Bulk acoustic wave resonators and components, filters, and electronic devices

Abstract

The present invention relates to a bulk acoustic wave resonator, comprising: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom and top electrodes, wherein an acoustic impedance structure is disposed between the piezoelectric layer and the substrate; the acoustic impedance structure comprises a first acoustic impedance layer and a second acoustic impedance layer disposed adjacent to each other in a lateral direction, the first acoustic impedance layer and the second acoustic impedance layer having different acoustic impedances; the acoustic mirror is positioned between the first acoustic impedance layers in the lateral direction of the resonator, and the bottom and / or top electrodes are provided with cantilevers and / or bridge structures. The present invention also relates to a bulk acoustic wave resonator component, a filter, and an electronic device.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of semiconductors, and in particular to a bulk acoustic wave resonator, a filter having the resonator, a bulk acoustic wave resonator component, and an electronic device. Background Art

[0002] With the increasing development of 5G communication technology, the requirements for communication frequency bands are becoming increasingly stringent. Traditional RF filters, due to structural and performance limitations, cannot meet the requirements of high-frequency communication. Film bulk acoustic resonator (FBAR), a new type of MEMS device, offers advantages such as small size, light weight, low insertion loss, wide bandwidth, and high quality factor. It is well suited to the upgrading of wireless communication systems, making FBAR technology a research hotspot in the communications field.

[0003] The FBAR structure consists of a "sandwich" structure consisting of electrodes, piezoelectric film, and electrodes: a layer of piezoelectric material sandwiched between two metal electrode layers. A sinusoidal signal is input between the two electrodes, and the FBAR converts the input electrical signal into mechanical resonance using the inverse piezoelectric effect. The piezoelectric effect then converts the mechanical resonance into an electrical output signal. FBARs primarily utilize the longitudinal piezoelectric coefficient of the piezoelectric film to generate the piezoelectric effect, resulting in a primary operating mode of longitudinal waves in the thickness direction. This means that the acoustic waves of the FBAR are primarily confined to the film bulk of the resonator, and the primary vibration direction is longitudinal. However, due to the presence of boundaries, Lamb waves can occur at these boundaries, non-perpendicular to the piezoelectric film. These transverse Lamb waves can then leak out of the piezoelectric film, resulting in acoustic losses and a reduced Q factor of the resonator.

[0004] There are already technologies that propose to use transversely alternating high and low acoustic impedance layers to reduce transverse Lamb wave leakage, but there is still a need to further reduce transverse Lamb wave leakage. Summary of the Invention

[0005] The present invention is proposed to further reduce the leakage of the transverse Lamb wave and improve the Q value of the bulk acoustic wave resonator.

[0006] According to one aspect of an embodiment of the present invention, a bulk acoustic wave resonator is provided, comprising:

[0007] substrate;

[0008] Acoustic mirror;

[0009] bottom electrode;

[0010] a top electrode; and

[0011] A piezoelectric layer is provided between the bottom electrode and the top electrode,

[0012] in:

[0013] An acoustic impedance structure is provided between the piezoelectric layer and the substrate;

[0014] The acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a lateral direction, the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances, and the acoustic mirror is located between the first acoustic impedance layers in the lateral direction of the resonator; and

[0015] The bottom electrode and / or the top electrode is provided with a cantilever and / or a bridge structure.

[0016] An embodiment of the present invention further relates to a bulk acoustic wave resonator assembly, comprising at least two of the above-mentioned resonators, wherein the at least two resonators share a same substrate.

[0017] An embodiment of the present invention further relates to a filter comprising the above-mentioned bulk acoustic wave resonator or resonator assembly.

[0018] An embodiment of the present invention also relates to an electronic device, comprising the above-mentioned filter or the above-mentioned resonator or component. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed herein, wherein like reference numerals denote like components throughout the drawings, wherein:

[0020] Figure 1 is a bottom view schematically showing a bulk acoustic wave resonator according to an exemplary embodiment of the present invention;

[0021] Figure 2A The bulk acoustic wave resonator according to an exemplary embodiment of the present invention is Figure 1 Schematic diagram of a cross section taken along the MOM' line in FIG, wherein the top electrode is provided with a cantilever and a bridge structure;

[0022] Figure 2B for Figure 2A A partial enlarged schematic diagram in FIG, schematically showing parameters related to the cantilever and bridge structure of the top electrode;

[0023] Figure 2C The bulk acoustic wave resonator according to an exemplary embodiment of the present invention is Figure 1 A schematic cross-sectional view taken along the MOM' line in FIG, wherein the top electrode is provided with a cantilever and a bridge structure, and a portion of the non-electrode connection end of the bottom electrode is covered by the first acoustic impedance layer;

[0024] Figure 2D The bulk acoustic wave resonator according to an exemplary embodiment of the present invention is Figure 1A schematic cross-sectional view taken along the NON' line in FIG, showing the non-electrode connection ends of the bottom electrode and the top electrode, wherein the non-electrode connection end of the bottom electrode on the side where the release hole is not provided is covered by a portion of the first acoustic impedance layer;

[0025] Figure 3A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of , wherein the bottom electrode is provided with a cantilever and a bridge structure, and the first acoustic impedance layer does not cover the bridge structure;

[0026] Figure 3B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 A schematic cross-sectional view taken along the NON' line in FIG, showing the non-electrode connection ends of the bottom electrode and the top electrode, and the non-electrode connection end of the bottom electrode is spaced apart from the first acoustic impedance layer;

[0027] Figure 4A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram;

[0028] Figure 4B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of , wherein the bridge structure of the top electrode partially overlaps with the first acoustic impedance layer in the thickness direction;

[0029] Figure 4C A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of , wherein the bridge structure of the bottom electrode partially overlaps with the first acoustic impedance layer in the thickness direction;

[0030] Figure 5A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The NON' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of FIG, showing that both the top electrode and the bottom electrode are provided with cantilevers;

[0031] Figure 5B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1The NON' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of , showing that both the top electrode and the bottom electrode are provided with cantilevers, and the bottom electrode is also provided with a bridge structure;

[0032] Figure 5C A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 A partial cross-sectional schematic diagram taken along the NON' line in FIG, showing that the non-electrode connection end of the top electrode is provided with a bridge structure, and the non-electrode connection end of the bottom electrode is provided with a cantilever;

[0033] Figure 6A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram, wherein the inner edges of the cantilever and the bridge structure of the top electrode are respectively located outside the inner edges of the bridge structure and the cantilever of the bottom electrode;

[0034] Figure 6B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram, wherein the inner edges of the cantilever and the bridge structure of the top electrode are respectively located inside the inner edges of the bridge structure and the cantilever of the bottom electrode;

[0035] Figure 7 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention;

[0036] Figures 8A-8L An example is shown similar to Figure 2A However, the local enlarged picture is Figure 4A The fabrication process of the structure shown;

[0037] Figure 9 A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 Schematic diagram of the cross section taken along the MOM' line. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further specifically described below through examples and in conjunction with the accompanying drawings. In the specification, the same or similar drawing numbers indicate the same or similar parts. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be understood as a limitation of the present invention. Some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.

[0039] First, the reference numerals in the accompanying drawings of the present invention are explained as follows:

[0040] 1: Single crystal piezoelectric layer, which can be selected from single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lead zirconate titanate, single crystal potassium niobate, single crystal quartz film, or single crystal lithium tantalate, etc., and can also contain rare earth element doping materials with a certain atomic ratio of the above materials, for example, it can be doped aluminum nitride, and the doped aluminum nitride contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0041] 2: Bottom electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys.

[0042] 3: Acoustic impedance layer 1 or the first acoustic impedance layer, the material can be aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon.

[0043] 4: Acoustic impedance layer 2 or the second acoustic impedance layer, which also serves as a sacrificial layer. The second acoustic impedance layer can be made of silicon dioxide, doped silicon dioxide, polycrystalline silicon, amorphous silicon, etc., but it is different from the first acoustic impedance layer material. The etchant for the second acoustic impedance layer is not easy to etch or does not etch the first acoustic impedance layer material.

[0044] 5: Substrate, optional materials include single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0045] 5a: Auxiliary substrate, the optional materials are single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc., and can also be single crystal piezoelectric substrates such as lithium niobate, lithium tantalate, potassium niobate, etc.

[0046] 6: Top electrode, which can be made of the same material as the bottom electrode. The materials can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals. The top and bottom electrodes are generally made of the same material, but can also be different.

[0047] 6a: Electrode connection part 1 (or electrode lead part), which can be made at the same time as the top electrode. The material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys.

[0048] 7: Electrode connection part 2 (Bonding PAD, or bottom electrode electrical connection layer), the material can be copper, gold or a composite of the above metals or their alloys.

[0049] 8: Acoustic mirror, which can be a cavity, a Bragg reflector layer or other equivalent forms. In the embodiment shown in the present invention, a cavity is used.

