Bulk acoustic wave resonator and electronic device

Abstract

The invention provides a bulk acoustic wave resonator and electronic equipment, belongs to the technical field of communication, and can solve the problem of energy loss caused by standing waves generated by an existing resonator. The bulk acoustic wave resonator comprises a substrate, and a first electrode, a piezoelectric layer and a second electrode which are sequentially arranged on the substrate, orthographic projections of any two of the first electrode, the piezoelectric layer and the second electrode on the substrate are at least partially overlapped; the outline of the orthographic projection of the first electrode on the substrate, the outline of the orthographic projection of the piezoelectric layer on the substrate and the outline of the orthographic projection of the second electrode on the substrate do not comprise parallel line segments.

Description

Technical Field

[0001] The present disclosure belongs to the field of communication technology, and particularly relates to a bulk acoustic wave resonator and an electronic device. Background Art

[0002] In the field of mobile communications, because the total available frequency range is relatively narrow and there are many frequency bands used for mobile communications, the spacing between adjacent frequency bands is very narrow (approximately a few MHz to tens of MHz), and the bandwidth of a single frequency band is very narrow (tens of MHz), the filters used in mobile phones must have the performance characteristics of small in-band ripple, large out-of-band suppression, and good rectangularity. Conventional microstrip filters are large in size, have insufficient out-of-band suppression, and poor rectangularity, making them unsuitable. Cavity filters are also large in size and cannot be matched. Dielectric filters have large in-band insertion loss and poor rectangularity, making them unsuitable. IPD filters have large in-band ripple and poor rectangularity, making them unsuitable.

[0003] BAW resonators, the basic structural unit of BAW filters, currently use a silicon wafer as the substrate material, with a sandwich structure consisting of a first electrode, a piezoelectric material, and a second electrode from bottom to top. The operating principle is that a radio frequency signal is transmitted through the electrode at one end of the resonator. It is then converted into a mechanical vibration acoustic wave signal through the inverse piezoelectric effect at the interface between the piezoelectric material and the metal electrode. This acoustic wave signal forms a resonant standing wave with a certain frequency in the sandwich structure of the first electrode, piezoelectric material, and second electrode. The frequency of the radio frequency signal is equal to the resonant frequency of the resonator. The acoustic wave signal is then transmitted to the electrode at the other end of the resonator, where it is converted into a radio frequency signal through the piezoelectric effect at the interface between the metal electrode and the piezoelectric material. A resonator has a fixed resonant frequency. When the RF signal's frequency equals the resonator's resonant frequency, the conversion efficiency from RF signal to acoustic signal to RF signal is high. When the RF signal's frequency differs from the resonator's resonant frequency, the conversion efficiency is very low, and the vast majority of RF signals cannot be transmitted through the resonator. In other words, the resonator functions as a filter, filtering the RF signal. To reduce insertion loss during the filtering process, the acoustic signal needs to be confined as much as possible within the piezoelectric material to prevent it from spreading outward. Therefore, acoustic reflectors are typically constructed on the upper and lower surfaces of the resonator. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art and provides a bulk acoustic wave resonator and an electronic device.

[0005] In a first aspect, the present disclosure provides a bulk acoustic wave resonator, comprising a substrate, and a first electrode, a piezoelectric layer, and a second electrode sequentially arranged on the substrate; the orthographic projections of any two of the first electrode, the piezoelectric layer, and the second electrode on the substrate at least partially overlap; wherein,

[0006] The outlines of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate do not include mutually parallel line segments.

[0007] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate is a first figure, and the first figure only includes straight line segments, and the straight line segments are not parallel to each other.

[0008] In some embodiments, the first graphic further includes a connecting segment, and the connecting segment is used to connect any two adjacent straight line segments;

[0009] The connecting segment is a straight line, and the angle formed between the connecting segment and the straight line segment connected to it is an obtuse angle.

[0010] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate is a first figure, and the first figure includes a straight line segment and an arc segment; the arc segment protrudes in a direction away from the straight line segment.

