Resonance device

Abstract

The invention relates to a resonance device. The vibrator includes a vibrator layer having a vibrating portion including a plurality of vibrating arms and a base portion, a holding portion configured to hold the vibrating portion, and a holding arm connecting the vibrating portion and the holding portion. The plurality of vibrating arms comprise a piezoelectric layer, an upper electrode layer arranged on a first main surface of the piezoelectric layer, and a lower electrode layer arranged on a second main surface opposite to the first main surface of the piezoelectric layer, and the base part is connected with the fixing ends of the plurality of vibrating arms; an upper cover layer provided on the upper electrode layer side of the oscillator layer; and a lower cover layer provided on the lower electrode layer side of the vibrator layer, the plurality of vibrating arms having at least one inner vibrating arm and at least two outer vibrating arms provided on both outer sides of the inner vibrating arm, respectively, in plan view of the vibrator layer. The inner vibrating arm and the outer vibrating arm are configured so as to be capable of out-of-plane bending vibration at mutually different phases, one of the upper cover layer and the lower cover layer has a first external terminal and a second external terminal provided on the opposite side from the side on which the vibrator layer is provided, and one of the inner vibrating arm and the outer vibrating arm has a second external terminal provided on the opposite side from the side on which the vibrator layer is provided. In one of the inner vibrating arm and the outer vibrating arm, the upper electrode layer and the lower electrode layer are each electrically connected to a first external terminal, in the other of the inner vibrating arm and the outer vibrating arm, any one of the upper electrode layer and the lower electrode layer is electrically connected to the first external terminal, and the other of the upper electrode layer and the lower electrode layer is electrically connected to a second external terminal.

Description

Technical Field

[0001] The present invention relates to a resonance device. Background Art

[0002] Resonance devices manufactured using MEMS (Micro Electro Mechanical Systems) technology are becoming widespread. For example, resonance devices having a three-terminal structure in which a lower electrode and a ground terminal are electrically connected are disclosed in Patent Documents 1, 2, and 3.

[0003] Patent Document 1: International Publication No. 2016 / 159018;

[0004] Patent Document 2: International Publication No. 2020 / 045503;

[0005] Patent Document 3: International Publication No. 2019 / 111439.

[0006] However, since the resonance devices of Patent Documents 1, 2, and 3 adopt a three-terminal structure, in the case of miniaturization, the area of each terminal is small, and in addition, the distance between each terminal is small. As a result, short circuits between terminals and poor solder coating may occur. In addition, in order to address the above problems, it is considered to make the ground terminal a floating electrode, but in this case, electromagnetic noise from the outside and the thermoelectric effect caused by temperature changes cause the floating electrode to accumulate charges, generating electrostatic attraction and frequency changes, which impairs reliability. Summary of the Invention

[0007] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a resonance device that is compatible with miniaturization and has high reliability.

[0008] A resonance device according to one embodiment of the present invention includes: an oscillator layer having a vibrating portion including a plurality of vibrating arms and a base portion, a holding portion configured to hold the vibrating portion, and a holding arm connecting the vibrating portion and the holding portion; the plurality of vibrating arms each having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface of the piezoelectric layer opposite to the first main surface; the base portion being connected to fixed ends of the plurality of vibrating arms; an upper cover layer provided on the side of the upper electrode layer of the oscillator layer; and a lower cover layer provided on the side of the lower electrode layer of the oscillator layer, the plurality of vibrating arms having at least one inner vibrating arm and at least two outer vibrating arms respectively provided on both sides of the inner vibrating arm when the oscillator layer is viewed from above, the inner vibrating arm and the outer vibrating arms being configured to be capable of performing out-of-plane bending vibrations with different phases from each other, either the upper cover layer or the lower cover layer having a first external terminal and a second external terminal provided on the side opposite to the side where the oscillator layer is provided, in either the inner vibrating arm or the outer vibrating arms, both the upper electrode layer and the lower electrode layer are electrically connected to the first external terminal, in the other of the inner vibrating arm and the outer vibrating arms, either one of the upper electrode layer and the lower electrode layer is electrically connected to the first external terminal, and the other of the upper electrode layer and the lower electrode layer is electrically connected to the second external terminal.

[0009] According to the above embodiment, the upper electrode layer and the lower electrode layer of the plurality of vibrating arms are electrically connected to either the first external terminal or the second external terminal. Thus, by making the external terminals have a two-terminal structure, a resonance device corresponding to miniaturization can be provided. In addition, by adopting the above structure, a resonance device with improved frequency stability can be provided as compared with a structure in which one of the upper electrode layer and the lower electrode layer is a floating electrode.

[0010] According to the present invention, a resonance device corresponding to miniaturization and having high reliability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a perspective view schematically showing the resonance device of the first embodiment.

