Method for manufacturing an elastic wave device

Abstract

There is a need to reduce spurious emissions from elastic wave equipment. [Solution] The method for manufacturing an elastic wave apparatus involves forming a plurality of strip electrodes on a substrate, forming a mask on the strip electrodes, forming an end face on the substrate by etching, and removing a portion of the first strip electrode, which is located closest to the end face in the elastic wave propagation direction, by etching.

Description

Technical Field

[0001] The present disclosure relates to an elastic wave device that uses elastic waves, a method for manufacturing the elastic wave device, a demultiplexer including the elastic wave device, and a communication device including the demultiplexer.

Background Art

[0002] Elastic wave devices that use elastic waves are known. An elastic wave device is, for example, a SAW (Surface Acoustic Wave) device. The elastic wave device has a structure that reflects the propagating elastic wave. The surface acoustic wave device disclosed in Patent Document 1 is an end face reflection type surface acoustic wave device having an end face as a reflection structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Reduction of spurious in the elastic wave device is required.

Means for Solving the Problems

[0005] A method for manufacturing an elastic wave device according to the present disclosure forms a plurality of strip electrodes above a substrate, forms a mask above the strip electrodes, forms an end face on the substrate by etching, and removes a part of a first strip electrode that is located closest to the end face side in the elastic wave propagation direction among the plurality of strip electrodes by the etching.

Effects of the Invention

[0006] According to one aspect of the present disclosure, spurious of the elastic wave device can be reduced.

Brief Description of the Drawings

[0007] [Figure 1] This is a schematic plan view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 2] This is a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 3A] This is a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 3B] This is a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 3C] This is a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 4A] This is a schematic plan view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 4B] This is a schematic plan view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 5] This is a schematic plan view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 6] This is a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure. [Figure 7] This figure shows a schematic cross-sectional view of an elastic wave apparatus according to an embodiment of the present disclosure, illustrating the manufacturing method. [Figure 8] This is a schematic circuit diagram of a demultiplexer according to an embodiment of the present disclosure. [Figure 9] This is a schematic circuit diagram of a communication device according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0008] Embodiments and comparative examples relating to this disclosure will be described below with reference to the drawings. The figures used in the following description are schematic, and the dimensional ratios shown in the drawings do not necessarily correspond to those of reality. Furthermore, the dimensional ratios do not necessarily match between drawings.

[0009] In this disclosure, a Cartesian coordinate system indicated by the D1, D2, and D3 axes is shown in the drawings. The D2 axis is parallel to the direction in which the excitation unit 311, described later, extends from the second busbar 351b, described later. The D1 axis is perpendicular to the D2 axis in the plane of the substrate 2. The D3 axis is perpendicular to the upper surface of the piezoelectric element 21. In other words, the D3 axis is the stacking direction of the substrate 2. In this disclosure, the positive direction of the D1 axis is the direction from the excitation unit 311, described later, toward one end face 41, described later. In this disclosure, the positive direction of the D1 axis is also referred to as the elastic wave propagation direction. In this disclosure, the negative direction of the D1 axis is also referred to as the direction opposite to the elastic wave propagation direction. The end face 41 may be located in both directions of the D1 axis with respect to the excitation unit 311, but in this disclosure, for the sake of explanation, the direction from the excitation unit 311 toward one end face 41 is conveniently referred to as the elastic wave propagation direction. Here, the elastic wave excited by the excitation unit 311 may be an acoustic surface wave or a plate wave. The positive direction of the D2 axis is the direction in which the second excitation unit 311b, described later, extends from the second busbar 351b, described later. The positive direction of the D3 axis is the direction from the substrate 2, described later, toward the electrode layer 3, described later. Also, when referring to a plan view or plan view, unless otherwise specified, it refers to a view in the direction of the D3 axis. For example, a plan view from above refers to a view from above with respect to the D3 axis.

[0010] The elastic wave apparatus 1 according to this disclosure may have either an upward or downward orientation, but for convenience, terms such as upper surface or lower surface may be used with the positive direction of the D3 axis as the upward orientation.

[0011] Furthermore, while the thickness of a layer may be mentioned in this disclosure, unless otherwise specified, it may be considered at the thickest part or the thinnest part in any cross-section.

