JP2008039867A - Micromirror, micromirror array, and optical switch using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure to avoid an electric short circuit of a micromirror. <P>SOLUTION: In a micromirror of an electrostatic drive type which is provided with a movable mirror panel and an electrode substrate supported by a beam and in which a movable mirror performs rotating operation about the beam as a center axis, the movable mirror has a reflection plane on one surface and has a mirror electrode part on the plane opposite to the reflection plane, the mirror electrode part is arranged to oppose the electrode substrate, the elctrode substrate has a driving electrode part for generating electrostatic attraction force across the mirror electrode part, the beam is a turn-back beam in which a bar shape member extended in the direction orthogonal to the center axis turns back two or more times, the driving electrode part is formed so as not to lap with the turn-back part looking from counter direction of the mirror electrode part and the electrode substrate, and an end part of the movable mirror is in the operational state in contact with the electrode substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatically driven micro movable structure (microdevice) used for an optical switch, an optical attenuator, and other optical devices, more specifically, a micromirror, and an optical switch using the same.

  Various micro movable structures (microdevices) manufactured using photolithography and etching have been proposed, and various driving methods such as electrostatic attraction, electromagnetic force, thermal deformation, and piezoelectric elements have been proposed. Among them, a micromirror using a gap closing type electrostatic drive system has been studied for a long time because it is relatively easy to manufacture and easily functions as a mirror on one electrode (Patent Document 1). ). Here, the gap closing type electrostatic driving method is a driving method in which electrostatic attraction is generated between the electrodes of the flat plate, and the driving is performed in the direction of reducing the electrode interval. The operation of the electrodes may be a translation operation in which both electrodes are kept parallel, or a rotation operation with respect to some central axis. In the case of a micro movable structure (micro device), particularly a micro mirror, a rotary operation type is often used for the purpose of changing the light reflection direction.

  The driving force in the electrostatic driving system is proportional to the electrode area. When expanding the electrode area, the device volume generally also increases. In general, since the area is proportional to the square of the length and the volume is proportional to the cube of the length, the relative driving force decreases as the micro movable structure (micro device) increases. That is, in the electrostatic drive system, the smaller the movable structure (micro device), the more advantageous. However, a small movable structure (microdevice) is required to have a certain size due to functional limitations. Specifically, for example, in the case of a micromirror in which the maximum dimension of the reflection surface is less than 1 mm, it is necessary to ensure a light reflection area. That is, the micro movable structure (micro device) becomes large. As a result, there arises a problem that the driving force is relatively small. Several countermeasures have been disclosed for this problem. For example, in Patent Document 1, a beam supporting a micromirror, which was a straight beam, is a bent beam, thereby forming a long beam in a small area to reduce the occupied area of the beam and reduce the rigidity of the beam. A method for obtaining a large operating angle with a small driving force is disclosed (Patent Document 2).

U.S. Pat. No. 4,317,611 JP-A-4-21218

  In response to the problem of securing the driving force described above, the present inventors set a beam on the mirror electrode portion side of the movable mirror, that is, on the side facing the electrode substrate, as in the micromirror disclosed in Japanese Patent Application No. 2006-70965. One of the effective solutions is a micromirror having a bent beam. However, when a so-called seesaw-type operation is performed, in this structure, the beam holding the micromirror and the drive electrode portion are close to each other, so that an electrical short circuit between them is a new problem. If the beam holding the micromirror is too close to the drive electrode portion, the beam is attracted to the drive electrode, and the two come into contact with each other, causing an electrical short circuit. At this time, there is a possibility that the current flows and the micromirror is fixed to the drive electrode part due to a kind of welding effect, and the current flows, and the components of the micromirror, especially the beam, are burned out. Could be damaged. For this reason, avoiding an electrical short circuit is a very important issue.

  In view of the above problems, an object of the present invention is to provide a structure that avoids an electrical short circuit of a micromirror.

  The present invention includes a movable mirror substrate having a movable mirror supported by a beam and an electrode substrate, wherein the movable mirror rotates about the beam as a central axis. And a mirror electrode portion on a surface opposite to the surface having the reflection surface, the mirror electrode portion being arranged to face the electrode substrate, and the electrode substrate being the mirror electrode portion. A drive electrode unit that generates electrostatic attraction between the beam and the beam is a folded beam in which a plurality of bar-shaped members extending in a direction perpendicular to the central axis are folded back, and the drive electrode unit is configured by the mirror electrode The micromirror is formed so as not to overlap the folded portion of the beam when viewed from the facing direction of the electrode and the electrode substrate, and has an operation state in which the end of the movable mirror is in contact with the electrode substrate. According to such a configuration, since the folded portion of the beam and the drive electrode portion are not close to each other, it is possible to achieve inoperability and avoidance of damage due to an electrical short circuit of the micromirror.

  In the micromirror, it is preferable that the thickness of the beam is smaller than the thickness of the movable mirror, and the beam supports the movable mirror at a position biased toward the mirror electrode portion in the thickness direction of the movable mirror. . According to this configuration, in addition to avoiding inoperability and damage due to an electrical short circuit of the micromirror, it is possible to achieve both excellent optical characteristics due to the high rigidity of the micromirror and securing of driving force due to the low rigidity beam. In addition, biasing the beam toward the mirror electrode portion is advantageous for easily realizing a structure that ensures the driving force by bringing the mirror electrode portion and the drive electrode portion close to each other.

  In the micromirror, it is preferable that the drive electrode portion is formed so as not to overlap the beam when viewed from the facing direction of the mirror electrode portion and the electrode substrate. According to this configuration, it is possible to more reliably realize inoperability and avoidance of damage due to an electrical short circuit of the micromirror.

  In the micromirror, it is preferable that a width of the drive electrode portion is larger than a width of the movable mirror except for a portion under the beam when viewed from a facing direction of the mirror electrode portion and the electrode substrate. Here, the width refers to the width of the drive electrode portion or the movable mirror in the central axis direction of the rotation operation of the movable mirror. According to such a configuration, in addition to avoiding inoperability and breakage due to an electrical short circuit of the micromirror, it is possible to prevent a reduction in driving force.

  In the micromirror, it is preferable that the movable mirror substrate is made of an SOI substrate. According to this configuration, it is possible to more easily produce a micromirror that can realize inoperability and avoidance of damage due to an electrical short circuit.

  The micromirror array of the present invention is a micromirror array in which a plurality of the above micromirrors are integrated. According to such a configuration, it is possible to integrate micromirrors that can realize inoperability and avoidance of damage due to an electrical short circuit.

  The optical switch of the present invention is an optical switch using any one of the above-described micromirrors or micromirror arrays. According to such a configuration, it is possible to avoid inoperability and damage due to an electrical short circuit of the optical switch.

  According to the present invention, there is provided a movable mirror substrate having a movable mirror supported by a beam and an electrode substrate, wherein the movable mirror rotates about the beam as a central axis. It is possible to prevent an electrical short circuit between the beam and the drive electrode portion provided, and to prevent the micromirror from becoming inoperable or damaged due to the electrical short circuit and a current flowing at that time. Further, it is possible to provide a micromirror array and an optical switch that avoid an electrical short circuit in the micromirror.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by these Examples.

  FIG. 1 shows an embodiment of an electrode substrate 120 applied to the micromirror 100 (FIG. 2) according to the present invention. The micromirror 100 is an electrostatically driven micromirror that uses an electrostatic attractive force as a driving force. Further, the micromirror 100 has a gap closing type electrostatic drive system in which the central axis of the rotation operation is defined by the beam 114, and the rotation operation is performed in a direction in which the distance between the movable mirror 111 and the electrode substrate 120 is reduced by electrostatic attraction. Used.

  FIG. 2 is a cross-sectional view of the micromirror 100 according to the present invention. FIG. 3 is a top view of the movable mirror substrate according to the present invention. The movable mirror 111 has a reflecting surface 112 on one surface. The movable mirror 111 is connected to the movable mirror substrate 110 by a beam 114, and the beam 114 supports the movable mirror 111 so as to be rotatable with respect to the movable mirror substrate 110. The beam 114 has elasticity, and is connected to the movable mirror as a pair of beams on both sides of the movable mirror. The movable mirror 111 is rotated about the beam 114 as a central axis 115, and is inclined at a predetermined angle using electrostatic attraction as a driving force.

