JP6642499B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an elastic wave device having a plurality of elastic wave filters having different pass bands.

  Conventionally, elastic wave devices have been widely used for mobile phones and the like. In the acoustic wave device described in Patent Literature 1 below, a step is provided on an IDT electrode forming surface of a piezoelectric substrate. This acoustic wave device has an IDT electrode provided on a thick portion of a piezoelectric substrate on an IDT electrode forming surface, and an IDT electrode provided on a thin portion of the piezoelectric substrate across a step. Thus, a plurality of acoustic wave filters having different electromechanical coupling coefficients are formed in the same chip. Here, being configured in the same chip means being configured in the same piezoelectric substrate.

JP 2012-169707 A

  In the acoustic wave device described in Patent Literature 1, for example, when the IDT electrode is formed by photolithography simultaneously on a thick portion of the piezoelectric substrate and on a thin portion separated by a step, Exposure tends to be less uniform due to steps. Therefore, an IDT electrode provided in a portion where the thickness of the piezoelectric substrate is large and an IDT electrode provided in a portion where the thickness is small across a step may not be the same quality electrode.

  Therefore, in order to form IDT electrodes of the same quality in a portion where the thickness of the piezoelectric substrate is thick and a portion where the thickness is small across a step, it is necessary to form the IDT electrodes in separate steps, not simultaneously. And the manufacturing process is complicated. Even in the case where a plurality of acoustic wave filters having different pass bands are manufactured in the same chip, the manufacturing process becomes complicated as in the case of the elastic wave device of Patent Document 1.

  An object of the present invention is to provide an elastic wave device which can easily manufacture a plurality of elastic wave filters having different pass bands in the same chip.

  In a wide aspect of the elastic wave device according to the present invention, the elastic wave device includes a support substrate, an intermediate layer provided directly or indirectly on the support substrate, and a piezoelectric thin film provided on the intermediate layer. A piezoelectric laminate, a first excitation electrode and a second excitation electrode provided on the piezoelectric thin film in the piezoelectric laminate, and provided on the same plane; The thickness of the portion where the first excitation electrode is provided is different from the thickness of the portion where the second excitation electrode is provided.

  In a specific aspect of the elastic wave device according to the present invention, in the piezoelectric thin film in the piezoelectric laminate, a thickness of a portion where the first excitation electrode is provided, and the second excitation electrode is provided. Different in thickness.

  In another specific aspect of the elastic wave device according to the present invention, in the intermediate layer of the piezoelectric laminate, a thickness of a portion where the first excitation electrode is provided, and the second excitation electrode is provided. The thickness of the part where it is different.

  In another broad aspect of the elastic wave device according to the present invention, a support substrate, an intermediate layer provided directly or indirectly on the support substrate, and a piezoelectric thin film provided on the intermediate layer And a first excitation electrode and a second excitation electrode provided on the piezoelectric thin film in the piezoelectric laminate and provided on the same plane. The thickness of the portion where the first excitation electrode is provided is the same as the thickness of the portion where the second excitation electrode is provided, and the piezoelectric thin film and the intermediate layer have the same thickness. The thickness of the portion where the excitation electrode is provided is different from the thickness of the portion where the second excitation electrode is provided.

  In still another specific aspect of the elastic wave device according to the present invention, the intermediate layer is provided on a surface of the piezoelectric thin film opposite to the first and second excitation electrodes, and the bulk wave Has a low sound speed film where the sound speed at which the sound wave propagates is lower than the sound speed of the elastic wave propagating through the piezoelectric thin film, and the supporting substrate has a sound speed at which the bulk wave propagates is lower than the sound speed of the elastic wave propagating at the piezoelectric thin film Is also a high-sonic substrate having a high speed, and the supporting substrate is provided on the low-sonic film. In this case, the energy of the elastic wave can be effectively confined.

  In another specific aspect of the elastic wave device according to the present invention, the intermediate layer is provided on a surface of the piezoelectric thin film on a side opposite to the first and second excitation electrodes, and a bulk wave is provided. A low-sonic film in which the speed of sound that propagates is lower than the speed of sound of the elastic wave propagating through the piezoelectric thin film, and a sound speed at which the sound speed at which the bulk wave propagates is provided on the low-sonic film and propagates through the piezoelectric thin film. A high sonic film that is faster than the sound speed of the waves. In this case, the energy of the elastic wave can be effectively confined.

  In still another specific aspect of the elastic wave device according to the present invention, the intermediate layer has at least one low acoustic impedance layer having a relatively low acoustic impedance and at least one layer having a relatively high acoustic impedance. And a high acoustic impedance layer. In this case, the energy of the elastic wave can be effectively confined.

  In still another specific aspect of the elastic wave device according to the present invention, the number of the acoustic reflection layers is two or more. In this case, since the reflection performance of the acoustic reflection layer is good, it is possible to change the characteristics of the elastic wave only by changing the thickness of the piezoelectric laminate. That is, the characteristics of the elastic wave device can be easily adjusted.

  In still another specific aspect of the elastic wave device according to the present invention, the elastic wave device further includes a support layer provided on the support substrate and having a portion provided between the support substrate and the intermediate layer. ing.

  In still another specific aspect of the elastic wave device according to the present invention, the support layer surrounds the piezoelectric thin film in a plan view. In this case, cracks and the like of the piezoelectric thin film hardly occur during dicing in the manufacturing process, and peeling between the piezoelectric thin film and the intermediate layer hardly occurs.

