Resonant device and method for manufacturing resonant device

Abstract

The present invention provides a resonant device capable of suppressing poor bonding at the joint and a method for manufacturing the resonant device. The resonant device (1) comprises: a MEMS substrate (50) including a resonator (10), a top cover (30), and a joint (60) having conductivity and bonding the MEMS substrate (50) and the top cover (30). The MEMS substrate (50) further comprises a wiring layer (81) electrically connected to a Si substrate (F2) serving as a lower electrode of the resonator (10), and an anti-diffusion layer (85) electrically connecting the wiring layer (81) and the joint (60).

Description

Technical Field

[0001] This invention relates to a resonant device and a method for manufacturing a resonant device. Background Technology

[0002] Previously, resonant devices manufactured using MEMS (Micro Electro Mechanical Systems) technology have become increasingly common. These devices are formed, for example, by bonding an upper substrate to a lower substrate containing a resonator.

[0003] For example, Patent Document 1 discloses a MEMS device comprising: a lower substrate having a resonator, an upper substrate disposed opposite to the element, and a joint portion joining the lower substrate and the upper substrate around the element, the joint portion having a region containing a hypereutectic alloy and a region containing a eutectic alloy. Because the hypereutectic alloy covers the eutectic alloy in this MEMS device, metal is prevented from being exposed from the joint surface of the eutectic joint.

[0004] Patent Document 1: International Publication No. 2017 / 047663

[0005] However, there are cases where the characteristics of MEMS devices can be improved by suppressing the generation of parasitic capacitance (floating capacitance) by connecting the junction to ground (GND). In this case, the junction and the lower electrode of the resonator are connected by aluminum (Al) wiring, which has good electrical connectivity.

[0006] However, during bonding, there is a concern that the metal constituting the bonding joint, such as germanium (Ge), may diffuse into the aluminum wiring and flow into the lower electrode side of the resonator. Therefore, there is a possibility that the ratio of the metal constituting the bonding joint may change, the eutectic ratio may change, or the eutectic reaction may become insufficient. As a result, bonding defects may occur, such as reduced bonding strength at the bonding joint. Summary of the Invention

[0007] The present invention was made in view of the following circumstances, and one of its objectives is to provide a resonant device capable of suppressing poor jointing at the joint and a method for manufacturing the resonant device.

[0008] A resonant device according to one aspect of the present invention comprises: a first substrate including a resonator; a second substrate; and a bonding portion having conductivity and bonding the first substrate and the second substrate. The first substrate further includes a wiring layer and an anti-diffusion layer, wherein the wiring layer is electrically connected to a lower electrode of the resonator, and the anti-diffusion layer is electrically connected to the wiring layer and the bonding portion.

[0009] Another aspect of the invention describes a method for manufacturing a resonant device, comprising: a step of preparing a first substrate, wherein the first substrate includes a first metal layer, a resonator, a wiring layer electrically connected to a lower electrode of the resonator, and an anti-diffusion layer electrically connecting the wiring layer and the first metal layer; a step of preparing a second substrate, wherein the second substrate includes a second metal layer; and a bonding step of forming a joint, which is a step of bonding the first substrate and the second substrate, wherein the joint includes a eutectic layer whose main component is a eutectic alloy of a first metal of the first metal layer and a second metal of the second metal layer.

[0010] According to the present invention, poor jointing of the joint can be suppressed. Attached Figure Description

[0011] Figure 1 This is a perspective view schematically showing the appearance of a resonant device according to one embodiment of the present invention.

[0012] Figure 2 It is a schematic representation Figure 1 An exploded perspective view of the structure of the resonant device shown.

[0013] Figure 3 It is a schematic representation Figure 2 The top view of the resonator structure shown.

[0014] Figure 4 It is a schematic representation along Figures 1 to 3 A cross-sectional view of the IV-IV line of the resonant device shown.

[0015] Figure 5 It is a schematic representation Figure 4 Enlarged sectional view of the main parts of the joint and its surrounding structure shown.

[0016] Figure 6 This is a flowchart illustrating a method for manufacturing a resonant device in one embodiment.

[0017] Figure 7 It is used for Figure 6 The sectional view illustrates the process shown.

[0018] Figure 8 It is used for Figure 6 The first example of the process shown is illustrated with an enlarged sectional view of the main part.

[0019] Figure 9 It is used for Figure 6 The second example of the process shown is illustrated with an enlarged sectional view of the main part.

[0020] Figure 10 It is used for Figure 6The third example of the process shown is illustrated with an enlarged sectional view of the main part.

[0021] Figure 11 It is used for Figure 6 The enlarged sectional view of the main part of the fourth example of the process shown is used to illustrate the process.

[0022] Figure 12 It is used for Figure 6 The enlarged sectional view of the main part illustrating the process shown.

[0023] Figure 13 It is used for Figure 6 An enlarged top view illustrating the main parts of the process shown.

[0024] Figure 14 It means Figure 5 Enlarged sectional view of the main part of the third modified example of the joint shown. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described. In the following drawings, the same or similar constituent elements are indicated by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of the parts are schematic; they should not be construed as limiting the scope of the present invention to these embodiments.

[0026] <Implementation Method>

[0027] First, refer to Figure 1 and Figure 2 The general structure of a resonant device according to one embodiment of the present invention will be described. Figure 1 This is a perspective view schematically showing the appearance of the resonant device 1 in one embodiment. Figure 2 It is a schematic representation Figure 1 An exploded perspective view of the structure of the resonant device 1 shown.

[0028] The resonant device 1 includes a lower cover 20, a resonator 10 (hereinafter, the lower cover 20 and the resonator 10 are also collectively referred to as "MEMS substrate 50"), and an upper cover 30. That is, the resonant device 1 is constructed by sequentially stacking the MEMS substrate 50, the bonding portion 60, and the upper cover 30. Furthermore, the MEMS substrate 50 corresponds to an example of the "first substrate" of the present invention, and the upper cover 30 corresponds to an example of the "second substrate" of the present invention.

[0029] The structure of the resonant device 1 will be described below. In the following description, the side of the resonant device 1 with the upper cover 30 will be referred to as the upper (or front) and the side with the lower cover 20 will be referred to as the lower (or back).

[0030] The resonator 10 is a MEMS oscillator manufactured using MEMS technology. The resonator 10 and the upper cover 30 are joined via the joining portion 60, which will be described later. Furthermore, the resonator 10 and the lower cover 20 are each formed using a silicon (Si) substrate (hereinafter referred to as "Si substrate"), and the Si substrates are bonded to each other. Alternatively, the MEMS substrate 50 (resonator 10 and lower cover 20) can also be formed using an SOI substrate.

