Resonance device and method for manufacturing same

Abstract

This resonance device (1) comprises: a resonator (10) comprising a vibration part (110) configured to be able to vibrate; a first substrate (30) comprising a first bottom plate part (32) provided to be spaced from the vibration part (110); and a second substrate (20) comprising a second bottom plate part (22) provided to be spaced from the vibration part (110) on the reverse side of the resonator (10) from the first substrate (30). The vibration part (110) has a piezoelectric layer (F3), a frequency adjustment film (125A-125D) for adjusting the frequency of the vibration part (110) by a mass addition effect, and a metal film (E1) comprising an excitation electrode for exciting the piezoelectric layer (F3) by applying voltage. The frequency adjustment film (125A-125D) is provided between the piezoelectric layer (F3) and the metal film (E1), the thickness of the frequency adjustment film (125A-125D) is larger than the thickness of the metal film (E1), and when viewed in plan view in a thickness direction in which the second substrate (20), the resonator (10), and the first substrate (30) overlap, the metal film (E1) overlaps at least an end portion of the frequency adjustment film (125A-125D).

Description

Resonant device and method of manufacturing the same

[0001] The present invention relates to a resonator device and a method for manufacturing the same.

[0002] Resonator devices are used for various purposes, such as timing devices, sensors, oscillators, etc., in various electronic devices, such as mobile communication terminals, communication base stations, and home appliances. One type of such resonator device is a so-called MEMS (Micro Electro Mechanical Systems) resonator, which includes a lower cover, an upper cover that forms a vibration space between the lower cover and the upper cover, and a resonator having a vibrating arm that is held so as to be vibrable in the vibration space.

[0003] For example, Patent Document 1 discloses a resonator device that includes a lower cover, an upper cover, and a resonator having a vibrating arm capable of flexural vibration, the vibrating arm having a tip end with a metal film on the side facing the upper cover, and a frequency adjustment film on the outermost surface of the tip end on the upper cover side.

[0004] International Publication No. 2023 / 112380

[0005] However, in the resonator device described in Patent Document 1, the thickness of the frequency adjustment film is greater than the thickness of the metal film etc. that constitutes the excitation electrode, and therefore the thermal stress of the frequency adjustment film is greater than that of the metal film etc. Therefore, when the frequency adjustment film is heated during the manufacturing process or the mounting process, the frequency adjustment film may peel off from the edge.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resonator device that can improve reliability, and a method for manufacturing the same.

[0007] A resonance device according to one embodiment of the present invention is a resonance device comprising a resonator having a vibration portion configured to be vibrable, a first substrate having a first bottom plate portion spaced apart from the vibration portion, and a second substrate having a second bottom plate portion spaced apart from the vibration portion on the opposite side of the resonator from the first substrate, wherein the vibration portion has a piezoelectric layer, a frequency adjustment film that adjusts the frequency of the vibration portion by the mass addition effect, and a metal film including an excitation electrode to which a voltage is applied to excite the piezoelectric layer, the frequency adjustment film being arranged between the piezoelectric layer and the metal film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps at least the end of the frequency adjustment film.

[0008] Another aspect of the present invention provides a method for manufacturing a resonator device comprising a resonator having a vibrating portion configured to be vibrable, a first substrate having a first bottom plate portion spaced apart from the vibrating portion, and a second substrate having a second bottom plate portion spaced apart from the vibrating portion on the opposite side of the resonator from the first substrate, the method including preparing the resonator, preparing the first substrate, preparing the second substrate, and sealing the resonator between the first substrate and the second substrate, wherein preparing the resonator includes providing a piezoelectric layer, providing a frequency adjustment film on one side of the piezoelectric layer, and providing a metal film including an excitation electrode on one side of the frequency adjustment film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps at least an end of the frequency adjustment film.

[0009] According to the present invention, it is possible to provide a resonator device and a method for manufacturing the same that can improve reliability.

[0010] 1 is a perspective view of a resonator device according to a first embodiment; 2 is an exploded perspective view of a resonator device according to a first embodiment; 3 is a plan view of the interior of a resonator device according to a first embodiment; 4 is a cross-sectional view of a resonator device according to a first embodiment; 5 is a flowchart showing a manufacturing method of a resonator device according to a first embodiment; 6 is a cross-sectional view of a resonator device according to a second embodiment; 7 is a cross-sectional view of a resonator device according to a third embodiment; 8 is a cross-sectional view of a resonator device according to a fourth embodiment; 9 is a cross-sectional view of a resonator device according to a fifth embodiment; 10 is a cross-sectional view of a resonator device according to a sixth embodiment;

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings of the present embodiment are merely examples, and the dimensions and shapes of each part are schematic, so the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0012] First Embodiment (Resonance Device 1) First, a schematic configuration of a resonance device 1 according to a first embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view of the resonance device 1 according to the first embodiment. Fig. 2 is an exploded perspective view of the resonance device 1 according to the first embodiment.

[0013] Each component of the resonance device 1 will be described below. For the sake of clarity and understanding of the positional relationships between the various components, each drawing may be accompanied by a Cartesian coordinate system consisting of an X-axis, a Y-axis, and a Z-axis. The directions parallel to the X-axis, the Y-axis, and the Z-axis are referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively. The plane defined by the X-axis and the Y-axis is referred to as the XY plane, and similarly for the YZ plane and the ZX plane.

[0014] The resonator device 1 includes a resonator 10, a lower cover 20, and an upper cover 30. The lower cover 20, the resonator 10, and the upper cover 30 are stacked in this order in the Z-axis direction. Hereinafter, the Z-axis direction in which the lower cover 20, the resonator 10, and the upper cover 30 are stacked will be referred to as the "thickness direction." The resonator 10 and the lower cover 20 are bonded together to form a MEMS substrate 50. The upper cover 30 is bonded to the resonator 10 of the MEMS substrate 50. In other words, the upper cover 30 is bonded to the lower cover 20 via the resonator 10. The lower cover 20 and the upper cover 30 face each other in the thickness direction, with the resonator 10 sandwiched between them. The lower cover 20 and the upper cover 30 form a package structure that forms a vibration space within which the resonator 10 vibrates, and the resonator 10 is sealed in the package structure. The upper cover 30 corresponds to an example of a first substrate, and the lower cover 20 corresponds to an example of a second substrate.

[0015] The resonator 10 is a MEMS vibration element manufactured using MEMS technology. The frequency band of the resonator 10 is, for example, 1 kHz to 1 MHz. The resonator 10 includes a vibration part 110, a holding part 140, and a support arm 150.

[0016] The vibrating section 110 is held so as to be vibrable in a vibration space provided between the lower cover 20 and the upper cover 30. The vibration mode of the vibrating section 110 is an out-of-plane bending vibration mode. The vibrating section 110 extends along the XY plane when in a non-vibrating state where no voltage is applied, and vibrates bending in the Z-axis direction when a voltage is applied and in a vibrating state.

[0017] The vibration mode of the vibrating part is not limited to the out-of-plane bending vibration mode. For example, the vibration mode of the vibrating part may be the in-plane bending vibration mode or the thickness-shear vibration mode. The vibrating part 110 in the non-vibrating state may bend in the Z direction due to its own weight.

[0018] For example, when the XY plane is viewed in a plan view in the Z-axis direction (hereinafter simply referred to as "plan view"), the holding unit 140 is provided in a frame shape so as to surround the vibrating unit 110. The holding unit 140, together with the lower cover 20 and the upper cover 30, forms a vibration space of the package structure.

[0019] The holding portion is not limited to a frame-like shape as long as it is provided around at least a part of the periphery of the vibrating portion.

[0020] In plan view, the support arm 150 is provided between the vibration section 110 and the holding section 140. The support arm 150 connects the vibration section 110 and the holding section 140.

