WO2022227928A1 - Résonateur acoustique en volume piézoélectrique monocristallin et son procédé de fabrication, filtre et dispositif électronique - Google Patents

Résonateur acoustique en volume piézoélectrique monocristallin et son procédé de fabrication, filtre et dispositif électronique Download PDF

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WO2022227928A1
WO2022227928A1 PCT/CN2022/081880 CN2022081880W WO2022227928A1 WO 2022227928 A1 WO2022227928 A1 WO 2022227928A1 CN 2022081880 W CN2022081880 W CN 2022081880W WO 2022227928 A1 WO2022227928 A1 WO 2022227928A1
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layer
resonator
temperature compensation
electrode
compensation layer
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PCT/CN2022/081880
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English (en)
Chinese (zh)
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张孟伦
庞慰
刘伯华
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诺思(天津)微系统有限责任公司
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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
    • 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
    • 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

Definitions

  • Embodiments of the present invention relate to the field of semiconductors, and in particular, to a single crystal piezoelectric bulk acoustic resonator and a method for manufacturing the same, a filter having the resonator, and an electronic device.
  • FBAR thin film bulk acoustic resonator
  • the structural main body of the thin film bulk acoustic wave resonator is a "sandwich" structure composed of an electrode-piezoelectric film-electrode, that is, a piezoelectric material is sandwiched between two metal electrode layers.
  • the FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into an electrical signal output.
  • the piezoelectric film commonly used in the prior art is the aluminum nitride piezoelectric film.
  • the use of the aluminum nitride piezoelectric film is not conducive to obtaining a large electromechanical coupling coefficient for the resonator.
  • the resonator using the aluminum nitride piezoelectric film has The electromechanical coupling coefficient is less than 8%, and generally in the range of 6-7%.
  • the resonator using the aluminum nitride piezoelectric film cannot meet the requirement.
  • the BAW resonator generally has a negative frequency temperature drift coefficient, and its frequency temperature drift coefficient is about -30ppm/°C to -300ppm/°C.
  • the piezoelectric material and electrode material of the BAW resonator have negative frequency temperature drift. coefficient, which means that the stiffness of these materials decreases with increasing temperature, and that decreasing stiffness decreases the speed of sound.
  • a temperature compensation layer is added to the resonator, but the addition of the temperature compensation layer will reduce the electromechanical coupling coefficient of the resonator.
  • the addition of the temperature compensation layer makes the use of aluminum nitride piezoelectric in the prior art. Layer-fabricated resonators have lower electromechanical coupling coefficients.
  • the bottom-up processing method is mostly used, in which 01 is the base, 02 is the cavity of the acoustic acoustic mirror, 03 is the bottom electrode, and 04 is the bottom electrode. Above the temperature compensation layer, 05 is the piezoelectric layer, 06 is the temperature compensation layer under the top electrode, and 07 is the top electrode.
  • the key step in manufacturing the traditional BAW resonator is to pattern the bottom electrode after sputtering the bottom electrode, and then continue to grow the piezoelectric layer, so that the piezoelectric layer will have an inclined structure 08 at the edge of the electrode.
  • the inclined structure The surface quality is relatively poor, and the quality of the piezoelectric layer film grown on it is also poor; and there is a sudden inflection point on the inclined structure, which makes the film grown on it prone to stress concentration, which ultimately affects the reliability of the resonator.
  • the temperature compensation layer structure is generally processed on the inner side of the electrode.
  • the existence of the temperature compensation layer on the one hand will make the inclined structure larger, and on the other hand, the existence of the inclined structure will also affect the temperature compensation effect of the temperature compensation layer on the resonator, which will eventually lead to an increase in the parasitic mode of the resonator, poor reliability, and temperature compensation.
  • the compensation effect is also not as expected, and it also reduces the electromechanical coupling coefficient of the resonator.
  • the present invention is proposed to alleviate or solve at least one aspect of the above-mentioned problems in the prior art, such as providing a bulk acoustic wave resonator with an electromechanical coupling coefficient of not less than 9%.
  • a bulk acoustic wave resonator wherein the piezoelectric layer of the resonator is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer, and the resonance
  • the electromechanical coupling coefficient of the device is not less than 9%.
