A TC-SAW resonator and a filter containing the same

Abstract

The present invention belongs to the technical field of surface acoustic waves. The present invention provides a TC-SAW resonator and a filter containing the same. The TC-SAW resonator includes a piezoelectric substrate, a functional layer including an interdigital transducer, and a temperature compensation layer which are stacked in sequence; it also includes two pairs of bimetallic strips arranged above the interdigital transducer, and each pair of the bimetallic strips includes a busbar edge metal strip and an active area metal strip. In the orthographic projection to the functional layer, one side edge of the busbar edge metal strip fits with one side edge of the corresponding busbar, and is arranged in the gap area of ​​the interdigital transducer; the active area metal strip has a portion overlapping with the active area of ​​the interdigital transducer. By providing a new structure of bimetallic strips, the sound velocity of the gap area can be adjusted, so that the waveguide capacity is improved, and the stray mode is effectively suppressed to prevent lateral energy leakage, thereby improving the quality factor of the resonator.

Description

Technical Field

[0001] The invention belongs to the field of surface acoustic waves and relates to a TC-SAW resonator and a filter containing the same. Background Art

[0002] Surface acoustic wave (SAW) is an elastic wave that propagates along the surface of a solid, and its energy is mainly concentrated near the surface. SAW technology is widely used in wireless communications, sensors, filters and other fields. Surface acoustic wave resonator (SAWR) is an important structure and device for the widespread application of SAW technology, with the characteristics of high Q value, miniaturization, and low power consumption.

[0003] Traditional surface acoustic wave resonators are composed of piezoelectric materials, interdigital transducers (IDTs) and reflective gratings. IDTs are used to excite and detect SAWs, and reflective gratings are used to reflect SAWs to form a resonant cavity. The propagation of surface acoustic waves depends on the elastic constant and density of the material, and these two properties are affected by temperature, which leads to the fact that traditional SAWRs using lithium niobate (LiNbO3) as piezoelectric materials have greater temperature sensitivity, limiting their development.

[0004] To overcome this challenge, predecessors designed a 128°YX lithium niobate substrate, silicon dioxide (SiO2) as a temperature compensation layer, and buried the temperature-compensated surface acoustic wave (TC-SAW) resonator of the interdigital transducer. The thermal expansion coefficient of silicon dioxide is opposite to that of lithium niobate, which produces a compensation effect and reduces the impact of temperature changes on the resonator performance. This temperature compensation method has been widely studied since the 1980s and is currently commercially used in mobile communications.

[0005] Depending on the IDT metal used, the operating mode (main mode) of TC-SAW can be horizontal shear surface acoustic wave (SH-SAW) or Rayleigh surface acoustic wave. However, TC-SAW resonators often encounter multiple spurious modes, including lateral modes, main modes, and multiple mode types in which the main mode is coupled with other modes. The presence of these spurious modes will produce passband ripples and limit out-of-band suppression, thereby impairing the performance of the acoustic wave filter. In this regard, a certain suppression effect can be achieved by properly selecting the cutting angle of piezoelectric materials such as lithium niobate, optimizing the IDT thickness, or optimizing the thickness of the temperature compensation layer. However, due to the strong anisotropy of lithium niobate, it is not easy to completely eliminate the excitation of horizontal shear surface acoustic waves.

[0006] Therefore, it is still necessary to study and develop a new solution to mitigate the TC-SAW spurious mode in order to improve the acoustic performance of acoustic wave resonators and devices such as filters containing them, and promote their further development in practical applications. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a TC-SAW resonator and a filter containing the same. The TC-SAW resonator has a new structure. Two pairs of bimetallic strips corresponding to the busbar are arranged above the interdigital transducer of the TC-SAW resonator, and each pair of bimetallic strips includes a busbar edge metal strip and an active area metal strip, thereby ensuring that the waveguide capacity of the gap area is improved, effectively suppressing the spurious mode and improving the quality factor of the resonator.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a TC-SAW resonator, which includes a piezoelectric substrate, a functional layer and a temperature compensation layer stacked in sequence; the functional layer includes an interdigital transducer and reflectors arranged opposite to each other on both sides of the interdigital transducer.

[0010] The interdigital transducer includes two busbars arranged opposite to each other; the two busbars are respectively connected with fingers, and the fingers extend toward the busbar on the opposite side but retain a gap therewith, so that the interdigital transducer includes an active area formed by alternatingly arranged fingers, and gap areas formed at both ends of the active area.

[0011] The TC-SAW resonator also includes two pairs of bimetallic strips, which are arranged above the IDT and have a first spacing with the plane where the surface of the IDT is located; each pair of the bimetallic strips includes a busbar edge metal strip and an active area metal strip that are parallel and opposite to each other.

[0012] In the orthographic projection to the functional layer, the two pairs of bimetallic strips are arranged between the two busbars and correspond to the two busbars respectively; in the extension direction parallel to the busbars, one side edge of the busbar edge metal strip is in contact with one side edge of the corresponding busbar; in the extension direction parallel to the finger strips, one side edge of the active area metal strip away from the corresponding busbar edge metal strip does not exceed the active area.

[0013] The present invention arranges a bimetallic strip in a temperature-compensated surface acoustic wave resonator as a new optimized structure. Without changing the structure of the interdigital transducer, the bimetallic strip is arranged above the interdigital transducer so that the orthographic projection of the bimetallic strip to the functional layer is in the IDT region (gap region and active region) to play a modulation role. Specifically, the busbar edge metal strip in the bimetallic strip is at the edge of the corresponding busbar, and its orthographic projection to the functional layer falls into the gap region, while the relatively parallel active region metal strip has a portion that overlaps with the active region; the active region metal strip reduces the speed of the surface acoustic wave in the necessary area, while the busbar edge metal strip suppresses the excitation and propagation of the stray mode in the gap region without seriously affecting the main resonance. Therefore, this bimetallic strip structure can effectively realize the adjustment of the acoustic wave speed and dispersion characteristics in the gap region, and realizes a stray signal-free response and a clearer signal output. In addition, the structure not only suppresses the stray mode, but also helps to confine the energy within the resonator, thereby reducing lateral energy leakage, which plays an important role in maintaining the quality factor.

