Acoustic wave resonator

Abstract

Disclosed is an acoustic wave resonator including a substrate including a first cavity, a first electrode formed above the substrate, a piezoelectric layer formed on one surface of the first electrode, and a second electrode formed on one surface of the piezoelectric layer. Herein, the piezoelectric layer includes a longitudinal face which does not cover a longitudinal face of the first electrode. Further, the second electrode covers the longitudinal face of the piezoelectric layer and extends to a first inter-electrode cavity which at least partially spaces the first electrode from the piezoelectric layer. A quality factor can be increased by addressing an increase in electrical resistance due to a thin film electrode.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0086243, filed on July 1, 2021, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a resonator for radio frequency (RF) communication, and more specifically, to a thin-film bulk acoustic resonator (FBAR) with low power loss. Background Technology

[0004] Wireless mobile communication technology requires various radio frequency (RF) components capable of effectively transmitting information within a limited frequency band. In particular, filters are one of the essential components used in mobile communication technology, enabling high-quality communication by selecting the signal desired by the user from multiple frequency bands or filtering the signal to be transmitted.

[0005] Currently, dielectric filters and surface acoustic wave (SAW) filters are mostly used as RF filters for wireless communication. Dielectric filters have advantages such as high dielectric constant, low insertion loss, high temperature stability, high vibration resistance, and high shock resistance. However, dielectric filters have limitations in the field of miniaturization and monolithic microwave integrated circuits (MMICs), which are the latest trends in technological development. Furthermore, compared to dielectric filters, SAW filters have smaller size, are easier to process signals, have simpler circuitry, and are manufactured using semiconductor processes for mass production. In addition, compared to dielectric filters, SAW filters have the advantage of transmitting and receiving advanced information due to their high side rejection within the passband. However, because the SAW filter process involves ultraviolet (UV) exposure processes, there is a drawback where the linewidth of the interdigital transducer (IDT) is limited to approximately 0.5 μm. Therefore, there is a problem that SAW filters cannot be used to cover ultra-high frequency bands above 3 GHz, thus posing fundamental difficulties in forming MMIC structures and single chips on semiconductor substrates.

[0006] To overcome these limitations and problems, a thin-film bulk acoustic resonator (FBAR) filter that can fully implement frequency control circuitry has been provided, which is integrated with other active devices on an existing semiconductor (Si or GaAs) substrate as a MMIC.

[0007] FBAR is a low-cost, small-size, high-quality-factor thin-film device suitable for wireless communication devices and military radar in various frequency bands from 900MHz to 10GHz. Furthermore, the size of FBAR is reduced to a fraction of that of dielectric filters and lumped-constant (LC) filters, and its insertion loss is much lower than that of SAW filters. Therefore, FBAR is considered one of the most suitable devices for MMICs requiring high stability and high quality factor.

[0008] FBAR filters are formed by depositing piezoelectric dielectric materials such as zinc oxide (ZnO) and aluminum nitride (AlN) on silicon (Si) or gallium arsenide (GaAs) substrates using RF sputtering methods, thus inducing resonance due to their piezoelectric properties. In other words, FBARs can generate resonance by depositing a piezoelectric thin film between two electrodes and inducing bulk acoustic waves.

[0009] To date, various forms of FBAR structures have been studied. In the case of film-type FBARs, a silicon oxide (SiO2) film is deposited on a substrate, and the film layer is formed using cavities formed in opposite sides of the substrate by isotropic etching. Furthermore, a lower electrode is formed on the SiO2 film, a piezoelectric layer is formed on the lower electrode by depositing a piezoelectric material using RF magnetron sputtering, and an upper electrode is formed on the piezoelectric layer.

[0010] The aforementioned film-type FBARs offer advantages such as lower power loss and dielectric loss due to their cavity design. However, film-type FBARs suffer from the following problems: due to the orientation of the silicon substrate, the device occupies a large area, and low structural stability during subsequent packaging processes leads to damage and reduced yield. Therefore, recently, to reduce losses caused by the film and simplify device manufacturing processes, air-gap type FBARs and Bragg reflector type FBARs have emerged.

[0011] Bragg reflector-type FBARs have a structure in which reflector layers are formed by alternately depositing materials with high acoustic impedance differences on a substrate, and then sequentially stacking a lower electrode, a piezoelectric layer, and a top electrode. Here, acoustic wave energy that has passed through the piezoelectric layer is not transmitted to the substrate and is entirely reflected by the reflector layer, thus effectively generating resonance. While Bragg reflector-type FBARs have a good structure and do not suffer from stress due to bending, they have the following drawbacks: it is difficult to precisely form the reflector layers, which have four or more layers thick for total internal reflection, and manufacturing requires significant time and expense.

[0012] On the other hand, in the case of a conventional FBAR with a structure that uses an air gap instead of a reflector layer to isolate the substrate from the resonant part, an FBAR is achieved by anisotropic etching on the surface of the silicon substrate, surface treatment by chemical mechanical polishing, sequential deposition of an insulating layer, a lower electrode, a piezoelectric layer and an upper electrode, and removal of the sacrificial layer, forming an air gap through vias.

[0013] In this conventional FBAR structure, a piezoelectric layer is formed between the upper and lower electrodes, and the upper and lower electrodes are only installed in the necessary areas of the piezoelectric layer to utilize the piezoelectric effect. Therefore, this conventional structure has a large mechanical anchorage loss, which leads to a reduction in mechanical energy.

[0014] In the case of upper or lower electrodes, molybdenum (Mo), ruthenium (Ru), tungsten (W), etc., are used to increase acoustic impedance. Since the skin depth of the electrode material depends on the frequency of the filter, and the thickness of the electrode is usually much smaller than the skin depth, the charge formed at the resonant point of the piezoelectric layer cannot be fully transferred through the leads, thus reducing the quality factor.

[0015] [Related Technical Documents]

[0016] [Patent Documents]

[0017] Patent document 0001: Korean Patent Publication No. 10-2004-0102390 (published on December 8, 2004). Summary of the Invention

[0018] The present invention aims to solve the problem of increased electrical loss caused by induction hardening and identified as a problem of thin film electrodes.

[0019] The present invention also aims to compensate for the electrical losses of conventional thin-film electrodes, which have been identified as a problem, by changing the position of the pads in the acoustic resonator and by changing the structure of the electrodes and piezoelectric layers.

[0020] The present invention also aims to provide an electrode structure suitable for removing parasitic capacitances that arise from electrodes arranged close to each other.

[0021] The present invention also aims to solve the problem of increased resistance caused by the thinning of electrodes due to the increase in the frequency of the signal that the filter must process.

