CN116346064A - Bulk acoustic wave resonator, manufacturing method thereof, filter and duplexer - Google Patents
Bulk acoustic wave resonator, manufacturing method thereof, filter and duplexer Download PDFInfo
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- 238000004519 manufacturing process Methods 0.000 title claims description 41
- 229910052751 metal Inorganic materials 0.000 claims abstract description 115
- 239000002184 metal Substances 0.000 claims abstract description 115
- 238000010438 heat treatment Methods 0.000 claims abstract description 51
- 238000001816 cooling Methods 0.000 claims abstract description 50
- 239000000758 substrate Substances 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims description 92
- 238000005530 etching Methods 0.000 claims description 16
- 238000000151 deposition Methods 0.000 claims description 11
- 238000000059 patterning Methods 0.000 claims description 6
- 239000000725 suspension Substances 0.000 claims 1
- 238000000137 annealing Methods 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 7
- 229920002120 photoresistant polymer Polymers 0.000 description 6
- 239000007772 electrode material Substances 0.000 description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 239000011733 molybdenum Substances 0.000 description 4
- 229910021426 porous silicon Inorganic materials 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 230000008021 deposition Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005224 laser annealing Methods 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910000577 Silicon-germanium Inorganic materials 0.000 description 1
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
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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
- H03H9/02086—Means for compensation or elimination of undesirable effects
- H03H9/02118—Means for compensation or elimination of undesirable effects of lateral leakage between adjacent resonators
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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
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
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Abstract
The invention provides a bulk acoustic wave resonator comprising: the piezoelectric device comprises a substrate, a bottom electrode, a piezoelectric layer and a top electrode, wherein the bottom electrode comprises a bottom electrode main body part and a bottom electrode reflecting part; the bottom electrode main body part sequentially comprises a first metal layer, a first space release layer after heating or cooling, a first air gap and a second metal layer from bottom to top, wherein the second metal layer is formed on the first metal layer and covers the first air gap and the first space release layer after heating or cooling, and the first air gap is formed by a space released by volume shrinkage of the first space release layer after heating or cooling; the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and positioned at the edge of the active area of the bulk acoustic wave resonator; wherein the horizontal projection overlap region of the top electrode, the piezoelectric layer, the second metal layer and the first air gap constitutes an effective region of the bulk acoustic wave resonator. The invention has the characteristics of simple process, low cost and excellent performance.
Description
Technical Field
The present invention relates to the field of semiconductor technologies, and in particular, to a bulk acoustic wave resonator, a method for manufacturing the bulk acoustic wave resonator, a filter, and a duplexer.
Background
Referring to fig. 1, fig. 1 is a schematic cross-sectional view of a conventional bulk acoustic wave resonator in the prior art. As shown, the bulk acoustic wave resonator includes a substrate 10, a bottom electrode 11, a piezoelectric layer 12, a top electrode 13, and a cavity 14. Wherein a recess is formed on the substrate 10, a bottom electrode 11 is formed on the substrate 10 over the recess, a piezoelectric layer 12 is formed on the bottom electrode 11, and a top electrode 13 is formed on the piezoelectric layer 12. The recess in the substrate 10 encloses with the bottom electrode 11 a cavity 14 for acoustic wave reflection. Further, the projected overlapping area of the top electrode 13, the piezoelectric layer 12, the bottom electrode 11, and the cavity 14 in the horizontal direction constitutes an effective region of the bulk acoustic wave resonator.
In the prior art, the cavity is formed by first etching the substrate to form a recess and filling the recess with a sacrificial material, and then removing the sacrificial material through the release channel with an etching solution after the top electrode is formed. This approach results in a complex process and high cost for the bulk acoustic wave resonator. Furthermore, the acoustic wave generated during the operation of the bulk acoustic wave resonator should ideally be completely confined within the active region, but in practice there will still be some leakage of the acoustic wave out of the active region (i.e. lateral leakage of the acoustic wave), resulting in a reduction in the quality factor of the bulk acoustic wave resonator.
Disclosure of Invention
In order to overcome the above-mentioned drawbacks of the prior art, the present invention provides a method of manufacturing a bulk acoustic wave resonator, the method comprising:
providing a substrate;
forming a bottom electrode on the substrate, wherein the bottom electrode comprises a bottom electrode main body part and a bottom electrode reflecting part, the bottom electrode main body part sequentially comprises a first metal layer, a first space release layer and a second metal layer from bottom to top, the second metal layer is formed on the first metal layer and covers the first space release layer, the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and are positioned at the edge of an effective area of the bulk acoustic wave resonator, and the first space release layer is heated or cooled and then has volume shrinkage;
forming a piezoelectric layer on the bottom electrode, and forming a top electrode on the piezoelectric layer;
the manufacturing method further comprises the steps of: heating or cooling the first space release layer to volume shrink the released space to form a first air gap in the bottom electrode body part;
wherein the horizontal projection overlap region of the top electrode, the piezoelectric layer, the second metal layer, and the first air gap constitutes the effective region of the bulk acoustic wave resonator.
According to an aspect of the present invention, in the manufacturing method, the step of forming the bottom electrode on the substrate includes: depositing a first metal layer on the substrate; depositing and patterning a space release material on the first metal layer to form a first space release layer; forming a second metal layer covering the first space release layer on the first metal layer; etching the second metal layer and the first metal layer to form a bottom electrode body portion; etching the upper surface of the bottom electrode body part to form a first concave frame and/or depositing the first convex frame on the upper surface of the bottom electrode body part.
According to another aspect of the present invention, in the manufacturing method, a material of the first metal layer is the same as a material of the second metal layer; or the material of the first metal layer is different from the material of the second metal layer.
According to still another aspect of the present invention, after forming a piezoelectric layer on the bottom electrode, the manufacturing method further includes: etching the upper surface of the piezoelectric layer to form a groove, wherein the groove is positioned at the edge of the effective area; forming a second space release layer in the groove, wherein the thickness of the second space release layer is larger than the depth of the groove, and the volume of the second space release layer is contracted after heating or cooling; the step of forming a top electrode on the piezoelectric layer includes: depositing and patterning a third metal layer on the piezoelectric layer to form a top electrode comprising a top electrode body portion and a top electrode connection portion connected to an edge of the top electrode body portion and located above the second space release layer; the manufacturing method further comprises the steps of: the second space release layer is heated or cooled to shrink its volume to release space to form a second air gap below the top electrode connection.
