JP2007024946A - Microelectromechanical element and microelectromechanical optical modulation element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical modulation element in which troubles are hardly caused by reducing occurrence of crack at the edge part of a hinge and the bending rigidity is remarkably enhanced without largely varying the torsional rigidity of the hinge part. <P>SOLUTION: A microstructure body comprises: a substrate provided with an electrode; a long deformable elastic beam mounted on the substrate across a gap; and a movable member which is mounted on the beam and can be displaced by the deformation of the beam and at least a part of which is provided with an electrically conductive part facing the electrode. The movable member is rocked and displaced by applying an electric voltage between the electrode and the electrically conductive part. Projected parts are provided in a thickness direction at the both ends of a free end on which the long beam is not mounted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microelectromechanical element, and more particularly to a long beam body of a microelectromechanical light modulation element.

A spatial light modulator (SLM) is a device that modulates incident light in a spatial pattern and forms a light image corresponding to an electrical or optical input. As one of the SLMs, there is a digital micromirror device (DMD) that produces a micromirror based on micromechanical technology and tilts the micromirror to deflect light. The DMD is a monolithic single-chip integrated circuit SLM, and is composed of a high-density array of movable micromirrors of about 16 microns square, for example. These mirrors are formed on the address circuit, form one pixel of the DMD array, reflect incident light to the projection lens at one of the two positions, and convert incident light to the optical absorber at the other position. To deflect. The projection lens focuses the modulated light on the display screen to form an image.
Light up.

FIG. 13 is a plan view of a reflection type light modulation element which is one of the objects of the present invention, and FIG. 14 is a plan view of the reflection type light modulation element, and FIG. FIG. 15 is a cross-sectional view of the substrate shown in FIG. 13, and FIG. 16 is a cross-sectional view of the substrate shown in FIG. FIG. 6 is an electrode wiring diagram of a reflective light modulation element.
13 and 14, the reflective light modulation element 100 includes a substrate 10, a lower electrode 20 (left and right 20a, 20b in the figure) disposed on the substrate 10, and a gap G (FIG. 14) from the substrate 10. And a movable body 30 formed on the hinge 40 (hereinafter referred to as “hinge”) 40. The hinge 40 is a long bridge (see FIG. 14C), and is supported on the substrate 10 by the support portions 41 at both ends in the longitudinal direction, and the central portion 40 is a gap between the lower electrode 20a and the lower electrode 20b. Is disposed substantially parallel to the substrate 10 via a gap G. The movable member 30 includes a conductive portion 31 and a light reflector (hereinafter referred to as “mirror portion”) 32 formed thereon, and the central portion of the conductive portion 31 and the hinge 40 are integrated.
Therefore, the movable member 30 is rotationally displaced by the twist of the hinge 40, and thus the mirror part 32 is rotationally displaced.

  The substrate 10 may use any material such as a Si substrate or a glass substrate. As a specific example of the substrate 10, as shown in FIG. 15, a circuit (usually a CMOS circuit 71 and its wiring circuit 73) for driving elements is formed on a Si substrate 70, and its upper surface is flattened by an insulating layer 75. It is preferable that the substrate is a simplified substrate. The lower electrode 20 is provided on the flattened upper surface of the insulating layer 75, and the above-described movable member 30 is provided above the lower electrode 20 with a gap G interposed therebetween. These are electrically connected through a contact hole (not shown) provided in the insulating layer 75.

  The lower electrode 20 includes a first lower electrode 20a and a second lower electrode 20b disposed on both sides around the hinge 40. Two lower electrodes (a first lower electrode 20a and a second lower electrode 20b) are disposed below the hinge 40 with the hinge 40 as a center. That is, the electrodes (first lower electrode 20a and second lower electrode 20b) that effectively apply electrostatic force around the torsion center 40C axis (FIG. 14B) of the movable member 30 that is swung around the axis. Are arranged in a space-saving manner. The first lower electrode 20a and the second lower electrode 20b are formed and fixed on the substrate 10. The first lower electrode 20a and the second lower electrode 20b may be any conductive material such as metal or semiconductor. Moreover, an insulating layer may be provided thereon.

The support portions 41 at both ends of the hinge 40 can have a shape in which the end portion of the hinge 40 formed in an elongated shape is recessed in a substantially quadrangular pyramid shape. Therefore, the cross-sectional shape of the support portion 41 (FIG. 14C) is an inverted triangle shape having a flat portion at the bottom. The flat portion of the hinge 40 is connected to the wiring circuit 73 (FIG. 15) through a contact hole (not shown) formed in the insulating layer 75 (FIG. 15). The positions of the first lower electrode 20a and the second lower electrode 20b are arranged substantially symmetrically with respect to the twist center 40C of the hinge 40. The hinge 40 should just be electroconductive. For example, metals and semiconductors are suitable. Further, it may be a composite of an insulator and a conductor.
The hinge 40 is fixed at both ends in the longitudinal direction, and can be rotationally displaced about the hinge axis by twisting the hinge 40 itself. The elastic force is arbitrarily determined by the shape (film thickness, width, length) of the hinge 40 and material properties (Young's modulus, Poisson's ratio, etc.). The movable member 30 is electrostatically driven by electrodes arranged on the left and right sides, and can be actively driven in the right and left rotations, so that the elastic force of the hinge 40 can be set small. Further, the support portion 41 of the hinge 40 may have any structure as long as it is fixed to the substrate 10.

