JP2003098444A - Mirror deflection device and light switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mirror deflection device which can deflect light to an arbitrary direction and can be driven by a low-voltage. SOLUTION: A projected part 112 on a substrate 107 side fits to a recessed part 102 provided at the center of a mirror substrate 101, and the mirror substrate 101 is oscillatably supported in the arbitrary direction with its approximate center as an oscillating center. A plurality of driving electrodes facing the mirror substrate 101 are provided at a recessed region of the substrate 107. The mirror substrate 101 is held in a neutral position when it is not driven by a holding part 103 of a folding construction coupled to an end of the mirror substrate 101 and the substrate 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror deflector which can be easily miniaturized by a micromachining technique, and more particularly to a mirror deflector of a type in which a minute mirror substrate having a mirror surface is tilted by an electrostatic force.

[0002]

2. Description of the Related Art In the mirror deflector disclosed in IBM J. Res. Develop Vol. 24 (1980), a mirror substrate supported by two beams arranged on the same straight line is opposed to the mirror substrate. By the electrostatic attraction between the electrode provided at the position
The two beams are reciprocally oscillated with the torsion axis of rotation. This mirror deflection device, which is formed by micromachining technology, has a simple structure and can be collectively formed by a semiconductor process, so that it is easy to miniaturize and the manufacturing cost is low. Since there is no variation in accuracy and the reciprocating scanning is performed, it is expected that the speed can be increased.

As such an electrostatically driven torsional vibration type mirror deflecting device, disclosed in Japanese Patent No. 2924200, the beam is S-shaped to reduce the rigidity so that a large deflection angle can be obtained with a small driving force. What is disclosed in JP-A-7-924
09, the beam thickness thinner than the mirror substrate and the frame substrate, Japanese Patent No. 3011144, or The 13th Annual International Workshop on MEM
S2000 (2000) 473-478, in which the fixed electrode is arranged at a position not overlapping in the vibration direction of the mirror part,
The 13th Annual International Workshop on MEMS2000
(2000) 645-650, there is a device in which the driving voltage is lowered without changing the deflection angle of the mirror by installing the counter electrode so as to be inclined from the center position of the deflection of the mirror.

Further, a device for deflecting a cantilever beam by electrostatic force to change the light reflection direction and switching, and an optical modulation system using the device were announced by KE Petersen in 1977 (Applied Physics Letters, Vol.31, No.8,
pp.521-523).

[0005]

SUMMARY OF THE INVENTION In a mirror deflecting device in which a mirror substrate is held from both sides by two beams as described above, and the beams are reciprocally oscillated by electrostatic attraction with the beams as torsional axes, The shake direction (light deflection direction) is
It is limited to only one direction with the torsion axis of rotation as the center of rotation. This also applies to the above-mentioned cantilever type optical switch. An optical switch using a cantilever beam has a weak point that it is difficult to secure the stability of the beam due to deformation of the beam due to stress relaxation, change over time, and the like. The magnitude of the electrostatic force acting on the mirror substrate is proportional to the square of the distance between the electrodes, and
Although it is proportional to the electrode area, there is a problem that the drive voltage becomes higher when the deflection angle of the mirror substrate is increased.

It is an object of the present invention to provide a novel mirror deflecting device which solves the above problems.
Another object of the present invention is high speed and low optical loss,
It is to provide an optical switching device having a simple structure.

[0007]

According to another aspect of the present invention, there is provided a mirror deflecting device, wherein a mirror substrate having a mirror surface is formed, and the mirror substrate has an arbitrary center about a swing center. A supporting member for supporting the substrate member so that the mirror substrate can be swung in the direction of, and a plurality of substrate members for applying an electrostatic attractive force for swinging the mirror substrate to the mirror substrate. Drive electrodes, and a plurality of holding members coupled to the mirror substrate and the substrate member for holding the mirror substrate at a predetermined neutral position when electrostatic attraction by the drive electrodes does not act. Characterize.

Another feature of the mirror deflecting device according to the present invention is, as in claim 2, in the structure of claim 1, in which a gap is provided on the surface of the mirror substrate opposite to the surface on which the mirror surface is formed. The plurality of drive electrodes are arranged on the surfaces of the substrate members facing each other.

Another feature of the mirror deflecting device according to the present invention is, as described in claim 3, in the structure of claim 1 or 2, wherein the surface of the substrate member on which the drive electrode is arranged is the mirror. The purpose is to make an inclined surface having a substantially conical shape with the vertex corresponding to the center of the substrate.

