Bulk acoustic wave resonator and manufacturing method, component, filter and electronic device

Abstract

The present invention relates to a bulk acoustic wave resonator and a method for manufacturing the same. The resonator comprises: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer, wherein: the overlapping portion of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator constitutes the effective area of ​​the resonator; at least one of the upper and lower sides of the piezoelectric layer is provided with a recessed portion, the bottom of the recessed portion is a flat surface; and corresponding electrodes of the top electrode and the bottom electrode are provided in the region of the recessed portion. The present invention also relates to a bulk acoustic wave resonator component, a filter and an electronic device.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductors, and in particular to a bulk acoustic wave resonator and a manufacturing method thereof, 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 data transmission rate are getting higher and higher. Corresponding to the data transmission rate is the high utilization rate of spectrum resources and the complexity of spectrum. The complexity of communication protocols has put forward strict requirements on various performances of RF systems. In RF front-end modules, RF filters play a vital role. They can filter out out-of-band interference and noise to meet the requirements of RF systems and communication protocols for signal-to-noise ratio.

[0003] Traditional RF filters are limited by their structure and performance and cannot meet the requirements of high-frequency communications. As a new type of MEMS device, film bulk acoustic resonator (FBAR) has the advantages of small size, light weight, low insertion loss, wide bandwidth and high quality factor, which is well adapted to the upgrading of wireless communication systems, making FBAR technology one of the research hotspots in the field of communications. However, since the frequency of FBAR is determined by its thickness, the existing technology can only achieve small-range frequency adjustment by adding an appropriate mass load layer. Therefore, how to integrate RF filters of different frequencies with large frequency intervals on a single substrate is still a major challenge facing FBAR technology.

[0004] On the other hand, the series resonator and the parallel resonator of the filter in the prior art work together to form the filter passband characteristics. By setting the series resonant frequencies of the series resonators to be different from each other and the electromechanical coupling coefficient Kt of the series resonators to be different from each other, ...ator frequencies to be different from each other and the electromechanical coupling coefficient Kt of the series resonators to be different from each other, the series resonator frequencies to be different from each other and the electromechanical coupling coefficient Kt of the series resonators to be different from each other, the series resonator frequencies to be different from each other and the series resonator frequencies to be different from each other. 2 The change of can effectively improve the roll-off characteristics on the right side of the filter passband. 2 Resonators are easy to achieve good roll-off characteristics, but once the design indicators (bandwidth, insertion loss, out-of-band suppression, etc.) are determined, the Kt of the resonator 2 It is basically determined that the filter bandwidth and the good roll-off characteristics of the filter are contradictory. It is difficult to achieve good roll-off characteristics in the wide bandwidth filter design under the conventional architecture. Moreover, under the condition that the resonator stack in the ordinary filter has been determined, the Kt of the 50Ohm resonator can be changed by changing the resonator structure. 2 The change is only about ±0.5%, which has limited improvement on the filter roll-off characteristics. Therefore, the Kt between each resonator is relaxed. 2 The restriction of the degrees of freedom is beneficial to improving the roll-off performance of the entire filter. Summary of the invention

[0005] To improve the Kt of BAW resonator2 The present invention proposes a technical solution for adjusting the thickness of the piezoelectric layer of a bulk acoustic wave resonator in order to provide a degree of freedom of choice.

[0006] Based on this technical solution, it is also suitable for manufacturing piezoelectric layers of different thicknesses on the same wafer. On the one hand, this can achieve a wide range of adjustment of the electromechanical coupling coefficient of the bulk acoustic wave resonator, which is beneficial to adjust the Kt of the resonator in a single filter. 2 The selection of the value provides greater freedom, and on the other hand, it can also realize the monolithic integration of multiple different frequency filters with large frequency intervals.

[0007] According to one aspect of an embodiment of the present invention, a bulk acoustic wave resonator is provided, comprising:

[0008] substrate;

[0009] Acoustic mirror;

[0010] bottom electrode;

[0011] a top electrode; and

[0012] Piezoelectric layer,

[0013] in:

[0014] The overlapping portion of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator constitutes the effective area of ​​the resonator;

[0015] At least one of the upper and lower sides of the piezoelectric layer is provided with a recessed portion, and the bottom of the recessed portion is a flat surface;

[0016] A corresponding electrode of the top electrode and the bottom electrode is arranged in the region of the recessed portion.

[0017] An embodiment of the present invention also relates to a bulk acoustic wave resonator component, which includes a first resonator and a second resonator, wherein the first resonator and the second resonator are both bulk acoustic wave resonators, and at least the second resonator is the above-mentioned resonator, the first resonator and the second resonator share the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator is the original thickness of the piezoelectric layer of the second resonator.

[0018] The present invention also relates to a method for manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode connected to an electrode lead-out portion; a top electrode connected to the top electrode lead-out portion; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of:

[0019] A recessed portion is provided on at least one of the upper and lower sides of the piezoelectric layer, wherein the bottom of the recessed portion is a flat surface; and

[0020] A corresponding electrode of the top electrode and the bottom electrode is disposed in the region of the recessed portion.

[0021] An embodiment of the present invention also relates to a method for adjusting an electromechanical coupling coefficient of a resonator in a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being the bulk acoustic wave resonator described above, the method comprising the steps of:

[0022] The depth of the recessed portion is selected to adjust the electromechanical coupling coefficient of the second resonator based on the thickness of the piezoelectric layer of the second resonator within the active area.

[0023] An embodiment of the present invention further relates to a filter, comprising the above-mentioned BAW resonator or resonator assembly.

[0024] 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

[0025] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed by the present invention, in which the same reference numerals always represent the same components, wherein:

[0026] Figure 1 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, wherein two bulk acoustic wave resonators are shown, the piezoelectric layer of the resonator on the right has recessed portions at both upper and lower sides, and the piezoelectric layer of the resonator on the left has no recessed portions;

[0027] Figure 2a-2s An example is shown Figure 1 The fabrication process of the BAW resonator assembly shown in ;

[0028] Figure 3 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that only the lower side of the piezoelectric layer of the resonator on the right has a recess;

[0029] Figure 4 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that only the upper side of the piezoelectric layer of the resonator on the right has a recess;

[0030] Figure 5 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the mass load layer of the resonator on the right is set on the bottom electrode side;

[0031] Figure 6 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the mass-loading layers of the resonator on the right are set on the top and bottom electrodes respectively;

[0032] Figure 7 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the electrode thickness of the left resonator is different from that of the right resonator;

[0033] Figure 8 is a cross-sectional schematic diagram of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, Figure 1 The structure shown is different in that Figure 8 In the embodiment, the angle between the outer side wall of the second acoustic impedance layer and the piezoelectric layer is greater than 90°, while in Figure 1 In the embodiment, the angle between the outer side wall of the first acoustic impedance layer and the piezoelectric layer is greater than 90°. DETAILED DESCRIPTION

[0034] 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 figure 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 in the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0035] First, the reference numerals in the accompanying drawings of the present invention are described as follows:

[0036] 1: The first substrate or 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.

