Air gap FBAR

Abstract

The air-gap diaphragm acoustic resonator (FBAR) according to the present invention may include: a substrate having an air gap on its upper surface; a lower electrode formed on the substrate; a piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer; a protective layer formed on the upper electrode; and a beam structure extending in an arched shape from one side of the upper electrode to define a space between the upper electrode and the piezoelectric layer, wherein one end of the beam structure is in contact with the piezoelectric layer.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0031326, filed with the Korean Intellectual Property Office on March 10, 2021, under 35 USC § 119(a), the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] The following description relates to film bulk acoustic resonators (FBARs) used in filters and duplexers for communication in the radio frequency (RF) band, and more specifically, to air-gap FBARs. Background Technology

[0004] Mobile communication technology requires a wide variety of radio frequency (RF) components that can efficiently transmit information within a limited bandwidth. In particular, RF filters are one of the key components in mobile communication technology. These filters are used to filter out countless waves in the air, allowing users to select or transmit the desired signals, thus achieving high-quality communication.

[0005] Currently, wireless communication RF filters are typically dielectric filters or surface acoustic wave (SAW) filters. Dielectric filters offer high dielectric constant, low insertion loss, high-temperature stability, and robustness against vibration and shock. However, dielectric filters have limitations in miniaturization and application in monolithic microwave integrated circuits (MMICs), which is a trend in recent technological developments. On the other hand, SAW filters offer small size, ease of signal processing, simplified circuitry, and can be mass-produced using semiconductor processes. Furthermore, compared to dielectric filters, SAW filters offer high side rejection in the passband, enabling them to transmit and receive high-quality information. However, using traditional interdigital transducers (IDTs) in SAW filters limits their linewidth because the manufacturing process involves exposure to ultraviolet (UV) light. Currently, the linewidth of such SAW filters is limited to around 0.5 μm. Therefore, SAW filters cannot cover high-frequency bands, for example, above 5 GHz. Moreover, integrating SAW filters with MMIC structures onto a semiconductor substrate as a single chip remains challenging.

[0006] To overcome the aforementioned limitations and problems, a membrane acoustic resonator (FBAR) filter has been proposed, in which the frequency control circuit can be fully integrated as an MMIC along with other active devices on an existing Si or GaAs semiconductor substrate.

[0007] FBARs are low-cost, small-size thin-film devices that can be designed to have high Q factors. Therefore, FBAR filters can be used in wireless communication devices across a wide frequency range, from 900 MHz to 10 GHz, as well as in military radar. FBARs can be an order of magnitude smaller than dielectric or lumped constant (LC) filters and have very low insertion loss compared to SAW filters. FBARs can be integrated with MMICs, providing filters with both high stability and high Q factors. For MMICs requiring high stability and high Q factors, FBARs may be the most suitable component.

[0008] FBAR filters incorporate piezoelectric dielectric materials, such as ZnO, AlN, or any suitable material with high acoustic velocities. The piezoelectric material can be deposited directly onto a Si or GaAs semiconductor substrate, for example, via RF sputtering. The resonance of the FBAR filter originates from the piezoelectric properties of the piezoelectric material used therein. More specifically, the FBAR filter includes a piezoelectric film disposed between two electrodes and generates bulk acoustic waves to induce resonance.

[0009] To date, various studies have been conducted on FBAR structures. In the case of film-type FBARs, a silicon oxide film (SiO2) is deposited on a substrate, and a film layer is formed on the opposite side of the substrate through a cavity formed by isotropic etching. Next, a lower electrode is formed on top of the silicon oxide film, and a piezoelectric material is deposited on top of the lower electrode by RF magnetron sputtering to form a piezoelectric layer, and an upper electrode is formed on top of the piezoelectric layer.

[0010] Due to the cavity, the film-type FBAR provides low substrate dielectric loss and low power loss. However, film-type FBARs occupy a large area due to the orientation of the silicon substrate and are easily damaged in subsequent packaging processes due to their low structural stability, resulting in low yield. Therefore, recently, air-gap and Bragg reflector-type FBARs have been developed to reduce losses caused by the film and simplify device manufacturing processes.

