CN114285389A - Preparation method of acoustic resonator and acoustic resonator - Google Patents
Preparation method of acoustic resonator and acoustic resonator Download PDFInfo
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- CN114285389A CN114285389A CN202110275987.8A CN202110275987A CN114285389A CN 114285389 A CN114285389 A CN 114285389A CN 202110275987 A CN202110275987 A CN 202110275987A CN 114285389 A CN114285389 A CN 114285389A
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- 238000002360 preparation method Methods 0.000 title abstract description 9
- 239000000758 substrate Substances 0.000 claims abstract description 72
- 239000000463 material Substances 0.000 claims abstract description 63
- 238000000151 deposition Methods 0.000 claims abstract description 49
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000011049 filling Methods 0.000 claims description 52
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- 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
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
The invention relates to a preparation method of an acoustic resonator and the acoustic resonator, wherein the preparation method of the acoustic resonator comprises providing a piezoelectric substrate comprising one of lithium niobate and lithium tantalate, and depositing a first acoustic reflection layer on a bottom electrode layer, and the acoustic resonator prepared by the preparation method of the acoustic resonator can be excited into a thickness direction shear vibration mode by selecting a specific direction of the piezoelectric substrate, and the acoustic resonator can support high electromechanical coupling at a frequency of more than 3GHz because the acoustic resonator adopts a more excellent thickness direction shear vibration mode and selects a lithium niobate or lithium tantalate material capable of supporting the vibration mode.
Description
Technical Field
The application relates to the technical field of resonators, in particular to a preparation method of an acoustic resonator and the acoustic resonator.
Background
The filter has a frequency selection function, i.e., allows signals with a desired frequency to pass through, and suppresses signals with an undesired frequency from passing through, and is an extremely important component in the field of microwave communication, and is widely used in the fields of mobile communication, satellite communication, radar, and other microwave communications. Filters are typically made up of a plurality of resonators interconnected by electrodes.
With the release of new communication standards (i.e. fifth generation mobile networks), it is necessary to extend the operating range of the resonators to higher frequencies while maintaining a high electromechanical coupling coefficient.
Disclosure of Invention
Based on this, there is a need for a method of manufacturing an acoustic resonator and an acoustic resonator capable of supporting high electromechanical coupling at frequencies above 3 GHz.
In a first aspect, a method for manufacturing an acoustic resonator is provided, including the steps of:
providing a piezoelectric substrate, wherein the piezoelectric substrate comprises lithium niobate and/or lithium tantalate;
forming a bottom electrode layer on the first surface of the piezoelectric substrate;
forming an acoustic mirror on the bottom electrode layer; the acoustic mirror comprises at least one first acoustic reflection layer and at least one second acoustic reflection layer, the acoustic impedance of each first acoustic reflection layer is smaller than that of each second acoustic reflection layer, and the first acoustic reflection layer and the second acoustic reflection layer are alternately stacked and are closest to the bottom electrode layer;
bonding a bearing wafer on the first surface of the acoustic mirror, wherein the first surface of the acoustic mirror is a surface deviating from the bottom electrode;
and forming an upper electrode layer on the second surface of the piezoelectric substrate.
In one embodiment, the forming the acoustic mirror on the bottom electrode layer includes forming three first acoustic reflective layers and two second acoustic reflective layers.
In one embodiment, the step of bonding a carrier wafer to the first surface of the acoustic mirror comprises:
depositing an auxiliary layer on the first surface of the acoustic mirror; and/or
And depositing an auxiliary layer on the bonding surface of the bearing wafer.
In one embodiment, the thickness of each first acoustic reflection layer gradually increases from the bottom electrode layer to the direction of the carrier wafer; the thickness of each second acoustic reflection layer gradually increases from the bottom electrode layer to the direction of the carrier wafer.
In one embodiment, the step of bonding a carrier wafer to the first surface of the acoustic mirror comprises:
etching the bottom electrode layer and the acoustic mirror;
and depositing a filling layer on the piezoelectric substrate, and filling the positions of the bottom electrode layer and the acoustic mirror which are etched and removed.
In one embodiment, the step of bonding a carrier wafer to the first surface of the acoustic mirror after the step of forming the bottom electrode layer on the first surface of the piezoelectric substrate comprises:
etching the bottom electrode layer;
depositing a filling material at the position where the bottom electrode layer is etched and removed to form a bottom electrode filling layer;
depositing a low acoustic impedance material on the bottom electrode filling layer to form a first acoustic reflection layer;
depositing a high acoustic impedance material on the first acoustic reflective layer to form a second acoustic reflective layer;
etching the second acoustic reflection layer;
depositing a filling material at the position where the second acoustic reflection layer is etched and removed to form a second acoustic reflection filling layer;
and sequentially and alternately forming the first acoustic reflection layer and the second acoustic reflection filling layer at intervals.
In one embodiment, the filling layer is the same material as each first acoustic reflection layer.
