JP5285030B2 - Micromirror element, mirror array and manufacturing method thereof - Google Patents

Description

  The present invention relates to a micromirror element using an electrostatic drive MEMS technology used for a wavelength selective switch for optical communication and the like, and a manufacturing method thereof.

  In the field of optical networks that serve as the foundation of Internet communication networks, optical MEMS (Micro Electro Mechanical Systems) technology is in the spotlight as a technology that realizes multi-channel, wavelength division multiplexing (WDM), and cost reduction. An optical switch using an optical MEMS technology has been developed (see, for example, Patent Document 1). The most characteristic component of the MEMS type optical switch is a micromirror array in which micromirror elements composed of a plurality of movable reflectors are arranged.

  The optical switch enables path switching without converting light into an electrical signal. If an optical switch is used, it is possible to switch paths without demultiplexing light for each wavelength even for multiplexed light. Such an optical switch is used, for example, to distribute a signal to another path when a failure occurs in the path being used and maintain a state where communication is possible.

In recent years, wavelength selective switches (WSS: Wavelength Selective Switches) that individually select the paths of light of each wavelength after demultiplexing multiplexed light for each wavelength have been researched and developed. A MEMS mirror element is also used in this WSS (see, for example, Patent Document 2).
In the case of WSS using MEMS, MEMS mirrors are arranged at different positions for each wavelength of light. In the case of a switch that handles n-wave light, n MEMS mirrors are arranged. By changing the relative angle between the light applied to the MEMS mirror and the MEMS mirror, control of the direction in which the reflected light propagates, that is, switching, is realized.

  When a wavelength dispersion element such as a grating is used for demultiplexing light, light of different wavelengths can be separated, but light of continuous wavelengths is demultiplexed into a continuous space as seen in a rainbow. That is, two lights having a small wavelength difference are demultiplexed into adjacent spaces. As light for communication, light having a center wavelength at a frequency called a grid defined by ITU (International Telecommunication Union) is used. Therefore, in WSS, it is essential to arrange the number of MEMS mirrors corresponding to the number of wavelengths that can be handled in close proximity at intervals according to wavelengths (more precisely, according to wavelengths and optical systems). In the current MEMS mirror, the distance between the mirrors is about 100 μm.

  In such a MEMS mirror array, a structure for driving a mirror using electromagnetic force or a structure for driving a mirror using electrostatic force is used. The mirror structure using any force is designed so that the force acts between the movable structure and the fixed structure, that is, between the separated structures.

  In MEMS mirrors used for WSS, in principle, the mirrors must be placed close to each other and the force acting between the distant structures is used. There is a problem that so-called interference occurs. When electrostatic attraction is used, electrical interference occurs. When electromagnetic force is used, magnetic interference occurs. In any case, in order to suppress interference, it is necessary to use a shielding technique such as an electric field shield or a magnetic shield. However, it is very difficult to place an effective shielding structure between MEMS mirrors close to about 100 μm. It is difficult to.

  As a method of preventing interference between mirrors, as shown in Patent Document 1, a wall-like structure is arranged between adjacent mirror structures, or as shown in Patent Document 2, There are a method of increasing the distance to the mirror or the wiring to be used, a method of using a multilayer structure in which a structure such as a wiring to which a potential is applied is arranged below the planar GND electrode, and the like. However, the MEMS mirror array used in WSS is required to place the mirror structure at the exact position determined by optical design, and the distance between the mirror structure and the distance between the wiring and the mirror structure can be freely increased. However, it is difficult to increase the electrical interference, and there is a problem that electrical interference increases.

  In addition, it is very effective to place a structure such as a wall between adjacent mirror structures, but considering the characteristics of the switch, the distance between adjacent mirrors should be as small as possible. There is a problem that a compromise must be made by lowering the characteristics of the switch. When a mirror is formed by a bulk micromachining technique for joining a mirror chip and an electrode chip, a structure for electric shielding is generally formed on the electrode chip side.

For example, in the case of an element adopting a structure in which the drive electrode structure is formed in three dimensions and the movable electrode enters into the electrode structure, the electric field that wraps around from the upper part of the movable electrode is the movable electrode of the adjacent element May be affected.
In order to shield such an electric field, for example, as shown in FIGS. 11A to 11C, FIG. 12, FIG. 13, and FIG. It is disclosed in Document 1. 11A to 11C are assembly process diagrams of the WSS mirror array chip disclosed in Non-Patent Document 1, FIG. 12 is a perspective view of the WSS mirror array chip disclosed in Non-Patent Document 1, and FIG. Is a cross-sectional view taken along the line AA ′ of the WSS mirror array chip of FIG. 12, and FIG. 14 is a cross-sectional view taken along the line BB ′ of the WSS mirror array chip of FIG.

The WSS mirror array chip joins the mirror substrate 100 and the electrode substrate 200 as shown in FIG. 11A, and has a rectangular opening 101 formed in the mirror substrate 100 as shown in FIG. 11B. The shield cap 300 is inserted into the structure.
The mirror substrate 100 includes a support layer 102 made of silicon, leaf springs 103 a and 103 b that are movable electrodes formed in the opening 101, a mirror 104, and a support that serves as a connecting portion between the leaf springs 103 a and 103 b and the mirror 104. Springs 105a and 105b. One ends of the leaf springs 103 a and 103 b are fixed to the support layer 102. In the example of FIGS. 11 to 14, the leaf spring 103 a and the leaf spring 103 b are aligned on a line parallel to the y-axis direction. Further, the plate spring 103a and the plate spring 103b each have a cantilever structure in which the other end can be displaced in the normal direction (z-axis direction) of the mirror substrate.

