JP2001150454A - Microstructure and method of fabricating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently fabricate a microstructure, of which the plating layer has a smooth surface, for a short time. SOLUTION: In a method of fabricating a microstructure, an insulating mask layer 3 is formed on the conductive part 2 of a substrate 1 and aperture parts 4 having a proper shape are formed on the mask layer 3 to expose the conductive part 2 and the exposed conductive part 2 is used as an electrode to perform pulse plating in at least a part of a process to form a plating layer 5 on the aperture parts 4 and the mask layer 3 through the aperture parts 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold or a mold master for a microstructure such as a mold or a mold master for a microlens array for producing a microlens array used in the field of optoelectronics or the like. It relates to a manufacturing method and the like.

[0002]

2. Description of the Related Art A microlens array has a plurality of microscopic substantially hemispherical lenses each having a diameter of several μm to several hundred μm, and is used for various purposes such as a liquid crystal display device, a light receiving device, and a connection between fibers in an optical communication system. It is being used for applications.

On the other hand, the development of surface emitting lasers and the like, in which the interval between light emitting elements can be narrowed and which can be easily arrayed, has been advanced, and the demand for microlenses having a large numerical aperture (NA) that can narrow the interval between lens arrays has increased.

[0004] Similarly, with the development of semiconductor process technology, the distance between the elements has been narrowed, and the size of the light receiving elements has been increasingly reduced as seen in CCDs and the like. As a result, here too, a microlens array with a small lens spacing and a large numerical aperture is required. In such a microlens, a microlens with a high light-collecting rate and high utilization efficiency of light incident on the lens surface is desired.

[0005] Further, there is a similar demand in optical parallel processing / calculation, optical interconnection and the like, which are expected fields of optical information processing in the future.

Further, electroluminescence (EL)
Research and development of self-luminous display devices such as the above have also been actively conducted, and high-definition and high-luminance displays have been proposed. In such a display, there is a demand for a low-cost, large-area microlens array in addition to a small and large numerical aperture microlens array.

[0007] Under the circumstances described above, the ion exchange method (M. Oikawa, et al., Jpn.
J. Appl. Phys. 20 (4) L51
-54, 1981), a method of manufacturing a microlens array in which a plurality of portions on a substrate made of multi-component glass are made to have a high refractive index to form a plurality of lenses. However, in this method, the lens diameter cannot be made larger than the distance between the lenses, and it is difficult to design a lens having a large numerical aperture. Further, in order to produce a large-area microlens array, a large-scale production device such as an ion diffusion device is required, and there is a problem that production is not easy. In addition, compared with molding using a mold, it is necessary to perform an ion exchange step for each glass, and if the manufacturing condition management of the manufacturing apparatus is not sufficiently performed, the quality of the lens, for example, variation in the focal length is large between lots. There was a problem of becoming. Also, this method is more expensive than the method using a mold.

Furthermore, in the ion exchange method, alkali ions for ion exchange are required in a glass substrate, and the substrate material is limited to alkali glass and is compatible with a semiconductor-based device on the premise that alkali ions are free. Is bad. Furthermore, since the thermal expansion coefficient of the glass substrate itself is significantly different from the thermal expansion coefficients of the light receiving device and the light emitting device substrate,
As the integration density of the devices increases, misalignment occurs due to mismatch of thermal expansion coefficients. Also, it has been known that the ion exchange method of glass surface originally leaves a compressive strain on the surface, which causes the glass to warp, and as the size of the microlens array becomes larger, bonding and bonding with a light receiving device or a light emitting device. Has become difficult.

As another method, a registry flow method (D. Daly, et al., Proc. Mi.)
crolens Array Tedgingto
n. , P23-34, 1991). In this method, a resin formed on a substrate is patterned into a cylindrical shape by using a photolithography process, and is heated and reflowed to produce a microlens array. By this method, lenses of various shapes can be manufactured at low cost. In addition, there is no problem such as a coefficient of thermal expansion or warpage as compared with the ion exchange method. However, in this method, the shape of the microlens strongly depends on the thickness of the resin, the wettability between the substrate and the resin, and the heating temperature. Likely to happen. Further, when adjacent lenses come into contact with each other by reflow, the desired lens shape cannot be maintained due to surface tension. That is, it is difficult to bring adjacent lenses into contact with each other to reduce the unused area between the lenses and increase the light collection rate.

