A warm and tonic type surface acoustic wave resonator and a manufacturing method thereof

Abstract

The application discloses a temperature compensation type surface acoustic wave resonator and a manufacturing method, and relates to the technical field of surface acoustic wave resonators. A first insertion layer is added on the side of the first temperature compensation layer away from the interdigital structure layer, a sound speed propagation area different along a first direction can be formed, a piston mode effect is generated in the direction of parallel fingers, reflection of transverse mode stray sound waves is generated on the interface of different media, the main acoustic propagation mode is not affected, and the transverse stray mode is effectively inhibited. The technical scheme sets the insertion layer with an edge flush with the position of the false finger end, so that the sound speed difference is greater when the sound wave propagates in the aperture area and the false finger area, thereby further inhibiting the transverse mode. The density of the second temperature compensation layer is smaller than that of the first temperature compensation layer, and the relatively loose second temperature compensation layer does not affect the temperature compensation effect and can shorten the deposition time.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) resonators, and more particularly to a temperature-compensated SAW resonator and its fabrication method. Background Technology

[0002] For TC-SAW (Temperature Compensated-Surface Acoustic Wave) resonators, there are transverse resonant modes, that is, clutter appears in and near the passband. This clutter increases device losses, causes the quality factor Q to fluctuate significantly, and reduces the performance of the resonator and filter.

[0003] To suppress transverse stray modes in temperature-compensated surface acoustic wave (SAW) resonators, one approach is to add a velocity change section. This involves adding a velocity change structure at the tip of the electrode fingers or similar locations to suppress transverse modes. However, due to limitations in photolithography, the formation of this velocity change section is often size-restricted, resulting in an excessively large device area and the potential for acoustic diffraction. Another approach is to modify the substrate structure by etching grooves into the substrate and creating velocity change structures within them to suppress transverse modes. However, this increases process complexity, the number of mask layers, and manufacturing costs, and the suppression effect is also affected by material limitations.

[0004] Therefore, how to suppress transverse stray modes in a temperature-compensated surface acoustic wave resonator is the key problem that this technical solution aims to solve. Summary of the Invention

[0005] In order to solve at least one of the technical problems mentioned in the background art, the present invention aims to provide a temperature-compensated surface acoustic wave resonator and its manufacturing method, which can utilize the Piston mode to reduce stray energy loss, improve the performance of the resonator, reduce the difficulty of the process, and accelerate the manufacturing speed.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a temperature-compensated surface acoustic wave resonator, including... piezoelectric substrate; An interdigitated structure layer is located on one side of the piezoelectric substrate along a third direction. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite each other in a first direction, and alternating fingers and pseudo-fingers arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in the second direction, and the fingers on the second busbar are also spaced apart in the second direction. The fingers on the first busbar correspond one-to-one with the pseudo-fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the pseudo-fingers on the first busbar. The corresponding fingers and pseudo-fingers are located on the same straight line, and there is a gap between the fingers and pseudo-fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other. A first temperature compensation layer, located on one side of the piezoelectric substrate along a third direction and completely covering the interdigitated structure layer in the third direction; further comprising: The first insertion layer is located on the side of the first temperature compensation layer away from the interdigital structure layer. Its projection in the third direction covers all finger strips but does not cover the prosthesis. Furthermore, the projection of the two side boundaries of the first insertion layer, which are parallel to the second direction, in the third direction is flush with the end of the prosthesis.

[0007] Furthermore, it also includes a second temperature compensation layer, which is located on one side of the first temperature compensation layer along the third direction and completely covers the first insertion layer in the third direction.

[0008] Furthermore, the material of the first insertion layer includes silicon nitride.

[0009] Furthermore, the material of the first temperature compensation layer and / or the second temperature compensation layer includes silicon dioxide.

[0010] Furthermore, the second temperature compensation layer has a lower density than the first temperature compensation layer.

[0011] Furthermore, the thickness of the first insertion layer is greater than or equal to 10 nm and less than or equal to 200 nm.

[0012] Secondly, embodiments of the present invention provide a method for fabricating a temperature-compensated surface acoustic wave resonator, including... Provide piezoelectric substrates; An interdigitated structure layer is formed on one side of a piezoelectric substrate. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite each other in a first direction, and fingers and pseudo-fingers alternately arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in a second direction, and the fingers on the second busbar are also spaced apart in the second direction. The fingers on the first busbar correspond one-to-one with the pseudo-fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the pseudo-fingers on the first busbar. The corresponding fingers and pseudo-fingers are located on the same straight line, and there is a gap between the fingers and pseudo-fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other. A first temperature compensation layer is formed on one surface of the piezoelectric substrate along a third-direction orientation, the first temperature compensation layer completely covering the interdigitated structure layer in the third-direction orientation; the substrate further includes: A first insertion layer is formed on the side of the first temperature compensation layer away from the interdigital structure layer. Its projection in the third direction covers all finger strips but not the prosthesis. The projection of the two side boundaries of the first insertion layer, which are parallel to the second direction, in the third direction is flush with the end of the prosthesis.

