Vibration device

Abstract

To provide a vibration device which enables the resonance frequency of torsional vibration and the resonance frequency of flexural vibration to be tuned independently of each other, and enables the difference in these resonance frequencies to be easily tuned to a predetermined value.SOLUTION: A vibration device includes: a vibration substrate that includes a base, a flexural vibration arm joined to the base, and a torsional vibration arm joined to the base; a flexural vibration driver disposed on the vibration substrate and causing flexural vibration of the flexural vibration arm; and a torsional vibration driver disposed on the vibration substrate and causing torsional vibration of the torsional vibration arm.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a vibration element. [Background technology]

[0002] For example, in the tuning fork type crystal resonator described in Patent Document 1, the difference in resonance frequency between bending vibration and torsional vibration is set to within 15%, so that the tuning fork type crystal resonator is driven in a mode in which bending vibration and torsional vibration are coupled, improving the resonance frequency temperature characteristic. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 62-46092 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the tuning fork type quartz crystal resonator of Patent Document 1, bending vibration and torsional vibration are excited by a common vibrating arm, so the resonant frequency of the torsional vibration and the resonant frequency of the bending vibration cannot be adjusted independently, and it is difficult to adjust the difference between these resonant frequencies to a predetermined value. [Means for solving the problem]

[0005] The vibration element according to the present invention includes a vibration substrate having a base, a bending vibration arm connected to the base, and a torsion vibration arm connected to the base; a flexural vibration drive section disposed on the vibration substrate and causing the flexural vibration arms to flexurally vibrate; The vibration actuator further comprises a torsional vibration drive section disposed on the vibration substrate and configured to torsionally vibrate the torsional vibration arm. [Brief description of the drawings]

[0006] [Figure 1] 1 is a plan view of a MEMS element according to a first embodiment. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] 2 is a cross-sectional view taken along line CC in FIG. 1. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 4 is a cross-sectional view of a bending vibrating arm. [Figure 9] 5A and 5B are diagrams illustrating a driving state of a vibration element. [Figure 10] FIG. 4 is a diagram showing resonant frequency temperature characteristics. [Figure 11] FIG. 4 is a diagram showing resonant frequency temperature characteristics. [Figure 12] 13 is a perspective view showing a torsional vibration arm of a vibration element according to a second embodiment. FIG. [Figure 13] 13 is a perspective view showing a torsional vibration arm of a vibration element according to a second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a vibration element of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[0008] First Embodiment FIG. 1 is a plan view of the MEMS element according to the first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a cross-sectional view taken along line BB in FIG. 1. FIG. 4 is a cross-sectional view taken along line CC in FIG. 1. FIG. 5 is a plan view of the vibration element. FIGS. 6 and 7 are cross-sectional views of the torsional vibration arms, respectively. FIG. 8 is a cross-sectional view of the bending vibration arms. FIG. 9 is a diagram showing the driving state of the vibration element. FIGS. 10 and 11 are diagrams showing the resonant frequency temperature characteristics, respectively.

[0009] For ease of explanation, each of Figures 1 to 9 illustrates an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other. The arrow side of each axis is also called the "plus side," and the opposite side is also called the "minus side." The plus side of the Z-axis is also called the "upper" and the minus side is also called the "lower."

[0010] 1, the MEMS element 1 includes an SOI (Silicon on Insulator) substrate 10 on which a vibration element 20 is formed, and a lid 5 for hermetically sealing the vibration element 20. The lid 5 is made of single crystal silicon or the like, and has a recess that opens to the bottom surface. The bottom surface of the lid 5 is bonded to the top surface of the SOI substrate 10.

[0011] 2 and 3, the SOI substrate 10 is a substrate in which a silicon layer 11, a BOX (Buried Oxide) layer 12, and a surface silicon layer 13 are laminated in this order. For example, the silicon layer 11 and the surface silicon layer 13 are made of single crystal silicon, and the BOX layer 12 is made of a silicon oxide layer (SiO2 or the like).

