TWI841740B - Bulk-acoustic wave resonator - Google Patents

Abstract

A bulk-acoustic wave resonator includes: a resonator comprising a central portion in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate, and an extension portion disposed along a periphery of the central portion; and an insertion layer disposed below the piezoelectric layer in the extension portion to raise the piezoelectric layer. The insertion layer may have a first inclined surface formed along a side surface facing the central portion, and the first electrode may have a second inclined surface extending from a lower end of the first inclined surface of the insertion layer.

Description

Bulk acoustic wave resonator

[Cross reference to related applications]

This application claims the priority rights of Korean Patent Application No. 10-2019-0110914 filed on September 6, 2019 and Korean Patent Application No. 10-2020-0000401 filed on January 2, 2020, both of which are incorporated herein by reference in their entirety for all purposes.

The present invention relates to a bulk acoustic wave resonator.

According to the trend of miniaturization of wireless communication devices, the demand for miniaturization of high-frequency component technology is increasing. For example, bulk acoustic wave (BAW) type filters using semiconductor thin film wafer manufacturing technology can be used.

Bulk acoustic wave (BAW) resonators are thin-film devices that are implemented as filters by depositing piezoelectric dielectric materials on silicon wafers, semiconductor substrates, and using their piezoelectric characteristics to generate resonance.

Recently, there has been an increasing focus on the technology of 5G communications, and the development of technologies that can be implemented in candidate frequency bands is being actively carried out.

However, in the case of 5G communication using the Sub 6GHz (4GHz to 6GHz) frequency band, the signal strength or power may increase as the bandwidth increases and the communication distance shortens. In addition, as the frequency increases, the loss generated in the piezoelectric layer or resonator may increase.

Therefore, there is a need for a BAW resonator that can minimize energy leakage in the resonator.

The above information is presented only as background information to assist in understanding the present invention. No determination or statement is made that any of the above may be applicable to prior art related to the present invention.

This disclosure is provided to introduce in simplified form a series of concepts that are further described below in the implementation method. This disclosure is not 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.

In a general aspect, a bulk acoustic wave resonator includes: a resonator including a central portion in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate and an extension portion arranged along the periphery of the central portion; and an insertion layer arranged below the piezoelectric layer in the extension portion to raise the piezoelectric layer. The insertion layer has a first inclined surface formed on a side surface facing the central portion, and the first electrode has a second inclined surface extending from the lower end of the first inclined surface of the insertion layer.

The second inclined surface may have an inclination angle lower than that of the first inclined surface.

The first electrode may include a thickness of a lower portion of the second inclined surface that is less than a thickness of an upper portion of the second inclined surface.

The second inclined surface may be arranged in the central portion.

The first electrode may be an upper surface in the central portion and an upper surface in the extended portion, and the upper surfaces are arranged on different planes from each other.

The BAW resonator may further include a diaphragm layer disposed below the first electrode and the insertion layer to support the resonator and a cavity separating the resonator from the substrate.

The third inclined surface may be arranged along the end of the first electrode, and the membrane layer may have a fourth inclined surface extending from the lower end of the third inclined surface.

The fourth inclined surface may include a lower inclination angle than the third inclined surface.

The end of the insertion layer can contact the third inclined surface of the first electrode.

The insertion layer may be thicker than the first electrode.

The BAW resonator may further include a cover that houses the resonator and is bonded to the substrate.

The BAW resonator may further include a plurality of via holes configured to penetrate the cover, and a plurality of connection conductors configured in the plurality of via holes to electrically connect the first electrode and the second electrode to the outside.

The BAW resonator may further include external electrodes bonded to a plurality of connecting conductors exposed to an external surface of the cover.

The BAW resonator may further include a first metal layer and a second metal layer, wherein the first metal layer and the second metal layer are disposed outside the resonator and are bonded to the first electrode and the second electrode, respectively. A plurality of connecting conductors may be electrically connected to the first electrode and the second electrode, respectively, through the first metal layer and the second metal layer.

The piezoelectric layer may include an inclined portion disposed on the first inclined surface, and the end of the second electrode may be disposed on the inclined portion of the piezoelectric layer.

In another general aspect, a bulk acoustic wave resonator includes: a resonator including a central portion in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate and an extension portion arranged along the periphery of the central portion; and an insertion layer arranged below the piezoelectric layer in the extension portion to elevate the piezoelectric layer, wherein the thickness of the first electrode in the central portion is less than the thickness in the extension portion.

In another general aspect, a BAW resonator includes: a central portion, which includes a first electrode, a piezoelectric layer, and a second electrode stacked in sequence on a substrate; and an extension portion arranged along the periphery of the central portion, which includes a first electrode, an insertion layer, a piezoelectric layer, and a second electrode stacked in sequence on the substrate, wherein the first electrode includes a first reflection interface in the central portion.

The first reflective interface may include an inclined surface extending from the lower end of the insertion layer toward the central portion.

The BAW resonator may further include a diaphragm layer disposed below the first electrode to support the first electrode and a cavity separating the first electrode from the substrate, wherein the diaphragm layer may include a second reflective interface in the extension portion.

The second reflective interface may include an inclined surface extending from the lower end of the first electrode away from the central portion.

