JP5056967B2 - MEMS vibrator - Google Patents

Description

The present invention relates to a structure of a MEMS vibrator. More specifically, the present invention relates to a structure of a MEMS vibrator in which a plurality of free beams at both ends are connected in a ring shape with a vibration node as a connecting portion, and the connecting portion is supported by a support member.

A drive body is made using a MEMS (Micro Electro Mechanical Systems) technology and can be used as a vibration element by being driven at a specific frequency, and a MEMS structure using such a MEMS technology has been proposed. Such a MEMS structure has a problem that a series resistance component when considered in an equivalent circuit is larger than that of a general vibrator and a loss such as a large vibration leakage is large.

As a structure of a MEMS vibrator for solving such problems, the corners of a plurality of rectangular vibrators are linearly connected, and the center of the plane of each vibrator is supported on a substrate by an anchor (support part). And
A MEMS vibrator that drives a plurality of vibrators at the same frequency is known (for example,
Non-patent document 1).

There is also known a MEMS vibrator in which both ends of a strip-shaped vibrating piece are connected and supported to a substrate, a plurality of the vibrating pieces are arranged in parallel, and the plurality of vibrating pieces are simultaneously driven at the same frequency. (For example, refer nonpatent literature 2).

M.M. U. Demirci, m. a. a. Abdelmoneum, and C.I. TC. Nguyen “Mechanically Corner-Coupled Square Microcontroller Array Array Reduced Slides Motional Resistance”, Solid-State Sensors & Actors (Trans03rds). 995-958, June 2003. S. Lee and C.L. TC. Nguyen “Mechanically Corner-Coupled Micromechanical Resonator Array for Improved Phase Noise”, IEEE Int. Ultrasonics, pp. 280-286, August 2004.

In Non-Patent Document 1 and Non-Patent Document 2 described above, a plurality of vibrators are driven at the same frequency, thereby reducing the series resistance component to reduce energy loss and improving drive characteristics. This structure corresponds to the fact that the resistors are connected in parallel when considered with an equivalent circuit, and lowers the series resistance component of the entire vibrator.

However, according to Non-Patent Document 1, by fixing the portion of the vibration node at one point,
Although it is possible to reduce the vibration leakage to the substrate and achieve a high Q value, the desired driving characteristics can be achieved even if the position is slightly shifted due to the structure in which the center part (node part) is supported by the anchor. There is a problem in manufacturing accuracy that cannot be obtained.

In Non-Patent Document 2, since both ends of the strip-like vibrator are directly connected to the substrate,
There is vibration leakage from the support portion to the substrate, and it is difficult to obtain a high Q value. Furthermore, since the support portions are provided at both ends of the vibrator, if five vibrators are provided, 10 places of support are required, which increases vibration leakage from the support portion. It is also possible.

An object of the present invention is to solve the above-described problems, and to provide a MEMS vibrator that is free from vibration leakage, reduces energy loss, has a high Q value, and can be driven with high efficiency.

The MEMS vibrator according to the present invention includes a substrate, a plurality of free beams at both ends formed on the surface of the substrate, and a plurality of free beams at both ends that are cross-connected with the positions serving as vibration nodes as connection portions. And a supporting member that extends from the connecting portion and supports the MEMS structure with a surface of the substrate and a gap, and simultaneously supports the plurality of free beams at both ends. It is characterized by driving at the same frequency.

According to the present invention, a plurality of free beams at both ends are cross-connected at the vibration node, and the connecting portion is supported by the support member, so that the displacement of the support member due to the vibration of the free beams at both ends is very small and Vibration leakage can be suppressed. Furthermore, since the structure supports the connecting portion, as in Non-Patent Document 2 described above, the number of supporting portions is reduced compared to a structure in which both ends of a vibrating piece (beam) are supported alone and a plurality are connected in parallel. Therefore, vibration leakage can be further suppressed, and the Q value can be increased.

In addition, by driving a plurality of free beams at both ends at the same resonance frequency, this corresponds to connecting the series resistance in the equivalent circuit in parallel, so the series resistance component can be reduced, so that the energy loss due to the series resistance component is reduced. Can be reduced.

The plurality of free beams at both ends are provided with 2n pieces (n is an integer of 2 or more), and among the plurality of free beams at both ends, adjacent free beams at both ends are driven at the same frequency and opposite phase. It is preferable.

