Low-loss elastic wave device and communication device

Abstract

The present application relates to the field of microelectronic technology, and particularly relates to a low-loss elastic wave device and a communication device. The low-loss elastic wave device comprises a piezoelectric film, a top electrode, a pair of interdigital electrodes, a first bus bar, a second bus bar, a plurality of reflection grating electrodes and a reflection grating bus bar, the ends of a plurality of first interdigital electrodes and second interdigital electrodes in the pair of interdigital electrodes form a first end track and a second end track respectively, and the absolute value of the included angle γ between the track tangent of the first end track or the second end track at the end position of any corresponding interdigital electrode and the group velocity direction is greater than or equal to 16°, and the false finger length D of at least one false interdigital electrode is greater than or equal to 2λ, wherein λ is the center distance between adjacent interdigital electrodes on the same bus bar. The present application maintains the low loss of the device without increasing the device area by using a large included angle to suppress longitudinal high-order modes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microelectronic technology, in particular to a low-loss elastic wave device and a communication device. BACKGROUND

[0002] Elastic wave devices have been widely used in wireless communication systems for frequency selection and filtering. With the update iteration of mobile communication technology, the number of filters in the radio frequency front end is increasing, so the filters are required to have lower insertion loss, flatter passband and steeper skirt, and thus the elastic wave devices that constitute the filters are required to have higher Q value and fewer spurs. However, due to the limited length of the transverse waveguide and the longitudinal waveguide, the transverse high-order mode and the longitudinal high-order mode appear between and near the resonant frequency and the anti-resonant frequency of the elastic wave resonator, which easily causes the jitter of the passband and the transition band.

[0003] In the related art, mainly for the suppression of the transverse high-order mode, for example, a piston mode structure, a tilted electrode structure, a variable trace electrode structure and the like are generally used to achieve. However, for the suppression of the longitudinal high-order mode, although the number of electrodes can be increased to weaken the longitudinal high-order mode, this method is easy to cause the increase of the device area. Therefore, how to provide a low-loss elastic wave device capable of suppressing the longitudinal high-order mode without increasing the device area has become a technical problem to be solved. SUMMARY

[0004] To solve the above technical problems caused by the suppression of the longitudinal high-order mode, the present application provides a low-loss elastic wave device and a communication device.

[0005] In one aspect, the present application discloses a low-loss elastic wave device, comprising a piezoelectric thin film and a top electrode located on one side of the piezoelectric thin film, the top electrode comprising a pair of interdigital electrodes, a first bus bar, a second bus bar, and a plurality of reflection grating electrodes located on both sides of the pair of interdigital electrodes and a reflection grating bus bar connected with the reflection grating electrodes.

[0006] The pair of interdigital electrodes comprises a plurality of first interdigital electrodes and a plurality of second interdigital electrodes arranged in a cross manner, and one end of each of the first and second interdigital electrodes is connected with the first bus bar and the second bus bar respectively, and the other end of each of the first and second interdigital electrodes forms a first end trajectory and a second end trajectory respectively.

[0007] The absolute value of the included angle γ between the trajectory tangent at any first interdigital electrode end position in the first end trajectory and the group velocity direction is greater than or equal to 16°, and the absolute value of the included angle γ between the trajectory tangent at any second interdigital electrode end position in the second end trajectory and the group velocity direction is greater than or equal to 16°.

[0008] The pair of interdigital electrodes further comprises a plurality of first dummy fingers and a plurality of second dummy fingers, the first dummy fingers are arranged with a spacing from the first interdigital electrodes, the second dummy fingers are arranged with a spacing from the second interdigital electrodes, a dummy finger length D of at least one of the first dummy fingers or the second dummy fingers is greater than or equal to 2λ, where λ is a center distance between adjacent interdigital electrodes on the same first bus bar or the second bus bar.

[0009] In some optional embodiments, a target envelope line is composed of a side of the first bus bar and the second bus bar close to the center region, a side of the reflective grid bus bar close to the center region, and a side of the last reflective grid electrode away from the center region. A shortest distance from an end of any of the first interdigital electrodes or any of the second interdigital electrodes to the target envelope line along the group velocity direction is g, a projection of the shortest distance on the phase velocity direction is an attenuation path p, and an attenuation path p corresponding to the i-th interdigital electrode satisfies the following condition: p i i ≥ 0.75 × λ / k i . 2 where k 2 is an electromechanical coupling coefficient.

[0010] In some optional embodiments, the attenuation path p i satisfies the following condition: p i ≥ λ / k 2 .

[0011] In some optional embodiments, the number of reflective grid electrodes on the two sides of the pair of interdigital electrodes is N1 and N2 respectively, and the attenuation path p i satisfies the following condition: p i ≥ (N1+N2) × λ / 4.

[0012] In some optional embodiments, the attenuation path p i satisfies the following condition: p i ≤ (N1+N2) × λ.

[0013] In some optional embodiments, the included angle γ remains constant at different positions.

[0014] In some optional embodiments, the dummy finger length of the first dummy fingers or the second dummy fingers remains constant at different positions; the dummy finger length D satisfies the following condition: D ≥ (λ / k 2 ) × tan(|γ|) - G, where G is an air gap length, and the air gap is a part between the end of the pair of interdigital electrodes and the opposite first dummy finger or second dummy finger.

[0015] In some alternative embodiments, if the included angle γ > 0°, the length D of the pseudo-finger below the first air gap in the lower left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the pseudo-finger above the last air gap in the upper right corner is ≤ 0.5λ.

[0016] If the included angle γ < 0°, the length D of the pseudo-finger above the first air gap in the upper left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the pseudo-finger below the last air gap in the lower right corner is ≤ 0.5λ.

[0017] In some alternative embodiments, the pseudofinger length D of either the first pseudofinger electrode or the second pseudofinger electrode is greater than or equal to 2λ.

[0018] In some alternative embodiments, the absolute value of the included angle γ at any position is greater than or equal to 20°, and the pseudofinger length D of at least one of the first pseudofinger electrodes or the second pseudofinger electrode is greater than or equal to 3λ.

[0019] In some alternative embodiments, the elastic wave device further includes at least one of the following:

[0020] The bottom electrode is located on the other side of the piezoelectric film;

[0021] A supporting substrate located on the other side of the piezoelectric film;

[0022] A dielectric layer located between the piezoelectric thin film and the supporting substrate;

[0023] A Bragg reflective layer located between the piezoelectric thin film and the supporting substrate.

[0024] In some alternative embodiments, the elastic wave device satisfies at least one of the following:

[0025] The piezoelectric film is made of one of lithium niobate, lithium tantalate, and potassium niobate, and the thickness of the piezoelectric film is 0.1λ to 1λ.

[0026] The supporting substrate material includes one or more of the following crystal types: sapphire, silicon, spinel, silicon carbide, diamond, diamond-like carbon, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate.

[0027] The material of the dielectric layer includes one or more of silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, polycrystalline silicon, and amorphous silicon.

