JPH09318888A - Microactuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microactuator whose turning angle is large and whose driving voltage is low by driving a movable part by attracting action based on electrostatic force between a recessed surface electrode fixed in the recessed part of a base plate and a projected surface movable electrode turhably arranged at a position deviated from a position opposed to the recessed electrode. SOLUTION: In a movable part 12; a semicylindrical projected surface 12a turnably opposed to the recessed surface 2a of the base plate 1 while keeping a specified distance between the surface 2a and the surface 12a is formed. The movable electrodes 5a and 5b are arranged at the positions deviated in a turning direction from the positions opposed to the fixed electrodes 3a and 3b on the surface 2a on the surface 12a. By impressing voltage between the electrodes 3a and 5b, parallel attractive force acts between both electrodes and the electrode 5a tries to move to a position facing to the electrode 3a, and the movable part 12 is rotated in a direction shown by an arrow B. By impressing voltage between the electrodes 3b and 5b, the parallel attractive force in a reverse direction acts, and the movable part 12 is rotated in a direction shown by an arrow C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microactuator used in, for example, an optical deflector.

[0002]

2. Description of the Related Art Currently, a liquid crystal cell or PLZT (Plumb Lanthanum Zir) is mainly used as an optical deflector.
There are optical shutters that utilize the electro-optical effect of ferroelectric materials such as concatenate titanates) and mechanical optical deflectors such as polygon mirrors (rotating polyhedral mirrors) used for laser light scanning of electrophotographic printers. Among them, the optical shutter has a high response speed and can be easily miniaturized and arrayed. Therefore, an optical switch used for switching an optical fiber transmission line or an optical communication terminal device, an optical head of a one-dimensional array used for an electrophotographic printer, , Is widely used in various applications such as a liquid crystal display device in which liquid crystal cells are two-dimensionally arranged. The mechanical optical deflector is an optical element for optical communication such as an optical switch that can deflect and shield regardless of wavelength, and is therefore useful when handling a multi-wavelength light source or when the wavelength of the light source varies. However, there are problems that some of them generate vibration, and that the response speed is low and miniaturization and arraying are difficult.

[0003]

By the way, in recent years, a technique for manufacturing a micromachine having an extremely fine movable mechanism has been developed using a semiconductor manufacturing technique such as a photolithography process, which is so-called microelectromechanics (MEMS). It's starting. The micromachine manufactured by the MEMS can be easily miniaturized, integrated, arrayed, and reduced in vibration, and there is a possibility that an optical deflector having a high response speed can be obtained by the miniaturization.

As an example of a mechanical optical deflector manufactured by MEMS, for example, Japanese Patent Laid-Open No. 2-8812 discloses
Larry J. Hornbeck (L.J. Hornbe
spatial light modulator (SLM: Spa) invented by ck
Tial Light Modulator) is disclosed. This spatial light modulator is an optical modulator that rotates a mirror by an electric signal to modulate the phase, reflection direction, etc. of incident light, and is used in many optical information processing devices, projection display devices, electrostatic printing devices, and the like. It is used for purposes. In addition, the magazine "IEEE SPECTRUM" 199
On November 27th, page 27, a twistable mirror (DMD: Di
A special article on a projection display device using a digital micromirror device is introduced.

FIG. 9 is a perspective view of the conventional spatial light modulator described in the above publication, and FIG. 10 is a sectional view of the spatial light modulator of FIG. 9 as seen from the direction AA. 9 and 10
As shown in, the spatial light modulator 90 includes a silicon substrate 91 and a fixed electrode 92 formed on the silicon substrate 91.
And the ground electrode 93, and the mirror 9 functioning as a light deflection plate.
4 and a support beam 95 that supports the mirror 94 on the substrate 91 in a twistable manner, and is manufactured by the above-described MEMS.
In order to deflect light using the spatial light modulator configured as described above, a voltage is applied between the mirror 94 and the fixed electrode 92, and the supporting beam 95 is twisted by the electrostatic force generated between the mirror 94 and the fixed electrode 92 to cause the mirror to move. 94 is rotated in the arrow direction B.

When the spatial light modulator 90 is used as an optical deflector for an electrophotographic printer or display device, it is necessary to reduce the space occupied by the optical system in order to downsize the printer or display device. For that purpose, it is desirable that the deflection angle B of the optical deflector is as large as possible. However, in the spatial light modulator 90 shown in FIG. 9 and FIG. 10, since the rotation angle (light deflection angle) B of the mirror 94 is determined by the gap G between the mirror 94 and the ground electrode 93, a large deflection angle B To get the distance G
Needs to be increased.