  • Embodiments of the present invention also relate to a method for manufacturing a bulk acoustic wave resonator, wherein the electromechanical coupling coefficient of the resonator is not less than 9%, and the method includes the steps of: providing a POI wafer, the POI wafer comprising a substrate, a single crystal piezoelectric layer and an insulating layer disposed between the first side of the single crystal piezoelectric layer and the substrate, wherein the piezoelectric layer is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer; and removing the substrate and at least a portion of the insulating layer, during the process of removing the substrate, the insulating layer acts as a barrier layer protecting the piezoelectric layer, the at least a portion of the insulating layer is removed to expose the piezoelectric layer, And the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator is removed.
  • Embodiments of the present invention also relate to a filter comprising the resonator described above.
  • Embodiments of the present invention also relate to an electronic device comprising the above-mentioned filter or the above-mentioned resonator.
  • FIG. 1-11 are schematic cross-sectional views of bulk acoustic wave resonators according to different exemplary embodiments of the present invention, respectively;
  • Figures 12 and 13 are schematic top views showing the relationship between the bottom electrode and the temperature compensation layer in Figure 9, respectively, according to different embodiments of the present invention.
  • FIG. 14A-14I are schematic cross-sectional views illustrating a manufacturing process of the bulk acoustic wave resonator shown in FIG. 5 according to an exemplary embodiment of the present invention
  • FIG. 15 is a schematic cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present invention, wherein the remaining insulating layer is shown between the electrode connection end of the top electrode and the piezoelectric layer;
  • 16 is a schematic cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present invention, showing the upper surface of the piezoelectric layer with the remaining insulating layer outside the top electrode;
  • 17 is a schematic cross-sectional view of a bulk acoustic wave resonator in the prior art.
  • Substrate the specific material can be silicon, silicon carbide, sapphire, silicon dioxide, or other silicon-based materials.
  • the material may be aluminum nitride, silicon nitride, polysilicon, silicon dioxide, amorphous silicon, boron-doped silicon dioxide, and other silicon-based materials.
  • Acoustic mirror which can be a cavity, or a Bragg reflector and other equivalent forms. Cavities are used in the illustrated embodiment of the present invention.
  • Passivation layer generally a dielectric material, such as silicon dioxide, aluminum nitride, silicon nitride, and the like.
  • Temperature compensation layer the material of the temperature compensation layer is a material opposite to the frequency temperature coefficient of the piezoelectric layer, which can be polysilicon, borophosphate glass (BSG), silicon dioxide (SiO 2 ), fluorine-doped silicon dioxide, Materials such as chromium (Cr) or tellurium oxide (TeO(x)).
  • BSG borophosphate glass
  • SiO 2 silicon dioxide
  • TiO(x) fluorine-doped silicon dioxide
  • Materials such as chromium (Cr) or tellurium oxide (TeO(x)
  • the stiffness of materials with a positive frequency temperature drift coefficient such as SiO 2 will increase as the temperature increases, so it is possible to compensate or reduce ordinary resonance by adding a layer of SiO 2 and other materials with a positive frequency temperature drift coefficient (ie, temperature compensation layer).
  • the speed of sound decreases due to the decrease in stiffness of the temperature compensation layer (excluding the temperature compensation layer) as the temperature rises, so as to reduce the negative drift of the frequency with the increase of temperature, and then zero temperature drift or frequency temperature drift coefficient can be achieved by setting the appropriate thickness of the temperature compensation layer. within ⁇ 5ppm/°C.
  • the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys.
  • a single crystal piezoelectric layer which is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer.
  • Top electrode the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys.
  • the material of the top electrode can be the same or different from the bottom electrode.
  • Bottom electrode electrical connection part the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys.
  • the material of the bottom electrode electrical connection portion may be the same as or different from that of the top electrode.
  • a bridge structure that defines a cavity or gap layer.
  • a cavity or gap layer which is defined by a bridge structure, which can be an air gap, or a vacuum gap, or a non-conductive dielectric layer.
  • the material may be polysilicon, amorphous silicon, silicon dioxide, phosphorus-doped silicon dioxide (PSG), zinc oxide, magnesium oxide, polymer polymers and similar materials.
  • Auxiliary substrate the specific material can be silicon, silicon carbide, sapphire, silicon dioxide, or other silicon-based materials.
  • Insulation layer which plays the role of electrical insulation, such as silicon dioxide.
  • a single crystal piezoelectric layer which is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer.
  • the piezoelectric layer is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate Piezoelectric layer.
