Vibration element

Abstract

To provide a vibration element that can reduce consumption power.SOLUTION: A vibration element includes: a vibration substrate having a first surface and a second surface that are in a front-back relation, and including a base part and a vibration arm extending from the base part; and a piezoelectric element disposed on the first surface of the vibration arm. The piezoelectric element includes a first electrode disposed on the first surface of the vibration arm, a piezoelectric layer disposed on a surface of the first electrode on the opposite side of the vibration arm, and a second electrode disposed on a surface of the piezoelectric layer on the opposite side of the first electrode. When a direction orthogonal to a first direction where the vibration arm extends is a second direction in a plan view of the vibration substrate, the length, in the second direction, in a region from the base part of the vibration arm to a tip of the second electrode is more than or equal to the length, in the second direction, at a base end of the vibration arm, and in the tip of the second electrode, the length of the second electrode in the second direction decreases toward the tip side.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] For example, the vibrating piece described in Patent Document 1 has a base, three arms extending from the base, and a piezoelectric element disposed on the upper surface of each arm. Each piezoelectric element has a lower electrode disposed on the upper surface of the arm, a piezoelectric layer disposed on the upper surface of the lower electrode, and an upper electrode disposed on the upper surface of the piezoelectric layer. In such a vibrating piece, the arms at both ends and the arm in the center vibrate in a bending manner in the Z-axis direction in opposite phases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-164130 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a vibrating arm such as that in Patent Document 1, if the upper electrode provided on the piezoelectric layer is formed wide in order to increase the amplitude of the bending vibration of the arm and reduce the equivalent series resistance R1 of the vibrating arm, the equivalent parallel capacitance C0 of the vibrating arm increases. When the equivalent parallel capacitance C0 increases, the effective resistance Re of the vibrating arm increases, and the power consumption when the vibrating arm is oscillated increases. When the load capacitance is CL, the effective resistance Re is expressed as Re=R1×(1+C0 / CL) 2 It is expressed as: [Means for solving the problem]

[0005] The vibration element according to the present invention includes a vibration substrate having a first surface and a second surface that are in a front-back relationship, a base portion, and a vibration arm extending from the base portion; a piezoelectric element disposed on the first surface of the vibrating arm; The piezoelectric element is A first electrode disposed on a first surface of the vibrating arm; a piezoelectric layer disposed on a surface of the first electrode opposite to the vibrating arm; a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode; In a plan view of the vibration substrate, when a direction perpendicular to a first direction in which the vibration arms extend is defined as a second direction, a length in the second direction in a region between the base of the vibrating arm and the tip of the second electrode is equal to or greater than a length in the second direction at the base end of the vibrating arm, At a tip portion of the second electrode, the length of the second electrode in the second direction decreases toward the tip side.

[0006] The vibration element according to the present invention includes a vibration substrate having a first surface and a second surface that are in a front-back relationship, a base portion, and a vibration arm extending from the base portion; a piezoelectric element disposed on the first surface of the vibrating arm; The piezoelectric element is A first electrode disposed on a first surface of the vibrating arm; a piezoelectric layer disposed on a surface of the first electrode opposite to the vibrating arm; a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode; In a plan view of the vibration substrate, when a direction perpendicular to a first direction in which the vibration arms extend is defined as a second direction, a length in the second direction in a region between the base of the vibrating arm and the tip of the second electrode is equal to or greater than a length in the second direction at the base end of the vibrating arm, the vibrating arm has a first region on the first surface and a second region located closer to a base end than the first region, a length of the first region in the second direction is equal to or less than a length of the second region in the second direction; The ratio of an area of ​​the second electrode disposed in the first region to an area of ​​the first region is smaller than the ratio of an area of ​​the second electrode disposed in the second region to an area of ​​the second region. [Brief description of the drawings]

[0007] [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] 2 is a plan view of a vibration element included in the MEMS element. FIG. [Figure 4] 3 is a cross-sectional view of a vibrating arm of the vibration element. FIG. [Diagram 5] FIG. 13 is a plan view showing a modified example of the vibration element. [Figure 6] 11A and 11B are diagrams illustrating stress distribution when a vibrating arm is bent and deformed. [Figure 7] FIG. 11 is a plan view showing a vibration element according to a second embodiment. [Figure 8] FIG. 11 is a plan view showing a vibration element according to a third embodiment. [Figure 9] FIG. 13 is a plan view showing a vibration element according to a fourth embodiment. [Figure 10] FIG. 13 is a plan view showing a vibration element according to a fifth embodiment. [Figure 11] FIG. 13 is a plan view showing a vibration element according to a sixth embodiment. [Figure 12] FIG. 13 is a plan view showing a vibration element according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 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.

