Vibration element

Abstract

To realize a vibration element having a high Q value by suppressing a decrease in vibration strength.SOLUTION: A vibration element 100 using a piezoelectric body made of a zinc-blende type single crystal includes: a vibration part 1 having a ring shape and in which a plurality of first vibration parts and a plurality of second vibration parts as a vibrator unit 10 are alternately arranged; and a reflection part 13 that reflects an incident transverse wave SV as a transverse wave SV. Each of the first vibration parts has a first electrode and a first connecting part, and each of the second vibration parts has a second electrode and a second connecting part. Each of the second vibration parts has the second electrode and the second connecting part, the plurality of first electrodes and the plurality of second electrodes are alternately disposed on a plane perpendicular to the [001] axis of the single crystal, and in the vibration part 1, the vibrator unit 10 is disposed on the piezoelectric body in parallel with at least the [100] axis of the single crystal, or is disposed on the piezoelectric body in parallel with the [010] axis of the single crystal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, various vibration elements have been known that vibrate a vibration part using a plurality of vibrator units. For example, Patent Document 1 discloses a Lame vibration quartz crystal vibrator in which a plurality of small vibration parts are two-dimensionally arranged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-111434 Summary of the Invention [Problem to be solved by the invention]

[0004] The Lame vibration quartz crystal unit of Patent Document 1 vibrates with equal intensity in two directions: the row direction, which is one of the two-dimensional array directions, and the column direction, which is perpendicular to the row direction. The resonant frequencies corresponding to these two directions depend on the width of the vibrating section. Therefore, to achieve coordinated vibration in these two directions, the row and column dimensions of the vibrating section must be matched. However, increasing the resonant frequency shortens the wavelength contributing to resonance, and therefore, when the resonant frequency is high, there is a risk that the vibration intensity will decrease due to errors in processing accuracy, etc. A decrease in vibration intensity reduces the Q value, which is the quality factor Q. [Means for solving the problem]

[0005] The vibration element of the present invention for solving the above problem is a vibration element using a piezoelectric material made of a zinc blende-type single crystal, and is equipped with a vibration part having a ring shape, in which a plurality of first vibration parts and a plurality of second vibration parts are alternately arranged as vibrator units in at least a part thereof, and a reflection part that reflects incident transverse waves as transverse waves, wherein each of the first vibration parts has a first electrode and a first connection part that electrically connects the first electrodes to each other, and each of the second vibration parts has a second electrode and a second connection part that electrically connects the second electrodes to each other, the plurality of first electrodes and the plurality of second electrodes are alternately arranged on a plane perpendicular to the

[0001] axis of the single crystal, and the vibration part is characterized in that the vibrator units are arranged on the piezoelectric material at least parallel to the

[0100] axis of the single crystal, or arranged on the piezoelectric material parallel to the

[0010] axis of the single crystal. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a perspective view of a vibration element according to an embodiment of the present invention, viewed from the (001) plane side of a cubic crystal. [Figure 2] 1 is a schematic diagram showing how a transverse wave is reflected as a transverse wave by a first reflecting section, and then reflected as a transverse wave by a second reflecting section. [Figure 3] Graph showing the relationship between the angle of incidence and the angle of reflection, the angle of incidence and the amplitude of reflection, and the angle of incidence and the phase change when a shear wave is incident. [Figure 4] FIG. 2 is a plan view showing the periphery of a first vibrating portion and a second vibrating portion of the vibration element according to the embodiment of the present invention. [Figure 5] 3 is a perspective view showing the vicinity of a position where a first connecting portion and a second connecting portion of a vibration element according to an embodiment of the present invention overlap. FIG. [Figure 6] 3 is a perspective view showing the vicinity of a position where a first connecting portion and a second connecting portion of a vibration element according to an embodiment of the present invention overlap. FIG. [Figure 7] 6 is a graph showing the change over time in voltage at the first electrode, the second electrode, and the common electrode of the vibration element according to the embodiment of the present invention. [Figure 8] FIG. 2 is a schematic plan view of a part of a vibration part of a vibration element according to an embodiment of the present invention, showing a state when no voltage is applied. [Figure 9] FIG. 2 is a schematic plan view of a part of a vibration part of a vibration element according to an embodiment of the present invention, illustrating a state when a voltage is applied. [Figure 10] 10 is a schematic plan view of a part of a vibration part of a vibration element according to an embodiment of the present invention, showing a state when a voltage having a phase opposite to that in FIG. 9 is applied. FIG. [Figure 11] FIG. 2 is a diagram showing the crystal structure of a single crystal of a piezoelectric body of a vibration element according to an embodiment of the present invention. [Figure 12] FIG. 1 is a schematic diagram showing a vibration element according to an embodiment of the present invention, viewed from the (001) plane side of a cubic crystal, for explaining the deformation state of each vibrator unit. DETAILED DESCRIPTION OF THE INVENTION

[0007] First, the present invention will be briefly described. The vibration element of a first aspect of the present invention for solving the above problem is a vibration element using a piezoelectric material made of a zinc blende-type single crystal, and is equipped with a vibration part having a ring shape, in which a plurality of first vibration parts and a plurality of second vibration parts are alternately arranged as vibrator units in at least a part thereof, and a reflection part that reflects incident transverse waves as transverse waves, wherein each of the first vibration parts has a first electrode and a first connection part that electrically connects the first electrodes to each other, and each of the second vibration parts has a second electrode and a second connection part that electrically connects the second electrodes to each other, the plurality of first electrodes and the plurality of second electrodes are alternately arranged on a plane perpendicular to the

[0001] axis of the single crystal, and the vibration part is characterized in that the vibrator units are arranged on the piezoelectric material at least parallel to the

[0100] axis of the single crystal, or arranged on the piezoelectric material parallel to the

[0010] axis of the single crystal.