[0037] 2: The piezoelectric layer can be a single crystal piezoelectric material, such as single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lead zirconate titanate (PZT), single crystal potassium niobate, single crystal quartz film, or single crystal lithium tantalate, etc. It can also be a polycrystalline piezoelectric material (corresponding to a single crystal, a non-single crystal material), such as polycrystalline aluminum nitride, zinc oxide, PZT, etc., and can also be a rare earth element doped with a certain atomic ratio of the above materials The material, for example, can be doped aluminum nitride, which 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.

[0038] 3: First hard mask layer: It can be the first barrier layer, and the material can be silicon nitride, molybdenum, silicon oxide, etc.

[0039] 4: Bottom electrode, the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys.

[0040] 5: Acoustic reflection layer or first acoustic impedance layer, which can be made of silicon nitride, silicon dioxide, polycrystalline silicon, amorphous silicon, aluminum nitride and other materials.

[0041] 6: The sacrificial layer, which is also the second acoustic impedance layer, can be made of silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon and other materials, but is different from the material of the first acoustic impedance layer 5 , and the etchant of the sacrificial layer is not easy to etch or does not etch the first acoustic impedance layer 5 .

[0042] 7: Second substrate, optional materials are single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0043] 8: Second hard mask layer: It can be a second barrier layer, and the material can be silicon nitride, molybdenum, silicon oxide, etc.

[0044] 9: Electrode connection hole, in which a conductive metal is arranged. The optional material is a metal material, such as molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, platinum, iridium, osmium, chromium or a composite of the above metals or an alloy thereof.

[0045] 10: Top electrode, the material can be the same as the bottom electrode, and the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys. The top electrode and the bottom electrode are generally made of the same material, but can also be different.

[0046] 11: Electrode connection part (PAD), the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys.

[0047] 12: Acoustic mirror, which can be a cavity, or a Bragg reflection layer or other equivalent forms. The embodiment of the present invention adopts the form of a cavity.

[0048] 13 and 14: frequency adjustment layer or mass load layer, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite or alloy of the above metals, etc. It can also be selected from dielectric materials such as silicon dioxide, aluminum nitride, zinc oxide, PZT, etc., and also includes rare earth element doping materials with a certain atomic ratio of the above piezoelectric materials.

[0049] Figure 1 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, Figure 1 In the embodiment, the BAW resonator assembly includes two BAW resonators with piezoelectric layers arranged in the same layer, the piezoelectric layer of the right resonator has recessed portions on both sides, and the piezoelectric layer of the left resonator does not have a recessed portion. In the present invention, the same layer arrangement means that the bottom sides or upper sides of the two piezoelectric layers are on the same surface or are formed in the same piezoelectric layer forming step.

[0050] More specifically, for Figure 1 The resonator on the right side of the middle comprises: a substrate 7; an acoustic mirror 12; a bottom electrode 4; a top electrode 10; and a piezoelectric layer 12, wherein: recessed portions are provided on both the upper and lower sides of the piezoelectric layer 2, the bottom of the recessed portion is a flat surface, and the bottom electrode is provided in the lower recessed portion, and the top electrode is provided in the upper recessed portion.

[0051] For BAW resonators, the frequency is determined by the thickness of each layer, and the relationship is inversely proportional, that is, a decrease in the thickness of any layer will lead to an increase in frequency. At the same time, its electromechanical coupling coefficient is determined by the thickness ratio of each layer. From the overall trend, when the total thickness of the upper and lower electrodes is greater than the thickness of the piezoelectric layer, the smaller the electromechanical coupling coefficient is. At the same time, when the thickness of the piezoelectric layer is constant, when the thickness ratio of the upper and lower electrodes is 1, the electromechanical coupling coefficient is the largest, and when the ratio of the upper and lower electrodes is greater than 1 or less than 1, the electromechanical coupling coefficient will decrease.

[0052] exist Figure 1 In the figure, for the right resonator, the piezoelectric layer thickness is smaller than that of the left resonator. When the electrode thickness is the same as that on the left, its resonant frequency will be higher, and at the same time, the electromechanical coupling coefficient will be lower. Optionally, a mass load layer can be further provided on the top electrode of the right resonator to reduce the frequency and further reduce its electromechanical coupling coefficient. Therefore, by reasonably selecting the depth of the recess (i.e., the thickness of the piezoelectric layer) and the thickness of the mass load layer, the frequencies of the left and right resonators can be comparable, but the electromechanical coupling coefficients differ greatly.

[0053] like Figure 1 As shown, the depression depth of the upper depression is h1, the depression depth of the lower depression is h2, the original thickness of the piezoelectric layer is h4, and the thickness of the piezoelectric layer between the two depressions is h3.

[0054] In one embodiment of the present invention, h1 and h2 may be the same or different. Optionally, h1 or h2 is not more than one half of h4. Optionally, h3 is not less than one fifth of h4.

[0055] Figure 1 The figure also shows the angle ɑ between the groove wall of the recess and the bottom (flat surface) of the recess. In an optional embodiment, the angle ɑ is in the range of 90°-160°. When the depth of the recess is smaller, the angle can be selected to be close to 90°; and when the depth of the recess is larger, the angle should be larger, such as 120°. When the depth of the recess is large, if the angle is close to 90°, the electrode on this interface (which can be the top electrode or the bottom electrode) will be poorly covered, and faults will easily occur, thereby disconnecting the electrical connection of adjacent resonators with different piezoelectric layer thicknesses.

[0056] like Figure 1 As shown, an acoustic impedance structure is arranged between the piezoelectric layer 4 and the substrate 7, and the acoustic impedance structure includes a first acoustic impedance layer 5 and a second acoustic impedance layer or a sacrificial layer 6 arranged adjacent to each other in the lateral direction, and the first acoustic impedance layer 5 and the second acoustic impedance layer 6 have different acoustic impedances. The acoustic mirror is located between the first acoustic impedance layer 5 in the lateral direction of the resonator. In other words, Figure 1 In the illustrated embodiment, when the acoustic mirror 12 is in the form of a cavity, the boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer 5 .