[0012] Figure 2 is an exploded perspective view schematically showing the structure of the resonance device of the first embodiment.

[0013] Figure 3 is a top view showing the structure of the oscillator layer of the first embodiment.

[0014] Figure 4 is a top view showing the structure of the upper cover layer of the first embodiment.

[0015] Figure 5 is along Figure 3 and Figure 4Cross-sectional view of the resonance device of the first embodiment of the V-V line.

[0016] Figure 6 It is along Figure 3 and Figure 4 Cross-sectional view of the resonance device of the first embodiment of the VI-VI line.

[0017] Figure 7 It is along Figure 3 and Figure 4 Cross-sectional view of the resonance device of the first embodiment of the VII-VII line.

[0018] Figure 8 It is along Figure 3 and Figure 4 Cross-sectional view of the resonance device of the first embodiment of the VIII-VIII line.

[0019] Figure 9 Cross-sectional view showing the structure of the vibration part of the modified example of the first embodiment.

[0020] Figure 10 Top view showing the structure of the upper cover layer of the second embodiment.

[0021] Figure 11 It is along Figure 10 Cross-sectional view of the XI-XI line. Detailed implementation mode

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings of this embodiment are illustrative, and the dimensions and shapes of each part are schematic. The technical scope of the present invention should not be limited to this embodiment for interpretation.

[0023] <Resonance device>

[0024] First, with reference to Figure 1 and Figure 2 the brief structure of the resonance device according to one embodiment will be described. Figure 1 It is a perspective view briefly showing the appearance of the resonance device 1 in one embodiment. Figure 2 It is briefly showing Figure 1 Exploded perspective view of the structure of the resonance device 1 shown.

[0025] As Figure 1 and Figure 2 shown, the resonance device 1 includes an oscillator layer 10, a lower cover layer 20 that forms a vibration space for the oscillator layer 10 to vibrate, and an upper cover layer 30. That is, the lower cover layer 20, the oscillator layer 10, and the upper cover layer 30 are stacked in this order to form the resonance device 1.

[0026] Hereinafter, each structure of the resonance device 1 will be described. In the following description, the side of the resonance device 1 provided with the upper cover layer 30 is referred to as the upper side (or the front side), and the side provided with the lower cover layer 20 is referred to as the lower side (or the back side).

[0027] The vibrator layer 10 is a MEMS vibrator manufactured using MEMS technology. The vibrator layer 10 and the upper cover layer 30 are bonded via a bonding frame V2 described later. In addition, the vibrator layer 10 and the lower cover layer 20 are respectively formed using a silicon (Si) substrate (hereinafter referred to as a "Si substrate"), and the Si substrates are bonded to each other. In addition, the vibrator layer 10, the lower cover layer 20, and the upper cover layer 30 can also be formed using a SOI (Silicon On Insulator) substrate stacked with a silicon layer and a silicon oxide film.

[0028] The upper cover layer 30 extends into a flat plate along the XY plane, and a recess 31 is formed on the side where the vibrator layer 10 is provided. The recess 31 has a flat bottom and a side wall 33 extending from the bottom to the side where the vibrator layer 10 is provided, thereby forming a space where the vibrator layer 10 vibrates, that is, a part of the vibration space. In addition, a glass layer G1 is provided in the recess 31. In addition, the upper cover layer 30 may not have the recess 31 and may have a flat plate shape. In addition, an intake layer for adsorbing exhaust gas may be formed on the surface of the vibrator layer 10 side of the recess 31 of the upper cover layer 30. When viewed from above, the length of the upper cover layer 30 in the X-axis direction is, for example, about 320 μm, and the length in the Y-axis direction is, for example, about 600 μm.

[0029] The lower cover layer 20 has a rectangular flat plate-shaped bottom plate 22 arranged along the XY plane, and a side wall 23 extending from the peripheral portion of the bottom plate 22 along the Z-axis direction, that is, along the stacking direction of the lower cover layer 20 and the vibrator layer 10. In the lower cover layer 20, a recessed portion 21 formed by the surface of the bottom plate 22 and the inner surface of the side wall 23 is formed on the surface opposite to the vibrator layer 10. The recessed portion 21 forms a part of the vibration space of the vibrator layer 10. In addition, the lower cover layer 20 may not have the recessed portion 21 and may be in a flat plate shape. In addition, an air absorption layer for adsorbing exhaust gas may be formed on the surface of the recessed portion 21 of the lower cover layer 20 on the vibrator layer 10 side.

[0030] In addition, the under cover layer 20 includes a protrusion 25 formed on the surface of the bottom plate 22. The detailed structure of the protrusion 25 will be described later.

[0031] By bonding the upper cover layer 30 to the vibrator layer 10 and the lower cover layer 20 , the vibration space of the vibrator layer 10 is hermetically sealed and maintained in a vacuum state. The vibration space may be filled with a gas such as an inert gas, for example.