[0012] In addition, the surface silicon layer 13 is formed with a vibration substrate 21 and a frame-shaped frame portion 131 surrounding the periphery of the vibration substrate 21. As shown in FIG. 2, a pair of electrode pads PAD1 and PAD2 are arranged on the upper surface of the frame portion 131. In addition, at positions overlapping with the electrode pads PAD1 and PAD2, through electrodes 14 and 15 are formed which penetrate the SOI substrate 10 in the thickness direction. The through electrode 14 is electrically connected to the electrode pad PAD1, and the through electrode 15 is electrically connected to the electrode pad PAD2. As a result, the electrode pads PAD1 and PAD2 are drawn out to the outside of the MEMS element 1.

[0013] The vibration element 20 has a vibration substrate 21 formed on the surface silicon layer 13. That is, the vibration substrate 21 is formed from a silicon substrate. This allows the vibration substrate 21 to be formed by a silicon wafer process, which makes it easy to process the vibration substrate 21 and allows the vibration substrate 21 to be formed with high processing accuracy. As shown in FIG. 1 to FIG. 4, the vibration substrate 21 has a base 210 supported by the silicon layer 11 and the BOX layer 12, three bending vibration arms 211, 212, and 213 separated from the BOX layer 12, and two torsion vibration arms 221 and 222 separated from the BOX layer 12. The vibration substrate 21 is formed with the same thickness as the surface silicon layer 13 in its entirety.

[0014] 5, the bending vibration arms 211, 212, and 213 each extend from a tip end, which is the end on the Y-axis direction positive side of the base 210, toward the Y-axis direction positive side, and are arranged side by side at equal intervals in the X-axis direction. The bending vibration arms 211, 212, and 213 are aligned to have the same shape. Each of the bending vibration arms 211, 212, and 213 bends and vibrates in the Z-axis direction.

[0015] Moreover, a frequency adjustment film M1 for adjusting the resonance frequency fr1 of the bending vibration is disposed on the upper surface of the tip of the bending vibration arms 211, 212, and 213. The resonance frequency fr1 can be adjusted by removing a part of the frequency adjustment film M1 by laser irradiation or the like as necessary. However, the configuration of the bending vibration arms 211, 212, and 213 is not particularly limited, and the frequency adjustment film M1 may be omitted.

[0016] The torsion vibration arm 221 extends from the end of the base 210 on the positive side in the X-axis direction toward the positive side in the X-axis direction, and the torsion vibration arm 222 extends from the end of the base 210 on the negative side in the X-axis direction toward the negative side in the X-axis direction. That is, the torsion vibration arms 221 and 222 are located on opposite sides of each other via the base 210. This allows the torsion vibration arms 221 and 222 to be arranged in a well-balanced manner within the vibration element 20. In addition, the torsion vibration arms 221 and 222 are aligned to have the same shape. These torsion vibration arms 221 and 222 each torsionally vibrate around their central axis J. That is, the torsion vibration arms 221 and 222 torsionally vibrate around the X-axis.

[0017] However, the arrangement of the torsion vibration arms 221, 222 is not particularly limited, and the torsion vibration arms 221, 222 may both extend from the end of the base 210 on the positive side in the X-axis direction toward the positive side in the X-axis direction, or the torsion vibration arms 221, 222 may both extend from the end of the base 210 on the negative side in the X-axis direction toward the negative side in the X-axis direction. In addition, the torsion vibration arms 221, 222 may extend from the end of the base 210 on the positive side in the Y-axis direction toward the positive side in the Y-axis direction in line with the flexion vibration arms 211, 212, 213.

[0018] Moreover, the torsion vibration arm 221 has an arm 221a extending from the base 210 to the positive side in the X-axis direction, and a weight 221b arranged at the tip of the arm 221a. Similarly, the torsion vibration arm 222 has an arm 222a extending from the base 210 to the negative side in the X-axis direction, and a weight 222b arranged at the tip of the arm 222a.

[0019] Also, as shown in FIGS. 6 and 7, the width W2a of the arms 221a and 222a, that is, the length in the Y-axis direction, is smaller than the thickness D2a of the arms 221a and 222a, that is, the length in the Z-axis direction. That is, W2a < D2a. As a result, the cross-sectional shape of the arms 221a and 222a becomes a rectangle extending in the Z-axis direction, so that the torsion vibration arms 221 and 222 are likely to torsionally vibrate about the X-axis. However, the shape of the arms 221a and 222a is not particularly limited, and for example, W2a > D2a or W2a = D2a may be possible as in the second embodiment described later.

