Vibration device and method for manufacturing the same

Abstract

To provide an inexpensive vibration device and a method for manufacturing the vibration device.SOLUTION: There is provided a method for manufacturing a vibration device 1, the vibration device having a base 20 that has a first surface 20a provided with a concave part 21 in its surface, a support part 22 that projects from the first surface 20a in a normal direction of the first surface 20a, and a vibration arm 24 that extends from the support part 22 along the first surface 20a with a gap from the first surface 20a, and the method includes the steps of: preparing a planar single-crystal silicon substrate 10; forming, by dry etching, at least two bottomed long grooves 41 arranged side by side at a predetermined interval on a second surface 20b that is one surface of the silicon substrate 10; and etching side faces 41a of the long grooves 41 by wet etching to communicate the two long grooves 41 between the second surface 20b and bottom faces 41b of the long grooves 41 in a thickness direction of the silicon substrate 10, thereby forming a vibration arm 24.SELECTED DRAWING: Figure 10

Description

[Technical field]

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

[0002] Conventionally, there is known a vibrator having a MEMS (Micro Electro Mechanical Systems) structure in which an excitation part including a piezoelectric thin film is configured on a silicon semiconductor layer. For example, the following Patent Document 1 discloses a vibrator in which one end of each of a plurality of vibrating arms is connected to a base. This vibrator uses an SOI (Silicon on Insulator) substrate, and has a structure in which two silicon oxide layers are laminated on a surface silicon layer that becomes the vibrating arms, and an excitation part is provided on the silicon oxide layer. In addition, the ratio of the thickness of the surface silicon layer, the thickness of the first silicon oxide layer, and the thickness of the second silicon oxide layer is set to a predetermined condition, thereby reducing the temperature coefficient of frequency (TCF), and a vibrator having good frequency temperature characteristics is disclosed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-101829 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the resonator described in Patent Document 1 is manufactured using an expensive SOI substrate, and therefore there is a problem in that it is difficult to reduce the cost of the resonator. [Means for solving the problem]

[0005] A manufacturing method for a vibration device having a base having a first surface with a recess provided on its surface, a support protruding from the first surface in a direction normal to the first surface, and a vibrating arm extending from the support along the first surface with a gap between the first surface and the support, the method comprising the steps of: preparing a flat single crystal silicon substrate; forming at least two bottomed long grooves arranged at a predetermined interval on a second surface, which is one of the surfaces of the silicon substrate, by dry etching; and etching the side surfaces of the long grooves by wet etching to connect the two long grooves between the second surface in the thickness direction of the silicon substrate and the bottom surfaces of the long grooves, thereby forming the vibrating arms.

[0006] The vibration device has a base having a first surface with a recess on its surface, a support protruding from the first surface in a direction normal to the first surface, a vibrating arm extending from the support along the first surface with a gap between it and the first surface, and a piezoelectric film arranged on a second surface of the vibrating arm opposite the surface facing the first surface, wherein the vibrating arm is made of a single crystal silicon substrate, and the vibrating arm has two side surfaces connected to both ends of the second surface in the width direction of the vibrating arm, and the two side surfaces become asymptotically closer as they move away from the second surface. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view showing a schematic configuration of a vibration device according to a first embodiment. [Diagram 2] Cross-sectional view taken along line AA in Figure 1. [Diagram 3] Cross-sectional view taken along line BB in Figure 1. [Figure 4] 1 is a cross-sectional view illustrating an etching characteristic of a silicon substrate. [Diagram 5] 1 is a cross-sectional view illustrating etching characteristics of a silicon substrate. [Figure 6] 1 is a cross-sectional view illustrating the etching characteristics of a silicon substrate having a long groove. [Figure 7] 1 is a cross-sectional view illustrating the etching characteristics of a silicon substrate having a long groove. [Figure 8] 4A to 4C are cross-sectional views illustrating the etching characteristics of a silicon substrate used in the resonator device according to the embodiment. [Figure 9] 4A to 4C are cross-sectional views illustrating the etching characteristics of a silicon substrate used in the resonator device according to the embodiment. [Figure 10] FIG. 4 is a flowchart showing a method for manufacturing a vibration device. [Figure 11] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 12] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 13] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 14] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 15] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 16] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration device. [Figure 17] FIG. 11 is a plan view showing a schematic configuration of a vibration device according to a second embodiment. [Figure 18] 18 is a cross-sectional view taken along line CC in FIG. 17. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1. First embodiment 1.1.Vibration Device First, a vibration device 1 according to a first embodiment will be described with reference to FIGS. 1, 2, and 3, taking a three-legged tuning fork vibrator having three vibrating arms as an example. For ease of explanation, in each of the following figures except for Fig. 10, the X-axis, Y-axis, and Z-axis are illustrated as three mutually perpendicular axes. The direction along the X-axis is called the "X direction", the direction along the Y-axis is called the "Y direction", and the direction along the Z-axis is called the "Z direction". The arrow side of each axis is also called the "plus side", the side opposite the arrow is called the "minus side", the plus side of the Z direction is also called the "up" and the minus side of the Z direction is also called the "down".

