JP2015227899A - Mirror driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mirror driving device capable of eliminating conduction failure due to a short circuit.SOLUTION: A mirror driving device 1 comprises a fixed frame, a movable frame 14, a mirror, and a permanent magnet 10. The movable frame 14 includes a substrate 100, a drive coil 18, a covering layer 102, and an insulator layer 104. The substrate 100 includes a groove part 100a located on the side of a main surface S4 and extending spirally. The drive coil 18 is made up of a metallic material disposed in the groove part 100a. The covering layer 102 extends to the main surface S4 so as to cover an opening of the groove part 100a and is made up of a metallic material preventing the diffusion of the metallic material of which the drive coil 18 is made up. The insulator layer 104 is disposed over the main surface S4 and the covering layer 102. A lead-out conductor 28b electrically connected to an inner end part of the drive coil 18 sterically intersects with the drive coil 18 through the insulator layer 104.

Description

  The present invention relates to a mirror driving device.

  2. Description of the Related Art In recent years, research on mirror driving devices using MEMS (Micro Electro Mechanical System) technology (also referred to as micromachine technology) in which mechanical elements and electronic circuit elements of minute sizes are fused has been actively conducted. As an example of the mirror drive device, Patent Document 1 discloses an electromagnetic mirror drive device including a fixed frame, a movable frame, a mirror, a drive coil, and a pair of permanent magnets.

  The movable frame is rotatably attached to the fixed frame via a pair of torsion bars extending on the same straight line. The mirror is disposed on the surface of the movable frame. The drive coil is disposed on the movable frame and is wound in a spiral shape when viewed from a direction orthogonal to the surface of the mirror. The pair of permanent magnets are arranged such that the drive coil is positioned in the direction intersecting the direction in which the pair of torsion bars extend.

  When a current flows through the drive coil, Lorentz force is generated in the drive coil due to the interaction with the magnetic field generated between the pair of permanent magnets, and the movable frame rotates relative to the fixed frame. When the movable frame rotates, the direction of the mirror disposed on the surface of the movable frame changes, and the optical path of the reflected light from the mirror is changed. Such a mirror driving device is applied to, for example, an optical switch for optical communication, an optical scanner, and the like.

JP 2008-122955 A

  The drive coil is formed by a so-called damascene method in which a metal material (for example, Cu) is buried in a spiral groove formed on the surface of a silicon substrate serving as a movable frame via a seed layer. In particular, when the metal material is Cu, the damascene method is preferably used because it is difficult to reduce the size by etching. After the metal material is embedded in the groove, the surface is flattened by, for example, chemical mechanical polishing (CMP).

  Since the drive coil is wound in a spiral shape when viewed from the direction orthogonal to the surface of the mirror, it requires a lead conductor for pulling out the end located inside. Therefore, after the planarization step, the surface of the drive coil excluding both ends is covered with an insulating layer, and the lead conductor is patterned so as to cross three-dimensionally with the drive coil via the insulating layer. Thus, one end of the lead conductor is connected to the inner end of the drive coil, and the other end of the lead conductor is drawn to the outside of the drive coil.

  However, the metal material constituting the drive coil may diffuse into the insulating layer, causing a short circuit between adjacent wires in the drive coil or between the drive coil and the lead conductor. In particular, when the metal material is Cu, it is easy to diffuse into the insulating layer, and the possibility of occurrence of a short circuit has increased.

  Therefore, an object of the present invention is to provide a mirror driving device capable of eliminating a conduction failure due to a short circuit.

