Electronic device and method of manufacturing electronic device

Abstract

To provide an electronic device in which a decrease in reliability can be suppressed.SOLUTION: A surface acoustic wave device 100 comprises: a substrate 10; an acoustic wave element 50 provided on the substrate 10; an annular bonding layer 32 which is provided on the substrate 10 encircling the acoustic wave element 50 in plan view and formed of solder, and has a first bonding part 35 and a second bonding part 36 differing in constituent element or composition ratio from the first bonding part 35 in plan view; and a lid 40 which is bonded to the annular bonding layer 32 opposite the substrate 10 across a gap 22, and seals the acoustic wave element 50 in the gap 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic device and a method for manufacturing an electronic device. [Background technology]

[0002] Electronic devices in which a functional element is sealed in a gap between a substrate and a cap or lid are known (e.g., Patent Documents 1 to 4). When the substrate and the cap or lid are bonded, if gas remains in the gap, the reliability of the device decreases. Therefore, it is known to provide a notch or a recess in the bonding layer in order to release the gas in the gap to the outside (e.g., Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-132413 [Patent Document 2] Japanese Patent Application Publication No. 6-232284 [Patent Document 3] Japanese Patent Application Publication No. 8-213496 [Patent Document 4] Special Publication No. 2007-516602 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is still room for improvement in terms of suppressing deterioration in device reliability.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to suppress a decrease in the reliability of a device. [Means for solving the problem]

[0006] The present invention is an electronic device comprising: a substrate; a functional element provided on the substrate; an annular bonding layer provided on the substrate surrounding the functional element in a planar view, the annular bonding layer being formed of solder and having a first bonding portion and a second bonding portion that, in the planar view, has constituent elements or a composition ratio different from that of the first bonding portion; and a lid bonded to the annular bonding layer across a gap between the substrate and the lid, sealing the functional element within the gap.

[0007] In the above configuration, the first bonding portion may have a lower melting point than the second bonding portion, and the area of ​​the first bonding portion may be larger than the area of ​​the second bonding portion in the plan view.

[0008] In the above configuration, the second joint portion may have a larger Young's modulus than the first joint portion, and the area of ​​the second joint portion may be larger than the area of ​​the first joint portion in the plan view.

[0009] In the above configuration, the gap may be provided between the substrate and the lid, and a columnar body having a bonding layer may be provided, and the bonding layer and the second bonding portion may have a larger Young's modulus than the first bonding portion.

[0010] In the above configuration, the first bonding portion may be made of gold-tin, and the second bonding portion may be made of gold-tin having a different composition ratio from that of the first bonding portion.

[0011] The present invention is a method for manufacturing an electronic device, comprising the steps of: forming a functional element on a substrate; forming an annular bonding layer on the substrate or on a lid, the annular bonding layer having a first bonding portion and a second bonding portion that has a higher melting point than the first bonding portion and is thicker; heating the first bonding portion and the second bonding portion to a first temperature that is higher than the melting point of the first bonding portion and lower than the melting point of the second bonding portion, and abutting the lid or the substrate against the second bonding portion so that a gap is formed between the lid and the first bonding portion or between the substrate and the first bonding portion; and, after the abutting step, heating the first bonding portion and the second bonding portion to a second temperature that is higher than the melting point of the second bonding portion to bond the lid or the substrate to the first bonding portion and the second bonding portion, and sealing the functional element in the gap between the substrate and the lid. [Effects of the Invention]

[0012] According to the present invention, it is possible to suppress a decrease in the reliability of the device. [Brief explanation of the drawings]

[0013] [Figure 1] 1A is a plan view of an acoustic wave device in accordance with a first embodiment, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1C is a cross-sectional view taken along line BB in FIG. 1A. [Figure 2] FIG. 2(a) is a plan view of the acoustic wave device according to the first embodiment, and FIG. 2(b) is a cross-sectional view of another example of the acoustic wave device according to the first embodiment. [Figure 3] 3(a) to 3(c) are cross-sectional views (part 1) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. [Figure 4] 4(a) to 4(c) are cross-sectional views (part 2) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. [Figure 5] 5(a) is a plan view of an acoustic wave device according to a modification of the first embodiment, FIG. 5(b) is a cross-sectional view taken along line AA in FIG. 5(a), and FIG. 5(c) is a cross-sectional view taken along line BB in FIG. 5(a). [Figure 6]6(a) to 6(c) are cross-sectional views (part 1) illustrating a method for manufacturing an acoustic wave device according to a modified example of the first embodiment. [Figure 7] 7(a) and 7(b) are cross-sectional views (part 2) illustrating a method for manufacturing an acoustic wave device according to a modified example of the first embodiment. [Figure 8] FIG. 8(a) is a plan view of an acoustic wave device in accordance with a second embodiment, and FIG. 8(b) is a plan view of an acoustic wave device in accordance with a modified example of the second embodiment. [Figure 9] FIG. 9 is a cross-sectional view of an acoustic wave device in accordance with a third embodiment. [Figure 10] FIG. 10(a) is a circuit diagram of a filter according to the fourth embodiment, and FIG. 10(b) is a circuit diagram of a duplexer according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, with reference to the drawings, an embodiment of the present invention will be described, taking an acoustic wave device as an example of an electronic device. [Example]

