WO2021258405A1

WO2021258405A1 - Thin film bulk acoustic resonator and manufacturing process therefor

Info

Publication number: WO2021258405A1
Application number: PCT/CN2020/098556
Authority: WO
Inventors: 李林萍; 盛荆浩; 江舟
Original assignee: 杭州见闻录科技有限公司
Priority date: 2020-06-24
Filing date: 2020-06-28
Publication date: 2021-12-30
Also published as: CN111900949A

Abstract

Disclosed is a thin film bulk acoustic resonator, comprising a bottom electrode layer, a piezoelectric layer and a top electrode layer, which are provided above a substrate where an acoustic wave reflection structure is located, wherein a part, which corresponds to the boundary of the acoustic wave reflection structure, of at least one of the bottom electrode layer, the piezoelectric layer and the top electrode layer is subjected to ion implantation treatment, so as to form an acoustic impedance abrupt-change portion. Further disclosed is a manufacturing process for the thin film bulk acoustic resonator. The manufacturing process comprises: manufacturing a bottom electrode layer on a substrate on which an acoustic wave reflection structure is formed or is to be formed, so as to cover the acoustic wave reflection structure; manufacturing a piezoelectric layer on the bottom electrode layer; manufacturing a top electrode layer on the piezoelectric layer; and performing a whole or partial ion implantation treatment on a part, which corresponds to the boundary of the acoustic wave reflection structure, of at least one of the bottom electrode layer, the piezoelectric layer and the top electrode layer, so as to form an acoustic impedance abrupt-change portion. According to the thin film bulk acoustic resonator and the manufacturing process therefor, ion implantation is performed in a specific area of a resonator functional layer, so as to form an acoustic impedance abrupt change, thereby inhibiting transverse waves from taking away energy, and increasing a resonator Q value.

Description

Thin film bulk acoustic wave resonator and manufacturing process thereof

Technical field

This application relates to the field of communication devices, and mainly relates to a thin-film bulk acoustic resonator and its manufacturing process.

Background technique

With the increasing congestion of the electromagnetic spectrum and the increase in frequency bands and functions of wireless communication equipment, the electromagnetic spectrum used in wireless communication has grown rapidly from 500MHz to above 5GHz, so there is a demand for high performance, low cost, low power consumption, and small size RF front-end modules. Also growing day by day. The filter is one of the radio frequency front-end modules, which can improve the transmission and reception of signals. It is mainly composed of multiple resonators connected through a topological network structure. Fbar (Thin film bulk acoustic resonator) is a bulk acoustic wave resonator. The filter composed of it has the advantages of small size, strong integration capability, high quality factor Q during high-frequency operation, and strong power tolerance. It is used as a radio frequency front-end The core device.

Fbar is a basic structure composed of upper and lower electrodes and a piezoelectric layer sandwiched between the electrodes. The piezoelectric layer mainly realizes the conversion of electrical energy and mechanical energy. When an electric field is applied to the upper and lower electrodes of Fbar, the piezoelectric layer converts electrical energy into mechanical energy, and the mechanical energy exists in the form of sound waves. Acoustic waves have two vibration modes: transverse wave and longitudinal wave. Longitudinal wave is the main mode in Fbar working state, and transverse wave is easy to leak from the edge of the resonator and take away energy. The Q value is an important index to measure the performance of the resonator, which is equal to the ratio of the energy stored by the resonator to the energy lost by the resonator. Therefore, the energy taken away by the transverse wave will inevitably attenuate the Q value and degrade the performance of the device.

In the prior art, the air gap at the cavity boundary reflects the transverse wave to suppress the energy taken by the transverse wave. The air gap is made by a process of releasing the internal sacrificial layer. The process is more complicated and the mechanical stability of the top electrode connection part on the upper part of the cavity needs to be ensured. . Or by processing a mass load layer (a circle around the inner side of the resonator, which can be of various materials) in the resonant region of the device to form the effect of sudden acoustic impedance, thereby suppressing the transverse wave mode and improving the Q value of the resonator. Or the arrangement of interlaced electrode structures on the effective resonance region of the resonator can suppress parasitic oscillations to a certain extent, but cannot suppress the energy carried by transverse waves from passing out of the resonator. Or by making grooves on the piezoelectric layer to suppress the energy taken by the transverse wave, thereby increasing the Q value of the device, but the grooves are made by an etching process, which will cause the crystal lattice of the piezoelectric layer at the bottom and sidewalls of the grooves Defects and micro-holes affect the performance of the resonator; on the other hand, reducing the area of the resonance area on the upper part of the cavity increases the size of the filter to a certain extent. Or the mass load layer on the top of the top electrode can form a sudden change in acoustic impedance to suppress the energy taken by the transverse wave, but the piezoelectric layer on the edge of the cavity will replicate the lattice defects and micropores caused by the etching process of the bottom electrode. Or, other extremely complicated processes, such as forming a recessed reflective structure in the piezoelectric layer, can achieve the effect of abrupt changes in acoustic impedance.

