CN112688657A

CN112688657A - Acoustic wave resonator and preparation method thereof

Info

Publication number: CN112688657A
Application number: CN202011560361.3A
Authority: CN
Inventors: 欧欣; 张丽萍; 张师斌; 周鸿燕; 吴进波
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2021-04-20

Abstract

The invention provides an acoustic wave resonator and a preparation method thereof, wherein the preparation method comprises the following steps: providing a piezoelectric material layer; performing ion implantation on at least part of the upper surface of the piezoelectric material layer and annealing to form a high-defect-density damaged layer with a preset thickness at a preset depth in the piezoelectric material layer; forming at least one corrosion window exposing the high defect density damage layer on the upper surface of the piezoelectric material layer; removing at least a portion of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer; the piezoelectric material layer is divided into a piezoelectric substrate and a piezoelectric film by the air gap, the piezoelectric film is positioned above the air gap, and the piezoelectric film and the piezoelectric substrate are in contact at the edge of the air gap; and forming a patterned electrode on the upper surface of the piezoelectric film. The acoustic wave resonator and the preparation method thereof provided by the invention solve the problem that the existing acoustic wave resonator cannot meet the requirement of 5G communication.

Description

Acoustic wave resonator and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductors, in particular to an acoustic wave resonator and a preparation method thereof.

Background

Compared with 4G and 4G-LTE communications, 5G communications require the use of a higher frequency spectrum, which puts higher demands on the center frequency, bandwidth, quality factor, etc. of the radio frequency filter. Taking the domestic Sub-6 GHz frequency band as an example, the central frequency of the radio frequency front-end filter is required to reach 3.5-5.0 GHz, and the relative bandwidth is about 8.8% at most; however, it is difficult for current commercial rf acoustic filters to meet the above requirements.

Therefore, it is necessary to design a new acoustic wave resonator and a method for manufacturing the same to meet the requirement of 5G communication.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention is directed to an acoustic wave resonator and a method for manufacturing the same, so as to solve the problem that the existing acoustic wave resonator cannot meet the requirement of 5G communication.

To achieve the above and other related objects, the present invention provides a method for manufacturing an acoustic wave resonator, the method comprising:

a) providing a piezoelectric material layer;

b) performing ion implantation on at least part of the upper surface of the piezoelectric material layer and annealing to form a high-defect-density damaged layer with a preset thickness at a preset depth in the piezoelectric material layer;

c) forming at least one corrosion window on the upper surface of the piezoelectric material layer to expose the high defect density damage layer;

d) removing at least a portion of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer; the piezoelectric material layer is divided into a piezoelectric substrate and a piezoelectric film by the air gap, the piezoelectric film is positioned above the air gap, and the piezoelectric film and the piezoelectric substrate are in contact at the edge of the air gap;

e) and forming a patterned electrode on the upper surface of the piezoelectric film.

Optionally, the steps in the preparation method are performed in an order of a), b), c), d), e), a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d); wherein, when the execution sequence of the steps in the preparation method is a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d), e) is that a patterned electrode is formed on the upper surface of the piezoelectric material layer.

Optionally, before forming the etch window, the preparation method further includes: forming a first protective layer on the surface of the piezoelectric material layer or the surface of the piezoelectric material layer and the surface of the patterned electrode; after forming the etch window, the method of making further comprises: a step of removing the first protective layer; the first protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold.

Optionally, before forming the air gap, the preparation method further includes: forming a second protective layer on the surface of the piezoelectric material layer or the surface of the piezoelectric material layer and the surface of the patterned electrode; after forming the air gap, the manufacturing method further includes: a step of removing the second protective layer; the second protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold.

Optionally, the preparation method further comprises: and forming a heat dissipation accelerating layer on at least the upper surface of the piezoelectric film and the surface of the patterned electrode.

Optionally, b) performing ion implantation and post-annealing treatment on the entire upper surface of the piezoelectric material layer to form a high defect density damage layer with a preset thickness at a preset depth in the piezoelectric material layer; at this time, d) removes a portion of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer.

Optionally, the method for forming the etching window in c) comprises:

defining the position of the air gap in the piezoelectric material layer, and forming a patterned window mask on the upper surface of the piezoelectric material layer, wherein an opening pattern for defining the shape and the position of the corrosion window is formed in the patterned window mask, and the opening pattern is positioned in the area where the air gap is defined;

etching the piezoelectric material layer based on the patterned window mask to form at least one corrosion window exposing the high defect density damage layer;

and removing the patterned window mask.

Optionally, b) performing ion implantation on a part of the upper surface of the piezoelectric material layer and performing annealing treatment to form a high defect density damaged layer with a preset thickness at a preset depth in the piezoelectric material layer; at this time, d) removing all of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer.

Optionally, the method of forming the high defect density damage layer in b) comprises:

forming a patterned implantation mask on the upper surface of the piezoelectric material layer, wherein an opening pattern for defining the shape and the position of the high-defect-density damage layer is formed in the patterned implantation mask;

performing ion implantation and post-annealing treatment on the piezoelectric material layer based on the patterned implantation mask so as to form a high-defect-density damaged layer with a preset thickness at a preset depth in the piezoelectric material layer;

removing the patterned implantation mask;

at this time, the method of forming the etch window in c) includes:

forming a patterned window mask on the upper surface of the piezoelectric material layer, wherein an opening pattern for defining the shape and the position of the corrosion window is formed in the patterned window mask;

and removing the patterned window mask.

Optionally, the ion implantation is performed in multiple times; the doses of the multiple ion implantations are the same, the energies of the multiple ion implantations are different, and the energy values of the multiple ion implantations are sequentially decreased progressively.

Optionally, defining contact of the piezoelectric film with the piezoelectric substrate at an edge of the air gap based on a shape and a position of the erosion window; the piezoelectric film and the piezoelectric substrate are provided with at least one contact point at the edge of the air gap, and/or the piezoelectric film and the piezoelectric substrate are provided with at least one contact surface at the edge of the air gap.

Optionally, the patterned electrode comprises: one or more of interdigital electrodes, fan-shaped strip electrodes, circular ring-shaped strip electrodes or hexagonal plate electrodes.

Optionally, when the patterned electrodes are interdigital electrodes and pairs of the interdigital electrodes are multiple pairs, the multiple pairs of the interdigital electrodes form an interdigital transducer.

Optionally, the preparation method further comprises: and forming a reflection gate electrode on the upper surface of the piezoelectric film on both sides of the interdigital transducer or the upper surface of the piezoelectric substrate.

The present invention also provides an acoustic wave resonator, including:

a layer of piezoelectric material;

an air gap with a preset thickness is formed at a preset depth of the piezoelectric material layer based on a corrosion window; the air gap divides the piezoelectric material layer into a piezoelectric substrate and a piezoelectric film, the piezoelectric film is positioned above the air gap, and the piezoelectric film and the piezoelectric substrate are in contact at the edge of the air gap;

and the patterned electrode is formed on the upper surface of the piezoelectric film.

Optionally, the target elastic wave excited by the piezoelectric film comprises: one or more of rayleigh waves, shear horizontal waves, symmetric lamb waves, anti-symmetric lamb waves, bulk waves or quasicidal waves.

Optionally, the piezoelectric film and the piezoelectric substrate have at least one contact point at the edge of the air gap, and/or the piezoelectric film and the piezoelectric substrate have at least one contact surface at the edge of the air gap.

