Vibration element

Abstract

The invention provides a resonator element capable of reducing power consumption. The resonator element includes: a resonator substrate having a first surface and a second surface in a front-back relationship, the resonator substrate having a base portion and a resonator arm extending from the base portion; and a piezoelectric element disposed on the first surface of the vibrating arm, the piezoelectric element having: a first electrode disposed on the first surface of the vibrating arm; a piezoelectric layer disposed on a surface of the first electrode on the opposite side from the vibrating arm; and a second electrode disposed on a surface of the piezoelectric layer on the opposite side of the first electrode, the second electrode being disposed on a surface of the piezoelectric layer on the opposite side of the first electrode, the second direction being a direction perpendicular to a first direction in which the vibrating arm extends in plan view of the vibrating substrate. The length in the second direction of a region between the base portion of the vibrating arm and the tip of the second electrode is equal to or greater than the length in the second direction at the base end of the vibrating arm, and the length in the second direction of the second electrode decreases toward the tip side at the tip portion of the second electrode.

Description

Technical Field

[0001] The present invention relates to a vibrating element. Background Art

[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. In addition, 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. The arms at both ends of such a vibrating piece and the arm at the center thereof bend and vibrate in the Z-axis direction in an anti-phase manner.

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2021-164130

[0005] However, in the vibrating piece as in Patent Document 1, when the upper electrode provided on the piezoelectric layer is formed wider in order to increase the amplitude of the bending vibration of the arm and reduce the equivalent series resistance R1 of the vibrating piece, the equivalent parallel electrostatic capacitance C0 of the vibrating piece becomes larger. When the equivalent parallel electrostatic capacitance C0 becomes larger, the effective resistance Re of the vibrating piece increases, thereby increasing the power consumption of the vibrating piece when oscillating. In addition, when the load capacitance is set to CL, the effective resistance Re is Re = R1 × (1 + C0 / CL) 2 express. Summary of the invention

[0006] The vibration element of the present invention has:

[0007] a vibration substrate having a first surface and a second surface in a front-rear relationship and formed with a base and a vibration arm extending from the base; and

[0008] a piezoelectric element disposed on the first surface of the vibration arm,

[0009] The piezoelectric element has:

[0010] A first electrode, which is disposed on a first surface of the vibration arm;

[0011] a piezoelectric layer disposed on a surface of the first electrode on the opposite side to the vibration arm; and

[0012] a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode;

[0013] When the vibration substrate is viewed from above, and a direction perpendicular to the first direction in which the vibration arm extends is set as a second direction,

[0014] The length of the region of the vibration arm from the base to the tip of the second electrode in the second direction is greater than or equal to the length of the base end of the vibration arm in the second direction.

[0015] At the distal end portion of the second electrode, the length of the second electrode in the second direction decreases toward the distal end side.

[0016] The vibration element of the present invention has:

[0017] a vibration substrate having a first surface and a second surface in a front-rear relationship and formed with a base and a vibration arm extending from the base; and

[0018] a piezoelectric element disposed on the first surface of the vibration arm,

[0019] The piezoelectric element has:

[0020] A first electrode, which is disposed on a first surface of the vibration arm;

[0021] a piezoelectric layer disposed on a surface of the first electrode on the opposite side to the vibration arm; and

[0022] a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode;

[0023] When the vibration substrate is viewed from above, and a direction perpendicular to the first direction in which the vibration arm extends is set as a second direction,

[0024] The length of the region of the vibration arm from the base to the tip of the second electrode in the second direction is greater than or equal to the length of the base end of the vibration arm in the second direction.

[0025] The vibration arm includes a first region and a second region on the base end side of the first region on the first surface.

[0026] The length of the first region in the second direction is less than the length of the second region in the second direction,

[0027] A ratio of an area of ​​the second electrode disposed in the first region to an area of ​​the first region is smaller than a 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

[0028] Figure 1 It is a top view of the MEMS element according to the first embodiment.

[0029] Figure 2 yes Figure 1 AA line section view in.

[0030] Figure 3 This is a top view of a vibration element included in a MEMS element.

[0031] Figure 4 It is a cross-sectional view of a vibration arm included in the vibration element.

[0032] Figure 5 It is a plan view showing a modified example of the vibration element.

[0033] Figure 6 It is a diagram showing stress distribution when the vibration arm is bent and deformed.

[0034] Figure 7 It is a plan view showing a vibration element according to a second embodiment.

[0035] Figure 8 It is a plan view showing a vibration element according to a third embodiment.