In order to obtain a lens diameter of about several tens to several hundreds of micrometers, a resin having a thickness sufficient to make it spherical by reflow must be applied. However, desired optical characteristics (refractive index, high light transmittance) are required. ) Is difficult to apply uniformly and thickly. That is, it is difficult to manufacture a microlens having a large curvature and a large lens diameter.

As another method, there is a method in which an original plate of a microlens array is produced, a lens material is applied to the original plate, and the applied lens material is peeled off. In manufacturing a mold serving as an original, a method of drawing using an electron beam (Japanese Patent Application Laid-Open No. 1-231001) and a method of etching and forming a part of a metal plate (Japanese Patent Application Laid-Open No. 5-303,099)
Publication). According to these methods, the microlens can be duplicated by molding, the variation hardly occurs for each lot, and the microlens can be manufactured at low cost. Further, as compared with the ion exchange method, problems such as occurrence of an alignment error and warpage due to a difference in thermal expansion coefficient can be avoided. However, in the method using an electron beam, an electron beam lithography apparatus is expensive and requires a large amount of capital investment. Since the lithography area is limited, it is difficult to produce a large-sized master having a size of 10 cm square or more. Problem.

Further, in the etching method, since isotropic etching mainly using a chemical reaction is used, there is a problem that even if the composition or the crystal structure of the metal plate is slightly changed, the metal plate cannot be etched into a desired shape. In addition, in the etching method, the etching is continued unless the water is immediately washed when a desired shape is obtained. When a minute microlens is formed, the shape may deviate from the desired shape due to etching that progresses from the time when the desired shape is obtained to the time of washing with water.

As another method for producing a master of a microlens array, a method using electroplating (Japanese Patent Laid-Open No.
-27302). This method uses an insulating film having an opening formed on one side of a conductive layer,
Electroplating is performed using the conductive layer as a cathode to form a convex material serving as a matrix of the lens on the surface of the insulating film. The process of the matrix produced by this method is simple,
Low cost can be realized.

[0014]

However, the above-mentioned method of producing an original microlens array using electroplating also has the following problems. That is, when a mold is manufactured using DC plating, it is very difficult to obtain a smooth surface if plating is performed at a high current density. This is because, when DC plating is performed at a high current density without stirring the plating bath, plating is performed in a state where metal ions consumed on the plating surface are not sufficiently supplied immediately. Therefore, in order to obtain a smooth surface, it is necessary to perform plating at a low current density for a long time. Therefore, the manufacturing time becomes longer, and the productivity of the mold is reduced.

The present invention has been made in view of the above-mentioned problems of the prior art. Its purpose is to enable a microstructure such as a mold for a microlens array or a mold master having a smooth surface of a plating layer serving as a lens matrix to be more efficiently manufactured in a shorter time than conventional techniques. An object of the present invention is to provide a method for manufacturing a microstructure such as a lens array mold or a microlens array mold master.

[0016]

Means for Solving the Problems To achieve the above object, the method for manufacturing a microstructure according to the present invention comprises the following steps: (1) a substrate having a conductive portion at least in part (a conductive substrate, a substrate having an electrode layer) And (2) a step of forming an insulating mask layer on the conductive portion, and (3) a plurality of or a single suitable shape (circular, elliptical, linear or curved slit shape) in the mask layer. Etc.) to form an opening to expose a conductive portion, and (4) pulse plating (in this specification, plating includes electroplating and electrodeposition) in at least a part of the process using the conductive portion as an electrode. In the sense, pulse plating refers to plating using a pulse current having an appropriate duty ratio and an average current density), thereby forming a plating layer on the opening and the mask layer through the opening. , Characterized by having a.

In the manufacturing method of the present invention, pulse plating is used in at least a part of the plating process, so that the average current density can be increased and the plating time can be shortened.

