CN111262551A - Air-gap type shear wave resonator based on lithium niobate thin film and preparation method thereof - Google Patents
Air-gap type shear wave resonator based on lithium niobate thin film and preparation method thereof Download PDFInfo
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 239000010409 thin film Substances 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title abstract description 7
- 239000010410 layer Substances 0.000 claims abstract description 119
- 239000000758 substrate Substances 0.000 claims abstract description 71
- 239000011241 protective layer Substances 0.000 claims abstract description 64
- 238000000034 method Methods 0.000 claims abstract description 48
- 238000000151 deposition Methods 0.000 claims abstract description 19
- 239000000463 material Substances 0.000 claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 claims abstract description 10
- 238000005498 polishing Methods 0.000 claims abstract description 6
- 238000001039 wet etching Methods 0.000 claims abstract description 4
- 238000005530 etching Methods 0.000 claims description 14
- 238000009616 inductively coupled plasma Methods 0.000 claims description 14
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 14
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 13
- 238000000137 annealing Methods 0.000 claims description 12
- 150000002500 ions Chemical class 0.000 claims description 9
- 230000008021 deposition Effects 0.000 claims description 8
- 229910052681 coesite Inorganic materials 0.000 claims description 7
- 229910052906 cristobalite Inorganic materials 0.000 claims description 7
- 239000000377 silicon dioxide Substances 0.000 claims description 7
- 229910052682 stishovite Inorganic materials 0.000 claims description 7
- 229910052905 tridymite Inorganic materials 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 238000001259 photo etching Methods 0.000 claims description 6
- IGELFKKMDLGCJO-UHFFFAOYSA-N xenon difluoride Chemical compound F[Xe]F IGELFKKMDLGCJO-UHFFFAOYSA-N 0.000 claims description 6
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 5
- 230000008878 coupling Effects 0.000 claims description 4
- 238000010168 coupling process Methods 0.000 claims description 4
- 238000005859 coupling reaction Methods 0.000 claims description 4
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 3
- 239000007772 electrode material Substances 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 239000007769 metal material Substances 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229920000620 organic polymer Polymers 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
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- 229910052814 silicon oxide Inorganic materials 0.000 claims description 2
- 239000010408 film Substances 0.000 abstract description 5
- 230000003071 parasitic effect Effects 0.000 abstract description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract 1
- 238000001312 dry etching Methods 0.000 abstract 1
- 238000005468 ion implantation Methods 0.000 abstract 1
- 229910052751 metal Inorganic materials 0.000 abstract 1
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- 229910052710 silicon Inorganic materials 0.000 abstract 1
- 239000010703 silicon Substances 0.000 abstract 1
- 238000004544 sputter deposition Methods 0.000 abstract 1
- 238000002347 injection Methods 0.000 description 8
- 239000007924 injection Substances 0.000 description 8
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 229920005591 polysilicon Polymers 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
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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
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
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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
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/853—Ceramic compositions
- H10N30/8542—Alkali metal based oxides, e.g. lithium, sodium or potassium niobates
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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
- H03H2003/023—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 the resonators or networks being of the membrane type
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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
- H03H2003/028—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 for obtaining desired values of other parameters
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- Acoustics & Sound (AREA)
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Abstract
The invention discloses an air-gap type shear wave resonator based on a lithium niobate film and a preparation method thereof, wherein the influence of a transverse wave parasitic mode is reduced through the optimized design of the aspects of electrode shape, electrode size, piezoelectric material taking, thickness and the like, so that the resonator only works in a shear wave mode, and the quality factor of the resonator is improved; depositing a protective layer and a sacrificial layer material on one surface of the double-polished high-resistance silicon wafer in sequence, and then chemically and mechanically polishing the substrate; transferring the lithium niobate thin film to the polished substrate by an ion implantation and wafer bonding method, and then sputtering a metal interdigital electrode on the surface of the lithium niobate thin film by utilizing a stripping process; finally, removing the sacrificial layer by using a dry etching or wet etching method; then protecting the surface, repeating the previous growth on the other surface, and removing the protective layer to obtain a finished device; and further, the mechanical strength and the reliability of the resonator are improved, and the resonator is suitable for large-scale manufacturing of the resonator.
