CN111342800A - Bulk acoustic wave resonator with discrete structure, filter, and electronic device - Google Patents
Bulk acoustic wave resonator with discrete structure, filter, and electronic device Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
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- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
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Abstract
Bulk acoustic wave resonators with discrete structures, filters, and electronics. The invention relates to a bulk acoustic wave resonator comprising: a substrate; an acoustic mirror; a bottom electrode disposed on an upper side of the substrate; a top electrode; and a piezoelectric layer disposed over the bottom electrode and between the bottom electrode and the top electrode, wherein: the overlapped area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the substrate is an effective area of the resonator; the resonator further comprises at least one discrete structure, the discrete structure is located on the inner side of the effective area and extends along the edge of the effective area in a strip shape, and each discrete structure comprises a plurality of discrete units. The invention also relates to a filter with the resonator and an electronic device with the filter or the resonator.
Description
Technical Field
Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a filter having the resonator, an electronic device having the filter, and a method of increasing parallel impedance of the resonator.
Background
With the rapid development of wireless mobile communication technology, the application field of the bulk acoustic wave device is more and more extensive. The film bulk acoustic wave resonator (FBAR for short) has the advantages of high resonant frequency, high quality factor, high power bearing capacity, low power consumption, low price and the like, and the bulk acoustic wave filter and the duplexer are formed by cascading the film bulk acoustic wave resonators, have the advantages of high working frequency, low insertion loss, high steep drop, high power bearing capacity and the like, and are generally considered to be the best scheme for replacing surface acoustic wave devices to solve the high-density frequency band duplexer of wireless communication in recent years.
The top view structure of the thin film piezoelectric acoustic resonator is shown in fig. 1A, and includes a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and an acoustic wave reflection structure 110 located below the bottom electrode. Fig. 1B is a cross-sectional view taken along a-a' in fig. 1A, in which a resonator body portion has a sandwich structure, and the principle is that resonance at a certain frequency is generated by using an inverse piezoelectric effect of a piezoelectric thin-film material.
The bulk acoustic wave resonator generally has two resonant frequencies, a frequency point with the minimum impedance is defined as a series resonant frequency fs, the corresponding impedance is defined as a series impedance Rs, a frequency point with the maximum impedance is defined as a parallel resonant frequency fp, the corresponding impedance is defined as a parallel impedance Rp, and the medium-voltage and medium-voltage conversion efficiency of the resonator is measured through an effective electromechanical coupling coefficient. In general, the series resonance frequency of the resonators determines the center frequency of the filter, while the effective electromechanical coupling coefficients of the resonators determine the maximum bandwidth achievable by the filter, and the series and parallel impedances of the resonators determine the pass-band insertion loss and return loss. In general, the higher the parallel impedance Rp of the resonator, the lower the series impedance Rs, and the better the passband insertion loss of the corresponding filter. Therefore, how to improve the performance of the resonator, especially the parallel impedance Rp of the resonator, is an important and fundamental issue in the design of the filter.
Ideally (the resonance region is infinite), the thin film bulk acoustic resonator excites only the principal vibration mode expanding in the longitudinal direction, as indicated by the arrow in fig. 1B. However, in practice, since the bulk acoustic wave resonator has a lateral boundary, a parasitic mode that propagates laterally is generated in the resonator, which is called a lamb wave, and a part of energy of a main vibration mode is coupled into the lamb wave. Such lamb waves may partially leak into the substrate from both sides of the resonator, thereby causing a loss of resonator energy, which is manifested in the electrical performance of the resonator as a decrease in the parallel impedance (parallel impedance Rp) or the quality factor (Qp) of the parallel resonance frequency.
Disclosure of Invention
The invention provides a technical scheme for improving the parallel impedance of a bulk acoustic wave resonator by arranging a discrete structure.
According to an aspect of an embodiment of the present invention, there is provided a bulk acoustic wave resonator including: a substrate; an acoustic mirror; a bottom electrode disposed on an upper side of the substrate; a top electrode; and a piezoelectric layer disposed on an upper side of the bottom electrode and between the bottom electrode and the top electrode, wherein: the overlapped area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the substrate is an effective area of the resonator; the resonator further comprises at least one discrete structure, the discrete structure is located on the inner side of the effective area and extends along the edge of the effective area in a strip shape, and each discrete structure comprises a plurality of discrete units.
