CN114070248A

CN114070248A - Bulk acoustic wave resonator assembly with acoustic decoupling layer, manufacturing method of bulk acoustic wave resonator assembly, filter and electronic device

Info

Publication number: CN114070248A
Application number: CN202010785118.5A
Authority: CN
Inventors: 庞慰; 张巍; 张孟伦
Original assignee: ROFS Microsystem Tianjin Co Ltd
Current assignee: ROFS Microsystem Tianjin Co Ltd
Priority date: 2020-08-06
Filing date: 2020-08-06
Publication date: 2022-02-18
Also published as: WO2022028402A1

Abstract

The invention relates to a bulk acoustic wave resonator assembly comprising: a substrate; at least two resonators which are bulk acoustic wave resonators and are stacked in a thickness direction of the substrate on one side of the substrate, the at least two resonators including a first resonator and a second resonator, the second resonator being above the first resonator, the first resonator having a first top electrode, a first piezoelectric layer, a first bottom electrode and a first acoustic mirror, the second resonator having a second top electrode, a second piezoelectric layer, a second bottom electrode and a second acoustic mirror, wherein: an acoustic decoupling layer in a cavity form is arranged between the first top electrode and the second bottom electrode and serves as the second acoustic mirror; at least one of the electrodes is provided with an acoustic boundary structure along the boundary of the active area of the corresponding resonator. The invention also relates to a method of manufacturing a bulk acoustic wave resonator assembly, a filter and an electronic device.

Description

Bulk acoustic wave resonator assembly with acoustic decoupling layer, manufacturing method of bulk acoustic wave resonator assembly, filter and electronic device

Technical Field

Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator assembly and a method of manufacturing the same, a filter having the resonator assembly, and an electronic device.

Background

With the rapid development of wireless communication technology, the application of miniaturized portable terminal equipment is becoming more and more extensive, and thus the demand for high-performance and small-size radio frequency front-end modules and devices is becoming more and more urgent. In recent years, filter devices such as filters and duplexers based on Film Bulk Acoustic Resonators (FBARs) have been increasingly favored in the market. On one hand, the material has excellent electrical properties such as low insertion loss, steep transition characteristic, high selectivity, high power capacity, strong anti-static discharge (ESD) capability and the like, and on the other hand, the material has the characteristics of small volume and easy integration.

However, there is a real need for further reduction of the size of the filter device.

In addition, in the prior art, bulk acoustic wave resonators are combined in series and parallel to form a filter, and a plurality of resonators are required to be formed on a substrate, and the resonators are separated at different horizontal positions of the substrate and connected by horizontal metal leads, as shown in fig. 1, wherein the top electrode 104 of the resonator 100 within the dashed box is connected to the bottom electrode 102 of the resonator 200 by a conductive via v, in order to ensure the electrical signal transmission and the limitation of the manufacturing process, the width of the connection between the conductive via v and the top electrode 104 of the resonator 100, the width of the conductive via v, the width of the top electrode 104 of the resonator 100 and the width of the bottom electrode 102 of the resonator 200 are required, and the total length is generally greater than 5 μm, which causes the connection line to introduce large electrical loss, especially for high-frequency resonators, at electrode thicknesses <1000A, the insertion loss is degraded by more than 0.1 dB.

In addition, in real applications, there is still a need to further suppress the sound wave in the transverse vibration mode to increase the parallel resonance impedance Rp of the resonator, thereby increasing the Q value of the resonator.

Disclosure of Invention

The present invention has been made to mitigate or solve at least one of the above-mentioned problems in the prior art.

According to an aspect of an embodiment of the present invention, there is provided a bulk acoustic wave resonator assembly including:

a substrate;

at least two resonators which are bulk acoustic wave resonators and are stacked in a thickness direction of the substrate on one side of the substrate, the at least two resonators including a first resonator and a second resonator, the second resonator being above the first resonator, the first resonator having a first top electrode, a first piezoelectric layer, a first bottom electrode and a first acoustic mirror, the second resonator having a second top electrode, a second piezoelectric layer, a second bottom electrode and a second acoustic mirror,

wherein:

an acoustic decoupling layer in a cavity form is arranged between the first top electrode and the second bottom electrode and serves as the second acoustic mirror;

at least one of the electrodes is provided with an acoustic boundary structure along the boundary of the active area of the corresponding resonator.

Embodiments of the present invention also relate to a bulk acoustic wave resonator assembly comprising:

at least two resonators adjacently stacked from bottom to top in a thickness direction of the assembly, the at least two resonators being bulk acoustic wave resonators, the at least two resonators including a first resonator and a second resonator, wherein:

an acoustic decoupling layer in a cavity form is arranged between the top electrode of the first resonator and the bottom electrode of the second resonator, and the acoustic decoupling layer is used as an acoustic mirror of the second resonator; and is

Embodiments of the present invention also relate to a method of manufacturing a bulk acoustic wave resonator assembly, comprising:

step 1: forming a first structure for a first bulk acoustic wave resonator on a surface of a substrate, the first bulk acoustic wave resonator comprising a first acoustic mirror, a first bottom electrode, a first piezoelectric layer, a first top electrode;

step 2: arranging a patterned sacrificial material layer on the first structure formed in the step 1;

and step 3: forming a second structure for a second bulk acoustic wave resonator on the structure of step 2, the second bulk acoustic wave resonator including a second acoustic mirror, a second bottom electrode, a second piezoelectric layer, and a second top electrode, the sacrificial material layer being located between the first top electrode and the second bottom electrode in a thickness direction of the substrate;

and 4, step 4: releasing the sacrificial material layer to form a cavity constituting a second acoustic mirror of a second bulk acoustic wave resonator,

wherein:

at least one of the first top electrode, the second top electrode, the first bottom electrode and the second bottom electrode is provided with an acoustic boundary structure along the effective area of the corresponding bulk acoustic wave resonator.