Another feature of the mirror deflecting device according to the present invention is, as in claim 4, in the structure of claim 2 or 3, wherein each of the plurality of drive electrodes is divided into a plurality of independent electrodes. Especially.

According to a fifth aspect of the present invention, there is provided an optical exchanging device, wherein a plurality of mirror deflecting devices according to any one of claims 1 to 4 and a light beam are incident on the plurality of mirror deflecting devices. And a second light transmission unit for receiving the light beam deflected by the plurality of mirror deflecting devices.
And a two-dimensional optical exchange between the first light transmitting means and the second light transmitting means.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1A and 1B illustrate a first embodiment of a mirror deflecting device of the present invention. FIG. 1A is a front view seen from the mirror surface side of the mirror deflecting device, and FIG. 1B is a sectional view of the mirror deflecting device. Is.

Reference numeral 101 denotes a mirror substrate 101, on the surface of which a mirror surface 111 having a sufficient reflectance for light used is formed. A concave portion 102 that opens downward is formed in the center of the surface of the mirror substrate 101 opposite to the mirror surface 111. A recessed portion for forming a space 108 with the mirror substrate 101 is formed on the substrate 107, and a convex portion 112 is formed at the center of the surface of the recessed portion facing the mirror substrate 101. The tip of the convex 112 is the mirror substrate 101.
The mirror substrate 101 is supported so as to be capable of swinging in any direction with the substantial center thereof as the swing center (strictly, the engaging point of the recess 102 and the convex portion 112 as the swing center). Board 107
Four drive electrodes 1 for applying an electrostatic attractive force to the mirror substrate 101 are provided on the surface of the recessed portion of the mirror substrate 101 facing the mirror substrate 101.
10 (1) to 110 (4) are dispersed and arranged so as to surround the convex 112.

At the end portions near the four corners of the mirror substrate 101, four holding portions 103 (1) to 103 (4) having a folding structure are provided.
One end is bonded to the substrate 107 and the other end is bonded to the substrate 107. These holding portions 103 are provided on the mirror substrate 1 when the electrostatic attraction by the drive electrode 110 does not act on the mirror substrate 101.
This is a member for holding 01 at the neutral position shown in FIG. 1 (b), and the cross-sectional size, shape, and length are set so as to have rigidity so that the required deflection angle of the mirror substrate 101 can be obtained. ing.

An example of a method of manufacturing this mirror deflecting device will be described with reference to FIGS. 2 (b), (d),
(H) and (j) of FIG. 3 are schematic front views showing the front structure in the corresponding step, and other drawings are schematic cross-sectional views showing the sectional structure in the corresponding step.

2 (a) and 2 (b): Silicon substrate to be the substrate 107
In 201, a recessed portion 202 and a convex portion 112 for the void 108 are formed by photolithography and dry etching techniques. The recessed portion 202 has, for example, a side length of 100 μ.
It is a square of m and its depth is 10 μm. The convex 112 is
For example, the height is 9.7 μm and the thickness is 10 μm. After that, the substrate 201 is thermally oxidized to form an oxide film on the surface with a thickness of 0.2 μm.

2 (c) and 2 (d): TiN is formed on the bottom surface of the recessed portion 202.
To form a thin film. This TiN thin film is formed to have a thickness of 0.1 μm by, for example, a reactive sputtering method using Ti as a target. Then, this TiN thin film was formed into a film with a side length of 4 by photolithography and dry etching.
The drive electrodes 110 (1) to 110 (4) having a square shape of 0 μm are formed.
Although not shown, some of these four drive electrodes 110 protrude from the recessed portion to the substrate surface for external connection.
Furthermore, a plasma nitride film as an electrode protective film on it.
Formed to a thickness of 05 μm.

FIG. 2 (e): Polycrystalline silicon is used as the sacrificial layer film 205 by the plasma CVD method to form the recessed portion 20 of the substrate 201.
Film is formed until 2 is filled.

FIG. 2 (f): The sacrificial layer film 205 is formed by CMP (Chemical Membrane).
chanical Polishing) method to obtain a flat sacrificial layer film 206 as shown.

2G and 2H: A pattern 208 for forming the concave portion 102 of the mirror substrate 101 is formed on the flattened sacrifice layer film 206 by a photolithography and dry etching method.

3 (i) and 3 (j): Next, a silicon nitride film as a material for the mirror substrate 101 and the holding portion 103 is blanket deposited to a thickness of 0.04 μm by a thermal CVD method. On this silicon nitride film, an Al thin film to be the mirror surface 111 is formed with a thickness of 0.05 μm by a sputtering method. Then, the mirror substrate 101 is formed by photolithography and dry etching.
Then, the four folding structure holding portions 103 are patterned. The mirror substrate 101 is a square with one side of 90 μm. In each of the holding portions 103 having the folding structure, the thickness of the beam portions at both ends thereof is 2 μm, and the length of the folding portion between the beam portions is 35 μm.

