Piezoelectric resonator and method for manufacturing the same

Abstract

The application provides a piezoelectric resonator, which comprises a bottom electrode, a piezoelectric layer, a top electrode, an acoustic wave reflection layer structure and a top electrode lead-out structure; the piezoelectric layer is stacked on the bottom electrode; the top electrode is stacked on the side of the piezoelectric layer away from the bottom electrode; the acoustic wave reflection layer structure is formed on the side of the bottom electrode away from the piezoelectric layer; and the top electrode lead-out structure is located on the side of the piezoelectric layer away from the bottom electrode; the space region formed by the bottom electrode, the piezoelectric layer, the top electrode and the acoustic wave reflection layer structure is defined as a resonance region; the top electrode lead-out structure is connected with the top electrode in the resonance region and extends from the resonance region to the outside of the resonance region, and the top electrode lead-out structure overlaps with the part of the top electrode which is orthogonally projected to the piezoelectric layer; and the application further provides a manufacturing method of the piezoelectric resonator; compared with the related art, the piezoelectric resonator manufacturing method can reduce the influence of the growth defects of the piezoelectric layer on the performance of the device, so that the piezoelectric resonator structure has a higher quality factor Q and a higher effective electromechanical coupling coefficient.

Description

[Technical Field]

[0001] This invention relates to the field of piezoelectric technology, and in particular to a piezoelectric resonator and its manufacturing method. [Background Technology]

[0002] With the increasing number of smart devices and the growing popularity of IoT and 5G technologies, the demand for high-performance filters and multiplexers is growing. Acoustic resonators, as a crucial component of filters and multiplexers, have been a key research focus in recent years. Currently, the mainstream acoustic resonance technologies include Surface Acoustic Wave (SAW) and Bulk Acoustic Wave (BAW). SAW resonators, due to their simple manufacturing process and low cost, dominate the mid-to-low frequency (below 2GHz) market. However, SAW resonators suffer from low quality factor, poor material temperature drift, and incompatible semiconductor processes. Filters constructed with these resonators exhibit poor rectangular coefficients, high insertion loss, and significant center frequency drift with temperature. More critically, as the frequency increases, the spacing between the interdigitated electrodes in SAW resonators decreases, placing higher demands on the manufacturing process and reducing device reliability. These drawbacks are hindering the application of SAW resonators to higher frequency bands. The emergence of BAW resonators has improved many of the shortcomings of SAW resonators, and mature semiconductor processes offer good compatibility for their manufacturing. However, due to the complexity and high manufacturing difficulty of BAW resonators, their cost remains high, making it difficult for them to completely replace SAW resonators in the mid-to-high frequency range, and even rendering them uncompetitive in the low-frequency range. Besides their development in the communications field, BAW resonators are also widely used in piezoelectric microphones, pressure sensors, and other sensor applications due to their superior performance.

[0003] Unlike SAW resonators, BAW resonators utilize the resonance generated by longitudinal waves in a piezoelectric thin film, with the propagation direction of the longitudinal waves being the thickness direction of the piezoelectric material. The resonant frequency can be easily adjusted by modifying the thickness of the piezoelectric and electrode materials. To generate resonance, in addition to the piezoelectric material and opposing electrode layers arranged above and below it to generate electrical excitation, acoustic mirrors are typically used to reflect wave energy at the interface. Air or Bragg mirrors are the most commonly used mirror structures. Bragg mirrors use alternating layers of low and high acoustic impedance materials to reflect waves. Although these mirrors have high reflectivity, energy leakage along the mirror is still unavoidable. Compared to Bragg mirrors, air reflects waves better and blocks the energy leakage path, thus often resulting in resonators with higher quality factors. To introduce air as a reflector in a resonant structure, the relevant technique involves creating a cavity structure in or on a substrate before depositing the electrode layer and piezoelectric layer. Taking the formation of a cavity in the substrate as an example, the cavity is filled with a sacrificial material to make the surface flat. Then, the electrode layer and piezoelectric layer are deposited on top of the cavity and the substrate. Finally, an etchant or atmosphere capable of corroding the sacrificial material is used to contact the sacrificial material through a pre-reserved release channel to release the cavity and form an air reflector structure.

[0004] When a BAW resonator operates, a high-frequency voltage is applied to the top and bottom electrodes. Under the influence of an alternating electric field, the piezoelectric material deforms, and the suspended film layer above the cavity or acoustic reflector oscillates, generating longitudinal waves parallel to the thickness direction and clutter propagating along the direction perpendicular to the thickness direction (lateral). Under a specific frequency alternating voltage, the suspended film will resonate, and the device will exhibit special electrical characteristics, thereby enabling the transmission of signals at a specific frequency.

