KR20010049190A - a microactuator and manufacturing methods of the same - Google Patents

Abstract

PURPOSE: A microactuator and a method for manufacturing the same are provided to manufacture the microactuator in a simple manner and maintain linearity in even case of moving in two-dimension. CONSTITUTION: A method for manufacturing a microactuator includes the steps of anodic-bonding a silicon substrate and a glass substrate by heating, thinning the exposed surface of the silicon substrate by lapping and polishing, applying a photosensitive film to the exposed surface of the silicon substrate and radiating light to the photosensitive film, developing the photosensitive film, etching the silicon substrate by using RIE(Reactive ion etching) for forming positioning controllers, removing polymer and the photosensitive film for completing positioning controller pattern, and wet-etching the glass substrate by making the positioning controllers as a mask and using HF solution.

Description

A microactuator and manufacturing methods of the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microactuator and a method for manufacturing the same, and more particularly, to a micro actuator including a micro positioning actuator and a method for manufacturing the same.

It is necessary to precisely control the position of the head, the probe, the lens, and the like of the recording apparatus or the optical system, and for this purpose, an external servo system may be introduced. However, the introduction of an external system not only increases the volume of the system but also requires a high cost to achieve high precision. In order to solve this problem, research on a micro driver using semiconductor micro machining has recently been conducted. The micro-precision driver using micro machining can be divided into constant power, electromagnetic force, piezoelectric and thermal driving force driving methods according to the driving method, and the driving method using the constant power is representative of them.

The constant power driving method uses a change in electrostatic energy stored in a capacitor of a system, and a representative example thereof is a comb drive actuator. Studies on comb-shaped actuators include P.-F. Indermuehle, C. Linder, J. Brugger, V.P. Jaecklin and N.F. de Rooij's article "Design and fabrication of an overhanging xy-microactuator with integrated tip for scanning surface profiling", Sensors and Actuators A, No. 43, 1994, pp. 346-350) and P.-F. Indermuehle, and NF de Rooij's paper, "Integration of large probes with high aspect ratios on XY-fine stages for AFM projection" ("INTEGRATION OF A LARGE TIP WITH HIGH ASPECT RATIO ON AN XY-MICRO STAGE FOR AFM IMAGING", Transducers) '95 · Eurosensors IX, June 1995, pp. 652-654). The actuator combines two pairs of comb-shaped actuators vertically for AFM (atomic force microscopy) for two-dimensional position control and a microscopic probe mounted on the center of the actuator to detect interatomic attraction. will be. However, this driver has fast response characteristics, but the manufacturing process is complicated and the maximum travel distance is short.

To increase the maximum travel distance, Rob Legtenberg, AW Groeneveld and Elwenspoek wrote in the paper "Comb-drive actuators for large displacements", J. Micromech. Microeng. 6, 1996, pp. 320-329. By adopting a folded beam spring structure, a unidirectional comb-shaped actuator having a displacement of 30 μm at a voltage of 20 V is proposed.

However, this method also has a problem that the manufacturing process is complicated and the direction of movement is limited.

One problem of the present invention is to simplify the manufacturing process of the micro driver.

Another object of the present invention is to realize a fine driver having two degrees of freedom and a wide moving range.

1 is a conceptual diagram of a micro driver according to an embodiment of the present invention,

FIG. 2 is a perspective view showing a position controller in the micro driver shown in FIG. 1;

3 is a conceptual diagram of a micro driver according to another embodiment of the present invention;

4 is a diagram conceptually illustrating a method of applying a signal voltage for position controller control according to an embodiment of the present invention;

5A through 5D are cross-sectional views illustrating, in process sequence, a method of manufacturing a position controller according to one embodiment of the present invention;

6a to 6d are views illustrating a method of manufacturing a position controller according to another embodiment of the present invention in a process sequence;

7A and 7B are perspective and cross-sectional views of a theoretical micro Fresnel lens, respectively;

8A and 8B are graphs showing a cross-sectional view and an intensity distribution in a focal plane of a binary fine Fresnel lens according to an embodiment of the present invention;

9A and 9B are cross-sectional views illustrating a method of manufacturing a binary fine Fresnel lens according to an embodiment of the present invention;

10A to 10C are cross-sectional views illustrating a method of manufacturing a fine spherical lens using a photosensitive film according to a process sequence;

11A to 11F are cross-sectional views illustrating a method of manufacturing a micro driver according to an experimental example of the present invention in a process sequence;

12 is a graph showing the degree of substrate thinning according to the heating temperature at the time of anode bonding,

13a to 13d are photographs showing the micro driver manufactured according to the experimental example of the present invention,

14A and 14B are diagrams illustrating a voltage application method and a change in displacement according to the one-way driving characteristic of the micro driver manufactured according to the experimental example of the present invention, respectively.

15A and 15B are diagrams illustrating a voltage application method and a displacement change according to the method for measuring the driving characteristics according to the application of the half-phase small signal of the micro driver manufactured according to the experimental example of the present invention, respectively.

16 is a graph showing the amount of mechanical interference of the micro actuator according to an embodiment of the present invention,

17 is a graph showing the displacement of the y-direction electrodes with respect to the x-direction applied voltage in a state in which various sizes of the y-direction voltage are applied to the micro driver manufactured according to the experimental example of the present invention.

18A to 18F are cross-sectional views illustrating a method of manufacturing a micro driver according to another embodiment of the present invention in a process sequence.

The micro driver according to the present invention for achieving the above object includes a fixed electrode fixed on the substrate and a moving electrode that can move on the substrate through electrical interaction with the fixed electrode. The mounting table on which the other element can be mounted is connected to the moving electrode through the elastic member, and moves in two dimensions in accordance with the movement of the moving electrode.

