JP2004093989A - Manufacturing method of polymer optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polymer optical waveguide for inexpensively, quickly, easily manufacturing a molding die for emboss. <P>SOLUTION: The polymer optical waveguide comprises: a cladding base part on which a core pattern consisting of a fine recess is recessed; a core formed in the core pattern at the cladding base part; and a cladding lid section for covering the exposure section of the core on the surface of the cladding base part. The core pattern at the cladding base part uses the molding die for emboss having the core pattern consisting of a fine projection and is pressed against the surface of the cladding base part for molding. The molding die for emboss is duplicated from an original on which the core pattern comprising the projection is formed by allowing a surface (110) of a silicon substrate to be subjected to anisotropic wet etching. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the production of polymer optical waveguides for transmitting optical information such as optical diffraction paths, optical demultiplexing paths and optical multiplexing paths, optical branching paths and photosynthetic paths, optical switches, optical circuits, and the like in optical information communication. It is about the method.
[0002]
[Prior art]
Conventionally, a polymer optical waveguide as described above has a core and a clad that covers the peripheral surface so as to surround the core. The core is formed of a colorless and transparent synthetic resin, and the clad is formed of a colorless and transparent synthetic resin having a lower refractive index than the synthetic resin forming the core. Then, the optical information is propagated in the core while being reflected at the interface between the core and the clad.
[0003]
This polymer optical waveguide was formed mainly by a reactive ion etching method (RIE method). That is, first, a thin-film core layer is formed on the surface of a thin-film lower clad formed on a substrate by spin coating or the like by a method such as spin coating. Next, a part of the core layer is removed by etching by the RIE method, so that a core made of a convex portion is formed on the surface of the lower clad so as to have a predetermined pattern shape. An upper clad was formed so as to cover the entire surface of the lower clad by a method such as spin coating, and a polymer optical waveguide was formed by covering the core on the surface of the lower clad with the upper clad. .
[0004]
However, this method of manufacturing a polymer optical waveguide by the RIE method requires individual processing such as etching for each polymer optical waveguide, which requires a slow processing speed, complicated work, and high manufacturing costs. However, there is a problem that mass production is difficult to achieve. Accordingly, methods such as a heating embossing method, a direct exposure method, and a photobleaching method have been proposed as methods for manufacturing a polymer optical waveguide that can be mass-produced. In particular, among these, the heating embossing method is easy to enhance the productivity, and is attracting attention as a method for producing a polymer optical waveguide.
[0005]
The cladding of the polymer optical waveguide manufactured by the heating embossing method is formed on a cladding base having a rectangular shape with a concave groove formed on the surface thereof, and on the surface of the cladding base so as to cover the opening of the concave groove. And a clad lid in the form of a plate. The concave line of the clad base is formed by engraving a concave line corresponding to the convex line by pressing an embossing mold having a convex line on the surface against the thermoplastic resin heated and softened. . Then, after forming the core in the concave stripe of the clad base, a clad lid is formed so as to cover the surface of the clad base and the core, whereby a polymer optical waveguide is manufactured.
[0006]
In the above-mentioned heating embossing method, the embossing die used for forming the concave streak in the clad base has been manufactured by the LIGA process method or the SIGA process method. The LIGA process method uses a synchrotron radiation device, irradiates a resist material with radiation in a predetermined range through a mask, and develops the resist material to remove a part of the resist material. This is a method for obtaining a concave shape. The concave shape obtained by the LIGA process is mainly used for forming a polymer optical waveguide having a core diameter of up to 600 μm. On the other hand, the above-mentioned SIGA process method is a method in which the surface of a silicon substrate where a portion other than a predetermined range is masked is etched by a method such as the RIE method to obtain a concave shape as an original plate. The concave shape obtained by the SIGA process is mainly used for forming a polymer optical waveguide having a core diameter of about 3 to 100 μm.