[0005] In existing technologies, although the dominant mode at resonance is the longitudinal wave mode, some parasitic modes are still formed along with the longitudinal wave excitation. These parasitic modes can be standing waves, forming clutter peaks on the device's electrical characteristic curve, increasing the filter's in-band ripple and insertion loss; or they can be laterally propagating clutter, causing energy leakage, increasing the filter's insertion loss, and reducing the device's quality factor (Q value).

[0006] Starting from a typical resonator structure, the shortcomings of existing technologies are as follows: 1. In the top electrode lead-out region, the part of the piezoelectric layer transitioning from the bottom electrode to the outside of the bottom electrode is prone to generating defect regions during formation, resulting in acoustic energy loss and a decrease in Q value; 2. Since the connection between the top electrode and the top electrode lead-out structure is commonly a left-right (lateral) structure, some accompanying lateral clutter will still leak out of the resonant region through the bridge / electrode lead-out part; 3. Since the top electrode and bottom electrode may have overlapping areas outside the cavity, the area of ​​the non-resonant region is increased, which is equivalent to adding parasitic capacitance in parallel, reducing the effective electromechanical coupling coefficient; on the other hand, the increase in the area of ​​the non-resonant region increases acoustic loss, resulting in a decrease in Q value; 4. Existing technologies may shorten the bottom electrode to the inside of the cavity, but the defect regions generated by the piezoelectric layer in the transition region are adjacent to the end of the resonant region. In practical applications, these defect regions will still cause energy loss, and shortening the bottom electrode leads to a reduction in the area of ​​the resonant region, which will still reduce the effective electromechanical coupling coefficient keff^2. At the same time, it will also reduce the contact area between the bottom electrode and the substrate, resulting in a decrease in the heat dissipation capacity and structural strength of the device. 5. In constructing the bridge structure of piezoelectric resonators, related technologies often first deposit a sacrificial layer or a low acoustic impedance material on the piezoelectric layer, pattern them, and then deposit the top electrode. During this process, the surface of the piezoelectric layer in the resonant region will come into contact with various solutions and high-energy plasmas, which increases surface defects, roughness, and surface quality, resulting in increased energy loss and decreased Q value of the piezoelectric resonator during operation.

[0007] Therefore, it is necessary to provide a new piezoelectric resonator and electronic device to solve the above-mentioned technical problems. [Summary of the Invention]

[0008] The purpose of this invention is to provide a piezoelectric resonator with a higher quality factor Q and a higher effective electromechanical coupling coefficient, and a method for manufacturing the same.

[0009] To achieve the above objectives, the present invention provides a piezoelectric resonator, comprising:

[0010] Bottom electrode;

[0011] A piezoelectric layer, wherein the piezoelectric layer is stacked on the bottom electrode;

[0012] A top electrode, which is stacked on the side of the piezoelectric layer away from the bottom electrode;

[0013] An acoustic wave reflecting layer structure, wherein the acoustic wave reflecting layer structure is formed on the side of the bottom electrode away from the piezoelectric layer; and...

[0014] A top electrode lead-out structure is located only on the side of the piezoelectric layer away from the bottom electrode;

[0015] The spatial region formed by the overlapping of the bottom electrode, the piezoelectric layer, the top electrode, and the acoustic wave reflecting layer is defined as the resonant region; the top electrode lead-out structure is connected to the top electrode within the resonant region and extends from within the resonant region to outside the resonant region, and the top electrode lead-out structure overlaps with the positive projection portion of the top electrode onto the piezoelectric layer.

[0016] Preferably, the top electrode lead-out structure includes an electrode connection end located at least partially within the resonant region and stacked on the side of the top electrode away from the piezoelectric layer to form an electrical connection, a bridge structure extending from the electrode connection end away from the top electrode to outside the resonant region, and a lead-out end extending from the bridge structure and connected to an external circuit or signal line; the top electrode lead-out structure is connected to the top electrode through the electrode connection end.

[0017] Preferably, the bridge structure is spaced from the piezoelectric layer to form a first air gap, and / or the bridge structure is spaced from the top electrode to form a second air gap.

[0018] Preferably, the piezoelectric resonator further includes a substrate supported on the side of the bottom electrode away from the top electrode, and the acoustic wave reflecting layer structure is a cavity formed by a recess on the side of the substrate near the bottom electrode, the cavity being at least partially located within the resonant region.

[0019] Preferably, the bottom electrode completely covers the cavity.

[0020] Preferably, the acoustic wave reflecting layer structure is an acoustic reflector stacked on the side of the bottom electrode away from the top electrode and at least partially located within the resonant region.

[0021] Preferably, the piezoelectric layer has a defect region, which is formed in a portion of the piezoelectric layer that abuts the edge of the bottom electrode and transitions to a portion of the area outside the bottom electrode.

