JP2025003073A - Filter device and communication device - Google Patents

Abstract

To provide a filter device having excellent filter characteristics.SOLUTION: A filter device includes a capacitive chip including an IDC element and a first acoustic wave chip including an acoustic wave resonator. The IDC element includes a first layer including a piezoelectric material or a dielectric material and a pair of first comb electrodes located on the first layer. The acoustic wave resonator includes a second layer including a piezoelectric material and a pair of second comb electrodes located on the second layer. The thickness of the first layer is greater than the thickness of the second layer.SELECTED DRAWING: Figure 12

Description

This disclosure relates to a filter device, which is an electronic component that utilizes elastic waves, and a communication device that includes the filter device.

A surface acoustic wave filter is disclosed in which each tooth of a comb-tooth electrode that forms a capacitor on a piezoelectric substrate has a narrow portion and a wide portion that is wider than the narrow portion, thereby suppressing resonance of the capacitor and achieving good characteristics.

JP 2022-20081 A

As in the surface acoustic wave filter described in Patent Document 1,
Since the transducer electrode and the conductive pattern forming the capacitor are formed on the same piezoelectric substrate, spurious resonance due to the conductive pattern may affect the frequency characteristics.

(1)
A filter device according to one embodiment of the present disclosure is a filter device comprising a capacitive chip including an IDC element and a first acoustic wave chip including an acoustic wave resonator, wherein the IDC element has a first layer including a piezoelectric material or a dielectric material and a pair of first comb-teeth electrodes located on the first layer, and the acoustic wave resonator has a second layer including a piezoelectric material and a pair of second comb-teeth electrodes located on the second layer, and the thickness of the first layer is greater than the thickness of the second layer.

(2)
A filter device according to one embodiment of the present disclosure is the filter device described in (1) above, wherein the first layer has a thickness of 1 μm or more, and the second layer has a thickness of less than 1 μm.

(3)
A filter device according to one embodiment of the present disclosure is the filter device described in (1) or (2) above, wherein the first layer contains lithium tantalate or lithium niobate.

(4)
A filter device according to an embodiment of the present disclosure is the filter device described in any one of (1) to (3) above, wherein a main resonant frequency of the acoustic wave resonator is 3 GHz or higher.

(5)
A filter device according to an embodiment of the present disclosure is the filter device described in any one of (1) to (4) above, in which the acoustic wave resonator excites a plate wave or a bulk wave as a primary resonance.

(6)
A filter device according to one embodiment of the present disclosure is the filter device described in any one of (1) to (5) above, wherein the acoustic wave resonator further has a support substrate and a low acoustic impedance layer located between the second layer and the support substrate and having a lower acoustic impedance than the second layer.

(7)
A filter device according to an embodiment of the present disclosure is the filter device described in any one of (1) to (6) above, wherein the IDC element is a capacitive element of an electromagnetic filter.

(8)
A filter device according to one embodiment of the present disclosure is a filter device as described in any one of (1) to (7) above, wherein an attenuation pole formed by the acoustic wave resonator is located closer to the passband than an attenuation pole formed by the electromagnetic filter.

(9)
A filter device according to one embodiment of the present disclosure is a filter device as described in any one of (1) to (8) above, wherein all capacitive elements included in the electromagnetic filter include comb-tooth electrodes located on the first layer.

(10)
A filter device according to one embodiment of the present disclosure is a filter device as described in any one of (1) to (9) above, wherein the duty of the multiple electrode fingers of the pair of second comb-tooth electrodes is smaller than the duty of the multiple electrode fingers of the pair of first comb-tooth electrodes.

(11)
A filter device according to one embodiment of the present disclosure is a filter device as described in any one of (1) to (10) above, wherein the difference between the maximum pitch and the minimum pitch of the multiple electrode fingers of the pair of first comb-tooth electrodes is greater than the difference between the maximum pitch and the minimum pitch of the multiple electrode fingers of the pair of second comb-tooth electrodes.

(12)
A filter device according to one embodiment of the present disclosure is a filter device as described in any one of (1) to (11) above, further comprising a second acoustic wave chip and a mounting substrate having a first surface, wherein the capacitive chip, the first acoustic wave chip and the second acoustic wave chip are located on the first surface, and when the first surface is viewed in a plane, a long side of the first acoustic wave chip and a long side of the second acoustic wave chip do not face each other.

(13)
A communication device according to one embodiment of the present disclosure includes an antenna, a filter device described in any one of (1) to (12) above connected to the antenna, and an IC connected to the filter device.

The above configuration makes it possible to provide a filter device and a communication device with excellent frequency characteristics.

FIG. 2 is a schematic plan view of a filter device according to an embodiment of the present disclosure. FIG. 2 is a schematic plan view of a capacitor chip according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view of a capacitor chip according to an embodiment of the present disclosure. FIG. 2 is a schematic plan view of an acoustic wave chip according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of an acoustic wave chip according to an embodiment of the present disclosure. FIG. 13 is a diagram showing frequency characteristics when the substrate of the capacitance chip is set to substrate condition 1. FIG. 13 is a diagram showing frequency characteristics when the substrate of the capacitance chip is set to substrate condition 2. FIG. 13 is a diagram showing frequency characteristics when the substrate of the capacitance chip is set to substrate condition 3. FIG. 13 is a diagram showing frequency characteristics when the substrate of the capacitance chip is set to substrate condition 4. FIG. 13 is a diagram showing frequency characteristics when the thickness of the first layer and the pitch of the IDC electrodes are changed. FIG. 13 is a diagram showing frequency characteristics when the thickness of the first layer and the pitch of the IDC electrodes are changed. 1 is a schematic diagram illustrating a duplexer as an example of a use of a filter device according to an embodiment of the present disclosure. 2 is a diagram illustrating a schematic diagram of a positional relationship between chips as viewed from a first surface of a mounting substrate according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram illustrating a communication device as an example of a use of a filter device according to an embodiment of the present disclosure.