Although not shown, the sacrifice layer film 206 is formed on the TMA.
By wet etching with H (tetra-methyle-anmonium-hydoride) to remove it, and finally, by forming an opening for external connection of the drive electrode 110 in the protective film, the mirror deflector having the configuration shown in FIG. Complete.

The operation of the mirror deflecting device of this embodiment will be described. FIG. 4 is an operation explanatory diagram.

Mirror substrate 101 (movable electrode) and drive electrode 1
When the drive voltage is not applied to any of the 10 and the electrostatic force does not act on the mirror substrate 101, the mirror substrate 1
01 is held in the neutral position as shown in FIG. 1 by the holding portion 102 having four folding structures. At this time, the light flux incident on the mirror surface 111 on the mirror substrate 101 at the incident angle θ is specularly reflected in the direction of the reflection angle θ, as indicated by the arrow in FIG.

Mirror substrate 101 and, for example, drive electrodes 110 (4)
If a drive voltage is applied during
An electrostatic force acts on the mirror substrate 101, and the mirror substrate 101 is attracted to the drive electrode 110 (4) side and swings by an angle α as shown in FIG. Therefore, the direction of the light reflected by the mirror surface 111 changes by 2α.

Even when a drive voltage is applied to the other drive electrodes 110 (2) to 110 (4), the reflected light can be similarly swung in the electrode position direction. Further, if a drive voltage is applied to two adjacent drive electrodes, for example, drive electrodes 103 (1) and 103 (2) at the same time, the mirror substrate 101 can be tilted in the middle direction of both electrodes and light can be swayed in that direction. it can. Furthermore, by differentiating the voltage applied to each of the two adjacent drive electrodes, the mirror substrate 101 can be tilted in any direction between the two electrodes, and light can be swayed in that direction.

When the drive voltage is not applied to any of the drive electrodes 110, the rigidity of the holding portion 103 causes the mirror substrate 101 to return to the neutral position as shown in FIG. 1B.

This mirror deflector is excellent in that it has a high degree of freedom in changing the traveling direction of light. Mirror substrate 101
Is held by a holding portion 103 having a folding structure. Since the holding portion 103 has a folding structure, a large degree of deformation can be achieved, and thus the holding substrate 103 is substantially a mirror substrate.
The shape of 101 is supported by the substrate 107 by the convex portion 112 fitted in the concave portion 102. Therefore, the mirror substrate 101 is supported so that the mirror substrate 101 can swing in any direction in the plane with the convex 112 as an axis. Therefore, as described above, by selecting the drive electrode 110 and adjusting the applied voltage, the luminous flux incident on the mirror surface 111 of the mirror substrate 101 at the incident angle θ is schematically shown in FIG. 4C. , Can be deflected in an arbitrary direction around the regular reflection direction as an axis at an angle (2α) that is twice the deflection angle α of the mirror substrate 101.

Since the driving electrode 110 is formed on the surface facing the mirror substrate 101, the electrode area can be easily increased as compared with the structure using the driving electrode facing the end surface of the mirror substrate 101. Therefore, the voltage for driving the mirror substrate 101 can be reduced.

A second embodiment of the mirror deflecting device according to the present invention will be described with reference to FIG. 5A is a front view seen from the mirror surface side, FIG. 5B is a front view showing a state in which the mirror substrate is removed, and FIG. 5C is a sectional view.

The overall structure of the mirror deflecting device of this embodiment is the same as that of the first embodiment, and the difference is that FIG.
As shown in (c), the surface on which the drive electrode 110 is formed is the convex portion 1
It has a conical inclined surface with the position of 12 as the apex. Furthermore, as shown in FIG. 5B, the four drive electrodes 110 (1) to 110 (4) are independent of each other. It is divided into electrodes. Although not shown, each of the divided electrodes can be drawn out to the surface of the substrate 107 to separately apply a voltage.

The manufacturing method of the mirror deflecting device of this embodiment is as follows.
The manufacturing method may be the same as that of the first embodiment except that the surface on which the electrode substrate 110 is formed is the inclined surface. Therefore, the manufacturing process related to the inclined surface will be described with reference to FIG.

FIG. 6A: First, the thickness 525 to be the substrate 107.
A dry film resist 502 having a thickness of 100 μm is formed on a silicon substrate 501 having a thickness of μm.

