A heterogeneous integration method of air-gap piezoelectric bulk acoustic wave device and the device

Abstract

The present invention provides a method for heterogeneous integration of air-gap piezoelectric bulk acoustic wave devices, characterized in that it includes: using a soft stamp to lift a bulk acoustic wave device film from a donor substrate; using a soft stamp to place the bulk acoustic wave device on an intermediate layer above a CMOS circuit, and at the same time making the bulk acoustic wave device located at a specified position of the intermediate layer, the specified position having a cavity, or the specified position having a support structure and a sacrificial layer. The method uses material transfer printing technology to transfer the transferable bulk acoustic wave device to a target system platform, and finally forms a 3D stacked integrated structure. The advantages of this method are: lower cost, higher integration, lower operating temperature requirements and shorter operating time.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a heterogeneous integration method of an air gap type piezoelectric bulk acoustic wave device and the device. Background Art

[0002] Heterogeneous Integration (HI) refers to the technology that can achieve integration on only one system platform. It is manufactured and assembled into complete electronic subsystems through a series of processes, such as MEMS (Micro-Electro-Mechanical System) devices, SOI / CMOS mixed-signal application-specific integrated circuits (ASICs), microscale passive components, and micropower systems. Heterogeneous integration is considered to be a key strategy for realizing System-on-Chip (SoC) and System-on-a-Package (SoP). At the same time, high-performance new applications represented by III-V group element compounds and carbon nanotubes have become increasingly widespread. If electronic components based on these high-performance materials are integrated with traditional silicon-based complementary metal oxide semiconductor (CMOS) circuits, electronic systems with higher integration and better performance can be further obtained, which is of great significance to the continuation of Moore's Law for integrated circuits. In fact, the high-performance materials mentioned above are not compatible with traditional CMOS processes in some processes. In this case, the corresponding electronic components often need to be manufactured independently, and then they are assembled on the same system platform through heterogeneous integration.

[0003] Existing heterogeneous integration methods are mainly divided into two categories: hybrid integration and monolithic integration. Hybrid integration is to manufacture electronic components with incompatible processes separately, and then make electrical connections at the system level or wafer level. In this process, one of the components needs to be flipped together with its substrate, and the connection protrusions need to be aligned and bonded. The bonding process establishes a stable molecular-level connection between the two contact bodies to form a whole, and finally removes unnecessary substrates, but this process often requires high temperature conditions to complete, and high temperature may damage certain electronic components. Monolithic integration is suitable for heterogeneous integration with not too large process differences. After the manufacture of one part of the components is completed, an electrical connection terminal is established on its surface to form a connection and a specific protective layer, and then the second part of the components is processed directly on this basis.

[0004] On the other hand, bulk acoustic wave resonators based on piezoelectric materials are attracting research attention. RF front-end filters / duplexers composed of bulk acoustic wave resonators have excellent filtering characteristics, such as low insertion loss, steep transition band, large power capacity and strong anti-electrostatic discharge (ESD) capability. High-frequency bulk acoustic wave oscillators with ultra-low frequency temperature drift have low phase noise, low power consumption and large bandwidth modulation range. In addition, these miniature bulk acoustic wave resonators can be mass-produced on silicon substrates by MEMS technology, thereby reducing unit cost. Taking the Film Bulk Acoustic Resonator (FBAR) as an example, its structure is shown in the figure below. Figure 1 As shown, the resonator has a typical "sandwich" structure, which includes, from top to bottom, the top electrode 110, the piezoelectric layer 120, and the bottom electrode 130. When a radio frequency voltage is applied between the two electrodes, the piezoelectric layer is excited to emit a bulk acoustic wave in the thickness direction accompanied by a slight deformation. The acoustic wave energy is lost or propagated in the resonator structure. When it reaches the boundary surface, it is transmitted to another medium or reflected back, eventually forming a standing wave, that is, entering a resonant state. When designing a bulk acoustic wave resonator, in addition to selecting low acoustic loss materials and other measures, more attention should be paid to constructing a high acoustic reflectivity interface. Air gap-type structures are often used as high acoustic reflectivity acoustic reflection surfaces. This is because the acoustic impedance characteristics of air and the resonator material are greatly different in order of magnitude, resulting in extremely high acoustic reflectivity. The air gap-type structure can be achieved by constructing a cavity 140 structure on the substrate material 150 in the thickness direction of the effective resonant area of ​​the resonator, such as Figure 1 As shown in the figure, when resonance occurs, the bulk acoustic wave propagates in the area enclosed by the upper surface of the top electrode, the lower surface of the bottom electrode and the effective resonance area. Note that the effective resonance area here is defined as the area where the top electrode, the piezoelectric layer and the bottom electrode overlap in the thickness direction.

