JP2011180534A - Mems element, movable mirror, and optical switch device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEMS element that can surely suppress generation of intra-plane pull in, and to provide a movable mirror and an optical switch device using this element. <P>SOLUTION: The MEMS element is equipped with a stationary comb-shaped electrode and a movable comb-shaped electrode which are arranged with a prescribed space apart, wherein the movable comb-shaped electrode moves in a direction angled to a movable reference plane, and wherein an electrostatic attraction operating surface of the stationary and the movable comb-shaped electrodes has a circular arcuate shape in the movable reference plane. Desirably, the center of the circular arcuate shape of the electrostatic operating surface coincides with a rotary shaft when the movable comb-shaped electrode rotates in the movable reference plane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS (Micro Electro Mechanical Systems) element having a fixed comb electrode and a movable comb electrode, and a movable mirror and an optical switch device using the same.

  In an optical transmission system, an optical switch device is used to switch the path of a wavelength division multiplexing (WDM) optical signal (see, for example, Patent Document 1). In such an optical switch device, a movable mirror that can change the reflection direction of light is used to switch the path of the optical signal. And in such a movable mirror, the mirror is moved using the MEMS element as an electrostatic actuator.

  The MEMS element as an electrostatic actuator includes a parallel electrode structure (for example, see Patent Document 2) and a vertical comb electrode structure (for example, see Non-Patent Document 1). The vertical comb electrode structure is such that a fixed comb electrode and a movable comb electrode having a thickness in a direction perpendicular to the extending direction and the arrangement direction of the comb electrodes are engaged with each other at a predetermined interval. The movable structure by the electrostatic attractive force acting between the electrodes and the arrangement direction of the fixed comb electrodes form an angle. A MEMS element having a vertical comb electrode structure has a strong electrostatic attraction acting between the electrodes and is unlikely to cause out-of-plane pull-in. The out-of-plane pull-in refers to a MEMS element in a direction (that is, an out-of-plane direction) that forms an angle with respect to the movable reference plane, with the plane formed by the extending direction and the arrangement direction of the fixed comb electrodes as a movable reference plane. This is a phenomenon in which the electrostatic attractive force acts beyond the restoring force for causing the movable comb electrode to be attracted to the fixed comb electrode.

  Further, in a MEMS element having a vertical comb electrode structure, in-plane pull-in may be a problem. In-plane pull-in is a phenomenon in which the movable comb electrode is attracted to the fixed comb electrode in the above-described direction within the movable reference plane. Such in-plane pull-in tends to cause a problem when the movable comb electrode and the fixed comb electrode are arranged in the axial direction of the rotation axis of the MEMS element. The reason is as follows. That is, in the optical switch device, since the spatial separation amount of each optical signal constituting the WDM optical signal is about several hundred μm, the width of the movable mirror for reflecting each optical signal is also several hundred μm. . Therefore, when the movable comb electrodes and fixed comb electrodes in the movable mirror are arranged in the axial direction of the rotation axis of the MEMS element, a large number of movable comb electrodes and fixed electrodes are within this width of several hundred μm. This is because in order to arrange the comb-teeth electrodes, the interval between them must be narrowed.

  On the other hand, a MEMS element having a vertical comb electrode structure in which in-plane pull-in is unlikely to occur is disclosed (for example, see Patent Document 3 and Non-Patent Document 2). The vertical comb electrode structure disclosed in Patent Document 3 and Non-Patent Document 2 is referred to as a Fishbone type vertical comb electrode structure. In this Fishbone type MEMS element, since the movable comb teeth and the fixed comb teeth are arranged in a direction perpendicular to the rotation axis of the MEMS element, it is said that occurrence of in-plane pull-in can be suppressed.

JP 2006-276487 A US Pat. No. 7,302,131 JP 2006-162663 A

Jin-Ho Lee, et al., “Bonding of silicon scanning mirror having vertical comb fingers” J. Micromech. Microeng. Vol.12 (2002) pp.644-649 Norinao Kouma, et al., “Fishbone-shaped vertical comb actuator for dual-axis 1-D analog micromirror array” The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005, 2E4.132

  However, even in the conventional Fishbone type MEMS element, when the movable part including the movable comb electrode rotates unintentionally in the plane, the asymmetry occurs in the distance between the movable comb electrode and the fixed comb electrode. As a result, in-plane pull-in may occur.