  • the single crystal lithium niobate piezoelectric layer or the single crystal lithium tantalate piezoelectric layer is not used in the resonator in the prior art.
  • an efficient manufacturing method can be employed to manufacture a resonator using a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer.
  • the value of the electromechanical coupling coefficient of the resonator using the single crystal lithium niobate piezoelectric layer or the single crystal lithium tantalate piezoelectric layer can be vary on a large scale.
  • the crystal orientation of single crystal lithium niobate or single crystal lithium tantalate can be flexibly selected, which can make the resonator in the It can maintain excellent performance while meeting the design parameters.
  • their crystal orientation is fixed, which limits their flexibility in the design of resonators or filters, which is not conducive to their further development. application and development.
  • the piezoelectric material is single crystal lithium niobate and the crystal orientation is X-cut (X-cut), its temperature drift coefficient is -105ppm/K, and the electromechanical coupling coefficient is 53; when the crystal orientation is Y+163°- When cutting (cutting), its temperature drift coefficient is -60ppm/K, and its electromechanical coupling coefficient is 26, that is, for single crystal lithium niobate, when the selected crystal orientation makes its electromechanical coupling coefficient higher, its temperature drift coefficient is too large, and when the selected crystal orientation makes its temperature drift coefficient low, its electromechanical coupling coefficient is too small.
  • the single crystal lithium niobate piezoelectric resonator can be When the crystal orientation is selected, it can have a high electromechanical coupling coefficient and a low temperature drift coefficient at the same time.
  • choosing to use a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer can make the electromechanical coupling coefficient of the resonator not less than 9%, and further, the electromechanical coupling coefficient of the resonator is not less than 10 %.
  • the BAW resonator shown in FIGS. 1-11 includes a temperature compensation layer 104 .
  • the provision of the temperature compensation layer 104 reduces the electromechanical coupling coefficient of the resonator.
  • the electromechanical coupling coefficient of the resonator will decrease, but its electromechanical coupling coefficient It can still keep not less than 9%, or the electromechanical coupling coefficient of the resonator is not less than 10%, and the existence of the temperature compensation layer can make up for the temperature drift coefficient of the resonator to make it close to or equal to zero, so that the resonator can be kept at a stable frequency The state will not change with the change of the outside temperature.
  • BAW resonators according to different embodiments of the present invention are exemplified one by one with reference to FIGS. 1-11 .
  • a support structure or support layer 101 is provided between the lower surface of the single crystal piezoelectric layer 106 and the upper surface of the substrate 100 , and the piezoelectric layer 106 is arranged substantially parallel to the substrate 100 .
  • the support layer 101 can be used to define the boundaries of the acoustic mirror cavity.
  • the single-crystal piezoelectric layer 106 is flat, and there is no inclined structure, which can avoid the existence of parasitic modes at the inclined structure in the conventional structure, and the poor quality and stress concentration of the grown piezoelectric film Moreover, the piezoelectric layer material is a single crystal material, which can make the piezoelectric loss lower, so as to obtain a higher Q value of the resonator, and at the same time, the electromechanical coupling coefficient and power capacity can be improved.
  • the temperature compensation layer 104 does not cover the inclined structure, the temperature compensation effect of the temperature compensation layer on the resonator is enhanced, while the temperature compensation effect of the conventional structure is deteriorated because the temperature compensation layer covers or is adjacent to the inclined structure.
  • the temperature compensation layer 104 is disposed on the lower side of the bottom electrode 105 , and the end of the temperature compensation layer 104 in the acoustic mirror cavity 102 is substantially aligned with the non-electrode connection end of the bottom electrode in the acoustic mirror cavity 102 flat.
  • a passivation layer 103 is provided, the passivation layer covers the lower side of the entire temperature compensation layer 104 in the cavity of the acoustic mirror, and covers the temperature compensation layer 104 in the cavity of the acoustic mirror. The end within cavity 102 and the non-electrode connection end of the bottom electrode.
  • the passivation layer 103 can protect the temperature compensation layer 104, that is, it can protect the passivation layer from being etched during the release process of the sacrificial material layer forming the cavity of the acoustic mirror.
  • FIG. 2 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • FIG. 2 is basically the same as FIG. 1 , except that in the embodiment shown in FIG. 2 , the temperature compensation layer 104 is located on the upper side of the top electrode and is covered by the passivation layer 103 , and the passivation layer 103 can play a role in the temperature compensation layer protection.