Optionally, the acoustic wave resonator further includes: and the at least one pair of reflection gate electrodes are formed on the upper surfaces of the piezoelectric films on two sides of the interdigital transducer or the upper surface of the piezoelectric substrate.

Optionally, the thickness of the patterned electrode is smaller than the thickness of the piezoelectric film, and the ratio of the thickness of the piezoelectric film to the wavelength of a target elastic wave excited by the piezoelectric film is smaller than 0.5.

Optionally, the acoustic wave resonator further includes: and the heat dissipation accelerating layer is at least formed on the upper surface of the piezoelectric film and the surface of the patterned electrode.

Optionally, the material of the piezoelectric material layer includes: any one of quartz, aluminum nitride, zinc oxide, lithium tantalate, lithium niobate, lithium tetraborate, bismuth germanate, bismuth silicate, lanthanum gallium silicate and zirconium titanium lead acid.

As described above, the acoustic wave resonator and the method for manufacturing the same according to the present invention have the following advantageous effects: according to the preparation method, the high-defect-density damaged layer is formed inside the piezoelectric material layer by means of ion implantation and post annealing, and then the high-defect-density damaged layer is removed through the corrosion window to obtain the suspended piezoelectric film, complex process procedures such as bonding, transferring, stripping and polishing are not needed, and therefore the preparation complexity is reduced. The preparation method provided by the invention has the advantages of simple process, high material utilization rate and low manufacturing cost, is beneficial to improving the bandwidth and the coverage frequency band of the resonator and the filter, and is suitable for large-scale production and use. The invention effectively limits the energy of a high-order sound wave mode with higher sound velocity in the piezoelectric film by utilizing the acoustic impedance extreme mismatching of the suspended piezoelectric film and the air gap, thereby improving the frequency, the electromechanical coupling coefficient, the bandwidth and the quality factor of the device and meeting the requirement of 5G communication.

Drawings

Fig. 1 shows a flow chart of a method for manufacturing an acoustic wave resonator according to the present invention.

FIGS. 2a-2e are schematic structural diagrams illustrating steps in a method of fabricating an acoustic resonator according to the present invention; fig. 2a is a schematic structural diagram of a piezoelectric material layer, fig. 2b is a schematic structural diagram of a damage layer with high defect density, fig. 2c is a schematic structural diagram of a patterned electrode, fig. 2d is a schematic structural diagram of an etching window, and fig. 2e is a schematic structural diagram of an air gap.

FIGS. 3a-3e are schematic structural diagrams illustrating steps in another method for fabricating an acoustic wave resonator according to the present invention; fig. 3a is a schematic structural diagram of a piezoelectric material layer, fig. 3b is a schematic structural diagram of a damage layer with high defect density, fig. 3c is a schematic structural diagram of a patterned electrode, fig. 3d is a schematic structural diagram of an etching window, and fig. 3e is a schematic structural diagram of an air gap.

FIGS. 4-11 illustrate contact patterns between a piezoelectric film and a piezoelectric substrate defined based on different locations and shapes of erosion windows in an acoustic resonator according to the present invention; in fig. 4 to 5, the piezoelectric thin film and the piezoelectric substrate are in point contact, in fig. 6 to 7, the piezoelectric thin film and the piezoelectric substrate are in surface contact, and in fig. 8 to 11, the piezoelectric thin film and the piezoelectric substrate are in point contact and surface contact.

Fig. 12 is a schematic diagram showing the structures of suspended film acoustic resonators described in examples 1 to 5.

Fig. 13 is a schematic view showing the structure of the solid-state fabricated acoustic wave resonator described in comparative examples 1 to 5.

FIG. 14a shows the electromechanical coupling coefficient K of the acoustic wave resonators described in example 1 and comparative example 1 in the zeroth order shear horizontal wave SH0 mode²FIG. 14b shows the variation of the in-plane propagation angle (0-180) as a function of the electromechanical coupling coefficient K at the change of the acoustic wavelength λ of the acoustic resonator in SH0 mode from h/λ of 0.5 to 0.04 for the acoustic resonators described in example 1 and comparative example 1²Fig. 14c is a graph showing vibration energy of the acoustic wave resonator described in example 1 in the SH0 mode, and fig. 14d is a graph showing vibration energy of the acoustic wave resonator described in comparative example 1 in the SH0 mode.

FIG. 15a is a graph showing an admittance curve of the acoustic resonator of example 2 in a zeroth order symmetric lamb wave S0 mode, FIG. 15b is a graph showing an admittance curve of the acoustic resonator of comparative example 2 in an S0 mode, FIG. 15c is a graph showing a vibration energy of the acoustic resonator of example 2 in an S0 mode, FIG. 15d is a graph showing a vibration energy of the acoustic resonator of comparative example 2 in an S0 mode, and FIG. 15e is a graph showing a time electric coupling coefficient K of the acoustic resonator of example 2 in an S0 mode, where λ is changed from 0.5 to 0.04 with h/λ²The change curve of (2).

FIG. 16a shows the electromechanical coupling coefficient K of the acoustic wave resonators in the zeroth order shear-horizontal-wave SH0 mode according to example 3 and comparative example 3²FIG. 16b shows the variation of the in-plane propagation angle (0 to 180) as a function of the electromechanical coupling coefficient K at the change of the acoustic wavelength λ of the acoustic resonator in SH0 mode from h/λ of 0.5 to 0.04 for the acoustic resonators described in example 3 and comparative example 3²Fig. 16c is a graph showing vibration energy of the acoustic wave resonator described in example 3 in the SH0 mode, and fig. 16d is a graph showing vibration energy of the acoustic wave resonator described in comparative example 3 in the SH0 mode.

FIG. 17a shows the mechanical-electrical coupling coefficient K of the acoustic wave wavelength λ of the acoustic resonator in example 4 in the first-order anti-symmetric lamb wave A1 mode as h/λ changes from 0.5 to 0.04²Fig. 17b shows an admittance curve of the acoustic resonator described in example 4 in the a1 mode, fig. 17c shows an admittance curve of the acoustic resonator described in comparative example 4 in the a1 mode, fig. 17d shows a vibration energy diagram of the acoustic resonator described in example 4 in the a1 mode, and fig. 17e shows a vibration energy diagram of the acoustic resonator described in comparative example 4 in the a1 mode.

FIG. 18a shows the mechanical-electrical coupling coefficient K of the acoustic wave wavelength λ of the acoustic resonator of example 5 in the first-order anti-symmetric lamb wave A1 mode as h/λ changes from 0.5 to 0.04²Fig. 18b shows the admittance curve of the acoustic resonator of example 5 in the a1 mode, fig. 18c shows the admittance curve of the acoustic resonator of comparative example 5 in the a1 mode, fig. 18d shows the vibration energy diagram of the acoustic resonator of example 5 in the a1 mode, fig. 18e shows the vibration energy diagram of comparative example 5 in the a1 modeFig. 18f is a graph showing vibration energy of the acoustic wave resonator in the a1 mode, and fig. 5 f is a graph showing vibration energy of the acoustic wave resonator in the quasi-bulk wave A3 mode.

