CN118074649A

CN118074649A - Transverse electric field excited film bulk acoustic resonator and filter

Info

Publication number: CN118074649A
Application number: CN202211479168.6A
Authority: CN
Inventors: 杨清瑞; 庞慰
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2022-11-23
Filing date: 2022-11-23
Publication date: 2024-05-24

Abstract

The application relates to the field of semiconductor devices and provides a thin film bulk acoustic resonator and a filter excited by a transverse electric field. The thin film bulk acoustic resonator includes a substrate and a piezoelectric thin film stacked in a first direction, and an acoustic reflection layer formed between the substrate and the piezoelectric thin film; and opposite first and second interdigital electrodes formed on both sides of the thin film, adjacent first and second fingers of the first interdigital electrode having first periodic pitches in a second direction, adjacent third and fourth fingers of the second interdigital electrode having second periodic pitches in the second direction, a width of at least one finger of the first interdigital electrode being unequal to a width of a corresponding finger of the second interdigital electrode, and/or at least one of all first periodic pitches of the first interdigital electrode being unequal to a corresponding second periodic pitch of the second interdigital electrode. Therefore, the coupling of an electric field and modal coupling generated by the upper electrode and the lower electrode are restrained, parasitic modes are reduced, and the performance of the resonator is improved.

Description

Transverse electric field excited film bulk acoustic resonator and filter

Technical Field

The application relates to the field of semiconductor devices, in particular to a thin film bulk acoustic resonator and a filter excited by a transverse electric field.

Background

Under the technical standard of fifth-generation mobile communication (5G), the new frequency band represented by n77, n78 and n79 has a frequency range of 3-5GHz and a relative bandwidth of 12% -24%, while the traditional radio frequency front-end filter is mostly realized by adopting a Surface Acoustic Wave (SAW) technology based on a bulk lithium niobate or lithium tantalate substrate and a Bulk Acoustic Wave (BAW) resonator technology based on an AlN or Sc doped AlN film, and the relative bandwidth is mostly below 10% or even not more than 5%, so that the radio frequency front-end filter facing 5G application faces double difficulties of frequency promotion and bandwidth expansion.

In recent years, as ion slicing technology is mature, a single crystal piezoelectric film of lithium niobate (LiNbO 3, abbreviated as LN) or lithium tantalate (LiTaO 3, abbreviated as LT) with a thickness of hundreds of nanometers to several micrometers can be realized on a silicon substrate or other composite substrates, and such single crystal piezoelectric film has excellent piezoelectric characteristics, and high frequency and large bandwidth filters manufactured by using such single crystal piezoelectric film are appeared in the prior art.

In some prior arts, by processing an LN or LT single crystal piezoelectric film substrate, interdigital electrodes are formed on the surface thereof, and a resonance wave is excited by a transverse electric field component (parallel to the direction of the piezoelectric film) formed in the piezoelectric film by the interdigital electrodes.

In some prior art, the resonator area is also reduced by disposing interdigital electrodes on both sides of the piezoelectric film, thereby miniaturizing the filter.

This section is intended to provide a background or context to the embodiments of the application that are recited in the claims. The description herein is not admitted to be prior art by inclusion in this section.

Disclosure of Invention

The inventors found that when interdigital electrodes are arranged on both sides of a piezoelectric film, the electric field and mode generated by the upper and lower electrodes are easy to generate coupling, thereby generating new parasitic modes and deteriorating the overall performance of the resonator.

To solve at least one of the above problems or other similar problems, embodiments of the present application provide a thin film bulk acoustic resonator and a filter excited by a transverse electric field.

According to a first aspect of an embodiment of the present application, there is provided a thin film bulk acoustic resonator excited by a transverse electric field, the thin film bulk acoustic resonator including a substrate and a thin film stacked in a first direction, the thin film bulk acoustic resonator further including: a cavity formed in the substrate, the film covering the cavity; and a first interdigital electrode formed on a surface of the thin film located in the cavity and a second interdigital electrode formed on a surface of the thin film located outside the cavity, the second interdigital electrode being disposed opposite to the first interdigital electrode in the first direction; the first interdigital electrode comprises first fingers and second fingers which are alternately arranged along a second direction, the first fingers are connected with a first polarity voltage, the second fingers are connected with a second polarity voltage, the second polarity voltage is opposite to the first polarity voltage in polarity, and the second direction is perpendicular to the first direction; the second interdigital electrode comprises third fingers and fourth fingers which are alternately arranged along the second direction, the third fingers are connected with the first polarity voltage, and the fourth fingers are connected with the second polarity voltage; the first finger of the first interdigital electrode is arranged corresponding to the third finger of the second interdigital electrode, and the second finger of the first interdigital electrode is arranged corresponding to the fourth finger of the second interdigital electrode; adjacent first and second fingers of the first interdigital electrode have a first periodic pitch in the second direction, adjacent third and fourth fingers of the second interdigital electrode have a second periodic pitch in the second direction, a width of at least one finger of the first interdigital electrode is not equal to a width of a corresponding finger of the second interdigital electrode, and/or at least one of all first periodic pitches of the first interdigital electrode is not equal to a corresponding second periodic pitch of the second interdigital electrode.

According to a second aspect of embodiments of the present application, there is provided a filter comprising a thin film bulk acoustic resonator excited by a transverse electric field according to an embodiment of the first aspect.

The embodiment of the application has the advantages that the width of the fingers of the interdigital electrodes at two sides of the film is different or the period interval is different, so that the coupling of an electric field and the modal coupling generated by the upper electrode and the lower electrode are restrained, the parasitic mode is reduced, and the performance of the resonator is improved.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a top view of a thin film bulk acoustic resonator in accordance with an embodiment of the first aspect of the present application.

Fig. 2 is a cross-sectional view of the thin film bulk acoustic resonator shown in fig. 1 along A-A.

Fig. 3 is an enlarged view of a portion B of one embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 4 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 3.

Fig. 5 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 6 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 5.

Fig. 7 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 8 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 7.

Fig. 9 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 10 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 9.

Fig. 11 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 12 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 13 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 12.

Fig. 14 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 15 is a partial enlarged view of a modification of the thin film bulk acoustic resonator shown in fig. 14.

Fig. 16 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 17 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 18 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 19 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 20 is a partial enlarged view of another embodiment of the thin film bulk acoustic resonator shown in fig. 2.

Fig. 21 is a schematic diagram of one implementation of the upper and lower electrodes of a thin film bulk acoustic resonator in accordance with an embodiment of the present application.

Fig. 22 is a schematic diagram of another implementation of the upper and lower electrodes of the thin film bulk acoustic resonator of an embodiment of the present application.

Fig. 23 is a schematic diagram of another implementation of the upper and lower electrodes of the thin film bulk acoustic resonator of the present application.

Fig. 24 is a schematic diagram of another implementation of the upper and lower electrodes of the thin film bulk acoustic resonator of an embodiment of the present application.

Fig. 25 is a schematic diagram of another implementation of the upper and lower electrodes of the thin film bulk acoustic resonator of an embodiment of the present application.

Fig. 26 is an electrical response curve of a comparative resonator obtained from finite element simulation.

Fig. 27 is an electrical response curve of one implementation of a thin film bulk acoustic resonator according to an example of the present application derived from finite element simulation.

Fig. 28 is an electrical response curve of another implementation of a thin film bulk acoustic resonator according to an example of the present application obtained from finite element simulation.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the embodiments of the present application will be described in further detail with reference to the accompanying drawings. The exemplary embodiments of the present application and their descriptions herein are for the purpose of explaining the present application, but are not to be construed as limiting the application.