[0014] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, in the orthographic projection to the functional layer, the center of the busbar edge metal strip is arranged in the gap area, and in the extension direction parallel to the finger strip, the edge of the busbar edge metal strip does not exceed the gap area and does not contact the corresponding active area metal strip, and a second gap is retained.

[0016] Preferably, the second intervals in the two pairs of bimetallic strips are equal.

[0017] As a preferred technical solution of the present invention, in the orthographic projection onto the functional layer, one side edge of the active area metal strip away from the corresponding busbar edge metal strip fits in with the boundary of the active area in the extension direction parallel to the busbar.

[0018] As a preferred technical solution of the present invention, in the extension direction parallel to the finger strips, the width of the busbar edge metal strip and the width of the active area metal strip are both 0.5~1λ, λ is the wavelength of the surface acoustic wave, and is further preferably 0.7~0.75λ, which is the optimal range for achieving spurious-free frequency response.

[0019] Preferably, the width of the busbar edge metal strip is equal to the width of the active area metal strip.

[0020] As a preferred technical solution of the present invention, in the orthographic projection onto the functional layer and in the extension direction parallel to the busbar, the reflector is arranged relatively on both sides of the active area and the gap area, and the edge of the busbar edge metal strip does not exceed the gap area, or exceeds the active area and covers the reflector.

[0021] Preferably, in an extension direction parallel to the busbar, two ends of the active area metal strip are flush with two ends of the busbar edge metal strip.

[0022] In the present invention, the bimetallic strip modulates the sound velocity in the gap region of the IDT, so its size characteristics (coverage area) need to match the IDT, especially the active region and the gap region. The placement position, length, width, thickness, first interval and second interval of the bimetallic strip should be reasonably selected and adjusted according to the actual design and needs to achieve the structural effectiveness and ensure the effect of suppressing stray modes and reducing energy leakage.

[0023] As a preferred technical solution of the present invention, in each pair of the bimetallic strips, a first mass load portion is provided between the busbar edge metal strip and the active area metal strip, and the first mass load portion connects the busbar edge metal strip and the corresponding active area metal strip.

[0024] Preferably, in each pair of the bimetallic strips, the busbar edge metal strip is connected with a second mass load portion, and in an orthographic projection onto the functional layer, the second mass load portion falls into the corresponding busbar.

[0025] Preferably, the size of the second mass load portion is equal to the size of the corresponding bus bar.

[0026] In the present invention, the mass load part can be set to further influence or cooperate with the value adjustment effect of the bimetallic strip. The mass load part helps to further modulate the speed of the sound waves in the gap area and helps to achieve better waveguide. It also helps to further prevent the excitation of other stray modes in the gap area. Therefore, the placement position, length, width and thickness of the mass load part should be adjusted according to the actual design and needs. Preferably, the first mass load part and the second mass load part are in the same plane as the bimetallic strip and have the same thickness. It is also possible to select either the first mass load part or the second mass load part to be set or to set them simultaneously, and a special case is that when only the second mass load part is set, the width of the metal strip at the edge of the busbar can be reduced until it becomes a straight line that fits the edge of one side of the busbar.

[0027] As a preferred technical solution of the present invention, the bimetallic strip is arranged on the surface of the temperature compensation layer, or is embedded in the temperature compensation layer, or is completely buried in the temperature compensation layer.

[0028] As a preferred technical solution of the present invention, for the portion of the bimetallic strip exposed outside the temperature compensation layer, a temperature compensation material is filled in the active area, and / or a heavy dielectric material is provided in the portion outside the active area.

[0029] As a preferred technical solution of the present invention, the temperature compensation material is the same as the temperature compensation layer; the acoustic impedance of the heavy dielectric material is different from that of the temperature compensation layer and the density is greater than that of the temperature compensation layer.

[0030] Preferably, the heavy dielectric material includes at least one of hafnium oxide, silicon nitride, barium strontium titanate, aluminum oxide or titanium dioxide.

[0031] In the present invention, the bimetallic strip can be completely disposed on the surface of the temperature compensation layer, that is, the first interval is equal to the thickness of the temperature compensation layer; or it can be embedded in the temperature compensation layer and at least the top surface is exposed, or it can be completely buried in the temperature compensation layer without exposing any surface. For the bimetallic strip exposed to the outside, the temperature compensation material can be set in the active area between the two active area metal strips or left blank (exposed to the air); further, other blank areas (such as the gap area) at this level can be filled with heavy dielectric materials. The selection of heavy dielectric materials will affect the performance of the TC-SAW resonator, including its temperature stability and frequency response.

[0032] As a preferred technical solution of the present invention, the temperature compensation layer has an opposite temperature elastic coefficient to that of the piezoelectric substrate; the temperature compensation layer has an opposite density property to that of the bimetallic strip; and the bimetallic strip, the reflector and the interdigital transducer are made of the same material.

[0033] Preferably, the material of the bimetallic strip includes at least one of aluminum, copper, gold, tungsten, molybdenum or silver.

[0034] Preferably, the temperature compensation layer is made of silicon dioxide.

[0035] Preferably, the material of the piezoelectric substrate includes at least one of lithium niobate, lithium tantalate or quartz.