[0028] In another aspect, this application also discloses a communication device including the aforementioned low-loss elastic wave device; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0029] This application provides a low-loss elastic wave device and a communication device. The device utilizes the ends of several first interdigital electrodes and second interdigital electrodes to form a first end trajectory and a second end trajectory, respectively. The absolute value of the angle γ between the tangent of the first or second end trajectory at any corresponding interdigital electrode end position and the group velocity direction is greater than or equal to 16°. Simultaneously, the pseudo-finger length D of at least one first or second pseudo-finger electrode is greater than or equal to 2λ, where λ is the center-to-center distance between adjacent interdigital electrodes on the same first or second busbar. Thus, by setting a large angle between the interdigital electrode end trajectory and the group velocity direction, the vibration of longitudinal higher-order modes is disrupted, and the leakage of longitudinal higher-order modes to areas outside the interdigital electrodes is enhanced, achieving the purpose of suppressing longitudinal higher-order modes. Furthermore, by setting a sufficiently long pseudo-finger electrode length, the problem of severe leakage of the main mode to the busbar region when the angle between the interdigital electrode end trajectory and the group velocity direction is large is solved. Therefore, the elastic wave device and communication device provided in this application maintain low device loss and do not increase device area while suppressing longitudinal high-order modes by adopting a large included angle. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a displacement distribution diagram of the transverse and longitudinal higher-order modes of an existing resonator;

[0032] Figure 2 This is a measured response of an existing elastic wave filter and the resonators that make up it.

[0033] Figure 3 This is a top view of a low-loss elastic wave device provided by this application.

[0034] Figure 4 This is a cross-sectional view of a low-loss elastic wave device provided by example in this application.

[0035] Figure 5 These are the admittance curves of a set of elastic wave resonators provided by example in this application.

[0036] Figure 6 These are the conductivity curves of a set of elastic wave resonators provided by example in this application.

[0037] Figure 7 These are Bode-Q curves of a set of elastic wave resonators provided by this application as an example.

[0038] Figure 8 This is a schematic diagram illustrating the variation of the Q value of a set of elastic wave resonators with γ, provided by example in this application.

[0039] Figure 9 These are Bode-Q curves of a set of elastic wave resonators provided by this application as an example.

[0040] Figure 10 This is a schematic diagram illustrating the variation of the Q value of a set of elastic wave resonators as a function of D, provided by example in this application.

[0041] Figure 11 This application provides an example of a mode displacement distribution diagram of an elastic wave resonator at the anti-resonance frequency.

[0042] Figure 12 This application provides an exemplary mode displacement distribution diagram of another elastic wave resonator at the anti-resonance frequency.

[0043] Figure 13 These are the conductivity curves of a set of elastic wave resonators provided by example in this application.

[0044] Figure 14 These are Bode-Q curves of a set of elastic wave resonators provided by this application as an example.

[0045] Figure 15 This is a top view of another low-loss elastic wave device provided by this application.

[0046] Figure 16 This is a top view of another low-loss elastic wave device provided by this application.

[0047] Figure 17 This is a top view of another low-loss elastic wave device provided by this application.

[0048] Figure 18 This is an example of the mode displacement distribution of another elastic wave resonator provided in this application at the anti-resonance frequency.

[0049] Figure 19 This is another set of Bode-Q curves for elastic wave resonators provided by example in this application.

[0050] Figures 20-26 These are cross-sectional views of some other low-loss elastic wave devices provided in the embodiments of this application.

[0051] The following is supplementary explanation of the attached figures:

[0052] 10-Piezoelectric thin film; 20-Top electrode; 30-Interdigitated electrode pair; 31-First interdigitated electrode; 32-Second interdigitated electrode; 33-First pseudo-finger electrode; 34-Second pseudo-finger electrode; 41-First busbar; 42-Second busbar; 50-Reflective gate electrode; 60-Reflective gate busbar; 70-Air gap; Lm-Target envelope; 71-Bottom electrode; 72-Bottom electrode; 711-Interdigitated electrode pair; 712-Reflective gate electrode; 73-Dielectric layer; 74-Supporting substrate; 75-Trap-rich layer; 76-Brag reflector layer. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0054] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0055] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0056] Elastic wave devices have been widely used in wireless communication systems for frequency selection and filtering. With the continuous advancement of mobile communication technology, the number of filters in the RF front-end is increasing, thus requiring filters to have lower insertion loss, flatter passbands, and steeper skirts. This, in turn, demands that the elastic wave devices comprising the filters have higher Q values ​​and less clutter. Due to the finite length of the transverse and longitudinal waveguides, higher-order transverse and longitudinal modes appear between and near the resonant and anti-resonant frequencies of the elastic wave resonator, easily causing jitter in the passband and transition band.

[0057] For a better understanding of horizontal and vertical higher-order modes, please refer to [link / reference]. Figure 1 , Figure 1 This is a displacement distribution diagram of the transverse and longitudinal higher-order modes of an existing resonator.

[0058] See Figure 1 As shown in (a), the transverse higher-order modes are higher-order standing waves along the aperture direction, which refers to the direction in which the interdigitated electrodes extend. Transverse higher-order modes typically appear between the resonant frequency and the anti-resonant frequency, and near the high-frequency side of the anti-resonant frequency. See also Figure 1 As shown in (b), the longitudinal higher-order modes are higher-order standing waves along the propagation direction, which is the normal direction of the interdigitated electrodes. Longitudinal higher-order modes typically appear on the low-frequency side of the resonant frequency and the high-frequency side of the anti-resonant frequency. Clearly, transverse higher-order modes and longitudinal higher-order modes are completely different parasitic modes.

[0059] In related technologies, research mainly focuses on suppressing higher-order transverse modes, typically employing methods such as piston-mode structures, tilted electrode structures, and apodization electrode structures. Please see [link to relevant documentation]. Figure 2 , Figure 2 This is a measured response of an existing elastic wave filter and the resonators that make it up. From... Figure 2The conductance curves of the resonators show that the transverse higher-order modes between the resonant and anti-resonant frequencies are sufficiently suppressed. However, the longitudinal higher-order modes on the low-frequency side of the resonant frequency and the high-frequency side of the anti-resonant frequency remain strong. Specifically, the longitudinal higher-order modes of the series resonator cause fluctuations in the filter's passband and a decrease in the out-of-band rejection of the stopband, while the longitudinal higher-order modes of the parallel resonator cause fluctuations in the high-frequency transition band of the filter. Therefore, although the transverse higher-order modes are sufficiently suppressed, the strong longitudinal higher-order modes still significantly affect the filter's performance.

[0060] However, research on suppressing longitudinal high-order modes in related technologies is limited. For example, increasing the number of electrode pairs can weaken longitudinal high-order modes to some extent, but this method tends to increase the device area. Therefore, how to provide a low-loss elastic wave device that can suppress longitudinal high-order modes without increasing the device area has become an urgent technical problem to be solved.