[0015] FIG. 1(a) is a plan view of an acoustic wave device 100 according to a first embodiment, FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a), and FIG. 1(c) is a cross-sectional view taken along line BB in FIG. 1(a). FIG. 1(a) illustrates a piezoelectric layer 12 and a frame 30 provided on a substrate 10. The X and Y directions are perpendicular to each other in the planar direction of the substrate 10. The Z direction is the stacking direction of the substrate 10 and the piezoelectric layer 12.

[0016] As shown in FIGS. 1(a) to 1(c), a piezoelectric layer 12 is bonded to a substrate 10. The substrate 10 is, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a quartz substrate, a silicon carbide substrate, or a silicon substrate, and has a thickness of 100 μm to 500 μm. The piezoelectric layer 12 is, for example, a single-crystal lithium tantalate layer, a single-crystal lithium niobate layer, or a single-crystal quartz layer, and has a thickness of 0.1 μm to 10 μm. An insulating layer such as silicon oxide, aluminum oxide, and / or aluminum nitride may be provided between the substrate 10 and the piezoelectric layer 12. In this manner, the piezoelectric layer 12 is bonded directly or indirectly to the substrate 10.

[0017] An acoustic wave element 50 is provided on a piezoelectric layer 12. FIG. 2A is a plan view of the acoustic wave element 50 according to the first embodiment. As shown in FIG. 2A, the acoustic wave element 50 is a surface acoustic wave resonator, and includes an interdigital transducer (IDT) 51 and a reflector 52 provided on the piezoelectric layer 12. The reflectors 52 are provided on both sides of the IDT 51. The IDT 51 includes a pair of opposing comb electrodes 53. The comb electrode 53 includes a plurality of electrode fingers 54 and a bus bar 55 to which the plurality of electrode fingers 54 are connected. An intersection region 56 is a region where the electrode fingers 54 of the pair of comb electrodes 53 intersect. The pair of comb electrodes 53 has the electrode fingers 54 alternately arranged in at least a portion of the intersection region 56. An acoustic wave excited primarily by the electrode fingers 54 in the intersection region 56 propagates primarily in the direction in which the electrode fingers 54 are arranged. The pitch of the electrode fingers 54 of one of the pair of interdigital transducers 53 (the pitch between the centers of the electrode fingers 54) is approximately equal to the wavelength λ of the acoustic wave. If the pitch of the electrode fingers 54 is D, the pitch of the electrode fingers 54 of one interdigital transducer 53 is D, which is the pitch of two electrode fingers 54. The reflector 52 reflects the acoustic waves (surface acoustic waves) excited by the electrode fingers 54. This confines the acoustic waves within the interdigital transducer 51 crossing region 56. The IDT 51 and the reflector 52 are formed of a metal film such as aluminum, copper, or molybdenum. An insulating film may be provided to cover the electrode fingers 54. The insulating film may function as a protective film or a temperature compensation film. The interdigital transducer 53 may have dummy electrode fingers.

[0018] FIG. 2(b) is a cross-sectional view of another example of acoustic wave element 50 according to the first embodiment. As shown in FIG. 2(b), acoustic wave element 50a may be a piezoelectric thin film resonator. A piezoelectric layer 12a is provided on substrate 10, and a lower electrode 61 and an upper electrode 62 are provided on either side of piezoelectric layer 12a. A gap 63 is formed between lower electrode 61 and substrate 10. A resonance region 64 is a region where lower electrode 61 and upper electrode 62 face each other, sandwiching at least a portion of piezoelectric layer 12a. In resonance region 64, lower electrode 61 and upper electrode 62 excite acoustic waves in piezoelectric layer 12a. Lower electrode 61 and upper electrode 62 are metal films, such as ruthenium films. Piezoelectric layer 12a is, for example, an aluminum nitride layer, a zinc oxide layer, a single-crystal lithium tantalate layer, or a single-crystal lithium niobate layer. An acoustic reflection film that reflects acoustic waves may be provided instead of gap 63.