Other features and aspects will be apparent from the following implementation methods, drawings, and patent application scope.

50: Cover

51: Side wall

100: Bulk acoustic wave resonator/acoustic wave resonator/resonator

200, 300, 400: Bulk acoustic wave resonator

110: Substrate

112: Access hole

113a, 113b: Connecting conductors

115: Insulation layer

117: External electrode

120:Resonator

121: First electrode

123: Piezoelectric layer

123a: Piezoelectric part

123b: curved part

1231: Inclined part

1232: Extension

125: Second electrode

125a: Second electrode

127: Protective layer

140: Sacrifice layer

145: Etch end part

150: Diaphragm layer

170: Insert layer

180: First metal layer

190: Second metal layer

A, B: Part

C: Cavity

E: Extension part

H: Suction hole

I-I', II-II', III-III': lines

L, L1, L2, L3, L4: inclined surface

Q1, Q2: reflection interface

S: Center part

t1, t2, t3, t4: thickness

θ, θ ₁ , θ ₂ , θ ₃ , θ ₄ : Tilt angle

FIG1 is a plan view of an acoustic wave resonator according to an embodiment of the present invention.

FIG2 is a cross-sectional view taken along line II' of FIG1.

FIG3 is a cross-sectional view taken along line II-II' of FIG1.

FIG. 4 is a cross-sectional view taken along line III-III' of FIG. 1 .

Figure 5 is an enlarged view of part A of Figure 2.

Figure 6 is an enlarged view of part B of Figure 4.

FIG7 is a cross-sectional view schematically illustrating a bulk acoustic wave resonator according to another embodiment of the present invention.

FIG8 is a cross-sectional view schematically illustrating a bulk acoustic wave resonator according to another embodiment of the present invention.

FIG9 is a cross-sectional view schematically illustrating a bulk acoustic wave resonator according to another embodiment of the present invention.

Throughout the drawings and detailed description, the same reference numbers refer to the same elements. The drawings may not be drawn to scale, and the relative size, proportions, and descriptions of the elements in the drawings may be exaggerated for clarity and convenience.

The following detailed description is provided to help the reader gain a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various variations, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will become apparent after understanding the present invention. For example, the order of operations described herein is merely an example and is not limited to the examples described herein, but except for operations that must occur in a certain order, the order of operations may be changed as is apparent after understanding the present invention. Again, for the purpose of improving clarity and brevity, the description of features known in the art may be omitted.

The features described herein may be embodied in different forms, and the features should not be construed as being limited to the examples described herein. Rather, the examples described herein are provided merely to illustrate some of the many possible ways of implementing the methods, apparatuses, and/or systems described herein that will be apparent upon understanding the present invention.

Throughout this specification, when an element such as a layer, region, or substrate is described as being "on another element," "connected to another element," or "coupled to another element," the element may be directly "on another element," "connected to another element," or "coupled to another element," or one or more other elements may be interposed. In contrast, when an element is described as being "directly above another element," "directly connected to another element," or "directly coupled to another element," no other elements may be interposed. As used herein, a "portion" of an element may include the entire element or less than the entire element.

As used herein, the term "and/or" includes any one and any combination of any two or more of the relevant listed items; similarly, "at least one of..." includes any one and any combination of any two or more of the relevant listed items.

Although terms such as "first", "second", and "third" may be used herein to describe various components, assemblies, regions, layers, or sections, these components, components, regions, layers, or sections are not limited to these terms. Rather, these terms are only used to distinguish one component, component, region, layer, or section from another component, component, region, layer, or section. Therefore, without departing from the teachings of the examples described herein, the first component, component, region, layer, or section referred to in the examples may also be referred to as the second component, component, region, layer, or section.

For ease of description, spatially relative terms (such as "above", "upper", "below", "lower", and the like) may be used herein to describe the relationship between one element and another element as shown in the figures. These spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figure is turned over, an element described as "above" or "upper" relative to another element would subsequently be described as "below" or "lower" relative to the other element. Thus, the term "above" covers both upper and lower orientations depending on the spatial orientation of the device. The device may also be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative terms used herein are interpreted accordingly.

The terms used herein are only used to describe various examples and are not intended to limit the present invention. Unless the context clearly indicates otherwise, the articles "a/an" and "the" are also intended to include plural forms. The terms "include", "comprise" and "have" specify the existence of the stated features, numbers, operations, components, elements and/or their combinations, but do not exclude the existence or addition of one or more other features, numbers, operations, components, elements and/or their combinations.

As will be apparent after understanding the present invention, the features of the examples described herein may be combined in various ways. Furthermore, although the examples described herein have multiple configurations, other configurations are possible as will be apparent after understanding the present invention.

In this document, it should be noted that the use of the term "may" with respect to an example (e.g., with respect to what an example may include or implement) means that there is at least one example that includes or implements this feature, but all examples are not limited to this.

One aspect of the present invention is to provide a bulk acoustic wave resonator capable of reducing energy leakage.

FIG. 1 is a plan view of an acoustic wave resonator according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line I-I' of FIG. 1 . FIG. 3 is a cross-sectional view taken along line II-II' of FIG. 1 , FIG. 4 is a cross-sectional view taken along line III-III' of FIG. 1 , and FIG. 5 is an enlarged view of a portion A of FIG. 2 .

