JP2004085869A - Mems element, and optical attenuator, optical switch, and optical scanner all using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an MEMS element having a large area in a relatively simple process without warp in a mirror in the MEMS element for optical control. <P>SOLUTION: A through-hole 32 is provided on a part of a lower electrode substrate 31. A supporting part 33 is provided on the lower electrode substrate 31 and a single crystal silicon mirror plate 35 is stuck through a hinge 34 to the supporting part 33. For the mirror plate 35, an upper electrode part facing the lower electrode substrate 31 and a mirror part corresponding to the through-hole are integrated. Thus, a mirror size is selected regardless of a tilt angle, and the MEMS element with less warp is manufactured in the simple process. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an MEMS element for optical control, and an optical attenuator, optical switch, and optical scanner using the same.
[0002]
[Prior art]
In recent years, with the development of optical communication technology, a MEMS (Micro Electro Mechanical System) element has attracted attention as an optical control element. Such a light control MEMS element has a mirror part in a part thereof, and basically changes a light reflection direction according to a voltage. Therefore, it is generally required that a MEMS element having a large-area mirror with little warpage can be manufactured by a simple process.
[0003]
As a conventional MEMS element, a cantilever element formed by an SOI process is known. As shown in FIG. 8A, a plan view, and FIG. 8B, a cross-sectional view taken along the line AA, a support portion 12 of an oxide layer is provided on a silicon substrate 11 also serving as an electrode. It has a structure in which the electrode 13 is attached. This element has a three-layer structure of a silicon substrate 11, an oxide layer, and a single crystal silicon serving as an upper electrode, formed by cutting an electrode portion on an upper surface, and removing an area other than a region serving as a support portion 12 of the oxide layer by etching. Can be manufactured by laminating the mirror 14 on the right side of the upper electrode. Then, by applying a voltage between the upper electrode 13 of the MEMS element and the silicon substrate 11 also serving as the lower electrode, an electrostatic attractive force acts, and the upper electrode 13 tilts in the direction of the arrow to change the light reflection angle. Can be. As described above, the MEMS element manufactured by the SIO process can be manufactured by a relatively simple process, and since the upper surface is a single crystal silicon plate, the mirror can be formed to have a large film thickness and has less warpage. be able to.
[0004]
A MEMS device using surface micromachining is also known. In this MEMS element, as shown in a plan view in FIG. 9A and a cross-sectional view taken along the line BB in FIG. 9B, the lower electrode 22 is laminated only on the left central portion of the non-conductive substrate 21. . Then, an oxide layer is provided on the left and right ends of the substrate 21 to form a support portion 23. The support portion 23 is formed by laminating an oxide layer on the entire surface of the substrate 21 having the lower electrode 22 and etching by masking required portions at both ends of the substrate. In a step before the etching, a polysilicon thin film mirror 24 having a surface facing the lower electrode as an upper electrode is formed on the upper surface of the oxide layer. The thin film mirror 24 has a region corresponding to the support portion 23, a thin hinge portion 25 extending therefrom, and a flat plate portion. The surface of the flat plate portion facing the left lower electrode is used as the upper electrode portion 26, and the right portion is used as the mirror portion 27. The upper electrode portion 26 is provided with a number of openings 28 called etching holes. The etching hole not only promotes the penetration of the etching solution, but also functions to reduce the viscous resistance of air called squeeze damping during operation and to operate at high speed. After such a thin film mirror 24 is formed, the oxide layer other than the support portion 23 is removed by etching, and the thin film mirror 24 on the upper surface is supported only by the hinge portion 25. In the MEMS element having the four-layer structure configured as described above, an electrostatic attractive force is applied by applying a voltage between the upper electrode portion 26 and the lower electrode 22 on the left side of the thin film mirror 24 to tilt the thin film mirror 24 in the direction of the arrow. Can be done.
[0005]
[Problems to be solved by the invention]
However, according to the MEMS device shown in FIG. 8, since the silicon mirror 13 serving also as the upper electrode approaches the silicon substrate 11 serving as the lower electrode, there is a trade-off between the mirror angle and the driving voltage for determining the tilt angle and the tilt angle. There is a disadvantage that the mirror size cannot be increased arbitrarily.