On the other hand, in order to reduce the size and cost of the entire printer or display device including peripheral circuits, the optical deflector is required to have a driving voltage as low as possible and power consumption low. In the spatial light modulator 90 shown in FIGS. 9 and 10, in order to drive the mirror 94 at a low voltage,
The gap G between the mirror 94 and the ground electrode 93 must be reduced. However, as described above, it is necessary to increase the gap G in order to obtain the large deflection angle B. As described above, in the conventional technique, it is extremely difficult to achieve both the problem of increasing the deflection angle of the optical deflector and the problem of reducing the drive voltage of the optical deflector.

The problems in the case where the spatial light modulator manufactured by the MEMS is used as an optical deflector have been described above. However, the spatial light modulator has various general small sizes in addition to its use as an optical deflector. It has various uses as an actuator in equipment. When used as a general actuator, as in the case of the optical deflector, a small actuator having a large turning angle and a low driving voltage is required.

In view of the above circumstances, it is an object of the present invention to provide a microactuator having a large turning angle and a low driving voltage.

[0010]

A microactuator of the present invention which achieves the above object is a substrate having a concave portion having a concave surface on the upper surface thereof, a fixed electrode arranged on the concave surface of the concave portion, and the concave surface. And a movable portion having a convex surface that rotatably faces the concave surface while keeping a predetermined distance between the movable portion and the movable surface, and the movable portion is provided on the convex surface of the movable portion more than the position on the convex surface facing the fixed electrode. It is characterized by comprising a movable electrode corresponding to the fixed electrode and a power supply device for applying a voltage between the fixed electrode and the movable electrode, which are arranged at positions displaced in the moving direction.

Here, the concave portion may have a hemispherical concave surface, or the concave portion may have a semi-cylindrical concave surface.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a plan view of a first embodiment of the microactuator of the present invention, and FIG. 2 shows the microactuator of FIG.
It is sectional drawing seen in the direction. As shown in FIGS. 1 and 2,
The microactuator 20 includes a substrate 1, fixed electrodes 3a and 3b, a movable portion 12, movable electrodes 5a and 5b.
And are provided. In addition to these, a power supply device (not shown) for applying a voltage between the fixed electrodes 3a and 3b and the movable electrodes 5a and 5b is provided.

The surface of the substrate 1 is covered with a SiO ₂ layer 1a, and a concave portion 2 having a semicylindrical concave surface 2a is formed on the upper surface thereof. Fixed electrodes 3a and 3b are arranged on the concave surface 2a of the substrate 1. The movable portion 12 is the substrate 1
A semi-cylindrical convex surface 12a rotatably opposed to the concave surface 2a is formed between the concave surface 2a and the concave surface 2a. On the convex surface 12a of the movable portion 12, the convex surface 1
Arrow B from the position facing the fixed electrodes 3a and 3b on 2a
The movable electrodes 5a and 5b are arranged at positions displaced by the distance D in the rotational direction indicated by arrow C and arrow C, respectively. The movable electrodes 5a and 5b correspond to the fixed electrodes 3a and 3b, respectively.

The movable portion 12 is provided with a holding material 6, an upper electrode 10 and wiring 9 in addition to the movable electrodes 5a and 5b. The lower surface of the holding material 6 is a convex surface 12a of the movable electrodes 5a and 5b.
Like the above, the movable electrode 5 is formed in a convex shape downward.
It has a function of holding a and 5b. The upper electrode 10 formed on the upper surface of the movable portion 12 also has a function as a light reflecting plate. The support beam 8 is, as shown in FIG.
It has a shape that penetrates 2 and extends long on both sides, and is formed integrally with the upper electrode 10. The support beam 8 is fixed to the substrate 1 via two support columns 11 formed on the substrate 1. Since the support beam 8 has flexibility, the movable portion 12 has a structure capable of being twisted with respect to the substrate 1. The wiring 9 electrically connects the movable electrodes 5a and 5b and the upper electrode 10. The fixed electrodes 3a, 3b and the movable electrodes 5a,
The interval G between 5b is about 1 to 10 μm.

Next, the operation of the microactuator 20 of this embodiment will be described. When a voltage is applied between the fixed electrode 3a and the movable electrode 5a, a parallel attractive force acts between both electrodes, and the movable electrode 5a tends to move to a position directly facing the fixed electrode 3a. Due to this force, a rotational moment about the support beam 8 acts on the movable portion 12, and the movable portion 12
Rotates in the direction of arrow B. Fixed electrode 3b and movable electrode 5b
When a voltage is applied between the two, the parallel attractive force in the opposite direction to the above acts, and the movable portion 12 rotates in the direction of arrow C. Therefore, by alternately applying a voltage to the fixed electrode 3a and the fixed electrode 3b, the light reflection plate on the upper surface of the movable portion 12 can be vibrated like a seesaw, and the microactuator 20 deflects and scans light. It can be used as an optical deflector. In addition, this microactuator 20
Can also be used as an optical switch by digitally driving.