Description
Technical Field
The invention relates to the technical field of film bulk acoustic resonators, in particular to an air-gap type shear wave resonator based on a lithium niobate film and a preparation method thereof.
Background
With the development of modern wireless communication technology towards high frequency and high speed, higher requirements are put forward on a front-end filter commonly used for radio frequency communication. The working frequency is continuously improved, and simultaneously, higher requirements on the size, the service performance, the stability and the integration of the device are also met. Thin film bulk acoustic filters based on aluminum nitride suffer from various drawbacks. The maximum electromechanical coupling coefficient of the aluminum nitride theory is only about 6%, so that the thin film bulk acoustic wave filter based on the aluminum nitride is not suitable for being applied to a broadband filter. And it is difficult to grow high quality, low defect aluminum nitride crystal material on top of the substrate material. Because the electromechanical coupling coefficient of lithium niobate is far higher than that of aluminum nitride, the lithium niobate shear wave resonator can be used for preparing a high-frequency broadband filter.
Disclosure of Invention
The invention aims to provide a lithium niobate resonator and a manufacturing method thereof, wherein the lithium niobate resonator can form shear wave resonance, simultaneously reduces the interference of a transverse vibration mode, and improves the mechanical strength and the reliability of the resonator.
The invention is realized by the following technical scheme:
a lithium niobate thin film based air gap type shear wave resonator comprising:
the device comprises a substrate, a first groove with an upward opening is arranged in the middle of the upper end of the substrate, and a second groove with a downward opening is arranged in the middle of the lower end of the substrate;
a first protective layer covering an inner surface grown in the first groove;
the first piezoelectric layer is grown on the upper end face of the substrate by covering the first groove; the first piezoelectric layer and the first protective layer jointly form a first air cavity; and
and the first electrode is grown on the upper end surface of the first piezoelectric layer through magnetron sputtering deposition.
Further, the piezoelectric device also comprises a second protective layer, a second piezoelectric layer and a second electrode; the second protective layer covers the inner surface of the second groove; the second piezoelectric layer covers the second groove and is grown on the lower end face of the substrate; the second piezoelectric layer and the second protective layer jointly form a second air cavity; and the second electrode is grown on the lower end surface of the second piezoelectric layer through magnetron sputtering deposition.
Further, the first protective layer and the second protective layer both adopt Si3N4、SiO2A material of (1); the thickness of first protective layer with the second protective layer is 1um ~ 3 um.
Furthermore, the first piezoelectric layer and the second piezoelectric layer are both made of lithium niobate piezoelectric materials; the thickness of the first piezoelectric layer and the second piezoelectric layer is 200 nm-6 um.
Further, the first electrode and the second electrode are made of one electrode material of Pt, Mo, Ag, Al and Au; the thickness of the first electrode and the thickness of the second electrode are both 50 nm-800 nm.
Further, the electrode distance of the first electrode is 400 nm-6 um; the width of the first electrode is 400 nm-4 um; the length of the first electrode is 40um ~ 200 um.
