CN115567021A - Acoustic wave device, filtering device and preparation method of acoustic wave device - Google Patents
Acoustic wave device, filtering device and preparation method of acoustic wave device Download PDFInfo
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- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
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- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
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- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
- H03H3/10—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves for obtaining desired frequency or temperature coefficient
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- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
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Abstract
The invention discloses an acoustic wave device, comprising a substrate and a piezoelectric layer which are oppositely arranged; the dielectric layer is positioned on the surface of one side, facing the substrate, of the piezoelectric layer; the dielectric layer is a low-acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient; and the interdigital electrodes are positioned on the surface of the piezoelectric layer, which is opposite to the substrate. A dielectric layer with the thickness not less than half wavelength of sound wave propagating in the dielectric layer is arranged on one side, facing the substrate, of the piezoelectric layer, and the dielectric layer is made to have a positive temperature coefficient, so that the frequency temperature coefficient of the acoustic wave device can be effectively improved through the dielectric layer. Meanwhile, the dielectric layer is made of a low-acoustic-impedance material compared with the piezoelectric layer, so that acoustic wave energy leakage in the longitudinal direction can be effectively inhibited. The invention also provides a filter device and a preparation method of the acoustic wave device, and the filter device and the preparation method have the beneficial effects.
Description
Technical Field
The present invention relates to the field of acoustic wave device technologies, and in particular, to an acoustic wave device, a filter device, and a method for manufacturing an acoustic wave device.
Background
The acoustic wave filter may be used in a high frequency circuit, for example, as a band pass filter. The acoustic wave filter is formed by combining a plurality of acoustic wave resonators. Acoustic wave resonators are generally classified into Surface Acoustic Wave (SAW) devices and Bulk Acoustic Wave (BAW) devices according to vibration modes. SAW devices use interdigital electrodes (IDTs) to convert electrical energy to acoustic energy, or conversely, acoustic energy to electrical energy. BAW devices, like SAW devices, rely on the piezoelectric effect of piezoelectric materials to create resonance. BAW resonators generally consist of a sandwich structure of an upper electrode layer, a piezoelectric layer, and a lower electrode layer, which generates resonance. Below the lower electrode is an air cavity (FBAR) or acoustically reflective layer (SMR), the resonance region occurring within the piezoelectric layer rather than at the surface. At present, liNbO3 and LiTaO3 have a high piezoelectric coefficient (K2) and are widely used in acoustic wave devices requiring high frequency and large bandwidth.
In recent years, filters, duplexers, and the like, which use acoustic wave resonators as basic units, are increasingly being downsized, made higher in frequency and wider in bandwidth, and are also required to have higher power-receiving capability. Since TCF (temperature coefficient of frequency) is an important parameter index of an acoustic wave device, how to effectively improve TCF of an acoustic wave device is an urgent problem to be solved by those skilled in the art.
Disclosure of Invention
An object of the present invention is to provide an acoustic wave device having a high temperature coefficient of frequency; another object of the present invention is to provide a filter device and a method of manufacturing an acoustic wave device having a high temperature coefficient of frequency.
To solve the above technical problem, the present invention provides an acoustic wave device comprising:
a substrate and a piezoelectric layer disposed opposite;
the dielectric layer is positioned on the surface of one side, facing the substrate, of the piezoelectric layer; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient;
and the interdigital electrodes are positioned on the surface of the piezoelectric layer on the side opposite to the substrate.
Optionally, the method further includes:
a Bragg reflection layer positioned on the surface of one side of the substrate, which faces the piezoelectric layer; the dielectric layer is positioned on the surface of one side, back to the substrate, of the Bragg reflection layer.
Optionally, the bragg reflection layer includes a low acoustic impedance layer and a high acoustic impedance layer that are alternately arranged along the thickness direction of the substrate, and the thickness of each film layer in the bragg reflection layer is approximately equal to a quarter of an equivalent wavelength at the resonance frequency.
Optionally, the method further includes:
and the protective layer is positioned on the surface of one side, back to the substrate, of the piezoelectric layer.
Optionally, the thickness of the dielectric layer is equal to a thickness corresponding to a frequency temperature coefficient of the acoustic wave device equal to 0 ppm/K.