[0061] Please see Figure 3 and Figure 4 , Figure 3 This is a top view of a low-loss elastic wave device provided by this application. Figure 4 This is a cross-sectional view of a low-loss elastic wave device provided by example in this application. This application discloses a low-loss elastic wave device, which includes at least a piezoelectric thin film 10 and a top electrode 20 located on one side of the piezoelectric thin film 10.

[0062] The top electrode 20 includes interdigitated electrode pairs 30, a first busbar 41, and a second busbar 42. The interdigitated electrode pairs 30 include a plurality of first interdigitated electrodes 31 and a plurality of second interdigitated electrodes 32 arranged in a cross configuration. Optionally, both the first interdigitated electrodes 31 and the second interdigitated electrodes 32 are finger-shaped electrode strips, and are periodically arranged in a cross configuration between the first busbar 41 and the second busbar 42, respectively. The arrangement period of the first interdigitated electrodes 31 can be λ, where λ is the center-to-center distance between adjacent interdigitated electrodes on the same first busbar 41, i.e., the distance between adjacent first interdigitated electrodes 31 is λ. Similarly, the arrangement period of the second interdigitated electrodes 32 can also be λ, where λ is the center-to-center distance between adjacent interdigitated electrodes on the same second busbar 42, i.e., the distance between adjacent second interdigitated electrodes 32 is also λ.

[0063] One end of the first interdigital electrode 31 and the second interdigital electrode 32 are respectively connected to the first busbar 41 and the second busbar 42, and the other ends of the two electrodes respectively form a first end trajectory and a second end trajectory. That is, one end of the first interdigital electrode 31 is connected to the first busbar 41, and the other end of the first interdigital electrode 31 is an end that does not contact other components, and the ends of multiple first interdigital electrodes 31 form the first end trajectory. Similarly, one end of the second interdigital electrode 32 is connected to the second busbar 42, and the other end of the second interdigital electrode 32 is an end that does not contact other components, and the ends of multiple second interdigital electrodes 32 form the second end trajectory. Optionally, the first end trajectory and the second end trajectory can be obtained by fitting the corresponding multiple interdigital electrode ends with, for example, a straight line or a smooth curve.

[0064] The top electrode 20 also includes a plurality of reflective grid electrodes 50 and reflective grid busbars 60. The reflective grid electrodes 50 are located on both sides of the interdigital electrode pair 30 along the propagation direction, and their extension direction is perpendicular to the phase velocity direction, which is the normal direction of the interdigital electrode pair 30. The reflective grid busbars 60 are located on both sides of the interdigital electrode pair 30, and are connected to the two ends of the corresponding reflective grid electrodes 50.

[0065] The absolute value of the angle γ between the tangent line of the trajectory at any end position of the first interdigital electrode 31 and the group velocity direction in the first terminal trajectory is greater than or equal to 16°. Here, the group velocity direction refers to the energy flow direction of the elastic wave. That is, for any end position of the first interdigital electrode 31 in the first terminal trajectory, the absolute value of the angle γ between the tangent line of the first terminal trajectory at that end position and the group velocity direction is greater than or equal to 16°. For example, the absolute value of this angle γ can be any integer or decimal value greater than or equal to 16°, such as, but not limited to, 16.2°, 16.8°, 17°, 17.5°, 18.4°, 19°, 20°, 22°, 35°, 46°, 58°, 66°, 73°, 75°, 80°, etc.

[0066] The absolute value of the angle γ between the tangent line of the trajectory at any end position of the second interdigital electrode 32 and the group velocity direction in the second terminal trajectory is greater than or equal to 16°. Here, the group velocity direction is the energy flow direction of the elastic wave. That is, for any end position of the second interdigital electrode 32 in the second terminal trajectory, the absolute value of the angle γ between the tangent line of the second terminal trajectory at that position and the group velocity direction is greater than or equal to 16°. For example, the absolute value of this angle γ can be any integer or decimal value greater than or equal to 16°, such as, but not limited to, 16.2°, 16.8°, 17°, 17.5°, 18.4°, 19°, 20°, 22°, 35°, 46°, 58°, 66°, 73°, 75°, 80°, etc.

[0067] The interdigital electrode pair 30 also includes a plurality of first pseudo-finger electrodes 33 and a plurality of second pseudo-finger electrodes 34. The first pseudo-finger electrodes 33 are spaced apart from the first interdigital electrodes 31, and the second pseudo-finger electrodes 34 are spaced apart from the second interdigital electrodes 32. In the top electrode 20, there is a partial overlap between the first interdigital electrodes 31 and the second interdigital electrodes 32. The first pseudo-finger electrodes 33 and the second pseudo-finger electrodes 34 are arranged in the non-overlapping area. The first interdigital electrodes 31 and the second pseudo-finger electrodes 34 are arranged opposite each other, and the second interdigital electrodes 32 and the first pseudo-finger electrodes 33 are arranged opposite each other. That is, each first interdigital electrode 31 corresponds to one second pseudo-finger electrode 34, and each second interdigital electrode 32 corresponds to one first pseudo-finger electrode 33. For any opposite first interdigital electrode 31 and second pseudo-finger electrode 34, or for any opposite second interdigital electrode 32 and first pseudo-finger electrode 33, there is a gap between them, namely an air gap 70.

[0068] The pseudofinger length D of at least one first pseudofinger electrode 33 or second pseudofinger electrode 34 is greater than or equal to 2λ, where λ is the center-to-center distance between adjacent interdigital electrodes on the same first busbar 41 or second busbar 42.

[0069] In this embodiment, by setting a large angle between the trajectory of the interdigital electrode tip and the group velocity direction, the vibration of longitudinal higher-order modes is disrupted, and the leakage of longitudinal higher-order modes to areas outside the interdigital electrode is enhanced, thereby suppressing longitudinal higher-order modes. Furthermore, by setting a sufficiently long pseudo-finger electrode, the problem of severe leakage of the main mode to the busbar region when the angle between the trajectory of the interdigital electrode tip and the group velocity direction is large is solved. Therefore, the elastic wave device and communication device provided in this application, while suppressing longitudinal higher-order modes by using a large angle, maintain low device loss and do not increase device area.

[0070] In some alternative embodiments, for ease of explanation, such as Figure 15 and Figure 16As shown, the target envelope Lm is formed by the side of the first busbar 41 and the second busbar 42 near the central region, the side of the reflector gate busbar 60 near the central region, and the side of the last reflector gate electrode 50 away from the central region. This target envelope Lm can be a closed virtual line that surrounds the ends of the interdigital electrode pair 30 and the reflector gate electrode 50 near their respective busbars.