In one embodiment, the forming a bottom electrode on the first surface of the piezoelectric substrate includes: depositing electrode material on the first surface of the piezoelectric substrate and etching to form the bottom electrode layer;
the forming of the acoustic mirror on the bottom electrode layer includes:
step A, depositing a low acoustic impedance material to form a first acoustic reflection layer;
step B, depositing a high acoustic impedance material on the low acoustic impedance material;
step C, etching the deposited high-acoustic-impedance material to form a second acoustic reflection layer;
repeating step A, B, C until a desired number of layers of first and second acoustic reflective layers are formed;
after the step of forming the acoustic mirror on the bottom electrode layer and before the step of bonding the bearing wafer on the first surface of the acoustic mirror, depositing a filling layer on the piezoelectric substrate, and filling the positions where the bottom electrode layer and the acoustic mirror are etched and removed;
wherein the low acoustic impedance material comprises at least one of silicon dioxide, aluminum, benzocyclobutene, polyimide, and spin-on glass, and the high acoustic impedance material comprises at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide, and silicon nitride.
In one embodiment, the forming the upper electrode layer on the second surface of the piezoelectric substrate includes:
depositing a first electrode layer;
patterning the first electrode layer;
and depositing a second electrode layer on the patterned first electrode layer, wherein the thickness of the second electrode layer is greater than that of the first electrode layer.
In one embodiment, the method further comprises the following steps: depositing a passivation layer on the first electrode layer.
In a second aspect, there is provided an acoustic resonator comprising:
the acoustic mirror comprises at least one first acoustic reflection layer and at least one second acoustic reflection layer, wherein the acoustic impedance of each first acoustic reflection layer is smaller than that of each second acoustic reflection layer;
the bottom electrode layer is positioned on the acoustic mirror, and a first sound reflecting layer of the acoustic mirror is closer to the bottom electrode layer than all second sound reflecting layers;
the piezoelectric substrate is positioned on the surface, which is far away from the acoustic mirror, of the bottom electrode layer, and the piezoelectric layer comprises lithium niobate and/or lithium tantalate;
and the upper electrode layer is positioned on one surface of the piezoelectric substrate, which is deviated from the bottom electrode layer.
The method for preparing the acoustic resonator provides a piezoelectric substrate comprising one of lithium niobate and lithium tantalate, and a first acoustic reflection layer is deposited on a bottom electrode layer, and the acoustic resonator prepared by the method for preparing the acoustic resonator can be excited into a thickness direction shear vibration mode by selecting a specific direction of the piezoelectric substrate, and can support high electromechanical coupling at a frequency of more than 3GHz because the acoustic resonator adopts a more excellent thickness direction shear vibration mode and selects a lithium niobate or lithium tantalate material capable of supporting the vibration mode.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a method of manufacturing an acoustic resonator provided in a first embodiment;
fig. 2 is a schematic cross-sectional structure diagram of a structure obtained in step S102 in a method for manufacturing an acoustic resonator according to an embodiment;
fig. 3 is a schematic cross-sectional structure diagram of a structure obtained in S104 in the manufacturing method of an acoustic resonator provided in an embodiment;
fig. 4 is a schematic cross-sectional structure diagram of a structure obtained in S106 in a manufacturing method of an acoustic resonator provided in an embodiment;
fig. 5 is a schematic cross-sectional structure diagram of a structure obtained in step S108 in a manufacturing method of an acoustic resonator provided in an embodiment;
fig. 6 is a schematic cross-sectional structure diagram of a structure obtained in S110 in a manufacturing method of an acoustic resonator provided in an embodiment;
fig. 7 is a flowchart of a technical process of S110 in a method for manufacturing an acoustic resonator provided in an embodiment;
fig. 8 is a schematic cross-sectional structure of the structure obtained in S702 in the technical process of "forming an upper electrode layer on the second surface of the piezoelectric substrate" provided in an embodiment;
fig. 9 is a schematic cross-sectional structure of the structure obtained in S704 during the "forming an upper electrode layer on the second surface of the piezoelectric substrate" in the embodiment;
fig. 10 is a schematic cross-sectional structure of the structure obtained in S706 during the "forming the upper electrode layer on the second surface of the piezoelectric substrate" in the embodiment;
FIG. 11 is a schematic cross-sectional view of a structure obtained by the process of depositing a passivation layer on the first electrode layer according to an embodiment;
fig. 12 is a schematic cross-sectional structure of a structure obtained by a technical process of "forming three first acoustic reflection layers and two second acoustic reflection layers" provided in an embodiment;
fig. 13 is a flowchart of a technical process before S108 in a method for manufacturing an acoustic resonator provided in an embodiment;
fig. 14a is a schematic cross-sectional structure diagram of a structure obtained in step S1302 in the technical process before step S108 in the method for manufacturing an acoustic resonator provided in the second embodiment;
fig. 14b is a schematic cross-sectional structure diagram of a structure obtained in step S1302 in the technical process before step S108 in the method for manufacturing an acoustic resonator provided in the third embodiment;
fig. 14c is a schematic cross-sectional structure diagram of a structure obtained in step S1302 in the technical process before step S108 in the method for manufacturing an acoustic resonator provided in the fourth embodiment;
fig. 15 illustrates a technical process between S104 and S108 in the method for manufacturing an acoustic resonator according to an embodiment;
fig. 16 is a schematic cross-sectional structure view of a structure obtained by a technical process between S104 and S108 in a manufacturing method of an acoustic resonator provided in an embodiment;
fig. 17 is a flowchart of a manufacturing method of an acoustic resonator provided in the fifth embodiment;
fig. 18 is a flowchart of a manufacturing method of an acoustic resonator provided in the sixth embodiment;
fig. 19 is a schematic cross-sectional structure diagram of an acoustic resonator provided in an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and/or sections, these elements, components, regions, layers, doping types and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or section from another element, component, region, layer, doping type or section. Thus, a first element, component, region, layer, doping type or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention; for example, the first doping type may be made the second doping type, and similarly, the second doping type may be made the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.