[0007]
A metal such as nickel is laminated on the concave surface obtained by the LIGA process or the SIGA process by a method such as electroforming, and the metal is peeled from the concave to form a convex made of the metal. An embossing mold had been produced. Then, the heating embossing method using the embossing die makes it possible to easily and in a short time form a concave streak on the surface of the clad base, thereby improving productivity and achieving mass production. Had become.
[0008]
[Problems to be solved by the invention]
However, the synchrotron radiation device used in the above-mentioned LIGA process method is very expensive and a large-scale device, and usable masks are limited to special ones and are very expensive. For this reason, the operation cost at the time of using the apparatus increases, and even if the productivity is improved, the manufacturing cost tends to rise rather than increase. In addition, the SIGA process method requires a long time to fabricate the concave mold, which is the original plate, by a method such as the RIE method, and requires processing work under a vacuum atmosphere. , And tended to be expensive. Therefore, in the method of manufacturing a polymer optical waveguide by the LIGA process method and the SIGA process method, there is a problem in that when manufacturing an embossing die, the manufacturing time becomes longer and the manufacturing cost rises.
[0009]
The present invention has been made in view of such problems existing in the conventional technology. An object of the present invention is to provide a method for manufacturing a polymer optical waveguide, which can easily and inexpensively produce an embossing mold in a short time.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention of the method for manufacturing a polymer optical waveguide according to the first aspect of the present invention provides a method for manufacturing a polymer optical waveguide, wherein the (110) plane of a silicon substrate is a surface, and the surface is masked with a coating film. A resist pattern forming step of forming a resist pattern with a resist film on the surface of the covering film, a masking pattern forming step of etching a covering film other than the resist pattern and forming a masking pattern by the covering film on the surface of the silicon substrate; An original plate manufacturing process of manufacturing an original plate having a core pattern formed of convex portions on the surface by etching the surface of the silicon substrate on which the masking pattern is formed by an anisotropic wet etching method; After the pattern is cast on the surface of the replica mold, use this replica mold to apply the original core pattern to the surface of the embossing mold. A duplication step of duplicating a core pattern consisting of one convex portion, and a heating embossing method using the same embossing die, after forming a clad base in which a core pattern composed of a concave portion is recessed on the surface, and then forming the concave portion An optical waveguide forming step of forming a clad lid on the surface of the clad base so as to cover the exposed portion of the core.
[0011]
According to a second aspect of the present invention, in the method for manufacturing a polymer optical waveguide according to the first aspect, the anisotropic wet etching is performed on the silicon substrate having a masking pattern formed on a surface thereof. Is immersed in an etching solution, and a strong alkaline solution having a pH of 12 or more is used as the etching solution.
[0012]
According to a third aspect of the present invention, in the method of the first or second aspect, in the resist pattern forming step, the positive or negative photoresist is coated with a surface of a coating film. Apply a resist film to form a resist film, irradiate the resist film with active energy rays, expose a positive or negative photoresist, draw a resist pattern, and develop it. In the case of a negative type photoresist, a resist pattern is formed by removing an unexposed portion of the resist film from the exposed portion of the resist film.
[0013]
According to a fourth aspect of the present invention, in the method of manufacturing a polymer optical waveguide according to any one of the first to third aspects, the coating film is formed by oxidizing a surface of a silicon substrate. An oxide film, wherein the silicon oxide film is etched using dilute hydrofluoric acid or buffered hydrofluoric acid in the masking pattern forming step.