[0036] In the present invention, the temperature compensation layer and the bimetallic strip have opposite density properties, which means that when the temperature compensation layer uses a material with a larger density, the metal material density of the bimetallic strip should be smaller, such as aluminum; when the metal material of the bimetallic strip is a heavy metal with a larger density (such as the above-mentioned copper and gold), the temperature compensation layer should use a material with a smaller density, such as silicon dioxide.

[0037] As a preferred technical solution of the present invention, the interdigital transducer has 10 to 1000 IDT periods.

[0038] As a preferred technical solution of the present invention, the reflector has 10 to 30 pairs of reflection gratings.

[0039] It should be noted that the present invention does not impose any specific restrictions on the specific materials and structures of the traditional TC-SAW structure (piezoelectric material, interdigital transducer and reflector) in the TC-SAW resonator. It should be understood that the connotation of the present invention, that is, providing a bimetallic strip in the TC-SAW that can adjust the sound velocity in the gap area, improve the waveguide capability, suppress stray modes and improve the resonator quality factor, is in compliance with the purpose of the present invention.

[0040] In a second aspect, the present invention provides a filter comprising the TC-SAW resonator described in the first aspect.

[0041] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0042] The present invention changes the acoustic wave velocity or dispersion characteristics in the gap region by setting a bimetallic strip above the interdigital transducer of the TC-SAW. The structure not only suppresses the stray mode, but also helps to confine the energy within the resonator, reduce lateral energy leakage, achieve no stray signal response and clearer signal output, and effectively improve the quality factor Q value. A higher Q value means lower insertion loss, which is widely applicable to high-frequency applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1A A schematic diagram of the three-dimensional structure of a TC-SAW resonator 100 in the present invention is shown;

[0044] Figure 1B Shows Figure 1A A top view of a TC-SAW resonator 100;

[0045] Figure 1C Shows Figure 1B Enlarged view of the middle dashed area M1;

[0046] Figure 1D Shows Figure 1C A cross-sectional view along section line N1-N1;

[0047] Figure 1E Shows Figure 1C A cross-sectional view along the N2-N2 section line;

[0048] Figure 1F Shows Figure 1D Enlarged view of the middle dashed area M2;

[0049] Figure 1G shows an enlarged view of a dotted line area M2 in another TC-SAW resonator 100' of the present invention;

[0050] Figure 2A A schematic diagram of the three-dimensional structure of another TC-SAW resonator 200 in the present invention is shown;

[0051] Figure 2B Shows Figure 2A A top view of the TC-SAW resonator 200;

[0052] Figure 2C Shows Figure 2B Enlarged view of the middle dashed area M3;

[0053] Figure 2D Shows Figure 2C A cross-sectional view along section line N3-N3;

[0054] Figure 3A A top view of another TC-SAW resonator 201 of the present invention is shown;

[0055] Figure 3B A top view of another TC-SAW resonator 202 of the present invention is shown;

[0056] Figure 4A A cross-sectional view along the N2-N2 section line of another TC-SAW resonator 110 of the present invention is shown;

[0057] Figure 4B A cross-sectional view along the N2-N2 section line of another TC-SAW resonator 120 of the present invention is shown;

[0058] Figure 4C A cross-sectional view along the N2-N2 section line of another TC-SAW resonator 130 of the present invention is shown;

[0059] Figure 4D Shows Figure 4C Enlarged view of the middle dashed area M4;

[0060] Figure 4E shows an enlarged view of a dotted area M4 in another TC-SAW resonator 131 of the present invention;

[0061] Figure 4F shows an enlarged view of a dotted line region M4 in another TC-SAW resonator 132 of the present invention;

[0062] Figure 5A A top view of another TC-SAW resonator 101 of the present invention is shown;

[0063] Figure 5B Shows Figure 5A A cross-sectional view of the TC-SAW resonator 101 along the N2-N2 section line;

[0064] Figure 5C A top view of another TC-SAW resonator 102 of the present invention is shown;

[0065] Figure 5D Shows Figure 5C A cross-sectional view of the TC-SAW resonator 102 along the N2-N2 section line;

[0066] Figure 5E A top view of another TC-SAW resonator 103 of the present invention is shown;

[0067] Fig. 5F Shows Figure 5E A cross-sectional view of the TC-SAW resonator 103 along the N2-N2 section line;

[0068] Figure 5G A cross-sectional view along the N2-N2 section line of another TC-SAW resonator 121 of the present invention is shown;

[0069] Figure 5H A cross-sectional view along the N2-N2 section line of another TC-SAW resonator 122 of the present invention is shown;

[0070] Fig. 6A An admittance diagram of a conventional TC-SAW resonator of Comparative Example 3 is shown;

[0071] Figure 6B shows a batch of admittance diagrams of TC-SAW resonators 130 based on Example 8;

[0072] Figure 6C Another batch of admittance diagrams of TC-SAW resonators 130 based on Example 8 are shown;

[0073] Fig.6D Another batch of admittance diagrams of TC-SAW resonators 130 based on Example 8 are shown;

[0074] In the figure: 10-piezoelectric substrate, 20-interdigital transducer, 21-busbar, 21A-first busbar, 21B-second busbar, 22-finger, 22A-first finger, 22B-second finger, 23-gap area, 23A-first gap area, 23B-second gap area, 24-active area, 30-reflector, 30A-first reflector, 30B-second reflector, 31-reflection grid busbar, 32-reflection grid bar, 40-temperature compensation layer, 41-temperature compensation material, 42-heavy dielectric material, 50-bimetallic strip, 51-busbar edge metal strip, 51A-first busbar edge metal strip, 51B-second busbar edge metal strip, 52-active area metal strip, 52A-first active area metal strip, 52B-second active area metal strip, 53-first mass load unit, 54-second mass load unit. DETAILED DESCRIPTION

[0075] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the implementation methods and examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0076] In some specific embodiments, such as Figure 1A As shown, the present invention provides a TC-SAW resonator, which includes a piezoelectric substrate 10, a functional layer and a temperature compensation layer 40 stacked in sequence; the functional layer includes an interdigital transducer 20 and a reflector 30 arranged opposite to each other on both sides of the interdigital transducer 20.

