JP3816506B2 - Micro movable device - Google Patents

Description

  In this invention, the movable part is held by a hinge on a substrate such as an optical switch having a mirror driven by an electrostatic drive part as a movable part, a relay device having a movable electrode as a movable part, and the two different bent states of the hinge Thus, the movable part stably holds the movable part, and the wall surface is formed on the substrate on both sides of the movable range of the hinge.

The movable part is not self-maintained in two stable states, but it is a micro-movable device with a movable part, especially on the substrate as produced by mask formation by photolithography and gas-reactive anisotropic dry etching. An optical switch having a function of switching the optical path by forming each element of a mirror, a hinge, an actuator, and an optical waveguide and inserting and removing the mirror in the optical waveguide will be described.
FIG. 3 shows the structure of a MEMS (Micro Electro Mechanical Systems) optical switch disclosed in Patent Document 1. Four fiber grooves 1A to 1D are continuously formed in a cross shape on the upper surface (100u) of the substrate 100 (in FIG. 3, divided into 100a and 100b but integrated). The substrate 100 between the fiber grooves 1A and 1B perpendicular to each other is used as a driving body forming portion 101, and slots 103 that form 45 degrees with respect to the fiber grooves 1A and 1B, respectively, are formed on the upper surface (100u). The movable rod 116 is disposed in the slot 103, one end of the support frames 134A and 134B is fixed to both sides of the movable rod 116, and the other end of the support frames 134A and 134B is fixed to the fixed support portion 130A by leaf spring hinges 128A and 128B. , 130B, and the movable rod 116 is movably held in its extending direction and parallel to the plate surface (upper surface 100u) of the substrate 100. There. Four optical fibers 106A to 106D are arranged in the fiber grooves 1A to 1D. The mirror 102 is positioned at the central portion 1c of the radial arrangement of the optical fibers 106A to 106D and supported by one end of the movable rod 116. A comb-teeth electrostatic actuator 122 is connected to the other end of the first electrode.

  In the comb-shaped electrostatic actuator 122, a movable comb electrode 110 and a fixed comb electrode 108 extended on both sides of the movable rod 116 are arranged in the extending direction of the movable rod 116, and the movable comb electrode 110 is formed on the movable rod 116. The fixed comb electrodes 108 are fixed to the driving body forming unit 101, respectively. A shallow rectangular recess 115 is formed in the region of the driving body forming portion 101 on the upper surface 100u of the substrate 100 so as to be connected to the slot 103. A movable rod 116 is extended and inserted into the recess 115, and the electrostatic actuator 122 and the hinges 128A and 128B. The support frames 134A and 134B are positioned, and the fixed comb electrode 108 and the fixed support portions 130A and 130B are fixed to the bottom of the recess 115, but there is a gap between the other movable portions and the bottom surface of the recess 115. It is floating. By applying a voltage between the comb electrodes 110 and 108, an electrostatic attraction force is generated, the movable rod 116 moves to the fixed comb electrode 108 side, and the mirror 102 is maintained in a state of being extracted from the central portion 1c. Let When this voltage application is released, the movable rod 116 is moved to the central portion 1c by the restoring force of the hinges 128A and 128B, and the mirror 102 is positioned at the central portion 1c and returns to the original state.

In a state where the mirror 102 is inserted into the central portion 1c, the light emitted from the optical fiber 106A is reflected by the mirror 102 and enters the optical fiber 106B, and the light emitted from the optical fiber 106D is reflected by the mirror 102 and is reflected by the optical fiber. Incident on 106C. When the mirror 102 is extracted from the central portion 1c, the light emitted from the optical fiber 106A enters the optical fiber 106C, and the light emitted from the optical fiber 106D enters the light receiving optical fiber 106B.
Special table 2003-506755 gazette