[0014]
According to a fifth aspect of the present invention, in the method according to any one of the first to fourth aspects, in the replication step, a liquid silicone rubber is applied to a surface of the original plate, After the silicone rubber is cured and peeled from the surface of the original plate, a duplicate mold having a core pattern composed of convex portions and a concave portion corresponding to the concave portion of the original plate is formed on the surface, and then formed in the concave portion of the duplicate mold. Filling a liquid active energy ray-curable resin, curing the active energy ray-curable resin by irradiating the active energy ray, and then peeling off the cured active energy ray-curable resin from the surface of the replica mold, thereby obtaining an active energy ray. The present invention is characterized in that an embossing mold made of a line-curable resin is formed.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIGS. 1A and 1B, the cladding base 11 constituting the polymer optical waveguide is formed in a rectangular shape, and a core pattern 12 composed of a plurality of fine recesses is formed on the surface thereof. ing. A core 13 having a square cross section is formed in the core pattern 12 of the clad base 11. Further, a thin plate-like clad lid 14 is attached to the surface of the clad base 11 so as to cover the exposed portion of the core 13.
[0016]
The clad base 11 is formed of a film made of a transparent synthetic resin, a substrate having a thickness of 1 mm or more, a film laminated on a surface of a silicon substrate, a metal substrate, a metal oxide substrate, a glass substrate, or the like by a spin coating method or the like. Have been. The clad lid 14 is formed by applying a transparent synthetic resin film, a substrate having a thickness of 1 mm or more to the surface of the clad base 11, or applying a liquid synthetic resin by dissolving in a solvent. , And cured. Examples of the synthetic resin used for the clad base 11 and the clad lid 14 include thermoplastic resins such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyarylate (PAr), and polystyrene (PS); Resin, ultraviolet curable resin such as ultraviolet curable acrylic resin and ultraviolet curable vinyl resin, and fluororesin. Among these, it is preferable to use a thermoplastic resin because the clad base 11 has a core pattern 12 formed on its surface by a heating embossing method as described later.
[0017]
As long as the core 13 is a transparent synthetic resin and has a higher refractive index than those used for the cladding base 11 and the cladding lid 14, any synthetic resin may be used. Specifically, as the synthetic resin used for the core 13, in addition to the thermoplastic resin, the ultraviolet curable resin, the fluororesin, and the like mentioned as the material of the clad base 11 and the clad lid 14, a thermosetting resin such as polyimide is used. No.
[0018]
In addition, regarding the synthetic resin used for the clad base 11, the clad lid 14, and the core 13, when it is used as a polymer optical waveguide, it indicates that the synthetic resin is transparent in a wavelength region of light to be propagated. The synthetic resin is not limited to a colorless and transparent resin, and may be a colored and transparent resin as long as it is transparent in the wavelength range of transmitted light, that is, does not absorb the transmitted light. Specifically, light having a wavelength range of 400 to 1600 nm is used as the light to be propagated, and light having a wavelength range of 650 nm, 850 nm, 1300 nm, and 1550 nm is mainly selected and used according to the application. For this reason, as a material used for the cladding base 11, the cladding lid 14, and the core 13, a transparent synthetic resin having a color tone that does not absorb light in these wavelength ranges is used.
[0019]
The clad base 11, the core 13, and the clad lid 14 constitute a polymer optical waveguide. This polymer optical waveguide is used for, for example, an optical diffraction path, an optical demultiplexing path and an optical multiplexing path, an optical branching and an optical combining path, an optical switch, an optical circuit, and the like, for transmitting optical information, such as an optical fiber connector and a splitter. used. Then, the input optical information is propagated in the core 13 while repeating reflection on the boundary surface between the clad base 11 or the clad lid 14 and the core 13 as light.
[0020]
In the cladding base 11, it is preferable to suppress the roughness of the inner surface of the core pattern 12 to one-twentieth or less of the wavelength range of the light to be used. Specifically, the arithmetic average roughness (Ra) of the inner surface of the core pattern 12 specified in JIS B0601-1994 is preferably 0.01 μm or more and less than 0.1 μm. When Ra is 0.1 μm or more, light may be irregularly reflected in the core 13 and optical information may not be transmitted accurately, which causes problems such as generation of noise. As the inner surface Ra of the core pattern 12 becomes smaller, light waves are less likely to be irregularly reflected, and optical information can be accurately transmitted. Occurs, resulting in an increase in manufacturing cost. Therefore, in a range where such a problem does not occur, the lower limit of Ra is preferably set to 0.01 μm.
