Acoustic resonator, method of manufacturing an acoustic resonator, and filter

Abstract

The application relates to the technical field of semiconductors, in particular to an acoustic resonator, a preparation method of the acoustic resonator and a filter. The acoustic resonator comprises: a piezoelectric structure; an interdigital transducer layer comprising an interdigital transducer, located on the surface of one side of the piezoelectric structure; the interdigital transducer comprises a first bus bar and a second bus bar oppositely arranged in a first direction, a first electrode finger strip connected to the first bus bar and a second electrode finger strip connected to the second bus bar; a first passivation layer is located on the surface of the side of the interdigital transducer layer away from the piezoelectric structure; a dielectric layer is located on the surface of the side of the first passivation layer away from the piezoelectric structure; the dielectric layer comprises a first dielectric strip and a second dielectric strip, the first dielectric strip is close to the end region of the first electrode finger strip, and the second dielectric strip is close to the end region of the second electrode finger strip; and a second passivation layer is located on the surface of the side of the dielectric layer away from the piezoelectric structure, covers the dielectric layer and extends to cover the first passivation layer. The application can inhibit a transverse stray acoustic mode.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to an acoustic resonator, a method for fabricating the acoustic resonator, and a filter. Background Technology

[0002] Interdigital transducers (IDTs) can convert between sound and electricity. Therefore, they are often used to build resonators for frequency selection, signal processing, and other applications.

[0003] Compared with traditional substrates, piezoelectric thin film substrates based on insulators have attracted much attention due to their superior electromechanical coupling coefficient, significantly reduced acoustic loss, better temperature stability, stronger power reliability and higher sound wave propagation speed, making piezoelectric thin film substrates on insulators more popular.

[0004] However, resonators fabricated using piezoelectric thin film substrates on insulators exhibit stray acoustic modes, which can affect various core performance characteristics of filters, such as frequency response. Summary of the Invention

[0005] Therefore, it is necessary to provide an acoustic resonator that can reduce stray acoustic modes, a method for fabricating the acoustic resonator, and a filter to address the aforementioned technical problems.

[0006] In a first aspect, this application provides an acoustic resonator, comprising:

[0007] piezoelectric structure;

[0008] An interdigitated transducer layer, including an interdigitated transducer, is located on one side of the piezoelectric structure; the interdigitated transducer includes a first busbar and a second busbar disposed opposite each other in a first direction, a first electrode finger connected to the first busbar, and a second electrode finger connected to the second busbar;

[0009] A first passivation layer is located on the surface of the interdigital transducer layer on the side away from the piezoelectric structure and extends to cover the piezoelectric structure;

[0010] A dielectric layer is located on the surface of the first passivation layer away from the piezoelectric structure; the dielectric layer includes a first dielectric strip and a second dielectric strip, the first dielectric strip being close to the end region of the first electrode finger strip, and the second dielectric strip being close to the end region of the second electrode finger strip;

[0011] The second passivation layer is located on the surface of the dielectric layer away from the piezoelectric structure, and covers the dielectric layer and extends to cover the first passivation layer.

[0012] In one embodiment, the first busbar and the second busbar extend along a second direction, respectively;

[0013] The length extension direction of the first medium strip is the same as that of the second medium strip, and parallel to the length extension direction of the first busbar.

[0014] In one embodiment, the orthographic projection of the first dielectric strip onto the piezoelectric structure and the orthographic projection of the first busbar onto the piezoelectric structure do not overlap.

[0015] The orthographic projection of the second dielectric strip onto the piezoelectric structure has no overlap with the orthographic projection of the second busbar onto the piezoelectric structure.

[0016] In one embodiment, the orthographic projection of the first dielectric strip onto the piezoelectric structure and the orthographic projection of the second busbar onto the piezoelectric structure do not overlap.

[0017] The orthographic projection of the second dielectric strip onto the piezoelectric structure has no overlap with the orthographic projection of the first busbar onto the piezoelectric structure.

[0018] In one embodiment, the first busbar has a first end and a second end along the second direction; the interdigitated transducer layer further includes a reflector located at the first end and / or the second end.

[0019] In one embodiment, the orthographic projections of the first dielectric strip and the second dielectric strip onto the piezoelectric structure overlap with the orthographic projections of the reflector onto the piezoelectric structure.

[0020] In one embodiment, the first dielectric strip and the second dielectric strip extend along the second direction to cover the entire interdigital transducer layer region.

[0021] In one embodiment, the length of the dielectric layer in the second direction is less than the length of the piezoelectric structure in the second direction;

[0022] The width of the dielectric layer in the first direction is equal to the width of the piezoelectric structure in the first direction.

[0023] In one embodiment, the contact connection surface between the first passivation layer and the interdigitated transducer layer divides the first dielectric strip into a first dielectric strip portion and a first dielectric extension portion, and divides the second dielectric strip into a second dielectric strip portion and a second dielectric extension portion, wherein the contact connection surface is parallel to the first direction and the second direction, respectively.

[0024] In one embodiment, the first medium extension portion and the second medium extension portion are spaced apart.

[0025] In one embodiment, the first medium extension portion is connected to the second medium extension portion.

[0026] In one embodiment, the second passivation layer includes:

[0027] The first passivation sub-part is parallel to the first direction and the second direction, respectively;

[0028] The second passivation sub-part is parallel to the first direction and the second direction, respectively;

[0029] The third passivation sub-part is connected to the first passivation sub-part and the second passivation sub-part, respectively;

[0030] The width of the third passivation sub-part gradually decreases in the direction away from the second passivation sub-part, wherein the cross-section is perpendicular to the contact surface between the interdigital transducer layer and the piezoelectric structure and parallel to the second direction.

[0031] In one embodiment, the widths of the first dielectric strip and the second dielectric strip both exhibit linear, nonlinear, or step-like variations along the first direction;

[0032] and / or;

[0033] The lengths of both the first and second dielectric strips exhibit linear, nonlinear, or step-like changes along the second direction.

[0034] In one embodiment, it further includes:

[0035] The third passivation layer is located on the surface of the second passivation layer away from the piezoelectric structure and completely covers the second passivation layer.

[0036] In one embodiment, the materials of the first passivation layer, the dielectric layer, and the second passivation layer are at least one of silicon nitride, silicon dioxide, tetraethyl orthosilicate, aluminum nitride, hafnium oxide, tungsten oxide, silicon carbide, tantalum pentoxide, benzocyclobutene, or parylene, and the material of the dielectric layer is different from the material of the first passivation layer.