[0031] The top cover 30 extends into a flat plate shape along the XY plane, and a recess 31, for example a flat cuboid shape, is formed on its back side. The recess 31 is surrounded by sidewalls 33, forming part of the space for the resonator 10 to vibrate. Additionally, an air-absorbing layer 34, described later, is formed on the resonator 10 side of the recess 31 of the top cover 30. Alternatively, the top cover 30 may not have the recess 31 and may have a flat plate structure.

[0032] The lower cover 20 has sidewalls 23 and a rectangular flat base plate 22, wherein the base plate 22 is disposed along the XY plane, and the sidewalls 23 extend from the periphery of the base plate 22 along the Z-axis direction; in other words, the lower cover 20 and the resonator 10 extend in the stacking direction. On the lower cover 20, a recess 21 is formed on the surface opposite to the resonator 10, by the surface of the base plate 22 and the inner surface of the sidewalls 23. The recess 21 forms part of the vibration space of the resonator 10. Alternatively, the lower cover 20 may not have the recess 21 and may be a flat plate structure. Furthermore, an air-absorbing layer may be formed on the resonator 10 side of the recess 21 of the lower cover 20.

[0033] Next, refer to Figure 3 The general structure of the resonator included in a resonant device according to one embodiment of the present invention will be described. Figure 3 It is a schematic representation Figure 2 A top view of the structure of the resonator 10 shown.

[0034] like Figure 3 As shown, resonator 10 is a MEMS oscillator manufactured using MEMS technology. Figure 3 Out-of-plane vibration occurs within the XY plane of an orthogonal coordinate system. Furthermore, the resonator 10 is not limited to a resonator using an out-of-plane bending vibration mode. The resonator of the resonant device 1 can also use, for example, extended vibration modes, thickness longitudinal vibration modes, Lamb wave vibration modes, in-plane bending vibration modes, and surface wave vibration modes. These oscillators are used, for example, in timing devices, RF filters, duplexers, ultrasonic transducers, gyroscope sensors, accelerometers, etc. Additionally, they can be used in piezoelectric mirrors with actuator functions, piezoelectric gyroscopes, piezoelectric microphones with pressure sensor functions, ultrasonic vibration sensors, etc. Furthermore, they can also be used in electrostatic MEMS elements, electromagnetically driven MEMS elements, and piezoresistive MEMS elements.

[0035] The resonator 10 includes a vibrating part 120, a holding part 140, and a holding arm 110.

[0036] The retaining portion 140 is formed in the shape of a rectangular frame to surround the outer side of the vibrating portion 120 along the XY plane. For example, the retaining portion 140 is integrally formed from a prism-shaped frame. Furthermore, the retaining portion 140 may be provided on at least a portion around the vibrating portion 120, and is not limited to a frame shape.

[0037] The retaining arm 110 is disposed inside the retaining part 140 and connects the vibrating part 120 and the retaining part 140.

[0038] The vibrating part 120 is disposed inside the holding part 140, and a space is formed between the vibrating part 120 and the holding part 140 at a predetermined interval. Figure 3 In the example shown, the vibrating part 120 has a base 130 and four vibrating arms 135A to 135D (hereinafter collectively referred to as "vibrating arms 135"). Furthermore, the number of vibrating arms is not limited to four; for example, it can be set to any number of more than one. In this embodiment, each vibrating arm 135A to 135D and the base 130 are integrally formed.

[0039] Viewed from above, the base 130 has long sides 131a and 131b in the X-axis direction and short sides 131c and 131d in the Y-axis direction. Long side 131a is an edge of the front end face (hereinafter referred to as "front end 131A") of the base 130, and long side 131b is an edge of the rear end face (hereinafter referred to as "rear end 131B") of the base 130. In the base 130, the front end 131A and the rear end 131B are positioned opposite each other.

[0040] The base 130 is connected to the vibrating arm 135 at the front end 131A and to the retaining arm 110 (described later) at the rear end 131B. Furthermore, in Figure 3 In the example shown, the base 130 has a generally rectangular shape when viewed from above, but is not limited to this. The base 130 can be formed approximately symmetrically with respect to the imaginary plane P defined by the perpendicular bisector of the long side 131a. For example, the base 130 could also be a trapezoid with the long side 131b shorter than 131a, or a semicircle with the long side 131a as its diameter. Furthermore, the surfaces of the base 130 are not limited to planes and could be curved surfaces. Additionally, the imaginary plane P is the plane passing through the center of the direction in which the vibrating arms 135 in the vibrating section 120 are arranged.

[0041] At the base 130, the longest distance between the front end 131A and the rear end 131B in the direction from the front end 131A to the rear end 131B, which is also the base length, is approximately 35 μm. In addition, in the width direction orthogonal to the base length direction, the longest distance between the side ends of the base 130, which is also the base width, is approximately 265 μm.

[0042] Vibration arms 135 extend along the Y-axis and have the same dimensions. Each vibration arm 135 is arranged parallel to the Y-axis between the base 130 and the holding portion 140, with one end connected to the front end 131A of the base 130 as a fixed end, and the other end being an open end. Furthermore, the vibration arms 135 are arranged side-by-side at predetermined intervals along the X-axis. For example, the width of each vibration arm 135 in the X-axis direction is approximately 50 μm, and its length in the Y-axis direction is approximately 465 μm.

[0043] Each vibrating arm 135, for example, has a wider portion in the X-axis direction at approximately 150 μm from the open end compared to other parts of the vibrating arm 135. This wider portion is called the counterweight portion G. For example, the counterweight portion G is 10 μm wider to the left and right along the X-axis direction compared to other parts of the vibrating arm 135, resulting in a width of approximately 70 μm in the X-axis direction. The counterweight portion G is integrally formed with the vibrating arm 135 in the same process. By forming the counterweight portion G, the weight per unit length on the open end side of the vibrating arm 135 is heavier than the weight per unit length on the fixed end side. Therefore, by having a counterweight portion G on the open end side of each vibrating arm 135, the amplitude of the vertical vibration in each vibrating arm can be increased.

[0044] A protective film 235, described later, is formed on the surface of the vibrating section 120 (the surface opposite to the top cover 30) to cover its entire surface. Furthermore, frequency adjustment films 236 are formed on the surface of the protective film 235 at the open end sides of the vibrating arms 135A to 135D, respectively. The resonant frequency of the vibrating section 120 can be adjusted using the protective film 235 and the frequency adjustment films 236.