[0032] Next, refer to Figure 3, and a brief structure of an oscillator layer in a resonant device according to an embodiment will be described. Figure 3 is a top view briefly showing Figure 2 the structure of the oscillator layer 10 shown.

[0033] As Figure 3 shown, the oscillator layer 10 is a MEMS oscillator manufactured using MEMS technology, and vibrates mainly in an out-of-plane bending vibration mode (hereinafter, also referred to as "main mode") in the XY plane of the orthogonal coordinate system of Figure 3 . These oscillators are applied to, for example, timing devices, RF filters, duplexers, ultrasonic transducers, gyro sensors, acceleration sensors, etc. In addition, they can also be used for piezoelectric mirrors with actuator functions, piezoelectric gyroscopes, piezoelectric microphones with pressure sensor functions, ultrasonic vibration sensors, etc. Moreover, they can also be applied to electrostatic MEMS elements, electromagnetic drive MEMS elements, and piezoresistive MEMS elements.

[0034] The oscillator layer 10 has a vibrating portion 120, a holding arm 140, and a holding portion 150.

[0035] The vibrating portion 120 has a rectangular contour extending along the Figure 3 XY plane of the orthogonal coordinate system. The vibrating portion 120 is disposed inside the bonding frame V2, and a separation groove 145 is formed at a predetermined interval between the vibrating portion 120 and the holding portion 150. In the Figure 3 example, the vibrating portion 120 has a base portion 130 and four vibrating arms 121A to 121D. The vibrating arms 121A to 121D and the holding arm 140 are respectively connected to the base portion 130. The vibrating arms 121A to 121D have a front end portion 125 provided on the front end side of the vibrating arms 121A to 121D and an arm portion 127 provided on the root side of the vibrating arms 121A to 121D. In addition, the number of vibrating arms is not limited to four. For example, the number of inner vibrating arms is set to any number of one or more, and the number of outer vibrating arms is set to any number of two or more provided on both outer sides of the inner vibrating arms. In the present embodiment, the front end portion 125, the arm portion 127, and the base portion 130 are integrally formed. In addition, the width of the front end portion 125 in the X-axis direction is, for example, about 42 μm, and the width of the arm portion 127 in the X-axis direction is, for example, about 22 μm. The length of the vibrating arm formed by combining the front end portion 125 and the arm portion 127 in the Y-axis direction is, for example, about 380 μm.

[0036] The vibrating arms 121A, 121B, 121C, and 121D extend along the Y-axis direction respectively and are arranged in parallel at a predetermined interval in the X-axis direction in this order. One end of the vibrating arm 121A is a fixed end connected to the front end portion of a base portion 130 described later, and the other end of the vibrating arm 121A is an open end provided away from the front end portion of the base portion 130. The vibrating arm 121A includes a conduction portion 126 and a mass addition portion formed at the front end portion 125 on the open end side, and an arm portion 127 extending from the fixed end and connected to the mass addition portion. Similarly, the vibrating arms 121B, 121C, and 121D also include a mass addition portion and an arm portion 127 respectively.

[0037] The vibrating arm 121 has a piezoelectric layer F2, an upper electrode layer E1 provided on the first main surface (the side facing the upper cover layer 30) of the piezoelectric layer F2, and a degenerate silicon layer F5 (a lower electrode layer E2 in the second embodiment) provided on the second main surface (the side facing the lower cover layer 20) of the piezoelectric layer F2.

[0038] The conduction portion 126 penetrates through the frequency adjustment film F4, the protective film F1, the upper electrode layer E1, and the piezoelectric layer F2 from the front end portion 125 and is provided up to the lower electrode layer E2. Through the conduction portion 126, the upper electrode layer E1 and the lower electrode layer E2 are electrically connected in the front end portion 125.

[0039] The mass addition portion has a mass addition film on each surface. Therefore, the weight per unit length of each of the mass addition portions (hereinafter, also simply referred to as "weight") is heavier than the weight of each of the arm portions. Thereby, the vibrating portion 120 can be miniaturized and the vibration characteristics can be improved. In addition, the mass addition films respectively not only have the function of increasing the weight of the front end portions 125 of the vibrating arms 121A to 121D, but also have the function of a so-called frequency adjustment film for adjusting the resonance frequencies of the vibrating arms 121A to 121D by shaving off a part thereof.

[0040] When looking down on the oscillator layer 10 from above (hereinafter, simply referred to as "looking down"), the mass addition portions are each substantially rectangular and have a curved surface shape with rounded corners at the four corners, for example, a so-called R shape. Similarly, the arm portions 127 are each substantially rectangular and have an R shape near the fixed end connected to the base portion 130 and near the connection portions connected to the respective mass addition portions. However, the shapes of the mass addition portion and the arm portion 127 are not limited to the examples of this embodiment. For example, the shapes of the mass addition portion and the arm portion 127 may each be substantially trapezoidal when looking down.