Here, the movable electrode and the fixed electrode may include first and second comb-shaped electrodes each having a plurality of electrode teeth, wherein the electrode teeth of the first and second comb-shaped electrodes are alternately disposed.

Here, each elastic member may include a first connecting member, a first pad, and a bending member. In this case, the first connection member is linear, both ends are connected to the moving electrode and the mounting table, the pad is fixed to the substrate, and the bending member is connected to the first pad and the first connection member when the bending member has a curved structure. The first connecting member is preferably arranged in a cross shape, wherein the mounting table is preferably located at the center of the cross shape. The flexure member may include a plurality of first portions extending from the middle of the first connecting member, a second portion connected to the first portion, and a third portion bent from both ends of the second portion and connected to the first pad. Can be.

The fixed electrode may further include a second pad fixed to the substrate, a second connecting member connecting the second comb-shaped electrode and the second pad, wherein the first and second comb-shaped electrodes, first and second The connecting member, the bent member and the mounting table should be spaced apart from the substrate. A first pad may be adjacent to the first and second connecting members, and the curved member may surround the first and second comb-shaped electrodes.

The substrate may be made of glass or silicon, wherein the fixed electrode and the moving electrode, the mounting table, and the elastic member may be made of metal. When the substrate is made of glass, the fixed electrode, the moving electrode, the mounting table, and the elastic member are preferably made of silicon, and a microlens may be fixed to the lower part of the mounting table. The fine lens may be a binary Fresnel lens made of the same layer as the substrate, or may be a spherical lens formed of a photosensitive film under the substrate.

Meanwhile, in the method of manufacturing a micro driver according to an aspect of the present invention, after bonding a first substrate and a second substrate and patterning the first substrate to form a driver pattern, the second substrate isotropically etched using the driver pattern as a mask. do.

In this case, the method may further include thinning the first substrate, and the bonding may be an anode bonding.

In the method of manufacturing a micro driver according to another aspect of the present invention, a plating mold is formed on the substrate in a reverse phase of the driver pattern, a plating layer is formed on the substrate using the plating mold, and then the substrate is removed using the plating layer as a mask. Isotropic etching.

In the above, the driver pattern preferably includes a plurality of pad portions and other portions narrower than the pads, so that after the isotropic etching step, the pad portions are fixed to the second substrate and the other portions are separated from the second substrate. Will be placed.

In the method for manufacturing a micro driver according to another aspect of the present invention, first, the first surface of the first substrate is patterned to form a driver pattern, and the bonding surface of the second substrate is anodized thereon. Thereafter, the second surface of the first substrate is polished until the bonding surface of the second substrate is visible, and then an etch stop layer is formed on the exposed surfaces of the first and second substrates. Finally, the second substrate is etched using the etch stop layer as a mask.

Here, the first and second substrates are preferably made of silicon and glass, respectively, and in this case, the microlenses may be formed by patterning the exposed surface of the second substrate or by patterning the photoresist on the second substrate.

Then, with reference to the accompanying drawings for the micro driver and the manufacturing method according to an embodiment of the present invention will be described in detail to be easily carried out by those of ordinary skill in the art.

First, a micro driver according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

1 is a schematic view of a fine driver according to an embodiment of the present invention, Figure 2 is a perspective view showing in detail the position controller of the driver shown in Figure 1, Figure 3 is a fine driver according to another embodiment of the present invention Perspective view.

As shown in Figs. 1 and 3, the micro driver according to the present embodiment is mounted in the center of the position controller 2 and the position controller 2 which are planarly formed in one layer on the support layer 1; Water (3). The support layer 1 may be made of glass or silicon and the position controller 2 may be made of silicon or metal. The payload 3 may be a magnetic or magneto-optical head of a high density magnetic or magneto-optical recording device, a probe of a probe type recording device, a micro Fresnel lens, a micro lens such as a micro spherical lens, and the like. It may be formed of the same layer as (1) or the position controller 2 or may be formed of another layer.

As can be seen in FIGS. 2 and 3, the position controller 2 according to the present embodiment is a two-axis planar driver having two degrees of freedom, which statically or dynamically moves the payload 3 to any position on the plane. In order to realize two degrees of freedom, two linear comb-shaped actuators have a cross-shaped structure in which they are vertically combined. The comb-shaped actuator has a fixed comb-shaped fixed electrode and a movable comb-shaped moving electrode in which electrodes are alternately arranged. The payload 3 is connected to the moving electrode and moves according to the movement of the moving electrode, and the final position of the payload 3 is determined by the vector sum of the two driving directions.

The position controller or the cruciform comb actuator according to the present embodiment consists of two parts, that is, the fixing parts 51, 52, 53 and the moving parts 60, 61, 62, 63, 64, 65, 66, 70, and the center part. It has a symmetrical structure with respect to. The moving parts 60, 61, 62, 63, 64, 65, 66, 70 are arranged in a cross shape, and the fixing parts 51, 52, 53 are moving parts 60, 61, 62, 63, 64, 65. , 66, 70) at each end.

The moving part includes a connection table 60, moving electrode parts 61 and 62, and elastic members 63, 64, 65 and 66, including a square mounting table 70 positioned at the center of the cross.

Each connecting member 60 serves to mechanically connect the mounting table 70 and the moving electrode parts 61 and 62, and one end of the mounting table 70 at the center of one side thereof, the moving electrode part 61, The other end is connected to the center of 62) and forms a cross shape as a whole perpendicular to each side of the mounting table 70.