[0005] According to the above-mentioned existing heterogeneous integration methods, it is difficult to achieve heterogeneous integration of piezoelectric bulk acoustic wave device films. Piezoelectric bulk acoustic wave device films refer to piezoelectric bulk acoustic wave resonators without peripheral structural protection measures, that is, they only contain top electrodes, piezoelectric layers, bottom electrodes and necessary metal conductive layers. Compared with other forms of piezoelectric bulk acoustic wave resonators, since there is no protection such as plastic packaging, the piezoelectric bulk acoustic wave device film retains the film structure as a whole, occupies a very small volume, and is easy to obtain a higher degree of integration. First, the bonding process in hybrid integration is not suitable for resonator materials and high temperatures may cause performance damage to the resonator. Secondly, even if it is carried out in the presence of a protective layer, the direct use of monolithic integration is likely to cause damage to the CMOS circuit and the process is complicated. At present, there is no efficient heterogeneous integration method for piezoelectric bulk acoustic wave device films under the premise of involving large-scale preparation. Summary of the invention

[0006] In view of this, the present invention aims to provide a method for heterogeneous integration of air-gap piezoelectric bulk acoustic wave devices, which has the advantages of being simple, easy to operate, efficient and reliable.

[0007] The heterogeneous integration method of the air gap type piezoelectric bulk acoustic wave device film of the present invention comprises: using a soft stamp to lift the bulk acoustic wave device film from a donor substrate; using the soft stamp to place the bulk acoustic wave device on an intermediate layer above a CMOS circuit, and at the same time making the bulk acoustic wave device located at a specified position of the intermediate layer, the specified position having a cavity, or the specified position having a support structure and a sacrificial layer.

[0008] Optionally, the middle layer is semi-solid UV glue.

[0009] Optionally, the designated position has a cavity, and before the step of placing the BAW device on an intermediate layer above the CMOS circuit using the soft stamp, the method further includes: forming an adhesive layer on the intermediate layer.

[0010] Optionally, the designated position has a support structure and a sacrificial layer, and before the step of placing the BAW device on the intermediate layer above the CMOS circuit using the soft stamp, the method further includes: forming an adhesive layer on the support structure.

[0011] Optionally, after the step of placing the bulk acoustic wave device on an intermediate layer above the CMOS circuit using the soft stamp, the method further includes: removing the sacrificial layer to form a cavity.

[0012] Optionally, the materials of the intermediate layer and the supporting structure include but are not limited to: silicon dioxide, silicon nitride or organic polymer.

[0013] Optionally, the material of the sacrificial layer includes but is not limited to silicon dioxide.

[0014] Optionally, the electrical connection between the BAW device and the CMOS circuit includes but is not limited to depositing a metal film or wire bonding.

[0015] Optionally, the CMOS circuit is based on a device substrate of the following materials: gallium arsenide, gallium nitride, silicon carbide, diamond, lithium niobate, lithium tantalate or quartz.

[0016] Optionally, the material of the adhesive layer includes but is not limited to ethyl cellulose, benzocyclobutene or an organic solution mixture.

[0017] The heterogeneous integration method of air-gap piezoelectric bulk acoustic wave devices of the present invention uses material transfer printing technology to transfer the transferable bulk acoustic wave devices to the target system platform, and finally forms a 3D stacked integrated structure. The advantages of this method include at least the following aspects: (1) Lower cost. This method directly operates on the bulk acoustic wave device film, and the process is more simplified. (2) Higher integration. The thin film bulk acoustic wave device film itself has the characteristics of small size and light weight. The thickness is one to two orders of magnitude smaller than the corresponding device in the conventional integration method, and the space occupancy rate is less than the traditional 2D and 3D integrated layout. (3) Lower operating temperature requirements. The piezoelectric bulk acoustic wave device with a transferable structure is integrated using transfer printing technology, and the operation can be completed at a lower temperature, avoiding the high temperature requirements of traditional bonding. (4) Shorter operation time. Compared with traditional bonding and other operations, the transfer process and its alignment and other operations take less time.

