Bulk acoustic wave resonator

Abstract

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 protective layer disposed to cover at least the metal pad.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0040838, filed on April 3, 2020, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

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

[0003] Typically, trimming processes may be required in the fabrication of bulk acoustic wave resonators to adjust frequency characteristics. In wafers that may exhibit dispersion due to the distribution of deposition or etching processes at each layer, trimming processes are performed to adjust the frequency characteristics within the wafer. In cases where filters comprise series / parallel (Se / Sh) resonators, trimming processes may be necessary to tune the filter waveform to adjust the frequency characteristics of each of the different types of series / parallel resonators.

[0004] However, there may be a problem that byproducts of the passivation layer removed during the finishing process may accumulate on the inner surface of the metal pads.

[0005] Furthermore, the thickness of the passivation layer may be unevenly formed in the effective area due to the trimming process. Summary of the Invention

[0006] This summary is provided to introduce the selected concepts in a simplified form, and these concepts are further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0007] In one general aspect, a bulk acoustic resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer configured to cover at least a portion of the first electrode; a second electrode configured to cover at least a portion of the piezoelectric layer; metal pads connected to the first electrode and the second electrode; and a protective layer configured to at least cover the metal pads.

[0008] The protective layer can be formed using any one of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), and silicon dioxide (SiO2).

[0009] The protective layer may be disposed outside the effective area where the first electrode, the piezoelectric layer, and the second electrode overlap.

[0010] The bulk acoustic resonator may further include an adhesive layer disposed between the protective layer and the metal pads.

[0011] The adhesive layer can be formed using either aluminum oxide (Al2O3) or aluminum nitride (AlN). The protective layer can be formed using either silicon nitride (SiN) or silicon dioxide (SiO2).

[0012] The bulk acoustic resonator may further include an insertion layer disposed between the first electrode and the piezoelectric layer.

[0013] The bulk acoustic resonator may further include: a diaphragm layer, wherein the diaphragm layer and the substrate form a cavity.

[0014] The bulk acoustic resonator may further include: an etch stop portion configured to surround the cavity; and a sacrificial layer configured to surround the etch stop portion.

[0015] The film layer may include an inclined portion disposed at an angle relative to the surface of the substrate on which the film layer is disposed, and a planar portion disposed parallel to the surface of the substrate in an effective region in which the first electrode, the piezoelectric layer and the second electrode overlap each other.

[0016] The second electrode may include a frame disposed on the edge of the effective region and having a thickness greater than that of other portions of the second electrode.

[0017] The substrate may include an insulating layer disposed at least below the cavity.

[0018] The metal pad may include a first metal pad connected to the first electrode and a second metal pad connected to the second electrode.

[0019] In another general aspect, a bulk acoustic 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 passivation layer disposed to cover the first electrode, a portion of the piezoelectric layer disposed on the outside of the first electrode, and the metal pad.

[0020] The bulk acoustic resonator may further include an adhesive layer disposed between the metal pad and the passivation layer.

[0021] The adhesive layer can be formed using insulating or metallic materials.

[0022] The passivation layer can be formed using a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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).

[0023] The bulk acoustic resonator may further include an adhesive layer disposed between the metal pads and the passivation layer, and formed using either aluminum oxide (Al2O3) or aluminum nitride (AlN).

[0024] The passivation layer may also be configured to cover the second electrode.

[0025] Other features and aspects will become apparent from the following detailed description, drawings, and claims. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view showing a bulk acoustic resonator according to an embodiment.

[0027] Figure 2 It is shown Figure 1 An enlarged view of part A.

[0028] Figure 3 It is shown Figure 1 An enlarged view of part B.

[0029] Figure 4 This is a cross-sectional view showing a bulk acoustic resonator according to an embodiment.

[0030] Figure 5 It is shown Figure 4 An enlarged view of part C.

[0031] Figure 6 It is shown Figure 4 An enlarged view of part D.

[0032] Figure 7 This is a cross-sectional view showing a bulk acoustic resonator according to an embodiment.

[0033] Figure 8 It is shown Figure 7 An enlarged view of part E.

[0034] Figure 9 It is shown Figure 7 An enlarged view of part F.

[0035] Figure 10 This is a cross-sectional view showing a bulk acoustic resonator according to an embodiment.

[0036] Figure 11 This is a cross-sectional view showing a bulk acoustic resonator according to an embodiment.