[0021] The lower cover 20 has a bottom plate portion 22 and a side wall portion 23. The bottom plate portion 22 is provided with a gap between it and the vibration portion 110 in the thickness direction. The bottom plate portion 22 is a plate-like portion having a main surface extending along the XY plane. The side wall portion 23 extends from the peripheral edge of the bottom plate portion 22 toward the upper cover 30. The side wall portion 23 is a frame-like portion that surrounds the vibration portion 110 in a plan view. The side wall portion 23 is joined to the holding portion 140 of the resonator 10. A cavity 21 surrounded by the bottom plate portion 22 and the side wall portion 23 is formed on the side of the lower cover 20 facing the vibration portion 110 of the resonator 10. The cavity 21 is a rectangular parallelepiped opening that opens toward the vibration portion 110.

[0022] The top cover 30 has a bottom plate portion 32 and a side wall portion 33. The bottom plate portion 32 is spaced apart from the vibrating portion 110 in the thickness direction. The bottom plate portion 32 is a plate-like portion having a main surface extending along the XY plane. The side wall portion 33 extends from the peripheral edge of the bottom plate portion 32 toward the bottom cover 20. The side wall portion 33 is a frame-like portion that surrounds the vibrating portion 110 in a plan view. The side wall portion 33 is joined to the holding portion 140 of the resonator 10. A cavity 31 surrounded by the bottom plate portion 32 and the side wall portion 33 is formed on the side of the top cover 30 facing the vibrating portion 110 of the resonator 10. The cavity 31 is a rectangular parallelepiped opening that opens toward the vibrating portion 110. The cavity 21 and the cavity 31 face each other across the vibrating portion 110 and form a vibration space for the resonator 10.

[0023] The top surface of the top cover 30 is provided with two power supply terminals ST1 and ST2, a ground terminal GT, and a dummy terminal DT. Hereinafter, the power supply terminals ST1 and ST2, the ground terminal GT, and the dummy terminal DT are collectively referred to as "external terminals." The power supply terminals ST1 and ST2 are used to provide a drive signal (drive voltage) to the resonator 10. The power supply terminals ST1 and ST2 are electrically connected to a metal film E1 corresponding to the upper electrode of the resonator 10, which will be described later. The ground terminal GT is used to provide a reference potential to the resonator 10. The ground terminal GT is electrically connected to a silicon layer F2 corresponding to the lower electrode of the resonator 10, which will be described later. The dummy terminal DT is used to balance electrical characteristics such as capacitance and mechanical strength. The dummy terminal DT is not electrically connected to the resonator 10.

[0024] Next, referring to Fig. 3, the schematic configuration of the vibrating portion 110, the holding portion 140, and the support arm 150 of the resonator 10 when viewed in a plane will be described. Fig. 3 is a plan view of the interior of the resonator device 1 according to the first embodiment. Note that Fig. 3 shows the shape of the resonator 10 when viewed in a plane from the top cover 30 side. Hereinafter, the shape when viewed in a plane will be referred to as the "planar shape." The dimension along the Y-axis direction will be referred to as the "length," and the dimension along the X-axis direction will be referred to as the "width."

[0025] The resonator 10 is formed, for example, to be plane-symmetrical with respect to an imaginary plane P parallel to the YZ plane. That is, the planar shapes of the vibrating part 110, the holding part 140, and the support arm 150 are formed to be approximately plane-symmetrical with respect to the imaginary plane P.

[0026] 3, the vibration section 110 has an excitation section 120 consisting of four vibrating arms 121A, 121B, 121C, and 121D, and a base section 130 connected to the excitation section 120. In this embodiment, the excitation section 120 and the base section 130 are integrally formed. A space is formed at a predetermined interval between the vibration section 110 and the holding section 140.

[0027] The number of vibrating arms is not limited to four, but can be set to any number equal to or greater than one.

[0028] The vibrating arms 121A to 121D each extend in the Y-axis direction and are arranged in this order at a predetermined interval in the X-axis direction. The vibrating arms 121A to 121D have a fixed end connected to the base 130 and an open end that is the farthest from the base 130. The vibrating arms 121A to 121D each have a tip 122A to 122D provided on the open end side and an arm 123A to 123D provided on the fixed end side. The arm 123A to 123D connect the base 130 and the tip 122A to 122D. An imaginary plane P is located between the vibrating arm 121B and the vibrating arm 121C.

[0029] Of the four vibrating arms 121A to 121D, two vibrating arms 121A and 121D are outer vibrating arms arranged on the outside in the X-axis direction, and two vibrating arms 121B and 121C are inner vibrating arms arranged on the inside in the X-axis direction. With respect to the imaginary plane P, the inner vibrating arm 121B and the inner vibrating arm 121C have a symmetrical structure to each other, and the outer vibrating arm 121A and the outer vibrating arm 121D have a symmetrical structure to each other.

[0030] The tip portions 122A to 122D are provided with frequency adjustment films 125A to 125D, respectively. The frequency adjustment films 125A to 125D adjust the resonant frequency of the resonator 10 by a mass addition effect that makes the mass per unit length of each of the tip portions 122A to 122D (hereinafter simply referred to as "mass") greater than the mass of each of the arm portions 123A to 123D. Alternatively, portions of the frequency adjustment films 125A to 125D may be trimmed away to reduce the mass of the tip portions 122A to 122D, thereby adjusting the resonant frequency of the resonator 10. Furthermore, by making the mass of the tip portions 122A to 122D greater than the mass of the arm portions 123A to 123D, the vibration portion 110 can be made smaller while increasing the amplitude.

[0031] The width of tip portion 122A is greater than the width of arm portion 123A. The same is true for tip portions 122B to 122D and arm portions 123B to 123D. As a result, the mass of each of tip portions 122A to 122D is even greater than the mass of each of arm portions 123A to 123D.

[0032] The relationship between the width of the tip and the width of the arm is not limited to the above, and the width of the tip may be equal to or smaller than the width of the arm.

[0033] The planar shape of each of tip portions 122A to 122D is a substantially rectangular shape with rounded curves (for example, so-called R-shapes) at the four corners. The planar shape of each of arm portions 123A to 123D is a substantially rectangular shape with R-shapes near the base portion connected to base portion 130 and near the connection portion connected to each of tip portions 122A to 122D.

[0034] The planar shapes of the tip and arm portions are not limited to those described above. For example, the planar shape of the tip may be trapezoidal or L-shaped. The planar shape of the arm portions may also be trapezoidal, and slits, recesses, protrusions, etc. may be formed in the arm portions.

[0035] The planar shape and size of each of the resonating arms 121A to 121D are approximately the same. The length of each of the resonating arms 121A to 121D is, for example, approximately 450 μm. For example, the length of each of the arm portions 123A to 123D is approximately 300 μm, and the width of each is approximately 50 μm. For example, the length of each of the tip portions 122A to 122D is approximately 150 μm, and the width of each is approximately 70 μm.

[0036] The base 130 has a front end 131A, a rear end 131B, a left end 131C, and a right end 131D. The front end 131A, the rear end 131B, the left end 131C, and the right end 131D are each part of the outer edge of the base 130. The front end 131A is an end that extends in the X-axis direction on the side of the vibrating arms 121A to 121D. The rear end 131B is an end that extends in the X-axis direction on the opposite side of the vibrating arms 121A to 121D. The left end 131C is an end that extends in the Y-axis direction on the side of the vibrating arm 121A when viewed from the vibrating arm 121D. The right end 131D is an end that extends in the Y-axis direction on the side of the vibrating arm 121D when viewed from the vibrating arm 121A. The vibrating arms 121A to 121D are connected to the front end 131A.

[0037] The planar shape of the base 130 is a substantially rectangular shape with the front end 131A and rear end 131B as long sides and the left end 131C and right end 131D as short sides. An imaginary plane P is defined along the perpendicular bisector of each of the front end 131A and rear end 131B. The base 130 is not limited to the above as long as it has a structure that is substantially symmetrical with respect to the imaginary plane P. For example, the base 130 may be trapezoidal in which one of the front end 131A and rear end 131B is longer than the other. Furthermore, at least one of the front end 131A, rear end 131B, left end 131C, and right end 131D may be bent or curved.