Optionally, the discrete structure is an annular discrete structure. Further, the lateral distance of the discrete structures from the edge of the active area remains constant.
Optionally, the at least one discrete structure comprises one discrete structure. Further, the discrete structure is arranged on the upper side of the top electrode.
Optionally, the discrete units are protrusions.
Optionally, the discrete units are recesses.
Optionally, the pitch between two adjacent discrete units is 1um-10um, or is an integer multiple of the wavelength of S1 mode lamb wave at the parallel resonance frequency of the resonator.
In further embodiments, the radial and/or lateral dimensions of a single discrete element are 0.5um-6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the resonator parallel resonance frequency. Optionally, the distance from the discrete structure to the edge of the active area is 0.
Optionally, the at least one discrete structure comprises at least two discrete structures, the at least two discrete structures being spaced apart in the radial direction.
Optionally, the at least two discrete structures comprise raised discrete structures comprised of raised protrusions and/or recessed discrete structures comprised of recessed recesses.
Optionally, the pitch of two discrete structures adjacent in the radial direction is 1um to 10um in the radial direction, or is an integral multiple of the wavelength of S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
Further optionally, the pitch of adjacent discrete units of each discrete structure in the transverse direction is 1um to 10um, or is an integer multiple of the wavelength of S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
In an alternative embodiment, the radial and/or lateral dimensions of the individual discrete elements are 0.5um to 6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
Furthermore, in the two discrete structures which are adjacent in the radial direction in the transverse direction, the transverse distance between one discrete unit of one discrete structure and one discrete unit which is adjacent to the discrete unit in the other discrete structure is 0-5um, or is one fourth of the lamb wave wavelength of the S1 mode at the parallel resonance frequency of the bulk acoustic wave resonator or integral multiple thereof.
Optionally, the radial distance of the outer discrete structure from the edge of the active area is 0.
Optionally, the area of the active area of the resonator occupied by the discrete structures is no more than 20%, optionally no more than 10%, of the total area of the active area of the resonator.
Optionally, the discrete structure is disposed on the piezoelectric layer, the top electrode, or the bottom electrode; or the resonator is further provided with a passivation layer covering the top electrode, the discrete structure being arranged on the lower side of the passivation layer.
According to another aspect of embodiments of the present invention, there is provided a filter including the bulk acoustic wave resonator described above.
According to a further aspect of an embodiment of the present invention, there is provided an electronic device including the above-described filter or the above-described resonator.
The invention also relates to a method for improving the parallel impedance of the bulk acoustic wave resonator, which comprises the following steps: at least one annular discrete structure is formed on the upper side of the top electrode of the resonator around the active area of the resonator.
Drawings
These and other features and advantages of the various embodiments of the disclosed invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like parts throughout, and in which:
FIG. 1A is a schematic top view of a prior art bulk acoustic wave resonator;
FIG. 1B is a cross-sectional view taken along line A-A' of FIG. 1A;
FIG. 2A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein only one annular discrete structure is provided;
FIG. 2B is a cross-sectional view of the bulk acoustic wave resonator of FIG. 2A taken along the direction B-B' in accordance with an exemplary embodiment of the present invention;
FIG. 2C is a cross-sectional view of the bulk acoustic wave resonator of FIG. 2A taken along the direction B-B' in accordance with an exemplary embodiment of the present invention;
FIG. 2D is a schematic size diagram of the discrete structures of FIG. 2A;
figure 3A is a schematic top view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention, wherein two annular discrete structures are provided;
FIG. 3B is a cross-sectional view of the bulk acoustic wave resonator of FIG. 3A taken along the direction C-C' in accordance with an exemplary embodiment of the present invention;
FIG. 3C is a cross-sectional view of the bulk acoustic wave resonator of FIG. 3A taken along the direction C-C' in accordance with an exemplary embodiment of the present invention;
FIG. 3D is a cross-sectional view of the bulk acoustic wave resonator of FIG. 3A taken along the direction C-C' in accordance with an exemplary embodiment of the present invention;
FIG. 3E is a cross-sectional view of the bulk acoustic wave resonator of FIG. 3A taken along the direction C-C' in accordance with an exemplary embodiment of the present invention;
FIG. 3F is a schematic size diagram of the discrete structures of FIG. 3A;
figure 4A is a schematic top view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention, wherein three annular discrete structures are provided;
FIG. 4B is a cross-sectional view of the bulk acoustic wave resonator of FIG. 4A taken along the direction D-D' in accordance with an exemplary embodiment of the present invention;
FIG. 4C is a cross-sectional view of the bulk acoustic wave resonator of FIG. 4A taken along the direction D-D' in accordance with an exemplary embodiment of the present invention;