[0011] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate is a first figure, and the first figure includes a straight line segment and multiple arc segments;

[0012] Each of the arc segments satisfies one of the following conditions:

[0013] Each of the arc segments protrudes toward a middle area away from the first figure;

[0014] Each of the arc segments protrudes toward a middle area close to the first figure;

[0015] Some of the arc segments bulge toward a middle area away from the first figure, and some of the arc segments bulge toward a middle area close to the first figure.

[0016] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate is a first figure, and the first figure includes a plurality of straight line segments and an arc segment;

[0017] The straight line segments are not parallel to each other; the arc segments protrude toward a middle area away from the first figure, or the arc segments protrude toward a middle area close to the first figure.

[0018] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate is a first figure, and the first figure includes a plurality of straight line segments and a plurality of arc segments;

[0019] The straight line segments are not parallel to each other; and the arc segments meet one of the following conditions:

[0020] Each of the arc segments protrudes toward a middle area away from the first figure;

[0021] Each of the arc segments protrudes toward a middle area close to the first figure;

[0022] Some of the arc segments bulge toward a middle area away from the first figure, and some of the arc segments bulge toward a middle area close to the first figure.

[0023] In some embodiments, the outline of at least one of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate is a first figure, and the first figure only includes arc segments.

[0024] In some embodiments, the first shape is a circle.

[0025] In some embodiments, an induction layer is further included between the first electrode and the piezoelectric layer, and the orthographic projection of the induction layer on the base substrate covers the orthographic projection of the piezoelectric layer on the base substrate.

[0026] In some embodiments, the base substrate has a groove on a side close to the first electrode, and the orthographic projection of the induction layer on the base substrate covers the orthographic projection of the groove on the base substrate.

[0027] In some embodiments, the substrate includes any one of glass, Si, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, and GaO.

[0028] In some embodiments, the first electrode and the second electrode each include any one of Mo, Al, Cu, Co, Ag, Ti, Pt, Ru, W, and Au.

[0029] In some embodiments, the piezoelectric layer includes ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , any one of BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, and PVDF.

[0030] In a second aspect, the present disclosure provides an electronic device comprising the above-mentioned bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of a back-etched bulk acoustic wave resonator;

[0032] Figure 2 Schematic diagram of the structure of a thin film bulk acoustic resonator;

[0033] Figure 3 It is a structural schematic diagram of a solid-state assembled bulk acoustic wave resonator;

[0034] Figure 4 A schematic structural diagram of a bulk acoustic wave resonator provided by the present disclosure;

[0035] Figure 5 A schematic diagram of a first type of graphic provided by the present disclosure;

[0036] Figure 6 A schematic diagram of another type of first graphic provided by the present disclosure;

[0037] Figure 7 A schematic diagram of another type of first graphic provided by the present disclosure;

[0038] Figure 8 A schematic diagram of another type of first graphic provided by the present disclosure;

[0039] Figure 9 A schematic diagram of another type of first graphic provided by the present disclosure;

[0040] Figure 10 A schematic diagram of another type of first graphic provided by the present disclosure;

[0041] Figure 11A schematic diagram of another type of first graphic provided by the present disclosure;

[0042] Figure 12 A schematic structural diagram of another bulk acoustic wave resonator provided by the present disclosure;

