JP2006340531A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator utilizing an electrostatic drive system which has large displacement amount and high positional accuracy. <P>SOLUTION: This actuator is provided with a board, fixed electrodes 2a, 2b fixed on the board, movable electrodes 1 arranged to face the fixed electrodes 2a, 2b and that can be displaced to the fixed electrodes 2a, 2b, and a movable plate 4 supported by a shaft fixed on the board and that, so as to be enabled to rock, has a connecting pillar 5 inserted into a hole 3 formed in the movable electrodes 1. The movable plate 4 rocks while interlocking with the displacement of the movable electrodes 1 via the connecting pillar 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an actuator, and more particularly to an actuator used in an optical device using a microelectromechanical system.

  An optical switch which is one of optical devices is mainly classified into three types: a mechanical type, a waveguide type, and a micro-electro-mechanical system (MEMS) type. Among these, in the MEMS type, the optical waveguide, the mirror, and the driving mechanism can be integrally formed on one silicon chip by using a micromachining technology formed by a semiconductor process. Moreover, the core diameter of the optical fiber used for optical communication is as small as 9 μm, and the MEMS type has been expected to be applied to an optical switch in terms of size and cost.

By the way, a spatial light modulator that selectively modulates incident light in a direction selected depending on the position of a mirror is conventionally known (see, for example, Patent Document 1). In Patent Document 1, the mirror is supported on the substrate by a torsion torsion bar. An attractive force due to static electricity is used for the driving principle of the mirror. The method is roughly divided into a method using a surface direction attractive force between two electrodes and a method using a surface parallel direction attractive force of the comb-shaped electrodes arranged opposite to each other. The latter method is excellent for obtaining a long stroke.
JP-A-9-101467

  In the mirror electrostatic drive system described above, if the gap between the electrodes is widened in order to increase the displacement, the electrostatic attractive force becomes small, and it becomes difficult to ensure the necessary drive force. Therefore, it is necessary to use a piezoelectric method or an electromagnetic method with large power consumption.

  An object of the present invention is to provide an actuator using an electrostatic drive system with a large amount of displacement and high positional accuracy.

  A feature of the present invention is that a substrate, a fixed electrode fixed to the substrate, a movable electrode disposed opposite to the fixed electrode and displaceable with respect to the fixed electrode, and a shaft fixed to the substrate And an oscillatable movable plate having a connecting column inserted into a hole formed in the movable electrode, the movable plate oscillating in conjunction with the displacement of the movable electrode by the connecting column. It is to be.

  ADVANTAGE OF THE INVENTION According to this invention, the actuator using the electrostatic drive system with a large displacement amount and high position accuracy can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

<First Embodiment>
Fig.1 (a) is a top view which shows the tilt mirror device using the actuator based on the 1st Embodiment of this invention, FIG.1 (b) is AA cut surface of Fig.1 (a). FIG. In FIG. 1A, the movable plate 4 and the connecting column 5 are omitted.

  As shown in FIGS. 1A and 1B, the actuator according to the first embodiment of the present invention includes conductive fixed electrodes 2a and 2b fixed to a substrate, and fixed electrodes 2a and 2b. And a swingable movable plate 4 supported by a shaft fixed to the substrate and having a connecting column 5 inserted into a hole 3 formed in the movable electrode 1. .

  The fixed electrodes 2a and 2b and the movable electrode 1 are comb-shaped electrodes, respectively. The comb teeth of the fixed electrodes 2a and 2b are arranged to face each other, and the movable electrode 1 is arranged between the fixed electrodes 2a and 2b. The comb teeth of the movable electrode 1 are formed on both sides of the electrode, and an electrostatic attractive force is formed on the fixed electrode 2a and the fixed electrode 2b. Opposing comb teeth are arranged so as to mesh with each other, and the movable electrode 1 is swung by electrostatic attraction generated parallel to the direction of the comb teeth. A hole 3 having a predetermined size is formed in the central portion of the movable electrode 1.

  The fixed electrodes 2a and 2b only need to drive the movable electrode 1, and do not necessarily have to be fixed. For example, the first and second side electrodes disclosed in the prior application (Japanese Patent Application Laid-Open No. 2005-96069) by the applicant of this application realize the latch function by moving themselves, but the fixed electrode 2a and 2b are concepts including first and second side electrodes.

  As shown in FIG. 1B, the movable plate 4 is disposed in an upper layer than the fixed electrodes 2 a and 2 b and the movable electrode 1. The movable plate 4 has a flat plate shape, and is fixed to the substrate through a shaft such as a torsion spring at the central portion thereof. The movable plate 4 includes a connecting column 5 that extends from the central portion thereof toward the hole 3 of the movable electrode 1. The connecting column 5 is connected or fitted to the hole 3. Further, the movable plate 4 can be displaced in the rotation direction around the axis by twisting the axis.