[0020] Also, as shown in FIG. 5, the width W2b of the weights 221b and 222b, that is, the length in the Y-axis direction, is larger than the width W2a of the arms 221a and 222a. That is, W2b > W2a. According to such a configuration, due to the mass effect of the weights 221b and 222b, even if the resonance frequency fr2 described later is the same as when the weights 221b and 222b are not present, the overall length of the torsion vibration arms 221 and 222 can be shortened. Therefore, the size of the vibration element 20 can be reduced. However, the configuration of the torsion vibration arms 221 and 222 is not particularly limited, and the weights 221b and 222b may be omitted.

[0021] In particular, the weights 221b and 222b each extend along the X-axis direction, that is, the extending direction of the bending vibration arms 211, 212, and 213. And the width W2b of the weights 221b and 222b is larger than the length L2b, that is, the length in the X-axis direction. That is, W2b > L2b. According to such a configuration, the weights 221b and 222b can be formed larger while suppressing the overall length of the vibration element 20 in the Y-axis direction. Therefore, the size of the vibration element 20 can be reduced. However, the configuration of the weights 221b and 222b is not particularly limited, and for example, W2b ≤ L2b may be possible.

[0022] 5, the ends of the weights 221b and 222b on the positive side in the Y-axis direction are located on the negative side in the Y-axis direction from the tips F1 of the bending vibration arms 211, 212, and 213, and the ends on the negative side in the Y-axis direction are located on the positive side in the Y-axis direction from the base end F2 of the base 210. With this configuration, it is possible to suppress the overall length of the vibration element 20 in the Y-axis direction while preventing an increase in the overall length of the vibration element 20 in the X-axis direction due to the addition of the torsional vibration arms 221 and 222. Therefore, it is possible to miniaturize the vibration element 20. However, the configuration of the weights 221b and 222b is not particularly limited, and for example, the ends of the weights 221b and 222b on the positive side in the Y-axis direction may be located on the positive side in the Y-axis direction from the tips of the bending vibration arms 211, 212, and 213, or the ends on the negative side in the Y-axis direction may be located on the negative side in the Y-axis direction from the base end of the base 210.

[0023] Furthermore, a frequency adjustment film M2 for adjusting the resonance frequency fr2 of the torsional vibration is disposed on the weights 221b and 222b. The resonance frequency fr2 can be adjusted by removing a part of the frequency adjustment film M2 by laser irradiation or the like as necessary. In particular, the frequency adjustment film M2 is disposed asymmetrically with respect to the central axis J in a plan view from the Z-axis direction. In this embodiment, the frequency adjustment film M2 is disposed at a distance from the central axis J on the positive side in the Y-axis direction. With this configuration, the centers of gravity of the torsional vibration arms 221 and 222 are shifted from the central axis J in a plan view from the Z-axis direction, so that it becomes easier to excite the torsional vibration of the torsional vibration arms 221 and 222. However, the arrangement of the frequency adjustment film M2 is not particularly limited.

[0024] As shown in FIG. 5, the vibration element 20 further includes a flexural vibration driver 23 that flexurally vibrates the flexural vibration arms 211, 212, and 213 in the Z-axis direction, and a torsional vibration driver 24 that flexurally vibrates the torsional vibration arms 221 and 222 around the X-axis.

[0025] 8, the bending vibration driving section 23 is disposed on the upper surface of the vibration substrate 21. Specifically, the bending vibration driving section 23 has a piezoelectric element 23A disposed on the upper surface of the bending vibration arm 211, a piezoelectric element 23B disposed on the upper surface of the bending vibration arm 212, and a piezoelectric element 23C disposed on the upper surface of the bending vibration arm 213. These piezoelectric elements 23A, 23B, and 23C have the same configuration. The piezoelectric elements 23A, 23B, and 23C each have a lower electrode 231 disposed on the upper surfaces of the bending vibration arms 211, 212, and 213, a piezoelectric layer 232 disposed on the upper surface of the lower electrode 231, and an upper electrode 233 disposed on the upper surface of the piezoelectric layer 232.

