WO2022012334A1

WO2022012334A1 - Bulk acoustic resonator with mass loads arranged on two sides of piezoelectric layer, filter and electronic device

Info

Publication number: WO2022012334A1
Application number: PCT/CN2021/103693
Authority: WO
Inventors: 庞慰; 杨清瑞; 张孟伦
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2020-07-13
Filing date: 2021-06-30
Publication date: 2022-01-20
Also published as: CN111934643B; CN111934643A

Abstract

The present disclosure relates to a bulk acoustic resonator and a manufacturing method therefor. The resonator comprises: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer provided between the bottom electrode and the top electrode, wherein a first mass load array and a second mass load array are respectively provided on upper and lower sides of the piezoelectric layer. The present disclosure also relates to a filter and an electronic device.

Description

Bulk acoustic wave resonator, filter and electronic equipment with mass loading on both sides of piezoelectric layer

technical field

Embodiments of the present disclosure relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a filter having the resonator, and an electronic device.

Background technique

As the basic elements of electronic equipment, electronic devices have been widely used, and their applications include mobile phones, automobiles, home appliances and so on. In addition, technologies such as artificial intelligence, the Internet of Things, and 5G communications that will change the world in the future still need to rely on electronic devices as their foundation.

Film Bulk Acoustic Resonator (FBAR, also known as Bulk Acoustic Resonator, also known as BAW) as an important member of piezoelectric devices is playing an important role in the field of communication, especially FBAR filter in radio frequency filter The market share in the field is increasing. FBAR has excellent characteristics such as small size, high resonant frequency, high quality factor, large power capacity, and good roll-off effect. Its filters are gradually replacing traditional surface acoustic wave (SAW) filters And ceramic filters, play a huge role in the field of wireless communication radio frequency, its high sensitivity advantage can also be applied to biological, physical, medical and other sensing fields.

The structural main body of the thin film bulk acoustic wave resonator is a "sandwich" structure composed of an electrode-piezoelectric film-electrode, that is, a piezoelectric material is sandwiched between two metal electrode layers. By inputting a sinusoidal signal between two electrodes, the FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into an electrical signal output.

In the prior art, it has been proposed to tune the frequency of the resonator by placing a complete mass load on the top electrode of the resonator. The amount of frequency adjustment in this method depends on the thickness control accuracy. If resonators with multiple frequencies are required, mass load layers with multiple thicknesses need to be deposited, the process is complicated, and the accuracy is not easy to control. In addition, it has also been proposed to provide patterned mass loading on the top electrode of the resonator to achieve frequency tuning by adjusting the pattern density of the mass loading layer. However, the introduction of mass loading by a single pattern structure may lead to increased spurious modes or losses in certain frequency ranges, thereby impairing the electrical performance of the resonator.

In addition, the thin-film bulk acoustic wave resonator mainly uses the longitudinal piezoelectric coefficient of the piezoelectric film to generate the piezoelectric effect, so its main operating mode is the longitudinal wave mode in the thickness direction, that is, the acoustic wave of the bulk acoustic wave resonator is mainly in the resonator. And the main vibration direction is in the longitudinal direction. However, due to the existence of a boundary, there will be Lamb waves that are not perpendicular to the piezoelectric film layer at the boundary. At this time, the lateral Lamb wave will leak out from the lateral direction of the piezoelectric film layer, resulting in acoustic loss, thus making the Q value of the resonator. decrease.

SUMMARY OF THE INVENTION

The present disclosure is made to alleviate or solve at least one aspect of the above-mentioned problems in the prior art.

According to an aspect of the embodiments of the present disclosure, a bulk acoustic wave resonator is proposed, comprising:

base;

acoustic mirror;

bottom electrode;

top electrode; and

a piezoelectric layer, arranged between the bottom electrode and the top electrode,

in:

The upper side of the piezoelectric layer and the lower side of the piezoelectric layer are respectively provided with a first mass load array and a second mass load array.

Embodiments of the present disclosure also relate to a filter comprising the above-mentioned bulk acoustic wave resonator.

Embodiments of the present disclosure also relate to an electronic device including the above-mentioned filter or the above-mentioned resonator.

Description of drawings

These and other features and advantages of the various embodiments disclosed in this disclosure may be better understood by the following description and accompanying drawings, wherein like reference numerals refer to like parts throughout, wherein:

1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present disclosure;

1B is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line M1-M2 in FIG. 1A according to an exemplary embodiment of the present disclosure;

1C is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line M1-M2 in FIG. 1A according to another exemplary embodiment of the present disclosure;

Figures 2A and 2B respectively exemplarily show a diagram of setting a mass load on the top electrode, wherein Figure 2A is an arrangement in Cartesian coordinates, and Figure 2B is a diagram in polar coordinates;

3A-3C are respectively schematic top views showing the composite of mass load arrays (arranged in Cartesian coordinates) provided on the upper and lower sides of the laminated structure of the resonator according to different exemplary embodiments of the present disclosure;

4 is a schematic top view showing a composite of mass load arrays (arranged in polar coordinates) provided on the upper and lower sides of the laminated structure of the resonator according to an exemplary embodiment of the present disclosure;

5A and 5B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to an exemplary embodiment of the present disclosure, and after compounding;

FIGS. 6A and 6B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to another exemplary embodiment of the present disclosure, and after compounding;

