CN111030631B - Method for manufacturing acoustic wave device and acoustic wave device - Google Patents
Method for manufacturing acoustic wave device and acoustic wave device Download PDFInfo
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- CN111030631B CN111030631B CN201911370470.6A CN201911370470A CN111030631B CN 111030631 B CN111030631 B CN 111030631B CN 201911370470 A CN201911370470 A CN 201911370470A CN 111030631 B CN111030631 B CN 111030631B
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- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
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- H03H9/02007—Details of bulk acoustic wave devices
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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 reflecting 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 the thickness of the second electrode layer is different from the thickness of the first electrode layer; and removing the protective layer and the second electrode layer which are positioned above the first electrode layer until the first electrode layer is exposed and covered.
Description
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
Along with the development of communication, the acoustic wave device is increasingly widely applied to communication, and the performance of the acoustic wave device directly influences the transmission quality of communication signals.
With the development of thin film and micro-nano manufacturing technology, electronic devices are rapidly developing 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 is a 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 an embodiment of the present disclosure, there is provided a method for manufacturing an acoustic wave device, including:
forming a first electrode layer covering the first reflecting 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 the thickness of the second electrode layer is different from the thickness of the first electrode layer;
and removing the protective layer and the second electrode layer which are positioned 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 area 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 is opposite to the second surface of the substrate, 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 reflecting structure and the second reflecting structure on the surface of the substrate; wherein the first reflective structure and the second reflective structure each comprise: 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.
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 with a first height formed based on the appearance of the second sacrificial layer after the second sacrificial layer is removed.
Optionally, the method further comprises:
removing the protective layer between the second electrode layer and the second region to form a fourth cavity having a second height based on the morphology of the protective layer between the second electrode layer and the second region, and the fourth cavity having the first height; wherein the second height is greater than the first height.
According to a second aspect of embodiments of the present disclosure, there is provided 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 first reflective structure; wherein the thickness of the second electrode layer is different from the thickness of the first electrode layer.
Optionally, the acoustic wave device further includes: and a protective layer between the second reflective structure and the second electrode layer.
Optionally, the first reflective structure includes: a first cavity extending through the substrate;
the second reflecting structure includes: a second cavity extending through the substrate.
Optionally, the first reflective structure includes: the first dielectric layers and the second dielectric layers are alternately stacked; wherein the acoustic impedance of the first dielectric layer is different from the acoustic impedance of the second dielectric layer;
the second reflecting structure includes: the first dielectric layers and the second dielectric layers are alternately stacked.
Optionally, the first reflective structure includes: a third cavity between the first electrode layer and the first region of the substrate;
the second reflecting structure includes: and 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 reflecting structure is formed on the same substrate on which the first reflecting structure and the second reflecting structure are formed in parallel, and the second electrode layer covering the second reflecting 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, the process is simple, a foundation is provided for forming resonators with different resonance frequencies based on the first electrode layer and the second electrode layer as bottom electrodes respectively, and resonators with different resonance frequencies can be formed on the same substrate at the same time, and the resonance frequency range of the acoustic wave device is enlarged. And, by forming the protective layer, the first electrode layer can be protected when the second electrode layer is formed, and the quality of the device can be ensured.
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 for manufacturing an acoustic wave device according to an example.
Fig. 3a to 3d are partial schematic views illustrating another method for manufacturing an acoustic wave device according to an example.
Fig. 4 is a partial top view of an acoustic wave device according to an exemplary embodiment.
Fig. 5 is a partial schematic diagram of an acoustic wave device according to an exemplary embodiment.
Fig. 6 is a partial schematic diagram of another acoustic wave device, shown in accordance with an exemplary embodiment.
Fig. 7 is a partial schematic diagram of yet another acoustic wave device, according to an exemplary embodiment.
Detailed Description
The technical scheme of the present disclosure will be further elaborated with reference to the drawings and examples. While exemplary embodiments 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 to 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 described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present disclosure will become more fully apparent from the following description and appended claims. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the disclosure.
In the embodiments of the present disclosure, the term "a is connected to B" includes a case where a is connected to B while A, B is in contact with each other, or a case where A, B is further interposed between the two while a is connected to B without contact.
In the presently disclosed embodiments, the terms "first," "second," and the like are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
The technical solutions described in the embodiments of the present disclosure may be arbitrarily combined without any 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 reflecting 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 in parallel on the substrate, 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; wherein the thickness of the second electrode layer is different from the thickness 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 0.5nm. 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, 1.5nm, or the like.