In the embodiments of the present application, the terms "first," "second," "upper," "lower," etc. are used to distinguish between different elements from each other by reference, but do not denote a spatial arrangement or a temporal order of the elements, which should not be limited by the terms. The term "and/or" includes any and all combinations of one or more of the associated listed terms. The terms "comprises," "comprising," "including," "having," and the like, are intended to reference the presence of stated features, elements, components, or groups of components, but do not preclude the presence or addition of one or more other features, elements, components, or groups of components.

In embodiments of the present application, the singular forms "a," an, "and" the "include plural referents and should be construed broadly to mean" one "or" one type "and not limited to" one "or" another; furthermore, the term "comprising" is to be interpreted as including both the singular and the plural, unless the context clearly dictates otherwise. Furthermore, the term "according to" should be understood as "based at least in part on … …", and the term "based on" should be understood as "based at least in part on … …", unless the context clearly indicates otherwise.

Example of the first aspect

Embodiments of the first aspect of the present application provide a thin film bulk acoustic resonator excited by a transverse electric field. Fig. 1 is a top view of a thin film bulk acoustic resonator according to an embodiment of the first aspect of the present application, and fig. 2 is a cross-sectional view of the thin film bulk acoustic resonator shown in fig. 1 taken along the A-A direction.

As shown in fig. 2, the thin film bulk acoustic resonator 1 includes a substrate 104 and a piezoelectric thin film 101 stacked in a first direction z, and further includes an acoustic reflection layer formed between the substrate 104 and the piezoelectric thin film 301.

In at least one embodiment, the acoustic reflection layer may be a cavity, a Bragg reflection layer, or other acoustic reflection structures having equivalent acoustic impedance characteristics similar to or similar to the acoustic impedance characteristics of the cavity or Bragg reflection layer. The embodiment of the application does not limit what kind of sound reflection structure is selected as the sound reflection layer of the film bulk acoustic resonator 3, and can be designed according to actual needs, for example, under the condition of higher Q value requirement of the resonator, a cavity can be selected as the sound reflection layer; in case of high requirements on the heat dissipation performance or the power of the resonator, the bragg reflection layer may be selected as the acoustic reflection layer.

The following description is given by taking the cavity as an example of the acoustic reflection layer, but those skilled in the art will recognize that the following description should not be construed as limiting the embodiments of the present application.

As shown in fig. 4, a cavity 102 is formed in a substrate 304, and a piezoelectric film 101 covers the cavity 102.

In at least one embodiment, the substrate 104 may be formed of a semiconductor material, and embodiments of the present application are not limited to the particular materials forming the substrate 104. For example, the substrate 104 may include only the base 141, the cavity 102 is formed on the base 141, the base 141 may be formed of, for example, single crystal silicon, for example, high-resistance silicon material having a resistivity of, for example, more than 1000Ω·cm, for example, a resistivity of >5000 Ω·cm, and the base 141 may be formed of lithium niobate, lithium tantalate, silicon carbide (SiC), sapphire (sapphire), quartz (Quartz), or the like. The substrate 104 may further include a base 141 and an auxiliary bonding layer 142, wherein the auxiliary bonding layer 142 is formed on the surface of the base 141, and the auxiliary bonding layer 142 may be formed of a semiconductor material such as silicon dioxide, silicon nitride, polysilicon, amorphous silicon, or a composite material composed of silicon dioxide, silicon nitride, polysilicon, amorphous silicon, or the like. In addition, the substrate 104 may be a substrate formed by compounding multiple layers of materials, and is not limited to the single material described in the embodiments of the present application, and the manner of forming the cavity is not limited to the embodiment of the present application shown in the drawings. For example: the cavity 102 may also be a through hole structure penetrating through the substrate 104, for example, penetrating through the auxiliary bonding layer 142 and the base 141, or the cavity 102 may be formed by surrounding the bonding layer 142 so as to be located between the base 141 and the piezoelectric film 101, that is, the cavity 102 is not located in the base 141 but located on the base 141, or may be formed in other ways, which are not limited in this embodiment of the present application. Alternatively, the cavity 102 may be replaced with a bragg reflection layer, for example, with alternately formed high and low acoustic impedance layers, and the bragg reflection layer has equivalent acoustic impedance characteristics close to those of the cavity.

The material forming the piezoelectric film 101 is not limited, and may be selected according to actual needs or performance requirements, for example, the piezoelectric material may be selected to form the piezoelectric film 101, for example, a material having a piezoelectric coupling coefficient corresponding to a larger lateral electric field excitation may be selected, for example, a single crystal piezoelectric material such as lithium niobate or lithium tantalate may be selected. According to the embodiment of the application, the lithium niobate or lithium tantalate has larger d11, d15 and d16 piezoelectric coupling coefficients by selecting proper interdigital electrodes and the included angles between the interdigital electrodes and the crystal axes, so that a zero-order symmetrical Lamb Wave (SYMMETRIC LAMB WAVE) mode, an S0 mode for short, a first-order antisym Lamb Wave (FIRST ANTISYMMETRIC Lamb Wave) mode, an A1 mode for short, a zero-order horizontal shearing (SH 0 mode for short and a high-order or low-order mode of the modes can be excited by the acoustic resonator respectively.

As shown in fig. 2, the thin film bulk acoustic resonator 1 further includes a first interdigital electrode 11 and a second interdigital electrode 12, and hereinafter, for simplicity of description, the first interdigital electrode 11 is sometimes referred to as a "lower electrode" and the second interdigital electrode 12 is referred to as an "upper electrode", but those skilled in the art will understand that the designations of "upper" and "lower" are merely for convenience of reading and do not indicate spatial arrangement.

The first interdigital electrode 11 is formed on the surface of the piezoelectric film 101 located inside the cavity 102, the second interdigital electrode 12 is formed on the surface of the piezoelectric film 101 located outside the cavity 102, and the second interdigital electrode 12 is disposed opposite to the first interdigital electrode 11 in the first direction z.

The structure of the first interdigital electrode 11 corresponds to that of the second interdigital electrode 12, and the structure of the second interdigital electrode 12 will be described below by taking fig. 1 as an example. As shown in fig. 1, the second interdigital electrode 12 includes third and fourth fingers 121 and 122 alternately arranged along the second direction x, the third and fourth fingers 121 and 122 extending in a third direction y, respectively, which is perpendicular to the first and second directions z and x. Further, the third finger 121 is connected to a first polarity voltage, and the fourth finger 122 is connected to a second polarity voltage. As shown in fig. 2, the plurality of third fingers 121 may be connected to the third bus portion 1201, and thus connected to the first polarity voltage via the third bus portion 1201, and the plurality of fourth fingers 122 may be connected to the fourth bus portion 1202, and thus connected to the second polarity voltage via the bus portion 1203.

As shown in fig. 2, the first interdigital electrode 11 includes first fingers 111 and second fingers 112 alternately arranged in the second direction x, the first fingers 111 being connected to a first polarity voltage, and the second fingers 112 being connected to a second polarity voltage. The first interdigital electrode 11 may include a first bus portion for connecting the plurality of first fingers 111 to a first polarity voltage, and a second bus portion for connecting the plurality of second fingers 112 to a second polarity voltage. In addition, the first polarity voltage is one of a positive voltage and a negative voltage, and the second polarity voltage is opposite to the first polarity voltage.

As shown in fig. 2, the first finger 111 of the first interdigital electrode 11 is provided corresponding to the third finger 121 of the second interdigital electrode 12, and the second finger 112 of the first interdigital electrode 11 is provided corresponding to the fourth finger 122 of the second interdigital electrode 12.

In at least one embodiment, the fingers of the first interdigital electrode 11 are arranged periodically in the second direction x, i.e., contain a number of first fingers and second fingers in one cycle, for example, contain 1 first finger and 1 second finger in one cycle, or contain a plurality of first fingers and second fingers in one cycle, wherein the number of first fingers and second fingers may be equal, or the number of first fingers and second fingers may differ by 1; the fingers of the second interdigital electrode 12 are arranged periodically in the second direction x, i.e., contain a number of third and fourth fingers in one cycle, for example, contain 1 third finger and 1 fourth finger in one cycle, or contain a plurality of third and fourth fingers in one cycle, wherein the number of third and fourth fingers may be equal, and the number of third and fourth fingers may differ by 1.