Based on the above basic configuration, more specific modes as described below are possible.

In step (4), if pulse plating is performed at least in the step portion including the final point, a plated layer having a smooth surface can be reliably obtained.

The step (4) may include a step of performing DC plating before forming the pulse plating to surely form a plating layer having a convex shape in the opening.

In the step (4), if DC plating is performed at a relatively low current density and then pulse plating is performed at a relatively high average current density, a convex plating layer can be reliably formed in the opening at the beginning. A hemispherical or semi-cylindrical microstructure having a smooth surface can be formed in a short time.

In the above step (4), even if pulse plating with a relatively low average current density is performed to form a plating layer having a convex shape in the opening and then switched to pulse plating with a relatively high average current density, the plating is initially performed. A hemispherical or semi-cylindrical microstructure having a smooth surface can be formed in a short time by reliably forming a convex plating layer in the opening. In this case, it is preferable that the duty ratio of the relatively low average current density pulse plating is set larger than the duty ratio of the relatively high average current density pulse plating so that the former pulse current is close to DC. .

In the steps (3) and (4), the opening is sufficiently smaller than the size of the counter electrode at the time of plating so that the plating layer grows isotropically with respect to the center or center line of the opening. By forming the microstructure, a hemispherical or semicylindrical microstructure can be surely formed.

In the step (4), the pulse plating is electroplating using a pulse current using the conductive portion as an anode, or an electrode plating using a pulse current using the conductive portion as a cathode or an anode. Or wearing clothes.

Further, a mold or a mold master for a microlens array according to the present invention for achieving the above-mentioned object has a flat surface formed by the above-mentioned method for producing a microstructure. Features.

As described above, in the method for manufacturing a microstructure of the present invention, typically, a conductive layer is formed on a substrate, an insulating mask layer is formed on the conductive layer, and the mask layer is formed. A single or a plurality of openings having an appropriate shape such as a circular shape or a slit shape is formed on the upper surface, and a plating layer is formed on the conductive layer through the openings by using pulse plating, thereby forming a mold for a microlens array. Alternatively, a microstructure such as a mold master is manufactured.

As the substrate material, any of metals, semiconductors and insulators can be used. If a metal material is used as the substrate, there is no need to form an electrode layer. In the case of using a semiconductor, it is not always necessary to form an electrode layer as long as the electrode has conductivity enough to allow electroplating. Since the substrate is used as a mold or a mold master, it is preferable to use a substrate having small undulation and surface roughness.

Further, since the substrate may be warped due to the internal stress or thermal stress of the plating layer, the substrate is preferably a metal plate, a glass substrate, a silicon wafer, or the like having good flatness and a large Young's modulus. The electrode layer is selected from materials that are not corroded by the plating bath used because they are exposed to the plating bath.

As a material that can be used as the mask layer, any of an organic material and an inorganic material can be used as long as it is an insulating material. The step of forming an opening in this mask layer will be described. In forming the openings, the openings are formed in the mask layer by a photolithography process capable of forming minute or narrow openings and etching. First, after forming a mask layer, an opening pattern of a photoresist is formed on the mask layer by a photolithography process, an opening pattern is formed in the mask layer by etching using the photoresist as a mask, and finally the photoresist is removed. . Thus, a mask layer having a desired opening is formed. It is also possible to use a photoresist as the mask layer, and if a photoresist is used, the step of etching the material of the mask layer can be omitted, so that the photoresist is preferably used as the mask layer material.

In the present invention, pulse plating is used in at least a part of the step of forming the plating layer (accordingly, DC plating, electroless plating, etc. may be used together with pulse plating). In general, pulse plating has advantages over DC plating in that (1) a smooth plating surface can be obtained, and (2) plating at a large average current density is possible (Hosokawa, Matsunaga: Metal surface technology 3
4, 98 (1983)).