[0057] In the present invention, the acoustic impedance of the first acoustic impedance layer 5 is different from that of the second acoustic impedance layer 6 to form an impedance mismatch, thereby forming a continuous reflection of the sound waves and forming a reflection structure for the lateral sound waves, thereby preventing the leakage of lateral sound waves and facilitating the locking of energy in the resonator, thereby improving the Q value.

[0058] In the present invention, it is utilized that when the piezoelectric layer is made of a single crystal piezoelectric material, the piezoelectric loss can be made lower, thereby obtaining a higher resonator Q value, and at the same time the electromechanical coupling coefficient and the power capacity can be improved.

[0059] In a further embodiment, the widths of the portions of the first acoustic impedance layer 5 and the second acoustic impedance layer 6 in contact with the piezoelectric layer 2 are respectively mλ 1 / 4 and nλ 2 / 4, where m and n are both odd numbers, such as 1, 3, 5, 7, etc., λ1 and λ 2 are the wavelengths of the acoustic waves propagating laterally at the resonant frequency of the first acoustic impedance layer 5 and the second acoustic impedance layer 6. The resonant frequency is a frequency within the resonant range of the resonator, which may be the series resonant frequency or the parallel resonant frequency of the resonator, or a frequency between the series and parallel resonant frequencies, or a frequency slightly lower than the series resonant frequency or slightly higher than the parallel resonant frequency. Figure 1 In the embodiment, the width of the first acoustic impedance layer 5 is represented by A, and the width of the second acoustic impedance layer 6 is represented by B. The above widths are selected to form an effective acoustic impedance mismatch, prevent lateral sound wave leakage, and further improve the Q value of the resonator. m and n can be the same or different, both within the scope of protection of the present invention.

[0060] The materials forming the first acoustic impedance layer 5 include aluminum nitride, silicon dioxide, silicon nitride, polycrystalline silicon, and amorphous silicon, and the materials forming the second acoustic impedance layer 6 include silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon. The material of the first acoustic impedance layer 5 and the material of the second acoustic impedance layer 6 are different from each other. Optionally, the material forming the first acoustic impedance layer 5 includes silicon dioxide, and the material forming the second acoustic impedance layer 6 includes polycrystalline silicon. Alternatively, the material forming the first acoustic impedance layer 5 includes silicon nitride or aluminum nitride, and the material forming the second acoustic impedance layer 6 includes silicon dioxide or doped silicon dioxide. In the present invention, in order to improve the degree of acoustic mismatch at the junction of the first acoustic impedance layer 5 and the second acoustic impedance layer 6, the difference in acoustic impedance between the two can be selected to be as large as possible.

[0061] As shown in the attached Figure 2a-2s As described above, in the process of manufacturing the resonator, the second acoustic impedance layer 6 is also used as a sacrificial layer. Therefore, when releasing the sacrificial layer, a suitable releasing etchant needs to be selected so that the etchant only etches the first acoustic impedance material and does not etch or etches a very small amount of the second acoustic impedance material.

[0062] like Figure 1 As shown, the non-electrode connection end ( Figure 1 The end surface of the left resonator on the left side and the right resonator on the right side) is separated from the first acoustic impedance layer 5 in the acoustic impedance structure in the lateral direction, so that the sound wave is also fully reflected at the lateral interface between the non-electrode connection end of the bottom electrode and the gap, thereby reducing the leakage of the sound wave. Based on the gap structure at the non-electrode connection end, the lateral leakage of the sound wave can be further prevented, and the Q value of the resonator can be improved. On the other hand, the non-electrode connection end of the bottom electrode 4 below the top electrode connection edge ( Figure 1If the end faces (the left end of the left resonator and the right end of the right resonator) are covered by the first acoustic impedance layer 5, parasitic capacitance will be formed with the part of the top electrode outside the cavity, thereby affecting the electromechanical coupling coefficient of the resonator.

[0063] In an alternative embodiment, in a longitudinal section of the resonator through the electrode connection end of the bottom electrode 4 (eg Figure 1 In the cross-sectional view shown in FIG. 1 , the distance between the end surface of the non-electrode connection end of the bottom electrode 4 and the acoustic impedance structure in the lateral direction is in the range of 0.5 μm-10 μm. In addition to the end value, the distance can also be, for example, 5 μm, 7 μm, etc.

[0064] exist Figure 1 In the illustrated embodiment, the bottom electrode 4 is wrapped by a continuous reflection layer or acoustic impedance structure formed by a first acoustic impedance layer 5 and a second acoustic impedance layer 6 on one side of the electrode connection end, and more specifically, is covered by the first acoustic impedance layer 5. 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 by the resonator during operation to the substrate or base through the electrode and the first acoustic impedance layer 5, 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 5, due to the presence of a reflection 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.

[0065] exist Figure 1 In the embodiment shown, the electrode connection end of the bottom electrode 4 is covered by the first acoustic impedance layer 5, but the present invention is not limited thereto. For example, the electrode connection end of the bottom electrode 4 may also be spaced apart from the first acoustic impedance layer 5 in the lateral direction. In this case, because the end surface of the non-electrode connection end and the end surface of the electrode connection end of the bottom electrode 4 are both spaced apart from the first acoustic impedance layer 5 in the lateral direction, the sound wave is also fully 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. Compared with Figure 1 The structure shown in the figure is also provided with a gap at the electrode connection end, which helps to further prevent the leakage of lateral acoustic waves. However, since the electrode does not form direct contact with the first acoustic impedance layer, the heat must be indirectly conducted to the first acoustic impedance layer and the substrate through the piezoelectric material, which will cause the power capacity to deteriorate.

[0066] In an optional embodiment, in another longitudinal section of the resonator passing through the non-electrode connection end of the bottom electrode 4 and the non-electrode connection end of the top electrode 10, the end face of the non-electrode connection end of the bottom electrode 4 may be spaced apart from the acoustic impedance structure in the lateral direction, with a spacing distance in the range of 0.5 μm-10 μm; or, the non-electrode connection end of the bottom electrode 4 is wrapped by a continuous reflective layer or acoustic impedance structure formed by the first acoustic impedance layer 5 and the second acoustic impedance layer 6, and more specifically, is covered by the first acoustic impedance layer 5.