[0071] Starting from the end of any first interdigital electrode 31 or any second interdigital electrode 32, the shortest distance to the target envelope Lm along the group velocity direction is g, and the projection of the shortest distance in the phase velocity direction is the attenuation path p. Then, the attenuation path p corresponding to the i-th interdigital electrode 30 is... i The following conditions must be met: p i ≥0.75×λ / k 2 Where λ is the center-to-center distance between adjacent interdigitated electrodes on the same first busbar 41 or second busbar 42, and k 2 This is the electromechanical coupling coefficient. That is, the attenuation path p corresponding to any first interdigital electrode 31 to 30. i The attenuation path p corresponding to any second interdigital electrode 32 30 i All are greater than or equal to the first reference parameter, which is 0.75 × λ / k. 2 Among them, the electromechanical coupling coefficient f s f is the resonant frequency. p It is the anti-resonant frequency.

[0072] In the above embodiment, since the length of the pseudo-finger electrode is determined by the attenuation path p of the acoustic wave in the pseudo-finger electrode region, by converting the setting of the pseudo-finger length into the attenuation path p of the acoustic wave in the pseudo-finger electrode region, the acoustic wave can undergo effective attenuation in the pseudo-finger electrode region without leaking into the busbar region when the attenuation path p is long enough. Thus, while setting a large γ angle, a suitable attenuation path p located in the pseudo-finger electrode region is matched. By limiting the range of the attenuation path p, the vibration of the master mode can be essentially attenuated to zero before entering the busbar region, and most of the energy of the longitudinal higher-order modes can still leak into the busbar region, thereby achieving a high Q value for the device and suppression of longitudinal higher-order modes, improving the reliability and performance of the device structure design.

[0073] In some alternative embodiments, to further improve device performance, the attenuation path p i The following conditions must be met: p i ≥λ / k 2 That is, the attenuation path p iThe first reference parameter is greater than or equal to the second reference parameter, which is the ratio of the center-to-center distance between adjacent interdigital electrodes to the electromechanical coupling coefficient. The value of the second reference parameter is greater than the value of the first reference parameter.

[0074] In some alternative embodiments, to further improve device performance, the number of reflective gate electrodes 50 on both sides of the interdigitated electrode pair 30 are N1 and N2, respectively, and the attenuation path p i The following conditions must be met: p i ≥(N1+N2)×λ / 4. That is, the attenuation path p i The third reference parameter is greater than or equal to the third reference parameter, which is the product of the sum of the number of reflective gratings on both sides and 1 / 4 of the center-to-center distance between adjacent interdigital electrodes. The value of the third reference parameter is greater than the value of the second reference parameter.

[0075] In some alternative embodiments, considering ohmic losses, the attenuation path p i The following conditions must be met: p i ≤(N1+N2)×λ. That is, the attenuation path p i Less than or equal to the fourth reference parameter, which is the product of the sum of the number of reflective gratings on both sides and one times the center-to-center distance between adjacent interdigitated electrodes. Combined with the attenuation path p above... i The lower limit of p is determined. i The condition is met: 0.75×λ / k 2 ≤p i ≤(N1+N2)×λ. Thus, by setting an upper limit for the attenuation path, the ohmic loss of the electrodes caused by an excessively long attenuation path can be reduced.

[0076] In some alternative embodiments, the included angle γ remains constant at different locations.

[0077] In some alternative embodiments, the pseudofinger length of the first or second pseudofinger electrode remains constant at different positions. That is, the included angle γ is the same at any end position on the first and second end trajectories. And / or, in the top electrode, the pseudofinger length D of each first and second pseudofinger electrode at different positions is the same.

[0078] In some alternative embodiments, the pseudo-finite finger length D satisfies the following condition: D≥(λ / k) 2 )×tan(|γ|)-G, where G is the air gap length, and the air gap is the portion between the end of the interdigital electrode pair and the opposite first or second pseudo-finger electrode.

[0079] It should be noted that the pseudofinger length D of at least one of the first or second pseudofinger electrodes is greater than or equal to 2λ, which can be understood to include at least the following two cases:

[0080] Case 1: In some optional embodiments, the pseudofinger length D of either the first pseudofinger electrode or the second pseudofinger electrode is greater than or equal to 2λ.

[0081] Case 2: In some optional embodiments, to reduce the device area, the pseudofinger length D of all first and second pseudofinger electrodes, except for the target pseudofinger electrode at the boundary position, is greater than or equal to 2λ, meaning the other pseudofinger lengths satisfy Case 1 above. The target pseudofinger electrode is related to the orientation of the included angle γ. If the tangent of the end trajectory is counterclockwise relative to the group velocity direction, the corresponding included angle γ is greater than 0°. If the tangent of the end trajectory is clockwise relative to the group velocity direction, the corresponding included angle γ is less than 0°. Specifically, as... Figure 16 As shown, Figure 16 If the tangent to the terminal trajectory in the equation is counterclockwise relative to the group velocity direction, then the corresponding included angle γ is greater than 0°. For example... Figure 17 As shown, Figure 17 If the tangent of the terminal trajectory is clockwise upward relative to the group velocity direction, then the corresponding included angle γ is less than 0°.

[0082] If the included angle γ > 0°, the length D of the pseudo-finger below the first air gap in the lower left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the pseudo-finger above the last air gap in the upper right corner is also ≤ 0.5λ. In this case, the target pseudo-finger electrode includes the second pseudo-finger electrode below the first air gap in the lower left corner of the interdigital electrode pair, and the first pseudo-finger electrode above the last air gap in the upper right corner. Here, γ > 0° means that the tangent of the end trajectory is counterclockwise relative to the group velocity direction.

[0083] If the included angle γ < 0°, the length D of the spurious finger above the first air gap in the upper left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the spurious finger below the last air gap in the lower right corner is ≤ 0.5λ. In this case, the target spurious finger electrode includes the first spurious finger electrode above the first air gap in the upper left corner of the interdigital electrode pair, and the second spurious finger electrode below the last air gap in the lower right corner.

[0084] In some alternative embodiments, to further improve device performance, the absolute value of the included angle γ at any position is greater than or equal to 20°, and the pseudofinger length D of at least one first pseudofinger electrode or second pseudofinger electrode is greater than or equal to 3λ. Similar to the two cases described above where the pseudofinger length D is greater than or equal to 2λ, the pseudofinger length D greater than or equal to 3λ defined here also includes the two cases described above, and will not be elaborated further here.

[0085] In some alternative embodiments, such as Figure 20 and Figure 21As shown, the elastic wave device also includes a bottom electrode 71 or a bottom electrode 72 located on the other side of the piezoelectric film 10. The bottom electrode can be an interdigitated electrode or a surface electrode.

[0086] In some alternative embodiments, such as Figure 22 As shown, the elastic wave device also includes a dielectric layer 73 located on the other side of the piezoelectric thin film 10.

[0087] In some alternative embodiments, such as Figure 23 As shown, the elastic wave device also includes a support substrate 74 located on the other side of the piezoelectric thin film 10.

[0088] In some alternative embodiments, such as Figure 24 As shown, the elastic wave device also includes a dielectric layer 73 located between the piezoelectric thin film 10 and the supporting substrate 74.

