Acoustic resonator and method of manufacturing the same, and filter including the same

Abstract

The present disclosure provides an acoustic resonator and a manufacturing method thereof, and a filter including the acoustic resonator. The acoustic resonator according to the present disclosure includes a substrate provided with a reflection member inside or on a surface thereof, and a piezoelectric stack provided above the substrate to overlap the reflection member to constitute an effective resonance region, the piezoelectric stack including a lower electrode, a piezoelectric layer, and an upper electrode provided in sequence in a vertical direction, wherein a cavity entirely wrapped by the upper electrode and / or the lower electrode is formed at a position corresponding to an edge of the effective resonance region in the upper electrode and / or the lower electrode. The acoustic resonator and the manufacturing method thereof according to the present disclosure can form a cavity around the effective resonance region of the acoustic resonator to confine resonance energy in the effective resonance region, thereby reducing loss of the resonance energy and improving a quality factor of the acoustic resonator.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of semiconductor technology, and in particular, the present disclosure relates to an acoustic resonator and a manufacturing method thereof, and a filter comprising the acoustic resonator. BACKGROUND

[0002] Resonators have been widely used in many fields. For example, in the field of wireless communication, resonators at radio frequency (RF) and microwave frequencies are used as filters to improve the reception and transmission of signals. With the need for miniaturization and micromation of communication devices, resonators based on the piezoelectric effect have been proposed. In resonators based on the piezoelectric effect, an acoustic resonance mode is generated in a piezoelectric material, in which acoustic waves are converted into radio waves.

[0003] Different types of acoustic resonators can be used depending on the application, such as film bulk acoustic resonators (FBAR), solidly mounted resonators (SMR), coupled resonator filters (CRF), stacked acoustic resonators (SBAR), and dual bulk acoustic resonators (DBAR). Currently, film bulk acoustic resonators have the advantages of small size, high frequency, large power capacity, high sensitivity, etc., so that in addition to being widely used in the field of wireless communication, film bulk acoustic resonators are also applied to the fields of biosensing, medical measurement, etc.

[0004] The main structure of a film bulk acoustic resonator is a "sandwich structure" composed of a lower electrode-piezoelectric layer-upper electrode. The film bulk acoustic resonator converts an input electrical signal into acoustic vibration by applying an electrical signal between the upper electrode and the lower electrode using the inverse piezoelectric effect, and then converts the acoustic vibration into an electrical signal output by the piezoelectric effect. Ideally, the film bulk acoustic resonator only excites longitudinal modes in the thickness direction, such as TE modes, which are longitudinal mechanical waves having a propagation vector along the direction of propagation. The TE modes ideally propagate along the thickness direction of the piezoelectric layer in the film bulk acoustic resonator.

[0005] However, in addition to the desired TE modes, there are also transverse modes, such as Rayleigh-Lamb modes, in the film bulk acoustic resonator. The Rayleigh-Lamb modes are mechanical waves whose propagation vector is perpendicular to the direction of the TE modes. These transverse modes propagate in the horizontal direction along the surface of the piezoelectric layer. Therefore, the transverse modes adversely affect the quality factor (Q) of the acoustic resonator. Specifically, the energy of the Rayleigh-Lamb modes is lost at the lateral boundaries of the acoustic resonator, resulting in a loss of energy of the desired longitudinal modes, thus reducing the quality factor Q. SUMMARY

[0006] A brief summary of the present disclosure is presented below in order to provide a basic understanding of some aspects of the present disclosure. It should be appreciated that this summary is not an exhaustive overview of the present disclosure, nor is it intended to determine key or essential parts of the present disclosure or identify critical aspects of the present disclosure. Rather, the purpose of this summary is merely to present some concepts of the present disclosure in a simplified form as a prelude to the more detailed description presented later.

[0007] An object of the present disclosure is to provide an acoustic resonator capable of improving a quality factor, a manufacturing method thereof, and a filter including the same.