[0067] In the present invention, the first acoustic impedance layer 5 and the second acoustic impedance layer 6 can together constitute an acoustic impedance structure. However, the present invention is not limited thereto. In other words, the arrangement of the acoustic impedance layer is not limited thereto. It may include a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction, or a first acoustic impedance layer, a second acoustic impedance layer and a first acoustic impedance layer, or a combination thereof.

[0068] exist Figure 1 In the BAW resonator assembly shown, three acoustic impedance layers are included between the acoustic mirrors of the two resonators, namely, the first acoustic impedance layer, the second acoustic impedance layer and the first acoustic impedance layer. The two resonators at least share the second acoustic impedance layer 4 located in the middle. Thus, for a single resonator, the acoustic impedance structure surrounding the acoustic mirror 12 includes the first acoustic impedance layer and the second acoustic impedance layer arranged in sequence from the inside to the outside.

[0069] exist Figure 1 In the illustrated embodiment, a first acoustic impedance layer 5, a second acoustic impedance layer 6, and a first acoustic impedance layer 5 are provided between the two resonators, but the present invention is not limited thereto. For example, five acoustic impedance layers are included between the acoustic mirrors of the two resonators, namely, 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 at least share the first acoustic impedance layer 5 located in the middle. Thus, for a single resonator, the acoustic impedance structure surrounding the acoustic mirror 12 includes a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer arranged sequentially from the inside to the outside. Therefore, the acoustic impedance structure between the two resonators shares at least one first acoustic impedance layer 5 or at least one second acoustic impedance layer 6.

[0070] Figure 3 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that only the lower side of the piezoelectric layer of the right resonator has a depression.

[0071] Figure 4FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that only the upper side of the piezoelectric layer of the right-hand resonator has a depression.

[0072] Figure 5 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the mass load layer of the resonator on the right is arranged on one side of the bottom electrode. Although the mass load layer is placed below the bottom electrode in the figure, it is easy to understand that the mass load layer can also be placed between the bottom electrode and the piezoelectric layer.

[0073] Figure 6 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the mass load layer of the resonator on the right is set on the top electrode and the bottom electrode respectively. Adding mass load layers on the top and bottom electrodes can flexibly change the thickness ratio of the bottom electrode, piezoelectric layer and top electrode, thereby ensuring better electrical performance, such as a higher Q value, on the basis of adjusting the electromechanical coupling coefficient.

[0074] Figure 7 FIG. 1 is a cross-sectional schematic diagram of a BAW resonator assembly according to an exemplary embodiment of the present invention, wherein two BAW resonators are shown. Figure 1 The difference is that the electrode thickness of the left resonator is different from that of the right resonator. In an optional embodiment, the electrode thickness of the left resonator is thicker than that of the right one, and its piezoelectric layer is also thicker than that of the right one, so that the left resonator has a lower frequency, which can realize the integration of two filters with a large frequency span (such as two filters in a duplexer). By adjusting the thickness of the top electrode, piezoelectric layer, and bottom electrode of the two resonators respectively, the combination of resonators of any frequency and electromechanical coupling coefficient on a single wafer can be realized, so that it can be used in different application scenarios.

[0075] Refer to the following Figure 2a-2s Example Figure 1 The fabrication process of the BAW resonator assembly is shown in FIG.

[0076] Step 1: If Figure 2aAs shown, a single crystal piezoelectric film layer (i.e., a single crystal piezoelectric layer) 2, such as single crystal aluminum nitride (AlN) or gallium nitride (GaN), is deposited on the surface of a substrate or an auxiliary substrate 1 (such as silicon or silicon carbide), and 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), LPE (liquid phase epitaxy), etc.; or an interface layer is formed on the surface of an auxiliary substrate 1 (such as lithium niobate or lithium tantalate substrate) by ion implantation, and a piezoelectric film layer 2 is formed above the interface layer. At this time, the material of the piezoelectric film layer 2 is the same as that of the substrate or the auxiliary substrate 1.

[0077] Step 2: If Figure 2b As shown, a hard mask layer 3 as a barrier layer is deposited and etched on the surface of the piezoelectric layer 2. The hard mask layer can be silicon nitride. In the present invention, other materials can also be used as the barrier layer of the piezoelectric layer, as long as the barrier layer can block, for example, the thickness of the piezoelectric layer of other parts of the resonator when the trimming process in the subsequent step three is formed to form a recessed portion, and for example, the barrier layer can still remain at the end of the trimming. The barrier layer can also be further selected so that there is no excessive loss of the piezoelectric layer when the barrier layer is removed.

[0078] Step 3: If Figure 2c As shown, a trimming process (trim) is used to bombard the target surface with a particle beam, such as argon gas, to bombard the single crystal piezoelectric layer 2 and the hard mask layer 3. During the trimming process, the thinning speed of the hard mask layer is slower than the thinning speed of the single crystal piezoelectric layer, until a recessed portion of a predetermined depth appears on the piezoelectric layer 2, as shown in FIG. Figure 2c As shown, the bottom of the recessed portion is a flat surface.

[0079] In the present invention, the trimming is to use particle beam to physically bombard the target surface. The bombardment does not have any chemical reaction, and the control accuracy is relatively high. The thickness accuracy can be controlled within 3%. For example, if the target is to be trimmed This is the range that is suitable for trimming. If the process time is too long, it can be achieved by combining partial etching and trimming. This kind of control precision cannot be matched by etching. The thickness of the bombarded material layer can be controlled very accurately by trimming, with simple process and high precision.

[0080] Step 4: If Figure 2d As shown, the hard mask layer remaining on the piezoelectric layer 2 is removed by dry or wet etching to expose the entire surface of the piezoelectric layer. Whether dry or wet etching, the effect on the piezoelectric layer when removing the hard mask layer needs to be fully considered.

[0081] Step 5: If Figure 2eAs shown, a bottom electrode material layer is deposited and etched to form a bottom electrode 4 .

[0082] Step 6: If Figure 2f As shown, a layer of first acoustic impedance material is deposited on the surface of the piezoelectric layer 2 and the bottom electrode 4 of the structure obtained in step five, and patterned to form a first acoustic impedance layer 5. The first acoustic impedance material can be aluminum nitride, silicon dioxide, silicon nitride, polycrystalline silicon, amorphous silicon, etc.

[0083] Step 7: If Figure 2g As shown, a second acoustic impedance material or a sacrificial layer material is deposited on the surface of the piezoelectric layer 2, the first acoustic impedance layer 5 and the bottom electrode 4 of the structure obtained in step six. The second acoustic impedance layer material can be silicon dioxide, doped silicon dioxide, polycrystalline silicon, amorphous silicon, etc., but is different from the first acoustic impedance layer material.