Each of the moving electrode parts 61 and 62 has a symmetrical structure with respect to the connecting member 62 and includes a comb-shaped electrode 61 made up of a plurality of electrodes extending outward with respect to the mounting table 70. Although the moving electrode parts 61 and 62 may include only one comb-shaped electrode 61 as in the case of FIG. 2, the plurality of comb-shaped electrodes 611, 612, 613, and 614 arranged in multiple stages as in the case of FIG. 3. ) May be included. The multi-stage arrangement of the comb-shaped electrodes 611, 612, 613, and 614 is for increasing the number of electrodes to increase the driving force. In this case, a connection member connecting the electrodes 611, 612, 613, and 614 in series is used. 62 is placed on the extension line of the connecting member 60.

The elastic members 63, 64, 65, 66 are fixed to the support layer 1, and are located near each of the connecting members 60, 62 or their extension lines, and four pads 63 and pads to which a voltage from the outside is applied. A flex member 64, 65, 66 connected to the 63 and the connecting member 60 or 62; The bending members 64, 65, 66 extend vertically to both sides from the connecting member 60 or 62 and have a structure that is bent twice vertically again and extends vertically to both sides from the connecting member 60 or 62. A first portion 64, a pair of second portions 65 which are respectively coupled perpendicularly to the ends of the first portions 64 located on both sides with respect to the connecting members 60, 62, and the second portion 65; A third portion 66 extending vertically from both ends of the pad toward the pad 63 and connected to the pad 63.

The fixed part is composed of four fixed electrode parts respectively disposed near the comb-shaped electrode 61 of the moving part, and each fixed electrode part is composed of a comb-shaped electrode 51 made up of a plurality of electrodes extending inward with respect to the mounting table 70, A connection member fixed to the support layer 1 and positioned on an extension line of the pad 53 to which a voltage is applied from the outside and the connection members 60 and 62 and connecting the comb-shaped electrode 51 to the pad 53 ( 52). The comb-shaped electrode 51 has a symmetrical structure with respect to the connecting member 52.

The electrode teeth of the comb-shaped electrode 51 are alternately arranged with the electrodes of the corresponding comb-shaped electrode 61, so that the electrostatic force generated by the potential difference between the two electrodes 51, 52 is comb-shaped electrode 61. Move it. The number of comb-shaped electrodes 51 included in the fixed electrode parts 51, 52, and 53 corresponds to the number of comb-shaped electrodes 61 included in the moving electrode parts 60 and 61. That is, in the case of FIG. 2, only one comb-shaped electrode 51 is included. In FIG. 3, a plurality of comb-shaped electrodes 511, 512, 513, and 514 arranged in multiple stages are included.

On the other hand, the comb-shaped electrodes 51 and 61 of the fixed part and the moving part are surrounded by the bent members 64, 65 and 66 and the connecting members 60 and 62. In particular, in the case of the multi-stage structure shown in FIG. 3, the comb-shaped electrodes 511 and 512 of the fixing part are referred to as the first stage, the second stage, the third stage, and the fourth stage in order from the closest to the mounting table 70. The first to third electrodes 511, 512 and 513 except for the fourth electrode 514 adjacent to the fixing pad 53 among the 513 and 514 are the bending members 64, 65 and 66. It cannot be connected to the pad 53 because it is blocked. In addition, since the connection member 62 penetrates through the center, the fixing electrode electrodes 511, 512, and 513 of the first to third ends are separated into two parts located at both sides of the connection member 62. Therefore, since the respective portions of the fixing electrodes 511, 512, and 513 of the first to third stages are isolated, pads 515 and 516 for applying a voltage to each of the portions and fixing the supporting layers 1 to the support layer 1 are provided. It is formed in each area surrounded by the bending members 64, 65, 66 and the connecting member 62. In FIG. 3, since the first portion 64 of the bending members 64, 65, 66 is not formed between the second end and the third end, one pad 516 is provided at each of the second end and the third end. Only two stages are installed to share. However, the first portion 64 of the bent members 64, 65, 66 may be provided anywhere.

When the voltage is applied to the pads 53, 63, 515, and 516 in the position controller, the comb-shaped electrode 61 of the moving part moves by the electrostatic force generated between the comb-shaped electrodes 51 and 61, and further, the mounting table 70 is provided. The whole moving part including) moves. This displacement change causes the restoring force of the elastic members 63, 64, 65, and 66, and the moving part stops moving at the point where the restoring force and the electrostatic force between the electrodes are balanced. When the moving part pad 63 is grounded to bring the potential to zero, the displacement of the mounting table 70 can be controlled by the voltage applied to the fixing part pad 53.

Applied in a linear comb-like driver voltage V and the relationship between _a mounting table 70, the displacement X _d are as follows.

Where g, h and N are the spacing between the electrode teeth of the comb-shaped electrodes 51 and 61, the height and the number of the electrode teeth, respectively, and k is the spring stiffness of the elastic members 63, 64, 65 and 66. )to be. As can be seen from this equation, the displacement X _d of the mounting table 70 is proportional to the square of the applied voltage, and the square of the applied voltage is also proportional to the electrostatic force.

As shown in Equation 1, in order to increase the maximum displacement of the mounting table 70, it is necessary to increase the ratio (h / g) of the height of the electrode bars to the spacing between electrodes and increase the number of electrode bars. Although it is best to reduce the spacing between the electrodes (g), but there is a limitation in the process, it is desirable to increase the number of electrodes (N) by increasing the height (h) of the electrodes and placing the electrodes in multiple stages.

