Membrane resonator and its resonator

Abstract

This invention discloses a MEMS resonator and its oscillator. The oscillator includes a resonant structure, an anchoring region spaced apart from the resonant structure, and a beam structure connecting the resonant structure and the anchoring region. One end of the beam structure is connected to the resonant structure, and the other end extends along a first direction to connect with the anchoring region to form a connection end. The anchoring region has a reflection groove at one end near the connection end, and the reflection groove extends along a second direction perpendicular to the first direction. When a mechanical wave propagates to the reflection groove, the propagation medium changes from solid to gaseous. The mechanical wave is reflected at the interface between different propagation media, thus reflecting more mechanical waves back to the beam structure, reducing the mechanical waves propagating from the anchoring region to the substrate, effectively reducing anchor point loss, and thereby improving the Q value of the MEMS resonator.

Description

Technical Field

[0001] This utility model relates to the field of microelectromechanical technology, and in particular to a MEMS resonator and its oscillator. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) resonators are key components of MEMS oscillators. They are transducer structures based on micro-electro-mechanical systems that can convert mechanical energy into electrical energy through vibration. The main performance indicators of MEMS resonators include resonant frequency, Q-factor (Quality Factor), and dynamic impedance. Among these, the Q-factor is an important performance parameter, representing the ratio of energy stored to energy dissipated per unit time. The main energy losses in resonators include air damping loss, anchor point loss, thermoelastic loss, and material loss. Anchor point loss is one of the most significant loss mechanisms affecting the Q-factor. During resonance, mechanical waves are not completely reflected back at the resonator's boundaries; some mechanical waves are transmitted to the substrate through the anchor point, forming anchor point loss and leading to a decrease in the Q-factor.

[0003] To reduce anchor point loss, current methods mainly include setting the coupling beam to 1 / 4 wavelength, placing the anchor point near the node, and using two different materials to create impedance mismatch. While these methods can reduce anchor point loss, they also introduce new problems, such as requiring changes to device size and increasing manufacturing complexity. Therefore, under current technological conditions, how to reduce anchor point loss without affecting device size and manufacturing difficulty has become a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a MEMS resonator and its oscillator that can reduce anchor point loss.

[0005] On one hand, this application provides an oscillator for a MEMS resonator, including a resonant structure, an anchoring region spaced apart from the resonant structure, and a beam structure connecting the resonant structure and the anchoring region. One end of the beam structure is connected to the resonant structure, and the other end extends along a first direction to connect with the anchoring region to form a connection end. The anchoring region has a reflection groove at one end near the connection end, and the reflection groove extends along a second direction perpendicular to the first direction.

[0006] In some embodiments, in the second direction, the length of the reflective groove is greater than the length of the connecting end, and both ends of the reflective groove extend beyond the connecting end.

[0007] In some embodiments, the anchoring region forms a flexible portion between the reflective groove and the connecting end, and the connecting end is connected to the flexible portion.

[0008] In some embodiments, the connecting end is connected to the middle position of the flexible portion in the second direction, and the two ends of the flexible portion extending out of the connecting end along the second direction are symmetrically arranged relative to the connecting end.

[0009] In some embodiments, the resonant structure is a vibrating arm, the beam structure includes a coupling beam and a connecting beam connected to the coupling beam, the coupling beam is connected to the vibrating arm and extends along the second direction, the connecting beam extends from the coupling beam to the connecting beam along the first direction, and the connecting end is located at the end of the connecting beam away from the coupling beam.

[0010] In some embodiments, the coupling beam is provided with a barrier groove extending along the first direction.

[0011] In some embodiments, the coupling beam is provided with a plurality of barrier grooves extending along the first direction, and the plurality of barrier grooves are arranged at intervals along the second direction.