  The present invention has been made in view of the above, and an object of the present invention is to provide a MEMS element that can more reliably suppress the occurrence of in-plane pull-in, and a movable mirror and an optical switch device using the MEMS element.

  In order to solve the above-described problems and achieve the object, a MEMS element according to the present invention includes a fixed comb electrode and a movable comb electrode arranged at a predetermined interval, and the movable comb electrode Is a MEMS element that moves in a direction that makes an angle with respect to the movable reference plane, and the electrostatic attraction acting surface of the fixed comb electrode and the movable comb electrode has an arc shape in the movable reference plane It is characterized by.

  Further, in the MEMS element according to the present invention, in the above invention, the center of the arc shape of the electrostatic force acting surface is coincident with a rotation axis when the movable comb electrode rotates in the movable reference plane. Features.

  Further, the MEMS element according to the present invention includes a plurality of sets of the fixed comb electrodes and the movable comb electrodes in the above-described invention, and the arc-shaped centers of the plurality of electrostatic force acting surfaces are all the same. It is characterized by being.

  The MEMS element according to the present invention is characterized in that, in the above invention, the fixed comb electrode and the movable comb electrode have a gap in a direction perpendicular to the movable reference plane.

  The MEMS element according to the present invention is the above-described invention, wherein the MEMS element is fixed to the fixed comb electrode and serves as an axis of movement of the movable comb electrode; A movable arm provided with a tooth electrode, and the center of the arc shape of the electrostatic force acting surface coincides with the intersection of the shaft and the movable arm.

  In the MEMS device according to the present invention, the distance between the fixed comb electrode and the movable comb electrode is increased according to a separation distance from the shaft body. .

  Moreover, the movable mirror which concerns on this invention is equipped with the MEMS element as described in any one of said invention, and the mirror fixed with respect to the said movable comb-tooth electrode of the said MEMS element, It is characterized by the above-mentioned. To do.

  An optical switch device according to the present invention includes the movable mirror described in the above invention.

  According to the present invention, since the electrostatic force acting surfaces of the fixed comb electrode and the movable comb electrode have an arc shape in the movable reference plane, it is possible to more reliably suppress the occurrence of in-plane pull-in. Play.

FIG. 1 is a schematic diagram of a movable mirror provided with the MEMS element according to the first embodiment. FIG. 2 is a schematic plan view of the movable mirror shown in FIG. 3 is a cross-sectional view taken along line AA of the movable mirror shown in FIG. FIG. 4 is an explanatory diagram for explaining the operation of the movable mirror shown in FIG. FIG. 5 is an explanatory view for explaining the shape of each comb electrode of the movable mirror shown in FIG. FIG. 6 is an explanatory diagram illustrating a case where in-plane rotation occurs in a conventional movable mirror as a comparative example. FIG. 7 is an explanatory diagram illustrating a case where in-plane rotation occurs in the movable mirror shown in FIG. FIG. 8 is an explanatory view for explaining a method of manufacturing the movable mirror shown in FIG. FIG. 9 is an explanatory view for explaining a method of manufacturing the movable mirror shown in FIG. FIG. 10 is an explanatory diagram for explaining a method of manufacturing the movable mirror shown in FIG. FIG. 11 is an explanatory diagram for explaining a method of manufacturing the movable mirror shown in FIG. FIG. 12 is an explanatory diagram illustrating the configuration and operation of the movable mirror according to the second embodiment. FIG. 13 is an explanatory diagram illustrating the configuration and operation of the movable mirror according to the third embodiment. FIG. 14 is a block diagram illustrating a configuration of the optical switch device according to the fourth embodiment. FIG. 15 is an explanatory diagram for explaining the operation of the optical switch device shown in FIG.

  Hereinafter, embodiments of a MEMS element, a movable mirror, and an optical switch device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Moreover, in each drawing, the same code | symbol is attached | subjected suitably to the same or corresponding element. Furthermore, it should be noted that the drawings are schematic, and the relationship between the thickness and width of each layer, the ratio of each layer, and the like may differ from the actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(Embodiment 1)
FIG. 1 is a schematic diagram of a movable mirror 100 including a MEMS element as an electrostatic actuator according to Embodiment 1 of the present invention. FIG. 2 is a schematic plan view of the movable mirror 100 shown in FIG. 3 is a cross-sectional view taken along line AA of the movable mirror 100 shown in FIG.