FIGS. 7A and 7B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and the composite structure;

FIGS. 8A and 8B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to still another exemplary embodiment of the present disclosure, and after compounding;

FIGS. 9A and 9B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and the composite structure;

FIGS. 10A and 10B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and the composite structure;

FIGS. 11A and 11B show a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and after compounding;

Figures 12A and 12B illustrate a schematic top view of mass load arrays arranged on the upper and lower sides of a laminated structure of a resonator according to yet another exemplary embodiment of the present disclosure, and a composite structure;

13A schematically shows impedance characteristic curves at the vicinity of the series resonance frequency (left side graph) and the parallel resonance frequency (right side graph) of a resonator in which a mass load array is provided only on one side of the resonator as a comparative example;

13B and 13C schematically illustrate the locations near the series resonant frequency (left panel) and the parallel resonant frequency (right panel) of a resonator provided with mass-loaded arrays on both the upper and lower sides of the resonator, respectively, according to an embodiment of the present disclosure. impedance characteristic curve.

detailed description

The technical solutions of the present disclosure will be further specifically described below through the embodiments and in conjunction with the accompanying drawings. The following description of the embodiments of the present disclosure with reference to the accompanying drawings is intended to explain the general disclosed concept of the present disclosure, and should not be construed as a limitation of the present disclosure.

1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present disclosure, and FIG. 1B is a schematic view of the bulk acoustic wave resonator according to an exemplary embodiment of the present disclosure taken along the line M1-M2 in FIG. 1A FIG. 1C is a schematic cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present disclosure, taken along the line M1-M2 in FIG. 1A .

Reference numerals in this disclosure are explained as follows:

100: Substrate, optional materials are single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

110: The first acoustic impedance layer or the first acoustic impedance layer, the material may be aluminum nitride, silicon dioxide, silicon nitride, polysilicon, or amorphous silicon.

120: The second acoustic impedance layer or the second acoustic impedance layer, which also serves as a sacrificial layer. The material of the second acoustic impedance layer can be silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon, etc., but it is different from the material of the first acoustic impedance layer, and the etchant of the second acoustic impedance layer is not easy to etch or The material of the first acoustic impedance layer is not etched.

130: Acoustic mirror, which can be a cavity, or a Bragg reflector and other equivalent forms. Cavities are employed in the embodiments shown in this disclosure.

140: Bottom electrode, the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys.

145: Lower Mass Load Array. The underside mass loading is a protrusion formed by the material of the bottom electrode itself or a depression formed on the bottom electrode. The material of the underside mass loading can also be different from the bottom electrode. The lower mass load is arranged on the lower side of the piezoelectric layer, which is not limited to be fabricated under the bottom electrode, but can also be fabricated between the piezoelectric layer and the bottom electrode, or fabricated in the bottom electrode.

150: Piezoelectric layer, which can be a single crystal piezoelectric material, optional, such as: single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lead zirconate titanate (PZT), single crystal Potassium niobate, single crystal quartz film, or single crystal lithium tantalate and other materials can also be polycrystalline piezoelectric materials (corresponding to single crystal, non-single crystal materials), optional, such as polycrystalline aluminum nitride, Zinc oxide, PZT, etc., can also be a rare earth element doped material containing a certain atomic ratio of the above materials, for example, can be doped aluminum nitride, and doped aluminum nitride contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and the like.

155: Release holes for etching the sacrificial layer to form a cavity.

160: The top electrode, the material of which can be the same as the bottom electrode, and the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys. The top and bottom electrode materials are generally the same, but can also be different.

165: Upper Mass Load Array. The upper mass load is a protrusion formed by the material of the top electrode itself or a depression formed on the top electrode, or in the case where a passivation layer or a process layer is provided on the top electrode, it can also be formed by the material of the process layer. Raised or recessed. The material supported by the upper mass may also be different from the top electrode or the process layer. For example, when the process layer on the upper surface of the top electrode is aluminum nitride, the material supported by the upper mass may be silicon dioxide or metal oxide. The upper mass load is arranged on the upper side of the piezoelectric layer, and is not limited to being fabricated above the top electrode, but can also be fabricated between the piezoelectric layer and the top electrode, or fabricated in the top electrode.

170: the top electrode lead-out part, which can be prepared at the same time as the top electrode, and the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys.

180: Electrode connection part one (Bonding PAD, or bottom electrode electrical connection layer), the material can be copper, gold or a composite of above metals or alloys thereof.

190: The second electrode connection part (Bonding PAD, or top electrode electrical connection layer), the material can be copper, gold or a composite of the above metals or their alloys, etc.

As shown in FIG. 1B , the upper side of the top electrode 160 is provided with a mass load array 165 , and the lower side of the bottom electrode 140 is provided with a mass load array 145 .

In the present disclosure, mass loads are provided on both the upper and lower sides of the stacked structure composed of the top electrode, the bottom electrode and the single crystal piezoelectric layer, so as to provide flexibility for adjusting the frequency reference of the resonator by the mass load, It is beneficial to realize the convenience and precision of the frequency control of the resonator.

In the present disclosure, by arranging mass load arrays on both the upper and lower sides of the laminated structure, the bulk acoustic wave resonator has better spatial symmetry in the thickness direction. It can be beneficial to suppress the spurious mode generated during the operation of the resonator, and improve the Q value of the resonator.