[0012] In some embodiments, the number of vibrating arms is two, the two vibrating arms are arranged opposite each other at a distance, and the two ends of the coupling beam are respectively connected to the two vibrating arms;

[0013] Two anchoring regions are provided between the two vibrating arms. The two anchoring regions are distributed at intervals on both sides of the coupling beam along the first direction. Each anchoring region is connected to the coupling beam through the connecting beam. Each anchoring region is provided with a reflective groove at one end near the connecting beam. The two ends of the coupling beam are provided with barrier grooves at the positions near the vibrating arms.

[0014] In some embodiments, the connecting beam is provided with a barrier groove extending in the second direction.

[0015] On the other hand, this application also provides a MEMS resonator, including the oscillator as described above.

[0016] The MEMS resonator provided by this invention uses a resonant structure to transmit mechanical waves generated during vibration to the anchoring region via a beam structure. Because a reflective groove is provided at the end of the anchoring region near the connection point, the mechanical waves propagate from the vibrating arm to the anchoring structure through this groove. When the mechanical waves reach the reflective groove, the propagation medium changes from solid to gas. Reflection occurs at the interface between different propagation media, reflecting more mechanical waves back to the beam structure and reducing the amount of mechanical waves propagating from the anchoring region to the substrate. This effectively reduces anchor point loss and improves the Q value of the MEMS resonator. Furthermore, optimizing the propagation path of mechanical waves by using a reflective groove in the anchoring region to reduce anchor point loss does not affect the size of the resonator. The reflective groove structure is simple and easy to manufacture, ultimately achieving a balance between not affecting the resonator size, reducing manufacturing difficulty, and minimizing anchor point loss. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the MEMS resonator provided in Embodiment 1 of this utility model;

[0018] Figure 2 for Figure 1 A structural schematic diagram of the coupling beam, connecting beam, and anchorage area shown in the figure;

[0019] Figure 3 for Figure 2 A schematic diagram of a structure with a barrier groove on the intermediate coupling beam;

[0020] Figure 4 A schematic diagram of the structure of a MEMS resonator provided in another embodiment of this utility model;

[0021] Figure 5 The simulation results show the normalized Qanchor values ​​for three types of MEMS resonators.

[0022] In the diagram: 10, oscillator; 12, resonant structure; 14, anchoring area; 16, beam structure; 18, connecting end; 20, reflector groove; 22, reflector surface; 24, flexible part; 28, coupling beam; 30, connecting beam; 32, barrier groove; 34, tooth structure. Detailed Implementation

[0023] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside, top, bottom, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship between the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] It should also be noted that when a component is referred to as "fixed to" or "set on" another component, the component may be directly on the other component or there may be an intervening component present. When a component is referred to as "connected to" another component, it may be directly connected to the other component or there may be an intervening component present.

[0026] Please see Figure 1 and Figure 2 An embodiment of this utility model provides an oscillator 10 for a MEMS resonator, including a resonant structure 12, an anchoring region 14 spaced apart from the resonant structure 12, and a beam structure 16 connecting the resonant structure 12 and the anchoring region 14. The resonant structure 12 is used for resonance, and the anchoring region 14 is used to connect to a substrate to support the resonant structure 12 and the beam structure 16. Mechanical waves generated when the resonant structure 12 resonates propagate sequentially to the beam structure 16 and the anchoring region 14. When the mechanical waves propagate to their boundary position on the anchoring region 14, part of the mechanical waves are reflected back to the beam structure 16, and part propagates to the substrate through the anchoring region 14.

[0027] One end of the beam structure 16 is connected to the resonant structure 12, and the other end extends along the first direction Y to connect with the anchoring region 14 to form a connecting end 18. That is, the end of the beam structure 16 connected to the anchoring region 14 is the connecting end 18, and the connecting end 18 extends towards the anchoring region 14 in the first direction Y. The anchoring region 14 has a reflective groove 20 at one end near the connecting end 18. The reflective groove 20 extends along a second direction X perpendicular to the first direction Y, and the reflective groove 20 and the connecting end 18 are arranged opposite each other in the first direction Y, that is, the reflective groove 20 and the connecting end 18 at least partially overlap in the first direction Y. The anchoring region 14 has an anchoring portion connected to the substrate. This anchoring portion is located on the side of the reflective groove 20 away from the connecting end 18 and is spaced a certain distance from the reflective groove 20.