The present invention also provides a filter arrangement comprising an acoustic wave device as defined in any of the above.
The invention also provides a preparation method of the acoustic wave device, which comprises the following steps:
sequentially arranging a dielectric layer and a piezoelectric layer on the surface of the substrate along the thickness direction of the substrate; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient;
and arranging interdigital electrodes on the surface of the piezoelectric layer on the side opposite to the substrate to manufacture the acoustic wave device.
Optionally, the method further includes:
a Bragg reflection layer is arranged on the surface of the substrate;
the dielectric layer and the piezoelectric layer are sequentially arranged on the surface of the substrate along the thickness direction of the substrate, and the method comprises the following steps:
and sequentially arranging a dielectric layer and a piezoelectric layer on the surface of one side, back to the substrate, of the Bragg reflection layer along the thickness direction of the substrate.
Optionally, the method further includes:
arranging the dielectric layer on the surface of the piezoelectric layer;
the step of sequentially arranging the dielectric layer and the piezoelectric layer on the surface of one side, back to the substrate, of the Bragg reflection layer along the thickness direction of the substrate comprises the following steps:
and bonding the dielectric layer and the Bragg reflection layer with each other.
Optionally, the method further includes:
performing ion implantation on the surface of the piezoelectric layer; the depth of the ion implantation is equal to the required thickness of the piezoelectric layer;
the step of arranging the dielectric layer on the surface of the piezoelectric layer comprises the following steps:
arranging the dielectric layer on the surface of the piezoelectric layer subjected to the ion implantation;
after bonding the dielectric layer and the Bragg reflector layer to each other, the method further comprises the following steps:
and peeling the piezoelectric layer along the interface of the piezoelectric layer after the ion implantation.
The invention provides an acoustic wave device, comprising a substrate and a piezoelectric layer which are oppositely arranged; the dielectric layer is positioned on the surface of one side, facing the substrate, of the piezoelectric layer; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of the sound wave transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient; and the interdigital electrodes are positioned on the surface of the piezoelectric layer on the side opposite to the substrate.
A dielectric layer with the thickness not less than half wavelength of sound wave transmitted in the dielectric layer is arranged on one side, facing the substrate, of the piezoelectric layer, and the dielectric layer is made to have a positive temperature coefficient, so that the frequency temperature coefficient of the sound wave device can be effectively improved through the dielectric layer. Meanwhile, the dielectric layer is made of a low-acoustic-impedance material compared with the piezoelectric layer, and the thickness of the dielectric layer is not smaller than the half wavelength of the sound waves transmitted in the dielectric layer, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.
The invention also provides a filter device and a preparation method of the acoustic wave device, which also have the beneficial effects and are not described herein again.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions of the present invention will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an acoustic wave device according to an embodiment of the present invention;
FIG. 2 is a graph comparing admittance curves before and after thickening of the medium layer of FIG. 1;
FIG. 3 is a temperature coefficient curve for the resonant frequency and the anti-resonator frequency before and after the dielectric layer is thickened in FIG. 1;
fig. 4 is a schematic structural view of a first specific acoustic wave device according to an embodiment of the present invention;
FIG. 5 is a schematic view of the longitudinal transfer of acoustic energy in FIG. 4;
FIG. 6 is a schematic view of longitudinal transfer of acoustic energy in the prior art;
fig. 7 is a flow chart of a method of fabricating an acoustic wave device according to an embodiment of the present invention;
fig. 8 is a flow chart of a specific method for fabricating an acoustic wave device according to an embodiment of the present invention.
In the figure: 1. the array substrate comprises a substrate, 2 dielectric layers, 3 piezoelectric layers, 4 interdigital electrodes and 5 Bragg reflecting layers.
Detailed Description
The core of the present invention is to provide an acoustic wave device. In the prior art, in order to improve the TCF of the acoustic wave device, a temperature compensation material is usually disposed to cover the interdigital electrodes, but the loading effect of the temperature compensation material may reduce the frequency of use of the acoustic wave device, and at the same time, more parasitic modes are generated.
The invention provides an acoustic wave device, which comprises a substrate and a piezoelectric layer which are oppositely arranged; the dielectric layer is positioned on the surface of one side, facing the substrate, of the piezoelectric layer; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of the sound wave transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient; and the interdigital electrodes are positioned on the surface of the piezoelectric layer, which is opposite to the substrate.