In FIG. 1B , an acoustic impedance structure is disposed between the piezoelectric layer 150 and the substrate 100 , and the acoustic mirror 130 is located between the acoustic impedance structures in the lateral direction of the resonator, the acoustic impedance structures including being adjacent to each other in the lateral direction The first acoustic impedance layer 110 and the second acoustic impedance layer 120 are provided, and more specifically, the acoustic mirror 130 is located between the first acoustic impedance layers 110 in the lateral direction of the resonator. The electrode connection end of the bottom electrode 140 is covered by a part of the first acoustic impedance layer 110 , and the non-electrode connection end of the bottom electrode 140 is spaced apart from the first acoustic impedance layer 110 in the lateral direction.

In the present disclosure, the acoustic impedances of the first acoustic impedance layer and the second acoustic impedance layer are different to form impedance mismatch, form continuous reflection for acoustic waves, and form a reflection structure for transverse acoustic waves, so as to prevent transverse acoustic waves from leaking, It is beneficial to lock the energy in the resonator, thereby improving the Q value.

In the present disclosure, the single crystal piezoelectric material is used, so that the piezoelectric loss can be lower, so as to obtain a higher Q value of the resonator, and at the same time, the electromechanical coupling coefficient and power capacity can be improved.

In a further embodiment, the widths A and B of the portions of the first acoustic impedance layer 110 and the second acoustic impedance layer 120 in contact with the piezoelectric layer 150 are mλ ₁ /4 and nλ ₂ /4, respectively, where m and n are odd numbers, such as 1, 3, 5, 7, etc., λ ₁ and λ ₂ are the wavelengths of acoustic waves propagating laterally at the resonance frequency of the first acoustic impedance layer and the second acoustic impedance layer, respectively. The resonant frequency is a certain frequency within the resonant interval of the resonator, which can be the series resonant frequency or the parallel resonant frequency of the resonator, or a certain frequency between the series and parallel resonant frequencies, or slightly lower than the series resonant frequency or A frequency slightly higher than the parallel resonant frequency. In the drawings, the width of the first acoustic impedance layer 110 is represented by A, and the width of the second acoustic impedance layer 120 is represented by B. Selecting the above-mentioned width is beneficial to form an effective acoustic impedance mismatch, prevent transverse acoustic wave leakage, and further improve the Q value of the resonator. m and n may be the same or different, which are all within the protection scope of the present disclosure.

The materials for forming the first acoustic impedance layer 110 include aluminum nitride, silicon dioxide, silicon nitride, polysilicon, and amorphous silicon, and the materials for forming the second acoustic impedance layer 120 include silicon dioxide, doped silicon dioxide, and polysilicon. , Amorphous silicon. The material of the first acoustic impedance layer 110 and the material of the second acoustic impedance layer 120 are different from each other. Optionally, the material for forming the first acoustic impedance layer 110 includes silicon dioxide, and the material for forming the second acoustic impedance layer 120 includes polysilicon. Alternatively, the first acoustic impedance layer 110 is formed of doped silicon dioxide. In the present disclosure, in order to improve the degree of acoustic mismatch at the junction of the first acoustic impedance layer 110 and the second acoustic impedance layer 120 , the difference between the acoustic impedances of the two may be selected as large as possible.

As shown in FIG. 1B , the end face of the non-electrode connection end (the right end in FIG. 1B ) of the bottom electrode 140 is spaced apart from the first acoustic impedance layer 110 in the acoustic impedance structure in the lateral direction, so that the acoustic wave is not in the bottom electrode. The lateral interface between the electrode connection end and the void also forms total reflection, thereby reducing acoustic leakage. Based on the void structure at the non-electrode connection end, transverse acoustic wave leakage can be further prevented and the Q value of the resonator can be improved. On the other hand, if the end face of the non-electrode connection end (the right end in FIG. 1B ) of the bottom electrode 140 is covered by the first acoustic impedance layer 3 , a parasitic capacitance will be formed with the part of the top electrode outside the cavity, thereby affecting the resonator The electromechanical coupling coefficient.

In an alternative embodiment, in a longitudinal section of the resonator passing through the electrode connecting end of the bottom electrode 140 (eg, the cross-sectional view shown in FIG. 1B ), the end face of the non-electrode connecting end of the bottom electrode 140 is transversely aligned with the The distance that the acoustic impedance structures are spaced apart may be in the range of 0.5 μm-20 μm. The distance may be, for example, 5 μm, 7 μm, or the like, in addition to the end value.

In the embodiment shown in FIG. 1B , the bottom electrode 140 is surrounded by a continuous reflective layer or an acoustic impedance structure formed by the first acoustic impedance layer 110 and the second acoustic impedance layer 120 on one side of the electrode connection end. More specifically, Covered by the first acoustic impedance layer 110, on the one hand, this structure is beneficial to improve the mechanical stability of the resonator, and it is easier to conduct the heat generated during the operation of the resonator to the substrate through the electrodes and the first acoustic impedance layer 110 , thereby improving the power capacity of the resonator. On the other hand, although the energy will leak into the first acoustic impedance layer 110 from the end face of the bottom electrode, due to the existence of the reflection interface formed by the second acoustic impedance layer and the first acoustic impedance layer , therefore, it is beneficial to lock as much energy as possible inside the resonator, so that the resonator maintains a high Q value.