[0022] Preferably, the orthogonal projections of the first air gap and the second air gap onto the piezoelectric layer completely cover the defect area to prevent the top electrode lead-out structure from contacting the defect area of ​​the piezoelectric layer.

[0023] Preferably, the first air gap and / or the second air gap are filled with functional materials for reflecting sound waves and / or for insulating.

[0024] Preferably, the functional material is at least one selected from AlN, SiO2, SiN, Si, SiC, and Al2O3.

[0025] Preferably, the piezoelectric resonator further includes a passivation layer, which is stacked on the side of the top electrode away from the piezoelectric layer and at least partially covers the top electrode.

[0026] Preferably, the piezoelectric resonator further includes a mass load formed on the side of the top electrode away from the piezoelectric layer, which can cause acoustic impedance mismatch, and the mass load at least partially overlaps with the orthogonal projection of the top electrode onto the piezoelectric layer.

[0027] Preferably, the piezoelectric resonator further includes a mass load formed on the side of the passivation layer away from the piezoelectric layer that can cause acoustic impedance mismatch, the mass load at least partially overlapping with the orthogonal projection of the top electrode onto the piezoelectric layer.

[0028] Preferably, the mass load is disposed at the edge of the top electrode and is at least partially located within the resonant region.

[0029] Preferably, the mass load and the top electrode lead-out structure together form a closed or open ring structure.

[0030] The present invention also provides a method for manufacturing the above-mentioned piezoelectric resonator, the method comprising the following steps:

[0031] The substrate is provided, and the surface of the substrate is etched to form the cavity;

[0032] The cavity is filled with sacrificial material and then smoothed by chemical mechanical polishing so that the sacrificial material is flush with the substrate.

[0033] The bottom electrode is deposited on the surfaces of the sacrificial material and the substrate, and the bottom electrode is patterned.

[0034] The piezoelectric layer is deposited on the side of the bottom electrode away from the substrate;

[0035] The top electrode is deposited on the side of the piezoelectric layer away from the bottom electrode, and the top electrode is patterned.

[0036] Simultaneously, a sacrificial layer is deposited on the side of the top electrode away from the piezoelectric layer and on the side of the piezoelectric layer away from the bottom electrode, and the sacrificial layer is patterned.

[0037] The top electrode lead-out structure is deposited on the side of the sacrificial layer away from the piezoelectric layer, such that both ends of the top electrode lead-out structure extend and connect to the side of the top electrode away from the piezoelectric layer and the side of the piezoelectric layer away from the bottom electrode, respectively;

[0038] A contact hole is etched in the piezoelectric layer, such that the contact hole extends from a layer of the piezoelectric layer away from the bottom electrode to the bottom electrode;

[0039] An interconnect metal is deposited and patterned on the side of the piezoelectric layer away from the bottom electrode, such that the interconnect metal fills the contact hole and connects to the bottom electrode;

[0040] Release the sacrifice layer.

[0041] Compared with related technologies, the piezoelectric resonator manufacturing method and piezoelectric resonator of the present invention have an up-down (vertical) connection between the top electrode and the top electrode lead-out structure, which is not a traditional left-right (lateral) structure design. Furthermore, an air gap or functional material is provided at the edge of the top electrode to laterally isolate the top electrode and the top electrode lead-out structure. This allows for a sudden change in the propagation medium during lateral clutter propagation, enabling sound wave energy to be reflected back to the resonant region. This prevents some lateral clutter from leaking out of the resonant region through the top electrode lead-out structure area, thereby improving the resonator's quality factor (Q value). Simultaneously, the up-down (vertical) connection design of the top electrode and the top electrode lead-out structure allows the connection ends of the electrode lead-out structures to be stacked on the top electrode. The formation of a mass load causes abrupt changes and mismatches in acoustic impedance, which can reflect sound waves propagating to this region back to the resonant region, preventing sound wave energy from leaking out of the resonant region and thus improving the Q value of the resonator. The introduction of the top electrode lead-out structure can reduce the area of ​​the non-resonant region, eliminate the problem of reduced effective electromechanical coupling coefficient caused by parasitic capacitance, reduce the area of ​​the non-resonant region, reduce acoustic loss, and further reduce the decrease in Q value. The bottom electrode extends to the outside of the sound wave reflecting layer structure (cavity), keeping the transition region of the piezoelectric layer away from the resonant region, reducing the energy loss caused by the growth defects of the piezoelectric layer in the transition region, and effectively increasing the strength and heat dissipation capacity of the piezoelectric resonator, avoiding the reduction of the resonant region and not causing a decrease in the effective electromechanical coupling coefficient. [Attached Image Description]

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0043] Figure 1 This is a schematic diagram of the structure of a piezoelectric resonator according to a first embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the structure of a second embodiment of the piezoelectric resonator of the present invention;

[0045] Figure 3 This is a schematic diagram of the structure of the piezoelectric resonator of Embodiment 3 of the present invention;

[0046] Figure 4 This is a schematic diagram of the structure of the piezoelectric resonator in embodiment four of the present invention;

[0047] Figure 5 This is a schematic diagram of the structure of the piezoelectric resonator in embodiment five of the present invention;

[0048] Figure 6 This is a flowchart of the piezoelectric resonator fabrication method of the present invention.

