CN111030631A - Method for manufacturing acoustic wave device and acoustic wave device - Google Patents

Method for manufacturing acoustic wave device and acoustic wave device Download PDF

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CN111030631A
CN111030631A CN201911370470.6A CN201911370470A CN111030631A CN 111030631 A CN111030631 A CN 111030631A CN 201911370470 A CN201911370470 A CN 201911370470A CN 111030631 A CN111030631 A CN 111030631A
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electrode layer
layer
substrate
cavity
acoustic wave
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CN111030631B (en
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廖珮淳
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Wuhan Yanxi Micro Devices Co ltd
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Wuhan Yanxi Micro Devices Co ltd
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    • 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
    • H03H9/02007—Details of bulk acoustic wave devices

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  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

The embodiment of the disclosure discloses a manufacturing method of an acoustic wave device and the acoustic wave device, wherein the manufacturing method comprises the following steps: forming a first electrode layer covering the first reflective structure; forming a protective layer covering the first electrode layer and the second reflective structure; the second reflecting structure and the first reflecting structure are arranged on the substrate in parallel, the first reflecting structure is positioned in a first area of the substrate, and the second reflecting structure is positioned in a second area of the substrate; forming a second electrode layer covering the protective layer; wherein a thickness of the second electrode layer is different from a thickness of the first electrode layer; and removing the protective layer and the second electrode layer above the first electrode layer until the first electrode layer is exposed and covered.

Description

Method for manufacturing acoustic wave device and acoustic wave device
Technical Field
The embodiment of the disclosure relates to the technical field of acoustic wave devices, in particular to a manufacturing method of an acoustic wave device and the acoustic wave device.
Background
With the development of communication, the application of acoustic wave devices in communication is wider and wider, and the performance of the acoustic wave devices directly affects the transmission quality of communication signals.
With the development of thin film and micro-nano manufacturing technology, electronic devices are rapidly developed in the direction of miniaturization and high-density multiplexing. Therefore, how to expand the application range of the acoustic wave device while ensuring the quality of the acoustic wave device becomes an urgent problem to be solved.
Disclosure of Invention
In view of this, the embodiments of the present disclosure provide a method for manufacturing an acoustic wave device and an acoustic wave device.
According to a first aspect of the embodiments of the present disclosure, there is provided a method of manufacturing an acoustic wave device, including:
forming a first electrode layer covering the first reflective structure;
forming a protective layer covering the first electrode layer and the second reflective structure; the second reflecting structure and the first reflecting structure are arranged on the substrate in parallel, the first reflecting structure is positioned in a first area of the substrate, and the second reflecting structure is positioned in a second area of the substrate;
forming a second electrode layer covering the protective layer; wherein a thickness of the second electrode layer is different from a thickness of the first electrode layer;
and removing the protective layer and the second electrode layer above the first electrode layer until the first electrode layer is exposed.
Optionally, the forming a first electrode layer covering the first reflective structure includes:
forming the first electrode layer covering the first region on the first surface of the substrate; forming a first cavity penetrating through the substrate from the second surface of the substrate until the first electrode layer is exposed; wherein the first surface of the substrate and the second surface of the substrate are opposite, and the first reflective structure comprises the first cavity;
the forming a protective layer covering the first electrode layer and the second reflective structure includes:
forming the protective layer covering the first electrode layer and the second region on the first surface of the substrate; forming a second cavity penetrating through the substrate from the second surface of the substrate until the protective layer is exposed; wherein the second reflective structure comprises the second cavity.
Optionally, the method further comprises:
forming the first and second reflective structures on the surface of the substrate; wherein the first and second reflective structures each comprise: the first dielectric layers and the second dielectric layers are alternately stacked; and the acoustic impedance of the first dielectric layer is different from that of the second dielectric layer.
Optionally, the method further comprises:
forming a first sacrificial layer and a second sacrificial layer which are arranged in parallel on the surface of the substrate; the first sacrificial layer covers a first area of the substrate, the first reflecting structure comprises a third cavity formed based on the appearance of the first sacrificial layer after the first sacrificial layer is removed, the second sacrificial layer covers a second area of the substrate, and the second reflecting structure comprises a fourth cavity formed based on the appearance of the second sacrificial layer after the second sacrificial layer is removed and having a first height.
Optionally, the method further comprises:
removing the protective layer between the second electrode layer and the second region to form a fourth cavity with a second height based on the morphology of the protective layer between the second electrode layer and the second region and the fourth cavity with the first height; wherein the second height is greater than the first height.
According to a second aspect of the embodiments of the present disclosure, there is provided an acoustic wave device including:
a substrate;
a first reflective structure located in a first region of the substrate;
the second reflecting structure is arranged in parallel with the first reflecting structure and is positioned in a second area of the substrate;
a first electrode layer covering the first reflective structure;
a second electrode layer covering the first reflective structure; wherein a thickness of the second electrode layer is different from a thickness of the first electrode layer.
Optionally, the acoustic wave device further comprises: a protective layer between the second reflective structure and the second electrode layer.
Optionally, the first reflective structure comprises: a first cavity extending through the substrate;
the second reflective structure includes: a second cavity extending through the substrate.