Spatial relational terms, such as "under," "below," "under," "over," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, in this specification, the term "and/or" includes any and all combinations of the associated listed items.
Embodiments of the invention are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention, such that variations from the shapes shown are to be expected, for example, due to manufacturing techniques and/or tolerances. Thus, embodiments of the invention should not be limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing techniques. For example, an implanted region shown as a rectangle will typically have rounded or curved features and/or implant concentration gradients at its edges rather than a binary change from implanted to non-implanted region. Also, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation is performed. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present invention.
Referring to fig. 1, the present invention provides a method for manufacturing an acoustic resonator, including the following steps:
s102: a piezoelectric substrate is provided, the piezoelectric substrate comprising lithium niobate and/or lithium tantalate.
As shown in fig. 2, a piezoelectric substrate 202 is provided. Specifically, the piezoelectric substrate 202 may include lithium niobate and/or lithium tantalate. In one embodiment of the present application, the thickness of the piezoelectric substrate is brought to a desired thickness by subjecting the piezoelectric substrate to a grinding and polishing process. The thickness of the piezoelectric substrate is not limited, and can be set according to the requirement. Optionally, the thickness of the piezoelectric substrate is less than 1 micron. The roughness of the surface of the piezoelectric substrate can be reduced through polishing treatment, so that a bright and smooth piezoelectric substrate surface is obtained, and the formation of a subsequent layer structure is facilitated.
S104: and forming a bottom electrode layer on the first surface of the piezoelectric substrate.
As shown in fig. 3, a bottom electrode layer 302 is formed on the first surface of the piezoelectric substrate 202. The bottom electrode layer 302 may have a single-layer structure or a multi-layer structure. Optionally, the bottom electrode layer 302 may include one or more of molybdenum, tungsten, ruthenium, platinum, titanium, aluminum copper, aluminum silicon copper, chromium.
S106: forming an acoustic mirror on the bottom electrode layer; the acoustic mirror comprises at least one first acoustic reflection layer and at least one second acoustic reflection layer, the acoustic impedance of each first acoustic reflection layer is smaller than that of each second acoustic reflection layer, and the first acoustic reflection layers and the second acoustic reflection layers are alternately stacked and are closest to the bottom electrode layer.
As shown in FIG. 4, an acoustic mirror 402 is formed on the bottom electrode layer 302. Specifically, the acoustic mirror 402 includes at least one first acoustic reflective layer and at least one second acoustic reflective layer, where acoustic impedance of each first acoustic reflective layer is smaller than acoustic impedance of each second acoustic reflective layer, and the first acoustic reflective layer and the second acoustic reflective layer are alternately stacked and closest to the bottom electrode layer 302 are the first acoustic reflective layers.
With continued reference to fig. 4, in an alternative embodiment of the present application, the acoustic mirror 402 includes two first acoustic reflective layers (first acoustic reflective layer 404, first acoustic reflective layer 406) and a second acoustic reflective layer (second acoustic reflective layer 408). The first acoustic reflective layer 404 is disposed on the bottom electrode layer 302, the second acoustic reflective layer 408 is disposed on the first acoustic reflective layer 404, and the first acoustic reflective layer 406 is disposed on the second acoustic reflective layer 408. Where the acoustic impedances of the first acoustic reflective layer 404 and the second acoustic reflective layer 406 are each less than the acoustic impedance of the second acoustic reflective layer 408. It will be appreciated that the acoustic mirror described above may also take other forms, and is not limited to the forms already mentioned in the above embodiments. Alternatively, the number of layers of the acoustic mirror may be set as desired. Alternatively, the number of layers of the acoustic mirror may be 2 to 7.
S108: and bonding a bearing wafer on the first surface of the acoustic mirror, wherein the first surface of the acoustic mirror is the surface which is far away from the bottom electrode.