[0028] By providing a reflective groove 20 extending along the second direction X at one end of the anchoring region 14 near the beam structure 16, and the reflective groove 20 being located between the beam structure 16 and the anchoring part, the mechanical wave generated when the resonant structure 12 resonates propagates through the beam structure 16 to the anchoring region 14. The mechanical wave then passes through the reflective groove 20. When the mechanical wave reaches the reflective groove 20, the propagation medium changes from solid to gaseous. The mechanical wave is reflected at the interface between different propagation media. That is, a reflective surface 22 (i.e., the interface between different propagation media) is formed on the inner wall of the reflective groove 20 near the beam structure 16, thereby reflecting more mechanical waves back to the beam structure 16, reducing the mechanical waves propagating from the anchoring region 14 to the substrate, effectively reducing anchor point loss, and thus improving the Q value of the MEMS resonator. Furthermore, the reflective groove 20 does not affect the size of the oscillator, and its simple structure reduces manufacturing difficulty, ultimately achieving the effect of not affecting the oscillator size, reducing manufacturing difficulty, and minimizing anchor point loss.

[0029] In the second direction X, the length of the reflective groove 20 is greater than the length of the connecting end 18, and both ends of the reflective groove 20 extend beyond the connecting end 18, forming a T-shaped structure with the connecting end 18. By setting the length of the reflective groove 20 to be greater than the length of the connecting end 18, the projection of the area where the connecting end 18 connects to the anchoring area 14 in the first direction Y is entirely within the reflective groove 20, thereby better reflecting mechanical waves from the beam structure 16 and reducing the risk of mechanical waves bypassing the reflective groove 20 from the side. In an optional example, the length of the reflective groove 20 is approximately three times the length of the connecting end 18.

[0030] In one embodiment, the anchoring region 14 forms a flexible portion 24 between the reflective groove 20 and the connecting end 18. The connecting end 18 is connected to the flexible portion 24, meaning the beam structure 16 is connected to the flexible portion 24 via the connecting end 18. The reflective groove 20 is located near the end of the anchoring region 14 connected to the beam structure 16. The distance between the reflective groove 20 and the outer surface of the anchoring region 14 near the beam structure 16 is relatively short. The overall thickness of the portion of the anchoring region 14 located between the reflective groove 20 and the connecting end 18 is low, resulting in low overall stiffness and thus forming a deformable flexible portion 24. After the resonant structure 12 transmits mechanical waves to the beam structure 16, the beam structure 16 first transmits the mechanical waves to the flexible portion 24, and then the flexible portion 24 propagates them towards the reflective groove 20.

[0031] During the packaging process of MEMS resonators, factors such as mismatched thermal expansion coefficients of materials and mechanical pressure may cause internal stress, i.e., packaging stress. This packaging stress is transmitted to the beam structure 16 of the oscillator 10, causing changes in the stiffness of the beam structure 16 and resulting in frequency drift, i.e., a deviation between the actual operating frequency and the design value. In this application, a reflective groove 20 is provided at one end of the anchoring region 14 near the beam structure 16. While reflecting mechanical waves, the reflective groove 20 also forms a relatively low-stiffness flexible part 24 between the reflective groove 20 and the beam structure 16. Since the beam structure 16 is connected to the flexible part 24, the packaging stress inside the beam structure 16 can be transmitted to the flexible part 24. The flexible part 24 absorbs the packaging stress through deformation, converting the packaging stress into elastic potential energy, allowing the packaging stress of the beam structure 16 to be released in the flexible part 24. This reduces the impact of packaging stress on the resonant frequency of the MEMS resonator, thereby improving the stability of the frequency output of the MEMS resonator.