[0037] Throughout the accompanying drawings and detailed embodiments, the same reference numerals indicate the same elements. The drawings may not be drawn to scale, and for clarity, illustration, and convenience, the relative sizes, scales, and depictions of the elements in the drawings may be exaggerated. Detailed Implementation

[0038] The following detailed embodiments are provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various modifications, variations, and equivalents of the methods, apparatus, and / or systems described herein will be apparent upon understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein; rather, changes may be made that will become apparent upon understanding the disclosure of this application, except for operations that must occur in a specific order. Furthermore, for clarity and brevity, descriptions of features well-known in the art may be omitted.

[0039] The features described herein may be implemented in different forms and should not be construed as being limited to the examples described herein. Rather, the examples provided herein are merely illustrative of some of the many feasible ways in which the methods, apparatus, and / or systems described herein will become apparent upon understanding the disclosure of this application.

[0040] It should be noted here that the use of the term "may" in relation to examples or embodiments (e.g., what an example or embodiment may include or implement) means that there exists at least one example or embodiment that includes or implements such a feature, but not all examples and embodiments are limited thereto.

[0041] Throughout the specification, when an element such as a layer, region, or substrate is described as being "on" another element, "connected" to another element, or "bonded" to another element, the element may be directly "on" another element, directly "connected" to another element, or directly "bonded" to another element, or there may be one or more other elements in between. In contrast, when an element is described as being "directly on" another element, directly "connected" to another element, or "bonded" to another element, there may be no other elements in between.

[0042] As used herein, the term “and / or” includes any one of the relevant listed items and any combination of any two or more.

[0043] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, assemblies, regions, layers, or parts, these components, assemblies, regions, layers, or parts are not limited by these terms. Rather, these terms are used only to distinguish one component, assembly, region, layer, or part from another. Therefore, without departing from the teaching of the examples described herein, the first component, first assembly, first region, first layer, or first part referred to as the first component, first assembly, first region, first layer, or first part may also be referred to as the second component, second assembly, second region, second layer, or second part.

[0044] For ease of description, spatial relative terms such as “above,” “over,” “below,” “under,” “front,” “back,” and “side” are used herein to describe the relationship between one element and another as shown in the accompanying drawings. Such spatial relative terms are intended to include not only the orientation depicted in the drawings but also different orientations of the device during use or operation. For example, if the device in the drawings is flipped, an element described as “above” or “over” relative to another element will then be “below” or “under” relative to that other element. Thus, the term “above” includes both “above” and “below” orientations depending on the spatial orientation of the device. As another example, if the device in the drawings is flipped, an element described as “in front” relative to another element will then be “behind” relative to that other element. Thus, the term “in front” includes both “in front” and “back” orientations depending on the spatial orientation of the device. The device may also be positioned in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative terms used herein will be interpreted accordingly.

[0045] The terminology used herein is for the purpose of describing various examples only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms “comprising,” “including,” and “having” enumerate the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0046] Due to manufacturing techniques and / or tolerances, variations in the shape shown in the accompanying drawings may occur. Therefore, the examples described herein are not limited to the specific shapes shown in the accompanying drawings, but include variations in shape that occur during manufacturing.

[0047] The features of the examples described herein can be combined in various ways that will become apparent upon understanding the disclosure of this application. Furthermore, while the examples described herein have multiple constructions, other constructions that will become apparent upon understanding the disclosure of this application are also possible.

[0048] Figure 1 This is a cross-sectional view showing a bulk acoustic resonator 100 according to an embodiment. Figure 2 It is shown Figure 1 An enlarged view of part A. Figure 3 It is shown Figure 1 An enlarged view of part B.

[0049] Reference Figures 1 to 3 The bulk acoustic wave resonator 100 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop portion 130, a film 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 protective layer 210.

[0050] 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.

[0051] An insulating layer 112 may be formed on the upper surface of the substrate 110, and the insulating layer 112 can electrically isolate components disposed on the upper surface of the substrate 110 from the substrate 110. Furthermore, when the insulating layer 112 forms the cavity C during the manufacturing process, the insulating layer 112 can prevent the substrate 110 from being etched by etching gas. In the bulk acoustic wave resonator 100, the substrate includes an insulating layer 112 disposed at least below the cavity C.