  In the embodiment of FIG. 2, the electrode substrate 120 on which the drive electrode portion 121 is disposed is disposed so as to face the movable mirror 111, and the opposite side of the surface having the reflecting surface of the movable mirror 111, that is, the side facing the electrode substrate 120. A mirror electrode portion 113 is provided on this surface. On the electrode substrate 120, a drive electrode portion 121 is disposed so as to face the mirror electrode portion 113. The mirror electrode portion 113 and the reflecting surface 112 are substantially parallel planes. “Substantially parallel” means that a manufacturing error is allowed. A configuration in which the mirror electrode portion 113 and the reflecting surface 112 are substantially parallel is easy to manufacture and ensures high accuracy. The reflective surface 112 is configured by forming a reflective film 132 on a base 119 of a movable mirror formed of at least one of a semiconductor and a semiconductor oxide.

  The base 119 has a thin portion 117 having a thickness smaller than that of a portion having a reflecting surface. The thin portion 117 has a surface having a height different from the height of the portion having the reflective surface on the surface having the reflective surface. That is, on the surface having the reflective surface, the surface of the thin portion is lower than the surface of the portion having the reflective surface, whereby a concave portion is formed in the movable mirror 111. In order to apply the electrostatic attractive force, the movable mirror needs to have a certain size and spread for securing the electrode area and the like, but the reflecting surface does not necessarily have to be formed on the entire surface of the movable mirror. The area of the reflecting surface 112 is limited to a necessary and sufficient size to reflect the light beam. On the other hand, the area of the mirror electrode 113 is made as large as possible within a range where there is no inconvenience in the configuration of the micromirror 100 to generate a strong electrostatic attraction. It is desirable that the portion not having the reflecting surface 112 be as thick as the beam 114 as much as possible.

Here, the warp R of the reflecting surface 112 includes the thickness h of the base 119, the Young's modulus E of the base 119, the Poisson's ratio ν of the base 119, the thickness t of the reflective film 132, and the thickness of the reflective film 132. Using stress σ, R = (E × h ² ) / {6 × (1−ν) × t × σ}
It is represented by Warpage resistance can be improved 10 times or more by setting the thickness of the portion having the reflecting surface 112 to 3.2 times or more of the thin portion. By adopting the above configuration, it is possible to suppress an increase in mass and moment of inertia of the movable mirror 111 while preventing the reflection surface 112 from warping. Therefore, in the embodiment of FIG. 2, a reflecting surface having a width necessary for the reflecting function is secured, and a thin portion is provided on the base 119 in other portions, thereby reducing the weight of the movable mirror and the high-speed controllability. Improvements are being made. Further, in order to prevent mirror warpage or the like, it is necessary to make the base 119 thick. However, since the thin portion 117 is provided in this embodiment, the thickness of the base is increased while suppressing an increase in mirror mass. Is possible.
It is preferable to reduce the volume and moment of inertia of the movable mirror 111 as the structure because the relative driving force is increased. However, in order to realize the inoperability and avoidance of damage due to an electrical short circuit, which is the object of the present invention, the movable mirror 111 has a structure having no thin portion, that is, a structure having a uniform thickness as a whole. There may be.

  In the embodiment shown in FIGS. 2 and 3, in addition to the portion having the reflective surface 112, the thick portion 116 having a thickness larger than the thin portion 117 has the reflective surface 112 with the thin portion 117 interposed therebetween. Is enclosed in a frame shape. The thick portion is formed in a linear shape when viewed from the reflecting surface side. In the present embodiment, the thickness of the base of the portion having the reflecting surface 112 and the thick portion 116 is the same. Such a thick portion 116 is not necessarily provided, and effects such as reduction in the weight of the mirror and prevention of warping can be obtained without providing the thick portion. However, it is preferable to provide a thick part in addition to the part having the reflecting surface, particularly from the viewpoint of preventing the warp of the mirror, particularly the warp at the thin part 117.

  In FIG. 1, the central axis of rotation is located at the center in the in-plane direction of the movable mirror, and the reflection surface 112 straddles the central axis 115 when viewed from the reflection surface side. . The center means that an error range that does not hinder the symmetrical operation of the movable mirror is allowed. With this configuration, an increase in the moment of inertia of the movable mirror 111 can be effectively suppressed, which contributes to an improvement in controllability.

  In the configuration of FIG. 2, the thickness of the movable mirror 111 is maximum in the portion having the reflecting surface 112, and this configuration has an advantage that it can be easily manufactured.

  The base of the part constituting the reflecting surface 112 is made thicker than the beam 114. The movable mirror 111 is provided with as many thin portions as possible, preferably the same thickness as the beam 114. However, there may be a part that is partially thicker than the beam 114, such as the thick part.

The beam 114 will be described with reference to FIG. The beam 114 is a bent beam (a meander beam) in which rod-shaped members extending in a direction orthogonal to the direction of the central axis 115 of the movable mirror 111 are connected. The beam 114 is positioned on the mirror electrode 113 side with respect to the thickness direction of the movable mirror 111. For example, in the case where the beam 114 is formed on the active layer in the movable mirror 111 made of the SOI substrate composed of the active layer (Si layer) / intermediate layer (SiO ₂ layer) / base layer (Si layer), the active layer side of the SOI substrate Is opposed to the electrode substrate 120. The folded portion 191 of the beam 114 is located on the inner side (that is, on the central axis side) than the end portion 118 of the mirror. Note that the beam 114 illustrated in FIG. 3 does not limit the structure of the beam 114. Therefore, the relative length of the beam 114 to the mirror need not be the ratio shown in the figure. Further, the number of turns of the beam 114 may be increased or decreased. The beam 114 supports the movable mirror 111 on the movable mirror substrate 110 and gives a restoring force to the displacement of the movable mirror 111. The beam 114 also has a function as a path for electrically connecting the mirror drive electrode portion 113 to an external circuit. However, the electrical connection between the mirror drive electrode portion 113 of the movable mirror 111 and an external circuit (not shown) is not shown.

  FIG. 3 does not limit the shape of the movable mirror 111 on the reflecting surface 112 side. 5A, 5B, and 5C illustrate another embodiment of the micromirror according to the present invention. FIG. 5A shows an embodiment in which only the reflective surface 112 disposed in the center of the movable mirror 111 has a thick portion. The portions other than the portion having the reflecting surface 112 are all thin portions 117, and the effect of reducing mass and moment of inertia is greatest. FIG. 5B shows an embodiment having a reflective surface 112 at the center of the movable mirror 111 and having a thin and thick portion 116 in the longitudinal direction of the mirror, that is, in the direction perpendicular to the central axis. The thick portions are extended from the portion having the reflecting surface 112 in a thin line shape toward the both ends in the longitudinal direction. The thickness of the thick portion 116 is matched with the thickness of the portion having the reflecting surface 112. The thick portion 116 has an effect of suppressing the thin portion 117 from being deformed by residual stress or thermal stress. FIG.5 (c) is another embodiment regarding the arrangement | positioning method of the thick part 116 which has the same effect as FIG.5 (b). Each thick portion extends from the portion having the reflecting surface 112 in a narrow line shape toward both ends in the longitudinal direction. Since the area of the thick part 116 is smaller than that in FIG. 5B, the mass and the moment of inertia are superior to the embodiment of FIG.

  The electrode substrate 120 has one or more, for example, a pair (two) of drive electrode portions 121. When the electrode substrate 120 has one drive electrode unit, the movable mirror operates in only one direction. FIG. 1 is an illustration of a configuration having a pair (two) of drive electrode portions 121. The pair of drive electrode portions are formed on both sides of the linear projection 122, that is, on both sides of the center axis 115 of the movable mirror. An electrostatic actuator is configured between the drive electrode unit 121 and the mirror electrode unit 113. By applying a potential difference between the drive electrode unit 121 and the mirror electrode unit 113, static electricity is provided between the two. An electric attractive force is generated, and the movable mirror 111 is operated.

