Bulk acoustic wave resonator, filter, communication device, and manufacturing method thereof

Abstract

The present disclosure provides a bulk acoustic wave resonator, which comprises a cavity formed in a substrate or a support layer formed on the substrate; a lower electrode, a piezoelectric layer and an upper electrode; an overlapping area of the lower electrode, the piezoelectric layer and the upper electrode constitutes a sandwich structure; in the sandwich structure, a projection shape of the lower electrode on a projection surface of the substrate is not completely coincident with a projection shape of the cavity on the projection surface, and the cavity and the lower electrode have at least two independent areas in a composite projection shape on the upper surface of the substrate, and the independent areas are respectively constituted by a part of the contour line of the cavity and a part of the contour line of the lower electrode. The resonator can improve the performance of the device, reduce the process difficulty, improve the product yield, and further improve the performance of the communication equipment.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a filter and a manufacturing method thereof, and more particularly, to a communication device with a film bulk acoustic resonator (FBAR) and a manufacturing method thereof. BACKGROUND

[0002] With the development of communication technology, filters for transmitting and / or receiving signals are included in portable and other types of communication devices. Different types of acoustic resonators, such as film bulk acoustic resonators (FBAR), solid mounted resonators (SMR), coupled resonator filters (CRF), bulk acoustic resonators (SBAR), and dual bulk acoustic resonators (DBAR), etc., can be used in the filters according to different applications.

[0003] In the prior art, film bulk acoustic resonators (FBAR) are more suitable for portable communication devices, which are compatible with standard integrated manufacturing technology. As shown in Figure 1 A conventional film bulk acoustic resonator (FBAR) generally has a structure including a substrate 1, a cavity 2 formed in the substrate, a lower electrode 3, an upper electrode 5, and a piezoelectric layer 4 sandwiched between the upper and lower electrodes. The upper and lower electrodes and the piezoelectric layer form a "sandwich" structure. In the case where an input electrical signal is applied between the upper and lower electrodes, the inverse piezoelectric effect causes the piezoelectric layer to mechanically expand or contract due to the polarization of the piezoelectric material. The expansion and contraction of the piezoelectric layer generate acoustic waves propagating in various directions, and are converted into electrical signals through the piezoelectric effect as the input electrical signal changes over time.

[0004] As shown in Figure 2 In the prior art, the lower electrode 3 fully covers the cavity 2 in the "sandwich" structure, resulting in a large contact area between the "sandwich" structure and the substrate outside the cavity 2 of the film bulk acoustic resonator (FBAR). During operation, a considerable amount of energy is leaked out along the boundary overlap, thereby affecting the quality factor and performance of the product.

[0005] Further, in order to release the sacrificial layer to form the cavity 2, and to reduce the impact of the release hole on the "sandwich" structure, it is necessary to set the release hole 7 slightly offset from the cavity, as shown in Figure 3 Thus, an additional release channel 6 is needed to extend the release hole 7 into the cavity, which on the one hand increases the process difficulty, and on the other hand causes the cavity material to be released incompletely.

[0006] The present disclosure is directed to the above technical problems, designs a novel film bulk acoustic resonator (FBAR) structure, which can better solve the harmful effects of the existing device structure design on the performance of the film bulk acoustic resonator (FBAR), improve the performance of the filter, and reduce the process difficulty, improve the product yield, and further improve the performance of the communication equipment. SUMMARY

[0007] Hereinafter, a brief summary of the present disclosure will be given in order to provide a basic understanding of certain aspects of the present disclosure. It should be understood that this summary is not an exhaustive overview of the present disclosure. It is not intended to identify key or important parts of the present disclosure nor is it intended to limit the scope of the present disclosure. Its purpose is merely to present some concepts in a simplified form as a prelude to a more detailed description to be discussed later.