  In the minute optical switch shown in FIG. 3, in order to maintain the state where the mirror 102 is removed from the central portion 1c, a voltage must be continuously applied between the comb electrodes 108 and 110, during which power consumption is achieved. Not economical. By using a hinge that can have a different bending state from this point, when a voltage is applied to the electrostatic actuator and the mirror 102 is positioned at the central portion 1c, or pulled out from the central portion 1c, We considered a micro optical switch that remains in that state even when voltage application is released. This optical switch will be described below. FIG. 4 is a plan view and FIG. 5 is a cross-sectional view thereof. A fiber groove 1 is formed in a cross shape on the upper surface 31 u of the substrate 31, and is radial with respect to the central portion 1 c of the cross-shaped fiber groove 1. The optical fibers 32A to 32D are respectively inserted into the four fiber grooves 1A to 1D, and the fiber grooves 1A to 1D are formed with a groove width sufficiently close to the optical fiber diameter as shown in FIG. Then, the optical fibers 32 </ b> A to 32 </ b> D are positioned with respect to the substrate 31 by being stably held between the both side walls of the groove and with the end faces of the optical fibers being abutted against the abutting protrusion 3 near the center portion 1 c. . The end face of each of the optical fibers 32A to 32D is an example in which a collimation fiber whose slope is polished at, for example, 6 ° is used.

  As shown in FIG. 4, one region divided into four by the cross-shaped fiber groove 1 on the upper surface 31 u side of the substrate 31 is a driving body forming portion 10, and the driving body forming portion 10 has a central portion so as to divide this into two. A rod groove 33 communicated with 1c is formed, the movable rod 7 is arranged in the rod groove 33, the mirror 4 is held at one end of the movable rod 7 on the central portion 1c side, and is connected to each of two positions on both sides of the movable rod 7. By the deformed S-shaped leaf spring hinges 6 </ b> A to 6 </ b> D, the movable rod 7 is supported by the drive body forming unit 10 so as to be movable in the extending direction. A comb-shaped electrostatic actuator is provided between the hinges 6A, 6C and 6B, 6D. The movable comb electrode 5 is fixed to both sides of the movable rod 7, and the movable comb electrode 5 is on the hinge 6C, 6D side. The first and second fixed comb electrodes 8 and 9 are fixed to the drive body forming portion 10 on the hinges 6A and 6B side. The leaf spring hinges 6A, 6B and 6C, 6D are disposed in hinge recesses 14a and 14b formed in the drive body forming portion 10.

Further, the cross-sectional shapes of the leaf spring hinges 6A to 6D are tapered surfaces whose both side surfaces are slightly inclined, for example, about θ1 = 0.5 °, closer to the inner surface than the surface 6s side on the surface (upper surface 31u) side of the substrate 31. Accordingly, it is preferable that the width gradually decreases. For example, a trapezoidal shape having a wide upper side with respect to the lower bottom side as shown in FIG. 7A or a wedge-shaped triangular shape as shown in FIG. 7B may be used.
The modified S-shaped leaf spring hinges 6A to 6D hold different bent states. Therefore, in the initial shape (first stable state) immediately after the fabrication of this optical device, for example, the mirror 4 is inserted into the central portion 1c. At this time, the light emitted from the optical fiber 32A is reflected by the mirror 4 and enters the optical fiber 32B. The light emitted from the optical fiber 32D is reflected and incident on the optical fiber 32C. The first fixed comb electrode in a state where the driving body forming portion 10 and the second fixed comb electrode 9 electrically connected to the movable rod 7, the movable comb electrode 5 and the leaf spring hinges 6A to 6D are grounded. When a voltage is applied to 8, an electrostatic attraction force acts between the first fixed comb electrode 8 and the movable comb electrode 5, and when the force is larger than the holding force in the first stable state, the leaf spring hinge 6A to 6D are inverted to the second stable state, and are self-held in that state even if the voltage application is stopped. At this time, as shown in FIG. 8, the mirror 4 is retracted from the central portion 1c, and the outgoing lights from the optical fibers 32A and 32D are incident on the optical fibers 32C and 32B, respectively. If a voltage is applied to the second fixed comb electrode 9 in a state where the driving body forming unit 10 and the first fixed comb electrode 8 are grounded, static electricity is generated between the second fixed comb electrode 9 and the movable comb electrode 5. When the electro-suction force is applied and the force is greater than the second stable state, the state returns to the first stable state again. In order to apply a voltage between the first or second fixed comb electrode 8 or 9 and the movable electrode 5, for example, a bonding wire is connected to each of the first and second fixed comb electrodes 8 and 9. A voltage may be applied between the bonding wires and the driving body forming unit 10. The leaf spring hinges 6A to 6B only need to be able to reverse between two stable different bent states.