[0013] Furthermore, it also includes: A second temperature compensation layer is formed on one side of the first temperature compensation layer along the third direction, and the second temperature compensation layer completely covers the first insertion layer in the third direction.

[0014] Furthermore, the material of the first insertion layer includes silicon nitride.

[0015] Furthermore, the material of the first temperature compensation layer and / or the second temperature compensation layer includes silicon dioxide.

[0016] Furthermore, the second temperature compensation layer has a lower density than the first temperature compensation layer.

[0017] Compared with the prior art, the beneficial effects of the present invention are: Adding a first insertion layer on the side of the first temperature compensation layer away from the interdigitated structure layer can form a sound propagation region with different sound speeds along the first direction, producing a piston mode effect in the direction parallel to the fingers, generating reflection of transverse mode stray sound waves at the interface of different media, without affecting the main acoustic propagation mode, effectively suppressing transverse stray modes, and improving the performance of the resonator. Because the pseudo-finger structure can create a region of abrupt change in sound speed, thereby reducing the energy dissipation of the transverse mode through reflection, this technical solution sets an insertion layer with the edge just flush with the end of the pseudo-finger, so that the sound wave has a greater sound speed difference when propagating in the aperture region and the pseudo-finger region, thereby further suppressing the transverse mode. The second temperature compensation layer has a lower density than the first temperature compensation layer. The relatively loose second temperature compensation layer will not affect the temperature compensation effect and can shorten the deposition time. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a temperature-compensated surface acoustic wave resonator in a vertical cross section is provided for an embodiment of the present invention; Figure 2 A top view of a temperature-compensated surface acoustic wave resonator provided in an embodiment of the present invention; Figure 3 A schematic diagram of a cross-sectional line provided for an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a double-layer temperature-compensated surface acoustic wave resonator in a vertical cross section, provided by an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the change in sound speed perpendicular to the direction of sound wave propagation, provided as an embodiment of the present invention. Figure 6 This is a simulation result comparing the admittance-frequency curves of a temperature-compensated surface acoustic wave resonator and a conventional resonator provided in an embodiment of the present invention. Figure 7 This is a simulation result comparing the conductance-frequency curves of a temperature-compensated surface acoustic wave resonator and a traditional resonator provided in an embodiment of the present invention. Figure 8 This is a schematic diagram of the structure of a SAW resonator in a vertical cross section, provided by an embodiment of the present invention. Figure 9 A schematic diagram of the structure of a TF-SAW resonator in a vertical cross section is provided for an embodiment of the present invention; Figure 10 A flowchart illustrating a method for fabricating a temperature-compensated surface acoustic wave resonator according to an embodiment of the present invention; Figure 11 A flowchart illustrating a method for fabricating a double-layer temperature-compensated surface acoustic wave resonator, as provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Surface acoustic wave (SAW) resonators and filters are widely used acoustic devices in the radio frequency (RF) field, combining low insertion loss and good suppression performance in a small size. They primarily utilize the piezoelectric effect to convert electrical energy into and out of mechanical energy. However, SAW also has limitations, one of which is its susceptibility to temperature changes: as temperature rises, the stiffness of the substrate material decreases, and the velocity of sound also decreases. Based on this, a new device design has gradually gained increasing application in RF filtering devices in recent years: temperature-compensated SAW filters (TC-SAW). TC-SAW improves temperature drift by coating the interdigitated electrode structure with a layer of material whose stiffness increases with temperature.

[0021] For TC-SAW resonators, laterally propagating acoustic waves cause the resonator to exhibit lateral resonant modes, i.e., clutter appearing in and near the passband. This clutter increases device losses, causes significant fluctuations in the Q value, and degrades the performance of the resonator and filter. Therefore, how to suppress lateral spurious modes in surface acoustic wave resonators with temperature compensation is the key problem that this technical solution aims to solve.

[0022] To address the aforementioned problems in the prior art, this invention provides a temperature-compensated surface acoustic wave resonator and its fabrication method, which will be described in detail below.

[0023] In a first aspect, embodiments of the present invention provide a temperature-compensated surface acoustic wave resonator.