Fig. 3 is an enlarged view of a portion B of one embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 4 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 3.

As shown in fig. 3, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one cycle, the width of the finger of the first interdigital electrode 11 being m, for example, the width of the first finger 111 being m1, the width of the second finger 112 being m2; the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one cycle, the width of the fingers of the second interdigital electrode 12 being n, for example, the width of the third finger 121 being n1, the width of the fourth finger 122 being n2, wherein "width of the fingers" means "dimension of the fingers in the second direction x".

As shown in fig. 3, adjacent first and second fingers 111 and 112 of the first interdigital electrode 11 have a first period pitch p in the second direction x, and adjacent third and fourth fingers 121 and 122 of the second interdigital electrode 12 have a second period pitch q in the second direction x.

In an embodiment of the present application, the width m of at least one finger of the first interdigital electrode 11 is not equal to the width n of the corresponding finger of the second interdigital electrode 12, and/or at least one of the total first period intervals p of the first interdigital electrode 11 is not equal to the corresponding second period interval q of the second interdigital electrode 12.

Therefore, the width of the electrode on the two sides of the film or the period interval is different, so that the coupling of the electric field generated by the upper electrode and the lower electrode and the modal coupling are restrained, parasitic modes are reduced, and the performance of the resonator is improved.

In at least one embodiment, the first periodic spacing of the first interdigitated electrodes is equal to the corresponding second periodic spacing of the second interdigitated electrodes, and the width of at least one finger of the first interdigitated electrodes is greater than the width of the corresponding finger of the second interdigitated electrodes.

In addition, in the embodiment of the present application, for the first interdigital electrode, the width of the first finger may be equal to or different from the width of the second finger, and the width of each first finger may be equal to or different from the width of each second finger; the width of the third finger and the width of the fourth finger may be equal or unequal to each other, and the width of each third finger may be equal or unequal to each other, and the width of each fourth finger may be equal or unequal to each other.

For example, in at least one embodiment, the first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, and the width m of any one finger of the first interdigital electrode 11 is greater than the width n of the corresponding finger of the second interdigital electrode 12.

For example, as shown in fig. 3, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is greater than the width n2 of the fourth finger 122.

In addition, as shown in fig. 3, the width m1 of the first finger 111 may be equal to the width m2 of the second finger, and the width n1 of the third finger 121 may be equal to the width n2 of the fourth finger 122.

In practical applications, as shown in fig. 4, a certain deviation Δm may exist between the centers of the first interdigital electrode 11 and the second interdigital electrode 12, and the deviation Δm may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set during design, and the maximum value of Δm may be set to, for example, 0.5× (m1+n1), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 4 is offset in the positive direction of x, but the deviation Δm may also be offset in the negative direction of x.

Fig. 5 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 6 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 5.

For example, as shown in fig. 5, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one period, and the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one period. The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is greater than the width n2 of the fourth finger 122.

The width m1 of the first finger 111 may be equal to the width m2 of the second finger, and the width n1 of the third finger 121 may be unequal to the width n2 of the fourth finger 122, for example, as shown in fig. 5, m1 may be equal to m2, n1 may be smaller than n2, or n1 may be larger than n2.

In practical applications, as shown in fig. 6, there may be a certain deviation Δm between the centers of the first interdigital electrode 11 and the second interdigital electrode 12, where the deviation Δm may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set during design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 6 is offset in the positive direction of x, but the deviation Δm may also be offset in the negative direction of x.

Fig. 7 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 8 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 7.

For example, as shown in fig. 7, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one period, and the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one period. The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is greater than the width n2 of the fourth finger 122.

In addition, the width m1 of the first finger 111 may be unequal to the width m2 of the second finger, and the width n1 of the third finger 121 may be unequal to the width n2 of the fourth finger 122. For example, as shown in fig. 7, m1 is smaller than m2, n1 is smaller than n2, that is, the wider fingers of the first interdigital electrode 11 correspond to the wider fingers of the second interdigital electrode 12, and the narrower fingers of the first interdigital electrode 11 correspond to the narrower fingers of the second interdigital electrode 12.

In practical applications, as shown in fig. 8, there may be a certain deviation Δm between the centers of the first interdigital electrode 11 and the second interdigital electrode 12, where the deviation Δm may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set during design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 8 is offset in the positive direction of x, but the deviation Δm may also be offset in the negative direction of x.

Fig. 9 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 10 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 9.

For example, as shown in fig. 9, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one period, and the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one period. The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is greater than the width n2 of the fourth finger 122.

In addition, the width m1 of the first finger 111 may be unequal to the width m2 of the second finger, and the width n1 of the third finger 121 may be unequal to the width n2 of the fourth finger 122. For example, as shown in fig. 9, m1 is greater than m2, and n1 is less than n2, that is, the wider fingers of the first interdigital electrode 11 correspond to the narrower fingers of the second interdigital electrode 12, and the narrower fingers of the first interdigital electrode 11 correspond to the wider fingers of the second interdigital electrode 12.

In practical applications, as shown in fig. 10, there may be a certain deviation Δm between the centers of the first interdigital electrode 11 and the second interdigital electrode 12, where the deviation Δm may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set during design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 10 is offset in the positive direction of x, but the deviation Δm may be offset in the negative direction of x.

In at least one embodiment, the first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m of any one finger of the first interdigital electrode 11 is greater than the width n of the corresponding finger of the second interdigital electrode 12, the width m1 of the first finger 111 is not equal to the width m2 of the second finger, and the width n1 of the third finger 121 is equal to the width n2 of the fourth finger 122. In addition, the widths of all the first fingers 111 of the first interdigital electrode 11 may be equal, the widths of all the second fingers 112 of the first interdigital electrode 11 may be equal, and the widths of all the fingers of the second interdigital electrode 12 may be equal.

In practical applications, the centers of the first interdigital electrode 11 and the second interdigital electrode 12 may have a certain deviation Δm, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two electrodes opposing each other overlaps in the thickness direction (first direction z).

As shown in fig. 11, N fingers are included in one cycle of the first interdigital electrode 11 and the second interdigital electrode 12, that is, the sum of the number of first fingers 111 and the number of second fingers 112 is N, and the sum of the number of third fingers 121 and the number of fourth fingers 122 is N, which is greater than or equal to 3. In one period, the centers of the 1 st finger of the first and second interdigital electrodes 11 and 12 are aligned, and the centers of the nth finger of the first and second interdigital electrodes 11 and 12 are aligned. However, it should be understood by those skilled in the art that the "alignment" described herein is not limited to the "absolute alignment" and is sometimes affected by the production process, and the centers of the fingers of the upper and lower electrodes may have a certain deviation, so long as the deviation is within a predetermined range, which may be referred to as "center alignment". Hereinafter, this period is sometimes referred to as "minimum repetition period".

The widths of the N fingers of the first interdigital electrode 11 are respectively denoted as m1, m2 … … mN, at least one of the m1 and m2 … … mN is different from the other width values, and the values of m1 and m2 … … mN may be arranged in order of magnitude or may not be arranged in order of magnitude; the widths of the N fingers of the second interdigital electrode 12 are denoted as N1, N2 … … nN, at least one of the N1 and N2 … … nN width values being different from the other width values, and the values of N1 and N2 … … nN may or may not be arranged in order of magnitude.

The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12 within a minimum repetition period. The first period p of each first interdigital electrode 11 may be equal to each other, or a first period different from the other first period may be present, and the second period q of each second interdigital electrode 12 may be equal to the corresponding first period p.