[0008] According to an aspect of the present disclosure, there is provided an acoustic resonator, including: a substrate provided with a reflection member inside or on a surface thereof; and a piezoelectric stack provided above the substrate to overlap the reflection member to constitute an effective resonance region, the piezoelectric stack including a lower electrode, a piezoelectric layer, and an upper electrode provided in this order in a vertical direction, wherein a cavity entirely wrapped by the upper electrode and / or the lower electrode is formed at a position corresponding to an edge of the effective resonance region in the upper electrode and / or the lower electrode.

[0009] According to an embodiment of the present disclosure, the acoustic resonator further includes a seed layer provided between the substrate and the lower electrode.

[0010] According to an embodiment of the present disclosure, the reflection member includes a reflection cavity or a Bragg reflector.

[0011] According to an embodiment of the present disclosure, the substrate is made of a material selected from at least one of silicon, silicon carbide, and gallium arsenide.

[0012] According to an embodiment of the present disclosure, each of the lower electrode and the upper electrode is made of a conductive material selected from at least one of molybdenum, tungsten, aluminum, a platinum / titanium stack, and a gold / chromium stack.

[0013] According to an embodiment of the present disclosure, the piezoelectric layer includes a wurtzite structure material or a perovskite structure material.

[0014] According to an embodiment of the present disclosure, a protrusion is provided in an upper surface and / or a lower surface of the upper electrode and / or the lower electrode at a position corresponding to the edge of the effective resonance region, and the cavity is formed in the protrusion.

[0015] According to an embodiment of the present disclosure, a cavity entirely wrapped by the piezoelectric layer is formed in the piezoelectric layer at a position corresponding to the edge of the effective resonance region.

[0016] According to another aspect of the present disclosure, there is provided a manufacturing method of an acoustic resonator, including: forming a reflection member inside or on a surface of a substrate; and sequentially forming, in a vertical direction above the substrate, a lower electrode, a piezoelectric layer, and an upper electrode which overlap the reflection member, the lower electrode, the piezoelectric layer, and the upper electrode constituting a piezoelectric stack, the piezoelectric stack overlapping the reflection member to constitute an effective resonance region, wherein the forming of the lower electrode and / or the upper electrode includes forming a cavity in the upper electrode and / or the lower electrode at a position corresponding to an edge of the effective resonance region, the cavity being entirely wrapped by the upper electrode and / or the lower electrode.

[0017] According to an embodiment of the present disclosure, the manufacturing method further includes forming a seed layer between the substrate and the lower electrode.

[0018] According to an embodiment of the present disclosure, the reflection member includes a reflection cavity or a Bragg reflector.

[0019] According to an embodiment of the present disclosure, the forming of the lower electrode and / or the upper electrode includes forming a protrusion in an upper surface and / or a lower surface of the upper electrode and / or the lower electrode at a position corresponding to the edge of the effective resonance region, the cavity being formed in the protrusion.

[0020] According to an embodiment of the present disclosure, the manufacturing method further includes forming a cavity in the piezoelectric layer at a position corresponding to the edge of the effective resonance region, the cavity being entirely wrapped by the piezoelectric layer.

[0021] According to still another aspect of the present disclosure, there are also provided bulk acoustic filters including the above-described acoustic resonator, and duplexers or multiplexers including the bulk acoustic filters.

[0022] According to the acoustic resonator and the manufacturing method thereof of the present disclosure, by forming a cavity in the upper electrode and / or the lower electrode at a position corresponding to an edge of an effective resonance region, the cavity is formed around the effective resonance region of the acoustic resonator to confine resonance energy in the effective resonance region, thereby reducing loss of the resonance energy and improving a quality factor of the acoustic resonator. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure.

[0024] Figure 1 A cross-sectional view of an acoustic resonator according to a first embodiment of the present disclosure is shown.

[0025] Figure 2 An enlarged cross-sectional view of an upper electrode of the acoustic resonator according to the first embodiment of the present disclosure is shown.

[0026] Figure 3 A comparative view of vibration displacement outside the effective resonance region of an acoustic resonator according to the prior art and an acoustic resonator according to the first embodiment of the present disclosure is shown.

[0027] Figure 4 A comparative view of impedance of an acoustic resonator according to the prior art and an acoustic resonator according to the first embodiment of the present disclosure is shown.

