KR101861271B1 - Filter including acoustic wave resonator - Google Patents

Abstract

A filter according to an embodiment of the present invention includes a laminated structure composed of a plurality of films and embodying a wiring line connected to a plurality of volume acoustic resonators and the plurality of volume acoustic resonators, Cap, and the filtering characteristics can be determined by the mutual inductance of the wiring line and the bonding line.

Description

FIELD OF THE INVENTION The present invention relates to a filter including a volume acoustic resonator,

The present invention relates to a filter comprising a volume acoustic resonator.

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 (hereinafter referred to as "FBAR") is known as a means for realizing such a compact lightweight filter, an oscillator, a resonant element, and an acoustic resonance mass sensor. FBARs 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, an FBAR has a structure including a resonator formed by sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate.

The principle of operation of the FBAR is as follows. First, electric energy is applied to the first and second electrodes to induce an electric field in the piezoelectric layer. This electric field induces a piezoelectric phenomenon of the piezoelectric layer so that the resonator portion vibrates in a predetermined direction. 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

A problem to be solved by the present invention is to provide a filter that can reflect a mutual inductance that may occur in a bonding line and a wiring line to a circuit design.

The filter according to an embodiment of the present invention may include a plurality of volume acoustic resonators and a cap for bonding the plurality of volume acoustic resonators to the bonding line, Can be changed by the mutual inductance generated between a part of the wiring lines of the plurality of volume acoustic resonators.

The filter according to an embodiment of the present invention can reduce the manufacturing cost and volume of the filter by reflecting the mutual inductance that may occur in the bonding line and the wiring line to the circuit design.

1 is a cross-sectional view of a filter according to an embodiment of the present invention.
Figures 2 and 3 are exemplary circuit diagrams of a filter in accordance with one embodiment of the present invention.
FIG. 4A shows a top view of a filter according to an embodiment of the present invention, and FIG. 4B shows an example of a circuit diagram according to an embodiment of the present invention.
5 to 9 are simulation graphs according to various embodiments 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 volume acoustic resonator 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 realized 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 a conventional silicon substrate 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 contain 1 to 20 at% of 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. Although one laminate structure is shown in FIG. 1 as being accommodated in one cap 200, a plurality of laminate structures may be accommodated in one cap 200, and each of the plurality of laminate structures may be interconnected . In this case, the plurality of stacked structures may be interconnected by providing wiring electrodes on the first electrode 140 and the second electrode 160 exposed to the outside.

The cap 200 may be bonded to the laminated structure to protect the resonance portion 135 from the external environment. The cap 200 may be formed in the form of a cover having an inner space in which the resonance part 135 is accommodated. Specifically, the cap 200 may have a receiving portion formed at the center thereof to accommodate the resonator portion 135, and the rim may be formed so as to be stepped relative to the receiving portion so as to engage with the laminated structure at the edge. The rim may be bonded directly or indirectly to the substrate 110 through the bonding agent 250 in a particular region. Although the cap 200 is shown as being bonded to the protective layer 170 deposited on the substrate 110 in FIG. 1, the cap 130 may be formed of a material that penetrates the protective layer 170, 125, an insulating layer 120, and a substrate 110. In this case,

The cap 200 may be bonded at the wafer level via wafer bonding. A substrate wafer in which a plurality of unit substrates 110 are coupled and arranged and a cap wafer in which a plurality of caps 200 are coupled are bonded to each other and the mutually bonded substrate wafer and cap wafer are cut through a cutting process, And a plurality of discrete volume acoustic resonators shown in Fig.

The cap 200 may be bonded to the substrate 110 by eutectic bonding. In this case, after the bonding agent 250 capable of eutectic bonding with the substrate 110 is deposited on the laminated structure, the substrate wafer and the cap wafer can be bonded by pressurization and heating. The bonding agent 250 may include an eutectic material of gold (Au) -stin (Sn), and may further include a solder ball.

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 the insulating layer 120, the etch stop layer 125, and 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, applying, or filling a conductive metal such as gold or copper along the inner wall of the via hole 113. In one example, the connection pattern 114 may be made of a titanium (Ti) -copper (Cu) alloy.

The connection pattern 114 may be connected to at least one of the first electrode 140 and the second electrode 160. For example, the connection pattern 114 may extend through at least a portion of the substrate 110, the membrane 130, 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 substrate connection pad 115 may be electrically connected to an external substrate, which may be disposed below the bulk acoustic resonator 100 through the bumps. 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. [

Figures 2 and 3 are exemplary circuit diagrams of a filter in accordance with one embodiment of the present invention. Each of the plurality of volume acoustic resonators employed in the filters of Figs. 2 and 3 may be formed by electrically connecting the volume acoustic resonators according to various embodiments of the present invention.

Referring to FIG. 2, the 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. 3, the 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.