[0043] Figure 13 A flow chart of a method for preparing a bulk acoustic wave resonator provided in the present disclosure. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0045] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "an" or "the" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0046] like Figure 1-3 As shown, in order to reduce the insertion loss during the filtering process, the BAW resonator needs to confine the acoustic signal as much as possible within the piezoelectric layer 13 between the first electrode 11 and the second electrode 12 to prevent the acoustic signal from spreading outward. Therefore, acoustic reflectors are usually constructed on the upper and lower surfaces of the resonator. The upper surface generally uses a low acoustic impedance air medium as a reflector. According to the different construction of the acoustic reflector on the lower surface, BAW resonators are divided into three major categories: back-etched BAW resonators, such as Figure 1 As shown; film bulk acoustic resonator (abbreviated as FBAR), thin film bulk acoustic resonator, such as Figure 2 As shown; solid mounted resonator (abbreviated as SMR), solid-state assembly type bulk acoustic wave resonator, such as Figure 3As shown in the figure, the FBAR uses a groove 15 etched into the substrate 10 below the first electrode to serve as an air gap. The SMR uses an acoustic reflector structure 18 formed by alternating layers of high acoustic impedance layers 181 and low acoustic impedance layers 182 below the first electrode 11. The back-etch type uses a first cavity 101 formed in the substrate 10 below the first electrode 11 to serve as an air layer by deeply etching the back of the silicon substrate to form a cavity.

[0047] The acoustic reflector structure 15 is composed of alternating high-acoustic impedance layers 151 and low-acoustic impedance layers 152. The acoustic impedance of a material is equal to the speed of sound waves propagating through it multiplied by its density. Theoretically, when the thickness of the high-acoustic impedance layer 151 is equal to one-quarter of the wavelength of sound waves at the resonant frequency of the bulk acoustic wave resonator propagating through the high-acoustic impedance layer 151, and the thickness of the low-acoustic impedance layer 152 is equal to one-quarter of the wavelength of sound waves at the resonant frequency of the bulk acoustic wave resonator propagating through the low-acoustic impedance layer 152, the alternating arrangement of high and low-acoustic impedance layers 152 (high / low / high / low, etc., or low / high / low / high, etc.) acts like an acoustic reflector, reflecting back sound signals leaking from above. The high-acoustic impedance layers 151 and low-acoustic impedance layers 152 form a reflector structure 15. Generally, three to four sets are required to achieve optimal acoustic reflection. Of course, more sets are better, but this increases the cost. Materials for high acoustic impedance layer 151 may include W, Ir, Pt, Ru, Au, Mo, Ta, Ti, Cu, Ni, Zn, Al, Al2O3, and Ag. Common low acoustic impedance materials may include SiO2, Si3N4, Mg, rubber, nylon, polyimide, polyethylene, polystyrene, and Teflon. Depending on the resonant frequency and the acoustic velocity of different materials, the thickness of a single high acoustic impedance layer 151 and a single low acoustic impedance layer 152 range from 1 nm to 10 μm. It should be noted that in this disclosure, the FBAR thin-film bulk acoustic resonator is used as an example.

[0048] Current BAW resonators are only applicable to the frequency range of 1GHz-6GHz and cannot cope with frequency bands greater than 6GHz. To address this problem, in the embodiment of the present disclosure, the sound velocity of the material of the piezoelectric layer in the BAW resonator is not less than 18,000m / s. For example, the material of the piezoelectric layer is boron nitride, specifically hexagonal boron nitride material. This material not only has piezoelectric properties, but also has a sound velocity of up to 18,600m / s, which is 64% higher than the sound velocity of the material of the conventional piezoelectric layer. Therefore, the BAW resonator in the embodiment of the present disclosure can be applied to a higher frequency range. The BAW resonator made of hexagonal boron nitride material has the advantages of low cost, high resonant frequency, small size, low insertion loss, small in-band ripple, large out-of-band suppression, and good rectangularity. It is widely used in various frequency bands greater than 1GHz in the field of mobile communications, especially the frequency bands greater than 6GHz to 30GHz, and can effectively filter out low-frequency interference signals and their higher harmonics in the terrestrial environment. The signal quality of mobile communications is improved.

