Bulk acoustic wave device and preparation method thereof

Abstract

The invention relates to the technical field of bulk acoustic wave devices, in particular to a bulk acoustic wave device and a preparation method thereof. The bulk acoustic wave filter comprises a substrate, a lower electrode, a piezoelectric layer and an upper electrode, wherein the upper surface of the substrate is provided with at least one cavity; the lower electrode is arranged on the substrate; the piezoelectric layer is arranged on the lower electrode; the packaging structure is arranged on the bulk acoustic wave filter to protect the bulk acoustic wave filter; the packaging structure comprises a wall layer which extends along the vertical direction to surround the peripheral part of the bulk acoustic wave filter; the first roof layer is of a plate-shaped structure and formed on the upper portion of the wall layer in the horizontal direction; the second roof layer surrounds the side part of the wall layer and the upper part of the first roof layer; and the redistribution layer is formed on one side of the second roof layer and is used for electrically connecting the packaging structure and the bulk acoustic wave filter. According to the invention, the packaging structure is independently manufactured and is connected with the bulk acoustic wave filter, so that the manufacturing process is simplified, and the packaging structure with a smaller size is realized.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from Korean Patent Application No. 10-2024-0050499 filed on April 16, 2024, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of bulk acoustic wave devices, and in particular to a bulk acoustic wave device and a method for preparing the same. Background Art

[0003] Wireless mobile communication technology requires a variety of radio frequency (RF) components that efficiently transmit information within limited frequency bands. Among these RF components, filters are a key component in mobile communication technology. They achieve high-quality communication by selecting the desired signal from numerous radio signals or filtering out signals to be transmitted.

[0004] Currently, the most widely used RF filters in wireless communications are dielectric filters and surface acoustic wave (SAW) filters. Dielectric filters offer advantages such as high dielectric constant, low insertion loss, high-temperature stability, and strong resistance to vibration and shock. However, dielectric filters have limitations in miniaturization and integration into monolithic microwave integrated circuits (MMICs), which have been a recent technological trend. Furthermore, compared to dielectric filters, SAW filters are more compact, offer simpler signal processing, a simpler circuit structure, and can be mass-produced using semiconductor processes. Furthermore, SAW filters exhibit higher sidelobe suppression within their passband than dielectric filters, enabling high-quality information transmission and reception. However, because the SAW filter manufacturing process includes a lithography step using ultraviolet (UV) light, the linewidth of their interdigital transducers (IDTs) is limited to approximately 0.5 microns. Therefore, SAW filters cannot cover the ultra-high frequency (UHF) band (5 GHz and above), and it is fundamentally difficult to configure an MMIC structure or a single chip on a semiconductor substrate.

[0005] To overcome the above limitations and problems, a bulk acoustic resonator (BAR) filter is provided, which can completely integrate the frequency control circuit into a monolithic microwave integrated circuit by integrating with other active components on an existing silicon (Si) or gallium arsenide (GaAs) substrate.

[0006] Bulk Acoustic Wave (BAW) filters are thin film devices that have the characteristics of low cost, small size, and high Q (high quality factor) and are suitable for various wireless communication devices, military radar systems, and the like for wide frequency band (900 MHz to 10 GHz) applications. In addition, BAW filters can be reduced to a size that is hundreds of times smaller than that of dielectric filters or lumped constant (LC) filters and have significantly lower insertion loss than SAW filters. Thus, BAW filters can be the most suitable devices for MMIC applications requiring high stability and high quality factor.

[0007] BAW filters are manufactured by depositing piezoelectric dielectric materials (e.g., zinc oxide (ZnO) or aluminum nitride (AlN)) on a semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs) through a radio frequency sputtering (RF sputtering) process and generating resonance using piezoelectric characteristics. Specifically, in a BAW filter, a piezoelectric thin film is deposited between two electrodes and resonance is achieved through generation of bulk acoustic waves.

[0008] Conventionally, to protect BAW filters from external environments, wafer bonding is used for packaging, i.e., a filter wafer (device) and a protective wafer (cover) are connected at a bonding interface using a metal material.

[0009] This packaging structure requires a large thickness due to the use of two wafers (i.e., a filter wafer and a protective wafer), a through silicon via for a redistribution layer formed in the protective wafer, and a large bonding layer area for bonding with the device wafer. Further, this structure results in an increase in the size and thickness of the device. In addition, the number of process steps increases due to the need to use a metal formation process for bonding and a through silicon via layer formation process for a redistribution layer, making the manufacturing process more complex.

