Resonator and resonant device

Abstract

The present application relates to a resonator and a resonating device. The present application provides a resonator and a resonating device capable of further improving DLD. The resonator (10) includes a vibration section (110) including a plurality of vibration arms (121A to 121D) each having a fixed end, at least two of which are out-of-plane bent at different phases, and a base section (130) having a front end section (131A) to which the fixed ends of the plurality of vibration arms (121A to 121D) are connected, and a rear end section (131B) opposite to the front end section (131A); a holding section (140) configured to hold the vibration section (110); and two support arms (151A, 151B) each having one end connected to the holding section (140), and the other end connected to one part of the rear end section (131B) of the base section (130).

Description

Technical Field

[0001] The present invention relates to a resonator and a resonant device for multiple vibrating arms vibrating in an out-of-plane bending vibration mode. Background Technology

[0002] Previously, resonant devices using MEMS (Micro Electro Mechanical Systems) technology were used, for example, as timing devices. These resonant devices are mounted on printed circuit boards assembled in electronic devices such as smartphones. The resonant device includes a lower substrate, an upper substrate forming a cavity between the lower substrate and the upper substrate, and a resonator disposed within the cavity between the lower and upper substrates.

[0003] For example, Patent Document 1 discloses a resonator having multiple vibrating arms. This resonator includes: a vibrating part having a base and multiple vibrating arms; the base having a front end and a rear end opposite the front end; fixed ends of the multiple vibrating arms being connected to the front end of the base and extending in a direction away from the front end; a holding part being disposed around at least a portion of the vibrating part; and a holding arm being disposed between the vibrating part and the holding part, one end being connected to the base, and the other end being connected to a region in the holding part closer to the front end than the rear end of the base. In the resonator of Patent Document 1, by making the connection position of the holding arm to the base less than 60% of the length of half the base length, the drive-level dependence (DLD) characteristic is improved.

[0004] Patent Document 1: International Publication No. 2016 / 175218

[0005] However, in recent years, the demand for miniaturization of resonators has become increasingly stringent. In resonators whose size is limited by miniaturization, it has become increasingly difficult to improve DLD by simply making the connection position of the holding arm relative to the length of the base length less than a specified proportion, as in Patent Document 1. Summary of the Invention

[0006] The present invention was made in view of the following situation, and one of its objectives is to provide a resonator and resonant device that can further improve DLD.

[0007] The resonator according to one aspect of the present invention includes: a vibrating part comprising a plurality of vibrating arms and a base, wherein the plurality of vibrating arms are three or more vibrating arms each having a fixed end, and at least two of them are bent out of plane at different phases; the base has one end for connecting to the fixed end of each of the plurality of vibrating arms and another end opposite to the fixed end; a holding part configured to hold the vibrating part; and two support arms, one end of each of the support arms being connected to the holding part, and the other end of each of the support arms being connected to a portion of the other end of the base.

[0008] One aspect of the resonant device relates to the present invention includes the resonator described above.

[0009] According to the present invention, DLD can be further improved. Attached Figure Description

[0010] Figure 1 This is a perspective view that briefly shows the appearance of the resonant device in one embodiment.

[0011] Figure 2 It is a brief representation Figure 1 An exploded perspective view of the structure of the resonant device shown.

[0012] Figure 3 It is a brief representation Figure 2 The diagram shows a top view of the resonator's construction.

[0013] Figure 4 It is a brief representation Figure 1 A cross-sectional view along the X-axis of the stacked structure of the resonant device shown.

[0014] Figure 5 It is a schematic representation Figure 1 A cross-sectional view along the Y-axis of the stacked structure of the resonant device shown.

[0015] Figure 6 It is a schematic representation Figure 3 A top view of the displacement distribution caused by the vibration of the vibrating part.

[0016] Figure 7 It is a schematic representation Figure 3 A three-dimensional diagram showing the displacement distribution caused by the vibration of the vibrating part.

[0017] Figure 8 It means by Figure 3 The graph shows the displacement of the base caused by the vibration of the vibrating part.

[0018] Figure 9 It means Figure 3 The diagram shows the relationship between the connection point at the base of the support arm and the DLD.

[0019] Figure 10 It is used for explanation Figure 3 A top view showing the dimensions of the vibrating part. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described. In the following drawings, the same or similar constituent elements are indicated by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of the parts are schematic and should not be construed as limiting the technical scope of the present invention to these embodiments.

[0021] First, refer to Figure 1 and Figure 2 A general structure of a resonant device according to one embodiment of the present invention will be described. Figure 1 This is a perspective view that briefly shows the appearance of the resonant device 1 in one embodiment. Figure 2 It is a brief representation Figure 1 An exploded perspective view of the structure of the resonant device 1 shown.

[0022] The resonant device 1 includes a lower cover 20, a resonator 10, and an upper cover 30. That is, the resonant device 1 is constructed by sequentially stacking the lower cover 20, the resonator 10, and the upper cover 30. The lower cover 20 and the upper cover 30 are arranged to face each other with a gap between them and the resonator 10. Furthermore, the lower cover 20 and the upper cover 30 are an example of the "cover" of the present invention.

[0023] The structure of the resonant device 1 will be described below. In the following description, the side of the resonant device 1 with the upper cover 30 will be referred to as the upper (or front) side, and the side with the lower cover 20 will be referred to as the lower (or back) side.

[0024] The resonator 10 is a MEMS oscillator manufactured using MEMS technology. The resonator 10 is bonded to the lower cover 20 and the upper cover 30 to seal the resonator 10 and form a vibration space for it. Furthermore, the resonator 10, the lower cover 20, and the upper cover 30 are each formed using a silicon (Si) substrate (hereinafter referred to as "Si substrate"), and the Si substrates are bonded together. Alternatively, the resonator 10, the lower cover 20, and the upper cover 30 can also be formed using an SOI (Silicon On Insulator) substrate with stacked silicon layers and silicon oxide films, respectively.