[0049] When a bulk acoustic wave resonator is operating normally, in addition to the sound waves propagating longitudinally, there are generally several acoustic modes propagating laterally along the resonator structure, namely parasitic modes. These modes propagate within and between the resonators, resulting in energy loss in the resonator and reducing the quality factor of the resonator. The planar shape of each resonator in the currently commercially available bulk acoustic wave filters is an irregular pentagon, in which any two sides of the resonator are not parallel. The advantage of this is that the sound waves propagating laterally cannot form standing waves because they cannot propagate back and forth between the two parallel sides, that is, they cannot be enhanced (if standing waves are formed, the standing wave mode will take away a large part of the energy from the longitudinal propagation mode). However, the irregular pentagon shape is not flexible enough in actual layout design. In the process of arranging the resonators into a filter, it is impossible to maximize the effective use of the chip area to fill the irregular pentagon, resulting in a large amount of invalid space in the layout design, increasing the size of the filter.

[0050] Based on the above problems, in the first aspect, the present disclosure provides a bulk acoustic wave resonator, referring to Figure 4The bulk acoustic wave resonator specifically includes a substrate 10, and a first electrode 11, a piezoelectric layer 13, and a second electrode 12 sequentially arranged on the substrate 10, and the orthographic projections of any of the first electrode 11, the piezoelectric layer 13, and the second electrode 12 on the substrate 10 at least partially overlap to ensure the normal propagation of electromagnetic waves. In particular, the orthographic projection of at least one of the first electrode 11 on the substrate 10, the orthographic projection of the piezoelectric layer 13 on the substrate 10, and the orthographic projection of the second electrode 12 on the substrate 10 are projected on the substrate 10 as a first figure. The first figure does not include parallel line segments to each other, so as to avoid the formation of standing waves and the waste of energy. Specifically, the first figure can be a regular figure such as a triangle, a quadrilateral, a circle, a fan, or an irregular figure such as a crescent, a parabola, etc., and can be designed as needed.

[0051] It should be noted that in the BAW resonator disclosed herein, the shapes of the various layers can be identical, for example, the first conductive layer, piezoelectric layer 13, and second electrode layer 12 are all circular. Alternatively, the shapes of the various layers can be different, for example, the first electrode layer 11 is triangular, the piezoelectric layer 13 is fan-shaped, and the second electrode layer 12 is circular. The specific shapes can be designed as needed, thereby significantly improving the space utilization of the layout.

[0052] In some examples, the first figure only includes straight line segments, each straight line segment is connected end to end and no two straight line segments are parallel. For example, the first figure can be a triangle, such as Figure 5 Optionally, in this embodiment, the inner angle of the first figure can be a chamfer. Specifically, the first figure further includes a connecting segment for connecting two adjacent straight line segments. The angle between the straight line segment and the adjacent straight line segment is an obtuse angle, that is, a chamfer is formed. Figure 5 As shown in b, two corners of the irregular trapezoid are chamfered and two corners are sharp corners. The setting of the chamfers can improve the durability and safety of the device. This disclosure only exemplifies the schematic diagram of the first figure being an irregular trapezoid. It should be understood that the first figure can also include polygons such as irregular pentagons, irregular hexagons, irregular heptagons, irregular octagons, irregular nonagons, and irregular decagons. Increasing the number of sides of the polygon can improve the flexibility of the design and adapt to more different scene requirements.

[0053] In some examples, the first graphic includes both straight line segments and arc segments, which can be divided into the following four cases. In the first case, the first graphic includes a straight line segment and an arc segment. Figure 6a. A straight line segment and an arc segment are connected end to end to form the first figure. The arc segment is convex in the direction away from the straight line segment. In this case, the first figure is an irregular semi-ellipse. In particular, if the arc segment is a symmetrical arc, that is, a complete parabola, the first figure is a parabola. Figure 6 b.

