A bulk-acoustic resonator module includes: a module substrate; a bulk-acoustic resonator connected to the module substrate by a connection terminal and disposed spaced apart from the module substrate; and a sealing portion sealing the bulk-acoustic resonator. The bulk-acoustic resonator includes a resonating portion disposed opposite to an upper surface of the module substrate. A space is disposed between the resonating portion and the upper surface of the module substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application Nos. 10-2018-0152385 and 10-2019-0042081 filed on Nov. 30, 2018 and Apr. 10, 2019, respectively, in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes.

BACKGROUND

The following description relates to a bulk-acoustic resonator module.

2. Description of Related Art

With the recent rapid development of mobile communication devices, chemical and biological devices, and the like, demand for a small, lightweight filter, an oscillator, a resonant element, an acoustic resonant mass sensor, and the like, which are used in such devices, is increasing.

Such an acoustic resonator may be configured as a device for implementing such a small, lightweight filter, an oscillator, a resonant element, an acoustic resonant mass sensor, and the like, and may be implemented as a thin bulk acoustic resonator (FBAR).

An FBAR may be mass-produced at a minimal cost, and may be configured to have subminiature size. In addition, the FBAR may implement a high quality factor (QF) value, which is a main characteristic of a filter, and may be used even in the microwave frequency band. For example, the FBAR may be used in bands of a personal communication system (PCS) and a digital cordless system (DCS).

Generally, the FBAR has a structure including a resonating portion formed by sequentially stacking a first electrode, a piezoelectric body, and a second electrode on a substrate.

A principle of operation of the FBAR is as follows. First, when electrical energy is applied to the first and second electrodes to induce an electric field in the piezoelectric layer, the electric field causes a piezoelectric phenomenon in the piezoelectric layer, such that the resonating portion vibrates by a predetermined distance. As a result, a bulk acoustic wave is generated in the same direction in which vibrations and resonance occur.

That is, the FBAR is an element using a bulk acoustic wave (BAW), and an effective electromechanical coupling coefficient (kt2) of the piezoelectric body is increased, such that the frequency characteristics of the acoustic wave element are improved and it is also possible to achieve a wide bandwidth.

SUMMARY

In one general aspect, a bulk-acoustic resonator module includes: a module substrate; a bulk-acoustic resonator connected to the module substrate by a connection terminal and disposed spaced apart from the module substrate; and a sealing portion sealing the bulk-acoustic resonator. The bulk-acoustic resonator includes a resonating portion disposed opposite to an upper surface of the module substrate. A space is disposed between the resonating portion and the upper surface of the module substrate.

The bulk-acoustic resonator may further include: a resonator substrate; an insulating layer disposed on a surface of the resonator substrate; a membrane layer forming a cavity together with the insulating layer, the resonating portion being disposed on the cavity, and comprising a first electrode, a piezoelectric layer, and a second electrode arranged in a stacked configuration; a protective layer disposed on the first electrode, the piezoelectric layer, and the second electrode in the resonating portion; and a hydrophobic layer disposed on the protective layer.

The hydrophobic layer may have a contact angle of 90° or more with water.

The hydrophobic layer may include either one or both of fluorine (F) and silicon (Si).

The hydrophobic layer may surround the cavity and the membrane layer.

The protective layer may include a first protective layer formed of a silicon oxide-based or a silicon nitride-based insulating material, and a second protective layer formed of any one of an aluminum oxide-based insulating material, an aluminum nitride-based insulating material, a magnesium oxide-based insulating material, a titanium oxide-based insulating materials, a zirconium oxide-based insulating material, and a zinc oxide-based insulating material.

A distance between the bulk-acoustic resonator and the module substrate may be 10 μm to 30 μm.

A trench may be formed in the upper surface of the module substrate. A portion of the connection terminal connecting the bulk-acoustic resonator to the module substrate may be disposed in the trench.

The bulk-acoustic resonator module of claim8, wherein a distance between the upper surface of the module substrate and a rim of a lower surface of the bulk-acoustic resonator is 0 μm to 20 μm.

A horizontal length of the trench may be shorter than a horizontal length of the bulk-acoustic resonator.

A depth of the trench may be 20 μm to 30 μm.

The bulk-acoustic resonator module may further include a blocking member disposed between the bulk-acoustic resonator and the module substrate.

The blocking member may be in contact with at least one surface of the connection terminal.

The blocking member may be spaced apart from the upper surface of the module substrate.

A trench may be formed in the upper surface of the module substrate, and the blocking member may be disposed in the trench.

The blocking member may be made of a conductive material, and may be spaced apart from the connection terminal.

The bulk-acoustic resonator module may further include a blocking member disposed outside of the connection terminal and formed to cover a side surface of the connection terminal.

The bulk-acoustic resonator module may further include an electronic device mounted on the module substrate so as to be disposed adjacent to the bulk-acoustic resonator.

The bulk-acoustic resonator may further include a resonator substrate. The resonating portion may include a first electrode, a piezoelectric layer, and a second electrode stacked on a cavity formed on the resonator substrate. The bulk-acoustic resonator module may further include a blocking member disposed between the bulk-acoustic resonator and the module substrate, outside of the connection terminal, and at least partially covering a side surface of the resonator substrate.

DETAILED DESCRIPTION

FIG. 1is a schematic cross-sectional view illustrating a bulk-acoustic resonator module500in which a bulk-acoustic resonator100is mounted, according to an embodiment.

Referring toFIG. 1, the bulk-acoustic resonator module500may include at least one bulk-acoustic resonator100, a module substrate510, and a sealing portion530.

The bulk-acoustic resonator100may be disposed on the module substrate510. Even though only one resonating portion120is shown disposed on a resonator substrate110inFIG. 1, it is also possible to dispose a plurality of resonating portions120on the resonator substrate110, if necessary.

The bulk-acoustic resonator100may have connection terminals522mounted on the module substrate510. The connection terminals522may electrically connect the resonating portion120to the module substrate510. Therefore, at least one connection terminal522may be connected to a first electrode121(see.FIG. 3) and at least one connection terminal522may be connected to a second electrode123(see.FIG. 3).

The connection terminal522may penetrate a protective layer127(see.FIG. 3) similarly to a first metal layer180(see.FIG. 3) and a second metal layer190(see.FIG. 3). For example, the connection terminal522may be configured to extend from the first metal layer180and the second metal layer190, but is not limited to such a configuration. The connection terminal522may be disposed separately from the first metal layer180and the second metal layer190.

The connection terminal522may be manufactured by a plating method, as illustrated inFIG. 22, and may be formed by stacking a tin-silver compound (SnAg)522a(seeFIG. 23) on the first electrode121or the second electrode123, or on the first metal layer180or the second metal layer190, and may be further formed by stacking copper (Cu)522bon the tin-silver compound (SnAg)522a(seeFIG. 23), but is not limited to such a configuration.

In addition, the connection terminal522may be bonded to one surface of the module substrate510through a conductive adhesive550such as a solder.

The bulk-acoustic resonator100may be mounted on the module substrate510in such a manner that the resonating portion120faces one surface (for example, a mounting surface) of the module substrate510. Therefore, a space between the resonating portion120and the module substrate510may be filled with gas or formed in a vacuum state.

A detailed description of the bulk-acoustic resonator100will be provided later.

Various types of circuit substrates (for example, a ceramic substrate, a printed circuit board, a glass substrate, a flexible substrate, and the like) that are well known in the art may be used.