  • the temperature compensation layer 104 is made of the same material as the sacrificial layer for forming the acoustic mirror cavity of the single crystal thin film acoustic wave resonator, the temperature compensation layer can be protected from being etched during the release process of the sacrificial layer.
  • FIG. 3 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 3 is basically the same as the structure shown in FIG. 1 , the difference is that: in the embodiment shown in FIG. 3 , the temperature compensation layer 104 is located on the upper side of the bottom electrode 105 or located on the bottom electrode 105 and the piezoelectric layer 106 between.
  • the temperature compensation layer 104 in FIG. 3 can be disposed at a position (closer to the piezoelectric layer) with a thinner thickness to achieve the same temperature compensation effect.
  • the end of the temperature compensation layer 104 in the acoustic mirror cavity 102 is substantially flush with the non-electrode connection end of the bottom electrode in the acoustic mirror cavity 102 .
  • a passivation layer 103 is provided, which covers the entire lower side of the bottom electrode 105 in the cavity of the acoustic mirror, and also covers the temperature compensation layer 104 in the cavity of the acoustic mirror. 102 and the non-electrode connection end of the bottom electrode 105 .
  • the passivation layer 103 can play a protective role for the temperature compensation layer 104, that is, it can protect the passivation layer from being etched during the release process of the sacrificial material layer forming the cavity of the acoustic mirror.
  • FIG. 4 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 4 is basically the same as that shown in FIG. 3 , with one difference: in the embodiment shown in FIG. 4 , the temperature compensation layer 104 located on one side of the cavity of the acoustic mirror is wrapped by the non-electrode connecting end of the bottom electrode 105 , which can protect the passivation layer from being etched during the release process of the sacrificial material layer forming the cavity of the acoustic mirror.
  • the structure shown in FIG. 4 is basically the same as that shown in FIG. 3 , except that in FIG.
  • the top electrode 107 has a bridge structure 109 and an air gap 110 under the bridge structure 109 .
  • the bridge structure spans the area on the left side of the bottom electrode that does not include the temperature compensation layer, so that in the top view of the resonator, the temperature compensation layer completely covers the effective area of the single crystal thin film acoustic wave resonator D, which maximizes the temperature compensation effect of the single-crystal thin-film acoustic resonator.
  • FIG. 5 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 5 is basically the same as that shown in FIG. 4 , except that in the embodiment shown in FIG. 5 , one end of the temperature compensation layer 104 located in the acoustic mirror cavity 102 is wrapped by the non-electrode connecting end of the bottom electrode 105 and The non-electrode connection end of the bottom electrode is further extended to the left, which can better cover the temperature compensation layer and have a better protection effect on it.
  • FIG. 6 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 6 is basically the same as that shown in FIG. 4, except that in the embodiment shown in FIG.
  • the temperature compensation layer 104 is located on the lower side of the top electrode 107 and is surrounded by the top electrode, and the bridge structure 109 is located on the bottom electrode 105, And spanning the area on the right side of the top electrode 107 without wrapping the temperature compensation layer, this can ensure that in the top view of the resonator, the temperature compensation layer completely covers the effective area D of the single crystal thin film acoustic wave resonator, so that the single crystal thin film acoustic wave resonates The temperature compensation effect of the device is the largest.
  • FIG. 7 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 7 is basically the same as the structure shown in FIG. 3 , the difference is that: in FIG. 7 , the temperature compensation layer 104 is located in the bottom electrode 105 , that is, the upper and lower sides of the temperature compensation layer are both parts of the bottom electrode and are on the right side.
  • the electrode connection ends of the side or bottom electrodes, and the bottom electrode parts on the upper and lower sides of the temperature compensation layer are connected together.
  • the temperature compensation layer can improve the temperature characteristics of the single crystal thin film acoustic wave resonant frequency, it will lead to a significant decrease in the electromechanical coupling coefficient value of the single crystal thin film acoustic wave resonator.
  • a decrease in the value of the electromechanical coupling coefficient results in a narrowing of the passband of the filter composed of the bulk-wave resonator. This is in contrast to many applications requiring wider bandwidth.
  • the temperature compensation layer is mostly composed of high-resistance materials (usually insulating materials)
  • the temperature compensation layer located between the two electrodes of the resonator acts as a series capacitor, and part of the voltage between the two electrodes will fall on the temperature compensation layer, so The voltage drop in the piezoelectric layer is reduced, and the electric field strength in the piezoelectric layer is correspondingly reduced.