[0025] The lower cover 20 includes a rectangular flat base plate 22 disposed along the XY plane, and a sidewall 23 extending from the periphery of the base plate 22 along the Z-axis direction, i.e., the stacking direction of the lower cover 20 and the resonator 10. In the lower cover 20, a recess 21 is formed on the surface opposite to the resonator 10, defined by the surface of the base plate 22 and the inner surface of the sidewall 23. The recess 21 forms at least a portion of the vibration space of the resonator 10. Alternatively, the lower cover 20 may not have the recess 21 and may have a flat plate structure. Furthermore, an air-absorbing layer may be formed on the resonator 10 side surface of the recess 21 of the lower cover 20.

[0026] In addition, the lower cover 20 has a protrusion 50 formed on the surface of the base plate 22. The detailed structure of the protrusion 50 will be described later.

[0027] The top cover 30 includes a rectangular flat base plate 32 disposed along the XY plane and a sidewall 33 extending from the periphery of the base plate 32 along the Z-axis. In the top cover 30, a recess 31 is formed on the surface opposite the resonator 10, defined by the surface of the base plate 32 and the inner surface of the sidewall 33. The recess 31 forms at least a portion of the space for the resonator 10 to vibrate, i.e., the vibration space. Alternatively, the top cover 30 may not have the recess 31 and may have a flat plate structure. Furthermore, an air-absorbing layer may be formed on the resonator 10 side surface of the recess 31 of the top cover 30.

[0028] By joining the upper cover 30, the resonator 10, and the lower cover 20, the vibration space of the resonator 10 is hermetically sealed, maintaining a vacuum state. Alternatively, the vibration space can be filled with a gas such as an inert gas.

[0029] Next, refer to Figure 3 A general structure of a resonator according to one embodiment is described. Figure 3 It is a brief representation Figure 2 A top view of the structure of the resonator 10 shown.

[0030] like Figure 3 As shown, resonator 10 is a MEMS oscillator manufactured using MEMS technology. Figure 3 In the XY plane of the orthogonal coordinate system, the vibration is dominated by the out-of-plane bending vibration mode (hereinafter also referred to as the "main mode").

[0031] The resonator 10 includes a vibration section 110, a holding section 140, and a support arm section 150.

[0032] The vibrating part 110 has a longitudinal direction Figure 3 The outline of a rectangle extended by the XY plane in an orthogonal coordinate system. The vibrating part 110 is disposed inside the holding part 140, and a space is formed between the vibrating part 110 and the holding part 140 at a predetermined interval. Figure 3In this example, the vibration unit 110 includes an excitation unit 120 composed of four vibration arms 121A to 121D (hereinafter collectively referred to as "vibration arms 121") and a base 130. Furthermore, the number of vibration arms is not limited to four; for example, it can be any number of three or more. In this embodiment, the excitation unit 120 and the base 130 are integrally formed.

[0033] Vibration arms 121A, 121B, 121C, and 121D extend along the Y-axis and are arranged side-by-side at predetermined intervals along the X-axis. One end of vibration arm 121A is a fixed end connected to the front end portion 131A of the base 130 (described later), and the other end is an open end located away from the front end portion 131A of the base 130. Vibration arm 121A includes a mass attachment portion 122A formed on the open end side and an arm portion 123A extending from the fixed end and connected to the mass attachment portion 122A. Similarly, vibration arms 121B, 121C, and 121D also include mass attachment portions 122B, 122C, and 122D, and arm portions 123B, 123C, and 123D, respectively. Furthermore, the arm portions 123A to 123D have, for example, a width of approximately 30 μm in the X-axis direction and a length of approximately 400 μm in the Y-axis direction.

[0034] In the excitation unit 120 of this embodiment, two vibrating arms 121A and 121D are arranged on the outer side in the X-axis direction, and two vibrating arms 121B and 121C are arranged on the inner side. The width of the gap (hereinafter referred to as the "release width") W1 formed between the arm portions 123B and 123C of the two inner vibrating arms 121B and 121C is, for example, set to be greater than the release width W2 between the arm portions 123A and 123B of the adjacent vibrating arms 121A and 121B in the X-axis direction, and the release width W2 between the arm portions 123D and 123C of the adjacent vibrating arms 121D and 121C in the X-axis direction. The release width W1 is, for example, about 25 μm, and the release width W2 is, for example, about 10 μm. In this way, by setting the release width W1 to be greater than the release width W2, the vibration characteristics and durability of the vibration unit 110 are improved. In addition, the release width W1 can be set to be smaller than the release width W2, or it can be set to be equally spaced, so as to enable the miniaturization of the resonant device 1.

[0035] The mass-addition parts 122A to 122D each have mass-addition films 125A to 125D on their respective surfaces. Therefore, the weight per unit length (hereinafter simply referred to as "weight") of each of the mass-addition parts 122A to 122D is greater than the weight of each of the arm parts 123A to 123D. This allows for miniaturization of the vibrating part 110 and improves its vibration characteristics. Furthermore, the mass-addition films 125A to 125D not only increase the weight of the end portions of the vibrating arms 121A to 121D, but also function as frequency-adjusting films, allowing for adjustment of the resonant frequency of the vibrating arms 121A to 121D by removing a portion of them.

[0036] In this embodiment, the width of each of the mass attachments 122A to 122D along the X-axis is, for example, about 70 μm, which is larger than the width of each of the arm portions 123A to 123D along the X-axis. This allows for a further increase in the weight of each of the mass attachments 122A to 122D. However, as long as the weight of each of the mass attachments 122A to 122D is greater than the weight of each of the arm portions 123A to 123D, the width of each of the mass attachments 122A to 122D along the X-axis is not limited to the example of this embodiment. The width of each of the mass attachments 122A to 122D along the X-axis may also be equal to or less than the width of each of the arm portions 123A to 123D along the X-axis.

[0037] When the resonator 10 is viewed from above (hereinafter referred to as "top view"), the mass attachments 122A to 122D are generally rectangular in shape and have curved shapes with rounded corners, such as arc shapes. Similarly, the arms 123A to 123D are generally rectangular in shape and have arc shapes near the fixed end connected to the base 130 and near the connection portion connected to each of the mass attachments 122A to 122D. However, the shapes of the mass attachments 122A to 122D and the arms 123A to 123D are not limited to the example of this embodiment. For example, the shapes of the mass attachments 122A to 122D may also be generally trapezoidal or generally L-shaped. In addition, the shapes of the arms 123A to 123D may also be generally trapezoidal. The mass attachments 122A to 122D and the arm portions 123A to 123D may also be formed with bottomed grooves having openings on either the surface side or the back side, and holes having openings on both the surface side and the back side. The grooves and holes may be separate from the side surfaces that connect the surface and the back side, or they may have openings on the side surfaces.