[0009] 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 plan view of a vibration element included in the MEMS element. Fig. 4 is a cross-sectional view of a vibrating arm included in the vibration element. Fig. 5 is a plan view showing a modified example of the vibration element. Fig. 6 is a diagram showing stress distribution when the vibrating arm is bent and deformed.

[0010] For ease of explanation, each of Figs. 1 to 5 illustrates an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other. The direction along the X-axis is also called the X-axis direction, the direction along the Y-axis is also called the Y-axis direction, and the direction along the Z-axis is also called the Z-axis direction. The X-axis direction corresponds to the "second direction," and the Y-axis direction corresponds to the "first direction." 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 direction is also called the "upper" and the negative side is also called the "lower."

[0011] 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.

[0012] 2, the SOI substrate 10 is a substrate in which a silicon layer 11 serving as a handle layer, a BOX (Buried Oxide) layer 12, and a surface silicon layer 13 serving as a device layer are laminated in this order. For example, the silicon layer 11 and the surface silicon layer 13 are each made of single crystal silicon, and the BOX layer 12 is made of a silicon oxide layer (SiO2, etc.).

[0013] 1, the surface silicon layer 13 is formed with a vibration substrate 21 and a frame-shaped frame portion 131 surrounding 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. At positions overlapping with the electrode pads PAD1 and PAD2, through electrodes 14 and 15 are formed to 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.

[0014] 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. By forming the vibration substrate 21 from a silicon substrate, the vibration substrate 21 can be formed using 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.

[0015] The vibration substrate 21 is plate-shaped and has an upper surface as a first surface and a lower surface as a second surface that are reversed. As shown in Fig. 3, the vibration substrate 21 has a base 210 and three vibrating arms 211, 212, and 213 extending from the base 210. As shown in Fig. 4, the base 210 is supported by the silicon layer 11 and the BOX layer 12, and the vibrating arms 211, 212, and 213 are separated from the BOX layer 12. The vibration substrate 21 is formed with the same thickness as the surface silicon layer 13.

[0016] 3, the vibrating arms 211, 212, and 213 each extend from a tip end, which is the end on the Y-axis positive side of the base 210, toward the Y-axis positive side, and are arranged at equal intervals in the X-axis direction. The vibrating arms 211, 212, and 213 are aligned to have the same shape. Each of the vibrating arms 211, 212, and 213 flexurally vibrates in the Z-axis direction.

[0017] Furthermore, the piezoelectric elements 23A, 23B, and 23C are disposed on the upper surfaces of the vibrating arms 211, 212, and 213. The width W1 in the region Q from the base end of the vibrating arms 211, 212, and 213 to the tip of the upper electrode 233 of the piezoelectric elements 23A, 23B, and 23C, that is, the length in the X-axis direction, is equal to or greater than the width at the base end of the vibrating arms 211, 212, and 213. In particular, in this embodiment, the vibrating arms 211, 212, and 213 are straight, and the width W1 is equal to the width at the base end of the vibrating arms 211, 212, and 213. However, this is not limited thereto, and for example, as shown in FIG. 5, the width W1 in the region Q of the vibrating arms 211, 212, and 213 may be greater than the width at the base end of the vibrating arms 211, 212, and 213.

[0018] As shown in FIG. 3, the vibration element 20 further includes a flexural vibration driving section 23 that flexibly vibrates the vibrating arms 211, 212, and 213 in the Z-axis direction. The flexural vibration driving section 23 includes a piezoelectric element 23A arranged on the upper surface of the vibrating arm 211, a piezoelectric element 23B arranged on the upper surface of the vibrating arm 212, and a piezoelectric element 23C arranged on the upper surface of the vibrating arm 213. The piezoelectric elements 23A, 23B, and 23C are shorter than the entire length of the vibrating arms 211, 212, and 213, and are arranged in an area about half the base end side of the vibrating arms 211, 212, and 213 in this embodiment. Such piezoelectric elements 23A, 23B, and 23C each expand and contract in the Y-axis direction by energization. Then, by expanding and contracting the piezoelectric elements 23A, 23B, and 23C in the Y-axis direction, the vibrating arms 211, 212, and 213 flexibly vibrate in the Z-axis direction.