[0012] Embodiments of this disclosure are shown below. Furthermore, the configurations described in the embodiments shown below may be freely combined with several other embodiments.

[0013] [First Embodiment] A first embodiment of the elastic wave device 1 according to the present disclosure will be described. FIG. 1 is a schematic diagram of the elastic wave device 1 in a plane. The elastic wave device 1 includes a substrate 2, an electrode layer 3 located above the substrate 2, and an end face 41 included in the substrate 2. FIG. 2 is a schematic diagram of the elastic wave device 1 in a cross-sectional view.

[0014] (Substrate) The substrate 2 has a piezoelectric body 21. As shown in FIG. 2, the substrate 2 may have a first layer 22 and / or a support substrate 23 located below the piezoelectric body 21.

[0015] The piezoelectric body 21 is composed of a piezoelectric single crystal containing lithium niobate (LiNbO3; hereinafter referred to as LN) or lithium tantalate (LiTaO3; hereinafter referred to as LT). For example, the piezoelectric body 21 may be composed of an LT layer with a 36 to 54°Y cut and X propagation.

[0016] Examples of the first layer 22 include silicon dioxide (SiO2). The first layer 22 can reduce surface waves leaking below the piezoelectric body 21 and reduce the insertion loss of the elastic wave device 1.

[0017] The support substrate 23 supports the electrode layer 3 and the piezoelectric body 21 and improves the strength of the substrate 2. When the support substrate 23 is provided, the first layer 22 improves the bonding strength between the piezoelectric body 21 and the support substrate 23.

[0018] (End face) As shown in FIG. 1, the substrate 2 includes an end face 41. One end face 41 is located in the elastic wave propagation direction with respect to an excitation portion 311 described later. The end face 41 may be located in both directions of the D1 axis with respect to the excitation portion 311. The end face 41 reflects elastic waves as reflected waves in the negative direction of the D1 axis. In other words, the end face 41 is a reflection structure.

[0019] The end face 41 may be a part of the groove portion 4. Specifically, as shown in FIG. 1, a part of the side surface of the groove portion 4 may be the end face 41. In this case, both side surfaces of the groove portion 4 can be used as the end face 41.

[0020] In a plan view, the end face 41 is positioned parallel to the direction in which the strip electrode 31 extends. Here, "parallel" may include errors within a range that does not significantly affect the specific characteristics of the elastic wave apparatus 1.

[0021] In this disclosure, “end face” is defined as a surface that reflects elastic waves. For example, the end face may be the edge surface of the substrate or the inner wall surface of a groove in the substrate.

[0022] (electrode layer) The electrode layer 3 is formed so as to be in direct or indirect contact with the upper surface of the piezoelectric body 21. Although not specifically shown, a base layer may be located between the electrode layer 3 and the piezoelectric body 21. The base layer can improve the adhesive strength between the electrode layer 3 and the piezoelectric body 21. Examples of base layer materials include titanium (Ti), chromium (Cr), or various dielectric materials.

[0023] The electrode layer 3 is composed of a conductive material. Various conductive materials can be used for the electrode layer 3, such as aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), titanium (Ti), or alloys thereof. Furthermore, multiple layers of these materials may be stacked. Although not shown in the figures, the electrode layer 3 may also be a stacked structure combining the above materials. For example, it may be a stacked structure of Al and CuAl2, or a stacked structure of Al and Ti. The etching selectivity ratio of LT to Al is lower than that of LT to Pt, Mo, Au, or Ti. Therefore, when an electrode layer 3 containing Al as the main component is used, it is easily thinned by etching, making it easier to form the first strip electrode 315 described later. In this disclosure, the main component may be the substance that accounts for the largest proportion by weight or molar ratio, or it may be the substance that accounts for more than half. Furthermore, in a cross-section cut in the direction of elastic wave propagation, the material may be the one that accounts for the largest proportion of the total thickness along the D3 axis, or it may be the material that accounts for more than half of the total thickness.

[0024] As shown in Figure 1, the electrode layer 3 has a plurality of strip electrodes 31. In this disclosure, a strip electrode 31 refers to one of a group of thin electrodes extending parallel to the D2 axis. The plurality of strip electrodes 31 each extend parallel to one another. The number of strip electrodes 31 may be set appropriately according to the electrical characteristics required of the elastic wave apparatus 1. It may be more or less than the number shown in the schematic cross-sectional and plan views in this disclosure.

