Acoustic wave resonator device

Abstract

The invention relates to an acoustic wave resonator device (100) comprising: a piezoelectric layer (102); a dielectric substrate (104); the dielectric substrate (104) is arranged on the piezoelectric layer (102), and the interdigital transducer (106) is arranged between the piezoelectric layer (102) and the dielectric substrate (104) and is used for supporting the piezoelectric layer (102) at the position of the dielectric substrate (104). The interdigital transducer (106) includes a first conductive electrode (112) connected to the first bus bar (122) and a second conductive electrode (114) connected to the second bus bar (124). The first conductive electrodes (112) and the second conductive electrodes (114) are alternately disposed in the interdigital transducer (106). The interdigital transducer (106) is configured to convert an electrical signal (ES) into an acoustic wave (AW) in the piezoelectric layer (102). Therefore, a structure with good power processing performance and very strong robustness is provided. Furthermore, the invention relates to an electronic communication device (200) comprising said acoustic wave resonator device (100).

Description

Technical Field

[0001] Embodiments of the present invention relate to acoustic wave resonator devices and electronic communication devices including such acoustic wave resonator devices. Background Art

[0002] A transversely excited bulk acoustic resonator (XBAR) device operating in the 5 GHz frequency range is proposed. The XBAR device is based on a lithium niobate (LN) membrane suspended over a cavity. The proposed XBAR device with the membrane suspended over the cavity is very fragile because the membrane is very thin. In addition, the power handling performance of the above XBAR device is poor due to the low thermal conductivity of the LN membrane. In addition, the long and thin electrodes have high resistivity, which increases the losses and heating of the XBAR device.

[0003] Another resonator device is described that utilizes the S0 Lamb mode in a LN film attached to a high-speed substrate such as SiC or diamond. The resonator device utilizing the S0 Lamb mode of the film attached to the high-speed substrate significantly reduces the degree of piezoelectric coupling.

[0004] Another proposed XBAR device includes a base frame supporting the suspended membrane in an attempt to reduce the fragility of the XBAR device. However, this can only partially alleviate the above-mentioned disadvantages. In particular, the power handling performance of such an XBAR device is still not optimal. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide a solution to reduce or solve the disadvantages and problems of the traditional solutions.

[0006] Another object of embodiments of the present invention is to provide a solution with improved power handling and mechanical robustness compared to conventional solutions.

[0007] The above objects and other objects are achieved by the subject matter claimed in the independent claims. Further embodiments of the invention are provided in the dependent claims.

[0008] According to a first aspect of the present invention, the above and other objects are achieved by an acoustic wave resonator device, the acoustic wave resonator device comprising:

[0009] Piezoelectric layer;

[0010] dielectric substrate;

[0011] An interdigital transducer is arranged between the piezoelectric layer and the dielectric substrate, and is used to support the piezoelectric layer at the dielectric substrate. The interdigital transducer includes a first conductive electrode connected to a first bus bar and a second conductive electrode connected to a second bus bar, wherein the first conductive electrode and the second conductive electrode are alternately arranged in the interdigital transducer, and the interdigital transducer is used to convert an electrical signal into an acoustic wave in the piezoelectric layer.

[0012] An advantage of the acoustic wave resonator device according to the first aspect is that power handling is improved compared to conventional solutions, because the heat generated in the piezoelectric layer and (mainly in) the electrodes can be transferred to the dielectric substrate with high thermal conductivity through the bottom side of the interdigital transducer electrodes. In addition, since the electrodes are fixed / attached to the dielectric substrate, parasitic vibrations / resonances in the electrodes are also reduced. Another advantage compared to conventional designs is that the electrodes in this design can be quite thick, so that resistive losses can be reduced. A further advantage is that the general structure of the acoustic wave resonator device according to the first aspect is more mechanically robust compared to conventional solutions.

[0013] In one implementation of the acoustic wave resonator device according to the first aspect, the acoustic wave is

[0014] S0 mode Lamb waves having predominantly longitudinal displacement in the piezoelectric layer; or

[0015] SHO plate modal waves with dominant shear displacement in the piezoelectric layer.

[0016] The advantage of this implementation is that the S0 Lamb mode has a very high velocity in lithium niobate (LN) (about 7 km / s) and a high degree of coupling with a properly chosen cut of the piezoelectric layer. This provides an acoustic wave resonator device with a frequency above 3 GHz for a device with a pitch p of about 1 μm, which is convenient for optical lithography. In contrast, the velocity of the horizontal shear (SH0) plate mode wave is not fast, but this wave can obtain a high degree of piezoelectric coupling and can be used to develop resonators with a resonant-antiresonant frequency gap greater than 10%. Therefore, this acoustic wave resonator device can be used in a "ladder" filter with a relatively large passband.

[0017] In an implementation of the acoustic wave resonator device according to the first aspect, the first conductive electrode and the second conductive electrode are equidistantly arranged in the interdigital transducer at a pitch p.

[0018] In contrast to XBARs (or FBARs), where the resonant frequency is determined primarily by the film thickness and has little to do with the pitch, this implementation has the advantage that the resonant frequency is determined by the pitch, p, and is roughly inversely proportional to it. In ladder filters, resonators with different resonant and anti-resonant frequencies are required. In this implementation, this can be easily achieved by varying the pitch, p (e.g., in a photolithography process).

[0019] In an implementation manner of the acoustic wave resonator device according to the first aspect, the pitch p is based on a resonant frequency of the acoustic wave resonator device.

[0020] The resonant frequency may be a desired or required resonant frequency of the acoustic wave resonator device.