In a minimum repetition period, the width m of any one finger of the first interdigital electrode 11 is larger than the width n of the corresponding finger of the second interdigital electrode 12, that is, m1 is larger than n1, m2 is larger than n2 … … mN is larger than nN.

In practical applications, the centers of the fingers of the upper and lower electrodes may have a certain deviation, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value of the deviation amount is 0.5× (m1+n1), 0.5× (m2+n2), …,0.5× (mN) +nn), that is, the minimum one of the two opposing electrodes is ensured to overlap at least in part in the thickness direction (first direction z).

In at least one embodiment, the first periodic pitch of the first interdigital electrode is equal to the corresponding second periodic pitch of the second interdigital electrode, the width of a portion of the fingers of the first interdigital electrode is greater than the width of the corresponding fingers of the second interdigital electrode, and the width of the fingers other than the portion of the fingers of the first interdigital electrode is less than the width of the corresponding fingers of the second interdigital electrode.

Fig. 12 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 13 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 12.

For example, as shown in fig. 12, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one period, and the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one period. The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is less than the width n2 of the fourth finger 122.

As shown in fig. 12, the width m1 of the first finger 111 is larger than the width m2 of the second finger 112, the width n1 of the third finger 121 is smaller than the width n2 of the fourth finger 122, the width m1 of the first finger 111 is the same as the width n2 of the fourth finger 122, and the width m2 of the second finger 112 is the same as the width n1 of the third finger 121. However, the embodiment of the present application is not limited thereto, for example, the width m1 of the first finger 111 and the width m2 of the second finger 112 may be equal and the width value is between the width n1 of the third finger 121 and the width n2 of the fourth finger 122; or the width n1 of the third finger 121 and the width n2 of the fourth finger 122 may be equal and have a width value between the width m1 of the first finger 111 and the width m2 of the second finger 112.

In practical applications, as shown in fig. 13, the centers of the first interdigital electrode 11 and the second interdigital electrode 12 may have a certain deviation Δm, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 13 is offset in the positive direction of x, but the deviation Δm may be offset in the negative direction of x.

Fig. 14 is an enlarged view of a portion B of another embodiment of the thin film bulk acoustic resonator shown in fig. 2, and fig. 15 is an enlarged view of a portion of a modification of the thin film bulk acoustic resonator shown in fig. 14.

For example, as shown in fig. 14, the first interdigital electrode 11 may include 1 first finger 111 and 1 second finger 112 in one period, and the second interdigital electrode 12 may include 1 third finger 121 and 1 fourth finger 122 in one period. The first period p of the first interdigital electrode 11 is equal to the corresponding second period q of the second interdigital electrode 12, the width m1 of the first finger 111 is greater than the width n1 of the third finger 121, and the width m2 of the second finger 112 is less than the width n2 of the fourth finger 122.

As shown in fig. 14, the width m1 of the first finger 111 is larger than the width m2 of the second finger 112, and the width n1 of the third finger 121 is smaller than the width n2 of the fourth finger 122.

As shown in fig. 14, the width m1 of the first finger 111 is smaller than the width n2 of the fourth finger 122, and the width m2 of the second finger 112 is larger than the width n1 of the third finger 121. However, embodiments of the present application are not limited thereto, for example, the width m1 of the first finger 111 may be greater than the width n2 of the fourth finger 122, and the width m2 of the second finger 112 may be greater than the width n1 of the third finger 121; or the width m1 of the first finger 111 may be greater than the width n2 of the fourth finger 122, and the width m2 of the second finger 112 may be less than the width n1 of the third finger 121; or the width m1 of the first finger 111 may be smaller than the width n2 of the fourth finger 122, and the width m2 of the second finger 112 may be smaller than the width n1 of the third finger 121.

In practical applications, as shown in fig. 15, the centers of the first interdigital electrode 11 and the second interdigital electrode 12 may have a certain deviation Δm, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value Δm may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m2+n2), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z). The deviation Δm shown in fig. 15 is offset in the positive direction of x, but the deviation Δm may be offset in the negative direction of x.

As shown in fig. 16, N fingers are included in one cycle of the first interdigital electrode 11 and the second interdigital electrode 12, that is, the sum of the number of the first fingers 111 and the number of the second fingers 112 is N, and the sum of the number of the third fingers 121 and the number of the fourth fingers 122 is N, which is greater than or equal to 3. Hereinafter, this period is sometimes referred to as "minimum repetition period".

In a minimum repetition period, the width m of the odd-numbered fingers of the first interdigital electrode 11 is larger than the width n of the corresponding odd-numbered fingers of the second interdigital electrode 12, the width m of the even-numbered fingers of the first interdigital electrode 11 is smaller than the width n of the corresponding even-numbered fingers of the second interdigital electrode 12, that is, m1 is larger than n1, m3 is larger than n3, … …, m2 is smaller than n2, m4 is smaller than n4, … …; or the width m of the odd-numbered fingers of the first interdigital electrode 11 is smaller than the width n of the corresponding odd-numbered fingers of the second interdigital electrode 12, the width m of the even-numbered fingers of the first interdigital electrode 11 is larger than the width n of the corresponding even-numbered fingers of the second interdigital electrode 12, that is, m1 is smaller than n1, m3 is smaller than n3, … …, m2 is larger than n2, m4 is larger than n4, … ….

However, the embodiment of the present application is not limited thereto, and the width of a part of the fingers at any position of the first interdigital electrode 11 may be larger than the width of the corresponding fingers of the second interdigital electrode 12, and the width of the other fingers of the first interdigital electrode 11 except for the part may be smaller than the width of the corresponding fingers of the second interdigital electrode 12. For example, in the N pairs of the first interdigital electrode 11 and the second interdigital electrode 12, at least one of the pairs of the opposing fingers is opposite to one of the other pairs of the opposing fingers, and the relationship of the widths of the fingers is reversed.

In practical applications, the centers of the fingers of the upper and lower electrodes may have a certain deviation, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value of the deviation amount is 0.5× (m1+n1), 0.5× (m2+n2), …, and 0.5× (mN) +nn, that is, the minimum one of the two opposing electrodes is ensured to overlap at least in part in the thickness direction (first direction z).

In at least one embodiment, the widths of the fingers corresponding to the first and second interdigital electrodes are equal, the sum of the first number of adjacent first periodic pitches of the first interdigital electrode is equal to the sum of the corresponding first number of second periodic pitches of the second interdigital electrode, at least one of the first number of first periodic pitches is not equal to the corresponding second periodic pitch, and the first number is 2 or more.

In at least one embodiment, the first interdigital electrode 11 and the second interdigital electrode 12 are periodically arranged on the surfaces of both sides of the piezoelectric film 101, respectively. As shown in fig. 17, in one cycle, n+1 fingers of the upper and lower electrodes are respectively included, and thus, N first cycle pitches p1 to pN are included, and N second cycle pitches q1 to qN are included, wherein p1+p2+ … … +pn is equal to q1+q2+ … … +qn, and N is greater than or equal to 2. At least one of the first period pitches p1 to pN of the first interdigital electrode 11 is not equal to the corresponding value of the second period pitches q1 to qN of the second interdigital electrode 12, for example, at least one pair of adjacent first period pitches p1 to pN of the first interdigital electrode 11 is different from the corresponding second period pitch of the second interdigital electrode 12, one of the adjacent pair of first period pitches is larger than the corresponding second period pitch, and the other of the adjacent pair of first period pitches is smaller than the corresponding second period pitch.

In at least one embodiment, at least one of the first number of first periodic intervals is not equal to the other first periodic intervals. For example, as shown in fig. 17, at least one of the N first period pitches p1 to pN is not equal to the other first period pitches. However, the embodiment of the present application is not limited thereto, the N first period pitches p1 to pN may be equal, and in the case where the N first period pitches p1 to pN are equal, at least two pitches that are not equal may exist in the N second period pitches q1 to qN.