[0036] Fig. 9 It is a plan view showing a vibration element according to a fourth embodiment.

[0037] Fig.10 It is a top view showing the vibration element according to the fifth embodiment.

[0038] Fig.11 It is a top view showing the vibration element according to the sixth embodiment.

[0039] Fig.12 It is a top view showing the vibration element according to the seventh embodiment.

[0040] Description of symbols

[0041] 1: MEMS element; 10: SOI substrate; 11: silicon layer; 12: BOX layer; 13: surface silicon layer; 131: frame; 14: through electrode; 15: through electrode; 20: vibration element; 21: vibration substrate; 210: base; 211: vibration arm; 211a: arm; 211b: weight; 212: vibration arm; 212a: arm; 212b: weight; 213: vibration arm; 213a: arm; 213b: weight; 23: bending vibration drive unit; 23A: piezoelectric element; 23B: piezoelectric element Component; 23C: piezoelectric element; 231: lower electrode; 232: piezoelectric layer; 233: upper electrode; 233a: first part; 233b: second part; 233c: third part; 5: cover; D: separation distance; H: hole; H1: hole; H2: 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. DETAILED DESCRIPTION

[0042] Hereinafter, the vibration element of the present invention will be described in detail based on the embodiments shown in the drawings.

[0043] <First Embodiment>

[0044] Figure 1 It is a top view of the MEMS element according to the first embodiment. Figure 2 yes Figure 1 AA line section view in. Figure 3 This is a top view of a vibration element included in a MEMS element. Figure 4 It is a cross-sectional view of a vibration arm included in the vibration element. Figure 5 It is a plan view showing a modified example of the vibration element. Figure 6 It is a diagram showing stress distribution when the vibration arm is bent and deformed.

[0045] In addition, for the sake of convenience, Figures 1 to 5 In each figure, an X-axis, a Y-axis, and a Z-axis perpendicular to each other are illustrated. In addition, the direction along the X-axis is also referred to as the X-axis direction, the direction along the Y-axis is also referred to as the Y-axis direction, and the direction along the Z-axis is also referred to as the Z-axis direction. Moreover, the X-axis direction is equivalent to the "second direction", and the Y-axis direction is equivalent to the "first direction". In addition, the arrow side of each axis is also referred to as the "positive side", and the opposite side is referred to as the "negative side". In addition, the positive side of the Z-axis direction is also referred to as the "upper", and the negative side is referred to as the "lower".

[0046] like Figure 1 As shown, the MEMS element 1 has an SOI (Silicon on Insulator) substrate 10 on which a vibration element 20 is formed and a cover 5 for airtightly sealing the vibration element 20. The cover 5 is made of single crystal silicon or the like and has a recessed portion opened on the lower surface. Moreover, the lower surface of the cover 5 is bonded to the upper surface of the SOI substrate 10.

[0047] like Figure 2 As shown, the SOI substrate 10 is a substrate having a silicon layer 11 as a processing layer, a BOX (Buried Oxide) layer 12, and a surface silicon layer 13 as a device layer stacked in sequence. For example, the silicon layer 11 and the surface silicon layer 13 are respectively composed of single crystal silicon, and the BOX layer 12 is composed of a silicon oxide layer (SiO2, etc.).

[0048] In addition, if Figure 1 As shown in FIG. 1 , a vibration substrate 21 and a frame portion 131 surrounding the vibration substrate 21 are formed on the surface silicon layer 13. Figure 2As shown, a pair of electrode pads PAD1 and PAD2 are arranged on the upper surface of the frame portion 131. In addition, through electrodes 14 and 15 are formed at positions overlapping with the electrode pads PAD1 and PAD2, penetrating the SOI substrate 10 in the thickness direction. Moreover, 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. Thus, the electrode pads PAD1 and PAD2 are led out to the outside of the MEMS element 1.

[0049] The vibration element 20 has a vibration substrate 21 formed on the surface silicon layer 13. That is, the vibration substrate 21 is formed 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, so the processing of the vibration substrate 21 becomes easy, and the vibration substrate 21 can be formed with high processing accuracy.

[0050] The vibration substrate 21 is plate-shaped and has an upper surface as a first surface and a lower surface as a second surface in a front-rear relationship. Figure 3 As shown, the vibration substrate 21 has a base 210 and three vibration arms 211, 212, and 213 extending from the base 210. Figure 4 As shown, the base 210 is supported by the silicon layer 11 and the BOX layer 12, and the vibration arms 211, 212, and 213 are separated from the BOX layer 12. In addition, the entire vibration substrate 21 is formed to have the same thickness as the surface silicon layer 13.