Optionally, the first reflective structure comprises: the first dielectric layers and the second dielectric layers are alternately stacked; the acoustic impedance of the first dielectric layer is different from that of the second dielectric layer;
the second reflective structure includes: the first dielectric layers and the second dielectric layers are alternately stacked.
Optionally, the first reflective structure comprises: a third cavity between the first electrode layer and the first region of the substrate;
the second reflective structure includes: a fourth cavity between the second electrode layer and the second region of the substrate.
Optionally, the height of the third cavity is different from the height of the fourth cavity.
Optionally, the acoustic wave device is a bulk acoustic wave filter.
In the embodiment of the disclosure, the first electrode layer covering the first reflection structure is formed on the same substrate on which the first reflection structure and the second reflection structure are formed and arranged in parallel, and the second electrode layer covering the second reflection structure is formed, wherein the thickness of the second electrode layer can be different from that of the first electrode layer, so that electrode layers with different thicknesses can be formed on the same substrate. And, through forming the protective layer, can protect the first electrode layer when forming the second electrode layer, guarantee device quality.
Drawings
Fig. 1 is a flow chart illustrating a method of fabricating an acoustic wave device according to an exemplary embodiment.
Fig. 2a to 2i are partial schematic views illustrating a method of fabricating an acoustic wave device according to an example.
Fig. 3a to 3d are partial schematic views illustrating another method of fabricating an acoustic wave device according to an example.
Fig. 4 is a partial top view of an acoustic wave device shown in accordance with an exemplary embodiment.
Fig. 5 is a partial schematic view of an acoustic wave device shown in accordance with an exemplary embodiment.
Fig. 6 is a partial schematic view of another acoustic wave device shown in accordance with an exemplary embodiment.
Fig. 7 is a partial schematic view of yet another acoustic wave device shown in accordance with an exemplary embodiment.
Detailed Description
The technical solutions of the present disclosure will be further explained in detail with reference to the drawings and examples. While exemplary implementations of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The present disclosure is more particularly described in the following paragraphs with reference to the accompanying drawings by way of example. Advantages and features of the present disclosure will become apparent from the following description and claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present disclosure.
In the disclosed embodiment, the term "a is connected to B" includes A, B where a is connected to B in contact with each other, or A, B where a is connected to B in a non-contact manner with other components interposed between the two.
In the embodiments of the present disclosure, the terms "first", "second", and the like are used for distinguishing similar objects, and are not necessarily used for describing a particular order or sequence.
The technical means described in the embodiments of the present disclosure may be arbitrarily combined without conflict.
Fig. 1 is a flow chart illustrating a method of fabricating an acoustic wave device according to an exemplary embodiment. Referring to fig. 1, the method includes the steps of:
s110: forming a first electrode layer covering the first reflective structure;
s120: forming a protective layer covering the first electrode layer and the second reflective structure; the second reflecting structure and the first reflecting structure are arranged on the substrate in parallel, the first reflecting structure is positioned in a first area of the substrate, and the second reflecting structure is positioned in a second area of the substrate;
s130: forming a second electrode layer covering the protective layer; the thickness of the second electrode layer is different from that of the first electrode layer.
Wherein a difference between the thickness of the first electrode layer and the thickness of the second electrode layer may be greater than or equal to 0.5 nm. For example, the difference between the thickness of the first electrode layer and the thickness of the second electrode layer may be: 0.5nm, 1nm, or 1.5nm, etc.
S140: and removing the protective layer and the second electrode layer above the first electrode layer until the first electrode layer is exposed.
The first reflecting structure and the second reflecting structure are both structures capable of reflecting sound waves transmitted by the sound wave device. For example, the first and second reflective structures may include: a cavity or a bragg reflector structure, etc. Here, the bragg reflection structure is formed by laminating two dielectric materials having different acoustic impedances.
In some embodiments, the first and second reflective structures may comprise the same structure, e.g., both the first and second reflective structures comprise a cavity. In some embodiments, the first reflective structure and the second reflective structure may comprise different structures, for example, the first reflective structure may comprise a cavity and the second reflective structure comprises a bragg reflective structure.
The constituent materials of the first electrode layer and the second electrode layer may include: a material having electrically conductive properties. For example, metals such as molybdenum (Mo) and tungsten (W). The first electrode layer and the second electrode layer are bottom electrodes of different resonators on the acoustic wave device, respectively. The method of forming the first electrode layer and the second electrode layer may include: physical vapor deposition, or the like.
The constituent materials of the protective layer may include: an oxide or a nitride. For example, silicon oxide or silicon nitride.
In S130, after forming the second electrode layer, the first reflective structure, the first electrode layer, the protective layer and the second electrode layer above the first reflective structure form a first overlapping region; the second reflection structure, the protective layer and the second electrode layer form a second overlapped area.
In S140, a Photo Resist (PR) covering the second overlap region and exposing the first overlap region may be formed by photolithography, and the PR is used to protect the second electrode layer in the second overlap region. The second electrode layer located in the first overlap region is then removed by an etching (Etch) process. When the second electrode layer in the first overlapping region is removed, the photoresist covers the second electrode layer in the second overlapping region, so that the second electrode layer in the second overlapping region is not removed.
