JP2018007239A - Acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic wave device which makes possible to readily manufacture a plurality of acoustic wave filters different in pass band in one chip.SOLUTION: An acoustic wave device 10 comprises: a support substrate 6; a piezoelectric laminate 4 having an intermediate layer directly or indirectly provided on the support substrate 6, and a piezoelectric thin film 2 provided on the intermediate layer; and a first IDT electrode 7A and a second IDT electrode 7B (i.e. a first excitation electrode and a second excitation electrode) which are provided on the piezoelectric thin film 2 in the piezoelectric laminate 4 in a common plane. In the piezoelectric laminate 4, a portion where the first IDT electrode 7A is provided is different, in thickness, from a portion where the second IDT electrode 7B is provided.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, elastic wave devices have been widely used in mobile phones and the like. In the elastic wave device described in Patent Document 1 below, a step is provided on the IDT electrode formation surface of the piezoelectric substrate. This elastic wave device has, on the IDT electrode forming surface, an IDT electrode provided in a portion where the thickness of the piezoelectric substrate is thick, and an IDT electrode provided in a portion where the thickness is thin with a step. Thus, a plurality of acoustic wave filters having different electromechanical coupling coefficients are configured 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 Document 1, for example, when the IDT electrode is formed simultaneously by a photolithography method on a portion where the thickness of the piezoelectric substrate is thick and a portion where the thickness is thin with a step difference, There is a tendency that the exposure is not uniform due to the step. For this reason, the IDT electrode provided in the portion where the thickness of the piezoelectric substrate is thick and the IDT electrode provided in the portion where the thickness is thin with a step difference may not be the same electrode.

  Therefore, in order to form IDT electrodes of the same quality on a portion where the thickness of the piezoelectric substrate is thick and a portion where the thickness is thin with a step, it is necessary to form the IDT electrodes in separate steps, not simultaneously. The manufacturing process was 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 elastic wave device of Patent Document 1.

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

  In a wide aspect of the acoustic 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. In the piezoelectric laminate, comprising: a piezoelectric laminate; 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 different from the thickness of the portion where the second excitation electrode is provided.

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

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

  In another broad aspect of the acoustic 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 are provided. A piezoelectric laminate having a first excitation electrode and a second excitation electrode that are 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. In the piezoelectric thin film and the intermediate layer, 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 a bulk wave Has a low sound velocity film whose sound velocity is lower than the sound velocity of the elastic wave propagating through the piezoelectric thin film, and the support substrate has a sound velocity at which the bulk wave propagates from the sound velocity of the elastic wave propagating through the piezoelectric thin film. The high-speed substrate has a high speed, and the support substrate is provided on the low-speed film. In this case, the energy of the elastic wave can be effectively confined.

  In another specific aspect of the acoustic 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 bulk waves are generated. A low sound velocity film whose propagation speed is lower than that of an elastic wave propagating through the piezoelectric thin film, and an elastic property provided on the low sound velocity film, and a sound velocity at which a bulk wave propagates propagates through the piezoelectric thin film. And a high sound velocity film that is faster than the sound velocity of the waves. In this case, the energy of the elastic wave can be effectively confined.

  In still another specific aspect of the acoustic wave device according to the present invention, the intermediate layer has at least one low acoustic impedance layer having relatively low acoustic impedance and at least one layer having relatively high acoustic impedance. 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 acoustic wave device according to the present invention, the number of stacked acoustic reflection layers is two or more. 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. That is, the characteristics of the elastic wave device can be easily adjusted.

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

  In still another specific aspect of the acoustic wave device according to the present invention, the support layer surrounds the piezoelectric thin film in a plan view. In this case, during dicing in the manufacturing process, the piezoelectric thin film is hardly cracked, and the piezoelectric thin film and the intermediate layer are hardly separated.

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

  ADVANTAGE OF THE INVENTION According to this invention, the elastic wave apparatus which can manufacture easily several elastic wave filters from which a pass band differs in the same chip | tip can be provided.