  A mirror driving device according to one aspect of the present invention is disposed on a surface of a movable frame, a movable frame supported rotatably with respect to the stationary frame via a torsion bar extending on the same straight line. The movable frame includes a mirror and a magnet that forms a magnetic field around the movable frame, and the movable frame includes a main surface and a groove that is located on the main surface side and extends in a spiral shape when viewed from a direction orthogonal to the main surface. The substrate includes the base metal, the first metal material disposed in the groove, and covers the drive coil wound in a spiral shape when viewed from the direction orthogonal to the main surface, and the opening of the groove A coating layer made of a second metal material that extends to the main surface and suppresses diffusion of the first metal material, and a first insulating layer disposed on the main surface and the coating layer Has the inner end of the drive coil The lead conductor is electrically connected to one end, the other end of the lead conductor is drawn to the outside of the drive coil, and the lead conductor is three-dimensionally connected to the drive coil via the first insulating layer. Crossed.

  In the mirror driving device according to one aspect of the present invention, the coating layer made of the second metal material that suppresses the diffusion of the first metal material extends to the main surface so as to cover the opening of the groove. Therefore, it is difficult for the first metal material constituting the drive coil to diffuse into the first insulating layer, and a short circuit occurs between adjacent wirings in the drive coil or between the drive coil and the lead conductor. Is prevented. Therefore, it is possible to eliminate a conduction failure due to a short circuit. Along with this, a drive coil wound at high density is realized, so that a larger current can be passed through the drive coil. As a result, since a larger Lorentz force can be applied to the drive coil, a mirror drive device with a large movable range of the mirror can be obtained.

  The first metal material may be Cu or Au. Even when Cu or Au, which has a low electrical resistivity but is relatively easy to diffuse, is used as the first metal material, the coating layer can suppress the diffusion of these materials. Therefore, it is possible to prevent the occurrence of a short circuit while reducing the electrical resistivity of the drive coil.

  The second metal material may be Al or an alloy containing Al. In this case, the diffusion of the first metal material can be suppressed extremely well.

  The base material may have a 2nd insulating layer arrange | positioned along the main surface and the inner wall face of a groove part.

  The base material may be made of silicon, and the second insulating layer may be made of silicon oxide obtained by thermally oxidizing silicon.

  A seed layer may be disposed between the second insulating layer and the first metal material. In this case, the first metal material can be grown on the seed layer using electroplating.

  The seed layer may be made of TiN.

  ADVANTAGE OF THE INVENTION According to this invention, the mirror drive device which can eliminate the conduction defect by a short circuit can be provided.

FIG. 1 is a plan view showing a mirror driving device according to this embodiment. 2 is a cross-sectional view taken along line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. 3 is a cross-sectional view taken along line IV-IV in FIG.

  Embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are exemplifications for explaining the present invention and are not intended to limit the present invention to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  As shown in FIGS. 1 and 2, the mirror drive device 1 according to the present embodiment includes a permanent magnet 10, a fixed frame 12, a movable frame 14, and a mirror 16.

  The permanent magnet 10 is a flat plate having a rectangular shape. The permanent magnet 10 has a pair of main surfaces 10a and 10b. The permanent magnet 10 forms a magnetic field around the movable frame 14 (around drive coils 18 and 20 described later). In the present embodiment, the main surface 10a side is the N pole, and the main surface 10b side is the S pole. The main surface 10a side may be the S pole, and the main surface 10b side may be the N pole. The thickness of the permanent magnet 10 can be set to about 2 mm to 3 mm, for example.

  The fixed frame 12 is a frame having a rectangular shape. The fixed frame 12 is disposed on the main surface 10 a of the permanent magnet 10. The thickness of the fixed frame 12 can be set to about 250 μm to 300 μm, for example.

  The movable frame 14 is located in the opening of the fixed frame 12. The movable frame 14 includes an outer portion 14a positioned on the outer side, an inner portion 14b positioned on the inner side of the outer portion 14a, and a mirror arrangement portion 14c positioned on the inner side of the inner portion 14b and on which the mirror 16 is disposed.

  The outer portion 14a and the inner portion 14b are flat frame bodies that have a rectangular shape. The outer portion 14 a is separated from the permanent magnet 10 and the fixed frame 12. The outer portion 14 a has a main surface S <b> 1 that faces away from the permanent magnet 10. The outer portion 14a is rotatably attached to the fixed frame 12 via a pair of torsion bars 22 extending on the same straight line. The torsion bar 22 may have a linear shape or a meandering shape.