According to still another aspect of the present invention, in the manufacturing method, the thickness of the heated or cooled second space release layer is larger than the depth of the groove, or the thickness of the heated or cooled second space release layer is equal to the depth of the groove, or the thickness of the heated or cooled second space release layer is smaller than the depth of the groove.
According to still another aspect of the present invention, in the manufacturing method, a portion of the top electrode connecting portion located above the second air gap has a stepped upper surface.
According to still another aspect of the present invention, in the manufacturing method, the top electrode further includes a top electrode reflecting portion including a second concave frame and/or a second convex frame formed at an upper surface of the top electrode main body portion at an edge of the effective region.
According to still another aspect of the present invention, after providing the substrate and before forming the bottom electrode on the substrate, the manufacturing method further includes: a seed layer is formed on the substrate.
The invention also provides a bulk acoustic wave resonator comprising:
a substrate, a bottom electrode formed on the substrate, a piezoelectric layer formed on the bottom electrode, and a top electrode formed on the piezoelectric layer, the bottom electrode including a bottom electrode main body portion and a bottom electrode reflection portion;
The bottom electrode main body part sequentially comprises a first metal layer, a first space release layer after heating or cooling, a first air gap and a second metal layer, wherein the second metal layer is formed on the first metal layer and covers the first air gap and the first space release layer after heating or cooling, and the first air gap is formed by a space released by volume shrinkage after heating or cooling of the first space release layer;
the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and positioned at the edge of the active area of the bulk acoustic wave resonator;
wherein the top electrode, the piezoelectric layer, the second metal layer, and the first air gap horizontally projected overlapping region constitute the active region of the bulk acoustic wave resonator.
According to an aspect of the present invention, in the bulk acoustic wave resonator, a material of the first metal layer is the same as a material of the second metal layer; or the material of the first metal layer is different from the material of the second metal layer.
According to another aspect of the invention, in the bulk acoustic wave resonator, the top electrode includes a top electrode main body and a top electrode connection portion connected to an edge of the top electrode main body, the top electrode connection portion including a suspended portion; and a groove is formed on the upper surface of the piezoelectric layer at the position opposite to the suspended part in the top electrode connecting part, a heated or cooled second space release layer is formed in the groove, and a second air gap is formed between the heated or cooled second space release layer and the top electrode connecting part and is formed by a space released by volume shrinkage of the heated or cooled second space release layer.
According to still another aspect of the present invention, in the bulk acoustic wave resonator, the thickness of the heated or cooled second space release layer is larger than the depth of the groove, or the thickness of the heated or cooled second space release layer is equal to the depth of the groove, or the thickness of the heated or cooled second space release layer is smaller than the depth of the groove.
According to still another aspect of the present invention, in the bulk acoustic wave resonator, an upper surface of a portion of the top electrode connection portion located above the second air gap is stepped.
According to still another aspect of the present invention, in the bulk acoustic wave resonator, the top electrode further includes a top electrode reflecting portion including a second concave frame and/or a second convex frame formed at an upper surface of the top electrode main body portion at an edge of the effective region.
According to yet another aspect of the present invention, the bulk acoustic wave resonator further comprises a seed layer formed between the substrate and the bottom electrode.
The invention also provides a filter comprising a bulk acoustic wave resonator formed by the manufacturing method or realized by the bulk acoustic wave resonator.
The invention also provides a duplexer, which comprises a transmitting filter and a receiving filter, wherein the transmitting filter and/or the receiving filter are/is realized by adopting the filters.
According to the bulk acoustic wave resonator and the manufacturing method thereof provided by the invention, on one hand, the air gap is formed inside the bottom electrode, and the acoustic wave entering the bottom electrode can be reflected back to the effective area, so that a cavity is not required to be formed between the substrate and the bottom electrode like the prior art. And the air gap inside the bottom electrode is formed by the space released by the shrinkage of the volume after heating/cooling by the space release layer filled inside the bottom electrode. Compared with the mode of etching the substrate, filling the sacrificial material and removing the sacrificial material by using an etching solution through a release channel to form a cavity between the substrate and the bottom electrode in the prior art, the air gap forming mode has simpler process and lower cost; on the other hand, a convex and/or concave bottom electrode reflecting part is formed on the upper surface of the bottom electrode at the edge of the effective region, and the bottom electrode reflecting part can provide discontinuity of acoustic impedance, so that when sound waves propagate from the inside of the effective region to the bottom electrode reflecting part, the sound waves are emitted back into the effective region, thereby effectively reducing the transverse leakage of the sound waves and further effectively improving the quality factor of the bulk acoustic wave resonator. Correspondingly, the filter and the duplexer formed by the bulk acoustic wave resonator have the characteristics of simple process, low cost and excellent performance.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:
FIG. 1 is a schematic cross-sectional view of a conventional bulk acoustic wave resonator of the prior art;
FIG. 2 is a flow chart of a method of manufacturing a bulk acoustic wave resonator according to a specific embodiment of the present invention;
fig. 3 (a) to 3 (j) are schematic cross-sectional views of stages in the manufacture of a bulk acoustic wave resonator according to the process flow shown in fig. 2;
fig. 4 (a) to 4 (f) are schematic sectional views of respective stages of forming a top electrode connection portion while forming a top electrode main body portion on the structure shown in fig. 3 (h);
fig. 5 is a schematic cross-sectional view of a bulk acoustic wave resonator according to a preferred embodiment of the present invention;
fig. 6 is a schematic cross-sectional view of a bulk acoustic wave resonator according to another preferred embodiment of the present invention.
The same or similar reference numbers in the drawings refer to the same or similar parts.
Detailed Description
For a better understanding and explanation of the present invention, reference will be made to the following detailed description of the invention taken in conjunction with the accompanying drawings.
The invention provides a method for manufacturing a bulk acoustic wave resonator. Referring to fig. 2, fig. 2 is a flowchart of a method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present invention. As shown, the manufacturing method includes:
In step S101, a substrate is provided;
in step S102, forming a bottom electrode on the substrate, where the bottom electrode includes a bottom electrode body portion and a bottom electrode reflecting portion, the bottom electrode body portion includes, in order from bottom to top, a first metal layer, a first space release layer, and a second metal layer, the second metal layer is formed on the first metal layer and covers the first space release layer, and the bottom electrode reflecting portion includes a first concave frame and/or a first convex frame formed on an upper surface of the bottom electrode body portion at an edge of an active region of the bulk acoustic wave resonator, where the first space release layer is heated or cooled and then has a volume that is shrunk;
in step S103, a piezoelectric layer is formed on the bottom electrode, and a top electrode is formed on the piezoelectric layer;
in step S104, the first space release layer is heated or cooled to shrink the volume of the released space to form a first air gap in the bottom electrode main body, wherein a horizontally projected overlapping area of the top electrode, the piezoelectric layer, the second metal layer, and the first air gap constitutes the effective region of the bulk acoustic wave resonator.