It is front sectional drawing of the elastic wave apparatus which concerns on the 1st Embodiment of this invention. (A)-(d) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave apparatus which concerns on 1st Embodiment. (A)-(c) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave apparatus which concerns on 1st Embodiment. It is front sectional drawing of the elastic wave apparatus which concerns on the modification of the 1st Embodiment of this invention. It is front sectional drawing of the elastic wave apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the impedance characteristic of the elastic wave filter with a four-layered acoustic reflection layer, and the elastic wave filter with a six-layered acoustic reflection layer. It is a figure which shows S11 return loss of the elastic wave filter with the lamination | stacking number of acoustic reflection layers of 4, and the elastic wave filter with the lamination | stacking number of acoustic reflection layers of 6. It is front sectional drawing of the elastic wave apparatus which concerns on the 3rd Embodiment of this invention. (A)-(d) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave apparatus which concerns on 3rd Embodiment. (A)-(c) is front sectional drawing for demonstrating an example of the manufacturing method of the elastic wave apparatus which concerns on 3rd Embodiment. It is front sectional drawing of the elastic wave apparatus which concerns on the 4th Embodiment of this invention. It is front sectional drawing of the elastic wave apparatus which concerns on the 5th Embodiment of this invention.

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

  It should be pointed out that each embodiment described in this specification is an exemplification, and a partial replacement or combination of configurations is possible between different embodiments.

  FIG. 1 is a front sectional view of an acoustic wave device according to a 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 elastic wave filters 1A and 1B are configured in the same chip. In the present specification, being configured in the same chip means being configured in the same piezoelectric thin film.

  More specifically, the acoustic wave device 10 includes a support substrate 6. The support substrate 6 is not particularly limited, and is made of, for example, silicon. A support layer 5 is provided on the support substrate 6. A 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 a piezoelectric thin film 2 provided on the intermediate layer. Although details will be described later, in the present embodiment, the intermediate layers are 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 reflecting layers 3A to 3C. Here, the vertical direction in FIG. 1 is the vertical direction of the acoustic wave device 10. At this time, the piezoelectric thin film 2 has the 1st, 2nd recessed parts 2c and 2d provided in the lower surface side. In the present embodiment, the thickness of the piezoelectric thin film 2 above the first recess 2c is thinner 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, piezoelectric ceramics.

  The thickness of the piezoelectric thin film 2 above the first and second recesses 2c and 2d is not less than 100 nm and not more than 2000 nm. 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 as first and second excitation electrodes are provided. By applying a voltage to the first and second IDT electrodes 7A and 7B, an elastic wave is excited. The first IDT electrode 7A is an IDT electrode constituting the pass band of the first elastic wave filter 1A. The second IDT electrode 7B is an IDT electrode constituting the pass band of the second elastic wave filter 1B.

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

  Therefore, in the present embodiment, as will be described later, since the intermediate layer that reflects the plate wave is provided directly 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 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 electrically connected to the first IDT electrode 7A are provided. On the main surface 2a, wirings 8Ba and 8Bb electrically connected to the second IDT electrode 7B are also provided. The first and second IDT electrodes 7A and 7B and the wirings 8Aa, 8Ab, 8Ba, and 8Bb are provided on the same plane. In the present specification, “on the same plane” indicates substantially on the same plane to the extent that the characteristics of the acoustic wave device are not affected.

  The first and second IDT electrodes 7A and 7B are formed 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. The first and second IDT electrodes 7A and 7B may be formed of a single layer or 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 made 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, and 8Bb may be composed of a single layer or 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 in the present embodiment is 10 nm or more and 1000 nm or less. The thickness of the wiring 8Aa, 8Ab, 8Ba, 8Bb is 100 nm or more and 1000 nm or less. The thicknesses of the first and second IDT electrodes 7A and 7B and the wirings 8Aa, 8Ab, 8Ba, and 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. A plurality of third acoustic reflection layers 3C are provided. More specifically, the first acoustic reflection layer 3 </ b> A is provided in the first recess 2 c 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 recesses 2c and 2d, respectively. The first and second acoustic reflection layers 3A and 3B may reach the outside of the first and second recesses 2c and 2d, or may continue to the third acoustic reflection layer 3C. In the present embodiment, the first to third acoustic reflecting layers 3A to 3C have the same thickness. In this specification, the same thickness means that the thickness is substantially the same 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 composed of the piezoelectric thin film 2 and the first to third acoustic reflection layers 3A to 3C is the same as that of the portion where the first IDT electrode 7A is provided and the second IDT electrode 7B. It is different in the part which is done.