[0038] The base length, which is the maximum distance in the Y-axis direction between the front end 131A and the rear end 131B, is, for example, approximately 35 μm. The base width, which is the maximum distance in the X-axis direction between the left end 131C and the right end 131D, is, for example, approximately 265 μm. In the example shown in FIG. 3 , the base length corresponds to the dimension of the left end 131C along the Y-axis direction or the dimension of the right end 131D along the Y-axis direction, and the base width corresponds to the dimension of the front end 131A along the X-axis direction or the dimension of the rear end 131B along the X-axis direction.

[0039] As shown in FIG. 3 , the holding unit 140 has a front frame 141A, a rear frame 141B, a left frame 141C, and a right frame 141D. The front frame 141A, the rear frame 141B, the left frame 141C, and the right frame 141D are each part of a substantially rectangular frame that surrounds the vibration unit 110. Specifically, the front frame 141A is a portion that extends in the X-axis direction on the positive Y-axis side of the vibration unit 110. The rear frame 141B is a portion that extends in the X-axis direction on the negative Y-axis side of the vibration unit 110. The left frame 141C is a portion that extends in the Y-axis direction on the negative X-axis side of the vibration unit 110. The right frame 141D is a portion that extends in the Y-axis direction on the positive X-axis side of the vibration unit 110. The front frame 141A and the rear frame 141B are each bisected by an imaginary plane P.

[0040] The end of the front frame 141A on the negative X-axis side is connected to the end of the left frame 141C on the positive Y-axis side. The end of the front frame 141A on the positive X-axis side is connected to the end of the right frame 141D on the positive Y-axis side. The end of the rear frame 141B on the negative X-axis side is connected to the end of the left frame 141C on the negative Y-axis side. The end of the rear frame 141B on the positive X-axis side is connected to the end of the right frame 141D on the negative Y-axis side.

[0041] The support arm 150 is provided inside the holding portion 140 and connects the base portion 130 and the holding portion 140. In the example shown in Fig. 3, the support arm 150 has a left support arm 151A and a right support arm 151B. An imaginary plane P is located between the right support arm 151B and the left support arm 151A, and the right support arm 151B and the left support arm 151A are plane-symmetrical to each other.

[0042] The left support arm 151A connects the rear end portion 131B of the base 130 to the left frame 141C of the holding portion 140. The right support arm 151B connects the rear end portion 131B of the base 130 to the right frame 141D of the holding portion 140. The left support arm 151A has a rear support arm 152A and a side support arm 153A, and the right support arm 151B has a rear support arm 152B and a side support arm 153B.

[0043] The rear support arms 152A and 152B extend from the rear end 131B of the base 130 between the rear end 131B of the base 130 and the holding portion 140. Specifically, the rear support arm 152A extends from the rear end 131B of the base 130 toward the rear frame 141B, then bends and extends toward the left frame 141C. The rear support arm 152B extends from the rear end 131B of the base 130 toward the rear frame 141B, then bends and extends toward the right frame 141D. The width of each of the rear support arms 152A and 152B is smaller than the width of each of the vibrating arms 121A to 121D.

[0044] The support side arm 153A extends along the Y-axis direction between the outer vibrating arm 121A and the holding portion 140. The support side arm 153B extends along the Y-axis direction between the outer vibrating arm 121D and the holding portion 140. Specifically, the support side arm 153A extends from the end of the rear support arm 152A on the left frame 141C side toward the front frame 141A, bends, and is connected to the left frame 141C. The support side arm 153B extends from the end of the rear support arm 152B on the right frame 141D side toward the front frame 141A, bends, and is connected to the right frame 141D. The widths of the support side arms 153A and 153B are approximately equal to the widths of the rear support arms 152A and 152B.

[0045] The support arm 150 is not limited to the above configuration. For example, the support arm 150 may be connected to the left end 131C and the right end 131D of the base 130. The support arm 150 may also be connected to the front frame 141A or the rear frame 141B of the holding part 140. The number of support arms 150 may be one, or three or more.

[0046] Next, the cross-sectional structure of the resonator device 1 according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view of the resonator device 1 according to the first embodiment. Fig. 4 is a diagram for conceptually explaining the layered structure of the resonator device 1, and the components shown in Fig. 4 are not necessarily located on the same cross section plane. For convenience, the direction from the lower cover 20 to the upper cover 30 will be referred to as "up (upward)" and the direction from the upper cover 30 to the lower cover 20 will be referred to as "down (downward)."

[0047] The resonator 10 is held between the bottom cover 20 and the top cover 30. Specifically, the holding portion 140 of the resonator 10 is joined to each of the side wall portion 23 of the bottom cover 20 and the side wall portion 33 of the top cover 30. In this way, the bottom cover 20, the top cover 30, and the holding portion 140 form a vibration space in which the vibration portion 110 can vibrate, and the vibration portion 110 is sealed in this vibration space. The bottom cover 20 and the top cover 30 include, for example, a silicon substrate, but may also include a compound semiconductor substrate, a glass substrate, a ceramic substrate, a resin substrate, or a substrate made of a combination of these, as long as the substrate can be processed using microfabrication technology.

[0048] As shown in FIG. 4 , the resonator 10 includes a silicon oxide film F21, a silicon layer F2, a piezoelectric layer F3, a metal film E1, and a protective film F5. The resonator 10 also includes frequency adjustment films 125A-125D at the tip portions 122A-122D. The vibrating portion 110, the holding portion 140, and the support arms 150 are integrally formed by the same process. Specifically, the vibrating portion 110, the holding portion 140, and the support arms 150 are formed by patterning a laminate including the silicon layer F2, the piezoelectric layer F3, the frequency adjustment films 125A-125D, the metal film E1, and the protective film F5, using a removal process. This removal process is performed by dry etching, for example. This removal process may also be performed by other methods, such as wet etching and laser etching.

[0049] The silicon oxide film F21 is provided on the side of the silicon layer F2 facing the lower cover 20, and is sandwiched between the silicon layer F2 and a silicon substrate P10 (described later). ２ The silicon oxide film F21 is formed of silicon oxide containing the above-mentioned. A portion of the silicon oxide film F21 is exposed to the cavity 21 of the bottom cover 20. The silicon oxide film F21 functions as a temperature characteristic correction layer that reduces the temperature coefficient of the resonant frequency of the resonator 10, i.e., the rate of change of the resonant frequency per unit temperature, at least at around room temperature. As a result, the silicon oxide film F21 improves the temperature characteristic of the resonator 10. When the resonator 10 and the bottom cover 20 are considered as a MEMS substrate 50, the silicon oxide film F21 of the resonator 10 corresponds to a buried oxide (BOX) layer of an SOI (silicon on insulator) substrate.

[0050] The silicon oxide film may be formed on the side of the silicon layer F2 facing the upper lid 30, or may be formed on both the side of the silicon layer F2 facing the lower lid 20 and the side facing the upper lid 30.

[0051] When the resonator 10 and the bottom cover 20 are considered as the MEMS substrate 50, the resonator 10 is formed of single crystal silicon. The silicon layer F2 is formed of, for example, a degenerate n-type silicon (Si) semiconductor with a thickness of approximately 6 μm. The n-type semiconductor silicon layer F2 contains an n-type dopant, such as phosphorus (P), arsenic (As), or antimony (Sb). The resistance value of the degenerate silicon (Si) used in the silicon layer F2 is, for example, less than 16 mΩ·cm, and more preferably 1.2 mΩ·cm or less. When the resonator 10 and the bottom cover 20 are considered as the MEMS substrate 50, the silicon layer F2 of the resonator 10 corresponds to the active layer (device layer) of the SOI substrate.

[0052] The silicon layer F2 functions as an excitation electrode that applies an alternating voltage to the piezoelectric layer F3. The silicon layer F2 is electrically connected to a ground terminal GT, which will be described later. The silicon layer F2 corresponds to an example of a lower electrode.

[0053] The silicon layer is not limited to one that functions as an excitation electrode, and a lower electrode may be further provided between the silicon layer and the piezoelectric layer.

[0054] The piezoelectric layer F3 is a thin film formed of a piezoelectric material that converts electrical energy into mechanical energy and vice versa. The piezoelectric layer F3 is, for example, stacked directly on the silicon layer F2. The piezoelectric material that constitutes the piezoelectric layer F3 is, for example, aluminum nitride (AlN). The thickness of the piezoelectric layer F3 is, for example, about 1 μm, but may be about 0.2 μm to 2 μm.

