Resonator and electronic equipment

Abstract

This resonator has a first spring part that is configured in a two-dimensional bellows shape so as to be able to expand and contract along a first axis. The first spring part has a plurality of first beams extending in parallel to each other along a second axis perpendicular to the first axis. At least one of the plurality of first beams has a first cavity part located between both side surfaces thereof in the direction of the first axis.

Description

Resonator and Electronic Device

[0001] The present disclosure relates to a resonator and an electronic device.

[0002] A resonator having a spring portion configured in a two-dimensional bellows shape is known (Patent Document 1 below).

[0003] Japanese National Publication of International Patent Application No. 2022-529131

[0004] A resonator according to one aspect of the present disclosure includes a first spring portion configured in a two-dimensional bellows shape that is expandable and contractible along a first axis. The first spring portion includes a plurality of first beams extending parallel to each other along a second axis perpendicular to the first axis. At least one of the plurality of first beams has a first cavity located between side surfaces on both sides in the direction of the first axis.

[0005] An electronic device according to one aspect of the present disclosure includes the above resonator, and a circuit that applies a voltage to the resonator.

[0006] A plan view of a resonator according to an embodiment; an enlarged view of region II in FIG. 1; and a cross-sectional view of the resonator in FIG. 1.

[0007] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, dimensional ratios and the like in the drawings do not necessarily match actual ones. In addition, dimensional ratios and the like may not match between different drawings. Specific shapes and / or dimensions may be exaggerated, and details may be omitted. However, this does not exclude that actual shapes and / or dimensions may be as shown in the drawings, or that features of shapes and / or dimensions may be extracted from the drawings.

[0008] FIG. 1 is a plan view of a resonator 1 according to an embodiment. For convenience, an orthogonal coordinate system D1D2D3 is attached to FIG. 1 and other drawings. The resonator 1 may be used in any orientation. However, for convenience, expressions based on the premise that the +D3 side is the upper side may be used without particular notice.

[0009] In describing embodiments, when we say, for example, that the shape and / or dimensions are "the same" or "symmetrical," it is natural that errors (tolerances) due to processing accuracy, etc., may exist. In piezoelectric materials (especially single crystals), shapes that should be "the same" or "symmetrical" may differ relatively significantly due to anisotropy caused by etching. These differences may also be included in the tolerance. The term "shape" may refer to the shape alone, or to a combination of shape and dimensions. Either interpretation is acceptable as long as it does not create any contradictions.

[0010] (Overall configuration of the resonator) The resonator 1 is, for example, a roughly plate-shaped electronic component with the D3 direction as the thickness direction. Its dimensions are arbitrary. For example, the length in the D1 direction and the length in the D2 direction of the resonator 1 (or the resonator body 1a described later) may be 100 μm or more and 1000 μm or less. The thickness of the resonator 1 or the resonator body 1a may be, for example, 3 μm or more and 100 μm or less.

[0011] The resonator 1 has a spring portion 3 configured in a two-dimensional bellows shape. The spring portion 3 is expandable and contractible in the D1 direction. The spring portion 3 has a piezoelectric element in the part that deforms as it expands and contracts. When a voltage is applied to the piezoelectric element, the spring portion 3 vibrates as it expands and contracts, and the electrical signal generated by this vibration is extracted. The resonator 1 can be used for any purpose, for example, as an oscillator, filter, or sensor.

[0012] In the resonator 1, for example, the principal vibration related to the expansion and contraction of the spring portion 3 may be used. The principal vibration is, in other words, the vibration of the fundamental mode. Theoretically, the wavelength of the fundamental mode vibration is four times the length of the first spring portion 5A or the second spring portion 5B, which is supported in a cantilevered manner and will be described later. The resonant frequency of the fundamental mode is often the lowest among the resonant frequencies related to expansion and contraction. Also, the displacement of the free end (or, from another perspective, the weight portion 9, which will be described later) in the vibration of the fundamental mode is the largest among the vibrations of the multiple modes related to expansion and contraction. The specific value of the resonant frequency of the principal vibration is arbitrary and may be, for example, 10 kHz or more and 300 kHz or less.