In one embodiment of the present disclosure, as shown in FIG. 1B , the angle θ1 formed between the surface where the outer surface of the first acoustic impedance layer 110 is located and the bottom surface of the piezoelectric layer can be selected to be in the range of 100°-160° , specifically, can be 100°, 120°, 160°, etc. Considering that the space corresponding to the acoustic mirror 130 is filled with the material of the second acoustic impedance layer 120 at the beginning (the acoustic mirror 130 is formed by etching the material of the second acoustic impedance layer later), therefore, choosing this angle is beneficial for patterning the first An acoustic impedance layer 110 is then filled with a second acoustic impedance layer 120 . In an embodiment of the present disclosure, as shown in FIG. 1B , the angle α1 formed between the outer side of the end surface of the bottom electrode 140 and the bottom surface of the piezoelectric layer 150 may be selected to be in the range of 90°-160°. 90°, 100°, 120°, 160°, etc. Selecting this angle is favorable for filling the first acoustic impedance layer 110 and the second acoustic impedance layer 120 .

1C is a schematic cross-sectional view of a bulk acoustic wave resonator similar to that taken along line M1-M2 in FIG. 1 , showing the electrode lead-out region of the bottom electrode and the top electrode, according to another exemplary embodiment of the present disclosure. and the electrode connection end of the bottom electrode is covered by a part of the first acoustic impedance layer 110 , and the non-electrode connection end of the bottom electrode is spaced apart from the first acoustic impedance layer 110 in the lateral direction. In the embodiment of the present disclosure, as shown in FIG. 1C , the angle θ2 formed between the surface where the outer surface of the first acoustic impedance layer 110 is located and the bottom surface of the piezoelectric layer 150 can be selected to be in the range of 20°-80° , specifically, can be 20°, 60°, 80°, etc. In addition, as shown in FIG. 1C , the angle α2 formed between the outer side of the end surface of the bottom electrode 140 and the bottom surface of the piezoelectric layer 150 can be selected to be in the range of 90°-160°, specifically, 90°, 100°, 120°, 160°, etc. Selecting this angle is favorable for filling the first acoustic impedance layer 110 and the second acoustic impedance layer 120 .

In the present disclosure, the first acoustic impedance layer 110 and the second acoustic impedance layer 120 may together constitute an acoustic impedance structure. However, the present disclosure is not limited thereto, in other words, the arrangement of the acoustic impedance layers is not limited thereto. It may include a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to one another in the lateral direction, or a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer, or a combination of the above. combination.

2A and 2B exemplarily show diagrams of disposing a mass load on the top electrode, respectively, wherein FIG. 2A is an arrangement in Cartesian coordinates, and FIG. 2B is a diagram in polar coordinates. When the mass load arrangement on one side of the laminated structure follows a certain coordinate form, the mass load arrangement on the other side also follows the same coordinate form, and on this basis, a positional fit is formed between the mass load arrays on both sides relation.

FIGS. 3A-3C are schematic top views showing the composite of mass load arrays (arranged in Cartesian coordinates) disposed on the upper and lower sides of the laminated structure of the resonator according to different exemplary embodiments of the present disclosure.

As shown in FIG. 3A , taking A1 as the mass load in the first mass load array and B1 as the mass load in the second mass load array, it can be seen that the second mass load array is relative to the first mass load array according to the vector ε ₀ for translation, and the translation here includes the lateral translation and the longitudinal translation in FIG. 3A . As can be understood, in an optional embodiment, the translation may only be a lateral translation or a longitudinal translation.

In FIG. 3A , the size of the mass load corresponding to A1 is the same as the size of the mass load corresponding to B1 . P1 and P2 are the distances between adjacent mass loads in the horizontal and vertical directions of the mass load array corresponding to A1, respectively. P1 and P2 can be the same or different, and their range is from 0.1 times to 10 times the total thickness of the resonator. Inside. In the present disclosure, the thicknesses of the mass-loaded arrays on the upper and lower sides of the resonator are

The thickness of the upper and lower sides can be the same or different.

In this disclosure, where the dimensions of two mass loads are compared, when the cross section of the mass load is circular, the size of the mass load refers to the radius of the cross section of the mass load; for other cross-sectional shapes, It can be determined by the equivalent radius of the cross section.

In an optional embodiment, in FIG. 3A , _{the length of the horizontal component of the vector ε 0} is in the range of 0-P1, and the length of the vertical component is in the range of 0-P2, where the endpoint values (such as 0, P1 or P2) means that the two arrays are completely coincident.

As shown in FIG. 3B , taking A1 and A2 as the mass loads in the first mass load array, and B1 and B2 as the mass loads in the second mass load array, it can be seen that the second mass load array is relative to the first mass load The array is translated by the vector ε ₀ , where the translation includes the lateral translation in FIG. 3B as well as the longitudinal translation. As can be understood, in an optional embodiment, the translation may only be a lateral translation or a longitudinal translation. P1 and P2 are the distances between adjacent mass loads in the horizontal and vertical directions of the mass load array corresponding to A1, respectively. P1 and P2 can be the same or different, and their range is from 0.1 times to 10 times the total thickness of the resonator. Inside. The mass load array corresponding to A2 can be regarded as the mass load array corresponding to A1 _{, which is translated according to ε 1. The} translation here includes only the lateral translation in FIG. 3B. In an optional embodiment, the translation can also be only the longitudinal translation. , or a combination of horizontal translation and vertical translation. Wherein, _{the length of the horizontal component of the vector ε 1} is within the range from the sum of the radii of the mass load cells A1 and A2 to P1, and the length of the vertical component is within the range from the sum of the radii of the mass load cells A1 and A2 to the range of P2; The length of the horizontal component of the vector ε ₀ is in the range of 0-P1, and the length of the vertical component is in the range of 0-P2, where 0 means that the two arrays are completely coincident (that is, all the mass loads of one array are in the range of the other array. Corresponding mass load coincidence).