In the embodiment ofFIG. 1, a printed circuit board in which a polymer (for example, an epoxy resin, a bismaleimide-triazine (BT) resin, or the like) is used as an insulator519may be used as the module substrate510. However, the disclosure is not limited to the foregoing examples.

The sealing portion530may seal the bulk-acoustic resonator100mounted on the module substrate510to protect the bulk-acoustic resonator100from external environments.

The sealing portion530may be formed by an injection molding method. For example, an epoxy mold compound (EMC) may be used as a material of the sealing portion530. However, the disclosure is not limited to this example, and the sealing portion530may be formed of various materials other than the epoxy mold compound (EMC). In addition, the sealing portion530may be manufactured by using various methods in which a semi-cured resin is pressed to form the sealing portion530, or the like.

The bulk-acoustic resonator module500may be manufactured by mounting the bulk-acoustic resonator100on the module substrate510and then forming the sealing portion530. However, when a molding resin as a raw material of the sealing portion530flows between the bulk-acoustic resonator100and the module substrate510in the process of forming the sealing portion530, the resonating portion120may be broken by the molding resin.

It has been confirmed that, if a distance D1between a lower surface of the bulk-acoustic resonator100and an upper surface of the module substrate510is 30 μm or less, a gap between the bulk-acoustic resonator100and the module substrate510is very narrow and the molding resin does not easily flow into the gap. In addition, if the distance D1is less than 10 μm, the resonating portion120may be disposed very close to the module substrate510such that the resonating portion120may be in contact with the module substrate510during the manufacturing process.

Therefore, according to an example, the bulk-acoustic resonator module500may have a distance D1between the bulk-acoustic resonator100and the module substrate510of 10 μm to 30 μm.

In addition, the bulk-acoustic resonator module500o may be disposed such that the resonating portion120directly faces the module substrate510. In the related art, the resonating portion120is disposed in a space formed by a member such as a cover, a cap, or the like, and the resonating portion120is thereby blocked from external spaces to prevent a hydroxyl group (OH group) from being adsorbed on the resonating portion120. Accordingly, in the related art, the resonating portion120is configured to face a member such as a cover, a cap, or the like.

In addition, a printed circuit board (PCB), in which a polymer is used as an insulator529, is generally used as a module substrate. However, since the polymer generally has hygroscopic properties, when the bulk-acoustic resonator100in the related art is mounted on such a printed circuit board, the hydroxyl group may be easily adsorbed to the resonating portion120. Therefore, in the related art, as described above, a member such as a cover, a cap, or the like is coupled to the bulk-acoustic resonator100to seal the space in which the resonant portion120is disposed in an airtight manner, and is mounted on the module substrate510.

However, the bulk-acoustic resonator100may suppress the adsorption of the hydroxyl group (OH group) to the resonating portion120through the protective layer127(see.FIG. 3) and the hydrophobic layer130(see.FIG. 3). Therefore, since it is not necessary to form an airtight seal of the space in which the resonating portion120is disposed, the bulk-acoustic resonator100, in which a member such as a cover, a cap, or the like is omitted, may be mounted directly on the module substrate510.

In addition, since the resonating portion120is not affected by a material of the insulator519of the module substrate510, the module substrate510may be manufactured with various materials.

Therefore, manufacturing of the bulk-acoustic resonator100is very easy and manufacturing costs may be reduced.

Hereinafter, the bulk-acoustic resonator100will be described in more detail.

FIG. 2is a plan view of the bulk-acoustic resonator100.FIG. 3is a cross-sectional view taken along line I-I′ ofFIG. 2.FIG. 4is a cross-sectional view taken along line II-II′ ofFIG. 2.FIG. 5is a cross-sectional view taken along line III-III′ ofFIG. 2.

Referring toFIGS. 2 to 5, the bulk-acoustic resonator100may be a film bulk acoustic resonator (FBAR), and may include the resonator substrate110, an insulating layer115, a membrane layer150, a cavity C, the resonating portion120, the protective layer127, and the hydrophobic layer130.

The resonator substrate110may be a silicon substrate. For example, a silicon wafer may be used as the resonator substrate110. Alternatively, a silicon on insulator (SOI) type substrate may be used.

The insulating layer115may be formed on an upper surface of the resonator substrate110, and the resonator substrate110may be electrically isolated from a structure/components disposed thereabove. In addition, the insulating layer115may prevent the resonator substrate110from being etched by an etching gas when a cavity C is formed during a manufacturing process.

In this case, the insulating layer115may be formed of any one or any combination of any two or more of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN), and may be formed through a process of chemical vapor deposition, RF magnetron sputtering or evaporation.

The sacrificial layer140may be formed on the insulating layer115, and the cavity C and the etch stop portion145may be disposed inside the sacrificial layer140.

The cavity C is formed as an empty space, and may be formed by removing a portion of the sacrificial layer140. Since the cavity C is formed in the sacrificial layer140, the resonating portion120, which is formed on an upper portion of the sacrificial layer140, may be formed to be flat as a whole.

The etch stop portion145may be disposed along a boundary of the cavity C. The etch stop portion145may prevent etching from progressing beyond a cavity region in a process of forming the cavity C. Thus, the horizontal area of the cavity C is defined/bounded by the etch stop portion145, and the vertical area is defined by the thickness of the sacrificial layer140.

The membrane layer150may be formed on the sacrificial layer140to define the thickness (or height) of the cavity C together with the resonator substrate110. Accordingly, the membrane layer150may be formed of a material which may not be easily removed in the process of forming the cavity C.

For example, when a halide-based etching gas such as fluorine (F), chlorine (Cl), or the like is used to remove a portion of the sacrificial layer140(for example, a cavity region), the membrane layer150may be formed of a material having low reactivity with the etching gas. In this case, the membrane layer150may include either one or both of silicon dioxide (SiO2) and silicon nitride (Si3N4).

In addition, the membrane layer150may be formed by a dielectric layer containing any one or any combination of any two or more of manganese oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO) and may be formed of a metal layer containing at least one of aluminum (Al), nickel (Ni), chrome (Cr), platinum (Pt), gallium (Ga), and hafnium (Hf). However, the present disclosure is not limited to these examples.

A seed layer (not shown) made of aluminum nitride (AlN) may be formed on the membrane layer150. Specifically, the seed layer may be disposed between the membrane layer150and the first electrode121. In addition to AlN, the seed layer may be formed using a dielectric material of metal having an HCP structure. In the case of metal, for example, the seed layer may be formed of titanium (Ti).

The resonating portion120may include a first electrode121, a piezoelectric layer123, and a second electrode125. In the resonating portion120, the first electrode121, the piezoelectric layer123, and the second electrode125may be stacked sequentially from a bottom of the resonating portion120. Therefore, the piezoelectric layer123may be disposed between the first electrode121and the second electrode125in the resonating portion120.

The resonating portion120is formed on the membrane layer150, such that the membrane layer150, the first electrode121, the piezoelectric layer123, and the second electrode125are sequentially stacked on the resonator substrate110to form the resonating portion120.

The resonating portion120may resonate the piezoelectric layer123according to a signal applied to the first electrode121and the second electrode125to generate a resonance frequency and an anti-resonance frequency.

When an insertion layer170to be described later is formed, the resonating portion120may be divided into a central portion S in which the first electrode121, the piezoelectric layer123, and the second electrode125are stacked substantially flat and an extension portion E in which the insertion layer170is interposed between the first electrode121and the piezoelectric layer123.

