivity of the piezoelectric layer is greater than the thermal conductivity of at least one of the first electrode and the second electrode.

2. The bulk acoustic wave resonator according to claim 1, wherein The base substrate has a first cavity penetrating along a thickness direction thereof.

3. The BAW resonator according to claim 1, wherein The base substrate has a first groove portion penetrating a portion of the base substrate along a thickness direction thereof, and an opening of the first groove portion faces the first electrode.

4. The BAW resonator according to claim 1, wherein The first electrode is bonded to the base substrate.

5. The BAW resonator according to claim 1, wherein The BAW resonator further includes a support layer provided between the base substrate and the first electrode, wherein the support layer is bonded to the base substrate.

6. The BAW resonator according to claim 1, wherein The bulk acoustic wave resonator also includes at least one acoustic reflector structure arranged between the substrate and the first electrode. The acoustic reflector structure is bonded to the first electrode and includes a first substructure layer and a second substructure layer arranged in sequence along a direction away from the substrate, and the acoustic impedance of the material of the first substructure layer is greater than the acoustic impedance of the material of the second substructure layer.

7. The BAW resonator according to claim 1, wherein The BAW resonator further includes a mass loading layer disposed on a side of the second electrode facing away from the substrate.

8. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein: The material of the piezoelectric layer includes at least one of single crystal AlN and single crystal BN.

9. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein: The materials of the first electrode and the second electrode include at least one of Mo, Al, Cu, Co, Ag, Ti, Pt, Ru, W, and Au.

10. A method for preparing a bulk acoustic wave resonator, comprising: providing a substrate; A first electrode, a piezoelectric layer, and a second electrode are respectively formed on one side of the substrate, wherein the second electrode is formed on a side of the first electrode facing away from the substrate, the piezoelectric layer is formed between the first electrode and the second electrode, and the orthographic projections of any two of the first electrode, the piezoelectric layer, and the second electrode on the substrate at least partially overlap; wherein the thermal conductivity of the piezoelectric layer is greater than the thermal conductivity of at least one of the first electrode and the second electrode.

11. The preparation method according to claim 10, wherein The steps of respectively forming a first electrode, a piezoelectric layer, and a second electrode on one side of the base substrate include: performing ion implantation on the piezoelectric substrate; forming a first structure to be bonded on one side of the piezoelectric substrate, wherein the first structure to be bonded includes at least the first electrode; Arranging the piezoelectric substrate having the first structure to be bonded and the second structure to be bonded opposite to each other, and bonding the first structure to be bonded and the second structure to be bonded to form a bonded assembly; the second structure to be bonded at least includes the substrate; Annealing the bonding assembly to diffuse the ions implanted in the piezoelectric substrate and aggregate into a gas, thereby separating the piezoelectric substrate into the piezoelectric layer and the redundant portion; A second electrode is formed on a side of the piezoelectric material layer away from the base substrate.

12. The preparation method according to claim 10, wherein In the step of implanting ions into the piezoelectric substrate, the implanted ions include hydrogen ions or helium ions.

13. The preparation method according to claim 10, wherein The material of the piezoelectric substrate includes at least one of single crystal AlN and single crystal BN.

14. The preparation method according to claim 10, wherein The first structure to be bonded further includes a support layer located on a side of the first electrode away from the piezoelectric substrate.

15. The preparation method according to claim 10, wherein The second structure to be bonded further includes at least one acoustic reflector structure located on one side of the substrate; the acoustic reflector structure includes a first substructure layer and a second substructure layer sequentially arranged in a direction away from the substrate, and the acoustic impedance of the material of the first substructure layer is greater than the acoustic impedance of the material of the second substructure layer; In the bonding assembly, the first electrode material layer is bonded to the acoustic reflector structure.

16. The preparation method according to any one of claims 10 to 15, wherein The preparation method further comprises: A mass loading layer is formed on a side of the second electrode facing away from the substrate.

17. The preparation method according to any one of claims 10 to 15, wherein The preparation method further comprises: The base substrate is processed to form a first cavity penetrating along a thickness direction of the base substrate.

18. The preparation method according to any one of claims 10 to 15, wherein The preparation method further comprises: Before forming the first electrode, the base substrate is processed to form a first groove portion penetrating a portion of the base substrate; wherein the opening of the first groove portion faces the first electrode.

19. An electronic device comprising the bulk acoustic wave resonator according to any one of claims 1 to 9.

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