[0010] In particular, conventional BAW filters protect the resonator portion from external environments by wafer bonding using a metal material at a bonding interface between a filter wafer (device) and a protective wafer (cover). The conventional structure requires a large thickness due to the use of two wafers, a through silicon via for a redistribution layer in the protective wafer, and a large bonding layer area for bonding with the device wafer. As a result, this results in an increase in the size and thickness of the device. In addition, the number of process steps increases due to the need to use a metal formation process for bonding and a through silicon via layer formation process for a redistribution layer, making the manufacturing process more complex.

[0011] Prior Art Document: Korean Laid-Open Patent No. 10-2004-0102390 (published on December 8, 2004). SUMMARY

[0012] An object of the present application is to provide a bulk acoustic wave device and a manufacturing method thereof to simplify a packaging process of a bulk acoustic wave filter and to realize a smaller size package.

[0013] The present application provides a bulk acoustic wave device, comprising, a bulk acoustic wave filter including a substrate having at least one cavity on an upper surface thereof, a lower electrode disposed on the substrate, a piezoelectric layer disposed on the lower electrode, and an upper electrode disposed on the piezoelectric layer; and a packaging structure disposed on the bulk acoustic wave filter to protect the bulk acoustic wave filter, wherein the packaging structure includes, a wall layer extending in a vertical direction to surround a peripheral portion of the bulk acoustic wave filter; a first roof layer having a plate shape and disposed on an upper portion of the wall layer in a horizontal direction; a second roof layer disposed around a side portion of the wall layer and an upper portion of the first roof layer; and a redistribution layer disposed on a side of the second roof layer to electrically connect the packaging structure and the bulk acoustic wave filter.

[0014] In some embodiments, the wall layer, the first roof layer, and the second roof layer are each made of a photosensitive polymer.

[0015] In some embodiments, the wall layer includes a partition wall extending in a vertical direction from an upper portion of the upper electrode.

[0016] In some embodiments, a reinforcing layer is further included, the reinforcing layer being disposed between the first roof layer and the second roof layer to support the first roof layer and the second roof layer.

[0017] In some embodiments, the redistribution layer is disposed on a side of the second roof layer and connects an electrode pad disposed on the bulk acoustic wave filter and an upper portion of the second roof layer.

[0018] The present application also provides a method of manufacturing a bulk acoustic wave device, comprising the steps of, manufacturing a glass wafer; manufacturing a separation layer on the glass wafer; manufacturing a first roof layer on the separation layer; manufacturing a wall layer extending in a vertical direction along an end portion of the first roof layer and surrounding the first roof layer, thereby forming a packaging structure; connecting the package structure to a bulk acoustic wave filter including a substrate, a lower electrode, a piezoelectric layer, and an upper electrode; removing the glass wafer and the separation layer from the package structure; preparing a second roof layer around a side of the wall layer and an upper portion of the first roof layer; preparing a redistribution layer to electrically connect the package structure and the bulk acoustic wave filter.

[0019] In some embodiments, the wall layer, the first roof layer, and the second roof layer are each made of a photosensitive polymer.

[0020] In some embodiments, the step of preparing the wall layer includes preparing a vertical partition wall on an upper portion of the upper electrode.

[0021] In some embodiments, further comprising, after removing the glass wafer and the separation layer from the package structure, preparing a reinforcement layer on the first roof layer to support the first roof layer and the second roof layer.

[0022] In some embodiments, the step of preparing the redistribution layer includes preparing a redistribution layer on a side of the second roof layer, the redistribution layer connecting an electrode pad disposed on the bulk acoustic wave filter and an upper portion of the second roof layer.

[0023] The present application simplifies the manufacturing process of a bulk acoustic wave device by separately manufacturing a package structure and connecting it with a bulk acoustic wave filter, and achieves a bulk acoustic wave package structure with a smaller size than a conventional package.

[0024] In particular, in some embodiments of the present application, the bulk acoustic wave filter is packaged by forming a double roof layer (a first roof layer and a second roof layer), and the package structure can firmly protect the bulk acoustic wave filter from the external environment. In addition, by forming a reinforcement layer between the first roof layer and the second roof layer, the rigidity of the roof layer and the wall layer of the bulk acoustic wave device can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 An exemplary cross-sectional side view of a bulk acoustic wave device according to an embodiment of the present application is shown.

[0027] Figure 2A flow chart of an exemplary method of fabricating a bulk acoustic wave device in one embodiment of the present application is shown.