Therefore, in a typical example of the present invention, a microstructure such as a mold for a microlens array or a mold master having a smooth plating layer surface by using a pulse plating method in a plating step including a plating final point. You can get the body. In addition, in the pulse plating method, even when plating is performed at a higher average current density than DC plating, ions are satisfactorily supplied on the plated surface, so that a smooth plated surface can be obtained. Accordingly, in the present invention, plating can be performed at a higher average current density than in the conventional technique, and the manufacturing time can be reduced. Therefore, productivity of a microstructure such as a mold for a microlens array or a mold master can be improved.

By the way, in a typical example of the present invention, it is necessary to form a convex plating layer in the opening at the beginning of plating. If a concave shape is formed without forming a convex shape in the opening, a concave portion remains in the optical axis portion of the plated layer after growth, or long-time plating is required until a hemispherical plated layer is formed. , Etc. Even when the plating layer is formed by pulse plating, if pulse plating is performed at a high average current density in the initial stage of plating, a convex shape may not be formed in the opening. Therefore, in one example of the present invention, DC plating may be performed for a shorter time to form a convex plating layer in the opening, and then the plating layer may be grown using pulse plating. As a result, the convex shape can be reliably formed in the opening, so that the above-described problem can be solved. Furthermore, after forming the convex shape, it becomes possible to perform pulse plating at a high average current density,
The manufacturing time can be reduced.

For the same purpose, in the initial stage of plating, a method of performing pulse plating of a relatively low average current density with a large duty ratio, which is pulse plating close to DC plating, and thereafter switching to pulse plating of a high average current density. Can also be adopted.

The main metal forming the plating layer is a single metal such as Ni, Au, Pt, Cr, Cu, Ag and Zn.
In alloys such as Cu-Zn, Sn-Co, Ni-Fe,
Although there are Ni-W, Zn-Ni, and the like, any other material that can be electroplated can be used.

In a typical example of the present invention, the opening is formed in a sufficiently small or thin circular shape or slit shape so that the plating layer is isotropically formed from the center of the opening or the center line of the slit. It grows and a hemispherical or semi-cylindrical plating layer can be formed.

In the electroplating bath, Al ₂ O ₃ , TiO
_2. Dispersion plating by adding dispersed particles such as PTFE can also be used for forming a microstructure such as a hemisphere in pulse plating. Thereby, the mechanical strength and corrosion resistance of the mold can be improved by the dispersed particles.

Further, a form in which an electrodepositable organic compound (anionic electrodeposited acrylic carboxylic acid resin, cationic electrodeposited epoxy resin, or the like) is electrodeposited on the conductive portion using a pulse current is also possible. is there.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) A first embodiment will be described with reference to the process sectional views of FIGS. First, a 6-inch silicon wafer is prepared and thermally oxidized using an oxidizing gas to form a 1-μm-thick silicon dioxide film on both surfaces. This is called substrate 1. Next, Cr and Au were each deposited on the substrate 1 by electron beam evaporation to a thickness of 100 nm.
An electrode layer 2 is formed by continuously forming a film at m and 200 nm (FIG. 1A). Further, a photoresist (trade name: AZ-1500: manufactured by Hoechst) is provided on the surface of the electrode layer 2.
Is applied by spin coating to form a mask layer 3 (FIG. 1A).

Next, an opening 4 is formed in the mask layer 3 by exposing and developing the mask layer 3 (photoresist), and the electrode layer 2 is exposed. In the present embodiment, the opening 4 has a circular shape and a diameter of 5 μm. The openings 4 are arranged in a 700 × 700 matrix (FIG. 1B).

Next, pulse plating is performed for 2 minutes in a Cu plating bath at a bath temperature of 55 ° C. using the substrate having the opening 4 as the work 6 and the electrode layer 2 as a cathode. As the Cu plating bath, hydrochloric acid was added to an aqueous solution having a weight ratio of 200 g: 50 g per liter of copper sulfate pentahydrate and sulfuric acid to 0.1 g.
The one added with 04 ml / l was used. The pulse conditions are as follows: duty cycle (duty cycle) 10%, frequency 1
0 Hz and a pulse current density of 1000 A / dm ² (average current density of 100 A / dm ² ). In this embodiment, pulse plating is performed from the beginning to the end, and various conditions of the pulse plating are performed so that a convex plating layer is first formed in the opening 4 and finally a smooth plating layer is formed. Duty ratio, average current density, etc.). The Cu plating used in the present embodiment is a plating in which the effect of pulse plating is easily exerted since Cu ions are less likely to diffuse than Ni ions or the like.