Description of the element reference numerals

101. 201 piezoelectric material layer

102. 202 high defect density damage layer

103. 203, 303 patterned electrodes

104. 204 reflective gate electrode

105. 205 etching of windows

106. 206 air gap

107. 207, 301 piezoelectric substrate

108. 208, 302 piezoelectric film

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Please refer to fig. 1 to 18 e. It should be noted that the drawings provided in the present embodiment are only schematic and illustrate the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

As shown in fig. 1, this embodiment provides a method for manufacturing an acoustic wave resonator, where the method includes:

a) providing a layer 101/201 of piezoelectric material;

b) performing ion implantation and post annealing treatment on at least a portion of the upper surface of the piezoelectric material layer 101/201 to form a high defect density damage layer 102/202 with a predetermined thickness at a predetermined depth in the piezoelectric material layer 101/201;

c) forming at least one etch window 105/205 in an upper surface of the piezoelectric material layer 101/201 to expose the high defect density damage layer 102/202;

d) removing at least a portion of the high defect density damage layer 102/202 based on the etch window 105/205 to form an air gap 106/206 in the piezoelectric material layer 101/201; wherein the air gap 106/206 separates the piezoelectric material layer 101/201 into a piezoelectric substrate 107/207 and a piezoelectric film 108/208, the piezoelectric film 108/208 being located above the air gap 106/206, the piezoelectric film 108/208 having contact with the piezoelectric substrate 107/207 at the edge of the air gap 106/206;

e) a patterned electrode 103/203 is formed on the upper surface of the piezoelectric film 108/208.

Optionally, the steps in the preparation method are performed in an order of a), b), c), d), e), a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d); wherein, when the steps of the manufacturing method are performed in an order of a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d), e) is performed, e) forms a patterned electrode 103/203 on the upper surface of the piezoelectric material layer 101/201.

The following describes the method for manufacturing the acoustic wave resonator according to this embodiment in detail, taking the execution sequence of the steps a), b), e), c), and d) as an example.

Step 1) provides a layer of piezoelectric material 101/201 (shown in fig. 2a/3 a).

By way of example, the piezoelectric material layer 101/201 is a single crystal piezoelectric material, and the material thereof includes: any one of quartz, aluminum nitride, zinc oxide, lithium tantalate, lithium niobate, lithium tetraborate, bismuth germanate, bismuth silicate, lanthanum gallium silicate and zirconium titanium lead acid; of course, other piezoelectric materials that can be used in the fabrication of acoustic wave resonators are equally suitable for this example.

Step 2) performing ion implantation and post annealing treatment on at least a portion of the upper surface of the piezoelectric material layer 101/201 to form a high defect density damage layer 102/202 with a predetermined thickness at a predetermined depth in the piezoelectric material layer 101/201 (as shown in fig. 2b/3 b).

In one example, step 2) is to perform ion implantation and post annealing treatment on the entire upper surface of the piezoelectric material layer 101, so as to form a high defect density damage layer 102 with a predetermined thickness H at a predetermined depth D in the piezoelectric material layer 101 (as shown in fig. 2 b).

In another example, step 2) is to perform ion implantation and post annealing treatment on a portion of the upper surface of the piezoelectric material layer 201, so as to form a high defect density damage layer 202 with a predetermined thickness H at a predetermined depth D in the piezoelectric material layer 201 (as shown in fig. 3 b). Specifically, the method for forming the high defect density damaged layer 202 includes: forming a patterned implantation mask on the upper surface of the piezoelectric material layer 201, wherein an opening pattern defining the shape and position of the high defect density damage layer 202 is formed in the patterned implantation mask; performing ion implantation and post-annealing treatment on the piezoelectric material layer 201 based on the patterned implantation mask to form a high defect density damage layer 202 with a preset thickness H at a preset depth D in the piezoelectric material layer 201; and finally removing the patterned implantation mask. In this example, patterned ion implantation is used to form the high defect density damage layer 202, which has the following advantages: an etching cut-off boundary is easy to set, the edge of an active area of the device is guaranteed to be in a solid contact type, namely, an air gap is formed just below the suspended piezoelectric film, the advantage of limiting sound wave energy due to impedance mismatching of the piezoelectric film and air is fully utilized, meanwhile, the contact area of the device and the piezoelectric substrate is maximized, and heat dissipation and structural stability of the device are effectively improved.

As an example, when the ion implantation is performed on the piezoelectric material layer 101/201, the ion implantation may be performed a plurality of times so as to control the thickness of the ion implanted layer, that is, the thickness H of the high defect density damage layer 102/202; the dose of the multiple ion implantations is the same, the energy is different, and the energy values of the multiple ion implantations are decreased progressively in sequence, so that the influence of the ion implantation with a large energy value on the ion implantation with a small energy value is avoided, and the longitudinal uniformity of the ion implantation is improved. If the piezoelectric material layer 101/201 is subjected to two ion implantations, the two ion implantations have the same dosage and different energy; the energy of the ion implantation depends on the forming depth position of the high defect density damage layer 102/202, large energy is selected to be implanted firstly to form a first ion implantation layer with a certain thickness at a deeper position, then small energy is implanted to form a second ion implantation layer with a certain thickness at a shallower position, and the upper surface of the first ion implantation layer and the lower surface of the second ion implantation layer can be superposed by reasonably designing the energy of the two times of ion implantation, so that the ion implantation layer with a larger thickness value is obtained; in a specific application, the implanted ions may be distributed in the piezoelectric material layer 101/201 in a gaussian manner, and the simulation software SRIM is used to perform simulation to obtain the energy of each ion implantation, which is well known to those skilled in the art and therefore will not be described in detail. It should be noted that by controlling the energy of the ion implantation, the thickness of the high defect density damage layer 102/202 can be equal to the difference between the thickness of the piezoelectric material layer 101/201 and the predetermined depth D; however, for device processing and storage purposes, the thickness of the high defect density damage layer 102/202 is generally made smaller than the difference between the thickness of the piezoelectric material layer 101/201 and the predetermined depth D. Specifically, the ion implantation can be realized by hydrogen ion, helium ion or hydrogen-helium co-implantation.

As an example, since the preset depth D is the thickness of the piezoelectric film 108/208 to be formed subsequently, when the piezoelectric material layer 102/202 is subjected to ion implantation, the ratio of the preset depth D to the wavelength of the target elastic wave excited by the piezoelectric film 108/208 may be designed to be less than 0.5, so that the ratio of the thickness of the piezoelectric film 108/208 to the wavelength of the target elastic wave excited by the piezoelectric film is less than 0.5, and a larger electromechanical coupling coefficient is obtained; further, the ratio may be less than 0.25 to obtain a greater electromechanical coupling coefficient.

As an example, the post-annealing process temperature is not higher than 550 ℃ and the process time is not longer than 4h, so as to recover the defects introduced into the piezoelectric material layer 101/201 by ion implantation and to agglomerate the defects, but not to bubble and crack the formed high defect density damage layer 102/202. It should be noted that, for piezoelectric material layers of different materials, the corresponding post-annealing process temperature and process time are different, and for different cut types of the same piezoelectric material layer, the corresponding post-annealing process temperature and process time are also different; therefore, in practical application, the post-annealing temperature and time can be selected according to the specific selected piezoelectric material.

Step 3) forming a patterned electrode 103/203 (as shown in fig. 2c/3 c) on the upper surface of the piezoelectric material layer 101/201.