[0006]
Further, the MEMS element shown in FIG. 9 has a structure in which the thin film mirror 24 is flipped up with the support portion 23 as a fulcrum, so that a large-area mirror can be manufactured. However, since a polysilicon thin film mirror is used, the mirror may be warped. Further, since the structure also has a four-layer structure, there is a disadvantage that the manufacturing process is more complicated than the MEMS element having the three-layer structure shown in FIG.
[0007]
The present invention has been made in view of such a problem of the conventional MEMS element, and there is provided a MEMS element capable of manufacturing a MEMS element having a large-area mirror without a warp of a mirror by a simple process. It is an object to provide an optical attenuator, an optical switch, and an optical scanner used.
[0008]
[Means for Solving the Problems]
The invention of claim 1 of the present application is directed to a mirror in which a plane is divided so that one region is an upper electrode portion, the other region is a mirror portion, and an end near a boundary between the upper electrode portion and the mirror portion is a hinge portion. Plate, a substrate formed of a conductive material or a semiconductor material, having a through hole at a position facing the mirror portion of the mirror plate, and a substrate provided at a position close to the through hole, the mirror plate being attached to the hinge portion. And a supporting portion to be held through the support portion.
[0009]
The invention of claim 2 of the present application is directed to a mirror in which a plane is divided so that one region is an upper electrode portion, the other region is a mirror portion, and an end near a boundary between the upper electrode portion and the mirror portion is a hinge portion. A plate formed of a conductive material or a semiconductor material and having a first through hole at a position facing the mirror portion of the mirror plate, and a second through hole around a portion facing the upper electrode portion; And a support portion provided on a side between the first and second through holes, and holding the mirror plate via the hinge portion.
[0010]
According to a third aspect of the present invention, there is provided the MEMS device according to the first or second aspect, a light incident portion that enters light into a mirror portion of the MEMS device, and emits light reflected by the mirror portion of the MEMS device. A light emitting unit, and a voltage control unit that changes a voltage applied to the MEMS element, and changes an attenuation rate by continuously changing a reflection angle of light incident on the MEMS element from the light incident unit. It is characterized by having.
[0011]
According to a fourth aspect of the present invention, there is provided the MEMS device according to the first or second aspect, a light incident portion that enters light into a mirror portion of the MEMS device, and emits light reflected by the mirror portion of the MEMS device. A voltage for changing a voltage applied to the light emitting unit and the MEMS element to reflect light incident on the MEMS element from the light incident unit and switching between a state of entering the light emitting unit and a state of not entering light. And a control unit.
[0012]
According to a fifth aspect of the present invention, there is provided the MEMS device according to the first or second aspect, a light incident portion for inputting light to a mirror portion of the MEMS device, and changing a voltage applied to the MEMS device to change the light incidence. And a voltage control unit that continuously changes the reflection angle of light incident on the MEMS element from the unit.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the MEMS device according to the first embodiment of the present invention will be described. FIG. 1 is a plan view of a MEMS device according to this embodiment, FIG. 2 is a cross-sectional view taken along the line CC, and FIG. 3 is a cross-sectional view showing a manufacturing process. In this embodiment, the semiconductor device is manufactured by a manufacturing process similar to a micromachining process using an SOI substrate. As shown in these figures, a silicon (Si) substrate is doped with impurities and used as a lower electrode substrate 31. As shown in FIG. 1 and FIG. 2, the lower electrode substrate 31 is a rectangular member, and a rectangular through hole 32 is provided at the right central portion below the mirror portion as shown in the figure. At a position adjacent to the through hole 32, a support portion 33 for supporting a mirror only on both sides of the substrate is provided as shown in the figure. A single-crystal silicon mirror plate 34 is stacked on the support 33. The single crystal silicon mirror 34 is formed by integrating the upper surface of the support 33 with the hinge 35, the upper electrode 36, and the mirror 37.
[0014]
Next, a manufacturing process of the MEMS device according to this embodiment will be described with reference to FIG. First, as shown in FIG. 3A, a wafer having a three-layer structure including a lower electrode substrate 31, an oxide layer 33A serving as a support, and a single-crystal silicon mirror plate 34 is prepared. Next, as shown in FIG. 3B, a pattern such as a hinge portion serving as the upper surface of the support portion 33 is formed on the single crystal silicon mirror plate 34 by photolithography and etching. In order to use the upper electrode portion 36 in the etching process, a large number of etching holes 38 are formed in a portion corresponding to the lower electrode as in FIG. Next, as shown in FIG. 3C, a through hole 32 is formed in the lower electrode substrate 31 on the back in the same manner. Then, as shown in FIG. 3D, the oxide layer 33A on the upper surface of the lower electrode substrate 31 is etched. At this time, a necessary portion is masked, and an etchant is permeated from the etching hole 38 to remove a portion other than the support portion 33, thereby forming the MEMS element.