  In still another specific aspect of the elastic wave device according to the present invention, the first and second excitation electrodes are first and second IDT electrodes.

  According to the present invention, it is possible to provide an elastic wave device capable of easily manufacturing a plurality of elastic wave filters having different pass bands in the same chip.

FIG. 2 is a front sectional view of the elastic wave device according to the first embodiment of the present invention. 3A to 3D are front cross-sectional views illustrating an example of a method for manufacturing an elastic wave device according to the first embodiment. (A)-(c) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave device which concerns on 1st Embodiment. It is a front sectional view of an elastic wave device concerning a modification of a 1st embodiment of the present invention. It is a front sectional view of an elastic wave device concerning a 2nd embodiment of the present invention. It is a figure which shows the impedance characteristic of the elastic wave filter with the lamination | stacking number of 4 acoustic reflection layers, and the acoustic wave filter with the lamination number of 6 acoustic reflection layers. It is a figure which shows S11 return loss of the elastic wave filter which the number of laminations of an acoustic reflection layer is four, and the elastic wave filter whose number of laminations of an acoustic reflection layer is six. It is a front sectional view of an elastic wave device concerning a 3rd embodiment of the present invention. (A)-(d) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave device which concerns on 3rd Embodiment. (A)-(c) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave device which concerns on 3rd Embodiment. It is a front sectional view of an elastic wave device concerning a 4th embodiment of the present invention. It is a front sectional view of an elastic wave device concerning a 5th embodiment of the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  It is to be noted that each embodiment described in the present specification is an example, and that partial replacement or combination of configurations between different embodiments is possible.

  FIG. 1 is a front sectional view of the elastic wave device according to the first embodiment of the present invention.

  The elastic wave device 10 includes first and second elastic wave filters 1A and 1B having different pass bands. The first and second acoustic wave filters 1A and 1B are configured in the same chip. In this specification, being configured in the same chip means being configured in the same piezoelectric thin film.

  More specifically, the elastic wave device 10 has a support substrate 6. The support substrate 6 is not particularly limited, but is made of, for example, silicon or the like. The support layer 5 is provided on the support substrate 6. The piezoelectric laminate 4 is provided on the support layer 5. As described above, in the acoustic wave device 10, the piezoelectric laminate 4 is indirectly provided on the support substrate 6.

  The piezoelectric laminate 4 has an intermediate layer provided on the support layer 5 and the piezoelectric thin film 2 provided on the intermediate layer. Although details will be described later, in the present embodiment, the intermediate layer is the first to third acoustic reflection layers 3A to 3C.

The piezoelectric thin film 2 has a main surface 2a located on the side opposite to the first to third acoustic reflection layers 3A to 3C. Here, the vertical direction in FIG. 1 is defined as the vertical direction of the elastic wave device 10. At this time, the piezoelectric thin film 2 has first and second concave portions 2c and 2d provided on the lower surface side. In the present embodiment, the thickness of the piezoelectric thin film 2 above the first recess 2c is smaller than the thickness of the piezoelectric thin film 2 above the second recess 2d. The piezoelectric thin film 2 is made of a piezoelectric single crystal such as LiNbO ₃ or LiTaO ₃ . The material of the piezoelectric thin film 2 is not particularly limited. The piezoelectric thin film 2 may be made of, for example, a piezoelectric ceramic.

  The thickness of the piezoelectric thin film 2 above the first and second concave portions 2c and 2d is 100 nm or more and 2000 nm or less. The thickness of the piezoelectric thin film 2 is not particularly limited.

  On the main surface 2a of the piezoelectric thin film 2, first and second IDT electrodes 7A and 7B are provided as first and second excitation electrodes. An elastic wave is excited by applying a voltage to the first and second IDT electrodes 7A and 7B. The first IDT electrode 7A is an IDT electrode forming a pass band of the first acoustic wave filter 1A. The second IDT electrode 7B is an IDT electrode forming a pass band of the second elastic wave filter 1B.

  Here, in the elastic wave device 10, various elastic waves can be used. Examples of the various elastic waves include a plate wave and a bulk wave. The plate wave is a general term for various waves excited in the piezoelectric thin film 2 having a thickness of 1λ or less when the wavelength of the excited plate wave is 1λ. The plate wave is a wave whose energy is concentrated in the piezoelectric thin film 2 or in the vicinity of the piezoelectric thin film 2.

  Therefore, in the present embodiment, as described later, since an intermediate layer that reflects a plate wave is provided immediately below the piezoelectric thin film 2, the plate wave can be excited.

  The first IDT electrode 7A shown in FIG. 1 is provided in a portion overlapping the first recess 2c in plan view. The second IDT electrode 7B is provided in a portion overlapping the second recess 2d in a plan view. Therefore, in the piezoelectric thin film 2, the thickness of the portion where the first IDT electrode 7A is provided is different from the thickness of the portion where the second IDT electrode 7B is provided.

  On the main surface 2a of the piezoelectric thin film 2, wirings 8Aa and 8Ab that are electrically connected to the first IDT electrode 7A are provided. Wirings 8Ba and 8Bb electrically connected to the second IDT electrode 7B are also provided on the main surface 2a. The first and second IDT electrodes 7A, 7B and the wirings 8Aa, 8Ab, 8Ba, 8Bb are provided on the same plane. In this specification, the term “on the same plane” means that the plane is substantially on the same plane so as not to affect the characteristics of the acoustic wave device.

