A thin film acoustic wave resonator and a method for manufacturing the same

Abstract

The present invention provides a thin film acoustic wave resonator and a manufacturing method thereof, wherein the thin film acoustic wave resonator comprises: a first substrate containing an acoustic reflection structure; an acoustic wave resonator unit, at least partly located on the acoustic reflection structure, the acoustic wave resonator unit sequentially comprising a stacked first electrode, a piezoelectric layer and a second electrode from bottom to top; a substrate, bonded to the first substrate through an annular cofferdam, and forming a cavity between the substrate and the acoustic wave resonator unit, the cavity comprising at least one acoustic wave resonator unit, at least one of the substrate and the annular cofferdam having the function of shielding electromagnetic waves. The present invention effectively blocks or attenuates the external propagation of electromagnetic waves generated by the resonator unit, thereby suppressing the external electromagnetic radiation of the resonator unit.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device manufacturing, and in particular to a thin film acoustic wave resonator and a manufacturing method thereof. Background Art

[0002] The structure of the film bulk acoustic wave resonator is a layer of piezoelectric film oriented in the c-axis (or z-axis) direction sandwiched between two layers of metal electrodes to form a sandwich structure. An alternating radio frequency voltage is applied between the two electrodes, and the piezoelectricity of the material is used to convert electrical energy into acoustic energy. The sound wave is reflected at the interface between the medium and the air, forming a standing wave oscillation between the two interfaces. At this time, the sound wave loss is minimal and is converted into electrical energy by the inverse piezoelectric effect. The sound wave excited by the film bulk acoustic wave resonator is a bulk acoustic wave, and its resonant frequency depends on the thickness of the piezoelectric film; by cascading several bulk acoustic wave resonators of different frequencies, a radio frequency filter that meets the requirements of wireless communication can be designed.

[0003] The electromagnetic waves generated by the densely arranged resonator units of the existing mass-produced thin-film acoustic resonators during operation will be emitted externally, causing electromagnetic interference and reducing the performance of the equipment. At the same time, the high acoustic impedance material of the Bragg reflection layer structure used in the resonator is tungsten, with an acoustic impedance of 54 to 55 Raman, and the low acoustic impedance material is silicon dioxide, with an acoustic impedance of 8 to 9 Raman. The ratio of high to low acoustic impedance is between 6 and 7, which is a small ratio, and the acoustic wave reflectivity is not high, resulting in a low quality factor.

[0004] Therefore, it is necessary to propose a new thin film acoustic wave resonator and a manufacturing method thereof, which can suppress the external electromagnetic radiation of the resonator unit. Summary of the invention

[0005] The object of the present invention is to provide a thin film acoustic wave resonator and a manufacturing method thereof, which has the function of suppressing the external electromagnetic radiation of the resonator unit.

[0006] In order to achieve the above object, the present invention provides a thin film acoustic wave resonator, comprising:

[0007] A first substrate including a sound reflecting structure;

[0008] an acoustic wave resonator unit, at least partially located on the acoustic reflection structure, the acoustic wave resonator unit comprising, from bottom to top, a stacked first electrode, a piezoelectric layer, and a second electrode;

[0009] The substrate is bonded to the first substrate via an annular cofferdam, and a cavity is formed between the substrate and the acoustic wave resonator unit, wherein the cavity includes at least one acoustic wave resonator unit, and at least one of the substrate and the annular cofferdam has the function of shielding electromagnetic waves.

[0010] The present invention also provides a method for manufacturing a thin film acoustic wave resonator, comprising:

[0011] Providing a first structure, the first structure comprising a first substrate including an acoustic reflection structure, and at least one acoustic wave resonator unit formed on the first substrate, the acoustic wave resonator unit comprising a stacked first electrode, a piezoelectric layer, and a second electrode;

[0012] Providing a substrate, wherein a shielding layer is provided on a first surface of the substrate;

[0013] forming an annular cofferdam on the first structure or on the first surface of the substrate;

[0014] The base plate is bonded to the first substrate via the annular dam, wherein the annular dam surrounds at least one acoustic wave resonator unit and forms a cavity between the base plate and the acoustic wave resonator unit.

[0015] The beneficial effects of the present invention are:

[0016] In the thin film acoustic wave resonator provided by the present invention, at least one of the substrate and the annular cofferdam has the function of shielding electromagnetic waves, effectively blocking or attenuating the external propagation of electromagnetic waves generated by the resonator unit, thereby suppressing the external electromagnetic radiation of the resonator unit.

[0017] Furthermore, utilizing the principle that metal materials can shield electromagnetic waves, the annular cofferdam or substrate is made of metal material or a shielding layer is provided inside, and the shielding layer can be metal.

[0018] Furthermore, by arranging a support column inside the cavity, the structural strength of the resonator is improved.

