WO2022148387A1 - 体声波谐振器及其制造方法、滤波器及电子设备 - Google Patents

体声波谐振器及其制造方法、滤波器及电子设备 Download PDF

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WO2022148387A1
WO2022148387A1 PCT/CN2022/070422 CN2022070422W WO2022148387A1 WO 2022148387 A1 WO2022148387 A1 WO 2022148387A1 CN 2022070422 W CN2022070422 W CN 2022070422W WO 2022148387 A1 WO2022148387 A1 WO 2022148387A1
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layer
resonator
piezoelectric
single crystal
thickness
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PCT/CN2022/070422
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French (fr)
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庞慰
徐洋
张孟伦
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诺思(天津)微***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
    • H03H9/15—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
    • 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

Definitions

  • Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a method for manufacturing a bulk acoustic wave resonator, a filter, and an electronic device.
  • thin film bulk acoustic resonator As a new type of MEMS device, thin film bulk acoustic resonator (FBAR) has the advantages of small size, light weight, low insertion loss, high frequency bandwidth and high quality factor, which is well adapted to the replacement of wireless communication systems.
  • the present invention is proposed to alleviate or solve at least one aspect of the above-mentioned problems in the prior art.
  • a bulk acoustic wave resonator comprising:
  • a piezoelectric layer including at least a first layer and a second layer stacked adjacent to each other in a thickness direction, the first layer having a first thickness and the second layer having a second thickness;
  • At least one of the first layer and the second layer is a single crystal piezoelectric layer, and the materials of the first layer and the second layer are different;
  • the resonator has an electromechanical coupling coefficient Kt 2 and Kt 2 >10%.
  • Embodiments of the present invention also relate to a method for manufacturing a bulk acoustic wave resonator, comprising the steps of:
  • a resonant film layer structure comprising at least a top electrode, a piezoelectric layer and a bottom electrode of the resonator
  • the piezoelectric layer includes at least a first layer and a second layer that are stacked adjacent to each other in a thickness direction, the first layer has a first thickness, the second layer has a second thickness, and one of the first layer and the second layer has a second thickness. At least one layer is a single crystal piezoelectric layer, and the materials of the first layer and the second layer are different;
  • the method includes the step of selecting at least the materials of the first layer and the second layer so that the electromechanical coupling coefficient Kt 2 of the resonator takes a value of Kt 2 >10%.
  • 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 is a diagram exemplarily showing the relationship between the quality factor Qmax value of the resonator and the kt 2 of the resonator;
  • Fig. 2 is a graph showing the variation of electromechanical coupling coefficients K 33 and K 34 in the Z direction of single crystal lithium niobate with the rotation angle of the X axis;
  • FIG. 3 is a graph exemplarily showing the relationship between the E/P value and the parallel resonance impedance Rp of the resonator
  • FIG. 4 is a graph exemplarily showing the relationship between the E/P value and the Qmax value of the resonator
  • FIG. 5 exemplarily shows a graph of E/P value versus Kt 2 of the resonator
  • FIG. 6-9 are schematic cross-sectional views of bulk acoustic wave resonators according to various exemplary embodiments of the present invention.
  • 10-20 are a series of schematic cross-sectional views exemplarily illustrating a manufacturing process of the bulk acoustic wave resonator shown in FIG. 7 .
  • Figure 1 shows the relationship between the quality factor Qmax of the resonator and the kt 2 of the resonator.
  • the scheme of increasing the kt 2 has certain drawbacks, that is, with As the kt 2 increases (doping concentration increases) the Q value of the resonator decreases. That is, as the concentration of doped Sc element in the piezoelectric material AlN increases, the preparation of high-quality thin films becomes more and more difficult, and the result is that the loss of the piezoelectric material begins to increase and the Q value decreases during the operation of the device. Therefore, the method of increasing kt 2 by continuously increasing the doping Sc concentration in AlN is no longer a good solution for larger kt 2 requirements, such as more than 10%.
  • single-crystal piezoelectric materials such as lithium niobate, can improve the Kt 2 of the resonator. of, for example, achieving a large Kt 2 (>10%) while still maintaining single crystal properties, thereby maintaining low material losses in device operation.
  • single crystal lithium niobate is in the coexistence state of K 33 and K 34 in most crystal tangents (X axis), in order to avoid mutual interference between the two and satisfy K 33 or K 34 greater than 10%
  • X axis crystal tangents
  • the X-axis rotation angle can be selected to be about 130° or 253°.
  • These two types of cuts are called (yxl) 40° and (yxl) 163°, corresponding to Kt 2 of about 29% and 53%, respectively. . Therefore, although the single crystal lithium niobate has a large variation range of Kt 2 with the tangential direction, the practical range of Kt 2 is very limited.
  • Fig. 3 is a diagram exemplarily showing the relationship between the layer thickness ratio E/P value (defined later) and the parallel resonance impedance Rp of the resonator.
  • the ordinate is the parallel resonance impedance Rp value of the resonator
  • the abscissa The coordinates are the layer thickness ratio E/P of the resonator.
  • FIG. 4 is a diagram exemplarily showing the relationship between the E/P value and the Qmax value of the resonator. In FIG. 4 , the ordinate is the Qmax value of the resonator, and the abscissa is the layer thickness ratio E/P of the resonator.
  • the layer thickness ratio E/P of the resonator is about 1, the parallel resonance impedance Rp and the quality factor Qmax of the resonator both reach a peak value.
  • the E/P value is farther from 1, both parameters show a downward trend.
  • the parallel resonance impedance Rp decreases relatively slowly on the side where E/P is greater than 1.
  • the layer thickness ratio E/P value is in the range of 0.75 ⁇ E/P ⁇ 3, further, 0.75 ⁇ E/P ⁇ 1.25, still further, 0.85 ⁇ E/P ⁇ 1.15, and further, 0.95 ⁇ E/P ⁇ 1.05.
  • FIG. 5 exemplarily shows a graph of the relationship between the E/P value and the Kt 2 of the resonator, wherein the abscissa is the E/P value and the ordinate is Kt 2 . More specifically, FIG. 5 exemplarily shows the change of kt 2 with the layer thickness ratio E/P when the piezoelectric layer is a piezoelectric layer of aluminum nitride doped with metal scandium element and the doping concentration is 8.2%. It can be seen that kt 2 increases as the layer thickness ratio E/P decreases. However, it is not possible to increase kt 2 by infinitely reducing the E/P value without seriously deteriorating the resonator performance.
  • the Kt 2 corresponding to the two preferred tangential directions of single crystal lithium niobate are about 29% and 53%. If you want to use it as a resonator with a Kt 2 of 17% similar to the wifi6 band, it is bound to increase the E/P value. (as shown in Figure 5) to lower Kt 2 , so both Rp and Qmax of the resonator will deteriorate.
