KR20180048238A - Filter - Google Patents

Abstract

According to an embodiment of the present invention, provided is a filter which can effectively block capacitance coupling. The filter comprises: a laminated structure including a plurality of films configuring a plurality of bulk acoustic wave resonators; and a cap formed of one of glass or a polymer, accommodating the plurality of bulk acoustic wave resonators, and bonded to the laminated structure.

Description

Filter {FILTER}

The present invention relates to a filter.

2. Description of the Related Art Demand for small and lightweight filters, oscillators, resonant elements, and acoustic resonant mass sensors used in such devices has been rapidly increasing due to recent rapid development of mobile communication devices, Is also increasing.

A thin film bulk acoustic resonator (FBAR) is known as a means for implementing such a compact lightweight filter, an oscillator, a resonant element, and an acoustic resonance mass sensor. Thin-film bulk acoustic resonators can be mass-produced at a minimum cost and can be implemented in a very small size. In addition, it is possible to implement a high quality factor (Q) value, which is a major characteristic of a filter, and can be used in a microwave frequency band. Particularly, a PCS (Personal Communication System) and a DCS (Digital Cordless System) There is an advantage that it can be.

2. Description of the Related Art Generally, a thin film bulk acoustic resonator has a structure including a resonator unit formed by sequentially laminating a first electrode, a piezoelectric layer, and a second electrode on a substrate. The principle of operation of the thin film bulk acoustic resonator is as follows. First, an electric field is induced in the piezoelectric layer by the electric energy applied to the first and second electrodes, a piezoelectric phenomenon occurs in the piezoelectric layer by the induced electric field, do. As a result, a bulk acoustic wave is generated in the same direction as the vibration direction, causing resonance.

U.S. Published Patent Application No. 2008-0081398

Disclosure of Invention Technical Problem [8] The present invention provides a filter that removes a bonding line formed when a cap and a laminated structure are bonded together, and effectively blocks capacitive coupling that may occur with an external substrate.

A filter according to an embodiment of the present invention includes a laminated structure including a plurality of membranes constituting a plurality of volume acoustic resonators and a cap accommodating the plurality of volume acoustic resonators and being bonded to the laminated structure, May be formed of one of a glass and a polymer.

According to one embodiment of the present invention, sealing bonding can be realized by securing reliability over a long period of time by bonding the caps through anodic bonding having strong bonding properties. Further, through the shield layer formed on the lower surface of the substrate, a stable and uniform reference potential for wafer level testing can be provided. Furthermore, the capacitive coupling that may occur between the external substrate and the filter constituted by a plurality of volume acoustic resonators can be effectively blocked, whereby the external substrate and the filter can be individually designed.

1 is a cross-sectional view of a filter according to an embodiment of the present invention.
2 is a view for explaining an anodic bonding according to an embodiment of the present invention.
3 is a bottom view of a substrate according to an embodiment of the present invention.
4 shows a simulation result according to an embodiment of the present invention.
5 and 6 are schematic circuit diagrams of a filter according to one embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

1 is a cross-sectional view of a filter according to an embodiment of the present invention.

Referring to FIG. 1, a filter 10 according to an embodiment of the present invention may include a plurality of volume acoustic resonators 100 and a cap 200. The volume acoustic resonator 100 may be a thin film bulk acoustic resonator (FBAR).

The volume acoustic resonator 100 may be constituted by a laminated structure composed of a plurality of films. The volume acoustic resonator 100 may include a substrate 110, an insulating layer 120, an air cavity 112, and a resonator 135.

The substrate 110 may be formed of silicon and an insulating layer 120 may be formed on the substrate 110 to electrically isolate the resonator 135 from the substrate 110. The insulating layer 120 may be formed by chemical vapor deposition (CVD), RF magnetron sputtering, or evaporation of one of silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₂ ) May be formed on the substrate 110.

The air cavity 112 may be disposed on the insulating layer 120. The air cavity 112 may be positioned below the resonator 135 so that the resonator 135 vibrates in a predetermined direction. The air cavity 112 is formed by forming an air cavity sacrificial layer pattern on the insulating layer 120, forming a membrane 130 on the air cavity sacrificial layer pattern, and then etching and removing the air cavity sacrificial layer pattern . The membrane 130 may function as a protective oxide layer or as a protective layer protecting the substrate 110.

An etch stop layer 125 may be additionally formed between the insulating layer 120 and the air cavity 112. The etch stop layer 125 serves to protect the substrate 110 and the insulating layer 120 from the etching process and may serve as a base for depositing other layers on the etch stop layer 125.

