Electrode structure, bulk acoustic wave resonator structure, filter and manufacturing method

Abstract

Provided in the present invention are an electrode structure, a bulk acoustic wave resonator structure, a filter and a manufacturing method. The bulk acoustic wave resonator structure comprises a piezoelectric film layer, a top electrode and a bottom electrode; the top electrode is located above the piezoelectric film layer; the top electrode comprises a plurality of top electrode metal layers, the acoustic impedance of a top electrode metal layer in contact with the piezoelectric film layer being greater than the acoustic impedance of top electrode metal layers which are not in contact with the piezoelectric film layer; the bottom electrode is located below the piezoelectric film layer; the bottom electrode comprises a plurality of bottom electrode metal layers, the number of the top electrode metal layers and the number of the bottom electrode metal layers being the same, and the material stacking sequence of the top electrode metal layers being mirror-symmetrical to that of the bottom electrode metal layers. In the present invention, the electrodes each have multiple metal layers, and the acoustic impedance of the metal layer in contact with piezoelectric film layers is greater than the acoustic impedance of the metal layers which are not in contact with the piezoelectric film layer, such that the sound intensity transmission coefficient can be reduced to force more acoustic energy to enter the piezoelectric film layer, thus improving the effective electromechanical coupling coefficient, and improving the performance of bulk acoustic wave resonators.

Description

Electrode structure, bulk acoustic wave resonator structure, filter and manufacturing method Technical Field

[0001] The present invention belongs to the technical field of microelectronic devices and relates to an electrode structure, a bulk acoustic wave resonator structure, a filter and a manufacturing method. Background Art

[0002] Currently, wireless data transmission requires RF filters operating at frequencies of 5 GHz or higher. The filters used in 5G communications are primarily bulk acoustic wave (BAW) and surface acoustic wave (SAW) filters. BAW devices have extremely high quality factors (Q) (above 4000) and operate in the 100 MHz to 20 GHz frequency range. They offer advantages such as high operating frequency, low insertion loss, high frequency selectivity, high power handling, and strong anti-static capabilities, making them the optimal solution for future RF front-ends.

[0003] In the traditional single metal electrode resonator structure, the device performance depends on the acoustic and electrical properties of a single metal material. Since the ideal electrode material should have high acoustic impedance, low resistivity, low density and other characteristics, the optimal values ​​of the above characteristics do not belong to a certain metal material at the same time. Currently, Mo, the most commonly used metal material as an electrode, has only relatively moderate acoustic impedance, resistivity and density, and its effective electromechanical coupling coefficient is relatively reduced, which limits its application in 5G high-frequency broadband filters. The existing technology mainly involves Sc doping in the piezoelectric film layer AlN to obtain Sc x Al (1-x) N(x>0), so that the piezoelectric coefficient e of the piezoelectric film layer 33 and relative dielectric constant ε r Improve the stiffness coefficient c 33 Reduce, thereby increasing the piezoelectric strain constant d of the piezoelectric film layer 33 and the piezoelectric coupling coefficient k t 2 , thereby improving the effective electromechanical coupling coefficient of the device, but element doping reduces the Young's modulus of the piezoelectric film, reduces the longitudinal sound velocity and temperature stability of the piezoelectric film, increases the dielectric loss, and because the doping elements such as Sc are expensive rare earth elements, the production cost is increased, and the segregation of the elements will also reduce the uniformity of the piezoelectric film.

[0004] Therefore, providing a new electrode structure, bulk acoustic wave resonator structure, filter and manufacturing method is a technical problem that needs to be solved urgently by those skilled in the art.

[0005] Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide an electrode structure, a bulk acoustic wave resonator structure, a filter and a manufacturing method, which are used to solve the problems of small effective electromechanical coupling coefficient and low performance of a single-metal electrode resonator in the prior art.

[0007] To achieve the above object and other related objects, the present invention provides an electrode structure, including a top electrode and a bottom electrode which are separately arranged:

[0008] The top electrode includes multiple top electrode metal layers stacked from bottom to top;

[0009] The bottom electrode includes multiple bottom electrode metal layers stacked from top to bottom;

[0010] The number of layers of the top electrode metal layer is the same as that of the bottom electrode metal layer, and the material layer stacking order of the top electrode metal layer and the bottom electrode metal layer is arranged in a mirror symmetry.

[0011] The present invention provides a bulk acoustic wave resonator structure, including:

[0012] A piezoelectric thin film layer;

[0013] A top electrode, located above the piezoelectric thin film layer, the top electrode includes multiple top electrode metal layers stacked from bottom to top, and the acoustic impedance of the top electrode metal layer in contact with the piezoelectric thin film layer is greater than that of the top electrode metal layer not in contact with the piezoelectric thin film layer;

[0014] A bottom electrode, located below the piezoelectric thin film layer, the bottom electrode includes multiple bottom electrode metal layers stacked from top to bottom, wherein the number of layers of the top electrode metal layer is the same as that of the bottom electrode metal layer, and the material layer stacking order of the top electrode metal layer and the bottom electrode metal layer is arranged in a mirror symmetry.

[0015] Optionally, the material of the top electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, Hf, and the thickness of the top electrode does not exceed 0.3μm.

[0016] Optionally, the top electrode includes a tungsten metal layer and a molybdenum metal layer stacked from bottom to top, and the bottom electrode includes a tungsten metal layer and a molybdenum metal layer stacked from top to bottom.

[0017] Optionally, the material of the piezoelectric thin film layer includes Al x Ga (1-x) N(0<x<1), Sc x Al (1-x) N(0<x<1), AlN, PZT, LiNbO3, ZnO, PbTiO3, etc. at least one.

[0018] Optionally, a substrate is further included, and the substrate is located below the bottom electrode.

[0019] Optionally, the substrate is provided with a groove opening upward, and the bottom electrode and the groove together form a cavity.

[0020] Optionally, a Bragg reflection layer is further included, and the Bragg reflection layer is located between the substrate and the bottom electrode.

[0021] The present invention further provides a filter, comprising any one of the above-mentioned bulk acoustic wave resonator structures.

[0022] The present invention also provides a method for manufacturing a bulk acoustic wave resonator, comprising the following steps:

[0023] providing a first substrate, and forming a piezoelectric thin film layer on the first substrate;

[0024] forming a first electrode on the piezoelectric film layer, wherein the first electrode comprises a plurality of stacked metal layers, wherein the acoustic impedance of the metal layer in contact with the piezoelectric film layer is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer;

[0025] forming a support layer covering the first electrode on the piezoelectric film layer and the first electrode, and patterning the support layer to form an opening exposing the first electrode;

[0026] Providing a second substrate, bonding the side of the support layer away from the piezoelectric film layer to the second substrate, and removing the first substrate;

[0027] forming a second electrode on a side of the piezoelectric film layer away from the second substrate, the second electrode comprising a plurality of stacked metal layers, wherein the second electrode has the same number of layers as the first electrode, and the material stacking sequence of the second electrode and the first electrode is mirror-symmetrically arranged;

[0028] A first electrode pad and a second electrode pad are formed on a side of the piezoelectric film layer away from the second substrate. The first electrode pad penetrates the piezoelectric film layer and is electrically connected to the first electrode. The second electrode pad is electrically connected to the second electrode.