[0051] like Figure 3 As shown, the vibration arms 211, 212, and 213 extend from the end portion of the base 210 on the positive side in the Y-axis direction, i.e., the terminal portion, toward the positive side in the Y-axis direction, and are arranged at equal intervals in the X-axis direction. In addition, the vibration arms 211, 212, and 213 are unified into the same shape as each other. In addition, these vibration arms 211, 212, and 213 are bent and vibrated in the Z-axis direction.

[0052] In addition, piezoelectric elements 23A, 23B, and 23C are arranged on the upper surfaces of the vibration arms 211, 212, and 213. Moreover, the width W1 of the region Q from the base end of the vibration arms 211, 212, and 213 to the end of the upper electrode 233 provided by the piezoelectric elements 23A, 23B, and 23C, that is, the length in the X-axis direction is greater than the width at the base end of the vibration arms 211, 212, and 213. In particular, in the present embodiment, the vibration arms 211, 212, and 213 are linear, and the width W1 is equal to the width at the base end of the vibration arms 211, 212, and 213. However, this is not limited to this, and for example, it may also be as follows Figure 5 As shown, the width W1 of the region Q of the vibration arms 211 , 212 , 213 is larger than the width at the base end of the vibration arms 211 , 212 , 213 .

[0053] like Figure 3 As shown, the vibration element 20 also has a bending vibration driving unit 23 that causes the vibration arms 211, 212, and 213 to bend and vibrate in the Z-axis direction. The bending vibration driving unit 23 has: a piezoelectric element 23A, which is arranged on the upper surface of the vibration arm 211; a piezoelectric element 23B, which is arranged on the upper surface of the vibration arm 212; and a piezoelectric element 23C, which is arranged on the upper surface of the vibration arm 213. In addition, the piezoelectric elements 23A, 23B, and 23C are shorter than the full length of the vibration arms 211, 212, and 213, and in this embodiment, are arranged in an area about half of the base end side of the vibration arms 211, 212, and 213. Such piezoelectric elements 23A, 23B, and 23C are respectively expanded and contracted in the Y-axis direction by powering on. Moreover, by expanding and contracting the piezoelectric elements 23A, 23B, and 23C in the Y-axis direction, the vibration arms 211, 212, and 213 are bent and vibrated in the Z-axis direction.

[0054] The piezoelectric elements 23A, 23B, and 23C have the same structure. Figure 4 As shown, the piezoelectric elements 23A, 23B, and 23C respectively include: a lower electrode 231 as a first electrode, which is arranged on the upper surface of the vibration arms 211, 212, and 213; a piezoelectric layer 232, which is arranged on the upper surface of the lower electrode 231; and an upper electrode 233 as a second electrode, which is 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. For example, the piezoelectric layer 232 is composed of aluminum nitride (AlN) or the like, and the lower electrode 231 and the upper electrode 233 are composed of titanium nitride (TiN) or the like. In addition, another layer may be present between the upper surface of the vibration 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.

[0055] In addition, if Figure 4 As shown, the lower electrode 231 and the piezoelectric layer 232 are arranged from the root to the end of the vibration arms 211, 212, and 213, that is, throughout the entire area in the extension direction. In contrast, the upper electrode 233 is arranged from the base end to the center of the vibration arms 211, 212, and 213, that is, throughout the area 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 by energizing, so only this area actually functions as a piezoelectric element. Therefore, as mentioned above, it can be said that "the piezoelectric elements 23A, 23B, and 23C are arranged in the area about half of the base end side of the vibration arms 211, 212, and 213."

[0056] In addition, by configuring the lower electrode 231 and the piezoelectric layer 232 over the entire region in the extension direction of the vibration arms 211, 212, and 213 as in the present embodiment, the mass of the vibration arms 211, 212, and 213 can be improved. Therefore, if the resonance frequency of the vibration element 20 is the same, the total length of the vibration arms 211, 212, and 213 can be shortened compared to the case where the lower electrode 231 and the piezoelectric layer 232 are set to the same length as the upper electrode 233. Therefore, the miniaturization of the vibration element 20 can be achieved. In addition, if the total length of the vibration arms 211, 212, and 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 set to the same length as the upper electrode 233. However, the structure of the piezoelectric elements 23A, 23B, and 23C is not particularly limited. For example, the lower electrode 231 and the piezoelectric layer 232 may be formed to have the same length as that of the upper electrode 233 .

