Patent ID: 12252393

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar components are denoted by the same or similar reference numerals. The drawings are illustrative, and dimensions and shapes of each part are schematic, and the technical scope of the present invention should not be construed as being limited to the embodiments.

EMBODIMENT

<Resonance Device1>

First, a schematic configuration of a resonance device according to an embodiment of the present invention will be described with reference toFIG.1andFIG.2.FIG.1is a perspective view schematically illustrating an appearance of a resonance device1according to an embodiment of the present invention.FIG.2is an exploded perspective view schematically illustrating a structure of the resonance device1illustrated inFIG.1.

The resonance device1includes a lower lid20, a resonator10(hereinafter, the lower lid20and the resonator10may be collectively referred to as a “MEMS substrate40”), and an upper lid30. That is, the resonance device1is configured by laminating the MEMS substrate40, the bonding portion60, and the upper lid30in this order. Note that the MEMS substrate40is an example of a first substrate, and the upper lid30is an example of a second substrate.

Hereinafter, each configuration of the resonance device1will be described. Note that in the following description, a side of the resonance device1on which the upper lid30is provided is referred to as an upper side (or a front side), and a side on which the lower lid20is provided is referred to as a lower side (or a back side). In addition, a state in which the MEMS substrate40and the upper lid30are laminated to configure the resonance device1will be described as a “bonded state”.

The resonator10is a MEMS vibrator manufactured using the MEMS technology. The resonator10and the upper lid30are bonded with a bonding portion60described later interposed therebetween. Further, the resonator10and the lower lid20are each formed using a silicon (Si) substrate (hereinafter referred to as “Si substrate”), and the Si substrates are bonded to each other. Note that the MEMS substrate40(resonator10and lower lid20) may be formed using an SOI substrate.

The upper lid30extends in a flat plate shape along an XY plane, and a recess31having, for example, a flat rectangular parallelepiped shape is formed on the back surface of the upper lid30. The recess31is surrounded by a side wall33and forms a part of a vibration space S in which the resonator10vibrates. In addition, a getter layer34, which will be described later, is formed on a surface of the recess31of the upper lid30on the resonator10side. Note that the upper lid30may be configured to have a flat plate shape without the recess31.

The lower lid20includes a rectangular flat plate-shaped bottom plate22provided along the XY plane, and a side wall23extending from a peripheral edge portion of the bottom plate22in a Z-axis direction, that is, in a lamination direction of the lower lid20and the resonator10. In the lower lid20, a recess21formed by a surface of the bottom plate22and an inner surface of the side wall23is formed on the surface facing the resonator10. The recess21forms a part of the vibration space S of the resonator10. Note that the lower lid20may be configured to have a flat plate shape without the recess21. In addition, a getter layer may be formed on the surface of the recess21of the lower lid20on the resonator10side.

Next, a schematic configuration of the resonator10according to an embodiment of the present invention will be described with reference toFIG.3.FIG.3is a plan view schematically illustrating the structure of the resonator10illustrated inFIG.2.

As illustrated inFIG.3, the resonator10is a MEMS vibrator manufactured using the MEMS technology, and performs out-of-plane vibration in the XY plane in an orthogonal coordinate system ofFIG.3. Note that the resonator10is not limited to a resonator using an out-of-plane bending vibration mode. The resonator of the resonance device1may use, for example, a spreading vibration mode, a thickness longitudinal vibration mode, a Lamb wave vibration mode, an in-plane bending vibration mode, or a surface acoustic wave vibration mode. These vibrators are applied to, for example, a timing device, an RF filter, a duplexer, an ultrasonic transducer, a gyro sensor, an acceleration sensor, and the like. In addition, these vibrators may be used for a piezoelectric mirror having an actuator function, a piezoelectric gyro, a piezoelectric microphone having a pressure sensor function, an ultrasonic vibration sensor, or the like. Further, these vibrators may be applied to an electrostatic MEMS element, an electromagnetic drive MEMS element, and a piezoresistive MEMS element.

The resonator10includes a vibrating portion120, a holding portion140, and a holding arm110.

The holding portion140is formed in a rectangular frame shape so as to surround an outside portion of the vibrating portion120along the XY plane. For example, the holding portion140is integrally formed from a frame body having a prism shape. Note that the holding portion140only needs to be provided in at least a part of a circumference of the vibrating portion120, and the shape thereof is not limited to the frame shape.

The holding arm110is provided on an inner side of the holding portion140and connects the vibrating portion120and the holding portion140.

The vibrating portion120is provided on the inner side of the holding portion140, and a space is formed at a predetermined interval between the vibrating portion120and the holding portion140. In the example illustrated inFIG.3, the vibrating portion120includes a base portion130and four vibrating arms135A to135D (hereinafter, also collectively referred to as “vibrating arms135”). Note that the number of vibrating arms is not limited to four, and is set to an arbitrary number of one or more, for example. In the present embodiment, each of the vibrating arms135A to135D and the base portion130are integrally formed.

The base portion130has long sides131aand131bin an X-axis direction and short sides131cand131din a Y-axis direction in a plan view. The long side131ais one side of a front end surface (hereinafter, also referred to as “front end131A”) of the base portion130, and the long side131bis one side of a rear end surface (hereinafter, also referred to as “rear end131B”) of the base portion130. In the base portion130, the front end131A and the rear end131B are provided so as to face each other.

The base portion130is connected to the vibrating arms135at the front end131A, and is connected to the holding arm110described later at the rear end131B. Note that in the example illustrated inFIG.3, the base portion130has a substantially rectangular shape in a plan view, but is not limited thereto. The base portion130may be formed substantially plane-symmetrically with respect to a virtual plane P defined along a perpendicular bisector of the long side131a. For example, the base portion130may have a trapezoidal shape in which the long side131bis shorter than the131a, or may have a semicircular shape in which the long side131ais a diameter. In addition, each surface of the base portion130is not limited to a flat surface, and may be a curved surface. Note that the virtual plane P is a plane passing through the center of the vibrating portion120in a direction in which the vibrating arms135are arranged.

In the base portion130, a base portion length which is the longest distance between the front end131A and the rear end131B in a direction from the front end131A toward the rear end131B is about 35 μm. In addition, a base portion width, which is the longest distance between the side ends of the base portion130, is a width direction orthogonal to a base portion length direction, and is about 265 μm.

The vibrating arms135extend in the Y-axis direction and each have the same size. Each of the vibrating arms135is provided between the base portion130and the holding portion140in parallel with the Y-axis direction, one end thereof is connected to the front end131A of the base portion130to be a fixed end, and the other end thereof is an open end. In addition, each of the vibrating arms135is provided in parallel at a predetermined interval in the X-axis direction. Note that the vibrating arms135have a width of about 50 μm in the X-axis direction and a length of about 465 μm in the Y-axis direction, for example.