[0022] According to one aspect of the present invention, an acoustic resonator is provided, comprising: a substrate including a first cavity; a first electrode formed above the substrate; a piezoelectric layer formed on one surface of the first electrode; and a second electrode formed on one surface of the piezoelectric layer. The first electrode and the piezoelectric layer include overlapping regions corresponding to one edge to another of the first cavity. The first electrode has a longitudinal surface beyond the overlapping region based on the other edge of the first cavity. The piezoelectric layer has a longitudinal surface that does not cover the longitudinal surface of the first electrode. The second electrode overlaps with the first cavity, covers the longitudinal surface of the piezoelectric layer, and extends to one or more inter-electrode cavities maintaining a gap between the second electrode and the first electrode.

[0023] The inter-electrode cavity may include a first inter-electrode cavity that covers a longitudinal surface of the first electrode and a portion of the substrate, contacts the bottom surface to which the second electrode extends, and is formed between the first electrode and the piezoelectric layer outside an overlapping area based on another edge of the first cavity.

[0024] In addition, the inter-electrode cavity may also include a second inter-electrode cavity, which is in contact with the longitudinal surface of the second electrode and the piezoelectric layer.

[0025] The acoustic resonator may also include a second inter-electrode cavity that contacts the second electrode, the longitudinal surface of the piezoelectric layer, and the first inter-electrode cavity.

[0026] The second electrode may include a wing region having a second cavity near an edge of the overlapping region between the second electrode and the piezoelectric layer.

[0027] The second electrode may include a wing region on one side and a bridge region on the other side, with the wing region having a second cavity and the bridge region having a third cavity between the second electrode and the piezoelectric layer. Furthermore, the second cavity, the third cavity, and the first inter-electrode cavity may be filled with air.

[0028] The first electrode and the piezoelectric layer include an overlapping region corresponding to one edge of the first cavity to the other, and the second electrode may be thicker in the extended region than in the overlapping region.

[0029] The second electrode may have a thickness that extends in a V-shape or U-shape depending on the shape of the longitudinal surface of the piezoelectric layer.

[0030] The piezoelectric layer can be longitudinally cut at a position that does not cover the longitudinal surface of the first electrode.

[0031] The acoustic resonator may also include a passivation layer formed on one surface of the second electrode.

[0032] The acoustic resonator may also include a conductive patterned layer formed above the first electrode, outside an overlapping region based on one edge of the first cavity.

[0033] The acoustic resonator may also include a conductive patterned layer formed above the second electrode, outside an overlapping region based on another edge of the first cavity.

[0034] According to another aspect of the present invention, an acoustic resonator is provided, comprising: a substrate having a first cavity; a first electrode formed above the substrate; a piezoelectric layer formed on one surface of the first electrode; and a second electrode formed on one surface of the piezoelectric layer. The first electrode and the piezoelectric layer include overlapping regions corresponding to one edge to another of the first cavity. The first electrode has a longitudinal surface outside the overlapping region based on the other edge of the first cavity. The piezoelectric layer is separated into a first portion and a second portion due to a valley-shaped etched region formed thereon, the overlapping region belonging to the first portion, the second portion not contacting the first electrode, and the first portion and the second portion each having a longitudinal surface formed thereon. Furthermore, the second electrode includes the overlapping region and is formed above the etched region according to the valley shape.

[0035] The second electrode may include a wing region having a second cavity between the second electrode and the piezoelectric layer near one edge of the overlapping region.

[0036] The second electrode may include a bridge region having a third cavity between the second electrode and the piezoelectric layer near another edge of the overlapping region.

[0037] The third cavity can extend to the longitudinal surface of the first part of the piezoelectric layer, the first electrode, and the second part.

[0038] The second electrode can be thicker in the etched region than in the overlapping region.

[0039] The second electrode may have a thickness that extends in a V-shape or U-shape according to the valley shape.

[0040] The second electrode may have a lowest surface within or above the height range of the first electrode, thereby including a cavity between the longitudinal surfaces of the second electrode and the first electrode, the depth of which is the thickness of the first electrode or greater.

[0041] The piezoelectric layer may have a first portion that is longitudinally cut at a position that does not cover the longitudinal surface of the first electrode.

[0042] The acoustic resonator may also include a passivation layer formed on one surface of the second electrode.

[0043] The acoustic resonator may also include a conductive patterned layer formed above the first electrode, outside an overlapping region based on one edge of the first cavity.

[0044] The acoustic resonator may also include a conductive patterned layer formed above the second electrode, outside an overlapping region based on another edge of the first cavity.

[0045] According to another embodiment of the present invention, a method for manufacturing an acoustic resonator is provided. The method includes: forming a first cavity in a partial region on a substrate; forming a first electrode that overlaps with one edge to another of the first cavity and is longitudinally cut outside the overlapping region based on the other edge of the first cavity; forming a piezoelectric layer that is longitudinally cut without covering the longitudinal surface of the first electrode; and forming a second electrode that covers the longitudinal surface of the piezoelectric layer and extends into one or more inter-electrode cavities that maintain a gap between the second electrode and the first electrode.

[0046] The method may further include forming a first spacer or sacrificial layer to form a first inter-electrode cavity between the longitudinal surface of the first electrode and the second electrode to cover the longitudinal surface of the first electrode.

[0047] The method may further include forming a second spacer disposed between the longitudinal surface of the first electrode and the second electrode, and covering the longitudinal surface of the first portion of the piezoelectric layer.

[0048] According to another aspect of the present invention, a method for manufacturing an acoustic resonator is provided. The method includes: forming a first cavity in a portion of a substrate; forming a first electrode that overlaps with one edge to another of the first cavity and is longitudinally cut outside the overlapping region based on the other edge of the first cavity; forming a piezoelectric layer that is longitudinally cut without covering the longitudinal surface of the first electrode; and forming a piezoelectric layer on a surface of the first electrode and on the substrate, the piezoelectric layer being separated into a first portion and a second portion due to a valley-shaped etched region formed thereon, the first portion having a longitudinal surface, the overlapping region belonging to the first portion, and the second portion not contacting the first electrode; and forming a second electrode that overlaps with the first cavity and is etched according to the valley shape in the etched region.

[0049] The method may also include forming a sacrificial layer for forming a second cavity and a third cavity near one edge and the other edge of the overlapping region between the second electrode and the piezoelectric layer.

[0050] The method may further include forming a sacrificial layer for forming cavities between the longitudinal surfaces of the second electrode and the first portion of the piezoelectric layer, and between the second electrode and the second portion of the piezoelectric layer, respectively.

[0051] The method may also include growing the thickness of the second electrode to be thicker above the etched region than in the overlapping region.

[0052] The method may also include etching the piezoelectric layer to form V-shaped or U-shaped valleys that separate the piezoelectric layer into a first part and a second part.

