Bulk Acoustic Wave Resonator

Abstract

The present disclosure provides a bulk acoustic wave resonator. The bulk acoustic wave resonator includes: a substrate; a first electrode, disposed on the substrate; a piezoelectric layer, disposed to cover at least a portion of the first electrode; a second electrode, disposed to cover at least a portion of the piezoelectric layer; a metal pad, connected to the first electrode and the second electrode; and a connecting member, connected to the upper surface of the metal pad. The lower end portion of the connecting member includes a tapered portion whose diameter decreases in a direction toward the lower end of the connecting member, and the angle between the inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°.

Description

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2020-0042080 filed on April 7, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety for all purposes by reference. Technical Field

[0002] The following description relates to a bulk acoustic wave resonator. Background Art

[0003] The copper pillar technology used in flip chip mounting is a commonly used technology. However, the Cupillar technology is difficult to apply to the mounting process of, for example, a bulk acoustic wave (BAW) resonator including an air cavity. This is because the mounting process must be performed without causing damage to the air cavity. Therefore, it is desirable to develop a structure that promotes the application of the Cu pillar technology to BAW. Summary of the invention

[0004] This summary is provided to introduce selected concepts in a simplified form, and the concepts are further described below in the detailed description. This summary is neither intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] In one general aspect, a bulk acoustic wave resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a connecting member connected to an upper surface of the metal pad. A lower end portion of the connecting member includes a tapered portion whose diameter decreases in a direction toward the lower end of the connecting member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°.

[0006] The upper end portion of the connection member may include a cylindrical portion having a constant diameter. The tapered portion may be disposed below the cylindrical portion.

[0007] The tapered portion may have a height of 6 μm or more.

[0008] A diameter of a bottom surface of the tapered portion may be 60 μm or more.

[0009] The connecting member may be made of any one of gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), copper-tin (Cu-Sn) alloy, aluminum (Al) and aluminum alloy, or made of a material containing any two or more of gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), copper-tin (Cu-Sn) alloy, aluminum (Al) and aluminum alloy.

[0010] The BAW resonator may further include an insertion layer disposed between the first electrode and the piezoelectric layer.

[0011] The BAW resonator may further include a membrane layer forming a cavity together with the substrate.

[0012] The BAW resonator may further include: an etch stopper disposed to surround the cavity; and a sacrificial layer disposed to surround the etch stopper.

[0013] The membrane layer may include an inclined portion disposed obliquely with respect to an upper surface of the substrate, and a flat portion disposed in an active region in which the first electrode, the piezoelectric layer, and the second electrode all overlap one another.

[0014] The second electrode may include a frame disposed at an edge of the active area. The frame may have a thickness greater than that of a remaining portion of the second electrode.

[0015] The BAW resonator may further include an insulating layer disposed on the substrate and below the cavity.

[0016] The metal pad may include a first metal pad connected to the first electrode and a second metal pad connected to the second electrode.

[0017] In another general aspect, a bulk acoustic wave resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a connecting member connected to an upper surface of the metal pad. The connecting member includes: a cylindrical portion disposed at an upper end of the connecting member and having a constant diameter; and a tapered portion disposed below the cylindrical portion, the tapered portion having a height of 6 μm or more and a smaller diameter at a lower end of the tapered portion than at an upper end of the tapered portion.

[0018] A bottom surface of the tapered portion may be in contact with the upper surface of the metal pad.

[0019] A diameter of the bottom surface of the tapered portion may be 60 μm or more.

[0020] In a cross-sectional view of the BAW resonator, a width of a bottom surface of the tapered portion may be smaller than a width of a flat portion of an upper surface of the metal pad.

[0021] Other features and aspects will be apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic cross-sectional view showing a bulk acoustic wave resonator according to an embodiment.

[0023] Figure 2 It is shown Figure 1 Magnified view of part A.

[0024] Figure 3 is a schematic cross-sectional view showing a bulk acoustic wave resonator according to an embodiment.

[0025] Figure 4 It is shown Figure 3 Magnified view of part B.

