JP2006115282A - Thin film resonance device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow each of resonators to have an independent relation and have a structure in which bandwidth of a frequency is minutely settable. <P>SOLUTION: This thin film resonance device is provided with: a thin film resonator A for inputting; a thin film resonator B for outputting and a coupling member C for partially and acoustically coupling a part between the respective thin film resonator A for inputting and thin film resonator B for outputting. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin film resonant device used for communication equipment and the like.

In recent years, thin film resonant devices (so-called FBARs) used for communication equipment and the like have been provided. This thin film resonant device can output a high resonance frequency in the GHz band by resonating a piezoelectric body formed in a thin film shape in the film thickness direction.

FIG. 9 is a diagram showing a conventional thin film resonant device (see, for example, Patent Document 1). As shown in FIG. 9, the thin film resonant device includes a substrate 1, an input thin film resonator B, and an output thin film resonator C. The input thin film resonator B includes a ground electrode 4, an input electrode 6, and an input piezoelectric body 5 sandwiched between the ground electrode 4 and the input electrode 6. The output thin film resonator C includes an output electrode 2 disposed on a space A formed in the base 1 and an input piezoelectric body 3 (two piezoelectric bodies 3a).
3b), a polarization electrode 2a sandwiched between piezoelectric bodies 3a and 3b which are input piezoelectric bodies 3, and a ground electrode 4. Each of the piezoelectric bodies 3a and 3b has polarization directions opposite to each other (see arrows shown in FIG. 9). Further, as shown in FIG. 9, the output piezoelectric body 3, the ground electrode 4, the input piezoelectric body 5, and the input electrode 6 are arranged in this order on the output electrode 2.

In the thin film resonant device configured as described above, when a high frequency signal is applied to the input electrode 6, the input thin film resonator B vibrates. When the input thin film resonator B vibrates at a specific frequency, the output thin film resonator C vibrates, and an output signal is output from the output electrode 2.
JP 2001-185984 A

However, in the thin film resonator device, the input thin film resonator B and the output thin film resonator C are coupled so that the entire lower surface of the input thin film resonator B is in close contact with the upper surface of the output thin film resonator C. Since the vibration of the input thin film resonator B is directly transmitted to the output thin film resonator C, the input thin film resonator B and the output thin film resonator C function as a single resonator. .
For this reason, each of the input thin film resonator B and the output thin film resonator C does not become independent resonators, and it is difficult to finely set the bandwidth of the frequency obtained from the conventional thin film resonator device. There was a problem.

Therefore, the present invention has been made in view of the above points, and it is possible to make each of the resonators independent of each other and to have a structure in which the frequency bandwidth can be set finely. The purpose is to provide a device.

The invention according to the present application has been made to solve the above-described problems, and includes a plurality of thin film resonators each including a pair of electrodes and a piezoelectric thin film sandwiched between the pair of electrodes. It has the coupling member which acoustically couples between containers partially.

According to the present invention, since a plurality of thin film resonators are acoustically coupled to each other so that each thin film resonator has an independent relationship, the frequency bandwidth is set finely in the thin film resonant device. it can.

Note that the coupling member is composed of one member or two or more different members that are connected.

In the above invention, each of the plurality of thin film resonators may be arranged in the film thickness direction. Here, the film thickness direction of the thin film resonator means the film thickness direction of the piezoelectric thin film. In this case,
Since each of the plurality of thin film resonators is arranged in the film thickness direction, an area for arranging the plurality of thin film resonators is reduced, so that the thin film resonance device can be downsized.

In the said invention, the end of a coupling member may be arrange | positioned in the center of the main surface of a thin film resonator.
Here, the main surface of the thin film resonator means the upper surface or the lower surface of the thin film resonator on the side where a pair of electrodes for sandwiching the piezoelectric thin film is formed. In this case, one end of the coupling member is arranged at the center of the main surface where the vibration amplitude of one thin film resonator is the largest, so that the coupling member transmits the vibration of one thin film resonator to the other thin film resonator. Can be transmitted efficiently.

In the above invention, the coupling member may be formed in a column shape. In this case, the plurality of thin film resonators can be partially coupled, and each of the plurality of thin film resonators has a more independent relationship. Can be set finely.

In the above invention, the coupling member may be an insulating member. In this case, since the electrical connection relationship between the plurality of thin film resonators can be separated, the input / output circuit of the thin film resonant device can be electrically separated.

In the above invention, the resonance frequencies of the plurality of thin film resonators may be different. In this case, since the resonance frequencies of the plurality of thin film resonators are different, the thin film resonance device can widen the frequency bandwidth when the resonance frequencies of the plurality of thin film resonators are not different.

According to the present invention, each resonator can be in an independent relationship, and a structure in which a frequency bandwidth can be finely set can be provided.