S140: and removing the protective layer and the second electrode layer which are positioned 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 reflective structure and the second reflective structure may comprise: cavities or bragg reflection structures, etc. The bragg reflection structure is formed by laminating two dielectric materials having different acoustic impedances.
In some embodiments, the first reflective structure and the second reflective structure may comprise the same structure, e.g., the first reflective structure and the second reflective structure each 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 conductive properties. For example, a metal such as molybdenum (Mo) or tungsten (W). The first electrode layer and the second electrode layer are respectively bottom electrodes of different resonators on the acoustic wave device. The method of forming the first electrode layer and the second electrode layer may include: physical vapor deposition, and the like.
The composition materials of the protective layer can include: oxide or nitride. For example, silicon oxide or silicon nitride, etc.
In S130, after forming the second electrode layer, the first reflective structure and the first electrode layer, the protective layer and the second electrode layer above the first reflective structure form a first overlapping region; the second reflecting structure, the protective layer above the second reflecting structure and the second electrode layer form a second overlapping region.
In S140, a Photoresist (PR) covering the second overlapping region and exposing the first overlapping region may be formed by photolithography, and the photoresist is used to protect the second electrode layer located in the second overlapping 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 overlap region is removed, the photoresist is covered on the second electrode layer in the second overlap region, so the second electrode layer in the second overlap region is not removed.
In S140, after removing the second electrode layer above the first electrode layer, that is, after removing the second electrode layer located in the first overlapping region, a protective layer covering the first electrode layer is exposed in the first overlapping region. At this time, the photoresist covering the second overlapping region may be removed, and the protective layer of the second overlapping region is located under the second electrode layer. Therefore, the etching agent which reacts with the protection layer but not reacts with the first electrode layer and the second electrode layer can be selected, the exposed protection layer in the first overlapping region can be directly removed through the etching process, and the blocking layer for protecting the second electrode layer in the second overlapping region does not need to be formed through a yellow light lithography process. Therefore, the quality of the first electrode layer and the second electrode layer is ensured, 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 materials of the first electrode layer and the second electrode layer are molybdenum, hydrogen Fluoride (HF) may be selected as an etchant, and the protective layer covering the first electrode layer in the first overlap region is removed by an etching process.
In the embodiment of the disclosure, the first electrode layer covering the first reflecting structure is formed on the same substrate on which the first reflecting structure and the second reflecting structure are formed in parallel, and the second electrode layer covering the second reflecting structure is formed, so that the thickness of the second electrode layer can be different from that of the first electrode layer, electrode layers with different thicknesses can be formed on the same substrate, the process is simple, a foundation is provided for forming resonators with different resonance frequencies based on the first electrode layer and the second electrode layer as bottom electrodes respectively, resonators with different resonance frequencies can be formed on the same substrate at the same time, and the resonance frequency range of the acoustic wave device is enlarged. And by forming the protective layer, the first electrode layer can be protected when the second electrode layer is formed, and the quality of the device can be ensured.
In some embodiments, an acoustic wave device may include: 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; wherein the first surface of the substrate is opposite to the second surface of the substrate, and the first reflective 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.
Before forming the first cavity and the second cavity, 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 the piezoelectric layer and the third electrode layer are formed, a first cavity and a second cavity are formed from the second surface of the substrate, respectively.
Compared with the method that the first cavity and the second cavity 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, 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 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 may include: the resonators (Solidly Mounted Resonator, SMR) are solid state assembled. The method further comprises the steps of:
forming a first reflecting structure and a second reflecting structure on the surface of the substrate; wherein, the first reflecting structure and the second reflecting structure each 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 laminated, so that the Bragg reflection structure can be formed.
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 constituent materials of the first dielectric layer 1311 may include: molybdenum or tungsten; the constituent materials 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 constituent materials of the first dielectric layer may include: silicon dioxide or aluminum; the constituent materials of the second dielectric layer may include: molybdenum or tungsten.
In some embodiments, an acoustic wave device may include: a cavity type film bulk acoustic resonator (Film Bulk Acoustic Resonator, FBAR). The method further comprises the steps of:
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 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 part 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 a 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 can be designed according to the actual requirements of the acoustic wave device. For example, the thickness of the first sacrificial layer and the second sacrificial layer may be 0.1 micrometers to 5 micrometers.
