CN113824420A - Preparation method of single crystal film bulk acoustic resonator with electrode with double annular structure - Google Patents
Preparation method of single crystal film bulk acoustic resonator with electrode with double annular structure Download PDFInfo
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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
- H03H3/04—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 frequency or temperature coefficient
-
- 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
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
- H03H9/132—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials characterized by a particular shape
-
- 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
- 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
-
- 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
- H03H3/04—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 frequency or temperature coefficient
- H03H2003/0414—Resonance frequency
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
The invention discloses a preparation method of a single crystal film bulk acoustic resonator with a double ring-shaped structure electrode, which comprises the following steps: depositing a stripping layer on a substrate, depositing a piezoelectric layer on the stripping layer, depositing a lower electrode on the piezoelectric layer, depositing a first lower annular structure, a second lower annular structure and a sacrificial layer wrapping the two annular structures on the lower electrode, depositing a lower protective layer wrapping the sacrificial layer and the lower electrode on the piezoelectric layer, and depositing a second layer to be bonded wrapping the lower protective layer on the piezoelectric layer; then, bonding the layer I to be bonded on the substrate with the layer II to be bonded, removing the stripping layer and the substrate, depositing an upper electrode on the piezoelectric layer, and depositing an upper annular structure I, an upper annular structure II and an upper protective layer wrapping the two annular structures on the upper electrode; and finally, forming a through hole on the piezoelectric layer, opening the bottom of the through hole on the surface of the sacrificial layer, and removing the sacrificial layer by using the through hole so as to form a cavity between the lower electrode and the lower protective layer. The two groups of annular structures can improve the Q value of the resonator.
Description
Technical Field
The invention relates to a film bulk acoustic resonator, in particular to a preparation method of a single crystal film bulk acoustic resonator with a dual-ring-structure electrode.
Background
The single crystal piezoelectric film has good crystal quality and few defects, and can be used for preparing a BAW resonator with higher frequency and Q value, thus becoming a research hotspot. However, the preparation process of the single crystal thin film BAW device is relatively difficult, and particularly, the structure preparation process of the lower electrode leads to a single structure of the lower electrode of the existing single crystal thin film BAW device, and researchers can only improve the structure of the upper electrode so as to improve the frequency and the Q value of the single crystal thin film BAW device. If different lower electrode structures can be prepared when a single crystal thin film BAW device is prepared, the original research limit is hopefully broken through, and the BAW resonator with higher frequency and Q value is prepared.
Disclosure of Invention
The invention aims to provide a preparation method of a single crystal film bulk acoustic resonator with a double-ring-structure electrode.
The invention is realized by adopting the following technical scheme:
The invention discloses a preparation method of a single crystal film bulk acoustic resonator with a double ring-shaped structure electrode, which comprises the following steps:
s1: both the substrate and the base were subjected to ultrasonic water washing.
S2: depositing a stripping layer on one side surface of the substrate; a piezoelectric layer is then deposited on the lift-off layer.
S3: and depositing a first layer to be bonded on one side surface of the substrate.
S4: and depositing metal on the surface of the piezoelectric layer and patterning to form a lower electrode.
S5: depositing metal on the surface of the lower electrode and patterning to form a first lower annular structure and a second lower annular structure; the lower annular structure II is arranged in the lower annular structure I at a distance;
s6: and forming a sacrificial layer wrapping the first lower annular structure and the second lower annular structure on the surface of the lower electrode through deposition and patterning.
S7: and depositing a lower protective layer wrapping the sacrificial layer and the lower electrode on the surface of the piezoelectric layer.
S8: and depositing a second layer to be bonded wrapping the lower protective layer on the surface of the piezoelectric layer, and flattening the surface of the second layer to be bonded.
S9: and connecting the first layer to be bonded on the substrate with the second layer to be bonded through a bonding process.
S10: and removing the stripping layer and the substrate by adopting a laser stripping technology, and flattening the surface of the piezoelectric layer.