[0084] The processing order of the above steps 6 and 7 can also be exchanged. For example, in step 6, the second acoustic impedance material is first deposited and patterned, and in step 7, the first acoustic impedance layer material is deposited. The obtained structure is as follows: Figure 8 As shown. Figure 8 In the embodiment, the angle between the outer side wall of the second acoustic impedance layer and the piezoelectric layer is greater than 90°, while in Figure 1 In the embodiment, the angle between the outer side wall of the first acoustic impedance layer and the piezoelectric layer is greater than 90°.

[0085] Step 8: If Figure 2h As shown, the second acoustic impedance material is polished by CMP (chemical mechanical polishing) until the first acoustic impedance layer 5 is exposed, the second acoustic impedance material located outside the first acoustic impedance layer 5 constitutes the second acoustic impedance layer 6, and the second acoustic impedance material located between the first acoustic impedance layers 5 constitutes a sacrificial layer. In other words, in this embodiment, the second acoustic impedance material is still a sacrificial material.

[0086] Step 9: If Figure 2i As shown, the substrate 7 is bonded to the lower side of the first acoustic impedance layer 5 and the second acoustic impedance layer 6. Optionally, the surface of the substrate 7 may also have an auxiliary bonding layer (not shown in the figure), such as silicon dioxide, silicon nitride and other materials.

[0087] Step 10: Figure 2j As shown, the substrate or auxiliary base 1 is removed by grinding, etching or ion implantation layer separation to expose the upper surface of the piezoelectric layer 2. Optionally, the separation interface is subjected to CMP treatment to make its surface smooth and have a lower roughness.

[0088] Step 11: Figure 2kAs shown, a hard mask layer 8 is deposited and etched on the structure in step 10. The hard mask layer may also be silicon nitride, or a mask layer different from the hard mask layer 3. The process of step 11 is similar to that of step 2.

[0089] Step 12: Figure 2l As shown, a trimming process (trim) is used to bombard the single crystal piezoelectric layer 2 and the hard mask layer 8 with a particle beam. During the trimming process, the thinning speed of the hard mask layer is slower than the thinning speed of the single crystal piezoelectric layer, until a recessed portion of a predetermined depth appears on the piezoelectric layer 2, as shown in FIG. Figure 2l As shown, the bottom of the concave portion is a flat surface. The process of step 12 is similar to step 3.

[0090] Step 13: Figure 2m As shown, the hard mask layer 8 remaining on the piezoelectric layer 2 is removed by dry or wet etching to expose the entire upper surface of the piezoelectric layer 2. The process of step thirteen is similar to that of step four.

[0091] Step 14: Figure 2n As shown, a through hole 9 is etched in the piezoelectric layer 2 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 2. The through hole is directly connected to the electrode connection end of the bottom electrode 4, or the release 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.

[0092] Step 15: Figure 2o As shown, an electrode material layer for the top electrode 10 is deposited, which covers the top surface of the piezoelectric layer 2 and enters into the through hole 9 and the release hole.

[0093] Step 16: Figure 2p As shown, a mass loading material layer is deposited on the top electrode 9 .

[0094] Step 17: Figure 2q As shown, the top electrode material layer and the mass load material layer are etched to remove the electrode material in the release hole, and patterned to form the top electrode 10 and the mass load layer 13. In the present invention, the frequency can be compensated by thickening the top electrode at the same time. Steps 16 and 17 can also be omitted.

[0095] Step 18: Figure 2r As shown, a conductive material is deposited by a thin film deposition process and then patterned to form an electrode connection portion 11, including a top electrode connection portion and a bottom electrode connection portion. Figure 2r As shown, the electrode connection part 11 is deposited and patterned to electrically connect the electrode lead-out parts (conductive through-holes) of the bottom electrodes of the two resonators.

[0096] Step 19: Figure 2sAs shown, 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 12 to obtain a corresponding Figure 1 structure.

[0097] The above steps are exemplary steps. As those skilled in the art can understand, the above processing sequence is not unique. For example, the top electrode 10 may be formed by deposition and patterning first, and then the through hole 9 may be made, and then the bottom electrode connection portion 11 may be deposited and formed. Those skilled in the art may adjust the above step sequence based on known techniques, which is within the scope of protection of the present invention.

[0098] The above reference Figure 2a-2s The process of manufacturing a resonator on one side with recessed portions on both the upper and lower sides of the piezoelectric layer is described. The process can also be used to manufacture Figure 3 and Figure 4 For example, for Figure 3 The structure can omit the above steps 2k-2m. Figure 4 The structure shown in the figure can omit the above steps 2a-2d.

[0099] Based on the above manufacturing process of the BAW resonator component, the present invention also proposes a manufacturing method of the BAW resonator, wherein the BAW resonator includes a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer, which is arranged between the bottom electrode and the top electrode. The method includes the steps of: providing a recessed portion on at least one of the upper and lower sides of the piezoelectric layer, wherein the bottom of the recessed portion is a flat surface; and providing corresponding electrodes in the top electrode and the bottom electrode in the region of the recessed portion.

[0100] The present invention uses thinning of the piezoelectric layer of the resonator and by coordinating the thickness of the top electrode and the bottom electrode to adjust the frequency and / or electromechanical coupling coefficient of the resonator over a wide range, thereby realizing the single-chip integration of a multi-frequency filter and adjusting the Kt of the resonator in the filter. 2 The value selection provides greater freedom. Figure 1 The difference in electromechanical coupling coefficients of the two resonators in the resonator assembly shown is relatively large, for example, more than 10%, and the difference can be obtained from Figure 1 The piezoelectric layer on the right side of the center is trimmed on both the upper and lower sides, so that the thickness of the piezoelectric layer is reduced significantly compared to the original thickness, which has a greater impact on the electromechanical coupling coefficient of the resonator on the right side. Figure 1 The difference in electromechanical coupling coefficients of the two resonators in the resonator assembly shown is small, for example, below 10%, so only Figure 1 The piezoelectric layer on the right side of the image is thinned, as shown in the figure, only the lower side is thinned ( Figure 3 ) or thinning only the upper side ( Figure 4)Thereby, the thickness of the piezoelectric layer is not much reduced relative to the original thickness, so as to have a smaller impact on the electromechanical coupling coefficient of the resonator on the right side.