[0029] Optionally, the material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the first electrode does not exceed 0.3 μm.

[0030] Optionally, the first electrode includes a stacked tungsten metal layer and a molybdenum metal layer, and the tungsten metal layer is in contact with the piezoelectric film layer.

[0031] Optionally, the material of the piezoelectric thin film layer includes Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), AlN, PZT, LiNbO3, ZnO, PbTiO3, or at least one of them.

[0032] The present invention also provides a method for manufacturing a bulk acoustic wave resonator, including the following steps:

[0033] Provide a first substrate, and form a piezoelectric thin film layer on the first substrate;

[0034] Form a first electrode on the piezoelectric thin film layer. The first electrode includes multiple stacked metal layers, and the acoustic impedance of the metal layer in the first electrode that contacts the piezoelectric thin film layer is greater than the acoustic impedance of the metal layer that does not contact the piezoelectric thin film layer;

[0035] Form a barrier layer covering the first electrode on the piezoelectric thin film layer, and form a sacrificial layer on the barrier layer. Horizontally, the sacrificial layer overlaps with the first electrode;

[0036] Form a support layer on the barrier layer, and the support layer covers the sacrificial layer;

[0037] Provide a second substrate, bond the side of the support layer away from the piezoelectric thin film layer to the second substrate, and remove the first substrate;

[0038] Form a second electrode on the side of the piezoelectric thin film layer away from the second substrate. The second electrode includes multiple stacked metal layers. Among them, the number of layers of the second electrode is the same as that of the first electrode, and the material layer stacking order of the second electrode and the first electrode is set in a mirror symmetry;

[0039] Form a first electrode pad and a second electrode pad on the side of the piezoelectric thin film layer away from the second substrate. The first electrode pad penetrates the piezoelectric thin film layer and is electrically connected to the first electrode, and the second electrode pad is electrically connected to the second electrode;

[0040] Remove the sacrificial layer to form a cavity.

[0041] Optionally, the material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, Hf, and the thickness of the first electrode does not exceed 0.3 μm.

[0042] Optionally, the first electrode includes a stacked tungsten metal layer and molybdenum metal layer, and the tungsten metal layer contacts the piezoelectric thin film layer.

[0043] Optionally, the material of the piezoelectric thin film layer includes Al x Ga (1-x) N(0 < x < 1), Sc x Al (1-x) N(0 < x < 1), AlN, PZT, LiNbO3, ZnO, PbTiO3, or at least one of them.

[0044] The present invention also provides a method for manufacturing a bulk acoustic wave resonator, including the following steps:

[0045] Provide a first substrate, and form a piezoelectric thin film layer on the first substrate;

[0046] Form a first electrode on the piezoelectric thin film layer. The first electrode includes a plurality of stacked metal layers, and the acoustic impedance of the metal layer in the first electrode that contacts the piezoelectric thin film layer is greater than the acoustic impedance of the metal layer that does not contact the piezoelectric thin film layer;

[0047] Form a Bragg reflector layer covering the first electrode on the piezoelectric thin film layer and the first electrode;

[0048] Form a dielectric layer on the Bragg reflector layer and planarize the dielectric layer;

[0049] Provide a second substrate, bond the side of the dielectric layer away from the piezoelectric thin film layer to the second substrate, and remove the first substrate;

[0050] Form a second electrode on the side of the piezoelectric thin film layer away from the second substrate. The second electrode includes a plurality of stacked metal layers. Among them, the number of layers of the second electrode is the same as that of the first electrode, and the material layer stacking order of the second electrode and the first electrode is set in a mirror-symmetrical manner;

[0051] Form a first electrode pad and a second electrode pad on the side of the piezoelectric thin film layer away from the second substrate. The first electrode pad penetrates through the piezoelectric thin film layer and is electrically connected to the first electrode, and the second electrode pad is electrically connected to the second electrode.

[0052] Optionally, the material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, Hf, and the thickness of the first electrode does not exceed 0.3 μm.

[0053] Optionally, the first electrode includes a stacked tungsten metal layer and molybdenum metal layer, and the tungsten metal layer contacts the piezoelectric thin film layer.

[0054] Optionally, the material of the piezoelectric thin film layer includes Al x Ga (1-x) N(0 < x < 1), Scx Al (1-x) At least one of N(0 < x < 1), AlN, PZT, LiNbO3, ZnO, and PbTiO3.

[0055] Optionally, the Bragg reflection layer includes alternately stacked low acoustic impedance material layers and high acoustic impedance material layers. The material of the low acoustic impedance material layer includes one or more of AlN, Si3N4, or SiO2, and the material of the high acoustic impedance material layer includes one or more of W, Mo, Pt, Au, Ni, or Ir.

[0056] As described above, in the electrode structure, bulk acoustic wave resonator structure, filter, and manufacturing method of the present invention, the electrode is composed of a composite of multiple metal layers. The acoustic impedance of the metal layer in contact with the piezoelectric thin film layer is greater than that of the metal layer not in contact with the piezoelectric thin film layer, that is, the acoustic impedance ratio with the piezoelectric thin film layer is relatively large, which can reduce the sound intensity transmission coefficient, force more acoustic energy to enter the piezoelectric thin film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and enhancing the performance of the bulk acoustic wave resonator. Description of the Drawings

[0057] FIG. 1 shows a schematic diagram of the bulk acoustic wave resonator structure of Embodiment 1 of the present invention.

[0058] FIG. 2 shows a schematic diagram of the bulk acoustic wave resonator structure of Comparative Example 1.

[0059] FIG. 3 shows a schematic diagram of the bulk acoustic wave resonator structure of Embodiment 1 of the present invention provided with two top electrode metal layers and two bottom electrode metal layers.

[0060] FIG. 4 shows an impedance spectrum diagram obtained by simulating the bulk acoustic wave resonator structure of Embodiment 1 of the present invention.

[0061] FIG. 5 shows an impedance spectrum diagram obtained by simulating the bulk acoustic wave resonator structure of Comparative Example 1.

[0062] FIG. 6 shows a schematic diagram of sound wave propagation in three dielectric layers.

[0063] FIG. 7 shows a diagram of the change in the transmission coefficient obtained by defining the impedance of the two side dielectric layers in FIG. 6 and changing the impedance of the middle layer.

[0064] FIG. 8 shows a schematic diagram of the bulk acoustic wave resonator structure of Comparative Example 2.

[0065] FIG. 9 shows a comparison diagram of the impedance spectrum diagram of Embodiment 1 of the present invention and the impedance spectrum diagram of Comparative Example 2.

[0066] FIG. 10 shows a schematic diagram of forming a piezoelectric thin film layer on the first substrate in Embodiment 2 of the present invention.

[0067] FIG. 11 is a schematic diagram showing a process of forming a first electrode on a piezoelectric film layer according to a second embodiment of the present invention.

[0068] FIG. 12 is a schematic diagram showing a process of forming a support layer on a piezoelectric film layer according to a second embodiment of the present invention.

[0069] FIG. 13 is a schematic diagram showing the formation of openings in a support layer according to a second embodiment of the present invention.