The configuration of the movable mirror 100 will be described with reference to FIGS. First, as shown in FIG. 1, the movable mirror 100 is formed by using a three-layer substrate formed by using an SOI (Silicon On Insulator) substrate as a material. Its three-layer substrate is constituted by the active layer L3 as a surface conductive layer made of Box (Buried Oxide) layer L2, Si as a support layer L1, an insulating layer made of SiO ₂ as a back-surface conductive layer made of Si. The thickness of each layer is not particularly limited, although the support layer L1 is 140 μm, the box layer L2 is 1 μm, and the active layer L3 is 60 μm.

  The movable mirror 100 includes a fixed base portion 10 and a movable portion 20. The fixed base 10 has a laminated structure of a support layer L1, a Box layer L2, and an active layer L3. On the other hand, the movable part 20 consists only of the active layer L3.

  Next, as shown in FIG. 2, six fixed bases 10 are provided inside each of the U-shaped support part 11 having two fixed arms 11 a and the two fixed arms 11 a of the support part 11. The fixed comb-teeth electrode 12 is provided, and a torsion bar 13 as a shaft provided so as to be bridged between the tip ends of the two fixed arms 11a. The size of the torsion bar 13 is, for example, about 75 μm long, about 5 μm wide, and about 4 μm thick, but is not particularly limited. The size of the fixed comb electrode 12 is, for example, an overall width of about 10 μm and a length of about 60 μm, and the shape will be described later.

  The movable portion 20 is supported by the torsion bar 13, and a movable arm 21 extending from the torsion bar 13 substantially parallel to the two fixed arms 11 a and six movable arms provided on both sides on one end side of the movable arm 21. A comb electrode 22 and a mirror portion 23 provided on the other end side of the movable arm 21 are provided. The size of the movable comb electrode 22 is, for example, about 10 μm in width and about 60 μm in length, and the shape will be described later.

  Further, as shown in FIG. 3, the movable comb electrode 22 is disposed so as to mesh with the fixed comb electrode 12 with a predetermined gap G1. The value of the gap G1 is, for example, 10 μm. The mirror part 23 has a width of about 100 μm and a length of about 500 μm. A gold mirror is formed on the upper surface 23a of the mirror portion 23 (hereinafter referred to as a gold mirror surface 23a).

  That is, this movable mirror 100 is a gold mirror fixed to a movable comb electrode 22 on a MEMS element including a fixed base 10 having a fixed comb electrode 12 and a movable portion 20 having a movable comb electrode 22. By forming the surface 23a, it is configured as a movable mirror.

  In the following, a plane formed by the extending direction and the arrangement direction of the fixed comb electrodes 12 and a plane parallel thereto, that is, a plane parallel to the paper surface in FIG. Shall be shown. The fixed comb electrode 12 and the movable comb electrode 22 have a gap corresponding to the thickness of the Box layer L2 in the direction perpendicular to the movable reference plane S, thereby forming a stepped comb structure. .

  Next, the operation of the movable mirror 100 will be described. FIG. 4 is an explanatory diagram for explaining the operation of the movable mirror 100. 4 shows the movable mirror 100 as viewed from the side.

  First, a voltage signal is applied between the active layer L3 insulated by the Box layer L2 and the support layer L1. Then, electrostatic attraction acts between the movable comb electrode 22 made of the active layer L3 and the fixed comb electrode 12. This electrostatic attraction is particularly between the electrostatic attraction acting surface 12a, which is the side surface of each fixed comb electrode 12, and the electrostatic attraction acting surface 22a, which is the side surface of each movable comb electrode 22, facing this. Act on. As a result, the movable comb electrode 22 is attracted to the fixed comb electrode 12.

