Patent Application
20240372525
The present disclosure relates to acoustic wave devices each including a piezoelectric layer (piezoelectric body layer) and methods for manufacturing acoustic wave devices.
For example, Japanese Unexamined Patent Application Publication No. 2012-257019 discloses an acoustic wave device that uses plate waves. The acoustic wave device described in Japanese Unexamined Patent Application Publication No. 2012-257019 includes a support, a piezoelectric substrate, and an IDT electrode. The support has a space portion. The piezoelectric substrate is provided on the support so as to overlap the space portion. The IDT electrode is provided on the piezoelectric substrate so as to overlap the space portion. In the acoustic wave device, a plate wave is excited by the IDT electrode. An end edge portion of the space portion does not include a linear portion extending parallel to the propagation direction of the plate wave excited by the IDT electrode.
There has recently been a demand for an acoustic wave device capable of reducing or preventing cracks in an intermediate layer of a support while reducing the manufacturing cost.
Example embodiments of the present invention provide acoustic wave devices and manufacturing methods thereof each capable of reducing or preventing cracks in an intermediate layer of a support while reducing the manufacturing cost.
An acoustic wave device according to an example embodiment of the present disclosure includes?.
A method for manufacturing an acoustic wave device according to another example embodiment of the present disclosure is a method for manufacturing an acoustic wave device including a support substrate including a support and an intermediate layer on the support, a piezoelectric body layer on the intermediate layer, and a functional electrode on the piezoelectric body layer, in which the piezoelectric body layer includes a through-hole extending through the piezoelectric body layer in a lamination direction of the support, the intermediate layer, and the piezoelectric body layer, and the support substrate includes a space portion at a position overlapping a portion of the functional electrode in the lamination direction, and a recess at a position at least partially overlapping the through-hole in the lamination direction, the recess being recessed in a direction separating from the piezoelectric body layer from the space portion, the method including forming the through-hole so as to extend through a sacrificial layer surrounded by the piezoelectric body layer and the support substrate in the lamination direction, and removing the sacrificial layer through the through-hole to form the space portion.
Example embodiments of the present disclosure provide acoustic wave devices and manufacturing methods thereof each capable of reducing or preventing cracks in an intermediate layer of a support while reducing the manufacturing cost.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Hereinafter, example embodiments of the present disclosure will be described with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, the applications of example embodiments of the present disclosure, or the use of example embodiments of the present disclosure. The drawings are schematic, and dimensional ratios and the like do not necessarily correspond to the actual ones.
With reference to
An acoustic wave device according to the first, second, and third aspects of example embodiments of the present disclosure of the present disclosure include a piezoelectric layer made of lithium niobate or lithium tantalate, for example, and a first electrode and a second electrode facing each other in a direction intersecting the thickness direction of the piezoelectric layer.
An acoustic wave device according to the first aspect of example embodiments of the present disclosure uses a bulk wave in a first-order thickness-shear mode.
In an acoustic wave device according to the second aspect of example embodiments of the present disclosure, the first electrode and the second electrode are adjacent to each other, and d/p is less than or equal to about 0.5, for example, where d is the thickness of the piezoelectric layer, and p is the center-to-center distance between the first electrode and the second electrode. With this configuration, in the first and second aspects, a Q factor can be increased even when the size of the acoustic wave device is reduced.
An acoustic wave device according to the third aspect of example embodiments of the present disclosure uses a Lamb wave as a plate wave. The Lamb wave can provide resonance characteristics.
An acoustic wave device according to the fourth aspect of example embodiments of the present disclosure includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode facing each other in the thickness direction of the piezoelectric layer with the piezoelectric layer interposed therebetween, and uses a bulk wave.
The present disclosure will be clarified by describing specific example embodiments of the acoustic wave devices according to the first to fourth aspects below with reference to the drawings.
It should be noted that each example embodiment described in this specification is illustrative, and partial substitution or combination of configurations described in different example embodiments is possible.
An acoustic wave device 1 includes a piezoelectric layer 2 made of LiNbO3. The piezoelectric layer 2 may be made of LiTaO3. The cut-angle of LiNbO3 or LiTaO3 is a Z-cut in this example embodiment, but may be a rotated Y-cut or X-cut. The propagation directions of Y propagation and X propagation about ±30° are preferable, for example. The thickness of the piezoelectric layer 2 is not particularly limited, but is preferably more than or equal to about 50 nm and less than or equal to about 1000 nm in order to effectively excite the first-order thickness-shear mode, for example.
