JP5160299B2 - Micro movable device and driving method thereof - Google Patents

Description

  The present invention includes a movable portion, a deformable member connected to the movable portion and performing a bistable operation, and an actuator that drives the movable portion on the base, and the movable portion is displaced between two stable states by the actuator. The present invention relates to a micro movable device configured as described above and a driving method thereof.

  FIG. 5 shows a configuration of a micro movable device described in Patent Document 1 as a conventional example of this type of micro movable device. In this example, the micro movable device constitutes an optical switch.

  A fiber groove 21 is formed in a cross shape on the upper surface 10 a of the substrate 10, and one region divided into four by the cross-shaped fiber groove 21 serves as a drive body forming portion 22. A rod groove 23 is formed in the drive body forming portion 22 so as to be divided into two, and is communicated with the center portion 21a of the cross-shaped fiber groove 21. The other end of the rod groove 23 is connected to the drive body forming portion 22. It communicates with the formed recess 24.

  A movable rod 25 is disposed in the rod groove 23, and a mirror 26 is provided at one end of the movable rod 25 on the center portion 21 a side. The other end of the movable rod 25 is extended into the recess 24, and two deformed S-shaped hinges (leaf spring hinges) 27a to 27d are connected to each of the two sides of the movable rod 25 located in the recess 24. The movable rod 25 is supported by the driving body forming portion 22 by these hinges 27a to 27d so as to be displaceable in the extending direction.

  A comb-teeth type electrostatic actuator is provided between the hinges 27a, 27b and 27c, 27d. The movable comb electrode 28 is fixed to both sides of the movable rod 25, and the hinges 27c, 27d side of the movable comb electrode 28 are provided. The first fixed comb electrode 31 and the second fixed comb electrode 32 are provided on the hinges 27a and 27b, respectively. The movable comb electrode 28 is formed on both sides of a support arm 33 projecting and extending on both sides of the movable rod 25, and the first and second fixed comb electrodes 31, 32 are respectively fixed portions 34 in the recess 24. , 35 are fixedly supported.

  The optical switch having the configuration as described above is manufactured using an SOI substrate, that is, the substrate 10 is an SOI substrate. In FIG. 5B, 11 indicates an intermediate insulating layer of the SOI substrate, and 12 and 13 indicate a handle layer and a device layer made of single crystal silicon, respectively.

  Each component is formed by etching the device layer 13, and the movable body such as the movable rod 25, the mirror 26, the hinges 27 a to 27 d, the movable comb electrode 28, and the support arm 33 is formed on the intermediate insulating layer 11 below the movable body. Is removed by etching and is movable. In FIG. 5A, reference numerals 36a to 36d denote optical fibers inserted and fixed in the fiber groove 21.

  The hinges 27a to 27d are supposed to perform a bistable operation, that is, can take two different stable states (stable bent states). For example, in the initial manufacturing state (first stable state) of the optical switch, it is assumed that the mirror 26 is positioned at the central portion 21a as shown in FIG. 5A. At this time, for example, light emitted from the optical fiber 36a is reflected by the mirror 26 and enters the optical fiber 36b, and light emitted from the optical fiber 36d is reflected by the mirror 26 and enters the optical fiber 36c.

  The first fixed comb in a state where the driving body forming portion 22 and the second fixed comb electrode 32 electrically connected to the movable comb electrode 28 through the support arm 33, the movable rod 25, and the hinges 27a to 27d are grounded. If a voltage is applied to the tooth electrode 31, an electrostatic attraction force acts between the first fixed comb electrode 31 and the movable comb electrode 28, and the force is greater than the holding force in the first stable state. 27a to 27d are inverted to the second stable state, and are maintained in that state even if the voltage is cut off. At this time, as shown in FIG. 6, the mirror 26 is retracted from the central portion 21a, and the outgoing lights from the optical fibers 36a and 36d are respectively incident on the optical fibers 36c and 36b.

If a voltage is applied to the second fixed comb electrode 32 in a state where the driving body forming unit 22 and the first fixed comb electrode 31 are grounded, the static electricity is generated between the second fixed comb electrode 32 and the movable comb electrode 28. When the electrosuction force is applied and the force is larger than the holding force in the second stable state, the hinges 27a to 27d are reversed and returned to the first stable state, and thus the optical path is switched. ing.
JP 2005-134895 A

  As described above, the conventional fine movable device supports the movable part (movable rod) by two hinges that can be bent in a stable state, and applies a voltage to the electrostatic actuator and is movable by the electrostatic attraction force. By driving the part to reverse the bent state of the hinge, the movable part is displaced between the two stable states, and the state is maintained even when the applied voltage is released.