[0008] According to this aspect, the vibrator units are arranged in the ring-shaped vibrating section at least parallel to the

[0100] axis of the single crystal and disposed on the piezoelectric body, or parallel to the

[0010] axis of the single crystal and disposed on the piezoelectric body, and the vibrating section further includes a reflecting section that reflects incident shear waves as shear waves. By arranging the first and second vibrating sections as multiple vibrator units in the ring-shaped vibrating section and providing a reflecting section, the vibration waves generated by each vibrator unit can be synchronized in phase and circulated around the ring-shaped vibrating section. Therefore, by circulating the vibration waves, the vibration strength can be increased, and a high Q value can be obtained.

[0009] A second aspect of the vibration element of the present invention is an aspect dependent on the first aspect, characterized in that the reflecting portion is arranged adjacent to one of the first vibration portion and the second vibration portion on the side where the transverse wave is incident, and is arranged adjacent to the other of the first vibration portion and the second vibration portion on the side where the transverse wave is emitted.

[0010] According to this aspect, the reflecting section is disposed adjacent to one of the first vibrating section and the second vibrating section on the side where the shear waves are incident, and is disposed adjacent to the other of the first vibrating section and the second vibrating section on the side where the shear waves are emitted. That is, the reflecting section reflects the shear waves incident from one of the first vibrating section and the second vibrating section as shear waves to the other of the first vibrating section and the second vibrating section. With this configuration, the phases of the vibration waves generated by each vibrator unit can be easily aligned and the waves can be circulated around the ring-shaped vibrating section.

[0011] A third aspect of the vibration element of the present invention is an aspect dependent on the second aspect, characterized in that the vibration part comprises a first part extending along the

[0100] axis of the single crystal and a second part extending along the

[0010] axis of the single crystal.

[0012] According to this aspect, the vibrating part includes a first portion extending along the <0100> axis of the single crystal and a second portion extending along the <0010> axis of the single crystal. With this configuration, multiple vibrator units can be efficiently arranged on the ring-shaped vibrating part, and vibration intensity can be efficiently increased.

[0013] A fourth aspect of the vibration element of the present invention is an aspect dependent on the third aspect, characterized in that the reflecting portion has a first reflecting surface that reflects the transverse wave incident from the first portion.

[0014] According to this aspect, the reflecting section includes a first reflecting surface that reflects the transverse wave incident from the first portion. With this configuration, the transverse wave incident from the first portion can be efficiently reflected by the first reflecting surface as a transverse wave toward the second portion.

[0015] The fifth aspect of the vibration element of the present invention is an aspect dependent on the fourth aspect, and is characterized in that the angle between the first reflecting surface and the

[0100] axis of the single crystal is greater than or equal to 44° and less than or equal to 46°.

[0016] According to this aspect, the angle between the first reflecting surface and the <0100> axis of the single crystal is 44° or more and 46° or less. With this configuration, the first reflecting surface can particularly efficiently reflect a transverse wave incident from the first portion to the second portion as a transverse wave.

[0017] A sixth aspect of the vibration element of the present invention is an aspect dependent on the fourth aspect, characterized in that the reflecting portion has a second reflecting surface that reflects the transverse wave incident from the second portion.

[0018] According to this aspect, the reflecting section includes, in addition to the first reflecting surface, a second reflecting surface that reflects the transverse wave incident from the second portion. With this configuration, the first reflecting surface can efficiently reflect the transverse wave incident from the first portion to the second portion as a transverse wave, and the second reflecting surface can efficiently reflect the transverse wave incident from the second portion to the first portion as a transverse wave.

[0019] The seventh aspect of the vibration element of the present invention is an aspect dependent on the sixth aspect, and is characterized in that the angle between the second reflecting surface and the

[0010] axis of the single crystal is greater than or equal to 44° and less than or equal to 46°.

[0020] According to this aspect, the angle between the second reflecting surface and the <0010> axis of the single crystal is 44° or more and 46° or less. With this configuration, the second reflecting surface can particularly efficiently reflect a transverse wave incident from the second portion back to the first portion as a transverse wave.

[0021] The eighth aspect of the vibration element of the present invention is an aspect dependent on any one of the first to seventh aspects, and is characterized in that it comprises a spacer between the first connection portion and the second connection portion at a position where the first connection portion and the second connection portion overlap when viewed from a direction parallel to the

[0001] axis of the single crystal, insulating the first connection portion from the second connection portion.

[0022] According to this aspect, a spacer is provided between the first and second connecting portions at a position where the first and second connecting portions overlap when viewed in a direction parallel to the

[0001] axis of the single crystal, insulating the first and second connecting portions from each other, thereby enabling a desired voltage to be stably applied to the first and second electrodes.

[0023] The vibration element of the ninth aspect of the present invention is an aspect dependent on any one of the first to seventh aspects, and is characterized by comprising: a base portion which is provided around at least a part of the periphery of the vibration portion when viewed from a direction parallel to the

[0001] axis of the single crystal, and in which a plurality of the first vibration portions and a plurality of the second vibration portions are not arranged; and a support portion which bridges the vibration portion and the base portion.

[0024] According to this aspect, the device includes a base portion provided around at least a portion of the periphery of the vibrating portion when viewed from a direction parallel to the

[0001] axis of the single crystal, on which the plurality of first vibrating portions and the plurality of second vibrating portions are not disposed, and a support portion bridging the vibrating portion and the base portion. With this configuration, it is possible to preferably provide a vibrating portion that vibrates when a voltage is applied to the electrodes, and a base portion that does not vibrate even when a voltage is applied to the electrodes.

