Surface acoustic wave resonator and filter

Abstract

The invention discloses a surface acoustic wave resonator and a filter. The resonator comprises an interdigital transducer arranged on a piezoelectric substrate, reflecting gratings located on the two sides of the interdigital transducer and at least one laminated protection structure arranged in the outer side area of the reflecting gratings. The laminated protection structure comprises an interdigital capacitor arranged on the surface of the piezoelectric substrate and an organic material layer covering the interdigital capacitor; two bus bars of the interdigital capacitor are electrically connected with two signal ports of the resonator respectively, and the interdigital capacitor is connected with the interdigital transducer in parallel. According to the invention, the anti-ESD capability of the resonator can be effectively improved under the condition of not increasing additional process steps and not changing the electrode structure of the normal working area of the resonator.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) filter technology, and more specifically, to a SAW resonator and filter. Background Technology

[0002] With the development of electronic and Internet of Things (IoT) technologies, various electronic devices rely on wireless communication to achieve different functions. These devices depend on transceivers composed of radio frequency (RF) front-end chips to achieve wireless information exchange. RF front-end chips contain multiple RF filters; currently, the most common type on the market is the surface acoustic wave (SAW) filter, which filters specific frequencies or frequency ranges. The electrostatic discharge (ESD) breakdown performance of SAW filters is a crucial factor affecting their performance and reliability.

[0003] Currently, conventional methods for improving the ESD resistance of surface acoustic wave (SAW) filters mainly focus on adjusting the structure and stacking of the interdigital electrodes. For example, one existing technique increases the ESD resistance by eliminating the hammer structure between adjacent fingers. However, if the adjustment range is too large, it will significantly degrade the filter's RF performance; if only a few fingers are adjusted, the ESD improvement effect is limited. Another existing technique stacks more passivation layers on the interdigital electrodes to form an electrostatic protection stack. This method is complex and requires additional photomasks, leading to increased costs. A third existing technique connects an equivalent resistor composed of a reflective grating array in parallel across the interdigital transducer to achieve electrostatic current shunting. However, adding such a resistor structure easily reduces the resonator's quality factor (Q value).

[0004] Therefore, there is an urgent need for a technical solution that can effectively improve the electrostatic discharge resistance of surface acoustic wave filters without significantly increasing process complexity and cost, and without affecting the core RF performance of the filters. Summary of the Invention

[0005] The purpose of this invention is to propose a surface acoustic wave resonator and filter. By introducing a special protective structure designed in conjunction with the resonator, the ESD resistance of the resonator can be effectively improved without adding extra process steps or changing the electrode structure in the normal operating area.

[0006] To achieve the above objectives, in a first aspect, the present invention proposes a surface acoustic wave resonator, comprising: an interdigital transducer disposed on a piezoelectric substrate, a reflective grating located on both sides of the interdigital transducer, and at least one stacked protective structure disposed in the outer region of the reflective grating. The stacked protective structure includes interdigitated capacitors disposed on the surface of the piezoelectric substrate, and an organic material layer covering the interdigitated capacitors. The two busbars of the interdigital capacitor are electrically connected to the two signal ports of the resonator, and the interdigital capacitor is connected in parallel with the interdigital transducer.

[0007] Optionally, the two signal ports of the resonator are connected to the two busbars of the interdigital capacitor via two signal traces. One signal trace is connected to the busbar at one end of the interdigital capacitor and the busbar at one end of the interdigital transducer, respectively, and the other signal trace is connected to the busbar at the other end of the interdigital capacitor and the busbar at the other end of the interdigital transducer, respectively.

[0008] Optionally, the interdigitated capacitor has multiple rectangular protrusions at the ends and sides of its fingers.

[0009] Optionally, the interdigitated capacitor has multiple protruding tip structures on both sides of the fingers.

[0010] Optionally, the spacing between the fingers of the interdigital capacitor is smaller than the spacing between the fingers of the interdigital transducer.

[0011] Optionally, at least one of the stacked protective structures is disposed on the same side of the interdigital transducer; Alternatively, at least one of the stacked protective structures may be provided on both sides of the interdigital transducer, and the number of the stacked protective structures provided on both sides of the interdigital transducer may be the same or different.

