Acoustic wave device

Abstract

Acoustic wave device comprising the following: a first electrode comprising a first edge; a piezoelectric layer arranged on the first electrode, comprising a flat region and a stepped region, the stepped region corresponding to the first edge of the first electrode; and a second electrode that is located on the flat area of ​​the piezoelectric layer; wherein, when projected onto a first plane, a projection of the first electrode, a projection of the piezoelectric layer, and a projection of the second electrode overlap at least partially, the first plane being perpendicular to a stacking direction of the first electrode, the piezoelectric layer, and the second electrode; and where, when projecting onto the first plane, a shortest distance between a projection of the stepped region and the projection of the second electrode is equal to or greater than a predetermined length.

Description

TECHNICAL AREA

[0001] The present disclosure relates to an acoustic wave device (also: acoustic wave apparatus) and in particular to an acoustic wave device with an improved quality factor. BACKGROUND

[0002] Modern high-frequency communication systems place increasingly stringent performance demands on high-frequency components, driving the development of acoustic resonator technology. Acoustic resonators can be used to achieve energy conversion between electrical and mechanical vibrational energy based on the piezoelectric effect and are therefore widely used in applications such as high-frequency filtering. Acoustic resonators can include, for example, SAW (surface acoustic wave) devices and BAW (bulk acoustic wave) devices, the latter of which can include FBAR (film bulk acoustic resonator) devices. Bulk acoustic wave devices can operate based on various wave modes within the piezoelectric materials. SUMMARY

[0003] Acoustic wave devices according to the invention are defined in the independent claims. The dependent claims define advantageous further applications thereof. One embodiment provides an acoustic wave device comprising a first electrode, a piezoelectric layer, and a second electrode. The first electrode comprises an edge. The piezoelectric layer is arranged on the first electrode and comprises a flat region and a stepped region. The stepped region corresponds to the edge of the first electrode. The second electrode is arranged on the flat region of the piezoelectric layer. When projected onto a first plane, projections of the first electrode, the piezoelectric layer, and the second electrode onto a first plane overlap each other at least partially. The first plane is perpendicular to a stacking direction of the first electrode, the piezoelectric layer, and the second electrode.When projecting onto a first plane, the shortest distance between a projection of the stepped area and a projection of the second electrode is equal to or greater than a predetermined length.

[0004] Another embodiment provides an acoustic wave device manufactured by a method. The method comprises forming a first electrode, which includes a border, and forming a piezoelectric layer on the first electrode. The piezoelectric layer comprises a flat region and a stepped region. The stepped region corresponds to the border of the first electrode. The manufacturing method further comprises forming a second electrode on the flat region of the piezoelectric layer. When projected onto a first plane, the projections of the first electrode, the piezoelectric layer, and the second electrode overlap at least partially. The first plane is perpendicular to a stacking direction of the first electrode, the piezoelectric layer, and the second electrode.When projecting onto the first plane, a shortest distance between a projection of the stepped area and a projection of the second electrode is equal to or greater than a predetermined length. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 illustrates a cross-sectional diagram of an acoustic wave device according to one embodiment. Fig. Figure 2 illustrates an exemplary flowchart of a manufacturing process for the acoustic wave device in Fig. 1. Fig. Figure 3 illustrates an exemplary top view of the acoustic wave device in Fig. 1. Fig. Figure 4 illustrates a cross-sectional diagram of an acoustic wave device according to another embodiment. Fig. Figure 5 illustrates a cross-sectional diagram of an acoustic wave device according to another embodiment. DETAILED DESCRIPTION

[0005] Exemplary embodiments are described in detail below with reference to the accompanying drawings, so that they can be easily implemented by a person skilled in the art. The inventive concept can be implemented in various forms without being limited to the exemplary embodiments presented herein. Descriptions of well-known parts may be omitted for the sake of clarity, and identical reference numerals may refer to the same elements throughout.