  • the present invention proposes a scheme in which a single crystal piezoelectric layer is mixed with other piezoelectric layers or non-piezoelectric dielectric layers of different materials, so as to satisfy the relatively good E/P value, and The Q value of the resonator will not be lost due to, for example, excessive doping of the polycrystalline piezoelectric layer with rare earth elements (such as Sc elements).
  • rare earth elements such as Sc elements
  • BAW resonators according to various embodiments of the present invention are exemplified below with reference to FIGS. 6-10 .
  • the descriptions of the reference numbers in the figures are as follows:
  • Substrate, optional materials are single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.
  • Acoustic mirror which can be a cavity, or a Bragg reflector and other equivalent forms.
  • the embodiment of the present invention adopts the form of a cavity.
  • Bottom electrode (including bottom electrode pins), 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.
  • Polycrystalline piezoelectric layer such as polycrystalline aluminum nitride, zinc oxide, PZT, etc., may also be a rare earth element doped material containing a certain atomic ratio of the above materials, such as doped aluminum nitride, doped nitride
  • Aluminum contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) et al.
  • the layer 104 contains at least one rare earth element, such as scandium (Sc
  • Single crystal piezoelectric layer such as: single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lithium tantalate, single crystal lead zirconate titanate (PZT), single crystal potassium niobate
  • Materials such as single crystal quartz thin films can also be rare earth element doped materials containing a certain atomic ratio of the above materials, for example, can be doped aluminum nitride, and doped aluminum nitride contains at least one rare earth element, such as scandium (Sc), Yttrium (Y), Magnesium (Mg), Titanium (Ti), Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Th
  • Top electrode (including top electrode pins), 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.
  • Passivation layer or process layer which can be aluminum nitride, silicon nitride or silicon dioxide, etc.
  • Metal Pad or electrode electrical connection optional high-conductivity materials such as gold, copper, and aluminum.
  • a through hole or an electrical connection hole which is provided in the piezoelectric layer and, in a specific embodiment, is used for depositing a conductive material to lead out the bottom electrode 103 to be coplanar with the top electrode 105 .
  • Support layer the material can be aluminum nitride, silicon nitride, polysilicon, silicon dioxide, amorphous silicon, boron-doped silicon dioxide and other silicon-based materials.
  • the specific material can be silicon, silicon carbide, sapphire, silicon dioxide, or other silicon-based materials.
  • an insulating layer which plays a role of protecting the piezoelectric layer or separating the electrode connecting end and the piezoelectric layer, such as silicon dioxide, silicon nitride, silicon carbide, sapphire, and the like.
  • the electromechanical coupling coefficient Kt 2 is related to the value of the layer thickness ratio E/P.
  • the Q value of the bulk acoustic wave resonator is related to the value of the layer thickness ratio E/P.
  • the thickness of the bottom electrode 103 is t1
  • the thickness of the dielectric layer 104a is t2
  • the thickness of the piezoelectric layer 104b is t3
  • the thickness of the top electrode 105 is t4
  • the thickness of the passivation layer 106 above the top electrode is t5.
  • the effect of the bottom electrode 103 on the resonant frequency Fs of the resonator is V1 nm/MHz
  • the effect of the dielectric layer 104a on the resonant frequency Fs of the resonator is V2 nm/MHz
  • the effect of the piezoelectric layer 104b on the resonant frequency Fs of the resonator is V3nm/MHz
  • the effect of the top electrode 105 on the resonant frequency Fs of the resonator is V4nm/MHz
  • the effect of the passivation layer 106 above the top electrode on the resonant frequency Fs of the resonator is V5nm/MHz
  • the layer thickness ratio E/ P is (t1/V1+t4/V4+t5/V5)/(t2/V2+t3/V3).
  • the layer thickness ratio E/P is (t1/V1+t4/V4)/(t2/V2+t3/V3).
  • the layer thickness ratio E/P can be determined in a similar manner as described above.
  • the doping concentration of the element doped in the piezoelectric layer is briefly described below.
  • Doping means that a portion of one or more elements in the original undoped piezoelectric material is replaced by a doping element.
  • the doping concentration is defined as: in a unit volume, the atomic number of the doping element, and the total atomic number of the above-mentioned one or more elements partially replaced by the doping element and the atomic number of the doping element and the ratio.
  • the piezoelectric layer is aluminum nitride and the doping element is scandium
  • the doping concentration is the ratio of the number of scandium atoms to the sum of the number of aluminum atoms and scandium atoms per unit volume. (Sc/Al+Sc).
  • the piezoelectric layer includes two layers, namely, the piezoelectric layer 104a and the piezoelectric layer 104b, which are stacked on each other.
  • Piezoelectric layer 104a is described above as a polycrystalline piezoelectric layer, such as a doped aluminum nitride piezoelectric layer
  • 104b is described above as a single crystal piezoelectric layer, such as a single crystal lithium niobate piezoelectric layer, single crystal niobate
  • the cut shape of the lithium piezoelectric layer is (yxl) 40° or (yxl) 163°.
  • the Kt 2 of the resonator is adjusted by selecting the thicknesses of the piezoelectric layer 104a and the piezoelectric layer 104b.
  • the corresponding Kt 2 of the piezoelectric layer 104a is 8%
  • the piezoelectric layer 104b is a single crystal lithium niobate with a cut shape of (yxl) 40°
  • the corresponding Kt 2 is 29%.
  • the piezoelectric layer 104a is doped aluminum nitride and has a thickness d1
  • its corresponding Kt2 is 8% (determined based on the doping concentration)
  • the piezoelectric layer 104b is a single crystal niobium with a cut shape of (yxl) 40° Lithium oxide has a corresponding Kt 2 of 29% and a thickness d2.
  • the ratio of d1 to d2 can be selected to achieve a Kt 2 of 17%, and an appropriate E/P value can be selected.
  • the layer thickness ratio E/P of the resonator can satisfy 0.75 ⁇ E/P ⁇ 1.25; and the electromechanical coupling coefficient Kt 2 of the resonator can satisfy Kt2>10%.
  • the doping concentration is lower than 20%, so as to minimize the loss of the Q value of the resonator due to the high concentration of doped rare earth elements impact is reduced.
  • the single crystal piezoelectric layer 104b is disposed on the upper surface of the polycrystalline piezoelectric layer 104a so that the polycrystalline piezoelectric layer 104a is disposed between the single crystal piezoelectric layer 104b and the support layer 111 .
  • the single crystal piezoelectric layer 104b may also be disposed on the lower surface of the polycrystalline piezoelectric layer 104a, so that the single crystal piezoelectric layer 104b is disposed between the polycrystalline piezoelectric layer 104a and the support layer 111, as shown in FIG. 7 .
  • the piezoelectric layer only includes one polycrystalline piezoelectric layer and one single crystal piezoelectric layer, but the present invention is not limited to this, and more layers may also be provided.