[0028] Figure 3 A step-by-step structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in Figure 2

[0029] A cross-sectional side view of a bulk acoustic wave device in another embodiment of the present application is shown. Figure 4

[0030] A flow chart of an exemplary method of fabricating a bulk acoustic wave device in another embodiment of the present application is shown. Figure 5

[0031] A step-by-step structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in Figure 6 Figure 5 A flow chart of an exemplary method of fabricating a bulk acoustic wave device in another embodiment of the present application is shown.

[0032] Figure 7 A step-by-step structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in

[0033] Figure 8 Figure 7 A structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in

[0034] Figure 9 A structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in Figure 7

[0035] A flow chart of an exemplary method of fabricating a bulk acoustic wave device in another embodiment of the present application is shown. Figure 10

[0036] A step-by-step structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in Figure 11 Figure 10 A structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in

[0037] Figure 12 Figure 10 A structural diagram of a bulk acoustic wave device obtained by the fabrication method shown in

[0038] BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION

[0039] Exemplary embodiments of the present application will be described in detail below with reference to the attached drawings. ​​​​

[0040] Embodiments of the present application are intended to more fully explain the present application to those with ordinary skill in the art, rather than to limit the scope of the present application. Embodiments of the present application can be changed in various forms, and the scope of the present application is not limited to the following embodiments. Rather, these embodiments are to make the disclosure more substantial and complete, and to fully convey the concept of the present application to those skilled in the art.

[0041] The terms used herein are intended to explain specific embodiments, not to limit the present application. Unless the context clearly dictates otherwise, the singular form of the expression used herein can include the plural meaning. In addition, the term "and / or" includes one or more combinations of the related items.

[0042] In addition, in the drawings, the same reference numerals denote the same elements, and the thickness, ratio, and size can be exaggerated for effective explanation of the technical content. Embodiments of the present application will be described below with reference to the accompanying drawings.

[0043] Figure 1 is a cross-sectional side view of a bulk acoustic wave (BAW) device 10A according to an embodiment of the present application.

[0044] Referring to Figure 1 , the bulk acoustic wave device 10A includes a bulk acoustic wave filter 100 and a package structure 200.

[0045] The bulk acoustic wave filter 100 includes a substrate 110, a lower electrode 120, a piezoelectric layer 130, an upper electrode 140, and an electrode pad 150.

[0046] When an external signal is applied between the lower electrode 120 and the upper electrode 140, a part of the electrical energy transmitted between the two electrodes is converted into mechanical energy and then converted back into electrical energy due to the piezoelectric effect. In this process, the bulk acoustic wave filter 100 resonates at its natural oscillation frequency according to the thickness of the piezoelectric layer 130.

[0047] The substrate 110 is a semiconductor substrate, which can be a general silicon wafer, and preferably can be a high resistivity silicon (HRS) substrate. An insulating layer (not shown in the figure) can be formed on the upper surface of the substrate 110. The insulating layer can be a thermal oxide film easily grown on the substrate 110, or alternatively an oxide film or a nitride film formed by a conventional deposition process such as chemical vapor deposition. In addition, the upper surface of the substrate 110 includes at least one cavity 110-1.

[0048] The lower electrode 120 is disposed above the substrate 110, and can be a structure completely covered by the piezoelectric layer 130 or a structure partially covered. The lower electrode 120 can be formed above the cavity 110-1 of the substrate 110 and completely or partially surround the upper portion of the cavity 110-1. The lower electrode 120 is formed by depositing a certain material on the upper portion of the substrate 110 and then patterning. The material of the lower electrode 120 is a typical conductive material such as a metal, and can be preferably one of aluminum (Al), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), palladium (Pd), or molybdenum (Mo).

[0049] The piezoelectric layer 130 is disposed above the lower electrode 120 and / or the substrate 110. The piezoelectric layer 130 can be formed by depositing a piezoelectric material on the upper portion of the lower electrode 120 and then patterning. When the piezoelectric layer 130 is formed above the lower electrode 120, it can completely cover the lower electrode 120 or partially cover the lower electrode 120. Thus, the lower electrode 120 can exist both in a portion completely covered by the piezoelectric layer 130 and in a portion partially covered.

[0050] The piezoelectric material can be aluminum nitride (AlN) or zinc oxide (ZnO). The deposition method can include a radio frequency magnetron sputtering method, an evaporation method, etc.

[0051] The upper electrode 140 is disposed above the piezoelectric layer 130. The upper electrode 140 can be formed by depositing and patterning a metal film on the upper portion of the piezoelectric layer 130. The upper electrode 140 can use the same material as the lower electrode 120, and can be formed using the same deposition and patterning method as the lower electrode 120.

