Elastic wave device, communication device, and method for manufacturing elastic wave device

Abstract

In the present invention, an elastic wave device having low electrical loss is realized using a simple configuration. θ1 < θ2 in a cross-section obtained by cutting a piezoelectric substrate in a plane parallel to a first direction and orthogonal to a first surface, θ1 being an angle formed by a first end surface and an extension of a line segment corresponding to the first surface, and θ2 being an angle formed by a second end surface and an extension of a line segment corresponding to a third surface.

Description

Acoustic wave device, communication device, and method for manufacturing an acoustic wave device

[0001] The present disclosure relates to an acoustic wave device, a communication device, and a method for manufacturing an acoustic wave device.

[0002] Patent Document 1 discloses an example of the configuration of an acoustic wave device.

[0003] International Publication No. 2016 / 185772

[0004] an IDT electrode disposed directly or indirectly on the first surface, the IDT electrode having a plurality of electrode fingers; a first direction being a direction perpendicular to an extension direction of any of the plurality of electrode fingers; a cross section of the piezoelectric substrate taken along a plane parallel to the first direction and orthogonal to the first surface; a first end face intersecting the first surface; a second layer having a second end face intersecting the third surface; the first end face and the second end face being located on the same side of the IDT electrode in the first direction; an angle θ1 formed between the first end face and an extension of a line segment corresponding to the first surface; and an angle θ2 formed between the second end face and an extension of a line segment corresponding to the third surface, such that θ1<θ2.

[0005] 1 is a cross-sectional view showing the configuration of an elastic wave device according to a first embodiment of the present disclosure; FIG. 2 is a cross-sectional view illustrating the principle of the Bosch process; FIG. 3 is a cross-sectional view showing the configuration of an elastic wave device according to a second embodiment of the present disclosure; FIG. 4 is a cross-sectional view showing the configuration of an elastic wave device according to a first comparative example; FIG. 5 is a cross-sectional view showing the configuration of an elastic wave device according to a second comparative example; FIG. 6 is a graph showing characteristics of the absolute value of impedance versus frequency for a simulation model of the elastic wave device according to the first comparative example and a simulation model of the elastic wave device according to the second comparative example; FIG. 7 is a graph showing characteristics of the phase of impedance versus frequency for a simulation model of the elastic wave device according to the first comparative example and a simulation model of the elastic wave device according to the second comparative example; FIG. 8 is another graph showing characteristics of the phase of impedance versus frequency for a simulation model of the elastic wave device according to the first comparative example and a simulation model of the elastic wave device according to the second comparative example; 10 is another graph showing characteristics of the phase of impedance versus frequency for a simulation model of an elastic wave device according to embodiment 2 of the present disclosure, a simulation model of an elastic wave device according to comparative example 1, and a simulation model of an elastic wave device according to comparative example 2. FIG. 11 is a graph showing characteristics of the absolute value of impedance versus frequency when θ1 is changed in the simulation model of the elastic wave device according to embodiment 2 of the present disclosure. FIG. 12 is a graph showing characteristics of the phase of impedance versus frequency when θ1 is changed in the simulation model of the elastic wave device according to embodiment 2 of the present disclosure. FIG. 13 is another graph showing characteristics of the phase of impedance versus frequency when θ1 is changed in the simulation model of the elastic wave device according to embodiment 2 of the present disclosure.10 is a graph showing characteristics of the absolute value of impedance versus frequency when θ′ is changed in a simulation model of an elastic wave device according to a comparative example. FIG. 11 is a graph showing characteristics of the phase of impedance versus frequency when θ′ is changed in a simulation model of an elastic wave device according to a comparative example. FIG. 12 is another graph showing characteristics of the phase of impedance versus frequency when θ′ is changed in a simulation model of an elastic wave device according to a comparative example. FIG. 13 is a graph showing characteristics of the maximum value of the phase of impedance versus the end face inclination angle. FIG. 14 is a graph showing characteristics of the absolute value of impedance versus frequency when scallops are present on the second end face in a simulation model of an elastic wave device according to a second embodiment of the present disclosure. FIG. 15 is a graph showing characteristics of the phase of impedance versus frequency when scallops are present on the second end face in a simulation model of an elastic wave device according to a second embodiment of the present disclosure. FIG. 16 is another graph showing characteristics of the phase of impedance versus frequency when scallops are present on the second end face in a simulation model of an elastic wave device according to a second embodiment of the present disclosure. FIG. 17 is a cross-sectional view showing the configuration of a piezoelectric substrate according to a third embodiment of the present disclosure. FIG. 18 is a cross-sectional view showing the configuration of a piezoelectric substrate according to a third embodiment of the present disclosure. FIG. 19 is a schematic diagram of a communication device according to a fourth embodiment of the present disclosure. FIG. 19 is a cross-sectional view showing the configuration of an elastic wave device according to a sixth embodiment of the present disclosure. 10A to 10C are cross-sectional views illustrating the configuration of an elastic wave device according to a seventh embodiment of the present disclosure; FIG. 10B are cross-sectional views illustrating the configuration of an elastic wave device according to an eighth embodiment of the present disclosure; FIG. 10C are cross-sectional views illustrating the configuration of an elastic wave device according to a ninth embodiment of the present disclosure;

[0006] It is desirable to realize an acoustic wave device with low electrical loss and a simple configuration.

[0007] According to one aspect of the present disclosure, an acoustic wave device with low electrical loss can be achieved with a simple configuration.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0009] 1 is a cross-sectional view illustrating a configuration of an acoustic wave device 101 according to a first embodiment of the present disclosure. The acoustic wave device 101 includes a first layer 1, a second layer 2, and a plurality of electrode fingers 3.

[0010] The first layer 1 has a first surface 4 and a second surface 5 located on the opposite side to the first surface 4. The first layer 1 includes a piezoelectric material. The first layer 1 may be a piezoelectric layer.