[0012] Optionally, the interdigital electrode structure of the interdigital transducer, the reflective grating, and the interdigital capacitor are all patterned from the same first metal layer.

[0013] Optionally, the interdigital electrode structure of the interdigital transducer is provided with a passivation layer, an isolation layer, and a second metal layer; The passivation layer covers the interdigitated electrode structure to protect it; the second metal layer is connected to the interdigitated electrode structure to provide metal traces for electrical connection between resonators; the isolation layer is disposed between the interdigitated electrode structure and the second metal layer to provide electrical isolation between them.

[0014] Optionally, the organic material layer and the isolation layer are made of the same material, and the organic material layer and the isolation layer are formed in the same process step; The organic material layer is made of polyimide.

[0015] Optionally, the stacked protection structure is arranged collinearly with respect to the interdigitated transducer in the layout; Alternatively, the stacked protective structure may be rotated by a set angle or non-collinearly arranged relative to the interdigital transducer in the layout.

[0016] In a second aspect, the present invention also proposes a surface acoustic wave filter, comprising a plurality of resonators, wherein at least one resonator is the surface acoustic wave resonator described in the first aspect, and the resonator is located on the electrostatic discharge path or at the port of the filter.

[0017] The beneficial effects of this invention are as follows: 1. This invention adds a stacked protection structure to the resonator and connects it in parallel with the interdigital transducer. The metal interdigital capacitor structure and the organic dielectric layer form an additional capacitor integrated inside the chip. When an ESD event occurs, this capacitor can store part of the instantaneous large current charge, effectively increasing the capacitive reactance in the ESD discharge path, thereby significantly reducing the peak value of the ESD current and voltage stress flowing into the working area of ​​the core resonator, transforming the sharp ESD pulse into a waveform with a smoother energy distribution, and improving the ESD withstand threshold of the device.

[0018] 2. Because the multilayered protection structure of this invention is located outside the resonator's operating area (interdigital transducer and reflector grating) and connected in parallel, it does not alter the electrode structure (such as finger width, spacing, and overlap length) of the interdigital transducer itself, which determines key performance characteristics such as resonant frequency and Q value. Therefore, after replacing the resonator with this multilayered protection structure, the core RF performance of the filter, such as center frequency, bandwidth, insertion loss, and out-of-band rejection, is maintained to the maximum extent, overcoming the problem of performance degradation caused by changing the IDT structure to resist ESD.

[0019] 3. The organic material layer (such as polyimide) covering the interdigitated capacitor of the multilayer protective structure can effectively absorb the sound wave energy and block the propagation of surface acoustic waves that may be excited in this area. This makes the protective structure appear as a pure and uniform capacitive element over a wide frequency range, without generating stray resonance peaks caused by the piezoelectric effect, thus ensuring the filter's good out-of-band rejection characteristics.

[0020] 4. By designing the electrode structure of the interdigitated capacitors in the multilayer protection structure (for example, making the spacing between the interdigitated capacitor bars in the protection structure smaller than the spacing between the IDT bars, or designing hammer or tip structures), the sensitivity of the multilayer protection structure to electrostatic discharge can be artificially made higher than that of the core resonator it is protecting. When subjected to extreme ESD impacts exceeding the design threshold, the multilayer protection structure will preferentially undergo controllable breakdown or loss, thereby protecting the IDT in the core area of ​​the resonator from irreversible damage and improving product reliability and production yield.

[0021] 5. The multilayer protective structure in this invention can be formed entirely by combining the first metal layer (forming interdigitated capacitors) and the organic material isolation layer (such as polyimide) process layer already present in the standard manufacturing process of surface acoustic wave filters. It does not require any additional photomask or the introduction of new process steps, and is fully compatible with existing production lines, avoiding the problems of increased manufacturing costs and extended production cycles caused by process complexity.

[0022] 6. The stacked protection structure in this invention can be laid out in coordination with the resonator body (including interdigital transducers and reflective grids), and can even be rotated or translated according to the layout space. There is no need to reserve special or additional chip area for ESD protection function, which is conducive to realizing the miniaturization and high integration of the device.