Hereinafter, this period is sometimes referred to as "minimum repetition period".

In the minimum repetition period, the widths of the fingers corresponding to the upper and lower electrodes are equal, for example, as shown in fig. 17, the width m1 of the first finger 111 is equal to the width N1 of the corresponding third finger 121, the width m2 of the second finger 112 is equal to the width N2 of the corresponding fourth finger 122, and the width m (n+1) of the n+1th finger of the … … first interdigital electrode 11 is equal to the width N (n+1) of the n+1th finger of the corresponding second interdigital electrode 12.

In the minimum repetition period, as shown in fig. 17, the centers of the 1 st finger of the first and second interdigital electrodes 11 and 12 are aligned, and the centers of the n+1 th finger of the first and second interdigital electrodes 11 and 12 are aligned. However, it should be understood by those skilled in the art that the "alignment" described herein is not limited to the "absolute alignment" and is sometimes affected by the production process, and the centers of the fingers of the upper and lower electrodes may have a certain deviation, so long as the deviation is within a predetermined range, which may be referred to as "center alignment".

In practical applications, there may be a certain deviation between the center of the 1 st finger of the upper and lower electrodes and the center of the n+1 th finger of the upper and lower electrodes, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value of the deviation amounts is the smaller one of 0.5× (m1+n1) and 0.5× (m (n+1))+n (n+1)), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z).

In at least one embodiment, the widths of the first and second fingers of the first interdigital electrode may also be equal, and the widths of the third and fourth fingers of the second interdigital electrode may also be equal, for example, m1=m2= … … =m (n+1), n1=n2= … … =n (n+1). However, in the embodiment of the present application, the width of each finger in the same interdigital electrode is not limited, for example, the width of a part of fingers of the first interdigital electrode may be equal, and the widths of the remaining parts may be different from each other or may be partially equal.

In at least one embodiment, the first interdigital electrode 11 and the second interdigital electrode 12 are periodically arranged on the surfaces of both sides of the piezoelectric film 101, respectively. As shown in fig. 18, in one minimum repetition period, each of the 3 fingers including the upper and lower electrodes is aligned with the center of the 1 st finger of the upper and lower electrodes, and the center of the 3 rd finger of the upper and lower electrodes is aligned. In the minimum repetition period, 2 first period pitches p1 and p2 are included, 2 second period pitches q1 and q1 are included, and p1+p2 is equal to q1+θ2. Where p1 is not equal to q1 and p2 is not equal to q2, e.g., p1 is greater than q1 and p2 is less than q2.

In the case where p1 is greater than q1 and p2 is less than q2, p1 may be equal to q2 and p2 may be equal to q1; or p1 is not equal to q2 and p2 is not equal to q1. In addition, the size relationship between p1 and q2 and the size relationship between p2 and q1 are not limited in the embodiment of the present application.

In addition, the size relationship between p1 and p2 is not limited, and the size relationship between q1 and q2 is not limited, for example, p1 may be equal to p2 and between q1 and q 2; or q1 and q2 are equal and between p1 and p 2.

In practical applications, there may be a certain deviation between the center of the 1 st finger of the upper and lower electrodes and the center of the 3 rd finger of the upper and lower electrodes, which may be caused by the alignment accuracy of the lithography machine, or may be a deviation amount set at the time of design, and the maximum value of the deviation amount may be, for example, the smaller one of 0.5× (m1+n1) and 0.5× (m3+n3), that is, it is ensured that at least a partial region of the two opposing electrodes overlaps in the thickness direction (first direction z).

In at least one embodiment, the width of at least one finger of the first interdigital electrode is greater than the width of a corresponding finger of the second interdigital electrode, the sum of a first number of adjacent first periodic pitches of the first interdigital electrode is equal to the sum of a corresponding first number of second periodic pitches of the second interdigital electrode, at least one of the first number of first periodic pitches is not equal to a corresponding second periodic pitch, and the first number is 2 or more.

In at least one embodiment, the first interdigital electrode 11 and the second interdigital electrode 12 are periodically arranged on the surfaces of both sides of the piezoelectric film 101, respectively. As shown in fig. 19, in one cycle, n+1 fingers of the upper and lower electrodes are respectively included, and thus, N first cycle pitches p1 to pN are included, and N second cycle pitches q1 to qN are included, wherein p1+p2+ … … +pn is equal to q1+q2+ … … +qn, and N is greater than or equal to 2. The widths of n+1 fingers of the first interdigital electrode 11 are denoted as m1 and m2 … … m (n+1), respectively, and the widths of N fingers of the second interdigital electrode 12 are denoted as N1 and N2 … … N (n+1), respectively. Hereinafter, this period is sometimes referred to as "minimum repetition period".

In a minimum repetition period, at least one of the first period pitches p1 to pN of the first interdigital electrode 11 is not equal to the corresponding value of the second period pitches q1 to qN of the second interdigital electrode 12, for example, at least one pair of adjacent first period pitches p1 to pN of the first interdigital electrode 11 is different from the corresponding second period pitch of the second interdigital electrode 12, and one of the adjacent pair of first period pitches is larger than the corresponding second period pitch, and the other of the adjacent pair of first period pitches is smaller than the corresponding second period pitch.

In a minimum repetition period, the widths of the fingers corresponding to at least one group of upper and lower electrodes are not equal, and the width of the fingers of the lower electrode is larger than that of the fingers of the upper electrode.

For example, the width of the finger of the corresponding lower electrode, which may be the 1 st finger of the minimum repetition period, is larger than the width of the finger of the upper electrode, for example, as shown in fig. 19, the width m1 of the first finger 111 is larger than the width n1 of the corresponding third finger 121; the width of the finger of the corresponding lower electrode of the last 1 finger of the minimum repetition period may be larger than the width of the finger of the upper electrode, and the width of the finger of the corresponding lower electrode of the middle finger of the minimum repetition period may be larger than the width of the finger of the upper electrode. In addition, the width m of the odd-numbered fingers of the first interdigital electrode 11 may be larger than the width n of the corresponding odd-numbered fingers of the second interdigital electrode 12, and the width m of the even-numbered fingers of the first interdigital electrode 11 may be smaller than the width n of the corresponding even-numbered fingers of the second interdigital electrode 12, that is, m1 is larger than n1, m3 is larger than n3, … …, m2 is smaller than n2, m4 is smaller than n4, … …; or the width m of the odd-numbered fingers of the first interdigital electrode 11 is smaller than the width n of the corresponding odd-numbered fingers of the second interdigital electrode 12, the width m of the even-numbered fingers of the first interdigital electrode 11 is larger than the width n of the corresponding even-numbered fingers of the second interdigital electrode 12, that is, m1 is smaller than n1, m3 is smaller than n3, … …, m2 is larger than n2, m4 is larger than n4, … ….

The values of the widths m1, m2 … … m (n+1) of the n+1 fingers of the first interdigital electrode 11 may be arranged in the order of magnitude or may be arranged out of the order of magnitude; the values of the widths N1, N2 … … N (n+1) d of the n+1 fingers of the second interdigital electrode 12 may be arranged in the order of magnitude or may be arranged out of the order of magnitude.

In the minimum repetition period, as shown in fig. 19, the centers of the 1 st finger of the first and second interdigital electrodes 11 and 12 are aligned, and the centers of the n+1 th finger of the first and second interdigital electrodes 11 and 12 are aligned. However, it should be understood by those skilled in the art that the "alignment" described herein is not limited to the "absolute alignment" and is sometimes affected by the production process, and the centers of the fingers of the upper and lower electrodes may have a certain deviation, so long as the deviation is within a predetermined range, which may be referred to as "center alignment".