The spacer 130 is disposed to provide a certain space between the electrode substrate 120 and the movable mirror 111. The spacer 130 may be made of a member independent of the movable mirror substrate 110 or the electrode substrate 120, or may be formed integrally with the movable mirror substrate 110 or the electrode substrate 120. FIG. 2 shows an example in which the spacer 130 is integrally formed with the electrode substrate 120. The movable mirror substrate 110 is made of, for example, a silicon (Si) substrate or an SOI (silicon on insulator) substrate in which a silicon oxide (SiO ₂ ) layer is sandwiched between silicon (Si) layers. It is desirable that the movable mirror 111 improve the reflectance by forming a reflective film on the reflective surface 112. The reflection film is selected in consideration of the wavelength of light to be reflected and the residual stress on the mirror. As the reflective film, gold (Au), aluminum (Al), various metal or non-metal multilayer films can be used. For the mirror electrode portion 113 of the movable mirror 111, for example, gold (Au), aluminum (Al), chromium (Cr), nickel (Ni), copper (Cu), platinum (Pt) or titanium (Ti) alone or A conductive film is formed by appropriately stacking. However, when the material constituting the movable mirror 111 has sufficient conductivity, for example, in the case of a silicon (Si) substrate with improved conductivity, a conductive film may not be formed on the mirror electrode portion 113.

  The spacer 130 can be manufactured using various materials. Depending on the configuration of the micromirror 100, the surface of the spacer 130 can be conductive or insulative. For example, by making the surface of the spacer 130 conductive, the mirror electrode portion 113 of the movable mirror 111 can be part of a path that electrically connects an external circuit (not shown). Alternatively, by making the surface of the spacer 130 insulative, the spacer 130 can be disposed on the electrode substrate 120 without an electrical short circuit with the wiring 123 on the electrode substrate 120. When the spacer 130 is formed independently of the movable mirror substrate 110 or the electrode substrate 120, the material constituting the spacer 130 has a thermal expansion coefficient close to that of the movable mirror substrate 110 and the electrode substrate 120, or the movable mirror substrate 110 and the electrode. A material whose thermal expansion coefficient is the same as that of the substrate 120 is desirable.

An electrode substrate 120 applied to the micromirror 100 of the present invention will be described with reference to FIGS. 1 and 4. The electrode substrate 120 shown in FIGS. 4A, 4 </ b> B, and 4 </ b> C is an example of an embodiment in which the contact area of the movable mirror 111, the protrusion 122, and the movable mirror 111 is changed. FIG. 4B shows an example in which the protrusion 122 is formed into a dot shape, and FIG. 4C shows an example in which the protrusion 122 is shortened and divided. However, FIG. 4 does not limit the combination of the notch 127 and the protrusion 122. The electrode substrate 120 is made of, for example, a silicon (Si) substrate, an SOI substrate in which a silicon oxide (SiO ₂ ) layer is sandwiched between silicon (Si) layers, a metal substrate, or an insulator substrate (for example, a glass substrate or a ceramic substrate). To do. When the material for forming the electrode substrate 120 is conductive, an insulating film (for example, oxide film SiO ₂ or nitride film SiN _{x in} the case of silicon) is formed on the surface of the electrode substrate 120, and the conductive film is formed on the insulating film. The drive electrode portion 121, the wiring 123, and the electrode pad 124 are formed. The conductive film is formed of, for example, gold (Au), aluminum (Al), chromium (Cr), nickel (Ni), copper (Cu), platinum (Pt), or titanium (Ti) alone or appropriately stacked. As another manufacturing method, the drive electrode portion 121 can be formed by plating or screen printing.

  The place farthest from the central axis 115 of the drive electrode portion 121 is located inside the position where the end 118 of the mirror contacts the electrode substrate 120 when the movable mirror 111 contacts the electrode substrate 120. The shape of the drive electrode part 121 is substantially rectangular, and has a cutout part 127 at least in part (FIGS. 4A and 4B). With this configuration, the drive electrode portion is formed at a position that does not overlap the folded portion 191 of the folded beam when viewed from the facing direction of the mirror electrode portion and the electrode substrate. Here, the cutout portion 127 is produced by partially removing the drive electrode portion 121 once formed or by not forming the drive electrode portion 121 in a portion corresponding to the cutout portion 127 from the beginning. A folded portion 191 of the beam 114 is disposed above the notch portion 127 so as to face the notch portion 127.

  By using the drive electrode portion 121 having such a structure, an electrical short circuit between the folded portion 191 of the beam and the drive electrode portion 121, that is, an electrical short circuit between the movable mirror 111 and the drive electrode portion 121 can be avoided.

  The drive electrode 121 located on the extension line of the notch 127 and inside the notch 127 (that is, the side on which the central axis is projected) mainly applies an electrostatic attractive force to the beam 114. The beam 114 is thinner than the movable mirror 111, and the beam 114 supports the movable mirror 111 at a position biased toward the mirror electrode part in the thickness direction of the movable mirror 111. In other words, in the micromirror 100 of the present invention, the beam 114 is formed not on the reflecting surface 112 side but on the mirror electrode portion 113 side, that is, on the side facing the electrode substrate 120, so the distance between the beam 114 and the drive electrode portion 121 is small. . When the movable mirror 111 is in contact with the electrode substrate 120, particularly strong electrostatic attraction is generated. For this reason, a non-negligible electrostatic attractive force is generated between the drive electrode portion 121 and the beam 114. The electrostatic attractive force on the beam 114 is not the main driving force of the movable mirror 111. On the other hand, since an electrostatic attractive force is generated on the beam 114 itself, there is a risk of contact between the beam 114 and the drive electrode unit 121 at a place other than the folded portion 191 of the beam. In order to avoid this, all the drive electrode portions 121 immediately below the beam 114 are formed as notches so that the drive electrode portion 121 does not overlap the beam when viewed from the opposing direction of the mirror electrode portion and the electrode substrate. (FIG. 4 (c)).

It is desirable that the width of the drive electrode portion 121 exceeds the width of the movable mirror 111 (M _{W in} FIG. 3). Here, the width of the drive electrode portion 121 and the width of the movable mirror 111 mean dimensions in the direction of the central axis 115. By making the width of the drive electrode portion 121 larger than the width of the movable mirror 111, it is possible to suppress a decrease in driving force due to an assembly position shift. The size of the notch 127 is given in consideration of the assumed maximum assembly deviation.

  Next, the movement of the movable mirror will be described. On the electrode substrate 120, a drive electrode portion 121 for driving the movable mirror 111 with an electrostatic actuator is formed. The positional relationship between the movable mirror 111 and the drive electrode unit 121 is such that the drive electrode unit 121 and the movable mirror 111 are not electrically short-circuited when the movable mirror 111 contacts the electrode substrate 120. Specifically, the drive electrode unit 121 is disposed only at a position where the drive electrode unit 121 and the movable mirror 111 do not contact each other. On the electrode substrate 120, a protrusion is formed at a position where the central axis 115 of the movable mirror 111 is projected to the lower part, that is, the electrode substrate 120 side. In the movable mirror 111, one end 118 of the movable mirror is in contact with the electrode substrate 120, and the vicinity of the center of the surface of the movable mirror 111 on the side where the mirror electrode portion 113 is formed is in contact with the protrusion 122. Thus, the operating angle of the movable mirror 111 is given mechanically and stably.