[0057] In addition, the end portion of the upper electrode 233 is formed to be tapered. That is, at the end portion of the upper electrode 233, the width W2 of the upper electrode 233, that is, the length in the X-axis direction, decreases toward the end side. In other words, the ratio of the width W2 of the upper electrode 233 to the width W1 of the vibration arms 211, 212, and 213, that is, W2 / W1, decreases toward the end side at the end portion of the upper electrode 233. In particular, in the present embodiment, the end portion of the upper electrode 233 is rounded. As a result, no sharp corners are formed at the end portion of the upper electrode 233, and the peeling of the upper electrode 233 starting from this portion can be effectively suppressed. Furthermore, at the end portion of the upper electrode 233, the width W2 continuously decreases toward the end side. As a result, the contour of the end portion of the upper electrode 233 does not form a step, and the peeling of the upper electrode 233 starting from this portion can be effectively suppressed.

[0058] In addition, if Figure 3As shown, the piezoelectric elements 23A, 23B, and 23C are wired so that the adjacent vibration arms 211, 212, and 213 are bent and vibrated in opposite phases to each other. That is, the piezoelectric elements 23A, 23B, and 23C are wired so that a first state in which the vibration arms 211 and 213 are bent and deformed upward and the vibration arm 212 is bent and deformed downward and a second state in which the vibration arms 211 and 213 are bent and deformed downward and the vibration arm 212 is bent and deformed upward are repeated alternately. Specifically, the lower electrodes 231 of the piezoelectric elements 23A and 23C and the upper electrodes 233 of the piezoelectric element 23B are electrically connected to the electrode pad PAD1 via wiring not shown in the figure, and the upper electrodes 233 of the piezoelectric elements 23A and 23C and the lower electrodes 231 of the piezoelectric element 23B are electrically connected to the electrode pad PAD2 via wiring not shown in the figure. In this way, by making the adjacent vibration arms 211, 212, and 213 bend and vibrate in opposite phases to each other, the vibrations of the vibration arms 211, 212, and 213 are offset, and the vibration leakage of the vibration element 20 can be effectively suppressed. The bending vibrations of the vibration arms 211, 212, and 213 are greatly excited at the resonance frequency, and the impedance becomes minimum. As a result, by connecting the MEMS element 1 to the oscillation circuit, it oscillates at an oscillation frequency determined by the resonance frequency.

[0059] By forming a structure in which the width W2 of the end portion of the upper electrode 233 decreases toward the end side as described above, the equivalent series resistance R1 of the vibration element 20 can be suppressed to be small, and the increase of the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. Therefore, the increase of 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. The basis of this effect is described in detail below.

[0060] By reducing the width W2 of the end portion of the upper electrode 233 toward the end side, the capacitance value of the piezoelectric elements 23A, 23B, and 23C can be reduced by the amount corresponding to the reduction in the opposing area between the lower electrode 231 and the upper electrode 233, compared with the case where the width W2 is not reduced toward the end side. Therefore, the increase in the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. On the other hand, by reducing the width W2 of the end portion of the upper electrode 233 toward the end side, the expansion and contraction amount at the end portion of the piezoelectric elements 23A, 23B, and 23C is reduced compared with the case where the width W2 is not reduced toward the end side, so there is a concern that the amplitude of the bending vibration of the vibration arms 211, 212, and 213 is reduced, and the equivalent series resistance R1 of the vibration element 20 is increased.

[0061] Figure 6 The stress distribution when the vibration arms 211, 212, and 213 are bent and deformed in the Z-axis direction is shown. Figure 6It can be seen that a large stress is applied to the base end of the vibration arms 211, 212, and 213, and the stress decreases toward the end. That is, the effect of bending and deforming the vibration arms 211, 212, and 213 in the Z-axis direction by the expansion and contraction of the piezoelectric elements 23A, 23B, and 23C is the largest at the base end of the vibration arms 211, 212, and 213, and decreases toward the end. Therefore, even if the width W2 of the end portion of the upper electrode 233 is reduced toward the end side so that the expansion and contraction amount at the end portion of the piezoelectric elements 23A, 23B, and 23C is reduced as in the present embodiment, the amplitude of the bending vibration of the vibration arms 211, 212, and 213 is hardly affected. Therefore, the amplitude of the bending vibration of the vibration arms 211, 212, and 213 remains at the same level as or slightly reduced to the level when the width W2 of the end portion of the upper electrode 233 is not reduced toward the end side. Therefore, the increase in the equivalent series resistance R1 of the vibration element 20 can also be effectively suppressed.

