Surface acoustic wave filter and vehicle-mounted device

Abstract

This application relates to the field of semiconductor technology, specifically to a surface acoustic wave (SAW) filter and an automotive device. The SAW filter includes a substrate, interdigitated electrodes, a temperature compensation layer, and substrate voids formed in the substrate. The interdigitated electrodes are disposed on the substrate. The temperature compensation layer is disposed on the substrate and covers the interdigitated electrodes. The substrate voids are filled with a metal filler. By creating voids in the substrate and filling them with metal to form a metal filler, the metal filler introduces an acoustic impedance discontinuity interface in the acoustic wave propagation path, effectively reflecting or absorbing stray wave energy, thereby suppressing stray waves. Combined with the temperature compensation layer, this improves the filter's temperature stability and avoids frequency drift. Simultaneously, the metal filler does not affect the temperature compensation function of the temperature compensation layer, maintaining the excellent temperature stability of the SAW filter.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, such as to a surface acoustic wave filter and an automotive device. Background Technology

[0002] Surface acoustic wave (SAW) filters are widely used in mobile communications, the Internet of Things (IoT), and automotive electronics due to their small size, light weight, and stable performance. With the continuous increase in communication frequencies and increasingly stringent requirements for filter performance, temperature-compensated SAW filters (TC-SAW) are becoming increasingly important. SurfaceAcoustic Wave was developed to meet this need.

[0003] TC-SAW significantly improves the frequency temperature coefficient by covering the interdigitated electrodes with a temperature compensation layer, using the positive temperature coefficient of the compensation layer to offset the negative temperature coefficient of the piezoelectric substrate. However, TC-SAW devices still suffer from noise issues during operation, which can affect the out-of-band rejection performance and signal purity of the filter, thus reducing the overall performance of the device.

[0004] In related technologies, methods for suppressing clutter mainly include optimizing the interdigitated electrode structure and adjusting the thickness of the temperature compensation layer. However, these methods have limited effectiveness in suppressing clutter and often have adverse effects on the dominant acoustic mode. Therefore, how to effectively suppress clutter while maintaining the excellent temperature characteristics of TC-SAW has become a pressing technical problem to be solved in this field.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0007] This disclosure provides a surface acoustic wave filter and an on-board device to solve the technical problem of effectively suppressing clutter while maintaining the excellent temperature characteristics of TC-SAW.

[0008] In some embodiments, a surface acoustic wave filter is provided, comprising: a substrate; interdigitated electrodes disposed on the substrate; a temperature compensation layer disposed on the substrate and covering the interdigitated electrodes; and substrate voids formed in the substrate, the substrate voids being filled with a metal filler.

[0009] Optionally, the substrate void is located in the end region of the interdigital electrode, and the end region is distributed along the extension direction of the line connecting the center points of the ends of two adjacent interdigital electrodes; or, the interdigital electrode includes: a first interdigital electrode and a second interdigital electrode; the substrate void is located below the ends of the first interdigital electrode and / or the second interdigital electrode.

[0010] Optionally, the thickness of the metal filler is 10 nanometers to 200 nanometers and is less than or equal to the thickness of the substrate; and / or, the ratio of the thickness of the metal filler to the thickness of the interdigitated electrode is at least 1:5.

[0011] Optionally, the ratio of the width of the metal filler to the width of the interdigitated electrode is at least 1:5, and the width of the metal filler does not exceed one-fifth of the gap width between two adjacent interdigitated electrodes.

[0012] Optionally, the material of the metal filler includes one or more of titanium, silver, chromium, and nickel; and / or, the metal filler includes a silver layer located at the bottom of the substrate void; and / or, the metal filler includes a silver layer located at the bottom of the substrate void, wherein the thickness of the silver layer is 1 / 10 of the thickness of the metal filler.

[0013] Optionally, the surface acoustic wave filter further includes a metal functional layer disposed on the temperature compensation layer, the metal functional layer being connected to the interdigitated electrodes.

