MEMS resonator and oscillator thereof

Abstract

The invention discloses an MEMS resonator and a vibrator thereof. The vibrator comprises two vibration arms arranged at an interval, an anchoring area located between the two vibration arms, and a coupling beam connecting the vibration arms and the anchoring area. Under the action of driving force, the two vibration arms swing in the first direction relative to the anchoring area, during swing of the vibration arms, a heat flow path opposite to the swing direction is formed between the two opposite sides in the first direction, and heat dividing grooves extending in the second direction perpendicular to the first direction are formed in the heat flow path of the vibration arms. The heat dividing grooves divide the heat flow path into multiple sections of first heat flow sub-paths, and the path length of the first heat flow sub-paths in the first direction is smaller than the width of the vibration arm in the first direction. The heat separation groove can reduce the length of a heat flow path and increase the heat frequency, so that the heat frequency is far away from the resonant frequency, the heat elastic loss is reduced, and the Q value of the MEMS resonator is improved.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical technology, and in particular to a MEMS resonator and an oscillator thereof. Background Art

[0002] MEMS (Micro-Electro-Mechanical Systems) resonator is a key component of the oscillator, and its Q value (Quality factor) is one of the key parameters to measure the performance of the resonator. The Q value represents the ratio of the energy stored in the resonator to the energy lost per unit time. The larger the Q value, the smaller the energy loss of the resonator and the more stable the resonator. The smaller the Q value, the greater the energy loss of the resonator and the more unstable the resonator. In the resonator, the main energy losses are air damping loss, anchor loss, thermoelastic loss, material loss, etc. And the following relationship is satisfied:

[0003]

[0004] Among them, Q air The quality factor representing the air damping loss, Q anchor The quality factor representing the anchor loss, Q ted Quality factor representing thermoelastic losses, Q material Quality factor representing material loss, Q other The quality factor that represents other losses. Q ted The larger the value, the smaller the thermoelastic loss. ted The smaller the value, the greater the thermoelastic loss.

[0005] For low-frequency resonators, thermoelastic loss is the primary factor limiting the Q value. This loss occurs primarily because during the vibration of a MEMS resonator, the temperature rises on one side of the vibrating arm due to compression, while the temperature drops on the other side due to tension. This creates a temperature gradient, which causes heat to flow until thermal equilibrium is reestablished. During this heat flow, thermal resistance leads to energy loss, which is the MEMS resonator's thermoelastic loss. The magnitude of the thermoelastic loss is related to the time it takes to establish thermal equilibrium, which is inversely proportional to frequency. The MEMS resonator's thermoelastic loss is greatest when the thermal frequency approaches the resonant frequency.

[0006] In order to further improve the Q value of MEMS resonators, reducing the impact of thermoelastic loss on the Q value has become a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0007] In view of this, the present invention provides a MEMS resonator and an oscillator thereof that can reduce thermoelastic loss to improve the Q value.

[0008] In one aspect, the present application provides a vibrator of a MEMS resonator, comprising two vibration arms spaced apart from each other, an anchoring region between the two vibration arms, and a coupling beam connecting the vibration arms and the anchoring region;

[0009] Under the action of the driving force, the two vibration arms swing along the first direction relative to the anchoring area. During the swinging of the vibration arms, a heat flow path opposite to the swinging direction is formed between the two opposite sides in the first direction. The vibration arms are provided with a heat dividing groove extending in a second direction perpendicular to the first direction in the heat flow path. The heat dividing groove divides the heat flow path into multiple first heat flow sub-paths. The path length of the first heat flow sub-path in the first direction is less than the width of the vibration arm in the first direction.

[0010] In some embodiments, each of the vibration arms includes two elastic beams and two mass beams, one end of the two elastic beams are interconnected and fixed to the coupling beam, and the other end is connected to the mass beams respectively, the stiffness of the elastic beams in the first direction is less than the stiffness of the mass beams, the heat separation groove is provided on the elastic beam, and the path length of the first heat flow path in the first direction is less than the width of the elastic beam in the first direction.

[0011] In some embodiments, the mass beam is provided with a plurality of mutually spaced slot groups in the first direction, each of the slot groups includes a plurality of slots spaced apart along the second direction, and the slots in adjacent slot groups are staggered.

[0012] During the arm swing, the mass beam forms a second heat flow sub-path between the opposite sides in the first direction, which passes through the spacing area between the grooves, and a plurality of third heat flow sub-paths formed by the grooves; the path length of the second heat flow sub-path is greater than the width of the mass beam in the first direction, and the path length of the third heat flow sub-path in the first direction is less than the width of the mass beam in the first direction.

[0013] In some embodiments, the length of the heat dividing groove in the second direction is 0.5 to 1.5 times the length of the elastic beam; and / or,

[0014] The width of the heat dividing groove in the first direction is one quarter to two thirds of the width of the elastic beam.

[0015] In some embodiments, each of the elastic beams is provided with a heat separation groove, and the two heat separation grooves on the same vibration arm are symmetrically arranged relative to the first symmetry axis, and the first symmetry axis extends along the first direction. The corresponding heat separation grooves on the two elastic beams are symmetrically arranged relative to the second symmetry axis, and the second symmetry axis extends along the second direction.