A thin film resonant device 100 according to the present invention will be described with reference to the drawings. FIG.
It is sectional drawing which shows the thin film resonant device 100 in this embodiment. FIG. 2 is a cross-sectional perspective view showing the thin film resonant device 100 in the present embodiment. The thin film resonant device 100 according to this embodiment includes a base 110, an input thin film resonator A, an output thin film resonator B, and a coupling member C. The base 110 is a pedestal for arranging the input thin film resonator A and the output thin film resonator B, and is made of Si, for example. In this base 110, a space 120 for ensuring vibration in the film thickness direction of the input thin film resonator A is formed.

The input thin film resonator A is disposed on the space 120 and includes a ground electrode 130, an input electrode 150, and an input piezoelectric body 140 sandwiched between the ground electrode 130 and the input electrode 150. The output thin film resonator B is disposed above the input thin film resonator A, and the first thin film resonator B
Output electrode 160, second output electrode 180, first output electrode 160, and second output electrode 180
And an output piezoelectric body 170 sandwiched between the two. Here, the input piezoelectric body 140 and the output piezoelectric body 170 are examples of the “piezoelectric thin film” of the present invention, and are formed of, for example, AlN. Also, the ground electrode 130 and the input electrode 150, or the first output electrode 160 and the second electrode
Each of the output electrodes 180 is an example of the “pair of electrodes” in the present invention, and is made of, for example, Mo. In the present embodiment, the input thin film resonator A and the output thin film resonator B are arranged in the film thickness direction of the input piezoelectric body 140 and the output piezoelectric body 170, respectively, and the respective surfaces are parallel to each other. Are arranged as follows.

The coupling member C is a member that partially acoustically couples between the input thin film resonator A and the output thin film resonator B, and is formed of, for example, an insulating member such as SiO ₂ . Further, the coupling member C is formed in a column shape (see FIG. 2). Here, the acoustic coupling is a coupling that enables an elastic wave generated by one thin film resonator to be transmitted to the other thin film resonator.

The coupling member C has a center D on the lower surface of the first output electrode 160 that is the main surface of the output thin film resonator B, one end of which faces the upper surface of the input electrode 150 that is the main surface of the input thin film resonator A. Is arranged. Note that the coupling member C is located at the center of the upper surface of the input electrode 150, which is the main surface of the input thin film resonator A, with one end thereof facing the lower surface of the first output electrode 160, which is the main surface of the output thin film resonator B. It may be arranged.

FIG. 3 is a diagram showing an equivalent circuit of the thin film resonant device 100 in the present embodiment. FIG.
In the thin film resonant device 100, the input side circuit including the input thin film resonator A and the output side circuit including the output thin film resonator B can be electrically separated from each other. The thin film resonator A can be configured as an unbalanced type, and the output thin film resonator B can be configured as a balanced type. Of course, the input thin film resonator A can be configured as a balanced type, and the output thin film resonator B can be configured as an unbalanced type. Further, both the input thin film resonator A and the output thin film resonator B can be configured as a balanced type or an unbalanced type. Here, the unbalanced type is a configuration in which one of the pair of terminals is grounded. For example, one terminal is grounded,
The relationship in which the other terminal is an antenna is an unbalanced type. In addition, the balanced type is a configuration in which a pair of terminals are not all grounded.

FIG. 4 is a diagram illustrating frequency characteristics of the thin film resonant device 100 according to the present embodiment. FIG. 4 shows frequency characteristics when the input thin film resonator A having a resonance frequency of 5 GHz is configured as an unbalanced type and the output thin film resonator B is configured as a balanced type. Indicates the transmittance of the output signal relative to the input signal, and the horizontal axis indicates the frequency of the signal. As shown in FIG. 4, when the resonant frequency of the output thin film resonator B is 5 GHz, the thin film resonant device 100
It can be seen that the -5 dB bandwidth is about 180 MHz (about 4.99 GHz to about 5.17 GHz) (see the solid line shown in FIG. 4). When the resonance frequency of the output thin film resonator B is increased by about 1% (about 50 MHz) with respect to the other resonance frequency, the −5 dB bandwidth of the thin film resonance device 100 is about 230 MHz (about 4.99 GHz). It can be seen that it is wider than the bandwidth of the frequency before the change (˜5.22 GHz) (see the dotted line shown in FIG. 4). In this case, the resonance frequency of each of the input thin film resonator A and the output thin film resonator B is different, so that the thin film resonance device 100 has the input thin film resonator A and the output thin film resonator B. The bandwidth when the resonance frequencies are equal can be widened.

According to the present invention, the input thin film resonator A and the output thin film resonator B are partially acoustically coupled between the input thin film resonator A and the output thin film resonator B. Therefore, the thin film resonant device 100 can have a structure in which the frequency bandwidth can be finely set. In addition, since each of the input thin film resonator A and the output thin film resonator B is disposed in the film thickness direction, an area for installing the input thin film resonator A and the output thin film resonator B is reduced. Therefore, the thin film resonant device 100 can be downsized.