[0050] 9: Release hole, which is used to etch the sacrificial layer to form a cavity.

[0051] 9a: Electrode opening or via, which can be made at the same time as the release hole, and is used to electrically connect the electrode connection portion 1 with the electrode connection end of the bottom electrode.

[0052] 10: Cantilevered wing.

[0053] 13: Bridge structure.

[0054] Figure 1 FIG2A is a bottom view of a BAW resonator according to an exemplary embodiment of the present invention. FIG2A is a bottom view of a BAW resonator according to an exemplary embodiment of the present invention. Figure 1 A schematic cross-sectional view taken along the MOM' line in FIG, showing the electrode lead-out region of the bottom electrode and the electrode lead-out region of the top electrode, wherein the electrode connection end of the bottom electrode is covered by a portion of the first acoustic impedance layer, and the non-electrode connection end of the bottom electrode is spaced apart from the first acoustic impedance layer in the lateral direction. Figure 2A In the embodiment, the top electrode is provided with a cantilever and a bridge structure.

[0055] like Figure 1 and Figure 2A As shown, the BAW resonator includes: a substrate 5; an acoustic mirror 8; a bottom electrode 2; a top electrode 6; and a single crystal piezoelectric layer 1 disposed between the bottom and top electrodes. An acoustic impedance structure is disposed between the piezoelectric layer 1 and the substrate 5. The acoustic mirror 8 is positioned between the acoustic impedance structure in the lateral direction of the resonator. The acoustic impedance structure includes a first acoustic impedance layer 3 and a second acoustic impedance layer 4 disposed adjacent to each other in the lateral direction. More specifically, the acoustic mirror 8 is positioned between the first acoustic impedance layer 3 in the lateral direction of the resonator.

[0056] exist Figure 2A In the embodiment, the top electrode 6 is provided with a cantilever 10 and a bridge structure 13, while the bottom electrode 2 is not provided with a cantilever or a bridge structure. As can be understood, an electrode may be provided with only a cantilever or only a bridge structure. Alternatively, the bottom electrode may be provided with a cantilever and / or a bridge structure, or both the top and bottom electrodes may be provided with a cantilever and / or a bridge structure.

[0057] In the present invention, the first acoustic impedance layer 3 and the second acoustic impedance layer 4 have different acoustic impedances, creating an impedance mismatch, which continuously reflects sound waves and forms a reflective structure for transverse sound waves. This prevents transverse sound wave leakage, helps lock energy within the resonator, and thus improves the Q value. The first acoustic impedance layer 3 and the second acoustic impedance layer 4 serve as the first acoustic reflection layer and the second acoustic reflection layer, forming an effective acoustic impedance mismatch layer that can prevent the leakage of transverse sound waves. By setting the width of the first acoustic impedance layer 3 and the second acoustic impedance layer 4, the leakage of transverse waves can be suppressed. This structure primarily reflects transverse waves that leak outside the resonator back into the resonator, thereby improving the Q value.

[0058] If there is only an external acoustic reflection structure formed by the first acoustic impedance layer 3 and the second acoustic impedance layer 4, the shear waves reflected by the first acoustic impedance layer 3 and the second acoustic impedance layer 4 into the resonator will still leak out of the boundary because there is no boundary structure to limit them. Therefore, it is necessary to further add a boundary structure to effectively lock this energy inside the resonator. In the present invention, by introducing a bridge structure and / or a cantilever structure into the electrode, on the one hand, a zero-impedance reflection surface can be formed by means of the air gap layer formed between the electrode and the piezoelectric layer, thereby changing the vertical stacking structure of the resonator, so that the transverse sound waves are effectively reflected back into the resonator at this interface. On the other hand, the cantilever beam free end structure formed by the electrode can generate secondary resonance under the excitation of the transverse wave, thereby confining the energy to the free end of the electrode. Therefore, by introducing a bridge structure and / or a wing structure, and optionally further setting the positional relationship between the bridge wing structure and the acoustic impedance layer, it is possible to prevent the leakage of internal shear waves and further lock the energy reflected by the first acoustic impedance layer 3 and the second acoustic impedance layer 4 inside the resonator, further effectively preventing the leakage of energy. The coordination between the acoustic impedance structure and the cantilever / bridge structure can effectively prevent the leakage of sound waves and improve the Q value of the resonator.

[0059] In the present invention, a single crystal piezoelectric material is used. Since its lattice has very few defect points, the material loss can be lowered, thereby obtaining a higher resonator Q value, while also improving the electromechanical coupling coefficient and power capacity.

[0060] In a further embodiment, the widths of the portions of the first acoustic impedance layer 3 and the second acoustic impedance layer 4 in contact with the piezoelectric layer 1 are mλ3 / 4 and nλ4 / 4, respectively, where m and n are both odd numbers, such as 1, 3, 5, 7, etc., and λ3 and λ4 are the wavelengths of acoustic waves propagating laterally at the resonant frequency at the corresponding portions of the first and second acoustic impedance layers in contact with the piezoelectric layer. The resonant frequency is a frequency within the resonant range of the resonator, which can be the series resonant frequency or the parallel resonant frequency of the resonator, a frequency between the series and parallel resonant frequencies, or a frequency slightly below the series resonant frequency or slightly above the parallel resonant frequency. In the accompanying drawings, the width of the first acoustic impedance layer 3 is represented by A, while the width of the second acoustic impedance layer 4 is represented by B. Selecting these widths facilitates forming an effective acoustic impedance mismatch, preventing lateral acoustic wave leakage, and further improving the Q value of the resonator. m and n can be the same or different, and are both within the scope of protection of the present invention.

[0061] The materials forming the first acoustic impedance layer 3 include aluminum nitride, silicon dioxide, silicon nitride, polycrystalline silicon, and amorphous silicon. The materials forming the second acoustic impedance layer 4 include silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon. The materials of the first acoustic impedance layer 3 and the second acoustic impedance layer 4 are different. Optionally, the material forming the first acoustic impedance layer 3 includes silicon dioxide, and the material forming the second acoustic impedance layer 4 includes polycrystalline silicon. Alternatively, the material forming the first acoustic impedance layer 3 includes silicon nitride or aluminum nitride, and the material forming the second acoustic impedance layer 4 includes silicon dioxide or doped silicon dioxide. In the present invention, to increase the degree of acoustic mismatch at the junction of the first acoustic impedance layer 3 and the second acoustic impedance layer 4, the difference in acoustic impedance between the two layers can be selected to be as large as possible.

[0062] Please refer to the attached Figures 8A-8L As described above, during the process of manufacturing the resonator, the second acoustic impedance layer is also used as a sacrificial layer. Therefore, when releasing the sacrificial layer, it is necessary to select a suitable releasing etchant so that the etchant only etches the second acoustic impedance material and does not etch or etches a very small amount of the first acoustic impedance material.

[0063] like Figure 2A As shown, the end surface of the non-electrode connection end of the bottom electrode 2 (the right end in 2A) is spaced apart from the first acoustic impedance layer 3 in the acoustic impedance structure in the lateral direction. This allows acoustic waves to be totally reflected at the lateral interface between the non-electrode connection end of the bottom electrode and the gap, thereby reducing acoustic wave leakage. The gap structure at the non-electrode connection end can further prevent lateral acoustic wave leakage and improve the Q value of the resonator.

[0064] In an alternative embodiment, in a longitudinal section of the resonator through the electrode connection end of the bottom electrode 2 (eg Figure 2AIn the cross-sectional view shown in FIG, the distance C between the end surface of the non-electrode connection end of the bottom electrode 2 and the acoustic impedance structure in the lateral direction is in the range of 0 μm to 50 μm. In addition to the end values, this distance may also be, for example, 5 μm, 7 μm, 30 μm, etc.

[0065] In e.g. Figure 2A In the illustrated embodiment, the bottom electrode 2 is wrapped on one side of the electrode connection end by a continuous reflective layer or acoustic impedance structure formed by the first acoustic impedance layer 3 and the second acoustic impedance layer 4. More specifically, it is covered by the first acoustic impedance layer 3. On the one hand, this structure is conducive to improving the mechanical stability of the resonator and more easily conducts the heat generated during operation of the resonator to the substrate through the electrode and the first acoustic impedance layer 3, thereby improving the power capacity of the resonator. On the other hand, although energy will leak from the end surface of the bottom electrode into the first acoustic impedance layer 3, due to the presence of the reflective interface formed by the second acoustic impedance layer and the first acoustic impedance layer, it is conducive to locking as much energy as possible inside the resonator, so that the resonator maintains a high Q value.