[0041] When looking down, the base portion 130 has a front end portion, a rear end portion, a left end portion, and a right end portion. As described above, the fixed ends of the vibrating arms 121A to 121D are connected to the front end portion. A holding arm 140 described later is connected to the rear end portion.

[0042] The holding arm 140 connects the vibrating portion 120 and the holding portion 150. The holding arm 140 extends from the rear end portion of the base portion 130 in the negative Y-axis direction and extends in the negative X-axis direction, and is connected to the holding portion 150. In addition, a connecting portion 135 is provided on the holding arm 140, and the vibrating arm 121 and the connecting electrode V11 of the holding portion 150 described later are electrically connected through the connecting portion 135.

[0043] The holding portion 150 is configured to hold the vibrating portion 120. The holding portion 150 is provided so as to surround the vibrating portion 120 in a plan view. More specifically, the holding portion 150 is configured such that the vibrating arms 121A to 121D can vibrate. In addition, connecting electrodes V11 and V12 are provided on the holding portion 150, and the electrodes of the vibrating arm 121 and the external terminals T1 and T2 provided on the upper cover layer 30 are electrically connected through the connecting electrodes V11 and V12.

[0044] In addition, the holding portion 150 may be disposed at least partially around the vibrating portion 120, and is not limited to a frame shape. For example, the holding portion 150 may be disposed around the vibrating portion 120 to such an extent that it can hold the vibrating portion 120 and be joined to the upper cover layer 30 and the lower cover layer 20.

[0045] The protruding portion 25 protrudes into the vibration space from the concave portion 21 of the lower cover layer 20. In a plan view, the protruding portion 25 is disposed between the arm portion 127 of the vibrating arm 121B and the arm portion 127 of the vibrating arm 121C. The protruding portion 25 extends in the Y-axis direction in parallel with the arm portion 127 and is formed in a prism shape. The length of the protruding portion 25 in the Y-axis direction is about 240 μm, and the length in the X-axis direction is about 15 μm. In addition, the number of the protruding portions 25 is not limited to one, and may be two or more. In this way, by disposing the protruding portion 25 between the vibrating arms 121B and 121C and protruding from the bottom plate 22 of the concave portion 21, the rigidity of the lower cover layer 20 can be improved, and the generation of the deflection of the oscillator layer 10 formed on the lower cover layer 20 and the warping of the lower cover layer 20 can be suppressed.

[0046] The separation groove 145 is configured to surround the vibrating portion 120 and the holding arm 140 as Figure 3 shown. In addition, the separation groove 145 is provided so as to surround the connecting electrodes V11 and V12 provided on the holding portion 150 in a plan view. By providing the separation groove 145 as described above, the vibrating portion 120 and the holding arm 140 are separated from the holding portion 150. In addition, the connecting electrodes V11 and V12 are separated from the joining frame V2 of the holding portion 150. Specifically, the separation groove 145 is a groove that penetrates from the surface of the oscillator layer 10 to the back surface, is formed in a predetermined region of the holding portion 150, and has a substantially rectangular frame shape in a plan view.

[0047] Next, refer to Figure 4, and the structure of the upper cover layer will be described. Figure 4 is Figure 1 and Figure 2 a top view of the upper cover layer 30 shown.

[0048] The upper cover layer 30 is provided with external terminals T1 and T2 on the side opposite to the side where the oscillator layer 10 is provided. Multilayer electrodes 34 are provided inside the external terminals T1 and T2. In addition, the upper cover layer 30 has silicon layers S1, S2, and S3. As Figure 4 such, the external terminal T1 and the silicon layer S1 are electrically connected via the multilayer electrode 34. Similarly, the external terminal T2 and the silicon layer S2 are electrically connected via the multilayer electrode 34 and a connection wiring 35 extending in the negative Y-axis direction from the multilayer electrode 34. The silicon layer S3 is provided at the outer peripheral portion of the upper cover layer 30, and the oscillator layer 10 and the upper cover layer 30 are joined via a bonding frame V2.

[0049] Next, referring to Figure 5 , Figure 6 and Figure 7 , the stacked structure and operation of the resonance device according to one embodiment will be described. Figure 5 is along Figure 3 and Figure 4 the cross-sectional view taken along the V-V line of. Figure 6 is along Figure 3 and Figure 4 the cross-sectional view taken along the VI-VI line of. Figure 7 is along Figure 3 and Figure 4 the cross-sectional view taken along the VII-VII line of.