[0037] In one embodiment, the thickness of the dielectric strip ranges from 10 to 200 nm.

[0038] In one embodiment, the width of the dielectric strip along the first direction ranges from 300 to 5000 nm.

[0039] Secondly, this application provides a method for fabricating an acoustic resonator, comprising:

[0040] A piezoelectric structure is provided, and an interdigitated transducer layer is formed on the surface of one side of the piezoelectric structure. The interdigitated transducer layer includes an interdigitated transducer, and the interdigitated transducer includes a first electrode finger and a second electrode finger.

[0041] A first passivation layer is formed on the surface of the interdigital transducer layer on the side away from the piezoelectric structure;

[0042] A dielectric layer is formed on the surface of the first passivation layer away from the piezoelectric structure;

[0043] The dielectric layer is etched to form a first dielectric strip and a second dielectric strip, such that the first dielectric strip is close to the end region of the first electrode finger and the second dielectric strip is close to the end region of the second electrode finger;

[0044] A second passivation layer is formed on the surface of the dielectric layer away from the piezoelectric structure, such that the second passivation layer covers the dielectric layer and extends to cover the first passivation layer.

[0045] In one embodiment, the dielectric layer includes a first dielectric sublayer and a second dielectric sublayer spaced apart; the interdigital transducer includes a first busbar and a second busbar; the orthographic projection of the first dielectric sublayer on the piezoelectric structure and the orthographic projection of the second busbar on the piezoelectric structure have no overlapping portions, and the orthographic projection of the second dielectric sublayer on the piezoelectric structure and the orthographic projection of the first busbar on the piezoelectric structure have no overlapping portions;

[0046] The formation processes of the first dielectric strip and the second dielectric strip include:

[0047] The first dielectric sublayer is etched to form the first dielectric strip;

[0048] The second dielectric sublayer is etched to form the second dielectric strip.

[0049] Thirdly, this application provides a filter, including the acoustic resonator described above, or an acoustic resonator prepared by the preparation method described above.

[0050] The aforementioned acoustic resonator includes a piezoelectric structure, an interdigital transducer layer, a first passivation layer, a dielectric layer, and a second passivation layer. The dielectric layer includes a first dielectric strip and a second dielectric strip, with a dielectric strip formed on the end regions of the two electrode strips of the interdigital transducer, which can effectively reduce lateral stray modes. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is one of the structural block diagrams of an acoustic resonator in one embodiment;

[0053] Figure 2 This is one of the top view schematic diagrams of the acoustic resonator in one embodiment;

[0054] Figure 3 This is a second top view of the acoustic resonator in one embodiment;

[0055] Figure 4 This is a top view of the acoustic resonator in one embodiment, shown as diagram three.

[0056] Figure 5 This is one of the cross-sectional structural schematic diagrams of an acoustic resonator in one embodiment;

[0057] Figure 6 This is a second cross-sectional structural schematic diagram of an acoustic resonator in one embodiment;

[0058] Figure 7 This is a top view of the acoustic resonator in one embodiment, shown as diagram four.

[0059] Figure 8 This is the fifth top view schematic diagram of the acoustic resonator in one embodiment;

[0060] Figure 9 This is a top view of the acoustic resonator in one embodiment, shown as diagram six.

[0061] Figure 10 This is the seventh top view schematic diagram of the acoustic resonator in one embodiment;

[0062] Figure 11 This is the eighth top view of the acoustic resonator in one embodiment;

[0063] Figure 12 This is a top view of the acoustic resonator in one embodiment, diagram number nine.

[0064] Figure 13 This is a third cross-sectional structural schematic diagram of an acoustic resonator in one embodiment;

[0065] Figure 14 This is a fourth cross-sectional structural schematic diagram of an acoustic resonator in one embodiment;

[0066] Figure 15 This is the fifth cross-sectional structural schematic diagram of an acoustic resonator in one embodiment;

[0067] Figure 16 This is a sixth cross-sectional structural schematic diagram of an acoustic resonator in one embodiment;

[0068] Figure 17 This is a top view of the acoustic resonator in one embodiment, shown as diagram number ten.

[0069] Figure 18 This is eleventh of the top view schematic diagrams of the acoustic resonator in one embodiment;

[0070] Figure 19 This is 12, a top view of the acoustic resonator in one embodiment;

[0071] Figure 20 This is thirteenth of a top view schematic diagram of the acoustic resonator in one embodiment;

[0072] Figure 21 This is the fourteenth top view schematic diagram of the acoustic resonator in one embodiment;

[0073] Figure 22 A comparison of admittance-frequency response curves for acoustic resonators with and without integrated dielectric stripes in one embodiment;

[0074] Figure 23 This is one of the flowcharts illustrating the fabrication method of an acoustic resonator in one embodiment;

[0075] Figure 24 This is a second schematic flowchart of the method for fabricating an acoustic resonator in one embodiment;

[0076] Figure 25 This is the third flowchart illustrating the fabrication method of the acoustic resonator in one embodiment;

[0077] Figure 26 This is a schematic flowchart of the fabrication method of the acoustic resonator in one embodiment;

[0078] Figure 27 This is a top view of the acoustic resonator in one embodiment, shown as schematic diagram number fifteen. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0080] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another 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, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0081] It should be noted that when an element is referred to as being "set on" or "located" in relation to another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. Unless otherwise expressly specified and limited, the terms "mounted," "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0082] It should be noted that, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0083] Generally, piezoelectric on insulator (POI) films are an ideal platform for high-performance surface acoustic wave (SAW) devices due to their numerous advantages. Despite these advantages, SAW resonators fabricated using POI substrates are still affected by stray acoustic modes, including bulk acoustic modes and transverse acoustic modes.