  • 8-9 are schematic cross-sectional views of BAW resonators according to other various exemplary embodiments of the present invention, showing three piezoelectric layers.
  • the piezoelectric layer includes a single crystal piezoelectric layer 104b, and two polycrystalline piezoelectric layers 104a disposed on the upper and lower sides of the single crystal piezoelectric layer 104b.
  • the thicknesses of the two polycrystalline piezoelectric layers are different, but may be the same in different embodiments.
  • the materials of the two polycrystalline piezoelectric layers may be the same or different.
  • the two polycrystalline piezoelectric layers may also be adjacent to each other in case their materials are different.
  • the piezoelectric layer includes a polycrystalline piezoelectric layer 104a, and two single crystal piezoelectric layers 104b disposed on the upper and lower sides of the polycrystalline piezoelectric layer 104a.
  • the thicknesses of the two single crystal piezoelectric layers are different, but may be the same in different embodiments.
  • the materials of the two single crystal piezoelectric layers may be the same or different. In FIG. 9 , in the case where the materials of the two single crystal piezoelectric layers are different, they may also be adjacent to each other.
  • the piezoelectric layer may also be a piezoelectric layer formed by combining more piezoelectric film layers.
  • one of the piezoelectric layers is a single crystal piezoelectric layer, and the other layers include single crystal piezoelectric layers of different materials or polycrystalline piezoelectric layers, but the present invention does not Limited to this, the additional layer may also be a dielectric layer of a non-piezoelectric material.
  • the manufacturing process of the bulk acoustic wave resonator shown in FIG. 7 is exemplarily described below with reference to FIGS. 10-20 .
  • a bulk acoustic wave resonator is fabricated based on a POI (Piezoelectrics on Insulator, single crystal piezoelectric layer on an insulator) wafer.
  • 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 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. damage of single-crystal piezoelectric films to obtain bulk acoustic wave resonators 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 technology.
  • Figure 10 shows a POI wafer.
  • the POI wafer includes an auxiliary substrate or an auxiliary base 201, an insulating layer 202 and a single crystal piezoelectric layer 104b.
  • the single crystal piezoelectric layer can be lithium niobate, lithium tantalate Isoelectric single crystal thin film.
  • the piezoelectric layer 104b may be a single crystal lithium niobate piezoelectric layer with a cut shape of (yxl) 163°.
  • FIG. 11 exemplarily shows the process of depositing an electrode film layer on the surface of the piezoelectric layer 104b and forming a pattern of the bottom electrode 103 .
  • a uniform electrode film layer may be deposited on the piezoelectric layer 104b first, and then the patterned bottom electrode 103 may be formed by wet or dry etching.
  • the pattern of the bottom electrode can also be directly formed by a lift-off process or a process such as printing.
  • FIG. 12 exemplarily shows a state in which a supporting material layer is deposited on the bottom electrode 103 and the single crystal piezoelectric layer 104 b and planarized to form a supporting material layer corresponding to the supporting layer 111 .
  • the thickness of the support material layer is greater than that of the bottom electrode 103 .
  • a polished flat support material layer is formed by a polishing process (such as CMP (chemical mechanical polishing, chemical mechanical polishing)).
  • FIG. 13 illustrates patterning (eg, by etching) a layer of support material to form cavities 102 and a patterned support layer 111 .
  • the substrate 101 is bonded to the support layer 111 .
  • the flat surface of the support layer 111 may also be provided with a special bonding layer, via which the substrate 101 may be bonded to the support layer 111 .
  • the substrate 101 and the support layer 111 may be bonded by physical or chemical means, and the material of the special bonding layer may be on the substrate 101 or the support layer 111 alone, or on both surfaces.
  • the substrate 101 and the support layer 111 can also be directly bonded without a special bonding layer, that is, a chemical bond can be formed between the substrate 101 and the support layer 111, or the surface can be polished to a very low surface roughness through intermolecular interaction.
  • the force forms a physical bond.
  • the support layer 111 is directly used for bonding and connection, and may also be referred to as a bonding layer.
  • the etching processes of the auxiliary substrate 201 and the insulating layer 202 are very different.
  • the auxiliary substrate 201 is silicon
  • the insulating layer 202 is silicon dioxide.
  • the insulating layer 202 can serve as a stop layer or barrier during the removal of the auxiliary substrate 201 Due to the function of the layer, the removal process of the insulating layer 202 is mild, and the damage to the other surface of the piezoelectric single crystal thin film during the process of removing the auxiliary substrate 201 is reduced or even avoided.
  • the surface release process of the piezoelectric single crystal thin film can be realized by removing all the auxiliary substrate 201 and all the insulating layer 202 .
  • the overall removal of the auxiliary substrate 201 may employ related processes such as grinding, grinding, polishing, wet or dry etching, or a combination of these processes.
  • the overall removal process of the insulating layer 202 may adopt a process such as wet etching or dry etching.
  • 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.
  • the auxiliary substrate 201 and the insulating layer 202 have been removed to expose the side covered by the piezoelectric layer 104b.
  • a polycrystalline piezoelectric layer 104a such as doped aluminum nitride, is deposited on the structure shown in FIG. 15, thereby forming a monocrystalline piezoelectric layer 104b and a polycrystalline piezoelectric layer 104a.
  • Hybrid piezoelectric layer structure As shown in FIG. 16, a polycrystalline piezoelectric layer 104a, such as doped aluminum nitride, is deposited on the structure shown in FIG. 15, thereby forming a monocrystalline piezoelectric layer 104b and a polycrystalline piezoelectric layer 104a. Hybrid piezoelectric layer structure.
  • the piezoelectric layer formed in FIG. 16 includes a piezoelectric layer 104a and a piezoelectric layer 104b that are stacked adjacent to each other in the thickness direction, the piezoelectric layer 104a has a first thickness, and the piezoelectric layer 104b has a second thickness, which can match
  • the values of the first thickness and the second thickness are selected so that the value of the resonator layer thickness ratio E/P is 0.75 ⁇ E/P ⁇ 1.25, and at least the piezoelectric layer 104a is selected
  • the material of the piezoelectric layer 104b makes the electromechanical coupling coefficient Kt 2 of the resonator take a value of Kt 2 >10%.
  • top electrode film and a passivation layer film on the surface of the structure shown in FIG. 16 and forming a pattern of the top electrode and the passivation layer is shown.
  • the top electrode and the passivation layer can be formed by first depositing a uniform electrode film layer and a passivation layer film, and then forming the patterned top electrode 105 and the passivation layer 106 by wet or dry etching.
  • the passivation layer 106 may not be provided, and a top electrode film is deposited on the surface of the structure shown in FIG. 16 , and then a patterned top electrode 105 is formed by wet or dry etching.