[0062] As described above, according to the vibration element 20, the equivalent series resistance R1 of the vibration element 20 can be suppressed to be small, and the increase of the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. Therefore, the increase of 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.

[0063] The MEMS element 1 has been described above. The vibration element 20 included in the MEMS element 1 includes: a vibration substrate 21 having an upper surface as a first surface and a lower surface as a second surface in a front-rear relationship, and having a base 210 and vibration arms 211, 212, 213 extending from the base 210; and piezoelectric elements 23A, 23B, 23C arranged on the upper surfaces of the vibration arms 211, 212, 213. In addition, the piezoelectric elements 23A, 23B, 23C include: a lower electrode 231 as a first electrode arranged on the upper surfaces of the vibration arms 211, 212, 213; a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231, i.e., the surface on the opposite side to the vibration arms 211, 212, 213; and an upper electrode 233 as a second electrode arranged on the upper surface of the piezoelectric layer 232, i.e., the surface on the opposite side to the lower electrode 231. In addition, when the vibration substrate 21 is viewed from above, when the direction perpendicular to the Y-axis direction as the first direction in which the vibration arms 211, 212, and 213 extend is set as the X-axis direction as the second direction, the length in the X-axis direction, that is, the width W1, of the region Q between the base 210 and the tip of the upper electrode 233 of the vibration arms 211, 212, and 213 is greater than the length in the X-axis direction at the base end of the vibration arms 211, 212, and 213. Moreover, at the tip end of the upper electrode 233, the length in the X-axis direction, that is, the width W2, of the upper electrode 233 decreases toward the tip end. According to such a structure, the equivalent series resistance R1 of the vibration element 20 can be suppressed to be small, and the increase in the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. Therefore, the 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.

[0064] In addition, as described above, the tip of the upper electrode 233 is rounded, so that a sharp corner is not formed at the tip of the upper electrode 233, and peeling of the upper electrode 233 starting from this portion can be effectively suppressed.

[0065] As described above, the width W2 of the upper electrode 233 decreases continuously toward the distal end. Thus, the contour of the distal end of the upper electrode 233 does not form a step, and peeling of the upper electrode 233 starting from this portion can be effectively suppressed.

[0066] As described above, the vibration substrate 21 is formed of a silicon substrate. Since the vibration substrate 21 can be formed using a silicon wafer process, the vibration substrate 21 can be easily processed and formed with high processing accuracy.

[0067] <Second Embodiment>

[0068] Figure 7It is a plan view showing a vibration element according to a second embodiment.

[0069] The vibration element 20 of this embodiment is the same as the vibration element 20 of the first embodiment described above, except that the structures of the vibration arms 211, 212, and 213 are different. In addition, in the following description, the description of this embodiment is centered on the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0070] like Figure 7 As shown, in the vibration element 20 of the present embodiment, the vibration arms 211, 212, 213 include: arm portions 211a, 212a, 213a, which extend from the base 210 toward the positive side in the Y-axis direction; and weight portions 211b, 212b, 213b, which are arranged at the end portions of the arm portions 211a, 212a, 213a.

[0071] The arm portions 211a, 212a, and 213a are linear, and their width W1 is constant along the extension direction, i.e., the Y-axis direction. The weight portions 211b, 212b, and 213b are wider than the arm portions 211a, 212a, and 213a, and their width W3, i.e., the length in the X-axis direction, is greater than the width W1 of the arm portions 211a, 212a, and 213a. That is, W1<W3.

[0072] According to such a structure, due to the mass effect of the weight portions 211b, 212b, 213b, 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 the case where the weight portions 211b, 212b, 213b are not present. Therefore, it is possible to miniaturize the vibration element 20. In addition, 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 the case where the weight portions 211b, 212b, 213b are not present.

[0073] According to such a second embodiment as well, it is possible to produce the same effects as those of the above-described first embodiment.

[0074] <Third Embodiment>

[0075] Figure 8 It is a plan view showing a vibration element according to a third embodiment.

[0076] The vibration element 20 of this embodiment is the same as the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is different. In addition, in the following description, the description of this embodiment is centered on the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0077] like Figure 8 As shown, in the vibration element 20 of the present embodiment, the width W2 of the terminal portion of the upper electrode 233 decreases stepwise toward the terminal side. The terminal portion of the upper electrode 233 of the present embodiment includes a first portion 233a, a second portion 233b located at the terminal side of the first portion 233a and having a smaller width W2 than the first portion 233a, and a third portion 233c located at the terminal side of the second portion 233b and having a smaller width W2 than the second portion 233b. According to such a structure, the width W2 of the terminal portion of the upper electrode 233 can be reduced toward the terminal side with a simple shape. However, the shape of the terminal portion of the upper electrode 233 is not particularly limited.