[0028] Figure 5 A cross-sectional view of an acoustic resonator according to the second embodiment of the present disclosure is shown.

[0029] Figure 6 An enlarged cross-sectional view of the upper electrode of an acoustic resonator according to the second embodiment of the present disclosure is shown.

[0030] Figure 7 A cross-sectional view of an acoustic resonator according to the third embodiment of the present disclosure is shown.

[0031] Figure 8 A cross-sectional view of an acoustic resonator according to the fourth embodiment of the present disclosure is shown.

[0032] Figure 9 A cross-sectional view of an acoustic resonator according to the fifth embodiment of the present disclosure is shown.

[0033] Figure 10 A flowchart of a manufacturing method of an acoustic resonator according to an embodiment of the present disclosure is shown.

[0034] Figure 11 A schematic view of an acoustic filter according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0035] In this specification, it will also be understood that when an element is referred to as being "on" or "connected to" another element, it can be directly on, connected to, or coupled to the other element, or intervening elements can also be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present.

[0036] The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout. Furthermore, in the drawings, the thickness of components, the ratio between sizes and the like are exaggerated for clarity.

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the terms "an", "a", "one", and "at least one" do not exclude a plurality. For example, the singular representation "a" or "an" means "at least one" unless specified otherwise by context. "At least one of" is used to indicate one or more of the listed items can be present along with zero or one of the listed items. The term "or" means "and / or". The term "and / or" includes combinations of one or more of the associated listed items.

[0038] Furthermore, "lower", "bottom", "upper", "top", and the like, are used for description only and are not necessarily used as terms of limitation. These terms are used interchangeably with each other.

[0039] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art. Terms, such as those defined in commonly utilized dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the specification.

[0040] "Include" or "comprise" or "comprising" or "including" mean including but not limited to, and should not be interpreted as being restricted to the means listed thereafter.

[0041] Embodiments are described herein with reference to cross-sectional illustrations that are idealized embodiments of the present disclosure. Constructions, therefore, can vary from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances. It is intended that the embodiments described herein be considered as exemplary only and not as limiting the scope of the concepts of the present disclosure. Thus, although the embodiments have been described in some detail for the purpose of clarity, it is not intended that any limitation be imposed on the overall scope thereof. For example, parts shown as flat can typically have rough and / or nonlinear features. Furthermore, sharp corners can be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims presented herein.

[0042] Furthermore, in this document, the terms "acoustic resonator" and "thin-film bulk acoustic resonator" are used interchangeably.

[0043] In the following description, exemplary embodiments according to this disclosure will be described with reference to the accompanying drawings.

[0044] Figure 1 A cross-sectional view of an acoustic resonator 100 according to a first embodiment of the present disclosure is shown.

[0045] like Figure 1 As shown, the acoustic resonator 100 according to the first embodiment of the present disclosure includes: a substrate 101, on which a reflective member 102 is disposed; and a piezoelectric stack 110 disposed above the substrate 101 and overlapping with the reflective member 102 to form an effective resonant region RA. The piezoelectric stack 110 includes a lower electrode 103, a piezoelectric layer 105 and an upper electrode 104 disposed sequentially in the vertical direction.

[0046] According to embodiments of this disclosure, substrate 101 may be a semiconductor substrate such as a silicon substrate, a silicon carbide substrate, or a gallium arsenide substrate.

[0047] like Figure 1 As shown, the reflective member 102 is formed in the form of a cavity inside the substrate 101. However, those skilled in the art will recognize that although embodiments of the present disclosure are described herein with the reflective member 102 formed inside the substrate 101 as an example, the present disclosure is not limited thereto. According to embodiments of the present disclosure, the reflective member 102 may also be formed on the surface of the substrate 101.

[0048] The reflective member 102 having a cavity form can be formed on the substrate 101 using various methods known in the art. For example, according to embodiments of the present disclosure, a trench can be formed in the substrate 101 by a photolithography process, and the trench can be filled using a sacrificial material. For example, according to embodiments of the present disclosure, the sacrificial material may include phosphosilicate glass (PSG), which may include 8% phosphorus and 92% silicon dioxide. Subsequently, the cavity 102 can be formed by removing the sacrificial material from the trench.