[0055] The piezoelectric layer F3 expands and contracts in the Y-axis direction in response to the electric field applied between the silicon layer F2 and the metal film E1. This expansion and contraction of the piezoelectric layer F3 bends the vibrating arms 121A to 121D, displacing their open ends toward the bottom plate portion 22 of the lower lid 20 and the bottom plate portion 32 of the upper lid 30. Alternating voltages of opposite phases are applied to the upper electrodes of the outer vibrating arms 121A and 121D and the upper electrodes of the inner vibrating arms 121B and 121C. Therefore, the outer vibrating arms 121A and 121D and the inner vibrating arms 121B and 121C vibrate in opposite phases. For example, when the open ends of the outer vibrating arms 121A and 121D displace toward the lower lid 20, the open ends of the inner vibrating arms 121B and 121C displace toward the upper lid 30. Such antiphase vibration generates a torsional moment around the rotation axis extending in the Y-axis direction in the vibrating part 110. The base part 130 is bent by this torsional moment, and the left end part 131C and the right end part 131D are displaced toward the lower cover 20 or the upper cover 30. In other words, the vibrating part 110 of the resonator 10 vibrates in an out-of-plane bending vibration mode.

[0056] The piezoelectric layer is not limited to being directly laminated on the silicon layer, as long as it is provided on the side of the silicon layer facing the upper lid. An insulating film, a metal film, or the like may be provided between the piezoelectric layer and the silicon layer.

[0057] Furthermore, the piezoelectric material constituting the piezoelectric layer is not limited to aluminum nitride, and may be, for example, a piezoelectric material having a wurtzite hexagonal crystal structure other than aluminum nitride. Examples of such wurtzite hexagonal crystal structure piezoelectric materials include nitrides or oxides such as scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), and indium nitride (InN). Scandium aluminum nitride is aluminum nitride in which part of the aluminum has been substituted with scandium. Similarly, examples of aluminum nitride in which part of the aluminum has been substituted with another element include a piezoelectric material in which the aluminum has been substituted with two elements, magnesium (Mg) and niobium (Nb), or magnesium (Mg) and zirconium (Zr).

[0058] The frequency adjustment films 125A-125D are laminated directly on the piezoelectric layer F3 at the tip portions 122A-122D. The thickness of the frequency adjustment films 125A-125D is greater than the thickness of the metal film E1. From the viewpoint of improving the efficiency of adjusting the resonant frequency when the frequency adjustment films 125A-125D are removed by trimming, it is desirable that the frequency adjustment films 125A-125D be formed from a material whose mass reduction rate due to etching is faster than that of the protective film F5. The mass reduction rate is expressed as the product of the etching rate and the density. The etching rate is the thickness removed per unit time. The etching rates of the protective film F5 and the frequency adjustment films 125A-125D can have any relationship as long as the relationship in mass reduction rate is as described above. Furthermore, from the viewpoint of efficiently adding mass to the tip portions 122A-122D, it is desirable that the frequency adjustment films 125A-125D be formed from a material with a high specific gravity. From the above two viewpoints, the frequency adjustment films 125A to 125D are made of, for example, titanium tungsten (TiW).

[0059] The frequency adjustment film is not limited to being laminated directly on the piezoelectric layer, as long as it is provided on the side facing the upper cover of the piezoelectric layer. An insulating film, a metal film, or the like may be provided between the frequency adjustment film and the piezoelectric layer.

[0060] Furthermore, the material of the frequency adjustment film is not limited to titanium tungsten, but may be, for example, molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), or an alloy containing these metals.

[0061] The metal film E1 is laminated directly on the frequency adjustment film 125A at the tip portion 122A, and directly on the piezoelectric layer F3 at the arm portions 123A. The metal film E1 at the tip portion 122A and the metal film E1 at the arm portions 123A are electrically isolated from each other. The metal film E1 at the tip portion 122A, for example, covers the entire frequency adjustment film 125A. By covering the frequency adjustment film 125A with the metal film E1, peeling of the frequency adjustment film 125A due to thermal stress is suppressed. The metal film E1 at the arm portions 123A functions as an excitation electrode that applies an AC voltage to the piezoelectric layer F3. The same applies to the metal films E1 at the tip portions 122B to 122D and the arm portions 123B to 123D. The metal film E1 of the arm portion 123A and the metal film E1 of the arm portion 123D are electrically connected to one of the two power supply terminals ST1 and ST2, and the metal film E1 of the arm portion 123B and the metal film E1 of the arm portion 123C are electrically connected to the other of the two power supply terminals ST1 and ST2. The metal film E1 corresponds to an example of an upper electrode.

[0062] The thickness of the metal film E1 is, for example, approximately 0.1 μm or more and 0.2 μm or less. The metal film E1 is made of, for example, titanium tungsten (TiW), similar to the frequency adjustment films 125A to 125D. By using a common material for the metal film E1 and the frequency adjustment films 125A to 125D, it is possible to share the same manufacturing equipment for the metal film E1 and the frequency adjustment films 125A to 125D, thereby enabling the overall manufacturing equipment for the resonator device 1 to be made smaller and at lower cost.

[0063] The metal film at the tip of the vibrating arm is not limited to being directly laminated on the frequency adjustment film, as long as it is provided on the side facing the upper cover of the frequency adjustment film. In other words, it is sufficient that the frequency adjustment film is provided between the piezoelectric layer and the metal film. An insulating film or the like may be provided between the metal film at the tip of the vibrating arm and the frequency adjustment film. Even in this embodiment, peeling of the frequency adjustment film due to thermal stress is suppressed by the metal film. However, from the viewpoint of improving the adhesion between the frequency adjustment film and the layer laminated thereon and further suppressing peeling of the frequency adjustment film, it is preferable that the metal film be laminated directly on the frequency adjustment film rather than indirectly on the frequency adjustment film via another layer. Furthermore, an insulating film or the like may be provided between the metal film at the arm portion of the vibrating arm and the piezoelectric layer.

[0064] Furthermore, the metal film at the tip of the vibrating arm is not limited to overlapping the entire frequency adjustment film, but only needs to overlap at least the end of the frequency adjustment film in a planar view. By covering the end, which is the starting point for peeling due to thermal stress of the frequency adjustment film, peeling of the frequency adjustment film is effectively suppressed. From the viewpoint of effectively suppressing peeling of the frequency adjustment film from all directions in the XY plane direction, it is desirable that the metal film overlap the entire periphery of the end of the frequency adjustment film. Furthermore, from the viewpoint of effectively suppressing peeling of the frequency adjustment film, it is even more desirable that the metal film overlap the entire surface of the frequency adjustment film.

[0065] Furthermore, the material of the metal film is not limited to titanium tungsten, but may be, for example, molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), or an alloy containing these metals.

[0066] The protective film F5 is laminated on the metal film E1. The protective film F5 covers the portion of the metal film E1 that functions as the excitation electrode. This prevents oxidation of the excitation electrode and reduces fluctuations in the resonant frequency. In plan view, the protective film F5 overlaps the end of the frequency adjustment film 125A. Covering the end, which is the starting point for peeling of the frequency adjustment film 125A due to thermal stress, further prevents peeling of the frequency adjustment film 125A. In plan view, the protective film F5 may be provided to avoid the center of the frequency adjustment film 125A. Compared to a configuration in which a protective film is also provided in the center of the frequency adjustment film, the ratio of the mass of the frequency adjustment film 125A to the total mass of the tip portion 122A is larger, and therefore the mass of the frequency adjustment film 125A has a greater effect on the resonant frequency. This improves the efficiency of resonant frequency adjustment by the frequency adjustment film 125A. The protective film F5 is provided for the frequency adjustment films 125B to 125D in the same manner as for the frequency adjustment film 125A.

[0067] The protective film F5 is made of, for example, aluminum nitride (AlN), the same as the piezoelectric layer F3. By using the same material for the protective film F5 and the piezoelectric layer F3, it is possible to share the same manufacturing equipment for the protective film F5 and the piezoelectric layer F3, thereby reducing the size and cost of the entire manufacturing equipment for the resonator device 1.