  • the passivation layer 106 may be patterned here to remove part of the passivation layer on the top electrode for subsequent signal extraction.
  • an electrical connection hole 108 of the bottom electrode connection portion is formed on the piezoelectric layer, which penetrates through the piezoelectric layer 104a and the piezoelectric layer 104b to expose the bottom electrode, which can be wet or dry etching, laser ablation, etc. A related process or a collection of these processes is used to obtain the electrical connection hole 108 .
  • the patterned electrode electrical connection portion 107 for the electrical connection of the top electrode 105 can be formed by first depositing a uniform conductive film layer and then by wet or dry etching, or by a lift-off process or a printing process. , and an electrode electrical connection portion 107 for electrical connection with the bottom electrode.
  • the hybrid piezoelectric layer formed of the single crystal piezoelectric layer and the polycrystalline piezoelectric layer was described as an example.
  • the piezoelectric mixed layer can also be formed by different single crystal piezoelectric layers.
  • each numerical range except that it is clearly indicated that it does not include the endpoint value, can be the endpoint value, and can also be the median value of each numerical range, and these are all within the protection scope of the present invention. .
  • 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 comprising:
  • a piezoelectric layer including at least a first layer and a second layer stacked adjacent to each other in a thickness direction, the first layer having a first thickness and the second layer having a second thickness;
  • At least one of the first layer and the second layer is a single crystal piezoelectric layer, and the materials of the first layer and the second layer are different;
  • the resonator has an electromechanical coupling coefficient Kt 2 and Kt 2 >10%.
  • One of the first layer and the second layer is a single crystal piezoelectric layer, and the other layer is a dielectric layer of non-piezoelectric material.
  • the first layer is a single crystal piezoelectric layer
  • the second layer is a polycrystalline piezoelectric layer.
  • the first layer is a single crystal lithium niobate piezoelectric layer, and the cut shape of the single crystal lithium niobate piezoelectric layer is (yxl) 40° or (yxl) 163°.
  • the second layer is a doped aluminum nitride piezoelectric layer or a doped silicon nitride piezoelectric layer or a doped zinc oxide piezoelectric layer, and the doping concentration is lower than 20%; and/or
  • the first layer is a single crystal lithium niobate piezoelectric layer or a single crystal lithium tantalate piezoelectric layer.
  • the cut shape of the single crystal lithium niobate piezoelectric layer is (yxl) 40°; or
  • the cut shape of the single crystal lithium niobate piezoelectric layer is (yxl) 163°.
  • the first layer is a single crystal piezoelectric layer
  • the second layer is a polycrystalline piezoelectric layer or a non-piezoelectric dielectric layer
  • the first layer is disposed between the second layer and the top electrode, or the second layer is disposed between the first layer and the top electrode.
  • the piezoelectric layer includes at least the first layer, the second layer and the third layer stacked in a thickness direction, the third layer having a third thickness;
  • the first layer is a single crystal piezoelectric layer, and the second layer and the third layer are polycrystalline piezoelectric layers or non-piezoelectric dielectric layers;
  • the materials of the two adjacently stacked layers are different.
  • the first layer is closer to the top electrode than the second and third layers; or
  • the first layer is closer to the bottom electrode than the second and third layers.
  • the first layer, the second layer and the third layer are all single crystal piezoelectric layers, and the materials of the adjacent layers are different.
  • Both the first layer and the second layer are single crystal piezoelectric layers.
  • the first layer is a single crystal lithium niobate piezoelectric layer with a cut shape of (yxl) 40°; or
  • the second layer is a single crystal lithium niobate piezoelectric layer with a cut shape of (yxl) 163°.
  • the resonator has a layer thickness ratio E/P, 0.75 ⁇ E/P ⁇ 3.
  • the resonator has a layer thickness ratio E/P, 0.75 ⁇ E/P ⁇ 1.25.
  • a method for manufacturing a bulk acoustic wave resonator comprising the steps of:
  • a resonant film layer structure comprising at least a top electrode, a piezoelectric layer and a bottom electrode of the resonator
  • the piezoelectric layer includes at least a first layer and a second layer that are stacked adjacent to each other in the thickness direction, the first layer has a first thickness, the second layer has a second thickness, and one of the first layer and the second layer has a second thickness. At least one layer is a single crystal piezoelectric layer, and the materials of the first layer and the second layer are different;
  • the method includes the step of selecting at least the materials of the first layer and the second layer so that the electromechanical coupling coefficient Kt 2 of the resonator takes a value of Kt 2 >10%.
  • the values of the first thickness and the second thickness are selected according to the thicknesses of other film layers of the resonant film layer structure, so that the value of the resonator layer thickness ratio E/P is 0.75 ⁇ E/P ⁇ 3.
  • a filter comprising a plurality of bulk acoustic wave resonators according to any of 1-16.
  • An electronic device comprising the filter according to 19, or the bulk acoustic wave resonator according to any one of 1-16.
  • 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.