[0026] In all drawings and detailed description, the same reference numerals refer to the same elements. The drawings may not be drawn to scale, and the relative sizes, proportions, and depictions of the elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0027] The following specific embodiments are provided to help the reader gain a comprehensive understanding of the methods, devices and / or systems described herein. However, after understanding the disclosure of the present application, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be apparent. For example, the order of operations described herein is merely an example and is not limited to the order set forth herein, but in addition to the operations that must occur in a particular order, changes that will be apparent after understanding the disclosure of the present application may be made. In addition, in order to improve clarity and brevity, descriptions of features known in the art may be omitted.

[0028] The features described herein may be implemented in different forms and shall not be construed as being limited to the examples described herein. Rather, the examples described herein are provided only to illustrate some of the many possible ways of implementing the methods, devices and / or systems described herein that will be apparent after understanding the disclosure of the present application.

[0029] Here, it is noted that the use of the term "may" with respect to an example or embodiment (e.g., with respect to what an example or embodiment may include or implement) means that there is at least one example or embodiment that includes or implements such feature, and all examples and embodiments are not limited thereto.

[0030] Throughout the specification, when an element such as a layer, a region, or a substrate is described as being “on,” “connected to,” or “coupled to” another element, the element may be directly “on,” “connected to,” or “coupled to” another element, or one or more other elements may be present in between. In contrast, when an element is described as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no other elements in between.

[0031] As used herein, the term "and / or" includes any one and any combination of any two or more of the associated listed items.

[0032] Although terms such as "first", "second", and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions are not limited by these terms. Rather, these terms are only used to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Thus, without departing from the teachings of the examples described herein, the first member, first component, first region, first layer, or first portion referred to may also be referred to as the second member, second component, second region, second layer, or second portion.

[0033] For ease of description, spatial relationship terms such as "above ...", "on ...", "below ...", "below ...", "in front of ...", "behind ...", and "on the side of ..." may be used herein to describe the relationship of one element relative to another element as shown in the figure. Such spatial relationship terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, the element described as "above" or "on" another element will then be "below" or "below" another element. Thus, the term "above ..." includes both the upper and lower orientations according to the spatial orientation of the device. For another example, if the device in the figure is turned over, the element described as "in front" relative to another element will be "behind" relative to another element. Therefore, according to the spatial orientation of the device, the term "in front of ..." covers both the front and rear orientations. The device may also be positioned in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relationship terms used herein will be interpreted accordingly.

[0034] The terms used herein are only used to describe various examples and are not used to limit the present disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms "comprise", "include" and "have" list the features, numbers, operations, components, elements and / or combinations thereof that are stated, but do not exclude the presence or addition of one or more other features, numbers, operations, components, elements and / or combinations thereof.

[0035] Due to manufacturing techniques and / or tolerances, variations may occur in the shapes shown in the figures. Therefore, the examples described herein are not limited to the specific shapes shown in the figures but include variations in shapes that occur during manufacturing.

[0036] The features of the examples described herein can be combined in various ways that will be apparent after understanding the disclosure of the present application. In addition, although the examples described herein have various configurations, other configurations that will be apparent after understanding the disclosure of the present application are feasible.

[0037] Figure 1 is a schematic cross-sectional view showing a bulk acoustic wave resonator 100 according to an embodiment. Figure 2 It is shown Figure 1 Magnified view of part A.

[0038] Reference Figure 1 and Figure 2 The BAW resonator 100 may include, for example, a substrate 110 , a sacrificial layer 120 , an etch stopper 130 , a membrane layer 140 , a first electrode 150 , a piezoelectric layer 160 , a second electrode 170 , an insertion layer 180 , a passivation layer 190 , a metal pad 200 , and a connection member 210 .

[0039] The substrate 110 may be a silicon substrate. For example, a silicon wafer or a silicon-on-insulator (SOI) type substrate may be used as the substrate 110 .

[0040] The insulating layer 112 may be disposed on the upper surface of the substrate 110 and may electrically isolate the substrate 110 from layers and components disposed thereon. In addition, when the cavity C is formed in the manufacturing process, the insulating layer 112 prevents the substrate 110 from being etched by an etching gas.

[0041] In an example, the insulating layer 112 may be formed using any one of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN) or any combination of any two or more thereof, and the insulating layer 112 may be formed by any one of chemical vapor deposition, RF magnetron sputtering and evaporation.

