Elastic wave device, method for manufacturing same, filter, and multiplexer

Abstract

The invention provides an elastic wave device, a method for manufacturing the same, a filter, and a multiplexer. The elastic wave device can suppress the occurrence of cracks in the wiring layer. This elastic wave device is provided with: a piezoelectric substrate (14); a series resonator (S4) provided on the piezoelectric substrate (14) and having a plurality of electrode fingers (18a); a parallel resonator (P4) provided on the piezoelectric substrate and having a plurality of electrode fingers (18b) made of a material different from that of the electrode fingers (18a); a first base conductive layer (36) which is provided on the piezoelectric substrate, is connected to the series resonator, and has the same layer structure as the electrode fingers (18a); a second base conductive layer (38) that is provided on the piezoelectric substrate, is connected to the parallel resonator, has the same layer structure as the electrode fingers (18b), and faces the first base conductive layer with a gap therebetween; and a wiring layer (34) that is provided from above the first base conductive layer to above the second base conductive layer and connects the series resonator and the parallel resonator.

Description

Technical Field

[0001] The present invention relates to an elastic wave device, a filter, a multiplexer, and a method for manufacturing the elastic wave device. Background Art

[0002] Surface acoustic wave (SAW) resonators are known as elastic wave devices used in communication devices such as smartphones. A surface acoustic wave resonator has an IDT (interdigital transducer) with multiple electrode fingers arranged on a piezoelectric substrate. Surface acoustic wave resonators are also known to be used in high-frequency filters for removing unwanted signals outside the frequency band used for communication (e.g., Patent Documents 1-3). It is also known to vary the number of electrode fingers stacked between two surface acoustic wave resonators (e.g., Patent Documents 4 and 5).

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-89069

[0004] Patent Document 2: Japanese Patent Application Laid-Open No. 2008-244523

[0005] Patent Document 3: Japanese Patent Application Laid-Open No. 2008-28980

[0006] Patent Document 4: International Publication No. 2003 / 005577

[0007] Patent Document 5: Japanese Patent Application Laid-Open No. 2006-333296

[0008] Sometimes, the electrode fingers in the first elastic wave resonator and the second elastic wave resonator are made of different materials. In this case, the first electrode finger of the first elastic wave resonator and the second electrode finger of the second elastic wave resonator are formed through different processes. The wiring layer connecting the first elastic wave resonator and the second elastic wave resonator is formed on the base conductive layer connected to each resonator. To simplify the manufacturing process, the first base conductive layer connected to the first elastic wave resonator is formed simultaneously with the first electrode finger, and the second base conductive layer connected to the second elastic wave resonator is formed simultaneously with the second electrode finger. In such a case, cracks may occur in the wiring layer formed from the first base conductive layer to the second base conductive layer, resulting in increased resistance or disconnection. Summary of the Invention

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to suppress the occurrence of cracks in a wiring layer.

[0010] The present invention is an elastic wave device comprising: a piezoelectric substrate; a first elastic wave resonator, disposed on the piezoelectric substrate, having a plurality of first electrode fingers; a second elastic wave resonator, disposed on the piezoelectric substrate, having a plurality of second electrode fingers made of a material different from that of the plurality of first electrode fingers; a first underlying conductive layer, disposed on the piezoelectric substrate, connected to the first elastic wave resonator, and having the same layer structure as the plurality of first electrode fingers; a second underlying conductive layer, disposed on the piezoelectric substrate, connected to the second elastic wave resonator, having the same layer structure as the plurality of second electrode fingers, and opposed to the first underlying conductive layer with a gap therebetween; and a wiring layer, disposed from the first underlying conductive layer to the second underlying conductive layer, connecting the first elastic wave resonator and the second elastic wave resonator.

[0011] In the above structure, the thickness of the first base conductive layer may be constant throughout the first base conductive layer, and the thickness of the second base conductive layer may be constant throughout the second base conductive layer.

[0012] In the above structure, the wiring layer may have a thickness that is at least twice as thick as the larger thickness of the first base conductive layer or the second base conductive layer.

[0013] In the above structure, the first and second base conductive layers may be opposed to each other with the gap therebetween by a distance that is at least one time the thickness of the larger of the first and second base conductive layers.

[0014] In the above configuration, the plurality of first electrode fingers and the plurality of second electrode fingers may be arranged in the same direction, and the gap may be provided between the first elastic wave resonator and the second elastic wave resonator in the direction of the arrangement.

[0015] The present invention is a filter including the elastic wave device described above.

[0016] In the above structure, the first elastic wave resonator can be a series resonator connected in series between an input terminal and an output terminal, the second elastic wave resonator can be a parallel resonator connected in parallel between the input terminal and the output terminal, the plurality of first electrode fingers can include a first conductive layer which is a titanium nitride layer and a second conductive layer provided on the first conductive layer, and the plurality of second electrode fingers can include a third conductive layer which is a titanium layer and a fourth conductive layer provided on the third conductive layer and made of the same material as the second conductive layer.

[0017] The present invention is a multiplexer comprising the filter described above.

[0018] The present invention is a method for manufacturing an elastic wave device, comprising the following steps: forming a first elastic wave resonator and a first underlying conductive layer on a piezoelectric substrate, the first elastic wave resonator having a plurality of first electrode fingers, the first underlying conductive layer being connected to the first elastic wave resonator and having the same layer structure as the plurality of first electrode fingers; forming a first mask layer on the piezoelectric substrate to cover the first elastic wave resonator and the first underlying conductive layer; forming a conductive film on the piezoelectric substrate using the first mask layer as a mask; and forming a second mask layer on the piezoelectric substrate after removing the first mask layer. The conductive film is etched using the second mask layer as a mask to form a second elastic wave resonator and a second underlying conductive layer. The second elastic wave resonator has a plurality of second electrode fingers. The second underlying conductive layer is connected to the second elastic wave resonator, has the same layer structure as the plurality of second electrode fingers, and is opposed to the first underlying conductive layer with a gap therebetween. After removing the second mask layer, a wiring layer is formed from above the first underlying conductive layer to above the second underlying conductive layer, connecting the first elastic wave resonator and the second elastic wave resonator.