[0014] Optionally, the metal functional layer includes: a first functional portion, one end of which is connected to an interdigitated electrode; and a second functional portion, one end of which is connected to the other end of the first functional portion, and the extension direction of the second functional portion is perpendicular to the thickness direction of the temperature compensation layer.

[0015] Optionally, the first functional part and the second functional part are arranged perpendicular to each other; or, the first functional part is arranged at an angle toward the second functional part; or, the first functional part is arranged at an angle toward the second functional part, and the angle of inclination is in the range of 0 degrees to 30 degrees.

[0016] Optionally, along the thickness direction of the temperature compensation layer, the second functional part is located in the middle of the temperature compensation layer or at the top of the temperature compensation layer away from the substrate.

[0017] Optionally, the ratio of the thickness of the second functional part to the thickness of the interdigital electrode is at least 1:5; and / or, the width of the second functional part is the same as the width of the interdigital electrode, and the width of the second functional part does not exceed one-fifth of the gap width between two adjacent interdigital electrodes.

[0018] Optionally, the ratio of the thickness of the first functional part to the thickness of the interdigital electrode is at least 1:5; and / or, the ratio of the width of the first functional part to the width of the interdigital electrode is at least 1:2, and the width of the first functional part does not exceed one-fifth of the gap width between two adjacent interdigital electrodes.

[0019] In some embodiments, an in-vehicle device is provided, including a surface acoustic wave filter as described in any of the above embodiments.

[0020] The surface acoustic wave filter and its manufacturing method, bulk acoustic wave filter, and vehicle-mounted equipment provided in this disclosure can achieve the following technical effects: The surface acoustic wave (SAW) filter provided in this embodiment forms a metal filler by creating voids in a substrate and filling them with metal. This metal filler introduces an acoustic impedance discontinuity interface along the acoustic wave propagation path, effectively reflecting or absorbing stray wave energy, thereby suppressing clutter. Combined with a temperature compensation layer, this improves the filter's temperature stability and prevents frequency drift. Furthermore, the metal filler does not affect the temperature compensation function of the temperature compensation layer, maintaining the excellent temperature stability of the SAW filter.

[0021] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of the structure of a surface acoustic wave filter provided in one embodiment of the present disclosure; Figure 2 yes Figure 1 The illustrated embodiment provides a cross-sectional view along the AA direction in a surface acoustic wave filter; Figure 3 This is a schematic diagram of the structure of a surface acoustic wave filter provided in another embodiment of the present disclosure; Figure 4 yes Figure 3 The illustrated embodiment provides a cross-sectional view along the BB direction in a surface acoustic wave filter; Figure 5 This is a schematic diagram of the structure of a surface acoustic wave filter provided in another embodiment of this disclosure; Figure 6 yes Figure 5 A cross-sectional view along the CC direction in one embodiment shown; Figure 7 yes Figure 5A cross-sectional view along the CC direction in another embodiment shown; Figure 8 yes Figure 5 A cross-sectional view along the CC direction in yet another embodiment shown; Figure 9 yes Figure 5 A sectional view along the DD direction in one embodiment shown; Figure 10 yes Figure 5 A cross-sectional view along the DD direction in yet another embodiment shown; Figure 11 This is a flowchart of a method for fabricating a surface acoustic wave filter according to an embodiment of this disclosure.

[0023] Figure label: 1. Surface acoustic wave filter; 10. Substrate; 12. Metal filler; 20 temperature compensation layers; 30 First forked finger extension portion; 31 Second forked finger extension portion; 32 First forked finger electrode; 33 Second forked finger electrode; 300 End region of the forked finger electrode; 310 Center region of the forked finger electrode; 40 Metal functional layer; 41 First functional part; 42 Second functional part; 50 First PAD metal layer; 51 Second PAD metal layer; 52 First PAD contact window; 53 Second PAD contact window; 60 passivation layer. Detailed Implementation

[0024] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0025] The terms "first," "second," etc., used in the technical solutions described in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0026] Unless otherwise stated, the term "multiple" means two or more.