1 to 5 , the acoustic wave resonator 100 according to an embodiment of the present invention may be a bulk-acoustic wave (BAW) resonator, and may include a substrate 110, a sacrificial layer 140, a resonator 120, and an insertion layer 170.

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

An insulating layer 115 may be provided on the upper surface of the substrate 110 to electrically isolate the substrate 110 from the resonator 120. In addition, the insulating layer 115 prevents the substrate 110 from being etched by etching gas when the cavity C is formed in the manufacturing process of the acoustic wave resonator.

In this case, the insulating layer 115 may be formed of at least one of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ) and aluminum nitride (AlN), and may be formed through any one of chemical vapor deposition, RF magnetron sputtering and evaporation.

The sacrificial layer 140 is formed on the insulating layer 115, and the cavity C and the etching stop portion 145 are disposed in the sacrificial layer 140.

The cavity C is formed as a blank space and may be formed by removing a portion of the sacrificial layer 140.

When the cavity C is formed in the sacrificial layer 140, the resonator 120 formed above the sacrificial layer 140 can be formed to be completely flat.

The etching stop portion 145 is arranged along the boundary of the cavity C. The etching stop portion 145 is provided to prevent the etching from being performed beyond the cavity area during the process of forming the cavity C.

The diaphragm layer 150 is formed on the sacrificial layer 140 and forms the upper surface of the cavity C. Therefore, the diaphragm layer 150 is also formed of a material that is not easy to remove in the process of forming the cavity C.

For example, when a halogenide-based etching gas such as fluorine (F), chlorine (Cl), or the like is used to remove a portion (e.g., the cavity region) of the sacrificial layer 140, the membrane layer 150 may be made of a material having low reactivity with the etching gas. In this case, the membrane layer 150 may include at least one of silicon dioxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ).

The membrane layer 150 may be made of a dielectric layer containing at least one material of magnesium oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), halogenated oxide _{( HfO2} ), aluminum oxide ( _Al2O3 ), titanium oxide ( _TiO2 ), and zinc oxide (ZnO), and a metal layer containing at least one material of aluminum (Al), nickel (Ni), chromium (Cr), platinum (Pt), gallium (Ga), and halogenated oxide (Hf). However, the present invention is not limited thereto.

The resonator 120 includes a first electrode 121, a piezoelectric layer 123, and a second electrode 125. The resonator 120 is configured such that the first electrode 121, the piezoelectric layer 123, and the second electrode 125 are stacked in order from the bottom. Therefore, the piezoelectric layer 123 in the resonator 120 is disposed between the first electrode 121 and the second electrode 125.

Since the resonator 120 is formed on the diaphragm layer 150, the diaphragm layer 150, the first electrode 121, the piezoelectric layer 123 and the second electrode 125 are sequentially stacked on the substrate 110 to form the resonator 120.

The resonator 120 can cause the piezoelectric layer 123 to resonate according to the signal applied to the first electrode 121 and the second electrode 125 to generate a resonant frequency and an anti-resonant frequency.

The resonator 120 can be divided into: a central portion S, where the first electrode 121, the piezoelectric layer 123, and the second electrode 125 are stacked to be substantially flat; and an extended portion E, where the insertion layer 170 is inserted between the first electrode 121 and the piezoelectric layer 123.

The central portion S is a region disposed at the center of the resonator 120, and the extension portion E is a region disposed along the periphery of the central portion S. Therefore, the extension portion E is a region extending outward from the central portion S, and refers to a region formed to have a continuous ring shape along the periphery of the central portion S. However, if necessary, the extension portion E may be configured to have a discontinuous ring shape in which some regions are separated.

Therefore, as shown in FIG. 2 , in the cross-section of the resonator 120 cut to intersect the central portion S, the extension portions E are respectively arranged at both ends of the central portion S. The insertion layer 170 is arranged on both sides of the central portion S in the extension portions E, which are arranged on both ends of the central portion S.

The insertion layer 170 has an inclined surface L, and its thickness becomes larger as the distance from the center portion S increases.

In the extension portion E, the piezoelectric layer 123 and the second electrode 125 are disposed on the insertion layer 170. Therefore, the piezoelectric layer 123 and the second electrode 125 located in the extension portion E have inclined surfaces along the shape of the insertion layer 170.

In the embodiment of the present invention, the extension portion E is included in the resonator 120, and therefore, resonance may occur in the extension portion E. However, the present invention is not limited thereto, and the resonance may not exist in the extension portion E depending on the structure of the extension portion E, but the resonance may occur only in the center portion S.

The first electrode 121 and the second electrode 125 may be formed of a conductor, for example, may be formed of the following: gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, nickel, or a metal containing at least one of them, but not limited thereto.

In the resonator 120, the first electrode 121 is formed to have a larger area than the second electrode 125, and the first metal layer 180 is arranged on the first electrode 121 along the periphery of the first electrode 121. Therefore, the first metal layer 180 can be arranged to be spaced a predetermined distance from the second electrode 125, and can be arranged in a form surrounding the resonator 120.