[0008] According to an aspect of the present disclosure, a bulk acoustic resonator is provided, which includes a cavity formed in a substrate or a support layer formed on the substrate; a lower electrode, a piezoelectric layer and an upper electrode; the overlapping area of the lower electrode, the piezoelectric layer and the upper electrode constitutes a sandwich structure; with the upper surface of the substrate as a projection surface, in the sandwich structure, the projection shape of the lower electrode on the projection surface does not completely coincide with the projection shape of the cavity on the projection surface, and the composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least two independent areas, the independent areas are respectively constituted by the part of the profile line of the cavity and the part of the profile line of the lower electrode.

[0009] Further, the projection shape of the cavity and the lower electrode on the projection surface is selected from irregular figures or regular figures.

[0010] Further, wherein the projection shape of the cavity and the projection shape of the lower electrode are polygons.

[0011] Further, wherein each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity.

[0012] Further, wherein each side of the lower electrode has a part of the upper surface of the substrate or a part of the upper surface of the support layer outside the cavity on the plane where the upper surface of the cavity is located.

[0013] Further, the regular figure is selected from a triangle, a rectangle, a pentagon, a hexagon and an octagon.

[0014] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0015] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0016] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0017] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0018] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0019] Further, the projection shape of the lower electrode is rotated clockwise or counterclockwise with the center position as the axis to form a partially covered shape compared with the projection shape of the cavity.

[0020] According to another aspect of the present disclosure, a method for manufacturing a bulk acoustic wave resonator is provided, which comprises: providing a substrate, etching a cavity in the substrate, and depositing a sacrificial layer in the cavity, or depositing a support layer on the substrate, etching a cavity in the support layer, and depositing a sacrificial layer in the cavity, and planarizing the sacrificial layer; depositing a lower electrode layer, etching the lower electrode layer to form a lower electrode as described in any one of the preceding embodiments; depositing a piezoelectric layer and a upper electrode layer.

[0021] Further, a passivation layer is deposited, the passivation layer is etched and the upper electrode is etched; or the passivation layer, the upper electrode layer, the piezoelectric layer and the lower electrode layer are etched.

[0022] Further, a release hole is formed in the piezoelectric layer or the sacrificial layer corresponding to the position of the sacrificial layer not covered by the lower electrode, and the sacrificial layer is removed through the release hole.

[0023] According to another aspect of the present disclosure, a filter is provided, which comprises at least one bulk acoustic wave resonator as described in any one of the preceding embodiments.

[0024] Further, a mass loading layer is formed on the upper electrode of at least one of the resonators. Further, a bonding layer is formed.

[0025] Further, a cover is bonded to the bonding layer to form a package.

[0026] According to another aspect of the present disclosure, a method for manufacturing a filter is provided, the filter comprising at least one resonator, the at least one resonator comprising the method for manufacturing a resonator as described above.

[0027] Further, a mass loading layer is deposited on the upper electrode layer of the at least one resonator before depositing the passivation layer, the mass loading layer being formed on the upper electrode layer by a lift-off process.

[0028] Further, the mass loading layer is formed by repeating the deposition and lift-off process to form a multi-layered composite structure.

[0029] Further, a bonding material is deposited to form a bonding layer by a lift-off process.

[0030] Further, the bonding layer is bonded to a lid.

[0031] Further, the encapsulation is completed by grinding.

[0032] According to another aspect of the present disclosure, a communication device is provided, comprising the filter as described above.

[0033] The present disclosure can at least help to achieve one of the following effects: reducing the energy leakage of a film bulk acoustic resonator (FBAR) in horizontal and vertical directions during operation, improving the quality factor and performance of the product, improving the electromechanical coupling coefficient Kt value, reducing the process difficulty, improving the product yield, and reducing the manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] The specific content of the present disclosure will be described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the present disclosure. The accompanying drawings are only to illustrate the principles of the present disclosure. In the drawings, the sizes and relative positions of elements are not necessarily drawn according to scale.