[0009] 1, 2, and 3, the vibration device 1 has a base 20, a support 22, three vibrating arms 24, a temperature characteristic adjustment film 12, and a piezoelectric driving unit 30. The base 20, the support 22, and the three vibrating arms 24 are formed from a single crystal silicon substrate 10.

[0010] The base 20 has a first surface 20a on which a plurality of recesses 21 are provided. The support 22 protrudes from the first surface 20a of the base 20 in the positive Z direction, which is the normal direction of the first surface 20a. The three vibrating arms 24 have gaps with the first surface 20a of the base 20, and each extends from the support 22 to the positive Y direction along the first surface 20a. Further, a frame portion 23 is provided surrounding the three vibrating arms 24 in plan view from the Z direction, and the frame portion 23 is connected to the support portion 22 and the base portion 20.

[0011] Each of the three vibrating arms 24 has two side surfaces 25 connected to both ends of the second surface 20b in the X direction, which is the width direction of the vibrating arms 24, and the two side surfaces 25 approach each other as they move away from the second surface 20b. That is, the three vibrating arms 24 are formed in a triangular shape in a cross-sectional view from the Y direction, which is the direction in which the vibrating arms 24 extend. The three vibrating arms 24 are also arranged in the X direction in a plan view from the Z direction, and are arranged in the order of the first vibrating arm 24a, the second vibrating arm 24b, and the third vibrating arm 24c from the positive side in the X direction on the second surface 20b, which is one surface of the silicon substrate 10 along the XY plane specified by the X and Y axes.

[0012] The temperature characteristic adjustment film 12 is disposed on the second surface 20b of the three vibrating arms 24, and by setting the ratio between the thickness of the vibrating arms 24 and the thickness of the temperature characteristic adjustment film 12 to a predetermined condition, the temperature coefficient of frequency (TCF) can be reduced, and a vibrating device 1 having good frequency-temperature characteristics can be configured. The temperature characteristic adjustment film 12 is a silicon oxide (SiO2) film. An oxide film 10a is disposed between the second surface 20b of the silicon substrate 10 and the temperature characteristic adjustment film 12, and protects the region that is not etched when etching the silicon substrate 10. The oxide film 10a is a silicon oxide film that is generated by thermally oxidizing the silicon substrate 10.

[0013] The piezoelectric driving section 30 is disposed on a second surface 20b, which is the surface opposite to the surface facing the first surface 20a of the vibrating arm 24. In addition, an oxide film 10a and a temperature characteristic adjustment film 12 are disposed between the second surface 20b of the vibrating arm 24 and the piezoelectric driving section 30. The piezoelectric driving section 30 has a laminated structure including a first electrode 31, a piezoelectric film 32, and a second electrode 33, which are provided on the second surface 20b side of the vibrating arm 24.

[0014] The multiple wirings 34 are electrically connected to the first electrode 31 and the second electrode 33 so as to vibrate the adjacent vibrating arms 24 in opposite phases. The multiple wirings 34 are also electrically connected to the electrode pads 35. Specifically, the first electrode 31 of the first vibrating arm 24a is electrically connected to the second electrode 33 of the second vibrating arm 24b and the first electrode 31 of the third vibrating arm 24c via the wirings 34, and the second electrode 33 of the first vibrating arm 24a is electrically connected to the first electrode 31 of the second vibrating arm 24b and the second electrode 33 of the third vibrating arm 24c via the wirings 34. By applying a voltage between the two electrode pads 35 from the outside, the adjacent vibrating arms 24 can be vibrated in opposite phases.