Embodiments of the present invention are also directed to a filter comprising the bulk acoustic wave resonator assembly described above.

Embodiments of the invention also relate to an electronic device comprising a filter as described above or a resonator assembly as described above.

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:

figure 1 is a schematic cross-sectional view of an electrical connection between two adjacent bulk acoustic wave resonators in a prior art design;

FIG. 2 is a schematic top view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention;

fig. 3A is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically connected to a bottom electrode of the upper resonator, according to an exemplary embodiment of the present invention;

fig. 3B is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line B-B' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically connected to a bottom electrode of the upper resonator, according to an exemplary embodiment of the present invention;

fig. 3C is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line C-C' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically connected to a bottom electrode of the upper resonator, according to an exemplary embodiment of the present invention;

FIG. 3D is a graph illustrating a comparison of insertion loss curves for the structure of FIG. 3A relative to the structure of FIG. 1;

fig. 4 to 8 are schematic cross-sectional views of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically connected to a bottom electrode of the upper resonator, according to various exemplary embodiments of the present invention;

fig. 9 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which non-electrode connection ends of top electrodes of upper and lower resonators are provided with a suspension wing, and the top electrode of the lower resonator is electrically connected to the bottom electrode of the upper resonator, according to still another exemplary embodiment of the present invention;

fig. 10 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which non-electrode connection ends of top electrodes of upper and lower resonators are provided with convex-concave portions, and the top electrode of the lower resonator is electrically connected to the bottom electrode of the upper resonator, according to still another exemplary embodiment of the present invention;

fig. 11 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically isolated from a bottom electrode of the upper resonator, according to still another exemplary embodiment of the present invention;

fig. 12 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically isolated from a bottom electrode of the upper resonator, according to still another exemplary embodiment of the present invention;

FIGS. 13A-13H are schematic diagrams illustrating a fabrication process for the structure shown in FIG. 3A;

FIGS. 14A and 14B are schematic diagrams illustrating a method of making the structure shown in FIGS. 7-8;

figure 15 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention.

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. Some, but not all embodiments of the invention are described. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The reference numerals in the present invention are explained as follows:

10: and the electrode of the bottom electrode of the lower resonator is led out.

20: the electrode of the top electrode of the upper resonator is led out.

S: the substrate can be selected from monocrystalline silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond and the like.

101,201: the acoustic mirror, the acoustic mirror 103, may be a cavity, and bragg reflector and other equivalent forms may also be used. The acoustic mirror 201 is a cavity, which constitutes an acoustic decoupling layer.

102,202: the bottom electrode is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy.

103,203: the piezoelectric layer can be a single crystal piezoelectric material, and can be selected from the following: the material may be polycrystalline piezoelectric material (corresponding to single crystal, non-single crystal material), optionally, polycrystalline aluminum nitride, zinc oxide, PZT, or a rare earth element doped material containing 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), erbium (Ho), erbium (holmium), thulium (Tm), ytterbium (Yb), lutetium (Lu), or the like.

104,204: the top electrode can be made of the same material as the bottom electrode, and 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 the alloy thereof, and the like. The top and bottom electrode materials are typically the same, but may be different.

105,205: a cantilever or a cavity between the top electrode and the piezoelectric layer.

106,206: and (4) a convex structure.

107,207: and (5) a concave structure.

Fig. 2 is a schematic top view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, in fig. 2, a line a-a ' corresponds to a section through non-electrode connection ends of top electrodes and bottom electrodes of upper and lower resonators, a line B-B ' corresponds to a section through electrode connection ends of top electrodes and bottom electrodes of upper resonators, and a line C-C ' corresponds to a section through electrode connection ends of top electrodes and bottom electrodes of lower resonators.

Fig. 3A is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2 according to an exemplary embodiment of the present invention.

Although not shown, the top electrode of the resonator may also have a process layer disposed thereon, which may cover the top electrode, and which may function as a mass tuning load or passivation layer. The passivation layer may be made of dielectric material, such as silicon dioxide, aluminum nitride, silicon nitride, etc.

Further, in the structure shown in fig. 3A, two resonators are formed at the same horizontal position of the substrate S, and the two resonators are different in spatial position in the vertical direction or in the thickness direction of the substrate.

As can be appreciated by those skilled in the art, three resonators or more may also be stacked. Figure 15 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention. As shown in fig. 15, the resonator assembly includes a first resonator, a second resonator, and a third resonator stacked in the thickness direction, an acoustic decoupling layer 201 (a cavity in this embodiment) is provided between a top electrode 104 of the first resonator and a bottom electrode 202 of the second resonator, an acoustic decoupling layer 301 (a cavity in this embodiment) is provided between a top electrode 204 of the second resonator and a bottom electrode 302 of the third resonator, and the acoustic decoupling layer 301 constitutes an acoustic mirror of the third resonator. As can be appreciated, the assembly structures shown in other embodiments of the invention may also be stacked.

In the structure shown in fig. 3A, two resonators above and below are shown, wherein the effective area of the upper resonator is the overlapping area of the top electrode 204, the piezoelectric layer 203, the bottom electrode 202, and the cavity 201 in the thickness direction. The lower resonator is an overlapping area of the cavity 201, the top electrode 104, the piezoelectric layer 103, the bottom electrode 102, and the acoustic mirror 101 in the thickness direction.

Accordingly, in fig. 15, the effective area of the uppermost third resonator is the overlapping area of the top electrode 304, the piezoelectric layer 303, the bottom electrode 302, and the cavity 301 in the thickness direction, the effective area of the middle second resonator is the overlapping area of the cavity 301, the top electrode 204, the piezoelectric layer 203, the bottom electrode 202, and the cavity 201 in the thickness direction, and the effective area of the lowermost first resonator is the overlapping area of the cavity 201, the top electrode 104, the piezoelectric layer 103, the bottom electrode 102, and the cavity 101 in the thickness direction.