Next, the above steps S101 to S104 will be described in detail with reference to fig. 3 (a) to 3 (j) in a specific embodiment.
Specifically, in step S101, as shown in fig. 3 (a), a substrate 100 is provided. The invention is not limited in the specific implementation of the substrate 100 and may be implemented using semiconductor materials such as silicon, germanium, silicon germanium, etc. Preferably, the thickness of the substrate 100 ranges from 50 μm to 1000 μm. It will be appreciated by those skilled in the art that the thickness of the substrate 100 should not be limited to the above-described range, but may be formulated accordingly according to actual design requirements.
Preferably, a seed layer (not shown) is deposited on the upper surface of the provided substrate 100. In this embodiment, the material of the seed layer may be aluminum nitride, scandium-doped aluminum nitride, or the like. The formation of the seed layer is beneficial to ensuring the crystal orientation growth of the bottom electrode.
In step S102, a bottom electrode is formed on the substrate 100, wherein the bottom electrode includes a bottom electrode main body portion and a bottom electrode reflection portion. In this embodiment, the bottom electrode is formed as follows:
first, as shown in fig. 3 (b), a first metal layer 101 is deposited on a substrate 100. The material of the first metal layer 101 may be made of an existing conventional metal electrode material, such as molybdenum, and for brevity, all possible materials of the first metal layer 101 are not listed here.
Next, as shown in fig. 3 (c), in the first metal layer101, a space release material (not shown, and hereinafter referred to as a first space release material) is deposited thereon, and then the first space release material is patterned to form a space release layer 102 (hereinafter referred to as a first space release layer 102). Wherein, after the space release layer 102 is formed, a portion of the upper surface of the first metal layer 101 is exposed. In this embodiment, the first space release material has a characteristic that the volume changes after heating or cooling, specifically, the volume shrinks after heating or cooling. The first space release material which is contracted in volume after heating may be porous material such as porous silicon oxide, porous silicon, or volatile material-containing material such as SiO containing moisture 2 Etc. For the sake of brevity, all possible materials that undergo shrinkage in volume upon cooling will not be described here. It should be noted that, in the present invention, the air gap is formed by utilizing the characteristic that the first space release material is heated or cooled to shrink to release a certain space, so that the first space release material needs to have a volume stability after being heated or cooled, that is, the volume of the first space release material which has shrunk after being heated or cooled is not changed substantially any more.
Next, as shown in fig. 3 (d), a second metal layer 103 is deposited on the structure shown in fig. 3 (c), and the second metal layer 103 covers the first metal layer 101 and the first space release layer 102. The material of the second metal layer 103 may also be made of an existing conventional metal electrode material such as molybdenum. Preferably, the material of the second metal layer 103 is the same as the material of the first metal layer 101. It will be appreciated by those skilled in the art that the material of the second metal layer 103 may also be different from the material of the first metal layer 101.
Next, as shown in fig. 3 (e), the second metal layer 103 and the first metal layer 101 are etched to form a metal layer structure filled with the first space release layer 102, which is hereinafter referred to as a bottom electrode body portion.
Next, as shown in fig. 3 (f), the upper surface of the bottom electrode main body portion (i.e., the upper surface of the second metal layer 103) is etched to form a recessed frame 104a (hereinafter, referred to as a first recessed frame 104 a), and a raised frame 104b (hereinafter, referred to as a first raised frame 104 b) is formed by deposition on the upper surface of the bottom electrode main body portion as shown in fig. 3 (g). Wherein the first concave frame 104a and the first convex frame 104b constitute a bottom electrode reflecting portion. In this embodiment, the bottom electrode reflection part is formed at the edge of the active region of the bulk acoustic wave resonator. The effective area of the bulk acoustic wave resonator refers to the horizontal projection overlapping area of the top electrode, the piezoelectric layer, the bottom electrode and the acoustic mirror. For the purposes of the present invention, the acoustic mirror is the air gap that is subsequently formed in the bottom electrode body portion by taking advantage of the volumetric shrinkage characteristics of the first space release layer. Here, since the position of the effective region is designed in advance before the actual fabrication of the bulk acoustic wave resonator, the bottom electrode reflecting portion may be formed at the edge of the effective region on the upper surface of the bottom electrode main body portion according to the design in advance. The bottom electrode reflecting portion is formed at the edge of the effective area of the bulk acoustic wave resonator means that the outer edge of the horizontal projection of the bottom electrode reflecting portion is located outside the horizontal projection of the effective area, and the inner edge of the bottom electrode reflecting portion coincides with the outer edge of the horizontal projection of the effective area or falls into the edge area of the horizontal projection of the effective area. Further, in the present embodiment, as shown in fig. 3 (g), the first convex frame 104b is located outside the first concave frame 104a, and there is no space in close proximity to both (i.e., the first convex frame 104b shares the same side wall as the first concave frame 104 a).
In the present embodiment, the formation process of the first concave frame 104a is as follows: firstly, forming a photoresist layer on the upper surface of the bottom electrode main body part, then patterning the photoresist layer to expose the area of the upper surface of the bottom electrode main body part for forming a first concave frame, then etching the exposed area to form the first concave frame, and finally removing the photoresist layer. The first bump frame 104b is formed as follows: firstly, forming a photoresist layer on the upper surface of the bottom electrode main body part, then patterning the photoresist layer to expose the area of the upper surface of the bottom electrode main body part for forming a first convex frame, then forming the first convex frame in the exposed area in a deposition mode, and finally removing the photoresist layer.
In the present embodiment, the first concave frame 104a and the first convex frame 104b each have an annular shape. Wherein, since the first concave frame 104a and the first convex frame 104b are formed at the edges of the effective area, the shape thereof is generally related to the effective area shape. For example, the effective area is in a regular pentagon shape, and the first concave frame and the first convex frame are in a regular pentagon ring shape respectively.