  In this optical device, the movable parts other than the mirror 4 have a line-symmetric structure with respect to a center line parallel to the mirror driving direction (center line of the movable rod 7), and the four leaf spring hinges 6A, 6B, The support points A, B, C, and D of the movable rod 7 by 6C and 6D (that is, the hinge reaction force action point) are related to the connecting portion of the movable comb electrode 5 and the movable rod 7 (that is, the driving force action point S). It is placed at the target position. Further, the driving force action point S is designed to substantially coincide with the center of gravity of the movable part. By adopting such a structure, for example, even when the driving force of the actuator contains a vector component different from the desired direction in which the movable portion should be driven, the unnecessary vector component of the driving force is Since the reaction force acts equally from the four leaf spring hinges 6A, 6B, 6C, 6D, the movement of the movable portion in a direction other than the desired driving direction can be effectively suppressed.

Even when a disturbance such as an impact force is applied, 1) the four leaf spring hinges 6A, 6B, 6C, 6D are provided at symmetrical positions with respect to the center of gravity of the movable part, and 2) a heavy structure. The four leaf spring hinges 6A, 6B, 6C, 6D are uniformly supported by the movable comb electrode 5 and the above two structural features effectively suppress unnecessary movement of the movable part. can do.
Next, as a method of manufacturing the optical device shown in FIGS. FIG. 9 shows a cross section taken along line 5A-5A in FIG.

As shown in FIG. 9A, a substrate in which two silicon single crystal layers 42 and 43 are bonded via an intermediate insulating layer 41, a so-called SOI substrate 31, is prepared. For example, a single crystal silicon substrate having a thickness of 350 μm is used as the silicon single crystal layer 42, a silicon oxide film 41 having a thickness of 3 μm is formed as an intermediate insulating layer on the silicon substrate 42, and a silicon single crystal layer 43 is further formed thereon. A single crystal silicon device layer 43 is formed to form the substrate 31.
A mask material layer 44 is formed on the substrate 31, that is, on the silicon device layer 43. For example, a silicon oxide film is used as the mask material layer 44.

Bending operation of the mirror 4, the hinges 6A to 6B, the movable rod 7, the movable comb electrode 5, the first and second fixed comb electrodes 8, 9 and the fiber groove 1, the rod groove 33, and the leaf spring hinges 6A to 6B. Pattern defining the mirror surface and the side wall surface perpendicular to the substrate plate surface other than the mirror surface, in this example the shape shown in FIG. The mask material layer 44 is patterned into a pattern, for example, using a photolithography technique, and the mask 45 is created as shown in FIG. 9B.
Next, for example, by dry etching using ICP (Inductively Coupled Plasma), using the mask 45 as a mask, the silicon device layer 43 is substantially perpendicular to the plate surface of the substrate 31 until the intermediate insulating layer 41 is exposed as shown in FIG. 9C. Etch into. As a result, the fiber groove 1, the rod groove 33, the hinge recess 14, the comb teeth of each comb-tooth electrode, and the like are formed.