The resonator portion 135 may include a first electrode 140, a piezoelectric layer 150, and a second electrode 160 that are sequentially stacked on the membrane 130. The common areas overlapping in the vertical direction of the first electrode 140, the piezoelectric layer 150, and the second electrode 160 may be located at the top of the air cavity 112. The first electrode 140 and the second electrode 160 may be formed of a metal such as gold (Au), titanium (Ti), tantalum (Ta), molybdenum (Mo), ruthenium (Ru), platinum (Pt), tungsten (Al), iridium (Ir), and nickel (Ni), or an alloy thereof.

The piezoelectric layer 150 may be formed of one of aluminum nitride (AlN), zinc oxide (ZnO), and lead zirconium titanium oxide (PZT), which is a part causing a piezoelectric effect to convert electrical energy into mechanical energy in the form of elastic waves have. In addition, the piezoelectric layer 150 may further include a rare earth metal. As an example, the rare earth metal may include at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). The piezoelectric layer 150 may comprise 1 to 20 atomic percent rare-earth metal.

A seed layer for improving the crystal orientation of the piezoelectric layer 150 may be additionally disposed under the first electrode 140. The seed layer may be formed of one of aluminum nitride (AlN), zinc oxide (ZnO), and lead zirconium titanium oxide (PZT; PbZrTiO) having the same crystallinity as the piezoelectric layer 150.

The resonator portion 135 may be partitioned into an active region and a non-active region. The active region of the resonator unit 135 vibrates in a predetermined direction by a piezoelectric effect generated in the piezoelectric layer 150 when electrical energy such as a radio frequency signal is applied to the first electrode 140 and the second electrode 160. [ And corresponds to a region in which the first electrode 140, the piezoelectric layer 150, and the second electrode 160 are superimposed in the vertical direction on the upper part of the air cavity 112. The inactive region of the resonance portion 135 corresponds to a region outside the active region, which is a region which does not resonate due to the piezoelectric effect even if the first electrode 140 and the second electrode 160 are applied with electric energy.

The resonance unit 135 outputs a radio frequency signal having a specific frequency by using a piezoelectric phenomenon. Specifically, the resonance part 135 can output a radio frequency signal having a resonance frequency corresponding to the vibration caused by the piezoelectric development of the piezoelectric layer 150. [

The passivation layer 170 may be disposed on the second electrode 160 of the resonator 135 to prevent the second electrode 160 from being exposed to the outside. The passivation layer 170 may be formed of one of a silicon oxide series, a silicon nitride series, and an aluminum nitride series.

At least one via hole 113 may be formed on the lower surface of the substrate 110 to penetrate the substrate 110 in the thickness direction. The via hole 113 may penetrate through the insulating layer 120, the etch stop layer 125, and a part of the membrane 130 in the thickness direction, in addition to the substrate 110. The connection pattern 114 may be formed in the via hole 113 and the connection pattern 114 may be formed on the inner surface of the via hole 113, that is, the entire inner wall.

The connection pattern 114 can be manufactured by forming a conductive layer on the inner surface of the via hole 113. [ For example, the connection pattern 114 may be formed by depositing or applying at least one conductive metal such as gold (Au), copper (Cu), and titanium (Ti) -copper (Cu) alloy along the inner wall of the via hole 113, Or by charging.

The connection pattern 114 may be connected to at least one of the first electrode 140 and the second electrode 160. The connection pattern 114 may extend through at least a portion of the substrate 110, the membrane 130 and the first electrode 140 and the piezoelectric layer 150 to form the first electrode 140 and the second electrode 160, As shown in FIG. The connection pattern 114 formed on the inner surface of the via hole 113 may extend to the lower surface side of the substrate 110 and may be connected to the substrate connection pad 115 provided on the lower surface of the substrate 110. [ In this way, the connection pattern 114 can electrically connect the first electrode 140 and the second electrode 160 to the substrate connection pad 115.

The connection pad 115 for a substrate can be electrically connected to an external substrate that can be disposed under the filter 10 through the bump. The volume acoustic resonator 100 can perform a filtering operation of a radio frequency signal by a signal applied to the first and second electrodes 110 and 120 through the substrate connection pad 115. [

The cap 200 is bonded to a laminate structure forming a plurality of volume acoustic resonators 100, so that the plurality of volume acoustic resonators 100 can be protected from the external environment. The cap 200 may be formed in the form of a cover having an internal space in which a plurality of volume acoustic resonators 100 are accommodated. The cap 200 may be formed in a hexahedron shape having a lower surface, and thus may include a plurality of side surfaces connected to the upper surface and the upper surface.