As shown in fig. 5, a carrier wafer 504 is bonded to the first surface of the acoustic mirror 402. In particular, the first surface of the acoustic mirror is the side facing away from the bottom electrode. Referring to fig. 5, a first surface of the acoustic mirror 402 is an upper surface of the first reflective layer 404. Specifically, the first surface of the acoustic mirror 402 and the bonding surface of the carrier wafer 404 are bonded as a single piece. Optionally, the carrier wafer may include one or more of silicon, sapphire, and quartz.
S110: and forming an upper electrode layer on the second surface of the piezoelectric substrate.
In an alternative embodiment of the present application, before step S110, the second surface of the piezoelectric substrate 202 is ground to reduce the thickness of the piezoelectric substrate 202 to a desired thickness. Optionally, the thickness of the piezoelectric substrate after grinding is less than 1 micron. As shown in fig. 6, an upper electrode layer 602 is formed on the second surface of the piezoelectric substrate 202. In an alternative embodiment of the present application, a conductive layer is formed on a piezoelectric substrate by a sputtering technique or the like, and then an upper electrode layer is formed by patterning.
Referring to fig. 7, an exemplary technical process of forming an upper electrode layer on a second surface of a piezoelectric substrate according to an embodiment of the present disclosure is shown, and as shown in fig. 7, the technical process may include the following steps:
s702: a first electrode layer is deposited.
As shown in fig. 8, a first electrode layer 802 is deposited on the second surface of the piezoelectric substrate 202. The first electrode layer is made of a metal material. Optionally, the first electrode layer comprises at least one of aluminum, titanium, chromium, molybdenum, tungsten, copper, aluminum silicon copper alloy (AlSiCu), or any other alloy of these materials.
S704: the first electrode layer is patterned.
As shown in fig. 9, the first electrode layer is patterned to form a patterned first electrode layer 902. The first electrode layer 902 includes an in-plane lateral reflective grating and interdigitated electrodes for driving the resonator.
S706: and depositing a second electrode layer on the patterned first electrode layer, wherein the thickness of the second electrode layer is greater than that of the first electrode layer.
As shown in fig. 10, a second electrode layer 1002 is deposited on the patterned first electrode layer 902, and the thickness of the second electrode layer 1002 is greater than that of the first electrode layer 902. Specifically, a second electrode layer 1002 is deposited and the second electrode layer 1002 is patterned to direct signals from the acoustic resonator to the pad. Optionally, the second electrode layer 1002 includes at least one of aluminum, titanium, chromium, molybdenum, tungsten, copper, aluminum silicon copper (AlSiCu), or any other alloy of these materials.
In an alternative embodiment of the present application, the structure formed by depositing and patterning the second electrode layer 1002 also includes the top of the bus bar region connecting all the interdigitated electrodes.
In an optional embodiment of the present application, step S706 may further include: and depositing a passivation layer on the first electrode layer.
As shown in fig. 11, a passivation layer 1102 is deposited over the first electrode layer 902. Optionally, the passivation layer 1102 may include one of silicon dioxide and silicon nitride. In an alternative embodiment of the present application, a passivation layer 1102 is deposited over the first electrode layer 902 and the passivation layer 1102 is patterned to provide passivation and temperature compensation for the acoustic resonator, as shown in fig. 11.
The method for preparing the acoustic resonator provides a piezoelectric substrate comprising one of lithium niobate and lithium tantalate, and a first acoustic reflection layer is deposited on a bottom electrode layer, and the acoustic resonator prepared by the method for preparing the acoustic resonator can be excited into a thickness direction shear vibration mode by selecting a specific direction of the piezoelectric substrate, and can support high electromechanical coupling at a frequency of more than 3GHz because the acoustic resonator adopts a more excellent thickness direction shear vibration mode and selects a lithium niobate or lithium tantalate material capable of supporting the vibration mode.
The above embodiments describe the arrangement of the number of layers of the acoustic mirror, and the different thicknesses of the layers of the acoustic mirror also affect the performance of the acoustic resonator. In order to further improve the performance of the acoustic resonator, the following embodiments will briefly describe the setting of the thicknesses of the first and second acoustic reflective layers of the acoustic resonator.
Optionally, the thicknesses of the first acoustic reflection layers are equal, and the thicknesses of the second acoustic reflection layers are equal; optionally, the thickness of each first acoustic reflection layer gradually decreases from the bottom electrode layer to the direction of bearing the wafer, and the thickness of each second acoustic reflection layer gradually decreases from the bottom electrode layer to the direction of bearing the wafer; optionally, the thickness of the first acoustic reflection layer closest to the bottom electrode layer and the first acoustic reflection layer closest to the base electrode is greater than the thickness of the first acoustic reflection layer of the intermediate layer, and the thickness of the second acoustic reflection layer closest to the bottom electrode layer and the thickness of the second acoustic reflection layer closest to the base electrode are greater than the thickness of the second acoustic reflection layer of the intermediate layer.
It is to be understood that the thickness combination of the first acoustic reflection layers and the second acoustic reflection layers of the above acoustic mirror may also take other forms, and is not limited to the forms already mentioned in the above embodiments.