[0049] Furthermore, those skilled in the art will recognize that although embodiments of this disclosure are described herein using a cavity-type reflective member 102 as an example, this disclosure is not limited thereto. The reflective member 102 can also be other types of reflective members, such as a Bragg reflector. According to embodiments of this disclosure, the reflective member 102 is used to reflect mechanical wave energy, thereby reducing energy loss and improving the electromechanical coupling coefficient and quality factor Q of the acoustic resonator.

[0050] like Figure 1As shown, the lower electrode 103, piezoelectric layer 105, and upper electrode 104 are sequentially disposed above the substrate 101 along the vertical direction, i.e., the y-direction, to cover the reflective member 102. Figure 1 As shown, the y-direction can be the thickness direction of the acoustic resonator 100. In the illustrated embodiment, the y-direction is the direction of the longitudinal mode of the acoustic resonator, such as the TE mode. Furthermore, in the illustrated embodiment, the x-direction is the horizontal direction along the surface direction of the acoustic resonator.

[0051] The lower electrode 103 and the upper electrode 104 may comprise conductive materials and are configured to provide an oscillating electric field along the y-direction when electrically excited. According to embodiments of this disclosure, the conductive material may include, but is not limited to, at least one of the following conductive materials: molybdenum (Mo), tungsten (W), aluminum (Al), platinum / titanium (Pt / Ti) stacks, or gold / chromium (Au / Cr) stacks. According to embodiments of this disclosure, the lower electrode 103 and the upper electrode 104 may be formed by depositing conductive materials on respective material layers and then patterning them.

[0052] According to embodiments of this disclosure, the piezoelectric layer 105 sandwiched between the lower electrode 103 and the upper electrode 104 can be formed of a piezoelectric material. For example, according to embodiments of this disclosure, the piezoelectric material may include inorganic piezoelectric (single-crystal or polycrystalline) materials or organic piezoelectric materials. The piezoelectric material may include, but is not limited to, at least one of the following piezoelectric materials: wurtzite structures, such as aluminum nitride (AlN) and zinc oxide (ZnO); perovskite structures, such as BaTiO3, Pb(Ti,Zr)O3, Li(Nb,Ta)O3, and (K,Na)NbO3; and organic piezoelectric materials, such as polyvinylidene fluoride (PVDF). According to embodiments of this disclosure, the piezoelectric layer 105 can be formed by sputtering a piezoelectric material onto the lower electrode 103.

[0053] Furthermore, according to embodiments of this disclosure, the piezoelectric layer 105 may be doped with dopant elements for adjusting the electromechanical coupling coefficient and quality factor of the piezoelectric layer 105. According to embodiments of this disclosure, the dopant element for adjusting the electromechanical coupling coefficient may be selected from at least one of Ti, Sc, Mg, Zr, Hf, Sb, Y, Sm, Eu, Er, Ta, and Cr. Furthermore, according to embodiments of this disclosure, the dopant element for adjusting the quality factor may be selected from at least one of B, Ga, and In.

[0054] According to embodiments of this disclosure, a piezoelectric stack 110 is formed by a lower electrode 103, a piezoelectric layer 105, and an upper electrode 104 stacked sequentially in a vertical direction. The area where the piezoelectric stack 110 overlaps with the reflective member 102 can form the effective resonant region RA of the acoustic resonator 100.

[0055] According to embodiments of the present disclosure, a seed layer (not shown) formed on the substrate 101 can also be included for facilitating growth of the lower electrode 103 in a subsequent process. The piezoelectric stack 110 can be disposed on the seed layer. The seed layer can be formed using the same piezoelectric material as the piezoelectric layer 105. Adding a seed layer in the acoustic resonator 100 can improve the electromechanical coupling coefficient and the quality factor Q, reduce the insertion loss, and avoid an unacceptably large thickness of the piezoelectric layer 105.

