Bulk acoustic wave device structure and device

Abstract

The invention provides a bulk acoustic wave device structure and device. The bulk acoustic wave device structure comprises a first piezoelectric layer, a first electrode and a second electrode, wherein the first piezoelectric layer is provided with a body part and a plurality of mutually-spaced lug bosses, and the first electrode and the second electrode are arranged on the two opposite sides of the first piezoelectric layer respectively; wherein the first electrodes are located on the first side of the body part, electrode fingers of the second electrodes extend in the second direction, are alternately arranged on the surfaces of the protruding parts at intervals in the first direction and are in one-to-one correspondence with the protruding parts, and meanwhile, vertical projections of the electrode fingers in the third direction fall into projection planes of the protruding parts and are also located in the projection range of the first electrodes. Through collaborative configuration optimization of the first piezoelectric layer and the first electrode, the problems of energy leakage, serious crosstalk, low electromechanical conversion efficiency and the like of a traditional bulk acoustic wave device are solved from two aspects of acoustic wave constraint and electric field coupling, the resonance performance and the working stability of the device are remarkably improved, and the device has important practical application value.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a structure and device for a bulk acoustic wave device. Background Technology

[0002] As wireless communication technology evolves, the number of frequency bands used is increasing. The application of frequency band superposition technologies such as carrier aggregation has made the mutual interference between wireless frequency bands more and more serious. At the same time, 5G and subsequent communication technologies have introduced higher communication frequency bands. The filtering performance of traditional bulk acoustic wave devices in high-frequency bands is limited. However, YBAR, relying on the working characteristics of longitudinal excitation shear wave, is more suitable for the filtering needs of high-frequency signals and is one of the key devices to solve the problems of high-frequency interference and filtering.

[0003] Bulk acoustic wave resonators (BAWs) are piezoelectric devices that confine acoustic wave energy within the device itself. Common types include thin-film BAWs and longitudinally excited shear wave resonators (YBARs). The resonant region of these devices is typically located above air or a vacuum environment, while the lower portion utilizes different support structures (such as cavities, stacked functional layers, and substrates) to further confine the energy, depending on the specific type. Within the resonant region of a BAW, two main propagation modes exist: a longitudinal-like mode propagating along the thickness of the piezoelectric layer, where the acoustic wave can undergo total reflection and form a standing wave due to the significant acoustic impedance difference between air, vacuum, and the metal electrodes—this is the target operating mode of the device; and a transverse mode, where the acoustic wave diffuses towards the device edge in a horizontal direction perpendicular to the longitudinal-like mode, which is prone to energy leakage and is a stray mode that needs to be suppressed.

[0004] Therefore, how to provide a bulk acoustic resonator structure and device that can suppress energy leakage caused by transverse modes, thereby improving the quality factor of the bulk acoustic resonator, has become a problem that those skilled in the art need to solve continuously. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art.

[0006] To achieve the above objectives, a first aspect of this application provides a bulk acoustic wave device structure, comprising: The first piezoelectric layer includes a body portion and a plurality of mutually spaced protrusions, the body portion including a first side and a second side opposite to each other, and the protrusions being located on the second side of the body portion; The first electrode is located on the first piezoelectric layer and on the first side of the body portion; The second electrode, located on the first piezoelectric layer, includes a plurality of electrode fingers that are alternately spaced in a first direction and extend along a second direction; The electrode fingers are located on the protrusions, and each electrode finger corresponds to each protrusion. In the third direction, the vertical projection of each electrode finger is located in the vertical projection plane of the corresponding protrusion, and the vertical projection of each electrode finger is located in the vertical projection plane of the first electrode. The first direction is orthogonal to the second direction, and the orthogonal plane is perpendicular to the third direction.

[0007] Optionally, the second side of the body portion includes a first surface and a second surface surrounding the first surface, and in the third direction, the first surface and the second surface have a height difference, and the vertical projection of each of the electrode fingers extending along the second direction is at least partially located on the first surface.

[0008] Optionally, the height difference between the first surface and the second surface in the third direction is less than the thickness of the electrode finger.

[0009] Optionally, the second side of the body portion further includes a boss structure, the first surface being the top surface of the boss structure, the second surface being a portion of the body portion surrounding the boss structure, and the height difference between the first surface and the second surface being a positive height difference.

[0010] Optionally, the second side of the body portion includes a groove structure, the first surface is the bottom surface of the groove structure, the second surface is a portion of the body portion surrounding the groove structure, and the height difference between the first surface and the second surface is a negative height difference.

[0011] Optionally, the second side of the body portion includes a groove structure, the second surface is the bottom surface of the groove structure, the first surface is a portion of the body portion surrounded by the groove structure, and the height difference between the first surface and the second surface is a negative height difference.

[0012] Optionally, adjacent electrodes alternately overlap in the first direction to form an overlapping area; in the second direction, the extension length of the first surface is less than the extension length of the overlapping area, and in the first direction, the extension length of the first surface is greater than the extension length of the overlapping area.

[0013] Optionally, adjacent electrodes alternately overlap in the first direction to form an overlapping area; in the second direction, the extension length of the first surface is not less than the extension length of the overlapping area, and in the first direction, the extension length of the first surface is greater than the extension length of the overlapping area.

[0014] Optionally, adjacent electrodes overlap alternately in the first direction to form an overlapping area; in the third direction, the vertical projection of the overlapping area lies within the vertical projection plane of the first electrode.

[0015] Optionally, the bulk acoustic wave device structure further includes a second piezoelectric layer, the second piezoelectric layer being located on the side of the first piezoelectric layer away from the second electrode, and the second electrode being located on the side of the second piezoelectric layer away from the first piezoelectric layer.