[0053] The method may also include forming a sacrificial layer for forming a cavity that contacts the longitudinal surface of the first electrode and a second portion of the piezoelectric layer. Attached Figure Description

[0054] The above and other objects, features, and advantages of the present invention will become more apparent to those skilled in the art from the detailed description of exemplary embodiments of the invention with reference to the accompanying drawings, wherein:

[0055] Figure 1 This is a top view of an acoustic resonator according to a first embodiment of the present invention;

[0056] Figure 2 This is a cross-sectional view of an acoustic resonator according to a first embodiment of the present invention;

[0057] Figure 3 This is a top view of an acoustic resonator according to a second embodiment of the present invention;

[0058] Figure 4 This is a cross-sectional view of an acoustic resonator according to a second embodiment of the present invention;

[0059] Figure 5 This is a top view of an acoustic resonator according to a third or fourth embodiment of the present invention;

[0060] Figure 6 This is a cross-sectional view of an acoustic resonator according to a third embodiment of the present invention;

[0061] Figure 7 This is a cross-sectional view of an acoustic resonator according to a fourth embodiment of the present invention;

[0062] Figure 8 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to an embodiment of the present invention;

[0063] Figure 9 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a first embodiment of the present invention;

[0064] Figure 10 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a second embodiment of the present invention;

[0065] Figure 11 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a third embodiment of the present invention; and

[0066] Figure 12 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a fourth embodiment of the present invention. Detailed Implementation

[0067] Before describing the invention in detail, it should be noted that the terms or words used in this specification should not be unconditionally limited to their general or dictionary meanings. Furthermore, in order to best describe the invention, the inventors may appropriately define the concepts of various terms. It should also be understood that these terms or words will be interpreted as having the meaning and concept of the technical concepts according to the invention.

[0068] That is, it should be noted that the terminology used herein is only for describing exemplary embodiments of the invention and is not intended to limit the scope of the invention in detail, and these terms are defined in view of the various possibilities of the invention.

[0069] In addition, it should be noted that the singular form may include the plural form, unless otherwise defined in the context, and vice versa.

[0070] Throughout this specification, when an element is described as "including" another element, unless otherwise specifically defined, that element does not exclude other elements and may further include other elements.

[0071] Furthermore, when a component is described as "present or mounted on and simultaneously connected to" another component, the component may be mounted on and simultaneously directly connected to the other component, in contact with the other component, or simultaneously spaced apart from the other component. When the component is mounted on and simultaneously spaced apart, there may also be other components or devices for securing or connecting the corresponding component to the other component. The description of the other components may be omitted.

[0072] On the other hand, when an element is described as being "directly connected to" or "directly in contact with" another element, it should be understood that there are no other elements or devices present.

[0073] Similarly, other terms describing the relationship between components, such as “between” and “completely between”, “adjacent” and “directly adjacent”, should be interpreted equally.

[0074] Furthermore, in the specification, terms such as "one surface," "another surface," "one side," "the other side," "first," and "second" are used to clearly distinguish one element from other elements, and it should be noted that the meaning of the corresponding element is not limited by the above terms.

[0075] Furthermore, it should be understood in the specification that position-related terms, such as “above,” “below,” “left,” “right,” etc., are used to indicate the relative positions of elements in the drawings, and unless an absolute position is defined, position-related terms are not intended to describe the absolute position of the elements.

[0076] Furthermore, in this specification, when elements in each figure are designated by reference numerals, the same reference numerals are used to indicate the element even in different figures; that is, similar elements are indicated by similar reference numerals throughout the specification.

[0077] In the accompanying drawings of this specification, in order to convey the concept of the invention with satisfactory accuracy or for ease of explanation, the dimensions, positions, and combinations of the elements included in the invention may be partially exaggerated, reduced, or omitted, and therefore their proportions or dimensions may not be precise.

[0078] In the following description of the invention, detailed descriptions of components in the prior art related to the invention will be omitted where it is deemed unnecessary to obscure the essence of the invention.

[0079] In the following text, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0080] According to one embodiment of the present invention, an acoustic resonator 100, 200, 300, or 400 can be formed by stacking multiple layers of different materials, and the multiple stacked layers can have a polygonal shape. However, for the sake of convenience, Figure 1 , Figure 4 and Figure 6 The top view of the quadrilateral structure shown partially reveals its entire shape.

[0081] Figure 1 and Figure 2 An acoustic resonator 100 according to a first embodiment of the present invention is shown.

[0082] Figure 1 This is a top view of an acoustic resonator according to a first embodiment of the present invention.

[0083] Figure 2 This is a cross-sectional view of an acoustic resonator according to a first embodiment of the present invention.

[0084] refer to Figure 1 and Figure 2 The diagram shows a substrate 111, a first electrode (lower electrode) 121, a piezoelectric layer 131, and a second electrode (upper electrode) 141 included in the acoustic resonator 100.

[0085] See again Figure 2The acoustic resonator 100 may include: a substrate 111 having a first cavity 112, a first electrode 121 formed above the substrate 111, a piezoelectric layer 131 formed on one surface of the first electrode 121, and a second electrode 141 formed on one surface of the piezoelectric layer 131.

[0086] The first electrode 121 and the piezoelectric layer 131 can be formed to include an overlapping region corresponding to one edge E1 to another edge E2 of the first cavity 112. The first electrode 121 may have a longitudinal surface that is outside the overlapping region based on the other edge E2 of the first cavity 112.

[0087] The piezoelectric layer 131 may have a longitudinal surface outside the overlapping region, similar to the first electrode 121, which does not cover the longitudinal surface of the first electrode 121. That is, the piezoelectric layer 131 may be formed to be longitudinally cut at a position that does not cover the longitudinal surface of the first electrode 121.

[0088] The second electrode 141 may be formed above the first cavity 112, including an overlapping region, covering the longitudinal surface of the piezoelectric layer 131, and extending to or beyond one or more inter-electrode cavities 122, and spaced apart from the first electrode 121.

[0089] refer to Figure 2 A portion of the first inter-electrode cavity 122 allows the first electrode 121 and the piezoelectric layer 131 to be at least partially spaced apart from each other. Furthermore, a portion of the first inter-electrode cavity 122 maintains the gap between the first electrode 121 and the second electrode 141. The second electrode 141 may be formed, for example, in a U-shape, to extend beyond, or within, a certain range without intruding into, the first inter-electrode cavity 122. Figure 1 The second part 131b of the piezoelectric layer 131.

[0090] refer to Figure 2 The second electrode 141 may include an extension region 141a extending in the direction of the first electrode 121 according to the shape of the longitudinal surface of the piezoelectric layer 131.