[0045] Furthermore, in this embodiment, the surface of the resonator 10 (the side opposite to the top cover 30) is covered by a protective film 235. The surface of the protective film 235 is also covered by a parasitic capacitance reduction film 240. However, the protective film 235 only needs to cover at least the vibrating arm 135, and is not limited to a structure that covers the entire surface of the resonator 10.

[0046] Next, refer to Figure 4 The stacked structure of a resonant device 1 according to one embodiment of the present invention will be described. Figure 4 It is a schematic representation along Figures 1 to 3 A cross-sectional view of the structure of the IV-IV line of the resonant device 1 shown.

[0047] like Figure 4 As shown, the resonant device 1 has a retaining portion 140 of the resonator 10 joined to the side wall 23 of the lower cover 20, and the retaining portion 140 of the resonator 10 is joined to the side wall 33 of the upper cover 30. Thus, the resonator 10 is held between the lower cover 20 and the upper cover 30, and the lower cover 20, the upper cover 30, and the retaining portion 140 of the resonator 10 form a vibration space for the vibrating arm 135 to vibrate. Furthermore, a terminal T4 is formed on the upper surface of the upper cover 30 (and the surface opposite to the surface opposite the resonator 10). The terminal T4 and the resonator 10 are electrically connected via a through electrode V3, a connecting wire 70, and contact electrodes 76A and 76B.

[0048] The top cover 30 is formed from a Si substrate L3 having a predetermined thickness. The top cover 30 is bonded to the holding portion 140 of the resonator 10 via a bonding portion 60 (described later) at its peripheral portion (sidewall 33). The surface of the top cover 30 opposite the resonator 10 is covered with a silicon oxide film L31. The silicon oxide film L31 is, for example, silicon dioxide (SiO2), formed on the surface of the Si substrate L3 by oxidation and chemical vapor deposition (CVD). Furthermore, the back side of the top cover 30 and the side of the through electrode V3 are also preferably covered with the silicon oxide film L31.

[0049] Furthermore, an air-absorbing layer 34 is formed on the side of the upper cover 30 opposite to the resonator 10 in the recess 31. The air-absorbing layer 34 is formed, for example, of titanium (Ti), and adsorbs the exhaust gas generated in the vibration space. Since the upper cover 30 of this embodiment has an air-absorbing layer 34 formed on almost the entire surface of the recess 31 opposite to the resonator 10, the reduction of the vacuum level in the vibration space can be suppressed.

[0050] Furthermore, the through electrode V3 of the upper cover 30 is formed by filling the through hole formed in the upper cover 30 with a conductive material. The conductive material used for filling is, for example, impurity-doped polycrystalline silicon (Poly-Si), copper (Cu), gold (Au), or impurity-doped monocrystalline silicon. The through electrode V3 serves as a wiring to electrically connect the terminal T4 to the voltage application part 141.

[0051] The bottom plate 22 and sidewall 23 of the lower cover 20 are integrally formed from a Si wafer L1. Furthermore, the lower cover 20 is joined to the holding portion 140 of the resonator 10 via the upper surface of the sidewall 23. The thickness of the lower cover 20, defined in the Z-axis direction, is, for example, 150 μm, and the depth of the recess 21 is, for example, 50 μm. Moreover, the Si wafer L1 is formed from undegenerate silicon, and its resistivity is, for example, 16 mΩ·cm or higher.

[0052] The holding portion 140, base 130, vibrating arm 135, and holding arm 110 in the resonator 10 are integrally formed in the same process. The resonator 10 has a piezoelectric thin film F3 formed on a Si substrate F2 (an example of a substrate) to cover the Si substrate F2, and a metal layer E2 is stacked on the piezoelectric thin film F3. Furthermore, a piezoelectric thin film F3 is stacked on the metal layer E2 to cover the metal layer E2, and a metal layer E1 is stacked on the piezoelectric thin film F3. A protective film 235 is stacked on the metal layer E1 to cover the metal layer E1, and a parasitic capacitance reduction film 240 is stacked on the protective film 235. The shapes of the holding part 140, the base 130, the vibrating arm 135 and the holding arm 110 are formed by removing the laminate composed of the Si substrate F2, the piezoelectric film F3, the metal layer E2, the metal layer E1 and the protective film 235 by dry etching irradiation with, for example, an argon (Ar) ion beam, and patterning.

[0053] The Si substrate F2 can also be formed, for example, from a degenerate n-type silicon (Si) semiconductor with a thickness of about 6 μm. The degenerate silicon (Si) can contain phosphorus (P), arsenic (As), antimony (Sb), etc., as n-type dopants. The resistivity of the degenerate silicon (Si) used for the Si substrate F2 is, for example, less than 16 mΩ·cm, more preferably less than 1.2 mΩ·cm.

[0054] Thus, since the Si substrate F2 is degenerate silicon (Si), for example by using a degenerate silicon substrate with low resistance, the Si substrate F2 itself can also serve as the lower electrode of the resonator 10. In this case, the aforementioned metal layer E2 can be omitted.

[0055] On the lower surface of the Si substrate F2, as an example of a temperature characteristic correction layer, a silicon oxide layer F21, such as silicon dioxide (SiO2), is formed. This improves temperature characteristics. Furthermore, the silicon oxide layer F21 can be formed on the upper surface of the Si substrate F2, or on both the upper and lower surfaces of the Si substrate F2.

[0056] Furthermore, the metal layers E1 and E2, for example, have a thickness of approximately 0.1 μm to 0.2 μm, and after film formation, are patterned into the desired shape through etching or other methods. The metal layers E1 and E2 are formed using metals with a body-centered cubic crystal structure. Specifically, the metal layers E1 and E2 are formed using materials such as Mo (molybdenum) and tungsten (W).

[0057] For example, the metal layer E1 is formed on the vibrating part 120 to serve as an upper electrode. In addition, the metal layer E1 is formed on the holding arm 110 and the holding part 140 to serve as wiring for connecting the upper electrode to an AC power supply provided outside the resonator 10.

[0058] On the other hand, the metal layer E2 is formed on the vibrating part 120 to serve as a lower electrode. In addition, the metal layer E2 is formed on the holding arm 110 and the holding part 140 to serve as wiring for connecting the lower electrode to a circuit provided outside the resonator 10.