  A mirror 104 is arranged between the leaf spring 103a and the leaf spring 103b by being connected by a pair of support springs 105a and 105b that can be bent. The mirror 104 is arranged in a row with the leaf spring 103a and the leaf spring 103b, and is disposed so as to be rotatable between the leaf spring 103a and the leaf spring 103b. The support spring 105a connects the other end of the leaf spring 103a and the mirror 104, and the support spring 105b connects the other end of the leaf spring 103b and the mirror 104. In the example of FIGS. 11 to 14, the leaf spring 103a, the support spring 105a, the mirror 104, the support spring 105b, and the leaf spring 103b are aligned in order on a line parallel to the y-axis direction.

  The mirror 104 passes through the pair of support springs 105a and 105b, and can rotate about a first rotation axis parallel to the y-axis, and a first mirror parallel to the x-axis orthogonal to the length direction of the mirror 104. It is possible to rotate around 2 rotation axes. A reflective film made of gold or aluminum is formed on the surface of the mirror 104 so that, for example, light in the infrared region can be reflected. The alignment of the plate spring 103a, the support spring 105a, the mirror 104, the support spring 105b, and the plate spring 103b as described above forms a structure on the mirror substrate side of one MEMS mirror element. A plurality of elements are arranged along the vertical x-axis direction to form a structure on the mirror substrate side of the WSS mirror array chip.

  On the other hand, on the electrode substrate 200, for each MEMS mirror element, driving fixed electrodes 201a and 201b for driving the leaf springs 103a and 103b, and driving fixed electrodes 202a and 201b for driving the mirror 104 are provided. 202b. A shield wall 203 is formed between the fixed driving electrodes 202a and 202b for driving one mirror 104 and the fixed driving electrodes 202a and 202b for driving the adjacent mirror 104. Further, a gap control bump 204 is formed on the electrode substrate 200 to fix the mirror substrate 100 at a predetermined distance.

  When the mirror substrate 100 and the electrode substrate 200 are joined, the driving fixed electrodes 201a and 201b are disposed so as to face the leaf springs 103a and 103b, respectively, and the driving fixed electrodes 202a and 202b face the mirror 104. Are arranged to be. The fixed driving electrodes 201a and 201b have a substantially U-shaped cross section in which grooves are formed along a direction parallel to the y-axis, that is, a direction parallel to the alignment direction of the leaf springs 103a and 103b. .

  The driving fixed electrodes 201a, 201b, 202a, 202b as described above form a structure on the electrode substrate side of one MEMS mirror element, and a plurality of such structures are arranged along the x-axis direction, and WSS A structure on the electrode substrate side of the mirror array chip is formed. That is, a pair of leaf springs 103a and 103b, a mirror 104, a pair of support springs 105a and 105b, a pair of driving fixed electrodes 201a and 201b, and a pair of driving fixed electrodes 202a and 202b constitute one MEMS mirror element. Is configured.

  A driving voltage for driving the leaf springs 103a and 103b is supplied to the driving fixed electrodes 201a and 201b via a fixed electrode wiring (not shown). A driving voltage for driving the mirror 104 is supplied to the driving fixed electrodes 202a and 202b via a fixed electrode wiring (not shown). The leaf springs 103a and 103b, the mirror 104, and the support springs 105a and 105b are equipotential (for example, ground potential).

  Next, the operation of the MEMS mirror element will be described. First, the rotation around the second rotation axis will be described. By applying a predetermined driving voltage to the driving fixed electrode 201b and applying a force that draws the leaf spring 103b toward the electrode substrate 200 by the generated electrostatic attraction, the leaf spring 103b is supported by the frame portion. The other end of the leaf spring 103b is displaced so as to be drawn toward the electrode substrate 200 side. As a result, the mirror 104 rotates with the support spring 105a as a fulcrum so that the support spring 105b side is pulled toward the electrode substrate 200 side. This means that the mirror 104 is rotated around the second rotation axis that passes through the central portion of the mirror 104 and is parallel to the arrangement direction (x-axis direction) of the MEMS mirror elements.

  On the other hand, by applying a predetermined driving voltage to the driving fixed electrode 201a to apply a force that attracts the leaf spring 103a to the electrode substrate 200 side by electrostatic attraction, the leaf spring 103a is supported by the frame portion. The other end of the leaf spring 103a is displaced so as to be drawn toward the electrode substrate 200 side. As a result, the mirror 104 rotates with the support spring 105b as a fulcrum so that the support spring 105a side is pulled toward the electrode substrate 200 side. In this rotation operation, the mirror 104 is rotated in the opposite direction to the case where the drive voltage is applied to the driving fixed electrode 201b.

  Next, the rotation around the first rotation axis will be described. By controlling the voltage applied to the driving fixed electrodes 202a and 202b, the mirror 104 can be rotated around the first rotation axis passing through the pair of support springs 105a and 105b. For example, when a voltage higher than that of the driving fixed electrode 202b is applied to the driving fixed electrode 202a, the mirror 104 rotates around the first rotation axis so as to tilt toward the driving fixed electrode 202a. Move. As described above, the mirror 104 rotates about two orthogonal axes.

JP 2007-248809 A International Publication WO06 / 073111

M.Usui, S.Uchiyama, E.Hashimoto, K.Hadama, Y.Ishii, N. Matsuura, T.Sakata, N.Shimoyama, Y.Sato, H.Ishii, T.Matsuura, F.Shimokawa, and Y Uenishi, “Electrically Separated Two-axis MEMS Mirror Array Module for Wavelength Selective Switches”, Proc. Of Optical MEMS '2009, Clearwater Beach, Florida, USA, Aug. 17-20, 2009, pp.158-159

  As shown in FIG. 11C, the shield cap 300 is disposed above the leaf springs 103a and 103b formed on the mirror substrate 100, but may be arranged so as not to contact the leaf springs 103a and 103b. Structurally desirable. However, actually, when the shield cap 300 is inserted into the opening 101 of the mirror substrate 100, the shield cap 300 may come into contact with the leaf springs 103a and 103b, and the shield cap 300 is in contact with the leaf spring 103a. , 103b increases the possibility of breakage of the mirror structure such as the leaf springs 103a, 103b, resulting in a decrease in device yield.