[0018] The present invention also provides a heterogeneous integrated air gap type piezoelectric bulk acoustic wave device, which is prepared by the method of the present invention.

[0019] The heterogeneously integrated air-gap piezoelectric bulk acoustic wave device of the present invention may include: a substrate, a CMOS circuit located above the substrate, an intermediate layer having a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, and an electrode plate, an electrode plate window and a metal conductive film.

[0020] The heterogeneously integrated air-gap piezoelectric bulk acoustic wave device of the present invention may include: a substrate, a CMOS circuit located above the substrate, a UV glue layer with a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, and an electrode plate, an electrode plate window and a metal conductive film.

[0021] The heterogeneously integrated air-gap piezoelectric bulk acoustic wave device of the present invention may include: a substrate, a CMOS circuit located above the substrate, a support structure located above the CMOS circuit, a bulk acoustic wave device film located above the support structure, and an electrode plate.

[0022] In the heterogeneously integrated air-gap piezoelectric bulk acoustic wave device of the present invention, an adhesive layer is provided on the intermediate layer or an adhesive layer is provided on the supporting structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0024] Figure 1 It is a schematic diagram of the structure of a thin film bulk acoustic resonator with a typical "sandwich" structure.

[0025] Figure 21 is a schematic flow chart of a heterogeneous integration method of an air-gap piezoelectric bulk acoustic wave device according to an embodiment of the present invention;

[0026] Figure 3 is a cross-sectional view of the main structure of an oscillator circuit in a heterogeneous integrated device according to an embodiment of the present invention;

[0027] Figure 4 is a cross-sectional view of an air-gap piezoelectric bulk acoustic wave device heterogeneous integrated device according to a first embodiment of the present invention;

[0028] Figure 5 is a cross-sectional view of an air-gap piezoelectric bulk acoustic wave device heterogeneous integrated device according to a second embodiment of the present invention;

[0029] 6( a ) and 6( b ) are cross-sectional views of an air-gap piezoelectric bulk acoustic wave device heterogeneous integrated device in an intermediate state and a final state, respectively, according to a third embodiment of the present invention;

[0030] Figure 7 It is a cross-sectional view of a partial structure of an adhesive layer integrated heterogeneous integrated device of an air gap type piezoelectric bulk acoustic wave device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0034] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] Figure 2 FIG. 1 is a flow chart of a heterogeneous integration method of an air gap type piezoelectric bulk acoustic wave device according to an embodiment of the present invention. Figure 2 As shown, the method includes: A. using a soft stamp to lift a bulk acoustic wave device film from a donor substrate; B. using the soft stamp to place the bulk acoustic wave device on an intermediate layer above a CMOS circuit, and at the same time, the bulk acoustic wave device is located at a designated position of the intermediate layer, the designated position has a cavity, or the designated position has a support structure and a sacrificial layer. The bulk acoustic wave device film here refers to a completely unpackaged bulk acoustic wave device with a thickness of only a few microns, which is much thinner than a packaged similar device.

[0037] The heterogeneous integration method of air-gap piezoelectric bulk acoustic wave devices of the present invention uses material transfer printing technology to transfer the transferable bulk acoustic wave devices to the target system platform, and finally forms a 3D stacked integrated structure. The advantages of this method include at least the following aspects: (1) Lower cost. This method directly operates on the bulk acoustic wave device film, and the process is more simplified. (2) Higher integration. The thin film bulk acoustic wave device film itself has the characteristics of small size and light weight. The thickness is one to two orders of magnitude smaller than the corresponding device in the conventional integration method, and the space occupancy rate is less than the traditional 2D and 3D integrated layout. (3) Lower operating temperature requirements. The piezoelectric bulk acoustic wave device with a transferable structure is integrated using transfer printing technology, and the operation can be completed at a lower temperature, avoiding the high temperature requirements of traditional bonding. (4) Shorter operation time. Compared with traditional bonding and other operations, the transfer process and its alignment and other operations take less time.