A dielectric layer with the thickness not less than half wavelength of sound wave propagating in the dielectric layer is arranged on one side, facing the substrate, of the piezoelectric layer, and the dielectric layer is made to have a positive temperature coefficient, so that the frequency temperature coefficient of the acoustic wave device can be effectively improved through the dielectric layer. Meanwhile, the thickness of the dielectric layer is not less than the half wavelength of the sound wave transmitted in the dielectric layer, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Referring to fig. 1, fig. 2 and fig. 3, fig. 1 is a schematic structural diagram of an acoustic wave device according to an embodiment of the present invention; FIG. 2 is a graph comparing admittance curves before and after thickening of the dielectric layer of FIG. 1; fig. 3 is a temperature coefficient change curve for the resonant frequency and the anti-resonator frequency before and after the thickening of the dielectric layer in fig. 1.
Referring to fig. 1, in an embodiment of the present invention, an acoustic wave device includes: a substrate 1 and a piezoelectric layer 3 disposed oppositely; a dielectric layer 2 positioned on the surface of one side of the piezoelectric layer 3 facing the substrate 1; the dielectric layer 2 is a low acoustic impedance layer, and the thickness of the dielectric layer 2 is not less than half wavelength of sound waves propagating in the dielectric layer 2; the dielectric layer 2 has a positive temperature coefficient; and the interdigital electrode 4 is positioned on the surface of the piezoelectric layer 3, which faces away from the substrate 1.
The substrate 1 is generally an insulating substrate 1, and the substrate 1 includes, but is not limited to, silicon, quartz, alumina, etc., as the case may be, and is not particularly limited thereto. One side of the substrate 1 is provided with a dielectric layer 2, which dielectric layer 2 needs to be a low acoustic impedance layer in the present embodiment, so that acoustic wave energy can propagate in the lateral direction within the piezoelectric layer 3 as well as the dielectric layer 2. The dielectric layer 2 needs to have a positive temperature coefficient to ensure that the dielectric layer 2 can play a role in improving the TCF of the acoustic wave device. In the embodiment of the present invention, the thickness of the dielectric layer 2 is not less than a half wavelength of the acoustic wave propagating in the dielectric layer 2, that is, the thickness of the dielectric layer 2 is not less than 1/2 λ, where λ is the corresponding acoustic wave wavelength of the dielectric layer 2 at the resonant frequency, which can further improve the TCF value of the acoustic wave device.
The piezoelectric layer 3 is usually located on the surface of the dielectric layer 2 opposite to the substrate 1, the piezoelectric layer 3 may be a piezoelectric material such as lithium niobate, lithium tantalate, aluminum nitride, or zinc oxide, and the specific material of the piezoelectric layer 3 may be set according to the actual situation. The interdigital electrode 4 is usually located on the surface of the piezoelectric layer 3 opposite to the substrate 1, and the material of the interdigital electrode 4 is usually a metal with good conductivity, which may be specifically aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, etc. compatible with semiconductor processes, or may be an alloy composed of the above metals, and may be set by itself according to actual circumstances, and is not limited specifically herein.
Referring to fig. 2 and 3, it can be seen from the simulation results that, when the thickness of the dielectric layer 2 is increased, for example, the thickness of the dielectric layer 2 is increased from 0.27 μm to 0.72 μm, the TCF of the resonant frequency of the acoustic wave device is increased from-43 ppm/K to-4 ppm/K, and the TCF of the anti-resonant frequency is also close to 0ppm/K, so that the zero temperature drift compensation is substantially realized. In order to implement zero temperature drift compensation, in the embodiment of the present invention, the thickness of the dielectric layer 2 may be equal to the thickness corresponding to the case where the frequency temperature coefficient of the resonant or anti-resonant frequency of the acoustic wave device is equal to 0ppm/K, so as to implement zero temperature drift compensation. Meanwhile, as can be seen from the admittance curve of fig. 2, after the dielectric layer 2 is thickened, other two stronger resonance modes appear in the frequency band from 3.5GHz to 6.5GHz, and are respectively located near 4.1GHz and 5.6 GHz. Although the parasitic modes (spurious) near these two resonances are strong, the equivalent coupling coefficient of their main resonance, i.e., k2eff, is sufficiently large to also be useful in forming a bandpass filter. Thus, multiple passband-shaped filters may be constructed using the same design architecture.