[0025] A vibration element according to a tenth aspect of the present invention is an aspect dependent on the ninth aspect, characterized in that the support portion bridges the nodal points of the vibration portion and the base portion.

[0026] According to this aspect, the support section bridges the nodal points of the vibration section and the base section. This configuration bridges the base section and the areas of the vibration section that do not vibrate even when the vibration section vibrates due to application of a voltage to the electrodes. Therefore, it is possible to prevent the base section from vibrating even when a voltage is applied to the electrodes.

[0027] The vibration element of the 11th aspect of the present invention is an aspect dependent on the 9th aspect, characterized in that the support portion extends parallel to the

[0100] axis of the single crystal or the

[0010] axis of the single crystal.

[0028] According to this aspect, the support portion extends parallel to the <0100> axis or the <0010> axis of the single crystal, and this configuration allows the vibrating portion and the base portion to be suitably bridged.

[0029] The vibration element of the twelfth aspect of the present invention is an aspect dependent on any one of the first to seventh aspects, and is characterized in that the piezoelectric body is made of any of SiC, GaN, GaAs, ZnS, CdS, and AlN.

[0030] According to this aspect, the piezoelectric body is made of any one of SiC, GaN, GaAs, ZnS, CdS, and AlN. With this configuration, a suitable piezoelectric body can be obtained.

[0031] Hereinafter, a vibration element 100 according to an embodiment of the present invention will be described with reference to the accompanying drawings, with reference to FIGS. 1 to 12. The vibration element 100 of this embodiment is a piezoelectric vibration element using a piezoelectric material made of a zinc blende single crystal. As shown in FIG. 1, the vibration element 100 of this embodiment is mainly composed of a vibration section 1 that vibrates when a voltage is applied, a base section 3 that does not vibrate even when a voltage is applied, and a support section 2 that bridges the vibration section 1 and the base section 3. Note that "does not vibrate even when a voltage is applied" does not strictly mean that it does not vibrate at all, but means that vibration is suppressed to a level that does not cause any malfunctions.

[0032] The vibration unit 1 is composed of a substrate of a zinc-blende single crystal (point group -43m) with a piezoelectric effect. Examples of zinc-blende single crystals include quartz crystal cut at a specific cut angle and cubic 3C-SiC single crystals. The vibration unit 1 is ring-shaped, and as will be described in detail later, multiple first vibration units and multiple second vibration units are arranged adjacent to each other in a portion of the ring, alternating in the direction of the single crystal's

[0100] axis and the direction of the single crystal's

[0100] axis. In Figures 1, 2, 4 to 6, and 8 to 12, the a1 axis corresponds to the single crystal's

[0100] axis, the a2 axis corresponds to the single crystal's

[0010] axis, and the a3 axis corresponds to the single crystal's

[0001] axis.

[0033] The vibrating section 1 is composed of an electrode group including electrode units 4 each consisting of electrodes 4a, 4b, 4c, 4d, and 4e formed on the surface of a single-crystal substrate having a piezoelectric effect, the positive side of the a3 axis, a solid electrode (not shown) formed on the back surface of the single-crystal substrate (the negative side of the a3 axis), and a reflecting section 13. The structure consisting of the electrode group on the front surface of the single-crystal substrate, the solid electrode on the back surface of the single-crystal substrate positioned so as to overlap with the electrode group in the a3 axis direction, and the region of the single-crystal substrate where shear stress is generated primarily due to the piezoelectric effect when a voltage is applied between the electrodes on the front and back surfaces of the single-crystal substrate functions as a single vibrator. In other words, this structure constitutes a vibrator unit 10.

[0034] For example, the single crystal substrate can be 3C-SiC single crystal, or AlN or GaN, which belong to the zinc blende single crystal (point group -43m).The electrode material can be Au, Pt, Al, or the like, and a layer of Ti or its compound can be provided between these metal materials and the single crystal to strengthen the adhesion.

[0035] In this specification, the

[0100] axis may refer to the direction of the arrow on the a1 axis, the [-100] axis may refer to the direction opposite to the direction of the arrow on the a1 axis, and the

[0100] axis may refer to the direction along the arrow on the a1 axis and its opposite direction. The

[0010] axis may refer to the direction of the arrow on the a2 axis, the [0-10] axis may refer to the direction opposite to the direction of the arrow on the a2 axis, and the

[0010] axis may refer to the direction along the arrow on the a2 axis and its opposite direction. The

[0001] axis may refer to the direction of the arrow on the a3 axis, the [00-1] axis may refer to the direction opposite to the direction of the arrow on the a3 axis, and the

[0001] axis may refer to the direction along the arrow on the a3 axis and its opposite direction.

[0036] In this specification, for example, the expression "0001" axis is merely a representative notation, and may refer to the "0100" axis, the "0010" axis, the [0-10] axis, the [00-1] axis, etc., taking into consideration the symmetry of the single crystal. Even when the names of the directions of the single crystal are different in this way, if the structure has an equivalent geometric relationship with the arrangement direction of the vibrator units 10 and the reflecting portions 13 or the extension direction of the support portion 2, the properties of the vibrating element 100 are also equivalent, and therefore are included in the present invention.

[0037] The excitation section 12, corresponding to the region where the electrode units 4 are formed, has a structure in which the oscillator units 10 are arranged in a matrix along the a1-a2 plane, i.e., the (001) plane of the cubic crystal. The shear displacement of each oscillator unit 10 generates a shear wave SV, which propagates in the longitudinal direction of the excitation section 12, i.e., the a2 direction. The component of the shear wave SV that elastically vibrates within the a1-a2 plane becomes a traveling wave. As will be described in detail later, this traveling wave is totally reflected by the reflecting section 13 and travels around the ring-shaped structure of the vibration section 1 by repeating excitation and reflection. In addition to the traveling wave component traveling in one direction, there is also a traveling wave component traveling in the opposite direction. These two traveling waves interfere with each other to generate a standing wave. Due to the structure of the vibration section 1, the center of this standing wave becomes a node.