[0070] FIG14 is a schematic diagram showing bonding of the support layer to the second substrate in the second embodiment of the present invention.

[0071] FIG. 15 is a schematic diagram showing the removal of the first substrate in the second embodiment of the present invention.

[0072] FIG. 16 is a schematic diagram showing a second electrode formed on a side of the piezoelectric film layer away from the second substrate in the second embodiment of the present invention.

[0073] FIG. 17 is a schematic diagram showing the formation of the first electrode through-hole in the second embodiment of the present invention.

[0074] FIG. 18 is a schematic diagram showing the formation of a first electrode pad and a second electrode pad in the second embodiment of the present invention.

[0075] FIG19 is a schematic diagram showing the formation of a barrier layer and a sacrificial layer in the third embodiment of the present invention.

[0076] FIG20 is a schematic diagram showing the formation of a support layer in the third embodiment of the present invention.

[0077] FIG21 is a schematic diagram showing bonding of the support layer to the second substrate in the third embodiment of the present invention.

[0078] FIG22 is a schematic diagram showing the removal of the first substrate in the third embodiment of the present invention.

[0079] FIG23 is a schematic diagram showing a second electrode formed on a side of the piezoelectric film layer away from the second substrate in a third embodiment of the present invention.

[0080] FIG24 is a schematic diagram showing the formation of a first electrode pad and a second electrode pad in the third embodiment of the present invention.

[0081] FIG. 25 is a schematic diagram showing the removal of the sacrificial layer in the third embodiment of the present invention.

[0082] FIG26 is a schematic diagram showing the formation of a support layer in the fourth embodiment of the present invention.

[0083] FIG. 27 is a schematic diagram showing the formation of a Bragg reflective layer in a fourth embodiment of the present invention.

[0084] FIG28 is a schematic diagram showing the formation of a dielectric layer in the fourth embodiment of the present invention.

[0085] FIG29 is a schematic diagram showing bonding the dielectric layer to the second substrate in the fourth embodiment of the present invention.

[0086] FIG30 is a schematic diagram showing the fourth embodiment of the present invention in which the first substrate is removed and a second electrode is formed on a side of the piezoelectric film layer away from the second substrate.

[0087] FIG31 is a schematic diagram showing the formation of a first electrode pad and a second electrode pad in a fourth embodiment of the present invention.

[0088] Component Reference Numerals 1 Piezoelectric film layer 2 Top electrode 20 First top electrode metal layer 21 Second top electrode metal layer 22 Nth top electrode metal layer 200 Tungsten metal layer 201 Molybdenum metal layer 3 Bottom electrode 30 First bottom electrode metal layer 31 Second bottom electrode metal layer 32 Nth bottom electrode metal layer 300 Tungsten metal layer 301 Molybdenum metal layer 4 Substrate 5 Cavity 6 First substrate 7 Piezoelectric film layer 8 First electrode 800 Tungsten metal layer 801 Molybdenum metal layer 802 First electrode through hole 803 First electrode pad 9 Support layer 900 Opening 10 Second substrate 11 Cavity 12 Second electrode 1200 Tungsten metal layer 1201 Molybdenum metal layer 1202 Second electrode pad 13 Barrier layer 14 Sacrificial layer 15 Bragg reflection layer 1500 High acoustic impedance material layer 1501 Low acoustic impedance material layer 16 Dielectric layer DETAILED DESCRIPTION

[0089] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0090] Please refer to Figures 1 to 31. It should be noted that the figures provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Although the figures only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation, the form, quantity, and proportion of each component in actual implementation may be changed arbitrarily, and the component layout may also be more complex.

[0091] Example 1

[0092] This embodiment provides an electrode structure, which includes a top electrode and a bottom electrode that are separately arranged, wherein the top electrode includes multiple top electrode metal layers stacked from bottom to top, and the bottom electrode includes multiple bottom electrode metal layers stacked from top to bottom, the top electrode metal layers and the bottom electrode metal layers have the same number of layers, and the material stacking sequence of the top electrode metal layers and the bottom electrode metal layers is mirror-symmetrically arranged.

[0093] This embodiment also provides a bulk acoustic wave resonator structure, which includes the above-mentioned electrode structure. Please refer to Figure 1. The bulk acoustic wave resonator structure includes a piezoelectric film layer 1, a top electrode 2 and a bottom electrode 3. The top electrode 2 is located above the piezoelectric film layer 1, and the top electrode 2 includes a plurality of top electrode metal layers stacked from bottom to top, and the acoustic impedance of the top electrode metal layer in contact with the piezoelectric film layer 1 is greater than the acoustic impedance of the top electrode metal layer not in contact with the piezoelectric film layer 1; the bottom electrode 3 is located below the piezoelectric film layer 1, and the bottom electrode 3 includes a plurality of bottom electrode metal layers stacked from top to bottom, wherein the top electrode metal layer and the bottom electrode metal layer have the same number of layers, and the material stacking sequence of the top electrode metal layer and the bottom electrode metal layer is arranged in a mirror-symmetrical manner.

[0094] As an example, the top electrode 2 includes a first top electrode metal layer 20, a second top electrode metal layer 21, ···, an Nth top electrode metal layer 22 stacked from bottom to top, where N is an integer greater than or equal to 2; the bottom electrode 3 includes a first bottom electrode metal layer 30, a second bottom electrode metal layer 31, ···, an Nth bottom electrode metal layer 32 stacked from top to bottom. Among them, the first top electrode metal layer 20 and the first bottom electrode metal layer 30 have the same material and thickness, the second top electrode metal layer 21 and the second bottom electrode metal layer 31 have the same material and thickness, ···, the Nth top electrode metal layer 22 and the Nth bottom electrode metal layer 32 have the same material and thickness, that is, the materials, thicknesses, and stacking orders of the top electrode 1 and the bottom electrode 2 are mirror-symmetric with respect to the piezoelectric thin film layer 1.

[0095] As an example, the material of the top electrode 2 includes at least two of Au (gold), Ag (silver), Ru (ruthenium), W (tungsten), Mo (molybdenum), Ir (iridium), Al (aluminum), Pt (platinum), Nb (niobium), Hf (hafnium), and can also be other suitable materials.

[0096] As an example, the thickness of the top electrode 2 does not exceed 0.3 μm. For example, it can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, etc. When the performance of the bulk acoustic wave resonator structure is satisfied, its thickness can be selected according to the actual situation.

[0097] As an example, the material of the piezoelectric thin film layer 1 includes Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), AlN, PZT, LiNbO3, ZnO, PbTiO3, etc. At least one of them, and the thickness of the piezoelectric thin film layer 1 does not exceed 2 μm. Preferably, the piezoelectric thin film layer 1 adopts a composite layer. By compounding piezoelectric film layers of various different materials, the piezoelectric performance of the piezoelectric thin film layer 1 can be improved, and then the effective electromechanical coupling coefficient and the quality factor Q value of the bulk acoustic wave resonator structure can be improved. Among them, the thickness of each piezoelectric film layer in the composite layer is not less than 0.1 μm.