Specifically, in the embodiment of the present invention, the acoustic wave device may further include a protective layer on a surface of the piezoelectric layer 3 on a side facing away from the substrate 1. The protective layer includes, but is not limited to, dielectric materials such as SiO2, siN, alN, etc. to protect the piezoelectric layer 3 from damage. The protection layer may be formed by a process of depositing and etching, or a stripping process, and the like, and is not particularly limited in the embodiment of the present invention.
It should be noted that, in the embodiment of the present invention, since the dielectric layer can effectively perform a temperature compensation function, even zero temperature drift compensation can be achieved. Therefore, the temperature compensation layer covering the interdigital electrode does not need to be arranged in the embodiment of the invention, so that the influence of the conventional temperature compensation layer on the performance of the device can be avoided.
The acoustic wave device provided by the embodiment of the invention comprises a substrate 1 and a piezoelectric layer 3 which are oppositely arranged; a dielectric layer 2 positioned on the surface of the piezoelectric layer 3 facing the substrate 1; the dielectric layer 2 is a low-acoustic-impedance layer, and the thickness of the dielectric layer 2 is not less than half wavelength of sound waves propagating in the dielectric layer 2; the medium layer 2 has a positive temperature coefficient; interdigital electrodes 4 located on a surface of the piezoelectric layer 3 on a side facing away from the substrate 1.
The dielectric layer 2 with the thickness not less than half wavelength of the sound wave propagating in the dielectric layer 2 is arranged on the side of the piezoelectric layer 3 facing the substrate 1, and the dielectric layer 2 is made to have positive temperature coefficient, so that the dielectric layer 2 can effectively improve the frequency temperature coefficient of the sound wave device. Meanwhile, the thickness of the dielectric layer 2 is not less than the half wavelength of the sound wave transmitted in the dielectric layer 2, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.
The detailed structure of an acoustic wave device according to the present invention will be described in detail in the following embodiments of the present invention.
Referring to fig. 4, 5 and 6, fig. 4 is a schematic structural diagram of a first specific acoustic wave device according to an embodiment of the present invention; FIG. 5 is a schematic view of the longitudinal transfer of acoustic energy in FIG. 4; FIG. 6 is a diagram illustrating longitudinal transfer of acoustic energy in accordance with the prior art.
The present embodiment further provides two structural schematic diagrams of the acoustic wave device on the basis of the above-described present embodiment, which is different from the above-described present embodiment. The rest of the contents are already described in detail in the above embodiments of the present invention, and are not described herein again.
First, the dielectric layer 2 may be directly located on the surface of the substrate 1 facing the piezoelectric layer 3. At this time, in order to better reflect the acoustic wave energy propagating in the longitudinal direction back to the piezoelectric layer 3 and suppress the transmission of the longitudinal acoustic wave energy, the substrate 1 generally needs to be a high acoustic velocity layer, that is, the material of the substrate 1 needs to be a high acoustic velocity material, at this time, the dielectric layer 2 can be a low acoustic velocity layer, the substrate 1 serves as a high acoustic velocity layer, at this time, the dielectric layer 2 and the substrate 1 respectively have a lower bulk acoustic velocity and a higher bulk acoustic velocity than the piezoelectric layer 3, and the larger the acoustic velocity difference is, the better the energy reflection effect is.
Secondly, referring to fig. 4, the acoustic wave device further includes a bragg reflector layer 5 on a surface of the substrate 1 facing the piezoelectric layer 3; the dielectric layer 2 is positioned on the surface of one side, back to the substrate 1, of the Bragg reflection layer 5. That is, the propagation of the acoustic wave energy in the longitudinal direction can be restricted by the bragg reflector layer 5 in the embodiment of the present invention. The bragg reflector 5 is generally composed of alternately arranged high acoustic impedance layers and low acoustic impedance layers, wherein the high acoustic impedance layers are made of materials including, but not limited to, W, mo, alN, and the like; the material of the low acoustic impedance layer includes, but is not limited to, siO2, porous silicon, etc.