[0038] As shown in Fig. 2, the reflecting unit 13 has a reflecting surface 13a, which is a flat end surface, for reflecting the traveling wave of the transverse wave SV generated in the exciting unit 12, thereby bending the transverse wave SV as it is toward the adjacent exciting unit 12. In Fig. 2, the exit angle of the transverse wave SV when the incident angle of the transverse wave SV (incident angle φ) is a variable is defined as the exit angle φ*. Here, the behavior of reflection at the reflecting unit 13 will be described below.

[0039] If the sound velocities of longitudinal waves P (P waves) and shear waves SV (SV waves) in a crystal are represented by α and β, respectively, the values ​​of α and β are generally different. For example, typical values ​​for 3C-SiC are α = 11,938 m / s and β = 7,608 m / s. In this case, when longitudinal waves P are reflected from a free surface, shear wave SV components are generated, which are emitted at different angles and separate from the longitudinal wave P components. Similarly, when shear waves SV are reflected from a free surface, they separate into shear wave SV components and longitudinal wave P components. The equations showing this reflection amplitude and phase change are shown in Table 1 below. The variables used here are shown in Equation 1 below. The emission angle can be calculated using Equation 1 below, and the results calculated using the incident angle of the shear wave SV as a variable are shown in the graph in Figure 3.

[0040] [Table 1]

[0041]

number

[0042] Under sound velocity conditions, longitudinal wave P components may also be generated in addition to shear wave SV components. However, as shown in the upper and middle graphs of Figure 3, when the incident angle φ is 45°, for example, longitudinal wave P components are not generated, and all vibration energy remains as shear wave SV and is totally reflected. Furthermore, as shown in Table 1, this characteristic occurs when p, defined in Equation 1, is equal to η and is independent of the values ​​of α and β. Furthermore, although a phase shift of -π [rad] occurs upon reflection, as shown in the lower graph of Figure 3, this value changes gradually with the incident angle φ, which has the advantage of being less affected by dimensional errors during manufacturing. Thus, when the incident angle φ is 45°, a unique reflection behavior is exhibited. However, when actually manufacturing the vibration element 100, it is desirable to keep the incident angle φ within the range of 45° ± 1°, i.e., between 44° and 46°, due to the phase shift at the reflecting surface 13a of the reflecting portion 13 and the tolerance of the output angle φ*.

[0043] Next, an example of a method for connecting the electrode units 4 will be described below based on this embodiment. To obtain constructive vibrations from the traveling waves generated by all the oscillator units 10 working together, the electrode units 4 are connected so that the directions of the electric fields applied in the direction of the

[0001] axis (a3 axis) are antiparallel to adjacent oscillator units 10 in the direction of the

[0100] axis (a1 axis) or the

[0010] axis (a2 axis). To achieve this, all the electrode units belong to either an a-electrode group corresponding to the first vibration part of the oscillator units 10, such as oscillator units 10a and 10c in FIG. 4, or a b-electrode group corresponding to the second vibration part of the oscillator units 10, such as oscillator units 10b and 10d in FIG. 4.

[0044] Here, Fig. 4 shows an enlarged structure of region R1 in Fig. 1. Electrodes 4a and 4c of the electrode unit 4 belong to electrode group a, and electrode 4e in Fig. 1 also belongs to electrode group a, and these are electrically connected to lead electrode 5a via first connection portion 16A, which is connection portion 16 of electrode group a. On the other hand, electrodes 4b and 4d of the electrode unit 4 in Figs. 1 and 4 belong to electrode group b, and these are electrically connected to lead electrode 5b via second connection portion 16B, which is connection portion 16 of electrode group b.

[0045] FIG. 5 shows an enlarged view of the electrode intersection 11 in FIG. 4. Electrodes 4b and 4d are connected by a second connection 16B, and electrodes 4c and 4e are connected by a first connection 16A. In the electrode intersection 11, the link portion 11c of the first connection 16A and the bridge portion 11b of the second connection 16B are electrically insulated by a spacer 11a. The spacer 11a can be made of, for example, an oxide such as SiO2, a nitride, or a resin material. Using this cross-connection method, all electrode units 4 belonging to electrode group a are connected by the first connection 16A. Similarly, all electrode units 4 belonging to electrode group b are connected by the second connection 16B. As a result of these connections, electrode units 4 with opposite polarities are arranged alternately on the (001) plane of the cubic crystal, which is the surface of the vibrating part 1. In addition, the solid electrode formed on the cubic (00-1) surface, which is the back surface of the vibrating part 1, is connected to a common electrode (not shown) on the cubic (00-1) surface, which is the back surface of the base part 3, via a connection part 16 formed on the cubic (00-1) surface, which is the back surface of the support part 2.

[0046] FIG. 6 shows an enlarged view of the electrode intersection 9 in FIG. 1. At the electrode intersection 9, the link portion 9c of the first connection portion 16A and the bridge portion 9b of the second connection portion 16B are electrically insulated by a spacer 9a. Like the spacer 11a, the spacer 9a can be made of an oxide such as SiO2, a nitride, or a resin material. Using this crossover connection method, the lead electrode 5a is connected to all of the electrode units 4 belonging to electrode group a via the first connection portion 16A. Similarly, the lead electrode 5b is connected to all of the electrode units 4 belonging to electrode group b via the second connection portion 16B.