[0038] All embodiments of the present invention are described by taking the heterogeneous integration between FBAR and oscillator CMOS integrated circuit as an example. It should be noted that piezoelectric bulk acoustic wave devices are not limited to FBAR, but also include but are not limited to other types of bulk acoustic wave devices, such as piezoelectric micromachined ultrasonic transducers (PMUT), Lamb wave resonators (LWR), MEMS microphones, etc. CMOS integrated circuits include but are not limited to oscillator circuits, and can also be filter circuits, duplexer circuits, etc. The transfer target system is not limited to CMOS integrated circuits, but also includes but is not limited to electronic components based on substrates such as gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), diamond, lithium niobate, lithium tantalate, and quartz.

[0039] like Figure 3 As shown, the main structure 200 of the oscillator circuit (CMOS integrated circuit) involved in the following embodiments includes: an electrode plate 210, a CMOS circuit 220 and a silicon substrate 230. Among them, the electrode plate 210 is used to establish an electrical connection with the outside world (including the connection with the FBAR). The FBAR is obtained by MEMS processing, and its core structure is a sandwich structure consisting of electrodes on both sides and a piezoelectric layer located between the electrodes. The FBAR electrode is any one of the following: osmium, magnesium, gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic doped gold. Optionally, the material of the FBAR piezoelectric layer is any one of the following: aluminum nitride, zinc oxide, lead zirconate titanate, lithium niobate, quartz, potassium niobate, lithium tantalate. Optionally, the material of the piezoelectric layer is aluminum nitride doped with rare earth elements. The above material is a piezoelectric film with a thickness of less than 10 microns. The aluminum nitride film is in a polycrystalline or single crystal form, and is grown by thin film sputtering or metal organic chemical vapor deposition (MOCVD).

[0040] The FBAR body is connected to the wafer through anchor points and has transferable properties. The soft stamp used for transfer is generally made of viscoelastic materials, such as polydimethylsiloxane (PDMS).

[0041] During the transfer, the FBAR device film is first lifted from the donor substrate (e.g., silicon wafer) using a soft stamp. During this process, the anchor structure used to bind the FBAR is broken, and the FBAR adheres to the soft stamp. Secondly, the soft stamp carrying the FBAR is aligned with the cavity structure on the oscillator circuit, and the soft stamp is moved downward so that the bottom surface of the FBAR is in contact with the cavity. Finally, the soft stamp is slowly lifted, and the FBAR is separated from the soft stamp and adhered to the oscillator circuit. The transfer operation can be performed in large quantities in an array.

[0042] In order to enable those skilled in the art to better understand, the present invention is described below in conjunction with specific embodiments.

[0043] Example 1

[0044] In this embodiment, an intermediate layer with a cavity structure is formed above the CMOS circuit, and then the device is transferred.

[0045] First, the intermediate layer material is added above the CMOS circuit by conventional methods such as spin coating or deposition; second, the cavity structure and the electrode plate window are formed directly by photolithography or photolithography plus etching, and the electrode plate window exposes the electrode plate; finally, the FBAR is transferred to the top of the cavity by transfer printing and establishes an electrical connection with the CMOS circuit. The obtained structure 300 is as shown in FIG. Figure 4 As shown, it includes: a metal conductive film 310, a FBAR device 320, an intermediate layer 330, a cavity structure 340 on the intermediate layer, an electrode plate window 350, an electrode plate 360, a CMOS circuit 370 and a silicon substrate 380.

[0046] In this embodiment, the intermediate layer material includes but is not limited to silicon dioxide (SiO2), silicon nitride (Si3N4), organic polymers (Polymer) such as polyimide (PI), etc. In addition to metal conductive films, the electrical connection between FBAR and CMOS circuit can also be achieved by wire bonding and other methods.