[0078] In the vibration element 20 as described above, the width W2 of the upper electrode 233 decreases stepwise toward the distal end. With such a configuration, the width W2 of the distal end of the upper electrode 233 can be decreased toward the distal end with a simple shape.

[0079] According to such a third embodiment as well, it is possible to produce the same effects as those of the above-described first embodiment.

[0080] <Fourth Embodiment>

[0081] Fig. 9 It is a plan view showing a vibration element according to a fourth embodiment.

[0082] The vibration element 20 of this embodiment is the same as the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is different. In addition, in the following description, the description of this embodiment is centered on the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0083] like Fig. 9As shown, in the vibration element 20 of the present embodiment, the end portion of the upper electrode 233 is branched into multiple parts, and each part obtained by the branching is formed to be tapered at the end. In particular, in the present embodiment, the end portion of the upper electrode 233 is branched into two parts, and each part obtained by the branching is tapered in a V-shaped manner with the separation distance D between each other gradually increasing toward the end side. In addition, in this case, the sum of the width W21 of one part obtained by the branching and the width W22 of the other part becomes the width W2 of the upper electrode 233. According to such a structure, the width W2 of the upper electrode 233 can also be reduced toward the end side with a simple structure.

[0084] In the vibration element 20 as described above, the tip portion of the upper electrode 233 is branched into a plurality of branches as described above. According to such a configuration, the width W2 of the upper electrode 233 can be reduced toward the tip side with a simple configuration.

[0085] According to such a fourth embodiment as well, it is possible to produce the same effects as those of the above-described first embodiment.

[0086] <Fifth Embodiment>

[0087] Fig.10 It is a top view showing the vibration element according to the fifth embodiment.

[0088] The vibration element 20 of this embodiment is the same as the vibration element 20 of the first embodiment described above, except that the shape of the upper electrode 233 is different. In addition, in the following description, the description of this embodiment is centered on the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0089] like Fig.10 As shown, in the vibration element 20 of this embodiment, the vibration arms 211, 212, and 213 are linear, and the width W1 is constant along the Y-axis direction. Similarly, the upper electrode 233 is linear, and the width W2 is constant along the Y-axis direction.

[0090] In addition, the vibration arms 211, 212, and 213 have a first region Q1, a second region Q2 closer to the base end side than the first region Q1, a third region Q3 closer to the base end side than the second region Q2, and a fourth region Q4 closer to the base end side than the third region Q3. In addition, the first region Q1, the second region Q2, and the third region Q3 are set to have equal lengths in the Y-axis direction, and the fourth region Q4 is set to be longer than the first region Q1, the second region Q2, and the third region Q3. The width W1 of the first region Q1 is set to be less than the width W1 of the second region Q2, and the width W1 of the second region Q2 is set to be less than the width W1 of the third region Q3. In the present embodiment, the widths W1 of the first region Q1, the second region Q2, the third region Q3, and the fourth region Q4 are respectively equal.

[0091] In addition, holes H are formed in the first region Q1, the second region Q2, and the third region Q3, respectively. In addition, the shape of each hole H is not particularly limited, and is a quadrilateral in the present embodiment. Hereinafter, the hole H formed in the first region Q1 is also referred to as hole H1, the hole H formed in the second region Q2 is also referred to as hole H2, and the hole H formed in the third region Q3 is also referred to as hole H3.

[0092] In particular, in the present embodiment, the same number of holes H are formed in the same arrangement in the first region Q1, the second region Q2, and the third region Q3. Specifically, six holes H1 are formed in a matrix of 2 columns × 3 rows in the first region Q1, six holes H2 are formed in a matrix of 2 columns × 3 rows in the second region Q2, and six holes H3 are formed in a matrix of 2 columns × 3 rows in the third region Q3. 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 in the first region Q1, the second region Q2, and the third region Q3.

[0093] In addition, 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. That is, Se1 / S1<Se2 / S2<Se3 / S3.