[0027] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0028] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0029] The term "correspondence" can refer to an association or binding relationship. The correspondence between A and B means that there is an association or binding relationship between A and B.

[0030] In some embodiments, combined with Figures 1 to 5 , Figure 9 and Figure 10 As shown, a surface acoustic wave (SAW) filter 1 is provided, comprising: a substrate 10, interdigitated electrodes, a temperature compensation layer 20, and substrate 10 voids formed in the substrate 10. The interdigitated electrodes are disposed on the substrate 10. The temperature compensation layer 20 is disposed on the substrate 10 and covers the interdigitated electrodes. The substrate 10 voids are filled with a metal filler 12.

[0031] The surface acoustic wave (SAW) filter 1 provided in this embodiment forms a metal filler 12 by creating voids in a substrate 10 and filling them with metal. This metal filler 12 introduces an acoustic impedance discontinuity interface along the acoustic wave propagation path, effectively reflecting or absorbing stray wave energy, thereby suppressing clutter. Combined with a temperature compensation layer 20, this enhances the filter's temperature stability and prevents frequency drift. Simultaneously, the metal filler 12 does not affect the temperature compensation function of the temperature compensation layer 20, maintaining the excellent temperature stability of the SAW filter 1.

[0032] Optionally, combined Figures 1 to 5 , Figure 9 and Figure 10 As shown, the surface acoustic wave filter 1 further includes a first interdigital electrode 30 and a second interdigital electrode 31. The interdigital electrodes include a plurality of first interdigital electrodes 32 and a plurality of second interdigital electrodes 33. The plurality of first interdigital electrodes 32 are arranged in parallel intervals. One end of each first interdigital electrode 32 is connected to the first interdigital electrode 30, and the edge region of the other end forms an interdigital electrode end opposite to the second interdigital electrode 31. The plurality of second interdigital electrodes 33 are arranged in a cross-parallel manner with the plurality of first interdigital electrodes 32. One end of each second interdigital electrode 33 is connected to the second interdigital electrode 31, and the edge region of the other end forms an interdigital electrode end opposite to the first interdigital electrode 30. Interdigital electrode center regions 310 are formed between the edge regions of the first interdigital electrodes 32 and the first interdigital electrodes 30, and between the edge regions of the second interdigital electrodes 33 and the second interdigital electrodes 31, respectively.

[0033] In some embodiments, combined with Figure 1 and Figure 2 As shown, the voids in the substrate 10 are located in the end region 300 of the interdigital electrode, and the end region 300 of the interdigital electrode is entirely filled with slots. The end regions are distributed along the extension direction of the line connecting the center points of the ends of two adjacent interdigital electrodes.

[0034] In this embodiment, the voids in the substrate 10 are located directly below the end regions of the interdigitated electrodes. The metal filler 12 forms an acoustic impedance discontinuity interface at the acoustic wave reflection source location, directly absorbing and scattering the reflected clutter generated by the electrode ends. The voids are continuously distributed along the line connecting the center points of adjacent electrode ends, cutting off the transverse acoustic wave propagation path between the electrode ends and disrupting the transmission channel of clutter energy between adjacent electrodes. By blocking the coupling path, the conditions for standing wave formation in the end region are eliminated, preventing the accumulation and enhancement of clutter energy at specific frequencies. The metal filler 12 changes the local acoustic impedance distribution, suppressing the conversion of the main acoustic wave mode to higher-order modes and improving the purity of the main mode. By comprehensively suppressing multiple clutter sources, out-of-band spurious signals are reduced, and the out-of-band rejection performance of the filter is improved. The voids are only located in the clutter generation region, avoiding unnecessary interference with the main acoustic wave propagation path and reducing excessive etching of the substrate 10.