[0016] In some embodiments, each of the elastic beams is provided with a heat separation groove, the two heat separation grooves on the same vibration arm are spaced apart from each other, and the portion of the vibration arm between the two heat separation grooves corresponds to the portion where the vibration arm and the coupling beam are connected.

[0017] In some embodiments, two side surfaces of the elastic beam in the first direction are parallel to each other; or,

[0018] The elastic beam extends from one end of the other elastic beam toward the corresponding mass beam in a manner of gradually decreasing width.

[0019] In some embodiments, the mass beam is provided with composite tooth portions on two opposite sides in the first direction, the composite tooth portion including a first tooth-shaped portion and a second tooth-shaped portion arranged along the second direction, the first tooth-shaped portion being closer to the elastic beam than the second tooth-shaped portion;

[0020] The first tooth-shaped portion includes a plurality of first teeth, and the second tooth-shaped portion includes a plurality of second teeth. The first teeth and the second teeth respectively protrude outward from corresponding sides of the mass beam. The first teeth and the second teeth both include a tooth bottom connected to the mass beam, a tooth top opposite to the tooth bottom, and a tooth side surface connected between the tooth bottom and the tooth top. The tooth side surface of the first tooth is parallel to the first direction, and the tooth side surface of the second tooth is inclined relative to the first direction.

[0021] In some embodiments, the first teeth are rectangular teeth, and the second teeth are triangular teeth.

[0022] On the other hand, the present application also provides a MEMS resonator, comprising the vibrator as described above, and a driving electrode and a sensing electrode arranged corresponding to the vibrating arm of the vibrator, the driving electrode and the sensing electrode being respectively located on opposite sides of the vibrating arm in the first direction and spaced apart from the vibrating arm.

[0023] The present invention provides a MEMS resonator vibrator, which can reduce the length of the heat flow path and increase the thermal frequency by setting a heat separation groove on the vibrating arm, thereby keeping the thermal frequency away from the resonant frequency of the MEMS resonator, reducing thermoelastic loss, and improving the Q value of the MEMS resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of a MEMS resonator;

[0025] Figure 2 for Figure 1 The resonant frequency and Q of the MEMS resonator are shown in ted Schematic diagram of the relationship between

[0026] Figure 3 A schematic structural diagram of a MEMS resonator provided in one embodiment of the present invention;

[0027] Figure 4 for Figure 3 Schematic diagram of the structure of the elastic beam shown in;

[0028] Figure 5 for Figure 3 Schematic diagram of the mass beam without the composite teeth shown in FIG;

[0029] Figure 6 for Figure 3 The resonant frequency and Q of the MEMS resonator are shown in ted Schematic diagram of the relationship between

[0030] Figure 7 A schematic structural diagram of a mass beam provided in another embodiment of the present invention;

[0031] Figure 8 for Figure 1 Schematic diagram of the mass beam structure shown in .

[0032] In the figure: 10, vibrator; 12, vibrating arm; 14, anchoring area; 16, coupling beam; 18, heat partitioning groove; 20, first heat flow path; 22, elastic beam; 24, mass beam; 26, slot group; 28, groove; 30, second heat flow path; 32, third heat flow path; 34, connecting beam; 36, composite tooth portion; 38, first tooth-shaped portion; 40, second tooth-shaped portion; 42, first tooth; 44, second tooth; 46, tooth bottom; 48, tooth top; 50, tooth side; 52, tooth groove. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0034] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside, top, bottom, etc.) are only used to explain the relative position relationship between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0035] It should also be noted that when an element is referred to as being “fixed on” or “disposed on” another element, the element may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0036] In the process of realizing the present invention, the inventors of this application conducted the following research on MEMS resonators:

[0037] like Figure 1 As shown, the vibrator 1 of the MEMS resonator includes two vibrating arms 2, a coupling beam 3, a connecting beam 4, and an anchor point 5. The two vibrating arms 2 are spaced apart and connected together by the coupling beam 3. The connecting beam 4 connects the anchor point 5 and the coupling beam 3 together. When the MEMS resonator is working, the two vibrating arms 2 bend in opposite directions, that is, the two vibrating arms 2 bend toward the direction approaching the anchor point 5 or bend away from the anchor point 5 at the same time. The vibrating arms 2 generate cyclic compressive stress and tensile stress at the bending point. The temperature of the area where the vibrating arms 2 are subjected to compressive stress rises, and the temperature of the area where the vibrating arms 2 are subjected to tensile stress drops, thereby forming a temperature gradient, and heat flow flows from the high temperature area to the low temperature area. Since the MEMS resonator operates at a certain frequency, the temperature gradient on the vibration arm 2 will appear alternately, that is, the pressure area and the tension area on the vibration arm alternately change. For example, when the vibration arm 2 bends toward the direction close to the anchor point 5, the side of the vibration arm 2 close to the anchor point 5 is the pressure area, and the side away from the anchor point 5 is the tension area. At this time, the temperature of the side of the vibration arm 2 close to the anchor point 5 is higher than the temperature of the side of the vibration arm 2 away from the anchor point 5, and the heat flow flows from the side of the vibration arm 2 close to the anchor point 5 to the side away from the anchor point 5; when the vibration arm 2 bends toward the direction away from the anchor point 5, the side of the vibration arm 2 away from the anchor point 5 is the pressure area, and the side close to the anchor point 5 is the tension area. At this time, the temperature of the side of the vibration arm 2 away from the anchor point 5 is higher than the temperature of the side of the vibration arm 2 close to the anchor point 5, and the heat flow flows from the side of the vibration arm 2 away from the anchor point 5 to the side close to the anchor point 5.