[0024] Example 1: like Figure 1 As shown, Figure 1 A schematic diagram of the structure of a temperature-compensated surface acoustic wave resonator in a vertical cross-section is provided for an embodiment of the present invention, including... Piezoelectric substrate 101; Interdigitated structure layer 102; First temperature compensation layer 103; First insertion layer 104.

[0025] and Figure 1 Correspondingly, such as Figure 2 As shown, Figure 2 This is a top view of a temperature-compensated surface acoustic wave resonator provided in an embodiment of the present invention.

[0026] The interdigitated structure layer 202 is located on the surface of the piezoelectric substrate 201 along a third direction, including a first busbar 2021 and a second busbar 2022 disposed opposite to each other in a first direction, and fingers 2023 and pseudo-fingers 2024 alternately arranged on the first busbar and the second busbar; the fingers 2023 on the first busbar 2021 are spaced apart in a second direction, and the fingers 2023 on the second busbar 2022 are spaced apart in a second direction; the fingers 2023 on the first busbar 2021 correspond one-to-one with the pseudo-fingers 2024 on the second busbar 2022, and the fingers 2023 on the second busbar 2022 correspond one-to-one with the pseudo-fingers 2024 on the first busbar 2021, the corresponding fingers 2023 and pseudo-fingers 2024 are located on the same straight line, and there is a gap between the fingers 2023 and pseudo-fingers 2024; the first direction and the second direction are parallel to the surface of the piezoelectric substrate 201, and the first direction and the second direction are perpendicular to each other.

[0027] The first temperature compensation layer (which coincides with the piezoelectric substrate in the top view and is therefore not shown in the figure) is located on one side of the piezoelectric substrate 201 along the third direction and completely covers the interdigitated structure layer 202 in the third direction.

[0028] The first insertion layer 204 (shaded area in the figure) is located on the side of the first temperature compensation layer away from the interdigital structure layer 202. Its projection in the third direction covers all the finger strips 2023 but does not cover the spur finger 2024. The two side boundaries of the first insertion layer 204, which are parallel to the second direction, are flush with the end of the spur finger 2024 in the projection in the third direction.

[0029] The aforementioned "first direction" refers to the direction parallel to the finger strip, the "second direction" refers to the direction parallel to the first bus bar / second bus bar, and the "third direction" refers to the direction perpendicular to the plane containing any surface of the piezoelectric substrate 201.

[0030] It should be noted that, Figure 1 The cross-sectional structure shown is a "schematic diagram" because it is necessary to simultaneously represent structural features such as busbars and electrode fingers in one diagram. Figure 1 It is equivalent to combining the feature parts of two vertical cross-sectional images.

[0031] like Figure 3 As shown, Figure 3 This is a schematic diagram of a cross-sectional line provided for an embodiment of the present invention. Figure 3 It contains two section lines, AA' and BB'. The sectional views obtained along these two section lines are combined to form a... Figure 1 The diagram shows a vertical cross-section.

[0032] The piezoelectric substrate 201 can be made of materials such as quartz, aluminum nitride, LN (lithium niobate, LiNbO3), LT (lithium tantalate, LiTaO3), etc. This invention does not limit the materials used, but lithium niobate or lithium tantalate is preferred. These materials have advantages such as excellent piezoelectric effect and electromechanical coupling effect, and are widely used in surface acoustic wave devices.

[0033] The interdigitated structure layer 202, deposited on the piezoelectric substrate 201, is the most basic unit constituting the surface acoustic wave resonator. It includes a first busbar 2021 and a second busbar 2022 spaced apart and opposite to each other in the first direction, as well as finger strips 2023 and dummy fingers 2024 on the first busbar 2021 and the second busbar 2022. The length of the dummy fingers can be adjusted according to the actual situation. Preferably, the length of the dummy fingers is 0.2 to 2 times (i.e. 0.2-2λ) of the wavelength of the sound wave in the main acoustic mode.

[0034] Since SAW devices are susceptible to temperature changes, temperature drift can be mitigated by coating them with a temperature compensation material that has a positive frequency temperature coefficient.

[0035] A first temperature compensation layer is coated on the interdigitated structure layer 202 and can be made of silicon dioxide, but is not limited to this material. The thickness of the first temperature compensation layer is greater than the thickness of the interdigitated structure layer 202 (i.e., it must completely cover the interdigitated structure layer), and is generally set in the range of 0.2 to 0.5 times (i.e., 0.2λ to 0.5λ) of the wavelength of the main acoustic mode. It is used to compensate for the negative temperature effect of the resonator. In addition, sandwiched between the interdigitated structure layer 202 and the first insertion layer 204, it can also provide an insulating effect. For certain special piezoelectric substrates (e.g., 128°YXLiNbO3 substrates), the first temperature compensation layer can effectively suppress the transverse shear wave mode excited by the finger strips.