[0050] As Figure 5 shown, in the resonance device 1, the holding portion 150 of the oscillator layer 10 is joined to the side wall 23 of the lower cover layer 20, and further the holding portion 150 of the oscillator layer 10 is joined to the side wall 33 of the upper cover layer 30 formed of the silicon layer S3. In this way, the oscillator layer 10 is held between the lower cover layer 20 and the upper cover layer 30, and a vibration space in which the vibration portion 120 vibrates is formed by the lower cover layer 20, the upper cover layer 30, and the holding portion 150 of the oscillator layer 10.

[0051] The vibrating portion 120, the holding arm 140, and the holding portion 150 in the oscillator layer 10 are integrally formed by the same process. The oscillator layer 10 is formed with a lower electrode layer E2 on the silicon oxide layer F3 in contact with the lower cover layer 20. Further, a piezoelectric layer F2 is laminated on the lower electrode layer E2 so as to cover the lower electrode layer E2, and an upper electrode layer E1 is laminated on the piezoelectric layer F2. A protective film F1 is laminated on the upper electrode layer E1 so as to cover the upper electrode layer E1. In the front end portion 125 of the vibrating portion 120, frequency adjustment films F4 are also laminated on the protective film F1 respectively. The outer shapes of the vibrating portion 120, the holding arm 140, and the holding portion 150 are formed by, for example, removing and patterning the laminate composed of the above-mentioned silicon oxide layer F3, lower electrode layer E2, piezoelectric layer F2, upper electrode layer E1, protective film F1, etc. using dry etching.

[0052] The lower electrode layer E2 is formed of, for example, degenerate n-type silicon (Si) semiconductor with a thickness of about 6 μm, and can contain phosphorus (P), arsenic (As), antimony (Sb), etc. as n-type dopants. In addition, the resistance value of the degenerate silicon (Si) for the lower electrode layer E2 is, for example, less than 1.6 mΩ·cm, and more preferably 1.2 mΩ·cm or less. And, as an example of the temperature characteristic compensation layer, a silicon oxide layer F3 is formed on the lower surface of the lower electrode layer E2. Thereby, the temperature characteristic can be improved.

[0053] As Figure 3 and Figure 5 shown, in the vibrating arms 121A and 121D, the upper electrode layer E1 is disconnected at the front end portion 125 and the arm portion 127. Further, as Figure 6 in the vibrating arms 121B and 121C, it is connected between the front end portion 125 and the arm portion 127. Thus, the upper electrode layer E1 of the inner vibrating arms 121B and 121C is electrically short-circuited with the lower electrode layer E2 and the frequency adjustment film F4, constituting Figure 8 the electrical wiring of the oscillator layer 10 as such.

[0054] The protective film F1 is desirably formed with a uniform thickness. In addition, the uniform thickness means that the deviation of the thickness of the protective film F1 is within ±20% from the average value of the thickness.

[0055] The frequency adjustment film F4 is disposed on the surfaces of the front end portions 125 of the vibrating arms 121A to 121D on the side of each upper cover layer 30. By trimming the frequency adjustment film F4 by removing a part of each, the frequency of the oscillator layer 10 is adjusted. From the viewpoint of the efficiency of frequency adjustment, it is preferable that the frequency adjustment film F4 is formed of a material having a mass reduction rate based on etching faster than that of the protective film F1. The mass reduction rate is represented by the product of the etching rate and the density. The etching rate is the thickness removed per unit time. If the relationship between the mass reduction rates of the protective film F1 and the frequency adjustment film F4 is as described above, the magnitude relationship of the etching rates is arbitrary. In addition, from the viewpoint of efficiently increasing the weight of the front end portion 125, it is preferable that the frequency adjustment film F4 is formed of a material having a relatively large specific gravity. For these reasons, the frequency adjustment film F4 is formed of a metal material such as molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), aluminum (Al), titanium (Ti), etc.

[0056] A part of the upper surface of each of the frequency adjustment films F4 is removed by trimming in the process of adjusting the frequency. The trimming process of the frequency adjustment film F4 can be performed, for example, by dry etching with an argon (Ar) ion beam irradiation.

[0057] Connection electrodes V11 and V12 are formed on the protective film F1 of the holding portion 150. As Figure 5 shown, the silicon layer S1 is connected to the connection electrode V1. As Figure 7 shown, the silicon layer S2 is connected to the connection electrode V12. Through these connections, the external terminal T1, the silicon layer S1, and the connection electrode V11 are electrically connected, and the external terminal T2, the silicon layer S2, and the connection electrode V12 are electrically connected.

[0058] A bonding frame V2 is formed between the side wall 33 of the upper cover layer 30 and the holding portion 150, and the upper cover layer 30 and the oscillator layer 10 are bonded through the bonding frame V2. The bonding frame V2 is formed in a frame shape surrounding the vibrating portion 120, the holding arm 140, and the connection electrodes V11 and V12. That is, the bonding frame V2 is formed in a closed ring shape surrounding the vibrating portion 120 in the XY plane so as to hermetically seal the vibrating space of the oscillator layer 10 in a vacuum state.