[0011] The second layer 2 is located on the side of the second surface 5. The second layer 2 has a third surface 6 directly or indirectly bonded to the first layer 1. The second layer 2 may be a support substrate. "Directly bonding" the first layer 1 and the third surface 6 means that the first layer 1 is bonded to the third surface 6 without any other member therebetween. "Indirectly bonding" the first layer 1 and the third surface 6 means that the first layer 1 is bonded to the third surface 6 via another member and / or another intermediate layer.

[0012] The plurality of electrode fingers 3 are located on the first surface 4 side. The plurality of electrode fingers 3 are arranged in a first direction D1. The first direction D1 is a direction perpendicular to the extension direction Da of any of the plurality of electrode fingers 3. The relationship between the first direction D1 and the extension direction Da is determined for each electrode finger 3 and is either (Pattern 1) or (Pattern 2) in FIG. 1 . The acoustic wave device 101 may include an IDT electrode 14 having a plurality of electrode fingers 3. IDT is an abbreviation for interdigital transducer. Examples of materials for the electrode fingers 3 include Al, an alloy mainly composed of Al, or a laminate of Al and another metal. The main component of a material may be defined as the atom with the largest number of atoms contained in the material.

[0013] The first layer 1 has a first end face 7. The second layer 2 has a second end face 8. When the plurality of electrode fingers 3 is viewed in a plan view, the first end face 7 and the second end face 8 are located on the same side of the plurality of electrode fingers 3 along the first direction D1.

[0014] A cross section of the piezoelectric substrate 191 cut along a plane parallel to the first direction D1 and perpendicular to the first surface 4 is also referred to as a cross section of interest. In this disclosure, unless otherwise specified, the angle formed by the first end face 7 and an extension line L1 of a line segment corresponding to the first surface 4 in the cross section of interest is defined as θ1. In this disclosure, unless otherwise specified, the angle formed by the second end face 8 and an extension line L2 of a line segment corresponding to the second surface 5 in the cross section of interest is defined as θ2. In this case, θ1<θ2. FIG. 1 can be said to be a diagram illustrating a cross section of interest. Hereinafter, when θ1 and θ2 are the same, θ may be used as a general term for θ1 and θ2.

[0015] In the present disclosure, when determining the angle θ1 between the first end face 7 and an extension line L1 of the line segment corresponding to the first surface 4, the “tangent line S1 at any point on the first end face 7” may be used as the “first end face 7.” In the present disclosure, when determining the angle θ2 between the second end face 8 and an extension line L2 of the line segment corresponding to the second surface 5, the “tangent line S2 at any point on the second end face 8” may be used as the “second end face 8.”

[0016] The acoustic wave device 101 may be construed as having the following configuration.

[0017] Acoustic wave device 101 includes piezoelectric substrate 191 having first surface 4 and second surface 5 opposite to first surface 4, and including a first layer 1 including a piezoelectric material, and second layer 2 having a third surface 6 directly or indirectly bonded to second surface 5. Acoustic wave device 101 includes IDT electrode 14 disposed directly or indirectly on first surface 4. IDT electrode 14 includes a plurality of electrode fingers 3.

[0018] A first direction D1 is a direction perpendicular to the extension direction of any of the plurality of electrode fingers 3. In this case, a cross section of the piezoelectric substrate 191 cut along a plane parallel to the first direction D1 and perpendicular to the first surface 4 has the following configuration.

[0019] The first layer 1 has a first end face 7 that intersects with the first surface 4. The second layer 2 has a second end face 8 that intersects with the third surface 6. The first end face 7 and the second end face 8 are located on the same side of the IDT electrode 14 in the first direction D1. In this case, θ1<θ2.

[0020] "The first member and the second member being indirectly joined" may mean that the first member and the second member are joined with a third member sandwiched therebetween. "The first member and the second member being indirectly arranged" may mean that the first member and the second member are arranged with a third member sandwiched therebetween.

[0021] Acoustic wave device 101 utilizes the function of reflecting acoustic waves at first end surface 7 and second end surface 8. To reduce electrical loss in acoustic wave device 101, it is necessary to make θ as close to 90° as possible. However, in reality, it is not easy to make θ as close to 90°. When attempting to make θ 90°, θ actually becomes significantly smaller than 90°, which increases electrical loss in acoustic wave device 101.

[0022] It is easier to make θ2 approach 90° in the second layer 2 than it is to make θ1 approach 90° in the first layer 1 including a piezoelectric material. For example, when the first layer 1 is made of lithium tantalate (LiTaO ３ ) or lithium niobate (LiNbO ３ ), it is difficult to bring θ1 close to 90°. For example, if second layer 2 contains a material that is relatively easy to etch, such as Si or sapphire, it is easier to bring θ2 close to 90° than to bring θ1 close to 90°. Therefore, if θ2 is made as close to 90° as possible while allowing θ1 to be an angle smaller than θ2, the difficulty of fabricating elastic wave device 101 can be reduced, and elastic wave device 101 can be realized with a simple configuration. Therefore, elastic wave device 101 with low electrical loss can be realized with a simple configuration.

[0023] Alternatively, θ2 may be 85°≦θ2≦90°. This allows elastic wave device 101 to have low electrical loss. θ1 may be 70°≦θ1<90°. This prevents excessive electrical loss in elastic wave device 101 when elastic wave device 101 is realized with a simple configuration.

[0024] The average interval at which the plurality of electrode fingers 3 are arranged is p. In the target cross section, the height Ha from an end 10 of the second end face 8 opposite to the end located on the third surface 6 side to an end 9 of the first end face 7 on the first surface 4 side may be 2p or more. One of the intervals at which the plurality of electrode fingers 3 are arranged may be the center-to-center distance X between two adjacent electrode fingers 3.

[0025] The average spacing between the electrode fingers 3 is p. The height H1 of the first end face 7 in the cross section of interest may be 2p or less. This allows the height H2 of the second end face 8 in the cross section of interest to account for a large proportion of the height Ha, thereby achieving acoustic wave device 101 with low electrical loss.