[0011] Bragg reflector-type FBARs are formed by vapor deposition in the order of reflective layer, lower electrode, piezoelectric layer, and upper electrode. Here, the reflective layer is formed by alternating vapor deposition on a substrate material with a large elastic impedance difference. Since all the elastic acoustic wave energy passing through the piezoelectric layer is reflected at the reflective layer instead of being transferred to the substrate, this structure of Bragg reflector-type FBAR element can effectively generate resonance. Bragg reflector-type FBARs have a robust structure, unaffected by bending stress, but it is difficult to form at least four precisely thick reflective layers for total internal reflection. Furthermore, it requires significant manufacturing time and high cost.

[0012] On the other hand, a conventional air-gap FBAR, which uses an air gap instead of a reflective layer to separate the substrate from the resonant portion, is manufactured as follows: A sacrificial layer is formed by isotropic etching of the surface of a silicon substrate, and the substrate is then chemically mechanically polished (CMP). An insulating layer, a lower electrode, a piezoelectric layer, and a upper electrode are then sequentially deposited by vapor deposition, and the sacrificial layer is removed through vias to form an air gap.

[0013] In traditional FBAR structures, the piezoelectric layer is formed between the upper and lower electrodes, and these electrodes are only located in the regions where the piezoelectric layer is needed to provide the piezoelectric effect. Therefore, mechanical anchor losses are high, potentially leading to a reduction in mechanical energy.

[0014] Mo, Ru, W, etc., are used in the upper or lower electrodes to increase acoustic impedance. The skin depth of the electrode material depends on the frequency of the filter. Typically, the electrode thickness is much smaller than the skin depth, so the charged charge at the resonant point of the piezoelectric layer cannot be fully transferred through the leads, resulting in a decrease in the quality factor.

[0015] [Existing 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] This overview is provided to introduce some concepts in a simplified form, which will be further described in the embodiments below. This overview is not intended to identify key or essential features of the subject matter to be protected, nor is it intended to help determine the scope of the claimed subject matter.

[0019] The following description relates to air-gap diaphragm acoustic resonators (FBARs) that can improve resonance characteristics.

[0020] In one general aspect of the invention, an air-gap diaphragm acoustic resonator (FBAR) includes: a substrate having an air gap on its upper surface; a lower electrode formed on the substrate; a piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer; a protective layer formed on the upper electrode; and a beam structure extending dome-shaped from one side of the upper electrode to define a space between the upper electrode and the piezoelectric layer, wherein one end of the beam structure contacts the piezoelectric layer.

[0021] The beam structure can be formed above the air gap relative to a vertical virtual surface extending from the gap edge of the air gap.

[0022] The space may be filled with either air or SiO2, the density of which is lower than the density of the material constituting the upper electrode or the piezoelectric layer.

[0023] The width of one end of the beam structure in contact with the piezoelectric layer can be from 100 nm to 200 nm.

[0024] One end of the beam structure may include a first end that contacts the piezoelectric layer with a predetermined width, and a second end that extends diagonally from the first end.

[0025] The end of the protective layer may extend beyond a predetermined length from the end of the beam structure.

[0026] The air-gap FBAR may further include a conductive metal pattern layer deposited at a predetermined distance from one end of the beam structure.

[0027] A structural groove can be formed on the lower surface of the beam structure, which corresponds to the upper part of the spatial portion.

[0028] A piezoelectric groove can be formed on the upper surface of the piezoelectric layer, which corresponds to the lower part of the space.

[0029] The lower part of the space may include an inclined portion of the upper surface of the piezoelectric layer.

[0030] The edge of the lower electrode, corresponding to one end of the lower electrode, can be located within the upper surface of the air gap.

[0031] Other features and aspects will be apparent from the following embodiments, drawings and claims. Attached Figure Description

[0032] Figure 1 This is a plan view of an air-gap diaphragm acoustic resonator (FBAR) according to an embodiment of the present invention.