  Each of the first and second IDT electrodes 7A and 7B is composed of a laminated metal film in which a Ti layer and an AlCu layer composed of 99% by weight of Al and 1% by weight of Cu are laminated. A Ti layer is laminated on the main surface 2a of the piezoelectric thin film 2, and an AlCu layer is laminated on the Ti layer. Note that the first and second IDT electrodes 7A and 7B may be formed of a single layer or may be a laminated metal film. The material of the first and second IDT electrodes 7A and 7B is not particularly limited.

  The wirings 8Aa, 8Ab, 8Ba, 8Bb are formed of a laminated metal film in which a Ti layer and an Al layer are laminated. A Ti layer is laminated on the main surface 2a of the piezoelectric thin film 2, and an Al layer is laminated on the Ti layer. The wirings 8Aa, 8Ab, 8Ba, 8Bb may be formed of a single layer, or may be a laminated metal film. The material of the wirings 8Aa, 8Ab, 8Ba, 8Bb is not particularly limited.

  The thickness of the first and second IDT electrodes 7A and 7B of the present embodiment is 10 nm or more and 1000 nm or less. The thickness of the wirings 8Aa, 8Ab, 8Ba, 8Bb is 100 nm or more and 1000 nm or less. The thicknesses of the first and second IDT electrodes 7A, 7B and the wirings 8Aa, 8Ab, 8Ba, 8Bb are not particularly limited.

  On the side opposite to the main surface 2a of the piezoelectric thin film 2, first to third acoustic reflection layers 3A to 3C are provided. Note that a plurality of third acoustic reflection layers 3C are provided. More specifically, the first acoustic reflection layer 3A is provided in the first concave portion 2c of the piezoelectric thin film 2. The second acoustic reflection layer 3B is provided in the second recess 2d. The plurality of third acoustic reflection layers 3C are provided in portions other than the first and second concave portions 2c and 2d, respectively. The first and second acoustic reflection layers 3A and 3B may extend outside the first and second concave portions 2c and 2d, or may be continuous with the third acoustic reflection layer 3C. In the present embodiment, the thicknesses of the first to third acoustic reflection layers 3A to 3C are the same. In the present specification, the same thickness means substantially the same thickness so as not to affect the characteristics of the acoustic wave device.

  As described above, the thickness of the piezoelectric thin film 2 is different between the portion where the first IDT electrode 7A is provided and the portion where the second IDT electrode 7B is provided. Therefore, the thickness of the piezoelectric laminate 4 including the piezoelectric thin film 2 and the first to third acoustic reflection layers 3A to 3C is also determined by the portion where the first IDT electrode 7A is provided and the second IDT electrode 7B. Is different from the part shown.

  As shown in FIG. 1, the first acoustic reflection layer 3A is a laminated film having low acoustic impedance layers 3A1 and 3A3 and high acoustic impedance layers 3A2 and 3A4. The low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 are alternately stacked, and the low acoustic impedance layer 3A1 is located closest to the piezoelectric thin film 2 side. The low acoustic impedance layers 3A1 and 3A3 have relatively low acoustic impedance. The high acoustic impedance layers 3A2 and 3A4 have relatively high acoustic impedance.

  The first acoustic reflection layer 3A reflects the elastic wave propagated from the piezoelectric thin film 2 to the piezoelectric thin film 2 side. Thereby, the energy of the elastic wave can be confined to the piezoelectric thin film 2 side, and the energy efficiency can be improved.

The low acoustic impedance layers 3A1 and 3A3 are made of, for example, silicon oxide having a relatively low acoustic impedance. Alternatively, the low acoustic impedance layers 3A1 and 3A3 may be made of a material containing silicon oxide as a main component, or may be made of a dielectric material or a metal material other than silicon oxide. The high acoustic impedance layers 3A2 and 3A4 are made of, for example, Pt having a relatively high acoustic impedance, another dielectric material, or a metal material. The high acoustic impedance layers 3A2 and 3A4 may be made of a metal other than Pt, such as Mo, Ta, or W. Alternatively, the high acoustic impedance layers 3A2 and 3A4 are not metal layers but may be layers made of ceramics such as AlN or SiN or piezoelectric single crystals such as LiNbO ₃ or LiTaO ₃ . The materials of the low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 are not particularly limited, and may be made of appropriate materials having different acoustic impedances.

  In the present embodiment, the number of stacked first acoustic reflection layers 3A is not particularly limited, but is four. The second and third acoustic reflection layers 3B and 3C are configured similarly to the first acoustic reflection layer 3A. Note that the third acoustic reflection layer 3C may not be provided.

  In the present embodiment, each of the low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 has a thickness of 100 nm or more and 1000 nm or less. The thicknesses of the low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 are not limited to the above.