After cleaning the surface of the silicon device layer 43 including the side wall formed by this etching, an etching solution selective for the intermediate insulating layer 41, for example, a 50% solution of hydrofluoric acid (HF) (or hydrofluoric acid and The intermediate insulating layer 41 is etched by immersing it in a mixed solution of ammonium fluoride. In this etching time, the intermediate insulating layer 41 corresponding to the movable portion such as the mirror 4, the movable comb electrode 5, the hinges 6A to 6D, and the movable rod 7 is completely removed, but the first and second fixed combs are removed. In the intermediate insulating layer 41 at a portion to be fixed to the base 31 such as a portion other than the comb teeth of the tooth electrodes 8 and 9, only a small portion at the periphery is removed. By this etching process,
The movable part is supported on the substrate 31 movably by leaf spring hinges 6A to 6D. In this example, the intermediate insulating layer 41 and the mask material layer 44 are made of the same material, and the mask 45 is also removed at the same time.

A mirror body is formed by coating a high-reflectance metal such as an Au / Pt / Ti multilayer film on both sides of the mirror 4 by sputtering.
As described above, by using a spring hinge having two different bent states, the mirror is displaced by applying a voltage to the drive unit, and then the mirror is displaced even if the application of this voltage is canceled. It is held and power consumption can be reduced.
However, when this optical switch was actually prototyped, as shown by the broken line in FIG. 4, one or more of the hinges were attached to the wall surface of the hinge recess 14 opposed thereto, It turns out that the yield cannot be expected. In order to prevent such a problem from occurring, the mechanical rigidity of the hinges 6A to 6D may be increased, for example, the thickness of the hinges 6A to 6D may be increased. However, this requires a large drive voltage for displacing the mirror, and thus it is not suitable to prepare a relatively large voltage source for a module or apparatus using a microdevice.

Therefore, in pursuit of the cause of the hinge being attached to the wall surface, after gas reactive dry etching, wet etching is performed, and after the subsequent drying process, the hinge is attached to the wall surface. There was found. Therefore, as a drying process, after replacing the etching solution with a liquid that sublimates under reduced pressure, the temperature is reduced to solidify and sublimated under reduced pressure, or the etching solution is replaced with liquefied carbon dioxide (CO ₂ ), and the gas phase is removed from the liquid phase. We investigated the supercritical drying method under high temperature and high pressure without phase change to the phase, or the method of simply substituting with a liquid with low surface tension and drying. Among these, it has been found that the method of drying from a liquid having a small surface tension is simple, but lacks certainty.

The movable contact of the relay is held by a bi-stable hinge, and the movable contact is switched and connected to two fixed contacts to make the state self-holding or to make the state self-hold by making contact or non-contact with the fixed contact. The relay device or the mirror part of the optical switch described above is used as a mass part, and instead of an electrostatic actuator, a capacitive displacement sensor is used. It is considered that the same problem occurs when an impact sensor or the like that switches between is configured as a micro device.
An object of the present invention is to provide a micro movable device that supports a movable part by a hinge having two different bent states and self-holds the displaced state of the movable part, and can be manufactured with high yield. It is in.

  According to the present invention, the movable part is supported by a hinge having two different bent states, and in one of the two stable bent states of the hinge, the distance between the hinge and the opposing wall surface that can come into contact with the hinges on both sides thereof is They are made equal at each point in the longitudinal direction of the hinge. Note that the distance between the wall surface at one end of the hinge and the wall surface at the other end may not be equal.

In the optical switch shown in FIG. 4, the distance between the hinges 6A to 6D and the opposite wall surfaces of the hinge recesses 14 on both sides thereof, for example, the distances D1 and D3 for the hinge 6A are different. In the drying process, as shown in FIG. 10, the evaporation state of the etching solution is unbalanced on both sides of the hinge 6 (6A), the timing at which the liquid on both sides of the hinge evaporates is shifted, and the wall surface on both sides of the hinge and the wall surface On the narrow side, the evaporation is delayed and the liquid remains, but on the wide side, the liquid disappears. In this state, the hinge 6 (6A) is attracted to the wall surface of the recess 14 by the surface tension of the liquid. Hinge 6 as it is
It is considered that (6A) remains on the wall surface.

