CN109889178B - bulk acoustic wave resonator - Google Patents

Abstract

The invention provides a bulk acoustic wave resonator which comprises a substrate, an acoustic mirror structure, a lower electrode, a piezoelectric film structure and an upper electrode which are sequentially arranged from bottom to top, wherein the upper surface and/or the lower surface of the upper electrode and/or the lower electrode is/are provided with an auxiliary structure, and the auxiliary structure is provided with a bulge or a recess in the direction vertical to the surface of the upper electrode.

Description

bulk acoustic wave resonator

technical field

The invention relates to the technical field of semiconductors, in particular to a bulk acoustic wave resonator.

Background technique

The traditional top view structure of a bulk acoustic wave resonator is shown in Figure 1, and the cross-sectional structure in Figure 2 can be obtained by cutting along the broken line AOA' in Figure 1. The basic structure of the bulk acoustic wave contained in Figure 1 and Figure 2 includes the substrate SUB, The acoustic mirror structure AM embedded on the substrate, the lower electrode BE located on the substrate and the acoustic mirror, the piezoelectric film structure PZ located on the lower electrode and the substrate, and the upper electrode TE located on the piezoelectric film. FIG. 1 also includes a lower electrode pin BEC and an upper electrode pin TEC, which are not shown in FIG. 2 .

The ideal working state of the bulk acoustic wave resonator is: when the upper and lower electrodes TE and BE are applied with RF input voltage, the piezoelectric film PZ will generate mechanical vibration in piston mode in response to the voltage, thereby converting electrical energy into mechanical energy. However, in the actual working state of the bulk wave resonator with the traditional structure, in addition to the vibration of the piston mode, a large number of spurious mode vibrations (clutter) will be generated, and the existence of clutter will occupy considerable energy and cause resonance The quality factor (Q value) of the resonator deteriorates, and the performance of the filter composed of multiple resonators will also be greatly reduced.

Contents of the invention

In view of this, the present invention provides a bulk acoustic wave resonator capable of reducing clutter and having a higher quality factor.

The bulk acoustic wave resonator of the present invention includes a substrate, an acoustic mirror structure, a lower electrode, a piezoelectric thin film structure, and an upper electrode arranged sequentially from bottom to top, and the upper surface and/or lower surface of the upper electrode and/or the lower electrode have The subsidiary structure has protrusions or depressions in a direction perpendicular to the surface of the upper electrode.

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Optionally, the height of the protrusion or the depth of the depression ranges from

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Optionally, the distribution form of the protrusions or depressions of the auxiliary structure has the following characteristics: it has a minimum unit cell structure, the unit cells are distributed along a straight line, and each unit cell is distributed in at least two different directions. It is distributed periodically.

Optionally, the unit cell has a central circle and three peripheral circles, and the three peripheral circles and the central circle are connected by three rod-shaped structures. Periodically distribute in the direction of the three connecting lines at the center of the circle.

Optionally, the unit cell has a central circle and six uniformly radially distributed identical rod-shaped structures, and the unit cell is periodically distributed along the three straight lines where the six rod-shaped structures are located.

Optionally, the distribution form of the protrusions or depressions of the auxiliary structure has the following characteristics: it has a minimum unit cell structure, and the unit cells are distributed in a plane along the trajectory of concentric closed curves.

Optionally, the distribution form of the protrusions or depressions of the auxiliary structure has the following characteristics: it has a minimum unit cell structure, and the unit cells are distributed in a plane along the trajectory of concentric closed curves.

Optionally, the concentric closed curves are concentric circles.

Optionally, the distribution form of the protrusions or depressions of the auxiliary structure has the following characteristics: it has a minimum unit cell structure, and the unit cells are planarly distributed along the trajectory of a helical curve or a helical broken line.

Optionally, in the distribution form of the protrusions or depressions of the auxiliary structures, the unit cells lack preset regularity.

Optionally, the duty cycle of the graphics of the auxiliary structure ranges from 5% to 95%.

Optionally, the base material includes: single crystal silicon, gallium arsenide, quartz or sapphire.