  The support layer 5 is disposed on the opposite side of the first to third acoustic reflection layers 3A to 3C from the piezoelectric thin film 2 side. The surface of the support layer 5 on the first to third acoustic reflection layers 3A to 3C side has an uneven shape. The uneven shape is a shape corresponding to the uneven shape on the surface of the piezoelectric thin film 2 on the first to third acoustic reflection layers 3A to 3C side. On the other hand, the surface of the support layer 5 opposite to the first to third acoustic reflection layers 3A to 3C has a flat shape. That is, the support layer 5 adjusts the difference between the thickness of the piezoelectric thin film 2 corresponding to the first IDT electrode 7A and the thickness of the piezoelectric thin film 2 corresponding to the second IDT electrode 7B. On the other hand, since the intermediate layer affects filter characteristics and the like, the difference between the thickness of the piezoelectric thin film 2 corresponding to the first IDT electrode 7A and the thickness of the piezoelectric thin film 2 corresponding to the second IDT electrode 7B is determined by the intermediate layer. If the adjustment is made by using, the filter characteristics and the like may be deteriorated. However, in the present embodiment, since the thickness difference in the piezoelectric thin film 2 is adjusted by the support layer 5, it is possible to prevent the resonator characteristics and the filter characteristics from deteriorating.

  Note that the support layer 5 is not particularly limited, but is made of silicon oxide or the like.

  Here, the feature of the present embodiment lies in the following configuration. 1) In the piezoelectric laminate 4, the thickness of the portion where the first IDT electrode 7A is provided is different from the thickness of the portion where the second IDT electrode 7B is provided. 2) The first and second IDT electrodes 7A and 7B are provided on the same plane. Thereby, the sound velocity of the elastic wave propagating in the portion where the first IDT electrode 7A is provided and the acoustic velocity of the elastic wave propagating in the portion where the second IDT electrode 7B are provided are the same. The speed of sound can be easily changed. Therefore, the first and second acoustic wave filters 1A and 1B having different pass bands can be easily manufactured in the same chip. The details will be described below together with a method for manufacturing the elastic wave device 10 according to the present embodiment.

  2A to 2D are front cross-sectional views illustrating an example of a method for manufacturing the elastic wave device according to the first embodiment. 3A to 3C are front cross-sectional views illustrating an example of a method for manufacturing the acoustic wave device according to the first embodiment.

  As shown in FIG. 2A, a mother substrate 2A made of a piezoelectric material is prepared. Next, as shown in FIG. 2B, the first and second concave portions 2Ac and 2Ad are formed on one main surface of the mother substrate 2A by a reactive ion etching method or the like. At this time, the first and second concave portions 2Ac and 2Ad are formed such that the first concave portion 2Ac is deeper than the second concave portion 2Ad. Here, the vertical direction in FIG. 2B is defined as the vertical direction of the mother substrate 2A. By forming the first and second concave portions 2Ac and 2Ad as described above, the thickness of the mother substrate 2A above the first concave portion 2Ac is larger than the thickness of the mother substrate 2A above the second concave portion 2Ad. make it thin.

  Next, as shown in FIG. 2C, a low acoustic impedance layer is formed on the side of the mother substrate 2A where the first and second concave portions 2Ac and 2Ad are provided. At this time, the low acoustic impedance layer 3A1 is formed in the first recess 2Ac. A low acoustic impedance layer is also formed in the second concave portion 2Ad and in a portion where the first and second concave portions 2Ac and 2Ad are not provided. Next, a high acoustic impedance layer is laminated on the low acoustic impedance layer. Similarly, the first to third acoustic reflection layers 3A to 3C as intermediate layers are formed by alternately stacking the low acoustic impedance layers and the high acoustic impedance layers. The low acoustic impedance layer and the high acoustic impedance layer can be formed by, for example, a sputtering method or a vapor deposition method.

  Next, as shown in FIG. 2D, a support layer 5A is laminated on the first to third acoustic reflection layers 3A to 3C on the side opposite to the mother substrate 2A side by a sputtering method or the like. Next, as shown in FIG. 3A, the surfaces of the support layer 5A opposite to the first to third acoustic reflection layers 3A to 3C are flattened by a CMP (Chemical Mechanical Polishing) method or the like. .

  Next, the support substrate 6A is bonded to the surface of the support layer 5A opposite to the first to third acoustic reflection layers 3A to 3C. For bonding the support layer 5A and the support substrate 6A, a resin adhesive can be used. However, the method of bonding the support layer 5A and the support substrate 6A is not particularly limited, and for example, surface activation bonding, atomic diffusion bonding, metal bonding, or the like may be used.

  Next, as shown in FIG. 3B, the mother substrate 2A is thinned. Thereby, the thickness of mother substrate 2A is set to a thickness that can efficiently excite an elastic wave. The thinning can be performed, for example, by polishing the surface of the mother substrate 2A on the side opposite to the first to third acoustic reflection layers 3A to 3C. Alternatively, in thinning, a smart cut method or the like in which ions are implanted into the mother substrate 2A and peeled off may be used. Thereby, a flat main surface 2Aa is formed on the side of the mother substrate 2A opposite to the first to third acoustic reflection layers 3A to 3C.

  Next, as shown in FIG. 3C, the first and second IDT electrodes 7A and 7B and the wirings 8Aa, 8Ab, 8Ba and 8Bb are formed on the main surface 2Aa of the mother substrate 2A. The first IDT electrode 7A is formed in a region where the first acoustic reflection layer 3A is provided in plan view. The second IDT electrode 7B is formed in a region where the second acoustic reflection layer 3B is provided in plan view. The first and second IDT electrodes 7A, 7B and the wirings 8Aa, 8Ab, 8Ba, 8Bb can be formed by, for example, a sputtering method or an evaporation method. Thereby, the first and second elastic wave filters 1A and 1B are manufactured.