In each of the vibrating arms135, for example, a portion having a distance of about 150 μm from the open end is wider in the X-axis direction than other portions of the vibrating arms135. This widened portion is called a weight portion G. The weight portion G is, for example, wider than the other portions of the vibrating arms135by 10 μm to the right and left along the X-axis direction, and the width in the X-axis direction is about 70 μm. The weight portion G is integrally formed by the same process as the vibrating arm135. Since the weight portion G is formed, a weight per unit length of the vibrating arms135is heavier on the open end side than on the fixed end side. Therefore, each of the vibrating arms135has the weight portion G on the open end side, so that it is possible to increase an amplitude of vibration in an up-down direction in each vibrating arm.

A protective film235, which will be described later, is formed on a surface of the vibrating portion120(a surface facing the upper lid30) so as to cover the entire surface thereof. In addition, a frequency adjustment film236is formed on a surface of the protective film235at each of tips on the open end sides of the vibrating arms135A to135D. A resonant frequency of the vibrating portion120can be adjusted by the protective film235and the frequency adjustment film236.

Note that in the present embodiment, substantially the entire surface of the surface of the resonator10(a surface facing the upper lid30) is covered with the protective film235. Further, substantially the entire surface of the protective film235is covered with a parasitic capacitance reducing film240. However, the protective film235only needs to cover at least the vibrating arms135, and is not limited to a configuration of covering substantially the entire surface of the resonator10.

Next, with reference toFIG.2toFIG.4, a laminated structure of the resonance device1according to an embodiment of the present invention will be described.FIG.4is a cross-sectional view schematically illustrating a configuration of a cross section taken along a line IV-IV of the resonance device1illustrated inFIG.1toFIG.3.

In the resonance device1, the holding portion140of the resonator10is bonded onto the side wall23of the lower lid20, and further, the holding portion140of the resonator10and the side wall33of the upper lid30are bonded by the bonding portion60. In this manner, the resonator10is held between the lower lid20and the upper lid30, and the vibration space S in which the vibrating arms135vibrate is formed by the lower lid20, the upper lid30, and the holding portion140of the resonator10. In addition, the upper lid30is grounded by a ground portion50. A terminal T4is formed on an upper surface (a surface opposite to a surface facing the resonator10) of the upper lid30. The terminal T4and the resonator10are electrically connected by a through-electrode V3, a connection wiring70, and contact electrodes76A and76B.

The upper lid30is formed of a silicon (Si) wafer (hereinafter referred to as “Si wafer”) L3having a predetermined thickness. The upper lid30is bonded to the holding portion140of the resonator10at a peripheral portion (side wall33) of the upper lid30by the bonding portion60described later. The front and back surfaces of the upper lid30facing the resonator10and a side surface of the through-electrode V3are preferably covered with a silicon oxide film L31. The silicon oxide film L31is an example of an insulating layer, and is formed on the Si wafer L3by, for example, oxidation of a surface of the Si wafer L3or chemical vapor deposition (CVD).

In addition, the getter layer34is formed on the surface of the recess31of the upper lid30on the side facing the resonator10. The getter layer34is formed of, for example, titanium (Ti) or the like, and adsorbs a released-gas generated in the vibration space S. In the upper lid30according to the present embodiment, since the getter layer34is formed on substantially the entire surface of the surface of the recess31facing the resonator10, it is possible to suppress a decrease in the degree of vacuum of the vibration space S.

In addition, the through-electrode V3of the upper lid30is formed by filling a through-hole formed in the upper lid30with a conductive material. The conductive material to be filled is, for example, impurity-doped polycrystalline silicon (Poly-Si), copper (Cu), gold (Au), impurity-doped single crystal silicon, or the like. The through-electrode V3serves as a wiring that electrically connects the terminal T4and a voltage application portion141.

The bottom plate22and the side wall23of the lower lid20are integrally formed by a Si wafer L1. In addition, the lower lid20is bonded to the holding portion140of the resonator10by an upper surface of the side wall23. A thickness of the lower lid20defined in the Z-axis direction is, for example, 150 μm, and a depth of the recess21is, for example, 50 μm. Note that the Si wafer L1is made of non-degenerated silicon and has a resistivity of, for example, equal to or more than 16 m Ω·cm.

The holding portion140, the base portion130, the vibrating arms135, and the holding arm110in the resonator10are integrally formed in the same process. In the resonator10, a piezoelectric thin film F3is formed on a silicon (Si) substrate (hereinafter, referred to as “Si substrate”) F2, which is an example of a substrate, so as to cover the Si substrate F2, and a metallic layer E2is laminated on the piezoelectric thin film F3. Then, the piezoelectric thin film F3is laminated on the metallic layer E2so as to cover the metallic layer E2, and a metallic layer E1is laminated on the piezoelectric thin film F3. The protective film235is laminated on the metallic layer E1so as to cover the metallic layer E1, and the parasitic capacitance reducing film240is laminated on the protective film235.

The Si substrate F2is formed of, for example, a degenerated n-type silicon (Si) semiconductor having a thickness of about 6 μm, and may contain phosphorus (P), arsenic (As), antimony (Sb), or the like as an n-type dopant. The degenerated silicon (Si) used in the Si substrate F2has a resistance value of, for example, less than 16 m Ω·cm, and more preferably equal to or less than 1.2 m Ω·cm. Further, on a lower surface of the Si substrate F2, a silicon oxide (for example, SiO2) layer F21is formed as an example of a temperature characteristic correction layer. This makes it possible to improve temperature characteristics. Note that the silicon oxide layer F21may be formed on an upper surface of the Si substrate F2, or may be formed on both the upper surface and the lower surface of the Si substrate F2.

In addition, the metallic layers E1and E2have a thickness of about 0.1 μm to 0.2 μm, for example, and are patterned into a desired shape by etching or the like after film formation. The metallic layers E1and E2are made of metals having a body-centered cubic structure as a crystal structure. Specifically, the metallic layers E1and E2are formed by using Mo (molybdenum), tungsten (W) or the like.

The metallic layer E1is formed so as to serve as an upper electrode, for example, on the vibrating portion120. In addition, the metallic layer E1is formed so as to serve as a wiring for connecting the upper electrode to an AC power supply provided outside the resonator10, on the holding arm110and the holding portion140.

On the other hand, the metallic layer E2is formed so as to serve as a lower electrode, on the vibrating portion120. In addition, the metallic layer E2is formed so as to serve as a wiring for connecting the lower electrode to a circuit provided outside the resonator10, on the holding arm110and the holding portion140.