FIG. 4D is a cross-sectional view of the bulk acoustic wave resonator of FIG. 4A taken along the direction D-D' in accordance with an exemplary embodiment of the present invention;
FIG. 4E is a cross-sectional view of the bulk acoustic wave resonator of FIG. 4A taken along the direction D-D' in accordance with an exemplary embodiment of the present invention;
FIG. 4F is a cross-sectional view of the bulk acoustic wave resonator of FIG. 4A taken along the direction D-D' in accordance with an exemplary embodiment of the present invention;
FIG. 5 is a dimensional schematic of a multi-turn discrete structure according to an exemplary embodiment of the present invention;
figure 6A is a schematic top view of a bulk acoustic wave resonator in which the discrete structures are single turns and the discrete elements have a square cross-section, according to an exemplary embodiment of the present invention;
FIG. 6B is a cross-sectional view of the bulk acoustic wave resonator of FIG. 6A taken along direction E-E' in accordance with an exemplary embodiment of the present invention;
FIG. 6C is a cross-sectional view of the bulk acoustic wave resonator of FIG. 6A taken along direction E-E' in accordance with an exemplary embodiment of the present invention;
FIG. 7 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein the discrete structure is a double turn and the discrete elements have a square cross-section;
figure 8 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein the discrete structure is three turns and the discrete elements have a square cross-section;
fig. 9 is a dispersion curve of the S1 mode at the parallel resonance frequency of the bulk acoustic wave resonator.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention.
A bulk acoustic wave resonator according to an embodiment of the present invention is described below with reference to the drawings.
Figure 2A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention; figure 2B is a cross-sectional view of the bulk acoustic wave resonator of figure 2A taken along direction B-B' in accordance with one exemplary embodiment of the present invention.
Fig. 2A shows an embodiment of a bulk acoustic wave resonator in a top view. The resonator comprises a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, a single turn of a discrete annular structure 150 arranged along the edge of the active area of the resonator, the single discrete structure being arranged in a circular shape.
Figure 2B illustrates an embodiment of a bulk acoustic wave resonator in cross-section taken along top view B-B' of figure 2A. The resonator includes a substrate 100 in order in a thickness direction; an acoustic mirror 110, which is located on the upper surface of the substrate or embedded inside the substrate, and which is formed as a cavity embedded in the substrate in fig. 2B, but any other acoustic mirror structure such as a bragg reflector is equally suitable; a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and a single turn discrete annular raised structure 150 disposed inside the edge of the top electrode.
It is noted that "inside the top electrode edge" in the present invention includes the case where the discrete structure is spaced apart from the top electrode edge, and also includes the case where the discrete structure is directly disposed at the edge or has zero distance from the edge.
In the present invention, the discrete structures are composed of discrete units, such as individual depressions or protrusions.
The first acoustic impedance is arranged in the effective area of the resonator, the second acoustic impedance is arranged in the single-turn discrete ring structure 150, and the first acoustic impedance is not matched with the second acoustic impedance, so that the transversely-propagated sound waves are reflected back at the edge of the electrode, the loss of sound wave energy in the resonator is reduced, and the parallel impedance Rp value and the corresponding Q value of the resonator are improved.
The single-turn discrete loop structures 150 may also be formed as recessed structures, as shown in FIG. 2C, in a cross-sectional view taken along top view B-B' of FIG. 2A.
The dimensions of the single turn discrete loop structure are shown in fig. 2D, with L1 being the lateral dimension of the discrete cells, S1 being the spacing or space of adjacent discrete cells, W1 being the longitudinal dimension of the discrete cells, P1 being the pitch of adjacent discrete cells, and D0 being the distance of the single turn discrete loop structure from the resonator edge. In alternative embodiments: the pitch P1 between two adjacent discrete cells is sized to be 1.5um-10um, e.g., 1.5um, 8um, 10um, etc., or an integer multiple, e.g., 1, of the wavelength λ of the S1 mode lamb wave at the resonator parallel resonant frequency; the longitudinal dimension W1 of a discrete element is one quarter or an odd multiple of the corresponding lamb wave wavelength, and S1 in the figure is the pitch between adjacent discrete protrusions or depressions (i.e., between adjacent discrete elements), as an alternative example, three quarters of the corresponding lamb wave wavelength; the distance D0 of the discrete structures from the active area edge may be selected to be 0; the transverse and longitudinal dimensions of the discrete cells are equal, i.e., L1 equals W1; in alternative embodiments, the radial and/or lateral dimensions of a single discrete element are 0.5um to 6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the parallel resonant frequency. The above embodiments are merely specific exemplary examples, and combinations between the above size data are also possible, and are within the scope of the present invention.