Since the first electrode 121 is disposed on the membrane layer 150, the first electrode 121 is formed flat as a whole. Since the second electrode 125 is disposed on the piezoelectric layer 123, a curving portion corresponding to the shape of the piezoelectric layer 123 can be formed.

The first electrode 121 can be used as one of an input electrode and an output electrode for inputting and outputting electrical signals such as radio frequency (RF) signals.

The second electrode 125 is completely disposed in the central portion S and partially disposed in the extended portion E. Therefore, the second electrode 125 can be divided into a portion disposed on the piezoelectric portion 123a of the piezoelectric layer 123 to be described later and a portion disposed on the bent portion 123b of the piezoelectric layer 123.

More specifically, in the embodiment of the present invention, the second electrode 125 is configured to cover the entire piezoelectric portion 123a and a portion of the inclined portion 1231 of the piezoelectric layer 123. Therefore, the second electrode (the second electrode 125a in FIG. 4 ) configured in the extension portion E is formed as an inclined surface having an area smaller than that of the inclined portion 1231, and the second electrode 125 in the resonator 120 is formed as an area smaller than that of the piezoelectric layer 123.

Therefore, as illustrated in FIG. 2 , in the cross section of the resonator 120 cut to intersect the central portion S, the end of the second electrode 125 is disposed in the extension portion E. In addition, at least a portion of the end of the second electrode 125 disposed in the extension portion E is configured to overlap with the insertion layer 170. Here, “overlap” means that when the second electrode 125 is projected on the plane on which the insertion layer 170 is disposed, the shape of the second electrode 125 projected on the plane overlaps with the insertion layer 170.

The second electrode 125 can be used as one of an input electrode and an output electrode for inputting and outputting electrical signals such as radio frequency (RF) signals or the like. That is, when the first electrode 121 is used as an input electrode, the second electrode 125 can be used as an output electrode, and when the first electrode 121 is used as an output electrode, the second electrode 125 can be used as an input electrode.

As illustrated in FIG. 4 , when the end of the second electrode 125 is positioned on the inclined portion 1231 of the piezoelectric layer 123 to be described later, since the local structure of the acoustic impedance of the resonator 120 is formed in a sparse/dense/dense structure from the center portion S, the reflection interface that reflects the side waves inward from the resonator 120 increases. Therefore, since most of the side waves do not flow outward from the resonator, but are reflected and then flow to the inside of the resonator 120, the performance of the acoustic wave resonator can be improved.

The piezoelectric layer 123 is a portion that converts electrical energy into mechanical energy in the form of elastic waves through the piezoelectric effect, and is formed on the first electrode 121 and the insertion layer 170 to be described later.

As the material of the piezoelectric layer 123, zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanium, quartz and the like can be selectively used. In the case of doped aluminum nitride, rare earth metals, transition metals or alkali earth metals can be further included. Rare earth metals can include at least one of styrene (Sc), erbium (Er), yttrium (Y) and ruthenium (La). Transition metals can include at least one of uranium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta) and niobium (Nb). In addition, alkali earth metals can include magnesium (Mg).

In order to improve the piezoelectric properties, when the content of the element doped with aluminum nitride (AlN) is less than 0.1 atomic %, piezoelectric properties higher than aluminum nitride (AlN) cannot be achieved. When the content of the element exceeds 30 atomic %, it is difficult to manufacture and control the composition used for deposition, so that uneven or undesirable crystalline phases may be formed.

Therefore, in the embodiment of the present invention, the content of the element doped with aluminum nitride (AlN) is in the range of 0.1 atomic % to 30 atomic %.

In the embodiment of the present invention, the piezoelectric layer is doped with piezoelectric (Sc) in aluminum nitride (AlN). In this case, the piezoelectric constant can be increased to increase the K _t ² of the acoustic wave resonator. However, the configuration of the present invention is not limited thereto.

The piezoelectric layer 123 according to the embodiment of the present invention includes a piezoelectric portion 123a disposed in the central portion S and a bent portion 123b disposed in the extended portion E.

The piezoelectric portion 123a is a portion directly stacked on the upper surface of the first electrode 121. Therefore, the piezoelectric portion 123a is inserted between the first electrode 121 and the second electrode 125 to form a flat shape together with the first electrode 121 and the second electrode 125.

The bent portion 123b can be understood as a region extending from the piezoelectric portion 123a to the outside and positioned in the extension portion E.

The bent portion 123b is disposed on the insertion layer 170 to be described later, and is formed into a shape in which the upper surface is raised along the shape of the insertion layer 170. Therefore, the piezoelectric layer 123 is bent at the boundary between the piezoelectric portion 123a and the bent portion 123b, and the bent portion 123b is raised corresponding to the thickness and shape of the insertion layer 170.

The bent portion 123b can be divided into an inclined portion 1231 and an extended portion 1232.

The inclined portion 1231 refers to a portion inclined along the inclined surface L of the insertion layer 170 to be described later. The extended portion 1232 refers to a portion extending from the inclined portion 1231 to the outside.

The inclined portion 1231 is formed parallel to the inclined surface L of the insertion layer 170, and the inclined angle of the inclined portion 1231 can be formed to be the same as the inclined angle of the inclined surface L of the insertion layer 170.