  The present invention has been made to solve the above-described problems, and provides a micromirror element capable of avoiding damage to the element during mounting and improving the yield of the element, and a method for manufacturing the same. Objective.

  The micromirror element of the present invention includes a first substrate, a second substrate disposed so as to face the first substrate, a movable electrode formed to be displaceable on the first substrate, and the first substrate The second substrate has a substantially U-shaped cross section for driving the movable electrode, disposed on the surface of the second substrate facing the first substrate with a gap provided between the movable substrate and the movable electrode. A fixed electrode; an insulating layer formed on the wall electrode portion of the fixed electrode; and a shield electrode formed on the insulating layer. The movable electrode includes a bottom portion of the fixed electrode and a wall electrode portion. And the insulating layer and the shield electrode.

  In addition, the micromirror element of the present invention includes a first substrate, a second substrate disposed to face the first substrate, a movable electrode formed to be displaceable on the first substrate, A substantially U-shaped cross-section for driving the movable electrode disposed on the surface of the second substrate facing the first substrate with a gap provided between the movable substrate and the movable electrode. A fixed electrode having a shape, an insulating layer formed higher than the wall electrode portion of the fixed electrode between the adjacent fixed electrodes, and a shield electrode formed on the insulating layer, the movable electrode comprising: The fixed electrode is disposed so as to enter a space surrounded by the bottom portion, the wall electrode portion, the insulating layer, and the shield electrode.

Moreover, in one configuration example of the micromirror element of the present invention, the height of the wall electrode portion of the fixed electrode is opposite to the second substrate of the movable electrode when a driving voltage is not applied to the fixed electrode. The height of the surface of the movable electrode is the same as or lower than the surface of the opposing side, and the position of the upper surface of the shield electrode is the second of the movable electrode when no driving voltage is applied to the fixed electrode. It is characterized by being located at the same position as the surface not facing the substrate or higher than the surface not facing the substrate.
In one configuration example of the micromirror element of the present invention, the shield electrode has the same potential as the movable electrode.
The mirror array of the present invention is characterized in that a plurality of micromirror elements are arranged so that the movable electrodes are arranged in an array.

  The method for manufacturing a micromirror element according to the present invention includes a movable electrode forming step for forming a movable electrode on a first substrate, and a fixed electrode forming step for forming a fixed electrode having a substantially U-shaped cross section on the second substrate. An insulating layer forming step for forming an insulating layer on the wall electrode portion of the fixed electrode, a shield electrode forming step for forming a shield electrode on the insulating layer, the first substrate, and the second electrode A substrate bonding step for arranging and bonding the substrate so that the movable electrode and the fixed electrode are spaced apart from each other, and the movable electrode includes a bottom portion of the fixed electrode, a wall electrode portion, and the insulating layer And the shield electrode are arranged so as to enter a space surrounded by the shield electrode.

  The method of manufacturing a micromirror element of the present invention includes a movable electrode forming step of forming a movable electrode on a first substrate, a fixed electrode bottom forming step of forming a bottom of the fixed electrode on the second substrate, An insulating layer forming step for forming a wall-like insulating layer between the bottoms of the adjacent fixed electrodes on the second substrate; and a fixed electrode for forming wall electrode portions of the fixed electrode at both ends of the bottom of the fixed electrode A step of forming a wall electrode part; a shield electrode forming step of forming a shield electrode on the insulating layer; and the first substrate and the second substrate, wherein the movable electrode and the fixed electrode are separated from each other. A substrate bonding step for arranging and bonding so as to oppose each other, wherein the height of the insulating layer is higher than the wall electrode portion of the fixed electrode, and the movable electrode includes a bottom portion of the fixed electrode and a wall electrode portion. The insulating layer and the sheet It is characterized in being arranged to enter into the space surrounded by the cathode electrode.

  The method for manufacturing a micromirror element of the present invention includes a movable electrode forming step for forming a movable electrode on a first substrate, and an insulating layer forming step for forming an insulating layer having a substantially trapezoidal cross section on the second substrate. A fixed electrode forming step for forming a fixed electrode on a second substrate between adjacent insulating layers and on an inclined side surface of the insulating layer; and a shield electrode forming step for forming a shield electrode on the insulating layer And a substrate bonding step for bonding the first substrate and the second substrate by arranging the movable electrode and the fixed electrode so that the movable electrode and the fixed electrode face each other apart from each other, and the height of the insulating layer Is higher than the wall electrode portion of the fixed electrode, and the movable electrode is disposed so as to enter a space surrounded by the bottom portion, the wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. Characterized by Than is.

Further, in one configuration example of the method for manufacturing a micromirror element of the present invention, the second substrate is formed of a multilayer SOI substrate in which a plurality of two-layer structures of an SOI layer and a buried oxide film are stacked, and the fixed electrode forming step, The insulating layer forming step and the shield electrode forming step are characterized in that the fixed electrode, the insulating layer, and the shield electrode are formed by successive etching of the SOI layer and the buried oxide film.
Further, in one configuration example of the manufacturing method of the micromirror element of the present invention, the height of the wall electrode portion of the fixed electrode is the same as the height of the surface of the movable electrode facing the second substrate, Alternatively, the position of the upper surface of the shield electrode is lower than the surface on the opposite side, and the same position as the surface of the movable electrode on the side not facing the second substrate, or higher than the surface on the non-facing side. It is characterized by being a position.

Moreover, one structural example of the manufacturing method of the micromirror element of the present invention is characterized in that the fixed electrode is formed by any one of plating, sputtering, and vapor deposition.
Also, one configuration example of the manufacturing method of the micromirror element of the present invention is characterized in that the insulating layer is formed of an inorganic material or a resin material, and the shield electrode is formed of a metal or a conductive resin material. It is.
In the mirror array manufacturing method according to the present invention, a plurality of micromirror elements are arranged so that the movable electrodes are arranged in an array.