In other words, the free beams at both ends are composed of an even number of 4 or more, and the adjacent free beams at both ends are driven in the opposite phase and the same frequency, so that the drive (vibration) of the entire MEMS structure is balanced, Therefore, it is possible to further suppress vibration leakage from the support member to the substrate.

Moreover, it is preferable that the said supporting member is a supporting beam extended radially toward the outer side or the inner side of the said MEMS structure from the side surface of the said connection part.

Since the support beam extends radially from the side of the connecting portion of the free beam at both ends, that is, the vibration node, the free beam at both ends and the support beam can be formed in the same process such as photolithography. It is possible to manage the positional relationship between the vibration node and the support beam with high accuracy, and to suppress the vibration leakage and the influence on the vibration characteristics due to the displacement.

Further, when the wavelength at the resonance frequency of the free beams at both ends is λ, the length of the support beam is preferably set to (1/4) λ.

By setting the length of the support beam in this way, vibration leakage from the support beam to the substrate (as torsional vibration of the support beam) can be further suppressed when a plurality of free beams at both ends vibrate.

Furthermore, it is preferable that the support member is a support column that connects a substantially planar center of the connecting portion and the substrate.

The fact that the support member is a support column means that this support column can be provided at the center of the connecting portion of the free beams at both ends (that is, the position of the vibration node), and thus has the effect of suppressing vibration leakage, The shape of the MEMS structure can be simplified.

Moreover, when the wavelength at the resonance frequency of the free beams at both ends is λ, the height of the support column is preferably set to (1/4) λ.

If the height (length) of the support column is set in this way, vibration leakage from the support column to the substrate will occur when a plurality of free beams at both ends vibrate, similar to the setting of the length of the support beam described above. Further suppression can be achieved.

Furthermore, a drive electrode that intersects the free beam at both ends with a gap is provided at a longitudinal center of each of the free beams at both ends on the surface of the substrate, and the free beams at both ends are connected to the substrate. It is desirable to be driven perpendicular to the surface.

If the both-end free beam and the drive electrode are configured in this way, the width of the both-end free beam determines the intersection area between the both-end free beam and the drive electrode, so that the thickness of the drive electrode ensures electrical characteristics. It only needs to have a certain thickness, can be formed by a thin film process, and is easy to manufacture.

FIG. 3 is a plan view showing a part of the MEMS vibrator according to the first embodiment of the invention. Sectional drawing which shows the AA cut surface of FIG. The structure of the MEMS vibrator | oscillator which concerns on Embodiment 1 of this invention is shown, (a) is a block diagram which shows a MEMS vibrator typically, (b) is an equivalent circuit. The drive form of the MEMS structure which concerns on Embodiment 1 of this invention is shown, (a) is a vibration form of one free beam of both ends, (b) is explanatory drawing which shows the whole vibration form. The graph which shows the resonance frequency when there is no support beam and the resonance frequency when there is a support beam. The top view which shows the modification of Embodiment 1 of this invention. The top view which shows a part of structure of the MEMS vibrator | oscillator concerning Embodiment 2 of this invention. The perspective view which shows typically the drive form of the MEMS structure which concerns on Embodiment 2 of this invention. FIG. 6 is a plan view showing a part of a MEMS vibrator according to a third embodiment of the invention. Sectional drawing which shows the BB cut surface of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show the structure of the MEMS vibrator according to the first embodiment of the present invention, FIG. 6 shows a modification of the first embodiment, FIGS. 7 and 8 show the second embodiment, and FIGS. 3 shows a MEMS resonator according to FIG.
(Embodiment 1)

FIG. 1 is a plan view showing a part of the MEMS vibrator according to the first embodiment, and FIG.
It is sectional drawing which shows a cut surface. 1 and 2, the MEMS vibrator 10 includes a MEMS structure 40 as a drive unit and drive electrodes 71 to 74 on the surface of a substrate 20.
The MEMS structure 40 is configured by connecting four vibrating bodies having the same shape in the shape of a rod having a rectangular cross section in a cross-beam shape.

These four vibrating bodies are formed as a single body in a shape in which portions that become vibration nodes are cross-connected. Therefore, these vibrating bodies are free-end beams that are movable at both ends in the longitudinal direction with the connecting portions 41 to 44 corresponding to vibration nodes as the base (see FIG. 4A). The free beams 31 to 34 at both ends are respectively connected by vibration nodes, and when these nodes are connected by a straight line, a regular square is formed. The MEMS structure 40 is point-symmetric with respect to the center of gravity G. And MEMS
The structure 40 is continued to the base 40a by the support beams 51 to 54.