The central portion C may be a region disposed at a center of the resonating portion120and the extension portion E may be a region disposed along a periphery of the central portion S. Therefore, the extension portion E may be a region extending outward from the central portion S.

The insertion layer170may have an inclined surface L at which the thickness increases as the distance from the central portion S increases.

Portions of the piezoelectric layer123and the second electrode125in the extension portion E may be disposed on the insertion layer170. Therefore, the portions of the piezoelectric layer123and the second electrode125located at the extension portion E may have an inclined surface along the shape of the insertion layer170.

In the embodiment ofFIGS. 2-5, the extension portion E is included in the resonating portion120, such that resonance may also occur in the extension portion E. However, the disclosure is not limited to this example. Depending on the structure of the extension portion E, resonance may not occur in the extension portion E, and resonance may occur only in the central portion S.

The first electrode121and the second electrode125may be formed of a conductive material such as gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, nickel, or an alloy containing any one or any combination of any two or more of gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, and nickel, but is not limited to these materials.

The first electrode121may be formed to have an area that is larger than an area of the second electrode125, and a first metal layer180may be disposed on the first electrode121along an outer periphery of the first electrode121. Accordingly, the first metal layer180may be disposed to surround the second electrode125.

The first electrode121may be disposed on the membrane layer150, such that the first electrode121may be formed to be substantially flat. The second electrode125may be disposed on the piezoelectric layer123, such that the second electrode125includes portions that are bent to correspond to the shape of the piezoelectric layer123.

The second electrode125may be disposed throughout the entirety of the central portion C and may be partially disposed in the extension portion E. Thus, the second electrode125may include a portion disposed on a piezoelectric portion123aof the piezoelectric layer123, to be described later, and a portion disposed on a bent portion123bof the piezoelectric layer123.

More specifically, the second electrode125may be disposed to cover an entirety of the piezoelectric portion123aand a portion of an inclined portion1231of the piezoelectric layer123. Therefore, a portion of the second electrode125adisposed in the extension portion E may be formed to have an area that is less than an area of an inclined surface of the inclined portion1231, and the second electrode125may be formed to have an area that is smaller than the piezoelectric layer123in the resonating portion120.

The piezoelectric layer123may be formed on the first electrode121. When the insertion layer, to be described later, is formed, the piezoelectric layer123may be formed on the first electrode121and the insertion layer170.

For example, zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanate, quartz, or the like, may be selectively used as a material of the piezoelectric layer123. The doped aluminum nitride may further include a rare earth metal, a transition metal, or an alkaline earth metal. As an example, the rare earth metal may include any one or any combination of any two or more of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). The transition metal may include any one or any combination of any two or more of hafnium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta), and niobium (Nb). In addition, the alkaline earth metal may include magnesium (Mg).

The piezoelectric layer123may include the piezoelectric portion123adisposed in the central portion S and the bent portion123bdisposed in the extension portion E.

The piezoelectric portion123amay be a portion directly stacked on an upper surface of the first electrode121. Accordingly, the piezoelectric portion123amay be interposed between the first electrode121and the second electrode125to be formed in a flat shape together with the first electrode121and the second electrode125.

The bent portion123bmay be a region extending outwardly of the piezoelectric portion123ato be located in the extension portion E.

The bent portion123bmay be disposed on the insertion layer170, to be described later, and may be formed in a raised shape along the shape of the insertion layer170. Thus, the piezoelectric layer123may be bent at a boundary of the piezoelectric portion123aand the bent portion123b, and the bent portion123bmay be raised corresponding to the thickness and shape of the insertion layer170.

As stated above, the bent portion123bmay include the inclined portion1231and the extension portion1232. The inclined portion1231may be inclined along an inclined surface L of the insertion layer170. The extension portion1232may be a portion extending outwardly of the inclined portion1231.

The inclined portion1231may be formed to be parallel to the inclined surface L of the insertion layer170, and an inclination angle of the inclined portion1231may be formed to be equal to the inclination angle (θ ofFIG. 4) of the inclined surface L of the insertion layer170.

The insertion layer170may be disposed along a surface formed by the membrane layer150, the first electrode121, and the etch stop portion145.

The insertion layer170may be disposed at a periphery of the central portion S to support the bent portion123bof the piezoelectric layer123. Therefore, the bent portion123bof the piezoelectric layer123may be divided into the inclined portion1231and the extension portion1232along the shape of the insertion layer170.

The insertion layer170may be disposed in a region excluding the central portion S. For example, the insertion layer170may be disposed over an entire region excluding the central portion S, or may be disposed in parts of a region excluding the central portion S.

In addition, at least a portion of the insertion layer170may be disposed between the piezoelectric layer123and the first electrode121.

A side surface of the insertion layer170disposed along the boundary of the central portion S may be formed in a thicker form as the distance from the central portion S increases. Thus, the insertion layer170may be formed of the inclined surface L having an inclination angle (θ) in which a side surface thereof, disposed adjacent to the central portion S, is constant.

In order to manufacture the insertion layer170such that the inclination angle (θ) of the side surface of the insertion layer170is less than 5°, the thickness of the insertion layer170may be formed to be very thin or an area of the inclined surface L may be extremely large. Such configurations may be substantially difficult to implement.

In addition, when the inclination angle (θ) of the side surface of the insertion layer170is formed to be larger than 70°, the inclination angle of the inclination portion1231of the piezoelectric layer123stacked on the insertion layer170may be also formed to be larger than 70°. In this case, since the piezoelectric layer123is excessively bent, cracking may occur in the bent portion of the piezoelectric layer123.

Therefore, in the embodiment ofFIGS. 2-5, the inclination angle (θ) of the inclination surface L may be equal to or greater than 5° and less than or equal to 70°.

The insertion layer170may be formed of a dielectric material such as silicon oxide (SiO2), aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), manganese oxide (MgO), zirconium oxide (ZrO2), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), zinc oxide (ZnO), or the like, but may be formed of a material different from the material of the piezoelectric layer123. In addition, if necessary, it is also possible to form a region in which the insertion layer170is provided as an air space. This may be realized by forming all of the resonating portion120in the manufacturing process, and then removing the insertion layer170.

The thickness of the insertion layer may be formed to be less than the thickness of the insertion layer123. When the insertion layer170is thicker than the piezoelectric layer123, it is difficult to form the bent portion123bin which bending is formed along the shape of the insertion layer170. In addition, when the thickness of the insertion layer170is 100 Å or more, it is possible to easily form the bent portion123band effectively prevent sound waves in a horizontal direction of the bulk-acoustic resonator, thereby improving the resonator performance.

The resonating portion120may be disposed to be spaced apart from the resonator substrate110through a cavity C formed as an air space.

The cavity C may be formed by supplying an etching gas (or an etching solution) to an inlet hole (H ofFIG. 2,FIG. 4) to remove a portion of a sacrificial layer140in the manufacturing process of the bulk-acoustic resonator100.

A protective layer127may be disposed along a surface of the bulk-acoustic resonator100to protect the bulk-acoustic resonator100from an outside environment. The protective layer127may be disposed along the second electrode125, the bent portion123bof the piezoelectric layer123, and the surface formed by the insertion layer170.

The protective layer127may include a first protective layer127aformed of a silicon oxide based insulating material or a silicon nitride based insulating material, and a second protective layer127bformed of any one of an aluminum oxide based insulating material, an aluminum nitride based insulating material, a magnesium oxide based insulating material, a titanium oxide based insulating material, a zirconium oxide based insulating material, and a zinc oxide based insulating material.

