KR100300965B1 - Micro mirror actuator and Fabricating method thereof - Google Patents

Abstract

The present invention describes a micromirror driver using an electrostatic force used as a secondary actuator of an optical disk drive. The micro-mirror driver of the optical disk drive using the electrostatic force according to the present invention is driven so that the micro-mirror reciprocates to an arbitrary angle with respect to the central axis, and the driving displacement of the mirror having a micro size is large or the size of the mirror is larger than the micro size. Although it is so large that the drive displacement is relatively increased, the force at the end of the swing arm of the optical disc drive is increased so that the force is generated regardless of the distance between the two conductors and the size of the displacement zone. Considering the weight and the degree of simplicity, the driver that drives the micro-mirror using the electrostatic force can be integrated with the mirror to reduce the size and weight and simplify the process.

Description

Micro mirror actuator and fabrication method of optical disk drive using electrostatic force {Micro mirror actuator and Fabricating method

The present invention relates to a micromirror driver using electrostatic force used as a secondary actuator of an optical disk drive.

Examples of the information storage device include a hard disk drive (HDD) and an optical disk drive (ODD). As the system environment changes to multimedia, a large amount of information storage and fast data access speed are required in the information storage device, and a new information storage device needs to be developed to satisfy this. In particular, in order to solve this problem in the conventional optical disk drive, as shown in Figure 1a, a method of mounting a micro mirror actuator (12) that can finely adjust the direction of light has been proposed. Due to this, the driving speed limit of the swing arm 11 is mirrored at an angle of about 45 ° to the end of the swing arm 11 that rotates in the rotational direction 16 of the swing arm as shown in FIG. 1B. Drive in the direction of rotation 15 of the micromirror to increase the conversion speed of the light path 14 in the light path conversion direction 17 to improve the data tracking speed on the track 18, By increasing the storage capacity, the storage density of the disk 13 is improved.

A data optical pick-up device, which is equipped with an auxiliary driver to improve data storage and tracking performance, has recently been researched and developed by Samsung Electronics and QUINTA of the United States, and related patents have not been found yet. However, the micro-optic mirror driver using electrostatic force itself is an optical scanning device (US Patent, 5635708) and Digital Micromirror Device (Paper: Jack M. Younse, 1995, 'Projection Display' Systems Based on the Digital Micromirror Device ', SPIE, Vol. 2641, pp 64-75).

As an example, most micro mirror drivers using a conventional electrostatic power, as shown in Figure 2, the substrate 21, a fixed electrode 22 provided on the substrate 21, a column fixed on the substrate ( 23, an elastic member 24 connected to the pillar 23, a variable plate 25 that is rotatable about the shaft and that faces the fixed electrode 22, and the variable flat plate 25 It consists of a mirror (26) placed on it. The driving principle of the micromirror driver is to drive the variable plate 25 using an electrostatic force generated perpendicular to the surface of the variable plate 25 by giving a potential difference between the fixed electrode 22 and the variable plate 25. . In this way, the electrostatic force is inversely proportional to the square of the distance between the two conductors (the fixed electrode 22 and the variable plate 25), so the force increases or decreases nonlinearly as the distance between the two conductors increases or decreases. Therefore, the application of the movement device by the electrostatic force is mainly limited to the micro-sized system in which the distance between the two conductors is close enough to effectively operate the electrostatic force. Therefore, there is a problem that the drive displacement must also be very small.

In addition, a patent using the electrostatic effect due to the comb structure has been described in US Patent No. 5025346, which has a comb structure in which the mobile conductor plate and the high-conductor plate are each connected in a repeating structure, and the suspension structure is horizontally resonated using this structure. A patent relates to a microgyroscopic structure that is excited using frequency.

3 shows a mirror driver using an electrostatic force proposed by NASA Jet Propulsion Labrotory (JPL). Here, the member number 61 is a stator substrate, the member number 62 is a slider, and the member number 63 is a spring that fixes the slider 62 to the stator substrate 61 so as to vibrate up and down. 64 is a mirror membrane attached to the slider 62.

The present invention was devised to improve the above problems, and has a size from micrometers to millimeters, the mirror is driven to reciprocate to an arbitrary angle about the central axis, and the driving displacement of the mirror is large. If the mirror size is considerably larger than the micro size, even if the displacement is relatively increased, the force is generated irrespective of the distance between the two conductors generating the electrostatic force and the size of the displacement zone. SUMMARY OF THE INVENTION An object of the present invention is to provide a micromirror driver of an optical disk drive using an electrostatic force having a structure of forming the same, and a manufacturing method thereof.

1A is a diagram of a typical optical disc drive system,

FIG. 1B is a view showing a state in which a micro mirror is attached in the optical disk drive system of FIG. 1A;

2 is a view of a mirror driver using a conventional electrostatic force,

3 is a view of a mirror driver proposed by NASA Jet Propulsion Labrotory (JPL) as another conventional mirror driver using electrostatic force,

4A is a partially cutaway perspective view of a micromirror driver using electrostatic force according to the present invention;

Figure 4b is a vertical cross-sectional view showing a cross section taken along the line AA 'of Figure 4a,

4C is an exploded perspective view of the auxiliary mirror driver of FIG. 4A;

FIG. 5A is a view for explaining a principle of electrostatic force driving of the auxiliary mirror driver of FIG. 4A;

FIG. 5B is a view for explaining the principle of electrostatic force driving viewed from the line BB ′ of FIG. 5A;

6 is a block diagram showing a schematic configuration of a driving and sensing circuit of the auxiliary mirror driver according to the present invention;

7 is a perspective view showing the overall structure of the wafer fabricated micromirror driver according to the present invention,

8A through 8H illustrate a method of fabricating a silicon frame on the upper part of the micromirror driver of FIG. 7 by using inductively coupled plasma reactive ion etching (ICPRIE) and etching using XeF ₂ gas using bulk silicon; Are cross-sectional views,

9A to 9J are cross-sectional views illustrating a method of manufacturing the upper silicon frame of the micromirror driver of FIG. 7 by using bulk silicon using ICPRIE and TetraMethyl Ammonium Hydroxide (TMAH) method.