[0038] Heat flows from the higher temperature area to the lower temperature area on the vibration arm 2 to re-establish thermal equilibrium. Its thermal decay time constant τ depends on the length of the temperature gradient and the parameters of the material, and can be expressed by the following expression: Where: b represents the heat flow path length, C prepresents the constant pressure heat capacity of the material, ρ represents the material density, and k represents the thermal conductivity of the material. It can be seen that the thermal decay time constant τ is positively correlated with the heat flow path length b, while the thermal frequency is inversely proportional to the thermal decay time constant τ. Therefore, as the heat flow path b becomes larger, the thermal decay time constant τ also becomes larger and the thermal frequency decreases. Conversely, as the heat flow path b becomes smaller, the thermal decay time constant τ also becomes smaller and the thermal frequency increases. Q represents the quality factor of thermoelastic loss ted , and the relationship between the thermal decay time constant τ can be expressed by the following formula: Where E is the Young's modulus of the material, α is the thermal expansion coefficient of the material, T is the device temperature, and f is the resonant frequency.

[0039] Figure 2 for Figure 1 The resonant frequency and Q of the MEMS resonator are shown in ted Since the thermal frequency is the same as the resonant frequency of the MEMS device, Q ted There is a minimum value, at which the thermoelastic loss of the MEMS resonator is the largest. Figure 2 It can be seen that when the resonant frequency is 1×10 5 With 1×10 6 When the middle position of Q ted The value is the smallest, that is, when the resonant frequency is 5×10 5 When the accessories are connected, the resonant frequency is close to the thermal frequency, and the Q ted In 1×10 4 to 1.5×10 4 The thermoelastic loss of the MEMS resonator is large. When the width of the vibration arm 2 changes, the length of the heat flow path and the thermal decay time constant τ will also change accordingly, causing the thermal frequency to change. However, this will also cause the resonant frequency to change, causing the resonant frequency to deviate from the design value. Based on this, the inventors of this application proposed a technical concept of providing a slot structure on the vibration arm to change the heat flow path, so as to reduce the thermoelastic loss without affecting the resonant frequency.

[0040] Figure 3 A MEMS resonator 10 provided in one embodiment of the present invention includes two spaced-apart vibration arms 12, an anchoring region 14 located between the two vibration arms 12, and a coupling beam 16 connecting the vibration arms 12 and the anchoring region 14. The two vibration arms 12 are spaced-apart along a first direction X, and the anchoring region 14 is used to connect to a substrate to support the vibration arms 12 and the coupling beam 16. The MEMS resonator includes a drive electrode spaced-apart on one side of the vibration arms 12 in the first direction X. The drive electrode and the vibration arms 12 can cooperate to form an electrostatic force, which serves as a driving force to drive the vibration arms 12 to vibrate.

[0041] Under the action of the driving force, the two vibration arms 12 swing along the first direction X relative to the anchoring area 14, that is, the vibration arms 12 use the coupling beam 16 as a fulcrum, and the two ends swing toward or away from the other vibration arm 12, and the two vibration arms 12 swing in opposite directions.

[0042] During the swinging of the arm 12, a heat flow path opposite to the swinging direction is formed between two opposite sides of the arm 12 in the first direction X (i.e., the side closer to the other arm 12 and the side farther away from the other arm 12), with heat flowing from one side to the other. When the arm 12 swings relative to the anchoring area 14, the stress distribution on the arm 12 changes. One side is subjected to compressive stress, causing the temperature to rise, while the other opposite side is subjected to tensile stress, causing the temperature to drop. A temperature gradient is formed on the arm 12, and heat flows from the higher temperature side to the lower temperature side, establishing thermal equilibrium. The flow direction of the heat flux on the vibration arm 12 is opposite to the swinging direction of the vibration arm 12. For example, when the vibration arm 12 swings toward the anchoring area 14, the side of the vibration arm 12 close to the anchoring area 14 is subjected to compressive stress, and the side away from the anchoring area 14 is subjected to tensile stress. At this time, the heat flux flows from the side of the vibration arm 12 close to the anchoring area 14 to the side away from the anchoring area 14; when the vibration arm 12 swings in the direction away from the anchoring area 14, the side of the vibration arm 12 away from the anchoring area 14 is subjected to compressive stress, and the side close to the anchoring area 14 is subjected to tensile stress. At this time, the heat flux flows from the side of the vibration arm 12 away from the anchoring area 14 to the side close to the anchoring area 14.