[0019] Furthermore, polycrystalline carbon is used as the material of the first acoustic impedance layer, and tungsten is used as the material of the second acoustic impedance layer, wherein the acoustic impedance of polycrystalline carbon is 2 to 3 million Rayles, and the high-low acoustic impedance ratio is between 18 and 28. Compared with the acoustic impedance of silicon dioxide, the acoustic impedance of polycrystalline carbon is smaller, which improves the high-low acoustic impedance ratio of the Bragg reflection layer, thereby improving the reflectivity of the sound wave, and further improving the quality factor of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which like reference numerals generally represent like components.

[0021] Figure 1 This is a schematic structural diagram of a thin film acoustic wave resonator according to Example 1 of the present invention.

[0022] Figure 2 Schematic diagram of the structure of the Bragg reflection layer according to Embodiment 1 of the present invention.

[0023] Figure 3 FIG. 4 is a flow chart of a method for manufacturing a thin film acoustic wave resonator according to an embodiment of the present invention.

[0024] Figures 4 to 24 The present invention is a schematic structural diagram corresponding to different steps in a manufacturing process of a thin film acoustic wave resonator manufacturing method according to an embodiment of the present invention.

[0025] Description of reference numerals:

[0026] 100-first substrate; 200-Bragg reflection layer structure; 210-first acoustic impedance layer; 2101-first first acoustic impedance layer; 2102-second first acoustic impedance layer; 2103-third first acoustic impedance layer; 220-second acoustic impedance layer; 2201-first second acoustic impedance layer; 2202-second second acoustic impedance layer; 300-acoustic resonator unit; 310-first electrode; 320-piezoelectric Layer; 320'-second side wall; 330-second electrode; 330'-first side wall; 340-insulating layer; 4000-seed layer; 4001-ring; 4002-first region; 400-cap; 410-annular cofferdam; 420-substrate; 4202-shielding layer; 4203-semiconductor layer; 430-support column; 500-cavity; 600a-first conductive plug; 600b-second conductive plug. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will become clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in a variety of different forms and is not limited to the specific embodiments described herein. The drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0028] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0029] Spatially relative terms such as "under," "below," "below," "under," "above," "above," etc., may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0030] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "a", "an" and " / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "consisting of" and / or "comprising" when used in this specification determine the presence of features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0031] If the method herein includes a series of steps, the order of the steps presented herein is not necessarily the only order in which the steps can be performed, and some steps may be omitted and / or some other steps not described herein may be added to the method. If the components in a certain figure are the same as those in other figures, although these components can be easily identified in all figures, in order to make the description of the figures clearer, this specification will not mark all the same component numbers in each figure.

[0032] Example 1

[0033] This embodiment provides a thin film acoustic wave resonator, wherein the thin film acoustic wave resonator is a solid assembly type resonator. Figure 1 FIG. 1 shows a schematic structural diagram of a thin film acoustic wave resonator of Example 1, Figure 2 FIG. 1 is a schematic diagram showing the structure of the Bragg reflection layer of Example 1. Please refer to FIG. Figure 1 and Figure 2 , the thin film acoustic wave resonator includes:

[0034] A first substrate 100 having an acoustic reflection structure; (in this embodiment, the acoustic reflection structure is a Bragg reflection layer structure, and in other embodiments it may be a cavity structure)

[0035] The acoustic wave resonator unit 300 (shown in the oval dashed box) is at least partially located on the acoustic reflection structure. The acoustic wave resonator unit 300 includes a first electrode 310, a piezoelectric layer 320, and a second electrode 330 from bottom to top;

[0036] The substrate 420 is bonded to the first substrate 100 through the annular cofferdam 410, and a cavity 500 is formed between the substrate 420 and the acoustic wave resonator unit 300, wherein the cavity 500 includes at least one acoustic wave resonator unit 300, and at least one of the substrate 420 and the annular cofferdam 410 has the function of shielding electromagnetic waves.

[0037] The substrate 420 and the annular cofferdam 410 together constitute the cover 400. The effective resonance region of the acoustic wave resonator unit 300 is the region where the first electrode 310, the piezoelectric layer 320, and the second electrode 330 overlap in a direction perpendicular to the first substrate 100. The annular cofferdam 410 is located above the first substrate 100, which does not mean that it needs to be in contact with the first substrate. In this embodiment, reference Figure 1 , the lower end of the annular cofferdam 410 is in contact with the insulating layer 340 .

[0038] In this embodiment, the cavity 500 includes two acoustic wave resonator units 300. The two acoustic wave resonator units 300 are independent of each other, and it can be understood that the first electrodes 310 of the two acoustic wave resonator units 300 are not connected, and the second electrodes 330 corresponding to the two acoustic wave resonator units 300 are not connected. In other embodiments, the number of acoustic wave resonator units 300 in a cavity can be one or more than three. When there are more than two acoustic wave resonator units 300, each different acoustic wave resonator unit 300 is independent of each other or designed in a series or parallel structure.