[0026] The etching rate of the second layer 2 in dry etching may be higher than the etching rate of the first layer 1. In other words, manufacturing of the acoustic wave device 101 includes a first step of preparing a piezoelectric substrate 191 including a first layer 1 that includes a piezoelectric body and has a first surface 4, and a second layer 2 that is disposed below the first layer 1; a second step of providing an IDT electrode 14 having a plurality of electrode fingers 3 directly or indirectly on the first surface 4; and a third step of etching the piezoelectric substrate 191 to form a first end face 7 located on the first layer 1 and a second end face 8 located on the second layer 2, the first end face 7 being located on the outer side of the IDT electrode 14 in the first direction, where the first direction is defined as a direction perpendicular to the extension direction of any of the plurality of electrode fingers 3 in a plan view. In this third step, the etching rate of the second layer 2 may be higher than that of the first layer 1. This makes it easier to satisfy the condition θ1<θ2.

[0027] The second layer 2 may contain Si, which makes it easy to form the second layer 2 in which θ2 is 90° or close to 90° by etching the material of the second layer 2.

[0028] The second end surface 8 may have scallops. The second end surface 8 may not have scallops. Scallops are grooves found on surfaces formed by the Bosch process. In other words, the second end surface 8 may be formed by the Bosch process, or may be formed by a process other than the Bosch process. If the second end surface 8 is formed by the Bosch process, the scallops on the second end surface 8 may or may not have been subjected to a flattening process.

[0029] Fig. 2 is a cross-sectional view showing the principle of the Bosch process. The element designated by reference numeral 51 in Fig. 2 is a photoresist. The element designated by reference numeral 52 in Fig. 2 is a fluorine radical. The element designated by reference numeral 53 in Fig. 2 is a protective film. The element designated by reference numeral 54 in Fig. 2 is a fluorocarbon radical. The element designated by reference numeral 55 in Fig. 2 is a fluorine ion.

[0030] By applying the Bosch process, it is easy to set θ2 to approximately 90° at the second end face 8 of the Si-containing second layer 2. On the other hand, when the Bosch process is applied to form the second end face 8, the second end face 8 will have scallops unless a planarization process is performed on the second end face 8.

[0031] The first layer 1 may contain at least one of lithium tantalate and lithium niobate. Lithium tantalate is LiTaO ３ Lithium niobate is LiNbO ３ It can also be said that...

[0032] When the first end face 7 and the second end face 8 are formed by etching, the various conditions for forming the first end face 7 and the various conditions for forming the second end face 8 may be the same as or different from each other.

[0033] In a plan view, the first end face 7 may be located inside the outer edge of the first layer 1, and the second end face 8 may be located inside the outer edge of the second layer 2. In this case, the first end face 7 and the second end face 8 are less likely to come into contact with the outside, reducing the possibility of damage to the surfaces of the first end face 7 and the second end face 8. As a result, the first end face 7 and the second end face 8 can stably reflect acoustic waves.

[0034] In a plan view, the first end face 7 and the second end face 8 may be parallel to the extension direction of any of the plurality of electrode fingers 3. In this disclosure, unless otherwise specified, the term "parallel" may allow for a degree of error that does not significantly affect the characteristics of the acoustic wave device 101.

[0035] First end facet 7 and second end facet 8 may inwardly reflect the main vibration of the acoustic wave excited by IDT electrode 14. Here, the "main vibration" refers to an acoustic wave in a frequency band utilized by acoustic wave device 101. For example, it refers to an acoustic wave in the pass band of an acoustic wave filter.

[0036] Second Embodiment FIG. 3 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to a second embodiment of the present disclosure. The elastic wave device 101 may include a third layer 11. The third layer 11 is located between the first layer 1 and the second layer 2. The third layer 11 has a fourth surface 12 located on the first layer 1 side. The third layer 11 also has a third end surface 13. The first end surface 7, the second end surface 8, and the third end surface 13 are located on the same side of the electrode fingers 3 along the first direction D1 when the electrode fingers 3 are viewed in a plan view. In this disclosure, unless otherwise specified, the angle θ3 is defined as the angle formed by the third end surface 13 and an extension line L3 of a line segment corresponding to the fourth surface 12 in the cross section of interest. In this case, θ1 < θ3 ≦ θ2 may be satisfied. FIG. 3 can be considered to be a diagram illustrating the cross section of interest.

[0037] In the present disclosure, when determining the angle θ3 between the third end face 13 and the extension line L3 of the line segment corresponding to the fourth face 12, the “tangent at any point on the third end face 13” may be used as the “third end face 13.”

[0038] An example of the third layer 11 is a layer provided for the purpose of compensating for the temperature dependency of at least one of the first layer 1 and the second layer 2, and a layer having a predetermined acoustic impedance. ２ may include:

[0039] A simulation was performed to verify the effects of elastic wave device 101 according to embodiment 2 of the present disclosure. In performing the simulation, a simulation model of elastic wave device 101 according to embodiment 2 of the present disclosure, a simulation model of elastic wave device 102 according to comparative example 1, and a simulation model of elastic wave device 102 according to comparative example 2 were prepared.

[0040] In the description of the simulations, the terms "Example," "Comparative Example 1," and "Comparative Example 2" are used. Example refers to a simulation model of elastic wave device 101 according to embodiment 2 of the present disclosure. Comparative Example 1 refers to a simulation model of elastic wave device 102 according to Comparative Example 1. Comparative Example 2 refers to a simulation model of elastic wave device 102 according to Comparative Example 2.

[0041] Fig. 4 is a cross-sectional view showing the configuration of elastic wave device 102 in accordance with Comparative Example 1. Fig. 5 is a cross-sectional view showing the configuration of elastic wave device 102 in accordance with Comparative Example 2. Figs. 4 and 5 each illustrate a cross section of interest. Hereinafter, when θ1, θ2, and θ3 are the same, θ' may be used as a general term for θ1, θ2, and θ3.