The second protective layer127bmay be stacked on an upper portion of the first protective layer127a. The protective layer127will be described later in more detail.

The first electrode121and the second electrode125may be formed to be extended to the outside of the resonating portion120, and a first metal layer180and a second metal layer190may be disposed on the upper surface of the extended portions of the first electrode121and the second electrode125, respectively.

The first metal layer180and the second metal layer190may be formed of a material such as gold (Au), a gold-tin (Au—Sn) alloy, copper (Cu), a copper-tin (Cu—Sn) alloy, aluminum (Al), an aluminum alloy, or the like.

The first metal layer180and the second metal layer190may function as connection wirings for electrically connecting the electrodes121and125of the bulk-acoustic resonator100and electrodes of other bulk-acoustic resonators disposed adjacent to each other, or may function as external terminals. However, the disclosure is not limited to these examples.

Although an example in which the insertion layer170is disposed below the second metal layer190is shown inFIG. 3, the disclosure is not limited to this configuration. If necessary, it is also possible to implement a structure in which the insertion layer170is removed below the second metal layer190.

The first metal layer180may be bonded to the first electrode121through the insertion layer170and the protective layer127.

In addition, as illustrated inFIG. 4, the first electrode121may be formed to have an area that is wider than an area of the second electrode125, and the first metal layer180may be formed at the periphery of the first electrode121.

Accordingly, the first metal layer180may be disposed along the periphery of the resonating portion120, and may be disposed to surround the second electrode125. However, the disclosure is not limited to this example.

As described above, the second electrode125\may be stacked on the piezoelectric portion123and the inclined portion1231of the piezoelectric layer123. A portion of the second electrode125disposed on the inclined portion1231of the piezoelectric layer123, that is, a second electrode portion125adisposed in the extension portion E, is not disposed on an entire inclined surface of the inclined portion1231but may be disposed on only a portion of the inclined portion1231.

FIG. 6is a graph illustrating the resonance attenuation of a bulk-acoustic resonator according to a second electrode structure of the bulk-acoustic resonator. That is,FIG. 6is a graph illustrating attenuation of the bulk-acoustic resonator shown in Tables 3 to 5 in which the thickness of the insertion layer170is 3000 Å and the inclination angle (θ) of the inclination surface L is 20°. Attenuation of the bulk-acoustic resonator was measured while changing the size of the second electrode125adisposed in the extension portion E in the bulk-acoustic resonator having the length of the inclination surface L (Is, or width) of 0.87 μm. InFIG. 5, the greater an attenuation value of the bulk-acoustic resonator, the better the structure that shields sound waves in the horizontal direction performs. The following Table 1 is a table summarizing the values of the graph shown in Table 6.

Since the inclined surface of the piezoelectric layer123is formed to have the same shape as the inclined surface L of the insertion layer L along the inclined surface L, the length of the inclined surface of the piezoelectric layer123can be considered to be equal to the length (Is) of the inclined surface L of the insertion layer170.

Referring toFIG. 6and Table 1, in the bulk-acoustic resonator in which the length (Is) of the inclined surface of the piezoelectric layer123in the extension portion E is 0.87 μm, the attenuation was measured to be greatest when the second electrode125ais stacked on the inclined surface of the piezoelectric layer123with a width of 0.5 μm. It was measured that the attenuation decreases and the resonance performance is deteriorated when a width of the second electrode125ais greater or less than 0.5 μm in the extension portion E.

Considering a ratio (We/Is) of a width (We) of the second electrode125and a length (Is) of the inclined surface in the extension portion E, as illustrated in Table 1, it can be seen that attenuation is maintained to be 37 dB or more when the ratio (We/Is) is 0.46 to 0.69.

Therefore, in order to provide the resonance performance, a range of the ratio (We/Is) of a maximum width (We) of the second electrode125aand the length (Is) of the inclined surface in the extension portion E of the bulk-acoustic resonator100may be 0.46 to 0.69. However, the disclosure is not limited to such an example. The range of the ratio We/Isbe changed according to the size of the inclination angle (θ) or the thickness change of the insertion layer170, and may be changed as the resonance frequency of the resonator changes.

According to the result of Table 1, it can be seen that the attenuation characteristic of the bulk-acoustic resonator100is better in the case in which an end of the second electrode125ais disposed on the inclined portion1231than the case in which an end of the second electrode125is disposed to the extension portion1232through the inclined portion1231.

When a bulk-acoustic resonator is used in a humid environment or is left at room temperatures for an extended period of time of time, a hydroxyl group (OH group) may be adsorbed by a protective layer of the bulk-acoustic resonator, such that frequency variations may increase due to mass loading or resonator performance may be deteriorated.

In order to solve this problem, the protective layer127in the bulk-acoustic resonator127may be formed by stacking at least two layers127aand127b, which are different from each other. In addition, the hydrophobic layer130may be disposed on the protective layer127.

FIG. 7illustrates that a hydroxyl group is adsorbed on a protective layer on which a hydrophobic layer is not formed, andFIG. 8illustrates a hydrophobic layer formed on a protective layer.

Referring toFIGS. 7 and 8, the protective layer127may include a first protective layer127aand a second protective layer127bstacked on the first protective layer127a. A hydrophobic layer130may be disposed on the second protective layer127b.

As illustrated inFIG. 7, when the hydrophobic layer130is not formed on the protective layer127, when the hydrophobic layer127is used in a humid environment or is left at room temperature for an extended period of time of time, a hydroxyl group (OH group) may be more easily adsorbed to the protective layer127to form hydroxylate. Since hydroxylate has high surface energy and is stable, mass loading occurs because it attempts to lower the surface energy by adsorbing water, or another fluid.

On the other hand, as illustrated inFIG. 8, when the hydrophobic layer130is formed on the protective layer, since the surface energy is low and stable, there is no need to lower the surface energy by adsorbing water, a hydroxyl group (OH group), and the like. Therefore, the hydrophobic layer130may serve to suppress adsorption of water, a hydroxyl group (OH group), and the like, thereby significantly reducing frequency variation, and thus maintaining uniform resonator performance.

FIG. 9is a graph illustrating changes in frequency according to humidity and time with respect to a bulk-acoustic resonator according to an embodiment (Embodiment) in which a hydrophobic layer is formed on a protective layer and a bulk-acoustic resonator according to a comparative example (Comparative Example), in which a hydrophobic layer is not formed on a protective layer. In an experimental method, the above-described Embodiment and Comparative Example were placed in a moisture absorption chamber, and the changes in frequency were measured while chaining the humidity as illustrated inFIG. 9.

Referring toFIG. 9, it can be seen that in the case of the bulk-acoustic resonator in which the hydrophobic layer is formed on the protective layer, an amount of frequency change according to the change in humidity and time is much smaller. In addition, in the case of the Embodiment, it can be seen that the amount of frequency change at the end of the experiment is smaller than the amount of frequency change at the start of the experiment.

The hydrophobic layer130may be formed of a self-assembled monolayer, not a polymer. When the hydrophobic layer130is formed of a polymer, mass due to the polymer affects to the resonating portion120. However, in the bulk-acoustic resonator100, since the hydrophobic layer130is formed of a self-assembled monolayer, it is possible to significantly reduce changes in frequency of the bulk-acoustic resonator100.