  However, an energy barrier that maximizes the reaction force of the hinge exists between the two stable states in a hinge that performs such bistable operation. The energy barrier must be exceeded. For this reason, an actuator that generates a large driving force is required in such a micro movable device having a deformable member that performs a bistable operation. Therefore, for example, the actuator becomes complicated, the voltage supplied from the outside increases, the energy ( The circuit that supplies the voltage) is increased in size and complexity.

  In view of such problems, the object of the present invention is to reduce the driving force required for the actuator, thereby simplifying the actuator and the circuit for driving the actuator, and reducing the supply voltage from the outside. Another object of the present invention is to provide a micro movable device that can be used, and to provide a driving method thereof.

According to the first aspect of the present invention, the movable portion on the base and the deformable member connected to the movable portion can take two stable bent states, and between the two stable states. A deformation member that performs a bistable operation due to the presence of an energy barrier and a main actuator that drives the movable portion are provided, and the movable portion is displaced between positions where the deformation member takes two stable states by the main actuator. in the fine moving device, temporarily lowers the energy barrier lowering means an energy barrier existing between the two stable states to the deformation member is provided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the energy barrier lowering means comprises a second actuator that temporarily displaces the end of the deformable member that is not connected to the movable portion.

  In the invention of claim 3, in the invention of claim 2, the deformable member is a buckling type hinge, and the end of the hinge not connected to the movable part is a leaf spring-like spring part fixed at both ends. A movable plate electrode is coupled to the opposite side of the spring portion to which the belly hinge is coupled, a fixed plate electrode is provided opposite the movable plate electrode, The actuator is a parallel plate type electrostatic actuator composed of a movable plate electrode and a fixed plate electrode.

  According to the invention of claim 4, the driving method of the fine movable device according to claim 1, wherein one of the two stable states of the deformable member has a relatively higher energy than the other, the energy of the deformable member is high. When the movable part is displaced from the stable state to the low stable state, the main actuator is not operated, and is displaced only by temporarily lowering the energy barrier by the energy barrier lowering means.

  According to this invention, the driving force required for the main actuator that drives the movable part can be reduced. Therefore, the main actuator and the circuit for driving the main actuator can be simplified, the voltage supplied from the outside can be lowered, and the cost can be reduced in these respects.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a main part of an embodiment of a micro movable device according to the present invention. In this example, the micro movable device constitutes an optical switch as in the conventional micro movable device shown in FIG. It has become.

  The deformable member that can perform a bistable operation and can take two stable states is a buckled leaf spring-shaped hinge 41 having a deformed S-shape as in FIG. 5, and in this example, the pair of hinges 41 are movable parts. The rod-like movable element 42 is supported by the pair of hinges 41 so as to be displaceable in the extending direction. A mirror 43 is formed at the tip of the movable element 42.

  The movable element 42 is driven by a comb-shaped electrostatic actuator, and a movable comb electrode 45 is formed on each side of a support arm 44 projecting and extending on both sides on the rear end side of the movable element 42. A first fixed comb electrode 46 and a second fixed comb electrode 47 are provided so as to sandwich the movable comb electrode 45 in the displacement direction (stretching direction) of the mover 42.

  The other end of the hinge 41 opposite to the one end connected to the mover 42 is connected to the antinode (the center in the extending direction) of the leaf spring-like spring portion 51. The spring part 51 extends in the displacement direction of the mover 42, and both ends are connected and fixed to the fixing part 52.

  A movable plate electrode 54 is connected to a side of the spring portion 51 opposite to the side to which the belly hinge 41 is connected via a connecting portion 53, and faces the movable plate electrode 54 with a predetermined gap. Thus, a fixed plate electrode 55 is provided. The movable plate electrode 54 and the fixed plate electrode 55 constitute a parallel plate type electrostatic actuator. The spring portion 51 supported at both ends by the fixed portion 52 is deformed (bends) in a direction orthogonal to the extending direction, but is deformed by the force received from the hinge 41 that performs a bistable operation. It has no rigidity.

  Similar to the conventional optical switch shown in FIG. 5, the optical switch having the above-described configuration is manufactured using an SOI substrate in which a handle layer made of single crystal silicon and a device layer are bonded via an intermediate insulating layer. can do. Each component is formed by etching the device layer and is positioned on the handle layer that forms the substrate. The movable body such as the hinge 41, the movable element 42, the mirror 43, the support arm 44, the movable comb electrode 45, the spring part 51, the connecting part 53, and the movable flat plate electrode 54 can be moved by etching away the intermediate insulating layer therebelow. It is said.