As an example, the patterned electrode 103/203 is formed on the upper surface of the piezoelectric material layer 101/201 by using a sputtering process or an electron beam evaporation process; the material of the patterned electrode 103/203 includes at least one of aluminum, gold, chromium, tungsten, titanium, copper, and silver, and of course, the material of the patterned electrode 103/203 may also be an alloy of two or more of the above metals. Specifically, the patterned electrode 103/203 may have a single-layer structure or a multi-layer structure.

By way of example, the patterned electrode 103/203 includes: one or more of interdigital electrodes, fan-shaped strip electrodes, circular ring-shaped strip electrodes or hexagonal plate electrodes. Specifically, when the patterned electrode 103/203 is an interdigital electrode, the interdigital electrodes are arranged in parallel with each other, and the arrangement direction of the interdigital electrodes is parallel to the bus bar direction, and meanwhile, the interdigital electrodes may have an inclination angle of less than ± 5 ° in a direction perpendicular to the bus bar. Specifically, when the patterned electrodes 103/203 are interdigitated electrodes and pairs of interdigitated electrodes are provided, the pairs of interdigitated electrodes form an interdigital transducer for generating an electric field. Optionally, the preparation method further comprises: a step of forming at least one pair of reflection gate electrodes 104/204 uniformly distributed on the upper surface of the piezoelectric material layer 101/201 on both sides of the interdigital transducer to confine acoustic wave energy by reflection thereof; the reflective gate electrode 104/204 can be formed on the upper surface of the suspended piezoelectric material layer (i.e., the piezoelectric film) or on the upper surface of the non-suspended piezoelectric material layer (i.e., the piezoelectric substrate), which has no influence on the function thereof.

As an example, the thickness of the patterned electrode 103/203 is less than the predetermined depth D, such that the thickness of the patterned electrode 103/203 is less than the thickness of the subsequently formed piezoelectric film 108/208.

Step 4) forming at least one etching window 105/205 exposing the high defect density damage layer 102/202 on the upper surface of the piezoelectric material layer 101/201 (as shown in fig. 2d/3 d).

In an example, when the step 2) is ion implantation on the entire upper surface of the piezoelectric material layer 101, the method for forming the etching window 105 includes: defining the position of the air gap 106 (as the area marked by the dotted line in fig. 2 d) in the piezoelectric material layer 101, and forming a patterned window mask on the upper surface of the piezoelectric material layer 101; wherein, an opening pattern defining the shape and position of the etching window is formed in the patterned window mask, and the opening pattern is located in the defined region where the air gap 106 is located; etching the piezoelectric material layer 101 based on the patterned window mask to form at least one etching window 105 exposing the high defect density damage layer 102; finally the patterned window mask is removed (as shown in fig. 2 d).

In another example, when step 2) is ion implantation on a portion of the upper surface of the piezoelectric material layer 201, the method for forming the etching window 205 includes: forming a patterned window mask on the upper surface of the piezoelectric material layer 201, wherein an opening pattern defining the shape and position of the etching window 205 is formed in the patterned window mask; etching the piezoelectric material layer 201 based on the patterned window mask to form at least one etching window 205 exposing the high defect density damage layer 202; finally the patterned window mask is removed (as shown in fig. 3 d). Specifically, the etching window 205 may be formed above the high defect density damaged layer 202, or may be formed outside the high defect density damaged layer 202.

By way of example, the piezoelectric material layer 101/201 may be etched using a dry etching process or a wet etching process to form the etch window 105/205.

As an example, before forming the etch window 105/205, the method of making further includes: a step of forming a first protection layer (not shown) on the surface of the piezoelectric material layer 101/201 and the surface of the patterned electrode 103/203, so as to protect the piezoelectric material layer 101/201 and the patterned electrode 103/203 when the etching window 105/205 is formed later; accordingly, after forming the etch window 105/205, the method further comprises: a step of removing the first protective layer; the first protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold. Optionally, when the manufacturing method further includes the step of forming the reflective gate electrode 104/204, the first protection layer is further formed on the surface of the reflective gate electrode 104/204, so as to protect the reflective gate electrode 104/204 during the subsequent formation of the etching window 105/205. Specifically, the first protective layer may be formed by a chemical vapor deposition process, a physical vapor deposition process, a molecular beam epitaxy process, an atomic layer deposition process, a pulsed laser deposition process, a sputtering process, or an electron beam evaporation process.

Step 5) removing at least a portion of the high defect density damage layer 102/202 based on the etch window 105/205 to form an air gap 106/206 in the piezoelectric material layer 101/201; wherein the air gap 106/206 divides the piezoelectric material layer 101/201 into a piezoelectric substrate 107/207 and a piezoelectric film 108/208, the piezoelectric film 108/208 is located above the air gap 106/206, and the piezoelectric film 108/208 has contact with the piezoelectric substrate 107/207 at the edge of the air gap 106/206 (as shown in fig. 2e/3 e).

In an example, when the step 2) is ion implantation on the entire upper surface of the piezoelectric material layer 101, the step 5) is to remove a portion of the high defect density damage layer 102 based on the etching window 105 to form an air gap 106 in the piezoelectric material layer 101 (as shown in fig. 2e in particular). Specifically, a dry etching process or a wet etching process may be used to etch a portion of the high defect density damage layer 102 to form the air gap 106. In practical applications, the etching size of the high defect density damaged layer 102 by the etching gas or the etching liquid can be controlled by controlling the lateral etching time, so as to prevent the high defect density damaged layer 102 from being completely etched away while forming the air gap 106.

In another example, when the step 2) is ion implantation on a portion of the upper surface of the piezoelectric material layer 201, the step 5) is to remove all of the high defect density damage layer 202 based on the etching window 205 so as to form the air gap 206 in the piezoelectric material layer 201 (as shown in fig. 3e in detail). Specifically, a dry etching process or a wet etching process may be used to etch a portion of the high defect density damage layer 102 to form the air gap 106.

As an example, the contact between the piezoelectric film 108/208 and the piezoelectric substrate 107/207 at the edge of the air gap 106/206 is defined based on the shape and position of the erosion window 105/205, so that the piezoelectric film 108/208 and the piezoelectric substrate 107/207 have at least one contact point at the edge of the air gap 106/206 (as shown in fig. 4-5, an undercut is made below the contact point), and the piezoelectric film 108/208 is completely suspended above the piezoelectric substrate 107/207 except for the contact point connection; the advantages of this structure are: four end faces of the piezoelectric film 108/208 in two directions are directly contacted with air to form extreme impedance mismatching, so that acoustic wave energy can be better limited, the electromechanical coupling coefficient is improved, and the occurrence of a mixed mode is reduced. Of course, it is also possible to provide the piezoelectric film 108/208 and the piezoelectric substrate 107/207 with at least one contact surface at the edge of the air gap 106/206 (as shown in fig. 6-7, no undercut below the contact surface), which is advantageous: at least one of four end faces of the piezoelectric film 108/208 in two directions is connected with the piezoelectric substrate 107/207, so that the device is in solid-state contact with the piezoelectric substrate 107/207, and the heat dissipation and structural stability of the device are enhanced; of course, it is also possible to provide the piezoelectric film 108/208 and the piezoelectric substrate 107/207 with at least one contact point and at least one contact surface at the edge of the air gap 106/206 (as shown in fig. 8-11, where the contact point is hollowed out below, the contact surface is not hollowed out below, and neither the contact point nor the contact surface is hollowed out in fig. 8-9), which is advantageous: at least one of the four end faces of the piezoelectric film 108/208 in two directions is connected to the piezoelectric substrate 107/207, so as to ensure that the device is in solid-state contact with the piezoelectric substrate 107/207, thereby enhancing the heat dissipation and structural stability of the device.