[0042] The sacrificial layer 120 may be formed on the insulating layer 112, and the cavity C and the etch stopper 130 may be disposed in the sacrificial layer 120. The cavity C may be formed by removing a portion of the sacrificial layer 120 during manufacturing. Therefore, since the cavity C is formed in the sacrificial layer 120, a portion of the first electrode 150 disposed on an upper portion of the sacrificial layer 120 and portions of other layers disposed on an upper portion of the sacrificial layer 120 may be formed flatly.

[0043] The etch stopper 130 is provided along the boundary of the cavity C. The etch stopper 130 is provided to prevent etching from proceeding beyond the cavity C region in the process of forming the cavity C.

[0044] The film layer 140 forms the cavity C together with the substrate 110. In addition, the film layer 140 may be made of a material having low reactivity with the etching gas when the sacrificial layer 120 is removed. The etching stopper 130 is inserted and disposed in the groove portion 142 formed by the film layer 140. The film layer 140 may include an inclined portion 140a disposed obliquely with respect to the upper surface of the substrate 110 and a flat portion 140b disposed in an effective area S in which the first electrode 150, the piezoelectric layer 160, and the second electrode 170 are all overlapped with each other. The film layer 140 may include a dielectric layer having any one of silicon nitride (Si3N4), silicon dioxide (SiO2), manganese oxide (MnO), magnesium oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO).

[0045] A seed layer (not shown) made of aluminum nitride (AlN) may be formed on the film layer 140, for example. That is, the seed layer may be disposed between the film layer 140 and the first electrode 150. In addition to aluminum nitride (AlN), the seed layer may also be formed using a dielectric or metal having a hexagonal close-packed (HCP) crystal structure. In an example in which the seed layer is formed using a metal, the seed layer may be formed using titanium (Ti).

[0046] The first electrode 150 is formed on the membrane layer 140 , and a portion of the first electrode 150 is disposed on an upper portion of the cavity C. In addition, the first electrode 150 may be configured as any one of an input electrode and an output electrode for respectively inputting or outputting an electrical signal such as a radio frequency (RF) signal.

[0047] The first electrode 150 may be made of, for example, an aluminum alloy material containing scandium (Sc). In an example in which the first electrode 150 is made of an aluminum alloy material containing scandium (Sc), high-power reactive sputtering may be possible due to increased mechanical strength. Under such deposition conditions, the surface roughness of the first electrode 150 may be prevented from increasing, and the piezoelectric layer 160 may also be induced to grow with high orientation.

[0048] In addition, by including scandium (Sc), the chemical resistance of the first electrode 150 can be increased, thereby compensating for the disadvantages that occur when the first electrode is made of pure aluminum. In addition, process stability in, for example, a dry etching or wet etching process during manufacturing can be ensured. In addition, when the first electrode is made of pure aluminum, oxidation is easily caused, but by forming the first electrode 150 using an aluminum alloy material containing scandium, chemical oxidation resistance can be improved.

[0049] However, the present disclosure is not limited to the examples described above, and the first electrode 150 may be formed using a conductive material such as molybdenum (Mo) or an alloy of molybdenum (Mo). In addition, for example, the first electrode 150 may be formed using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

[0050] The piezoelectric layer 160 may be formed to cover at least a portion of the first electrode 150 disposed on an upper portion of the cavity C. The piezoelectric layer 160 is a portion configured to generate a piezoelectric effect that converts electrical energy into mechanical energy in the form of elastic waves, and includes, for example, an aluminum nitride (AlN) material.

[0051] In addition, a dopant such as a rare earth metal or a transition metal may be doped into the piezoelectric layer 160. As an example, the rare earth metal used as a dopant may include any one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La), or any combination of any two or more thereof. In addition, the transition metal used as a dopant may include any one of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb), or any combination of any two or more thereof. In addition, the piezoelectric layer 160 may also include magnesium (Mg) as a divalent metal.

[0052] The second electrode 170 is formed to cover at least a portion of the piezoelectric layer 160 disposed on the upper portion of the cavity C. The second electrode 170 may be configured as any one of an input electrode and an output electrode for respectively inputting or outputting an electrical signal such as a radio frequency (RF) signal, etc. That is, when the first electrode 150 is configured as an input electrode, the second electrode 170 is configured as an output electrode, and when the first electrode 150 is configured as an output electrode, the second electrode 170 is configured as an input electrode.