[0023] 7. By adjusting the electrode size and number of interdigitated capacitors in the stacked protection structure, the parallel capacitance value can be precisely adjusted. This capacitor can be directly used to optimize the impedance matching of the filter input / output ports, which helps to replace or reduce discrete capacitor components in the external matching circuit, thereby saving system board area, reducing assembly costs, and improving module integration.

[0024] 8. The organic material layer (such as polyimide) covering the interdigital capacitor can serve as an additional heat conduction path, which helps to dissipate the heat generated by the resonator during operation (especially under high power conditions) more effectively, improves the thermal management capability of the device, and enhances its power capacity and long-term reliability.

[0025] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0026] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0027] Figure 1 This is a top view of a surface acoustic wave resonator according to Embodiment 1 of the present invention.

[0028] Figure 2 This is a partially enlarged view of a surface acoustic wave resonator according to Embodiment 1 of the present invention.

[0029] Figure 3 for Figure 1 A sectional view along line A-A'.

[0030] Figure 4 This is a schematic diagram of the film structure of the interdigital transducer in a surface acoustic wave resonator according to Embodiment 1 of the present invention.

[0031] Figure 5 This is a schematic diagram of the electrode structure of an interdigital capacitor as an example in Embodiment 1 of the present invention.

[0032] Figure 6 This is a schematic diagram of the electrode structure of an interdigital capacitor, which is another example of the present invention, in Embodiment 1.

[0033] Figure 7 This is a schematic diagram of a surface acoustic wave filter according to Embodiment 2 of the present invention. Detailed Implementation

[0034] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment provides a surface acoustic wave resonator, including: an interdigital transducer 2 (IDT) disposed on a piezoelectric substrate 1, a reflective grating 3 located on both sides of the interdigital transducer 2, and at least one stacked protective structure 4 disposed in the outer region of the reflective grating 3. The stacked protective structure 4 includes an interdigitated capacitor 401 disposed on the surface of the piezoelectric substrate 1, and an organic material layer 402 covering the interdigitated capacitor 401. The two busbars of the interdigital capacitor 401 are electrically connected to the two signal ports of the resonator, and the interdigital capacitor 401 is connected in parallel with the interdigital transducer 2.

[0037] Specifically, from Figure 1 and Figure 2As can be seen, the resonator structure in this embodiment adds an additional stacked protection structure 4 outside the reflective gate 3. The interdigital capacitor 401 of the stacked protection structure 4 is formed by an interdigital electrode structure similar to an IDT electrode (including two opposing busbars and alternating fingers between the two busbars) formed by a metal layer, and an organic material layer 402 is added on top of it by photolithography. The interdigital capacitor 401 and the organic dielectric layer covering it form an additional capacitor integrated inside the chip. The two busbars of the interdigital capacitor 401 of the stacked protection structure 4 are electrically connected to the two signal ports of the interdigital transducer 2, and the interdigital capacitor 401 is connected in parallel with the interdigital transducer 2. When an ESD event occurs, this capacitor can store part of the instantaneous large current charge, effectively increasing the capacitive reactance in the ESD discharge path, thereby significantly reducing the peak ESD current and voltage stress flowing into the working area of ​​the core resonator, converting the sharp ESD pulse into a waveform with a smoother energy distribution, and improving the ESD withstand threshold of the device. Meanwhile, since the added multilayer protection structure 4 is located outside the resonator operating area (interdigital transducer 2 and reflector grating 3) and connected in parallel with the interdigital transducer 2, no changes are made to the electrode structure (such as finger width, spacing, and overlap length) of the interdigital transducer 2 itself, which determines key performance characteristics such as resonant frequency and Q value. Therefore, by adopting the resonator structure of this embodiment, the core RF performance of the filter, such as center frequency, bandwidth, insertion loss, and out-of-band rejection, is maintained to the maximum extent, overcoming the problem of performance degradation caused by changing the IDT structure to resist ESD. The organic material layer 402 covering the interdigital capacitor 401 in the multilayer protection structure 4 can effectively absorb acoustic wave energy and block the propagation of surface acoustic waves that may be excited in this area, so that the multilayer protection structure 4 presents itself as a pure and uniform capacitive element over a wide frequency range, without generating stray resonance peaks caused by piezoelectric effect, thereby ensuring the filter's good out-of-band rejection characteristics.