[0033] Figure 2 yes Figure 1 The diagram shows the vertical cross-sectional view of region AA', BB', or CC' of the air gap FBAR.

[0034] Figure 3 It is shown Figure 2 The diagram shows the working state of the air gap FBAR.

[0035] Figure 4 It is used to describe Figure 2 The figure shows the performance characteristics of the air gap FBAR.

[0036] Figure 5This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0037] Figure 6 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0038] Figure 7 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0039] Figure 8 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0040] Figure 9 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0041] Figure 10 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0042] Throughout the accompanying drawings and detailed description, unless otherwise described, the same reference numerals will be understood to refer to the same elements, features, and structures. For clarity, illustrative purposes, and convenience, the relative sizes and descriptions of these elements may be exaggerated. Detailed Implementation

[0043] In the following description, exemplary embodiments of the present invention will be illustrated in detail with reference to the accompanying drawings.

[0044] The embodiments of the present invention are provided to illustrate the invention more fully to those skilled in the art. Various modifications can be made to the following embodiments, and the scope of the invention is not limited thereto. These embodiments are provided to make this disclosure more substantial and complete, and to fully convey the concept of the invention to those skilled in the art.

[0045] The terminology used herein is for the purpose of explaining particular embodiments and is not intended to limit the invention. As used herein, the singular form may include the plural form unless the context otherwise defines. Furthermore, as used herein, the term "and / or" includes any and all combinations or plurality of associated listed items. In the following, embodiments of the invention will be described with reference to the accompanying drawings, which schematically illustrate embodiments.

[0046] Figure 1 This is a plan view of an air-gap diaphragm acoustic resonator (FBAR) according to an embodiment of the present invention. Figure 2 yes Figure 1 The diagram shows a vertical cross-sectional view of region AA', BB', or CC' of the air-gap FBAR. Similar reference numerals used herein refer to similar elements having the same or similar function or structure.

[0047] Reference Figure 2 The air gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300A, an upper electrode 400A, a beam structure 500A, and a protective layer 600A.

[0048] In an air-gap FBAR, when a signal is applied from the outside into the space between the lower electrode 200A and the upper electrode 400A, a portion of the electrical energy input into the space between the two electrodes is converted into mechanical energy according to the piezoelectric effect. During the process of converting mechanical energy back into electrical energy, resonance occurs at a natural vibration frequency that depends on the thickness of the piezoelectric layer 300A.

[0049] The substrate 100, which serves as the semiconductor substrate, can be a conventional silicon wafer, preferably a high-resistivity silicon substrate (HRS). An insulating layer (not shown) can be formed on the upper surface of the substrate 100. As the insulating layer, a thermal oxide film that can be easily grown on the substrate 100 can be used, or optionally, an oxide film or a nitride film using a conventional deposition process such as chemical vapor deposition can be used.

[0050] The air gap 110 is formed as follows: After forming a cavity in the substrate 100, an insulating layer is formed in the cavity, a sacrificial layer is deposited on the insulating layer, planarization is performed by etching, and then the sacrificial layer is removed to form the air gap 110. Here, the sacrificial layer is made of a material with excellent surface roughness that allows for easy formation and removal of the sacrificial layer, such as polycrystalline silicon or ZnO. For example, tetraethyl orthosilicate (TEOS) or polycrystalline silicon can be used as the sacrificial layer. TEOS or polycrystalline silicon has excellent surface roughness and is easy to form and remove. Specifically, the sacrificial layer can be removed by dry etching in a subsequent process.

[0051] The lower electrode 200A is formed on the substrate 100, wherein a sacrificial layer exists in the air gap 110. The lower electrode 200A is formed by depositing a predetermined material on the substrate 100 and then patterning it. The material used for the lower electrode 200A is a general conductive material, such as a metal, and preferably, it can be one of aluminum (Al), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), palladium (Pd), and molybdenum (Mo). The thickness of the lower electrode 200 can be from 10 nm to 1000 nm.