[0066] Although not shown, in an optional embodiment, the end surface of the non-electrode connection end and the end surface of the electrode connection end of the bottom electrode 2 can be spaced apart from the first acoustic impedance layer 3 in the lateral direction, so that the sound wave is also totally reflected at the lateral interface between the bottom electrode and the gap, thereby reducing the leakage of the sound wave and improving the Q value of the resonator. Figure 2A The structure shown in the figure also has a gap at the electrode connection end, which further prevents transverse acoustic wave leakage. However, because the bottom electrode and the first acoustic impedance layer are not in direct contact, heat must be indirectly conducted through the piezoelectric material to the first acoustic impedance layer and the substrate, resulting in poor power handling. Similarly, the distance between the end face of the electrode connection end and the acoustic impedance structure in the transverse direction can be C, or a value different from C.

[0067] Figure 2B for Figure 2A A locally enlarged schematic diagram in FIG, schematically illustrating the parameters related to the cantilever and bridge structure of the top electrode.

[0068] exist Figure 2B In the embodiment, the non-electrode connection end of the bottom electrode 2 is a non-cantilever structure ( Figure 2B There is no cantilever at the non-electrode connection end, that is, a non-cantilever structure). Figure 2BAs shown, the width of the bridge structure is d12a, optionally ranging from 0 to 50 μm. The overlapping area of ​​the non-electrode connection end of the bottom electrode and the bridge structure of the top electrode in the thickness direction of the resonator (or the lateral distance between the inner edge of the bridge structure and the endpoint of the corresponding non-electrode connection end) is d43a, the value of which has a significant impact on the performance of the resonator. d43a is smaller than d12a, and the width of d43a is within the range of 0 μm–20 μm to ensure that the non-electrode connection end of the bottom electrode falls within the projection of the bridge structure of the top electrode. In this case, the effective area of ​​the resonator is limited by the bridge structure of the top electrode and the inner edge of the cantilever.

[0069] exist Figure 2B In the figure, the non-connected edge of the top electrode ( Figure 2B The lateral distance between the outer edge of the top electrode's cantilever (in the figure) and the first acoustic impedance layer 3 is d40a, the lateral distance between the non-connected edge of the bottom electrode and the first acoustic impedance layer 3 is d44b, and the lateral distance between the outer edge of the top electrode's bridge structure and the first acoustic impedance layer 3 is d41a. In optional embodiments, d40a is within the range of 0–50 μm; and / or d44b is within the range of 0–50 μm; and / or d41a is within the range of 0–50 μm.

[0070] In addition, d41a and d44b can also be negative. When d41a is negative and d44b is positive, the outer edge of the top electrode bridge structure crosses the first acoustic impedance layer 3, and the first acoustic impedance layer 3 is spaced from the non-connected end of the bottom electrode, similar to Figure 4B shown.

[0071] When d41a and d44b are both negative, the first acoustic impedance layer 3 covers the non-connected end of the bottom electrode. At the same time, in order to avoid the formation of parasitic capacitance between the bottom electrode portion extending into the acoustic impedance layer and the connecting edge of the top electrode, thereby reducing the electrical performance of the resonator (including Q value and electromechanical coupling coefficient, etc.), the inner end of the bridge structure needs to cross the edge of the first acoustic impedance layer 3, and the outer end needs to cross the edge of the non-connected end of the bottom electrode, that is, to ensure that the absolute value of d41a is less than d12a, and d43a is also less than d12a. Figure 2C This situation is beneficial for improving the mechanical stability of the resonator and more easily transferring the heat generated by the resonator during operation to the substrate through the electrode and the first acoustic impedance layer 3, thereby increasing the power capacity of the resonator. At the same time, although energy will leak from the end surface of the bottom electrode into the first acoustic impedance layer 3, due to the presence of the reflection interface formed by the second acoustic impedance layer and the first acoustic impedance layer, as much energy as possible can be locked inside the resonator, so that the resonator maintains a high Q value.

[0072] like Figure 2BAs shown, the width of the top electrode cantilever structure is d11a, and optionally, the range of d11a is 0-50μm; the outer edge of the cantilever structure is inside the edge of the first acoustic impedance layer 3, and the lateral distance between the outer edge of the cantilever structure and the first acoustic impedance layer 3 is d40a, and optionally, d40a is in the range of 0-50μm. In this case, the lateral distance between the inner edge of the cantilever of the top electrode 6 and the first acoustic impedance layer 3 is the sum of the cantilever width d11a and d40a. In addition, d40a can also be a negative value, similar to the subsequent attached Figure 4C As shown, the outer edge of the top electrode's cantilever structure crosses the edge of the first acoustic impedance layer 3. At this time, the lateral distance between the inner edge of the cantilever of the top electrode 6 and the first acoustic impedance layer 3 is the absolute value of the cantilever width d11a minus d40a. It is necessary to set d11a and d40a so that the inner edge of the cantilever structure is always inside the edge of the first acoustic impedance layer 3.

[0073] In an optional embodiment, d11a, d12a, d40a, d41a, and d43a may be odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally at the resonant frequency of the stacked structure in the thickness direction of each distance corresponding to the region. In a specific example, the interval d11a corresponds to the top electrode cantilever portion, the interval d12a corresponds to the top electrode bridge portion, the intervals d40a and d43a correspond to the bottom electrode and piezoelectric layer portion, and the interval d41a corresponds to the top electrode and piezoelectric layer portion.

[0074] Figure 2D The bulk acoustic wave resonator according to an exemplary embodiment of the present invention is Figure 1 The schematic cross-sectional view taken along the NON' line in the figure shows the non-electrode connection ends of the bottom electrode and the top electrode, and the non-electrode connection end of the bottom electrode 2 on the side where the release hole is not provided is covered by a portion of the first acoustic impedance layer 3, and the width of the covered area is equal to the lateral distance d44b between the non-connected edge of the bottom electrode and the first acoustic impedance layer 3. On the one hand, this structure is conducive to improving the mechanical stability of the resonator, and it is easier to conduct the heat generated when the resonator is working to the substrate through the electrode and the first acoustic impedance layer 3, thereby improving the power capacity of the resonator; on the other hand, although energy will leak from the end surface of the bottom electrode to the first acoustic impedance layer 3 in this structure, due to the presence of a reflective interface formed by the second acoustic impedance layer and the first acoustic impedance layer, it is conducive to locking as much energy as possible inside the resonator, so that the resonator maintains a high Q value. In addition, along Figure 1 In the cross section taken by the NON' line in FIG, the first acoustic impedance layer 3 can also be separated from the non-connected edge of the bottom electrode, so that the sound wave is totally reflected at the lateral interface between the bottom electrode and the gap, thereby reducing the leakage of the sound wave and improving the Q value of the resonator.

[0075] like Figure 2DAs shown, the non-electrode connection end of the bottom electrode 2 is a non-cantilever structure, and a release hole 9 can be provided between the outer edge of the non-electrode connection end and the first acoustic impedance layer 3 in the lateral direction of the resonator.

[0076] In alternative embodiments, d11a is within the range of 0–50 μm; and / or d40a is within the range of 0–50 μm; and / or d44b is within the range of 0–50 μm.

[0077] In an optional embodiment, d11a, d40a, and d44b may be odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally at the resonant frequency of the stacked structure in the thickness direction of the corresponding region at each distance. Specifically, the interval d11a corresponds to the top electrode cantilever portion, the interval d40a corresponds to the bottom electrode and piezoelectric layer portion, and the interval d44b corresponds to the first acoustic impedance layer, the bottom electrode, and the piezoelectric layer portion. Figure 3A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of the bottom electrode 2, which shows that the electrode connection end of the bottom electrode 2 is covered by a portion of the first acoustic impedance layer, and the non-electrode connection end of the bottom electrode 2 is spaced apart from the first acoustic impedance layer 3 in the lateral direction. Figure 3A In the embodiment, the bottom electrode is provided with a cantilever 10 and a bridge structure 13, and the first acoustic impedance layer 3 does not cover the bridge structure.

[0078] exist Figure 3A In the embodiment, the non-electrode connection end of the bottom electrode 2 is a cantilever structure, and the non-electrode connection end of the top electrode 6 is a non-cantilever structure. Figure 3A As shown, the width of the bridge structure 13 is d12b, and optionally, the range of d12b is 0-50μm; the overlapping area of ​​the non-electrode connection end of the top electrode and the bridge structure of the bottom electrode in the thickness direction of the resonator (or the lateral distance between the inner edge of the bridge structure and the endpoint of the non-electrode connection end) is d43b, and its value has a significant impact on the performance of the resonator. d43b is smaller than d12b, and the width of d43b is within the range of 0μm–20μm, thereby ensuring that the non-electrode connection end of the top electrode falls within the projection of the bridge structure of the bottom electrode. At this time, the effective area of ​​the resonator is limited by the inner edge of the bridge of the bottom electrode and the cantilever structure.