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Abstract

本发明涉及一种体声波谐振器，包括：基底；声学镜；底电极；压电层，包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度；和顶电极，其中：第一层和第二层中的至少一层为单晶压电层，所述谐振器具有机电耦合系数Kt 2，且Kt 2＞10％。本发明也涉及一种体声波谐振器的制造方法，一种滤波器和一种电子设备。

Description

体声波谐振器及其制造方法、滤波器及电子设备 技术领域
本发明的实施例涉及半导体领域，尤其涉及一种体声波谐振器、一种体声波谐振器的制造方法、以及一种滤波器和一种电子设备。
背景技术
随着5G通信技术的发展，新兴频段除了频率越来越高以外，带宽也越来越大。通信技术对滤波器的大带宽提出了越来越高的要求。在这种前提下，滤波器的设计就对具有更大有效机电耦合系数(kt7)的谐振器提出了迫切需求。例如Wifi6频段对谐振器的kt7需求已经达到了17％左右。
薄膜体声波谐振器(FBAR)作为一种新型的MEMS器件，具有体积小、质量轻、***损耗低、频带宽以及品质因子高等优点，很好地适应了无线通信***的更新换代。
现有技术中，仍然有在保持谐振器的kt 2较大的情况下还提高谐振器的Q值的需求。
发明内容
为缓解或解决现有技术中的上述问题的至少一个方面，提出本发明。
根据本发明的实施例的一个方面，提出了一种体声波谐振器，包括：
基底；
声学镜；
底电极；
压电层，包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度；和
顶电极，
其中：
第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
所述谐振器具有机电耦合系数Kt 2，且Kt 2＞10％。
本发明的实施例也涉及一种体声波谐振器的制造方法，包括步骤：
提供谐振膜层结构，所述谐振膜层结构至少包括所述谐振器的顶电极、 压电层和底电极，
其中：
所述压电层包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度，第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
所述方法包括步骤：至少选择第一层和第二层的材料使得谐振器的机电耦合系数Kt 2的取值为Kt 2＞10％。
本发明的实施例还涉及一种滤波器，包括上述的谐振器。
本发明的实施例也涉及一种电子设备，包括上述的滤波器或者上述的谐振器。
附图说明
以下描述与附图可以更好地帮助理解本发明所公布的各种实施例中的这些和其他特点、优点，图中相同的附图标记始终表示相同的部件，其中：
图1为示例性示出谐振器的品质因子Qmax值与谐振器的kt 2关系图；
图2为单晶铌酸锂Z方向机电耦合系数K 33和K 34随X轴旋转角度变化的曲线图；
图3为示例性示出E/P值和谐振器的并联谐振阻抗Rp之间的关系图；
图4为示例性示出E/P值和谐振器的Qmax值之间的关系图；
图5示例性示出了E/P值与谐振器的Kt 2的关系图；
图6-9为根据本发明的不同示例性实施例的体声波谐振器的截面示意图；
图10-20为示例性示出了图7所示的体声波谐振器的制造过程的一系列截面示意图。
具体实施方式
下面通过实施例，并结合附图，对本发明的技术方案作进一步具体的说明。在说明书中，相同或相似的附图标号指示相同或相似的部件。下述参照附图对本发明实施方式的说明旨在对本发明的总体发明构思进行解释，而不应当理解为对本发明的一种限制。发明的一部分实施例，而并不是全部的实施例。基于本发明中的实施例，本领域普通技术人员所获得的所有其他实施 例，都属于本发明保护的范围。
图1为谐振器的品质因子Qmax值与谐振器的kt 2关系图，如图1所示，对于利用掺杂Sc元素AlN压电层的谐振器，提升kt 2的方案存在一定弊端，就是随着kt 2提升(掺杂浓度提升)谐振器的Q值却在下降。即，随着压电材料AlN中掺杂Sc元素的浓度增加，高质量的薄膜制备变得越来越难，导致的结果是在器件工作中压电材料损耗开始增大而致使Q值降低。因此通过不断提升AlN中掺杂Sc浓度而提升kt 2的方法对于更大kt 2需求，比如10％以上，已经不再是好的解决方案。
相对于AlN掺杂Sc元素的多晶压电材料所面临的通过掺杂提升Kt 2但是谐振器的Q值下降的问题，单晶压电材料，如铌酸锂，可以提升谐振器的Kt 2的，例如，在实现大Kt 2(＞10％)的情况下仍然保持单晶特性，从而保持在器件工作中较低的材料损耗。然而，如图2所示，单晶铌酸锂在大多数晶体切向下(X轴)K 33和K 34为共存状态，为避免二者的互相干扰并且满足K 33或K 34大于10％的状态，通常只能选择X轴旋转角度为130°或者253°左右，这两种切型被称为(yxl)40°和(yxl)163°，对应Kt 2分别为29％和53％左右。因此，单晶铌酸锂虽然Kt 2随切向改变范围较大，但实际Kt 2可选择范围十分受限。
图3为示例性示出层厚比E/P值(后面有定义)和谐振器的并联谐振阻抗Rp之间的关系图，图3中，纵坐标为谐振器的并联谐振阻抗Rp值，横坐标为谐振器的层厚比E/P。图4为示例性示出E/P值和谐振器的Qmax值之间的关系图，图4中，纵坐标为谐振器的Qmax值，横坐标为谐振器的层厚比E/P。
如图3和图4所示，当谐振器的层厚比E/P值在1左右时，谐振器的并联谐振阻抗Rp和品质因子Qmax均达到一个峰值。当E/P值越远离1时，该两个参数均呈现下降趋势。此外，如图3所示，并联谐振阻抗Rp在E/P大于1的一侧下降相对缓慢一些。基于以上，本发明的一个实施例中，层厚比E/P值的范围为0.75≤E/P≤3，进一步的，为0.75≤E/P≤1.25，再进一步的，0.85≤E/P≤1.15，还进一步的，0.95≤E/P≤1.05。
图5示例性示出了E/P值与谐振器的Kt 2的关系图，其中横坐标为E/P值，纵坐标为Kt 2。更具体的，图5示例性示出了当压电层为氮化铝掺杂金属钪元素的压电层时，掺杂浓度为8.2％时，kt 2随层厚比E/P的变化。可以看到，随着层厚比E/P降低，kt 2升高。然而，在保证谐振器性能不严重恶化的前提下，不能通过无限降低E/P值来提升kt 2。
单晶铌酸锂的两个优选切向对应的Kt 2在29％和53％左右，如果想利用 其做类似于wifi6频段的Kt 2为17％的谐振器时，势必需要提升E/P值(如图5所示)来降低Kt 2，因此谐振器的Rp和Qmax均会发生恶化。
为解决以上技术问题，本发明提出一种单晶压电层和其他不同材料的压电层或者非压电介质层混合使用的方案，从而做到既满足相对较优的E/P值，又不会因例如多晶压电层掺杂过多稀土元素(比如Sc元素)过高而损失谐振器的Q值。
下面参照图6-10示例性说明根据本发明的不同实施例的体声波谐振器。图中附图标记的说明如下：