[0047] Here, the support portion 2 is a portion for holding the vibrating portion 1 in a relative position with respect to the base portion 3. The same single-crystal substrate as the vibrating portion 1 can be used as the material, but it can also be formed by bonding other materials. To minimize vibration leakage from the vibrating portion 1 to the base portion 3, it is desirable to connect the support portion 2 to the vibrating portion 1 at a location where there is no vibration displacement of the vibrating portion 1, i.e., a node position. While it is desirable to minimize the thickness of the support portion 2 to minimize vibration leakage from the vibrating portion 1 to the base portion 3, it is also desirable to ensure the necessary strength by making the support portion 2 of an appropriate thickness to prevent damage to the support portion 2 due to external vibration or impact. Furthermore, while FIG. 1 shows the support portion 2 as a straight, rectangular columnar shape, its length can be optimized or a curved structure can be incorporated to alleviate stress concentration and improve impact resistance. In this embodiment, electrodes are formed on the surface of the support portion 2, which also serves to electrically connect the vibrating portion 1 to the electrodes formed on the base portion 3.

[0048] The base portion 3 is fixed in a hermetically sealed package that surrounds the piezoelectric vibrator. It can be made of the same single-crystal substrate as the vibrating portion 1 and supporting portion 2, but it can also be formed by bonding other materials. All of the electrode units 4 in electrode group a are electrically connected to lead electrode 5a formed on the surface of the base portion 3 shown in FIG. 1 via electrodes formed on the surface of supporting portion 2. On the other hand, all of the electrode units 4 in electrode group b are electrically connected to lead electrode 5b shown in FIG. 1. Furthermore, lead electrode 5a and lead electrode 5b are connected to an oscillator circuit (not shown) installed in the same package by wire bonding or the like to supply power to the vibrating portion 1.

[0049] In the vibrating element 100 of this embodiment, applying a voltage between the electrode unit 4 and the opposing common electrode allows an electric field to be applied to the single-crystal substrate in the

[0001] axial direction (a3 axis). This action enables the single crystal of each vibrator unit 10 to operate in contour shear vibration. Contour shear vibration is a vibration mode in which, when an electric field corresponding to a certain phase is applied to a certain vibrator unit 10, it expands in a specific direction and contracts in a direction perpendicular to that direction. When the electric field direction is reversed, it contracts in a specific direction and expands in a direction perpendicular to that direction. This contour shear vibration allows equal amounts of expansion and contraction to occur simultaneously in different directions in a localized area within the single-crystal substrate, eliminating volumetric changes and providing advantages in terms of thermoelastic loss and Akhiezer loss due to phonon scattering.

[0050] Here, examples of voltage waveforms applied to the lead electrodes 5a, 5b, and common electrode are shown in FIG. 7. These voltage waveforms can be generated by the oscillator circuit (not shown) described above. In FIG. 7, the lead electrode 5a is represented by a solid line, the lead electrode 5b by a dashed line, and the common electrode by a two-dot dashed line. The voltage waveforms applied to the lead electrodes 5a and 5b are sine waves with the same amplitude but are shifted in phase by π [rad] for half a cycle. The common electrode voltage is the average voltage applied to the lead electrodes 5a and 5b. As shown in FIG. 7, when the voltages applied to the lead electrodes 5a and 5b have opposite signs but the same amplitude, the voltage of the common electrode is a constant value.

[0051] A desired vibration operation is possible by applying an AC voltage of a frequency at which the vibrating section 1 resonates to the lead electrodes 5a and 5b. FIG. 8 shows the outline shape of each vibrator unit 10 when no voltage is applied between the lead electrodes 5a and 5b. As shown in FIG. 8, the outline shape of each vibrator unit 10 at this time is square. Here, the vibrator units 10 hatched in the same direction have electrode units 4 that belong to the same electrode group formed therein. In detail, the electrode units 4 hatched with lines extending from the upper right to the lower left correspond to electrode group a, and the electrode units 4 hatched with lines extending from the upper left to the lower right correspond to electrode group b.

[0052] When the relative phase of the AC voltage is 0 [rad], for example, when a positive voltage is applied between lead electrode 5a and lead electrode 5b, the contour of each transducer unit 10 is displaced in a diamond shape as shown in Figure 9. This displacement is known as "contour slip." When transducer units 10 with different displacement directions are alternately arranged, a wave-like displacement distribution is formed as shown by the wavy line in Figure 9.

[0053] On the other hand, when the relative phase is π [rad], the applied voltage is reversed relative to the state shown in Figure 9. A negative voltage is applied between the lead electrodes 5a and 5b, resulting in the state shown in Figure 10, which shows a displacement distribution with an opposite phase to the state shown in Figure 9. Although the diamond shape of each vibrator unit 10 is exaggerated in Figures 9 and 10, even when the voltage application direction is continuously reversed, the boundary surfaces of adjacent vibrator units 10 are smooth and have a concave-convex relationship where the warping is matched, preventing unnecessary distortion. Similarly, by repeatedly reversing the voltage application direction in accordance with the resonant frequency, all vibrator units 10 cooperate and constructively interact with each other, enabling stable, low-loss vibration. This reverses the phases of adjacent loops of the standing wave, resulting in a stable standing wave.

[0054] Here, we will explain which polarity is appropriate for the electrode units 4 of the two transducer units 10 adjacent to the reflecting section 13. As described above with reference to Figure 3, the reflecting surface 13a of the reflecting section 13 undergoes a phase change of -π [rad]. At the same time, when converted from the length of the path that the shear wave SV takes through the reflecting section 13, the shear wave undergoes a phase change of -π [rad] due to the propagation delay during this period. In other words, the path length L1 of the shear wave SV in the transducer unit 10 shown in Figure 8 and the path length L2 of the shear wave SV in the reflecting section 13 located between the transducer units 10 are both half the wavelength of the wavy line shown in Figure 9.