Further, a method for manufacturing an air-gap type shear wave resonator based on a lithium niobate thin film comprises the following steps:
step (1), the substrate is subjected to acid cleaning to remove organic matters and dirt on the surface, and the substrate is dried;
growing a third protective layer on the lower end face of the cleaned substrate by using a plasma enhanced chemical vapor deposition method, and etching a first groove in the middle of the upper end face of the substrate by using an inductively coupled plasma etching machine;
step (3), growing a first protective layer on the inner surface of the first groove by a thermal oxidation method; depositing a first sacrificial layer in the first groove by using a plasma enhanced chemical vapor deposition method, and polishing the substrate to be flush with the surface of the first sacrificial layer; the root mean square roughness of the polished substrate is less than 0.5 nm;
bonding a first piezoelectric layer on the upper end face of the substrate by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the first piezoelectric layer and the first protective layer jointly form a first air cavity, and annealing for 2 hours;
step (5), injecting positive ions into the first piezoelectric layer by an inductive coupling plasma method;
depositing a first electrode on the first piezoelectric layer by using a magnetron sputtering method, and carrying out photoetching on the first electrode to obtain an interdigital electrode;
step (7), releasing the first sacrificial layer in the first groove by adopting a dry release mode, wherein the released gas is xenon fluoride;
step (8), after the first sacrificial layer is released, a fourth protective layer is grown on the first electrode in a covering mode through a plasma enhanced chemical vapor deposition method; turning the substrate upside down, and removing the third protective layer on the lower end face of the substrate;
step (9), after removing the third protective layer, etching a second groove in the middle of the upper end face of the substrate by using an inductively coupled plasma etching machine;
step (10), growing a second protective layer on the inner surface of the second groove by a thermal oxidation method; depositing a second sacrificial layer in the second groove by using a plasma enhanced chemical vapor deposition method, and polishing the substrate to be flush with the surface of the second sacrificial layer; the root mean square roughness of the polished substrate is less than 0.5 nm;
step (11), bonding a second piezoelectric layer on the lower end face of the substrate by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the second piezoelectric layer and the second protective layer jointly form a second air cavity, and annealing for 2 hours;
a step (12) of injecting positive ions into the second piezoelectric layer by an inductively coupled plasma method;
step (13), depositing a second electrode on the second piezoelectric layer by using a magnetron sputtering method, and carrying out photoetching on the second electrode to obtain an interdigital electrode;
step (14), releasing the second sacrificial layer in the second groove by adopting a dry release mode, wherein the released gas is xenon fluoride;
and (15) removing the fourth protective layer by adopting wet etching to obtain a complete sample.
Further, the first air cavity and the second air cavity are 1um ~ 20um in depth.
Further, the first sacrificial layer and the second sacrificial layer are made of one of silicon oxide, phosphorosilicate glass, polycrystalline silicon, organic polymer and metal material.
Furthermore, positive ions injected into the first piezoelectric layer and the second piezoelectric layer are both H+。
The invention has the beneficial effects that:
(1) in the preparation method provided by the invention, the sacrificial layer is introduced firstly and then the release method is adopted, so that the etched area is limited to the part filled with the sacrificial layer, the transverse corrosion during the etching of the substrate is avoided, the mechanical strength and the reliability of the resonator are further improved, the yield of the product is improved at the same time, and the preparation method is suitable for the large-scale manufacturing of the resonator.
(2) By optimally designing the size of the electrodes, the electrode spacing and the thickness of the lithium niobate piezoelectric material and selecting a proper crystal tangent, the influence of a transverse wave parasitic mode is reduced, so that the resonator only works in a shear wave mode, and the quality factor of the resonator is improved.
Drawings
FIG. 1 is a cross-sectional view of an embodiment of a lithium niobate shear wave resonator on one side of a substrate without release;
FIG. 2 is a cross-sectional view of an embodiment after release of a lithium niobate shear wave resonator on one side of a substrate;
FIG. 3 is a cross-sectional view of the embodiment after turning over one side of the substrate;
FIG. 4 is a cross-sectional view of another lithium niobate shear wave resonator fabricated on the other side after being flipped in the embodiment;
fig. 5 is a complete cross-sectional view of the device prepared in the example.
In the drawings: 101-a substrate; 102-a third protective layer; 103-a first protective layer; 104-a first sacrificial layer; 105-a first piezoelectric layer; 106-a first electrode; 107-a fourth protective layer; 108-a second protective layer; 110-a second piezoelectric layer; 111-a second electrode.
Detailed Description
The invention will be described in detail with reference to the drawings and specific embodiments, which are illustrative of the invention and are not to be construed as limiting the invention.
It should be noted that all the directional indications (such as up, down, left, right, front, back, upper end, lower end, top, bottom … …) in the embodiments of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indication is changed accordingly.