[0019] As shown in FIGS. 1(a) to 1(c), the piezoelectric layer 12 is not provided in the peripheral region of the substrate 10. In a plan view from the +Z direction, a frame body 30 is provided in the peripheral region of the substrate 10, surrounding the piezoelectric layer 12 and the acoustic wave element 50. The frame body 30 includes an annular metal layer 31 and an annular bonding layer 32. The thickness of the annular metal layer 31 is, for example, 15 μm to 30 μm. The thickness of the annular bonding layer 32 is, for example, 3 μm to 10 μm. In a plan view from the +Z direction, the frame body 30 is substantially rectangular and has a pair of first sides 33 and a pair of second sides 34. The length L1 of the first sides 33 is greater than the length L2 of the second sides 34. The first sides 33 and the second sides 34 are formed by extensions of the annular metal layer 31 and the annular bonding layer 32.

[0020] The annular bonding layer 32 includes a first bonding portion 35 formed of a first solder material and a second bonding portion 36 formed of a second solder material different from the first solder material. For example, the first bonding portion 35 is formed of gold-tin (AuSn), and the second bonding portion 36 is formed of gold-tin (AuSn) with a different composition ratio from that of the first bonding portion 35. As an example, the first bonding portion 35 is formed of Au-80Sn, which has a composition ratio of 20 wt% Au and 80 wt% Sn, and has a melting point of 252°C. The second bonding portion 36 is formed of Au-30Sn, which has a composition ratio of 70 wt% Au and 30 wt% Sn, and has a melting point of 278°C. Thus, the first bonding portion 35 has a lower melting point than the second bonding portion 36. Furthermore, when the first bonding portion 35 is formed of Au-80Sn and the second bonding portion 36 is formed of Au-30Sn, the Young's modulus of the main intermetallic compound formed in the first bonding portion 35 is approximately 43 GPa, and the Young's modulus of the main intermetallic compound formed in the second bonding portion 36 is approximately 69 GPa. Therefore, the Young's modulus of the second bonding portion 36 is greater than that of the first bonding portion 35.

[0021] The first bonding portion 35 is provided on the first side 33, and the second bonding portion 36 is provided on the second side 34. In a plan view seen from the +Z direction, the area of ​​the first bonding portion 35 is larger than the area of ​​the second bonding portion 36.

[0022] A lid 40 is provided on the frame 30, sandwiching a gap 22 between the frame 30 and the substrate 10. The lid 40 is bonded to a first bonding portion 35 and a second bonding portion 36 of the annular bonding layer 32. The lid 40 and the frame 30 seal the acoustic wave element 50 in the gap 22.

[0023] Terminals 14 are provided on the lower surface of substrate 10. Via wiring 16 is provided to penetrate substrate 10. Wiring 20 is provided from the upper surface of substrate 10 to the upper surface of piezoelectric layer 12. Acoustic wave element 50 is connected to terminals 14 via wiring 20 and via wiring 16.

[0024] The terminal 14, via wiring 16, and wiring 20 are each a single layer of a metal such as copper, gold, silver, titanium, nickel, or tungsten, or a laminate of these. The annular metal layer 31 of the frame 30 is a single layer of a metal such as copper, gold, or nickel, or a laminate of these. The lid 40 includes a metal layer such as an iron alloy such as Kovar or 42 alloy, an aluminum alloy such as duralumin, nickel, copper, cupronickel, or nickel silver. These metal layers of the lid 40 are exposed to the void 22. The lid 40 may also include an insulating layer such as sapphire, alumina, spinel, or silicon. These insulating layers are provided on the opposite side of the metal layer from the void 22.