[0055] This means that the path of the shear wave SV passing through the reflecting section 13 located between the transducer units 10 undergoes a phase change of -2π [rad]. Considering the periodicity of the shear wave SV, this means that the substantial phase change while passing through the reflecting section 13 is equivalent to zero. Therefore, by giving different polarities to the electrode units 4 of the two transducer units 10 adjacent to the reflecting section 13, it is possible to form a shear wave SV whose phase changes continuously. In other words, as shown in Figure 4, if the electrode 4c adjacent to the reflecting section 13 belongs to the a electrode group, it is desirable that the electrode 4d belong to the b electrode group.

[0056] With the above configuration, by applying an AC voltage and displacing it, it is possible to induce transverse waves SV that travel clockwise and counterclockwise when viewed from the axial direction of the ring-shaped vibrating part 1. When the AC frequency matches the resonant frequency of the vibrating part 1, the transverse waves SV excited in all the vibrator units 10 cooperate and reinforce each other. This makes it possible to obtain a stable, low-loss standing wave, i.e., contour shear vibration.

[0057] Next, we will explain the appropriate crystal orientation for achieving the above-mentioned vibration operation. Figure 11 shows the crystal structure of 3C-SiC used in the vibration element 100 of this example. The single crystal's

[0100] axis, single crystal's

[0010] axis, and single crystal's

[0001] axis correspond to the a1 axis, a2 axis, and a3 axis, respectively, and confirm the displacement when an electric field is applied.

[0058] In general, the piezoelectric tensor e of e form in a crystal of point group -43m is described by Equation 2 below:

[0059]

number

[0060] On the other hand, the piezoelectric tensor d of the d-form is the elastic compliance tensor S E Using the following equation 3, the following equation 4 can be derived.

[0061]

number

[0062]

number

[0063] Here, the displacement tensor S when an electric field E having components E1, E2, and E3 in the directions of the a1, a2, and a3 axes, respectively, is applied can be expressed by the following equation 5.

[0064]

number

[0065] Here, when an electric field is applied in the axial direction of the a3 axis, only the component of E3 becomes non-zero, and therefore only the component S6 of the displacement tensor S becomes non-zero. The definition equation for this component S6 is Equation 6 below.

[0066]

number

[0067] Here, u1 and u2 represent the amount of displacement in the axial direction of the a1 axis and the a2 axis, respectively. Next, we will use Figure 12 to explain how the above-mentioned amount of displacement actually causes deformation of the vibrating part 1. In particular, since component S6 does not have a component in the axial direction of the a3 axis, it is expressed in a two-dimensional plane including the a1 axis and the a2 axis. First, from the defining formula 6, we obtain the following formula 7, and from formula 7, we obtain the following formula 8.

[0068]

number

[0069]

number

[0070] Here, if we assume that component S6 is a positive value, then S12 and S21 will also be positive values. When moving only a small distance +Δa1 from the S12 component of the defining equation (Equation 6), the change in displacement will be +Δu2, and similarly, when moving +Δa2 from the S21 component, the displacement will be +Δu1. The displacement obtained by combining these will be in the positive direction of the a1' axis in Figure 9. Conversely, at positions (-Δa1, -Δa2), the displacements will be -Δu1, -Δu2, so the combined displacement will be in the negative direction of the a1' axis. As a result, the small area within the oscillator unit 10 will be elongated and deformed in the axial direction of the a1' axis.

[0071] On the other hand, at position (Δa1, -Δa2), there is a positive displacement along the a2' axis, and at position (-Δa1, Δa2), there is a negative displacement along the same axis, resulting in contraction deformation along the a2' axis. Then, when the direction of applied voltage is reversed, the sign of component S6 is also reversed, and the expansion and contraction directions are swapped.

[0072] As explained above, by assigning the

[0001] axis to the a3 axis, the

[0110] axis to the a1' axis, and the [-110] axis to the a2' axis shown in Figure 1, the displacement required for the desired contour shear vibration can be obtained. Furthermore, at points (Δa1, 0), (-Δa1, 0), (0, Δa2), and (0, -Δa2), contour shear vibration occurs but there is no displacement at all; in other words, they are vibration nodes. Therefore, providing the support 2 in this direction can suppress vibration leakage to the base 3. Therefore, it is desirable to provide the support 2 in one of the crystal orientations

[0100] , [-100],

[0010] , or [0-10] from the center of gravity of any oscillator unit 10. As shown in Figure 1, the vibration element 100 of this embodiment has such a configuration, and for example, the vibrator unit 10 corresponding to the electrode unit 4 has a support portion 2 provided in the [-100] direction from its center of gravity.

[0073] That is, in the vibration element 100 of this embodiment, the support portion 2 bridges the nodal points of the vibration portion 1 and the base portion 3. By being configured in this manner, the vibration element 100 of this embodiment can bridge the regions of the vibration portion 1 that do not vibrate even when the vibration portion 1 vibrates by applying a voltage to the electrode units 4 as electrodes, and the base portion 3. Therefore, the vibration element 100 of this embodiment can prevent the base portion 3 from vibrating even when a voltage is applied to the electrode units 4.

[0074] From another perspective, assuming that the support portion 2 bridges the nodes of the vibration portion 1 and the base portion 3, the support portion 2 is connected to the four sides of the vibration portion 1, two of which extend along the <0100> axis (a1 axis) of the single crystal, and the remaining two extend parallel to the <0010> axis (a2 axis) of the single crystal. With this configuration, the vibration element 100 of this embodiment can suitably bridge the vibration portion 1 and the base portion 3.

[0075] An oscillator can be constructed by combining the above-described vibration element 100 with an oscillation circuit. Furthermore, a more stable oscillator can be obtained by housing these in a vacuum package. While this embodiment uses a piezoelectric body made of a 3C-SiC single crystal, materials other than 3C-SiC single crystal may be used as long as the piezoelectric body is made of a zinc blende single crystal.