[0043] See also Figure 3 and Figure 4 The vibrating arm 12 is provided with a heat dividing groove 18 in the heat flow path. The heat dividing groove 18 extends along the second direction Y perpendicular to the first direction X, and the heat flow flows along the first direction X. Therefore, the heat flow dividing groove can hinder the flow of heat flow, thereby dividing the heat flow path into multiple first heat flow sub-paths 20. The path length of the first heat flow sub-path 20 in the first direction X is less than the width of the vibrating arm 12 in the first direction X. When the heat flow flows in the portion where the heat dividing groove 18 is provided in the vibrating arm 12, the heat flow flows in the first heat flow sub-path 20 along the first direction X, and there is a heat dividing groove 18 between adjacent first heat flow sub-paths 20. Therefore, the sum of the lengths of the multiple first heat flow sub-paths 20 in the first direction X will be less than the width of the vibrating arm 12, and the distance that the heat flow flows in the first direction X is less than the width of the vibrating arm 12, thereby achieving the effect of reducing the path length. The change in path length causes the thermal frequency to change accordingly. The reduction in path length causes the thermal frequency to increase, thereby making the thermal frequency away from the resonant frequency of the MEMS resonator, effectively improving Q. ted , reducing thermoelastic loss and improving the Q value of the MEMS resonator, thereby improving the overall performance of the MEMS resonator.

[0044] In the present application, the outer contour of the vibration arm 12 is substantially rectangular, the first direction X is consistent with the width direction of the vibration arm 12 , and the second direction Y is consistent with the length direction of the vibration arm 12 .

[0045] In the first direction X, the number of heat dividing grooves 18 provided on each vibration arm 12 can be one, thereby forming two sections of first heat flow sub-paths 20, or can be multiple, thereby forming three or more sections of first heat flow sub-paths 20.

[0046] In an optional example, each vibrating arm 12 is provided with a heat dividing groove 18 in the first direction X, and the heat dividing groove 18 is located in the middle of the vibrating arm 12 in the first direction X, so that the stiffness of the vibrating arm 12 located on opposite sides of the heat dividing groove 18 is substantially the same, and the stress distribution on both sides of the heat dividing groove 18 is more uniform during deformation. A heat dividing groove 18 can be divided to form two first heat flow sub-paths 20, one of which is located between the vibrating arm 12 and the two adjacent sides of the heat dividing groove 18 in the first direction X, and the other first heat flow sub-path 20 is located between the vibrating arm 12 and the other two adjacent sides of the heat dividing groove 18 in the first direction X. The heat flow flows from one side of the vibrating arm 12 to the side adjacent to the heat dividing groove 18, and from the other opposite side of the heat dividing groove 18 to the other opposite side of the vibrating arm 12. At this time, the path length of the heat flow is the width of the vibrating arm 12 minus the width of the heat dividing groove 18.

[0047] like Figure 3 As shown, in one embodiment, each vibration arm 12 includes two elastic beams 22 and two mass beams 24. The elastic beams 22 and the mass beams 24 are arranged along the second direction Y. One ends of the two elastic beams 22 are interconnected and fixed to the coupling beam 16, and the other ends are respectively connected to the mass beams 24. That is, the two mass beams 24 are respectively connected to the two opposite ends of the two elastic beams 22.

[0048] The stiffness of the elastic beam 22 in the first direction X is less than the stiffness of the mass beam 24 in the first direction X. Therefore, the deformation of the elastic beam 22 is greater than the deformation of the mass beam 24. Of the elastic beam 22 and the mass beam 24, the elastic beam 22 is primarily used to achieve vibration of the vibrating arm 12, while the mass beam 24 is used to cooperate with the sensing electrode of the MEMS resonator to sense the vibration of the vibrating arm 12. The mass beam 24 is heavier than the elastic beam 22, and the weight is related to the resonant frequency. Therefore, the resonant frequency can be adjusted by adjusting the weight of the mass beam 24 during the production process.

[0049] The heat separation groove 18 is provided on the elastic beam 22, and the path length of the first heat flow sub-path 20 in the first direction X is less than the width of the elastic beam 22 in the first direction X. The heat separation groove 18 is provided on the elastic beam 22 of the vibrating arm 12, which reduces the flow path of the heat flow when flowing on the elastic beam 22, increases the thermal frequency of the elastic beam 22, and reduces the thermoelastic loss. Moreover, during the vibration of the vibrating arm 12, the deformation of the elastic beam 22 is greater than the deformation of the mass beam 24, so the heat distributed on the elastic beam 22 is greater than that on the mass beam 24, that is, the heat generated by the vibration of the vibrating arm 12 is mainly concentrated on the elastic beam 22, and the heat is more concentrated on the elastic beam 22, which is conducive to enhancing its effect and further reducing the thermoelastic loss.

[0050] It is understandable that the heat dividing groove 18 may be entirely located on the corresponding elastic beam 22 , or may be mostly located on the elastic beam 22 with a small portion extending to the mass beam 24 connected to the elastic beam 22 .

[0051] In the second direction Y, the length of the heat separation groove 18 is between 0.5 and 1.5 times the length of the elastic beam 22. When the length exceeds 1 times the length of the elastic beam 22, one end of the heat separation groove 18 extends to the corresponding mass beam 24. Keeping the length of the heat separation groove 18 within this range prevents the problem of excessive heat separation groove 18 length leading to insufficient overall strength of the boom 12, while also preventing the problem of insufficient heat flow resistance due to excessive length. In an alternative embodiment, the heat separation groove 18 is entirely located on the elastic beam 22, and its length approximates the length of the elastic beam 22.

[0052] In the first direction X, the width of the heat dividing groove 18 is between one-quarter and two-thirds of the width of the elastic beam 22. This prevents the heat dividing groove 18 from being too narrow, which would result in an insignificant reduction in path length, and also prevents the elastic beam 22 from being too weak, which would result in an overall weakening of the elastic beam 22, due to being too wide. In an alternative embodiment, the width of the heat dividing groove 18 is approximately one-third of the width of the elastic beam 22.