[0053] However, the present disclosure is not limited to the examples provided above, and the second electrode 170 may be formed using a conductive material such as molybdenum (Mo) or an alloy of molybdenum (Mo). In addition, the second electrode 170 may be formed using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

[0054] The insertion layer 180 is disposed between the first electrode 150 and the piezoelectric layer 160. The insertion layer 180 may be formed using a dielectric layer including silicon dioxide (SiO2), aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), manganese oxide (MnO), magnesium oxide (MgO), zirconium oxide (ZrO2), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), titanium oxide (TiO2), zinc oxide (ZnO), etc., but may be formed using a material different from that of the piezoelectric layer 160. In addition, if necessary, the region in which the insertion layer 180 is disposed may also be formed as an air space. The air space may be realized by removing the insertion layer 180 in the manufacturing process.

[0055] As an example, the insertion layer 180 may be disposed along a surface of the membrane layer 140, a surface of the first electrode 150, and a surface of the etch stop 130. At least a portion of the insertion layer 180 may be disposed between the piezoelectric layer 160 and the first electrode 150.

[0056] The passivation layer 190 is formed in a region excluding portions of the first electrode 150 and the second electrode 170. The passivation layer 190 prevents the second electrode 170 and the first electrode 150 from being damaged during a manufacturing process.

[0057] In addition, a portion of the passivation layer 190 may be removed by etching in the final process for adjusting the frequency characteristics. That is, the thickness of the passivation layer 190 may be adjusted. For example, a dielectric layer including any one of silicon nitride (Si3N4), silicon dioxide (SiO2), manganese oxide (MnO), magnesium oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO) may be used to form the passivation layer 190.

[0058] The metal pad 200 is formed on a region of the first electrode 150 and the second electrode 170 on which the passivation layer is not formed. As an example, the metal pad 200 may be made of a material such as gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, and aluminum (Al), an aluminum alloy, etc. For example, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy.

[0059] The metal pad 200 may include a first metal pad 202 connected to the first electrode 150 and a second metal pad 204 connected to the second electrode 170 .

[0060] The connection member 210 is connected to the metal pad 200, and the diameter of the upper end of the connection member 210 is larger than the diameter of the lower end of the connection member 210. As an example, the connection member 210 may include: a cylindrical portion 211, which is provided at the upper end of the connection member 210 and has a constant diameter; and a tapered portion 212, which extends from the cylindrical portion 211, is located at the lower end of the connection member 210, and has a decreasing diameter in a direction toward the lower end of the connection member 210. The angle θ between the inclined surface 212a of the tapered portion 212 and the metal pad 200 may be 45° to 80°. In addition, the height h of the tapered portion 212 may be 6 μm or more. In addition, the minimum diameter (e.g., the diameter at the bottom end / bottom surface of the tapered portion 212) d1 of the tapered portion 212 may be 60 μm or more. The maximum diameter (e.g., the diameter of the cylindrical portion 211) d2 of the connection member 210 may be 90 μm or more.

[0061] In the manufacturing method of the connection member 210, first, a protective photoresist is laminated on the metal pad 200, and then a seed layer is laminated on the protective photoresist. Thereafter, a plating photoresist for forming the connection member 210 is laminated, and a hole for forming the connection member 210 is formed in the plating photoresist. Thereafter, after the connection member 210 is formed, the plating photoresist and the seed layer are removed. Thereafter, by removing the protective photoresist, a tapered portion 212 is formed at the lower end portion of the connection member 210.

[0062] Thus, by removing the protective resist, tapered portion 212 is formed at the lower end of connection member 210. Accordingly, tapered portion 212 is formed to have a height (h) of 6 μm or more, and an angle θ between inclined surface 212a of tapered portion 212 and metal pad 200 is 45° to 80°.

[0063] As an example, the connection member 210 may be made of a material such as gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, and aluminum (Al), an aluminum alloy, etc. The connection member 210 may be made of the same material as the material of the metal pad 200, or may be made of a material different from the material of the metal pad 200. As an example, in an example in which the metal pad 200 is made of a gold (Au) material, the connection member 210 may be made of a copper (Cu) material.

[0064] As described above, since the tapered portion 212 is provided in the connection member 210 , stress applied to the lower portion of the connection member 210 may be reduced to improve reliability.

[0065] Furthermore, by reducing the diameter of the lower end of connecting member 210 connected to metal pad 200 and increasing the diameter of the upper end of connecting member 210 , connecting member 210 can be easily connected to metal pad 200 even if the area of ​​metal pad 200 is insufficient to mount connecting member 210 .