[0019] In the above structure, in the step of forming the second mask layer, the second mask layer may be formed so that the opening is located in a protrusion formed at the end portion of the conductive film.

[0020] In the above configuration, in the step of forming the first mask layer, the first mask layer may be formed in a region larger than a region where the first elastic wave resonator and the first underlying conductive layer are formed so as to completely cover the first elastic wave resonator and the first underlying conductive layer.

[0021] According to the present invention, it is possible to suppress the occurrence of cracks in the wiring layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a plan view of the filter of Example 1.

[0023] Figure 2 (a) is a plan view of the surface acoustic wave resonator. Figure 2 (b) is a cross-sectional view of the electrode fingers of the series resonator of Example 1, Figure 2 (c) is a cross-sectional view of the electrode fingers of the parallel resonator.

[0024] Figure 3 (a) and Figure 3 (b) is a cross-sectional view of structure A and structure B of the elastic wave resonator used in the experiment.

[0025] Figure 4 (a) is a diagram showing the pass characteristics of the ladder filter A, Figure 4 (b) is a graph showing the pass characteristics of the ladder filter B.

[0026] Figure 5 (a) is Figure 1 Planar diagram of the vicinity of the series resonator and the parallel resonator, Figure 5 (b) is along Figure 5 (a) is a cross-sectional view of line AA, Figure 5 (c) is Figure 5 (b) is a cross-sectional view near the wiring layer.

[0027] Figure 6 (a) to Figure 6 (c) is a cross-sectional view (part 1) illustrating a method for manufacturing the series resonator, the parallel resonator, and the wiring layer according to the first embodiment.

[0028] Figure 7 (a) to Figure 7 (c) is a cross-sectional view (part 2) illustrating the method for manufacturing the series resonator, the parallel resonator, and the wiring layer of the first embodiment.

[0029] Figure 8 (a) to Figure 8 (c) is a cross-sectional view (part 3) illustrating the method for manufacturing the series resonator, the parallel resonator, and the wiring layer of the first embodiment.

[0030] Figure 9 (a) to Figure 9 (c) is a cross-sectional view (part 1) illustrating a method for manufacturing a series resonator, a parallel resonator, and a wiring layer according to a comparative example.

[0031] Figure 10 (a) to Figure 10 (c) is a cross-sectional view (part 2) illustrating a method for manufacturing a series resonator, a parallel resonator, and a wiring layer according to a comparative example.

[0032] Figure 11 This is a circuit diagram of a duplexer according to the second embodiment.

[0033] Label Description

[0034] 10: Support substrate; 11: Insulating layer; 12: Insulating layer; 13: Insulating layer; 14: Piezoelectric substrate; 15: Frame; 18, 18a, 18b: Electrode fingers; 19: Bus bar; 20: Comb-shaped electrode; 22: IDT; 24: Reflector; 25: Crossover region; 30: Terminal; 32: Via wiring; 34: Wiring layer; 35: First layer; 36: First base conductive layer; 37: Second layer; 38: Second base conductive layer; 40: Surface acoustic wave resonator; 42a, 42b: Conductive film; 43: First conductive layer; 43a: First conductive film; 44: Second conductive layer; 44a: Second conductive film; 45: Third conductive layer; 45a: Third conductive film; 46: Fourth conductive layer; 46a: Fourth conductive film; 50: Gap; 60: Ti layer; 62: AlCu alloy layer; 64: TiN layer; 66: Protrusion; 67: Crack; 70: Transmitting filter; 72: Receiving filter; 80: Mask layer; 82: Mask layer; 84: Mask layer; 100: Filter; 200: Duplexer. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0036] [Example 1]

[0037] In the first embodiment, an example of a filter is described. Figure 1 This is a plan view of the filter 100 according to Example 1. The arrangement direction of the electrode fingers 18 is defined as the X direction, the extension direction of the electrode fingers 18 is defined as the Y direction, and the thickness direction of the piezoelectric substrate 14 is defined as the Z direction. The X and Y directions do not necessarily correspond to the X and Y axis directions of the crystal orientation of the piezoelectric substrate 14. If the piezoelectric substrate 14 is a rotated Y-cut X-propagation substrate, the X direction corresponds to the X axis direction of the crystal orientation.

[0038] like Figure 1 As shown, a piezoelectric substrate 14 is provided on a support substrate 10. One or more series resonators S1 to S6 and one or more parallel resonators P1 to P5 are provided on the piezoelectric substrate 14. Multiple terminals 30 are provided on the lower surface of the support substrate 10. The multiple terminals 30 include an input terminal Tin, an output terminal Tout, and a ground terminal Tg. The series resonators S1 to S6 are connected in series between the input terminal Tin and the output terminal Tout via a via wiring 32 and a wiring layer 34 that penetrates the support substrate 10. Parallel resonators P1 to P5 have one end connected between the series resonators S1 to S6 via a wiring layer 34, and the other end connected to the ground terminal Tg via the wiring layer 34 and the via wiring 32.

[0039] The support substrate 10 may be, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a crystal substrate, a silicon carbide substrate, or a silicon substrate. The piezoelectric substrate 14 may be, for example, a single-crystal lithium tantalate substrate, a single-crystal lithium niobate substrate, or a crystal substrate. The piezoelectric substrate 14 may be, for example, a rotated Y-cut X-propagation lithium tantalate substrate or a rotated Y-cut X-propagation lithium niobate substrate, for example, a 30° to 50° rotated Y-cut X-propagation lithium tantalate substrate. An insulating film such as silicon oxide and / or aluminum oxide may be provided between the support substrate 10 and the piezoelectric substrate 14.