[0013] The resonator 1 may have, in addition to the spring portion 3, the following components: • Support beam 7 (first support beam 7A and second support beam 7B): Supports the spring portion 3. • Weight portion 9: Supported by the spring portion 3 and displaced in accordance with the expansion and contraction of the spring portion 3. • Support base portion 11: Supports the support beam 7. The combination of the spring portion 3, support beam 7, and weight portion 9 (in other words, the portion of the resonator 1 excluding the support base portion 11) is sometimes referred to as the resonator body 1a (indicated in Figure 3). Contrary to the explanation herein, only the resonator body 1a may be considered as the resonator.

[0014] The spring portion 3 has one or more (multiple in the illustrated example) cavities 17 (first cavity 17A and second cavity 17B). In piezoelectric materials, the temperature rises and / or falls with compression and / or tension. Consequently, energy loss occurs due to heat conduction. The cavities 17 contribute, for example, to reducing heat conduction. This improves the Q value.

[0015] The resonator body 1a (or resonator 1; the same applies hereinafter in this paragraph) has a shape that is symmetrical with respect to an axis of symmetry (not shown) parallel to the D2 direction, for example. The resonator body 1a also has a shape that is symmetrical with respect to an axis of symmetry (not shown) parallel to the D1 direction, for example. The resonator body 1a also has a shape that is point-symmetrical with respect to a point of symmetry (not shown). Each of the above axes of symmetry passes through, for example, the central portion 3a of the spring portion 3, and more specifically, through the center of gravity G of the resonator body 1a. The above point of symmetry is located, for example, the central portion 3a, and more specifically, at the center of gravity G of the resonator body 1a. The center of gravity G may be considered as the center of gravity of the vibrating part (combination of spring portion 3 and weight portion 9) that vibrates in conjunction with the expansion and contraction of the spring portion 3.

[0016] (Spring section) The spring section 3 has, for example, a first spring section 5A and a second spring section 5B connected in series with each other in the direction of expansion and contraction. A central section 3a is interposed between the first spring section 5A and the second spring section 5B. The center of gravity G is located, for example, at the center of the central section 3a. Ideally, the first spring section 5A and the second spring section 5B expand and contract together at the same time. Also, ideally, the center of gravity G does not displace.

[0017] The first spring section 5A and the second spring section 5B are supported by the central section 3a, and the central section 3a is supported by the support beam 7. Consequently, the ends of the first spring section 5A and the second spring section 5B that are connected to the central section 3a are fixed ends. The ends on the opposite side of the central section 3a (towards the weight section 9) are free ends. The fixed ends are restricted from intentional displacement, while the free ends are permitted to be intentionally displaced.

[0018] The first spring section 5A has a plurality of beams 13 (six in the illustrated example) that extend in parallel to each other in the D2 direction from the central side in the D2 direction to the +D2 side (the portion shown as region II). The plurality of beams 13 are arranged in the D1 direction, with their +D2 side ends and -D2 side ends alternately connected by bases 15. That is, the plurality of beams 13 and the plurality of bases 15 as a whole extend in a zigzag pattern. The number of beams 13 and bases 15 is arbitrary. For example, the number of beams 13 may be two or more, or six or more.

[0019] The portion of the first spring 5A on the +D2 side has been described, but the same applies to the portion of the first spring 5A on the -D2 side. Furthermore, the base portion 15 located on the central side in the D2 direction of the first spring 5A connects the multiple beams 13 on the +D2 side and the multiple beams 13 on the -D2 side. In other words, the first spring 5A as a whole, including the portion on the +D2 side and the portion on the -D2 side, has a shape in which the two-dimensional bellows-like inner (central side in the D2 direction) bends are connected every other.