[0035] Figures 1-3 A structural schematic diagram of a film bulk acoustic resonator (FBAR) in the prior art is shown;

[0036] Figures 4-6 A structural schematic diagram of a resonator according to a first embodiment and a process flow are shown;

[0037] Figures 7a-16 A structural schematic diagram of a resonator according to a first embodiment and a process flow are shown;

[0038] Figures 17-18 A structural schematic diagram of a resonator according to a second embodiment is shown. DETAILED DESCRIPTION

[0039] The exemplary disclosure of the present disclosure will be described hereinafter with reference to the drawings. For the purpose of clarity and a concise description, all the features that implement the present disclosure are not described in the specification. However, it should be appreciated that many decisions with respect to the present disclosure can be made in developing any such implementation of the present disclosure in order to achieve the specific goals of the developer, and these decisions can vary from one implementation of the present disclosure to another.

[0040] It should also be noted that, in the drawings, only the device structures closely related to the scheme according to the present disclosure are shown, and other details not closely related to the present disclosure are omitted, in order to avoid obscuring the present disclosure due to unnecessary details.

[0041] It should be understood that the present disclosure is not limited to the described embodiments by virtue of the following description with reference to the drawings. Herein, the features between different embodiments can be replaced or borrowed, and one or more features can be omitted in one embodiment, if possible.

[0042] First embodiment

[0043] Referring to Figures 4-6 A first embodiment of the acoustic wave filter structure of the present disclosure is shown, in which the same reference numerals denote the same components. Among them Figure 4 is a top view of the structure of the filter of the present embodiment, Figure 5 is a cross-sectional view along the A-A section in Figure 4 is a cross-sectional view along the A-A section in

[0044] A substrate 100 is provided, in which an acoustic wave reflection region composed of a cavity 200 is formed. The substrate can be, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, aluminum oxide 、 A material compatible with the semiconductor process, such as SiC, etc., is formed. The cavity can be formed by etching.

[0045] A lower electrode layer 300 partially covering the acoustic wave reflection region is formed on the substrate 100. The lower electrode layer 300 can be a single layer or multiple layers. The projection shape of the lower electrode layer 300 partially covering the acoustic wave reflection region on the upper surface of the substrate 100 and the projection shape of the cavity 200 on the upper surface of the substrate 100 can be various shapes. Preferably, the projection shapes are both polygons, and the projection shapes do not completely overlap each other. The composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least two independent regions. The independent regions are respectively formed by a part of the contour line of the cavity and a part of the contour line of the lower electrode. The contour line refers to a reference point in the center of the composite projection shape. That is, for the contour line in the independent region, the contour line farther from the center of the composite projection shape is defined as the outer contour line, and the contour line closer to the center of the composite projection shape is defined as the inner contour line.

[0046] It should be noted that the composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least three independent regions, which is a more preferred arrangement for the subsequent release hole. The release and removal of the cavity filling material are faster and more reliable.

[0047] Further, at least each side of the polygon formed by the projection of the lower electrode intersects two sides of the polygon formed by the projection of the cavity.

[0048] Further, the lower electrode 300 has a part on the upper surface of the substrate 100 outside the cavity 200.

[0049] It can be understood that the present disclosure does not further limit the shape of the acoustic wave reflection region formed by the cavity 200 and the lower electrode 300. The projection shape of the cavity 200 and the lower electrode 300 on the lower surface of the substrate can be an irregular polygon, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc.

[0050] Preferably, the projection shape of the cavity 200 and the lower electrode 300 on the lower surface of the substrate 100 in the present disclosure is a pentagon, the contour center positions of the two are the same, and the pentagon formed by the projection of the lower electrode 300 on the upper surface of the substrate 100 is rotated clockwise or counterclockwise around the center position to form a shape partially covering the projection shape of the cavity 200. Specifically, see Figure 6As shown, the angle θ between each side of the pentagon projected on the upper surface of the substrate 100 by the cavity 200 and each side of the pentagon projected on the upper surface of the substrate 100 by the lower electrode 300 is formed in the four quadrants of the projection plane on which the upper surface of the substrate 100 lies, and the value of θ is in the range of 90° < θ < 180°. More preferably, the value of θ is in the range of 110° < θ < 160°.