[0059] Piezoelectric film F3 is a thin film that converts applied voltage into vibrations of a piezoelectric element. Piezoelectric film F3 is formed from materials with a wurtzite-type hexagonal crystal structure, and can be primarily composed of nitrides and oxides such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), and indium nitride (InN). Furthermore, scandium aluminum nitride is formed by replacing a portion of the aluminum in aluminum nitride with scandium; alternatively, it can be replaced by two elements such as magnesium (Mg) and niobium (Nb), or magnesium (Mg) and zirconium (Zr). Additionally, piezoelectric film F3 has a thickness of, for example, 1 μm, but thicknesses of approximately 0.2 μm to 2 μm can also be used.

[0060] The piezoelectric film F3 extends and contracts in the in-plane direction (Y-axis direction) of the XY plane according to the electric field applied to the piezoelectric film F3 through the metal layers E1 and E2. Through the extension and contraction of the piezoelectric film F3, the vibrating arm 135 displaces its free end to the inner surface of the lower cover 20 and the upper cover 30, vibrating in an out-of-plane bending vibration mode.

[0061] In this embodiment, the phases of the electric fields applied to the outer vibrating arms 135A and 135D and the phases of the electric fields applied to the inner vibrating arms 135B and 135C are set to be opposite phases. Therefore, the outer vibrating arms 135A and 135D and the inner vibrating arms 135B and 135C are displaced in opposite directions. For example, if the outer vibrating arms 135A and 135D displace their free ends to the inner surface of the upper cover 30, then the inner vibrating arms 135B and 135C displace their free ends to the inner surface of the lower cover 20.

[0062] The protective film 235 prevents oxidation of the metal layer E2, which serves as the upper electrode for piezoelectric vibration. The protective film 235 is preferably formed of a material whose rate of mass reduction due to etching is slower than that of the frequency-tuning film 236. The rate of mass reduction is expressed by the etching rate, i.e., the product of the thickness and density removed per unit time. The protective film 235 can be formed of insulating films such as silicon nitride (SiN), silicon dioxide (SiO2), and aluminum oxide (Al2O3), in addition to piezoelectric films such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), and indium nitride (InN). The thickness of the protective film 235 is, for example, about 0.2 μm.

[0063] After the frequency adjustment film 236 is formed on approximately the entire surface of the vibrating part 120, it is formed only in a specified area through processing such as etching. The frequency adjustment film 236 is formed from a material whose mass reduction due to etching is faster than that of the protective film 235. Specifically, the frequency adjustment film 236 is made of metals such as molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), and titanium (Ti).

[0064] Furthermore, the relationship between the etching rate and the mass reduction rate of the protective film 235 and the frequency adjustment film 236 is arbitrary, as long as the relationship between them is as described above.

[0065] The parasitic capacitance reduction film 240 is formed of tetraethyl orthosilicate (TEOS). The thickness of the parasitic capacitance reduction film 240 is approximately 1 μm. It reduces parasitic capacitance in the winding wiring section and functions as an insulating layer when wiring crosses at different potentials and as a standoff for expanding the vibration space.

[0066] The connecting wiring 70 is electrically connected to the terminal T4 via the through electrode V3, and is also electrically connected to the contact electrodes 76A and 76B.

[0067] Contact electrode 76A is formed to contact the metal layer E1 of resonator 10 and electrically connects the connection wiring 70 to resonator 10. Contact electrode 76B is formed to contact the metal layer E2 of resonator 10 and electrically connects the connection wiring 70 to resonator 10. Specifically, when contact electrode 76A and metal layer E1 are connected, a portion of the piezoelectric film F3, protective film 235, and parasitic capacitance reduction film 240 stacked on metal layer E1 is removed, exposing metal layer E1 and forming via V1. The via V1 is filled with the same material as contact electrode 76A, connecting metal layer E1 and contact electrode 76A. Similarly, when contact electrode 76B and metal layer E2 are connected, a portion of the piezoelectric film F3 and parasitic capacitance reduction film 240 stacked on metal layer E2 is removed, exposing metal layer E2 and forming via V2. Contact electrode 76B is filled into via V2, connecting metal layer E2 and contact electrode 76B. The contact electrodes 76A and 76B are made of metals such as aluminum (Al), gold (Au), and tin (Sn). Furthermore, the connection points between the metal layer E1 and the contact electrode 76A, and between the metal layer E2 and the contact electrode 76B, are preferably located in the outer region of the vibrating part 120, and in this embodiment, they are connected via the holding part 140.

[0068] The joining portion 60 is formed in a rectangular ring shape along the XY plane around the vibrating portion 120 in the resonator 10, for example on the holding portion 140, between the MEMS substrate 50 (resonator 10 and lower cover 20) and the upper cover 30. The joining portion 60 joins the MEMS substrate 50 and the upper cover 30, thereby sealing the vibration space of the resonator 10. As a result, the vibration space is hermetically sealed, maintaining a vacuum state.

[0069] In this embodiment, the bonding portion 60 includes a first metal layer 61 formed on the MEMS substrate 50 and a second metal layer 62 formed on the top cover 30. The MEMS substrate 50 and the top cover 30 are bonded by eutectic bonding of the first metal layer 61 and the second metal layer 62.

[0070] Furthermore, in this embodiment, an example has been described in which the joint 60 is disposed entirely around the vibrating part 120 in the resonator 10 to seal the vibration space of the resonator 10, but this is not a limitation. For example, the joint 60 may also be formed in part around the vibrating part 120 in the resonator 10, as long as the joint 60 joins the MEMS substrate 50 and the top cover 30.

[0071] Next, refer to Figure 5 The structure of the joint and its surrounding area of ​​a resonant device according to one embodiment of the present invention will be described. Figure 5 It is a schematic representation Figure 4 An enlarged sectional view of the main parts of the joint 60 and its surrounding structure is shown. Furthermore, Figure 5 The position of the X coordinate and Figure 4 The cross-sections shown are different ZY plane cross-sections. Furthermore, in the following description, unless otherwise explicitly stated, the Si substrate F2 is degenerate silicon (Si), and the Si substrate F2 itself also functions as the lower electrode of the resonator 10. Therefore, the aforementioned metal layer E1 is not included.

[0072] like Figure 5 As shown, the joint 60 includes a eutectic layer 65 with a eutectic alloy as the main component. The eutectic alloy of the eutectic layer 65 is, for example, a eutectic alloy with a first metal layer 61 with aluminum (Al) as the main component and a second metal layer 62 with germanium (Ge) as the main component.

[0073] exist Figure 5In the example shown, the first metal layer 61 and the second metal layer 62 are described as separate layers, but in reality, these interfaces are eutectic bonded. That is, the eutectic layer 65 is composed of a eutectic alloy with aluminum (Al) as the main component and germanium (Ge) as the second metal. Thus, since the joint 60 includes a eutectic layer 65 composed of a eutectic alloy with aluminum (Al) as the main component and germanium (Ge) as the second metal, it is easy to achieve a joint 60 with high conductivity and bonding strength.

