CN220067386U - A bulk acoustic wave resonator and filter - Google Patents

Abstract

This application discloses a bulk acoustic wave resonator and filter, which relates to the technical field of resonators. It includes a substrate and a piezoelectric layer provided on the substrate. An electrode structure and a pseudo-electrode structure are provided on the piezoelectric layer. The electrode structure includes multiple A first electrode sheet and a plurality of second electrode sheets arranged at intervals; the plurality of first electrode sheets are connected through electrical connectors and bus bars to form a first interdigital electrode, and the plurality of second electrode sheets are connected to form a second interdigital electrode. Electrode; the first interdigital electrode and the second interdigital electrode are at opposite potentials; the dummy electrode structure includes a plurality of dummy electrode sheets arranged between the first interdigital electrode and the second interdigital electrode, and two adjacent dummy electrodes There is a third distance between the sheets, and the third distance is equal to the first distance, and/or the third distance is equal to the second distance; the dummy electrode sheets are at a floating potential and are not connected to electrical signals. The bulk acoustic wave resonator and filter provided by this application can suppress the pseudo modes of the bulk acoustic wave resonator and improve the performance of the bulk acoustic wave resonator.

Description

A bulk acoustic wave resonator and filter

Technical field

The present application relates to the field of resonator technology, specifically, to a bulk acoustic wave resonator and filter.

Background technique

With the rapid development of wireless communications, wireless signals are becoming more and more crowded, which puts forward new requirements for filters working in the radio frequency band such as integration, miniaturization, low power consumption, high performance, and low cost. Traditional surface acoustic wave filters will increasingly be unable to meet such standards due to limitations in frequency and power. Thin film bulk acoustic resonators have gradually become a hot spot in radio frequency filter research due to their characteristics of CMOS process compatibility, high quality factor (Q value), low loss, low temperature coefficient, and high power carrying capacity. However, it is difficult for thin film bulk acoustic resonators to achieve ultra-high operating frequencies above 5 GHz, and their bandwidth does not meet the needs of 6G communications.

In the existing technology, ultra-high frequency bulk acoustic wave resonators based on lithium niobate and lithium tantalate thin film materials can achieve ultra-high frequency operation. Although this type of resonator has the advantages of ultra-high operating frequency of 5GHz and above and an effective electromechanical coupling coefficient of 20% and above, this type of bulk acoustic wave resonator will excite many pseudo modes during operation, resulting in the bulk acoustic wave When applied to filters, ripples are generated within the filter band, seriously affecting filter performance.

Utility model content

The purpose of this application is to provide a bulk acoustic wave resonator and filter that can suppress pseudo modes of the bulk acoustic wave resonator and improve the performance of the bulk acoustic wave resonator.

On the one hand, embodiments of the present application provide a bulk acoustic wave resonator, including a substrate and a piezoelectric layer provided on the substrate. An electrode structure and a dummy electrode structure are provided on the piezoelectric layer. The electrode structure includes a plurality of spaced apart electrode structures. A first electrode sheet and a plurality of second electrode sheets arranged at intervals, with a first distance between two adjacent first electrode sheets, and a second distance between two adjacent second electrode sheets; a plurality of first electrodes The sheets are connected through electrical connectors and bus bars to form a first interdigital electrode, and a plurality of second electrode sheet electrodes are connected through electrical connectors and bus bars to form a second interdigital electrode; the first interdigital electrode and the second interdigital electrode are in Opposite potential; the dummy electrode structure includes a plurality of dummy electrode sheets disposed between the first interdigital electrode and the second interdigital electrode. There is a third distance between two adjacent dummy electrode sheets, and the third distance is equal to the first distance, and/or, the third distance is equal to the second distance; the dummy electrode sheet is at a floating potential and is not connected to the electrical signal.

As an implementable manner, the dummy electrode sheets are staggered with the first electrode sheets, or the dummy electrode sheets are staggered with the second electrode sheets.