[0039] At least one of the substrate and the annular cofferdam has the function of shielding electromagnetic waves, which can be achieved in various forms, such as the substrate is made of metal; or the substrate is a composite structure, and the side of the substrate close to the cavity includes a shielding layer; or the side of the annular cofferdam facing the cavity is provided with a shielding layer; or the material of the annular cofferdam is metal, wherein the material of the shielding layer can be metal. The substrate can have the function of shielding electromagnetic waves, the annular cofferdam can have the function of shielding electromagnetic waves, or both the substrate and the annular cofferdam can have the function of shielding electromagnetic waves.

[0040] In this embodiment, a shielding layer 4202 is provided on the side of the substrate 420 facing the cavity 500, and the material of the shielding layer 4202 is metal. The side of the substrate 420 away from the cavity 500 includes a semiconductor layer 4203, and the material of the semiconductor layer 4203 is the same as that of the first substrate 100, and the semiconductor layer 4203 is convenient for subsequent packaging, cutting, molding and other steps. The first substrate 100 can be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), carbon silicon (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, etc., and can also be a ceramic substrate such as aluminum oxide, a quartz or glass substrate, etc.

[0041] In this embodiment, the projection of the annular cofferdam 410 on the first substrate 100 forms a closed ring, such as an irregular polygon, a circle or an ellipse. The substrate 420 is bonded to the annular cofferdam 410, and the annular cofferdam 410 is covered to form a closed cavity 500. Through the shielding effect of the metal inner wall in the cover 400 on electromagnetic waves, the external electromagnetic radiation generated by the resonator unit inside the cavity 500 during operation can be effectively blocked or attenuated, reducing the electromagnetic interference generated by itself. Metal can be regarded as an ideal conductor, which is an equipotential body. The electric field lines cannot penetrate the equipotential body, so electromagnetic waves can be shielded. In other embodiments, under the premise of satisfying the structural firmness, the projection of the annular cofferdam 410 may not be a completely closed figure, and the cavity 500 may not be completely closed. It should be understood that when the projection of the annular cofferdam 410 and the cavity 500 are both closed, it is more conducive to suppressing the external electromagnetic radiation of the resonator unit. In this embodiment, the height of the annular cofferdam 410 is greater than 3 microns, and the thickness of the shielding layer 4202 is between 1 micron and 3 microns.

[0042] In this embodiment, the cavity 500 further includes a support column 430, which is disposed on the first substrate 100 (being disposed on the first substrate should be understood as being located above the first substrate 100, and does not need to be in contact with the first substrate 100, such as in this embodiment, the support column 430 is in contact with the piezoelectric layer 320 between the two acoustic wave resonator units 300), and is located in a region outside the effective resonance region of the acoustic wave resonator unit 300, and the top surface of the support column 430 is in contact with the shielding layer 4202 of the substrate. In this embodiment, the material of the support column 430 is metal. In this embodiment, there are four support columns 430, which are disposed on the first substrate 100, located between two adjacent acoustic wave resonator units 300 in the cavity 500 and outside the effective resonance region, and the top surface of the support column 430 is bonded to the shielding layer 4202 of the substrate, which can strengthen the support of the cavity 500. In other embodiments, the number of support pillars 430 may be one, two, three or more than four, all of which are located outside the effective resonance region of the acoustic wave resonator unit 300, so that the resonator structure is more solid and the substrate 420 is prevented from collapsing. The material of the shielding layer 4202, the annular cofferdam 410, and the support pillars 430 may include at least one of copper, tin or gold, but is not limited to the above materials. The shielding layer 4202 is bonded to the annular cofferdam 410 or the support pillars 430 by metal bonding, relying on metal bonds, thermal diffusion, thermal melting, etc.

[0043] refer to Figure 2The Bragg reflection layer structure 200 includes a first acoustic impedance layer 210 and a second acoustic impedance layer 220 stacked in sequence, the first acoustic impedance layer 210 and the second acoustic impedance layer 220 have different impedances, and the thicknesses of the first acoustic impedance layer 210 and the second acoustic impedance layer 220 are both odd multiples of a quarter of the wavelength of the acoustic wave. In this embodiment, the material of the first acoustic impedance layer 210 is polycrystalline carbon, and the material of the second acoustic impedance layer 220 is tungsten. The impedance of the first acoustic impedance layer 210 is less than the impedance of the second acoustic impedance layer 220, wherein the acoustic impedance of polycrystalline carbon is 2 to 3 mega-Rayles, and the acoustic impedance of tungsten is 54 to 55 mega-Rayles, and the high-low acoustic impedance ratio is between 18 and 28. The acoustic impedance of silicon dioxide, a commonly used low acoustic impedance layer material in mass production, is 8 to 9 mega-Rayles. Compared with silicon dioxide, the acoustic impedance of polycrystalline carbon is smaller, which improves the high-low acoustic impedance ratio of the Bragg reflection layer, thereby improving the reflectivity of the sound wave, and further improving the quality factor of the product. In other embodiments, the material of the first acoustic impedance layer 210 and the material of the second acoustic impedance layer 220 can be other material combinations that meet the acoustic impedance ratio requirements, and the number of layers of the first acoustic impedance layer 210 and the second acoustic impedance layer 220 can also be more than one pair.