In at least one embodiment, the widths of the first and second fingers of the first interdigital electrode may be equal, and the widths of the third and fourth fingers of the second interdigital electrode may be equal. For example, m1=m2= … … =m (n+1), n1=n2= … … =n (n+1). However, in the embodiment of the present application, the width of each finger in the same interdigital electrode is not limited, for example, the width of a part of fingers of the first interdigital electrode may be equal, and the widths of the remaining parts may be different from each other or may be partially equal.

In at least one embodiment, for example, as shown in fig. 20, the first interdigital electrode 11 and the second interdigital electrode 12 are periodically arranged on the surfaces of both sides of the piezoelectric film 101, respectively. In a minimum repetition period, each of the 3 fingers including the upper and lower electrodes is aligned with the center of the 1 st finger of the upper and lower electrodes, and the center of the 3 rd finger of the upper and lower electrodes is aligned. In addition, the widths of 3 fingers of the first interdigital electrode 11 are m1, m2, and m3, respectively, the widths of 3 fingers of the second interdigital electrode 12 are n1, n2, and n3, respectively, as shown in fig. 20, m1 is greater than n1, m2 is equal to n2, and m3 is less than n3, but the embodiment of the present application is not limited thereto, and for example, the widths m1, m2, and m3 of 3 fingers of the first interdigital electrode 11 may be greater than the widths n1, n2, and n3 of 3 fingers of the second interdigital electrode 12, or the widths m2 of the middle finger may be greater than n2, and the widths m1 of the two fingers are equal to n1 and m3 are equal to m3. In addition, the embodiment of the present application does not limit the size relationship of the widths m1, m2, and m3 of the 3 fingers of the first interdigital electrode 11, and does not limit the size relationship of the widths n1, n2, and n3 of the 3 fingers of the second interdigital electrode 12, for example, as shown in fig. 20, m2 and m3 are equal and less than m1, n1 and n2 are equal and less than n3, and in addition, m3 may be equal to m3.

In the minimum repetition period, 2 first period pitches p1 and p2 are included, 2 second period pitches q1 and q2 are included, and p1+p2 is equal to q1+q2. Where p1 is not equal to q1 and p2 is not equal to q2, for example, as shown in fig. 20, p1 is greater than q1 and p2 is less than q2.

In the case where p1 is greater than q1 and p2 is less than q2, p1 may be equal to q2 and p2 may be equal to q1; or p1 is not equal to q2, and p2 is not equal to q1, and in addition, the size relationship between p1 and q2 and the size relationship between p2 and q1 are not limited in the embodiment of the present application.

In at least one embodiment, at least one pair of adjacent fingers of the first interdigitated electrode are relatively inclined along a third direction, the third direction being perpendicular to the second direction; adjacent fingers of the second interdigital electrode corresponding to the at least one pair of adjacent fingers that are not parallel in the first interdigital electrode are relatively inclined in the third direction, and are opposite to the inclination direction of the at least one pair of adjacent fingers in the first interdigital electrode.

As shown in fig. 21, adjacent first fingers 111-1 and second fingers 112-1 of the first interdigital electrode 11 are inclined relatively along the third direction y, for example, the inclination angle of the second fingers 112-1 is a forward included angle θ with the second direction x; the third finger 121-1 and the fourth finger 122-1 of the second interdigital electrode 12 corresponding to the first finger 111-1 and the second finger 112-1 are inclined relatively in the third direction y, and are opposite to the inclined directions of the first finger 111-1 and the second finger 112-1, for example, the inclined angle of the fourth finger 122-1 is a negative angle θ with respect to the second direction x, for example, θ is 70 θ++.θ < 90 °.

The other adjacent first fingers (for example, first finger 111-2) and second fingers (for example, second finger 112-2) of the first interdigital electrode 11 may be relatively parallel to each other in the third direction y, but may be relatively inclined in the third direction y, and the inclination angle may be the same as the inclination angle of the second finger 112-1, and the other adjacent fingers (for example, third finger 121-2 and fourth finger 122-2) of the second interdigital electrode 12 may be opposite to the direction of the fingers of the first interdigital electrode 11.

As shown in fig. 21, the overlapping section length of two fingers of the same interdigital electrode is L0, and at a position half the length, the period pitch between adjacent fingers is the same, for example, the first period pitch of the first interdigital electrode 11 is p0 at a position half the length, and at one end of the overlapping region, the first period pitch is p1 and p2 alternately, and at the other end of the overlapping region, the first period pitch is p2 and p1 alternately. And p2 > p0 > p1, and p2+p1=2×p0; the second interdigital electrode 12 corresponds to the first interdigital electrode 11, for example, the second periodic pitch of the second interdigital electrode 12 is q0 at a position of half the length, the second periodic pitch is q1 and q2 alternately appearing at one end of the overlapping region, and the second periodic pitch is q2 and q1 alternately appearing at the other end of the overlapping region. And q2 > q0 > q1, and q2+q1=2×q0.

In at least one embodiment, the first and second interdigital electrodes 11 and 12 may include a plurality of inclined fingers in one minimum period unit, and the inclination angles thereof may be various. For example, as shown in fig. 22, in the first interdigital electrode 11, the second fingers 112-1 and 112-2 having two different inclination angles within one minimum period unit P, the inclination angle of the second finger 112-1 is a positive angle θ1 with the second direction x, the inclination angle of the second finger 112-2 is a positive angle θ2 with the second direction x, and the inclination directions of the fourth fingers 122-1 and 122-2 in the corresponding second interdigital electrode 12 are opposite to the second fingers 112-1 and 112-2, that is, the inclination angle of the fourth finger 122-1 is a negative angle θ1 with the second direction x, and the inclination angle of the fourth finger 122-2 is a negative angle θ2 with the second direction x. Wherein θ1 is, for example, an acute angle, for example, 70+.θ1 < 90 °, θ2 is, for example, an obtuse angle, for example, 90+.ltoreq.θ2.ltoreq.110 °, but θ2 may also be an acute angle, for example, 70+.ltoreq.θ2 < 90 °, but θ2 is different from θ1.

In at least one embodiment, at least one finger of the first interdigital electrode is formed to be offset in the second direction, and a finger of the second interdigital electrode corresponding to the finger formed to be offset in the first interdigital electrode is formed to be offset in the second direction, and is opposite to the direction of the offset of the first interdigital electrode.

Fig. 23 is a schematic diagram of another embodiment of the upper and lower electrodes of the film bulk acoustic resonator according to an embodiment of the present application, fig. 24 is a schematic diagram of another embodiment of the upper and lower electrodes of the film bulk acoustic resonator according to an embodiment of the present application, and fig. 25 is a schematic diagram of another embodiment of the upper and lower electrodes of the film bulk acoustic resonator according to an embodiment of the present application.

As shown in fig. 23, the second finger 112-1 of the first interdigital electrode 11 is formed to be shifted in the second direction x, for example, the first interdigital electrode 11 has a second bus portion 1102 connecting a plurality of second fingers (for example, the second fingers 112-1 and 112-2, etc.) with the second polarity voltage and a first bus portion 1101 connecting a plurality of first fingers (for example, the first fingers 111-1 and 111-2, etc.) with the first polarity voltage, and a portion of the second finger 112-1 close to the second bus portion 1102 is located in a negative direction x with respect to a portion close to the first bus portion 1101; the corresponding fourth finger 122-1 of the second interdigital electrode 12 is formed offset in the second direction x, and is opposite to the direction of the offset of the second finger 112-1, for example, a portion of the fourth finger 122-1 near the fourth bus bar portion 1202 is located in the forward direction of the second direction x with respect to a portion near the third bus bar portion 1201. In addition, the offset of the misalignment is no more than half the width of the finger.