[0035] In some embodiments, combined with Figure 3 and Figure 4 As shown, the cavity in substrate 10 is located below the end of the first interdigital electrode 32. And / or, the cavity in substrate 10 is located below the end of the second interdigital electrode 33.

[0036] In this embodiment, the voids in the substrate 10 are positioned directly below the ends of each interdigital electrode, which can specifically suppress parasitic acoustic wave modes generated by the ends of the interdigital electrodes. These modes are often the main source of clutter. Through precise positioning, interference with the main acoustic wave modes is reduced while ensuring the effectiveness of clutter suppression.

[0037] Optionally, the thickness of the metal filler 12 is 10 nanometers to 200 nanometers, and is less than or equal to the thickness of the substrate 10.

[0038] In this embodiment, the thickness of the metal filler 12 is controlled within the range of 10 nanometers to 200 nanometers. A thickness greater than or equal to 10 nanometers ensures sufficient acoustic depth for effective modulation of sound wave propagation. A thickness less than or equal to 200 nanometers controls process complexity, avoids over-etching of the substrate 10, and prevents excessive influence on the main acoustic wave mode. By controlling the thickness of the metal filler 12, the acoustic impedance modulation effect is improved, effectively influencing sound wave propagation without excessive etching. Furthermore, the thickness of the metal filler 12 must be less than or equal to the thickness of the substrate 10; that is, voids cannot penetrate the substrate 10, ensuring structural integrity and preventing process runaway caused by etching through-holes, thus preserving the piezoelectric properties of the substrate 10.

[0039] Optionally, the thickness of the metal filler 12 may be, but is not limited to, 10 nanometers, 50 nanometers, 100 nanometers, 150 nanometers, or 200 nanometers. It should be noted that the specific thickness of the metal filler 12 is selected and set according to the specific dimensions of the surface acoustic wave filter 1.

[0040] Optionally, the ratio of the thickness of the metal filler 12 to the thickness of the interdigitated electrode is at least 1:5.

[0041] In this embodiment, the thickness of the interdigital electrode determines the electroacoustic coupling strength, and the metal filler 12 needs to reach a considerable thickness to generate sufficient acoustic impedance modulation. By ensuring that the ratio of the thickness of the metal filler 12 to the thickness of the interdigital electrode is at least 1:5, the metal filler 12 and the interdigital electrode have comparable acoustic influence, providing sufficient relative thickness to produce a significant acoustic effect.

[0042] Optionally, the ratio of the thickness of the metal filler 12 to the thickness of the interdigitated electrode is in the range of 1:3 to 1:2, so as to achieve a balance between the suppression effect and the influence of the master mold.

[0043] Optionally, the ratio of the width of the metal filler 12 to the width of the interdigitated electrode is at least 1:5, and the width of the metal filler 12 does not exceed one-fifth of the gap width between two adjacent interdigitated electrodes.

[0044] In this embodiment, the defined width ratio ensures that the metal filler 12 has sufficient lateral dimensions to influence sound wave propagation, while avoiding excessive width that could adversely affect the electric field distribution between adjacent interdigital electrodes. The limitation of not exceeding one-fifth of the gap width prevents the metal filler 12 from excessively encroaching on the effective acoustic region between the interdigital electrodes. By setting the ratio of the width of the metal filler 12 to the width of the interdigital electrode to at least 1:5, sufficient lateral coverage of the filler is achieved. The maximum width of the metal filler 12 is one-fifth of the gap width between two adjacent interdigital electrodes to prevent excessive encroachment of the filler into the inter-electrode gap.

[0045] Optionally, the ratio of the width of the metal filler 12 to the width of the interdigitated electrode is in the range of 1:3 to 1:2, achieving a balance between the suppression effect and the influence of the master mold.

[0046] The width of the interdigitated electrode refers to the width of a single interdigitated electrode perpendicular to its extension direction. The gap width between two adjacent interdigitated electrodes refers to the distance between two adjacent interdigitated electrodes. The width of the metal filler 12 refers to its width dimension along the width direction of the interdigitated electrode.