  • all the voltage drop is located in the piezoelectric layer, so the electric field in the piezoelectric layer is relatively stronger.
  • the electric field of the temperature compensation layer will weaken the electric field strength in the piezoelectric layer, so it has a great influence on the electromechanical coupling coefficient of the single crystal thin film acoustic wave resonator.
  • the temperature compensation layer 104 is wrapped by the bottom electrode 105 and the bottom electrodes on the upper and lower sides of the temperature compensation layer are connected together on the right side of the temperature compensation layer, the upper and lower surfaces of the temperature compensation layer are connected together. With the same electric potential, there is no electric field at the temperature compensation layer, so the electromechanical coupling coefficient of the resonator can be improved while the temperature stability of the single crystal thin film acoustic wave resonator is improved.
  • a passivation layer 103 is provided in the resonator.
  • the passivation layer 103 covers the bottom electrode 105, the non-electrode connecting end of the bottom electrode and the end of the temperature compensation layer in the acoustic mirror cavity in the acoustic mirror cavity.
  • the passivation layer 103 can play a protective role for the temperature compensation layer 104, that is, it can protect the passivation layer from being etched during the release process of the sacrificial material layer forming the cavity of the acoustic mirror.
  • FIG. 8 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 8 is basically the same as that shown in FIG. 7 .
  • the temperature compensation layer 104 is completely wrapped by the bottom electrode 105 , that is, the bottom electrodes on the upper and lower sides of the temperature compensation layer are The left and right sides are connected together.
  • a bridge structure 109 is also provided in FIG. 8 , which defines an air gap or gap layer 110 .
  • a passivation layer 3 may also be provided, and the passivation layer 3 covers at least the bottom electrode 105 in the cavity of the acoustic mirror, so as to protect the bottom electrode from being damaged during the release process of the sacrificial material layer forming the cavity of the acoustic mirror. etching.
  • FIG. 9 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 9 is basically the same as that shown in FIG. 7 , except that in the embodiment shown in FIG. 9 , the temperature compensation layer 104 is disconnected, and the disconnected gap is the part of the bottom electrode 105 . In this way, the electric field intensity in the temperature compensation layer can be guaranteed to be zero, and the electromechanical coupling coefficient of the single crystal thin film acoustic wave resonator can be improved.
  • FIG. 10 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 10 is basically the same as that shown in FIG. 7, except that in the embodiment shown in FIG. 10, the temperature compensation layer 104 is located in the top electrode 107, that is, it is surrounded by the top electrode, and the upper and lower sides of the temperature compensation layer are The top electrodes are connected together on the left and right sides.
  • a bridge structure 109 is also provided in FIG. 8 , which defines an air gap or gap layer 110 .
  • FIG. 11 is a schematic cross-sectional view of a single crystal thin film acoustic wave resonator according to another exemplary embodiment of the present invention.
  • the structure shown in FIG. 11 is basically the same as that shown in FIG. 10 , the difference is that: in the embodiment shown in FIG. 11 , the temperature compensation layer 104 is disconnected, and the disconnected gap is a part of the top electrode 107 . In this way, the electric field intensity in the temperature compensation layer can be guaranteed to be zero, which is beneficial to improve the electromechanical coupling coefficient of the single crystal thin film acoustic wave resonator.
  • FIG. 12 and 13 are schematic top views, respectively, illustrating the relationship between the bottom electrode and the temperature compensation layer of FIG. 9, and showing the communication that electrically connects the upper and lower portions of the bottom electrode to each other, according to different embodiments of the present invention.
  • FIG. 9 may be a cross-sectional view taken along line AA in FIGS. 12 or 13 .
  • a plurality of concentrically arranged continuous split rings are arranged in the temperature compensation layer 104
  • FIG. 13 a plurality of annular array structures are arranged concentrically in the temperature compensation layer 105 .
  • the opening for connecting the bottom electrodes on the upper and lower sides of the temperature compensation layer may be a single annular structure with continuous openings, or a single annular array structure composed of multiple openings.
  • the openings 104A may also be distributed in any shape on the portion of the temperature compensation layer 104 located in the bottom electrode 105 .
  • FIG. 5 The fabrication process of the structure shown in FIG. 5 is exemplarily described below with reference to FIGS. 14A-14I.