In the present embodiment, the depth of the first recessed frame 104a (i.e., the vertical distance between the bottom surface of the first recessed frame 104a and the upper surface of the second metal layer 103, denoted by H in fig. 3 (f)) 1 Representation) of the range is
To->
Width (i.e., vertical distance between sidewalls of the first recessed frame 104a, W in fig. 3 (f)) 1 Indicated) is in the range of 0.1 μm to 20 μm. The height of the first bump frame 104b (i.e., the vertical distance between the top surface of the first bump frame 104b and the upper surface of the second metal layer 103, shown as H in FIG. 3 (g)) 2 Representation) range is +.>
To->
Width (i.e., vertical distance between sidewalls of first bump frame 104b, in W in FIG. 3 (g)) 2 Indicated) is in the range of 0.1 μm to 20 μm. It will be appreciated by those skilled in the art that the specific dimensions of the bottom electrode reflecting portion are not limited to the above embodiments, and in other embodiments, may be formulated accordingly according to actual design requirements.
The first bump frame (1) is made of a conventional metal electrode material, and may be the same as or different from the material of the first metal layer and the second metal layer. (2) The first raised frame may be formed first and then the first recessed frame may be formed, or vice versa. (3) It is also possible to form only the first concave frame or only the first convex frame, i.e., the bottom electrode reflecting portion includes only the first concave frame or only the first convex frame.
In step S103, first, as shown in fig. 3 (h), a piezoelectric material (not shown) that covers the bottom electrode is deposited on the substrate 100, and the piezoelectric material is subjected to a planarization operation to form a piezoelectric layer 105 with a flat upper surface. It should be noted that, in other embodiments, the piezoelectric material may be deposited to directly form the piezoelectric layer without performing the planarization operation. Next, as shown in fig. 3 (i), a top electrode 106 is formed on the piezoelectric layer 105. The material of the top electrode 106 may be made of an existing conventional metal electrode material, such as molybdenum, and may be the same as or different from the metal material in the bottom electrode.
In step S104, as shown in fig. 3 (j), the structure shown in fig. 3 (i) is subjected to a heating process or a cooling process. For example, the heat treatment may be a tube annealing at 300 to 1100 ℃ for not more than 10 hours, a spike annealing at 650 to 1300 ℃ for not more than 20 seconds, or a laser annealing or a flash annealing at 700 to 1500 ℃ for not more than 20 milliseconds. Of course, the heating process should not be limited to the above-described annealing operation only, but a corresponding manner may be selected according to the specific characteristics of the material of the first space release layer. The cooling process may likewise be selected in accordance with the specific properties of the material of the first space release layer, and for the sake of brevity, all possible ways of cooling process are not listed here. After the heating or cooling treatment, the first space release layer 102 is shrunk in volume to release a certain space under the second metal layer 103, so that an air gap 107 (hereinafter referred to as a first air gap 107) is formed in the bottom electrode. By a reasonable choice of the material and thickness of the first space release layer, the thickness of the first air gap 107 is preferably made larger than 10 μm to ensure the sound wave reflection effect. It should be noted here that the heating or cooling treatment of the first space release layer should not be limited to the formation of the top electrode, but may be performed at any time after the deposition of the second metal layer 103 in fig. 3 (d), for example, immediately after the formation of the structure shown in fig. 3 (d), or after the formation of the entire bottom electrode, after the formation of the piezoelectric layer, or even after the formation of the passivation layer (typically formed over the top electrode), which is not limited in any way herein.
For the present invention, the first air gap 107 is an acoustic mirror of the bulk acoustic wave resonator, and there is a projected overlapping area (hereinafter referred to as overlapping area) with the second metal layer 103, the piezoelectric layer 105, and the top electrode 106 in the horizontal direction, and the overlapping area constitutes an effective area of the bulk acoustic wave resonator. When the acoustic wave in the active region of the bulk acoustic wave resonator is transmitted to the interface between the second metal layer 103 and the first air gap 107, it is reflected back to the active region by the first air gap 107. That is, for the present invention, although a cavity is not formed between the substrate and the bottom electrode as in the prior art, reflection of the acoustic wave can be achieved as well, ensuring normal operation of the bulk acoustic wave resonator. And the first air gap inside the bottom electrode is formed by filling the first space release material inside the bottom electrode and then heating or cooling it, it is apparent that the manufacturing process can be effectively simplified and the manufacturing cost can be reduced, compared to the prior art, since the present invention is implemented without etching the substrate, without forming the release channel, nor removing the sacrificial material with the etching solution. Particularly, in the case of adopting a rapid heating or cooling mode (such as millisecond annealing and the like), the manufacturing time of the bulk acoustic wave resonator can be effectively shortened, so that the manufacturing efficiency is improved. In addition, the bottom electrode reflecting part on the upper surface of the bottom electrode can provide discontinuity of impedance, and sound waves are reflected back into the effective area when transmitted to the bottom electrode reflecting part, so that transverse leakage of the sound waves can be effectively reduced, and the quality factor of the bulk acoustic wave resonator is effectively improved.
In a preferred embodiment, the top electrode comprises a top electrode body portion and a top electrode connection portion, wherein the top electrode body portion is located within the bulk acoustic wave resonator active area, and the top electrode connection portion is connected to an edge of the top electrode body portion. The top electrode connection may be an air wing and/or an air bridge. The air wing part is a structure with one end connected with the top electrode main body part and the other end suspended, and the air bridge part is a structure with one end connected with the top electrode main body part and the other end formed on the piezoelectric layer and partially suspended between the two ends. A method of manufacturing a bulk acoustic wave resonator according to the present invention will be described below by taking a top electrode connection portion including an air wing portion and an air bridge portion formed on the structure shown in fig. 3 (h) as an example.
Specifically, first, as shown in fig. 4 (a), the upper surface of the piezoelectric layer 105 is etched to form a groove 108a and a groove 108b, wherein the groove 108a corresponds to an air wing portion to be formed, and the groove 108b corresponds to a portion of the air bridge portion to be formed that is suspended. Since the air wing portion and the air bridge portion are connected to the edge of the main body portion of the top electrode located in the active region, grooves 108a and 108b are formed on the upper surface of the piezoelectric layer 105 at the edge of the active region, respectively.
Next, a layer of space release material (not shown, and hereinafter referred to as a second space release material) is deposited on the upper surface of the piezoelectric layer 105, and the second space release material is subjected to a planarization operation as shown in fig. 4 (b). The second space release material after the planarization operation is denoted by reference numeral 109 in the figure. In this embodiment, the planarized second space release material has an upper surface higher than the upper surface of the piezoelectric layer 105. The second space release material has the same characteristics as the first space release material in that the volume shrinks after heating or cooling and the volume remains stable after shrinking. Wherein the second space release material may be the same or different from the first space release material.