[0021]
The diameter of the core 13, that is, the length of one side is preferably 3 to 1000 μm. For example, when the light from the optical fiber is incident on the polymer optical waveguide or the light emitted from the polymer optical waveguide is incident on the optical fiber, the diameter of the core 13 of the polymer optical waveguide and the core diameter of the optical fiber are determined. Must be equivalent. This is because if one of the diameters is different from the other, there is light that is not incident on a part of the diameter and a connection loss occurs. Since the core diameter of a generally used optical fiber is 3 to 1000 μm, it is preferable that the diameter of the core 13 be 3 to 1000 μm. In this embodiment, the diameter of the core 13 is set to 100 μm or more because the positioning in the connection operation can be simplified.
[0022]
Next, a method for manufacturing the polymer optical waveguide having the above configuration will be described.
As shown in FIGS. 6A and 6B, the polymer optical waveguide is manufactured through an embossing process and a forming process in an optical waveguide forming process. First, in the embossing step, the core pattern 12 of the clad base 11 is formed by a heating embossing method using the embossing mold 27. The embossing mold 27 is formed from a glass plate 26 and a synthetic resin stamper 25 provided on the back surface of the glass plate 26. On the lower surface of the stamper 25, a third core pattern 25a including a convex portion is formed so as to have a pattern shape inverted from the core pattern 12.
[0023]
When the clad base 11 is formed by the heating embossing method, first, the embossing mold 27 is heated until the temperature thereof becomes equal to or higher than the glass transition point (Tg) of the synthetic resin as the material of the clad base 11. Next, as shown by an arrow in FIG. 6A, the heated embossing mold 27 is pressed against the surface of the clad base 11 while being pressed from the surface side. Then, after cooling to a temperature equal to or lower than the glass transition point of the synthetic resin, the embossing mold 27 is separated from the surface of the clad base 11. Then, as shown in FIG. 6B, a core pattern 12 having a pattern shape reversed from the third core pattern 25a is engraved on the surface of the clad base 11.
[0024]
In order to facilitate the production of the embossing mold 27, the material of the stamper 25 is an active energy ray-curable resin that is cured from the liquid state by irradiation with active energy rays such as X-rays, ultraviolet rays, and electron beams. It is preferred to use. Further, since the embossing mold 27 is heated, it is preferable to use a material having a higher glass transition point than that of the synthetic resin that is the material of the clad base 11 as the material of the stamper 25. Further, since the embossing mold 27 is pressed against the clad base 11 in a pressurized state, it is preferable to use a stamper 25 having a higher hardness than the synthetic resin that is the material of the clad base 11. . Examples of the active energy ray-curable resin that satisfies these conditions include the above-described ultraviolet-curable resins, and preferably use a cationic polymerization type ultraviolet-curable epoxy resin.
[0025]
Subsequently, in the forming step, first, as shown in FIG. 1A, a core 13 is formed in the core pattern 12 of the clad base 11 as a previous step. The core 13 is formed by filling the core pattern 12 with the above-described ultraviolet curable resin and then irradiating the core pattern 12 with ultraviolet light. In addition, the core pattern 12 is filled with a synthetic resin which is made liquid by dissolving in a solvent or the like, and the solvent is volatilized under a reduced pressure atmosphere or a temperature atmosphere equal to or lower than Tg of the synthetic resin which is the material of the cladding base 11. Alternatively, the core 13 may be formed by curing a synthetic resin or the like.
[0026]
Thereafter, as shown in FIG. 1B, a cladding lid 14 is formed on the surface of the cladding base 11, as shown in FIG. 1B, and a polymer optical waveguide is manufactured. The clad lid 14 is formed by applying the above-described film, applying an ultraviolet curable resin to the surface of the clad base 11, curing the resin by irradiation with ultraviolet light, and applying a liquid synthetic resin by spin coating or the like. , Curing, etc.