[0053] The heat dividing groove 18 extends along the second direction Y. Its length in the second direction Y is greater than its width in the first direction X, giving the heat dividing groove 18 an elongated shape. The specific shape of the heat dividing groove 18 is not limited, and can be, for example, rectangular or elliptical. In an optional embodiment, the heat dividing groove 18 is a rectangular groove.

[0054] See also Figure 3 and Figure 5 In one embodiment, the mass beam 24 is provided with a plurality of mutually spaced slot groups 26 in the first direction X, each slot group 26 includes a plurality of slots 28 spaced apart along the second direction Y, and the slots 28 in adjacent slot groups 26 are staggered.

[0055] During the swinging process of the vibrating arm 12, a second heat flow sub-path 30 is formed between the opposite sides of the mass beam 24 in the first direction X, passing through the spaced area between the grooves 28, and a plurality of third heat flow sub-paths 32 are formed by dividing the grooves 28. The path length of the second heat flow sub-path 30 is greater than the width of the mass beam 24 in the first direction X, and the length of the plurality of third heat flow sub-paths 32 in the first direction X is less than the width of the mass beam 24 in the first direction X. The multiple grooves 28 of the same groove group 26 are spaced apart along the second direction Y, so that a spaced area is formed between two adjacent grooves 28 of each groove group 26. Since the grooves 28 of different groove groups 26 are staggered along the second direction Y, the spaced area of one groove group 26 is staggered along the second direction Y with the spaced area of another adjacent groove group 26. That is, in the second direction Y, the spaced area of one groove group 26 is located between two adjacent spaced areas of another adjacent groove group 26, and part of the heat flow flows from one side of the vibrating arm 12 to the spaced area of the adjacent groove group 26. After passing through the area, the heat flow first flows in the interval area along the first direction X, and then, under the action of the groove 28 of the other slot group 26, flows along the second direction Y toward the adjacent interval area of the other slot group 26, and finally flows through the corresponding interval areas of multiple slot groups 26 in sequence and flows to the other side of the vibrating arm 12. During the flow process, the heat flow not only flows in the first direction X, but also flows in the second direction Y, forming an effect of flowing along a bending path, namely the second heat flow sub-path 30, so that the length of the second heat flow sub-path 30 is greater than the width of the vibrating arm 12. A plurality of slot groups 26 are spaced apart along the first direction X, thereby dividing the vibrating arm 12 into a plurality of third heat flow sub-paths 32, namely, third heat flow sub-paths 32 are formed between adjacent slot groups 26, and between the two outermost slot groups 26 and the corresponding side surfaces of the vibrating arm 12. Part of the heat flow flows along the first direction X between one side of the vibrating arm 12 and the slot group 26, and between adjacent slot groups 26. At this time, the length of the path through which the heat flow flows is the width of the vibrating arm 12 minus the sum of the widths of the plurality of slot groups 26 in the first direction X. The length of the path through which the heat flow flows is less than the width of the vibrating arm 12. The length of the second heat flow sub-path 30 is greater than the width of the vibrating arm 12, and the length of the third heat flow sub-path 32 is less than the width of the vibrating arm 12. Both of these will cause the corresponding thermal frequencies to change. The thermal frequency of the heat flowing through the second heat flow sub-path 30 decreases, while the thermal frequency of the heat flowing through the third heat flow sub-path 32 increases. Both of these can keep the corresponding thermal frequencies away from the resonant frequency of the MEMS resonator, effectively improving Q. ted , reducing thermoelastic losses and thus improving the Q value of the MEMS resonator.

[0056] Optionally, the mass beam 24 is provided with five slot groups 26 arranged in sequence along the first direction X, and the distance between any two adjacent slot groups 26 in the first direction X is the same.

[0057] Figure 6The resonant frequency and Q of the MEMS resonator of the present invention when the heat partition groove 18 and the groove 28 are provided on the vibrator 10 are shown in FIG. ted The relationship diagram from Figure 6 It can be seen that when the resonant frequency is 5×10 5 When nearby, Q ted The value is 6×10 4 nearby. Figure 2 for Figure 1 The resonant frequency and Q of the MEMS resonator ted The heat separation groove 18 and the groove 28 are not provided on the vibration arm 12 of the MEMS resonator. Figure 2 It can be seen that when the resonant frequency is 5×10 5 When near, Q ted In 1×10 4 to 1.5×10 4 It can be concluded that at the same resonant frequency, the scheme in which the heat dividing groove 18 and the groove 28 are provided on the vibration arm 12 is compared with the scheme in which the heat dividing groove 18 and the groove 28 are not provided on the vibration arm 12. ted The value of is increased by about 4-6 times. Therefore, the solution of the present application can effectively improve the Q of the MEMS resonator by setting the heat partition groove 18 on the elastic beam 22 and the groove 28 on the mass beam 24. ted , reducing thermoelastic losses to improve the overall performance of MEMS resonators.