The S1 mode lamb wave wavelength λ at the resonator parallel resonance frequency is briefly described below. As shown in fig. 9, when the bulk acoustic wave resonator is operated, a large amount of vibration is generated in the sandwich structureIf these vibrations are plotted as dispersion curves in terms of their frequency (f) and wavenumber (k), then curves of multiple modes can be obtained, of which the curve of 1 mode is called the S1 mode (the curves of the remaining modes are not shown in fig. 9), which has a dispersion curve of the shape shown in fig. 9, with the abscissa being the wavenumber and the ordinate being the vibration frequency. The vibration frequency being the parallel resonance frequency fpWhen the corresponding wave number is kpAnd the wavelength λ of the S1 mode is defined as:
it should be noted that the description of the dimensions of the single-turn annular discrete structure may also be applied to a single-turn structure in a two-turn or multi-turn annular discrete structure.
Fig. 3A shows an embodiment of a bulk acoustic wave resonator in a top view. The top electrode 140 of the resonator is provided with two circles of discrete ring structures: a first ring of discrete annular structures 160 and a second ring of discrete annular structures 162.
Figure 3B illustrates an embodiment of a bulk acoustic wave resonator in cross-section taken along top view C-C' of figure 3A. The resonator includes a substrate 100 in order in a thickness direction; an acoustic mirror 110, which is located on the upper surface of the substrate or embedded inside the substrate, and which is formed as a cavity embedded in the substrate in fig. 3B, but any other acoustic mirror structure such as a bragg reflector is equally suitable; a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and a first ring of discrete annular raised structures 160 and a second ring of discrete annular raised structures 162 disposed inboard of the top electrode edge.
The first acoustic impedance is arranged in the effective area of the resonator, the second acoustic impedance is arranged in the annular convex structure, and the first acoustic impedance is not matched with the second acoustic impedance, so that the transversely-propagated sound waves are reflected back at the edge of the electrode, the loss of sound wave energy in the resonator is reduced, and the parallel impedance Rp value and the Q value of the resonator are improved.
The first ring of discrete loop structures 160 and the second ring of discrete loop structures 162 may also be formed as recessed structures throughout, as shown in fig. 3C, which is a cross-sectional view taken along top view C-C' of fig. 3A.
The first ring of discrete ring structures 160 and the second ring of discrete ring structures 162 can also be made into different structures, as shown in fig. 3D, the first ring of discrete ring structures 160 is a convex structure, and the second ring of discrete ring structures 162 is a concave structure; alternatively, as shown in fig. 3E, the first ring of discrete annular structures 160 is a recessed structure and the second ring of discrete annular structures 162 is a raised structure.
The dimensions of the double-turn discrete loop structure are shown in fig. 3F, with L2 being the transverse dimension of the discrete elements of the second turn of discrete loop structure, S2 being the spacing or space between adjacent discrete elements of the second turn of discrete loop structure, W2 being the longitudinal dimension of the discrete elements of the second turn of discrete loop structure, and P2 being the pitch of the adjacent discrete elements of the second turn of discrete loop structure. D1 is the horizontal pitch of the discrete elements of the first turn of discrete loop structure and the adjacent discrete elements of the second turn of discrete loop structure, and D1 is the spacing of the first turn of discrete loop structure and the second turn of discrete loop structure. In an alternative embodiment: p2 is equal to P1 and is equal to the S1 mode lamb wave wavelength at the resonator parallel resonance frequency, W2 and W1 are one quarter of the corresponding lamb wave wavelength, S2 and S1 are three quarters of the corresponding lamb wave wavelength, D0 is 0, D1 is three quarters of the corresponding lamb wave wavelength, D1 is 0 or one quarter or one half of the corresponding lamb wave wavelength. Optionally, L2 is equal to W2.