In S140, after removing the second electrode layer over the first electrode layer, that is, after removing the second electrode layer located in the first overlapping region, the protective layer covering the first electrode layer is exposed in the first overlapping region. At this time, the photoresist covering the second overlap region is removed, and the passivation layer of the second overlap region is located under the second electrode layer. Therefore, the protective layer exposed in the first overlap region can be removed directly by an etching process by selecting an etchant that reacts with the protective layer but does not react with the first electrode layer and the second electrode layer, and a barrier layer for protecting the second electrode layer in the second overlap region does not need to be formed by a photolithography process. Therefore, the quality of the first electrode layer and the second electrode layer is guaranteed, meanwhile, the process steps are reduced, the process cost is reduced, and the production efficiency is improved.
Illustratively, when the constituent material of the protective layer is silicon oxide and the material of the first electrode layer and the second electrode layer is molybdenum, Hydrogen Fluoride (HF) may be selected as an etchant to remove the protective layer covering the first electrode layer in the first overlap region by an etching process.
In the embodiment of the disclosure, the first electrode layer covering the first reflection structure is formed on the same substrate on which the first reflection structure and the second reflection structure are formed in parallel, and the second electrode layer covering the second reflection structure is formed, wherein the thickness of the second electrode layer can be different from that of the first electrode layer, so that electrode layers with different thicknesses can be formed on the same substrate. And, through forming above-mentioned protective layer, can protect the first electrode layer when forming the second electrode layer, guarantee the quality of the device.
In some embodiments, an acoustic wave device can include: a back cavity type film bulk acoustic resonator. At this time, S110 may include: forming a first electrode layer covering the first region on the first surface of the substrate; forming a first cavity penetrating through the substrate from the second surface of the substrate until the first electrode layer is exposed; the first surface of the substrate and the second surface of the substrate are opposite, and the first reflecting structure comprises a first cavity;
s120 may include: forming a protective layer covering the first electrode layer and the second region on the first surface of the substrate; forming a second cavity penetrating through the substrate from the second surface of the substrate until the protective layer is exposed; wherein the second reflective structure comprises a second cavity.
Prior to forming the first and second cavities, the method further comprises: a piezoelectric layer and a third electrode layer are formed on the first electrode layer and the second electrode layer, respectively. After forming the piezoelectric layer and the third electrode layer, a first cavity and a second cavity are formed from the second surface of the substrate, respectively.
Compared with the first cavity and the second cavity which are formed first and then the piezoelectric layer and the third electrode layer are formed, in the embodiment, the piezoelectric layer and the third electrode layer are formed on the first surface of the substrate first and then the first cavity and the second cavity are formed on the second surface of the substrate, so that the mechanical hardness of the substrate formed with the first electrode layer and the second electrode layer can be improved, the influence of the process of forming the first cavity and the second cavity on the first electrode layer and the second electrode layer is reduced, and the quality of the acoustic wave device is ensured.
In some embodiments, an acoustic wave device can include: solid state assembled resonators (SMR). The method further comprises the following steps:
forming a first reflecting structure and a second reflecting structure on the surface of a substrate; wherein, first reflecting structure and second reflecting structure all include: the first dielectric layers and the second dielectric layers are alternately stacked; the acoustic impedance of the first dielectric layer is different from the acoustic impedance of the second dielectric layer.
The first dielectric layers and the second dielectric layers with different acoustic resistances are alternately stacked to form a Bragg reflection structure.
Illustratively, the acoustic resistance of the first dielectric layer may be greater than the acoustic resistance of the second dielectric layer. At this time, the composition material of the first dielectric layer 1311 may include: molybdenum or tungsten; the composition material of the second dielectric layer may include: silicon dioxide (SiO)2) Or aluminum.
Illustratively, the acoustic impedance of the first dielectric layer may be less than the acoustic impedance of the second dielectric layer. At this time, the composition material of the first dielectric layer may include: silicon dioxide or aluminum; the composition material of the second dielectric layer may include: molybdenum or tungsten.
In some embodiments, an acoustic wave device can include: a Film Bulk Acoustic Resonator (FBAR) of the cavity type. The method further comprises the following steps:
forming a first sacrificial layer and a second sacrificial layer which are arranged in parallel on the surface of a substrate; the first sacrificial layer covers a first area of the substrate, the first reflecting structure comprises a third cavity formed based on the appearance of the first sacrificial layer after the first sacrificial layer is removed, the second sacrificial layer covers a second area of the substrate, and the second reflecting structure comprises a fourth cavity with a first height formed based on the appearance of the second sacrificial layer after the second sacrificial layer is removed.
S110 may include: forming a first electrode layer on at least a portion of the first sacrificial layer; removing the first sacrificial layer between the first electrode layer and the substrate to form a third cavity between the first electrode layer and the substrate; wherein the first reflective structure comprises a third cavity;
s120 may include:
forming a protective layer on the first electrode layer and the second sacrificial layer; removing the second sacrificial layer to form a fourth cavity having the first height between the protective layer and the substrate; wherein the second reflective structure comprises a fourth cavity having the first height.
