CN117639701A

CN117639701A - Single crystal filter and manufacturing method thereof

Info

Publication number: CN117639701A
Application number: CN202311679637.3A
Authority: CN
Inventors: 王国军; 赖志国; 杨清华
Original assignee: Suzhou Huntersun Electronics Co Ltd
Current assignee: Suzhou Huntersun Electronics Co Ltd
Priority date: 2023-12-08
Filing date: 2023-12-08
Publication date: 2024-03-01

Abstract

The present disclosure provides a single crystal filter and a method of manufacturing the same, the method of manufacturing the single crystal filter including the steps of providing a first substrate including a first region; forming an acoustic wave reflecting region in a first region of a first substrate; forming a first insulating layer on a first substrate; providing a second substrate, forming a single crystal piezoelectric layer on the second substrate, and forming a lower electrode on the single crystal piezoelectric layer; forming a second insulating layer on the second substrate; bonding the first substrate and the second substrate through the first insulating layer and the second insulating layer, and removing the second substrate to expose the single crystal piezoelectric layer; and forming an upper electrode on the exposed surface of the single crystal piezoelectric layer, wherein the lower electrode, the single crystal piezoelectric layer and the upper electrode form a sandwich structure, and the projection of the sandwich structure on the surface of the first substrate falls on the first area.

Description

Single crystal filter and manufacturing method thereof

Technical Field

The present disclosure relates to the field of electronics, and more particularly, to a single crystal type filter and a method of manufacturing the same.

Background

With the continuous development of wireless communication systems, communication standards for communication devices that need to be integrated are increasing, the number of frequency bands is increasing, and in the case that more and more data services need higher frequencies, a small, reliable, high-performance rf filter is needed, and thus, more demands are being made on acoustic resonators that form highly oriented or monocrystalline piezoelectric films of the rf filter.

At present, when a single crystal type film bulk acoustic resonator product is prepared, a back cavity type structure is mostly adopted, a substrate is required to be bonded and etched for many times to form the back cavity, then the cavity is required to be formed in advance in the preparation method, so that the requirement on a vacuum process in the subsequent process is high, the risk of film rupture is high, the manufacturing cost is high, and the yield is low.

It is necessary to provide a single crystal filter product and a manufacturing method thereof, so as to simplify the manufacturing process, reduce the manufacturing cost and improve the yield.

Disclosure of Invention

The present disclosure is directed to the above-mentioned technical problems, and designs a single crystal filter, an electronic device, and a manufacturing method, which can overcome the above-mentioned technical problems existing in the prior art, thereby providing a single crystal filter product and a manufacturing method, reducing process difficulty and manufacturing cost, improving yield, facilitating industrial mass production, and matching application requirements of high frequency and multiple modes.

A brief summary of the disclosure will be presented below in order to provide a basic understanding of some aspects of the disclosure. It should be understood that this summary is not an exhaustive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to delineate the scope of the disclosure. Its purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

According to an aspect of the present disclosure, there is provided a method of manufacturing a single crystal type filter, including the steps of: s1: providing a first substrate, wherein the first substrate comprises a first area; s2: forming an acoustic wave reflecting region in a first region of a first substrate; s3: forming a first insulating layer on a first substrate; s4: providing a second substrate, forming a single crystal piezoelectric layer on the second substrate, and forming a lower electrode on the single crystal piezoelectric layer; s5: forming a second insulating layer on the second substrate; s6: bonding the first substrate and the second substrate through the first insulating layer and the second insulating layer, and removing the second substrate to expose the single crystal piezoelectric layer; s7: and forming an upper electrode on the exposed surface of the single crystal piezoelectric layer, wherein the lower electrode, the single crystal piezoelectric layer and the upper electrode form a sandwich structure, and the projection of the sandwich structure on the surface of the first substrate falls on the first area.

Further, step S4 further includes: forming a lower electrode pad while forming a lower electrode;

step S7 further includes: the upper electrode pad is formed simultaneously with the upper electrode.