  The movable mirror 111 illustrated in FIGS. 5A, 5B, 5C, and 5D has the shape of the end 118 of the mirror for the purpose of reducing the contact area between the movable mirror 111 and the electrode substrate 120. This is a modified embodiment. By reducing the contact area, when the movable mirror 111 contacts the electrode substrate 120 during operation, it contributes to suppression of adhesion between the movable mirror 111 and the electrode substrate 120. 5 (a), (b), (c), and (d) show examples of the shape on the reflecting surface side and each example of the shape of the end 118 of the mirror, but the combination of the two is not limited. Absent. 5 (a) and 5 (b), the thin portion 117 has a contact portion between the movable mirror 111 and the electrode substrate 120. However, in the embodiment of FIGS. 5 (c) and 5 (d), the movable mirror 111 and The thick portion 116 has a contact portion with the electrode substrate 120. In the embodiment of FIG. 5 (b), since the curve is formed at the end 118 of the mirror, the movable mirror 111 and the electrode substrate 120 are in point contact, and the contact area reduction effect is greatest. In the embodiment of FIG. 5C, the end 118 of the mirror having a thickness can be confirmed from the reflective surface 112 side. However, the end part of the mirror having the thick part is a part. FIG. 5D shows an example in which the mirror end portion 118 is not a thin portion. In the embodiment of FIG. 5D, the mirror end portion 118 having a thick portion is realized by partially processing the mirror electrode portion 113 side. In the form of FIG. 5D, the entire mirror end portion 118 has a thick portion. Since the end 118 of the mirror having the thick portion is strong, it is difficult to break. The end 118 of the mirror having the shape illustrated in FIGS. 5A, 5B, 5C, and 5D reduces the contact portion between the movable mirror 111 and the electrode substrate 120. FIG. Since the vicinity of the contact portion is a region where the movable mirror 111 and the electrode substrate 120 are close to each other, reducing the region changes the operating angle of the movable mirror due to foreign matter (dust) mixed in the region. This has the effect of avoiding this. The foreign matter (dust) contributes to an electrical short circuit.

  FIG. 6 shows another embodiment of the electrode substrate 120. The electrode substrate 120 in FIG. 6 has a dug portion 128. In the electrode substrate 120 shown in FIG. 6A, the digging portion 128 is at least from the end far from the central axis of the drive electrode portion 121 to the position where the end 118 of the movable mirror is in contact with the electrode substrate 120. Present in some. In the electrode substrate 120 shown in FIG. 6B, the digging portion 128 exists at a part of the position where the end 118 of the movable mirror contacts the electrode substrate 120. This figure shows that the digging portion 128 exists at a part of the position where the end 118 of the movable mirror contacts the electrode substrate 120, and the number of the digging portions 128 is not limited. The position where the digging portion 128 exists is a region where the movable mirror 111 and the electrode substrate 120 are close to each other. The digging portion 128 existing in the region has an effect of avoiding fluctuations in the operating angle of the movable mirror due to foreign matter (dust) mixed in the region. The foreign matter (dust) contributes to an electrical short circuit. FIG. 7 is a diagram showing the shape of the drive electrode portion 121 applied to the micromirror of the present invention in comparison with the movable mirror 111. FIG. 7 shows an example in which the width of the drive electrode portion 121 is larger than the width of the movable mirror 111. In FIG. 7, the drive electrode portion 121 and the positioning pattern 129 are indicated by dotted lines, and the outer shapes of the movable mirror 111, the beam 114, and the movable mirror substrate 110 are indicated by solid lines. Illustration of protrusions on the electrode substrate and unevenness of the movable mirror is omitted. In FIG. 7A, the entire bottom of the beam 114 is a notch 127. Since the distance between the movable mirror 111 and the movable mirror substrate 110 is wide, the end in the width direction of the drive electrode portion 121 can be confirmed from above. Therefore, it is possible to confirm the positional deviation between the assembled movable mirror substrate 110 and the electrode substrate 120. In FIG. 7B, the entire lower portion of the beam 114 is a notch 127. The distance between the movable mirror 111 and the movable mirror substrate 110 is partially wide and partially narrowed. By narrowing the distance between the movable mirror 111 and the movable mirror substrate 110, displacement of the movable mirror 111 when an impact in the width direction, that is, the vertical and horizontal directions in the drawing can be suppressed. On the other hand, the portion where the distance between them is wide, that is, the air vent hole 192 alleviates the slowing of the operation speed of the movable mirror 111 due to air resistance. Although the position and size of the air vent hole 192 are not limited in the figure, the air vent hole is preferably formed by providing a recess on the side of the movable mirror substrate 110 facing the movable mirror. According to such a configuration, the air escape function can be exhibited without changing the shape and strength of the movable mirror and without inhibiting the function of suppressing the displacement of the movable mirror in the vertical and horizontal directions in the drawing. When the width of the drive electrode portion 121 is larger than the width of the movable mirror 111, the end in the width direction of the drive electrode portion 121 cannot be confirmed from above. Therefore, by arranging the positioning pattern 129, the positional deviation between the assembled movable mirror substrate 110 and the electrode substrate 120 is confirmed.

  The positioning pattern 129 is also illustrated in FIG. The positioning pattern 129 is arranged on a line obtained by projecting the center axis 115 onto the electrode substrate, that is, along the center line dividing the pair of drive electrode portions 121. The positioning pattern 129 is arranged at a certain distance from the drive electrode portion. The position of the positioning pattern 129 is confirmed from the gap between the beams 114. One positioning pattern 129 may be arranged for one micromirror, for example, only on one side of the drive electrode portion 121. However, if it is arranged on both sides of the drive electrode portion 129 as in the example of FIG. Easy to recognize the position. The shape of the positioning pattern 129 is not limited. It may not be the illustrated square shape. For example, the positional relationship can be made clearer by making the positioning pattern a triangle and making the apex coincide with the center line. A triangular positioning pattern is illustrated in FIG. The positioning pattern 129 has the same potential as the movable mirror 111. Even if the beam 114 and the positioning pattern 129 come into contact with each other, no current flows. As a method of setting the positioning pattern 129 and the movable mirror 111 to the same potential, they may be connected via wiring arranged on the surface of the electrode substrate, or may be connected via the inside of the electrode substrate. The illustrated positioning pattern 129 is brought close to the drive electrode unit 121, that is, attached to the micromirror, but may be arranged near the outer periphery of the movable mirror substrate 110. In particular, when a plurality of micromirrors are arrayed, the positioning patterns of the plurality of micromirrors can be shared by a small number of positioning patterns arranged near the outer periphery of the movable mirror substrate. When the positioning pattern is disposed on the outer periphery of the movable mirror substrate, more precisely, when the positioning pattern is disposed outside the operation range of each movable mirror 111, the potential of the positioning pattern 129 does not need to be shared with the potential of the movable mirror 111. At this time, the potential of the positioning pattern may be in a state of floating in terms of an electric circuit. Further, it is not necessary to confirm the position of the positioning pattern 129 from the gap between the beams 114 of the micromirror. Such a positioning pattern is illustrated in FIG.

  The movable mirror 111 can be easily manufactured by maximizing the thickness of the portion having the reflecting surface 112. As an example of a method for manufacturing the movable mirror substrate 110, a manufacturing method using an SOI substrate will be described with reference to FIGS. An SOI substrate is used as a substrate on which the movable mirror substrate 110 is formed (FIG. 8A). A mirror electrode portion 113 is formed on the active layer 173 (Si layer) side of the SOI substrate, and a reflective surface is formed on the base layer (Si layer) 171. The SOI substrate is mirror-polished on both sides. The reason why the mirror electrode portion 113 is formed in the active layer 173 (Si layer) is that the active layer (Si layer) 173 side is thinner than the base layer (Si layer) 171 side. If the side is thicker than the base layer (Si layer) 171 side, the reflecting surface 112 is formed on the active layer (Si layer) 173 side. Usually, since the active layer (Si layer) 173 side is thinner than the base layer (Si layer) 171 side, a manufacturing method when the mirror electrode portion 113 is formed on the active layer (Si layer) 173 side will be described below.