[0015]
In the MEMS element thus configured, an electrostatic attraction acts between these electrodes by applying a voltage between the lower electrode substrate 31 and the upper electrode section 36. At this time, since the through hole 32 is provided below the mirror section 37 as shown in the figure, there is no corresponding electrode, and no electrostatic attraction acts on the mirror section. For this reason, electrostatic attraction acts only on the upper electrode portion, and the mirror portion 37 can be tilted so as to flip up as shown by an arrow. The size and shape of the mirror section 37 together with the through-hole 32 of the lower electrode substrate 31 can be arbitrarily selected. Therefore, a MEMS element having a large-area mirror section without distortion of the mirror section can also be configured.
[0016]
Next, a MEMS device according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a plan view of the MEMS device according to the present embodiment, FIG. 5A is a cross-sectional view taken along the line DD, and FIG. 5B is a cross-sectional view taken along the line EE. The same parts as those described above are denoted by the same reference numerals, and detailed description is omitted. In the present embodiment, the lower electrode substrate 31 is provided with not only a rectangular through hole 32 in the mirror portion but also a through hole 39 having a U-shaped cross section in the outer peripheral portion of the upper electrode portion 36. Other configurations are the same as those of the first embodiment. By providing the through-holes 39 in this manner, a driving force in the lateral direction that is generated when an electrode is present in an opposing portion other than the upper electrode is eliminated, and unnecessary operation modes are suppressed.
[0017]
Next, an optical attenuator using the MEMS device according to the present embodiment will be described. FIG. 6 is a sectional view showing the optical attenuator. In this figure, a capillary 41 holds an optical fiber 42 for incidence and an optical fiber 43 for emission, and a lens holder 44 is provided at the tip thereof. An aspheric lens 45 as shown in the figure is provided substantially at the center of the lens holder 44. The aspheric lens 45 converts the light emitted from the optical fiber 42 into substantially parallel light and focuses the reflected light on the optical fiber 43. Here, the capillary 41, the optical fiber 42, the lens holder 44, and the aspherical lens 45 constitute a light incident part for entering light into the mirror part of the MEMS element, and the capillary 41, the optical fiber 43 for emission, and the lens holder 44 The aspheric lens 45 constitutes a light emitting unit that emits light reflected by the mirror unit of the MEMS element. On the optical axis of the lens holder 44, a MEMS element 46 for light control is arranged. The MEMS element 46 is the MEMS element according to the first or second embodiment described above, and has a voltage control unit 47 for supplying a variable voltage to the lower electrode substrate and the upper electrode unit.
[0018]
If no voltage is applied to the MEMS element 46, the light incident from the optical fiber 42 is incident on the mirror portion of the MEMS element 46 as parallel rays by the aspheric lens 45 of the lens holder 44. This light is reflected as it is, and is again guided to the optical fiber 43 for emission through the aspheric lens 45. Here, when a voltage is applied between the upper electrode and the lower electrode, the mirror is tilted as described above, and the peak position at which the reflected light enters the output optical fiber changes. Therefore, by gradually changing the voltage and continuously changing the tilt angle of the mirror, the level at which the reflected light enters the optical fiber 43 can be changed continuously. Therefore, the amount of light attenuation can be changed by voltage control.
[0019]
By switching between a state in which no voltage is applied to the MEMS element and a state in which a predetermined voltage is applied by switching with the same structure, a first state in which almost 100% of reflected light is obtained, and a state in which reflected light is emitted Optical switch that switches to the second state in which the light does not enter the optical fiber 43 for use.