The material of the first sacrificial layer and the second sacrificial layer may be a silicide, such as silicon dioxide. The thicknesses of the first sacrificial layer and the second sacrificial layer may be designed according to the actual requirements of the acoustic wave device. For example, the first sacrificial layer and the second sacrificial layer may have a thickness of 0.1 to 5 micrometers.
Illustratively, the first sacrificial layer and the second sacrificial layer may be formed on the substrate by means of chemical vapor deposition. Taking the example that the constituent material of the first sacrificial layer and the second sacrificial layer is silicon dioxide, silicon dioxide can be generated by the reaction of silane and oxygen. The generated silicon dioxide is deposited on the surface of the substrate, and then a first sacrificial layer is formed on a first area of the surface of the substrate through a photolithography and etching technology, and a second sacrificial layer is formed on a second area of the surface of the substrate.
In step S140, a photoresist for protecting the second electrode layer covering the second sacrificial layer may be formed on the second electrode layer covering the second sacrificial layer by a photolithography process. And then removing the second electrode layer positioned above the first electrode layer by a dry etching process. When the second electrode layer located above the first electrode layer is removed by dry etching, the second electrode layer covered by the photoresist is not removed by the dry etching process, that is, the second electrode layer located above the second sacrificial layer is not removed.
In step S140, after the second electrode layer located above the first electrode layer is removed, the protection layer covering the first electrode layer is exposed, and the protection layer covering the second sacrificial layer is located below the second electrode layer. At this time, the protective layer under the second electrode layer is covered by the second electrode layer, so that the exposed protective layer can be directly removed by an etching process by selecting an etchant which reacts with the protective layer but does not react with the first electrode layer and the second electrode layer, and a barrier layer for protecting the second electrode layer is not required to be formed by a photolithography process. Therefore, the quality of the first electrode layer and the second electrode layer is guaranteed, meanwhile, the process steps are reduced, the process cost is reduced, and the production efficiency is improved.
In the embodiment of the disclosure, the first sacrificial layer and the second sacrificial layer which are arranged in parallel are formed on the substrate of the same acoustic wave device, the first electrode layer is formed on the first sacrificial layer, and the second electrode layer is formed on the second sacrificial layer, wherein the thickness of the second electrode layer is different from that of the first electrode layer, so that the electrode layers with different thicknesses can be formed on the same substrate. And, through forming the protective layer, can protect the first electrode layer when forming the second electrode layer, guarantee device quality.
In some embodiments, after removing the second electrode layer and the protective layer covering the first electrode layer, the method further comprises: forming a first piezoelectric layer overlying the first electrode layer and a second piezoelectric layer overlying the second electrode layer; a third electrode layer is formed partially overlying the first piezoelectric layer and a fourth electrode layer is formed partially overlying the second piezoelectric layer.
In some embodiments, after removing the second electrode layer and the protective layer covering the first electrode layer, the method further comprises: forming a piezoelectric layer overlying the first electrode layer and the second electrode layer;
a third electrode layer partially covering the piezoelectric layer is formed in a region corresponding to the first electrode layer, and a fourth electrode layer partially covering the piezoelectric layer is formed in a region corresponding to the second electrode layer. At this time, the piezoelectric layer may be formed into a specific shape without photolithography development and etching techniques.
Wherein, the component materials of piezoelectric layer, first piezoelectric layer and second piezoelectric layer include: a material having a piezoelectric effect. For example, aluminum nitride (AlN), zinc oxide (ZnO) or lithium tantalate (LiTaO)3) And the like.
The composition material of the third electrode layer and the fourth electrode layer may be the same as that of the first electrode layer or the second electrode layer.
In some embodiments, when the acoustic wave device includes a cavity-type thin film bulk acoustic resonator, forming a first electrode layer on at least a portion of the first sacrificial layer includes: forming a first electrode layer in a middle region of the first sacrificial layer;
the method further comprises the following steps:
and forming a third through hole penetrating through the first piezoelectric layer and the edge area of the first sacrificial layer, removing the first sacrificial layer through etching of the third through hole, and forming a third cavity based on the appearance of the first sacrificial layer.
In step S110, a region where the first electrode layer needs to be deposited may be defined on the surface of the first sacrificial layer by photolithography. Specifically, a photoresist covering the edge region of the first sacrificial layer may be formed by photolithography, exposing the middle region of the first electrode layer. In this way, during the deposition of the first electrode layer, the material of the first electrode layer deposited toward the edge region of the first sacrificial layer adheres to the surface of the photoresist. Therefore, after the first electrode layer is deposited, the first electrode layer material only covers the middle area of the first sacrificial layer by removing the photoresist covering the edge area of the first sacrificial layer.
The third cavity is a resonant cavity of the first resonator with the first electrode layer as a bottom electrode.
According to the embodiment of the disclosure, the first electrode layer covering the middle area of the first sacrificial layer is formed, the third through hole penetrating through the edge areas of the first piezoelectric layer and the first sacrificial layer is formed, and the third electrode layer partially covering the first sacrificial layer and the first piezoelectric layer is formed.
In some embodiments, the method further comprises:
and forming a fourth through hole penetrating through the edge areas of the second piezoelectric layer and the second sacrificial layer, etching and removing the second sacrificial layer through the fourth through hole, and forming a fourth cavity with the first height based on the appearance of the second sacrificial layer. The fourth cavity is a resonant cavity of the second resonator with the second electrode layer as a bottom electrode.