In the embodiment of the present invention, the dielectric layer 2 is a low acoustic impedance layer and is located on a surface of the bragg reflector 5 facing the piezoelectric layer 3. In this case, the dielectric layer 2 may be considered as the uppermost film layer of the bragg reflector 5 and is in direct contact with the piezoelectric layer 3. Specifically, the thickness of the dielectric layer 2, i.e., the uppermost layer of the bragg reflector 5, is not less than half the wavelength of the sound wave propagating in the dielectric layer 2, and the thickness of each layer of the bragg reflector 5 is generally equal to one quarter of the equivalent wavelength at the resonant frequency. It is therefore possible in particular in the embodiment of the present invention to increase the TCF of the acoustic wave device while suppressing the acoustic wave energy leakage in the longitudinal direction by increasing the thickness of the uppermost film layer in the bragg reflector 5 in contact with the piezoelectric layer 3.
In particular, comparing fig. 5 and fig. 6, it can be seen that after the dielectric layer 2 is thickened, the displacement distribution of the acoustic wave on the piezoelectric layer 3 is not substantially affected. More energy will be concentrated to the low acoustic impedance layer on the top layer to obtain better temperature compensation effect.
According to the acoustic wave device provided by the embodiment of the invention, the dielectric layer 2 with the thickness not less than half wavelength of acoustic wave transmitted in the dielectric layer 2 can be arranged on one side of the piezoelectric layer 3 facing the substrate 1, and the dielectric layer 2 has a positive temperature coefficient, so that the frequency temperature coefficient of the acoustic wave device can be effectively improved by the dielectric layer 2. Meanwhile, the thickness of the dielectric layer 2 is not less than the half wavelength of the sound wave transmitted in the dielectric layer 2, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.
The invention also provides a filtering device which comprises the acoustic wave device provided by any one of the embodiments of the invention. The rest of the filtering device can refer to the prior art and will not be described herein.
Because the filtering device is provided with the acoustic wave device provided by any one of the above embodiments of the invention, the acoustic wave device installed in the filtering device has higher TCF, and therefore, the filtering device has good performance.
A method of manufacturing an acoustic wave device that can be referred to in correspondence with an acoustic wave device provided by the above-described embodiment of the present invention will be provided below.
Referring to fig. 7, fig. 7 is a flowchart of a method for fabricating an acoustic wave device according to an embodiment of the present invention.
Referring to fig. 7, in an embodiment of the present invention, a method of manufacturing an acoustic wave device includes:
s101: and sequentially arranging a dielectric layer and a piezoelectric layer on the surface of the substrate along the thickness direction of the substrate.
In the embodiment of the present invention, the dielectric layer 2 is a low acoustic impedance layer, and the thickness of the dielectric layer 2 is not less than a half wavelength of a sound wave propagating in the dielectric layer 2; the dielectric layer 2 has a positive temperature coefficient. The specific structure of the acoustic wave device has been described in detail in the above embodiments of the present invention, and will not be described in detail herein.
Prior to this step, it generally comprises: a Bragg reflection layer 5 is arranged on the surface of the substrate 1. That is, it is usually necessary to provide the bragg reflector 5 on the surface of the substrate 1 for limiting the longitudinal acoustic wave propagation of the acoustic wave device in this step, and the bragg reflector 5 is usually grown on the surface of the substrate 1 based on a growth process to suppress the propagation of the acoustic wave energy to the substrate 1.
In this step, a dielectric layer 2 and a piezoelectric layer 3 are sequentially disposed, which are generally embodied as: and sequentially arranging a dielectric layer 2 and a piezoelectric layer 3 on the surface of one side of the Bragg reflection layer 5 back to the substrate 1 along the thickness direction of the substrate 1. The detailed structures of the substrate 1, the bragg reflector 5, the dielectric layer 2, and the piezoelectric layer 3 are described in detail in the above embodiments of the invention, and are not described herein again.
S102: interdigital electrodes are arranged on the surface of the piezoelectric layer on the side opposite to the substrate to form the acoustic wave device.
In this step, the interdigital electrode 4 generally needs to be disposed by a deposition process and an etching process in sequence, and reference may be made to the prior art for a specific structure of the interdigital electrode 4, which is not described herein again.