[0036] The first insertion layer 204 is deposited on the first temperature compensation layer and can be made of silicon nitride (Si3N4). Silicon nitride can improve the sound velocity. The sound wave of the main acoustic mode propagates along the length of the busbar in the interdigital structure layer 202. The projection of the first insertion layer 204 in the third direction covers all the fingers 2023 but not the dummy fingers 2024. Furthermore, the two side boundaries of the first insertion layer 204, which are parallel to the second direction, are flush with the ends of the dummy fingers 2024. Figure 2 For example, Figure 2 The first insertion layer 204 is rectangular, with its longer side covering all the finger strips 2023. The projections of the two boundaries of the first insertion layer 204 parallel to the second direction onto the third direction do not cover the spur finger 2024, and the projections of these two boundaries onto the third direction (i.e., the projections in the vertical direction) are flush with the spur finger 2024 on the corresponding side.

[0037] The first insertion layer 204 produces a Piston Mode effect by changing the sound speed. Combined with the pseudo-finger design in the interdigitated structure layer 202, it enables the resonator to generate more distinct regions of different sound speeds in the direction parallel to the finger strip, thereby suppressing the resonance of clutter in that direction.

[0038] Sound waves are a typical type of elastic wave. When elastic waves propagate through matter, they encounter the interface between different media (i.e., regions with different sound velocities), which reflects waves whose propagation direction is not parallel to the interface direction. This prevents the formation of stray modes and thus avoids energy dissipation. Therefore, by increasing the sound velocity in this region through the first insertion layer, sound waves in directions other than the propagation direction of the main acoustic mode are reflected at the sound velocity interface, thereby dissipating their energy (i.e., Piston mode). The way the first insertion layer is set (projecting in a third direction to cover all fingers) ensures that the sound waves in the propagation direction of the main acoustic mode (i.e., along the direction of the busbar) are not affected, thus achieving the removal of transverse stray modes. Because the pseudo-finger structure can already form a region of abrupt change in sound velocity, thereby reducing the energy dissipation of transverse modes through reflection, this technical solution, by setting the insertion layer with its edge flush with the end of the pseudo-finger, creates a larger sound velocity difference when the sound wave propagates in the aperture region and the pseudo-finger region, thereby further suppressing transverse modes.

[0039] Example 2: Based on Embodiment 1, a second temperature compensation layer is also included, located on one side of the first temperature compensation layer along the third direction, and completely covering the first insertion layer in the third direction.

[0040] like Figure 4 As shown, Figure 4 This is a schematic diagram of the structure of a double-layer temperature-compensated surface acoustic wave resonator in a vertical cross section, provided as an embodiment of the present invention.

[0041] Unlike Embodiment 1, a second temperature compensation layer 405 is added above the first insertion layer. This second temperature compensation layer can be made of silicon dioxide or other temperature compensation materials with a positive frequency temperature coefficient. The present invention does not limit the choice of these materials. The second temperature compensation layer covers the first insertion layer and has a thickness of 1 to 1.5 times that of the first insertion layer. It can be used to fine-tune the frequency of the resonator through a trimming process. It can protect the first insertion layer and the internal structure of the resonator, and further compensate for negative temperature effects. In a preferred embodiment, the width of the second temperature compensation layer is consistent with the width of the first temperature compensation layer. Both layers cover an interdigitated structure layer in the third direction, which can further improve the temperature drift phenomenon without increasing the additional process cost.

[0042] Example 3: Based on Example 2, a faster deposition rate is used when forming the second temperature compensation layer, resulting in a more porous temperature compensation layer. Those skilled in the art can select an appropriate deposition rate based on their experience. Since the second temperature compensation layer is used to improve the temperature compensation effect and protect the insertion layer, it does not affect the temperature compensation effect, improves thickness uniformity, and shortens the time required for the vapor deposition process.

[0043] For refractory materials like SiO2, electron beam evaporation is a commonly used process. This involves vaporizing the material, allowing particles to condense and form a film on the substrate surface. Upon reaching the surface, particles undergo reflection, surface diffusion, and collisions, forming clusters. When the number of particles exceeds a certain critical value, these clusters become stable nuclei, attracting further particles and ultimately forming a thin film. Clearly, for dense structures, the higher diffusion and collision rates amplify the critical value, leading to a greater thickness variation and poorer uniformity compared to porous structures. Therefore, using a porous structure can improve thickness uniformity while reducing the evaporation process time.