In order to increase the maximum displacement, it is also necessary to select an elastic member structure or a spring structure having a small modulus of elasticity. In this spring structure, the pad 63 is fixed to both ends of the first portion 64 with only the first portion 64. A simple beam structure, a crab-leg structure in which the pads 63 are fixed to the ends of each second portion 65 with only the first and second portions 64, 65, and folded as in this embodiment. For example, a folded-beam structure. In the case of the simple beam structure, as the displacement increases, the axial force (axial force: the force in the longitudinal direction of the connecting member 62) increases, so that linearity can be maintained only for a very small displacement. In the case of the crab leg structure, the elastic modulus is smaller than that of the simple beam structure, but it is sensitive to the force in the direction perpendicular to the connecting member 62. However, in the case of the folded beam structure as in the present embodiment, it has the same elastic modulus as the simple beam structure, but since the bending members 64, 65 and 66 reduce the axial force, linearity can be maintained even at large displacements. . In addition, since the stiffness ratio is the same value as that of the simple beam structure, it is not significantly affected by the vertical disturbance.

In addition, in order to reduce interference in the vertical direction, it is also necessary to reduce the elastic modulus of the connecting member 62.

As mentioned above, the position controller 2 according to the present embodiment has independent four directional electrodes that can be controlled individually, but is opposed to a pair of livestock electrodes facing each other in order to obtain linear driving characteristics with respect to the voltage control signal. Control is by applying an out-of-phase voltage. 4 is a diagram conceptually illustrating a method of applying a signal voltage for controlling the position controller 2. As shown in FIG. 4, a voltage of (V _bias ± V _cx ) is applied to the fixing part electrodes 531 and 532 in the -x and + x directions, respectively, and the fixing part electrodes 533, which are in the -y and + y directions, respectively. A voltage of (V _bias ± V _cy ) is applied to the 534, and the moving part electrode 61 is grounded. At this time, the force F _x received by the mounting table 70 in the x direction is as follows.

As can be seen in Equation 2, the force applied to the mounting table 70 is linearly proportional to the control voltage V _cx , and thus a linear displacement can be obtained with respect to V _cx . The same is true for the y direction.

The method of manufacturing such a microcontroller will now be described in detail.

As mentioned above, the support layer 1 may be made of glass or silicon, and the position controller 2 may be made of silicon or metal.

Then, first, the supporting layer 1 is made of glass, and the position controller 2 is made of silicon in detail with reference to Figs. 5A to 5D.

First, as shown in FIG. 5A, the glass substrate 30, which serves as the support layer 1, is bonded to the surface of the silicon substrate 20 while anodic bonding. Anodic bonding, also known as field assisted bonding or electrostatic bonding, requires heat and a strong electric field. When positive and negative voltages are applied to the silicon substrate 20 and the glass substrate 30, respectively, and the heat is applied, the applied heat increases the mobility of positive ions in the glass substrate 30 and moves. The increased positive ions are reduced by being attracted to the negative electrode in contact with the glass substrate 30 by a strong electric field between the glass substrate 30 and the silicon substrate 20. As a result, depletion of cations occurs near the interface between the silicon substrate 20 and the glass substrate 30, and eventually all voltages applied are applied to the interface between the substrates. A strong electric field is formed. This strong electric field allows a covalent bond between the silicon substrate 20 and the glass substrate 30 and the two substrates 20 and 30 are permanently bonded.

As shown in FIG. 5B, the exposed surface of the silicon substrate 20 is wrapped and polished by a mechanical chemical method to thin the silicon substrate 20 to a thickness of about 30 μm.

Subsequently, a photoresist film (not shown) is applied to the exposed surface of the silicon substrate 20, and then a photosensitive film is irradiated with ultraviolet light through a single chrome mask (not shown) having a position controller pattern engraved thereon. do. Thereafter, the silicon substrate 20 is etched using deep reactive ion etching (RIE) using chlorine at room temperature to form the position controllers 100 and 200. Subsequently, an oxygen (O ₂ ) plasma process is performed to remove the polymer and the photosensitive film formed on the walls of the position controllers 100 and 200, thereby completing the position controllers 100 and 200 pattern as shown in FIG. 5C. The oxygen plasma process serves to prevent contamination by residual polymers in subsequent processes. In this case, in FIG. 5C, there are a large portion 200 and a small portion 100, and the portion 200 corresponds to the pads 53, 63,... It is equivalent to other parts.

Finally, as shown in FIG. 5D, the microcontroller according to the present embodiment is completed by wet etching the glass substrate 30 using the position controllers 100 and 200 as a mask and using 49 wt% of HF solution. At this time, by adjusting the etching time to keep the large portion 200 bonded to the glass substrate 30 and the remaining portion 100 is separated from the glass substrate 30. By doing in this way, the pads 53 and 63 will be in the state fixed to the glass substrate 30, and the remainder will be in the state which can separate and move from the glass substrate 30. FIG. In this process, isotropic dry etching may be used instead of wet etching.

Next, the manufacturing method of the micro driver in the case where the support layer 1 is made of glass or silicon and the position controller 2 is made of metal will be described in detail with reference to FIGS. 6A to 6D. In this embodiment, the micro driver is manufactured by a LIGA process.

First, as shown in FIG. 6A, the microplating mold 85 is fabricated on the substrate 30 made of glass or silicon in the reverse phase of the position controller pattern. Subsequently, as illustrated in FIG. 6B, the position controllers 100 and 200 are formed on the substrate 30 by electrolytic or electroless plating. As in the previous embodiment, reference numeral 200 denotes pads 53 and 63 and reference numeral 100 denotes other structures. Thereafter, as shown in FIG. 6C, the plating mold 85 is removed, and the substrate 30 is etched using the manufactured position controllers 100 and 200 as masks, and the remaining portions except the pad 200 are removed as shown in FIG. 6D. Away from the substrate 30. When the substrate 30 is glass, wet etching is used, and in the case of silicon, wet etching or isotropic dry etching is used.