[0098] As an example, compared with a single metal electrode resonator structure (comparative example 1), as shown in Figure 2, the top electrode 2 adopts a single molybdenum metal layer, the bottom electrode 3 adopts a single molybdenum metal layer, and the acoustic reflection interface includes the interface between the piezoelectric film layer and the electrode and the interface between the electrode and the air. In this application, the top electrode 2 and the bottom electrode 3 adopt a multi-layer metal film stacking method, and the acoustic reflection interface includes the interface between the piezoelectric film layer and the electrode, the interface between the electrode and the air, and the interface between adjacent metal film layers in the electrode. By regulating the acoustic impedance of different metal film layers, the distribution of acoustic energy in the resonance area changes, thereby effectively regulating the electromechanical coupling efficiency.

[0099] Specifically, as shown in FIG3 , taking the two-layer top electrode metal layer as an example, the piezoelectric film layer 1 is an AlN layer, the top electrode 2 includes a tungsten metal layer 200 and a molybdenum metal layer 201 stacked from bottom to top, and the bottom electrode 3 includes a tungsten metal layer 300 and a molybdenum metal layer 301 stacked from top to bottom. The thickness of the AlN layer is set to 300 nm, the thickness of the tungsten metal layer 200 and the molybdenum metal layer 201 are set to 60 nm and 61.1 nm respectively, and the thickness of the tungsten metal layer 300 and the molybdenum metal layer 301 are set to 60 nm and 61.1 nm respectively. The impedance spectrum obtained by simulation is shown in FIG4 , and the series resonance frequency f s is 5.001GHZ, the parallel resonant frequency f p 5.175 GHZ; Taking the single-layer metal electrode in the prior art as the comparative example 1 (the structure shown in FIG2 ), the piezoelectric film layer 1 is set to be a 300 nm thick AlN layer, the top electrode 2 is set to be a 160.4 nm thick molybdenum metal layer, and the bottom electrode 3 is set to be a 160.4 nm thick molybdenum metal layer. The impedance spectrum obtained by simulation is shown in FIG5 , and the series resonant frequency f s is 5.001GHZ, the parallel resonant frequency f p The frequency is 5.154 GHz. According to the calculation formula of the effective electromechanical coupling coefficient:

[0100] It can be obtained that the effective electromechanical coupling coefficient of the bulk acoustic wave resonator of the present invention is The effective electromechanical coupling coefficient of the bulk acoustic wave resonator in Example 1 is 8.02%. It is 7.1%, that is, inserting W between AlN and Mo can increase the electromechanical coupling and improve the performance.

[0101] Specifically, as shown in FIG6 , a plane wave propagation diagram is shown in which a plane wave is incident on three dielectric layers. In medium 1, a plane wave is incident on the interface. According to the generalized ray method and impedance transfer, the transmission coefficient of the sound intensity can be obtained as:

[0102] Where z1, z2, and z3 are the characteristic impedances (acoustic impedances) of medium 1, medium 2, and medium 3, respectively. k2 = w / c2 is the waveband of the intermediate layer (medium 2), and d is the thickness of the intermediate layer (medium 2). It can be seen that the transmission coefficient is related to the frequency and thickness of the intermediate layer. The thickness of the intermediate layer is normalized to the wavelength, k2d / 2π = d / λ2. Considering the case where the characteristic impedances of medium 1 and medium 3 differ greatly:

[0103] (1) When z2 = z3 or z2 = z1, which is equivalent to d = 0 (single interface), the transmission coefficient of sound intensity is:

[0104] That is, the transmission coefficient does not change with thickness and frequency;

[0105] (2) When z2 is between z1 and z3, the intermediate layer increases the transmission coefficient as long as the thickness is not equal to an integer multiple of half the wavelength. When , the transmission coefficient is maximum;

[0106] (3) When z2 is not between z1 and z3, the intermediate layer reduces the transmission coefficient as long as the thickness is not equal to an integer multiple of half the wavelength.

[0107] Specifically, z1=1, z3=10, and z2=0.2, 0.5, 1, 2, 3.16, 5, 10, 20, and 50 are taken, respectively. The obtained sound intensity transmission coefficient variation diagram is shown in FIG7. When z2 is 1 or 10, that is, z2=z3 or z2=z1, the transmission coefficient does not change; when z2 is 2, 3.16 or 5, that is, z2 is between z1 and z3, the transmission coefficient increases; when z2 is 0.2, 0.5, 20 or 50, that is, z2 is not between z1 and z3, the transmission coefficient decreases. In the present invention, z AlN =33.7, z w =105.6, z Mo =66.42, that is, in the top electrode 2, a tungsten metal layer 200 is provided between the piezoelectric film layer 1 and the molybdenum metal layer 201, and in the bottom electrode 3, a tungsten metal layer 300 is provided between the piezoelectric film layer 1 and the molybdenum metal layer 301. Since the characteristic impedance of W is not between AlN and Mo, as long as the thickness of the tungsten metal layer 200 and the tungsten metal layer 300 is not equal to an integer multiple of half the wavelength, the transmission coefficient is reduced. For the piezoelectric resonator, the sound intensity partially resides outside the piezoelectric material in the form of a stress field, thereby reducing the electromechanical coupling. Therefore, on the basis of the Mo single electrode, W is inserted between AlN and Mo to reduce the sound intensity transmission coefficient, forcing more sound energy to enter the piezoelectric film layer, thereby increasing the acoustic energy in the piezoelectric material, thereby increasing the electromechanical coupling and improving the working passband width of the filter.

[0108] As an example, the positions of the molybdenum metal layer and the tungsten metal layer in the electrode are set oppositely as comparative example 2, as shown in FIG8 , the piezoelectric film layer 1 is a single-layer AlN layer with a thickness of 300 nm, the top electrode 1 is set to include a molybdenum metal layer 201 and a tungsten metal layer 200 stacked from bottom to top, and the thickness of the molybdenum metal layer 201 and the tungsten metal layer 200 are 60 nm respectively, and the bottom electrode 3 is set to include a molybdenum metal layer 301 and a tungsten metal layer 300 stacked from top to bottom, and the thickness of the molybdenum metal layer 301 and the tungsten metal layer 300 are 60 nm respectively; the structure of the present invention is shown in FIG3 , the piezoelectric film layer 1 is set to an AlN layer with a thickness of 300 nm, the thickness of the tungsten metal layer 200 and the molybdenum metal layer 201 are set to be 60 nm respectively, and the thickness of the tungsten metal layer 300 and the molybdenum metal layer 301 is 60 nm. The impedance spectrum obtained by simulation is shown in FIG9 , wherein the series resonance frequency f s is 5.017 GHZ, the parallel resonant frequency f p is 5.191 GHZ, the effective electromechanical coupling coefficient is 7.99%, and the series resonant frequency f in Example 2 is s is 4.788GHZ, the parallel resonant frequency f p It is 4.938 GHZ, and the effective electromechanical coupling coefficient is 7.27%, indicating that the metal electrodes have the same thickness and the stacking order is opposite, the resonant frequency and the electromechanical coupling coefficient change, and the device structure performance is better when the high acoustic impedance material W is close to the piezoelectric film layer 1.