[0101] In such Figure 7 In the embodiment shown, it is also possible to select Figure 7 The thickness h3-h8 shown in Fig. 1 further affects the electromechanical coupling coefficient of each resonator. Figure 7 In the figure, h5-h8 are the thicknesses of the corresponding electrodes.

[0102] In such Figure 3 In the illustrated embodiment, the electromechanical coupling coefficient of each resonator is also adjusted by selecting the mass loading layer.

[0103] In the present invention, although a single crystal piezoelectric layer is used as an example for description, in the present invention, the material of the piezoelectric layer may also be a non-single crystal material.

[0104] In the present invention, when there are upper and lower grooves, the edges of the upper and lower grooves are not limited to the upper and lower alignment as shown in the corresponding embodiment diagram, but the projection of the upper groove in the vertical direction may fall into the lower groove, or the lower groove may fall into the projection of the upper groove in the vertical direction, or the upper and lower grooves may have a certain overlapping area, all of which are within the protection scope of the present invention.

[0105] It should also be pointed out that in the present invention, two resonators are arranged on the same substrate as an example to illustrate the BAW resonator assembly, but the present invention is not limited to this. For example, more resonators can be arranged on the same substrate, and the multiple resonators can have two or more piezoelectric layer thicknesses. For example, the resonator assembly can have three resonators, and two of the resonators have upper and lower concave portions, and at the same time, the upper and lower concave portions of the two resonators have different depths.

[0106] In the present invention, inside and outside refer to the lateral or radial direction relative to the center of the effective area of ​​the resonator. The side or end of a component close to the center is the inside or the inner end, and the side or end of the component away from the center is the outside or the outer end.

[0107] 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.

[0108] In the present invention, the numerical range mentioned may be not only the endpoint values, but also the median values ​​or other values ​​between the endpoint values, all of which are within the protection scope of the present invention.

[0109] As can be understood by those skilled in the art, the BAW resonator according to the present invention can be used to form a filter or other semiconductor devices.

[0110] Based on the above, the present invention proposes the following technical solutions:

[0111] 1. A bulk acoustic wave resonator, comprising:

[0112] substrate;

[0113] Acoustic mirror;

[0114] bottom electrode;

[0115] a top electrode; and

[0116] Piezoelectric layer,

[0117] in:

[0118] The overlapping portion of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator constitutes the effective area of ​​the resonator;

[0119] At least one of the upper and lower sides of the piezoelectric layer is provided with a recessed portion, and the bottom of the recessed portion is a flat surface;

[0120] A corresponding electrode of the top electrode and the bottom electrode is arranged in the region of the recessed portion.

[0121] 2. The resonator according to item 1, wherein:

[0122] The concave depth of the concave portion does not exceed half of the thickness of the piezoelectric layer.

[0123] 3. The resonator according to item 1, wherein:

[0124] Concave parts are arranged on both the upper and lower sides of the piezoelectric layer, and the top electrode and the bottom electrode are arranged in the corresponding concave parts respectively.

[0125] 4. The resonator according to 3, wherein:

[0126] In the thickness direction of the resonator, the thickness of the piezoelectric layer between the recessed portions is not less than one fifth of the original thickness of the piezoelectric layer.

[0127] 5. The resonator according to item 1, wherein:

[0128] The included angle between the side wall of at least one recessed portion and the bottom of the recessed portion is in the range of 90°-160°.

[0129] 6. A resonator according to any one of 1 to 5, wherein:

[0130] An acoustic impedance structure is provided between the piezoelectric layer and the substrate;

[0131] 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.

[0132] 7. The resonator according to 6, wherein:

[0133] The widths of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ respectively. 1 / 4 and nλ 2 / 4, where m and n are both odd numbers, λ 1 and λ 2 are the wavelengths of sound waves propagating in the lateral direction at the resonance frequency of the first acoustic impedance layer and the second acoustic impedance layer respectively.

[0134] 8. The resonator according to item 7, wherein:

[0135] m is the same as n.

[0136] 9. The resonator according to 6, wherein:

[0137] 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, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

[0138] 10. The resonator according to 6, wherein:

[0139] The acoustic mirror is an acoustic mirror cavity;

[0140] The boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

[0141] 11. A resonator according to any one of 1 to 10, wherein:

[0142] The piezoelectric layer is a single crystal piezoelectric layer.

[0143] 12. A bulk acoustic wave resonator assembly, comprising:

[0144] A first resonator and a second resonator, the first resonator and the second resonator are both bulk acoustic wave resonators, and at least the second resonator is a resonator according to any one of 1-11, the first resonator and the second resonator share the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator is the original thickness of the piezoelectric layer of the second resonator.

[0145] 13. The resonator assembly according to 12, wherein:

[0146] The first resonator and the second resonator are adjacent to each other in a 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 or at least one second acoustic impedance layer.

[0147] 14. The resonator assembly according to 12 or 13, wherein:

[0148] The thickness of the piezoelectric layer of the first resonator within its active area is the original thickness of the piezoelectric layer of the second resonator.

[0149] 15. The assembly according to any one of 12 to 14, further comprising:

[0150] A third resonator, the third resonator is a bulk acoustic wave resonator and is a resonator according to any one of 1-11, the third resonator shares a same piezoelectric layer with the first resonator and the second resonator.

[0151] 16. The assembly according to 15, wherein:

[0152] The thickness of the piezoelectric layer of the third resonator located within the active region of the third resonator is different from the thickness of the piezoelectric layer of the second resonator located within the active region of the second resonator.

[0153] 17. The assembly according to any one of items 12 to 16, wherein:

[0154] The sum of the thickness of the top electrode and the bottom electrode of at least one resonator is different from the sum of the thickness of the top electrode and the bottom electrode of another resonator, or the thickness of one electrode of at least one resonator is different from the thickness of the corresponding electrode of another resonator; and / or

[0155] At least one resonator is provided with a mass loading layer.

[0156] 18. A method for manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of:

[0157] A recessed portion is provided on at least one of the upper and lower sides of the piezoelectric layer, wherein the bottom of the recessed portion is a flat surface; and

[0158] A corresponding electrode of the top electrode and the bottom electrode is disposed in the region of the recessed portion.