  Conventionally, an electric field shield structure has been realized by mounting a separate shield cap, but in the present invention, a shield electrode can be formed at the time of manufacturing the second substrate. In addition, the shield cap and the movable electrode plate can be prevented from colliding with each other when the shield cap is mounted, and the movable electrode can be prevented from being damaged, and the yield of the element can be improved.

1 is a cross-sectional view of a WSS mirror array chip according to a first embodiment of the present invention. 1 is a cross-sectional view of a WSS mirror array chip according to a first embodiment of the present invention. It is a figure explaining operation | movement of the mirror element of the WSS mirror array chip based on the 1st Embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the electrode substrate of the WSS mirror array chip which concerns on the 1st Embodiment of this invention. It is sectional drawing of the WSS mirror array chip concerning the 2nd Embodiment of this invention. It is a figure explaining operation | movement of the mirror element of the WSS mirror array chip concerning the 2nd Embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the electrode substrate of the WSS mirror array chip concerning the 2nd Embodiment of this invention. It is sectional drawing of the WSS mirror array chip based on the 3rd Embodiment of this invention. It is a figure explaining operation | movement of the mirror element of the WSS mirror array chip concerning the 3rd Embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the electrode substrate of the WSS mirror array chip concerning the 3rd Embodiment of this invention. It is an assembly process figure of the conventional WSS mirror array chip. It is a perspective view of the conventional WSS mirror array chip. It is sectional drawing of the conventional WSS mirror array chip. It is sectional drawing of the conventional WSS mirror array chip.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 are cross-sectional views of a WSS mirror array chip, which is a micromirror element according to a first embodiment of the present invention. FIG. 11 (A) to FIG. 11 (C), FIG. 12, FIG. The same components as those in FIG. 14 are denoted by the same reference numerals. 1 corresponds to the cross-sectional view shown in FIG. 13, and FIG. 2 corresponds to the cross-sectional view shown in FIG.

As in the prior art, the WSS mirror array chip has a structure in which the mirror substrate 100 and the electrode substrate 200 are joined.
Since the structure of the mirror substrate 100 is the same as the conventional one, it will be described briefly. The mirror substrate 100 includes a support layer 102 made of silicon, a BOX layer 106 made of a silicon oxide film, and an SOI (Silicon on Insulator) layer 107. An opening 101 through which the SOI layer 107 is exposed is formed in the support layer 102 and the BOX layer 106. Plate springs 103a and 103b, mirror 104, and support springs 105a and 105b are formed on the SOI layer 107 of the opening 101. One end of each of the leaf springs 103a and 103b is fixed to a frame portion (not shown) which is a peripheral SOI layer 107. The alignment of the leaf spring 103a, the support spring 105a, the mirror 104, the support spring 105b and the leaf spring 103b forms a structure on the mirror substrate side of one mirror element, and such a structure is in the x-axis direction perpendicular to the alignment direction. Are arranged along the mirror substrate to form a structure on the mirror substrate side of the WSS mirror array chip.

  On the other hand, on the electrode substrate 200, for each mirror element, fixed driving electrodes 201a and 201b for driving the leaf springs 103a and 103b and fixed driving electrodes 202a and 202b for driving the mirror 104 are provided. And are provided. A shield wall 203 for shielding an electric field is formed between the fixed driving electrodes 202a and 202b for driving one mirror 104 and the fixed driving electrodes 202a and 202b for driving the adjacent mirror 104. Has been.

  When the mirror substrate 100 and the electrode substrate 200 are joined, the driving fixed electrodes 201a and 201b are disposed so as to face the leaf springs 103a and 103b, respectively, and the driving fixed electrodes 202a and 202b face the mirror 104. Are arranged to be. The fixed driving electrodes 201a and 201b have a substantially U-shaped cross section in which grooves are formed along a direction parallel to the y-axis, that is, a direction parallel to the alignment direction of the leaf springs 103a and 103b. . As shown in FIG. 1, the size of the driving fixed electrodes 201a and 201b is such that the leaf springs 103a and 103b do not touch the opposing driving fixed electrodes 201a and 201b, and are in the grooves of the driving fixed electrodes 201a and 201b. Is set to be able to enter.

  The present embodiment is different from the conventional one in that insulating layers 205a and 205b are formed on the wall electrode portions of the driving fixed electrodes 201a and 201b, respectively, and shield electrodes 206a and 206b are formed on the insulating layers 205a and 205b. It is formed. The shield electrodes 206a and 206b are formed so as to surround a position higher than the leaf springs 103a and 103b.

  The driving fixed electrodes 201a, 201b, 202a, 202b, the insulating layers 205a, 205b, and the shield electrodes 206a, 206b as described above form a structure on the electrode substrate side of one mirror element. A plurality of electrodes are arranged along the axial direction to form a structure on the electrode substrate side of the WSS mirror array chip.

  A driving voltage for driving the leaf springs 103a and 103b is supplied to the driving fixed electrodes 201a and 201b via a not-shown leaf spring driving fixed electrode wiring. Further, a driving voltage for driving the mirror 104 is supplied to the driving fixed electrodes 202a and 202b via a mirror driving fixed electrode wiring (not shown). The same potential (for example, ground potential) is applied to the leaf springs 103a and 103b, the mirror 104, and the support springs 105a and 105b.

  Since the operation of each mirror element of the WSS mirror array chip is the same as that of the conventional WSS mirror array chip disclosed in Non-Patent Document 1, detailed description thereof is omitted. When the element of the present embodiment is used as a WSS mirror array chip, as shown in FIG. 2, the signal light is reflected by being incident on the mirror 104 through the opening 101, and again through the opening 101. Will be emitted. By controlling the driving voltage applied to the fixed driving electrodes 201a and 201b and the fixed driving electrodes 202a and 202b, the rotation angle of the mirror 104 can be controlled, and the incident light can be reflected at a desired angle. It has become.