[0025] Of the multiple strip electrodes 31, at least some of the strip electrodes 31 are excitation units 311 capable of exciting elastic waves. For example, as shown in Figure 1, the excitation unit 311 may be included in the IDT electrode 35. Elastic waves can be excited by the IDT electrode 35, which is composed of the excitation unit 311 and the busbar 351.

[0026] When the elastic wave apparatus 1 has an IDT electrode 35, the IDT electrode 35 includes an excitation section 311 and a busbar 351. Here, the busbar 351 refers to the portion that electrically connects to the strip electrode 31, which is the excitation section 311. The IDT electrode 35 has two opposing busbars, a first busbar 351a and a second busbar 351b, which are not electrically connected to each other, as the busbar 351. The excitation section 311 has a first excitation section 311a extending from the first busbar 351a toward the second busbar 351b, and a second excitation section 311b extending from the second busbar 351b toward the first busbar 351a.

[0027] The lengths of the excitation sections 311 are, for example, equal. The IDT electrodes 35 may be apodized, in which the length of the excitation section 311 changes according to the position in the propagation direction. Apodization can make the elastic wave propagating as the principal resonance more dominant.

[0028] Although not specifically shown in the diagram, the IDT electrode 35 may have dummy electrode fingers extending from one busbar 351 toward the opposite busbar 351. The dummy electrode fingers may be shorter in the D2 axis compared to the excitation section 311. The width of the IDT electrode 35 between the excitation sections 311 may vary, or it may be inclined with respect to the D1 axis.

[0029] The multiple strip electrodes 31 include a first strip electrode 315 located closest to the end face 41 in the elastic wave propagation direction, and a second strip electrode 3117 located further from the end face than the first strip electrode 315. Here, the second strip electrode 3117 is an excitation unit 311. The second strip electrode 3117 may be any of the excitation units 311 that excite the main resonance of the elastic wave device 1.

[0030] In the elastic wave apparatus 1, the average thickness of the excitation section 311 in a cross-section cut in the direction of elastic wave propagation is adjusted as appropriate to contribute to the propagation of elastic waves in the positive direction of the D1 axis. In other words, the average thickness of the excitation section 311 may be determined for the propagation of elastic waves. In this disclosure, unless otherwise specified, the term "average thickness" refers to the thickness in a cross-section cut in the direction of elastic wave propagation. In this disclosure, the average thickness of each strip electrode 31 may be determined by dividing the cross-sectional area of ​​the strip electrode 31 by the lower edge of the strip electrode 31 in a cross-section cut along the D1 axis of the elastic wave apparatus 1, or by various other methods.

[0031] In the elastic wave apparatus 1 according to the first embodiment, the average thickness of the first strip electrode 315 is smaller than the average thickness of the second strip electrode 3117. As a result, the behavior of the propagating elastic waves changes between the second strip electrode 3117, which is the excitation section 311, and the first strip electrode 315. A portion of the elastic wave energy that becomes spurious near the first strip electrode 315 can be leaked downward. Furthermore, the elastic wave apparatus 1 utilizes reflected waves reflected at the end face 41. By leaking a portion of the elastic wave energy that becomes spurious from the reflected waves downward near the end face 41 where the reflected waves are generated, the spurious emissions of the elastic wave apparatus 1 can be reduced.

[0032] The average thickness of the first strip electrode 315 may be set to an appropriate size to adjust specific characteristics. As described above, the first strip electrode 315, by having a small average thickness, can leak some of the elastic waves that become spurious downwards, thereby reducing the spurious emissions of the elastic wave device 1. On the other hand, the first strip electrode 315 leaks some of the elastic waves that become the main resonance, increasing the loss of the elastic wave device 1. For example, the average thickness of the first strip electrode 315 may be adjusted to balance the loss and spurious emissions of the elastic wave device 1. For example, it may be adjusted to reduce both loss and spurious emissions.