[0038] like Figure 1 and Figure 2 As shown, in this embodiment, the two signal ports of the resonator are connected to the two busbars of the interdigital capacitor 401 through two signal lines 5. One signal line 5 is connected to the busbar 403 at one end of the interdigital capacitor 401 and the busbar 201 at one end of the interdigital transducer 2, respectively. The other signal line 5 is connected to the busbar 403 at the other end of the interdigital capacitor 401 and the busbar 201 at the other end of the interdigital transducer 2, respectively.

[0039] Specifically, one signal port of the resonator is connected via a signal trace 5 to a busbar 201 of the interdigital transducer 2 and a busbar 403 of the interdigital capacitor 401 of the stacked protection structure 4. The other signal port is connected via another signal trace 5 to another busbar 201 of the interdigital transducer 2 and another busbar 403 of the interdigital capacitor 401 of the stacked protection structure 4. The two signal ports are not interconnected. This connection relationship achieves parallel connection between the stacked protection structure 4 (interdigital capacitor 401) and the resonator's operating region (interdigital transducer 2). In this embodiment, the two signal traces 5 are the input signal line and ground signal line of the resonator, respectively.

[0040] Figure 3 This is a schematic cross-sectional view along the AA' direction in the structure shown in Figure 9 (its presence is ignored in the schematic view because the passivation layer 8 is widely covered). Figure 3 As shown, in this embodiment, the interdigital electrode structure of the interdigital transducer 2, the reflective grating 3, and the interdigital capacitor 401 are all patterned from the same first metal layer 6. The number of fingers in the interdigital capacitor 401 within the stacked protective structure 4 can be adjusted according to actual needs and layout area. Simultaneously, the coverage area of ​​the organic material layer 402 does not need to cover all fingers and can be set according to the actual layout rules.

[0041] like Figure 4 As shown, the interdigital transducer 2 has a passivation layer 8, an isolation layer 9, and a second metal layer 7 on its interdigital electrode structure (first metal layer 6). The passivation layer 8 covers the interdigital electrode structure (first metal layer 6) and protects it. The second metal layer 7 is connected to the interdigital electrode structure and serves as a metal trace for electrical connection between resonators. The isolation layer 9 is disposed between the interdigital electrode structure and the second metal layer 7 to achieve electrical isolation between them. In this embodiment, the organic material layer 402 and the isolation layer 9 are made of the same material and are formed in the same process step. The organic material layer 402 is made of polyimide.

[0042] Specifically, the first metal layer 6 is the metal layer constituting the IDT electrode of the interdigital transducer 2, the array of reflective gratings 3, and the interdigital capacitor 401 in the stacked protective structure 4 of the resonator. It is disposed on the piezoelectric substrate 1. The first metal layer 6 is mainly composed of various metals and metal alloys, such as aluminum (Al), chromium (Cr), titanium (Ti), copper (Cu), gold (Au), or combinations thereof. In this embodiment, the IDT electrode of the interdigital transducer 2, the array of reflective gratings 3, and the interdigital capacitor 401 in the stacked protective structure 4 can be simultaneously formed by depositing the first metal layer 6 on the piezoelectric substrate 1 and then patterning it. The IDT composed of the first metal layer 6 is generally thinner than the second metal layer 7 and is the main acoustic-electric excitation structure, which performs acoustic-electric transduction by applying voltage. The piezoelectric substrate 1 can be formed of various materials, including aluminum nitride, zinc oxide, lithium tantalate (LiTaO3), or lithium niobate (LiNbO3), or doped with these materials.

[0043] Above the first metal layer 6 is a passivation layer 8, which protects the first metal layer 6 to form the interdigital transducer 2. Since the IDT electrode needs to perform acoustic-electric energy conversion in the external air environment, it is easily affected by external substances. Therefore, the main function of the passivation layer 8 is to protect the metal electrode from oxidation, burn-out, etc. Common passivation layers 8 are composed of silicon nitride (SiN), silicon oxide (SiO), etc. The passivation layer 8 can also be composed of multiple materials stacked together to further improve the protection effect. Optionally, the interdigital capacitor 401 can also be covered with a passivation layer 8, with an organic dielectric layer covering the passivation layer 8. The passivation layer 8 on the interdigital transducer 2 and the interdigital capacitor 401 can be completed in the same process step by depositing materials such as silicon nitride (SiN) and silicon oxide (SiO).