[0015] As for the materials constituting these, for example, the piezoelectric film 32 is made of aluminum nitride (AlN) or the like, the first electrode 31 and the second electrode 33 are made of titanium nitride (TiN) or the like, and the multiple wirings 34 and the electrode pads 35 are made of aluminum (Al) or copper (Cu) or the like.

[0016] When a voltage is applied between the first electrode 31 and the second electrode 33 via the two electrode pads 35, the piezoelectric film 32 expands and contracts, vibrating the vibrating arm 24. The piezoelectric driver 30 causes the vibrating arm 24 to perform bending vibration in the Z direction perpendicular to the second surface 20b, that is, out-of-plane vibration in which the arm is displaced in a direction not along the second surface 20b.

[0017] As described above, the resonator device 1 of the present embodiment is formed from an inexpensive single crystal silicon substrate 10, and therefore a low-cost resonator device 1 can be obtained.

[0018] 1.2.Etching characteristics Next, the etching characteristics of the silicon substrate 10 involved in the method of manufacturing the resonator device 1 will be described with reference to FIGS.

[0019] Generally, when wet etching single crystal silicon using an alkaline aqueous solution (KOH, TMAH), the etching speed varies depending on the crystal plane orientation. Compared to the (100) and (110) planes, the (111) plane is hardly etched, resulting in anisotropic processing.

[0020] As shown in FIG. 4, in a single crystal silicon substrate 10 with a (100) surface orientation and a (110) orientation flat, when an opening 40 is formed in an oxide film 10a, which serves as an etching protective film, by photolithography and wet etching is performed, a (111) plane is precipitated having an angle θ of 54.7 degrees with the (100) plane, as shown in FIG. 5. Eventually, the two (111) planes come into contact, stopping the etching and making it impossible to etch any deeper. If the length of the opening 40 is L, the etching depth d can be calculated by equation (1). d = (L / 2) × tan54.7 = 0.706 × L (1)

[0021] On the other hand, as shown in FIG. 6, when a silicon substrate 10 having an opening 40 with a length L in the oxide film 10a is vertically processed by dry etching to form a bottomed long groove 41 with a length d1 to the bottom surface 41b, the bottom surface 41b becomes the (100) plane and the side surface 41a becomes the (110) plane. When wet etching is performed in this state, as shown in FIG. 7, the bottom surface 41b of the long groove 41 is etched in the negative Z direction, and similar to FIG. 5, an (111) plane with an angle θ of 54.7 degrees with respect to the (100) plane is deposited. When two (111) planes are in contact, the etching stops. Also, for the two side surfaces 41a of the long groove 41, an (111) plane with an angle θ of 54.7 degrees with respect to the (100) plane is deposited by etching in the positive or negative X direction. When two (111) planes are in contact, the etching stops.

[0022] Note that the etching depth S of the side surface 41a can be calculated by Equation (2). S = d1 / (2 × tan54.7) = 0.354 × d1 (2) Therefore, when the distance between two adjacent long grooves 41 is w, the condition for two adjacent long grooves 41 to communicate by etching is w / 2 < S. Thus, from Equation (2), Equation (3) is derived. 0.354 × d1 × 2 > w (3) Also, since the calculation of the etching depth of the bottom surface 41b having the (100) plane is the same as Equation (1), the etching depth d2 in the Z direction of the silicon substrate 10 can be calculated by Equation (4). d2 = d1 + 0.706 × L (4) Therefore, as a condition for the silicon substrate 10 with a thickness of t not to be penetrated in the thickness direction by etching, from Equation (4), Equation (5) is derived. d1 + 0.706 × L < t (5)

[0023] Using such an etching mechanism, a silicon substrate 10 in which a plurality of long grooves 41 having a predetermined interval W, an opening 40 length L, and a length d1 to a bottom surface 41b have been processed by dry etching is wet etched as shown in Fig. 8. As a result, the side surfaces 41a of adjacent long grooves 41 are etched, and the second surface 20b of the silicon substrate 10 communicates with the bottom surfaces 41b of the long grooves 41, and as shown in Fig. 9, a vibrating arm 24 having a triangular cross section is formed when viewed from the Y direction, and an internal space 27 that is a cavity is formed below the vibrating arm 24.