[0006] This document provides at least one detail to facilitate understanding of the present disclosure. However, the person skilled in the art will understand that the implementation of the present disclosure is not limited to these details. In some cases, to avoid obscuring the present disclosure, this document may not describe in detail some known features, such as components, steps, programs, circuits, materials, and the like. Some embodiments may include equivalents of the listed features, additional features (for example, additional components or steps), or may omit some features. Without departing from the spirit of the present disclosure and without conflict, features in different embodiments may be substituted, recombined, mixed, and modified to achieve another embodiment that still falls within the scope of the present disclosure.Features described in a drawing or embodiment need not be limited to that drawing or embodiment. Those skilled in the art should understand that in the industry, the same components / steps may be referred to by different names or symbols. This document is not intended to differentiate between components / steps that have the same function but different names. When an element is described as selectively arranged or optionally arranged, this means that the element can be arranged or removed as needed, all of which falls within the scope of this disclosure.

[0007] In this document, terms such as "include," "contain," "exhibit," and "possess" are open terms that should be interpreted as meaning "include, but not be limited to." Accordingly, when used, these terms can indicate the presence of corresponding features but do not exclude the presence of other features. When "and / or" is used to link multiple objects, it means at least one of these objects or any combination thereof. For example, "X, Y, and / or Z" can include any of the following: X alone, Y alone, Z alone, a combination of X and Y, a combination of X and Z, a combination of Y and Z, and a combination of all three: X, Y, and Z. When an element is described as being coupled to another element, it can be directly coupled or indirectly coupled.Direct coupling can include, for example, contact, direct electrical coupling, and the like, such as coupling solely through metal wires. Indirect coupling can include, for example, coupling through another element (such as an active or passive element), coupling through signals, and the like. Directional terms mentioned in this document, such as "above," "below," "front," "back," "left," "right," "inside," "outside," and the like, are used to describe relative positions in a general way and are not intended to limit the scope of this disclosure.

[0008] When an object is described as being arranged or formed on another object, this describes a spatial relationship of relative positioning in place or in the manufacturing process, and the two objects may or may not be in direct contact. Since the areas occupied by the two objects may differ, when object A is described as being arranged or formed on object B, this can be interpreted as at least a portion of object A being arranged or formed on at least a portion of object B, such that projections of object A and object B along their stacking direction may at least partially overlap. When object A and object B are described as overlapping, this can mean that projections of object A and object B overlap at least partially, and the two objects may be in a contact or non-contact state.For the sake of brevity, the drawings may only illustrate some of the components / steps and may not necessarily be drawn to scale.

[0009] In general, thin-film deposition techniques can be used to fabricate any layer structure in acoustic wave resonators. For example, a piezoelectric layer can be formed on an electrode. However, since the electrode has a specific thickness, the crystal structure of the piezoelectric layer at the electrode's edge may be irregular, affecting its piezoelectric effect. This can impact the quality factor (Q-value) and the electromechanical coupling coefficient (kt). 2) of the acoustic wave resonator. This problem can be particularly significant in high-frequency applications. For example, the influence of the irregular crystal structure is more pronounced in thinner piezoelectric layers.

[0010] Fig. Figure 1 illustrates a cross-sectional diagram of an exemplary acoustic wave device 100. The acoustic wave device 100 can include a substrate 105, a first electrode 110, a piezoelectric layer 115, and a second electrode 120. As shown, the substrate 105 can include a cavity A1. The first electrode 110 can be formed on the substrate 105 and can cover the cavity A1. The piezoelectric layer 115 can cover the first electrode 110 and can further cover the substrate 105. The second electrode 120 can be formed on the piezoelectric layer 115. For example, the first electrode 110 can be a lower electrode, the second electrode 120 can be an upper electrode, and the piezoelectric layer 115 can be formed at least partially between the first electrode 110 and the second electrode 120.

[0011] In some embodiments, the substrate 105 material can comprise silicon, glass, ceramic, gallium arsenide, and silicon carbide. The cavity A1 of the substrate 105 can be filled with air. Alternatively, the cavity A1 can be filled with polymer materials, porous materials, or inert gases, depending on the desired acoustic properties. The first electrode 110 and the second electrode 120 can be conductors comprising, for example, molybdenum (Mo), copper (Cu), aluminum (Al), gold (Au), platinum (Pt), tungsten (W), other suitable metals, and / or combinations thereof.