Next, considering that a partial region of the top electrode body portion, and the air bridge portion will be formed on the piezoelectric layer, the second space release material 109 is etched to expose a region (hereinafter, denoted as a first region) of the piezoelectric layer upper surface for forming the top electrode body portion and the air bridge portion. As shown in fig. 4 (c), after the etching of the second space release material is completed, a second space release layer 110a is formed in the groove 108a, a second space release layer 110b is formed in the groove 108b, and a second space release layer 110c is formed in the other region of the upper surface of the piezoelectric layer 105 than the first region. In other embodiments, the second space release layer 110c may be removed, leaving only the second space release layer 110a within the recess 108a and the second space release layer 110b within the recess 108 b.
Next, a third metal layer 111 is deposited on the piezoelectric layer 105 as shown in fig. 4 (d), and the third metal layer 111 is patterned as shown in fig. 4 (e), and a portion of the third metal layer 111 on the second space release layer 110c is removed to form a top electrode. The portion of the top electrode above the bottom electrode (i.e., in the active area) is referred to as a top electrode body 112a, the portion of the top electrode above the second space release layer 110a is referred to as an air wing 112b, and the portion of the top electrode above the piezoelectric layer and the second space release layer 110b is referred to as an air bridge 112c.
Finally, as shown in fig. 4 (e), the second space release layer 110a and the second space release layer 110b are subjected to a heating treatment or a cooling treatment. After the heat treatment or the cooling treatment, the second space release layer 110a volume is contracted to release a certain space below the air wing portion 112b to form an air gap 113a (hereinafter, referred to as a second air gap 113 a), and likewise, the second space release layer 110b volume is contracted to release a certain space below the air bridge wing portion 112c to form an air gap 113b (hereinafter, referred to as a second air gap 113 b). In this way, the air wing 112b is suspended in the air, and the portion of the air bridge 112c above the second space release layer 110b is also suspended in the air in an arch bridge shape. In this embodiment, the first space release material is the same as the second space release material, and thus the first air gap 107 and the second air gaps 113a and 113b can be formed at one time by performing the heating process or the cooling process at the same time. In other embodiments, if the processing conditions of the first space release material and the second space release material are different, the heating process or the cooling process may be performed separately.
It should be noted that (1) in this embodiment, the material of the second space release layers in the grooves 108a and 108b is the same, and in other embodiments, the material of the second space release layers in the grooves 108a and 108b may be different. (2) The material of the second space release layer is different, and the volume of the second space release layer after shrinkage is also different, in this embodiment, the thickness of the heated or cooled second space release layer is greater than the depth of the groove (i.e. the upper surface of the second space release layer is higher than the upper surface of the piezoelectric layer), in other embodiments, the thickness of the heated or cooled second space release layer may be just equal to the depth of the groove (i.e. the upper surface of the second space release layer is flush with the upper surface of the piezoelectric layer), or less than the depth of the groove (i.e. the upper surface of the second space release layer is lower than the upper surface of the piezoelectric layer). (3) Preferably, the materials of the first space release layer and the second space release layer have opposite temperature coefficients to those of the piezoelectric layer, so that the temperature compensation function can be effectively achieved.
The top electrode connection portion and the grooves of the second space release layer formed on the piezoelectric layer can also provide discontinuity of acoustic impedance, which is beneficial to reflecting sound waves back into the effective area of the bulk acoustic wave resonator, so that transverse leakage of the sound waves is reduced, and the quality factor of the bulk acoustic wave resonator is further improved. In the prior art, the space below the air bridge part and the air wing part is also removed by the corrosive solution, and the invention is formed by utilizing the characteristics of the material with volume shrinkage after heating or cooling, and has simple process and low cost.
In another preferred embodiment, as shown in fig. 5, the upper surface of the portion of the top electrode connecting portion above the second air gap (i.e., the portion where the top electrode connecting portion is suspended) is stepped (the portion encircled by the dotted line in the figure). Wherein the step shape is in a trend from low to high with distance from the top electrode main body part. The step shape of the upper surface of the top electrode connection portion can further provide discontinuity of acoustic impedance, so that lateral leakage of sound waves is further reduced, and the quality factor of the bulk acoustic wave resonator is further improved.
In yet another preferred implementation, as shown in fig. 6, the top electrode may further include a top electrode reflecting portion further including a second concave frame 114a and a second convex frame 114b. The top electrode reflecting portion is formed on the upper surface of the top electrode main body portion at the edge of the effective region, corresponding to the bottom electrode reflecting portion. The forming steps, dimensional parameters, and the like of the second concave frames 114a and the second convex frames 114b may be referred to the first concave frames 104a and the first convex frames 104b, respectively. Those skilled in the art will appreciate that in other embodiments, the top electrode reflector may also include only the second concave frame 114a, or only the second convex frame 114b. The top electrode reflector also provides an acoustic impedance discontinuity, as does the bottom electrode reflector, which can reflect sound waves back into the active region to reduce lateral leakage of sound waves and thereby improve the quality factor of the bulk acoustic wave resonator.
Correspondingly, the invention also provides a bulk acoustic wave resonator, which comprises:
a substrate, a bottom electrode formed on the substrate, a piezoelectric layer formed on the bottom electrode, and a top electrode formed on the piezoelectric layer, the bottom electrode including a bottom electrode main body portion and a bottom electrode reflection portion;
the bottom electrode main body part sequentially comprises a first metal layer, a first space release layer after heating or cooling, a first air gap and a second metal layer, wherein the second metal layer is formed on the first metal layer and covers the first air gap and the first space release layer after heating or cooling, and the first air gap is formed by a space released by volume shrinkage after heating or cooling of the first space release layer;
the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and positioned at the edge of the active area of the bulk acoustic wave resonator;
wherein the horizontal projection overlap region of the top electrode, the piezoelectric layer, the second metal layer, and the first air gap constitutes the effective region of the bulk acoustic wave resonator.
The respective constituent elements of the above-described bulk acoustic wave resonator will be described below with reference to fig. 3 (j).
Specifically, as shown, the bulk acoustic wave resonator provided by the present invention includes a substrate 100. The materials, dimensions, etc. of the substrate 100 may be referred to in the description of the relevant portions of the foregoing manufacturing method, and for brevity, will not be described in detail herein.