[0044] Subsequently, an isolation layer 9 is formed in a predetermined area using photolithography. Isolation layer 9 is a thin film that isolates electrical properties; it is composed of non-conductive organic materials, such as polyimide. This organic thin film is used to isolate the first metal layer 6 and the second metal layer 7, enabling complex circuit connections and providing designers with greater flexibility in layout. In this embodiment, isolation layer 9 can be simultaneously formed on the interdigital transducer 2 and the interdigital capacitor 401 using the same process step. The isolation layer 9 formed on the interdigital capacitor 401 is the organic dielectric layer.

[0045] The second metal layer 7 is disposed on the interdigital transducer 2, and is mainly composed of aluminum (Al), copper (Cu), or various alloys. It is thicker than the first metal layer 6 of the interdigital electrodes and interdigital capacitors 401 of the stacked protective structure 4 that make up the interdigital transducer 2, exhibiting a smaller sheet resistance. By stacking the second metal layer 7 between the first metal layers 6, the resistance caused by layout traces in the filter can be effectively reduced, thereby improving the insertion loss of the filter. Simultaneously, combining and alternating the first metal layer 6, the second metal layer 7, and the isolation layer 9 allows for complex circuit connections. Therefore, the second metal layer 7 mainly realizes the connection of traces between resonators.

[0046] refer to Figure 3 In this embodiment, the two signal traces 5 of the resonator are composed of a first metal layer 6 and a second metal layer 7 stacked together. The two signal traces 5 can be fabricated simultaneously in the steps of patterning the first metal layer 6 to fabricate the IDT electrode and the interdigital capacitor 401 and in the step of patterning the second metal layer 7.

[0047] Furthermore, in this embodiment, the fingers of the interdigitated capacitor 401 of the stacked protection structure 4 can be designed in various optional forms according to ESD protection requirements.

[0048] In one example, such as Figure 2 As shown, the fingers of the interdigital capacitor 401 can be designed as straight fingers, the same as those of the interdigital transducer 2. For straight fingers, the pitch between the fingers of the interdigital capacitor 401 needs to be designed to be smaller than that between the fingers of the interdigital transducer 2, so that the stacked protection structure 4 is more sensitive to electrostatic shock than the interdigital transducer 2 when the resonator is working normally.

[0049] In another example, such as Figure 5 As shown, the spacing between the fingers of the interdigitated capacitor 401 in the stacked protection structure 4 can be further reduced according to the actual capacitance value requirements. Multiple rectangular bumps 404 (hammer head structure) can be added to the ends and sides of the fingers of the interdigitated capacitor 401 in the stacked protection structure 4 to increase the capacitance value.

[0050] In yet another example, such as Figure 6 As shown, multiple protruding tip structures 405 can be added to both sides of the interdigital capacitor 401 of the stacked protection structure 4, depending on the requirements. This structure can further enhance the sensitivity of the interdigital capacitor 401, which is used to release charge and make it act as a sacrificial electrode to protect the normally functioning interdigital transducer 2 and reflective grid 3.

[0051] In this embodiment, a stacked protection structure 4 is provided on both sides of the resonator operating region (interdigital transducer 2 and reflective grating 3). In other embodiments, depending on the layout requirements, one or more of the stacked protection structures 4 can be provided on the same side of the interdigital transducer 2, and no stacked protection structure 4 can be provided on the other side of the interdigital transducer 2; or, stacked protection structures 4 can be provided on both sides of the interdigital transducer 2, and the number of stacked protection structures 4 provided on both sides of the interdigital transducer 2 is different, for example, one stacked protection structure 4 is provided on one side and two stacked protection structures 4 are provided on the other side.

[0052] In this embodiment, the stacked protective structure 4 is arranged collinearly with respect to the interdigital transducer 2 in the layout. That is, the central axis of the interdigital structure of the interdigital capacitor 401, the central axis of the interdigital transducer 2, and the central axis of the periodic structure of the reflector grating 3 are designed to be located on the same straight line. They are arranged in a straight line along the propagation direction of surface acoustic waves, and the extension directions of the fingers of the interdigital capacitor 401, the fingers of the interdigital transducer 2, and the fingers of the reflector grating 3 are all perpendicular to the propagation direction of surface acoustic waves.