As an implementable manner, the dummy electrode sheets are arranged in multiple columns, and the dummy electrode sheets in two adjacent columns are arranged in a staggered manner.

As an implementation manner, the cross-sectional shape of the dummy electrode sheet is circular or polygonal.

As an implementation manner, the piezoelectric layer is provided with an acoustic reflection structure, and the acoustic reflection structure is arranged outside the electrode structure.

As an implementable manner, the sound reflection structure is provided on both sides of the electrode structure. The sound reflection structure includes a plurality of sound reflection holes. The sound reflection holes are staggered with the adjacent first electrode sheets, or the sound reflection holes are arranged with adjacent first electrode sheets. The adjacent second electrode sheets are arranged in a staggered manner.

As an implementable method, multiple sound reflection holes are arranged in an array, and the sound reflection holes are through holes, blind holes or stepped holes.

As an implementable manner, a filling piece is provided in the sound reflection hole.

As an implementable manner, the electrode structure further includes a bottom electrode, and the bottom electrode is disposed on a side of the piezoelectric layer close to the substrate.

Another aspect of embodiments of the present application provides a filter including the above-mentioned bulk acoustic wave resonator.

The beneficial effects of the embodiments of this application include:

The bulk acoustic wave resonator provided by this application includes a substrate and a piezoelectric layer provided on the substrate. An electrode structure and a dummy electrode structure are provided on the piezoelectric layer. The electrode structure includes a plurality of first electrode sheets arranged at intervals and a plurality of The second electrode sheets are spaced apart, with a first distance between two adjacent first electrode sheets, and a second distance between two adjacent second electrode sheets; the plurality of first electrode sheets are connected through electrical connectors and busses The strips are connected to form a first interdigital electrode, and a plurality of second electrode sheet electrodes are connected to form a second interdigital electrode; the first interdigital electrode and the second interdigital electrode are at opposite potentials; the dummy electrode structure includes a A plurality of dummy electrode pieces between the electrode and the second interdigital electrode, there is a third distance between two adjacent dummy electrode pieces, the third distance is equal to the first distance, and/or the third distance is equal to the second distance; The dummy electrode sheet is at a floating potential and is not connected to the electrical signal. The first interdigital electrode and the interdigital electrode are used to connect with external signals. Under the action of the external signal, sound waves propagating from the first interdigital electrode to the second interdigital electrode are generated in the piezoelectric layer. Among them, the operating frequency of the ultra-high frequency bulk acoustic wave resonator is determined by the relationship (1.1):

Among them, f is the operating frequency of the bulk acoustic wave resonator, m, n are the order of the mode, and the value is a positive integer such as 1, 2, 3, 4, etc., θ ₀ represents the sound speed, and p represents the first two adjacent branches. The distance between the finger electrode and the second interdigital electrode, L represents the distance between the dummy electrode structure and the first interdigital electrode and the second interdigital electrode in the extension direction of the first interdigital electrode. It can be seen from the relationship (1.1) that when the p value is larger, any pseudo mode f _n,m is smaller, which means that the frequency of the pseudo mode is reduced and pushed to a frequency point away from the main resonant frequency, which affects the main resonance frequency. The influence of the modal resonant frequency is reduced. In the embodiment of the present application, some of the first interdigital electrodes and the second interdigital electrode are set into a dummy electrode structure, and the dummy electrode structure is not connected to an external signal, thereby increasing the capacitance of the resonator without affecting the capacitance of the resonator. The distance between the first interdigital electrode and the second interdigital electrode increases p, thereby suppressing pseudo modes and improving the performance of the bulk acoustic wave resonator.

Description of the drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is one of the structural schematic diagrams of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 2 is the second structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 3 is the third structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 4 is one of the performance comparison diagrams between the bulk acoustic wave resonator provided by the embodiment of the present application and the prior art;

Figure 5 is the fourth structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 6 is a cross-sectional view along A-A in Figure 5;

Figure 7 is a fifth structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 8 is a cross-sectional view along A-A of Figure 7;

Figure 9 is the second performance comparison diagram between the bulk acoustic wave resonator provided by the embodiment of the present application and the prior art;

Figure 10 is a sixth structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 11 is a seventh structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 12 is the eighth structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application;

Figure 13 is a ninth structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application.