[0052] The electrode pad 150 is disposed above the lower electrode 120. The electrode pad 150 is a layer for electrically connecting with the package structure 200, and thus can be formed of a conductive metal material.

[0053] The package structure 200 is a structure for protecting the bulk acoustic wave filter 100. To this end, the package structure 200 includes a wall layer 210, a first roof layer 220, a second roof layer 230, and a redistribution layer 240.

[0054] The wall layer 210 is disposed above the bulk acoustic wave filter 100 and extends in a vertical direction to form an outer wall around the peripheral portion of the bulk acoustic wave filter 100.

[0055] The wall layer 210 can be an outer wall extending in a vertical direction from the upper portion of the piezoelectric layer 130 or the electrode pad 150 of the bulk acoustic wave filter 100. In addition, the wall layer 210 can be a partition wall extending in a vertical direction from the upper portion of the upper electrode 140 of the bulk acoustic wave filter 100.

[0056] AsFigure 1 As shown, the wall layer 210 can take the form of an outer wall 210-1 extending in a vertical direction from a side portion of the piezoelectric layer 130 or from an upper portion of the electrode pad 150 to surround the bulk acoustic wave filter 100, or can take the form of a partition wall 210-2 extending in a vertical direction from an upper portion of the upper electrode 140. In some embodiments, the wall layer 210 can include both the outer wall 210-1 and the partition wall 210-2.

[0057] The minimum height of the wall layer 210 can be set so that the upper electrode 140, which moves due to the vibration of the piezoelectric layer 130, does not come into contact with the first roof layer 220. The wall layer 210 can be formed of a photosensitive polymer. The photosensitive polymer can include a photosensitive polyimide, a photosensitive polybenzoxazole (PBO), an epoxy resin, benzocyclobutene (BCB), etc.

[0058] Since the wall layer 210 has a sufficient height to prevent the upper electrode 140, which moves due to the vibration of the piezoelectric layer 130, from coming into contact with the first roof layer 220, a cavity will be formed between the bulk acoustic wave filter 100 and the package structure 200.

[0059] The first roof layer 220 is a plate-shaped structure layer disposed at an upper portion of the wall layer 210 and extending in a horizontal direction. The first roof layer 220 is disposed above the wall layer 210 to protect the bulk acoustic wave filter 100. The end of the first roof layer 220 can be located in the same plane as the side end of the wall layer 210, or can extend further than the side end of the wall layer 210.

[0060] The first roof layer 220 can be formed of a photosensitive polymer. Such a photosensitive polymer can include a photosensitive polyimide, a photosensitive polybenzoxazole (PBO), an epoxy resin, etc.

[0061] The second roof layer 230 is a layer disposed at an upper portion and side portions of the first roof layer 220 to protect the bulk acoustic wave filter 100. To this end, the second roof layer 230 is a layer disposed to surround the side portions of the wall layer 210 and the upper portion of the first roof layer 220.

[0062] That is, the second roof layer 230 includes an upper pattern 230-1 surrounding the upper portion of the first roof layer 220, and a side pattern 230-2 surrounding the side portions of the wall layer 210.

[0063] The upper pattern 230-1 of the second roof layer 230 includes a plate-shaped structure extending in a horizontal direction on the upper portion of the first roof layer 220. In addition, the side pattern 230-2 of the second roof layer 230 extends downward along the side of the wall layer 210 and includes an outer wall structure in contact with the piezoelectric layer 130 and the electrode pad 150 of the bulk acoustic wave filter 100. Accordingly, the second roof layer 230 can have a structure surrounding the outer surface of the first roof layer 220 and the wall layer 210.

[0064] The second roof layer 230 can also be formed of a photosensitive polymer, such as a photosensitive polyimide, a photosensitive polybenzoxazole (PBO), an epoxy resin, etc.

[0065] As described above, the first roof layer 220 and the second roof layer 230 can be formed of photosensitive polymer materials, but they can use different photosensitive polymer materials. For example, when the first roof layer 220 is made of a photosensitive polyimide, the second roof layer 230 can be made of a photosensitive polybenzoxazole (PBO).

[0066] In addition, even if the first roof layer 220 and the second roof layer 230 are formed of the same photosensitive polymer material, some inherent properties (e.g., elastic modulus, tensile strength, water absorption, molecular weight, linear expansion coefficient, thermal conductivity, weather resistance, heat resistance, etc.) thereof can be different. For example, even if the first roof layer 220 and the second roof layer 230 are both made of a photosensitive polyimide, the first roof layer 220 can be a photosensitive polyimide having a first tensile strength, and the second roof layer 230 can be a photosensitive polyimide having a second tensile strength.