[0026] 9, the piezoelectric elements 23A, 23B, and 23C are wired so that the adjacent bending vibration arms 211, 212, and 213 bend and vibrate in opposite phases. That is, the piezoelectric elements 23A, 23B, and 23C are wired so that a first state in which the bending vibration arms 211 and 213 bend and deform upward and the bending vibration arm 212 bends and deforms downward, and a second state in which the bending vibration arms 211 and 213 bend and deform downward and the bending vibration arm 212 bends and deforms upward are alternately repeated. Specifically, the lower electrodes 231 of the piezoelectric elements 23A and 23C and the upper electrode 233 of the piezoelectric element 23B are electrically connected to the electrode pad PAD1 via wiring (not shown), and the upper electrodes 233 of the piezoelectric elements 23A and 23C and the lower electrode 231 of the piezoelectric element 23B are electrically connected to the electrode pad PAD2 via wiring (not shown). In this way, by making the adjacent flexural vibration arms 211, 212, and 213 flexurally vibrate in opposite phases to each other, the vibrations of the flexural vibration arms 211, 212, and 213 are cancelled out, and vibration leakage of the vibration element 20 can be effectively suppressed.

[0027] As shown in FIG. 5, the torsional vibration driving unit 24 is disposed on the upper surface of the vibration substrate 21. Specifically, the torsional vibration driving unit 24 has a pair of piezoelectric elements 24A and 24B disposed on the upper surface of the arm portion 221a of the torsional vibration arm 221, and a pair of piezoelectric elements 24C and 24D disposed on the upper surface of the arm portion 222a of the torsional vibration arm 222. The pair of piezoelectric elements 24A and 24B are disposed so as to sandwich the central axis J of the arm portion 221a between them in a plan view from the Z-axis direction. That is, the piezoelectric element 24A is disposed on the positive side of the central axis J in the Y-axis direction, and the piezoelectric element 24B is disposed on the negative side of the Y-axis direction. With this arrangement, it is easy to torsionally vibrate the torsional vibration arm 221. Similarly, the pair of piezoelectric elements 24C and 24D are disposed so as to sandwich the central axis J of the arm portion 222a between them in a plan view from the Z-axis direction. That is, the piezoelectric element 24C is disposed on the positive side in the Y axis direction of the central axis J, and the piezoelectric element 24D is disposed on the negative side in the Y axis direction of the central axis J. With such an arrangement, it is possible to easily cause the torsional vibration arm 222 to torsionally vibrate.

[0028] As shown in Figures 6 and 7, these piezoelectric elements 24A, 24B, 24C, and 24D have the same configuration as each other, and have a lower electrode 241 arranged on the upper surfaces of the arms 221a and 222a, a piezoelectric layer 242 arranged on the upper surface of the lower electrode 241, and an upper electrode 243 arranged on the upper surface of the piezoelectric layer 242.

[0029] 9, the piezoelectric elements 24A, 24B, 24C, and 24D are wired so that the torsional vibration arms 221 and 222 vibrate in opposite phases. That is, the piezoelectric elements 24A, 24B, 24C, and 24D are wired so that, in a plan view from the positive side in the X-axis direction, a first state in which the torsional vibration arm 221 is torsionally deformed clockwise and the torsional vibration arm 222 is torsionally deformed counterclockwise and a second state in which the torsional vibration arm 221 is torsionally deformed counterclockwise and the torsional vibration arm 222 is torsionally deformed clockwise are alternately repeated. Specifically, the upper electrodes 243 of the piezoelectric elements 24A and 24D and the lower electrodes 241 of the piezoelectric elements 24B and 24C are electrically connected to the electrode pad PAD1 via wiring (not shown), and the lower electrodes 241 of the piezoelectric elements 24A and 24D and the upper electrodes 243 of the piezoelectric elements 24B and 24C are electrically connected to the electrode pad PAD2 via wiring (not shown). In this way, by causing the torsional vibration arms 221 and 222 to torsionally vibrate in opposite phases to each other, the vibrations of the torsional vibration arms 221 and 222 are cancelled, and vibration leakage of the vibration element 20 can be effectively suppressed.

[0030] In this manner, the piezoelectric elements 23A, 23B, and 23C of the bending vibration drive unit 23 and the piezoelectric elements 24A, 24B, 24C, and 24D of the torsional vibration drive unit 24 are electrically connected to the electrode pads PAD1 and PAD2, thereby electrically coupling the bending vibration drive unit 23 and the torsional vibration drive unit 24. Note that the constituent materials of the piezoelectric elements 23A, 23B, 23C, 24A, 24B, 24C, and 24D are not particularly limited, but for example, the piezoelectric layers 232 and 242 are made of aluminum nitride (AlN) or the like, and the lower electrodes 231 and 241 and the upper electrodes 233 and 243 are made of titanium nitride (TiN) or the like.