[0053] In other embodiments, depending on the layout requirements, the stacked protection structure 4 can be rotated by a set angle relative to the interdigital transducer 2 in the layout (i.e., there is an angle between the extension direction of the interdigital capacitor 401 and the extension direction of the interdigital transducer 2), or the stacked protection structure 4 and the interdigital transducer 2 can be arranged non-collinearly.

[0054] The protection principle of the multilayer protective structure 4 in this embodiment against electrostatic shock is based on the following two points: 1. The multilayered protection structure 4 adds an additional path for the release of electrostatic current, thereby protecting the resonator during normal operation. From an electrical performance perspective, the electrodes formed by the first metal layer 6 in the multilayered protection structure 4 intersect to form interdigital capacitors 401. Connecting the two ends of the interdigital capacitors 401 to both sides of the resonator's basic structure (including the interdigital transducer 2 and the reflective grid 3) is equivalent to adding an additional energy storage element. The interdigital capacitors 401 absorb external electrostatic current to a certain extent, increasing the capacitive reactance at ESD weak points and effectively reducing the current peak during ESD discharge, thereby improving the protection effect. The larger the capacitance, the more significant the protection effect.

[0055] When ESD current enters through signal trace 5, the resonator's capacitive reactance is low. The larger the ESD current, the worse the protection capability. Conversely, if the capacitive reactance is high, the peak value of the ESD current at the input is lower, and the ESD pulse current is smoother. Therefore, in the ESD discharge path, by combining the stacked protection structure 4 with the resonator's basic structure, the capacitive reactance at the resonator can be increased, thereby reducing the peak value of the ESD pulse, making the ESD waveform smoother, and the energy distribution more dispersed, which is beneficial for ESD protection.

[0056] 2. The sensitivity of the multilayer protective structure 4 to electrostatic discharge (ESD) is adjusted by artificial means to make it more sensitive than the operating area of ​​the resonator (interdigital transducer 2 and reflector grating 3) during normal operation. When an external ESD event occurs, the multilayer protective structure 4 will be damaged due to its higher sensitivity, thus protecting the normally operating interdigital transducer 2 and reflector grating 3. The most common method to adjust the sensitivity is to make the spacing of the interdigital structure of the multilayer protective structure 4 smaller than that of the normally operating resonator. The shape of the electrodes in the multilayer protective structure 4 can also be adjusted, for example, by adding hammerheads or pointed structures to the finger strips of the interdigital capacitor 401 in the multilayer protective structure 4.

[0057] The laminated protective structure 4 in this embodiment also has the following additional advantages: 1. By using organic materials as the dielectric layer of the laminated protective structure 4, the capacitance value is effectively improved. Since the dielectric constant of the dielectric layer (approximately 3.5) is greater than that of air, the capacitive reactance is further increased. 2. By isolating the air with organic materials, the transmitted sound waves are absorbed, hindering the propagation of the sound waves. Therefore, the stacked protective structure 4 exhibits a uniform capacitance over a wide frequency range and will not have stray modes excited by the piezoelectric effect, which would affect the out-of-band suppression effect of the filter. 3. Integrated process: The stacked protective structure formed by the interdigital capacitor 401 and the organic material layer 402 can be implemented in the same process as the surface acoustic wave filter, without the need for additional process steps, thus saving costs. 4. Adding organic layer materials can further increase the heat dissipation passband of the resonator under high power, and further improve the power tolerance of the filter.

[0058] Example 2

[0059] This embodiment provides a surface acoustic wave filter, including multiple resonators, wherein at least one resonator is the surface acoustic wave resonator described in Embodiment 1, and the resonator is located on the electrostatic discharge path or at the port of the filter.

[0060] The surface acoustic wave (SAW) filter of this embodiment may include both a conventional SAW resonator (with only interdigital transducers and reflector grids) and the SAW resonator with stacked protection structure 4 of Embodiment 1. When designing the filter, the location of the resonator with weak ESD protection located on the electrostatic discharge path or at the port of the filter is identified in advance. The SAW resonator with stacked protection structure 4 of Embodiment 1 is used at the location with weak ESD protection to improve the ESD resistance.