[0040] The series resonators S1 to S6 and the parallel resonators P1 to P5 are surface acoustic wave resonators. Figure 2 (a) is a plan view of the surface acoustic wave resonator 40. Figure 2 As shown in (a), the surface acoustic wave resonator 40 has an IDT 22 and a reflector 24. The reflector 24 is arranged on both sides of the IDT 22 in the X direction. The IDT 22 has a pair of opposing comb-shaped electrodes 20. The comb-shaped electrode 20 has a plurality of electrode fingers 18 and a bus bar 19 connected to the plurality of electrode fingers 18. The area where the electrode fingers 18 of the pair of comb-shaped electrodes 20 intersect is the intersection area 25. In the pair of comb-shaped electrodes 20, the electrode fingers 18 are alternately arranged one by one in at least a part of the intersection area 25. In the intersection area 25, the elastic waves mainly excited by the plurality of electrode fingers 18 propagate mainly in the X direction. The pitch of the electrode fingers 18 of one of the comb-shaped electrodes 20 (the pitch between the centers of the electrode fingers 18) is approximately the wavelength λ of the elastic wave. If the pitch of the plurality of electrode fingers 18 is set to D, the pitch of the electrode fingers 18 of one of the comb-shaped electrodes 20 is twice the pitch D of the electrode fingers 18. Reflectors 24 reflect elastic waves (surface acoustic waves) excited by electrode fingers 18. Thus, the elastic waves are confined within intersection regions 25 of IDT 22. An insulating film may be provided to cover electrode fingers 18. The insulating film functions as a protective film or a temperature compensation film.

[0041] Figure 2 (b) is a cross-sectional view of the electrode finger 18a of the series resonators S1 to S6 of Example 1. Figure 2 (c) is a cross-sectional view of the electrode finger 18b of the parallel resonator P1 to P5. Figure 2As shown in (b), in series resonators S1 to S6, the IDT 22, such as the electrode finger 18a, and the reflector 24 are formed by a conductive film 42a provided on the piezoelectric substrate 14. The conductive film 42a includes a first conductive layer 43 provided on the piezoelectric substrate 14 and a second conductive layer 44 provided on the first conductive layer 43. The first conductive layer 43 is, for example, a polycrystalline or amorphous titanium nitride (TiN) layer. In addition to titanium (Ti) and nitrogen (N), the first conductive layer 43 may contain desired or undesired impurities. The sum of the titanium content and the nitrogen content of the first conductive layer 43 is, for example, 80 atomic % or more, or 90 atomic % or more. The ratio of the nitrogen content (atomic %) to the sum of the titanium content (atomic %) and the nitrogen content (atomic %) is, for example, 0.01 or more and 0.99 or less, and typically 0.3 or more and 0.6 or less. The second conductive layer 44 is, for example, a polycrystalline or amorphous aluminum (Al) layer or an aluminum alloy layer.

[0042] like Figure 2 As shown in (c), in parallel resonators P1 to P5, the IDT 22, such as the electrode finger 18b, and the reflector 24 are formed by a conductive film 42b provided on the piezoelectric substrate 14. The conductive film 42b includes a layer made of a material different from that of the conductive film 42a. The conductive film 42b includes a third conductive layer 45 provided on the piezoelectric substrate 14 and a fourth conductive layer 46 provided on the third conductive layer 45. The third conductive layer 45 is, for example, a polycrystalline or amorphous titanium (Ti) layer. In addition to titanium, the third conductive layer 45 may also contain desired or undesired impurities. The fourth conductive layer 46 is formed of the same material as the second conductive layer 44 of the series resonators S1 to S6, for example, a polycrystalline or amorphous aluminum layer or aluminum alloy layer.

[0043] When the second conductive layer 44 and the fourth conductive layer 46 are aluminum layers, they may contain desired or undesired impurities in addition to aluminum. When the second conductive layer 44 and the fourth conductive layer 46 are aluminum alloy layers, they may contain, in addition to aluminum, at least one element selected from copper (Cu), magnesium (Mg), scandium (Sc), zirconium (Zr), titanium (Ti), neodymium (Nd), and silicon (Si). When the second conductive layer 44 and the fourth conductive layer 46 are aluminum alloy layers, they may contain, in addition to aluminum and the metal elements constituting the aluminum alloy, desired or undesired impurities. The aluminum content of the second conductive layer 44 and the fourth conductive layer 46 is, for example, 80 atomic % or greater, or 90 atomic % or greater. The second conductive layer 44 and the fourth conductive layer 46 may also be a metal layer such as a copper layer, a copper alloy layer, a molybdenum layer, or a molybdenum alloy layer.

[0044] like Figure 1As shown in FIG, the piezoelectric substrate 14 is not provided in the peripheral area of ​​the support substrate 10. On the support substrate 10, a frame 15 is provided so as to surround the piezoelectric substrate 14 and the series resonators S1 to S6 and the parallel resonators P1 to P5 provided on the piezoelectric substrate 14 when viewed from the +Z direction. Although a cover is provided on the frame 15 so as to form a gap between the frame 15 and the piezoelectric substrate 14, Figure 1 The series resonators S1 to S6 and the parallel resonators P1 to P5 are sealed in a gap formed in the piezoelectric substrate 14 by the frame 15 and the cover.