[0033] The average thickness of the majority of the strip electrodes 31 that constitute the excitation section 311 is the same as that of the second strip electrode 3117. This allows the elastic wave excited as the main resonance of the elastic wave device 1 to be more dominant. In this disclosure, "same" average thickness may include errors within a range that does not significantly affect specific characteristics of the elastic wave device 1. In this disclosure, "majority of the strip electrodes 31 that constitute the excitation section 311" means the majority of the strip electrodes 31 that constitute the excitation section 311, including the second strip electrode 3117. For example, this may be determined by finding the average thickness of the strip electrodes 31 that constitute the excitation section 311 and counting the number of strip electrodes 31 that have the same average thickness as the second strip electrode 3117.

[0034] The first strip electrode 315 may have a reduced thickness in some areas. For example, if the first strip electrode 315 has the shape shown in Figures 3A-C, spurious emissions can be further reduced. In this case, for example, it becomes easier to adjust the balance between loss and spurious emissions.

[0035] As shown in Figures 3A-C, the first strip electrode 315 may have a portion on the end face 41 side that is thinner. In other words, the first strip electrode 315 includes a first portion 315a and a second portion 315b which is thinner than the first portion 315a in a cross-section cut in the direction of elastic wave propagation, and in the direction of elastic wave propagation, the second portion 315b is located on the end face 41 side than the first portion 315a.

[0036] As shown in Figure 3A, the first strip electrode 315 may be stepped toward the negative direction of the D2 axis. In other words, the first strip electrode 315 has a lower surface R, a first upper surface T1, a second upper surface T2 located on the end surface 41 side of the first upper surface T1 in the elastic wave propagation direction, and a riser surface K connecting the first upper surface T1 and the second upper surface T2, and the first upper surface T1 may be located above the second upper surface T2. In this case, a portion of the elastic wave that becomes spurious propagates along the second upper surface T2 located below and is more likely to leak downward. As a result, the spurious emissions of the elastic wave device 1 can be further reduced.

[0037] As shown in Figure 3B, the strip electrode has a trapezoidal shape, and its top surface may be inclined. In other words, the first strip electrode 315 has a bottom surface R, a first surface S located on the end surface 41 side of the side surface in contact with the bottom surface R in the elastic wave propagation direction, and a top surface T in contact with the first surface S, and the top surface T may be inclined with respect to the bottom surface R. In this case, a portion of the spurious elastic waves is leaked downward along the inclined top surface T. As a result, the spurious emissions of the elastic wave device 1 can be further reduced.

[0038] As shown in Figure 3C, the vertex portion on the end face 41 side may be curved. In other words, the first strip electrode 315 has a lower surface R, a first surface S located on the end face 41 side of the side contacting the lower surface R in the elastic wave propagation direction, an upper surface T in contact with the first surface S, and a second surface U connecting the first surface S and the upper surface T, and the second surface U may be curved. In this case, a portion of the elastic waves that would become spurious leaks downward along the curved second surface U. As a result, spurious emissions from the elastic wave device 1 can be reduced.

[0039] As shown in Figure 4A, the first strip electrode 315 may be a floating electrode 313 that is not electrically connected to the excitation unit 311. The influence of the first strip electrode 315, which has a small average thickness, on the excitation of the elastic waves in the excitation unit 311 can be reduced. In addition, the floating electrode 313 can be used to adjust the sound velocity of the excited elastic waves and / or reflected waves.

[0040] As shown in Figure 4B, the electrode layer 3 may have a reflector 37. In this case, the first strip electrode 315 refers to the strip electrode 31 of the reflector 37 that is located furthest towards the end face 41 in the direction of elastic wave propagation.

[0041] The side surface and end surface 41 of the first strip electrode 315 do not necessarily have to be continuous, but as shown in Figure 1, the side surface of the first strip electrode 315 may be continuous with the end surface 41. In this case, the first strip electrode 315 and the end surface 41 can be formed by etching in a single step.

[0042] The width of the D1 axis of the first strip electrode 315 may be varied compared to the other strip electrodes 31. In this case, the mode of the reflected wave can be adjusted to reduce spurious emissions from the elastic wave apparatus 1. For example, as shown in Figure 5, the width of the first strip electrode 315 in the elastic wave propagation direction may be made larger compared to the second strip electrode 3117. In this case, the possibility of etching of the second strip electrode 3117 in the manufacturing method described later is reduced.