[0089] In some alternative embodiments, such as Figure 25 As shown, the elastic wave device also includes a dielectric layer 73 and a trap-rich layer 75 located between the piezoelectric thin film 10 and the support substrate 74.

[0090] In some alternative embodiments, such as Figure 26 As shown, the elastic wave device also includes a Bragg reflector layer 76 located between the piezoelectric thin film 10 and the support substrate 74.

[0091] In some alternative embodiments, the material of the piezoelectric film 10 includes one of lithium niobate, lithium tantalate, and potassium niobate, and the thickness of the piezoelectric film 10 is 0.1λ to 1λ.

[0092] In some alternative embodiments, the material of the support substrate 74 includes one or more of various crystal forms of sapphire, silicon, spinel, silicon carbide, diamond, diamond-like carbon, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate.

[0093] In some alternative embodiments, the material of the dielectric layer 73 includes one or more of silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, polycrystalline silicon, and amorphous silicon.

[0094] To demonstrate the technical effects of the embodiments of this application, a detailed description is provided below with reference to specific examples.

[0095] like Figure 3 and Figure 4 In the structure, the center-to-center distance between adjacent electrode fingers connected to the same busbar is λ, the air gap length is G, the attenuation path is p, and the left and right reflective grid electrodes 50 are N1 and N2 respectively. The lengths of the first pseudo-finger electrode 33 and the second pseudo-finger electrode 34 are D respectively, and the lengths of the first and second pseudo-fingers are the same at different positions. The group velocity direction and the phase velocity direction are parallel or coincident. Continuing as...Figure 3 As shown, the ends of several first interdigital electrodes 31 can form a first end trajectory (not shown). The tangent of this first end trajectory at the end position of one of the first interdigital electrodes 31 is L1, and the angle between the trajectory tangent L1 and the group velocity direction is γ. Since the group velocity direction and the phase velocity direction are parallel or coincident, the angle between the trajectory tangent L1 and the phase velocity direction is also γ.

[0096] like Figure 5 and Figure 6 As shown, Figure 5 These are the admittance curves of a set of elastic wave resonators provided by example in this application, corresponding to... Figure 3 and Figure 4 The structure shown. Figure 6 These are the conductance curves of a set of elastic wave resonators provided by example in this application, and... Figure 5 Correspondingly, the structural parameters of each group of elastic wave resonators include: the piezoelectric film 10 is Y42-cut lithium tantalate with a thickness of 600 nm; the top electrode 20 is 160 nm thick aluminum; the wavelength λ is 2 μm; the first interdigital electrode 31 has 61 electrodes; the second interdigital electrode 32 has 60 electrodes; and the two side reflective grid electrodes 50 each have 20 electrodes. The air gap length G is 0.2λ, and the pseudo-finger length D is 1λ. To reflect the influence of the included angle γ, the angle γ between the trajectory tangent of the interdigital electrode end in each group of elastic wave resonators and the group velocity direction is set to 0 to 20°, for example, the included angles γ are set to 0°, 5°, 7°, 9°, 12°, 16°, and 20° respectively. Figure 5 As can be seen from the admittance curves, when the included angle γ is small, resonance peaks caused by longitudinal higher-order modes exist on both the low-frequency side of the resonant frequency and the high-frequency side of the anti-resonant frequency. From Figure 6 The conductivity curves show that when γ reaches 5°, the transverse higher-order modes located between the resonant and anti-resonant frequencies are sufficiently suppressed, but the longitudinal higher-order modes remain relatively strong. When γ is between 5° and 16°, the longitudinal higher-order modes still exist. Only when γ reaches 16° are the longitudinal higher-order modes essentially suppressed.

[0097] like Figure 7 and Figure 8 As shown, Figure 7 These are Bode-Q curves of a set of elastic wave resonators provided by example in this application, and... Figure 5 correspond. Figure 8 This is a schematic diagram illustrating the variation of the Q value of a set of elastic wave resonators provided by this application with γ, and... Figure 5 Corresponding. Q max This refers to the maximum value of the Bode-Q curve corresponding to the master model. Q p This refers to the Q value near the anti-resonant frequency, which is directly related to the mechanical losses of the device. From... Figure 7 andFigure 8 It can be seen that when γ reaches 7°, the Q value of the elastic wave resonator reaches its maximum, and the transverse higher-order modes are suppressed. When γ reaches 16°, the longitudinal higher-order modes are suppressed, but the Q value of the elastic wave resonator drops significantly and can no longer meet the requirements of practical applications.

[0098] according to Figure 8 It is evident that increasing the angle γ between the trajectory tangent of each interdigital electrode and the group velocity direction, even to a value greater than or equal to 10°, will cause a rapid decrease in the Q value of the elastic wave resonator. In other words, when the absolute value of the angle γ exceeds a certain threshold, increasing the angle γ and increasing the Q value are mutually exclusive. Based on this, considering practical application requirements, the industry generally does not easily overcome this technical bias by increasing the absolute value of the angle γ to a value greater than 10°, or even greater than or equal to 16°, to suppress higher-order longitudinal modes.

[0099] This application's embodiments overcome the aforementioned technical biases. While suppressing longitudinal high-order modes by increasing the absolute value of the included angle γ, it also considers the Q value of the elastic wave resonator. By constraining at least one pseudo-finger length D to be greater than or equal to 2λ, it balances the suppression of longitudinal high-order modes and the maintenance of the elastic wave resonator's Q value. To demonstrate the technical effect of constraining the pseudo-finger length D, the following describes... Figures 9-14 To elaborate.

[0100] like Figure 9 and Figure 10 As shown, Figure 9 These are Bode-Q curves of a set of elastic wave resonators provided by example in this application, corresponding to... Figure 3 and 4 The structure shown. (As illustrated) Figure 10 As shown, Figure 10 This is a schematic diagram illustrating the variation of the Q value of a set of elastic wave resonators provided by this application as a function of D, and... Figure 9 Correspondingly, the structural parameters of each set of elastic wave resonators include: the piezoelectric thin film 10 is Y42-cut lithium tantalate with a thickness of 600 nm; the top electrode 20 is 160 nm thick aluminum; the wavelength λ is 2 μm; the first interdigital electrode 31 has 61 electrodes; the second interdigital electrode 32 has 60 electrodes; the two side reflective grid electrodes 50 each have 20 electrodes; the air gap length G is 0.2λ; and the angle γ between the tangent of the trajectory at the end of the interdigital electrode and the group velocity direction is 16°. Multiple sets of elastic wave resonators are configured with pseudo-finger electrode lengths D ranging from 1 to 4λ, for example, 1λ, 2λ, 3λ, and 4λ respectively.

[0101] from Figure 9 and Figure 10It can be seen that as the length D of the spurious electrode increases, the Q value of the resonator increases rapidly. When the spurious electrode length reaches 2λ, the Q value of the resonator can meet the requirements of practical applications. When the spurious electrode length reaches 3λ, it basically tends to stabilize.