Referring to fig. 3F, the radial distance W2+ D1 of the centerlines of two discrete structures may be defined as the pitch of two adjacent discrete structures in the radial direction. The pitch may be 1um to 10um, or an integer multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
The above is merely illustrative, and it is within the scope of the present invention that each discrete loop structure of the two loop structures may take other dimensions, or that the specific dimensions and combinations thereof described in the single turn discrete loop structure. Fig. 4A shows an embodiment of a bulk acoustic wave resonator in a top view. Three discrete ring structures are provided on the FBAR top electrode 140: a first turn of discrete ring structures 170, a second turn of discrete ring structures 172, and a third turn of discrete ring structures 174.
Figure 4B illustrates an embodiment of a bulk acoustic wave resonator in cross-section taken along top view D-D' of figure 4A. The resonator includes a substrate 100 in order in a thickness direction; an acoustic mirror 110, which is located on the upper surface of the substrate or embedded inside the substrate, and which is formed as a cavity embedded in the substrate in fig. 4B, but any other acoustic mirror structure such as a bragg reflector is equally suitable; the bottom electrode 120, the piezoelectric layer 130, the top electrode 140, and the first ring of discrete annular raised structures 170, the second ring of discrete annular raised structures 172, and the third ring of discrete annular raised structures 174 disposed inboard of the top electrode edge.
The first acoustic impedance is arranged in the effective area of the resonator, the second acoustic impedance is arranged in the annular convex structure, and the first acoustic impedance is not matched with the second acoustic impedance, so that the transversely-propagated sound waves are reflected back at the edge of the electrode, the loss of sound wave energy in the resonator is reduced, and the parallel impedance Rp value and the Q value of the resonator are improved.
The first ring of discrete ring structures 170, the second ring of discrete ring structures 172, and the third ring of discrete ring structures 174 may all be made as recessed structures, as shown in FIG. 4C along a cross-sectional view taken along the top view D-D' of FIG. 4A.
The first ring of discrete ring structures 170, the second ring of discrete ring structures 172, and the third ring of discrete ring structures 174 may also be made into different concave-convex structures, as shown in fig. 4D, the first ring of discrete ring structures 170 and the second ring of discrete ring structures 172 are convex structures, and the third ring of discrete ring structures 174 is a concave structure; alternatively, as shown in fig. 4E, the first ring of discrete annular structures 170 and the third ring of discrete annular structures 174 are convex structures, and the second ring of discrete annular structures 172 are concave structures; alternatively, as shown in fig. 4F, the first ring of discrete annular structures 170 is a raised structure and the second ring of discrete annular structures 172 and the third ring of discrete annular structures 174 is a recessed structure. In the invention, only a part of the combination forms are shown in the drawings, and other combination forms can be also provided, and the invention is not listed.
Example 3 lists a bulk acoustic wave resonator in which the top electrode is provided with three discrete annular structures, and four or more turns may also be provided.
The dimensions of the multi-turn discrete ring structure are shown in fig. 5, Ln is the transverse dimension of the nth turn of discrete ring structure, Sn is the interval or space between adjacent discrete units of the nth turn of discrete ring structure, Wn is the longitudinal dimension of the nth turn of discrete ring structure, and Pn is the pitch of adjacent discrete units of the nth turn of discrete ring structure. Dn-1 is the horizontal pitch of one discrete unit of the n-1 th circle of discrete ring structure and one adjacent discrete unit of the n-1 th circle of discrete ring structure, and Dn-1 is the (radial or longitudinal) spacing of the n-1 th circle of discrete ring structure and the n-1 th circle of discrete ring structure. In one optional example: pn are equal and equal to S1 mode lamb wave wavelength at the resonator parallel resonance frequency, Wn is one quarter of the corresponding lamb wave wavelength, Sn is three quarters of the corresponding lamb wave wavelength, D0 is 0, Dn-1 is three quarters of the corresponding lamb wave wavelength, and Dn-1 is 0 or one quarter or one half of the corresponding lamb wave wavelength. The above is merely exemplary, and the plurality of discrete annular structures may be other sizes. It is within the scope of the present invention that each discrete loop structure of the plurality of loop structures may take on other dimensions, or that the specific dimensions and combinations thereof described in the single turn discrete loop structures are within the scope of the present invention.