[0067] The redistribution layer 240 is a layer disposed on one side of the second roof layer 230, which is used to electrically connect the package structure 200 and the bulk acoustic wave filter 100. The redistribution layer 240 connects the second roof layer 230 of the package structure 200 and the electrode pad 150 disposed on the bulk acoustic wave filter 100. To this end, the redistribution layer 240 is formed of a conductive metal material, such as copper (Cu), nickel (Ni), gold (Au), or tin (Sn), etc.

[0068] The redistribution layer 240 is disposed along the side of the second roof layer 230. In addition, one end of the redistribution layer 240 is horizontally disposed on the upper surface of the second roof layer 230, and the other end is connected to the electrode pad 150 disposed on the bulk acoustic wave filter 100.

[0069] As Figure 1 illustrated, one end of the redistribution layer 240 is in contact with the upper surface of the second roof layer 230, and the other end of the redistribution layer 240 is connected to the electrode pad 150 disposed on the lower electrode 120 of the bulk acoustic wave filter 100.

[0070] Figure 2is a flowchart showing a method of manufacturing a bulk acoustic wave device according to an embodiment of the present application, Figure 3 is a cross-sectional view showing a bulk acoustic wave device manufactured by the manufacturing method shown in Figure 2 is a cross-sectional view showing a bulk acoustic wave device manufactured by the manufacturing method shown in

[0071] First, a glass wafer for a packaging structure is prepared (step S1000). The glass wafer can be made of borosilicate glass, which has a thermal expansion coefficient similar to that of silicon and has laser wavelength transmissivity.

[0072] After step S1000, a separation layer is prepared above the glass wafer (step S1100). The separation layer is used to remove the glass wafer later. The separation layer can be made of a polymer material that reacts with a laser and breaks polymer bonds.

[0073] After step S1100, a first roof layer is prepared above the separation layer (step S1200). The first roof layer can be formed of a photosensitive polymer. Such a photosensitive polymer can include photosensitive polyimide, photosensitive polybenzoxazole (PBO), epoxy, benzocyclobutene (BCB), etc.

[0074] After step S1200, a wall layer extending in a vertical direction along the end of the first roof layer is formed, thereby forming an outer wall (step S1300). Like the first roof layer, the wall layer can also be formed of a photosensitive polymer.

[0075] The wall layer can be formed by extending in a vertical direction along the end of the first roof layer, thereby forming an outer wall surrounding the first roof layer (210-1 in Figure 1 In addition, it can also include a partition wall structure extending in a vertical direction from the center region of the first roof layer (210-2 in Figure 1 The minimum height of the wall layer can be set so that the upper electrode moving due to the vibration of the piezoelectric layer does not come into contact with the first roof layer.

[0076] After step S1300, the packaging structure including the first roof layer and the wall layer is connected to the bulk acoustic wave filter (step S1400). The wall layer of the packaging structure is connected to the piezoelectric layer or the upper electrode of the bulk acoustic wave filter.

[0077] Referring to Figure 1 and Figure 3 , the end of the wall layer of the packaging structure provided at the end of the first roof layer is connected to the upper surface of the piezoelectric layer and the electrode pad of the bulk acoustic wave filter. The end of the wall layer provided at the center region of the first roof layer is connected to the upper surface of the upper electrode of the bulk acoustic wave filter. At this time, the photosensitive polymer constituting the wall layer can be connected to the piezoelectric layer and the upper electrode of the bulk acoustic wave filter by adhesion.

[0078] After step S1400, the glass wafer and the separation layer are removed from the package structure (step S1500). The glass wafer can be separated by irradiating the separation layer with a laser to break its polymer bonds, and then the remaining separation layer left on the first roof layer is removed using a wet or ashing process.

[0079] After step S1500, a second roof layer is prepared around the first roof layer and the wall layer in the package structure (step S1600). The second roof layer is used to protect the first roof layer and the wall layer.