In the structure shown in fig. 3A, the upper resonator is acoustically separated from the lower resonator by a cavity 201, i.e. the cavity 201 constitutes an acoustic decoupling layer between the upper and lower resonators, thereby completely avoiding the acoustic coupling problem that may result from the adjacent stacking of the upper and lower resonators.

The cavity 201 is used as an acoustic decoupling layer, complete acoustic decoupling of the upper resonator and the lower resonator can be achieved, and therefore the performance of the resonators is better. Further, in the case that the cavity 201 is directly surrounded by the top electrode 104 of the lower resonator and the bottom electrode 202 of the upper resonator (the structure defining the cavity position in other embodiments further includes the piezoelectric layer of the upper resonator and/or the lower resonator), such as the structures shown in fig. 3A to 3C and 11, the overall structure is stable and reliable, and the processing process is simple.

As can be understood by those skilled in the art, the cavity 201 is disposed between the bottom electrode of the upper resonator and the top electrode of the lower resonator in the thickness direction of the resonator, including not only the case where at least a portion of the upper and lower boundaries of the cavity is defined by the lower surface of the bottom electrode of the upper resonator and the upper surface of the top electrode of the lower resonator, but also the case where the upper surface of the top electrode of the lower resonator is provided with a process layer (e.g., a passivation layer) such that the process layer defines at least a portion of the lower boundary of the cavity 201. These are all within the scope of the present invention.

In the structure shown in fig. 3A, since the plurality of resonators are formed at the same horizontal position of the substrate S, the spatial positions of the plurality of resonators in the vertical direction or in the thickness direction of the substrate are different, and therefore, the area of the filter can be greatly reduced, for example, in the case where two resonators are provided as well, from the area P1 shown in fig. 1 to the area P2 shown in fig. 3A.

As shown in fig. 3A, the bottom electrode 202 of the upper resonator and the top electrode 104 of the lower resonator are electrically connected to each other at a non-electrode connection terminal. Under the condition that the bottom electrode of the upper resonator is directly connected with the top electrode of the lower resonator, the bottom electrode of the upper resonator is directly and electrically connected with the top electrode of the lower resonator, and the length of the connecting part is shorter than that in the figure 1, namely, the transmission path is shortened, and the transmission loss is reduced; in addition, the transmission loss of the electrical signal output is further reduced by the sum of the thicknesses of the top electrode of the lower resonator and the bottom electrode of the upper resonator through the metal thickness. By reducing the electrical losses, the insertion loss of the final filter is optimized. As shown in fig. 3A, the length of the transmission path formed by the bottom electrode of the upper resonator and the top electrode of the lower resonator at the non-electrode-connecting end is d, which may be less than 5 μm.

With the structure of fig. 3A to 3C, for example, since the current transmission path to the lower resonator is short, it can be less than 5 μm, the transmission loss is reduced, and the thickness of the top electrode 104 of the lower resonator and the thickness of the bottom electrode 202 of the upper resonator can be thinned, which is beneficial to further miniaturization of the resonator. In the case where the bottom electrode of the upper resonator and the top electrode of the lower resonator are electrically connected to each other, the electrode film thickness of the bottom electrode of the upper resonator and the top electrode of the upper resonator can be further reduced simultaneously while reducing the circuit transmission path loss to the bottom electrode of the upper resonator and the current transmission path loss to the top electrode of the lower resonator. Accordingly, in the case where the resonance frequency of the lower resonator is greater than 0.5GHz, the thickness of the top electrode 104 is smaller than

And/or the thickness of the bottom electrode 202 is less than in the case where the resonance frequency of the upper resonator is greater than 0.5GHz

In a further embodiment, in the case where the resonance frequency of the lower resonator is more than 3GHz, the thickness of the top electrode 104 may be designed to be less than

And/or in case the resonance frequency of the upper resonator is larger than 3GHz, the thickness of the bottom electrode 202 of the upper resonator may also be smaller than

As can be understood, in the present invention, the thinning of the thickness of the electrode means thinning of the thickness of the electrode in the effective region of the resonator.

Fig. 3D is a graph schematically illustrating a comparison of insertion loss curves for the structure of fig. 3A with respect to the structure of fig. 1. Fig. 3D is a comparison between the insertion loss curve (solid line) of the 3.5G band using the structure of fig. 3A of the present invention and the insertion loss curve (dotted line) of the conventional structure of fig. 1, and it can be seen that the insertion loss is improved by about 0.1dB due to the reduction of the electrode loss using the structure of fig. 3A of the present invention.

In the case where the bottom electrode of the upper resonator and the top electrode of the lower resonator are electrically connected to each other, in the structure shown in fig. 3A, the non-electrode connection ends of the bottom electrode of the upper resonator and the top electrode of the lower resonator are connected to each other. However, other connection methods than the one shown in fig. 3A are also possible. For example, the bottom electrode of the upper resonator and the top electrode of the lower resonator may be electrically connected to each other only at a part of the non-electrode connection terminal; alternatively, the bottom electrode of the upper resonator and the top electrode of the lower resonator may be electrically connected to each other only at the electrode connection end; or the bottom electrode of the upper resonator and the top electrode of the lower resonator may be electrically connected to each other only at all or part of the non-electrode connection terminals; or the bottom electrode of the upper resonator and the top electrode of the lower resonator are electrically connected to each other not only at the electrode connection end but also at the non-electrode connection end. These are all within the scope of the present invention.

