CN215871345U

CN215871345U - Acoustic wave device and filtering device

Info

Publication number: CN215871345U
Application number: CN202121509029.4U
Authority: CN
Inventors: 彭波华; 胡念楚; 贾斌
Original assignee: Maims Communication Technology Shenzhen Co ltd; Mcmus Communication Technology Shanghai Co ltd; Kaiyuan Communication Technology Xiamen Co ltd
Current assignee: Maims Communication Technology Shenzhen Co ltd; Mcmus Communication Technology Shanghai Co ltd; Kaiyuan Communication Technology Xiamen Co ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2022-02-18
Anticipated expiration: 2031-07-01

Abstract

The utility model 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 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 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 the acoustic wave energy leakage in the longitudinal direction can be effectively inhibited. The utility model also provides a filtering device which also has the beneficial effects.

Description

Acoustic wave device and filtering device

Technical Field

The present invention relates to the field of acoustic wave devices, and in particular, to an acoustic wave device and a filter apparatus.

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 of an upper electrode layer, a piezoelectric layer, and a lower electrode layer, which creates resonance. Below the lower electrode is an air cavity (FBAR) or acoustically reflective layer (SMR), with the resonance region occurring within the piezoelectric layer rather than at the surface. At present, LiNbO3 and LiTaO3 are widely used in acoustic wave devices with high frequency and large bandwidth requirements due to their high piezoelectric coefficient (K2).

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.

SUMMERY OF THE UTILITY MODEL

An object of the present invention is to provide an acoustic wave device having a high temperature coefficient of frequency; it is another object of the present invention to provide a filter device whose acoustic wave device has 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 reflector includes low acoustic impedance layers and high acoustic impedance layers alternately arranged along the thickness direction of the substrate, and the thickness of each film layer in the bragg reflector is approximately equal to one quarter of the equivalent wavelength at the resonant frequency.

Optionally, the method further includes:

and the protective layer is positioned on the surface of the piezoelectric layer, which faces away from the substrate.

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 one of the above.

The utility model 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 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, and the thickness of the dielectric layer is not less than half wavelength of sound waves transmitted in the dielectric layer, so that the sound wave energy leakage in the longitudinal direction can be effectively inhibited.

The utility model also provides a filtering device, which has the beneficial effects and is not repeated herein.

Drawings

In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly described below, and 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 based on these 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 of FIG. 4;

FIG. 6 is a schematic diagram of longitudinal acoustic energy transfer in the prior art.

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 utility model 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 on the side 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 utility model 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 utility model, and not restrictive of the full scope of the utility model. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within 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 medium 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 transmitted 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 half the 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, according to the simulation results, after 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 basically 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 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 (spur i ous) near these two resonances are strong, the equivalent coupling coefficient of their main resonance, i.e., k2eff, is large enough to form 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, SiO2, SiN, AlN, and other dielectric materials 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 utility model, 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 utility model 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 transmitted in the dielectric layer 2; the medium layer 2 has a positive temperature coefficient; and the interdigital electrodes 4 are positioned on the surface of the piezoelectric layer 3, which is opposite to 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 specific 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 of FIG. 4; FIG. 6 is a schematic diagram of longitudinal acoustic energy transfer in the prior art.

Different from the embodiment of the present invention, the embodiment of the present invention further provides two kinds of structural schematic diagrams of the acoustic wave device on the basis of the embodiment of the present invention. The rest of the contents have been described in detail in the above embodiments, and are not described again.

First, the above-mentioned 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 reflective 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 of the Bragg reflection layer 5, which faces away from the substrate 1. That is, the propagation of the acoustic wave energy in the longitudinal direction may be limited 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 is concentrated to the low acoustic impedance layer of the top layer to obtain better temperature compensation effect.

According to the acoustic wave device provided by the embodiment of the utility model, the dielectric layer 2 with the thickness not less than half wavelength of the acoustic wave transmitted in the dielectric layer 2 can be arranged on the piezoelectric layer 3 towards the substrate 1, and the dielectric layer 2 has a positive temperature coefficient, so that the dielectric layer 2 can effectively improve the frequency temperature coefficient of the acoustic 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 utility model also provides a filter device, which comprises the acoustic wave device provided by any embodiment of the utility model. The rest of the filtering device can refer to the prior art and will not be described herein.

Because the filter equipment is provided with the acoustic wave device that any above-mentioned utility model embodiment provided for the acoustic wave device of filter equipment installation has higher TCF, consequently makes filter equipment have good performance.

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.

Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be 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 phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

An acoustic wave device and a filter device provided by 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

1. An acoustic wave device, comprising:

a substrate and a piezoelectric layer disposed opposite;

2. The acoustic wave device of claim 1, further comprising:

3. An acoustic wave device as claimed in claim 2, wherein the bragg reflector layer comprises low and high acoustic impedance layers alternately arranged along the thickness of the substrate, the thickness of each film layer in the bragg reflector layer being equal to one quarter of the equivalent wavelength at the resonance frequency.

4. An acoustic wave device according to claim 3, further comprising:

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.