As shown in the drawing, the bulk acoustic wave resonator provided by the present invention further includes a bottom electrode formed on the substrate 100, the bottom electrode including a bottom electrode main body portion and a bottom electrode reflection portion. In this embodiment, the bottom electrode body portion includes, in order from below, a first metal layer 101, a heated or cooled first space release layer 102, a first air gap 107, and a second metal layer 103. Wherein the second metal layer 103 is formed on the first metal layer 101 and covers the first air gap 107 and the heated or cooled first space release layer 102.
The first metal layer 101 and the second metal layer 103 may be made of an existing conventional metal electrode material such as molybdenum, wherein the materials of the first metal layer 101 and the second metal layer 103 may be the same or different. If the materials of the first metal layer 101 and the second metal layer 103 are the same, the first metal layer 101 and the second metal layer 103 may be formed as an integrated structure, and in this case, the lower surface of the first space release layer 102 may be defined as a boundary, and a portion of the bottom electrode below the lower surface of the first space release layer 102 may be defined as the first metal layer, and a portion above the lower surface of the first space release layer 102 may be defined as the second metal layer.
The material of the first space release layer 102 has a characteristic that the volume changes after heating or cooling, specifically, the volume shrinks after heating or cooling. The first space release layer 102, which is shrunk in volume after heating, may be porous material such as porous silicon oxide, porous silicon, or volatile material containing material such as SiO containing moisture 2 Etc. For the sake of brevity, all possible materials that undergo shrinkage in volume upon cooling will not be described here. The first space release layer 102 before heating or cooling completely fills the space between the first metal layer 101 and the second metal layer 103, and after heating or cooling, the first space release layer 102 volume shrinks to release a certain space to form a first air gap 107. The thickness of the first air gap 107 is preferably greater than 10 μm to ensure an acoustic wave reflection effect. It should be noted that the first air gap 107 is formed by heating the first space release layer 102 orThe first space release layer 102 needs to have a volume stability after heating or cooling, that is, the volume of the first space release layer 102 that has been shrunk after heating or cooling is not substantially changed, in order to ensure the stability of the first air gap.
The present invention is not limited in any way with respect to the heating or cooling treatment to which the first space release layer 102 is subjected. For example, the heat treatment may be a tube annealing at 300 to 1100 ℃ for not more than 10 hours, a spike annealing at 650 to 1300 ℃ for not more than 20 seconds, or a laser annealing or a flash annealing at 700 to 1500 ℃ for not more than 20 milliseconds. Of course, the heating process should not be limited to only the annealing operation described above, and a corresponding manner may be selected according to the specific characteristics of the first space release layer 102. For the cooling process, the specific properties of the first space release layer 102 may likewise be selected accordingly, and for the sake of brevity, all possible ways of cooling process are not listed here.
In the present embodiment, the bottom electrode reflecting portion includes a first concave frame 104a and a first convex concave 104b. In other embodiments, the bottom electrode reflecting portion may also include only the first concave frame 104a or only the first convex concave 104b. The bottom electrode reflecting portion is formed at the edge of the active region of the bulk acoustic wave resonator. The effective area of the bulk acoustic wave resonator refers to the horizontal projection overlapping area of the top electrode, the piezoelectric layer, the bottom electrode and the acoustic mirror. For the present invention, the acoustic mirror is the first air gap 102, and correspondingly the active area of the bulk acoustic wave resonator is the horizontal projection overlap area of the top electrode, the piezoelectric layer, the second metal layer 103 and the first air gap 102. The bottom electrode reflecting portion is formed at the edge of the effective area of the bulk acoustic wave resonator means that the outer edge of the horizontal projection of the bottom electrode reflecting portion is located outside the horizontal projection of the effective area, and the inner edge of the bottom electrode reflecting portion coincides with the outer edge of the horizontal projection of the effective area or falls into the edge area of the horizontal projection of the effective area. Further, in the present embodiment, as shown, the first convex frame 104b is located outside the first concave frame 104a, and both are immediately adjacent to each other without any space (i.e., the first convex frame 104b shares the same side wall as the first concave frame 104 a).
In the present embodiment, the first concave frame 104a and the first convex frame 104b each have an annular shape. Wherein, since the first concave frame 104a and the first convex frame 104b are formed at the edges of the effective area, the shape thereof is generally related to the effective area shape. For example, the effective area is in a regular pentagon shape, and the first concave frame and the first convex frame are in a regular pentagon ring shape respectively.
In this embodiment, the dimensions (including depth, height, width, material, etc.) of the first concave frame 104a and the first convex frame 104b may refer to the relevant content in the foregoing manufacturing method, and for brevity, they will not be described herein.
As shown, the bulk acoustic wave resonator provided by the present invention further includes a piezoelectric layer 105 formed over the bottom electrode and a top electrode 106 formed over the piezoelectric layer 105. The materials, dimensions, etc. of the piezoelectric layer 105 and the top electrode 106 may be referred to in the foregoing manufacturing method, and are not described herein for brevity.
Preferably, the bulk acoustic wave resonator provided by the present invention further includes a seed layer (not shown) formed between the substrate and the bottom electrode. In this embodiment, the material of the seed layer may be aluminum nitride, scandium-doped aluminum nitride, or the like. The presence of the seed layer is beneficial to ensuring the crystal orientation growth of the bottom electrode.
According to the bulk acoustic wave resonator provided by the invention, on one hand, the first air gap is formed in the bottom electrode, so that the acoustic wave entering the bottom electrode can be reflected back to the effective area, and therefore, a cavity is not required to be formed between the substrate and the bottom electrode as in the prior art. And the first air gap inside the bottom electrode is formed by the space released by the shrinkage of the volume after heating/cooling of the first space release layer filled inside the bottom electrode. Compared with a cavity structure formed between a substrate and a bottom electrode by etching the substrate, filling the sacrificial material and removing the sacrificial material through a release channel by using an etching solution in the prior art, the bulk acoustic wave resonator provided by the invention has the advantages of simpler process and lower cost; on the other hand, the upper surface of the bottom electrode is provided with a convex and/or concave bottom electrode reflecting part at the edge of the effective area, and the bottom electrode reflecting part can provide discontinuity of acoustic impedance, so that sound waves can be emitted back into the effective area when propagating from the inside of the effective area to the bottom electrode reflecting part, thereby effectively reducing the transverse leakage of the sound waves and further effectively improving the quality factor of the bulk acoustic wave resonator.