[0047] Optionally, the material of the metal filler 12 includes one or more of titanium, silver, chromium, and nickel.

[0048] In this embodiment, metallic materials such as titanium, silver, chromium, and nickel have good electrical conductivity and acoustic properties, making them suitable as filler materials.

[0049] Optionally, the metal filler 12 includes a silver layer located at the bottom of the void in the substrate 10.

[0050] In this embodiment, a silver layer is placed at the bottom of the cavity. By utilizing the high conductivity and acoustic impedance characteristics of silver, the acoustic performance of the filling structure can be further optimized.

[0051] Optionally, the metal filler 12 includes a silver layer located at the bottom of the void in the substrate 10, the thickness of the silver layer being 1 / 10 of the thickness of the metal filler 12.

[0052] In this embodiment, a silver layer is placed at the bottom of the cavity. The high conductivity and acoustic impedance of silver further optimize the acoustic performance of the filling structure. The design of a silver layer thickness of 1 / 10 ensures the acoustic effect at the bottom interface while also considering material cost and process feasibility.

[0053] In some embodiments, combined with Figures 5 to 10 As shown, the surface acoustic wave filter 1 also includes a metal functional layer 40 disposed on the temperature compensation layer 20, and the metal functional layer 40 is connected to the interdigitated electrodes.

[0054] In this embodiment, a metal functional layer 40 connected to the ends of the interdigitated electrodes is provided in the temperature compensation layer 20 to form an additional clutter suppression structure. This metal functional layer 40 works synergistically with the metal filler 12 in the voids of the substrate 10 to suppress clutter from different dimensions, further improving the out-of-band suppression performance of the filter.

[0055] Optionally, combined Figures 6 to 8 As shown, the metal functional layer 40 includes a first functional portion 41 and a second functional portion 42. One end of the first functional portion 41 is connected to the interdigitated electrode. One end of the second functional portion 42 is connected to the other end of the first functional portion 41, and the extending direction of the second functional portion 42 is perpendicular to the thickness direction of the temperature compensation layer 20.

[0056] In this embodiment, the metal functional layer 40 is designed as an L-shaped structure composed of a first functional part 41 and a second functional part 42. The first functional part 41 extends along the thickness direction, and the second functional part 42 extends along the horizontal direction, forming a three-dimensional suppression structure. This structure can simultaneously regulate the propagation of sound waves in both vertical and horizontal directions, enhancing the clutter suppression effect. Specifically, the first functional part 41 guides the clutter energy reflected at its end vertically upward, preventing the lateral diffusion of clutter and concentrating the energy into the horizontal structure. The second functional part 42 extends horizontally, providing a larger energy dissipation area, increasing the propagation distance of sound waves in the metal, and resulting in more efficient heat dissipation.

[0057] Optionally, the first functional part 41 is made of the same material as the interdigital electrode, with matching acoustic impedance, no reflection loss in sound wave transmission, and efficient removal of clutter. The second functional part 42 is made of the same material as the metal filler 12.

[0058] Optionally, combined Figure 6 and Figure 8 As shown, the first functional unit 41 and the second functional unit 42 are arranged perpendicularly to each other.

[0059] In this embodiment, when the first functional unit 41 and the second functional unit 42 are arranged perpendicularly to each other, the structure is regular and the process is easy to implement.

[0060] Optionally, the first functional unit 41 is inclined toward the second functional unit 42.

[0061] In this embodiment, combined with Figure 7 As shown, when the first functional unit 41 is tilted towards the second functional unit 42, the reflection direction of the sound wave at the interface can be changed, causing the clutter energy to scatter in a specific direction, thereby further optimizing the suppression effect.

[0062] Optionally, the first functional unit 41 is tilted toward the second functional unit 42, and the tilt angle ranges from 0° to 30°.