[0068] The protective film is not limited to the above arrangement as long as it covers the portion of the metal film that functions as the excitation electrode. When viewed from above, the protective film may be provided so as to avoid the frequency adjustment film, or may overlap the entire frequency adjustment film.

[0069] Furthermore, the material of the protective film F5 is not limited to the above, and may be, for example, an oxide, nitride, or oxynitride containing aluminum (Al), silicon (Si), or tantalum (Ta). A parasitic capacitance reducing film that reduces the parasitic capacitance formed between the internal wirings of the resonator may be laminated on the protective film.

[0070] Lead wiring C1 and C2 are formed on the protective film F5 of the holding portion 140. The lead wiring C1 is electrically connected to the silicon layer F2 through a through hole formed in the piezoelectric layer F3 and the protective film F5. The lead wiring C2 is electrically connected to the metal film E1 of the outer vibrating arms 121A and 121D through a through hole formed in the protective film F5. Although not shown in the figure, lead wiring electrically connected to the metal film E1 of the inner vibrating arms 121B and 121C is also formed on the protective film F5. The lead wiring C1 and C2 are multilayer films in which, for example, aluminum (Al), titanium (Ti), and aluminum (Al) are stacked in this order.

[0071] The material of the lead-out wiring is not limited to the above, and may be, for example, titanium tungsten (TiW), similar to the frequency adjustment film and metal film. This allows the manufacturing equipment for the lead-out wiring, metal film, and frequency adjustment film to be shared, thereby reducing the size and cost of the entire manufacturing equipment for the resonator device. The material of the lead-out wiring may include silicon (Si), germanium (Ge), gold (Au), silver (Ag), copper (Cu), tin (Sn), zinc (Zn), indium (In), lead (Pb), or an alloy thereof.

[0072] The bottom plate portion 22 and sidewall portion 23 of the lower cover 20 are integrally formed from a silicon substrate P10. The silicon substrate P10 is formed from a non-degenerate silicon semiconductor and has a resistivity of, for example, 10 Ω·cm or more. The silicon substrate P10 is doped with, for example, an n-type dopant. The thickness of the lower cover 20 is greater than the thickness of the silicon layer F2 and is, for example, approximately 150 μm. If the resonator 10 and the lower cover 20 are considered as a MEMS substrate 50, for example, the silicon substrate P10 of the lower cover 20 corresponds to the support substrate (handle layer) of the SOI substrate.

[0073] The bottom plate portion 32 of the top lid 30 is formed of a glass substrate Q15, and the side wall portion 33 of the top lid 30 is formed of a silicon substrate Q10 and a glass substrate Q15. The silicon substrate Q10 is formed of a non-degenerate silicon semiconductor, and its resistivity is, for example, 10 Ω·cm or more. The silicon substrate Q10 is doped with, for example, an n-type dopant. The glass substrate Q15 is formed of a silicon oxide (for example, SiO ２ The glass substrate Q15 is formed of inorganic glass containing SiO as a main component. Here, the main component of the glass refers to a component that accounts for 50% by mass or more of all the components that make up the glass. As an example, the glass substrate Q15 is formed of inorganic glass containing SiO ２ The upper cover 30 is made of silicate glass containing silicon dioxide as a main component. The portion surrounding the through electrodes V1 and V2 (described later) and the portion in contact with the external terminals are made of a glass substrate Q15. A plurality of internal terminals are provided on the underside of the side wall portion 33, and the portions of the silicon substrate Q10 in contact with the respective internal terminals are electrically isolated from each other by the glass substrate Q15. The thickness of the upper cover 30 is, for example, about 150 μm.

[0074] The top cover 30 includes a metal film 70, through electrodes V1 and V2, a ground terminal GT, and a power supply terminal ST2.

[0075] The metal film 70 is provided on the side of the bottom plate portion 32 of the top lid 30 facing the vibration portion 110. The metal film 70 is a getter that absorbs gases in the vibration space formed by the cavity 21 of the bottom lid 20 and the cavity 31 of the top lid 30 to improve the degree of vacuum, such as hydrogen gas and outgassing. The metal film 70 contains, for example, titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), tantalum (Ta), or an alloy containing at least one of these. The metal film 70 may also contain an oxide of an alkali metal or an oxide of an alkaline earth metal. A layer (not shown), such as a layer that improves adhesion between the glass substrate Q15 and the metal film 70, may be provided between the silicon substrate Q10 and the metal film 70.

[0076] The metal film 70 is provided in the thickness direction so as to avoid the areas facing the tip portions 122A to 122D. That is, in the areas of the bottom plate portion 32 of the top lid 30 facing the tip portions 122A to 122D, the lower surface is provided by the glass substrate Q15.

[0077] The through electrodes V1 and V2 are provided on the side wall portion 33 of the top cover 30. The through electrodes V1 and V2 are provided by a silicon substrate Q10. The through electrodes V1 and V2 are surrounded by a glass substrate Q15 and are insulated from each other. The through electrodes V1 and V2 may be provided by polycrystalline silicon (Poly-Si), copper (Cu), gold (Au), or the like, filled in through holes that pass through the side wall portion 33 in the Z-axis direction.

[0078] The ground terminal GT and the power terminal ST2 are provided on the upper surface of the side wall portion 33 of the top cover 30. The ground terminal GT and the power terminal ST2 are electrically insulated from each other by the glass substrate Q15. The ground terminal GT is electrically connected to the lead-out wiring C1 via a through electrode V1. The power terminal ST2 is electrically connected to the lead-out wiring C2 via a through electrode V2. The ground terminal GT and the power terminal ST2 are formed by plating a metallized layer (base layer) of, for example, chromium (Cr), tungsten (W), nickel (Ni), or the like with nickel (Ni), gold (Au), silver (Ag), copper (Cu), or the like.

[0079] Although not shown, the side wall portion 33 of the upper cover 30 is further provided with a through electrode that electrically connects the metal film E1 of the inner vibrating arms 121B and 121C to the power supply terminal ST1.

[0080] A joint H is provided between the side wall portion 33 of the top cover 30 and the holding portion 140 of the resonator 10. In plan view, the joint H is provided in the shape of a continuous frame in the circumferential direction so as to surround the vibrating portion 110, and hermetically seals the vibration space formed by the cavities 21 and 31 in a vacuum state. The joint H is an alloy formed by, for example, forming a first multilayer metal film on the resonator 10 by laminating an aluminum (Al) film, a titanium (Ti) film, and an aluminum (Al) film in this order, forming a second multilayer metal film on the top cover 30 by laminating a titanium (Ti) film and a germanium (Ge) film in this order, and then subjecting the first and second multilayer metal films to a eutectic reaction. The joint H may include gold (Au), tin (Sn), copper (Cu), titanium (Ti), aluminum (Al), germanium (Ge), silicon (Si), or an alloy containing at least one of these. Furthermore, in order to improve the adhesion between the resonator 10 and the top cover 30, the joint H may contain a metal compound such as titanium nitride (TiN) or tantalum nitride (TaN).

[0081] The material of the bonding portion is not limited to the above metals, and may be selected appropriately depending on the required sealing performance. For example, the bonding portion may be formed using an organic polymer adhesive or an inorganic glass adhesive.

[0082] (Method of Manufacturing Resonator Device 1) Next, a method of manufacturing the resonator device 1 according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the method of manufacturing the resonator device 1 according to the first embodiment.

[0083] First, the first substrate (upper cover 30) and the second substrate (lower cover 20) are prepared (S10).

[0084] Next, the resonator 10 is prepared.

[0085] Specifically, first, a silicon layer F2 is provided (S20). A silicon plate is cut out from a silicon block. The silicon plate is doped with an n-type dopant and activated to provide the silicon layer F2. One side of the silicon layer F2 is thermally oxidized to provide a silicon oxide film F21. Alternatively, the silicon block may be activated by doping before being cut out into a silicon plate.