The other adjacent second finger (for example, second finger 112-2) of the first interdigital electrode 11 may be formed without dislocation, or may be formed with dislocation direction and dislocation value identical to those of the second finger 112-1, or may be different from those of the second interdigital electrode 12, and the other adjacent finger (for example, fourth finger 122-2) is opposite to those of the first interdigital electrode 11, and the dislocation value corresponds to those of the second interdigital electrode. For example, as shown in fig. 24, the portions of the second fingers 112-1 of the first interdigital electrode 11 near the second bus line portion 1102 are located in the negative direction x with respect to the portions near the first bus line portion 1101, and the portions of the second fingers 112-2 near the second bus line portion 1102 are located in the positive direction x with respect to the portions near the first bus line portion 1101, so that they are alternately formed; the portion of the fourth finger 122-1 of the second finger electrode 12 corresponding to the second finger 112-1 near the fourth bus bar 1202 is located in the positive direction of the second direction x with respect to the portion near the third bus bar 1201, and the portion of the fourth finger 122-2 of the second finger electrode 12 corresponding to the second finger 112-2 near the fourth bus bar 1202 is located in the negative direction of the second direction x with respect to the portion near the third bus bar 1201.

As shown in fig. 23, the overlapping section length of two fingers of the same interdigital electrode is L0, and the fingers formed in a staggered manner are divided into two segments, for example, each segment length is 0.5×l0, but the embodiment of the present application is not limited thereto, and may be divided into other lengths, for example: one section is 0.4 xL 0, one section is 0.6 xL 0, and the length of the two sections is equal to L0. As shown in fig. 23, the two sections have the same width and the middle line is offset, but the embodiment of the application is not limited thereto, and the two sections may have different widths and the middle line is offset.

As shown in fig. 23, in the first interdigital electrode 11, the second finger 112-1 is offset in the second direction x and formed in two steps in the third direction y, thereby forming two different first periodic pitches p1 and p2 with respect to the adjacent first fingers 111-1 and 111-2, the first periodic pitches p1 and p2 alternately appearing at one end of the overlap region, for example, at one end near the second bus portion 1102, and the first periodic pitches p2 and p1 alternately appearing at the other end of the overlap region, for example, at one end near the first bus portion 1101; the second interdigital electrode 12 is disposed corresponding to the first interdigital electrode 11, for example, the fourth finger 122-1 of the second interdigital electrode 12 is also formed in two sections with the same length as the section corresponding to the second finger 112-1, and further two different second period pitches q1 and q2 are formed with respect to the adjacent third finger, the second period pitches q2 and q1 alternate at one end of the overlapping region, for example, at the end near the fourth bus portion 1202, and the second period pitches q1 and q2 alternate at the other end of the overlapping region, for example, at the end near the third bus portion 1201.

In at least one embodiment, as shown in fig. 23, in the minimum period unit P of the first interdigital electrode 11, the period length is p1+p2, and in the minimum period unit Q of the second interdigital electrode 12, the period length is q1+q2, wherein p1+p2 is equal to q1+q2.

In at least one embodiment, each interdigitated electrode may comprise a plurality of segmented fingers in a minimum periodic unit, and the segmentation may be varied. For example, in the same interdigital electrode, the dislocation distance of the fingers of two segments is different, or the period interval formed after the segments is different, or the width of each segment of the same value is different. For example, as shown in fig. 24, in the first interdigital electrode 11, in one minimum period unit P, the second finger 112-1 and the second finger 112-2 are two-segmented fingers, the period spacing between the second finger 112-1 and the adjacent first finger is P1 and P2, the period spacing between the second finger 112-2 and the adjacent first finger is P3 and P4, and P1 is not equal to P2 and P3 is not equal to P4. In the second interdigital electrode 12 corresponding to the first interdigital electrode 11, in one minimum period unit Q, the fourth finger 122-1 and the fourth finger 122-2 are two-segmented fingers, the period spacing between the fourth finger 122-1 and the adjacent third finger is Q1 and Q2, the period spacing between the fourth finger 122-2 and the adjacent third finger is Q3 and Q4, and Q1 is not equal to Q2 and Q3 is not equal to Q4.

In addition, in alternative embodiments, in a minimum periodic unit of the same interdigital electrode, at least one non-segmented finger is contained at the initial position, and a non-segmented finger may exist between a plurality of segmented fingers, and in addition, the segmented fingers may also be directly adjacent. The embodiment of the application does not limit the specific segmentation mode, and can be designed according to actual needs or performance requirements and the like.

In addition, the number of segments of each finger is not limited in the embodiment of the present application, and the above description has been given by taking two segments of each finger as an example, but the fingers of the upper and lower electrodes in the embodiment of the present application may be formed in more than 3 segments in a staggered manner, and the structure of the segments in the embodiment of the present application is not limited and may be designed according to actual needs or performance requirements. For example, for a finger with a center line offset of 3 or more segments, the center position of the position where each segment covers in the second direction x is taken as the center line of the entire finger, the center lines of the fingers of the upper and lower electrodes are aligned, and each segment of the corresponding finger of the upper and lower electrodes is symmetrically distributed with respect to the center line.

For example, as shown in FIG. 25, in the first interdigital electrode 11, the second finger 112-1 and the second finger 112-2 are formed in 3 segments shifted in the third direction y, for example, in the second finger 112-1, 3 segments are respectively denoted as 112-11, 112-12, 112-13, and the center line c1 of the second finger 112-1 is the center position of 112-11, 112-12, 112-13 in the second direction x; in the second interdigital electrode 12, the fourth finger 122-1 and the fourth finger 122-2 are formed to be 3 segments shifted in the third direction y, for example, in the fourth finger 122-1, 3 segments are respectively denoted as 122-11, 122-12, 122-13, and the center line c2 of the fourth finger 122-1 is the center position of 122-11, 122-12, 122-13 in the second direction x. The midline c1 and midline c2 are located at the same position in the second direction x, and the 3 segments 112-11, 112-12, 112-13 of the second finger 112-1 and the 3 segments 122-11, 122-12, 122-13 of the fourth finger 122-1 are symmetrical with respect to the midline c 1/midline c2, as viewed in the first direction z.

In addition, in alternative embodiments, at least two different numbers of segments of different fingers may be included in a single minimum period unit of the same interdigitated electrode. For example, as shown in fig. 25, in the minimum period unit P of the first interdigital electrode 11, the second finger 112-1 and the second finger 112-2 divided into 3 segments are included, and the second finger 112-3 divided into 2 segments is included, and in the minimum period unit Q of the second interdigital electrode 12, the fourth finger 122-1 and the fourth finger 122-2 divided into 3 segments are included, and the fourth finger 122-3 divided into 2 segments is also included.

According to the embodiment of the application, the widths of the fingers of the interdigital electrodes at the two sides of the film are different or the period intervals are different, so that the coupling of an electric field generated by the upper electrode and the lower electrode and the modal coupling are restrained, parasitic modes are reduced, and the performance of the resonator is improved.

The inventors have also simulated some performance metrics of resonators of some embodiments of the present application by finite element simulation, and fig. 26 to 28 are electrical response curves of resonators obtained from finite element simulation.

The structural parameters of the comparative resonator are set as follows: the thickness of the piezoelectric layer is 0.5um, the period pitch p=4um, the widths of the fingers of the interdigital electrodes on the upper side and the lower side are m=800 nm, and as a simulation result, as shown in fig. 26, a parasitic mode appears near the frequency fs, and two parasitic modes appear near the frequency fp.

The simulation structure parameters of one implementation mode of the embodiment of the application are set as follows: the piezoelectric layer thickness is 0.5um, the period pitch p=4um, the finger width of one side of the interdigital electrode is m2=800 nm, the finger width of the other side of the interdigital electrode is m1=kxm2, where k is smaller than 1, for example, k is 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, respectively, and the simulation results obtained are shown in fig. 27. Wherein when k=0.95, both spurious modes closest to the frequency fs and fp can be significantly reduced, and when k=0.9 to 0.75, the spurious modes closest to the left of the frequency fs are substantially eliminated.