Icon: 10-bulk acoustic resonator; 11-piezoelectric layer; 12-interdigital electrode structure; 121-first interdigital electrode; 122-second interdigital electrode; 123-electrode pair; 13-pseudo electrode structure; 131 -Dummy electrode sheet; 14-sound reflection hole; 15-sound reflection material; 16-bottom electrode.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments These are part of the embodiments of this application, but not all of them. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the application provided in the appended drawings is not intended to limit the scope of the claimed application, but rather to represent selected embodiments of the application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

It should be noted that similar reference numerals and letters represent similar items in the following figures, therefore, once an item is defined in one figure, it does not need further definition and explanation in subsequent figures.

In addition, the terms "first", "second", "third", etc. are only used to distinguish descriptions and shall not be understood as indicating or implying relative importance.

The embodiment of the present application provides a bulk acoustic wave resonator 10, as shown in Figures 1, 2 and 3, including a substrate and a piezoelectric layer 11 provided on the substrate. An electrode structure is provided on the piezoelectric layer 11. Dummy electrode structure 13. The electrode structure includes a plurality of first electrode sheets arranged at intervals and a plurality of second electrode sheets arranged at intervals. There is a first distance between two adjacent first electrode sheets, and two adjacent second electrode sheets There is a second distance between the sheets; a plurality of first electrode sheets are connected through electrical connectors and bus bars to form a first interdigital electrode 121, and a plurality of second electrode sheets are connected to form a second interdigital electrode 122; The electrode 121 and the second interdigital electrode 122 are at opposite potentials; the dummy electrode structure 13 includes a plurality of dummy electrode sheets 131 arranged between the first interdigital electrode 121 and the second interdigital electrode 122. Two adjacent dummy electrodes There is a third distance between the pieces 131, and the third distance is equal to the first distance, and/or the third distance is equal to the second distance; the dummy electrode pieces 131 are at a floating potential and are not connected to electrical signals.

When the bulk acoustic wave resonator 10 provided by the embodiment of the present application works, the first interdigital electrode 121 and the second interdigital electrode 122 are connected to external signals, and the voltage between the first interdigital electrode 121 and the second interdigital electrode 122 A voltage difference is formed on the electrical layer 11. The piezoelectric layer 11 is made of piezoelectric material. Under the action of the voltage difference, according to the inverse piezoelectric effect, the voltage between the first interdigital electrode 121 and the second interdigital electrode 122 is Sound waves are generated on the electrical layer 11 , and the sound waves propagate along the arrangement direction of the first interdigital electrodes 121 and the second interdigital electrodes 122 . The dummy electrode structure 13 is not connected to external signals, and is disposed between the first interdigital electrode 121 and the second interdigital electrode 122 as an unconnected electrode.

Among them, the operating frequency of the bulk acoustic wave resonator 10 is determined by the relationship:

Among them, f is the operating frequency of the bulk acoustic wave resonator 10, m, n are the order of the modes, and their values are positive integers such as 1, 2, 3, and 4, θ ₀ represents the sound speed, and p represents the two adjacent first The distance between the interdigital electrode 121 and the second interdigital electrode 122 , L, represents the distance between the dummy electrode structure 13 and the first interdigital electrode 121 and the second interdigital electrode 122 in the extending direction of the first interdigital electrode 121 . When the operating frequency of the bulk acoustic wave resonator 10 is determined, the larger p is, the smaller the values of m and n are, and the smaller any pseudo-mode f _n,m is. In the embodiment of the present application, some of the first interdigital electrodes 121 and the second interdigital electrodes 122 are set as dummy electrode structures 13. The dummy electrode structures 13 are not connected to external signals, thereby increasing the size of the first interdigital electrodes 121 and the second interdigital electrodes 122. The distance between the two interdigital electrodes 122 increases P, so that the frequency f of the pseudo mode is reduced and pushed to a frequency point away from the main resonant frequency. The influence on the resonant frequency of the main mode is reduced, and the body is improved. Acoustic Resonator 10 Performance.