When a hydrophobic layer is formed of a polymer, the thickness of the hydrophobic layer may become uneven when the hydrophobic layer is formed in the cavity C through inlet holes (H ofFIG. 1andFIG. 3). The thickness of the hydrophobic layer in the cavity C, close to the inlet holes H, may be greater and the thickness of the hydrophobic layer formed in a central portion of the cavity C, far from the inlet holes H, may be less.

In addition, when the polymer has high viscosity, the polymer may not penetrate smoothly into the cavity C such that the hydrophobic layer may not be formed inside the cavity C.

However, since the hydrophobic layer130of the bulk-acoustic resonator100is formed of a self-assembled monolayer, the thickness of the hydrophobic layer130may be uniform according to positions in the cavity C.

In order to improve adhesion between the self-assembled monolayer constituting the hydrophobic layer130and the protective layer127, a precursor may be used. As illustrated inFIG. 10, the precursor may be a hydrocarbon having a silicon head or siloxane having a silicon head.

The hydrophobic layer130may be fluorocarbon, referring toFIG. 11, but is not limited thereto. The hydrophobic layer130may be formed of a material having a contact angle of 90° or more with water after deposition. For example, the hydrophobic layer130may contain a fluorine (F) component, and may include fluorine (F) and silicon (Si).

Since the hydrophobic layer130is formed after forming the first metal layer180and the second metal layer190, as described later, the hydrophobic layer130may be formed on an upper portion of the protective layer170, excluding a portion in which the first metal layer180and the second metal layer190are formed on the protective layer127.

In addition, the hydrophobic layer130may be disposed not only on an upper portion of the protective layer127, but also on an inner surface of the cavity C.

As described later, the hydrophobic layer130formed on the cavity C may be formed at the same time that the hydrophobic layer130formed on the protective layer127is formed.

The hydrophobic layer130formed in the cavity C may be formed on the upper surface of the cavity C, thereby suppressing the adsorption of a hydroxyl group to the resonant portion. Since the adsorption of the hydroxyl group of the resonator occurs not only on the protective layer127, but also on the upper surface of the cavity C, in order to prevent the frequency drop due to mass loading due to the adsorption of hydroxyl group, it is desirable to prevent the adsorption of the hydroxyl group on the protective layer127and the upper surface of the cavity C. In addition, the hydrophobic layer130may be formed not only on the upper surface of the cavity C, but also on at least a portion or an entirety of the lower surface and the side surface of the cavity C.

In addition, the protective layer127may include the first protective layer127adisposed along a surface below which the second electrode125, the bent portion123bof the piezoelectric layer123, and the insertion layer170are formed, and the second protective layer127bstacked on the first protective layer127a.

The first protective layer127amay be used for frequency trimming and may be made of a material suitable for the frequency trimming. For example, the first protective layer127amay be formed of any one of silicon dioxide (SiO2), silicon nitride (Si3N4), amorphous silicon (a-Si), and polycrystalline silicon (p-Si).

In the case of silicon dioxide (SiO2), silicon nitride (Si3N4), amorphous silicon (a-Si), and polycrystalline silicon (p-Si), there may be a disadvantage that the adsorption of the hydroxyl group easily occurs in a wet process, which is a subsequent process. The reason for this result is that, because, a film quality of thin films such as silicon dioxide (SiO2), silicon nitride (Si3N4), amorphous silicon (a-Si) and polycrystalline silicon (p-Si) is not dense, there are many sites in which the adsorption of hydroxyl group may occur not only on the surface but also inside the thin films. Therefore, in the bulk-acoustic resonator100, the second protective layer127bmay be formed by stacking a material that resists absorption of a hydroxyl group on the first protective layer127a.

Accordingly, the second protective layer127bmay be made of a material having high density. For example, the second protective layer127bmay be made of any one of aluminum oxide (Al2O3), aluminum nitride (AlN), magnesium oxide (MgO), titanium oxide (TiO2), zirconium oxide (ZrO2), and zinc oxide (ZnO).

Since the second protective layer127bhas a more dense film quality than the first protective layer127a, the adsorption of a hydroxyl group may occur only on the surface of the second protective layer127b.

The first protective layer127awas formed of silicon dioxide (SiO2) having a thickness of 2000 Å and a reliability test was performed in a high temperature, high humidity, and high pressure environment without a hydrophobic layer, and as a result, an amount of frequency variation of the resonating portion120was measured to be 0.9 Mhz. It was measured that the amount of frequency variation of the resonating portion120is 0.7 Mhz when a hydrophobic layer is formed on the above-described first protective layer127a.

In addition, a reliability test was performed when the first protective layer127awas formed of silicon nitride (Si3N4) having a thickness of 2000 Å, without the hydrophobic layer. As a result, it was measured that the amount of frequency variation of the resonating portion120is 0.7 Mhz, and it was measured that the amount of frequency variation measured after forming the hydrophobic layer is 0.5 Mhz.

On the other hand, when the first protective layer127ais formed of silicon nitride (Si3N4) having a thickness of 2000 Å, and the second protective layer127bis formed of aluminum oxide (Al2O3) having a thickness of 500 Å, and the hydrophobic layer is disposed on the second protective layer127b, it was measured that the amount of frequency variation of the resonating portion120is 0.3 Mhz.

Therefore, it can be seen that the amount of frequency variation is remarkably improved when the protective layer127is formed of a plurality of layers, and the hydrophobic layer130is stacked thereon.

When the amount of frequency variation is about 0.3 Mhz as a result of the reliability test, it is not necessary to seal the resonating portion120in order to block penetrating moisture into the resonating portion120. Therefore, it is not necessary to add additional components in order to provide airtightness of the resonating portion120.

FIGS. 12 to 15are explanatory diagrams for explaining a manufacturing method of the bulk-acoustic resonator100, according to an embodiment.

Referring toFIG. 12, a manufacturing method of the bulk-acoustic resonator100includes steps of forming the insulating layer115and the sacrificial layer140on the resonator substrate110, and forming a pattern P penetrating the sacrificial layer140. Therefore, the insulating layer115may be exposed to the outside environment through the pattern P.

The insulating layer115may be formed of manganese oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO), silicon nitride (Si3N4), or silicon dioxide (SiO2), but is not limited to these examples.

The pattern P may be formed to have a trapezoidal cross-section having a width on an upper surface that is wider than a width on the lower surface.

The sacrificial layer140may be partially removed through a subsequent etching process to form the cavity C (FIG. 3). Therefore, the sacrificial layer140may be made of a material such as polysilicon, polymer, or the like, but is not limited to these examples.

Subsequently, the membrane layer150may be formed on the sacrificial layer140. The membrane layer150may be formed with a constant thickness along the surface of the sacrificial layer140. The thickness of the membrane layer150may be less than the thickness of the sacrificial layer140.

The membrane layer150may include either one or both of silicon dioxide (SiO2) and silicon nitride (Si3N4). In addition, the membrane layer150may be made of a dielectric layer containing any one or any combination of any two or more of manganese oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO) or may be formed of a metal layer containing at least one of aluminum (Al), nickel (Ni), chrome (Cr), platinum (Pt), gallium (Ga), hafnium (Hf), and titanium (Ti). However, the disclosure is not limited to these examples.

Although not illustrated, a seed layer may be formed on the membrane layer150.