[0024] In addition, in FIG. 9, the width of the first vibrating arm 24a is W, the distance between the first vibrating arm 24a and the second vibrating arm 24b is L, and the distance from the second surface 20b of the vibrating arm 24 to the recess 21 on the first surface 20a is d2. If W, L, and d2 represent the condition for two adjacent long grooves 41 to communicate by etching, then the following equation (6) is obtained. (W / 0.708)+0.706×L <d2 (6)

[0025] 1.3. Manufacturing method of vibration device Next, a method for manufacturing the vibration device 1 according to the first embodiment will be described with reference to FIGS. As shown in FIG. 10, the method for manufacturing the vibration device 1 of this embodiment includes a substrate preparation step, an oxide film formation step, a piezoelectric driver formation step, a protective film formation step, a long groove formation step, a vibrating arm formation step, and a protective film removal step.

[0026] 1.3.1 Board preparation process First, in step S101, a flat single crystal silicon substrate 10 is prepared.

[0027] 1.3.2 Oxide film formation process In step S102, as shown in FIG. 11, the silicon substrate 10 is thermally oxidized to form an oxide film 10a of silicon oxide (SiO2) on the second surface 20b, which is one surface of the silicon substrate, to protect areas that are not to be etched when the silicon substrate 10 is etched.

[0028] 1.3.3 Piezoelectric actuator formation process In step S103, the temperature characteristic adjustment film 12, which is a silicon oxide film, is formed on the oxide film 10a by sputtering or CVD, and the oxide film 10a and the temperature characteristic adjustment film 12 are patterned into the shape of the vibration device 1 by photolithography and etching. After that, the first electrode 31, the piezoelectric film 32, and the second electrode 33, which become the piezoelectric driving unit 30, are formed and patterned in this order on the temperature characteristic adjustment film 12, to form the piezoelectric driving unit 30 as shown in Fig. 12. Note that since the oxide film 10a also has a temperature characteristic adjustment function, the temperature characteristic adjustment film 12 may be omitted by having the oxide film 10a also function as the temperature characteristic adjustment film 12, in which case the piezoelectric driving unit 30 is formed on the oxide film 10a. The details of the method for forming the piezoelectric driving unit 30 are as follows: first, a first electrode 31 such as titanium nitride (TiN) is formed by sputtering, and the shape of the piezoelectric driving unit 30 is patterned by photolithography and etching. Next, an ashing process is performed using oxygen gas to turn the surface of the titanium nitride into amorphous titanium oxynitride (TiON). Next, a piezoelectric film 32 such as aluminum nitride (AlN) is formed on the titanium oxynitride (TiON) film by sputtering, and the shape of the piezoelectric driving unit 30 is patterned by photolithography and etching. Therefore, the piezoelectric driving unit forming process includes a process of forming the piezoelectric film 32 on the surface of the second surface 20b on which the vibrating arm 24 is formed. After that, a second electrode 33 such as titanium nitride is formed on the piezoelectric film 32 by sputtering, and the shape of the piezoelectric driving unit 30 is patterned by photolithography and etching.

[0029] 1.3.4 Protective film formation process In step S104, as shown in FIG. 13, in order to protect the piezoelectric film 32 of the piezoelectric driving unit 30 from the alkaline aqueous solution (KOH, TMAH) that etches the silicon substrate 10, a protective film 36 which is a silicon oxide film is also formed on the side walls of the piezoelectric driving unit 30 by sputtering or CVD, and the shape of the vibration device 1 is patterned by photolithography and etching techniques.

[0030] 1.3.5 Long groove forming process In step S105, as shown in FIG. 14, at least two bottomed long grooves 41 are formed at a predetermined interval on the second surface 20b, which is one surface of the silicon substrate 10. In this embodiment, four long grooves 41 are formed to form three vibrating arms 24. To explain this step in more detail, the silicon substrate 10 in the area exposed from the oxide film 10a, the temperature characteristic adjustment film 12, and the protective film 36 is dry etched to form a groove including the long groove 41 having a desired depth. In this embodiment, the groove between the vibrating arms 24 in the shape of the vibration device 1 is particularly referred to as the long groove 41.