It should be noted that the dummy electrode structure 13 in the embodiment of the present application increases the distance between the first interdigital electrode 121 and the second interdigital electrode 122 based on the existing technology, and due to the existence of the dummy electrode structure 13 , and will not affect the connection between the capacitance of the bulk acoustic wave resonator 10 and external signals.

It should also be noted that the form of the dummy electrode structure 13 is not limited in the embodiment of the present application. For example, it may be the same as the structure of the first interdigital electrode 121 or it may be different. The specific number and location of the dummy electrode structures 13 are not specifically limited. The first interdigital electrode 121 and the second interdigital electrode 122 form an electrode pair 123. Each of the first interdigital electrode 121 and the second interdigital electrode 122 can It can be provided between the finger electrodes 122, or between each electrode pair 123, or a dummy electrode structure 13 can be provided at intervals of several electrode pairs 123. In addition, in order to facilitate the connection of the plurality of first interdigital electrodes 121 and the second interdigital electrodes 122 with the positive and negative poles of external signals respectively, electrode bus bars can be respectively provided at both ends of the first interdigital electrode 121, one electrode bus bar The other electrode bus bar is connected to the same-side ends of the plurality of first interdigital electrodes 121 , and the other electrode bus bar is connected to the same-side ends of the plurality of second interdigital electrodes 122 .

Specifically, when the bulk acoustic wave resonator 10 is operating, there are transverse acoustic waves propagating along the arrangement direction of the first interdigital electrode 121 and the second interdigital electrode 122 in the piezoelectric layer 11 , and there are also lateral sound waves extending along the first interdigital electrode 121 For longitudinal sound waves propagating in the direction, the frequency f of the bulk acoustic wave resonator is also given by the relationship Determine, where d is the thickness of the piezoelectric layer 11; θ _l is the longitudinal wave acoustic velocity in the piezoelectric layer 11; θ _t is the transverse acoustic wave velocity in the piezoelectric layer 11, and l is the distance between the first electrode sheets. When the first interdigital electrode uses a plurality of first electrode pieces, and the second interdigital electrode uses a plurality of second electrode pieces, the value of L is reduced, thus f can be increased, and the volume acoustic wave resonator 10 can be increased. operating frequency.

The third distance is equal to the first distance, and/or, the third distance is equal to the second distance; that is, the distance between two adjacent dummy electrode sheets 131 is the same as the distance between two adjacent first electrode sheets; or, The distance between two adjacent dummy electrode sheets 131 is the same as the distance between two adjacent second electrode sheets; or, the distance between two adjacent dummy electrode sheets 131 is the same as the distance between two adjacent first electrode sheets. The distance between two adjacent second electrode sheets is the same, the third distance is equal to the first distance, and/or the third distance is equal to the second distance; so that sound waves of the same frequency and wavelength can be transmitted through the piezoelectric propagated within layer 11.

The specific form of the electrical connector is not limited in the embodiments of this application. For example, it can be an electrical connection or an electric bridge as shown in Figure 1. Those skilled in the art can set point connections or bridge, or other form of electrical connection.

In the bulk acoustic wave resonator 10 provided by this application, the first interdigital electrode 121 and the interdigital electrode are used to connect the positive and negative poles of the external signal. Under the action of the external signal, the first interdigital electrode is generated in the piezoelectric layer 11 The sound wave propagates from the electrode 121 to the second interdigital electrode 122 . Among them, the operating frequency of the ultra-high frequency bulk acoustic wave resonator 10 is determined by the relationship (1.1):

It can be seen from the relationship (1.1) that when the p value is larger, any pseudo mode f _n,m is smaller, which means that the frequency of the pseudo mode is reduced and pushed to a frequency point away from the main resonant frequency, which affects the main resonance frequency. The influence of the modal resonant frequency is reduced. In the embodiment of the present application, some of the first interdigital electrodes 121 and the second interdigital electrodes 122 are set as dummy electrode structures 13. The dummy electrode structures 13 are not connected to external signals, without affecting the capacitance of the resonator. The distance between the first interdigital electrode 121 and the second interdigital electrode 122 is increased, that is, p is increased, thereby suppressing pseudo modes and improving the performance of the bulk acoustic wave resonator 10 .