[0079] exist Figure 3A In the embodiment, the width of the wing structure is d11b, and optionally, the range of d11b is 0-50 μm; the non-connected edge of the bottom electrode ( Figure 3AThe lateral distance between d40b (outer edge of the bottom electrode cantilever) and the first acoustic impedance layer 3 is d40b; the lateral distance between the outer edge of the bottom electrode bridge structure and the first acoustic impedance layer 3 is d41b. Because the first acoustic impedance layer 3 has a reflective effect on the transverse waves leaking out of the filter, and its distance plays an important role in the reflection of waves and energy, the setting or selection of d40b and d41b has a great influence on the performance of the resonator. In an optional embodiment, d40b is in the range of 0–50μm; and / or d41b is in the range of 0–50μm. In addition, d41b can also be a negative value. When d41b is a negative value, that is, the first acoustic impedance layer 3 covers a part of the bottom electrode bridge structure, it is necessary to ensure that d12b is greater than the absolute value of d41b, that is, the edge of the first acoustic impedance layer 3 falls into the bottom electrode bridge structure. In an optional embodiment, d11b, d12b, d40b, d41b, and d43b may be odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally at the resonant frequency of the stacked structure along the thickness direction of the corresponding region at each distance. Specifically, the d11b interval corresponds to the bottom electrode cantilever portion, the d12b interval corresponds to the bottom electrode bridge portion, the d40b and d43b intervals correspond to the top electrode and piezoelectric layer portions, and the d41b interval corresponds to the bottom electrode and piezoelectric layer portions.

[0080] Figure 3B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The schematic cross-sectional view taken along the NON' line in FIG. 1 shows the non-electrode connection ends of the bottom electrode 2 and the top electrode 6, and the non-electrode connection end of the bottom electrode 2 is spaced apart from the first acoustic impedance layer. Figure 3B In the lateral direction, when there is no release hole 9 between the cantilever and the first acoustic impedance layer 3, the distance between the outer edge of the cantilever and the first acoustic impedance layer 3 is d40b.

[0081] exist Figure 3B In the figure, the non-connected edge of the top electrode ( Figure 3B The lateral distance between the non-electrode connection end (without a cantilever, that is, a non-cantilever structure) and the first acoustic impedance layer 3 on the side where the release hole 9 is not set is d44a; the distance between the outer edge of the cantilever of the bottom electrode and the non-electrode connection end of the top electrode is d49b. Among them, d49b can be positive or negative. When d49b is a negative value, that is, the non-connected edge of the top electrode falls in the projection of the cantilever structure of the bottom electrode, it is necessary to set d11b to be greater than the absolute value of d49b, so that the effective area of ​​the resonator is defined by the inner edge of the cantilever structure of the bottom electrode. In addition, d49b can be further set to be greater than d40b, so that the non-connected edge of the top electrode partially overlaps with the first acoustic impedance layer 3.

[0082] like Figure 3BAs shown, the non-electrode connection end of the top electrode 6 is a non-cantilever structure, and a release hole 9 can be provided between the outer edge of the non-electrode connection end and the first acoustic impedance layer 3 in the lateral direction of the resonator.

[0083] In alternative embodiments, d40b is within the range of 0 μm–50 μm; and / or d44a is within the range of 0 μm–50 μm; and / or d49b is within the range of 0 μm–20 μm.

[0084] In an optional embodiment, d11b, d49b, and d44a may be odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally at the resonant frequency of the stacked structure along the thickness direction of the corresponding region at each distance. Specifically, the d11b interval corresponds to the bottom electrode cantilever portion, the d49b interval corresponds to the top electrode and piezoelectric layer portion, and the d44a interval corresponds to the piezoelectric layer portion.

[0085] In the present invention, the widths of the cantilevers and bridge structures on the top electrode can be the same as or different from those of the cantilevers and bridge structures on the bottom electrode. For the cantilevers or bridge structures on the top or bottom electrodes, the widths of the cantilevers or bridge structures on different sides of the same resonator polygon can be the same or different, all within the scope of the present invention.

[0086] Figure 4A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B The enlarged partial cross-sectional schematic diagram of FIG, which shows that both the bottom electrode and the top electrode are provided with a cantilever 10 and a bridge structure 13. Figure 4A In the embodiment, the bridge structure of the electrode is spaced apart from the first acoustic impedance layer 3 in the lateral direction, that is, Figure 4A d41a and d41b are both greater than 0. In alternative embodiments, d41a and d41b may be odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally at the resonant frequency of the stacked structure along the thickness direction of each distance corresponding to the region. Specifically, the interval d41a corresponds to the top electrode and piezoelectric layer, and the interval d41b corresponds to the bottom electrode and piezoelectric layer.

[0087] It should be pointed out that, in the present invention, the same marks have the same or similar meanings. For the parameter marks explained or shown in the reference drawings, when the marks are shown in other drawings, they have the same or similar meanings as the above descriptions. Accordingly, the descriptions of these parameters are also applicable to the descriptions of these parameters in the corresponding embodiments, and will not be repeated here.

[0088] Figure 4BA bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B The enlarged partial cross-sectional schematic diagram shows that both the bottom electrode and the top electrode are provided with cantilevers and bridge structures, wherein the bridge structure of the top electrode 6 partially overlaps with the first acoustic impedance layer 3 in the thickness direction. Figure 4B As shown, in the lateral direction of the resonator, the outer edge of the bridge structure of the top electrode is outside the boundary of the first acoustic impedance layer 3. The width of this overlapping portion corresponds to d41a.

[0089] exist Figure 4B In the figure, the cantilever and bridge structure as well as the first and second acoustic impedance layers are all for enhancing the reflection of shear waves. Therefore, in order to achieve a synergistic enhancement effect of the cantilever and bridge structure and the acoustic impedance layer on the reflection of shear waves, Figure 4B The boundary of the first acoustic impedance layer 3 in the top electrode partially overlaps with the bridge structure region of the top electrode. In an optional embodiment, d41a and d40b are odd multiples of λ / 4, where λ is the wavelength of acoustic waves propagating laterally in the stacked structure at the resonant frequency along the thickness direction of each distance corresponding to the region. In this specific example, the interval d41a corresponds to the piezoelectric layer and the first acoustic impedance layer, while the interval d40b corresponds to the piezoelectric layer.

[0090] Figure 4C A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of FIG, showing that both the bottom electrode and the top electrode are provided with cantilevers and bridge structures, wherein the bridge structure of the bottom electrode partially overlaps with the first acoustic impedance layer in the thickness direction. Figure 4CAs shown, in the lateral direction of the resonator, the outer edge of the bridge structure of the bottom electrode is outside the boundary of the first acoustic impedance layer 3, that is, the first acoustic impedance layer 3 covers a portion of the bottom electrode bridge structure. The lateral distances between the cantilever of the top electrode and the cantilever of the bottom electrode and the first acoustic impedance layer 3 are d40a and d40b, respectively, and the lateral distances between the bridge structure of the top electrode and the bridge structure of the bottom electrode and the first acoustic impedance layer 3 are d41a and d41b, respectively. By adjusting the size of d41b, the actual suspended width of the bottom electrode bridge (the difference between d12b and d41b) can be changed, thereby changing the reflection characteristics of the bridge structure for shear waves, achieving a synergistic enhancement effect of the reflection of shear waves by the cantilever / bridge structure and the acoustic impedance layer. In an optional embodiment, d41b and d12b-d41b are odd multiples of λ / 4, where λ is the wavelength of the acoustic wave propagating laterally at the resonant frequency in the stacked structure in the thickness direction of the corresponding region at each distance. In a specific example, the d41b interval corresponds to the bottom electrode bridge structure portion and the first acoustic impedance layer portion, and the d12b-d41b interval corresponds to the bottom electrode bridge structure portion.

[0091] Figure 4B and 4C The structure shown can also be integrated into one structure, where the edge of the first acoustic impedance layer below the top electrode connecting edge falls into the projection of the top electrode connecting edge bridge structure, and the edge of the first acoustic impedance layer below the bottom electrode connecting edge falls into the projection of the bottom electrode connecting edge bridge structure.

[0092] Figure 5A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The NON' line in the Figure 2B An enlarged partial cross-sectional diagram of FIG, showing that both the top electrode and the bottom electrode non-connected edges are provided with cantilevers. Figure 5A As shown, the inner edges and outer edges of the cantilevers of the top electrode and the bottom electrode are flush in the thickness direction, that is, the widths of the upper and lower cantilevers are the same.