Further, the method further comprises the step S8 of: a passivation layer is formed on the resonator, the passivation layer including a first passivation layer covering the upper electrode and a second passivation layer covering the upper electrode pad.

Further, the acoustic wave reflecting area in step S2 includes an air chamber, and step S2 further includes: filling the air cavity with a sacrificial layer material; or the acoustic wave reflecting region in step S2 includes a bragg reflecting layer;

further, step S9: and forming a bonding metal including a first bonding metal and a second bonding metal formed on exposed portions of the lower electrode pad and the upper electrode pad, respectively.

Further, the method further comprises the step S10: and removing the sacrificial layer material in the air cavity to form an intermediate structure.

Further, step S11 is also included: a cover portion is provided, the cover portion comprising a cover layer and a protective layer formed on the cover layer, bonding the cover portion and the intermediate structure, the cover portion comprising electrical connection structures therein for guiding out the input signal and the output signal of the filter.

Further, step S11 is also included: a capping layer is provided and bonded to the intermediate structure, and an electrical connection structure is included in the first substrate for routing the input and output signals of the filter.

Further, it is characterized in that: the single crystal piezoelectric layer includes single crystal ScAlN or single crystal AlN.

According to another aspect of the present disclosure, there is provided a single crystal filter fabricated by any one of the foregoing fabrication methods provided by the present disclosure.

Drawings

The above and other objects, features and advantages of the present disclosure will be more readily appreciated by reference to the following description of the specific details of the disclosure taken in conjunction with the accompanying drawings. The drawings are only for the purpose of illustrating the principles of the present disclosure. The dimensions and relative positioning of the elements in the figures are not necessarily drawn to scale.

Fig. 1 shows a schematic configuration of a filter of a first embodiment of the present disclosure;

fig. 2-16 show schematic views of a method of manufacturing a filter according to a first embodiment of the present disclosure;

fig. 17 is a schematic diagram showing a modified structure of a filter of the first embodiment of the present disclosure;

fig. 18 shows another modified structure schematic diagram of the filter of the first embodiment of the present disclosure.

Detailed Description

Exemplary disclosure of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an implementation of the present disclosure are described in the specification. It will be appreciated, however, that in the development of any such actual implementation, numerous implementation-specific decisions may be made to achieve the developers' specific goals, and that these decisions may vary from one implementation to another.

Here, it is also to be noted that, in order to avoid obscuring the present disclosure with unnecessary details, only device structures closely related to the scheme according to the present disclosure are shown in the drawings, while other details not greatly related to the present disclosure are omitted.

In general, it should be understood that the drawings and the various elements depicted therein are not drawn to scale. Moreover, the use of relative terms (e.g., "above," "below," "top," "bottom," "upper," and "lower") to describe various elements' relationships to one another should be understood to encompass different orientations of the device and/or elements in addition to the orientation depicted in the figures.

It is to be understood that the present disclosure is not limited to the described embodiments due to the following description with reference to the drawings. Herein, features between different embodiments may be replaced or borrowed, where possible, and one or more features may be omitted in one embodiment, where like reference numerals refer to like parts. It should be understood that the manufacturing steps of the present disclosure are exemplary in embodiments, and that the order of the steps may be varied.

First embodiment

Referring to fig. 1, fig. 1 shows a device structure of a first embodiment of a single crystal type filter provided by the present disclosure.

As shown in fig. 1, the single crystal type filter includes: a carrier portion, a functional component portion, a cover portion, and an electrical connection component portion. Wherein the functional component part is arranged on the carrier part, the cover part is arranged on the functional component part, and the electric connection component is used for transmitting electric signals of the functional component part.