[0061] In one example, such as Figure 7 As shown, the surface acoustic wave filter is provided with a metal trace 10, and a first input port A1, a second input port A2, a first output port B1, a second output port B2, a first ground port C1, and a second ground port C2 are connected to the metal trace 10. The first surface acoustic wave filter 100 with the stacked protection structure 4 of embodiment 1 is set at the first output port A1 and the first output port B1 where the filter's ESD protection is weak, so as to improve the filter's ESD resistance. Multiple conventional second surface acoustic wave resonators 200 are used at other positions.

[0062] Meanwhile, based on the actual usage requirements of the filter, a first surface acoustic wave filter 100 with an added stacked protection structure 4 is used near the input and output ports of the filter. The impedance matching of the input and output terminals can be adjusted according to the capacitance value. Thus, the interdigitated capacitor 401 in the stacked protection structure 4 replaces the external matching capacitor that was originally required, so that the filter can achieve 50-ohm matching with a single device, further reducing the area of ​​module integration.

[0063] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A surface acoustic wave resonator, characterized in that, include: An interdigital transducer disposed on a piezoelectric substrate, a reflective grating located on both sides of the interdigital transducer, and at least one stacked protective structure disposed in the outer region of the reflective grating; The stacked protective structure includes interdigitated capacitors disposed on the surface of the piezoelectric substrate, and an organic material layer covering the interdigitated capacitors. The two busbars of the interdigital capacitor are electrically connected to the two signal ports of the resonator, and the interdigital capacitor is connected in parallel with the interdigital transducer.

2. The surface acoustic wave resonator according to claim 1, characterized in that, The two signal ports of the resonator are connected to the two busbars of the interdigital capacitor through two signal lines. One signal line is connected to the busbar at one end of the interdigital capacitor and the busbar at one end of the interdigital transducer, respectively. The other signal line is connected to the busbar at the other end of the interdigital capacitor and the busbar at the other end of the interdigital transducer, respectively.

3. The surface acoustic wave resonator according to claim 1, characterized in that, The interdigitated capacitor has multiple rectangular protrusions at the ends and sides of the fingers.

4. The surface acoustic wave resonator according to claim 1, characterized in that, The interdigitated capacitor has multiple protruding tip structures on both sides of the fingers.

5. The surface acoustic wave resonator according to claim 1, characterized in that, The spacing between the fingers of the interdigital capacitor is smaller than the spacing between the fingers of the interdigital transducer.

6. The surface acoustic wave resonator according to claim 1, characterized in that, At least one of the aforementioned stacked protective structures is disposed on the same side of the interdigital transducer; Alternatively, at least one of the stacked protective structures may be provided on both sides of the interdigital transducer, and the number of the stacked protective structures provided on both sides of the interdigital transducer may be the same or different.

7. The surface acoustic wave resonator according to claim 1, characterized in that, The interdigital electrode structure of the interdigital transducer, the reflective grating, and the interdigital capacitor are all patterned from the same first metal layer.

8. The surface acoustic wave resonator according to claim 7, characterized in that, The interdigital transducer has a passivation layer, an isolation layer, and a second metal layer on its interdigital electrode structure. The passivation layer covers the interdigitated electrode structure to protect it; the second metal layer is connected to the interdigitated electrode structure to provide metal traces for electrical connection between resonators; the isolation layer is disposed between the interdigitated electrode structure and the second metal layer to provide electrical isolation between them.

9. The surface acoustic wave resonator according to claim 8, characterized in that, The organic material layer and the isolation layer are made of the same material, and the organic material layer and the isolation layer are formed in the same process step; The organic material layer is made of polyimide.

10. The surface acoustic wave resonator according to claim 1, characterized in that, The layered protective structure is arranged collinearly with respect to the interdigitated transducer in the layout; Alternatively, the stacked protective structure may be rotated by a set angle or non-collinearly arranged relative to the interdigital transducer in the layout.

11. A surface acoustic wave filter, characterized in that, It includes multiple resonators, wherein at least one resonator is a surface acoustic wave resonator according to any one of claims 1 to 10, and the resonator is located on the electrostatic discharge path or at the port of the filter.

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