[0027]
Next, a method of manufacturing the embossing mold 27 will be described.
This embossing mold is manufactured through a resist pattern forming step, a masking pattern forming step, an original plate manufacturing step, and a duplicating step in order.
[0028]
In the resist pattern forming step, the surface of the silicon substrate that is the material of the original plate is masked with a coating film, and a resist pattern is formed on the surface of the coating film. In this step, first, as shown in FIG. 2A, the silicon substrate 21 is fired in a high-temperature electric furnace or the like with the (110) plane facing the surface. Then, a coating film 22 made of a silicon oxide film is formed on the surface of the silicon substrate 21, and the surface of the silicon substrate 21 is masked by the coating film 22. The (hkl) plane indicates the definition of the lattice plane by the Miller index.
[0029]
A liquid resist material is applied to the surface of the coating film 22 by spin coating or the like so as to have a uniform thickness. Then, by heating and drying the resist material, a resist film 23 is formed on the surface of the coating film 22. Thereafter, the resist film 23 is exposed to ultraviolet light, which is an active energy ray, from above the resist film 23 via a mask, so that the resist film 23 is exposed. Then, by developing the resist film 23, a part of the resist film 23 is removed as shown in FIG. 2B, and a resist pattern 23a is formed on the coating film 22.
[0030]
It is preferable that the coating film 22 has a thickness of about three thousandths of the diameter of the core 13. This is because, when the silicon substrate 21 is etched in the original plate manufacturing process described later, the etching rate of the silicon substrate 21 with respect to the etching solution is 1000, whereas the etching rate of the silicon oxide film as the coating film 22 with respect to the same etching solution. Is about 2. When the thickness of the coating film 22 is less than three thousandths of the diameter of the core 13, the coating film 22 may be removed by etching before the diameter of the core 13 reaches a desired value. If the coating film 22 is etched before the diameter of the core 13 reaches the desired value, the surface of the silicon substrate 21 becomes rough, and the inner surface Ra of the core pattern 12 becomes 0.1 μm or more. There is a possibility that the diameter of the core 13 cannot be set to a desired value. The upper limit of the thickness of the coating film 22 is 50 μm. This is because it is possible to sufficiently protect the surface of the silicon substrate 21 with the coating film 22 having a thickness of 50 μm or less, and it is difficult to form the coating film 22 having a thickness of more than 50 μm. Because it is bulky.
[0031]
As the resist material, a positive or negative photoresist that can be exposed to active energy rays such as electron beams, X-rays, and ultraviolet rays is used. When a positive photoresist is used, a mask having the same pattern shape as the resist pattern 23a is used as the mask. In the case of a positive photoresist, the exposed portion of the resist film 23 becomes soluble, and the exposed portion is removed by development, whereby a resist pattern 23a is formed in the unexposed portion. On the other hand, when a negative photoresist is used, a mask having a pattern inverted from that of the resist pattern 23a is used as the mask. In the case of a negative photoresist, the exposed portion of the resist film 23 becomes insoluble, and the unexposed portion is removed by development, so that the exposed portion becomes a resist pattern 23a.
[0032]
In the masking pattern forming step, the silicon substrate 21 having the resist pattern 23a formed on the surface of the coating film 22 is immersed in an etching agent, so that the coating film exposed to the outside except for the resist pattern 23a. 22 is etched and removed. Then, as shown in FIG. 3A, a masking pattern 22a having the same pattern shape as the resist pattern 23a is formed on the surface of the silicon substrate 21. A chemical solution that can dissolve the silicon oxide film is used as the etching agent. Examples of such a chemical solution include diluted hydrofluoric acid or buffered hydrofluoric acid.