In the present invention, the size of the plurality of discrete structures may be in the form of:
for example, the pitch of two discrete structures adjacent in the radial direction is 1um to 10um in the radial direction, or is an integral multiple of the wavelength of S1 mode lamb waves at the parallel resonance frequency of the bulk acoustic wave resonator.
As another example, the pitch of adjacent discrete cells of each discrete structure in the lateral direction is 1um to 10um, or an integer multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
As another example, the radial dimension and/or lateral dimension of a single discrete element is 0.5um to 6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
Optionally, in two discrete structures adjacent in the transverse direction, in the radial direction (or in the longitudinal direction), the transverse pitch between one discrete unit of one discrete structure and one discrete unit adjacent to the discrete unit in the other discrete structure is 0-5um, or is a quarter of the lamb wave wavelength of the S1 mode at the parallel resonance frequency of the bulk acoustic wave resonator or an integral multiple thereof.
In an alternative embodiment, the discrete annular structures occupy no more than 20%, preferably less than 10%, of the total area of the resonator active area.
Optionally, the longitudinal dimension of the discrete elements is the same as the lateral dimension, i.e., Ln equals Wn.
In addition to a circular structure, the discrete ring structure on the top electrode of the film bulk acoustic wave resonator structure can also be made into a square shape, as shown in fig. 6A. 210 is a single turn discrete loop configuration.
Figure 6B illustrates an embodiment of a bulk acoustic wave resonator in cross-section taken along top view E-E' of figure 6A. The resonator includes a substrate 100 in order in a thickness direction; an acoustic mirror 110, which is located on the upper surface of the substrate or embedded inside the substrate, and which is formed as a cavity embedded in the substrate in fig. 6B, but any other acoustic mirror structure such as a bragg reflector is equally suitable; a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and a single turn discrete ring structure 210 disposed inside the top electrode edge.
The first acoustic impedance is arranged in the effective area of the resonator, the second acoustic impedance is arranged in the annular convex structure, and the first acoustic impedance is not matched with the second acoustic impedance, so that the transversely-propagated sound waves are reflected back at the edge of the electrode, the loss of sound wave energy in the resonator is reduced, and the parallel impedance Rp value and the Q value of the resonator are improved.
The single turn discrete loop structures 210 may also be formed as recessed structures, as shown in FIG. 6C, which is a cross-sectional view taken along top view E-E' of FIG. 6A.
And a two-circle, three-circle or multi-circle square discrete annular structure can also be arranged on the top electrode of the film bulk acoustic wave resonance structure. Fig. 7 is a double circle square discrete ring structure, and fig. 8 is a three circle square discrete ring structure.
In the present invention, the size of the square structure of the cross section of the protrusion or the recess is required to satisfy the same size requirement as that of the protrusion or the recess of the circular cross section. The cross-section of the discrete cells in the discrete annular structures may be other shapes besides circular or square.
In the present invention, the discrete structures may be a metal or dielectric material, or may be the same material as the piezoelectric layer or the electrode. The dielectric material may be aluminum nitride, silicon dioxide, silicon nitride, or the like. The metal may be gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), or the like.
Based on the above, the present invention provides a bulk acoustic wave resonator, comprising:
a substrate 100;
an acoustic mirror 110;
a bottom electrode 120 disposed on an upper side of the substrate 100;
a top electrode 140; and
a piezoelectric layer 130 disposed on the upper side of the bottom electrode and between the bottom electrode and the top electrode,
wherein:
the overlapping area of the acoustic mirror 110, the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140 in the thickness direction of the substrate 100 is the effective area of the resonator;
the resonator further comprises at least one discrete structure 150, 160 or 170 extending in strips inside the active area, each discrete structure comprising a plurality of discrete units. The discrete elements herein may be considered as, for example, individual protrusions or depressions.
Taking the discrete structure on the top electrode as an example, by adding the regularly distributed discrete raised or recessed structures on the inner side of the effective area of the top electrode, the structure can cause impedance mismatching at the edge of the effective area, so that sound waves are reflected back to the effective excitation area at the boundary, and therefore the sound waves are converted into a main vibration mode, energy loss in the resonator is reduced, and parallel impedance Rp is improved.
In the invention, a discrete structure is processed on, for example, a top electrode at one side or multiple edges of an effective area of the resonator, and in practice, by selecting a proper discrete structure size, acoustic waves leaked into a substrate can be effectively reflected, so that the parallel impedance Rp value of the resonator is effectively improved.