[0094] According to such a structure, 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, the same effect as the case where the width W2 is reduced toward the end side as in the first embodiment described above can be exerted. Therefore, the equivalent series resistance R1 of the vibration element 20 can be suppressed to be small, and the increase of the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. Therefore, the increase of 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 this embodiment, by providing three regions Q1, Q2, and Q3 in which the holes H are formed, the average value of the width W2 can be gradually reduced toward the end side. Therefore, the piezoelectric elements 23A, 23B, and 23C can be stably expanded and contracted. In addition, by forming the holes H in each region Q1, Q2, and Q3, the relationship of Se1 / S1<Se2 / S2<Se3 / S3 can be set with a simple structure.

[0095] As described above, the vibration element 20 as described above includes: a vibration substrate 21 having an upper surface as a first surface and a lower surface as a second surface in a front-rear relationship, and formed with a base 210 and vibration arms 211, 212, 213 extending from the base 210; and piezoelectric elements 23A, 23B, 23C arranged on the upper surfaces of the vibration arms 211, 212, 213. In addition, the piezoelectric elements 23A, 23B, 23C include: a lower electrode 231 as a first electrode arranged on the upper surfaces of the vibration arms 211, 212, 213; a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231, i.e., the surface on the opposite side to the vibration arms 211, 212, 213; and an upper electrode 233 as a second electrode arranged on the upper surface of the piezoelectric layer 232, i.e., the surface on the opposite side to the lower electrode 231. In addition, when the vibration substrate 21 is viewed from above, when the direction perpendicular to the Y-axis direction as the first direction in which the vibration arms 211, 212, and 213 extend is set as the X-axis direction as the second direction, the length in the X-axis direction of the region Q between the base 210 and the end of the upper electrode 233 of the vibration arms 211, 212, and 213, that is, the width W1, is greater than the length in the X-axis direction at the base end of the vibration arms 211, 212, and 213. In addition, the vibration arms 211, 212, and 213 have a first region Q1 and a second region Q2 on the base end side of the first region Q1 on the upper surface, and the width W2 of the first region Q1 is less than the width W2 of the second region Q2. Moreover, 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. According to such a structure, the equivalent series resistance R1 of the vibration element 20 can be suppressed to be small, and the increase of the equivalent parallel electrostatic capacitance C0 of the vibration element 20 can be suppressed. Therefore, the increase of 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.

[0096] In addition, as described above, the vibration arms 211, 212, and 213 have a third region Q3 that is closer to the base end side than the second region Q2, and the width W2 of the second region Q2 is less than the width W2 of the third region Q3. Moreover, 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 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 this way, by providing three regions Q1, Q2, and Q3 having different ratios of electrode area to area, the piezoelectric elements 23A, 23B, and 23C can be stably expanded and contracted.

[0097] As described above, the holes H are formed in each of the first region Q1 , the second region Q2 , and the third region Q3 . According to such a configuration, the relationship of Se1 / S1 < Se2 / S2 < Se3 / S3 can be achieved with a simple configuration.

[0098] According to such a fifth embodiment, the same effect as the first embodiment can be achieved. However, the structure of the vibration element 20 is not limited to this. For example, the third region Q3 and the fourth region Q4 may be omitted. That is, the upper electrode 233 may also be composed of the first region Q1 arranged on the tip side and the second region Q2 arranged on the base side. In addition, in this case, the hole H may also be omitted from the second region Q2.

[0099] <Sixth Implementation Method>

[0100] Fig.11 It is a top view showing the vibration element according to the sixth embodiment.

[0101] The vibration element 20 of this embodiment is the same as the vibration element 20 of the fifth embodiment described above, except that the structure of the hole H is different. In addition, in the following description, the description of this embodiment is centered on the differences from the fifth embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0102] like Fig.11 As shown, in the vibration element 20 of the present embodiment, each hole H is a notch opened at the outer edge of the upper electrode 233. Specifically, each hole H arranged in a row on the positive side in the X-axis direction is a notch opened at the side of the upper electrode 233 on the positive side in the X-axis direction, and each hole H arranged in a row on the negative side in the X-axis direction is a notch opened at the side of the upper electrode 233 on the negative side in the X-axis direction. In this way, by forming the holes H with notches, the densely packed portion of the upper electrode 233 can be concentrated in the central portion of the vibration arms 211, 212, 213 in the X-axis direction. Therefore, the expansion and contraction of the piezoelectric elements 23A, 23B, 23C can be efficiently transmitted to the vibration arms 211, 212, 213, and the vibration arms 211, 212, 213 can be made to bend and vibrate with a larger amplitude.