FIG. 6B: Next, the exposure depth of the dry film resist 502 was made to have a distribution by using a photomask having a distribution of the aperture ratio. This distribution is designed such that the convex shape and the electrode shape are inclined.
By developing this dry film resist, a dry film resist shape 503 reflecting the electrode shape is formed.

FIG. 6C: By dry etching the silicon substrate 501 using this dry film resist as a mask, the dry film resist shape is transferred to the silicon substrate according to the etching selection ratio of the resist and silicon.

FIG. 6D: Next, a SiO 2 film 504 is formed by thermal oxidation as an insulating material on the surface of the silicon substrate. Through the above steps, the substrate 107 having the inclined electrode formation surface and the convex portion 112 can be formed.

The operation of the mirror deflecting device of this embodiment is the same as that of the first embodiment, but in this embodiment, the formation surface of the drive electrode 110 is an inclined surface as described above, When the mirror substrate 101 swings toward one of the drive electrodes 110, the drive electrode is entirely covered by the mirror substrate 101.
And approach the same distance. Further, if the size of the mirror substrate 101 is the same, the area of the electrode formation surface can be increased by an amount corresponding to the inclination, and the area of the drive electrode can be increased accordingly. Due to the above two factors, the mirror deflecting device of this embodiment can reduce the voltage for driving the mirror substrate 101 to a desired deflection angle.

Further, in the mirror deflecting device of this embodiment, the four drive electrodes 110 are divided into four (generally a plurality of) independent electrodes, so that each of the divided electrodes is divided into four separate electrodes. By selectively applying the drive voltage and further adjusting the drive voltage, the strength and direction of the electrostatic attractive force applied to the mirror substrate 101 can be controlled with high accuracy. Therefore, it is possible to control the deflection angle and the deflection direction of the mirror substrate 101 with higher accuracy than in the case where each drive electrode 110 is not divided.

In order to control the deflection angle and the deflection direction of the mirror substrate 101 with high accuracy, it is necessary to detect the deflection angle in each direction. As a method of detecting the deflection angle, for example,
A method of detecting the deflection angle in the corresponding direction based on the electrostatic capacitance between the divided electrodes of the four drive electrodes 110 can be adopted. That is, it can be utilized that the capacitance of the capacitor formed between the divided electrodes changes depending on the deflection angle and the deflection direction of the mirror substrate 101. In other words, the deflection angle detecting means is composed of the divided electrodes of the drive electrode 110. By incorporating a general feedback control for reducing the difference between the deflection angle in a plurality of directions detected in this way and the target value into the drive system of the drive electrode, the deflection angle and the deflection direction of the mirror substrate 101 High precision control is possible.

Also in the mirror deflecting device of the first embodiment, similarly to the present embodiment, by dividing each drive electrode 110 into a plurality of independent electrodes, the deflection angle and the deflection direction of the mirror substrate 101 can be further improved. It can be controlled with high precision. It goes without saying that the mirror deflecting device having such a structure is also included in the present invention.

FIG. 7 is a front view for explaining the third embodiment of the mirror deflecting device according to the present invention. In the mirror deflecting device of this embodiment, the planar shape of the mirror substrate 101 is circular, and correspondingly, a circular recessed portion is also formed on the substrate 107, and twelve fan-shaped drive electrodes 110 (1) to 110. (12) are arranged radially from the swing center of the mirror substrate 101.
The other structure is the same as that of the first embodiment. In this way, since a large number of drive electrodes 110 are arranged radially, it is possible to select a drive electrode for applying a drive voltage by
The shake direction of the mirror substrate 101 can be controlled more easily. Further, the deflection angle and the deflection direction of the mirror substrate 101 can be detected by measuring the electrostatic capacitance between the adjacent drive electrodes.

In this embodiment also, the drive electrode 101
The surface on which is formed is a conical inclined surface similar to that in the second embodiment, and a low drive voltage can be achieved. The mirror deflecting device having such a structure is naturally included in the present invention.

Next, an embodiment of the optical exchanging device of the present invention to which the above-mentioned mirror deflecting device is applied will be described with reference to FIG.