Furthermore, one end of the coupling member C is arranged at the center of the main surface where the vibration amplitude of one thin film resonator is the largest, so that the coupling member C transmits the vibration of one thin film resonator to the other thin film resonator. It can be transmitted efficiently. Further, since the coupling member C is formed in a columnar shape, the input thin film resonator A and the output thin film resonator B can be partially coupled, and the input thin film resonator A and the output thin film resonator A can be coupled. Since each of the thin film resonators B and the thin film resonator B has a more independent relationship, it is possible to have a structure in which the bandwidth of the thin film resonant device 100 can be set more finely.

Also, since the coupling member C is an insulating member, the electrical connection relationship between the input thin film resonator A and the output thin film resonator B can be separated, so that the input side including the input thin film resonator A includes And the output side circuit including the output thin film resonator B can be electrically separated, so that one of the input side circuit and the output side circuit is a balanced type and the other is an unbalanced type. be able to.

FIG. 5 is a cross-sectional view showing another example 1 of the thin film resonant device in the present embodiment. A thin film resonant device 200 shown in FIG. 5 includes a base 210, an input thin film resonator A, an output thin film resonator B, coupling members C1 to C3, and a thin film 290. The thin film resonator A for input is disposed on a space 220 formed on the base 210, and includes a ground electrode 230 and an input electrode 2.
50 and an input piezoelectric body 240 sandwiched between the ground electrode 230 and the input electrode 250. The output thin film resonator B is disposed above the input thin film resonator A, and is sandwiched between the first output electrode 260, the second output electrode 280, the first output electrode 260, and the second output electrode 280. Output piezoelectric body 270. The input electrode 250 and the thin film 290
Between the second output electrode 280 and the thin film 290, spaces 295a and 295b are formed.

In FIG. 1, only one coupling member C is disposed between the input thin film resonator A and the output thin film resonator B. However, the coupling member C includes the input thin film resonator A and the output thin film resonator B. A plurality of them may be arranged between the two. Specifically, as shown in FIG. 5, a thin film 290 disposed between the input thin film resonator A and the output thin film resonator B is disposed, and between the input thin film resonator A and the thin film 290. Are coupled to each other, and coupling members C2 and C3 that partially acoustically couple between the output thin-film resonator B and the thin film 290 are disposed. Since the thin film 290 constitutes a part of the coupling member, the thin film resonator A for input is constituted by the coupling members C1 to C3 and the thin film 290.
Can be transmitted to the output thin film resonator B.

In this case, since the thin film 290 can also operate as a resonator, the thin film 290 can change the overall frequency characteristics of the thin film resonant device. Further, by arranging a plurality of coupling members C2 to C3 between the input thin film resonator B and the thin film 290,
The frequency characteristics of the thin film resonant device can be increased by several decibels as a whole.

The thin film 290 may be a thin film resonator including a pair of electrodes and a piezoelectric thin film sandwiched between the electrodes. In this case, by replacing the thin film 290 with a thin film resonator, the thin film resonant device 200 can have a frequency characteristic different from the frequency characteristic obtained by the thin film 290. On the other hand, when the thin film 290 is disposed, the manufacturing process is easier and the cost can be reduced than when the thin film resonator is disposed.

FIG. 6 is a cross-sectional view showing another example 2 of the thin film resonant device in the present embodiment. The thin film resonator device 300 shown in FIG. 6 includes an input thin film resonator A, an output thin film resonator B, a coupling member C4, a reflective layer 320 in which high impedance layers 320a and low impedance layers 320b are alternately stacked, A reflective layer 321 in which high impedance layers 321a and low impedance layers 321b are alternately stacked. The input thin film resonator A is disposed on the reflective layer 320 on the substrate 310, and includes a ground electrode 330, an input electrode 350, and a ground electrode 330.
And an input piezoelectric member 340 sandwiched between the input electrodes 350. The output thin film resonator B is disposed on the reflective layer 321 on the input thin film resonator A, and the first output electrode 36
0, a second output electrode 380, and an output piezoelectric body 370 sandwiched between the first output electrode 360 and the second output electrode 380.

In FIG. 1, a space 120 is formed below the input thin film resonator A, and a space 200 is formed between the input thin film resonator A and the output thin film resonator B. , 2
As shown in FIG. 6, a reflective layer 320 in which high impedance layers 320a and low impedance layers 320b are alternately stacked may be disposed between the input thin film resonator A and the substrate 310. The film thicknesses of the high impedance layer 320a and the low impedance layer 320b are preferably ¼ of the wavelength at a desired frequency.