[0066] Figure 3 is a cross-sectional view showing a bulk acoustic wave resonator 300 according to an embodiment. Figure 4 It is shown Figure 3 Magnified view of part B.

[0067] Reference Figure 3 and Figure 4 The BAW resonator 300 may include, for example, a substrate 310 , a membrane layer 320 , a first electrode 330 , a piezoelectric layer 340 , a second electrode 350 , a passivation layer 360 , a metal pad 370 , and a connection member 380 .

[0068] The substrate 310 may be a silicon substrate. For example, a silicon wafer or a silicon-on-insulator type substrate may be used as the substrate 310 .

[0069] The insulating layer 312 may be formed on the upper surface of the substrate 310 and may electrically isolate the substrate 310 from layers and components disposed thereon. In addition, when the cavity C is formed in the manufacturing process, the insulating layer 312 prevents the substrate 310 from being etched by an etching gas.

[0070] In an example, the insulating layer 312 may be formed using any one of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN) or any combination of any two or more thereof, and the insulating layer 312 may be formed by any one of chemical vapor deposition, RF magnetron sputtering and evaporation.

[0071] The membrane layer 320 forms a cavity C together with the substrate 310. The membrane layer 320 may include an inclined portion 320a disposed obliquely relative to the upper surface of the substrate 310 and a flat portion 320b disposed in an effective area S, in which the first electrode 330, the piezoelectric layer 340, and the second electrode 350 are all stacked on each other. In addition, the membrane layer 320 may be made of a material having low reactivity with an etching gas when a sacrificial layer (not shown) is removed. The membrane layer 320 may include a dielectric layer having any one of silicon nitride (Si3N4), silicon dioxide (SiO2), manganese oxide (MnO), magnesium oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO).

[0072] A seed layer (not shown) made of aluminum nitride (AlN) may be formed on the film layer 320. That is, the seed layer may be disposed between the film layer 320 and the first electrode 330. In addition to aluminum nitride (AlN), the seed layer may also be formed using a dielectric or metal having an HCP crystal structure. In an example in which the seed layer is a metal, the seed layer may be formed using titanium (Ti).

[0073] The first electrode 330 may be disposed on the film layer 320 , and a portion of the first electrode 330 may be disposed on an upper portion of the cavity C. In addition, the first electrode 330 may be configured as any one of an input electrode and an output electrode for respectively inputting or outputting an electrical signal such as a radio frequency (RF) signal.

[0074] As an example, the first electrode 330 may be formed using a conductive material such as molybdenum (Mo) or an alloy of molybdenum (Mo). However, the present disclosure is not limited to this example, and the first electrode 330 may be formed using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

[0075] The piezoelectric layer 340 may be formed to cover at least a portion of the first electrode 330 disposed on the upper portion of the cavity C. The piezoelectric layer 340 is a portion configured to generate a piezoelectric effect that converts electrical energy into mechanical energy in the form of elastic waves, and may be formed using any one of aluminum nitride (AlN), zinc oxide (ZnO), and lead zirconate titanate (PZT; PbZrTiO). For example, when the piezoelectric layer 340 is made of aluminum nitride (AlN), the piezoelectric layer 340 may also include a rare earth metal or a transition metal. As an example, the rare earth metal may include any one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La), or any combination of any two or more thereof. In addition, as an example, the transition metal may include any one of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb), or any combination of any two or more thereof. In addition, magnesium (Mg) as a divalent metal may also be included.

[0076] The second electrode 350 is formed to cover at least a portion of the piezoelectric layer 340 disposed on the upper portion of the cavity C. The second electrode 350 may be configured as any one of an input electrode and an output electrode for inputting and outputting an electrical signal such as a radio frequency (RF) signal, respectively. That is, when the first electrode 330 is configured as an input electrode, the second electrode 350 may be configured as an output electrode, and when the first electrode 330 is configured as an output electrode, the second electrode 350 may be configured as an input electrode.

[0077] As an example, the second electrode 350 may be formed using a conductive material such as molybdenum (Mo) or an alloy of molybdenum (Mo). However, the present disclosure is not limited to this example, and the second electrode 350 may be formed using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

[0078] The second electrode 350 may include a frame 352 disposed at an edge of the active region S. As described above, the active region S is, for example, a region where the first electrode 330, the piezoelectric layer 340, and the second electrode 350 all overlap each other. The frame 352 may have a thickness greater than that of the rest of the second electrode 350.