[0077] The IDT 20 includes two busbars 21 arranged opposite to each other; the two busbars 21 are respectively connected with fingers 22, and the fingers 22 extend toward the busbar 21 on the opposite side but keep a gap therebetween, so that the IDT 20 includes an active area 24 formed by the fingers 22 arranged alternately, and gap areas 23 formed at both ends of the active area 24; that is, the section where the fingers 22 are connected to the busbar 21 is the starting end, and the other end facing the busbar 21 on the opposite side is the end, and the end forms a gap with the busbar 21 on the opposite side. The area covered by the IDT 20 is an IDT area, which includes the busbar area covered by the busbar 21, the gap area 23, and the active area 24.

[0078] The TC-SAW resonator further includes two pairs of bimetallic strips 50, which are disposed above the IDT 20 and have a first spacing with the plane where the surface of the IDT 20 is located; each pair of the bimetallic strips 50 includes a busbar edge metal strip 51 and an active area metal strip 52 which are parallel and opposite to each other; wherein the first spacing of the busbar edge metal strip 51 is denoted as g1, and the first spacing of the active area metal strip 52 is denoted as g2, g1>0 and g2>0, such as Figure 1Fshown.

[0079] In the orthographic projection onto the functional layer, the two pairs of bimetallic strips 50 are arranged between the two busbars 21 and correspond to the two busbars 21 respectively; in the extension direction parallel to the busbars 21, one side edge of the busbar edge metal strip 51 is in contact with the corresponding side edge of the busbar 21; in the extension direction parallel to the finger strips 22, one side edge of the active area metal strip 52 away from the corresponding busbar edge metal strip 51 does not exceed the active area 24.

[0080] In one embodiment, g1=g2.

[0081] In one embodiment, g1=g2=0.01~0.1λ, for example, it can be 0.01λ, 0.02λ, 0.03λ, 0.04λ, 0.05λ, 0.06λ, 0.07λ, 0.08λ, 0.09λ or 0.1λ, etc., preferably 0.015~0.09λ, and further preferably 0.03~0.06λ. It is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0082] In one embodiment, the piezoelectric substrate 10, the interdigital transducer 20, the reflector 30, and the temperature compensation layer 40 respectively have corresponding widths in the X direction (or the first dimension direction), corresponding lengths in the Y direction (or the second dimension direction), and corresponding thicknesses in the Z direction (or the third direction); the X direction, the Y direction, and the Z direction constitute a three-dimensional coordinate space.

[0083] In one embodiment, if Figure 1B As shown, the busbar 21 includes a first busbar 21A and a second busbar 21B; the first busbar 21A and the second busbar 21B both extend along the X direction and are arranged relatively spaced apart in the Y direction; the first busbar 21A and the second busbar 21B have a length in the X direction and a width in the Y direction.

[0084] In one embodiment, if Figure 1B As shown, the first busbar 21A is connected to a first finger 22A, and the first finger 22A extends toward the second busbar 21B along the Y direction, but does not contact the second busbar 21B, forming a first gap area 23A, and the length of the first gap area 23A is w1. Figure 1D As shown; the second busbar 21B is connected to a second finger 22B, the second finger 22B extends along the Y direction toward the first busbar 21A, but does not contact the first busbar 21A, forming a second gap area 23B, the length of the second gap area 23B is w2, as shown Figure 1EAs shown; the first finger 22A and the second finger 22B have a length in the X direction and a width in the Y direction; the area between the first gap region 23A and the second gap region 23B constitutes an active area 24, the length of which is w3, as shown Figure 1D and Figure 1E As shown; the size of the first gap area 23A, the second gap area 23B and the active area 24 in the Y direction is the width; the first finger 22A and the second finger 22B are arranged alternately along the X direction and do not contact each other; along the X direction, the distance from the edge of a first finger 22A to the corresponding edge of the same side of the most adjacent second finger 22B is the length p1 of an IDT period, as shown in FIG. Figure 1C As shown, one IDT period is a pair of transducers, or a repeating unit.

[0085] In one embodiment, w1=w2.

[0086] In one embodiment, the number of IDT periods of the interdigital transducer 20 is 10 to 1000, for example, 10, 30, 50, 80, 100, 200, 300, 400, 500, 600, 700, 800, 900 or 1000, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0087] In some specific embodiments, such as Figure 1A and Figure 1B As shown, the reflectors 30 are arranged opposite to each other on both sides of the active area 24 and the gap area 23 .

[0088] In one embodiment, the reflectors 30 are arranged opposite to each other on both sides of the IDT 20 along the X direction to form a first reflector 30A and a second reflector 30B; Figure 2A , Figure 2B , Figure 2C and Figure 2D As shown, the first reflector 30A and the second reflector 30B both include relatively arranged reflection grating busbars 31, the reflection grating busbars 31 extend along the X direction, and one side edge is in the same straight line with the side edge of the busbar 21 close to the finger bar 22; the two relatively opposite reflection grating busbars 31 are connected with reflection grating bars 32 extending along the Y direction, that is, the reflection grating bars 32 are arranged parallel to the finger bar 22; the reflection grating bars 32 are alternately arranged along the X direction and do not contact each other; along the X direction, the distance from the edge of a reflection grating bar 32 to the corresponding edge of the same side of the most adjacent reflection grating bar 32 is the length p2 of a reflection grating period; and a reflection grating period includes a pair of reflection grating bars 32.

