WO2021109444A1

WO2021109444A1 - Bulk acoustic resonator, fabrication method therefor, filter and electronic device

Info

Publication number: WO2021109444A1
Application number: PCT/CN2020/088705
Authority: WO
Inventors: 庞慰; 郝龙; 徐洋; 张孟伦; 杨清瑞
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2019-12-04
Filing date: 2020-05-06
Publication date: 2021-06-10
Also published as: CN111245393B; CN111245393A

Abstract

The present invention relates to a bulk acoustic resonator, which comprises: a substrate, an acoustic mirror, a bottom electrode, a top electrode, and a piezoelectric layer that is disposed between the bottom electrode and the top electrode. The bottom electrode is provided with at least one void layer. Along the thickness direction of the bottom electrode, there is distance between the void layer and the top and bottom surface of the bottom electrode. The bottom electrode also comprises a seed layer, and the seed layer defines at least one side among the the upper side and lower side of the void layer. The present invention further relates to a fabrication method for the bulk acoustic resonator, a filter having the foregoing resonator and an electronic device having the filter or the resonator.

Description

Bulk acoustic wave resonator and its manufacturing method, filter and electronic equipment

Technical field

The embodiments of the present invention relate to the field of semiconductors, in particular to a bulk acoustic wave resonator, a filter having the resonator, a method for manufacturing the bulk acoustic wave resonator, and an electronic device having the resonator or the filter equipment.

Background technique

As the basic element 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, Internet of Things, and 5G communications that will change the world in the future still need to rely on electronic devices as their foundation.

Electronic devices can exert different characteristics and advantages according to different working principles. Among all electronic devices, devices that use the piezoelectric effect (or inverse piezoelectric effect) are a very important category. Piezoelectric devices have a very wide range of application scenarios. . Film Bulk Acoustic Resonator (FBAR for short, also known as Bulk Acoustic Wave Resonator, also known as BAW) as an important member of piezoelectric devices is playing an important role in the field of communications, especially FBAR filters in radio frequency filters The market share in the field is increasing. FBAR has excellent characteristics such as small size, high resonance 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 and radio frequency, and their high sensitivity advantages can also be applied to sensing fields such as biology, physics, and medicine.

The main structure of the film bulk acoustic wave resonator is a "sandwich" structure composed of electrode-piezoelectric film-electrode, that is, a layer of piezoelectric material is sandwiched between two metal electrode layers. By inputting a sinusoidal signal between two electrodes, 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 electrical signal output.

The rapid development of communication technology requires the continuous improvement of the working frequency of the filter. For example, the frequency of the 5G communication band (sub-6G) is 3GHz-6GHz, which is higher than 4G and other communication technologies. For bulk acoustic wave resonators and filters, the high operating frequency means that the film thickness, especially the film thickness of the electrode, must be further reduced; however, the main negative effect brought about by the reduction of the electrode film thickness is the resonator Q caused by the increase in electrical loss. The value decreases, especially the Q value near the series resonance point and its frequency. Correspondingly, the performance of the high-frequency bulk acoustic wave filter also deteriorates greatly as the Q value of the bulk acoustic wave resonator decreases.

In order to improve the Q value, a bulk acoustic wave resonator with gap electrodes has been proposed, as shown in FIG. 5 and FIG. 6. FIG. 5 is a schematic top view of the proposed bulk acoustic wave resonator, and FIG. Schematic cross-section cut. In Figures 5 and 6, 10 is the substrate, 20 is the acoustic mirror cavity, 30 is the first bottom electrode, 31 is the second bottom electrode, 40 is the piezoelectric layer, 50 is the top electrode, and 36 is the bottom electrode connection part or The bottom electrode pin, 56 is the top electrode connection part or the top electrode pin, and 61 is the void layer or air gap. The overlapping area of the top electrode, the piezoelectric layer, the bottom electrode and the acoustic mirror cavity in the thickness direction of the resonator is the effective area of the resonator.