[0025] [Manufacturing method] 3(a) to 4(c) are cross-sectional views illustrating a manufacturing method of the acoustic wave device 100 according to the first embodiment. The left-hand diagrams in FIGS. 3(a) to 4(c) are cross-sectional views corresponding to FIG. 1(b), and the right-hand diagrams are cross-sectional views corresponding to FIG. 1(c). As shown in FIG. 3(a), via holes are formed in the upper surface of the substrate 10 by, for example, irradiating the substrate with laser light, and a metal layer such as copper is formed in the via holes by, for example, electrolytic plating. The metal layer is then planarized by, for example, CMP (Chemical Mechanical Polishing) so that the upper surface of the substrate 10 is exposed. This results in via wiring 16 in the substrate 10. Note that the via wiring 16 does not yet penetrate the substrate 10. Next, a piezoelectric substrate is bonded to the upper surface of the substrate 10 at room temperature by, for example, surface activation. The substrate 10 and the piezoelectric substrate may be directly bonded via an amorphous layer of several nanometers or indirectly bonded via an insulating layer. The upper surface of the piezoelectric substrate is then polished by, for example, CMP to form a piezoelectric layer 12 of the desired thickness.

[0026] 3(b), a portion of the piezoelectric layer 12 is removed, for example, by etching, to expose the via wiring 16. Next, the acoustic wave element 50 is formed on the piezoelectric layer 12, for example, by photolithography and etching. The wiring 20 electrically connected to the acoustic wave element 50 is formed, for example, by lift-off. The wiring 20 is provided from above the piezoelectric layer 12 to above the via wiring 16, and electrically connects the acoustic wave element 50 and the via wiring 16.

[0027] As shown in FIG. 3( c), a frame 30 is formed on the substrate 10 by, for example, electroplating so as to surround the piezoelectric layer 12 and the acoustic wave element 50. The frame 30 includes an annular metal layer 31 and an annular bonding layer 32. The annular bonding layer 32 includes a first bonding portion 35 formed of a first solder material and a second bonding portion 36 formed of a second solder material different from the first solder material and having a higher melting point than the first bonding portion 35. As an example, the first bonding portion 35 is formed of Au-80Sn, and the second bonding portion 36 is formed of Au-30Sn. In this case, the melting point of the first bonding portion 35 is 252°C, and the melting point of the second bonding portion 36 is 278°C. The second bonding portion 36 is formed so that its thickness T2 is greater than the thickness T1 of the first bonding portion 35. For example, the thickness T1 is about 3 μm to 10 μm, the thickness T2 is about 4 μm to 11 μm, and the difference (T2−T1) is 1 μm or more.

[0028] As shown in FIG. 4A, the first bonding portion 35 and the second bonding portion 36 are heated at a first temperature equal to or higher than the melting point of the first bonding portion 35 and lower than the melting point of the second bonding portion 36, and the lid 40 is brought into contact with the second bonding portion 36. As an example, if the melting point of the first bonding portion 35 is 252°C and the melting point of the second bonding portion 36 is 278°C, the lid 40 is heated at a first temperature equal to or higher than 252°C and lower than 278°C, and the lid 40 is brought into contact with the second bonding portion 36. Because the first bonding portion 35 is melted but the second bonding portion 36 is not, a void 42 having a height of 1 μm or more is formed between the lid 40 and the first bonding portion 35. By heating at the first temperature, moisture absorbed in the annular metal layer 31, the annular bonding layer 32, the lid 40, the wiring 20, the piezoelectric layer 12, the acoustic wave element 50, etc. evaporates, generating gas. The gas is then released to the outside through the void 42. To release the gas, it is preferable to heat the lid 40 at the first temperature and maintain the state in which the lid 40 is in contact with the second bonding portion 36 for a predetermined time (for example, several seconds to several tens of seconds).

[0029] 4(b), the first bonding portion 35 and the second bonding portion 36 are heated to a second temperature equal to or higher than the melting point of the second bonding portion 36, and the lid 40 is bonded to the first bonding portion 35 and the second bonding portion 36. As a result, the acoustic wave element 50 is sealed in the gap 22 between the substrate 10 and the lid 40.

[0030] 4(c), the lower surface of the substrate 10 is polished by, for example, CMP. As a result, the via wiring 16 is exposed from the lower surface of the substrate 10. Next, terminals 14 connected to the via wiring 16 are formed on the lower surface of the substrate 10. The terminals 14 are formed by, for example, electrolytic plating. In this way, the acoustic wave device 100 in accordance with the first embodiment is formed.

[0031] [Variations] Fig. 5(a) is a plan view of an acoustic wave device 110 according to a modification of the first embodiment, Fig. 5(b) is a cross-sectional view taken along line AA in Fig. 5(a), and Fig. 5(c) is a cross-sectional view taken along line BB in Fig. 5(a). As shown in Figs. 5(a) to 5(c), in the modification of the first embodiment, the frame 30 has an annular bonding layer 32 on the substrate 10 side and an annular metal layer 31 on the lid 40 side. The other configurations are the same as those in the first embodiment, and therefore will not be described again.