[0058] like Figure 3 As shown, in one embodiment, each elastic beam 22 is provided with a heat dividing groove 18. That is, two heat dividing grooves 18 are provided on the same vibration arm 12, and the vibrator 10 is provided with a total of four heat dividing grooves 18. The two dividing grooves on the same vibration arm 12 are symmetrically arranged with respect to a first symmetry axis C1, which extends along a first direction X. The corresponding heat dividing grooves 18 on the two elastic beams 22 are symmetrically arranged with respect to a second symmetry axis C2, which extends along a second direction Y. That is, the first symmetry axis C1 and the second symmetry axis C2 are mutually perpendicular axes of symmetry.

[0059] Optionally, the two elastic beams 22 and the mass beam 24 of the same vibration arm 12 are symmetrically arranged relative to the first symmetry axis C1, and the two vibration arms 12 are symmetrically arranged relative to the second symmetry axis C2. By symmetrically arranging the two vibration arms 12 and the heat dividing grooves 18 and the grooves 28 on the vibration arms 12, the deformation consistency of the two vibration arms 12 is ensured, and the heat is more evenly distributed on the different elastic beams 22 and the different mass beams 24.

[0060] The vibrator 10 also includes a connecting beam 34 connected to the coupling beam 16. The connecting beam 34 extends along the second direction Y, and the coupling beam 16 extends along the first direction X. Therefore, the two are perpendicular to each other and arranged in a cross shape. The coupling beam 16 is perpendicularly connected to the vibrating arm 12, and the connection point between the two is located at the midpoint of the vibrating arm 12 in the second direction Y. The connecting beam 34 is respectively connected to an anchoring region 14 at each end. The anchoring region 14 is connected to the coupling beam 16 through the connecting beam 34. The portions of the connecting beam 34 located on opposite sides of the coupling beam 16 and the two anchoring regions 14 are symmetrically arranged with respect to the first symmetry axis C1. The portions of the coupling beam 16 located on opposite sides of the connecting beam 34 are also symmetrically arranged with respect to the first symmetry axis C1.

[0061] In one embodiment, each elastic beam 22 is provided with a heat partitioning groove 18. The two heat partitioning grooves 18 on the same vibrating arm 12 are spaced apart from each other, and the portion of the vibrating arm 12 between the two heat partitioning grooves 18 corresponds to the portion where the vibrating arm 12 is connected to the coupling beam 16. By spacing the heat partitioning grooves 18 on the two elastic beams 22 a certain distance apart, the portion between the two heat partitioning grooves 18 can enhance the strength of the elastic beam 22, thereby preventing the heat partitioning grooves 18 on the vibrating arm 12 from being too long, which would weaken the elastic beam 22. Furthermore, the portion between the two heat partitioning grooves 18 corresponds to the portion where the coupling beam 16 is connected to the vibrating arm 12. Since the vibrating arm 12 swings around the coupling beam 16, the portion where the vibrating arm 12 is connected to the coupling beam 16 does not deform or deforms only slightly, resulting in relatively less heat distribution there. Consequently, the portion between the two heat partitioning grooves 18 has a relatively small impact on the thermal frequency.

[0062] Optionally, the width of a portion of the vibration arm 12 between the two heat dividing grooves 18 in the second direction Y is substantially the same as the width of the coupling beam 16 in the second direction Y.

[0063] like Figure 3 As shown, in one embodiment, the outline of the elastic beam 22 is a rectangle, and the two side surfaces of the elastic beam 22 in the first direction X are parallel to each other, so the distance between the two side surfaces of the elastic beam 22 is the same.

[0064] like Figure 7As shown, in another embodiment, the elastic beam 22 is trapezoidal, and the elastic beam 22 extends from one end of the other elastic beam 22 toward the corresponding mass beam 24 in a manner that gradually decreases in width, forming a gradient design. At this time, the width of the end where the elastic beam 22 is connected to the mass beam 24 is the smallest, and the stress is more concentrated at this location. At the same time, the reduced width can further reduce the length of the heat flow path at this location, thereby shifting the thermal frequency at this location to a higher frequency. Moreover, the gradient design does not directly increase or decrease the overall width of the vibration arm 12. It has different widths at different locations. Therefore, the equivalent stiffness of the elastic beam 22 can be adjusted by adjusting the length of the elastic beam 22 and the width at different locations, so that the equivalent stiffness of the elastic beam 22 does not change, so as to achieve the change of the thermal frequency without affecting the thermal frequency, thereby reducing the thermoelastic loss.

[0065] It is understood that both side surfaces of the elastic beam 22 in the first direction X can be inclined surfaces, or one can be a plane perpendicular to the first direction X and the other an inclined surface, as long as the gradient design is achieved. In this embodiment, both opposing side surfaces of the elastic beam 22 are inclined surfaces, and the two inclined surfaces gradually converge from the other elastic beam 22 toward the corresponding mass beam 24, thereby gradually decreasing the width of the elastic beam 22 as it approaches the mass beam 24.

[0066] Optionally, the two inclined surfaces have the same inclination relative to the second direction Y, so that the profile of the elastic beam 22 is similar to an isosceles trapezoid.