[0016] Optionally, the bulk acoustic wave device structure further includes a substrate and a functional layer located on the substrate, the functional layer being located between the substrate and the first piezoelectric layer, the first electrode being embedded in the functional layer on the side away from the substrate, and the first piezoelectric layer being in contact with the surface of the first piezoelectric layer on the side closer to the substrate.

[0017] Optionally, the bulk acoustic wave device structure further includes a substrate, the first piezoelectric layer is located on the substrate and forms a cavity between the first piezoelectric layer and the substrate, and the first electrode is located on the surface of the first piezoelectric layer exposed in the cavity.

[0018] Optionally, the bulk acoustic wave device structure further includes a reflective gate electrode, which is formed on the first piezoelectric layer and spaced apart on both sides of the second electrode along the first direction.

[0019] Optionally, the second electrode further includes a plurality of dummy fingers that extend along the second direction and maintain a distance from the electrode fingers in the second direction, and each dummy finger corresponds one-to-one with each electrode finger.

[0020] To achieve the above objectives, a second aspect of this application provides a bulk acoustic wave device, wherein the bulk acoustic wave includes the bulk acoustic wave device structure described in any one of the above claims.

[0021] The bulk acoustic wave device structure and apparatus provided in this application have at least the following beneficial effects: This application provides a bulk acoustic wave (BAW) device structure and apparatus, including a first piezoelectric layer having a body portion and a plurality of mutually spaced protrusions, and a first electrode and a second electrode respectively disposed on opposite sides of the first piezoelectric layer. The first electrode is located on a first side of the body portion, and the electrode fingers of the second electrode extend along a second direction and are alternately arranged along a first direction on the surface of the protrusions, corresponding one-to-one with each protrusion. Simultaneously, the vertical projection of the electrode fingers in a third direction falls both within the projection plane of the protrusions and within the projection range of the first electrode. This application, through the synergistic configuration optimization of the first piezoelectric layer and the first electrode, solves the problems of energy leakage, severe crosstalk, and low electromechanical conversion efficiency in traditional BAW devices from both acoustic wave confinement and electric field coupling perspectives. It significantly improves the resonant performance and operational stability of the device, providing a new structural design concept for the development of high-frequency BAW devices in fields such as radio frequency communication and signal processing, and possesses significant practical application value.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a cross-sectional structural schematic diagram of the first type of bulk acoustic wave device structure according to an embodiment of this application.

[0024] Figure 2 This is a top view schematic diagram of the structure of a first type of bulk acoustic wave device according to an embodiment of this application.

[0025] Figure 3 This is a cross-sectional schematic diagram of the first type of bulk acoustic wave device structure corresponding to different negative height differences.

[0026] Figure 4 This is a cross-sectional schematic diagram of the second type of bulk acoustic wave device structure corresponding to different negative height differences.

[0027] Figure 5 This is a cross-sectional schematic diagram of the third type of bulk acoustic wave device structure corresponding to different negative height differences.

[0028] Figure 6 This is a cross-sectional schematic diagram of the fourth type of bulk acoustic wave device structure corresponding to different negative height differences.

[0029] Figure 7 This is a cross-sectional schematic diagram of the fifth type of bulk acoustic wave device structure corresponding to different negative height differences.

[0030] Figure 8This is a cross-sectional schematic diagram of the sixth type of bulk acoustic wave device structure corresponding to different negative height differences.

[0031] Figure 9 for Figure 8 Performance diagram of a corresponding bulk acoustic wave device structure.

[0032] Figure 10 This is a performance diagram of a conventional bulk acoustic wave device structure.

[0033] Figure 11 This is a top view schematic diagram of the second type of bulk acoustic wave device structure according to an embodiment of this application.

[0034] Figure 12 This is a top view schematic diagram of the third type of bulk acoustic wave device structure according to an embodiment of this application.

[0035] 100 Substrate; 101 Cavity; 200 Functional Layer; 300 First Electrode; 400 First Piezoelectric Layer; 401 First Surface; 402 Second Surface; 410 Body; 420 Protrusion; 500 Second Electrode; 510 Electrode Finger; 511 First Electrode Finger; 512 Second Electrode Finger; 521 First Busbar; 522 Second Busbar; 530 Pseudo Finger; 600 Second Piezoelectric Layer; 700 Reflective Grid. Detailed Implementation

[0036] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0037] According to one aspect of this application, a bulk acoustic wave device structure is provided, such as... Figure 1 and Figure 2 As shown, the structure typically includes a first piezoelectric layer 400, and a first electrode 300 and a second electrode 500 formed on opposite sides of the first piezoelectric layer 400.

[0038] The first piezoelectric layer 400 includes a body portion 410 and a plurality of spaced-apart protrusions 420. The body portion 410 includes a first side and a second side opposite to each other. A first electrode 300 is located on the first side of the body portion 410, and the protrusions 420 are located on the second side of the body portion 410. A second electrode 500 is located on the surface of the protrusion 420 on the side away from the body portion 410. The second electrode 500 includes a plurality of electrode fingers 510 that are alternately and spaced apart along a first direction and extend along a second direction. Each protrusion 420 also extends along the second direction, such that each electrode finger 510 can be formed one-to-one on each protrusion 420. Furthermore, in a third direction, the vertical projection of each electrode finger 510 is located within the vertical projection plane of the protrusion 420, and simultaneously, the vertical projection of each electrode finger 510 is located within the vertical projection plane of the first electrode 300.

[0039] For ease of description, the direction in which the electrode fingers 510 are arranged alternately is defined as the first direction, i.e., the X direction in the figure; the direction in which the electrode fingers 510 extend is defined as the second direction, i.e., the Y direction in the figure, and the first direction and the second direction are orthogonal to each other; and the direction in which the substrate 100 thickness extends is defined as the third direction, i.e., the Z direction in the figure, and the third direction is perpendicular to the plane orthogonal to the first direction and the second direction.