[0052] In this example, the insulating layer 112 can be formed using any one or any combination of two or more of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN), and can be formed by any one of chemical vapor deposition, RF magnetron sputtering and evaporation processes.

[0053] The sacrificial layer 120 may be formed on the insulating layer 112, and the cavity C and the etch stop portion 130 may be disposed on the inner side of the sacrificial layer 120. The cavity C may be formed by partially removing the sacrificial layer 120 during the manufacturing process. Since the cavity C is formed on the inner side of the sacrificial layer 120, the portion of the first electrode 150 disposed on the sacrificial layer 120 and the portions of other layers disposed on the sacrificial layer can be uniformly disposed.

[0054] The etching stop portion 130 may be provided along the boundary of cavity C. The etching stop portion 130 can prevent etching beyond the cavity area during the process of forming cavity C.

[0055] The film layer 140 can form a cavity C with the substrate 110. The film layer 140 can also be formed using a material that has low reactivity with the etching gas during the removal of the sacrificial layer 120. For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the film layer 140.

[0056] A seed layer (not shown) made of aluminum nitride (AlN) can be formed on the film layer 140. The seed layer can be disposed between the film layer 140 and the first electrode 150. The seed layer can be formed using a dielectric material or a metal having an HCP (hexagonal close-packed) crystal structure instead of aluminum nitride (AlN). As an example, when the seed layer is a metal, it can be formed using titanium (Ti).

[0057] However, the seed layer is not limited to the examples provided above, and when the seed layer is formed using a material with low reactivity with the etching gas, film layer 140 can be removed. In other words, the seed layer can replace film layer 140.

[0058] The first electrode 150 may be formed on the film layer 140, and a portion of the first electrode 150 may be disposed on the cavity C. The first electrode 150 may be configured as either an input electrode or an output electrode capable of inputting and outputting electrical signals such as radio frequency (RF) signals.

[0059] The first electrode 150 can be formed using an aluminum alloy material containing scandium (Sc). Because the first electrode 150 is formed using an aluminum alloy material containing scandium (Sc), its mechanical strength is increased, allowing high-power reactive sputtering to be used to form the first electrode 150. Under the aforementioned deposition conditions, the increase in surface roughness of the first electrode 150 can be reduced or prevented, and a highly oriented growth of the piezoelectric layer 160 can be induced.

[0060] Furthermore, since the first electrode 150 contains scandium (Sc), its chemical resistance is increased, mitigating potential problems that may occur when the first electrode is formed using pure aluminum. Additionally, it provides process stability for both dry and wet etching processes during manufacturing. Moreover, oxidation may easily occur when the first electrode is formed using pure aluminum. However, since the first electrode 150 is formed using an aluminum alloy material containing scandium, its chemical resistance and oxidation resistance are improved.

[0061] However, the first electrode 150 is not limited to the foregoing examples, and for example, the first electrode 150 may be formed using a conductive material such as molybdenum (Mo) or an alloy of Mo. Furthermore, 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 Ru, W, Ir, Pt, Cu, Ti, Ta, Ni, or Cr.

[0062] The piezoelectric layer 160 may be configured to at least cover the portion of the first electrode 150 disposed on the cavity C. The piezoelectric layer 160 may be a layer configured to generate a piezoelectric effect that converts electrical energy into mechanical energy in the form of elastic waves, and may include, for example, an aluminum nitride (AlN) material.

[0063] The piezoelectric layer 160 may be doped with dopants such as rare earth metals or transition metals. As an example, rare earth metals used as dopants may include any one or any combination of two or more of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). Furthermore, transition metals used as dopants may include any one or any combination of two or more of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb). Additionally, the piezoelectric layer 160 may include divalent magnesium (Mg).

[0064] The second electrode 170 may cover at least a portion of the piezoelectric layer 160 disposed on the cavity C. The second electrode 170 may be configured as either an input electrode or an output electrode, capable of respectively inputting and outputting electrical signals such as radio frequency (RF) signals. When the first electrode 150 is configured as an input electrode, the second electrode 170 may be configured as an output electrode. When the first electrode 150 is configured as an output electrode, the second electrode 170 may be configured as an input electrode.

[0065] However, the second electrode 170 is not limited to the foregoing examples, and for example, the second electrode 170 may be formed using a conductive material such as molybdenum (Mo) or an alloy of Mo. Alternatively, 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 Ru, W, Ir, Pt, Cu, Ti, Ta, Ni, or Cr.