In at least one embodiment, the widths of the fingers of the upper and lower interdigitated electrodes differ by less than 25%, e.g., the widths of the fingers of the upper and lower interdigitated electrodes differ by less than 5%.

The simulation structure parameters of another implementation mode of the embodiment of the application are set as follows: the center of the upper and lower electrodes was shifted based on the comparison resonator, and the shift Δm was 20nm, 40nm, 60nm, 80nm, 100nm, and 150nm, respectively, and the simulation results obtained are shown in fig. 28. Wherein when the offset Δm is small, for example Δm=20 nm, i.e., the offset Δm is 2.5% of the width m of the finger of the interdigital electrode, both spurious modes closest to the frequency fs and the frequency fp can be significantly reduced; when the offset Δm is large, for example, Δm=80 nm (10% ×m), the spurious mode on the left side of the frequency fs gradually shifts to the right to mix into the frequency fs, thereby deteriorating Rs (impedance at the series resonance frequency), and when the offset Δm is larger, for example, Δm=100 nm (12.5% ×m), a significant spurious mode occurs between the frequency fs and the frequency fp.

In at least one embodiment, the offset Δm of the centers of the corresponding fingers of the upper and lower interdigital electrodes is 10% or less of the width of the finger of any interdigital electrode, for example, the offset Δm is 5% or less of the width of the finger of any interdigital electrode.

According to the embodiment of the first aspect of the application, the width of the fingers of the interdigital electrodes at two sides of the film is different or the periodic intervals are different, so that the coupling of an electric field generated by the upper electrode and the lower electrode and the modal coupling are restrained, parasitic modes are reduced, and the performance of the resonator is improved.

Embodiments of the second aspect

An embodiment of the second aspect of the present application provides a filter including the thin film bulk acoustic resonator according to the embodiment of the first aspect, and since in the embodiment of the first aspect, the structure and features of the thin film bulk acoustic resonator have been described in detail, the contents thereof are incorporated herein and the description thereof is omitted herein.

In addition, the filter according to the embodiment of the present application may further include other electronic devices, for example, a capacitor, an inductor, a resistor, etc., as required, and the selection of these electronic devices may refer to the related art, which is not limited by the embodiment of the present application.

In addition, the filter of the embodiment of the application can be applied to communication equipment conforming to the fifth-generation mobile communication standard, for example, can be applied as a radio frequency front-end filter.

According to the embodiment of the second aspect of the application, the width of the fingers of the interdigital electrodes at two sides of the film or the periodic interval is different, so that the coupling of an electric field generated by the upper electrode and the lower electrode and the modal coupling are restrained, parasitic modes are reduced, the performance of the resonator is improved, and a high-frequency and large-bandwidth filter is realized.

The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the application, and is not meant to limit the scope of the application, but to limit the application to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the application are intended to be included within the scope of the application.

Claims

1. A thin film bulk acoustic resonator excited by a transverse electric field, the thin film bulk acoustic resonator comprising a substrate and a piezoelectric film laminated in a first direction, characterized in that,

The thin film bulk acoustic resonator further includes:

An acoustic reflection layer formed between the substrate and the piezoelectric film; and

A first interdigital electrode formed on a surface of the piezoelectric film facing the acoustic reflection layer and a second interdigital electrode formed on a surface of the piezoelectric film remote from the acoustic reflection layer, the second interdigital electrode being disposed opposite to the first interdigital electrode in the first direction;

The first interdigital electrode comprises first fingers and second fingers which are alternately arranged along a second direction, the first fingers are connected with a first polarity voltage, the second fingers are connected with a second polarity voltage, the second polarity voltage is opposite to the first polarity voltage in polarity, and the second direction is perpendicular to the first direction;

the second interdigital electrode comprises third fingers and fourth fingers which are alternately arranged along the second direction, the third fingers are connected with the first polarity voltage, and the fourth fingers are connected with the second polarity voltage;

The first finger of the first interdigital electrode is arranged corresponding to the third finger of the second interdigital electrode, and the second finger of the first interdigital electrode is arranged corresponding to the fourth finger of the second interdigital electrode;

Adjacent first and second fingers of the first interdigital electrode have a first periodic pitch in the second direction, adjacent third and fourth fingers of the second interdigital electrode have a second periodic pitch in the second direction,

The width of at least one finger of the first interdigital electrode is not equal to the width of the corresponding finger of the second interdigital electrode, and/or,

At least one of the total first periodic pitches of the first interdigital electrodes is not equal to the corresponding second periodic pitch of the second interdigital electrodes.

2. The thin film bulk acoustic resonator according to claim 1, characterized in that,

The first periodic interval of the first interdigital electrode is equal to the corresponding second periodic interval of the second interdigital electrode, and the width of at least one finger of the first interdigital electrode is larger than the width of the corresponding finger of the second interdigital electrode.

3. The thin film bulk acoustic resonator according to claim 2, characterized in that,

The first period spacing of the first interdigital electrode is equal to the corresponding second period spacing of the second interdigital electrode, and the width of any one finger of the first interdigital electrode is larger than the width of the corresponding finger of the second interdigital electrode.

4. The thin film bulk acoustic resonator according to claim 2, characterized in that,

The first periodic interval of the first interdigital electrode is equal to the corresponding second periodic interval of the second interdigital electrode, the width of a part of fingers of the first interdigital electrode is larger than the width of corresponding fingers of the second interdigital electrode, and the width of fingers other than the part of fingers of the first interdigital electrode is smaller than the width of corresponding fingers of the second interdigital electrode.

5. The thin film bulk acoustic resonator according to claim 1, characterized in that,

The widths of the fingers corresponding to the first interdigital electrode and the second interdigital electrode are equal,

The sum of first number of adjacent first period pitches of the first interdigital electrode is equal to the sum of corresponding first number of second period pitches of the second interdigital electrode, at least one of the first number of first period pitches is not equal to the corresponding second period pitch, and the first number is more than 2.

6. The thin film bulk acoustic resonator according to claim 5, characterized in that,

The widths of the first finger and the second finger of the first interdigital electrode are equal, and the widths of the third finger and the fourth finger of the second interdigital electrode are equal.

7. The thin film bulk acoustic resonator according to claim 5, characterized in that,

At least one of the first number of first periodic intervals is not equal to the other first periodic intervals.

8. The thin film bulk acoustic resonator according to claim 1, characterized in that,

The width of at least one finger of the first interdigital electrode is greater than the width of the corresponding finger of the second interdigital electrode,

9. The thin film bulk acoustic resonator according to claim 1, characterized in that,

At least one pair of adjacent fingers of the first interdigital electrode are relatively inclined along a third direction, and the third direction is perpendicular to the first direction and the second direction;

Adjacent fingers of the second interdigital electrode corresponding to the at least one pair of adjacent fingers that are not parallel in the first interdigital electrode are relatively inclined in the third direction, and are opposite to the inclination direction of the at least one pair of adjacent fingers in the first interdigital electrode.

10. The thin film bulk acoustic resonator according to claim 1, characterized in that,

At least one finger of the first interdigital electrode is formed in a staggered manner in the second direction,

The second interdigital electrode is formed with a dislocation in the second direction, and the direction of the dislocation of the second interdigital electrode is opposite to that of the first interdigital electrode.

11. The thin film bulk acoustic resonator according to any of claims 1 to 10, characterized in that,

The piezoelectric thin film is formed of a single crystal piezoelectric material.

12. The thin film bulk acoustic resonator of claim 11, wherein,

The single crystal piezoelectric material is lithium niobate or lithium tantalate.

13. The thin film bulk acoustic resonator according to any of claims 1 to 10, characterized in that,

The acoustic reflection layer is a cavity or a Bragg reflection layer.

14. A filter comprising the thin film bulk acoustic resonator of any one of claims 1 to 13.