[0040] It is understandable that the first electrode 300, as the bottom electrode, works in conjunction with the second electrode 500 to excite and propagate bulk waves. When an alternating electrical signal is input to the second electrode 500, a periodic alternating electric field is formed between adjacent electrode fingers 510. This electric field penetrates the first piezoelectric layer 400 perpendicularly and acts on the first electrode 300, causing the piezoelectric material of the first piezoelectric layer 400 to undergo an inverse piezoelectric effect, thereby exciting bulk acoustic waves. These bulk acoustic waves propagate cyclically along the thickness direction (third direction) of the first piezoelectric layer 400 between the first electrode 300 and the electrode fingers 510 of the second electrode 500, ultimately forming a stable bulk acoustic wave resonance state.

[0041] Since the second electrode 500 includes multiple electrode fingers 510, and the electrode fingers 510 are located on the protrusions 420 and correspond one-to-one with the protrusions 420, each electrode finger 510 can independently form an independent excitation unit with the piezoelectric material in the corresponding region of the protrusion 420. This effectively constrains the propagation of bulk acoustic waves in the local region of the piezoelectric material corresponding to a single protrusion 420, avoiding the energy leakage problem caused by the diffusion of acoustic waves to the non-excitation region of the piezoelectric layer in traditional bulk acoustic wave devices. At the same time, the one-to-one correspondence between the electrode fingers 510 and the protrusions 420 also improves the acoustic energy density of each excitation unit, thereby enhancing the frequency response sharpness and signal processing accuracy of the device.

[0042] Furthermore, from the third-party perspective, since the vertical projection of each electrode finger 510 is located within the vertical projection plane of the protrusion 420, and the vertical projection of each electrode finger 510 is located within the vertical projection plane of the first electrode 300, the electrode finger 510 and the protrusion 420 achieve precise regional matching. This prevents the electrode finger 510 from exceeding the protrusion 420 and generating additional electric field coupling with the electrode finger 510 of the adjacent protrusion 420, effectively reducing the risk of crosstalk between electrodes. At the same time, the projection of the electrode finger 510 is limited to the range of the first electrode 300, which ensures that a concentrated and stable electric field distribution is formed between the first electrode 300, the first piezoelectric layer 400, and the electrode finger 510 of the second electrode 500. This maximizes the coupling efficiency between the electric field and the piezoelectric layer, reduces electromechanical conversion losses caused by electric field leakage, and further improves the electrical performance stability of the device structure.

[0043] In summary, this application addresses the technical problems of traditional bulk acoustic wave devices, such as severe acoustic energy leakage, low electromechanical conversion efficiency, and large inter-electrode crosstalk, by designing a first piezoelectric layer 400 with a body portion 410 and multiple spaced protrusions 420, and by setting the electrode fingers 510 of the second electrode 500 in a one-to-one correspondence with the protrusions 420, while limiting the vertical projection range of the electrode fingers 510. This achieves the technical effects of improving acoustic wave confinement capability, increasing electromechanical conversion efficiency, reducing electrode crosstalk, and enhancing device performance stability. Furthermore, it enables the bulk acoustic wave device structure to be adapted to higher frequency and higher precision communication, sensing, and other electronic equipment scenarios, providing a feasible structural solution for miniaturized, high-performance radio frequency front-end devices.

[0044] In some embodiments, such as Figures 3-5 As shown, the second side of the body portion 410 includes a first surface 401 and a second surface 402 surrounding the first surface 401. In the third direction, the first surface 401 and the second surface 402 have a height difference. The vertical projection of each electrode finger 510 extending in the second direction is at least partially located on the first surface 401.

[0045] It is understandable that, since there is a height difference between the first surface 401 on the second side of the body part 410 and the second surface 402 on the periphery, the piezoelectric layer thickness distribution in the corresponding area of ​​the body part 410 is actually changed through structural design. That is, the thickness of the body part 410 area corresponding to the first surface 401 and the thickness of the body part 410 area corresponding to the second surface 402 are controlled, thereby achieving precise adjustment of the electric field-vibration coupling strength and realizing the purpose of flexible adjustment of the electromechanical coupling coefficient (K²) of the device structure.

[0046] Specifically, since the vertical projection of the electrode finger 510 of the second electrode 500 is at least partially located on the first surface 401, the alternating electric field formed by the alternating electrical signal input to the second electrode 500 will mainly concentrate in the piezoelectric layer region corresponding to the first surface 401 and its boundary region with the second surface 402; while the excitation of bulk acoustic waves depends on the inverse piezoelectric effect of the piezoelectric layer, the difference in the thickness of the piezoelectric layer will directly change the intensity distribution of the bulk wave in the body part 410 region. At the same time, the propagation speed of the bulk wave in different thickness regions will also be adjusted with the thickness change. This change in the distribution of the intensity and propagation speed of the bulk wave will directly affect the conversion efficiency of electrical energy to mechanical energy (bulk wave or bulk acoustic wave).

[0047] The height difference causes a gradient change in the potential distribution in the body 410 region, meaning there is a difference in the electric field distribution in the piezoelectric layer regions corresponding to the first surface 401 and the second surface 402. Meanwhile, the mechanical vibration of the bulk acoustic wave undergoes abrupt deformation at the interface of the height difference, increasing the number of coupling sites between the electric field and the mechanical vibration and altering the interaction intensity. By adjusting the height difference between the first surface 401 and the second surface 402, this electric field-vibration coupling strength can be precisely adjusted, thereby enabling flexible adjustment of the device's electromechanical coupling coefficient (K²). Simultaneously, the structural interface formed by the height difference optimizes the reciprocating reflection path of the bulk acoustic wave within the piezoelectric layer, suppressing parasitic modes of the bulk wave in the lateral direction (such as non-resonant frequency noise), and improving the stability of the device's resonant performance.