When the maximum width of the effective area of the resonator is larger than the height of the cavity, the upper resonator and the lower resonator may be contacted in the cavity due to bending and the like, for example, the height of the cavity is

When the maximum width of the resonator effective area is larger than 100 μm, in order to ensure the complete formation of the cavity 201 in the upper and lower resonator effective areas, the stress of the lower resonator can be controlled to bend towards the lower air cavity, and/or the stress of the upper resonator can be controlled to bend towards the upper air cavity, and the top electrode of the finally formed lower resonator is concave downwards, and/or the bottom electrode of the upper resonator is convex upwards.

Although controlling the stress can reduce the probability of the upper resonator and the lower resonator contacting each other, when the resonator area is larger, a support member can be added between the upper resonator and the lower resonator in the cavity 201, the support member can contact with the top or the top electrode of the lower resonator, the height of the support member is less than or equal to the cavity height, which means that the top end of the support member contacts with the bottom or the bottom electrode of the upper resonator, the height of the support member is less than the cavity height, which means that the top end of the support member does not contact with the upper resonator, when the local thickness of the cavity is reduced due to the bending of the resonator, the top end of the support member contacts with the upper resonator to play a supporting role.

The resonator mainly utilizes the piezoelectric/inverse piezoelectric effect to convert the elastic energy of longitudinal vibration and the electric energy of an external electric field into each other, and the energy loss in the working process comprises three parts: (1) thermal losses of vibrations inside the piezoelectric layer, (2) electrode losses, (3) lateral wave dissipation losses: the first loss reduction requires the piezoelectric material itself to be improved, for example, a single crystal aluminum nitride with low loss is adopted; the second loss generally plays a major role only at high frequencies (>3GHz) when the electrode thickness is very thin; in order to reduce the lateral wave dissipation losses, an acoustic boundary structure is provided in the resonator assembly according to the invention, as shown in fig. 3A.

In fig. 3A, the top electrode 204 of the upper resonator is formed with the concave structure 207, and the resonance frequency of the portion where the concave structure 207 is provided is higher than the resonance frequency of the effective region of the upper resonator, so that the transverse wave loss below the resonance frequency of the effective region can be suppressed, and the suppression degree is proportional to the width d207 of the structure. The top electrode of the upper resonator is also provided with a convex structure 206, the resonance frequency of the part provided with the convex structure 206 is lower than the resonance frequency of the effective area of the upper resonator, so that the transverse wave loss above the resonance frequency of the effective area can be inhibited, the inhibition degree and the width d206 of the convex structure are periodically changed, the width of the convex structure needs to be properly selected, in addition, the acoustic impedance of the part is different from the effective area, and therefore, the transverse wave capacity of the part can be reflected, and the energy loss is reduced. The top electrode 204 of the upper resonator is further provided with a suspension wing 205, and the suspension wing 205 forms a gap structure (the gap can also be provided with a dielectric material) between the top electrode of the upper resonator and the piezoelectric layer, which changes the electric field on the surface of the piezoelectric layer 203, and further changes the local vibration form of the piezoelectric layer 203, so that the overflow of the transverse wave energy is suppressed, and the suppression degree changes periodically with the width d205 of the suspension wing 205. By properly selecting the values of d205\ d206\ d207, the three boundary structures can improve the Q value of the resonator in the whole frequency range.

The top electrode of the lower resonator is provided with a recessed structure 107, a raised structure 106, and a suspension wing 105, the suspension wing 105 forming a void structure (the void may also be provided with a dielectric material) between the top electrode and the piezoelectric layer of the lower resonator. The action principle of the concave structure 107, the convex structure 106 and the suspension wings 105 is the same as that of the above, and the detailed description is omitted.

In the embodiment of the present invention, the example that the convex-concave portion includes both the convex and the concave is described, but as can be understood by those skilled in the art, the convex-concave portion may include only the convex or only the concave. In addition, in the illustrated embodiment, in the convex-concave portion where the protrusion and the recess are provided at the same time, the protrusion is located outside the recess, but the present invention is not limited thereto, and the protrusion may be located inside the recess. All of the above are within the scope of the present invention.

In one embodiment of the invention, the boundary of the cavity 201 is outside the inner edge of the flap 105 in the lateral direction, and for the flap 105, the lateral distance between the inner edge of the flap 105 and the boundary of the acoustic mirror 101 is taken as the width d105 of the flap 105 in fig. 3A, as shown in fig. 3A. The Q value of the lower resonator can be improved by properly selecting the values of d105\ d106\ d107 through the three boundary structures.

In the present invention, the wing bridge portion means a structure having a cantilever and/or a bridge portion, and in the structure shown in fig. 3A, both the

top electrodes

104 and 204 are provided with the wing bridge portion.

Fig. 3B is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line B-B' in fig. 2 according to an exemplary embodiment of the present invention, and in fig. 3B, the upper and lower resonators are also provided with a wing bridge portion and a convex recess portion, similar to those in fig. 3A, and the top electrode 104 of the lower resonator is electrically connected to the bottom electrode 202 of the upper resonator. In fig. 3B, it can be seen that the electrode connection portion of the top electrode 204 is provided with a bridge portion.

Fig. 3C is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line C-C' in fig. 2, in which fig. 3C, upper and lower resonators are provided with a wing bridge portion and a convex-concave portion, and a top electrode 104 of the lower resonator is electrically connected to a bottom electrode 202 of the upper resonator, according to an exemplary embodiment of the present invention. In fig. 3C, a bridge portion is provided in the electrode connection portion of the lower resonator.

In fig. 3A-3C, the outer edge of the wing bridge portion 105 provided at the bottom electrode is outside the edge of the bottom electrode 102 in the lateral direction, which is advantageous in preventing the vertical structure of the top electrode 104, the piezoelectric layer 103, the bottom electrode 102, which would degrade the resonator performance, from being formed outside the effective area of the lower resonator.

It should be noted that in the present invention, the same reference numerals in different embodiments have the same definitions or meanings, and therefore, the description of the parameters or components or structures made above with reference to fig. 3A to 3C also applies to the same parameters, components or structures in the subsequent embodiments.