[0044] like Figure 5 As shown, Figure 5 This is a schematic diagram illustrating the change in sound speed perpendicular to the direction of sound wave propagation, provided as an embodiment of the present invention. Figure 5 In the middle, the sound speed is highest in the gap between the finger bar and the prosthetic finger. The prosthetic finger and the busbar reduce the sound speed. The sound speed in the prosthetic finger is higher than that in the busbar because the busbar area is near the edge and has been attenuated by energy dissipation. The first insertion layer, being made of silicon nitride, can increase the sound speed. Therefore, the sound speed in the first insertion layer area is higher than that in the finger bar areas not covered by the first insertion layer. The sound speed in the gap between the finger bar and the prosthetic finger is higher than that in the finger bar areas covered by the first insertion layer because the finger bar reduces the sound speed.

[0045] By combining the pseudo-finger structure with the first insertion layer to form different sound speed propagation regions, the sound speed difference at the interface is maximized, generating as many reflections of transverse mode stray sound waves as possible at this interface, thereby suppressing clutter without affecting the main acoustic propagation mode. Since the pseudo-finger structure can already form a region of abrupt change in sound speed, thereby reducing the energy dissipation of the transverse mode through reflection, this technical solution further suppresses the transverse mode by setting the insertion layer with its edge flush with the end of the pseudo-finger, so that the sound wave propagation has a greater sound speed difference between the aperture region and the pseudo-finger region.

[0046] like Figure 6 As shown, Figure 6 This is a simulation comparison of the admittance-frequency curves of a temperature-compensated surface acoustic wave resonator (SAW) provided in this embodiment of the invention and a conventional resonator. The solid line represents the conventional resonator, and the dashed line represents the temperature-compensated SAW resonator provided in this embodiment of the invention.

[0047] Due to the excitation of transverse modes, the resonant frequency and anti-resonant frequency of a conventional resonator without the first insertion layer 404 exhibit irregular fluctuations. However, by adding the first insertion layer, the admittance-frequency curve becomes smooth, demonstrating that it can effectively suppress transverse spurious modes in the passband range and improve the performance of the resonator.

[0048] like Figure 7 As shown, Figure 7 This is a simulation comparison of the conductance-frequency curves of a temperature-compensated surface acoustic wave resonator provided in this embodiment of the invention and a conventional resonator. The solid line represents the conventional resonator, and the dashed line represents the resonator provided in this embodiment of the invention that suppresses transverse spurious modes.

[0049] In the improved resonator's conductance-frequency curve, interference is greatly reduced. Taking a frequency of around 830MHz as an example, the excitation of transverse modes at this frequency is suppressed by more than 15dB.

[0050] Example 4: The design of the first insertion layer in Embodiment 1 or Embodiment 2 described above can also be used in ordinary SAW resonators. For example... Figure 8 As shown, Figure 8 A schematic diagram of the structure of a SAW resonator in a vertical cross-section is provided for an embodiment of the present invention, including... 801 piezoelectric substrate; An interdigitated structure layer 802 is located on the surface of the piezoelectric substrate 801 along a third direction, including a first busbar 8021 and a second busbar 8022 disposed opposite to each other in a first direction, and fingers 8023 and pseudo-fingers 8024 alternately arranged on the first and second busbars; the fingers 8023 on the first busbar 8021 are spaced apart in a second direction, and the fingers 8023 on the second busbar 8022 are also spaced apart in a second direction; the fingers 8023 on the first busbar 8021 correspond one-to-one with the pseudo-fingers 8024 on the second busbar 8021, and the fingers 8023 on the second busbar 8022 correspond one-to-one with the pseudo-fingers 8024 on the first busbar 8021, the corresponding fingers 8023 and pseudo-fingers 8024 are located on the same straight line, and there is a gap between the fingers 8023 and pseudo-fingers 8024; the first direction and the second direction are parallel to the surface of the piezoelectric substrate 801, and the first direction and the second direction are perpendicular to each other; The first dielectric layer 803 is located on one side of the piezoelectric substrate 801 along the third direction and completely covers the interdigitated structure layer 802 in the third direction. The first insertion layer 804 is located on the side of the first dielectric layer 803 away from the interdigital structure layer 802. Its projection in the third direction covers all the finger strips 8023 but does not cover the spur finger 8024. The two side boundaries of the first insertion layer 804, which are parallel to the second direction, are flush with the end of the spur finger 8024 in the projection in the third direction. The second dielectric layer 805 is located on one side of the first dielectric layer 803 along the third direction and completely covers the first insertion layer 804 in the third direction.