In the bulk acoustic wave resonator of FIG. 5 and FIG. 6, the process flow of forming the void layer 61 can be briefly described as follows: First, the upper surface of the first lower electrode 30 is made by chemical vapor deposition (CVD) or other equivalent processes. Layer and patterning, the conventional material of the sacrificial layer is silicon dioxide or phosphorus-doped silicon dioxide (PSG); secondly, a second bottom electrode 31 and a piezoelectric layer are successively formed on the sacrificial layer and the first bottom electrode 30 40. The top electrode 50 and other ancillary structures; again, the sacrificial layer is removed by a liquid or gaseous etchant to form an air gap 61.

The problem with the above process structure is that the sacrificial layer material (silicon dioxide, etc.) used will have an adverse effect on the lattice structure of the electrode material grown on it, and the change of the electrode material lattice will further affect the piezoelectric The lattice structure of the layer material ultimately causes the performance of the resonator to decline, which is manifested as a decrease in the electromechanical coupling coefficient and a decrease in the Q value.

Summary of the invention

In order to alleviate or solve at least one aspect of the above-mentioned problems, the present invention is proposed.

In the present invention, the present invention proposes a structure of covering the seed layer on the sacrificial layer to prevent or reduce the adverse effect of the sacrificial layer on the lattice structure of the material located above it.

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

Base

Acoustic mirror

Bottom electrode

Top electrode; and

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

among them:

The bottom electrode has at least one gap layer, and in the thickness direction of the bottom electrode, there is a distance between the gap layer and the top and bottom surfaces of the bottom electrode;

The bottom electrode further includes a seed layer that defines at least one of the upper side and the lower side of the void layer.

The embodiment of the present invention also relates to a method for manufacturing a bulk acoustic wave resonator. The bottom electrode of the resonator has a gap layer. In the thickness direction of the bottom electrode, the gap layer and the top and bottom surfaces of the bottom electrode There is a distance,

The bottom electrode has an upper electrode portion above the gap layer, and a lower electrode portion below the gap layer. The upper electrode portion and the lower electrode portion are electrically connected to each other, and the method includes the steps:

A seed layer is formed on the lower side of the upper electrode part and/or the upper side of the lower electrode part, and the seed layer defines at least a part of the boundary of the void layer.

The embodiment of the present invention also relates to a filter including the above-mentioned bulk acoustic wave resonator.

The embodiment of the present invention also relates to an electronic device including the above-mentioned filter or the above-mentioned resonator.

Description of the drawings

The following description and drawings can better help understand these and other features and advantages in the various embodiments disclosed in the present invention. The same reference numerals in the figures always indicate the same components, among which:

Fig. 1 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention;

Fig. 2 is a schematic cross-sectional view taken along A1OA2 in Fig. 1 according to an exemplary embodiment of the present invention;

2A is a schematic cross-sectional view taken along A1OA3 in FIG. 1 according to another exemplary embodiment of the present invention;

2B is a schematic cross-sectional view taken along A1OA3 in FIG. 1 according to still another exemplary embodiment of the present invention;

3A-3E are process diagrams of a method for manufacturing the bulk acoustic wave resonator in FIG. 2 according to an exemplary embodiment of the present invention, in which a seed layer is provided on the upper side of the void layer;

4A-4E are process diagrams of a method for manufacturing the bulk acoustic wave resonator in FIG. 2A according to an exemplary embodiment of the present invention, in which a seed layer is provided on the lower side of the void layer;

Fig. 5 is a schematic top view of the proposed bulk acoustic wave resonator;

Fig. 6 is a schematic cross-sectional view taken along A1OA2 in Fig. 5.

Detailed ways

In the following, the technical solution of the present invention will be further described in detail through the embodiments and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate 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 a limitation to the present invention.

FIG. 1 is a schematic top view of a resonator structure according to an exemplary embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of FIG. 1 taken along the broken line A1OA2 of FIG. 1. The reference signs are as follows:

10: Substrate, optional materials are monocrystalline silicon, gallium arsenide, sapphire, quartz, etc.

20: Acoustic mirror, can be air cavity, Bragg reflector or other equivalent acoustic reflection structure.

30: The first bottom electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a combination of the above metals or their alloys, etc.

31: The second bottom electrode, the material selection range is the same as that of the first bottom electrode 30, but the specific material is not necessarily the same as that of the first bottom electrode 30.

35: Seed layer, the material of the seed layer can be aluminum nitride, zinc oxide, lead zirconate titanate, etc.