Here, if the thickness of the glass substrate 30 is about several hundred μm, the process may be controlled so that the structure floats several ten μm or more from the bottom after etching, thereby preventing the structure from sticking to the floor.

As described above, the micro driver according to the present embodiment can be manufactured using only one mask, thereby simplifying the process.

On the other hand, the mount 3 mounted on the mounting table 70 may be a microlens, and the microlens may be further divided into a diffractive lens and a refraction lens, among which a micro Fresnel lens is a typical diffraction lens. The lens is characterized by having a very small volume compared to the refractive lens.

As shown in FIGS. 7A and 7B (a view taken along the line Ⅶb-Ⅶb in FIG. 7A), the Fresnel lens is concentric in shape and the cross section of each concentric circle is a blade shape. Fresnel zone. The cross-sectional shape of the Fresnel zone is designed so that the light passing through the zone always experiences a phase retardation of 2π for the thickest part of the interval, and the light passing through the Fresnel zone interferes with constructive interference. The focal point is where the floor of light is located. Solving the phase equation that satisfies this relationship, that is, the relationship between the phase of light before and after passing through the lens, the radius of the _mth Fresnel zone (r _m ) and the thickness along the radius (d _m ) are given by Is given.

Where λ and f are the wavelength and focal length of the light, and n _FL and n _i are the refractive indices of the lens and air, respectively. As such, the shape of the fine Fresnel lens is determined by the optical standard, the focal length, the wavelength, the refractive constant, and the like.

As shown in FIGS. 7A and 7B, the shape of the Fresnel lens obtained in Equations 3 and 4 has a different curvature for each zone, and even within one zone, the curvature continuously varies with radius, so that mechanical processing is not easy. Therefore, in the present embodiment, a binary Fresnel lens having a form in which a continuous curved surface is quantized with a step at a predetermined interval is used. The diffraction efficiency of a binary Fresnel lens is smaller than that of a Fresnel lens with a continuous curved surface due to the scattering of light generated at the interface of the quantized step.

8A illustrates a cross-sectional view of a binary fine Fresnel lens according to an embodiment of the present invention compared with a theoretical continuous plane lens, in which the horizontal axis represents distance from the lens center and the vertical axis represents thickness. As shown in FIG. 8A, the fine Fresnel lens according to the present embodiment is a binary optical system quantized in eight stages, and each step has the same height.

FIG. 8B is a simulation graph showing the theoretical intensity distribution in the focal plane of the fine Fresnel lens shown in FIG. 8A compared to a continuous plane lens and a lens quantized in four stages, with the horizontal axis representing the distance from the lens center. The vertical axis represents normalized intensity. The lens was made of glass having a refractive index of 1.5185, a focal length of 3 mm, and light having a wavelength of 635 nm. As can be seen here, the eight-stage lens showed almost the same intensity distribution as that of the continuous plane lens, and in particular, the intensity of 94.97% at the center of the lens. On the other hand, the four-stage lens showed 81% intensity at the center of the lens, showing a little distance from the continuous lens. On the other hand, although not shown in the drawings, the two-stage lens showed an efficiency of 41%.

Fine Fresnel lenses can be made of silicon or glass, with silicon used for infrared and glass used for visible light.

Next, a method of manufacturing the four-stage quantized binary fine Fresnel lens will be described in detail with reference to FIGS. 9A and 9B.

Four-phase microlenses are made using a two-shot process and RIE. First, as shown in FIG. 9A, the glass substrate 30 is patterned one step by the RIE method using the first mask 41. Next, as shown in FIG. 9B, the two-phase patterning of the glass substrate 30 by the RIE method using the second mask 42 completes the four-phase fine lens 3. However, the etching thickness in the two-step patterning should be 1/2 of the etching thickness in the one-step patterning.

In the case of an 8-phase fine Fresnel lens, after the previous two-step patterning, the photographic process and the RIE process are performed once more, and the etching thickness should be 1/2 of the etching thickness in the two-step patterning. .

As the payload 3, a fine spherical lens may be provided instead of a fine Fresnel lens, and the fine spherical lens is manufactured by using a photosensitive film. This will be described with reference to FIGS. 10A to 10C.

First, as shown in FIG. 10A, a photosensitive film 80 is coated on the glass substrate 30. As the photosensitive film 80, a positive photosensitive agent, for example, PMER PLA900F manufactured by TOK, can be used. Subsequently, the photosensitive film 80 is irradiated with ultraviolet rays through a chrome mask engraved with a disc pattern, and then developed as shown in FIG. 10B. Finally, when the photoresist film 80 is reflowed by a heat treatment process, as shown in FIG. 10C, a spherical lens 32 is formed. Since the photoresist film 80 is present on the glass substrate 30, the surface tension is large. It becomes rounder. The radius of curvature of this lens 32 depends on the coating thickness of the photosensitive film 80. As a result of the experiment, the focal length of the spherical lens coated with a thickness of 20 μm was measured using a microscope and found to be about 31 μm.

However, a general photoresist tends to change color to dark brown after heat treatment, so a non-photosensitive resin may be used to compensate for this, and in this case, it may be patterned using RIE instead of a photo process.

The position controller 2 and the fine lens 3 as described above have been made in a series of processes and will be described in detail.

First, an experimental example will be described with reference to FIGS. 11A to 11B.

First, as shown in FIG. 7A, the glass substrate 30, which serves as the support layer 1 on the surface of the silicon substrate 20, and the material of the fine Fresnel lens 3, was anodized while applying heat.