Next, a second embodiment of the present invention will be described. FIG. 3 is a plan view of the second embodiment of the present invention. As shown in FIG. 3, this microactuator 3
0 means that the concave shape of the concave portion 32 of the substrate 31 is hemispherical,
Accordingly, the planar shape (the same shape as the upper electrode 34) of the movable portion 33 having the convex surface that rotatably faces the concave surface is circular. The other parts are the same as those of the microactuator 20 of the first embodiment, and the cross section of the microactuator 30 of FIG. 3 viewed in the AA direction is almost the same as that of FIG.

Depending on the manufacturing process of the microactuator, the concave shape of the concave portion 2 and the convex shape of the movable portion 12 as shown in FIG. 1 may be a semi-cylindrical shape, and the concave surface of the concave portion 32 as shown in FIG. Since the manufacturing cost may be different when the shape and the convex shape of the movable portion 33 are made hemispherical, it is necessary to appropriately select whether the shape is semicylindrical or hemispherical according to the manufacturing process.

When the microactuator of each of the above embodiments is used as an optical deflector, one microactuator is used alone as an optical deflector.
There are cases where a large number of microactuators are used in an array. FIG. 4 is a plan view of an optical deflector array in which a large number of microactuators shown in FIG. 1 are arrayed on a single substrate to form an array.

As shown in FIG. 4A, the optical deflector array 40 is an array in which a large number of microactuators 42 are arranged on a single substrate 41. Further, the optical deflector array 40 'shown in FIG. 4 (b) is an array in which a plurality of microactuators 42' having a shape elongated in the direction of the rotation axis of the mirror are arranged in an array.
Next, an example in which the microactuator of the present invention is applied to an electrophotographic printer and a projection display will be described.

FIG. 5 is a diagram showing an example in which the microactuator shown in FIG. 4 is used as an optical scanning device of an electrophotographic printer. In FIG. 5, an optical deflector array 51 and s
An objective optical system 52 including an in ^-1 θ lens and a photosensitive drum 53 that rotates in the direction of arrow B are shown. A laser beam carrying image information emitted from a laser light source (not shown) is applied to the optical deflector array 51, and the mirrors formed on the upper surface of each microactuator of the optical deflector array 51 vibrate at the same time, and the direction of arrow A is indicated. Then, the objective optical system 52 focuses the light on the photoconductor drum 53. Since the microactuator forming the optical deflector array 51 is extremely small, it can be driven at high speed, and vibration and noise can be significantly reduced as compared with the case where a conventional polygon mirror is used.

FIG. 6 is a diagram showing an example in which the microactuator shown in FIG. 4 is used in an optical system of a projection type display. This optical system includes an illumination system 61 and a light deflector 62.
, Aperture 63, projection lens 64, screen 65
And a light shielding plate 66. Optical deflector 62
As shown in FIG. 4A, is composed of a large number of microactuators arranged in an array on a single substrate. Each of these microactuators is driven based on a signal for each pixel from an image signal processing device (not shown). The light from the illumination system 61 is reflected by the mirror on the upper surface of each microactuator forming the light deflector 62, and is projected onto the screen 65 via the diaphragm 63 and the projection lens 64. When no image is displayed, the light from the illumination system 61 is reflected toward the light shielding plate 66 by changing the angle of each micro mirror of the light deflector 62.

Next, a method for manufacturing the microactuator of the present invention will be described. 7 is a process chart of the first half of the manufacturing process of the microactuator of the present invention shown in FIG. 1, and FIG. 8 is a process diagram of the latter half of the manufacturing process of the microactuator of the present invention shown in FIG. is there. First, as shown in FIG. 7A, on the silicon substrate 71,
Semi-cylindrical concave surface 7 by halftone mask process
After forming the concave portion 72 having 2a or depositing SiO ₂ as a mask layer, a linear slit is formed to wet or CDE (Chemical Dry Etc).
Hing) isotropic etching to form a concave portion 72 having a semi-cylindrical concave surface 72a.
After forming the concave portion 72, the SiO ₂ layer 72 is formed on the surface of the silicon substrate 71 including the concave surface 72a by an oxidation method or a film forming method.
b is formed.