[0038] When viewed from above, the base 130 has a front end 131A, a rear end 131B, a left end 131C, and a right end 131D. As described above, the fixed ends of the vibrating arms 121A to 121D are connected to the front end 131A. The connecting arm 155 of the support arm portion 150, which will be described later, is connected to the rear end 131B.

[0039] The front end portion 131A, rear end portion 131B, left end portion 131C, and right end portion 131D are all parts of the outer edge of the base 130. Specifically, the front end portion 131A and the rear end portion 131B are ends extending along the X-axis direction, and are arranged opposite each other. The left end portion 131C and the right end portion 131D are ends extending along the Y-axis direction, and are arranged opposite each other. The two ends of the left end portion 131C are connected to one end of the front end portion 131A and one end of the rear end portion 131B, respectively. The two ends of the right end portion 131D are connected to the other end of the front end portion 131A and the other end of the rear end portion 131B, respectively.

[0040] When viewed from above, the base 130 has a generally rectangular shape with the front end 131A and rear end 131B as its long sides and the left end 131C and right end 131D as its short sides. The base 130 is generally symmetrical with respect to an imaginary plane P defined along the perpendicular bisectors of the front end 131A and rear end 131B. Furthermore, the shape of the base 130 is not limited to… Figure 3 The rectangular shape shown can also be other shapes that are approximately symmetrical with respect to the imaginary plane P. For example, the shape of the base 130 can also be a trapezoidal shape in which one of the front end 131A and the rear end 131B is longer than the other. In addition, at least one of the front end 131A, the rear end 131B, the left end 131C, and the right end 131D can be bent or curved.

[0041] Furthermore, the imaginary plane P corresponds to the plane of symmetry of the entire vibrating section 110. Therefore, the imaginary plane P is also a plane passing through the center of the vibrating arms 121A to 121D in the X-axis direction, located between vibrating arms 121B and 121C. Specifically, each of the adjacent vibrating arms 121A and 121B is symmetrically formed with each of the adjacent vibrating arms 121D and 121C, separated by the imaginary plane P.

[0042] In the base 130, the longest distance in the Y-axis direction between the front end portion 131A and the rear end portion 131B, i.e., the base length, is for example approximately 30 μm. Additionally, the longest distance in the X-axis direction between the left end portion 131C and the right end portion 131D, i.e., the base width, is for example approximately 245 μm. Furthermore, in... Figure 3In the example shown, the base length is equivalent to the length of the left end 131C or the right end 131D, and the base width is equivalent to the length of the front end 131A or the rear end 131B.

[0043] The holding part 140 is configured to hold the vibrating part 110. More specifically, the holding part 140 is configured to enable the vibrating arms 121A to 121D to vibrate. Specifically, the holding part 140 is formed symmetrically with respect to the imaginary plane P. When viewed from above, the holding part 140 has a rectangular frame shape and is arranged to surround the outer side of the vibrating part 110 along the XY plane. In this way, the holding part 140 has a frame shape when viewed from above, thereby making it easy to realize the holding part 140 surrounding the vibrating part 110.

[0044] Furthermore, the retaining part 140 need only be disposed around at least a portion of the vibrating part 110, and is not limited to a frame shape. For example, the retaining part 140 need only be disposed around the vibrating part 110 to a degree that can retain the vibrating part 110 and engage with the upper cover 30 and the lower cover 20.

[0045] In this embodiment, the retaining part 140 includes integrally formed frame bodies 141A to 141D. For example... Figure 3 As shown, frame 141A is positioned opposite the open ends of vibrating arms 121A-121D, with its long side parallel to the X-axis. Frame 141B is positioned opposite the rear end 131B of base 130, with its long side parallel to the X-axis. Frame 141C is positioned opposite the left end 131C of base 130 and vibrating arm 121A, with its long side parallel to the Y-axis, and its two ends are connected to one end of frames 141A and 141B, respectively. Frame 141D is positioned opposite the right end 131D of base 130 and vibrating arm 121D, with its long side parallel to the Y-axis, and its two ends are connected to the other ends of frames 141A and 141B, respectively. Frames 141A and 141B are positioned opposite each other in the Y-axis direction across the vibrating part 110. Frames 141C and 141D are positioned opposite each other in the X-axis direction, separated by the vibrating part 110.

[0046] The support arm portion 150 is disposed inside the retaining portion 140, connecting the base portion 130 and the retaining portion 140. The support arm portion 150 is formed symmetrically with respect to the imaginary plane P. Specifically, when viewed from above, the support arm portion 150 includes two support arms, support arm 151A and support arm 151B. In addition, the support arm portion 150 also includes a connecting arm 155.

[0047] Support arm 151A includes a rear support arm 152A and a side support arm 153A, and support arm 151B includes a rear support arm 152B and a side support arm 153B.

[0048] A support arm 153A extends parallel to the vibrating arm 121A between the vibrating arm 121A and the retaining portion 140. A support arm 153B extends parallel to the vibrating arm 121D between the vibrating arm 121D and the retaining portion 140. Specifically, the support arm 153A extends from one end (the left end or the end on the side of the frame 141C) of the support rear arm 152A toward the frame 141A along the Y-axis and bends in the X-axis direction to connect with the frame 141C. Similarly, the support arm 153B extends from one end (the right end or the end on the side of the frame 141D) of the support rear arm 152B toward the frame 141A along the Y-axis and bends in the X-axis direction to connect with the frame 141D. In other words, one end of each of the support arms 151A and 151B is connected to the retaining portion 140.

[0049] The rear support arms 152A and 152B are connected between the rear end portion 131B of the base 130 and the retaining portion 140. Specifically, the rear support arms 152A and 152B extend along the rear end portion 131B and the frame 141B. Furthermore, the other end (right end) of the rear support arm 152A and the other end (left end) of the rear support arm 152B are connected at the center in the X-axis direction of the rear support arms 152A and 152B.