  Specifically, as shown in FIG. 1 (c), an electrostatic attractive force is applied by applying a predetermined voltage between the movable electrode 1 and the fixed electrodes 2a and 2b, so that the movable electrode 1 is fixed to the fixed electrode 2b. When it is displaced in the horizontal direction, the connecting column 5 inserted in the hole 3 receives a stress in the horizontal direction from the movable electrode 1, and the movable plate 4 has an angle θ in the clockwise direction around the axis of the central portion. Tilt in.

  As shown in FIG. 1 (d), a reverse polarity voltage is applied between the movable electrode 1 and the fixed electrodes 2a and 2b to apply an electrostatic attractive force in the reverse direction, so that the movable electrode 1 is fixed to the fixed electrode 2b. When it is displaced in the direction, the connecting column 5 inserted in the hole 3 receives stress from the movable electrode 1 in the horizontal direction, and the movable plate 4 tilts at an angle −θ in the counterclockwise direction around the axis of the central portion. To do. In this way, the movable electrode 1 and the movable plate 4 are interlocked.

  As shown in FIG. 2, the movable electrode 1 is connected to one ends of flexible hinges 8a and 8b, and the other ends of the hinges 8a and 8b are connected to fixed portions 7a and 7b fixed to the substrate. Has been. The electrostatic attraction generated between the electrodes causes the hinges 8a and 8b to bend, and the movable electrode 1 is driven in the direction of the arrow in FIG.

  Further, the movable electrode 1 and the fixed electrodes 2a and 2b are not limited to those having a comb-like shape as shown in FIG. 1 (a), but as shown in FIG. It may be a shape. In this case, the movable electrode 1 is driven by the electrostatic attractive force generated between the flat plates.

  Further, the surface of the movable plate 4 may be subjected to a process with a high light reflectance. That is, a mirror surface may be formed. In this case, the movable plate 4 can function as a reflecting plate.

  As described above, the movable plate 4 is provided with the movable column 4 supported by the shaft fixed to the substrate and including the connecting column 5 inserted into the hole 3 formed in the movable electrode 1. The movable plate 4 swings in conjunction with the displacement of 1. Thereby, the driving force in the horizontal direction of the movable electrode 1 can be converted into the movement of the movable plate 4 in the rotational direction, and the movable plate 4 can be tilted. Therefore, the electrostatic attractive force of the actuator can be efficiently conducted, and a large displacement can be achieved with low power consumption.

  The fixed electrodes 2a and 2b and the movable electrode 1 are comb-shaped electrodes, respectively. Thereby, a large electrostatic attraction can be generated, and the movable electrode 1 and the movable plate 4 can be displaced more greatly. The electrostatic attraction can be controlled to a desired value by increasing or decreasing the number of comb teeth.

<Example>
Specific dimensions of the tilt mirror device will be described with reference to FIG. 1 and FIG. The movable electrode 1 and the fixed electrode 2a have comb teeth that mesh with each other. In addition, since what kind of structure is provided between the fixed electrodes 2b, illustration and description are omitted. The horizontal length wm of the device, the vertical length lm of the device, the length l of the hinge 8, the width w of the hinge 8, the thickness tm of the movable plate 4, the height tp of the movable plate 4 from the substrate, the maximum inclination of the movable plate 4 θ, comb tooth length lc, comb tooth interval gc, and comb tooth width wc are as follows.

wm = 7000μm
lm = 5000μm
l = 10000μm
w = 10μm
tm = 18μm
tp = 220μm
θ = 20deg
lc = 85 μm
gc = 4.5μm
wc = 3μm
FIG. 3B shows the relationship between the thickness of the hinge 8 and the mirror operation thrust when the width w of the hinge 8 is 10 μm and 20 μm. The operable range is about 150 μN or less, the thickness when the width w of the hinge 8 is 10 μm is about 18 μm or less, and the thickness when the width w of the hinge 8 is 20 μm is about 12 μm or less.

<Second Embodiment>
The tilt mirror device described in the first embodiment includes a stopper that can contact the movable plate 4 when the movable electrode 1 is in operation and can be positioned with the movable plate 4 tilted. It doesn't matter.

  That is, as shown in FIGS. 4A and 4B, the tilt mirror device is a stopper that determines an angle at which the movable plate 4 swings by contacting the movable plate 4 when the movable electrode 1 is displaced. 9a, 9b may be further provided. The stoppers 9a and 9b are formed on the substrate in FIG. 4B, but may be formed below the movable plate 4.