The carrier portion includes a first substrate 1000, a first insulating layer 1300, and a second insulating layer 2400. Wherein the first substrate 1000 may be, for example, high resistance silicon, gallium arsenide, indium phosphide, glass, sapphire, aluminum oxide _、 SiC, and the like, is formed of materials compatible with semiconductor processes. It should be noted in particular that when the first substrate 1000 is made of a glass material, it has a low dielectric constant, high resistance efficiency, and more advantageous in high-frequency performance. An acoustic wave reflecting region 1100 formed of a structure such as an air cavity or a bragg reflecting layer, which may be formed by stacking films of different acoustic impedances, is formed in the first substrate 1000.

The material of the first insulating layer 1300 and the second insulating layer 2400 may be at least one selected from insulating materials such as silicon oxide, silicon nitride, silicon oxynitride, or TEOS, and the material of the first insulating layer 1300 and the second insulating layer 2400 should be a material suitable for both insulation and fusion bonding to each other.

The functional component part includes a single-crystal type resonator component formed on the carrier part. Illustratively, the single crystal resonator assembly includes at least one single crystal resonator including a functional structural layer including at least a sandwich structure formed by a stack of a lower electrode, a single crystal piezoelectric layer, and an upper electrode. Wherein the single crystal piezoelectric layer is composed of a single crystal piezoelectric material. The single crystal piezoelectric material may be, for example, single crystal ScAlN, single crystal AlN, or the like, which is compatible with semiconductor processes. It will be appreciated that other structures such as a mass loading structure, a frame structure, a temperature compensation layer, a passivation layer, etc. may be disposed in the functional structural layer of a specific bulk acoustic wave resonator according to the design requirements of the specific resonator. The frame structure is beneficial to reflecting transverse waves, weakening or reducing adverse effects of energy attenuation and the like of the resonator caused by transverse modes, improving the quality factor of the resonator and reducing the loss caused by parasitic oscillation of the resonator. And providing a mass-loading structure on the surface of the upper electrode of the bulk acoustic wave resonator enables the resonance frequency to be shifted to a prescribed value.

The capping portion includes a capping layer 3000 and a protective layer 3100. The capping layer 3000 is made of a material having good sealing and solder resist effects. Illustratively, it may be selected from SU-8 functional polymers, epoxy resins, poly-p-phenylene benzobisoxazole fibers, polyimide layers, glass frit layers. The material of the protective layer 3100 may be selected from a dry film, a solder mask, a polyimide layer, and a glass paste layer.

The electrical connection assembly part includes an electrical connection structure for drawing out input signals and output signals of the filter, such as the first bond metal 2330, the second bond metal 2530, the lower electrode pad 2320, the upper electrode pad 2520, the conductive post 2700, the re-wiring 2800, and the bump 2900.

Specifically, in one embodiment, the first substrate 1000 includes a first region in which the air chamber 1100 is formed. The first insulating layer 1300, the second insulating layer 2400 are stacked on the first substrate 1000 and cover the air chamber 1100. The functional structural layer of the resonator is formed on the first insulating layer 1300 and the second insulating layer 2400 at a position corresponding to the air chamber 1100. Specifically, the functional structure layers of the resonator include a lower electrode 2310, a single crystal piezoelectric layer 2200, and an upper electrode 2510.

An upper surface of the lower electrode pad 2320 is coplanar with an upper surface of the lower electrode 2310, and an upper surface of the upper electrode pad 2520 is coplanar with an upper surface of the upper electrode 2510 for electrical connection with the resonator. The lower electrode pad 2320, the lower electrode 2310, the upper electrode pad 2520, and the upper electrode 2510 may be formed of one or more conductive materials, for example, various metals compatible with semiconductor processes including tungsten, molybdenum, iridium, aluminum, platinum, ruthenium, niobium, or hafnium. It is preferable that the conductive materials of the lower electrode pad 2320 and the lower electrode 2310 are the same, and the conductive materials of the upper electrode pad 2520 and the upper electrode 2510 are the same. The conductive materials of the lower electrode 2310 and the upper electrode 2510 may be the same or different.