Detailed Implementation Methods

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The following descriptions of the embodiments are made with reference to the accompanying drawings, illustrating specific embodiments in which the invention can be implemented. Directional terms used in this invention, such as up, down, front, back, left, right, inside, outside, side, etc., are merely directional references to the accompanying drawings. Therefore, the directional terms used are for illustrative and understanding purposes only, and not for limiting the invention.

[0051] Example 1

[0052] Please see Figure 1 This is a schematic diagram of the structure of a piezoelectric resonator according to a first embodiment of the present invention. The present invention provides a piezoelectric resonator 100, comprising: a bottom electrode 1, a piezoelectric layer 2, a top electrode 3, an acoustic wave reflecting layer structure 42, and a top electrode lead-out structure 5.

[0053] The piezoelectric layer 2 is stacked on the bottom electrode 1.

[0054] The top electrode 3 is stacked on the side of the piezoelectric layer 2 away from the bottom electrode 1.

[0055] The acoustic wave reflecting layer structure 42 is formed on the side of the bottom electrode 1 away from the piezoelectric layer 2. That is, the acoustic wave reflecting layer structure 42 is formed below the top electrode 3, the piezoelectric layer 2, and the bottom electrode 1.

[0056] The top electrode lead-out structure 5 is located on the side of the piezoelectric layer 2 away from the bottom electrode 1.

[0057] The space formed by the overlapping of the bottom electrode 1, the piezoelectric layer 2, the top electrode 3, and the acoustic wave reflecting layer structure 42 is defined as the resonant region A, also known as the effective active region. Specifically, the direction in which the bottom electrode 1, the piezoelectric layer 2, and the top electrode 3 are stacked sequentially is defined as the thickness direction of the piezoelectric resonator. The overlapping portion of the bottom electrode 1, the piezoelectric layer 2, the top electrode 3, and the acoustic wave reflecting layer structure 42 forms a layer structure. The layer structure and the space covered by its projection along the thickness direction together form the aforementioned resonant region A. In this embodiment, the top electrode 3 is completely located within the resonant region A, while the bottom electrode 1 is partially located within the resonant region A and partially extends outside of it. Of course, depending on the needs, the top electrode can also be partially located outside the resonant region, and the bottom electrode may not completely cover the acoustic wave reflecting layer structure.

[0058] The top electrode lead-out structure 5 is connected to the top electrode 3 within the resonant region A and extends from within the resonant region A to outside the resonant region A. The orthographic projection of the top electrode lead-out structure 5 onto the piezoelectric layer 2 overlaps with the orthographic projection of the top electrode 3 onto the piezoelectric layer 2. This structural arrangement ensures that the interconnection between the top electrode 3 and the top electrode lead-out structure 5 is not a horizontal structure but a vertical structure with vertical layers. In other words, the top electrode lead-out structure 5 and the top electrode 3 are not in the same layer, but can be made of the same material, and they are not formed in the same process step.

[0059] Specifically, in this embodiment, the top electrode lead-out structure 5 includes an electrode connection end 51, at least partially located within the resonant region A and stacked on the side of the top electrode 3 away from the piezoelectric layer 2 to form an electrical connection; a bridge structure 52 extending from the electrode connection end 51 away from the top electrode 3 to outside the resonant region A; and a lead-out end 53 extending from the bridge structure 52 and connected to an external circuit or signal line. The top electrode lead-out structure 5 is connected to the top electrode 3 through the electrode connection end 51. The electrode connection end 51 in this structure is formed in a vertically stacked configuration within the resonant region A, creating a mass load structure. This results in a sudden change and mismatch in acoustic impedance, reflecting sound waves propagating to this region and preventing sound wave energy leakage outside the resonant region A, thereby improving the Q value of the piezoelectric resonator 100.

[0060] Moreover, in the above structure, the top electrode is first formed on the piezoelectric layer 2, and then the top electrode lead-out structure 5 is formed. In this way, the piezoelectric layer 2 of the resonant region A is not subjected to complex process treatment directly. Therefore, the surface quality of the piezoelectric layer 2 can be guaranteed to the greatest extent, and the energy loss and Q value decrease caused by the reduction of the surface quality of the piezoelectric layer 2 can be prevented.