The filters 1000 and 2000 of FIGS. 2 and 3 are constructed by connecting inductors provided on the external substrate in addition to the volume acoustic resonators 1100, 1200, 2100, 2200, 2300, and 2400. For example, in order to filter a designed frequency band, some volume acoustic resonators may be connected to ground through an inductor provided on an external substrate.

The design of each element of the filter is becoming more complicated and integrated in accordance with the demand for miniaturization and slimness of the filter. In this trend, an unintended mutual inductance component can be generated between the wiring line and the bonding line which are designed and arranged adjacent to each other of the volume acoustic resonator, and the inductance component generated by the mutual inductance, The inductance of the capacitor C may deteriorate.

1, and the bonding line may correspond to a junction region of the laminated structure of the bulk acoustic resonator 100 and the cap 200 .

The filter according to an embodiment of the present invention may be designed to have a mutual inductance occurring between the wiring line of the volume acoustic resonator 100 and the bonding line of the cap 200 and the laminated structure of the volume acoustic resonator 100, The inductance of the inductor provided on the external substrate can be reduced or eliminated to reduce the manufacturing cost and the volume of the filter.

FIG. 4A shows a top view of a filter according to an embodiment of the present invention, and FIG. 4B shows an example of a circuit diagram according to an embodiment of the present invention.

4A and 4B, a filter according to an embodiment of the present invention may include at least one series resonator (S1-S7) and at least one shunt resonator (Sh1-Sh4). At least one series resonator (S1-S7) and at least one shunt resonator (Sh1-Sh4) may be constituted by the above-described laminated structure. The laminated structure can be received by the cap 200, and the laminated structure and the cap 200 can be bonded through the bonding line.

At least one series resonator (S1-S7) and at least one shunt resonator (Sh1-Sh4) may be electrically connected to an external substrate, which may be located under the filter, through a wiring line such as a connection pattern and a wiring electrode .

4A, the wiring lines A1, A2, A3, and A4 connected to at least one shunt resonator Sh1-Sh4 are disposed adjacent to the bonding line B to form wiring lines A1, A2, A3 , A4) and the bonding line (B). The wiring lines A1, A2, A3, and A4 are formed by mutual inductance between the wiring lines A1, A2, A3, A4 connected to at least one shunt resonator Sh1-Sh4 and the bonding line B, (I1 ', i2', i3 ', i4') flow in the bonding line when currents i1, i2, i3 and i4 flow through the bonding line.

The filter according to an embodiment of the present invention is designed to have mutual inductance between the wiring lines A1, A2, A3, A4 connected to at least one shunt resonator Sh1-Sh4 and the bonding line B, . At this time, the mutual inductance between the wiring lines A1, A2, A3, A4 connected to at least one shunt resonator Sh1-Sh4 and the bonding line B is the inductance of the inductors Lt1, Lt2, Lt3, Lt4).

The inductance of the mutual inductors Lt1, Lt2, Lt3 and Lt4 is determined by the inductance of the wiring lines A1, A2, A3 and A4, the inductance of the bonding line B and the inductances of the wiring lines A1, A2, A3 and A4 Can be determined according to the coupling coefficient of the inductance of the bonding line (B).

At this time, the inductance of the wiring line can be determined by the length and the area of the wiring lines A1, A2, A3 and A4, and the inductance of the bonding line B can be determined by the length and the area of the bonding line. For example, the inductance of the bonding line B may be determined by the length and area of the bonding line located within a predetermined distance from the wiring lines A1, A2, A3, and A4. The coupling coefficient may be determined according to the separation distance between the wiring lines A1, A2, A3, A4 and the bonding line B. [

The filter according to an embodiment of the present invention can adjust the inductance of the wiring line by adjusting at least one of the length, the area and the separation distance of the wiring lines A1, A2, A3, A4 and the bonding line B, Lt1, Lt2, Lt3, and Lt4) can be changed. Also, the filter according to an embodiment of the present invention can adjust the filtering characteristics by changing the inductance of the mutual inductors Lt1, Lt2, Lt3, and Lt4. In one example, the position of the pole point that determines the frequency band of the filter can be adjusted.

5 to 9 are simulation graphs according to various embodiments of the present invention.

The graph of the radio frequency signal indicated by the dotted line in FIGS. 5 to 9 corresponds to the comparative example, and the graph of the radio frequency signal indicated by the solid line corresponds to the embodiments of the present invention. The comparative example assumes that the bonding line and the wiring line are sufficiently spaced apart so that the inductance of the bonding line and the inductance of the wiring line are not coupled to each other.