[0109] As an example, in the comparative example 1 structure (as shown in FIG2 ), the thickness of the top electrode 2 (molybdenum metal layer) and the bottom electrode 3 (molybdenum metal layer) are set to 120 nm respectively, and the series resonance frequency f is obtained. s is 4.788GHZ, the parallel resonant frequency f p is 4.939GHZ, the effective electromechanical coupling coefficient is 7.27%, and the f s 、f p and As shown in Table 1 below, it can be seen from Table 1 that inserting W between AlN and Mo is beneficial to improving the effective electromechanical coupling coefficient. If Mo is inserted between AlN and W, it is not conducive to improving the effective electromechanical coupling coefficient, further verifying that the device structure performance of the high acoustic impedance material close to the piezoelectric thin film layer is better.

[0110] Table 1:

[0111] As an example, a substrate 4 is also included, which is located below the bottom electrode 3. The substrate 4 is provided with a groove opening upward, and the bottom electrode 3 and the groove together form a cavity 5. The existence of the cavity 5 makes the lower surface of the bottom electrode 3 exposed in the cavity 5, that is, the lower area of ​​the effective working area of ​​the bulk acoustic wave resonator structure is exposed to the cavity 5, which reduces the dissipation of the acoustic wave energy when the bulk acoustic wave resonator is working, and further improves the key indicators of the effective electromechanical coupling coefficient and quality factor Q value of the bulk acoustic wave resonator structure, thereby improving the working passband width or out-of-band suppression capability of the filter.

[0112] As an example, the substrate 4 includes a Si substrate, a SiC substrate, a Ge substrate or a sapphire substrate. The resonant frequency of the bulk acoustic wave resonator structure is determined by the distance between the bottom surface of the cavity 5 and the top electrode 2. While meeting the required resonant frequency during the operation of the bulk acoustic wave resonator, the depth and opening size of the substrate groove can be selected according to actual conditions without specific restrictions.

[0113] As an example, in another example, no groove is provided in the substrate 4, and a Bragg reflection layer is provided between the substrate 4 and the bottom electrode 3, and the Bragg reflection layer includes alternatingly stacked high acoustic impedance material layers and bottom acoustic impedance material layers. By designing the alternatingly stacked high acoustic impedance material layers and low acoustic impedance material layers, the mechanical sound waves generated by the piezoelectric film layer 1 can be reflected back to the piezoelectric film layer 1, thereby reducing the electromechanical loss and improving the effective electromechanical coupling coefficient and the quality factor Q value; the material of the high acoustic impedance material layer includes one or more of W, Mo, Pt, Au, Ni or Ir, and the material of the low acoustic impedance material layer includes one or more of AlN, Si3N4 or SiO2, wherein the thickness of each layer in the Bragg reflection layer is 1 / 4 or 3 / 4 of the wavelength of the sound wave corresponding to the resonant frequency of the resonator.

[0114] In addition, this embodiment further provides a filter, which includes the above-mentioned bulk acoustic wave resonator structure.

[0115] As described above, in the electrode structure, bulk acoustic wave resonator structure and filter of this embodiment, the top electrode and the bottom electrode are both composed of a multi-layer metal layer composite. The acoustic impedance of the metal layer in contact with the piezoelectric film layer is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer, that is, the acoustic impedance of the metal layer is larger than that of the piezoelectric film layer, which can reduce the sound intensity transmission coefficient and force more sound energy to enter the piezoelectric film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator.

[0116] Example 2

[0117] This embodiment provides a method for manufacturing a bulk acoustic wave resonator. The method for manufacturing the bulk acoustic wave resonator in this embodiment will be described in detail below with reference to specific drawings.

[0118] First, please refer to FIG. 10 and perform step S1: Provide a first substrate 6, and form a piezoelectric thin film layer 7 on the first substrate 6.

[0119] As an example, the material of the first substrate 6 includes but is not limited to materials such as single crystal silicon, SOI substrate, silicon carbide, sapphire, or gallium nitride, etc.; in this embodiment, the first substrate 6 is preferably a single crystal silicon substrate.

[0120] As an example, the piezoelectric thin film layer 7 is formed on the first substrate 6 by physical vapor deposition, chemical vapor deposition, spin coating or other suitable methods. The material of the piezoelectric thin film layer 7 includes AlN, Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), PZT, LiNbO3, ZnO, PbTiO3, etc., the single layer thickness is not less than 0.1 μm, and the total thickness does not exceed 2 μm; in this embodiment, the piezoelectric thin film layer 7 is preferably a single crystal AlN layer.

[0121] Next, please refer to FIG. 11 and perform step S2: Form a first electrode 8 on the piezoelectric thin film layer 7. The first electrode 8 includes a stacked multi-layer metal layer, and the acoustic impedance of the metal layer in the first electrode 8 that contacts the piezoelectric thin film layer 7 is greater than the acoustic impedance of the metal layer that does not contact the piezoelectric thin film layer 7.

[0122] As an example, a stacked metal material layer is formed on the piezoelectric thin film layer 7 by chemical vapor deposition or physical vapor deposition and patterned to obtain the first electrode 8. The number of metal layers in the first electrode 8 is not less than two. The first electrode 8 includes at least two of Au (gold), Ag (silver), Ru (ruthenium), W (tungsten), Mo (molybdenum), Ir (iridium), Al (aluminum), Pt (platinum), Nb (niobium), Hf (hafnium), etc., and can also be other suitable materials; the thickness of the first electrode 8 does not exceed 0.3 μm. For example, it can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, etc. When the performance of the bulk acoustic wave resonator is satisfied, its thickness can be selected according to the actual situation. Among them, the thickness of each metal layer in the first electrode 8 does not exceed 100 nm.

[0123] Specifically, in this embodiment, the first electrode 8 includes a stacked tungsten metal layer 800 and molybdenum metal layer 801, where the tungsten metal layer 800 contacts the piezoelectric thin film layer 7.

[0124] Next, referring to FIG. 12 and FIG. 13 , step S3 is performed: a support layer 9 covering the first electrode 8 is formed on the piezoelectric film layer 7 and the first electrode 8 , and the support layer 9 is patterned to form an opening 900 exposing the first electrode 8 .

[0125] As an example, as shown in FIG12 , the support layer 9 is formed by a deposition method. The material of the support layer 9 includes but is not limited to SiO2, Si, AlN or SiC. After the support layer 9 is formed, the surface of the support layer 9 is flattened by chemical mechanical polishing or deposition of a bonding layer.

[0126] As an example, as shown in FIG. 13 , the support layer 9 is patterned by etching or other suitable methods to form the opening 900 .

[0127] Next, referring to FIG. 14 and FIG. 15 , step S4 is performed: providing a second substrate 10 , bonding the side of the support layer 9 away from the piezoelectric film layer 7 to the second substrate 10 , and removing the first substrate 6 .

[0128] As an example, the material of the second substrate 10 includes but is not limited to single crystal silicon, SOI substrate, silicon carbide, sapphire or gallium nitride; preferably, in order to improve the bonding efficiency, a bonding layer can be deposited on the bonding surface of the second substrate 10, and the bonding layer is composed of materials including but not limited to Si, SiN, PSG or SiO2.