[0086] Next, a piezoelectric layer F3 is provided (S30). An aluminum nitride (AlN) film is formed by sputtering on the side of the silicon layer F2 opposite to the side on which the silicon oxide film F21 is provided. The aluminum nitride is patterned by wet etching to provide the piezoelectric layer F3 made of the aluminum nitride.

[0087] Next, frequency adjustment films 125A to 125D are provided (S40). Titanium tungsten (TiW) is formed on the piezoelectric layer F3 by sputtering. The titanium tungsten is patterned by wet etching to provide frequency adjustment films 125A to 125D made of titanium tungsten.

[0088] Next, a metal film E1 is provided (S50). Titanium tungsten is formed by sputtering on the piezoelectric layer F3 and the frequency adjustment films 125A to 125D. The titanium tungsten is patterned by wet etching into portions that will become excitation electrodes and portions that cover the frequency adjustment films 125A to 125D. At this time, the portions that will become excitation electrodes are separated from the portions that cover the frequency adjustment films 125A to 125D.

[0089] Next, a protective film F5 is provided (S60). Aluminum nitride is deposited by sputtering on the piezoelectric layer F3, the frequency adjustment films 125A-125D, and the metal film E1. The aluminum nitride is patterned by wet etching to provide a protective film F5 made of aluminum nitride. Because the protective film F5 and the piezoelectric layer F3 are made of the same material, the patterning of the protective film F5 and the piezoelectric layer F3 may be performed simultaneously in this process. In this case, the number of aluminum nitride patterning steps can be reduced from two to one, thereby reducing manufacturing costs.

[0090] In this way, because the frequency adjustment films 125A-125D, the metal film E1, and the protective film F5 are provided in this order, each film can be patterned by wet etching, which is less expensive than dry etching. More specifically, providing the protective film F5 on a step may cause cracks in the protective film F5. In particular, when the protective film F5 is provided using aluminum nitride, the aluminum nitride grows columnarly, making it prone to cracks in the protective film F5 at the step. If the protective film were patterned between the patterning of the frequency adjustment film and the patterning of the metal film, wet etching of the metal above the protective film would result in the etching solution penetrating through the cracks in the protective film and etching the metal below the protective film. This posed a problem: the metal above the protective film could not be patterned by wet etching. However, in this embodiment, the frequency adjustment film and the metal film are patterned before the protective film is patterned. Therefore, even if each film is patterned by wet etching, undesired etching due to the penetration of the etching solution does not occur. This allows patterning by inexpensive wet etching.

[0091] Next, the resonant frequency is adjusted by a trimming process (S70). While monitoring the resonant frequency of the resonator 10, the tip portions 122A to 122D are trimmed by ion milling. Because the resonant frequency of the resonator 10 changes depending on the change in mass of the vibrating arms 121A to 121D, the trimming process is terminated when the appropriate resonant frequency is reached. At this time, the metal film E1 covering the frequency adjustment films 125A to 125D is trimmed, but the frequency adjustment films 125A to 125D may also be trimmed.

[0092] Next, the resonator 10 is sealed (S80). The silicon oxide film F21 of the resonator 10 and the silicon substrate P10 of the bottom cover 20 are hydrophilically bonded. Specifically, the silicon oxide film F21 is activated by atmospheric pressure plasma, hydrophilized by wet processing, temporarily bonded to the silicon substrate P10, and then heated (post-annealing) to form Si-O-Si bonds. In this manner, the resonator 10 and the bottom cover 20 are directly bonded without using organic adhesives, metal solder, or the like. The resonator 10 and the top cover 30 are also eutectic-bonded by the bonding portion H. Specifically, a first multilayer metal film is formed by laminating aluminum, titanium, and aluminum in this order on the resonator 10, and a second multilayer metal film is formed by laminating titanium and germanium in this order on the top cover 30, and the first and second multilayer metal films are each patterned. The first and second multilayer metal films are sandwiched between the resonator 10 and the top cover 30 and heated to a temperature equal to or higher than the eutectic point to cause a eutectic reaction between the first and second multilayer metal films, thereby forming a joint H made of a eutectic alloy of aluminum, titanium, and germanium. The cavities 21 and 31 are hermetically sealed by direct bonding and eutectic bonding.

[0093] In this embodiment, the piezoelectric layer F3, the frequency adjustment films 125A-125D, the metal film E1, and the protective film F5 are formed by sputtering, but this is not a limitation. The film formation method can be selected appropriately from chemical vapor deposition (CVD) and physical vapor deposition (PVD). In this embodiment, the piezoelectric layer F3, the frequency adjustment films 125A-125D, the metal film E1, and the protective film F5 are patterned by wet etching, but this is not a limitation and they may also be patterned by dry etching.

[0094] As described above, the resonator 10 of the resonance device 1 has a piezoelectric layer F3, a metal film E1 including an excitation electrode, and frequency adjustment films 125A to 125D that are thicker than the metal film E1. The frequency adjustment films 125A to 125D are provided between the piezoelectric layer F3 and the metal film E1. In addition, when viewed in a plan view, the metal film E1 overlaps at least the ends of the frequency adjustment films 125A to 125D.

[0095] This effectively prevents peeling of the frequency adjustment films 125A to 125D by covering the ends that are the starting points for peeling due to thermal stress of the frequency adjustment films 125A to 125D, thereby preventing peeling of the frequency adjustment films 125A to 125D due to heat from soldering the resonator device 1, and improving the reliability of the resonator device 1.

[0096] In this embodiment, the metal film E1 overlaps the entire periphery of the end portions of the frequency adjustment films 125A to 125D.

[0097] This effectively prevents the frequency adjustment films 125A to 125D from peeling off in all directions.

[0098] In this embodiment, the metal film E1 overlaps the entire surfaces of the frequency adjustment films 125A to 125D.

[0099] This effectively prevents the frequency adjustment films 125A to 125D from peeling off.

[0100] In this embodiment, the material of the frequency adjustment films 125A to 125D is the same type of metal as that of the metal film E1.

[0101] This allows the manufacturing equipment for the metal film E1 and the frequency adjustment films 125A to 125D to be shared, and the manufacturing equipment for the entire resonator device 1 can be made smaller and less expensive.

[0102] In this embodiment, the resonator 10 further includes a protective film F5 that covers at least the portion of the metal film E1 that functions as an excitation electrode.

[0103] This makes it possible to suppress mass fluctuations due to oxidation of the excitation electrodes and reduce fluctuations in the resonant frequency.

[0104] In this embodiment, the protective film F5 overlaps at least the ends of the frequency adjustment films 125A to 125D.

[0105] This covers the end portions of the frequency adjustment films 125A to 125D, which are the starting points for peeling due to thermal stress, thereby more effectively suppressing peeling of the frequency adjustment films 125A to 125D.

[0106] In this embodiment, the material of the protective film F5 is the same as the material of the piezoelectric layer F3.

[0107] This allows the protective film F5 and the piezoelectric layer F3 to be manufactured using the same equipment, thereby reducing the size and cost of the entire manufacturing equipment for the resonator device 1.

[0108] Furthermore, in the manufacturing method of the resonator device 1 according to this embodiment, preparing the resonator 10 includes providing a piezoelectric layer F3, then providing frequency adjustment films 125A to 125D, and then providing a metal film E1.

[0109] This effectively prevents peeling of the frequency adjustment films 125A to 125D by covering the ends that are the starting points for peeling due to thermal stress of the frequency adjustment films 125A to 125D, thereby preventing peeling of the frequency adjustment films 125A to 125D due to heat from soldering the resonator device 1, and improving the reliability of the resonator device 1.

[0110] Moreover, preparing the resonator 10 further includes providing a protective film F5 after providing the metal film E1.

[0111] This allows the frequency adjustment films 125A to 125D, the metal film E1, and the protective film F5 to be patterned by wet etching.

[0112] Other embodiments will be described below. Note that components that are the same as or similar to those in the first embodiment are denoted by the same or similar reference numerals, and descriptions thereof will be omitted as appropriate. Furthermore, similar effects resulting from similar components will not be mentioned one after another.

[0113] Second Embodiment Next, the structure of a resonator device 2 according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view of the resonator device 2 according to the second embodiment.