[0051] Similar to Embodiment 1 or Embodiment 2, the SAW resonator with the introduction of a first insertion layer design avoids the formation of stray modes and thus prevents energy dissipation compared to traditional SAW resonators. The first insertion layer increases the sound velocity in this region and reflects sound waves from directions other than the main acoustic mode propagation direction at the sound velocity interface, thus dissipating their energy (i.e., Piston mode). The placement of the first insertion layer (projecting in a third direction to cover all fingers) ensures that sound waves in the main acoustic mode propagation direction (i.e., along the busbar direction) are unaffected, thereby achieving the removal of lateral stray modes. Since the dummy finger structure can inherently create a region of abrupt changes in sound velocity, thereby reducing energy dissipation of lateral modes through reflection, this technical solution, by setting an insertion layer with its edge flush with the end of the dummy finger, creates a greater sound velocity difference between the aperture region and the dummy finger region, further suppressing lateral modes.

[0052] Example 5: The design of the first insertion layer in Embodiment 1 or Embodiment 2 described above can also be used in TF-SAW resonators. For example... Figure 9 As shown, Figure 9 A schematic diagram of the structure of a TF-SAW resonator in a vertical cross-section is provided for an embodiment of the present invention, including... Piezoelectric substrate 901; A piezoelectric thin film 902 covers a piezoelectric substrate 901; An interdigitated structure layer 903 is located on the surface of the piezoelectric substrate 901 along a third direction, including a first busbar 9031 and a second busbar 9032 disposed opposite to each other in a first direction, and fingers 9033 and pseudo-fingers 9034 alternately arranged on the first and second busbars; the fingers 9033 on the first busbar 9031 are spaced apart in a second direction, and the fingers 9033 on the second busbar 9032 are also spaced apart in a second direction; the fingers 9033 on the first busbar 9031 correspond one-to-one with the pseudo-fingers 9034 on the second busbar 9031, and the fingers 9033 on the second busbar 9032 correspond one-to-one with the pseudo-fingers 9034 on the first busbar 9031, the corresponding fingers 9033 and pseudo-fingers 9034 are located on the same straight line, and there is a gap between the fingers 9033 and pseudo-fingers 9034; the first direction and the second direction are parallel to the surface of the piezoelectric substrate 901, and the first direction and the second direction are perpendicular to each other; The first dielectric layer 904 is located on one side of the piezoelectric substrate 901 along the third direction and completely covers the interdigitated structure layer 903 in the third direction. The first insertion layer 905 is located on the side of the first dielectric layer 904 away from the interdigital structure layer 903. Its projection in the third direction covers all the fingers 9033 but does not cover the ends of the fingers. The two side boundaries of the first insertion layer 905, which are parallel to the second direction, are flush with the ends of the spur fingers 9034 in the projection in the third direction. The second dielectric layer 906 is located on one side of the first dielectric layer 904 along the third direction and completely covers the first insertion layer 905 in the third direction.

[0053] Similar to Embodiment 1 or Embodiment 2, the TF-SAW resonator with the introduction of a first insertion layer avoids the formation of stray modes and thus prevents energy dissipation compared to the traditional TF-SAW resonator. The first insertion layer increases the sound velocity in this region and reflects sound waves from directions other than the main acoustic mode propagation direction at the sound velocity interface, thus dissipating their energy (i.e., Piston mode). The arrangement of the first insertion layer (projecting in a third direction to cover all fingers) ensures that sound waves in the main acoustic mode propagation direction (i.e., along the busbar direction) are unaffected, thereby achieving the removal of lateral stray modes. Since the pseudo-finger structure can inherently create a region of abrupt changes in sound velocity, thereby reducing energy dissipation of lateral modes through reflection, this technical solution, by setting an insertion layer with its edge flush with the end of the pseudo-finger, creates a larger sound velocity difference between the aperture region and the pseudo-finger region, further suppressing lateral modes.

[0054] Secondly, corresponding to the above-described embodiments of the temperature-compensated surface acoustic wave resonator, the present invention also provides a method for manufacturing a temperature-compensated surface acoustic wave resonator.

[0055] Example 6: like Figure 10 As shown, Figure 10 A flowchart illustrating a method for fabricating a temperature-compensated surface acoustic wave resonator according to an embodiment of the present invention includes the following steps: Step 1001: Provide a piezoelectric substrate.

[0056] Specifically, piezoelectric substrates can be formed by physical vapor deposition sputtering or chemical vapor deposition. The materials used can be quartz, aluminum nitride, LN (lithium niobate, LiNbO3), LT (lithium tantalate, LiTaO3), etc. This invention does not limit the materials used, but lithium niobate or lithium tantalate is preferred. These materials have advantages such as excellent piezoelectric effect and electromechanical coupling effect, and are widely used in surface acoustic wave devices.