A filter device and a communication device according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that the figures used in the following description are schematic diagrams, and the dimensional ratios and the like in the drawings do not necessarily match those of the actual filter device and communication device.

For convenience, the drawings may be illustrated with an orthogonal coordinate system consisting of an X-axis, a Y-axis, and a Z-axis. The X-axis is defined to be parallel to the propagation direction of the elastic wave used as the main resonance among the elastic waves propagating through the second layer 30 described later, the Y-axis is defined to be parallel to the extension direction of the electrode fingers 312 of the elastic wave resonator 3 described later, and the Z-axis is defined to be perpendicular to the upper surface 30a of the second layer 30 described later.

The Cartesian coordinate system used in this disclosure is an example, and the X-axis, Y-axis, and Z-axis directions may be defined in directions different from those of the Cartesian coordinate system used in this disclosure. For convenience, in this disclosure, the Z-axis direction may be the up-down direction and the terms top surface and bottom surface may be used.

The embodiments of the filter device according to the present disclosure are merely illustrative. Therefore, different embodiments may be partially substituted with each other. Also, different embodiments may be partially combined with each other.

FIG. 1 is a schematic plan view of a filter device 100 according to an embodiment of the present disclosure. As shown in FIG. 1, the filter device 100 according to an embodiment of the present disclosure filters a signal input from an antenna terminal 102 and outputs the signal to a first terminal 103.

The filter device 100 according to an embodiment of the present disclosure includes a capacitor chip 12, a first acoustic wave chip 13, and a mounting substrate 15. The capacitor chip 12 and the first acoustic wave chip 13 are
The capacitance chip 12 and the first acoustic wave chip 13 are located on one surface of the mounting substrate 15. Of the surfaces of the mounting substrate 15, the surface on which the capacitance chip 12 and the first acoustic wave chip 13 are located may be referred to as a first surface. In Fig. 1, the capacitance chip 12 is located closer to the antenna terminal 102 than the first acoustic wave chip 13, but this is not limiting. For example, the positional relationship between the capacitance chip 12 and the first acoustic wave chip 13 may be reversed.

2 is a plan view of a capacitance chip 12 according to an embodiment of the present disclosure, viewed from the Z-axis direction. The capacitance chip 12 according to an embodiment of the present disclosure includes at least one IDC (Interdigital Capacitor) element 2. The IDC element 2 has a first layer 20 and a pair of first comb-tooth electrodes 21. The first layer 20 has an upper surface 20a and a lower surface 20b perpendicular to the Z-axis, with the Z-axis being the up-down direction. The lower surface 20b is located opposite the upper surface 20a. The first comb-tooth electrode 21 is located on the upper surface 20a side of the first layer 20.

The first layer 20 includes a piezoelectric material or a dielectric material. Examples of the piezoelectric material include single crystals of lithium tantalate (LiTaO3; hereinafter referred to as LT) and single crystals of lithium niobate (LiNbO3; hereinafter referred to as LN). Examples of the dielectric material include tantalum oxide (Ta2O5), hafnium oxide (HfO2), silicon oxide (SiO2), titanium oxide (TiO2), and sapphire (Al2O3). For example, in one embodiment of the present disclosure, an example in which the first layer 20 includes tantalum oxide (Ta2O5) will be described.

The first comb-tooth electrode 21 is located on the upper surface 20a side of the first layer 20. The first comb-tooth electrode 21 is made of a conductive material. As the conductive material, various conductive materials such as aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), or alloys thereof can be used. The first comb-tooth electrode 21 may also be made by stacking multiple layers of various conductive materials such as those described above. In one embodiment of the present disclosure, specifically, the first comb-tooth electrode 21 is Al. Note that the first comb-tooth electrode 21 may be referred to as an IDC electrode to distinguish it from the second comb-tooth electrode 31 described later.

As shown in FIG. 2, the first comb-tooth electrode 21 includes a plurality of arranged electrode fingers 212. The first comb-tooth electrode 21 also includes a pair of bus bars 211 located in the extension direction of the plurality of electrode fingers 212 and connected to the plurality of electrode fingers 212. In other words, the plurality of electrode fingers 212 extend from the bus bar 211. The plurality of electrode fingers 212 are arranged such that the electrode finger 212a connected to one bus bar 211a and the electrode finger 212b connected to the other bus bar 211b interdigitate with each other. Note that the first comb-tooth electrode 21 does not necessarily need to be arranged such that the plurality of electrode fingers 212a and the plurality of electrode fingers 212b interdigitate with each other. For example, the plurality of electrode fingers 212b may be arranged in succession next to the plurality of electrode fingers 212a arranged in succession. In addition, one bus bar 211a, the other bus bar 211b, the electrode fingers 212a, and the electrode fingers 212b are sometimes collectively referred to simply as the second comb-tooth electrode 31.