[0050] The connecting arm 155 connects the other ends of the two supporting arms 151A and 151B to the rear end 131B of the base 130. When viewed from above, the connecting arm 155 is connected to the center of the rear end 131B of the base 130, that is, a part of the position through which the imaginary plane P passes.

[0051] A protrusion 50 protrudes from the recess 21 of the lower cover 20 into the vibration space. Viewed from above, the protrusion 50 is positioned between arm portion 123B of vibrating arm 121B and arm portion 123C of vibrating arm 121C. The protrusion 50 extends parallel to the arms 123B and 123C along the Y-axis, forming a prism shape. The length of the protrusion 50 in the Y-axis direction is approximately 240 μm, and its length in the X-axis direction is approximately 15 μm. Furthermore, the number of protrusions 50 is not limited to one; there can be two or more. Thus, by positioning the protrusion 50 between vibrating arms 121B and 121C and protruding from the bottom plate 22 of the recess 21, the rigidity of the lower cover 20 can be improved, thereby suppressing the deflection of the resonator 10 formed on the lower cover 20 and the warping of the lower cover 20.

[0052] Next, refer to Figure 4 and Figure 5 The stacked structure and operation of a resonant device according to one embodiment will be described. Figure 4 It is a brief representation Figure 1 A cross-sectional view along the X-axis of the stacked structure of the resonant device 1 shown. Figure 5 It is a schematic representation Figure 1 A cross-sectional view along the Y-axis of the stacked structure of the resonant device 1 shown.

[0053] like Figure 4 and Figure 5 As shown, the resonant device 1 connects the holding portion 140 of the resonator 10 to the side wall 23 of the lower cover 20, and connects the holding portion 140 of the resonator 10 to the side wall 33 of the upper cover 30. In this way, the resonator 10 is held between the lower cover 20 and the upper cover 30, and a vibration space for the vibrating part 110 to vibrate is formed by the lower cover 20, the upper cover 30 and the holding portion 140 of the resonator 10.

[0054] The resonator 10's vibrating portion 110, holding portion 140, and support arm portion 150 are integrally formed using the same process. The resonator 10 has a metal film E1 stacked on a Si substrate F2, which is an example of a substrate. Then, a piezoelectric film F3 is stacked on the metal film E1 to cover it, and a metal film E2 is further stacked on the piezoelectric film F3. A protective film F5 is stacked on the metal film E2 to cover it. In the mass-adding portions 122A to 122D, the aforementioned mass-adding films 125A to 125D are further stacked on the protective film F5, respectively. The shapes of the vibrating portion 110, holding portion 140, and support arm portion 150 are formed by removing and patterning the laminate composed of the Si substrate F2, metal film E1, piezoelectric film F3, metal film E2, and protective film F5 using, for example, dry etching irradiated with an argon (Ar) ion beam.

[0055] In this embodiment, an example is shown where the resonator 10 includes a metal film E1, but it is not limited thereto. For example, the resonator 10 can use a degenerate silicon substrate with low resistance on the Si substrate F2, so that the Si substrate F2 itself can also serve as the metal film E1, or the metal film E1 can be omitted.

[0056] The Si substrate F2 is formed, for example, from a degenerate n-type silicon (Si) semiconductor with a thickness of about 6 μm. The n-type dopant can include phosphorus (P), arsenic (As), antimony (Sb), etc. Furthermore, the resistivity of the degenerate silicon (Si) used in the Si substrate F2 is, for example, less than 1.6 mΩ·cm, more preferably less than 1.2 mΩ·cm. Additionally, a silicon oxide layer F21, such as SiO2, is formed on the lower surface of the Si substrate F2 as a temperature characteristic correction layer. This improves the temperature characteristics.

[0057] In this embodiment, the silicon oxide layer F21 refers to a layer that, compared to the case where the silicon oxide layer F21 is not formed on the Si substrate F2, has a temperature coefficient, i.e., a rate of change per unit temperature, at least near room temperature, that reduces the frequency of the vibration section 110 when a temperature correction layer is formed on the Si substrate F2. The vibration section 110 has the silicon oxide layer F21, thereby, for example, reducing the accompanying temperature change in the resonant frequency of the stacked structure composed of the Si substrate F2, metal films E1 and E2, piezoelectric film F3, and silicon oxide layer F21. The silicon oxide layer may be formed on the upper surface of the Si substrate F2, or on both the upper and lower surfaces of the Si substrate F2.

[0058] The silicon oxide layer F21 of the mass addition parts 122A to 122D is preferably formed with a uniform thickness. Furthermore, uniform thickness means that the deviation of the thickness of the silicon oxide layer F21 is within ±20% of the average thickness.

[0059] Metal films E1 and E2 each include excitation electrodes for exciting vibrating arms 121A-121D and lead-out electrodes for electrically connecting the excitation electrodes to an external power source. The portions of metal films E1 and E2 that function as excitation electrodes are located in the arm portions 123A-123D of vibrating arms 121A-121D, and are positioned opposite each other across a piezoelectric film F3. The portions of metal films E1 and E2 that function as lead-out electrodes are, for example, led from the base 130 to the holding portion 140 via the support arm portion 150. Metal film E1 is electrically continuous throughout the resonator 10. Metal film E2 is electrically separated in the portions formed in vibrating arms 121A and 121D and in the portions formed in vibrating arms 121B and 121C.

[0060] The thicknesses of the metal films E1 and E2 are, for example, approximately 0.1 μm to 0.2 μm. After deposition, the metal films E1 and E2 are patterned into excitation electrodes, lead-out electrodes, etc., by etching or other removal processes. The metal films E1 and E2 are formed, for example, from a metal material with a body-centered cubic crystal structure. Specifically, the metal films E1 and E2 are formed using Mo (molybdenum), tungsten (W), etc. In this way, by using metals with a body-centered cubic crystal structure as the main component, metal films E1 and E2 suitable for the lower and upper electrodes of the resonator 10 can be easily realized.