[0056] According to embodiments of the present disclosure, as shown in FIG. 1, a cavity 106 entirely wrapped by the upper electrode 104 is formed in the upper electrode 104 at a position corresponding to an edge of an active resonance area RA. According to embodiments of the present disclosure, the cavity 106 is filled with air, but the present disclosure is not limited thereto. Figure 1

[0057] Figure 2 An enlarged cross-sectional view of the upper electrode 104 of the acoustic resonator 100 according to the first embodiment of the present disclosure is shown. According to embodiments of the present disclosure, the thickness of the upper electrode 104 can be, for example, 0.12 μm to 0.3 μm, preferably 0.16 μm. The width of the cavity 106 in the x-direction can be, for example, 2 μm to 7 μm, preferably 5 μm. Further, the distance L of the cavity 106 from the edge of the upper electrode 104 can be, for example, 1 μm to 5 μm, preferably 3 μm, and the distance N of the cavity 106 from the upper and lower surfaces of the upper electrode 104 can be, for example, 0.05 μm to 0.1 μm, preferably 0.05 μm.

[0058] Since air is a good sound reflecting medium, by adding the cavity 106 filled with air in the upper electrode 104 at a position corresponding to the edge of the active resonance area RA, the acoustic impedance difference of the upper electrode 104 at the edge of the active resonance area RA can be increased, the lateral acoustic wave is reflected back to the active resonance area, thereby being able to confine the acoustic wave energy and improve the quality factor of the acoustic resonator.

[0059] Figure 3 A comparative view of the vibration displacement outside the active resonance area of an acoustic resonator according to the prior art and the acoustic resonator 100 according to the first embodiment of the present disclosure is shown.

[0060] Figure 3 (a) in FIG. 1 shows the vibration displacement outside the active resonance area of an acoustic resonator according to the prior art without a cavity in the upper electrode, while Figure 3 (b) in FIG. 1 shows the vibration displacement outside the active resonance area of the acoustic resonator 100 according to the first embodiment of the present disclosure with a cavity in the upper electrode. By Figure 3 ​A comparison between (a) and (b) shows that, compared to the acoustic resonator without a cavity structure on the upper electrode, the addition of a cavity structure at the edge of the upper electrode significantly reduces the vibration amplitude outside the effective resonance region, indicating that less acoustic wave energy leaks outside the effective resonance region. In other words, the cavity structure in the upper electrode plays a role in confining the acoustic wave energy.

[0061] Figure 4 A comparative view of the impedances of an acoustic resonator according to the prior art and an acoustic resonator 100 according to a first embodiment of the present disclosure is shown.

[0062] Figure 4 The solid line in the figure shows the impedance-frequency curve of an acoustic resonator without a cavity in the upper electrode according to the prior art, while Figure 4 The dashed line in the figure shows the impedance-frequency curve of an acoustic resonator 100 having a cavity in the upper electrode according to a first embodiment of the present disclosure. Figure 4 It can be seen that, compared to an acoustic resonator without a cavity structure on the upper electrode, adding a cavity structure at the edge of the upper electrode increases the parallel resonant impedance (Rp) by approximately 200 ohms, indicating a corresponding improvement in the quality factor. In other words, adding a cavity of appropriate size in the upper electrode at a position corresponding to the edge of the effective resonant region can improve the overall quality factor of the acoustic resonator.

[0063] Figure 5 A cross-sectional view of an acoustic resonator 200 according to a second embodiment of the present disclosure is shown. Figure 5 In and Figure 1 Components that are identical in the figures are indicated by the same reference numerals, and their corresponding descriptions are omitted. The following will only refer to... Figure 5 Acoustic resonator 200 and Figure 1 The differences between the acoustic resonators 100 are described.

[0064] like Figure 5 As shown, according to the second embodiment of this disclosure, a protrusion 208 is provided on the upper surface of the upper electrode 104 at a position corresponding to the edge of the effective resonant region RA, and a cavity 106 is formed in the protrusion 208.