The shape of the mirror electrode portion 113 and the shape of the beam 114 are patterned on the surface on the active layer (Si layer) 173 side by photolithography using a photoresist, an aluminum film, a silicon oxide film, or another mask material, and dried. Etching is performed (FIG. 8B). The arrows shown in FIG. 8B indicate the direction of etching. The thickness of the beam 114 is given by the thickness of the active layer (Si layer) 173. The movable mirror shape on the reflecting surface 112 side is patterned on the base layer (Si layer) 171 side with a photoresist, an aluminum film, a silicon oxide film, or other mask material, and dry etching is performed (FIG. 8C )). The arrows shown in FIG. 8C indicate the direction of etching. The movable mirror shape to be patterned on the reflecting surface 112 side is, for example, the shape shown in FIG. Since the thickness of the portion having the reflective surface 112 is given by the thickness of the base layer (Si layer) 171, the thickness of the movable mirror 111 is maximized in the portion having the reflective surface 112. The thickness of the thin portion 117 thinned by dry etching is a thickness obtained by adding the intermediate layer (SiO ₂ layer) 172 to the thickness of the active layer (Si layer) 173. The intermediate layer (SiO ₂ layer) 172 is removed by wet etching (FIG. 8D). The arrow shown in FIG. 8D indicates the etching progress direction. By this process, the movable mirror is connected to the movable mirror substrate 110 only by the beam 114. That is, it is in a state of being rotatable around the central axis 115 provided by the beam 114. The thickness of the thin portion 117 thinned by dry etching matches the thickness of the beam 114. An element constituting the movable mirror in the state shown in FIG. That is, the base body 119 indicates a portion formed of only the substrate used as a constituent material among the constituent elements of the movable mirror 111. Finally, a reflective film is formed on the reflective surface 112, and a conductive film is formed on the mirror electrode portion 113, for example, by sputtering or vapor deposition (FIG. 8E). Thereafter, the movable mirror substrate 110 is integrated with the electrode substrate 120 so that the active layer (Si layer) 173 side, that is, the beam 114 side faces the electrode substrate 120.

In the case of the method for manufacturing the movable mirror substrate 110 using the above-described SOI substrate, the thickness of each part of the movable mirror 111 can be controlled by the thickness of each layer of the SOI substrate, so that the manufacturing is easy. The reflecting surface 112 and the mirror electrode portion 113 are particularly required to be flat in order to maintain the optical characteristics. The flatness of the reflecting surface 112 and the mirror electrode portion 113 is ensured by the flatness of the SOI substrate whose both surfaces are mirror-polished. In the example of the manufacturing method described above, since the etching surface is not used as the reflection surface 112, it is not necessary to request flatness of the etching surface. In the above-described procedure, the intermediate layer (SiO ₂ layer) 172 of the SOI substrate can be used as an etch stop layer in dry etching (FIGS. 8B and 8C), so that the manufacturing can be facilitated. Similarly, when a layer having different etching rates is prepared by doping a dopant and a silicon substrate that functions as an etch stop layer is used as a material, the movable mirror substrate 110 can be easily manufactured. Description of an example of a manufacturing method using the substrate is based on a manufacturing method using an SOI substrate, and thus the description is omitted.

  In addition, the manufacturing method mentioned above is an example, Comprising: The manufacturing method of the micromirror 100 of this invention is not limited. For example, a structure in which silicon on the base layer (Si layer) 171 side is partially etched to an appropriate depth (for example, half) and the etching surface is used as the reflection surface 112 may be employed. FIG. 9A shows an embodiment of the electrostatically driven micromirror 100 in which the movable mirror 111 is etched by a certain amount and the etched surface is the reflecting surface 112. The reflective surface 112 is lower than the surface of the movable mirror substrate 110, and the portion having the reflective surface 112 is thinner than the movable mirror substrate 110. Further, the surface of the thick part 116 formed is also lower than the surface of the movable mirror substrate 110, and the thick part is also thinner than the movable mirror substrate 110. In the example of FIG. 9A, the thickness is the same as that of the reflecting surface 112. In the configuration of FIG. 9A, the movable mirror substrate 110 can be made thick, and the mass of the movable mirror substrate can be reduced while keeping the rigidity of the substrate high.

  As another example, a configuration example in which the thickness of the thick portion 116 is thinner than the thickness of the portion having the reflecting surface 112 and thicker than the thickness of the thin portion 117 which is the thinnest portion of the movable mirror 111 is shown in FIG. Shown in b). The configuration shown in FIG. 9B can be realized, for example, by intentionally generating side etching (the progress of etching from the side surface by the etchant that wraps around from the side surface of the mask) in the thick portion 116. Alternatively, it can be realized by intentionally etching the thick portion 116 in the middle of the etching process of FIG. 9C by making the mask thickness of the portion having the reflecting surface 112 thicker than the mask thickness of the thick portion 116. Can do. By reducing the thickness of the thick portion 116, the mass and moment of inertia of the movable mirror 111 can be reduced. In particular, reducing the thickness of the thick portion 116 near the end 118 of the mirror effectively contributes to the reduction of the moment of inertia. Although not clearly shown in the figure, the thickness of the thin portion 116 may not be uniform, and may be partially thinned. For example, the thickness near the reflecting surface 112 is the same as the thickness of the reflecting surface 112, and the thickness can be gradually decreased as the end 118 of the mirror is approached.

Next, an example of a method for manufacturing the electrode substrate 120 will be described with reference to FIGS. The electrode substrate 120 in FIG. 10 is an example in which the spacer 130 is integrally formed with the electrode substrate, and corresponds to a manufacturing example of the electrode substrate 120 used in the micromirror 100 in FIG. A silicon (Si) substrate 181 is used as a substrate for forming the electrode substrate 120 (FIG. 10A). The surface of the spacer 130 is patterned on the surface by photolithography using a photoresist, a silicon oxide film, or another mask material, and anisotropic wet etching using KOH (potassium hydroxide aqueous solution) or the like is performed on the etchant ( FIG. 10 (b)). The arrows shown in FIG. 10B indicate the direction of etching. In this step, a difference between the height of the spacer 130 and the height of the protrusion 122 is formed. The shape of the spacer 130 and the shape of the protrusion 122 are patterned on the surface by photolithography, and anisotropic wet etching using KOH (potassium hydroxide aqueous solution) or the like is performed on the etchant (FIG. 10C). The arrows shown in FIG. 10C indicate the direction of etching. A thermal oxide film (SiO ₂ ) is formed as an insulating film on the surface of the silicon (Si) substrate 181 (FIG. 10D). The digging portion 128 shown in FIG. 6 can be formed, for example, by removing the thermal oxide film. Finally, the conductive drive electrode portion 121, the wiring 123, and the electrode pad 124 are formed by sputtering or vapor deposition, for example (FIG. 10E). The drive electrode unit 121 has a notch 127. The positioning pattern 129 is efficient when manufactured in the same process as the drive electrode portion 121, but may be manufactured in a separate process.

  The above-described manufacturing method is an example, and the manufacturing method of the electrode substrate 120 is not limited. For example, the etching method may be isotropic wet etching or dry etching. Alternatively, the protrusion 122 and the spacer 130 can be formed by stacking. Since the height of the spacer 130 and the height of the protrusion 122 are different in the electrode substrate 120 of the present embodiment, the etching is performed twice. However, the heights of the both may be the same. It can be once. The electrode substrate 120 of this embodiment is an example in which the spacers 130 are integrally formed. However, when the spacers 130 are made of different members, the number of etchings can be one. Although a manufacturing method in the case where the spacer 130 is manufactured independently of the movable mirror substrate 110 and the electrode substrate 120 is not illustrated, the spacer 130 can be formed by adjusting the thickness of a silicon (Si) substrate by etching, for example. Furthermore, if necessary, the surface can be thermally oxidized to provide insulation, or a conductive film can be formed on the surface to provide conductivity.