[0042] In Comparative Example 1, θ' is 90°. In Comparative Example 2, θ' is 70°. Unless otherwise specified, in the examples, θ1 is 70°, θ2 is 90°, and θ3 is 90°.

[0043] The configuration other than θ1, θ2, and θ3 is common to the example, comparative example 1, and comparative example 2. The material of the first layer 1 is lithium tantalate (LiTaO ３ The second layer 2 is made of Si and has a height H2 of 1.3 μm. The third layer 11 is made of SiO ２and the height H3 of the third end face 13 is 0.2 μm. The height Ha is 2 μm. The average value p of the interval at which the multiple electrode fingers 3 are arranged is 1 μm. The width of each of the multiple electrode fingers 3 in the first direction D1 is 0.5 μm, except for the electrode finger 3 at the end of the multiple electrode fingers 3 in the first direction D1. In other words, the duty of the IDT electrode 14 having multiple electrode fingers 3 is 0.5. The number of electrode fingers 3 is 150. The width in the first direction D1 of the electrode finger 3 at the end of the multiple electrode fingers 3 in the first direction D1 is 0.25 μm.

[0044] FIG. 6 is a graph showing the absolute value of impedance versus frequency characteristics for Comparative Example 1 and Comparative Example 2. FIG. 7 is a graph showing the phase of impedance versus frequency characteristics for Comparative Example 1 and Comparative Example 2. FIG. 8 is another graph showing the phase of impedance versus frequency characteristics for Comparative Example 1 and Comparative Example 2. Elastic wave device 101 according to the second embodiment of the present disclosure, elastic wave device 102 according to Comparative Example 1, and elastic wave device 102 according to Comparative Example 2 each utilize the function of reflecting elastic waves at first end surface 7, second end surface 8, and third end surface 13. For reference, FIGS. 6 to 8 also show the characteristics of an elastic wave device that does not utilize this function but instead has 20 reflectors.

[0045] Comparative Example 1 has the smallest electrical loss among the example, comparative example 1, and comparative example 2, because θ' is 90°. However, it is practically difficult to actually fabricate elastic wave device 102 according to comparative example 1. Comparative Example 2 has the largest electrical loss among the example, comparative example 1, and comparative example 2, because θ' is 70°.

[0046] Fig. 9 is a graph showing the characteristics of the absolute value of impedance versus frequency for Example, Comparative Example 1, and Comparative Example 2. Fig. 10 is a graph showing the characteristics of the phase of impedance versus frequency for Example, Comparative Example 1, and Comparative Example 2. Fig. 11 is another graph showing the characteristics of the phase of impedance versus frequency for Example, Comparative Example 1, and Comparative Example 2.

[0047] In the example, θ1 is 70°, θ2 is 90°, and θ3 is 90°, so the electrical loss is smaller than that of the comparative example 2 and larger than that of the comparative example 1.

[0048] Fig. 12 is a graph showing the characteristics of the absolute value of impedance versus frequency when θ1 is changed in the example. Fig. 13 is a graph showing the characteristics of the phase of impedance versus frequency when θ1 is changed in the example. Fig. 14 is another graph showing the characteristics of the phase of impedance versus frequency when θ1 is changed in the example.

[0049] The term "comparative example" may be used as a general term for comparative example 1 and comparative example 2. Fig. 15 is a graph showing the characteristics of the absolute value of impedance versus frequency when θ' is changed in the comparative example. Fig. 16 is a graph showing the characteristics of the phase of impedance versus frequency when θ' is changed in the comparative example. Fig. 17 is another graph showing the characteristics of the phase of impedance versus frequency when θ' is changed in the comparative example.

[0050] Fig. 18 is a graph showing the characteristics of the maximum impedance phase versus the end face inclination angle. The end face inclination angle corresponds to θ1 in the example and θ' in the comparative example. For reference, Figs. 12 to 18 also show the characteristics of an elastic wave device in which the elastic wave reflection function at first end face 7, second end face 8, and third end face 13 is not utilized, but 20 reflectors are provided.

[0051] The smaller the end face inclination angle, the smaller the maximum value of the impedance phase. It can be seen that in the example, the amount of decrease in the maximum value of the impedance phase with respect to the amount of decrease in the end face inclination angle is smaller than in the comparative example.

[0052] Fig. 19 is a graph showing the characteristics of the absolute value of impedance versus frequency depending on whether or not scallops are present on the second end face 8 in an example. Fig. 20 is a graph showing the characteristics of the phase of impedance versus frequency depending on whether or not scallops are present on the second end face 8 in an example. Fig. 21 is another graph showing the characteristics of the phase of impedance versus frequency depending on whether or not scallops are present on the second end face 8 in an example.

[0053] In the example, the impedance characteristics versus frequency are slightly better when the second end face 8 does not have scallops than when the second end face 8 has scallops, but they are not worse when the second end face 8 has scallops. The difference in the impedance characteristics versus frequency between the presence and absence of scallops on the second end face 8 is small.

[0054] 22 and 23 are cross-sectional views showing a configuration of a piezoelectric substrate 191 according to a third embodiment of the present disclosure. The piezoelectric substrate 191 shown in Fig. 22 can be considered to be elastic wave device 101 according to the first embodiment of the present disclosure, with some electrode fingers 3 removed. The piezoelectric substrate 191 shown in Fig. 23 can be considered to be elastic wave device 101 according to the second embodiment of the present disclosure, with some electrode fingers 3 removed.

[0055] 22 and 23, piezoelectric substrate 191 can be interpreted as acoustic wave device 101 without a plurality of electrode fingers 3. That is, piezoelectric substrate 191 has the following configuration.