[0059] The bonding frame V2 has conductivity and is formed, for example, of a metal film formed by sequentially laminating an aluminum (Al) film, a germanium (Ge) film, and an aluminum (Al) film and eutectic bonding. In addition, the bonding frame V2 may also be formed of a combination of films appropriately selected from gold (Au), tin (Sn), copper (Cu), titanium (Ti), silicon (Si), etc. In addition, in order to improve the adhesion, the bonding frame V2 may include a metal compound such as titanium nitride (TiN) or tantalum nitride (TaN) between the films.

[0060] In the holding portion 150, a separation groove 145 is formed through the protective film F1 formed on the surface to the silicon oxide layer F3. In addition, the separation groove 145 electrically separates the connection electrodes V11 and V12 from the bonding frame V2. Thus, as described above, since the separation groove 145 is formed to surround the connection electrodes V11 and V12 provided in the holding portion 150 in a plan view, the outside of the oscillator layer 10 and the vibrating portion 120 are separated by the separation groove 145, and the conduction path reaching the vibrating portion 120 from the outside of the oscillator layer 10 via the holding portion 150 is cut off before bonding. Therefore, noise propagation to the vibrating portion 120 via the holding portion 150 can be suppressed, and for example, the resonance frequency can be adjusted with high accuracy during frequency adjustment. In addition, by electrically isolating the oscillator layer 10 from the periphery of the oscillator layer 10 by the separation groove 145, the parasitic capacitance during substrate mounting based on flip chip bonding or the like can be reduced.

[0061] Next, with reference to Figure 8 , the electrical wiring of the oscillator layer 10 will be described. Figure 8 is a cross-sectional view along the Figure 3 and Figure 4 VIII-VIII line in

[0062] As Figure 8 shown, the holding portion 150 is electrically isolated from the vibrating arms 121A to 121D. In addition, the upper electrode layers E1 of the outer vibrating arms 121A and 121D are electrically connected to the external terminal T1. The upper electrode layers E1 of the inner vibrating arms 121B and 121C are electrically connected to the external terminal T2. The lower electrode layers E2 of the vibrating arms 121A to 121D are electrically connected to the external terminal T2. Thus, the external terminals can be of a two-terminal structure. In addition, compared with a structure in which the lower electrode layer E2 is a floating electrode to form a two-terminal structure, it is less susceptible to thermoelectric charges and external noise, and the frequency stability of the resonance device 1 can be improved.

[0063] In the present embodiment, the upper electrode layers E1 and the lower electrode layers E2 of the inner vibrating arms 121B and 121C are electrically connected, but it is not limited thereto. For example, the upper electrode layers E1 and the lower electrode layers E2 of the outer vibrating arms 121A and 121D may be electrically connected to the external terminal T1, the upper electrode layers E1 of the inner vibrating arms 121B and 121C may be electrically connected to the external terminal T2, and the lower electrode layers E2 of the vibrating arms 121A to 121D may be electrically connected to the external terminal T1. And the lower electrode layers E2 of each of the inner vibrating arms 121B and 121C and the outer vibrating arms 121A and 121D are electrically connected to any one of the external terminals T1 and T2.

[0064] As described above, in the resonance device 1 of the present embodiment, the upper electrode layers E1 of the outer vibrating arms 121A and 121D are electrically connected to the external terminal T1, the lower electrode layers E2 of the outer vibrating arms 121A and 121D are electrically connected to the external terminal T2, and the upper electrode layers E1 and the lower electrode layers E2 of the inner vibrating arms 121B and 121C are electrically connected to the external terminal T2. According to this electrical wiring, since the lower electrode layers E2 of the vibrating arms 121A to 121D are electrically connected to the external terminal T2, the frequency stability is improved as compared with the structure in which the lower electrode layer is a floating electrode. In addition, by making the external terminal a two-terminal structure, miniaturization of the resonance device can be achieved.

[0065] In the present embodiment, the lower electrode layer E2 has been described as a layer using degenerate silicon, but it is not limited thereto. For example, as Figure 9 shown, a degenerate silicon layer F5 may be provided on the silicon oxide layer F3, and a lower electrode layer E2 made of a metal layer may be separately provided on the degenerate silicon layer F5.

[0066] Hereinafter, the structure of the resonance device according to other embodiments of the present invention will be described. In addition, in the following modification examples and embodiments, descriptions of matters common to the above-described first embodiment are omitted, and only differences will be described. In particular, the same operational effects based on the same structure are not mentioned in sequence.