[0091] The first inter-electrode cavity 122 may cover a portion of the longitudinal surface of the first electrode 121 and the substrate 111, contact the bottom surface to which the second electrode 141 extends, and be formed between the first electrode 121 and the piezoelectric layer 131, outside the overlapping area based on another edge of the first cavity 112. The first inter-electrode cavity 122 may prevent the generation of parasitic capacitance between the first electrode 121 and the second electrode 141.

[0092] The first inter-electrode cavity 122 may include air or a dielectric material. Furthermore, the second cavity 142 formed below the wing region of the second electrode 141 and the third cavity 143 formed below the bridge region may also include air or a dielectric material. The first inter-electrode cavity 122 filled with dielectric material is referred to as the first spacer. Therefore, the second cavity 142, the third cavity 143, and the first inter-electrode cavity 122 filled with air can be formed above one edge E1 and the other edge E2 of the first cavity 112. Since the first inter-electrode cavity 122 and the second cavity 142 can have dielectric constants different from those of the adjacent dielectrics, effects such as reduced electrical losses and increased quality factor can be obtained.

[0093] The second electrode 141 may include a wing region that includes a second cavity 142 between the second electrode 141 and the piezoelectric layer 131 near one edge of the overlapping region. Furthermore, the second electrode 141 may include a bridge region that includes a third cavity 143 between the second electrode 141 and the piezoelectric layer 131 near another edge of the overlapping region.

[0094] The third cavity 143 formed by the second electrode 141 and the first spacer 122 formed to cover the longitudinal surface of the first electrode 121 can be formed to overlap each other with a gap G1.

[0095] The second electrode 141 may be thicker in the extended region than in the overlapping region.

[0096] Depending on the shape of the longitudinal surface of the piezoelectric layer 131, the second electrode 141 may have a thickness that extends in a V-shape or a U-shape.

[0097] In addition, a first passivation layer 113 may be selectively formed between the substrate 111 and the first electrode 121, and a second passivation layer 150 may be formed on one surface of the second electrode 141.

[0098] Furthermore, the acoustic resonator 100 may also include a first metal pattern layer 161 and a second metal pattern layer 162 referred to as pads. That is, the acoustic resonator 100 may also include conductive metal pattern layers 161 and 162 formed above the first electrode 121 outside the overlapping region based on one edge of the first cavity 112.

[0099] Among various substrate materials, a semiconductor substrate can be used to realize substrate 111. In particular, a silicon wafer can be used. For example, a silicon substrate with high resistivity can be used.

[0100] The first cavity 112 can be formed in a portion of the substrate 111. That is, the first cavity 112 can be formed on one surface of the substrate 111 in the form of a trench extending along the X-axis from one edge E1 to another edge E2. Figure 2 In a portion of the upper surface of the cavity. The first cavity 112 can be formed in a sacrificial layer formation process or by bonding a pre-formed first electrode. The first cavity 112 can be filled with air or SiO2.

[0101] The first cavity 112 can function as a reflective element, and its placement within the acoustic resonator is of significant importance. (Reference) Figure 2 For the first cavity 112, the left and right sides of the width forming the first cavity 112 will be referred to as an edge E1 and another edge E2, respectively. Apart from the first electrode 121, piezoelectric layer 131 and second electrode 141 forming the overlapping region, the modified structure of the second electrode 141 is related to the first cavity 112 having a width formed by one edge and another edge.

[0102] The first cavity 112 can be formed by forming a trench region on one surface of the substrate 111, forming an insulating layer in the trench region, depositing, etching and planarizing a sacrificial layer over the insulating layer, and then removing the sacrificial layer. Furthermore, a spatial region of the first cavity 112 can be formed, and a pre-formed first electrode can be bonded to its top.

[0103] Materials that have excellent surface roughness and are easy to form or remove, such as polycrystalline silicon, tetraethyl orthosilicate (TEOS), and phosphosilicate glass (PSG), can be used as sacrificial layers. For example, polycrystalline silicon, which has high surface roughness and is easy to form or remove, can be used as a sacrificial layer, and in particular, it can be removed using dry etching in subsequent processes.

[0104] Without removing the sacrificial layer in the overlapping area of ​​the first cavity 112, a first passivation layer 113 can be selectively formed covering the sacrificial layer and the surface of the substrate 111. To achieve the first passivation layer 113, a thermal oxide film that can be easily grown on the substrate 111 can be used, or an oxide film or nitride film formed using a general deposition process such as chemical vapor deposition can be selectively used.

[0105] The first electrode 121 can be formed on one surface of the substrate 111. That is, when there is no first passivation layer 113, the first electrode 121 can be suspended above the first cavity 112 and cover the entire or part of the substrate 111 where the first cavity 112 is not present. Figure 2 A first electrode 121 is shown, formed to cover a portion of a first cavity 112 and a substrate 111. The first electrode 121 may be formed by longitudinally cutting into an outer region of the first cavity 112 based on another edge E2 of the first cavity 112. (Reference) Figure 2 The edge of the longitudinal surface region of the first electrode 121 can be completed with a downward slope.

[0106] The first electrode 121 and the second electrode 141 correspond to the input terminal and output terminal of the electrical signal, respectively. The first electrode 121 can be made of a conductive material.

[0107] The first electrode 121 may be formed over the first passivation layer 113 or the substrate 111. When the sacrificial layer is present in the first cavity region of the substrate 111, the first electrode 121 may be formed over the sacrificial layer.

[0108] The first electrode 121 can be formed by depositing and then patterning a material on one surface of the substrate 111. The material of the first electrode 121 can be a common conductor, such as a metal, particularly one of aluminum (Al), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), palladium (Pd), ruthenium (Ru), rhenium (Re), and molybdenum (Mo). The first electrode 121 can have a thickness in the range of 10 to 1000 nm.

[0109] The piezoelectric layer 131 can be formed on the surface of the first electrode 121 opposite to the surface of the contact substrate 111. The piezoelectric layer 131 formed on the first electrode 121 can be formed so as not to cover a portion of the first electrode 121. For example, refer to... Figure 2 The first metal pattern layer 161 can be formed in the exposed portion of the first electrode 121 that is not covered by the piezoelectric layer 131.

[0110] Furthermore, the piezoelectric layer 131 can be longitudinally cut along the longitudinal surface of the first electrode 121, thereby forming a slanted edge. Therefore, the piezoelectric layer 131 can be formed so as not to cover the longitudinally cut edge of the first electrode 121.

[0111] The piezoelectric layer 131 may include a piezoelectric element and is named after that element. When an electrical signal is applied between the first electrode 121 and the second electrode 141, the piezoelectric layer 131 generates acoustic waves due to the piezoelectric material.