[0032] [Manufacturing method] 6(a) to 7(b) are cross-sectional views showing a manufacturing method of an acoustic wave device 110 according to a modified example of Example 1. The left-hand diagrams of FIGS. 6(a) to 7(b) are cross-sectional views of a portion corresponding to FIG. 5(b), and the right-hand diagrams are cross-sectional views of a portion corresponding to FIG. 5(c). As shown in FIG. 6(a), first, the steps described with reference to FIGS. 3(a) and 3(b) are carried out.

[0033] 6(b), a frame 30 including an annular metal layer 31 and an annular bonding layer 32 is formed on a lid 40 using, for example, electrolytic plating. The annular bonding layer 32 includes a first bonding portion 35 formed of a first solder material and a second bonding portion 36 formed of a second solder material different from the first solder material and having a higher melting point than the first bonding portion 35. The second bonding portion 36 is formed so that a thickness T2 is greater than a thickness T1 of the first bonding portion 35.

[0034] 6(c), the first bonding portion 35 and the second bonding portion 36 are heated at a first temperature that is equal to or higher than the melting point of the first bonding portion 35 and lower than the melting point of the second bonding portion 36, and the second bonding portion 36 formed on the lid 40 is brought into contact with the substrate 10. Because the first bonding portion 35 is melted but the second bonding portion 36 is not melted, a gap 42 is formed between the substrate 10 and the first bonding portion 35. By heating at the first temperature, moisture absorbed in the annular metal layer 31, the annular bonding layer 32, the lid 40, the wiring 20, the piezoelectric layer 12, the acoustic wave element 50, etc. evaporates to generate gas, which is then released to the outside through the gap 42.

[0035] 7(a), the first bonding portion 35 and the second bonding portion 36 are heated to a second temperature equal to or higher than the melting point of the second bonding portion 36, and the first bonding portion 35 and the second bonding portion 36 formed on the lid 40 are bonded to the substrate 10. As a result, the acoustic wave element 50 is sealed in the gap 22 between the substrate 10 and the lid 40.

[0036] 7(b), the lower surface of the substrate 10 is polished by, for example, CMP. As a result, the via wiring 16 is exposed from the lower surface of the substrate 10. Next, terminals 14 connected to the via wiring 16 are formed on the lower surface of the substrate 10. The terminals 14 are formed by, for example, electrolytic plating. In this manner, an acoustic wave device 110 according to a modified example of the first embodiment is formed.

[0037] According to the first embodiment and its modifications, an annular bonding layer 32 is provided on a substrate 10 to surround an acoustic wave element 50. The annular bonding layer 32 is formed of solder and includes a first bonding portion 35 and a second bonding portion 36 having a different composition ratio from that of the first bonding portion 35. As an example, the first bonding portion 35 is formed of Au-80Sn, and the second bonding portion 36 is formed of Au-30Sn. The first bonding portion 35 and the second bonding portion 36 have different melting points due to their different composition ratios. Therefore, as shown in FIGS. 4( a) and 6(c), when the annular bonding layer 32 is melted to seal the acoustic wave element 50 in the gap 22 between the substrate 10 and the lid 40, the difference in melting points between the first bonding portion 35 and the second bonding portion 36 can be used to release gases such as moisture absorbed by each component from the gap 42 to the outside. Therefore, even if the device temperature drops, the formation of water droplets and the like in the gap 22 is suppressed, and the deterioration of the electrical characteristics of the acoustic wave device can be suppressed, thereby suppressing the deterioration of the reliability of the device.

[0038] Furthermore, the first bonding portion 35 and the second bonding portion 36 have different Young's moduli due to their different composition ratios. For example, the volume of gas in the void 22 may expand due to temperature increases during manufacturing and / or use. In this case, if the annular bonding layer 32 is formed only with the first bonding portion 35, which has a smaller Young's modulus than the first bonding portion 35 and the second bonding portion 36, stress caused by the volumetric expansion of the gas in the void 22 may deform the first bonding portion 35, causing the lid 40 to peel off from the annular bonding layer 32. In contrast, by providing the second bonding portion 36, which has a larger Young's modulus, in addition to the first bonding portion 35, the second bonding portion 36 is less likely to deform even when stress is applied, preventing the lid 40 from peeling off from the annular bonding layer 32. This prevents a decrease in device reliability.