[0102] like Figure 11 As shown, Figure 11 This application provides an exemplary mode displacement distribution diagram of an elastic wave resonator at the anti-resonance frequency, corresponding to... Figure 3 and Figure 4 The structure is shown. Specifically, the structural parameters of the elastic wave resonator include: the piezoelectric thin film 10 is Y42-cut lithium tantalate with a thickness of 600 nm; the top electrode 20 is 160 nm thick aluminum; the wavelength λ is 2 μm; there are 61 first interdigital electrodes 31, 60 second interdigital electrodes 32, and 20 reflective grid electrodes 50 on each side; the air gap length G is 0.2λ; the angle γ between the tangent of the trajectory at the end of the interdigital electrode and the group velocity direction is 16°; and the pseudo-finger electrode length D is 1λ. Figure 11 Figure (a) is a top view of the displacement distribution of the model, and Figure (b) is the displacement amplitude at the intercepted position aa'.

[0103] from Figure 11 It can be seen that after the master mode enters the reflector grid electrode and the pseudo-finger electrode, the displacement amplitude gradually decreases. Then, due to the large angle γ and the short pseudo-finger electrode, the master mode enters the busbar region without experiencing sufficient attenuation, resulting in a large amount of energy leakage into the busbar region.

[0104] like Figure 12 As shown, Figure 12 This application provides an exemplary mode displacement distribution diagram of another elastic wave resonator at the anti-resonance frequency. Figure 11 The difference lies in the fact that the pseudo-electrode length D here is 3λ. In Figure 12 Figure (a) is a top view of the displacement distribution of the model, and Figure (b) is the displacement amplitude at the intercepted bb' position.

[0105] As shown in Figure 12, after the master mode enters the reflector grating electrode and the dummy finger electrode, the displacement amplitude gradually decreases, and the attenuation rate is the same in the reflector grating region and the dummy finger electrode region. Here, because the dummy finger is long enough, the sound wave is sufficiently attenuated before entering the busbar, and almost no energy leaks into the busbar.

[0106] like Figure 13 As shown, Figure 13 These are the conductance curves of a set of elastic wave resonators provided by example in this application, corresponding to... Figure 3 and 4The structure is shown. Specifically, the structural parameters of each group of elastic wave resonators include: the piezoelectric film 10 is Y42-cut lithium tantalate with a thickness of 600 nm, and the top electrode 20 is 160 nm thick aluminum. The wavelength λ is 2 μm, the first interdigital electrode 31 has 61 electrodes, the second interdigital electrode 32 has 60 electrodes, and the two side reflective grating electrodes 50 each have 20 electrodes. The air gap length G is 0.2λ. The angle γ between the tangent of the trajectory of the interdigital electrode end and the group velocity direction, and the pseudo-finger electrode length D of each group of elastic wave resonators are set differently, namely: γ = 7°, D = 1λ; γ = 16°, D = 3λ; γ = 20°, D = 5λ. Obviously, the longitudinal higher-order modes corresponding to an angle γ ≥ 16° are suppressed.

[0107] like Figure 14 As shown, Figure 14 These are Bode-Q curves of a set of elastic wave resonators provided by example in this application, and... Figure 13 Correspondingly, even if the included angle γ ≥ 16°, when a suitable pseudo-finite length D is used, its Q value is comparable to that when the included angle γ = 7°, and may even exceed that when γ = 7°.

[0108] The above describes an elastic wave device structure where the group velocity direction coincides with the phase velocity direction and the pseudo-finger electrode length is the same at different positions. Two other elastic wave device structures are described below.

[0109] like Figure 15 As shown, Figure 15 This is a top view of another low-loss elastic wave device provided by this application. The elastic wave device here is similar to... Figure 3 The difference between the elastic wave devices in the two systems is that the group velocity direction does not coincide with the phase velocity direction, and the length of the pseudo-finger electrode varies at different locations.

[0110] For ease of explanation, the target envelope Lm will be formed here by the side of the first busbar 41 and the second busbar 42 near the central region, the side of the reflective grid busbar 60 near the central region, and the side of the last reflective grid electrode 50 away from the central region. Figure 15 It can be seen that the target envelope Lm can be a closed virtual line, so that the interdigitated electrode pair 30 and the reflective grid electrode 50 are respectively surrounded by the target envelope Lm at the ends of the corresponding busbars.

[0111] like Figure 15 In the structure, the center-to-center distance between adjacent electrode fingers connected to the same busbar is λ, the air gap length is G, and the left and right reflective grid electrodes 50 are N1 and N2 respectively. The lengths of the first pseudo-finger electrode 33 and the second pseudo-finger electrode 34 are denoted as D, respectively. The lengths of the first pseudo-finger and the second pseudo-finger are different at different positions. The group velocity direction and the phase velocity direction do not coincide, that is, their directions are different. Continuing as...Figure 15 As shown, the ends of several first interdigital electrodes 31 can form a first end trajectory m1, and the ends of several second interdigital electrodes 32 can form a second end trajectory m2. In the first end trajectory, the trajectory tangent at the end position of one of the first interdigital electrodes 31 is L2, and the angle between the trajectory tangent L2 and the group velocity direction is γ.

[0112] Continue as Figure 15 As shown, the shortest distance from the end of any second interdigital electrode 32 (e.g., at position A) along the group velocity direction to the target envelope Lm is g. The projection of this shortest distance g onto the phase velocity direction is the attenuation path p. To suppress higher-order longitudinal modes and maintain low loss in the elastic wave device, γ is determined to be no less than 16°, and p ≥ 0.75 × λ / k. 2 Where λ is the center-to-center distance between adjacent interdigitated electrodes on the same first busbar 41 or second busbar 42, and k 2 This is the electromechanical coupling coefficient.

[0113] It should be noted that here the attenuation path p ≥ 0.75 × λ / k 2 The limitation, although it applies to device structures where the group velocity direction and phase velocity direction do not coincide, and the pseudo-finger electrode lengths differ at different locations, still applies to attenuation paths where p ≥ 0.75 × λ / k. 2 The same limitation applies to pseudo-electrodes of the same length and with the same gap. Figure 3 The device structure described above is also applicable to the following. Figure 16 The device structure. Furthermore, compared to the previous constraint on the pseudo-finger length D, the constraint method using the attenuation path is more effective.

[0114] Generally, pseudofinger electrodes are used in elastic wave devices with concave slow-velocity curves to prevent lateral leakage of acoustic waves. In some applications, they are combined with short apertures to suppress higher-order lateral modes. When used in conjunction with tilted electrodes, their function is to reduce acoustic leakage to the busbar. However, in many past cases, the length of pseudofinger electrodes has typically been set at around one wavelength, so it is generally believed that large tilt angles lead to increased losses in the master mode, thus avoiding the use of large tilt angles.