The seed layer may be disposed between the membrane layer150and a first electrode121, to be described later. The seed layer may be manufactured of aluminum nitride (AlN), but is not limited thereto. The seed layer may be formed using a dielectric and metal having an HCP structure. For example, when metal is used to form the seed layer, the seed layer may be formed of titanium (Ti).

Subsequently, as illustrated inFIG. 13, an etch stop layer145amay be formed on the membrane layer150. The etch stop layer145amay also be filled in the pattern P.

The etch stop layer145amay be formed to have a thickness that completely fills the pattern P. Therefore, the etch stop layer145amay be formed to be thicker than the sacrificial layer140.

The etch stop layer145amay be formed of the same material as the insulating layer115, but is not limited thereto.

Subsequently, the etch stop layer145amay be partially removed such that the membrane layer150is exposed to the outside. In this case, the portion of the etch stop layer145afilled in the pattern P may remain, and may form the etch stop portion145.

Subsequently, as illustrated inFIG. 14, the first electrode121may be formed on the upper surface of the membrane layer150.

The first electrode121may be formed of a conductive material, such as gold (Au), molybdenum (Mo), ruthenium (Ru), iridium (Ir), aluminum (Al) platinum (Pt), titanium (Ti), tungsten (W), palladium (Pd), tantalum (Ta), chromium (Cr), nickel (Ni) or a metal including any one or any combination of any two or more of gold (Au), molybdenum (Mo), ruthenium (Ru), iridium (Ir), aluminum (Al) platinum (Pt), titanium (Ti), tungsten (W), palladium (Pd), tantalum (Ta), chromium (Cr), nickel and (Ni). However, the first electrode121is not limited to the listed materials.

The first electrode121may be formed on the upper portion of a region in which the cavity C (FIG. 3) is to be formed.

The first electrode121may be formed by forming a conductive layer covering the entirety of the membrane layer150, and then removing unnecessary portions of the conductive layer.

Subsequently, the insertion layer170may be formed, if necessary. The insertion layer170may be formed on the first electrode121, and may be extended to the upper portion of the membrane layer150. When the insertion layer170is formed, the extension portion123bof the resonating portion120is formed to be thicker than the central portion123a, such that vibrations generated in the resonating portion120are prevented from leaking to the outside, such that a Q-factor may be improved.

The insertion layer170may be formed to cover the entirety of the surface formed by the membrane layer150and the first electrode121and the etch stop portion145, and then may be completed by removing a portion disposed in a region corresponding to the central portion S.

Accordingly, a central portion of the first electrode121corresponding to the central portion S may be exposed to the outside of the insertion layer170. In addition, the insertion layer170may be formed to cover a portion of the first electrode121along the periphery of the first electrode121. Therefore, a rim portion of the first electrode121disposed in the extension portion E may be disposed under the insertion layer170.

A side surface of the insertion layer170disposed adjacent to the central portion S may be formed of an inclined surface L. The insertion layer170may be formed to be thinner toward the central portion S. Accordingly, the lower surface of the insertion layer170may be formed in a more extended form toward the central portion S than the upper surface of the insertion layer170. In this case, the inclination angle of the inclined surface L of the insertion layer170may be formed in a range of 5° to 70°, as described above.

The insertion layer170may be formed of a dielectric material such as silicon oxide (SiO2), aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), manganese oxide (MgO), zirconium oxide (ZrO2), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), zinc oxide (ZnO), or the like, but may be formed of a material different from that of the piezoelectric layer123.

Subsequently, the piezoelectric layer123may be formed on the first electrode121and the insertion layer170.

The piezoelectric layer123may be formed of aluminum nitride (AlN). However, the piezoelectric layer123is not limited to AlN, and zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanate, quartz, or the like, may be selectively used as a material of the piezoelectric layer123. The doped aluminum nitride may further include a rare earth metal, a transition metal, or an alkaline earth metal. As an example, the rare earth metal may include any one or any combination of any two or more of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La), and the rare earth metal content may be 1 to 20 at %. The transition metal may include any one or any combination of any two or more of hafnium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta), and niobium (Nb). In addition, the alkaline earth metal may include magnesium (Mg).

In addition, the piezoelectric layer123may be formed of a material different from that of the insertion layer170.

The piezoelectric layer123may be formed by forming a piezoelectric material on an entire surface formed by the first electrode121and the insertion layer170, and then partially removing unnecessary portions of the piezoelectric material. In the embodiment ofFIGS. 12-15, the unnecessary portions of the piezoelectric material are removed, after the second electrode125is formed, to complete the piezoelectric layer123. However, it is also possible to complete the piezoelectric layer123before forming the second electrode125.

The piezoelectric layer123may be formed to cover portions of the first electrode121and the insertion layer170, and thus the piezoelectric layer123may be formed along the shape formed by the first electrode121and the insertion layer170.

As described above, only a portion of the first electrode121corresponding to the central portion S may be exposed to the outside of the insertion layer170. Therefore, the portion of the piezoelectric layer123formed on the first electrode121may be located in the central portion S. The bent portion123bformed on the insertion layer170may be located in the extension portion E.

Subsequently, the second electrode125may be formed on the piezoelectric layer123. The second electrode125may be formed of a conductive material such as gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, nickel, or metal including any one or any combination of any two or more of gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, and nickel, but is not limited to these examples.

The second electrode125may be mostly formed on the piezoelectric portion123aof the piezoelectric layer123. As described above, the piezoelectric portion123aof the piezoelectric layer123may be located in the central portion S. Therefore, the portion of the second electrode125disposed on the piezoelectric layer123may also be disposed in the central portion S.

In addition, the second electrode125may be further formed on the inclined portion1231of the piezoelectric layer123. As described above, the second electrode125may be disposed in the entirety of the central portion S and partially in the extension portion E. By partially disposing the second electrode125in the extension portion123b, it is possible to provide remarkably improved resonance performance.

Subsequently, as illustrated inFIG. 15, the first protective layer127amay be formed.

The first protective layer127amay be formed along the surface formed by the second electrode125and the piezoelectric layer123. In addition, although not shown, the first protective layer127amay also be formed on the externally exposed portion of the insertion layer170.

The first protective layer127amay be formed of either one of a silicon oxide based insulating material and a silicon nitride based insulating material, but is not limited to these examples.

For example, the first protective layer127amay be formed of any one of silicon dioxide (SiO2), silicon nitride (Si3N4), amorphous silicon (a-Si), and polycrystalline silicon (p-Si).

Subsequently, the first protective layer127aand the piezoelectric layer123may be partially removed to partially expose the first electrode121and the second electrode125, and a first metal layer180and a second metal layer190may be formed on the exposed portions of the first electrode121and the second electrode125, respectively.

The first metal layer180and the second metal layer190may be formed of a material such as gold (Au), a gold-tin (Au—Sn) alloy, copper (Cu), a copper-tin (Cu—Sn) alloy, aluminum (Al), an aluminum alloy, or the like, and may be deposited on the first electrode121or the second electrode125in a desired form. However, the first electrode121and the second electrode125are not limited to the example materials.

Subsequently, the cavity C may be formed by removing a portion of the sacrificial layer140located inside the etch stop portion145, and the portion of the sacrificial layer140removed in this process may be removed by an etching method.

When the sacrificial layer140is formed of a material such as polysilicon or polymer, the sacrificial layer140may be removed by a dry etching method using a halide-based etching gas (for example, XeF2) such as fluorine (F) or chlorine (Cl), or the like.

Subsequently, a trimming process partially removing a first protective layer127athrough a wet process may be performed to obtain a target frequency characteristic.