It is to be understood that the thickness relationship between the first acoustic reflection layer and the second acoustic reflection layer is not limited in the embodiments of the present application. Alternatively, the thickness relationship between the first acoustic reflective layer and the second acoustic reflective layer may be set according to the materials of the first acoustic reflective layer and the second acoustic reflective layer.
In an optional embodiment of the present application, the thickness of the first acoustic reflection layer of the acoustic mirror provided in the above embodiments gradually increases from the bottom electrode layer toward the direction of the carrier wafer; the thickness of each second acoustic reflection layer gradually increases from the bottom electrode layer to the direction of bearing the wafer. The acoustic mirror provided by the embodiment can realize the maximum quality factor under the same condition.
In an alternative embodiment of the present application, there is provided an exemplary "forming an acoustic mirror on a bottom electrode layer" process, the process comprising: three first acoustic reflection layers and two second acoustic reflection layers are formed.
Specifically, as shown in fig. 12, a second acoustic reflection layer 1204 is formed on the first acoustic reflection layer 1202, a first acoustic reflection layer 1206 is formed on the second acoustic reflection layer 1204, a second acoustic reflection layer 1208 is formed on the first acoustic reflection layer 1206, and a first acoustic reflection layer 1210 is formed on the second acoustic reflection layer 1208. The first surface of the acoustic mirror 1200 provided in this embodiment is an opposite surface of a contact surface of the first acoustic reflection layer 1210 and the second acoustic reflection layer 1208, which is beneficial to achieving bonding of the acoustic mirror 1200 and the carrier wafer.
Further, in an optional embodiment of the present application, there is provided a method for manufacturing an exemplary acoustic resonator, before the step of bonding the carrier wafer to the first surface of the acoustic mirror in the above embodiment, the following technical processes may be further included:
depositing an auxiliary layer on the first surface of the acoustic mirror; and/or
And depositing an auxiliary layer on the bonding surface of the bearing wafer.
In particular, an auxiliary layer is deposited on the first surface of the acoustic mirror and/or on the bonding face of the carrier wafer before bonding the first surface of the acoustic mirror and the bonding face of the carrier wafer. Optionally, the auxiliary layer provided in the above embodiments may be a silicon dioxide layer. Depositing the auxiliary layer on the first surface of the acoustic mirror and/or the bonding face of the carrier wafer may improve the growth quality of the subsequent layers and simplify the handling of the subsequent layers. It should be noted that the thickness and material of the auxiliary layer are not limited in the present application as long as the auxiliary layer can achieve the functions of improving the growth quality of the subsequent layers and simplifying the processing of the subsequent layers.
In order to improve the practicability of the acoustic resonator, it is necessary to arrange an electrical structure on the acoustic resonator, and then the following embodiments will provide a method for manufacturing the acoustic resonator to manufacture the acoustic resonator which is beneficial to the arrangement of the electrical structure.
Referring to fig. 13, as shown in fig. 13, the method for manufacturing an acoustic resonator according to the foregoing embodiment may further include, before the step of bonding a carrier wafer to the first surface of the acoustic mirror:
s1302: the bottom electrode layer and the acoustic mirror are etched.
Optionally, the bottom electrode layer and the acoustic mirror are etched simultaneously, so that all layer structures comprised by the bottom electrode layer and the acoustic mirror have similar lateral dimensions (the etched bottom electrode layer 1402 and acoustic mirror 1404 are shown in fig. 14 a) to simplify the etching operation. Alternatively, only the bottom electrode layer and the second acoustic reflective layer are etched. Optionally, the structure formed after etching the bottom electrode layer and the second acoustic reflection layer is: the lateral dimensions of each etched second acoustic reflective layer gradually increase from the bottom electrode layer toward the carrier wafer (the etched bottom electrode layer 1406 and the second acoustic reflective layer 1408 are shown in fig. 14 b), or the lateral dimensions of each etched second acoustic reflective layer gradually decrease from the bottom electrode layer toward the carrier wafer (the etched bottom electrode layer 1410 and the second acoustic reflective layer 1412 are shown in fig. 14 c).
S1304: and depositing a filling layer on the piezoelectric substrate, and filling the positions where the bottom electrode layer and the acoustic mirror are etched and removed.
Specifically, the bottom electrode layer and the etched area of the acoustic mirror are formed through the above step S1302, and the filling layer is deposited in the area. It should be noted that the fill layer should comprise a material that is compatible with the process flow, i.e., the fill layer should comprise a material that does not react with other structures of the acoustic resonator, resulting in a change in the properties of the other structures.
Optionally, the fill layer may include one or more of silicon dioxide, molybdenum, tungsten oxide, or silicon nitride. In an alternative embodiment of the present application, the material of the filling layer is the same as the material of each first acoustic reflection layer, which improves the quality factor of the acoustic resonator.
The above embodiments provide an auxiliary layer material that facilitates the arrangement of the electrical structure. Furthermore, a filling layer is deposited in the etching area, so that the flatness of the acoustic resonator is improved.