[0056] The piezoelectric substrate 191 has a first layer 1 including a piezoelectric material and having a first surface 4 and a second surface 5 located opposite the first surface 4, and a second layer 2 located on the second surface 5 side and having a third surface 6 directly or indirectly bonded to the first layer 1. The first layer 1 has a first end surface 7. The second layer 2 has a second end surface 8. When the piezoelectric substrate 191 is viewed in plan, the first end surface 7 and the second end surface 8 are located on the same side of the piezoelectric substrate 191 along a first direction D1 that is parallel to the first surface 4. A cross section of the piezoelectric substrate 191 cut along a plane parallel to the first direction D1 and perpendicular to the first surface 4 is also referred to as a cross section of interest. In the cross section of interest, the angle formed by an extension line L1 of the line segment corresponding to the first surface 4 and a tangent line S1 at an arbitrary point on the first end surface 7 is defined as θ1, and the angle formed by an extension line L2 of the line segment corresponding to the third surface 6 and a tangent line S2 at an arbitrary point on the second end surface 8 is defined as θ2. In this case, θ1<θ2. Each of FIGS. 22 and 23 can be said to be a diagram illustrating the cross section of interest.

[0057] 24 is a schematic diagram of a communication device 201 according to a fourth embodiment of the present disclosure. The communication device 201 is an application example of the acoustic wave device 101 or the piezoelectric substrate 191, and performs wireless communication using radio waves. The communication device 201 may include a transmit filter 111 and a receive filter 112. Each of the transmit filter 111 and the receive filter 112 may include the acoustic wave device 101 or the piezoelectric substrate 191.

[0058] In the communication device 201, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised by an RF-IC 113 and converted into a transmission signal TS. RF-IC is an abbreviation for radio frequency-integrated circuit. In other words, frequency-raising is conversion into a high-frequency signal having a carrier frequency. A band-pass filter 114 may remove unnecessary components from the transmission signal TS outside the transmission passband. Next, the transmission signal TS after removing the unnecessary components may be amplified by an amplifier 115 and input to the transmission filter 111.

[0059] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via the antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio signals to the outside of the communication device 201.

[0060] The antenna 116 may convert a received external radio wave into a received signal RS, which is an electrical signal, and input the received signal RS to the receive filter 112 via the antenna terminal. The receive filter 112 may remove unnecessary components outside the receive passband from the input received signal RS. The receive filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receive passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0061] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals containing appropriate information. The low-frequency signals may be baseband signals. For example, the transmit information signal TIS and the receive information signal RIS may be analog audio signals or digitized audio signals. The passband of the radio signals may be set appropriately and may comply with various known standards.

[0062] Fifth Embodiment FIG. 25 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to a fifth embodiment of the present disclosure.

[0063] Piezoelectric substrate 191 has first groove 15, and first end face 7 and second end face 8 may be part of the side surface of first groove 15. When first end face 7 is part or all of the side surface of first groove 15, acoustic waves excited in an area other than IDT electrode 14 closest to the outer edge of piezoelectric substrate 191 can also be reflected by first end face 7. As a result, the size of the grating reflector can be reduced, and acoustic wave device 101 can be made more compact.

[0064] Sixth Embodiment FIG. 26 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to a sixth embodiment of the present disclosure.

[0065] The acoustic wave device 101 may further include a floating electrode 16 disposed directly or indirectly on the first surface 4. The floating electrode 16 may not be electrically connected to the IDT electrode 14 and may be located between the first end surface 7 and the IDT electrode 14 in the first direction D1 in a plan view.

[0066] In the first direction D1, the width W16 of the floating electrode 16 may be larger than the average value of the widths of the plurality of electrode fingers 3.

[0067] Seventh Embodiment FIG. 27 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to a seventh embodiment of the present disclosure.

[0068] When the electrode finger 3 among the multiple electrode fingers 3 that is closest to the first end face 7 in the first direction D1 is defined as the first electrode finger 17, the width W17 of the first electrode finger 17 in the first direction D1 may be larger than the average width of the other electrode fingers 3.

[0069] Eighth Embodiment FIG. 28 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to an eighth embodiment of the present disclosure.

[0070] Acoustic wave device 101 may include a third layer 11 located between first layer 1 and second layer 2 and having a fourth surface 12 directly or indirectly bonded to second surface 5. In the cross section of interest, third layer 11 may have a third end surface 13 intersecting with fourth surface 12, and first end surface 7, second end surface 8, and third end surface 13 may be located on the same side of first direction D1 with respect to IDT electrode 14. In the cross section of interest, θ1<θ3≦θ2 may be satisfied.

[0071] 29 is a cross-sectional view showing a configuration of an elastic wave device 101 according to a ninth embodiment of the present disclosure. The elastic wave device 101 may be construed as having the following configuration.

[0072] The acoustic wave device 101 includes a piezoelectric substrate 191 including: a first layer 1 having a first surface 4 and a second surface 5 located opposite the first surface 4 and including a piezoelectric material; a second layer 2 having a third surface 6 directly or indirectly bonded to the second surface 5; and a third layer 11 located between the first layer 1 and the second layer 2 and having a fourth surface 12 directly or indirectly bonded to the second surface 5. The acoustic wave device 101 includes an IDT electrode 14 disposed directly or indirectly on the first surface 4. The IDT electrode 14 includes a plurality of electrode fingers 3.

[0073] A first direction D1 is a direction perpendicular to the extension direction of any of the plurality of electrode fingers 3. In this case, a cross section of the piezoelectric substrate 191 cut along a plane parallel to the first direction D1 and perpendicular to the first surface 4 has the following configuration.

[0074] The first layer 1 has a first end face 7 that intersects with the first surface 4. The third layer 11 has a third end face 13 that intersects with the third surface 6. The first end face 7 and the third end face 13 are located on the same side of the IDT electrode 14 in the first direction D1. In this case, θ1<θ3.