[0066] An insertion layer 180 may be disposed between the first electrode 150 and the piezoelectric layer 160. The insertion layer 180 may be formed using dielectric materials such as silicon dioxide (SiO2), aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), magnesium oxide (MgO), manganese oxide (MnO), zirconium oxide (ZrO2), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), titanium oxide (TiO2), and zinc oxide (ZnO), and may be formed using a material different from that of the piezoelectric layer 160. Furthermore, if desired, the region where the insertion layer 180 is disposed may alternatively be formed from empty space (air). Empty space can be achieved by removing the insertion layer 180. Additionally, the insertion layer 180 may be formed using metallic materials such as aluminum (Al) and titanium (Ti).

[0067] As an example, the insertion layer 180 may be disposed along the surface of the film layer 140, the first electrode 150, and the etch stop portion 130. Furthermore, at least a portion of the insertion layer 180 may be disposed between the piezoelectric layer 160 and the first electrode 150.

[0068] The passivation layer 190 may be formed in a region excluding a portion of each of the first electrode 150 and the second electrode 170. The passivation layer 190 prevents the first electrode 150 and the second electrode 170 from being damaged during the manufacturing process.

[0069] The passivation layer 190 can be partially removed by an etching process to adjust the frequency characteristics in the final manufacturing process. Therefore, the thickness of the passivation layer 190 can be adjusted. For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the passivation layer 190.

[0070] Metal pads 200 may be formed on the portions of each of the first electrode 150 and the second electrode 170 where the passivation layer 190 is not formed. As an example, the metal pads 200 may be formed using materials such as gold (Au), gold-tin (Au-Sn) alloys, copper (Cu), copper-tin (Cu-Sn) alloys, and aluminum (Al) or aluminum alloys. For example, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy.

[0071] 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.

[0072] The protective layer 210 may at least cover the metal pads 200. In other words, the protective layer 210 may be configured to at least cover the surface of the metal pads 200. The protective layer 210 may be disposed outside the effective region. The effective region is, for example, the region in which the first electrode 150, the piezoelectric layer 160, and the second electrode 170 overlap each other. In other words, the protective layer 210 may not be disposed within the effective region.

[0073] As an example, the protective layer 210 may be formed using a material that may not be easily trimmed in the trimming process compared to the passivation layer 190, or the protective layer 210 may have a thickness greater than that of the passivation layer 190.

[0074] The protective layer 210 can be formed using any one of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), and silicon dioxide (SiO2). As an example, when the metal pad 200 is formed using gold (Au) material, the protective layer 210 can be formed using any one of aluminum oxide (Al2O3) and aluminum nitride (AlN).

[0075] As described above, since the protective layer 210 is formed to cover the metal pad 200, byproducts of the passivation layer 190 removed during the process of trimming the passivation layer 190 can be prevented from stacking on the inner surface of the metal pad 200.

[0076] Furthermore, after the finishing process is completed, it can prevent the passivation layer 190 from forming unevenly in the effective area.

[0077] More specifically, a template mask can typically be used to perform the process of trimming the passivation layer 190. However, when using a template mask to perform the trimming process, there may be disadvantages in terms of process implementation accuracy, reproducibility, and design flexibility due to the deterioration of the alignment and reproducibility of the apparatus, template mask, and trimming apparatus; the ion beam shadowing effect caused by the gap between the bulk acoustic resonator and the template mask; and the ion beam shadowing effect caused by the exposure of layers other than the layer requiring the trimming process.

[0078] Alternatively, when using photoresist to perform the trimming process, it may be difficult to perform a uniform masking process due to the differences in the shape of the bulk acoustic wave resonators at different locations in the wafer, which could be a disadvantage. Furthermore, without performing a uniform masking process, the surface potential may be non-uniform in the trimming region due to the difference in surface potential between the metal pads 200 and the passivation layer 190. Therefore, trimming may be performed non-uniformly in trimming processes using argon ions.

[0079] In addition, when using photoresist to perform the trimming process, there may be a problem that byproducts of the passivation layer 190 generated during the trimming process (byproducts generated from the removal of the passivation layer 190) may stack on the inner surface of the metal pad 200.

