KR100759099B1 - An independent two-axis micro-electro-mechanical systems mirror using an elctrostatic force - Google Patents

Abstract

An independent two-axis driven MEMS(Micro-Electro-Mechanical System) mirror using electrostatic force is provided to independently drive in the directions of first and second axes crossing each other and to move at the specific angle correspondently to the input driving voltage by an analog control method. An independent two-axis driven MEMS mirror(300) using electrostatic force is composed of a substrate; a lower silicon layer(310) formed on the substrate; an interlayer insulating film disposed formed on the lower silicon layer; an upper silicon layer(350) arranged on the interlayer insulating film; and a mirror plate disposed on the upper silicon layer. One of the lower and upper silicon layers is a driving unit layer receiving driving voltage and the other is a ground layer receiving ground voltage.

Description

Independent Two-Axis-Drive Ultra-Micro Electromechanical System Mirrors Using Constant Power {AN INDEPENDENT TWO-AXIS MICRO-ELECTRO-MECHANICAL SYSTEMS MIRROR USING AN ELCTROSTATIC FORCE}

1 is a diagram showing an example of various driving methods that can be used in a MEMS mirror, and FIGS. 1A to 1D are diagrams illustrating an electrostatic driving method, an electromagnetic driving method, a thermal driving method, and a piezoelectric driving method, respectively. The left side in 1a shows the parallel plate electrostatic drive system, and the right side shows the comb type electrostatic drive system.

2A and 2B are diagrams showing an example of a two-axis MEMS mirror 200 using an electrostatic driving method, and FIGS. 2A and 2B are diagrams showing that the MEMS mirror rotates about two axes perpendicular to each other. .

3 is a view showing an independent two-axis drive MEMS mirror using an electrostatic force according to an embodiment of the present invention, not showing the lower substrate and the upper mirror plate.

4 is a view showing an independent two-axis drive MEMS mirror using a constant power according to another embodiment of the present invention, a cross-sectional view (A-A ') showing a cross section of the comb-shaped drive unit, showing a cross section of the outer spring structure A cross-sectional view (B-B ') and an enlarged cross-sectional view showing a comb-shaped drive section showing the direction of the force acting on the comb-shaped drive section by the electrostatic force.

FIG. 5 is a view showing the MEMS mirror shown in FIG. 4 together with a mirror plate, and FIGS. 5A, 5B, and 5C are a plan view, a rear view, and a sectional view, respectively.

6 is a view showing a simulation result of the MEMS mirror according to an embodiment of the present invention, Figure 6a is a view showing the rotation of the X-axis, Figure 6b is a view showing the rotation of the Y-axis.

<Explanation of symbols for main parts of the drawings>

200: MEMS mirror using the electrostatic drive method

210: mirror plate

220: first driving electrode

230: gimbal

240: outer spring

250: second driving electrode

260: inner spring

300: MEMS mirror (according to one embodiment of the present invention)

310: bottom silicon layer (ground layer)

314: third spring structure

316: fifth comb finger

324: fourth spring structure

326: sixth comb finger

334: fifth spring structure

336: seventh comb finger

344: sixth spring structure

346: eighth comb finger

350: upper silicon layer (drive part layer)

352: first electrode

354: first spring structure

356: first comb finger

362: second electrode

364: second spring structure

366: second comb-shaped finger

372: third electrode

376: 3rd comb-shaped finger

382: fourth electrode

386: fourth comb finger

390: external gimbal

392: Internal Gimbal

394: second internal gimbal

410: upper silicon layer

416: comb-type fingers corresponding to the insulating layer of the comb-type drive unit

420: interlayer insulating film

430: bottom silicon layer

432 drive electrode

436: comb-shaped fingers corresponding to the drive layer of the comb-shaped drive unit

440: Substrate

510: Mirror Plate

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an independent two axis-driven microelectromechanical system (MEMS) mirror using electrostatic force, and more particularly, a first axis direction and a second axis direction orthogonal to each other using electrostatic force. The present invention relates to an independent two-axis drive MEMS mirror which can be driven independently and has greatly improved fill-factor.