[0045] [experiment]

[0046] Elastic wave resonators of structure A and structure B were fabricated. Figure 3 (a) and Figure 3 (b) is a cross-sectional view of the elastic wave resonator structure A and structure B used in the experiment. Figure 3 As shown in (a), in structure A, an insulating layer 11, an insulating layer 12, and an insulating layer 13 are sequentially provided on a supporting substrate 10. A piezoelectric substrate 14 is provided on the insulating layer 13. The insulating layer 12 is a temperature compensation film. By providing the insulating layer 12, the frequency temperature coefficient can be reduced. The insulating layer 11 is a boundary layer. By providing the insulating layer 11, the main mode surface acoustic wave can be confined within the piezoelectric substrate 14 and the insulating layer 12, and the stray waves caused by useless waves can be suppressed. The insulating layer 13 is a bonding layer. By providing the insulating layer 13, the bonding between the insulating layer 12 and the piezoelectric substrate 14 becomes stronger. The interface between the supporting substrate 10 and the insulating layer 11 is a rough surface. As a result, the useless waves are scattered at the interface, and the stray waves can be suppressed. The other interfaces are mirror surfaces. The electrode fingers 18 provided on the piezoelectric substrate 14 are a laminated film of a titanium (Ti) layer 60 and an aluminum-copper alloy (AlCu) layer 62.

[0047] like Figure 3 As shown in (b), in structure B, the electrode fingers 18 provided on the piezoelectric substrate 14 are a laminated film of a titanium nitride (TiN) layer 64 and an aluminum-copper alloy (AlCu) layer 62. The remaining structure is the same as that of structure A, and therefore description thereof is omitted.

[0048] The fabrication conditions for structures A and B are as follows.

[0049] Common conditions for constructing A and B

[0050] Support substrate 10: 150 μm thick sapphire substrate with a rough upper surface

[0051] Insulating layer 11: Aluminum oxide layer with a thickness T1 of 2.8 μm

[0052] Insulating layer 12: Silicon oxide layer with a thickness T2 of 0.45 μm

[0053] Insulation layer 13: Aluminum oxide layer with a thickness T3 of 0.01 μm

[0054] Piezoelectric substrate 14: 42° rotated Y-cut X-spread lithium tantalate substrate with a thickness T4 of 0.7 μm

[0055] Conditions for constructing A

[0056] Ti layer 60 of electrode finger 18: thickness 0.07 μm

[0057] AlCu alloy layer 62 of electrode finger 18: thickness 0.12 μm

[0058] Conditions for constructing B

[0059] TiN layer 64 of electrode finger 18: thickness 0.07 μm

[0060] AlCu alloy layer 62 of electrode finger 18: thickness 0.12 μm

[0061] A ladder filter A using elastic wave resonators with structure A for series and parallel resonators and a ladder filter B using elastic wave resonators with structure B for series and parallel resonators were prepared, and the temperature characteristics of the transmission characteristics were measured. Figure 4 (a) is a diagram showing the pass characteristics of the ladder filter A, Figure 4 (b) is a graph showing the pass characteristics of the ladder-type filter B. The pass characteristics are shown when the ambient temperatures are 25°C, 50°C, and 85°C.

[0062] like Figure 4 (a) and Figure 4As shown in (b), for both ladder filter A and ladder filter B, the frequency increases as the temperature increases on the low-frequency side of the passband. On the other hand, the frequency decreases as the temperature increases on the high-frequency side of the passband. This is believed to be because, in elastic wave resonators, the temperature characteristics at the resonant frequency differ from the temperature characteristics at the antiresonant frequency. The frequency change on the low-frequency side with respect to temperature change is smaller for ladder filter A than for ladder filter B. For example, when the attenuation is -20 dB, the temperature coefficient of frequency (TCF) on the low-frequency side of ladder filter A is approximately 0 ppm / K, while the TCF on the low-frequency side of ladder filter B is approximately +10 ppm / K. The frequency change on the high-frequency side with respect to temperature change is larger for ladder filter A than for ladder filter B. For example, when the attenuation is -20 dB, the TCF on the high-frequency side of ladder filter A is approximately -25 ppm / K, while the TCF on the high-frequency side of ladder filter B is approximately -15 ppm / K. This is believed to be because the elastic wave resonator with structure A used in ladder filter A uses a Ti layer 60 as the base layer for electrode fingers 18, while the elastic wave resonator with structure B used in ladder filter B uses a TiN layer 64 as the base layer for electrode fingers 18. Specifically, the Young's modulus of the titanium (or titanium nitride) and aluminum that constitute electrode fingers 18 varies with temperature and is greater than the temperature variation of the Young's modulus of piezoelectric substrate 14. On the other hand, the Young's modulus of titanium nitride is greater than that of titanium. Therefore, even if the Young's modulus of TiN layer 64 and AlCu alloy layer 62 varies with temperature, TiN layer 64 is less likely to deform. Therefore, it is believed that the TCF shifts in the positive direction when TiN layer 64 is used compared to when Ti layer 60 is used.

[0063] The low-frequency shoulder of the ladder filter is formed by a parallel resonator, while the high-frequency shoulder is formed by a series resonator. Therefore, to minimize frequency-temperature variations on both the low-frequency and high-frequency sides, it is preferable that the electrode fingers of the series resonator of the ladder filter use a TiN base layer, while the electrode fingers of the parallel resonator use a Ti base layer.

[0064] Thus, for example, from the viewpoint of reducing frequency temperature variation on both the low-frequency side and the high-frequency side, the electrode fingers of the series resonator and the electrode fingers of the parallel resonator may be formed using different materials.

[0065] Figure 5 (a) is Figure 1 A plan view of the vicinity of the series resonator S4 and the parallel resonator P4, Figure 5 (b) is along Figure 5 (a) is a cross-sectional view of line AA, Figure 5 (c) is Figure 5(b) is a cross-sectional view of the wiring layer 34 and its vicinity. Figure 5 In (a), the wiring layer 34 connecting the series resonator S4 and the parallel resonator P4 is hatched. Figure 5 (a) to Figure 5 As shown in FIG. 5( c ), a first base conductive layer 36 connected to the series resonator S4 and a second base conductive layer 38 connected to the parallel resonator P4 are provided on the piezoelectric substrate 14 .