101：基底，可选材料为单晶硅、氮化镓、砷化镓、蓝宝石、石英、碳化硅、金刚石等。
102：声学镜，可为空腔，也可采用布拉格反射层及其他等效形式。本发明的实施例中采用的是空腔的形式。
103：底电极(包括底电极引脚)，材料可选钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上金属的复合或其合金等。
104a：多晶压电层，如多晶氮化铝、氧化锌、PZT等，还可是包含上述材料的一定原子比的稀土元素掺杂材料，例如可以是掺杂氮化铝，掺杂氮化铝至少含一种稀土元素，如钪(Sc)、钇(Y)、镁(Mg)、钛(Ti)、镧(La)、铈(Ce)、镨(Pr)、钕(Nd)、钷(Pm)、钐(Sm)、铕(Eu)、钆(Gd)、铽(Tb)、镝(Dy)、钬(Ho)、铒(Er)、铥(Tm)、镱(Yb)、镥(Lu)等。需要指出的是，在本发明的其他实施例中，层104a也可以替换为非压电材料的介质层，例如其材料例如为多晶二氧化硅。
104b：单晶压电层，如：单晶氮化铝、单晶氮化镓、单晶铌酸锂、单晶钽酸锂、单晶锆钛酸铅(PZT)、单晶铌酸钾、单晶石英薄膜等材料，还可是包含上述材料的一定原子比的稀土元素掺杂材料，例如可以是掺杂氮化铝，掺杂氮化铝至少含一种稀土元素，如钪(Sc)、钇(Y)、镁(Mg)、钛(Ti)、镧(La)、铈(Ce)、镨(Pr)、钕(Nd)、钷(Pm)、钐(Sm)、铕(Eu)、钆(Gd)、铽(Tb)、镝(Dy)、钬(Ho)、铒(Er)、铥(Tm)、镱(Yb)、镥(Lu)等。
105：顶电极(包括顶电极引脚)，材料可选钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上金属的复合或其合金等。
106：钝化层或工艺层，其可以是氮化铝、氮化硅或二氧化硅等。
107：金属Pad或电极电连接部，可选金，铜，铝等高电导率材料。
108：通孔或者电连接孔，设置在压电层中，在具体的实施例中，用于沉积导电材料，将底电极103引出到与顶电极105共面。
111：支撑层，材料可以为氮化铝、氮化硅、多晶硅、二氧化硅、无定形 硅、硼掺杂二氧化硅及其他硅基材料等。
201：辅助基底，具体材料可选为硅、碳化硅、蓝宝石、二氧化硅、或者其他硅基材料。
202：绝缘层，起到保护压电层或者隔开电极连接端与压电层的作用，例如二氧化硅、氮化硅、碳化硅、蓝宝石等。
对于体声波谐振器而言，其机电耦合系数Kt 2与层厚比E/P的值有关。此外，体声波谐振器的Q值与层厚比E/P的值相关。
下面首先简单说明层厚比E/P。
如图6所示，底电极103的厚度为t1，介质层104a的厚度为t2，压电层104b的厚度为t3，顶电极105的厚度为t4，以及顶电极以上的钝化层106的厚度为t5。另外，底电极103对谐振器的谐振频率Fs的影响为V1nm/MHz，介质层104a对谐振器的谐振频率Fs的影响为V2nm/MHz，压电层104b对谐振器的谐振频率Fs的影响为V3nm/MHz，顶电极105对谐振器的谐振频率Fs的影响为V4nm/MHz，以及顶电极以上的钝化层106对谐振器的谐振频率Fs的影响为V5nm/MHz，则层厚比E/P为(t1/V1+t4/V4+t5/V5)/(t2/V2+t3/V3)。
如能够理解的，在没有设置钝化层的情况下，层厚比E/P为(t1/V1+t4/V4)/(t2/V2+t3/V3)。
对于其他的膜层结构，可以采用上述类似的方式确定层厚比E/P。
下面简单说明在压电层中掺杂的元素的掺杂浓度。
掺杂意味着原来没有掺杂的压电材料中的一种或多种元素的一部分被掺杂元素所代替。此时掺杂浓度定义为：在单位体积中，掺杂元素的原子数，与上述提及的一种或多种被掺杂元素部分代替的元素的总原子数与掺杂元素的原子数之和的比值。例如，在压电层为氮化铝、掺杂元素为钪的情况下，部分铝原子被钪原子替代，掺杂浓度为单位体积中钪原子数与铝原子数和钪原子数的和的比值(Sc/Al+Sc)。
在图6中，压电层包括两层，分别是压电层104a和压电层104b，两者彼此叠置。压电层104a如上描述的为多晶压电层，例如掺杂氮化铝压电层，而104b如上描述为单晶压电层，例如为单晶铌酸锂压电层，单晶铌酸锂压电层的切型为(yxl)40°或(yxl)163°。
下面简单说明一下，如果通过选择压电层104a和压电层104b的厚度来调整谐振器的Kt 2。例如，压电层104a对应的Kt 2为8％，压电层104b为切型为(yxl)40°的单晶铌酸锂对应Kt 2为29％。
假定压电层104a为掺杂氮化铝且具有厚度d1，其对应的Kt 2为8％(基 于掺杂浓度确定)，而压电层104b为切型为(yxl)40°的单晶铌酸锂其对应的Kt 2为29％且具有厚度d2，为了实现谐振器的Kt 2为17％，可以通过选择d1与d2的比例从而实现Kt 2为17％，并且选择合适的E/P值。
在本发明中，通过混用单晶压电层和多晶压电层，可以使得谐振器的层厚比E/P满足0.75≤E/P≤1.25；以及使得谐振器的机电耦合系数Kt 2满足Kt2＞10％。
在本发明的实施例中，在使用掺杂稀土元素的多晶压电层的情况下，掺杂浓度低于20％，以尽量将因掺杂稀土元素浓度过高而损失谐振器的Q值的影响降低。
在图6所示的实施例中，单晶压电层104b设置在多晶压电层104a的上表面，从而多晶压电层104a设置在单晶压电层104b与支撑层111之间。
单晶压电层104b也可以设置在多晶压电层104a的下表面，从而单晶压电层104b设置在多晶压电层104a与支撑层111之间，如图7所示。
在图6-7所示的实施例中，压电层仅包括一层多晶压电层和一层单晶压电层，但是本发明不限于此，也可以设置更多层。图8-9为根据本发明的其他不同示例性实施例的体声波谐振器的截面示意图，其中示出了三层压电层。
如图8所示，压电层包括单晶压电层104b，以及设置在单晶压电层104b的上下两侧的两个多晶压电层104a。在图8中，两个多晶压电层的厚度不同，但是，在不同的实施例中，也可以相同。此外，在图8中，两个多晶压电层的材料可以相同，也可以不同。在图8中，在两个多晶压电层的材料不同的情况下，其也可以彼此邻接。
如图9所示，压电层包括多晶压电层104a，以及设置在多晶压电层104a的上下两侧的两个单晶压电层104b。在图9中，两个单晶压电层的厚度不同，但是，在不同的实施例中，也可以相同。此外，在图9中，两个单晶压电层的材料可以相同，也可以不同。在图9中，在两个单晶压电层的材料不同的情况下，其也可以彼此邻接。
虽然没有示出，压电层还可以是更多层的压电膜层组合形成的压电层。
在参照图6-9描述的实施例中，压电层中的一层为单晶压电层，另外的层包括不同材料的单晶压电层或者为多晶压电层，但是本发明不限于此，另外的层还可以为非压电材料的介质层。
下面参照图10-20为示例性说明图7所示的体声波谐振器的制造过程。
在本发明中，基于POI(Piezoelectrics on Insulator，绝缘体上的单晶压电层)晶圆制作体声波谐振器。POI晶圆包括辅助衬底、单晶压电层以及设 置在单晶压电层与辅助衬底之间的绝缘层。