  • a bulk acoustic wave resonator is fabricated based on a POI (Piezoelectrics on Insulator, single crystal piezoelectric layer on an insulator) substrate.
  • the POI wafer includes an auxiliary substrate, a single crystal piezoelectric layer, and an insulating layer disposed between the single crystal piezoelectric layer and the auxiliary substrate.
  • the substrate used in this embodiment is a POI substrate, and its structure is shown in FIG. 14A , wherein 112 is a silicon auxiliary substrate, 113 is an insulating layer such as a silicon dioxide layer, and 114 is a single crystal lithium niobate piezoelectric layer.
  • the insulating layer can better protect the single-crystal piezoelectric film (ie, the single-crystal piezoelectric layer), thereby reducing or even avoiding the subsequent removal of the auxiliary substrate.
  • the damage to the single crystal piezoelectric film can be reduced or even avoided to obtain a bulk acoustic wave resonator with excellent performance.
  • the existence of the insulating layer is also conducive to the diversification of the auxiliary substrate removal scheme and simplify the device processing process.
  • Step 1 As shown in FIG. 14B, first deposit a temperature compensation material layer on the POI substrate, and then use dry etching or wet etching to form a pattern to form the temperature compensation layer 104, and then use the same method to form the bottom electrode 105. Other methods of forming the temperature compensation layer 104 and the bottom electrode 105 may also be used.
  • Step 2 As shown in Figure 14C, deposit a layer of sacrificial material film, the sacrificial material can be polysilicon, amorphous silicon, silicon dioxide, doped silicon dioxide and other materials, and then etch by wet or dry method A patterned sacrificial material layer 111 is formed.
  • the layer of sacrificial material corresponds to the cavity of the acoustic mirror.
  • Step 3 As shown in FIG. 14D , a support material layer is deposited on the surfaces of the sacrificial material layer 111 and the bottom electrode 105 , and the support material layer is polished by chemical mechanical polishing (CMP) method to form the support layer 101 .
  • CMP chemical mechanical polishing
  • Step 4 As shown in FIG. 14E, the substrate 100 and the structure shown in FIG. 14D are bonded together by a bonding method.
  • the substrate 100 and the support layer 101 may be physically or chemically bonded through a special bonding layer (not shown), and the material of the bonding layer may be on the substrate 100 or the support layer 101 alone, or on both surfaces.
  • the substrate 100 and the support layer 101 may also be directly bonded without a bonding layer, but a chemical bond may be formed between the substrate 100 and the support layer 101, or the surface may be polished to a very low surface roughness through intermolecular forces. physical bond.
  • Step 5 As shown in FIG. 14F, the structure shown in FIG. 14E is turned over, and the auxiliary substrate 112 and the insulating layer 113 are removed to form the structure shown in FIG. 14F, which is referred to as the piezoelectric single crystal film surface release process.
  • the etching processes of the auxiliary substrate 112 and the insulating layer 113 are very different.
  • the auxiliary substrate 112 is silicon
  • the insulating layer 113 is silicon dioxide.
  • the removal process of the insulating layer 113 is mild, and the damage to the other surface of the piezoelectric single crystal thin film during the process of removing the auxiliary substrate 112 is reduced or even avoided.
  • the surface release process of the piezoelectric single crystal thin film can be realized by removing all the substrate 112 and all the insulating layer 113 .
  • the piezoelectric single crystal thin film surface release process may use a release hole on the substrate 112 first, and then release the material of the insulating layer 113 through the release hole.
  • the process for the overall removal of the substrate 112 or the formation of the release holes may be related processes such as grinding, grinding, polishing, wet or dry etching, laser ablation, or a combination of these processes.
  • the overall removal process of the insulating layer 113 may adopt related processes such as grinding, grinding, polishing, wet or dry etching, laser ablation, or a combination of these processes.
  • the surface of the piezoelectric single crystal film is partially damaged, especially the effective area of the resonator or the filter formed by the resonator is damaged, the surface of the piezoelectric film can be polished through a polishing process.
  • Step 6 As shown in FIG. 14G , the piezoelectric layer 106 and the temperature compensation layer 104 are etched to form through holes, and the connection portion of the bottom electrode 105 is leaked out.
  • Forming vias can be accomplished by wet or dry etching, laser ablation, and other related processes, or a combination of these processes.