For example, the first sacrificial layer and the second sacrificial layer may be formed on the substrate by chemical vapor deposition. Taking silicon dioxide as an example, the composition material of the first sacrificial layer and the second sacrificial layer can react with oxygen to generate silicon dioxide through silane. The silicon dioxide is deposited on the surface of the substrate, then a first sacrificial layer is formed on a first area of the surface of the substrate, and a second sacrificial layer is formed on a second area of the surface of the substrate through a yellow light lithography and etching technology.
In step S140, a photoresist is formed on the second electrode layer covering the second sacrificial layer by a photolithography process, wherein the photoresist is used for protecting the second electrode layer covering the second sacrificial layer. And then removing the second electrode layer positioned above the first electrode layer through a dry etching process. When the second electrode layer 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, i.e., the second electrode layer above the second sacrificial layer is not removed.
In step S140, after the second electrode layer above the first electrode layer is removed, a protective layer covering the first electrode layer is exposed, and the protective layer covering the second sacrificial layer is located below the second electrode layer. At this time, the protective layer below 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 that reacts with the protective layer but does not react with the first electrode layer and the second electrode layer, and a blocking 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 ensured, 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 electrode layers with different thicknesses can be formed on the same substrate, the process is simple, a foundation is provided for the subsequent formation of resonators with different resonance frequencies based on the first electrode layer and the second electrode layer as bottom electrodes respectively, so that resonators with different resonance frequencies can be formed on the same substrate at the same time, and the resonance frequency range of the acoustic wave device is enlarged. And, by forming the protective layer, the first electrode layer can be protected when the second electrode layer is formed, and the quality of the device can be ensured.
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 covering the first electrode layer and a second piezoelectric layer covering the second electrode layer; a third electrode layer partially covering the first piezoelectric layer and a fourth electrode layer partially covering the second piezoelectric layer are formed.
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 covering 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 using a yellow development and etching technique.
Wherein, the constituent 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 ) Etc.
The constituent materials of the third electrode layer and the fourth electrode layer may be the same as those 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 an intermediate region of the first sacrificial layer;
the method further comprises the steps of:
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 third through hole etching, 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 to expose the middle region of the first electrode layer. Thus, during the deposition of the first electrode layer, the first electrode layer material deposited toward the edge region of the first sacrificial layer adheres to the photoresist surface. Therefore, after the first electrode layer is deposited, the photoresist covering the edge area of the first sacrificial layer is removed, so that the first electrode layer material only covers the middle 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 first piezoelectric layer and the edge area of the first sacrificial layer is formed, and the third electrode layer partially covering the first sacrificial layer and the first piezoelectric layer is formed, and due to the fact that the photoresist covers, the overlapped area of the first electrode layer, the third electrode layer and the first piezoelectric layer located in the middle area of the first sacrificial layer cannot be exposed through the third through hole, namely the thickness of the first electrode layer, the thickness of the third electrode layer and the thickness of the first piezoelectric layer cannot be influenced in the process of etching the third through hole, so that the quality of the acoustic wave device can be guaranteed.
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, removing the second sacrificial layer through fourth through hole etching, 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 having a second height based on the morphology of the protective layer between the second electrode layer and the second region and the fourth cavity having the first height; wherein the second height is greater than the first height.
According to the embodiment of the disclosure, the influence of the protective layer on the working frequency of the acoustic wave device can be reduced by removing the protective layer.
Illustratively, the protective layer may be composed of the same material as the second sacrificial layer. Thus, 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, namely, the protective layer and the second sacrificial layer can be removed at one time by adopting the same etchant, compared with the situation that the materials of the protective layer and the second sacrificial layer are not removed at the same time by different etchants, the protective layer and the second sacrificial layer are formed by adopting the same material in the embodiment of the disclosure, and the protective layer can be removed at the same time when the second sacrificial layer is removed, so that the process steps are saved.
It is easy to understand 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, a thickness of a protective layer is added on the second sacrificial layer, and the fourth cavity height finally formed is greater than the first cavity height.