  In the present embodiment, the first and second IDT electrodes 7A and 7B and the wirings 8Aa, 8Ab, 8Ba and 8Bb can be formed on the same plane. Therefore, a complicated process is not required although the thickness of the mother substrate 2A is different between the first and second concave portions 2Ac and 2Ad. Thus, the first and second elastic wave filters 1A and 1B having different pass bands can be easily manufactured.

  Further, in the present embodiment, the first to third acoustic reflection layers 3A to 3C have the same number of layers, so that the first and second acoustic wave filters 1A and 1B can be manufactured more easily. .

  Next, dicing is performed along dicing lines II and II-II in FIG. Thereby, the individual acoustic wave devices 10 shown in FIG. 1 can be obtained.

  In this embodiment, even if the thickness of the portion other than the first and second concave portions 2c and 2d of the piezoelectric thin film 2 is increased, the excitation efficiency and the like are hardly affected. Further, for example, a structure may be employed in which the third acoustic reflection layer 3C is not formed in a portion located at the dicing lines II and II-II, and the support layer 5A is in contact with the mother substrate 2A. As a result, the number of interfaces of the thin films located at the dicing lines II and II-II can be reduced, and peeling due to dicing can be suppressed.

  Returning to FIG. 1, it is preferable that the first to third acoustic reflection layers 3A to 3C have two or more laminated layers. In this case, since the reflection performance of the acoustic reflection layer is improved, it is possible to change the characteristics of the elastic wave only by changing the thickness of the piezoelectric laminate 4. That is, the characteristics of the elastic wave device 10 can be easily adjusted.

  The piezoelectric thin film 2 is provided with first and second concave portions 2c and 2d. It is sufficient that the thickness of the piezoelectric thin film 2 is different between the portions where the first and second IDT electrodes 7A and 7B are provided, and the first and second recesses 2c and 2d are not necessarily provided. Good.

  Since the elastic wave device 10 is reinforced by the support substrate 6, the strength of the elastic wave device 10 can be increased. Note that the support substrate 6 may not be provided.

  FIG. 4 is a front sectional view of an elastic wave device according to a modification of the first embodiment.

  In the acoustic wave device 60, the thickness of the first acoustic reflection layer 3A is different from the thickness of the second acoustic reflection layer 63B, and the thickness of the piezoelectric thin film 2 where the first IDT electrode 7A is provided. And the thickness of the portion where the second IDT electrode 7B is provided is different. Thus, in the piezoelectric laminate 64, the thickness of the portion where the first IDT electrode 7A is provided is equal to the thickness of the portion where the second IDT electrode 7B is provided. The elastic wave device 60 has the same configuration as the elastic wave device 10 of the first embodiment except for the above points.

  The thickness of the first acoustic reflection layer 3A is larger than the thickness of the second acoustic reflection layer 63B. For example, the thickness of the first acoustic reflection layer 3A and the thickness of the second acoustic reflection layer 63B may be varied by varying the number of layers. In the present embodiment, the number of layers of the first acoustic reflection layer 3A is four, and the number of layers of the second acoustic reflection layer 63B is two.

  In the modification shown in FIG. 4, optimal first and second acoustic reflections are made in a portion of the piezoelectric thin film 2 where the first IDT electrode 7A is formed and a portion where the second IDT electrode 7B is formed. The number of layers and the thickness of the layers 3A and 63B can be the same. Therefore, the filter characteristics of the first and second elastic wave filters 1A and 1B can be effectively improved.

  Further, similarly to the first embodiment, the first and second elastic wave filters 1A and 1B having different pass bands can be easily manufactured in the same chip.

  FIG. 5 is a front sectional view of the elastic wave device according to the second embodiment.

  The elastic wave device 20 is different from the first embodiment in that the thickness of the portion of the piezoelectric thin film 22 where the first IDT electrode 7A is provided is the same as the thickness of the portion where the second IDT electrode 7B is provided. Different from the first embodiment. The acoustic wave device 20 also differs from the first embodiment in that the thickness of the first acoustic reflection layer 3A is different from the thickness of the second acoustic reflection layer 23B. Except for the above points, the elastic wave device 20 has the same configuration as the elastic wave device 10 of the first embodiment.

  The thickness of the second acoustic reflection layer 23B is larger than the thickness of the first acoustic reflection layer 3A. Similar to the modification of the first embodiment shown in FIG. 4, for example, by changing the number of layers, the thickness of the first acoustic reflection layer 3A and the thickness of the second acoustic reflection layer 23B may be different. Good. In the present embodiment, the number of layers of the first acoustic reflection layer 3A is four, and the number of layers of the second acoustic reflection layer 23B is six. As described above, by making the thicknesses of the first and second acoustic reflection layers 3A and 23B as the intermediate layers different, the portion of the piezoelectric laminate 24 where the first and second IDT electrodes 7A and 7B are provided. May have different thicknesses.

  Here, a plurality of acoustic wave filters having the same configuration except that the number of layers of the acoustic reflection layer was changed and the thickness of the acoustic reflection layer was changed, and impedance characteristics and return loss were compared. The acoustic wave filter having four acoustic reflection layers and the acoustic wave filter having six acoustic reflection layers were compared.

  FIG. 6 is a diagram illustrating impedance characteristics of an acoustic wave filter having four acoustic reflection layers and an acoustic wave filter having six acoustic reflection layers. FIG. 7 is a diagram illustrating the S11 return loss of an acoustic wave filter having four acoustic reflection layers and an acoustic wave filter having six acoustic reflection layers. 6 and 7, the solid line shows the result of the acoustic wave filter having six acoustic reflection layers, and the broken line shows the result of the elastic wave filter having four acoustic reflection layers.