[0020]
This MEMS element can also be used as an optical scanner used for various applications such as a laser scanning microscope. FIG. 7 is a diagram illustrating an example of the optical scanner. In this figure, an optical fiber 51 guides light, and a collimating lens 52 is provided on the optical axis thereof, and the light is directed from the angle of about 45 ° to the MEMS element 53 according to the first or second embodiment. Leading. The optical fiber 51 and the collimating lens 52 are light incident portions for inputting the optical fiber to the MEMS element. Further, the MEMS element 53 is provided with a voltage control unit 54 for applying a continuously changing voltage. In this way, by changing the voltage of the voltage control unit 54 in various waveforms such as a sine waveform and a sawtooth waveform, the incident light can be scanned at a desired speed.
[0021]
【The invention's effect】
As described in detail above, according to the present invention, a MEMS element can be manufactured by a relatively simple process as in a micromachine process using an SOI substrate. Since an opening is provided on the substrate and the structure is a flip-up structure, an arbitrary large-area mirror can be manufactured. In addition, since a single crystal silicon thick film mirror is used, the warpage of the mirror can be reduced as compared with a thin film mirror, which is suitable as a light control device. Further, an optical attenuator, an optical switch and an optical scanner can be realized by using the MEMS element.
[Brief description of the drawings]
FIG. 1 is a plan view showing a structure of a MEMS device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of the MEMS device according to the present embodiment taken along line CC.
FIG. 3 is a schematic diagram showing a manufacturing process of the MEMS device according to the present embodiment.
FIG. 4 is a plan view of a MEMS device according to a second embodiment of the present invention.
5A is a cross-sectional view of the MEMS element according to the second embodiment taken along line DD, and FIG. 5B is a cross-sectional view of the MEMS element according to the second embodiment taken along line EE.
FIG. 6 is a sectional view showing a structure of an optical attenuator and an optical switch using the MEMS device according to the present embodiment.
FIG. 7 is a schematic diagram showing an optical scanner using a MEMS device according to an embodiment of the present invention.
8A and 8B are a plan view and a cross-sectional view illustrating a structure of a MEMS device formed by a conventional SOI process.
FIG. 9 is a plan view and a cross-sectional view showing the structure of a conventional MEMS device formed by surface micromachining.
[Explanation of symbols]
31 Lower electrode substrate 32, 39 Through hole 33 Supporting part 33A Oxide layer 34 Single crystal silicon mirror 35 Hinge 36 Upper electrode part 37 Mirror part 38 Etching hole 41 Capillary 42, 43, 51 Optical fiber 44 Lens holding part 45 Aspherical lens 46 , 53 MEMS elements 47, 54 Voltage controller 52 Collimating lens

Claims (5)

A mirror plate having a plane divided into one region serving as an upper electrode portion, the other region serving as a mirror portion, and an end near a boundary between the upper electrode portion and the mirror portion serving as a hinge portion;
A substrate formed of a conductive material or a semiconductor material and having a through hole at a position facing the mirror portion of the mirror plate,
A support portion provided at a position close to the through-hole and holding the mirror plate via the hinge portion. A mirror plate having a plane divided into one region serving as an upper electrode portion, the other region serving as a mirror portion, and an end near a boundary between the upper electrode portion and the mirror portion serving as a hinge portion;
A substrate formed of a conductive material or a semiconductor material, having a first through hole at a position facing the mirror portion of the mirror plate, and a second through hole around a portion facing the upper electrode portion;
A MEMS element, comprising: a support portion provided on a side between the first and second through holes, for holding the mirror plate via the hinge portion. A MEMS device according to claim 1 or 2,
A light incidence part for entering light into a mirror part of the MEMS element;
A light emitting unit that emits light reflected by the mirror unit of the MEMS element;
A voltage control unit that changes a voltage applied to the MEMS element, and continuously changes a reflection angle of light incident on the MEMS element from the light incident unit, thereby changing an attenuation rate. And an optical attenuator. A MEMS device according to claim 1 or 2,
A light incidence part for entering light into a mirror part of the MEMS element;
A light emitting unit that emits light reflected by the mirror unit of the MEMS element;
A voltage control unit that changes a voltage applied to the MEMS element, reflects light incident on the MEMS element from the light incident unit, and switches between a state of entering the light emitting unit and a state of not entering light. An optical switch, comprising: A MEMS device according to claim 1 or 2,
A light incidence part for entering light into a mirror part of the MEMS element;
An optical scanner, comprising: a voltage controller that changes a voltage applied to the MEMS element and continuously changes a reflection angle of light incident on the MEMS element from the light incident part.

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