[0044] In this embodiment, the first acoustic impedance layer 210 has three layers, the second acoustic impedance layer 220 has two layers, the first first acoustic impedance layer 2101 is formed on the upper surface of the first substrate 100, the first second acoustic impedance layer 2201 is formed on the upper surface of the first acoustic impedance layer 2101, and then the second first acoustic impedance layer 2102, the second second acoustic impedance layer 2202, and the third first acoustic impedance layer 2103 are stacked in sequence. The inclination angle between the side wall of the second acoustic impedance layer 220 and the plane where the second acoustic impedance layer 220 is located is greater than 90 degrees, and the inclined side wall can prevent the leakage of lateral sound waves, reduce the loss of sound waves, and thus improve the quality factor of the product.

[0045] The acoustic wave resonator unit 300 includes a first electrode 310, a piezoelectric layer 320, and a second electrode 330 from bottom to top. In this embodiment, the first electrode 310 is located on the upper surface of the Bragg reflector layer structure 200; the piezoelectric layer 320 is located on the first electrode 310, and the piezoelectric layer 320 includes a second side wall 320', and the inclination angle between the second side wall 320' and the plane where the piezoelectric layer 320 is located is greater than 90 degrees; the second electrode 330 is located on the piezoelectric layer 320, and the second electrode 330 includes a first side wall 330', and the inclination angle between the first side wall 330' and the plane where the second electrode 330 is located is greater than 90 degrees. The first electrode 310, the piezoelectric layer 320, and the second electrode 330 above the Bragg reflector layer structure 200 are provided with an overlapping area in a direction perpendicular to the first substrate 100, and the overlapping area includes an effective resonance area. The effective resonance area is defined by the second side wall 320' and the first side wall 330', and the inclined side wall at the boundary can better prevent the leakage of lateral sound waves, reduce the loss of sound waves, and thus improve the quality factor of the product. In this embodiment, the second side wall 320' and the first side wall 330' have the same inclination angle, and the two are located on the same plane.

[0046] The materials of the first electrode 310 and the second electrode 330 can be any suitable conductive material or semiconductor material known to those skilled in the art, wherein the conductive material can be a metal material with conductive properties, for example, made of one of metals such as molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), or a stack of the above metals, and the semiconductor material can be, for example, Si, Ge, SiGe, SiC, SiGeC, etc. The first electrode 310 and the second electrode 330 can be formed by physical vapor deposition such as magnetron sputtering and evaporation or chemical vapor deposition. The material of the piezoelectric layer 320 can be a piezoelectric material having a wurtzite crystal structure, such as aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz (Quartz), potassium niobate (KNbO3) or lithium tantalate (LiTaO3), and a combination thereof. When the piezoelectric layer 320 includes aluminum nitride (AlN), the piezoelectric layer 320 may also include a rare earth metal, such as at least one of scandium (Sc), erbium (Er), yttrium (Y) and lanthanum (La). In addition, when the piezoelectric layer 320 includes aluminum nitride (AlN), the piezoelectric layer 320 may also include a transition metal, such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn) and hafnium (Hf). The piezoelectric layer 320 may be deposited and formed using any suitable method known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition or atomic layer deposition. Optionally, in this embodiment, the first electrode 310 and the second electrode 330 are made of metal molybdenum (Mo), and the piezoelectric layer 320 is made of aluminum nitride (AlN).

[0047] In this embodiment, an insulating layer 340 is also included, which covers the upper surface of the acoustic wave resonator unit 300. The insulating layer 340 is used to adjust the frequency of each acoustic wave resonator unit. The frequency of the resonator is related to the thickness of the effective resonance area. When making a filter, the thickness of the first electrode 310, the second electrode 320 and the piezoelectric layer 330 of different resonators are the same. In order to make the frequencies of different resonators different, insulating layers 340 of different thicknesses can be set. In this embodiment, the insulating layer 340 can also prevent the cap 400 from connecting to the resonator unit 300 for electrical conduction, and has an insulating function. In this embodiment, the material of the insulating layer 340 includes silicon oxide or silicon nitride. In other embodiments, the material of the insulating layer 340 can also be: ethyl silicate, silicon oxynitride or silicon carbonitride.

[0048] In this embodiment, a first conductive plug 600a and a second conductive plug 600b are also included. The specific structure is as follows:

[0049] A first conductive plug 600a is formed from the side where the first substrate 100 is located, penetrates the first substrate 100, and is electrically connected to the first electrode 310 of the acoustic wave resonator unit; a second conductive plug 600b is formed from the side where the first substrate 100 is located, penetrates the first substrate 100, and is electrically connected to the second electrode 330 of the same acoustic wave resonator unit to electrically lead out the acoustic wave resonator unit.

[0050] In one embodiment, the cavity includes at least two of the acoustic wave resonator units, a wiring layer is provided on the side of the first substrate away from the cover, the first conductive plug and the second conductive plug are connected to the wiring layer, and a plurality of the acoustic wave resonator units are connected in parallel or in series through the wiring layer.