In the present invention, unless expressly stated or limited otherwise, the term "coupled" is to be interpreted broadly, e.g., "coupled" may be fixedly coupled, detachably coupled, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature; in addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
Referring to fig. 1 and 2, a lithium niobate thin film-based air gap type shear wave resonator includes:
the device comprises a substrate 101, wherein a first groove with an upward opening is formed in the middle of the upper end of the substrate 101, and a second groove with a downward opening is formed in the middle of the lower end of the substrate 101; the substrate 101 is high-resistance double-polished monocrystalline silicon; a first protective layer 103, wherein the first protective layer 103 covers the inner surface of the first groove; a first piezoelectric layer 105, wherein the first piezoelectric layer 105 is grown on the upper end face of the substrate 101 covering the first groove; the first piezoelectric layer 105 and the first protective layer 103 together form a first air cavity; and
a first electrode 106, wherein the first electrode 106 is grown on the upper end face of the first piezoelectric layer 105 by magnetron sputtering deposition.
Specifically, in this embodiment, the device further includes a second protective layer 108, a second piezoelectric layer 110, and a second electrode 111; the second protection layer 108 covers the inner surface of the second groove; the second piezoelectric layer 110 is grown on the lower end surface of the substrate 101 covering the second groove; the second piezoelectric layer 110 and the second protection layer 108 together form a second air cavity; the second electrode 111 is grown on the lower end face of the second piezoelectric layer 110 by magnetron sputtering deposition.
Specifically, in this embodiment, the first protective layer 103 and the second protective layer 108 both adopt Si3N4、SiO2A material of (1); the thickness of the first protective layer 103 and the second protective layer 108 is 1um to 3 um.
Specifically, in this embodiment, the first piezoelectric layer 105 and the second piezoelectric layer 110 are both made of a lithium niobate piezoelectric material; the thickness of the first piezoelectric layer 105 and the second piezoelectric layer 110 are both 200nm to 6 um.
Specifically, in this embodiment, the first electrode 106 and the second electrode 111 are made of one electrode material of Pt, Mo, Ag, Al, and Au; the thicknesses of the first electrode 106 and the second electrode 111 are both 50nm to 800 nm.
Specifically, in the embodiment, the electrode distance of the first electrode 106 is 400nm to 6 um; the width of the first electrode 106 is 400 nm-4 um; the length of the first electrode 106 is 40um to 200 um. It should be noted that, in order to make the lithium niobate resonator only work in the shear wave mode, the distance between the electrodes must be much larger than the thickness of the piezoelectric material; the positive and negative electrodes of the first electrode 106 are alternately arranged crosswise.
Referring to fig. 3 to 5, in this embodiment, a method for manufacturing an air-gap type shear wave resonator based on a lithium niobate thin film includes the following steps:
step (1), the substrate 101 is acid-washed to remove organic matters and dirt on the surface, and the substrate 101 is dried; note that, a substrate 101 having a crystal orientation (100) is selected as an epitaxial substrate, and first, the substrate 101 is subjected to a high concentration H2SO 4: H2O 2: cleaning in SPM solution of H2O (volume ratio of 1.6:1.6:4) at 60 deg.C for 15min, and washing with H2O: BOE solution of HF (15: 1 by volume) for 10min (concentrated H2SO4, H2O2, BOE, HF commercially available);
step (2), growing a third protective layer 102 on the lower end face of the cleaned substrate 101 by using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, wherein the third protective layer 102 is made of SiO2, and etching a first groove with the depth of 2 microns in the middle of the upper end face of the substrate 101 by using an inductively coupled plasma etching machine;
step (3), growing a first protective layer 103 with the thickness of 1um on the inner surface of the first groove by a thermal oxidation method; the material of the first protective layer 103 is SiO2, a first sacrificial layer 104 with the thickness of 5um is deposited in the first groove by using a plasma enhanced chemical vapor deposition method, and the substrate 101 is polished to be flush with the surface of the first sacrificial layer 104 by chemical mechanical polishing; the root mean square roughness of the polished substrate 101 is less than 0.5 nm;
step (4), bonding a first piezoelectric layer 105 on the upper end surface of the substrate 101 by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the thickness of the first piezoelectric layer 105 is 1um, the first piezoelectric layer 105 and the first protective layer 103 form a first air cavity together, and annealing for 2 hours;
a step (5) of injecting positive ions into the first piezoelectric layer 105 by an inductively coupled plasma method; specifically, in this embodiment, the cations injected into the first piezoelectric layer 105 and the second piezoelectric layer 110 are both H+The injection equipment is ICP (inductively coupled plasma), the injection concentration is 2%, and the injection time is different according to the concentration of the introduced gas, so that the piezoelectric film is prevented from being cracked due to injection;