[0065] Figure 6An enlarged cross-sectional view of the upper electrode 104 of an acoustic resonator 200 according to a second embodiment of the present disclosure is shown. According to the embodiment of the present disclosure, the thickness of the upper electrode 104 may be, for example, 0.12 μm to 0.3 μm, preferably 0.16 μm, and the width W of the protrusion 208 in the x-direction may be, for example, 5 μm to 15 μm, preferably 10 μm, and the height H in the y-direction may be, for example, 0.06 μm to 0.15 μm, preferably 0.1 μm. Furthermore, the height of the cavity 106 in the y-direction may be, for example, 0.02 μm to 0.25 μm, preferably 0.06 μm, and the width in the x-direction may be, for example, 2 μm to 7 μm, preferably 5 μm. Furthermore, the distance L between the cavity 106 and the edge of the upper electrode 104 can be 1 μm to 5 μm, preferably 2.5 μm, and the distance N between the cavity 106 and the lower surface of the upper electrode 104 can be 0.05 μm to 0.15 μm, preferably 0.1 μm.

[0066] According to the second embodiment of this disclosure, by providing a protrusion 208 on the upper surface of the upper electrode 104 at a position corresponding to the edge of the effective resonant region RA, compared to... Figure 1 The acoustic resonator 100 can further increase the volume of the cavity 106, thereby better confining the sound wave energy and correspondingly improving the quality factor.

[0067] Figure 7 A cross-sectional view of an acoustic resonator 300 according to a third embodiment of the present disclosure is shown.

[0068] Figure 7 In and Figure 5 Components that are identical in the figures are indicated by the same reference numerals, and their corresponding descriptions are omitted. The following will only refer to... Figure 7 Acoustic resonator 300 and Figure 5 The differences between the acoustic resonators 200 are described.

[0069] like Figure 7 As shown, according to the third embodiment of this disclosure, a protrusion 308 is provided on both the upper and lower surfaces of the upper electrode 104 at a position corresponding to the edge of the effective resonant region RA, and a cavity 106 is formed in the protrusion 308.

[0070] According to the third embodiment of this disclosure, by providing a protrusion 308 at the edge of the effective resonance region on both the upper and lower surfaces of the upper electrode 104, compared to... Figure 5 The acoustic resonator 200 can further increase the volume of the cavity 106, thereby better confining the sound wave energy and correspondingly improving the quality factor.

[0071] Those skilled in the art will recognize that although embodiments of the present disclosure are described herein in connection with cavities provided in the upper electrode, the present disclosure is not limited thereto. According to embodiments of the present disclosure, the lower electrode can also be provided with a cavity structure in the same manner as described above for the upper electrode.

[0072] Figure 8 A cross-sectional view of an acoustic resonator 400 according to a fourth embodiment of the present disclosure is shown.

[0073] Figure 8 The same components as in Figure 1 are denoted by the same reference numerals, and the corresponding description is omitted. Hereinafter, only the differences between the acoustic resonator 400 of Figure 8 and the acoustic resonator 100 of Figure 1 will be described.

[0074] As shown in Figure 8 , according to the fourth embodiment of the present disclosure, a cavity 406 entirely wrapped by the lower electrode 103 is formed in the lower electrode 103 at a position corresponding to the edge of the active resonance region RA. According to embodiments of the present disclosure, the cavity 406 is filled with air, but the present disclosure is not limited thereto.

[0075] Since air is a good sound reflection medium, by adding the cavity 406 filled with air in the lower electrode 103 at a position corresponding to the edge of the active resonance region RA, the acoustic impedance difference of the lower electrode 103 at the edge of the active resonance region RA can be increased, the transverse acoustic wave is reflected back to the active resonance region, thereby being able to confine the acoustic wave energy and improve the quality factor of the acoustic resonator.

[0076] Figure 9 A cross-sectional view of an acoustic resonator 500 according to a fifth embodiment of the present disclosure is shown.

[0077] Figure 9 The same components as in Figure 8 are denoted by the same reference numerals, and the corresponding description is omitted. Hereinafter, only the differences between the acoustic resonator 500 of Figure 9 and the acoustic resonator 400 of Figure 8 will be described.

[0078] As shown in Figure 9 , according to the fifth embodiment of the present disclosure, a protrusion 508 is provided in the upper surface of the lower electrode 103 at a position corresponding to the edge of the active resonance region RA, and a cavity 406 is formed in the protrusion 508.