In some embodiments, the method further comprises: removing the protective layer between the second electrode layer and the second region to form a fourth cavity with a second height based on the morphology of the protective layer between the second electrode layer and the second region and the fourth cavity with the first height; wherein the second height is greater than the first height.
The disclosed embodiments can reduce the influence of the protective layer on the operating frequency of the acoustic wave device by removing the protective layer.
Illustratively, the constituent material of the protective layer may be the same as that of the second sacrificial layer. Therefore, when the second sacrificial layer between the protective layer and the substrate is removed, the protective layer covering the second sacrificial layer can be removed at the same time to form a fourth cavity with a second height, that is, the protective layer and the second sacrificial layer can be removed at one time by using the same etchant, and compared with the situation that the materials of the protective layer and the second sacrificial layer are different, the second sacrificial layer and the protective layer are removed by using different etchants respectively.
It is easily understood that the height of the first cavity may be controlled by adjusting the thickness of the first sacrificial layer, and the height of the fourth cavity may be controlled by adjusting the thickness of the second sacrificial layer and/or the protective layer.
In one implementation, the thicknesses of the first sacrificial layer and the second sacrificial layer may be set to be the same, for example, the thickness of the protective layer is added to the second sacrificial layer, and the height of the finally formed fourth cavity is greater than the height of the first cavity.
In another implementation manner, the thicknesses of the first sacrificial layer and the second sacrificial layer may be set to be different, for example, the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer, in this case, the height of the fourth cavity may be greater than the height of the third cavity by controlling the thickness of the protective layer, and the height of the fourth cavity may also be equal to the height of the third cavity. Or, for example, the thickness of the first sacrificial layer is smaller than that of the second sacrificial layer, and at this time, the height of the fourth cavity may be made smaller than or greater than or equal to the height of the third cavity by controlling the thickness of the protective layer.
According to the embodiment of the disclosure, the second electrode layer covering the middle area of the second sacrificial layer is formed, the fourth through hole penetrating through the edge areas of the second piezoelectric layer and the second sacrificial layer is formed, and the fourth electrode layer partially covering the second piezoelectric layer is formed.
In some embodiments, in forming the third electrode layer and the fourth electrode layer, the third electrode layer may be formed in a shape on the surface of the first piezoelectric layer and the fourth electrode layer may be formed in a shape on the surface of the second piezoelectric layer by a photolithography and etching technique, such that the third electrode layer does not cover the third through hole and the fourth electrode layer does not cover the fourth through hole.
Example 1
In the design of the bulk acoustic wave filter, the related characteristics and flexibility can be improved by changing the thickness of the electrode. However, in the prior art, the process of forming electrodes with different thicknesses is not easy to control. In addition, electrodes with different thicknesses are usually generated in sequence, so that the quality of the electrode formed in advance is easily influenced in the manufacturing process of the electrode formed later, and the quality of a device is influenced.
For example, when performing an etching process, overetching is usually required to ensure that the residual metal is completely removed and to avoid short circuit of the device due to the metal residue, but the overetching process easily reduces the thickness of the electrode formed first, thereby affecting the stability of the thickness of the electrode formed first. In practical application, the difference between the thicknesses of different electrodes on a filter is usually in the nanometer level, so that the process difficulty is high, and the influence on the characteristics of a device is large.
Accordingly, the present example provides a method of manufacturing an acoustic wave device in which bottom electrodes having different thicknesses are formed for different resonators on the same substrate. The following description will be given by taking an example in which 3 resonators, namely a first resonator, a second resonator and a third resonator, are required to be formed on a substrate, bottom electrodes of the three resonators are a first electrode layer, a second electrode layer and a fifth electrode layer in sequence, the thickness of the first electrode layer is x, the thickness of the second electrode layer is y, and the thickness of the fifth electrode layer is z.
When three bottom electrodes with different thicknesses need to be formed, three processes of thin film deposition, exposure development and etching are needed. If x is greater than y and y is greater than z, a first electrode layer is formed to a thickness of x, and then a protective layer (e.g., silicon dioxide, SiO) is deposited over the formed first electrode layer2) The protective layer is used for protecting the first electrode layer so as to reduce the influence of an etching process on the first electrode layer with the thickness of x in the forming process of the second electrode layer with the thickness of y, and the like.
In some examples, when it is desired to form bottom electrodes of a plurality of different thicknesses, fabrication can also be started from a bottom electrode of any one thickness. For example, if two bottom electrodes with thicknesses x and y are required to be formed, and x is greater than y, the bottom electrode with thickness x may be formed as the first electrode layer, then the protective layer is formed, and then the bottom electrode with thickness y may be formed as the second electrode layer. Alternatively, the bottom electrode with the thickness of y may be formed as the first electrode layer, then the protective layer is formed, and then the bottom electrode with the thickness of x may be formed as the second electrode layer.
It should be noted that, when there are electrodes with the same thickness in the bottom electrodes with different thicknesses, the electrodes with the same thickness can be simultaneously manufactured. For example, when a plurality of first electrode layers having the same thickness are included in the acoustic wave device, the plurality of first electrode layers having the same thickness can be simultaneously formed.