  As shown in FIG. 1, the first acoustic reflection layer 3A is a laminated film having low acoustic impedance layers 3A1, 3A3 and high acoustic impedance layers 3A2, 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 propagating 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 mainly composed of silicon oxide, or may be made of a dielectric material other than silicon oxide or a metal material. 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 and SiN, or piezoelectric single crystals such as LiNbO ₃ and LiTaO _{3, for} example. The materials of the low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 are not particularly limited as long as they are 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 also configured in the same manner as the first acoustic reflection layer 3A. Note that the third acoustic reflection layer 3C may not be provided.

  In the present embodiment, the thicknesses of the low acoustic impedance layers 3A1 and 3A3 and the high acoustic impedance layers 3A2 and 3A4 are 100 nm or more and 1000 nm or less. In addition, each thickness of low acoustic impedance layer 3A1, 3A3 and high acoustic impedance layer 3A2, 3A4 is not limited 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 surfaces of the support layer 5 on the first to third acoustic reflection layers 3A to 3C side have an uneven shape. The uneven shape is a shape corresponding to the uneven shape on the surfaces of the piezoelectric thin film 2 on the first to third acoustic reflecting 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 as the intermediate layer. If you try to adjust with, the filter characteristics may deteriorate. However, since the thickness difference in the piezoelectric thin film 2 is adjusted by the support layer 5 in the present embodiment, it is possible to prevent the resonator characteristics and the filter characteristics from being deteriorated.

  The support layer 5 is not particularly limited, and is made of silicon oxide or the like.

  Here, the feature of this embodiment is 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, in the same piezoelectric laminate 4, the acoustic velocity of the elastic wave propagating in the portion where the first IDT electrode 7A is provided and the acoustic wave propagating in the portion where the second IDT electrode 7B is provided. The speed of sound can be easily changed. Therefore, the first and second elastic wave filters 1A and 1B having different pass bands can be easily manufactured in the same chip. This detail is demonstrated below with the manufacturing method of the elastic wave apparatus 10 which concerns on this embodiment.

  2A to 2D are front sectional views for explaining an example of a method for manufacturing the acoustic wave device according to the first embodiment. 3A to 3C are front sectional views for explaining an example of the 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, first and second recesses 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 recesses 2Ac and 2Ad are formed so that the first recess 2Ac is deeper than the second recess 2Ad. Here, the vertical direction in FIG. 2B is the vertical direction of the mother substrate 2A. By forming the first and second recesses 2Ac and 2Ad as described above, the thickness of the mother substrate 2A above the first recess 2Ac is made larger than the thickness of the mother substrate 2A above the second recess 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 recesses 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 recess 2Ad and in portions where the first and second recesses 2Ac and 2Ad are not provided. Next, a high acoustic impedance layer is laminated on the low acoustic impedance layer. Similarly, low acoustic impedance layers and high acoustic impedance layers are alternately stacked to form first to third acoustic reflection layers 3A to 3C as intermediate 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 by sputtering or the like on the side of the first to third acoustic reflection layers 3A to 3C opposite to the mother substrate 2A side. Next, as shown in FIG. 3A, the surface of the support layer 5A opposite to the first to third acoustic reflecting layers 3A to 3C is planarized 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. A resin adhesive can be used for joining the support layer 5A and the support substrate 6A. However, the method for bonding the support layer 5A and the support substrate 6A is not particularly limited, and for example, surface activated 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 the mother substrate 2A is set to a thickness capable of efficiently exciting the elastic wave. Thinning can be performed, for example, by polishing the surface of the mother substrate 2A opposite to the first to third acoustic reflection layers 3A to 3C. Alternatively, for thinning, a smart cut method or the like in which ions are implanted into the mother substrate 2A and separated may be used. Thereby, the flat main surface 2Aa is formed on the opposite side of the mother substrate 2A from the first to third acoustic reflection layers 3A to 3C.

  Next, as shown in FIG. 3C, first and second IDT electrodes 7A and 7B and 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 and 7B and the wirings 8Aa, 8Ab, 8Ba, and 8Bb can be formed by, for example, a sputtering method or a vapor deposition method. Thereby, 1st, 2nd elastic wave filter 1A, 1B is 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, although the thickness of the mother substrate 2A is different between the first and second recesses 2Ac and 2Ad, a complicated process is not required. Thus, the 1st, 2nd elastic wave filters 1A and 1B from which a pass band differs can be manufactured easily.