Optionally, the materials of the upper electrode and the lower electrode include: molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites or alloys of the above metals.

Optionally, the material of the auxiliary structure includes: silicon dioxide, aluminum nitride, silicon nitride, silicon carbide, polymer, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium , chromium or the composite of the above metals or their alloys.

Optionally, the material of the piezoelectric layer includes: aluminum nitride, zinc oxide, lead zirconate titanate, doped aluminum nitride, and doped zinc oxide, and the piezoelectric layer is doped with one of the following elements or more: scandium, yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium.

The bulk acoustic wave resonator of the present invention suppresses the parasitic vibration mode in the resonator by adding an auxiliary structure to the upper and lower surfaces of the electrodes of the resonator, and changing the structure of the upper surface of the piezoelectric film, so as to improve the Q value of the resonator and improve The purpose of the performance of resonators and filters or other electronic devices composed of them. At the same time, the auxiliary structure also functions to adjust the vibration frequency of the resonator.

Description of drawings

The accompanying drawings are used to better understand the present invention, and do not constitute improper limitations to the present invention. in:

Fig. 1 is a top view of a traditional structure of a bulk acoustic wave resonator;

Fig. 2 is a sectional view of a traditional structure of a bulk acoustic wave resonator;

Fig. 3 is a schematic diagram of the auxiliary structure of the bulk acoustic wave resonator according to the embodiment of the present invention located on the upper surface of the upper electrode;

Fig. 4 is a schematic diagram of the auxiliary structure of the bulk acoustic wave resonator according to the embodiment of the present invention located at the lower surface of the upper electrode;

Fig. 5 is a schematic diagram of the auxiliary structure of the bulk acoustic wave resonator according to the embodiment of the present invention located on the upper surface and the lower surface of the upper electrode;

Fig. 6 is a schematic top view of the additional structure of the upper electrode with a pattern of the bulk acoustic wave resonator according to the embodiment of the present invention;

Fig. 7a is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the first embodiment;

Figure 7b is the projection of the unit cell pattern in the case of full close-packing without defects corresponding to Figure 7a;

Fig. 8 is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the second embodiment;

Fig. 9 is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the third embodiment;

Fig. 10 is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the fourth embodiment;

Fig. 11 is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the fifth embodiment;

Figure 12a is a schematic diagram of a single helix;

Figure 12b is a schematic diagram of five helices;

Figure 13a is a schematic diagram of a unit cell with helically distributed strip-shaped protrusions or depressions with a constant width;

Fig. 13b is a schematic diagram of a unit cell with helically distributed strip-shaped protrusions or depressions with gradually changing widths.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Orientation or position indicated by "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. The relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, therefore It should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may include direct contact between the first and second features, and may also include the first and second features Not in direct contact but through another characteristic contact between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

The bulk acoustic wave resonator of the embodiment of the present invention includes a substrate, an acoustic mirror structure, a lower electrode, a piezoelectric film structure, and an upper electrode arranged in order from bottom to top, wherein the upper surface and/or lower surface of the upper electrode and/or the lower electrode The surface has subsidiary structures having protrusions or depressions in a direction perpendicular to the surface of the upper electrode.

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优选范围

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类似的，也可以在下电极的上表面和/或下表面设置附属结构。Specifically, in the resonator structure shown in FIG. 3 , the additional layer MLU1 is located on the upper surface of the upper electrode TE. In the resonator structure shown in FIG. 4 the additional layer MLL2 is located between the lower surface of the top electrode TE2 and the piezoelectric layer. In the resonator structure shown in FIG. 5, the additional layers MLU3 and MLL3 are located on the upper surface and the lower surface of the upper electrode TE3, respectively. Wherein the auxiliary structure has a convex or concave shape in a direction perpendicular to the surface of the upper electrode. Raised height or sunken depth ranges from

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preferred range

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Similarly, subsidiary structures may also be provided on the upper surface and/or the lower surface of the lower electrode.