[0112] The piezoelectric layer 131 can be formed by depositing and patterning a piezoelectric material on the surfaces of the first electrode 121 opposite to the surface of the contact substrate 111. Aluminum nitride (AlN) or zinc oxide (ZnO) can be used as the piezoelectric material for the piezoelectric layer 131. Radio frequency (RF) magnetron sputtering, evaporation, or other deposition methods can be used. The piezoelectric layer 131 can have a thickness in the range of 5 to 500 nm.

[0113] The first electrode 121 and the second electrode 141 correspond to the input terminal and output terminal of the electrical signal, respectively. The second electrode 141 can be implemented using a conductive material.

[0114] The second electrode 141 can be formed by depositing and patterning a metal film for use as an electrode in a specific region on a surface of the substrate 131. The second electrode 141 can be formed using the same materials, deposition methods, and patterning methods used for the first electrode 121. The second electrode 141 can have a thickness in the range of 5 to 1000 nm.

[0115] As the material for the second electrode 141, a general conductor such as metal can be used, particularly one of Al, W, Au, Pt, Ni, Ti, Cr, Pd, Ru, Re and Mo.

[0116] When an electrical signal is input to the acoustic resonator 100 through the first electrode 121 and the second electrode 141, a portion of the input electrical energy is converted into mechanical energy according to the piezoelectric effect, and the mechanical energy is converted into electrical energy. During this process, resonance occurs about the natural frequency according to the thickness of the piezoelectric layer 131.

[0117] According to one embodiment of the present invention, the acoustic resonator 100 may include an active region where planar regions of a first electrode and a second electrode and a piezoelectric layer 131 overlap. Furthermore, the substrate 111 may be formed with a first cavity 112 between the substrate 111 and the first electrode 121, the first cavity 112 corresponding to a reflecting region overlapping the active region. That is, the first cavity 112 may overlap with the active region above it and be formed between the first electrode 121 and the substrate 111.

[0118] Above one edge of the first cavity 112 that overlaps with the active region, a wing region of the second electrode 141 and a second cavity 142 formed therefrom are disposed. Above the other edge of the first cavity 112, a bridge region of the second electrode 141 and a third cavity 143 formed therefrom may be disposed.

[0119] The active region can be distributed above the area where the planar regions of the first electrode 121, the piezoelectric layer 131, and the second electrode 141 overlap. The wing region of the second electrode can be disposed on one edge of the active region, and the bridge region of the second electrode can be disposed on its other edge.

[0120] When the first electrode 121 is deviated from the overlapping region (i.e., the active region) and is longitudinally cut, the piezoelectric layer 131 can be formed to be longitudinally cut accordingly. Thus, the piezoelectric layer 131 can be formed to not cover the region of the edge of the first electrode 121.

[0121] Among the various functions of the active region, the heat generated in the active region can be transferred to the substrate 111.

[0122] With the further development of mobile communications, the frequency bands used are increasing. Therefore, the size and thickness of filters are gradually decreasing. As a drawback of thin films, mechanical problems related to the structure, electrical problems related to conductivity, and thermodynamic problems related to heat transfer have been pointed out.

[0123] As a thermodynamic issue, the electrodes of the radio frequency (RF) filter consume a large amount of power, and the charge increases rapidly, thus increasing the heat generation rate. Furthermore, as an electrical issue, according to Ohm's law, the resistance of the electrodes increases with the thin-film filter.

[0124] According to Ohm's law, increasing the electrode thickness can be considered as a way to compensate for increased electrode electrical losses.

[0125] The acoustic resonator 100 according to one embodiment of the present invention is a structure for compensating for electrical losses in the various problems described above, and may include a second electrode 141 having a region with increased thickness. That is, the second electrode 141 may be formed to have an extended region that is thicker than the overlapping region at a location adjacent to at least either one of the edges E1 and the other edge E2 of the overlapping region (i.e., the active region).

[0126] The wing region can be disposed above one edge of the overlapping region (i.e., the active region), specifically above one edge of the first cavity 112. The second electrode 141 of the wing region can be formed to have a second cavity 142 between the second electrode 141 and the piezoelectric layer 131. Furthermore, the upper surface of the second electrode 141 of the wing region can be offset and have an increased thickness. One edge and the other edge of the wing region can contact the piezoelectric layer 131 to form the second cavity 142, which can be closed. The second cavity 142 can be filled with spacers or air.

[0127] The second electrode 141 can be formed to include a bridge region extending from the outside of the overlapping region based on another edge of the active region (i.e., the overlapping region). Furthermore, the bridge region of the second electrode 141 can be formed to have a third cavity 143 between the second electrode 141 and the piezoelectric layer 131. That is, due to the bridge region of the second electrode, a third cavity 143 can be formed between the piezoelectric layer 131 and the second electrode 141.

[0128] To form the third cavity 143, the second electrode 141 needs to be separated from the piezoelectric layer 131 in a certain region. A bridge-shaped structure is suitable for forming the separated state.

[0129] Like the second cavity 142, the third cavity 143 can be formed as a closed cavity. The third cavity 143 can also be filled with spacers or air.

[0130] According to the second embodiment, a third cavity 143 may be formed in one surface of the piezoelectric layer 131, and another cavity may be formed in the longitudinal surface of the piezoelectric layer 131. Furthermore, in the third and fourth embodiments, depending on the extension of the second electrode, the third cavity 143 may be connected to the cavity formed in the longitudinal surface of the piezoelectric layer 131, extending to the longitudinal surface of the first electrode 121 and the longitudinal surface of the separated second portion of the piezoelectric layer 131.

[0131] The height of the third cavity 143 can be half or less of the thickness of the piezoelectric layer 131. Because the third cavity 143 is formed, the piezoelectric layer 131 can have different thicknesses in different regions. Since the height of the third cavity 143 is half or less of the thickness of the piezoelectric layer 131, a minimum thickness is ensured that allows for easy release of heat generated internally. Furthermore, the lateral width of the third cavity 143 can be one-quarter or more of the wavelength of energy released through the piezoelectric layer 131.

[0132] The third cavity 143 can be formed by depositing, planarizing, etching, and patterning a sacrificial layer over the piezoelectric layer 131, stacking the second electrode 141 over the piezoelectric layer 131 including other portions of the sacrificial layer, and then removing the sacrificial layer. In this case, the cavity portion can be formed in a partial region on the piezoelectric layer 131, and then the sacrificial layer can be deposited.

[0133] Here, materials with excellent surface roughness and easy formation or removal, such as polysilicon, TEOS, and PSG, can be used as the sacrificial layer. The process for forming the third cavity 143 can be applied to the second cavity 142.