The support beams 51 to 54 have the same thickness as that of the MEMS structure 40 (both ends free beams 31 to 34) and are continuous to the corners of the connecting portion where both ends free beams 31 to 34 intersect. Is set to be (1/4) λ, where λ is the wavelength of the resonance frequency of the free beams 31 to 34 at both ends.
The substrate 20 has both ends of the free beams 31 to 34 at the lower portion of the longitudinal center of the free beams 31 to 34.
The drive electrodes 71 to 74 are formed so as to intersect with each other with a gap.

The substrate 20 is made of a silicon (Si) substrate, and a drive electrode 71 is provided below the free beams 31 at both ends.
A drive electrode 72 is provided below the free beams 32 at both ends, a drive electrode 73 is provided below the free beams 33 at both ends, and a drive electrode 74 is provided below the free beams 34 at both ends. This drive electrode 71,
73 is the same potential (tentatively + potential), and the drive electrodes 72 and 74 are the same potential (tentatively -potential), and each is connected to a drive control circuit (not shown) so that an alternating voltage of the same frequency and opposite phase is applied. It is configured.

Subsequently, a manufacturing method of the MEMS vibrator 10 of the present embodiment will be described with reference to FIG. 2 (also refer to FIG. 1). Since the shapes of the free beams at both ends are the same, the free beams 32 at both ends will be described as an example. First, the above-described drive electrode 71 on the surface of the substrate 20 made of silicon (Si).
The insulating layer 60 is formed in the region where .about.74 is to be formed. Next, after a metal (Au or Al) layer is formed by a thin film process, a drive electrode 7 having a predetermined shape is formed using a photolithography technique.
1 to 74 are formed.

Subsequently, a sacrificial layer (Si) is formed on a portion excluding the shape of the MEMS structure 40 including the support beams 51 to 54.
After forming O ₂ ), a MEMS structure 40 made of polysilicon is formed by a CVD method or the like, and a sacrificial layer is removed by an etching method, whereby a space 80 is formed between both free beams 31 to 34 and the substrate 20. As a result, the MEMS structure 40 is formed in a state where the free ends 31 to 34 having the ends of the support beams 51 to 54 connected to the base 40 a are lifted from the substrate 20. Also, MEM
The S structure 40 is connected to the surface of the substrate 20 so that a DC potential is applied during driving.
In addition, the manufacturing method mentioned above showed one example of the manufacturing method of a MEMS structure, and is not limited to this.

Next, the configuration of the MEMS vibrator 10 according to the present embodiment will be described with reference to an equivalent circuit.
FIG. 3A is a configuration diagram schematically showing the MEMS vibrator 10 in the present embodiment, and FIG.
Is an equivalent circuit. The configuration of the MEMS vibrator 10 of this embodiment can be expressed as shown in FIG. The free beams 31 to 34 at both ends correspond to parallel connection. An AC voltage (Vi) having the same frequency is applied to the free beams 31 to 34 at both ends, currents ix1 to ix4 flow from each, and a total current i0 flows. This is represented as an equivalent circuit in FIG.

The equivalent circuit of the MEMS vibrator 10 is L (inductance component), C (capacitor component),
It is represented by an LCR circuit having R (series resistance component) as a constituent element. Here, since the shapes of the free beams at both ends are the same, Lx, Cx, and Rx have the same value and are connected in parallel. That is, each series resistance Rx is configured to correspond to a parallel connection because the free beams 31 to 34 at both ends are connected in a continuous ring shape. Accordingly, the series resistance component of the MEMS vibrator 10 can be reduced as compared with the case where there is one free beam at both ends or in the case of series connection, and therefore the loss due to the series resistance component is reduced.

Next, a description will be given of the series resistance component described above. In general, a vibrator having such an equivalent circuit has a large series resistance component, and it is known that energy loss due to the series resistance component affects driving efficiency.

Here, the series resistance component of the resonator element (free beams at both ends) is Rx, the spring constant is kr, and the natural circular vibration ω
_When the bias voltage is V _DC , the gap distance between the free beam at both ends and the drive electrode is g, the dielectric constant is ε ₀ , and the intersection area between the free beam at both ends and the drive electrode is A ₀ , the series resistance component Rx is It is expressed by the following formula. Q is represented by a Q value.
That is, the series resistance component Rx is represented by Rx = (kr / ε ₀ QV _DC ² ) · (g ⁴ / ε ₀ ² A ₀ ² ).