By configuring the first comb electrode 21 as described above, a capacitance can be generated between the electrode fingers 212a and 212b. Therefore, the IDC element 2 can function, for example, as an additional capacitance of the circuit, and can also function, for example, as a capacitive element that constitutes the capacitive component of the first electromagnetic filter 105a described below.

In the first comb-tooth electrode 21, the repeat pitch of the multiple electrode fingers 212 in the arrangement direction is defined as P2. In addition, in the first comb-tooth electrode 21, the width of the multiple electrode fingers 212 in the arrangement direction is defined as W2. P2 and W2 are designed appropriately according to the desired capacitance characteristics.

Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 2. Fig. 3A is a cross-sectional view of a capacitive chip 12 according to an embodiment of the present disclosure, and Fig. 3B is a cross-sectional view of a capacitive chip 12 according to another embodiment of the present disclosure. The thickness of the first layer 20 is defined as T1. Note that T1 does not necessarily have to be constant, and T1 may have multiple values. When T1 has multiple values, the largest value may be defined as T1.

As shown in FIG. 3A, for example, the substrate of the capacitance chip 12 may be composed of only the first layer 20. In such a configuration, the elastic waves excited by the first comb-tooth electrode 21 leak to the underside of the first layer 20, so that the resonance of the IDC element 2 can be reduced. As a result, the effect of the resonance of the IDC element 2 on the frequency characteristics of the filter device 100 can be reduced.

Also, as shown in FIG. 3B, for example, the substrate of the capacitance chip 12 may have a first layer 20 and a support substrate 51 located on the lower surface 20b side of the first layer 20. The thickness of the support substrate 51 is not particularly limited, and for example, the thickness of the support substrate 51 may be greater than T1.

The material of the support substrate 51 is not particularly limited. For example, the material of the support substrate 51 may be a material with a smaller linear expansion coefficient than the first layer 20. Examples of such materials for the support substrate 51 include sapphire (Al2O3), silicon carbide (SiC), and silicon (Si). With this configuration, deformation of the first layer 20 due to temperature changes can be reduced, and changes in the frequency characteristics of the capacitance chip 12 due to temperature changes can be reduced.

FIG. 4 is a plan view of the first acoustic wave chip 13 according to an embodiment of the present disclosure, viewed from the Z-axis direction. The first acoustic wave chip 13 according to an embodiment of the present disclosure has at least one acoustic wave resonator 3. The acoustic wave resonator 3 has a second layer 30 and a pair of second comb-tooth electrodes 31. The second layer 30 has an upper surface 30a and a lower surface 30b perpendicular to the Z axis, with the Z axis being the up-down direction. The lower surface 30b is located opposite the upper surface 30a. The second comb-tooth electrode 31 is located on the upper surface 30a side of the second layer 30.

The second layer 30 contains a piezoelectric material. Examples of piezoelectric materials include single crystals of LT and single crystals of LN. The second layer 30 has piezoelectric properties, and when a high-frequency signal is applied to the second comb electrode 31 (described later), an elastic wave propagating through the second layer 30 is excited.

The elastic wave to be excited may be set appropriately. As an example, the elastic wave excited as the main resonance may be a plate wave or a bulk wave. Since plate waves and bulk waves have a higher propagation speed than other types of elastic waves, the main resonance frequency of the elastic wave resonator 3 can be set in a relatively high frequency range by using a plate wave or a bulk wave as the main resonance. As a result, by using a plate wave or a bulk wave as the main resonance, a filter device 100 can be provided in which the frequency characteristics in the high frequency range can be designed.

As an example, the main resonant frequency of the elastic wave resonator 3 may be 3 GHz or more, or 3.5 GHz or more. Also, the main resonant frequency of the elastic wave resonator 3 may be 4 GHz or more, or 5 GHz or more.

The type and propagation mode of the plate wave or bulk wave may also be set according to the desired frequency characteristics. For example, examples of the type of plate wave include Lamb waves and SH waves. For example, examples of the propagation mode of Lamb waves include the A1 mode, which is an asymmetric mode, and the S mode, which is a symmetric mode.

The Euler angles (φ, θ, ψ) of the piezoelectric single crystal contained in the second layer 30 are appropriately designed according to the type and propagation mode of the plate wave or bulk wave used as the main resonance. For example, when the second layer 30 is LT, the A1 mode of the Lamb wave can be used as the main resonance by setting the Euler angles (φ, θ, ψ) of the LT to (0°±10°, 0° to 55°, 0°±10°). When the second layer 30 is LN, the A1 mode of the Lamb wave can be used as the main resonance by setting the Euler angles (φ, θ, ψ) of the LN to (0°±10°, 0° to 55°, 0°±10°).

The thickness of the second layer 30 may be set appropriately. For example, the thickness of the second layer 30 may be less than 1 μm. In this case, plate waves or bulk waves can be used as the main resonance.

The second comb-tooth electrode 31 is located on the upper surface 30a side of the second layer 30. The second comb-tooth electrode 31 is made of a conductive material. The material of the second comb-tooth electrode 31 may be the same as or similar to the material of the first comb-tooth electrode 21. The second comb-tooth electrode 31 is sometimes called an IDT electrode to distinguish it from the above-mentioned first comb-tooth electrode 21.