[0134] According to an embodiment of the present invention, the acoustic resonator 100 may further include a first metal patterned layer 161, which is conductive and is formed in the region where the piezoelectric layer 131 is longitudinally cut and thus exposes the first electrode 121 to cover the edge formed by the longitudinal surface of the piezoelectric layer 131.

[0135] Furthermore, the acoustic resonator 100 according to an embodiment of the present invention may also include a second metal pattern layer 162 formed in the region where the second passivation layer 150 is longitudinally cut and thus exposes the second electrode 141.

[0136] According to an embodiment of the present invention, the metal patterned layers 161 and 162 can be configured as close as possible to the active region. By configuring them close to the active region, the electrical losses of the first electrode 121 and the second electrode 141 can be reduced.

[0137] Metal pattern layers 161 and 162 correspond to metal pads to which signal lines of external circuit devices connected to the first electrode 121 and the second electrode 141 are connected. One edge of metal pattern layers 161 and 162 may be formed as a slope to have a uniform thickness to correspond to the shape of one edge of piezoelectric layer 131.

[0138] The metal patterned layers 161 and 162 can be formed of conductive metal at locations outside the active region. Metals forming the metal patterned layers 161 and 162 include Au, copper (Cu), Al, and aluminum-copper alloys (AlCu), etc. The formation of the metal patterned layers 161 and 162 can increase the quality factor.

[0139] Figure 3 and Figure 4 A second embodiment of the present invention is shown.

[0140] Figure 3 This is a top view of an acoustic resonator according to a second embodiment of the present invention.

[0141] Figure 4 This is a cross-sectional view of an acoustic resonator according to a second embodiment of the present invention.

[0142] The second electrode 241 may include a wing region, a bridge region, and an extension region 241a. The wing region is used to form a second cavity 242 near one edge E1 of the overlapping region with the first cavity 212, and the bridge region is used to form a third cavity 243 near another edge E2.

[0143] The extended region 241a may overlap with the longitudinal surface of the first electrode 221 outside the overlapping region based on another edge E2.

[0144] Based on Figure 4 The acoustic resonator 200 of the second embodiment shown may further include a second inter-electrode cavity 244, one surface of which is in contact with the second electrode 241, and the other surface is in contact with the longitudinal surface of the piezoelectric layer 231 and the first inter-electrode cavity 222.

[0145] When the first inter-electrode cavity 222 covers the longitudinal surface of the first electrode 221, the second inter-electrode cavity 244 can be formed to cover the longitudinal surface of the piezoelectric layer. The first inter-electrode cavity 222 and the second inter-electrode cavity 244 can overlap each other between the first electrode 221 and the second electrode 241.

[0146] refer to Figure 4The second inter-electrode cavity 244 can be formed to contact a portion of the longitudinal surface of the piezoelectric layer 231, the lower surface of the second electrode 241, and the upper surface of the first inter-electrode cavity 222. The second inter-electrode cavity 244 can supplement the function of the first inter-electrode cavity 222, namely, to prevent the generation of parasitic capacitance between the first electrode 221 and the second electrode 241.

[0147] On the other hand, at least one of the second cavity 242, the third cavity 243, the first interpole cavity 222, and the second interpole cavity 244 may be filled with air or dielectric material.

[0148] Figure 5 This is a top view of an acoustic resonator according to a third embodiment of the present invention.

[0149] Figure 6 This is a cross-sectional view of an acoustic resonator according to a third embodiment of the present invention.

[0150] refer to Figure 5 and Figure 6 According to a third embodiment of the present invention, the acoustic resonator 300 may include: a substrate 311, which includes a first cavity 312; a first electrode 320 formed on the substrate 311; piezoelectric layers 331a and 331b formed on one surface of the first electrode 320; and a second electrode 341 formed on one surface of the piezoelectric layers 331a and 331b.

[0151] Furthermore, the first electrode 320 and piezoelectric layers 331a and 331b include overlapping regions corresponding to one edge to the other edge of the first cavity 312. The first electrode 320 includes a longitudinal surface outside the overlapping region based on the other edge of the first cavity 312. The piezoelectric layers 331a and 331b can have longitudinal surfaces at the first portion 331a to which the overlapping region belongs and the second portion 331b that does not contact the first electrode 320 due to the valley-shaped etched regions 331c formed thereon.

[0152] The second electrode 341 can overlap with the first cavity 312 and be formed along the valley shape above the etched region 331c.

[0153] The piezoelectric layers 331a and 331b can be etched to have a valley shape in the outer region of another edge E2 based on the overlapping region. That is, the piezoelectric layers 331a and 331b can be divided into a first part 331a and a second part 331b, with an etched region between them. The first part 331a and the second part 331b can be completely separated, as... Figure 6 As shown, or only their lower regions can be interconnected.

[0154] The second electrode 341 may extend toward the first electrode 320 along the shape of the longitudinal surfaces of the first portion 331a and the second portion 331b of the piezoelectric layer. The second electrode 341 may extend in a V-shape or a U-shape depending on the curvature.

[0155] Furthermore, the first portion 331a and the second portion 331b of the piezoelectric layer 331 may have different heights depending on the longitudinal surface of the first electrode 320.

[0156] Figure 7 This is a cross-sectional view of the acoustic resonator according to the fourth embodiment of the present invention.

[0157] refer to Figure 7 The second electrode 441 may have a longitudinal surface on each of the first portion 431a and the second portion 431b of the piezoelectric layer 431, and the first portion 431a and the second portion 431b of the piezoelectric layer 431 are separated by an etched region 431c outside the overlapping region based on another edge E2 of the overlapping region.

[0158] Compared with the third embodiment, the acoustic resonator 400 according to the fourth embodiment of the present invention includes a fourth cavity 444 at a position parallel to the longitudinal plane of the first electrode 420.

[0159] The height difference between the lowermost surface of the extension region 441a of the second electrode 441 and the lowermost surface of the first electrode 420 ensures sufficient space for the fourth cavity 444 to adequately suppress parasitic capacitance. The fourth cavity 444 can be formed at the same height as the longitudinally cut first electrode 420.

[0160] In order to form the fourth cavity 444, a sacrificial layer other than the sacrificial layer used for the second cavity 442 and the third cavity 443 can also be formed.

[0161] Return to reference Figure 6 As described above, the second electrode 341 may include a wing region, a bridge region, and an extension region. The extension region is connected to the bridge region and has a lowermost surface that is below the first portion 331a of the piezoelectric layer and the upper surface of the first electrode 320. Here, the bridge region and the extension region may be formed with peaks and valleys resembling folds.