[0047] Example 2

[0048] In this embodiment, UV glue and hot stamping are used to achieve reliable integration. The material of the cavity layer is semi-solid UV glue, which has the characteristics of being able to be easily pasted on a specified surface, being shaped and being irreversibly cured when irradiated with ultraviolet light. The final structure is as follows Figure 5 As shown, the structural unit 400 includes, from top to bottom, a metal conductive film 410 , a FBAR device 420 , a UV adhesive layer 430 , a cavity structure 440 on the UV adhesive layer, an electrode plate window 450 , an electrode plate 460 , a CMOS circuit 470 and a silicon substrate 480 .

[0049] After the UV glue is pasted on the surface of the CMOS circuit, the cavity structure is embossed by hot stamping. The specific method is: cover the UV glue with a transparent hard material with a raised structure, such as glass, and continue to apply a certain pressure and temperature. Then, irradiate it with ultraviolet light for a short time. The short-term irradiation causes the UV glue to be incompletely cured, and the hard material is separated but maintains a certain viscosity. After removing the hard material, the transfer operation is performed, and then irradiated with ultraviolet light to completely cure the UV glue. Finally, an electrical connection is established between the CMOS circuit and the FBAR.

[0050] In this embodiment, in addition to depositing a metal film, the electrical connection can also be achieved by wire bonding or other methods.

[0051] Example 3

[0052] In this embodiment, the FBAR structure is suspended by establishing a support structure, thereby constructing an acoustic reflection interface at the bottom. The support structure and the sacrificial layer are first established, and then the FBAR is transferred to the top of the support structure, and the formed structure is shown in Figure 6(a). In Figure 6(a), the structural unit 5000 includes: an FBAR device 5010, a support structure 5020, a sacrificial layer 5030, an electrode plate 5040, a CMOS circuit 5050 and a silicon substrate 5060. Finally, the sacrificial layer material is released, so that the FBAR effective resonance area is suspended and an electrical connection between the FBAR and the CMOS circuit is established, and the final structure is shown in Figure 6(b). In Figure 6(b), the structure 5100 includes: a metal conductive film 5110, an FBAR device 5120, a support structure 5130, an electrode plate 5140, a CMOS circuit 5150 and a silicon substrate 5160.

[0053] In this embodiment, the supporting material includes but is not limited to silicon dioxide (SiO2), silicon nitride (Si3N4), organic polymer (Polymer) such as polyimide (PI), etc., and the sacrificial layer material includes but is not limited to silicon dioxide (SiO2), etc. It should be noted that the sacrificial layer release process should not cause etching and other effects on the supporting structure. The electrical connection method includes but is not limited to depositing a metal film, wire bonding, etc.

[0054] Example 4

[0055] In this embodiment, an adhesive layer is introduced between the cavity structure and the FBAR to make the connection between the cavity structure and the FBAR more reliable. Figure 7 The structural unit 600 includes, from top to bottom, a FBAR device 610, an adhesive layer 620, and an intermediate layer 640 with a cavity structure 630. Alternatively, an adhesive layer may be applied in Embodiment 3, in which case the adhesive layer is located on the supporting structure in Embodiment 3.

[0056] In this embodiment, the adhesive layer is thermosetting. The adhesive layer is heated and cured after the FBAR is transferred, thereby forming a stable and reliable connection relationship. There is no unique way to form the adhesive layer. For an adhesive layer that is initially liquid, the adhesive liquid can be applied to a thin layer by spin coating or 3D printing, and the solvent is evaporated after the transfer is completed. In order to speed up the solvent evaporation process, the entire platform can be heated without damaging the circuit structure.

[0057] In this embodiment, the adhesive layer material includes but is not limited to ethyl cellulose (EC), benzocyclobutene (BCB), an organic solution mixture (such as PI and N-methylpyrrolidone), and the like.

[0058] The present invention also provides a heterogeneous integrated air gap type piezoelectric bulk acoustic wave device, which is prepared by the method of the present invention.

[0059] The heterogeneous integrated air-gap piezoelectric bulk acoustic wave device of the embodiment of the present invention can be Figure 4 As shown, it includes: a substrate, a CMOS circuit located above the substrate, an intermediate layer with a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, and an electrode plate, an electrode plate window and a metal conductive film.