Illustratively, the process of forming the bottom electrode with three different thicknesses is described as an example. Here, the bottom electrodes of the three different thicknesses are a first electrode layer, a second electrode layer, and a fifth electrode layer in this order, the first electrode layer being a bottom electrode of the first resonator, the second electrode layer being a bottom electrode of the second resonator, and the fifth electrode layer being a bottom electrode of the third resonator.
Fig. 2a to 2i are partial schematic views showing a method of manufacturing an acoustic wave device of the present example, including the steps of:
the method comprises the following steps: as shown in fig. 2a, a first sacrificial layer (sacrifice layer), a second sacrificial layer, and a third sacrificial layer are formed on a substrate in parallel. Here, the thicknesses of the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer are the same, and the constituent materials may be silicon dioxide.
Step two: as shown in fig. 2b, a first electrode layer is formed overlying the first sacrificial layer.
Step three: as shown in fig. 2c, a first protective layer is formed covering the first electrode layer, the second sacrificial layer and the third sacrificial layer. Here, the first protective layer may be composed of silicon dioxide, and the thickness of the first protective layer is 200 nm.
Step four: forming a second electrode layer covering the first protective layer, as shown in fig. 2 d; and covering a second electrode layer covering the second sacrificial layer with photoresist, and etching the second electrode layer covering the first electrode layer and the third sacrificial layer.
Step five: as shown in fig. 2e, the first protective layer covering the first electrode layer and the third sacrificial layer is etched by hydrogen fluoride to form the structure shown in fig. 2 f.
Step six: as shown in fig. 2g, after removing the protective layer covering the first electrode layer and the third sacrificial layer, forming a second protective layer covering the first electrode layer, the second electrode layer and the third sacrificial layer, and forming a fifth electrode layer covering the second protective layer; wherein, the second protective layer and the first protective layer are made of the same material.
Step seven: as shown in fig. 2g, forming a photoresist on the fifth electrode layer covering the third sacrificial layer; the fifth electrode layer, which covers the first electrode layer and the second electrode layer, is etched to form the structure shown in fig. 2 h.
Step eight: as shown in fig. 2h, the photoresist formed on the fifth electrode layer covering the third sacrificial layer is removed, and the second protective layer covering the first electrode layer and the second electrode layer is etched by using hydrogen fluoride, so as to form the structure shown in fig. 2 i.
Fig. 2d, and 3 a-3 d are partial schematic views of another acoustic wave device fabrication method according to an exemplary illustration, including the steps of:
the method comprises the following steps: forming a second electrode layer covering the first protective layer, as shown in fig. 2 d; and covering a second electrode layer covering the second sacrificial layer with photoresist, and etching the second electrode layer covering the first electrode layer and the third sacrificial layer.
Step two: forming a third protective layer covering the first protective layer and the second electrode layer, as shown in fig. 3 a; forming a fifth electrode layer covering the third protective layer; the third protective layer is made of the same material as the first protective layer.
Step three: as shown in fig. 3b, a photoresist is formed on the fifth electrode layer covering the third sacrificial layer, and the fifth electrode layer covering the first electrode layer and the second electrode layer is etched until the third protective layer covering the first electrode layer and the second electrode layer is exposed.
Step four: as shown in fig. 3c, the third and first protective layers covering the first and second electrode layers are removed until the first and second electrode layers are exposed, and the photoresist on the fifth electrode layer is removed, so as to form the structure shown in fig. 3 d.
As can be seen from comparison of the structures shown in fig. 2i and 3d, in the first acoustic wave device manufactured according to the method of manufacturing an acoustic wave device shown in fig. 2a to 2i, a protective layer (i.e., a second protective layer) and a third sacrificial layer are provided between the fifth electrode layer and the substrate; in the second acoustic wave device manufactured according to the method of manufacturing an acoustic wave device shown in fig. 2a to 2d and 3a to 3d, two protective layers (i.e., a first protective layer and a third protective layer) and a third sacrificial layer are provided between the fifth electrode layer and the substrate. That is, the height of a cavity formable between the fifth electrode layer and the substrate in the first acoustic wave device is smaller than the height of a cavity formable between the fifth electrode layer and the substrate in the second acoustic wave device.
In some embodiments, when three or more resonators are fabricated on the surface of the same substrate, starting with the second resonator, after the bottom electrode layer (e.g., the second electrode layer in fig. 2 d) of the second resonator is formed, the previous protective layer (e.g., the first protective layer in fig. 2 c) may be optionally removed, and then the bottom electrode layer (e.g., the fifth electrode layer in fig. 2 d) of the third resonator and the bottom electrode layers of the resonators therebehind are formed in the manner described above.
In some embodiments, when three or more resonators are fabricated on the surface of the same substrate, starting from the second resonator, after the bottom electrode layer (e.g., the second electrode layer in fig. 2 d) of the second resonator is formed, a protection layer (e.g., the third protection layer in fig. 3 b) may be directly formed without removing the protection layer formed before, until the bottom electrode layer of the last resonator is fabricated, and one or more protection layers on the bottom electrode layer of each resonator formed in front of the last resonator are removed again until each bottom electrode layer is exposed.