[0080] However, in the example embodiment described herein, the protective layer 210 may be configured to cover the surface of the metal pad 200. Therefore, byproducts of the portion of the passivation layer 190 removed during the trimming process can be prevented from stacking on the inner surface of the metal pad 200, and the thickness of the passivation layer 190 can be prevented from becoming uneven in the effective area after the trimming process is completed.

[0081] As described above, the protective layer 210 prevents byproducts of the portion of the passivation layer 190 removed during the trimming process from stacking on the inner surface of the metal pad 200, and also prevents the thickness of the passivation layer 190 from becoming uneven in the effective area after the trimming process is completed.

[0082] In the following description, variant embodiments of the bulk acoustic resonator will be described. For the sake of brevity, variations of the same resonator will not be repeated. Figures 1 to 3 The same elements as those in the embodiments are described in detail.

[0083] Figure 4 This is a cross-sectional view showing a bulk acoustic resonator 300 according to an embodiment. Figure 5 It is shown Figure 4 An enlarged view of part C. Figure 6 It is shown Figure 4 An enlarged view of part D.

[0084] Reference Figures 4 to 6 The bulk acoustic wave resonator 300 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop portion 130, a film 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, an adhesive layer 410, and a protective layer 420.

[0085] Substrate 110, sacrificial layer 120, etch stop portion 130, film layer 140, first electrode 150, piezoelectric layer 160, second electrode 170, insertion layer 180, passivation layer 190, and metal pad 200 are compatible with... Figures 1 to 3 The descriptions are the same, therefore, the detailed descriptions of these components will not be repeated.

[0086] The adhesive layer 410 allows the protective layer 420 to be easily laminated onto the surface of the metal pad 200. The adhesive layer 410 can be laminated onto the surface of the metal pad 200. In other words, the adhesive layer 410 can be disposed between the protective layer 420 and the metal pad 200. For example, the adhesive layer 410 can be formed using either alumina (Al2O3) or aluminum nitride (AlN).

[0087] The protective layer 420 may be configured to at least cover the adhesive layer 410. In other words, the protective layer 420 may be configured to at least cover the adhesive layer 410 stacked on the surface of the metal pad 200. The protective layer 420 may be disposed outside the effective area. In other words, the protective layer 420 may not be disposed within the effective area.

[0088] As an example, the protective layer 420 may be formed using a material that may not be easily trimmed in the trimming process compared to the passivation layer 190, or the protective layer 420 may have a thickness greater than that of the passivation layer 190.

[0089] The protective layer 420 can be formed using either silicon nitride (SiN) or silicon dioxide (SiO2). As an example, when the metal pad 200 is formed using gold (Au) and the adhesive layer 410 is formed using either aluminum oxide (Al2O3) or aluminum nitride (AlN), the protective layer 420 can be formed using either silicon nitride (SiN) or silicon dioxide (SiO2).

[0090] As described above, since the protective layer 420 is formed to cover the metal pad 200, byproducts of the portion of the passivation layer 190 removed during the process of trimming the passivation layer 190 can be prevented from stacking on the inner surface of the metal pad 200.

[0091] Furthermore, after the finishing process is completed, it can prevent the passivation layer 190 from forming unevenly in the effective area.

[0092] Figure 7 This is a cross-sectional view showing a bulk acoustic resonator 500 according to an embodiment. Figure 8 It is shown Figure 7 An enlarged view of part E. Figure 9 It is shown Figure 7 An enlarged view of part F.

[0093] Reference Figures 7 to 9 The bulk acoustic wave resonator 500 may include, for example, a substrate 510, a film layer 520, a first electrode 530, a piezoelectric layer 540, a second electrode 550, a passivation layer 560, a metal pad 570, and a protective layer 580.

[0094] The substrate 510 can be a silicon substrate. For example, a silicon wafer or a silicon-on-insulator (SOI) type substrate can be used as the substrate 510.

[0095] An insulating layer 512 may be formed on the upper surface of the substrate 510, and the insulating layer 512 can electrically isolate the components disposed on the upper surface of the substrate 510 from the substrate 510. In addition, when the insulating layer 512 forms cavity C in the manufacturing process, the insulating layer 512 can prevent the substrate 510 from being etched by etching gas.

[0096] In this example, the insulating layer 512 can be formed using any one or any combination of two or more of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN), and can be formed by any one of chemical vapor deposition, RF magnetron sputtering and evaporation processes.