[0061] The piezoelectric film F3 is a thin film formed by a piezoelectric body that converts electrical energy into mechanical energy. The piezoelectric film F3 expands and contracts along the Y-axis in the in-plane direction of the XY plane, based on the electric field generated by the metal films E1 and E2 within the piezoelectric film F3. Through this expansion and contraction of the piezoelectric film F3, the vibrating arms 121A to 121D are displaced with their open ends toward the base plate 22 of the lower cover 20 and the base plate 32 of the upper cover 30, respectively. As a result, the resonator 10 vibrates in an out-of-plane bending vibration mode.

[0062] The thickness of the piezoelectric film F3 is, for example, about 1 μm, but it can also be about 0.2 μm to 2 μm. The piezoelectric film F3 is formed from a material with a wurtzite-type hexagonal crystal structure, and can be primarily composed of nitrides or oxides such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), and indium nitride (InN). Furthermore, scandium aluminum nitride is a material formed by replacing a portion of the aluminum in aluminum nitride with scandium; it can also be replaced by magnesium (Mg) and niobium (Nb), or magnesium (Mg) and zirconium (Zr). Thus, the piezoelectric film F3, with a wurtzite-type hexagonal crystal structure as its main component, can easily achieve a piezoelectric film F3 suitable for the resonator 10.

[0063] The protective film F5 protects the metal film E2 from oxidation. Furthermore, since the protective film F5 is only disposed on the side of the upper cover 30, it need not be exposed relative to the bottom plate 32 of the upper cover 30. For example, a parasitic capacitance reduction film that reduces the capacitance of the wiring formed on the resonator 10 can be formed to cover the protective film F5. The protective film F5 can be formed, for example, from piezoelectric films such as aluminum nitride (AlN), scandium aluminum nitride (ScAlN), zinc oxide (ZnO), gallium nitride (GaN), and indium nitride (InN), or from insulating films such as silicon nitride (SiN), silicon oxide (SiO2), aluminum oxide (Al2O3), and tantalum pentoxide (Ta2O5). The thickness of the protective film F5 is less than half the thickness of the piezoelectric film F3, and in this embodiment, it is, for example, about 0.2 μm. More preferably, the thickness of the protective film F5 is about one-quarter the thickness of the piezoelectric film F3. Furthermore, when the protective film F5 is formed of a piezoelectric material such as aluminum nitride (AlN), it is preferable to use a piezoelectric material having the same orientation as the piezoelectric film F3.

[0064] The protective film F5 of the mass additions 122A to 122D is preferably formed with a uniform thickness. Furthermore, uniform thickness means that the deviation of the thickness of the protective film F5 is within ±20% of the average thickness.

[0065] The mass-adding films 125A to 125D constitute the surface of the upper cover 30 side of each of the mass-adding parts 122A to 122D, and correspond to the frequency adjustment films of each of the vibrating arms 121A to 121D. The frequency of the resonator 10 is adjusted by trimming a portion of each of the mass-adding films 125A to 125D. From the perspective of frequency adjustment efficiency, the mass-adding films 125A to 125D are preferably formed of a material whose mass reduction rate is faster than that of the protective film F5 based on etching. The mass reduction rate is expressed as the product of the etching rate and the density. The etching rate refers to the thickness removed per unit time. The relationship between the etching rates of the protective film F5 and the mass-adding films 125A to 125D is arbitrary as long as the relationship between their mass reduction rates is as described above. Furthermore, from the viewpoint of effectively increasing the weight of the mass-adding parts 122A to 122D, the mass-adding films 125A to 125D are preferably formed of a material with a high specific gravity. For these reasons, the mass-added films 125A to 125D are formed of metallic materials such as molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), aluminum (Al), and titanium (Ti).

[0066] A portion of the upper surface of each of the mass-added films 125A to 125D is removed during the frequency adjustment process by a finishing treatment. This finishing treatment of the mass-added films 125A to 125D can be performed, for example, by dry etching with an argon (Ar) ion beam. While the ion beam provides excellent processing efficiency over a wide range of irradiations, there is a concern that the mass-added films 125A to 125D may become charged due to their electrical charge. To prevent changes in the vibration trajectory of the vibrating arms 121A to 121D caused by the charging of the mass-added films 125A to 125D, which could degrade the vibration characteristics of the resonator 10, it is preferable to ground the mass-added films 125A to 125D.

[0067] Lead wires C1, C2, and C3 are formed on the protective film F5 of the holding part 140. Lead wire C1 is electrically connected to the metal film E1 through a through hole formed in the piezoelectric film F3 and the protective film F5. Lead wire C2 is electrically connected to the portion of the metal film E2 formed in the vibrating arms 121A and 121D through a through hole formed in the protective film F5. Lead wire C3 is electrically connected to the portion of the metal film E2 formed in the vibrating arms 121B and 121C through a through hole formed in the protective film F5. Lead wires C1 to C3 are formed of metal materials such as aluminum (Al), germanium (Ge), gold (Au), and tin (Sn).

[0068] In this embodiment, Figure 4The diagram shows an example where arms 123A-123D, leads C2 and C3, and through electrodes V2 and V3 are located on the same plane, but they are not necessarily located on the same plane. For example, through electrodes V2 and V3 may also be formed at a position away from the cross-section along the Y-axis, which is parallel to the ZX plane defined by the Z-axis and X-axis and cuts off arms 123A-123D.

[0069] Similarly, in this embodiment, in Figure 5 The example shown is an example where the mass attachment 122A, arm 123A, leads C1, C2, through electrodes V1, V2, etc. are located on the same plane cross section, but they are not necessarily located on the same plane cross section.

[0070] The bottom plate 22 and sidewall 23 of the lower cover 20 are integrally formed from a Si substrate P10. The Si substrate P10 is formed from undegenerate silicon, and its resistivity is, for example, 10 Ω·cm or higher. The Si substrate P10 is exposed inside the recess 21 of the lower cover 20. A silicon oxide layer F21 is formed on the upper surface of the protrusion 50. However, from the viewpoint of suppressing the charging of the protrusion 50, a Si substrate P10 with a lower resistivity than the silicon oxide layer F21 may also be exposed on the upper surface of the protrusion 50, and a conductive layer may also be formed there.