[0089] In one embodiment, the first reflector 30A and the second reflector 30B respectively have 10 to 30 pairs of reflective grating bars 32, such as 10 pairs, 13 pairs, 15 pairs, 18 pairs, 20 pairs, 22 pairs, 24 pairs, 26 pairs, 28 pairs or 30 pairs, but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0090] In some specific embodiments, such as Figures 1B to 1E As shown, the bimetallic strip 50 close to the first busbar 21A includes a first busbar edge metal strip 51A and a first active area metal strip 52A, and the bimetallic strip 50 close to the second busbar 21B includes a second busbar edge metal strip 51B and a first active area metal strip 52B; in the orthographic projection to the functional layer, one side edge of the first busbar edge metal strip 51A is in contact with one side edge of the first busbar 21A and extends along the X direction; one side edge of the second busbar edge metal strip 51B is in contact with one side edge of the second busbar 21B and extends along the X direction.

[0091] In one embodiment, if Figure 1F As shown, the dimension of the bimetallic strip 50 in the Z direction is the thickness; the dimension of the bimetallic strip 50 in the Y direction is the width; wherein the thickness of the busbar edge metal strip 51 is h1, the width is d1, the thickness of the active area metal strip 52 is h2, the width is d2, as shown in FIG. Figure 1F shown.

[0092] In one embodiment, h1=h2.

[0093] In one embodiment, the width d1 of the busbar edge metal strip 51 and the width d2 of the active area metal strip 52 are both 0.5-1λ, where λ is the wavelength of the surface acoustic wave, for example, 0.5λ, 0.52λ, 0.54λ, 0.56λ, 0.58λ, 0.6λ, 0.62λ, 0.64λ, 0.66λ, 0.68λ, 0.7λ, 0.705λ, 0.71λ, 0.715λ, 0.72λ, 0.725λ, 0.73 λ, 0.735λ, 0.74λ, 0.745λ, 0.75λ, 0.78λ, 0.8λ, 0.82λ, 0.83λ, 0.85λ, 0.88λ, 0.9λ, 0.92λ, 0.95λ, 0.98λ or 1λ, etc., λ is the wavelength of the surface acoustic wave, and is further preferably 0.7~0.75λ, which is the optimal range for achieving spurious-free frequency response, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0094] In one embodiment, d1=d2.

[0095] In some specific embodiments, in the orthographic projection to the functional layer, the center of the busbar edge metal strip 51 is arranged in the gap area 23, and in the Y direction, the edge of the busbar edge metal strip 51 does not exceed the gap area 23, and does not contact the corresponding active area metal strip 52, and retains a second interval with the corresponding active area metal strip 52; that is, Figure 1C As shown, the second interval of a pair of bimetallic strips 50 close to the first busbar 21A is recorded as s1, and the second interval of another pair of bimetallic strips 50 close to the second busbar 21B is recorded as s2. At the same time, the distance between the two active area metal strips 52 is recorded as the third interval s3, then d1<w1 and d1<w2, s1>0 and s2>0.

[0096] In one embodiment, the second intervals in the two pairs of bimetallic strips 50 are equal, that is, s1 = s2.

[0097] In one embodiment, in the orthographic projection onto the functional layer, an edge of the active area metal strip 52 that is away from the corresponding busbar edge metal strip 51 is aligned with the boundary of the active area 24 in the X direction, that is, s3=w3, at this time s1+d1+d2=w1, s2+d1+d2=w2.

[0098] In some specific embodiments, in the orthographic projection onto the functional layer and in the X direction, the edge of the busbar edge metal strip 51 does not exceed the gap area 23, or exceeds the active area 24 and covers the reflector 30, such as FIG. 2A to FIG. 2C that is, the dimension of the bimetal strip 50 in the X direction is a length that is less than or equal to the width of the IDT 20 , or greater than the width of the IDT 20 but less than or equal to the maximum distance between the edges of a pair of reflectors 30 .

[0099] In one embodiment, in the X direction, two ends of the active area metal strip 52 are flush with two ends of the busbar edge metal strip 51 , that is, the length of the active area metal strip 52 is equal to the length of the busbar edge metal strip 51 .

[0100] In some specific embodiments, such as Figure 3A As shown, in each pair of the bimetallic strips 50, a first mass load portion 53 is provided between the busbar edge metal strip 51 and the active area metal strip 52, and the first mass load portion 53 connects the busbar edge metal strip 51 and the corresponding active area metal strip 52; the orthographic projection of the first mass load portion 53 to the functional layer does not fall into the IDT region.

[0101] In some specific embodiments, such as Figure 3BAs shown, in each pair of the bimetallic strips 50 , the busbar edge metal strip 51 is connected with a second mass load portion 54 , and in the orthographic projection to the functional layer, the second mass load portion 54 falls into the busbar region of the corresponding busbar 21 .

[0102] In one embodiment, the size of the second mass load portion 54 is equal to the size of the corresponding bus bar 21 .

[0103] In some specific embodiments, the bimetallic strip 50 is disposed on the surface of the temperature compensation layer 40 (eg Figures 1A to 2D ), or embedding the temperature compensation layer 40 (as shown Figure 4A and Figure 4B ), or completely burying the temperature compensation layer 40 (as shown Figure 4C as shown).

[0104] In one embodiment, for the portion of the bimetallic strip 50 exposed outside the temperature compensation layer 40, a blank (eg, Figure 5G as shown) or filled with temperature compensation material 41 (as Figure 5A and Figure 5B ), and / or providing a heavy dielectric material 42 (such as FIG. 5C to FIG. 5F and Figure 5H as shown).