[0033]
In the original plate manufacturing process, first, the resist pattern 23a is removed using a resist remover such as concentrated sulfuric acid, hydrogen peroxide solution or the like, and then the silicon substrate 21 having the masking pattern 22a formed on the surface is subjected to anisotropic wet etching. Etched by the method. Then, as shown in FIG. 3B, a part of the surface of the silicon substrate 21 is removed, and an original plate 21a having a first core pattern 21b formed of a protrusion on the surface is produced.
[0034]
The first core pattern 21b formed of the convex portion has the same pattern shape as the third core pattern 25a of the embossing mold 27, and serves as a prototype of the core pattern 12 formed of the concave portion of the clad base 11. . For this reason, Ra of the upper surface and both side surfaces of the convex portion forming the first core pattern 21b is preferably 0.01 μm or more and less than 0.1 μm, like the Ra of the inner surface of the core pattern 12. This is because, when the upper surface and both side surfaces of the original projection are rough, the roughness is transferred to the inner surface of the core pattern 12. When Ra on the upper surface and both side surfaces of the convex portion exceeds 0.1 μm, a low-quality polymer optical waveguide in which the inner surface of the core pattern 12 is roughened is produced. Further, it is difficult to reduce Ra to less than 0.01 μm because the production becomes longer and more complicated, and the production cost is rather increased.
[0035]
The anisotropic wet etching method is a method in which the silicon substrate 21 is etched to have a desired shape by utilizing the fact that the etching rate varies depending on the crystal plane. That is, the silicon substrate has the property that the etching rate in the direction along the (111) plane is the slowest, and when the silicon substrate is etched until the (111) plane appears, other planes with a higher etching rate are removed. For example, when the surface of the silicon substrate is the (100) plane, the (100) plane and the (111) plane intersect at an angle of 54.7 °. It is etched like drawing. On the other hand, when the surface of the silicon substrate is the (110) plane, the (110) plane and the (111) plane intersect at an angle of 90 °, so that the surface of the silicon substrate is etched into an uneven cross section. . Then, in the present invention, by using the silicon substrate 21 whose surface is the (110) plane, the silicon substrate 21 is etched such that the protruding portions remain on the surface.
[0036]
This anisotropic wet etching method is performed by immersing the silicon substrate 21 in a heated etching solution. At this time, since a part of the surface of the silicon substrate 21 is masked by the masking pattern 22a, the surface of the silicon substrate 21 exposed to the outside in a part other than the masking pattern 22a is etched and removed. Then, on the surface of the silicon substrate, a convex portion is formed, the upper surface of which is constituted by the original (110) surface protected by the masking pattern 22a, and the both side surfaces are constituted by the (111) surface which has appeared by etching.
[0037]
Any etchant may be used as long as it is a strongly alkaline solution having a pH of 12 or more. For example, as the strongly alkaline solution, as the inorganic solution, an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, an aqueous cesium hydroxide solution and the like can be mentioned. Examples of the organic solution include an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of ethylenediamine / pyrocatechol, aqueous ammonia, hydrazine, and choline. As the etchant of this embodiment, an aqueous potassium hydroxide solution is used because it is easily available and low in cost.
[0038]
When an aqueous solution of potassium hydroxide is used as an etching solution, the concentration is preferably 20 to 45% by weight, more preferably 23 to 32% by weight. If the concentration is less than 20% by weight, the (110) plane formed between the projections forming the first core pattern 21b is roughened, and the cross-sectional shape of the first core pattern 21b is distorted due to the roughness. There is a risk. On the other hand, if the concentration exceeds 45% by weight, the etching rate of the (311) plane is lower than the etching rate of the (110) plane, so that the (311) plane appears on the surface of the etched surface and is formed. The inner shape of the core pattern 12 may be lost.