Micro-electro-mechanical systems (MEMS), a combination of small mechanical devices such as sensor valves, gears, reflectors, and semiconductor chip actuators, has recently come to the fore. MEMS, also known as 'smart meters', are devices that have a microcircuit of tiny silicon chips that are used in the manufacture of mechanical devices such as reflectors or sensors, inflating the airbag to match the speed detected by the car airbag and the weight of the guardian. Global positioning system sensor for continuous tracking and handling of cargo transport, interactive sensor to detect changes in air flow according to the surface air resistance of the aircraft wing, and to produce optical signals at speeds of 20 nanoseconds It is used in many applications such as light switching devices, sensor-operated cold and warm devices, and sensors in buildings that change the flexibility of materials reacting to atmospheric pressure. As such, MEMS has been widely applied in various fields because it greatly improves the performance of the product to which the application is applied, and at the same time, the size and size are reduced.

Such MEMS is also applied to implement a mirror. The mirror implemented by MEMS (hereinafter referred to as 'MEMS mirror') is a mirror using electrostatic force, a mirror using electromagnetic force, a mirror using piezoelectric force and thermal deformation according to the driving method of driving the mirror. It can be divided into a used mirror and the like. The mirror using the electrostatic force can be further divided into a parallel plate driving method and a comb-drive method. 1 is a diagram illustrating examples of various driving schemes that can be used in a MEMS mirror. 1A to 1D are diagrams illustrating a driving method using a constant power, a driving method using an electromagnetic force, a driving method using a thermal deformation, and a driving method using a piezoelectric force, respectively. The left side shows the parallel plate drive system, and the right side shows the comb-shaped drive system. Each driving scheme shown in FIG. 1 has its own advantages and disadvantages compared to other driving schemes. Among the various driving schemes shown in FIG. 1, (1) manufacturing is easy and (2) power consumption is low. (3) The comb-tooth type drive system which is small and excellent in driving force, torque and maximum stroke is most widely used.

2A and 2B are diagrams showing an example of a two-axis MEMS mirror 200 using an electrostatic driving method, and FIGS. 2A and 2B are diagrams showing that the MEMS mirror rotates about two axes perpendicular to each other. to be. First, referring to FIG. 2A, the illustrated MEMS mirror 200 includes a mirror plate 210 corresponding to an actual reflection surface, a first driving electrode 220 generating an electrostatic driving force to rotate in a first axial direction, and a gimbal. and an external spring 240 connected to the gimbal 230 and the gimbal 230. When a driving voltage is applied to the first driving electrode 220, a gap between the first driving electrode 220 and the gimbal 230 is provided. By the generated electrostatic force, the rotational force in the first axis direction is generated in the gimbal 230 through the external spring 240 connected to the gimbal 230. Meanwhile, referring to FIG. 2B, a second driving electrode 250 and an inner spring 260 which generate an electrostatic driving force to rotate in a second axial direction perpendicular to the first axis are further included. ) Is connected to the mirror plate 210 by the electrostatic force generated between the second drive electrode 250 and the mirror plate 210 (exactly, the ground layer below the mirror plate 210). The rotation force in the second axial direction is generated in the mirror plate 210 through the spring 260. Here, the MEMS mirror 200 shown in FIG. 2 corresponds to a two-axis-driven MEMS mirror that enables rotation about two axes orthogonal to each other, but the rotation about the two axes is not independent of each other. Be careful with This is because the first driving electrode 220 and the second driving electrode 250 include a common part, and thus generate mechanical coupling with each other.

Unlike the MEMS mirrors shown in FIGS. 2A and 2B, there have been cases in which an independent two-axis drive MEMS mirror that can be driven independently with respect to two orthogonal axes is attempted to be implemented using electrostatic power. However, in those cases, it is not an analog driving method for controlling to move at a specific angle, but a digital driving method that vibrates at a resonant frequency, it is difficult to realize a large angular displacement, and the area of the driving part is larger than that of the mirror area. The problem is that the fill factor is low. Therefore, it is possible to control in an analog manner to move at a specific angle in response to the input driving voltage, to implement a large angular displacement, and to implement an independent two-axis-driven MEMS mirror with a large fill-factor using constant power. have.