[0084] Bulk acoustic modes typically affect out-of-band far-end suppression characteristics, potentially impacting the performance of techniques such as carrier aggregation. In contrast, transverse modes appear within or near the passband, directly affecting the filter's frequency response characteristics by introducing ripple or degrading adjacent-band suppression. Therefore, suppressing transverse spurious acoustic modes is crucial for maintaining the core performance indicators of filters. Transverse spurious acoustic modes are particularly prominent in low-loss devices such as POI substrate surface acoustic wave resonators. Currently, to reduce ohmic and insertion losses, more and more acoustic resonators are employing narrow-aperture structures, which generate stronger transverse spurious modes, making them more difficult to suppress. To suppress spurious acoustic modes in acoustic devices (including SAW (Surface Acoustic Wave) filters), various techniques have been developed. The following analyzes existing methods for suppressing transverse spurious modes in acoustic resonators:

[0085] The first method involves interfering with the formation of transverse stray acoustic modes. For example, this can be achieved by altering the overlap length or finger length of the IDT fingers in the aperture direction to disrupt the coherence of stray modes. While this suppresses unwanted stray acoustic modes, it leads to a decrease in the quality factor of desired resonant modes, reduced power reliability, and decreased capacitance density. Alternatively, non-driven additional fingers can be placed at the resonator edges to interfere with the excitation and propagation of stray modes, but this has limited suppression effects and reduces layout utilization.

[0086] The second approach involves flattening the lateral dispersion curve. For example, by optimizing the stacking structure of the substrate material layers and metallization layers, the lateral dispersion curve can be flattened, effectively suppressing lateral stray modes. However, this method has multiple design constraints: the stacked structure must operate normally within the target frequency band, maintain a high electromechanical coupling coefficient, and minimize bulk acoustic wave radiation loss. These limitations often make it difficult to implement schemes that suppress stray modes through stacking adjustments. Alternatively, lateral mode coupling can be reduced by introducing a lateral offset between the relative IDT fingers to change the acoustic wave propagation angle. While tilted layouts are effective in most cases, they can lead to structural asymmetry, potentially reducing the dominant mode quality factor and decreasing area utilization.

[0087] Thirdly, for example, strong acoustic boundaries can be constructed by etching cavity structures in a piezoelectric substrate. This technique can suppress stray acoustic modes, but the need to etch on brittle piezoelectric materials significantly increases process complexity. This limitation restricts the scalability and cost-effectiveness of this technique in large-scale mass production.

[0088] In summary, while many existing solutions have shown some effectiveness in suppressing lateral stray acoustic modes, these techniques often come with additional problems such as increased acoustic loss, higher design complexity, or more complex manufacturing processes. Therefore, there is an urgent need for a method that can effectively suppress stray acoustic modes while being compatible with the manufacturing processes of acoustic devices based on standard interdigital transducers.

[0089] In view of this, in order to solve the above problems, this application proposes an acoustic resonator, a method for fabricating the acoustic resonator, and a filter.

[0090] The acoustic resonator, its fabrication method, and filter according to embodiments of this application are described below with reference to the accompanying drawings.

[0091] Figure 1 This is one of the structural schematic diagrams of an acoustic resonator provided in an embodiment of this application. (Reference) Figure 1 This application provides an acoustic resonator, which may include a piezoelectric structure 100, an interdigital transducer layer 200, a first passivation layer 300, a dielectric layer 400, and a second passivation layer 500.

[0092] In some embodiments, the piezoelectric structure 100 is a stacked structure, which may include a silicon layer 110, a polysilicon layer 120, a silicon dioxide layer 130, and a piezoelectric layer 140 stacked sequentially. The silicon layer 110 serves as support and a process carrier; the polysilicon layer 120 serves as structural support and electrical adaptation; and the silicon dioxide layer 130 serves as acoustic isolation and stress modulation. Optionally, the thickness of the silicon layer 110 can be 675 μm, but other ranges are not limited here; the thickness of the polysilicon layer 120 can be 1000 nm, but other ranges are not limited here; and the thickness of the silicon dioxide layer 130 can be 500 nm, but other ranges are not limited here.

[0093] Interdigitated transducer layer 200 is located on one side of the piezoelectric structure 100. Interdigitated transducer layer 200 includes interdigitated transducers 210. It is understood that interdigitated transducer layer 200 is located on the surface of piezoelectric layer 140 in piezoelectric structure 100 to enable synergy between interdigitated transducer layer 200 and piezoelectric layer 140.

[0094] In one embodiment, Figure 2 A top view of an interdigital transducer 210 on a piezoelectric structure 100 is shown, the interdigital transducer 210 including a first direction (e.g., Figure 2The interdigitated transducer 210 comprises a first busbar 211 and a second busbar 212 arranged opposite each other along the X-axis direction, a first electrode finger 213 connected to the first busbar 211, and a second electrode finger 214 connected to the second busbar 212. Optionally, the thickness of the interdigitated transducer 210 can be 180 nm, but it can also be in other ranges, depending on the actual application scenario. It is understood that the materials of the first busbar 211, the second busbar 212, the first electrode finger 213, and the second electrode finger 214 can be the same or different, and there is no restriction on this.

[0095] In some embodiments, the structure of the first electrode finger 213, the second electrode finger 214, the first bus bar 211, and / or the second bus bar 212 may be a stacked structure. Exemplarily, this stacked structure may include a bottom titanium (Ti) layer, a copper (Cu) layer, an aluminum-copper alloy layer (AlCu), and a top titanium (Ti) layer stacked sequentially. The number of first electrode fingers 213 and second electrode fingers 214 is not limited here; for example, it can be 451 pairs of electrode fingers (one first electrode finger 213 and one opposite second electrode finger 214 form a pair of electrode fingers). Optionally, the spacing between adjacent electrode fingers can be 1020 nm, and the metallization coverage is 50%. Other spacings and coverage rates are also possible and are not limited here.

[0096] The first passivation layer 300 is located on the surface of the interdigital transducer layer 200 away from the piezoelectric structure 100 and extends to cover the piezoelectric structure 100. The first passivation layer 300 forms a protective layer on the interdigital transducer layer 200 to prevent performance degradation of the metal layer during subsequent processes, thereby avoiding instability and long-term reliability of the device under high power. Simultaneously, it effectively prevents damage to the interdigital transducer 210 during subsequent etching of the dielectric layer 400, thus preventing impact on the resonator's performance. Understandably, since the orthographic projection of the interdigital transducer layer 200 onto the piezoelectric structure 100 does not completely cover the surface of the piezoelectric structure 100, the first passivation layer 300, while covering the interdigital transducer layer 200, also extends to cover a portion of the piezoelectric structure 100 not covered by the interdigital transducer layer 200.