As an example, before forming the air gap 106/206, the method of making further includes: a step of forming a second passivation layer (not shown) on the surface of the piezoelectric material layer 101/201 and the surface of the patterned electrode 103/203, so as to protect the piezoelectric material layer 101/201 and the patterned electrode 103/203 when the air gap 106/206 is formed subsequently; accordingly, after forming the air gap 106/206, the method further includes: a step of removing the second protective layer; the second protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold. Optionally, when the manufacturing method further includes the step of forming the reflective gate electrode 104/204, the second protective layer is further formed on the surface of the reflective gate electrode 104/204, so as to protect the reflective gate electrode 104/204 during the subsequent formation of the air gap 106/206. Specifically, the second protective layer may be formed by a chemical vapor deposition process, a physical vapor deposition process, a molecular beam epitaxy process, an atomic layer deposition process, a pulsed laser deposition process, a sputtering process, or an electron beam evaporation process.

As an example, the preparation method further comprises: a step of forming a heat dissipation accelerating layer (not shown) on at least the upper surface of the piezoelectric film 108/208 and the surface of the patterned electrode 103/203 to accelerate heat dissipation of the device; of course, the accelerated heat dissipation layer may also be formed on the upper surface of the entire device structure. Specifically, the material of the accelerated heat dissipation layer is a high thermal conductivity material such as silicon, silicon carbide, aluminum nitride, and the like. Optionally, when the manufacturing method further includes the step of forming a reflective gate electrode 104/204, the heat dissipation acceleration layer is further formed on the surface of the reflective gate electrode 104/204.

Correspondingly, as shown in fig. 2e, 3e, and 4-11, the present embodiment further provides an acoustic wave resonator, including:

a layer 101/201 of piezoelectric material;

an air gap 106/206 having a predetermined thickness, formed at a predetermined depth of the piezoelectric material layer 101/201 based on an erosion window 105/205; the air gap 106/206 divides the piezoelectric material layer 101/201 into a piezoelectric substrate 107/207 and a piezoelectric film 108/208, the piezoelectric film 108/208 being located over the air gap 106/206, the piezoelectric film 108/208 having contact with the piezoelectric substrate 107/207 at the edge of the air gap 106/206;

and a patterned electrode 103/203 formed on an upper surface of the piezoelectric film 108/208.

As an example, the etch window 105/205 can be formed over the air gap 106/206 and can also be formed outside the air gap 106/206. Specifically, the contact between the piezoelectric film 108/208 and the piezoelectric substrate 107/207 at the edge of the air gap 106/206 is defined based on the shape and the position of the erosion window 105/205, so that the piezoelectric film 108/208 and the piezoelectric substrate 107/207 have at least one contact point at the edge of the air gap 106/206 (as shown in fig. 4-5, an undercut treatment is performed below the contact point), and the piezoelectric film 108/208 is completely suspended on the piezoelectric substrate 107/207 except for the contact point connection; the advantages of this structure are: four end faces of the piezoelectric film 108/208 in two directions are directly contacted with air to form extreme impedance mismatching, so that acoustic wave energy can be better limited, the electromechanical coupling coefficient is improved, and the occurrence of a mixed mode is reduced. Of course, it is also possible to provide the piezoelectric film 108/208 and the piezoelectric substrate 107/207 with at least one contact surface at the edge of the air gap 106/206 (as shown in fig. 6-7, no undercut below the contact surface), which is advantageous: at least one of four end faces of the piezoelectric film 108/208 in two directions is connected with the piezoelectric substrate 107/207, so that the device is in solid-state contact with the piezoelectric substrate 107/207, and the heat dissipation and structural stability of the device are enhanced; of course, it is also possible to provide the piezoelectric film 108/208 and the piezoelectric substrate 107/207 with at least one contact point and at least one contact surface at the edge of the air gap 106/206 (as shown in fig. 8-11, where the contact point is hollowed out below, the contact surface is not hollowed out below, and neither the contact point nor the contact surface is hollowed out in fig. 8-9), which is advantageous: at least one of the four end faces of the piezoelectric film 108/208 in two directions is connected to the piezoelectric substrate 107/207, so as to ensure that the device is in solid-state contact with the piezoelectric substrate 107/207, thereby enhancing the heat dissipation and structural stability of the device.

As an example, the ratio of the thickness of the piezoelectric film 108/208 to the wavelength of the target elastic wave excited thereby is less than 0.5, so as to obtain a larger electromechanical coupling coefficient; further, the ratio may be less than 0.25 to obtain a greater electromechanical coupling coefficient.

By way of example, the patterned electrode 103/203 includes: one or more of interdigital electrodes, fan-shaped strip electrodes, annular strip electrodes or hexagonal plate electrodes; the material of the patterned electrode 103/203 includes at least one of aluminum, gold, chromium, tungsten, titanium, copper, and silver, and of course, the material of the patterned electrode 103/203 may also be an alloy of two or more of the above metals. Specifically, the patterned electrode 103/203 may have a single-layer structure or a multi-layer structure. Specifically, when the patterned electrode 103/203 is an interdigital electrode, the interdigital electrodes are arranged in parallel with each other, and the arrangement direction of the interdigital electrodes is parallel to the bus bar direction, and meanwhile, the interdigital electrodes may have an inclination angle of less than ± 5 ° in a direction perpendicular to the bus bar. Specifically, when the patterned electrodes 103/203 are interdigitated electrodes and pairs of interdigitated electrodes are provided, the pairs of interdigitated electrodes form an interdigital transducer for generating an electric field. Optionally, the acoustic wave resonator further includes: at least one pair of reflection gate electrodes 104/204 formed on both sides of the interdigital transducer for restricting acoustic wave energy by reflection thereof; the reflective gate electrode 104/204 can be formed on the upper surface of the piezoelectric thin film 108/208 or on the upper surface of the piezoelectric substrate 107/207, which has no effect on the operation.

As an example, the patterned electrode 103/203 has a thickness that is less than the thickness of the piezoelectric film 108/208.

As an example, the acoustic wave resonator further includes: an accelerated heat dissipation layer (not shown) formed on at least the upper surface of the piezoelectric film 108/208 and the surface of the patterned electrode 103/203 for accelerating heat dissipation of the device; of course, the accelerated heat dissipation layer may also be formed on the upper surface of the entire device structure. Specifically, the material of the accelerated heat dissipation layer is a high thermal conductivity material such as silicon, silicon carbide, aluminum nitride, and the like. Optionally, when the acoustic wave resonator further includes a reflection gate electrode 104/204, the accelerated heat dissipation layer is further formed on the surface of the reflection gate electrode 104/204.