The present invention is derived from the above problem and need recognition, and is an independent two-axis drive MEMS mirror capable of driving independently in the first and second axial directions orthogonal to each other, a specific angle corresponding to the input drive voltage The objective is to implement an independent two-axis driven MEMS mirror that can be controlled in an analog manner, realizes large angular displacements, and has a greatly improved fill factor.

According to a feature of the present invention for achieving the above object, an independent two-axis-driven ultra-fine electromechanical system (MEMS) mirror using electrostatic power,

(1) a substrate;

(2) a lower silicon layer provided on the substrate;

(3) an interlayer insulating film provided on the lower silicon layer;

(4) an upper silicon layer provided on the interlayer insulating film;

(5) including a mirror plate provided on the upper silicon layer,

(6) either the lower silicon layer or the upper silicon layer is a driver layer to which a driving voltage is applied, and the other is a ground layer to which a ground voltage is applied;

(7) The drive layer includes a first electrode in a first axial direction, a first spring structure connected with the first electrode, a first comb finger connected with the first spring structure, and a second An electrode, a second spring structure connected to the second electrode, and a second comb-shaped finger connected to the second spring structure in a symmetrical form, and comprising a third in a second axial direction perpendicular to the first axial direction. An electrode, a third comb-shaped finger connected with the third electrode, and a fourth electrode, a fourth comb-shaped finger connected with the fourth electrode in a symmetrical form,

(8) said grounding layer corresponding to said third spring structure corresponding to said first spring structure, said fifth comb-toothed finger corresponding to said first comb-toothed finger, and said second spring structure in said first axial direction; A fourth spring structure, a sixth comb-like finger corresponding to the second comb-like finger in a symmetrical form, and a seventh comb-like finger corresponding to the third comb-like finger in the second axial direction; A symmetrical form comprising a five spring structure, and an eighth comb-like finger corresponding to the fourth comb-like finger, a sixth spring structure,

(9) The ground layer is externally connected to the third spring structure, the fourth spring structure, the fifth spring structure, the sixth spring structure, the seventh comb-type finger and the eighth comb-type finger, respectively. And a gimbal, and an inner gimbal connected to the fifth spring structure, the sixth spring structure, the fifth comb-shaped finger, and the sixth comb-type finger, respectively, wherein the driving unit layer includes: Further comprising a corresponding second internal gimbal,

(10) the fifth comb-like finger corresponding to the first comb-like finger, the sixth comb-like finger corresponding to the second comb-like finger, and the seventh comb-like finger corresponding to the third comb-like finger. , And the fourth comb-type fingers and the eighth comb-type fingers each form a comb actuator,

(11) the mirror plate is provided on the inner gimbal or the second inner gimbal of the upper silicon layer, and the inner gimbal or the second inner gimbal is kept floating with respect to the substrate. It features.

Independent two-axis drive MEMS mirror using electrostatic force according to another feature of the invention is characterized in that the substrate is a glass substrate (glass substrate).

Independent two-axis drive MEMS mirror using electrostatic force according to another feature of the invention is characterized in that each comb-shaped drive is formed by self-alignment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a diagram illustrating an independent two-axis drive MEMS mirror using electrostatic force according to an embodiment of the present invention, and illustrates a lower substrate and an upper mirror plate. As shown in FIG. 3, the MEMS mirror 300 according to an exemplary embodiment of the present invention may include a lower silicon layer (one of which is a driver layer to which a driving voltage is applied and the other of which is a ground layer to which a ground voltage is applied). 310 and the upper silicon layer 350. In the example shown, the lower silicon layer 310 is the ground layer and the upper silicon layer 350 is the driver layer.

The upper silicon layer 350, which is a driver layer, is connected to the first spring structure 354 and the first spring structure 354 connected to the first electrode 352 and the first electrode 352 in the first axial direction. The first comb-shaped finger 356 and the second electrode 362, the second spring structure 364 connected with the second electrode 362, and the second comb-type finger connected with the second spring structure 364 ( A third comb-like finger 376 connected to the third electrode 372, the third electrode 372, and a fourth in a second axial direction orthogonal to the first axial direction, and including a third shape in a symmetrical form; An electrode 382 and a fourth comb-shaped finger 386 connected to the fourth electrode 382 are included in a symmetrical form.