[0080] The second roof layer is disposed above the first roof layer, i.e., the position of the glass wafer and the separation layer that have been removed from the package structure. In addition to being formed above the first roof layer, the second roof layer is also disposed to surround the side portions of the wall layer. The second roof layer is disposed to extend in a horizontal direction in a plate form at the upper portion of the first roof layer, and to extend downward along the side portions of the wall layer to contact the piezoelectric layer and the electrode pad of the bulk acoustic wave filter. Thus, the second roof layer has a structure that surrounds the outer surfaces of the first roof layer and the wall layer. The second roof layer can also be formed of a photosensitive polymer, such as photosensitive polyimide, photosensitive polybenzoxazole (PBO), epoxy resin, etc.

[0081] After step S1600, a redistribution layer is prepared for electrically connecting the package structure and the bulk acoustic wave filter (step S1700). The redistribution layer is disposed along the upper and side portions of the second roof layer. At this time, one end of the redistribution layer is connected to the upper surface of the second roof layer, and the other end is connected to the electrode pad disposed on the bulk acoustic wave filter.

[0082] Reference Figures 1 to 3 One end of the redistribution layer is in horizontal contact with the upper surface of the second roof layer, and the other end of the redistribution layer is in horizontal contact with the upper surface of the electrode pad disposed on the lower electrode of the bulk acoustic wave filter.

[0083] Figure 4 is a cross-sectional side view of a bulk acoustic wave device 10B according to another embodiment of the present application.

[0084] Reference Figure 4 The bulk acoustic wave device 10B includes a bulk acoustic wave filter 100 and a package structure 200.

[0085] The bulk acoustic wave filter 100 includes a substrate 110, a lower electrode 120, a piezoelectric layer 130, an upper electrode 140, and an electrode pad 150. The detailed structure of the bulk acoustic wave filter 100 is the same as that of the bulk acoustic wave device 10A, and thus a detailed description thereof is omitted here.

[0086] The package structure 200 is a structure for protecting the BAW filter 100. To this end, the package structure 200 includes a layer 210, a first roof layer 220, a second roof layer 230, a redistribution layer 240, and a reinforcement layer 250.

[0087] Among the components of the package structure 200 , the specific structures of the wall layer 210 , the first roof layer 220 , the second roof layer 230 and the redistribution layer 240 are the same as those in the BAW device 10A, and thus detailed descriptions thereof are omitted here.

[0088] However, Figure 4 The bulk acoustic wave device 10B in Figure 1 The difference between the BAW device 10A and the BAW device 10A is that a reinforcement layer 250 is added. Therefore, only the reinforcement layer 250 will be described below.

[0089] The reinforcement layer 250 is a layer for supporting the shape of the first roof layer 220. The reinforcement layer 250 may be a plate-like structure horizontally disposed above the first roof layer 220. Therefore, the reinforcement layer 250 may be located between the first roof layer 220 and the second roof layer 230.

[0090] Only one reinforcement layer 250 may be provided, or two or more reinforcement layers 250 may be arranged at intervals. Formation of the reinforcement layer 250 can firmly support the first roof layer 220 and the second roof layer 230, thereby enhancing the protective function of the bulk acoustic wave filter 100. The reinforcement layer 250 can be made of a metal material to increase the rigidity of the roof layer.

[0091] Figure 5 FIG. 1 is a flow chart showing a method for preparing a bulk acoustic wave device in another embodiment of the present invention. Figure 6 is through Figure 5 The step-by-step structure diagram of the bulk acoustic wave device formed by the preparation method shown. Figure 5 The preparation method of the bulk acoustic wave device shown in FIG. Figure 1 The description of the repeated parts will be omitted.

[0092] First, a glass wafer for packaging structure is prepared (step S2000 ).

[0093] After step S2000 , a separation layer is formed on the glass wafer (step S2100 ).

[0094] After step S2100 , a first roofing layer is prepared on the separation layer (step S2200 ). The first roofing layer may be made of a photosensitive polymer.

[0095] After step S2200, a wall layer extending in a vertical direction along the end of the first roof layer is prepared, thereby forming an outer wall (step S2300). Like the first roof layer, the wall layer can also be formed of a photosensitive polymer.

[0096] After step S2300, the package structure including the first roof layer and the wall layer is connected to the bulk acoustic wave filter (step S2400). The wall layer of the package structure is connected to the piezoelectric layer or the upper electrode constituting the bulk acoustic wave filter.

[0097] After step S2400, the glass wafer and the separation layer are removed from the package structure (step S2500).

[0098] After step S2500, a reinforcing layer is prepared above the first roof layer to support the first roof layer and the second roof layer (step S2600). The reinforcing layer can be a plate-shaped structure provided in a horizontal direction on the upper portion of the first roof layer. There can be only one reinforcing layer, or two or more reinforcing layers can be provided at intervals.