In another implementation, 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, at which time, the height of the fourth cavity may be made greater than the height of the third cavity, or the height of the fourth cavity may be made equal to the height of the third cavity, by controlling the thickness of the protective layer. Alternatively, for example, the thickness of the first sacrificial layer is smaller than the thickness 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 second piezoelectric layer and the edge area of the second sacrificial layer and the fourth electrode layer partially covering the second piezoelectric layer are formed, and due to the coverage of the photoresist, the second electrode layer located in the middle area of the second sacrificial layer, the overlapping area of the second piezoelectric layer and the fourth electrode layer cannot be exposed through the fourth through hole, namely, in the process of etching the fourth through hole, the thicknesses of the second electrode layer, the second piezoelectric layer and the fourth electrode layer cannot be influenced, so that the quality of the acoustic wave device is guaranteed.
In some embodiments, when forming the third electrode layer and the fourth electrode layer, the shape of the third electrode layer may be formed on the surface of the first piezoelectric layer and the shape of the fourth electrode layer may be formed on the surface of the second piezoelectric layer by photolithography and etching techniques 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 one
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 sequentially, so that the quality of the electrode formed in advance is easily affected in the manufacturing process of the electrode formed later, and the quality of the device is affected.
For example, in performing an etching process, it is often necessary to perform over-etching in order to ensure that the remaining metal is completely removed and to avoid a device short circuit caused by the metal remaining, but the over-etching process tends to reduce the thickness of the electrode formed first, thereby affecting the stability of the thickness of the electrode formed first. In practical application, the difference of the thicknesses of different electrodes on the filter is usually nano-scale, so that the process difficulty is high and the influence on the characteristics of the device is large.
Thus, the present example provides a method of fabricating an acoustic wave device that produces bottom electrodes of different thicknesses for different resonators on the same substrate. The substrate is required to be formed into 3 resonators of a first resonator, a second resonator and a third resonator, the bottom electrodes of the three resonators are sequentially a first electrode layer, a second electrode layer and a fifth electrode layer, 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 it is required to form the bottom electrodes of three different thicknesses, three thin film deposition, exposure development, and etching processes are required. If x is greater than y and y is greater than z, then a first electrode layer of thickness x is formed and then a protective layer (e.g., silicon dioxide SiO) is deposited over the formed first electrode layer 2 ) The protective layer is used for protecting the first electrode layer to reduce the influence of an etching process on the first electrode layer with the thickness x during the formation of the second electrode layer with the thickness y, and the like.
In some examples, when it is desired to form bottom electrodes of a plurality of different thicknesses, fabrication may also begin with bottom electrodes of any one thickness. For example, if two bottom electrodes having a thickness of x and y, respectively, are required to be formed, and x is greater than y, then the bottom electrode having a thickness of x may be formed as the first electrode layer, then the protective layer is formed, and then the bottom electrode having a thickness of y may be formed as the second electrode layer. Alternatively, a bottom electrode having a thickness y may be formed as the first electrode layer, then the protective layer is formed, and then a bottom electrode having a thickness x may be formed as the second electrode layer.
It should be noted that, when there are electrodes with the same thickness among the plurality of bottom electrodes with different thicknesses, the electrodes with the same thickness may be fabricated at the same time. 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 may be simultaneously fabricated.
The process of forming the bottom electrodes of three different thicknesses is exemplified as an example. Here, the three bottom electrodes with different thicknesses are a first electrode layer, a second electrode layer and a fifth electrode layer in sequence, wherein the first electrode layer is used as the bottom electrode of the first resonator, the second electrode layer is used as the bottom electrode of the second resonator, and the fifth electrode layer is used as the bottom electrode of the third resonator.
Fig. 2a to 2i are partial schematic views showing a method for manufacturing an acoustic wave device according to the present embodiment, including the steps of:
step one: as shown in fig. 2a, a first sacrificial layer (sacrificial layer), a second sacrificial layer, and a third sacrificial layer are formed in parallel on a substrate. Here, the first sacrificial layer, the second sacrificial layer and the third sacrificial layer have the same thickness, and the constituent materials may be silicon dioxide.
Step two: as shown in fig. 2b, a first electrode layer is formed to cover the first sacrificial layer.
Step three: as shown in fig. 2c, a first protective layer is formed to cover the first electrode layer, the second sacrificial layer, and the third sacrificial layer. Here, the first protective layer may be formed 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 the photoresist on the second electrode layer covering the second sacrificial layer, 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 is etched over the first electrode layer and the third sacrificial layer by hydrogen fluoride, forming the structure shown in fig. 2 f.