[0066] The first underlying conductive layer 36 connected to the series resonator S4 has the same layer structure as the electrode fingers 18a of the series resonator S4. Specifically, the first underlying conductive layer 36 includes a first conductive layer 43, which is a titanium nitride layer, provided on the piezoelectric substrate 14, and a second conductive layer 44, which is an aluminum layer or an aluminum alloy layer, provided on the first conductive layer 43. The first conductive layer 43 of the first underlying conductive layer 36 and the electrode fingers 18a have the same thickness, and the second conductive layer 44 has the same thickness. The term "same thickness" means that a difference within the acceptable range of manufacturing tolerances is acceptable.

[0067] The second underlying conductive layer 38 connected to the parallel resonator P4 has the same layer structure as the electrode fingers 18b of the parallel resonator P4. Specifically, the second underlying conductive layer 38 includes a third conductive layer 45, which is a titanium layer, provided on the piezoelectric substrate 14, and a fourth conductive layer 46, which is an aluminum layer or an aluminum alloy layer, provided on the third conductive layer 45. In the second underlying conductive layer 38 and the electrode fingers 18b, the third conductive layer 45 has the same thickness, and the fourth conductive layer 46 has the same thickness.

[0068] The first base conductive layer 36 and the second base conductive layer 38 face each other with a gap 50 therebetween. The gap L between the first base conductive layer 36 and the second base conductive layer 38 across the gap 50 is, for example, 1 to 10 times the thickness of the larger of the thickness T11 of the first base conductive layer 36 and the thickness T12 of the second base conductive layer 38. For example, the thickness T11 of the first base conductive layer 36 and the thickness T12 of the second base conductive layer 38 are 400 nm to 500 nm, and the gap L of the gap 50 is 500 nm to 5 μm.

[0069] A wiring layer 34 is provided from the first base conductive layer 36 to the second base conductive layer 38. The wiring layer 34 is provided to fill the gap 50 between the first base conductive layer 36 and the second base conductive layer 38. The series resonator S4 and the parallel resonator P4 are electrically connected via the wiring layer 34. The wiring layer 34 includes a first layer 35 and a second layer 37 provided on the first layer 35. The first layer 35 is, for example, a titanium (Ti) layer, serving as an adhesion layer. The second layer 37 is, for example, a gold (Au) layer. The thickness T13 of the wiring layer 34 is at least twice the thickness of the larger of the thickness T11 of the first base conductive layer 36 and the thickness T12 of the second base conductive layer 38. For example, the thickness T13 of the wiring layer 34 is 1 μm to 2 μm. Furthermore, for example, the spacing L of the gap 50 is at least 0.5 times and at most 3 times the thickness T13 of the wiring layer 34. The wiring layer 34 may completely fill the gap 50 or may have a void in part of the gap 50. The wiring layer 34 is provided on the first base conductive layer 36 and the second base conductive layer 38 to reduce the resistance caused by the electrical connection between the series resonator S4 and the parallel resonator P4, thereby stabilizing the characteristics and improving reliability.

[0070] In addition, Figure 5 (a) to Figure 5 FIG. 5( c ) shows a connection point between the series resonator S4 and the parallel resonator P4 , but the connection points between other series resonators and parallel resonators also have the same structure.

[0071] [Manufacturing method]

[0072] Figure 6 (a) to Figure 8 (c) is a cross-sectional view showing a method for manufacturing the series resonator S4, the parallel resonator P4, and the wiring layer 34 of the first embodiment. Figure 6 (a) to Figure 8 (c) shows the Figure 5 (b) The cross section of the corresponding part. Figure 6 As shown in (a), the piezoelectric substrate 14 is bonded to the support substrate 10 at room temperature using, for example, a surface activation method, and then the piezoelectric substrate 14 is polished using, for example, CMP (Chemical Mechanical Polishing). This forms the piezoelectric substrate 14, which is directly or indirectly bonded to the upper surface of the support substrate 10. Next, a first conductive film 43a and a second conductive film 44a are sequentially formed on the piezoelectric substrate 14 using, for example, sputtering or vacuum deposition.

[0073] like Figure 6As shown in FIG. 5( b ), a mask layer 80 is formed on the second conductive film 44 a so as to cover the region where the series resonator S4 and the first underlying conductive layer 36 are formed. The mask layer 80 is formed of, for example, a resist.

[0074] like Figure 6 As shown in (c), the second conductive film 44a and the first conductive film 43a are removed using, for example, etching, using the mask layer 80 as a mask. The mask layer 80 is then removed. This results in: a series resonator S4 having electrode fingers 18a formed of the first conductive layer 43 and the second conductive layer 44; and a first base conductive layer 36 connected to the series resonator S4 and having the same layer structure as the electrode fingers 18a.

[0075] like Figure 7 As shown in FIG. 1A , a mask layer 82 is formed on the piezoelectric substrate 14 to cover the series resonator S4 and the first underlying conductive layer 36. The mask layer 82 is formed, for example, of a resist. The mask layer 82 is formed in an area larger than the area where the series resonator S4 and the first underlying conductive layer 36 are formed, so as to completely cover the series resonator S4 and the first underlying conductive layer 36.

[0076] like Figure 7 As shown in FIG. 8( b ), the mask layer 82 is used as a mask, and a sputtering method or a vacuum evaporation method are used to sequentially form the third conductive film 45 a and the fourth conductive film 46 a on the piezoelectric substrate 14. At this time, the third conductive film 45 a and the fourth conductive film 46 a are formed with protrusions 66 that protrude along the side surfaces of the mask layer 82.

[0077] like Figure 7 As shown in (c), the mask layer 82 is removed by, for example, a lift-off method. After the mask layer 82 is removed, the protrusions 66 formed on the third conductive film 45a and the fourth conductive film 46a remain. The protrusions 66 are also called burrs. The height of the protrusions 66 from the upper surface of the fourth conductive film 46a also depends on the thickness of the third conductive film 45a and the fourth conductive film 46a, and is, for example, 300 nm to 800 nm.