Further, the filter further includes a passivation layer, preferably including a first passivation layer 2610 and a second passivation layer 2620, the first passivation layer 2610 covering the upper electrode 2510 and the second passivation layer 2620 covering the upper electrode pad 2520. The first passivation layer 2610 and the second passivation layer 2620 may be dielectric materials such as silicon dioxide, silicon nitride, silicon oxynitride, TEOS, etc. for protecting the corresponding components.

Further, a sealing cover 3000 is further included, a sealed cavity area is formed between the sealing cover 3000 and the functional component part, and a conductive post 2700 for making electrical connection is formed in the sealing cover 3000 to transmit an input signal and an output signal of the filter. The first and second bond metals 2330 and 2530 are electrically connected to the lower and upper electrode pads 2320 and 2520, respectively, and bond the capping layer 3000 to the carrier portion through the bond metals. The first bond metal 2330 and the second bond metal 2530 are preferably gold. A redistribution line 2800 is further formed on the capping layer 3000, and a protective layer 3100 is formed on the redistribution line 2800 to protect the redistribution line 2800. And a via hole is formed in the protective layer 3100, a conductive post 2700 is formed in the via hole, a bump 2900 is formed on the conductive post 2700, or a spacer layer 2810 and a bump 2900 are formed on the conductive post 2700.

The single crystal filter disclosed by the invention has the advantages that the resonator is suitable for preparing the single crystal piezoelectric layer, the risk of cracking of the single crystal piezoelectric layer is avoided, the preparation process is simple, the industrial mass production is convenient, and the application requirements of high frequency and multiple modes can be matched.

Second embodiment

Referring to fig. 2-16, fig. 2-16 illustrate a method of manufacturing a single crystal type filter according to a first embodiment of the present disclosure.

Referring to fig. 2, a first substrate 1000 is provided, and the selection of materials of the first substrate 1000 is as before and will not be described herein. The first substrate 1000 mainly plays a role of a supporting carrier, and for example, a Si substrate has good mechanical robustness, and can ensure firmness and reliability in the processing and packaging processes.

With continued reference to fig. 2, an acoustic wave reflecting region is formed at a first region of the first substrate 1000. By way of example, air cavity 1100 may be employed as the acoustic reflection region of a resonator in a single crystal type filter. In a variant embodiment provided by the present disclosure, the bragg reflection layer 1300 (see fig. 18) may also be formed as an acoustic reflection region of a resonator in a single crystal filter. The bragg reflection layer 1300 is a multilayer film of different acoustic impedances stacked in the thickness direction of the first substrate 1000.

Referring to fig. 3, when the air cavity 1100 is employed as an acoustic wave reflecting region of the resonator, the air cavity 1100 is filled with a sacrificial layer material. Specifically, a sacrificial layer material may be deposited on the upper surface of the first substrate 1000 such that the sacrificial layer material completely fills the air cavity 1100, and then chemical mechanical polishing CMP is performed to remove the sacrificial layer material outside the first region of the first substrate 1000, forming the sacrificial layer 1200 in the air cavity 1100. The upper surface of the sacrificial layer 1200 is located on the same plane as the upper surface of the first substrate 1000.

Referring to fig. 4, a first insulating layer 1300 is formed on the first substrate 1000 by deposition, and the material of the first insulating layer 1300 is selected as before and will not be described herein. The thickness of the first insulating layer 1300 after planarization may be set to be greater than 0.1 μm for the first insulating layer 1300 while serving as a bonding layer for subsequent fusion bonding with the second insulating layer 2400.

Referring to fig. 5-6, a second substrate 2000 is provided, a single crystal piezoelectric layer 2200 of a single crystal type filter is formed on the second substrate 2000, and the single crystal piezoelectric layer 2200 is formed of the material as described above. For different single crystal piezoelectric materials, a second substrate with a lattice mismatch with the single crystal piezoelectric layer within a certain range can be adopted, so that the growth or deposition of the single crystal piezoelectric layer is facilitated. Specifically, the second substrate 2000 may be a substrate compatible with semiconductor processes such as Si, gallium arsenide, indium phosphide, gallium nitride, sapphire, aluminum oxide, siC, or the like, and for single crystal scann, single crystal AlN, for example, a substrate such as sapphire, aluminum oxide, gallium nitride, si, siC, or the like may be selected.