[0067] See also Figure 3 and Figure 8 In one embodiment, the mass beam 24 is provided with composite teeth 36 on opposite sides in the first direction X, and the driving electrode and the sensing electrode of the MEMS resonator are respectively arranged at intervals on opposite sides of the vibration arm 12 in the first direction X, and the driving electrode and the sensing electrode are respectively provided with another composite tooth portion 36 that cooperates with the composite tooth portion 36 on the mass beam 24. The design of the composite tooth portion 36 can increase the capacitance area between the driving electrode, the sensing electrode and the vibration arm 12, improve the signal-to-noise ratio, and thus enhance the performance of the MEMS resonator.

[0068] The composite tooth portion 36 on the mass beam 24 includes a first tooth 42-shaped portion 38 and a second tooth 44-shaped portion 40 arranged along the second direction Y. The first tooth 42-shaped portion 38 and the second tooth 44-shaped portion 40 are two different tooth shapes, and the first tooth 42-shaped portion 38 is closer to the elastic beam 22 than the second tooth 44-shaped portion 40. The first tooth 42-shaped portion 38 includes a plurality of first teeth 42 spaced apart along the second direction Y, and the second tooth 44-shaped portion 40 includes a plurality of second teeth 44. The first teeth 42 and the second teeth 44 extend outward from corresponding sides of the mass beam 24, that is, extend away from the mass beam 24 along the first direction X. The first teeth 42 and the second teeth 44 each include a tooth base 46 connected to the mass beam 24, a tooth top 48 opposite the tooth base 46, and a tooth flank 50 connecting the tooth base 46 and the tooth top 48. The tooth flank 50 of the first teeth 42 is parallel to the first direction X, while the tooth flank 50 of the second teeth 44 is inclined relative to the first direction X.

[0069] The composite tooth portion 36 refers to a tooth-shaped portion comprising at least two teeth of different shapes. For ease of description and distinction, in the present embodiment, the teeth of different shapes in the composite tooth portion 36 are referred to as first teeth 42 and second teeth 44, respectively. Both the first teeth 42 and the second teeth 44 extend along the first direction X and include a tooth base 46, a tooth top 48, and a tooth flank 50. The tooth base 46 refers to the end of each tooth connected to the mass beam 24, the tooth top 48 refers to the end of the tooth extending away from the mass beam 24 along the first direction X, and the tooth flank 50 refers to the side surface connecting the tooth top 48 and the tooth base 46. The tooth flanks 50 of the first teeth 42 are parallel to the first direction X, and a tooth groove 52 of constant width (i.e., width in the second direction Y) is formed between the tooth flanks 50 of two adjacent first teeth 42. The tooth flanks 50 of the second teeth 44 are inclined relative to the first direction X, and a tooth groove 52 of varying width in the second direction Y is formed between the tooth flanks 50 of two adjacent second teeth 44. The teeth on the electrodes of the MEMS resonator are respectively inserted into the corresponding tooth grooves 52, so that the composite tooth portion 36 on the electrode and the composite tooth portion 36 on the mass beam 24 form a meshing effect. The teeth on the electrode and the teeth on the mass beam 24 are alternately arranged along the second direction Y, and a gap capacitor is formed between the tooth side surfaces 50 of two adjacent teeth.

[0070] In the above embodiment, by making the first teeth 42 close to the elastic beam 22 parallel to the first direction X and the second teeth 44 away from the elastic beam 22 inclined relative to the first direction X, during the operation of the MEMS resonator, when the vibration arm 12 swings along the first direction X, the displacement of the mass beam 24 at the end away from the elastic beam 22 is greater than the displacement at the end close to the elastic beam 22, that is, the displacement of the second tooth 44-shaped portion 40 is greater than that of the first tooth 42-shaped portion 38. Therefore, the second tooth 44-shaped portion 40 is more likely to enter the nonlinear region, which can increase the size of the nonlinear working region of the MEMS resonator. The first tooth 42-shaped portion 38, which is relatively close to the elastic beam 22, can maintain good linearity within a larger torsion angle, thereby increasing the change in gap capacitance per unit torsion angle in the MEMS resonator. The design of the composite tooth portion 36 effectively solves the compatibility problem of using an ultra-small capacitor gap to improve the electromechanical transduction coefficient of the electrostatically driven resonator and improving the linear working region under the ultra-small capacitor gap.

[0071] In the MEMS resonator 10 employing this composite tooth portion 36, in the second tooth 44-shaped portion 40 relatively far from the elastic beam 22, the second tooth 44 utilizes an inclined tooth side surface 50. This prevents the occurrence of a very small gap and entry into the nonlinear region when the vibrating arm 12 is twisted, thereby increasing the size of the MEMS resonator's nonlinear operating region. Furthermore, in the first tooth 42-shaped portion 38 relatively close to the elastic beam 22, the use of parallel tooth side surfaces 50 increases the area of the capacitance surface within a unit volume. Furthermore, both the tooth side surface 50 and the tooth top 48 of the first tooth 42 can serve as capacitance coupling surfaces. Compared to the second tooth 44, the capacitance coupling surface is larger, potentially increasing the change in gap capacitance per unit torsion angle.

[0072] In an optional example, the first teeth 42 are rectangular teeth, with the tooth base 46, tooth top 48, and tooth side surface 50 of the first teeth 42 all being linear, and the tooth groove 52 between two adjacent first teeth 42 forming a rectangular groove. The second teeth 44 are triangular teeth, with the tooth base 46 of the second teeth 44 being linear and the tooth top 48 being pointed. Adjacent second teeth 44 are spaced a certain distance apart in the second direction Y, thereby forming an isosceles trapezoidal tooth groove 52 between the two adjacent second teeth 44, and the width of the tooth groove 52 gradually decreases in the direction away from the mass beam 24.