[0031] In step S105, the side surface 41a of the long groove 41 is the (110) surface of the silicon substrate 10, and the bottom surface 41b is the (100) surface of the silicon substrate 10.

[0032] 1.3.6 Vibrating arm formation process In step S106, the side surface 41a of the long groove 41 is etched by wet etching, and the two long grooves 41 are connected between the second surface 20b in the Z direction, which is the thickness direction of the silicon substrate 10, and the bottom surface 41b of the long groove 41 to form the vibrating arm 24. More specifically, the groove including the long groove 41 is wet etched with an alkaline aqueous solution (KOH, TMAH) to connect the side surfaces 41a of the two long grooves 41 and form a cavity below the vibrating arm 24. During the etching, as shown in FIG. 15, the side surface 41a and the bottom surface 41b of the long groove 41 are etched, and the (111) plane having an angle θ of 54.7 degrees with the (100) plane described in FIG. 7 is precipitated. When the etching is continued until the precipitated (111) planes come into contact, an internal space 27 is formed below the vibrating arm 24, as shown in FIG. 16, and the vibrating arm 24 is formed with a triangular cross section from the Y direction.

[0033] In step S106, the vibrating arm 24 formed has two side surfaces 25 connected to both ends of the second surface 20b, and the two side surfaces 25 approach each other as they move away from the second surface 20b. The two side surfaces 25 are the (111) surfaces of the silicon substrate 10.

[0034] 1.3.7 Protective film removal process In step S107, the protective film 36 is removed using hydrofluoric acid (HF) to obtain a vibration device 1 having an internal space 27 below the vibrating arm 24 and a triangular cross section of the vibrating arm 24 from the Y direction, as shown in FIG. 3.

[0035] As described above, the method for manufacturing the resonator device 1 of the present embodiment allows the resonator device 1 to be manufactured by etching the inexpensive single crystal silicon substrate 10, and therefore makes it possible to obtain a low-cost resonator device 1.

[0036] In this embodiment, four long grooves 41 are formed to form three vibrating arms 24, but this is not limited to this, and it is also possible to form at least two or more bottomed long grooves 41 arranged at a predetermined interval to form the vibrating device 1.

[0037] 2. Second embodiment Next, a vibration device 1a according to a second embodiment will be described with reference to Fig. 17 and Fig. 18. Note that the same reference numerals are used to designate parts common to the first embodiment, and detailed descriptions thereof will be omitted. The following description will focus on parts different from the first embodiment.

[0038] As shown in FIGS. 17 and 18, a vibration device 1a of the second embodiment is different from the vibration device 1 of the first embodiment in the cross-sectional shape of the vibrating arm 51 and the shape of the first surface 50a.

[0039] As shown in Fig. 17, the vibration device 1a is the same as the vibration device 1 of the first embodiment in plan view from the Z direction. However, as shown in Fig. 18, in cross-sectional view from the Y direction, the cross section of the vibration arm 51 is trapezoidal, and the cross-sectional shapes of the first vibrating arm 51a, the second vibrating arm 51b, and the third vibrating arm 51c are the same. In addition, in the base 50, the protruding portion on the second surface 20b side formed by the two recesses 21 is trapezoidal, and the upper side of the trapezoid becomes the first surface 50a having a certain gap with the vibrating arm 51.

[0040] In the manufacturing method of the resonating device 1a of this embodiment, in the above-mentioned resonating arm forming process, after the side surfaces 41a of the two long grooves 41 penetrate each other, wet etching is continued for a desired time, so that the cross section of the resonating arm 51 can be formed into a trapezoidal shape. This is because the (100) plane is precipitated by performing etching for a long time in the part where the (111) planes constituting the side surfaces 25 of the resonating arm 51 contact each other. Therefore, the surface opposite to the second surface 20b of the resonating arm 51 and the first surface 50a become (100) planes. Note that the "trapezoidal shape" includes a case where the upper side and the lower side are each straight and parallel, as well as a case where they are slightly deviated from a straight line or parallel within a range that can be regarded as the same as a straight line or parallel from a technical common sense perspective.