Step six: after removing the protective layers covering the first electrode layer and the third sacrificial layer, a second protective layer covering the first electrode layer, the second electrode layer, and the third sacrificial layer is formed, and a fifth electrode layer covering the second protective layer is formed, as shown in fig. 2 g; wherein the second protective layer is made of the same material as the first protective layer.
Step seven: as shown in fig. 2g, a photoresist is formed 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 hydrogen fluoride to form the structure shown in fig. 2 i.
Fig. 2d, and fig. 3a to 3d are partial schematic views illustrating another method for manufacturing an acoustic wave device according to an exemplary embodiment, including the steps of:
step one: forming a second electrode layer covering the first protective layer as shown in fig. 2 d; and covering the photoresist on the second electrode layer covering the second sacrificial layer, and etching the second electrode layer covering the first electrode layer and the third sacrificial layer.
Step two: as shown in fig. 3a, a third protective layer is formed to cover the first protective layer and the second electrode layer; forming a fifth electrode layer covering the third protective layer; the composition material of the third protective layer is the same as that of 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 protective layer and the first protective layer covering the first electrode layer and the second electrode layer are removed until the first electrode layer and the second electrode layer 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 by comparing the structures shown in fig. 2i and 3d, in the first acoustic wave device manufactured according to the method for manufacturing the acoustic wave device shown in fig. 2a to 2i, a protective layer (i.e., a second protective layer) and a third sacrificial layer are disposed between the fifth electrode layer and the substrate; in the second acoustic wave device manufactured according to the manufacturing method of the 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 disposed between the fifth electrode layer and the substrate. I.e., the height of the cavity that can be formed between the fifth electrode layer and the substrate in the first acoustic wave device is smaller than the height of the cavity that can be formed between the fifth electrode layer and the substrate in the second acoustic wave device.
In some embodiments, when three or more resonators are formed on the surface of the same substrate, starting from the second resonator, after forming the bottom electrode layer of the second resonator (e.g., the second electrode layer in fig. 2 d), the previous protective layer (e.g., the first protective layer in fig. 2 c) may be optionally removed, and then the bottom electrode layer of the third resonator (e.g., the fifth electrode layer in fig. 2 d) and the bottom electrode layers of the subsequent resonators may be 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 forming the bottom electrode layer (e.g., the second electrode layer in fig. 2 d) of the second resonator, a protective layer (e.g., the third protective layer in fig. 3 b) is directly formed without removing the protective layer formed before, until the bottom electrode layer of the last resonator is completed, and removing one or more protective layers on the bottom electrode layer of each resonator formed before until each bottom electrode layer is exposed.
Compared with the method for manufacturing the acoustic wave device shown in fig. 2a to 2d and 3a to 3d, the method for manufacturing the acoustic wave device shown in fig. 2a to 2i is advantageous in ensuring the process stability of the acoustic wave device by forming the fifth electrode layer covering only the third sacrificial layer, removing the third protective layer and the first protective layer covering the first electrode layer and the second electrode layer, removing the first protective layer covering the first electrode layer and the third sacrificial layer, and forming the fifth electrode layer covering only the third sacrificial layer.
Fig. 4 is a partial schematic diagram of an acoustic wave device 100 according to an exemplary illustration, the acoustic wave device 100 being fabricated using a fabrication method as described in embodiments of the present disclosure. Referring to fig. 4, the acoustic wave device 100 includes:
a substrate 101;
a first reflective structure located in a first region of the substrate 101;
a second reflective structure arranged in parallel with the first reflective structure and located in a second region 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, the acoustic wave device 100 may include: a bulk acoustic wave filter. Such as cavity type thin film bulk acoustic resonators, back cavity type thin film bulk acoustic resonators, solid state assembly resonators, and 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 conductive properties. For example, a metal such as molybdenum (Mo) or 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 using the first electrode layer 102 as the bottom electrode is different from the resonance frequency of the resonator using 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 0.5nm. 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 the smaller the difference in thickness between the first electrode layer 102 and the second electrode layer 103, the 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.
According to the embodiment of the disclosure, 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 forming resonators with different resonance frequencies based on the first electrode layer and the second electrode layer as bottom electrodes respectively, the design flexibility of the acoustic wave device is improved, and the application range of the acoustic wave device is enlarged.
Illustratively, referring to FIG. 5, acoustic wave device 100 further comprises: a protective layer 1003 located between the second reflective structure and the second electrode layer 103.