[0054] In the second case, the first figure includes a straight line segment and multiple arc segments, wherein the multiple arc segments can all protrude toward the middle area away from the first figure. It should be noted that the first figure is a closed figure and therefore has a relative inner side and outer side. The middle area of ​​the first figure refers to the inner area of ​​the first figure. In this embodiment, each arc segment can all protrude toward the middle area away from the first figure. Figure 7 a, Figure 7 The shape of a is half a cloud shape. Figure 7 a only shows three arc segments as an example, and of course it can also include two or more arc segments; each arc segment can also protrude toward the middle area close to the first figure, referring to Figure 7 b, Figure 7 The first figure of b can define more sharp corners, so that electromagnetic fields of different intensities can be designed. Figure 7 b only shows two arc segments as an example, and the first figure may also include more arc segments; each arc segment may include both an arc segment protruding toward the middle area away from the first figure and an arc segment protruding toward the middle area close to the first figure, Figure 7 c, Figure 7 The first figure in c includes two arc segments facing away from the central area of ​​the first figure, and includes one arc segment facing away from the central area of ​​the first figure.

[0055] In the third case, the first figure includes multiple straight line segments and an arc segment, wherein the straight lines are not parallel to each other, and the arc segment can bulge toward the middle area away from the first figure or toward the middle area close to the first figure. For example, when the first figure includes two straight line segments of equal length and an arc segment bulging toward the middle area, the first figure can be a sector, referring to Figure 8 a; The first graphic may also include Figure 8 The figure shown in b includes three straight line segments connected in sequence and an arc segment, and the arc segment protrudes toward the central area close to the first figure.

[0056] In the fourth case, the first figure includes multiple straight line segments and multiple arc segments, wherein the straight line segments are not parallel, and the arc segments can be all convex segments, or all concave segments, or a combination of convex segments and concave segments. For example, the shape of the first figure can be a figure composed of three straight line segments and three convex segments arranged at intervals and connected end to end, that is, a triangle with three rounded corners, such as Figure 9 a; and illustratively, referring to Figure 9 b. The first shape may be an ice cream shape, which includes two straight line segments and five arc segments connected in sequence, which may increase the aesthetics; and for example, referring to Figure 8 b, the first figure may include two straight line segments and two arc segments convex toward and away from the middle area of ​​the first figure, the straight line segments and the arc segments are arranged at intervals; another exemplary embodiment, referring to Figure 8 c. The first figure includes three straight line segments and two arc segments protruding toward the middle area of ​​the first figure. Figure 8 The first figure of c defines two recessed portions at the upper left and upper right corners, which facilitates combination and connection with other circular components.

[0057] In some examples, the first graphic includes only arc segments. For example, the first graphic may include only one arc segment, such as a circle ( Figure 10 a) Oval ( Figure 10 b) Teardrop shape ( Figure 10 c), etc., such a shape can increase the durability of the device; illustratively, the first shape can also include two or more arc segments, such as a heart shape ( Figure 11 a) Crescent-shaped ( Figure 11 b) Flower shape ( Figure 11 c) wavy ( Figure 11 d), etc., can be designed differently as needed, among which, Figure 11 The heart shape shown in a includes two arc segments that are symmetrically arranged and both protrude away from the central area of ​​the first figure. Figure 11 The crescent shape shown in b includes an arc segment convex toward and away from the central area of ​​the first figure and an arc segment convex toward and away from the central area of ​​the first figure, and the curvature of the former is greater than the curvature of the latter. Figure 11 The flower-shaped pattern of c includes five "petals", each of which protrudes in a direction away from the central area of ​​the first graphic. Of course, the flower-shaped pattern can also include other numbers of petals, such as four or six. Figure 11The wavy shape shown in d includes ten arc segments connected end to end, some of which protrude away from the center of the first figure, while others protrude toward the center of the first figure. The description of this disclosure only exemplifies the shape of the first figure. It should be understood that other shapes that meet the above conditions also fall within the scope of protection of this disclosure.