As shown in FIG. 3B , the size of the mass load corresponding to A1 and the mass load corresponding to A2 are different; the size of the mass load corresponding to B1 and the mass load corresponding to B2 are different.

The size of the mass load corresponding to A1 may be the same as or different from the size of the mass load corresponding to B1, and the size of the mass load corresponding to A2 may be the same or different from the size of the mass load corresponding to B2.

As shown in FIG. 3C , with A1 as the mass load in the first mass load array and B1 as the mass load in the second mass load array, similarly, the second mass load array is translated by a vector relative to the first mass load array , the translation here includes the lateral translation and the longitudinal translation in FIG. 3A . As can be understood, in an optional embodiment, the translation may only be a lateral translation or a longitudinal translation.

In FIG. 3C, the size of the mass load corresponding to A1 is different from the size of the mass load corresponding to B1.

In the following, the simulation results are used to illustrate that, compared with the single-sided mass load, the double-sided mass load can not only have the effect of frequency adjustment, but also the effect of improving the Q value of the resonator.

Figure 13A shows that only a certain thickness is provided on the top electrode (such as

) The series resonant frequency and the parallel resonant frequency of the resonator of the mass load array (the mass load array corresponding to A1 in Figure 3A, and P1=P2=2 times the total thickness of the resonator, and the diameter of the mass load unit is half of P1) Impedance characteristic curve in the vicinity.

Figure 13B shows that the same thickness is set on both the upper and lower sides of the resonator (such as

) the impedance characteristic curve of the resonator at the series resonance frequency and the parallel resonance frequency of the mass load array (the mass load array corresponding to A1 and B1 in FIG. 3A , and ε _{0 =0).} It can be seen that under the condition that the total thickness of the mass load is the same, the distribution on the upper and lower sides can achieve a larger mass load effect than the single-side distribution, that is, a larger frequency change amplitude; at the same time, the series impedance is significantly reduced (from 2.44 Ω is reduced to 0.84Ω, the reduction range is about 60%), the corresponding Q value will be significantly improved, indicating that in this embodiment, the mass load distributed on the upper and lower sides can generate a forbidden band for shear wave propagation near the series resonance frequency, thus Concentrate more energy in the vibration mode of the series resonance, and increase the Q value of the resonator series resonance point; in addition, the parallel impedance will be slightly reduced (from 2420Ω to 2300Ω, the reduction range is about 5%), and the degree of deterioration is far less than the series impedance improvement.

Figure 13C shows that the same thickness is set on both the upper and lower sides of the resonator (such as

) mass-loaded arrays but the two have a certain lateral translation relationship (as shown in Figure 3A for the mass-loaded arrays corresponding to A1 and B1, and when ε ₀ =0.5×P1) of the resonator’s series resonant frequency and parallel resonant frequency Impedance characteristic curve. It can be seen that compared to the single-sided mass load results shown in Figure 13A, the series impedance shown in Figure 13C has a significant reduction (from 2.44Ω to 1.07Ω, a reduction of about 56%), and the parallel impedance has a certain degree of reduction. The improvement (from 2420Ω to 2565Ω, the improvement range is about 6%), that is, compared with Figure 13B, only the Q value near the series resonance frequency is increased. The embodiment shown in Figure 13C can fully Increase the Q value of the resonator in the whole frequency band (including the Q value near the series resonance frequency and the parallel resonance frequency).

FIG. 4 is a schematic top view showing a composite of mass load arrays (arranged in polar coordinates) disposed on the upper and lower sides of the laminated structure of the resonator according to an exemplary embodiment of the present disclosure.

As shown in FIG. 4 , A1 is used as the mass load in the first mass load array, and B1 is used as the mass load in the second mass load array. Among them, the mass load array corresponding to A1 has N mass load units in the circumferential direction, N is greater than or equal to 3, the adjacent mass loads have an included angle α ₃ (its value is 360°/N), and the adjacent mass load units in the radial direction are The spacing between them is P3, which is in the range of 0.1 times to 10 times the total thickness of the resonator, and in an optional embodiment, from the center of the resonator to the outside, the distance P3 between adjacent mass loads of each layer can be The same can also be changed from small to large, or from large to small. The second mass load array is rotated relative to the first mass load array by an angle α ₀ , and its rotation direction can be clockwise or counterclockwise, and the range of the angle can be in the range of 0-α ₃ , where the endpoint value is (eg 0 or α ₃ ) means that the two arrays are fully coincident (ie all mass loadings of one array coincide with the corresponding mass loadings of the other array).

The mating of the two arrays can also be a complementary mating relationship. For example, the mass load array can be distributed on one side of the stack structure in Cartesian or polar coordinates, then the array can be divided into several areas in a certain way, and the array in a certain area can be transferred to the other side (ie, a mass load provided in a specific position on one side is not provided in a corresponding specific position on the other side), thereby forming a complementary relationship of the arrays on both sides of the stacked structure.