[0103] In the vibration element 20 as described above, the hole H is a notch opened at the outer edge of the upper electrode 233. According to such a structure, the dense portion of the upper electrode 233 can be concentrated in the central part of the vibration arms 211, 212, 213. Therefore, the expansion and contraction of the piezoelectric elements 23A, 23B, 23C can be efficiently transmitted to the vibration arms 211, 212, 213, and the vibration arms 211, 212, 213 can be made to bend and vibrate with a larger amplitude.

[0104] According to such a sixth embodiment as well, it is possible to produce the same effects as those of the fifth embodiment described above.

[0105] <Seventh Embodiment>

[0106] Fig.12 It is a top view showing the vibration element according to the seventh embodiment.

[0107] The vibration element 20 of this embodiment is the same as the vibration element 20 of the fifth embodiment described above, except that the structure of the hole H is different. In addition, in the following description, the description of this embodiment is centered on the differences from the fifth embodiment described above, and the description of the same matters is omitted. In addition, in the figures of this embodiment, the same reference numerals are marked for the same structures as those in the above embodiment.

[0108] like Fig.12 As shown, in the vibration element 20 of the present embodiment, the shapes and sizes of the holes H are the same. Also, 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.

[0109] According to such a seventh embodiment, it is possible to achieve the same effects as those of the fifth embodiment described above.

[0110] The vibration element of the present invention is described above based on the illustrated embodiments, but the present invention is not limited thereto. The structure of each part can be replaced with any structure having the same function. In addition, other arbitrary structures can also be added to the present invention. In addition, the present invention can also combine any two or more structures in the above-mentioned embodiments.

Claims

1. A vibration element, characterized in that: The vibration element has: a vibration substrate having a first surface and a second surface in a front-rear relationship and formed with a base and a vibration arm extending from the base; and a piezoelectric element disposed on the first surface of the vibration arm, The piezoelectric element has: A first electrode, which is disposed on a first surface of the vibration arm; a piezoelectric layer disposed on a surface of the first electrode on the opposite side to the vibration arm; as well as a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode; When the vibration substrate is viewed from above, and a direction perpendicular to the first direction in which the vibration arm extends is set as a second direction, The length of the region of the vibration arm from the base to the tip of the second electrode in the second direction is greater than or equal to the length of the base end of the vibration arm in the second direction. At the distal end portion of the second electrode, the length of the second electrode in the second direction decreases toward the distal end side.

2. The vibration element according to claim 1, wherein A distal end portion of the second electrode is rounded.

3. The vibration element according to claim 1 or 2, wherein: The length of the second electrode in the second direction continuously decreases toward the distal end side.

4. The vibration element according to claim 1 or 2, wherein: The length of the second electrode in the second direction decreases stepwise toward the end side.

5. The vibration element according to claim 1 or 2, wherein: The end portion of the second electrode has a plurality of branches.

6. A vibration element, characterized in that: The vibration element has: a vibration substrate having a first surface and a second surface in a front-rear relationship and formed with a base and a vibration arm extending from the base; and a piezoelectric element disposed on the first surface of the vibration arm, The piezoelectric element has: A first electrode, which is disposed on a first surface of the vibration arm; a piezoelectric layer disposed on a surface of the first electrode on the opposite side to the vibration arm; as well as a second electrode disposed on a surface of the piezoelectric layer opposite to the first electrode; When the vibration substrate is viewed from above, and a direction perpendicular to the first direction in which the vibration arm extends is set as a second direction, The length of the region of the vibration arm from the base to the tip of the second electrode in the second direction is greater than or equal to the length of the base end of the vibration arm in the second direction. The vibration arm includes a first region and a second region on the base end side of the first region on the first surface. The length of the first region in the second direction is less than the length of the second region in the second direction, A ratio of an area of ​​the second electrode disposed in the first region to an area of ​​the first region is smaller than a ratio of an area of ​​the second electrode disposed in the second region to an area of ​​the second region.

7. The vibration element according to claim 6, wherein: The vibration arm has a third region located closer to the base end than the second region. The length of the second region in the second direction is less than the length of the third region in the second direction. A ratio of an area of ​​the second electrode disposed in the second region to an area of ​​the second region is smaller than a ratio of an area of ​​the second electrode disposed in the third region to an area of ​​the third region.

8. The vibration element according to claim 7, wherein: Holes are formed in each of the first region, the second region, and the third region.

9. The vibration element according to claim 8, wherein: The hole is a notch opened at the outer edge of the second electrode.

10. The vibration element according to claim 1 or 6, wherein: The vibration substrate is formed of a silicon substrate.

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