As shown in Figure 6, the upper electrode of the resonator with the electrode auxiliary structure according to the embodiment of the present invention has an additional structure TEM, and the additional structure has a certain concave-convex pattern (the partial shadow pattern of the TEM is only a schematic illustration and does not represent a specific figure) . This type of pattern can effectively weaken the standing wave formed by the spurious mode, thereby greatly reducing the energy loss caused by the spurious mode.

It can be seen from the above that the bulk acoustic wave resonator of the embodiment of the present invention suppresses the parasitic vibration mode in the resonator by adding an auxiliary structure to the upper and lower surfaces of the upper electrode of the resonator, and changing the structure of the upper surface of the piezoelectric film, so as to improve the resonator. The Q value, and the purpose of improving the performance of resonators and filters or other electronic devices composed of them. At the same time, the auxiliary structure added to the upper electrode also functions to adjust the vibration frequency of the resonator.

The distribution forms of the protrusions or depressions of the subsidiary structures can be specifically divided into three types: periodic distribution, concentric distribution, and spiral distribution. The following describes in detail in conjunction with specific embodiments.

(1) Periodic distribution

This type of distribution form has a minimum "unit cell" structure, and the unit cells are distributed along a straight line, and each unit cell is periodically distributed in at least two different directions. At the same time, a "defect" mode can be introduced into this type of distribution, that is, some unit cells are removed from the pattern according to certain rules or requirements.

(1) Fig. 7a is a schematic diagram of the distribution form of the protrusions or depressions of the auxiliary structure of the first embodiment. In Fig. 7a, the unit cell EU1 has a central circle and three peripheral circles, and the three peripheral circles and the central circle are connected by three rod-like structures. The unit cells are periodically distributed along the three connecting lines between the center of the central circle and the centers of the three surrounding circles, namely the directions DR1, DR2 and DR3 shown in the figure.

Optionally, the radii of the three peripheral circles are not necessarily identical, and the centers of the three peripheral circles may form any triangle.

Optionally, the size of the circles in the unit cell, the distance between the centers of the circles and the width of the rod-like structures are all greater than 1 μm, preferably in the range of 0.5-1.5 times the wavelength of the acoustic wave.

Optionally, the spatial period of the periodic distribution of the unit cells along the three connecting lines between the center of the central circle and the centers of the three peripheral circles is greater than 1 μm, preferably in the range of 0.5-1.5 times the wavelength of the acoustic wave.

Alternatively, the unit cell pattern may be convex or concave relative to materials outside the pattern along a direction perpendicular to the surface of the upper electrode.

Optionally, defect modes can also be introduced, for example, the unit cells shown by the dotted lines in FIG. 7 are eliminated.

Optionally, in order to obtain better device performance, the duty ratio R of the unit cell can be regulated. Fig. 7b is the projection of the unit cell pattern corresponding to Fig. 7a in the case of full close packing without defects. As shown in FIG. 7 b , the total area of the rectangular range is A0, and the total area of the unit cell shadow is A1, then the duty ratio R is defined by the following formula: R=A1/A0. A preferred value range of the duty ratio R is 5%-95%. When the duty ratio R is lower than 50%, the pattern is a convex structure, and when the duty ratio R is higher than 50%, the pattern is a concave structure.

(2) FIG. 8 is a schematic diagram of the distribution form of protrusions or depressions of the auxiliary structure of the second embodiment. In FIG. 8 , the unit cell EU2 has a central circle and six identical rod-shaped structures distributed radially on average, and the unit cell is periodically distributed along the three straight lines where the six rod-shaped structures are located. The specific address, as shown in Figure 8, shows that all the circles in the figure are congruent, and the centers of the three nearest adjacent circles, such as points A, O, and B, form an equilateral triangle, and the two nearest adjacent circles are formed by The rod-shaped structures are connected; the polygon ABCDEF and the polygon GHIJKL are regular hexagons, and each vertex of the hexagon GHIJKL, such as point H, is the center of the regular triangle where it is located, such as triangle AOB. The shaded part is bounded by circles, hexagonal GHIJKL and some rod-like structure edges. The unit cell of A200 repeats periodically along the direction connecting the center O and the three vertices A, B, and C of the hexagon, namely DR1, DR2, and DR3.