[0058] Optionally, the BAW resonator of the present disclosure further includes an induction layer 14 disposed between the first electrode 11 and the piezoelectric layer 13, such as Figure 12 As shown, the orthographic projection of the induction layer 14 on the base substrate 10 covers the orthographic projection of the piezoelectric layer 13 on the base substrate 10. Furthermore, the base substrate 10 has a groove 15 on the side close to the first electrode 11, and the orthographic projection of the induction layer 14 on the base substrate 10 covers the orthographic projection of the groove 15 on the base substrate 10. In this case, the RF signal is automatically Figure 9 The sound is transmitted from the upper left corner of the BAW resonator. It is then converted into an acoustic wave signal through the inverse piezoelectric effect at the interface between second electrode 12 and piezoelectric layer 13. This acoustic wave propagates longitudinally through piezoelectric layer 13. Upon reaching the interface between first electrode 11, inductive layer 14, and piezoelectric layer 13, it is converted into an RF signal through the piezoelectric effect. This signal is then transmitted upward through the conductive via in the lower right corner of first electrode 11, ultimately exiting at the upper right corner of second electrode 12. The groove 15 below the BAW resonator and the air layer above it act as acoustic reflectors, confining the acoustic signal within the resonator structure rather than dissipating it, thereby reducing resonator losses.

[0059] Among them, the material constituting the base substrate 10 is preferably glass, and materials such as Si, sapphire, SiC, GaAs, GaN, InP, BN, and ZnO can also be selected. The thickness of the base substrate 10 ranges from 0.1 μm to 10 mm.

[0060] The material constituting the piezoelectric layer 13 is preferably hBN, and cBN and wBN can also be selected. Of course, the material of the piezoelectric layer 1312 can also be selected from AlN, ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO14, BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF, etc. The piezoelectric layer 1312 in this embodiment can be one of the piezoelectric materials mentioned above, or it can be a stack of the above piezoelectric materials. The thickness of the piezoelectric layer 1312 ranges from 10 nm to 100 μm.

[0061] The preferred material for the first electrode 11 is Cu, as its lattice size closely matches that of hexagonal boron nitride (hBN). Other materials include Al, Mo, Co, Ag, Ti, Pt, Ru, W, and Au, as well as alloys of these metals. The thickness of the first electrode 11 ranges from 1 nm to 10 μm.

[0062] The induction layer 14 is located between the first electrode 11 and the piezoelectric layer 13. Its function is to assist the growth of the piezoelectric layer 13 and improve the material quality of the piezoelectric layer 13 (for example, the half-width of the rocking curve of the X-ray diffraction is less than 1.5°). In this embodiment, the induction layer 14 is preferably graphene, which can be single-layer graphene, double-layer graphene, or multi-layer graphene. That is, the thickness ranges from 0.1 nm to 100 nm.

[0063] The material constituting the second electrode 12 may include Cu, Al, Mo, Co, Ag, Ti, Pt, Ru, W, Au, or an alloy of the above metals. The thickness of the second electrode 12 ranges from 1 nm to 10 μm.

[0064] In some examples, the BAW resonator further includes an encapsulation layer 16 disposed on a side of the second electrode 12 facing away from the substrate 10 , which is used to protect the device and isolate it from water and oxygen corrosion.

[0065] In a second aspect, the present disclosure provides a method for preparing the bulk acoustic wave resonator, as shown in the flow chart. Figure 13 As shown, the specific steps include:

[0066] S1. Provide a base substrate 10.

[0067] In this step, the base substrate 10 may be cleaned and then dried by an air knife.

[0068] S2 . Form the groove 15 on the base substrate 10 .

[0069] In some examples, step S2 may include first depositing a mask material on the base substrate 10 (optional mask materials include photoresist, inorganic mask, or metal mask), followed by glue coating (or spraying), pre-baking, exposure, development, post-baking, and finally etching to form a mask. The etching process may be dry etching or wet etching, preferably wet etching. Next, the base substrate 10 is etched to form the groove 15. The etching process may be wet etching or dry etching, preferably wet etching. For example, if the base substrate 10 is a glass substrate, the etching solution used at this time is a mixed solution of 3% to 7% hydrofluoric acid, 20% to 30% ammonium fluoride, and deionized water.

[0070] S3. Form a first electrode 11 on the base substrate 10 after completing the above steps.