The piezoelectric thin film F3is a thin film of a piezoelectric body that converts an applied voltage into vibration. The piezoelectric thin film F3is formed of a material having a wurtzite type hexagonal crystal structure as a crystal structure, and may be mainly composed of nitrides or oxides such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), indium nitride (InN) and the like, for example. Note that scandium aluminum nitride is obtained from aluminum nitride in which part of aluminum is substituted with scandium, and instead of scandium, may be substituted with two elements such as magnesium (Mg) and niobium (Nb), magnesium (Mg) and zirconium (Zr) or the like. In addition, the piezoelectric thin film F3has a thickness of, for example, 1 μm, but may have a thickness of about 0.2 μm to 2 μm.

The piezoelectric thin film F3expands and contracts in an in-plane direction of the XY plane, that is, in the Y-axis direction according to an electric field applied to the piezoelectric thin film F3by the metallic layers E1and E2. By the expansion and contraction of the piezoelectric thin film F3, the vibrating arms135displace free ends thereof toward inner surfaces of the lower lid20and the upper lid30, and vibrate in an out-of-plane bending vibration mode.

In the present embodiment, phases of electric fields applied to the outer vibrating arms135A and135D and phases of electric fields applied to the inner vibrating arms135B and135C are set to be opposite to each other. Accordingly, the outer vibrating arms135A and135D and the inner vibrating arms135B and135C are displaced in directions opposite to each other. For example, when the outer vibrating arms135A and135D displace the free ends toward the inner surface of the upper lid30, the inner vibrating arms135B and135C displace the free ends toward the inner surface of the lower lid20.

The protective film235prevents oxidation of the metallic layer E2which is the upper electrode for piezoelectric vibration. The protective film235is preferably formed using a material whose mass reduction rate by etching is lower than that of the frequency adjustment film236. The mass reduction rate is expressed by the etching rate, that is, the product of the thickness removed per unit time and the density. The protective film235is formed of, for example, an insulating film such as silicon nitride (SiN), silicon oxide (SiO2), alumina oxide (Al2O3) or the like, other than a piezoelectric film such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), indium nitride (InN) or the like. A thickness of the protective film235is, for example, about 0.2 μm.

The frequency adjustment film236is formed on substantially the entire surface of the vibrating portion120, and then formed only in a predetermined region by processing such as etching. The frequency adjustment film236is formed of a material whose mass reduction rate by etching is higher than that of the protective film235. Specifically, the frequency adjustment film236is made of a metal such as molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti) or the like.

Note that the magnitude relationship between the etching rates of the protective film235and the frequency adjustment film236is arbitrary as long as the relationship between the mass reduction rates is as described above.

The parasitic capacitance reducing film240is an example of an insulating layer and is formed of tetraethyl orthosilicate (TEOS). A thickness of the parasitic capacitance reducing film240is about 1 μm. The parasitic capacitance reducing film240reduces parasitic capacitance in a lead-out wiring portion, and has a function as an insulating layer when wirings having different potentials cross each other and a function as a stand-off for expanding the vibration space S.

The connection wiring70is electrically connected to the terminal T4via the through-electrode V3, and is electrically connected to the contact electrodes76A and76B.

The contact electrode76A is formed so as to be in contact with the metallic layer E1of the resonator10, and electrically connects the connection wiring70and the resonator10. The contact electrode76B is formed so as to be in contact with the metallic layer E2of the resonator10, and electrically connects the connection wiring70and the resonator10. To be specific, when the contact electrode76A and the metallic layer E1are connected, the piezoelectric thin film F3, the protective film235, and the parasitic capacitance reducing film240laminated on the metallic layer E1are partially removed so that the metallic layer E1is exposed, thereby forming a via V1. An inside of the formed via V1is filled with the same material as that of the contact electrode76A, and the metallic layer E1and the contact electrode76A are connected. Similarly, when the contact electrode76B and the metallic layer E2are connected, the piezoelectric thin film F3and the parasitic capacitance reducing film240laminated on the metallic layer E2are partially removed so that the metallic layer E2is exposed, thereby forming a via V2. An inside of the formed via V2is filled with the contact electrode76B, and the metallic layer E2and the contact electrode76B are connected. The contact electrodes76A and76B are made of metals such as aluminum (Al), gold (Au), tin (Sn) and the like, for example. Note that a connection point between the metallic layer E1and the contact electrode76A and a connection point between the metallic layer E2and the contact electrode76B are preferably regions in an outer side portion of the vibrating portion120, and are connected by the holding portion140in the present embodiment.

The bonding portion60is an example of a second eutectic reaction layer, and is, for example, an alloy layer formed by a eutectic reaction of a plurality of metals (i.e., a eutectic reaction product of the plurality of metals). The bonding portion60is provided between the MEMS substrate40and the upper lid30so as to be in contact with the MEMS substrate40and the upper lid30. In addition, when viewed in a plan view, the bonding portion60is formed in a rectangular ring shape along the XY plane around the vibrating portion120of the resonator10, for example, on the holding portion140.

In addition, the bonding portion60bonds the MEMS substrate40and the upper lid30so as to seal the vibration space S of the resonator10. In the bonded state, the bonding portion60is connected to the upper lid30in an insulating manner via the silicon oxide film L31provided in the upper lid30. In addition, the bonding portion60is connected to the MEMS substrate40in an insulating manner via the parasitic capacitance reducing film240provided in the MEMS substrate40.

In this way, the vibration space S is air-tightly sealed by the bonding of the bonding portion60, and the vacuum state of the vibration space S is maintained. In addition, the airtightness of the bonding of the bonding portion60affects the degree of vacuum of the vibration space S. The degree of vacuum of the vibration space S according to the present embodiment is ensured to be about 1 Pa to 2 Pa due to the high airtightness of the bonding of the bonding portion60. Note that details of the bonding portion60will be described later together with the detailed description of a ground portion50.

The ground portion50is an example of a first eutectic reaction layer, and is, for example, an alloy layer formed by a eutectic reaction of a plurality of metals. The ground portion50according to the present embodiment has the same component (material) as the bonding portion60. The ground portion50is provided between the MEMS substrate40and the upper lid30so as to be in contact with the MEMS substrate40and the upper lid30. In addition, the ground portion50is provided around the vibrating portion120of the resonator10and on an inner side of the bonding portion60without being in contact with the bonding portion60. The shape of the ground portion50in the XY plane may be any shape, and is, for example, a rectangular shape.