  In the present embodiment, the shield electrodes 206a and 206b and the leaf springs 103a and 103b are set to the same potential (for example, ground potential) through the wiring, and are connected to either the driving fixed electrode 201a or the driving fixed electrode 201b. The leaf spring 103a or the leaf spring 103b is pulled downward by electrostatic attraction generated by applying the drive voltage. At this time, in the mirror element to which the drive voltage is applied, as shown in FIG. 3, the wraparound of the electric field to the adjacent mirror element can be suppressed by the shield electrodes 206a and 206b. It is possible to suppress electrical interference (crosstalk).

  That is, in the WSS mirror array chip, since the interval between the mirror elements is narrow, the electrostatic attractive force affects not only the leaf spring of the mirror element but also the leaf spring of the adjacent mirror element. May be displaced. As a result, crosstalk may occur between adjacent mirror elements. In the conventional WSS mirror array chip disclosed in Non-Patent Document 1, the fixed electrodes for driving 201a and 201b are U-shaped in cross section, and a shield cap is disposed above the leaf springs 103a and 103b. The influence of the electric field that circulates from the upper part of the driving fixed electrodes 201a and 201b on the leaf springs 103a and 103b of the adjacent mirror element is suppressed.

  On the other hand, in the present embodiment, shield electrodes 206a and 206b are formed on the wall electrode portions of the driving fixed electrodes 201a and 201b via the insulating layers 205a and 205b, and the shield electrodes 206a and 206b are formed as leaf springs. By setting the same potential as 103a and 103b, it is possible to prevent the electric field from wrapping around as shown in FIG. 3, and to suppress crosstalk without providing a shield cap.

  As described above, in the conventional WSS mirror array chip disclosed in Non-Patent Document 1, the electric field shield structure is realized by mounting a separate shield cap. In the present embodiment, the electrode substrate 200 is provided. Since the shield electrodes 206a and 206b are collectively formed at the time of fabrication, it is possible to prevent the leaf spring from being damaged due to the collision between the shield cap and the leaf spring when the shield cap is mounted as in the prior art. Yield can be improved.

  The heights (H in FIG. 1) of the wall electrode portions of the driving fixed electrodes 201a and 201b are the same as the gap interval (G in FIG. 1) after joining the electrode substrate 200 and the mirror substrate 100, or the gap interval G Slightly lower. On the other hand, the positions of the upper surfaces of the shield electrodes 206a and 206b after the electrode substrate 200 and the mirror substrate 100 are joined are the upper surfaces of the leaf springs 103a and 103b when no driving voltage is applied to the driving fixed electrodes 201a and 201b. The positions are the same or higher than the upper surfaces of the leaf springs 103a and 103b. Thus, in the present embodiment, the shield electrodes 206a and 206b can be formed so as to surround the leaf springs 103a and 103b, and a higher electric field separation effect can be obtained.

  Next, a method for manufacturing the WSS mirror array chip of the present embodiment will be described. First, a method for manufacturing the mirror substrate 100 will be briefly described. The mirror substrate 100 is manufactured using an SOI substrate. The plate springs 103a and 103b, the mirror 104, and the support springs 105a and 105b are formed on the SOI layer 107 using a known lithographic technique and DRIE (Deep Reactive Ion Etching) etching technique with the SOI substrate as a starting substrate.

  Subsequently, the silicon of the unnecessary support layer 102 where the leaf springs 103a and 103b, the mirror 104, and the support springs 105a and 105b are formed on the SOI layer 107 is removed by etching. After removal, cleaning is performed to expose a clean silicon surface. Next, the BOX layer 106 is removed by etching. Thus, by removing the support layer 102 and the BOX layer 106 by etching, an opening 101 having a rectangular shape in plan view could be formed in the mirror substrate 100.

  Finally, a metal film is deposited on the front and back surfaces of the mirror 104 in order to reflect light having a communication wavelength. Here, for example, a metal such as gold or aluminum is deposited in order to increase the reflectance of infrared rays to be used. When the surface of the structure is silicon, an adhesion improving layer such as titanium or chromium is used in order to improve adhesion of deposited gold or aluminum to silicon. With the above method, the mirror substrate 100 including the rotatable mirror 104 is formed.

Next, a method for manufacturing the electrode substrate 200 will be described. 4A to 4D are process cross-sectional views illustrating a method for manufacturing the electrode substrate 200 of the present embodiment.
First, a thermal oxide film (not shown) is formed on the surface of the base substrate 220. On this thermal oxide film, a fixed electrode wiring (not shown) for driving the leaf springs 103a and 103b and a fixed electrode wiring (not shown) for driving the mirror 104 are formed using, for example, a plating method. On the base substrate 220 on which the fixed electrode wiring is formed, an insulating film, for example, a silicon oxide film (not shown) is deposited by a CVD (Chemical Vapor Deposition) method or the like. A via hole (not shown) is formed in this insulating film using a known lithography technique and etching technique.

  Next, a metal sputtered film is deposited on the surface of the insulating film on the base substrate 220 and used as a seed layer for the subsequent plating process. A resist is applied, and a resist pattern for forming the driving fixed electrodes 201a, 201b, 202a, 202b is formed using a lithography technique. Then, the bottoms of the driving fixed electrodes 201a and 201b are formed by plating using the resist pattern as a mask, and the driving fixed electrodes 202a and 202b are formed (FIG. 4A). The fixed electrodes for driving 201a and 201b and the fixed electrode wiring for driving the leaf springs below the fixed electrodes are connected via via holes formed in the insulating film. Similarly, the driving fixed electrodes 202a and 202b and the lower mirror driving fixed electrode wiring are connected via via holes. After the bottoms of the fixed driving electrodes 201a and 201b and the fixed driving electrodes 202a and 202b are formed, the resist used as a mask is peeled off and the surface is cleaned.

  Next, as shown in FIG. 4B, wall electrode portions of the driving fixed electrodes 201a and 201b are formed at both ends of the bottom portions of the driving fixed electrodes 201a and 201b. In order to form the wall electrode portion, a resist is applied, a resist pattern for forming the wall electrode portion is formed by using a lithography technique, and the resist pattern is used as a mask by an electrolytic plating method or an electroless plating method. What is necessary is just to form a wall electrode part. After the wall electrode portion is formed, the resist used as a mask is peeled off and washed so that the surface is clean.