[0071] The thickness of the lower cover 20 in the Z-axis direction is specified to be about 150 μm, and similarly, the depth of the recess 21 is specified to be about 50 μm.

[0072] The bottom plate 32 and sidewall 33 of the top cover 30 are integrally formed from a Si substrate Q10. Preferably, the surface, back surface, and inner surface of the through hole of the top cover 30 are covered with a silicon oxide film Q11. The silicon oxide film Q11 is formed on the surface of the Si substrate Q10, for example, by oxidation or chemical vapor deposition (CVD). The Si substrate Q10 is exposed inside the recess 31 of the top cover 30. In addition, a gas-absorbing layer may be formed on the side of the recess 31 of the top cover 30 opposite to the resonator 10. The gas-absorbing layer is formed, for example, from titanium (Ti), and absorbs the exhaust gas released from the joint 40, etc., described later, suppressing the decrease in the vacuum level of the vibration space. In addition, the air-absorbing layer can also be formed on the side of the recess 21 of the lower cover 20 opposite to the resonator 10, or on the side of the recess 21 of the lower cover 20 and the recess 31 of the upper cover 30 opposite to the resonator 10.

[0073] The thickness of the top cover 30 in the Z-axis direction is specified to be about 150 μm, and the depth of the recess 31 is specified to be about 50 μm.

[0074] Terminals T1, T2, and T3 are formed on the upper surface of the cover 30 (the side opposite to the surface facing the resonator 10). Terminal T1 is a mounting terminal for grounding the metal film E1. Terminal T2 is a mounting terminal for electrically connecting the metal film E2 of the vibrating arms 121A and 121D to an external power supply. Terminal T3 is a mounting terminal for electrically connecting the metal film E2 of the vibrating arms 121B and 121C to an external power supply. Terminals T1 to T3 are formed, for example, by plating a metallization layer (base layer) of chromium (Cr), tungsten (W), nickel (Ni), etc., with nickel (Ni), gold (Au), silver (Ag), or copper (Cu). In addition, for the purpose of adjusting parasitic capacitance and balancing mechanical strength, a dummy terminal electrically insulated from the resonator 10 may also be formed on the upper surface of the cover 30.

[0075] Through electrodes V1, V2, and V3 are formed inside the sidewall 33 of the upper cover 30. Through electrode V1 electrically connects terminal T1 to lead C1, through electrode V2 electrically connects terminal T2 to lead C2, and through electrode V3 electrically connects terminal T3 to lead C3. Through electrodes V1 to V3 are formed by filling conductive material into through holes that penetrate the sidewall 33 of the upper cover 30 along the Z-axis direction. The conductive material used for filling is, for example, polysilicon (Poly-Si), copper (Cu), or gold (Au).

[0076] A joining portion 40 is formed between the sidewall 33 of the upper cover 30 and the retaining portion 140, through which the upper cover 30 is joined to the resonator 10. The joining portion 40 is formed in a closed loop surrounding the vibrating portion 110 in the XY plane, so as to hermetically seal the vibration space of the resonator 10 in a vacuum state. The joining portion 40 is formed, for example, by stacking aluminum (Al) film, germanium (Ge) film and aluminum (Al) film in sequence and bonding them eutecticly. In addition, the joining portion 40 can also be formed by a combination of films appropriately selected from gold (Au), tin (Sn), copper (Cu), titanium (Ti), silicon (Si), etc. In addition, in order to improve the tightness, the joining portion 40 can also include metal compounds such as titanium nitride (TiN) and tantalum nitride (TaN) between the films.

[0077] In this embodiment, terminal T1 is grounded, and alternating voltages with opposite phases are applied to terminals T2 and T3. Therefore, the phase of the electric field formed by the piezoelectric film F3 in vibrating arms 121A and 121D is opposite to the phase of the electric field formed by the piezoelectric film F3 in vibrating arms 121B and 121C. Consequently, the outer vibrating arms 121A and 121D and the inner vibrating arms 121B and 121C are displaced in opposite directions.

[0078] For example, such as Figure 4As shown, when the mass attachments 122A, 122D and arms 123A, 123D of each of the vibrating arms 121A and 121D move toward the inner surface of the upper cover 30, the mass attachments 122B, 122C and arms 123B, 123C of each of the vibrating arms 121B and 121C move toward the inner surface of the lower cover 20. Although the diagram is omitted, conversely, when the mass attachments 122A, 122D and arms 123A, 123D of each of the vibrating arms 121A and 121D move toward the inner surface of the lower cover 20, the mass attachments 122B, 122C and arms 123B, 123C of each of the vibrating arms 121B and 121C move toward the inner surface of the upper cover 30. Thus, at least two of the four vibrating arms 121A to 121D undergo out-of-plane bending at different phases.

[0079] Thus, between adjacent vibrating arms 121A and 121B, vibrating arms 121A and 121B vibrate in opposite vertical directions around a central axis r1 extending along the Y-axis. Similarly, between adjacent vibrating arms 121C and 121D, vibrating arms 121C and 121D vibrate in opposite vertical directions around a central axis r2 extending along the Y-axis. This generates torsional moments in opposite directions on the central axes r1 and r2, resulting in bending vibration in the vibrating section 110. The maximum amplitude of vibrating arms 121A to 121D is approximately 50 μm, and the amplitude during normal operation is approximately 10 μm.

[0080] Next, refer to Figure 6 and Figure 7 The displacement caused by the vibration of the vibrating part is explained. Figure 6 It is a schematic representation Figure 3 A top view of the displacement distribution caused by the vibration of the vibrating part 110 shown. Figure 7 It is a schematic representation Figure 3 A three-dimensional view of the displacement distribution caused by the vibration of the vibrating part 110 is shown. Furthermore, in Figure 6 and Figure 7 In the vibrating section 110 shown, the darker colored areas represent larger displacements, and the lighter colored areas represent smaller displacements.