This step plays an important role in the overall process, in particular, when the substrate 20, 30 during the anodic bonding, the thermal expansion coefficient of the two substrates (20, 30) due to the stress (stress) generated due to different stresses And 30), the greater the warpage, the more likely the substrate itself is damaged during the process or the microstructures created in subsequent processes. In addition, when polishing the silicon substrate 20, there is a high possibility of not polishing the same thickness. Since the degree of warpage of the substrates 20 and 30 has a value proportional to the difference in curvature before and after bonding, the degree of warpage can be known by measuring the change in curvature, and the two substrates 20 and 30 at a voltage of 1,000 V in FIG. 12. When the anodic bonding is performed, the curvature change (Δ (1 / R), R is the radius of curvature) of the substrates 20 and 30 before and after the bonding, depending on the heating temperature of the substrates 20 and 30.

It can be seen from FIG. 12 that the warpage of the substrates 20, 30 increases with the heating temperature of the substrates 20, 30. As can be seen from the figure, when the heating temperature is less than 380 ℃, the degree of warpage of the substrates 20 and 30 is small, but the bonding state is poor and the bonding time takes longer, on the contrary, if it is larger than 500 ℃, 30) was found to be excessively curved. Therefore, the heating temperature at the time of anodic bonding is suitable for 380 ℃ to 500 ℃, especially 400 ℃ to 450 ℃, even 400 ℃ was the best. As for the voltage applied to the board | substrates 20 and 30, about 700V-1,200V are suitable.

Next, as shown in FIG. 11B, the exposed surface of the silicon substrate 20 was thinned to about 30 μm in thickness using a method such as chemical mechanical lapping and polishing.

Then, as illustrated in FIG. 11C, the exposed surface of the glass substrate 30 was etched to form an eight-stage fine Fresnel lens 3. The flow rate of CHF ₃ gas, CF ₄ gas, and Ar gas is 25 sccm, 5 sccm, 75 sccm, respectively, and P-5000 is applied with 130 mTorr pressure, 600 W radio frequency (RF) power, and 250 Gauss magnetic field. As a result of fabricating an 8-stage fine Fresnel lens using an etcher (Applied Materials), the etching rate of the glass substrate 30 was about 3,600 µs / min, and the roughness after etching was less than 100 µs.

Subsequently, a photosensitive film (not shown) is coated on the silicon substrate 20 and a chrome mask (not shown) having the position controller 2 pattern engraved thereon so that the center of the mounting table 70 is located at the center of the fine Fresnel lens. Aligned. After irradiating ultraviolet rays to the photoresist through a mask, the photoresist film was developed, and then the exposed silicon substrate 20 was patterned by using deep reactive ion etching (RIE) to form the position controllers 100 and 200. As a photoresist, the silicon substrate 20 was etched using a AZ1512 (manufactured by Hoechst) of 1.2 μm thickness, which was heat treated at a high temperature, and a Bosch process using Deep Etcher of Plasma Therm. Etch selectivity was about 80: 1, lateral etch width was about 2,000 Å and etch anisotropy was more than 0.98. A trench having a width of 3 μm was measured to have an etch rate of about 70% based on the fully opened portion, and was sufficiently overetched in consideration of this. As a result, the etching of the side surface did not proceed further, but in the portion where the glass substrate 30 was exposed, the bottom part of the structure was etched and separated from the glass substrate 30. However, even in this case, since the part of the pad 200 supporting the structure is not largely damaged, the structure is not destroyed.

Subsequently, an oxygen (O ₂ ) plasma process was performed to remove the polymer and the photosensitive film formed on the walls of the position controllers 100 and 200, thereby completing the position controllers 100 and 200 pattern as illustrated in FIG. 11D. Oxygen plasma process conditions were 200 sccm oxygen flow, 200 Pa pressure, 300 W coil power, and 20 minutes process time.

Next, when the glass substrate 30 isotropically etched with the HF solution, an etch stop layer 40 which prevents other portions from being etched is deposited to a thickness of about 3,300 mm 3. As the etch stop layer 40, amorphous silicon, which is hardly etched in the HF solution, was used, and a low pressure chemical vapor deposition (LPCVD) was used as the deposition method. Amorphous silicon is also excellent in adhesion to the glass substrate 30, and because it is not directional during film formation, it is deposited evenly regardless of the irregularities of the surface. Amorphous silicon is a good material for the etch stop layer 40 because the deposition temperature is about 550 ° C. and slightly higher, but does not deform the substrates 20 and 30 during or after deposition.

Then, as shown in FIG. 11E, the amorphous silicon layer 40 is selectively removed by reactive ion etching, wherein the surface of the glass substrate 30 and the microlens positioned on the surface of the position controller 2 and the side controller 2 are selectively removed. (3) The surface should be covered with an amorphous silicon layer 40. The gases used in this process were SF ₆ 30 sccm and O ₂ 5 sccm, pressure was 100 mTorr, RF power was 200 W and the etching time was 1.5 minutes.

Finally, as shown in FIG. 11F, the glass substrate 30 having the amorphous silicon layer 40 formed thereon is immersed in 49 wt% HF solution at room temperature to etch the glass substrate 30 and remove the amorphous silicon layer 40. To complete. At this time, the etching rate of the glass substrate 30 was 7 μm / min.