  As shown in FIG. 1C, when the movable electrode 1 is displaced in the horizontal direction toward the fixed electrode 2b by the electrostatic attractive force applied between the movable electrode 1 and the fixed electrodes 2a and 2b, The connecting column 5 inserted in the plate 3 receives stress from the movable electrode 1 in the horizontal direction, and the movable plate 4 tilts in the clockwise direction about the axis of the central portion at an angle θ. In a state where the movable plate 4 is tilted at an angle θ, the right end of the movable plate 4 comes into contact with the stopper 9a, and the position of the movable plate 4 is maintained.

  As shown in FIG. 1D, when the movable electrode 1 is displaced in the horizontal direction toward the fixed electrode 2a by the electrostatic attractive force applied between the movable electrode 1 and the fixed electrodes 2a and 2b, The connecting column 5 inserted in the plate 3 receives stress from the movable electrode 1 in the horizontal direction, and the movable plate 4 tilts at an angle −θ in the clockwise direction around the axis of the central portion. In a state of tilting at an angle −θ, the left end of the movable plate 4 comes into contact with the stopper 9b, and the position of the movable plate 4 is maintained.

  As described above, when the movable electrode 1 is displaced, it comes into contact with the movable plate 4 to further provide the stoppers 9a and 9b for determining the angle at which the movable plate 4 swings, thereby enabling precise positioning, particularly precise movable. The inclination angle θ of the plate 4 can be set.

  In addition, although illustrated about the stoppers 9a and 9b which contact | abut with the movable plate 4 here, this invention is not limited to this. Other than this, for example, a stopper that contacts the movable electrode 1 when the movable electrode 1 is displaced may be provided. Also in this case, like the stoppers 9a and 9b that come into contact with the movable plate 4, the movable electrode 1 can be precisely positioned, and hence the movable plate 4 can be precisely positioned.

  Next, a manufacturing method of the tilt mirror device shown in FIGS. 4A and 4B will be described with reference to FIGS.

  (A) First, as shown in FIG. 5A, an etching mask 12 having a predetermined shape is formed on the surface of a substrate 11 made of single crystal silicon.

  (B) An anisotropic etching process is performed on the surface of the substrate 11 through the etching mask 12, and the substrate 11 on which the etching mask 12 is not formed is selectively removed. After the end of the digging to a predetermined depth and the formation of the groove, the etching is terminated, and a new etching mask 13 is formed on the bottom surface of the groove as shown in FIG.

  (C) The anisotropic etching process is further continued using the etching masks 12 and 13, and the movable plate 4 and the connecting column 5 are formed as shown in FIG. Then, as shown in FIG. 5D, the front and back surfaces are reversed.

  (D) On the other hand, as shown in FIG. 5E, an SOI substrate comprising an upper layer 15, an intermediate layer 16, and a lower layer 17 is prepared, and an etching mask 14 having a predetermined shape is formed on the upper layer 15. Form on top. An anisotropic etching process is performed on the surface of the upper layer 15 through the etching mask 14 to selectively remove the upper layer 15 on which the etching mask 14 is not formed. Thereafter, the etching mask 14 is removed. Thereby, a part of the actuator having the movable electrode 1 and the fixed electrodes 2a and 2b as shown in FIG. 5 (f) is formed.

  (E) As shown in FIG. 5G, these two structures are joined. As shown in FIG. 5H, wet etching is performed using an etching solution having a high etching rate of the intermediate layer 16 with respect to the substrate 11, the upper layer 15 and the lower layer 17, and corresponds to the movable electrode 1 and the fixed electrodes 2a and 2b. The upper layer 15 to be separated is separated from the lower layer 17 (substrate 10). Through the above steps, the tilt mirror device shown in FIGS. 4A and 4B is completed.

  In this way, the two substrates are overlapped and joined, whereby the connecting column 5 of the movable plate 4 and the hole 3 of the movable electrode 1 are connected or fitted. By manufacturing the movable plate 4 and the actuator portion using different substrates, the manufacturing yield of each structure is improved.

<Third Embodiment>
In the tilt mirror device described in the first embodiment, a latch portion formed on the fixed electrodes 2a, 2b and the movable electrode 1, and the latch portions are fitted to each other when the movable electrode 1 is stationary. Then, the fixed electrodes 2a and 2b and the movable electrode 1 may be positioned. The latch unit has the same function as the latch unit disclosed in the prior application (Japanese Patent Laid-Open No. 2005-96069) by the applicant of this application.

  That is, each of the fixed electrodes 2a and 2b and the movable electrode 1 may include a latch portion that holds the state of the movable electrode 1 at rest. When the movable electrode 1 is driven, the latch portion is engaged so that the movable electrode 1 can be held in a displaced state. For example, when the latch portion is fitted in the state where the hinges 8a and 8b in FIG. 2 are bent, the hinges 8a and 8b are bent even if no potential difference is applied between the movable and fixed electrodes, that is, the movable portion is movable. The state in which the electrode 1 is displaced can be maintained.