[0061] The lead-out terminal 53 is used to connect to external circuits or signal lines to connect external electrical signals to the top electrode 3. Similarly, the bottom electrode 1 has a bottom electrode lead-out structure 11 formed outside the resonant region to connect to external circuits or signal lines, thus connecting external electrical signals to the bottom electrode 1.

[0062] More preferably, in this embodiment, the bridge structure 52 and the piezoelectric layer 2 are spaced apart to form a first air gap 61, and / or the bridge structure 52 and the top electrode 3 are spaced apart to form a second air gap 62.

[0063] The introduction of bridge structure 52 and first air gap 61 can reduce the area of ​​non-resonant region, reduce the problem of reduced effective electromechanical coupling coefficient caused by parasitic capacitance, and improve electromechanical conversion capability; at the same time, due to the reduction of non-resonant region area, acoustic loss is reduced, thereby also reducing the decrease in quality factor Q value.

[0064] The structure of the second air gap 62 is designed so that an air gap structure is set at the edge of the top electrode 3, which achieves lateral isolation between the top electrode 3 and the bridge structure 52. In this way, during the propagation of lateral clutter, a sudden change in the propagation medium is caused, and the sound wave energy can be reflected back to the resonant region, preventing some lateral clutter from leaking out of the resonant region A through this region, thereby improving the Q value of the piezoelectric resonator 100.

[0065] In this embodiment, the piezoelectric resonator 100 further includes a substrate 41 supported on the side of the bottom electrode 1 away from the top electrode 3. The acoustic wave reflecting layer structure 42 is a cavity 421 formed by a recess on the side of the substrate 41 near the bottom electrode 1, and the cavity 421 is at least partially located within the resonant region A. Preferably, the bottom electrode 1 completely covers the cavity 421. This structural arrangement allows the bottom electrode 1 to extend outside the cavity 421, that is, outside the resonant region A, so that the transition region between the piezoelectric layer 2 and the bottom electrode 1 is far away from the resonant region A, reducing the energy loss caused by growth defects (defect regions) in the piezoelectric layer of the transition region, and improving the overall performance; it also increases the structural strength and heat dissipation capacity of the piezoelectric resonator 100; at the same time, it avoids the reduction of the resonant region A, thereby avoiding the reduction of the effective electromechanical coupling coefficient caused by the reduction of the resonant region.

[0066] Of course, the acoustic wave reflecting layer structure 42 can also be another structure, such as an acoustic reflector layer 42 stacked on the side of the bottom electrode 1 away from the top electrode 3 and at least partially located within the resonant region A. This is easy to conceive of, and its principle is the same as the structure of the substrate 41 with cavity 421 described above. Furthermore, when the piezoelectric layer 2 is deposited on the bottom electrode 1, the piezoelectric layer 2 forms a stepped structure with an inclined surface at the position corresponding to the edge of the bottom electrode 1, thereby forming a defect region within the piezoelectric layer 2. The defect region is formed in the portion of the piezoelectric layer 2 that abuts against the edge of the bottom electrode 1 and transitions to the portion of the region outside the bottom electrode 1. In this embodiment, the defect region is formed in a portion of the piezoelectric layer 2 that is disposed opposite to the bridge structure 52.

[0067] More preferably, the orthogonal projections of the first air gap 61 and the second air gap 62 onto the piezoelectric layer 2 completely cover the defect region, preventing the top electrode lead-out structure 5 from contacting the defect region of the piezoelectric layer 2. In this embodiment, the defect region and the bridge structure 52 are separated by the first spatial gap 61, and combined with the structure extending the bottom electrode 1 outside the cavity 421, the transition region of the piezoelectric layer 2 is kept away from the resonant region, reducing the energy loss caused by piezoelectric layer growth defects (i.e., defect regions) in the transition region.

[0068] Implementation Method 2

[0069] This invention also provides another embodiment, please refer to... Figure 2 The diagram shown is a structural schematic of a second embodiment of the piezoelectric resonator of the present invention. The structure of this piezoelectric resonator 200 is basically the same as that of the first embodiment described above, except that:

[0070] The second air gap 262 is filled with a functional material 20, which can isolate the bridge structure from the top electrode, reflect sound waves, reflect sound wave energy back to the resonant region, prevent some transverse noise from leaking out of the resonant region 2A through this region, thereby improving the Q value of the piezoelectric resonator 200.

[0071] The first air gap 261 is filled with a functional material 20, which can reduce the area of ​​the non-resonant region and reduce the problem of reduced effective electromechanical coupling coefficient caused by parasitic capacitance; at the same time, due to the reduction of the area of ​​the non-resonant region, acoustic loss is reduced and the decrease in Q value is reduced.