[0020] The first spring section 5A has been described, and the same applies to the second spring section 5B. In the above explanation, the beam 13 located on the +D2 side and the beam 13 located on the -D2 side of the spring section 3 were treated as separate entities. However, two beams 13 connected in series may be treated as a single beam.

[0021] The specific shapes and dimensions of the beams 13, bases 15, and central portion 3a are arbitrary. For example, multiple beams 13 basically have the same shape and dimensions as each other (except for the beams 13 connected to the central portion 3a). Multiple bases 15 on the central side of the spring portion 3 in the D2 direction have the same shape and dimensions as each other. Multiple bases 15 on both sides of the spring portion 3 in the D2 direction have the same shape as each other. The beams 13, bases 15, and central portion 3a are each roughly rectangular parallelepipeds.

[0022] In the illustrated example, the length of the central portion 3a in the D2 direction is longer than the length of the central base portion 15 of the spring portion 3 in the D2 direction. As a result, among the multiple beams 13, the beam 13 connected to the central portion 3a is shorter than the other beams 13. However, the length of the central portion 3a in the D2 direction may be the same as the length of the central base portion 15 in the D2 direction.

[0023] (Support beam, weight section, and support base) The support beam 7 extends, for example, from the central section 3a to the +D2 side or the -D2 side. The shape and dimensions of the support beam 7 are arbitrary. In the illustrated example, the support beam 7 is a rectangular parallelepiped extending parallel to the D2 direction. Its width may be smaller than, the same as, or larger than the width of the beam 13.

[0024] The weight portion 9 is provided, for example, one on each side of the spring portion 3 in the D1 direction (two in total). The weight portion 9 is connected, for example, to the central position of the spring portion 3 in the D2 direction. The shape and dimensions of the weight portion 9 are arbitrary. In the illustrated example, the weight portion 9 is a rectangular parallelepiped with the same length as the length of the spring portion 3 in the D2 direction. The length of the weight portion 9 in the D1 direction may be smaller than, equal to, or larger than the width (length in the D1 direction) of the beam 13.

[0025] The support base 11 is connected to the opposite side of the central portion 3a of the support beam 7. Each support beam 7 is supported in a cantilevered manner by the support base 11. The two support beams 7 and the central portion 3a as a whole form a double-ended support beam. The shape and dimensions of the support base 11 are arbitrary. In the illustrated example, the support base 11 is configured as a frame surrounding the resonator body 1a. The cross-sectional shape is, for example, rectangular.

[0026] (Example of electrodes) Figure 2 shows an example of electrodes on the resonator 1. This figure is an enlarged view of region II in Figure 1.

[0027] The resonator 1 has a piezoelectric layer, as will be described later with reference to Figure 3. The piezoelectric layer extends, for example, across at least a number of beams 13. Alternatively, for example, the piezoelectric layer extends across the entire resonator body 1a or the entire resonator 1. A conductor layer is superimposed on the upper surface of the piezoelectric layer, either directly or indirectly via a relatively thin insulating film. In Figure 2, hatching is applied to the surface of the conductor layer for convenience.

[0028] The resonator 1 has two types of electrodes 31 (a first electrode 31A and a second electrode 31B) with different potentials. Each electrode 31 extends along the edge of the upper surface of each beam 13. The first electrode 31A and the second electrode 31B extend along the opposite edges of each beam 13. In each beam 13, the position of the first electrode 31A and the second electrode 31B on the +D1 side and the -D1 side are reversed between the +D2 side and the -D2 side of each beam 13, and also reversed between adjacent beams 13. In the center of each beam 13, the first electrode 31A and the second electrode 31B intersect in three dimensions via an insulator (not shown).