Therefore, the series resistance component Rx can be reduced as the gap distance g is decreased and the bias voltage V _DC is increased. However, the gap distance g has a limit value depending on the manufacturing process, and when the bias voltage V _DC is increased, the spring constant is increased in amplitude from the relationship of kr, and contact with the drive electrode is considered. _It is necessary to adjust the balance with _DC . Here, as shown by an equivalent circuit, the structure in which the series resistance component Rx is connected in parallel makes it possible to reduce energy loss due to the series resistance component.

Subsequently, the driving mode of the MEMS structure according to the present embodiment will be described with reference to the drawings.
4A and 4B show the drive form of the MEMS structure 40. FIG. 4A is an explanatory view showing the vibration form of one free beam at both ends, and FIG. 4B is an explanatory view showing the whole vibration form. First, the vibration mode of one free beam at both ends will be described. In addition, since the free beams 31 to 34 at both ends exhibit the same vibration form, the free beams 3 at both ends
2 will be described as an example.

In FIG. 4A, the free beams 32 at both ends support the connecting portions 42 and 43 provided at the vibration nodes by the support beams 52 and 53. When a DC voltage is applied to the free beams 32 at both ends and an AC voltage is applied to the drive electrodes 72, the free beams 32 at both ends bend and vibrate as indicated by arrows with the connecting portion as a vibration node. That is, the free ends 32a and 32b bend downward when the center portion of the free beams 32 at both ends bend upward, and the free ends 32a and 32b bend upward when the center portion of the free beams 32 at both ends bend downward. Mu
Next, the entire movement of the MEMS structure 40 is shown in FIG.

In FIG. 4B, the free beams 31 to 34 at both ends are applied with a drive voltage having the same frequency and vibrate at a predetermined resonance frequency. Here, the free-phase free beams 31 and 33 and the free-end free beams 32 and 34 are applied with driving voltages having opposite phases, so that the vibration phase is also reversed. That is, both ends free beam 31
, 33 vibrate so that the center portion is bent upward (in the direction of arrow F1) and the tip portion (free end) is bent downward. In addition, the free ends 32 and 34 at both ends are bent downward (in the direction of arrow F2) at the center, and the tip (
It vibrates so that the free end is bent upward.

Since the connecting portions 41 to 44 of the free beams at both ends are continuous at positions corresponding to vibration nodes, the propagation of vibration is suppressed, and the free beams 31 to 34 at both ends are twisted at the connecting portions. Vibration form. Here, the length of the support beams 51 to 54 that support the MEMS structure 40 is set to be (1/4) λ when the wavelength of the resonance frequency is λ.

In the above-described mathematical expression, the series resistance line segment Rx is shown to be smaller as the Q value is larger. Although the Q value is determined by various factors such as the material, shape, and cut angle of the resonator element, it is known that the vibration leakage from the support portion affects. Here, as a structure for suppressing vibration leakage, the length of the support beams 51 to 54 is (1/4) when the wavelength of the resonance frequency is λ.
) A structure with λ will be described.

FIG. 5 is a graph showing the resonance frequency when there is no support beam 51 to 54 and the resonance frequency when there is a support beam. In FIG. 5, the MEMS structure 40 ideally has a drive form in which the structure without the support beam is the most natural, and the resonance frequency is affected by providing the support beams 51 to 54. Then, as shown in FIG. 5, the resonance frequency tends to decrease as the support beam becomes longer. The position where the resonance frequency when the support beam is not present and the resonance frequency when the support beam is provided corresponds to the length of the support beam as (1/4) λ when the wavelength of the resonance frequency is λ. By making such a length, vibration leakage can be suppressed.
Note that the support beams 51 to 54 can be provided inside the MEMS structure 40.
(Modification of Embodiment 1)

FIG. 6 is a plan view showing a modification of the first embodiment of the present invention. This modification is characterized in that it extends in the inner direction of the MEMS structure 40 in which the support beams are connected in a ring shape, and the configurations of the free beams 31 to 34 and the drive electrodes 71 to 74 at both ends are as follows. Since it is the same as Embodiment 1 mentioned above, description is abbreviate | omitted. In FIG. 6, the support beams 51 to 54 extend from the inner corners of the connecting portions 41 to 44 of the free ends 31 to 34 to the base portion 40 a at the center.