[0129] As an example, the method of removing the first substrate 6 includes but is not limited to ion implantation stripping, wet etching, dry etching, etc. The selected method cannot cause loss to the lattice of the piezoelectric film layer 7, or can be repaired by high-temperature annealing after doping damage occurs.

[0130] As an example, the second substrate 10 and the opening 900 together form a cavity 11 .

[0131] Next, please refer to Figure 16 and execute step S5: form a second electrode 12 on the side of the piezoelectric film layer 7 away from the second substrate 10, and the second electrode 12 includes a stacked multi-layer metal layer, wherein the second electrode 12 has the same number of layers as the first electrode 8, and the material stacking sequence of the second electrode 12 and the first electrode 8 is arranged in a mirror-symmetrical manner.

[0132] As an example, the acoustic impedance of the metal layer in the second electrode 12 that is in contact with the piezoelectric film layer 7 is greater than the acoustic impedance of the metal layer that is not in contact with the piezoelectric film layer 7. The second electrode 12 includes at least two of Au (gold), Ag (silver), Ru (ruthenium), W (tungsten), Mo (molybdenum), Ir (iridium), Al (aluminum), Pt (platinum), Nb (niobium), and Hf (hafnium), and may also be other suitable materials; the thickness of the second electrode 7 does not exceed 0.3μm, for example, it can be 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, etc., and its thickness can be selected according to actual conditions while meeting the performance of the bulk acoustic wave resonator.

[0133] Specifically, the material, thickness and stacking order of the second electrode 12 and the first electrode 8 are mirror-symmetrical about the piezoelectric film layer 7. In this embodiment, the second electrode 12 includes a stacked tungsten metal layer 1200 and a molybdenum metal layer 1201, wherein the tungsten metal layer 1200 is in contact with the piezoelectric film layer 7.

[0134] Next, please refer to Figures 17 to 18 and execute step S6: form a first electrode pad 803 and a second electrode pad 1202 on the side of the piezoelectric film layer 7 away from the second substrate 10, the first electrode pad 803 passes through the piezoelectric film layer 7 and is electrically connected to the first electrode 8, and the second electrode pad 1202 is electrically connected to the second electrode 12.

[0135] As an example, as shown in Figure 17, before forming the first electrode pad 803 and the second electrode pad 1202, a step of forming a first electrode through-hole 802 in the piezoelectric film layer 7 is also included. The first electrode through-hole 802 is used for the first electrode pad 803 to pass through the piezoelectric film layer 7 and electrically connect to the first electrode 8. The method of forming the first electrode through-hole 802 includes but is not limited to dry or wet etching.

[0136] As an example, as shown in Figure 18, the process of forming the first electrode pad 803 and the second electrode pad 1202 includes a thin film deposition and patterning process. The first electrode pad 803 and the second electrode pad 1202 should be composed of materials with high adhesion, high conductivity and oxidation resistance. One or more combinations of metals or metalloids including but not limited to Ti, Al, Au, Cu or TiN can be used, preferably a combination of Ti and Au.

[0137] As shown above, the method for manufacturing the bulk acoustic wave resonator of this embodiment increases the number of times the electrode metal layer is deposited, so that the acoustic impedance of the metal layer in contact with the piezoelectric film layer in the first electrode and the second electrode is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer, that is, the ratio of the acoustic impedance to the piezoelectric film layer is large, which can reduce the sound intensity transmission coefficient and force more sound energy to enter the piezoelectric film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator, and has the advantages of simple process and reliability.

[0138] Example 3

[0139] This embodiment provides a method for manufacturing a bulk acoustic wave resonator. The method for manufacturing the bulk acoustic wave resonator of this embodiment is described in detail below with reference to specific drawings.

[0140] First, referring to FIG. 10 , step S1 is performed: providing a first substrate 6 , and forming a piezoelectric film layer 7 on the first substrate 6 .

[0141] Next, please refer to Figure 11, and perform step S2: forming a first electrode 8 on the piezoelectric film layer 2, the first electrode 8 includes a stacked multi-layer metal layer, and the acoustic impedance of the metal layer in the first electrode 8 that is in contact with the piezoelectric film layer 7 is greater than the acoustic impedance of the metal layer that is not in contact with the piezoelectric film layer 7.

[0142] As an example, regarding the material of the first substrate 6, the material and thickness of the piezoelectric film layer 7, the material, thickness, deposition method, etc. of the first electrode 8, please refer to Example 2, which will not be described in detail here.

[0143] Next, referring to FIG. 19 , step S3 is performed: a barrier layer 13 covering the first electrode 8 is formed on the piezoelectric film layer 7 , and a sacrificial layer 14 is formed on the barrier layer 13 . In a horizontal direction, the sacrificial layer 14 overlaps with the first electrode 8 .

[0144] As an example, the barrier layer 13 is formed by a deposition process, and the barrier layer 13 also covers the exposed upper surface of the piezoelectric film layer 7. The material of the barrier layer 13 includes SiN. The barrier layer 13 is used to protect the first electrode 8 and the piezoelectric film layer 7 when the sacrificial layer 14 is subsequently released and removed.

[0145] As an example, the sacrificial layer 14 is formed by a deposition process and an etching process. The material of the sacrificial layer 14 includes Si or SiO 2 , wherein at least a portion of the sacrificial layer 14 is located directly above the first electrode 8 .

[0146] Next, referring to FIG. 20 , step S4 is performed: forming a support layer 9 on the barrier layer 13 , wherein the support layer 9 covers the sacrificial layer 14 .

[0147] As an example, the support layer 9 is made of Si3N4, SiN or amorphous AlN, which has a significant difference in performance from the sacrificial layer 14, so that the sacrificial layer 14 will not react with the support layer 9 when it is subsequently released and removed using a release liquid or a release gas.

[0148] As an example, after the support layer 9 is formed, the method further includes a step of planarizing the upper surface of the support layer 9 by using a chemical mechanical polishing process.

[0149] Next, referring to FIG. 21 and FIG. 22 , step S5 is performed: providing a second substrate 10 , bonding the side of the support layer 9 away from the piezoelectric film layer 7 to the second substrate 10 , and removing the first substrate 6 .

[0150] Next, please refer to Figure 23 and execute step S6: form a second electrode 12 on the side of the piezoelectric film layer 7 away from the second substrate 10, the second electrode 12 includes a stacked multi-layer metal layer, wherein the second electrode 12 has the same number of layers as the first electrode 8, and the material stacking sequence of the second electrode 12 and the first electrode 8 is arranged in a mirror-symmetrical manner.

[0151] Next, please refer to Figure 24 and execute step S7: form a first electrode pad 803 and a second electrode pad 1202 on the side of the piezoelectric film layer 7 away from the second substrate 10, the first electrode pad 803 passes through the piezoelectric film layer 7 and is electrically connected to the first electrode 8, and the second electrode pad 1202 is electrically connected to the second electrode 12.

[0152] As an example, regarding the material of the second substrate 10, the method of removing the first substrate 6, the material and thickness of the second electrode 12, the material and formation method of the first electrode pad 803 and the second electrode pad 1202, etc., please refer to Example 2 and will not be described in detail here.

[0153] Next, referring to FIG. 25 , step S8 is performed: removing the sacrificial layer 14 to form a cavity 11 .