Further, in the bonded state, similarly to the bonding portion60, the ground portion50is connected to the MEMS substrate40in an insulating manner via the parasitic capacitance reducing film240provided in the MEMS substrate40. On the other hand, unlike the bonding portion60, since a part of the silicon oxide film L31at a position where the upper lid30is connected to the ground portion50is removed, the ground portion50is extended to an inside of the upper lid30and is electrically connected to the upper lid30.

In this way, the ground portion50grounds the upper lid30, reduces the contact resistance with the upper lid30, and achieves reduction in the parasitic capacitance of the upper lid30. Note that the details of the ground portion50will be described later.

<Laminated Structure of Ground Portion50and Bonding Portion60>

Next, with reference toFIG.5, a laminated structure of the ground portion50and the bonding portion60according to an embodiment of the present invention will be described.FIG.5is an enlarged cross-sectional view of a main part schematically illustrating a configuration of the ground portion50and the bonding portion60illustrated inFIG.4. In addition, in the example illustrated inFIG.5, for convenience of description, three metal layers for generating the ground portion50and the bonding portion60, that is, a eutectic reaction layer80before the bonding by the eutectic reaction are each illustrated as independent layers, but actually, the interfaces thereof are eutectic-bonded.

Here, in the present embodiment, the ground portion50and the bonding portion60have the same components. In addition, as described above, the difference between the ground portion50and the bonding portion60is that, in the bonded state, the ground portion50is extended to an inside of the upper lid30and is electrically connected to the upper lid30, but the bonding portion60is connected to the upper lid30in an insulating manner by the silicon oxide film L31provided in the upper lid30. Therefore, in the following description, the configuration of the ground portion50will be mainly described, and the description of the configuration of the bonding portion60will be simplified.

As illustrated inFIG.5, the ground portion50includes a first ground portion51and a second ground portion52in this order from the MEMS substrate40toward the upper lid30. The first ground portion51includes an aluminum layer511. The second ground portion52includes a germanium layer521and a titanium layer522.

The aluminum layer511of the first ground portion51is provided on the parasitic capacitance reducing film240of the MEMS substrate40, and is connected to the MEMS substrate40in an insulating manner. The titanium layer522of the second ground portion52is provided in a portion where a part of the silicon oxide film L31of the upper lid30is removed, and is electrically connected to the upper lid30. The germanium layer521of the second ground portion52is provided on the titanium layer522(under the titanium layer522inFIG.5).

In addition, in the display ofFIG.5, although the titanium layer522appears to be extended to an inside of the upper lid30, in actually, not the titanium layer522but an AlGeTi alloy layer generated by the eutectic reaction of the aluminum layer511, the germanium layer521, and the titanium layer522is extended to the inside of the upper lid30. That is, the aluminum component is diffused to the inside of the upper lid30. In this manner, the ground portion50grounds the upper lid30, thereby achieving reduction in the contact resistance of the upper lid30.

Similarly, the bonding portion60is a eutectic reaction layer containing an AlGeTi alloy as a main component, and includes a first bonding portion61and a second bonding portion62in this order from the MEMS substrate40toward the upper lid30. The first bonding portion61includes an aluminum layer611. In addition, the second bonding portion62includes a germanium layer621and a titanium layer622. The titanium layer622is provided on the silicon oxide film L31of the upper lid30, and the germanium layer621is provided on the titanium layer622(under the titanium layer622inFIG.5).

In addition, the ground portion50and the bonding portion60configure the eutectic reaction layer80. Specifically, the first ground portion51and the first bonding portion61on the MEMS substrate40side configure a first metal layer81, and the second ground portion52and the second bonding portion62on the upper lid30side configure a second metal layer82. The first metal layer81and the second metal layer82configure the eutectic reaction layer80.

In the present embodiment, a thickness of the aluminum layers511and611is preferably about 0.70 μm and a thickness of the germanium layers521and621is preferably about 0.38 μm in order to cause aluminum, germanium, and titanium to sufficiently have the eutectic reaction. In addition, since the titanium layers522and622function as a close contact layer for causing the germanium layers521and621to come into close contact with the upper lid30, a thickness of the titanium layers522and622does not affect the eutectic reaction. Thus, the thickness of the titanium layers522and622may be an arbitrary thickness, for example, about 0.10 μm.

In addition, in the present embodiment, since the aluminum layers511and611are not originally provided on the upper lid30side, a concentration of aluminum of the ground portion50and the bonding portion60on the upper lid30side is lower than a concentration of aluminum on the MEMS substrate40side in a case where the eutectic reaction is not completely generated or in a case where an amount of aluminum is equal to or more than an amount necessary for the eutectic reaction. On the other hand, in a case where the eutectic reaction has been completely generated, the concentration of aluminum of the ground portion50and the bonding portion60on the upper lid30substrate side is the same as the concentration of aluminum on the MEMS substrate40side.

<State of Ground Portion50and Bonding Portion60>

Next, with reference toFIG.6, a state of the ground portion50and the bonding portion60according to the embodiment of the present invention, that is, a state of the eutectic reaction layer80will be described.FIG.6is a phase diagram when three elements of aluminum (Al), germanium (Ge), and titanium (Ti) are made to have a eutectic reaction. InFIG.6, a horizontal axis represents a rate (at %) of germanium (Ge), and a vertical axis represents a temperature (° C.).

On the other hand, in a case where three elements, for example, aluminum (Al), germanium (Ge), and titanium (Ti) are made to have the eutectic reaction and bonded, a liquid of eutectic molten metal (denoted by L inFIG.6) and an aluminum-germanium-titanium alloy (AlGeTi alloy) (denoted by τ1inFIG.6) are generated in a range surrounded by a thick line illustrated inFIG.6. Thus, in a given ternary eutectic reaction, an alloy can be formed and no interface of different materials is formed.

Accordingly, the formation of an interface of different materials is suppressed by the alloy layer made of aluminum (Al), germanium (Ge), and titanium (Ti) in the ground portion50and the bonding portion60. Therefore, voids and interface peeling that may occur in the ground portion50and the bonding portion60are reduced, and the airtightness and the bonding strength of the ground portion50and the bonding portion60can be improved.

In addition, when the ground portion50or the bonding portion60is generated, as described above, since a solid alloy is formed together with the eutectic molten metal which is liquid at a eutectic point or higher, the fluidity of the eutectic molten metal decreases, and the protrusion (splash) of the eutectic molten metal in a planar direction is suppressed. Therefore, it is possible to reduce a short circuit caused by the protrusion of the bonding portion60, and it is possible to improve the degree of freedom of the layout of the resonance device1.

It is preferable that each component of the ground portion50or the bonding portion60have a predetermined concentration rate. For example, the concentration of aluminum (Al) is preferably 58 at % to 82 at %, the concentration of germanium (Ge) is preferably 10 at % to 32 at %, and the concentration of titanium (Ti) is preferably 7 at % to 32 at %. Accordingly, it is possible to easily realize the ground portion50or the bonding portion60with improved airtightness and bonding strength.