Optionally, the dummy electrode sheets 131 are staggered with the first electrode sheets, or the dummy electrode sheets 131 are staggered with the second electrode sheets.

In an implementable manner of the embodiment of the present application, the dummy electrode sheets 131 are provided in multiple columns, and the dummy electrode sheets 131 in two adjacent columns are arranged in a staggered manner.

When the dummy electrode structure 13 includes multiple rows of dummy electrode sheets 131 , the distance between the first interdigital electrode 121 and the second interdigital electrode 122 can be further increased, thereby further suppressing the occurrence of pseudo modes and improving the volumetric acoustic wave resonator 10 performance.

When the dummy electrode structure 13 includes multiple dummy electrode strips, the distance between two adjacent dummy electrode strips is the same as the original distance between the first interdigital electrode 121 and the second interdigital electrode 122 .

Optionally, as shown in FIGS. 2 and 3 , the shape of the dummy electrode sheet 131 is circular or polygonal.

As shown in FIG. 2 , the shapes of the dummy electrode sheets 131 are circular, which is the same shape as the first electrode sheet and the second electrode sheet. As shown in FIG. 3 , the shapes of the first electrode sheet and the second electrode sheet are circular. The dummy electrode sheet 131 is formed into a diamond shape, and the shapes between the two are different. Those skilled in the art can set the shapes of the dummy electrode sheet 131 and the first electrode sheet and the second electrode sheet according to actual conditions.

In order to further verify that the acoustic reflection structure of the embodiment of the present application improves the performance of the bulk acoustic wave resonator 10, the performance of the bulk acoustic wave resonator 10 without the dummy electrode structure 13 and with the dummy electrode structure 13 was tested. Specifically, the test The data is shown in Figure 4. The solid line in Figure 9 is the performance curve of bulk acoustic wave resonance without the dummy electrode structure 13, and the dotted line is the performance curve of the bulk acoustic wave resonator 10 according to the embodiment of the present application. It can be seen from Figure 9 that, The curve of the embodiment of the present application is located above the curve without the dummy electrode structure 13 , that is, the bulk acoustic wave resonator 10 provided by the embodiment of the present application has better performance.

In an implementable manner of the embodiment of the present application, as shown in Figures 5 and 6, the piezoelectric layer 11 is provided with an acoustic reflection structure, and the acoustic reflection structure is arranged outside the electrode structure.

When the first interdigital electrode 121 and the second interdigital electrode 122 are connected to an external signal, transversely propagating sound waves can be generated in the piezoelectric layer 11 between the first interdigital electrode 121 and the first interdigital electrode 121. When the propagating sound wave propagates in the piezoelectric layer 11, it is unavoidable that it will be transmitted to the edge of the piezoelectric layer 11 and then leak. In the embodiment of the present application, a sound reflection structure is provided on the piezoelectric layer 11, and the sound reflection structure can reflect the sound wave propagating here. The sound wave is thereby prevented from leaking, thereby improving the quality factor of the bulk acoustic wave resonator 10 .

Optionally, the sound reflection structure is provided on both sides of the electrode structure. The sound reflection structure includes a plurality of sound reflection holes 14. The sound reflection holes 14 are staggered with the adjacent first electrode sheets, or the sound reflection holes 14 are arranged with the adjacent first electrode sheets. The second electrode sheets are arranged in a staggered manner.

The acoustic reflection structure is disposed on both sides of the electrode structure, which can reflect sound waves from both sides, thereby improving the quality factor of the bulk acoustic wave resonator 10 .