[0012] In some embodiments, the material of the piezoelectric layer 115 can comprise piezoelectric single-crystal materials, piezoelectric polycrystalline (for example, piezoelectric ceramic) materials, piezoelectric polymers, and piezoelectric composite materials. For example, the material of the piezoelectric layer 115 can comprise zinc oxide (ZnO), aluminum nitride (AlN), lithium tantalate (for example, LiTaO3), lithium niobate (for example, LiNbO3), quartz (QZ), lead titanate (for example, PTO), lead zirconate titanate (for example, PZT), and / or combinations thereof. In some embodiments, the piezoelectric layer 115 can further be doped with scandium (Sc).

[0013] In this document, whenever chemical formulas are mentioned, their stoichiometric ratios are provided as examples. Reasonable adjustments to the stoichiometric ratios to accommodate different process conditions or performance requirements without affecting the fundamental properties of the materials can all fall within the scope of embodiments. For example, lithium niobate can be LiNbO3, or other variations such as Li x NbO y be (where x and y can be integer or non-integer parameters), silicon nitride can be Si3N4 or other variations such as SiN x , all of which fall within the scope of the embodiments.

[0014] Furthermore, the substrate 105, the first electrode 110, the piezoelectric layer 115, and the second electrode 120 can be stacked sequentially along a first direction DR1 such that, when projected onto the first plane P1, the projection of the cavity A1 of the substrate 105, the projection of the first electrode 110, the projection of the piezoelectric layer 115, and the projection of the second electrode 120 can overlap at least partially. For example, the first plane P1 can be perpendicular to the first direction DR1. For example, when projected onto the first plane P1 along the first direction DR1, the overlapping area of ​​the cavity A1, the first electrode 110, the piezoelectric layer 115, and the second electrode 120 can correspond to a resonance region R1 of the acoustic wave device 100.In other words, the resonance region R1 of the acoustic wave device 100 can include the overlapping area, along the first direction DR1, of the cavity A1, the first electrode 110, the piezoelectric layer 115, and the second electrode 120. In some cases, the resonance region R1 of the acoustic wave device 100 can also be referred to as an active region, serving as a primary region of the piezoelectric effect and designed to enable electroacoustic coupling and resonance functions.

[0015] In some embodiments, the acoustic wave device 100 may further include a protective layer 130. The protective layer 130 may be arranged at least on the second electrode 120 to protect the second electrode 120 and other material layers. As shown, a section of the protective layer 130 may be arranged on the piezoelectric layer 115. A metal pad 140 may be arranged on the protective layer 130.

[0016] For example, the material of the protective layer 130 can comprise at least one of the following: silicon dioxide (SiO₂). x ), silicon nitride (SiN x) and silicon oxynitride (SiON). For example, the protective layer 130 can include silicon dioxide (for example, SiO2) and / or silicon nitride (for example, Si3N4). The protective layer 130 can provide electrical insulation protection, moisture resistance, corrosion resistance, contamination resistance, and dirt resistance. The protective layer 130 can also be configured to fine-tune an operating frequency. In some embodiments, the protective layer 130 can also act as a guide layer that modulates the propagation speed of the acoustic wave to improve sensitivity to surface disturbances. In some embodiments, the thickness H of the protective layer 130 can be from 270 nanometers (nm) to 330 nanometers.

[0017] In some embodiments, the acoustic wave device 100 may further include a metal pad 140 and a connecting section 150. The metal pad 140 may be arranged on the protective layer 130. For example, the metal pad 140 may be electrically connected to the second electrode 120 via a conductive via 133 in the protective layer 130. Signals can be transmitted to the second electrode 120 via the metal pad 140 or transmitted from the second electrode 120 to external components. The connecting section 150 may be electrically connected to the metal pad 140, for example, may be arranged on the metal pad 140, and may serve as a connecting component between the acoustic wave device 100 and other components. In other cases, the connecting section 150 may also serve as a support for the acoustic wave device 100.