The lower silicon layer 310, which is a ground layer, has a third spring structure 314 corresponding to the first spring structure 354 and a fifth comb-shaped finger corresponding to the first comb-shaped finger 356 in the first axial direction. 316, and a fourth spring structure 324 corresponding to the second spring structure 364, a sixth comb-shaped finger 326 corresponding to the second comb-shaped finger 366, and in a symmetrical form, Eighth comb-like finger 336 corresponding to third comb-like finger 376, fifth spring structure 334, and fourth comb-like finger 386 in a second axial direction. 346, a sixth spring structure 344 in a symmetrical form.

In addition, the lower silicon layer 310, which is a ground layer, includes a third spring structure 314, a fourth spring structure 324, a fifth spring structure 334, a sixth spring structure 344, and a seventh comb-shaped finger. An outer gimbal 390 connected to the 336 and the eighth comb-shaped fingers 346, respectively, the fifth spring structure 334, the sixth spring structure 344, the fifth comb-shaped finger 316, and the sixth An inner gimbal 392 is further connected to the comb-shaped finger 326, respectively, and the upper silicon layer 320 as the driver layer further includes a second inner gimbal 394 corresponding to the inner gimbal 392.

As shown in FIG. 3, the fifth comb-like finger 316 corresponding to the first comb-like finger 356 and the sixth comb-like finger 326 corresponding to the second comb-like finger 366 may include a first comb. A comb-shaped drive for rotation in the axial direction, respectively, and comprising a third comb-like finger 376 and a seventh comb-like finger 336 and a fourth comb-like finger 386 and an eighth comb-type Fingers 346 respectively form comb-shaped drives for rotation in the second axial direction. What is important here is that the comb-shaped drive for rotation in the first axial direction and the comb-shaped drive for rotation in the second axial direction are substantially almost independent.

4 is a view showing an independent two-axis drive MEMS mirror using a constant power according to another embodiment of the present invention, a cross-sectional view (A-A ') showing a cross section of the comb-shaped drive unit, showing a cross section of the outer spring structure A cross-sectional view B-B 'and an enlarged sectional view of a comb-shaped drive unit showing the direction of a force acting on the comb-shaped drive unit by electrostatic force. In the MEMS mirror shown in FIG. 4, unlike the MEMS mirror shown in FIG. 3, the upper silicon layer is an insulating layer, and the lower silicon layer is a driver layer. As can be seen from the cross-sectional view (A-A ') showing the cross section of the comb-shaped drive, the comb-shaped finger 416 corresponding to the insulating layer of the comb-type drive and the comb-like finger 436 corresponding to the drive layer of the comb-type drive are shown. ) Are staggered to form a comb-shaped drive. When a driving voltage is applied to the driving electrode 432, the comb-shaped finger 436 is fixed to the substrate 440 together with the driving electrode 432, so that the floating comb-shaped finger 416 is in a downward state. It is moved by force. This can be clearly seen through the enlarged cross-sectional view of the comb-shaped drive of FIG. 4. From the enlarged cross-sectional view of the comb-shaped drive of FIG. 4, it can be clearly seen that the comb-drive is self-aligned, where the self-alignment means that the upper comb-shaped part of the comb-drive is formed. The finger and the lower comb-toothed fingers, as the word self-aligned, mean that each finger is aligned so that they do not overlap each other. Self-alignment is necessary in the comb-type drive. If an alignment miss occurs at the horizontal distance between the comb-type fingers, a displacement in the horizontal direction occurs when the driver is driven, thereby causing a pull-in state. Is generated, and accordingly a short may occur.

On the other hand, through the cross-sectional view (B-B ') showing the cross section of the outer spring structure, it can be confirmed the outer spring structure. As shown in the cross-sectional view B-B ', the outer spring structure includes an upper silicon layer 410, an interlayer insulating film 420, and a lower silicon layer 430. In contrast, as shown in FIG. 4, the inner spring structure consists only of the upper silicon layer. A buried oxide layer (BOX) is used as the interlayer insulating film 420 (ie, an SOI wafer in which an insulating film is formed between the upper silicon layer and the lower silicon layer is used in the present invention). In addition, by using the substrate 440 as a glass substrate, that is, by using a silicon on glass (SiOG) structure, a driving electrode and a spring having a desired thickness may be more easily formed in the lower silicon layer.