10A through 10E are cross-sectional views illustrating a method of fabricating a lower structure of the micromirror driver of FIG. 7 by ICPRIE using bulk silicon, in a step-by-step manner;

FIG. 11 is a cross-sectional view illustrating a state in which the upper silicon frame of FIG. 8H and the lower structure of FIG. 9J are combined;

12 is a photograph taken after the manufacturing process of the micro mirror driver is completed as described above,

13 is an enlarged photograph of the circle portion (comb electrode structure) of FIG. 12.

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

11. Swing arm 12. Micro mirror driver

13. Disk 14. Light Path

15. Direction of rotation of the micro mirror 16. Direction of rotation of the swing arm

17. Light Path Conversion Direction 18. Track

21. Substrate 22. Fixed electrode

23. Column 24. Elastic member

25. Adjustable flatbed 26. Mirror

31. Substrate 32. Fixed electrode

33. Detection electrode 34. Common electrode

35. Mirror body 36. Mirror

37. Elastic member 38. Frame

41. Supporting end 42. Fixed conductor plate

43. Moving conductor plate support end 44. Spring

45. DC voltage Vo 51. Common ground

52. Alternating voltage 53, 54. Sign inverter

55. Bias DC Voltage 56. Final Output

57. C-V Converter 61. Stator Board

62. Slider 63. Spring

64. Mirror membrane 101. Bulk silicon substrate

103. Silicon Nitride Mask Pattern 105. Silicon Oxide Mask Pattern

107. Photoresist Pattern 109. Silicon Oxide Film

120. Metal mirror 130. Elastic member

140. Top comb structure 201. Bulk silicon substrate

203 '. SiO ₂ film 203. Silicon oxide film mask pattern

205. Photoresist pattern 207. Side etching prevention film

209. Silicon Oxide Mask Pattern 211. Comb Electrode Structure

220. Metal mirror 230. Elastic member

240. Upper comb structure 300. Glass substrate

301. Silicon substrate 302 '. Silicon oxide

302. Silicon Oxide Mask Pattern 303. Photoresist Pattern

305. Comb electrode structure 306. Silicone frame

307. Fishing Pole

In order to achieve the above object, the micro-mirror drive of the optical disk drive using the electrostatic force according to the present invention, the substrate; A frame fixed to the upper surface of the substrate; An elastic member connected to the frame; A mirror body connected to the opposite side on an axis in a first direction parallel to the substrate and spaced apart from the upper surface of the substrate so as to reciprocate about the first direction axis; A mirror mounted on the mirror body; Under the mirror body, a plate structure having a certain thickness, width, and length is placed perpendicular to the first direction, and the length direction of the plate is perpendicular to the first direction and with the substrate. A common electrode placed in parallel in a second parallel direction and having three or more plate structures arranged in the first direction at regular intervals; It has the same structure as the common electrode and faces the common electrode spaced apart from the first direction by a predetermined distance, and overlaps a predetermined distance in a third direction perpendicular to the first direction and the second direction, and in the second direction. A fixed electrode which is spaced apart from each other by a predetermined distance to the opposite structure, and fixed to the substrate to provide an electrostatic force to the common electrode in the third direction when a voltage is applied; A sensing electrode having the same structure and arrangement as the fixed electrode, fixed to the substrate, and sensing a change in capacitance when the common electrode is moved; A power supply for applying a potential to the fixed electrode to generate a potential difference between the common electrode and the fixed electrode; A detector measuring a change in capacitance at the common electrode and the sensing electrode; And a controller for adjusting the power supply.

In the present invention, the fixed electrode and the sensing electrode is present on the substrate in a certain order and proportion on one side, based on the axis in the first direction, the other side is present on the substrate in the same order and irrespective of the order, The power supply preferably applies a constant bias voltage to the fixed electrode and alternately applies an alternating voltage that gradually modulates a voltage having the same magnitude over time, and the sensing electrode has the common electrode rotated along an axis in the first direction. It is desirable to detect the increase and decrease of the capacitance when rotating a certain amount on both sides of the rotation axis and to obtain a double detection effect by changing the absolute sum of the detected value as the total capacitance, the frame, the elastic member, The mirror body and the common electrode are integrally formed, and the frame, the elastic member, the mirror body and the common electrode are elastic and conductive materials. The mirror is directly mounted on an upper surface of the mirror body, and the mirror body is formed by electrostatic force to a width at a portion where the fixed electrode or the sensing electrode does not overlap the common electrode by a distance spaced from each other in the second direction. The bending deformation of the structure is reduced to be within a predetermined limit condition, and the frame, the elastic member, the mirror body, and the common electrode are integrally manufactured by using reactive ion etching using bulk silicon, respectively, and the frame, the elastic member, It is preferable that a mirror body, an integral upper structure having a common electrode and a lower structure having the substrate, the fixed electrode, and the sensing electrode are formed, respectively, and then bonded by anodic bonding.

In addition, in order to achieve the above object, the manufacturing method of the micro-mirror driver of the optical disk drive using the electrostatic force according to the present invention, (A) the upper comb electrode structure by etching the bulk silicon substrate by ICPRIE method and XeF ₂ gas etching method Forming an upper frame having a; (B) etching the bulk silicon deposited on the glass substrate by ICPRIE to form a lower structure having a lower comb electrode structure corresponding to the upper comb electrode structure; And (c) joining the upper frame manufactured in the step (a) to the lower structure manufactured in the step (b) such that the upper comb electrode structure is engaged with the lower comb electrode structure. do.