[0081] like Figure 6 and Figure 7As shown, the vibrating part 110 vibrates in an out-of-plane bending vibration mode, thus increasing the displacement of the vibrating arms 121A to 121D. As the vibrating arms 121A to 121D displace, the base 130, held in the holding part 140 by the support arm 150, also flexes and displaces. In this embodiment, since the other ends of the support arms 151A and 151B are connected to a portion of the rear end 131B of the base 130, the flexure of the base 130 is greater than in the conventional embodiment, and its displacement, more specifically, the displacement of the left end 131C and right end 131D of the base 130, is also greater.

[0082] Here, refer to Figure 8 The displacement of the base caused by the vibration of the vibrating part is explained. Figure 8 It means by Figure 3 A graph showing the displacement of the base 130 caused by the vibration of the vibrating part 110. Figure 8 In the diagram, the horizontal axis is based on the left end 131C of the base 130, i.e., the distance when it is set to zero, and the vertical axis represents the relative value of the displacement. Furthermore, in... Figure 8 In the diagram, the displacement of the resonator 10 in this embodiment is represented by a solid line, while the displacement of a conventional resonator is represented by a dashed line for comparison. The conventional resonator is identical to the resonator 10 except that the two support arms are connected to the rear ends of the base, i.e., connected at two locations.

[0083] like Figure 8 As shown by the dashed line, in existing resonators, the displacement of the base is minimal near the connection points with each support arm and maximum near the center of the base.

[0084] In contrast, such as Figure 8 As shown by the solid line, in the resonator 10 of this embodiment, the displacement of the base 130 is smallest near the center of the base 130 and largest at both ends of the base 130, namely the left end 131C and the right end 131D. Furthermore, the displacements at the left end 131C and the right end 131D are larger in absolute value than the displacements near the center of the base of conventional resonators. Therefore, it can be seen that the resonator 10 of this embodiment has a larger displacement of the base 130 compared to conventional resonators.

[0085] Thus, the other ends of each of the two support arms 151A and 151B are connected to a portion of the rear end 131B of the base 130. This results in greater deflection of the base 130 compared to existing resonators. Consequently, the rate of change of the resonant frequency per unit power (described later as an indicator of DLD) can be negatively altered. Therefore, the rate of change of the resonant frequency per unit power can be reduced, thereby further improving the DLD.

[0086] In addition, the other ends of each of the two support arms 151A and 151B are connected, and the connecting arm 155 connects the other ends of each of the two support arms to the rear end 131B of the base 130, so that the other ends of each of the two support arms 151A and 151B can be easily connected to a part of the rear end 131B of the base 130 via the connecting arm 155.

[0087] In addition, when viewed from above, the other ends of the two support arms 151A and 151B are connected to a central part of the rear end 131B of the base 130, which can easily increase the deflection of the base 130.

[0088] Next, refer to Figure 9 The relationship between the connection position at the base of the support arm and the DLD is explained. Figure 9 It means Figure 3 A diagram showing the relationship between the connection portion at the base 130 of the support arm 150 and the DLD. Figure 9 In the diagram, the horizontal axis is the distance from the center of the rear end 131B of the base 130 (set to zero) to the connection point of the two support arms 151A and 151B, divided by half the width of the base. The vertical axis represents the rate of change of the resonant frequency (f) per unit power (f), an indicator of the DLD (Distributed Leading Module). Furthermore, in... Figure 9 In the diagram, the frequency change rate per unit power in the resonator 10 of this embodiment is depicted with a black circle, while the frequency change rate per unit power in a conventional resonator is depicted with a white circle for comparison.

[0089] like Figure 9 As depicted by the white circle, in the case of an existing resonator where the two support arms and the rear end of the base are connected at two locations, the frequency variation rate per unit power can only achieve an accuracy of about 380 [ppm / μm].

[0090] In contrast, such as Figure 9 As shown by the black circle, in the resonator 10 of this embodiment, the other ends of each of the two support arms 151A and 151B are connected to a portion of the rear end 131B of the base 130, thereby causing the frequency change rate per unit power to change in the negative direction. In this embodiment, when viewed from above, the other ends of each of the two support arms 151A and 151B are connected to a portion at the center of the rear end 131B of the base 130, so the frequency change rate per unit power can be approximately 0 [ppm / μm].

[0091] Next, refer to Figure 10 The dimensions of the vibrating part when viewed from above are described. Figure 10 It is used for explanation Figure 3A top view showing the dimensions of the vibrating part 110.

[0092] like Figure 10 As shown, in the resonator 10 of this embodiment, the width WG of each of the mass additions 122A to 122D along the X-axis direction is, for example, 70 μm. Furthermore, the width WA of each of the vibration arms 121A to 121D along the X-axis direction is, for example, 30 μm, and the length LA of each of the vibration arms 121A to 121D along the Y-axis direction is, for example, 400 μm.

[0093] Furthermore, in the base 130, the distance in the length direction from the front end 131A to the rear end 131B, i.e., the length of the base width WB, is, for example, 245 μm. On the other hand, the distance in the width direction from the left end 131C to the right end 131D, i.e., the length of the base length LB, is, for example, 30 μm.

[0094] Here, the inventors of this invention have discovered that when the ratio of the length of the base length LB to the length of the base width WB is a predetermined multiple or less, the rate of change of the resonant frequency per unit power can be reduced. More specifically, it has been found that it is preferable that the length of the base length LB is 0.3 times or less relative to the length of the base width WB. This effectively reduces the rate of change of the resonant frequency per unit power.

[0095] Specifically, in the miniaturized resonator 10, the length of the base length LB is 90 μm or less, and the length of the base width WB is 300 μm or less. Therefore, even in the miniaturized and size-constrained resonator 10, the rate of change of the resonant frequency per unit power can be effectively reduced.

[0096] In addition, in the support arm portion 150, the length of the support arm width WS along the X-axis direction of each of the support arms 151A and 151B is, for example, 25 μm, and the length of the support arm length LS along the Y-axis direction of each of the support arms 151A and 151B is, for example, 225 μm.

[0097] Here, the inventors of this invention have discovered that when the ratio of the length of the support arm LS to the length of the support arm WS is a predetermined multiple or more, the rate of change of the resonant frequency per unit power can be reduced. More specifically, it has been found that it is preferable for the length of the support arm LS to be at least four times the length of the support arm WS. This effectively reduces the rate of change of the resonant frequency per unit power.