[0063] In this embodiment, when the first functional unit 41 is tilted towards the second functional unit 42, the reflection direction of the sound wave at the interface can be changed, causing clutter energy to scatter in a specific direction, thereby further optimizing the suppression effect. Controlling the tilt angle within the range of 0° to 30° achieves both good scattering effect and avoids excessive tilting that would increase manufacturing complexity.

[0064] The first functional unit 41 is inclined toward the second functional unit 42, and the specific value of the inclination angle includes, but is not limited to, 10°, 15°, 20°, 25° or 30°. In some embodiments, combined with Figure 9 As shown, along the thickness direction of the temperature compensation layer 20, the second functional part 42 is located in the middle of the temperature compensation layer 20.

[0065] In this embodiment, the position of the second functional unit 42 can be selected according to specific clutter suppression requirements. When located in the central region of the temperature compensation layer 20, it provides balanced suppression of clutter propagating in the vertical direction and can better form a synergistic effect with the metal filler 12 in the voids of the substrate 10.

[0066] In some embodiments, combined with Figure 10 As shown, along the thickness direction of the temperature compensation layer 20, the second functional part 42 is located at the top of the temperature compensation layer 20 away from the substrate 10.

[0067] In this embodiment, the position of the second functional unit 42 can be selected according to specific clutter suppression requirements. When located at the top, it enhances the suppression of surface propagating clutter and provides stronger control over surface wave modes.

[0068] Optionally, the ratio of the thickness of the second functional part 42 to the thickness of the interdigital electrode is at least 1:5; and / or, the width of the second functional part 42 is the same as the width of the interdigital electrode, and the width of the second functional part 42 does not exceed one-fifth of the gap width between two adjacent interdigital electrodes.

[0069] In this embodiment, the thickness determines the modulation capability of the metal functional layer 40 to sound waves, and the thickness ratio of at least 1:5 ensures that the second functional part 42 has sufficient structural strength and modulation capability to sound waves. The design of the width being the same as the width of the interdigital electrodes and not exceeding one-fifth of the gap allows the second functional part 42 to form good acoustic coupling with the interdigital electrodes, while avoiding adverse effects on the electric field between adjacent electrodes.

[0070] Optionally, the ratio of the thickness of the second functional part 42 to the thickness of the interdigitated electrode is in the range of 1:5 to 1.2.

[0071] Optionally, the ratio of the thickness of the first functional part 41 to the thickness of the interdigitated electrode is at least 1:5.

[0072] In this embodiment, the thickness of the first functional part 41 determines the vertical acoustic wave guiding length. Sufficient thickness ensures that the acoustic waves fully enter the horizontal structure, and the thickness ratio is comparable to that of the interdigitated electrodes, avoiding abrupt changes in acoustic impedance. By setting the thickness ratio of the first functional part 41 to at least 1:5, it has sufficient vertical extension height.

[0073] Optionally, the ratio of the thickness of the first functional part 41 to the thickness of the interdigitated electrode can be in the range of 1:5 to 1.2.

[0074] Optionally, the ratio of the width of the first functional part 41 to the width of the interdigital electrode is at least 1:2, and the width of the first functional part 41 does not exceed one-fifth of the gap width between two adjacent interdigital electrodes.

[0075] In this embodiment, the width of the first functional part 41 is at least half the width of the interdigital electrode, which improves the connection strength between the first functional part 41 and the end of the interdigital electrode; at the same time, the width does not exceed one-fifth of the gap, so as to avoid adverse effects on the surrounding structure.

[0076] Optionally, combined Figure 2 , Figure 4 , Figure 9 and Figure 10 As shown, the surface acoustic wave filter 1 further includes: a first PAD metal layer 50, connected to the first forked guide portion 30 through a first interdigital via; a second PAD metal layer 51, connected to the second forked guide portion 31 through a second interdigital via; and a temperature compensation layer 20 covering the surfaces of the first interdigital electrode 32, the second interdigital electrode 33, the first forked guide portion 30, and the second forked guide portion 31; wherein, the first interdigital via exposes the surface of the first forked guide portion 30 at its bottom by etching the temperature compensation layer 20; and the second interdigital via exposes the surface of the second forked guide portion 31 at its bottom by etching the temperature compensation layer 20.