[0021] The advantage of this implementation is that as many different resonant frequency values ​​as possible can be easily obtained according to the needs of different filter applications.

[0022] In an implementation of the acoustic wave resonator device according to the first aspect, the spacing p is determined based on the following formula:

[0023] p=V S0 / F res / 2

[0024] Among them, V S0 is the velocity of the S0 mode Lamb wave, F res is the resonant frequency; or

[0025] p=V SH0 / F res / 2

[0026] Among them, V SH0 is the velocity of the zero-order SH0 plate mode wave, F res is the resonant frequency.

[0027] In an implementation of the acoustic wave resonator device according to the first aspect, the thickness d of the piezoelectric layer is P In the range between 0.05 and 2.0 of the pitch p.

[0028] In an implementation of the acoustic wave resonator device according to the first aspect, the piezoelectric layer is any one of the following: a lithium niobate layer, a lithium tantalate layer, an aluminum nitride layer, or an aluminum scandium nitride layer.

[0029] The advantage of this implementation is that these materials have good properties, such as high piezoelectric coupling, good mechanical properties, developed technology, commerciality, etc.

[0030] In an implementation of the acoustic wave resonator device according to the first aspect, the cut of the lithium niobate layer is a Z-cut, an X-cut or a rotated Y-cut.

[0031] In an implementation of the acoustic wave resonator device according to the first aspect, the cutout of the lithium niobate layer is any one of the following:

[0032] [90,90,γ]X cut with a propagation angle γ substantially close to 30°;

[0033] [0, β, 90] rotated Y-cut with a cutting angle β substantially close to 124°;

[0034] [90,90,γ]X-cut with a propagation angle γ substantially close to 170° (+ / –5°); or

[0035] [0, β, 0] rotated Y-cut with a cutting angle β substantially close to 30°.

[0036] For S0 Lamb modes, a [90,90,γ] X-cut with a propagation angle γ substantially close to 30° (+ / –5°), or a [0,β,90] rotated Y-cut with a cut angle β substantially close to 124° (+ / –5°) is suitable. For SH0 plate modes, a [90,90,γ] X-cut with a propagation angle γ substantially close to 170° (+ / –5°), or a [0,β,0] rotated Y-cut with a cut angle β substantially close to 120° (+ / –5°) is suitable.

[0037] One advantage of this implementation is that the performance of the mentioned cutouts is improved.

[0038] In an implementation of the acoustic wave resonator device according to the first aspect, a phase velocity of the acoustic wave propagating in the dielectric substrate is greater than a phase velocity of the acoustic wave in the piezoelectric layer.

[0039] In an implementation manner of the acoustic wave resonator device according to the first aspect, the dielectric substrate is any one of the following: a diamond substrate, a silicon carbide substrate, a sapphire substrate, a yttrium aluminum garnet (YAG) substrate, or a boron nitride substrate.

[0040] The advantage of this implementation is that these materials have good properties.

[0041] In an implementation of the acoustic wave resonator device according to the first aspect, the first conductive electrode and the second conductive electrode are arranged along a common row in the interdigital transducer, wherein a propagation direction of the acoustic wave in the piezoelectric layer is perpendicular to a direction of the common row.

[0042] In an implementation of the acoustic wave resonator device according to the first aspect, the interdigital transducer includes at least one third conductive electrode arranged at a first end of the common row and at least one fourth conductive electrode arranged at a second end of the common row, thereby surrounding the first conductive electrode and the second conductive electrode in the common row, wherein the third conductive electrode and the fourth conductive electrode are not connected to the first bus bar or the second bus bar, thereby having a floating potential.

[0043] An advantage of this implementation is that a reflector element is provided to improve the performance of the acoustic wave resonator device.

[0044] In an implementation of the acoustic wave resonator device according to the first aspect, the third conductive electrode and the fourth conductive electrode are equidistantly arranged in the interdigital transducer with respect to the first conductive electrode and the second conductive electrode at a pitch p.

[0045] In an implementation of the acoustic wave resonator device according to the first aspect, the piezoelectric layer includes a first vertical wall and a second vertical wall arranged opposite to the first vertical wall, wherein the distance from the first vertical wall or the second vertical wall to the nearest conductive electrode is equal to the spacing p.

[0046] An advantage of this implementation is that the performance of the acoustic wave resonator device is improved.

[0047] In an implementation of the acoustic wave resonator device according to the first aspect, the piezoelectric layer is arranged in a first plane, and the dielectric substrate is arranged in a second plane parallel to the first plane, wherein a surface area of ​​the piezoelectric layer in the first plane is smaller than a surface area of ​​the dielectric substrate in the second plane.

[0048] An advantage of this implementation is that parasitic generation of acoustic waves in the outer portion of the piezoelectric layer not facing the IDT can be avoided.

[0049] In an implementation of the acoustic wave resonator device according to the first aspect, the surface area of ​​the piezoelectric layer is equal to an overlapping surface area covering any of the following:

[0050] the first conductive electrode and the second conductive electrode; or

[0051] The first conductive electrode, the second conductive electrode, the third conductive electrode and the fourth conductive electrode.

[0052] An advantage of this implementation is that parasitic generation of acoustic waves in the outer portion of the piezoelectric layer not facing the IDT can be avoided.

[0053] In an implementation of the acoustic wave resonator device according to the first aspect, the piezoelectric layer comprises through holes, wherein each through hole is aligned with a tip of the first conductive electrode or a tip of the second conductive electrode.