36: Electrode pin, the material is the same as the first bottom electrode.

40: Piezoelectric film layer, optional aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO ₃ ), quartz (Quartz), potassium niobate (KNbO ₃ ) Or lithium tantalate (LiTaO ₃ ) and other materials may also contain rare earth element doped materials with a certain atomic ratio of the above materials.

50: Top electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a combination of the above metals or their alloys.

56: Electrode pin, the material is the same as the first top electrode.

61: An air gap or gap layer located in the bottom electrode, between the first bottom electrode 30 and the second bottom electrode 31.

In FIGS. 1-2, the bottom electrode has a gap layer 61, and in the thickness direction of the bottom electrode, there is a distance between the gap layer 61 and the top and bottom surfaces of the bottom electrode.

As shown in FIG. 2, the seed layer 35 is provided on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer (for example, corresponding to the second bottom electrode 31 mentioned above), and the seed layer 35 and the gap electrode are in the gap layer. The lower electrode portions on the lower side (for example, corresponding to the above-mentioned first bottom electrode 30) collectively define the void layer.

In the present invention, the material of the seed layer is usually the same material as the piezoelectric layer or a material similar to the crystal lattice structure of the piezoelectric layer. Specifically, the material of the seed layer can be aluminum nitride, silicon nitride, or silicon carbide. , Zinc oxide, lead zirconate titanate, etc. The "lattice structure approximate" here means the same kind of crystal system structure. In a specific embodiment, when the material of the piezoelectric layer is aluminum nitride or doped aluminum nitride or a stack combination of doped aluminum nitride with different concentrations, the material of the seed layer is selected from aluminum nitride.

Commonly used piezoelectric materials, such as AlN, are in the hexagonal system, while the crystal lattice of metal materials is generally in the tetragonal system. In the bulk acoustic wave resonator structure, the main excitation is the longitudinal wave directed along the c-axis of the AlN crystal, so splashing is required. Shoot AlN to grow along the c-axis. Using AlN as the seed layer can promote the metal layer to have a vertically oriented crystal lattice, thereby enabling the piezoelectric layer to have a c-axis oriented crystal lattice. In addition, the sacrificial layer (the material is usually silicon dioxide or phosphosilicate glass (PSG)) made by chemical vapor deposition (CVD) in a conventional process has a relatively loose microstructure and a relatively high surface roughness. The roughness will adversely affect the crystal orientation of the electrode layer and piezoelectric layer subsequently deposited on the sacrificial layer. The seed layer made of AlN has good compactness and surface finish. Therefore, placing the seed layer on the upper or lower side of the sacrificial layer can effectively improve or indirectly improve the crystal phase of the electrode layer and the piezoelectric layer.

As shown in FIG. 2, the seed layer 35 (that is, the upper seed layer provided on the upper side of the void layer) completely covers the upper surface and sidewalls of the air gap (sacrificial layer) 61. The thickness of the upper seed layer will affect the resonance frequency. Therefore, it should be as thin as possible to guide the growth of the Mo electrode lattice. However, when the thickness of the upper seed layer is too thin, it will not be able to fully prevent the sacrificial layer from interacting with the crystal. The role of adverse effects. When the seed layer is too thick, it will adversely affect the acoustic performance of the resonator. Therefore, the present invention limits the thickness of the upper seed layer (disposed on the upper side of the void layer) in the range of 1-100 nm, and further, in the range of 5-50 nm.

When the resonator is working, an alternating electric field is applied to the piezoelectric layer 40 through the electrodes. Due to the coupling and mutual conversion of acousto-electric energy, current will flow through the electrodes. Since the bottom electrode of this embodiment has a double-layer electrode parallel structure, It can effectively reduce the electrical loss of the resonator. Under the excitation of the alternating electric field, the piezoelectric layer generates sound waves. When the sound waves are conducted downward to the interface between the air gap 61 in the bottom electrode and the second bottom electrode 50, the sound wave energy will be reflected back to the piezoelectric layer 40 (because the air It does not match the acoustic impedance of the electrode to a great extent), and it does not enter the first bottom electrode 30. The electrode structure containing the air gap in the present invention can significantly reduce the electrical loss of the resonator on the one hand (expressed as an increase in the Q value at and near the series resonance frequency). On the other hand, the air gap plays a role in the first bottom electrode 30. Acoustic isolation, thereby basically avoiding the negative effects of the first bottom electrode 30 on the performance of the resonator (such as changes in resonance frequency and electromechanical coupling coefficient).