[0051] Example 2

[0052] An embodiment of the present invention provides a method for manufacturing a thin film acoustic wave resonator, please refer to Figure 3 , Figure 3 This is a flow chart of a method for manufacturing a thin film acoustic wave resonator according to an embodiment of the present invention. The manufacturing method includes:

[0053] S01: providing a first structure, wherein the first structure comprises a first substrate including an acoustic reflection structure, and at least one acoustic wave resonator unit formed on the first substrate, wherein the acoustic wave resonator unit comprises a stacked first electrode, a piezoelectric layer, and a second electrode;

[0054] S02: providing a substrate, wherein a shielding layer is provided on a first surface of the substrate;

[0055] S03: forming an annular cofferdam on the first structure or the first surface of the substrate;

[0056] S04: bonding the substrate to the first substrate via the annular dam, wherein the annular dam surrounds at least one acoustic wave resonator unit and forms a cavity between the substrate and the acoustic wave resonator unit.

[0057] Please refer to the following Figures 4 to 24 The manufacturing method of thin film acoustic wave resonator is explained. Figures 4 to 24 1 is a schematic diagram of the structure corresponding to each step of the method for manufacturing a thin film acoustic wave resonator of this embodiment. Steps S0N do not represent the order of precedence.

[0058] refer to Figure 4The acoustic wave resonator of this embodiment is a solid-assembly type resonator, and the acoustic reflection structure is a Bragg reflection layer structure. In other embodiments, the acoustic reflection structure can also be a cavity structure. Forming the first structure includes: providing a first substrate, forming an acoustic wave resonator unit on the first substrate, and the acoustic wave resonator unit includes a stacked first electrode, a piezoelectric layer, and a second electrode. The first substrate 100 is used to carry the Bragg reflection layer structure. The material of the first substrate 100 refers to Example 1 and is not repeated here. In this embodiment, the material of the first substrate 100 is single crystal silicon.

[0059] refer to Figures 5 to 12 A Bragg reflection layer structure 200 is formed on the first substrate 100 , and the Bragg reflection layer structure 200 includes a first acoustic impedance layer 210 and a second acoustic impedance layer 220 stacked sequentially from bottom to top.

[0060] In this embodiment, forming the Bragg reflection layer structure 200 includes: referring to Figure 5 , forming a first acoustic impedance layer 2101, covering the first substrate 100. Figure 6 , forming a first second acoustic impedance layer 2201, covering the first first acoustic impedance layer 2101. Figure 7 After forming the first second acoustic impedance layer, the first second acoustic impedance layer is patterned (this embodiment is described by forming two Bragg reflection layer structures 200) to form two first second acoustic impedance layers 2201 separated from each other, and the angle a between the side wall of the second acoustic impedance layer 2201 and the plane where it is located is greater than 90 degrees. Figure 8 , forming a second first acoustic impedance layer 2102, covering the first second acoustic impedance layer 2201. Fig. 9 , forming a second second acoustic impedance layer 2202, covering the second first acoustic impedance layer 2102. Fig.10 After forming the second second acoustic impedance layer, the second second acoustic impedance layer is patterned (the present embodiment is described by forming two Bragg reflection layer structures 200) to form two second second acoustic impedance layers 2202 separated from each other, so that the angle a' between the side wall of the patterned second second acoustic impedance layer 2202 and the plane where it is located is greater than 90 degrees. Fig.11 , forming a third first acoustic impedance layer 2103, covering the second second acoustic impedance layer 2202. Fig.12 The first acoustic impedance layer 210 includes a first first acoustic impedance layer 2101, a second first acoustic impedance layer 2102, and a third first acoustic impedance layer 2103, and the second acoustic impedance layer 220 includes a first second acoustic impedance layer 2201 and a second second acoustic impedance layer 2202. The inclined sidewall of the second acoustic impedance layer 220 can prevent the leakage of lateral sound waves and reduce the loss of sound waves, thereby improving the quality factor of the product.

[0061] The materials of the first acoustic impedance layer 210 and the second acoustic impedance layer 220 can use any suitable material known to those skilled in the art. It should be noted that the acoustic impedance ratio of the first acoustic impedance layer 210 and the second acoustic impedance layer 220 meets the numerical requirements of the reflectivity of the acoustic impedance layer. In this embodiment, the material of the first acoustic impedance layer 210 is polycrystalline carbon, and the material of the second acoustic impedance layer 220 is tungsten. The acoustic impedance of polycrystalline carbon is 2 to 3 mega-Rayles, the acoustic impedance of tungsten is 54 to 55 mega-Rayles, and the high-low acoustic impedance ratio is between 18 and 28. The acoustic impedance of silicon dioxide, a commonly used low acoustic impedance layer material in mass production, is 8 to 9 mega-Rayles. Compared with silicon dioxide, the acoustic impedance of polycrystalline carbon is smaller, which increases the high-low acoustic impedance ratio of the Bragg reflection layer, thereby increasing the reflectivity of the sound wave, and further increasing the quality factor of the product. The first acoustic impedance layer 210 and the second acoustic impedance layer 220 are formed by a deposition process. In this embodiment, the first acoustic impedance layer 210 is formed by low-temperature chemical vapor deposition, and the second acoustic impedance layer 220 is formed by physical vapor deposition. The thickness of the first acoustic impedance layer and the second acoustic impedance layer is set according to design requirements, and the optional range is 2000 angstroms to 10000 angstroms.