The cap 200 may be formed at the center to accommodate the resonating part 135 of the plurality of volume acoustic resonators 100. The cap 200 may have a stepped portion, . The bonding region of the laminated structure may correspond to the edge of the laminated structure.

The cap 200 may be bonded to the substrate 110, which is laminated on the substrate 110. The cap 200 may also be bonded to at least one of the passivation layer 170, the membrane 130, the etch stop layer 125, and the insulating layer 120.

Conventionally, the cap 200 is formed of silicon (Si), and the cap 200 formed of silicon (Si) is bonded to the laminated structure through eutectic bonding. At the eutectic bonding, a bonding line formed at the bonding region of the cap formed of silicon (Si) and the substrate 110 provides a reference potential equal to the ground potential. However, the bonding line for providing the reference potential causes a parasitic inductance and an unnecessary coupling path in the volume acoustic resonator, thereby deteriorating the overall performance of the filter.

The cap 200 according to an embodiment of the present invention may be formed of glass to eliminate parasitic inductance and an unnecessary coupling path caused by a bonding line. At this time, the cap 200 and the laminated structure can be bonded through anodic bonding.

2 is a view for explaining an anodic bonding according to an embodiment of the present invention. In the anodic bonding step, a voltage is applied in a state in which heat is applied, and the cap 200 corresponding to the object to be bonded can be directly bonded to the laminated structure without intervention of an intermediate medium. Therefore, the bonding line formed at the eutectic bonding can be removed.

Specifically, referring to FIG. 2, glass and silicon corresponding to the object to be bonded are arranged on a hot plate, and a voltage Vs is applied through a cathode, Can be bonded. At this time, the object to be bonded can be bonded by applying voltage and heat for a predetermined time in a range of a temperature of about 180 to 500 ° C and a voltage of about 200 to 1000V. The predetermined time may correspond to about 5 to 10 minutes, and the anodic bonding may be performed in a vacuum.

In order to improve the bonding performance between the objects to be bonded, the surface condition of the object to be bonded needs to be adjusted. Further, since the direct bonding is made between the dissimilar materials, the coefficients of thermal expansion between the objects to be bonded must be similar. When the working temperature of the bonding increases, a thermal stress is generated due to the difference in thermal expansion coefficient between the bonding targets, so that the bonding process is generally performed at a temperature within 450 ° C. That is, the anodic bonding can be performed in a region similar to the eutectic bonding temperature of eutectic bonding of 363 ° C.

3 is a bottom view of a substrate according to an embodiment of the present invention.

1 and 3, on the lower surface of a substrate 110 of a volume acoustic resonator 100 according to an embodiment of the present invention, an electromagnetic (electromagnetic) A shield layer 123 for shielding interference may be provided. The shield layer 123 is provided on the lower surface of the substrate 110 to provide a reference potential equal to the ground potential, thereby preventing the coupling between the bulk acoustic resonator 100 and the external substrate. The shield layer 123 may be formed of a mesh type electrode and the shield layer 123 may be formed on the lower surface of the substrate 110 except for the region where the connection pattern 114 and the substrate connection pad 115 are formed. May be formed on the front surface.

According to an embodiment of the present invention, by bonding the substrate 110 of the bulk acoustic resonator 100 and the cap 200 formed of glass through anodic bonding having stronger bonding characteristics than the eutectic bonding, Can be achieved. Also, a stable and uniform reference potential (GND) for wafer level testing can be maintained through the shield layer 123 formed on the lower surface of the substrate 110. Furthermore, the capacitive coupling which may occur between the external substrate and the filter constituted by a plurality of volume acoustic resonators is effectively blocked, so that the external substrate and the filter can be individually designed.

In the above description, the cap 200 according to an embodiment of the present invention is formed of glass. However, the cap 200 may be formed of a polymer. Also, in the above description, the shield layer 123 according to an embodiment of the present invention is formed of a mesh-shaped electrode. However, the shield layer 123 may be formed of a solid electrode . On the other hand, a cap made of glass and polymer, and an electrode configured in a mesh form and a solid form can be applied to various embodiments of the present invention.

4 shows a simulation result according to an embodiment of the present invention.

In FIG. 4, the first graph (Graph 1) is the simulation graph of the mBVD (modified Butterworth-Van-Dyke) model according to the comparative example, and the second graph (Graph 2) A third graph (Graph 3) is a graph according to the EM simulation result according to the comparative example, and a fourth graph (Graph 4) is a graph according to the EM simulation result according to the embodiment. In this case, the comparative example can be understood as a filter in which a cap made of silicon is bonded to the substrate through eutectic bonding, and a shield layer is not provided on the lower surface of the substrate.