Illustratively, 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 reflective structure includes: a first cavity 1001 through the substrate 101;
the second reflecting structure includes: a second cavity 1002 extending through the substrate 101.
In the back cavity type thin film bulk acoustic resonator, a protective layer 1003 is located between the second cavity 1002 and the second electrode layer 103.
Illustratively, when acoustic wave device 100 includes a solid state mounted resonator, referring to FIG. 6, the first reflective structure comprises: a first dielectric layer 1011 and a second dielectric layer 1012 which are alternately stacked; wherein the acoustic impedance of the first dielectric layer 1011 and the acoustic impedance of the second dielectric layer 1012 are different;
the second reflective structure 1010 includes: the first dielectric layer 1011 and the second dielectric layer 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.
Illustratively, when the acoustic wave device 100 includes a cavity type thin film bulk acoustic resonator, as shown with reference to fig. 7, the first reflecting 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 reflecting 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, referring to fig. 5 and 6, acoustic wave device 100 further comprises:
a third electrode layer 106;
the piezoelectric layer 107 is located between the first electrode layer 102 and the third electrode layer 106, and is 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 manners. The foregoing is merely specific embodiments of the disclosure, but the protection scope of the disclosure is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the disclosure, and it is intended to cover the scope of the 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 manufacturing an acoustic wave device, comprising:
forming a first electrode layer covering only 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 the thickness of the second electrode layer is different from the thickness of the first electrode layer;
and removing the protective layer and the second electrode layer which are positioned above the first electrode layer until the first electrode layer is exposed.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the forming a first electrode layer covering only the first reflective structure includes:
forming the first electrode layer covering the first area 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 is opposite to the second surface of the substrate, 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 according to claim 1, wherein the method further comprises:
forming the first reflecting structure and the second reflecting structure on the surface of the substrate; wherein the first reflective structure and the second reflective structure each comprise: 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.
4. The method according to claim 1, wherein 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 with a first height formed based on the appearance of the second sacrificial layer after the second sacrificial layer is removed.
5. The method according to claim 4, wherein the method further comprises:
removing the protective layer between the second electrode layer and the second region to form a fourth cavity having a second height based on the morphology of the protective layer between the second electrode layer and the second region, and the fourth cavity having the first height; wherein the second height is greater than the first height.
6. An acoustic wave device fabricated by the method of any one of claims 1 to 5; the acoustic wave device includes:
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 the thickness of the second electrode layer is different from the thickness of the first electrode layer.
7. The acoustic wave device of claim 6 wherein,
the acoustic wave device further includes: and a protective layer positioned between the second reflecting structure and the second electrode layer.
8. The acoustic wave device of claim 6 wherein,
the first reflective structure includes: a first cavity extending through the substrate;
the second reflecting structure includes: a second cavity extending through the substrate.
9. The acoustic wave device of claim 6 wherein,
the first reflective structure includes: the first dielectric layers and the second dielectric layers are alternately stacked; wherein the acoustic impedance of the first dielectric layer is different from the acoustic impedance of the second dielectric layer;
the second reflecting structure includes: the first dielectric layers and the second dielectric layers are alternately stacked.
10. The acoustic wave device of claim 6 wherein,
the first reflective structure includes: a third cavity between the first electrode layer and the first region of the substrate;
the second reflecting structure includes: and a fourth cavity between the second electrode layer and the second region of the substrate.
11. The acoustic wave device of claim 10 wherein,
the height of the third cavity is different from the height of the fourth cavity.
12. The acoustic wave device of claim 6 wherein,
the acoustic wave device is a bulk acoustic wave filter.
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| JP2008011483A (en) * | 2006-05-30 | 2008-01-17 | Kyocera Corp | Acoustic wave resonator, filter, and communication equipment |
| CN103166596A (en) * | 2013-04-11 | 2013-06-19 | 天津大学 | Resonator and filter |
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| US6472954B1 (en) * | 2001-04-23 | 2002-10-29 | Agilent Technologies, Inc. | Controlled effective coupling coefficients for film bulk acoustic resonators |
| US8350445B1 (en) * | 2011-06-16 | 2013-01-08 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Bulk acoustic resonator comprising non-piezoelectric layer and bridge |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2008011483A (en) * | 2006-05-30 | 2008-01-17 | Kyocera Corp | Acoustic wave resonator, filter, and communication equipment |
| CN103166596A (en) * | 2013-04-11 | 2013-06-19 | 天津大学 | Resonator and filter |
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