Next, as shown in FIG. 7B, the concave surface 72
On top of a, sputtering method or CVD (Chemic
al Vapor Deposition) method, etc.
A fixed electrode layer made of 1, Ta or the like is deposited. Next, after forming an antireflection layer on the surface of the fixed electrode layer, the fixed electrodes 73a and 73b are formed by photolithography and etching.
Pattern. The patterning may be lift-off.

Next, as shown in FIG. 7C, a first sacrificial layer 74 made of polyimide is formed in a uniform thickness on the entire substrate by a dipping method or a CVD method, and a movable electrode layer 75 is formed thereon. Is formed with a uniform thickness, and the movable electrodes 75a and 75b are patterned by photolithography and etching. Then, as shown in FIG. 7D, S
A holding material 76 such as iO ₂ is deposited, and unnecessary portions near the support columns 11 (see FIG. 1) are removed.

Next, as shown in FIG. 8A, the recess 72 is formed.
A second sacrificial layer 77 (polyimide) is deposited on the
2 is filled with polyimide 77, a polyimide layer 77 is further formed on the entire substrate 71, the surface of the polyimide layer 77 is heat-treated to be planarized, and then etched back to be formed.
The flat surface 77a as shown in FIG. Next, a material (Si, Al alloy, etc.) to be the support beam 78 is deposited,
The support beam 78 is patterned by photolithography.

Next, as shown in FIG. 8B, a contact hole is formed in the second sacrificial layer 77 by photolithography and etching, and then Al 79a to be the upper electrode 80 (mirror) and wiring 79 is formed. Apply the film. Next, FIG.
As shown in (c), the upper electrode 80 (mirror) is patterned by photolithography and etching.

Next, as shown in FIG. 8D, after the holding material 76 is removed by etching using the upper electrode 80 as a mask, two sacrificial layers 7 are formed by O ₂ + CF ₄ ashing or the like.
Remove 4,77. As a result, the substrate 71, the movable electrodes 75a and 75b, the holding material 76, the support beam 78, the wiring 7
9 and the movable part 81 composed of the upper electrode 80 are separated, and the microactuator 82 is completed.

[0028]

As described above, according to the microactuator of the present invention, the concave electrode fixed in the concave portion of the substrate and the rotatably arranged at the position deviated from the position facing the electrode. Since the movable electrode is driven by the attraction action based on the electrostatic force between the convex electrode and the movable electrode, a large rotation angle can be obtained even if the distance between both electrodes is small. Therefore, a microactuator having a large rotation angle and a low driving voltage can be obtained. Further, when the microactuator of the present invention is used as an optical deflector, vibration and noise can be reduced as compared with the case where a conventional polygon mirror is used.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of a microactuator of the present invention.

FIG. 2 is a cross-sectional view of the microactuator of FIG. 1 viewed in the AA direction.

FIG. 3 is a plan view of a second embodiment of the present invention.

FIG. 4 is a plan view of an optical deflector array in which a large number of microactuators shown in FIG. 1 are arrayed on a single substrate to form an array.

5 is a diagram showing an example in which the microactuator shown in FIG. 4 is used as an optical scanning device of an electrophotographic printer.

6 is a diagram showing an example in which the microactuator shown in FIG. 4 is used in an optical system of a projection type display.

FIG. 7 is a process drawing of the first half of the manufacturing process of the microactuator of the present invention shown in FIG.

FIG. 8 is a process drawing of the latter half of the manufacturing process of the microactuator of the present invention shown in FIG.

FIG. 9 is a perspective view of a conventional spatial light modulator.

10 is a cross-sectional view of the spatial light modulator of FIG. 9 viewed from the AA direction.

[Explanation of symbols]

1 substrate 1a SiO ₂ layer 2 recesses 2a concave 3a, 3b fixed electrodes 5a, 5b movable electrode 6 holding member 8 supporting beam 9 line 10 upper electrode 11 support posts 12 movable portion 12a convex 20 microactuator

Claims (3)

[Claims] 1. A substrate on which a concave portion having a concave surface is formed on an upper surface, a fixed electrode arranged on the concave surface of the concave portion, and a rotation with respect to the concave surface while maintaining a predetermined space between the concave surface and the fixed electrode. A movable portion having freely opposing convex surfaces, and the fixed electrode arranged on the convex surface of the movable portion at a position displaced in the rotational direction from a position on the convex surface facing the fixed electrode. A microactuator comprising a movable electrode and a power supply device for applying a voltage between the fixed electrode and the movable electrode. 2. The microactuator according to claim 1, wherein the concave portion has a hemispherical concave surface. 3. The microactuator according to claim 1, wherein the recess has a semicylindrical concave surface.