[0057] Step 1002: An interdigitated structure layer is formed on one side of the piezoelectric substrate. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite to each other in a first direction, and fingers and dummy fingers alternately arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in a second direction, and the fingers on the second busbar are spaced apart in a second direction. The fingers on the first busbar correspond one-to-one with the dummy fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the dummy fingers on the first busbar. The corresponding fingers and dummy fingers are located on the same straight line, and there is a gap between the fingers and dummy fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other.

[0058] A metal thin film is deposited on one side of the piezoelectric substrate, and then etched to form fingers, pseudo-fingers, and busbars, forming an interdigitated structure layer.

[0059] Step 1003: A first temperature compensation layer is formed on one side of the piezoelectric substrate along the third direction, and the first temperature compensation layer completely covers the interdigitated structure layer in the third direction.

[0060] To mitigate temperature drift, a first temperature compensation layer is deposited on the interdigitated structure layer. Silicon dioxide can be used, but is not limited to this material. The thickness of the first temperature compensation layer is greater than the thickness of the interdigitated structure layer (i.e., it must completely cover the interdigitated structure layer). It is typically set within 0.2 to 0.5 times the wavelength of the dominant acoustic mode (i.e., 0.2λ to 0.5λ) to compensate for the negative temperature effect of the resonator. Furthermore, sandwiched between the interdigitated structure layer 202 and the first insertion layer 204, it also provides insulation. For certain piezoelectric substrates (e.g., 128°YXLiNbO3 substrates), the first temperature compensation layer can effectively suppress transverse shear wave modes excited by the fingers.

[0061] Step 1004: A first insertion layer is formed on the side of the first temperature compensation layer away from the interdigital structure layer. The projection of the first insertion layer in the third direction covers all finger strips but does not cover the prosthesis. The projection of the two side boundaries of the first insertion layer parallel to the second direction in the third direction is flush with the end of the prosthesis.

[0062] A first insertion layer, made of silicon nitride (Si3N4), is deposited on the first temperature compensation layer. Silicon nitride can increase the sound velocity. The sound wave of the main acoustic mode propagates along the length of the busbar in the interdigital structure layer. The projection of the first insertion layer in the third direction covers all the fingers but not the prosthetic finger. Furthermore, the projection of the two side boundaries parallel to the second direction in the third direction is flush with the end of the prosthetic finger. Because the prosthetic finger structure can create a region of abrupt change in sound velocity, thereby reducing the energy dissipation of the transverse mode through reflection, this technical solution, by setting an insertion layer whose edge is just flush with the end of the prosthetic finger, creates a greater sound velocity difference when the sound wave propagates in the aperture region and the prosthetic finger region, thereby further suppressing the transverse mode.

[0063] Example 7: like Figure 11 As shown, Figure 11 A flowchart illustrating a method for fabricating a double-layer temperature-compensated surface acoustic wave resonator according to an embodiment of the present invention includes the following steps: Step 1101: Provide a piezoelectric substrate; Step 1102: An interdigitated structure layer is formed on one side of the piezoelectric substrate. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite each other in a first direction, and alternating fingers and pseudo-fingers arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in a second direction, and the fingers on the second busbar are spaced apart in a second direction. The fingers on the first busbar correspond one-to-one with the pseudo-fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the pseudo-fingers on the first busbar. The corresponding fingers and pseudo-fingers are located on the same straight line, and there is a gap between the fingers and pseudo-fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other. Step 1103: A first temperature compensation layer is formed on one side of the piezoelectric substrate along the third direction, and the first temperature compensation layer completely covers the interdigitated structure layer in the third direction. Step 1104: A first insertion layer is formed on the side of the first temperature compensation layer away from the interdigital structure layer. The projection of the first insertion layer in the third direction covers all the finger strips but does not cover the prosthesis. The two side boundaries of the first insertion layer that are parallel to the second direction are flush with the end of the prosthesis in the projection of the first insertion layer in the third direction. Step 1105: A second temperature compensation layer is formed on one side of the first temperature compensation layer along the third direction, and the second temperature compensation layer completely covers the first insertion layer in the third direction.

[0064] The difference from Embodiment Six lies only in step 1105, where a second temperature compensation layer is deposited on the first insertion layer. This second temperature compensation layer can be made of silicon dioxide or other temperature compensation materials with a positive frequency temperature coefficient; the present invention does not limit this. The second temperature compensation layer covers the first insertion layer and has a thickness of 1 to 1.5 times that of the first insertion layer. It can be used to fine-tune the frequency of the resonator through a trimming process, protect the first insertion layer and the internal structure of the resonator, and further compensate for negative temperature effects. In a preferred embodiment, the width of the second temperature compensation layer is consistent with the width of the first temperature compensation layer, and both cover an interdigitated structure layer in the vertical projection direction, which can further improve the temperature drift phenomenon without increasing additional process costs.