如后面提及的，在谐振器转移加工过程中，绝缘层能够更好的保护单晶压电薄膜(即单晶压电层)，从而可以减小甚至避免后续去除辅助衬底的过程中对单晶压电薄膜的损伤，以得到性能优异的体声波谐振器。
另外，绝缘层的存在，也有利于辅助衬底去除方案的多样化，简化器件加工工艺。
图10示出了POI晶圆。如图10所示，POI晶圆包括辅助衬底或辅助基底201、绝缘层202和单晶压电层104b，如前已经提及的，单晶压电层可以是铌酸锂、钽酸锂等压电单晶薄膜。
POI晶圆中压电单晶薄膜的晶向是多样的，不受压电薄膜生长条件的限制，因此可以根据需要选择特殊晶向的压电单晶薄膜，制作多种性能的谐振器和滤波器。例如在本发明的一个实施例中，压电层104b可以是切型为(yxl)163°的单晶铌酸锂压电层。
图11示例性示出了在压电层104b表面沉积电极膜层及形成底电极103的图案的过程。
可以先在压电层104b上沉积一均匀电极膜层，然后通过湿法或者干法刻蚀的方式形成图案化的底电极103。可选的，也可以通过剥离工艺(1ift-off)或打印等工艺直接形成底电极的图案。
图12示例性示出了底电极103和单晶压电层104b上沉积支撑材料层并平坦化形成了对应于支撑层111的支撑材料层的状态。支撑材料层厚度大于底电极103的厚度。通过抛光过程(比如CMP(chemical mechanical polishing，化学机械抛光))形成抛光后的平坦的支撑材料层。
图13示例性示出了对支撑材料层图形化(例如通过刻蚀)以形成空腔102和图形化的支撑层111。
在图14中，基底101与支撑层111键合连接。
虽然没有示出，支撑层111的平坦面还可以设置有专门的键合层，基底101可经由其键合连接到支撑层111。基底101与支撑层111可以通过物理或化学方式键合，该专门键合层的材料可单独在基底101或支撑层111上，或二者表面皆有。
基底101和支撑层111也可以不经专门的键合层而直接键合，即可以在基底101和支撑层111之间形成化学键，也可以是表面抛光至表面粗糙度极低时通过分子间作用力形成物理键合。此时，支撑层111直接用于键合连接，也可以被称为键合层。
接着是将图14中的器件反转，以及将辅助基底201和绝缘层202移除 的过程。
辅助基底201和绝缘层202(阻隔层)的刻蚀工艺迥异，比如辅助基底201是硅，绝缘层202是二氧化硅，绝缘层202可以在辅助基底201移除过程中起到终止层或阻挡层的作用，绝缘层202的去除工艺温和，减少甚至避免了压电单晶薄膜的另一表面在移除辅助基底201的过程受到的伤害。
压电单晶薄膜表面释放工艺可以采用全部去除辅助基底201、全部去除绝缘层202的方式实现。
辅助基底201的整体去除可以采用磨削、研磨、抛光、湿法或干法刻蚀等相关工艺或者这些工艺的集合。绝缘层202的整体去除工艺可以采用湿法或干法刻蚀等工艺。
绝缘层202去除以后，如果压电单晶薄膜的表面有部分损伤，尤其是谐振器或由谐振器形成的滤波器的有效区域有损伤，可以通过抛光过程对压电薄膜表面进行抛光处理。
如图15所示，辅助基底201和绝缘层202已经被移除以露出压电层104b的被其覆盖的一侧。
如图16所示，在图15所示的结构上沉积一层多晶压电层104a，例如为掺杂氮化铝，从而形成由单晶压电层104b和多晶压电层104a组成的混合压电层结构。
在图16中形成的压电层包括在厚度方向上彼此相邻叠置的压电层104a和压电层104b，压电层104a具有第一厚度，压电层104b具有第二厚度，可以配合谐振器的叠置结构的其他膜层厚度选择第一厚度和第二厚度的值而使得谐振器层厚比E/P的取值为0.75≤E/P≤1.25，以及至少选择压电层104a和压电层104b的材料使得谐振器的机电耦合系数Kt 2的取值为Kt 2＞10％。
参见图17，示出了在图16所示结构的表面沉积顶电极薄膜和钝化层膜层，及形成顶电极和钝化层的图案的过程。形成顶电极和钝化层可通过首先沉积均匀电极膜层和钝化层膜层，然后通过湿法或干法刻蚀的方式形成图案化的顶电极105和钝化层106。
也可以不设置钝化层106，则在图16所示结构的表面沉积顶电极薄膜，然后通过湿法或干法刻蚀的方式形成图案化的顶电极105。
如图18所示，可以在此图形化钝化层106，以移除部分顶电极上的钝化层以用于后续引出信号。
参见图19，在压电层上形成底电极连接部的电连接孔108，其贯穿压电层104a和压电层104b而露出底电极，可以通过湿法或干法刻蚀、激光烧蚀等相关工艺或者这些工艺的集合来获得该电连接孔108。
参见图20，可通过首先沉积均匀导电膜层然后通过湿法或干法刻蚀的方式，或者通过剥离工艺或打印等工艺，形成图案化的用于顶电极105电连接的电极电连接部107，以及用于与底电极电连接的电极电连接部107。
在以上的实施例中，以单晶压电层与多晶压电层形成的混合压电层为例进行了说明。但是，可选的，也可以不同的单晶压电层构成压电混合层。
需要指出的是，在本发明中，各个数值范围，除了明确指出不包含端点值之外，除了可以为端点值，还可以为各个数值范围的中值，这些均在本发明的保护范围之内。
在本发明中，上和下是相对于谐振器的基底的底面而言的，对于一个部件，其靠近该底面的一侧为下侧，远离该底面的一侧为上侧。
在本发明中，内和外是相对于谐振器的有效区域(压电层、顶电极、底电极和声学镜在谐振器的厚度方向上的重叠区域构成有效区域)的中心(即有效区域中心)在横向方向或者径向方向上而言的，一个部件的靠近有效区域中心的一侧或一端为内侧或内端，而该部件的远离有效区域中心的一侧或一端为外侧或外端。对于一个参照位置而言，位于该位置的内侧表示在横向方向或径向方向上处于该位置与有效区域中心之间，位于该位置的外侧表示在横向方向或径向方向上比该位置更远离有效区域中心。
如本领域技术人员能够理解的，根据本发明的体声波谐振器可以用于形成滤波器或电子设备。
基于以上，本发明提出了如下技术方案：
1、一种体声波谐振器，包括：
基底；
声学镜；
底电极；
压电层，包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度；和
顶电极，
其中：
第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
所述谐振器具有机电耦合系数Kt 2，且Kt 2＞10％。
2、根据1所述的谐振器，其中：
所述第一层和第二层中的一层为单晶压电层，另一层为非压电材料的介质层。
3、根据1所述的谐振器，其中：
第一层为单晶压电层，第二层为多晶压电层。
4、根据3所述的谐振器，其中：
所述第一层为单晶铌酸锂压电层，单晶铌酸锂压电层的切型为(yxl)40°或(yxl)163°。
5、根据3所述的谐振器，其中：
所述第二层为掺杂氮化铝压电层或掺杂氮化硅压电层或者掺杂氧化锌压电层，掺杂浓度低于20％；和/或
所述第一层为单晶铌酸锂压电层或单晶钽酸锂压电层。
6、根据5所述的谐振器，其中：