[0115] Continue as Figure 11 and 12 It is evident that when the angle γ between the tangent of the interdigital electrode's end trajectory and the group velocity direction is not 0°, the pseudo-finger electrode does not reflect the sound wave back to the interdigital electrode region along the aperture direction, but rather along the propagation direction. Therefore, in order to achieve energy constraint on the master mode, it is necessary to restrict the attenuation path p.

[0116] The number of pseudo-finger electrodes the primary mode passes through before reaching the busbar is determined by the attenuation path p; that is, the longer the attenuation path p, the more pseudo-finger electrodes it passes through. The reflection coefficient of a single pseudo-finger electrode is related to the electromechanical coupling coefficient k of the elastic wave. 2 Inversely proportional, limiting the attenuation path p ≥ 0.75 × λ / k 2 That is, 1.5×λ / k is needed. 2 The reflection is accomplished by using a pseudo-electrode.

[0117] For example, under the condition that the attenuation path p ≥ 0.75 × λ / k 2 In the case of, Figures 9 to 12 The electromechanical coupling coefficient of the structure shown is 12%, meaning the attenuation path should be greater than 6.25λ. Since the pseudo-finger electrode length is the same at different locations, i.e., D+G=p×tan(|γ|), the pseudo-finger electrode length should be greater than 1.6λ. Figure 10 As can be seen, when D≥1.6λ, the Q value almost doubles compared to D=1λ. Therefore, it is evident that, given a limited attenuation path p≥0.75×λ / k... 2 In this case, losses can be significantly reduced.

[0118] Preferably, in the case of a limited attenuation path p≥λ / k 2 That is, D≥2.2λ, the Q value is further improved.

[0119] Preferably, the attenuation path is limited to p≥(N1+N2)×λ / 4, that is, D≥2.7λ. At this time, the Q value is close to the maximum value, and its Q value is comparable to that when γ=7° and D=1λ.

[0120] like Figure 16 As shown, Figure 16 This is a top view of another low-loss elastic wave device provided by this application. The elastic wave device here is similar to... Figure 3 The difference between the elastic wave devices in the two systems is that the length of the pseudo-finger electrode is different at different locations.

[0121] like Figure 16 In the structure, the center-to-center distance between adjacent electrode fingers connected to the same busbar is λ, the air gap length is G, and the left and right reflective grid electrodes 50 are N1 and N2 respectively. The lengths of the first pseudo-finger electrode 33 and the second pseudo-finger electrode 34 are denoted as D, respectively. The lengths of the first pseudo-finger and the second pseudo-finger are different at different positions. The group velocity direction and the phase velocity direction coincide, that is, their directions are the same. Continuing as... Figure 16 As shown, the ends of several first interdigital electrodes 31 can form a first end trajectory (not shown). In the first end trajectory, the trajectory tangent at the end position of one of the first interdigital electrodes 31 is L3, and the angle between the trajectory tangent L3 and the group velocity direction is γ, which remains constant at different positions.

[0122] Figure 16 In addition to satisfying Figure 15 The absolute value of the included angle γ of the structure is not less than 16°, and p ≥ 0.75 × λ / k 2 In addition to the condition, it also satisfies: when γ>0°, counting from left to right, the length of the pseudo-finger below the first air gap in the lower left corner D≤0.5λ, and the length of the pseudo-finger above the last air gap in the upper right corner D≤0.5λ.

[0123] Figure 17 This is a top view of another low-loss elastic wave device provided by this application. Figure 17 In addition to satisfying Figure 15 The absolute value of the included angle γ of the structure is not less than 16°, and p ≥ 0.75 × λ / k 2 In addition to the condition, it also satisfies: when γ<0°, counting from left to right, the length of the pseudo-finger above the first air gap in the upper left corner is D≤0.5λ, and the length of the pseudo-finger below the last air gap in the lower right corner is D≤0.5λ.

[0124] Figure 16 and Figure 17 All cases demonstrate the scenario where the target pseudo-index length is 0. Specifically, in Figure 16 At point A, there is no second pseudo-finger electrode, meaning the pseudo-finger length below the first air gap in the lower left corner is 0; while at point B, there is no first pseudo-finger electrode, meaning the pseudo-finger length above the last air gap in the upper right corner is 0. Figure 17 At point C, there is no first pseudo-finger electrode, meaning the pseudo-finger length above the first air gap in the upper left corner is 0; while at point D, there is no second pseudo-finger electrode, meaning the pseudo-finger length below the last air gap in the lower right corner is 0.

[0125] according to Figure 12 The top view of the mode displacement distribution shown in Figure (a) shows the acoustic wave incident on the pseudo-finger electrode region along the group velocity direction. Taking γ greater than 0° as an example, there is no acoustic energy distribution below the first pair of interdigital electrodes, and the energy leakage to the busbar is small. Therefore, the pseudo-finger electrodes here can be omitted, or shorter pseudo-finger electrodes can be used. In this way, the device size is reduced and ohmic losses are reduced by shortening the pseudo-finger length.

[0126] Figure 18 Another elastic wave resonator provided as an example in this application has a mode displacement distribution at the anti-resonance frequency, compared with... Figure 16 The structure shown corresponds to this. (And) Figure 12 The difference in the mode displacement distribution diagrams is that, counting from left to right, the length of the pseudo-finger electrode below the first air gap in the lower left corner is 0, and the length of the pseudo-finger electrode above the last air gap in the upper right corner is 0.

[0127] As can be seen from Figure 18, despite shortening the length of some of the pseudo-finger electrodes, and even reducing some to D=0, there was no significant energy leakage to the busbar. Shortening these pseudo-finger electrodes that do not participate in reflection not only does not increase leakage but also helps reduce ohmic losses.

[0128] Figure 19 Bode-Q curves of another set of elastic wave resonators provided as an example in this application, and Figure 15 and 16 The structures shown correspond to the specifications. Specifically, the structural parameters of each set of elastic wave resonators include: the piezoelectric film 10 is Y42-cut lithium tantalate with a thickness of 600 nm; the top electrode 20 is 160 nm thick aluminum; the wavelength λ is 2 μm; the first interdigital electrode 31 has 61 electrodes; the second interdigital electrode 32 has 60 electrodes; the two side reflective gate electrodes 50 each have 20 electrodes; the air gap length G is 0.2λ; and the angle γ between the tangent of the interdigital electrode end trajectory and the group velocity direction is 16°. One elastic wave resonator has a pseudo-finger electrode length D maintained at 3λ, while the other elastic wave resonator shortens the pseudo-finger electrode that does not participate in reflection. As can be seen from Figure 19, the maximum Bode-Q of the two is almost the same. However, the latter reduces the device size and ohmic loss.

[0129] Figure 20 Figure 26 These are cross-sectional views of some other low-loss elastic wave devices provided in the embodiments of this application.