[0105] In one embodiment, the temperature compensation material 41 is the same as the temperature compensation layer 40 ; the acoustic impedance of the heavy dielectric material 42 is different from that of the temperature compensation layer 40 and the density is greater than that of the temperature compensation layer 40 .

[0106] In one embodiment, the heavy dielectric material 42 includes at least one of hafnium oxide, silicon nitride, barium strontium titanate, aluminum oxide, or titanium dioxide.

[0107] In some specific embodiments, the temperature elastic coefficient of the temperature compensation layer 40 is opposite to that of the piezoelectric substrate 10; the density properties of the temperature compensation layer 40 are opposite to those of the bimetallic strip 50; and the material density of the bimetallic strip 50 is greater than or equal to the material density of the reflector 30 and the interdigital transducer 20.

[0108] In one embodiment, the bimetallic strip 50 , the reflector 30 , and the IDT 20 are made of the same material.

[0109] In one embodiment, the bimetallic strip 50 is made of at least one of aluminum, copper, gold, tungsten, molybdenum or silver.

[0110] In one embodiment, the temperature compensation layer 40 is made of silicon dioxide.

[0111] In one embodiment, the material of the piezoelectric substrate 10 includes at least one of lithium niobate, lithium tantalate or quartz.

[0112] In a second aspect, the present invention provides a filter comprising the TC-SAW resonator described in the first aspect.

[0113] Example 1

[0114] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 100, such as Figures 1A to 1F As shown, in the TC-SAW resonator 100, the temperature compensation layer 40 covers the entire functional layer; the bimetallic strip 50 is arranged on the surface of the temperature compensation layer 40 away from the functional layer and exposed to the air; in the orthographic projection to the functional layer: the edge of one side of the active area metal strip 52 close to the busbar edge metal strip 51 is in contact with the boundary of the active area 24 in the X direction, and the other side edge is located in the active area 24, that is, at this time, s1+d1=w1, s2+d1=w2, and s1=s2, d1=d2, w1=w2, h1=h2, g1=g2; and in the X direction, the two ends of the active area metal strip 52 are flush with the two ends of the busbar edge metal strip 51 and the lengths are equal to the width of the active area 24, so that the two ends of the active area metal strip 52 are respectively located at the edges of the active area 24, and the two ends of the busbar edge metal strip 51 are respectively located at the edges of the gap area 23. At this time, the bimetal strip 50 only covers the IDT region.

[0115] Example 2

[0116] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 100', such as Figure 1G As shown, the difference between the TC-SAW resonator 100' and the TC-SAW resonator 100 in Example 1 is that in the orthographic projection to the functional layer, one edge of the active area metal strip 52 away from the busbar edge metal strip 51 is aligned with the boundary of the active area 24 in the X direction, and the other edge is located in the active area 24, that is, at this time, s1+d1+d2=w1, s2+d1+d2=w2. Except for the above, other conditions are exactly the same as those in Example 1.

[0117] Example 3

[0118] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 200, such as FIG. 2A to FIG. 2DAs shown, the difference between the TC-SAW resonator 200 and the TC-SAW resonator 100 in Example 1 is that in the orthographic projection to the functional layer and in the X direction, the two ends of the active area metal strip 52 and the two ends of the busbar edge metal strip 51 are respectively flush and the lengths are equal to the maximum distance between the edges of a pair of reflectors 30, so that one end edge of the active area metal strip 52 and the busbar edge metal strip 51 coincides with the edge of one side of the first reflector 30A away from the interdigital transducer 20, and the other end edge coincides with the edge of one side of the second reflector 30B away from the interdigital transducer 20. At this time, the bimetallic strip 50 covers the IDT area and the reflector 30. Except for the above, other conditions are exactly the same as those in Example 1.

[0119] Example 4

[0120] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 201, such as Figure 3A As shown, the difference between the TC-SAW resonator 201 and the TC-SAW resonator 200 in Example 3 is that: in each pair of the bimetallic strips 50, a first mass load portion 53 is provided in the portion outside the gap region between the busbar edge metal strip 51 and the active region metal strip 52, and the first mass load portion 53 connects the busbar edge metal strip 51 and the corresponding active region metal strip 52; the orthographic projection of the first mass load portion 53 to the functional layer covers the gap region 23 and does not fall into the IDT region. Except for the above, other conditions are exactly the same as those in Example 3.

[0121] Example 5

[0122] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 202, such as Figure 3B As shown, the difference between the TC-SAW resonator 202 and the TC-SAW resonator 201 in Example 4 is that the busbar edge metal strip 51 is also connected to a second mass load portion 54, and in the orthographic projection to the functional layer, the second mass load portion 54 falls into the busbar area of ​​the corresponding busbar 21, and the size of the second mass load portion 54 is completely equal to the size of the corresponding busbar 21. Except for the above, other conditions are exactly the same as those in Example 4.

[0123] Example 6

[0124] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 110, such as Figure 4AAs shown, the TC-SAW resonator 110 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that the bimetallic strips 50 are half-embedded in the temperature compensation layer 40, and the unembedded part is exposed to the air. Except for the above, other conditions are exactly the same as those in Example 1.

[0125] Example 7

[0126] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 120, such as Figure 4B As shown, the TC-SAW resonator 120 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that the bimetallic strips 50 are all embedded in the temperature compensation layer 40, and the unembedded top surface portion is exposed to the air. Except for the above, other conditions are exactly the same as those in Example 1.

[0127] Example 8

[0128] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 130, such as Figure 4C and Figure 4D As shown, the TC-SAW resonator 130 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that the bimetallic strips 50 are all buried in the temperature compensation layer 40, without any exposed parts. Except for the above, other conditions are exactly the same as those in Example 1.