The plating layer 5 spreads over the mask layer 2 as it grows, forming a hemispherical structure 5 (FIG. 1).
(C), FIG. 1 (d)). The diameter of the hemispherical plating layer 5 is about 5
0 μm. At this stage, the adjacent plating layers 5 are not connected but are independent (FIG. 1D).

FIG. 2 is a schematic view of a plating apparatus used in this embodiment. The plating apparatus includes a work 6, an anode plate 7 having a size sufficiently larger than the opening 4, a plating bath 8, a constant current power supply 9, and a pulse generator 10.

When the surface of the hemispherical plating layer 5 formed in this example was observed using an SEM (scanning electron microscope), a smooth surface was obtained.

On the other hand, for comparison, direct current plating was performed at a bath temperature of 55 ° C. and a current density of 4 A / dm ² using the same substrate as a workpiece, the electrode layer as a cathode, and the same plating bath. In order to form a 50 μm-diameter hemispherical structure using the DC plating under the above conditions, plating had to be performed for 40 minutes.

In the present embodiment, the use of pulse plating makes it possible to grow the plating layer at a higher average current density than in the case of direct current plating, so that the production time is greatly reduced as compared with the prior art. Could be shortened. In this way, the productivity of manufacturing a mold for a microlens or a mold master having a smooth surface could be improved.

(Second Embodiment) In the second embodiment, a substrate having an opening 4 similar to that of the first embodiment is manufactured. Then, first, the substrate is used as a work 6, and the electrode layer 2
Is used as a cathode, Cu direct current plating is performed for 10 seconds using a constant current power supply 9 to deposit a convex plating layer 5 having a curvature in the opening 4 as shown in FIG. Cu
As a plating bath, an aqueous solution in which the weight ratio of copper sulfate pentahydrate to sulfuric acid per liter is 200 g: 50 g,
A solution to which 0.04 ml / l of hydrochloric acid is added is used. The plating conditions were a plating bath temperature of 55 ° C. and a DC plating current density of 4 A / dm ² .

Next, using the same Cu plating bath, a bath temperature of 5
Pulse plating is performed at 5 ° C. for 1 minute and 20 seconds using the pulse generator 10 to further grow the plating layer 5. The pulse condition is a duty cycle (duty cycle).
e) 10%, frequency 10 Hz, pulse current density 1500
A / dm ² (average current density 150 A / dm ² ).
The plating layer 5 spread over the mask layer 3 as it grew, forming a hemispherical structure. The diameter of the hemispherical plating layer 5 is about 50 μm.

When the surface of the hemispherical plating layer 5 formed in this embodiment was observed using a scanning electron microscope (SEM), a smooth surface was obtained as in the first embodiment.

In this embodiment, the opening 4 is formed by DC plating.
The first embodiment (in this example, it is necessary to initially form the convex plating layer 5) by forming the convex plating layer 5 therein and then growing the plating layer 5 using pulse plating. Therefore, it is necessary to perform pulse plating at a relatively low average current density). This allows
Compared with the first embodiment, a mold for a microlens or a mold master could be manufactured in a shorter time without lowering the surface smoothness.

In the initial stage of plating, the duty cycle was increased (for example, 70%).
% Or 80%) Under conditions close to DC plating, pulse plating is performed at a low average current density to form a plating layer having a convex shape, and then pulse plating is performed at a high average current density (in this case, sufficiently smooth). (The duty ratio may be reduced in order to obtain a smooth surface.) The same effect as that of the present embodiment can be obtained by a method of growing a plating layer.

The mold formed as described above may be used as it is as a mold for a microlens, or it may be used as a master to form a mold thereon and peel the mold from a substrate. Thus, a mold for microlenses that is inverted with respect to the mold for microlenses (the irregularities are reversed) may be formed.