[0099] After step S2600, a second roof layer is formed around the first roof layer, the wall layer, and the reinforcing layer (step S2700). The second roof layer serves to protect the first roof layer, the wall layer, and the reinforcing layer.

[0100] The second roof layer is provided around the upper portions of the first roof layer and the reinforcing layer and the side portions of the wall layer. The second roof layer extends in a horizontal direction in a plate shape on the upper portion of the first roof layer and extends downward along the side portions of the wall layer to contact the piezoelectric layer and the electrode pad of the bulk acoustic wave filter.

[0101] After step S2700, a redistribution layer for electrically connecting the package structure and the bulk acoustic wave filter is prepared (step S2800). The redistribution layer is provided along the upper and side portions of the second roof layer. At this time, one end of the redistribution layer is connected to the upper surface of the second roof layer, and the other end is connected to the electrode pad provided on the bulk acoustic wave filter.

[0102] Figure 7 a flowchart showing a method of manufacturing a bulk acoustic wave device according to another embodiment of the present application, Figure 8 by the manufacturing method shown in FIG. 4, Figure 7 a stepwise structural diagram of a bulk acoustic wave device formed by the manufacturing method shown in FIG. 4. In addition, Figure 9 by the manufacturing method shown in FIG. 4, Figure 7 a structural diagram of a bulk acoustic wave device formed by the manufacturing method shown in FIG. 4.

[0103] First, a glass wafer for a package structure is prepared (step S3000).

[0104] After step S3000, a separation layer is formed over the glass wafer (step S3100). The separation layer is used to remove the glass wafer later.

[0105] After step S3100, a roof layer is formed over the separation layer (step S3200). The roof layer can be formed of a photosensitive polymer.

[0106] After step S3200, a wall layer is formed along the vertical direction of the end of the roof layer and around the roof layer, thereby forming an encapsulation structure (step S3300). Like the roof layer, the wall layer can also be formed of a photosensitive polymer.

[0107] The wall layer can be disposed vertically along the end of the side surface of the roof layer, thereby forming an outer wall around the roof layer. In addition, unlike the portion extending along the end of the side surface of the roof layer, the wall layer can include a partition wall structure vertically extending in the central region of the roof layer. The minimum height of the wall layer can be set such that the upper electrode moved by the vibration of the piezoelectric layer does not come into contact with the roof layer.

[0108] After step S3300, the encapsulation structure is connected to the bulk acoustic wave filter including the substrate, the lower electrode, the piezoelectric layer, and the upper electrode (step S3400).

[0109] The wall layer can be connected to the piezoelectric layer or the upper electrode of the bulk acoustic wave filter. Referring to Figure 9 , the wall layer disposed at the end of the side surface of the roof layer is connected to the upper surface of the piezoelectric layer of the bulk acoustic wave filter. The wall layer disposed in the central region of the roof layer is connected to the upper surface of the upper electrode of the bulk acoustic wave filter. At this time, the photosensitive polymer constituting the wall layer can be combined with the piezoelectric layer and the upper electrode of the bulk acoustic wave filter by adhesion.

[0110] After step S3400, the glass wafer and the separation layer are removed from the encapsulation structure (step S3500).

[0111] After step S3500, a redistribution layer is formed on the encapsulation structure (step S3600). The redistribution layer can be disposed along the side of the roof layer and connected to one side of the roof layer at one end and to an electrode pad disposed on the substrate of the bulk acoustic wave filter at the other end. The redistribution layer is made of a conductive metal material.

[0112] Referring to Figure 9 , the redistribution layer is disposed vertically along the side of the wall layer. One end of the redistribution layer is in horizontal contact with the upper surface of the roof layer, and the other end of the redistribution layer is in horizontal contact with the upper surface of the electrode pad disposed on the substrate of the bulk acoustic wave filter.

[0113] Figure 10 A flowchart illustrating a method of manufacturing a bulk acoustic wave device according to another embodiment of the present application is shown,Figure 11 is formed by Figure 10 is a step-by-step structural diagram of a bulk acoustic wave device formed by the preparation method shown in Figure 12 is a structural diagram of a bulk acoustic wave device formed by the preparation method shown in Figure 10

[0114] First, a glass wafer for a packaging structure is prepared (step S4000).

[0115] After step S4000, a separation layer is prepared above the glass wafer (step S4100). The separation layer is used for subsequent removal of the glass wafer.

[0116] After step S4100, a roof layer is prepared above the separation layer (step S4200). The roof layer can be made of a photosensitive polymer.