  Furthermore, in this embodiment, since the number of laminated layers of the first to third acoustic reflection layers 3A to 3C is the same, the first and second acoustic wave filters 1A and 1B can be more easily manufactured. .

  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 the present embodiment, even if the thickness of the piezoelectric thin film 2 other than the first and second recesses 2c and 2d is increased, the excitation efficiency is hardly affected. In addition, for example, the third acoustic reflection layer 3C may not be formed in the portions located on the dicing lines II and II-II, and the support layer 5A may be in contact with the mother substrate 2A. As a result, the number of thin film interfaces located on the dicing lines II and II-II can be reduced, and peeling due to dicing can be made difficult to occur.

  Returning to FIG. 1, the first to third acoustic reflection layers 3 </ b> A to 3 </ b> C preferably have two or more 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 acoustic wave device 10 can be easily adjusted.

  The piezoelectric thin film 2 is provided with first and second recesses 2c and 2d. Note that the thickness of the piezoelectric thin film 2 only needs to be different in 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 cross-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 portion 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. Thereby, in the piezoelectric laminate 64, 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. 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 thicker than the thickness of the second acoustic reflection layer 63B. For example, the thickness of the first acoustic reflection layer 3A and the second acoustic reflection layer 63B may be varied by changing the number of layers. In the present embodiment, the number of stacked first acoustic reflection layers 3A is four, and the number of stacked second acoustic reflection layers 63B is two.

  In the modification shown in FIG. 4, the optimal first and second acoustic reflections in the portion of the piezoelectric thin film 2 where the first IDT electrode 7A is formed and the portion where the second IDT electrode 7B is formed. The number of layers 3A and 63B and the thickness can be set. 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 acoustic wave device according to the second embodiment.

  In the acoustic wave device 20, 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 elastic wave device 20 differs from the first embodiment in that the thickness of the first acoustic reflection layer 3A and the thickness of the second acoustic reflection layer 23B are different. Except for the above points, the acoustic wave device 20 has the same configuration as the acoustic wave device 10 of the first embodiment.

  The thickness of the second acoustic reflection layer 23B is thicker than the thickness of the first acoustic reflection layer 3A. Similar to the modification of the first embodiment shown in FIG. 4, for example, the thickness of the first acoustic reflection layer 3 </ b> A and the second acoustic reflection layer 23 </ b> B may be varied by changing the number of layers. Good. In the present embodiment, the number of stacked first acoustic reflection layers 3A is four, and the number of stacked second acoustic reflection layers 23B is six. Thus, the part in which the 1st, 2nd IDT electrodes 7A and 7B are provided in the piezoelectric laminated body 24 by making thickness of the 1st, 2nd acoustic reflection layer 3A, 23B as an intermediate | middle layer differ. You may vary the thickness of.

  Here, a plurality of acoustic wave filters having the same configuration were produced except that the number of acoustic reflection layers was varied and the thickness of the acoustic reflection layer was varied, and impedance characteristics and return loss were compared. Note that an acoustic wave filter having four acoustic reflection layers and an 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 with four acoustic reflection layers and an acoustic wave filter with six acoustic reflection layers. 6 and 7, the solid line indicates the result of the acoustic wave filter having six acoustic reflection layers, and the broken line indicates the result of the acoustic 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 varied by varying the thickness of the acoustic reflection layer. Here, the wavelength of the elastic wave to be 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 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 1λ, the specific frequency in the pass band can be shifted from 1 GHz by changing the thickness of the acoustic reflection film as described above. .

  Also in this 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.

  Furthermore, 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 acoustic wave device according to the third embodiment.

  The acoustic wave device 30 is different from the first embodiment in that the piezoelectric thin film 32 and the support layer 35 and the third acoustic reflection layer are not included. 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 includes first and second acoustic reflection layers 3A and 3B as intermediate layers and portions provided between the piezoelectric thin film 32 and the support substrate 6, and is a plan view. 1 surrounds the piezoelectric thin film 32.

  The piezoelectric thin film 32 has the first recess 32c, but does not have the second recess. Note that 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 8 </ b> Aa and 8 </ b> Bb, 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 3 </ b> B may be disposed in a portion other than the concave portion of the piezoelectric thin film 32.

  In the acoustic wave device 30, during the dicing in the manufacturing process, the piezoelectric thin film 32 is not easily cracked, and the piezoelectric thin film 32 is not easily separated from the first and second acoustic reflecting layers 3A and 3B. This will be described below together with a method for manufacturing the acoustic wave device 30.