  A drive coil 18 is disposed on the main surface S1 side of the outer portion 14a. The drive coil 18 is wound in a plurality of turns in a spiral shape when viewed from a direction orthogonal to the main surface S1 (the surface of the mirror 16). One end of the drive coil 18 is located outside the drive coil 18, and the other end of the drive coil 18 is located inside the drive coil 18. One end of a lead conductor 28 a is electrically connected to the outer end of the drive coil 18. One end of the lead conductor 28 b is electrically connected to the inner end of the drive coil 18.

  The lead conductors 28a and 28b are drawn from the outer portion 14a to the fixed frame 12 via the torsion bar 22. The other ends of the lead conductors 28 a and 28 b are electrically connected to electrodes 30 a and 30 b disposed on the surface of the fixed frame 12. The electrodes 30a and 30b are connected to a power source (not shown). The lead conductor 28b crosses the drive coil 18 three-dimensionally so as to pass above the drive coil 18.

  The inner part 14b is separated from the outer part 14a. The inner portion 14 b has a main surface S <b> 2 that faces away from the permanent magnet 10. The inner side part 14b is rotatably attached to the outer side part 14a via a pair of torsion bars 24 extending on the same straight line as the torsion bar 22. The torsion bar 24 may have a linear shape or a meandering shape.

  A drive coil 20 is disposed on the main surface S2 side of the inner portion 14b. The drive coil 20 is wound in a plurality of turns in a spiral shape when viewed from a direction orthogonal to the main surface S2 (the surface of the mirror 16). One end of the drive coil 20 is located outside the drive coil 20, and the other end of the drive coil 20 is located inside the drive coil 20. One end of the lead conductor 32 a is electrically connected to the outer end of the drive coil 20. One end of the lead conductor 32 b is electrically connected to the inner end of the drive coil 20.

  The lead conductors 32 a and 32 b are drawn from the inner part 14 b to the fixed frame 12 through the torsion bar 22, the outer part 14 a and the torsion bar 22. The other ends of the lead conductors 32a and 32b are electrically connected to electrodes 34a and 34b arranged on the surface of the fixed frame 12. The electrodes 34a and 34b are connected to a power source (not shown). The lead conductor 32a crosses the drive coil 18 in three dimensions so as to pass over the drive coil 18. The lead conductor 32b crosses the drive coils 18 and 20 in three dimensions so as to pass above the drive coils 18 and 20.

  The mirror arrangement part 14c is a circular disk. The mirror arrangement portion 14 c has a main surface S <b> 3 that faces away from the permanent magnet 10. The mirror arrangement part 14c is attached to the inner part 14b via a pair of support beams 26 extending on the same straight line. Since the mirror arrangement portion 14c is connected to the inner portion 14b via the support beam 26, Joule heat generated in the drive coils 18 and 20 can hardly be transferred to the mirror arrangement portion 14c, and the mirror arrangement portion 14c is deformed. Can be suppressed. In this embodiment, the facing direction of the support beam 26 intersects the facing direction of the torsion bars 22 and 24.

  The mirror 16 is arrange | positioned on main surface S3 of the mirror arrangement | positioning part 14c. The mirror 16 is a light reflecting film composed of a metal thin film. Examples of the metal material used for the mirror 16 include aluminum (Al), gold (Au), and silver (Ag).

  Next, the detailed configuration of the drive coils 18 and 20 will be described below. Since the configuration of the drive coils 18 and 20 is the same in this embodiment, the drive coil 18 will be described below, and the description of the drive coil 20 will be omitted.