In the present invention, the step (a) comprises (a-1) a sub-step of sequentially depositing SiN and SiO ₂ on a bulk silicon substrate having a thickness of about 200 μm by chemical vapor deposition to form a silicon nitride film and a silicon oxide film. ; (A-2) a sub-step of patterning the silicon oxide film and the silicon nitride film, wherein the silicon nitride film is patterned with phosphoric acid (H ₃ PO ₄ ) to form a mask pattern for forming a comb electrode structure; (A-3) a sub-step of forming a photoresist mask pattern for forming a comb structure and an array pole by applying and patterning photoresist on an edge on the bulk silicon substrate on which the oxide and nitride mask patterns are formed; (A-4) forming a comb structure by etching the bulk silicon substrate to a thickness of 10-20 μm in the vertical direction by ICPRIE method using the oxide film, nitride film mask pattern and the photoresist pattern, and then removing the photoresist pattern. A sub-step; (A-5) a sub-step of forming a silicon oxide film by oxidizing the entire surface of the silicon substrate having the comb structure while removing the silicon oxide mask pattern on the comb structure to expose the silicon nitride film mask pattern; (A-6) substep of removing the silicon nitride film mask pattern on the comb structure to expose silicon only on the upper part of the comb structure, etching only the comb structure to a suitable length using XeF ₂ gas, and then removing the silicon oxide film ; (A-7) a sub-step of forming the upper frame of the micromirror driver by etching the bulk silicon substrate from the rear surface without the comb structure by using the photolithography method and the ICPRIE method to etch through unnecessary parts; And (A-8) sub-steps of depositing Al on the rear surface of the upper frame to form conductive wires in the metal mirror and the elastic member.

In addition, in the present invention, the step (a) is performed by wet oxidation (wet oxidation) for about 3 hours at 1100 ° C. on the front and rear surfaces of the bulk silicon substrate having a (100) plane having a thickness of (A-1) 200 μm. Forming a 1 μm thick SiO ₂ film; (A-2) a substep of patterning the silicon oxide film by photolithography to form a mask pattern for forming the comb electrode structure; (A-3) sub-etching the silicon substrate to a depth of 140 μm in the vertical direction by using the ICPRIE method and then removing only the photoresist pattern; (A-4) Deposition of 0.2 μm thick SiN on the exposed silicon wall by CVD, and then removing all nitride films other than the nitride film deposited on the wall by ion milling. Forming a sub-step; (A-5) a sub-step of etching the bottom surface of the exposed silicon substrate in a vertical direction further by a depth of 50 μm using the ICPRIE method, and forming a silicon oxide film mask pattern on the etched surface by a wet oxidation method; (A-6) removing the silicon nitride film mask pattern using phosphoric acid (H ₃ PO ₄ ); (A-7) a sub-step of etching the comb tooth structure of the silicon substrate by TMAH to form the comb electrode structure to a predetermined length; (A-8) substeps of removing the silicon oxide films; (A-9) a sub-step of forming an upper frame of the micro mirror driver by penetrating an unnecessary portion of the silicon substrate from the rear surface without the comb structure by etching using photolithography and ICPRIE; And (A-10) a sub-step of depositing Al on the rear surface of the upper frame to form conductive wires on the metal mirror and the elastic member. Further, among these processes, (A-1) sub-step In this case, a bulk silicon substrate having the (100) plane or another crystal direction is used, and in the sub-step (A-7), etching of only the comb structure to a predetermined length using XeF ₂ gas instead of the TMAH method is also possible. desirable.

In addition, in the present invention, the step (b) may include: (b-1) a sub-step of oxidizing a high concentration p-type silicon substrate having a thickness of 170 μm as a whole to form an oxide film; (B-2) After patterning the silicon oxide film on the entire surface of the silicon wafer to form a silicon oxide mask pattern for forming a comb electrode structure, the oxide film on the back is completely removed, and the silicon substrate is 50μm using photolithography and ICPRIE. A substep of etching to a depth of degree; (B-3) bonding the back surface of the etched silicon substrate to a 1 mm thick glass substrate using an anodic bonding process; (B-4) A photoresist pattern is formed to cover the silicon oxide mask pattern formed on the silicon substrate, and the IC substrate is vertically downward while leaving only the portion where the comb electrode support and the surrounding alignment poles are to be formed. A substep of etching to a depth of 70 μm using the method; (B-5) After removing the photoresist pattern, the silicon substrate is etched by the ICPRIE method to form a lower comb electrode structure, and an unnecessary portion of the silicon substrate is etched and penetrated into and around the comb electrode structure. It is preferable to include; sub-steps to complete the substructure of the micro mirror driver leaving only the silicon frame structure and the alignment pole.

In addition, in the present invention, the step (c) may include arranging poles provided at four corners of the lower structure such that the upper comb electrode structure is engaged with the lower comb electrode structure on the glass substrate. Coupling the upper frame to the lower structure; And bonding the upper frame to the lower structure using anodic bonding using an anodic bonding.

Hereinafter, the micro mirror driver of the optical disk drive using the electrostatic force according to the present invention will be described in detail with reference to the drawings.

The present invention can be fabricated using a micromachined process and has an electrostatic force mirror driver having a size from micrometers to millimeters, the mirror can be driven to reciprocate to any angle about the central axis, The distance between the two conductors is increased so that the driving displacement of the mirror having a micro size is large or the size of the mirror is considerably larger than the micro size, so that the driving displacement is relatively increased to improve the inadequacy of the electrostatic driving method as shown in FIG. The force must be generated regardless of the size of the displacement section, and it must be designed to have a structure in which the force increases as the mirror size increases. Created to satisfy this design condition is a micro-mirror driver using the electrostatic force as shown in Fig. 4a. When the micromirror driver is cut along the line A-A ', it becomes a cross-sectional view as shown in FIG. 4B, and when disassembled and arranged, it is as shown in FIG. 4C.

The micromirror driver of the optical disk drive using the electrostatic force according to the present invention is largely divided into an upper structure and a lower structure as shown in FIG. 4C. The lower structure includes a substrate 31, a fixed electrode 32 and a sensing electrode 33 attached thereto. The upper structure includes a common electrode 34 corresponding to the fixed electrode 32 and the sensing electrode 33, a mirror body 35, a mirror 36, an elastic member 37 supporting them and being a driving shaft, and a lower structure. A frame 38 is provided to be connected. Also, although not shown in FIGS. 4A, 4B, and 4C, a power supply device for driving a driver, a sensing device for detecting rotation of the mirror body, and a controller for adjusting reciprocating rotational change of the mirror body 35 are provided. ) Is further provided.