5A and 5B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to an exemplary embodiment of the present disclosure, and composited.

As shown in FIG. 5A, the mass-loaded array on one side of the laminated structure has a Cartesian coordinate distribution, the array is divided into two parts by a pentagon boundary P1, and the array located outside the pentagon is transferred To the other side of the stack, the mating relationship of the arrays on both sides of the stack as shown in FIG. 5B is finally formed. Among them, there are several division principles for the array cells that fall "on" the boundary of P1 (part of it falls within the boundary, and part of it falls outside the boundary). It can be determined according to the ratio of the top-view area of a certain display unit divided by the boundary P1. If the area falling on the outside of P1 is larger than the internal area, the unit will be classified outside the boundary of P1, otherwise, it will be classified as the inside. If P1 just bisects the display The unit top view area is divided into any one of the inner and outer areas.

In Figure 5B, it can be seen that the array on one side is a polygon, while the array on the other side is an annular polymorph, and the polygon fits with the inner edge of the annular polygon. In further embodiments, the shape of the array or polygon on the left side of FIG. 5B is similar to the shape of the ring-shaped polygon on the right side of FIG. 5B or the shape of the active area of the resonator.

Although not shown, a polygonal ring may also be provided in the embodiment shown in Figures 5A and 5B, similar to that shown in the subsequent Figure 7B.

6A and 6B illustrate a schematic top view of mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to another exemplary embodiment of the present disclosure, and the composite structure.

As shown in FIG. 6A , the array on one side of the laminated structure has a polar coordinate distribution, and the array is divided into two parts by a circular boundary C1, and the array located on the outer side of the circle is transferred to the laminated structure. On the other side, the mating relationship of the arrays on both sides of the laminated structure shown in FIG. 6B is finally formed.

7A and 7B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and the composite structure.

As shown in Figures 7A and 7B, in the embodiment of Figures 6A-6B, a plurality of circular boundaries may be provided, so that as shown in Figure 7A, the array distributed in polar coordinates on one side of the laminated structure is surrounded by 2 circles The shape boundary C1C2 is divided into 3 parts, and the annular array in the two circular parts spaced from each other is transferred to the other side of the laminated structure to form the mating relationship in FIG. 7B .

The shape of the dividing boundary is not limited to closed geometric shapes such as circles, polygons, and rings, and can also be other geometric shapes, such as straight lines or geometric shapes formed by a combination of multiple straight lines. 8A and 8B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to still another exemplary embodiment of the present disclosure, and composited.

In Fig. 8A, the array distributed according to Cartesian coordinates is alternately divided into several vertical strip-shaped regions by several straight lines (obviously, it can also be divided into horizontal strip-shaped regions), and these regions are alternately marked as P1, Q1..., so the All of the arrays in the Q1 (or P1 ) region can be transferred to the other side to form the mating relationship in FIG. 8B .

FIGS. 9A and 9B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and composited. In FIG. 9A, the array distributed according to Cartesian coordinates is alternately divided into several inclined strip-shaped regions by several straight lines, and these regions are alternately marked as P2, Q2..., so that all the arrays in the Q2 (or P2) region can be divided into Transfer to the other side, thereby forming the array position matching relationship in FIG. 9B.

10A and 10B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and composited. The lines used to divide the regions do not have to be parallel to each other. For example, in Figure 10A, the array arranged on one side of the laminated structure in polar coordinates is alternately divided into P3, Q3... regions by a set of rays emanating from a certain center. , If all the lattice units that are divided into the P3 or Q3 area are transferred to the other side of the laminated structure, the array position matching relationship shown in FIG. 10B can be obtained.

FIGS. 11A and 11B illustrate mass load arrays arranged on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and a schematic top view after compounding. In the embodiment shown in FIG. 11A , the rectangular boundary P4 divides the array distributed according to Cartesian coordinates into a plurality of cells, wherein a certain cell shares three mass loads with its adjacent cells. In each cell, the central array cell of rectangular boundary Q4 is isolated. If all the array units in the P4 or Q4 area are transferred to the other side of the stacked structure, the array position matching relationship in FIG. 11B can be obtained.

12A and 12B illustrate a schematic top view of mass load arrays disposed on the upper and lower sides of the laminated structure of the resonator according to yet another exemplary embodiment of the present disclosure, and the composite structure. In Fig. 12A, the lattice is divided into a checkerboard by several orthogonal straight lines, each grid contains 4 mass loads, and the grid areas P5 and Q5 are staggered in the form of illustration (for example, the "up and down" of P5 There are Q5 in the left and right, and P5 in the upper left, lower left, upper right and lower right). If all the array elements in the P5 or Q5 area are transferred to the other side of the stacked structure, the array position matching relationship in FIG. 12B can be obtained.

It should be pointed out that, in the present disclosure, each numerical range, except that it is explicitly stated that it does not include the endpoint value, may be the endpoint value, but also the middle value of each numerical range, and these are all within the protection scope of the present disclosure. .

In the present disclosure, upper and lower are relative to the bottom surface of the base of the resonator, and for a component, the side close to the bottom surface is the lower side, and the side away from the bottom surface is the upper side.