[0031] Here, when the resonant frequency of the bending vibration of the bending vibration arms 211, 212, and 213 is fr1, and the resonant frequency of the torsional vibration of the torsional vibration arms 221 and 222 is fr2, the resonant frequencies fr1 and fr2 are adjusted so that the difference Δfr (=|fr1-fr2|) between the resonant frequency fr1 and the resonant frequency fr2 is 1% or less of the resonant frequency fr1. Specifically, the resonant frequency fr1 is adjusted to a desired frequency, for example, 32 kHz, and the resonant frequency fr2 is adjusted to be within 1% of the resonant frequency fr1. This makes it possible to simultaneously excite the bending vibration of the bending vibration arms 211, 212, and 213 and the torsional vibration of the torsional vibration arms 221 and 222, and to couple the torsional vibration with the bending vibration.

[0032] The difference Δfr may be 1% or less of the resonance frequency fr1, but is preferably 0.1% or less, more preferably 0.01% or less, and even more preferably zero. This makes it possible to more reliably excite the bending vibration of the bending vibration arms 211, 212, and 213 and the torsional vibration of the torsional vibration arms 221 and 222 simultaneously. In this embodiment, the "bending vibration" refers to a fundamental wave (fundamental wave mode), not a harmonic wave (higher mode). Similarly, the "torsional vibration" refers to a fundamental wave (fundamental wave mode), not a harmonic wave (higher mode).

[0033] In this way, the torsional vibration and the bending vibration are coupled, and thus the resonant frequency temperature characteristic of the vibration element 20 can be improved. For example, as shown in FIG. 10, the resonant frequency temperature characteristic of the vibration element 20 in which the torsional vibration is coupled to the bending vibration has a smaller change in frequency with respect to temperature than the resonant frequency temperature characteristic of the vibration element 20 having only the bending vibration, and has excellent resonant frequency temperature characteristics. Note that FIG. 10 shows a first-order resonant frequency temperature characteristic, but in the case where the vibration substrate 21 is formed from the ion-doped surface silicon layer 13, for example, as shown in FIG. 11, the resonant frequency temperature characteristic becomes a second-order resonant frequency temperature characteristic. Even in this case, the resonant frequency temperature characteristic of the vibration element 20 in which the torsional vibration is coupled to the bending vibration has a smaller change in frequency with respect to temperature than the resonant frequency temperature characteristic of the vibration element 20 having only the bending vibration, and has excellent resonant frequency temperature characteristics.

[0034] In the vibration element 20, since the bending vibration arms 211, 212, and 213 and the torsional vibration arms 221 and 222 are separately provided, the resonance frequencies fr1 and fr2 can be adjusted independently. Therefore, the difference Δfr can be easily adjusted to within a predetermined value while easily adjusting the resonance frequency fr1 to a desired frequency.

[0035] The resonant frequency fr2 is likely to be higher than the resonant frequency fr1. For example, in the case of a quartz crystal resonator, due to the limit of processing accuracy of wet etching, when the resonant frequency fr1 is 32 kHz, the resonant frequency fr2 can only be reduced to about 100 kHz. In contrast, in the case of the resonator element 20 formed from a silicon substrate (surface silicon layer 13) as in this embodiment, high-precision microfabrication is possible using a silicon wafer process, i.e., dry etching, and it is possible to form the width W2a of the arm parts 221a, 222a of the torsional resonating arms 221, 222 narrower. Therefore, the resonant frequency fr2 can be easily reduced to the level of the resonant frequency fr1.

[0036] In the vibration element 20 having such a configuration, by applying a driving voltage between the electrode pads PAD1 and PAD2, as shown in FIG. 9, the piezoelectric elements 23A and 23C and the piezoelectric element 23B expand and contract in opposite phases, the adjacent bending vibration arms 211, 212, and 213 bend and vibrate in opposite phases in the Z-axis direction, and the piezoelectric elements 24A and 24D and the piezoelectric elements 24B and 24C expand and contract in opposite phases, and the torsional vibration arms 221 and 222 torsionally vibrate in opposite phases around the X-axis. As a result, the torsional vibration of the torsional vibration arms 221 and 222 is coupled to the bending vibration of the bending vibration arms 211, 212, and 213, and the above-mentioned effect is exerted. The bending vibration of the bending vibration arms 211, 212, and 213 is greatly excited at the resonance frequency fr1, and the impedance becomes the minimum. As a result, by connecting this MEMS element 1 to an oscillation circuit, it transmits at an oscillation frequency determined by the resonance frequency fr1.

