CN216649643U - Bulk acoustic wave resonator - Google Patents
Bulk acoustic wave resonator Download PDFInfo
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- CN216649643U CN216649643U CN202123298806.8U CN202123298806U CN216649643U CN 216649643 U CN216649643 U CN 216649643U CN 202123298806 U CN202123298806 U CN 202123298806U CN 216649643 U CN216649643 U CN 216649643U
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Abstract
The present invention provides a bulk acoustic wave resonator comprising: a substrate; the acoustic reflection layer is arranged on the substrate, and an opening is formed in one side, far away from the substrate, of the acoustic reflection layer; a first electrode layer disposed on the acoustic reflection layer and forming a cavity with the opening of the acoustic reflection layer; a piezoelectric layer disposed on the first electrode layer; a second electrode layer disposed on the piezoelectric layer.
Description
Technical Field
The utility model relates to the technical field of resonators, in particular to a bulk acoustic wave resonator.
Background
Bulk acoustic wave resonators are fabricated using substrates such as silicon, by micro-electro-mechanical techniques, and thin film techniques. The wireless transceiver has the advantages of small size, good performance, integration and the like, and realizes the functions of image elimination, parasitic filtering, channel selection and the like in the wireless transceiver.
A bulk acoustic wave resonator in the related art, as shown in fig. 10, generally includes a substrate 1 formed with a cavity, a bottom electrode 3 formed above the cavity, a piezoelectric layer 4 formed on the bottom electrode 3, and an upper electrode 5 formed on the piezoelectric layer 4. When a voltage is applied between the bottom electrode 3 and the upper electrode 5, the piezoelectric layer 4 generates mechanical deformation due to the inverse piezoelectric effect and excites bulk acoustic waves in the membrane and reflects back and forth between the first electrode layer 3 and the second electrode layer 5, forming mechanical resonance. The vibration energy of the bulk acoustic wave resonator may leak to the substrate 1 through the contact portion of the bottom electrode 3 and the substrate 1 as shown by a in fig. 10, resulting in a decrease in the Q value of the resonator.
SUMMERY OF THE UTILITY MODEL
Therefore, the technical problem to be solved by the present invention is to overcome the defect that the energy in the bulk acoustic wave resonator in the prior art is easy to leak.
To this end, the present invention provides a bulk acoustic wave resonator comprising: a substrate; the acoustic reflection layer is arranged on the substrate, and an opening is formed in one side, far away from the substrate, of the acoustic reflection layer; a first electrode layer disposed on the acoustic reflection layer and forming a cavity with the opening of the acoustic reflection layer; a piezoelectric layer disposed on the first electrode layer; a second electrode layer disposed on the piezoelectric layer.
Further, the acoustic reflection layer remains at the bottom of the opening.
The bulk acoustic wave resonator provided by the utility model further comprises: at least one support structure formed within the opening for supporting the first electrode layer.
Further, the support structure and the acoustic reflective layer are comprised of the same material.
In the bulk acoustic wave resonator provided by the utility model, the part of the first electrode layer, which is close to at least one side edge of the cavity, is bent upwards to form an air bridge structure.
Further, the air bridge structure is filled with high-resistance materials.
In the bulk acoustic wave resonator provided by the utility model, the first electrode layer and/or the second electrode layer comprise tungsten or molybdenum.
Further, the piezoelectric layer comprises aluminum nitride or doped aluminum nitride.
The bulk acoustic wave resonator provided by the utility model is characterized in that the acoustic reflection layer comprises at least one group of overlapped high-resistance material layers and low-resistance material layers.
Further, the high-resistance material layer comprises a silicon oxide layer, and the low-resistance material layer comprises a metal tungsten layer.
The technical scheme of the utility model has the following advantages:
1. the utility model provides a bulk acoustic wave resonator, comprising: a substrate; the acoustic reflection layer is arranged on the substrate, and an opening is formed in one side, far away from the substrate, of the acoustic reflection layer; a first electrode layer disposed on the acoustic reflection layer and forming a cavity with the opening of the acoustic reflection layer; a piezoelectric layer disposed on the first electrode layer; a second electrode layer disposed on the piezoelectric layer.
In the utility model, the acoustic reflection layer is arranged on the substrate, and an opening is formed on one side of the acoustic reflection layer, which is far away from the substrate. Through the arrangement of the acoustic reflection layer, energy flowing out of the first electrode layer can be effectively reflected, and therefore energy dissipation is avoided.