In the present disclosure, inside and outside are relative to the center of the effective area of the resonator (the overlapping area of the piezoelectric layer, the top electrode, the bottom electrode and the acoustic mirror in the thickness direction of the resonator constitutes the effective area) (ie, the center of the effective area). ) in the transverse or radial direction, the side or end of a component close to the center of the effective area is the inner or inner end, and the side or end of the component away from the center of the effective area is the outer or outer end. For a reference position, being located on the inside of the position means being between the position and the center of the effective area in the lateral or radial direction, and being located outside of the position means being further away from the position in the lateral or radial direction than the position Effective regional center.

As can be appreciated by those skilled in the art, bulk acoustic wave resonators according to the present disclosure may be used to form filters or electronic devices.

Based on the above embodiments and the accompanying drawings, the present disclosure proposes the following technical solutions:

1. A bulk acoustic wave resonator, comprising:

base;

acoustic mirror;

bottom electrode;

top electrode; and

The piezoelectric layer is arranged between the bottom electrode and the top electrode,

in:

The upper side of the piezoelectric layer and the lower side of the piezoelectric layer are respectively provided with a first mass load array and a second mass load array;

The first mass load array includes a plurality of mass loads on the upper side of the piezoelectric layer, and the second mass load array includes a plurality of mass loads on the lower side of the piezoelectric layer.

2. The resonator according to 1, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates.

3. The resonator according to 2, wherein:

The arrangement relationship between the first mass load array and the second load array is that at least a part of one array is an array in which a corresponding part of the other array is translated at least once.

4. The resonator according to 1, wherein:

Both the first mass load array and the second load array are arranged in polar coordinates.

5. The resonator according to 4, wherein:

The arrangement relationship between the first mass load array and the second load array is that at least a part of one array is an array in which a corresponding part of the other array is rotated by an angle.

6. The resonator according to 1, wherein:

The arrangement relationship of the first mass load array and the second load array is a complementary array. In the top view of the resonator, the first mass load array and the second load array together form a new array, and the first mass load array and the second mass load array form a new array. Each constitutes a different component of the new array.

7. The resonator according to 6, wherein:

One of the first mass load array and the second load array has at least one unit to be filled, and the other array has at least one filled unit.

8. The resonator according to 7, wherein:

The shape of the unit to be filled is one or more of a polygon, a circle, a circular ring, a polygonal ring, a straight line or a polyline, and the shape of the at least one unit to be filled is the same as the shape of the at least one unit to be filled. The shape of the unit corresponds.

9. The resonator of 8, wherein:

The shape of the unit to be filled is a polygon or a polygonal ring;

The outer contour of the polygon or polygonal ring of the unit to be filled is similar to the shape of the active area of the resonator.

10. The resonator of 8, wherein:

The unit to be filled includes a plurality of units to be filled in the shape of a straight line.

11. The resonator of 10, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates, and the plurality of cells to be filled are spaced parallel to each other; or

Both the first mass load array and the second load array are arranged in polar coordinates, and ends of the plurality of cells to be filled in the circumferential direction are spaced apart from each other.

12. The resonator according to 6, wherein:

One of the first mass load array and the second mass load array includes a plurality of mass load points to be filled, and the other of the first mass load array and the second mass load array includes a plurality of mass loads associated with the plurality of mass loads. Multiple mass loads corresponding to the positions of the points to be filled.

13. The resonator of 12, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates;

The one of the first mass load array and the second load array has a plurality of cells to be filled, each cell to be filled includes at least one point to be filled with a mass load, and the plurality of cells to be filled constitute a first polygon shaped cell array.

14. The resonator of 13, wherein:

Each unit to be filled contains a mass-loaded point to be filled.

15. The resonator of 13, wherein:

Each unit to be filled contains a plurality of points to be filled with mass load;

The other of the first mass load array and the second mass load array includes a plurality of filling cells, each filling cell includes a plurality of mass loads, and the plurality of filling cells constitute a second cell array;

The new array is a cell array formed by complementing the first polygonal cell array and the second polygonal cell array.

16. The resonator according to 1, wherein:

The geometry of the mass loads in the first array of mass loads is different from the geometry of the mass loads in the second array of mass loads.

17. The resonator of any of 1-16, wherein:

An acoustic impedance structure is arranged between the piezoelectric layer and the substrate;

The acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction, the acoustic impedance of the first acoustic impedance layer and the second acoustic impedance layer are different, and the acoustic mirror is in the The resonator is located between the first acoustic impedance layers in the lateral direction.

18. The resonator of 17, wherein:

The widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ ₁ /4 and nλ ₂ /4, respectively, where m and n are odd numbers, and λ ₁ and λ ₂ are respectively the first Wavelengths of acoustic waves propagating laterally at the resonant frequency of the acoustic impedance layer and the second acoustic impedance layer.

19. The resonator of 17, wherein:

A material forming one of the first acoustic impedance layer and the second acoustic impedance layer is selected from aluminum nitride, silicon dioxide, silicon nitride, polysilicon, and amorphous silicon to form the first acoustic impedance layer and the second acoustic impedance layer The material of another layer in the impedance layer is selected from silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

20. The resonator of 17, wherein:

The acoustic mirror is an acoustic mirror cavity;

The boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

21. The resonator according to 1, wherein:

The piezoelectric layer is a single crystal piezoelectric layer.