In the upper structure, the mirror body 35 is connected to an elastic member 37 serving as a rotation spring in the center of both sides in the shape of a rectangular parallelepiped, which is connected to the frame 38. On the upper surface of the mirror body 35, a mirror 36 is covered in a film form. The lower part of the mirror body 35 has a shape in which one or more plates having a predetermined thickness, width, and length are arranged at regular intervals to be spaced apart at regular intervals. In other words, when viewed from the front of the mirror body 35, the plate is arranged in two or more consecutively to form a comb-like structure, the surface of the plate is also connected to the drive axis of rotation of the mirror (resilient members connected to both mirror body shafts) Axis; and an elastic member axis). The vertical length of the comb plate of this comb structure is equal to the mirror length and the width of the comb plate up to a certain distance from the rotation axis, which is a small moment due to the electrostatic force, as shown in FIG. 4B for mass reduction. By the bending deformation of the mirror body 35 is present within a certain limit condition to reduce the degree to which the flatness of the mirror can be sufficiently maintained. The portion reduced in the width of the comb plate becomes a portion which is not engaged with the fixed electrode 32 and the sensing electrode 33 of the lower structure. Since the comb tooth structure including the mirror body 35 is a conductor, all of them are constituted by the common electrode 34.

A fixed electrode 32 for driving and a sensing electrode 33 for position control are formed on the substrate 31 on both sides of the elastic member 37 serving as an axis in the lower structure. The structure in which these electrodes are formed is the same as that of the common electrode 34 that rests on the mirror body 35. First, two or more plates forming a comb structure on one side of the elastic member 37 are used for the fixed electrode 32 and the sensing electrode 33, respectively. The sensing electrodes 33 are insulated from each other and formed. Similarly, the fixed electrode 32 and the sensing electrode 33 are formed on the other side of the elastic member 37, respectively. That is, the left and right fixed electrodes 32 and the sensing electrodes 33 with respect to the elastic member 37 are arranged diagonally to each other or symmetrically arranged on the elastic member 37. The electrode structures of the lower structure are arranged in a state of being engaged with each other while maintaining the same distance from each other, without being in contact with the common electrode 34 of the upper structure.

The operation principle of the optical disk drive micro mirror driver using the electrostatic force having the above structure is as follows.

The principle of generating the electrostatic force which is the fundamental force of the micro-mirror driving is as shown in Figs. 5a and 5b, the fixed conductor plate 42 and the moving conductor plate 43 having a predetermined thickness (c) and length (d) When the potential difference is applied in a state where) is spaced apart from each other by a predetermined interval (g) in a direction perpendicular to the substrate 31, the movable conductor plate 43 is fixed to the support end 41 by the electrostatic force. The movable conductor plate 43 is returned and reciprocally straightened by a spring 44 drawn in the direction (42) and connecting the support end 41 and the movable conductor plate 43. The electrostatic force F acting on one of the mobile conductor plates 43 is theoretically determined by conformal mapping using a complex number, and this value is the interval g between the facing combs and the thickness of the comb teeth c. And the length of the comb teeth d, and are obtained as follows.

F = F (c, d, g) = εV2 [d / g + (Ksinα / Kcosβ) K [sinα] / K [cosβ]]

α = πc / 2 (c + g),

In Equation 1, ε is a vacuum permittivity, and V is a potential difference between two conductors.

In other words, the driving principle of the micromirror driver is that a potential difference is given between the moving electrode 34, which is a comb structure existing on the lower surface of the mirror body 35, and the fixed electrode 32, which is present on the substrate 31 and faces the corresponding electrode 31. When the electrostatic force acts perpendicular to the mirror surface is a principle that the mirror to rotate relative to the elastic member (axis) (37).

As shown in FIG. 6, the driving circuit and the sensing circuit of the micromirror driver operating on the same principle include two fixed electrodes 32 for driving the mirror body 35 in a reciprocal rotation with respect to the elastic member 37. Sign inverters 53 and 54 having different signs so that the phase difference is 180 degrees to the two fixed electrodes 32 by applying the same bias DC voltage Vo (55) to each other and applying an alternating voltage 52 having amplitude magnitude Vo. Pass through. Then, in one fixed electrode 32, the bias DC voltage 55 and the AC voltage 52 are added together, while the other side is canceled. In the summation of the voltages, the common electrode 34 of the common ground 51 and the electrostatic force due to the voltage difference are generated. This force acts as a distribution load in the region where the fixed electrode 32 and the common electrode 34 overlap each other, and the action point has a certain amount of distance from the elastic member 37, thereby generating a corresponding moment to generate a mirror body ( 35). The magnitude of the DC voltage 55 and the magnitude of the maximum amplitude of the AC voltage 52 are controlled by the controller, and the phase difference and the period of the AC voltage 52 are controlled, whereby the positions at which the electrostatic force is generated with time are mutually different. In turn, the magnitude of the electrostatic force, the time the electrostatic force is applied is adjusted, so that the mirror body 35 makes a reciprocating rotational movement at a controlled rotation angle and rotation speed. As the mirror body 35 is driven, the common electrode 34 also rotates with respect to the elastic member 37, and a change in capacitance occurs between the common electrode 34 and the sensing electrode 33. At this time, since the sensing electrodes 33 exist on both sides of the elastic member 37, the capacitance increases on the inclined side to the common electrode 34 and the sensing electrode 33, and decreases on the other side. The absolute values of the capacitances measured in these two parts are added together to be regarded as the change of the total capacitance, and thus the detection capability is doubled. The capacitance change value is converted into a change value of the voltage through the C-V converter 57, and finally represents the degree of rotation of the mirror body 35 by the final output unit 56.

The method of manufacturing the optical disk drive micromirror driver using the electrostatic force operating as described above is as follows.