[0075] It is easier to make θ3 approach 90° in the third layer 11 than it is to make θ1 approach 90° in the first layer 1 including a piezoelectric material. For example, when the first layer 1 is made of lithium tantalate (LiTaO ３ ) or lithium niobate (LiNbO ３ For example, when the third layer 11 contains a material that is difficult to etch, such as SiO ２When the material includes a material that is relatively easy to etch, such as silicon nitride or SiN, it is easier to bring θ3 closer to 90° than to bring θ1 closer to 90°. Therefore, by making θ3 as close to 90° as possible while allowing θ1 to be an angle smaller than θ3, the difficulty of fabricating elastic wave device 101 can be reduced, and elastic wave device 101 can be realized with a simple configuration. Therefore, elastic wave device 101 with low electrical loss can be realized with a simple configuration.

[0076] The piezoelectric substrate 191 may have a second groove portion 18 , and the first end surface 7 and the third end surface 13 may be part of the side surface of the second groove portion 18 .

[0077] The etching rate of the third layer 11 in dry etching may be higher than the etching rate of the first layer 1. In other words, manufacturing of the acoustic wave device 101 includes a first step of preparing a piezoelectric substrate 191 including a first layer 1 that includes a piezoelectric body and has a first surface 4, and a third layer 11 disposed below the first layer 1; a second step of providing an IDT electrode 14 having a plurality of electrode fingers 3 directly or indirectly on the first surface 4; and a third step of etching the piezoelectric substrate 191 to form a first end face 7 located on the first layer 1 and a third end face 13 located on the third layer 8, the first end face 7 being located on the outer side of the IDT electrode 14 in the first direction, where the first direction is defined as a direction perpendicular to the extension direction of any of the plurality of electrode fingers 3 in a plan view. In this third step, the etching rate of the third layer 13 may be higher than that of the first layer 1. This makes it easier to satisfy the condition θ1<θ3.

[0078] [Summary] An elastic wave device according to a first aspect of the present disclosure includes a piezoelectric substrate having a first surface and a second surface opposite to the first surface, the piezoelectric substrate including a first layer including a piezoelectric body and a second layer having a third surface directly or indirectly bonded to the second surface; and an IDT electrode directly or indirectly disposed on the first surface, the IDT electrode having a plurality of electrode fingers, wherein when a first direction is a direction perpendicular to an extension direction of any of the plurality of electrode fingers, in a cross section of the piezoelectric substrate taken along a plane parallel to the first direction and orthogonal to the first surface, the first layer has a first end surface that intersects with the first surface, the second layer has a second end surface that intersects with the third surface, the first end surface and the second end surface are located on the same side of the IDT electrode in the first direction, and when θ1 is an angle formed by the first end surface and an extension line of a line segment corresponding to the first surface, and θ2 is an angle formed by the second end surface and an extension line of a line segment corresponding to the third surface, θ1<θ2.

[0079] An elastic wave device according to a second aspect of the present disclosure is the same as the first aspect, wherein, in a planar view, the first end face is located inside the outer edge of the first layer and the second end face is located inside the outer edge of the second layer.

[0080] According to a third aspect of the present disclosure, in the elastic wave device of the first or second aspect, the piezoelectric substrate has a first groove, and the first end surface and the second end surface are part of the side surfaces of the first groove.

[0081] An elastic wave device according to a fourth aspect of the present disclosure is any one of the first to third aspects, wherein, in a plan view, the first end surface and the second end surface are parallel to a direction in which any one of the plurality of electrode fingers extends.

[0082] An elastic wave device according to aspect 5 of the present disclosure, in any one of aspects 1 to 4, further includes a floating electrode arranged directly or indirectly on the first surface, the floating electrode being not electrically connected to the IDT electrode and being located between the first end surface and the IDT electrode in the first direction in a planar view.

[0083] According to a sixth aspect of the present disclosure, in the elastic wave device of the fifth aspect, the width of the floating electrode is greater than the average width of the plurality of electrode fingers in the first direction.

[0084] An elastic wave device according to aspect 7 of the present disclosure is, in any one of aspects 1 to 6, such that when the electrode finger closest to the first end face in the first direction among the plurality of electrode fingers is defined as the first electrode finger, the width of the first electrode finger in the first direction is larger than the average width of the other electrode fingers.

[0085] An elastic wave device according to an eighth aspect of the present disclosure is based on any one of the first to seventh aspects, wherein the first end surface and the second end surface inwardly reflect a main vibration of an elastic wave excited by an IDT electrode.

[0086] An elastic wave device according to a ninth aspect of the present disclosure is the elastic wave device according to any one of the first to eighth aspects, wherein 85°≦θ2≦90°.

[0087] An elastic wave device according to a tenth aspect of the present disclosure is the elastic wave device of any one of the first to ninth aspects, wherein 70°≦θ1<90°.

[0088] An elastic wave device according to aspect 11 of the present disclosure is any one of aspects 1 to 10, in which the average spacing at which the plurality of electrode fingers are arranged is p, and the height in the cross section from the end opposite the end on the second end face that is located on the third surface side to the end on the first end face that is on the first surface side is 2p or more.

[0089] An elastic wave device according to aspect 12 of the present disclosure is any one of aspects 1 to 11, wherein the average spacing between the plurality of electrode fingers is p, and the height of the first end face in the cross section is 2p or less.

[0090] According to a thirteenth aspect of the present disclosure, in the elastic wave device of any one of the first to twelfth aspects, the second layer contains Si.

[0091] According to a fourteenth aspect of the present disclosure, in the elastic wave device of any one of the first to thirteenth aspects, the second end surface has a scallop.

[0092] An elastic wave device according to a fifteenth aspect of the present disclosure is the elastic wave device of any one of the first to thirteenth aspects, wherein the second end surface does not have a scallop.

[0093] A sixteenth aspect of the present disclosure provides an elastic wave device in any one of the first to fifteenth aspects, wherein the first layer includes at least one of lithium tantalate and lithium niobate.