The insertion layer 170 is disposed along a surface formed by the membrane layer 15, the first electrode 121, and the etching stop portion 145. Therefore, the insertion layer 170 is partially disposed in the resonator 120 and disposed between the first electrode 121 and the piezoelectric layer 123.

The insertion layer 170 is arranged around the central portion S to support the curved portion 123b of the piezoelectric layer 123. Therefore, the curved portion 123b of the piezoelectric layer 123 can be divided into an inclined portion 1231 and an extended portion 1232 along the shape of the insertion layer 170.

The insertion layer 170 is disposed in an area other than the central portion S. For example, the insertion layer 170 may be disposed on the substrate 110 in the entire area other than the central portion S or in some areas.

The insertion layer 170 is formed so that the thickness increases as the side surface facing the center portion S moves away from the center portion S. Thus, the insertion layer 170 is formed by the inclined surface L having a constant inclination angle θ and the side surface facing the center portion S.

When the inclination angle θ of the side surface of the insertion layer 170 is formed to be less than 5°, in order to manufacture the insertion layer 170, it is difficult to implement in practice because the insertion layer 170 should be formed to be extremely thin or the area of the inclined surface L should be particularly large.

In addition, when the inclination angle θ of the side surface of the insertion layer 170 is greater than 70°, the inclination angle of the piezoelectric layer 123 or the second electrode 125 stacked on the insertion layer 170 is also formed to be greater than 70°. In this case, since the piezoelectric layer 123 or the second electrode 125 stacked on the inclined surface L is excessively bent, cracks may be generated in the bent portion.

Therefore, in the embodiment of the present invention, the inclination angle θ of the inclined surface L is formed within the range of 5° or more and 70° or less.

In the embodiment of the present invention, the inclined portion 1231 of the piezoelectric layer 123 is formed along the inclined surface L of the insertion layer 170, and is thus formed to have the same inclination angle as the inclined surface L of the insertion layer 170. Therefore, the inclination angle of the inclined portion 1231 is also formed within the range of 5° or more and 70° or less, similar to the inclined surface L of the insertion layer 170. The configuration is also applicable to the second electrode 125 stacked on the inclined surface L of the insertion layer 170.

The insertion layer 170 may be formed of a dielectric material such as silicon oxide ( _SiO2 ), aluminum nitride (AlN), aluminum oxide ( _Al2O3 ), silicon _nitride ( _Si3N4 ), magnesium oxide (MgO), zirconium oxide ( _ZrO2 ), lead zirconate titanate ( _PZT ), and gallium arsenide (GaAs), helium oxide ( _HfO2 ), titanium oxide ( _TiO2 ), and zinc oxide (ZnO), but may be formed of a material from the piezoelectric layer 123.

In addition, the insertion layer 170 may be implemented by a metal material. When the bulk acoustic wave resonator of the embodiment of the present invention is used for 5G communication, a large amount of heat is generated by the resonator, and therefore, it is necessary to smoothly release the heat generated by the resonator 120. For this purpose, the insertion layer 170 of this embodiment may be made of an aluminum alloy material containing plutonium (Sc).

The resonator 120 is configured to be separated from the substrate 110 via the cavity C configured below the diaphragm layer 150. Therefore, the diaphragm layer 150 is configured below the first electrode 121 and the insertion layer 170 to support the resonator 120.

The cavity C is formed as a blank space and can be formed by supplying an etching gas (or etching solution) to a suction hole (suction hole H in FIG. 1 ) to remove a portion of the sacrificial layer 140 during the process of manufacturing the acoustic wave resonator.

The protective layer 127 is disposed along the surface of the acoustic wave resonator 100 to protect the acoustic wave resonator 100 from the outside. The protective layer 127 may be disposed along the surface formed by the second electrode 125 and the bent portion 123b of the piezoelectric layer 123.

The protective layer 127 may be formed as a dielectric layer containing any one of silicon nitride (Si ₃ N ₄ ), silicon oxide (SiO ₂ ), magnesium oxide (MgO), zirconium oxide (ZrO ₂ ), aluminum nitride (AlN), lead titanate (PZT), gallium arsenide (GaAs), helium oxide (HfO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and zinc oxide (ZnO), but is not limited thereto.

The protective layer 127 may be formed as a single layer, but may be formed by stacking two layers having different materials as needed. In addition, the protective layer 127 may be partially removed to adjust the frequency in the final process. For example, the thickness of the protective layer 127 may be adjusted in the frequency fine-tuning process.

The first electrode 121 and the second electrode 125 may extend outside the resonator 120. The first metal layer 180 and the second metal layer 190 may be respectively disposed on the upper surface of the extension portion.

The first metal layer 180 and the second metal layer 190 may be made of gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), copper-tin (Cu-Sn) alloy, aluminum (Al), aluminum alloy or a combination thereof. Here, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy or an aluminum-silicon (Al-Sc) alloy.

The first metal layer 180 and the second metal layer 190 can serve as connection wiring for electrically connecting the first electrode 121 and the second electrode 125 of the acoustic wave resonator according to the embodiment of the present invention on the substrate 110 and electrically connecting the electrodes of other acoustic wave resonators arranged adjacent to each other, or serve as terminals for external connection. However, it is not limited to this.