[0097] The dielectric layer 400 is located on the surface of the first passivation layer 300 away from the piezoelectric structure 100; the dielectric layer 400 includes a first dielectric strip 410 and a second dielectric strip 420, such as... Figure 2 As shown, the first dielectric strip 410 is located near the end region of the first electrode finger 213 (e.g., Figure 2 The first end region 201 shown), the second dielectric strip 420 near the end region of the second electrode finger 214 (as shown) Figure 2 The second end region 202 shown). The end region of the first electrode finger strip 213 (as shown). Figure 2 The first end region 201 shown) and the end region of the second electrode finger strip 214 (as shown) Figure 2 The second end region 202 shown is a key location where stray acoustic modes are generated due to boundary reflections and acoustic discontinuities. By precisely patterning the dielectric strip, the acoustic impedance of the target region can be locally controlled, making the modal shape more uniform (exhibiting piston-like vibration characteristics), thereby effectively attenuating unnecessary transverse stray modes and achieving the purpose of suppressing stray acoustic modes. The dielectric strip is deposited above the interdigital transducer 210 (i.e., from the surface of the piezoelectric structure 100 towards the piezoelectric layer 140, along a direction away from the piezoelectric structure 100 and perpendicular to the surface of the piezoelectric structure 100) to achieve a passivation effect. If the dielectric layer 400 is deposited below the interdigital transducer 210, the passivation effect cannot be achieved.

[0098] Optionally, the material of the first dielectric strip 410 and / or the second dielectric strip 420 may be at least one of silicon nitride, silicon dioxide, aluminum nitride, hafnium oxide, tantalum pentoxide, benzocyclobutene or parylene, and of course other materials may also be used, which are not limited here.

[0099] Optionally, the thickness of the dielectric layer 400 (including the first dielectric strip 410 and the second dielectric strip 420) can be in the range of 10nm to 200nm, or other ranges, which are not limited here.

[0100] Optionally, such as Figure 3 As shown, the widths of the first dielectric strip 410 and the second dielectric strip 420 along the aforementioned first direction (X-axis direction) are (e.g.) Figure 3 The width L of the second medium strip 420 k1 The range can be 300nm~5000nm, and of course, other ranges are also possible, which are not restricted here.

[0101] Optionally, the width of the first dielectric strip 410 and / or the second dielectric strip 420 is 2040 nm and the thickness is 90 nm.

[0102] Optionally, the first dielectric strip 410 and / or the second dielectric strip 420 can be a laminated structure. Of course, this is not a limitation and depends on the actual situation.

[0103] Optionally, the first dielectric strip 410 and the second dielectric strip 420 extend along the second direction to cover the entire interdigital transducer layer 200 region. The second direction is perpendicular to and parallel to the first direction and the interdigital transducer layer 200, for example... Figure 2 The Y-axis direction in the diagram.

[0104] Understandably, since the overall area of ​​the dielectric layer 400 is smaller than the area of ​​the first passivation layer 300, in the top view (not shown) from the dielectric layer 400 toward the first passivation layer 300, in addition to the orthographic projection of the dielectric layer 400 onto the first passivation layer 300, there is also an exposed first passivation layer 300. Therefore, "extended coverage" means that the second passivation layer 500 covers not only the dielectric layer 400 but also the aforementioned exposed first passivation layer 300. Please refer to [reference needed]. Figures 4 to 6 , Figure 5 Show Figure 4 One of the side cross-sectional views of the portion cut along line AA' (e.g., parallel to the second direction). Since there is no first dielectric strip 410 and second dielectric strip 420 at the position of line AA', the first passivation layer 300 is exposed, so that the second passivation layer 500 directly covers the surface of the first passivation layer 300. Figure 6 It shows Figure 4 One of the side cross-sectional views of the portion cut along line BB' (e.g., parallel to the second direction), where the second passivation layer 500 covers the dielectric strip due to the presence of a first dielectric strip 410 or a second dielectric strip 420 at the position of line BB'.

[0105] Optionally, the length of the dielectric layer 400 in the second direction is less than the length of the piezoelectric structure 100 in the second direction (i.e., the length of the surface of the piezoelectric layer 140 in the piezoelectric structure 100).

[0106] Optionally, the length of the first dielectric strip 410 and / or the second dielectric strip 420 covers the entire aperture area.

[0107] Optionally, the width of the dielectric layer 400 in the first direction is smaller than the width of the piezoelectric structure 100 in the first direction.

[0108] Optionally, the widths of the first dielectric strip 410 and the second dielectric strip 420 both exhibit linear, nonlinear, or step-like variations along the aforementioned first direction. For example, rectangular... Figures 7-8 Trapezoids in Figures 9-10 Curved surfaces, etc.

[0109] Optionally, the lengths of the first dielectric strip 410 and the second dielectric strip 420 both exhibit linear, nonlinear, or step-like variations along the second direction. For example, Figures 11 to 12 The first dielectric strip 410 and the second dielectric strip 420 in the middle.

[0110] Optionally, the widths of the first dielectric strip 410 and the second dielectric strip 420 both exhibit linear, nonlinear, or step-like variations along the aforementioned first direction. For example, rectangular... Figures 7-8 Trapezoids in Figures 9-10The curved surface, etc. Furthermore, the lengths of the first dielectric strip 410 and the second dielectric strip 420 both exhibit linear, nonlinear, or step-like changes along the second direction. For example, Figures 11 to 12 The first dielectric strip 410 and the second dielectric strip 420 in the middle.

[0111] It is understandable that the shape and size of the first dielectric strip 410 and the second dielectric strip 420 may be the same or different, and there are no restrictions here.

[0112] In some embodiments, such as Figures 13-14 As shown, the contact surface between the first passivation layer 300 and the interdigitated transducer layer 200 divides the first dielectric strip 410 into a first dielectric strip portion 411 and a first dielectric extension portion 412, and divides the second dielectric strip 420 into a second dielectric strip portion 421 and a second dielectric extension portion 422, wherein the contact surface is respectively connected to the first direction (e.g., Figure 3 (in the X direction) and the second direction (such as) Figure 3 (The Y direction in the middle) is parallel.

[0113] Understandably, such as Figure 13 The straight line CC' divides the first dielectric strip 410 into a first dielectric strip portion 411 and a first dielectric extension portion 412 along the contact connection surface; as shown... Figure 14 The straight line DD' divides the second dielectric strip 420 into a second dielectric strip portion 421 and a second dielectric extension portion 422 along the contact connection surface.