The piezoelectric layer 2 includes a first main surface 2a and a second main surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first main surface 2a. Here, the electrode 3 is an example of a “first electrode” and the electrode 4 is an example of a “second electrode”. In
The electrode 3 and the electrode 4 each have a rectangular or substantially rectangular shape and have a length direction. In a direction orthogonal to the length direction, the electrode 3 and the electrode 4 adjacent thereto face each other. An interdigital transducer (IDT) electrode is thus formed, including the plurality of electrodes 3 and 4, the first busbar 5, and the second busbar 6. The length direction of the electrodes 3 and 4 and the direction orthogonal to the length direction of the electrodes 3 and 4 each are a direction intersecting a thickness direction of the piezoelectric layer 2. Therefore, it can also be said that the electrode 3 and the electrode 4 adjacent thereto face each other in a direction intersecting the thickness direction of the piezoelectric layer 2.
Further, the length direction of the electrodes 3 and 4 may be replaced with the direction orthogonal to the length direction of the electrodes 3 and 4 illustrated in
A plurality of pairs of structures in which the electrode 3 connected to one potential and the electrode 4 connected to the other potential are adjacent to each other are provided in the direction orthogonal to the length direction of the electrodes 3 and 4 described above. Here, the electrode 3 and the electrode 4 being adjacent to each other refers not to a case where the electrode 3 and the electrode 4 are arranged so as to be in direct contact with each other but to a case where the electrode 3 and the electrode 4 are arranged with an interval therebetween.
In addition, when the electrode 3 and the electrode 4 are adjacent to each other, an electrode connected to a hot electrode or a ground electrode, including the other electrodes 3 and 4, is not arranged between the electrode 3 and the electrode 4. The number of pairs need not be integer pairs, but may be 1.5 pairs, 2.5 pairs, or the like. The center-to-center distance between the electrodes 3 and 4, that is, the pitch is preferably in the range of more than or equal to about 1 μm and less than or equal to about 10 μm, for example. In addition, the center-to-center distance between the electrodes 3 and 4 is a distance connecting the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the center of the width dimension of the electrode 4 in the direction orthogonal to the length direction of the electrode 4. Further, in a case where at least one of the electrodes 3 and 4 includes a plurality of electrodes (when the electrodes 3 and 4 define a pair of electrodes and there are 1.5 or more pairs of electrodes), the center-to-center distance between the electrodes 3 and 4 refers to the average value of the center-to-center distances between the respective adjacent electrodes 3 and 4 of the 1.5 or more pairs of electrodes 3 and 4. In addition, the width of the electrodes 3 and 4, that is, the dimension of the electrodes 3 and 4 in their facing direction, is preferably in the range of more than or equal to about 150 nm and less than or equal to about 1000 nm, for example. The center-to-center distance between the electrodes 3 and 4 is a distance connecting the center of the dimension (width dimension) of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the center of the dimension (width dimension) of the electrode 4 in the direction orthogonal to the length direction of the electrode 4.
In this example embodiment, since the Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrodes 3 and 4 is a direction orthogonal to the polarization direction of the piezoelectric layer 2. This does not apply when a piezoelectric body of another cut-angle is used as the piezoelectric layer 2. Here, “orthogonal” is not limited to strictly orthogonal but may be substantially orthogonal (an angle between the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, approximately 90°±10°).
A support 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an insulating layer 7 interposed therebetween. The insulating layer 7 and the support 8 have a frame shape and include cavities 7a and 8a as illustrated in
The insulating layer 7 is made of silicon oxide. However, the insulating layer 7 can be made of an appropriate insulating material such as silicon oxynitride or alumina in addition to silicon oxide. The support 8 is made of Si. The plane orientation of the surface of Si on the piezoelectric layer 2 side may be (100), (110), or (111). Preferably, high-resistance Si having a resistivity of more than or equal to about 4 kΩ is desirable, for example. However, the support 8 can also be made using an appropriate insulating material or semiconductor material. Examples of the material of the support 8 include piezoelectric bodies such as aluminum oxide, lithium tantalate, lithium niobate, or quartz crystal, various ceramics such as alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite, dielectrics such as diamond or glass, semiconductors such as gallium nitride, or the like.