[0062] The method for patterning the second acoustic impedance layer 220 includes: spin coating a photoresist layer on the second acoustic impedance layer 220, exposing and developing the photoresist layer to form a patterned photoresist layer, wherein the patterned photoresist layer exposes a portion of the surface of the second acoustic impedance layer 220; and etching the second acoustic impedance layer 220 using the patterned photoresist layer as a mask to form a first second acoustic impedance layer 2201 and a second second acoustic impedance layer 2202, respectively.

[0063] refer to Figures 13 to 16 , an acoustic wave resonator unit 300 is formed on the Bragg reflection layer structure, and the acoustic wave resonator unit 300 includes a first electrode 310, a piezoelectric layer 320, and a second electrode 330 which are sequentially formed on the Bragg reflection layer structure.

[0064] In this embodiment, forming the acoustic wave resonator unit 300 includes: referring to Fig.13 , a first electrode 310 is formed on the Bragg reflection layer structure. Fig.14 , patterning the first electrode 310 so that the first electrodes of two adjacent acoustic wave resonator units are separated from each other. Fig.15 , forming a piezoelectric layer 320 to cover the surface of the first electrode 310 and the Bragg reflection layer structure, and forming a second electrode 330 to cover the surface of the piezoelectric layer 320, the first electrode 310, and the Bragg reflection layer structure. Fig.16, the second electrode 330 is patterned to form a first side wall 330', and the inclination angle c between the first side wall 330' and the plane where the second electrode 320 is located is greater than 90 degrees. The piezoelectric layer 320 is patterned to form a second side wall 320', and the inclination angle b between the second side wall 320' and the plane where the piezoelectric layer 320 is located is greater than 90 degrees. The area of ​​the effective resonance zone is defined by the second side wall 320' and the first side wall 330'. At the same time, the inclined side wall at the boundary can prevent the leakage of lateral sound waves, reduce the loss of sound waves, and thus improve the quality factor of the product. In this embodiment, the second side wall 320' and the first side wall 330' have the same inclination angle, and the two are located on the same plane. The second side wall 320' and the first side wall 330' are formed by a one-step etching process, which simplifies the process flow.

[0065] refer to Fig.17 , after the resonator unit 300 is formed in this embodiment, it also includes: forming an insulating layer 340 on the surface of the resonator unit 300. The material of the insulating layer 340 may include silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride or ethyl silicate. In this embodiment, the material of the insulating layer 340 is silicon oxide or silicon nitride. The method of forming the insulating layer 340 includes physical vapor deposition or chemical vapor deposition. The insulating layer 340 can be used to adjust the frequency of the resonator or as a passivation layer. The frequency of the resonator is related to the thickness of the effective resonance area. When making a filter, the thickness of the first electrode, the second electrode and the piezoelectric layer of different resonators are the same. In order to make the frequencies of different resonators different, insulating layers 340 of different thicknesses can be set.

[0066] The method for forming an annular cofferdam on the first structure may be: 1. Forming a seed layer to cover the first structure; forming a barrier layer to cover the seed layer; removing the barrier layer in the first region to expose the seed layer below, the first region being the region where the annular cofferdam is formed; forming the annular cofferdam in the first region by electroplating; removing the barrier layer. 2. Forming a seed layer to cover the first structure; etching the seed layer to retain the seed layer in the first region; forming a metal plating layer on the seed layer by electroplating, the metal plating layer in the first region constituting the annular cofferdam.

[0067] refer to Fig.18 In this embodiment, an annular cofferdam is formed on the first structure, specifically: a seed layer 4000 is formed by physical vapor deposition or chemical vapor deposition, the seed layer 4000 covers the insulating layer 340, and the material of the seed layer 4000 is copper (Cu) and / or titanium (Ti).

[0068] refer to Fig.19The patterned seed layer forms a ring 4001 , and the ring 4001 surrounds at least one acoustic wave resonator unit 300 . It should be noted that the ring 4001 in this embodiment refers to a closed ellipse, surrounding two resonator units 300 .

[0069] In this embodiment, the method of patterning the seed layer 4000 to form the ring 4001 includes: spin coating a photoresist layer on the seed layer 4000, exposing and developing the photoresist layer to form a patterned photoresist layer, wherein the patterned photoresist layer exposes a portion of the surface of the seed layer 4000; and etching the seed layer 4000 using the patterned photoresist layer as a mask to form the ring 4001.

[0070] In this embodiment, when the ring 4001 is formed, the patterned seed layer 4000 retains a first region 4002 , the first region 4002 is located inside the ring 4001 and outside the acoustic wave resonator unit 300 , and the first region 4002 is four dispersed regions.