[0052] The lower electrode 200A can be patterned on the insulating layer and sacrificial layer of the substrate 100. The lower electrode 200A is formed above the air gap 110 of the substrate 100 and can have a shape that surrounds the entire upper portion of the air gap 110. In this case, the lower electrode edge BE corresponding to one end of the lower electrode 200A can be formed at a predetermined distance or more from the gap edge GE of the air gap 110. In this case, the lower electrode edge BE formed on the substrate 100 can be formed to be inclined along a diagonal direction.

[0053] A piezoelectric layer 300A is formed on the lower electrode 200A. The piezoelectric layer 300A can be formed by depositing a piezoelectric material on the lower electrode 200A and then patterning it. Common piezoelectric materials include aluminum nitride (AlN) or zinc oxide (ZnO). Deposition methods include radio frequency (RF) magnetron sputtering and evaporation. The thickness of the piezoelectric layer 300A can range from 5 nm to 500 nm.

[0054] The upper electrode 400A is formed on the piezoelectric layer 300A. The upper electrode 400A can be formed by depositing and patterning a metal film for the upper electrode on the piezoelectric layer 300A. The upper electrode 400A can use the same material, the same deposition method, and the same patterning method as the lower electrode 200A. The thickness of the upper electrode 400A can be from 5 nm to 1000 nm. At the end of the upper electrode 400A, a raised frame thicker than the active region is formed around the resonator to reduce transverse vibration modes, thereby increasing the Q value.

[0055] The beam structure 500A extends in an arched shape from one side of the upper electrode 400A to define the space 500A-1 between the upper electrode 400A and the piezoelectric layer 300A. At this time, one end 500A-2 of the beam structure 500A is in contact with or deposited on the piezoelectric layer 300A.

[0056] like Figure 2 As shown, beam structure 500A includes regions represented by length L1 and length L2, respectively. The region of beam structure 500A represented by length L1 has an arched shape.

[0057] One end 500A-2 of the beam structure 500A corresponds to the frame of the beam structure 500A and can be positioned above the air gap 110 relative to the vertical virtual surface extending from the gap edge GE of the air gap 110. Since one end 500A-2 of the beam structure 500A is in contact with or deposited on the piezoelectric layer 300A, it is used to prevent energy from flowing out to the side surface.

[0058] In addition, such as Figure 2 As shown, the length 2 of the width of one end 500A-2 of the beam structure 500A that is in contact with or deposited on the piezoelectric layer 300A is preferably 50 nm to 200 nm. In this case, as the length L2 of the width of the end 500A-2 in contact with the piezoelectric layer 300A increases, the Q-value performance may decrease. However, in terms of performance and robustness, the structure in contact with the piezoelectric layer 300A at one end is superior to the structure where that end is not in contact with the piezoelectric layer 300A.

[0059] The space 500A-1 is formed between the lower surface of the beam structure 500A and the upper surface of the piezoelectric layer 300A. The space 500A-1 may be filled with either air or SiO2, the density of which is lower than the density of the material constituting the upper electrode 400A or the piezoelectric layer 300A.

[0060] After depositing a sacrificial layer on the piezoelectric layer 300A, a conductive material for forming the upper electrode 400A and the beam structure 500A is deposited on the piezoelectric layer 300A, including the sacrificial layer. The sacrificial layer is then removed to form the beam structure 500A. Here, the sacrificial layer is made of a material such as polycrystalline silicon, tetraethyl orthosilicate (TEOS), or phosphosilicate glass (PSG), which has excellent surface roughness and allows for easy formation and removal. Alternatively, the beam structure 500A can be formed by depositing SiO2 instead of the sacrificial layer, followed by the deposition of the conductive material.

[0061] The height of the space section 500A-1 can be less than half the thickness of the upper electrode 400A. The thickness of the upper electrode 400A can be varied for each region using the beam structure 500A. By ensuring that the height of the space section 500A-1 is less than half the thickness of the upper electrode 400A, a minimum thickness is ensured that heat generated internally can easily escape. Furthermore, the length L1 of the horizontal width of the space section 500A-1 can be from 1 μm to 5 μm.