As shown in FIGS. 6 and 7, it can be seen that even if the thickness of the piezoelectric thin film is the same, the impedance characteristics and the return loss can be changed by changing the thickness of the acoustic reflection layer. Here, the wavelength of the elastic wave used is λ. For example, when the thickness of the piezoelectric thin film is 1λ and the specific frequency in the pass band is 1 GHz, the specific frequency in the pass band can be set to 2 GHz by setting the thickness of the piezoelectric thin film to 0.5λ. On the other hand, even when the thickness of the piezoelectric thin film is not changed and the thickness is set to 1λ, the specific frequency in the pass band can be shifted from 1 GHz by changing the thickness of the acoustic reflection layer as described above. .

  Also in the present embodiment shown in FIG. 5, the first and second acoustic wave filters 21A and 22B having different pass bands can be easily manufactured in the same chip.

  Further, as described above, in the piezoelectric thin film 22, the thickness of the portion where the first IDT electrode 7A is provided is the same as the thickness of the portion where the second IDT electrode 7B is provided. Therefore, the piezoelectric thin film 22 can be easily manufactured.

  FIG. 8 is a front sectional view of the elastic wave device according to the third embodiment.

  The acoustic wave device 30 differs from the first embodiment in that the configuration of the piezoelectric thin film 32 and the support layer 35 and the absence of the third acoustic reflection layer are provided. Except for the above points, the elastic wave device 30 has the same configuration as the elastic wave device 10 of the first embodiment.

More specifically, the support layer 35 has first and second acoustic reflection layers 3A and 3B as intermediate layers, and a portion provided between the piezoelectric thin film 32 and the support substrate 6, and is viewed in plan. Has a portion surrounding the piezoelectric thin film 32.

  The piezoelectric thin film 32 has a first concave portion 32c, but does not have a second concave portion. The thickness of the portion of the piezoelectric thin film 32 where the first IDT electrode 7A is provided is different from the thickness of the portion where the second IDT electrode 7B is provided. The first and second IDT electrodes 7A and 7B are provided on the same plane. Therefore, similarly to the first embodiment, the first and second elastic wave filters 31A and 31B having different pass bands can be easily manufactured in the same chip.

  Like the wirings 8Aa and 8Bb, the wiring may have a portion provided on the support layer 35.

  The first acoustic reflection layer 3A only needs to overlap the first IDT electrode 7A in plan view, and may be provided in a part of the first recess 32c. As in the present embodiment, the second acoustic reflection layer 3B may be arranged in a portion other than the concave portion of the piezoelectric thin film 32.

  In the elastic wave device 30, cracks and the like of the piezoelectric thin film 32 are less likely to occur during dicing in the manufacturing process, and separation between the piezoelectric thin film 32 and the first and second acoustic reflection layers 3A and 3B is less likely to occur. This will be described below together with a method of manufacturing the elastic wave device 30.

  FIGS. 9A to 9D are front cross-sectional views illustrating an example of a method for manufacturing an acoustic wave device according to the third embodiment. 10A to 10C are front cross-sectional views illustrating an example of a method for manufacturing an acoustic wave device according to the third embodiment.

  As shown in FIG. 9A, a mother substrate 32A made of a piezoelectric material is prepared. Next, as shown in FIG. 9B, first and third concave portions 32Ac and 32Ae are formed on one main surface of the mother substrate 32A by a reactive ion etching method or the like. At this time, the first and third concave portions 32Ac and 32Ae are formed so that the thickness of the portion of the mother substrate 32A where the third concave portion 32Ae is located is smaller than the thickness of the portion where the first concave portion 32Ac is located. I do.

  Next, as shown in FIG. 9C, the first and second acoustic reflection layers 3A and 3A as intermediate layers are provided on the side of the mother substrate 32A where the first and third concave portions 32Ac and 32Ae are provided. Form 3B. The first acoustic reflection layer 3A is formed in the first recess 32Ac. The second acoustic reflection layer 3B is formed in portions other than the first and third concave portions 32Ac and 32Ae.

  Next, similarly to the method for manufacturing the elastic wave device 10 of the first embodiment, as shown in FIGS. 9D and 10A, a support layer 35A and a support substrate 6A are provided.

  Next, the mother substrate 32A is thinned. At this time, the surfaces of the mother substrate 32A opposite to the first and second acoustic reflection layers 3A and 3B are polished or the like to expose the support layer 35A as shown in FIG. Thereby, the piezoelectric thin film 32 is obtained.

  Next, as shown in FIG. 10C, the first and second IDT electrodes 7A and 7B and the wirings 8Ab and 8Ba are formed on the main surface 32a of the piezoelectric thin film 32. The wiring 8Aa is formed on the main surface 32a and the support layer 35A, and the wiring 8Bb is formed on the support layer 35A.

  Also in this embodiment, the first and second IDT electrodes 7A and 7B and the wirings 8Aa, 8Ab, 8Ba and 8Bb can be formed on the same plane. Therefore, the first and second elastic wave filters 31A and 31B having different pass bands can be easily manufactured.