S11: depositing metal on the surface of the piezoelectric layer and patterning to form an upper electrode; then, depositing metal on the surface of the upper electrode and patterning to form an upper ring structure I and an upper ring structure II; the upper annular structure II is arranged in the upper annular structure I, and the upper annular structure II and the upper annular structure I are arranged at a distance.
S12: depositing an upper protective layer wrapping the first annular structure and the second annular structure on the surface of the upper electrode, and forming a first annular bulge and a second annular bulge on the upper protective layer; the first annular bulge is aligned with the first annular structure, and the second annular bulge is aligned with the second upper annular structure.
S13: forming a through hole on the piezoelectric layer by adopting a plasma etching or wet etching process, wherein the bottom of the through hole is opened on the surface of the sacrificial layer; then, the sacrificial layer is removed by a wet etching process or a dry etching process using the through-hole, thereby forming a cavity between the lower electrode and the lower protective layer.
Preferably, the substrate and the base are made of one or more of glass, silicon carbide, silicon nitride or ceramic in any proportion.
Preferably, the piezoelectric layer is made of one or more of single crystal aluminum nitride, polycrystalline aluminum nitride, zinc oxide, single crystal lithium tantalate, lead zirconate titanate and lithium niobate in any proportion, and the thickness of the piezoelectric layer is 10nm-4000 nm.
Preferably, the material of the first layer to be bonded and the material of the second layer to be bonded are both one or two of silicon oxide and silicon in any proportion, and the thickness of the first layer to be bonded and the second layer to be bonded are both 0.1-10 μm.
Preferably, the lower electrode has a thickness of 50nm to 500nm and a lateral width of 30 to 600 μm.
Preferably, the sacrificial layer is made of one or two of polysilicon, amorphous silicon, silicon dioxide and doped carbon dioxide according to any proportion; the thickness of the sacrificial layer is 0.5-3 μm, and the lateral width is 20-500 μm.
Preferably, the materials of the lower electrode, the first lower annular structure, the second lower annular structure, the upper electrode, the first upper annular structure and the second upper annular structure are the same and are one or more of copper, aluminum, silver, titanium, tungsten, gold, nickel and molybdenum which are combined according to any proportion.
Preferably, the thickness of the lower ring structure I, the thickness of the lower ring structure II, the thickness of the upper ring structure I and the thickness of the upper ring structure II are all 20nm-300nm, and the lateral width of each of the lower ring structure I, the lower ring structure II, the upper ring structure I and the upper ring structure II is greater than 0 μm and less than 10 μm.
Preferably, the diameter of the through hole is in the range of 5um-50 um.
The invention has the following beneficial effects:
the invention can arrange the lower annular structure I and the lower annular structure II on the lower electrode of the resonator, and arrange the upper annular structure I and the upper annular structure II on the upper electrode, which can optimize the leakage problem of the main resonance sound wave of the resonator, because the air layer between the first lower ring structure, the second lower ring structure and the first lower ring structure and the second lower ring structure can form alternating high and low acoustic resistance antireflection layers, and similarly, the air layer between the first upper ring structure, the second upper ring structure and the first upper ring structure and the second upper ring structure can form alternating high and low acoustic resistance antireflection layers, when the energy of the sound wave is transmitted from the low acoustic resistance material to the high acoustic resistance material, the energy transfer efficiency is low, most of the energy is limited in the low acoustic impedance layer (i.e. the ring structure), therefore, the acoustic wave energy is limited in the resonator, leakage is reduced, and the Q value of the resonator is improved.
Drawings
FIG. 1 is a cross-sectional view of the present invention preparing a lift-off layer on a substrate and a piezoelectric layer on the lift-off layer.
Fig. 2 is a cross-sectional view of a first layer to be bonded on a substrate.
Fig. 3 is a cross-sectional view of a lower electrode fabricated on the structure of fig. 1.
Fig. 4 is a cross-sectional view of a first lower ring structure and a second lower ring structure fabricated on the structure of fig. 3.
Fig. 5 is a cross-sectional view of a sacrificial layer fabricated on the structure of fig. 4.
Fig. 6 is a cross-sectional view of a lower protective layer formed on the structure of fig. 5.
Fig. 7 is a cross-sectional view of a second layer to be bonded on the structure of fig. 6 and a chemical mechanical polishing process is performed.