The height of the air gap can be in the following range:

The height of the air gap is generally greater than the typical amplitude of the resonator (about 10nm), for example, the height of the air gap is

This facilitates the decoupling of acoustic energy between the bottom electrode and the resonant cavity (in this embodiment, a composite structure composed of the top electrode 50, the piezoelectric layer 40, and the bottom electrode) when the resonator is working at high power.

It should be noted that the air gap constitutes a void layer, but in the present invention, the void layer may be a vacuum gap layer in addition to an air gap layer, or a void layer filled with another gas medium.

In the above-mentioned embodiment of the present invention, the substrate 10 is provided with an acoustic cavity 20, and the overlapping area of the acoustic cavity, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator constitutes the effective area of the resonator. However, the present invention is not limited to this. For example, when the bottom electrode is a void electrode, the void layer in the bottom electrode can also serve as an acoustic mirror structure itself. At this time, the overlapping area of the top electrode, bottom electrode, piezoelectric layer, and gap layer in the thickness direction of the resonator constitutes the effective area of the resonator. In this case, the acoustic cavity 20 may be omitted, or of course, the acoustic cavity may be left. Cavity 20, and in the top view of the resonator, the gap layer completely covers the acoustic cavity.

In the present invention, a void layer is provided in the top electrode and/or the bottom electrode of the bulk acoustic wave resonator. The air gap located in the electrode can effectively reflect the sound wave, greatly reducing the sound wave energy entering the additional electrode on the side away from the piezoelectric film (or piezoelectric layer), thereby effectively suppressing or eliminating the additional electrode due to the participation in acoustic vibration. Negative effects. In addition, the two layers (multi-layer) electrodes surrounding the air gap can form a parallel circuit structure, which can effectively reduce the electrical loss of the resonator and increase the Q value of the resonator, especially the Q value at the series resonance point and its nearby frequencies .

Therefore, the additional electrode is acoustically decoupled from the resonator cavity due to the existence of the air gap (most of the sound waves are reflected back to the cavity at the air gap and do not enter the additional electrode), and the existence and parameter changes of the additional electrode do not affect the resonator except Other key parameters besides Q value (such as resonance frequency, electromechanical coupling coefficient, etc.).

On the one hand, the seed layer can weaken the influence of the lattice structure caused by the sacrificial layer, and on the other hand, it can use its own lattice structure to actively guide the lattice structure of each layer of material grown on it, thereby improving the performance of the resonator .

In FIG. 2, the seed layer is disposed on the upper electrode portion 30 with the bottom electrode on the upper side of the corresponding gap layer, and the gap layer is disposed between the seed layer and the lower electrode portion 30.

Because the seed layer is added, compared with the method of manufacturing a bulk acoustic wave resonator shown in FIGS. 5 and 6, the method of manufacturing a bulk acoustic wave resonator according to the present invention adds steps of forming a sacrificial layer and a seed layer. . The method of manufacturing a bulk acoustic wave resonator will be exemplarily described below with reference to FIGS. 3A-3E.

First, as shown in FIG. 3A, the first bottom electrode (corresponding to the lower electrode portion) 30 under the gap layer of the bottom electrode is formed and patterned; wherein the acoustic mirror cavity located under the first bottom electrode 30 has been filled Sacrificial material 25a.

Secondly, as shown in FIG. 3B, a sacrificial layer 35a is formed and patterned on the first bottom electrode 30. Optionally, during the patterning process, a part 35e of the sacrificial layer 35a can be extended to the acoustics. The upper surface of the sacrificial material 25 of the mirror 20 is in contact with it, so as to subsequently connect the release channel of the material 35a with the release channel of the material 25a.

Again, as shown in FIG. 3C, a seed layer 35 covering the sacrificial layer 35a is formed and patterned.