step (6), depositing a first electrode 106 on the first piezoelectric layer 105 by using a magnetron sputtering method, wherein the first electrode 106 is a Mo electrode, and performing photoetching on the first electrode 106 to obtain an interdigital electrode;
step (7), releasing the first sacrificial layer 104 in the first groove by adopting a dry release mode, wherein the first sacrificial layer 104 is made of polysilicon, and the release gas is xenon fluoride (XeF 2);
step (8), after the first sacrificial layer 104 is released, a fourth protective layer 107 is blanket grown on the first electrode 106 by a Plasma Enhanced Chemical Vapor Deposition (PECVD) method; the fourth protective layer 107 is made of SiO2, the substrate 101 is turned upside down, and the third protective layer 102 on the lower end face of the substrate 101 is removed;
step (9), after removing the third protective layer 102, etching a second groove in the middle of the upper end face of the substrate 101 by using an inductively coupled plasma etching machine; the depth of the second groove is 2 um;
a step (10) of growing a second protective layer 108 on the inner surface of the second groove by a thermal oxidation method; the material of the second protection layer 108 is SiO2, a second sacrificial layer is deposited in the second groove by using a plasma enhanced chemical vapor deposition method, the thickness of the second sacrificial layer is 5um, and the substrate 101 is polished to be flush with the surface of the second sacrificial layer; the root mean square roughness of the polished substrate 101 is less than 0.5 nm;
step (11), bonding a second piezoelectric layer 110 on the lower end surface of the substrate 101 by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the thickness of the second piezoelectric layer 110 is 1 um; the second piezoelectric layer 110 and the second protective layer 108 form a second air cavity together, and annealing is carried out for 2 hours;
a step (12) of injecting positive ions into the second piezoelectric layer 110 by an inductively coupled plasma method; the positive ions injected into the first piezoelectric layer 105 and the second piezoelectric layer 110 are both H+The injection equipment is ICP (inductively coupled plasma), the injection concentration is 2%, and the injection time is different according to the concentration of the introduced gas, so that the piezoelectric film is prevented from being cracked due to injection;
step (13), depositing a second electrode 111 on the second piezoelectric layer 110 by using a magnetron sputtering method, wherein the second electrode 111 is a Mo electrode; photoetching the second electrode 111 to obtain an interdigital electrode;
step (14), releasing the second sacrificial layer in the second groove by adopting a dry release mode, wherein the second sacrificial layer is made of polysilicon, and the release gas is xenon fluoride (XeF 2);
and (15) removing the fourth protective layer 107 by wet etching to obtain a complete sample. The material of the fourth protective layer 107 is SiO 2.
Specifically, in the embodiment, the depths of the first air cavity and the second air cavity are both 1um to 20 um.
Specifically, in this embodiment, the first sacrificial layer 104 and the second sacrificial layer may further adopt one of phosphosilicate glass, polysilicon, an organic polymer, and a metal material.
The invention arranges a first groove in the middle of the upper end of a substrate 101, and arranges a second groove in the middle of the lower end of the substrate 101; the first protection layer 103 covers the inner surface of the first groove; the first piezoelectric layer 105 is grown on the upper end face of the substrate 101 covering the first groove; the first piezoelectric layer 105 and the first protective layer 103 together form a first air cavity; a first electrode 106, wherein the first electrode 106 is grown on the upper end surface of the first piezoelectric layer 105 through magnetron sputtering deposition; the second protection layer 108 covers the inner surface of the second groove; the second piezoelectric layer 110 is grown on the lower end surface of the substrate 101 covering the second groove; the second piezoelectric layer 110 and the second protection layer 108 together form a second air cavity; the second electrode 111 is grown on the lower end face of the second piezoelectric layer 110 through magnetron sputtering deposition; in the preparation method provided by the invention, the sacrificial layer is introduced firstly and then the release method is adopted, so that the etched area is limited to the part filled with the sacrificial layer, the transverse corrosion of the substrate 101 during etching is avoided, the mechanical strength and the reliability of the resonator are further improved, the yield of the product is improved, and the method is suitable for large-scale manufacturing of the resonator. By optimally designing the size of the electrodes, the electrode spacing and the thickness of the lithium niobate piezoelectric material and selecting a proper crystal tangent, the influence of a transverse wave parasitic mode is reduced, so that the resonator only works in a shear wave mode, and the quality factor of the resonator is improved.