[0039]
When an aqueous potassium hydroxide solution is used, the temperature is preferably 30 to 90 ° C. When the temperature is lower than 30 ° C., the etching rate is reduced, and a long manufacturing time may be required. If the temperature exceeds 90 ° C., the etching rate becomes excessively high, and it becomes difficult to form the core 13 with a correct diameter, or the masking pattern 22a is etched before the core 13 reaches a desired diameter. May be removed.
[0040]
Here, the reason for forming the first core pattern 21b including the convex portion on the original plate 21a will be described. When an original plate is manufactured, two methods are conceivable: a method of forming a core pattern composed of convex portions on the surface thereof and a method of forming a core pattern composed of concave portions. When the core pattern including the concave portion is formed as in the latter method, the state of the inner bottom surface of the concave portion is transferred to the inner bottom surface of the core pattern 12. In the concave portion, both inner side surfaces are constituted by the (111) plane that has appeared by etching, and the inner bottom surface is constituted by the (110) plane that has appeared by etching. For this reason, the inner surface of the core pattern 12 is formed on the surface roughened by the etching, which is not suitable as an original plate.
[0041]
One reason for the reason why the etching particularly damages the inner bottom surface of the concave portion is that air bubbles generated in the etching solution during the etching stay in the minute concave portion without escaping and change the etching rate. It is estimated that. In addition, it is presumed that the etching rate of the (110) plane is high, and that the (110) plane generated by etching is roughened at a high probability. Comparing the (111) plane and the (110) plane actually appeared by etching, the (111) plane is a smooth plane and the (110) plane is a rough plane. The inventors think that there is one.
[0042]
On the other hand, when the core pattern including the protrusions is formed as in the former method, the state of the upper surface of the protrusions is transferred to the inner bottom surface of the core pattern 12. The convex portion has an upper surface composed of an unetched (110) surface that originally constituted the surface of the silicon substrate 21, and both side surfaces have a smooth (111) surface that has appeared by etching. . Therefore, the inner surface of the core pattern 12 is formed by the (110) surface that is not roughened by the etching and the smooth (111) surface that appears by the etching, and the inner surface can be made smooth, and The occurrence of problems due to irregular reflection can be suppressed. For this reason, the inventors have adopted a method of forming a core pattern composed of convex portions on an original plate.
[0043]
After the above-mentioned original plate manufacturing process, the masking pattern 22a is removed from the surface of the original plate 21a in the masking removing step as shown in FIG. To remove the masking pattern 22a, the etching agent used in the above-described masking process is used. The masking removal step is performed in order to prevent the silicone rubber from sticking to the silicon oxide film forming the masking pattern 22a in the duplication step described later.
[0044]
In the duplication step, first, as shown in FIG. 4B, liquid silicone rubber is applied to the surface of the original plate 21a, and the silicone rubber is cured to form the duplication mold 24. Then, a second core pattern 24a composed of a concave portion is formed on the back surface of the duplication mold 24 so as to form a pattern shape that is opposite to the first core pattern 21b.
[0045]
The liquid silicone rubber includes a condensation reaction type and an addition reaction type, and any of them may be used. However, it is more preferable to use an addition reaction type silicone rubber. This is because the addition reaction type does not generate by-products at the time of curing and has a small volume shrinkage at the time of curing, so that the first core pattern 21b can be molded with more precise dimensional accuracy. That's why.
[0046]
Thereafter, in the duplication step, as shown in FIG. 5A, the duplication mold 24 is peeled off from the surface of the original plate 21a, and is arranged such that the second core pattern 24a is on the front side. In this state, an ultraviolet curable resin which is an active energy ray curable resin is applied to the surface of the replication mold 24, and a glass plate 26 is placed so as to be in contact with the ultraviolet curable resin.
[0047]
Thereafter, as indicated by the arrow in the figure, the glass plate 26 is pressed against the replication mold 24 and irradiated with ultraviolet rays as active energy rays from above the glass plate 26. Then, the ultraviolet curable resin is cured, and an embossing mold 27 including the stamper 25 and the glass plate 26 made of the ultraviolet curable resin is manufactured. A third core pattern 25a is formed on the back surface of the stamper 25. The third core pattern 25a has a pattern shape that is reversed from the second core pattern 24a, that is, a convex portion having the same pattern shape as the first core pattern 21b is duplicated. You.