Here, omitting the forming of the etch stop layer 40 (FIG. 11e) and the eliminating the etch stop layer may yield only a position controller without a fine Fresnel lens. FIGS. 13a to 13d are photographs of the structure thus obtained. 13B is a whole structure, FIG. 13B is a pair of movable and fixed electrode portions, FIG. 13C is a mounting table 70, and FIG. 13D is a cross-sectional photograph of the pad portion 200. Here, the etching depth of the glass substrate 30 is 100 μm, the size of the pad portion 200 is 300 μm × 300 μm, and the width of the other portion 100 is within 100 μm. Referring to FIG. 13D, the lower portion of the pad portion 200 is shown. Shows that the glass substrate 30 is etched by a thickness of about 100 μm in the down and lateral directions (X _h , X _v ). 13A and 13B, the comb-shaped electrodes 51 and 61 are composed of four stages (assuming the first stage, the second stage, the third stage, and the fourth stage from the center) and the first portion 64 of the elastic member. ) Are two, passing between the first stage and the second stage and between the third stage and the fourth stage, respectively. Here, a pair of fixing part comb-shaped electrodes are formed at each of the first to third ends, and each of the fixing part comb-shaped electrodes 51 of the first end is formed of the first to third portions 64, 65, and 66. And pads enclosed by the connecting member 62 and formed in the enclosed area. The electrodes positioned on the same side with respect to the connecting member 62 among the fixing electrode electrodes 51 of the second and third stages are surrounded by the first and second parts 64 and 65 and the connecting member 62 and are in the enclosed area. It is connected to the formed pad. The spacing between the electrode teeth of the comb-shaped electrodes 51 and 61 is 3 µm, and the number of electrode electrode pairs is 330. In addition, the length of the third part 66 is 1,500 μm, the width of the first and third parts is 5 μm, the width of the connecting member 62 is 5 μm and the length is 1,900 μm. The modulus of elasticity of the connecting member 62 itself is about one half of the elastic members 63, 64, 65, 66 and as a result a pair of folded beam springs are connected in parallel with respect to one driving direction. It becomes.

In order to examine the one-way driving characteristic of the driver manufactured as described above, as shown in FIG. 14A, the voltage applied to the corresponding fixed electrode 51 is changed while the one movable electrode 61 is grounded. 70) was measured (arrow moving direction). FIG. 14B is a graph showing the displacement of the mounting table 70 as a function of the square of the applied voltage and compared with the theoretical value.

As can be seen in FIG. 14B, the maximum travel distance of this position controller 2 is 29 μm with respect to an applied voltage of 23 V, which is almost consistent with the theory in the interval of 0-20 V. However, when the applied voltage exceeds 23 V, the two electrodes 51 and 61 stick together.

On the other hand, to check whether the linearity as shown in Equation 2 can be obtained when applying the small signal (V _cx ) of the half-phase with the bias voltage (V _bias ) to the two comb electrodes on the same axis (arrow direction) As shown in FIG. 15A, voltages of (V _bias + V _cx ) and (V _bias -V _cx ) are respectively applied to the two fixed electrodes 51 facing in the horizontal direction. The result of measuring the displacement of the mounting table 70 according to the change in the magnitude of the small signal V _cx with respect to several bias voltages (V _bias ) is shown in FIG. 15B. Linearity is shown with respect to the bias voltage.

Next, the mechanical interference between the two driving directions was measured. The measuring method first moves the mounting table 70 in the x direction, and then moves the mounting table 70 in the direction y perpendicular to the mounting table 70. At this time, the amount of change in the x-direction displacement due to the y-direction is defined as the amount of mechanical interference. FIG. 16 is a graph showing the mechanical interference amount of the actuator thus measured, and the mechanical interference amount was observed within 1 μm over the entire driving range, and particularly, the range within 24 μm from the center was free from mechanical interference.

FIG. 17 is a graph showing a contraction operation of electrode teeth (or combs) of the y-direction electrode 61 when driving in the x direction, in which the horizontal axis represents the square of the applied voltage in the x direction and the vertical axis represents the comb teeth of the y-direction electrode 61. Indicates the contracted displacement. As can be seen in FIG. 17, the comb teeth of the y-direction electrode 61 are further reduced as the x-direction displacement of the mounting table 70 increases, which is due to an increase in the elastic modulus of the elastic members 63, 64, 65, and 66. Seems to be. In other words, driving in the x direction produces an axial force in the y direction, which reduces the displacement of the comb teeth of the y-direction electrode 61. The amount of shrinkage is then determined by the equilibrium condition between the axial force and the restoring force of the elastic members 63, 64, 65, 66. In FIG. 17, the amount of reduction of the comb teeth of the y-direction electrode 61 increases as the voltage applied to the x-direction electrode 61 increases and the voltage applied to the y-direction electrode 61 increases. It can also be seen that the reduction of the comb displacement is symmetrical with respect to the + y and -y directions. As a result, the reduction of the comb displacement only compensates for the generated axial force and does not affect the displacement of the mounting table 70 because the elastic members 62, 63, 64, and 65 cancel it out through deformation.

In the experimental examples described so far, anodic bonding, thinning of the silicon substrate 20, formation of the fine Fresnel lens 3, formation of the position controllers 100 and 200, amorphous silicon patterning, and the glass substrate 30 Although the fine driver is manufactured in the order of etching, it may be manufactured by a different method. This will be described in detail with reference to FIGS. 18A to 18F.