[0037] The above has described the MEMS element 1. As described above, the vibration element 20 provided in such a MEMS element 1 includes a vibration substrate 21 having a base 210, bending vibration arms 211, 212, and 213 connected to the base 210, and torsional vibration arms 221 and 222 connected to the base 210, a bending vibration driver 23 arranged on the vibration substrate 21 and causing the bending vibration arms 211, 212, and 213 to bend and vibrate, and a torsional vibration driver 24 arranged on the vibration substrate 21 and causing the torsional vibration arms 221 and 222 to bend and vibrate. In this way, by separately providing the bending vibration arms 211, 212, and 213 that bend and the torsional vibration arms 221 and 222 that bend and vibrate, the resonance frequency fr1 of the bending vibration and the resonance frequency fr2 of the torsional vibration can be adjusted independently. Therefore, the difference Δfr between the resonance frequencies fr1 and fr2 can be easily adjusted to within a predetermined value while keeping the resonance frequency fr1 in a desired frequency band.

[0038] As described above, the torsional vibrating arms 221, 222 have the arms 221a, 222a extending from the base 210. The width W2a of the arms 221a, 222a is smaller than the thickness D2a of the arms 221a, 222a. This allows the torsional vibrating arms 221, 222 to have a shape that easily vibrates torsionally.

[0039] As described above, the torsional vibration arms 221 and 222 have weights 221b and 222b disposed at the tips of the arms 221a and 222a, and the width W2b of the weights 221b and 222b is greater than the width W2a of the arms 221a and 222a. With this configuration, the mass effect of the weights 221b and 222b allows the overall length of the torsional vibration arms 221 and 222 to be shorter than the case where the weights 221b and 222b are not present, even if the resonant frequency fr2 described below is the same. Therefore, the vibration element 20 can be made smaller.

[0040] As described above, the weights 221b and 222b extend along the extension direction of the bending vibration arms 211, 212, and 213. This allows the weights 221b and 222b to be formed larger while suppressing the length of the vibration element 20 in the Y-axis direction. This allows the vibration element 20 to be made smaller.

[0041] As described above, the vibration substrate 21 has a pair of torsional vibration arms 221, 222 located on opposite sides of the base 210. The torsional vibration driver 24 torsionally vibrates the pair of torsional vibration arms 221, 222 in opposite phases to each other. This cancels out the vibrations of the torsional vibration arms 221, 222, making it possible to effectively suppress vibration leakage from the vibration element 20.

[0042] As described above, the vibration substrate 21 has three flexural vibration arms 211, 212, and 213 arranged side by side in a direction perpendicular to the extension direction, i.e., in the X-axis direction. The flexural vibration driver 23 flexurally vibrates the pair of flexural vibration arms 211 and 213 located on both sides and the flexural vibration arm 212 located in the center in opposite phases. This cancels out the vibrations of the flexural vibration arms 211, 212, and 213, making it possible to effectively suppress vibration leakage from the vibration element 20.

[0043] As described above, the vibration substrate 21 is formed from the surface silicon layer 13, which is a silicon substrate. This allows the vibration substrate 21 to be formed by a silicon wafer process, which makes it easy to process the vibration substrate 21 and allows the vibration substrate 21 to be formed with high processing accuracy.

[0044] <Second embodiment> 12 and 13 are perspective views showing torsional vibrating arms of the vibration element according to the second embodiment.

[0045] This embodiment is similar to the first embodiment described above, except that the shapes of the torsional vibration arms 221 and 222 are different. In the following description, the present embodiment will be described focusing on the differences from the first embodiment described above, and the description of the similarities will be omitted. In addition, in each drawing of this embodiment, the same reference numerals are used for the same configurations as the above-mentioned embodiment.