2. In the bulk acoustic wave resonator provided by the utility model, the part of the first electrode layer, which is close to at least one side edge of the cavity, is bent upwards to form an air bridge structure. Through the arrangement mode, some high-resistance materials can be filled in the air bridge structure, so that the air bridge structure plays a role in acoustic impedance; or air can be directly filled in the air bridge structure, and a certain discontinuous acoustic impedance can be formed between the first electrode layer and the cavity, so that the sound loss is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural diagram corresponding to step S1 in embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram corresponding to step S2 in embodiment 1 of the present invention;
fig. 3 is a schematic structural diagram corresponding to step S3 in embodiment 1 of the present invention;
fig. 4 is a schematic structural diagram corresponding to step S3 in embodiment 1 of the present invention;
fig. 5 is a schematic structural diagram corresponding to step S4 in embodiment 1 of the present invention;
fig. 6 is a schematic structural diagram corresponding to step S6 in embodiment 1 of the present invention;
fig. 7 is a schematic structural diagram corresponding to step S7 in embodiment 1 of the present invention;
fig. 8 is a schematic structural diagram of a bulk acoustic wave resonator provided in the present invention;
fig. 9 is a schematic structural diagram of a bulk acoustic wave resonator provided in the present invention;
fig. 10 is a schematic structural diagram of a bulk acoustic wave resonator provided in the background of the utility model.
Description of reference numerals:
1. a substrate; 2. an acoustic reflective layer; 21. a high-resistance material layer; 22. a low resistance material layer; 23. an opening; 24. a support structure; 3. a first electrode layer; 31. an air bridge structure; 4. a piezoelectric layer; 5. a second electrode layer; 7. silicon element.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The present embodiment provides a bulk acoustic wave resonator, as shown in fig. 7, including:
a substrate 1, in particular, the substrate 1 may be made of silicon;
and the acoustic reflection layer 2 is arranged on the substrate 1, and an opening 23 is formed on one side, far away from the substrate 1, of the acoustic reflection layer 2. As shown in fig. 1, an acoustic reflection layer 2 is provided on a substrate 1.
As an embodiment, as shown in fig. 8, a plurality of support structures 24 may be formed in the opening, through which the support effect on the first electrode layer is achieved. Specifically, the shape of the support structure is not limited, and a point-type structure or a line-type structure may be adopted, and a plurality of support structures may form a matrix structure with different arrangements.
Meanwhile, the material of the support structure itself is not limited, and as an embodiment, the support structure itself is made of the same material as the acoustic reflection layer. For example, when the acoustic reflection layer is provided as a bragg structure, the corresponding support structure is in the same arrangement as the bragg structure.
The first electrode layer 3 is disposed on the acoustic reflection layer 2, and forms a cavity with the opening 23 of the acoustic reflection layer 2, as shown in fig. 7.
The piezoelectric layer 4 is arranged on the first electrode layer 3, and the piezoelectric layer 4 is made of a piezoelectric material, in this embodiment, the piezoelectric material may include aluminum nitride, doped aluminum nitride, or the like;
a second electrode layer 5 disposed on the piezoelectric layer 4.
When a voltage is applied between the first electrode layer and the second electrode layer, the piezoelectric material in the piezoelectric layer undergoes mechanical deformation due to the inverse piezoelectric effect and excites bulk acoustic waves in the membrane and reflects back and forth between the planes of the first electrode layer 3 and the second electrode layer 5, forming a mechanical resonance.
In this embodiment, the material of the first electrode layer 3 and the second electrode layer 5 is not limited as long as the conductive function can be achieved, and the material may include metals such as molybdenum, tungsten, and gold.
As an embodiment, the depth of the opening itself may be kept consistent with the thickness of the acoustic reflective layer, when the opening penetrates the acoustic reflective layer.
As another embodiment, in the example of fig. 7, a part of the acoustic reflection layer remains at the bottom of the opening. As shown in fig. 7 or 8, a layer of high resistance material and a layer of low resistance material remain below the opening 23, respectively. By leaving part of the acoustic reflection layer at the bottom of the opening, using for example XeF2When the gas substances carry out gas-phase etching on the sacrificial layer in the cavity to remove the sacrificial layer, the reserved part of the acoustic reflection layer can prevent etching gas from damaging the substrate.
In this embodiment, the structure of the acoustic reflection layer 2 is not limited, as shown in fig. 7, the acoustic reflection layer may adopt a bragg layer structure, and the acoustic reflection layer 2 includes at least one set of high resistance material layer 21 and low resistance material layer 22 that are overlapped. Further, the low-resistance material layer may be made of tungsten, molybdenum, or the like. Meanwhile, the high-resistance material layer may be provided as a silicon oxide layer or a silicon nitride layer. In this embodiment, the high-resistance material layer 21 is a silicon oxide layer, and the low-resistance material layer is a combination of a metal tungsten layer.
As shown by an arrow B in fig. 7, by providing the acoustic reflection layer 2, it is possible to effectively reflect the energy flowing out through the first electrode layer 3, so as to avoid energy from further flowing into the substrate, which causes energy dissipation.
In the bulk acoustic wave resonator provided in this embodiment, as shown in fig. 9, a portion of the first electrode layer near at least one side edge of the cavity 23 is bent upward to form an air bridge structure 31, and as shown in the view angle shown in fig. 9, an air bridge structure 31 protruding upward is formed on the lower surface of the first electrode layer 3.