[0073] The present invention also provides a MEMS resonator, comprising a driving electrode, a sensing electrode, and the vibrator 10 in the above-mentioned embodiment, wherein the driving electrode and the sensing electrode are arranged corresponding to the vibrating arm 12 of the vibrator 10, wherein the driving electrode is used to drive the vibrator 10 to vibrate, and the sensing electrode is used to sense the vibration of the vibrating arm 12. The driving electrode and the sensing electrode are respectively located on opposite sides of the vibrating arm 12 in the first direction X, and the driving electrode and the sensing electrode are respectively spaced apart from the vibrating arm 12 to leave space required for the vibration of the vibrating arm 12. Since the MEMS resonator adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0074] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A vibrator of a MEMS resonator, characterized in that: The invention comprises two vibration arms arranged at intervals, an anchoring area located between the two vibration arms, and a coupling beam connecting the vibration arms and the anchoring area; Under the action of the driving force, the two vibration arms swing along the first direction relative to the anchoring area. During the swinging of the vibration arms, a heat flow path opposite to the swinging direction is formed between the two opposite sides in the first direction. The vibration arms are provided with a heat dividing groove extending in a second direction perpendicular to the first direction in the heat flow path. The heat dividing groove divides the heat flow path into multiple first heat flow sub-paths. The path length of the first heat flow sub-path in the first direction is less than the width of the vibration arm in the first direction.

2. The oscillator of the MEMS resonator according to claim 1, wherein: Each of the vibration arms includes two elastic beams and two mass beams, one end of the two elastic beams is connected to each other and fixed to the coupling beam, and the other end is connected to the mass beam respectively, the stiffness of the elastic beam in the first direction is less than the stiffness of the mass beam, the heat separation groove is provided on the elastic beam, and the path length of the first heat flow path in the first direction is less than the width of the elastic beam in the first direction.

3. The oscillator of the MEMS resonator according to claim 2, wherein: The mass beam is provided with a plurality of mutually spaced slot groups in the first direction, each of the slot groups includes a plurality of slots spaced apart along the second direction, and the slots in adjacent slot groups are staggered; During the arm swing, the mass beam forms a second heat flow sub-path between the opposite sides in the first direction, which passes through the spacing area between the grooves, and a plurality of third heat flow sub-paths formed by the grooves; the path length of the second heat flow sub-path is greater than the width of the mass beam in the first direction, and the path length of the third heat flow sub-path in the first direction is less than the width of the mass beam in the first direction.

4. The oscillator of the MEMS resonator according to claim 2, wherein: The length of the heat dividing groove in the second direction is 0.5 to 1.5 times the length of the elastic beam; and / or, The width of the heat dividing groove in the first direction is one quarter to two thirds of the width of the elastic beam.

5. The oscillator of the MEMS resonator according to claim 2, wherein: Each of the elastic beams is provided with a heat separation groove, and the two heat separation grooves on the same vibration arm are symmetrically arranged relative to a first symmetry axis, and the first symmetry axis extends along the first direction. The corresponding heat separation grooves on the two elastic beams are symmetrically arranged relative to a second symmetry axis, and the second symmetry axis extends along the second direction.

6. The oscillator of the MEMS resonator according to claim 2, wherein: Each elastic beam is provided with a heat dividing groove, the two heat dividing grooves on the same vibration arm are spaced apart from each other, and the portion of the vibration arm between the two heat dividing grooves corresponds to the portion where the vibration arm and the coupling beam are connected.

7. The oscillator of the MEMS resonator according to claim 2, wherein: The two side surfaces of the elastic beam in the first direction are parallel to each other; or, The elastic beam extends from one end of the other elastic beam toward the corresponding mass beam in a manner of gradually decreasing width.

8. The oscillator of the MEMS resonator according to any one of claims 2 to 7, characterized in that: The mass beam is provided with composite tooth portions on two opposite sides in the first direction, the composite tooth portions comprising a first tooth-shaped portion and a second tooth-shaped portion arranged along the second direction, the first tooth-shaped portion being closer to the elastic beam than the second tooth-shaped portion; The first tooth-shaped portion includes a plurality of first teeth, and the second tooth-shaped portion includes a plurality of second teeth. The first teeth and the second teeth respectively protrude outward from corresponding sides of the mass beam. The first teeth and the second teeth both include a tooth bottom connected to the mass beam, a tooth top opposite to the tooth bottom, and a tooth side surface connected between the tooth bottom and the tooth top. The tooth side surface of the first tooth is parallel to the first direction, and the tooth side surface of the second tooth is inclined relative to the first direction.

9. The oscillator of the MEMS resonator according to claim 8, characterized in that: The first teeth are rectangular teeth, and the second teeth are triangular teeth.

10. A MEMS resonator, characterized in that: It comprises a vibrator according to any one of claims 1 to 9, and a driving electrode and a sensing electrode arranged corresponding to the vibrating arm of the vibrator, wherein the driving electrode and the sensing electrode are respectively located on opposite sides of the vibrating arm in the first direction and are respectively spaced apart from the vibrating arm.

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