Table 1 below is a table showing coupling coefficients (K1, K2, K3, K4) of the mutual inductors Lt1, Lt2, Lt3, and Lt4 in the embodiments of the present invention shown in Figs. 5 to 9, the inductances L1, L2, L3 and L4 of the wiring lines were 0.3 nH and the inductances L1 ', L2', L3 'and L4' of the bonding lines were 0.5 nH, The coupling coefficients K1, K2, K3, and K4 of the mutual inductors Lt1, Lt2, Lt3, and Lt4 in Table 5 were changed by adjusting the spacing distance between the bonding lines.

The coupling coefficients K1, K2, K3 and K4 increase and the coupling coefficients K1, K2, K3 and K4 increase as the distance between the wiring line and the bonding line becomes longer, It can be understood that the interval between the bonding line and the wiring line decreases from FIG. 5 to FIG.

K1 K2 K3 K4 5 0.1 0.1 0.1 0.1 6 0.1 0.1 0.15 0.15 7 0.15 0.15 0.15 0.15 8 0.3 0.3 0.15 0.15 9 0.3 0.3 0.3 0.3

5 to 9, the left pole of the comparative example corresponds to -160 dB at 1.815 GHz, the left pole of FIG. 5 corresponds to -85.6 dB at 1.781 GHz, and the left pole of FIG. 6 corresponds to 1.776 GHz 7, the left pole in FIG. 7 corresponds to -82.5 dB at 1.769 GHz, the left pole in FIG. 8 corresponds to -80.4 dB at 1.753 GHz, and the left pole in FIG. 9 corresponds to -78.8 dB, respectively.

Comparing the embodiment and the comparative example, the embodiment of the present invention can reduce the gain and the frequency of the left pole, as compared with the comparative example in which the bonding line and the wiring line are sufficiently spaced. 5 to 9, as the distance between the bonding line and the wiring line decreases from FIG. 5 to FIG. 9, the gain and frequency of the left pole move in a direction of gradually decreasing Can be confirmed.

That is, the filter according to the embodiment of the present invention can adjust the position of the pole to determine the frequency band by the coupling coefficient determined according to the distance between the wiring line and the bonding line.

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
125: etch stop layer
130: Membrane
135:
140: first electrode
150: piezoelectric layer
160: Second electrode
170: protective layer
200: cap
250: Bonding agent
1000, 2000: filter
10, 20, 100, 1100, 1200, 2100, 2200, 2300, 2400: a volume acoustic resonator

Claims (15)

A laminated structure composed of a plurality of films and embodying a plurality of volume acoustic resonators and wiring lines connected to the plurality of volume acoustic resonators; And
A cap coupled to the laminate structure at a bonding line; / RTI >
Wherein a filtering characteristic is determined by mutual inductance between the wiring line and the bonding line.
The method according to claim 1,
Wherein the plurality of volume acoustic resonators comprise at least one series resonator and at least one shunt resonator.
3. The method of claim 2,
Wherein the filtering characteristic is determined by a mutual inductance between an inductance of the wiring line connected to the at least one shunt resonator and an inductance of the bonding line.
The method of claim 3,
Wherein the mutual inductance is coupled to the at least one shunt resonator.
The method according to claim 1,
Wherein the inductance of the wiring line is determined by the length and area of the wiring line.
The method according to claim 1,
Wherein the inductance of the bonding line is determined by a length and an area of the bonding line which is located within a predetermined distance from the wiring line.
The method according to claim 1,
Wherein the mutual inductance is determined by an inductance of the wiring line, an inductance of the bonding line, and a coupling coefficient of an inductance of the wiring line and an inductance of the bonding line.
8. The method of claim 7,
Wherein the coupling coefficient is determined according to a distance between the wiring line and the bonding line.
9. The method of claim 8,
Wherein a position of a pole for determining a frequency band is changed according to a distance between the wiring line and the bonding line.
10. The method of claim 9,
Wherein a gain and a frequency of a left pole for determining a frequency band decrease as the distance between the wiring line and the bonding line decreases.
A plurality of series resonators disposed between a signal input terminal and a signal output terminal;
A plurality of shunt resonators disposed between each of said plurality of series resonators and a ground; And
An inductor disposed between at least one of the plurality of shunt resonators and ground; Lt; / RTI >
Wherein the inductor is implemented by mutual inductance of a bonding line formed by a cap accommodating the plurality of series resonators and the plurality of shunt resonators and a wiring line connected to at least one of the plurality of shunt resonators.
12. The method of claim 11,
Wherein the mutual inductance is determined by an inductance of the wiring line, an inductance of the bonding line, and a coupling coefficient of an inductance of the wiring line and an inductance of the bonding line.
13. The method of claim 12,
Wherein the coupling coefficient is determined according to a distance between the wiring line and the bonding line.
14. The method of claim 13,
Wherein a position of a pole for determining a frequency band is changed according to a distance between the wiring line and the bonding line.
15. The method of claim 14,
Wherein a gain and a frequency of a left pole for determining a frequency band decrease as the distance between the wiring line and the bonding line decreases.

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