Subsequently, insulating layers 205a and 205b are formed on the wall electrode portions of the driving fixed electrodes 201a and 201b, respectively (FIG. 4C). In order to form the insulating layers 205a and 205b, a resist having a thickness exceeding the wall electrode portion is applied, a resist pattern for forming the insulating layers 205a and 205b is formed using a lithography technique, and the resist pattern is formed. The insulating layers 205a and 205b may be formed using a mask. After the insulating layers 205a and 205b are formed, the resist used as a mask is peeled off and washed so that the surface is clean. Here, the insulating layers 205a and 205b made of an inorganic material such as SiO ₂ may be formed by a method such as sputtering or vapor deposition, or the insulating layers 205a and 205b made of an organic material are locally dispenser or inkjet. You may form using a method etc.

  Further, shield electrodes 206a and 206b are formed on the insulating layers 205a and 205b, respectively (FIG. 4D). In order to form the shield electrodes 206a and 206b, a resist having a thickness exceeding the insulating layers 205a and 205b is applied, and a resist pattern for forming the shield electrodes 206a and 206b is formed using a lithography technique. The shield electrodes 206a and 206b may be formed using the pattern as a mask. After the shield electrodes 206a and 206b are formed, the resist used as a mask is peeled off and washed so that the surface is clean. As the shield electrodes 206a and 206b, metal, conductive resin, or the like can be used. By using metal or conductive resin, there is an effect that the shield electrodes 206a and 206b can be selectively formed on the insulating layers 205a and 205b.

  Subsequently, gap control bumps (not shown) for forming a gap interval between the electrode substrate 200 and the mirror substrate 100 are formed on the insulating film outside the driving fixed electrodes 201a, 201b, 202a, 202b. The gap control bump can be formed by, for example, a plating method.

The electrode substrate 200 is formed by the above method. In the method of forming the electrode substrate 200 described above, gold is used as the material for the driving fixed electrodes 201a, 201b, 202a, 202b, the shield electrodes 206a, 206b, the fixed electrode wiring, and the gap control bumps. It is not limited. Gold, copper, nickel, aluminum, tungsten, tantalum, titanium, tin, silver, etc. can be used as materials for these electrodes, wirings and gap control bumps, and compounds of these materials may be used. . Further, as described above, a conductive resin may be used for the shield electrodes 206a and 206b.
When a plurality of chips are formed on the wafer, the electrode substrate 200 is completed after a process called dicing, which is performed by cutting the wafer and cutting the wafer into chips.

  After the mirror substrate 100 and the electrode substrate 200 are separately formed, the mirror substrate 100 and the electrode substrate 200 are aligned, and an Ag paste is applied to the upper surface of the gap control bump at the joint portion of the electrode substrate 200. In a state where the SOI layer 107 of 100 and the gap control bump of the electrode substrate 200 are in contact with each other, the Ag paste is solidified by pressurization and heating, and the mirror substrate 100 is bonded to the electrode substrate 200. Thus, the mirror substrate 100 and the electrode substrate 200 are arranged in parallel to each other, and the mirror substrate 100 is fixed on the electrode substrate 200 at a predetermined distance.

In order to manufacture the electrode substrate 200, a multi-layer SOI substrate in which a plurality of two-layer structures of an SOI layer and a buried oxide film are stacked is used, and driving fixed electrodes 201a, 201b, 202a, 202b, insulating layers 205a, 205b, It is also possible to form the shield electrodes 206a and 206b by continuous etching of the SOI layer and the buried oxide film.
That is, the first SOI layer from the top of the multilayer SOI substrate is etched to form shield electrodes 206a and 206b made of silicon, and the buried oxide film under the first SOI layer is etched to shield the shield. Insulating layers 205a and 205b are formed under the electrodes 206a and 206b, and the second SOI layer under the buried oxide film is etched to form driving fixed electrodes 201a, 201b, 202a and 202b made of silicon. do it.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a cross-sectional view of a WSS mirror array chip, which is a micromirror element according to the second embodiment of the present invention. The same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
Also in this embodiment, the structure of the mirror substrate 100 is the same as that of the conventional WSS mirror array chip and the first embodiment.

  In this embodiment, instead of forming the insulating layer and the shield electrode on the wall electrode portions of the driving fixed electrodes 201a and 201b, the insulating layer 207 is provided between the adjacent driving fixed electrodes 201b as shown in FIG. And a shield electrode 208 is formed on the insulating layer 207. Similarly, an insulating layer 207 is formed between adjacent driving fixed electrodes 201 a, and a shield electrode 208 is formed on the insulating layer 207.

  As in the first embodiment, the shield electrode 208 and the leaf springs 103a and 103b are set to the same potential (for example, ground potential) through the wiring. In the mirror element in which the driving voltage is applied to either the driving fixed electrode 201a or the driving fixed electrode 201b, the wraparound of the electric field to the adjacent mirror element is suppressed by the shield electrode 208 as shown in FIG. Therefore, as in the first embodiment, electrical interference (crosstalk) between adjacent mirror elements can be suppressed.

  Similar to the first embodiment, the position of the upper surface of the shield electrode 208 after joining the electrode substrate 200 and the mirror substrate 100 is the same position as the upper surfaces of the leaf springs 103a and 103b of the mirror substrate 100, or the leaf spring. The position is higher than the upper surfaces of 103a and 103b. Further, in order to prevent an electrical short circuit between the shield electrode 208 and the driving fixed electrodes 201a and 201b, the height of the insulating layer 207 needs to be higher than the wall electrode portions of the driving fixed electrodes 201a and 201b. .