Summary of the invention

In order to solve the technical problems of various acoustic impedance mutations that suppress the energy carried away by transverse waves in the prior art, the process is complicated, and the mechanical stability of the top electrode connection part of the upper cavity needs to be considered, the size of the filter is increased, and the performance of the resonator is affected. The present invention proposes a thin-film bulk acoustic resonator and its manufacturing process to solve the above-mentioned problems.

According to one aspect of the present invention, a thin film bulk acoustic wave resonator is provided, which includes a bottom electrode layer, a piezoelectric layer, and a top electrode layer disposed on a substrate where an acoustic wave reflection structure is located, wherein the bottom electrode layer, the piezoelectric layer, and the A portion of at least one of the top electrode layers corresponding to the boundary of the acoustic wave reflection structure is subjected to ion implantation to form an acoustic impedance mutation portion. By performing ion implantation modification on the resonator functional layer in a specific area to form a sudden change in acoustic impedance, it is possible to suppress the transverse wave from taking energy from the resonant area of the resonator and increase the Q value of the resonator.

In some embodiments, ion implantation is partially applied to the sudden change of acoustic impedance. Setting a part of the ion implantation area according to the performance requirements of the device can facilitate the production of devices that meet the expected performance requirements at a minimum cost.

In some embodiments, ion implantation is all applied to the abrupt acoustic impedance portion. Applying ion implantation to the entire acoustic impedance mutation part can obtain a better modification effect.

In some embodiments, the projection area of the acoustic impedance mutation portion on the substrate spans at least from the area outside the acoustic wave reflection structure to the inside of the acoustic wave reflection structure. With the setting of this area, the effect of suppressing the energy of the resonator from being carried away by the transverse wave can be better obtained.

In some embodiments, the ion implantation range of the acoustic impedance mutation portion is less than or equal to the total thickness of the electrode and/or the piezoelectric layer at the location corresponding to the boundary of the acoustic wave reflection structure. This setting can improve the performance of the resonator by matching the range of ion implantation through the selection and design of a specific area.

In some embodiments, the acoustic impedance abrupt portion is differently doped to form multiple annular bands surrounding the acoustic wave reflection structure in a direction parallel to the piezoelectric layer. With the setting of multiple annular bands, multiple acoustic impedance mutation regions can be formed to obtain a better reflection effect of transverse waves, so that the performance of the resonator can be greatly improved.

In some embodiments, the different doping includes ion doping of different elements and/or ion doping of different doses. This setting can realize the effect of different degrees of reflection of transverse waves on the functional layer.

In some embodiments, the acoustic wave reflecting structure is a cavity. The cavity structure can enhance the reflection effect of sound waves and improve the Q value of the device.

In some embodiments, the acoustic wave reflection structure is a Bragg reflection structure.

In some embodiments, the Bragg reflection structure is a Bragg reflection structure after ion implantation is applied. With ion implantation on the Bragg reflection structure, a better reflection effect can be obtained and the performance of the resonator can be improved.

According to the second aspect of the present invention, a manufacturing process of a thin-film bulk acoustic resonator is proposed, which includes:

Fabricating a bottom electrode layer on the substrate on which the acoustic wave reflection structure is formed or to be formed to cover the acoustic wave reflection structure;

Making a piezoelectric layer on the bottom electrode layer;

Making a top electrode layer on the piezoelectric layer;

Wherein, the process further includes performing ion implantation on a part of at least one of the bottom electrode layer, the piezoelectric layer, and the top electrode layer, which corresponds to the boundary of the acoustic wave reflection structure, to form an acoustic impedance mutation part.

By implanting ions into at least one of the piezoelectric layer, the bottom electrode layer and the top electrode layer, the acoustic impedance outside the effective area of the resonator device can be changed to achieve the purpose of reflecting transverse waves and improve the performance of the resonator.