7 is a perspective view showing the overall structure of the wafer fabricated micro-mirror driver according to the present invention. Here, the left half shows the state in which the mirror body 35 and the micromirror 36 are removed, and the right half shows the state in which the mirror body 35 and the micromirror 36 are formed. As described above, the micro-mirror driver according to the present invention comprises a silicon frame 38 having a mirror body 35 on which the upper comb electrode 36 is formed on the glass substrate 31 on which the lower comb electrode 33 is formed. 31 is a structure that is combined using the array pole 100 formed at the four corners. Therefore, the manufacturing method of the micro mirror driver according to the present invention is largely a process of forming the lower comb electrode 33 and the metal wiring 39 on the glass substrate 31 and the mirror body 35 on which the upper comb electrode 36 is formed. Is a step of forming a silicon frame 38 having a) and a step of combining the two.

Here, the upper frame silicon frame 35 is manufactured using bulk silicon. 8A to 8H using the inductively coupled plasma reactive ion etching (ICPRIE) method and the etching method using XeF ₂ gas as the method of fabricating the upper structure, and FIGS. 9A to 9J using the ICPRIE method and the TetraMethyl Ammonium Hydroxide (TMAH) method. Two methods are presented, one presented. The first method is as follows.

First, as shown in FIG. 8A, SiN and SiO ₂ are sequentially deposited on the 200 μm-thick bulk silicon substrate 101 by chemical vapor deposition (CVD) to form a silicon nitride film 103 ′ and a silicon oxide film 105. Form ').

Next, as shown in FIG. 8B, the silicon oxide film 105 ′ and the silicon nitride film 103 ′ are patterned to form mask patterns 103 and 105 for forming the comb electrode structure. In this case, the silicon nitride film 103 is patterned with phosphoric acid (H ₃ PO ₄ ), but may be patterned using a plasma etching process.

Next, as shown in FIG. 8C, a photoresist is applied and patterned to form a photoresist mask pattern 107 for comb structure and alignment pole formation.

Next, as shown in FIG. 8D, the bulk silicon substrate 101 is etched to form only the comb structure after the ICPRIE method is used to etch deeply in the vertical direction, leaving only a final thickness of 10 to 20 μm, and then removing the photoresist pattern 107. Thus, only the silicon oxide film mask pattern 105 and the silicon nitride film mask pattern 103 are left. Here, the ICPRIE method can focus plasma ions more than the RIE method, which is more advantageous for precise anisotropic etching in the vertical direction.

Next, as illustrated in FIG. 8E, the entire surface of the silicon substrate 101 having the comb structure is oxidized while the silicon oxide film mask pattern 105 is removed to expose the silicon nitride mask pattern 103 on the comb structure. To form a silicon oxide film 109. At this time, no oxide film is formed where the silicon nitride film mask pattern 103 remains.

Next, the silicon nitride film mask pattern 103 on the comb structure is removed so that the silicon is exposed only on the upper part of the comb structure, and as shown in FIG. 8F, the thickness of the comb structure is appropriately lengthened using XeF ₂ gas. Is etched and then the silicon oxide film 109 is removed. At this time, an oxide film still remains on the surrounding frame. Here, isotropic etching is performed by the XeF ₂ gas etching method, and the etching rate is high. Silicon etching rate compared to the oxide film SiO ₂ / Si is about 1/8000 silicon etching rate is fast.

Next, as shown in FIG. 8G, the upper frame of the micromirror driver is formed by etching through the unnecessary silicon substrate portion on the rear surface without the comb structure by using the photolithography method and the ICPRIE method. Here, the figure is rotated 90 degrees differently from the figures to show the penetrating portion.

Next, as shown in FIG. 8H, Al is deposited on the rear surface of the upper frame to form conductive wires in the metal mirror 120 and the elastic member 130. Reference numeral 140 is an upper comb structure. This figure also shows a 90-degree rotational cross section as in the previous figures as in FIG. 8G.

The second method of manufacturing the upper frame of the micro mirror driver according to the present invention proceeds in the following order.

First, as shown in FIG. 9A, the front and rear surfaces of the 200 μm-thick bulk silicon substrate 201 are oxidized by wet oxidation at 1100 ° C. for about 3 hours to form a 1 μm-thick SiO ₂ film 203 ′. Form.

Next, as shown in FIG. 9B, the silicon oxide film 203 'is patterned on the silicon oxide film 203' by photolithography to form a mask pattern 203 for forming a comb electrode structure. Here, reference numeral 205 denotes a photoresist pattern.

Next, as shown in FIG. 9C, the bulk silicon substrate 201 is etched to about 140 μm deep in the vertical direction using the ICPRIE method, and then the photoresist pattern 205 is removed to remove only the silicon oxide mask pattern 203. Leave

Next, as shown in FIG. 9D, a silicon nitride film deposited on the surface of the exposed silicon substrate 201 was deposited on the surface of the silicon substrate 201 deposited by CVD on the entire surface, and then etched by ion milling. All other nitride films (particularly, nitride films on the bottom surface) are removed to form the side etch stop film 207.

Next, as shown in FIG. 9E, the bottom surface of the exposed silicon substrate 201 is etched more deeply in the vertical direction by using the ICPRIE method, and the etched surface is wet oxidized to wet oxidation. The mask pattern 209 is formed. At this time, the etching depth is about 50 μm deeper. Therefore, the total etching depth of the silicon substrate 201 is about 190 μm. The oxide film does not occur where the silicon nitride film mask pattern 207 remains.

Next, as shown in FIG. 9F, the silicon nitride film (SiN) mask pattern 207 is removed using phosphoric acid (H ₃ PO ₄ ).