  FIGS. 9A to 9D are front sectional views for explaining an example of the method for manufacturing the acoustic wave device according to the third embodiment. FIGS. 10A to 10C are front sectional views for explaining an example of the method for manufacturing the 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 recesses 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 recesses 32Ac and 32Ae are formed so that the thickness of the portion where the third recess 32Ae is located in the mother substrate 32A is thinner than the thickness of the portion where the first recess 32Ac is positioned. To do.

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

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

  Next, the mother substrate 32A is thinned. At this time, the surface of the mother substrate 32A opposite to the first and second acoustic reflection layers 3A and 3B is polished, and the support layer 35A is exposed as shown in FIG. 10B. Thereby, the piezoelectric thin film 32 is obtained.

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

  Also 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, the 1st, 2nd elastic wave filters 31A and 31B from which a pass band differs can be manufactured easily.

  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 positioned on the dicing lines II and II-II. Therefore, in the support layer 35A, a 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 layers in the first and second acoustic reflection layers 3A and 3B is not located. Can be diced. Therefore, the piezoelectric thin film 32 is not easily cracked, and the piezoelectric thin film 32 is peeled off from the first and second acoustic reflecting layers 3A and 3B and between the first and second acoustic reflecting layers 3A and 3B. Is unlikely to occur.

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

  The acoustic wave device 40 is different from the first embodiment in that the intermediate layer has the low sound velocity film 45 and the high sound velocity film 46, the support layer is not provided, and the piezoelectric thin film 42 does not have the second recess. Different. Except for the above points, the elastic wave device 40 has the same configuration as the elastic wave device 10 of 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 1st recessed part 42c is provided, the thickness of the part in which the 1st, 2nd IDT electrodes 7A and 7B are provided differs. In the present embodiment, the thickness of the piezoelectric laminate 44 is the same in the portions where the first and second IDT electrodes 7A and 7B are provided. In addition, the thickness of the piezoelectric laminated body 44 may differ in the part in which the 1st, 2nd IDT electrodes 7A and 7B are provided.

  The low acoustic 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 sonic film 46 is provided on the low sonic film 45. A support substrate 6 is provided on the high acoustic velocity film 46. A support layer may be provided between the high acoustic velocity film 46 and the support substrate 6. In this case, the adhesion strength between the low sound velocity film 45 and the high sound velocity film 46 as the intermediate layer and the support substrate 6 can be suitably increased.

  Here, the low acoustic velocity film 45 is a membrane in which the acoustic velocity at which the bulk wave propagates is slower than the acoustic velocity of the elastic wave that propagates through the piezoelectric thin film 42. The low sound velocity film 45 may be a material having a relatively low sound velocity, 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 acoustic velocity film 46 is a membrane in which the acoustic velocity at which the bulk wave propagates is faster than the acoustic velocity of the elastic wave that propagates through the piezoelectric thin film 42. The high sound velocity film 46 may be any material having a relatively high sound velocity, such as aluminum nitride, aluminum oxide, silicon, silicon carbide, silicon nitride, silicon oxynitride, a DLC film, or a material mainly composed of diamond. Become.

  Since the acoustic wave device 40 includes the piezoelectric laminate 44 including the piezoelectric thin film 42, the low acoustic velocity film 45, and the high acoustic velocity film 46, the energy of the acoustic wave can be effectively confined.

  Also in this 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. Furthermore, since it is not necessary to provide an acoustic reflection film composed of one or more low acoustic impedance layers and one or more high acoustic impedance layers, the first and second acoustic wave filters 41A and 41B can be easily manufactured. it can.

  FIG. 12 is a front sectional view of an acoustic wave device according to a fifth embodiment.

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

  The high sound speed substrate 56 is provided on the low sound speed film 45. The high acoustic velocity substrate 56 is a substrate in which the acoustic velocity at which the bulk wave propagates is faster than the acoustic velocity of the elastic wave that propagates through the piezoelectric thin film 42. The high sonic substrate 56 can be made of the same material as that of the high sonic film 46 in the fourth embodiment.