[0114] Understandably, please combine Figure 3 , Figure 13 and Figure 14 Because the interdigital transducer layer 200 has a concave-convex structure, the first passivation layer 300 also has a concave-convex structure. Therefore, the first dielectric extension portion 412 extends from the protruding portion of the first passivation layer 300 to the concave portion (e.g., the concave portion between two adjacent first electrode fingers 213 and second electrode fingers 214), and the second dielectric extension portion 422 also extends from the protruding portion of the first passivation layer 300 to the concave portion. The extension directions include a first direction and a second direction. In the first direction, the first dielectric extension portion 412 and the second dielectric extension portion 422 may be connected or not connected to the concave portion of the first passivation layer 300. Therefore, the following two optional structures are given.

[0115] Optionally, the first medium extension portion 412 and the second medium extension portion 422 are spaced apart.

[0116] Optionally, the first medium extension portion 412 is connected to the second medium extension portion 422.

[0117] In some embodiments, the structure of the dielectric layer 400 includes two types; please refer to [reference needed]. Figure 4 The first type, in Figure 4 In the cross-section along line AA', neither the first dielectric strip 410 nor the second dielectric strip 420 has an extended portion (e.g., Figure 5 (as shown); the second type, such as Figure 15 As shown, in Figure 4 In the cross section along the straight line AA', both the first dielectric strip 410 and the second dielectric strip 420 have extended portions.

[0118] In some embodiments, the second passivation layer 500 includes a first passivation sub-part 510, a second passivation sub-part 520, and a third passivation sub-part 530. Figure 16 for Figure 4 One of the side cross-sectional views is taken along line BB' (e.g., parallel to the second direction). In this side cross-sectional view, the second passivation layer 500 is divided into a first passivation sub-part 510, a second passivation sub-part 520, and a third passivation sub-part 530 along lines EE', FF', and GG'. The first passivation sub-part 510 is parallel to both the first and second directions. The second passivation sub-part 520 is also parallel to both the first and second directions. The third passivation sub-part 530 connects the first passivation sub-part 510 and the second passivation sub-part 520.

[0119] Understandably, in the side sectional view, the waist structure of the interdigital transducer layer 200, the first passivation layer 300, the dielectric layer 400, and the second passivation layer 500 may not be perpendicular to the contact surface between the interdigital transducer layer 200 and the piezoelectric structure 100.

[0120] Optionally, in Figure 4 In the side cross-sectional view along BB', the width of the third passivation sub-section 530 can gradually change, which is beneficial for suppressing mismodes in the resonator. Specifically, the width of the third passivation sub-section 530 gradually decreases in the direction away from the second passivation sub-section 520. The cross-section (e.g., plane FF' or plane GG') is perpendicular to the contact surface between the interdigital transducer layer 200 and the piezoelectric structure 100, and the cross-section is parallel to the second direction.

[0121] Optionally, in Figure 4In the side cross-sectional view along AA', the width of the third passivation sub-section 530 can gradually change, which is beneficial for suppressing mismodes in the resonator. Specifically, the width of the third passivation sub-section 530 gradually decreases in the direction away from the second passivation sub-section 520. The cross-section is perpendicular to the contact surface between the interdigital transducer layer 200 and the piezoelectric structure 100, and parallel to the second direction. Furthermore, in the side cross-sectional view along line AA', both the first dielectric strip 410 and the second dielectric strip 420 have extended portions. (This can be seen in the side cross-sectional view along line AA' (refer to reference)). Figure 15 and Figure 16 In the second passivation layer 500, the second passivation layer 500 is divided into a first passivation sub-part 510, a second passivation sub-part 520 and a third passivation sub-part 530. The width of the third passivation sub-part 530 in the cross section gradually decreases in the direction away from the second passivation sub-part 520.

[0122] In some embodiments, the first busbar 211 and the second busbar 212 are respectively along a second direction (e.g., Figure 2 It extends along the Y-axis direction. It is understood that the X-axis and Y-axis directions mentioned above are not one direction but rather... Figure 2 The X and Y axes point in the direction of the axis and the opposite direction of the axis.

[0123] Optionally, the length extension direction of the first dielectric strip 410 is the same as the length extension direction of the second dielectric strip 420, and parallel to the length extension direction of the first busbar 211.

[0124] Optionally, the orthographic projection of the first dielectric strip 410 onto the piezoelectric structure 100 does not overlap with the orthographic projection of the first busbar 211 onto the piezoelectric structure 100. Furthermore, the orthographic projection of the second dielectric strip 420 onto the piezoelectric structure 100 does not overlap with the orthographic projection of the second busbar 212 onto the piezoelectric structure 100. Exemplarily, as... Figure 17 As shown, the first dielectric strip 410 faces the first busbar 211, and the distance between the first dielectric strip 410 and the first busbar 211 is L1, then L1 > 0. The second dielectric strip 420 faces the second busbar 212, and the distance between the second dielectric strip 420 and the second busbar 212 is L2, then L2 > 0.

[0125] Optionally, the orthographic projection of the first dielectric strip 410 onto the piezoelectric structure 100 does not overlap with the orthographic projection of the second busbar 212 onto the piezoelectric structure 100, and the orthographic projection of the second dielectric strip 420 onto the piezoelectric structure 100 does not overlap with the orthographic projection of the first busbar 211 onto the piezoelectric structure 100. Exemplarily, as... Figure 18As shown, the first dielectric strip 410 faces the second busbar 212, and the distance between the first dielectric strip 410 and the second busbar 212 is L3, so L3 > 0. The second dielectric strip 420 faces the first busbar 211, and the distance between the second dielectric strip 420 and the first busbar 211 is L4, so L4 > 0. Preferably, the distance between the end of the first electrode finger 213 and the second busbar 212 is L5, and the distance between the end of the second electrode finger 214 and the first busbar 211 is L6, so L5 = L3, L6 = L4.

[0126] Optionally, such as Figure 19 As shown, the offset range L7 between the first dielectric strip 410 and the end of the first electrode finger 213 is 0~500nm; the offset range L8 between the second dielectric strip 420 and the end of the second electrode finger 214 is 0~500nm. It can be understood that the offset direction of the finger end is either the X-axis direction or the opposite direction.

[0127] In some embodiments, the first busbar 211 has a first end and a second end along a second direction, and the interdigital transducer layer 200 further includes a reflector located at the first end and / or the second end. The reflector is used to enhance the reflection and confinement of sound waves, thereby improving the device's resonance characteristics, energy efficiency, and frequency stability.