[0162] In other words, the extension region 341a of the second electrode 341 can be formed to penetrate the virtual first electrode extending from the longitudinally cut first electrode 320 with at least a partial thickness. That is, the height of the lowermost surface of the second electrode 341 in the extension region 341a can be lower than the height of the uppermost surface of the first electrode 320.

[0163] When the bridge region and extension region 341a are compared with the stratum, the bridge region and the third downward region of the second electrode 341 may have a folded peak and valley structure, and the turning point of the valley may be lower than a surface of the first electrode 320.

[0164] The extension region 341a of the second electrode 341 may include a fourth cavity 344 located between the extension region 341a and the edge of the first electrode 320, the edge of the first electrode 320 being longitudinally cut without intruding into a virtual first electrode extending from the longitudinally cut first electrode 320.

[0165] The second electrode 341 may also include an extension region 341a extending at an acute angle and having a V-shape or U-shape. The third cavity 343 may extend along with the extension of the second electrode 341.

[0166] Because the resistance of the second electrode 341, which has a reinforced thickness outside the active region, decreases, current is collected at the edge of the electrode and flows to the electrode leads, thus increasing the quality factor. In other words, due to the reduced resistance in the reinforced region of the second electrode 341, the charge flow rate per unit time can be increased.

[0167] Furthermore, the heat accumulated in the active area can be transferred to the outside through the substrate 311.

[0168] Furthermore, by compensating for the thickness of the first electrode 320, the heat generated in the active region is transferred to the substrate, thus improving heat transfer.

[0169] Return to reference Figure 6 The acoustic resonator 300 may include a second passivation layer 350. The second passivation layer 350 may be formed on the surface of the second electrode 341 opposite to the surface that contacts the piezoelectric layer 331. Trenches may be formed in a portion of the opposite surface of the second passivation layer 350.

[0170] The second passivation layer 350 can perform a passivation function to protect the first electrode 320, the piezoelectric layer 331, and the second electrode 341. One edge of the second passivation layer 350 can coincide with one edge of the second electrode 341, such as... Figure 6 As shown.

[0171] The technical features included in the acoustic resonator 100 according to an embodiment of the present invention can be implemented by a manufacturing method. Since the detailed process for manufacturing the acoustic resonator 100 has been described above, the features will be briefly described.

[0172] Figure 8 This is a flowchart illustrating a method (S10) for manufacturing an acoustic resonator 100 according to an embodiment of the present invention.

[0173] refer to Figure 2 and Figure 8 The method of manufacturing an acoustic resonator (S10) may include: forming a first cavity 112 in a portion of a substrate 111 (S11); forming a longitudinally cut first electrode 121 outside an overlapping region based on another edge E2 of the overlapping region (S12); forming a piezoelectric layer 131 cut into a first portion 131a and a second portion 131b by a valley-shaped etched region (S13); and forming a second electrode 141 along a valley shape above the overlapping region and the etched region.

[0174] The first cavity 112 may be formed in a portion of the substrate 111 in the form of a trench (S11). The first cavity 112 may be formed to have a width from one edge E1 to another edge E2.

[0175] The first electrode 121 can be formed above the substrate 111 including the first passivation layer 113. That is, when the first passivation layer 113 is not present, the first electrode 121 can be formed on the upper surface of the substrate 111, and when the first passivation layer 113 is present above the substrate 111, the first electrode 121 can be formed above the first passivation layer 113.

[0176] The first electrode 121 may include an overlapping region corresponding to one edge E1 to the other edge E2 of the first cavity 112. Furthermore, the first electrode 121 may be formed to be longitudinally cut outside the overlapping region of the other edge E2 based on the overlapping region.

[0177] The piezoelectric layer 131 may be formed on one surface of the first electrode, and longitudinally cut outside the overlapping region as the first electrode 121. However, the piezoelectric layer 131 may be formed longitudinally cut before the first electrode 121 so as not to cover the longitudinal surface of the first electrode 121.

[0178] The second electrode 141 can extend along the longitudinal surface of the piezoelectric layer 131 toward the first electrode 121.

[0179] In the following text, in order to distinguish the features in the manufacturing methods of acoustic resonators according to the various embodiments, the parts related to the features will be described.

[0180] Figure 9 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a first embodiment of the present invention.

[0181] refer to Figure 9The method for manufacturing an acoustic resonator according to the first embodiment of the present invention (S100) may include: forming a first cavity (S110); forming a sacrificial layer (S120); forming a first electrode (S130); forming a spacer (S131); forming a piezoelectric layer (S140); forming a sacrificial layer (S150); etching the piezoelectric layer (S160); forming a second electrode (S170); forming a pad (S180); and releasing the cavity (S190).

[0182] refer to Figure 2 and Figure 9 The method for manufacturing an acoustic resonator according to the first embodiment of the present invention (S100) may include: forming a first spacer 122 of a first inter-electrode cavity to cover the longitudinally cut edge region of the first electrode 121 (S131).

[0183] After the piezoelectric layer 131 is formed (S140), a sacrificial layer (S150) for forming the second cavity 142 and the third cavity 143 can be formed.

[0184] Similar to the first electrode 121, the piezoelectric layer 131 can be longitudinally cut during etching (S160) so as not to cover the longitudinally cut edges of the first electrode 121. The longitudinal surface of the piezoelectric layer 131 can be formed as a bevel.

[0185] The second electrode 141 can extend along the longitudinal surface of the piezoelectric layer 131 toward the first electrode 121 (S170).

[0186] When the first spacer 122 is removed by the cavity release (S190), a first interpole cavity can be formed at the location of the first spacer.

[0187] The third cavity 143 and the first spacer 122 of the first inter-electrode cavity, or a filling gas such as air, can be formed to overlap each other through a gap G1 in the outer region based on another edge E2 of the first cavity 112. The third cavity 143 on the gap G1 overlaps with the first inter-electrode cavity 122, thus increasing the quality factor of the active region.

[0188] Figure 10 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a second embodiment of the present invention.

[0189] refer to Figure 10The method for manufacturing an acoustic resonator according to a second embodiment of the present invention (S200) may include: forming a first cavity (S210); forming a sacrificial layer (S220); forming a first electrode (S230); forming a spacer (S231); forming a piezoelectric layer (S240); etching the piezoelectric layer (S250); forming the sacrificial layer and the spacer (S260); forming a second electrode (S270); forming a pad (S280); and releasing the cavity (S290).

[0190] According to a second embodiment of the present invention, a second sacrificial layer and a second inter-electrode cavity 244 may be formed above the piezoelectric layer 231 (S260). The second inter-electrode cavity 244 is filled with a dielectric material and is referred to as a second spacer 244. The second spacer 244 of the second inter-electrode cavity 244 is formed to contact the second electrode 241 and to reduce the electrical loss of the second electrode 241 due to the dielectric constant of the dielectric material.