[0154] As an example, before removing the sacrificial layer 14 , a release hole (not shown) is formed in the sacrificial layer 14 , and an etching solution is used to remove the sacrificial layer 14 through the release hole to form the cavity 11 .

[0155] Example 4

[0156] This embodiment provides a method for manufacturing a bulk acoustic wave resonator. The method for manufacturing the bulk acoustic wave resonator of this embodiment is described in detail below with reference to specific drawings.

[0157] First, referring to FIG. 10 , step S1 is performed: providing a first substrate 6 , and forming a piezoelectric film layer 7 on the first substrate 6 .

[0158] Next, please refer to Figure 11, and perform step S2: forming a first electrode 8 on the piezoelectric film layer 7, the first electrode 8 includes a stacked multi-layer metal layer, and the acoustic impedance of the metal layer in the first electrode 8 that is in contact with the piezoelectric film layer 7 is greater than the acoustic impedance of the metal layer that is not in contact with the piezoelectric film layer 7.

[0159] As an example, regarding the material of the first substrate 6, the material and thickness of the piezoelectric film layer 7, the material, thickness, deposition method, etc. of the first electrode 8, please refer to Example 2, which will not be described in detail here.

[0160] Next, referring to FIG. 26 and FIG. 27 , step S3 is performed: a Bragg reflection layer 15 covering the first electrode 8 is formed on the piezoelectric film layer 7 and the first electrode 8 .

[0161] As an example, as shown in FIG26 , before forming the Bragg reflector 15, a step of forming a support layer 9 is also included. After forming the support layer 9, a planarization process is performed to make the surface of the support layer 9 flat, which is conducive to the subsequent formation of the Bragg reflector 15. Specifically, the support layer 9 is made of a low acoustic impedance material, including AlN, Si3N4, or SiO2.

[0162] As an example, before forming the support layer 9 , the method further includes patterning the piezoelectric film layer 7 to form openings in the piezoelectric film layer, so as to release stress in the piezoelectric film layer 7 and prevent the piezoelectric film layer 7 from cracking.

[0163] As an example, as shown in Figure 27, the Bragg reflector 15 is formed on the supporting layer 9, and the Bragg reflector 15 includes alternating high acoustic impedance material layers 1500 and low acoustic impedance material layers 1501. The material of the high acoustic impedance material layer 1500 includes one or more metals such as W, Mo, Pt, Au, Ni, Ir, etc., and the method of forming the high acoustic impedance material layer 1500 includes magnetron sputtering or evaporation, etc., preferably magnetron sputtering; the material of the low acoustic impedance material layer 1501 includes one or more materials such as AlN, Si3N4, SiO2, etc., and the method of forming the low acoustic impedance material layer 1501 includes PECVD, ICPCVD, ALD, MBE, PLD, etc., preferably ICPCVD; the thickness of each layer in the Bragg reflector 15 is 1 / 4 or 3 / 4 of the wavelength of the sound wave corresponding to the resonant frequency of the resonator.

[0164] As an example, the Bragg reflection layer 15 includes alternately stacked high acoustic impedance material layers 1500 and low acoustic impedance material layers 1501. By designing the alternately stacked high acoustic impedance material layers 1500 and low acoustic impedance material layers 1501, the mechanical sound waves generated by the piezoelectric film layer 7 can be reflected back to the piezoelectric film layer 7, thereby reducing the electromechanical loss and further improving the effective electromechanical coupling coefficient and the quality factor Q value.

[0165] Next, referring to FIG. 28 , step S4 is performed: forming a dielectric layer 16 on the Bragg reflective layer 15 and planarizing the dielectric layer 16 .

[0166] As an example, the dielectric layer 16 includes, but is not limited to, materials such as Si, SiN, or PSG. The dielectric layer 16 can protect the outermost high acoustic impedance material layer 1500 from oxidation and can protect the Bragg reflector layer 15 from damage during subsequent bonding with the second substrate 10 (see subsequent FIG. 29 ). In addition, the dielectric layer 16 is planarized to make its surface smooth, thereby improving the subsequent bonding success rate with the second substrate 10.

[0167] Next, referring to FIG. 29 , step S5 is performed: providing a second substrate 10 , bonding the side of the dielectric layer 16 away from the piezoelectric film layer 7 to the second substrate 10 , and removing the first substrate 10 .

[0168] Next, please refer to Figure 30 and execute step S6: form a second electrode 12 on the side of the piezoelectric film layer 7 away from the second substrate 10, the second electrode 12 includes a stacked multi-layer metal layer, wherein the second electrode 12 has the same number of layers as the first electrode 8, and the material stacking sequence of the second electrode 12 and the first electrode 8 is arranged in a mirror-symmetrical manner.

[0169] Next, please refer to Figure 31 and execute step S7: form a first electrode pad 803 and a second electrode pad 1202 on the side of the piezoelectric film layer 7 away from the second substrate 10, the first electrode pad 803 passes through the piezoelectric film layer 7 and is electrically connected to the first electrode 8, and the second electrode pad 1202 is electrically connected to the second electrode 12.

[0170] As an example, regarding the material of the second substrate 10, the method of removing the first substrate 6, the material and thickness of the second electrode 12, the material and formation method of the first electrode pad 803 and the second electrode pad 1202, etc., please refer to Example 2 and will not be described in detail here.

[0171] In summary, the electrode structure, BAW resonator structure, filter, and fabrication method of the present invention utilize multiple metal layers as the composite electrode. The acoustic impedance of the metal layer in contact with the piezoelectric thin film layer is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric thin film layer. This results in a greater acoustic impedance than the piezoelectric thin film layer. This reduces the acoustic transmission coefficient, forcing more acoustic energy into the piezoelectric thin film layer, thereby increasing the acoustic energy within the piezoelectric material, improving the effective electromechanical coupling coefficient, and enhancing BAW resonator performance. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and possesses high industrial value.

[0172] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An electrode structure, characterized in that: Includes top and bottom electrodes that are separately set: The top electrode comprises a plurality of top electrode metal layers stacked from bottom to top; The bottom electrode comprises a plurality of bottom electrode metal layers stacked from top to bottom; The top electrode metal layer and the bottom electrode metal layer have the same number of layers, and the material stacking sequence of the top electrode metal layer and the bottom electrode metal layer is arranged in a mirror-symmetrical manner.

2. A bulk acoustic wave resonator structure, characterized in that: include: Piezoelectric film layer; A top electrode, located above the piezoelectric film layer, the top electrode comprising a plurality of top electrode metal layers stacked from bottom to top, the acoustic impedance of the top electrode metal layer in contact with the piezoelectric film layer being greater than the acoustic impedance of the top electrode metal layer not in contact with the piezoelectric film layer; A bottom electrode is located below the piezoelectric film layer, and the bottom electrode includes a plurality of bottom electrode metal layers stacked from top to bottom, wherein the top electrode metal layer and the bottom electrode metal layer have the same number of layers, and the material stacking sequence of the top electrode metal layer and the bottom electrode metal layer is arranged in a mirror-symmetrical manner.