[0051] Referring to Figure 6 As shown, since the cavity 200 is not completely covered by the lower electrode 300, a release hole 201 can be vertically arranged in the area of the cavity 200 not covered by the lower electrode 300, without the need for additional release channels, thereby reducing the possibility of incomplete release of the cavity filling material, lowering the process difficulty, and saving economic cost. More importantly, the energy leakage of the resonator / filter in the horizontal and vertical directions is reduced, and the quality factor of the product and the electromechanical coupling coefficient Kt value are improved.

[0052] A piezoelectric layer 400 is formed on the lower electrode 300, and the piezoelectric layer 400 can also extend to cover the lower electrode 300, the cavity 200, and the substrate 100. An upper electrode 500 is arranged on the piezoelectric layer 400, and the upper electrode 500 can be single-layer or multi-layer. The upper / lower electrode can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes, including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb), or hafnium (Hf). The materials of the upper electrode and the lower electrode can be the same or different. The piezoelectric layer 400 can be formed of any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AIN), doped aluminum nitride, or titanate zirconate (PZT). The piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode. The upper electrode, the piezoelectric layer, and the lower electrode overlapping part above the acoustic wave reflection area constitute the sandwich structure of the acoustic wave resonator.

[0053] A mass load 600 is adaptively formed on the upper electrode 500, and then a passivation layer 700 and a bonding layer 900 are formed (see Figure 16 The bonding layer material can be Au or other suitable bonding materials. The device package is formed by bonding, thinning, and bonding through the bonding layer 900 and the cap wafer 800.

[0054] It can be understood that the substrate 100 in the above filter device structure, in which the acoustic wave reflection region composed of the cavity 200 is formed, the lower electrode layer 300 partially covering the acoustic wave reflection region is formed on the substrate 100, the piezoelectric layer 400 formed on the lower electrode 300, and the upper electrode 500 arranged on the piezoelectric layer 400 constitute a bulk acoustic wave resonator. If necessary, the bulk acoustic wave resonator can be deposited with a passivation layer 700 to constitute an independent device. The filter device structure based on the first embodiment of the present disclosure will be further described below with regard to its manufacturing method. Figures 7a-16 as shown below.

[0055] Step one: providing a substrate 100, the selection of the substrate material is as described above, which will not be repeated here. The substrate mainly plays the role of a support carrier. For example, a Si substrate has good mechanical robustness, which can ensure that it is firm and reliable during processing and packaging.

[0056] Step two: referring to Figure 7a and 7b , photoresist is coated on the substrate 100, the substrate 100 is exposed and etched to form a cavity 200 with a shape as described above, and a sacrificial layer 202 is conformally deposited on the substrate forming the cavity. The sacrificial layer 202 can be selected from phosphosilicate glass, silicon dioxide, amorphous silicon, etc. which can be compatible with the deposition temperature of the subsequent thin film, does not contaminate the process system, has good etching selectivity and chemical polishing properties. Then the sacrificial layer outside the cavity is removed by a planarization process such as CMP, so that the sacrificial layer fills the cavity. The projected shape of the cavity 200 on the upper surface of the substrate can be an irregular shape, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc.

[0057] Step three: referring to Figure 8a and 8b , then the lower electrode layer is formed on the substrate 100. It should be understood that the material of the lower electrode layer is not limited to the electrode material as described above, but an electrode material with high acoustic impedance and high acoustic velocity. Then photoresist is coated, the lower electrode layer is exposed and etched, and the projected shape of the lower electrode 300 on the upper surface of the substrate can be an irregular shape, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc. The lower electrode 300 also has a connection part 301 connected to an external circuit.

[0058] Step four: referring to Figure 9a and 9bAs shown, a piezoelectric layer 400 is formed on the lower electrode 300. The material of the piezoelectric layer can be selected to meet the bandwidth requirement of the wireless mobile communication transceiver. As mentioned above, the material compatible with the semiconductor process, such as aluminum nitride (AIN) or zirconate titanate (PZT), is preferred.

[0059] Step five: as shown in Figure 10a and 10b A layer of upper electrode material 500 is formed on the piezoelectric layer 400.