[0039] According to the manufacturing methods of the first embodiment and its modifications, an acoustic wave element 50 is formed on a substrate 10 as shown in FIGS. 3(b) and 6(a). As shown in FIGS. 3(c) and 6(b), an annular bonding layer 32 including a first bonding portion 35 and a second bonding portion 36 having a higher melting point and a greater thickness than the first bonding portion 35 is formed on the substrate 10 or the lid 40. As shown in FIGS. 4(a) and 6(c), the first bonding portion 35 and the second bonding portion 36 are heated to a first temperature equal to or higher than the melting point of the first bonding portion 35 and lower than the melting point of the second bonding portion 36, and the lid 40 or the substrate 10 is brought into contact with the second bonding portion 36 so that a gap 42 is formed between the lid 40 and the first bonding portion 35 or between the substrate 10 and the first bonding portion 35. As shown in FIGS. 4(b) and 7(a), the first bonding portion 35 and the second bonding portion 36 are heated to a second temperature equal to or higher than the melting point of the second bonding portion 36 to bond the lid 40 or the substrate 10 to the first bonding portion 35 and the second bonding portion 36, thereby sealing the acoustic wave element 50 in the gap 22 between the substrate 10 and the lid 40. As a result, gases such as moisture absorbed by each component when the device is heated to the first temperature equal to or higher than the melting point of the first bonding portion 35 and lower than the melting point of the second bonding portion 36 as shown in FIGS. 4(a) and 6(c) are released from the gap 42 to the outside. Therefore, even if the device temperature drops, the formation of water droplets in the gap 22 can be suppressed, thereby suppressing degradation of the electrical characteristics of the acoustic wave device. This, in turn, can suppress degradation of the device reliability.

[0040] From the viewpoint of releasing gases such as moisture absorbed by each of the constituent members, the first temperature is preferably equal to or higher than the temperature closest to the melting point of the first bonding portion 35 among the three temperatures at the boundaries of each of the four equal divisions of the temperature between the melting points of the first bonding portion 35 and the second bonding portion 36, and is lower than the melting point of the second bonding portion 36. It is more preferable that the first temperature is equal to or higher than the middle temperature among the three temperatures and is lower than the melting point of the second bonding portion 36. It is even more preferable that the first temperature is equal to or higher than the temperature closest to the melting point of the second bonding portion 36 among the three temperatures and is lower than the melting point of the second bonding portion 36. Furthermore, the melting point of the first bonding portion 35 is preferably 0.6 times or higher than the melting point of the second bonding portion 36, more preferably 0.7 times or higher, and even more preferably 0.8 times or higher.

[0041] Furthermore, in Example 1 and its modified examples, the area of ​​the first bonding portion 35 is larger than the area of ​​the second bonding portion 36 in a plan view. Because the area of ​​the first bonding portion 35, which has a lower melting point, is larger than the area of ​​the second bonding portion 36, which has a higher melting point, gases such as moisture absorbed by each of the components in FIGS. 4(a) and 6(c) are more likely to be released to the outside from the void 42. Therefore, even if the device temperature drops, the formation of water droplets and the like in the void 22 can be suppressed. From the viewpoint of releasing gases to the outside from the void 42, the area of ​​the first bonding portion 35 is preferably 1.2 times or more, more preferably 1.3 times or more, and even more preferably 1.4 times or more, the area of ​​the second bonding portion 36 in a plan view.

[0042] In Example 1 and its modified examples, the first bonding portions 35 are provided on the pair of first sides 33, and the second bonding portions 36 are provided on the pair of second sides 34. By providing the first bonding portion 35, which has a lower melting point, on the longer first side 33, gases such as moisture absorbed by each component are more easily released to the outside from the gap 42. By providing the second bonding portion 36, which has a higher Young's modulus, on the second side 34, the lid 40 is less likely to peel off from the annular bonding layer 32, even if the volume of gas in the gap 22 expands due to a temperature rise during manufacturing and / or use.

[0043] In Example 1 and its modified examples, the first bonding portion 35 is made of gold-tin (e.g., Au-80Sn), and the second bonding portion 36 is made of gold-tin (e.g., Au-30Sn) having a different composition ratio from that of the first bonding portion 35. This ensures the bonding strength between the annular bonding layer 32 and the lid 40 or the substrate 10. This also facilitates the formation of the voids 42 for gas release shown in FIGS. 4(a) and 6(c).