[0097] The film layer 520 can form a cavity C with the substrate 510. The film layer 520 can also be formed using a material that has low reactivity with the etching gas during the removal of the sacrificial layer (not shown). For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the film layer 520.

[0098] A seed layer (not shown) formed using aluminum nitride (AlN) can be formed on film layer 520. The seed layer can be disposed between film layer 520 and first electrode 530. A dielectric material or a metal having an HCP crystal structure can be used instead of aluminum nitride (AlN) to form the seed layer. As an example, when the seed layer is a metal, it can be formed using titanium (Ti).

[0099] The film layer 520 may include an inclined portion 522 disposed at an angle relative to the upper surface (e.g., horizontal direction) of the substrate 510, and a planar portion (e.g., horizontal or horizontal portion) 524 disposed in the effective region in which the first electrode 530, the piezoelectric layer 540 and the second electrode 550 overlap with each other. The planar portion 524 may be disposed parallel to the upper surface of the substrate 510.

[0100] The first electrode 530 may be formed on the film layer 520, and a portion of the first electrode 530 may be disposed on the cavity C. Furthermore, the first electrode 530 may be configured as either an input electrode or an output electrode capable of inputting and outputting electrical signals such as radio frequency (RF) signals.

[0101] For example, the first electrode 530 may be formed using a conductive material such as molybdenum (Mo) or an alloy of Mo. However, the first electrode 530 is not limited to the foregoing example, and the first electrode 530 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 Ru, W, Ir, Pt, Cu, Ti, Ta, Ni, or Cr.

[0102] The piezoelectric layer 540 may be configured to at least cover the portion of the first electrode 530 disposed on the cavity C. The piezoelectric layer 540 may be a layer configured to generate a piezoelectric effect that converts electrical energy into mechanical energy in the form of elastic waves, and may be formed using, for example, aluminum nitride (AlN), zinc oxide (ZnO), or lead zirconate titanate (PZT; PbZrTiO). When the piezoelectric layer 540 is formed using aluminum nitride (AlN), the piezoelectric layer 540 may also include rare earth metals or transition metals. As an example, rare earth metals may include any one or any combination of two or more of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). Furthermore, as an example, transition metals may include any one or any combination of two or more of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb). Additionally, divalent metal magnesium (Mg) may be included.

[0103] The second electrode 550 may cover at least a portion of the piezoelectric layer 540 disposed on the cavity C. The second electrode 550 may be configured as either an input electrode or an output electrode, respectively, to input and output electrical signals such as radio frequency (RF) signals. When the first electrode 530 is configured as an input electrode, the second electrode 550 may be configured as an output electrode. When the first electrode 530 is configured as an output electrode, the second electrode 550 may be configured as an input electrode.

[0104] For example, the second electrode 550 can be formed using a conductive material such as a molybdenum (Mo) or an alloy of Mo. However, the second electrode 550 is not limited to the foregoing example. The second electrode 550 can 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 Ru, W, Ir, Pt, Cu, Ti, Ta, Ni, or Cr.

[0105] A frame 552 disposed on the edge of the effective region may be included in the second electrode 550. The frame 552 may be disposed on the edge of the effective region and have a thickness greater than the thickness of other portions of the second electrode 550 (i.e., the portions of the second electrode 550 other than the frame 552).

[0106] The passivation layer 560 may be formed in a region other than a portion of the first electrode 530 and the second electrode 550. The passivation layer 560 prevents the first electrode 530 and the second electrode 550 from being damaged during the manufacturing process.

[0107] The passivation layer 560 can be partially removed by an etching process to adjust the frequency characteristics in the final manufacturing process. Therefore, the thickness of the passivation layer 560 can be adjusted. For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the passivation layer 560.

[0108] Metal pads 570 can be connected to a first electrode 530 and a second electrode 550 exposed from the passivation layer 560. As an example, the metal pads 570 can be formed using materials such as gold (Au), gold-tin (Au-Sn) alloys, copper (Cu), copper-tin (Cu-Sn) alloys, and aluminum (Al) or aluminum alloys. For example, the aluminum alloy could be an aluminum-germanium (Al-Ge) alloy.

[0109] The metal pad 570 may include a first metal pad 572 connected to the first electrode 530 and a second metal pad 574 connected to the second electrode 550.

[0110] The protective layer 580 may at least cover the metal pads 570. In other words, the protective layer 580 may be configured to cover the surface of the metal pads 570. The protective layer 580 may be disposed outside the effective area. Therefore, the protective layer 580 may not be disposed within the effective area.