[0076] Here, the vibration element 100 of this embodiment will be described from another perspective. As described above, the vibration element 100 of this embodiment has a ring shape and includes a vibration section 1 in which a plurality of first vibration sections, such as vibrator unit 10a, vibrator unit 10c, and vibrator unit 10e, and a plurality of second vibration sections, such as vibrator unit 10b and vibrator unit 10d, are alternately arranged in at least a portion of the vibration element 100. The vibration element 100 also includes a reflection section 13 that reflects incident shear waves SV as shear waves SV. Here, each first vibration section includes a first electrode, such as electrode 4a, electrode 4c, and electrode 4e, and a first connection section 16A that electrically connects the first electrodes to each other. Each second vibration section includes a second electrode, such as electrode 4b and electrode 4d, and a second connection section 16B that electrically connects the second electrodes to each other. The plurality of first electrodes and the plurality of second electrodes are arranged alternately on a plane perpendicular to the

[0001] axis of the single crystal, and the vibrating part 1 has vibrator units 10 arranged on the piezoelectric body parallel to the

[0100] axis of the single crystal, and also arranged on the piezoelectric body parallel to the

[0010] axis of the single crystal.

[0077] In this way, the vibrator units 10 are arranged in the piezoelectric body at least parallel to the

[0100] axis of the single crystal, or arranged in the piezoelectric body parallel to the

[0010] axis of the single crystal, and further configured to include a reflecting section 13 that reflects the incident shear wave SV as a shear wave SV, thereby making it possible to match the phases of the vibration waves generated by each vibrator unit 10 and cause them to circulate in the ring-shaped vibrating section 1. Therefore, the vibrating element 100 of this embodiment configured in this way generates a shear wave SV and causes it to circulate, thereby increasing the vibration strength and achieving a high Q value.

[0078] Furthermore, in the vibration element 100 of this embodiment, the reflecting portion 13 is disposed between the first electrode and the second electrode. For example, as shown in FIG. 4, the reflecting portion 13 is provided between the first electrode 4c and the second electrode 4d. In other words, the reflecting portion 13 is disposed adjacent to one of the first vibrating portion and the second vibrating portion on the side where the shear wave SV is incident, and is disposed adjacent to the other of the first vibrating portion and the second vibrating portion on the side where the shear wave SV is emitted. With this configuration, the vibration element 100 of this embodiment can reflect the shear wave SV incident from one of the first vibrating portion and the second vibrating portion as a shear wave SV to the other of the first vibrating portion and the second vibrating portion. In other words, with this configuration, the vibration element 100 of this embodiment can easily align the phases of the vibration waves generated by each vibrator unit 10 and circulate around the ring-shaped vibration portion 1.

[0079] 1, in the vibration element 100 of this embodiment, the vibration part 1 includes a first part 1A extending along the <0100> axis of the single crystal and a second part 1B extending along the <0010> axis of the single crystal. With this configuration, it is possible to efficiently arrange a plurality of vibrator units 10 in the ring-shaped vibration part 1, and it is possible to efficiently increase the vibration strength.

[0080] Here, the reflecting portion 13 has a reflecting surface 13a, and the reflecting surface 13a can be considered to have a first reflecting surface that reflects the transverse wave SV incident from the first portion 1A to the second portion 1B. With this configuration, the transverse wave SV incident from the first portion 1A can be efficiently reflected by the first reflecting surface as a transverse wave SV to the second portion 1B.

[0081] On the other hand, as described above, in the vibration element 100 of this embodiment, the shear wave SV can be caused to circulate clockwise and counterclockwise in the ring-shaped vibration portion 1 when viewed from the

[0001] axial direction, so the reflecting surface 13a can also be considered to serve as a second reflecting surface that reflects the shear wave SV incident from the second portion 1B to the first portion 1A. Therefore, with this configuration, the first reflecting surface can efficiently reflect the shear wave SV incident from the first portion 1A to the second portion 1B as a shear wave SV, and the second reflecting surface can efficiently reflect the shear wave SV incident from the second portion 1B to the first portion 1A as a shear wave SV.

[0082] Here, the angle formed by the reflecting surface 13a and the <0100> axis of the single crystal is preferably 44° or more and 46° or less. This is because, with such a configuration, the generation of longitudinal waves P is suppressed, and the first reflecting surface can particularly efficiently reflect the shear waves SV incident from the first portion 1A to the second portion 1B as shear waves SV, and the second reflecting surface can particularly efficiently reflect the shear waves SV incident from the second portion 1B to the first portion 1A as shear waves SV.

[0083] 5, the vibration element 100 of this embodiment includes a spacer 11a between the first connection portion 16A and the second connection portion 16B at the electrode intersection 11 where the first connection portion 16A and the second connection portion 16B overlap when viewed in a direction parallel to the

[0001] axis of the single crystal, insulating the first connection portion 16A from the second connection portion 16B. Therefore, the vibration element 100 of this embodiment can stably apply a desired voltage to the first electrode and the second electrode.

[0084] 6, the vibration element 100 of this embodiment includes a spacer 9a between the first connection portion 16A and the second connection portion 16B at the electrode intersection 9 where the first connection portion 16A and the second connection portion 16B overlap when viewed in a direction parallel to the

[0001] axis of the single crystal, which insulates the first connection portion 16A from the second connection portion 16B. Therefore, the vibration element 100 of this embodiment can stably apply a desired voltage to the first electrode and the second electrode.