[0093] Figure 5B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MON line in the intercept is similar to Figure 2B An enlarged partial cross-sectional schematic diagram of FIG, which shows that the non-connected side of the top electrode is provided with a cantilever, and the non-connected side of the bottom electrode is provided with a bridge structure. Figure 5BIn the figure, it can be seen that there is an overlapping area between the bridge structure of the bottom electrode and the first acoustic impedance layer 3, and the lateral width of this area corresponds to d41b. By optimizing the widths of d41b and d12b, it is possible to achieve a synergistic enhancement effect on the reflection of transverse waves by the bridge structure and the acoustic impedance layer. In an optional embodiment, d41b and d12b-d41b are odd multiples of λ / 4, and λ is the wavelength of the sound wave propagating laterally at the resonant frequency in the stacked structure in the thickness direction of each distance corresponding to the region. In the specific example, the d41b interval corresponds to the bottom electrode bridge structure portion and the first acoustic impedance layer portion, and the d12b-d41b interval corresponds to the bottom electrode bridge structure portion. At the same time, compared to Figure 5A The structure shown, Figure 5B The illustrated structure improves the mechanical stability of the resonator and more easily conducts heat generated during operation of the resonator to the substrate through the electrodes and the first acoustic impedance layer 3, thereby increasing the power capacity of the resonator. However, the present invention is not limited to this. The first acoustic impedance layer 3 may not overlap with the bridge structure of the bottom electrode, but still cover the end of the bottom electrode. Alternatively, the first acoustic impedance layer 3 may be spaced apart from the bottom electrode.

[0094] Figure 5C A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The NON' line in the Figure 2B An enlarged partial cross-sectional schematic diagram of FIG, wherein the non-connected side of the top electrode is provided with a bridge structure, and the non-connected side of the bottom electrode is provided with a cantilever structure. Figure 5C As shown, the edge of the top electrode bridge structure is on the inner side of the edge of the first acoustic impedance layer 3, but the present invention is not limited to this. The edge of the top electrode bridge structure can also cross the edge of the first acoustic impedance layer 3, so that the top electrode bridge structure and the first acoustic impedance layer 3 partially overlap.

[0095] exist Figures 5A-5C In the example shown, the width of the cantilever on the top electrode can be the same as or different from that of the cantilever on the bottom electrode. The widths of the cantilever and bridge structure on the top or bottom electrode can be the same or different for different sides of the same resonator polygon.

[0096] The position and width changes of the boundary structure of the resonator will have a great influence on the propagation and reflection of the shear wave. Taking the relative position relationship between the cantilever and / or bridge structure on the top electrode and the bottom electrode as an example, when the two overlap (for example Figure 5AAs shown, the cantilever is flush in the thickness direction), there is only one change in the interval stacking structure caused by the cantilever and the bridge structure, that is, the top electrode, bottom electrode and piezoelectric layer stacking structure are on the inner side of the inner edge of the cantilever structure, while the piezoelectric layer is on the outer side of the inner edge of the cantilever structure. As a result, an acoustic impedance mismatch interface is generated at the inner edges of the upper and lower cantilever structures, so the reflection or suppression of the shear wave can only occur once. When there is a position difference between the top electrode and the bottom electrode of the cantilever and the bridge structure, such as the attached Figure 6A When Δd1 and Δd5 are not equal to zero, it will have a greater benefit on improving the Q value of the resonator. Figure 5A When the upper and lower parts shown are both cantilever structures, that is, the inner edges of the upper and lower electrode cantilever structures are not aligned, for example, the inner edge of the cantilever structure of the top electrode may be inside the inner edge of the cantilever structure of the bottom electrode. At this time, there are at least two changes in the stacking structure from the inside to the outside of the resonator, namely, the top electrode, the bottom electrode and the piezoelectric layer stacking structure are inside the inner edge of the cantilever structure of the top electrode, the piezoelectric layer and the bottom electrode stacking structure are outside the inner edge of the cantilever structure of the top electrode to the inner edge of the cantilever structure of the bottom electrode, and the piezoelectric layer is outside the inner edge of the cantilever structure of the bottom electrode. Thus, two impedance mismatch interfaces are generated, which can further enhance the Q value of the resonator.

[0097] Figure 6A A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram shows that both the top electrode and the bottom electrode are provided with cantilevers and bridge structures, wherein the inner edges of the cantilevers and the bridge structure of the top electrode are respectively located outside the inner edges of the bridge structure and the cantilevers of the bottom electrode.

[0098] Figure 6B A bulk acoustic wave resonator according to another exemplary embodiment of the present invention is similar to Figure 1 The MOM' line in the Figure 2B An enlarged partial cross-sectional schematic diagram shows that both the top electrode and the bottom electrode are provided with cantilevers and bridge structures, wherein the inner edges of the cantilevers and the bridge structure of the top electrode are respectively located on the inner sides of the bridge structure and the inner edges of the cantilevers of the bottom electrode.

[0099] More specifically, Figure 6A and 6B As shown, the lateral distance or spacing between the inner edge of the cantilever of the top electrode and the inner edge of the bridge structure of the bottom electrode is Δd1, and the lateral distance or spacing between the inner edge of the cantilever of the bottom electrode and the inner edge of the bridge structure of the top electrode is Δd5.

[0100] The values ​​of Δd1 and Δd5 have a great influence on the performance of the resonator. In one embodiment of the present invention, Δd1 is in the range of 0–20 μm; and / or Δd5 is in the range of 0–20 μm. In addition, Figure 6A It is necessary to ensure that d12b is greater than Δd1 (left side). Figure 6B It is necessary to ensure that d12a is greater than Δd5 (right side), that is, when the inner edge of the cantilever structure is outside the inner edge of the other side bridge structure, it is necessary to ensure that the inner edge of the cantilever structure does not exceed the outer edge of the other side bridge structure. In other words, it is necessary to ensure that the inner edge of the cantilever structure falls within the projection of the other side bridge structure. Alternatively, the inner edge of the cantilever structure is inside the inner edge of the other side bridge structure, such as Figure 6A The right side of the case shown and Figure 6B The left side is shown.

[0101] As Figure 6A Taking the left side structure as an example, the interval stacking structure caused by the cantilever and the bridge structure changes three times, namely, the top electrode, the bottom electrode and the piezoelectric layer stacking structure are on the inner side of the inner edge of the bridge structure, the top electrode and the piezoelectric layer stacking structure are on the outer side of the inner edge of the bridge structure to the inner side of the inner edge of the cantilever structure, the piezoelectric layer is on the outer side of the inner edge of the cantilever structure to the inner side of the outer edge of the bridge structure, and the bottom electrode and the piezoelectric layer stacking structure are on the outer side of the outer edge of the bridge structure. This produces three acoustic impedance mismatching interfaces, which is conducive to the shear wave to generate multiple reflections on these impedance matching interfaces. By reasonably setting the width of these intervals, the resonator Q value can be greatly improved. In an optional embodiment, Δd1, d12b-Δd1, d41b is an odd multiple of λ / 4, and λ is the wavelength of the acoustic wave propagating laterally at the resonant frequency in the stacking structure in the thickness direction of the corresponding region at each distance. Figure 6A The right side structure and Figure 6B The medium structure can also be optimized using similar analysis methods. Figure 7 FIG. 4 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention. Figure 7 Two BAW resonators are shown in FIG, which share the same substrate 5. Figure 7 In the example, the number of resonators can be more. In addition, Figure 7 In the embodiment shown, the top and bottom electrodes of the two resonators are provided with cantilever and bridge structures, but the present invention is not limited thereto. The resonators in the assembly may be Figure 1-6B The resonator corresponding to any of the structures shown in .

[0102] In the present invention, the first acoustic impedance layer 3 and the second acoustic impedance layer 4 may together form an acoustic impedance structure. However, the present invention is not limited thereto. In other words, the arrangement of the acoustic impedance layers is not limited thereto. Alternatively, the acoustic impedance structure may include a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a transverse direction, or a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer, or a combination thereof.

[0103] In a further embodiment, the two resonators are adjacent in the lateral direction and respectively have a first acoustic impedance structure and a second acoustic impedance structure, and the two acoustic impedance structures share at least one first acoustic impedance layer 3 or at least one second acoustic impedance layer 4 .

[0104] In one embodiment, three acoustic impedance layers are included between the acoustic mirrors of the two resonators, namely, a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer. The two resonators at least share the second acoustic impedance layer 4 located in the middle.

[0105] In one embodiment, five acoustic impedance layers are located between the acoustic mirrors of the two resonators: a first acoustic impedance layer, a second acoustic impedance layer, a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer. The two resonators share at least the first acoustic impedance layer 3 located in the middle. For a single resonator, the acoustic impedance structure surrounding the acoustic mirror 8 includes, arranged from the inside to the outside, the first acoustic impedance layer 3, the second acoustic impedance layer 4, and the first acoustic impedance layer 3.

[0106] The connection method between adjacent resonators is not limited to the above. Adjacent resonators may not be electrically connected, but multiple acoustic impedance layers may be present between them. Furthermore, only one acoustic impedance layer (the first acoustic impedance layer) may be present between adjacent resonators. Adding more first acoustic impedance layers 3 and second acoustic impedance layers 4 can create more reflective interfaces, further reducing acoustic wave leakage and increasing the Q value of the resonator. Furthermore, by selecting the number and / or width of the first and second acoustic impedance layers, the pattern density of the first and second acoustic impedance layers 3 and 4 can be made more uniform, making it easier to form a flat film using a CMP (chemical mechanical polishing) process.