[0111] As an example, the protective layer 580 may be formed using a material that may not be easily trimmed in the trimming process compared to the passivation layer 560, or the protective layer 580 may have a thickness greater than that of the passivation layer 560.

[0112] The protective layer 580 can be formed using any one of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), and silicon dioxide (SiO2). As an example, when the metal pad 570 is formed using gold (Au) material, the protective layer 580 can be formed using any one of aluminum oxide (Al2O3) and aluminum nitride (AlN).

[0113] Furthermore, as an example, when the metal pad 570 is formed using gold (Au) material, and an adhesive layer (not shown) formed using aluminum oxide (Al2O3) or aluminum nitride (AlN) is laminated on the metal pad 570, the protective layer 580 can be formed using either silicon nitride (SiN) or silicon dioxide (SiO2).

[0114] Since the protective layer 580 covers the metal pad 570, it prevents byproducts of the portion of the passivation layer 560 removed during the process of trimming the passivation layer 560 from accumulating on the inner surface of the metal pad 570.

[0115] In addition, it can prevent the passivation layer 560 from forming unevenly in the effective area after the finishing process is completed.

[0116] Figure 10 This is a cross-sectional view showing a bulk acoustic resonator 700 according to an embodiment.

[0117] Reference Figure 10 The bulk acoustic wave resonator 700 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop portion 130, a film layer 140, a first electrode 150, a piezoelectric layer 160, a second electrode 170, an insertion layer 180, a passivation layer 790, a metal pad 200, and an adhesive layer 810.

[0118] The substrate 110, sacrificial layer 120, etch stop portion 130, film layer 140, first electrode 150, piezoelectric layer 160, second electrode 170, insertion layer 180 and metal pad 200 are the same as those described in the previous embodiments, therefore, detailed descriptions of these components will not be repeated.

[0119] The adhesive layer 810 allows the passivation layer 790 to be easily laminated onto the surface of the metal pad 200. The adhesive layer 810 can be laminated onto the surface of the metal pad 200. In other words, the adhesive layer 810 can be disposed between the passivation layer 790 and the metal pad 200. The adhesive layer 810 can be formed using, for example, an insulating material or a metallic material.

[0120] The passivation layer 790 can be configured to cover the surface of the bulk acoustic wave resonator 700. As an example, the passivation layer 790 can be configured to cover the adhesive layer 810. Furthermore, the passivation layer 790 can be disposed on the upper surface of the second electrode 170 and the upper surface of the piezoelectric layer 160. The passivation layer 790 can serve as a protective layer 210 for the bulk acoustic wave resonator 100 described above.

[0121] The passivation layer 790 can be partially removed by an etching process to adjust the frequency in the final manufacturing process. Therefore, the thickness of the passivation layer 790 can be adjusted. For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the passivation layer 790.

[0122] Figure 11 This is a cross-sectional view showing a bulk acoustic resonator 900 according to an embodiment.

[0123] Reference Figure 11 The bulk acoustic wave resonator 900 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop portion 130, a film layer 140, a first electrode 150, a piezoelectric layer 160, a second electrode 170, an insertion layer 180, a passivation layer 990, and a metal pad 200.

[0124] The substrate 110, sacrificial layer 120, etch stop portion 130, film layer 140, first electrode 150, piezoelectric layer 160, second electrode 170, insertion layer 180 and metal pad 200 are the same as those described in the previous embodiments, therefore, detailed descriptions of these components will not be repeated.

[0125] The passivation layer 990 can be configured to cover the surface of the bulk acoustic wave resonator 900. As an example, the passivation layer 990 can be configured to cover the first electrode 150, the second electrode 170, the piezoelectric layer 160, the film layer 140, and the metal pad 200. The passivation layer 990 can be used as a protective layer 210 of the bulk acoustic wave resonator 100 described above.

[0126] The passivation layer 990 can be partially removed by an etching process to adjust the frequency characteristics in the final process. Therefore, the thickness of the passivation layer 990 can be adjusted. For example, a dielectric layer comprising any one of silicon nitride (Si3N4), silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), 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) can be used as the passivation layer 990.

[0127] The embodiments described herein can provide the effect of preventing byproducts of the portion of the passivation layer removed during the finishing process from stacking on the inner surface of the metal pads.