Referring to fig. 15, a method for manufacturing an exemplary acoustic resonator according to an embodiment of the present application is shown, where after the step of "forming a bottom electrode layer on the first surface of the piezoelectric substrate" in the above embodiment, before the step of "bonding a carrier wafer on the first surface of the acoustic mirror", the following technical processes may be further included:
s1502: and etching the bottom electrode layer.
It can be understood that the etching position and the etching area of the bottom electrode layer are not limited in the present application, and can be limited as required as long as the bottom electrode layer formed by etching does not affect the performance of the acoustic resonator.
S1504: and depositing a filling material at the position where the bottom electrode layer is etched and removed to form a bottom electrode filling layer.
As shown in FIG. 16, a filling material is deposited at the position where the bottom electrode layer is etched away to form a bottom electrode filling layer 1602. It should be noted that the filling material should be compatible with the process flow, i.e. the filling material does not react with other structures of the acoustic resonator, resulting in changes of the properties of the other structures.
Optionally, the fill material may include one or more of silicon dioxide, molybdenum, tungsten oxide, or silicon nitride. In an alternative embodiment of the present application, the filling material is the same as the material of the respective first acoustic reflection layer, improving the quality factor of the acoustic resonator.
S1506: and depositing a low-acoustic-impedance material on the bottom electrode filling layer to form a first acoustic reflection layer.
As shown in FIG. 16, a first acoustic reflective layer 1604 is formed by depositing a low acoustic impedance material on the bottom electrode fill layer 1602. Alternatively, the low acoustic impedance material may include at least one of silicon dioxide, aluminum, Benzocyclobutene (BCB), polyimide (polyimide), and spin on glass (spin on glass).
S1508: a second acoustically reflective layer is formed by depositing a high acoustic impedance material on the first acoustically reflective layer.
Alternatively, the high acoustic impedance material may include at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide, and silicon nitride.
S1510: the second acoustic reflection layer is etched.
It can be understood that the etching position and the etching area of the second acoustic reflection layer are not limited in the present application, and can be limited as needed as long as the bottom second acoustic reflection layer formed by etching does not affect the performance of the acoustic resonator.
S1512: and depositing a filling material at the position where the second acoustic reflection layer is etched and removed to form a second acoustic reflection filling layer.
As shown in fig. 16, a second acoustic reflection filling layer 1606 is formed by depositing a filling material at the position where the second acoustic reflection layer is etched away. Note that the second acoustic reflection fill layer 1606 includes a structure formed by depositing a fill material at the etched second acoustic reflection layer and the etched location where the second acoustic reflection layer is removed.
S1514: and sequentially and alternately forming a first acoustic reflection layer and a second acoustic reflection filling layer at intervals.
As shown in fig. 16, the acoustic resonator 1600 is alternately formed with two first acoustic reflection layers (first acoustic reflection layer 1604 and first acoustic reflection layer 1608) and two second acoustic reflection filling layers (second acoustic reflection filling layer 1606 and second acoustic reflection filling layer 1610) in this order.
It should be noted that, in the embodiments of the present application, the number of the first acoustic reflection layer and the second acoustic reflection filling layer is not limited, as long as the first acoustic reflection layer and the second acoustic reflection filling layer are sequentially stacked.
According to the preparation method of the acoustic resonator provided by the embodiment, the low-acoustic-resistance material is deposited to form the first acoustic reflection layer after the bottom electrode is etched and filled, and the low-acoustic-resistance material is deposited to form the first acoustic reflection layer after the second acoustic reflection layer is etched and filled, so that the preparation is simple. Furthermore, the acoustic resonator prepared by the preparation method of the acoustic resonator provided by the embodiment has higher flatness.
Referring to fig. 17, which illustrates a method for manufacturing an acoustic resonator according to an embodiment of the present application, as shown in fig. 17, the method for manufacturing an acoustic resonator may include:
s1702: a piezoelectric substrate is provided.
Specifically, the piezoelectric substrate includes lithium niobate and/or lithium tantalate.
S1704: and depositing an electrode material on the first surface of the piezoelectric substrate and etching to form a bottom electrode layer.
Optionally, the electrode material may comprise one or more of molybdenum, tungsten, ruthenium, platinum, titanium, aluminum copper, aluminum silicon copper, chromium.
S1706: a low acoustic impedance material is deposited to form a first acoustic reflective layer.
S1708: a high acoustic impedance material is deposited over the low acoustic impedance material.
S1710: the deposited high acoustic impedance material is etched to form a second acoustic reflective layer.
S1712: s1706 to S1710 are repeated until a desired number of layers of the first acoustic reflective layer and the second acoustic reflective layer are formed.