[0107] In one embodiment of the present invention, Figure 2A As shown, the angle α formed between the outer surface of the first acoustic impedance layer 3 and the bottom surface of the piezoelectric layer can be selected to be in the range of 100°-160°, specifically, 100°, 120°, 160°, etc. Selecting this angle facilitates filling the second acoustic impedance layer 4 after patterning the first acoustic impedance layer 3.

[0108] In one embodiment of the present invention, Figure 2A As shown, the angle β formed between the outer side of the end surface of the bottom electrode 2 and the bottom surface of the piezoelectric layer 1 can be selected to be in the range of 90°-160°, specifically, 90°, 100°, 120°, 160°, etc. Selecting this angle facilitates filling the first acoustic impedance layer 3 and the second acoustic impedance layer 4.

[0109] Figure 9 A bulk acoustic wave resonator according to an exemplary embodiment of the present invention is similar to Figure 1 A schematic cross-sectional view taken along the MOM' line in FIG, showing the electrode lead-out region of the bottom electrode and the electrode lead-out region of the top electrode, wherein the electrode connection end of the bottom electrode is covered by a portion of the first acoustic impedance layer, and the non-electrode connection end of the bottom electrode is spaced apart from the first acoustic impedance layer in the lateral direction. Figure 9 In the embodiment, both the top electrode and the bottom electrode are provided with cantilever and bridge structures. Figure 2A In the example, angle α is an obtuse angle, while in Figure 9 In the embodiment of the present invention, the angle α is an acute angle. Figure 9 As shown, the angle α formed between the outer side surface of the first acoustic impedance layer 3 and the bottom surface of the piezoelectric layer can be selected to be in the range of 20°-80°, specifically, 20°, 60°, 80°, etc.

[0110] For example, Figure 2A As shown, the piezoelectric layer 1 is provided with a bottom electrode via 9a (see FIG. 8I described later), and the electrode lead portion 6a is electrically connected to the electrode connection end of the bottom electrode 2 through the via 9a. Figure 8J and 8K As shown, the electrode lead portion 6a is formed of the same material as the top electrode 6 and has a lead portion arranged in the same layer as the top electrode 6. However, it is not excluded that the electrode lead portion 6a can also be formed separately from other materials different from the top electrode 6.

[0111] Refer to the following Figures 8A-8L An example description similar to Figure 2A (However, the top electrode and the bottom electrode are both provided with cantilever and bridge structures (the specific enlarged diagram corresponds to Figure 4A )) shows the fabrication process of the single crystal piezoelectric thin film bulk acoustic resonator.

[0112] like Figure 8AAs shown, a single crystal piezoelectric thin film layer (i.e., a single crystal piezoelectric layer) 1, such as single crystal aluminum nitride (AlN) or gallium nitride (GaN), is deposited on the surface of a substrate 5a (e.g., silicon or silicon carbide). The deposition process used includes, but is not limited to, MOCVD (metal organic chemical vapor deposition), MBE (molecular beam epitaxy), CBE (chemical molecular beam epitaxy), and LPE (liquid phase epitaxy). Alternatively, an interface layer is formed on the surface of an auxiliary substrate Aux1 (e.g., lithium niobate or lithium tantalate substrate) through ion implantation, and the piezoelectric thin film layer 1 is formed above the interface layer. In this case, the material of the piezoelectric thin film layer 1 is the same as that of the substrate 5a. The upper surface of the piezoelectric layer 1 is bonded to the substrate 5a.

[0113] like Figure 8B As shown, a sacrificial layer of bottom electrode cantilever and bridge structure is prepared on the piezoelectric layer. The material of the sacrificial layer can be a dielectric material such as silicon nitride and silicon oxide. The sacrificial layer structure 14 is obtained by patterning through an etching process.

[0114] like Figure 8C As shown, a bottom electrode layer is deposited on the single crystal piezoelectric layer by a thin film deposition process similar to CVD (chemical vapor deposition), PVD (physical vapor deposition), PECVD (plasma enhanced chemical vapor deposition), evaporation, sputtering, etc., and then the bottom electrode 2 is obtained by an etching process.

[0115] like Figure 8D As shown, in Figure 8C A layer of first acoustic impedance material is deposited on the surface of the piezoelectric layer 1 and the bottom electrode 2 of the structure shown, and patterned to form a first acoustic impedance layer 3. The first acoustic impedance material can be aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon, etc.

[0116] like Figure 8E As shown, in Figure 8D The second acoustic impedance material is deposited on the surface of the piezoelectric layer 1, the first acoustic impedance layer 3 and the bottom electrode 2 of the obtained structure, so that the second acoustic impedance material fills the gap between the first acoustic impedance layer 3 (the gap corresponds to the acoustic mirror cavity). The material of the second acoustic impedance layer can be silicon dioxide, doped silicon dioxide, polycrystalline silicon, amorphous silicon, etc., but is different from the material of the first acoustic impedance layer.

[0117] like Figure 8F As shown, the second acoustic impedance material is polished flat by CMP (chemical mechanical polishing) until the first acoustic impedance layer 3 is exposed. The second acoustic impedance material located outside the first acoustic impedance layer 3 constitutes the second acoustic impedance layer 4, while the second acoustic impedance material located between the first acoustic impedance layers 3 constitutes a sacrificial layer. In other words, in this embodiment, the second acoustic impedance material is also a sacrificial material.

[0118] like Figure 8GAs shown, the substrate 5 is bonded to the lower side of the first acoustic impedance layer 3 and the second acoustic impedance layer 4. Optionally, the surface of the substrate 5 may also have an auxiliary bonding layer (not shown in the figure), such as silicon dioxide, silicon nitride, etc.

[0119] like Figure 8H As shown, the substrate 5a is removed by grinding, etching or ion implantation layer separation to expose the upper surface of the piezoelectric layer 1. Optionally, the separation interface is subjected to CMP treatment to make the surface smooth and have low roughness.

[0120] like Figure 8I As shown, a through hole 9a is etched in the piezoelectric layer 1 by photolithography and etching processes. At the same time, a sacrificial layer release hole (not shown in the figure) is etched on the piezoelectric layer 1. The through hole is directly connected to the electrode connection end of the bottom electrode, or the through hole is directly connected to the acoustic mirror cavity or directly connected to the second acoustic impedance material located in the acoustic mirror cavity, namely the sacrificial layer.

[0121] like Figure 8J As shown, a sacrificial layer of a top electrode cantilever and a bridge structure is prepared on the piezoelectric layer. The material of the sacrificial layer can be a dielectric material such as silicon nitride and silicon oxide, and is patterned by an etching process.

[0122] like Figure 8K As shown, an electrode material layer for the top electrode 6 is deposited, which covers the top surface of the piezoelectric layer and enters the via 9a and the release hole. The electrode material layer is then etched to remove the electrode material in the release hole and patterned to form the top electrode 6.

[0123] like Figure 8L As shown, a conductive material is deposited by a thin film deposition process and then patterned to form an electrode connection portion (bonding pad) or an electrode electrical connection layer 7, including a top electrode connection layer and a bottom electrode connection layer.

[0124] Afterwards, an etchant is introduced through the release hole to release the second acoustic impedance layer material or the sacrificial layer in the acoustic mirror cavity 8, and a corresponding Figure 2A However, the top electrode and the bottom electrode are both provided with cantilever and bridge structures (the specific enlarged figure corresponds to Figure 4A ) structure.

[0125] In the above manufacturing process, the first acoustic impedance layer 3 is manufactured first, and then the second acoustic impedance layer 4 is manufactured. Therefore, the angle α formed between the outer side surface of the first acoustic impedance layer 3 and the bottom surface of the piezoelectric layer is within the range of 100°-160°. However, the second acoustic impedance layer 4 can also be manufactured first, and then the first acoustic impedance layer 3. Based on different manufacturing processes, the angle between the outer side surface of the first acoustic impedance layer 3 and the bottom surface of the piezoelectric layer can be Figure 2A Different than shown in .

[0126] In the present invention, the numerical range mentioned may be not only the endpoint values, but also the median value or other values ​​between the endpoint values, all of which are within the protection scope of the present invention.

[0127] In the present invention, the terms "up" and "down" are relative to the bottom surface of the base of the resonator. For a component, the side close to the bottom surface is the lower side, and the side away from the bottom surface is the upper side.