[0072] Specifically, in this embodiment, the functional material 20 can be a material with certain acoustic and / or electrical properties, such as at least one of AlN, SiO2, SiN, Si, SiC, and Al2O3.

[0073] Apart from the differences mentioned above, its structure is the same as that of Implementation Method 1, and the technical problems it solves and the technical effects it achieves are also the same, so they will not be repeated here.

[0074] Example 3

[0075] This invention also provides another embodiment, please refer to... Figure 3 The diagram shown is a structural schematic of a third embodiment of the piezoelectric resonator of the present invention. The structure of this piezoelectric resonator 300 is basically the same as that of the first embodiment described above, except that:

[0076] The piezoelectric resonator 300 further includes a passivation layer 30, which is stacked on the side of the top electrode 303 away from the piezoelectric layer 302 and at least partially covers the top electrode 303. Of course, the electrode connection end 351 needs to penetrate the passivation layer 30 and connect to the top electrode 303.

[0077] The purification layer 30 can effectively protect the top electrode 303 and the piezoelectric layer 302, improving the structural reliability.

[0078] Apart from the differences mentioned above, its structure is the same as that of Implementation Method 1, and the technical problems it solves and the technical effects it achieves are also the same, so they will not be repeated here.

[0079] Example 4

[0080] This invention also provides another embodiment, please refer to... Figure 4 The diagram shown is a structural schematic of Embodiment 4 of the piezoelectric resonator of the present invention. The structure of this piezoelectric resonator 400 is basically the same as that of Embodiment 1 above, except that:

[0081] The piezoelectric resonator 400 further includes a mass load 40 formed on the side of the top electrode 403 away from the piezoelectric layer 402. The orthographic projection of the mass load 40 onto the piezoelectric layer 402 at least partially overlaps with the orthographic projection of the top electrode 403 onto the piezoelectric layer 402. That is, the mass load 40 is formed on the top electrode 403 in a longitudinally stacked structure. The arrangement of the mass load 40 causes an acoustic impedance mismatch, so that waves propagating laterally to the left and right are reflected back into the resonant region 4A when they reach this position, preventing acoustic energy from leaking out of the resonant region 4A, thereby improving the Q value of the piezoelectric resonator 400.

[0082] In this embodiment, the mass load 40 is disposed at the edge of the top electrode 403 and is at least partially located within the resonant region 4A.

[0083] More preferably, the mass load 40 and the top electrode lead-out structure 405 together form a ring structure, specifically, the mass load 40 and the electrode connection end 4051 of the top electrode lead-out structure 405 together form a ring structure.

[0084] The ring structure can be a closed ring or a partially closed ring. For example, the mass load 40 is connected to the top electrode lead-out structure 405 to form a closed ring structure together. Alternatively, the mass load 40 and the top electrode lead-out structure 405 can be spaced apart and together form a partially closed ring structure, which are both feasible.

[0085] The presence of the mass load 40 causes an acoustic impedance mismatch, resulting in lateral waves propagating through the mass load 40 being reflected back to the resonant region 4A. In other words, the mass load 40 causes a change in the acoustic impedance of the piezoelectric resonator 400, making the acoustic impedance at the location where the mass load 40 is present different from that at the location where the mass load 40 is not present. Therefore, the acoustic impedance of the piezoelectric resonator 400 at the locations where the mass load 40 is present and those at the locations where the mass load 40 is not present is discontinuous, thus making the mass load 40 act as a lateral acoustic wave reflecting structure.

[0086] Apart from the differences mentioned above, its structure is the same as that of Implementation Method 1, and the technical problems it solves and the technical effects it achieves are also the same, so they will not be repeated here.

[0087] Example 5

[0088] This invention also provides another embodiment, please refer to... Figure 5 The diagram shown is a structural schematic of Embodiment 5 of the piezoelectric resonator of the present invention. The structure of this piezoelectric resonator 500 is basically the same as that of Embodiment 3 above, except that:

[0089] The piezoelectric resonator 500 further includes a mass load 50 formed on the passivation layer 530 on the side away from the piezoelectric layer 502, the mass load 50 at least partially overlapping with the orthographic projection of the top electrode 503 onto the piezoelectric layer. That is, the mass load 50 is located above the top electrode 503.

[0090] The orthographic projection of the mass load 50 onto the piezoelectric layer 502 at least partially overlaps with the orthographic projection of the top electrode 503 onto the piezoelectric layer 502. That is, the mass load 50 is formed on the purification layer 530 and located above the top electrode 503, forming a longitudinally stacked structure. The mass load 50 creates an acoustic impedance mismatch, causing waves propagating laterally to be reflected back into the resonant region 5A when they reach this position, preventing acoustic energy leakage outside the resonant region 5A, thereby improving the Q value of the piezoelectric resonator 500. Specifically, the structure and function of the mass load 50 are the same as in Embodiment 4, and will not be repeated here.