The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained herein by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; meanwhile, for a person skilled in the art, according to the embodiments of the present invention, there may be variations in the specific implementation manners and application ranges, and in summary, the content of the present description should not be construed as a limitation to the present invention.
Claims (10)
1. An air-gap type shear wave resonator based on a lithium niobate thin film, comprising:
the device comprises a substrate, a first groove with an upward opening is arranged in the middle of the upper end of the substrate, and a second groove with a downward opening is arranged in the middle of the lower end of the substrate;
a first protective layer covering an inner surface grown in the first groove;
the first piezoelectric layer is grown on the upper end face of the substrate by covering the first groove; the first piezoelectric layer and the first protective layer jointly form a first air cavity; and
and the first electrode is grown on the upper end surface of the first piezoelectric layer through magnetron sputtering deposition.
2. The lithium niobate thin film-based air gap type shear wave resonator of claim 1, wherein: the piezoelectric device further comprises a second protective layer, a second piezoelectric layer and a second electrode; the second protective layer covers the inner surface of the second groove; the second piezoelectric layer covers the second groove and is grown on the lower end face of the substrate; the second piezoelectric layer and the second protective layer jointly form a second air cavity; and the second electrode is grown on the lower end surface of the second piezoelectric layer through magnetron sputtering deposition.
3. The lithium niobate thin film-based air gap type shear wave resonator of claim 2, wherein: the first protective layer and the second protective layer both adopt Si3N4、SiO2A material of (1); the thickness of first protective layer with the second protective layer is 1um ~ 3 um.
4. The lithium niobate thin film-based air gap type shear wave resonator of claim 2, wherein: the first piezoelectric layer and the second piezoelectric layer are both made of lithium niobate piezoelectric materials; the thickness of the first piezoelectric layer and the second piezoelectric layer is 200 nm-6 um.
5. The lithium niobate thin film-based air gap type shear wave resonator of claim 2, wherein: the first electrode and the second electrode are made of one electrode material of Pt, Mo, Ag, Al and Au; the thickness of the first electrode and the thickness of the second electrode are both 50 nm-800 nm.
6. The lithium niobate thin film-based air gap type shear wave resonator of claim 5, wherein:
the electrode distance of the first electrode is 400 nm-6 um; the width of the first electrode is 400 nm-4 um; the length of the first electrode is 40um ~ 200 um.