[0060] Step six: as shown in Figure 11a and 11b A mass loading layer 600, which can be Mo, Al or W, is formed on the layer of upper electrode material 500. The mass loading layer is removed by coating, exposing, developing and then using a lift-off process to remove the excess mass loading layer material, so as to further deposit a mass loading layer on the upper electrode layer of at least one of the resonators. It can be understood that the mass loading layer can be formed into a multi-layer composite mass loading layer by repeating the above steps multiple times.

[0061] Step seven: as shown in Figure 12a and 12b A passivation layer material 700, which can be AIN, is further deposited.

[0062] Step eight: as shown in Figure 13a and 13b A photoresist is coated on the passivation layer material, and exposed, developed and etched to form the upper electrode. It can be understood that the lower electrode layer can not be etched in step three, but the piezoelectric layer and the lower electrode layer can be etched at the same time when etching the upper electrode, so that the sandwich structure composed of the upper electrode, the lower electrode and the piezoelectric layer has the same profile shape and arrangement as mentioned above in the projection plane. The profile shape of the upper electrode in the projection plane can be the same as that of the lower electrode in the projection plane. Figure 14a and 14b As shown, a release hole 201 is formed in the piezoelectric layer 400 at the position corresponding to the sacrificial layer 202 not covered by the lower electrode 300. It can be understood that when the upper electrode layer is etched, the piezoelectric layer and the lower electrode layer are etched at the same time, and the release hole 201 is formed in the sacrificial layer 202 not covered by the lower electrode 300.

[0063] Step ten: as shown in Figure 15a and 15bAs shown, the sacrificial layer 202 is removed through the release hole 201 to form the cavity 200. Specifically, according to the material of the sacrificial layer, the sacrificial layer 202 can be removed by oxidation or selective etching.

[0064] Step eleven: see Figure 16 As shown, photoresist is coated on the substrate after the sacrificial layer is removed, and after exposure and development, a bonding material such as Au is deposited. Then, through a stripping process, the photoresist in other areas and the Au thereon are stripped to form a bonding layer 900, and then the bonding layer 900 is bonded to a cap wafer 800.

[0065] Step twelve: the bonded device is thinned and ground to form a package.

[0066] It can be understood that the method for manufacturing the bulk acoustic wave resonator can be prepared according to the specific layer structure by referring to the above method for manufacturing the filter, and thus will not be described here.

[0067] Second embodiment

[0068] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. Figures 17-18 The same reference numbers in different drawings represent the same or similar elements.

[0069] A substrate 100 is provided, which can be, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, aluminum oxide 、 The substrate 100 is formed of a material compatible with the semiconductor process, such as SiC, etc.

[0070] A support layer 101 is formed on the substrate 100, and a cavity 200 is formed by etching the support layer 101 to constitute an acoustic wave reflection region.

[0071] A lower electrode 300 partially covering the sound wave reflecting area is formed on the support layer 101, and the lower electrode 300 can be a single layer or multiple layers. The projection shape of the lower electrode 300 partially covering the sound wave reflecting area on the substrate upper surface as a projection plane and the projection shape of the cavity 200 on the substrate upper surface as a projection plane can be various shapes, and preferably are polygons and do not completely overlap each other. The composite projection shape of the cavity and the lower electrode on the substrate upper surface has at least two independent areas, and the independent areas are respectively formed by a part of the contour line of the cavity and a part of the contour line of the lower electrode.

[0072] It should be noted that the composite projection shape of the cavity and the lower electrode on the substrate upper surface has at least three independent areas, which is a more preferred arrangement for the subsequent release hole, and provides a faster and more reliable guarantee for the release and removal of the cavity filling material.

[0073] Further, each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity.

[0074] Further, the lower electrode 300 has a part on the substrate upper surface on the plane of the upper surface of the support layer 101.

[0075] It can be understood that the present disclosure does not further limit the shape of the sound wave reflecting area formed by the cavity 200 and the lower electrode 300. The projection shape of the cavity 200 and the lower electrode 300 on the substrate upper surface can be an irregular figure, or a regular polygon such as a rectangle or a pentagon.