[0074] The first metal of the first metal layer 61 is, for example, aluminum (Al), or an aluminum-copper alloy (AlCu alloy), or an aluminum-silicon-copper alloy (AlSiCu alloy). Since aluminum or aluminum alloys can be easily eutectic bonded to germanium (Ge) in the second metal layer 62, and are metals frequently used in wiring in resonant devices, the manufacturing process of the resonant device 1 can be simplified, and the bonding portion 60 connecting the MEMS substrate 50 and the top cover 30 can be easily formed.

[0075] In the following description, unless otherwise explicitly stated, the first metal of the first metal layer 61 is aluminum (Al), the second metal of the second metal layer 62 is germanium (Ge), and the eutectic layer 65 is primarily composed of aluminum-germanium. In this case, the eutectic layer 65 may also contain aluminum (Al) and germanium (Ge) in addition to aluminum-germanium.

[0076] Around the junction 60, a wiring layer 81 is provided on the parasitic capacitance reduction film 240. The wiring layer 81 is configured to be conductive and electrically connected to the Si substrate F2, which functions as the lower electrode of the resonator 10. The formation of the wiring layer 81 involves first removing a portion of the parasitic capacitance reduction film 240 and the piezoelectric film F3 to form a hole. Then, a conductive material is filled into the hole to electrically connect it to the Si substrate F2.

[0077] Furthermore, an anti-diffusion layer 85 is provided on the parasitic capacitance reduction film 240. The anti-diffusion layer 85 is configured to be conductive and electrically connects the wiring layer 81 and the junction 60. The anti-diffusion layer 85 has the function of blocking and preventing the diffusion of the metal constituting the junction 60.

[0078] In this way, since the MEMS substrate 50 (resonator 10 and lower cover 20) includes a wiring layer 81 electrically connected to the Si substrate F2, which serves as the lower electrode of the resonator 10, the potential of the junction 60 can be reduced to the reference potential (GND) of the resonant device 1 via the anti-diffusion layer 85, and the generation of parasitic capacitance (floating capacitance) can be suppressed. Furthermore, since the MEMS substrate 50 (resonator 10 and lower cover 20) includes an anti-diffusion layer 85 electrically connecting the wiring layer 81 and the junction 60, when the upper cover 30 and the MEMS substrate 50 are joined, the metal constituting the junction 60 can be prevented from diffusing into the wiring layer 81 via the anti-diffusion layer 85. Therefore, the change in the metal ratio of the junction 60 caused by diffusion can be reduced, and poor bonding of the junction 60 can be suppressed.

[0079] Furthermore, the wiring layer 81 is formed at a distance from the end of the junction 60. In other words, the wiring layer 81 is disposed on the MEMS substrate 50 (resonator 10 and lower cover 20) at a distance from the end of the junction 60. Therefore, an anti-diffusion layer 85 can be disposed between the junction 60 and the wiring layer 81. Thus, compared to the case where the anti-diffusion layer 85 is formed directly below the junction 60 (described later), the anti-diffusion layer 85 can be thinned, thereby reducing the product cost of the resonant device 1.

[0080] The material of the wiring layer 81 is preferably a metal with aluminum (Al) as the main component. For example, the metal with aluminum (Al) as the main component is aluminum (Al), or an aluminum-copper alloy (AlCu alloy), or an aluminum-silicon-copper alloy (AlSiCu alloy). Therefore, the oxide film formed on the surface of the Si substrate F2, which serves as the lower electrode of the resonator 10, can be removed (reduced) by heat treatment at a relatively low temperature, for example, 450°C.

[0081] Furthermore, the material of wiring layer 81 is not limited to a metal with aluminum as the main component. For example, the material of wiring layer 81 can also be a metal such as titanium (Ti).

[0082] When wiring layer 81 is made of a metal with aluminum as the main component, such as Figure 5 As shown by dashed lines, so-called alloy spikes may occur at the interface between wiring layer 81 and Si substrate F2, where aluminum (Al) and silicon (Si) diffuse into each other. In this case, the silicon in Si substrate F2 becomes more susceptible to dissolution into the junction 60, making the role of the anti-diffusion layer 85 located between it and the junction 60 more important.

[0083] The anti-diffusion layer 85 is made of a metal with lower diffusivity than the metal in the junction 60. The material of the anti-diffusion layer 85 is preferably, for example, molybdenum (Mo) or tungsten (W). This allows for easy blocking of the diffusion of aluminum (Al) and germanium (Ge) from the eutectic layer 65.

[0084] In the following description, unless otherwise specified, the material of wiring layer 81 is aluminum (Al) and the material of anti-diffusion layer 85 is molybdenum (Mo).

[0085] Next, refer to Figures 6 to 13 A method for manufacturing a resonant device according to one embodiment of the present invention will be described. Figure 6 This is a flowchart illustrating a method for manufacturing a resonant device 1 in one embodiment. Figure 7 It is used for Figure 6 The cross-sectional view shown illustrates process S301. Figure 8 It is used for Figure 6 The first example of process S302 shown is illustrated by an enlarged sectional view of the main part. Figure 9 It is used for Figure 6 The enlarged sectional view of the main part of the second example of process S302 shown is used to illustrate this. Figure 10 It is used for Figure 6 The enlarged sectional view of the main part of the third example of process S302 shown is used to illustrate this. Figure 11 It is used for Figure 6 The enlarged sectional view of the main part of the fourth example of process S302 shown is used to illustrate this. Figure 12 It is used for Figure 6 The enlarged sectional view of the main part of process S303 shown is used to explain the process. Figure 13 It is used for Figure 6 An enlarged sectional view of the main parts illustrating process S304 is shown. Furthermore, in... Figures 7 to 13 For convenience, one of the multiple resonant devices 1 manufactured by the manufacturing method is shown in the illustration.

[0086] like Figure 6 As shown, firstly, a MEMS substrate 50 and a top cover 30 (S301) are prepared. Specifically, as... Figure 7 As shown, a MEMS substrate 50 containing the resonator 10 and a top cover 30 are prepared as described above. The through electrode V3 and the resonator 10 are connected vias... Figure 4 The connecting wiring 70 shown has not yet been formed. Additionally, for... Figure 5 The joint 60, wiring layer 81, and anti-diffusion layer 85 shown are also not formed.