  Hereinafter, a method for forming the micromirror 100 will be described. The micromirror 100 illustrated in FIG. 2 is formed by bonding, bonding, or fastening the electrode substrate 120 integrally formed with the spacer 130 illustrated in FIG. 1 and the movable mirror substrate 110 illustrated in FIG. The positional relationship between the movable mirror substrate 110 and the electrode substrate 120 is such that the surface having the beam 114 is close to the electrode substrate 120. The translational position of the movable mirror substrate 110 and the electrode substrate 120 in which the spacer 130 is integrally formed is formed by, for example, forming a positioning hole (not shown) in both and inserting a pin or a sphere into the positioning hole. The translational position of both can be controlled. As another example, a positioning pattern can be formed on the movable mirror substrate 110 and the electrode substrate 120 integrally formed with spacers, and the translational position of both can be controlled by pattern recognition (for example, image processing). The distance in the stacking direction between the movable mirror substrate 110 and the electrode substrate 120 is given by the accuracy of the spacer 130. When the micromirror 100 is formed by bonding, for example, an ultraviolet curable resin can be used as the adhesive. Alternatively, a thermosetting resin can be used. When the micromirror 100 is formed by bonding, for example, gold-tin solder or the like can be used. When the spacer 130 is manufactured independently of the movable mirror substrate 110 and the electrode substrate 120, or when the spacer 130 is formed integrally with the movable mirror substrate 110, the micromirror 100 can be manufactured by the same method.

  FIG. 11 shows another embodiment of the micromirror 100 of the present invention. A micromirror 100 shown in FIG. 11A is characterized in that the micromirror 100 is housed in a case 140 that can be sealed, and the inside of the case is filled with optical oil 150. Since the optical oil 150 filled around the micromirror 100 functions as a restraining force when an impact is applied to the movable mirror 111, the impact resistance of the movable mirror 111 can be improved. FIG. 11B is a view of the electrode substrate 120 shown in FIG. 11A viewed from the movable mirror substrate 110 side. The basic configuration is the same as that of the electrode substrate 120 described with reference to FIG. 1, but is characterized in that the end portion 118 of the movable mirror 111 has a resistance wiring 125 near the electrode substrate 120. The resistance wiring 125 is not in contact with the movable mirror 111. When the movable mirror 111 is started to operate, at least the resistance wiring 125 on the side where the end portion 118 of the movable mirror is approaching is energized, thereby generating bubbles 151 in the optical oil 150 on the resistance wiring 125. By applying a pushing force to the movable mirror 111 with the bubbles 151, an initial speed is given to the movable mirror 111, the operation of the movable mirror 111 is assisted, and the movable mirror 111 is prevented from sticking. The generation of bubbles 151 is shown in FIG.

  Since all the configurations based on the above-described embodiments have a configuration that avoids an electrical short circuit between the beam 114 that supports the micromirror 100 and the drive electrode unit 121, it is possible to avoid inoperability and breakage of the micromirror. A plurality of movable mirrors 111 constituting the micromirror 100 having the configuration are formed on the movable mirror substrate 110, and a corresponding number of drive electrode portions 129 are formed on the electrode substrate 120. The movable mirror substrate 111 and the electrode substrate By combining 120 and an appropriately provided spacer 130, a micromirror array in which a plurality of the above-described micromirrors 100 are integrated can be realized. The micromirror array can avoid inoperability and breakage of individual micromirrors. FIG. 12 shows a configuration example of the micromirror array 400. Although the micromirror array 400 of FIG. 12 is an array of the micromirrors 100 of the present invention, the micromirror array 400 of FIG. 12 does not limit the number of arrays of the micromirrors 100, the array arrangement, or the like. The number of arrays may be increased or decreased, and the array arrangement may be a two-dimensional matrix. In FIG. 12, the positioning pattern 129 is shared by eight micromirrors 110 arrayed. The positioning pattern is arranged on both the movable mirror substrate 110 and the electrode substrate 120.

  An optical switch using the micromirror of the present invention will be described with reference to FIG. Since the above-described micromirror 100 performs binary digital driving, a 1-input 2-output optical switch (1 × 2 optical switch) can be realized using the micromirror 100. FIG. 13 shows an embodiment of an electrostatic drive type 1-input 2-output optical switch (1 × 2 optical switch) using the micromirror of the present invention.

  The optical switch 200 shown in FIG. 13 includes an input port having an input side optical fiber 202a and an input side collimating lens 204a, a cylindrical lens 205, any one of the above-described micromirrors 100, output side collimating lenses 204b and 204c, and an output side. An output port 100 having optical fibers 202b and 202c is included as a component. In the embodiment shown in FIG. 13, the condensing optical system is arranged between the collimating lens and the micromirror, and the light beam is condensed on the reflection surface using the condensing optical system. In FIG. 13, a cylindrical lens is used as the condensing optical system.

Since the cylindrical lens 205 is used as a condensing optical system for condensing the light beam 209 on the reflection surface 112 of the micromirror 100 as a component of the optical switch 200, the reflection surface 112 of the micromirror 100 can be reduced in size. This will be described with reference to FIG. A region indicated by D ₀ in FIG. 14 is a light beam diameter on the reflection surface 112 when the condensing optical system is not used. The length of the reflecting surface 112 of the micro mirrors 100 to fully cover the region _{D 0} is _{L 0.} On the other hand, a hatched area D is the diameter of the light beam on the reflecting surface 112 when a cylindrical lens is used as the condensing optical system. The length L of the reflecting surface 112 that sufficiently covers the region D is obtained. That is, the reflecting surface 112 can be made small. As a result, since the mass and moment of inertia of the micromirror 100 can be reduced, the impact resistance and high-speed controllability of the micromirror 100 are improved. Note that the cylindrical lens 205 can be replaced with another condensing optical element (lens) as long as the light beam 209 has a property of condensing on the reflecting surface 112.

  The optical switch shown in FIG. 13 will be described in further detail together with its function. FIG. 13 includes one input-side optical fiber 202a and two output-side optical fibers 202b and 202c, and any one of the above-described micromirrors 100 includes the input-side optical fiber 202a and the first output-side optical fiber. In this configuration example, a first posture for forming an optical path between the optical fiber 202b and a second posture for forming an optical path between the input-side optical fiber 202a and the second output-side optical fiber 202c are selected. The optical switch 200 having such a configuration not only prevents inoperability and breakage due to an electrical short circuit, but also excels in temporal stability of the operating angle, and is effective in improving the optical characteristics of the optical switch. In the optical switch 200 having such a configuration, since the input side optical fiber 202a and the output side optical fibers 202b and 202c can be arranged in a straight line, a cylindrical lens can be applied as a condensing optical system.

  FIG. 13A is a diagram showing an optical path forming state from the input side optical fiber 202a to the first output side optical fiber 202c. In FIG. 13 (a), the movable mirror 111 takes the first posture. FIG. 13B is a diagram showing an optical path formation state from the input side optical fiber 202a to the second output side optical fiber 202b. In FIG. 13 (c), the movable mirror 111 takes the second posture. FIG. 13C is a diagram showing a state where no driving force is applied to the movable mirror 111.

  The optical switch of the present invention can also be realized by each configuration shown in FIG. FIG. 15A shows a configuration of an optical switch in which the optical fibers 202 are arranged at an angle. Any of the micromirrors according to the present invention is used as the light deflection means. Incident light from the optical fiber 202 a is collimated by the collimating lens 204 a and enters the reflecting surface 112 of the movable mirror 111. The optical path 209 is switched by the rotation of the movable mirror 111 to switch the coupling between the optical fibers 202b and 202c. The light reflected by the movable mirror 111 is collected by the collimating lens 204b or 204c before being recombined with the optical fiber 202b or 202c. The optical switch 200 having this configuration can avoid inoperability or damage due to an electrical short circuit between the beam 114 and the drive electrode unit 121 and a current flow by using any one of the micromirrors according to the present invention.