When the trimming process is completed, a process of stacking a second protective layer127bon the first protective layer127amay be performed. As described above, a material having a higher density than that of the first protective layer127amay be used in the second protective layer127b. For example, aluminum oxide (Al2O3) may be used in the second protective layer127b. However, the disclosure is not limited to this example.

The second protective layer127bmay be formed to have a thickness that is less than the thickness of the first protective layer127a, and may be formed by a vapor deposition method, or the like.

Subsequently, the hydrophobic layer130may be formed on the second protective layer127bto complete the bulk-acoustic resonator100illustrated inFIGS. 3 and 4.

The hydrophobic layer130may be formed by depositing a hydrophobic material by a chemical vapor deposition (CVD) method.

As illustrated inFIG. 16, hydroxylate is formed on the surface of the second protective layer127b, and by using a precursor having a silicon head, a hydrolyzed silane reaction is performed to the hydroxylate such that the surface of the protective layer127is surface-treated.

Thereafter, when a fluorocarbon functional group is formed on a surface of the surface-treated protective layer127, the hydrophobic layer130may be formed on the protective layer127as illustrated inFIG. 8.

It is also possible to form the hydrophobic layer130by directly forming the fluorocarbon functional group on the protective layer127, omitting the surface treatment, depending on the material of the protective layer.

The hydrophobic layer130may be formed on the entire surface of the bulk-acoustic resonator100, but the hydrophobic layer130may be formed on only part of the surface of the bulk-acoustic resonator100, if necessary.

For example, the hydrophobic layer130may be formed on an upper surface of the cavity C through inlet holes H (FIGS. 2 and 4) in the above-described hydrophobic layer formation step. In addition, the hydrophobic layer130may also be formed on at least a portion of the upper surface and the lower surface and the side surface of the cavity C, and it is also possible to form the hydrophobic layer130on the entirety of the upper surface, the lower surface, and the side surface of the cavity C.

In addition, by forming the hydrophobic layer130as a self-assembled monolayer, rather than a polymer, it is possible to prevent a mass load due to the hydrophobic layer130from being applied to the resonant portion120, and the thickness of the hydrophobic layer130may be uniform.

Hereinafter, modified embodiments of a bulk-acoustic resonator will be described.

FIGS. 17 and 18are schematic cross-sectional views illustrating a bulk-acoustic resonator according to a modification of the embodiment ofFIGS. 2-5. That is,FIG. 17is a cross-sectional view corresponding to I-I′ ofFIG. 2, andFIG. 18is a cross-sectional view corresponding to II-II′ ofFIG. 2.

Referring toFIGS. 17 and 18, only a portion of the insertion layer170supporting the piezoelectric layer123in the resonating portion120remains in the bulk acoustic wave resonator, and all remaining portions are removed. Thus, the insertion layer170may be partially provided in comparison to the embodiment ofFIGS. 2-5, if necessary.

When the bulk-acoustic resonator is configured as illustrated inFIGS. 17 and 18, the insertion layer170may be disposed so as not to contact the first metal layer180or the etch stop portion145. In addition, the insertion layer170may not be disposed outside of the resonating portion120, and may be disposed in the upper region of the cavity C. However, a region in which the insertion layer170may be is disposed is not limited to the regions illustrated inFIGS. 17 and 18, and may be extended to various positions if necessary.

FIG. 19is a schematic cross-sectional view illustrating a modified example of the bulk-acoustic resonator module500illustrated inFIG. 1.

As illustrated inFIG. 19, the bulk-acoustic resonator module may be configured in a package form in which at least one electronic device560is mounted in addition to the bulk-acoustic resonator100.

FIG. 20is a schematic cross-sectional view illustrating a bulk-acoustic resonator module, according to another embodiment.FIG. 12illustrates a modified example of the bulk-acoustic resonator module illustrated inFIG. 20.

Referring toFIG. 20, in the bulk-acoustic resonator module, a trench524may be formed on one surface of the module substrate510, and the bulk-acoustic resonator100may be disposed in the trench524.

In this embodiment, a horizontal area of the trench524may be formed to be smaller than a horizontal area of the bulk-acoustic resonator100. For example, in the cross-sectional view ofFIG. 20, a horizontal length L2of the trench524may be configured to be less than a horizontal length L1of the bulk-acoustic resonator100by 10 μm or more.

According to the configuration described above, a rim portion of a lower surface of the bulk-acoustic resonator100may be disposed to be closely adjacent to an upper surface of the module substrate510. In this embodiment, the lower surface of the bulk-acoustic resonator100may be disposed to be spaced apart from the upper surface of the module substrate510.

A shortest distance D2between the rim portion of the lower surface of the bulk-acoustic resonator100and the upper surface of the module substrate510may be in a range of 0 μm to 20 μm. Thus, it is possible to prevent a module resin from flowing into the trench524through a gap between the bulk-acoustic resonator100and the upper surface of the module substrate510when the sealing portion530is formed.

However, the configuration of the disclosure is not limited to the example described above, and various modifications may be made. For example, the rim portion of the lower surface of the bulk-acoustic resonator100may be configured to be in contact with the upper surface of the module substrate510, if necessary.

In addition, the depth of the trench524may be in a range of 20 μm to 30 μm, but is not limited thereto.

It is also possible that the bulk-acoustic resonator module may be formed such that the horizontal area of the trench524is formed to be larger than the horizontal area of the bulk-acoustic resonator100, if necessary. In this case, the shortest distance between the rim portion of the lower surface of the bulk-acoustic resonator100and the module substrate510-1may be in the range of 0 μm to 20 μm. In addition, it is also possible that the at least a portion of the module substrate510may be disposed to be in the trench524, if necessary.

The bulk-acoustic resonator module may be configured as a single package form including only the bulk-acoustic resonator100as illustrated inFIG. 20, but is not limited to such an example. As illustrated inFIG. 21, the bulk-acoustic resonator module may be configured as a package form in which at least one electronic device560is mounted on the module substrate510-1in addition to the bulk-acoustic resonator100.

FIG. 22is a schematic cross-sectional view of a bulk-acoustic resonator module, according to another embodiment.FIG. 23is a partial enlarged view enlarging portion A ofFIG. 22.

Referring toFIGS. 22 and 23, the bulk-acoustic resonator100according may include a blocking member540.

In the case of the above-described embodiments, the shortest distance between the module substrate510and the bulk-acoustic resonator100may be significantly reduced to block inflow of the molding resin. However, the distance between the module substrate510and the bulk-acoustic resonator100may not be specified and the blocking member540may be used.

The blocking member540may be disposed between the bulk-acoustic resonator100and the module substrate510to block the molding resin from flowing between the resonating portion120and the module substrate510when the sealing portion530is manufactured. Therefore, the blocking member540may be disposed on an entire circumference of the resonating portion120in a manner to surround the resonating portion120.

The blocking member540may be formed of a material having insulation. For example, the blocking member540may be formed of a polymer material, but is not limited thereto.

The blocking member540may be formed in a manufacturing process of the bulk-acoustic resonator100. For example, after a process forming the hydrophobic layer130ofFIG. 3in the bulk-acoustic resonator100, the blocking member540may be formed by stacking an insulating film on the surface of the bulk-acoustic resonator100in which the resonating portion120ofFIG. 3is formed, and by patterning the insulating film.