[0054] In an implementation of the acoustic wave resonator device according to the first aspect, the piezoelectric layer, the dielectric substrate and the interdigital transducer are aligned with each other around a central axis of the acoustic wave resonator device.

[0055] According to a second aspect of the present invention, the above and other objects are achieved by an electronic communication device for a communication system, the electronic communication device comprising at least one acoustic wave resonator device according to any one of the preceding claims.

[0056] Other applications and advantages of embodiments of the present invention will be apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings are intended to illustrate and explain different embodiments of the present invention, in which:

[0058] Figure 1 An acoustic wave resonator device according to an embodiment of the present invention is shown;

[0059] Figure 2 Shows Figure 1 An acoustic wave resonator device in which the piezoelectric layer has been removed for illustration purposes;

[0060] Figure 3 shows the surface area of ​​the piezoelectric layer relative to the surface area of ​​the dielectric substrate according to an embodiment of the present invention;

[0061] Figure 4 shows a surface area of ​​a piezoelectric layer relative to a surface area of ​​a dielectric substrate according to yet another embodiment of the present invention;

[0062] Figure 5a to Figure 5c shows a through hole in a piezoelectric layer according to an embodiment of the present invention;

[0063] Figure 6 An acoustic wave resonator device including a reflector element according to an embodiment of the present invention is shown;

[0064] Figure 7a The FEM simulation resonator performance with Nt=50 pairs of electrodes is shown;

[0065] Figure 7b The displacement in the S0 Lamb mode of the first embodiment is shown;

[0066] Figure 7c The performance when using diamond and SiC substrates is shown;

[0067] Figure 7d The performance when using Si substrate is shown;

[0068] Figure 8 The piezoelectric modulus e11 for the Z-cut and the Y-cut rotated 120° of LN with Euler angles of [0 30 90] is shown;

[0069] Figure 9a shows the relative Y crys An acoustic wave resonator device using the SH0 plate mode in an X-cut LN piezoelectric layer with the propagation direction of the axis at 170°;

[0070] Figure 9b shows the resonance time u y The displacement of the dominant component;

[0071] Fig.9c A 30° Y-cut of LN with Euler angles of [0–60 0] is shown;

[0072] Fig.10 An electronic communication device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0073] As described above, XBAR devices based on membranes suspended on cavities, S0 Lamb mode devices with membranes attached to high-speed substrates, or XBARs with supporting bases have been proposed. However, these XBAR devices and S0 Lamb mode devices have their disadvantages, and thus a solution is needed to alleviate the disadvantages of these conventional solutions. Therefore, an acoustic wave resonator device 100 and an electronic communication device 200 that can alleviate the above disadvantages are disclosed herein.

[0074] Figure 1 1 shows an acoustic wave resonator device 100 according to an embodiment of the present invention, Figure 2 Shows Figure 1 FIG. 1 is an acoustic wave resonator device 100 in which the piezoelectric layer 102 has been removed for illustration purposes. It can be noted that Figure 1 Shows Figure 2 1 is a cross-sectional view of the acoustic wave resonator device 100 along line AA.

[0075] refer to Figure 1 and Figure 2, the acoustic wave resonator device 100 shown in the figure includes a piezoelectric layer 102 and a dielectric substrate 104. The acoustic wave resonator device 100 also includes an interdigital transducer (IDT) 106, which is disposed between the piezoelectric layer 102 and the dielectric substrate 104 and is used to support the piezoelectric layer 102 at the dielectric substrate 104. The IDT 106 further includes a first conductive electrode 112 connected to a first bus bar 122 and a second conductive electrode 114 connected to a second bus bar 124, see Figure 2 , for illustration purposes, Figure 2 The acoustic wave resonator device 100 is shown without the piezoelectric layer 102. The first conductive electrodes 112 and the second conductive electrodes 114 are alternately arranged in the interdigital transducer 106. The IDT 106 is used to convert the electrical signal ES into an acoustic wave AW in the piezoelectric layer 102. Due to the lateral (horizontal) electric field generated by the conductive electrodes in the piezoelectric layer 102, the electrical signal ES can be applied to the bus bars 122 and 124, thereby being converted into the acoustic wave AW in the piezoelectric layer 102.

[0076] Therefore, the IDT 106 also serves as a support structure for the piezoelectric layer 102 between the piezoelectric layer 102 and the dielectric substrate 104. This means that the IDT 106 is directly fixed / attached to the piezoelectric layer 102 and the dielectric substrate 104. For the attachment of different layers, suitable bonding techniques can be used to provide a strong attachment of the different layers. For example, a thin bonding layer (e.g., Ti) can be used. Since imperfect or low-quality bonding can result in a reduction in the electric field in the piezoelectric layer and / or a reduction in the heat discharged to the dielectric substrate 104, the conductive electrodes 112 and 114 are fully bonded to the dielectric substrate 104 and the piezoelectric layer 102. By making direct mechanical contact with the piezoelectric layer 102 and the dielectric substrate 104, the heat generated in the piezoelectric layer 102 can be efficiently transferred to the dielectric substrate 104 via the IDT 106 to improve the cooling effect. In addition, a very robust resonator structure is provided. It can be noted that Figure 1 The dimensions and sizes of the different parts of the acoustic wave resonator device 100 shown may not correspond to actual implementations of the invention, but are provided for illustration purposes.

[0077] In addition, the IDT 106 may include any number of first conductive electrodes 112 and second conductive electrodes 114, for example, from a few conductive electrodes to thousands of conductive electrodes. The number of first conductive electrodes 112 and second conductive electrodes 114 may be the same in a symmetrical configuration. The conductive electrodes are naturally made of any suitable conductive material, such as different metals.