Further, between the input thin film resonator A and the output thin film resonator B, a coupling member C4 that partially acoustically couples between the input thin film resonator A and the output thin film resonator B is provided inside. Including reflective layer 321
May be arranged. In this case, in addition to the reflective layer 321 being disposed between the input thin film resonator A and the output thin film resonator B, the coupling member C4 is disposed, whereby the reflective layer 3
21 and the coupling member C4 can change the coupling force in the partial acoustic coupling between the input thin film resonator A and the output thin film resonator B, and change the overall frequency characteristics of the thin film resonant device. Can be given.

FIG. 7 is a cross-sectional perspective view showing another example 3 of the thin film resonant device in the present embodiment. A thin film resonant device 400 shown in FIG. 7 includes an input thin film resonator A, an output thin film resonator B, and coupling members C5 and C6. The input thin film resonator A is disposed on a space 420 formed on the base 410, and includes a ground electrode 430, an input electrode 450, and an input piezoelectric body 440 sandwiched between the ground electrode 430 and the input electrode 450. And. The output thin film resonator B is disposed on a space 490 formed on the base 410, and the first output electrode 460.
And a second output electrode 480 and an output piezoelectric body 470 sandwiched between the first output electrode 460 and the second output electrode 480.

In FIG. 1, the input thin film resonator A and the output thin film resonator B are piezoelectric thin films 140 and 170.
However, as shown in FIG. 7, the input thin film resonator A and the output thin film resonator B may be provided side by side in the plane direction of the piezoelectric thin films 440 and 470. In this case, as shown in FIG. 7, the input thin film resonator A disposed in the plane direction of the piezoelectric thin films 440 and 470.
Between one and a plurality of coupling members (for example, two coupling members C5, C5)
By disposing C6), the input thin film resonator A and the output thin film resonator B can be partially acoustically coupled.

FIG. 8 is a cross-sectional perspective view showing another example 4 of the thin film resonant device in the present embodiment. A thin film resonant device 500 shown in FIG. 8 includes an input thin film resonator A, an output thin film resonator B, and a coupling member C7. The input thin film resonator A has a space 52 formed on the substrate 510.
0, and includes a ground electrode 530, an input electrode 550, and an input piezoelectric body 540 sandwiched between the ground electrode 530 and the input electrode 550. The output thin film resonator B is disposed above the input thin film resonator A, and includes a first output electrode 560 and a second output electrode 5.
80 and the output piezoelectric member 57 sandwiched between the first output electrode 560 and the second output electrode 580.
0. A space 590 is formed between the input electrode 550 and the first output electrode 560.

In FIG. 1, the coupling member C is formed in a cylindrical shape, but as shown in FIG. 8, the coupling member C7
May be formed in a wall shape.

It is sectional drawing which shows the thin film resonant device in this embodiment. It is a cross-sectional perspective view which shows the thin film resonant device in this embodiment. It is a figure which shows the equivalent circuit of the thin film resonant device in this embodiment. It is a figure which shows the frequency characteristic of the thin film resonant device in this embodiment. It is sectional drawing which shows the other example of the thin film resonant device in this embodiment. It is sectional drawing which shows the other example of the thin film resonant device in this embodiment. It is a cross-sectional perspective view which shows the other example of the thin film resonant device in this embodiment. It is a cross-sectional perspective view which shows the other example of the thin film resonant device in this embodiment. It is a figure which shows the conventional thin film resonant device.

Explanation of symbols

A ... thin film resonator for input, B ... thin film resonator for output, C ... coupling member, 100 ... thin film resonant device, 110 ... base, 120, 200 ... space, 130 ... ground electrode, 140, 170 ... piezoelectric thin film, DESCRIPTION OF SYMBOLS 150 ... Input electrode, 160 ... 1st output electrode, 170 ... Output piezoelectric material, 180 ... 2nd output electrode, 200 ... Space, 200 ... Thin film resonance device, 290 ... Thin film, 320 ... Reflective layer, 320a ... High impedance layer 320b ... low impedance layer, 321 ... reflective layer, 3
21a ... high impedance layer, 321b ... low impedance layer,

Claims (6)

A plurality of thin film resonators comprising a pair of electrodes and a piezoelectric thin film sandwiched between the pair of electrodes,
A thin-film resonance device comprising a coupling member that partially acoustically couples the plurality of thin-film resonators. The thin film resonator device according to claim 1, wherein each of the plurality of thin film resonators is disposed in a film thickness direction. 3. The thin film resonant device according to claim 2, wherein one end of the coupling member is disposed at the center of the main surface of the thin film resonator. 4. The thin film resonant device according to claim 1, wherein the coupling member is formed in a columnar shape. The thin-film resonant device according to claim 1, wherein the coupling member is an insulating member. 6. The thin film resonant device according to claim 1, wherein the resonance frequency of each of the plurality of thin film resonators is different.

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