The inner front ends of the support beams 51 to 54 are connected to the base 40a of the substrate 20, and the MEMS
The structure 40 (both free beams 31 to 34) can be bent in the vertical direction of the substrate 20. Accordingly, the free beams 31 to 34 at both ends have the same drive form as that of the first embodiment (see FIG. 4).
The length of the support beams 51 to 54 in this modification is also set to be (1/4) λ when the wavelength of the resonance frequency is λ.

Therefore, according to the present embodiment, the four free ends 31 to 34 are cross-connected at the vibration node,
And since this connection part 41-44 is supported by the support beams 51-54, the vibration leak to the board | substrate 20 can be suppressed. Further, since the structure supports the vibration node, as described in Non-Patent Document 2 described above, the above-described implementation is performed in comparison with a structure in which a plurality of vibration pieces (beams) supported at both ends of the vibration piece are connected in parallel. The same effect as in the first mode is obtained. That is, since the number of support beams can be reduced, vibration leakage can be suppressed, and this has the effect of increasing the Q value.

In addition, by configuring the four free ends 31 to 34 at the same resonance frequency,
Since the series resistance component in the equivalent circuit can be reduced, energy loss due to the series resistance component can be reduced.

Further, since the support beams 51 to 54 extend radially from the portion that becomes a vibration node, that is, the side surfaces of the connecting portions 41 to 44 of the free ends of the free ends 31 to 34, the free ends of the free ends 31 to 34 and the support beams 5
1 to 54 can be manufactured in the same process such as photolithography, and the positional relationship between the vibration nodes (connecting portions 41 to 44) and the support beams 51 to 54 is managed with high accuracy. Therefore, it is possible to suppress the vibration leakage due to the position shift and the influence on the vibration characteristics.

Also, when the wavelength at the resonance frequency of the free beams at both ends is λ, the length of the support beams 51 to 54 is set to (1/4) λ, and therefore, as shown in FIG. 31-34
When the beam vibrates, vibration leakage (as torsional vibration) from the support beams 51 to 54 to the substrate 20 can be suppressed.
(Embodiment 2)

Next, a MEMS vibrator according to Embodiment 2 of the present invention will be described with reference to the drawings. The second embodiment is characterized in that six free beams at both ends are connected to each other.
Since the shape, vibration mode, and manufacturing method of the individual pieces can be the same as those of the first embodiment described above, description thereof will be omitted.
FIG. 7 is a plan view showing a part of the structure of the MEMS vibrator 100 of the present embodiment. In FIG. 7, the MEMS vibrator 100 according to this embodiment includes a MEMS structure 140 configured by connecting six free ends 121 to 126 at the positions of the nodes of the respective vibrations and connecting them, and the substrate 2.
Drive electrodes 141 to 146 formed on the surface of zero.

From the outer corners of the connecting portions 151 to 156 of the free beams 121 to 126 at both ends, the support beams 131 to 136 extend radially outward and continue to the base (not shown) of the substrate 20. . The MEMS structure 140 in which the free beams 121 to 126 at both ends are connected to each other has a regular hexagonal shape. The MEMS structure 140 according to the present embodiment can be configured in the same manner as in the first embodiment described above (see FIG. 2) except for the number of free beams at both ends, and the connection structure with the support beams can be configured in detail. Description is omitted.

The length of each of the support beams 131 to 136 is (1/4) when the wavelength of the resonance frequency is λ.
) Λ. Also in the present embodiment, as in the modification of the first embodiment described above (see FIG. 6), the support beams 131 to 136 are in the center (center of gravity) direction of the MEMS structure 140 from the coupling portions 151 to 156. It is possible to adopt a structure extending toward the front.

Moreover, the lower part (upper surface of the board | substrate 20) of the longitudinal direction center part of each free beam 121-126 of both ends
The drive electrodes 141 to 146 are formed. An alternating voltage having the same frequency is applied to these drive electrodes. Here, the drive electrodes 141, 143, and 145 have the same potential (for example, -potential), and the drive electrodes 142, 144, and 146 have the opposite potential (for example, + potential) to the drive electrodes 141, 143, and 145. When applied, the free beams 121, 123, 125 at both ends and the free beams 122, 124, 126 at both ends vibrate in opposite phases.