[0076] Preferably, the projection shape of the cavity 200 and the lower electrode 300 on the substrate upper surface are both pentagons, the center positions of the two outlines are the same, and the pentagon formed by the projection of the lower electrode 300 on the substrate surface partially covers the pentagon formed by the projection of the cavity on the substrate upper surface, with the center position as the axis of clockwise or counterclockwise rotation. Specifically, the included angle θ formed by each side of the pentagon formed by the projection of the cavity 200 on the substrate upper surface and each side of the pentagon formed by the projection of the lower electrode 300 on the substrate upper surface in the four quadrants of the plane on which the substrate upper surface lies is in the range of 90°<θ<180°. More preferably, the included angle θ is in the range of 110°<θ<160°.

[0077] Further, since the cavity 200 is not completely covered by the lower electrode 300, a release hole 201 can be vertically arranged in the area of the cavity 200 not covered by the lower electrode 300, without the need for additional release channels, thereby reducing the possibility of incomplete release of the cavity filling material, reducing process difficulty, and saving economic cost. More importantly, the energy leakage of the resonator / filter in the horizontal and vertical directions is reduced, the quality factor of the product is improved, and the electromechanical coupling coefficient Kt value is improved.

[0078] The piezoelectric layer 400 formed on the lower electrode 300 and the upper electrode 500 arranged on the piezoelectric layer 400 can be single-layer or multi-layer. The upper / lower electrode can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb), or hafnium (Hf), etc. The materials of the upper electrode 500 and the lower electrode 300 can be the same or different. The piezoelectric layer 400 can be formed of any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AIN), doped aluminum nitride, or titanate zirconate (PZT), etc. The piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode. The overlapping part of the upper electrode 500, the piezoelectric layer 400, and the lower electrode 300 above the acoustic wave reflection area constitutes the sandwich structure of the acoustic wave resonator.

[0079] It can be understood that the projection of the upper electrode 500 and the piezoelectric layer 400 on the substrate 100 in the sandwich structure can fall within the projection of the lower electrode 300 on the substrate 100, or overlap with the projection of the lower electrode 300 on the substrate, etc.

[0080] A mass loading layer 600 is formed on the upper electrode 500, and then a passivation layer 700 and a bonding layer 900, such as Au, are formed on the upper electrode / mass loading layer. The device package is formed by bonding the bonding layer to a cap wafer 800.

[0081] It can be understood that the substrate 100 in the above filter device structure, the support layer 101 forming the cavity 200 constituting the acoustic wave reflection area, the lower electrode layer 300 formed on the support layer 101 and partially covering the acoustic wave reflection area, the piezoelectric layer 400 formed on the lower electrode 300, the upper electrode 500 disposed on the piezoelectric layer 400, constitute a bulk acoustic wave resonator. If necessary, the bulk acoustic wave resonator can be deposited with a passivation layer 700 to constitute an independent device.

[0082] The filter structure based on the second embodiment of the present disclosure has a main difference from the first embodiment in that a support layer is introduced in the device. The manufacturing method of the second embodiment is similar to that of the first embodiment, and the manufacturing method of the second embodiment is described in detail below in combination with Figures 7a-16 , and the device structure of Figures 17-18 .

[0083] Step one: providing a substrate 100, the selection of the substrate material is as described above, and will not be repeated here. The substrate mainly plays the role of a support carrier. For example, a Si substrate has good mechanical robustness, which can ensure that it is firm and reliable during processing and packaging.

[0084] Step two: forming a support layer 101 on the substrate, then coating photoresist, exposing and etching the support layer to form a cavity 200 with a shape as described above, and then conformally depositing a sacrificial layer on the support layer forming the cavity. The sacrificial layer can be selected from phosphosilicate glass, silicon dioxide, amorphous silicon, and other thin film materials that can be compatible with the deposition temperature of the subsequent thin film, do not contaminate the process system, have good etching selectivity and chemical polishing properties. Then the sacrificial layer outside the cavity is removed by a planarization process such as CMP, so that the sacrificial layer fills the cavity 200. The projection shape of the cavity 200 on the upper surface of the substrate can be an irregular shape, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc.