[0078] like Figure 8 As shown in FIG. 5( a ), a mask layer 84 is formed. The mask layer 84 covers the series resonator S4 and the first base conductive layer 36, and covers the region where the parallel resonator P4 and the second base conductive layer 38 are formed. The mask layer 84 has openings at the ends of the third conductive film 45 a and the fourth conductive film 46 a where the protrusions 66 are formed. The mask layer 84 is formed of, for example, a resist.

[0079] like Figure 8As shown in (b), the mask layer 84 is used as a mask, and the fourth conductive film 46a and the third conductive film 45a are removed using, for example, etching. Then, the mask layer 84 is removed. As a result, a parallel resonator P4 is formed, which has an electrode finger 18b including the third conductive layer 45 and the fourth conductive layer 46; and a second base conductive layer 38 is formed, which is connected to the parallel resonator P4 and has the same layer structure as the electrode finger 18b. The second base conductive layer 38 is formed opposite to the first base conductive layer 36 with a gap 50 therebetween. Furthermore, the protrusion 66 formed on the third conductive film 45a and the fourth conductive film 46a is removed by etching. Therefore, the thickness of the second base conductive layer 38 is constant throughout the entire second base conductive layer 38.

[0080] like Figure 8 As shown in (c), the first layer 35 and the second layer 37 are formed using, for example, vacuum deposition and lift-off methods, thereby forming a wiring layer 34 from above the first base conductive layer 36 to above the second base conductive layer 38. The wiring layer 34 is formed by filling the gap 50. The series resonator S4 and the parallel resonator P4 are electrically connected via the wiring layer 34.

[0081] As described above, the electrode fingers 18a of the series resonator S4 and the electrode fingers 18b of the parallel resonator P4 are made of different materials. Therefore, the series resonator S4 and the parallel resonator P4 are formed using different processes. Consequently, the first base conductive layer 36 connected to the series resonator S4 and the second base conductive layer 38 connected to the parallel resonator P4 are also formed using different processes.

[0082] [Comparative Example]

[0083] Figure 9 (a) to Figure 10 (c) is a cross-sectional view showing a method for manufacturing the series resonator S4, the parallel resonator P4, and the wiring layer 34 of the comparative example. Figure 6 (a) to Figure 6 The same process as that shown in step (c) is then performed. Figure 9 As shown in (a), a mask layer 82 is formed on the piezoelectric substrate 14 to cover the series resonator S4 and the first base conductive layer 36. At this time, the end of the first base conductive layer 36 is not covered with the mask layer 82 so that the first base conductive layer 36 and the second base conductive layer 38 are connected.

[0084] like Figure 9As shown in FIG. 1 , a third conductive film 45 a and a fourth conductive film 46 a are sequentially formed on the piezoelectric substrate 14 using, for example, sputtering or vacuum deposition. Since the ends of the first underlying conductive layer 36 are not covered by the mask layer 82, the third conductive film 45 a and the fourth conductive film 46 a are also formed on the ends of the first underlying conductive layer 36. The third conductive film 45 a and the fourth conductive film 46 a have protrusions 66 formed on the first underlying conductive layer 36 that protrude along the side surfaces of the mask layer 82.

[0085] like Figure 9 As shown in (c), the mask layer 82 is removed by, for example, a lift-off method. After the mask layer 82 is removed, the protrusions 66 formed on the third conductive film 45a and the fourth conductive film 46a remain.

[0086] like Figure 10 As shown in FIG. 8( a ), a mask layer 84 is formed to cover the series resonator S4 and the first base conductive layer 36, and to cover the region where the parallel resonator P4 and the second base conductive layer 38 are formed. The protrusions 66 formed on the third conductive film 45 a and the fourth conductive film 46 a are also covered by the mask layer 84.

[0087] like Figure 10 As shown in (b), using mask layer 84 as a mask, the fourth conductive film 46a and the third conductive film 45a are removed using, for example, etching. Mask layer 84 is then removed. This results in: a parallel resonator P4 having electrode fingers 18b formed of third conductive layer 45 and fourth conductive layer 46; and a second base conductive layer 38 connected to parallel resonator P4 and having the same layer structure as electrode fingers 18b. The protrusion 66 remains because it is covered by mask layer 84.

[0088] like Figure 10 As shown in (c), the first layer 35 and the second layer 37 are formed using, for example, a vacuum evaporation method and a lift-off method, thereby forming the wiring layer 34 from the first base conductive layer 36 to the second base conductive layer 38. Since the end of the second base conductive layer 38 is provided on the first base conductive layer 36, the wiring layer 34 has a thinner portion at the end of the second base conductive layer 38. Furthermore, since the protrusion 66 is formed at the end of the second base conductive layer 38, the thickness of the wiring layer 34 tends to become thinner. Therefore, cracks 67 may sometimes form in the thinner portion of the wiring layer 34. When cracks 67 form, the resistance of the wiring layer 34 increases, and if the cracks 67 are large, the wiring layer 34 may be disconnected.

[0089] On the other hand, according to Example 1, Figure 5 (a) and Figure 5As shown in (b), the first base conductive layer 36 and the second base conductive layer 38 are disposed opposite each other with a gap 50 therebetween. Therefore, the wiring layer 34 disposed from the first base conductive layer 36 to the second base conductive layer 38 is less likely to have a thinner portion. This can suppress cracking in the wiring layer 34, and can also suppress an increase in resistance and disconnection in the wiring layer 34.