[0079] According to the fifth embodiment of this disclosure, by providing a protrusion 508 on the upper surface of the lower electrode 103 at a position corresponding to the edge of the effective resonant region RA, compared to... Figure 8 The acoustic resonator 400 can further increase the volume of the cavity 406, thereby better confining the sound wave energy and correspondingly improving the quality factor.

[0080] Those skilled in the art should recognize that the above-mentioned combination Figures 1 to 9 The described embodiments can be used in combination. Furthermore, those skilled in the art will recognize that a cavity structure can also be provided in the piezoelectric layer in the same manner as described above for the upper and lower electrodes. Variations and combinations of the embodiments described above can achieve the technical effects of this disclosure and should all be covered within the scope of this disclosure.

[0081] Figure 10 A flowchart of a filter manufacturing method 1000 according to an embodiment of the present disclosure is shown.

[0082] like Figure 10 As shown, the method 1000 for manufacturing an acoustic resonator according to an embodiment of the present disclosure includes the following steps:

[0083] S1010: Forming a reflective member inside or on the surface of a substrate; and

[0084] S1020: A lower electrode, a piezoelectric layer, and an upper electrode are sequentially formed in a vertical direction above the substrate, overlapping with the reflective member. The lower electrode, the piezoelectric layer, and the upper electrode constitute a piezoelectric stack. The piezoelectric stack overlaps with the reflective member to form an effective resonant region. The formation of the lower electrode and / or the upper electrode includes forming a cavity completely enclosed by the upper electrode and / or the lower electrode at the edge of the effective resonant region in the upper electrode and / or the lower electrode.

[0085] The above steps of the filter manufacturing method according to the embodiments of this disclosure can be implemented by semiconductor processes known to those skilled in the art, such as deposition, etching, sputtering, etc. Therefore, the specific process details are not described in more detail here.

[0086] As a specific example of the method 1000 for manufacturing an acoustic resonator, to prepare Figure 5As shown in the acoustic resonator 200, a groove serving as a reflection cavity is first etched on a silicon (Si) substrate using an inductively coupled reactive ion etching (ICP-RIE) method. Subsequently, a sacrificial layer is deposited on the silicon substrate. Subsequently, the substrate surface is planarized by a chemical mechanical polishing (CMP) process. Subsequently, a lower electrode is prepared by a magnetron sputtering process. Subsequently, a piezoelectric layer is sputter-grown on the lower electrode. Subsequently, a sacrificial layer is deposited at the edge before an upper electrode is sputter-grown, at which time a portion of the upper electrode is grown more at the edge. Finally, the sacrificial layer is released to form a reflection cavity in the substrate and a cavity at the edge of the upper electrode.

[0087] According to the acoustic resonator and the manufacturing method thereof of the present disclosure, by forming a cavity at the edge of the effective resonance region in the upper electrode and / or the lower electrode, which is completely wrapped by the upper electrode and / or the lower electrode, a cavity can be formed around the effective resonance region of the acoustic resonator to confine the resonance energy in the effective resonance region, thereby reducing the loss of resonance energy and improving the quality factor of the acoustic resonator.

[0088] According to still another aspect of the present disclosure, there are also provided an acoustic filter including the above-described acoustic resonator, and a duplexer or a multiplexer including the acoustic filter.

[0089] When connected in a selected topology, a plurality of acoustic resonators 100, 200, 300, 400, and / or 500 can constitute an acoustic filter. Figure 11 A schematic diagram of an acoustic filter 1100 according to an embodiment of the present disclosure is shown. The acoustic filter 1100 includes an acoustic resonator 1101 connected in series and an acoustic resonator 1102 connected in parallel. The acoustic resonators 1101 and 1102 can include at least one of the acoustic resonators 100, 200, 300, 400, and 500 described above with reference to FIGS. 1 to 9. Figures 1 to 9 The acoustic filter 1100 is generally referred to as a ladder-type acoustic filter and can be used, for example, in a duplexer application. Those skilled in the art will recognize that, Figure 11 The topology of the acoustic filter 1100 shown is merely exemplary, and other topologies can be contemplated. Moreover, in addition to the duplexer and the multiplexer, the acoustic resonator according to an embodiment of the present disclosure can be contemplated to have other applications.