[0130] like Figure 20 As shown, Figure 20 The low-loss elastic wave device shown is Figure 4 The structural difference lies in that the low-loss elastic wave device also includes a bottom electrode 71 located below the piezoelectric film 10, which is an interdigitated electrode. Similar to the top electrode 20, the bottom electrode 71 includes an interdigitated electrode pair 711 and a reflective grid electrode 712.

[0131] like Figure 21 As shown, Figure 21 The low-loss elastic wave device shown is Figure 4 The structural difference is that the low-loss elastic wave device also includes a bottom electrode 72 located below the piezoelectric film 10, which is a surface electrode or a block electrode.

[0132] like Figure 22 As shown, Figure 22 The low-loss elastic wave device shown is Figure 4 The structural difference is that the low-loss elastic wave device also includes a dielectric layer 73, which is located below the piezoelectric film 10.

[0133] like Figure 23 As shown, Figure 23 The low-loss elastic wave device shown isFigure 4 The structural difference is that the low-loss elastic wave device also includes a support substrate 74, which is located on the side of the piezoelectric film 10 away from the top electrode 20.

[0134] like Figure 24 As shown, Figure 4 The low-loss elastic wave device shown is Figure 23 The structural difference is that the low-loss elastic wave device also includes a dielectric layer 73, which is located between the piezoelectric thin film 10 and the supporting substrate 74.

[0135] like Figure 25 As shown, Figure 25 The low-loss elastic wave device shown is Figure 24 The structural difference is that the low-loss elastic wave device also includes a trap-rich layer 75, which is located between the dielectric layer 73 and the support substrate 74.

[0136] like Figure 26 As shown, Figure 26 The low-loss elastic wave device shown is Figure 23 The structural difference is that the low-loss elastic wave device also includes a Bragg reflector layer 76, which is located between the piezoelectric thin film 10 and the support substrate 74.

[0137] In another aspect, this application also discloses a communication device including the aforementioned low-loss elastic wave device; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0138] The above description is only an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A low-loss elastic wave device, characterized in that, It includes a piezoelectric thin film and a top electrode located on one side of the piezoelectric thin film. The top electrode includes an interdigital electrode pair, a first busbar, a second busbar, and a plurality of reflective gate electrodes located on both sides of the interdigital electrode pair and a reflective gate busbar connected to the reflective gate electrodes. The interdigitated electrode pair includes a plurality of first interdigitated electrodes and a plurality of second interdigitated electrodes arranged in a cross configuration, with one end of each electrode connected to the first busbar and the second busbar respectively, and the other ends of each electrode forming a first end trajectory and a second end trajectory respectively. The absolute value of the angle γ between the trajectory tangent at any of the first interdigital electrode ends and the group velocity direction in the first terminal trajectory is greater than or equal to 16°, and the absolute value of the angle γ between the trajectory tangent at any of the second interdigital electrode ends and the group velocity direction in the second terminal trajectory is greater than or equal to 16°. The interdigitated electrode pair further includes a plurality of first pseudo-finger electrodes and a plurality of second pseudo-finger electrodes. The first pseudo-finger electrodes are spaced apart from the first interdigitated electrodes, and the second pseudo-finger electrodes are spaced apart from the second interdigitated electrodes. The pseudo-finger length D of at least one of the first pseudo-finger electrodes or the second pseudo-finger electrode is greater than or equal to 2λ, where λ is the center-to-center distance between adjacent interdigitated electrodes on the same first busbar or the second busbar.

2. The low-loss elastic wave device according to claim 1, characterized in that, The target envelope is formed by the sides of the first and second busbars near the center region, the side of the reflector grid busbar near the center region, and the side of the last reflector grid electrode away from the center region. The shortest distance from the end of any of the first or second interdigital electrodes to the target envelope along the group velocity direction is g. The projection of this shortest distance onto the phase velocity direction is the attenuation path p. The attenuation path p corresponding to the i-th interdigital electrode... i The following conditions must be met: p i ≥0.75×λ / k 2 , where k 2 This is the electromechanical coupling coefficient.

3. The low-loss elastic wave device according to claim 2, characterized in that, The attenuation path p i The following conditions must be met: p i ≥λ / k 2 .

4. The low-loss elastic wave device according to claim 2, characterized in that, The number of reflective grid electrodes on both sides of the interdigitated electrode pair are N1 and N2, respectively, and the attenuation path p i The following conditions must be met: p i ≥(N1+N2)×λ / 4.

5. The low-loss elastic wave device according to claim 2, characterized in that, The attenuation path p i The following conditions must be met: p i ≤(N1+N2)×λ.

6. The low-loss elastic wave device according to claim 1 or 3, characterized in that, The included angle γ remains constant at different positions.

7. The low-loss elastic wave device according to claim 6, characterized in that, The pseudofinger length of the first pseudofinger electrode or the second pseudofinger electrode remains constant at different positions; the pseudofinger length D satisfies the following condition: D≥(λ / k) 2 )×tan( γ )-G, where G is the air gap length, and the air gap is the portion between the end of the interdigital electrode pair and the opposite first or second pseudo-finger electrode.

8. The low-loss elastic wave device according to claim 6, characterized in that, If the included angle γ > 0°, the length D of the pseudo-finger below the first air gap in the lower left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the pseudo-finger above the last air gap in the upper right corner is ≤ 0.5λ. If the included angle γ < 0°, the length D of the pseudo-finger above the first air gap in the upper left corner of the interdigital electrode pair is ≤ 0.5λ, and the length D of the pseudo-finger below the last air gap in the lower right corner is ≤ 0.5λ.

9. The low-loss elastic wave device according to claim 1, characterized in that, The pseudofinger length D of either the first pseudofinger electrode or the second pseudofinger electrode is greater than or equal to 2λ.

10. The low-loss elastic wave device according to claim 1, characterized in that, The absolute value of the included angle γ at any position is greater than or equal to 20°, and the pseudofinger length D of at least one of the first pseudofinger electrodes or the second pseudofinger electrode is greater than or equal to 3λ.

11. The low-loss elastic wave device according to any one of claims 1-5, characterized in that, The elastic wave device further includes at least one of the following: The bottom electrode is located on the other side of the piezoelectric film; A supporting substrate located on the other side of the piezoelectric film; A dielectric layer located between the piezoelectric thin film and the supporting substrate; A Bragg reflective layer located between the piezoelectric thin film and the supporting substrate.

12. The low-loss elastic wave device according to claim 11, characterized in that, The elastic wave device satisfies at least one of the following: The piezoelectric film is made of one of lithium niobate, lithium tantalate, and potassium niobate, and the thickness of the piezoelectric film is 0.1λ~1λ. The supporting substrate material includes one or more of the following crystal types: sapphire, silicon, spinel, silicon carbide, diamond, diamond-like carbon, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate. The material of the dielectric layer includes one or more of silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, polycrystalline silicon, and amorphous silicon.

13. A communication device, characterized in that, Includes the low-loss elastic wave device as described in any one of claims 1-12; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

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