In some embodiments, the ion implantation process specifically includes:

Depositing a hard mask or coating photoresist on the functional layer that needs to be ion implanted;

Patterning the hard mask or photoresist so that at least the part of the functional layer corresponding to the boundary of the acoustic wave reflection structure is exposed;

Perform ion implantation on the exposed part of the functional layer;

The hard mask or photoresist is removed; wherein the functional layer includes at least one of a bottom electrode layer, a piezoelectric layer, and a top electrode layer.

In some embodiments, ion implantation of different elements and/or different doses is used to form a sudden change in acoustic impedance of multiple annular bands surrounding the acoustic wave reflection structure. The multiple annular bands formed by ion implantation of different elements and/or different doses can form multiple acoustic impedance mutation regions to obtain a better effect of reflecting transverse waves, so that the performance of the resonator is greatly improved.

In some embodiments, the acoustic wave reflection structure is a cavity or a Bragg reflection structure. Acoustic reflection structure can choose cavity or Bragg reflection structure according to different application effects.

In some embodiments, the Bragg reflection structure is subjected to ion implantation in advance. Ion implantation of the Bragg reflection structure can obtain a better reflection effect and improve the performance of the resonator.

According to the third aspect of the present invention, a thin-film bulk acoustic resonator is provided, which is manufactured through the above-mentioned manufacturing process.

The resonator functional layer in a specific area of a thin film bulk acoustic wave resonator of the present invention is modified by ion implantation to form an acoustic impedance mutation part, which can reflect the transverse wave transmitted from the effective resonance region to suppress energy leakage , Thereby improving the Q value and improving the performance of the device. Compared with the prior art using air gap and other processes to reflect the transverse wave to suppress the energy taken away by the transverse wave, the process is simpler, and there is no need to worry about the mechanical stability of the top electrode connection part. At the same time, according to a manufacturing process of a thin film bulk acoustic resonator according to another aspect of the present invention, all parts corresponding to the boundary of the acoustic wave reflection structure of at least one of the bottom electrode layer, the piezoelectric layer and the top electrode layer are performed. Or part of the ion implantation process to form the acoustic impedance mutation part, the ion implantation area can be selected according to different device performance requirements and cost requirements, and thin film bulk acoustic wave resonators with different cost or performance requirements can be fabricated.

Description of the drawings

The drawings are included to provide a further understanding of the embodiments and the drawings are incorporated into this specification and constitute a part of this specification. The drawings illustrate the embodiments and together with the description serve to explain the principles of the present invention. It will be easy to recognize the other embodiments and the many expected advantages of the embodiments because they become better understood by quoting the following detailed description. The elements of the drawings are not necessarily in proportion to each other. The same reference numerals refer to corresponding similar parts.

Fig. 1 shows a cross-sectional view of a thin-film bulk acoustic resonator with a parallel structure according to an embodiment of the present invention;

Figure 2 shows a cross-sectional view of a thin film bulk acoustic resonator with a series structure according to an embodiment of the present invention;

Figure 3 shows a cross-sectional view of a thin film bulk acoustic resonator with an SMR structure according to a specific embodiment of the present invention;

Figures 4a-k show a process flow diagram of a thin film bulk acoustic resonator according to an embodiment of the present invention;

5a-j show cross-sectional views of thin film bulk acoustic resonators in ion implantation regions of different functional layers according to a specific embodiment of the present invention.

detailed description

The application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described here are only used to explain the related invention, but not to limit the invention. In addition, it should be noted that, for ease of description, only the parts related to the relevant invention are shown in the drawings.

It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other if there is no conflict. Hereinafter, the present application will be described in detail with reference to the drawings and in conjunction with the embodiments.

FIG. 1 shows a cross-sectional view of a thin-film bulk acoustic resonator with a parallel structure according to an embodiment of the present invention. As shown in FIG. 1, the thin-film bulk acoustic resonator includes a substrate 101, a bottom electrode 103, and a piezoelectric layer 104. And the top electrode 105, wherein the surface of the substrate 101 is processed with a support portion 102, the substrate 101 and the bottom electrode 103 form a cavity 106 with an acoustic reflection structure between the support portion 102, and the piezoelectric layer 104 outside the boundary of the cavity 106 The longitudinal region with the bottom electrode 103 forms the acoustic impedance mutation part 107 by ion implantation. The acoustic impedance mutation part 107 can reflect the transverse wave transmitted from the effective resonance region to suppress energy leakage and improve the Q value of the device. Preferably, the acoustic impedance mutation portion 107 can be set to local ion implantation according to device performance requirements, so that devices that meet the expected performance requirements can be manufactured at a minimum cost; all ion implantation can also be performed to achieve better functional layer modification effects.