  According to the present invention, since the distance from the corresponding wall surface on both sides of the hinge is equal to each other at each point in the longitudinal direction of the hinge, liquid is similarly reduced on both sides of the hinge in the drying process after wet etching in device fabrication. Therefore, it is difficult for the hinge to be attached to the wall.

An embodiment in which the optical switch shown in FIG. 4 is applied to the present invention is shown in FIG. 1 with the same reference numerals assigned to the portions corresponding to those in FIG. 4 and FIG.
In this embodiment, when the optical switch is manufactured in the initial state, the longitudinal direction of the leaf spring hinges 6A, 6B, 6C, 6D with the mirror 4 positioned in the central portion 1c of the cross-shaped fiber groove 1 in FIG. The distances (distances) between the opposing wall surfaces 14a1, 14a2, 14a3, 14a4, 14b1, 14b2, 14b3, 14b4 of the hinge recesses 14a, 14b on both sides of each point in the direction are made equal to each other. In the example of FIG. 1, the hinges 6A to 6D and the corresponding wall surfaces of the hinge recesses 14a and 14b facing each other are parallel to each other, and the distances (distances) D1, D3 between the hinges 6A and 6B and the wall surfaces on both sides thereof The distances (distances) D2 and D4 between 6C and 6D and the opposing wall surfaces on both sides thereof are all equal to D1 = D2 = D3 = D4. However, D1 = D3 and D2 = D4, but D1 ≠ D2. Further, the distances (distances) between the hinges 6A to 6D and the wall surfaces on both sides of the hinges 6A to 6D do not have to be the same, that is, not uniform at each point in the hinge longitudinal direction. That is, as shown in FIG. 2, the distance (distance) D3a and D1a between the hinge 6 and the opposed wall surfaces 14a1 and 14a2 at the end of the hinge 6 (6A) on the movable rod 7 side is equal, and at the opposite end of the hinge 6 The distances (distances) D3b and D1b between the hinge 6 and the opposing wall surfaces 14a1 and 14a2 are the same, but the distances D3a and D3b between these ends may be different from each other. Further, equalization of D3b and D1b described above may be established at each point in the longitudinal direction that can contact at least the opposing wall surfaces, even if it does not extend over the entire length of the hinges 6A to 6D.

  Further, in this embodiment, the comb electrodes and hinges of the substrate 31 are formed in the recesses in which the movable comb electrodes 5, the first and second fixed electrodes 8 and 9, and the hinges 6A to 6D are formed and accommodated. The groove 31 is formed on the surface 31 u and is open to the edge of the substrate 31. In this example, the hinge recess 14 a is connected to the central portion 1 c of the cross-shaped fiber groove 1 through the rod groove 33. The end of the fiber groove 1 (1A to 1D) opposite to the central portion 1c is opened to the outside from each corner of the substrate 31. Further, in the extending direction of the rod groove 33, the opening groove 16 is formed so as to extend in the direction opposite to the central portion 1c until the edge of the substrate 31 is reached, and the hinge recess 14b is connected to the opening groove 16. Yes. Further, the comb electrode side of the hinge recesses 14 a and 14 b are connected to each other by communication grooves 17 and 18 along a wall surface parallel to the movable rod 7. Preferably, open grooves 19 and 20 that are connected to the communication grooves 17 and 18 and reach the edge of the substrate 31 (the lower edge in FIG. 1) are formed.

The optical switch shown in Embodiment 1 can be manufactured in the same manner as the manufacturing method shown in FIG. In this case, when patterning the mask material layer 44, the leaf spring hinges 6A to 6B are set to one of two stable bent shapes (target initial shape) and the hinge recess 14a. , 14b and the interval between the wall surface and the hinge are as described above, and the opening grooves 16, 19, 20 and the communication grooves 17, 18 are formed. That is, patterning may be performed in the planar shape shown in FIG.
In the first embodiment, since the distance between the hinges 6A to 6D and the wall surfaces of the hinge recesses 14a and 14b on both sides at the respective points in the longitudinal direction is equal, the liquid 15 delayed in evaporation as shown in FIG. It becomes the same amount on both sides of the hinges 6 </ b> A to 6 </ b> D, and there is no possibility that the hinges remain pulled toward the wall surface. Moreover, direct drying from a simple liquid can be used in the drying step after the wet etching during production, and the yield is improved.