[0071] refer to Fig.19 and Fig. 20 , four support columns 430 are formed in four dispersed first areas 4002 by an electroplating process. The support columns 430 strengthen the support for the substrate. In other embodiments, the support columns 430 may be one, two, three or more than four. It should be understood that a plurality of dispersed support columns 430 can better strengthen the support for the substrate. When the support strength is insufficient, support columns 430 may be added to the first area 4002. An annular cofferdam 410 is formed on the ring 4001 by an electroplating process. The projection of the annular cofferdam 410 on the first substrate 100 forms a closed ellipse. In other embodiments, under the premise of satisfying the structural firmness, the projection of the annular cofferdam 410 may not be a completely closed figure. It should be understood that when the projection of the annular cofferdam 410 is closed, it is more conducive to suppressing the external electromagnetic radiation of the resonator unit.

[0072] refer to Fig.21 , before bonding the substrate to the annular cofferdam 410, it also includes: removing the seed layer, patterning the insulating layer 340, to form insulating layers 340 of different thicknesses, to achieve frequency modulation. In this embodiment, after patterning the insulating layer 340, it also includes a second patterning of the second electrode 330 and the first electrode, so that the second electrodes 330 corresponding to two adjacent acoustic wave resonator units are not connected, and the first electrodes 310 corresponding to two adjacent acoustic wave resonator units are also not connected, so as to form two independent acoustic wave resonator units. When two acoustic wave resonator units are connected in series or in parallel, the electrodes of the two acoustic wave resonator units can also be connected.

[0073] The method of patterning the insulating layer 340 includes dry etching, and the dry etching includes but is not limited to reactive ion etching (RIE), ion beam etching, and plasma etching. The frequency of the resonator is tested through the first electrode 310 and the second electrode 330, and according to the frequency distribution diagram, the insulating layer 340 on the surface of the resonator that needs frequency modulation is etched, and the thickness of the insulating layer 340 is adjusted to achieve the effect of frequency modulation; after the frequency modulation is completed, the frequency of the resonator is tested again, and when the frequency requirement is not met, the insulating layer 340 needs to be repeatedly etched.

[0074] refer to Fig. 22 and Fig.23 , providing a substrate 420. Bonding the substrate 420 to the annular cofferdam 410 to form a closed cavity 500. In this embodiment, the substrate 420 includes a semiconductor layer 4203 and a shielding layer 4202, and the shielding layer 4202 faces the cavity 500. The material of the shielding layer is metal, and the shielding layer 4202 is formed on the semiconductor layer 4203 by a physical vapor deposition process. Through the shielding effect of the shielding layer 4202 on electromagnetic waves, the external electromagnetic radiation generated by the resonator unit inside the cavity 500 during operation is effectively blocked or attenuated, reducing the electromagnetic interference generated by itself.

[0075] In this embodiment, the shielding layer 4202, the annular cofferdam 410, and the support column 430 may be made of at least one of copper, tin, or gold, but are not limited to the above materials. The shielding layer 4202 is bonded to the annular cofferdam 410 or the support column 430 by metal bonding.

[0076] refer to Fig.24 In this embodiment, after the base plate is bonded to the first substrate, the method further includes:

[0077] A first conductive plug 600a is formed from the side where the first substrate 100 is located and passes through the first substrate 100, and the first conductive plug 600a is electrically connected to the first electrode of one of the acoustic wave resonator units; a second conductive plug 600b is formed from the side where the first substrate 100 is located and passes through the first substrate 100, and the second conductive plug 600b is electrically connected to the second electrode of the same acoustic wave resonator unit to electrically lead out the acoustic wave resonator unit; a wiring layer is formed on the side of the first substrate away from the base plate, and the first conductive plug and the second conductive plug are connected to the wiring layer, and a plurality of the acoustic wave resonator units are connected in parallel or in series through the wiring layer.

[0078] In this embodiment, after the acoustic wave resonator is formed, the steps of cutting and packaging the resonator, and molding and shipping are also included, which will not be repeated here.

[0079] It should be noted that the various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0080] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A thin film acoustic wave resonator, characterized in that: include: A first substrate including a sound reflecting structure; an acoustic wave resonator unit, at least partially located on the acoustic reflection structure, the acoustic wave resonator unit comprising, from bottom to top, a stacked first electrode, a piezoelectric layer, and a second electrode; A substrate, bonded to the first substrate via an annular cofferdam, and forming a cavity between the substrate and the acoustic wave resonator unit, wherein the cavity includes at least one acoustic wave resonator unit, and at least one of the substrate and the annular cofferdam has a function of shielding electromagnetic waves; The acoustic reflection structure includes a Bragg reflection layer structure; The Bragg reflection layer structure comprises a first acoustic impedance layer and a second acoustic impedance layer which are overlapped, wherein the impedance of the first acoustic impedance layer is smaller than the impedance of the second acoustic impedance layer, wherein the material of the first acoustic impedance layer is polycrystalline carbon, and the material of the second acoustic impedance layer is tungsten; The inclination angle between the side wall of each second acoustic impedance layer and the plane where it is located is greater than 90 degrees; The substrate is a composite structure, and a side of the substrate close to the cavity includes a shielding layer; A shielding layer is provided on one side of the annular cofferdam facing the cavity; The material of the shielding layer is metal; A side of the substrate away from the cavity is a semiconductor layer; The annular cofferdam and the substrate are made of metal.