[0090] Furthermore, in Example 1, Figure 5 (b) and Figure 5 As shown in (c), the thickness T11 of the first base conductive layer 36 is constant throughout the entire first base conductive layer 36. The thickness T12 of the second base conductive layer 38 is constant throughout the entire second base conductive layer 38. That is, the first and second base conductive layers 36 and 38 do not form protrusions 66, as in the second base conductive layer 38 of the comparative example. This prevents the wiring layer 34 from having thinner areas, and thus prevents the wiring layer 34 from cracking. Furthermore, the term "consistent thickness" means that variations in manufacturing tolerances are acceptable, with the difference between the maximum and minimum thicknesses being 5% or less relative to the average thickness.

[0091] According to the manufacturing method of Example 1, Figure 6 As in (c), a series resonator S4 (first elastic wave resonator) and a first base conductive layer 36 are formed on the piezoelectric substrate 14. The series resonator S4 has electrode fingers 18a, and the first base conductive layer 36 is connected to the series resonator S4 and has the same layer structure as the electrode fingers 18a. Figure 7 As in (a), a mask layer 82 (first mask layer) is formed on the piezoelectric substrate 14 to cover the series resonator S4 and the first underlying conductive layer 36. Figure 7 As in (b), the third conductive film 45a and the fourth conductive film 46a (conductive film) are formed on the piezoelectric substrate 14 using the mask layer 82 as a mask. Figure 8 As in (a), after removing the mask layer 82, a mask layer 84 (second mask layer) is formed on the piezoelectric substrate 14. The mask layer 84 has at least openings at the ends of the third conductive film 45a and the fourth conductive film 46a. Figure 8 As in (b), the third conductive film 45a and the fourth conductive film 46a are etched using the mask layer 84 as a mask to form the parallel resonator P4 (second elastic wave resonator) and the second base conductive layer 38. The parallel resonator P4 has the electrode fingers 18b. The second base conductive layer 38 is connected to the parallel resonator P4 and has the same layer structure as the electrode fingers 18b. The second base conductive layer 38 is opposed to the first base conductive layer 36 with a gap 50 therebetween. Figure 8As in (c), after removing the mask layer 84, the wiring layer 34 connecting the series resonator S4 and the parallel resonator P4 is formed from above the first base conductive layer 36 to above the second base conductive layer 38. This can prevent the wiring layer 34 from having a thinner portion and can prevent the wiring layer 34 from cracking.

[0092] Furthermore, in the manufacturing method of Example 1, Figure 8 As in (a), the mask layer 84 (second mask layer) is formed so that the opening is located at the protrusion 66 formed at the end of the third conductive film 45a and the fourth conductive film 46a. Figure 8 As shown in (b), the protrusion 66 is removed by etching the third conductive film 45a and the fourth conductive film 46a using the mask layer 84 as a mask, thereby suppressing the occurrence of thin film thickness areas in the wiring layer 34. Therefore, cracks in the wiring layer 34 can be suppressed.

[0093] Furthermore, in the manufacturing method of Example 1, Figure 7 As in (a), a mask layer 82 (first mask layer) is formed in a region larger than the region where the series resonator S4 and the first base conductive layer 36 are formed so as to completely cover the series resonator S4 and the first base conductive layer 36. Figure 8 In (b), the difference between the etching amount of the region where the parallel resonator P4 is formed and the etching amount of the region where the protrusion 66 is formed is reduced, so that manufacturing is facilitated.

[0094] Furthermore, in Example 1, the thickness T13 of the wiring layer 34 is at least twice the thickness of the larger of the thickness T11 of the first base conductive layer 36 and the thickness T12 of the second base conductive layer 38. This ensures that even in areas where the wiring layer 34 is relatively thin, it still has a considerable thickness, thereby suppressing cracks in the wiring layer 34.

[0095] Furthermore, in Example 1, the distance L of the gap 50 between the first and second base conductive layers 36 and 38 is greater than or equal to 1 times and less than or equal to 10 times the thickness of the larger thickness T11 of the first and second base conductive layers 36 and 38. By making the distance L greater than or equal to the greater thickness T11 or T12, the wiring layer 34 is easily formed in the gap 50, thereby improving the reliability of the electrical connection between the series resonator S4 and the parallel resonator P4 using the wiring layer 34. To improve electrical connection reliability, the distance L is preferably greater than or equal to 1.5 times, more preferably greater than or equal to 2 times, and even more preferably greater than or equal to 2.5 times the greater thickness T11 or T12. Furthermore, by making the distance L less than or equal to 10 times the greater thickness T11 or T12, the gap 50 can be formed in the narrow space between the series resonator S4 and the parallel resonator P4. The X-direction spacing between series resonator S4 and parallel resonator P4 is, for example, 1 / 4 the length of electrode finger 18 of the shorter of the two resonators in the Y direction. From the perspective of miniaturizing the device by narrowing the width between resonators, spacing L is preferably 8 times or less, more preferably 6 times or less, and even more preferably 4 times or less, the larger of thickness T11 and thickness T12.

[0096] Furthermore, in Example 1, a gap 50 is provided between the first base conductive layer 36 and the second base conductive layer 38 in the X-direction between the series resonator S4 and the parallel resonator P4. While the elastic waves excited by the series resonator S4 and the parallel resonator P4 propagate primarily in the X-direction, the gap 50 can reduce interference caused by the propagation of the elastic waves between the series resonator S4 and the parallel resonator P4.

[0097] Furthermore, in Example 1, the electrode finger 18a of the series resonator S4 includes a first conductive layer 43 which is a TiN layer and a second conductive layer 44 provided on the first conductive layer 43. The electrode finger 18b of the parallel resonator P4 includes a third conductive layer 45 which is a Ti layer and a fourth conductive layer 46 which is provided on the third conductive layer 45 and is made of the same material as the second conductive layer 44. Figure 4 (a) and Figure 4 As described in (b), the frequency temperature change on both the low-frequency side and the high-frequency side of the passband can be reduced.