[0087] Furthermore, an example is shown in which the MEMS substrate 50 and the top cover 30 are prepared in process S301, but it is not limited to this. For example, it may be divided into a process of preparing the MEMS substrate 50 and a process of preparing the top cover 30, and the MEMS substrate 50 and the top cover 30 are prepared separately.

[0088] Return to Figure 6 Next, a first metal layer 61, a wiring layer 81, and an anti-diffusion layer 85 are formed on the MEMS substrate 50 prepared in process S301 (S302).

[0089] Specifically, such as Figure 8 As shown, on the prepared MEMS substrate 50 (resonator 10), firstly, holes are formed by removing the parasitic capacitance reduction film 240 and the piezoelectric thin film F3 at specified locations through etching or the like. A wiring layer 81 is formed by filling the formed holes with aluminum (Al) to electrically connect to the Si substrate F2. Next, a diffusion-resistant layer 85 is formed by stacking molybdenum (Mo) on the ends of the parasitic capacitance reduction film 240 and the wiring layer 81, and by etching or the like to shape the stacked molybdenum (Mo) into a desired shape. Then, a first metal layer 61 is formed by stacking aluminum (Al) on the ends of the parasitic capacitance reduction film 240 and the diffusion-resistant layer 85, and by etching or the like to shape the stacked aluminum (Al) into a desired shape.

[0090] Alternatively, after the first metal layer 61 is formed, the MEMS substrate 50 can be subjected to a heat treatment for degassing at a high temperature, such as around 435°C. Even when the first metal layer 61, which is mainly composed of aluminum (Al), is subjected to heat treatment at a high temperature, the effects caused by thermal diffusion are minimal.

[0091] exist Figure 8 The diagram illustrates an example where a first metal layer 61, a wiring layer 81, and an anti-diffusion layer 85 are formed on a MEMS substrate 50 in the order of wiring layer 81, anti-diffusion layer 85, and first metal layer 61, but the example is not limited to this. For example, as shown... Figure 9 As shown, in the prepared MEMS substrate 50 (resonator 10), firstly, a molybdenum (Mo) anti-diffusion layer 85 is formed on the parasitic capacitance reduction film 240. Next, holes are formed at predetermined positions on the parasitic capacitance reduction film 240 and aluminum (Al) is filled into the holes. Aluminum (Al) is then stacked on the ends of the parasitic capacitance reduction film 240 and the anti-diffusion layer 85 to form a wiring layer 81 and a first metal layer 61.

[0092] Additionally, for example, such as Figure 10 As shown, a wiring layer 81 and a first metal layer 61 can also be formed on the prepared MEMS substrate 50 (resonator 10) by first forming a hole at a predetermined position of the parasitic capacitance reduction film 240 and filling the hole with aluminum (Al), and then stacking aluminum (Al) on the parasitic capacitance reduction film 240 to form a wiring layer 81 and a first metal layer 61. Next, a molybdenum (Mo) layer is stacked on the ends of the parasitic capacitance reduction film 240, the wiring layer 81 and the first metal layer 61 to form an anti-diffusion layer 85.

[0093] In this way, by forming the first metal layer 61 and the wiring layer 81 before or after forming the anti-diffusion layer 85, the first metal layer 61 and the wiring layer 81 can be formed on the upper or lower layer of the anti-diffusion layer 85. Therefore, the number of steps in forming the first metal layer 61 and the wiring layer 81 can be reduced, thereby reducing manufacturing costs.

[0094] And, for example, such as Figure 11 As shown, the anti-diffusion layer 85 can also be composed of two or more layers. In this case, molybdenum (Mo) is stacked on the piezoelectric thin film F3 to form a metal layer E1 that functions as the upper electrode of the resonator 10 and a first layer 85a of the anti-diffusion layer 85. Next, a parasitic capacitance reduction film 240 is stacked on the piezoelectric thin film F3, covering the metal layer E1, and a protective film 235 is stacked at a predetermined position on the parasitic capacitance reduction film 240. Next, molybdenum (Mo) is stacked at the predetermined position on the protective film 235 and on the first layer 85a to form a frequency adjustment film 236 and a second layer 85b of the anti-diffusion layer 85. Then, by forming holes at predetermined positions on the parasitic capacitance reduction film 240 and filling the holes with aluminum (Al), and stacking aluminum (Al) on the ends of the parasitic capacitance reduction film 240 and the anti-diffusion layer 85, a wiring layer 81 and a first metal layer 61 are formed.

[0095] In this way, by forming a first layer 85a of the anti-diffusion layer 85 and a second layer 85b of the anti-diffusion layer 85 on the first layer 85a, the anti-diffusion layer 85 can be thickened, thereby improving the barrier properties against the diffusion of the metal constituting the joint 60.

[0096] Furthermore, process S302 is not limited to being performed separately from process S301. For example, the formation of the first metal layer 61, the wiring layer 81, and the anti-diffusion layer 85 can be performed as part of process S301, or as part of the process of preparing the MEMS substrate 50, which is separated from process S301.

[0097] Return to Figure 6 Next, the second metal layer 62 is formed on the top cover 30 prepared in process S301 (S303).

[0098] Specifically, such as Figure 12 As shown, germanium (Ge) is stacked on the surface of the silicon oxide film L31 on the back side of the top cover 30 to form a second metal layer 62 at a predetermined position. The predetermined position for forming the second metal layer 62 is, for example, a position on the back side of the top cover 30 that is opposite or substantially opposite to the first metal layer 61 formed on the MEMS substrate 50 when the surface of the MEMS substrate 50 is facing the back side of the top cover 30.

[0099] After the second metal layer 62 is formed, the top cover 30 is subjected to a heat treatment for degassing at a high temperature, for example, around 435°C. This allows for the sufficient release (evaporation) of the gases contained in the top cover 30 and the second metal layer 62, thereby reducing the generation of exhaust gases.

[0100] Furthermore, process S303 is not limited to being performed separately from process S301. For example, the formation of the second metal layer 62 can be performed as part of process S301, or as part of the process of preparing the top cover 30, which is separated from process S301.

[0101] Return to Figure 6 Next, the MEMS substrate 50, in which the first metal layer 61, wiring layer 81, and anti-diffusion layer 85 are formed in step S302, and the top cover 30, in which the second metal layer 62 is formed in step S303, are bonded together (S304). Step S304 includes the step of forming a bonding portion 60, wherein the bonding portion 60 includes a eutectic layer 65 whose main components are a first metal with aluminum (Al) as the main component and a second metal with germanium (Ge).