  As shown in FIGS. 3 and 4, the outer portion 14 a includes a base material 100, a drive coil 18, a covering layer 102, and an insulating layer 104. The base material 100 has a groove portion 100 a having a shape corresponding to the drive coil 18. That is, the groove portion 100a extends in a spiral shape when viewed from the main surface S4 side of the base material 100a. Such a groove portion 100a can be formed, for example, by forming a mask having a predetermined pattern on the surface of the flat substrate 100 and then etching the substrate 100 through the mask. The base material 100 is made of, for example, Si. The thickness of the base material 100 can be set to, for example, about 20 μm to 60 μm.

An insulating layer 100b is disposed on the surface S4 of the substrate 100 and the inner wall surface of the groove portion 100a. The insulating layer 100b is a thermal oxide film obtained by thermally oxidizing the base material 100. Insulating layer 100b is, for example, SiO _2. A seed layer 100c is disposed on the inner wall surface of the groove 100a. That is, the seed layer 100 c is located between the insulating layer 100 b and the drive coil 18. The seed layer 100c is obtained by sputtering a dense metal material having adhesion to the metal material constituting the drive coil 18 on the substrate 100 (insulating layer 100b). An example of the metal material constituting the seed layer 100c is TiN.

  A metal material constituting the drive coil 18 is disposed in the groove 100a and on the seed layer 100c. The drive coil 18 is obtained by embedding the metal material on the seed layer 100c by the damascene method. Examples of a method for embedding the metal material in the groove 100a include plating, sputtering, and CVD.

  After disposing the metal material in the groove 100a, the main surface S4 side may be flattened by chemical mechanical polishing. In this flattening step, a boundary portion 100d of the drive coil 18 that contacts the seed layer 100c may be locally thinned due to a potential difference generated between the drive coil 18 and the seed layer 100c. Examples of the metal material include Cu or Au. The thickness of the drive coil 18 can be set to about 5 μm to 10 μm, for example.

  The covering layer 102 extends to the main surface S4 so as to cover the opening of the groove 100a. That is, the coating layer 102 covers the entire surface on the main surface S1, S4 side of the drive coil 18 when viewed from the direction orthogonal to the main surfaces S1, S4 (surface of the mirror 16), and Of these, the periphery of the groove 100a is covered. The coating layer 102 is obtained by depositing a metal material on the entire upper surface of the substrate 100 by, for example, a sputtering method or a CVD method, and then patterning.

  The metal material constituting the coating layer 102 has a function of suppressing diffusion of the metal material constituting the drive coil 18. Examples of the metal material constituting the coating layer 102 include Al or an alloy containing Al. Examples of the alloy containing Al include an Al—Si alloy, an Al—Cu alloy, and an Al—Si—Cu alloy. The composition ratio of the Al—Si alloy can be, for example, 99% for Al and 1% for Si. The composition ratio of the Al—Cu alloy can be, for example, 99% for Al and 1% for Cu. The composition ratio of the Al—Si—Cu alloy can be, for example, Al 98%, Si 1%, and Cu 1%. The thickness of the covering layer 102 can be set to about 1 μm, for example.

The insulating layer 104 is disposed so as to cover the substrate 100 and the covering layer 102. Examples of the material forming the insulating layer 104 include SiO ₂ , SiN, and TEOS. On the insulating layer 104, lead conductors 28a, 28b, 32a, 32b are arranged. That is, the lead conductors 28 a and 28 b are separated from the drive coil 18 through the insulating layer 104 and the covering layer 102.

  In the present embodiment as described above, the covering layer 102 is made of a metal material that suppresses the diffusion of the metal material that constitutes the drive coils 18 and 20, and on the main surface S4 so as to cover the opening of the groove portion 100a. It extends to. Therefore, it is difficult for the metal material constituting the drive coils 18 and 20 to diffuse into the insulating layer 104, and between the adjacent wirings of the drive coils 18 and 20, or between the drive coils 18 and 20 and the lead conductors 28b, 32a, and 32b. The occurrence of a short circuit is prevented. Therefore, it is possible to eliminate a conduction failure due to a short circuit. Accordingly, the drive coils 18 and 20 wound at a high density are realized, so that a larger current can be supplied to the drive coils 18 and 20. As a result, since a larger Lorentz force can be applied to the drive coils 18 and 20, the mirror drive device 1 having a large movable range of the mirror 16 can be obtained.