  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 elastic wave filters 51A and 51B having different pass bands can be easily manufactured in the same chip. Furthermore, since the piezoelectric laminate 54 is composed of the piezoelectric thin film 42 and the low acoustic velocity film 45, the number of laminated layers can be reduced. Therefore, the first and second elastic wave filters 51A and 51B can be more easily manufactured.

  In addition, in the piezoelectric laminate 54, the number of thin film interfaces can be reduced. Therefore, peeling due to dicing hardly occurs during the manufacturing process.

  In the first to fifth embodiments, an example of an elastic wave device having two elastic wave filters has been shown. However, the present invention is also applicable to an elastic wave device having three or more elastic wave filters having different pass bands. 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 shown. 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.

DESCRIPTION OF SYMBOLS 1A, 1B ... 1st, 2nd elastic wave filter 2 ... Piezoelectric thin film 2a ... Main surface 2c, 2d ... 1st, 2nd recessed part 2A ... Mother board 2Aa ... Main surface 2Ac, 2Ad ... 1st, 2nd Recess 3A ... 1st acoustic reflection layer 3A1, 3A3 ... Low acoustic impedance layer 3A2, 3A4 ... High acoustic impedance layer 3B, 3C ... 2nd, 3rd 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, 22d ... first and second recesses 23B ... second acoustic reflection layer 24 ... piezoelectric laminate 30 ... elastic wave devices 31A, 31B ... first and second elastic wave filters 32 ... piezoelectric thin film 32a ... Main surface 32c ... First recess 32A Mother substrates 32Ac, 32Ae ... first and third recesses 35, 35A ... support layer 40 ... elastic wave devices 41A, 41B ... first and second elastic wave filters 42 ... piezoelectric thin film 42c ... first recess 44 ... piezoelectric Laminated body 45 ... low acoustic velocity film 46 ... high acoustic velocity film 50 ... acoustic wave devices 51A and 51B ... first and second acoustic wave filters 54 ... piezoelectric laminated body 56 ... high acoustic velocity substrate 60 ... acoustic wave device 63B ... second Acoustic reflection layer 64 ... piezoelectric laminate

Claims (11)

A support substrate;
A piezoelectric laminate having an intermediate layer directly or indirectly provided on the support substrate, and 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
In the piezoelectric laminate, an elastic wave device in which 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.   The thickness of the part in which the said 1st excitation electrode is provided in the said piezoelectric thin film in the said piezoelectric laminated body differs from the thickness in the part in which the said 2nd excitation electrode is provided. Elastic wave device.   The thickness of the part in which the said 1st excitation electrode is provided in the said intermediate | middle layer in the said piezoelectric laminated body differs from the thickness of the part in which the said 2nd excitation electrode is provided. Elastic wave device. A support substrate;
A piezoelectric laminate having an intermediate layer directly or indirectly provided on the support substrate, and 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
In the piezoelectric laminate, the thickness of the portion where the first excitation electrode is provided and the thickness of the portion where the second excitation electrode is provided are the same thickness,
In the piezoelectric thin film and the intermediate layer, 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. The intermediate layer is provided on the surface of the piezoelectric thin film opposite to the first and second excitation electrode sides, and the sound velocity at which the bulk wave propagates is higher than the sound velocity of the elastic wave propagating through the piezoelectric thin film. Has a low-speed membrane that is also slow,
The support substrate is a high sound velocity substrate in which a sound velocity at which a bulk wave propagates is higher than a sound velocity of an elastic wave propagating through the piezoelectric thin film;
The elastic wave device according to claim 1, wherein the support substrate is provided on the low sound velocity film.   The intermediate layer is provided on the surface of the piezoelectric thin film opposite to the first and second excitation electrode sides, and the sound velocity at which the bulk wave propagates is higher than the sound velocity of the elastic wave propagating through the piezoelectric thin film. A low-velocity film having a low velocity, and a high-velocity film that is provided on the low-speed film and that has a velocity of propagation of bulk waves higher than that of elastic waves propagating through the piezoelectric thin film. The elastic wave device according to any one of claims 1 to 4.   The intermediate layer is an acoustic reflection layer having at least one low acoustic impedance layer having relatively low acoustic impedance and at least one high acoustic impedance layer having relatively high acoustic impedance. The elastic wave apparatus of any one of Claims 1-4.   The elastic 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 surrounds the piezoelectric thin film in a plan view.   The acoustic wave device according to any one of claims 1 to 10, wherein the first and second excitation electrodes are first and second IDT electrodes.

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