[0071] In some examples, step S3 may include preparing the first conductive film using a deposition process, preferably DC magnetron sputtering (RF magnetron sputtering is also acceptable), and may also include pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, or copper foil attachment. Glue is then applied (or sprayed) onto the first conductive film, followed by pre-baking, exposure, development, and post-baking. Finally, etching is performed, preferably using a wet etching process, but a dry etching process may also be used, to form a pattern including the first electrode 11.

[0072] S4. Forming an induction layer 14 on the base substrate 10 after completing the above steps.

[0073] In some examples, the material of the induction layer 14 is preferably a graphene film, which can be a single layer, a double layer or a multilayer. If the material of the first electrode 11 formed in step S3 is Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Au metal or Co-Ni, Au-Ni alloy, taking the induction layer 14 as an example of graphene material, it can be directly grown by magnetron sputtering chemical vapor deposition or microwave plasma chemical vapor deposition. The specific steps are to introduce a mixed gas of methane, nitrogen and argon, heat the substrate to 600-800°C, and react to form a graphene film. If the first electrode 11 formed in step S3 is not the above metal or alloy, the induction layer can be prepared in two steps: (a) The first step is the preparation of the graphene film. A metal foil, such as Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Au, or a Co-Ni or Au-Ni alloy, is placed in a reaction chamber and grown via magnetron sputtering chemical vapor deposition (CVD) or microwave plasma CVD. Specifically, a mixture of methane, nitrogen, and argon is introduced, and the substrate is heated to 600-800°C to form a graphene film. (b) The second step is to transfer the prepared graphene film from the metal foil to the first electrode 11. First, polymethyl methacrylate (PMMA) is sprayed or spin-coated on the metal foil / graphene in an inert gas atmosphere and heated to 120°C for 3-5 minutes for drying and curing. The metal foil / graphene / PMMA is then placed in a corresponding solution to dissolve the metal. For copper foil, a 20% FeCl3 solution is used. The remaining graphene / PMMA floats on the surface of the solution. The graphene / PMMA is taken out and washed in deionized water, then transferred to the first electrode 11 and dried by irradiation with an infrared lamp for 10 to 15 minutes. Finally, the PMMA is dissolved with an organic solvent such as acetone, and the induction layer 1418 is prepared.

[0074] S5. Forming a piezoelectric layer 1312 on the first base substrate 1010 after completing the above steps.

[0075] In some examples, taking hBN as the material of the piezoelectric layer 13, in step S5, the piezoelectric material can be first oriented and grown, preferably by radio frequency magnetron sputtering, with hBN as the target material. By controlling the Ar and N2 gas pressures and temperatures during the deposition process, as well as the post-annealing time and temperature, an oriented hBN film rich in nitrogen vacancies is formed (whose piezoelectric properties are much better than BN without nitrogen vacancies). The preferred growth orientation is (100), and can also be (001) and (111). The film deposition method can also be selected from pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), plasma enhanced chemical vapor deposition (PECVD), etc.

[0076] S6. Forming the second electrode 12 on the base substrate 10 after the above steps.

[0077] In some examples, step S6 may include first depositing a second conductive film, preferably by DC magnetron sputtering (RF magnetron sputtering is also acceptable), and alternative methods include pulsed laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, and electron beam evaporation. The second conductive film is then sequentially coated with a resin (or sprayed), pre-baked, exposed, developed, and post-baked, and finally etched to form the second electrode 12, preferably by a wet etching process, but also by a dry etching process.

[0078] The preparation of the BAW resonator in the above embodiment is now completed. The BAW resonator disclosed in the present invention has a flexible design space, can avoid the formation of standing waves, and has good energy utilization.

[0079] S7 . Forming a packaging layer 16 on the base substrate 10 after completing the above steps.

[0080] In some examples, the material of the encapsulation layer 16 may be an organic material polyimide. In this case, step S7 may include applying the organic material liquid, specifically by spin coating, spraying, inkjet printing, transfer printing, etc., and then heating and curing to form a pattern of the encapsulation layer 16.