[0062] The beam structure 500A can be formed around a virtual surface extending vertically from the gap edge GE of the air gap element 110. Specifically, as Figure 2 As shown, the beam structure 500A can be positioned above the air gap 110 relative to the vertical virtual surface extending from the gap edge GE of the air gap 110. Therefore, the beam structure 500A can prevent energy from flowing out to the side.

[0063] In beam structure 500A, the vertical cross-section structure of the space portion 500A-1 forming the arched space can have a trapezoidal structure. (Refer to...) Figure 2 The vertical cross-sectional structure of the space section 500A-1 has a quadrilateral structure, and more specifically, a trapezoidal structure in which the horizontal width of the lower surface is longer than the horizontal width of the upper surface. However, the trapezoidal structure is exemplary, and the upper surface may have a curved shape instead of a horizontal surface.

[0064] A protective layer 600A is formed on the upper electrode 400A and the beam structure 500A. The protective layer 600A serves as a cover to cover and protect the lower electrode 200A, the piezoelectric layer 300A, the upper electrode 400A, and the beam structure 500A. One end of the protective layer 600A corresponds to one end 500A-2 of the beam structure 500A. (Example...) Figure 2As shown, a recessed frame is formed by reducing the thickness of the protective layer preceding the front end of the raised frame. The recessed frame is used to reduce spurious modes occurring in the 50 to 60 MHz frequency range. Spurious modes typically occur shortly before the resonant frequency in a bulk acoustic wave (BAW) resonator. This recessed frame can also be disposed on the upper electrode.

[0065] Figure 3 It is shown Figure 2 The diagram shown illustrates the operating state of an air-gap FBAR. Figure 4 It is a description Figure 2 The graph shows the performance characteristics of the air-gap FBAR.

[0066] Figure 4 The horizontal axis of the graph shows the total length (L1+L2) of the entire region constituting beam structure 500A, and the vertical axis represents the Q value. (Refer to...) Figure 4 Compared to existing technologies, the configuration where the beam structure 500A extends from the upper electrode 400A has the highest Q value when the length of the space section 500A-1 is close to 4.5 μm. However, even when the length of the space section 500A-1 is 2.0 μm, a higher Q value than that of a conventional cantilever FBAR is obtained.

[0067] Figure 5 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0068] Reference Figure 5 The air-gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300A, an upper electrode 400A, a beam structure 500A, and a protective layer 600B. Details regarding the components will not be described in detail. Figure 2 The same label references the components in Figure 5 The components in, and the following description will focus on the components in, and Figure 2 The components are different from other components.

[0069] The beam structure 500B extends in an arched shape from one side of the upper electrode 400A to define a space 500B-1 between the upper electrode 400A and the piezoelectric layer 300A. In this case, one end 500A-2 of the beam structure 500A is in contact with or deposited on the piezoelectric layer 300A.

[0070] One end of the beam structure 500B has a first end 500B-2 that contacts the piezoelectric layer 300A with a predetermined width, and a second end 500B-3 that extends obliquely upward from the first end 500B-2.

[0071] The length of the first end 500B-2 is preferably 100 nm to 200 nm. In addition, the second end 500B-3 extends upward relative to the horizontal plane at a predetermined angle, and the Q value can be improved due to the second end 500B-3.

[0072] A protective layer 600B is formed on the upper electrode 400A and the beam structure 500A. The protective layer 600B serves as a cover for at least partially covering and protecting the lower electrode 200A, the piezoelectric layer 300A, the upper electrode 400A, and the beam structure 500A. The protective layer 600B extends in a diagonal direction corresponding to the first end 500B-2 and the second end 500B-3, which are one end of the beam structure 500B.

[0073] Figure 6 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0074] Reference Figure 6 The air-gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300A, an upper electrode 400A, a beam structure 500A, and a protective layer 600C. Details regarding the components will not be described in detail. Figure 2 The same label references the components in Figure 6 The components in, and the following description will focus on the components in, and Figure 2 The components are different from other components.