[0043] [Second Embodiment] A second embodiment relating to this disclosure will now be described. In the following, the parts that are common to the first embodiment will be omitted, and only the parts that differ will be described.

[0044] (end face) In the second embodiment, the elastic wave device 1 has an inclined end face 41, as shown in Figure 2. In other words, the angle α formed by the extension of the upper surface of the piezoelectric body 21 and the tangent at any point on the end face 41 is less than 90°. The inclination of the end face 41 allows some of the elastic waves that would otherwise be spurious to leak downwards, thereby reducing the spurious emissions of the elastic wave device 1.

[0045] In this disclosure, when determining the angle formed by a "tangent," any point on a straight line shall be determined by considering that straight line as the "tangent." The phrase "tangent at any point on the end face" does not limit the end face to being a curved or curved surface.

[0046] The angle α may be set to an appropriate size to adjust specific characteristics. As described above, the inclination of the end face 41 allows some of the elastic waves that become spurious downwards to leak out, thereby reducing the spurious emissions of the elastic wave device 1. On the other hand, the end face 41 also allows some of the elastic waves that become the main resonance to leak out, increasing the loss of the elastic wave device 1. For example, the angle α may be adjusted to balance the loss and spurious emissions of the elastic wave device 1. For example, it may be adjusted to reduce both loss and spurious emissions. The elastic wave device 1 according to the second embodiment has the first strip electrode 315 and the end face 41 as structures that reduce spurious emissions, making it easier to adjust the balance between loss and spurious emissions.

[0047] Furthermore, when the end face 41 is inclined, the distance along the D1 axis from the IDT electrode 35 to the end face 41 differs depending on the coordinate of the D2 axis. As a result, spurious emissions are more likely to occur due to the reflection of elastic waves by the end face 41, so the first strip electrode 315, which leaks elastic wave energy near the end face 41, can further reduce spurious emissions. For example, when the angle α is less than 82°, spurious emissions are particularly likely to occur near the end face 41, so the first strip electrode 315 can further reduce spurious emissions.

[0048] [Third Embodiment] A third embodiment relating to this disclosure will now be described. In the following, the parts that are common to the first embodiment will be omitted, and only the parts that differ will be described.

[0049] (end face) As shown in Figure 6, the end face 41 includes a first end face 41a and a second end face 41b. The first end face 41a is located on the upper side of the piezoelectric element 21, and the second end face 41b is located on the lower side of the piezoelectric element 21. As shown in Figure 6, the first end face 41a is steeper inclined than the second end face 41b. In other words, the angle α formed by the extension of the upper surface of the piezoelectric element 21 and the tangent at any point on the first end face 41a is greater than the angle β formed by the extension of the upper surface of the piezoelectric element 21 and the tangent at any point on the second end face 41b.

[0050] In the elastic wave apparatus 1 according to the second embodiment, the upper surface of the piezoelectric body 21 on which the main resonant elastic wave propagates becomes steeper, and the first end face 41a reflects the desired elastic wave more effectively, contributing to a reduction in losses.

[0051] Furthermore, since the end face 41 has a first end face 41a and a second end face 41b with different inclination angles, it becomes easy to adjust specific characteristics of the end face 41 by adjusting the inclination angles of each. For example, it becomes easier to balance losses and spurious emissions.

[0052] [Manufacturing method] The manufacturing method for the elastic wave apparatus 1 according to this disclosure will now be described. Figure 7 shows the manufacturing process, which proceeds in the order of A, B, C, and D.

[0053] The elastic wave apparatus 1 is manufactured by stacking a substrate 2 and an electrode layer 3 in that order. Subsequently, multiple strip electrodes 31 are formed on top of the substrate 2.

[0054] The elastic wave apparatus 1 forms a mask 5 above the strip electrode 31 as shown in Figure 7A and etches it. By etching, an end face 41 can be formed on the piezoelectric body 21.

[0055] The elastic wave apparatus 1 forms a mask 5 above the strip electrode 31 as shown in Figure 7A and etches it. By etching, the strip electrode 31 is thinned, and the first strip electrode 315 can be formed.