[0029] The piezoelectric layer is, for example, polarized in the D1 direction. Therefore, when a voltage of one polarity is applied to the first electrode 31A and the second electrode 31B, one beam 13 expands and the other beam 13 contracts at the +D2 side portion of two beams 13 connected to each other at their +D2 sides. As a result, the +D2 side portions of the two beams 13 bend to one side in the D1 direction. Similarly, the -D2 side portions of two beams 13 connected to each other at their -D2 sides bend to the same one side in the D1 direction. If the polarity is reversed, each portion bends to the opposite side (the other side in the D1 direction). This causes the +D2 side portion of the first spring portion 5A to expand and contract in the D1 direction.

[0030] Although not specifically shown in the figures, two types of electrodes 31 may be arranged in the -D2 side portion of the first spring portion 5A, the +D2 side portion of the second spring portion 5B, and the -D2 side portion of the second spring portion 5B, similar to the +D2 side portion of the first spring portion 5A. The direction of polarization in each portion (whether it is the +D1 side or the -D1 side) and the arrangement of the two types of electrodes 31 (the relationship between the direction from the first electrode 31A to the second electrode 31B and the positive and negative of the D1 direction) may be appropriately set so that the spring portion 3 as a whole extends or contracts in the D1 direction. For example, in the first spring portion 5A, the +D2 side portion and the -D2 side portion have the same polarization direction, and the arrangement of the two types of electrodes 31 is symmetrical with respect to an axis of symmetry parallel to the D1 direction. The first spring portion 5A and the second spring portion 5B have opposite polarization directions, and the arrangement of the two types of electrodes 31 is symmetrical with respect to an axis of symmetry parallel to the D2 direction.

[0031] The configuration of the electrodes of the resonator 1 is not limited to those described above. For example, various electrode configurations disclosed in Patent Document 1 may be applied to this embodiment.

[0032] (Example of a laminated structure) Figure 3 is a cross-sectional view showing an example of a laminated structure of the resonator 1. Details are omitted in this figure. Therefore, Figure 3 can be considered as a cross-sectional view of the resonator 1 viewed in any direction perpendicular to the D3 direction.

[0033] In the illustrated example, the resonator 1 has layers L1 to L5 stacked on top of each other. The resonator body 1a is composed of, for example, the upper layers L1 to L3. Layers L1 to L3 have, for example, the same planar shape as each other, as well as the planar shape shown in Figure 1. The resonator 1 or the support base 11 may also be considered to be composed of layers L1 to L3. Layer L4 is located only in the region of the resonator 1 that overlaps with the support base 11. Therefore, the portion of layers L1 to L3 that constitutes the resonator body 1a is separated upward from layer L5. As a result, the displacement and / or deformation of the resonator body 1a in the D1D2 plane relative to the support base 11 is facilitated.

[0034] Layer L1 is a conductive layer. The conductive layer includes, for example, an electrode 31 and wiring extending from the electrode 31 (only a portion is shown in Figure 2). The material of the conductive layer is arbitrary and may be, for example, Al, Mo, Au, or polysilicon. The thickness of layer L1 is arbitrary and may be, for example, 0.5 μm or more and 2 μm or less.

[0035] Layer L2 is a piezoelectric layer. The material of the piezoelectric layer may be a single crystal or a polycrystalline material. The specific material is also arbitrary. For example, the material of the piezoelectric layer may be AlN, ScAlN, or ZnO. The thickness of layer L2 is arbitrary and may be, for example, 0.5 μm or more and 2 μm or less.

[0036] Layer L3 is a device silicon layer. The device silicon layer is composed of, for example, a single crystal of silicon. The device silicon layer may or may not contain a dopant. The relationship between the crystal orientation and the shape of the resonator 1 is arbitrary. The thickness of layer L3 is arbitrary and may be, for example, 2 μm or more and 20 μm or less.

[0037] Layers L4 and L5 do not directly affect the characteristics of the resonator 1, so they can be made of any material and have any thickness. Layer L4 is an embedded oxide layer. Its material is SiO ２ Layer L5 is the handle silicone layer.