After that, as shown in FIG. 3D, a second bottom electrode (corresponding to the upper electrode portion) 31 above the gap layer of the bottom electrode is formed. The second bottom electrode 31 covers the seed layer 35 and the first bottom electrode 30 and is connected to the first bottom electrode. The bottom electrode 30 is electrically connected. This part of the process can also include continuing to fabricate the remaining functional layers (such as the piezoelectric layer 40 and the top electrode 50) and the process structure (such as the release hole or channel 41 on the piezoelectric layer) on the basis of the above-mentioned structure.

Finally, as shown in FIG. 3E, the sacrificial layer 35a between the seed layer and the first bottom electrode 30 is released to form a void layer 61.

In the embodiment shown in 2, the seed layer is provided on the upper side of the void layer, but the present invention is not limited to this, the seed layer can also be provided on the lower side of the void layer, or on the upper and lower sides of the void layer .

Fig. 2A is a schematic cross-sectional view taken along A1OA3 in Fig. 1, showing an exemplary embodiment in which the seed layer is disposed on the lower side of the void layer. In FIG. 2A, the seed layer 35 (the seed layer located on the lower side of the gap layer is the lower seed layer) is provided on the lower electrode portion 30 of the bottom electrode on the lower side of the corresponding gap layer, and the gap layer 61 is provided on the bottom electrode portion 30. The seed layer and the bottom electrode are between the upper electrode portion 31 on the upper side of the gap layer.

The seed layer in FIG. 2A can positively affect the crystal orientation of the piezoelectric layer and the electrode layer by influencing the crystal orientation of the sacrificial layer located above it.

The seed layer in FIG. 2A can also prevent the lower electrode portion 30 from being etched by the etchant used to etch the material of the sacrificial layer. That is, when the seed layer is arranged on the lower side of the void layer, the seed layer can be used as an etching agent. Barrier layer. Specifically, silicon dioxide is used as the sacrificial layer, and dry etching is required to make the side surface of silicon dioxide have a certain angle. The gas used for dry etching will also etch the bottom electrode of the bottom electrode (for example, formed of Mo) Partly, therefore, adding an etching barrier layer (such as ALN) under the silicon dioxide helps prevent or reduce the etching of the lower electrode part.

The thickness of the lower seed layer does not affect the resonance frequency, so it can be appropriately thickened, so that the additional electrode (or the lower electrode part) can be better protected when the sacrificial material of the void layer is etched. The thickness of the lower seed layer is in the range of 5-300 nm, and further in the range of 10-100 nm.

2B is a schematic cross-sectional view taken along A1OA3 in FIG. 1 according to another exemplary embodiment of the present invention. In FIG. 2B, the upper and lower sides of the gap layer 61 are provided with seed layers. Specifically, the seed layer includes a first seed layer 37 provided on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer, and a first seed layer 37 provided on the lower electrode portion of the bottom electrode on the lower side of the corresponding gap layer. The second seed layer 35 is formed between the first seed layer and the second seed layer.

Hereinafter, a method of manufacturing the bulk acoustic wave resonator in FIG. 2A will be described with reference to FIGS. 4A-4E.

First, as shown in FIG. 4A, the first bottom electrode (corresponding to the lower electrode portion) 30 of the bottom electrode located under the gap layer is formed and patterned; wherein the acoustic mirror cavity located below 30 has been filled with sacrificial material 25a.

Next, as shown in FIG. 4B, a seed layer 35 is provided and patterned on the first bottom electrode.

Again, as shown in FIG. 4C, a sacrificial layer 35a is formed and patterned on the seed layer 35. Optionally, a portion 35e of the sacrificial layer 35a can be extended to the acoustic mirror during the patterning process. The upper surface of the sacrificial material 25 of 20 is in contact with it, so as to subsequently connect the release channel of the material 35a with the release channel of the material 25a.

Then, as shown in FIG. 4D, a second bottom electrode (corresponding to the upper electrode portion) 31 located above the gap layer of the bottom electrode is formed. The second bottom electrode 31 covers the sacrificial layer 35a and the first bottom electrode 30 and is connected to the first bottom electrode. The electrode 30 is electrically connected. This part of the process may also include continuing to fabricate the remaining functional layers (such as the piezoelectric layer 40 and the upper electrode 50) and the process structure (such as the release hole or channel 41 on the piezoelectric layer) on the basis of the above structure.