In addition, each component of the ground portion50or the bonding portion60preferably has a predetermined concentration ratio. For example, the concentration ratio of aluminum (Al), germanium (Ge), and titanium (Ti) is preferably 3:1:1. This further suppresses the formation of an interface of different materials in the ground portion50or the bonding portion60.

<Manufacturing Steps of Resonance Device1>

Next, a method of manufacturing the resonance device1according to an embodiment of the present invention will be described with reference toFIG.7toFIG.11.FIG.7is a flowchart illustrating the method of manufacturing the resonance device1according to the embodiment of the present invention.FIG.8is a cross-sectional view illustrating a step S301illustrated inFIG.7.FIG.9is a cross-sectional view illustrating a step S302illustrated inFIG.7.FIG.10is a cross-sectional view illustrating a step S303illustrated inFIG.7.FIG.11is a cross-sectional view illustrating a step S304illustrated inFIG.7. Note that inFIG.8toFIG.11, one resonance device1among a plurality of resonance devices1manufactured by the manufacturing method will be described for the sake of convenience.

As illustrated inFIG.7, first, the MEMS substrate40and the upper lid30are prepared (S301).

Specifically, as illustrated inFIG.8, the above-described MEMS substrate40including the resonator10and the upper lid30having the through-electrode V3are each prepared. However, in this case, the connection wiring70(seeFIG.4) connecting the through-electrode V3and the resonator10is not yet formed.

Returning toFIG.7, next, in the MEMS substrate40prepared in the step S301, the first metal layer81including the first ground portion51and the first bonding portion61is formed around the vibrating portion120of the resonator10(S302).

Specifically, as illustrated inFIG.9, the aluminum layer511configuring the first ground portion51and the aluminum layer611configuring the first bonding portion61are simultaneously formed on the prepared MEMS substrate40(resonator10), respectively.

More specifically, first, in the prepared MEMS substrate40(resonator10), for example, aluminum (Al) is laminated on the parasitic capacitance reducing film240formed on the piezoelectric thin film F3. Next, by forming the laminated aluminum (Al) into a desired shape by etching or the like, in the MEMS substrate40, the first metal layer81, that is, the aluminum layer511of the first ground portion51and the aluminum layer611of the first bonding portion61are formed in an outer side portion of the vibrating portion120. Thus, the first metal layer81is formed on the MEMS substrate40. In addition, the first metal layer81is formed around the resonance space of the resonator10in a plan view of the MEMS substrate40. The aluminum layer511is formed on an inner side of the aluminum layer611without being in contact with the aluminum layer611.

After the first metal layer81is formed, a first annealing treatment (heat treatment) for degassing is performed with respect to the MEMS substrate40. In addition, the first annealing temperature of the first annealing treatment is, for example, about 450° C.

Here, the first metal layer81includes only the aluminum layer511and the aluminum layer611, and each of the aluminum layer511and the aluminum layer611is prevented from directly being in contact with the MEMS substrate40by the parasitic capacitance reducing film240. Therefore, even when the heat treatment is performed at a high temperature of about 450° C., the influence of thermal diffusion on the MEMS substrate40is small. Therefore, by degassing the first metal layer81more reliably and effectively, the degree of vacuum of the vibration space S after sealing can be improved.

Returning toFIG.7, next, in the upper lid30prepared in the step S301, when the MEMS substrate40and the upper lid30are made to face each other, the second metal layer82including the second ground portion52and the second bonding portion62which are continuously provided from the MEMS substrate40side is formed (S303).

Specifically, as illustrated inFIG.10, the titanium layer522and the germanium layer521configuring the second ground portion52and the titanium layer622and the germanium layer621configuring the second bonding portion62are simultaneously formed on the back surface of the prepared upper lid30.

More specifically, first, for example, titanium (Ti) is laminated on a portion where a part of the silicon oxide film L31is removed in advance and a portion where the silicon oxide film L31is not removed on the back surface of the upper lid30. Next, by forming the laminated titanium (Ti) into a desired shape by etching or the like, in the upper lid30, the titanium layer522in the portion where a part of the silicon oxide film L31is removed in advance and the titanium layer622in the portion where the silicon oxide film L31is not removed are simultaneously formed. In addition, a predetermined position where the titanium layer522and the titanium layer622are formed is, for example, a position on the back surface of the upper lid30facing or substantially facing the first metal layer81formed in the MEMS substrate40when the front surface of the MEMS substrate40and the back surface of the upper lid30are made to face each other. Then, for example, germanium (Ge) is laminated on each of the titanium layer522and the titanium layer622(under each of the titanium layer522and the titanium layer622inFIG.10) to provide the germanium layer521and the germanium layer621. Thus, the second metal layer82is formed at a predetermined position of the upper lid30.

After the second metal layer82is formed, a second annealing treatment (heat treatment) for degassing is performed on the upper lid30. In addition, the second annealing temperature of the second annealing treatment is the same as the first annealing temperature, and is, for example, about 450° C.

Here, since a material of the upper lid30is silicon, the upper lid30is more likely to be affected by thermal diffusion generated during annealing treatment than the MEMS substrate40. In addition, since the second ground portion52of the second metal layer82is in direct contact with the upper lid30without interposing the silicon oxide film L31therebetween, thermal diffusion to the upper lid30is more likely to occur than in a case where an insulating layer such as the silicon oxide film L31is employed. However, the second metal layer82provided in the upper lid30includes only the titanium layer522and the titanium layer622, and the germanium layer521and the germanium layer621. That is, the second metal layer82does not contain an aluminum component that is likely to thermally diffuse to silicon. Therefore, even when the upper lid30is made of a silicon material that is easily affected by the annealing temperature of the annealing treatment, it is possible to avoid thermal diffusion of aluminum into silicon, and there is no need to lower the second annealing temperature. As a result, as the second annealing temperature of the second annealing treatment, for example, a high temperature of about 450° C. can be adopted, similarly to the first annealing temperature.

Note that for example, in a case where aluminum is contained in the second metal layer82on the upper lid30side made of a silicon material, only about 400° C. as the annealing temperature for degassing the second metal layer82can be adopted in order to avoid thermal diffusion of aluminum to silicon. In this case, the degree of vacuum of the vibration space S bonded after annealing treatment at about 400° C. is about 10 Pa. On the other hand, the degree of vacuum of the vibration space S sealed after the annealing treatment at about 450° C. according to the present embodiment is about 1 Pa to 2 Pa. Therefore, the degree of vacuum of the vibration space S after the annealing treatment at about 450° C. is clearly improved as compared with the case of the annealing treatment at about 400° C. That is, performing the annealing treatment at the high temperature of about 450° C. more reliably and effectively degasses the first metal layer81and the second metal layer82than performing the annealing treatment at the temperature of about 400° C., and thus it is possible to improve the degree of vacuum of the vibration space S after bonding and sealing.