Fig. 4 to 8 are schematic cross-sectional views of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which upper and lower resonators are provided with a wing bridge portion and a convex recess portion, and a top electrode of the lower resonator is electrically connected to a bottom electrode of the upper resonator, according to various exemplary embodiments of the present invention.

As shown in fig. 4, the non-electrode connecting end of the top electrode 104 is provided with the bridge portion 105, and the non-electrode connecting end of the top electrode 204 is provided with the overhang 205. In the embodiment shown in fig. 4, the acoustic boundary structure includes a bridge 105 disposed in the top electrode 104 and a cantilever 205 in the top electrode 204. As shown in fig. 4, the inner edges of the bridge 105 and the suspension wings 205 are located inside the boundary of the cavity 201 in the lateral direction.

For the flap 105, in fig. 4, the lateral distance between the inner edge of the flap 105 and the boundary of the acoustic mirror 101 is taken as the width d105 of the flap 105; regarding the bridge 205, in fig. 4, the lateral distance between the inner edge of the bridge 205 and the boundary of the cavity 201 is taken as the width d205 of the bridge 205, and in fig. 4, since the outer edge of the bridge 205 is outside the boundary of the cavity 201, the width d205 of the bridge 205 is the distance in the lateral direction from the inner edge of the bridge 205 to the boundary of the acoustic mirror 101, not the actual width of the bridge 205.

As shown in fig. 5, the non-electrode connection end of the top electrode 104 is provided with the convex structure 106 and the concave structure 107, and the non-electrode connection end of the top electrode 204 is provided with the convex structure 206 and the concave structure 207. In the embodiment shown in fig. 5, the acoustic boundary structure includes a raised structure 106, a recessed structure 107, a cantilever 105 disposed at the non-electrode connecting end of the top electrode 104, and a bridge 205, a raised structure 206 and a recessed structure 207 at the non-electrode connecting end of the top electrode 204.

As shown in fig. 5, the outer edges of the raised and recessed structures provided by the top electrode define the boundaries of the active area of the corresponding resonator. As shown in fig. 5, the outer edges of the raised and lowered structures are located inside the boundaries of the cavity 201 in the lateral direction. The bridge 205 and the inner edge of the suspension wing 105 are located laterally inside the boundary of the cavity 201.

For the flap 105, in fig. 5, the lateral distance between the inner edge of the flap 105 and the boundary of the acoustic mirror 101 is taken as the width d105 of the flap 105; regarding the bridge 205, in fig. 5, the lateral distance between the inner edge of the bridge 205 and the boundary of the cavity 201 is taken as the width d205 of the bridge 205, and in fig. 5, because the outer edge of the bridge 205 is outside the boundary of the cavity 201, the width d205 of the bridge 205 is the distance between the inner edge of the bridge 205 and the boundary of the cavity 201 in the lateral direction and is not the actual width of the bridge 205.

As shown in fig. 5, the outer edge of the bridge 205 is outside the boundary of the cavity 201 in the lateral direction, which is advantageous for preventing the formation of a vertical structure formed by the top electrode 204, the piezoelectric layer 203, the bottom electrode 202 outside the active area of the upper resonator, which vertical structure affects the performance of the upper resonator.

Although in the above illustrated embodiments, the recesses, protrusions, and tabs are in the top electrode region, it is also possible to form the recesses, protrusions in a similar location on the bottom electrode. In the embodiments shown in fig. 7 and 8, the bottom electrode is provided with a raised and recessed structure.

As shown in fig. 6, the non-electrode connection end of the top electrode 104 is provided with the convex structure 106 and the concave structure 107, and the bridge portion 105, while the non-electrode connection end of the top electrode 204 is provided with the convex structure 206 and the concave structure 207, and the bridge portion 205. In the embodiment shown in fig. 6, the acoustic boundary structure includes raised and recessed structures and bridges disposed in the top electrode.

As shown in fig. 6, the outer edges of the convex and concave structures provided to the top electrode, or the inner edges of the bridges, define the boundaries of the active area of the corresponding resonator. As shown in fig. 6, the outer edges of the raised and recessed structures are located laterally inward of the boundaries of the cavity 201, and the inner edges of the

bridges

105 and 205 are located laterally inward of the boundaries of the cavity 201.

As for the bridge 105, in fig. 6, the lateral distance between the inner edge of the bridge 105 and the boundary of the acoustic mirror 101 is taken as the width d105 of the bridge 105; regarding the bridge 205, in fig. 6, the lateral distance between the inner edge of the bridge 205 and the boundary of the cavity 201 is taken as the width d205 of the bridge 205, and in fig. 6, because the outer edge of the bridge 205 is outside the boundary of the cavity 201, the width d205 of the bridge 205 is the distance between the inner edge of the suspension wing 205 and the boundary of the cavity 201 in the lateral direction rather than the actual width of the bridge 205.

As shown in fig. 7, the non-electrode connection end of the top electrode 104 is provided with the convex structure 106 and the concave structure 107, and the bridge portion 105, while the non-electrode connection end of the top electrode 204 is provided with the convex structure 206 and the concave structure 207, and the overhang 205; further, the bottom electrode 202 of the upper resonator is provided with a convex structure 208 and a concave structure 209. In the embodiment shown in fig. 7, the acoustic boundary structures include raised and recessed structures, bridges and overhangs, disposed at the non-electrode connecting end of the

top electrodes

104 and 204, and raised and recessed structures disposed at the non-electrode connecting end of the bottom electrode 202 of the upper resonator.

As shown in fig. 7, the outer edges of the raised and recessed structures provided by the top electrode, or the inner edges of the bridges or cantilevers, define boundaries corresponding to the active area of the resonator. As shown in fig. 7, the outer edges of the raised and recessed structures of the top electrode are laterally inward of the boundaries of the cavity 201, and the inner edges of the bridges or

flaps

105 and 205 are laterally inward of the boundaries of the cavity 201.