[0159] 19. The method according to 18, wherein: the method comprises:

[0160] Step 1: forming a piezoelectric layer on a substrate, wherein the substrate is disposed on a first side of the piezoelectric layer;

[0161] Step 2: forming a second recessed portion on the second side of the piezoelectric layer, wherein the bottom of the second recessed portion is a flat surface;

[0162] Step 3: depositing and patterning a bottom electrode material layer on the second side of the piezoelectric layer to form a bottom electrode in the second recess;

[0163] Step 4: after step 3, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a lateral direction on the piezoelectric layer, one of the first acoustic impedance layer and the second acoustic impedance layer bridges the side wall of the second recessed portion, an acoustic mirror space is formed between adjacent first acoustic impedance layers in the lateral direction, at least a portion of the bottom electrode is located in the space in the lateral direction, and the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances;

[0164] Step 5: connecting the substrate to the first acoustic impedance layer and the second acoustic impedance layer, and removing the substrate to expose the first side of the piezoelectric layer; and

[0165] Step 6: Form a top electrode and a corresponding electrode electrical connection structure on the first side of the piezoelectric layer.

[0166] 20. The method according to 19, wherein:

[0167] Step 6 includes:

[0168] Step 61: forming a first recessed portion on a first side of the piezoelectric layer, wherein the bottom of the first recessed portion is a flat surface;

[0169] Step 62: Depositing and patterning a top electrode material layer on the first side of the piezoelectric layer to form a top electrode in the first recess.

[0170] 21. The method according to 18, wherein: the method comprises:

[0171] Step 1: forming a piezoelectric layer on a substrate, wherein the substrate is disposed on a first side of the piezoelectric layer;

[0172] Step 2: depositing and patterning a bottom electrode material layer on the second side of the piezoelectric layer to form a bottom electrode;

[0173] Step 3: After step 2, a first acoustic impedance layer and a second acoustic impedance layer are formed on the piezoelectric layer, the first acoustic impedance layer and the second acoustic impedance layer are arranged adjacent to each other in the lateral direction, an acoustic mirror space is formed between the adjacent first acoustic impedance layers in the lateral direction, at least a portion of the bottom electrode is located in the space in the lateral direction, and the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances;

[0174] Step 4: connecting the substrate to the first acoustic impedance layer and the second acoustic impedance layer, and removing the substrate to expose the first side of the piezoelectric layer;

[0175] Step 5: forming a first recessed portion on the first side of the piezoelectric layer, wherein the bottom of the first recessed portion is a flat surface;

[0176] Step 6: depositing and patterning a top electrode material layer on the first side of the piezoelectric layer to form a top electrode and a corresponding electrode electrical connection structure in the first recess.

[0177] 22. The method according to any one of 19 to 21, wherein:

[0178] The step of forming a recessed portion on one side of the piezoelectric layer comprises:

[0179] forming and patterning a barrier layer on the one side of the piezoelectric layer;

[0180] The barrier layer and the exposed piezoelectric layer are simultaneously thinned by a trimming process, wherein the thinning speed of the barrier layer is lower than the thinning speed of the piezoelectric layer, and a concave portion with a flat bottom is formed on the one side of the piezoelectric layer based on the thinning of the exposed piezoelectric layer;

[0181] The barrier layer remaining on the one side of the piezoelectric layer is removed.

[0182] 23. The method according to any one of 19-22, wherein:

[0183] The widths of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ respectively. 1 / 4 and nλ 2 / 4, where m and n are both odd numbers, λ 1 and λ 2 are the wavelengths of sound waves propagating in the lateral direction at the resonance frequency of the first acoustic impedance layer and the second acoustic impedance layer respectively.

[0184] 24. A method for adjusting the electromechanical coupling coefficient of a resonator in a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being a bulk acoustic wave resonator according to any one of 1 to 11, the method comprising the steps of:

[0185] The depth of the recessed portion is selected to adjust the electromechanical coupling coefficient of the second resonator based on the thickness of the piezoelectric layer of the second resonator within the active area.

[0186] 25. The method according to 24, wherein:

[0187] The filter includes at least two second resonators, and the method includes the steps of: adjusting the thickness of the piezoelectric layer of one of the at least two second resonators within the effective area to be different from the thickness of the piezoelectric layer of another second resonator in the effective area of ​​the at least two second resonators based on the depth of the recessed portion, so that the at least two second resonators have different electromechanical coupling coefficients.

[0188] 26. The method according to 24 or 25, further comprising the steps of:

[0189] The sum of the thickness of the top electrode and the bottom electrode of at least one second resonator and / or the thickness of a single electrode of at least one resonator is selected, and / or a mass loading layer is provided in at least one second resonator to adjust the electromechanical coupling coefficient of the second resonator.

[0190] 27. A filter comprising the BAW resonator according to any one of 1 to 11, or the BAW resonator assembly according to any one of 12 to 17.

[0191] 28. An electronic device comprising the filter according to 27, or the BAW resonator according to any one of 1-11, or the BAW resonator assembly according to any one of 12-17.

[0192] The electronic equipment here includes but is not limited to intermediate products such as RF front-end, filter amplification modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0193] 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 Piezoelectric layer, in: The overlapping portion of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator constitutes the effective area of ​​the resonator; At least one of the upper and lower sides of the piezoelectric layer is provided with a recessed portion, and the bottom of the recessed portion is a flat surface; A corresponding electrode of the top electrode and the bottom electrode is disposed in the region of the recessed portion; An acoustic impedance structure is provided between the piezoelectric layer and the substrate; The acoustic impedance structure comprises 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; The lower surfaces of the first acoustic impedance layer and the second acoustic impedance layer are in contact with the upper surface of the substrate, and the upper surface of the substrate is flat.

2. The resonator according to claim 1, wherein: The concave depth of the concave portion does not exceed half of the original thickness of the piezoelectric layer.

3. The resonator of claim 1, wherein: Concave parts are arranged on both the upper and lower sides of the piezoelectric layer, and the top electrode and the bottom electrode are arranged in the corresponding concave parts respectively.

4. The resonator of claim 3, wherein: In the thickness direction of the resonator, the thickness of the piezoelectric layer between the recessed portions is not less than one fifth of the original thickness of the piezoelectric layer.

5. The resonator of claim 1, wherein: The included angle between the side wall of at least one recessed portion and the bottom of the recessed portion is in the range of 90°-160°.

6. The resonator of claim 1, wherein: The widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ1 / 4 and nλ2 / 4 respectively, where m and n are both odd numbers, and λ1 and λ2 are the wavelengths of the sound waves of the first acoustic impedance layer and the second acoustic impedance layer propagating laterally at the resonant frequency respectively.

7. The resonator of claim 6, wherein: m is the same as n.

8. The resonator of claim 1, 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, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

9. 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.