  The central portion of the hinge 40 (conductive portion 31) is widened with respect to both end portions and has a wing shape extending in the horizontal left-right direction (left-right direction in FIG. 13). The extended plan view has a substantially H shape. The mirror portion 32 has an H shape that is substantially the same shape as the hinge central portion. The mirror part 32 or the mirror part 32 and the hinge 40 are made of metal, semiconductor, etc., have conductivity, and the surface (light incident surface) opposite to the substrate 10 has reflectivity.

FIG. 16 is a diagram for explaining the configuration and operation of the reflective light modulation element shown in FIG. 13. (1) is a diagram showing the electrode wiring, (2) is the left-side tilted state of the reflective light modulation element, 3) is an operation explanatory view showing the right-side tilt situation.
As shown in (1), in the reflective light modulation device 100, the first lower electrode 20a is electrically connected to become the first drive electrode 81a, and the second lower electrode 20b is electrically connected to perform the second drive. The conductive portion 31 of the movable member 30 becomes the movable body electrode 80 as the electrode 81b.
Of the first lower electrode 20a and the second lower electrode 20b disposed around the torsion center 40C axis of the movable member 30, the first lower electrode 20a and the second lower electrode 20b are connected to different power sources, respectively. Can be applied. By applying a voltage to these electrodes and the conductive portion 31 of the movable member 30, it is possible to apply a vertical rotational moment to both ends of the movable member 30 across the torsion center 40 </ b> C, and a large rotational driving force F Can be obtained. One operation can be controlled by three electrodes.

Next, the tilting operation of the reflective light modulation device 100 configured as described above will be described with reference to (2) and (3) of FIG.
As a basic operation, the reflective light modulation element 100 deflects the reflection direction of light by swinging and displacing the mirror portion 32 by applying a voltage to the lower electrode 20 and the conductive portion 31.
When a potential difference is applied to the first lower electrode 20a and the second lower electrode 20b with respect to the conductor of the mirror part / hinge complex (conductive part 31), the respective electrodes and the conductor of the mirror part / hinge complex An electrostatic force is generated between them, and a rotational torque acts around the twist center 40C axis of the hinge 40. Therefore, the mirror part 32 can be rotationally displaced by controlling the potential of each electrode. The displacement position is determined by the state of the mirror portion 32, the electrostatic force generated by each electrode at that time, and the elastic force of the hinge 40.

For example, as shown in FIG. 16B, the potential V1 is applied to the first drive electrode 81a in which the first lower electrode 20a is connected on the substrate 10. In addition, the potential V2 is applied to the second drive electrode 81b in which the second lower electrode 20b is connected on the substrate 10. Further, a potential Vm is applied to the movable body electrode 80 that is the conductive portion 31 of the mirror portion 32 and the hinge 40. The potentials V1, V2, and Vm are supplied and controlled by a semiconductor integrated circuit (for example, a CMOS circuit 71) formed on the substrate 10.
Here, the potential difference of V1 with respect to Vm is V (1), and the potential difference of V2 with respect to Vm is V (2). When V (1) = V (2) = 0, the external force generated in the mirror section 32 is zero, and the state at the time of element formation is maintained. The mirror section 32 is as shown in FIG. , Approximately horizontal to the substrate 10. This state is stable due to the elastic force of the hinge 40.

  When V (1) = V (2) ≠ 0, the electrostatic force generated in the mirror portion 32 is symmetric about the twist center 40C of the hinge 40, and the mirror portion 32 is still in the substrate formation state while maintaining the state at the time of element formation. 10 is substantially horizontal.

  When at least one of V (1) and V (2) is not zero and is different from each other, the electrostatic force generated in the mirror part 32 is asymmetrical about the twist center 40C axis of the hinge 40, and the mirror part 32 is not applied to the substrate 10. Lean against.

For example, when V (1)> V (2), as shown in FIG. 16 (2), the electrostatic force F generated by the first lower electrode 20a is larger than the electrostatic force f generated by the second lower electrode 20b. The mirror part 32 is tilted to the left. Conversely, when V (1) <V (2), the electrostatic force F generated by the second lower electrode 20b is larger than the electrostatic force f generated by the first lower electrode 20a as shown in FIG. 16 (3). Thus, the mirror part 32 tilts to the right.
At this time, if V (1) and V (2) are sufficiently large, the mirror portion 32 can be easily rotated and displaced in an arbitrary direction from the flat state even if the difference between V (1) and V (2) is small. Is possible. For example, if the potentials to be controlled are V1 and V2, the potential difference is small, so that the voltage of the control circuit can be lowered, and this has the advantage of being superior in cost and integration.
In this way, by appropriately supplying potentials to V1, V2, and Vm, the mirror portion 32 is rotated clockwise, counterclockwise, flat, etc. from the electrostatic force generated in each electrode and the elastic force of the hinge 40. It can be displaced to an arbitrary position. The driving method at this time may be either analog control (control to an arbitrary displacement) or digital control (for example, control to a binary displacement).

  In the above rotational drive, the rotation angle can be accurately controlled by providing an appropriate rotation stopper and rotationally displacing the mirror portion 32 until it contacts the stopper. Moreover, it is also possible to rotationally displace the mirror part 32 without making contact using a linear region of voltage and displacement characteristics. In this case, since there is no contact portion, problems such as sticking do not occur, and reliability can be increased. Note that the above-described electrode wiring and the displacement operation method of the mirror unit 32 by each potential control are only examples, and are not limited thereto.