As for the bridge 105, in fig. 7, the lateral distance between the inner edge of the bridge 105 and the boundary of the acoustic mirror 101 is taken as the width d105 of the bridge 105; regarding the suspension wing 205, in fig. 7, the lateral distance between the inner edge of the suspension wing 205 and the boundary of the cavity 201 is taken as the width d205 of the suspension wing 205, and in fig. 7, the width d205 of the bridge 205 is the actual width of the suspension wing 205 because the outer edge of the suspension wing 205 is inside the boundary of the cavity 201.

The structure shown in fig. 8 differs from the structure shown in fig. 7 in that in fig. 8 the bottom electrode 102 of the lower resonator is provided with a raised structure 108 as well as a recessed structure 109. In fig. 8, to increase the structural symmetry of the top and bottom electrodes of the lower resonator, the outer edges of the raised structures 108 of the bottom electrode 102 are flush with the outer edges of the raised structures 108 of the top electrode 104, and the inner edges of the recessed structures 109 of the bottom electrode 102 are flush with the inner edges of the recessed structures 107 of the top electrode 104.

Further, in the present invention, although not shown, in the case where both the bottom electrode and the top electrode of one resonator are provided with the convex structure and the concave structure, the concave structure of one electrode may be inside the concave structure of the other electrode and the convex structure of one electrode may be inside the convex structure of the other electrode in the lateral direction.

In fig. 8, the definitions or explanations above with reference to fig. 3A-7 apply for the widths d105 and d 205.

Fig. 9 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2 according to still another exemplary embodiment of the present invention, in fig. 9, non-electrode connection ends of top electrodes of upper and lower resonators are provided with

suspension wings

105 and 205, respectively, and the top electrode of the lower resonator is electrically connected to the bottom electrode of the upper resonator. In fig. 9, the inner edges of

flaps

105 and 205 are located laterally inward of the boundaries of cavity 201.

Fig. 10 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2, in which non-electrode connection ends of top electrodes of upper and lower resonators are provided with

convex structures

106 and 206, and

concave structures

107 and 207, respectively, and the top electrode of the lower resonator is electrically connected to the bottom electrode of the upper resonator, according to still another exemplary embodiment of the present invention. As shown in fig. 10, the outer edges of the raised and recessed structures provided by the top electrode define the boundaries of the active area of the corresponding resonator. As shown in fig. 10, the outer edge of the convex and concave structure of the top electrode is located inside the boundary of the cavity 201 in the lateral direction.

In the above embodiments shown in fig. 3A-10, the bottom electrode 202 of the upper resonator and the top electrode 104 of the lower resonator are electrically connected to each other. The present invention is not limited thereto and the bottom electrode 202 of the upper resonator and the top electrode 104 of the lower resonator may be electrically isolated from each other.

Fig. 11 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along line a-a' in fig. 2 according to still another exemplary embodiment of the present invention. In fig. 11, at least a part of the end portion of the non-electrode connecting end of the bottom electrode 202 of the upper resonator in the circumferential direction is provided on the upper surface of the piezoelectric layer 103, and the end portion of the at least a part is located outside the acoustic boundary structure (the wing bridge portion and the convex recess portion) of the top electrode 104 in the horizontal direction. Thus, in fig. 11, the top electrode 104 of the lower resonator is electrically isolated from the bottom electrode 102 of the upper resonator.

Fig. 12 is a schematic cross-sectional view of a bulk acoustic wave resonator taken along the line a-a' in fig. 2, in which upper and lower resonators are provided with an acoustic boundary structure including a wing bridge portion and a convex recess portion, according to still another exemplary embodiment of the present invention, in fig. 12, an end portion of a part (e.g., see the left end in fig. 12) of the non-electrode connecting end of the bottom electrode 202 of the upper resonator in the circumferential direction is provided on the upper surface of the piezoelectric layer 103, an end portion of the other part (e.g., the right end in fig. 12) of the non-electrode connecting end of the bottom electrode 202 in the circumferential direction is located inside the boundary of the cavity 201 in the horizontal direction, and the top electrode 104 of the lower resonator is electrically isolated from the bottom electrode 202 of the upper resonator.

In FIGS. 9-12, the definitions or explanations above with reference to FIGS. 3A-7 apply for the expressions 105-107 and 205-207, and for d105, d106 and d107, and d205, d206 and d 207.

In the present invention, as shown in fig. 3A-3C, 4-12, the effective area of the upper resonator is a2 and the effective area of the lower resonator is a 1. In the embodiment shown, the active areas a1 and a2 are both laterally inboard of the boundary of the cavity 201.

In fig. 3A-3C, 4-8, and 10-12, the regions between the inner edges of the convex-concave structures are region I1 and region I2 for the lower resonator and the upper resonator, respectively.

In an alternative embodiment, as shown in FIGS. 3A-3C, 4-8, and 10-12, the boundary of active area A2 is inside the boundary of active area A1, and the boundary of area I2 is inside the boundary of area I1. If the boundary of the effective region a2 exceeds the boundary of the effective region a1 in the lateral direction, or the boundary of the region I2 exceeds the boundary of the region I1 in the lateral direction, this will result in an increase in the lateral acoustic wave loss of the upper resonator and a decrease in the Q value of the upper resonator. Therefore, in a further embodiment, the present invention restricts the boundaries of the effective region a2 and the region I2 to the inner sides of the boundaries of the effective region a1 and the region I1, respectively, which contributes to further increase the Q value of the upper resonator.

The fabrication of the structure shown in fig. 3A is illustrated with reference to fig. 13A-13G.