  Here, the movable arm 21 provided with the movable comb electrode 22 is supported by a torsion bar 13 fixed to the fixed comb electrode 12. As a result, when the movable comb electrode 22 is attracted, the entire movable portion 20 including the mirror portion 23 rotates within a predetermined angular range about the torsion bar 13 in the direction indicated by the arrow Ar1. The angle of this rotation depends on the magnitude of the voltage signal applied between the active layer L3 and the support layer L1. In addition, the element shown with the broken line in FIG. 4 has shown the position of the movable comb electrode 22 and the mirror part 23 in the state operated so that the movable part 20 may rotate only 4 degree | times. Thus, the movable comb electrode 22 moves in a direction that forms an angle with respect to the movable reference plane S.

  Moreover, when the movable part 20 rotates, the torsion bar 13 is twisted, so that internal stress is accumulated. Therefore, when the application of the voltage signal is stopped, the movable part 20 restores to the position before the voltage signal application using the internal stress of the torsion bar 13 as a restoring force. In this manner, the movable mirror 100 moves the angle of the gold mirror surface 23a to a desired angle by the action as an electrostatic actuator of the MEMS element including the fixed comb electrode 12 and the movable comb electrode 22. be able to.

  Next, the shapes of the fixed comb electrode 12 and the movable comb electrode 22 will be described. FIG. 5 is an explanatory diagram for explaining the shape of each comb electrode of the movable mirror 100. In FIG. 5, the movable mirror 100 is viewed from a direction perpendicular to the movable reference plane S. As shown in FIG. 5, each fixed comb electrode 12 and each movable comb electrode 22 are each concentric circles around the intersection O of the torsion bar 13 and the movable arm 21 in the movable reference plane S. Along the C, it is formed to have an equal width and an arc shape. As a result, the movable mirror 100 can more reliably suppress the occurrence of in-plane pull-in.

  This will be specifically described below. First, in the structure like the movable mirror 100 according to the first embodiment, when a voltage signal is applied between the active layer L3 and the support layer L1, due to slight asymmetry or perturbation of the structure, The movable part 20 may rotate within the movable reference plane S (in-plane rotation). In this case, the rotation axis is, for example, an intersection between the torsion bar 13 and the movable arm 21.

  FIG. 6 shows, as a comparative example, a structure substantially similar to that of the movable mirror 100, but in-plane rotation occurred in a conventional movable mirror in which the fixed comb electrode and the movable comb electrode are linear. It is explanatory drawing explaining a case. As shown in FIG. 6, when the movable arm 81 provided with the movable comb electrode 82 rotates slightly in the plane as shown by the broken line with respect to the fixed comb electrode 72 provided on the fixed arm 71, The distance between the electrostatic attraction acting surface 72a of the fixed comb electrode 72 and the electrostatic attraction acting surface 82a of the movable comb electrode 82 approaches. As a result, the electrostatic attractive force acts in the direction of increasing the rotation, and further rotates the movable comb electrode 82 and the movable arm 81. That is, since positive feedback acts on the in-plane rotation due to electrostatic attraction, the movable comb electrode 82 becomes closer to the fixed comb electrode 72 and in-plane pull-in is likely to occur.

  On the other hand, FIG. 7 is an explanatory diagram for explaining a case where in-plane rotation occurs in the movable mirror 100. As shown in FIG. 7, the electrostatic attractive force acting surface 12a of the fixed comb electrode 12 provided on the fixed arm 11a and the electrostatic attractive force acting surface 22a of the movable comb electrode 22 provided on the movable arm 21 are: Each of them has an arc shape along a concentric circle centered on the center O shown in FIG.

  Therefore, even if the movable comb electrode 22 and the movable arm 21 rotate in-plane with respect to the fixed comb electrode 12 as indicated by the broken line, the electrostatic attractive force acting surface 22a only moves on the concentric circle. It is. For this reason, the gap G1 between the electrostatic attractive force acting surface 12a and the electrostatic attractive force acting surface 22a hardly changes. As a result, positive feedback does not act on the rotation due to electrostatic attraction, so that the movable comb electrode 22 does not approach the fixed comb electrode 12 more and more, so the occurrence of in-plane pull-in is more reliably suppressed. It is done.