[0078] The acoustic wave resonator device 100 may also include an input and an output (not shown) so that an electrical signal can be applied to the first bus bar and the second bus bar for exciting the electrical signal into an acoustic wave AW in the piezoelectric layer 102. The acoustic wave AW may have different properties and characteristics. However, in an embodiment of the present invention, the acoustic wave AW is an S0 mode Lamb wave having a main longitudinal displacement in the piezoelectric layer 102, or the acoustic wave AW is an SHO plate mode wave having a main shear displacement in the piezoelectric layer 102. In general, different plate modes may be used herein. In this embodiment, an S0 Lamb mode may be used, which has a main horizontal displacement in the piezoelectric layer 102 and is substantially uniform over the thickness of the layer. The advantage of using this mode is that the wave speed is fast, which can reach 7 km / s in the LN piezoelectric layer. The cut of the LN is selected so as to provide a strong interaction of the horizontal electric field in the layer between the longitudinally deformed electrodes. This means that there must be a large piezoelectric modulus e1,1 available. It is also possible to use a shear plate mode SH0, which is similar to a bulk shear wave propagating in a direction perpendicular to the electrodes and displaced parallel to the electrodes. The advantage of using this mode is that the cut of the LN piezoelectric layer is known and the maximum value of the piezoelectric modulus e1,6 is responsible for the excitation of the shear wave by the horizontal electric field. In this embodiment, the maximum resonance-anti-resonance (RaR) relative frequency distance can be achieved, so a broadband filter can be realized based on the resonator according to an embodiment of the present invention.

[0079] In general, the stress present in the electrodes will generate bulk waves in the dielectric substrate 104, and thus some wave energy will be lost. Such losses will inevitably reduce the Q factor of the acoustic wave resonator device 100 and should be avoided. If the phase velocity of the acoustic wave propagating in the dielectric substrate 104 is greater than the phase velocity of the acoustic wave AW in the piezoelectric layer 102, it is impossible to generate bulk waves. More specifically, the phase velocity of the acoustic wave AW velocity in the propagation direction (i.e., along the X-axis in the horizontal plane) is less than the phase velocity of any bulk acoustic wave propagating in the dielectric substrate 104, i.e.

[0080] k x，bulk <2π / p

[0081] Among them, k x，bulk is the horizontal X component of the body wave vector in the dielectric substrate 104. In order to satisfy such acoustic wave characteristics, the properties and combinations of the piezoelectric layer 102 and the dielectric substrate 104 must be carefully selected. This means that it is very important to select the corresponding materials of the piezoelectric layer 102 and the dielectric substrate 104. Generally, a dielectric substrate with a fast acoustic velocity is required, such as diamond, SiC, etc.

[0082] Therefore, in the embodiment of the present invention, the piezoelectric layer 102 is any one of the following: a lithium niobate (LN) layer, a lithium tantalate layer, an aluminum nitride layer, or an aluminum scandium nitride layer.

[0083] LN was chosen because of its very high piezoelectric modulus, excellent mechanical properties, commercial availability of large wafers with ion-sliced ​​sub-micron thick LN layers, and relatively low price. However, LN has a fairly high frequency temperature coefficient, which can be a problem in some applications. Lithium tantalate (LT) is similar to LN, but its piezoelectric modulus is significantly smaller (about 30% lower) than that of LN, while its frequency temperature coefficient is about 2 times lower than that of LN. LT may be a good choice if maximum RaR coupling is not required. In addition, LN and LT have commercial availability for use as ion-sliced ​​layers on Si and other substrates. Aluminum nitride can be deposited on large (e.g., 6-inch) wafers of good quality. However, aluminum nitride has a lower piezoelectric coupling and is available in only one orientation, which may not be the best choice. Currently, AlScN is being actively developed to significantly increase the piezoelectric modulus.

[0084] In the case where the piezoelectric layer 102 is an LN layer, the cut of the LN layer is a Z cut, an X cut or a rotated Y cut. Specifically, the cut of the LN layer is any of the following:

[0085] The [90,90,γ]X cutout with a propagation angle γ substantially close to 30° provides strong coupling to the S0 Lamb mode;

[0086] In the [0, β, 90] rotated Y-cut with a cutting angle β substantially close to 124°, a stronger coupling with the S0 mode can be found;

[0087] For embodiments utilizing SHO waves, a [90, 90, γ] X-cut with a propagation angle γ substantially close to 170° (+ / –5°); or

[0088] • A [0, β, 0] rotated 30° Y-cut with a cutting angle β substantially close to 30° to 90° may be used for embodiments utilizing SHO waves.

[0089] It should be noted that the angles indicated above may include a range of values.

[0090] On the other hand, according to an embodiment of the present invention, the dielectric substrate 104 is any one of the following: a diamond substrate, a silicon carbide substrate, a sapphire substrate, a yttrium aluminum garnet (YAG) substrate, or a boron nitride substrate. It is important that the acoustic body wave velocity in the dielectric substrate 104 is greater than the phase velocity of the wave mode used in the piezoelectric layer 102. The ideal material is diamond, but single crystal diamond in the form of several micron layers on a large substrate is not yet possible. The velocity in SiC is high enough, so this substrate can replace diamond. In addition, the thermal conductivity of the SiC substrate is also very high, almost 2 orders of magnitude higher than the thermal conductivity of LN.