Specifically, the sound reflection structure includes a plurality of sound reflection holes 14 provided in the piezoelectric layer 11. The sound reflection holes 14 are filled with air. The air has a certain reflection effect on sound waves. When the sound waves in the piezoelectric layer 11 propagate to When the sound reflection hole 14 is installed, the sound reflection hole 14 reflects the sound wave propagating there back into the piezoelectric layer 11 , thereby avoiding the leakage of sound waves and improving the quality factor of the bulk acoustic wave resonator 10 .

The depth and cross-sectional shape of the sound reflection hole 14 are not limited in the embodiments of this application. Specifically, the hole depth of the sound reflection hole 14 can be a part of the piezoelectric layer 11, or it can penetrate the entire piezoelectric layer 11; sound reflection The cross-section of the hole 14 may be circular, quadrilateral, elliptical, pentagonal or other irregular shapes.

Optionally, as shown in FIG. 5 , a plurality of sound reflection holes 14 are arranged in multiple rows at both ends of the interdigital electrode structure 12 , and the sound reflection holes 14 in two adjacent rows are staggered.

In order to prevent sound waves from leaking from the piezoelectric layer 11 between two adjacent sound reflection holes 14, the embodiment of the present application is provided with multiple rows of sound reflection holes 14, and the two adjacent rows of sound reflection holes 14 are disposed in an offset manner. In this way, when The sound waves leaked between the two sound reflection holes 14 in the previous row continue to propagate and meet the sound reflection holes 14 in the next row, and are reflected back into the effective resonance area by the sound reflection holes 14 in the next row, thereby further avoiding the leakage of sound waves. , improving the quality factor of the bulk acoustic wave resonator 10.

In an implementable manner of the embodiment of the present application, as shown in FIG. 5 , the sound reflection hole 14 is a through hole, a blind hole or a stepped hole.

Optionally, as shown in Figures 7 and 8, the sound reflection hole 14 is filled with fillers.

There is a filling piece in the sound reflection hole 14. The filling piece has a different reflectivity from the piezoelectric layer 11. An example filling piece may be a sound reflection material 15. The sound reflection material 15 has a higher reflectivity than air, thereby making more The sound wave is reflected back into the piezoelectric layer 11 by the sound reflective material 15 and propagates, thereby further improving the quality factor of the bulk acoustic wave resonator 10 .

The specific material of the acoustic reflective material 15 is not limited in the embodiments of this application, as long as it has a large acoustic reflectivity and is different from the material of the piezoelectric layer 11 , for example, it can be silicon nitride, aluminum nitride, tungsten , or multiple combinations thereof.

In order to further verify that the acoustic reflection structure of the embodiment of the present application improves the quality factor of the bulk acoustic wave resonator 10, the performance of the bulk acoustic wave resonator 10 without the acoustic reflection mechanism and with the acoustic reflection structure is tested. Specifically, the impedance is tested. The curve is shown in Figure 9. The dotted line in Figure 9 is the impedance curve of bulk acoustic wave resonance without a sound reflection mechanism, and the solid line is the impedance curve of the bulk acoustic wave resonator 10 according to the embodiment of the present application. It can be seen from Figure 9 that this The impedance curve of the embodiment of the application is sharper. The quality factor of the bulk acoustic wave resonator 10 without the acoustic reflection structure is calculated to be 349.9. The quality factor of the lifted wave resonator of the embodiment of the application is 872.4. The quality factor provided by the embodiment of the application is The quality factor of BAW resonator 10 is improved by more than two times.

In an implementable manner of the embodiment of the present application, as shown in Figures 10, 11, 12 and 13, the electrode structure also includes a bottom electrode 16. The bottom electrode 16 is disposed on a side of the piezoelectric layer 11 close to the substrate. side.

Specifically, a bottom electrode 16 is also provided between the piezoelectric layer 11 and the substrate. The bottom electrode 16 includes any one of three types: a patterned bottom electrode 16, a suspended plate bottom electrode 16, and a ground plate bottom electrode 16.