  In the configuration example of FIG. 15B, a collimating lens array is disposed between the optical fibers 202a, 202b, 202c and the movable mirror 111, and collimating lenses 204a, 204b, 204c are placed on the respective optical fibers. Yes. Here, at least some of the plurality of optical fibers, for example, in the example of FIG. 15B, collimating lenses 204a and 204c facing the optical fibers 202a and 202c are offset. The offset arrangement means that the optical axis of the optical fiber is shifted from the optical axis of the collimating lens. When the optical axis of the optical fiber is shifted from the optical axis of the collimating lens, the optical axis of the light beam 209 after passing through the collimating lens is deflected in the direction opposite to the direction of shift of the optical fiber. Therefore, when the optical fiber 202a is shifted in the direction away from the optical fiber 202b with respect to the collimating lens 204a in FIG. 15B, the optical axis of the light beam 209 is deflected toward the center of the micromirror. As a result, incident light from the optical fiber 202 a is reflected by the reflecting surface of the movable mirror 111. When the reflected light is directed to the collimating lens 204c, the light beam is coupled to the optical fiber 202c by shifting the optical fiber 202c away from the optical fiber 202b with respect to the collimating lens 204c. In this configuration, the number of optical elements can be reduced by eliminating the need for a cylindrical lens while taking advantage of the characteristics of the micromirror 100 of the present invention, that is, the feature that can prevent the optical switch from becoming inoperable or damaged. Further, since the input / output side optical fibers 202 are arranged in parallel, they are easily arranged.

  15C, the fixed mirror 230 is disposed between the collimating lenses 204a, 204b, and 205c and the movable mirror 111, and the incident light from the optical fiber 202a is collected on the reflecting surface of the movable mirror 111. The light reflected by the reflecting surface is coupled to the optical fiber 202c. Instead of the offset arrangement of the collimating lens in FIG. 15B, a fixed mirror 230 is used. The optical fibers 202 on the input / output side are arranged in parallel as in the case of FIG. Since the fixed mirror 230 is an optical component excellent in reflection loss and wavelength dependent loss, in this configuration, the use of the micromirror 100 of the present invention can prevent the optical switch from becoming inoperable or damaged. In addition, an improvement in optical characteristics of the optical switch 200 can be expected. Further, the fixed mirror 230 has an advantage that it can be easily manufactured as compared with a condensing optical system (lens).

  FIGS. 13 and 15 show examples in which the micromirror of the present invention is applied to an optical switch. However, instead of a part of the optical fiber, a photodetector such as a photodiode is arranged to constitute a photodetector. Also good. Or you may comprise the optical device which switches the advancing direction of the light emitted from the laser light source with the micromirror of the present invention and couples it to a desired optical fiber. While the micromirror of the present invention is excellent as a light deflecting means as described above, there is no limitation on its application form, so that it can be widely applied to optical components that require the light deflecting means. That is, various optical components can be configured by using the micromirror of the present invention as a light deflection unit.

  An example in which the micromirror according to the present invention is applied to the 1 × 2 optical switch shown in FIG. 13 and the 1 × 2 optical switch is arrayed to form an optical switch array 300 is shown in FIG. The mirror, micromirror array, and optical switch will be described in more detail.

  The optical switch array 300 illustrated in FIG. 16 includes an optical fiber array 203, a collimating lens array 204, a cylindrical lens 205, and an electrostatically driven micromirror 100 as constituent elements. The optical switch array 300 shown in FIG. 16 is an optical switch array in which 8 sets of 1 × 2 optical switches that operate independently are integrated. However, FIG. 16 does not limit the number of 1 × 2 optical switches that can be integrated. Moreover, the application device of the micromirror 100 of this invention is not limited. Each 1 × 2 optical switch element has the structure shown in FIG. The micromirror 100 used in each 1 × 2 optical switch element is the micromirror shown in FIGS. The movable mirror 111 determines the operating angle when the end 118 of the mirror and the vicinity of the center of the mirror electrode portion 113 are in contact with the electrode substrate 120 and the protrusion 122. During the switching operation of the optical switch 200, the contact between the movable mirror 111 and the protrusion 122 is temporarily released.

  The optical fiber array 203 includes 24 optical fibers 202 and substrates (optical fiber alignment substrates) 218 and 219 for aligning the fibers as constituent elements. Since the present embodiment integrates eight sets of 1 × 2 optical switches, 24 optical fibers 2 are arranged in three directions in one direction and eight in a direction orthogonal thereto. Here, the three arranged optical fibers correspond to one input optical fiber and two output optical fibers corresponding to one 1 × 2 optical switch. This arrangement direction is defined as a switching direction. An arrangement direction orthogonal to the switching direction is defined as an integration direction. The definition of the switching direction and the integration direction is described in FIG.

  In this embodiment, the optical fiber pitch in the switching direction is 0.5 mm, and the optical fiber pitch in the integration direction is 1 mm. In the optical fiber array 203, the optical fibers are accurately aligned. In this embodiment, the optical fibers are aligned using an optical fiber alignment substrate 218 having optical fiber alignment holes formed therein. The alignment accuracy of the optical fiber array 203 is given by the accuracy of the optical fiber alignment holes formed in the optical fiber alignment substrate 218.

  In this embodiment, since 8 sets of 1 × 2 optical switches are integrated, three collimating lens arrays 204 are arranged in the switching direction, and a total of 24 collimating lenses arranged in the integration direction are used as constituent elements. Have. Here, the definition of the switching direction and the integration direction conforms to the direction defined by the optical fiber array 203. The pitch of the collimating lens array 204 is made to correspond to the pitch of the optical fiber array 203. In this embodiment, the collimating lens array has a switching direction pitch of 0.5 mm and an integration direction pitch of 1 mm. In this embodiment, the collimating lens array 204 is manufactured by etching a silicon substrate having a substrate thickness of 0.625 mm. An antireflection film corresponding to the wavelength of light to be used (1300 to 1650 nm) is formed on the front and back surfaces of the collimating lens array 204. The collimating lens array 204 has a structure in which a side facing the optical fiber array 203 is a flat surface and a convex lens is formed on the side facing the cylindrical lens 205. Each collimating lens constituting the collimating lens array 204 is a spherical convex lens having a lens diameter of 0.45 mm, and its radius of curvature is 3 mm. The gap between the optical fiber alignment substrate 218 and the collimating lens array 204 is selected so that the light emitted from the input optical fiber becomes a collimated beam having desired characteristics.

  In the present embodiment, one cylindrical lens 205 is shared by eight 1 × 2 optical switches. The cylindrical lens 205 is made of optical glass (BK7), has a radius of curvature of 3.58 mm, and a focal length of 7.15 mm. On the cylindrical lens 205, an antireflection film corresponding to the wavelength (1300 to 1650 nm) of light used on the front and back surfaces is formed. The cylindrical lens 205 is arranged so that the curved surface side faces the collimating lens array 204 and the flat surface side faces the micromirror 110.

  Since this embodiment integrates eight sets of 1 × 2 optical switches, it has eight micromirrors 100 of the present invention. Each micromirror 100 has a uniaxially rotatable structure taking a central axis 115 in the arrangement direction of the micromirrors. The arrangement direction of the micromirrors is a direction corresponding to the integration direction of the optical fiber array 203 and the collimating lens array 204. Therefore, the micromirrors 100 are arranged in a line at a pitch corresponding to the pitch in the integration direction of the optical fiber array 203. In this embodiment, the pitch of the micromirrors 100 is 1 mm.

The movable mirror substrate 110 is made of an SOI having an active layer (Si layer) 173 thickness of 10 μm, an intermediate layer (SiO ₂ layer) 172 thickness of 1 μm, and a base layer (Si layer) 171 thickness of 300 μm. The movable mirror 111 is manufactured by the method shown in FIG. The thickness of the portion having the reflecting surface 112 and the thickness of the thick portion of the movable mirror are 311 μm, which is the same as the initial thickness of the SOI substrate. The thickness of the thin part 117 of the movable mirror and the thickness of the beam 114 are 10 μm, which is the thickness of the SOI active layer (Si layer).

The length (M _{L in} FIG. 3) in the direction orthogonal to the central axis 115 of the surface opposite to the side having the reflecting surface of the movable mirror is 1735 μm, and the maximum width in the direction along the central axis 115 (M _{W in} FIG. 3). ) Is 500 μm. The movable mirror 111 is operated until it contacts the electrode substrate 120. In the movable mirror 111 and the electrode substrate 120, the end 118 of the mirror is in contact with the electrode substrate 120, and the vicinity of the center of the surface opposite to the side having the reflecting surface is in contact with the protrusion 122, thereby realizing an inclination angle of 1 degree. . The drive electrode portion 121 is not disposed at the portion of the electrode substrate 120 where the mirror end portion 118 contacts.