[0091] Another example Figure 2 As shown, the first conductive electrode 112 and the second conductive electrode 114 are arranged along a common row r in the IDT 106. Therefore, the propagation direction of the acoustic wave AW in the piezoelectric layer 102 is parallel to the direction of the common row r and perpendicular to the electrodes.

[0092] Figure 3 and Figure 4 The surface area of ​​the piezoelectric layer 102 relative to the surface area of ​​the dielectric substrate 104 is shown in accordance with an embodiment of the present invention.

[0093] like Figure 3 As shown, when the piezoelectric layer 102 is arranged in a first plane P1 and the dielectric substrate 104 is arranged in a second plane P2 parallel to the first plane P1, the surface area A1 of the piezoelectric layer 102 in the first plane P1 is smaller than the surface area A2 of the dielectric substrate 104 in the second plane P2. The first plane P1 and the second plane P2 can also be represented as horizontal planes, which means that the planes perpendicular to the first plane and the second plane can be represented as vertical planes. With respect to the vertical plane, a top surface and a top surface area and a bottom surface and a bottom surface area can be defined. The top surface faces the anti-gravity direction, while the bottom surface faces the opposite direction.

[0094] The filter using multiple acoustic wave resonator devices 100 disclosed in this article includes multiple bus bars with different potentials, so that electric fields are generated nearby. If these electric fields penetrate into the piezoelectric layer 102, some stress and vibration will be generated, thereby absorbing some energy. Therefore, preferably, the surface area of ​​the piezoelectric layer 102 is limited to the area where the electrodes overlap and the required Lamb mode S0 wave or SHO wave is generated. In order to enhance the robustness of the structure, the piezoelectric layer 102 can be partially overlapped or supported by the bus bars. The vertical ends Z1 and Z2 of the piezoelectric layer 102 parallel to the electrodes can also be used as reflectors of waves escaping from the acoustic wave resonator device 100.

[0095] Therefore, in Figure 4 In the illustrated embodiment, the surface area A1 of the piezoelectric layer 102 is equal to or approximately equal to the overlapping surface area 130 covering the first conductive electrode 112 and the second conductive electrode 114 .

[0096] Figure 5a to Figure 5c Yet another design of the piezoelectric layer 102 according to embodiments of the present invention is shown. In these embodiments, the piezoelectric layer 102 includes through holes, wherein each through hole 140 is aligned with the tip 120 of the first conductive electrode 112 or the tip 120 of the second conductive electrode 114. Figure 5aA top perspective view of an acoustic wave resonator device 100 is shown, and a tip 120 of a conductive electrode is shown. The tip 120 can be understood as the end of the conductive electrode opposite to the end connected to the bus bar. Therefore, the tip of the conductive electrode is a free end that is not in mechanical contact with the bus bar. Figure 5b A top view of an acoustic wave resonator device 100 is shown, and a plurality of holes 140 in two rows are shown, wherein a first row of holes is disposed in the piezoelectric layer above the tip of a first conductive electrode 112, and a second row of holes is disposed in the piezoelectric layer above the tip of a second conductive electrode 114. Since the first conductive electrodes 112 and the second conductive electrodes 114 are alternately disposed relative to each other, the first row of holes and the second row of holes are alternately disposed relative to each other. The through holes 140 in the piezoelectric layer 102 are located above the gap between the fingertips of the conductive electrodes and the bus bar, and do not overlap with the conductive electrodes or the bus bar in the vertical direction, as shown in FIG. Figure 5c shown. Figure 5c A top view of a portion of the acoustic wave resonator device 100 is shown, wherein the conductive electrodes and bus bars disposed below the piezoelectric layer 102 are shown with dashed lines. Such holes can prevent acoustic energy from leaking in the lateral direction parallel to the conductive electrodes, thereby improving the Q factor of the acoustic wave resonator device 100.

[0097] Figure 6 An acoustic wave resonator device 100 according to yet another embodiment of the present invention is shown. The first conductive electrode 112 and the second conductive electrode 114 are equidistantly arranged in the interdigital transducer 106 at a pitch p. The pitch p can be defined as the center-to-center distance between two adjacent conductive electrodes, which is the geometric / mechanical period of the IDT 106 structure. Since the electrode polarity is alternating, the actual period is equal to 2p.

[0098] In order to determine the spacing p, the resonant frequency of the acoustic wave resonator device 100 must be considered. Therefore, in an embodiment of the present invention, the spacing p is determined based on the following formula:

[0099] p=V S0 / F res / 2

[0100] If the acoustic wave resonator device 100 operates in the S0 mode Lamb wave mode, then V S0 is the velocity of the S0 mode Lamb wave, which is mainly determined by the cut of the LN used, F res is the resonant frequency. If the acoustic wave resonator device 100 is used in a ladder filter circuit, the frequency is determined by the filter specifications (such as center frequency, etc.) and the filter design. Therefore, the filter frequency can be considered as a design parameter.

[0101] Therefore, if the acoustic wave resonator device 100 utilizes the SHO plate mode and has the necessary LN cut, the spacing p can also be determined based on the following formula:

[0102] p=V SH0 / F res / 2

[0103] Among them, V SH0 is the velocity of the zero-order SH0 plate mode wave, F res is the resonant frequency.

[0104] The values ​​given by the above formula are only approximate and do not necessarily correspond to the exact values ​​of the spacing that provide the necessary resonant frequency and anti-resonant frequency values. The velocity values ​​in the above formula are approximately known only for the free piezoelectric layer, but are affected by the presence, shape and material of the attached electrodes. The exact geometry of the acoustic wave resonator device 100 is optimized during the design process by performing FEM modeling of the acoustic wave resonator device 100, etc.