[0032] In an alternative example, the width of the flexible portion 24 in the first direction Y is smaller than the width of the reflective groove 20 in the first direction Y.

[0033] The connecting end 18 is connected to the middle position of the flexible part 24 in the second direction X. Both ends of the flexible part 24 extend beyond the connecting end 18 in the second direction X, and these two ends are symmetrically arranged relative to the connecting end 18, meaning that the distance between the two end faces of the flexible part 24 in the second direction X and the connecting end 18 is the same. By symmetrically arranging the flexible part 24 relative to the connecting end 18, the stiffness of the two parts of the flexible part 24 outside the connecting end 18 can be kept the same or substantially the same, so that the stress distribution of the flexible part 24 is more uniform when subjected to the force of the coupling beam 28.

[0034] The specific shape of the resonant structure 12 is not limited. It can be a ring-shaped resonant ring or a similar rectangular vibrating arm. In this application, the resonant structure 12 is a vibrating arm that extends along the first direction Y and is spaced a certain distance from the anchoring region 14 in the second direction X.

[0035] Please see Figure 1 and Figure 3In one embodiment, the resonant structure 12 is a vibrating arm, and the beam structure 16 includes a coupling beam 28 and a connecting beam 30 connected to the coupling beam 28. The coupling beam 28 is connected to the vibrating arm and extends along a second direction X, while the connecting beam 30 extends along a first direction Y, thereby creating a mutually perpendicular effect between the connecting beam 30 and the coupling beam 28. The connecting beam 30 extends along the first direction Y from the coupling beam 28 to the anchorage region 14, and its two ends are connected to the coupling beam 28 and the anchorage region 14, respectively. The connecting end 18 is the end of the connecting beam 30 connected to the anchorage region 14. When the mechanical wave generated by the vibration of the vibrating arm propagates through the coupling beam 28 to the connecting beam 30, and then propagates from the connecting beam 30 to the anchorage region 14, the reflector groove 20, near the connecting end 18 of the connecting beam 30, reflects the mechanical wave back to the connecting beam 30.

[0036] There are two vibrating arms, which are arranged opposite each other at intervals along the second direction X. The coupling beam 28 extends along the first direction Y, which is perpendicular to the second direction X, and its two ends are connected to the two vibrating arms respectively. The coupling beam 28 is connected to the middle position of the vibrating arms, so that the two vibrating arms and the coupling beam 28 form an H-shaped structure.

[0037] Two anchorage areas 14 are provided between the two vibrating arms. Each anchorage area 14 is provided with a reflective groove 20. The two anchorage areas 14 are spaced apart along the first direction Y and are located on opposite sides of the coupling beam 28. Each anchorage area 14 is connected to the coupling beam 28 by a corresponding connecting beam 30. The two connecting beams 30 and the coupling beam 28 form a cross-like shape.

[0038] Optionally, the two vibrating arms are arranged symmetrically with respect to the connecting beam 30, and the two anchoring areas 14 are arranged symmetrically with respect to the coupling beam 28.

[0039] In one embodiment, the coupling beam 28 extends along the second direction X, and the coupling beam 28 is provided with a blocking groove 32 extending along the first direction Y. During the propagation of mechanical waves from the vibrating arm to the anchoring region 14, the mechanical waves first pass through the coupling beam 28 and propagate along the second direction X on the coupling beam 28. When the mechanical waves propagate to the blocking groove 32 on the coupling beam 28, the propagation medium changes from the coupling beam 28 to the air in the blocking groove 32, that is, the propagation medium changes from solid to gas. The wall surface of the blocking groove 32 in the second direction X forms a reflective surface 22, which reflects the passing mechanical waves, reducing the mechanical waves propagating from the coupling beam 28 to the connecting beam 30, thereby correspondingly reducing the mechanical waves propagating from the connecting beam 30 to the anchoring region 14. During the propagation of mechanical waves from the anchoring region 14 to the substrate, they are reflected by the reflective groove 20, further reducing the mechanical waves propagating to the substrate and further reducing the anchor point loss.