[0128] In some embodiments, the interdigitated transducer layer 200 includes a first reflector and a second reflector. The first reflector is located at a first end of the first busbar 211 along a second direction, and the second reflector is located at a second end of the first busbar 211 along the second direction. Optionally, the first and second reflectors can have identical structures, and the number of gratings in the first and second reflectors is not limited; for example, it can be three or four, etc. Figure 20 As shown, the first reflector 220 and the second reflector 230 are located at the two ends of the first busbar 211 along the second direction, and the number of grids of the first reflector and the second reflector in the figure is 3 each.

[0129] Optionally, the orthographic projections of the first dielectric strip 410 and the second dielectric strip 420 onto the piezoelectric structure 100 overlap with the orthographic projections of the reflector onto the piezoelectric structure 100, respectively. For example... Figure 21 As shown, the first dielectric strip 410 is along the second direction (including...) Figure 21 The second medium strip 420 extends to the reflector region along the second direction (the direction in which the Y-axis points and the opposite direction of the direction of the Y-axis).

[0130] The second passivation layer 500 is located on the surface of the dielectric layer 400 away from the piezoelectric structure 100, and covers the dielectric layer 400 and extends to cover the first passivation layer 300. The second passivation layer 500 is a tuning layer used to adjust the device frequency. By changing the physical properties of the second passivation layer 500, such as its thickness, distribution, and material, the propagation speed of sound waves can be changed. Since the frequency of the device is directly related to the speed of sound, the frequency can be indirectly adjusted by precisely controlling the parameters of the second passivation layer 500.

[0131] In some embodiments, the acoustic resonator further includes a third passivation layer (not shown) located on the surface of the second passivation layer 500 away from the piezoelectric structure 100, and completely covering the second passivation layer 500. The third passivation layer is used to encapsulate and protect the other layers (including the second passivation layer 500 and the dielectric layer 400) to act as an encapsulation barrier, completely isolating the underlying structures such as the dielectric layer 400 and the second passivation layer 500 from environmental stress factors (such as moisture and contaminants) to ensure long-term reliability.

[0132] Optionally, the materials of the first passivation layer 300, dielectric layer 400, second passivation layer 500, and third passivation layer are at least one selected from silicon nitride, silicon dioxide, tetraethyl orthosilicate, aluminum nitride, hafnium oxide, tungsten oxide, silicon carbide, tantalum pentoxide, benzocyclobutene, or parylene. It is understood that since the dielectric layer 400 is in contact with the first passivation layer 300, and the purpose of the first passivation layer 300 is to prevent performance degradation of the metal layer during subsequent processes and to prevent damage to the interdigital transducer 210, the material of the dielectric layer 400 is different from that of the first passivation layer 300. Furthermore, since the second passivation layer 500 and the third passivation layer have different functions, their materials are also different to better utilize the function of each layer. The second passivation layer 500 is used for frequency tuning. Therefore, the material of the second passivation layer 500 and the material of the dielectric layer 400 can be the same or different. It can be designed according to the specific application scenario, and there are no restrictions here.

[0133] Optionally, the first passivation layer 300 is made of silicon nitride (Si3N4), the dielectric layer 400 is made of silicon dioxide (SiO2), the second passivation layer 500 is made of silicon dioxide (SiO2), and the third passivation layer is made of silicon nitride (Si3N4).

[0134] Optionally, the thickness of the first passivation layer 300 is 10 nm, the thickness of the second passivation layer 500 is 20 nm, and the thickness of the third passivation layer is 10 nm.

[0135] Optionally, the first passivation layer 300 is made of silicon nitride (Si3N4) with a thickness of 10 nm, the second passivation layer 500 is made of silicon dioxide (SiO2) with a thickness of 20 nm, and the third passivation layer is made of silicon nitride (Si3N4) with a thickness of 10 nm.

[0136] Optionally, the thickness of the first passivation layer 300 is 10 nm, the thickness of the dielectric layer 400 is 90 nm, the thickness of the second passivation layer 500 is 20 nm, and the thickness of the third passivation layer is 10 nm.

[0137] Optionally, the first passivation layer 300 is made of silicon nitride (Si3N4) with a thickness of 10 nm; the dielectric layer 400 is made of silicon dioxide (SiO2) with a thickness of 90 nm; the second passivation layer 500 is made of silicon dioxide (SiO2) with a thickness of 20 nm; and the third passivation layer is made of silicon nitride (Si3N4) with a thickness of 10 nm.

[0138] This application employs a simple multi-layer stacking process to sequentially deposit a first passivation layer 300, a dielectric layer 400, and a second passivation layer 500 in the finger-end region of the interdigital transducer 210. Specifically, depositing a dielectric strip in the finger-end region of the interdigital transducer 210 creates local impedance discontinuities, thereby suppressing lateral stray acoustic modes and improving the frequency response cleanliness of the resonator, thus enhancing its performance and reliability. Furthermore, the first passivation layer 300 prevents damage to the interdigital transducer 210 during dielectric strip etching and prevents subsequent power variations caused by dielectric strip metal degradation. More importantly, while suppressing lateral stray acoustic modes, this application boasts a simple process that effectively ensures process compatibility. Because the size of the dielectric strip is decoupled from the IDT linewidth and step size, this solution has universal applicability, especially offering significant advantages for acoustic resonators across a wide frequency range. The method is particularly suitable for surface acoustic wave (SAW) resonators based on piezoelectric thin film on insulator (POI) for RF filtering applications in mobile and wireless communication systems, and can meet the technical requirements of high spectral cleanliness, low insertion loss, and stringent environmental adaptability and power reliability.

[0139] like Figure 22As shown in the figure, the admittance-frequency response curves of acoustic resonators with and without integrated dielectric strips are illustrated. The horizontal axis represents frequency, and the vertical axis represents admittance. Curve y1 represents the admittance-frequency response curve of the resonator with integrated dielectric strips; curve y2 represents the admittance-frequency response curve of the resonator without integrated dielectric strips. It can be seen from the figure that the acoustic resonator exhibits transverse spurious modes after series resonance, as indicated by the peak characteristics of the admittance curves in the figure. The admittances of the resonators with and without integrated dielectric strips are 1.6 dB and 13.1 dB, respectively, when generating the first transverse odd harmonic, while those without integrated dielectric strips are 4.9 dB and 9.9 dB, respectively, when generating the second transverse odd harmonic, respectively. Clearly, the acoustic resonator with integrated dielectric strips suppresses the first transverse odd harmonic by more than approximately 11 dB and the second transverse odd harmonic by approximately 5 dB, verifying the effectiveness of the dielectric strip in improving spectral fidelity.