[0085] Step three: then, the lower electrode layer is deposited on the support layer 101, it should be understood that the material of the lower electrode layer is not limited to the electrode material as described above, but also the electrode material with high acoustic impedance and high acoustic velocity. Then coat photoresist, expose and etch the lower electrode layer to form the lower electrode 300, the projection shape of the lower electrode 300 on the upper surface of the substrate can be irregular shape, or regular polygon such as triangle, rectangle, pentagon, hexagon, octagon, etc. Wherein the lower electrode 300 also has a connecting part 301 connected with the external circuit.

[0086] Step four: a piezoelectric layer 400 is deposited on the lower electrode 300, the material of the piezoelectric layer is selected to meet the bandwidth requirement of wireless mobile communication transceiver signal, as described above, the material compatible with the semiconductor process is preferred, such as aluminum nitride (AlN) or titanate (PZT).

[0087] Step five: an upper electrode material layer is deposited on the piezoelectric layer 400.

[0088] Step six: a mass loading layer is deposited on the upper electrode material layer, which can be Mo, Al or W, etc. The excess mass loading layer is removed by coating, exposing, developing and using lift-off process (LIFT OFF) on the mass loading layer, so as to further deposit a mass loading layer on the upper electrode layer of at least one of the resonators. It can be understood that the mass loading layer can form a multi-layer composite mass loading layer 600 by repeating the above steps.

[0089] Step seven: a passivation layer 700 is deposited on the mass loading layer, which can be AlN or other materials.

[0090] Step eight: photoresist is coated on the passivation layer, and the passivation layer, mass loading layer and upper electrode layer are exposed, developed and etched to realize the preparation of the upper electrode. The contour shape of the upper electrode on the projection plane can be the same as that of the lower electrode on the projection plane. It can be understood that the lower electrode layer can not be etched in step three, but the piezoelectric layer and the lower electrode layer can be etched at the same time when etching the upper electrode, so that the sandwich structure composed of the upper electrode, the lower electrode and the overlapping area of the piezoelectric layer has the contour shape and arrangement mode as described above on the projection plane. It can be understood that photoresist can be coated on the passivation layer, and the passivation layer, mass loading layer and upper electrode layer are exposed, developed and etched to realize the preparation of the sandwich structure.

[0091] Step nine: etching to form a release hole 201 at the position of the sacrificial layer not covered by the lower electrode. It can be understood that when the upper electrode layer is etched, the piezoelectric layer and the lower electrode layer are etched at the same time, and the release hole 201 is formed at the position of the sacrificial layer 202 not covered by the lower electrode 300.

[0092] Step ten: removing the sacrificial layer through the release hole 201 to form a cavity 200.

[0093] Step eleven: coating photoresist on the substrate after removing the sacrificial layer, exposing and developing, depositing bonding material such as Au, and then stripping the photoresist and Au on other areas by a stripping process to form a bonding layer 900, and then bonding the bonding layer with a cap wafer 800.

[0094] Step twelve: thinning and grinding the device after bonding.

[0095] It can be understood that the manufacturing method of the bulk acoustic wave resonator can be prepared according to the specific layer structure of the bulk acoustic wave resonator by referring to the manufacturing method of the filter described above, and thus will not be described here.

[0096] Third embodiment

[0097] A filter can be used in the field of portable communication devices such as mobile phones, personal digital assistants (PDAs), electronic game devices, etc., and the filter can include any of the acoustic wave resonators in the above embodiments.

[0098] The present disclosure is described above in conjunction with specific embodiments, but it should be clear to those skilled in the art that these descriptions are exemplary and are not a limitation on the scope of protection of the present disclosure. Those skilled in the art can make various modifications and changes to the present disclosure according to the spirit and principles of the present disclosure, and these modifications and changes are also within the scope of the present disclosure.