[0019] The piezoelectric elements 23A, 23B, and 23C have the same configuration. As shown in FIG. 4, the piezoelectric elements 23A, 23B, and 23C each have a lower electrode 231 as a first electrode arranged on the upper surface of the vibrating arms 211, 212, and 213, a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231, and an upper electrode 233 as a second electrode arranged on the upper surface of the piezoelectric layer 232. The constituent materials of each part of the piezoelectric elements 23A, 23B, and 23C are not particularly limited, but for example, the piezoelectric layer 232 is made of aluminum nitride (AlN) or the like, and the lower electrode 231 and the upper electrode 233 are made of titanium nitride (TiN) or the like. Note that another layer may be interposed between the upper surface of the vibrating arms 211, 212, and 213 and the lower electrode 231, between the lower electrode 231 and the piezoelectric layer 232, and between the piezoelectric layer 232 and the upper electrode 233.

[0020] 4, the lower electrode 231 and the piezoelectric layer 232 are disposed from the base to the tip of the vibrating arms 211, 212, 213, that is, over the entire area in the extension direction. In contrast, the upper electrode 233 is disposed from the base to the center of the vibrating arms 211, 212, 213, that is, over about half of the base side. Only the area where the piezoelectric layer 232 is sandwiched between the lower electrode 231 and the upper electrode 233 expands and contracts when electricity is applied, so only this area actually functions as a piezoelectric element. Therefore, as described above, it can be said that "the piezoelectric elements 23A, 23B, 23C are disposed in about half of the base end side of the vibrating arms 211, 212, 213."

[0021] In addition, as in this embodiment, by disposing the lower electrode 231 and the piezoelectric layer 232 over the entire area in the extension direction of the vibrating arms 211, 212, 213, the mass of the vibrating arms 211, 212, 213 can be increased. Therefore, if the resonance frequency of the vibration element 20 is the same, the total length of the vibrating arms 211, 212, 213 can be shortened compared to the case where the lower electrode 231 and the piezoelectric layer 232 are made to be approximately the same length as the upper electrode 233. Therefore, the vibration element 20 can be made smaller. Also, if the total length of the vibrating arms 211, 212, 213 is the same, the resonance frequency of the vibration element 20 can be lowered compared to the case where the lower electrode 231 and the piezoelectric layer 232 are made to be approximately the same length as the upper electrode 233. However, the configuration of the piezoelectric elements 23A, 23B, 23C is not particularly limited, and for example, the lower electrode 231 and the piezoelectric layer 232 may be made to be approximately the same length as the upper electrode 233.

[0022] Moreover, the tip of the upper electrode 233 is tapered. That is, the width W2 of the upper electrode 233 at its tip, that is, the length in the Y-axis direction, decreases toward the tip side. In other words, W1 / W2, which is the ratio of the width W2 of the upper electrode 233 to the width W1 of the vibrating arms 211, 212, and 213, decreases toward the tip side at the tip of the upper electrode 233. In particular, in this embodiment, the tip of the upper electrode 233 is rounded. As a result, a sharp corner is not formed at the tip of the upper electrode 233, and peeling of the upper electrode 233 starting from this part can be effectively suppressed. Furthermore, at the tip of the upper electrode 233, the width W2 continuously decreases toward the tip side. As a result, a step is not formed in the outline of the tip of the upper electrode 233, and peeling of the upper electrode 233 starting from this part can be effectively suppressed.

[0023] 3, the piezoelectric elements 23A, 23B, and 23C are wired so that adjacent vibrating arms 211, 212, and 213 flex and vibrate in opposite phases. That is, the piezoelectric elements 23A, 23B, and 23C are wired so that a first state in which the vibrating arms 211 and 213 flex and deform upward and the vibrating arm 212 flex and deform downward and a second state in which the vibrating arms 211 and 213 flex and deform downward and the vibrating arm 212 flex and deform 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 vibrating arms 211, 212, and 213 flexurally vibrate in opposite phases, the vibrations of the vibrating arms 211, 212, and 213 are cancelled out, and vibration leakage of the vibration element 20 can be effectively suppressed. The flexural vibration of the vibrating arms 211, 212, and 213 is greatly excited at the resonant frequency, and the impedance becomes minimum. As a result, by connecting this MEMS element 1 to an oscillation circuit, it oscillates at an oscillation frequency determined by the resonant frequency.

[0024] As described above, by configuring the width W2 of the tip of the upper electrode 233 to decrease toward the tip side, it is possible to suppress an increase in the equivalent parallel capacitance C0 of the vibration element 20 while keeping the equivalent series resistance R1 of the vibration element 20 small. Therefore, it is possible to effectively suppress an increase in the effective resistance Re of the vibration element 20, and it is possible to reduce the power consumption when oscillating the vibration element 20. The basis of this effect will be described in detail below.