In the drawings of the present invention, the discrete structures are annular discrete structures. However, the discrete structure may also be a plurality of discrete structure segments spaced apart from one another and disposed along the inner side around the active area. For example, the discrete structure segments may be one or more discrete structure segments disposed on one or more sides of the active area of the polygon shown in fig. 2A.
In the present invention, as shown in the drawings, in an alternative embodiment, the lateral distance of the discrete structures from the active area remains constant.
In one exemplary embodiment of the invention, the discrete structures are each formed on the top electrode. However, the present invention is not limited thereto. Discrete structures may be provided on the lower or upper side of the piezoelectric layer; or a discrete structure is disposed on the underside of the top electrode; or the discrete structure is arranged on the upper side or the lower side of the bottom electrode; or the resonator is further provided with a passivation layer covering the top electrode, said discrete structures being provided on the underside of said passivation layer, etc.
In the present invention, "upper side" in the orientation means a side distant from the substrate in the thickness direction of the resonator, and "lower side" means a side close to the substrate in the thickness direction of the resonator.
Based on the above, embodiments of the present invention also relate to a filter including the bulk acoustic wave resonator described above.
Embodiments of the invention also relate to an electronic device comprising a filter or resonator as described above. It should be noted that the electronic device herein includes, but is not limited to, intermediate products such as a radio frequency front end and a filtering and amplifying module, and terminal products such as a mobile phone, WIFI, and an unmanned aerial vehicle.
Correspondingly, the invention also provides a method for improving the parallel impedance of the bulk acoustic wave resonator, which comprises the following steps: at least one annular discrete structure is formed on the upper side of the top electrode of the resonator around the active area of the resonator.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Claims (25)
1. A bulk acoustic wave resonator comprising:
a substrate;
an acoustic mirror;
a bottom electrode disposed on an upper side of the substrate;
a top electrode; and
a piezoelectric layer disposed on the upper side of the bottom electrode and between the bottom electrode and the top electrode,
wherein:
the overlapped area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the substrate is an effective area of the resonator;
the resonator further comprises at least one discrete structure, the discrete structure is located on the inner side of the effective area and extends along the edge of the effective area in a strip shape, and each discrete structure comprises a plurality of discrete units.
2. The resonator of claim 1, wherein:
the discrete structure is an annular discrete structure.
3. The resonator of claim 2, wherein:
the lateral distance of the discrete structures from the edge of the active area remains constant.
4. The resonator of any of claims 1-3, wherein:
the at least one discrete structure comprises one discrete structure.
5. The resonator of claim 4, wherein:
the discrete structures are disposed on an upper side of the top electrode.
6. The resonator of claim 5, wherein:
the discrete units are protrusions.
7. The resonator of claim 5, wherein:
the discrete cells are recesses.
8. The resonator of any of claims 5-7, wherein:
the pitch between two adjacent discrete units is 1um-10um or integral multiple of S1 mode lamb wave wavelength at the parallel resonance frequency of the bulk acoustic wave resonator.
9. The resonator of claim 7 or 8, wherein:
the radial and/or lateral dimensions of the individual discrete elements are 0.5um-6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency.
10. The resonator of claim 9, wherein:
the distance from the discrete structure to the edge of the active area is 0.
11. The resonator of any of claims 1-3, wherein:
the at least one discrete structure comprises at least two discrete structures spaced apart in a radial direction.
12. The resonator of claim 11, wherein:
the at least two discrete structures comprise raised discrete structures comprised of raised protrusions and/or recessed discrete structures comprised of recessed recesses.
13. The resonator of claim 11 or 12, wherein:
the pitch of two discrete structures adjacent in the radial direction is 1um-10um or integral multiple of S1 mode lamb wave wavelength at the parallel resonance frequency of the bulk acoustic wave resonator.
14. The resonator of claim 13, wherein:
the pitch of adjacent discrete units of each discrete structure in the transverse direction is 1um-10um or is integral multiple of S1 mode lamb wave wavelength at the parallel resonance frequency of the bulk acoustic wave resonator.
15. The resonator of claim 14, wherein:
the radial dimension and/or lateral dimension of a single discrete element is 0.5um-6um, or one quarter or an odd multiple of the wavelength of the S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
16. The resonator of claim 14 or 15, wherein:
in the transverse direction, the transverse pitch between one discrete unit of one discrete structure and one adjacent discrete unit of the other discrete structure in two discrete structures which are adjacent in the radial direction is 0-5um, or is one fourth or integral multiple of S1 mode lamb wave at the parallel resonance frequency of the bulk acoustic wave resonator.