Therefore, according to the reflection-type light modulation element 100 described above, the movable member 30 includes the twistable hinge 40 including the mirror portion 32 and the conductive portion 31, thereby reducing the mass of the entire movable portion and increasing the inertia. The moment can be reduced and high speed movement is possible.
Note that when the lower electrode 20 is disposed on the substrate 10 side and an upper electrode is further installed on the opposite side of the lower electrode 20 with the movable member 30 interposed therebetween, it is activated by electrostatic force from above and below regardless of the spring force of the hinge 40. In particular, the movable member 30 can be swung (actively). From this, the spring force of the hinge 40 required for the structure in which the movable member 30 is restored using the spring force does not have to be large, and the driving resistance when the spring force is increased is reduced. High-speed and low-voltage driving is possible.

As described above, the hinge 40 used has a rectangular shape when viewed in a cross section on a plane perpendicular to the longitudinal direction. However, in a hinge having a rectangular cross section, when it is attempted to increase the bending rigidity of the hinge portion, the torsional rigidity of the hinge portion similarly increases, and it is difficult to widen the servo band of the micromirror device.
In order to solve this drawback, an invention has been disclosed in which only the bending rigidity is significantly increased without significantly changing the torsional rigidity of the hinge portion (see Patent Document 1).
JP2001-1117026

FIG. 17B is a perspective view of the vicinity of the hinge portion described in Patent Document 1 of the micromirror device (light modulation element). In the figure, 200 is a micromirror device (light modulation element) according to the invention described in Patent Document 1, 230 is a movable member, 240 is a hinge, 240a is a base, and 240b is formed at the center of the base 240 along the longitudinal direction. It is a projected part.
Since the conventional hinge 40 (FIG. 14B) has a rectangular cross section, the flexural rigidity in the longitudinal direction (perpendicular to the paper surface in FIG. 14) was weak. By forming a protrusion 240b projecting in the thickness direction at the center in the longitudinal direction, the flexural rigidity in the longitudinal direction of the hinge 240 is greatly increased.
FIG. 17A is a perspective view of the vicinity of the hinge portion according to the present invention. (This will be described later).

As described above, in the light modulation element 200 described in Patent Document 1, since the protrusion 240b is formed in the thickness direction at the center of the base 240a of the hinge 240 in the longitudinal direction, the length of the hinge 240 is long. The bending rigidity in the scale direction can be greatly increased.
However, in the light modulation element manufactured in this way, the hinge is damaged in the dry etching process and the use for many years in the manufacturing process of the hinge as in the conventional device so far, and the light modulation element functions. Sometimes it disappeared.

When the applicant examined the cause of the hinge breakage, it was found that cracks are likely to occur at the edge portion of the hinge, and most of the hinge breakage is caused by the crack at the edge portion.
Accordingly, an object of the present invention is to make it difficult to generate cracks at the edge portion of the hinge, thereby overcoming the disadvantages of the invention described in Patent Document 1 and increasing the productivity of the light modulation element. It is an object of the present invention to provide an optical modulation element that can greatly increase only the bending rigidity without significantly changing the torsional rigidity of the hinge portion.

  In order to solve the above-mentioned problems, the invention according to claim 1 relates to a microelectromechanical element, comprising a substrate and a deformable elastic beam body installed on the substrate via a gap, the elastic beam body. Is a micro-electromechanical element that is operated by twisting or bending (hereinafter referred to as “deformation”), and protrusions projecting in the thickness direction are formed at both ends of the elastic beam body. It is characterized by.

  The invention according to claim 2 relates to a microelectromechanical element, and includes a substrate provided with electrodes, a deformable long elastic beam body laid on the substrate via a gap, and attached to the beam body. A movable member having at least a part of the conductive portion opposed to the electrode and capable of being displaced by deformation of the beam, and a microstructure that swings and displaces the movable member by applying a voltage to the electrode and the conductive portion. The long beam body is characterized in that protrusions projecting in the thickness direction are formed at both ends of the free end where the elongate beam body is not installed.

  According to a third aspect of the present invention, there is provided a microelectromechanical light modulation device comprising: a substrate provided with electrodes; a torsionally deformable long elastic beam member that is laid on the substrate via a gap; and the beam member. A movable member that is provided with a conductive portion facing at least a part of the beam body and is capable of rotational displacement by twisting of the beam, an optical functional film provided on a surface of the movable member, the electrode, and the conductive member. In an optical modulation element that modulates light by swinging and displacing the optical functional film by applying a voltage to the portion, it projects in the thickness direction at both ends of the free end where the elongated beam body is not installed. It is characterized in that a protruding portion is formed.

  The invention according to claim 4 relates to a microelectromechanical light modulator, a substrate provided with an electrode, an elongated elastic beam body that can be bent and deformed via a gap on the substrate, and the beam body And a member parallel to the electrode having a conductive portion opposed to the electrode at least partially and capable of being vertically displaced by bending of the beam, and applying the voltage to the electrode and the conductive portion. In the light modulation element that modulates light by displacing in parallel with the electrodes, protrusions that protrude in the thickness direction are formed at both ends of the free end where the long beam body is not installed. It is characterized by that.

  According to a fifth aspect of the present invention, in the element according to any one of the first to fourth aspects, the cross-sectional shape of the elastic beam body is a substantially concave shape or a substantially circular shape in which both end portions are protrusions and the central portion is thinned. It is characterized by an arc shape or a substantially elliptical arc shape.