It should be explained that S1706 to S1710 are repeated until the desired number of layers of the first acoustic reflection layer and the second acoustic reflection layer are formed, and it is not necessary to form the acoustic mirror with the period of S1706 to S1710, that is, the first surface of the acoustic mirror may be a surface of the first acoustic reflection layer or a surface of the second acoustic reflection layer. It should be noted that the first acoustic reflective layer and the second acoustic reflective layer may be provided as needed. Optionally, the low acoustic impedance material may include at least one of silicon dioxide, aluminum, Benzocyclobutene (BCB), polyimide (polyimide), and spin on glass (spin on glass), and optionally, the high acoustic impedance material may include at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide, and silicon nitride.
S1714: and depositing a filling layer on the piezoelectric substrate, and filling the positions where the bottom electrode layer and the acoustic mirror are etched and removed.
S1716: and bonding a bearing wafer on the first surface of the acoustic mirror.
In particular, the first surface of the acoustic mirror is the side facing away from the bottom electrode.
S1718: and thinning the piezoelectric substrate to form a piezoelectric film.
S1720: and forming an upper electrode layer on the second surface of the piezoelectric film.
Referring to fig. 18, which illustrates a method for manufacturing an acoustic resonator according to an embodiment of the present application, as shown in fig. 18, the method for manufacturing an acoustic resonator may include:
s102: a piezoelectric substrate is provided, the piezoelectric substrate comprising lithium niobate and/or lithium tantalate.
S104: and forming a bottom electrode layer on the first surface of the piezoelectric substrate.
S1502: and etching the bottom electrode layer.
S1504: and depositing a filling material at the position where the bottom electrode layer is etched and removed to form a bottom electrode filling layer.
S1506: and depositing a low-acoustic-impedance material on the bottom electrode filling layer to form a first acoustic reflection layer.
S1508: a second acoustically reflective layer is formed by depositing a high acoustic impedance material on the first acoustically reflective layer.
S1510: the second acoustic reflection layer is etched.
S1512: and depositing a filling material at the position where the second acoustic reflection layer is etched and removed to form a second acoustic impedance filling layer.
S1514: and sequentially and alternately forming a first acoustic reflection layer and a second acoustic reflection filling layer at intervals.
S1716: a substrate is bonded to the first surface of the acoustic mirror.
In particular, the first surface of the acoustic mirror is the side facing away from the bottom electrode.
S1718: and thinning the piezoelectric substrate to form a piezoelectric film.
S1720: and forming an upper electrode layer on the second surface of the piezoelectric film.
It should be understood that, although the individual steps in the flowcharts of fig. 1, 7, 13, 15, and 17-18 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1, 7, 13, 15, and 17-18 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least some of the other steps.
Referring to fig. 19, an embodiment of the present application further provides an acoustic resonator, including: an acoustic mirror 402, a bottom electrode layer 302, a piezoelectric substrate 202, and an upper electrode layer 602.
Specifically, the acoustic mirror 402 includes at least one first acoustic reflective layer and at least one second acoustic reflective layer, and the acoustic impedance of each first acoustic reflective layer is smaller than the acoustic impedance of each second acoustic reflective layer. With continued reference to fig. 19, the acoustic mirror 402 optionally includes a first acoustic reflective layer 404, a second acoustic reflective layer 408, and a first acoustic reflective layer 406.
Specifically, the bottom electrode layer 302 is positioned on the acoustic mirror 402, with one of the first acoustic reflective layers of the acoustic mirror 402 being closer to the bottom electrode layer 302 than all of the second acoustic reflective layers. For example, referring to fig. 19, the first acoustic reflective layer 404 is closer to the bottom electrode layer than the second acoustic reflective layer 408.
Specifically, the piezoelectric substrate 202 is located on the bottom electrode layer 302. Specifically, the piezoelectric substrate 202 includes lithium niobate and/or lithium tantalate. The upper electrode layer 602 is located on the piezoelectric substrate 202.
The descriptions of the acoustic mirror, the bottom electrode layer, the piezoelectric substrate, and the top electrode layer are given in detail in the above embodiments, and are not repeated here.
The acoustic resonator provided by the embodiment of the application sequentially comprises an acoustic mirror, a bottom electrode layer, a piezoelectric substrate and an upper electrode layer, wherein the piezoelectric substrate comprises lithium niobate and/or lithium tantalate, the first acoustic reflection layer is located above the bottom electrode layer, and the acoustic resonator can be excited into a thickness direction shear vibration mode by selecting a specific direction of the piezoelectric substrate.
Further, the acoustic resonator provided by the above embodiment may use a single crystal material to reduce attenuation of acoustic waves and improve quality factor of the acoustic resonator. An acoustic resonator is obtained that is capable of supporting high electromechanical coupling and a high quality factor at frequencies above 3 GHz.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features of the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for manufacturing an acoustic resonator, comprising the steps of:
providing a piezoelectric substrate comprising lithium niobate and/or lithium tantalate;
forming a bottom electrode layer on the first surface of the piezoelectric substrate;
forming an acoustic mirror on the bottom electrode layer; the acoustic mirror comprises at least one first acoustic reflection layer and at least one second acoustic reflection layer, the acoustic impedance of each first acoustic reflection layer is smaller than that of each second acoustic reflection layer, and the first acoustic reflection layers and the second acoustic reflection layers are alternately stacked and are closest to the bottom electrode layer;
bonding a bearing wafer on the first surface of the acoustic mirror, wherein the first surface of the acoustic mirror is a surface deviating from the bottom electrode;
and forming an upper electrode layer on the second surface of the piezoelectric substrate.