The recesses for forming and receiving the hinge recesses 14a and 14b and the comb electrodes 5, 8, and 9 are formed in the substrate 31, and the fiber groove 1 and the release grooves 16, 19, and 20 that are released to the outside. Since they are connected, in the drying process after the wet etching at the time of manufacturing, the etching solution can flow out from the substrate 31 and the drying process can be shortened accordingly. Since the concave portions 14a and 14b for the hinges are connected to each other by the gap between the leaf spring hinges 6A to 6D and the movable rod 7 and the bottom surfaces of the concave portions 14a and 14b. Even in the configuration in which only the opening groove 16 is provided without providing the grooves 19 and 20, the etching solution is allowed to flow out and the effect of shortening the drying process can be obtained. However, in the case of the configuration having only the opening groove 16, the hinges 6A and 6B of the recess 14a directly connected to the groove opened to the outside of the substrate 31 and the wall surfaces 14a1 and 14a3 side portions of the recess 14a and the hinges 6C and 6D of the recess 14b are wall surfaces. The etchant at the portions on the 14b2 and 14b4 side is discharged faster, and the outflow of the etchant at each portion on the wall surfaces 14a2, 14a4 and 14b1, 14b3 side is relatively slower than the hinges 6A to 6D of the recesses 14a and 14b. Therefore, the opening grooves 19 and 20 are also provided to promote the outflow of the liquid on the wall surfaces 14a2, 14a4, 14b1 and 14b3 from the hinges 6A to 6D, and the liquid on both sides of the hinge in the drying process is promoted. It is desirable to ensure a more balanced reduction.

  This invention uses not only a micro optical switch but also a movable part with a hinge that can have two different stable bending states by using photolithography, deep etching dry etching, and wet etching as described above. It can be applied to a minute movable device such as a relay device or an impact sensor that is supported by the driving body forming portion and selectively holds the movable portion in one of two positions.

The top view which shows embodiment of this invention. The figure which shows the residual state of the liquid in the middle of the drying after a wet etching at the time of producing this invention device, and a process. The top view which shows the conventional optical switch. The top view which shows an example of the optical switch which can hold | maintain both of 2 stable states. The figure which shows the 5A-5A line cross section of the optical switch shown in FIG. 4, the 5B-5B line cross section, and the 5C-5C line cross section. The enlarged plan view for demonstrating the structure of the center part vicinity of the cross-shaped fiber groove | channel of the optical switch shown in FIG. The expanded sectional view of the leaf | plate spring hinge used for the optical switch shown in FIG. FIG. 5 is a plan view showing a state in which the mirror is removed from the fiber groove center portion 1c in the optical switch shown in FIG. FIG. 5 is a cross-sectional view taken along line 5A-5A in FIG. 4 in each step for explaining a method for manufacturing the optical switch shown in FIG. The figure which shows the residual state of the liquid in the middle of the drying process after the wet etching at the time of preparation of the optical switch shown in FIG.

Claims (2)

A movable part formed on the substrate and displaced in parallel with the substrate plate surface, a driver forming part formed on the substrate, the movable part and the driver forming part are connected at both ends, A hinge that performs a bi-stable operation that self-holds the movable part in two positions in different bending states, and a wall surface that is formed on the drive body forming part opposite to the hinge on both sides of the movable range of the hinge A micro movable device comprising:
The minute movement is characterized in that the distance between the hinge and the wall surfaces on both sides that can come into contact with the hinge is equal to each other at each point in the longitudinal direction of the hinge in one of two stable bent states of the hinge. device.   Each groove formed by the hinge and the wall surfaces on both sides is formed on the driving body forming portion forming surface of the substrate and is continuous with the groove opened to the edge of the substrate. The micro movable device according to claim 1.

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