Optionally, the diameter of the circles, the distance between the centers of the two closest adjacent circles and the width of the rod-like structure are greater than 1 μm, preferably in the range of 0.5-1.5 times the wavelength of the acoustic wave.

Alternatively, the unit cell pattern may be convex or concave relative to materials outside the pattern along a direction perpendicular to the surface of the upper electrode.

Optionally, defect modes may also be introduced, such as removing several island structures indicated by dotted lines in FIG. 8 .

(2) Concentric distribution

This type of distribution contains several concentric ring structures, and the ring structures are used as the arrangement track of the unit cell. The top view shape of the unit cell can be circular, elliptical, polygonal, or other special shapes surrounded by curves, and the direction perpendicular to the surface of the upper electrode can be columnar protrusions or depressions. At the same time, a "defect" mode can be introduced into this type of distribution, that is, some unit cells are removed from the pattern according to certain rules or requirements.

(1) FIG. 9 is a schematic diagram of the distribution of protrusions or depressions of the auxiliary structure of the third embodiment. In Fig. 9, the distribution track of the unit cell UE3 is a series of concentric circles Cn. It should be noted that although the unit cell EU3 is represented by a circle, it does not represent a specific pattern of the unit cell. The actual desirable patterns of unit cells include circles, ellipses, various polygons, various rings and special-shaped closed curves, and combinations of the above shapes.

It should be noted that since the boundary of the upper electrode is usually not a circle, but a polygonal or closed curve TEB1 as shown in Figure 9, when the unit cells are arranged along the circumference CM1, the The unit cells are eliminated, and only the unit cells within the boundary TEB1 are kept.

Optionally, the innermost circle in the concentric circle family of unit cell arrangement loci is denoted as C ₀ , and its radius is denoted as R ₀ . The circles from inside to outside are C1, C2, C3, etc., and their radii are R1, R2, R3, etc. in turn. The radius of a certain circle Cn is Rn, and the difference between the radii of two adjacent circles increases or remains unchanged as n increases, that is, R _n+1 -R _n ≤ _{R n+2} -R _n+1 , n=0,1,2...

Optionally, the relationship between the radius Rn of a certain circle Cn and the number of turns n can be controlled by the following mathematical formula:

(a) Power function type (including linear type)

R _n =R ₀ ×(n+1) ^r , n=0,1,2...

Where R ₀ is the radius of the innermost circle, ranging from 2 to 30 μm; or the area of the circle with R ₀ as the radius does not exceed half of the area of the resonator.

r is used to control the speed at which the radius of the circle expands with the number of turns, and it can be a real number not less than 1. When r=1, the radius of the circle varies linearly.

(b) Exponential

R _n =R ₀ exp(kn),n=0,1,2...

Where R ₀ is the radius of the innermost circle in the range of 2-30 μm; or the area of the circle with R ₀ as the radius does not exceed half the area of the resonator.

k is used to control the speed at which the radius of the circle expands with the number of turns, and it can be a real number greater than 0.

If there are P _n unit cells arranged on a circular trajectory C _n with a radius R _n , then the unit cell density D _n on the circular trajectory is defined as:

D _n =P _n /(2πR _n )

Also make sure the following relationship holds:

Dn _{+ 1≤Dn}

That is to ensure that the unit cell density does not increase from the inside to the outside.

A300 can also introduce defect modes, such as selectively removing several unit cells or a few complete circles of unit cells, for example, removing all unit cells on the unit cell arrangement track intercepted by the upper electrode boundary.

(2) FIG. 10 is a schematic diagram of the distribution form of protrusions or depressions of the accessory structure of the fourth embodiment. In FIG. 10 , the cell arrangement tracks CM2 and TEB2 closest to the upper electrode edge TEB2 have similar shapes, and then gradually change in shape inwardly, and become circular in the area close to the center. The maximum distance from the center of each circle arrangement track Cn is Rn, and its variation law is the same as that of the third embodiment. The definition and requirements of the unit cell density Dn are the same as those in the third embodiment. The unit cell top view shape, concavo-convex conditions and size requirements are the same as those of the third embodiment.