Finally, as shown in FIG. 4E, the sacrificial layer 35a between the seed layer 35 and the second bottom electrode 31 is released to form a gap layer 61.

In the present invention, the mentioned numerical range can be not only the endpoint value, but also the median value between the endpoint values or other values, all of which fall within the protection scope of the present invention.

As those skilled in the art can understand, the bulk acoustic wave resonator according to the present invention can be used to form a filter.

Based on the above, the present invention proposes the following technical solutions:

1. A bulk acoustic wave resonator, including:

Base

Acoustic mirror

Bottom electrode

Top electrode; and

among them:

The bottom electrode has a gap layer, and in the thickness direction of the bottom electrode, there is a distance between the gap layer and the top and bottom surfaces of the bottom electrode;

2. The resonator according to 1, wherein:

The seed layer is disposed on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer, and the gap layer is disposed between the seed layer and the lower electrode portion of the bottom electrode on the lower side of the gap layer .

3. The resonator according to 1, wherein:

The seed layer is disposed on the lower electrode portion of the bottom electrode on the lower side of the corresponding gap layer, and the gap layer is disposed between the seed layer and the upper electrode portion of the bottom electrode on the upper side of the gap layer .

4. The resonator according to 1, wherein:

The seed layer includes a first seed layer disposed on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer, and a second seed crystal disposed on the bottom electrode portion of the bottom electrode on the lower side of the corresponding gap layer The gap layer is formed between the first seed layer and the second seed layer.

5. The resonator according to 1, wherein:

The acoustic mirror is an acoustic mirror cavity;

The gap layer communicates with the cavity at one end of the non-pin end of the bottom electrode.

6. The resonator according to 5, wherein:

The gap layer has at least one opening communicating with the cavity at one end of the non-lead end of the bottom electrode.

7. The resonator according to 6, wherein:

The piezoelectric layer has a release channel communicating with the gap layer and the cavity outside the effective area of the resonator.

8. The resonator according to 6, wherein:

The opening of the void layer is inclined with respect to the extension direction of the main body of the void layer and opens into the cavity.

9. The resonator according to 8, wherein:

The opening portion is arranged along the edge of the non-lead end of the bottom electrode.

10. The resonator according to any one of 1-9, wherein:

The material of the seed layer is the same as the piezoelectric layer; or

The crystal lattice structure of the seed layer is similar to that of the piezoelectric layer.

11. The resonator according to 10, wherein:

The material of the seed layer is at least one of aluminum nitride, silicon nitride, silicon carbide, zirconium oxide, and zirconium titanic acid.

12. The resonator according to 11, wherein:

The material of the piezoelectric layer is doped aluminum nitride or a stack combination of doped aluminum nitride of different concentrations, and the material of the seed layer is aluminum nitride.

13. The resonator according to any one of 1-9, wherein:

The gap layer constitutes the acoustic mirror, and the overlapping area of the top electrode, the bottom electrode, the piezoelectric layer, and the gap layer in the thickness direction of the resonator constitutes an effective area of the resonator.

14. The resonator according to 13, wherein:

The resonator further includes an acoustic cavity provided on the substrate, and in a plan view of the resonator, the void layer completely covers the acoustic cavity.

15. The resonator according to 2, wherein:

The thickness of the seed layer is in the range of 1-100 nm.

16. The resonator according to 15, wherein:

The thickness of the seed layer is in the range of 5-50 nm.

17. The resonator according to 3, wherein:

The thickness of the seed layer is in the range of 5-300 nm.

18. The resonator according to 17, wherein:

The thickness of the seed layer is in the range of 10-100 nm.

19. The resonator according to any one of 1-18, wherein:

The gap layer is an air gap layer or a vacuum gap layer.

20. The resonator according to 19, wherein:

The thickness of the void layer is

In the range.

21. The resonator according to 20, wherein:

The thickness of the void layer is

In the range.