[0114] In a plan view, the metal film E2 provided on the tip 222A of the vibrating arm 221A covers only the ends of the frequency adjustment film 225A and is provided so as to avoid the center of the frequency adjustment film 225A. As a result, the frequency adjustment film 225A is exposed to the glass substrate Q15 of the upper cover 30. The thickness of the center of the frequency adjustment film 225A is smaller than the thickness of the ends of the frequency adjustment film 225A.

[0115] The center of the frequency adjustment film 125A is recessed by a frequency adjustment process performed before or after sealing the resonator 210. In this post-sealing frequency adjustment process, the metal film E2 and the frequency adjustment film 225A are trimmed by laser ablation to reduce the mass of the tip 222A, thereby adjusting the resonant frequency of the resonator 210. When frequency adjustment by laser ablation is performed after sealing, a laser is irradiated from outside the resonator device 2 through the glass substrate Q15 of the top cover 30. The recess in the frequency adjustment film 125A is a trace of the removal process performed by laser ablation.

[0116] This allows the variation in the resonant frequency of the resonator 210 before and after sealing to be corrected after sealing, thereby improving the accuracy of the resonant frequency of the resonator 210.

[0117] Third Embodiment Next, the structure of a resonator device 3 according to a third embodiment will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view of the resonator device 3 according to the third embodiment.

[0118] The tip 322A of the vibrating arm 321A has a first portion P1A located on the fixed end side of the vibrating arm 321A and a second portion P2A located on the open end side of the vibrating arm 321A. The first portion P1A and the second portion P2A are made of different materials for their surfaces. The first portion P1A is provided with a piezoelectric layer F33, a frequency adjustment film 325A, and a metal film E3. The surface of the second portion P2A facing the top cover 30 is provided with a silicon layer F32. The corners of the second portion P2A facing the top cover 30 have, for example, a rounded R-shape due to a frequency adjustment process after sealing. This is due to the frequency adjustment process after sealing the resonator 310. In this frequency adjustment process after sealing, the vibrating arm 321A is overexcited and the second portion P2A of the tip 322A is caused to collide with the top cover 30, thereby grinding off the corners of the second portion P2A facing the top cover 30. This reduces the mass of the tip portion 322A and adjusts the resonant frequency of the resonator 310.

[0119] According to this, since the resonant frequency is adjusted before sealing, it is possible to correct the fluctuation in the resonant frequency before and after sealing of the resonator 310. Therefore, it is possible to improve the accuracy of the resonant frequency of the resonator 310.

[0120] Furthermore, because the top lid 30 side of the second portion P2A is formed by the silicon layer F32, when the vibrating arm 321A is over-excited, the frequency adjustment film 325A does not come into contact with the top lid 30, but the silicon layer F32 comes into contact with the top lid 30. Because the impact of the collision is not absorbed by the frequency adjustment film 325A, the frequency adjustment process is not hindered, and the silicon layer F32 can be efficiently removed.

[0121] The object against which the silicon layer F32 of the second portion P2A is collided is preferably the glass substrate Q15 of the top cover 30. Because the glass substrate Q15 has a greater breaking stress than the silicon layer F32, when the glass substrate Q15 and the silicon layer F32 collide, it is possible to abrade the silicon layer F32 while suppressing chipping of the glass substrate Q15. Therefore, it is possible to suppress the generation of dust from the top cover 30 during the frequency adjustment process after sealing, and to reduce the total amount of dust generated in the vibration space.

[0122] Fourth Embodiment Next, the structure of a resonator device 4 according to a fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the resonator device 4 according to the fourth embodiment.

[0123] The silicon oxide film F421 is provided so as to avoid at least the second portion P2A of the tip portion 422A of the vibrating arm 421A, and the surface of the tip portion 422A that faces the bottom lid 20 is provided by the silicon layer F42. The corner of the second portion P2A of the tip portion 422A on the side that faces the bottom lid 20 has, for example, a rounded R shape. This is because, in the frequency adjustment process using overexcitation after sealing, the second portion P2A of the tip portion 422A is collided with the bottom lid 20, thereby cutting off the corner of the second portion P2A on the side that faces the bottom lid 20.

[0124] According to this, in the frequency adjustment process by overexcitation after sealing, the tip portion 422A is caused to collide with both the lower cover 20 and the upper cover 30, thereby improving the efficiency of adjusting the resonance frequency.

[0125] Fifth Embodiment Next, the structure of a resonator device 5 according to a fifth embodiment will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the resonator device 5 according to the fifth embodiment.

[0126] A silicon oxide film P11 is provided on the side of the bottom plate portion 522 of the lower cover 520 facing the resonator 410.

[0127] According to this, in the frequency adjustment process by over-excitation after sealing, the silicon layer F42 can be collided against the silicon oxide film P11, which is less susceptible to wear than the silicon substrate P10, thereby suppressing the generation of dust from the lower cover 520.

[0128] The bottom plate of the lower cover may be made of a glass substrate primarily composed of silicon oxide. In this case, the bottom plate of the lower cover is transparent, allowing the resonator to be observed from the outside through the lower cover. Therefore, defects that occur inside the resonator device after sealing can be detected by visual inspection.

[0129] Sixth Embodiment Next, the structure of a resonator device 6 according to a sixth embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of the resonator device 6 according to the sixth embodiment.

[0130] The silicon layer F62 of the resonator 610 and the silicon substrate P10 of the lower lid 20 are directly bonded without a silicon oxide film therebetween. The silicon layer F62 and the silicon substrate P10 are both n-type or both p-type.

[0131] This allows the silicon substrate P10 to be electrically connected to the ground electrode via the silicon layer F62, thereby grounding the silicon substrate P10, thereby suppressing fluctuations in the characteristics of the resonator device 6 due to parasitic capacitance.

[0132] Some or all of the embodiments of the present invention will be described below, but the present invention is not limited to the following descriptions.

[0133] <1> A resonance device comprising: a resonator having a vibration part configured to be able to vibrate; a first substrate having a first bottom plate part spaced apart from the vibration part; and a second substrate having a second bottom plate part spaced apart from the vibration part on the opposite side of the resonator from the first substrate, wherein the vibration part has a piezoelectric layer, a frequency adjustment film that adjusts the frequency of the vibration part by a mass addition effect, and a metal film including an excitation electrode that applies a voltage to excite the piezoelectric layer, the frequency adjustment film being provided between the piezoelectric layer and the metal film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps at least a portion of an end of the frequency adjustment film.

[0134] <2> The resonator device according to <1>, wherein, when viewed in plan in the thickness direction, the metal film overlaps the entire periphery of the end of the frequency adjustment film.

[0135] <3> The resonator device according to <1> or <2>, wherein the metal film overlaps the entire surface of the frequency adjustment film when viewed in a plan view in the thickness direction.

[0136] <4> The resonator device according to any one of <1> to <3>, wherein the material of the frequency adjustment film is a metal.

[0137] <5> The resonator device according to any one of <1> to <4>, wherein the material of the frequency adjustment film is the same as the material of the metal film.

[0138] <6> The resonator device according to any one of <1> to <5>, wherein the vibrating section further includes a protective film that covers at least the excitation electrode of the metal film.

[0139] <7> The resonator device according to <6>, wherein the protective film overlaps at least an end portion of the frequency adjustment film.

[0140] <8> The resonator device according to <6> or <7>, wherein the material of the protective film is the same as the material of the piezoelectric layer.

[0141] <9> The resonator device according to any one of <1> to <8>, wherein the vibrating section has a vibrating arm configured to be able to bend out of the plane, and the frequency adjustment film is provided at a tip of the vibrating arm.

[0142] <10> The resonator device according to <9>, wherein the resonator further includes a silicon layer provided on the second substrate side of the piezoelectric layer and a silicon oxide film provided on the second substrate side of the silicon layer, the first substrate being formed of a silicon substrate and a glass substrate, and the second substrate being formed of a silicon substrate.

[0143] <11> The resonator device according to <10>, wherein at least a portion of the frequency adjustment film is exposed to the glass substrate of the first substrate.