单晶铌酸锂压电层的切型为(yxl)40°；或者
单晶铌酸锂压电层的切型为(yxl)163°。
7、根据1所述的谐振器，其中：
第一层为单晶压电层，第二层为多晶压电层或非压电介质层；且
第一层设置在第二层与顶电极之间，或者第二层设置在第一层与顶电极之间。
8、根据1所述的谐振器，其中：
所述压电层包括在厚度方向上叠置的至少所述第一层、所述第二层和第三层，第三层具有第三厚度；
第一层为单晶压电层，第二层和第三层为多晶压电层或非压电介质层；
相邻叠置的两层的材料不同。
9、根据8所述的谐振器，其中：
第一层相比于第二层和第三层靠近顶电极；或者
第一层相比于第二层和第三层靠近底电极。
10、根据1所述的谐振器，其中：
第一层、第二层和第三层均为单晶压电层，相邻层的材料不同。
11、根据1所述的谐振器，其中：
第一层与第二层均为单晶压电层。
12、根据11所述的谐振器，其中：
第一层为切型为(yxl)40°的单晶铌酸锂压电层；或者
第二层为切型为(yxl)163°的单晶铌酸锂压电层。
13、根据1-12中任一项所述的谐振器，其中：
所述谐振器具有层厚比E/P，0.75≤E/P≤3。
14、根据13所述的谐振器，其中：
所述谐振器具有层厚比E/P，0.75≤E/P≤1.25。
15、根据14所述的谐振器，其中：
0.85≤E/P≤1.15。
16、根据15所述的谐振器，其中：
0.95≤E/P≤1.05。
17、一种体声波谐振器的制造方法，包括步骤：
提供谐振膜层结构，所述谐振膜层结构至少包括所述谐振器的顶电极、压电层和底电极，
其中：
所述压电层包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度，第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
所述方法包括步骤：至少选择第一层和第二层的材料使得谐振器的机电耦合系数Kt 2的取值为Kt 2＞10％。
18、根据17所述的方法，还包括步骤：
配合所述谐振膜层结构的其他膜层厚度选择第一厚度和第二厚度的值而使得谐振器层厚比E/P的取值为0.75≤E/P≤3。
19、一种滤波器，包括多个根据1-16中任一项所述的体声波谐振器。
20、一种电子设备，包括根据19所述的滤波器，或根据1-16中任一项所述的体声波谐振器。
这里的电子设备，包括但不限于射频前端、滤波放大模块等中间产品，以及手机、WIFI、无人机等终端产品。
尽管已经示出和描述了本发明的实施例，对于本领域的普通技术人员而言，可以理解在不脱离本发明的原理和精神的情况下可以对这些实施例进行变化，本发明的范围由所附权利要求及其等同物限定。

Claims (20)

  1. 一种体声波谐振器，包括：
    基底；
    声学镜；
    底电极；
    压电层，包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度；和
    顶电极，
    其中：
    第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
    所述谐振器具有机电耦合系数Kt 2，且Kt 2＞10％。
  2. 根据权利要求1所述的谐振器，其中：
    所述第一层和第二层中的一层为单晶压电层，另一层为非压电材料的介质层。
  3. 根据权利要求1所述的谐振器，其中：
    第一层为单晶压电层，第二层为多晶压电层。
  4. 根据权利要求3所述的谐振器，其中：
    所述第一层为单晶铌酸锂压电层，单晶铌酸锂压电层的切型为(yxl)40°或(yxl)163°。
  5. 根据权利要求3所述的谐振器，其中：
    所述第二层为掺杂氮化铝压电层或掺杂氮化硅压电层或者掺杂氧化锌压电层，掺杂浓度低于20％；和/或
    所述第一层为单晶铌酸锂压电层或单晶钽酸锂压电层。
  6. 根据权利要求5所述的谐振器，其中：
    单晶铌酸锂压电层的切型为(yxl)40°；或者
    单晶铌酸锂压电层的切型为(yxl)163°。
  7. 根据权利要求1所述的谐振器，其中：
    第一层为单晶压电层，第二层为多晶压电层或非压电介质层；且
    第一层设置在第二层与顶电极之间，或者第二层设置在第一层与顶电极 之间。
  8. 根据权利要求1所述的谐振器，其中：
    所述压电层包括在厚度方向上叠置的至少所述第一层、所述第二层和第三层，第三层具有第三厚度；
    第一层为单晶压电层，第二层和第三层为多晶压电层或非压电介质层；
    相邻叠置的两层的材料不同。
  9. 根据权利要求8所述的谐振器，其中：
    第一层相比于第二层和第三层靠近顶电极；或者
    第一层相比于第二层和第三层靠近底电极。
  10. 根据权利要求1所述的谐振器，其中：
    第一层、第二层和第三层均为单晶压电层，相邻层的材料不同。
  11. 根据权利要求1所述的谐振器，其中：
    第一层与第二层均为单晶压电层。
  12. 根据权利要求11所述的谐振器，其中：
    第一层为切型为(yxl)40°的单晶铌酸锂压电层；或者
    第二层为切型为(yxl)163°的单晶铌酸锂压电层。
  13. 根据权利要求1-12中任一项所述的谐振器，其中：
    所述谐振器具有层厚比E/P，0.75≤E/P≤3。
  14. 根据权利要求13所述的谐振器，其中：
    0.75≤E/P≤1.25。
  15. 根据权利要求14所述的谐振器，其中：
    0.85≤E/P≤1.15。
  16. 根据权利要求15所述的谐振器，其中：
    0.95≤E/P≤1.05。
  17. 一种体声波谐振器的制造方法，包括步骤：
    提供谐振膜层结构，所述谐振膜层结构至少包括所述谐振器的顶电极、压电层和底电极，
    其中：
    所述压电层包括在厚度方向上彼此相邻叠置的至少第一层和第二层，第一层具有第一厚度，第二层具有第二厚度，第一层和第二层中的至少一层为单晶压电层，且第一层与第二层的材料不同；
    所述方法包括步骤：至少选择第一层和第二层的材料使得谐振器的机电耦合系数Kt 2的取值为Kt 2＞10％。
  18. 根据权利要求17所述的方法，还包括步骤：
    配合所述谐振膜层结构的其他膜层厚度选择第一厚度和第二厚度的值而使得谐振器层厚比E/P的取值为0.75≤E/P≤3。
  19. 一种滤波器，包括多个根据权利要求1-16中任一项所述的体声波谐振器。
  20. 一种电子设备，包括根据权利要求19所述的滤波器，或根据权利要求1-16中任一项所述的体声波谐振器。
PCT/CN2022/070422 2021-01-07 2022-01-06 体声波谐振器及其制造方法、滤波器及电子设备 WO2022148387A1 (zh)

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