By way of example, the target elastic wave excited by the piezoelectric film 108/208 includes: one or more (i.e., two or more) of rayleigh waves, shear horizontal waves, symmetric lamb waves, anti-symmetric lamb waves, bulk waves, or quasicidal waves. In practical applications, when the patterned electrode is an interdigital electrode, the piezoelectric film may be configured to excite one or more different types of acoustic wave modes by adjusting an interdigital arrangement direction of the interdigital electrode, for example, by adjusting the interdigital arrangement direction of the interdigital electrode, the piezoelectric film may be configured to excite one of a rayleigh wave, a horizontal shear wave, a symmetric lamb wave, an anti-symmetric lamb wave, a bulk wave and a quasi-bulk wave, or may be configured to excite two or more of a rayleigh wave, a horizontal shear wave, a symmetric lamb wave, an anti-symmetric lamb wave, a bulk wave and a quasi-bulk wave, or may even be configured to excite all acoustic wave modes simultaneously. When the target elastic wave excited by the piezoelectric film 108/208 is an acoustic wave mode with a low wave velocity (such as rayleigh wave and horizontal shear wave), the acoustic wave resonator of the present embodiment can improve the device performance by using the suspended piezoelectric film, for example, the device has a higher electromechanical coupling coefficient and a higher quality factor; when the target elastic wave excited by the piezoelectric film 108/208 is an acoustic wave mode with a high wave velocity (e.g., a symmetric lamb wave or an anti-symmetric lamb wave), the acoustic wave resonator of this embodiment can limit the energy of the high-order acoustic wave mode in the suspended piezoelectric film by using the suspended piezoelectric film, improve the frequency and bandwidth of the device by exciting the high-order acoustic wave mode, and enable the device to have a large electromechanical coupling coefficient.

Example one

The performance of the suspended film-type acoustic wave resonator of the present invention in the zero-order horizontal shear wave SH0 mode will be described by taking an X-cut LN (lithium niobate) piezoelectric single crystal material to fabricate a suspended film-type acoustic wave resonator (corresponding structure is shown in fig. 12) of the present invention as example 1, taking silicon as a substrate, and an X-cut LN piezoelectric single crystal material as a piezoelectric film to fabricate a solid fabricated acoustic wave resonator (corresponding structure is shown in fig. 13) as comparative example 1; the example 1 and the comparative example 1 are different only in device structure, and the others are the same, for example, the thickness of the piezoelectric film is 500nm, and the wavelength λ of the excited sound wave is 2 μm.

FIG. 14a shows the electromechanical coupling coefficient K of the acoustic wave resonators in SH0 mode according to example 1 and comparative example 1²The curve of the variation with the in-plane propagation angle (0 ° -180 °) can be seen from the figure: k of two structures²The trend with the in-plane propagation angle is uniform, and K of example 1²Significantly greater than K in comparative example 1²。

FIG. 14b is a graph showing the electromechanical coupling coefficient K when the acoustic wave length λ of the acoustic wave resonator described in example 1 and comparative example 1 in the SH0 mode is changed from 0.5 to 0.04 with h/λ²Can be seen from the figure: k of two structures²The trend of variation with h/lambda is greater, comparative example 1K²Exhibits a maximum value as a function of h/lambda, i.e. K is 0.25_max ²19.8 percent; k of example 1²The gradient of the gradient<0.4, K of example 1²K, initially significantly greater than in comparative example 1²When h/λ is 0.04, K of example 1²Up to 40%; as can be seen, the method of example 1The suspended film type acoustic wave resonator can play a role in improving the electromechanical coupling coefficient in an SH0 mode, and the dispersion characteristic can be used for adjusting and selecting the proper piezoelectric film thickness and the interdigital electrode period.

Fig. 14c is a graph of vibration energy (with an in-plane propagation angle of 10 °) of the acoustic resonator described in example 1 in the SH0 mode, as can be seen from the graph: SH0 elastic waves in the piezoelectric film are effectively confined inside the piezoelectric film.

Fig. 14d is a graph of the vibration energy of the acoustic resonator described in comparative example 1 in the SH0 mode (with an in-plane propagation angle of 10 °), as can be seen: the SH0 elastic waves in the piezoelectric film still leak slightly energy to the underlying substrate.

Compared with a solid assembled acoustic wave resonator taking Si as a substrate, the suspended film type acoustic wave resonator has a larger electromechanical coupling coefficient in an SH0 mode.

Example two

A description will be given of the performance of the suspended thin-film acoustic resonator of the present invention in the zeroth order symmetric lamb wave S0 mode, by taking an X-cut LN (lithium niobate) piezoelectric single crystal material as an example 2 to make the suspended thin-film acoustic resonator of the present invention (the corresponding structure is shown in fig. 12), and taking silicon as a substrate and an X-cut LN piezoelectric single crystal material as a piezoelectric film to make a solid assembly acoustic resonator (the corresponding structure is shown in fig. 13) as a comparative example 2; the example 2 and the comparative example 2 are different only in device structure, and the others are the same, for example, the thickness of the piezoelectric film is 500nm, and the wavelength λ of the excited sound wave is 2 μm.

Fig. 15a is the admittance curve of the acoustic wave resonator of example 2 in the S0 mode, and it can be seen from the figure that: the S0 elastic wave in the piezoelectric film can be effectively resonated.

Fig. 15b is the admittance curve of the acoustic resonator described in comparative example 2 in the S0 mode, from which it can be seen that: the S0 elastic wave in the piezoelectric film cannot form an effective resonance peak, i.e., cannot form resonance.

Fig. 15c is a graph of vibration energy (with an in-plane propagation angle of 30 °) of the acoustic wave resonator of example 2 in the S0 mode, as can be seen from the graph: the S0 elastic wave in the piezoelectric film is effectively confined inside the piezoelectric film.

Fig. 15d is a graph of the vibration energy of the acoustic wave resonator described in comparative example 2 in the S0 mode (with an in-plane propagation angle of 30 °), from which it can be seen that: the leakage of the energy of the S0 elastic waves in the piezoelectric film to the Si substrate is severe, i.e., the Si substrate cannot limit the S0 mode in which the acoustic waves are high.

FIG. 15e is a graph showing the electromechanical coupling coefficient K when the acoustic wave length λ of the acoustic wave resonator of example 2 in the S0 mode is changed from 0.5 to 0.04 with h/λ²The variation curve of (d); as can be seen from the figure: when h/lambda is 0.04, K²Up to 31%, and it can be seen from the trend that, in the case of determining the thickness of the piezoelectric film, h/λ can be adjusted by varying the value of λ, when h/λ decreases, K²Continuing to increase; obviously, this represents the advantage of the suspended film acoustic resonator described in example 2 in terms of high acoustic energy limitation, and it can more effectively confine acoustic energy, prevent acoustic energy from leaking to the lower layer, and thus improve the electromechanical coupling coefficient of the S0 mode, improve the electromechanical conversion efficiency, and thus can improve the bandwidth and quality factor of the acoustic resonator.

Compared with a solid assembled acoustic wave resonator with Si as a substrate, the suspended film type acoustic wave resonator can excite the S0 mode with higher sound velocity, keeps energy from leaking and has a larger electromechanical coupling coefficient.

EXAMPLE III

A suspended film type acoustic wave resonator (the corresponding structure is shown in fig. 12) according to the present invention is manufactured by using Y42 ° LT (lithium tantalate) piezoelectric single crystal material as example 3, and a solid assembled acoustic wave resonator (the corresponding structure is shown in fig. 13) is manufactured by using silicon as a substrate and Y42 ° LT piezoelectric single crystal material as a piezoelectric film as comparative example 3, so as to explain the performance of the suspended film type acoustic wave resonator according to the present invention in the zero-order horizontal shear wave SH0 mode; the example 3 and the comparative example 3 are different only in device structure, and all other parts are the same, for example, the thickness of the piezoelectric film is 500nm, and the wavelength λ of the excited sound wave is 2 μm.