  In addition, when a simulation calculation was performed in which a voltage of 200 V was applied between the active layer L3 and the support layer L1 of the movable mirror 100, the movable portion 20 has a practical rotation angle with the torsion bar 13 as the central axis. The movable comb electrode 22 was moved by about 40 μm at the maximum. On the other hand, the displacement of the movable comb electrode 22 on the movable reference plane S is about 1 μm at the maximum, and it was confirmed that almost no in-plane rotation occurred.

  As described above, the movable mirror 100 according to the first embodiment can more reliably suppress the occurrence of in-plane pull-in.

  In the first embodiment, the fixed comb electrode 12 and the movable comb electrode 22 have the same width, so that a larger number of comb teeth can be arranged at a high density, and the size can be reduced. is there. Further, since the tip portion is less likely to be chipped as compared with the case where the comb teeth have a tapered shape, the manufacturing yield is higher.

(Production method)
Next, an example of a method for manufacturing the movable mirror 100 according to the first embodiment will be described. Here, the film formation of the gold mirror surface 23a is not described, but the process is appropriately performed as necessary. Hereinafter, description will be made in accordance with the end surface of the cross section along line AA of the movable mirror 100 shown in FIG.

8-11 is explanatory drawing explaining the manufacturing method of the movable mirror 100. FIG. First, as shown in FIG. 8, Box layer L2 comprising a supporting layer L1, SiO ₂ consisting of Si, and an active layer L3 made of Si, for example, an SOI substrate S 4 inch diameter (101.6 mm) . Next, oxide films O1 and O2 having a thickness of, for example, about 1.5 μm are formed on the surfaces of the support layer L1 and the active layer L3, respectively. Hereinafter, the surface on the active layer L3 side is appropriately described as the upper surface, and the surface on the support layer L1 side is appropriately described as the lower surface.

Next, a positive resist is applied to the upper surface, and exposure and development are performed using an exposure mask. By utilizing the resist pattern, performing SiO ₂ etching the oxide film O2 of the upper surface. Then, the resist applied on the upper surface is peeled off. The upper diagram in FIG. 9 shows the SOI substrate S after the resist applied on the upper surface is removed. At this time, the region where the oxide film O2 is etched is a region in the vicinity where the torsion bar 13 is to be formed.

Similarly, a positive resist is applied to the lower surface, and exposure and development are performed using an exposure mask. Using the resist pattern, SiO ₂ etching of the oxide film O1 on the lower surface is performed. Then, the resist applied on the lower surface is peeled off. The lower diagram in FIG. 9 shows the SOI substrate S after the resist applied on the lower surface is removed. At this time, when the oxide film O1 is etched, the oxide film O1 in the region of the fixed comb electrode 12 and the fixed base portion 10 is left.

Next, as shown in FIG. 10, a positive resist is applied again on the upper surface, and exposure and development are performed using an exposure mask to form a resist pattern R1. Next, SiO ₂ etching of the oxide film O2 on the upper surface is performed using the resist pattern R1. At this time, when the oxide film O2 is etched, the oxide film O2 in the regions of the support portion 11, the torsion bar 13, the movable arm 21, the movable comb electrode 22, and the mirror portion 23 is left.

Next, dry etching of the active layer L3 is performed using the resist pattern R1 and the resist pattern R1 is peeled off. As for dry etching, in order to prevent side etching, reactive ion etching (ICP-RIE) using inductively coupled plasma using SF ₆ gas or CF-based gas as a reactive gas. Is preferably used. Further, it is more preferable to use the so-called Bosch method in which O ₂ gas is added to the reactive gas, because side etching is further prevented and the pattern hole can be formed with high accuracy.

  Next, as shown in FIG. 11, the active layer L3 is dry-etched using the pattern of the oxide film O2 on the upper surface so that the torsion bar 13 has a desired thickness. Here, the active layer L3 in the region corresponding to the torsion bar 13 is etched.

  Next, the support layer L1 is dry-etched using the pattern of the oxide film O1 on the lower surface. Then, the oxide film O2 on the upper surface, the oxide film O1 on the lower surface, and SiO2 in the region exposed outside the Box layer L2 are etched to remove the excess oxide film and release the movable part. The movable mirror 100 according to the first embodiment can be manufactured by the process described above.