[0040] Optionally, the length of the barrier groove 32 in the first direction Y is greater than the width of the barrier groove 32 in the second direction X, and the barrier groove 32 penetrates the coupling beam 28 along the thickness direction perpendicular to the first direction Y and the second direction X, so as to increase the area of ​​the reflective surface 22 of the barrier groove 32 and improve the reflection effect on mechanical waves.

[0041] Preferably, the coupling beam 28 has multiple blocking grooves 32, and these multiple blocking grooves 32 are arranged at intervals along the second direction X to further enhance the reflection effect on mechanical waves. Optionally, the number of blocking grooves 32 is even, and the multiple coupling beams 28 are symmetrically arranged with respect to an axis of symmetry extending along the first direction Y.

[0042] Among the multiple blocking grooves 32, two blocking grooves 32 are respectively located at both ends of the coupling beam 28, so that these two blocking grooves 32 are relatively close to the connection between the coupling beam 28 and the vibrating arm. When the mechanical wave propagates from the vibrating arm to the coupling beam 28, it needs to pass through the connection between the coupling beam 28 and the vibrating arm. The blocking grooves 32 are set close to this connection to form a better reflection effect on the mechanical wave propagating from the vibrating arm to the coupling beam 28.

[0043] Among the multiple blocking grooves 32, two blocking grooves 32 are located in the middle of the coupling beam 28 and close to the connecting beam 30. The connection between the connecting beam 30 and the coupling beam 28 is located between these two blocking grooves 32. When mechanical waves propagate from the coupling beam 28 to the connecting beam 30, they need to pass through the connection between the connecting beam 30 and the coupling beam 28. Blocking grooves 32 are provided on both sides of this connection to better reflect the mechanical waves propagating from the coupling beam 28 to the connecting beam 30.

[0044] In other embodiments, since mechanical waves need to pass through the connecting beam 30 to propagate from the coupling beam 28 to the anchorage area 14, it is also possible to provide a blocking groove 32 extending along the second direction X on the connecting beam 30 to reflect the mechanical waves propagating from the connecting beam 30 to the anchorage area 14, thereby reducing the mechanical waves propagating from the connecting beam 30 to the anchorage area 14 and further reducing anchor point loss.

[0045] Please see Figure 4In another embodiment, the oscillator 10 includes two arms, a coupling beam 28 connecting the two arms, two anchoring regions 14 located on opposite sides of the coupling beam 28, and a connecting beam 30 connecting the respective anchoring regions 14 and the coupling beam 28. Each anchoring region 14 has a reflective groove 20 at one end near the connecting beam 30, and the two reflective grooves 20 are parallel to each other and symmetrically arranged relative to the coupling beam 28. The coupling beam 28 has multiple blocking grooves 32 arranged along its extension direction. During propagation, the mechanical wave passes through the corresponding blocking grooves 32 sequentially from the arms to the coupling beam 28 and from the coupling beam 28 to the connecting beam 30. The reflective surface 22 of the blocking groove 32 reflects the mechanical wave. When the remaining mechanical wave propagates through the connecting beam 30 to the anchoring region 14, it first passes through the reflective grooves 20 to reflect the mechanical wave, reducing the propagation of the mechanical wave to the anchoring region 14, thereby reducing the mechanical wave propagating from the oscillator 10 to the substrate and lowering anchor point loss.

[0046] In this embodiment, the vibrating arm is provided with toothed structures 34 on both sides in the width direction. The toothed structures 34 are used to cooperate with the toothed structures 34 on the electrodes of the MEMS resonator, thereby increasing the capacitance area of ​​the vibrating arm and the electrodes to improve product performance.