[0038] The resonator 1 may be made of, for example, an SOI substrate (Silicon on Insulator). The resonator 1 may have a configuration different from the one illustrated in Figure 3. For example, various laminated structures disclosed in Patent Document 1 may be applied to this embodiment. Furthermore, the resonator 1 (or resonator body 1a) may be made of layers L1 and L2 alone.

[0039] (Cavity) The cavity 17 shown in Figures 1 and 2 is either filled with gas or in a vacuum state after the resonator 1 is packaged (or, from another perspective, during use of the resonator 1). The gas may be air or another gas (e.g., an inert gas). Typically, the gas has lower thermal conductivity and / or thermal transfer properties compared to the material constituting the resonator body 1a.

[0040] The cavity 17 is located, for example, in a plan view, in a region of the resonator body 1a where the conductive layer (layer L1 in the example of Figure 3) is not present. It is also located in the portion of the resonator body 1a that constitutes the thickness excluding the conductive layer (layers L1 and L2 in the example of Figure 3). This portion is sometimes referred to as the "structural portion."

[0041] The cavity 17 may be a through-hole penetrating the structural part in the thickness direction (D3 direction), or it may be a recess indented from the upper or lower surface of the structural part. Both a recess on the upper surface and a recess on the lower surface may be formed. Furthermore, if the structural part has a laminated structure of three or more layers, the cavity 17 can also be formed inside. The cavity 17 may be configured to be located in the area where the conductive layer is arranged.

[0042] When the cavity 17 is a recess, its depth is arbitrary. For example, in the example in Figure 3, the depth of the recess on the upper surface may correspond to only a part of the thickness of layer L2, or to the entire thickness of layer L2, or to the entire thickness of layer L2 and a part of the thickness of layer L3. The depth of the recess on the lower surface may correspond to only a part of the thickness of layer L3, or to the entire thickness of layer L3, or to the entire thickness of layer L3 and a part of the thickness of layer L2.

[0043] In a plan view, the cavity 17 is located, for example, on at least one of the beams 13. The cavity 17 located on the beam 13 is situated between the sides of the beam 13 in the D1 direction. In other words, the cavity 17 is separated from the sides of the beam 13 in the D1 direction. The cavity 17 may be located at any other appropriate location besides the beam 13.

[0044] In a plan view, the position and number of cavities 17 are arbitrary. In the example of FIG. 1, except for the beam 13 connected to the central portion 3a, all beams 13 have cavities 17 at both ends (in a broader concept, both end sides relative to the center in the length direction). The cavities 17 at both ends (both end sides) are spaced apart from each other. The beam 13 connected to the central portion 3a has the cavity 17 only at the end portion opposite to the central portion 3a. Note that, unlike the illustrated example, the cavity 17 extending over the entire length of the beam 13 (extending from one end to the other end) may be provided.

[0045] As described above, the shape of the resonator body 1a is point-symmetrical. Therefore, it can be said that the first cavity 17A of the first spring portion 5A and the second cavity 17B of the second spring portion 5B have a point-symmetrical positional relationship.

[0046] In the example of FIG. 2, in the portion on the central side in the length direction of the beam 13 (the portion at the position where the first electrode 31A and the second electrode 31B intersect), the electric field applied in the polarization direction is smaller than that in other portions (most part of the beam 13). Consequently, when the spring portion 3 expands and contracts, the above-mentioned other portions are likely to have larger bending deformation and / or larger stress as compared with the central portion. Therefore, it can be said that the cavity 17 is not located at a portion where bending deformation is relatively small and / or stress is relatively small, but is located at a portion where bending deformation is relatively large and / or stress is relatively large.