[0090] Although the present disclosure has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications can be made thereto without departing from the spirit and scope of the present disclosure as set forth in the appended claims.

Claims

1. An acoustic resonator, comprising: A substrate, wherein a reflective member is disposed inside or on the surface of the substrate; as well as A piezoelectric stack is disposed above the substrate to overlap with the reflective member to form an effective resonant region. The piezoelectric stack includes a lower electrode, a piezoelectric layer, and an upper electrode arranged sequentially along a vertical direction. The feature is that a cavity completely enclosed by the upper electrode and / or the lower electrode is formed at a position corresponding to the edge of the effective resonant region in the upper electrode and / or the lower electrode; A protrusion is provided on the upper and / or lower surfaces of the upper and / or lower electrodes at a position corresponding to the edge of the effective resonant region, and the cavity is formed in the protrusion; The protrusion has a width of 5 μm to 15 μm in the horizontal direction and a height of 0.06 μm to 0.15 μm in the vertical direction; The protrusion and its internal cavity are formed by the following process: when forming the upper electrode and / or lower electrode, a sacrificial layer is first deposited at the position corresponding to the edge, and then the upper electrode and / or lower electrode are sputtered and grown. At this time, an additional portion of the upper electrode and / or lower electrode is grown at the edge. Finally, the sacrificial layer is released to form the cavity at the edge of the upper electrode and / or lower electrode.

2. The acoustic resonator according to claim 1, further comprising: A seed layer is disposed between the substrate and the lower electrode.

3. The acoustic resonator according to claim 1, wherein, The reflective component includes a reflective cavity or a Bragg reflector.

4. The acoustic resonator according to claim 1, wherein, The substrate is made of a material selected from at least one of the following: silicon, silicon carbide, and gallium arsenide.

5. The acoustic resonator according to claim 1, wherein, Each of the lower electrode and the upper electrode is made of a conductive material selected from at least one of the following: molybdenum, tungsten, aluminum, platinum / titanium stack, and gold / chromium stack.

6. The acoustic resonator according to claim 1, wherein, The piezoelectric layer comprises a wurtzite structure material or a perovskite structure material.

7. A filter comprising an acoustic resonator according to any one of claims 1 to 6.

8. A method for manufacturing an acoustic resonator, comprising: Forming reflective components inside or on the surface of the substrate; as well as A lower electrode, a piezoelectric layer, and an upper electrode are sequentially formed vertically above the substrate, overlapping with the reflective member. The lower electrode, the piezoelectric layer, and the upper electrode constitute a piezoelectric stack, which overlaps with the reflective member to form an effective resonant region. The feature is that forming the lower electrode and / or the upper electrode includes forming a cavity in the upper electrode and / or the lower electrode at a position corresponding to the edge of the effective resonant region, which is completely enclosed by the upper electrode and / or the lower electrode; Forming the lower electrode and / or the upper electrode includes forming a protrusion on the upper surface and / or lower surface of the upper electrode and / or the lower electrode at a position corresponding to the edge of the effective resonant region, and forming the cavity in the protrusion; The protrusion has a width of 5 μm to 15 μm in the horizontal direction and a height of 0.06 μm to 0.15 μm in the vertical direction; The protrusion and its internal cavity are formed by the following process: when forming the upper electrode and / or lower electrode, a sacrificial layer is first deposited at the position corresponding to the edge, and then the upper electrode and / or lower electrode are sputtered and grown. At this time, an additional portion of the upper electrode and / or lower electrode is grown at the edge. Finally, the sacrificial layer is released to form the cavity at the edge of the upper electrode and / or lower electrode.

9. The manufacturing method according to claim 8, further comprising: A seed layer is formed between the substrate and the lower electrode.

10. The manufacturing method according to claim 8, wherein, The reflective component includes a reflective cavity or a Bragg reflector.

11. A filter comprising an acoustic resonator manufactured by the manufacturing method according to any one of claims 8 to 10.

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