In practical applications, the requirements for the electromechanical coupling coefficient of the bulk acoustic wave resonator 10 are different. In order to make the electromechanical coupling coefficient of the bulk acoustic wave resonator 10 adjustable, the embodiment of the present application proposes a variety of bottom electrode 16 methods. Specifically, As shown in Figure 10, there is no bottom electrode 16 provided under the piezoelectric layer 11; as shown in Figure 11, interdigital electrodes are provided under the piezoelectric layer 11, which are patterned bottom electrodes 16; as shown in Figure 12, the piezoelectric layer A suspended plate bottom electrode 16 is provided under the layer 11; as shown in Figure 13, a ground plate bottom electrode 16 is provided under the piezoelectric layer 11. Different bottom electrodes 16 have different electromechanical coupling coefficients, and those skilled in the art can select the form of the bottom electrode 16 according to actual conditions.

An embodiment of the present application also discloses a filter, including the above-mentioned bulk acoustic wave resonator 10. This filter contains the same structure and beneficial effects as the bulk acoustic wave resonator 10 in the previous embodiment. The structure and beneficial effects of the bulk acoustic wave resonator 10 have been described in detail in the foregoing embodiments and will not be described again here.

The above descriptions are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included in the protection scope of this application.

Claims (10)

1. The bulk acoustic wave resonator is characterized by comprising a substrate and a piezoelectric layer arranged on the substrate, wherein an electrode structure and a pseudo electrode structure are arranged on the piezoelectric layer, the electrode structure comprises a plurality of first electrode plates arranged at intervals and a plurality of second electrode plates arranged at intervals, a first distance is reserved between two adjacent first electrode plates, and a second distance is reserved between two adjacent second electrode plates; the plurality of first electrode plates are connected through an electric connector and a bus bar to form a first interdigital electrode, and the plurality of second electrode plates are connected through the electric connector and the bus bar to form a second interdigital electrode; the first interdigital electrode and the second interdigital electrode are in opposite potentials; the dummy electrode structure comprises a plurality of dummy electrode plates arranged between the first interdigital electrode and the second interdigital electrode, wherein a third distance is arranged between two adjacent dummy electrode plates, and/or the third distance is equal to the first distance; the dummy electrode plate is at a floating potential and is not connected with an electric signal.

2. The bulk acoustic wave resonator according to claim 1, characterized in that the dummy electrode pads are arranged interleaved with the first electrode pads or the dummy electrode pads are arranged interleaved with the second electrode pads.

3. The bulk acoustic wave resonator according to claim 1, characterized in that the dummy electrode pads are provided in a plurality of columns, the dummy electrode pads of adjacent two columns being staggered.

4. A bulk acoustic wave resonator according to any of claims 1 to 3, characterized in that the cross-sectional shape of the dummy electrode pads is circular or polygonal.

5. The bulk acoustic wave resonator according to claim 4, characterized in that an acoustic reflection structure is provided on the piezoelectric layer, which is arranged outside the electrode structure.

6. The bulk acoustic wave resonator according to claim 5, characterized in that the acoustic reflection structure is provided separately on both sides of the electrode structure, the acoustic reflection structure comprises a plurality of acoustic reflection holes, and the acoustic reflection holes are staggered with the adjacent first electrode plates, or the acoustic reflection holes are staggered with the adjacent second electrode plates.

7. The bulk acoustic resonator of claim 6, wherein a plurality of acoustic reflection holes are arranged in an array, the acoustic reflection holes being through holes, blind holes, or stepped holes.

8. The bulk acoustic resonator according to claim 6 or 7, characterized in that a filler is provided in the acoustic reflection hole.

9. The bulk acoustic wave resonator according to claim 1, characterized in that the electrode structure further comprises a bottom electrode, which bottom electrode is arranged at a side of the piezoelectric layer close to the substrate.

10. A filter comprising a bulk acoustic wave resonator as claimed in any one of claims 1 to 9.