As described above, when the hydrophobic layer130is formed in the bulk-acoustic resonator100, the blocking member540having the polymer material may not be firmly coupled onto the bulk-acoustic resonator100by the hydrophobic layer130.

Therefore, in this case, an attaching position of the insulating film may be changed in the process of patterning the insulating film or in the process of mounting the bulk-acoustic resonator on the module substrate510.

Thus, in order to suppress the movement of the insulating film, the blocking member540may be disposed so as to be in contact with at least one connection terminal522.

At least a portion of the side surface of the connection terminal522may be bonded to the blocking member540to suppress the movement of the blocking member540. Therefore, the insulating film may be patterned to be connected to at least one connection terminal522in the above-described patterning process.

However, the disclosure is not limited to the example above. For example, when the insulating film is formed on the module substrate510, without being formed on the bulk-acoustic resonator100, the insulating film may be firmly stacked on the module substrate510. Therefore, in this case, since the insulating film is stably and fixedly disposed, the blocking member540may be disposed to be spaced apart from the connection terminal522of the bulk-acoustic resonator100.

Referring toFIG. 23, the hydrophobic layer130may be formed on the entire surface of the bulk-acoustic resonator, as described above, and accordingly, the hydrophobic layer130may also be disposed on the surface of the connection terminal522. Thus, when the hydrophobic layer130is disposed on the surface of the connection terminal522, the surface of the connection terminal522may be prevented from being oxidized.

The hydrophobic layer130may also be disposed at the end of the connection terminal522in the process of forming the hydrophobic layer130, but this the portion of the hydrophobic layer130at the end of the connection terminal522may be removed in the process of mounting the connection terminal522on the module substrate510. Therefore, only a conductive adhesive550may be interposed between the end of the connection terminal522and the module substrate510, without the hydrophobic layer130.

The blocking member540may be disposed between the connection terminal522and the bulk-acoustic resonator100. Thus, the blocking member540may be bonded to the inner side surface (side surface facing the resonating portion) of the connection terminal522. A sealing portion530may be filled outside of the connection terminal522, and the sealing portion530may be bonded to the outer side surface of the connection terminal522. However, the disclosure is not limited to such a configuration.

In the bulk-acoustic resonator module illustrated inFIG. 24, the blocking member540may be disposed outside of the connection terminal522, and thus may be bonded to the outer side surface of the connection terminal522.

The bulk-acoustic resonator module illustrated inFIG. 25may have connection terminals522disposed in the blocking member540. Thus, the blocking member540may be disposed to surround the connection terminals522, and an entirety of side surfaces of the connection terminals522may be bonded to the blocking member540.

In the bulk-acoustic resonator module illustrated inFIG. 26, the blocking member540and the module substrate510may be spaced apart from each other by a predetermined distance. Therefore, a gap502may be formed between a lower surface of the blocking member540and an upper surface of the module substrate510.

The distance by which the blocking member540and the module substrate510are spaced apart from each other may be limited to 30 μm or less. Thus, a molding resin may be blocked from flowing between the blocking member540and the module substrate510

The lower surface of the blocking member540may be disposed on the same plane as the lower surface of the connection terminal522. However, the disclosure is not limited to this configuration.

The bulk-acoustic resonator module illustrated inFIG. 27may have the trench524formed on one surface of the module substrate510, as illustrated inFIG. 20, and the blocking member540may be disposed in the trench524between the bulk-acoustic resonator100and the module substrate510in the trench524. InFIG. 27, the blocking member540may be disposed to surround the connection terminal522similarly to the bulk-acoustic resonator module illustrated inFIG. 24. However, the disclosure is not limited to this configuration, and various modifications are be possible, such as configuring the blocking member540in a form illustrated inFIGS. 22 and 24.

In the bulk-acoustic resonator module illustrated inFIG. 28, a blocking member540amay be formed of a conductive material. Therefore, the blocking member540amay be disposed between the lower surface of the bulk-acoustic resonator100and the module substrate510, and may be spaced apart from the connection terminal522.

The blocking member540amay be formed together with the connection terminal522in the process of forming the connection terminal522. Therefore, the blocking member540amay be made of the same material as the connection terminal522.

In addition, since the blocking member540ais bonded to the conductive material of the bulk-acoustic resonator100, the blocking member540amay be firmly bonded to the bulk-acoustic resonator100, unlike the blocking member540ofFIG. 25, using the polymer. Therefore, even if the blocking member540ais not bonded to the connection terminal522, the blocking member540amay be fixedly disposed at a desired position.

An example in which the blocking member540ais disposed to surround the outside of the connection terminals522inFIG. 28. However, the disclosure is not limited to this configuration, and various modifications, for example, the blocking member540abeing disposed on the inner side (for example, between the resonating portion and the connection terminals522) of the connection terminals522, or a portion of the blocking member540abeing disposed outside the connection terminals522and a remaining portion of the blocking member540abeing disposed inside the connection terminals522, or the like, may be made.

The bulk-acoustic resonator module illustrated inFIG. 29may include a blocking member540bdisposed on the side surfaces of the bulk-acoustic resonator100.

In the bulk-acoustic resonator module of the present embodiment, the bulk-acoustic resonator100is mounted on the module substrate510, and then the blocking member540bis formed along the rim of the bulk-acoustic resonator100.

The blocking member540bmay be formed by injecting a liquid insulating material between the rim and the module substrate510through a needle and curing the insulating material. The liquid insulating material may be a polymer, but is not limited thereto.

By forming the blocking member540bby using the above-described method, the blocking member540bmay be disposed not only between the lower surface of the bulk-acoustic resonator100and the module substrate510, but also between the side surface of the resonator substrate110of the bulk-acoustic resonator100and the module substrate510. In addition, although not shown, the blocking member540bmay be extended and disposed on the upper surface of the bulk-acoustic resonator100if necessary.

InFIG. 29, an example in which the blocking member540bis in contact with the connection terminal522is illustrated. However, since the blocking member540bis applied on the module substrate510, the movement of the blocking member540bmay be suppressed. Therefore, it is also possible for the blocking member540bto be spaced apart from the connection member522.

FIGS. 30 and 31are schematic circuit diagrams of filters, according to embodiments, respectively.

Each of the bulk-acoustic resonators employed in the filters ofFIGS. 30 and 31correspond to the bulk-acoustic resonator100illustrated inFIG. 3.

Referring toFIG. 30, a filter1000, according to an embodiment, may have a ladder type filter structure. Specifically, the filter1000may include bulk-acoustic resonators1100and1200.

The first bulk-acoustic resonator1100may be connected in series between a signal input terminal to which the input signal RFin is input and a signal output terminal to which the output signal RFout is output, and the second bulk-acoustic resonator1200may be connected to the signal output terminal and a ground.

Referring toFIG. 31, a filter2000, according to an embodiment, may have a lattice type filter structure. Specifically, the filter2000may include bulk-acoustic resonators2100,2200,2300, and2400, and may output RFout+ and RFout− output signals by filtering balanced input signals RFin+ and RFin−.

In addition, a filter may be formed to have a filter structure including a combination of the ladder type filter structure shown inFIG. 30and the lattice type filter structure shown inFIG. 31.

As disclosed herein, a protective layer is formed by stacking a first protective layer and a second protective layer having different materials, and a hydrophobic layer is disposed on the second protective layer. Therefore, even when the acoustic resonator is used in a humid environment or is left at room temperature for an extended period of time of time, a frequency variation may be significantly reduced and uniform resonator performance may be maintained.