Next, the comb-tooth structure of the silicon substrate 201 is etched by the TMAH method, so that the comb-tooth electrode structure 211 is formed to an appropriate length, as shown in FIG. 9G. In this case, the comb-tooth structure of the portion covered with the oxide film 209 remains as it is. This is because TMAH (TetraMethyl Ammonium Hydroxide) method is a wet etching method using anisotropy etched along the crystal plane. In this process, the anisotropic etching property of the crystal plane allows the etching of the comb electrode structure to stop at a certain point. to be. For this purpose, it is preferable to use a silicon wafer having a (100) plane as the substrate. In addition, in this step, not only the TMAH method but also the XeF ₂ gas introduced in the first manufacturing method can be used to etch only the comb tooth structure to an appropriate length. Isotropic etching is performed by XeF ₂ gas etching, and the etching rate is high. Silicon etching rate compared to the oxide film SiO ₂ / Si is about 1/8000 silicon etching rate is fast.

Next, as shown in Fig. 9H, the silicon oxide films 203 and 209 are removed.

Next, as shown in FIG. 9I, the upper frame of the micromirror driver is formed by etching through the unnecessary silicon substrate portion using the photolithography method and the ICPRIE method on the back surface having no comb structure. Here, the figure is rotated 90 degrees differently from the figures to show the penetrating portion.

Next, as shown in FIG. 9J, Al is deposited on the rear surface of the upper frame to form conductive wires in the metal mirror 220 and the elastic member 230. Reference numeral 240 is an upper comb structure. This figure also shows a 90-degree rotational cross section as in the previous figures as in FIG. 9I.

As described above, the method of forming the lower comb electrode and the metal wiring on the glass substrate 31 corresponding to the comb electrode structure of the upper frame is as follows.

First, as shown in FIG. 10A, an oxide film 302 ′ is formed by completely oxidizing a 170 μm-thick high concentration p-type silicon wafer 301.

Next, as shown in FIG. 10B, the silicon oxide film 302 ′ on the front surface is patterned to form a silicon oxide mask pattern 302 for comb electrode structure formation, and then the oxide film 302 ′ on the back surface is completely removed. . The oxide film etching on the back surface is such that only the support (Si island) of the comb electrode is bonded to the glass substrate. This is because otherwise, the upper mirror silicon is not bonded to the glass substrate later. Next, the silicon substrate 301 is etched to a depth of about 50 μm using the photolithography method and the ICPRIE method. Reference numeral 303 denotes a photoresist pattern.

Next, as shown in FIG. 10C, the back surface of the etched silicon substrate 301 is bonded to the glass substrate 300 having a thickness of 1 mm using an anodic bonding process. At this time, only the comb-tooth support part and the surrounding silicon-array pole are joined in the part to be joined.

Next, as shown in FIG. 10D, a photoresist pattern 303 covering the silicon oxide film mask pattern 302 formed on the silicon substrate 301 is formed, and the comb electrode supporting portion of the silicon substrate 301 is formed by the ICPRIE method. Etch deeply to the depth of about 70μm vertically, leaving only the part where the surrounding pole is to be formed.

Next, after removing the photoresist pattern 303, as shown in FIG. 10E, the silicon substrate 301 is etched by the ICPRIE method to form the lower comb electrode structure 305, and at the same time, By etching through the unnecessary portion, only the silicon frame 306 structure and the alignment pole 307 are left in and around the comb electrode structure, thereby completing the lower structure of the micromirror driver.

As shown in FIG. 11, the completed upper frame and the lower frame have four corners of the glass substrate such that the upper comb electrode structures 140 and 240 are engaged with the lower comb electrode structure 300 on the glass substrate 300. A micro mirror driver is completed by coupling the upper frame to the lower structure by using the array pawls 307 provided at each one. When aligning for the coupling of the upper and lower structures, the align pole plays an important role. In other words, before the line becomes an array, it acts as a stopper to prevent the upper and lower comb electrode structures from colliding with each other. Pyrex glass substrates are bonded.

12 is a photograph taken after the manufacturing process of the micro mirror driver is completed as described above. FIG. 13 is an enlarged photograph of a circle part (comb electrode structure) of FIG. 12.

As described above, the micro-mirror driver of the optical disk drive using the electrostatic force according to the present invention is driven so that the micro-mirror reciprocates to an arbitrary angle about the central axis, the driving displacement of the mirror having a micro size is large or the size of the mirror Is considerably larger than the micro size, so that the drive displacement is relatively increased, so that the force is generated regardless of the distance between the two conductors and the size of the displacement section, and the force increases as the mirror size increases. By considering the size, weight, and simplicity at the end of the mirror, the actuator that drives the micro-mirror using the electrostatic force is manufactured integrally with the mirror, so that the size and weight can be reduced and simplified. Even if the size of the mirror increases from micro to millimeters, the structure of the comb teeth is used, so it is not restricted to generate the electrostatic force due to the size compared to other electrostatic driver methods. Will increase. When driven, they are driven symmetrically with respect to the axis of rotation of the mirror, thus obtaining twice the driving displacement with the same force compared to one drive. In addition, both detectors are present and detect, improving detection performance twice as much as having only one. And because of the structure of the mirror, the comb teeth structure under the mirror body is perpendicular to the axis of rotation, so that the mirror body under the electrostatic force can be obtained with the effect of preventing the bending of the mirror itself when rotating about the axis. That is, the mirror driver according to the present invention has a merit that the problem of flatness of the mirror plane can also be solved, and that the driver and the mirror plate are not separated from each other.

In addition, in the manufacturing method, the micro mirror is deposited on the upper surface of the bulk silicon (bulk silicon) and the bulk micromachining including the mirror body, the common electrode having a comb structure, the elastic member, and the frame includes ICPRIE which is a micro machine process. ) As a bulk silicon material to produce a unitary structure. The lower structure is made of Pyrex glass as a substrate, a comb-tooth structure is formed by using bulk silicon or resist, and a fixed electrode and a sensing electrode are made. In this case, the fixed electrode and the sensing electrode are formed of silicon to insulate each other or formed by coating a conductor film on the resist comb structure. The completed superstructure and substructure are joined by anodic bonding at the contact surface of the frame in the superstructure and the substrate of the substructure. The fabrication method described so far is one example, and the micro mirror driver as shown in FIG. 4A can also be fabricated by other fabrication methods.