2. The thin film acoustic wave resonator according to claim 1, characterized in that: The cavity includes a plurality of the acoustic wave resonator units, a support column is provided between two adjacent acoustic wave resonator units, and the top surface of the support column is in contact with the surface of the substrate on one side close to the cavity.

3. The thin film acoustic wave resonator according to claim 2, characterized in that: The material of the support column includes metal.

4. The thin film acoustic wave resonator according to claim 1, characterized in that: Each of the acoustic wave resonator units further comprises: A first conductive plug is formed from the side where the first substrate is located, penetrates the first substrate, and is electrically connected to the first electrode of the acoustic wave resonator unit; A second conductive plug is formed from the side where the first substrate is located, penetrates the first substrate, and is electrically connected to the second electrode of the same acoustic wave resonator unit to electrically lead out the acoustic wave resonator unit.

5. The thin film acoustic wave resonator according to claim 4, characterized in that: The cavity includes at least two acoustic wave resonator units, a wiring layer is provided on the side of the first substrate away from the cover, the first conductive plug and the second conductive plug are connected to the wiring layer, and a plurality of the acoustic wave resonator units are connected in parallel or in series through the wiring layer.

6. The thin film acoustic wave resonator according to claim 1, characterized in that: The piezoelectric layer includes a second side wall, and the inclination angle between the second side wall and the plane where the piezoelectric layer is located is greater than 90 degrees; and / or the second electrode includes a first side wall, and the inclination angle between the first side wall and the plane where the second electrode is located is greater than 90 degrees.

7. A method for manufacturing a thin film acoustic wave resonator, characterized in that: include: Providing a first structure, the first structure comprising a first substrate including an acoustic reflection structure, and at least one acoustic wave resonator unit formed on the first substrate, the acoustic wave resonator unit comprising a stacked first electrode, a piezoelectric layer, and a second electrode; Providing a substrate, wherein a shielding layer is provided on a first surface of the substrate; forming an annular cofferdam on the first structure or on the first surface of the substrate; Bonding the substrate to the first substrate via the annular cofferdam, wherein the annular cofferdam surrounds at least one of the acoustic wave resonator units and forms a cavity between the substrate and the acoustic wave resonator unit; The acoustic reflection structure comprises a first acoustic impedance layer and a second acoustic impedance layer which are overlapped, wherein the impedance of the first acoustic impedance layer is smaller than the impedance of the second acoustic impedance layer, the material of the first acoustic impedance layer comprises polycrystalline carbon, and the material of the second acoustic impedance layer comprises tungsten; The materials of the annular cofferdam and the shielding layer include metal, and the bonding method includes metal bonding; The side of the substrate away from the cavity comprises a semiconductor layer, and the shielding layer is formed on the semiconductor layer by a physical vapor deposition process.

8. The method for manufacturing a thin film acoustic wave resonator according to claim 7, characterized in that: The step of forming the annular cofferdam on the first structure comprises: forming a seed layer to cover the first structure; forming a barrier layer to cover the seed layer; removing the barrier layer in a first area to expose the seed layer underneath, wherein the first area is an area where the annular cofferdam is formed; forming the annular cofferdam in the first region by an electroplating process; removing the barrier layer; or, forming a seed layer to cover the first structure; etching the seed layer to retain the seed layer in the first area; A metal coating is formed on the seed layer by an electroplating process, and the metal coating in the first region constitutes the annular cofferdam.

9. The method for manufacturing a thin film acoustic wave resonator according to claim 8, characterized in that: There are multiple acoustic wave resonator units, and the method further includes: A support column is formed between two adjacent acoustic wave resonator units, and when the substrate is bonded, the top surface of the support column is in contact with the substrate.

10. The method for manufacturing a thin film acoustic wave resonator according to claim 9, characterized in that: The annular cofferdam is made of the same material as the support column, and the support column is formed when the annular cofferdam is formed.

11. The method for manufacturing a thin film acoustic wave resonator according to claim 9, characterized in that: After bonding the substrate to the first substrate, the method further comprises: forming a first conductive plug penetrating through the first substrate from the side where the first substrate is located, wherein the first conductive plug is electrically connected to the first electrode of one of the acoustic wave resonator units; forming a second conductive plug penetrating the first substrate from the side where the first substrate is located, wherein the second conductive plug is electrically connected to the second electrode of the same acoustic wave resonator unit to electrically lead out the acoustic wave resonator unit; A wiring layer is formed on a side of the first substrate away from the base plate, the first conductive plug and the second conductive plug are connected to the wiring layer, and a plurality of the acoustic wave resonator units are connected in parallel or in series through the wiring layer.

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