[0094] An elastic wave device according to aspect 17 of the present disclosure is, in any one of aspects 1 to 16, a third layer located between the first layer and the second layer and having a fourth surface directly or indirectly joined to the second surface, wherein in the cross section, the third layer has a third end surface that intersects with the fourth surface, the first end surface, the second end surface, and the third end surface are located on the same side of the IDT electrode in a first direction, and when θ3 is an angle formed by an extension of a line segment corresponding to the third end surface and the fourth surface in the cross section, θ1<θ3≦θ2.

[0095] An elastic wave device according to Aspect 18 of the present disclosure is the elastic wave device according to Aspect 17, wherein the third layer is made of SiO ２ Includes:

[0096] An elastic wave device according to a nineteenth aspect of the present disclosure includes a piezoelectric substrate including: a first layer having a first surface and a second surface located opposite the first surface and including a piezoelectric body; a second layer having a third surface directly or indirectly bonded to the second surface; and a third layer located between the first layer and the second layer and having a fourth surface directly or indirectly bonded to the second surface; and an IDT electrode directly or indirectly disposed on the first surface, wherein the IDT electrode has a plurality of electrode fingers and extends perpendicular to a direction in which any of the plurality of electrode fingers extends. When a first direction is a direction parallel to the first direction and perpendicular to the first surface, in a cross section of the piezoelectric substrate cut along a plane parallel to the first direction and perpendicular to the first surface, the first layer has a first end surface that intersects with the first surface, the third layer has a third end surface that intersects with the third surface, the first end surface and the third end surface are located on the same side of the IDT electrode in the first direction, and when an angle formed by an extension of a line segment corresponding to the first end surface and the first surface is defined as θ1 and an angle formed by an extension of a line segment corresponding to the third end surface and the fourth surface is defined as θ3, θ1<θ3.

[0097] According to a twentieth aspect of the present disclosure, in the elastic wave device of the nineteenth aspect, the piezoelectric substrate has a second groove portion, and the first end surface and the third end surface are part of the side surface of the second groove portion.

[0098] An elastic wave device according to aspect 21 of the present disclosure is, in any one of aspects 1 to 20, further comprising a grating reflector arranged directly or indirectly on the first surface, the grating reflector being positioned between the IDT electrode and the first end surface in the first direction in a planar view.

[0099] A communication device according to a twenty-second aspect of the present disclosure includes the acoustic wave device according to any one of the first to twenty-first aspects.

[0100] A method for manufacturing an elastic wave device according to aspect 23 of the present disclosure includes a first step of preparing a piezoelectric substrate including a first layer including a piezoelectric material and having a first surface, and a second layer disposed below the first layer; a second step of providing, directly or indirectly, an IDT electrode having a plurality of electrode fingers on the first surface; and a third step of etching the piezoelectric substrate, when a direction perpendicular to the extension direction of any of the plurality of electrode fingers is defined as a first direction, to form a first end face on the first layer that is positioned outside the IDT electrode in the first direction, and to form a second end face on the second layer that is positioned outside the IDT electrode in the first direction, wherein the etching rate for the second layer in the third step is higher than that for the first layer.

[0101] A method for manufacturing an elastic wave device according to aspect 24 of the present disclosure includes a first step of preparing a piezoelectric substrate including a first layer including a piezoelectric material and having a first surface, and a third layer disposed below the first layer; a second step of providing, directly or indirectly, an IDT electrode having a plurality of electrode fingers on the first surface; and a third step of etching the piezoelectric substrate, when a direction perpendicular to the extension direction of any of the plurality of electrode fingers is defined as a first direction, to form a first end face on the first layer that is positioned outside the IDT electrode in the first direction, and to form a third end face on the third layer that is positioned outside the IDT electrode in the first direction, wherein the etching rate for the third layer in the third step is higher than that for the first layer.

[0102] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0103] REFERENCE SIGNS LIST 1 First layer 2 Second layer 3 Electrode finger 4 First surface 5 Second surface 6 Third surface 7 First end surface 8 Second end surface 9 End portion on the first surface side of the first end surface 10 End portion on the second end surface opposite to the end portion located on the third surface side 11 Third layer 12 Fourth surface 13 Third end surface 14 IDT electrode 15 First groove 16 Floating electrode 17 First electrode finger 18 Second groove 101 Acoustic wave device 191 Piezoelectric substrate 201 Communication device D1 First direction Da Extension direction of any of the plurality of electrode fingers H1 Height of first end surface H2 Height of second end surface H3 Height of third end surface Ha Height from the end portion of the second end surface opposite to the third surface to the end portion of the first end surface on the first surface side L1 Extension line of the line segment corresponding to the first end surface and the first surface L2 L2: Extension of the line segment corresponding to the second end face and the second surface L3: Extension of the line segment corresponding to the third end face and the fourth surface S1: Tangent at an arbitrary point on the first end face S2: Tangent at an arbitrary point on the second end face S3: Tangent at an arbitrary point on the third end face W16: Width of the floating electrode W17: Width of the first electrode finger θ1: Angle formed by the extension of the line segment corresponding to the first end face and the first surface θ2: Angle formed by the extension of the line segment corresponding to the second end face and the second surface θ3: Angle formed by the extension of the line segment corresponding to the third end face and the fourth surface

Claims

1. An elastic wave device comprising: a piezoelectric substrate having a first surface and a second surface opposite to the first surface, the piezoelectric substrate including a first layer including a piezoelectric material, and a second layer having a third surface directly or indirectly bonded to the second surface; and an IDT electrode directly or indirectly disposed on the first surface, wherein the IDT electrode has a plurality of electrode fingers, and when a first direction is a direction perpendicular to the extension direction of any of the plurality of electrode fingers, in a cross section of the piezoelectric substrate taken along a plane parallel to the first direction and orthogonal to the first surface, the first layer has a first end face that intersects with the first surface, and the second layer has a second end face that intersects with the third surface, the first end face and the second end face are located on the same side of the IDT electrode in the first direction, and when θ1 is an angle formed by the first end face and an extension of a line segment corresponding to the first surface, and θ2 is an angle formed by the second end face and an extension of a line segment corresponding to the third surface, θ1 < θ2.