In FIG. 8, reference numeral 701 is a two-dimensional array type optical transmission device composed of an optical fiber bundle. Reference numeral 702 is another two-dimensional array-like optical transmission device including an optical fiber bundle. In this embodiment, the light emitting ends of the optical fibers of the array-shaped light transmitting device 701 form an array of 3 rows × 5 columns, and the light incident ends of the optical fibers of the other array-shaped optical transmitting device 702 are 3 rows × 5. Although it is an array of rows, the size of the array is not limited to this. Reference numeral 703 is a mirror deflection array in which the above-described mirror deflection devices of the present invention are two-dimensionally arranged. In this embodiment, the mirror deflector array 703 has the mirror deflectors of the present invention arranged in 3 rows × 5 rows, but the arrangement is not limited to this arrangement.

This optical switching device uses a mirror deflection array to convert a light beam incident from an arbitrary light emitting end of the light transmitting device 701.
The light is deflected by 703 and guided to an arbitrary light incident end of the light transmission device 702 to perform a two-dimensional light exchange operation. In the example shown in FIG. 8, the light beam L transmitted to the light emission end at the (1,1) position of the light transmission device 701 is incident on the mirror surface of the mirror deflection array 703 at the (1,1) position, and The light is deflected toward the light incident end at the (4, 2) position of the light transmission device 702 by the mirror surface, so that the light exchange from (1, 1) to (4, 2) is performed.

Since the mirror deflecting device of the present invention is capable of two-dimensional light deflection as described with reference to FIG. 4C, the two-dimensional optical exchange is possible with a simple structure as in this embodiment. Is possible. Further, since the mirror deflecting device of the present invention can operate at high speed and has a small optical loss, the optical exchanging device of the present invention can perform optical switching at high speed and with little loss.

[0047]

As is apparent from the above description, (1)
The mirror deflecting device according to the first to fourth aspects is capable of deflecting light in an arbitrary direction. (2) In the mirror deflection device according to the second aspect, the drive voltage of the mirror substrate can be lowered. (3) The mirror deflecting device according to claim 3 can be driven at a lower voltage. (4) In the mirror deflecting device according to the fourth aspect, the angle and direction of the light deflection can be controlled with high precision. (5) The optical exchanging device according to claim 5 has effects such as a simple structure, high-speed operation, and two-dimensional optical exchanging with little optical loss.

[Brief description of drawings]

FIG. 1 is a front view and a sectional view for explaining a first embodiment of a mirror deflecting device according to the present invention.

FIG. 2 is a process explanatory diagram for explaining an example of the method for manufacturing the mirror deflecting device according to the first embodiment.

FIG. 3 is a process explanatory diagram for explaining an example of the method for manufacturing the mirror deflecting device according to the first embodiment.

FIG. 4 is an operation explanatory view of the mirror deflecting device of the present invention.

5A and 5B are a front view and a sectional view for explaining a second embodiment of the mirror deflecting device according to the present invention.

FIG. 6 is a process explanatory view for explaining an example of the manufacturing method of the second embodiment.

FIG. 7 is a front view for explaining a third embodiment of the mirror deflecting device according to the present invention.

FIG. 8 is a schematic view for explaining one embodiment of the optical switching device according to the present invention.

[Explanation of symbols]

101 mirror substrate 102 recess 103 holding unit 107 substrate 108 void 110 drive electrode 112 convex 701 Optical transmission device 702 Optical transmission device 703 Mirror deflection array

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shizukazu Kato             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Ken Nanjo             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H041 AA16 AB14 AC06 AZ01 AZ05                       AZ08

Claims (5)

[Claims] 1. A mirror substrate on which a mirror surface is formed, and a support member for supporting the mirror substrate on a substrate member so that the mirror substrate can be swung in an arbitrary direction with a substantially center thereof as a swing center. And a plurality of drive electrodes provided on the substrate member for applying an electrostatic attractive force for swinging the mirror substrate, and the mirror substrate when the electrostatic attractive force by the drive electrodes does not act. And a plurality of holding members coupled to the substrate member for holding the mirror at a predetermined neutral position. 2. The plurality of drive electrodes are arranged on the surface of the substrate member facing the surface of the mirror substrate opposite to the surface on which the mirror surface is formed with a gap. Item 1. The mirror deflecting device according to item 1. 3. The surface of the substrate member on which the drive electrodes are arranged is a substantially conical inclined surface having an apex at a position corresponding to the center of the mirror substrate. The described mirror deflection device. 4. The mirror deflection device according to claim 2, wherein each of the plurality of drive electrodes is divided into a plurality of independent electrodes. 5. A plurality of mirror deflecting devices according to claim 1, first light transmitting means for causing a light beam to enter the plurality of mirror deflecting devices, and the plurality of mirrors. A second light transmission means on which the light beam deflected by the deflection device is incident, and two-dimensional optical exchange is performed between the first light transmission means and the second light transmission means. An optical switching device.