[0079] The passivation layer 360 is formed in a region excluding portions of the first electrode 330 and the second electrode 350. The passivation layer 360 prevents the second electrode 350 and the first electrode 330 from being damaged during a manufacturing process.

[0080] In addition, a portion of the passivation layer 360 may be removed by etching for adjusting the frequency characteristics in the final process of the manufacturing process. That is, the thickness of the passivation layer 360 may be adjusted. For example, the passivation layer 360 may be formed using a dielectric layer including any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO).

[0081] The metal pad 370 is connected to the regions of the first electrode 330 and the second electrode 350 exposed from the passivation layer 360. As an example, the metal pad 370 may be made of a material such as gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, and aluminum (Al), an aluminum alloy, etc. For example, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy.

[0082] The metal pad 370 may include a first metal pad 372 connected to the first electrode 330 and a second metal pad 374 connected to the second electrode 350 .

[0083] The connection member 380 is connected to the metal pad 370, and the diameter of the upper end of the connection member 380 is larger than the diameter of the lower end of the connection member 380. As an example, the connection member 380 may include: a cylindrical portion 381, which is provided at the upper end of the connection member 380 and has a constant diameter; and a tapered portion 382, ​​which extends from the cylindrical portion 381, is located at the lower end of the connection member 380, and has a diameter that decreases in a direction toward the lower end of the connection member 380. The angle θ between the inclined surface 382a of the tapered portion 382 and the metal pad 370 may be 45° to 80°. In addition, the height h of the tapered portion 382 may be 6μm or more. In addition, the minimum diameter (e.g., the diameter at the bottom end / bottom surface of the tapered portion 382) d1 of the tapered portion 382 may be 60μm or more. The maximum diameter (e.g., the diameter of the cylindrical portion 381) d2 of the connection member 380 may be 90μm or more.

[0084] Hereinafter, the manufacturing method of the connection member 380 will be briefly discussed. First, a protective photoresist is stacked on the metal pad 370, and then a seed layer is stacked on the protective photoresist. Thereafter, a plating photoresist for forming the connection member 380 is stacked, and a hole for forming the connection member 380 is formed in the plating photoresist. Thereafter, after the connection member 380 is formed, the plating photoresist and the seed layer are removed. Thereafter, by removing the protective photoresist, a tapered portion 382 is formed at the lower end portion of the connection member 380.

[0085] Thus, by removing the protective resist, a tapered portion 382 is formed at the lower end of the connection member 380. Accordingly, the tapered portion 382 is formed to have a height (h) of 6 μm or more, and an angle θ between an inclined surface 382a of the tapered portion 382 and the metal pad 370 is 45 to 80 degrees.

[0086] As an example, the connection member 380 may be made of a material such as gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, and aluminum (Al), an aluminum alloy, etc. The connection member 380 may be made of the same material as that of the metal pad 370, or may be made of a material different from that of the metal pad 370. In an example in which the metal pad 370 is made of a gold (Au) material, the connection member 380 may be made of a copper (Cu) material.

[0087] As described above, since the tapered portion 382 is provided in the connection member 380 , stress applied to the lower portion of the connection member 380 may be reduced to improve reliability.

[0088] Furthermore, even if the area of ​​metal pad 370 is insufficient to mount connection member 380 , connection member 380 may be easily connected to metal pad 370 by reducing the diameter of the lower end portion of connection member 380 connected to metal pad 370 and increasing the diameter of the upper end portion of connection member 380 .

[0089] As described above, according to the embodiments disclosed herein, the reliability of a BAW resonator can be improved by reducing stress applied to the lower portion of a connection member.

[0090] Although the present disclosure includes specific examples, it will be apparent after understanding the disclosure of the present application that various changes can be made to these examples in form and detail without departing from the spirit and scope of the claims and their equivalents. The examples described herein will be considered as descriptive meanings only, not for the purpose of limitation. The description of the features or aspects in each example will be considered as being applicable to similar features or aspects in other examples. If the described techniques are performed in different orders, and / or if the components in the described systems, architectures, devices, or circuits are combined in different ways, and / or the components in the described systems, architectures, devices, or circuits are replaced or added by other components or their equivalents, suitable results can be obtained. Therefore, the scope of the present disclosure is not limited by specific embodiments, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents will be interpreted as being included in the present disclosure.