  • Step 7 As shown in FIG. 14H , deposit a sacrificial material layer on the single crystal piezoelectric layer 106 and etch to form a bridge sacrificial layer 110A corresponding to the shape of the air gap 110 of the bridge structure 109 .
  • Step 8 As shown in FIG. 14I , deposit and form the top electrode 107 , the bridge structure 109 and the electrode connecting portion 108 of the bottom electrode over the single crystal piezoelectric layer 106 and the bridge sacrificial layer 110A.
  • Step 9 Finally, release the sacrificial layer of the bridge structure and the sacrificial material layer 111 corresponding to the cavity of the acoustic mirror to form the structure shown in FIG. 5 .
  • the present invention also proposes a method for manufacturing a resonator, which includes the steps of: providing a POI wafer, the POI wafer including a substrate, a single crystal piezoelectric layer, and a first side of the single crystal piezoelectric layer.
  • the insulating layer between the substrate and the substrate, the piezoelectric layer is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer; and removing the substrate and at least a part of the insulating layer, after removing the substrate
  • the insulating layer acts as a barrier layer to protect the piezoelectric layer, the at least a part of the insulating layer is removed to expose the piezoelectric layer, and the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator removed.
  • the insulating layer 113 is completely removed during the surface release process of the piezoelectric single crystal thin film.
  • the present invention is not limited thereto, in other words, in the present invention, only a part of the insulating layer may be removed to expose the 106 or 114 of the piezoelectric layer, and the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator removed.
  • FIG. 15 is a schematic cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present invention, showing the remaining insulating layer between the electrode connection end of the top electrode and the piezoelectric layer.
  • an insulating layer 113 is provided between the top electrode and the piezoelectric layer.
  • the insulating layer 113 can also cover the surface of the piezoelectric layer at the same time.
  • FIG. 16 is a schematic cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present invention, showing the upper surface of the piezoelectric layer with the remaining insulating layer outside the top electrode.
  • the insulating layer covers at least part of the surface of the other piezoelectric layers except the top electrode and the bottom electrode connecting portion 108 , so that the piezoelectric layer can also play a protective role.
  • upper and lower are relative to the bottom surface of the base of the resonator.
  • the side close to the bottom surface is the lower side, and the side away from the bottom surface is the upper side.
  • the center of the effective area of the resonator (the overlapping area of the piezoelectric layer, the top electrode, the bottom electrode and the acoustic mirror in the thickness direction of the resonator constitutes the effective area) (ie, the center of the effective area).
  • the side or end of a component close to the center of the effective area is the inner or inner end
  • the side or end of the component away from the center of the effective area is the outer or outer end.
  • BAW resonators may be used to form filters or electronic devices.
  • a bulk acoustic wave resonator wherein:
  • the piezoelectric layer of the resonator is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer;
  • the electromechanical coupling coefficient of the resonator is not less than 9%.
  • the acoustic mirror of the resonator is an acoustic mirror cavity, and the temperature compensation layer is arranged in the bottom electrode;
  • One end of the temperature compensation layer is flush with the non-electrode connection end of the bottom electrode
  • the resonator further includes a protective layer, the protective layer covers the bottom electrode from the lower side of the bottom electrode, and the protective layer covers at least the non-electrode connection end of the bottom electrode and the temperature compensation layer in the cavity of the acoustic mirror. Ends.
  • the electrode on which the temperature compensation layer is located comprises an upper electrode layer and a lower electrode layer respectively located on the upper side and the lower side of the temperature compensation layer, the upper electrode layer or the lower electrode layer electrically connected to each other.
  • thermoelectric layer is provided with a communication part, and the communication part connects the upper electrode layer or the lower electrode layer on the upper and lower sides of the temperature compensation layer of the electrode where the temperature compensation layer is located. electrical connection.
  • the communicating ring includes at least one annular opening, the annular opening being a continuous annularly extending annular opening; or
  • the communication ring includes a plurality of communication holes, and the plurality of communication holes are arranged in at least one annular shape; or
  • the at least one communicating ring includes a plurality of communicating rings arranged concentrically.
  • thermoelectric layer is disposed between the top electrode or the bottom electrode and the piezoelectric layer.
  • the acoustic mirror of the resonator is an acoustic mirror cavity
  • the non-electrode connecting end of the bottom electrode of the resonator covers at least the end of the temperature compensation layer in the cavity of the acoustic mirror.