Electromagnetism simulation results were performed under Wafer Level Test (WLT) conditions. Here, the wafer level test (WLT) is performed directly by using a pad for a wafer level package (WLP) exposed at the wafer level at a wafer level before a solder bump ball is formed in the filter, (Ground-Signal-Ground) probe. Therefore, in the filter circuit model, when the shunt end of the filter is connected directly to the ground (GND), the input and output ends of the filter are terminated by 50 ohms without a matching inductor, To confirm.

First, comparing the first graph (Graph 1) and the third graph (Graph 3) based on the second graph (Graph 2), the third graph (Graph 3) is compared with the first graph (Graph 1) (Graph 2). This is because, in the mBVD model of the first graph (Graph 1), parasitic inductance and parasitic capacitance due to the layout or connection of the volume acoustic resonator that can not be reflected are reflected in the EM simulation. In other words, the mBVD model has a certain difference from the measured result of the actually fabricated filter.

Meanwhile, the fourth graph (Graph 4) corresponding to the EM simulation result according to the embodiment of the present invention is very similar to the first graph (Graph 1). Thus, it can be seen that the embodiment of the present invention effectively blocks parasitic inductance and parasitic capacitance that can not be reflected in the mBVD model. Therefore, even when the external substrate and the filter are individually designed from the above results, it can be expected that similar results can be obtained as in the case of the integrated design.

5 and 6 are schematic circuit diagrams of a filter according to one embodiment of the present invention. Each of the plurality of volume acoustic resonators employed in the filters of Figs. 5 and 6 may be formed by electrically connecting the volume acoustic resonators according to various embodiments of the present invention.

Referring to FIG. 5, a filter 1000 according to an embodiment of the present invention may be formed of a ladder type filter structure. Specifically, the filter 1000 may include a plurality of volume acoustic resonators 1100, 1200.

The first volume acoustic resonator 1100 may 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 volume acoustic resonator 1200 may be connected to the signal output terminal It is connected between ground. Referring to FIG. 6, a filter 2000 according to an embodiment of the present invention may be formed of a lattice type filter structure. Specifically, the filter 2000 includes a plurality of volume acoustic resonators 2100, 2200, 2300, and 2400 to filter the balanced input signals RFin +, RFin- to produce balanced output signals RFout +, RFout- Can be output.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

110: substrate
112: air cavity
113: Via hole
114: connection pattern
115: connection pad for substrate
123: Shield layer
125: etch stop layer
130: Membrane
135:
140: first electrode
150: piezoelectric layer
160: Second electrode
170: protective layer
200: cap
1000, 2000: filter
10, 20, 1100, 1200, 2100, 2200, 2300, 2400: volume acoustic resonator

Claims (16)

A laminated structure including a plurality of films constituting a plurality of volume acoustic resonators; And
A cap which receives the plurality of volume acoustic resonators and is bonded to the laminated structure; Wherein the cap is formed of one of a glass and a polymer.
The method according to claim 1,
Wherein the plurality of films comprise a substrate, a first electrode stacked on the substrate, a piezoelectric layer, and a second electrode.
3. The method of claim 2,
Wherein the substrate is formed of silicon.
The method of claim 3,
Wherein the cap is directly bonded to the substrate.
The method of claim 3,
Wherein the cap and the substrate are bonded through anodic bonding.
3. The method of claim 2,
A shield layer provided on a lower surface of the substrate; ≪ / RTI >
The method according to claim 6,
Wherein the shield layer is formed of a mesh-shaped electrode.
The method according to claim 6,
Wherein the shield layer provides a reference potential.
A laminated structure constituting a plurality of volume acoustic resonators each including a substrate, a first electrode stacked on the substrate, a piezoelectric layer, and a second electrode;
A cap which receives the plurality of volume acoustic resonators and is bonded to the laminated structure; And
A shield layer provided on a lower surface of the substrate; / RTI >
10. The method of claim 9,
Wherein the shield layer is formed of a mesh-shaped electrode.
10. The method of claim 9,
Wherein the shield layer is formed of a solid-shaped electrode.
10. The method of claim 9,
Wherein the shield layer provides a reference potential.
13. The method of claim 12,
Wherein the reference potential corresponds to a ground potential.
10. The method of claim 9,
Wherein the cap is directly bonded to the substrate through anodic bonding.
14. The method of claim 13,
Wherein the cap is formed of one of a glass and a polymer.
14. The method of claim 13,
Wherein the substrate is formed of silicon.

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