KR20060018683A - Electrostatic mems scanning micromirror and fabrication method thereof - Google Patents

Abstract

According to an embodiment of the present invention, a constant power driving scanning micromirror includes an upper and a lower substrate stacked on top of each other, a mirror plate rotatably installed inside an intermediate space of the upper substrate, and a lower surface of the mirror plate to input light. A torsion beam connected between both end portions in the longitudinal direction of the upper substrate and both end portions of the mirror plate to support the mirror plate to rotate, and the mirror plate is inserted into the middle portion of the lower substrate. Rotatable space portions formed to rotate so as to be rotated, both side space portions formed on both sides of the upper substrate in the width direction of both torsion beams, and movable sides formed on both side space portions formed on both sides in the longitudinal direction of the central space portion of the lower substrate. A comb-shaped electrode and a fixed comb-shaped electrode, an insulating layer formed between the upper and lower substrates, and the upper and lower substrates. And electrodes formed to apply a drive voltage to the group movable comb-shaped electrode and the fixed comb-shaped electrode is configured to include the government. According to the present invention, a method for manufacturing a constant power driving scanning micromirror is formed by forming a thin film for etching masks 1, 2, and 3 used as an etch mask in an etching process, respectively, in upper and lower portions of a substrate using a lower silicon substrate in a wafer form as a starting material. And anisotropically etching the upper surface of the silicon lower substrate on which the two layer etching masks are formed to a predetermined depth, removing the etching mask 2 after etching, and bonding the upper substrate on the lower substrate; Forming and patterning the etching mask thin films 4 and 5 to be used as an etching mask on the upper substrate, and then anisotropically etching the lower substrate using the etching mask 3 to a predetermined depth, and the etching mask 4 and the etching mask 5 Anisotropically etching the upper substrate by a predetermined depth using the method, and removing the etching mask 5 and etching mask 4 Anisotropically etching the upper substrate using a predetermined depth to form a mirror plate having a predetermined thickness, removing the etch mask 4, and etching the joining surfaces of the inner and lower substrates of the upper and lower substrates. Floating and forming a reflective surface under the mirror plate. The present invention is an element that can be used to scan a beam emitted from a light source to a predetermined region to form information such as an image or to read data such as a position or an image. Such a scanning micromirror is a micromachining technique and a semiconductor integrated process. It can be implemented in small size and light weight form by remarkably improving optical and mechanical performance by reducing the cost of parts, and driving power can be significantly reduced by constant power driving.

Description

Constant Power Driven Scanning Micromirror and Manufacturing Method Thereof {ELECTROSTATIC MEMS SCANNING MICROMIRROR AND FABRICATION METHOD THEREOF}

1 to 7 relates to a constant power driving scanning micromirror according to the present invention,

1 is a perspective view of a micromirror.

2 is a bottom perspective view of the micromirror.

3 is an exploded perspective view of the micromirror.

4 is a plan view of a micromirror.

5 is a cross-sectional view taken along the line A-A of FIG.

6 and 7 are longitudinal cross-sectional views showing the configuration and operation of the micromirror.

8A to 8G are process explanatory diagrams of a method for manufacturing a constant power driving scanning micromirror according to the present invention;

<Description of the symbols for the main parts of the drawings>

100: upper substrate 101: intermediate space portion

102: both side space portion 110: mirror plate

111: reinforcement frame structure 112: protrusion

113: groove 114: etching hole

115: reflection surface 120: movable comb-shaped electrode

130: control electrode 140: torsion beam

150 230: electrode fixing part 200: lower substrate

201: central space portion 202: both space portions

210: insulating layer 220: fixed comb-shaped electrode

301,302,303 Etch Masks 1,2,3 401,402 Etch Masks 4,5

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant power driving scanning micromirror and a method of manufacturing the same, and more particularly, to an optical scanning device for modulating a path of reflected light by operating a micromirror that reflects input light by applying a predetermined voltage. A laser printer that scans a beam emitted from a light source to a predetermined area in one dimension (line) or two dimensions (plane) to form an image such as an image or read data such as a position or an image. Applicable to microscope, barcode scanner, scanning display and various sensors, and also to the optical power switch scanning micromirror which can be applied to optical switch element that arbitrarily adjusts the path of reflected light in addition to scanning and its manufacture It is about a method.