  Next, dicing is performed along dicing lines II and II-II in FIG. At this time, the piezoelectric thin film 32 and the first and second acoustic reflection layers 3A and 3B are not located on the dicing lines II and II-II. Therefore, in the support layer 35A, the portion where the interface between the piezoelectric thin film 32 and the first and second acoustic reflection layers 3A and 3B and the interface between the respective layers in the first and second acoustic reflection layers 3A and 3B are not located. Can be diced. Accordingly, cracking of the piezoelectric thin film 32 is unlikely to occur, and separation between the piezoelectric thin film 32 and the first and second acoustic reflection layers 3A and 3B and separation between the respective layers of the first and second acoustic reflection layers 3A and 3B. Is unlikely to occur.

  FIG. 11 is a front sectional view of the elastic wave device according to the fourth embodiment.

  The elastic wave device 40 differs from the first embodiment in that the intermediate layer has the low sound speed film 45 and the high sound speed film 46, does not have the support layer, and the piezoelectric thin film 42 does not have the second concave portion. different. Except for the above points, the elastic wave device 40 has the same configuration as the elastic wave device 10 according to the first embodiment. In the acoustic wave device 40, the piezoelectric laminate 44 is provided directly on the support substrate 6.

  In the piezoelectric thin film 42, since the first concave portion 42c is provided, the thickness of the portion where the first and second IDT electrodes 7A and 7B are provided is different. In the present embodiment, the thickness of the piezoelectric laminate 44 is the same in the portion where the first and second IDT electrodes 7A and 7B are provided. Note that the thickness of the piezoelectric laminate 44 may be different in a portion where the first and second IDT electrodes 7A and 7B are provided.

  The low sound velocity film 45 is provided on the surface of the piezoelectric thin film 42 opposite to the first and second IDT electrodes 7A and 7B. A high sound speed film 46 is provided on the low sound speed film 45. The support substrate 6 is provided on the high sonic film 46. Note that a support layer may be provided between the high sonic film 46 and the support substrate 6. In this case, the adhesion strength between the low sonic film 45 and the high sonic film 46 as the intermediate layers and the support substrate 6 can be suitably increased.

  Here, the low sound speed film 45 is a film in which the sound speed at which the bulk wave propagates is lower than the sound speed of the elastic wave propagating through the piezoelectric thin film 42. The low sound speed film 45 may be a material having a relatively low sound speed, for example, a material mainly composed of glass, silicon oxide, silicon oxynitride, tantalum oxide, or a compound obtained by adding fluorine, carbon, or boron to silicon oxide. Etc.

  The high sound speed film 46 is a film in which the sound speed at which the bulk wave propagates is higher than the sound speed of the elastic wave propagating through the piezoelectric thin film 42. The high sonic film 46 may be a material having a relatively high sonic speed, for example, aluminum nitride, aluminum oxide, silicon, silicon carbide, silicon nitride, silicon oxynitride, a DLC film or a material containing diamond as a main component. Become.

  Since the elastic wave device 40 has the piezoelectric laminate 44 including the piezoelectric thin film 42, the low sound speed film 45, and the high sound speed film 46, the energy of the elastic wave can be effectively confined.

Also in the present embodiment, similarly to the first embodiment, the first and second elastic wave filters 41A and 41B having different pass bands can be easily manufactured in the same chip. Further, since there is no need to provide an acoustic reflection layer including one or more low acoustic impedance layers and one or more high acoustic impedance layers, the first and second elastic wave filters 41A and 41B can be easily manufactured. it can.

  FIG. 12 is a front sectional view of the elastic wave device according to the fifth embodiment.

  The acoustic wave device 50 differs from the fourth embodiment in that the intermediate layer is formed of the low sonic film 45 and the supporting substrate is the high sonic substrate 56. Except for the above points, the elastic wave device 50 has the same configuration as the elastic wave device 40 of the fourth embodiment.

  The high-sonic substrate 56 is provided on the low-sonic film 45. The high-sonic substrate 56 is a substrate in which the sound speed at which the bulk wave propagates is higher than the sound speed of the elastic wave propagating through the piezoelectric thin film 42. The same material as the high sonic film 46 in the fourth embodiment can be used for the high sonic substrate 56.

  Also in the present embodiment, the energy of the elastic wave can be effectively confined as in the fourth embodiment. In addition, the first and second acoustic wave filters 51A and 51B having different pass bands can be easily manufactured in the same chip. Further, since the piezoelectric laminate 54 includes the piezoelectric thin film 42 and the low sonic film 45, the number of layers can be reduced. Therefore, the first and second elastic wave filters 51A and 51B can be manufactured more easily.

  In addition, in the piezoelectric laminate 54, the interface between the thin films can be reduced. Therefore, peeling due to dicing hardly occurs in the manufacturing process.

  In the first to fifth embodiments, examples of the elastic wave device having two elastic wave filters have been described. However, the present invention is also applicable to an elastic wave device having three or more elastic wave filters having different pass bands from each other. It can be suitably applied.

  On the other hand, in the first to fifth embodiments, the example in which the excitation electrode is an IDT electrode has been described. However, the present invention is also suitable for a boundary acoustic wave device having a plurality of elastic wave filters using bulk waves. Can be applied.