Step 1: as shown in fig. 13A, the lower resonator is fabricated by a conventional FBAR process, including fabrication of a first sacrificial material layer corresponding to the acoustic mirror 101, the bottom electrode 102, and the piezoelectric layer 103; a second layer of sacrificial material, which may be the same material as the first layer of sacrificial material, such as phosphosilicate glass, is then fabricated on the piezoelectric layer 103 corresponding to the voids defined by the flaps 105, and the first and second layers of sacrificial material are removed together in a subsequent step. In fig. 13A to 13G, a passivation layer, a layer whose frequency is adjusted to be less relevant to the idea of the present patent, and the like are not shown.

Step 2: as shown in fig. 13B, an electrode metal layer for forming the top electrode 104 of the lower resonator is deposited on the structure of step 1 by a sputtering or evaporation process, and then, the electrode metal layer corresponding to the top electrode 104 is etched by a photolithography and etching process, and the top electrode metal layer for forming the top electrode 104 is patterned.

And step 3: on the structure of step 2, a raised structure 106 is deposited on the metal layer of the top electrode 104 by a lift-off process, and a recessed structure 107 is formed by depositing a top electrode metal material at a position other than the recessed structure 107, and finally, a pattern structure of the top electrode 104 is formed as shown in fig. 13C.

And 4, step 4: a third sacrificial material layer for forming the cavity 201 is deposited, and the material of the third sacrificial material layer is PSG (phosphosilicate glass), amorphous silicon, BSG (borosilicate glass), BPSG (borophosphosilicate glass), USG (silicate glass), etc., and for the film quality of the upper resonator, the surface of the deposited third sacrificial material layer may be planarized by using a CMP (chemical mechanical polishing) method to obtain the structure shown in fig. 13D. The third layer of sacrificial material will eventually be removed to form a cavity 201 acoustically isolating the upper and lower resonators.

And 5: the bottom electrode 202 of the upper resonator, the piezoelectric layer 203 are fabricated on the structure formed in step 4, and then a fourth sacrificial material layer corresponding to the gap defined by the suspension wings 205 is fabricated on the piezoelectric layer 203 to form the structure shown in fig. 13E, where the fourth sacrificial material layer may be the same material as the first sacrificial material layer, such as phosphosilicate glass, and the first sacrificial material layer and the fourth sacrificial material layer are removed together in a subsequent step.

Step 6: the top electrode 204 of the upper resonator is fabricated on the structure formed in step 5, resulting in the structure shown in fig. 13F.

And 7: the raised structures 206 are deposited by lift-off process, etc., and the recessed structures 207 are fabricated by depositing a top electrode metal material at locations other than the recessed structures 207, resulting in the patterned structure of the top electrode 104 shown in fig. 13G.

And 8: all of the sacrificial material layers are removed to form the structure shown in fig. 3A.

The above fabrication process for the structure shown in fig. 3A can also be applied to the structures shown in fig. 3B-3C, 4-6, with only slight changes to the shape of the top electrode in the case where the suspension wings are replaced with bridge portions.

For the fabrication of the structure shown in fig. 7, the previous steps 1-4 are the same as described above. Thereafter, as shown in fig. 14A, a bump (corresponding to the recessed structure 209) and a recessed structure (corresponding to the raised structure 208) are formed on the third sacrificial material layer corresponding to the cavity 201. Thereafter, a bottom electrode metal layer for the bottom electrode 202 is deposited on the structure of fig. 14A, and the bottom electrode metal layer is planarized using a CMP process, resulting in the structure shown in fig. 14B. The subsequent steps are similar to steps 5-8 described above.

For the fabrication process of the structure shown in fig. 8, which is similar to the fabrication process of the structure shown in fig. 7, just as much as the convex structure 108 and the concave structure 109 are fabricated on the lower surface of the bottom electrode of the lower resonator, which is similar to the formation of the convex corresponding to the concave structure 209 and the concave corresponding to the convex structure 208 in fig. 14A-14B, the concave corresponding to the convex structure 108 and the convex corresponding to the concave structure 109 may be formed at the time of forming the first sacrificial material layer corresponding to the acoustic mirror 101 in the previous step 1. The other steps are the same as those for manufacturing the structure shown in fig. 7.

The manufacturing process of the structure shown in fig. 9 can be achieved by omitting the above-mentioned step 3 and step 7.

The manufacturing process for the structure shown in fig. 10 can be achieved by omitting the previous steps 1 and 5.

It is to be noted that, in the present invention, each numerical range, except when explicitly indicated as not including the end points, can be either the end points or the median of each numerical range, and all fall within the scope of the present invention.

In the present invention, the upper and lower are with respect to the bottom surface of the base of the resonator, and with respect to one component, the side thereof close to the bottom surface is the lower side, and the side thereof far from the bottom surface is the upper side.

In the present invention, the inner and outer are in the lateral direction or the radial direction with respect to the center of the effective area of the resonator (i.e., the effective area center), and one side or one end of a component close to the effective area center is the inner side or the inner end, and one side or one end of the component away from the effective area center is the outer side or the outer end. For a reference position, being inside of the position means being between the position and the center of the effective area in the lateral or radial direction, and being outside of the position means being further away from the center of the effective area than the position in the lateral or radial direction.

As can be appreciated by those skilled in the art, the bulk acoustic wave resonator according to the present invention may be used to form a filter or an electronic device. The electronic device 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.

Based on the above, the invention provides the following technical scheme:

1. a bulk acoustic wave resonator assembly comprising:

a substrate;

wherein:

an acoustic decoupling layer is arranged between the first top electrode and the second bottom electrode and serves as the second acoustic mirror;

2. The assembly of claim 1, wherein:

the acoustic boundary structure includes a wing bridge.

3. The assembly of claim 2, wherein:

the first top electrode or the first bottom electrode is provided with a first bridge and/or the second top electrode or the second bottom electrode is provided with a second bridge.