  By the way, in the flattening process, when the boundary portion in contact with the seed layer of the drive coil is locally thinned, in the conventional mirror drive device without the covering layer 102, the drive coil and the insulating layer covering the drive coil The distance from the formed lead conductor is reduced, and in particular, a short circuit is likely to occur. However, in the present embodiment, the covering layer 102 extends to the main surface S4 so as to cover not only the surfaces of the drive coils 18 and 20 but also the opening of the groove 100a. Therefore, even if the boundary portion 100d is locally thinned, it is possible to prevent a conduction failure due to a short circuit.

  In the present embodiment, the metal material constituting the drive coils 18 and 20 is Cu or Au. Even when the drive coils 18 and 20 are configured using Cu or Au, which is a material that has a low electrical resistivity and is relatively easy to diffuse, the coating layer 102 can suppress the diffusion of these materials. Therefore, the occurrence of a short circuit can be prevented while lowering the electrical resistivity of the drive coils 18 and 20.

  In the present embodiment, a seed layer 100c having adhesiveness to the metal material constituting the drive coils 18 and 20 is disposed between the insulating layer 100b and the drive coils 18 and 20. Therefore, the metal material constituting the drive coils 18 and 20 can be grown on the seed layer 100c using electroplating.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to above-described embodiment. For example, although the mirror driving device 1 has been described in the present embodiment, the present invention is widely applied to electronic parts in which a metal material is embedded by a damascene method inside a groove or a recess (dent) that is recessed from the surroundings. Can do.

  DESCRIPTION OF SYMBOLS 1 ... Mirror drive device, 10 ... Permanent magnet, 12 ... Fixed frame, 14 ... Movable frame, 16 ... Mirror, 18, 20 ... Drive coil, 22, 24 ... Torsion bar, 28a, 28b, 32a, 32b ... Lead-out conductor, DESCRIPTION OF SYMBOLS 100 ... Base material, 100a ... Concave groove part, 100b ... Insulating layer, 100c ... Seed layer, 102 ... Covering layer, 104 ... Insulating layer, S1-S4 ... Main surface.

Claims (7)

A fixed frame;
A movable frame supported rotatably with respect to the fixed frame via a torsion bar extending on the same straight line;
A mirror disposed on the surface of the movable frame;
A magnet that forms a magnetic field around the movable frame;
The movable frame is
A base material including a main surface and a groove portion that is located on the main surface side and extends in a spiral shape when viewed from a direction orthogonal to the main surface;
A drive coil that is configured by the first metal material disposed in the groove and wound in a spiral shape when viewed from a direction orthogonal to the main surface;
A coating layer made of a second metal material that extends to the main surface so as to cover the opening of the groove and suppresses diffusion of the first metal material;
A first insulating layer disposed on the main surface and on the covering layer;
One end of the lead conductor is electrically connected to the inner end of the drive coil,
The other end of the lead conductor is drawn to the outside of the drive coil,
The mirror driving device, wherein the lead conductor intersects the driving coil three-dimensionally via the first insulating layer.   The mirror driving device according to claim 1, wherein the first metal material is Cu or Au.   The mirror driving device according to claim 1, wherein the second metal material is Al or an alloy containing Al.   The said base material is a mirror drive device as described in any one of Claims 1-3 which has a 2nd insulating layer arrange | positioned along the said main surface and the inner wall face of the said groove part. The base material is made of silicon,
The mirror driving device according to claim 4, wherein the second insulating layer is made of silicon oxide obtained by thermally oxidizing silicon.   The mirror driving device according to claim 4, wherein a seed layer is disposed between the second insulating layer and the first metal material.   The mirror driving device according to claim 6, wherein the seed layer is made of TiN.

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