In a preferred embodiment, the top electrode comprises a top electrode body portion and a top electrode connection portion, wherein the top electrode body portion is located within the bulk acoustic wave resonator active area, and the top electrode connection portion is connected to an edge of the top electrode body portion and comprises a suspended portion. The top electrode connection may be an air wing and/or an air bridge. The air wing part is a structure with one end connected with the top electrode main body part and the other end suspended, and the air bridge part is a structure with one end connected with the top electrode main body part and the other end formed on the piezoelectric layer and partially suspended between the two ends. The following will take fig. 4 (f) as an example.
Specifically, as shown, the top electrode includes a top electrode main body 112a, and an air wing 112b and an air bridge 112c connected to edges of the top electrode main body 112a, respectively. A groove is formed in the upper surface of the piezoelectric layer 105 at a position corresponding to the air wing 112b, a heated or cooled second space release layer 110a is formed in the groove, and a second air gap 113a is formed between the heated or cooled second space release layer 110a and the air wing 112b, and the air wing 112b is suspended in the air due to the presence of the second air gap 113 a. A groove is also formed in the upper surface of the piezoelectric layer 105 at a position corresponding to the air bridge 112c, and a heated or cooled second space release layer 110b is formed in the groove, and a second air gap 113b is formed between the heated or cooled second space release layer 110b and the air bridge 112c, and a portion between both ends of the air bridge 112c is suspended in the air due to the presence of the second air gap 113 b. Here, since the air wing portion and the air bridge portion are connected to the edge of the main body portion of the top electrode located in the active area, the recess on the upper surface of the piezoelectric layer and the second space release layer in the recess are located at the edge of the active area.
The material of the second space release layer has the same characteristics as the material of the first space release layer 102, i.e. the volume shrinks after heating or cooling and the volume remains stable after shrinking. Wherein the material of the second space release layer and the material of the first space release layer may be the same or different.
The space between the piezoelectric layer 105 and the air wing 112b is completely filled with the second space release layer 110a before heating or cooling, and the second space release layer 110a is contracted in volume to release a certain space after heating or cooling to form a second air gap 113a. Similarly, the space between the piezoelectric layer 105 and the air bridge 112c is completely filled with the second space release layer 110b before heating or cooling, and the second space release layer 110b is volume-contracted to release a certain space after heating or cooling to form the second air gap 113b.
In this embodiment, (1) the material of the second space release layer below the air wing portion and the air bridge portion is the same, and may be different in other embodiments. (2) The material of the second space release layer is different, and the volume of the second space release layer after shrinkage is also different, in this embodiment, the thickness of the heated or cooled second space release layer is greater than the depth of the groove (i.e. the upper surface of the second space release layer is higher than the upper surface of the piezoelectric layer), in other embodiments, the thickness of the heated or cooled second space release layer may be just equal to the depth of the groove (i.e. the upper surface of the second space release layer is flush with the upper surface of the piezoelectric layer), or less than the depth of the groove (i.e. the upper surface of the second space release layer is lower than the upper surface of the piezoelectric layer). (3) Preferably, the materials of the first space release layer and the second space release layer have opposite temperature coefficients to those of the piezoelectric layer, so that the temperature compensation function can be effectively achieved.
The top electrode connection portion and the grooves of the second space release layer formed on the piezoelectric layer can also provide discontinuity of acoustic impedance, which is beneficial to reflecting sound waves back into the effective area of the bulk acoustic wave resonator, so that transverse leakage of the sound waves is reduced, and the quality factor of the bulk acoustic wave resonator is further improved. In the prior art, the space below the air bridge part and the air wing part is also removed by the corrosive solution, and the invention is formed by utilizing the characteristics of the material with volume shrinkage after heating or cooling, and has simple process and low cost.
In another preferred embodiment, as shown in fig. 5, the upper surface of the portion of the top electrode connecting portion above the second air gap (i.e., the portion where the top electrode connecting portion is suspended) is stepped (the portion encircled by the dotted line in the figure). Wherein the step shape is in a trend from low to high with distance from the top electrode main body part. The step shape of the upper surface of the top electrode connection portion can further provide discontinuity of acoustic impedance, so that lateral leakage of sound waves is further reduced, and the quality factor of the bulk acoustic wave resonator is further improved.
In yet another preferred implementation, as shown in fig. 6, the top electrode may further include a top electrode reflecting portion further including a second concave frame 114a and a second convex frame 114b. The top electrode reflecting portion is formed on the upper surface of the top electrode main body portion at the edge of the effective region, corresponding to the bottom electrode reflecting portion. The forming steps, dimensional parameters, and the like of the second concave frames 114a and the second convex frames 114b may be referred to the first concave frames 104a and the first convex frames 104b, respectively. Those skilled in the art will appreciate that in other embodiments, the top electrode reflector may also include only the second concave frame 114a, or only the second convex frame 114b. The top electrode reflector also provides an acoustic impedance discontinuity, as does the bottom electrode reflector, which can reflect sound waves back into the active region to reduce lateral leakage of sound waves and thereby improve the quality factor of the bulk acoustic wave resonator.
The invention also provides a filter comprising the bulk acoustic wave resonator provided by the invention. For the sake of brevity, the bulk acoustic wave resonator provided by the present invention will not be described repeatedly herein, and reference may be made to the relevant portions of the foregoing. The bulk acoustic wave resonator may be disposed in a series and/or parallel branch of the filter, nor is the invention limited in this regard. Since there are numerous possibilities for the structure of the filter, all possible structures of the filter are not listed here for the sake of brevity. The filter formed by the bulk acoustic wave resonator provided by the invention has the characteristics of simple process, low cost and excellent performance.
The invention also provides a duplexer, which comprises a transmitting filter and a receiving filter, wherein the transmitting filter and/or the receiving filter are/is realized by adopting the filter provided by the invention. For the sake of brevity, the description of the filter provided by the present invention will not be repeated here, and the structure thereof may be referred to in the relevant part of the foregoing. The duplexer formed based on the filter provided by the invention has the characteristics of simple process, low cost and excellent performance.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is evident that the word "comprising" does not exclude other elements, units or steps, and that the singular does not exclude a plurality. Various components, units or means recited in the system claims may also be implemented by means of software or hardware by means of one component, unit or means.