Compared with the manufacturing methods of the acoustic wave devices shown in fig. 2a to 2d and fig. 3a to 3d, the manufacturing method of the acoustic wave device shown in fig. 2a to 2i is advantageous in ensuring the process stability of the acoustic wave device by first forming the fifth electrode layer only covering the third sacrificial layer, and then removing the third protective layer and the first protective layer covering the first electrode layer and the second electrode layer, and in the manufacturing method of the acoustic wave device shown in fig. 2a to 2i, first removing the first protective layer covering the first electrode layer and the third sacrificial layer, and then forming the fifth electrode layer only covering the third sacrificial layer.
Fig. 4 is a partial schematic view of an exemplary illustrative acoustic wave device 100, the acoustic wave device 100 being fabricated using a fabrication method as described in embodiments of the present disclosure. Referring to fig. 4, an acoustic wave device 100 includes:
a substrate 101;
a first reflective structure located in a first region of the substrate 101;
the second reflecting structure is arranged in parallel with the first reflecting structure and is positioned in a second area of the substrate 101;
a first electrode layer 102 covering the first reflective structure;
a second electrode layer 103 covering the second reflective structure; wherein, the thickness of the second electrode layer 103 is different from the thickness of the first electrode layer 102.
Illustratively, acoustic wave device 100 can include: a bulk acoustic wave filter. For example, a cavity type film bulk acoustic resonator, a back cavity type film bulk acoustic resonator, a solid-state mount resonator, or the like.
The substrate 101 may be a silicon wafer.
The constituent materials of the first electrode layer 102 and the second electrode layer 103 may include: a material having electrically conductive properties. For example, metals such as molybdenum (Mo) and tungsten (W). The first electrode layer 102 and the second electrode layer 103 are bottom electrodes of different resonators on the acoustic wave device 100, respectively.
Since the thickness of the bottom electrode changes the resonance frequency of the resonator, the resonance frequency of the resonator having the first electrode layer 102 as the bottom electrode is different from the resonance frequency of the resonator having the second electrode layer 103 as the bottom electrode.
The difference between the thickness of the first electrode layer 102 and the thickness of the second electrode layer 103 may be greater than or equal to 0.5 nanometers. For example, the difference between the thicknesses of the first electrode layer 102 and the second electrode layer 103 may be: 0.5nm, 1nm, or 1.5nm, etc. It is understood that, as the difference in thickness between the first electrode layer 102 and the second electrode layer 103 is smaller, the difference between the operating frequencies of the two types of resonators having the first electrode layer 102 and the second electrode layer 103 as bottom electrodes, respectively, is smaller.
According to the embodiment of the invention, the first electrode layer and the second electrode layer with different thicknesses are formed on the same substrate of the acoustic wave device, so that a foundation is provided for subsequently forming resonators with different resonant frequencies based on the first electrode layer and the second electrode layer as bottom electrodes, the design flexibility of the acoustic wave device is improved, and the application range of the acoustic wave device is expanded.
Illustratively, referring to FIG. 5, acoustic wave device 100 further includes: a protective layer 1003 located between the second reflective structure and the second electrode layer 103.
Exemplarily, when the acoustic wave device 100 includes a back cavity type thin film bulk acoustic resonator, as shown with reference to fig. 5, the first reflection structure includes: a first cavity 1001 extending through the substrate 101;
the second reflective structure includes: a second cavity 1002 extending through the substrate 101.
In the cavity-backed thin film bulk acoustic resonator, the protective layer 1003 is located between the second cavity 1002 and the second electrode layer 103.
Exemplarily, when the acoustic wave device 100 includes a solid-state mount resonator, as shown with reference to fig. 6, the first reflection structure includes: first dielectric layers 1011 and second dielectric layers 1012 alternately stacked; the acoustic impedance of the first dielectric layer 1011 is different from that of the second dielectric layer 1012;
the second reflective structure 1010 includes: first dielectric layers 1011 and second dielectric layers 1012 are alternately stacked.
The acoustic wave device 100 further includes: and a protective layer 1003 between the second reflective structure and the second electrode layer 103.
Exemplarily, when the acoustic wave device 100 includes a cavity type thin film bulk acoustic resonator, as shown with reference to fig. 7, the first reflection structure includes: a third cavity 104, the third cavity 104 being located between the first electrode layer 102 and the first region of the substrate 101;
the second reflective structure includes: a fourth cavity 105, the fourth cavity 105 being located between the second electrode layer 103 and the second region of the substrate 101.
In some embodiments, the height of the third cavity 104 and the height of the fourth cavity 105 may be the same. In other embodiments, the height of the third cavity 104 and the height of the fourth cavity 105 may also be different.
In some embodiments, as illustrated with reference to fig. 5 and 6, acoustic wave device 100 further comprises:
a third electrode layer 106;
and a piezoelectric layer 107 located between the first electrode layer 102 and the third electrode layer 106, and located between the second electrode layer 103 and the third electrode layer 106.
The composition materials of the piezoelectric layer include: a material having a piezoelectric effect. For example, aluminum nitride, zinc oxide, lithium tantalate, or the like.