As shown in FIG. 4, the second comb-tooth electrode 31 includes a plurality of arranged electrode fingers 312. The second comb-tooth electrode 31 also includes a pair of bus bars 311 that are located in the extension direction of the plurality of electrode fingers 312 and are connected to the plurality of electrode fingers 312. In other words, the plurality of electrode fingers 312 extend from the bus bar 311. The plurality of electrode fingers 312 are arranged such that the electrode finger 312a connected to one bus bar 311a and the electrode finger 312b connected to the other bus bar 311b interdigitate with each other. Note that the one bus bar 311a, the other bus bar 311b, the electrode finger 312a, and the electrode finger 312b may be collectively referred to simply as the second comb-tooth electrode 31.

In the second comb-tooth electrode 31, the repeat pitch of the multiple electrode fingers 312 in the arrangement direction is defined as P3. In addition, in the second comb-tooth electrode 31, the width of the multiple electrode fingers 312 in the arrangement direction is defined as W3. P3 and W3 are designed appropriately according to the desired capacitance characteristics. Note that the repeat pitch and width of the multiple electrode fingers 312 do not need to be strictly constant. For example, if the repeat pitch has multiple values, the largest value may be represented as P3. For example, if the width of the multiple electrode fingers 312 has multiple values, the largest value may be represented as W3.

When a high-frequency signal is applied to such a second comb-tooth electrode 31, an elastic wave with a wavelength λ defined as twice the P3 of the multiple electrode fingers 312 is excited and propagates through the second layer 30.

In the elastic wave resonator 3 according to an embodiment of the present disclosure, the second comb electrode 31 may include a plurality of dummy electrode fingers 313 located between each of the plurality of electrode fingers 312. The plurality of dummy electrode fingers 313 include dummy electrode fingers 313a connected to one bus bar 311a and facing electrode fingers 312b extending from the other bus bar 311b, and dummy electrode fingers 313b connected to one bus bar 311b and facing electrode fingers 312a extending from the other bus bar 311a. In the present disclosure, "facing" does not necessarily require that the opposing surfaces are parallel to each other, and the opposing surfaces may be inclined.

The elastic wave resonator 3 according to an embodiment of the present disclosure may have a pair of reflectors 32 located on the upper surface 30a side of the second layer 30. For example, the pair of reflectors 32 are located on both sides of the second comb electrode 31 in the X-axis direction. The reflector 32 includes a pair of reflector bus bars 321 facing each other and a plurality of strip electrodes 322 extending between the pair of reflector bus bars 321.

In the elastic wave resonator 3 according to the embodiment of the present disclosure, the length of the electrode fingers 312 of the second comb electrode 31 in the extension direction may be set appropriately depending on required electrical characteristics, etc. For example, the lengths of the electrode fingers 312 in the extension direction may be equal to each other. The second comb electrode 31 may be apodized, in which the length of the electrode fingers 312 in the extension direction changes depending on the position in the X-axis direction.

Figure 5 is a schematic cross-sectional view of the V-V line shown in Figure 4. Note that the reflector 32 is omitted in Figure 5. Figure 5A is a cross-sectional view of the first acoustic wave chip 13 in one embodiment of the present disclosure, and Figure 5B is a cross-sectional view of the first acoustic wave chip 13 in another embodiment of the present disclosure. The thickness of the second layer 30 is defined as T2. Note that T2 does not necessarily have to be constant, and T2 may have multiple values. When T2 has multiple values, the largest value may be defined as T2.

As shown in FIG. 5A, for example, the first acoustic wave chip 13 may have a support substrate 52 located on the lower surface 30b side of the second layer 30. The thickness of the support substrate 52 is not particularly limited, and for example, the thickness of the support substrate 52 may be greater than T2. In addition, the material of the support substrate 52 is not particularly limited, and for example, the support substrate 52 may include the same or similar material as the support substrate 51 included in the capacitance chip 12.

As shown in FIG. 5A, the first acoustic wave chip 13 may further include an acoustic reflection layer 6 between the second layer 30 and the support substrate 52. The acoustic impedance of the acoustic reflection layer 6 is different from the acoustic impedance of the second layer 30. For example, the material of the acoustic reflection layer 6 may be silicon oxide (SiO2). In this configuration, a difference in acoustic impedance occurs between the second layer 30 and the acoustic reflection layer 6, making it easier to confine the excited acoustic waves in the second layer 30. As a result, the resonance loss due to the second comb electrode 31 is reduced, and the frequency characteristics of the filter device 100 can be improved.

As shown in FIG. 5B, for example, the acoustic reflection layer 6 may be composed of multiple layers. For example, the acoustic reflection layer 6 may be composed of multiple low acoustic impedance layers 61 and multiple high acoustic impedance layers 62 alternately stacked. The acoustic impedance of the low acoustic impedance layer 61 is smaller than the acoustic impedance of the second layer 30. The acoustic impedance of the high acoustic impedance layer 62 is larger than the acoustic impedance of the low acoustic impedance layer 61. With this configuration, the elastic wave leaking from the lower surface 30b side of the second layer 30 is reflected to the second layer 30 side at the interface between the low acoustic impedance layer 61 and the high acoustic impedance layer 62, so that the leakage of the excited elastic wave can be more effectively reduced. As a result, the resonance loss due to the second comb electrode 31 is reduced, and the frequency characteristics of the filter device 100 can be improved.