Recently, with the development of optical device technology, various technologies using optical as an input / output terminal and information transfer medium of various information have emerged. Scanning and using beams from light sources are among the traditional applications of these technologies, such as barcode scanners and basic scanning laser displays.

These beam scanning techniques require various scanning speeds and scanning ranges depending on the application. Conventional beam scanning requires a galvanic mirror or a rotating polygon mirror. The main method is to control the angle of incidence between the reflective surface of the mirror and the incident light. Galvanic mirrors are suitable for applications requiring scan rates of several to tens of hertz (Hz), and polygon mirrors can achieve scan rates of several kilohertz (kHz).

With the development of various technologies, efforts have recently been made to apply beam scanning technology to new devices or to further improve performance in existing application cases employing such technology. A good example is a projection display system with excellent primary color reproduction, a head mounted display (HMD), and a laser printer. In systems requiring beam scanning requiring such high spatial resolution, a scanning mirror that can realize high scanning speed and large angular displacement or tilting angle is usually required. In the conventional method using the polygon mirror, since the polygon mirror is mounted on the motor rotating at high speed, the scanning speed is proportional to the rotation angle of the polygon mirror, which is dependent on the rotation speed of the drive motor. Due to the limitation of the motor rotation speed, there is a limit to increase the scan speed, and it is difficult to reduce the volume and power consumption of the entire system. In addition, the mechanical friction noise of the drive motor unit must be fundamentally solved, and it is difficult to expect cost reduction due to the complicated structure.

In a scanning apparatus using a polygon mirror according to the prior art, input light emitted from a light source passes through optical systems such as various lenses and is reflected by the polygon mirror. Accordingly, by rotating the polygon mirror using the lower motor, the reflected light can be scanned in the direction defined by the rotation direction of the polygon mirror.

Therefore, in the case of the scanning device using the polygon mirror, it is possible to implement a relatively fast scanning in one direction, but there is a limit to the high resolution display.

In addition, in the case of a scanning device using a micromirror, bidirectional scanning is possible, and a high scanning speed of several tens of kHz can be realized, but when driven under such severe conditions, a so-called dynamic deflection in which the micromirror flutters due to the driving principle is used. ) Occurs, which causes deterioration of the reflecting surface and reflected light. Therefore, in order to implement a high performance optical scanning device, it is necessary to select a material and a structure of a micromirror that can suppress such dynamic deformation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and defects, and an object of the present invention is to provide a constant power driving scanning micromirror which is driven using electromagnetic phenomena and can be integrated and applied to an optical scanning device. It is to.

Still another object of the present invention is to provide a constant power driving scanning micromirror that applies a thin film and a frame structure to the micromirror to suppress deformation of the reflective surface during driving and to realize a large scanning angle and a high scanning speed. will be.

It is still another object of the present invention to provide a method for manufacturing a constant power driving scanning micromirror that can reduce the weight and size of an optical scanning device by manufacturing the constant power driving scanning micromirror by applying a semiconductor integrated process and micromachining technology. .

The present invention provides an electrostatic scanning micromirror manufactured by a micromachining technique or a micromachining process.

A feature of the present invention is that it has a function of adjusting the direction of the reflected light by driving the micromirror reflecting the input light.

The micromirror is connected to the substrate by an elastically rotating support element of an elastic flexure structure (spring element), such as a cantilever or torsion beam.