[0098] Specifically, in the miniaturized resonator 10, the length of the support arm LS is less than 300 μm, and the length of the support arm width WS is less than 60 μm. Thus, even in the miniaturized and size-constrained resonator 10, the frequency variation rate of the resonant frequency per unit power can be effectively reduced.

[0099] In this embodiment, the vibrating section 110 using the resonator 10 includes four vibrating arms 121A to 121D, but it is not limited to this. The vibrating section 110 may also include three or more vibrating arms, for example. In this case, at least two vibrating arms bend out of plane at different phases.

[0100] The exemplary embodiments of the present invention have been described above. According to one embodiment, the resonator connects the other ends of each of the two support arms to a portion of the rear end of the base. As a result, compared to conventional resonators, the deflection of the base is increased, and consequently, the rate of change of the resonant frequency per unit power, a key indicator of DLD (Dissonance Detection and Reduction), can be negatively altered. Therefore, the rate of change of the resonant frequency per unit power can be reduced, thereby further improving the DLD.

[0101] Furthermore, in the aforementioned resonator, the other ends of each of the two support arms are connected, and a connecting arm connects the other ends of the two support arms to the rear end of the base. Thus, the other ends of each of the two support arms can be easily connected to a portion of the rear end of the base via the connecting arm.

[0102] Furthermore, in the aforementioned resonator, when viewed from above, the other end of each of the two support arms is connected to a central portion of the rear end of the base. This makes it prone to increased deflection of the base.

[0103] Furthermore, in the aforementioned resonator, the length of the base portion is 0.3 times or less than the length of the base width. Here, the inventors of this invention have discovered that when the ratio of the base portion length to the base width is a predetermined multiple or less, more specifically 0.3 times or less, the frequency variation rate of the resonant frequency per unit power can be reduced. Therefore, the frequency variation rate of the resonant frequency per unit power can be effectively reduced.

[0104] Furthermore, in the aforementioned resonator, the base length is 90 μm or less, and the base width is 300 μm or less. Therefore, even in miniaturized resonators with limited size, the rate of change of resonant frequency per unit power can be effectively reduced.

[0105] Furthermore, in the aforementioned resonator, the length of the support arm is at least four times the width of the support arm. Here, the inventors of this invention have discovered that when the ratio of the length of the support arm to the width of the support arm is a predetermined multiple, more specifically, at least four times, the rate of change of the resonant frequency per unit power can be reduced. Therefore, the rate of change of the resonant frequency per unit power can be effectively reduced.

[0106] Furthermore, in the aforementioned resonator, the length of the support arm is 300 μm or less, and the width of the support arm is 60 μm or less. Therefore, even in miniaturized resonators with limited size, the rate of change of the resonant frequency per unit power can be effectively reduced.

[0107] Furthermore, the resonant device according to one embodiment includes the aforementioned resonator. This allows for a resonant device that further improves the DLD.

[0108] Furthermore, the aforementioned resonant device also includes a lower cover and an upper cover. This allows for the easy formation of a vibration space for an out-of-plane bending vibration section.

[0109] Furthermore, the embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit the invention. The present invention can be modified / improved without departing from its spirit, and the present invention also includes its equivalents. That is, any appropriate design changes made by those skilled in the art to the embodiments and / or variations, as long as they possess the features of the present invention, are included within the scope of the present invention. For example, the elements, their configurations, materials, conditions, shapes, dimensions, etc., of the embodiments and / or variations are not limited to those illustrated and can be appropriately modified. In addition, the embodiments and variations are illustrative, and naturally, partial substitutions or combinations of the structures shown in different embodiments and / or variations are possible; as long as they contain the features of the present invention, they are included within the scope of the present invention.

[0110] Explanation of reference numerals in the attached figures

[0111] 1…Resonant device; 10…Resonator; 20…Lower cover; 21…Recess; 22…Base plate; 23…Side wall; 30…Upper cover; 31…Recess; 32…Base plate; 33…Side wall; 40…Joint; 50…Protrusion; 110…Vibrating part; 120…Excitation part; 121…Vibrating arm; 121A, 121B, 121C, 121D…Vibrating arm; 122A, 122B, 122C, 122D…Mass attachment; 123A, 123B, 123C, 123D…Arm; 125A, 125B, 125C, 125D…Mass attachment membrane; 130 …Base; 131A…Front end; 131B…Rear end; 131C…Left end; 131D…Right end; 140…Retaining part; 141A, 141B, 141C, 141D…Frame; 150…Support arm; 151A, 151B…Support arm; 152A, 152B…Support rear arm; 153A, 153B…Support side arm; 155…Connecting arm; LA…Vibration arm length; LB…Base length; LS…Support arm length; P…Imaginary plane; r1, r2…Central axis; WA…Vibration arm width; WB…Base width; WG…Width; WS…Support arm width.

Claims

1. A resonator, wherein, have: The vibrating part includes multiple vibrating arms and a base. The multiple vibrating arms are three or more vibrating arms, each having a fixed end, and at least two of them bend out of plane at different phases. The base has one end for connecting to the fixed end of each of the multiple vibrating arms and another end opposite to that end. The retaining part is configured to retain the vibrating part; and Each of the two support arms has one end connected to the retaining part. The other ends of the two support arms are directly connected. When viewed from above, the other end of each of the two connected support arms is connected via a connecting arm to a central portion of the other end of the base.

2. The resonator according to claim 1, wherein, The length of the base in the length direction from one end of the base toward the other end is less than 0.3 times the length of the base in the width direction orthogonal to the length direction of the base.

3. The resonator according to claim 2, wherein, The base length is less than 90 μm, and the base width is less than 300 μm.

4. The resonator according to claim 1 or 2, wherein, The length of each of the two support arms is more than four times the width of the support arm.

5. The resonator according to claim 4, wherein, The length of the support arm is less than 300 μm, and the width of the support arm is less than 60 μm.

6. A resonant device, wherein, The resonator is provided with any one of claims 1 to 5.

7. The resonant device according to claim 6, wherein, It also has a cover.

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