  According to a sixth aspect of the present invention, in the micro electromechanical light modulation device according to the fifth aspect, the protrusion is formed of the same material as that of the elastic beam member.

  According to a seventh aspect of the present invention, in the micro electromechanical light modulator according to the fifth aspect, the protrusion is formed of a material different from that of the elastic beam member.

  The invention according to claim 8 is the element according to any one of claims 1 to 7, characterized in that the protrusions are formed on an upper surface and a lower surface of the elastic beam body.

As described above, according to the present invention, the end portions of the beam body are reinforced by projecting the protrusions in the thickness direction at both ends in the direction perpendicular to the longitudinal direction of the long beam body. Therefore, a micro electromechanical element in which the edge portion of the hinge is difficult to break can be obtained.
Further, since the reinforcement of the end portion of the long beam body is made of the same material as that of the member of the beam body, the productivity is increased and the boundary between the reinforcement and the beam body is eliminated and the strength is increased.
Alternatively, since the end portion is made of a material different from that of the member of the beam body, an inexpensive material can be used, and the cost is reduced.

Hereinafter, the present invention will be described with reference to FIGS. 1 and 2.
1 is a plan view of a reflective light modulation device according to the present invention, and FIG. 2 is a cross-sectional view taken along lines AA, BB, CC, and DD in FIG. It is sectional drawing represented to (c) and (d).
1 and 2, the reflective light modulation element 100 includes a substrate 10 and a beam body (hereinafter referred to as “hinge”) 40 via a gap G (FIG. 2) on the substrate 10 (conductive portion 31). And a movable member 30 having a light reflector (hereinafter referred to as a “mirror part”) 32 that can be rotationally displaced by twisting of the hinge 40 and having a conductive part 31 at least in part. The lower electrode 20 is disposed on the substrate 10 side and faces the movable member 30 through the gap G. According to the present invention, the shape of the hinge 40 is characteristic, and the other members are the same as those of the conventional device of FIG.
In this embodiment, a mirror that reflects incident light is applied as the optical functional film.

  The hinge 40 is composed of a base portion 40a and a protrusion 40b (see FIG. 2B), and the protrusion 40b is at both ends of the base portion 40a (that is, an end portion perpendicular to the longitudinal direction of the base portion 40a). The cross section is formed into a concave shape as a whole. And the protrusion 40b has reached to the both ends of the elongate direction of the hinge 40 (refer FIG.2 (c)).

FIG. 17A is a perspective view of the vicinity of a hinge portion according to the present invention of a micromirror device (light modulation element). In the figure, 100 is a light modulation element, 30 is a movable member, 40 is a hinge, 40a is a base, and 40b is a protrusion formed at both ends along the longitudinal direction of the base 40.
The hinge 240 in FIG. 17B has a protrusion 240b formed at the center along the longitudinal direction, but here by forming protrusions 40b protruding at both ends of the base 40a of the hinge 40. Further, it is possible to make it easier to twist while maintaining the bending rigidity equivalent to that of the hinge 240.

FIG. 3 is a diagram showing simulation results on the flexural rigidity and torsional rigidity of the hinges of the element according to the present invention (FIG. 17A) and the conventional element (FIG. 17B).
In the figure, the vertical axis is displacement, the horizontal axis is voltage, the deflection diagram, ▲ is the element according to the present invention, ● is the conventional element, * in the torsional diagram is the element according to the present invention, and ■ is the conventional element .
As can be seen from the figure, regarding the bending, the element (▲) according to the present invention is difficult to bend even when a voltage is applied as in the conventional element (●). It can be seen that it becomes easier to twist with a slight voltage compared to.

In the above simulation diagram, the cross section of the element according to the present invention was examined for the concave shape shown in FIG. 17 (a), and the cross section of the conventional element was examined for the convex shape of FIG. 17 (b). Simulations of flexural rigidity and torsional rigidity were performed for other cross-sectional hinges. FIG. 4 shows another cross-sectional shape for which simulation was performed.
As can be seen from the figure, there are two types of cross-sections of the element according to the present invention, (1) only one side is bent in a substantially arc shape or a substantially elliptic arc shape from both end portions toward the central portion, (2) There are two types of cross-sections of both sides of the conventional element, which are bent in a substantially arc shape or a substantially elliptical arc shape from both ends toward the center portion. (1) Only one side is from both ends. (2) Both sides swell in a substantially arc shape or a substantially elliptical arc shape from both ends toward the center portion. It is what is.
As a result of performing simulations with the respective cross-sections shown in FIG. 4, regarding the bending, the element according to the present invention is not easily bent even when a voltage is applied as in the conventional element. In comparison, it was found that there was a tendency to twist easily with a slight voltage.

As described above, according to the present invention, since the edge portion of the hinge is formed on the protrusion 40b, even if the hinge end portion is started to be damaged by a dry etching process or a long-time use in the manufacturing process of the hinge, Since it is reinforced, it becomes difficult to break.
Further, since the protrusion 40b extends in the longitudinal direction of the hinge 40, the bending rigidity can be greatly increased, and since the two protrusions 40b extend in parallel, the torsional rigidity of the hinge part is the conventional device. There is no change compared with.