[0140] This application also provides a method for fabricating an acoustic resonator, which is used to fabricate the acoustic resonator in any of the above embodiments. In one embodiment, Figure 23 This is a flowchart of a method for fabricating an acoustic resonator in one embodiment. The method for fabricating the acoustic resonator includes steps S710 to S750:

[0141] Step S710: Provide a piezoelectric structure and form an interdigitated transducer layer on the surface of one side of the piezoelectric structure. The interdigitated transducer layer includes an interdigitated transducer, and the interdigitated transducer includes a first electrode finger and a second electrode finger.

[0142] Step S720: A first passivation layer is formed on the surface of the interdigital transducer layer away from the piezoelectric structure.

[0143] Step S730: A dielectric layer is formed on the surface of the first passivation layer away from the piezoelectric structure.

[0144] Step S740: Etch the dielectric layer to form a first dielectric strip and a second dielectric strip, such that the first dielectric strip is close to the end region of the first electrode finger and the second dielectric strip is close to the end region of the second electrode finger.

[0145] Step S750: A second passivation layer is formed on the surface of the dielectric layer away from the piezoelectric structure, so that the second passivation layer covers the dielectric layer and extends to cover the first passivation layer.

[0146] During the patterning of dielectric strips, the first passivation layer serves as an etching stop layer, ensuring precise thickness control while preventing damage to the underlying metal layer.

[0147] In some embodiments, such as Figure 24 Step S710 further includes:

[0148] Step S711: Provide a piezoelectric structure and form a stacked interdigitated transducer layer on the surface of one side of the piezoelectric structure.

[0149] Step S712: Etch the interdigital transducer layer to form the interdigital transducer.

[0150] In this embodiment, an interdigitated transducer layer is first deposited, and then the interdigitated transducer layer is etched to obtain the interdigitated transducer. The interdigitated transducer includes a first bus bar, a second bus bar, a first electrode finger, and a second electrode finger.

[0151] In some embodiments, such as Figure 25 Step S710 further includes:

[0152] Step S711: Provide a piezoelectric structure and form a stacked interdigitated transducer layer on the surface of one side of the piezoelectric structure.

[0153] Step S713: Etch the interdigital transducer layer to form the interdigital transducer and the first reflector.

[0154] In this embodiment, an interdigitated transducer layer is first deposited, and then etched to obtain the interdigitated transducer. The interdigitated transducer includes a first bus bar, a second bus bar, a first electrode finger, and a second electrode finger. The interdigitated transducer layer includes the interdigitated transducer and a first reflector.

[0155] In some embodiments, such as Figure 26 Step S710 further includes:

[0156] Step S711: Provide a piezoelectric structure and form a stacked metal layer on the surface of one side of the piezoelectric structure.

[0157] Step S714: Etch the metal layer to form the interdigital transducer, the first reflector, and the second reflector.

[0158] In this embodiment, an interdigitated transducer layer is first deposited, and then etched to obtain the interdigitated transducer. The interdigitated transducer includes a first bus bar, a second bus bar, a first electrode finger, and a second electrode finger. The interdigitated transducer layer includes the interdigitated transducer, a first reflector, and a second reflector.

[0159] In some embodiments, the dielectric layer can be a single layer deposited and then etched to form a first dielectric stripe and a second dielectric stripe, or two dielectric sublayers can be deposited separately and then etched separately to obtain a first dielectric stripe and a second dielectric stripe.

[0160] In some embodiments, such as Figure 27As shown, the dielectric layer 400 includes a first dielectric sublayer 401 and a second dielectric sublayer 402 spaced apart. The interdigital transducer includes a first busbar and a second busbar. The orthographic projection of the first dielectric sublayer onto the piezoelectric structure has no overlap with the orthographic projection of the second busbar onto the piezoelectric structure, and the orthographic projection of the second dielectric sublayer onto the piezoelectric structure has no overlap with the orthographic projection of the first busbar onto the piezoelectric structure.

[0161] The formation process of the first dielectric strip and the second dielectric strip includes: etching the first dielectric sublayer 401 to form the first dielectric strip; and etching the second dielectric sublayer 402 to form the second dielectric strip.

[0162] Understandably, please combine Figure 27 , Figure 4 and Figures 7 to 12 Therefore, it can be seen that... Figure 27 The first dielectric sublayer 401 in the middle can be etched to obtain Figure 4 and Figures 7 to 12 The first dielectric strip 410 in; will Figure 27 Etching the second dielectric sublayer 402 in the middle can yield... Figure 4 and Figures 7 to 12 The second dielectric strip 420 in the solution. This solution can save etching material and dielectric layer material.

[0163] This application employs a simple multi-layer stacking process to sequentially deposit a first passivation layer, a dielectric layer, and a second passivation layer in the finger-end region of an interdigital transducer. Specifically, depositing dielectric strips in the finger-end region creates local impedance discontinuities, thereby suppressing lateral stray acoustic modes. While suppressing lateral stray acoustic modes, this application boasts a simple process, effectively ensuring process compatibility and possessing universal applicability.

[0164] This application also proposes a filter that includes any of the aforementioned acoustic resonators, or includes an acoustic resonator prepared by the aforementioned method. Examples include surface acoustic wave (SAW) filters, SAW resonator filters, and stepped SAW filters.

[0165] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0166] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An acoustic resonator, characterized in that, include: piezoelectric structure; An interdigitated transducer layer, including interdigitated transducers, is located on one side of the piezoelectric structure; The interdigital transducer includes a first busbar, a second busbar, a first electrode finger connected to the first busbar, and a second electrode finger connected to the second busbar, all arranged opposite each other in a first direction. A first passivation layer is located on the surface of the interdigital transducer layer away from the piezoelectric structure and extends to cover the piezoelectric structure; the thickness of the first passivation layer is less than the thickness of the interdigital transducer layer. A dielectric layer is located on the surface of the first passivation layer away from the piezoelectric structure; The dielectric layer includes only a first dielectric strip and a second dielectric strip, the first dielectric strip being close to the end region of the first electrode finger strip, and the second dielectric strip being close to the end region of the second electrode finger strip; The distance between the first dielectric strip and the second busbar is equal to the distance between the end of the first electrode finger and the second busbar; the distance between the second dielectric strip and the first busbar is equal to the distance between the end of the second electrode finger and the first busbar. The second passivation layer is located on the surface of the dielectric layer away from the piezoelectric structure, and covers the dielectric layer and extends to cover the first passivation layer.