[0075] One end of the protective layer 600C can extend beyond one end 500A2 of the beam structure 500A by a predetermined length L3. By extending the end of the protective layer 600C beyond one end 500A-2 of the beam structure 500A, the Q value can be improved.

[0076] Figure 7 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0077] Reference Figure 7 The air gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300B, an upper electrode 400A, a beam structure 500A, a protective layer 600A, and a metal pattern layer 700.

[0078] A piezoelectric layer 300B is deposited on the lower electrode 200A. The piezoelectric layer 300B does not surround the entire area of ​​the lower electrode 200A, but is deposited such that a portion of the lower electrode 200A is exposed. At this time, a metallic pattern layer 700 is formed on the area where the piezoelectric layer 300B is not deposited.

[0079] The metal pattern layer 700 is made of a conductive metal material and is formed around an air gap FBAR at a predetermined distance of 500A-2 from one end of the beam structure. Here, the metal forming the metal pattern layer 700 includes gold (Au), copper (Cu), aluminum (Al), and aluminum-copper alloys (AlCu). By forming the metal pattern layer 700, the Q value can be further improved.

[0080] Figure 8 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0081] Reference Figure 8 The air gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300A, an upper electrode 400A, a beam structure 500C, and a protective layer 600D.

[0082] The beam structure 500C extends in an arched shape from one side of the upper electrode 400A to define the space 500C-1 between the upper electrode 400A and the piezoelectric layer 300A. In this case, one end 500C-2 of the beam structure 500C is in contact with or deposited on the piezoelectric layer 300A.

[0083] A structural groove 500C-11 is formed on the lower surface of the beam structure 500C, which corresponds to the upper part of the spatial portion 500C-1. The structural groove 500C-11 corresponds to the upper protrusion of the spatial portion 500C-1.

[0084] A protective layer 600D is formed on the upper electrode 400A and the beam structure 500A. The upper surface of the protective layer 600D may have a protective layer groove 600D-1 formed at a position symmetrical to the structural groove 500C-11 of the beam structure 500C. By forming the structural groove 500C-11 and the protective layer groove 600D-1, the Q value can be improved.

[0085] Figure 9 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0086] Reference Figure 9 The air gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200A, a piezoelectric layer 300C, an upper electrode 400A, a beam structure 500D, and a protective layer 600A.

[0087] A piezoelectric layer 300C is formed on the lower electrode 200A. In this case, a piezoelectric groove 300C-1 is formed on the upper surface of the piezoelectric layer 300C, which corresponds to the lower part of the beam structure 500D. The piezoelectric groove 300C-1 corresponds to the lower protrusion of the beam structure 500D.

[0088] The beam structure 500D includes a space 500D-1 formed between the upper and lower surfaces of the piezoelectric layer 300C. The space 500D-1 can be formed in the piezoelectric layer 300C on which piezoelectric grooves 300C-1 are formed. By forming the piezoelectric grooves 300C-1, the Q value can be improved.

[0089] Figure 10 This is a cross-sectional view of an air-gap FBAR according to another embodiment of the present invention.

[0090] Reference Figure 10 The air gap FBAR includes a substrate 100, an air gap portion 110, a lower electrode 200B, a piezoelectric layer 300D, an upper electrode 400A, a beam structure 500E, and a protective layer 600A.

[0091] A lower electrode 200B is formed on the substrate 100, wherein a sacrificial layer exists in the air gap 110. In this case, the lower electrode edge BE corresponding to one end of the lower electrode 200B can be formed to be spaced at a predetermined distance or more from the gap edge GE of the air gap 110, and can be located within the upper surface of the air gap 110. The lower electrode edge BE formed on the substrate 100 can be formed to be inclined in a diagonal direction.