[0105] Another example Figure 6 The thickness d of the piezoelectric layer 102 is shown P It is also related to the pitch p for achieving appropriate performance of the acoustic wave resonator device 100. In the embodiment of the present invention, the thickness d of the piezoelectric layer 102 is P In the range of 0.05 to 2.0 of the pitch p. For the S0 Lamb mode and the SH0 plate mode, it is important that the horizontal electric field couples to the quasi-uniform (i.e., across the thickness) stress distribution in the LN layer, thereby providing efficient excitation of the wave. The LN layer has an optimal thickness. A layer that is too thin cannot contain enough mechanical energy, so that the excited wave is too disturbed by the electrode. On the contrary, in a layer that is too thick, vibrations cannot be excited throughout the thickness, i.e., the electric field is not uniform and is more concentrated near the electrode.

[0106] As mentioned earlier, Figure 6 The acoustic wave resonator device 100 in the embodiment of the present invention further includes reflector elements according to an embodiment of the present invention, which are respectively represented as a third conductive electrode 116 and a fourth conductive electrode 118. The purpose of the reflector elements is to avoid energy loss at the end of the piezoelectric layer 102 in the horizontal direction.

[0107] Therefore, the interdigital transducer 106 in the embodiment includes at least one third conductive electrode 116 disposed at the first end of the common row r and at least one fourth conductive electrode 118 disposed at the second end of the common row r, thereby surrounding the first conductive electrode 112 and the second conductive electrode 114 in the common row r. The number and configuration of the reflector elements depend on the application. The third conductive electrode 116 connected between the reflector elements is not connected to the first bus bar 122, and accordingly, the fourth conductive electrode 118 connected between the reflector elements is not connected to the second bus bar 124, thereby having a floating potential. This means that the potential of the third conductive electrode 116 and the fourth conductive electrode 118 is not determined by the voltage applied to the bus bar, but depends on the parasitic capacitance between these electrodes and other conductors. Therefore, the reflector electrode does not generate many acoustic waves, but only reflects the waves from the IDT106 back.

[0108] The third conductive electrode 116 and the fourth conductive electrode 118 used as reflector elements can be arranged equidistantly at a pitch p or at different pitches. Therefore, in the example, all the first conductive electrodes 112, the second conductive electrodes 114, the third conductive electrodes 116 and the fourth conductive electrodes 118 can be arranged equidistantly at the same pitch p, thereby generating a mechanical periodic synchronization structure.

[0109] In addition, the piezoelectric layer 102 may further include a first vertical wall Z1 and a second vertical wall Z2 disposed opposite to the first vertical wall Z1. Figure 6 As shown. In an embodiment of the present invention, the distance from the first vertical wall Z1 or the second vertical wall Z2 to the nearest conductive electrode is equal to the pitch p. In this case, the reflected wave coherently interferes with the wave already present in the transducer, and the amplitude of the wave increases, which ultimately means that the coupling degree and the RaR distance increase.

[0110] The closest conductive electrode may be any one of the following: the first conductive electrode 112, the second conductive electrode 114, the third conductive electrode 116, and the fourth conductive electrode 118. In a non-limiting example, the third conductive electrode 116 and the fourth conductive electrode 118 are the conductive electrodes closest to the vertical walls Z1, Z2. However, in the absence of a reflector element, the first conductive electrode 112 or the second conductive electrode 114 would constitute the closest conductive electrode relative to the vertical wall.

[0111] In an embodiment of the present invention, the surface area A1 of the piezoelectric layer 102 is equal to or approximately equal to the overlapping surface area 130 covering the first conductive electrode 112, the second conductive electrode 114, the third conductive electrode 116, and the fourth conductive electrode 118. Therefore, the overlapping surface area also covers any reflector elements of the acoustic wave resonator device 100.

[0112] also, Figure 6It is also shown that an optional protective layer 150 (e.g., a dielectric layer or an oxide layer) can be disposed above the piezoelectric layer 102, because with this solution, there is no need to provide a conductive electrode on the top surface of the piezoelectric layer 102. The protective layer 150 can be a SiO2 layer, which can be used for different reasons, such as: a passivation layer to protect other layers from oxidation, water molecules, etc.; for small changes in velocity and fine-tuning the resonant frequency of the device; for improving thermal conductivity and removing heat from the layer; using a SiO2 layer to increase the temperature coefficient of frequency (TCF); using high sound velocity materials such as diamond and SiC to increase wave speed.

[0113] 7 to 9 show performance results of different embodiments of the present invention.

[0114] In the first embodiment, the geometry of the acoustic wave resonator device 100 in the simulation is set to:

[0115] Nt = 50 pairs of electrodes;

[0116] a = 0.3 μm electrode width;

[0117] p = 0.5e–6 spacing;

[0118] W = 50e–6 aperture;

[0119] crystal_cut_angles = [90 90 30] X cut, 30° propagation direction relative to the crystal Y axis;

[0120] sidewall_angle = 90;

[0121] The electrode should be rectangular;

[0122] h_LN = 200e–9m thickness of the piezoelectric layer;

[0123] h_Al = 100e–9m electrode height.

[0124] A simulation was performed on an acoustic wave resonator device 100 using a diamond substrate as the dielectric substrate 104. The simulation results are as follows:

[0125] The resonant frequency is 6224.3MHz;

[0126] Resonant Q factor is 190;

[0127] The resonant admittance of each pair of electrodes is 0.046;

[0128] The anti-resonance frequency is 6898.5MHz;

[0129] Anti-resonance Q factor is 615;

[0130] The relative RaR is 10.28%.