(3) Spiral distribution

In this type of distribution, the unit cells are arranged along the spiral curve extending clockwise or counterclockwise from the center and the area near the center. The top view shape of the unit cell can be surrounded by circles, ellipses, polygons, or other curves. Irregular shape, which can be columnar protrusions or depressions in the direction perpendicular to the surface of the upper electrode. At the same time, a "defect" mode can be introduced into this type of distribution, that is, some unit cells are removed from the pattern according to certain rules or requirements.

(1) FIG. 11 is a schematic diagram of the distribution of protrusions or depressions of the accessory structure of the fifth embodiment. In Fig. 11, the arrangement track of the unit cell EU5 is a continuous smooth helix HL3. Wherein, the distance between adjacent spirals satisfies: DT _n ≤ _{DT n+1} , and the intercellular distance satisfies: S _n ≤ _{S n+1} .

Alternatively, the spiral shape can be determined by equations in polar coordinates. The specific form of the equation can be divided into:

(a) Constant velocity spiral type (Archimedes spiral)

ρ＝P ₀ +Pθ

Among them, ρ is the distance from a certain point on the spiral to the pole, θ is the angle formed between the above distance and the horizontal direction, the P ₀ parameter is used to control the distance from the starting point of the spiral to the pole, and the P parameter is used to control the pitch of the spiral. The range of P ₀ is 0-30 μm, or the area of a circle with P ₀ as the radius does not exceed half the area of the resonator, and the range of P is 0.3-8 μm.

(b) Logarithmic spiral

ρ=Qexp(λθ)

Among them, ρ is the distance from a certain point on the spiral to the pole, θ is the angle formed between the above distance and the horizontal direction, and the parameters Q and λ determine the change of the pitch of the spiral. The range of Q is 0-30μm (not including 0), the range of λ is 0-50, the preferred range is 0-20 (not including 0), or the area of the circle with Q as the radius does not exceed half the area of the resonator

Other optional mathematical forms of the spiral include: golden spiral, chain spiral, hyperbolic spiral and so on.

It should be noted that the number M of spirals can be greater than 1, which can be obtained by rotating a single spiral around the center by a certain angle. Examples of the two cases of M=2 and M=5 are shown in Fig. 12a and Fig. 12b respectively.

Optionally, defect modes can also be introduced, for example, only all unit cells up to the first intersection of each helix with boundary TEB3 can be retained.

(2) The unit cells are distributed along the segmented helical curve or helical broken line, which can be continuous distribution or discrete distribution. The distribution locus is similar to the shape of the edge near the edge TEB4 of the electrode, and gradually becomes a zigzag shape toward the center.

In this embodiment, the continuous distribution of unit cells forms a strip-shaped protrusion or depression structure, and the width DS1 of the strip-shaped structure can always remain unchanged, as shown in Figure 13a; or the width DS2 of the strip-shaped structure gradually becomes thinner from the center to the outside, as shown in FIG. Figure 13b shows. Wherein the width of the strip structure is greater than 1 μm, preferably in the range of 0.5 to 1.5 times the wavelength of the acoustic wave. If the form of discrete distribution of unit cells is adopted, the size of a single unit cell remains unchanged or gradually decreases from the inside to the outside.

In the bulk acoustic wave resonator of the embodiment of the present invention, the material composition of each structure may be as follows:

The material of the substrate can be: single crystal silicon (preferred), gallium arsenide, quartz, sapphire, etc.

The material of the upper and lower electrodes can be: molybdenum (preferably), ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, etc. or composites or alloys of the above metals.

The material of the auxiliary structure can be selected from one or more of the electrode materials or their alloys, and non-metallic materials such as silicon dioxide, aluminum nitride, silicon nitride, silicon carbide, and polymers can also be selected.