FIG. 16a is an acoustic wave resonator as described in example 3 and comparative example 3Electromechanical coupling coefficient K in SH0 mode²The curve of the variation with the in-plane propagation angle (0 ° -180 °) can be seen from the figure: k of two structures²Trend is consistent with the variation of in-plane propagation angle, and K of example 3²K is significantly greater than in comparative example 3²。

FIG. 16b is a graph showing the electromechanical coupling coefficient K when the acoustic wave wavelength λ of the acoustic wave resonator described in example 3 and comparative example 3 in the SH0 mode is changed from 0.5 to 0.04 with h/λ²Can be seen from the figure: k of two structures²The variation trend along with h/lambda is large, and the acoustic wave resonator in the comparative example 3 does not have obvious dispersion in an SH0 mode, namely K²Does not change with the change of h/lambda and is kept at about 8.6 percent; while the acoustic wave resonator described in example 3 is in SH0 mode K²The gradient of the gradient<At 0.15, K²>15%, which shows that the acoustic wave resonator described in example 3 can function to improve the electromechanical coupling coefficient, and can select an appropriate piezoelectric film thickness and interdigital electrode period by using such dispersion characteristic adjustment.

Fig. 16c is a graph of vibration energy (with an in-plane propagation angle of 0 °) of the acoustic resonator of example 3 in the SH0 mode, as can be seen from the graph: SH0 elastic waves in the piezoelectric film are effectively confined inside the piezoelectric film.

Fig. 16d is a graph of the vibration energy of the acoustic resonator described in comparative example 3 in the SH0 mode (with an in-plane propagation angle of 0 °), from which it can be seen that: the SH0 elastic wave in the piezoelectric film still has a slight amount of energy leaking to the substrate.

Example four

A suspended film type acoustic wave resonator (corresponding to the structure shown in fig. 12) according to the present invention is manufactured by using a Y128 ° LN piezoelectric single crystal material as an example 4, and a solid assembly type acoustic wave resonator (corresponding to the structure shown in fig. 13) is manufactured by using a silicon as a substrate and a Y128 ° LN piezoelectric single crystal material as a piezoelectric film as a comparative example 4, so as to describe the performance of the suspended film type acoustic wave resonator according to the present invention in a first-order antisymmetric lamb wave a1 mode; in example 4, the device structure is different from that of comparative example 4, and the thicknesses of the piezoelectric films are all 500nm, and the wavelength λ of the excited sound wave is 2 μm.

FIG. 17a is a graph showing the electromechanical coupling coefficient K when the acoustic wave wavelength λ of the acoustic wave resonator of example 4 in the A1 mode is changed from 0.5 to 0.04 with h/λ²Can be seen from the figure: the A1 mode exhibits significant dispersion, K²Continuously increases with decreasing h/lambda when h/lambda<At 0.2, K²>20%, and the working frequency covers 3.5-5.3 GHz; when h/lambda<0.0625, K²The frequency can reach more than 50%, and the working frequency is also in the high-frequency range of 3.5-4.5 GHz; and, at h/λ ═ 0.12, K²There is a trend towards an increasing trend, which is very suitable for 5G communication with high frequency, large bandwidth filter requirements.

Fig. 17b is the admittance curve of the acoustic resonator of example 4 in the a1 mode, as can be seen from the figure: the a1 elastic wave in the piezoelectric film can be effectively resonated.

Fig. 17c is the admittance curve of the acoustic resonator described in comparative example 4 in the a1 mode, as can be seen from the figure: the a1 elastic wave in the piezoelectric film cannot form an effective resonance peak, i.e., cannot form resonance.

Fig. 17d is a graph of vibration energy (with an in-plane propagation angle of 0 °) of the acoustic wave resonator of example 4 in the a1 mode, as can be seen from the graph: the a1 elastic wave in the piezoelectric film can be effectively confined inside the piezoelectric film.

Fig. 17e is a graph of the vibration energy of the acoustic wave resonator described in comparative example 4 in the a1 mode (the in-plane propagation angle thereof is 0 °), from which it can be seen that: the leakage of the energy of the a1 elastic waves in the piezoelectric film to the substrate is severe, i.e., the Si substrate cannot limit the a1 mode in which the acoustic waves are high.

Compared with a solid assembled acoustic wave resonator with Si as a substrate, the suspended film type acoustic wave resonator can excite the A1 mode with higher sound velocity, keeps energy from leaking and has a larger electromechanical coupling coefficient.

EXAMPLE five

A description will be given of the performance of the suspended film-type acoustic resonator of the present invention in the first-order antisymmetric lamb wave a1 mode, by taking a Z-cut LN (lithium niobate) piezoelectric single crystal material as an example 5 to produce the suspended film-type acoustic resonator of the present invention (the corresponding structure is shown in fig. 12), and taking silicon as a substrate and a Z-cut LN piezoelectric single crystal material as a piezoelectric film to produce a solid-state fabricated acoustic resonator (the corresponding structure is shown in fig. 13) as a comparative example 5; of these, example 5 is different from comparative example 5 only in device structure, and all other things are the same, for example, the thickness of the piezoelectric film is 500nm, and the wavelength λ of the excited acoustic wave is 2 μm.

FIG. 18a is a graph showing the electromechanical coupling coefficient K when the acoustic wave wavelength λ of the acoustic wave resonator of example 5 in the A1 mode is changed from 0.5 to 0.04 with h/λ²Can be seen from the figure: the A1 mode exhibits significant dispersion, K²Continuously increases with decreasing h/lambda when h/lambda<At 0.15, K²>20%, and the working frequency covers 3.6-4.7 GHz; when h/lambda is 0.04, K²The filter can reach 40%, the working frequency is also in a high-frequency range of 3.5-4.3 GHz, and the filter is also very suitable for the requirements of 5G communication on high-frequency and large-bandwidth filters.

Fig. 18b is the admittance curve of the acoustic resonator of example 5 in the a1 mode, as can be seen from the figure: the a1 elastic wave in the piezoelectric film can be effectively resonated.

Fig. 18c is the admittance curve of the acoustic resonator described in comparative example 5 in the a1 mode, as can be seen from the figure: the a1 elastic wave in the piezoelectric film cannot form an effective resonance peak, i.e., cannot form resonance.

Fig. 18d is a graph of the vibration energy of the acoustic wave resonator of example 5 in the a1 mode (with an in-plane propagation angle of 30 °), as can be seen: the a1 elastic wave in the piezoelectric film can be effectively confined inside the piezoelectric film.

Fig. 18e is a graph of the vibration energy of the acoustic resonator described in comparative example 5 in the a1 mode (with an in-plane propagation angle of 30 °), from which it can be seen that: the leakage of the energy of the a1 elastic wave in the piezoelectric film to the bottom substrate is severe, i.e., the Si substrate cannot limit the a1 mode in which the acoustic wave is high.