In a specific embodiment, the projection area of the acoustic impedance mutation portion 107 on the substrate 101 may span from the area outside the cavity 106 to the edge of the cavity 106 or within the cavity 106. All or part of ion implantation may be performed only at both ends of the original acoustic impedance mutation portion 107, or all or part of the ion implantation may be performed at both ends and bottom of the original acoustic impedance mutation portion 107 at the same time to obtain different degrees of acoustic impedance effects. It should be noted that the injection area can be multiple combinations to form multiple ring-shaped areas from the effective area of the resonator. For example, the injected elements and/or concentration of the two ends and bottom of the acoustic impedance mutation portion 107 can be different. identical.

In a specific embodiment, an important invention of the present invention is to dope the electrode or the specific area of the piezoelectric layer, the doping element causes the crystal structure distortion or the crystal type transformation of the Mo doped system or the AlN doped system, Therefore, the doped area is modified to form a sudden change in acoustic impedance and reflect the transverse wave, which improves the Q value of the device. For example, in the Er-doped piezoelectric layer AlN, ^{the ionic radius of Er 3+} (0.0881 nm) is larger than that of Al ³⁺ (0.0535 nm), so the Er-N bond length is greater than the Al-N bond length. As the amount of Er doping increases, the unit cell parameters, unit cell volume and bond length of the doping system increase accordingly, causing the crystal structure of the doping system to be distorted but the crystal type does not change. It still belongs to the hexagonal system; when the doping content When it is high enough (such as >50%), the crystal form of the doped system will change.

In other embodiments, the electrode may be a composite electrode of Pt, Ru, Al, W, or TiN and this type of metal (including but not limited to this type of metal material). The piezoelectric layer can be AlN, AlScN, LiNbO ₃ , KNbO ₃ , LiTaO ₃ , PZT, Quartz, ZnO and other piezoelectric materials or partially doped single piezoelectric materials or composite multilayer piezoelectric materials (including but not limited to these Piezoelectric materials). The above-mentioned doping elements and methods depend on the materials of the electrode and the piezoelectric layer, and the final matching is performed, which also includes the matching of the doping of the piezoelectric layer and the electrode doping.

In a specific embodiment, multiple groups of resonators are connected in parallel on the same substrate 101 (the right side of the resonator in FIG. 1 is only partially shown), and the top electrode 105 of the previous group of resonators is connected to the top electrode of the next resonator through The setting of the acoustic impedance mutation part 107 suppresses energy leakage and improves the Q value of the device by reflecting transverse waves. FIG. 2 shows a cross-sectional view of a thin film bulk acoustic wave resonator with a series structure according to an embodiment of the present invention. As shown in FIG. 2, multiple sets of resonators are connected in series on the same substrate 101 (only Partial schematic) The top electrode 105 of the previous resonator is connected to the bottom electrode 103 of the latter resonator to realize the series connection of the resonators, and the acoustic impedance mutation part 207 is respectively provided on the piezoelectric layer 104 where the two resonators are connected in series. The transverse wave transmitted from the resonance area is reflected to suppress energy leakage and improve the Q value of the device.

Compared with the prior art using the air gap formed by releasing the internal sacrificial layer at the boundary of the cavity 106 to reflect the transverse wave, the process is more complicated and the mechanical stability of the connection part of the top electrode 105 on the upper part of the cavity 106 needs to be ensured. In the present invention, ion implantation is applied to a specific area to form an acoustic impedance mutation area to reflect the transverse wave, only a hard mask is used to protect the non-implanted area, the process is relatively simple, and there is no need to worry about the mechanical stability of the top electrode 105 connection portion.