<Fourth embodiment>
In the tilt mirror device described in the first embodiment, the latch part is formed on the movable plate 4 and the substrate, and the latch part is fitted in a state where the movable plate 4 is tilted, The movable plate 4 and the movable electrode 1 may be positioned.

  That is, the movable plate 4 may include a latch portion that holds the stationary state.

  Thereby, the inclination angle when the movable plate 4 tilts is determined, and the movable plate 4 can be kept stationary at a predetermined inclination angle. Therefore, the movable plate 4 can be held by itself even if no potential difference is applied between the movable / fixed electrodes.

(Other embodiments)
As described above, the present invention has been described according to the first to fourth embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the tilt mirror device described in the first to fifth embodiments, the contact portion between the connecting column 5 and the hole 3 is preferably point contact or line contact. Thereby, when the movable electrode 1 and the movable plate 4 are driven, the contact portion between the connection column 5 and the hole 3 is not a surface contact but a point contact or a line contact. Sticking can be avoided.

  Each structure may be subjected to water repellent treatment such as SAM coating. In this case, since the monomolecular layer is coated on the surface of each structure, the surface energy is lowered and it is difficult to fix. Therefore, the contact portion between the connecting column 5 and the hole 3, the stoppers 9a and 9b, and the latch portion can be avoided.

  A metal may be coated on the surface of the movable plate 4. By coating a highly reflective metal on the surface of the flat movable plate 4, incident light can be reflected at a desired angle according to the state of the movable plate 4, and it is practical as a reflective spatial light modulator. Can be It is desirable to select the type of metal to be coated according to the wavelength of light used.

  A diffraction grating may be formed on the surface of the movable plate 4. In this case, the light incident on the diffraction grating can be dispersed by designing the pitch of the diffraction grating to a predetermined value. Thus, by forming a mirror corresponding to RGB on the movable plate 4, color projection can be performed with a single plate.

  By connecting an optical component to the movable plate 4 or the movable electrode 1, an optical device using the above-described actuator can be realized. The "optical component" here is a mirror with a reflective surface that reflects the incident light, the above-mentioned diffraction grating, prism, and other processing applied to the incident light, and the result is emitted as output light. To be included. In the case of a mirror, the optical path of incident light such as laser light can be switched. Thereby, the optical component provided with a large area can be greatly displaced taking advantage of the characteristics of the actuator described above. Therefore, it becomes possible to handle light with a large beam diameter, and since the driving angle is large, a multi-port optical device can be provided.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

  The present invention can be used for an optical switch that performs optical path switching in an optical device used for optical communication.

FIG. 1A is a plan view showing a tilt mirror device using the actuator according to the first embodiment of the present invention, and FIG. 1B is along the AA section of FIG. FIG. FIG. 1C and FIG. 1D are cross-sectional views showing the operation of the movable electrode and the movable plate. It is a top view which shows the case where a movable electrode and a fixed electrode have a flat shape. FIG. 3A is a plan view showing the structure and dimensions of the comb electrode, and FIG. 3B is a graph showing the relationship between the hinge thickness and the mirror operating thrust. FIG. 4A is a plan view showing a tilt mirror device using the actuator according to the second embodiment of the present invention, and FIG. 4B is a cross-sectional view of FIG. FIG. 5A to FIG. 5H are cross-sectional views showing the main manufacturing steps of the tilt mirror device using the actuator according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Movable electrode 2a, 2b ... Fixed electrode 3 ... Hole 4 ... Movable plate 5 ... Connection pillar 7a, 7b ... Fixed part 8a, 8b ... Hinge 9a, 9b ... Stopper 10, 11 ... Substrate 12-14 ... Etching mask 15 ... Upper layer 16 ... intermediate layer 17 ... lower layer

Claims (4)

A substrate,
A fixed electrode fixed to the substrate;
A movable electrode disposed opposite the fixed electrode and displaceable with respect to the fixed electrode;
A swingable movable plate supported by a shaft fixed to the substrate and having a connecting column inserted into a hole formed in the movable electrode;
An actuator characterized in that the movable plate swings in conjunction with the displacement of the movable electrode by the connecting column.   2. The actuator according to claim 1, wherein each of the fixed electrode and the movable electrode is a comb-shaped electrode.   3. The actuator according to claim 1, wherein each of the fixed electrode and the movable electrode includes a latch portion that holds a state of the movable electrode when stationary. 4.   The actuator according to any one of claims 1 to 3, further comprising a stopper that determines an angle at which the movable plate swings by contacting the movable plate when the movable electrode is displaced.

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