Next, a method for manufacturing the reflective light modulation element 100 according to the present invention will be described.
FIGS. 5A to 5D are explanatory views showing examples of a general manufacturing process of the reflective light modulation element, which are shown in FIGS.
As shown in FIG. 5A, in the drive circuit substrate 10, a CMOS circuit 71 (FIG. 15) is formed on a Si substrate 70, and a first SiO2 insulating film (not shown) is formed thereon. After the surface is flattened by CMP or the like, contact holes for connecting the output of the drive circuit to each electrode of the element are formed.
A first aluminum thin film (not shown) (preferably an aluminum alloy containing a refractory metal) is formed on the drive circuit substrate 10 by sputtering, and patterned into a desired electrode shape by ordinary photolithography etching to form a first lower electrode. 20a and the second lower electrode 20b are formed. At this time, a contact hole is formed in the insulating layer 75 (see FIG. 15), and both the first lower electrode 20a and the second lower electrode 20b are connected to the output of the CMOS circuit 71 via the wiring circuit 73. Thus, each potential can be supplied.

  Next, as shown in FIG. 5B, a first positive resist 61 is applied, and a portion to be the support portion 41 of the hinge 40 is patterned and hard-baked. Due to the surface tension during resist film formation, the resist surface becomes flat regardless of the level difference of the underlying film. The first resist layer 61 functions as a sacrificial layer and is removed in a process described later. Accordingly, the film thickness of the resist after hard baking determines the gap G between the lower electrode 20 and the hinge 40 (and the mirror part 32) in the future. Photosensitive polyimide can also be used in place of the resist 61.

Then, as shown in FIG. 5C, a second aluminum thin film (preferably an aluminum alloy containing a refractory metal) 93 to be the hinge 40 and its supporting portion 41 is formed by sputtering. Then, depositing a SiO ₂ by PE-CVD (Plasma CVD) (not shown). This SiO ₂ film functions as an etching mask for the second aluminum thin film 93. Next, the SiO ₂ film is patterned by photolithographic etching so that the desired hinge 40 and its supporting portion 41 are formed (Note that another figure is used for the formation of protrusions at both ends of the hinge 40 according to the present invention). To explain.)
Next, a third aluminum thin film (preferably an aluminum alloy containing a refractory metal) 95 to be the mirror portion 32 is formed by sputtering. Then, depositing a SiO ₂ by PE-CVD (Plasma CVD) (not shown). This SiO ₂ film functions as an etching mask for the third aluminum thin film 95. Next, the SiO ₂ film is patterned so as to have a desired mirror shape by photolithography.
Further, the third aluminum thin film 95 and the second aluminum thin film 93 are successively etched using the SiO ₂ film as an etching mask, and finally the SiO ₂ film is removed by plasma etching. The aluminum thin film is etched by wet etching with an aluminum etchant (mixed aqueous solution of phosphoric acid, nitric acid, and acetic acid) or plasma etching with a chlorine-based gas. In addition, a contact hole is formed in the first SiO ₂ insulating film, and the hinge 40 (mirror part 32) is connected to the output of the drive circuit and supplied with a potential.

  Finally, as shown in FIG. 5D, the first resist layer 91 which is a sacrificial layer is removed by oxygen gas-based plasma etching to form a gap G. As a result, the reflective light modulation element 100 in which the movable member 30 is disposed via the gap G on the substrate 10 provided with the first lower electrode 20a and the second lower electrode 20b is obtained.

  In addition to the above, the manufacturing method of the reflective light modulation element 100 has the following process variations. That is, the hinge 40 and the mirror part 32 may be constituted by a single aluminum thin film. In this case, although the thickness of the hinge 40 and the thickness of the mirror part 32 become equal, there exists an advantage which can reduce a process.

  The mirror part 32 may be a composite of a conductor and an insulator. For example, the mirror part 32 may be formed integrally with the hinge 40 or separately from a conductor such as metal or semiconductor, and a multilayer mirror may be stacked thereon. As the multilayer mirror, for example, an interference mirror which is a dielectric multilayer film or a dielectric / metal multilayer film can be used, thereby reducing the absorption of the reflection surface by incident light as much as possible and extremely increasing the reflectance. And the effect of reflecting light of a specific wavelength can be obtained. The mirror part 32 may be a composite of a conductor and an insulator, and a reflective member may be formed on a part of the mirror part 32. The mirror part 32 may be made of the same material as the hinge 40. The conductive part 31 is formed on a part (here, the lower surface) of the mirror part 32 by any one of the configurations described above.

  The mirror part 32 or the mirror part 32 and the hinge 40 have conductivity, and can be electrically connected on the substrate 10 via the support part 41 (FIG. 2C) of the hinge 40. As described above, the mirror part 32 and the hinge 40 can be rotationally displaced around the hinge axis (twisting center 40C) by the hinge structure, and the mirror part 32 or the mirror part 32 and the hinge 40 are conductive. And any structure and material may be used as long as they can be electrically connected to the substrate 10 via the support portion 41.

The structural material of the lower electrode 20 and the hinge 40 may be a conductive material other than aluminum. For example, crystalline Si, polycrystalline Si, metal (Cr, Mo, Ta, Ni, etc.), metal silicide, conductive organic material, etc. can be used suitably. Further, the conductive portion 31 may be laminated with a protective insulating film (for example, SiO ₂ , SiNx) thereon. In this case, a hybrid structure in which a conductive thin film such as a metal is laminated on an insulating thin film such as SiO ₂ , SiNx, BSG, metal oxide film, or polymer can also be used.