[0047] The inertial force in the D1 direction accompanying expansion and contraction of the spring portion 3 is more likely to be converted into a larger bending moment toward the end side of the beam 13 (the base 15 side from another perspective). In particular, in an aspect where the weight portion 9 is connected to the central side of the spring portion 3 in the D2 direction, a large bending moment is likely to be applied to the end portion on the +D2 side or -D2 side of the spring portion 3. Consequently, when the spring portion 3 expands and contracts, the end portion of the beam 13 is likely to have larger bending deformation and / or larger stress as compared with the intermediate portion of the beam 13. Therefore, it can be said that the cavity 17 is not located at a portion where bending deformation is relatively small and / or stress is relatively small, but is located at a portion where bending deformation is relatively large and / or stress is relatively large.

[0048] The position, shape, and dimensions of the cavity 17 in plan view are arbitrary. The planar shape (including dimensions) of the cavity 17 may be constant in the D3 direction, or it may vary depending on the position in the D3 direction. In the description of the embodiment, excluding the errors described above, the planar shape of the cavity 17 will be assumed to be constant in the D3 direction.

[0049] In the illustrated example, the cavity 17 is elongated in the direction in which the beam 13 extends (slit-like or groove-like). Its aspect ratio is arbitrary; for example, the length in the longitudinal direction (for example, the maximum length if the cavity 17 is not rectangular; the same applies to the length in the transverse direction; the same applies hereafter) may be 2 times or more, or 5 times or more, the length in the transverse direction. The width of the cavity 17 may be, for example, less than half the width of the beam 13, or 1 / 2 or more. The cavity 17 can reduce heat transfer even if its width is small, so it may be made as small as possible. The length of the cavity 17 may be, for example, 1 / 3 or less, or 1 / 5 or less, of the length of the beam 13.

[0050] In an embodiment where cavities 17 are located at both ends of the beam 13, the cavity 17 located on the central side of the spring portion 3 in the D2 direction and the cavities 17 located on the +D2 side or -D2 side of the spring portion 3 may be the same in position, shape, dimensions, etc., or they may be different. In the illustrated example, the cavities 17 on the +D2 side or -D2 side are longer in the D2 direction than the cavities 17 located on the central side. The difference and / or ratio is arbitrary; for example, the former is 1.1 times or more the latter. In terms of other dimensions, etc., they are the same.

[0051] In plan view, the beam 13 is connected to the surface of the base 15 facing the D2 direction (in other words, the side surface of the beam 13 is not considered to be connected to the base 15). From another perspective, as can be understood from the reference numeral of the base 15 shown in the upper left of Figures 1 and 2, a virtual line passing through the position of the surface of the base 15 facing the D2 direction and parallel to the D1 direction is considered the boundary line between the base 15 and the beam 13 (in other words, a virtual line extending the side surface of the beam 13 toward the base 15 is not considered the boundary line).

[0052] When the cavity 17 is located at the end of the beam 13, the cavity 17 may or may not reach the boundary between the beam 13 and the base 15 (as shown in the illustration). In the latter case, whether or not the cavity 17 is located at the end can be determined, for example, by whether or not the distance from the boundary to the cavity 17 is shorter than the width of the beam 13 or the width of the cavity 17. Also, the cavity 17 may or may not be located at the base 15 beyond the boundary between the beam 13 and the base 15 (as shown in the illustration).

[0053] The specific dimensions of the cavity 17 when it is located on the base 15 are also arbitrary. For example, the length of the cavity 17 in the D2 direction at the base 15 may be less than half the length of the base 15 in the D2 direction, or it may be half or more. The length of the cavity 17 in the D2 direction at the base 15 may be shorter than, equal to, or longer than the length of the cavity 17 in the D2 direction at the beam 13.

[0054] (Examples of other configurations) Although not specifically illustrated, examples of other configurations are given.