[0128] In the present invention, "inside" and "outside" refer to the center of the effective area of ​​the resonator (the overlapping area of ​​the piezoelectric layer, top electrode, bottom electrode, and acoustic mirror in the thickness direction of the resonator constitutes the effective area) in the lateral direction or radial direction. The side or end of a component close to the center is the inner side or inner end, while the side or end of the component away from the center is the outer side or outer end. For a reference position, being located inside the position means being between the position and the center (the center of the resonator effective area) in the lateral direction or radial direction, and being located outside the position means being further away from the center (the center of the resonator effective area) than the position in the lateral direction or radial direction.

[0129] It should be pointed out that in Figure 1 In the embodiment, the first acoustic impedance layer and the second acoustic impedance layer both form a ring around the acoustic mirror of the resonator. However, the second acoustic impedance layer may be embedded in a local position of the first acoustic impedance layer, which is within the scope of protection of the present invention.

[0130] In the present invention, the material of the piezoelectric layer may also be a non-single crystal material.

[0131] As those skilled in the art will appreciate, the BAW resonator according to the present invention can be used to form filters or other semiconductor devices.

[0132] Based on the above, the present invention proposes the following technical solutions:

[0133] 1. A bulk acoustic wave resonator, comprising:

[0134] substrate;

[0135] Acoustic mirror;

[0136] bottom electrode;

[0137] a top electrode; and

[0138] A piezoelectric layer is provided between the bottom electrode and the top electrode,

[0139] in:

[0140] An acoustic impedance structure is provided between the piezoelectric layer and the substrate;

[0141] The acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a lateral direction, the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances, and the acoustic mirror is located between the first acoustic impedance layers in the lateral direction of the resonator; and

[0142] The bottom electrode and / or the top electrode is provided with a cantilever and / or a bridge structure.

[0143] 2. The resonator according to item 1, wherein:

[0144] The non-electrode connection end of the bottom electrode and / or the top electrode is provided with a cantilever, and in the lateral direction of the resonator, there is a first distance in the lateral direction from the outer edge of the cantilever to the corresponding first acoustic impedance layer; or the non-electrode connection end of the bottom electrode and / or the top electrode is a non-cantilever structure, and in the lateral direction of the resonator, there is a third distance in the lateral direction from the outer edge of the non-electrode connection end to the corresponding first acoustic impedance layer.

[0145] 3. The resonator according to 2, wherein:

[0146] The first distance is in the range of 0-50 μm; and / or

[0147] The third distance is in the range of 0-50 μm.

[0148] 4. The resonator according to 2, wherein:

[0149] In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the cantilever of the top electrode is outside the boundary of the first acoustic impedance layer; or

[0150] In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the cantilever of the top electrode is inside the boundary of the first acoustic impedance layer; or

[0151] The non-electrode connection end of the top electrode is a non-cantilever structure, the non-electrode connection portion of the bottom electrode includes a cantilever, and in the lateral direction of the resonator, the edge of the non-electrode connection end of the top electrode is outside the inner end of the cantilever of the bottom electrode.

[0152] 5. The resonator according to 2, wherein:

[0153] The first distance is an odd multiple of λ1 / 4, and λ1 is the wavelength of the sound wave propagating laterally at the resonance frequency of the stacked structure in the thickness direction of the region corresponding to the first distance.

[0154] 6. The resonator according to 2, wherein:

[0155] In the lateral direction of the resonator, the cantilever width is in the range of 0–50 μm.

[0156] 7. The resonator according to 2, wherein:

[0157] Of the bottom electrode and the top electrode, only the non-electrode connection end of the top electrode or only the non-electrode connection end of the bottom electrode is provided with a cantilever.

[0158] 8. The resonator according to any one of 1 to 7, wherein:

[0159] The electrode connection end and / or the non-electrode connection end of the bottom electrode and / or the top electrode are provided with a bridge structure; and

[0160] In the lateral direction of the resonator, there is a fifth distance between the outer edge of the bridge structure and the corresponding first acoustic impedance layer.

[0161] 9. The resonator according to 8, wherein:

[0162] The fifth distance is in the range of 0-50 μm.

[0163] 10. The resonator according to 8, wherein:

[0164] In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the bridge structure is outside the boundary of the first acoustic impedance layer.

[0165] 11. The resonator according to 8, wherein:

[0166] The fifth distance is an odd multiple of λ2 / 4, and λ2 is the wavelength of the sound wave propagating laterally at the resonance frequency of the stacked structure in the thickness direction of the region corresponding to the fifth distance.

[0167] 12. The resonator according to 8, wherein:

[0168] The width of the bridge structure is in the range of 0–50 μm.

[0169] 13. The resonator according to any one of 8 to 12, wherein:

[0170] The electrode connection end and / or the non-electrode connection end of one of the top electrode and the bottom electrode is provided with a bridge structure, and the non-electrode connection end of the other of the top electrode and the bottom electrode is provided with a cantilever or a bridge structure.

[0171] 14. The resonator according to 13, wherein:

[0172] Both the top electrode and the bottom electrode are provided with cantilever and bridge structures.

[0173] 15. The resonator according to 13, wherein:

[0174] In the thickness direction of the resonator, an inner edge of the cantilever of one of the top electrode and the bottom electrode is aligned with an inner edge of the bridge structure or the cantilever structure of the other of the top electrode and the bottom electrode.

[0175] 16. The resonator according to 13, wherein:

[0176] An inner edge of the cantilever of one of the top electrode and the bottom electrode is offset from an inner edge of a corresponding bridge structure or cantilever structure of the other of the top electrode and the bottom electrode in the lateral direction.

[0177] 17. The resonator according to 16, wherein:

[0178] There is a first gap in the lateral direction between an inner edge of the cantilever of one of the top electrode and the bottom electrode and an inner edge of a corresponding bridge structure or cantilever structure of the other of the top electrode and the bottom electrode.

[0179] 18. The resonator according to 17, wherein:

[0180] The first interval is in the range of 0–50 μm.

[0181] 19. The resonator according to 8, wherein:

[0182] The electrode connection end of the top electrode is provided with a bridge structure, and the first acoustic impedance layer covers a portion of the non-electrode connection end of the bottom electrode, in the lateral direction, the boundary of the first acoustic impedance layer is located inside the edge of the non-electrode connection end of the bottom electrode, the inner side of the bridge structure of the top electrode is located inside the boundary of the first acoustic impedance layer, and the outer side of the bridge structure of the top electrode is located outside the edge of the non-electrode connection end of the bottom electrode; or

[0183] The non-electrode connection end of the top electrode is provided with a cantilever, and the first acoustic impedance layer covers a portion of the electrode connection end of the bottom electrode, and in the lateral direction, the inner end of the cantilever of the top electrode is located inside the boundary of the first acoustic impedance layer covering the electrode connection end of the bottom electrode; or

[0184] The electrode connection end or the non-electrode connection end of the bottom electrode includes a bridge structure, the first acoustic impedance layer partially covers the electrode connection end or the non-electrode connection end of the bottom electrode, and in the lateral direction, the inner end of the bridge structure of the bottom electrode is on the inner side of the boundary of the first acoustic impedance layer; or

[0185] The non-electrode connection end of one of the top electrode or the bottom electrode is a non-cantilever structure, the electrode connection end or the non-electrode connection end of the other of the top electrode or the bottom electrode comprises a bridge structure, and in the lateral direction, the edge of the non-electrode connection end of the one electrode is between the inner end and the outer end of the corresponding bridge structure of the other electrode; or

[0186] The non-electrode connection end of one of the top electrode or the bottom electrode is provided with a cantilever, the electrode connection end or the non-electrode connection end of the other electrode of the top electrode or the bottom electrode is provided with a bridge structure, and the inner end of the cantilever is located between the inner end and the outer end of the corresponding bridge structure in the lateral direction, or the inner end of the cantilever is located on the inner side of the inner end of the corresponding bridge structure in the lateral direction.

[0187] 20. The resonator according to item 1, wherein:

[0188] The electrode connection end of one of the top electrode and the bottom electrode is provided with a bridge structure, and the non-electrode connection end of the other of the top electrode and the bottom electrode has an overlapping area with the bridge structure in the thickness direction of the resonator.

[0189] 21. The resonator according to item 1, wherein:

[0190] The acoustic mirror is an acoustic mirror cavity;

[0191] The boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

[0192] 22. The resonator according to any one of 1 to 21, wherein:

[0193] The piezoelectric layer is a single crystal piezoelectric layer.

[0194] 23. The resonator according to any one of 1 to 22, wherein:

[0195] The widths of the portions of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ3 / 4 and nλ4 / 4, respectively, where m and n are both odd numbers, and λ3 and λ4 are the wavelengths of acoustic waves propagating laterally at the resonant frequency at the corresponding portions of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer.

[0196] 24. The resonator according to any one of 1 to 22, wherein:

[0197] The material forming one of the first acoustic impedance layer and the second acoustic impedance layer is selected from aluminum nitride, silicon dioxide, silicon nitride, polycrystalline silicon, and amorphous silicon, and the material forming the other of the first acoustic impedance layer and the second acoustic impedance layer is selected from silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon. The material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

[0198] 25. The resonator according to any one of 1 to 22, wherein:

[0199] The electrode connection end of the bottom electrode is covered by a portion of the first acoustic impedance layer.