[0018] In some embodiments, the acoustic wave device 100 may further include a metal pad 142 and a connecting section 152, and the metal pad 142 may be arranged on the protective layer 130. For example, the metal pad 142 may be electrically connected to the first electrode 110 via a conductive through-hole 136 in the protective layer 130. Signals can be transmitted to the first electrode 110 via the metal pad 142 or transmitted from the first electrode 110 to external components. The connecting section 152 may be electrically connected to the metal pad 142, for example, arranged on the metal pad 142, and may serve as a connecting component between the acoustic wave device 100 and other components. In other cases, the connecting section 152 may also serve as a carrier or support element for the acoustic wave device 100.

[0019] For example, the material of the metal pads 140 and / or 142 can include aluminum or gold, or other suitable metal pads can be used, depending on the packaging processes and technical requirements. The material of the connecting sections 150 and / or 152 can include aluminum (Al), copper (Cu), gold (Au), nickel (Ni), tin-silver-copper alloy (SAC), tin-silver alloy (SnAg), tin-lead alloy (SnPb), silver (Ag), and / or tin-based alloys.

[0020] The following describes the connection between the first electrode 110 and external circuits. The connection section 150 can include bond pads, solder balls, conductive bumps, and / or conductive pillars, and a suitable connection section 150 can be selected based on encapsulation processes or technical requirements. In some embodiments, the acoustic wave device 100 can be mounted on an encapsulation substrate through the connection section 150 using flip-chip bonding technology. This bonding technology offers advantages such as short electrical paths, low parasitic effects, and excellent high-frequency characteristics.Additionally, the connection section 150 can also be used in conjunction with other encapsulation technologies, such as wire bonding, BGA (Ball Grid Array) encapsulation or wafer-level encapsulation (WLP), to enable an electrical connection and mechanical fixation between the acoustic wave device 100 and an encapsulation body, thereby ensuring the performance of the acoustic wave device 100 under different encapsulation architectures.

[0021] In some embodiments, the acoustic wave device 100 can utilize a piezoelectric effect to perform an electroacoustic conversion. When a high-frequency electrical signal is applied between the first electrode 110 and the second electrode 120, an electric field can be generated in the piezoelectric layer 115, causing the piezoelectric material to vibrate along a specific direction (for example, along the first direction DR1). If the thickness of the piezoelectric layer 115 is an integer multiple of half the acoustic wavelength, a standing wave resonance can be formed.A resonant frequency can be determined, for example, by the thickness and acoustic velocity of the piezoelectric layer 115 and can be expressed as fr = n × v / (2 × t), where fr is the resonant frequency, v is the acoustic velocity, t is the thickness of the piezoelectric layer 115, and n is a predetermined integer. Signal filtering at specific frequencies can be achieved using the acoustic wave device 100.

[0022] In some embodiments, the resonant frequency band of the acoustic wave device 100 can be located in the range of 100 MHz to 20 GHz. This frequency range covers several important communication frequency bands. By adjusting the thickness of the piezoelectric layer 115, the dimensions of the first electrode 110 and the second electrode 120, and the material compositions, the resonant frequency band of the acoustic wave device 100 can be tuned to target frequency bands to meet the specification requirements of desired communication protocols.

[0023] With reference to Fig. As described above, one section of the piezoelectric layer 115 can be arranged on the first electrode 110, and another section can be arranged on the substrate 105. As shown, the first electrode 110 can include a first edge E1. The piezoelectric layer 115 can include a flat area 115A and a stepped area 115B. The stepped area 115B corresponds to the first edge E1 of the first electrode 110. The second electrode 120 can be arranged on the flat area 115A of the piezoelectric layer 115.