The plurality of electrodes 3 and 4 and the first and second busbars 5 and 6 are made of an appropriate metal or alloy such as Al or an AlCu alloy. In this example embodiment, the electrodes 3 and 4 and the first and second busbars 5 and 6 have a structure in which an Al film is laminated on a Ti film. A material other than the Ti film may be used for an adhesion layer.
At the time of driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first busbar 5 and the second busbar 6. This makes it possible to obtain resonance characteristics using a bulk wave in the first-order thickness-shear mode excited in the piezoelectric layer 2.
In the acoustic wave device 1, d/p is less than or equal to about 0.5, for example, where d is the thickness of the piezoelectric layer 2, and p is the center-to-center distance between any adjacent electrodes 3 and 4 of the plurality of pairs of electrodes 3 and 4. Therefore, the bulk wave in the first-order thickness-shear mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d/p is less than or equal to about 0.24, for example, in which case even better resonance characteristics can be obtained.
In a case where at least one of the electrodes 3 and 4 includes a plurality of electrodes as in this example embodiment, that is, in a case where the electrodes 3 and 4 define a pair of electrodes and there are 1.5 or more pairs of the electrodes 3 and 4, the center-to-center distance p between the adjacent electrodes 3 and 4 is an average distance of the center-to-center distances between the respective adjacent electrodes 3 and 4.
Since the acoustic wave device 1 according to this example embodiment has the configuration described above, a Q factor is less likely to be reduced even when the number of pairs of the electrodes 3 and 4 is reduced in an attempt to achieve a reduction in size. This is because the resonator does not require reflectors on both sides and has a small propagation loss. In addition, the reason why the above reflector is not required is that the bulk wave in the first-order thickness-shear mode is used.
With reference to
On the other hand, as illustrated in
As illustrated in
As described above, in the acoustic wave device 1, at least a pair of electrodes including the electrode 3 and the electrode 4 are arranged. Since waves are not propagated in the X direction, the plurality of pairs of electrodes including the electrodes 3 and 4 are not always necessary. That is, only at least a pair of electrodes may be provided.
For example, the electrode 3 is an electrode connected to the hot potential, and the electrode 4 is an electrode connected to the ground potential. However, the electrode 3 may be connected to the ground potential and the electrode 4 may be connected to the hot potential. In this example embodiment, as described above, at least a pair of electrodes are the electrode connected to the hot potential or the electrode connected to the ground potential, and a floating electrode is not provided.
The length of the excitation region C is a dimension of the excitation region C in the length direction of the electrodes 3 and 4.
In this example embodiment, the electrode-to-electrode distances of the electrode pairs including the electrodes 3 and 4 are all equal in the plurality of pairs. That is, the electrodes 3 and the electrodes 4 are arranged with equal pitches.
As is clear from
As described above, in this example embodiment, d/p is less than or equal to about 0.5, more preferably less than or equal to about 0.24, for example, where d is the thickness of the piezoelectric layer 2 and p is the center-to-center distance between the electrode 3 and the electrode 4. This will be described with reference to
A plurality of acoustic wave devices are obtained in the same manner as the acoustic wave device having the resonance characteristics illustrated in
As illustrated in FIG. 6, when d/2p exceeds about 0.25, that is, d/p>about 0.5, the fractional bandwidth is less than about 5% even when d/p is adjusted, for example. On the other hand, when d/2p≤about 0.25, that is, d/p≤about 0.5, the fractional bandwidth can be more than or equal to about 5% by changing d/p within the range, that is, the resonator having a high coupling coefficient can be provided, for example. When d/2p is less than or equal to about 0.12, that is, d/p is less than or equal to about 0.24, the fractional bandwidth can be increased to more than or equal to about 78, for example. In addition, when d/p is adjusted within this range, a resonator having a wider fractional bandwidth can be obtained, and a resonator having a higher coupling coefficient can be realized. Therefore, as in the case of the acoustic wave device according to the second aspect of example embodiments of the present disclosure, it is understood that by setting d/p to less than or equal to about 0.5, for example, a resonator having a high coupling coefficient using the bulk wave in the first-order thickness-shear mode described above can be provided.