The first metal layer 180 can penetrate the protective layer 127 and bond to the first electrode 121.

In addition, in the resonator 120, the first electrode 121 is formed to have a larger area than the second electrode 125, and the first metal layer 180 is formed on the periphery of the first electrode 121.

Therefore, the first metal layer 180 is arranged along the periphery of the resonator 120, and is thus arranged in a form surrounding the second electrode 125. However, it is not limited thereto.

In the BAW resonator 100 according to the embodiment of the present invention configured as described above, as shown in FIGS. 4 to 6 , the second inclined surface L2 is formed on the upper surface of the first electrode 121.

The second inclined surface L2 is formed to extend from the inclined surface of the above-mentioned insertion layer 170 (hereinafter referred to as the first inclined surface L), and is formed to have an inclined angle θ2 smaller than the inclined angle θ of the first inclined surface L.

In the cross-section of the resonator 120 cut to intersect the central portion S, the insertion layer 170 may be respectively arranged in the extension portions E located on both sides of the central portion S. The second inclined surface L2 is arranged on both sides of the central portion S in the form of extending from the first inclined surface L. Thus, the second inclined surface L2 may be formed along the entire first inclined surface L formed in the insertion layer 170.

Since the insertion layer 170 is arranged in the extension part E along the boundary of the center part S, the second inclined surface L2 is arranged in the center part S along the boundary of the center part S. In addition, the upper surface of the first electrode 121 extending from the lower end of the second inclined surface L2 is formed as a flat surface. Therefore, in the first electrode 121, the upper surface in the center part S and the upper surface in the extension part E are arranged on different planes. In addition, with respect to the second inclined surface L2, the thickness t1 of the first electrode 121 arranged in the center part S (which is the lower end part of the second inclined surface L2) is formed to be smaller than the thickness t2 of the first electrode 121 arranged in the extension part E (which is the upper end part of the second inclined surface L2).

The second inclined surface L2 may be formed by etching a portion of the upper surface of the first electrode 121 positioned in the center portion S. In this process, the insertion layer 170 may be used as a mask. Therefore, the second inclined surface L2 is formed in the form of extending from the first inclined surface L.

When the second inclined surface L2 is provided in the first electrode 121 as described above, the reflective interface Q1 can be formed along the boundary between the flat surface of the first electrode 121 and the second inclined surface L2. Therefore, in addition to the sparse/dense/sparse/dense structure shown in FIG. 4, since an additional reflective interface Q1 is provided, it is possible to further suppress the energy in the resonator 120 from leaking out of the resonator 120, thereby improving the performance of the bulk acoustic wave resonator.

In addition, the BAW resonator according to the embodiment of the present invention may include a fourth inclined surface L4 formed in the diaphragm layer 150, as shown in FIG. 5.

The fourth inclined surface L4 is formed to extend from the inclined surface L3 (hereinafter referred to as the third inclined surface) formed at the end of the first electrode 121.

Similar to the second inclined surface L2, the fourth inclined surface L4 is formed to have an inclination angle θ4 that is smaller than the inclination angle θ3 of the third inclined surface L3.

Regarding the fourth inclined surface L4, the thickness t3 of the diaphragm layer 150 in the lower end portion of the fourth inclined surface L4 is formed to be smaller than the thickness t4 of the diaphragm layer 150 in the upper end portion of the fourth inclined surface L4.

The fourth inclined surface L4 may be formed in the diaphragm layer 150 along the entire third inclined surface L3 formed on the first electrode 121.

The fourth inclined surface L4 can be formed by partially etching the upper surface of the membrane layer 150. In this process, the first electrode 121 can be used as a mask. Therefore, the fourth inclined surface L4 is formed by extending from the third inclined surface L3.

When the fourth inclined surface L4 is provided in the diaphragm layer 150 as described above, the reflective interface Q2 can be formed along the boundary of the fourth inclined surface L4. Therefore, since an additional reflective interface Q2 is provided, it is possible to further suppress the energy in the resonator 120 from leaking out of the resonator 120.

The present invention is not limited to the above-described embodiments, and various modifications are possible.

FIG7 is a cross-sectional view schematically illustrating a bulk acoustic wave resonator according to another embodiment of the present invention.

Referring to FIG. 7 , the configuration of the BAW resonator 200 described in the embodiment of the present invention is similar to that of the BAW resonator described in FIG. 3 and the shape difference of the insertion layer 170 disposed on the end side of the first electrode 121 is the largest. Therefore, the detailed description of the components that are the same as those in the above-mentioned embodiment can be omitted, and the differences will be mainly further described.

As shown in FIG. 7 , in the cross-section of the resonator 120 cut to intersect the center portion S, the insertion layer 170 is respectively arranged in the extension portions E respectively located on both sides of the center portion S, wherein the right-side insertion layer 170 contacting the end of the first electrode 121 is configured to contact only the third inclined surface L3, which is the inclined surface of the end of the first electrode 121 without covering the upper surface of the first electrode 121. For example, in the portion where the third inclined surface L3 is formed, the insertion layer 170 is formed to contact only the third inclined surface L3 without contacting the upper surface of the first electrode 121.