Although the arrangements of the acoustic impedance mutation part of the cavity structure resonator structure are shown in Figs. 1-2, it should be recognized that the solution of forming the acoustic impedance mutation part by ion implantation is also applicable to the SMR structure. The technical effect of the present invention can be achieved. FIG. 3 shows a cross-sectional view of a thin film bulk acoustic wave resonator with an SMR structure according to another embodiment of the present invention. As shown in FIG. 3, the SMR structure thin film bulk acoustic resonator is similar to the thin film bulk acoustic resonator shown in FIG. With a similar structure, the cavity 106 of the reflection structure in FIG. 1 is changed to the Bragg reflection structure 306, and the acoustic impedance mutation part 107 can also achieve the technical effect of suppressing the energy of the resonator from being carried away by the transverse wave. It should be realized that ion implantation can also be applied to the Bragg reflection structure 306 to obtain a better reflection effect and further improve the performance of the resonator.

Figures 4a-k show a manufacturing process of a thin film bulk acoustic resonator according to an embodiment of the present invention. The process includes the following processes:

First, as shown in FIG. 4a, a cavity pit is etched on a substrate 401 and a supporting portion 402 for supporting the electrode and the piezoelectric layer is formed. The substrate 401 may be Si, SiC, sapphire, spinel, or the like. Preferably, the depth of the pit is 2-4 μm. The sacrificial layer 403 is grown in the cavity through a CVD process, as shown in FIG. 4b, where the material of the sacrificial layer 403 can be PSG (P-doped SiO ₂ ), and the sacrificial layer 403 is chemically mechanically polished, preferably, chemical mechanical The height of the cavity after polishing is 1-2 μm. As shown in FIG. 4c, a bottom electrode 404 is fabricated on the support portion 402 and the sacrificial layer 403, and the bottom electrode 404 is intermittently arranged on the support portion 402. The material of the bottom electrode 404 can be molybdenum, and it is used on the basis of the bottom electrode 404. The piezoelectric layer 405 is fabricated by the PVD process, wherein the piezoelectric layer 405 is aluminum nitride, and the specific structure is shown in FIG. 4d.

Continuing to refer to Figures 4e and 4f, a hard mask 406 is deposited on the surface of the piezoelectric layer 405 by CVD. The hard mask 406 is an inorganic thin film material. The main components include SiN or SiO ₂ and the hard mask 406 is formed by photolithography and etching. It should be noted that the shape of the hard mask 406 area is the same as the shape of the subsequent top electrode, and the blocking area is the effective area of the resonator. Alternatively, it is also possible to directly use the technology of photoresist development to make the opening pattern, that is, to replace the hard mask 406 with photoresist, which can also achieve the technical effects of the present invention.

As shown in FIGS. 4g and 4h, ion implantation is performed on the area of the piezoelectric layer 405 exposed to the hard mask 406, where the implanted ions can be Ni/Fe/Cr/Mn/Co/V/Y/Si/Er/Sc Wait.

Continuing to refer to FIG. 4i, the hard mask 406 is removed with a hydrofluoric acid etchant. It should be noted that regardless of the ion implantation area of any shape, the ion implantation area on each side does not exceed the range of the cavity, that is, the ion implantation area is vertical The projection in the direction can partially overlap the cavity boundary or extend slightly into the cavity.

Finally, referring to FIGS. 4j and 4k, the top electrode 408 is fabricated on the surface of the piezoelectric layer 405 by PVD, photolithography and etching processes, where the material of the top electrode 408 is molybdenum. The sacrificial layer 403 is released by the hydrofluoric acid etchant to obtain the cavity 409, and the manufacturing process of the thin film bulk acoustic wave resonator is completed. This process uses the deposition of the hard mask 406 to expose the piezoelectric layer 405 that needs ion implantation. By applying ion implantation to the piezoelectric layer 405 exposed outside the hard mask 406, the piezoelectric layer in this area can be modified to form In the acoustic impedance mutation area, the corresponding ion implantation area can also be selected comprehensively according to the cost and the performance of the device to meet the manufacturing process of different types of thin-film bulk acoustic wave resonators.

In a specific embodiment, FIGS. 5a-j show cross-sectional views of thin film bulk acoustic resonators in ion implantation regions of different functional layers according to a specific embodiment of the present invention. The upper surface of the support portion 502 processed on the substrate 501 is sequentially processed with a bottom electrode 504, a piezoelectric layer 505, and a top electrode 508. The projection of the ion implantation area in the vertical direction must coincide with the boundary of the cavity 509 or extend slightly to the cavity Within 509, it cannot exceed the range of cavity 509. The larger the ion implantation area is, the more obvious the modification effect is, but the cost increases. Therefore, the ion implantation area can be selected by weighing the cost and device performance requirements. The ion implantation area of the piezoelectric layer 505, the top electrode 508, or the bottom electrode 504, which is projected in the vertical direction and outside the cavity 509, can be changed for selection and design to improve the performance of the resonator.