Note that, as described above, the at least one pair of electrodes may be a pair of electrodes, and in the case of one pair of electrodes, p is the center-to-center distance between the adjacent electrodes 3 and 4. Further, in the case of 1.5 or more pairs of electrodes, p may be the average distance of the center-to-center distances between the adjacent electrodes 3 and 4.
When the piezoelectric layer 2 has variations in thickness d, a value obtained by averaging the thicknesses may be used.
In the acoustic wave device 1, preferably, it is desirable that the metallization ratio MR of any adjacent electrodes 3 and 4 of the plurality of electrodes 3 and 4 with respect to the excitation region C, which is a region where the adjacent electrodes 3 and 4 overlap as seen in their facing direction, satisfies MR≤about 1.75 (d/p)+0.075, for example. In other words, a region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap as seen in a direction in which the adjacent first electrode fingers and second electrode fingers face each other is an excitation region (intersection region), and it is preferable that MR≤about 1.75 (d/p)+0.075 is satisfied, for example, where MR is the metallization ratio of the plurality of first electrode fingers and the plurality of second electrode fingers to the excitation region. In that case, it is possible to effectively reduce spurious.
This will be described with reference to
The metallization ratio MR will be described with reference to
When a plurality of pairs of electrodes are provided, the ratio of the metallization portion included in the entire excitation region to the total area of the excitation region may be MR.
In a region surrounded by an ellipse J in
(0°±10°, 0° to 20°, any ψ) Expression (1)
(0°±10°, 20° to 80°, 0° to 60° (1−(θ−50)2/900)1/2) or (0°±10°, 20° to 80°, [180°−60°(1−(θ−50)2/900)1/2] to 180°) Expression (2)
(0°±10°, [180°−30°(1−(ψ−90)2/8100)1/2] to 180°, any ψ) Expression (3)
Therefore, in the case of the Euler angle range of Expression (1), Expression (2), or Expression (3), the fractional bandwidth can be sufficiently widened, which is preferable.
In the acoustic wave device 81, a Lamb wave as a plate wave is excited by applying an AC electric field to the IDT electrode 84 above the space portion 9. Since the reflectors 85 and 86 are provided on both sides, resonance characteristics due to the Lamb wave can be obtained.
As described above, an acoustic wave device according to an example embodiment of the present disclosure may use a plate wave.
With reference to
As illustrated in
In this example embodiment, the functional electrode 120 is an IDT electrode including a plurality of electrode fingers. The plurality of electrode fingers of the functional electrode 120 each extend in the Y direction and are spaced apart in the X direction. Each electrode finger of the functional electrode 120 is connected to one of the two wiring electrodes 130.
As illustrated in
With reference to
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As described above, in the acoustic wave device 1 according to the present disclosure, the configuration described above allows an etchant to reach the bottom surface of the sacrificial layer 91 from the start of etching when removing the sacrificial layer 91 to form the space portion 9. This makes it possible to efficiently remove the sacrificial layer 91. As a result, the manufacturing cost of the acoustic wave device 1 can be reduced.
In an acoustic wave device 100 (see
The acoustic wave device 1 can also be configured as follows.
The recess 111 is not limited to being recessed to the surface of the support 8, and may be recessed into the support 8, as illustrated in
The bottom surface of the recess 111 is not limited to reaching the support 8, and does not have to reach the support 8, as illustrated in
The space portion 9 is not limited to being located in the insulating layer 7, and may be located across the insulating layer 7 and the support 8, for example.
At least a portion of the configuration of the acoustic wave device 1 of the present disclosure may be added to the acoustic wave devices of the first to fourth aspects of example embodiments of the present disclosure, or at least a portion of the configuration of the acoustic wave devices of the first to fourth aspects of example embodiments of the present disclosure may be added to the acoustic wave device 1 of the present disclosure.
Various example embodiments of the present disclosure have been described in detail above with reference to the drawings.
Any of the various example embodiments or modifications may be appropriately combined to achieve the effects thereof. In addition, combinations of example embodiments, combination of examples, or combinations of example embodiments and examples is possible, or combinations of features of different example embodiments or examples are also possible.
While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
This application claims the benefit of priority to Provisional Application No. 63/301, 546 filed on Jan. 21, 2022 and is a Continuation Application of PCT Application No. PCT/JP2023/001755 filed on Jan. 20, 2023. The entire contents of each application are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63301546 | Jan 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/001755 | Jan 2023 | WO |
| Child | 18777668 | US |