Claims

1. A bulk acoustic wave resonator, comprising: substrate; A first electrode is disposed on the substrate; a piezoelectric layer, arranged to cover at least a portion of the first electrode; a second electrode, arranged to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; as well as a connecting member connected to an upper surface of the metal pad, wherein the lower end portion of the connection member includes a tapered portion whose diameter decreases in a direction toward the lower end of the connection member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°, Wherein, the tapered portion has a height of 6 μm or greater.

2. The BAW resonator according to claim 1, wherein: The upper end portion of the connection member includes a cylindrical portion having a constant diameter, and wherein the tapered portion is disposed below the cylindrical portion.

3. The BAW resonator according to claim 1, wherein: The diameter of the top surface of the tapered portion is 90 μm or more.

4. The BAW resonator according to any one of claims 1 to 3, wherein: The bottom surface of the tapered portion has a diameter of 60 μm or more.

5. The BAW resonator according to any one of claims 1 to 3, wherein: The connection member is made of any one of gold, gold-tin alloy, copper, copper-tin alloy, aluminum and aluminum alloy, or a material containing any two or more of gold, gold-tin alloy, copper, copper-tin alloy, aluminum and aluminum alloy. 6 . The BAW resonator of claim 1 , further comprising an insertion layer disposed between the first electrode and the piezoelectric layer. 7 . The BAW resonator of claim 1 , further comprising a membrane layer forming a cavity together with the substrate.

8. The BAW resonator according to claim 7, further comprising: an etch stop disposed around the cavity; as well as A sacrificial layer is arranged to surround the etching stopper.

9. The BAW resonator according to claim 7, wherein: The film layer includes an inclined portion disposed obliquely with respect to an upper surface of the substrate and a flat portion disposed in an effective region in which the first electrode, the piezoelectric layer, and the second electrode are all overlapped with each other.

10. The BAW resonator according to claim 9, wherein: The second electrode includes a frame disposed at an edge of the active area, and wherein the frame has a thickness greater than a thickness of a remaining portion of the second electrode.

11. The BAW resonator of claim 7, further comprising an insulating layer disposed on the substrate and below the cavity.

12. The BAW resonator according to claim 1, wherein: The metal pads include a first metal pad connected to the first electrode and a second metal pad connected to the second electrode.

13. A bulk acoustic wave resonator, comprising: substrate; A first electrode is disposed on the substrate; a piezoelectric layer, arranged to cover at least a portion of the first electrode; a second electrode, arranged to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; as well as a connecting member connected to an upper surface of the metal pad, Wherein, the connecting member comprises: a cylindrical portion provided at an upper end portion of the connection member and having a constant diameter; and A tapered portion is provided below the cylindrical portion, the tapered portion having a height of 6 μm or more and a smaller diameter at a lower end of the tapered portion than at an upper end of the tapered portion.

14. The BAW resonator according to claim 13, wherein: A bottom surface of the tapered portion contacts the upper surface of the metal pad.

15. The BAW resonator according to claim 14, wherein: The bottom surface of the tapered portion has a diameter of 60 μm or more.

16. The BAW resonator according to any one of claims 13 to 15, wherein: In a cross-sectional view of the BAW resonator, a width of a bottom surface of the tapered portion is smaller than a width of a flat portion of the upper surface of the metal pad.

17. A bulk acoustic wave resonator, comprising: substrate; A first electrode is disposed on the substrate; a piezoelectric layer, arranged to cover at least a portion of the first electrode; a second electrode, arranged to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; as well as a connecting member connected to an upper surface of the metal pad, wherein the lower end portion of the connection member includes a tapered portion whose diameter decreases in a direction toward the lower end of the connection member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°, Wherein, a diameter of a bottom surface of the tapered portion is 60 μm or greater.

18. A bulk acoustic wave resonator, comprising: substrate; A first electrode is disposed on the substrate; a piezoelectric layer, arranged to cover at least a portion of the first electrode; a second electrode, arranged to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; as well as a connecting member connected to an upper surface of the metal pad, wherein the lower end portion of the connecting member includes a tapered portion whose diameter decreases in a direction toward the lower end of the connecting member, Wherein, the tapered portion has a height of 6 μm or greater.

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