As an embodiment, the air bridge structure may be filled with only air;
as another embodiment, a high-resistance material may be filled, and cdo (carbon deposition oxide), silicon carbide, or another insulating material may be put in the air bridge structure 31, and the high-resistance material may be provided to form a discontinuous acoustic impedance, thereby reducing energy loss.
In this embodiment, necessary microstructures may be further disposed on the second electrode layer 5, such as a raised structure, a recessed structure, a connecting bridge, an air foil, and the like, disposed on the second electrode layer 5.
The present embodiment provides a structure in which energy in the bulk acoustic wave resonator can be prevented from leaking to the substrate by providing the acoustic reflection layer. Further, by providing the air bridge structure, energy leakage to the substrate, which causes energy loss, can be further prevented.
The bulk acoustic wave resonator provided in the embodiment mainly includes the following processing steps:
s1, as shown in figure 1, depositing an acoustic reflection layer 2 on a substrate 1, wherein the thickness of the acoustic reflection layer meets the depth requirement of a resonant cavity. Specifically, silicon dioxide and tungsten may be alternately deposited to form the acoustic reflection layer 2 of the bragg structure;
s2, as shown in FIG. 2, patterning the acoustic reflection layer to the upper surface of the lowest low-resistance material layer 22 in a photoetching, etching and photoresist removing mode to form an opening 23;
s3, as shown in the figures 3 and 4, filling the opening 23 with a sacrificial layer 7;
s4, as shown in FIG. 5, depositing a first electrode layer 3 on the upper surface of the acoustic reflection layer, wherein the first electrode layer 3 can be directly made of metal tungsten;
s5, carrying out graphical operation on the first electrode layer 3;
s6, depositing a piezoelectric layer 4 as shown in FIG. 6;
s7, as shown in the figure 7, depositing a second electrode layer 5, and carrying out patterning operation on the piezoelectric layer 4 and the second electrode layer 5;
and S8, removing the sacrificial layer in the opening 23 to form a cavity structure.
In this step, XeF may be used2And removing the silicon sacrificial layer by gas phase etching, wherein the following reaction occurs in the step: 2XeF2+Si→2Xe(g)+SiF4(g) The gas-phase product formed is discharged through the discharge channel.
It should be noted that, when it is required to form the air bridge structure 31 on the first electrode layer 3, a sacrificial layer may be firstly disposed at a position corresponding to the air bridge structure 31, the first electrode layer 3 is further deposited in the corresponding region, and then the sacrificial layer is released, so as to form the air bridge structure 31 on the first electrode layer 3. In this step, when the materials of the sacrificial layer in the air bridge structure 31 and the sacrificial layer in the cavity 23 are the same, the sacrificial layer in the air bridge structure 31 and the sacrificial layer in the cavity 23 may be released together; the release may also be performed separately for the sacrificial layer in the air bridge structure 31 from the sacrificial layer in the cavity 23 when the materials used are not uniform.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the utility model.
Claims (10)
1. A bulk acoustic wave resonator, comprising:
a substrate;
the acoustic reflection layer is arranged on the substrate, and an opening is formed in one side, far away from the substrate, of the acoustic reflection layer;
a first electrode layer disposed on the acoustic reflection layer and forming a cavity with the opening of the acoustic reflection layer;
a piezoelectric layer disposed on the first electrode layer;
a second electrode layer disposed on the piezoelectric layer.
2. The bulk acoustic wave resonator according to claim 1, wherein the acoustic reflective layer remains at the bottom of the opening.
3. The bulk acoustic wave resonator according to claim 1, further comprising:
at least one support structure formed within the opening for supporting the first electrode layer.
4. The bulk acoustic wave resonator according to claim 3, characterized in that the support structure and the acoustic reflection layer are composed of the same material.
5. The bulk acoustic wave resonator according to claim 1, wherein a portion of the first electrode layer near at least one side edge of the cavity is bent upward to form an air bridge structure.
6. The bulk acoustic wave resonator according to claim 5, characterized in that the air bridge structure is filled with a high-resistance material.
7. The bulk acoustic wave resonator according to claim 1, characterized in that the first electrode layer and/or the second electrode layer comprises tungsten or molybdenum.
8. The bulk acoustic wave resonator according to claim 1, wherein the piezoelectric layer comprises a layer of aluminum nitride or doped aluminum nitride.
9. The bulk acoustic wave resonator according to any one of claims 1 to 8, wherein the acoustic reflection layer comprises at least one set of layers of high resistance material and low resistance material arranged to overlap.
10. The bulk acoustic wave resonator according to claim 9, wherein the high resistance material layer comprises a silicon oxide layer, and the low resistance material layer comprises a metal tungsten layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123298806.8U CN216649643U (en) | 2021-12-27 | 2021-12-27 | Bulk acoustic wave resonator |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123298806.8U CN216649643U (en) | 2021-12-27 | 2021-12-27 | Bulk acoustic wave resonator |
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| CN216649643U true CN216649643U (en) | 2022-05-31 |
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| CN202123298806.8U Active CN216649643U (en) | 2021-12-27 | 2021-12-27 | Bulk acoustic wave resonator |
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