[0081] In a third aspect, the present disclosure provides an electronic device comprising the bulk acoustic wave resonator according to any one of the above embodiments.

[0082] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A bulk acoustic wave resonator, comprising a substrate, and a first electrode, a piezoelectric layer, and a second electrode sequentially disposed on the substrate; the orthographic projections of any two of the first electrode, the piezoelectric layer, and the second electrode on the substrate at least partially overlap; wherein: The outlines of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate do not include mutually parallel line segments.

2. The bulk acoustic wave resonator according to claim 1, wherein The outline of at least one of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate is a first figure, and the first figure only includes straight line segments, and the straight line segments are not parallel to each other.

3. The bulk acoustic wave resonator according to claim 2, wherein The first graph further includes a connecting segment, and the connecting segment is used to connect any two adjacent straight line segments; The connecting segment is a straight line, and the angle formed between the connecting segment and the straight line segment connected to it is an obtuse angle.

4. The BAW resonator according to claim 1, wherein The outline of at least one of the orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate is a first figure, and the first figure includes a straight line segment and an arc segment; the arc segment protrudes in a direction away from the straight line segment.

5. The BAW resonator according to claim 1, wherein The orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate, the outline of at least one of the three is a first figure, and the first figure includes a straight line segment and multiple arc segments; Each of the arc segments satisfies one of the following conditions: Each of the arc segments protrudes toward a middle area away from the first figure; Each of the arc segments protrudes toward a middle area close to the first figure; Some of the arc segments bulge toward a middle area away from the first figure, and some of the arc segments bulge toward a middle area close to the first figure.

6. The BAW resonator according to claim 1, wherein The orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate, the outline of at least one of the three is a first figure, and the first figure includes a plurality of straight line segments and an arc segment; The straight line segments are not parallel to each other; the arc segments protrude toward a middle area away from the first figure, or the arc segments protrude toward a middle area close to the first figure.

7. The BAW resonator according to claim 1, wherein The orthographic projection of the first electrode on the substrate, the orthographic projection of the piezoelectric layer on the substrate, and the orthographic projection of the second electrode on the substrate, the outline of at least one of the three is a first figure, and the first figure includes a plurality of straight line segments and a plurality of arc segments; The straight line segments are not parallel to each other; and the arc segments meet one of the following conditions: Each of the arc segments protrudes toward a middle area away from the first figure; Each of the arc segments protrudes toward a middle area close to the first figure; Some of the arc segments bulge toward a middle area away from the first figure, and some of the arc segments bulge toward a middle area close to the first figure.

8. The BAW resonator according to claim 1, wherein The outline of at least one of the orthographic projection of the first electrode on the base substrate, the orthographic projection of the piezoelectric layer on the base substrate, and the orthographic projection of the second electrode on the base substrate is a first figure, and the first figure only includes arc segments.

9. The BAW resonator according to claim 8, wherein The first figure is a circle.

10. The BAW resonator according to claim 1, wherein An induction layer is further included between the first electrode and the piezoelectric layer, and the orthographic projection of the induction layer on the base substrate covers the orthographic projection of the piezoelectric layer on the base substrate.

11. The BAW resonator according to claim 10, wherein: The base substrate has a groove portion on a side close to the first electrode, and the orthographic projection of the induction layer on the base substrate covers the orthographic projection of the groove portion on the base substrate.

12. The BAW resonator according to claim 1, wherein The substrate includes any one of glass, Si, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, and GaO.

13. The BAW resonator according to claim 1, wherein The first electrode and the second electrode each include any one of Mo, Al, Cu, Co, Ag, Ti, Pt, Ru, W, and Au.

14. The BAW resonator according to claim 1, wherein The piezoelectric layer includes ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 , any one of BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, and PVDF.

15. An electronic device comprising the bulk acoustic wave resonator according to any one of claims 1 to 14.

Images