22. A method for manufacturing a bulk acoustic wave resonator, wherein the bottom electrode of the resonator has a gap layer, and in the thickness direction of the bottom electrode, there is a distance between the gap layer and the top and bottom surfaces of the bottom electrode, so The bottom electrode has an upper electrode portion above the gap layer, and a lower electrode portion below the gap layer, and the upper electrode portion and the lower electrode portion are electrically connected to each other, and the method includes the steps:

23. The method according to 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming and patterning a sacrificial layer on the lower electrode part;

Forming a first seed layer covering the sacrificial layer;

Forming the upper electrode part, the upper electrode part covers the first seed layer and the lower electrode part and is electrically connected to the lower electrode part;

The sacrificial layer material between the first seed layer and the lower electrode portion is released to form the void layer.

24. The method according to 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming a second seed layer on the upper side of the lower electrode part;

Forming and patterning a sacrificial layer on the second seed layer;

Forming the upper electrode part, the upper electrode part covers the second seed layer and the lower electrode part and is electrically connected to the lower electrode part;

The sacrificial layer material between the second seed layer and the upper electrode portion is released to form the void layer.

25. The method according to 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming a second seed layer on the upper side of the lower electrode part;

Forming and patterning a sacrificial layer on the second seed layer;

Forming a first seed layer covering the sacrificial layer;

The sacrificial layer material between the first seed layer and the second seed layer is released to form the void layer.

26. The method according to any one of 23-25, wherein:

The method further includes forming an acoustic mirror cavity on the substrate and filling the cavity with a sacrificial material in the cavity;

In the step of forming the sacrificial layer, the sacrificial layer covers the edge of the non-lead end of the lower electrode part and is connected with the cavity sacrificial material in the cavity;

In the step of releasing the sacrificial layer material, the cavity sacrificial material and the sacrificial layer material are simultaneously released.

27. The method according to 26, wherein:

In the step of releasing the sacrificial layer material, the sacrificial layer material and the cavity sacrificial material are released through a release hole provided on the piezoelectric layer outside the effective area of the resonator.

28. A filter comprising the bulk acoustic wave resonator according to any one of 1-21 or the bulk acoustic wave resonator manufactured according to any one of 22-27.

29. An electronic device comprising the filter according to 28 or the resonator according to any one of 1-21.

Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it will be understood that these embodiments can be changed without departing from the principle and spirit of the present invention, and the scope of the present invention is determined by The appended claims and their equivalents are defined.

Claims

A bulk acoustic wave resonator, including:

Base

Acoustic mirror

Bottom electrode

Top electrode; and

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

among them:

The bottom electrode has a gap layer, and in the thickness direction of the bottom electrode, there is a distance between the gap layer and the top and bottom surfaces of the bottom electrode;

The bottom electrode further includes a seed layer that defines at least one of the upper side and the lower side of the void layer.
The resonator according to claim 1, wherein:

The seed layer is disposed on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer, and the gap layer is disposed between the seed layer and the lower electrode portion of the bottom electrode on the lower side of the gap layer .
The resonator according to claim 1, wherein:

The seed layer is disposed on the lower electrode portion of the bottom electrode on the lower side of the corresponding gap layer, and the gap layer is disposed between the seed layer and the upper electrode portion of the bottom electrode on the upper side of the gap layer .
The resonator according to claim 1, wherein:

The seed layer includes a first seed layer disposed on the upper electrode portion of the bottom electrode on the upper side of the corresponding gap layer and a second seed crystal disposed on the bottom electrode portion of the bottom electrode on the lower side of the corresponding gap layer The gap layer is formed between the first seed layer and the second seed layer.
The resonator according to claim 1, wherein:

The acoustic mirror is an acoustic mirror cavity;

The gap layer communicates with the cavity at one end of the non-pin end of the bottom electrode.
The resonator according to claim 5, wherein:

The gap layer has at least one opening communicating with the cavity at one end of the non-lead end of the bottom electrode.
The resonator according to claim 6, wherein:

The piezoelectric layer has a release channel communicating with the gap layer and the cavity outside the effective area of the resonator.
The resonator according to claim 6, wherein:

The opening of the void layer is inclined with respect to the extension direction of the main body of the void layer and opens into the cavity.
The resonator according to claim 8, wherein:

The opening portion is arranged along the edge of the non-lead end of the bottom electrode.
The resonator according to any one of claims 1-9, wherein:

The material of the seed layer is the same as the piezoelectric layer; or

The crystal lattice structure of the seed layer is similar to that of the piezoelectric layer.
The resonator according to claim 10, wherein:

The material of the seed layer is at least one of aluminum nitride, silicon nitride, silicon carbide, zirconium oxide, and zirconium titanic acid.
The resonator according to claim 11, wherein:

The material of the piezoelectric layer is doped aluminum nitride or a stack combination of doped aluminum nitride of different concentrations, and the material of the seed layer is aluminum nitride.
The resonator according to any one of claims 1-9, wherein:

The gap layer constitutes the acoustic mirror, and the overlapping area of the top electrode, the bottom electrode, the piezoelectric layer, and the gap layer in the thickness direction of the resonator constitutes an effective area of the resonator.
The resonator according to claim 13, wherein:

The resonator further includes an acoustic cavity provided on the substrate. In a top view of the resonator, the gap layer completely covers the acoustic cavity.
The resonator according to claim 2, wherein:

The thickness of the seed layer is in the range of 1-100 nm.
The resonator according to claim 15, wherein:

The thickness of the seed layer is in the range of 5-50 nm.
The resonator according to claim 3, wherein:

The thickness of the seed layer is in the range of 5-300 nm.
The resonator of claim 17, wherein:

The thickness of the seed layer is in the range of 10-100 nm.
The resonator according to any one of claims 1-18, wherein:

The gap layer is an air gap layer or a vacuum gap layer.
The resonator of claim 19, wherein:

The thickness of the void layer is
In the range.
The resonator according to claim 20, wherein:

The thickness of the void layer is
In the range.
A method for manufacturing a bulk acoustic wave resonator. The bottom electrode of the resonator has a gap layer. In the thickness direction of the bottom electrode, there is a distance between the gap layer and the top and bottom surfaces of the bottom electrode. The electrode has an upper electrode portion above the gap layer, and a lower electrode portion below the gap layer. The upper electrode portion and the lower electrode portion are electrically connected to each other. The method includes the steps:

A seed layer is formed on the lower side of the upper electrode part and/or the upper side of the lower electrode part, and the seed layer defines at least a part of the boundary of the void layer.
The method according to claim 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming and patterning a sacrificial layer on the lower electrode part;

Forming a first seed layer covering the sacrificial layer;

Forming the upper electrode part, the upper electrode part covers the first seed layer and the lower electrode part and is electrically connected to the lower electrode part;

The sacrificial layer material between the first seed layer and the lower electrode portion is released to form the void layer.
The method according to claim 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming a second seed layer on the upper side of the lower electrode part;

Forming and patterning a sacrificial layer on the second seed layer;

Forming the upper electrode part, the upper electrode part covers the second seed layer and the lower electrode part and is electrically connected to the lower electrode part;

The sacrificial layer material between the second seed layer and the upper electrode portion is released to form the void layer.
The method according to claim 22, comprising the steps:

Forming the lower electrode part under the gap layer of the bottom electrode;

Forming a second seed layer on the upper side of the lower electrode part;

Forming and patterning a sacrificial layer on the second seed layer;

Forming a first seed layer covering the sacrificial layer;

Forming the upper electrode part, the upper electrode part covers the first seed layer and the lower electrode part and is electrically connected to the lower electrode part;

The sacrificial layer material between the first seed layer and the second seed layer is released to form the void layer.
The method according to any one of claims 23-25, wherein:

The method further includes forming an acoustic mirror cavity on the substrate and filling the cavity with a sacrificial material in the cavity;

In the step of forming the sacrificial layer, the sacrificial layer covers the edge of the non-lead end of the lower electrode part and is connected with the cavity sacrificial material in the cavity;

In the step of releasing the sacrificial layer material, the cavity sacrificial material and the sacrificial layer material are simultaneously released.
The method of claim 26, wherein:

In the step of releasing the sacrificial layer material, the sacrificial layer material and the cavity sacrificial material are released through a release hole provided on the piezoelectric layer outside the effective area of the resonator.
A filter comprising the bulk acoustic wave resonator according to any one of claims 1-21 or the bulk acoustic wave resonator manufactured by the method according to any one of claims 22-27.
An electronic device comprising the filter according to claim 28 or the resonator according to any one of claims 1-21.