[0025] By reducing the width W2 of the tip of the upper electrode 233 toward the tip side, the opposing area between the lower electrode 231 and the upper electrode 233 is reduced, and the capacitance value of the piezoelectric elements 23A, 23B, and 23C can be reduced compared to when the width W2 is not reduced toward the tip side. Therefore, the increase in the equivalent parallel capacitance C0 of the vibration element 20 can be suppressed. On the other hand, by reducing the width W2 of the tip of the upper electrode 233 toward the tip side, the amount of expansion and contraction at the tip of the piezoelectric elements 23A, 23B, and 23C is reduced compared to when the width W2 is not reduced toward the tip side, so that the amplitude of the bending vibration of the vibrating arms 211, 212, and 213 may decrease, and the equivalent series resistance R1 of the vibration element 20 may increase.

[0026] FIG. 6 shows the stress distribution when the vibrating arms 211, 212, and 213 are bent and deformed in the Z-axis direction. As can be seen from FIG. 6, a large stress is applied to the base end of the vibrating arms 211, 212, and 213, and the stress decreases toward the tip. In other words, the effect of bending and deforming the vibrating arms 211, 212, and 213 in the Z-axis direction by the expansion and contraction of the piezoelectric elements 23A, 23B, and 23C is greatest at the base end of the vibrating arms 211, 212, and 213, and decreases toward the tip. Therefore, even if the amount of expansion and contraction at the tip of the piezoelectric elements 23A, 23B, and 23C decreases by reducing the width W2 of the tip of the upper electrode 233 toward the tip side as in this embodiment, it has almost no effect on the amplitude of the bending vibration of the vibrating arms 211, 212, and 213. Therefore, the amplitude of the flexural vibration of the vibrating arms 211, 212, and 213 is the same as or slightly decreased when the width W2 of the tip of the upper electrode 233 does not decrease toward the tip. Therefore, the increase in the equivalent series resistance R1 of the vibration element 20 can also be effectively suppressed.

[0027] As described above, according to the vibration element 20, it is possible to suppress an increase in the equivalent parallel capacitance C0 of the vibration element 20 while keeping the equivalent series resistance R1 of the vibration element 20 small. Therefore, it is possible to effectively suppress an increase in the effective resistance Re of the vibration element 20, and it is possible to reduce the power consumption when the vibration element 20 is oscillated.

[0028] The above describes the MEMS element 1. The vibration element 20 of the MEMS element 1 has an upper surface as a first surface and a lower surface as a second surface that are in a front-back relationship, and has a vibration substrate 21 on which a base 210 and vibration arms 211, 212, and 213 extending from the base 210 are formed, and piezoelectric elements 23A, 23B, and 23C arranged on the upper surfaces of the vibration arms 211, 212, and 213. The piezoelectric elements 23A, 23B, and 23C each have a lower electrode 231 as a first electrode arranged on the upper surfaces of the vibration arms 211, 212, and 213, a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231, i.e., on the surface opposite to the vibration arms 211, 212, and 213, and an upper electrode 233 as a second electrode arranged on the upper surface of the piezoelectric layer 232, i.e., on the surface opposite to the lower electrode 231. In addition, in a plan view of the vibration substrate 21, when a direction perpendicular to the Y-axis direction as a first direction in which the vibration arms 211, 212, and 213 extend is defined as an X-axis direction as a second direction, a width W1, which is a length in the X-axis direction in a region Q between the base 210 of the vibration arms 211, 212, and 213 and the tip of the upper electrode 233, is equal to or greater than the length in the X-axis direction at the base end of the vibration arms 211, 212, and 213. Then, at the tip of the upper electrode 233, a width W2, which is a length in the X-axis direction of the upper electrode 233, decreases toward the tip side. With this configuration, it is possible to suppress an increase in the equivalent parallel capacitance C0 of the vibration element 20 while suppressing an equivalent series resistance R1 of the vibration element 20 to be small. Therefore, it is possible to effectively suppress an increase in the effective resistance Re of the vibration element 20, and to reduce power consumption when the vibration element 20 is oscillated.

[0029] As described above, the tip of the upper electrode 233 is rounded. This prevents sharp corners from being formed at the tip of the upper electrode 233, and effectively prevents the upper electrode 233 from peeling off starting from this portion.

[0030] As described above, the width W2 of the upper electrode 233 decreases continuously toward the tip side, so that no step is formed in the contour of the tip of the upper electrode 233, and peeling of the upper electrode 233 starting from this portion can be effectively suppressed.