22. A filter comprising the bulk acoustic wave resonator of any one of 1-21.

23. An electronic device comprising the filter according to 22, or the bulk acoustic wave resonator according to any one of 1-21.

It should be pointed out that the electronic equipment here includes but is not limited to intermediate products such as RF front-end, filter and amplifier modules, and terminal products such as mobile phones, WIFI, and drones.

Although embodiments of the present disclosure have been shown and described, it will be understood by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present disclosure, the scope of which is determined by It is defined by the appended claims and their equivalents.

Claims

A bulk acoustic wave resonator, comprising:

base;

acoustic mirror;

bottom electrode;

top electrode; and

a piezoelectric layer, arranged between the bottom electrode and the top electrode,

in:

The upper side of the piezoelectric layer and the lower side of the piezoelectric layer are respectively provided with a first mass load array and a second mass load array;

The first mass load array includes a plurality of mass loads on the upper side of the piezoelectric layer, and the second mass load array includes a plurality of mass loads on the lower side of the piezoelectric layer.
The resonator of claim 1, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates.
The resonator of claim 2, wherein:

The arrangement relationship between the first mass load array and the second load array is that at least a part of one array is an array in which the corresponding part of the other array is translated at least once.
The resonator of claim 1, wherein:

Both the first mass load array and the second load array are arranged in polar coordinates.
The resonator of claim 4, wherein:

The arrangement relationship between the first mass load array and the second load array is that at least a part of one array is an array in which a corresponding part of the other array is rotated by an angle.
The resonator of claim 1, wherein:

The arrangement relationship of the first mass load array and the second load array is a complementary array. In the top view of the resonator, the first mass load array and the second load array together form a new array, and the first mass load array and the second mass load array form a new array. Each constitutes a different component of the new array.
The resonator of claim 6, wherein:

One of the first mass load array and the second load array has at least one unit to be filled, and the other array has at least one filled unit.
The resonator of claim 7, wherein:

The shape of the unit to be filled is one or more of a polygon, a circle, a circular ring, a polygonal ring, a straight line or a polyline, and the shape of the at least one unit to be filled is the same as the shape of the at least one unit to be filled. The shape of the unit corresponds.
The resonator of claim 8, wherein:

The shape of the unit to be filled is a polygon or a polygonal ring;

The outer contour of the polygon or polygonal ring of the unit to be filled is similar to the shape of the active area of the resonator.
The resonator of claim 8, wherein:

The unit to be filled includes a plurality of units to be filled in the shape of a straight line.
The resonator of claim 10, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates, and the plurality of cells to be filled are spaced parallel to each other; or

Both the first mass load array and the second load array are arranged in polar coordinates, and ends of the plurality of cells to be filled in the circumferential direction are spaced apart from each other.
The resonator of claim 6, wherein:

One of the first mass load array and the second mass load array includes a plurality of mass load points to be filled, and the other of the first mass load array and the second mass load array includes a plurality of mass loads associated with the plurality of mass loads. Multiple mass loads corresponding to the positions of the points to be filled.
The resonator of claim 12, wherein:

Both the first mass load array and the second load array are arranged in Cartesian coordinates;

The one of the first mass load array and the second load array has a plurality of cells to be filled, each cell to be filled includes at least one point to be filled with a mass load, and the plurality of cells to be filled constitute a first polygon shaped cell array.
The resonator of claim 13, wherein:

Each unit to be filled contains a mass-loaded point to be filled.
The resonator of claim 13, wherein:

Each unit to be filled contains a plurality of points to be filled with mass load;

the other of the first mass load array and the second mass load array includes a plurality of filling cells, each filling cell includes a plurality of mass loads, and the plurality of filling cells constitute a second cell array;

The new array is a cell array formed by complementing the first polygonal cell array and the second polygonal cell array.
The resonator of claim 1, wherein:

The geometry of the mass loads in the first array of mass loads is different from the geometry of the mass loads in the second array of mass loads.
The resonator of any of claims 1-16, wherein:

An acoustic impedance structure is arranged between the piezoelectric layer and the substrate;

The acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction, the acoustic impedance of the first acoustic impedance layer and the second acoustic impedance layer are different, and the acoustic mirror is in the The resonator is located between the first acoustic impedance layers in the lateral direction.
The resonator of claim 17, wherein:

The widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are mλ 1 /4 and nλ 2 /4, respectively, where m and n are odd numbers, and λ 1 and λ 2 are respectively the first Wavelengths of acoustic waves propagating laterally at the resonant frequency of the acoustic impedance layer and the second acoustic impedance layer.
The resonator of claim 17, wherein:

A material forming one of the first acoustic impedance layer and the second acoustic impedance layer is selected from aluminum nitride, silicon dioxide, silicon nitride, polysilicon, and amorphous silicon to form the first acoustic impedance layer and the second acoustic impedance layer The material of another layer in the impedance layer is selected from silicon dioxide, doped silicon dioxide, polycrystalline silicon, and amorphous silicon, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.
The resonator of claim 17, wherein:

The acoustic mirror is an acoustic mirror cavity;

The boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.
The resonator of claim 1, wherein:

The piezoelectric layer is a single crystal piezoelectric layer.
A filter comprising a bulk acoustic wave resonator according to any one of claims 1-21.
An electronic device comprising the filter according to claim 22, or the bulk acoustic wave resonator according to any one of claims 1-21.