In the above description, the resist material is used as the sacrificial layer, but the present invention is not limited to this. For example, a metal such as aluminum or Cu, or an insulating material such as SiO ₂ is suitable as the sacrificial layer. In this case, a material that is not corroded or damaged when the sacrificial layer is removed is appropriately selected as the structural material.
In the above embodiment, the mask is made of SiO ₂ , but any material (eg, resist) may be used as long as the selection ratio is the same as the structural material.

In addition to the dry etching (plasma etching) described above, the sacrificial layer removal method can use wet etching depending on the combination of the structural material and the sacrificial layer. In the case of wet etching, a supercritical drying method or a drying method using a freeze drying method is preferable in order to prevent the structure from sticking due to surface tension in the rinsing / drying step after etching.
In addition, the structure, material, and process are not limited to the above examples as long as they meet the gist of the present invention.

Next, the formation process of the recessed part which concerns on this invention is demonstrated with the perspective view of FIGS.
In the Si substrate K of FIG. 6A, as described above, a CMOS circuit is formed inside, a first SiO 2 insulating film is formed thereon, and the surface is flattened by CMP or the like. A contact hole for connecting the output of the drive circuit to each electrode of the element is formed, an aluminum thin film is formed on the drive circuit substrate 10 and patterned into a desired electrode shape by photolithography etching to form the first lower electrode and A second lower electrode is formed. A contact hole is formed in the insulating layer, and both the first lower electrode and the second lower electrode are connected to the output of the CMOS circuit via the wiring circuit, and potentials can be supplied respectively.

  6 (2), the sacrificial layer (resist G) is applied to a thickness equal to the width of the gap G over which the Si substrate K is laid on the concave hinge of the present invention, and the portion that becomes the support portion of the hinge is patterned to hard Bake. This sacrificial layer G is removed in a later step. The resist film thickness after hard baking determines the gap between the lower electrode and the hinge.

  In FIG. 6 (3), the first material D1 is formed by sputtering with an aluminum thin film serving as a hinge and its support. This aluminum thin film portion is the thickness of the central portion of the concave hinge of the present invention.

Thereafter, in FIG. 7 (4), SiO ₂ is formed by PE-CVD (plasma CVD) to form a first mask, and then the shape of the portion that becomes the central depression of the recess of the present invention is formed by photolithography etching. The first mask (SiO ₂ film) is patterned to obtain a first mask M1 as shown in the figure. The horizontal width of the first mask M1 is the horizontal width of the recess of the concave hinge of the present invention.

  Next, in FIG. 7 (5), a second material D2 (aluminum thin film) is formed by sputtering. This thickness is the height of the protrusion of the concave hinge of the present invention.

Further, in FIG. 7 (6), a mask is formed with a SiO ₂ film thereon by PE-CVD (plasma CVD), and then SiO ₂ is formed by photolithographic etching so as to have the width of the projection of the concave hinge of the present invention. _Two films are patterned to form a second mask M2.

Thereafter, in FIG. 8 (7), the aluminum thin film is continuously etched in the vertical direction using the SiO ₂ film as an etching mask to form the concave hinge of the present invention under the two masks M1 and M2.

  In FIG. 8 (8), when the two-layer masks M1 and M2 are removed, the concave hinge of the present invention is formed from the base by the first material (aluminum thin film) D1 and from the protrusion by the second material (aluminum thin film) D2. It ’s done.

  Finally, as shown in FIG. 8 (9), when the sacrificial layer G is removed by oxygen gas-based plasma etching, a gap G is formed, and a bridge-like hinge is obtained (in the figure, a bridge bridging portion is drawn). And the support portions at both ends are not drawn, so it appears to float in the air from the Si substrate K).

  In addition to the above, the manufacturing method of the reflective light modulation element has the following process variations. That is, the hinge 40 and the mirror part 32 may be constituted by a single aluminum thin film. In this case, although the thickness of the hinge 40 and the thickness of the mirror part 32 become equal, there exists an advantage which can reduce a process.

The above embodiments have been shown as examples in which the concave hinge of the present invention is applied to a reflective light modulation element in which the torsion is rotated. However, the present invention is not limited to this, and the hinge is bent and displaced up and down. Needless to say, the present invention may be applied to such a parallel plate type light modulation element.
The parallel plate light modulation element is, for example, a flexible thin film made of a transparent electrode and a diaphragm, which is installed on a fixed electrode on a substrate via a support portion. In this parallel plate type light modulation element, a predetermined voltage is applied between the two electrodes to generate an electrostatic force between the electrodes, and the flexible thin film is bent toward the fixed electrode. Along with this, the optical characteristics of the element itself change, and light is transmitted to the light modulation element. On the other hand, by setting the applied voltage to zero, the flexible thin film is elastically restored, and the light modulation element blocks light. In this way, light modulation is performed.
FIG. 9 is a cross-sectional view showing an internal configuration of a parallel plate type light modulation element of the type using interference. FIG. 9A shows a case where the voltage between the electrodes is zero, and FIG.
In FIG. 9, 190 is a parallel plate type light modulation element, 191 is a glass substrate, 192 and 196 are upper and lower transparent electrodes, 193 and 195 are upper and lower transparent insulating films, 194 is a spacer, and 197 is a transparent spacer. Further, the transparent insulating films 193 and 195 have a half mirror function.
In this light modulation element, upper and lower transparent electrodes 192 and 196 are formed on the upper surface of a glass substrate 191 with a space therebetween, a transparent insulating film 193 is disposed on the lower transparent electrode 192, and a spacer A transparent insulating film 195 is disposed with 194 interposed therebetween, and a transparent electrode 196 is disposed thereon. In the space between the two transparent insulating films 193 and 195 and the two spacers 194, a transparent spacer 197 made of an insulator is formed in contact with the lower transparent insulating film 193.