(Embodiment 2)
Next, a movable mirror according to Embodiment 2 of the present invention will be described. The movable mirror according to the second embodiment has substantially the same configuration as the movable mirror 100 according to the first embodiment, but has a large number of fixed comb electrodes and movable comb electrodes, and fixed comb teeth. The difference is that the distance between the electrode and the movable comb electrode is increased according to the separation distance from the torsion bar serving as the rotation axis. Below, this difference is demonstrated.

  FIG. 12 is an explanatory diagram for explaining the configuration and operation of the movable mirror 200 according to the second embodiment. FIG. 12 shows the movable mirror 200 as viewed from the side. As shown in FIG. 12, in this movable mirror 200, the gap G2 between the fixed comb electrode 32-1 and the movable comb electrode 33-1 close to the torsion bar 31 serving as the rotation axis of the movable part is 10 μm. The distance between the fixed comb electrode 32 and the movable comb electrode 33 is substantially proportional to the separation distance from the torsion bar 31, and the fixed comb electrode 32-11 and the movable comb farthest from the torsion bar 31. The gap G3 with the tooth electrode 33-11 is 15 μm.

  As with the movable mirror 100, when the movable mirror 200 is operated by applying a voltage signal, the movable portion rotates about the torsion bar 31 as a rotation axis, and the movable comb electrode 33 moves in the direction indicated by the arrow Ar2. Next, it moves so as to form an angle with respect to the movable reference plane S. In addition, the element shown with the broken line in FIG. 12 has shown the position of the movable comb electrode 33 in the state operated so that a movable part may rotate only 4 degree | times.

  Here, as the movable comb electrode 33 moves away from the torsion bar 31 so as to draw a longer arc, the movable comb electrode 33 is closer to the fixed comb electrode 32 located on the torsion bar 31 side. To move. On the other hand, in this movable mirror 200, the distance between the fixed comb electrode 32 and the movable comb electrode 33 is substantially proportional to the separation distance from the torsion bar 31, so that the fixed comb during operation is The interval between the tooth electrode 32 and the movable comb electrode 33 can be made the same regardless of the distance from the torsion bar 31. As a result, an equal electrostatic attraction can be applied between the fixed comb electrode 32 and the movable comb electrode 33 regardless of the position.

  Therefore, the movable mirror 200 according to the second embodiment can more reliably suppress the occurrence of in-plane pull-in and more reliably suppress the out-of-plane pull-in.

(Embodiment 3)
Next, a movable mirror according to Embodiment 3 of the present invention will be described. Unlike the movable mirrors 100 and 200 according to the first and second embodiments, the movable mirror according to the third embodiment has a fixed comb electrode and a movable comb electrode in a direction perpendicular to the movable reference plane. A MEMS element having a step comb structure that does not have a gap is provided.

  FIG. 13 is an explanatory diagram for explaining the configuration and operation of the movable mirror 300 according to the third embodiment. FIG. 13 shows the movable mirror 300 as viewed from the side. As shown in the upper diagram of FIG. 13, the movable mirror 300 includes a step comb in which the fixed comb electrode 41 and the movable comb electrode 42 do not have a gap in the direction perpendicular to the movable reference plane S. A MEMS element having a tooth structure is provided. The movable mirror 300 has the same structure as the movable mirror 100 shown in FIG. 2 when viewed from the direction perpendicular to the movable reference plane S.

  Next, the operation of the movable mirror 300 will be described. When the movable mirror 300 is operated by applying a voltage signal, the movable comb electrode 42 is translated in the direction indicated by the arrow Ar3 so as to form an angle substantially perpendicular to the movable reference plane S. Then, since the movable arm provided with the movable comb electrode 42 is supported by the torsion bar, it rotates with the portion of the torsion bar fixed to the fixed base as a fulcrum. As a result, the mirror part 43 having the gold mirror surface 43a and connected to the movable arm also rotates in the direction indicated by the arrow Ar4, and the state shown in the lower diagram of FIG. It becomes.

  Therefore, the movable mirror 300 having such a stepped comb structure can also more reliably suppress the occurrence of in-plane pull-in.

(Embodiment 4)
Next, an optical switch device according to a fourth embodiment of the present invention will be described. The optical switch device according to the fourth embodiment is a wavelength selective optical switch device that selects an optical signal having a predetermined wavelength from an input wavelength-multiplexed optical signal, and switches and outputs a path for each wavelength of the optical signal.