[0117] After step S4200, at least one reinforcing layer is formed above the roof layer (step S4300). The reinforcing layer is a layer for supporting the shape of the roof layer.

[0118] After step S4300, a wall layer is formed vertically along the end of the roof layer and around the roof layer, thereby forming a packaging structure (step S4400). The wall layer can be arranged vertically along the end of the side surface of the roof layer to form an outer wall around the roof layer.

[0119] After step S4400, the packaging structure is connected to a bulk acoustic wave filter including a substrate, a lower electrode, a piezoelectric layer, and an upper electrode (step S4500). The wall layer can be connected to the piezoelectric layer or the upper electrode of the bulk acoustic wave filter.

[0120] After step S4500, the glass wafer and the separation layer are removed from the packaging structure (step S4600).

[0121] After step S4600, a rewiring layer is formed on the packaging structure (step S4700). The rewiring layer can be arranged along the side of the roof layer and connected to one side of the roof layer at one end and to an electrode pad arranged on the substrate of the bulk acoustic wave filter at the other end. The rewiring layer is made of a conductive metal material.

[0122] The above describes exemplary embodiments of the present application. Those of ordinary skill in the art can understand that modifications can be made without departing from the scope of the present application. Therefore, the disclosed embodiments of the present application should be considered as descriptive rather than limiting. The scope of the present application will be embodied in the claims rather than the above description, and all differences within the equivalent scope should be interpreted as included in the present application.​

Claims

1. A bulk acoustic wave device, characterized by, A bulk acoustic wave filter including a substrate having at least one cavity in an upper surface thereof, a lower electrode disposed on the substrate, a piezoelectric layer disposed on the lower electrode, and an upper electrode disposed on the piezoelectric layer; and A packaging structure disposed on the bulk acoustic wave filter to protect the bulk acoustic wave filter, wherein the packaging structure includes a wall layer extending in a vertical direction to surround a peripheral portion of the bulk acoustic wave filter; a first roof layer having a plate shape and disposed in a horizontal direction on an upper portion of the wall layer; a second roof layer disposed around a side portion of the wall layer and an upper portion of the first roof layer; and a redistribution layer disposed on a side of the second roof layer to electrically connect the packaging structure and the bulk acoustic wave filter. The wall layer, the first roof layer, and the second roof layer are each made of a photosensitive polymer. The wall layer includes a partition wall extending in a vertical direction from an upper portion of the upper electrode.

2. The bulk acoustic wave device of claim 1, wherein, A reinforcing layer is further included, the reinforcing layer being disposed between the first roof layer and the second roof layer to support the first roof layer and the second roof layer.

3. The bulk acoustic wave device of claim 1, wherein, The redistribution layer is disposed on a side of the second roof layer and connects electrode pads disposed on the bulk acoustic wave filter and an upper portion of the second roof layer.

4. The bulk acoustic wave device of claim 1, wherein, A glass wafer is prepared; 5. The bulk acoustic wave device of claim 1, wherein, A separation layer is prepared on the glass wafer; 6. A method of fabricating a bulk acoustic wave device, characterized by, A first roof layer is prepared on the separation layer; A wall layer extending in a vertical direction along an end portion of the first roof layer and surrounding the first roof layer is prepared, thereby forming a packaging structure; The packaging structure is connected to a bulk acoustic wave filter including a substrate, a lower electrode, a piezoelectric layer, and an upper electrode; The glass wafer and the separation layer are removed from the packaging structure; A second roof layer surrounding a side portion of the wall layer and an upper portion of the first roof layer is prepared; A redistribution layer is prepared to electrically connect the packaging structure and the bulk acoustic wave filter. The wall layer, the first roof layer, and the second roof layer are each made of a photosensitive polymer. The step of preparing the wall layer includes preparing a partition wall extending in a vertical direction on an upper portion of the upper electrode. Further included is, after the glass wafer and the separation layer are removed from the packaging structure, a reinforcing layer is prepared on the first roof layer to support the first roof layer and the second roof layer.

7. The method of fabricating a bulk acoustic wave device of claim 6, wherein, The step of preparing the redistribution layer includes preparing a redistribution layer on a side of the second roof layer, the redistribution layer connecting electrode pads disposed on the bulk acoustic wave filter and an upper portion of the second roof layer.

8. The method of fabricating a bulk acoustic wave device of claim 6, wherein, ​ 9. The method of claim 6, wherein the method further comprises: ​ 10. The method of fabricating a bulk acoustic wave device of claim 6, wherein, ​

Images