Fig. 8 is a cross-sectional view of the structure of fig. 2 and the structure of fig. 7 formed by bonding.
Fig. 9 is a cross-sectional view of the structure of fig. 8 with the exfoliation layer and substrate removed.
Fig. 10 is a cross-sectional view of an upper electrode fabricated on the structure of fig. 9 and upper ring structures one and two fabricated on the upper electrode.
Fig. 11 is a cross-sectional view of an upper protective layer fabricated on the structure of fig. 10.
Fig. 12 is a cross-sectional view of a via fabricated on the structure of fig. 11.
Fig. 13 is a graph plotting Q-values at series resonant frequency for a resonator as a function of lateral width using a particular set of structural dimensions in accordance with the present invention.
Fig. 14 is a graph plotting Q-values at the parallel resonant frequency of a resonator as a function of lateral width using a particular set of structural dimensions in accordance with the present invention.
Detailed Description
The invention will be further explained with reference to the drawings.
The preparation method of the single crystal film bulk acoustic resonator with the electrode with the double ring-shaped structure comprises the following specific steps:
(1) ultrasonic water washing is performed on both the substrate 100 and the base 108 using acetone and isopropyl alcohol; the substrate and the base are made of one or more of glass, silicon carbide, silicon nitride or ceramic according to any proportion.
(2) As shown in fig. 1, a lift-off layer 114 is deposited on one side surface of a substrate 100 using a metal organic chemical vapor deposition process (MOCVD); the material of the lift-off layer 114 is GaN; a piezoelectric layer 101 is then formed (which may be deposited using a metal organic chemical vapor deposition process) on the lift-off layer 114 to a thickness of 10nm to 4000 nm.
(3) As shown in fig. 2, a first layer 109 to be bonded is deposited on one side surface of the substrate 108 by a Low Pressure Chemical Vapor Deposition (LPCVD) process, and the first layer 109 to be bonded is planarized by chemical mechanical polishing, wherein the first layer 109 to be bonded is made of one or a combination of silicon oxide and silicon at any ratio, and has a thickness of 0.1-10 μm.
(4) As shown in fig. 3, a metal is deposited on the surface of the piezoelectric layer 101 by thermal evaporation or magnetron sputtering, and is patterned by plasma or wet etching to form the lower electrode 102, and the lateral width of the lower electrode 102 is 30-600 μm.
(5) As shown in fig. 4, depositing metal on the surface of the lower electrode 102 by thermal evaporation or magnetron sputtering, and patterning by plasma or wet etching to form a first lower annular structure 103 and a second lower annular structure 104; the second lower annular structure 104 is arranged in the first lower annular structure 103 at a distance;
(6) as shown in fig. 5, polysilicon or amorphous silicon is deposited on the surface of the lower electrode 102 by using a plasma chemical vapor deposition process, and is patterned by using a plasma or wet etching method to form a sacrificial layer 105 wrapping the first lower ring structure 103 and the second lower ring structure 104.
(7) As shown in fig. 6, a lower protective layer 106 is deposited on the surface of the piezoelectric layer 101 by a metal organic chemical vapor deposition process to encapsulate the sacrificial layer 105 and the lower electrode 102.
(8) As shown in fig. 7, a second layer 107 to be bonded, which wraps the lower protection layer 106, is deposited on the surface of the piezoelectric layer 101 by using a Low Pressure Chemical Vapor Deposition (LPCVD) process, and the surface of the second layer 107 to be bonded is made flat by using a chemical mechanical polishing method, wherein the second layer 107 to be bonded is made of one or two of silicon oxide and silicon in any proportion.
(9) As shown in fig. 8, a first layer 109 to be bonded on a substrate 108 is attached to a second layer 107 to be bonded, and is connected by a bonding process, so that a dense interface is formed between the first layer 109 to be bonded and the second layer 107 to be bonded.
(10) As shown in fig. 9, the peeling layer 114 and the substrate 100 are removed by a laser peeling technique, and the surface of the piezoelectric layer 101 is planarized.