  FIG. 14 is a block diagram showing a configuration of the optical switch device according to the fourth embodiment. As shown in FIG. 14, the optical switch device 1000 includes four input / output optical fibers 51 to 54 that are arranged in the depth direction of the drawing and are connected to different optical fiber transmission paths, and the input / output optical fiber 51. To anamorphic prism pair 55, diffraction grating 56, condenser lens 57, λ / 4 wavelength plate 58, and movable mirror 100 according to the first embodiment, which are sequentially arranged with respect to ˜54. It has a configuration and includes three movable mirrors 102 to 104 arranged in an array. The optical switch device 1000 further includes a monitor element 59 and a control circuit 60 for controlling the three movable mirrors 102 to 104. Since the optical path is actually bent in the diffraction grating 56, each element from the anamorphic prism pair 55 to the movable mirrors 102 to 104 is arranged with an angle before and after the diffraction grating 56. FIG. In FIG. 1, they are arranged in series for simplification.

  Next, the operation of the optical switch device 1000 will be described. FIG. 15 is an explanatory diagram for explaining the operation of the optical switch device 1000 shown in FIG. FIG. 15 is a diagram of the optical switch device 1000 viewed from a direction perpendicular to the direction of FIG. First, the input / output optical fiber 51 outputs the wavelength-multiplexed optical signal OS <b> 1 transmitted through a certain optical fiber transmission line to the anamorphic prism pair 55. The anamorphic prism pair 55 expands the beam diameter of the wavelength multiplexed optical signal OS1 in the grating arrangement direction of the diffraction grating 56 so as to increase the resolution of wavelength selection so that the wavelength multiplexed optical signal OS1 hits many gratings. I have to. The diffraction grating 56 outputs an optical signal OS1a having a predetermined wavelength included in the incident wavelength multiplexed optical signal OS1 at a predetermined angle. The condensing lens 57 condenses the optical signal OS 1 a on the movable mirror 102 through the λ / 4 wavelength plate 58.

  The movable mirror 102 reflects the collected optical signal OS1a by its mirror surface. The reflected light at this time is input to the input / output optical fiber 52 as the reflected light signal OS2 through the λ / 4 wavelength plate 58, the condenser lens 57, the diffraction grating 56, and the anamorphic prism pair 55 in this order. And output to the optical fiber transmission line connected to the input / output optical fiber 52. Note that the λ / 4 wavelength plate 58 changes the polarization state of the optical signal OS1a and the reflected light signal OS2 so that the polarization states of the light are orthogonal to each other. Thereby, the polarization dependence of the anamorphic prism pair 55 and the diffraction grating 56 is compensated.

  The diffraction grating 56 outputs optical signals OS1b and OS1c having other predetermined wavelengths included in the wavelength multiplexed optical signal OS1 to other predetermined angles, respectively. The optical signals OS1b and OS1c are reflected by the movable mirrors 103 and 104, respectively, and the reflected light signal OS3 or reflected light signal OS4 is used as a λ / 4 wavelength plate 58, a condensing lens 57, a diffraction grating 56, and an anamorphic prism. The pair 55 is sequentially input to the input / output optical fiber 53 or the input / output optical fiber 54 and output to the input / output optical fiber 53 or the optical fiber transmission line connected to the input / output optical fiber 54.

  Here, the movable mirrors 102 to 104 monitor the wavelength and intensity of the light from which the monitor element 59 branches a part of the reflected light signals OS2 to OS4, and the movable mirrors 102 to 104 are based on the results of the monitoring. By independently moving the respective mirror portions, the reflection angles of the respective reflected light signals OS2 to OS4 are controlled to be optimum. The reflected light signals OS2 to OS4 are branched by, for example, providing a branching coupler in a part of the input / output optical fibers 51 to 54 or providing a branching mirror at an appropriate position in the optical switch device 1000. Can do. The monitor element 59 includes, for example, an AWG (Arrayed Waveguide Grating) element and a plurality of photodiodes.

  Since the optical switch device 1000 includes the movable mirrors 102 to 104 having the same configuration as the movable mirror 100 according to the first embodiment, the occurrence of in-plane pull-in can be more reliably suppressed.