Before this step, the method for manufacturing an acoustic wave device according to an embodiment of the present invention generally further includes: the surface of the piezoelectric layer 3 is polished, typically by Chemical Mechanical Polishing (CMP). That is, in this step, the interdigital electrodes 4 are usually disposed on the surface of the piezoelectric layer 3 that is flat after polishing, so as to ensure the structural integrity of the interdigital electrodes 4. After polishing, the acoustic wave device manufacturing method provided by the embodiment of the present invention generally further includes: the piezoelectric layer 3 is heated to restore the piezoelectricity of the piezoelectric layer 3. That is, after the wafer is polished, the piezoelectric layer 3 and the substrate 1 can be subjected to heating treatment, so that the piezoelectric performance and the crystal orientation of the piezoelectric material are restored, and the quality of the piezoelectric layer 3 is improved.
After this step, it is usually necessary to provide a protective layer covering the piezoelectric layer 3 on the surface of the piezoelectric layer 3 facing away from the substrate 1, and the protective layer includes, but is not limited to, siO2, siN, alN, and other dielectric materials, so as to protect the piezoelectric layer 3 from being damaged. The protection layer may be formed by a process of depositing and etching, or a stripping process, and the like, and is not particularly limited in the embodiment of the present invention.
According to the preparation method of the acoustic wave device provided by the embodiment of the invention, the dielectric layer 2 with the thickness not less than half wavelength of the acoustic wave transmitted in the dielectric layer 2 is arranged on the side, facing the substrate 1, of the piezoelectric layer 3, and the dielectric layer 2 has a positive temperature coefficient, so that the frequency temperature coefficient of the acoustic wave device can be effectively improved by the dielectric layer 2. Meanwhile, the thickness of the dielectric layer 2 is not less than the half wavelength of the sound wave transmitted in the dielectric layer 2, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.
The details of the method for manufacturing an acoustic wave device according to the present invention will be described in detail in the following embodiments of the invention.
Referring to fig. 8, fig. 8 is a flowchart of a method for fabricating an acoustic wave device according to an embodiment of the present invention.
Referring to fig. 8, in an embodiment of the present invention, a method of manufacturing an acoustic wave device includes:
s201: a Bragg reflection layer is arranged on the surface of the substrate.
This step has already been described in detail in S101 in the above embodiment of the present invention, and is not described herein again.
S202: and arranging a dielectric layer on the surface of the piezoelectric layer.
Ion implantation may typically be performed at the surface of the piezoelectric layer 3 prior to this step. Wherein the depth of the ion implantation may need to be equal to the desired thickness of the piezoelectric layer 3, thereby facilitating the peeling of the piezoelectric layer 3 to the desired preset thickness in the subsequent step.
In this step, the function of ion implantation is mainly to create an interface between the ion implanted region and the general piezoelectric material in the thickness direction of the piezoelectric layer 3, thereby facilitating the subsequent peeling operation. For details of ion implantation, reference may be made to the prior art, and further description is omitted here. In general, the step may specifically be: and arranging the dielectric layer 2 on the surface of the piezoelectric layer 3 subjected to the ion implantation. It should be noted that there is no specific sequence between S201 and S202, and S201 may be executed first, S202 may be executed first, or both S201 and S202 may be executed in parallel, which is not limited specifically herein according to specific situations.
S203: and bonding the dielectric layer and the Bragg reflection layer with each other.
In this step, specifically, the piezoelectric layer 3 provided with the dielectric layer 2 and the substrate 1 provided with the bragg reflector 5 may be bonded to each other by a layer transfer technique, and the dielectric layer 2 and the bragg reflector 5 may be bonded to each other in a specific manner. The specific bonding process in this step may be a direct bonding process, an ion activated bonding process, an electrostatic bonding process, or the like, as the case may be, and is not particularly limited herein.
S204: and peeling the piezoelectric layer along the interface of the piezoelectric layer after ion implantation.
In this step, a part of the piezoelectric layer 3 is specifically peeled off along the interface of ion implantation, thereby ensuring that the piezoelectric layer 3 having a thickness only of a predetermined thickness and the substrate 1 provided with the bragg reflector 5 are bonded to each other.