[0031] As described above, the vibration substrate 21 is made of a silicon substrate. By forming the vibration substrate 21 from a silicon substrate, the vibration substrate 21 can be formed using 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.

[0032] <Second embodiment> FIG. 7 is a plan view showing the vibration element according to the second embodiment.

[0033] The vibration element 20 of this embodiment is similar to the vibration element 20 of the first embodiment described above, except that the configurations of the vibration arms 211, 212, and 213 are different. In the following description, the present embodiment will be described with a focus on the differences from the first embodiment described above, and the description of the similarities will be omitted. In addition, in the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0034] As shown in FIG. 7, in the vibration element 20 of this embodiment, the vibrating arms 211, 212, 213 have arm portions 211a, 212a, 213a extending from a base portion 210 to the positive side in the Y-axis direction, and weight portions 211b, 212b, 213b arranged at the tips of the arms 211a, 212a, 213a.

[0035] Each of the arms 211a, 212a, and 213a is straight and has a constant width W1 along the extension direction, i.e., the Y-axis direction. The weights 211b, 212b, and 213b are wider than the arms 211a, 212a, and 213a, and their width W3, i.e., length in the X-axis direction, is greater than the width W1 of the arms 211a, 212a, and 213a. <W3である。

[0036] According to this configuration, if the resonance frequency of the vibration element 20 is the same, the total length of the vibration arms 211, 212, 213 can be shortened compared to a case in which the weights 211b, 212b, 213b are not present, due to the mass effect of the weights 211b, 212b, 213b. Therefore, it is possible to miniaturize the vibration element 20. Furthermore, if the total length of the vibration arms 211, 212, 213 is the same, the resonance frequency of the vibration element 20 can be lowered compared to a case in which the weights 211b, 212b, 213b are not present.

[0037] The second embodiment as described above can also achieve the same effects as the first embodiment described above.

[0038] <Third embodiment> FIG. 8 is a plan view showing a vibration element according to a third embodiment.

[0039] The vibration element 20 of this embodiment is similar to the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is 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 the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0040] As shown in FIG. 8, in the vibration element 20 of this embodiment, the width W2 of the tip of the upper electrode 233 decreases stepwise toward the tip side. The tip of the upper electrode 233 of this embodiment has a first portion 233a, a second portion 233b located on the tip side of the first portion 233a and having a width W2 smaller than that of the first portion 233a, and a third portion 233c located on the tip side of the second portion 233b and having a width W2 smaller than that of the second portion 233b. With this configuration, the width W2 of the tip of the upper electrode 233 can be decreased toward the tip side with a simple shape. However, the shape of the tip of the upper electrode 233 is not particularly limited.

[0041] In the above vibration element 20, as described above, the width W2 of the upper electrode 233 decreases stepwise toward the tip side. With this configuration, the width W2 of the tip portion of the upper electrode 233 can be decreased toward the tip side with a simple shape.

[0042] The third embodiment as described above can also achieve the same effects as the first embodiment described above.

[0043] <Fourth embodiment> FIG. 9 is a plan view showing a vibration element according to a fourth embodiment.

[0044] The vibration element 20 of this embodiment is similar to the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is 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 the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0045] As shown in FIG. 9, in the vibration element 20 of this embodiment, the tip of the upper electrode 233 is branched into multiple parts, and each of the branches is tapered. In particular, in this embodiment, the tip of the upper electrode 233 is branched into two parts, and each of the branches is tapered in a V shape so that the distance D between them gradually decreases toward the tip side. In this case, the sum of the width W21 of one of the branched parts and the width W22 of the other part is the width W2 of the upper electrode 233. Even with this simple configuration, the width W2 of the upper electrode 233 can be reduced toward the tip side.

[0046] In the vibration element 20 as described above, as described above, the tip of the upper electrode 233 is branched into multiple parts. With such a configuration, the width W2 of the upper electrode 233 can be reduced toward the tip side with a simple configuration.

[0047] The fourth embodiment as described above can also achieve the same effects as the first embodiment.

[0048] <Fifth embodiment> FIG. 10 is a plan view showing a vibration element according to a fifth embodiment.

[0049] The vibration element 20 of this embodiment is similar to the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is 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 the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0050] 10, in the vibration element 20 of this embodiment, the vibration arms 211, 212, and 213 are straight and have a constant width W1 along the Y-axis direction. Similarly, the upper electrode 233 is straight and has a constant width W2 along the Y-axis direction.