The micromirror is composed of a mirror plate thin film on which a reflecting surface is formed and a reinforcement frame structure for supporting it and suppressing dynamic deformation of the mirror plate. The micromirror may be a flat plate structure having a uniform thickness.

The reinforcing frame structure may be composed of one or more unit frame structures and arranged in an array form.

A movable comb electrode of a constant power driving element for driving is formed at a predetermined position of the edge region of the micromirror structure in which the frame is integrated. The movable comb-shaped electrodes are formed on both sides or one side about the rotation axis. A stator comb electrode corresponding to the movable comb-shaped electrode is formed on the substrate partially overlapping the movable comb-shaped electrode or spaced a predetermined distance apart.

The micromirror may be formed by adding a control electrode capable of adjusting a driving force by applying a potential difference between the micromirror and the control electrode or between the control electrode and the movable comb-shaped electrode.

The present invention may be configured as a constant power driving scanning M × N micromirror array configured by arranging the micromirrors in an array consisting of M rows and N columns (M = 1, 2, 3, N = 1,2,3,).

The present invention may be configured as an optical scanning device using the scanning micromirror.

According to the present invention, the scanning micromirror is manufactured in large quantities by processing by a micromachining technique and a semiconductor integrated manufacturing process.

The scanning micromirror according to the present invention as described above scans a beam emitted from a light source to a predetermined area in one dimension (line) or two dimensions (surface) to form information such as an image or to locate an image or the like. It can be applied to laser printers, confocal microscopes, barcode scanners, scanning displays, and various sensors that read data from the camera. In addition to scanning, the present invention can be applied to an optical switch device that arbitrarily adjusts the path of reflected light.

Since the scanning micromirror according to the present invention does not require an additional assembly process requiring high precision after the micromachining process, the mass production is high, the device price is expected to be lowered, and the power consumption is low and small due to the constant power driving method. It is suitable for light weight. It is also suitable for high performance scanning systems that require fast scanning speed and wide scan range with improved structural stability, optical performance and reduced mass compared to conventional micromirrors, and can be applied to systems requiring static displacement of micromirrors. It is believed that the application is possible.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail as follows.

The upper substrate 100 and the lower substrate 200 are stacked up and down, and the upper substrate 100 has the mirror plate 110 rotatably installed inside the intermediate space 101, and the upper substrate 100. A pair of torsion beams (torsion beams) 140 are formed between the end portions of both sides) and both end portions of the mirror plate 110 to support the mirror plate 110 to rotate.

As described above, the mirror plate 110 has a pair of torsion beams 140 connected to both ends of the upper substrate 100 in the form of a simple beam, thereby rotating the torsion beams 140 upward and downward on a rotation axis. .

A rotating space 201 is formed in the middle portion of the lower substrate 200 so that the mirror plate 110 is inserted inside and rotated, and both sides of the torsion beam 140 in the width direction of the upper substrate 100 are rotated. The movable comb-shaped electrode 120 and the fixed comb-shaped electrode are formed on both side space parts 102 formed on the lower substrate 200 and both side space parts 202 formed on both sides in the longitudinal direction of the central space part 201 on the lower substrate 200. 220 are formed, respectively.

An insulating layer 210 is formed between the upper and lower substrates 100 and 200, and the movable comb-shaped electrode 120 and the fixed comb-shaped electrode are formed on the upper and lower substrates 100 and 200. Electrode fixing parts 150 and 230 are formed to apply a driving voltage to the electrode 220.

The mirror plate 110 of the upper substrate 100 is formed with a continuous reinforcement frame structure 111 having a plurality of diamond-like protrusions 112 and a triangular groove 113 in a continuous (periodic) form, each protrusion ( A plurality of etching holes 114 are formed in the 112, and the reflecting surface (reflective layer) 115 reflecting the input light is formed in the form of a thin film having a uniform thickness on the lower surface portion (the opposite surface on which the frame structure is formed).