Fig. 5a shows a cross-sectional view of a thin film bulk acoustic resonator in a multiple-combination ion implantation region. The ion implantation region 507a includes regions 507a1 and 507a2 on both sides above the support portion 502, and a region 507a3 at the bottom, of which regions 507a1 on both sides , 507a2 and the bottom area 507a3 are different doping elements, forming a multiple ring area outward from the effective area of the resonator (as shown in Fig. 5b). It should also be realized that the doping elements may also be different between different resonators.

5c shows a cross-sectional view of the thin film bulk acoustic resonator defined by the range of the ion implantation region in the horizontal direction. The ion implantation region 507c includes regions 507c1 and 507c2 on both sides above the support portion 502. Under the condition that the projection of the ion implantation area in the vertical direction coincides with the boundary of the cavity 509 or slightly extends into the cavity 509 and does not exceed the scope of the cavity 509, the width of the areas 507c1 and 507c2 in the horizontal direction can be adjusted according to requirements Adjust the settings.

FIG. 5d shows a cross-sectional view of the thin film bulk acoustic resonator defined by the range of the ion implantation area in the vertical direction. The ion implantation area 507d can be adjusted and set along the thickness direction of the piezoelectric layer 505 according to requirements. FIG. 5e shows a cross-sectional view of a thin film bulk acoustic resonator defined by the ion implantation area in the horizontal and vertical directions. The ion implantation area 507e in the two directions can be adjusted simultaneously according to requirements.

In other specific embodiments, the ion implantation area is not limited to the area where the piezoelectric layer 505 is located, and the implantation area can also be changed by ion implantation for any multilayer combination of the top electrode 508 or the bottom electrode 504 or the functional layer. The acoustic impedance. Connect multiple sets of resonators in parallel (as shown in FIG. 5f) through the ion implantation area 507f of the top electrode 508 to achieve the effect of acoustic impedance; connect multiple sets of resonators in series (as shown in FIG. 5g) through ion implantation at the top electrode 508 The area 507g achieves the effect of acoustic impedance; connects multiple sets of resonators in parallel (as shown in Figure 5h) to achieve the effect of acoustic impedance through the ion implantation area 507h of the bottom electrode 504; connects multiple sets of resonators in series (as shown in Figure 5i) The effect of acoustic impedance is achieved by the ion implantation area 507i of the bottom electrode 504; or the area 507j (as shown in FIG. 5j) formed by simultaneous ion implantation on the top electrode 508 and the piezoelectric layer 505 can achieve the effect of acoustic impedance.

The thin film bulk acoustic resonator produced by the manufacturing process shown in Figures 4a-4k is formed by ion implantation of the resonator functional layer in a specific area or a specific range to form an acoustic impedance mutation part to change the acoustic impedance of the specific area, and the reflected transverse wave is transmitted , Thereby suppressing the transverse wave from taking energy away from the resonant region of the upper part of the resonator cavity, thereby increasing the Q value of the resonator. When performing ion implantation on other functional layers, the ion implantation process in Figures 4e-4i is adjusted accordingly to the manufacturing process of the functional layer that requires ion implantation. For example, if the bottom electrode needs to be locally modified, then The ion implantation process in FIGS. 4e-4i is adjusted accordingly after the bottom electrode fabrication process is completed (FIG. 4c).

It should be realized that the method of using ion implantation to change the acoustic impedance can not only be used in the manufacturing process of the above-mentioned thin film bulk acoustic resonator, but also applicable to all different types of radio frequency filter components of SAW and BAW, as well as MEMS piezoelectric devices. In the manufacturing process of all MEMS devices including gyroscopes and radar chips, for example, when used in SAW devices, the acoustic impedance is changed in the IDT end area to improve the performance of SAW devices; or in BAW devices with SMR structure, SMR reflection The layer structure is doped to achieve better reflection effect; or in stacked bulk acoustic resonator (SBAR) devices, RBAR (reverse bluk acoustic resonator) devices, double bulk acoustic resonator (DBAR) devices or coupled resonator filters In the resonator stack of the (CRF) device, ion implantation is used to change the acoustic impedance of the electrode, piezoelectric layer, or dielectric layer, which can also achieve the purpose of improving the performance of the device.