Compared with a solid assembled acoustic wave resonator with Si as a substrate, the suspended film type acoustic wave resonator can excite the A1 mode with higher sound velocity, keeps energy from leaking and has a larger electromechanical coupling coefficient. Furthermore, as can be seen from fig. 18b, the suspended film-type acoustic resonator of the present example can excite and confine not only the higher-order first-order antisymmetric lamb wave mode but also the higher-order quasicidal wave A3 mode, which can be seen from the vibration energy diagram (whose in-plane propagation angle is 30 °) shown in fig. 18f, and the A3 elastic wave in the piezoelectric film can be effectively confined inside the piezoelectric film; wherein the resonant frequency of the first-order antisymmetric lamb wave mode is 5.9GHz, and the electromechanical coupling coefficient K²16.78%; the resonance frequency of the quasi-body wave mode is 13.8GHz, and the electromechanical coupling coefficient K²4.1 percent; this means that the extension of resonators and filters to higher frequency bands is possible and is no longer limited to the crowded 3GHz band.

In summary, the acoustic wave resonator and the preparation method thereof of the invention have the following beneficial effects: according to the preparation method, the high-defect-density damaged layer is formed inside the piezoelectric material layer by means of ion implantation and post annealing, and then the high-defect-density damaged layer is removed through the corrosion window to obtain the suspended piezoelectric film, complex process procedures such as bonding, transferring, stripping and polishing are not needed, and therefore the preparation complexity is reduced. The preparation method provided by the invention has the advantages of simple process, high material utilization rate and low manufacturing cost, is beneficial to improving the bandwidth and the coverage frequency band of the resonator and the filter, and is suitable for large-scale production and use. The invention effectively limits the energy of a high-order sound wave mode with higher sound velocity in the piezoelectric film by utilizing the acoustic impedance extreme mismatching of the suspended piezoelectric film and the air gap, thereby improving the frequency, the electromechanical coupling coefficient, the bandwidth and the quality factor of the device and meeting the requirement of 5G communication. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A method for manufacturing an acoustic wave resonator, the method comprising:

a) providing a piezoelectric material layer;

2. The method for manufacturing an acoustic wave resonator according to claim 1, wherein the steps in the manufacturing method are performed in an order of a), b), c), d), e), a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d); wherein, when the execution sequence of the steps in the preparation method is a), e), b), c), d), a), b), e), c), d), or a), b), c), e), d), e) is that a patterned electrode is formed on the upper surface of the piezoelectric material layer.

3. The method of manufacturing an acoustic resonator according to claim 2, wherein before the forming the erosion window, the method further comprises: forming a first protective layer on the surface of the piezoelectric material layer or the surface of the piezoelectric material layer and the surface of the patterned electrode; after forming the etch window, the method of making further comprises: a step of removing the first protective layer; the first protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold.

4. The method of manufacturing an acoustic resonator according to claim 2, wherein before forming the air gap, the method further comprises: forming a second protective layer on the surface of the piezoelectric material layer or the surface of the piezoelectric material layer and the surface of the patterned electrode; after forming the air gap, the manufacturing method further includes: a step of removing the second protective layer; the second protective layer is made of any one of silicon dioxide, silicon nitride, chromium and gold.

5. The method of manufacturing an acoustic resonator according to claim 2, further comprising: and forming a heat dissipation accelerating layer on at least the upper surface of the piezoelectric film and the surface of the patterned electrode.

6. The method according to claim 1, wherein b) ion implantation and post-annealing are performed on the entire upper surface of the piezoelectric material layer to form a high defect density damage layer having a predetermined thickness at a predetermined depth in the piezoelectric material layer; at this time, d) removes a portion of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer.

7. The method of manufacturing an acoustic resonator according to claim 6, wherein the method of forming the erosion window in c) includes:

and removing the patterned window mask.

8. The method according to claim 1, wherein b) ion implantation and post-annealing are performed on a portion of the upper surface of the piezoelectric material layer to form a high defect density damage layer having a predetermined thickness at a predetermined depth in the piezoelectric material layer; at this time, d) removing all of the high defect density damage layer based on the etch window to form an air gap in the piezoelectric material layer.

9. The method of manufacturing an acoustic resonator according to claim 8, wherein the method of forming the high defect density damage layer in b) includes:

removing the patterned implantation mask;

at this time, the method of forming the etch window in c) includes:

and removing the patterned window mask.

10. The method of manufacturing an acoustic wave resonator according to claim 1, wherein the ion implantation is performed a plurality of times; the doses of the multiple ion implantations are the same, the energies of the multiple ion implantations are different, and the energy values of the multiple ion implantations are sequentially decreased progressively.

11. The method of manufacturing an acoustic resonator according to claim 1, wherein the contact of the piezoelectric thin film with the piezoelectric substrate at the edge of the air gap is defined based on the shape and position of the erosion window; the piezoelectric film and the piezoelectric substrate are provided with at least one contact point at the edge of the air gap, and/or the piezoelectric film and the piezoelectric substrate are provided with at least one contact surface at the edge of the air gap.

12. The method of manufacturing an acoustic resonator according to claim 1, wherein the patterned electrode comprises: one or more of interdigital electrodes, fan-shaped strip electrodes, circular ring-shaped strip electrodes or hexagonal plate electrodes.

13. The method for manufacturing an acoustic wave resonator according to claim 12, wherein when the patterned electrode is an interdigital electrode and the number of pairs of interdigital electrodes is plural, the plural pairs of interdigital electrodes form an interdigital transducer.

14. The method of manufacturing an acoustic resonator according to claim 13, further comprising: and forming a reflection gate electrode on the upper surface of the piezoelectric film on both sides of the interdigital transducer or the upper surface of the piezoelectric substrate.

15. An acoustic wave resonator, comprising:

a layer of piezoelectric material;

16. The acoustic resonator according to claim 15, wherein the target elastic wave excited by the piezoelectric thin film comprises: one or more of rayleigh waves, shear horizontal waves, symmetric lamb waves, anti-symmetric lamb waves, bulk waves or quasicidal waves.

17. The acoustic resonator according to claim 15, wherein the piezoelectric film and the piezoelectric substrate have at least one contact point at an edge of the air gap, and/or wherein the piezoelectric film and the piezoelectric substrate have at least one contact surface at an edge of the air gap.

18. The method of manufacturing an acoustic resonator according to claim 15, wherein the patterned electrode comprises: one or more of interdigital electrodes, fan-shaped strip electrodes, circular ring-shaped strip electrodes or hexagonal plate electrodes.

19. The method for manufacturing an acoustic wave resonator according to claim 18, wherein when the patterned electrode is an interdigital electrode and the number of pairs of interdigital electrodes is plural, the plural pairs of interdigital electrodes form an interdigital transducer.

20. The method of manufacturing an acoustic resonator according to claim 19, wherein the acoustic resonator further comprises: and the at least one pair of reflection gate electrodes are formed on the upper surfaces of the piezoelectric films on two sides of the interdigital transducer or the upper surface of the piezoelectric substrate.

21. The acoustic resonator of claim 15, wherein the patterned electrode has a thickness less than the thickness of the piezoelectric film, and wherein the ratio of the thickness of the piezoelectric film to the wavelength of a target elastic wave excited by the piezoelectric film is less than 0.5.

22. The method of manufacturing an acoustic resonator according to claim 15, wherein the acoustic resonator further comprises: and the heat dissipation accelerating layer is at least formed on the upper surface of the piezoelectric film and the surface of the patterned electrode.

23. The method of manufacturing an acoustic wave resonator according to claim 15, wherein the material of the piezoelectric material layer includes: any one of quartz, aluminum nitride, zinc oxide, lithium tantalate, lithium niobate, lithium tetraborate, bismuth germanate, bismuth silicate, lanthanum gallium silicate and zirconium titanium lead acid.