The foregoing disclosure is only illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (17)
1. A method of manufacturing a bulk acoustic wave resonator, the method comprising:
providing a substrate;
forming a bottom electrode on the substrate, wherein the bottom electrode comprises a bottom electrode main body part and a bottom electrode reflecting part, the bottom electrode main body part sequentially comprises a first metal layer, a first space release layer and a second metal layer from bottom to top, the second metal layer is formed on the first metal layer and covers the first space release layer, the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and are positioned at the edge of an effective area of the bulk acoustic wave resonator, and the first space release layer is heated or cooled and then has volume shrinkage;
forming a piezoelectric layer on the bottom electrode, and forming a top electrode on the piezoelectric layer;
the manufacturing method further comprises the steps of: heating or cooling the first space release layer to volume shrink the released space to form a first air gap in the bottom electrode body part;
wherein the horizontal projection overlap region of the top electrode, the piezoelectric layer, the second metal layer, and the first air gap constitutes the effective region of the bulk acoustic wave resonator.
2. The manufacturing method according to claim 1, wherein the step of forming a bottom electrode on the substrate comprises:
depositing a first metal layer on the substrate;
depositing and patterning a space release material on the first metal layer to form a first space release layer;
forming a second metal layer covering the first space release layer on the first metal layer;
etching the second metal layer and the first metal layer to form a bottom electrode body portion;
etching the upper surface of the bottom electrode body part to form a first concave frame and/or depositing the first convex frame on the upper surface of the bottom electrode body part.
3. The manufacturing method according to claim 2, wherein:
the material of the first metal layer is the same as the material of the second metal layer; or (b)
The material of the first metal layer is different from the material of the second metal layer.
4. The manufacturing method according to claim 1, wherein:
after forming the piezoelectric layer on the bottom electrode, the manufacturing method further includes: etching the upper surface of the piezoelectric layer to form a groove, wherein the groove is positioned at the edge of the effective area; forming a second space release layer in the groove, wherein the thickness of the second space release layer is larger than the depth of the groove, and the volume of the second space release layer is contracted after heating or cooling;
The step of forming a top electrode on the piezoelectric layer includes: depositing and patterning a third metal layer on the piezoelectric layer to form a top electrode comprising a top electrode body portion and a top electrode connection portion connected to an edge of the top electrode body portion and located above the second space release layer;
the manufacturing method further comprises the steps of: the second space release layer is heated or cooled to shrink its volume to release space to form a second air gap below the top electrode connection.
5. The manufacturing method according to claim 4, wherein:
the thickness of the heated or cooled second space release layer is larger than the depth of the groove, or the thickness of the heated or cooled second space release layer is equal to the depth of the groove, or the thickness of the heated or cooled second space release layer is smaller than the depth of the groove.
6. The manufacturing method according to claim 4, wherein a portion of the top electrode connecting portion located above the second air gap is stepped on an upper surface thereof.
7. The manufacturing method according to claim 4, wherein:
the top electrode further includes a top electrode reflecting portion including a second concave frame and/or a second convex frame formed at an upper surface of the top electrode main body portion at an edge of the effective region.
8. The manufacturing method according to claim 1, after providing a substrate and before forming a bottom electrode on the substrate, further comprising:
a seed layer is formed on the substrate.
9. A bulk acoustic wave resonator, the bulk acoustic wave resonator comprising:
a substrate, a bottom electrode formed on the substrate, a piezoelectric layer formed on the bottom electrode, and a top electrode formed on the piezoelectric layer, the bottom electrode including a bottom electrode main body portion and a bottom electrode reflection portion;
the bottom electrode main body part sequentially comprises a first metal layer, a first space release layer after heating or cooling, a first air gap and a second metal layer, wherein the second metal layer is formed on the first metal layer and covers the first air gap and the first space release layer after heating or cooling, and the first air gap is formed by a space released by volume shrinkage after heating or cooling of the first space release layer;
the bottom electrode reflecting part comprises a first concave frame and/or a first convex frame which are formed on the upper surface of the bottom electrode main body part and positioned at the edge of the active area of the bulk acoustic wave resonator;
wherein the horizontal projection overlap region of the top electrode, the piezoelectric layer, the second metal layer, and the first air gap constitutes the effective region of the bulk acoustic wave resonator.
10. The bulk acoustic wave resonator according to claim 9, wherein
The material of the first metal layer is the same as the material of the second metal layer; or (b)
The material of the first metal layer is different from the material of the second metal layer.
11. The bulk acoustic wave resonator of claim 9, wherein:
the top electrode comprises a top electrode main body and a top electrode connecting part connected with the edge of the top electrode main body, wherein the top electrode connecting part comprises a suspension part;
and a groove is formed on the upper surface of the piezoelectric layer at the position opposite to the suspended part in the top electrode connecting part, a heated or cooled second space release layer is formed in the groove, and a second air gap is formed between the heated or cooled second space release layer and the top electrode connecting part and is formed by a space released by volume shrinkage of the heated or cooled second space release layer.
12. The bulk acoustic wave resonator of claim 11, wherein:
the thickness of the heated or cooled second space release layer is larger than the depth of the groove, or the thickness of the heated or cooled second space release layer is equal to the depth of the groove, or the thickness of the heated or cooled second space release layer is smaller than the depth of the groove.
13. The bulk acoustic wave resonator according to claim 11, wherein a portion of the top electrode connection portion located above the second air gap has a stepped upper surface.
14. The bulk acoustic wave resonator of claim 11, wherein:
the top electrode further includes a top electrode reflecting portion including a second concave frame and/or a second convex frame formed at an upper surface of the top electrode main body portion at an edge of the effective region.
15. The bulk acoustic wave resonator according to claim 9, further comprising:
a seed layer formed between the substrate and the bottom electrode.
16. A filter comprising a bulk acoustic wave resonator, wherein the bulk acoustic wave resonator is fabricated using the fabrication method of any one of claims 1 to 8, or is implemented using the bulk acoustic wave resonator of any one of claims 9 to 15.
17. A diplexer comprising a transmit filter and a receive filter, wherein the transmit filter and/or the receive filter are implemented using the filter of claim 16.
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| CN117134737A (en) * | 2023-10-27 | 2023-11-28 | 象朵创芯微电子(苏州)有限公司 | Bulk acoustic wave resonator chip structure and manufacturing method |
| CN117134737B (en) * | 2023-10-27 | 2024-01-30 | 象朵创芯微电子(苏州)有限公司 | Bulk acoustic wave resonator chip structure and manufacturing method |
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