(11) As shown in fig. 10, depositing a metal on the surface of the piezoelectric layer 101 by thermal evaporation or magnetron sputtering, and patterning by plasma or wet etching to form an upper electrode 110; then, depositing metal on the surface of the upper electrode 110 by adopting a thermal evaporation or magnetron sputtering method, and patterning by adopting a plasma or wet etching method to form an upper annular structure I111 and an upper annular structure II 112; the second upper ring structure 112 is arranged in the first upper ring structure 111, and the two are arranged at a distance;
(12) as shown in fig. 11, depositing an upper protective layer 113 on the surface of the upper electrode 110 by using a metal organic compound chemical vapor deposition (mocvd) process, the upper protective layer 113 wrapping the first upper ring structure 111 and the second upper ring structure 112, and forming a first annular protrusion and a second annular protrusion on the upper protective layer 113; the first annular protrusion is aligned with the first annular structure 111, and the second annular protrusion is aligned with the second upper annular structure 112.
(13) As shown in fig. 12, a through hole is formed on the piezoelectric layer 101 by using a plasma etching or wet etching process, and the bottom of the through hole is opened on the surface of the sacrificial layer 105; the diameter of the through hole is within the range of 5um-50 um. Then, the sacrificial layer 105 is removed by a wet etching process or a dry etching process using a via hole, thereby forming a cavity 105a between the lower electrode 102 and the lower protective layer 106.
The invention sets a lower ring structure 103 and a lower ring structure 104 on the lower electrode of the resonator, and sets an upper ring structure 111 and an upper ring structure 112 on the upper electrode, which can optimize the leakage problem of the main resonance sound wave of the resonator, because the air layer between the lower ring structure 103, the lower ring structure 104 and the lower ring structure 103 and the lower ring structure 104 can form alternate high and low acoustic resistance antireflection layers, similarly, the air layer between the upper ring structure 111, the upper ring structure 112 and the upper ring structure 111 and the upper ring structure 112 can form alternate high and low acoustic resistance antireflection layers, when the energy of the sound wave is transmitted from the low acoustic resistance material to the high acoustic resistance material, the energy transmission efficiency is very low, most energy is limited in the low acoustic resistance layer (i.e. the ring structure), thereby the sound wave energy is limited in the resonator, leakage is reduced, and the Q value of the resonator is improved.
A specific set of structural dimensions is given below:
a substrate 108 (using Si) with a thickness of 500 μm; the thickness of the first layer to be bonded and the thickness of the second layer to be bonded (adopting Si) are both 5 mu m; the thickness of the lower protective layer (adopting AlN) is 30nm, and the transverse width is 150 mu m; the thickness of the lower electrode (adopting Mo) is 170nm, and the transverse width is 150 μm; the thickness of the piezoelectric layer (AlN is adopted) is 700nm, and the transverse width is 200 mu m; the thickness of the upper electrode (adopting Mo) is 17nm, and the transverse width is 150 μm; the thickness of the upper protective layer (adopting AlN) is 5nm, and the transverse width is 150 mu m; the transverse width of the cavity is 160um, and the thickness is 2 μm; the thicknesses of the first upper ring structure 111, the second upper ring structure 112, the first upper ring structure 111 and the second upper ring structure 112 are all 200 nm.
Assuming that the lateral widths of the first lower ring structure 103, the second lower ring structure 104, the first upper ring structure 111 and the second upper ring structure 112 are all H, a Q value curve at the series resonance frequency and a Q value curve at the parallel resonance frequency of the resonator of the present invention varying with the lateral width H are plotted using the above specific set of structure dimensions, as shown in fig. 13 and 14, respectively. As can be seen from fig. 13, when the lateral width H is 0 μm, that is, the lower ring structure one 103, the lower ring structure two 104, the upper ring structure one 111, and the upper ring structure two 112 are not provided, the Q value (Qs) at the series resonance frequency of the resonator is small and 952; the maximum Q value (Qs) at the series resonance frequency of the resonator is 1045 when the lateral width H is 2 μm. As can be seen from fig. 14, when the lateral width H is 0 μm, the Q value (Qp) at the parallel resonance frequency of the resonator is small, 948; when the lateral width H is 4.5 μm, the Q value (Qp) at the series resonance frequency of the resonator is maximum and 1135.