Next, a method for manufacturing the WSS mirror array chip of the present embodiment will be described. The manufacturing method of the mirror substrate 100 is as described in the first embodiment.
FIG. 7A to FIG. 7D are process cross-sectional views illustrating a method for manufacturing the electrode substrate 200 of the present embodiment. Since the process up to FIG. 7A is the same as the process up to FIG. 4A of the first embodiment, the description is omitted.

After the bottom portions of the driving fixed electrodes 201a and 201b are formed, a wall-like insulating layer 207 is formed between the bottom portions of the adjacent driving fixed electrodes 201a, and at the same time, a wall shape is formed between the bottom portions of the adjacent driving fixed electrodes 201b. The insulating layer 207 is formed (FIG. 7B). In order to form the insulating layer 207, a resist is applied, a resist pattern for forming the insulating layer 207 is formed using a lithography technique, and the insulating layer 207 is formed using the resist pattern as a mask. After the insulating layer 207 is formed, the resist used as a mask is peeled off and cleaning is performed so that the surface is clean. Here, the insulating layer 207 made of an inorganic material such as SiO ₂ may be formed using a method such as plasma TEOS, or the insulating layer 207 made of an organic material such as polyimide may be formed. The present invention does not depend on the formation method of the insulating layer 207 and the material of the insulating layer 209.

  Next, as shown in FIG. 7C, wall electrode portions of the driving fixed electrodes 201a and 201b are formed at both ends of the bottom portions of the driving fixed electrodes 201a and 201b. The method for forming the wall electrode portion is as described in the first embodiment.

Next, the shield electrode 208 is formed over the insulating layer 207 (FIG. 7D). In order to form the shield electrode 208, a resist having a thickness exceeding the insulating layer 207 is applied, a resist pattern for forming the shield electrode 208 is formed using a lithography technique, and the shield is formed using the resist pattern as a mask. The electrode 208 may be formed. As the shield electrode 208, metal, conductive resin, or the like can be used. After the shield electrode 208 is formed, the resist used as a mask is peeled off and the surface is cleaned. Since the manufacturing process after forming the shield electrode is the same as that of the first embodiment, the description thereof is omitted.
As described above, in this embodiment, the same effect as that of the first embodiment can be obtained by forming the shield electrode 208.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 8 is a cross-sectional view of a WSS mirror array chip, which is a micromirror element according to the third embodiment of the present invention. The same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
Also in this embodiment, the structure of the mirror substrate 100 is the same as that of the conventional WSS mirror array chip and the first embodiment.

  In the present embodiment, as in the second embodiment, an insulating layer 209 is formed between adjacent driving fixed electrodes 201a, and an insulating layer 209 is also formed between adjacent driving fixed electrodes 201b. The shield electrode 210 is formed on these insulating layers 209.

  Similar to the first embodiment, the shield electrode 210 and the leaf springs 103a and 103b are set to the same potential (for example, ground potential) through the wiring. In a mirror element in which a driving voltage is applied to either the driving fixed electrode 201a or the driving fixed electrode 201b, the shield electrode 210 suppresses the wraparound of the electric field to the adjacent mirror element as shown in FIG. Therefore, as in the first embodiment, electrical interference (crosstalk) between adjacent mirror elements can be suppressed.

  Similar to the first embodiment, the position of the upper surface of the shield electrode 210 after joining the electrode substrate 200 and the mirror substrate 100 is the same position as the upper surface of the leaf springs 103a and 103b of the mirror substrate 100, or the leaf spring. The position is higher than the upper surfaces of 103a and 103b. The height of the insulating layer 209 needs to be higher than the wall electrode portions of the driving fixed electrodes 201a and 201b.

This embodiment differs from the second embodiment in that the cross-sectional shape of the insulating layer 209 in the mirror element arrangement direction (x-axis direction) is substantially trapezoidal, and the bottom and wall electrodes of the driving fixed electrodes 201a and 201b It is the point which forms a part simultaneously.
Hereinafter, a method for manufacturing the WSS mirror array chip of the present embodiment will be described. The manufacturing method of the mirror substrate 100 is as described in the first embodiment.

FIG. 10A to FIG. 10D are process cross-sectional views illustrating a method for manufacturing the electrode substrate 200 of the present embodiment.
The processes until the thermal oxide film, the fixed electrode wiring, the insulating film, and the via hole are sequentially formed on the base substrate 220 are as described in the first embodiment.

Next, an insulating layer 209 is formed over an insulating film (not shown) of the base substrate 220 (FIG. 10A). In order to form the insulating layer 209 having a substantially trapezoidal cross section, a film having the thickness of the insulating layer 209 may be formed and then etched. As the film to be the insulating layer 209, an inorganic material such as SiO ₂ formed by a method such as plasma TEOS may be used, or an organic material such as polyimide may be used.

  Subsequently, the driving fixed electrodes 201a and 201b are formed on the insulating film of the base substrate between the adjacent insulating layers 209 and on the inclined side surfaces of the insulating layer 209 (FIG. 10B). Here, the bottom portions and the wall electrode portions of the driving fixed electrodes 201a and 201b are formed simultaneously. The bottom and wall electrode portions of the driving fixed electrodes 201a and 201b can be formed by plating, sputtering, vapor deposition, or the like, but the present invention does not depend on the electrode forming method or the electrode material.

Next, the shield electrode 210 is formed over the insulating layer 209 (FIG. 10D). In order to form the shield electrode 210, a resist having a thickness exceeding the insulating layer 209 is applied, a resist pattern for forming the shield electrode 210 is formed by using a lithography technique, and the shield is formed using the resist pattern as a mask. The electrode 210 may be formed. As the shield electrode 210, metal, conductive resin, or the like can be used. After the shield electrode 210 is formed, the resist used as a mask is peeled off and washed so that the surface becomes clean. Since the manufacturing process after forming the shield electrode is the same as that of the first embodiment, the description thereof is omitted.
As described above, in the present embodiment, the same effect as that of the first embodiment can be obtained by forming the shield electrode 210.

  The present invention can be applied to electrostatically driven MEMS elements such as wavelength selective switches.