[0131] The parameter RaR = (FAR-FR) / FR describes the anti-resonance (F AR ) and resonance (F R ). When such an acoustic wave resonator device 100 is used in a low-loss ladder filter, the relative passband of the filter is close to RaR in an ideal / optimal state, which means that a very wideband filter is to be designed, and accordingly a large RaR parameter is required. In the above example, a high coupling degree of 10.3% is obtained, which is suitable for designing a wideband filter with a relative passband of 8% to 12% for 5G mobile phones in the 5GHz frequency range. Figure 7b It shows that the main displacement component in the piezoelectric layer is u x , which is consistent with the longitudinal wave propagating in the horizontal direction. It can also be seen that there is no obvious body wave penetrating into the diamond substrate.

[0132] Figure 7a The simulation performance results of the first embodiment using the S0 Lamb mode in an LN film on a diamond substrate are shown, namely the resonator admittance Re(Y) and abs(Y). In the above simulations, the spacing p=0.5μm and the electrode width a=0.3μm used, which means a gap of 0.2μm - which is too small for optical lithography. If the spacing is increased to 0.6μm, the frequency will be lower, about 4.8GHz, but it is still attractive for many applications and suitable for optical lithography. The number of electrode pairs is set to Nt=200.

[0133] Currently, diamond substrates are not commercially available in large wafer form. Figure 7c The results obtained using a commercially available SiC substrate (dashed line) are shown, which performs almost as well as a diamond substrate, with only a slightly reduced degree of coupling. Since the bulk velocity in SiC is higher than the velocity of the S0 Lamb mode in the cut of the selected LN (about 6200 m / s in the above example), SiC wafers can replace diamond. In contrast, Figure 7d As shown, Si substrates are unacceptable because of the strong generation of bulk waves above about 6 GHz - the velocity of bulk shear acoustic waves in Si can be lower than the velocity of the S0 Lamb mode in LN, and strong synchronous bulk wave radiation occurs. The above examples are only illustrative of the resonator parameters that can be achieved. Further optimization of the thickness of the piezoelectric layer, the geometry of the electrodes and the material can significantly increase the coupling.

[0134] In the second embodiment, Figure 8The Y120° to Y124° (and so on) cuts of the LN when the propagation direction is 90° are shown using dashed lines. Figure 8 ) can be obtained in the S0 mode (in the suspended membrane). However, the FEM simulation of the acoustic wave resonator device 100 proves that the coupling degree RaR is reduced by about 7% and there are parasitic modes (not shown in the figure). In this simulation, p = 0.6 μm, the electrode width a = 0.3 μm, and the other parameters are the same as those in the first embodiment. The cut also has a stronger modulus e3i, which is responsible for exciting the wave by the vertical component of the electric field present under the electrode of the IDT 106.

[0135] Figure 9a The performance results of the third embodiment are shown. By using a suitable cut of LN (X cut Y170°), the shear plate mode SH0 can be exploited using a geometry roughly the same as the geometry of the acoustic wave resonator device 100. The thickness of the layer is 180nm, and the thickness of the Al electrode is also 180nm. The spacing p=0.5μm, the electrode width is 0.3μm, and the admittance Re(Y) and abs(Y) of the Nt=50 pairs of electrodes with an aperture W=50μm are recalculated. RaR=10.6% is obtained. This mode has the largest coupling among all known plate modes. However, its speed is lower than that of the S0 mode, resulting in a lower achievable frequency. Figure 9b It shows that the main shear component u exists at resonance y Even when RaR = 12.6%, the coupling degree can be Fig.9c The LN layer cutouts shown were obtained with Euler angles [0 120 0]. The same resonator geometry as in the previous example was used for FEM modeling.

[0136] The above examples are only illustrative of the resonator parameters that can be achieved. Further optimization of the thickness of the piezoelectric layer, the geometry and materials of the electrodes can significantly increase the coupling.

[0137] Fig.10An electronic communication device 200 for a communication system 300 according to an embodiment of the present invention is shown. The electronic communication device 200 includes at least one acoustic wave resonator device 100 according to an embodiment of the present invention. A non-limiting example of the electronic communication device 200 is a user equipment (UE) or a base station (BS) in a wireless communication system, for example, 3GPP 4G and 5G new radio (NR). The acoustic wave resonator device 100 can be part of a filter network in such a device. For example, in order to obtain a low-loss broadband filter for a 5G mobile device, the resonator device preferably has a low impedance at resonance, typically less than 1 ohm, and a high impedance (for example, greater than 1000 ohms) at anti-resonance. This can be achieved by the acoustic wave resonator device of the present invention. In addition, the relative frequency gap (RaR) from resonance to anti-resonance can be greater than 10% or even up to 25%, and the static capacitance corresponds to about j*50 ohms at the operating frequency, which can be achieved by the acoustic wave resonator device of the present invention.

[0138] In addition, it should be appreciated that the electronic communication device 200 includes necessary communication capabilities in the form of functions, modules, units, elements, etc., for performing or implementing embodiments of the present invention. Examples of other such components, units, elements and functions are: processors, memories, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selection units, switches, interleavers, deinterleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiving units, transmitting units, DSPs, TCM encoders, TCM decoders, power supply units, power supply feeds, communication interfaces, communication protocols, etc., which are appropriately arranged together to perform the scheme.

[0139] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the attached independent claims.