[0060] The heterogeneous integrated air-gap piezoelectric bulk acoustic wave device of the embodiment of the present invention can be Figure 5 As shown, it includes: a substrate, a CMOS circuit located above the substrate, a UV adhesive layer with a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, and an electrode plate, an electrode plate window and a metal conductive film.

[0061] The heterogeneously integrated air-gap piezoelectric bulk acoustic wave device of an embodiment of the present invention may be as shown in FIG6(b), including: a substrate, a CMOS circuit located above the substrate, a support structure located above the CMOS circuit, a bulk acoustic wave device film located above the support structure, and an electrode plate.

[0062] In the heterogeneous integrated air gap piezoelectric bulk acoustic wave device of the embodiment of the present invention, an adhesive layer (such as Figure 7 as shown) or an adhesive layer is provided on the support structure.

[0063] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for heterogeneous integration of air-gap piezoelectric bulk acoustic wave devices, characterized in that: include: The BAW device film is lifted from the donor substrate using a soft stamp; Using the soft stamp, the BAW device is placed on an intermediate layer above the CMOS circuit, and at the same time, the BAW device is located at a designated position of the intermediate layer, the designated position has a cavity, or the designated position has a support structure and a sacrificial layer; An electrode plate window is opened in the middle layer, the electrode plate is located in the electrode plate window and connected to the CMOS circuit, and the electrode plate is connected to the bulk acoustic wave device via a metal conductive film or a bonding wire.

2. The method according to claim 1, characterized in that The middle layer is semi-solid UV glue.

3. The method according to claim 1, characterized in that The designated position has a cavity, and before the step of placing the bulk acoustic wave device on the intermediate layer above the CMOS circuit using the soft stamp, the method further includes: forming an adhesive layer on the intermediate layer.

4. The method according to claim 1, characterized in that: The designated position has a support structure and a sacrificial layer, and before the step of placing the BAW device on the intermediate layer above the CMOS circuit using the soft stamp, the method further includes: forming an adhesive layer on the support structure.

5. The method according to claim 1 or 4, characterized in that: After the step of placing the bulk acoustic wave device on an intermediate layer above the CMOS circuit using the soft stamp, the method further includes: removing the sacrificial layer to form a cavity.

6. A heterogeneously integrated air-gap piezoelectric bulk acoustic wave device, characterized in that: The air-gap piezoelectric bulk acoustic wave device is prepared by the method according to any one of claims 1 to 5.

7. A heterogeneously integrated air-gap piezoelectric bulk acoustic wave device, characterized in that: include: A substrate, a CMOS circuit located above the substrate, an intermediate layer with a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, an electrode plate, an electrode plate window and a metal conductive film, wherein the electrode plate window is opened in the intermediate layer, the electrode plate is located in the electrode plate window and connected to the CMOS circuit, and the metal conductive film is connected to the electrode plate and the bulk acoustic wave device.

8. A heterogeneously integrated air-gap piezoelectric bulk acoustic wave device, characterized in that: include: A substrate, a CMOS circuit located above the substrate, a UV adhesive layer with a cavity located above the CMOS circuit, a bulk acoustic wave device film located above the cavity, an electrode plate, an electrode plate window and a metal conductive film, wherein the electrode plate window is opened in the UV adhesive layer, the electrode plate is located in the electrode plate window and connected to the CMOS circuit, and the metal conductive film is connected to the electrode plate and the bulk acoustic wave device.

9. A heterogeneously integrated air-gap piezoelectric bulk acoustic wave device, characterized in that: include: A substrate, a CMOS circuit located above the substrate, a supporting structure located above the CMOS circuit, a bulk acoustic wave device film located above the supporting structure, and an electrode plate, wherein the electrode plate is connected to the CMOS circuit and is connected to the bulk acoustic wave device film using a metal film or bonding wire, and the supporting material is silicon dioxide, silicon nitride or an organic polymer.

10. The heterogeneously integrated air-gap piezoelectric bulk acoustic wave device according to claim 8 or 9, characterized in that: An adhesive layer is disposed on the intermediate layer or an adhesive layer is disposed on the supporting structure.

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