[0048] It should be noted that, in order to ensure the continuity of the electrode finger 510 extending in the second direction and to avoid breakage or poor contact due to excessive height difference, the height difference between the first surface 401 and the second surface 402 should not exceed the thickness of the electrode finger 510. In other words, adjusting this height difference within the thickness range of the electrode finger 510 allows for a smooth transition of different electromechanical coupling coefficients (K²), thereby meeting the flexible application requirements of bulk acoustic wave devices from narrowband to broadband.

[0049] As an example, such as Figure 3 As shown, the second side of the body portion 410 also includes a boss structure. The first surface 401 is the top surface of the boss structure, and the second surface 402 is a part of the surface of the body portion 410 surrounding the boss structure. The height difference between the first surface 401 and the second surface 402 is a positive height difference.

[0050] Because the boss structure increases the thickness of the piezoelectric material corresponding to the body portion 410, the thicker piezoelectric material breaks the energy confinement characteristics of bulk acoustic waves in the piezoelectric layer thickness direction. The energy of the bulk acoustic waves should ideally be concentrated within the piezoelectric layer thickness range that matches the electrode (usually an integer multiple of half the bulk acoustic wave wavelength, which is the core region for electromechanical conversion), where the energy can efficiently participate in the interconversion of electrical and mechanical energy. When a boss structure is formed on the second side of the body portion 410, and the thickness of the piezoelectric material in the corresponding region increases, the energy distribution range of the bulk acoustic waves extends to the region corresponding to the thicker boss structure, exceeding the optimal conversion thickness range, causing some of the bulk wave energy to diffuse to the interface region between the body portion 410 and the first electrode 300. The first electrode 300 is made of metal, and its acoustic impedance differs significantly from that of piezoelectric materials. Some of the bulk wave energy will undergo ineffective reciprocating oscillations at this interface, eventually being converted into heat loss. At the same time, the excessively thick piezoelectric material in the region corresponding to the protrusion structure will also prolong the propagation path of the bulk wave. Some of the energy will be dissipated inside the piezoelectric material due to lattice damping. The combined effect of these two situations will reduce the proportion of bulk wave energy that effectively participates in electromechanical conversion, directly causing a decrease in the electromechanical coupling coefficient (K²).

[0051] Meanwhile, the increased thickness of the region corresponding to the boss structure may also induce lattice distortion within the material, thereby increasing the propagation speed of bulk acoustic waves. The regularity of the lattice arrangement of piezoelectric materials determines the interatomic bonding force and material stiffness (such as Young's modulus). When the thickness of the piezoelectric material increases, stress during the fabrication process or the material's own stress can easily cause minor deformations in the lattice (such as reduced interatomic spacing and bond angle adjustment). This distortion enhances the interatomic bonding force, increasing the overall stiffness of the piezoelectric material. When the change in material density is negligible, the increase in Young's modulus inevitably leads to an increase in the propagation speed of bulk acoustic waves in this region. The resonant frequency of a bulk acoustic wave device is directly related to the sound velocity and the thickness of the piezoelectric layer. Therefore, an increase in the sound velocity will manifest as an increase in the device's resonant frequency. At the same time, the accelerated propagation speed of bulk acoustic waves in the region corresponding to the boss structure will also shorten its interaction time with the alternating electric field. The coupling period between the bulk wave and the electric field per unit thickness decreases, and thus, the electromechanical coupling coefficient (K²) will further decrease as the positive height difference between the first surface 401 and the second surface 402 increases.

[0052] As an example, such as Figure 4 As shown, the second side of the body portion 410 includes a groove structure, the first surface 401 is the bottom surface of the groove structure, the second surface 402 is a part of the surface of the body portion 410 surrounding the groove structure, and the height difference between the first surface 401 and the second surface 402 is a negative height difference.

[0053] Because the groove structure reduces the thickness of the piezoelectric material corresponding to the body portion 410, the thinner piezoelectric material also alters the energy constraint and distribution characteristics of bulk acoustic waves in the piezoelectric layer thickness direction. When the thickness of the area of ​​the body portion 410 corresponding to the groove structure decreases, if the thickness is less than the optimal matching value of half the wavelength of the bulk acoustic wave, the energy distribution range will be excessively compressed, making it impossible to form a stable reciprocating reflection resonance within the piezoelectric layer. Some of the bulk wave energy will directly penetrate the thinned body portion 410 area and rapidly diffuse towards the first electrode 300. Since the acoustic impedance of the first electrode 300 differs significantly from that of the piezoelectric material, the penetrating bulk wave energy will undergo strong reflection at the electrode interface. The reflected clutter interferes with the main wave, disrupting the stability of the resonance. Simultaneously, the effective electric field range that the thinned piezoelectric layer area can bear is reduced, limiting the space for the conversion of electrical energy into mechanical energy. This results in a decrease in the proportion of bulk wave energy effectively participating in electromechanical conversion, leading to a phased decrease in the electromechanical coupling coefficient (K²).