For this purpose, the insertion layer 170 of the embodiment of the present invention may be formed to be thicker than the first electrode 121.

As in the above-mentioned embodiment, the first electrode 121 of the bulk acoustic wave resonator 200 of the embodiment of the present invention has a second inclined surface L2 extending from the first inclined surface L of the insertion layer 170 and a third inclined surface L3 formed at the end, and the diaphragm layer 150 has a fourth inclined surface L4 extending from the third inclined surface L3. In addition, the second inclined surface L2 is formed to have an inclination angle smaller than the inclination angle of the first inclined surface L, and the fourth inclined surface L4 is formed to have an inclination angle smaller than the inclination angle of the third inclined surface L3.

In addition, the above-mentioned right-side insertion layer 170 is configured so that its end contacts the third inclined surface L3 of the first electrode 121 and the fourth inclined surface L4 of the membrane layer 150. Therefore, the right-side insertion layer 170 configured to contact the end of the first electrode 121 has three inclined surfaces having different inclination angles at the end. As described above, the insertion layer 170 of the present invention can be modified in various forms.

FIG8 is a cross-sectional view schematically illustrating a BAW resonator according to another embodiment of the present invention. Referring to FIG8 , the BAW resonator 300 shown in the embodiment of the present invention includes the BAW resonator and the cover 50 shown in FIG2 .

A cover 50 is provided to protect the resonator 120 from the external environment.

The cover 50 may be formed in the form of a cover plate having an inner space for accommodating the resonator 120. Therefore, the cover 50 is bonded to the substrate 110 in the form of a side wall 51 surrounding the periphery of the resonator 120.

The cover 50 can be bonded to the substrate 110 via a bonding member. Therefore, the lower surface of the side wall 51 serves as a bonding surface with the substrate 110.

The cover 50 can be formed by wafer bonding at the wafer level. That is, a substrate wafer on which a plurality of unit substrates 110 are arranged and a cover wafer on which a plurality of covers 50 are arranged can be integrally formed by bonding with each other. Silicon (Si) can be used as a material for the cover, but is not limited thereto.

The substrate 110 of the embodiment of the present invention has a plurality of via holes 112 penetrating the substrate 110 on its lower surface. In addition, a connecting conductor 113a and a connecting conductor 113b are formed inside each of the via holes 112.

The connecting conductor 113a and the connecting conductor 113b may be formed on the entire inner surface of the via hole 112, but are not limited thereto, or may be partially formed or formed in a form that completely fills the inner space of the via hole 112.

In addition, one end of the connecting conductor 113a and the connecting conductor 113b is connected to the external electrode 117 formed on the lower surface of the substrate 110, and the other end thereof is connected to the first electrode 121 or the second electrode 125.

For example, according to an embodiment of the present invention, the first connecting conductor 113a electrically connects the first electrode 121 and the external electrode 117, and the second connecting conductor 113b electrically connects the second electrode 125 and another external electrode 117.

Therefore, the first connecting conductor 113a can penetrate the substrate 110 and the diaphragm layer 150 and be electrically connected to the first electrode 121, and the second connecting conductor 113b can penetrate the substrate 110 and the diaphragm layer 150 and be electrically connected to the second electrode 125. In this case, the second connecting conductor 113b can be electrically connected to the second electrode 125 via the second metal layer 190.

In the embodiment of the present invention, only two via holes 112 and two connecting conductors 113a and 113b are illustrated and described, but the present invention is not limited thereto, and a larger number of via holes 112 and connecting conductors 113a and 113b may be provided if necessary.

FIG9 is a cross-sectional view schematically illustrating a bulk acoustic wave resonator according to another embodiment of the present invention.

Referring to FIG. 9 , the configuration of the BAW resonator 400 described in the embodiment of the present invention is similar to the BAW resonator described in FIG. 8 , except that the via hole 112 and the connecting conductors 113a and 113b are configured to penetrate the cover 50 instead of the substrate 110.

Therefore, in the embodiment of the present invention, the via hole 112 and the connecting conductor 113a and the connecting conductor 113b are positioned above the first metal layer 180 and the second metal layer 190, and the connecting conductor 113a and the connecting conductor 113b are connected to the first metal layer 180 and the second metal layer 190 respectively through the via hole 112.

Therefore, the connecting conductor 113a and the connecting conductor 113b are electrically connected to the first electrode 121 and the second electrode 125 via the first metal layer 180 and the second metal layer 190, respectively.

In this case, the upper surfaces (or bonding surfaces) of the first metal layer 180 and the second metal layer 190 can be arranged on the same plane, so that the cover 50 can be firmly bonded to the first metal layer 180 and the second metal layer 190.

In the BAW resonator 400 according to the embodiment of the present invention configured as described above, the external electrode 117 may be disposed on the upper surface of the outer surface of the cover 50 (see FIG. 9 ). In this case, the upper surface of the cover 50 may be used as a mounting surface.

As described above, according to the present invention, since the BAW resonator provides an additional reflection interface through the inclined surface provided on the first electrode, the energy in the resonator can be suppressed as much as possible from leaking out of the resonator, thereby improving the performance of the BAW resonator.