[0065] Example 8: Building upon Example 7, a faster deposition rate is used when forming the second temperature compensation layer, resulting in a more porous temperature compensation layer. Those skilled in the art can select an appropriate deposition rate based on their experience. Since the second temperature compensation layer is used to improve the temperature compensation effect and protect the insertion layer, it does not affect the temperature compensation effect, improves thickness uniformity, and shortens the time required for the vapor deposition process.

[0066] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0067] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," 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 components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0069] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via 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. Similarly, "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.

[0070] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element present. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A temperature-compensated surface acoustic wave resonator, comprising: piezoelectric substrate; An interdigitated structure layer is located on one side of the piezoelectric substrate along a third direction. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite each other in a first direction, and fingers and pseudo-fingers alternately arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in a second direction, and the fingers on the second busbar are also spaced apart in the second direction. The fingers on the first busbar correspond one-to-one with the pseudo-fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the pseudo-fingers on the first busbar. The corresponding fingers and pseudo-fingers are located on the same straight line, and there is a gap between the fingers and pseudo-fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other. A first temperature compensation layer, located on one side of the piezoelectric substrate along a third direction and completely covering the interdigitated structure layer in the third direction; characterized in that it further comprises: The first insertion layer is located on the side of the first temperature compensation layer away from the interdigital structure layer. Its projection in the third direction covers all finger strips but does not cover the prosthesis. Furthermore, the projection of the two side boundaries of the first insertion layer, which are parallel to the second direction, in the third direction is flush with the end of the prosthesis.

2. The temperature-compensated surface acoustic wave resonator according to claim 1, characterized in that, It also includes a second temperature compensation layer, which is located on one side of the first temperature compensation layer along the third direction and completely covers the first insertion layer in the third direction.

3. The temperature-compensated surface acoustic wave resonator according to claim 1, characterized in that, The material of the first insertion layer includes silicon nitride.

4. The temperature-compensated surface acoustic wave resonator according to claim 2, characterized in that, The material of the first temperature compensation layer and / or the second temperature compensation layer includes silicon dioxide.

5. The temperature-compensated surface acoustic wave resonator according to claim 2, characterized in that, The second temperature compensation layer has a lower density than the first temperature compensation layer.

6. The temperature-compensated surface acoustic wave resonator according to claim 1, characterized in that, The thickness of the first insertion layer is greater than or equal to 10 nm and less than or equal to 200 nm.

7. A method for fabricating a temperature-compensated surface acoustic wave resonator, comprising: Provide piezoelectric substrates; An interdigitated structure layer is formed on one side of a piezoelectric substrate. The interdigitated structure layer includes a first busbar and a second busbar disposed opposite each other in a first direction, and fingers and pseudo-fingers alternately arranged on the first busbar and the second busbar. The fingers on the first busbar are spaced apart in a second direction, and the fingers on the second busbar are also spaced apart in the second direction. The fingers on the first busbar correspond one-to-one with the pseudo-fingers on the second busbar, and the fingers on the second busbar correspond one-to-one with the pseudo-fingers on the first busbar. The corresponding fingers and pseudo-fingers are located on the same straight line, and there is a gap between the fingers and pseudo-fingers. The first direction and the second direction are parallel to the surface of the piezoelectric substrate, and the first direction and the second direction are perpendicular to each other. A first temperature compensation layer is formed on one surface of the piezoelectric substrate along a third direction, the first temperature compensation layer completely covering the interdigitated structure layer in the third direction; characterized in that it further comprises: A first insertion layer is formed on the side of the first temperature compensation layer away from the interdigital structure layer. Its projection in the third direction covers all finger strips but not the prosthesis. The projection of the two side boundaries of the first insertion layer, which are parallel to the second direction, in the third direction is flush with the end of the prosthesis.

8. The method for fabricating a temperature-compensated surface acoustic wave resonator according to claim 7, characterized in that, Also includes: A second temperature compensation layer is formed on one side of the first temperature compensation layer along the third direction, and the second temperature compensation layer completely covers the first insertion layer in the third direction.

9. The method for fabricating a temperature-compensated surface acoustic wave resonator according to claim 7, characterized in that, The material of the first insertion layer includes silicon nitride.

10. The method for fabricating a temperature-compensated surface acoustic wave resonator according to claim 8, characterized in that, The material of the first temperature compensation layer and / or the second temperature compensation layer includes silicon dioxide.

11. The method for fabricating a temperature-compensated surface acoustic wave resonator according to claim 8, characterized in that, The second temperature compensation layer has a lower density than the first temperature compensation layer.

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