[0200] 26. A bulk acoustic wave resonator assembly comprising:

[0201] At least two resonators according to any one of 1-25, the at least two resonators sharing a same substrate.

[0202] 27. A filter comprising the BAW resonator according to any one of 1 to 25, or the BAW resonator assembly according to 26.

[0203] 28. An electronic device comprising the filter according to 27, or the BAW resonator according to any one of 1 to 25, or the BAW resonator assembly according to 26.

[0204] The electronic equipment here includes but is not limited to intermediate products such as RF front-ends, filter amplification modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0205] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bulk acoustic wave resonator, comprising: substrate; Acoustic mirror; bottom electrode; Top electrode; and A piezoelectric layer is provided between the bottom electrode and the top electrode, in: An acoustic impedance structure is provided between the piezoelectric layer and the substrate; The acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a lateral direction, the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances, and the acoustic mirror is located between the first acoustic impedance layers in the lateral direction of the resonator; and The bottom electrode and / or the top electrode is provided with a cantilever and / or a bridge structure.

2. The resonator according to claim 1, wherein: The non-electrode connection end of the bottom electrode and / or the top electrode is provided with a cantilever, and in the lateral direction of the resonator, there is a first distance in the lateral direction from the outer edge of the cantilever to the corresponding first acoustic impedance layer; or the non-electrode connection end of the bottom electrode and / or the top electrode is a non-cantilever structure, and in the lateral direction of the resonator, there is a third distance in the lateral direction from the outer edge of the non-electrode connection end to the corresponding first acoustic impedance layer.

3. The resonator according to claim 2, wherein: The first distance is in the range of 0-50 μm; and / or The third distance is in the range of 0-50 μm.

4. The resonator according to claim 2, wherein: In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the cantilever of the top electrode is inside the boundary of the first acoustic impedance layer; or In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the cantilever of the top electrode is outside the boundary of the first acoustic impedance layer; or The non-electrode connection end of the top electrode is a non-cantilever structure, the non-electrode connection portion of the bottom electrode includes a cantilever, and in the lateral direction of the resonator, the edge of the non-electrode connection end of the top electrode is outside the inner end of the cantilever of the bottom electrode.

5. The resonator according to claim 2, wherein: The first distance is an odd multiple of λ1 / 4, and λ1 is the wavelength of the sound wave propagating laterally at the resonance frequency of the stacked structure in the thickness direction of the region corresponding to the first distance.

6. The resonator according to claim 2, wherein: In the lateral direction of the resonator, the cantilever width is in the range of 0–50 μm.

7. The resonator according to claim 2, wherein: Of the bottom electrode and the top electrode, only the non-electrode connection end of the top electrode or only the non-electrode connection end of the bottom electrode is provided with a cantilever.

8. The resonator according to any one of claims 1 to 7, wherein: The electrode connection end and / or the non-electrode connection end of the bottom electrode and / or the top electrode are provided with a bridge structure; and In the lateral direction of the resonator, there is a fifth distance between the outer edge of the bridge structure and the corresponding first acoustic impedance layer.

9. The resonator of claim 8, wherein: The fifth distance is in the range of 0-50 μm.

10. The resonator of claim 8, wherein: In the lateral direction of the resonator, on the side of the electrode connection terminal of the bottom electrode, the outer edge of the bridge structure is outside the boundary of the first acoustic impedance layer.

11. The resonator according to claim 8, wherein: The fifth distance is an odd multiple of λ2 / 4, and λ2 is the wavelength of the sound wave propagating laterally at the resonance frequency of the stacked structure in the thickness direction of the region corresponding to the fifth distance.

12. The resonator of claim 8, wherein: The width of the bridge structure is in the range of 0–50 μm.

13. The resonator of claim 8, wherein: The electrode connection end and / or the non-electrode connection end of one of the top electrode and the bottom electrode is provided with a bridge structure, and the non-electrode connection end of the other of the top electrode and the bottom electrode is provided with a cantilever or a bridge structure.

14. The resonator of claim 13, wherein: Both the top electrode and the bottom electrode are provided with cantilever and bridge structures.

15. The resonator of claim 13, wherein: In the thickness direction of the resonator, an inner edge of the cantilever of one of the top electrode and the bottom electrode is aligned with an inner edge of a corresponding bridge structure or cantilever structure of the other of the top electrode and the bottom electrode.

16. The resonator of claim 13, wherein: An inner edge of the cantilever of one of the top electrode and the bottom electrode is offset from an inner edge of a corresponding bridge structure or cantilever structure of the other of the top electrode and the bottom electrode in the lateral direction.

17. The resonator of claim 16, wherein: There is a first gap in the lateral direction between an inner edge of the cantilever of one of the top electrode and the bottom electrode and an inner edge of a corresponding bridge structure or cantilever structure of the other of the top electrode and the bottom electrode.

18. The resonator of claim 17, wherein: The first interval is in the range of 0–50 μm.

19. The resonator of claim 8, wherein: The electrode connection end of the top electrode is provided with a bridge structure, and the first acoustic impedance layer covers a portion of the non-electrode connection end of the bottom electrode, in the lateral direction, the boundary of the first acoustic impedance layer is located inside the edge of the non-electrode connection end of the bottom electrode, the inner side of the bridge structure of the top electrode is located inside the boundary of the first acoustic impedance layer, and the outer side of the bridge structure of the top electrode is located outside the edge of the non-electrode connection end of the bottom electrode; or The non-electrode connection end of the top electrode is provided with a cantilever, and the first acoustic impedance layer covers a portion of the electrode connection end of the bottom electrode, and in the lateral direction, the inner end of the cantilever of the top electrode is located inside the boundary of the first acoustic impedance layer covering the electrode connection end of the bottom electrode; or The electrode connection end or the non-electrode connection end of the bottom electrode includes a bridge structure, the first acoustic impedance layer partially covers the electrode connection end or the non-electrode connection end of the bottom electrode, and in the lateral direction, the inner end of the bridge structure of the bottom electrode is on the inner side of the boundary of the first acoustic impedance layer; or The non-electrode connection end of one of the top electrode or the bottom electrode is a non-cantilever structure, the electrode connection end or the non-electrode connection end of the other of the top electrode or the bottom electrode comprises a bridge structure, and in the lateral direction, the edge of the non-electrode connection end of the one electrode is between the inner end and the outer end of the corresponding bridge structure of the other electrode; or The non-electrode connection end of one of the top electrode or the bottom electrode is provided with a cantilever, the electrode connection end or the non-electrode connection end of the other electrode of the top electrode or the bottom electrode is provided with a bridge structure, and the inner end of the cantilever is located between the inner end and the outer end of the corresponding bridge structure in the lateral direction, or the inner end of the cantilever is located on the inner side of the inner end of the corresponding bridge structure in the lateral direction.

20. The resonator of claim 1, wherein: The electrode connection end of one of the top electrode and the bottom electrode is provided with a bridge structure, and the non-electrode connection end of the other of the top electrode and the bottom electrode has an overlapping area with the bridge structure in the thickness direction of the resonator.

21. The resonator of claim 1 , wherein: The acoustic mirror is an acoustic mirror cavity; The boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

22. The resonator according to any one of claims 1 to 7, 9 to 12, or 14 to 21, wherein: The piezoelectric layer is a single crystal piezoelectric layer.

23. The resonator according to any one of claims 1 to 7, 9 to 12, or 14 to 21, wherein: The widths of the portions of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ3 / 4 and nλ4 / 4, respectively, where m and n are both odd numbers, and λ3 and λ4 are the wavelengths of acoustic waves propagating laterally at the resonant frequency at the corresponding portions of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer.

24. The resonator according to any one of claims 1 to 7, 9 to 12, or 14 to 21, wherein: The material forming one of the first acoustic impedance layer and the second acoustic impedance layer is selected from aluminum nitride, silicon dioxide, silicon nitride, polycrystalline silicon, and amorphous silicon, and the material forming the other of the first acoustic impedance layer and the second acoustic impedance layer is selected from silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon. The material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

25. The resonator according to any one of claims 1 to 7, 9 to 12, or 14 to 21, wherein: The electrode connection end of the bottom electrode is covered by a portion of the first acoustic impedance layer.

26. A bulk acoustic wave resonator assembly comprising: At least two resonators according to any one of claims 1 to 25, the at least two resonators sharing a same substrate.

27. A filter comprising the BAW resonator according to any one of claims 1 to 25, or the BAW resonator assembly according to claim 26.

28. An electronic device comprising the filter according to claim 27, or the BAW resonator according to any one of claims 1 to 25, or the BAW resonator assembly according to claim 26.

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