The specific implementations of this application are described above, but the scope of protection of this application is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and they should be covered Within the scope of protection of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

In the description of this application, it needs to be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. It is convenient to describe the application and simplify the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore cannot be understood as a limitation of the application. The word'comprising' does not exclude the presence of elements or steps not listed in the claims. The wording'a' or'one' in front of an element does not exclude the existence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Industrial applicability

In the embodiment of the present invention, ion implantation modification is performed on the resonator functional layer in a specific area to form an acoustic impedance mutation portion. The ion implantation area can be selected according to different device performance requirements and cost requirements, and thin film bodies with different cost or performance requirements can be fabricated. Acoustic resonator. The manufacturing process is simple, the manufacturing cost is low, and it is convenient for large-scale industrial production.

Claims

A thin film bulk acoustic wave resonator, characterized in that it comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer arranged on the upper part of the substrate where the acoustic wave reflection structure is located, wherein the bottom electrode layer, the piezoelectric layer and the A portion of at least one of the top electrode layers corresponding to the boundary of the acoustic wave reflection structure in a direction perpendicular to the substrate is subjected to ion implantation to form an acoustic impedance mutation portion.
The thin-film bulk acoustic resonator according to claim 1, wherein ion implantation is partially applied to the abrupt acoustic impedance portion.
The thin-film bulk acoustic resonator according to claim 1, wherein the acoustic impedance mutation part is completely ion-implanted.
The film bulk acoustic resonator according to any one of claims 1 to 3, wherein the projection area of the acoustic impedance mutation portion on the substrate at least spans from the area outside the acoustic wave reflection structure Into the acoustic reflection structure.
The thin-film bulk acoustic resonator according to claim 1, wherein the ion implantation range of the acoustic impedance mutation part is less than or equal to the total thickness of the electrode and/or the piezoelectric layer at the position corresponding to the boundary of the acoustic reflection structure .
The thin-film bulk acoustic resonator according to claim 1, wherein the acoustic impedance mutation portion is subjected to different ion implantation to form multiple layers surrounding the acoustic wave reflection structure in a direction parallel to the piezoelectric layer. Annular belt.
7. The thin film bulk acoustic resonator according to claim 6, wherein the different ion implantation includes ion implantation of different elements and/or ion implantation of different doses.
The thin film bulk acoustic resonator according to any one of claims 1-3 and 5-7, wherein the acoustic wave reflection structure is a cavity.
The thin film bulk acoustic resonator according to any one of claims 1-3 and 5-7, wherein the acoustic wave reflection structure is a Bragg reflection structure.
9. The thin film bulk acoustic resonator according to claim 9, wherein the Bragg reflection structure is a Bragg reflection structure after ion implantation is applied.
A manufacturing process of a thin film bulk acoustic wave resonator, which is characterized in that it comprises:

Fabricating a bottom electrode layer on the substrate on which the acoustic wave reflection structure is formed or will be formed to cover the acoustic wave reflection structure;

Fabricating a piezoelectric layer on the bottom electrode layer;

Fabricating a top electrode layer on the piezoelectric layer;

Wherein, the process further includes performing all or part of ion implantation treatment on a portion of at least one of the bottom electrode layer, the piezoelectric layer, and the top electrode layer that corresponds to the boundary of the acoustic wave reflection structure. A sudden change in acoustic impedance is formed.
The manufacturing process according to claim 11, wherein the ion implantation treatment specifically comprises:

Depositing a hard mask or coating photoresist on the functional layer that needs to be ion implanted;

Patterning the hard mask or the photoresist so that at least a part of the functional layer corresponding to the boundary of the acoustic wave reflection structure is exposed;

Performing ion implantation on the exposed part of the functional layer;

The hard mask or photoresist is removed; wherein the functional layer includes at least one of the bottom electrode layer, the piezoelectric layer, and the top electrode layer.
The manufacturing process according to any one of claims 11-12, characterized in that ion implantation of different elements and/or different doses is used to form the acoustic impedance mutation part of the multiple annular zone surrounding the acoustic wave reflection structure.
The manufacturing process according to any one of claims 11-12, wherein the acoustic wave reflection structure is a cavity or a Bragg reflection structure.
14. The manufacturing process of claim 14, wherein the Bragg reflection structure is subjected to ion implantation in advance.
A thin film bulk acoustic wave resonator, characterized in that it is manufactured by the manufacturing process of any one of claims 11-15.