After this step, it is also necessary to polish the surface of the piezoelectric layer 3 after the peeling, and heat treat the piezoelectric layer 3 after the polishing. Since the ion implantation applies a certain stress to the crystal lattice of the piezoelectric layer 3, the heating treatment can effectively recover the piezoelectric performance and the crystal orientation of the piezoelectric material, and improve the quality of the piezoelectric layer 3.
S205: interdigital electrodes are arranged on the surface of the piezoelectric layer on the side opposite to the substrate to form the acoustic wave device.
This step is already described in detail in S102 in the above embodiment of the present invention, and is not described herein again.
According to the preparation method of the acoustic wave device provided by the embodiment of the invention, the defects of uneven thickness, crystal orientation, insufficient compactness and the like caused by a growth process can be effectively avoided through the layer transfer technology, and meanwhile, the crystal orientation of the piezoelectric layer 3 cannot be limited through the layer transfer technology, so that the acoustic wave device can be conveniently subjected to various corner cut design considerations during design, and the performance of the piezoelectric layer 3 can be exerted to the maximum extent.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Finally, it should also be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The acoustic wave device, the filter device, and the method for manufacturing the acoustic wave device according to the present invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (10)
1. An acoustic wave device, comprising:
a substrate and a piezoelectric layer disposed opposite;
the dielectric layer is positioned on the surface of one side, facing the substrate, of the piezoelectric layer; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient;
and the interdigital electrodes are positioned on the surface of one side, opposite to the substrate, of the piezoelectric layer.
2. The acoustic wave device of claim 1, further comprising:
a Bragg reflection layer positioned on the surface of one side of the substrate, which faces the piezoelectric layer; the dielectric layer is positioned on the surface of one side, back to the substrate, of the Bragg reflection layer.
3. An acoustic wave device in accordance with claim 2, wherein said bragg reflection layer includes low acoustic impedance layers and high acoustic impedance layers alternately arranged in a thickness direction of said substrate, a thickness of each film layer in said bragg reflection layer being equal to a quarter of an equivalent wavelength at a resonance frequency.
4. An acoustic wave device according to claim 3, further comprising:
and the protective layer is positioned on the surface of the piezoelectric layer, which faces away from the substrate.
5. The acoustic wave device of claim 1, wherein a thickness of the dielectric layer is equal to a thickness corresponding to a temperature coefficient of frequency of the acoustic wave device equal to 0 ppm/K.
6. A filter arrangement comprising an acoustic wave device according to any of claims 1 to 5.
7. A method of fabricating an acoustic wave device, comprising:
sequentially arranging a dielectric layer and a piezoelectric layer on the surface of the substrate along the thickness direction of the substrate; the dielectric layer is a low acoustic impedance layer, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer; the dielectric layer has a positive temperature coefficient;
and arranging interdigital electrodes on the surface of the piezoelectric layer on the side opposite to the substrate to manufacture the acoustic wave device.
8. The method of claim 7, further comprising:
a Bragg reflection layer is arranged on the surface of the substrate;
the dielectric layer and the piezoelectric layer are sequentially arranged on the surface of the substrate along the thickness direction of the substrate, and the method comprises the following steps:
and sequentially arranging a dielectric layer and a piezoelectric layer on the surface of one side, back to the substrate, of the Bragg reflection layer along the thickness direction of the substrate.
9. The method of claim 8, further comprising:
arranging the dielectric layer on the surface of the piezoelectric layer;
the setting of the dielectric layer and the piezoelectric layer on the surface of one side, back to the substrate, of the Bragg reflection layer in sequence along the thickness direction of the substrate comprises the following steps:
and bonding the dielectric layer and the Bragg reflection layer with each other.
10. The method of claim 9, further comprising:
performing ion implantation on the surface of the piezoelectric layer; the depth of the ion implantation is equal to the required thickness of the piezoelectric layer;
the step of arranging the dielectric layer on the surface of the piezoelectric layer comprises the following steps:
arranging the dielectric layer on the surface of the piezoelectric layer subjected to the ion implantation;
after bonding the dielectric layer and the bragg reflector layer to each other, the method further includes:
and peeling the piezoelectric layer along the interface of the piezoelectric layer after the ion implantation.
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