Examples of materials for such low acoustic impedance layer 61 include silicon oxide (SiO2). Examples of materials for high acoustic impedance layer 62 include tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), tungsten (W), and molybdenum (Mo).

In one embodiment of the present disclosure, the thickness T2 of the second layer 30 of the first acoustic wave chip 13 may be set appropriately according to the desired frequency characteristics. For example, the thickness T2 of the second layer 30 may be less than 1 μm.

When the passband of the filter device 100 is set in a high frequency range, it is necessary to set the main resonance frequency of the acoustic wave resonator 3 of the first acoustic wave chip 13 in the high frequency range. When the thickness T2 of the second layer 30 is less than 1 μm, plate waves or bulk waves can be effectively used as the main resonance of the acoustic wave resonator 3, and the main resonance frequency can be set in a relatively high frequency range. For example, the thickness T2 of the second layer 30 may be 0.9 μm. On the other hand, when the thickness T1 of the first layer 20 of the capacitance chip 12 is set to be equal to or smaller than the thickness T2 of the second layer 30, spurious noise occurs in the high frequency range.

Figure 6 shows the frequency characteristics of the IDC element 2 when the substrate of the capacitance chip 12 is set to substrate condition 1 below. The substrate configuration of substrate condition 1 is the same as the substrate configuration of the first acoustic wave chip 13 shown in Figure 5A, and has an acoustic reflection layer and a support substrate in addition to the first layer. The pitch P2 of the electrode fingers 212 of the first comb electrode 21 is 0.7 μm. The left vertical axis of Figure 6 indicates impedance |Z| (ohm), the right vertical axis indicates phase (°), and the horizontal axis indicates frequency (MHz).

As can be seen from FIG. 6, when the substrate of the capacitance chip 12 is set to substrate condition 1, spurious signals are generated in the region of about 3500 MHz to 5500 MHz.
Substrate condition 1: "First layer (material: LT, thickness T1: 0.5 μm), acoustic reflection layer (material: SiO2, thickness: 0.2 μm), support substrate (material: Si)"

Figure 7 shows the frequency characteristics of the IDC element 2 when the substrate of the capacitance chip 12 is set to substrate condition 2 below. The substrate configuration of substrate condition 2 is the same as the substrate configuration of the first acoustic wave chip 13 shown in Figure 5B, and has a low acoustic impedance layer, a high acoustic impedance layer, and a support substrate in addition to the first layer. The pitch P2 of the electrode fingers 212 of the first comb-tooth electrode 21 is 0.7 μm. The left vertical axis of Figure 7 indicates |Z| (ohm), the right vertical axis indicates phase (°), and the horizontal axis indicates frequency (MHz).

As can be seen from FIG. 7, when the substrate of the capacitance chip 12 is set to substrate condition 2, spurious signals are generated in the region of about 3500 MHz to 5500 MHz.
Substrate condition 2: “First layer (material: LN, thickness T1: 0.46 μm), low acoustic impedance layer (material: SiO 2 ), high acoustic impedance layer (material: HfO 2 ), support substrate (material: Si)”

In this way, when the thickness T1 of the first layer 20 of the capacitance chip 12 is set to be equal to or smaller than the thickness T2 of the second layer 30, spurious noise caused by the capacitance chip 12 occurs in the high frequency range. Therefore, when the passband of the filter device 100 is set in the high frequency range, spurious noise caused by the capacitance chip 12 may affect the frequency characteristics near the passband.

Therefore, in one embodiment of the present disclosure, the thickness T1 of the first layer 20 of the capacitance chip 12 is made greater than the thickness T2 of the second layer 30 of the first acoustic wave chip 13. With such a configuration, it is possible to reduce spurious noise caused by the capacitance chip 12 in the high frequency range, and to provide a filter device with good frequency characteristics.

Figure 8 shows the frequency characteristics of the IDC element 2 when the substrate of the capacitance chip 12 is set to substrate condition 3 below. The substrate configuration for substrate condition 3 is the same as the substrate configuration shown in Figure 3A, and consists of only the first layer 20. The pitch P2 of the electrode fingers 212 of the first comb-tooth electrode 21 is 1.5 μm. The left vertical axis of Figure 8 indicates impedance |Z| (ohm), the right vertical axis indicates phase (°), and the horizontal axis indicates frequency (MHz).

As can be seen from FIG. 8, when the substrate of the capacitance chip 12 is substrate condition 3, the spurious is reduced in the region around 3500 MHz to 5500 MHz, compared with substrate condition 1 and substrate condition 2.
Substrate condition 3 "First layer (material: LT, thickness T1: 2300 μm)"

FIG. 9 shows the IDC when the substrate of the capacitance chip 12 is set to the following substrate condition 4.
9 shows the frequency characteristics of element 2. The substrate configuration under substrate condition 4 is the same as that shown in FIG. 3B, and includes a support substrate 51 in addition to the first layer. The pitch P2 of the electrode fingers 212 of the first comb-tooth electrode 21 is 2.5 μm. The left vertical axis in FIG. 9 shows |Z| (ohm), the right vertical axis shows phase (°), and the horizontal axis shows frequency (MHz).