Before forming the single crystal piezoelectric layer 2200, a buffer layer, a seed layer, etc. may be formed on the second substrate 2000 in order to reduce stress between the single crystal piezoelectric layer 2200 and the second substrate 2000 due to lattice mismatch, thereby reducing defects inside the single crystal piezoelectric layer 2200 and further improving device performance. For example, when the second substrate 2000 is a sapphire substrate and the single crystal piezoelectric layer 2200 is single crystal ScAlN, the GaN buffer layer 2100 may be formed on the sapphire substrate.

Referring to fig. 7 and 8, the lower electrode 2310 is formed on the single crystal piezoelectric layer 2200, and in particular, the lower electrode material 2300 may be formed on the single crystal piezoelectric layer 2200 first, the lower electrode material 2300 may be selected as described above, and then the lower electrode 2310 may be formed by patterning, optionally, the lower electrode pad 2320 may be formed simultaneously with the formation of the lower electrode 2310. The present disclosure adjusts the order of formation of the lower electrode and the piezoelectric layer, ensures that the single crystal piezoelectric layer 2200 is formed on a flat substrate surface, reduces the possibility of cracking thereof, and ensures the growth quality of the single crystal piezoelectric layer 2200.

Referring to fig. 9, a second insulating layer 2400 is conformally formed on the second substrate 2000, and the material of the second insulating layer 2400 is selected as before and will not be described herein. The second insulating layer 2400 may be thinned using a CMP process such that the thickness of the second insulating layer 2400 after planarization is greater than 0.5 microns, more preferably greater than 1 micron.

Referring to fig. 10, the second substrate 2000 and the first substrate 1000 are bonded, contacted with the first bonding layer 1300 through the second insulating layer 2400, and fusion bonded. By adopting the fusion bonding process, the high requirement of the cavity forming first and then the follow-up process vacuum degree in the prior art can be avoided, the manufacturing cost is reduced, and the yield is improved.

Referring to fig. 11, the second substrate 2000 is removed to expose the surface of the single crystal piezoelectric layer 2200. Conventional processes, such as etching, polishing, etc., may be used to remove the second substrate 2000. It is understood that if a buffer layer is present, a corresponding removal is required.

Referring to fig. 12 and 13, an upper electrode 2510 is formed on the exposed surface of the single crystal piezoelectric layer 2200. Specifically, the upper electrode material 2500 may be deposited first, the upper electrode material 2500 is selected as described previously, and then the upper electrode 2510 is formed by patterning. Alternatively, the upper electrode pad 2520 is formed simultaneously with the upper electrode 2510.

Alternatively, referring to fig. 14, a passivation layer material is deposited over the resonator, and etched to form a passivation layer. The passivation layer includes a first passivation layer 2610 to cover the upper electrode 2510. Optionally, the passivation layer further includes a second passivation layer 2620 covering the upper electrode pad 2520. The first passivation layer 2610 and the second passivation layer 2620 may be formed by a selective deposition method, or the first passivation layer 2610 and the second passivation layer 2620 may be simultaneously formed by a patterning method after conformally forming a passivation layer material, and the passivation layer material may protect the corresponding components by forming the passivation layer as described above.

Referring to fig. 15, a bonding metal is formed. Specifically, the bond metal includes a first bond metal 2330 and a second bond metal 2530. The first bond metal 2330 is electrically connected to the lower electrode pad 2320, and the second bond metal 2530 is electrically connected to the upper electrode pad 2520. Specifically, the single crystal piezoelectric layer 2200 on the lower electrode pad 2320 may be removed to form an opening, exposing the lower electrode pad 2320, through a patterning process. And removing the second passivation layer 2620 on the upper electrode pad 2520 through a patterning process to form an opening, exposing the upper electrode pad 2520, and then forming the first bond metal 2330 on the exposed portion of the lower electrode pad 2320. A second bond metal 2530 is formed on the exposed portion of the upper electrode pad 2520. The upper surfaces of first bond metal 2330 and second bond metal 2530 should be ensured to be coplanar.