[0067] <Second Embodiment>

[0068] Next, with reference to Figure 10 and Figure 11 , the structure of the resonance device of the second embodiment will be described. Figure 10 is a top view schematically showing the upper cover of the resonance device of the second embodiment. Figure 11 is a cross-sectional view taken along the line XI-XI in Figure 10 .

[0069] In the present embodiment, different from the first embodiment, as Figure 10 shown, a connection wiring 36 is provided on the upper cover layer 30. As Figure 10 and Figure 11In this way, the connection wiring 36 extends from the multilayer electrode 34 in the positive Y-axis direction to electrically connect the external terminal T2 and the silicon layer S3. Thus, by connecting the silicon layer S3 of the upper cover layer 30 and the external terminal T2, the parasitic capacitance between the upper cover layer 30 and the lower cover layer 20 can be suppressed. In addition, when mounting the substrate by flip-chip bonding or the like, frequency drift may occur. However, by connecting the silicon layer S3 and the external terminal T2 as in this embodiment, frequency drift can be suppressed. In this embodiment, the way of leading out the connection wiring 36 from the external terminal T2 has been described, but it is not limited thereto. For example, the connection wiring 36 may also be led out from the external terminal T1.

[0070] Hereinafter, a part or all of the embodiments of the present invention will be noted. In addition, the present invention is not limited to the following notes.

[0071] <1>

[0072] As described above, according to one aspect of the present invention, there is provided a resonance device including: an oscillator layer having a vibration part including a plurality of vibration arms and a base part, a holding part configured to hold the vibration part, and a holding arm connecting the vibration part and the holding part; the plurality of vibration arms having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface of the piezoelectric layer opposite to the first main surface; the base part being connected to fixed ends of the plurality of vibration arms respectively; an upper cover layer provided on the side of the upper electrode layer of the oscillator layer; and a lower cover layer provided on the side of the lower electrode layer of the oscillator layer, the plurality of vibration arms having at least one inner vibration arm and at least two outer vibration arms respectively provided on both sides of the inner vibration arm when looking down on the oscillator layer, the inner vibration arm and the outer vibration arms being configured to be capable of performing out-of-plane bending vibrations with different phases from each other, either the upper cover layer or the lower cover layer having a first external terminal and a second external terminal provided on the side opposite to the side where the oscillator layer is provided, in either the inner vibration arm or the outer vibration arms, both the upper electrode layer and the lower electrode layer are electrically connected to the first external terminal, in the other of the inner vibration arm and the outer vibration arms, either the upper electrode layer or the lower electrode layer is electrically connected to the first external terminal, and the other of the upper electrode layer and the lower electrode layer is electrically connected to the second external terminal.

[0073] According to the above aspect, by electrically connecting the lower electrode layers of the inner vibration arm and the outer vibration arms to the first external terminal or the second external terminal, a resonance device with a two-terminal structure having improved frequency stability can be provided as compared with a structure in which the lower electrode layer is a floating electrode.

[0074] <2>

[0075] As one aspect, it is the resonant device according to <1>, wherein the upper cover layer has a first external terminal and a second external terminal. When looking down at the oscillator layer, the holding portion is arranged to surround the vibrating portion. Between the upper cover layer and the holding portion, a first connection electrode electrically connected to the first external terminal, a second connection electrode electrically connected to the second external terminal, and a bonding frame that is formed in a frame shape when looking down at the oscillator layer so as to surround the vibrating portion, the holding arm, and the first connection electrode and the second connection electrode are respectively provided.

[0076] According to the above aspect, it is possible to reduce the parasitic capacitance between the upper cover layer and the lower cover layer generated when mounting the substrate, and further stabilize the frequency.

[0077] <3>

[0078] As one aspect, it is the resonant device according to <2>, wherein between the upper cover layer and the holding portion, a first connection electrode electrically connected to the first external terminal, a second connection electrode electrically connected to the second external terminal, and a bonding frame that is formed in a frame shape when looking down at the oscillator layer so as to surround the vibrating portion, the holding arm, and the first connection electrode and the second connection electrode are respectively provided. In the holding portion, a separation groove for electrically separating the first connection electrode and the second connection electrode from the bonding frame is provided.

[0079] According to the above aspect, by using the separation groove to separate the oscillator layer from the outer periphery of the oscillator layer, it is possible to reduce the parasitic capacitance and further stabilize the frequency.

[0080] <4>

[0081] As one aspect, it is the resonant device according to any one of <1> to <3>, wherein the lower electrode layer is composed of a degenerate silicon layer.

[0082] <5>

[0083] As one aspect, it is the resonant device according to any one of <1> to <3>, wherein the lower electrode layer is composed of a metal layer, and the vibrating portion further includes a silicon layer provided on the side opposite to the side where the piezoelectric layer is provided in the lower electrode layer.