  In the above embodiment, the SOI substrate is used as the material for forming the MEMS element, but another semiconductor substrate having two semiconductor layers stacked with an insulating layer interposed therebetween may be used. The present invention can also be applied to the case of forming other structures in which comb electrodes are meshed. Further, the substrate may be made of a conductive material such as another semiconductor or metal.

  In the above embodiment, the MEMS element includes a plurality of fixed comb electrodes and movable comb electrodes, but the number thereof is not limited and includes at least one set of fixed comb electrodes and movable comb electrodes. Just do it.

  In the above embodiment, the movable reference plane is defined by the plane formed by the extending direction of the fixed comb electrodes and the arrangement direction. However, the definition of the movable reference plane is not limited to this. For example, a MEMS element is formed. It may be defined by the main surface of the substrate as a material for the purpose, or may be defined by any surface perpendicular to the electrostatic attractive force acting surface of the fixed comb electrode.

  In the above embodiment, the fixed comb electrode and the movable comb electrode are both formed to have the same width. The attractive force acting surface only needs to have an arc shape in the movable reference surface. Moreover, it is preferable that the center of the arc shape of each comb electrode coincides with a portion that becomes an axis when in-plane rotation of the movable comb electrode occurs according to the structure of the MEMS element.

  Moreover, although the said embodiment concerns a movable mirror, the MEMS element which concerns on this invention is not limited to a movable mirror, It can apply also to another use.

  Further, the present invention is not limited by the above embodiment. What comprised each component of each said embodiment combining suitably is also contained in this invention. For example, the movable mirror according to the second and third embodiments may be applied to the optical switch device according to the fourth embodiment.

DESCRIPTION OF SYMBOLS 10 Fixed base part 11 Support part 11a Fixed arm 12, 32, 41 Fixed comb electrode 12a, 22a Electrostatic attraction action surface 13, 31 Torsion bar 20 Movable part 21 Movable arm 22, 33, 42 Movable comb electrode 23, 43 Mirror Portion 23a, 43a Gold mirror surface 51-54 Input / output optical fiber 55 Anamorphic prism pair 56 Diffraction grating 57 Condensing lens 58 λ / 4 wave plate 59 Monitor element 60 Control circuit 100-300, 102-104 Movable mirror 1000 Optical switch device Ar1 to Ar4 Arrow E1 to E4 Region C Concentric circles G1 to G3 Distance H Through pattern hole L1 Support layer L2 BOX layer L3 Active layer M Alignment mark O Center O1, O2 Thermal oxide film OS1 Wavelength multiplexed optical signal OS1a to OS1c Light Signal OS2 to OS4 Reflected light signal R1 ~ R7 resist S SOI substrate

Claims (8)

A MEMS element comprising a fixed comb electrode and a movable comb electrode arranged with a predetermined interval, wherein the movable comb electrode moves in a direction that forms an angle with respect to a movable reference plane,
The MEMS element, wherein the electrostatic attractive force acting surfaces of the fixed comb electrode and the movable comb electrode have an arc shape in the movable reference plane.   The MEMS element according to claim 1, wherein the center of the arc shape of the electrostatic force acting surface coincides with a rotation axis when the movable comb electrode rotates in the movable reference plane.   3. The MEMS element according to claim 2, comprising a plurality of sets of the fixed comb electrodes and the movable comb electrodes, wherein the arc-shaped centers of the plurality of electrostatic force acting surfaces are all the same.   The MEMS element according to claim 1, wherein the fixed comb electrode and the movable comb electrode have a gap in a direction perpendicular to the movable reference plane.   A shaft body fixed to the fixed comb electrode and serving as an axis of movement of the movable comb electrode; and a movable arm supported by the shaft body and provided with the movable comb electrode. The MEMS element according to claim 1, wherein a center of the arc shape of the working surface coincides with an intersection of the shaft body and the movable arm.   The MEMS element according to claim 5, wherein an interval between the fixed comb electrode and the movable comb electrode is increased in accordance with a separation distance from the shaft body. The MEMS element according to any one of claims 1 to 6,
A mirror fixed to the movable comb electrode of the MEMS element;
A movable mirror comprising:   An optical switch device comprising the movable mirror according to claim 7.

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