Claims (34)

Board; A frame fixed to the upper surface of the substrate; An elastic member connected to the frame; A mirror body connected to the opposite side on an axis in a first direction parallel to the substrate and spaced apart from the upper surface of the substrate so as to reciprocate about the first direction axis; A mirror mounted on the mirror body; Under the mirror body, a plate structure having a certain thickness, width, and length is placed perpendicular to the first direction, and the length direction of the plate is perpendicular to the first direction and with the substrate. A common electrode placed in parallel in a second parallel direction and having three or more plate structures arranged in the first direction at regular intervals; It has the same structure as the common electrode and faces the common electrode spaced apart from the first direction by a predetermined distance, and overlaps a predetermined distance in a third direction perpendicular to the first direction and the second direction, and in the second direction. A fixed electrode which is spaced apart from each other by a predetermined distance to the opposite structure, and fixed to the substrate to provide an electrostatic force to the common electrode in the third direction when a voltage is applied; A sensing electrode having the same structure and arrangement as the fixed electrode, fixed to the substrate, and sensing a change in capacitance when the common electrode is moved; A power supply for applying a potential to the fixed electrode to generate a potential difference between the common electrode and the fixed electrode; A detector measuring a change in capacitance at the common electrode and the sensing electrode; And A controller for adjusting the power; Micro mirror drive of the optical disk drive using the electrostatic force, characterized in that provided. The method of claim 1, The fixed electrode and the sensing electrode are present on the substrate in a certain order and proportion on one side with respect to the axis in the first direction, the other side is the same as the ratio and the electrostatic force is present on the substrate regardless of the order Micro mirror drive of optical disk drive. The method of claim 2, The power supply is applied to a fixed bias voltage to the fixed electrode and the micro-mirror drive of the optical disk drive using an electrostatic force, characterized in that by applying an alternating voltage that alternately adds or subtracts a voltage of the same magnitude over time. The method of claim 2, The sensing electrode senses the increase or decrease of the capacitance when the common electrode rotates a predetermined amount by rotating the axis in the first direction as the rotation axis, and doubles the absolute sum of the sensed values as the change in the total capacitance. Micro mirror drive of the optical disk drive using the electrostatic force, characterized in that to obtain a sensing effect. The method of claim 1, The frame, the elastic member, the mirror body and the common electrode is a micro mirror drive of the optical disk drive using an electrostatic force, characterized in that formed integrally. The method of claim 1, The frame, the elastic member, the mirror body, the common electrode is a micro-mirror drive of the optical disk drive using an electrostatic force, characterized in that formed of an elastic and conductive material. The method of claim 1, The mirror is a micro mirror drive of the optical disk drive using an electrostatic force, characterized in that mounted directly on the mirror body. The method of claim 1, The fixed electrode or the sensing electrode to reduce the width of the portion in the non-overlapping area with the common electrode by the distance spaced from each other in the second direction so that the bending deformation of the mirror body due to the electrostatic force is within a certain constraint condition. Micro-mirror drive of optical disk drive using electrostatic force. The method of claim 1, And the frame, the elastic member, the mirror body, and the common electrode are integrally manufactured by using a reactive ion etching method using bulk silicon, respectively. The method of claim 1, The substrate is formed of Pyrex glass, and the structure for the fixed electrode and the sensing electrode is formed using bulk silicon, and the fixed electrode and the sensing electrode is formed of silicon Micro mirror drive of optical disc drive. The method of claim 1, The upper structure including the frame, the elastic member, the mirror body, and the common electrode and the lower structure including the substrate, the fixed electrode, and the sensing electrode are formed, respectively, and then bonded by anodic bonding. Micro mirror drive of optical disk drive using electrostatic force. (A) etching the bulk silicon substrate by ICPRIE method and XeF ₂ gas etching method to form an upper frame having an upper comb electrode structure; (B) etching the bulk silicon deposited on the glass substrate by ICPRIE to form a lower structure having a lower comb electrode structure corresponding to the upper comb electrode structure; And (C) bonding the upper frame fabricated in step (A) to the lower structure fabricated in step (B) such that the upper comb electrode structure is engaged with the lower comb electrode structure; Micro mirror drive manufacturing method of the optical disk drive using the electrostatic force, characterized in that it comprises a. The method of claim 12, Step (a), (A-1) sub-steps of forming a silicon nitride film and a silicon oxide film on the bulk silicon substrate; (A-2) forming a mask pattern for forming a comb electrode structure by patterning the silicon oxide layer and the silicon nitride layer; (A-3) a sub-step of forming a photoresist mask pattern for forming a comb structure and an array pole by applying and patterning photoresist on an edge on the bulk silicon substrate on which the oxide and nitride mask patterns are formed; (A-4) a sub-step of etching the bulk silicon substrate in the vertical direction by using the oxide film and the nitride film mask pattern and the photoresist pattern to form a comb structure, and then removing the photoresist pattern; (A-5) a sub-step of forming a silicon oxide film by oxidizing the entire surface of the silicon substrate having the comb structure while removing the silicon oxide mask pattern on the comb structure to expose the silicon nitride film mask pattern; (A-6) substep of removing the silicon nitride film mask pattern on the comb structure to expose silicon only on the upper part of the comb structure, etching only the comb structure to a suitable length using XeF ₂ gas, and then removing the silicon oxide film ; (A-7) a sub-step of forming the upper frame of the micromirror driver by etching the bulk silicon substrate from the rear surface without the comb structure by using the photolithography method and the ICPRIE method to etch through unnecessary parts; And (A-8) sub-steps of depositing Al on the rear of the upper frame to form conductive wires in the metal mirror and the elastic member; Micro mirror drive manufacturing method of the optical disk drive using the electrostatic