As can be seen from FIG. 9, when the substrate of the capacitance chip 12 is substrate condition 4, the spurious is reduced in the region around 3500 MHz to 5500 MHz, compared with substrate condition 1 and substrate condition 2.
Substrate condition 4: "First layer (material: LT, thickness T1: 3.48 μm), supporting substrate (material: Si)"

In this way, when the thickness T1 of the first layer 20 of the capacitance chip 12 is set to be greater than the thickness T2 of the second layer 30, the spurious noise caused by the IDC element 2 in the high frequency range is reduced. Therefore, even when the passband of the filter device 100 is set in the high frequency range, the possibility of affecting the frequency characteristics near the passband can be reduced.

In one embodiment of the present disclosure, the thickness T1 of the first layer 20 of the capacitive chip 12 may be 1 μm or more. Figures 10 and 11 show frequency characteristics when the thickness T1 of the first layer 20 and the pitch P2 of the IDC elements 2 are changed in the capacitive chip 12 in one embodiment of the present disclosure. In both Figures 10 and 11, the horizontal axis shows the value of P2, and P2 is changed in the range of 1 μm to 4 μm. In both Figures 10 and 11, the vertical axis shows the value of T1, and T1 is changed in the range of 0.2 μm to 6.0 μm.

Each cell in Figure 10 shows the phase (°) of the spurious response caused by the IDC element 2 in the frequency range around 2.4 GHz to 2.5 GHz when T1 and P2 are changed. The closer the color of the cell is to black, the greater the phase of the spurious response caused by the IDC element 2. As shown in Figure 10, when the thickness T1 of the first layer 20 is less than 1 μm, the intensity of the spurious response caused by the IDC element 2 is high. On the other hand, when the thickness T1 of the first layer 20 is 1 μm or more, the intensity of the spurious response caused by the IDC element 2 is significantly reduced.

Each cell in Figure 11 shows the phase (°) of the spurious response caused by the IDC element 2 in the frequency range around 5.2 GHz to 7.1 GHz when T1 and P2 are changed. The closer the color of the cell is to black, the greater the phase of the spurious response caused by the IDC element 2. As shown in Figure 11, when the thickness T1 of the first layer 20 is less than 1 μm, the intensity of the spurious response caused by the IDC element 2 is high. On the other hand, when the thickness T1 of the first layer 20 is 1 μm or more, the intensity of the spurious response caused by the IDC element 2 is significantly reduced.

As can be seen from Figures 10 and 11, when the thickness T1 of the first layer 20 of the capacitive chip 12 in the present disclosure is set to 1 μm or more, the spurious noise caused by the IDC element 2 is significantly reduced in a wide frequency range, improving the freedom to set the passband of the filter device 100. Note that the thickness T1 of the first layer 20 may be 2 μm or more, or 5 μm or more. In this case, the spurious noise caused by the IDC element 2 is more significantly reduced.

In addition, in one embodiment of the disclosure, the pitch P2 of the first comb-tooth electrodes 21 in the capacitance chip 12 may be 2 μm or more. As can be seen from Fig. 11, when the pitch P2 of the first comb-tooth electrodes 21 in the capacitance chip 12 is 2 μm or more, the spurious caused by the IDC element 2 in the frequency range around 5.2 GHz to 7.1 GHz is significantly reduced. Therefore, the degree of freedom in setting the pass band of the filter device 100 in the high frequency range is improved.

In the example shown in FIG. 2, P2 is constant for all electrode fingers 212 of the first comb-tooth electrode 21, but this is not limited to the example. For example, P2 may be different values for the multiple electrode fingers 212 of the first comb-tooth electrode 21. For example, P2 may be designed to increase stepwise, or to have multiple types of repeat intervals. For example, the difference between the maximum P2 and the minimum P2 among the P2 of the multiple electrode fingers 212 may be larger than the difference between the maximum P3 and the minimum P3 among the P3 of the multiple electrode fingers 312 of the second comb-tooth electrode 31.

As described above, when P2 in the first comb-tooth electrode 21 is not constant and has multiple values, the resonance of the IDC element 2 can be reduced. As a result, the effect of the resonance of the IDC element 2 on the frequency characteristics of the filter device 100 can be reduced.

Also, as in the example shown in FIG. 2, the IDC element 2 may be configured not to have a reflector, which will be described later. With such a configuration, the resonance of the IDC element 2 can be further reduced.Also, as in the example shown in FIG. 2, the first comb-tooth electrode 21 may be configured not to have a dummy electrode, which will be described later. With such a configuration, the resonance of the IDC element 2 can be further reduced.

The duty D3 of the multiple electrode fingers 312 of the second comb-tooth electrode 31 of the elastic wave resonator 3 may be smaller than the duty D2 of the multiple electrode fingers 212 of the first comb-tooth electrode 21 of the IDC element 2. The duty is the value obtained by dividing the width of the electrode fingers by the pitch of the electrode fingers. In other words, D2 is expressed as W2/P2, and D3 is expressed as W3/P3.

In one embodiment of the present disclosure, the IDC element 2 in the capacitance chip 12 may be an additional capacitance for adjusting the frequency characteristics of an acoustic wave resonator included in the filter device 100, but is not limited to this example. For example, the IDC element 2 in the capacitance chip 12 may be a capacitance element of an electromagnetic filter included in the filter device 100.