The mirror plate 110 is supported by a torsion beam 140 acting as a rotating shaft at both ends and acting a restoring force torque during driving, and is connected to the periphery of the upper substrate 100. In addition, a pair of movable comb electrodes 120 are formed on both sides of the torsion beam 140 for driving, and the movable comb electrodes 120 are formed only on one side of the torsion beam 140. You may.

The lower substrate 200 has stator comb electrodes 220 electrically separated from each other at predetermined intervals to correspond to the movable comb-shaped electrodes 120 of the upper substrate 100. Each of them has a shape attached to the electrode fixing part 230 of the lower substrate 200.

The upper and lower substrates 100 and 200 are electrically separated by the insulating layer 210 to apply a voltage for driving, and a silicon-on-insulator (SOI) substrate is formed to form such a structure. It can also be used, and it is also possible to manufacture two substrates by bonding.

The mirror plate 110, the torsion beam 140, and the movable comb-shaped electrode 120 are electrically connected to each other by a movable comb-shaped electrode through the electrode fixing part 150 to which the torsion beam 140 is connected for driving. Voltage is applied to 120.

The lower substrate 200 includes two electrode fixing parts 230 electrically separated from each other, and incident light incident on the reflective surface 115 of the mirror plate 110 and reflected light reflected through the lower substrate 200 may pass through the center of the lower substrate 200. The penetrated central space 201 is formed.

FIG. 8 is a cross-sectional schematic diagram of a main manufacturing process step of a movable part showing a process of manufacturing a silicon microstructure of a constant power driving scanning micromirror using a semiconductor device integrated manufacturing process technology and a micromachining technique that is a precision micromachining method.

 The following is a detailed description of the manufacturing method according to each process step shown in the figure, for the sake of convenience, a schematic diagram of the above device is shown, but in the actual manufacturing process, a wafer type substrate in which a plurality of devices shown in the figure are formed. It is manufactured in large quantities at the same time using a semiconductor processing process in which the process proceeds in the form.

As shown in FIG. 8A, a thin film for etching masks 1, 2, 3 (301, which are used as an etch mask in an etching process after the upper and lower portions of a wafer-shaped silicon lower substrate 200 are used as starting materials, respectively). 302 and 303 are formed and patterned. Etch mask 2 302 should also have selectivity with silicon and other etching masks 1, 3 (301, 303) as substrates, and etching mask 1 301 should be a material suitable for subsequent wafer bonding processes. The material of the etching mask is a semiconductor device integrated manufacturing process such as coating, deposition, plating, etc., which has high etch selectivity with silicon depending on the etching method and the chemicals causing the etching reaction in the subsequent silicon etching process. Form with the skill of. As an etching mask material, an insulating thin film such as a photoresist, a metal film, a silicon oxide film, or a silicon nitride film may be used.

As shown in FIG. 8B, an upper surface of the silicon lower substrate 200 having the two-layer etching mask formed thereon is an anisotropic shape processing technology, which is an anisotropic shape processing technique, which is a kind of reactive ion etching or silicon deep reactive ion etching (silicon). deep RIE). Subsequent substrate anisotropic etching processes use the same method. After etching, the etching mask 2 302 is removed.

As shown in FIG. 8C, the upper substrate 100 is bonded to the lower substrate 200, and the upper substrate 100 has a predetermined thickness. The upper substrate 100 may be processed by bonding to a predetermined thickness, or may be processed to a predetermined thickness after bonding. Bonding can use a variety of methods, including known processes (fusion bonding, anodic bonding, eutectic bonding, frit bonding) and bonding with adhesives.

After forming and patterning the etching mask thin films 401 and 402 to be used as an etching mask on the upper substrate 100 as shown in FIG. 8D, the lower substrate is anisotropically etched by a predetermined depth using the etching mask 3 303. The etching mask 5 402 should have a selectivity and a bonding surface material between the silicon, which is a substrate, and another etching mask 4 401, and the upper substrate 100 and the lower substrate 200.