force, characterized in that it comprises a. The method of claim 13, In the sub-step (A-1), the bulk silicon substrate has a thickness of 200μm or more, characterized in that the micro mirror drive manufacturing method of the optical disk drive using the electrostatic force. The method of claim 13, In the sub-step (A-1), the silicon nitride film and the silicon oxide film are formed by sequentially depositing SiN and SiO ₂ by chemical vapor deposition. The method of claim 13, In the sub-step (A-2), the silicon nitride film is patterned with phosphoric acid (H ₃ PO ₄ ) or patterned using a plasma etching process. The method of claim 13, In the sub-step (A-4), the bulk silicon substrate is etched so that only a thickness of 10 to 20μm is left. The method of claim 12, Step (a), (A-1) sub-steps of forming a SiO ₂ film on the front and back surfaces of the bulk silicon substrate having the (100) plane; (A-2) a substep of patterning the silicon oxide film by photolithography to form a mask pattern for forming the comb electrode structure; (A-3) sub-etching the silicon substrate in the vertical direction by using the ICPRIE method and removing only the photoresist pattern; (A-4) a sub-step of forming a side etch stop layer using a nitride film on the exposed silicon wall; (A-5) a sub-step of etching the bottom surface of the exposed silicon substrate further deeply by a predetermined depth in the vertical direction by using the ICPRIE method, and forming a silicon oxide mask pattern on the etched surface; (A-6) substep of removing the silicon nitride film mask pattern; (A-7) a sub-step of etching the comb tooth structure of the silicon substrate by TMAH to form the comb electrode structure to a predetermined length; (A-8) substeps of removing the silicon oxide films; (A-9) sub-step of forming an upper frame of the micro mirror driver by etching through the unnecessary portion of the silicon substrate from the back surface without the comb structure; And (A-10) sub-step of forming a conductive wire on the metal mirror and the elastic member by depositing a metal on the back of the upper frame; Micro mirror drive manufacturing method of the optical disk drive using the electrostatic force, characterized in that it comprises a. The method of claim 18, In the sub-step (A-1), the bulk silicon substrate has a thickness of 200μm, the method of manufacturing a micro mirror drive of the optical disk drive using an electrostatic force. The method of claim 18, The sub-step (A-1) is a method of manufacturing a micro-mirror drive of an optical disk drive using an electrostatic force, characterized in that the oxidation by wet oxidation method at 1100 ℃ for about 3 hours to form a SiO ₂ film of 1μm thickness. The method of claim 18, In the sub-step (A-3), the silicon substrate is etched to a depth of 140μm in the vertical direction, the method of manufacturing a micro mirror drive of the optical disk drive using an electrostatic force. The method of claim 18, In the sub-step (A-4), the side etch stop layer formed of the nitride layer is deposited on the entire surface of SiN having a thickness of 0.2 μm by CVD, and then all other than the nitride layer deposited on the wall surface by ion milling. A method of manufacturing a micromirror driver for an optical disk drive using an electrostatic force, characterized in that formed by removing the nitride film. The method of claim 18, In the sub- (A-5) step, the additional etching depth is 50μm characterized in that the micro mirror drive manufacturing method of the optical disk drive using the electrostatic force. The method of claim 18, In the sub-step (A-5), the silicon oxide film mask pattern is formed by a wet oxidation method. The method of claim 18, In step (A-6), the silicon nitride film mask pattern is removed using phosphoric acid (H ₃ PO ₄ ). The method of claim 18, In the sub-step (A-1), a bulk silicon substrate having the (100) plane or another crystal direction is used, and in the sub-step (A-7), only the comb-tooth structure is used by using XeF ₂ gas instead of the TMAH method. A method of manufacturing a micromirror driver for an optical disk drive using an electrostatic force, which is etched to have a predetermined length. The method of claim 18, The sub-step (A-9) is performed by using a photolithography method and an ICPRIE method. The method of claim 18, In the sub-step (A-10), Al is used as the metal, the method of manufacturing a micro mirror driver of an optical disc drive using an electrostatic force. The method of claim 12, The (b) step, (B-1) sub-oxidizing the silicon substrate as a whole to form an oxide film; (B-2) forming a silicon oxide mask pattern for forming a comb electrode structure by patterning a silicon oxide film on the entire surface of the silicon wafer, and then completely removing the back oxide film and etching the silicon substrate to a predetermined depth; (B-3) bonding the back surface of the etched silicon substrate to a glass substrate having a predetermined thickness using an anodic bonding process; (B-4) A photoresist pattern is formed to cover the silicon oxide mask pattern formed on the silicon substrate, and the silicon substrate is vertically downward while leaving only the portion where the comb electrode support and the surrounding alignment poles are to be formed. A substep of etching to the depth of; (B-5) After removing the photoresist pattern, the silicon substrate is etched by the ICPRIE method to form a lower comb electrode structure, and an unnecessary portion of the silicon substrate is etched and penetrated into and around the comb electrode structure. A substep of completing the substructure of the micromirror driver leaving only the silicon frame structure and the alignment poles; Micro mirror drive manufacturing method of the optical disk drive using the electrostatic force, characterized in that it comprises a. The method of claim 29, In the step (b-1), a high-concentration p-type silicon substrate having a thickness of 170 μm is used as the silicon substrate. The method of claim 29, In the step (b-2), the silicon substrate is etched to a depth of about 50μm using a photolithography method and an ICPRIE method. The method of claim 29, In the step (b-3), a 1 mm-thick Pyrex glass substrate is used as the glass substrate, and only the lower comb electrode support and the array pole are bonded to the rear surface of the etched silicon substrate. How to make a micro mirror drive of a drive. The method of claim 29, In the step (b-4), the etching process is a micro mirror driver manufacturing method of the optical disk drive using an electrostatic force, characterized in that the etching to the depth of 70μm by ICPRIE method. The method of claim 12, The (c) step, Coupling the upper frame to the lower structure by inserting align poles provided at each of four corners of the lower structure into the holes of the lower structure so that the upper comb electrode structure is engaged with the lower comb electrode structure on the glass substrate; And Bonding the upper frame to the lower structure using anodic bonding using anodic bonding; A method of manufacturing a micro mirror driver of an optical disk drive using an electrostatic force, characterized in that it comprises a.