  Since no voltage is applied between the upper and lower transparent electrodes 192 and 196 in the light modulation element 109 shown in FIG. 9A, the upper transparent insulating films 193 and 195 are formed on the transparent spacer 197. As a result, the light Li emitted from the light source disposed on the lower side of the glass substrate 191 is transmitted by the lower transparent insulating film, that is, the half mirror 193. It is reflected and does not pass through the light modulation element body 190.

  FIG. 9B is a cross-sectional view showing an internal state when the voltage Von is applied between the upper and lower transparent electrodes 192 and 196 in the light modulation element 190 shown in FIG. 9A. In the light modulation element 190 shown in FIG. 9B, as a result of applying a voltage between the upper and lower transparent electrodes 192 and 196, an electrostatic force due to the applied voltage acts between the transparent electrodes 192 and 196. The upper transparent electrode 196 and the lower upper transparent insulating film (half mirror) 195 are pushed downward, and the upper half mirror 195 is brought into close contact with the transparent spacer 197 between the upper and lower half mirrors 193 to 195. The distance of t2 becomes t2, and the light transmittance of the optical path perpendicular to the two upper and lower half mirrors 193 and 195 increases. As a result, the light Li emitted from the light source passes through the light modulation element body 190. Thus, the light modulation element 190 can be pulled out upward. As described above, the parallel plate light modulation element 190 can also transmit and block light by using interference. Therefore, as a shape of one or both of the transparent insulating film 195 and the transparent electrode 196 that are movable films of the parallel plate type light modulation element 190, the thickness direction is provided at both ends of the free end where the long beam body is not installed. By adopting a shape (FIG. 17A) in which a protruding portion is formed, deformation due to film stress can be made difficult to occur as shown below.

FIG. 10 shows a simulation result of the hinge flexural rigidity and the hinge film stress (b) when the hinge according to the present invention (FIG. 17A) is applied to a parallel plate light modulation element. It is a diagram shown with the case of 17 (b)).
In FIG. 10A, the vertical axis is displacement, the horizontal axis is voltage, ▲ is an element according to the present invention, and ● is a conventional element.
As can be seen from the drawing, it can be seen that the element (▲) according to the present invention has the same tendency as the conventional element (●) with respect to the bending.
In FIG. 10 (b), the vertical axis represents the amount of deformation, the horizontal axis represents the stress, * represents the element according to the present invention, and ▪ represents the conventional element.
As can be seen from the figure, regarding the stress, the element (*) according to the present invention is less likely to be deformed by the film stress of the hinge than the conventional element (■).
As described above, since the hinge can use not only the twist but also the deflection, the term “deformation” is used as a superordinate concept thereof.

As described above, the cross section of the element according to the present invention is the concave shape shown in FIG. 2 or the arc shape shown in FIG. 4, but the present invention is not limited to this, and may have a cross sectional shape as shown in FIG. .
As can be seen from the figure, (1) has an H-shaped cross section 91 and (2) has an E shape. Both have the same shape as that shown in FIG. 2 and FIG. 4 in that both have convex shapes at both ends. If it does in this way, it will become difficult to bend about bending, and it will become easy to twist about a twist with a slight voltage.

Furthermore, in the above description, it has been described that the height of the convex portion at the end portion is constant in the longitudinal direction (see 42 in FIG. 2C), but the convex portion in the longitudinal direction of the element according to the present invention. The height of the part does not necessarily have to be constant, and may have a changing shape.
FIG. 12 is a perspective view showing an example in which the height of the convex portion at the end of the element 90 according to the present invention changes in the longitudinal direction. (1) is an example in which the height L1 of the convex portion at the element end is constant in the longitudinal direction, and (2) is that the height L2 of the convex portion at the element end is low in the longitudinal direction and both ends are low. (3) shows an example in which the height L3 of the convex portion at the end of the element changes so that both ends are high in the longitudinal direction and the central portion is low. The example L2 in (2) tends to be less likely to bend and twist with respect to bending and twisting, and the example L3 in (3) tends to be more likely to bend and twist with respect to bending and twisting. The example of L1 in (1) is intermediate It is located in. Therefore, since it is determined what kind of bending and twisting is desirable depending on the material and shape / structure of the beam to be used and the method of using the beam, etc., it is appropriately selected from (1) to (3) accordingly. Or they may be used in combination.

In addition to the reflection type light modulation element and the parallel plate type light modulation element described above, when applied to a cantilever type light modulation element in which the light modulation part (movable part) is cantilevered, there is a significant effect compared to the conventional one. Needless to say.
Further, in the light modulation element according to the present invention, the optical functional film is not limited to the mirror used in the reflection type light modulation element, but includes a modulation method such as an interference film or a light transmissive film used in the parallel plate type light modulation element. A known member can be used depending on the case.

  In addition, the hinge according to the present invention is not limited to a light modulation element, but can be applied to other fields, for example, a microswitch of a microelectromechanical element by contact / non-contact of two parallel electrodes to obtain a switch that is unlikely to fail. It is done.