FIG. 8 is a perspective view schematically showing a drive form of the MEMS structure 140 of the present embodiment.
In FIG. 8, the free beams 121 to 126 at both ends apply a drive voltage having the same frequency and vibrate at a predetermined resonance frequency. Here, the free beams 121, 123, and 125 at both ends and the free beams at both ends 122,
Since a drive voltage having an opposite phase to that of 124 and 126 is applied, the vibration phase is also opposite to the phase. That is, the free beams 121, 123, and 125 at both ends vibrate so that the center portion is bent downward (in the direction of arrow F2) and the tip portion (free end) is bent upward. Further, the free beams 122, 124, and 126 at both ends vibrate so that the center portion is bent upward (in the direction of arrow F1) and the tip portion (free end) is bent downward.

Since the connecting portions 151 to 156 of the free beams on both ends are provided at positions corresponding to the vibration nodes, the vibration does not propagate to the substrate 20 (base), and the free beams 121 to 126 on both ends are connected to the connecting portion 15.
It becomes a vibration form like a twist with 1 to 156 as nodes.

Although not shown, the MEMS vibrator 100 can also be represented by an equivalent circuit in this embodiment, and in the equivalent circuit shown in FIG. 3B, six series resistors Rx are connected in parallel. Can be replaced.
Therefore, the series resistance component can be reduced, and energy loss due to the series resistance component can be reduced.

Therefore, in this embodiment, even if the both-end free beams 121 to 126 are configured by six pieces, it is possible to reduce the number of support beams as compared to a structure in which a plurality of vibrators (beams) supporting both ends are connected independently. The number of free beams at both ends is composed of an even number, and the adjacent free beams at both ends are driven in the opposite phase and at the same frequency, so that the drive (vibration) of the MEMS structure 140 as a whole can be balanced. Since the length of the support beams 131 to 136 is set to (1/4) λ when the wavelength is λ, the same effect as in the first embodiment can be obtained.

As described above, the first embodiment has four free beams at both ends, and the second embodiment has six free beams at both ends.
Although the EMS vibrator has been described, the number of free beams at both ends is not limited to these and can be arbitrarily selected and configured. That is, the present invention is configured in such a manner that it is connected at the node of vibration of the free beams at both ends and is configured in a continuous ring, the phase of vibration of the adjacent free beams at both ends is reversed, and the series resistance in the equivalent circuit is configured in parallel connection. Can be realized. That is, the number of free beams at both ends may be 2n (n is an integer of 2 or more).
(Embodiment 3)

Next, the structure of the MEMS vibrator according to the third embodiment of the invention will be described with reference to the drawings. This embodiment is characterized in that a columnar support column is provided as a support member of the MEMS structure at a portion that becomes a vibration node of the free beams at both ends, that is, at a connecting portion. Here, the configuration of the first embodiment having four free beams at both ends as a basic structure will be described as an example, and description of the common portion and the drive mode will be omitted.

FIG. 9 is a plan view showing a part of the MEMS vibrator 10 according to the present embodiment, and FIG. 10 is a cross-sectional view showing a BB cut surface of FIG. 9 and 10, the MEMS structure 40 is supported by connecting cylindrical support columns 45 to 48 to the substrate 20 at the lower portions of the connecting portions 41 to 44 of the free beams 31 to 34 at both ends.

The support pillars 45 to 48 are cylinders centering on the centers (positions of vibration nodes) of the coupling parts 41 to 44, and are formed integrally with the MEMS structure 40. The lengths (heights) of the support columns 45 to 48 are also set to (1/4) λ, where λ is the wavelength of the resonance frequency.
Moreover, the cross-sectional shape of the support columns 45 to 48 is not particularly limited, and may be circular or rectangular. Further, the size of the cross section is not particularly limited as long as the structural strength as the support pillar of the MEMS structure can be secured within the crossing area of the connecting portion.

The manufacturing method of the MEMS vibrator 10 according to the present embodiment can be the same as that of the first embodiment. First, an insulating layer is formed in the region where the above-described drive electrodes 71 to 74 are formed on the surface of the substrate 20 made of silicon (Si). 60 is formed. Next, after a metal (Au or Al) layer to be the drive electrodes 71 to 74 is formed, the drive electrode 71 having a predetermined shape is used by using a photolithography technique.
~ 74 are formed.

Subsequently, a sacrificial layer (SiO ₂ ) is formed on a portion excluding the shape of the MEMS structure 40 including the support pillar, and then the MEMS structure 40 made of polysilicon is formed, and the sacrificial layer is removed by an etching method. In the state where the support columns 45 to 48 are connected to the surface of the substrate 20, the MEMS structure 40 in which the free beams 31 to 34 at both ends float from the substrate 20 is formed. M
A DC voltage is applied to the EMS structure 40 during driving.