Returning toFIG.7, next, the MEMS substrate40in which the first metal layer81is formed in the step S302and the upper lid30in which the second metal layer82is formed in the step S303are bonded to each other so as to seal the vibration space S of the resonator10(S304). This step S304includes forming the bonding portion60and the ground portion50, that is, the eutectic reaction layer80, including a eutectic alloy (AlGeTi alloy) of the first metal layer81containing aluminum (Al) as a main component and the second metal layer82containing germanium (Ge) and titanium (Ti) of a third metal as a main component.

Specifically, the positions of the MEMS substrate40and the upper lid30are aligned so that the first metal layer81and the second metal layer82coincide with each other. After the alignment, the MEMS substrate40and the upper lid30are sandwiched by a heater or the like, and heat treatment for ternary eutectic reaction is performed. At this time, the upper lid30is moved toward the MEMS substrate40. As a result, as illustrated inFIG.11, the germanium layer521of the second metal layer82is in contact with the aluminum layer511of the first metal layer81.

The eutectic temperature in the heat treatment for the ternary eutectic reaction is preferably equal to or higher than the temperature of the eutectic point and lower than the melting point in a case of aluminum (Al) alone of the first metal. That is, in a case where the second metal is germanium (Ge) and the third metal is titanium (Ti), the temperature is preferably equal to or higher than 422° C., which is the eutectic point, and lower than about 620° C., which is the melting point of aluminum (Al) alone.

In addition, the heating time is preferably about 5 minutes to 30 minutes. In the present embodiment, the heat treatment of the eutectic reaction is performed at about 440° C. as a eutectic temperature for about 15 minutes as a heating time.

At the time of heating, the upper lid30and the MEMS substrate40are pressed from the upper lid30to the MEMS substrate40as indicated by a black arrow inFIG.11. The pressing force is, for example, about 15 Mpa, and is preferably about 5 MPa to 25 MPa.

In addition, after the heat treatment for the ternary eutectic reaction, a cooling treatment is performed by natural cooling, for example. Note that, the cooling treatment is not limited to natural cooling, and various cooling temperatures and cooling speeds can be selected as long as a eutectic layer65containing a eutectic alloy as a main component can be formed in the bonding portion60.

As a result of performing the step S304illustrated inFIG.7, the ground portion50and the bonding portion60(seeFIG.4andFIG.5) are formed.

In addition, an aluminum (Al) film may be formed when forming the first metal layer81, a germanium (Ge) film may be formed when forming the second metal layer82, and these layers are eutectic-bonded, whereby the connection wiring70(seeFIG.4) for connecting the through-electrode V3and the resonator10may be provided.

As described above, the present embodiment adopts a configuration in which the aluminum layer is not provided but only the germanium layer and the titanium layer are provided in the upper lid30that is easily affected by the heat of the annealing treatment, and the aluminum layer is provided in the MEMS substrate40that is hardly affected by the heat of the annealing treatment. With such a configuration, even when the upper lid30is easily affected by the heat of the annealing treatment, thermal diffusion to the upper lid30due to aluminum does not occur when the annealing treatment is performed, therefore, it is not necessary to lower the annealing temperature. Therefore, an annealing temperature at which the germanium layer and the titanium layer provided in the upper lid30can be sufficiently degassed can be adopted, and the degree of vacuum can be improved. In addition, the thermal diffusion of aluminum has little influence on the MEMS substrate40. Therefore, even when an aluminum layer is provided in the MEMS substrate40, an annealing temperature at which the aluminum layer can be sufficiently degassed can be adopted. As a result, the first metal layer81(containing aluminum as a main component) and the second metal layer82(containing germanium and titanium as main components) can be reliably and effectively degassed, and the degree of vacuum vibration space S after sealing can be improved.

In addition, in the present embodiment, an alloy layer can be formed by causing aluminum (Al), germanium (Ge), and titanium (Ti) to have the eutectic reaction. Therefore, as compared with a structure in which an alloy layer is not easily formed, formation of an interface of different materials can be suppressed, problems such as voids, interface peeling and the like due to an interface of different materials can be reduced, and airtightness of bonding and bonding strength can be improved.

Further, in the present embodiment, by expanding the eutectic reaction layer to the inside of the upper lid30, the aluminum component can be diffused into the inside of the upper lid30. Therefore, the upper lid30is grounded by the aluminum component diffused inside the upper lid30, and reduction in the contact resistance of the upper lid30is achieved.

[Modification]

The present invention is not limited to the above-described embodiment and can be variously modified and applied. Hereinafter, modifications according to the present invention will be described.

(First Modification)

FIG.12is an enlarged cross-sectional view of a main part illustrating a first modification of the ground portion50and the bonding portion60illustrated inFIG.5. Note that, in the first modification, the same components as those of the ground portion50and the bonding portion60illustrated inFIG.5are denoted by the same reference numerals, and the description thereof will be appropriately omitted. In addition, the same operation and effect by the same configuration will not be sequentially described. Note that, since the bonding portion60has the same components as the ground portion50, the following description will focus on the configuration of the ground portion50, and the description of the bonding portion60will be omitted. Note that, the same applies to a second modification, a third modification, and the like, which will be described later.

As illustrated inFIG.12, the first ground portion51further includes a titanium layer512formed on the MEMS substrate40side. The aluminum layer511is provided on the titanium layer512.

Similarly to the titanium layer522provided on the upper lid30side, the titanium layer512has a function as a close contact layer, and can improve a property of close contact between the ground portion50and the MEMS substrate40. Therefore, the bonding strength of the ground portion50can be further improved. The same applies to the bonding portion60.

In a manufacturing method of the first modification, the titanium layer512and the aluminum layer511are continuously provided from the MEMS substrate40side in the step S302illustrated inFIG.9.

In addition, in the step S304according to the first modification, the ternary eutectic reaction is the same as in the above-described example.

(Second Modification)

FIG.13is an enlarged cross-sectional view of a main part illustrating a second modification of the ground portion50and the bonding portion60illustrated inFIG.5. The first ground portion51includes the aluminum layer511and the titanium layer512according to the first modification, and further includes an aluminum layer513provided beneath the titanium layer512. That is, the first ground portion51according to the second modification has a laminated structure of aluminum-titanium-aluminum.