[0098] In addition, in Example 1, it is also possible to Figure 3 (a) and Figure 3As in structure A and structure B in (b), an insulating layer 11, an insulating layer 12, and an insulating layer 13 are provided between the supporting substrate 10 and the piezoelectric substrate 14. It is also possible that only the insulating layer 13 is provided or only the insulating layer 12 and the insulating layer 13 are provided. Furthermore, the interface between the supporting substrate 10 and the insulating layer 11 is not limited to a rough surface, but may be a mirror surface, or the interface between the supporting substrate 10 and the insulating layer 11 may be a rough surface and the interface between the insulating layer 11 and the insulating layer 12 may also be a rough surface. In the case where the insulating layer 11 is not provided, the interface between the supporting substrate 10 and the insulating layer 12 may also be a rough surface. Furthermore, the piezoelectric substrate 14 may not be provided on the supporting substrate 10.

[0099] In Example 1, two elastic wave resonators connected by providing a wiring layer on two base conductive layers disposed with a gap therebetween are used as a filter, but the present invention is not limited to this case and may also be used in other cases such as a sensor having these two elastic wave resonators.

[0100] [Example 2]

[0101] Figure 11 FIG. 2 is a circuit diagram of the duplexer 200 according to the second embodiment. Figure 11 As shown, the duplexer 200 has a transmit filter 70 connected between a common terminal Ant and a transmit terminal Tx. A receive filter 72 is connected between the common terminal Ant and a receive terminal Rx. The transmit filter 70 allows signals in the transmit frequency band of the high-frequency signal input from the transmit terminal Tx to pass through the common terminal Ant as transmit signals, while suppressing signals of other frequencies. The receive filter 72 allows signals in the receive frequency band of the high-frequency signal input from the common terminal Ant to pass through the receive terminal Rx as receive signals, while suppressing signals of other frequencies. At least one of the transmit filter 70 and the receive filter 72 can be the filter of Example 1. While a duplexer is shown as an example of a multiplexer, a triplexer or a quadplexer may also be used.

[0102] While the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. An elastic wave device comprising: Piezoelectric substrate; a first elastic wave resonator provided on the piezoelectric substrate and having a plurality of first electrode fingers; a second elastic wave resonator provided on the piezoelectric substrate and having a plurality of second electrode fingers made of a material different from that of the plurality of first electrode fingers; a first underlying conductive layer provided on the piezoelectric substrate, connected to the first elastic wave resonator, and having the same layer structure as the plurality of first electrode fingers; a second underlying conductive layer provided on the piezoelectric substrate, connected to the second elastic wave resonator, having the same layer structure as the plurality of second electrode fingers, and facing the first underlying conductive layer with a gap therebetween; and A wiring layer is provided from above the first base conductive layer to above the second base conductive layer, and connects the first elastic wave resonator and the second elastic wave resonator.

2. The elastic wave device according to claim 1, wherein The thickness of the first base conductive layer is constant throughout the first base conductive layer. The thickness of the second base conductive layer is constant throughout the second base conductive layer.

3. The elastic wave device according to claim 1 or 2, wherein: The wiring layer has a thickness that is at least twice as thick as the larger thickness of the first base conductive layer or the second base conductive layer.

4. The elastic wave device according to claim 1 or 2, wherein: The first and second base conductive layers are opposed to each other with the gap therebetween, and the distance between them is at least one time the thickness of the larger of the first and second base conductive layers.

5. The elastic wave device according to claim 1 or 2, wherein: The plurality of first electrode fingers and the plurality of second electrode fingers are arranged in the same direction, The gap is provided between the first elastic wave resonator and the second elastic wave resonator in the arrangement direction. A filter comprising the elastic wave device according to claim 1 or 2.

7. The filter according to claim 6, wherein The first elastic wave resonator is a series resonator connected in series between the input terminal and the output terminal. The second elastic wave resonator is a parallel resonator connected in parallel between the input terminal and the output terminal. The plurality of first electrode fingers include a first conductive layer which is a titanium nitride layer and a second conductive layer provided on the first conductive layer. The plurality of second electrode fingers include a third conductive layer that is a titanium layer and a fourth conductive layer that is provided on the third conductive layer and is made of the same material as the second conductive layer. A multiplexer comprising the filter according to claim 6 .

9. A method for manufacturing an elastic wave device, comprising the following steps: forming a first elastic wave resonator and a first underlying conductive layer on a piezoelectric substrate, the first elastic wave resonator having a plurality of first electrode fingers, the first underlying conductive layer being connected to the first elastic wave resonator and having the same layer structure as the plurality of first electrode fingers; forming a first mask layer on the piezoelectric substrate so as to cover the first elastic wave resonator and the first underlying conductive layer; forming a conductive film on the piezoelectric substrate using the first mask layer as a mask; After removing the first mask layer, forming a second mask layer on the piezoelectric substrate, the second mask layer having at least an opening at an end portion of the conductive film; The conductive film is etched using the second mask layer as a mask to form a second elastic wave resonator and a second underlying conductive layer. The second elastic wave resonator has a plurality of second electrode fingers. The second underlying conductive layer is connected to the second elastic wave resonator, has the same layer structure as the plurality of second electrode fingers, and faces the first underlying conductive layer with a gap therebetween. as well as After the second mask layer is removed, a wiring layer connecting the first elastic wave resonator and the second elastic wave resonator is formed from above the first underlying conductive layer to above the second underlying conductive layer.

10. The method for manufacturing an elastic wave device according to claim 9, wherein: In the step of forming the second mask layer, the second mask layer is formed so that the opening is located in a protrusion formed at the end portion of the conductive film.

11. The method for manufacturing an elastic wave device according to claim 9 or 10, wherein: In the step of forming the first mask layer, the first mask layer is formed in a region larger than a region where the first elastic wave resonator and the first underlying conductive layer are formed so as to completely cover the first elastic wave resonator and the first underlying conductive layer.

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