[0191] Figure 11 This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a third embodiment of the present invention.

[0192] refer to Figure 11 The method for manufacturing an acoustic resonator according to the third embodiment of the present invention (S300) may include: forming a first cavity 312 (S310); forming a sacrificial layer (S320); forming a first electrode 320 (S330); forming a piezoelectric layer 331 (S340); etching the piezoelectric layer 331 (S350); forming a sacrificial layer (S360); forming a second electrode 341 (S370); forming pads 361 and 362 corresponding to the metal pattern layer (S380); and cavity release (S390).

[0193] According to the third embodiment of the present invention, the piezoelectric layer 331 may include a first portion and a second portion due to the valley-shaped etched region formed thereon, the overlapping region belonging to the first portion, and the second portion not in contact with the first electrode (S350).

[0194] The method for manufacturing an acoustic resonator according to a third embodiment of the present invention may include forming a sacrificial region for forming cavities between the wing region of the piezoelectric layer 331 and the bridge region of the second electrode 341, respectively (S360).

[0195] The second region 341 may include an extension region 341a, which is formed to penetrate at least partially into a virtual piezoelectric layer extending from the longitudinally cut piezoelectric layer 331. The extension region 341a has a shape resembling the peaks and valleys of folds in geological formations (S370).

[0196] Figure 12This is a flowchart illustrating a method for manufacturing an acoustic resonator according to a fourth embodiment of the present invention.

[0197] refer to Figure 12 The method for manufacturing an acoustic resonator according to the fourth embodiment of the present invention (S400) may include: forming a first cavity (S410); forming a sacrificial layer (S420); forming a first electrode (S430); forming a sacrificial layer (S431); forming a piezoelectric layer (S440); etching the piezoelectric layer (S450); forming a sacrificial layer (S460); forming a second electrode (S470); forming a pad (S480); and releasing the cavity (S490).

[0198] According to the fourth embodiment of the present invention, such as Figure 7 As shown, a second sacrificial layer can be formed to create a fourth cavity 444 (S431) corresponding to the height difference d between the first electrode 420 and the second electrode 441 based on the lowermost surface. The fourth cavity 444 can be formed in the longitudinal surface of the first electrode 420, the second electrode 441, and the second portion 431b of the piezoelectric layer.

[0199] After the second sacrificial layer is formed, a piezoelectric layer is formed and then etched. The piezoelectric layer 431 can be divided into a first part 431a and a second part 431b, with a valley-shaped etched region between them.

[0200] The second electrode 441 may include a second cavity 442 formed by a wing region near one edge of the first cavity 412 and a third cavity 443 formed by a bridge region near its other edge.

[0201] Furthermore, the second electrode 441 may extend in a V-shape or U-shape over the etched area along the shape of the valley-shaped piezoelectric layer 431 toward the first electrode 420 (S470).

[0202] The first cavity 412, the second cavity 442, the third cavity 443, and the fourth cavity 444 included in the substrate 111 can be released by cavity release (S490). In particular, the extended third cavity 443 and the fourth cavity 444 can suppress the occurrence of parasitic capacitance between the first electrode 420 and the second electrode 441 that are close to each other.

[0203] According to an embodiment of the present invention, the acoustic resonator 100 can reduce the electrical loss of the electrodes by setting metal patterned layers 161 and 162 and increasing the thickness of the second electrode 141.

[0204] Furthermore, the quality factor can be increased by using a resonance formed by a wing region formed near one edge of the overlapping region and a bridge region formed near the other edge to lock the transverse wave escaping from the active region (i.e., the overlapping region of the second electrode 141).

[0205] As described above, according to one embodiment of the present invention, the increased electrical loss of the thin-film electrode, which has been identified as a problem, can be resolved.

[0206] In addition, it can suppress the occurrence of parasitic capacitance caused by electrodes arranged close to each other.

[0207] Furthermore, the quality factor can be increased by addressing the increased resistance caused by the thin-film electrode.

[0208] Although various exemplary embodiments of the present invention have been described above by way of example, the above description of various embodiments is merely exemplary, and various modifications or equivalents of the present invention can be made based on the above description, which will be obvious to those skilled in the art.

[0209] Furthermore, since the present invention can be implemented in many other forms, it is not limited to the above description. The above description is intended to complete the disclosure of the present invention and provide complete information on the scope of the invention to those skilled in the art. It should be noted that the present invention is defined only by the claims.

Claims

1. An acoustic resonator, comprising: A substrate, comprising a first cavity; A first electrode is formed above the substrate; A piezoelectric layer is formed on one surface of the first electrode; and A second electrode is formed on one surface of the piezoelectric layer. The piezoelectric layer includes a longitudinal surface, which does not contact the longitudinal surface of the first electrode. The first inter-electrode cavity extends at least partially between the longitudinal surface of the first electrode and the longitudinal surface of the piezoelectric layer. The piezoelectric layer includes an end face extending from one surface of the piezoelectric layer, the end face partially defining a longitudinal surface of the piezoelectric layer, and the end face being spaced apart from the longitudinal surface of the first electrode by the first inter-electrode cavity. The second electrode contacts the longitudinal surface of the piezoelectric layer and extends to and contacts the first inter-electrode cavity, the first inter-electrode cavity at least partially separating the first electrode from the piezoelectric layer. The piezoelectric layer is formed by longitudinally cutting at a position where it does not contact the longitudinal surface of the first electrode.

2. The acoustic resonator of claim 1, wherein the first interelectrode cavity covers the longitudinal surface of the first electrode and a portion of the substrate, and contacts the bottom surface to which the second electrode extends.

3. The acoustic resonator according to claim 1 further includes a second inter-electrode cavity, the second inter-electrode cavity at least partially separating the second electrode from the piezoelectric layer.

4. The acoustic resonator of claim 1, wherein the second electrode includes a wing region having a second cavity between the second electrode and the piezoelectric layer, and the wing region is formed such that the second cavity is closed.

5. The acoustic resonator of claim 1, wherein the second electrode comprises a wing region on one side and a bridge region on the other side, the wing region having a second cavity, and the bridge region having a third cavity between the second electrode and the piezoelectric layer, and The second cavity, the third cavity, and the first interpole cavity are filled with air.

6. The acoustic resonator of claim 1, wherein the first electrode and the piezoelectric layer comprise overlapping regions corresponding to one edge to the other edge of the first cavity, and The second electrode is formed to be thicker in the extended region than in the overlapping region.

7. The acoustic resonator of claim 1, wherein the second electrode has a thickness extending in a V-shape or U-shape according to the shape of the longitudinal surface of the piezoelectric layer.

Images