2. The acoustic wave device according to claim 1, wherein, in a plan view, the first end face is located inside the outer edge of the first layer, and the second end face is located inside the outer edge of the second layer.

3. The acoustic wave device according to claim 1 or 2, wherein the piezoelectric substrate has a first groove portion, and the first end face and the second end face are part of the side surface of the first groove portion.

4. The acoustic wave device according to claim 1, wherein, in a plan view, the first end face and the second end face are parallel to a direction in which one of the plurality of electrode fingers extends.

5. An elastic wave device according to any one of claims 1 to 4, further comprising a floating electrode arranged directly or indirectly on the first surface, the floating electrode not being electrically connected to the IDT electrode and positioned between the first end surface and the IDT electrode in the first direction in a planar view.

6. The acoustic wave device according to claim 5, wherein the width of the floating electrode in the first direction is greater than the average width of the plurality of electrode fingers.

7. An elastic wave device according to any one of claims 1 to 6, wherein, when the electrode finger closest to the first end face in the first direction among the plurality of electrode fingers is defined as a first electrode finger, the width of the first electrode finger in the first direction is larger than the average width of the other electrode fingers.

8. The acoustic wave device according to claim 1, wherein the first end face and the second end face reflect inward the main vibration of the acoustic wave excited by the IDT electrode.

9. The elastic wave device according to any one of claims 1 to 8, wherein 85°≦θ2≦90°.

10. The elastic wave device according to any one of claims 1 to 9, wherein 70°≦θ1<90°.

11. An elastic wave device according to any one of claims 1 to 10, wherein the average spacing at which the plurality of electrode fingers are arranged is p, and the height in the cross section from the end of the second end face opposite the end facing the third surface to the end of the first end face facing the first surface is 2p or more.

12. The elastic wave device according to claim 1, wherein the average spacing between the electrode fingers is p, and the height of the first end face in the cross section is 2p or less.

13. The acoustic wave device according to claim 1, wherein the second layer contains Si.

14. The acoustic wave device according to claim 1, wherein the second end surface has a scallop.

15. The acoustic wave device according to claim 1, wherein the second end surface does not have a scallop.

16. The acoustic wave device according to claim 1, wherein the first layer includes at least one of lithium tantalate and lithium niobate.

17. The elastic wave device according to any one of claims 1 to 16, further comprising a third layer located between the first layer and the second layer and having a fourth surface directly or indirectly bonded to the second surface, wherein in the cross section, the third layer has a third end surface that intersects with the fourth surface, the first end surface, the second end surface, and the third end surface are located on the same side of the IDT electrode in a first direction, and when θ3 is an angle formed by an extension of a line segment corresponding to the third end surface and the fourth surface in the cross section, θ1 < θ3 ≦ θ2.

18. The third layer is SiO ２ The acoustic wave device according to claim 17 , comprising:

19. A piezoelectric substrate including: a first layer having a first surface and a second surface located opposite to the first surface and including a piezoelectric body; a second layer having a third surface bonded directly or indirectly to the second surface; and a third layer located between the first and second layers and having a fourth surface bonded directly or indirectly to the second surface; and an IDT electrode directly or indirectly disposed on the first surface, wherein the IDT electrode has a plurality of electrode fingers, and when a first direction is a direction perpendicular to the extension direction of any of the plurality of electrode fingers, in a cross section of the piezoelectric substrate cut along a plane parallel to the first direction and orthogonal to the first surface, the first layer has a first end face intersecting with the first surface, and the third layer has a third end face intersecting with the third surface, and the first end face and the third end face are located on the same side of the IDT electrode in the first direction, an angle formed by the first end face and an extension of a line segment corresponding to the first surface is θ1, and an angle formed by the third end face and an extension of a line segment corresponding to the fourth surface is θ3, where θ1 is less than θ3.

20. The acoustic wave device according to claim 19, wherein the piezoelectric substrate has a second groove portion, and the first end face and the third end face are part of a side surface of the second groove portion.

21. The elastic wave device according to any one of claims 1 to 20, further comprising a grating reflector disposed directly or indirectly on the first surface, the grating reflector being located between the IDT electrode and the first end surface in the first direction in a planar view.

22. A communication device comprising the acoustic wave device according to any one of claims 1 to 21.

23. A method for manufacturing an elastic wave device, comprising: a first step of preparing a piezoelectric substrate including a first layer including a piezoelectric material and having a first surface, and a second layer disposed below the first layer; a second step of providing, directly or indirectly, an IDT electrode having a plurality of electrode fingers on the first surface; and a third step of etching the piezoelectric substrate to form, on the first layer, a first end face positioned on the outside of the IDT electrode in the first direction, when a direction perpendicular to the direction in which any of the plurality of electrode fingers extends is defined as a first direction, and to form, on the second layer, a second end face positioned on the outside of the IDT electrode in the first direction, wherein the etching rate for the second layer in the third step is higher.

24. A method for manufacturing an elastic wave device, comprising: a first step of preparing a piezoelectric substrate including a first layer including a piezoelectric material and having a first surface, and a third layer arranged below the first layer; a second step of providing, directly or indirectly, an IDT electrode having a plurality of electrode fingers on the first surface; and a third step of etching the piezoelectric substrate to form, on the first layer, a first end face positioned on the outside of the IDT electrode in the first direction, when a direction perpendicular to the direction in which any of the plurality of electrode fingers extends is defined as a first direction, and to form, on the third layer, a third end face positioned on the outside of the IDT electrode in the first direction, wherein the etching rate for the third layer in the third step is higher.

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