[0102] Specifically, the MEMS substrate 50 and the top cover 30 are aligned to align the first metal layer 61 and the second metal layer 62. After alignment, the MEMS substrate 50 and the top cover 30 are clamped together by a heater or the like, and a heat treatment for the eutectic reaction is performed. At this time, the top cover 30 moves toward the MEMS substrate 50. As a result, as... Figure 13 As shown, the second metal layer 62 is in contact with the first metal layer 61.

[0103] The temperature used in the heat treatment for eutectic bonding is preferably above the eutectic point and below the melting point of aluminum (Al) monomer, i.e., above 424°C and below approximately 620°C. Furthermore, the heating time is preferably 10 minutes or more and 20 minutes or less. In this embodiment, the heat treatment is performed for approximately 15 minutes at a temperature of 430°C or more and 500°C or less.

[0104] When heated, such as Figure 13 As indicated by the black arrow, the top cover 30 and the MEMS substrate 50 are pressed together. The pressing pressure is preferably between 5 MPa and 25 MPa.

[0105] In addition, after the heat treatment for eutectic bonding, a cooling treatment is performed, for example, by natural cooling. Furthermore, the cooling treatment is not limited to natural cooling; as long as a eutectic layer 65 can be formed at the bonding portion 60, various cooling temperatures and cooling rates can be selected.

[0106] Performed Figure 6 The result of process S304 shown is as follows: Figure 5 As shown, a joint 60 is formed containing a eutectic layer 65, wherein the eutectic layer 65 is mainly composed of a eutectic alloy of a first metal and a second metal.

[0107] Alternatively, an aluminum (Al) film can be formed at a predetermined location on the MEMS substrate 50 during the formation of the first metal layer 61, and a germanium (Ge) film can be formed at a predetermined location on the upper cover 30 during the formation of the second metal layer 62, and these films can be eutectic bonded together to provide a connection for the through electrode V3 and the resonator 10. Figure 4 The connection wiring 70 is shown.

[0108] In this embodiment, an example is shown where the wiring layer 81 is positioned at a distance from the ends of the MEMS substrate 50 and the junction 60, but this is not a limitation. The position where the wiring layer 81 is formed and positioned can be appropriately changed.

[0109] (Modified Example)

[0110] Figure 14 It is a schematic representation Figure 5 The enlarged sectional view of the main part of a modified example of the joint 60 and its surrounding structure is shown. Furthermore, in the modified example, for the... Figure 5 The joint 60 shown has the same structure, is labeled with the same reference numerals, and its description is omitted where appropriate. Furthermore, the same effects achieved by the same structure are not mentioned sequentially.

[0111] like Figure 14 As shown, the wiring layer 81A and the anti-diffusion layer 85A can also be disposed below the junction 60. In this case, the wiring layer 81A is formed around a portion of the vibrating portion 120 in the resonator 10. An anti-diffusion layer 85A is formed on the wiring layer 81A to cover it. Furthermore, a first metal layer 61 is formed on the anti-diffusion layer 85A. Thus, the junction 60, which includes the eutectic layer 65, is formed by eutectic bonding of the first metal layer 61 formed on the anti-diffusion layer 85A of the MEMS substrate 50 and the second metal layer 62 formed on the back side of the top cover 30.

[0112] The exemplary embodiments of the present invention have been described above. In a resonant device according to one embodiment, the MEMS substrate includes a wiring layer electrically connected to the lower electrode of the resonator. This allows the potential of the junction to be reduced to the reference potential (GND) of the resonant device via the anti-diffusion layer, and suppresses the generation of parasitic capacitance (floating capacitance). Furthermore, the MEMS substrate includes an anti-diffusion layer electrically connecting the wiring layer and the junction. This prevents the metal constituting the junction from diffusing into the wiring layer when the top cover and the MEMS substrate are joined. Therefore, changes in the metal ratio of the junction caused by diffusion can be reduced, and poor bonding of the junction can be suppressed.

[0113] Furthermore, in the aforementioned resonant device, the joint includes a eutectic layer, which is a eutectic alloy consisting primarily of a first metal layer with aluminum (Al) as the main component and a second metal layer with germanium (Ge) as the second metal layer. This allows for the easy realization of a joint that possesses both high conductivity and strong bonding.

[0114] Furthermore, in the aforementioned resonant device, the anti-diffusion layer is made of molybdenum (Mo) or tungsten (W). This effectively blocks the diffusion of aluminum (Al) and germanium (Ge) from the eutectic layer.

[0115] Furthermore, in the aforementioned resonant device, the Si substrate is made of degenerate silicon (Si). Thus, by using a degenerate silicon substrate with low resistance, the Si substrate itself can also function as the lower electrode of the resonator.

[0116] Furthermore, in the aforementioned resonant device, the wiring layer is made of a metal with aluminum (Al) as its main component. This allows the oxide film formed on the surface of the Si substrate, which serves as the lower electrode of the resonator, to be removed (reduced) through a relatively low-temperature heat treatment, such as 450°C.

[0117] Furthermore, in the aforementioned resonant device, the wiring layer is positioned on the MEMS substrate at a distance from the end of the junction. This allows for the placement of an anti-diffusion layer between the junction and the wiring layer. Therefore, compared to forming the anti-diffusion layer directly beneath the junction, the anti-diffusion layer can be thinned, thus reducing the product cost of the resonant device.

[0118] In a method for manufacturing a resonant device according to one embodiment, a step of preparing a MEMS substrate is included. The MEMS substrate includes a first metal layer, a resonator, a wiring layer electrically connected to a Si substrate serving as the lower electrode of the resonator, and an anti-diffusion layer electrically connecting the wiring layer and the first metal layer. This allows the potential of the junction to be reduced to the reference potential (GND) of the resonant device via the anti-diffusion layer, and suppresses the generation of parasitic capacitance (floating capacitance). Furthermore, the MEMS substrate includes an anti-diffusion layer electrically connecting the wiring layer and the junction. Therefore, when bonding the top cover and the MEMS substrate, the anti-diffusion layer prevents the metal constituting the junction from diffusing into the wiring layer. Thus, changes in the metal ratio of the junction caused by diffusion can be reduced, and poor bonding at the junction can be suppressed.

[0119] Furthermore, in the aforementioned method for manufacturing a resonant device, the process of preparing the MEMS substrate includes forming a first metal layer and a wiring layer before or after forming the anti-diffusion layer. This allows the first metal layer and wiring layer to be formed on or below the anti-diffusion layer. Therefore, the number of steps involved in forming the first metal layer and wiring layer can be reduced, thus lowering manufacturing costs.