2. The method of claim 1, wherein forming the acoustic mirror on the bottom electrode layer comprises forming three first acoustic reflective layers and two second acoustic reflective layers.
3. The method of claim 2, wherein the step of bonding a carrier wafer to the first surface of the acoustic mirror is preceded by:
depositing an auxiliary layer on the first surface of the acoustic mirror; and/or
And depositing an auxiliary layer on the bonding surface of the bearing wafer.
4. The method according to claim 1, wherein the thickness of each first acoustic reflection layer gradually increases from the bottom electrode layer to the direction of the carrier wafer; the thickness of each second acoustic reflection layer gradually increases from the bottom electrode layer to the direction of the bearing wafer.
5. The method of claim 1, wherein the step of bonding a carrier wafer to the first surface of the acoustic mirror is preceded by:
etching the bottom electrode layer and the acoustic mirror;
and depositing a filling layer on the piezoelectric substrate, and filling the positions of the bottom electrode layer and the acoustic mirror which are etched and removed.
6. The method of claim 5, wherein the step of forming the bottom electrode layer on the first surface of the piezoelectric substrate and the step of bonding the carrier wafer on the first surface of the acoustic mirror comprise:
etching the bottom electrode layer;
depositing a filling material at the position where the bottom electrode layer is etched and removed to form a bottom electrode filling layer;
depositing a low-acoustic-impedance material on the bottom electrode filling layer to form a first acoustic reflection layer;
depositing a high acoustic impedance material on the first acoustic reflective layer to form a second acoustic reflective layer;
etching the second acoustic reflection layer;
depositing a filling material at the position where the second acoustic reflection layer is etched and removed to form a second acoustic impedance filling layer;
and sequentially and alternately forming the first acoustic reflection layer and the second acoustic reflection filling layer at intervals.
7. The method of claim 5, wherein the filler layer is the same material as each first acoustic reflective layer.
8. The method of claim 1, wherein forming a bottom electrode layer on the first surface of the piezoelectric substrate comprises: depositing an electrode material on the first surface of the piezoelectric substrate and etching to form the bottom electrode layer;
said forming an acoustic mirror on said bottom electrode layer comprises:
step A, depositing a low acoustic impedance material to form a first acoustic reflection layer;
step B, depositing a high acoustic impedance material on the low acoustic impedance material;
step C, etching the deposited high-acoustic-impedance material to form a second acoustic reflection layer;
repeating step A, B, C until a desired number of layers of first and second acoustic reflective layers are formed;
after the step of forming the acoustic mirror on the bottom electrode layer and before the step of bonding the bearing wafer on the first surface of the acoustic mirror, depositing a filling layer on the piezoelectric substrate, and filling the positions where the bottom electrode layer and the acoustic mirror are etched and removed;
wherein the low acoustic impedance material comprises at least one of silicon dioxide, aluminum, benzocyclobutene, polyimide, and spin-on glass, and the high acoustic impedance material comprises at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide, and silicon nitride.
9. The method of claim 1, wherein the forming an upper electrode layer on the second surface of the piezoelectric substrate comprises:
depositing a first electrode layer;
patterning the first electrode layer;
and depositing a second electrode layer on the patterned first electrode layer, wherein the thickness of the second electrode layer is greater than that of the first electrode layer.
10. An acoustic resonator, comprising:
the acoustic mirror comprises at least one first acoustic reflection layer and at least one second acoustic reflection layer, and the acoustic impedance of each first acoustic reflection layer is smaller than that of each second acoustic reflection layer;
the bottom electrode layer is positioned on the acoustic mirror, and a first sound reflecting layer of the acoustic mirror is closer to the bottom electrode layer than all second sound reflecting layers;
the piezoelectric substrate is positioned on the surface, which is far away from the acoustic mirror, of the bottom electrode layer, and the piezoelectric layer comprises lithium niobate and/or lithium tantalate;
and the upper electrode layer is positioned on one surface of the piezoelectric substrate, which is deviated from the bottom electrode layer.
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| PCT/CN2021/092031 WO2022193419A1 (en) | 2021-03-15 | 2021-05-07 | Preparation method for acoustic resonator, and acoustic resonator |
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| US9099983B2 (en) * | 2011-02-28 | 2015-08-04 | Avago Technologies General Ip (Singapore) Pte. Ltd. | Bulk acoustic wave resonator device comprising a bridge in an acoustic reflector |
| DE102018107496B3 (en) * | 2018-03-28 | 2019-07-11 | RF360 Europe GmbH | Volumetric wave resonator device and method for its production |
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