[0024] In the embodiments described above, when the piezoelectric layer 115 is formed on the first electrode 110 during a deposition process, the piezoelectric material at the first edge E1 of the first electrode 110 may not be flat due to the thickness of the first electrode 110. Consequently, a stepped structure, namely the stepped region 115B, may form near the first edge E1. Compared to the flat region 115A of the piezoelectric layer 115, the crystal arrangement of the stepped region 115B may be irregular. In other words, the crystal orientation uniformity in the stepped region 115B may be lower than that in the flat region 115A. As described above, the resonance area R1 of the acoustic wave device 100 can include an overlapping area along the first direction DR1, of the cavity A1, the first electrode 110, the piezoelectric layer 115 and the second electrode 120.

[0025] In some embodiments, it is desirable that the resonance region R1 of the acoustic wave device 100 be located as far away as possible from the stepped region 115B within a reasonable range in order to avoid or mitigate adverse effects of the stepped region 115B of the piezoelectric layer 115. Furthermore, it is desirable that the second electrode 120 formed on the piezoelectric layer 115 be located within a reasonable range from the stepped region 115B. For example, a distance Dt along a horizontal direction between the stepped region 115B and the second electrode 120 may be equal to or greater than a predetermined length. Furthermore, the distance Dt may be defined as the shortest distance between a projection of the stepped region 115B onto the first plane P1 and a projection of the second electrode 120 onto the same plane P1. The second electrode 120 may also include a second edge E2.The shortest distance can refer to the shortest distance between the projection of the stepped region 115B and that of the second boundary E2 onto the first plane P1. For example, the distance Dt can be equal to or greater than 6 micrometers, which can be expressed as Dt ≥ 6 µm.

[0026] In contrast, if the resonance region R1 of the acoustic wave device is too close to or overlaps with the stepped region 115B of the piezoelectric layer 115, crystal orientation defects of the stepped region 115B can be detrimental by causing scattering losses for the propagation of the acoustic wave and thereby leading to a deterioration of the quality factor and the electromechanical coupling coefficient of the acoustic wave device 100, which can affect its performance. The structure of the embodiments of the present disclosure can effectively avoid the aforementioned problems. Fig. 1, since the shortest distance Dt can be equal to or greater than a predetermined length, it can be effectively prevented that the resonance region R1 is too close to the stepped region 115B of the piezoelectric layer 115.

[0027] Fig. Figure 2 illustrates an exemplary flowchart of a manufacturing process 200 of an acoustic wave device according to one embodiment. In particular, an acoustic wave device manufactured according to this process is protected. As in Fig. 1 and Fig. As shown in Figure 2, the manufacturing process 200 can include the following steps.

[0028] Step 205: Providing a substrate 105;

[0029] Step 210: Forming a first electrode 110 on the substrate 105;

[0030] Step 215: Forming a piezoelectric layer 115 on the first electrode 110;

[0031] Step 220: Forming a second electrode 120 on the piezoelectric layer 115;

[0032] Step 225: Forming a protective layer 130 on the second electrode 120;

[0033] Step 230: Forming a conductive via 133 in the protective layer 130 and forming a metal pad 140 on the protective layer 130, wherein the metal pad 140 is electrically connected to the second electrode 120 via the conductive via 133; and

[0034] Step 235: Forming a connecting section 150 that is electrically connected to the metal pad 140.

[0035] In some embodiments, the manufacturing process 200 can further include forming a conductive via 136 in the protective layer 130 and forming a metal pad 142 on the protective layer 130. The metal pad 142 is electrically connected to the first electrode 110 via the conductive via 136. Optionally, a connection section 152 can be formed to be electrically connected to the metal pad 142.

[0036] Each layer structure of the acoustic wave device 100 has been described above and is not repeated here. The preceding steps can be carried out sequentially, or the order of the preceding steps can be adjusted according to the requirements of semiconductor processes, all of which is within the scope of the embodiments.

[0037] Fig. Figure 3 illustrates a top view of the acoustic wave device 100. Fig. 1. Fig. Figure 3 represents the substrate 105, the first electrode 110, the piezoelectric layer 115, and the second electrode 120. For clarity and explanation, the protective layer 130, the cavity A1, the metal pads 140 and 142, the conductive vias 133 and 136, and the connecting sections 150 and 152 can be shown in Figure 3. Fig. 3 should be omitted.