[0084] <6>

[0085] As one aspect, it is the resonant device according to any one of <1> to <5>, wherein the lower electrode layers of the inner vibrating arm and the outer vibrating arm are each electrically connected to any one of the first external terminal and the second external terminal.

[0086] In addition, the embodiments described above are for facilitating the understanding of the content of the present invention and are not for limiting or interpreting the content of the present invention. The present invention can be changed / improved without departing from its gist, and its equivalents are also included in the present invention. That is, as long as the structures obtained by appropriately applying design changes to each embodiment by those skilled in the art have the features of the present invention, they are also included in the scope of the present invention. For example, each element, its configuration, material, condition, shape, size, etc. possessed by each embodiment are not limited to the illustrated content and can be appropriately changed. In addition, the elements possessed by each embodiment can be combined within the technically feasible range, and as long as the structure obtained by combining them has the features of the present invention, it is also included in the scope of the present invention.

[0087] Description of Reference Numerals

[0088] 1…Resonator

[0089] 10…Oscillator layer

[0090] 20…Lower cover layer

[0091] 21…Recess

[0092] 22…Bottom plate

[0093] 23…Side wall

[0094] 25…Protrusion

[0095] 30…Upper cover layer

[0096] 31…Recess

[0097] 33…Side wall

[0098] 34…Multi-layer electrode

[0099] 35, 36…Connection wiring

[0100] 120…Vibration part

[0101] 121A, 121B, 121C, 121D…Vibration arm

[0102] 125…Front end

[0103] 126…Conduction part

[0104] 127…Arm part

[0105] 130…Base part

[0106] 135…Connection part

[0107] 140…Holding arm

[0108] 145…Separation groove

[0109] 150…Retention part

[0110] S1, S2, S3…Silicon layer

[0111] T1, T2…External terminal

[0112] V11, V12…Connection electrode

[0113] V2…Bonding frame

[0114] E1…Upper electrode layer

[0115] E2…Lower electrode layer

[0116] F0…Organic insulating film

[0117] F1…Protective film

[0118] F2…Piezoelectric layer

[0119] F3…Silicon oxide layer

[0120] F4…Frequency adjustment film

[0121] F5…Degenerate silicon layer

[0122] G1…Glass layer

Claims

1. A resonant device, wherein, Comprising: An oscillator layer having a vibrating portion including a plurality of vibrating arms and a base portion, a holding portion configured to hold the vibrating portion, and a holding arm connecting the vibrating portion and the holding portion. The plurality of vibrating arms each have a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface of the piezoelectric layer opposite to the first main surface. The base portion is connected to fixed ends of the plurality of vibrating arms respectively; An upper cover layer provided on the side of the upper electrode layer of the oscillator layer; and A lower cover layer provided on the side of the lower electrode layer of the oscillator layer, The plurality of vibrating arms include at least one inner vibrating arm and at least two outer vibrating arms respectively provided on both sides of the inner vibrating arm when the oscillator layer is viewed from above, The inner vibrating arm and the outer vibrating arms are configured to be capable of performing out-of-plane bending vibrations with different phases from each other, Either the upper cover layer or the lower cover layer has a first external terminal and a second external terminal provided on the side opposite to the side where the oscillator layer is provided, In any one of the inner vibrating arm and the outer vibrating arms, both the upper electrode layer and the lower electrode layer are electrically connected to the first external terminal, In the other of the inner vibrating arm and the outer vibrating arms, either one of the upper electrode layer and the lower electrode layer is electrically connected to the first external terminal, and the other of the upper electrode layer and the lower electrode layer is electrically connected to the second external terminal.

2. The resonance device according to claim 1, wherein The upper cover layer has the first external terminal and the second external terminal, When the oscillator layer is viewed from above, the holding portion is provided to surround the vibrating portion, Between the upper cover layer and the holding portion, a first connection electrode electrically connected to the first external terminal, a second connection electrode electrically connected to the second external terminal, and a bonding frame formed in a frame shape to surround the vibrating portion, the holding arm, and the first connection electrode and the second connection electrode are respectively provided when the oscillator layer is viewed from above.

3. The resonance device according to claim 2, wherein A separation groove for electrically separating the first connection electrode and the second connection electrode from the bonding frame is provided in the holding portion.

4. The resonance device according to any one of claims 1 to 3, wherein The lower electrode layer is composed of a degenerate silicon layer.

5. The resonance device according to any one of claims 1 to 3, wherein The lower electrode layer is composed of a metal layer, The vibrating portion further includes a silicon layer provided on the side opposite to the side where the piezoelectric layer is provided in the lower electrode layer.

6. The resonance device according to any one of claims 1 to 5, wherein The lower electrode layers of the inner vibrating arm and the outer vibrating arms are each electrically connected to either the first external terminal or the second external terminal.

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