First, as shown in FIG. 18A, the junction surface of the silicon substrate 20 is patterned using deep reactive ion etching (RIE) to form the position controller 2 pattern, and as shown in FIG. 18B. The bonding surface of the glass substrate 30 is anodically bonded to the substrate 20 bonding surface. Then, as shown in FIG. 18C, the glass substrate 30 is etched to form the fine lens 3, and as shown in FIG. 18D, the silicon substrate 20 is thinned to a thickness of about 30 μm using a method such as polishing. In the first step of the present embodiment, the glass substrate 30 is exposed through the etched portion, and at the same time, the shape of the position controller 2 is completed. Thereafter, the amorphous silicon layer 40 having a thickness of about 3,300 kPa is deposited on the surfaces of the position controller 2 and the glass substrate 30 by a low pressure chemical vapor deposition (LPCVD) process, and then reactive ions as shown in FIG. 18E. Patterning is performed by etching or the like. In this case, the surface of the position controller 2 and the surface of the glass substrate 30 and the surface of the microlens 3 positioned on the position controller 2 should be covered with an amorphous silicon layer 40. Finally, as shown in FIG. 18F, the glass substrate 30 is etched using the amorphous silicon layer 40 as a mask and 49 wt% HF solution is removed, and the amorphous silicon layer 40 is removed. Complete the driver.

As such, the micro driver according to the present invention can be manufactured by a simple method, and maintains linearity even with large displacement while moving in two dimensions.

Claims (28)

Bonding the first substrate to the second substrate, Patterning the first substrate to form a driver pattern; Isotropically etching the second substrate Method of manufacturing a fine driver comprising a. In claim 1, The method of manufacturing a micro driver further comprising the step of thinning the first substrate. In claim 2, And the first and second substrates are each made of silicon and glass. In claim 3, Bonding in the bonding step is a method of manufacturing a fine driver using anodic bonding. In claim 3, The etching in the etching step is a manufacturing method of a fine driver made by using the driver pattern as an etching mask. In claim 3, And forming an etch stop layer covering the driver pattern, wherein the etching in the etch step comprises using the etch stop layer as an etch mask. In claim 6, And forming a microlens by patterning the second substrate, wherein the etch stop layer covers the microlens. In claim 3, And forming a microlens with a photosensitive film or resin on the second substrate. Forming a plating mold in a reverse phase of the driver pattern on the substrate, Forming a plating layer on the substrate on which the plating mold is formed; Removing the plating mold; Isotropically etching the substrate using the plating layer as a mask Method of manufacturing a fine driver comprising a. In claim 9, The substrate is a method of manufacturing a fine driver made of silicon or glass. In claim 10, The isotropic etching is a wet or dry etching method of manufacturing a fine driver. The method according to any one of claims 9 to 11, The driver pattern includes a plurality of pad portions and other portions narrower than the pads, and after the isotropic etching step, the pad portions are fixed to the substrate and the other portions are spaced apart from the substrate. Manufacturing method. In claim 12, The pad portion includes a first pad and a second pad, The other part, A plurality of fixed electrodes connected to the first pad, A plurality of bending members connected to the second pads, A plurality of moving electrodes connected to the bending member and movable through an electrical action with the fixed electrode, A mounting table connected to the bending member to move in accordance with the movement of the moving electrode and to which other elements may be mounted Method of manufacturing a fine driver comprising a. Patterning a first surface of a first substrate having a first surface and a second surface to form a driver pattern, Anodic bonding the bonding surface of the second substrate having the bonding surface and the exposed surface on the first surface of the first substrate, Polishing the second surface of the first substrate until the bonding surface of the second substrate is visible, Forming an etch stop layer on a second surface of the first substrate, a bonding surface and an exposed surface of the second substrate, Etching the second substrate using the etch stop layer as a mask Method of manufacturing a fine driver comprising a. The method of claim 14, And the first and second substrates are each made of silicon and glass. The method according to any one of claims 1 to 8 and 13 to 15, The driver pattern may include a plurality of pad portions fixed to the second substrate and other portions spaced apart from the second substrate. The method of claim 16, The pad portion includes a first pad and a second pad, The other part, A plurality of fixed electrodes connected to the first pad, A plurality of bending members connected to the second pads, A plurality of moving electrodes connected to the bending member and movable through an electrical action with the fixed electrode, A mounting table connected to the bending member to move in accordance with the movement of the moving electrode and to which other elements may be mounted Method of manufacturing a fine driver comprising a. Board, A plurality of fixed electrodes fixed on the substrate, A plurality of moving electrodes formed on the substrate and moving through an electrical action with the fixed electrode, A mounting table connected to the moving electrode and moving in two dimensions in accordance with the movement of the moving electrode, and on which other elements may be mounted; A plurality of elastic members connected to the moving electrodes Including; A portion of the substrate under the fixed and movable electrode, the mounting table, and the elastic member is etched. Fine driver. The method of claim 18, The moving electrode and the fixed electrode each include a first and second comb-shaped electrode having a plurality of electrodes, wherein the electrode teeth of the first and second comb-like electrodes are arranged to be staggered with each other. The method of claim 19, Each of the elastic members may include a first pad fixed to the substrate, and a bent member connected to the first pad and the moving electrode and having a bent structure. The method of claim 20, The fixed electrode further includes a second pad fixed to the substrate and connected to the second comb-shaped electrode. The method of claim 21, And the first and second comb-shaped electrodes, the curved member, and the mounting table are spaced apart from the substrate. The method according to any one of claims 18 to 22, The substrate is a fine driver made of glass or silicon. The method of claim 23, And the fixed electrode and the moving electrode, the mounting table, and the elastic member are made of metal. The method according to any one of claims 18 to 22, The substrate is a fine driver made of glass. The method of claim 24, And the fixed electrode and the moving electrode, the mounting table, and the elastic member are made of silicon. The method of claim 25, The micro driver further comprises a micro lens fixed to the same layer as the substrate below the mounting table. The method of claim 25, The fine lens is a spherical lens formed of a photosensitive film or a resin under the substrate.