In the embodiments provided in the present disclosure, it should be understood that the disclosed apparatus, system, and method may be implemented in other ways. The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present disclosure, and all the changes or substitutions should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (12)

1. A method of fabricating an acoustic wave device, comprising:
forming a first electrode layer covering the first reflective structure;
forming a protective layer covering the first electrode layer and the second reflective structure; the second reflecting structure and the first reflecting structure are arranged on the substrate in parallel, the first reflecting structure is positioned in a first area of the substrate, and the second reflecting structure is positioned in a second area of the substrate;
forming a second electrode layer covering the protective layer; wherein a thickness of the second electrode layer is different from a thickness of the first electrode layer;
and removing the protective layer and the second electrode layer above the first electrode layer until the first electrode layer is exposed.
2. The method of claim 1,
the forming a first electrode layer covering the first reflective structure includes:
forming the first electrode layer covering the first region on the first surface of the substrate; forming a first cavity penetrating through the substrate from the second surface of the substrate until the first electrode layer is exposed; wherein the first surface of the substrate and the second surface of the substrate are opposite, and the first reflective structure comprises the first cavity;
the forming a protective layer covering the first electrode layer and the second reflective structure includes:
forming the protective layer covering the first electrode layer and the second region on the first surface of the substrate; forming a second cavity penetrating through the substrate from the second surface of the substrate until the protective layer is exposed; wherein the second reflective structure comprises the second cavity.
3. The method of claim 1, further comprising:
forming the first and second reflective structures on the surface of the substrate; wherein the first and second reflective structures each comprise: the first dielectric layers and the second dielectric layers are alternately stacked; and the acoustic impedance of the first dielectric layer is different from that of the second dielectric layer.
4. The method of claim 1, further comprising:
forming a first sacrificial layer and a second sacrificial layer which are arranged in parallel on the surface of the substrate; the first sacrificial layer covers a first area of the substrate, the first reflecting structure comprises a third cavity formed based on the appearance of the first sacrificial layer after the first sacrificial layer is removed, the second sacrificial layer covers a second area of the substrate, and the second reflecting structure comprises a fourth cavity formed based on the appearance of the second sacrificial layer after the second sacrificial layer is removed and having a first height.
5. The method of claim 4, further comprising:
removing the protective layer between the second electrode layer and the second region to form a fourth cavity with a second height based on the morphology of the protective layer between the second electrode layer and the second region and the fourth cavity with the first height; wherein the second height is greater than the first height.
6. An acoustic wave device, comprising:
a substrate;
a first reflective structure located in a first region of the substrate;
the second reflecting structure is arranged in parallel with the first reflecting structure and is positioned in a second area of the substrate;
a first electrode layer covering the first reflective structure;
a second electrode layer covering the second reflective structure; wherein a thickness of the second electrode layer is different from a thickness of the first electrode layer.
7. An acoustic wave device according to claim 6,
the acoustic wave device further includes: and the protective layer is positioned between the second reflecting structure and the second electrode layer.
8. An acoustic wave device according to claim 6,
the first reflective structure includes: a first cavity extending through the substrate;
the second reflective structure includes: a second cavity extending through the substrate.
9. An acoustic wave device according to claim 6,
the first reflective structure includes: the first dielectric layers and the second dielectric layers are alternately stacked; the acoustic impedance of the first dielectric layer is different from that of the second dielectric layer;
the second reflective structure includes: the first dielectric layers and the second dielectric layers are alternately stacked.
10. An acoustic wave device according to claim 6,
the first reflective structure includes: a third cavity between the first electrode layer and the first region of the substrate;
the second reflective structure includes: a fourth cavity between the second electrode layer and the second region of the substrate.
11. An acoustic wave device according to claim 10,
the height of the third cavity is different from the height of the fourth cavity.
12. An acoustic wave device according to claim 6,
the acoustic wave device is a bulk acoustic wave filter.
CN201911370470.6A 2019-12-26 2019-12-26 Method for manufacturing acoustic wave device and acoustic wave device Active CN111030631B (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020153965A1 (en) * 2001-04-23 2002-10-24 Ruby Richard C. Controlled effective coupling coefficients for film bulk acoustic resonators
JP2008011483A (en) * 2006-05-30 2008-01-17 Kyocera Corp Acoustic wave resonator, filter, and communication equipment
US20120319534A1 (en) * 2011-06-16 2012-12-20 Avago Technologies Wireless Ip (Singapore) Pte. Ltd. Bulk acoustic resonator comprising non-piezoelectric layer and bridge
CN103166596A (en) * 2013-04-11 2013-06-19 天津大学 Resonator and filter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020153965A1 (en) * 2001-04-23 2002-10-24 Ruby Richard C. Controlled effective coupling coefficients for film bulk acoustic resonators
JP2008011483A (en) * 2006-05-30 2008-01-17 Kyocera Corp Acoustic wave resonator, filter, and communication equipment
US20120319534A1 (en) * 2011-06-16 2012-12-20 Avago Technologies Wireless Ip (Singapore) Pte. Ltd. Bulk acoustic resonator comprising non-piezoelectric layer and bridge
CN103166596A (en) * 2013-04-11 2013-06-19 天津大学 Resonator and filter

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