  DESCRIPTION OF SYMBOLS 100 ... Mirror board | substrate, 101 ... Opening part, 102 ... Support layer, 103a, 103b ... Leaf spring, 104 ... Mirror, 105a, 105b ... Support spring, 106 ... BOX layer, 107 ... SOI layer, 200 ... Electrode board, 201a, 201b, 202a, 202b ... fixed electrode for driving, 203 ... shield wall, 205a, 205b, 207, 209 ... insulating layer, 206a, 206b, 208, 210 ... shield electrode.

Claims (13)

A first substrate;
A second substrate disposed opposite the first substrate;
A movable electrode formed to be displaceable on the first substrate;
A substantially U-shaped cross-section for driving the movable electrode disposed on the surface of the second substrate facing the first substrate with a gap provided between the movable substrate and the movable electrode. A fixed electrode in shape,
An insulating layer formed on the wall electrode portion of the fixed electrode;
A shield electrode formed on the insulating layer;
The micromirror element, wherein the movable electrode is disposed so as to enter a space surrounded by a bottom portion, a wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. A first substrate;
A second substrate disposed opposite the first substrate;
A movable electrode formed to be displaceable on the first substrate;
A substantially U-shaped cross-section for driving the movable electrode disposed on the surface of the second substrate facing the first substrate with a gap provided between the movable substrate and the movable electrode. A fixed electrode in shape,
An insulating layer formed higher than the wall electrode portion of the fixed electrode between the adjacent fixed electrodes;
A shield electrode formed on the insulating layer;
The micromirror element, wherein the movable electrode is disposed so as to enter a space surrounded by a bottom portion, a wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. The micromirror element according to claim 1 or 2,
The height of the wall electrode portion of the fixed electrode is the same as or opposite to the height of the surface of the movable electrode facing the second substrate when no driving voltage is applied to the fixed electrode. Lower than the side face,
The position of the upper surface of the shield electrode is the same as the surface of the movable electrode that is not opposed to the second substrate when no driving voltage is applied to the fixed electrode, or the surface that is not opposed to the second electrode. A micromirror element characterized by having a high position. In the micromirror element according to any one of claims 1 to 3,
The micromirror element, wherein the shield electrode has the same potential as the movable electrode.   5. A mirror array comprising a plurality of the micromirror elements according to claim 1 arranged so that the movable electrodes are arranged in an array. A movable electrode forming step of forming a movable electrode on the first substrate;
A fixed electrode forming step of forming a fixed electrode having a substantially U-shaped cross section on the second substrate;
An insulating layer forming step of forming an insulating layer on the wall electrode portion of the fixed electrode;
A shield electrode forming step of forming a shield electrode on the insulating layer;
A substrate bonding step for arranging and bonding the first substrate and the second substrate so that the movable electrode and the fixed electrode are spaced apart and face each other;
The method of manufacturing a micromirror element, wherein the movable electrode is disposed so as to enter a space surrounded by a bottom portion, a wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. A movable electrode forming step of forming a movable electrode on the first substrate;
A fixed electrode bottom forming step of forming a bottom of the fixed electrode on the second substrate;
An insulating layer forming step of forming a wall-like insulating layer between the bottoms of the adjacent fixed electrodes on the second substrate;
A fixed electrode wall electrode part forming step for forming wall electrode parts of the fixed electrode at both ends of the bottom of the fixed electrode;
A shield electrode forming step of forming a shield electrode on the insulating layer;
A substrate bonding step for arranging and bonding the first substrate and the second substrate so that the movable electrode and the fixed electrode are spaced apart and face each other;
The height of the insulating layer is higher than the wall electrode portion of the fixed electrode,
The method of manufacturing a micromirror element, wherein the movable electrode is disposed so as to enter a space surrounded by a bottom portion, a wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. A movable electrode forming step of forming a movable electrode on the first substrate;
Forming an insulating layer having a substantially trapezoidal cross section on the second substrate;
A fixed electrode forming step of forming a fixed electrode on the second substrate between the adjacent insulating layers and on the inclined side surface of the insulating layer;
A shield electrode forming step of forming a shield electrode on the insulating layer;
A substrate bonding step for arranging and bonding the first substrate and the second substrate so that the movable electrode and the fixed electrode are spaced apart and face each other;
The height of the insulating layer is higher than the wall electrode portion of the fixed electrode,
The method of manufacturing a micromirror element, wherein the movable electrode is disposed so as to enter a space surrounded by a bottom portion, a wall electrode portion, the insulating layer, and the shield electrode of the fixed electrode. In the manufacturing method of the micromirror element of Claim 6,
The second substrate is composed of a multilayer SOI substrate in which a plurality of two-layer structures of an SOI layer and a buried oxide film are stacked;
The fixed electrode forming step, the insulating layer forming step, and the shield electrode forming step are characterized in that the fixed electrode, the insulating layer, and the shield electrode are formed by continuous etching of the SOI layer and the buried oxide film. A method of manufacturing a micromirror element. In the manufacturing method of the micromirror element of any one of Claims 6 thru | or 9,
The height of the wall electrode portion of the fixed electrode is the same as the height of the surface of the movable electrode facing the second substrate or lower than the surface of the facing electrode,
The position of the upper surface of the shield electrode is the same as the surface of the movable electrode that does not face the second substrate, or is higher than the surface that does not face the micromirror element Manufacturing method. In the manufacturing method of the micromirror element according to any one of claims 6 to 10,
The method of manufacturing a micromirror element, wherein the fixed electrode is formed by any one of plating, sputtering, and vapor deposition. In the manufacturing method of the micromirror element according to any one of claims 6 to 11,
Forming the insulating layer from an inorganic material or a resin material;
A method of manufacturing a micromirror element, wherein the shield electrode is formed of a metal or a conductive resin material.   A method of manufacturing a mirror array, comprising: arranging a plurality of the micromirror elements according to any one of claims 6 to 12 so that the movable electrodes are arranged in an array.

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