[0054] Meanwhile, the thinning of the piezoelectric material in the corresponding region of the body 410 due to the groove structure may also induce lattice distortion within the material, thereby altering the propagation speed of bulk acoustic waves. The lattice arrangement of the piezoelectric material is affected by both fabrication and structural stresses. When the thickness of the body 410 decreases, the internal stress of the material redistributes, and the lattice is prone to stretching distortions (such as increased interatomic spacing and bond angle expansion). This distortion weakens the interatomic bonding forces, reducing the overall stiffness of the material (such as Young's modulus). When the change in material density is negligible, the decrease in Young's modulus leads to a reduction in the propagation speed of bulk acoustic waves in this region. The resonant frequency of a bulk acoustic wave device is directly related to the sound velocity and the effective thickness of the piezoelectric material. Therefore, the decrease in bulk acoustic wave propagation speed combined with the reduction in thickness causes the device's resonant frequency to exhibit a non-linear change: when the thickness reduction is small, the decrease in sound velocity dominates, and the resonant frequency decreases slightly; when the thickness reduction exceeds a critical value, the effect of the thickness reduction dominates, and the resonant frequency rises rapidly. Furthermore, the propagation speed of bulk acoustic waves slows down in the thinner region, which prolongs their interaction time with the alternating electric field. However, due to clutter interference caused by energy constraint failure, the effective coupling period between the bulk wave and the electric field per unit thickness does not increase synchronously. Ultimately, this leads to the electromechanical coupling coefficient (K²) continuously decreasing as the absolute value of the negative height difference between the first surface 401 and the second surface 402 increases.

[0055] As an example, such as Figure 5 As shown, the second side of the body portion 410 includes a groove structure. The second surface 402 is the bottom surface of the groove structure, and the first surface 401 is a portion of the surface of the body portion 410 surrounded by the groove structure. The height difference between the first surface 401 and the second surface 402 is a positive height difference. This example is basically the same as the example corresponding to the boss structure described above, and will not be elaborated here.

[0056] In some embodiments, adjacent electrode fingers 510 alternately overlap in a first direction to form an overlapping area, and in a second direction, the extension length of the first surface 401 is less than the extension length of the overlapping area, while in the first direction, the extension length of the first surface 401 is greater than the extension length of the overlapping area.

[0057] It is understandable that the second direction is the extension direction of the electrode finger 510, which is also the propagation direction of the bulk acoustic wave along the piezoelectric layer. Since the extension length of the first surface 401 in the second direction is less than that of the overlapping region, the effective area of ​​the piezoelectric layer corresponding to the first surface 401 precisely covers the core excitation segment of the overlapping region, rather than covering the entire length. This design can confine the alternating electric field to the piezoelectric layer region corresponding to the first surface 401, preventing the electric field from spreading to the non-core segments at both ends of the overlapping region. This constrains the bulk acoustic wave to resonate and propagate only within the second direction defined by the first surface 401, reducing the dissipation of bulk wave energy at the ends of the electrode finger 510 in the extension direction. At the same time, this dimensional relationship can weaken the edge electric field effect at the ends of the electrode finger 510, preventing stray electric fields at the ends from exciting non-resonant bulk wave clutter and improving the purity of the bulk wave resonance.

[0058] The first direction is the alternating interval direction of the electrode fingers 510, and also the electric field coupling direction of adjacent electrode fingers 510. Since the extension length of the first surface 401 in the first direction is greater than that of the overlapping area, the first surface 401 can completely cover the electric field coupling range of the overlapping area in the corresponding region of the body part 410, providing sufficient space for the piezoelectric material to act in the alternating electric field. This design can avoid the electric field "squeezing" effect caused by insufficient effective area of ​​piezoelectric material, ensure the uniformity of electric field distribution between adjacent electrode fingers 510, and thus make the intensity distribution of bulk acoustic waves in the first direction more stable. At the same time, the area of ​​the first surface 401 that extends beyond the overlapping area can serve as a buffer area for bulk waves, absorbing a small amount of stray bulk wave energy in the first direction, suppressing lateral crosstalk between adjacent excitation units, and improving the isolation when the device is arrayed.

[0059] Furthermore, the size and structure design of the first surface 401 and the overlapping area can also be adjusted by changing the ratio of the extension length of the first surface 401 in two directions, so as to flexibly control the resonance range and intensity distribution of the bulk wave and adapt to the application requirements of bulk acoustic wave devices with different frequencies and power levels.

[0060] In some embodiments, adjacent electrodes 510 alternately overlap in a first direction to form an overlapping area, and in a third direction, the vertical projection of the overlapping area lies within the vertical projection plane of the first electrode 300.

[0061] Understandably, in the third direction, since the vertical projection of the overlapping area lies within the vertical projection plane of the first electrode 300, the core excitation region of the alternating electric field formed by adjacent electrode fingers 510 in the second electrode 500 achieves complete spatial matching and coverage with the first electrode 300 in the thickness direction. This not only allows the alternating electric field in the overlapping area to form a complete closed loop within the first electrode 300, the first piezoelectric layer 400, and the overlapping area, preventing the electric field from leaking to the outside of the first piezoelectric layer 400 and improving the coupling efficiency between the electric field and the first piezoelectric layer 400, but also ensures the volume generated by the core excitation region. When the sound wave is reflected back and forth along the thickness direction, it is completely reflected back to the first piezoelectric layer 400 by the first electrode 300, which optimizes the bulk wave reflection path and improves the energy concentration. At the same time, it eliminates the basis for the generation of stray electric fields, suppressing the excitation of non-resonant clutter and the transverse crosstalk between adjacent excitation units from the source. The synergistic effect formed by the concentrated coupling of the electric field and the stable resonance of the bulk wave not only improves the conversion efficiency of electrical energy to mechanical energy, but also makes the key parameters of the device structure, such as the electromechanical coupling coefficient and resonant frequency, less affected by the external environment, thereby significantly enhancing the performance stability of the device structure under complex working conditions.

[0062] In some embodiments, such as Figure 6 and Figure 7 As shown, the bulk acoustic wave device structure also includes a substrate 100, a first piezoelectric layer 400 located on the substrate 100 and forming a cavity 101 between the first piezoelectric layer 400 and the substrate 100, and a first electrode 300 located on the surface of the first piezoelectric layer 400 exposed in the cavity 101.