  The light emitted from the input-side optical fiber 202a and converted into a collimated beam by the corresponding collimator lens 204a becomes a quasi-elliptical shape having a major axis in the moving mirror arrangement direction on the reflecting surface 112 of the movable mirror by the action of the cylindrical lens 205 ( (See FIG. 14). On the reflecting surface 112, the light is 0.2 to 0.25 mm in the major axis direction and 0.1 to 0.15 mm in the minor axis direction, so that the reflecting surface 112 of the movable mirror is 0.4 mm × 0.3 mm. The shape of the thick portion 116 on the reflecting surface side is the shape shown in FIG. The line width of the thick portion 116 is 50 μm.

  The movable mirror 111 is supported by a pair of beams 114, which are elastic members, and the beams 114 are connected to a substrate (movable mirror substrate) 110 on which the movable mirror is formed. The beam 114 secures a relatively large electrostatic attraction as a folded beam so that the movable mirror 111 rotates and sinks, that is, the movable mirror 111 is easily displaced in the direction in which the movable mirror 111 contacts the protrusion 122. The beam width is 15 μm, and the beam thickness is 10 μm, which is the same as the thickness of the active layer (Si layer) of the SOI substrate on which the movable electrode substrate is manufactured. The length of the beam, that is, the length of the rod-shaped member constituting the beam 114 is 760 μm. The number of beam folds is three. By providing a beam of the above dimensions, the optical switch 200 can be operated at 40V.

A drive electrode portion 121 for driving the movable mirror 111 is formed on the electrode substrate 120. On the electrode substrate 120, a 15 μm protrusion 122 and an 18 μm spacer 130 are formed. The electrode substrate 120 is manufactured by the method shown in FIG. The electrode substrate 120 is made of silicon (Si), and after a thermal oxide film (SiO ₂ film) is formed on the surface of the silicon substrate, the drive electrode portion 121 having the notch 127, the wiring 123, the electrode pad 124, ( The positioning pattern 129) is formed of a film having a gold (Au) surface. The width of the drive electrode portion 121 is set to be larger by 50 μm on one side than the maximum width 500 μm of the movable mirror 111, that is, the width is 600 μm. The notch 127 is enlarged by 50 μm in each direction over the entire area where the beam 114 is projected.

The micromirror of this example has a mass and a moment of inertia of 2.5 × 10 ⁻⁷ [kg] and 6.3 × 10 ⁻¹⁴ [kg · m ² ], respectively. However, the density of silicon (Si) was 2330 [kg / m ³ ]. The mass and moment of inertia of the configuration example in which the entire movable mirror is 311 μm, which is the initial thickness of the SOI substrate, are 6.3 × 10 ⁻⁷ [kg] and 1.8 × 10 ⁻¹³ [kg · m. ² ] is reduced to 0.4 times and 0.35 times, respectively. Therefore, when supported by a beam having the same rigidity, the impact resistance is inversely proportional to the mass and is improved by 2.5 times, and the resonance frequency of the rotational operation is inversely proportional to the square root of the moment of inertia and is improved by 1.7 times. Further, when the entire movable mirror is 10 μm, which is the thickness of the active layer (Si layer), the resistance to warpage is improved to the square of the thickness, that is, 900 times or more. Note that the SOI substrate of this embodiment has a sufficient thickness and is suitable in terms of easy handling. By using the micromirror according to the present invention for the optical switch of this configuration, it is possible to provide an optical switch that avoids inoperability and damage due to an electrical short circuit. In the above-described embodiment, the configuration according to the present invention is applied to a micromirror having a maximum reflective surface dimension of less than 1 mm. However, a mirror having a maximum reflective surface dimension of 1 mm or more is allowed if functional and structural restrictions permit. It is also possible to apply to.

It is a figure which shows embodiment of the electrode substrate applied to the micromirror of this invention. It is sectional drawing which shows embodiment of the micromirror of this invention. It is a figure which shows the shape by the side of the reflective surface of the movable mirror board | substrate applied to the micromirror of this invention. It is a figure which shows the shape of the electrode substrate applied to the micromirror of this invention. It is a figure which shows the shape by the side of the reflective surface of the movable mirror applied to the micromirror of this invention. It is a figure which shows embodiment of the micromirror of this invention. It is a figure which shows the shape of the electrode substrate applied to the micromirror of this invention. It is a figure which shows the example of a manufacturing method of the movable mirror board | substrate applied to the micromirror of this invention. It is a figure which shows embodiment of the micromirror of this invention. It is a figure which shows the example of the preparation methods of the electrode substrate applied to the micromirror of this invention. It is a figure which shows embodiment of the micromirror of this invention. It is a figure which shows embodiment of the micromirror array of this invention. It is a figure which shows embodiment of the optical switch using the micromirror of this invention. It is a figure which shows the effect of using a condensing optical element in embodiment of the optical switch using the micromirror of this invention. It is a figure which shows embodiment of the optical switch using the micromirror of this invention. It is a figure which shows embodiment of the optical switch array which arrayed the optical switch using the micromirror of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Micro mirror 110: Movable mirror board | substrate 111: Movable mirror 112: Reflecting surface 113: Mirror electrode part 114: Beam 115: Center axis 116: Thick part 117: Thin part 118: End part 119: Base | substrate 120: Electrode board 121 : Driving electrode part 122: protrusion 123: wiring 124: electrode pad 125: resistance wiring 126: resistance wiring pad
127: Notch portion 128: Dimmed portion 129: Positioning pattern 130: Spacer 132: Reflective film 140: Housing 150: Optical oil 151: Bubble 160: Outer frame portion 162: Second beam portion 171: Base layer 172: Intermediate layer 173: active layer 181: silicon substrate
191: Folding part 192: Air vent hole 200: Optical switch 202, 202a, 202b, 202c: Optical fiber 203: Optical fiber array 204: Collimating lens array 204a, 204b, 204c: Collimating lens 205: Cylindrical lens 209: Optical path (light beam)
218, 219: Optical fiber alignment substrate 230: Fixed mirror 300: Optical switch array 400: Micro mirror array

Claims (7)

In an electrostatically driven micromirror that includes a movable mirror substrate having a movable mirror supported by a beam and an electrode substrate, and the movable mirror rotates about the beam as a central axis.
The movable mirror has a reflective surface on one surface, and has a mirror electrode portion on a surface opposite to the surface having the reflective surface,
The mirror electrode portion is disposed opposite to the electrode substrate,
The electrode substrate has a drive electrode unit that generates electrostatic attraction between the mirror electrode unit,
The beam is a folded beam in which a plurality of bar-shaped members extending in a direction perpendicular to the central axis are folded back,
The drive electrode portion is formed so as not to overlap the folded portion of the beam as seen from the facing direction of the mirror electrode portion and the electrode substrate.
The micromirror which has the operation state which the edge part of the said movable mirror contacts with the said electrode substrate.   The thickness of the beam is thinner than the thickness of the movable mirror, and the beam supports the movable mirror at a position biased toward the mirror electrode portion in the thickness direction of the movable mirror. The micromirror described in 1.   3. The micromirror according to claim 1, wherein the drive electrode portion is formed so as not to overlap the beam when viewed from a facing direction of the mirror electrode portion and the electrode substrate.   The width of the drive electrode portion is larger than the width of the movable mirror except for a portion under the beam when viewed from the opposing direction of the mirror electrode portion and the electrode substrate. 4. The micromirror according to any one of 3.   5. The micromirror according to claim 1, wherein the movable mirror substrate is made of an SOI substrate.   A micromirror array in which a plurality of the micromirrors according to any one of claims 1 to 5 are integrated.   An optical switch using the micromirror or the micromirror array according to any one of claims 1 to 6.

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