By employing the above aluminum layer513, wiring can be lead out from the aluminum layer513in the MEMS substrate40.

In addition, a material of the aluminum layer513preferably contains an aluminum-copper alloy (AlCu alloy) or an aluminum-silicon-copper alloy (AlSiCu alloy) as a main component other than the case where aluminum (Al) is contained as a main component. Accordingly, the aluminum layer513has conductivity, the manufacturing process can be simplified, and the ground portion50that seals the vibration space S of the resonator10can be easily formed. The same applies to the bonding portion60.

In a manufacturing method of the second modification, the aluminum layer513, the titanium layer512, and the aluminum layer511are continuously provided from the MEMS substrate40side in the step S302illustrated inFIG.9.

In addition, in the step S304according to the second modification, the ternary eutectic reaction is the same as in the above-described example.

(Third Modification)

FIG.14is an enlarged cross-sectional view of a main part illustrating a third modification of the ground portion50and the bonding portion60illustrated inFIG.5. The first ground portion51includes the aluminum layer511, the titanium layer512, and the aluminum layer513according to the second modification, and further includes the titanium layer514provided beneath the aluminum layer513. That is, the first ground portion51according to the third modification has a laminated structure of aluminum-titanium-aluminum-titanium.

As described above, the titanium layer functioning as the close contact layer is provided between the aluminum layer and the aluminum layer and also between the aluminum layer and the MEMS substrate40. Therefore, the bonding strength of the ground portion50can be further improved as compared with the first modification and the second modification. The same applies to the bonding portion60.

In a manufacturing method of the third modification, the titanium layer514, the aluminum layer513, the titanium layer512, and the aluminum layer511are continuously provided from the MEMS substrate40side in the step S302illustrated inFIG.9.

In addition, in the step S304according to the third modification, the ternary eutectic reaction is the same as in the above-described example.

(Other Modifications)

In the above-described embodiment, although the ground portion50and the bonding portion60are described as eutectic reaction layers (eutectic alloy layers) formed by a ternary or higher-order eutectic reaction, the present invention is not limited to the above-described configuration. For example, the ground portion50and the bonding portion60may be a eutectic reaction layer (eutectic alloy layer) configured by a first metal containing aluminum (Al) as a main component and a second metal containing germanium (Ge) as a main component. That is, the ground portion50and the bonding portion60may be formed by a binary eutectic reaction.

However, in a case where two elements, for example, aluminum (Al), and germanium (Ge) are made to have a eutectic reaction and bonded, an aluminum-germanium alloy (AlGe alloy) is hardly formed, and an aluminum (Al) single layer and a germanium (Ge) single layer are formed. As a result, there are many interfaces between the aluminum (Al) single layer and the germanium (Ge) single layer. At the interface between such different materials, voids or peeling (interface peeling) is likely to occur due to the difference in thermal stress, and the airtightness and bonding strength of the bonding portion may decrease. Therefore, it is preferable to employ a ternary or higher-order eutectic reaction capable of forming an alloy layer.

In the above-described embodiment, the ground portion50and the bonding portion60are described as eutectic reaction layers (eutectic alloy layers) generated by the eutectic reaction of aluminum (Al), germanium (Ge), and titanium (Ti), but the present invention is not limited to the above-described configuration. For example, a eutectic reaction layer (eutectic alloy layer) formed by a eutectic reaction of aluminum (Al), germanium (Ge), and nickel (Ni), a eutectic reaction of aluminum (Al), silicon (Si), and titanium (Ti), and a eutectic reaction of aluminum (Al), silicon (Si), and nickel (Ni) may be used. In addition, in these cases, a liquid of eutectic molten metal and an alloy are generated.

In the above embodiment, the first annealing temperature and the second annealing temperature are about 450° C., but are not limited thereto. For example, the annealing temperature may be changed by changing the metal of the eutectic reaction. In addition, the first annealing temperature and the second annealing temperature may be different from each other. In addition, similarly, the eutectic temperature has been described as being about 440° C., but is not limited thereto. For example, the eutectic temperature may be changed by changing the metal of the eutectic reaction.

In the above-described embodiment and the first to third modifications, the ground portion50and the bonding portion60have the same components, but the present invention is not limited to the above-described configuration. For example, the ground portion50and the bonding portion60may have different components.

Exemplary embodiments of the present invention have been described above.

A resonance device according to an embodiment of the present invention includes the MEMS substrate40which is an example of a first substrate including the resonator10, the upper lid30which is an example of a second substrate provided so as to seal the vibration space S of the resonator10, and the ground portion50which is an example of a first eutectic reaction layer positioned between the MEMS substrate40and the upper lid30, extended to an inside of the upper lid30, and electrically connected to the upper lid30. As a result, reduction in the contact resistance of the substrate can be achieved, and an excellent degree of vacuum can be obtained by suppressing the occurrence of outgassing.

In addition, in the above-described resonance device, the parasitic capacitance reducing film240, which is an example of an insulating layer, may be provided on substantially the entire surface of the resonator10of the upper lid30, and the ground portion50may be electrically connected to the upper lid30so as to ground the upper lid30and may be connected to the MEMS substrate40in an insulating manner with the parasitic capacitance reducing film240interposed therebetween. As a result, it is possible to ground the substrate and achieve reduction in the contact resistance in the substrate.

In addition, in the resonance device described above, the material of the upper lid30may be silicon. Thus, the contact resistance of the silicon substrate can be reduced.

In addition, in the above-described resonance device, the main component of the ground portion50may include aluminum and germanium. Thus, the contact resistance of the silicon substrate can be reduced more effectively by employing aluminum, which is a material suitable for reducing the ground/contact resistance with the silicon substrate.

In addition, in the above-described resonance device, the main component of the ground portion50may further include titanium, and the ground portion50may be an alloy layer containing a eutectic reaction product of the aluminum, the germanium, and the titanium. Thus, formation of an interface of different materials can be suppressed.

In addition, in the above-described resonance device, the ground portion50may be formed such that the concentration of aluminum on the upper lid30side is lower than the concentration of aluminum on the MEMS substrate40side, or the concentration of aluminum on the upper lid30substrate side is the same as the concentration of aluminum on the MEMS substrate40side. As such, the influence of thermal diffusion of aluminum on the substrate can be reduced.

In addition, the above-described resonance device may further include the bonding portion60that bonds the MEMS substrate40and the upper lid30and is an example of a second eutectic reaction layer, and the bonding portion60may be positioned on the outer peripheral side of the ground portion50and may be connected to each of the MEMS substrate40and the upper lid30in an insulating manner via the parasitic capacitance reducing film240and the silicon oxide film L31, respectively. Thus, the degree of vacuum can be improved.