[0055] The resonator 1 may have only one of the first spring portion 5A and the second spring portion 5B. In the embodiment where only the first spring portion 5A is provided, the support beam 7 and the central portion 3a may be extended flat (i.e., without gaps) toward the support base 11 toward the -D1 side (in other words, the support beam 7 and the central portion 3a may be omitted). Alternatively, the weight portion 9 toward the -D1 side may be directly connected to the central portion 3a. In this case, the weight portion 9 may be made larger than in the illustrated example to maintain the position of the center of gravity G of the resonator body 1a (or the portion supported by the support beam 7).

[0056] In the first spring section 5A and / or the second spring section 5B, the beam 13 closest to the free end (or, from another viewpoint, the beam 13 furthest from the center of gravity G) among the plurality of beams 13 may not have a cavity 17.

[0057] The beam 13 near the fixed end is subjected to the inertial force of the beam 13 near the free end, and therefore tends to deform (or stress, from another perspective) more than the beam 13 near the free end. In the beam 13 where the deformation is relatively small, by not providing the cavity 17, it is possible to prioritize securing the volume of the piezoelectric material over thermal insulation. As a result, vibration can be generated efficiently. The difference and / or ratio between the number of beams 13 with cavity 17 and the number of beams 13 without cavity 17 is arbitrary.

[0058] In the first spring section 5A and / or the second spring section 5B, the plurality of beams 13 may include beams 13 having a cavity 17 (an example of a third beam) and beams 13 having a cavity 17 and being closer to the free end than the third beam (an example of a fourth beam). The cavity 17 of the third beam may be longer than the cavity 17 of the fourth beam in a direction parallel to the D2 direction.

[0059] In this case, for example, an effect similar to that described for the configuration in which the beam 13 closest to the free end does not have a cavity 17 is achieved. The difference and / or ratio between the length of the cavity 17 of the third beam and the length of the cavity 17 of the fourth beam are arbitrary.

[0060] In the first spring section 5A and / or the second spring section 5B, the plurality of beams 13 may include beams 13 having a cavity 17 (an example of a fifth beam) and beams 13 that do not have a cavity 17 and are shorter than the fifth beam (an example of a sixth beam).

[0061] The longer the beam 13, the greater the bending moment (or bending deformation, from another perspective) near the end. Therefore, by not providing a cavity 17 in the relatively shorter beam 13, it is possible to prioritize securing the volume of the piezoelectric material over heat insulation in the shorter beam 13. The difference and / or ratio between the length of the fifth beam and the length of the sixth beam are arbitrary.

[0062] Layer L3 may contain a high concentration of dopant and function as a lower electrode. Alternatively, a lower electrode may be provided between layer L2 and layer L3. The lower electrode may extend over the entire layer L2 (piezoelectric layer). The piezoelectric layer may be polarized in the D3 direction. A constant potential (e.g., a reference potential) may be applied to the lower electrode. Potentials with opposite polarities (high and low relative to the constant potential) may be alternately applied to the first electrode 31A and the second electrode 31B.

[0063] In this case, in each of the -D2 side portion and the +D2 side portion of each beam 13, one of the -D1 side portion and the +D1 side portion may extend in the D2 direction, and the other may contract in the D2 direction. Consequently, each of the -D2 side portion and the +D2 side portion may be deformed by deflection in the D1 direction. The direction of deflection in the D1 direction may be opposite for the -D2 side portion and the +D2 side portion. For adjacent beams 13, the direction of deflection of the -D2 side portions may be opposite, and the direction of deflection of the +D2 side portions may be opposite.

[0064] (Electronic device) The resonator 1 may be packaged, for example, in a box-shaped package, or packaged using WLP (wafer level chip size package) technology. It may then be mounted on a circuit board or the like to constitute an electronic device 35 (Figure 2). The electronic device 35 may have, for example, a circuit 33 that applies voltage to two types of electrodes 31 (in Figure 2, for convenience, the symbol for an AC power supply is shown).