[0129] Example 9

[0130] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 131, such as Figure 4E As shown, the TC-SAW resonator 131 is based on the TC-SAW resonator 130 in Example 8, and the difference from the TC-SAW resonator 130 is that the width of the busbar edge metal strip 51 is reduced and a second mass load portion 54 is provided, and the sum of the width of the busbar edge metal strip 51 and the width of the second mass load portion 54 is equal to the original width of the busbar edge metal strip 51 that has not been reduced, which is equivalent to translating the busbar edge metal strip 51 in the Y direction away from the gap region 23. Except for the above, other conditions are exactly the same as those in Example 8.

[0131] Example 10

[0132] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 132, such as Figure 4FAs shown, the TC-SAW resonator 132 is based on the TC-SAW resonator 130 in Example 8, and the difference from the TC-SAW resonator 130 is that the width of the busbar edge metal strip 51 is reduced to the width of a straight line and a second mass load portion 54 is provided, and the sum of the width of the busbar edge metal strip 51 and the width of the second mass load portion 54 is equal to the original width of the busbar edge metal strip 51 that has not been reduced, which is equivalent to translating the busbar edge metal strip 51 in the Y direction away from the gap area 23 until, in the orthographic projection of the functional layer, the edge of the busbar edge metal strip 51 originally close to the active area is aligned with the edge of the busbar 21. Except for the above, other conditions are exactly the same as those in Example 8.

[0133] Embodiment 11

[0134] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 101, such as Figure 5A and Figure 5B As shown, the TC-SAW resonator 101 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that the temperature compensation material 41 is filled in the area between the two active area metal strips 52 (active area 24), and the thickness of the temperature compensation material 41 is equal to the thickness of the bimetallic strip 50; the remaining blank area is still exposed to the air. Except for the above, the other conditions are exactly the same as those in Example 1.

[0135] Example 12

[0136] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 102, such as Figure 5C and Figure 5D As shown, the TC-SAW resonator 102 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that a heavy dielectric material 42 is provided in the outer region outside the active region 24 between the two active region metal strips 52, and the thickness of the heavy dielectric material 42 is equal to the thickness of the bimetallic strip 50. Except for the above, other conditions are exactly the same as those in Example 1.

[0137] Example 13

[0138] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 103, such as Figure 5E and Fig. 5FAs shown, the TC-SAW resonator 103 is based on the TC-SAW resonator 100 in Example 1, and the difference from the TC-SAW resonator 100 is that the temperature compensation material 41 is filled in the area between the two active area metal strips 52 (active area 24), and the thickness of the temperature compensation material 41 is equal to the thickness of the bimetallic strip 50; at the same time, the remaining blank area is provided with a heavy dielectric material 42, and the thickness of the heavy dielectric material 42 is equal to the thickness of the bimetallic strip 50. Except for the above, other conditions are exactly the same as those in Example 1.

[0139] Embodiment 14

[0140] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 121, such as Figure 5G As shown, the TC-SAW resonator 121 is based on the TC-SAW resonator 120 in Example 7, and the difference from the TC-SAW resonator 120 is that the area (gap area 23) between the busbar edge metal strip 51 and the active area metal strip 52 in the bimetal strip 50 is left blank and exposed to the air. Except for the above, other conditions are exactly the same as those in Example 7.

[0141] Embodiment 15

[0142] This embodiment adopts a TC-SAW resonator provided by the above-mentioned implementation mode, numbered 122, such as Figure 5H As shown, the TC-SAW resonator 122 is based on the TC-SAW resonator 121 in Example 14, and the difference from the TC-SAW resonator 121 is that a heavy dielectric material 42 is provided in the blank area (gap area 23) between the busbar edge metal strip 51 and the active area metal strip 52 in the bimetal strip 50, and the thickness of the heavy dielectric material 42 is equal to the thickness of the bimetal strip 50. Except for the above, other conditions are exactly the same as those in Example 14.

[0143] Comparative Example 1

[0144] This comparative example adopts a TC-SAW resonator, numbered CP1, which, compared with the TC-SAW resonator 100 in Example 1, does not contain the busbar edge metal strip 51 in the double metal strip 50, and only has the active area metal strip 52. Except for the above, other conditions are exactly the same as those in Example 1.

[0145] Comparative Example 2

[0146] This comparative example adopts a TC-SAW resonator, numbered CP2. Compared with the TC-SAW resonator 100 in Example 1, the TC-SAW resonator CP2 does not contain the active area metal strip 52 in the double metal strip 50, and only has the busbar edge metal strip 51. Except for the above, other conditions are exactly the same as those in Example 1.

[0147] Comparative Example 3

[0148] This comparative example adopts a TC-SAW resonator, numbered CP3, which does not include the bimetallic strip 50 compared to the TC-SAW resonator 100 in Example 1. Except for the above, other conditions are exactly the same as those in Example 1.

[0149] Fig. 6A An admittance diagram of a conventional TC-SAW resonator without a double metal strip in Comparative Example 3 is shown, which does not have any structure to suppress spurious modes. Figure 6B The admittance diagram of the TC-SAW resonator 130 based on a batch of Embodiment 8 is shown, wherein in each TC-SAW resonator, h1=h2 and varies in the range of 0.005λ (10nm) to 0.03λ (60nm), while d1=d2=1.4μm, g1=g2=50nm; Figure 6C The admittance diagram of the TC-SAW resonator 130 based on a batch of Embodiment 8 is shown. In each TC-SAW resonator, h1=h2=40nm, d1=d2 and varies in the range of 0.5λ (1μm) to 1λ (2μm), g1=g2=50nm; Fig.6D The admittance diagram of the TC-SAW resonator 130 based on a batch of Embodiment 8 is shown. In each TC-SAW resonator, h1=h2=40nm, d1=d2=1.4μm, and g1=g2 varies in the range of 0.015λ (30nm) to 0.08λ (160nm); Figure 6B , 6C and 6D display, with Fig. 6A Compared with the curve of , almost all the transverse modes are suppressed. This shows that the embodiments of the present invention significantly improve the performance of the TC-SAW resonator.