[0047] The tooth structure 34 can be a composite tooth structure 34, that is, a structure that includes at least two different shapes of teeth. In this embodiment, the tooth structure includes rectangular teeth and triangular teeth, with the rectangular teeth being closer to the coupling beam 28 than the triangular teeth.

[0048] This invention also provides a MEMS resonator, including the oscillator in the above embodiments. Since this MEMS resonator employs the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0049] Figure 5 The normalized Qanchor values ​​(Anchor Quality Factors) of three different MEMS resonators are presented in the finite element method simulation. The Qanchor value is a quality factor that measures anchor point loss; a larger value indicates lower loss, and a smaller value indicates higher loss. The three types of MEMS resonators simulated are: a MEMS resonator without reflective and blocking slots, a MEMS resonator with only reflective slots, and a MEMS resonator with both reflective and blocking slots. As can be seen from the figure, the Qanchor value of the MEMS resonator with reflective slots is significantly improved compared to the MEMS resonator without reflective and blocking slots. Furthermore, the Qanchor value of the MEMS resonator with both reflective and blocking slots is also improved compared to the MEMS resonator with only reflective slots.

[0050] The above embodiments are merely preferred embodiments of this utility model and should not be construed as limiting the scope of protection of this utility model. Any non-substantial changes and substitutions made by those skilled in the art based on this utility model shall fall within the scope of protection claimed by this utility model.

Claims

1. An oscillator for a MEMS resonator, characterized in that, The device includes a resonant structure, an anchoring region spaced apart from the resonant structure, and a beam structure connecting the resonant structure and the anchoring region. One end of the beam structure is connected to the resonant structure, and the other end extends along a first direction to connect with the anchoring region to form a connecting end. The anchoring region has a reflective groove at one end near the connecting end, and the reflective groove extends along a second direction perpendicular to the first direction.

2. The oscillator of the MEMS resonator according to claim 1, characterized in that, In the second direction, the length of the reflective groove is greater than the length of the connecting end, and both ends of the reflective groove extend beyond the connecting end.

3. The oscillator of the MEMS resonator according to claim 2, characterized in that, The anchoring area forms a flexible portion between the reflective groove and the connecting end, and the connecting end is connected to the flexible portion.

4. The oscillator of the MEMS resonator according to claim 3, characterized in that, The connecting end is connected to the middle position of the flexible part in the second direction, and the two ends of the flexible part extending out of the connecting end along the second direction are symmetrically arranged with respect to the connecting end.

5. The oscillator of the MEMS resonator according to any one of claims 1-4, characterized in that, The resonant structure is a vibrating arm, and the beam structure includes a coupling beam and a connecting beam connected to the coupling beam. The coupling beam is connected to the vibrating arm and extends along the second direction. The connecting beam extends from the coupling beam to the connecting beam along the first direction, and the connecting end is located at the end of the connecting beam away from the coupling beam.

6. The oscillator of the MEMS resonator according to claim 5, characterized in that, The coupling beam is provided with a barrier groove extending along the first direction.

7. The oscillator of the MEMS resonator according to claim 6, characterized in that, The coupling beam is provided with a plurality of barrier grooves extending along the first direction, and the plurality of barrier grooves are arranged at intervals along the second direction.

8. The oscillator of the MEMS resonator according to claim 6, characterized in that, The number of vibrating arms is two, and the two vibrating arms are arranged opposite each other at a distance. The two ends of the coupling beam are respectively connected to the two vibrating arms. Two anchoring regions are provided between the two vibrating arms. The two anchoring regions are distributed at intervals on both sides of the coupling beam along the first direction. Each anchoring region is connected to the coupling beam through the connecting beam. Each anchoring region is provided with a reflective groove at one end near the connecting beam. The two ends of the coupling beam are provided with barrier grooves at the positions near the vibrating arms.

9. The oscillator of the MEMS resonator according to claim 5, characterized in that, The connecting beam is provided with a barrier groove extending along the second direction.

10. A MEMS resonator, characterized in that, Including the oscillator as described in any one of claims 1-9.

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