Referring to fig. 16, the sacrificial layer material 1200 in the air cavity 1100 is removed, releasing the cavity.

Referring to fig. 1, a capping layer 3000 is then provided. Capping layer 3000 is bonded to first substrate 1000 by a bonding metal. Specifically, bonding metals (not shown) on the capping layer 3000 are bonded to the first bonding metal 2330 and the second bonding metal 2530, respectively, so as to be integrated with the first bonding metal 2330 and the second bonding metal 2530, respectively. Then, the subsequent process is continuously performed, the surface of the capping layer 3000, which is far away from the functional component part, is thinned, the capping layer 3000 is etched to form a through hole, a conductive post 2700 is formed in the through hole, a rerouting line 2800 is formed on the surface of the capping layer 3000, which is far away from the functional component part, a protection layer 3100 is formed on the rerouting line 2800 layer, the material of the protection layer 3100 is not described herein, the etching protection layer 3100 forms a through hole, a conductive post 2700 is formed in the through hole, a bump 2900 is formed on the conductive post 2700, or an electrical connection structure such as a spacer layer and the bump 2900 is formed on the conductive post 2700, and the electrical connection structure is used for guiding out an input signal and an output signal of the filter. Among them, the conductive post 2700 is preferably made of a metal having excellent conductivity, such as copper, for better electric signal transmission, and the bump 2900 may be made of a metal material having a low melting point, such as tin, lead (Pb), aluminum, or the like, for easy melt molding. Further, a spacer layer 2810 may be provided between the conductive pillars 2700 and the bumps 2900. The spacer layer is selected to provide spacer protection, such as nickel, based on the conductive post 2700 material and bump 2900 material.

In a variant embodiment provided by the present disclosure, the capping portion may include only the capping layer 3000 without forming the protective layer 3100. And electrical connection structures such as the conductive pillars 2700, the rewiring 2800 layers, the spacer layers, and the bumps 2900 are not formed in the cap portion. And the electrical connection structure is formed in the carrier portion. Referring to fig. 17, a via hole may then be formed in the first substrate 1000, the first insulating layer 1300, a conductive post 2700 is formed in the via hole, the conductive post 2700 is directly connected to the lower electrode pad 2320, and a via hole is formed in the first substrate 1000, the first insulating layer 1300, the second insulating layer 2400, and the single crystal piezoelectric layer 2200, in which the conductive post 2700 is directly connected to the upper electrode pad 2520. A redistribution line 2800 is formed on a surface of the first substrate 1000 on a side far from the functional component part, a protective layer 3100 is deposited on the redistribution line 2800 layer, a material of the protective layer 3100 is as described above, and not described herein, the protective layer 3100 is etched to form a through hole, a conductive post 2700 is formed in the through hole, a bump 2900 is formed on the conductive post 2700, or an electrical connection structure such as a spacer layer and the bump 2900 is formed on the conductive post 2700, and the electrical connection structure is used for guiding out an input signal and an output signal of the filter.

Alternatively, referring to fig. 18, as a modification of the acoustic wave reflecting region of the resonator, a bragg reflection layer 1300, which is a multilayer film of different acoustic impedances stacked along the thickness direction of the first substrate 1000, may be formed instead of the air cavity 1100 as the acoustic wave reflecting region, other processes and structures are the same as those of the air cavity structure, and the bragg reflection layer structure is adopted compared with the air cavity structure, so that the steps of forming the sacrifice layer and removing the sacrifice layer may be unnecessary, and the flow steps of the manufacturing process may be reduced.