Therefore, according to the third embodiment, the support structure of the MEMS structure 40 is the first embodiment described above.
However, since the technical idea is common, the same effect as in the first embodiment can be obtained.

Moreover, since the center part (position of the vibration node) of each of the support columns 45 to 48 and the connecting portions 41 to 44 is the center of the support column, vibration leakage from the free beams at both ends can be further suppressed.

Also in this embodiment, the number of free beams at both ends is 2n (n is an integer of 2 or more).
The configuration is not limited as long as it is configured as follows.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
That is, although the present invention has been illustrated and described with particular reference to particular embodiments, it is not intended to depart from the technical spirit and scope of the invention. Various modifications can be made by those skilled in the art in terms of materials, combinations, other detailed configurations, and processing methods between manufacturing processes.

Therefore, the description limited to the shape, material, manufacturing process and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. Descriptions of the names of members from which some or all of the limitations such as materials and combinations are removed are included in the present invention.

For example, in the above-described first to third embodiments, the MEMS vibrator having a structure in which the free beams at both ends are driven in the direction perpendicular to the substrate 20 is illustrated. It is also possible to adopt a structure for driving in parallel to the surface of the substrate 20. In other words, driving electrodes are provided on one or both sides in the width direction, and the free beams at both ends are driven in parallel with the surface of the substrate 20 by applying an alternating voltage of opposite phase to the adjacent free beams at both ends at the same frequency. it can.

Moreover, it is also possible to combine the above-mentioned Embodiment 1 and its modification examples. That is, the support beam can be configured to extend from the connecting portion to both the outside and the inside of the MEMS structure. In this way, the width of the support beam can be reduced, and even with the above-described structure, the MEMS structure can be more reliably supported without increasing energy loss during driving.

Therefore, according to the above-described first to third embodiments, it is possible to provide a MEMS vibrator that has a high Q value and can be driven with high efficiency by preventing vibration leakage and reducing energy loss.

The MEMS vibrator of the present invention can be applied as a filter, a switch, and an actuator in addition to a resonator.

DESCRIPTION OF SYMBOLS 10 ... MEMS vibrator, 20 ... Board | substrate, 31-34 ... Free beam on both ends, 40 ... MEMS structure 41-44 ... Connection part, 51-54 ... Support beam.

Claims (7)

A substrate and a plurality of free beams at both ends formed on the surface of the substrate;
A plurality of free beams at both ends are cross-connected with a position serving as a vibration node as a connecting portion, and a MEMS structure configured in a continuous ring;
A support member that extends from the connecting portion and supports the MEMS structure so as to have a gap with the surface of the substrate ;
A plurality of drive electrodes provided on the surface of the substrate so as to have gaps between the plurality of free beams at both ends ; and
The MEMS structure and the support member are made of polysilicon, and a direct current potential is applied thereto,
A MEMS vibrator in which a driving potential having the same frequency is applied to the plurality of driving electrodes . The MEMS resonator according to claim 1,
The plural free beams at both ends are provided with 2n (n is an integer of 2 or more), and among the plural free beams at both ends, the adjacent free beams at both ends are driven at the same frequency and opposite phase. MEMS vibrator characterized by the above. The MEMS resonator according to claim 1 or 2,
The MEMS vibrator according to claim 1, wherein the support member is a support beam radially extending from a side surface of the coupling portion toward an outer side or an inner side of the MEMS structure. The MEMS vibrator according to claim 3,
A length of the support beam is set to (1/4) λ, where λ is the wavelength at the resonance frequency of the free beams at both ends. The MEMS resonator according to claim 1 or 2 ,
The MEMS vibrator according to claim 1, wherein the support member is a support column that connects the center of the connecting portion and the substrate in plan view. The MEMS vibrator according to claim 5,
The MEMS vibrator, wherein a height of the support column is set to (1/4) λ, where λ is a wavelength at a resonance frequency of the free beams at both ends. The MEMS vibrator according to any one of claims 1 to 6, wherein
The drive electrode is provided at a lower portion of a center portion in the longitudinal direction of each of the plurality of free beams at both ends on the surface of the substrate,
The MEMS vibrator characterized in that the plurality of free beams at both ends are driven perpendicular to the surface of the substrate.

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