[0051] Also, the vibrating arms 211, 212, and 213 have a first region Q1, a second region Q2 located closer to the base end than the first region Q1, a third region Q3 located closer to the base end than the second region Q2, and a fourth region Q4 located closer to the base end than the third region Q3. Also, the first region Q1, the second region Q2, and the third region Q3 are set to have the same length in the Y-axis direction, and the fourth region Q4 is set to be longer than the first, second, and third regions Q1, Q2, and Q3. The width W1 of the first region Q1 is set to be equal to or smaller than the width W1 of the second region Q2, and the width W1 of the second region Q2 is set to be equal to or smaller than the width W1 of the third region Q3. In this embodiment, the widths W1 of the first, second, third, and fourth regions Q1, Q2, Q3, and Q4 are equal to each other.

[0052] Also, a hole H is formed in each of the first, second, and third regions Q1, Q2, and Q3. The shape of each hole H is not particularly limited, but is rectangular in this embodiment. Hereinafter, the hole H formed in the first region Q1 will also be referred to as hole H1, the hole H formed in the second region Q2 will also be referred to as hole H2, and the hole H formed in the third region Q3 will also be referred to as hole H3.

[0053] In particular, in this embodiment, the first, second, and third regions Q1, Q2, and Q3 each have the same number of holes H formed in the same arrangement. Specifically, six holes H1 are formed in the first region Q1, six holes H2 are formed in the second region Q2, and six holes H3 are formed in the third region Q3 in a matrix of 2 columns x 3 rows. However, the number and arrangement of the holes H1, H2, and H3 are not particularly limited. In addition, the number and arrangement of the holes H may be different between the first, second, and third regions Q1, Q2, and Q3.

[0054] Also, the area of ​​each hole H1 is larger than the area of ​​each hole H2, and the area of ​​each hole H2 is larger than the area of ​​each hole H3. Therefore, the total area of ​​the six holes H1>the total area of ​​the six holes H2>the total area of ​​the six holes H3. Therefore, the ratio Se1 / S1 of the area Se1 of the upper electrode 233 arranged in the first region Q1 to the area S1 of the first region Q1 is smaller than the ratio Se2 / S2 of the area Se2 of the upper electrode 233 arranged in the second region Q2 to the area S2 of the second region Q2, and the ratio Se2 / S2 is smaller than the ratio Se3 / S3 of the area Se3 of the upper electrode 233 arranged in the third region Q3 to the area S3 of the third region Q3. In other words, Se1 / S1 <Se2 / S2<Se3 / S3である。

[0055] According to such a configuration, since the average value of the width W2 of the fourth region Q4 > the average value of the width W2 of the third region Q3 > the average value of the width W2 of the second region Q2 > the average value of the width W2 of the first region Q1, it is possible to exhibit the same effect as reducing the width W2 toward the tip side as in the first embodiment described above. Therefore, while suppressing the equivalent series resistance R1 of the vibration element 20 to be small, an increase in the equivalent parallel capacitance C0 of the vibration element 20 can be suppressed. For this reason, an increase in the effective resistance Re of the vibration element 20 can be effectively suppressed, and the power consumption when the vibration element 20 is oscillated can be reduced. In particular, as in the present embodiment, by providing the three regions Q1, Q2, and Q3 in which the holes H are formed, the average value of the width W2 can be gradually decreased toward the tip side. Therefore, the piezoelectric elements 23A, 23B, and 23C can be stably expanded and contracted. Further, by forming the holes H in the respective regions Q1, Q2, and Q3, the relationship of Se1 / S1 < Se2 / S2 < Se3 / S3 can be achieved with a simple configuration.