[0077] Optionally, combined Figure 2 , Figure 4 , Figure 9 and Figure 10 As shown, the surface acoustic wave filter 1 further includes: a passivation layer 60 covering the surface of the temperature compensation layer 20, the first PAD metal layer 50, and the second PAD metal layer 51; a first PAD contact window 52 formed by etching the passivation layer 60, exposing the first PAD metal layer 50 at its bottom; and a second PAD contact window 53 formed by etching the passivation layer 60, exposing the second PAD metal layer 51 at its bottom.

[0078] In some embodiments, combined with Figure 11 As shown, a method for fabricating the above-mentioned surface acoustic wave filter is provided, comprising: S1101, Substrate preparation.

[0079] In this step, a piezoelectric substrate is provided, and the substrate surface is cleaned and pretreated to remove surface contaminants and oxide layers. The substrate may include a piezoelectric material, lithium niobate, or lithium tantalate.

[0080] S1102 uses photolithography to define void patterns at the ends of the interdigital electrodes. Reactive ion etching or inductively coupled plasma etching is then used to etch the substrate, forming the voids.

[0081] S1103 uses electron beam evaporation or sputtering to deposit a silver layer at the bottom of a substrate cavity.

[0082] In this step, the deposition time is controlled so that the thickness of the silver layer is approximately 1 / 10 of the total thickness of the metal filler.

[0083] S1104 uses sputtering or evaporation processes to deposit a titanium layer on a silver layer, completely filling the voids in the substrate.

[0084] After filling is completed, chemical mechanical polishing is used to remove excess metal from the substrate surface to make the substrate surface smooth.

[0085] S1105 uses a vapor deposition process to deposit an aluminum metal layer on the substrate surface, the thickness of which is determined according to design requirements. A photoresist pattern is formed using a photolithography process, and excess metal is removed using dry or wet etching to form the first interdigital electrode and the second interdigital electrode.

[0086] S1106 employs plasma-enhanced chemical vapor deposition to deposit a temperature compensation layer on the substrate.

[0087] The temperature compensation layer covers the interdigitated electrodes and fills the voids in the substrate. The temperature compensation layer material can be a single layer of SiO2, or a thin layer of SiN, AlN, amorphous silicon, GaN, or other materials stacked with a thick layer of SiO2.

[0088] S1107, a first PAD metal layer 50 and a second PAD metal layer 51 are formed, and the first finger electrode lead-out part is connected through the first interdigital through hole, and the second interdigital electrode lead-out part is connected through the second interdigital through hole.

[0089] S1108, deposit a passivation layer to protect the first PAD metal layer 50 and the second PAD metal layer 51 and to serve as a filter frequency adjustment layer.

[0090] S1109, etch the passivation layer to form the first PAD contact window 52 and the second PAD contact window 53 for external electrical connection.

[0091] In some embodiments, an in-vehicle device is provided, including a surface acoustic wave filter as described in any of the above embodiments.

[0092] The vehicle-mounted device provided in this disclosure includes the surface acoustic wave filter described in any of the above embodiments. Therefore, it possesses all the beneficial technical effects of the surface acoustic wave filter described in any of the above embodiments, which will not be elaborated further here.