7. The method for manufacturing a lithium niobate thin film-based air gap type shear wave resonator according to any one of claims 1 to 6, comprising the steps of:
step (1), the substrate is subjected to acid cleaning to remove organic matters and dirt on the surface, and the substrate is dried;
growing a third protective layer on the lower end face of the cleaned substrate by using a plasma enhanced chemical vapor deposition method, and etching a first groove in the middle of the upper end face of the substrate by using an inductively coupled plasma etching machine;
step (3), growing a first protective layer on the inner surface of the first groove by a thermal oxidation method; depositing a first sacrificial layer in the first groove by using a plasma enhanced chemical vapor deposition method, and polishing the substrate to be flush with the surface of the first sacrificial layer; the root mean square roughness of the polished substrate is less than 0.5 nm;
bonding a first piezoelectric layer on the upper end face of the substrate by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the first piezoelectric layer and the first protective layer jointly form a first air cavity, and annealing for 2 hours;
step (5), injecting positive ions into the first piezoelectric layer by an inductive coupling plasma method;
depositing a first electrode on the first piezoelectric layer by using a magnetron sputtering method, and carrying out photoetching on the first electrode to obtain an interdigital electrode;
step (7), releasing the first sacrificial layer in the first groove by adopting a dry release mode, wherein the released gas is xenon fluoride;
step (8), after the first sacrificial layer is released, a fourth protective layer is grown on the first electrode in a covering mode through a plasma enhanced chemical vapor deposition method; turning the substrate upside down, and removing the third protective layer on the lower end face of the substrate;
step (9), after removing the third protective layer, etching a second groove in the middle of the upper end face of the substrate by using an inductively coupled plasma etching machine;
step (10), growing a second protective layer on the inner surface of the second groove by a thermal oxidation method; depositing a second sacrificial layer in the second groove by using a plasma enhanced chemical vapor deposition method, and polishing the substrate to be flush with the surface of the second sacrificial layer; the root mean square roughness of the polished substrate is less than 0.5 nm;
step (11), bonding a second piezoelectric layer on the lower end face of the substrate by using a bonding method under the condition that the annealing temperature is 800 ℃, wherein the second piezoelectric layer and the second protective layer jointly form a second air cavity, and annealing for 2 hours;
a step (12) of injecting positive ions into the second piezoelectric layer by an inductively coupled plasma method;
step (13), depositing a second electrode on the second piezoelectric layer by using a magnetron sputtering method, and carrying out photoetching on the second electrode to obtain an interdigital electrode;
step (14), releasing the second sacrificial layer in the second groove by adopting a dry release mode, wherein the released gas is xenon fluoride;
and (15) removing the fourth protective layer by adopting wet etching to obtain a complete sample.
8. The method for manufacturing a lithium niobate thin film-based air gap type shear wave resonator according to claim 7, characterized in that: the first air chamber with the degree of depth of second air chamber is 1um ~ 20 um.
9. The method for manufacturing a lithium niobate thin film-based air gap type shear wave resonator according to claim 7, characterized in that: the first sacrificial layer and the second sacrificial layer are made of one of silicon oxide, phosphorosilicate glass, polycrystalline silicon, organic polymer and metal materials.
10. The method for manufacturing a lithium niobate thin film-based air gap type shear wave resonator according to claim 7, characterized in that: positive ions injected into the first piezoelectric layer and the second piezoelectric layer are both H+。
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| CN112689376A (en) * | 2021-03-15 | 2021-04-20 | 四川大学 | Microwave plasma jet excitation device adopting piezoelectric material |
| CN112953444A (en) * | 2021-04-13 | 2021-06-11 | 广东广纳芯科技有限公司 | Resonator and method for manufacturing resonator |
| CN112953449A (en) * | 2021-03-04 | 2021-06-11 | 偲百创(深圳)科技有限公司 | Method for manufacturing acoustic resonator with transverse excitation of shear mode |
| CN116545402A (en) * | 2023-07-06 | 2023-08-04 | 广州市艾佛光通科技有限公司 | Film bulk acoustic resonator and preparation method thereof |
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| CN112953449A (en) * | 2021-03-04 | 2021-06-11 | 偲百创(深圳)科技有限公司 | Method for manufacturing acoustic resonator with transverse excitation of shear mode |
| CN112689376A (en) * | 2021-03-15 | 2021-04-20 | 四川大学 | Microwave plasma jet excitation device adopting piezoelectric material |
| CN112689376B (en) * | 2021-03-15 | 2021-06-18 | 四川大学 | Microwave plasma jet excitation device adopting piezoelectric material |
| CN112953444A (en) * | 2021-04-13 | 2021-06-11 | 广东广纳芯科技有限公司 | Resonator and method for manufacturing resonator |
| CN112953444B (en) * | 2021-04-13 | 2024-02-09 | 广东广纳芯科技有限公司 | Resonator and method for manufacturing resonator |
| CN116545402A (en) * | 2023-07-06 | 2023-08-04 | 广州市艾佛光通科技有限公司 | Film bulk acoustic resonator and preparation method thereof |
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