As shown in FIG. 8E, the upper substrate 100 is anisotropically etched by a predetermined depth using the etching mask 4 401 and the etching mask 5 402.

As shown in FIG. 8F, the etch mask 5 402 is removed and the upper substrate 100 is anisotropically etched by a predetermined depth using the etch mask 4 401 so that the mirror plate 110 has a predetermined thickness.

As shown in FIG. 8G, the etching mask 4 401 is removed, and the bonding surface of the inner side except the outside of the substrate of the upper and lower substrates 100 and 200 is etched to float the structure and the reflecting surface 115 below the mirror plate 110. ).

6 and 7 are cross-sectional views showing the configuration and operation of the constant power driving scanning micromirror according to the present invention, as shown in the lower substrate for driving the constant power driving scanning micromirror according to the present invention as described above. The voltage is applied between the fixed comb-shaped electrode 220 and the movable comb-shaped electrode 120 through both electrode fixing parts 230 of the 200.

In the initial state of FIG. 6, when voltage is applied between the electrode fixing part 150 of the upper substrate 100 and the electrode fixing part 230 of the lower substrate 200, a movable comb-shaped electrode electrically connected to each of them ( An electric potential difference is formed between the 120 and the fixed comb-shaped electrode 220 to act as an electrostatic force, and all structures connected to the mirror plate 110 rotate about the torsion beam 140 as shown in FIG. 7. You exercise. Accordingly, as shown in FIG. 7, the direction of the reflected light with respect to the incident light is also modulated from the direction L1 before the driving to the direction L2 after the driving to implement the scanning function.

Therefore, when voltage is sequentially applied between the fixed comb-shaped electrodes 220 and the movable comb-shaped electrodes 120 formed on both sides, the mirror plate 110 rotates to the left and right. Even when the movable comb-shaped electrode 120 and the fixed comb-shaped electrode 220 are formed only on one side of the torsion beam 140 as the rotation axis, when the voltage is applied and removed, the mirror plate ( Since 110 is driven in the opposite direction, bidirectional driving can be implemented.

In order to adjust the driving force of the micromirror, an electric potential difference may be applied between the mirror plate 110, the movable comb-shaped electrode 120, and the control electrode 130 to apply an electrostatic force that hinders driving.

The electrostatic force driving scanning micromirror according to the present invention as described above is an element that can be used to scan information, such as an image or read data, such as a position, an image by scanning a beam emitted from a light source to a predetermined region, This scanning micromirror can be fabricated using micromachining technology and semiconductor integrated process to realize a compact and lightweight form with remarkably improved optical and mechanical performance, reduced component cost, and driven by constant power driving. The power can be significantly lowered.

Claims (19)