Further, in the above-described method for manufacturing a mold or a mold master, the growth of forming a convex plating layer on the mask layer may be continued, and plating may be performed until adjacent plating layers are integrated. . Thereby, a mold or a mold master for a fly-eye lens or the like can be formed.

Further, in the above-described method for manufacturing a mold or a mold master, the opening for the micro lens such as a spherical lens or a lenticular lens may be formed in a circular shape or a long and elongated rectangular shape. A mold or a mold master can be manufactured.

The microlens is manufactured by applying a lens material (made of resin or the like) onto the microlens mold manufactured by the above-described microlens mold manufacturing method, and then removing the lens material from the mold. It forms by peeling.

Also, of course, the microstructure manufactured by the manufacturing method of the present invention is typically used as a mold for a microlens array or a mold master. Can also be used.

[0057]

As described above, in the method for manufacturing a microstructure such as a mold for a microlens array or a mold master according to the present invention, at least a part of the method is compared with a direct current plating method by using a pulse plating method. Then, the plating layer can be obtained by growing the plating layer at a high average current density. This makes it possible to efficiently produce a microstructure such as a mold for a microlens array or a mold master in a shorter time and more efficiently than in the prior art, thereby improving productivity. Further, by using the manufacturing method of the present invention, a microstructure such as a mold for a microlens array or a mold master having a plating layer having a smooth surface can be obtained.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a mold or a mold master for a microlens array according to a first embodiment and a second embodiment of the present invention.

FIG. 2 is a schematic view of a plating apparatus used in a first embodiment and a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode layer 3 Mask layer 4 Opening 5 Plating layer 6 Work 7 Anode plate 8 Plating bath 9 Constant current power supply 10 Pulse generator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Ushijima 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yasuhiro Shimada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Takayuki Yagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 4F202 AH74 CD03 CD12 CD22

Claims (13)

[Claims] 1. A method for manufacturing a microstructure, comprising: (1) a step of preparing a substrate having a conductive portion at least in part; and (2) a step of forming an insulating mask layer on the conductive portion. (3) a step of forming a plurality of or a single appropriate-shaped opening in the mask layer to expose a conductive portion; and (4) performing pulse plating in at least a part of the process using the conductive portion as an electrode. Forming a plating layer on the opening and the mask layer through the opening. 2. The method according to claim 1, wherein in the step (4), pulse plating is performed at least in a step portion including a final point.
A method for producing the microstructure according to the above. 3. The method of manufacturing a microstructure according to claim 1, wherein said step (4) includes a step of performing DC plating to form a convex plating layer in the opening before performing pulse plating. . 4. The method according to claim 3, wherein in the step (4), DC plating is performed at a relatively low current density, and then pulse plating is performed at a relatively high average current density. 5. The method according to claim 1, wherein in step (4), pulse plating is performed at a relatively low average current density to form a plating layer having a convex shape in the opening, and thereafter, switching to pulse plating is performed at a relatively high average current density. Or the manufacturing method of the microstructure of 2. 6. The method of manufacturing a microstructure according to claim 5, wherein a duty ratio of the pulse plating having a relatively low average current density is set to be larger than a duty ratio of the pulse plating having a relatively high average current density. 7. The method according to claim 1, wherein in the step (3), the opening has a circular shape. 8. The method according to claim 1, wherein in the step (3), the opening has a slit shape. 9. In the steps (3) and (4), an opening is formed so that the plating layer grows isotropically with respect to the center or center line of the opening, and the plating layer is formed. Claim 1
9. The method for manufacturing a microstructure according to any one of claims 1 to 8. 10. The method for manufacturing a microstructure according to claim 1, wherein said microstructure is a mold for a microlens array or a mold master. 11. The method according to claim 1, wherein in the step (4), the pulse plating is electroplating using a pulse current using the conductive portion as an anode. . 12. The microstructure according to claim 1, wherein in the step (4), the pulse plating is electrodeposition using a pulse current using the conductive portion as a cathode or an anode. Method of manufacturing. 13. A mold or a mold master for a microlens array, characterized in that a surface produced by using the production method according to claim 1 has a smooth plating layer.