[0044] The first bonding portion 35 and the second bonding portion 36 are not limited to having the same constituent elements but different composition ratios, and may have different constituent elements. For example, the first bonding portion 35 and the second bonding portion 36 may be formed of different solders arbitrarily selected from various solders having different constituent elements, such as gold-tin (AuSn), tin-silver (SnAg), tin-copper (SnCu), tin-silver-copper (SnAgCu), and tin-indium (SnIn). However, from the viewpoint of the bonding strength between the annular bonding layer 32 and the lid 40 or the substrate 10, it is preferable that the first bonding portion 35 and the second bonding portion 36 have the same constituent elements but different composition ratios. [Example]

[0045] Fig. 8(a) is a plan view of an acoustic wave device 200 in accordance with Example 2. As shown in Fig. 8(a), in Example 2, first bonding portions 35 are provided on a pair of second sides 34, and second bonding portions 36 are provided on a pair of first sides 33. The other configurations are the same as those in Example 1, and therefore description thereof will be omitted.

[0046] According to Example 2, the area of ​​the second bonding portion 36 is larger than the area of ​​the first bonding portion 35 in a plan view. The area of ​​the second bonding portion 36, which has a larger Young's modulus, is larger than the area of ​​the first bonding portion 35, which has a smaller Young's modulus. This effectively prevents the lid 40 from peeling off from the annular bonding layer 32, even when the volume of gas in the gap 22 expands due to a temperature rise during manufacturing and / or use. From the viewpoint of preventing peeling of the lid 40, the area of ​​the second bonding portion 36 is preferably 1.2 times or more, more preferably 1.3 times or more, and even more preferably 1.4 times or more, the area of ​​the first bonding portion 35 in a plan view. Furthermore, the Young's modulus of the second bonding portion 36 is preferably 1.1 times or more, more preferably 1.3 times or more, and even more preferably 1.5 times or more, the Young's modulus of the first bonding portion 35.

[0047] Furthermore, according to the second embodiment, the second bonding portions 36 are provided on the pair of first sides 33, and the first bonding portions 35 are provided on the pair of second sides 34. By providing the second bonding portion 36, which has a large Young's modulus, on the longer first side 33, it is possible to effectively prevent the lid 40 from peeling off from the annular bonding layer 32, even if the volume of gas in the gap 22 expands due to a temperature rise during manufacturing and / or use. By providing the first bonding portion 35, which has a low melting point, on the second side 34, gas such as moisture absorbed by each of the components is more easily released from the gap 42 to the outside.

[0048] Fig. 8(b) is a plan view of an acoustic wave device 210 according to a modified example of Example 2. As shown in Fig. 8(b), in Example 2, second bonding portions 36 are provided at four corner portions 37 of the annular bonding layer 32, and first bonding portions 35 are provided in other portions of the annular bonding layer 32. The other configurations are the same as those in Example 1, and therefore description thereof will be omitted.

[0049] According to the modified example of Example 2, the second bonding portions 36 are provided at the corners 37 of the annular bonding layer 32, and the first bonding portions 35 are provided in other parts of the annular bonding layer 32. Therefore, gas such as moisture can be effectively removed as described in Figures 4(a) and 6(c) of Example 1. [Example]

[0050] FIG. 9 is a cross-sectional view of an acoustic wave device 300 according to a third embodiment. As shown in FIG. 9, in the third embodiment, a pillar 80 is provided in a gap 22 near the center of the substrate 10, between the substrate 10 and the lid 40. The pillar 80 is provided, for example, in an opening 11 penetrating the piezoelectric layer 12, and is in contact with the substrate 10 and the lid 40. The pillar 80 includes a metal layer 81 and a bonding layer 82. The metal layer 81 has the same layer structure and thickness as, for example, the annular metal layer 31. The bonding layer 82 is formed of a second solder material that forms the second bonding portion 36 of the annular bonding layer 32. As an example, the bonding layer 82 is formed of Au-30Sn. The lid 40 is bonded to the bonding layer 82. The other configurations are the same as those in the first embodiment, and therefore will not be described again.

[0051] According to the third embodiment, pillars 80 are provided between substrate 10 and lid 40 within cavity 22. This reduces deflection of lid 40 even when pressure is applied to lid 40 from above. This prevents lid 40 from coming close to or contacting acoustic wave element 50 and wiring 20, which could cause deterioration of electrical characteristics.