[0056] The end face 41 and the first strip electrode 315 may be formed separately by multiple etching steps, or they may be formed simultaneously or continuously by a single etching step.

[0057] When both the end face 41 and the first strip electrode 315 are formed by etching, by appropriately adjusting the material and thickness of the mask 5, the plasma generation conditions in dry etching, or various other conditions, when the end face 41 is formed, the mask 5 gradually recedes from the positive direction to the negative direction of the D1 axis by etching, as shown in Figure 7B, and the end face 41 side of the first strip electrode 315 is exposed. Since it is exposed from the end face 41 side, the mask 5 can be formed such that the average thickness of only the first strip electrode 315 is smaller. For example, the mask 5 can be formed such that the second portion 315b is located in the elastic wave propagation direction more than the first portion 315a.

[0058] Compared to etching the end face 41 and the first strip electrode 315 separately, this avoids the difficulty of accurately forming the mask 5, making it easier to manufacture the acoustic wave apparatus 1. The retracted mask 5 forms the first strip electrode 315, as shown in Figure 7C. Finally, the acoustic wave apparatus 1 can be manufactured by removing the mask 5, as shown in Figure 7D.

[0059] When etching both the end face 41 and the first strip electrode 315, etching may be performed after removing a portion of the mask 5 located above the first strip electrode 315. This makes it easier to expose a portion of the first strip electrode 315.

[0060] Furthermore, after a portion of the first strip electrode 315 is exposed, the first strip electrode 315 becomes a metal mask, as shown in Figure 7B. Since a metal mask is less susceptible to etching than a resin mask, the end face 41 can be formed more steeply. In other words, the first end face 41a formed after a portion of the first strip electrode 315 is exposed is steeper than the second end face 41b formed before exposure. An elastic wave apparatus 1 according to the third embodiment can be manufactured. For example, when an electrode layer 3 containing Ti as the main component is used, the etching selectivity ratio of LT to Ti is higher than that of LT to Al, making it easier to function as a metal mask. As a result, the first end face 41a can be made even steeper.

[0061] Etching may be performed by dry etching.

[0062] For mask 5, for example, a resist for i-lines may be used. A positive resist type resist may be used. A novolac resin may be used.

[0063] [First usage example: Duplexer] Figure 8 is a schematic circuit diagram showing the configuration of the demultiplexer 8 as an example of the use of the elastic wave device 1.

[0064] The demultiplexer 8 includes, for example, a transmit filter 83 that filters the transmit signal from the transmit terminal 81 and outputs it to the antenna terminal 82, and a receive filter 85 that filters the receive signal from the antenna terminal 82 and outputs it to a pair of receive terminals 84.

[0065] The transmitting filter 83 is configured, for example, by having multiple elastic wave devices 1 arranged in a ladder-type filter. That is, the transmitting filter 83 has multiple (or even just one) elastic wave devices 1 connected in series between the transmitting terminal 81 and the antenna terminal 82, and multiple (or even just one) elastic wave devices 1 (parallel arms) connecting the series line (series arm) to the reference potential.

[0066] The receiving filter 85 comprises, for example, an elastic wave device 1 and a multimode filter (including a double-mode filter) 87. The multimode filter 87 has multiple (three in the illustrated example) IDT electrodes 35 arranged in the direction of the arrangement of multiple strip electrodes 31.

[0067] The example described above includes a transmit filter 83 and a receive filter 85 as the demultiplexer 8, but it is not limited to this. The demultiplexer 8 may be, for example, a diplexer, or a multiplexer including three or more filters.

[0068] [Second usage example: Communication device] Figure 9 is a block diagram showing the main components of a communication device 9 as an example of the use of a demultiplexer 8. The communication device 9 performs wireless communication using radio waves and includes a demultiplexer 8.