The material of the piezoelectric layer (especially the active region of the piezoelectric layer) can be: aluminum nitride (preferred), zinc oxide, lead zirconate titanate, doped aluminum nitride or zinc oxide with a certain atomic ratio. The above material is a piezoelectric film with a thickness less than 10 microns. The aluminum nitride thin film is in polycrystalline or single crystal form, and is grown by thin film sputtering (sputtering) or metal organic chemical vapor deposition (MOCVD).

Wherein the piezoelectric layer is doped with one or more of the following elements: scandium (preferred), yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, Erbium, Thulium, Ytterbium, Lutetium.

The above specific implementation methods do not constitute a limitation to the protection scope of the present invention. It should be apparent to those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. A bulk acoustic wave resonator, comprising a substrate, an acoustic mirror structure, a lower electrode, a piezoelectric thin film structure, and an upper electrode arranged sequentially from bottom to top, it is characterized in that the upper surface of the upper electrode and/or the lower electrode and /or the lower surface has an auxiliary structure, and in the direction perpendicular to the surface of the upper electrode, the auxiliary structure has protrusions or depressions, wherein the distribution form of the protrusions or depressions of the auxiliary structure has the following characteristics: has a minimal unit cell structure, the unit cells are planarly distributed along a straight line trajectory, and each of the unit cells is periodically distributed in at least two different directions; or, have a minimal unit cell structure that is planarly distributed along the trajectory of concentric closed curves; or, It has a minimum unit cell structure, and the unit cells are distributed in a plane along the trajectory of a helical curve or a helical broken line. 2. The bulk acoustic wave resonator according to claim 1, wherein the height of the protrusion or the depth of the depression ranges from 50Å to 500Å. 3. The bulk acoustic wave resonator according to claim 1, characterized in that, the distribution form of the protrusions or depressions in the auxiliary structure is: a minimum unit cell structure, and the unit cells are distributed in a plane along a straight line track, And when each of the unit cells is periodically distributed in at least two different directions, the unit cell has a central circle and three peripheral circles, and the three peripheral circles and the central circle are composed of three Each rod-like structure is connected, and the unit cells are periodically distributed along the three connecting center lines of the center of the central circle and the centers of the three surrounding circles. 4. The bulk acoustic wave resonator according to claim 1, characterized in that, the distribution form of the protrusions or depressions in the auxiliary structure is: a minimum unit cell structure, and the unit cells are distributed in a plane along a straight line track, And when each of the unit cells is periodically distributed in at least two different directions, the unit cells have a central circle and six uniformly radially distributed identical rod-shaped structures, and the unit cells along the The three straight-line directions where the six rod-like structures are located are periodically distributed. 5. The bulk acoustic wave resonator according to claim 1, characterized in that, the distribution form of the protrusions or depressions in the auxiliary structure is to have a minimum unit cell structure, and the unit cell proceeds along the trajectory of the concentric closed curve. In the case of distribution: the concentric closed curves are concentric circles. 6 . The bulk acoustic wave resonator according to claim 1 , characterized in that, in the distribution form of the protrusions or depressions of the subsidiary structures, the unit cell has a lack of preset regularity. 7 . 7. The bulk acoustic wave resonator according to claim 1, characterized in that, the duty cycle of the pattern of the auxiliary structure ranges from 5% to 95%. 8. The bulk acoustic wave resonator according to claim 1, wherein the base material comprises: single crystal silicon, gallium arsenide, quartz or sapphire. 9. The bulk acoustic wave resonator according to claim 1, wherein the materials of the upper electrode and the lower electrode include: molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium , chromium or the composite of the above metals or their alloys. 10. The bulk acoustic wave resonator according to claim 1, wherein the material of the auxiliary structure comprises: silicon dioxide, aluminum nitride, silicon nitride, silicon carbide, polymer, molybdenum, ruthenium, gold , aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys. 11. The bulk acoustic wave resonator according to claim 1, wherein the material of the piezoelectric layer comprises: aluminum nitride, zinc oxide, lead zirconate titanate, doped aluminum nitride, doped zinc oxide, The piezoelectric layer is doped with one or more of the following elements: scandium, yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, Thulium, ytterbium, lutetium.

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