[0063] It is understandable that, since the first piezoelectric layer 400 is located on the substrate 100 and forms a cavity 101 with the substrate 100, and the first electrode 300 is located on the surface of the first piezoelectric layer 400 exposed in the cavity 101, the bulk acoustic wave device achieves efficient isolation and confinement of bulk acoustic wave energy through the structural combination of the first piezoelectric layer 400 and the cavity 101, while optimizing the reflection and propagation path of the bulk wave.

[0064] Specifically, the cavity 101 structure utilizes the low acoustic impedance characteristics of air to block the conduction and leakage of bulk acoustic wave energy to the substrate 100, avoiding absorption or stray reflection of bulk wave energy by the substrate 100. This allows the bulk wave to propagate primarily within the resonant space formed by the first piezoelectric layer 400, the first electrode 300, and the second electrode 500, significantly improving the utilization rate of bulk wave energy. Simultaneously, the first electrode 300 is located on the surface of the first piezoelectric layer 400 within the cavity 101, eliminating the need for the bulk wave to penetrate the additional substrate 100 or adhesive layer when propagating towards the first electrode 300. This reduces dielectric loss during propagation and optimizes the reflection efficiency and resonant stability of the bulk wave. Furthermore, the cavity 101 eliminates the mechanical stress coupling between the substrate 100 and the first piezoelectric layer 400, reducing the impact of substrate 100 deformation on the piezoelectric layer lattice structure, thereby reducing the drift of the device's resonant frequency and improving the overall performance stability.

[0065] In another embodiment, such as Figures 3-5 As shown, the bulk acoustic wave device structure also includes a substrate 100 and a functional layer 200 located on the substrate 100. The functional layer 200 is located between the substrate 100 and the first piezoelectric layer 400. The first electrode 300 is embedded in the functional layer 200 on the side away from the substrate 100 and is in contact with the surface of the first piezoelectric layer 400 on the side close to the substrate 100.

[0066] It is understandable that, since the functional layer 200 is located between the substrate 100 and the first piezoelectric layer 400, and the first electrode 300 is embedded in the side of the functional layer 200 away from the substrate 100 and in contact with the surface of the first piezoelectric layer 400, the first electrode 300 is mechanically supported and fixed by the functional layer 200, avoiding the peeling and detachment problems that are prone to occur in traditional surface mount electrodes, and improving the stability of the contact between the electrode and the first piezoelectric layer 400 and the mechanical reliability of the device structure.

[0067] Furthermore, the functional layer 200 can form an acoustic buffer interface between the substrate 100 and the first piezoelectric layer 400 by selecting an acoustically impedance-matched material. This blocks the conduction and leakage of bulk acoustic wave energy to the substrate 100, reduces the absorption loss of bulk waves by the substrate 100, and optimizes the resonance efficiency of bulk waves within the piezoelectric layer. Simultaneously, the functional layer 200 can disperse the thermal and mechanical stresses between the substrate 100 and the first piezoelectric layer 400, preventing the deformation of the substrate 100 from being directly transmitted to the first piezoelectric layer 400 and causing lattice distortion, thereby suppressing the drift of the device's resonant frequency.

[0068] In some embodiments, such as Figure 8 As shown, the bulk acoustic wave device structure also includes a second piezoelectric layer 600, which is located on the side of the first piezoelectric layer 400 away from the second electrode 500, and the second electrode 500 is located on the side of the second piezoelectric layer 600 away from the first piezoelectric layer 400.

[0069] It is understandable that, since the second piezoelectric layer 600 is located on the side of the first piezoelectric layer 400 away from the second electrode 500, and the second electrode 500 is located on the side of the second piezoelectric layer 600 away from the first piezoelectric layer 400, the bulk acoustic wave device of this application forms a double piezoelectric layer stacked structure. The second electrode 500 and the double piezoelectric layer stacked structure achieve a layered coupling excitation mode, which not only enhances the coupling effect between the electric field and the piezoelectric material and improves the electromechanical coupling coefficient, but also forms a multi-interface reflection system through the interlayer interface of the double piezoelectric layers and the electrode surface, strengthening the ability to confine bulk acoustic wave energy and reducing bulk wave energy leakage. At the same time, by adjusting the material parameters and thickness ratio of the first piezoelectric layer 400 and the second piezoelectric layer 600, the resonant frequency and bandwidth range of the device structure can be flexibly adjusted, improving the adaptability of the device structure to different application scenarios. It can also weaken the stray electric field at the edge of the electrode finger 510, reduce the excitation of non-resonant clutter, and suppress lateral crosstalk between adjacent excitation units, enhancing the stability and purity of the device's frequency response. In addition, the double piezoelectric layer stack structure can disperse the stress concentration of a single piezoelectric layer and reduce the fatigue loss of the device during operation.

[0070] It should be noted that, Figure 8 The device structure corresponding to the second piezoelectric layer is only used as an example and should not be construed as a limitation of this application. That is to say, the second layer can also be applied to the bulk acoustic wave device structure in other embodiments.

[0071] Furthermore, the substrate 100 serves as the bottom mechanical support and stability support of the device structure, preventing device deformation and thermal drift. It is typically a non-piezoelectric material with high thermal conductivity and high stiffness to optimize the device's thermal management and acoustic performance. For example, the substrate 100 is a SiC high-velocity acoustic substrate.

[0072] The first electrode 300 and the second electrode 500 serve as electrode units constituting the acoustic device structure. They can be composed of high-density conductive metal or alloy materials, including but not limited to one of the metals such as titanium, chromium, copper, silver, aluminum, platinum, tungsten, and molybdenum, or their metal alloys. They can be single-layer metal films or stacked metal films with multiple metal layers.

[0073] The materials of the first piezoelectric layer 400 and the second piezoelectric layer 600 include, but are not limited to, one of the following materials with various cuts: LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz, zinc oxide (ZnO), and aluminum nitride (AlN). For example, the first piezoelectric layer 400 and the second piezoelectric layer 600 are preferably made of lithium niobate or lithium tantalate, which have excellent piezoelectric and electromechanical coupling effects and have been widely used in bulk acoustic wave device structures.