[0069] In the communication device 9, the transmission information signal TIS, which contains the information to be transmitted, is modulated and its frequency is increased (converted to a high-frequency signal of the carrier frequency) by the RF-IC (Radio Frequency Integrated Circuit) 91 to become the transmission signal TS. The transmission signal TS has unwanted components other than the transmission passband removed by the bandpass filter 92a, is amplified by the amplifier 93a, and input to the demultiplexer 8 (transmission terminal 81). The demultiplexer 8 (transmission filter 83) then removes unwanted components other than the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after removal to the antenna terminal 82 or antenna 95. Antenna 95 converts the input electrical signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

[0070] Furthermore, in the communication device 9, the radio signal (radio wave) received by the antenna 95 is converted into an electrical signal (received signal RS) by the antenna 95 and input to the demultiplexer 8 (antenna terminal 82). The demultiplexer 8 (receive filter 85) removes unwanted components other than the passband for reception from the input received signal RS, amplifies it by the amplifier 93b from the receiving terminal 84, and removes unwanted components other than the passband for reception by the bandpass filter 92b. The received signal RS is then frequency-downgraded and demodulated by the RF-IC 91 to become the received information signal RIS.

[0071] The transmitted information signal TIS and the received information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog or digitized audio signals. Wireless signal passbands (e.g., 5 GHz or higher) are also possible. The modulation scheme may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. While Figure 9 illustrates a direct conversion circuit, other appropriate circuit schemes may be used, such as a double superheterodyne circuit. Furthermore, Figure 9 schematically shows only the essential components; low-pass filters or isolators may be added at appropriate locations, and the positions of amplifiers may be changed.

[0072] (summary) (1) An elastic wave apparatus according to a first aspect of the present disclosure includes a substrate having a piezoelectric material and including an end face, and a plurality of strip electrodes located above the substrate and extending parallel to each other. At least some of the plurality of strip electrodes are excitation units capable of exciting elastic waves. The end face is parallel to the direction in which the strip electrodes extend when viewed from above and is located in the direction of elastic wave propagation relative to the excitation units. The plurality of strip electrodes include a first strip electrode located closest to the end face in the direction of elastic wave propagation, and a second strip electrode located further from the end face than the first strip electrode in the direction of elastic wave propagation. The second strip electrode is an excitation unit. In a cross section cut in the direction of elastic wave propagation, the average thickness of the first strip electrode is smaller than the average thickness of the second strip electrode.

[0073] (2) In the first embodiment, the elastic wave apparatus according to a second aspect of the present disclosure includes a first strip electrode comprising a first portion and a second portion having less thickness than the first portion in a cross-section cut in the direction of elastic wave propagation. In the direction of elastic wave propagation, the second portion is located closer to the end face than the first portion.

[0074] (3) In the third embodiment of the present disclosure, the elastic wave apparatus has a first strip electrode having a lower surface, a first upper surface, a second upper surface located on the end face side of the first upper surface in the elastic wave propagation direction, and a riser surface connecting the first upper surface and the second upper surface, wherein the first upper surface is located above the second upper surface.

[0075] (4) In the fourth aspect of the present disclosure, the elastic wave apparatus, in the first to third aspects described above, has a first strip electrode having a lower surface, a first surface located on the end face side of the side surface in contact with the lower surface in the elastic wave propagation direction, and an upper surface in contact with the first surface. The upper surface is inclined downward with respect to the lower surface.

[0076] (5) In the fifth aspect of the present disclosure, the elastic wave apparatus, in the first to fourth aspects described above, has a first strip electrode having a lower surface, a first surface located on the end face side of the side surface in contact with the lower surface in the elastic wave propagation direction, an upper surface in contact with the first surface, and a second surface connecting the first surface and the upper surface. The second surface is curved.

[0077] (6) In the elastic wave apparatus according to the sixth aspect of the present disclosure, the average thickness of the majority of the strip electrodes which are the excitation section is the same as that of the second strip electrode.

[0078] (7) In the seventh aspect of the present disclosure, the elastic wave apparatus, in the first to sixth aspects described above, has an angle α less than 90° between the extension of the upper surface of the piezoelectric body and the tangent at any point on the end face in a cross section cut in the direction of elastic wave propagation.

[0079] (8) In the eighth aspect of the present disclosure, the elastic wave apparatus is such that the angle α is less than 82° in the first to seventh aspects described above.

[0080] (9) In the ninth aspect of the present disclosure, the elastic wave apparatus has an end face which is a first end face located on the upper side of the piezoelectric body and a second end face located on the lower side of the piezoelectric body. In a cross section cut in the direction of elastic wave propagation, the angle formed by the extension of the upper surface of the piezoelectric body and the tangent at any point on the first end face is greater than the angle formed by the extension of the upper surface of the piezoelectric body and the tangent at any point on the second end face.