Although specific examples have been shown and described above, it will be apparent after understanding the present invention that various changes in form and details may be made in these examples without departing from the spirit and scope of the scope of the claims and their equivalents. The examples described herein should be considered in a descriptive sense only and not for restrictive purposes. The description of features or aspects in each example should be considered to be applicable to similar features or aspects in other examples. Appropriate results may be achieved if the described techniques are performed in a different order, and/or if components in the described systems, architectures, devices, or circuits are combined in a different manner and/or replaced or supplemented with other components or their equivalents. Therefore, the scope of the present invention is defined not by the detailed description but by the scope of the patent application and its equivalents, and all changes within the scope of the patent application and its equivalents should be interpreted as included in the present invention.

100: Bulk acoustic wave resonator/acoustic wave resonator/resonator

110: Substrate

115: Insulation layer

120:Resonator

121: First electrode

123: Piezoelectric layer

123a: Piezoelectric part

123b: curved part

1231: Inclined part

1232: Extension

125: Second electrode

127: Protective layer

140: Sacrifice layer

145: Etch end part

150: Diaphragm layer

170: Insert layer

180: First metal layer

190: Second metal layer

A: Partial

C: Cavity

E: Extension part

I-I': line

L: inclined surface

S: Center part

Claims (19)

A bulk acoustic wave resonator, comprising: a resonator, comprising a central portion in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate and an extension portion arranged along the periphery of the central portion; and an insertion layer arranged below the piezoelectric layer in the extension portion to raise the piezoelectric layer, wherein the insertion layer comprises a first inclined surface formed along a side surface facing the central portion, and the first electrode comprises a second inclined surface extending from a lower end of the first inclined surface of the insertion layer. A bulk acoustic wave resonator as claimed in claim 1, wherein the second inclined surface comprises a lower inclination angle than the first inclined surface. A bulk acoustic wave resonator as claimed in claim 1, wherein the first electrode includes a thickness of a lower portion of the second inclined surface that is less than a thickness of an upper portion of the second inclined surface. A bulk acoustic wave resonator as claimed in claim 1, wherein the second inclined surface is arranged in the central portion. A bulk acoustic wave resonator as claimed in claim 1, wherein the first electrode includes an upper surface in the central portion and an upper surface in the extended portion, and the upper surfaces are arranged on different planes from each other. The bulk acoustic wave resonator of claim 1 further comprises: a diaphragm layer disposed below the first electrode and the insertion layer to support the resonator; and a cavity separating the resonator from the substrate. A bulk acoustic wave resonator as claimed in claim 1, wherein the third inclined surface is arranged along the end of the first electrode, and wherein the diaphragm layer includes a fourth inclined surface extending from the lower end of the third inclined surface. A bulk acoustic wave resonator as claimed in claim 7, wherein the fourth inclined surface comprises a lower inclination angle than the third inclined surface. A bulk acoustic wave resonator as claimed in claim 7, wherein the end of the insertion layer contacts the third inclined surface of the first electrode. A bulk acoustic wave resonator as claimed in claim 9, wherein the insertion layer is thicker than the first electrode. The bulk acoustic wave resonator of claim 1 further comprises a cover, wherein the cover accommodates the resonator therein and is bonded to the substrate. The bulk acoustic wave resonator of claim 11 further comprises: a plurality of via holes configured to penetrate the cover; and a plurality of connecting conductors configured in the plurality of via holes to electrically connect the first electrode and the second electrode to the outside. The BAW resonator of claim 12 further comprises an external electrode bonded to the plurality of connecting conductors exposed on the outer surface of the cover. The bulk acoustic wave resonator of claim 12 further includes a first metal layer and a second metal layer, wherein the first metal layer and the second metal layer are arranged outside the resonator and are respectively bonded to the first electrode and the second electrode, wherein the plurality of connecting conductors are respectively electrically connected to the first electrode and the second electrode via the first metal layer and the second metal layer. A bulk acoustic wave resonator as claimed in claim 1, wherein the piezoelectric layer includes a tilted portion disposed on the first tilted surface, and wherein the end of the second electrode is disposed on the tilted portion of the piezoelectric layer. A bulk acoustic wave resonator, comprising: a resonator including a central portion in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate and an extension portion arranged along the periphery of the central portion; and an insertion layer arranged below the piezoelectric layer in the extension portion to elevate the piezoelectric layer, wherein the thickness of the first electrode in the central portion is smaller than that in the extension portion. A bulk acoustic wave resonator comprises: a central portion, comprising a first electrode, a piezoelectric layer and a second electrode stacked in sequence on a substrate; and an extension portion arranged along the periphery of the central portion, comprising the first electrode, an insertion layer, the piezoelectric layer and the second electrode stacked in sequence on the substrate, wherein the first electrode comprises a first reflection interface in the central portion, wherein the first reflection interface comprises an inclined surface extending from the lower end surface of the insertion layer toward the central portion. The bulk acoustic wave resonator of claim 17 further comprises a diaphragm layer disposed below the first electrode to support the first electrode; and a cavity separating the first electrode from the substrate, wherein the diaphragm layer comprises a second reflective interface in the extension portion. A bulk acoustic wave resonator as claimed in claim 18, wherein the second reflective interface comprises an inclined surface extending from the lower end of the first electrode away from the central portion.

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