10. The resonator according to any one of claims 1 to 9, wherein: The piezoelectric layer is a single crystal piezoelectric layer.

11. A bulk acoustic wave resonator assembly comprising: A first resonator and a second resonator, wherein the first resonator and the second resonator are both bulk acoustic wave resonators, and at least the second resonator is a resonator according to any one of claims 1 to 10, wherein the first resonator and the second resonator share the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator is the original thickness of the piezoelectric layer of the second resonator.

12. The resonator assembly of claim 11, wherein: The first resonator and the second resonator are adjacent to each other in a 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 or at least one second acoustic impedance layer.

13. The resonator assembly of claim 11, wherein: The thickness of the piezoelectric layer of the first resonator within its active area is the original thickness of the piezoelectric layer of the second resonator.

14. The assembly of claim 11, further comprising: A third resonator, the third resonator is a bulk acoustic wave resonator and is the resonator according to any one of claims 1 to 10, the third resonator shares the same piezoelectric layer with the first resonator and the second resonator.

15. The assembly of claim 14, wherein: The thickness of the piezoelectric layer of the third resonator located within the active region of the third resonator is different from the thickness of the piezoelectric layer of the second resonator located within the active region of the second resonator.

16. An assembly according to any one of claims 11 to 15, wherein: The sum of the thickness of the top electrode and the bottom electrode of at least one resonator is different from the sum of the thickness of the top electrode and the bottom electrode of another resonator, or the thickness of one electrode of at least one resonator is different from the thickness of the corresponding electrode of another resonator; and / or At least one resonator is provided with a mass loading layer.

17. A method for manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of: A recessed portion is provided on at least one of the upper and lower sides of the piezoelectric layer, and the bottom of the recessed portion is a flat surface; and Disposing a corresponding electrode of the top electrode and the bottom electrode in the region of the recessed portion; The method comprises: Step 1: forming a piezoelectric layer on a substrate, wherein the substrate is disposed on a first side of the piezoelectric layer; Step 2: depositing and patterning a bottom electrode material layer on the second side of the piezoelectric layer to form a bottom electrode; Step 3: After step 2, a first acoustic impedance layer and a second acoustic impedance layer are formed on the piezoelectric layer, the first acoustic impedance layer and the second acoustic impedance layer are arranged adjacent to each other in the lateral direction, an acoustic mirror space is formed between the adjacent first acoustic impedance layers in the lateral direction, at least a portion of the bottom electrode is located in the space in the lateral direction, and the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances; Step 4: connecting the substrate to the first acoustic impedance layer and the second acoustic impedance layer, and removing the substrate to expose the first side of the piezoelectric layer; Step 5: forming a first recessed portion on the first side of the piezoelectric layer, wherein the bottom of the first recessed portion is a flat surface; Step 6: depositing and patterning a top electrode material layer on the first side of the piezoelectric layer to form a top electrode and a corresponding electrode electrical connection structure in the first recess.

18. The method of claim 17, wherein: The method comprises: Step 1: forming a piezoelectric layer on a substrate, wherein the substrate is disposed on a first side of the piezoelectric layer; Step 2: forming a second recessed portion on the second side of the piezoelectric layer, wherein the bottom of the second recessed portion is a flat surface; Step 3: depositing and patterning a bottom electrode material layer on the second side of the piezoelectric layer to form a bottom electrode in the second recess; Step 4: after step 3, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in a lateral direction on the piezoelectric layer, one of the first acoustic impedance layer and the second acoustic impedance layer bridges the side wall of the second recessed portion, an acoustic mirror space is formed between adjacent first acoustic impedance layers in the lateral direction, at least a portion of the bottom electrode is located in the space in the lateral direction, and the first acoustic impedance layer and the second acoustic impedance layer have different acoustic impedances; Step 5: connecting the substrate to the first acoustic impedance layer and the second acoustic impedance layer, and removing the substrate to expose the first side of the piezoelectric layer; and Step 6: Form a top electrode and a corresponding electrode electrical connection structure on the first side of the piezoelectric layer.

19. The method of claim 18, wherein: Step 6 includes: Step 61: forming a first recessed portion on a first side of the piezoelectric layer, wherein the bottom of the first recessed portion is a flat surface; Step 62: Depositing and patterning a top electrode material layer on the first side of the piezoelectric layer to form a top electrode in the first recess.

20. The method according to claim 18 or 19, wherein: The step of forming a recessed portion on one side of the piezoelectric layer comprises: forming and patterning a barrier layer on the one side of the piezoelectric layer; The barrier layer and the exposed piezoelectric layer are simultaneously thinned by a trimming process, wherein the thinning speed of the barrier layer is lower than the thinning speed of the piezoelectric layer, and a concave portion with a flat bottom is formed on the one side of the piezoelectric layer based on the thinning of the exposed piezoelectric layer; The barrier layer remaining on the one side of the piezoelectric layer is removed.

21. The method according to claim 18 or 19, wherein: The widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ1 / 4 and nλ2 / 4 respectively, where m and n are both odd numbers, and λ1 and λ2 are the wavelengths of the sound waves of the first acoustic impedance layer and the second acoustic impedance layer propagating laterally at the resonant frequency respectively.

22. A method for adjusting the electromechanical coupling coefficient of a resonator in a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being a bulk acoustic wave resonator according to any one of claims 1 to 10, the method comprising the steps of: The depth of the recessed portion is selected to adjust the electromechanical coupling coefficient of the second resonator based on the thickness of the piezoelectric layer of the second resonator within the active area.

23. The method of claim 22, wherein: The filter includes at least two second resonators, and the method includes the steps of: adjusting the thickness of the piezoelectric layer of one of the at least two second resonators within the effective area to be different from the thickness of the piezoelectric layer of another second resonator in the effective area of ​​the at least two second resonators based on the depth of the recessed portion, so that the at least two second resonators have different electromechanical coupling coefficients.

24. The method according to claim 22 or 23, further comprising the steps of: The sum of the thickness of the top electrode and the bottom electrode of at least one second resonator and / or the thickness of a single electrode of at least one second resonator is selected, and / or a mass loading layer is provided in at least one second resonator to adjust the electromechanical coupling coefficient of the second resonator.

25. A filter comprising the BAW resonator according to any one of claims 1 to 10, or the BAW resonator assembly according to any one of claims 11 to 16.

26. An electronic device comprising the filter according to claim 25, or the BAW resonator according to any one of claims 1-10, or the BAW resonator assembly according to any one of claims 11-16.

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