[0046] 12 and 13, in the vibration element 20 of this embodiment, the width W2a of the arms 221a, 222a is larger than the thickness D2a of the arms 221a, 222a. In other words, W2a>D2a. This makes the cross-sectional shape of the arms 221a, 222a a rectangle extending in the Y-axis direction, which makes it easier for the torsional vibration arms 221, 222 to vibrate torsionally.

[0047] In particular, in this embodiment, the thickness D2a of the arms 221a and 222a is thinner than the thickness D of the vibration substrate 21, that is, the thickness of the surface silicon layer 13. This reduces the rigidity of the arms 221a and 222a, and the resonant frequency fr2 can be easily reduced to the level of the resonant frequency fr1. Such arms 221a and 222a are formed by thinning the vibration substrate 21 from the upper surface side. This makes it easy to form the arms 221a and 222a. However, this is not limited to the above, and for example, the arms 221a and 222a may be formed by thinning the vibration substrate 21 from the lower surface side.

[0048] In the vibration element 20 as described above, the torsional vibrating arms 221, 222 have arm portions 221a, 222a extending from the base portion 210. The width W2a of the arm portions 221a, 222a is greater than the thickness D2a of the arm portions 221a, 222a. This allows the torsional vibrating arms 221, 222 to have a shape that easily vibrates torsionally.

[0049] The second embodiment as described above can also achieve the same effects as the first embodiment.

[0050] Although the vibration element of the present invention has been described above based on the illustrated embodiment, the present invention is not limited thereto. The configuration of each part can be replaced with any configuration having a similar function. In addition, any other configuration may be added to the present invention. In addition, the present invention may be a combination of any two or more configurations of the above-mentioned embodiments. [Explanation of symbols]

[0051] 1...MEMS element, 10...SOI substrate, 11...silicon layer, 12...BOX layer, 13...surface silicon layer, 131...frame portion, 14...through electrode, 15...through electrode, 20...vibration element, 21...vibration substrate, 210...base portion, 211...flexural vibration arm, 212...flexural vibration arm, 213...flexural vibration arm, 221...torsion vibration arm, 221a...arm portion, 221b...weight portion, 222...torsion vibration arm, 222a...arm portion, 222b...weight portion, 23...flexural vibration drive portion, 23A...piezoelectric element, 23B...piezoelectric element, 2 3C...piezoelectric element, 231...lower electrode, 232...piezoelectric layer, 233...upper electrode, 24...torsional vibration drive unit, 24A...piezoelectric element, 24B...piezoelectric element, 24C...piezoelectric element, 24D...piezoelectric element, 241...lower electrode, 242...piezoelectric layer, 243...upper electrode, 5...lid, D...thickness, D2a...thickness, F1...tip, F2...base end, J...center axis, M1...frequency adjustment film, M2...frequency adjustment film, PAD1...electrode pad, PAD2...electrode pad, W2a...width, W2b...width, L2b...length

Claims

1. a vibration substrate having a base, a bending vibration arm connected to the base, and a torsion vibration arm connected to the base; a flexural vibration drive section disposed on the vibration substrate and causing the flexural vibration arms to flexurally vibrate; a torsional vibration drive section disposed on the vibration substrate and configured to torsionally vibrate the torsional vibration arms,

2. The torsional vibration arm has an arm portion extending from the base portion, The vibration element according to claim 1 , wherein the width of the arm portion is smaller than the thickness of the arm portion.

3. The torsional vibration arm has an arm portion extending from the base portion, The vibration element according to claim 1 , wherein the width of the arm portion is greater than the thickness of the arm portion.

4. The torsional vibration arm has a weight portion disposed on a tip side of the arm portion, The vibration element according to claim 2 , wherein the width of the weight portion is greater than the width of the arm portion.

5. The vibration element according to claim 4 , wherein the weight portion extends along the extending direction of the flexural vibration arms.

6. the vibration substrate has a pair of the torsional vibration arms positioned on opposite sides of the base, The vibration element according to claim 1 , wherein the torsional vibration drive section causes the pair of torsional vibration arms to torsionally vibrate in opposite phases to each other.

7. The vibration substrate has three of the bending vibration arms arranged side by side in a direction perpendicular to the extension direction, The vibration element according to claim 1 , wherein the flexural vibration drive section flexibly vibrates the pair of flexural vibration arms located on both sides and the flexural vibration arm located in the center in mutually opposite phases.

8. The vibration element according to claim 1 , wherein the silicon substrate is formed from a silicon substrate.

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