  Next, a method for driving this optical switch will be described. The movable comb electrode 45 is electrically connected to the fixed portion 52 via the support arm 44, the movable element 42, the hinge 41, and the spring portion 51, and the movable plate electrode 54 is connected to the connecting portion 53 and the spring portion 51. It is electrically connected to the fixing part 52 via The fixed part 52 is grounded.

  In the first stable state shown in FIG. 1, when a voltage is applied to the first fixed comb electrode 46, the electrostatic attractive force between the first fixed comb electrode 46 and the movable comb electrode 45 causes A driving force in the second direction indicated by the arrow is generated. In order for the bent state of the hinge 41 to be reversed and to be in the second stable state, a driving force greater than the maximum reaction force of the hinge 41 being deformed is required, and the reaction force of the hinge 41 depends on the bent hinge shape. Occur.

  Therefore, when a voltage is applied to the fixed plate electrode 55 simultaneously with the voltage application to the first fixed comb electrode 46 (start of hinge deformation) or before or after the voltage is applied to the first fixed comb electrode 46, the fixed plate electrode 1, the right movable plate electrode 54 in FIG. 1 has a third direction indicated by an arrow, and the left movable plate electrode 54 has a fourth direction indicated by an arrow. A driving force is generated, whereby the spring portions 51 are deformed to pull the hinge 41, and the hinge 41 is substantially linearized.

  Due to the straightening of the hinge 41, the mover 42 moves in the second direction, and at the same time, the reaction force of the hinge 41 decreases due to the straightening of the hinge 41. Therefore, the voltage applied to the first fixed comb electrode 46 is higher than the conventional voltage. Even if it is low, that is, the movable element 42 moves to an intermediate state as shown in FIG.

  Next, the voltage applied to the fixed plate electrode 55 is released while the voltage is applied to the first fixed comb electrode 46 (the fixed plate electrode 55 is grounded). The driving force of the parallel plate type electrostatic actuator disappears, and the spring portion 51 returns to the original linear state. When the spring part 51 returns to the linear state, the hinge 41 is pushed (compressed force is applied) and bent. This bending attempts to push the mover 42 in either the first direction or the second direction. However, since the driving force in the second direction is generated by the first fixed comb electrode 46, the mover 42. Moves in the second direction. As a result, the movable element 42 and the hinge 41 are in the second stable state shown in FIG. 3, and the state is maintained even when the voltage applied to the first fixed comb electrode 46 is released.

  In this manner, in this example, driving from the first stable state to the second stable state is performed. The driving from the second stable state to the first stable state is performed by applying voltage to the first fixed comb electrode 46 in the driving method from the first stable state to the second stable state. This is performed by replacing (reading) the voltage application to the fixed comb electrode 47.

  As described above, in this example, apart from the comb-shaped electrostatic actuator (main actuator) that drives the mover 42, the end of the hinge 41 that is not connected to the mover 42 is temporarily displaced. A parallel plate type electrostatic actuator (second actuator) is provided, and the mover 42 displaces the energy barrier existing between the two stable states of the hinge 41 by the second actuator. It can be temporarily lowered. As a result, in this example, the driving force required for the main actuator can be reduced, so that the main actuator and the circuit for driving the main actuator can be simplified, and the supply voltage from the outside can be reduced. Therefore, it is possible to reduce the cost in these respects.

Here, description will be made based on specific numerical examples.
The length of each hinge 41 is 1 mm, and the dimensions of each part shown in FIG.

Hinge 41 width: W ₁ = 2 μm
Length of the spring part 51: L ₂ = 302 μm
Width of the spring part 51: W ₂ = 4 μm
Width of connecting portion 53: W ₃ = 5 μm
Opposing width of movable plate electrode 54 and fixed plate electrode 55: W ₄ = 300 μm
Gap between movable plate electrode 54 and fixed plate electrode 55: G = 1.5 μm
Note that the thickness (height) of the hinge 41, the spring part 51, the connecting part 53, and the movable plate electrode 54 is the device layer thickness of the SOI substrate = 100 μm.

  The specifications of the hinge 41 and the parallel plate type electrostatic actuator as the second actuator are as described above. Now, the parallel plate type electrostatic actuator is not operated temporarily. When the movable element 42 is displaced from the first stable state of FIG. 1 to the second stable state of FIG. 3 by operating only the actuator, the voltage applied to the first fixed comb electrode 46 is 65 V or more. Voltage is required.

  On the other hand, when operating the parallel plate type electrostatic actuator, the end portion connected to the spring portion 51 of the hinge 41 can be displaced by a maximum of 0.8 μm with a voltage of 50 V applied to the fixed plate electrode 55 ( In FIG. 2, the displacement is indicated by x), so that the voltage applied to the first fixed comb electrode 46 necessary for displacing the mover 42 from the first stable state to the second stable state is 50 V or less. It was possible to reduce.