2. The acoustic resonator according to claim 1, characterized in that, The first busbar and the second busbar extend along the second direction, respectively; The length extension direction of the first medium strip is the same as that of the second medium strip, and parallel to the length extension direction of the first busbar.

3. The acoustic resonator according to claim 2, characterized in that, The orthographic projection of the first dielectric strip onto the piezoelectric structure and the orthographic projection of the first busbar onto the piezoelectric structure have no overlap. The orthographic projection of the second dielectric strip onto the piezoelectric structure has no overlap with the orthographic projection of the second busbar onto the piezoelectric structure.

4. The acoustic resonator according to claim 2, characterized in that, The orthographic projection of the first dielectric strip onto the piezoelectric structure and the orthographic projection of the second busbar onto the piezoelectric structure have no overlap. The orthographic projection of the second dielectric strip onto the piezoelectric structure has no overlap with the orthographic projection of the first busbar onto the piezoelectric structure.

5. The acoustic resonator according to claim 2, characterized in that, The first busbar has a first end and a second end along the second direction; the interdigitated transducer layer further includes a reflector located at the first end and / or the second end.

6. The acoustic resonator according to claim 5, characterized in that, The orthographic projections of the first dielectric strip and the second dielectric strip onto the piezoelectric structure overlap with the orthographic projections of the reflector onto the piezoelectric structure, respectively.

7. The acoustic resonator according to claim 2, characterized in that, The first dielectric strip and the second dielectric strip extend along the second direction to cover the entire interdigital transducer layer region.

8. The acoustic resonator according to claim 2, characterized in that, The length of the dielectric layer in the second direction is less than the length of the piezoelectric structure in the second direction; The width of the dielectric layer in the first direction is smaller than the width of the piezoelectric structure in the first direction.

9. The acoustic resonator according to claim 2, characterized in that, The contact connection surfaces of the first passivation layer and the interdigitated transducer layer divide the first dielectric strip into a first dielectric strip portion and a first dielectric extension portion, and divide the second dielectric strip into a second dielectric strip portion and a second dielectric extension portion, wherein the contact connection surfaces are parallel to the first direction and the second direction, respectively.

10. The acoustic resonator according to claim 9, characterized in that, The first medium extension portion and the second medium extension portion are spaced apart.

11. The acoustic resonator according to claim 9, characterized in that, The second passivation layer includes: The first passivation sub-part is parallel to the first direction and the second direction, respectively; The second passivation sub-part is parallel to the first direction and the second direction, respectively; The third passivation sub-part is connected to the first passivation sub-part and the second passivation sub-part, respectively; The width of the third passivation sub-part gradually decreases in the direction away from the second passivation sub-part, wherein the cross-section is perpendicular to the contact surface between the interdigital transducer layer and the piezoelectric structure and parallel to the second direction.

12. The acoustic resonator according to any one of claims 2 to 11, characterized in that, The widths of both the first and second dielectric strips exhibit linear, nonlinear, or step-like variations along the first direction. And / or, The lengths of both the first and second dielectric strips exhibit linear, nonlinear, or step-like changes along the second direction.

13. The acoustic resonator according to claim 1, characterized in that, Also includes: The third passivation layer is located on the surface of the second passivation layer away from the piezoelectric structure and completely covers the second passivation layer.

14. The acoustic resonator according to claim 1, characterized in that, The materials of the first passivation layer, the dielectric layer, and the second passivation layer are at least one of silicon nitride, silicon dioxide, tetraethyl orthosilicate, aluminum nitride, hafnium oxide, tungsten oxide, silicon carbide, tantalum pentoxide, benzocyclobutene, or parylene, and the material of the dielectric layer is different from that of the first passivation layer.

15. The acoustic resonator according to claim 1, characterized in that, The thickness of the dielectric strip ranges from 10 to 200 nm.

16. The acoustic resonator according to claim 1, characterized in that, The width of the dielectric strip along the first direction ranges from 300 to 5000 nm.

17. A method for fabricating an acoustic resonator, characterized in that, include: A piezoelectric structure is provided, and an interdigitated transducer layer is formed on the surface of one side of the piezoelectric structure. The interdigitated transducer layer includes an interdigitated transducer, and the interdigitated transducer includes a first bus bar, a second bus bar, a first electrode finger connected to the first bus bar, and a second electrode finger connected to the second bus bar, which are disposed opposite to each other in a first direction. A first passivation layer is formed on the surface of the interdigital transducer layer on the side away from the piezoelectric structure; The thickness of the first passivation layer is less than the thickness of the interdigitated transducer layer; A dielectric layer is formed on the surface of the first passivation layer away from the piezoelectric structure; The dielectric layer is etched to form only a first dielectric strip and a second dielectric strip, such that the first dielectric strip is close to the end region of the first electrode finger, and the second dielectric strip is close to the end region of the second electrode finger; the distance between the first dielectric strip and the second busbar is equal to the distance between the end of the first electrode finger and the second busbar; the distance between the second dielectric strip and the first busbar is equal to the distance between the end of the second electrode finger and the first busbar. A second passivation layer is formed on the surface of the dielectric layer away from the piezoelectric structure, such that the second passivation layer covers the dielectric layer and extends to cover the first passivation layer.

18. The method for fabricating an acoustic resonator according to claim 17, characterized in that, The dielectric layer includes a first dielectric sublayer and a second dielectric sublayer spaced apart; the interdigital transducer includes a first busbar and a second busbar; the orthographic projection of the first dielectric sublayer on the piezoelectric structure and the orthographic projection of the second busbar on the piezoelectric structure have no overlapping portions, and the orthographic projection of the second dielectric sublayer on the piezoelectric structure and the orthographic projection of the first busbar on the piezoelectric structure have no overlapping portions; The formation processes of the first dielectric strip and the second dielectric strip include: The first dielectric sublayer is etched to form the first dielectric strip; The second dielectric sublayer is etched to form the second dielectric strip.

19. A filter, characterized in that, Includes an acoustic resonator as described in any one of claims 1 to 16, or includes an acoustic resonator prepared by the preparation method as described in any one of claims 17 to 18.

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