FIG. 12 is a schematic diagram showing the configuration of a duplexer 101 as an example of use of a filter device 100 according to an embodiment of the present disclosure. The duplexer 101 has, for example, a first filter 105 that filters a signal input from an antenna terminal 102 and outputs the signal to a first terminal 103, and a second filter 106 that filters a signal input from the antenna terminal 102 and outputs the signal to a second terminal 104. The pass band of the first filter 105 and the pass band of the second filter 106 are different and do not overlap.

A splitter 101 according to an embodiment of the present disclosure includes a filter device 100 according to the present disclosure in at least one of a first filter 105 and a second filter 106. For example, in the splitter 101 shown in FIG. 12, the first filter 105 is a filter device 100.

The first filter 105 may have a first electromagnetic filter 105a and a first acoustic wave filter 105b. The first electromagnetic filter 105a is composed of one or more capacitance elements and one or more inductance elements. The attenuation pole of the first electromagnetic filter 105a is formed by the capacitance elements and the inductance elements included in the first electromagnetic filter 105a. The first acoustic wave filter 105b includes one or more acoustic wave resonators. Note that in this specification, a filter having only one acoustic wave resonator is also considered to be a filter. The attenuation pole of the first acoustic wave filter 105b is formed by the acoustic wave resonator included in the first acoustic wave filter 105b.

When the first filter 105 is the filter device 100 of the present disclosure, at least one of the capacitive elements included in the first electromagnetic filter 105a is the IDC element 2 in the capacitive chip 12. In other words, the IDC element 2 in the capacitive chip 12 constitutes at least one of the capacitive elements of the first electromagnetic filter 105a. In such a configuration, the IDC element 2 can have its capacitance characteristics fine-tuned by the first comb-tooth electrode 21, so that the frequency characteristics of the first electromagnetic filter 105a can be precisely controlled.

When the first filter 105 is the filter device 100 of the present disclosure, the first acoustic wave filter 105b includes an acoustic wave resonator 3 in the first acoustic wave chip 13. In other words, the acoustic wave resonator 3 in the first acoustic wave chip 13 constitutes at least one of the acoustic wave resonators of the first acoustic wave filter 105b.

The first filter 105 may function as one filter by combining the first electromagnetic filter 105a and the first acoustic wave filter 105b. For example, the first electromagnetic filter 105a may be any one of a band-pass filter, a high-pass filter, and a low-pass filter, and the first acoustic wave filter 105b may function as a band elimination filter. The attenuation pole formed by the first acoustic wave filter 105b may be located closer to the pass band of the first filter 105 than the attenuation pole formed by the first electromagnetic filter 105a. For example, when the first acoustic wave filter 105b is composed of an acoustic wave resonator 3, the attenuation pole formed by the acoustic wave resonator 3 may be located closer to the pass band of the first filter 105 than the attenuation pole formed by the first electromagnetic filter 105a.

In the above configuration, the first electromagnetic filter 105a, which has a wide pass characteristic, mainly forms the pass band of the first filter 105, and the attenuation pole of the first acoustic wave filter 105b, which has a steep attenuation characteristic, is located in a band close to the pass band. As a result, the pass band of the first filter 105 can be made wider and steeper.

In addition, an example in which at least one of the capacitive elements included in the first electromagnetic filter 105a is configured by the IDC element 2 in the capacitive chip 12 has been shown, but this is not limited to this example. For example, all of the capacitive elements included in the first electromagnetic filter 105a may be configured by the IDC element 2 in the capacitive chip 12. In other words, all of the capacitive elements included in the first electromagnetic filter 105a are located on the first layer 20 in the capacitive chip 12. In other words, all of the capacitive elements included in the first electromagnetic filter 105a are configured by the first comb electrode 21. In this configuration, the possibility that spurious due to the capacitive element will affect the frequency characteristics near the pass band can be further reduced compared to the case in which one of the multiple capacitive elements included in the first electromagnetic filter 105a is configured by the IDC element 2 in the capacitive chip 12.

The second filter 106 may be a ladder-type filter configured by connecting multiple elastic wave resonators in a ladder configuration. However, the second filter 106 is not limited to this example. For example, the second filter 106 may be an electromagnetic filter, or a filter that combines an electromagnetic filter and an elastic wave filter.

The second filter 106 may also have a second acoustic wave chip 14 that is a chip different from the first acoustic wave chip 13. The second acoustic wave chip 14 is located on the first surface of the mounting substrate 15, like the capacitance chip 12 and the first acoustic wave chip 13. The positional relationship between the capacitance chip 12, the first acoustic wave chip 13, and the second acoustic wave chip 14 may be set as appropriate.

13 is a schematic diagram showing the positional relationship of each chip when the first surface of the mounting substrate 15 according to an embodiment of the present disclosure is viewed in plan. The capacitive chip 12, the first acoustic wave chip 13, and the second acoustic wave chip 14 each have a substantially rectangular shape. Note that wiring connecting each chip is omitted in FIG.