[0120] Furthermore, in the aforementioned method for manufacturing a resonant device, the process of preparing the MEMS substrate includes: forming a first anti-diffusion layer, and forming a second anti-diffusion layer on the first layer. This allows for a thicker anti-diffusion layer and improves the barrier properties against the diffusion of metals constituting the junction.

[0121] Furthermore, in the aforementioned resonant device manufacturing method, the process of preparing the MEMS substrate includes forming a wiring layer on the MEMS substrate at a distance from the end of the bonding portion. This allows an anti-diffusion layer to be disposed between the bonding portion and the wiring layer. Therefore, compared to forming the anti-diffusion layer directly below the bonding portion, the anti-diffusion layer can be thinned, and the product cost of the resonant device can be reduced.

[0122] Furthermore, in the aforementioned method for manufacturing a resonant device, the first metal of the first metal layer is aluminum (Al), and the second metal of the second metal layer is germanium (Ge). This allows for the easy fabrication of a joint that possesses both high conductivity and strong bonding.

[0123] Furthermore, in the aforementioned method for manufacturing the resonant device, the material of the anti-diffusion layer is molybdenum (Mo) or tungsten (W). This allows for easy blocking of the diffusion of aluminum (Al) and germanium (Ge) in the eutectic layer.

[0124] Furthermore, in the aforementioned method for manufacturing the resonant device, the material of the Si substrate is degenerate silicon (Si). Thus, by using a degenerate silicon substrate with low resistance, the Si substrate itself can also function as the lower electrode of the resonator.

[0125] Furthermore, in the aforementioned resonant device manufacturing method, the wiring layer is made of a metal with aluminum (Al) as its main component. Therefore, by heat treatment at a relatively low temperature, such as 450°C, the oxide film formed on the surface of the Si substrate, which serves as the lower electrode of the resonator, can be removed (reduced).

[0126] Furthermore, the embodiments described above are for the purpose of readily understanding the present invention and are not intended to limit the interpretation of the present invention. The present invention can be modified / improved without departing from its spirit, and its equivalents are also included. That is, structures for which those skilled in the art have made appropriate design changes to the various embodiments are also included within the scope of the present invention, provided they possess the features of the present invention. For example, the elements, their configurations, materials, conditions, shapes, dimensions, etc., of the embodiments are not limited to the illustrated structures and can be appropriately modified. In addition, the embodiments are illustrative, and of course, partial substitutions or combinations of the structures shown in different embodiments are possible; such structures are included within the scope of the present invention as long as they contain the features of the present invention.

[0127] Explanation of reference numerals in the attached figures

[0128] 1…Resonant device, 10…Resonator, 20…Lower cover, 21…Recess, 22…Base plate, 23…Side wall, 30…Upper cover, 31…Recess, 33…Side wall, 34…Gas-absorbing layer, 50…MEMS substrate, 60…Joint, 61…First metal layer, 62…Second metal layer, 65…Eutectic layer, 70…Connection wiring, 76A…Contact electrode, 76B…Contact electrode, 81, 81A…Wiring layer, 85, 85A…Anti-diffusion layer, 85a…First layer, 85b…Second layer, 110…Holding arm, 120…Vibrating part, 130…Base, 131a…Long side, 131A…Front end, 13 1b…long side, 131B…rear end, 131c…short side, 131d…short side, 135, 135A, 135B, 135C, 135D…vibrating arm, 140…holding part, 141…voltage application part, 235…protective film, 236…frequency adjustment film, 240…parasitic capacitance reduction film, E1…metal layer, E2…metal layer, F2…Si substrate, F3…piezoelectric film, F21…silicon oxide layer, G…weight part, L1…Si wafer, L3…Si substrate, L31…silicon oxide film, P…imaginary plane, T4…terminal, V1…via, V2…via, V3…through electrode.

Claims

1. A resonant device comprising: A first substrate includes a resonator; Second substrate; and The bonding portion is conductive and bonds the first substrate and the second substrate. The first substrate further includes a wiring layer and an anti-diffusion layer, wherein, The aforementioned wiring layer is electrically connected to the lower electrode of the aforementioned resonator, and the aforementioned anti-diffusion layer electrically connects the wiring layer to the aforementioned junction.

2. The resonant device according to claim 1, wherein, The aforementioned joint includes a eutectic layer, which is composed primarily of a eutectic alloy of a first metal, aluminum, and a second metal, germanium.

3. The resonant device according to claim 2, wherein, The material of the aforementioned anti-diffusion layer is molybdenum or tungsten.

4. The resonant device according to any one of claims 1 to 3, wherein, The material of the lower electrode mentioned above is degenerate silicon.

5. The resonant device according to claim 4, wherein, The material of the aforementioned wiring layer is a metal with aluminum as its main component.

6. The resonant device according to any one of claims 1 to 3, wherein, The aforementioned wiring layer is disposed on the first substrate at a distance from the end of the aforementioned junction.

7. A method for manufacturing a resonant device, comprising: The process of preparing the first substrate, in which, The first substrate includes a first metal layer, a resonator, a wiring layer electrically connected to the lower electrode of the resonator, and an anti-diffusion layer electrically connecting the wiring layer and the first metal layer; The process of preparing a second substrate, wherein the second substrate includes a second metal layer; and The bonding process for forming the joint is a process of bonding the first substrate and the second substrate, wherein the joint includes a eutectic layer whose main components are a eutectic alloy of the first metal of the first metal layer and the second metal of the second metal layer.

8. The method for manufacturing a resonant device according to claim 7, wherein, The above-mentioned process for preparing the first substrate includes: The first metal layer and the wiring layer are formed before or after the formation of the anti-diffusion layer.

9. The method for manufacturing a resonant device according to claim 7 or 8, wherein, The above-mentioned process for preparing the first substrate includes: The first layer forming the aforementioned anti-diffusion layer; and A second layer of the aforementioned anti-diffusion layer is formed on top of the first layer.

10. The method for manufacturing a resonant device according to claim 7 or 8, wherein, The above-mentioned process for preparing the first substrate includes: The wiring layer is formed on the first substrate at a position that is separated from the end of the first metal layer.

11. The method for manufacturing a resonant device according to claim 7 or 8, wherein, The first metal mentioned above is a metal with aluminum as its main component. The second metal mentioned above is germanium.

12. The method for manufacturing a resonant device according to claim 11, wherein, The material of the aforementioned anti-diffusion layer is molybdenum or tungsten.

13. The method for manufacturing a resonant device according to claim 7 or 8, wherein, The material of the lower electrode mentioned above is degenerate silicon.

14. The method for manufacturing a resonant device according to claim 13, wherein, The material of the aforementioned wiring layer is a metal with aluminum as its main component.

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