In addition, in the above-described resonance device, the bonding portion60may have the same component as the ground portion50. Thus, by having the same components, manufacturing is simplified and productivity can be improved.

In addition, the degree of vacuum of the vibration space S may be 1 Pa to 2 Pa. Thus, a good degree of vacuum can be obtained.

A resonance device manufacturing method according to an embodiment of the present invention includes preparing the MEMS substrate40including the resonator10, and the upper lid30capable of sealing the vibration space S of the resonator10, forming the first metal layer81around the vibrating portion120of the resonator10in the MEMS substrate40, forming the second metal layer82having a component different from that of the first ground portion51at a position of the upper lid30facing the first ground portion51, and bonding the MEMS substrate40and the upper lid30together, in the bonding, the first ground portion51of the first metal layer81and the second ground portion52of the second metal layer82have the eutectic reaction to generate the ground portion50, and the ground portion50is extended to an inside of the upper lid30and is electrically connected to the upper lid30. As a result, the contact resistance of the substrate can be reduced, and an excellent degree of vacuum can be obtained by suppressing the occurrence of outgassing.

In addition, in the above-described resonance device manufacturing method, the ground portion50may be positioned between the MEMS substrate40and the upper lid30, a portion of the ground portion50on the upper lid30side may be extended to an inside of the upper lid30and electrically connected to the upper lid30so as to ground the upper lid30, and a portion of the ground portion50on the MEMS substrate40may be connected to the MEMS substrate40in an insulating manner via the parasitic capacitance reducing film240provided on the MEMS substrate40. As a result, it is possible to ground the substrate and achieve reduction in the contact resistance in the substrate.

In addition, in the above-described resonance device manufacturing method, the material of the upper lid30may be silicon, the first ground portion51may include at least an aluminum layer, and the second ground portion52may include at least a germanium layer. Thus, reduction in the contact resistance in the substrate can be achieved.

In addition, in the above-described resonance device manufacturing method, the thickness of the aluminum layer may be about 0.70 μm, and the thickness of the germanium layer may be about 0.38 μm. Thus, the eutectic reaction layer can be sufficiently generated.

In addition, in the above-described resonance device manufacturing method, the second ground portion52may further include a titanium layer, the titanium layer may be provided closer to the upper lid30side than the germanium layer, and the ground portion50may be an alloy layer containing a eutectic reaction product of the aluminum, the germanium, and the titanium. Thus, formation of an interface of different materials can be suppressed.

In addition, in the above-described resonance device manufacturing method, the thickness of the titanium layer may be about 0.10 μm. Thus, the property of close contact of the bonding can be improved.

In addition, the above-described resonance device manufacturing method may further include a first annealing treatment for degassing the first ground portion51of the MEMS substrate40and a second annealing treatment for degassing the second ground portion52of the upper lid30, and the first annealing treatment and the second annealing treatment may be performed before the bonding is performed. Thus, a good degree of vacuum can be obtained.

In addition, in the above-described resonance device manufacturing method, the annealing temperature of each of the first annealing treatment and the second annealing treatment may be about 450° C. Thus, the degree of vacuum can be improved by performing sufficient degassing.

In addition, in the above-described resonance device manufacturing method, the eutectic temperature for having the eutectic reaction in the bonding may be about 440° C. Thus, the eutectic reaction layer can be sufficiently generated.

In addition, in the above-described resonance device manufacturing method, when viewed in a plan view, the first metal layer81may include the first bonding portion61positioned around a vibrating portion of a first substrate and the first ground portion51positioned on an inner side of the first bonding portion without being in contact with the first bonding portion, when viewed in a plan view, the second metal layer82may include the second bonding portion62at a position facing the first bonding portion61and the second ground portion52at a position facing the first ground portion51when the MEMS substrate40and the upper lid30are made to face each other, and the bonding may include causing the first bonding portion61and the second bonding portion62to have a eutectic reaction and generating a bonding portion60and causing the first ground portion51and the second ground portion52to have a eutectic reaction and generating a ground portion50, in which the ground portion50may be a first eutectic reaction layer and the bonding portion60may be a second eutectic reaction layer having the same component as that of the first eutectic reaction layer. As a result, it is possible to ground the substrate and achieve reduction in the contact resistance in the substrate.

In addition, in the above-described resonance device manufacturing method, the bonding portion60may be positioned between the MEMS substrate40and the upper lid30, and may be connected to the MEMS substrate40and the upper lid30in an insulating manner without being extended to an inside of the MEMS substrate40and the upper lid30by the parasitic capacitance reducing film240and the silicon oxide film L31provided in the MEMS substrate40and the upper lid30, respectively. Thus, a good degree of vacuum can be obtained.

Note that the embodiments described above are intended to facilitate understanding of 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 the spirit thereof, and the present invention includes equivalents thereof. In other words, embodiments obtained by applying appropriate design changes to each embodiment by those skilled in the art are also included in the scope of the present invention as long as they have the features of the present invention. For example, each element included in the embodiment and the arrangement, material, condition, shape, size, and the like thereof are not limited to those exemplified, and can be appropriately changed. In addition, the embodiment is an example, and it is needless to say that partial replacement or combination of configurations illustrated in different embodiments is possible, and these are also included in the scope of the invention as long as they include the features of the invention.

REFERENCE SIGNS LIST

1RESONANCE DEVICE10RESONATOR20LOWER LID21RECESS22BOTTOM PLATE23SIDE WALL30UPPER LID31RECESS33SIDE WALL34GETTER LAYER40MEMS SUBSTRATE50GROUND PORTION60BONDING PORTION66FIRST CONDUCTIVE LAYER67SECOND CONDUCTIVE LAYER68FIRST CLOSE CONTACT LAYER69SECOND CLOSE CONTACT LAYER70CONNECTION WIRING76A,76B CONTACT ELECTRODE80EUTECTIC REACTION LAYER90SECOND LAYER110HOLDING ARM120VIBRATING PORTION130BASE PORTION131aLONG SIDE131A FRONT END131bLONG SIDE131B REAR END131cSHORT SIDE131dSHORT SIDE135,135A,135B,135C,135D VIBRATING ARM140HOLDING PORTION141VOLTAGE APPLICATION PORTION235PROTECTIVE FILM236FREQUENCY ADJUSTMENT FILM240PARASITIC CAPACITANCE REDUCING FILME1, E2METALLIC LAYERF2Si SUBSTRATEF3PIEZOELECTRIC THIN FILMF21SILICON OXIDE LAYERG WEIGHT PORTIONL1WAFERL3Si WAFERL31SILICON OXIDE FILMP VIRTUAL PLANET4TERMINALV1, V2VIAV3THROUGH-ELECTRODE