In a second embodiment of the present disclosure, a single crystal piezoelectric layer is first grown on a flat surface, reducing the likelihood of breakage of the single crystal piezoelectric layer; secondly, the lower electrode can be formed after the single crystal piezoelectric layer is formed through fusion bonding, so that the growth quality of the single crystal piezoelectric layer is further ensured; thirdly, the single crystal filter is prepared by only one time of fusion bonding process in the present disclosure, and multiple bonding and substrate peeling process steps are not needed as in the prior art process flow, thereby greatly simplifying the manufacturing steps; finally, the difficulty of the subsequent process after the single crystal piezoelectric layer is transferred is reduced through the sacrificial layer, and the possibility of cracking of the single crystal piezoelectric layer is further reduced. The technological process related to the present disclosure can improve yield and device performance, and is convenient for industrial mass production.

Third embodiment

A third embodiment of the present disclosure provides an electronic device including the single crystal-type filter provided by the present disclosure. The electronic device provided by the present disclosure may be a cell phone, a personal digital assistant (Personal Digital Assistant, PDA), a personal wearable device, an electronic gaming device, or the like.

The present disclosure has been described in connection with specific embodiments, but it should be apparent to those skilled in the art that the description is intended to be illustrative and not limiting of the scope of the disclosure. Various modifications and alterations of this disclosure may be made by those skilled in the art in light of the spirit and principles of this disclosure, and such modifications and alterations are also within the scope of this disclosure.

Claims

1. A method for manufacturing a single crystal filter, comprising the steps of:

s1: providing a first substrate, wherein the first substrate comprises a first area;

s2: forming an acoustic wave reflecting region in a first region of a first substrate;

s3: forming a first insulating layer on a first substrate;

s4: providing a second substrate, forming a single crystal piezoelectric layer on the second substrate, and forming a lower electrode on the single crystal piezoelectric layer;

s5: forming a second insulating layer on the second substrate;

s6: bonding the first substrate and the second substrate through the first insulating layer and the second insulating layer, and removing the second substrate to expose the single crystal piezoelectric layer;

s7: and forming an upper electrode on the exposed surface of the single crystal piezoelectric layer, wherein the lower electrode, the single crystal piezoelectric layer and the upper electrode form a sandwich structure, and the projection of the sandwich structure on the surface of the first substrate falls on the first area.

2. The method of manufacturing as claimed in claim 1, wherein:

step S4 further includes: forming a lower electrode pad while forming a lower electrode;

3. The method of manufacturing as claimed in claim 2, wherein: further comprising step S8:

a passivation layer is formed on the resonator, the passivation layer including a first passivation layer covering the upper electrode and a second passivation layer covering the upper electrode pad.

4. A method of manufacturing as claimed in any one of claims 1 to 3, wherein: the acoustic wave reflecting region in step S2 includes an air chamber, and step S2 further includes: filling the air cavity with a sacrificial layer material; or the acoustic wave reflecting region in step S2 includes a bragg reflecting layer.

5. A method of manufacturing as claimed in claim 3, wherein: further comprising step S9: and forming a bonding metal including a first bonding metal and a second bonding metal formed on exposed portions of the lower electrode pad and the upper electrode pad, respectively.

6. The method of manufacturing according to claim 5, wherein: further comprising step S10: and removing the sacrificial layer material in the air cavity to form an intermediate structure.

7. The method of manufacturing according to claim 6, wherein: further comprising step S11: a cover portion is provided, the cover portion comprising a cover layer and a protective layer formed on the cover layer, bonding the cover portion and the intermediate structure, the cover portion comprising electrical connection structures therein for guiding out the input signal and the output signal of the filter.

8. The method of manufacturing according to claim 6, wherein: further comprising step S11: a capping layer is provided and bonded to the intermediate structure, and an electrical connection structure is included in the first substrate for routing the input and output signals of the filter.

9. The manufacturing method according to any one of claims 1 to 3, 5 to 8, wherein: the single crystal piezoelectric layer includes single crystal ScAlN or single crystal AlN.

10. A single crystal-type filter, comprising: the single crystal filter is manufactured by the manufacturing method of any one of claims 1-9.