3. The BAW resonator structure according to claim 2, characterized in that: The material of the top electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the top electrode does not exceed 0.3 μm 4. The BAW resonator structure according to claim 2, characterized in that: The top electrode includes a tungsten metal layer and a molybdenum metal layer stacked from bottom to top, and the bottom electrode includes a tungsten metal layer and a molybdenum metal layer stacked from top to bottom.

5. The BAW resonator structure according to claim 2, characterized in that: The material of the piezoelectric thin film layer includes Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), at least one of AlN, PZT, LiNbO3, ZnO, PbTiO3.

6. The BAW resonator structure according to claim 2, characterized in that: Also included is a substrate, which is located below the bottom electrode.

7. The BAW resonator structure according to claim 6, characterized in that: The substrate is provided with a groove opening upward, and the bottom electrode and the groove are surrounded by a cavity.

8. The BAW resonator structure according to claim 6, characterized in that: The invention also includes a Bragg reflection layer, wherein the Bragg reflection layer is located between the substrate and the bottom electrode.

9. A filter, characterized in that: The filter comprises a BAW resonator structure as claimed in any one of claims 2 to 8.

10. A method for manufacturing a bulk acoustic wave resonator, characterized in that: The following steps are involved: Providing a first substrate, and forming a piezoelectric film layer on the first substrate; forming a first electrode on the piezoelectric film layer, wherein the first electrode comprises a plurality of stacked metal layers, wherein the acoustic impedance of the metal layer in contact with the piezoelectric film layer in the first electrode is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer; forming a support layer covering the first electrode on the piezoelectric film layer and the first electrode, and patterning the support layer to form an opening exposing the first electrode; Providing a second substrate, bonding the side of the support layer away from the piezoelectric film layer to the second substrate, and removing the first substrate; A second electrode is formed on a side of the piezoelectric film layer away from the second substrate, wherein the second electrode comprises a plurality of stacked metal layers, wherein the second electrode has the same number of layers as the first electrode, and the material stacking sequence of the second electrode and the first electrode is arranged in mirror symmetry; A first electrode pad and a second electrode pad are formed on a side of the piezoelectric film layer away from the second substrate, the first electrode pad penetrates the piezoelectric film layer and is electrically connected to the first electrode, and the second electrode pad is electrically connected to the second electrode.

11. The method for manufacturing a bulk acoustic wave resonator according to claim 10, characterized in that: The material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the first electrode does not exceed 0.3 μm.

12. The method for manufacturing a bulk acoustic wave resonator according to claim 10, characterized in that: The first electrode includes a stacked tungsten metal layer and a molybdenum metal layer, and the tungsten metal layer is in contact with the piezoelectric film layer.

13. The method for manufacturing a bulk acoustic wave resonator according to claim 10, characterized in that: The material of the piezoelectric thin film layer includes Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), at least one of AlN, PZT, LiNbO3, ZnO, PbTiO3.

14. A method for manufacturing a bulk acoustic wave resonator, characterized in that: The following steps are involved: Providing a first substrate, and forming a piezoelectric film layer on the first substrate; forming a first electrode on the piezoelectric film layer, wherein the first electrode comprises a plurality of stacked metal layers, wherein the acoustic impedance of the metal layer in contact with the piezoelectric film layer in the first electrode is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer; forming a barrier layer covering the first electrode on the piezoelectric film layer, and forming a sacrificial layer on the barrier layer, wherein the sacrificial layer overlaps the first electrode in a horizontal direction; forming a supporting layer on the barrier layer, wherein the supporting layer covers the sacrificial layer; Providing a second substrate, bonding the side of the support layer away from the piezoelectric film layer to the second substrate, and removing the first substrate; A second electrode is formed on a side of the piezoelectric film layer away from the second substrate, wherein the second electrode comprises a plurality of stacked metal layers, wherein the second electrode has the same number of layers as the first electrode, and the material stacking sequence of the second electrode and the first electrode is arranged in mirror symmetry; forming a first electrode pad and a second electrode pad on a side of the piezoelectric film layer away from the second substrate, wherein the first electrode pad penetrates the piezoelectric film layer and is electrically connected to the first electrode, and the second electrode pad is electrically connected to the second electrode; The sacrificial layer is removed to form a cavity.

15. The method for manufacturing a bulk acoustic wave resonator according to claim 14, characterized in that: The material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the first electrode does not exceed 0.3 μm.

16. The method for manufacturing a bulk acoustic wave resonator according to claim 14, characterized in that: The first electrode includes a stacked tungsten metal layer and a molybdenum metal layer, and the tungsten metal layer is in contact with the piezoelectric film layer.

17. The method for manufacturing a bulk acoustic wave resonator according to claim 14, characterized in that: The material of the piezoelectric thin film layer includes Al x Ga (1-x) N (0 < x < 1), Sc x Al (1-x) N (0 < x < 1), at least one of AlN, PZT, LiNbO3, ZnO, PbTiO3.

18. A method for manufacturing a bulk acoustic wave resonator, characterized in that: The following steps are involved: Providing a first substrate, and forming a piezoelectric film layer on the first substrate; forming a first electrode on the piezoelectric film layer, wherein the first electrode comprises a plurality of stacked metal layers, wherein the acoustic impedance of the metal layer in contact with the piezoelectric film layer in the first electrode is greater than the acoustic impedance of the metal layer not in contact with the piezoelectric film layer; forming a Bragg reflection layer covering the first electrode on the piezoelectric film layer and the first electrode; forming a dielectric layer on the Bragg reflection layer, and planarizing the dielectric layer; Providing a second substrate, bonding the side of the dielectric layer away from the piezoelectric film layer to the second substrate, and removing the first substrate; A second electrode is formed on a side of the piezoelectric film layer away from the second substrate, wherein the second electrode comprises a plurality of stacked metal layers, wherein the second electrode has the same number of layers as the first electrode, and the material stacking sequence of the second electrode and the first electrode is arranged in mirror symmetry; A first electrode pad and a second electrode pad are formed on a side of the piezoelectric film layer away from the second substrate, the first electrode pad penetrates the piezoelectric film layer and is electrically connected to the first electrode, and the second electrode pad is electrically connected to the second electrode.

19. The method for manufacturing a bulk acoustic wave resonator according to claim 18, characterized in that: The material of the first electrode includes at least two of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the first electrode does not exceed 0.3 μm.

20. The method for manufacturing a bulk acoustic wave resonator according to claim 18, characterized in that: The first electrode includes a stacked tungsten metal layer and a molybdenum metal layer, and the tungsten metal layer is in contact with the piezoelectric film layer.

21. The method for manufacturing a bulk acoustic wave resonator according to claim 18, characterized in that: The material of the piezoelectric thin film layer includes Al x Ga (1-x) N(0 < x < 1), Sc x Al (1-x) N(0 < x < 1), at least one of AlN, PZT, LiNbO3, ZnO, PbTiO3.

22. The method for manufacturing a bulk acoustic wave resonator according to claim 18, characterized in that: The Bragg reflection layer includes alternately stacked low acoustic impedance material layers and high acoustic impedance material layers, the material of the low acoustic impedance material layers includes one or more of AlN, Si3N4 or SiO2, and the material of the high acoustic impedance material layers includes one or more of W, Mo, Pt, Au, Ni or Ir.

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