[0091] Apart from the differences mentioned above, its structure is the same as that of Implementation Method 3, and the technical problems it solves and the technical effects it achieves are also the same, so they will not be repeated here.

[0092] This invention also provides a method for manufacturing a piezoelectric resonator, so as to... Figure 1 The following explanation uses the piezoelectric resonator of Embodiment 1 as an example. Please refer to... Figure 1 and Figure 6 The method includes the following steps:

[0093] Step S1: Provide the substrate and etch the surface of the substrate to form the cavity.

[0094] Step S2: Fill the cavity with sacrificial material and polish it flat with chemical mechanical polishing so that the sacrificial material is flush with the substrate.

[0095] Step S3: Deposit the bottom electrode on the surface of the sacrificial material and the substrate, and pattern the bottom electrode.

[0096] Step S4: Deposit the piezoelectric layer on the side of the bottom electrode away from the substrate.

[0097] Step S5: Deposit the top electrode on the side of the piezoelectric layer away from the bottom electrode, and pattern the top electrode.

[0098] Step S6: Simultaneously deposit a sacrificial layer on the side of the top electrode away from the piezoelectric layer and on the side of the piezoelectric layer away from the bottom electrode, and pattern the sacrificial layer.

[0099] Step S7: Deposit the top electrode lead-out structure on the side of the sacrificial layer away from the piezoelectric layer, such that both ends of the top electrode lead-out structure extend and connect to the side of the top electrode away from the piezoelectric layer and the side of the piezoelectric layer away from the bottom electrode, respectively.

[0100] Step S8: Etch contact holes in the piezoelectric layer, such that the contact holes extend from a layer of the piezoelectric layer away from the bottom electrode to the bottom electrode.

[0101] Step S9: Deposit and pattern interconnect metal on the side of the piezoelectric layer away from the bottom electrode, such that the interconnect metal fills the contact hole and connects to the bottom electrode.

[0102] Step S10: Release the sacrificial layer.

[0103] In the piezoelectric resonator made by the above method, a top electrode is first formed on the piezoelectric layer, and then the top electrode lead-out structure is formed. In this way, the piezoelectric layer in the resonant region is not directly subjected to complex processing, so the surface quality of the piezoelectric layer can be guaranteed to the greatest extent and energy loss and Q value reduction caused by reduced surface quality can be prevented.

[0104] Compared with related technologies, the piezoelectric resonator manufacturing method and piezoelectric resonator of the present invention have an up-down (vertical) connection between the top electrode and the top electrode lead-out structure, which is not a traditional left-right (lateral) structure design. Furthermore, an air gap or functional material is provided at the edge of the top electrode to laterally isolate the top electrode and the top electrode lead-out structure. This allows for a sudden change in the propagation medium during lateral clutter propagation, enabling sound wave energy to be reflected back to the resonant region. This prevents some lateral clutter from leaking out of the resonant region through the top electrode lead-out structure area, thereby improving the resonator's quality factor (Q value). Simultaneously, the up-down (vertical) connection design of the top electrode and the top electrode lead-out structure allows the connection ends of the electrode lead-out structures to be stacked on the top electrode. The formation of a mass load causes abrupt changes and mismatches in acoustic impedance, which can reflect sound waves propagating to this region back to the resonant region, preventing sound wave energy from leaking out of the resonant region and thus improving the Q value of the resonator. The introduction of the top electrode lead-out structure can reduce the area of ​​the non-resonant region, eliminate the problem of reduced effective electromechanical coupling coefficient caused by parasitic capacitance, reduce the area of ​​the non-resonant region, reduce acoustic loss, and further reduce the decrease in Q value. The bottom electrode extends to the outside of the sound wave reflecting layer structure (cavity), keeping the transition region of the piezoelectric layer away from the resonant region, reducing the energy loss caused by the growth defects of the piezoelectric layer in the transition region, and effectively increasing the strength and heat dissipation capacity of the piezoelectric resonator, avoiding the reduction of the resonant region and not causing a decrease in the effective electromechanical coupling coefficient.

[0105] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of the present invention, but these improvements all fall within the protection scope of the present invention.