As described above, according to the present invention, the hinge manufacturing process can be performed in any of the reflection type light modulation element, the parallel plate type light modulation element, and the cantilever type light modulation element by forming the edge portion of the hinge at the protrusion. Even if the end of the hinge is damaged by the dry etching process or long-time use, the end of the hinge is reinforced, so that it is difficult to be damaged.
Moreover, since the protrusions extend in the longitudinal direction of the hinge, the bending rigidity can be greatly increased, and since the two protrusions extend in parallel, the torsional rigidity of the hinge part is compared with that of the conventional device. Will not change.

It is a top view of the reflection type light modulation element to which the hinge concerning the present invention is applied. It is sectional drawing which represented each sectional view of AA of FIG. 1, BB, CC, DD to (a), (b), (c), (d). It is a diagram which shows the result about the bending rigidity and torsional rigidity of the hinge of the element which concerns on this invention (FIG. 17 (a)), and a conventional element (FIG.17 (b)). It is a diagram which shows the simulation result about the bending rigidity and the torsional rigidity of the hinge of the element (FIG. 17A) according to the present invention and the conventional element (FIG. 17B). It is a figure which shows the other cross-sectional shape of the hinge which performed simulation. It is explanatory drawing which represented the manufacturing process example of the reflection type light modulation element shown in FIG. 1 to (A)-(d) according to AA and CC cross sections. It is a perspective view of process (1)-(3) of the example of a manufacturing process of the reflection type light modulation element shown in FIG. It is a perspective view of process (4)-(6) of the example of a manufacturing process of the reflective light modulation element shown in FIG. It is a perspective view of process (7)-(9) of the manufacturing process example of the reflective light modulation element shown in FIG. It is sectional drawing which shows the internal structure of the parallel plate type | mold light modulation element of the type using interference, (a) is a case where the voltage between electrodes is zero, (b) is a case where the voltage between electrodes is present. About the flexural rigidity of the hinge and the film stress (b) of the hinge when the hinge according to the present invention (FIG. 17A) and the conventional hinge (FIG. 17B) are applied to a parallel plate type light modulation element. It is a diagram which shows a simulation result. It is an example which shows other cross-sectional shapes other than FIG. 2 and FIG. It is a perspective view which shows the example from which the height of the convex part of the element edge part which concerns on this invention changes to a elongate direction. It is a top view of the reflection type light modulation element concerning a conventional apparatus. It is sectional drawing which represented each sectional view of AA of FIG. 13, BB, CC, and DD to (a), (b), (c), (d). It is sectional drawing of the board | substrate shown in FIG. FIG. 13 (1) showing the electrode wiring of the reflection type light modulation element shown in FIG. 13, an operation explanatory diagram (2) showing the left side inclination state of the reflection type light modulation element, and an operation explanatory diagram showing the right side inclination state (3). These are perspective views of the vicinity of the hinge part (a) according to the present invention of the micromirror device (light modulation element) and the vicinity of the hinge part (b) described in Patent Document 1, respectively.

Explanation of symbols

10 Substrate 20 Lower electrode 20a First lower electrode 20b Second lower electrode 30 Movable member 31 Conductive part 32 Mirror part (light reflector)
40 Hinge (beam)
40a Base part 40b Projection part 41 Support part 80 Movable body electrode 81a First drive electrode 81b Second drive electrode 100 Reflective light modulation element G Gap

Claims (8)

  A micro electromechanical element comprising a substrate and a deformable elastic beam body erected on the substrate via a gap, and operated by deformation of the elastic beam body, the both ends of the elastic beam body A microelectromechanical element characterized in that a protrusion protruding in the thickness direction is formed on the portion. A substrate with electrodes;
A deformable long elastic beam body erected on the substrate via a gap;
A movable member attached to the beam body and having a conductive portion facing the electrode at least in part and capable of being displaced by deformation of the beam body;
In the microstructure that swings and displaces the movable member by applying a voltage to the electrode and the conductive portion,
A microelectromechanical element characterized in that protrusions projecting in the thickness direction are formed at both ends of a free end where the long beam body is not installed. A substrate with electrodes;
A torsionally deformable long elastic beam body erected on the substrate via a gap;
A movable member attached to the beam body and having a conductive portion opposed to the electrode at least in part and capable of rotational displacement by twisting of the beam body;
An optical functional film provided on the surface of the movable member;
In a light modulation element that modulates light by swinging and displacing the optical functional film by applying a voltage to the electrode and the conductive portion,
2. A micro electro mechanical light modulation element characterized in that protrusions projecting in the thickness direction are formed at both ends of a free end where the long beam body is not installed. A substrate with electrodes;
A long elastic beam body that can be flexibly deformed and is laid on the substrate via a gap;
A member that is attached to the beam body and has a conductive portion facing the electrode at least in part, and that is parallel to the electrode that can be vertically displaced by bending of the beam body;
In a light modulation element that modulates light by displacing the member in parallel with the electrode by applying a voltage to the electrode and the conductive portion,
2. A micro electro mechanical light modulation element characterized in that protrusions projecting in the thickness direction are formed at both ends of a free end where the long beam body is not installed.   The cross-sectional shape of the elastic beam body is any one of a substantially concave shape, a substantially arc shape, and a substantially elliptical arc shape in which both end portions are protrusions and the central portion is thinned. Item 1. The device according to item 1.   6. The micro electro mechanical light modulation element according to claim 5, wherein the protrusion is made of the same material as that of the elastic beam member.   6. The micro electro mechanical light modulation element according to claim 5, wherein the protrusion is made of a material different from that of the elastic beam member.   The element according to claim 1, wherein the protrusion is formed on an upper surface and a lower surface of the elastic beam body.

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