Claims (9)
1. The preparation method of the single crystal film bulk acoustic resonator with the electrode with the double ring-shaped structure is characterized by comprising the following steps of: the method comprises the following specific steps:
s1: carrying out ultrasonic water washing on the substrate and the base;
s2: depositing a stripping layer on one side surface of the substrate; then depositing a piezoelectric layer on the lift-off layer;
S3: depositing a first layer to be bonded on the surface of one side of the substrate;
s4: depositing metal on the surface of the piezoelectric layer and patterning to form a lower electrode;
s5: depositing metal on the surface of the lower electrode and patterning to form a first lower annular structure and a second lower annular structure; the lower annular structure II is arranged in the lower annular structure I at a distance;
s6: forming a sacrificial layer wrapping the first lower annular structure and the second lower annular structure on the surface of the lower electrode through deposition and patterning;
s7: depositing a lower protective layer wrapping the sacrificial layer and the lower electrode on the surface of the piezoelectric layer;
s8: depositing a second layer to be bonded wrapping the lower protective layer on the surface of the piezoelectric layer, and flattening the surface of the second layer to be bonded;
s9: connecting a first layer to be bonded on the substrate with a second layer to be bonded through a bonding process;
s10: removing the stripping layer and the substrate by adopting a laser stripping technology, and flattening the surface of the piezoelectric layer;
s11: depositing metal on the surface of the piezoelectric layer and patterning to form an upper electrode; then, depositing metal on the surface of the upper electrode and patterning to form an upper ring structure I and an upper ring structure II; the upper annular structure II is arranged in the upper annular structure I, and the upper annular structure II and the upper annular structure I are arranged at intervals;
s12: depositing an upper protective layer wrapping the first annular structure and the second annular structure on the surface of the upper electrode, and forming a first annular bulge and a second annular bulge on the upper protective layer; the first annular bulge is aligned with the first annular structure, and the second annular bulge is aligned with the second upper annular structure;
S13: forming a through hole on the piezoelectric layer by adopting a plasma etching or wet etching process, wherein the bottom of the through hole is opened on the surface of the sacrificial layer; then, the sacrificial layer is removed by a wet etching process or a dry etching process using the through-hole, thereby forming a cavity between the lower electrode and the lower protective layer.
2. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the substrate and the base are made of one or more of glass, silicon carbide, silicon nitride or ceramic according to any proportion.
3. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the piezoelectric layer is made of one or more of single crystal aluminum nitride, polycrystalline aluminum nitride, zinc oxide, single crystal lithium tantalate, lead zirconate titanate and lithium niobate according to any proportion, and the thickness of the piezoelectric layer is 10nm-4000 nm.
4. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the material of the first layer to be bonded and the material of the second layer to be bonded are one or two of silicon oxide and silicon in any proportion, and the thickness of the first layer to be bonded and the second layer to be bonded are both 0.1-10 mu m.
5. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the thickness of the lower electrode is 50nm-500nm, and the transverse width is 30-600 μm.
6. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the sacrificial layer is made of one or two of polycrystalline silicon, amorphous silicon, silicon dioxide and doped carbon dioxide according to any proportion; the thickness of the sacrificial layer is 0.5-3 μm, and the lateral width is 20-500 μm.
7. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the lower electrode, the lower annular structure I, the lower annular structure II, the upper electrode, the upper annular structure I and the upper annular structure II are made of the same material and are all one or more of copper, aluminum, silver, titanium, tungsten, gold, nickel and molybdenum in any proportion.
8. The method for manufacturing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1 or 7, wherein: the thicknesses of the lower ring structure I, the lower ring structure II, the upper ring structure I and the upper ring structure II are all 20nm-300nm, and the transverse widths are all larger than 0 mu m and smaller than 10 mu m.
9. The method for preparing a single crystal thin film bulk acoustic resonator having electrodes with a dual ring structure according to claim 1, wherein: the diameter of the through hole is selected within the range of 5um-50 um.
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