[0092] A piezoelectric layer 300D is formed on the lower electrode 200B. In this case, the piezoelectric layer 300D is formed as an inclined surface corresponding to the inclined surface of the lower electrode edge BE of the lower electrode 200B, and the height of the piezoelectric layer 300D changes accordingly.

[0093] The beam structure 500E extends in an arched shape from one side of the upper electrode 400A to define the space 500E-1 between the upper electrode 400A and the piezoelectric layer 300D. In this case, one end 500E-2 of the beam structure 500E contacts or is deposited on one end of the piezoelectric layer 300D at a different height.

[0094] At this time, the lower part of the space portion 500E-1 includes an inclined portion on the upper surface of the piezoelectric layer 300D. Since the lower part of the space portion 500E-1 includes an inclined structure, the Q value can be improved.

[0095] The air-gap FBAR described above has a structure in which the RF signal input to the upper electrode 400 is output to the lower electrode 200 through the piezoelectric layer 300. Since the piezoelectric layer 300 has a constant resonant frequency, only the RF signal with the frequency of the input RF signal that matches the frequency of the piezoelectric layer 300 is output, and other frequencies are suppressed. Therefore, by configuring the lower electrode 200, piezoelectric layer 300, and upper electrode 400 as described above, an FBAR filter with a constant center frequency and bandwidth can be realized.

[0096] According to the present invention, a substrate, a lower electrode, a piezoelectric layer, and an upper electrode are provided, and a beam structure is further included that defines a space between a lower surface of one end of the upper electrode and an upper surface of the piezoelectric layer, wherein one end of the beam structure is in contact with the piezoelectric layer. Therefore, transverse waves can be prevented from escaping from the active region, thereby improving the quality factor.

[0097] Numerous examples have been described above. However, it should be understood that various modifications can be made. For example, suitable results may be achieved if the described techniques and / or components in the described system, architecture, device, or circuit are combined in different ways and / or replaced or supplemented by other components or their equivalents. Therefore, other embodiments are within the scope of the appended claims.

Claims

1. A FBAR (Fiber Optic Acoustic Resonator) with an air gap, characterized in that, include: A substrate having an air gap on its upper surface; A lower electrode is formed on the substrate; A piezoelectric layer is formed on the lower electrode; The upper electrode is formed on the piezoelectric layer; A protective layer is formed on the upper electrode; as well as A beam structure on which the protective layer is formed, and which extends in an arched shape from one side of the upper electrode to define the space between the upper electrode and the piezoelectric layer. One end of the beam structure is in contact with the piezoelectric layer. The end of the protective layer extends beyond a predetermined length from the end of the beam structure.

2. The air gap FBAR according to claim 1, wherein the beam structure is formed above the air gap relative to a vertical virtual surface extending from the gap edge of the air gap.

3. The air gap FBAR according to claim 1, wherein the space is filled with one of air and SiO2, and the density of the filled air or SiO2 is lower than the density of the material constituting the upper electrode or the piezoelectric layer.

4. The air-gap FBAR according to claim 1, wherein the width of one end of the beam structure in contact with the piezoelectric layer is 50 nm to 200 nm.

5. The air gap FBAR according to claim 4, wherein the height of the space is less than 1 / 2 of the thickness of the upper electrode, and the length of the horizontal width of the space is 1 μm to 5 μm.

6. The air-gap FBAR according to claim 1, further comprising a conductive metal pattern layer deposited at a predetermined distance from one end of the beam structure.

7. The air gap FBAR according to claim 1, wherein a structural groove is formed on the lower surface of the beam structure, the lower surface of the beam structure corresponding to the upper part of the space portion.

8. The air gap FBAR according to claim 1, wherein a piezoelectric groove is formed on the upper surface of the piezoelectric layer, the upper surface of the piezoelectric layer corresponding to the lower part of the space portion.

9. The air gap FBAR according to claim 1, wherein the lower part of the space includes an inclined portion of the upper surface of the piezoelectric layer.

10. The air-gap FBAR according to claim 9, wherein the edge of the lower electrode corresponding to one end of the lower electrode is located within the upper surface of the air gap.

Images