1A, 1B ... first and second elastic wave filters 2 ... piezoelectric thin film 2a ... main surfaces 2c and 2d ... first and second concave portions 2A ... mother substrate 2Aa ... main surfaces 2Ac and 2Ad ... first and second Concave portion 3A First acoustic reflection layer 3A1, 3A3 Low acoustic impedance layer 3A2, 3A4 High acoustic impedance layer 3B, 3C Second and third acoustic reflection layer 4 Piezoelectric laminate 5, 5A Support layer 6 , 6A ... support substrates 7A, 7B ... first and second IDT electrodes 8Aa, 8Ab, 8Ba, 8Bb ... wiring 10 ... elastic wave device 20 ... elastic wave devices 21A, 21B ... first and second elastic wave filters 22 ... Piezoelectric thin films 22c and 22d first and second concave portions 23B second acoustic reflection layer 24 piezoelectric laminate 30 elastic wave devices 31A and 31B first and second elastic wave filters 32 piezoelectric thin film 32a ... Main surface 32c ... First concave portion 32A Mother substrates 32Ac, 32Ae: first and third concave portions 35, 35A: support layer 40: elastic wave devices 41A, 41B: first and second elastic wave filters 42: piezoelectric thin film 42c: first concave portion 44: piezoelectric Laminate 45 ... Low sonic film 46 ... High sonic film 50 ... Elastic wave devices 51A and 51B ... First and second elastic wave filters 54 ... Piezoelectric laminate 56 ... High sonic substrate 60 ... Elastic wave device 63B ... Second Acoustic reflection layer 64: piezoelectric laminate

Claims (10)

A support substrate;
An intermediate layer provided directly or indirectly on the support substrate, and a piezoelectric thin film having a piezoelectric thin film provided on the intermediate layer,
A first excitation electrode and a second excitation electrode provided on the piezoelectric thin film in the piezoelectric laminate and provided on the same plane;
With
The first excitation electrode and the second excitation electrode form a part of an elastic wave filter having different pass bands from each other, and the first excitation electrode is a first IDT electrode for exciting a plate wave. , The second excitation electrode is a second IDT electrode for exciting a plate wave,
In the piezoelectric laminate, a thickness of the piezoelectric laminate at a portion where the first excitation electrode is provided is different from a thickness of the piezoelectric laminate at a portion where the second excitation electrode is provided, Elastic wave device.   2. The piezoelectric thin film in the piezoelectric laminate according to claim 1, wherein a thickness of a portion where the first excitation electrode is provided is different from a thickness of a portion where the second excitation electrode is provided. 3. Elastic wave device.   2. The intermediate layer of the piezoelectric laminate according to claim 1, wherein a thickness of a portion where the first excitation electrode is provided is different from a thickness of a portion where the second excitation electrode is provided. 3. Elastic wave device. A support substrate;
An intermediate layer provided directly or indirectly on the support substrate, and a piezoelectric thin film having a piezoelectric thin film provided on the intermediate layer,
A first excitation electrode and a second excitation electrode provided on the piezoelectric thin film in the piezoelectric laminate and provided on the same plane;
With
The first excitation electrode and the second excitation electrode form a part of an elastic wave filter having different pass bands from each other, and the first excitation electrode is a first IDT electrode for exciting a plate wave. , The second excitation electrode is a second IDT electrode for exciting a plate wave,
The intermediate layer is a first acoustic reflection layer and a second acoustic reflection layer,
In a plan view, the first IDT electrode and the first acoustic reflection layer overlap, the second IDT electrode and the second IDT electrode overlap,
In the piezoelectric laminate, a thickness of a portion where the first IDT electrode is provided is equal to a thickness of a portion where the second IDT electrode is provided,
In the piezoelectric thin film, the thickness of the portion where the first IDT electrode is provided is different from the thickness of the portion where the second IDT electrode is provided, and the thickness of the first acoustic reflection layer is different from the thickness of the first acoustic reflection layer. The thickness of the second acoustic reflection layer is different,
The first acoustic reflection layer and the second acoustic reflection layer each have at least one low acoustic impedance layer with relatively low acoustic impedance and at least one high acoustic impedance layer with relatively high acoustic impedance. An acoustic wave device comprising: an acoustic impedance layer. The intermediate layer is provided on a surface of the piezoelectric thin film opposite to the first and second excitation electrodes, and a sound speed at which a bulk wave propagates is lower than a sound speed of an elastic wave propagating through the piezoelectric thin film. Also has a low sound velocity membrane that is slow,
The support substrate is a high sonic speed substrate at which the sound speed at which the bulk wave propagates is higher than the sound speed of the elastic wave propagating through the piezoelectric thin film,
The elastic wave device according to any one of claims 1 to 3, wherein the supporting substrate is provided on the low sound velocity film.   The intermediate layer is provided on a surface of the piezoelectric thin film opposite to the first and second excitation electrodes, and a sound speed at which a bulk wave propagates is lower than a sound speed of an elastic wave propagating through the piezoelectric thin film. A low sound speed film that is also low speed, and a high sound speed film that is provided on the low sound speed film and has a sound speed at which a bulk wave propagates and is higher than a sound speed of an elastic wave propagating through the piezoelectric thin film. The elastic wave device according to any one of claims 1 to 3.   The intermediate layer is an acoustic reflection layer having at least one low acoustic impedance layer having a relatively low acoustic impedance and at least one high acoustic impedance layer having a relatively high acoustic impedance. The elastic wave device according to claim 1.   The acoustic wave device according to claim 7, wherein the number of stacked acoustic reflection layers is two or more.   The elastic wave device according to any one of claims 1 to 8, further comprising a support layer provided on the support substrate and having a portion provided between the support substrate and the intermediate layer. .   The acoustic wave device according to claim 9, wherein the support layer has a portion surrounding the piezoelectric thin film in a plan view.

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