Claims

1. An acoustic wave resonator device (100), characterized in that: include: A piezoelectric layer (102); A dielectric substrate (104); An interdigital transducer (106) is arranged between the piezoelectric layer (102) and the dielectric substrate (104) and is used to support the piezoelectric layer (102) at the dielectric substrate (104). The interdigital transducer (106) includes a first conductive electrode (112) connected to a first bus bar (122) and a second conductive electrode (114) connected to a second bus bar (124). The first conductive electrode (112) and the second conductive electrode (114) are alternately arranged in the interdigital transducer (106). The interdigital transducer (106) is used to convert an electrical signal (ES) into an acoustic wave (AW) in the piezoelectric layer (102).

2. The acoustic wave resonator device (100) according to claim 1, characterized in that: The acoustic wave (AW) is S0 mode Lamb waves having a predominantly longitudinal displacement in the piezoelectric layer (102); or An SHO plate modal wave having a dominant shear displacement in the piezoelectric layer (102).

3. The acoustic wave resonator device (100) according to claim 2, characterized in that: The first conductive electrode (112) and the second conductive electrode (114) are equidistantly arranged in the interdigital transducer (106) at a pitch p.

4. The acoustic wave resonator device (100) according to claim 3, characterized in that: The pitch p is based on a resonant frequency of the acoustic wave resonator device (100).

5. The acoustic wave resonator device (100) according to claim 4, characterized in that: The spacing p is determined based on the following formula: p=V S0 / F res / 2 Among them, V S0 is the velocity of the S0 mode Lamb wave, F res is the resonant frequency; or p=V SH0 / F res / 2 Among them, V SH0 is the velocity of the zero-order SH0 plate mode wave, F res is the resonant frequency.

6. The acoustic wave resonator device (100) according to any one of claims 3 to 5, characterized in that: The thickness d of the piezoelectric layer (102) P In the range of 0.05 to 2.0 of the pitch p.

7. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The piezoelectric layer (102) is any one of the following: a lithium niobate layer, a lithium tantalate layer, an aluminum nitride layer or an aluminum scandium nitride layer.

8. The acoustic wave resonator device (100) according to claim 7, characterized in that: The incision of the lithium niobate layer is a Z-incision, an X-incision or a rotated Y-incision.

9. The acoustic wave resonator device (100) according to claim 8, characterized in that: The cutout of the lithium niobate layer is any one of the following: [90,90,γ] X-cut with a propagation angle γ substantially close to 30° (+ / –5°); [0, β, 90] rotated Y-cut with a cutting angle β substantially close to 124° (+ / –5°); [90,90,γ]X-cut with a propagation angle γ substantially close to 170° (+ / –5°); or [0, β, 0] rotated Y-cut with a cutting angle β substantially close to 120° (+ / –5°).

10. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The phase velocity of the acoustic wave propagating in the dielectric substrate (104) is greater than the phase velocity of the acoustic wave (AW) in the piezoelectric layer (102).

11. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The dielectric substrate (104) is any one of the following: a diamond substrate, a silicon carbide substrate, a sapphire substrate, a yttrium aluminum garnet (YAG) substrate or a boron nitride substrate.

12. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The first conductive electrode (112) and the second conductive electrode (114) are arranged along a common row (r) in the interdigital transducer (106), wherein the propagation direction of the acoustic wave (AW) in the piezoelectric layer (102) is perpendicular to the direction of the common row (r).

13. The acoustic wave resonator device (100) according to claim 12, characterized in that: The interdigital transducer (106) includes at least one third conductive electrode (116) arranged at a first end of the common row (r) and at least one fourth conductive electrode (118) arranged at a second end of the common row (r), thereby surrounding the first conductive electrode (112) and the second conductive electrode (114) in the common row (r), wherein the third conductive electrode (116) and the fourth conductive electrode (118) are not connected to the first bus bar (122) or the second bus bar (124), thereby having a floating potential.

14. The acoustic wave resonator device (100) according to claim 13, characterized in that: The third conductive electrode (116) and the fourth conductive electrode (118) are equidistantly arranged in the interdigital transducer (106) at a pitch p relative to the first conductive electrode (112) and the second conductive electrode (114).

15. The acoustic wave resonator device (100) according to any one of claims 12 to 14, characterized in that: The piezoelectric layer (102) includes a first vertical wall (Z1) and a second vertical wall (Z2) arranged opposite to the first vertical wall (Z1), wherein the distance from the first vertical wall (Z1) or the second vertical wall (Z2) to the nearest conductive electrode (112, 114, 116, 118) is equal to the spacing p.

16. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The piezoelectric layer (102) is arranged in a first plane (P1), and the dielectric substrate (104) is arranged in a second plane (P2) parallel to the first plane (P1), wherein a surface area (A1) of the piezoelectric layer (102) in the first plane (P1) is smaller than a surface area (A2) of the dielectric substrate (104) in the second plane (P2).

17. The acoustic wave resonator device (100) according to claim 16, characterized in that The surface area (A1) of the piezoelectric layer (102) is equal to an overlapping surface area (130) covering any of: the first conductive electrode (112) and the second conductive electrode (114); or The first conductive electrode (112), the second conductive electrode (114), the third conductive electrode (116) and the fourth conductive electrode (118).

18. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The piezoelectric layer (102) includes through holes (140), wherein each through hole (140) is aligned with a tip (120) of the first conductive electrode (112) or a tip (120) of the second conductive electrode (114).

19. An electronic communication device (200) for a communication system (300), characterized in that: The electronic communication device (200) comprises at least one acoustic wave resonator device (100) according to any one of the preceding claims.

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