[0052] Furthermore, in Example 3, the bonding layer 82 has a larger Young's modulus than the first bonding portion 35. By using the bonding layer 82 with a larger Young's modulus in this way, it is possible to further reduce the deflection of the lid 40 even when pressure is applied to the lid 40 from above.

[0053] In Example 1 and its modifications, Example 2 and its modifications, and Example 3, the acoustic wave element is used as the functional element provided on the substrate 10, but elements other than the acoustic wave element may be used. For example, a MEMS (Micro Electro Mechanical System) element, an odor sensor element, or elements other than a piezoelectric element may be used. [Example]

[0054] FIG. 10(a) is a circuit diagram of a filter 400 according to a fourth embodiment. As shown in FIG. 10(a), one or more series resonators S1 to S4 are connected in series between an input terminal Tin and an output terminal Tout. One or more parallel resonators P1 to P3 are connected in parallel between the input terminal Tin and the output terminal Tout. The acoustic wave device according to the first embodiment and its modifications, the second embodiment and its modifications, or the third embodiment can be used for at least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P3. The number of resonators in the ladder filter can be set as appropriate. The filter may be a multimode filter.

[0055] FIG. 10(b) is a circuit diagram of a duplexer 410 according to a modified example of the fourth embodiment. As shown in FIG. 10(b), a transmit filter 70 is 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 passes, to the common terminal Ant, signals in the transmit band among the high-frequency signals input from the transmit terminal Tx as transmit signals, and suppresses signals of other frequencies. The receive filter 72 passes, to the receive terminal Rx, signals in the receive band among the high-frequency signals input from the common terminal Ant as receive signals, and suppresses signals of other frequencies. At least one of the transmit filter 70 and the receive filter 72 can be the filter of the third embodiment. Although a duplexer has been described as an example of a multiplexer, a triplexer or a quadplexer may also be used.

[0056] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0057] 10...substrate, 12, 12a...piezoelectric layer, 14...terminal, 16...via wiring, 20...wiring, 22...gap, 30...frame, 31...annular metal layer, 32...annular bonding layer, 33...first edge, 34...second edge, 35...first bonding portion, 36...second bonding portion, 37...corner portion, 40...lid, 50, 50a...acoustic wave element, 51...IDT, 52...reflector, 53...comb-shaped electrode, 54...electrode finger, 55...bus bar, 56...intersection region, 61...lower electrode, 62...upper electrode, 63...gap, 64...resonance region, 70...transmitting filter, 72...receiving filter, 80...columnar body, 81...metal layer, 82...bonding layer, 100, 110, 200, 300...acoustic wave device, 400...filter, 410...duplexer

Claims

1. A substrate; a functional element provided on the substrate; an annular bonding layer provided on the substrate surrounding the functional element in a plan view, the annular bonding layer being formed of solder and having a first bonding portion and a second bonding portion having a different constituent element or composition ratio from the first bonding portion in the plan view; a lid bonded to the annular bonding layer with a gap sandwiched between the substrate and the lid, sealing the functional element within the gap.

2. the first bonding portion has a lower melting point than the second bonding portion; The electronic device according to claim 1 , wherein an area of ​​the first joint portion is larger than an area of ​​the second joint portion in the plan view.

3. the second joint portion has a larger Young's modulus than the first joint portion; The electronic device according to claim 1 , wherein an area of ​​the second joint portion is larger than an area of ​​the first joint portion in the plan view.

4. a pillar-shaped body having a bonding layer, the pillar-shaped body being provided between the substrate and the lid in the gap; The electronic device according to claim 1 , wherein the bonding layer and the second bonding portion have a Young's modulus greater than that of the first bonding portion.

5. The electronic device according to claim 1 , wherein the first bonding portion is made of gold-tin, and the second bonding portion is made of gold-tin having a different composition ratio from that of the first bonding portion.

6. forming a functional element on a substrate; forming an annular bonding layer on the substrate or the lid, the annular bonding layer having a first bonding portion and a second bonding portion having a higher melting point and a greater thickness than the first bonding portion; heating the first bonding portion and the second bonding portion to a first temperature equal to or higher than the melting point of the first bonding portion and lower than the melting point of the second bonding portion, and bringing the lid or the substrate into contact with the second bonding portion so that a gap is formed between the lid and the first bonding portion or between the substrate and the first bonding portion; after the abutting step, heating the first bonding portion and the second bonding portion to a second temperature that is equal to or higher than the melting point of the second bonding portion to bond the lid or the substrate to the first bonding portion and the second bonding portion, and sealing the functional element in the gap between the substrate and the lid.

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