FIG. 5 is a view showing the MEMS mirror shown in FIG. 4 together with a mirror plate, and FIGS. 5A, 5B, and 5C are plan views, rear views, and cross-sectional views, respectively. As can be seen from FIG. 5, the mirror plate 510 can be freely rotated by the electrostatic driving force generated by the comb-shaped drive unit while maintaining the floating state with respect to the substrate.

6 is a view showing a simulation result of the MEMS mirror according to an embodiment of the present invention, Figure 6a is a view showing the rotation of the X-axis, Figure 6b is a view showing the rotation of the Y-axis. As shown in FIG. 6, when 100 V DC voltage was applied as the driving voltage, the result was rotated to 6.11 degrees in the X-axis direction and 6.72 degrees in the Y-axis direction. This results in a large rotational displacement (12.22 degrees (6.11 degrees x 2) for the entire X-axis, 13.44 degrees for the entire Y-axis) while being able to drive almost independently with respect to the X- and Y-axis orthogonal to each other. (6.72 degrees x 2)), it can be interpreted that the application range of the present invention can be very diverse considering the ease of manufacture and low power consumption when using the electrostatic power.

The present invention described above may be variously modified or applied by those skilled in the art, and the scope of the technical idea according to the present invention should be defined by the following claims.

According to the present invention, it can be driven independently in the first axis direction and the second axis direction orthogonal to each other, can be controlled in an analog manner to move at a specific angle in response to the input driving voltage, the implementation of a large angular displacement It is possible to implement an independent two-axis driven MEMS mirror with significantly improved fill-factor using constant power.

Claims (3)

As an independent two-axis-drive Micro-Electro-Mechanical Systems (MEMS) mirror using electrostatic force, Board; A lower silicon layer provided on the substrate; An interlayer insulating film provided on the lower silicon layer; An upper silicon layer provided on the interlayer insulating film; Includes a mirror plate (mirror plate) provided on the upper silicon layer, One of the lower silicon layer or the upper silicon layer is a driver layer to which a driving voltage is applied, and the other is a ground layer to which a ground voltage is applied. The driving unit layer may include a first electrode, a first spring structure connected with the first electrode, a first comb finger connected with the first spring structure, and a second electrode in the first axial direction, A second spring structure connected with a second electrode, a second comb-shaped finger connected with the second spring structure in a symmetrical form, and having a third electrode in a second axial direction orthogonal to the first axial direction; A third comb-shaped finger connected with a third electrode, and a fourth electrode, and a fourth comb-shaped finger connected with the fourth electrode in a symmetrical form, The ground layer may include a third spring structure corresponding to the first spring structure, a fifth comb-like finger corresponding to the first comb-like finger, and a fourth spring structure corresponding to the second spring structure in the first axial direction. A spring structure, a seventh comb-like finger corresponding to the second comb-like finger in a symmetrical form, and corresponding to the third comb-like finger in the second axial direction, a fifth spring structure And an eighth comb-like finger corresponding to the fourth comb-like finger, a sixth spring structure in a symmetrical form, The ground layer has an external gimbal connected to the third spring structure, the fourth spring structure, the fifth spring structure, the sixth spring structure, the seventh comb-shaped finger, and the eighth comb-type finger, respectively. And an inner gimbal connected to the fifth spring structure, the sixth spring structure, the fifth comb-shaped finger, and the sixth comb-type finger, respectively, wherein the driving unit layer corresponds to the inner gimbal. Further includes 2 internal gimbals, The fifth comb-like finger corresponding to the first comb-like finger, the sixth comb-like finger corresponding to the second comb-like finger, the seventh comb-like finger corresponding to the third comb-like finger, and the A fourth comb-type finger and the eighth comb-type finger each form a comb actuator, And the mirror plate is provided on the inner gimbal or the second inner gimbal of the upper silicon layer, and the inner gimbal or the second inner gimbal maintains a floating state with respect to the substrate. The method of claim 1, And the substrate is a glass substrate. The method of claim 1, And each comb-shaped drive is formed by self-alignment.

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