[0038] Fig. Figure 3 shows the positions of different layers and components in a top view, while their vertical stacking relationship is shown as in Fig. 1 can be shown. As in Fig. As shown in Figure 3, the shortest distance Dt between a projection of the second edge E2 of the second electrode 120 and a projection of the stepped region 115B of the piezoelectric layer 115 can be equal to or greater than a predetermined length (for example, but not limited to, 6 micrometers). Therefore, a deterioration of the quality factor and the electromechanical coupling coefficient resulting from the stepped region can be effectively avoided. Fig. Figure 3 shows each of the substrate 105, the first electrode 110, the piezoelectric layer 115, and the second electrode 120 in a rectangular configuration, but this is merely an example. In some embodiments, the shapes can also be polygonal, circular, elliptical, or other suitable geometric configurations.

[0039] In some embodiments, a multitude of acoustic wave devices can share some components. Fig. Figure 4 illustrates a schematic diagram of the acoustic wave device 100 and an acoustic wave device 400 according to another embodiment. Similarities between Fig. 4 and Fig. Number 1 will not be repeated here. Fig. Figure 4 also shows the acoustic wave device 400.

[0040] As in Fig. As shown in Figure 4, the substrate 105 can further comprise a cavity A4. The first electrode 110 of the acoustic wave device 100 can extend to cover the cavity A4. The piezoelectric layer 115 can further extend to cover the extended first electrode 110. The acoustic wave device 400 can further comprise a second electrode 420 formed on the piezoelectric layer 115. The protective layer 130 can extend to cover the second electrode 420. For the acoustic wave device 400, projections of the cavity A4, the first electrode 110, the piezoelectric layer 115, and the second electrode 420 onto the first plane P1 overlap each other at least partially. The resonance region R4 of the acoustic wave device 400 can include an overlapping area of ​​the cavity A4, the first electrode 110, the piezoelectric layer 115 and the second electrode 420 along the first direction DR1.The resonance region R4 can be an active region of the acoustic wave device 400. In the above implementation, the substrate 105, the first electrode 110, the piezoelectric layer 115, and the protective layer 130 are shared by the acoustic wave devices 100 and 400.

[0041] In some embodiments, the acoustic wave device 400 may further include a metal pad 440 and a connecting section 450, and the metal pad 440 may be electrically connected to the second electrode 420 via a conductive through-hole 433 in the protective layer 130. Signals can be transmitted to the second electrode 420 via the metal pad 440 or from the second electrode 420 to external circuits. As shown in Fig. As shown in Figure 4, the connecting section 450 can be electrically connected to the metal pad 440; for example, it can be formed on the metal pad 440. The materials, shapes, and applications of the metal pad 440 and the connecting section 450 may be similar to those of the metal pad 140 and the connecting section 150, respectively, and are therefore not repeated here.

[0042] Similar to in Fig. In the acoustic wave device 400, the second electrode 420 can be arranged on the flat area 115A of the piezoelectric layer 115. The first electrode 110 can further include a further edge E11. The piezoelectric layer 115 can have a stepped area 415B. The stepped area 415B corresponds to the edge E11 of the first electrode 110. The second electrode 420 can have a second edge E42. The shortest distance (designated as D4) between a projection of the second edge E42 and a projection of the stepped region 415B onto the first plane P1 can be greater than or equal to a predetermined length (for example, 6 micrometers), thereby avoiding or mitigating a deterioration of the quality factor and a reduction of the electromechanical coupling coefficient caused by crystal orientation irregularities in the stepped region 415B of the piezoelectric layer 115.

[0043] Fig. Figure 5 illustrates a schematic diagram of the acoustic wave device 100 and an acoustic wave device 500 according to another embodiment. Similarities between Fig. 5 and Fig. Number 1 will not be repeated here. Fig. Figure 5 also shows the acoustic wave device 500.