  • thermoelectric layer is provided on the upper surface of the top electrode, or is provided on the lower surface of the bottom electrode.
  • the temperature compensation layer is arranged on the lower surface of the bottom electrode, the acoustic mirror of the resonator is an acoustic mirror cavity, and the resonator further includes a protective layer, and the protective layer covers the temperature compensation layer from the lower side of the temperature compensation layer. layer, and the protective layer covers at least the non-electrode connection end of the bottom electrode and the end of the temperature compensation layer in the cavity of the acoustic mirror; or
  • the temperature compensation layer is disposed on the upper surface of the temperature compensation layer disposed on the top electrode, and the resonator further includes a protective layer covering at least the upper surface of the temperature compensation layer.
  • a support structure is provided between the lower surface of the piezoelectric layer and the upper surface of the substrate, and the piezoelectric layer and the substrate are arranged substantially parallel to each other;
  • At least a portion of the upper surface of the piezoelectric layer is provided with an insulating layer.
  • a POI wafer is provided, the POI wafer includes a substrate, a single crystal piezoelectric layer, and an insulating layer disposed between the first side of the single crystal piezoelectric layer and the substrate, and the piezoelectric layer is single crystal niobate A lithium piezoelectric layer or a single crystal lithium tantalate piezoelectric layer; and
  • the substrate and at least a portion of the insulating layer that acts as a barrier to protect the piezoelectric layer during removal of the substrate the at least a portion of the insulating layer is removed to expose the piezoelectric layer, and The insulating layer of the piezoelectric layer corresponding to the active area of the resonator is removed.
  • the electromechanical coupling coefficient controlling the resonator is not less than 9%.
  • the temperature compensation layer is disposed in a top electrode or a bottom electrode of the resonator.
  • the electrode on which the temperature compensation layer is located includes an upper electrode layer and a lower electrode layer respectively located on the upper side and the lower side of the temperature compensation layer, and the upper electrode layer or the lower electrode layer is electrically connected to each other.
  • the insulating layer remains between the top electrode and the piezoelectric layer in a region corresponding to a portion of the top electrode of the resonator that is outside the effective region.
  • a filter comprising the bulk acoustic wave resonator of any of 1-19.
  • An electronic device comprising the filter according to 24, or the bulk acoustic wave resonator according to any one of 1-19.
  • the electronic equipment here includes but is not limited to intermediate products such as RF front-end, filter and amplifier modules, and terminal products such as mobile phones, WIFI, and drones.

Landscapes

  • 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

La présente invention concerne un résonateur acoustique en volume, dans lequel une couche piézoélectrique du résonateur est une couche piézoélectrique de niobate de lithium monocristallin ou une couche piézoélectrique de tantalate de lithium monocristallin ; et le coefficient de couplage électromécanique du résonateur n'est pas inférieur à 9 %. La présente invention concerne en outre un procédé de fabrication du résonateur acoustique en volume. Le coefficient de couplage électromécanique du résonateur n'est pas inférieur à 9 %. Le procédé comprend les étapes consistant à : fournir une tranche de POI, la tranche de POI comprenant un substrat, une couche piézoélectrique monocristalline, et une couche isolante qui est disposée entre un premier côté de la couche piézoélectrique monocristalline et le substrat, et la couche piézoélectrique est une couche piézoélectrique de niobate de lithium monocristallin ou une couche piézoélectrique de tantalate de lithium monocristallin ; et éliminer le substrat et au moins une partie de la couche isolante, la couche isolante servant de couche barrière pour protéger la couche piézoélectrique pendant le processus d'élimination du substrat, l'au moins une partie de la couche isolante est éliminée pour exposer la couche piézoélectrique, et la couche isolante de la couche piézoélectrique qui correspond à une zone efficace d'un résonateur est éliminée. La présente invention concerne en outre un filtre et un dispositif électronique.
PCT/CN2022/081880 2021-04-27 2022-03-21 Résonateur acoustique en volume piézoélectrique monocristallin et son procédé de fabrication, filtre et dispositif électronique WO2022227928A1 (fr)

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CN115694409A (zh) * 2022-11-10 2023-02-03 武汉敏声新技术有限公司 一种谐振器封装结构及方法
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CN117375568B (zh) * 2023-12-07 2024-03-12 常州承芯半导体有限公司 体声波谐振装置及体声波谐振装置的形成方法

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