As shown in Figures 13A to 13C, the positional relationship between the capacitance chip 12, the first acoustic wave chip 13, and the second acoustic wave chip 14 may be set as appropriate. In particular, as shown in Figures 13A and 13B, a configuration may be used in which the long side of the first acoustic wave chip 13 and the long side of the second acoustic wave chip 14 do not face each other. The first acoustic wave chip 13 and the second acoustic wave chip 14 are more likely to resonate than the capacitance chip 12, and are more likely to become a heat source when power is applied. Therefore, by configuring the long side of the first acoustic wave chip 13, which is likely to become a heat source, and the long side of the second acoustic wave chip 14 not to face each other, it is possible to reduce the effects of heat and provide a filter device 100 with excellent temperature characteristics.

(Example of use of splitter 101: communication device)
14 is a schematic diagram showing a main part of a communication device 111 as an example of a use of the duplexer 101. The communication device 111 includes the filter device 100 or the duplexer 101, and performs wireless communication using radio waves.

In the communication device 111, a transmission information signal TIS containing information to be transmitted is modulated and frequency-raised by an RF-IC (Radio Frequency Integrated Circuit) 113 to produce a transmission signal TS. Unnecessary components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 115a, amplified by an amplifier 114a, and input to the first terminal 103. The first filter 105 then removes unnecessary components outside the transmission passband from the input transmission signal TS, and outputs the removed transmission signal TS from the antenna terminal 102 to the antenna 112. The antenna 112 converts the input transmission signal TS into a wireless signal and transmits it.

In addition, in the communication device 111, a radio signal received by the antenna 112 is converted by the antenna 112 into a received signal RS and input to the antenna terminal 102. The second filter 106 removes unnecessary components outside the receiving passband from the input received signal RS and outputs it from the second terminal 104 to the amplifier 114b. The output received signal RS is amplified by the amplifier 114b, and unnecessary components outside the receiving passband are removed by the bandpass filter 115b. The received signal RS is then frequency-downshifted and demodulated by the RF-IC 113 to become a received information signal RIS.

The transmission information signal TIS and the reception information signal RIS may be low-frequency signals containing appropriate information, for example, analog audio signals or digitized audio signals. The passband of the wireless signal may be set appropriately, and in one embodiment of the present disclosure, a relatively high frequency passband is also possible. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. Although the direct conversion method is exemplified in FIG. 14 as the circuit method, it is not limited to this example and may be, for example, a double superheterodyne method. Also, FIG. 14 shows only the main parts in a schematic manner, and a low-pass filter or an isolator may be added at an appropriate position, and the position of the amplifier may be changed.

1: Filter device 12: Capacitive chip 13: First acoustic wave chip 14: Second acoustic wave chip 15: Mounting substrate 2: IDC element 20: First layer 21: First comb electrode 3: First acoustic wave resonator 30: Second layer 31: Second comb electrode 32: Reflectors 51, 52: Support substrate 6: Acoustic reflection layer 61: Low acoustic impedance layer 62: High acoustic impedance layer 101: Splitter 102: Antenna terminal 103: First terminal 104: Second terminal 105: First filter 105a: First electromagnetic filter 105b: First acoustic wave filter 106: Second filter 111: Communication device 112: Antenna 113: RF-IC
114: Amplifier

Claims (13)

A filter device including a capacitance chip including an IDC element and a first acoustic wave chip including an acoustic wave resonator,
The IDC element is
a first layer comprising a piezoelectric or dielectric material;
a pair of first comb-teeth electrodes located on the first layer;
having
The elastic wave resonator includes:
a second layer including a piezoelectric material;
a pair of second comb-teeth electrodes located on the second layer;
having
The thickness of the first layer is greater than the thickness of the second layer.
Filter device. The first layer has a thickness of 1 μm or more, and the second layer has a thickness of less than 1 μm.
The filter device of claim 1 . the first layer includes lithium tantalate or lithium niobate;
The filter device of claim 1 . The main resonant frequency of the elastic wave resonator is 3 GHz or more.
The filter device of claim 1 . The elastic wave resonator excites a plate wave or a bulk wave as a primary resonance.
The filter device of claim 1 . The elastic wave resonator includes:
A support substrate;
a low acoustic impedance layer located between the second layer and the support substrate, the low acoustic impedance layer having an acoustic impedance smaller than that of the second layer;
Further comprising
The filter device of claim 1 . The IDC element is a capacitive element of an electromagnetic filter.
The filter device of claim 1 . an attenuation pole formed by the elastic wave resonator is located closer to the passband than an attenuation pole formed by the electromagnetic filter;
The filter device of claim 7. all capacitance elements included in the electromagnetic filter are formed of comb-teeth electrodes located on the first layer;
The filter device of claim 7. a duty of the plurality of electrode fingers of the pair of second comb-tooth electrodes is smaller than a duty of the plurality of electrode fingers of the pair of first comb-tooth electrodes;
The filter device of claim 1 . a difference between a maximum pitch and a minimum pitch among the pitches of the electrode fingers of the pair of first comb-tooth electrodes is larger than a difference between a maximum pitch and a minimum pitch among the pitches of the electrode fingers of the pair of second comb-tooth electrodes;
The filter device of claim 1 . A second acoustic wave chip; and
a mounting substrate having a first surface;
Further equipped with
the capacitance chip, the first acoustic wave chip, and the second acoustic wave chip are located on a first surface;
When the first surface is viewed in plan, a long side of the first elastic wave chip and a long side of the second elastic wave chip do not face each other.
The filter device of claim 1 . The antenna,
A filter device according to claim 1 connected to the antenna;
an IC connected to the filter device;
Communications equipment.