17. The resonator of claim 16, wherein:
the radial distance of the discrete structures on the outer side from the edge of the active area is 0.
18. The resonator of any of claims 1-17, wherein:
the discrete structures occupy no more than 20% of the total area of the active area of the resonator.
19. The resonator of claim 18, wherein:
the discrete structures occupy no more than 10% of the total area of the active area of the resonator.
20. The resonator of any of claims 1-3, wherein:
the discrete structure is arranged on the piezoelectric layer, the top electrode or the bottom electrode; or
The resonator is further provided with a passivation layer covering the top electrode, and the discrete structures are arranged on the lower side of the passivation layer.
21. The resonator of any of claims 1-3, wherein:
the material forming the discrete structures comprises a metal, a dielectric material, or the same material as the piezoelectric layer or the electrodes.
22. The resonator of any of claims 1-3, wherein:
the cross-sectional shape of the discrete units is circular or square.
23. A filter comprising the bulk acoustic wave resonator according to any one of claims 1-22.
24. An electronic device comprising a filter according to claim 23 or a resonator according to any of claims 1-22.
25. A method of increasing the parallel impedance of a bulk acoustic wave resonator, comprising the steps of:
at least one annular discrete structure is formed on the upper side of the top electrode of the resonator around the active area of the resonator.
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| CN201811558423.XA CN111342800A (en) | 2018-12-19 | 2018-12-19 | Bulk acoustic wave resonator with discrete structure, filter, and electronic device |
| PCT/CN2019/121095 WO2020125354A1 (en) | 2018-12-19 | 2019-11-27 | Bulk acoustic wave resonator with discrete structure, filter and electronic device |
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| CN201811558423.XA CN111342800A (en) | 2018-12-19 | 2018-12-19 | Bulk acoustic wave resonator with discrete structure, filter, and electronic device |
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|---|---|---|---|---|
| CN111934641A (en) * | 2020-07-08 | 2020-11-13 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonator, frequency adjustment method for bulk acoustic wave resonator, filter, and electronic device |
| CN113364422A (en) * | 2021-06-18 | 2021-09-07 | 深圳市封神微电子有限公司 | Film bulk acoustic resonator with ring electrode |
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| US20060071736A1 (en) * | 2004-10-01 | 2006-04-06 | Ruby Richard C | Acoustic resonator performance enhancement using alternating frame structure |
| CN107404304A (en) * | 2016-05-18 | 2017-11-28 | 三星电机株式会社 | Acoustic resonator and its manufacture method |
| CN107733396A (en) * | 2016-08-12 | 2018-02-23 | 三星电机株式会社 | Bulk acoustic wave resonator |
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| TWI365603B (en) * | 2004-10-01 | 2012-06-01 | Avago Technologies Wireless Ip | A thin film bulk acoustic resonator with a mass loaded perimeter |
| CN102223142B (en) * | 2011-08-13 | 2019-09-10 | 张�浩 | Acoustic resonator |
| CN108649920B (en) * | 2017-12-29 | 2021-12-03 | 苏州汉天下电子有限公司 | Piezoelectric acoustic resonator, piezoelectric acoustic wave filter, duplexer, and radio frequency communication module |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060071736A1 (en) * | 2004-10-01 | 2006-04-06 | Ruby Richard C | Acoustic resonator performance enhancement using alternating frame structure |
| CN107404304A (en) * | 2016-05-18 | 2017-11-28 | 三星电机株式会社 | Acoustic resonator and its manufacture method |
| CN107733396A (en) * | 2016-08-12 | 2018-02-23 | 三星电机株式会社 | Bulk acoustic wave resonator |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111934641A (en) * | 2020-07-08 | 2020-11-13 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonator, frequency adjustment method for bulk acoustic wave resonator, filter, and electronic device |
| CN111934641B (en) * | 2020-07-08 | 2021-06-01 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonator, frequency adjustment method for bulk acoustic wave resonator, filter, and electronic device |
| CN113364422A (en) * | 2021-06-18 | 2021-09-07 | 深圳市封神微电子有限公司 | Film bulk acoustic resonator with ring electrode |
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