[0150] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0151] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0152] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A TC-SAW resonator, characterized in that: The TC-SAW resonator comprises a piezoelectric substrate (10), a functional layer and a temperature compensation layer (40) which are stacked in sequence; the functional layer comprises an interdigital transducer (20) and reflectors (30) arranged opposite to each other on both sides of the interdigital transducer (20); The interdigital transducer (20) comprises two busbars (21) arranged opposite to each other; the two busbars (21) are respectively connected to fingers (22), the fingers (22) extending towards the busbar (21) on the opposite side but leaving a gap therebetween, so that the interdigital transducer (20) comprises an active region (24) formed by alternately arranging the fingers (22), and gap regions (23) formed at both ends of the active region (24); The TC-SAW resonator further comprises two pairs of bimetallic strips (50), which are arranged above the interdigital transducer (20) and have a first spacing from the plane where the surface of the interdigital transducer (20) is located; each pair of the bimetallic strips (50) comprises a busbar edge metal strip (51) and an active region metal strip (52) which are parallel to and opposite to each other; In the orthographic projection onto the functional layer, the two pairs of bimetallic strips (50) are arranged between the two busbars (21) and correspond to the two busbars (21) respectively; the center of the busbar edge metal strip (51) is arranged in the gap area (23); in the extension direction parallel to the busbar (21), one side edge of the busbar edge metal strip (51) is in contact with one side edge of the corresponding busbar (21); and in the extension direction parallel to the finger strip (22), the edge of the busbar edge metal strip (51) does not exceed the gap area (23) and does not contact the corresponding active area metal strip (52), and a second interval is retained; in the extension direction parallel to the finger strip (22), one side edge of the active area metal strip (52) away from the corresponding busbar edge metal strip (51) does not exceed the active area (24).

2. The TC-SAW resonator according to claim 1, characterized in that: The second intervals in the two pairs of bimetallic strips (50) are equal.

3. The TC-SAW resonator according to claim 1, characterized in that: In an orthographic projection onto the functional layer, an edge of one side of the active area metal strip (52) that is away from the corresponding busbar edge metal strip (51) is aligned with a boundary of the active area (24) in an extension direction parallel to the busbar (21).

4. The TC-SAW resonator according to claim 1, characterized in that: In an extension direction parallel to the finger strips (22), the width of the busbar edge metal strip (51) and the width of the active area metal strip (52) are both 0.5 to 1λ, where λ is the wavelength of the surface acoustic wave; The width of the busbar edge metal strip (51) is equal to the width of the active area metal strip (52).

5. The TC-SAW resonator according to any one of claims 1 to 4, characterized in that: In an orthographic projection onto the functional layer and in an extension direction parallel to the busbar (21), the reflector (30) is arranged opposite to the active area (24) and the gap area (23), and an edge of the busbar edge metal strip (51) does not extend beyond the gap area (23), or extends beyond the active area (24) and covers the reflector (30); In an extension direction parallel to the busbar (21), two ends of the active area metal strip (52) are respectively flush with two ends of the busbar edge metal strip (51).

6. The TC-SAW resonator according to claim 1, characterized in that: In each pair of the bimetallic strips (50), a first mass load portion (53) is provided between the busbar edge metal strip (51) and the active region metal strip (52), and the first mass load portion (53) connects the busbar edge metal strip (51) and the corresponding active region metal strip (52); In each pair of the bimetallic strips (50), the busbar edge metal strip (51) is connected to a second mass load portion (54), and in an orthographic projection onto the functional layer, the second mass load portion (54) falls into the corresponding busbar (21); The size of the second mass load portion (54) is equal to the size of the corresponding bus bar (21).

7. The TC-SAW resonator according to claim 1, characterized in that: The bimetallic strip (50) is arranged on the surface of the temperature compensation layer (40), or is embedded in the temperature compensation layer (40), or is completely buried in the temperature compensation layer (40).

8. The TC-SAW resonator according to claim 1 or 7, characterized in that: For the portion of the bimetallic strip (50) exposed outside the temperature compensation layer (40), a temperature compensation material (41) is filled in the active area (24), and / or a heavy dielectric material (42) is provided in the portion outside the active area (24); The temperature compensation material (41) is the same as the temperature compensation layer (40); the acoustic impedance of the heavy dielectric material (42) is different from that of the temperature compensation layer (40) and the density is greater than that of the temperature compensation layer (40); The heavy dielectric material (42) includes at least one of hafnium oxide, silicon nitride, barium strontium titanate, aluminum oxide or titanium dioxide.

9. The TC-SAW resonator according to claim 1, characterized in that: The temperature compensation layer (40) and the piezoelectric substrate (10) have opposite temperature elastic coefficients; the temperature compensation layer (40) and the bimetallic strip (50) have opposite density properties; the bimetallic strip (50), the reflector (30) and the interdigital transducer (20) are made of the same material; The material of the bimetallic strip (50) includes at least one of aluminum, copper, gold, tungsten, molybdenum or silver; The material of the temperature compensation layer (40) includes silicon dioxide; The material of the piezoelectric substrate (10) includes at least one of lithium niobate, lithium tantalate or quartz.

10. A filter, characterized in that: A TC-SAW resonator comprising any one of claims 1 to 9.

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