[0093] The foregoing description and accompanying drawings fully illustrate embodiments of this disclosure to enable those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, procedural, and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. Moreover, the terminology used in this application is for describing embodiments only and is not intended to limit the technical solutions described herein. As used in the technical solutions described herein, the singular forms “a,” “an,” and “the” are intended to equally include the plural forms unless the context clearly indicates otherwise. Similarly, the term “and / or” as used herein refers to any and all possible combinations of one or more of the associated listed elements. Additionally, when used in this application, the term "comprise" and its variations "comprises" and / or "comprising" refer to the presence of stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. Without further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, or apparatus that includes said element. In this document, each embodiment may focus on the differences from other embodiments, and similar or identical parts between embodiments can be referred to mutually. For methods, products, etc., disclosed in the embodiments, if they correspond to the method section disclosed in the embodiments, the relevant parts can be referred to the description of the method section.

Claims

1. A surface acoustic wave filter, characterized by, include: Substrate; Interdigitated electrodes are disposed on the substrate; A temperature compensation layer is disposed on the substrate and covers the interdigitated electrodes; Substrate voids formed on the substrate, with the voids filled with a metal filler.

2. The surface acoustic wave filter according to claim 1, characterized in that, Substrate voids are located in the end regions of the interdigitated electrodes, and the end regions are distributed along the extension direction of the line connecting the center points of the ends of two adjacent interdigitated electrodes. or, The interdigitated electrode includes: a first interdigitated electrode and a second interdigitated electrode; The substrate void is located below the ends of the first interdigital electrode and / or the second interdigital electrode.

3. The surface acoustic wave filter according to claim 1, characterized in that, The thickness of the metal filler is 10 nanometers to 200 nanometers, and is less than or equal to the thickness of the substrate; and / or, The ratio of the thickness of the metal filler to the thickness of the interdigitated electrode is at least 1:

5.

4. The surface acoustic wave filter according to claim 1, characterized in that, The ratio of the width of the metal filler to the width of the interdigitated electrode is at least 1:5, and the width of the metal filler does not exceed one-fifth of the gap width between two adjacent interdigitated electrodes.

5. The surface acoustic wave filter according to any one of claims 1 to 4, characterized in that, The materials for the metal filler include one or more of titanium, silver, chromium, and nickel; and / or, The metal filler includes a silver layer located at the bottom of the substrate voids; and / or, The metal filler includes a silver layer located at the bottom of the substrate void, and the thickness of the silver layer is 1 / 10 of the thickness of the metal filler.

6. The surface acoustic wave filter according to any one of claims 1 to 4, characterized in that, Also includes: A metal functional layer is disposed on the temperature compensation layer and is connected to the interdigitated electrodes.

7. The surface acoustic wave filter according to claim 6, characterized in that, The metallic functional layer includes: First functional unit, one end of which is connected to interdigital electrodes; The second functional part has one end connected to the other end of the first functional part, and the extension direction of the second functional part is perpendicular to the thickness direction of the temperature compensation layer.

8. The surface acoustic wave filter according to claim 7, characterized in that, The first functional section and the second functional section are arranged perpendicularly to each other; or The first functional unit is inclined toward the second functional unit; or... The first functional unit is tilted toward the second functional unit, and the tilt angle ranges from 0 degrees to 30 degrees.

9. The surface acoustic wave filter according to claim 7, characterized in that, Along the thickness direction of the temperature compensation layer, the second functional part is located in the middle of the temperature compensation layer or at the top of the temperature compensation layer away from the substrate.

10. The surface acoustic wave filter according to claim 7, characterized in that, The ratio of the thickness of the second functional section to the thickness of the interdigitated electrode is at least 1:5; and / or, The width of the second functional part is the same as the width of the interdigital electrode, and the width of the second functional part does not exceed one-fifth of the gap width between two adjacent interdigital electrodes.

11. The surface acoustic wave filter according to claim 7, characterized in that, The ratio of the thickness of the first functional part to the thickness of the interdigitated electrode is at least 1:5; and / or, The ratio of the width of the first functional part to the width of the interdigital electrode is at least 1:2, and the width of the first functional part does not exceed one-fifth of the width of the gap between two adjacent interdigital electrodes.

12. A vehicle-mounted device, characterized in that, include: The surface acoustic wave filter as described in any one of claims 1 to 11.

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