[0041] With this configuration, it is possible to obtain the same effect as the vibration device 1 of the first embodiment. In addition, the rigidity of the vibration arm 51 in the Z direction is weakened, which makes it easier to vibrate the bending vibration displaced in the Z direction perpendicular to the second surface 20b, and it is possible to obtain a vibration device 1a having stable vibration. [Explanation of symbols]

[0042] Reference Signs List 1,1a...vibration device, 10...silicon substrate, 10a...oxide film, 20...base, 20a...first surface, 20b...second surface, 21...recess, 22...support, 23...frame, 24...vibration arm, 24a...first vibrating arm, 24b...second vibrating arm, 24c...third vibrating arm, 25...side, 27...internal space, 30...piezoelectric driving part, 31...first electrode, 32...piezoelectric film, 33...second electrode, 34...wiring, 35...electrode pad, 36...protective film, 40...opening, 41...long groove, 41a...side, 41b...bottom.

Claims

1. A base having a first surface along a first direction; The base portion is disposed on the first surface side thereof with a gap therebetween, and the base portion is disposed along the first direction. a vibrating arm extending from the first surface and having a second surface on an opposite side to the first surface; a first end of the vibrating arm in the first direction, the first end being provided on the first surface of the base and connected to the first end of the vibrating arm in the first direction; a support portion connecting the A method for manufacturing a vibration device comprising: A step of preparing a flat silicon substrate made of single crystal silicon; The silicon substrate is provided with openings on one side thereof at predetermined intervals by dry etching. forming at least two adjacent bottomed slots; The side surface of the groove is etched by wet etching to form a silicon substrate. The two long grooves are connected between the one surface in the thickness direction and a bottom surface of the long groove, The vibrating arm is formed with the portion of the one surface sandwiched between the two openings as the second surface. and A method for manufacturing a vibration device.

2. the side surface of the long groove is a (110) surface of the silicon substrate; The bottom surface of the long groove is a (100) surface of the silicon substrate. The method for manufacturing the vibration device according to claim 1 .

3. The vibrating arm has two ends connected to the second surface in the width direction of the vibrating arm. It has a side surface, The two side surfaces approach each other as they move away from the second surface. A method for manufacturing a vibration device according to claim 1 or 2.

4. The two side surfaces are (111) surfaces of the silicon substrate. The method for manufacturing the vibration device according to claim 3 .

5. A cross section of the vibrating arm is trapezoidal when viewed from the first direction. The method for manufacturing a vibration device according to claim 3 or 4.

6. When the predetermined interval is w and the depth of the long groove is d1, 0.354×d1×2>w meets the following criteria: A method for manufacturing a vibration device according to any one of claims 1 to 5.

7. When the width of the long groove is L and the thickness of the silicon substrate is t, d1+0.706×L<t meets the following criteria: The method for manufacturing a vibration device according to claim 6 .

8. A piezoelectric element is disposed on a portion of the silicon substrate that is to become the second surface of the vibrating arm. forming a film; A method for manufacturing a vibration device according to any one of claims 1 to 7.

9. A base having a first surface along a first direction; The base portion is disposed on the first surface side thereof with a gap therebetween, and the base portion is disposed along the first direction. a vibrating arm extending from the a first end of the vibrating arm in the first direction, the first end being provided on the first surface of the base and connected to the first end of the vibrating arm in the first direction; a support portion connecting the A piezoelectric element is disposed on a second surface of the vibrating arm, the second surface being opposite to the first surface. a membrane; The vibrating arm, the base, and the support are made of a silicon substrate made of single crystal silicon. It consists of a board, The vibrating arm has two ends connected to the second surface in the width direction of the vibrating arm. It has a side surface, The two side surfaces approach each other as they move away from the second surface. Vibration devices.

10. The vibration arms include first vibration arms arranged along a second direction perpendicular to the first direction. A second vibrating arm, the base includes a recess in the first surface; The width of the first vibrating arm is W, the distance between the first vibrating arm and the second vibrating arm is L, When the distance from the second surface of the arm to the bottom of the recess on the first surface is d2, (W / 0.708)+0.706×L<d2 meets the following criteria: The vibration device according to claim 9.

11. The cross section of the vibrating arm is trapezoidal when viewed from the direction in which the vibrating arm extends. A vibration device according to claim 9 or 10.

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