A mirror plate rotatably formed on the substrate to reflect the input light, an elastic rotation support element formed on the substrate to rotatably support the mirror plate, and formed on the substrate by the potential difference between electrodes A constant power drive scanning micromirror comprising a constant power drive element that rotates at a constant power to adjust the direction of reflected light. The electrostatically rotating scanning micromirror of claim 1, wherein the elastic rotation supporting element is configured by connecting one side of the substrate and a mirror plate to one of a cantilever beam and a torsion beam. 2. The constant power driving scanning micromirror of claim 1, wherein the mirror plate comprises a reflective surface stacked on a lower surface thereof and a reinforcing frame structure for suppressing dynamic deformation of the mirror plate. 2. The constant power drive scanning micromirror of claim 1, wherein the mirror plate is a flat plate structure of uniform thickness. The constant power driving scanning micromirror of claim 1, wherein the constant power driving element is formed by forming a movable comb-shaped electrode and a fixed comb-shaped electrode on the substrate. The scanning power mirror of claim 3, wherein the reinforcement frame structure comprises one or more unit frame structures arranged in an array. 6. The constant power drive scanning micromirror according to claim 5, wherein the movable comb-shaped electrode is formed on both sides or one side of the elastic rotating support element. 6. The fixed power drive scanning micromirror according to claim 5, wherein the fixed comb-shaped electrode corresponding to the movable comb-shaped electrode is formed to be partially overlapped with the movable comb-shaped electrode or spaced by a predetermined distance. 6. The constant-power driving scanning micromirror according to claim 5, further comprising a control electrode for adjusting a driving force of the mirror plate by applying a potential difference between the mirror plate and the movable comb-shaped electrode. The constant power driving scanning micromirror of claim 6, wherein the unit frame structure has a structure in which a side close to the elastic rotation support element is wider than a side far from the elastic rotation support element. 7. The constant power driving scanning micromirror of claim 6, wherein the unit frame structure has a thickness closer to the elastic rotation support element than a side far from the elastic rotation support element. 7. The constant power driving scanning micromirror of claim 6, wherein the unit frame structure has a structure in which a predetermined portion reduces via mass. Upper and lower substrates stacked on top of each other, A mirror plate rotatably installed inside the middle space portion of the upper substrate; A reflection surface formed on a bottom surface of the mirror plate to reflect input light; A torsion beam connected between both end portions in the longitudinal direction of the upper substrate and both end portions of the mirror plate to support the mirror plate to rotate; A rotation space portion formed so that the mirror plate is inserted into the middle portion of the lower substrate to rotate therein; A movable comb-shaped electrode and a fixed comb-shaped electrode formed on both upper space portions formed on both sides of the upper substrate in both width directions of the torsion beams, and on both side space portions formed on both sides in the longitudinal direction of the central space portion of the lower substrate; An insulating layer formed between the upper and lower substrates; And an electrode fixing part formed on the upper and lower substrates to apply a driving voltage to the movable comb-shaped electrode and the fixed comb-shaped electrode. 15. The method of claim 13, wherein the mirror plate is formed of a continuous reinforcement frame structure of a plurality of diamond-shaped protrusions and triangular groove portion formed in succession, each projection is characterized in that a plurality of etching holes are formed is formed Scanning Micromirror. The constant power driving scanning micromirror of claim 13, wherein the reflective surface of the mirror plate is formed in a thin film shape having a uniform thickness on a lower surface of the upper substrate. An array consisting of M rows and N columns of micromirrors comprising a mirror plate for reflecting input light on a substrate, an elastic support element for rotatably supporting the mirror plate, and a constant power driving element for rotating the mirror plate. An array of constant power driven scanning micromirrors arranged. An optical scanning device comprising the electrostatic force driving scanning micromirror according to any one of claims 1 to 16 provided in the scanning unit. A method for manufacturing a constant power drive scanning micromirror, wherein the constant power drive scanning micromirror according to any one of claims 1 to 16 is processed in a micromachining technique and a semiconductor integrated manufacturing process to produce a large quantity. 19. The method of claim 18, further comprising: forming and patterning thin films 1, 2, and 3 for etching masks, which are used as an etching mask in an etching process, respectively, above and below the substrate using a silicon lower substrate in the form of a wafer; Anisotropically etching the upper surface of the silicon lower substrate on which the two layer etching masks are formed by a predetermined depth, and removing the etching mask 2 after etching; Bonding an upper substrate to the lower substrate; Forming and patterning the etching mask thin films 4 and 5 to be used as an etching mask on the upper substrate, and then anisotropically etching the lower substrate using the etching mask 3 to a predetermined depth; Anisotropically etching the upper substrate by a predetermined depth using the etching mask 4 and the etching mask 5; Removing the etching mask 5 and anisotropically etching the upper substrate using the etching mask 4 to a predetermined depth to form a mirror plate having a predetermined thickness; Removing the etch mask 4 and etching the joining surfaces of the inner and lower substrates of the upper and lower substrates to lift the structure and form a reflective surface under the mirror plate. Manufacturing method.

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