[0085] Moreover, the vibration element 100 of this embodiment includes a base portion 3 that is provided around at least a portion of the periphery of the vibration portion 1 when viewed from a direction parallel to the

[0001] axis of the single crystal, and on which the plurality of first vibration portions and the plurality of second vibration portions are not arranged, and a support portion 2 that bridges the vibration portion 1 and the base portion 3. By being configured in this manner, the vibration element 100 of this embodiment can suitably include the vibration portion 1 that vibrates when a voltage is applied to the electrode units 4, and the base portion 3 that does not vibrate even when a voltage is applied to the electrode units 4.

[0086] Although there are no particular limitations on the material of the piezoelectric body as long as it is made of a zinc blende single crystal, it is preferable that the piezoelectric body be made of any of SiC, GaN, GaAs, ZnS, CdS, and AlN, as this configuration will result in a suitable piezoelectric body.

[0087] As described above, by arranging multiple vibrator units 10 operating in contour vibration mode in a ring shape, the phases of the acoustic waves generated by each vibrator unit 10 are aligned and rotated, resulting in a single constructive vibration mode and a high Q value. Furthermore, by forming two electrode groups with different polarities on the front surface of the vibrating part 1 and a common electrode on the back surface, alignment of the front and back surfaces is not required during patterning, improving productivity. Additionally, by using zinc blende crystals on a single crystal substrate and arranging them in the appropriate crystal orientation, strong contour vibration can be achieved. Due to these effects, the vibrating element 100 of this embodiment can generate a large-amplitude, stable signal from the vibrating part 1, resulting in an oscillator with low phase noise.

[0088] The present invention is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit of the present invention. For example, the present invention can be applied to local oscillators incorporating the vibration element 100 of each of the above-described embodiments, distance measurement / positioning systems using the same local oscillator, and highly sensitive MEMS sensors. The technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0089] 1...vibration part, 1A...first part, 1B...second part, 2...support part, 3...base part, 4...electrode unit, 4a...electrode (first electrode), 4b...electrode (second electrode), 4c...electrode (first electrode), 4d...electrode (second electrode), 4e...electrode (first electrode), 5a...lead electrode, 5b...lead electrode, 9...electrode intersection part, 9a...spacer, 9b...bridge part, 9c...link part, 10...vibrator unit, 10a...vibrator unit (first vibrating part), 10b...vibration vibrator unit (second vibrating section), 10c... vibrator unit (first vibrating section), 10d... vibrator unit (second vibrating section), 10e... vibrator unit (first vibrating section), 11... electrode intersection, 11a... spacer, 11b... bridge section, 11c... link section, 12... excitation section, 13... reflecting section, 13a... reflecting surface (first reflecting surface, second reflecting surface), 16... connection section, 16A... first connecting section, 16B... second connecting section, 100... vibrating element, P... longitudinal wave, R1... area, SV... transverse wave

Claims

1. A vibration element using a piezoelectric body made of a zinc blende single crystal, a vibration section having a ring shape, in which a plurality of first vibration sections and a plurality of second vibration sections are alternately arranged as vibrator units in at least a part of the vibration section; a reflecting portion that reflects the incident transverse wave as a transverse wave, each of the first vibration portions has a first electrode and a first connection portion that electrically connects the first electrodes to each other; each of the second vibration portions has a second electrode and a second connection portion that electrically connects the second electrodes to each other; the plurality of first electrodes and the plurality of second electrodes are alternately arranged on a plane perpendicular to the [001] axis of the single crystal; The vibration element is characterized in that the vibrator units of the vibration section are arranged in the piezoelectric body at least parallel to the [100] axis of the single crystal, or arranged in the piezoelectric body parallel to the [010] axis of the single crystal.

2. The vibration element according to claim 1 , A vibration element characterized in that the reflection portion is arranged adjacent to one of the first vibration portion and the second vibration portion on the side where the transverse wave is incident, and is arranged adjacent to the other of the first vibration portion and the second vibration portion on the side where the transverse wave is emitted.

3. The vibration element according to claim 1 , A vibration element characterized in that the vibration part comprises a first portion extending along the [100] axis of the single crystal and a second portion extending along the [010] axis of the single crystal.

4. The vibration element according to claim 3, The vibration element, wherein the reflecting portion has a first reflecting surface that reflects the transverse wave incident from the first portion.

5. The vibration element according to claim 4, A vibration element, wherein the angle formed between the first reflecting surface and the [100] axis of the single crystal is 44° or more and 46° or less.

6. The vibration element according to claim 4, The vibration element, characterized in that the reflecting portion has a second reflecting surface that reflects the transverse wave incident from the second portion.

7. The vibration element according to claim 6, A vibration element, wherein the angle formed between the second reflecting surface and the [010] axis of the single crystal is 44° or more and 46° or less.

8. The vibration element according to any one of claims 1 to 7, A vibration element characterized in that a spacer is provided between the first connection portion and the second connection portion at a position where the first connection portion and the second connection portion overlap when viewed from a direction parallel to the [001] axis of the single crystal, insulating the first connection portion from the second connection portion.

9. The vibration element according to any one of claims 1 to 7, A vibration element characterized by comprising: a base portion that is provided around at least a portion of the vibration portion when viewed from a direction parallel to the [001] axis of the single crystal, and on which multiple first vibration portions and multiple second vibration portions are not arranged; and a support portion that bridges the vibration portion and the base portion.

10. The vibration element according to claim 9, The vibration element is characterized in that the support portion bridges the nodal points of the vibration portion and the base portion.

11. The vibration element according to claim 9, The vibration element, wherein the support portion extends parallel to the [100] axis or the [010] axis of the single crystal.

12. The vibration element according to any one of claims 1 to 7, A vibration element characterized in that the piezoelectric body is made of any one of SiC, GaN, GaAs, ZnS, CdS, and AlN.

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