[0044] As in Fig. As shown in Figure 5, the substrate 105 can further comprise a cavity A5. The acoustic wave device 500 can further comprise a first electrode 112, which can be formed on the substrate 105 and cover the cavity A5. The piezoelectric layer 115 can cover the first electrode 112. Furthermore, the first electrode 112 of the acoustic wave device 500 can be electrically isolated from the first electrode 110 of the acoustic wave device 100. The second electrode 120 of the acoustic wave device 100 can extend to serve as an upper electrode for the acoustic wave device 500. For the acoustic wave device 500, the projection of the cavity A5, the projection of the first electrode 112, the projection of the piezoelectric layer 115, and the projection of the second electrode 120 onto the first plane P1 overlap each other at least partially.The resonance region R5 of the acoustic wave device 500 can include an overlapping area of ​​the cavity A5, the first electrode 112, the piezoelectric layer 115, and the second electrode 120 along the first direction DR1. The resonance region R5 can be an active region of the acoustic wave device 500. In the above implementation, the substrate 105, the piezoelectric layer 115, the second electrode 120, and the protective layer 130 are shared by the acoustic wave devices 100 and 500.

[0045] In some embodiments, the acoustic wave device 500 may further include a metal pad 540 and a connecting section 550. The metal pad 540 may be electrically connected to the first electrode 112 by means of a conductive via 533. For example, the conductive via 533 may extend through the protective layer 130 and may also extend through the piezoelectric layer 115.

[0046] In the acoustic wave device 500, the first electrode 112 can include a rim E12. The piezoelectric layer 115 can have a stepped region 515B, wherein the stepped region 515B corresponds to the rim E12 of the first electrode 112. The second electrode 120 can have a rim E52, wherein a minimum distance (denoted D5) between a projection of the rim E52 and a projection of the stepped region 515B onto the first plane P1 can be greater than or equal to a predetermined length (for example, but not limited to, 6 micrometers), thereby avoiding or mitigating adverse effects caused by crystal orientation irregularities of the stepped region 515B of the piezoelectric layer 115.

[0047] The embodiments described above of Fig. 4 and Fig.Figure 5 is used merely to illustrate configurations of a plurality of acoustic wave devices and is not intended to limit the present disclosure. In further embodiments, lower electrodes, upper electrodes, or both can be selectively extended as required to enable the formation of three or more acoustic wave devices.

[0048] In summary, the exemplary acoustic wave devices 100, 400, and 500 provided by the embodiments can optimize the shortest distance between the resonant region and the stepped region of the piezoelectric layer (for example, 6 micrometers or more) in order to position the upper electrode away from the stepped region of the piezoelectric layer, thereby avoiding or mitigating adverse effects resulting from the irregular crystal structure of the stepped region. Therefore, the quality factor and the electromechanical coupling coefficient can be effectively improved. The technical solutions of the embodiments are not only applicable to a single acoustic wave device but can also integrate a variety of acoustic wave devices.

[0049] Furthermore, the acoustic wave device provided by the embodiments can be advantageous in terms of low transmission loss, excellent electromagnetic interference resistance and compact size, and can exhibit good applicability in a broadband range from 100 MHz to 20 GHz, which can meet the requirements of various communication protocols such as mobile communication systems (such as GSM, CDMA, WCDMA, LTE, LTE-A, 5G, 6G), wireless network protocols (such as WiFi, Bluetooth, WiMAX) and other communication technologies (such as IoT, V2X, mmWave, etc.), but is not limited to these.

[0050] The person skilled in the art will readily recognize that numerous modifications and changes to the apparatus and the method can be made while retaining the teachings of the invention. Accordingly, the foregoing disclosure should be interpreted as being limited only by the scope and boundaries of the appended claims.