[0056] As described above, the vibration element 20 has an upper surface as a first surface and a lower surface as a second surface that are in a front-back relationship, a base 210, a vibration substrate 21 on which the vibration arms 211, 212, and 213 extending from the base 210 are formed, and piezoelectric elements 23A, 23B, and 23C arranged on the upper surfaces of the vibration arms 211, 212, and 213. The piezoelectric elements 23A, 23B, and 23C each have a lower electrode 231 as a first electrode arranged on the upper surfaces of the vibration arms 211, 212, and 213, a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231, i.e., on the surface opposite the vibration arms 211, 212, and 213, and an upper electrode 233 as a second electrode arranged on the upper surface of the piezoelectric layer 232, i.e., on the surface opposite the lower electrode 231. In addition, in a plan view of the vibration substrate 21, when a direction perpendicular to the Y-axis direction as a first direction in which the vibrating arms 211, 212, and 213 extend is defined as an X-axis direction as a second direction, a width W1 that is a length in the X-axis direction in a region Q between the base 210 of the vibrating arms 211, 212, and 213 and the tip of the upper electrode 233 is equal to or greater than the length in the X-axis direction at the base end of the vibrating arms 211, 212, and 213. In addition, the vibrating arms 211, 212, and 213 have a first region Q1 on the upper surface and a second region Q2 located closer to the base end than the first region Q1, and the width W2 of the first region Q1 is equal to or less than the width W2 of the second region Q2. The ratio Se1 / S1 of the area Se1 of the upper electrode 233 arranged in the first region Q1 to the area S1 of the first region Q1 is smaller than the ratio Se2 / S2 of the area Se2 of the upper electrode 233 arranged in the second region Q2 to the area S2 of the second region Q2. With this configuration, it is possible to suppress an increase in the equivalent parallel capacitance C0 of the vibration element 20 while keeping the equivalent series resistance R1 of the vibration element 20 small. Therefore, it is possible to effectively suppress an increase in the effective resistance Re of the vibration element 20, and to reduce the power consumption when the vibration element 20 is oscillated.

[0057] Also, as described above, the vibrating arms 211, 212, and 213 have a third region Q3 located on the proximal end side of the second region Q2, and the width W2 of the second region Q2 is less than or equal to the width W2 of the third region Q3. And the ratio Se2 / S2 of the area Se2 of the upper electrode 233 disposed in the second region Q2 to the area S2 of the second region Q2 is smaller than the ratio Se3 / S3 of the area Se3 of the upper electrode 233 disposed in the third region Q3 to the area S3 of the third region Q3. Thus, by providing three regions Q1, Q2, and Q3 with different ratios of electrode area to the region, the piezoelectric elements 23A, 23B, and 23C can be stably expanded and contracted.

[0058] Also, as described above, holes H are formed in the first region Q1, the second region Q2, and the third region Q3, respectively. According to such a configuration, with a simple configuration, the relationship of Se1 / S1 < Se2 / S2 < Se3 / S3 can be achieved.

[0059] Also, according to such a fifth embodiment, the same effects as those of the first embodiment described above can be exhibited. However, the configuration of the vibrating element 20 is not limited to this. For example, the third region Q3 and the fourth region Q4 may be omitted. That is, it may be composed of the first region Q1 where the upper electrode 233 is disposed on the distal end side and the second region Q2 where the upper electrode 233 is disposed on the proximal end side. Also, in this case, the hole H may be omitted from the second region Q2.

[0060] <Sixth Embodiment> FIG. 11 is a plan view showing a vibrating element according to the sixth embodiment.

[0061] The vibrating element 20 of this embodiment is the same as the vibrating element 20 of the fifth embodiment described above, except that the configuration of the hole H is different. In the following description, regarding this embodiment, the description will focus on the differences from the first embodiment described above, and the description of the same matters will be omitted. Also, in the drawings of this embodiment, the same reference numerals are given to the same configurations as those of the above-described embodiments.

[0062] As shown in FIG. 11, in the vibration element 20 of this embodiment, each hole H is a notch that opens to the outer edge of the upper electrode 233. Specifically, each hole H arranged in a row on the positive side of the X-axis direction is a notch that opens to the side of the upper electrode 233 on the positive side of the X-axis direction, and each hole H arranged in a row on the negative side of the X-axis direction is a notch that opens to the side of the upper electrode 233 on the negative side of the X-axis direction. In this way, by configuring the holes H as notches, the dense part of the upper electrode 233 can be concentrated in the center part of the X-axis direction of the vibrating arms 211, 212, and 213. Therefore, the expansion and contraction of the piezoelectric elements 23A, 23B, and 23C can be efficiently transmitted to the vibrating arms 211, 212, and 213, and the vibrating arms 211, 212, and 213 can be flexurally vibrated with a larger amplitude.

[0063] In the vibration element 20 as described above, the hole H is a notch that opens to the outer edge of the upper electrode 233. With this configuration, the dense portion of the upper electrode 233 can be concentrated in the center of the vibrating arms 211, 212, and 213. Therefore, the expansion and contraction of the piezoelectric elements 23A, 23B, and 23C can be efficiently transmitted to the vibrating arms 211, 212, and 213, and the vibrating arms 211, 212, and 213 can be flexurally vibrated with a larger amplitude.

[0064] The sixth embodiment as described above can also achieve the same effects as the first embodiment described above.

[0065] Seventh embodiment FIG. 12 is a plan view showing the vibration element according to the seventh embodiment.