Claims

1. A bulk acoustic resonator, characterized by Comprising: a cavity formed in a substrate or in a support layer formed on a substrate; a lower electrode, a piezoelectric layer and an upper electrode; an overlapping region of the lower electrode, the piezoelectric layer and the upper electrode forms a sandwich structure; in the sandwich structure, the lower electrode and the cavity both form a polygon in a projection on a projection surface which is the upper surface of the substrate, the projection of the lower electrode and the projection of the cavity on the projection surface do not completely overlap, and the combined projection of the cavity and the lower electrode on the upper surface of the substrate has at least two independent regions, each of the independent regions is formed by a part of the outline of the cavity and a part of the outline of the lower electrode, and each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity; wherein the piezoelectric layer has a release hole at a position corresponding to the cavity which is not covered by the lower electrode.

2. The bulk acoustic wave resonator of claim 1, wherein the projection of the shape of the cavity and the shape of the lower electrode on the projection surface is selected from an irregular polygon or a regular polygon.

3. The bulk acoustic wave resonator of claim 2, wherein the projection of the cavity and the projection of the lower electrode are both polygons.

4. The bulk acoustic wave resonator of claim 3, wherein each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity.

5. The bulk acoustic wave resonator of claim 4, wherein each side of the lower electrode has a portion which is above the upper surface of the substrate or a portion which is above the upper surface of the support layer outside the cavity.

6. The bulk acoustic wave resonator of claim 2, wherein the regular polygon is selected from a triangle, a rectangle, a pentagon, a hexagon and an octagon.

7. The bulk acoustic wave resonator of claim 2, wherein the projection of the lower electrode is partially overlapped with the projection of the cavity by rotating the projection of the lower electrode or the projection of the cavity around the center of the projection of the lower electrode or the projection of the cavity.

8. The bulk acoustic wave resonator of claim 3, wherein each side of the projection of the lower electrode and each side of the projection of the cavity form an angle θ in the projection plane, and the value of θ is in the range of 90° < θ < 180°.

9. The bulk acoustic wave resonator of claim 8, wherein the value of θ is in the range of 110° < θ < 160°.

10. The bulk acoustic wave resonator of claim 1, wherein the projection of the upper electrode is the same as or different from the projection of the lower electrode.

11. The bulk acoustic wave resonator of claim 10, wherein a passivation layer is further formed on the upper electrode.

12. A method for manufacturing the bulk acoustic wave resonator of any one of claims 1-11, comprising: A substrate is provided, a cavity is etched in the substrate and a sacrificial layer is deposited in the cavity, or a support layer is deposited on the substrate, a cavity is etched in the support layer and a sacrificial layer is deposited in the cavity, and the sacrificial layer is planarized; A lower electrode layer is deposited, the lower electrode layer is etched; A piezoelectric layer and an upper electrode layer are deposited.

13. The method of claim 12, further depositing a passivation layer, the passivation layer is formed on the upper electrode, the passivation layer and the upper electrode are etched; or the passivation layer, upper electrode layer, piezoelectric layer and lower electrode layer are etched.

14. The method of claim 13, wherein a release hole is etched in the piezoelectric layer or the sacrificial layer corresponding to the position of the sacrificial layer not covered by the lower electrode, and the sacrificial layer is removed through the release hole.

15. A filter comprising at least one bulk acoustic wave resonator of claims 1-11.

16. The filter of claim 15, wherein a mass loading layer is formed on the upper electrode of at least one of the resonators.

17. The filter of claim 15 or 16, further comprising a bonding layer.

18. The filter of claim 17, further comprising a cap bonded to the bonding layer to form a package.

19. A method of manufacturing a filter comprising at least one resonator, the at least one resonator comprising a resonator manufactured according to any one of claims 13-14.

20. The method of claim 19, further comprising depositing a mass loading layer on the upper electrode layer of at least one of the resonators before depositing the passivation layer, the mass loading layer is formed on the upper electrode layer by a lift-off process.

21. The method of claim 20, further comprising forming a mass loading layer of a multi-layered composite structure by repeating the deposition and lift-off process.

22. The method of claim 21, further comprising depositing a bonding material to form a bonding layer by a lift-off process.

23. The method of claim 22, further comprising bonding the bonding layer to a cap.

24. The method of claim 23, further comprising completing the package by grinding and thinning.

25. A communication device comprising a filter according to any one of claims 15-24.

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