4. The assembly of claim 3, wherein:

the inner edge of the wing bridge is horizontally inside the boundary of the acoustic decoupling layer.

5. The assembly of claim 4, wherein:

the first top electrode is provided with a first wing bridge part, and the second top electrode is provided with a second wing bridge part;

the inner edge of one of the first and second wing bridges is located outside the inner edge of the other of the first and second wing bridges in the horizontal direction.

6. The assembly of claim 4, wherein:

the inner edge of the first bridge is horizontally inside the boundary of the first acoustic mirror.

7. The assembly of claim 6, wherein:

the non-electrode connecting end of the first bottom electrode is positioned outside the boundary of the acoustic mirror; and is

The outer edge of the first wing bridge part is located outside the non-electrode connecting end of the first bottom electrode in the horizontal direction.

8. The assembly of claim 4, wherein:

the wing bridge part comprises a bridge part arranged at the non-electrode connecting end of the second top electrode;

an inner edge of the bridge is horizontally inside a boundary of the acoustic decoupling layer, and an outer edge of the bridge is horizontally outside the boundary of the acoustic decoupling layer.

9. The assembly of any one of claims 1-8, wherein:

the acoustic boundary structure comprises a convex recess comprising a protrusion and/or a recess.

10. The assembly of claim 9, wherein:

the first top electrode or the first bottom electrode is provided with a first protrusion and/or a first recess, and/or the second top electrode or the second bottom electrode is provided with a second protrusion and/or a second recess.

11. The assembly of claim 8, wherein:

the outer edge of the raised recess defines the boundary of the active area of the corresponding resonator.

12. The assembly of claim 9, wherein:

the inner edge of the first projection is located outside the inner edge of the second projection in the horizontal direction; and/or

The inner edge of the first recess is located outside the inner edge of the second recess in the horizontal direction.

13. The assembly of claim 10, wherein:

13. The assembly of claim 9, wherein:

the outer edge of the raised recess is horizontally inward of the boundary of the acoustic decoupling layer.

14. The assembly of any one of claims 1-13, wherein:

the first top electrode and the second bottom electrode are electrically connected to each other.

15. The assembly of claim 14, wherein:

the acoustic boundary structure includes a first wing bridge portion disposed at an electrode non-connecting end of the first overhead electrode;

the second bottom electrode is electrically connected to the first top electrode at the first wing bridge portion.

16. The assembly of any one of claims 1-13, wherein:

the first top electrode and the second bottom electrode are electrically isolated from each other.

17. The assembly of claim 16, wherein:

at least a part of an end portion of the non-electrode connecting end of the second bottom electrode in the circumferential direction is provided on the upper surface of the first piezoelectric layer, and the at least a part of the end portion is located outside the first wing bridge portion in the horizontal direction.

18. The assembly of claim 17, wherein:

an end of a part of the non-electrode connecting end of the second bottom electrode in the circumferential direction is provided on the upper surface of the first piezoelectric layer, and an end of the other part of the non-electrode connecting end of the second bottom electrode in the circumferential direction is located inside a boundary of the acoustic decoupling layer in the horizontal direction.

19. The assembly of any one of claims 1-18, wherein:

the first resonator has a first effective area, the second resonator has a second effective area, and a boundary of the first effective area is located outside a boundary of the second effective area in a horizontal direction.

20. A bulk acoustic wave resonator assembly comprising:

an acoustic decoupling layer is arranged between the top electrode of the first resonator and the bottom electrode of the second resonator, and the acoustic decoupling layer is used as an acoustic mirror of the second resonator; and is

21. The assembly of

claim

1 or 20, wherein:

the at least two resonators include a first resonator, a second resonator, and a third resonator stacked in a thickness direction;

a first acoustic decoupling layer is arranged between the top electrode of the first resonator and the bottom electrode of the second resonator, a second acoustic decoupling layer is arranged between the top electrode of the second resonator and the bottom electrode of the third resonator, and the second acoustic decoupling layer forms an acoustic mirror of the third resonator.

22. The assembly of claim 21, wherein:

the boundary of the second acoustic decoupling layer is outside the boundary of the first acoustic decoupling layer in the horizontal direction.

23. A method of manufacturing a bulk acoustic wave resonator assembly, comprising:

wherein:

24. A filter comprising a bulk acoustic wave resonator assembly according to any one of claims 1-22.

25. An electronic device comprising the filter of 24 or the bulk acoustic wave resonator assembly of any one of claims 1-22.

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

1. A bulk acoustic wave resonator assembly comprising:

a substrate;

wherein:

2. The assembly of claim 1, wherein:

the acoustic boundary structure includes a wing bridge.

3. The assembly of claim 2, wherein:

4. The assembly of claim 3, wherein:

5. The assembly of claim 4, wherein:

6. The assembly of claim 5, wherein:

7. The assembly of claim 4, wherein:

8. The assembly of any one of claims 1-7, wherein:

9. The assembly of claim 8, wherein:

10. The assembly of claim 9, wherein:

11. The assembly of claim 9, wherein:

12. The assembly of claim 8, wherein:

13. The assembly of any one of claims 1-12, wherein:

14. The assembly of claim 13, wherein:

15. The assembly of any one of claims 1-12, wherein:

16. The assembly of claim 15, wherein:

17. The assembly of claim 16, wherein:

18. The assembly of any one of claims 1-17, wherein:

19. A bulk acoustic wave resonator assembly comprising:

20. The assembly of claim 1 or 19, wherein:

21. The assembly of claim 20, wherein:

22. A method of manufacturing a bulk acoustic wave resonator assembly, comprising:

wherein:

23. A filter comprising the bulk acoustic wave resonator assembly of any one of claims 1-21.

24. An electronic device comprising the filter of claim 24 or the bulk acoustic wave resonator assembly of any one of claims 1-21.