[0128] The embodiments described herein can also provide the effect of preventing uneven formation of the passivation layer thickness in the effective area after the finishing process is completed.

[0129] While this disclosure includes specific examples, it will be apparent upon understanding the disclosure of this application that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example is to be considered applicable to similar features or aspects in other examples. Suitable results may be obtained if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner and / or if components in the described system, architecture, apparatus, or circuit are replaced or supplemented by other components or their equivalents. Furthermore, the various embodiments may be combined with each other. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as included in this disclosure.

Claims

1. A bulk acoustic wave resonator, comprising: a substrate; a first electrode provided on the substrate; a piezoelectric layer provided to cover at least a portion of the first electrode; a second electrode provided to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; a protective layer provided to cover at least the metal pad; and a passivation layer provided on the first electrode and extending under the protective layer, the metal pad includes a first metal pad connected to the first electrode and a second metal pad connected to the second electrode. the protective layer is formed using any one of aluminum oxide, aluminum nitride, silicon nitride, and silicon dioxide.

2. The bulk acoustic resonator of claim 1, wherein, the protective layer is provided outside of an active area in which the first electrode, the piezoelectric layer, and the second electrode overlap each other.

3. The bulk acoustic resonator of claim 1, wherein, 4. The bulk acoustic wave resonator according to claim 1, further comprising: an adhesive layer provided between the protective layer and the metal pad. the adhesive layer is formed using any one of aluminum oxide and aluminum nitride, and 5. The bulk acoustic resonator of claim 4, wherein, wherein the protective layer is formed using any one of silicon nitride and silicon dioxide.

6. The bulk acoustic wave resonator according to claim 1, further comprising: an interposed layer provided between the first electrode and the piezoelectric layer.

7. The bulk acoustic wave resonator according to claim 1, further comprising: a membrane layer forming a cavity with the substrate.

8. The bulk acoustic wave resonator according to claim 7, further comprising: an etch stopper provided to surround the cavity; and a sacrificial layer provided to surround the etch stopper. the membrane layer includes an inclined portion provided obliquely with respect to a surface of the substrate on which the membrane layer is provided and a planar portion provided parallel to the surface of the substrate in an active area in which the first electrode, the piezoelectric layer, and the second electrode overlap each other. the second electrode includes a frame provided on an edge of the active area and having a thickness greater than a thickness of other portions of the second electrode.

9. The bulk acoustic resonator of claim 7, wherein, the substrate includes an insulating layer provided at least under the cavity.

10. The bulk acoustic resonator of claim 9, wherein, the passivation layer is formed using a dielectric layer including any one of silicon nitride, silicon dioxide, magnesium oxide (MgO), manganese oxide (MnO), zirconium oxide, aluminum nitride, lead zirconate titanate, gallium arsenide, hafnium oxide, aluminum oxide, titanium oxide, and zinc oxide, the passivation layer being provided to further cover a portion of the piezoelectric layer provided on an outer side of the first electrode.

11. The bulk acoustic resonator of claim 7, wherein, 13. A bulk acoustic wave resonator, comprising:

12. The bulk acoustic resonator of claim 1, wherein, a substrate; a first electrode provided on the substrate; a piezoelectric layer provided to cover at least a portion of the first electrode; a second electrode provided to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; a passivation layer provided to cover the first electrode, a portion of the piezoelectric layer provided on an outer side of the first electrode, and the metal pad; and an adhesive layer provided between the metal pad and the passivation layer. ​ ​ ​ The metal pads include a first metal pad connected to the first electrode and a second metal pad connected to the second electrode.

14. The bulk acoustic resonator of claim 13, wherein, The adhesive layer is formed using an insulating material or a metallic material.

15. The bulk acoustic resonator of claim 13, wherein, The passivation layer is formed using a dielectric layer including any one of silicon nitride, silicon dioxide, magnesium oxide (MgO), manganese oxide (MnO), zirconium oxide, aluminum nitride, lead zirconate titanate, gallium arsenide, hafnium oxide, aluminum oxide, titanium oxide, and zinc oxide.

16. The bulk acoustic wave resonator of claim 15, wherein, The adhesive layer is formed using any one of aluminum oxide and aluminum nitride.

17. The bulk acoustic resonator of claim 13, wherein, The passivation layer is further provided to cover the second electrode.

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