  For example, a booster circuit that multiplies the basic voltage 27V by an integer is used as a drive circuit for the electrostatic actuator, and a triple booster (81V) circuit, which has conventionally been a large circuit size and has become an obstacle to the package, is used. In contrast to the necessity, in this example, the drive voltage can be reduced to 50 V or less as described above. Therefore, a double booster (54 V) circuit having a small size and advantageous for a package can be employed.

Hereinafter, a driving method different from the above-described method when driving the optical switch shown in FIG. 1 will be described.
For example, when the optical switch is manufactured using the first stable state shown in FIG. 1 as an initial state, the first stable state has almost no stress in the hinge 41, but the second stable state becomes bistable. Then, since the hinge 41 is deformed from the initial state (first stable state), stress is included. That is, the second stable state contains higher energy than the first stable state. Therefore, if the energy barrier existing between the two bistable stable states is removed, the movable element 42 is spontaneously displaced to the first stable state, which is a lower energy state.

  In this example, an energy barrier is formed by the bent hinge 41, and the energy barrier can be removed by straightening the hinge 41. That is, when a voltage is applied to the fixed plate electrode 55 in the second stable state, the spring portion 51 is deformed to pull the hinge 41, and the hinge 41 is linearized. As a result, the movable element 42 is displaced to the intermediate state shown in FIG. 2 and the energy barrier is removed. Then, when the voltage applied to the fixed plate electrode 55 is released, the spring portion 51 returns to the linear state, and the hinge 41 Is bent and the mover 42 is displaced to the first stable state with lower energy.

  As described above, according to this driving method, it is not necessary to apply a voltage to the second fixed comb electrode 47 when the second stable state is displaced to the first stable state, or the applied voltage is extremely small. That's it. When the voltage application to the second fixed comb electrode 47 is not required, the second fixed comb electrode 47 itself is not required, thereby making it possible to reduce the size of the device and simplify the control for applying the voltage. Can be achieved. Further, since the movable comb electrode 45 corresponding to the second fixed comb electrode 47 is not necessary, the weight of the movable element 42 (movable body) can be reduced, and the impact resistance can be improved in that respect. it can.

  As described above, the optical switch has been described as an example, but the fine movable device according to the present invention supports the movable part with a deformable member that performs a bistable operation, and selectively positions the movable part at one of two positions. The present invention can be applied to various devices having a self-holding structure, and an example can be applied to a relay device or the like.

The top view which shows the principal part structure of one Example of the fine movable device by this invention. The top view which shows the intermediate state in the middle of the micro movable device shown in FIG. 1 being driven and displacing from a 1st stable state to a 2nd stable state. The top view which shows the state (2nd stable state) after the displacement of the fine movable device shown in FIG. The top view which expanded and showed the 2nd actuator with which the micro movable device shown in FIG. 1 is provided. The figure which shows the example of a conventional structure of a micro movable device, A is a top view, B is CC sectional drawing. FIG. 6 is a plan view showing a state after the fine movable device shown in FIG. 5 is driven and displaced from the first stable state to the second stable state.

Claims (4)

A movable part and a deformable member connected to the movable part, which can be in a stable state that is two stable bent states, and an energy barrier between the two stable states are provided on the base. In a fine movable device that includes a deformable member that performs a stable operation and a main actuator that drives a movable portion, and the movable portion is displaced between positions where the deformable member takes two stable states by the main actuator.
Wherein the deformable member, the two of the fine moving device, characterized in that temporarily lowers the energy barrier lowering means an energy barrier is provided which exists between stable states. The micro movable device according to claim 1,
The energy barrier lowering means includes a second actuator that temporarily displaces an end portion of the deformable member that is not connected to the movable portion. The micro movable device according to claim 2,
The deformable member is a buckled hinge,
The end of the hinge that is not connected to the movable part is connected to the abdomen of a leaf spring-like spring part fixed at both ends,
A movable plate electrode is connected to the side of the belly of the spring portion opposite to the side to which the hinge is connected,
A fixed plate electrode is provided facing the movable plate electrode,
The micro movable device according to claim 2, wherein the second actuator is a parallel plate type electrostatic actuator composed of the movable plate electrode and the fixed plate electrode. The method for driving a micro movable device according to claim 1, wherein one of the two stable states of the deformable member has a relatively higher energy than the other.
When the movable part is displaced from a stable state with high energy of the deformable member to a stable state with low energy, the main actuator is not operated, and is displaced only by temporarily lowering the energy barrier by the energy barrier lowering means. A method for driving a fine movable device.

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