[0066] The vibration element 20 of this embodiment is similar to the vibration element 20 of the above-described fifth embodiment, except for the configuration of the hole H. In the following description, the present embodiment will be described with a focus on the differences from the above-described fifth embodiment, and the description of the similarities will be omitted. In the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-described embodiment.

[0067] 12, in the vibration element 20 of this embodiment, the holes H have the same shape and size. More holes H are formed in the second region Q2 than in the third region Q3, and more holes H are formed in the first region Q1 than in the second region Q2.

[0068] The seventh embodiment as described above can also achieve the same effects as the fifth embodiment.

[0069] 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]

[0070] 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...vibrating arm, 211a...arm portion, 211b...weight portion, 212...vibrating arm, 212a...arm portion, 212b...weight portion, 213...vibrating arm, 213a...arm portion, 213b...weight portion, 23...flexural vibration drive portion, 23A...piezoelectric element, 23B ...piezoelectric element, 23C...piezoelectric element, 231...lower electrode, 232...piezoelectric layer, 233...upper electrode, 233a...first part, 233b...second part, 233c...third part, 5...lid part, D...separation distance, H...hole, H1...hole, H 2...hole, H3...hole, PAD1...electrode pad, PAD2...electrode pad, Q...area, Q1...first area, Q2...second area, Q3...third area, Q4...fourth area, W1...width, W2...width, W21...width, W22...width, W3...width

Claims

1. A vibrating substrate comprising a base portion including a first surface and a second surface that are in a front-back relationship with respect to each other, and a vibrating arm extending in a first direction from the base portion, A piezoelectric element disposed on the first surface of the vibrating arm, Includes, The piezoelectric element is The first electrode is positioned on the first surface of the vibrating arm, A piezoelectric layer is disposed on the side of the first electrode opposite to the side of the vibrating arm, A second electrode is disposed on the side of the piezoelectric layer opposite to the side of the first electrode, Includes, In a plan view, when the direction perpendicular to the first direction is defined as the second direction, The width of the vibrating arm along the second direction in the region between the base end of the vibrating arm and the tip of the second electrode is greater than or equal to the width along the second direction at the base end. A vibrating element characterized in that the width of the second electrode along the second direction decreases toward the tip side of the second electrode.

2. In Claim 1, In a plan view, the tip side of the second electrode is rounded, forming a vibrating element.

3. In claim 1 or 2, A vibrating element in which, in a plan view, the width of the second electrode along the second direction decreases continuously toward the tip side.

4. In claim 1 or 2, In a plan view, the width of the second electrode along the second direction decreases in a stepwise manner towards the tip side of the vibrating element.

5. In claim 1 or 2, In a plan view, the tip side of the second electrode is a vibrating element that is branched into multiple parts.

6. A vibrating substrate including a base portion having a first surface and a second surface that are in a front-back relationship with each other, and a vibrating arm extending in a first direction from the base portion, A piezoelectric element disposed on the first surface of the vibrating arm, Includes, The piezoelectric element is The first electrode is positioned on the first surface of the vibrating arm, A piezoelectric layer is disposed on the side of the first electrode opposite to the side of the vibrating arm, A second electrode is disposed on the side of the piezoelectric layer opposite to the side of the first electrode, Includes, In a plan view, when the direction perpendicular to the first direction is defined as the second direction, The width of the vibrating arm along the second direction in the region between the base end of the vibrating arm and the tip of the second electrode is greater than or equal to the width along the second direction at the base end. The vibrating arm includes a first region on the first surface and a second region located closer to the base end than the first region. The width of the first region along the second direction is less than or equal to the width of the second region along the second direction. A vibrating element characterized in that the ratio of the area of ​​the second electrode located in the first region to the area of ​​the first region is smaller than the ratio of the area of ​​the second electrode located in the second region to the area of ​​the second region.

7. In claim 6, The vibrating arm includes a third region located closer to the base end than the second region, The width of the second region along the second direction is less than or equal to the width of the third region along the second direction. A vibrating element in which the ratio of the area of ​​the second electrode located in the second region to the area of ​​the second region is smaller than the ratio of the area of ​​the second electrode located in the third region to the area of ​​the third region.

8. In claim 7, A vibrating element in which holes are provided in the first region, the second region, and the third region, respectively.

9. In claim 8, The hole is a notch opening in the outer edge of the second electrode, which is a vibrating element.

10. In claim 1 or 6, The aforementioned vibrating substrate is a vibrating element formed from a silicon substrate.

Images