[0065] (Summary) As described above, the resonator 1 according to the embodiment has a first spring portion 5A configured in a two-dimensional bellows shape that can expand and contract along the D1 axis (an example of a first axis). The first spring portion 5A has a plurality of beams 13 (an example of a first beam) that extend in parallel to each other along the D2 axis (an example of a second axis) perpendicular to the D1 axis. At least one of the plurality of beams 13 has a first cavity portion 17A located between the sides on both sides in the direction of the D1 axis. Therefore, for example, energy loss due to heat conduction can be reduced and the Q value can be improved.

[0066] In the above embodiments, axis D1 is an example of a first axis. Axis D2 is an example of a second axis. The beam 13 of the first spring section 5A is an example of a first beam. The beam 13 of the second spring section 5B is an example of a second beam. The central portion of the beam 13 in the longitudinal direction is an example of a first portion, and the end portion of the beam 13 is an example of a second portion. Layer L3 is an example of a silicon layer. The portion connected to the central portion 3a of the first spring section 5A (or the central portion 3a) is an example of a fixed end. The portion connected to the weight portion 9 of the first spring section 5A is an example of a free end.

[0067] 1...Resonator, 3...Spring section, 5A...First spring section, 5B...Second spring section, 13...Beam (First beam or Second beam), 17A...First cavity section, 17B...Second cavity section.

Claims

1. A resonator having a first spring portion configured in a two-dimensional bellows shape that is expandable and contractible along a first axis, wherein the first spring portion has a plurality of first beams extending in parallel to each other along a second axis perpendicular to the first axis, and at least one of the plurality of first beams has a first cavity located between the sides on both sides in the direction of the first axis.

2. The resonator according to claim 1, having a second spring portion configured in a two-dimensional bellows shape that is expandable and contractible along the first axis, the second spring portion having a plurality of second beams extending in parallel to each other along the second axis, at least one of the plurality of second beams having a second cavity portion located between the sides on both sides in the direction of the first axis, the first spring portion and the second spring portion being connected via a central portion that supports the first spring portion and the second spring portion so that they are in series with each other along the first axis, and the first cavity portion and the second cavity portion having a point-symmetric positional relationship with respect to a point of symmetry located in the central portion.

3. The resonator according to claim 1 or 2, wherein at least one of the plurality of first beams has a first cavity located at one end and a first cavity located at the other end that is not connected to the first cavity at the one end.

4. The resonator according to any one of claims 1 to 3, wherein the first spring portion has a base portion that connects the ends of adjacent first beams, and at least one of the plurality of first beams has a first cavity portion at the end connected to the base portion.

5. The resonator according to claim 4, wherein the base portion has a part of the first cavity portion located at the end portion.

6. The resonator according to any one of claims 1 to 5, wherein the first beam having the first cavity has a first portion and a second portion which undergoes greater bending deformation than the first portion when the spring portion expands and contracts along the first axis, and the second portion has the first cavity.

7. The resonator according to any one of claims 1 to 6, wherein each of the plurality of first beams has a silicon layer extending along the first axis and the second axis, and at least a portion of the first cavity is located in the silicon layer.

8. The resonator according to any one of claims 1 to 7, wherein the first spring portion has a fixed end on one side in the direction of the first axis and a free end on the other side in the direction of the first axis, and among the plurality of first beams, the first beam closest to the free end does not have a first cavity.

9. The resonator according to any one of claims 1 to 8, wherein the first spring portion has a fixed end on one side in the direction of the first axis and a free end on the other side in the direction of the first axis, and the plurality of first beams include a third beam having the first cavity and a fourth beam having the first cavity and being closer to the free end than the third beam, and the first cavity of the third beam is longer in the direction parallel to the second axis than the first cavity of the fourth beam.

10. The resonator according to any one of claims 1 to 9, wherein the plurality of first beams include a fifth beam having the first cavity and a sixth beam that does not have the first cavity and is shorter than the fifth beam.

11. An electronic device having a resonator according to any one of claims 1 to 10, and a circuit for applying a voltage to the resonator.

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