[0074] The material of functional layer 200 can be composed of a film layer with a relatively low sound velocity, so that the propagation speed of bulk sound waves in the second functional layer 200 is lower than the propagation speed in the first piezoelectric layer 400 or the second piezoelectric layer 600. Functional layer 200 includes, but is not limited to, materials primarily composed of silicon oxide, glass, silicon oxynitride, tantalum oxide, etc., or compounds obtained by adding fluorine, carbon, or boron to silicon oxide. Exemplarily, functional layer 200 preferably uses a silicon oxide film (SiO2). x Such as SiO2 film. The temperature coefficient of SiO2 is positive. This allows the functional layer 200 to interact with the first piezoelectric layer 400 or the second piezoelectric layer 600, and makes the TCF of the resonant unit close to 0, so that the device structure can have smaller frequency shift and more stable performance under high and low temperature operating conditions.

[0075] In some embodiments, such as Figure 2 As shown, the second electrode 500 can be an IDT electrode. The IDT electrode includes a first busbar 521 and a second busbar 522 spaced apart along a first direction. The electrode finger 510 includes a first electrode finger 511 and a second electrode finger 512. The first electrode finger 511 and the second electrode finger 512 each include an extension end and a connection end opposite to each other along a second direction. Specifically, the connection end of the first electrode finger 511 is connected to the first busbar 521, and its opposite extension end extends along the first direction towards the side closer to the second busbar, maintaining a distance from the second busbar 522. The connection end of the second electrode finger 512 is connected to the second busbar 522, and its opposite extension end extends along the first direction towards the side closer to the first busbar 521, maintaining a distance from the first busbar 521.

[0076] Furthermore, a plurality of dummy fingers 530 are also included between the extended ends of the first busbar 521 and the second electrode finger 512, and between the extended ends of the second busbar 522 and the first electrode finger 511, extending from one side of the first busbar 521 or the second busbar 522 along a first direction and maintaining a distance from each other. That is, each dummy finger 540 connected to the first busbar 521 corresponds one-to-one with each second electrode finger 512, and each dummy finger 530 connected to the second busbar 522 corresponds one-to-one with each first electrode finger 511.

[0077] In addition, the first piezoelectric layer 400 may also include a reflective grating 700, and the reflective grating 700 is disposed on both sides of the second electrode 500 along the first direction to limit the lateral diffusion of bulk acoustic waves, thereby preventing energy from being lost to the periphery of the device structure and thus improving the quality factor (Q value) of the device structure.

[0078] Furthermore, such as Figure 2 and Figure 8 As shown, by reasonably controlling the spacing width of the interval area formed between the dummy finger 530 and the electrode finger 510... d pore size of IDT electrode w (i.e., the length of the overlapping area in the second direction), the spacing width between the extended end of the first electrode finger 511 or the second electrode finger 512 and the edge of the adjacent first surface 401 along the second direction. a The distance between the pseudo-finger 530 and the extended end of the first electrode finger 511 or the second electrode finger 512 b Combined with the height difference between the first surface 401 and the second surface 402 hA and the extension length of the first surface 401 along the second direction l It can also adaptively adjust the propagation speed of bulk acoustic waves in the interval region, thereby effectively suppressing the transverse mode of the bulk acoustic wave device structure and improving the Q value of the bulk acoustic wave device.

[0079] As an example, the extension length of the first surface 401 along the second direction l Smaller than the aperture of the IDT electrode w The first electrode 300 is an Al metal electrode with a wavelength λ of 1050 nm, a metallization rate of 0.6, and a thickness of 50 nm; the second electrode 500 is a Mo metal electrode with a length range along the second direction of [missing information]. w~w+2a The height difference between the first surface 401 and the second surface 402 hA -25nm, pitch width a The spacing width is 0.5λ. b The spacing width is 0.5λ. d The extension length is 2λ. l for w-2a Therefore, this bulk acoustic wave device structure can achieve the following results under the excitation of an electrical signal: Figure 9 The resonance effect shown is compared to Figure 10 The resonance effect shown by conventional bulk acoustic wave device structures can be effectively suppressed by this application for transverse modes.

[0080] It should be noted that this application refers to the extension length of the first surface 401 along the second direction. l No specific limitations are required; for example, in other embodiments, such as... Figure 11 and Figure 12 As shown, the extension length of the first surface 401 along the second direction l It can also be equal to or greater than the aperture of the IDT electrode. w But no greater than w+2dThis allows for adaptive adjustment of the propagation speed of bulk acoustic waves in the spaced region, thereby effectively suppressing the transverse mode of the bulk acoustic wave device structure and improving the Q value of the bulk acoustic wave device.

[0081] According to a second aspect of this application, a bulk acoustic wave device is also provided, comprising the bulk acoustic wave device structure described in any of the above embodiments. The specific type of the bulk acoustic wave device includes, but is not limited to, any one of a bulk acoustic wave resonator and a bulk acoustic wave filter.

[0082] In summary, this application provides a bulk acoustic wave device structure and apparatus, including a first piezoelectric layer 400 having a body portion 410 and a plurality of mutually spaced protrusions 420, and a first electrode 300 and a second electrode 500 respectively disposed on opposite sides of the first piezoelectric layer 400; wherein, the first electrode 300 is located on the first side of the body portion 410, and the electrode fingers of the second electrode 500 extend along a second direction and are alternately arranged on the surface of the protrusions 420 along a first direction, and correspond one-to-one with the protrusions 420, which not only effectively constrains the propagation range of bulk acoustic waves in a local area within the first piezoelectric layer 400 and avoids the energy leakage problem caused by bulk acoustic wave diffusion, but also improves the energy density of bulk acoustic waves, thereby enhancing the frequency response sharpness and signal processing accuracy of the device structure.