[0144] <12> The resonator device according to <10> or <11>, wherein the tip of the vibrating arm has a first portion provided on the fixed end side and a second portion provided on the open end side of the first portion, the first portion is provided with a frequency adjustment film, and the surface of the second portion facing the first substrate is provided with a silicon layer.

[0145] <13> The resonator device according to any one of <10> to <12>, wherein the tip of the vibrating arm has a first portion provided on the fixed end side and a second portion provided on the open end side of the first portion, a frequency adjustment film is provided on the first portion, and a surface of the second portion facing the second substrate is provided by a silicon layer.

[0146] <14> The resonator device according to <13>, wherein a silicon oxide film is provided on a surface of the second bottom plate portion of the second substrate that faces the vibrating portion.

[0147] <15> The resonator device according to any one of <10> to <14>, wherein the silicon layer of the resonator is directly bonded to the silicon substrate of the second substrate.

[0148] <16> The resonator device according to <15>, wherein the silicon layer of the resonator and the silicon substrate of the second substrate are both n-type or both p-type.

[0149] <17> A method for manufacturing a resonance device including a resonator having a vibrating portion configured to be able to vibrate, a first substrate having a first bottom plate portion spaced apart from the vibrating portion, and a second substrate having a second bottom plate portion spaced apart from the vibrating portion on the opposite side of the resonator from the first substrate, the method comprising: preparing the resonator; preparing the first substrate; preparing a second substrate; and sealing the resonator between the first substrate and the second substrate, wherein preparing the resonator includes providing a piezoelectric layer; providing a frequency adjustment film on one side of the piezoelectric layer; and providing a metal film including an excitation electrode on one side of the frequency adjustment film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps with at least a portion of an end of the frequency adjustment film.

[0150] <18> The method for manufacturing a resonance device according to <17>, wherein preparing the resonator further includes providing a protective film on at least one side of the excitation electrodes, and providing the metal film is performed after providing the frequency adjustment film, and providing the protective film is performed after providing the metal film.

[0151] <19> The method for manufacturing a resonator device according to <17> or <18>, further comprising adjusting the frequency of the resonator by irradiating a frequency adjustment film of the resonator with a laser.

[0152] <20> The method for manufacturing a resonator device according to any one of <17> to <19>, further comprising overexciting the sealed resonator and contacting it with at least one of the first substrate and the second substrate, thereby adjusting the frequency of the resonator.

[0153] The embodiments of the present invention can be appropriately applied to any device that utilizes the frequency characteristics of a resonator, such as a timing device, a sound generator, an oscillator, or a load sensor, without any particular limitations.

[0154] As described above, according to one aspect of the present invention, it is possible to provide a resonator device and a manufacturing method thereof that can improve reliability.

[0155] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from its spirit, and equivalents are also included within the scope of the present invention. In other words, designs modified appropriately by those skilled in the art are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements of the embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of the embodiments can be combined to the extent technically possible, and such combinations are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention.

[0156] DESCRIPTION OF SYMBOLS 1...Resonator device 10...Resonator 20...Lower cover 30...Upper cover 21, 31...Cavity 22, 32...Bottom plate portion 23, 33...Side wall portion 50...MEMS substrate 70...Metal film 110...Vibration portion 120...Excitation portion 121A to 121D...Vibration arms 122A to 122D...Tip portion 123A to 123D...Arm portion 130...Base portion 140...Holding portion 150...Support arm F2...Silicon layer F21...Silicon oxide film F3...Piezoelectric layer 125A to 125D...Frequency adjustment film E1...Metal film F5...Protective film P10, Q10...Silicon substrate Q15...Glass substrate H...Joint portion

Claims

1. A resonance device comprising: a resonator having a vibrating part configured to be able to vibrate; a first substrate having a first bottom plate part spaced apart from the vibrating part; and a second substrate having a second bottom plate part spaced apart from the vibrating part on the opposite side of the resonator from the first substrate, wherein the vibrating part has a piezoelectric layer, a frequency adjustment film that adjusts the frequency of the vibrating part by a mass addition effect, and a metal film including an excitation electrode that applies a voltage to excite the piezoelectric layer, the frequency adjustment film being provided between the piezoelectric layer and the metal film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps at least a part of the edge of the frequency adjustment film.

2. The resonator device according to claim 1, wherein, when viewed in a plan view in the thickness direction, the metal film overlaps the entire periphery of the end portion of the frequency adjustment film.

3. The resonator device according to claim 1 or 2, wherein, when viewed in a plan view in the thickness direction, the metal film overlaps the entire surface of the frequency adjustment film.

4. The resonator device according to any one of claims 1 to 3, wherein the material of the frequency adjustment film is a metal.

5. A resonator device according to any one of claims 1 to 4, wherein the material of the frequency adjustment film is the same as the material of the metal film.

6. The resonator device according to any one of claims 1 to 5, wherein the vibrating section further has a protective film that covers at least the excitation electrode of the metal film.

7. The resonator device according to claim 6, wherein the protective film overlaps at least the end portion of the frequency adjustment film.

8. The resonator device according to claim 6 or 7, wherein the material of the protective film is the same as the material of the piezoelectric layer.

9. A resonator device according to any one of claims 1 to 8, wherein the vibrating section has a vibrating arm configured to be capable of out-of-plane bending, and the frequency adjustment film is provided at the tip of the vibrating arm.

10. The resonator device according to claim 9, wherein the resonator further comprises a silicon layer provided on the second substrate side of the piezoelectric layer and a silicon oxide film provided on the second substrate side of the silicon layer, the first substrate being formed of a silicon substrate and a glass substrate, and the second substrate being formed of a silicon substrate.

11. The resonator device according to claim 10, wherein at least a portion of the frequency adjustment film is exposed to the glass substrate of the first substrate.

12. A resonator device as described in claim 10 or 11, wherein the tip of the vibrating arm has a first portion provided on the fixed end side and a second portion provided on the open end side of the first portion, the frequency adjustment film is provided on the first portion, and the surface of the second portion facing the first bottom plate portion is provided by the silicon layer.

13. A resonator device as described in any one of claims 10 to 12, wherein the tip of the vibrating arm has a first portion provided on the fixed end side and a second portion provided on the open end side of the first portion, the first portion is provided with the frequency adjustment film, and the surface of the second portion facing the second bottom plate portion is provided with the silicon layer.

14. The resonator device according to claim 13, wherein a silicon oxide film is provided on a surface of the second bottom plate portion of the second substrate that faces the vibrating portion.

15. The resonator device according to any one of claims 10 to 14, wherein the silicon layer of the resonator is directly bonded to the silicon substrate of the second substrate.

16. The resonator device according to claim 15, wherein the silicon layer of the resonator and the silicon substrate of the second substrate are both n-type or both p-type.

17. A method for manufacturing a resonance device comprising a resonator having a vibrating part configured to be able to vibrate, a first substrate having a first bottom plate part spaced apart from the vibrating part, and a second substrate having a second bottom plate part spaced apart from the vibrating part on the side of the resonator opposite the first substrate, the method comprising: preparing the resonator; preparing the first substrate; preparing the second substrate; and sealing the resonator between the first substrate and the second substrate, wherein preparing the resonator comprises providing a piezoelectric layer; providing a frequency adjustment film on one side of the piezoelectric layer; and providing a metal film including an excitation electrode on the one side of the frequency adjustment film, the thickness of the frequency adjustment film being greater than the thickness of the metal film, and when viewed in a plane in the thickness direction in which the second substrate, the resonator, and the first substrate overlap, the metal film overlaps with at least a portion of an end of the frequency adjustment film.

18. A method for manufacturing a resonator device according to claim 17, wherein preparing the resonator further includes providing a protective film on at least one side of the excitation electrodes, and providing the metal film is performed after providing the frequency adjustment film, and providing the protective film is performed after providing the metal film.

19. The method for manufacturing a resonator device according to claim 17 or 18, further comprising adjusting the frequency of the resonator by irradiating the frequency adjustment film of the resonator with a laser.

20. A method for manufacturing a resonator device according to any one of claims 17 to 19, further comprising adjusting the frequency of the sealed resonator by overexciting the sealed resonator and contacting it with at least one of the first substrate and the second substrate.

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