Claims

1. A piezoelectric resonator, characterized by, The piezoelectric resonator comprises: a bottom electrode; a piezoelectric layer stacked on the bottom electrode; a top electrode stacked on a side of the piezoelectric layer away from the bottom electrode; a sound wave reflection layer structure formed on a side of the bottom electrode away from the piezoelectric layer; and a top electrode lead-out structure on a side of the piezoelectric layer away from the bottom electrode; the bottom electrode, the piezoelectric layer, the top electrode and the sound wave reflection layer structure together define a resonant region in a space region formed by overlapping; the top electrode lead-out structure is connected to the top electrode in the resonant region and extends from the resonant region to outside the resonant region, and the top electrode lead-out structure overlaps with a part of the top electrode projected onto the piezoelectric layer; the top electrode lead-out structure comprises an electrode connecting end at least partially located in the resonant region and stacked on a side of the top electrode away from the piezoelectric layer to form an electrical connection, a bridge structure extending from the electrode connecting end to outside the resonant region away from the top electrode, and a lead-out end connected to an external circuit or signal line; the top electrode lead-out structure is connected to the top electrode through the electrode connecting end; the bridge structure is spaced apart from the piezoelectric layer to form a first air gap, and the bridge structure is spaced apart from the top electrode to form a second air gap; the first air gap is at least partially located in the resonant region, and the first air gap and the second air gap are both located on the same side of the piezoelectric layer.

2. The piezoelectric resonator according to claim 1, characterized by, The piezoelectric resonator further comprises a substrate supported on a side of the bottom electrode away from the top electrode, and the sound wave reflection layer structure is a cavity formed by recessing a side of the substrate close to the bottom electrode, and the cavity is at least partially located in the resonant region.

3. The piezoelectric resonator according to claim 2, wherein The bottom electrode completely covers the cavity.

4. The piezoelectric resonator of claim 1, wherein, The sound wave reflection layer structure is a sound reflection mirror stacked on a side of the bottom electrode away from the top electrode and at least partially located in the resonant region.

5. The piezoelectric resonator of claim 1, wherein, The piezoelectric layer forms a defect region, which is formed in a part of the piezoelectric layer abutting against an edge of the bottom electrode and transitions to a part of the bottom electrode outside.

6. The piezoelectric resonator according to claim 5, wherein The first air gap and the second air gap completely cover the defect region projected onto the piezoelectric layer to prevent the top electrode lead-out structure from contacting the defect region of the piezoelectric layer.

7. The piezoelectric resonator of claim 1, wherein, The first air gap and / or the second air gap are filled with a functional material for reflecting sound waves and / or isolating insulation.

8. The piezoelectric resonator according to claim 7, wherein The functional material is at least one of AlN, SiO2, SiN, Si, SiC, Al2O3.

9. The piezoelectric resonator of claim 1, wherein, The piezoelectric resonator further comprises a passivation layer stacked on a side of the top electrode away from the piezoelectric layer and at least partially covering the top electrode.

10. The piezoelectric resonator of claim 1, wherein, The piezoelectric resonator further comprises a mass load formed on a side of the top electrode away from the piezoelectric layer to cause acoustic impedance mismatch, and the mass load and the top electrode respectively at least partially overlap with the projection onto the piezoelectric layer.

11. The piezoelectric resonator of claim 9, wherein, The piezoelectric resonator further comprises a mass load formed on a side of the passivation layer distal to the piezoelectric layer to cause acoustic impedance mismatch, the mass load at least partially overlapping the positive projections of the top electrode and the top electrode lead structure onto the piezoelectric layer respectively.

12. The piezoelectric resonator according to claim 10 or 11, characterized in that, The mass load is disposed at the edge of the top electrode and at least partially within the resonant region.

13. The piezoelectric resonator according to claim 10 or 11, characterized in that, The mass load and the top electrode lead structure together enclose a closed or non-closed loop structure.

14. A method of fabricating a piezoelectric resonator as claimed in claim 2, characterized by, The method comprises the following steps: providing the substrate, etching a surface of the substrate to form the cavity; filling the cavity with a sacrificial material and polishing the sacrificial material to be flush with the substrate using chemical mechanical polishing; depositing the bottom electrode on the surface of the sacrificial material and the substrate and patterning the bottom electrode; depositing the piezoelectric layer on a side of the bottom electrode distal to the substrate; depositing the top electrode on a side of the piezoelectric layer distal to the bottom electrode and patterning the top electrode; simultaneously depositing a sacrificial layer on a side of the top electrode distal to the piezoelectric layer and on a side of the piezoelectric layer distal to the bottom electrode and patterning the sacrificial layer; depositing the top electrode lead structure on a side of the sacrificial layer distal to the piezoelectric layer and extending two ends of the top electrode lead structure to be connected to a side of the top electrode distal to the piezoelectric layer and a side of the piezoelectric layer distal to the bottom electrode respectively; etching a contact hole in the piezoelectric layer and extending the contact hole from a side of the piezoelectric layer distal to the bottom electrode to the bottom electrode; depositing an interconnection metal on a side of the piezoelectric layer distal to the bottom electrode and patterning the interconnection metal so that the interconnection metal fills the contact hole and is connected to the bottom electrode; releasing the sacrificial layer.

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