[0083] Simultaneously, the vertical projection of the third-party upward electrode finger 510 falls within both the projection plane of the protrusion 420 and the projection range of the first electrode 300. This achieves precise regional matching between the electrode finger 510 and the protrusion 420, reducing the risk of crosstalk between electrodes, and ensures a concentrated and stable electric field distribution among the first electrode 300, the first piezoelectric layer 400, and the second electrode 500. This maximizes the coupling efficiency between the electric field and the piezoelectric layer, reduces electromechanical conversion losses, and improves the stability of the device's electrical performance.

[0084] Furthermore, this application, through the dual-limiting design of the projection range of the electrode finger 510, optimizes the synergistic configuration of the piezoelectric layer and the electrode, solving the problems of energy leakage, severe crosstalk, and low electromechanical conversion efficiency of traditional bulk acoustic wave devices from both aspects of bulk acoustic wave confinement and electric field coupling. This significantly improves the resonant performance and operational stability of the device, providing a new structural design concept for the research and development of high-frequency bulk acoustic wave devices in fields such as radio frequency communication and signal processing, and has important practical application value.

[0085] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A structure for a bulk acoustic wave device, characterized in that, include: The first piezoelectric layer includes a body portion and a plurality of mutually spaced protrusions, the body portion including a first side and a second side opposite to each other, and the protrusions being located on the second side of the body portion; The first electrode is located on the first piezoelectric layer and on the first side of the body portion; The second electrode, located on the first piezoelectric layer, includes a plurality of electrode fingers that are alternately spaced in a first direction and extend along a second direction; The electrode fingers are located on the protrusions, and each electrode finger corresponds one-to-one with each protrusion. In the third direction, the vertical projection of each electrode finger is located in the vertical projection plane of the corresponding protrusion, and the vertical projection of each electrode finger is located in the vertical projection plane of the first electrode; the first direction is orthogonal to the second direction, and the orthogonal plane is perpendicular to the third direction.

2. The bulk acoustic wave device structure according to claim 1, characterized in that, The second side of the body portion includes a first surface and a second surface surrounding the first surface, and in the third direction, the first surface and the second surface have a height difference, and the vertical projection of each of the electrode fingers extending along the second direction is at least partially located on the first surface.

3. The bulk acoustic wave device structure according to claim 2, characterized in that, The height difference between the first surface and the second surface in the third direction is less than the thickness of the electrode finger.

4. The bulk acoustic wave device structure according to claim 3, characterized in that, The second side of the main body also includes a boss structure, the first surface is the top surface of the boss structure, the second surface is a portion of the main body surface surrounding the boss structure, and the height difference between the first surface and the second surface is a positive height difference.

5. The bulk acoustic wave device structure according to claim 3, characterized in that, The second side of the body portion includes a groove structure, the first surface is the bottom surface of the groove structure, the second surface is a portion of the body portion surrounding the groove structure, and the height difference between the first surface and the second surface is a negative height difference.

6. The bulk acoustic wave device structure according to claim 3, characterized in that, The second side of the body portion includes a groove structure, the second surface is the bottom surface of the groove structure, the first surface is a portion of the body portion surrounded by the groove structure, and the height difference between the first surface and the second surface is a negative height difference.

7. The bulk acoustic wave device structure according to claim 3, characterized in that, Adjacent electrodes are alternately overlapped in the first direction to form an overlap area; in the second direction, the extension length of the first surface is less than the extension length of the overlap area, and in the first direction, the extension length of the first surface is greater than the extension length of the overlap area.

8. The bulk acoustic wave device structure according to claim 3, characterized in that, Adjacent electrodes are alternately overlapped in the first direction to form an overlapping area; in the second direction, the extension length of the first surface is not less than the extension length of the overlapping area, and in the first direction, the extension length of the first surface is greater than the extension length of the overlapping area.

9. The bulk acoustic wave device structure according to claim 3, characterized in that, Adjacent electrodes are alternately overlapped in the first direction to form an overlapping area; in the third direction, the vertical projection of the overlapping area lies within the vertical projection plane of the first electrode.

10. The bulk acoustic wave device structure according to claim 1, characterized in that, The bulk acoustic wave device structure further includes a second piezoelectric layer, which is located on the side of the first piezoelectric layer away from the second electrode, and the second electrode is located on the side of the second piezoelectric layer away from the first piezoelectric layer.

11. The bulk acoustic wave device structure according to claim 1, characterized in that, The bulk acoustic wave device structure further includes a substrate and a functional layer located on the substrate. The functional layer is located between the substrate and the first piezoelectric layer. The first electrode is embedded in the functional layer on the side away from the substrate and is in contact with the surface of the first piezoelectric layer on the side closer to the substrate.

12. The bulk acoustic wave device structure according to claim 1, characterized in that, The bulk acoustic wave device structure further includes a substrate, the first piezoelectric layer is located on the substrate and forms a cavity between the first piezoelectric layer and the substrate, and the first electrode is located on the surface of the first piezoelectric layer exposed in the cavity.

13. The bulk acoustic wave device structure according to claim 1, characterized in that, The bulk acoustic wave device structure further includes a reflective gate electrode, which is formed on the first piezoelectric layer and spaced apart on both sides of the second electrode along the first direction.

14. The bulk acoustic wave device structure according to claim 1, characterized in that, The second electrode also includes a plurality of dummy fingers that extend along the second direction and maintain a distance from the electrode fingers in the second direction, and each dummy finger corresponds one-to-one with each electrode finger.

15. A bulk acoustic wave device, characterized in that, The bulk acoustic wave device includes the bulk acoustic wave device structure as described in any one of claims 1 to 14.

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