Claims

[1] Acoustic wave device comprising the following: a first electrode comprising a first edge; a piezoelectric layer arranged on the first electrode, comprising a flat region and a stepped region, the stepped region corresponding to the first edge of the first electrode; and a second electrode that is located on the flat area of ​​the piezoelectric layer; wherein, when projected onto a first plane, a projection of the first electrode, a projection of the piezoelectric layer, and a projection of the second electrode overlap at least partially, the first plane being perpendicular to a stacking direction of the first electrode, the piezoelectric layer, and the second electrode; and where, when projecting onto the first plane, a shortest distance between a projection of the stepped region and the projection of the second electrode is equal to or greater than a predetermined length. [2] Acoustic wave device according to claim 1, wherein the predetermined length is substantially 6 micrometers. [3] Acoustic wave device according to claim 1 or 2, wherein, in the piezoelectric layer, the crystal orientation uniformity in the stepped region is lower than the crystal orientation uniformity in the flat region. [4] Acoustic wave device according to one of claims 1 to 3, wherein the second electrode comprises a second edge and the shortest distance refers to a shortest distance between the projection of the stepped area and a projection of the second edge. [5] Acoustic wave device according to any one of claims 1 to 4, further comprising: a substrate, wherein the first electrode is arranged on the substrate. [6] Acoustic wave device according to claim 5, wherein a substrate material comprises at least one of the following: silicon, glass, ceramic, gallium arsenide and silicon carbide. [7] Acoustic wave device according to claim 5 or 6, wherein: the substrate includes a cavity, and When projected onto the first plane, a projection of the cavity, the projection of the first electrode, the projection of the piezoelectric layer, and the projection of the second electrode will at least partially overlap. [8] Acoustic wave device according to claim 7, wherein, when projected onto the first plane, an overlapping area of ​​the cavity, the first electrode, the piezoelectric layer and the second electrode corresponds to a resonance area of ​​the acoustic wave device. [9] Acoustic wave device according to any one of claims 1 to 8, further comprising: a protective layer that is arranged at least on the second electrode. [10] Acoustic wave device according to claim 9, further comprising: a metal pad that is arranged on the protective layer, wherein the metal pad is electrically connected to the second electrode by means of a via in the protective layer. [11] Acoustic wave device according to claim 10, wherein a material of the metal pad comprises aluminium or gold. [12] Acoustic wave device according to claim 10 or 11, further comprising: a connecting section that is electrically connected to the metal pad. [13] Acoustic wave device according to claim 12, wherein the connecting section comprises a bond pad, a solder ball, a conductive bump and / or a conductive column. [14] Acoustic wave device according to any one of claims 1 to 13, wherein the first electrode extends to serve as an electrode for another acoustic wave device. [15] Acoustic wave device according to any one of claims 1 to 14, wherein the second electrode extends to serve as an electrode for another acoustic wave device. [16] Acoustic wave device according to any one of claims 1 to 15, wherein a resonant frequency band of the acoustic wave device is in a range from 100 MHz to 20 GHz. [17] Acoustic wave device according to any one of claims 1 to 16, wherein a material of the piezoelectric layer comprises at least one of the following: zinc oxide, aluminium nitride, lithium tantalate, lithium niobate, quartz, lead titanate, lead zirconate titanate and scandium. [18] Acoustic wave device according to any one of claims 1 to 17, wherein a material of the first electrode or a material of the second electrode comprises at least one of the following: Molybdenum, copper, aluminum, gold, platinum and tungsten. [19] Acoustic wave device manufactured by a method comprising: Forming a first electrode, wherein the first electrode comprises a first edge; Forming a piezoelectric layer, wherein the piezoelectric layer is arranged on the first electrode and comprises a flat region and a stepped region, the stepped region corresponding to the first edge of the first electrode; and Forming a second electrode, wherein the second electrode is arranged on the flat area of ​​the piezoelectric layer; wherein, when projected onto a first plane, a projection of the first electrode, a projection of the piezoelectric layer, and a projection of the second electrode overlap at least partially, the first plane being perpendicular to a stacking direction of the first electrode, the piezoelectric layer, and the second electrode; and where, when projecting onto the first plane, a shortest distance between a projection of the stepped region and the projection of the second electrode is equal to or greater than a predetermined length. [20] Acoustic wave device according to claim 19, wherein the predetermined length is substantially 6 micrometers.

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