[0081] (10) In the tenth aspect of the present disclosure, the elastic wave apparatus is such that the first strip electrode is an excitation unit, as in the first to ninth aspects described above.

[0082] (11) In the eleventh aspect of the present disclosure, the elastic wave apparatus is such that the first strip electrode is a floating electrode that is not electrically connected to the excitation unit, in the first to ten aspects described above.

[0083] (12) In the elastic wave apparatus according to the twelfth aspect of the present disclosure, the first strip electrode has a greater width in the elastic wave propagation direction than the second strip electrode, as described in the first to eleventh aspects.

[0084] (13) In the elastic wave apparatus according to the thirteenth aspect of the present disclosure, the first strip electrode comprises Al as a main component, in the first to twelfth aspects described above.

[0085] (14) In the fourteenth aspect of the present disclosure, the elastic wave apparatus, in the first to thirteenth aspects described above, has a substrate having a groove on its upper surface, and the end face is the side surface of the groove.

[0086] (15) In the first to 14 embodiments of the present disclosure, the acoustic wave apparatus comprises a substrate comprising a support substrate and a first layer located between the support substrate and the piezoelectric element.

[0087] (16) A method for manufacturing an elastic wave apparatus according to the 16th aspect of the present disclosure, according to the first to 15 aspects described above, comprises a first step of forming a plurality of strip electrodes on a substrate; a second step of forming a mask on the strip electrodes after the first step; and a third step of forming an end face on the substrate by etching and removing a portion of the first strip electrode, which is located furthest to the end face in the elastic wave propagation direction, from among the plurality of strip electrodes by etching.

[0088] (17) A method for manufacturing an elastic wave apparatus according to the 17th aspect of the present disclosure involves removing a portion of the mask located above the first strip electrode, and then performing a second step, in the 16th aspect described above.

[0089] (18) A method for manufacturing an elastic wave apparatus according to the 18th aspect of the present disclosure, in the 17th aspect, the third step is that the mask is gradually retracted in the direction opposite to the direction of elastic wave propagation.

[0090] (19) A demultiplexer according to a 19th aspect of the present disclosure includes an antenna terminal, a transmit filter configured to filter a transmit signal and output it to the antenna terminal, and a receive filter configured to filter a receive signal from the antenna terminal. At least one of the transmit filter and the receive filter includes an acoustic wave apparatus according to the first to 15 aspects described above.

[0091] (20) A communication device according to the 20th aspect of the present disclosure includes an antenna, a demultiplexer according to the 19th aspect described above with an antenna terminal connected to the antenna, and an IC connected to a transmit filter and a receive filter. [Explanation of Symbols]

[0092] 1: Elastic wave device 2: Circuit board 21: Piezoelectric 22: 1st layer 23: Support substrate 3: Electrode layer 31: Strip electrodes 311: Excitation Unit 311a: 1st excitation part 311b: Second excitation section 3117: Second strip electrode 313: Floating electrode 315: First strip electrode 35:IDT electrode 351: Bus bar 351a: First bus bar 351b: Second bus bar 37:Reflector 4: Groove 41: End face 41a: First end surface 41b: Second end surface 5: Mask 8: Duplexer 9: Communication equipment

Claims

1. Multiple strip electrodes are formed on the substrate, a mask is formed on the strip electrodes, an end face is formed on the substrate by etching, and a portion of the first strip electrode, which is located closest to the end face in the elastic wave propagation direction, is removed by etching. A method for manufacturing an elastic wave apparatus.

2. A portion of the first strip electrode is Located on the end face side of the first strip electrode in a cross-sectional view, Located on the opposite side of the aforementioned substrate A method for manufacturing an elastic wave apparatus according to claim 1.

3. After removing a portion of the mask located above the first strip electrode, an end face is formed on the substrate by etching. A method for manufacturing an elastic wave apparatus according to claim 1.

4. The etching process forms an end face on the substrate, and the mask gradually retracts in the direction opposite to the direction of elastic wave propagation. A method for manufacturing an elastic wave apparatus according to claim 1.

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