[0048]
The effects exerted by the above embodiment will be described below.
The polymer optical waveguide of the embodiment is manufactured by forming the core pattern 12 on the clad base 11 using the embossing mold 27 and then forming the core 13 and the clad lid 14 in this order. The embossing mold 27 is a replica of an original plate 21a produced by an anisotropic wet etching method utilizing the properties of the (110) plane of the silicon substrate 21. For this reason, large-scale equipment is not required, the manufacturing operation is simple, and the operation can be completed in a short time. Therefore, the embossing mold 27 can be easily manufactured at low cost in a short time.
[0049]
In the anisotropic wet etching method, a strongly alkaline etching solution having a pH of 12 or more is used. The etching liquid has a strong etching ability for the silicon substrate 21 and an etching ability inferior to the silicon substrate 21 for the masking pattern 22a made of a silicon oxide film. Therefore, the exposed portion other than the masking pattern 22a on the surface of the silicon substrate 21 can be efficiently and promptly etched with precise dimensional accuracy.
[0050]
In the resist pattern forming step, a resist film 23 is formed from a positive or negative photoresist, and a resist pattern 23a having the same pattern shape as the first core pattern 21b is formed from the resist film 23. Therefore, the resist pattern 23a can be formed easily and quickly, and the time required for manufacturing the embossing mold 27 can be further reduced.
[0051]
A silicon oxide film is used for the coating film 22 that forms the masking pattern 22a, and dilute hydrofluoric acid or buffered hydrofluoric acid is used as an etching agent for etching the silicon oxide film. The diluted hydrofluoric acid or the buffered hydrofluoric acid hardly shows an etching ability for the silicon substrate 21 and has a strong etching ability for the silicon oxide film. Therefore, the masking pattern 22a can be formed with precise dimensional accuracy without affecting the surface of the silicon substrate 21.
[0052]
The stamper 25 of the embossing mold 27 is made of an ultraviolet curable resin which is an active energy ray curable resin. Further, the surface of the embossing mold 27 is formed of a glass plate 26, and is configured to transmit ultraviolet rays, which are active energy rays. Therefore, even if the glass plate 26 is placed in a state where the liquid ultraviolet curing resin is applied to the replication mold 24 in advance, the ultraviolet curing resin can be easily and quickly cured. In addition, work can be performed under a normal environment without using a special environment such as a heating atmosphere or a reduced pressure atmosphere, and the glass plate 26 can be pressed against the duplicate mold 24 even under the normal environment. Work can be done. Further, the stamper 25 fixed to the glass plate 26 can be easily separated from the duplicate mold 24 while reinforcing the stamper 25 with the glass plate 26. Therefore, workability during the production of the embossing mold 27 can be improved.
[0053]
The portion of the embossing mold 27 that is pressed when the heating embossing method is performed is formed of a glass plate 26 having a smooth surface. Therefore, the entire embossing mold 27 can be pressed with uniform pressure, and the core pattern 12 can be formed with precise dimensional accuracy.
[0054]
This embodiment can be embodied with the following modifications.
For example, as shown in FIG. 5B, a metal embossing mold 27 is formed by depositing a metal element such as nickel (Ni) on the surface of the replication mold 24 by an electroforming method or the like. May be. With this configuration, the strength and durability of the embossing mold 27 can be improved.
[0055]
The replication mold 24 is not necessarily formed of silicone rubber, but may be formed of a synthetic resin such as the above-described ultraviolet curable resin, thermoplastic resin, fluororesin, thermosetting resin, or a thermoplastic elastomer. Good. Alternatively, the duplicate mold 24 may be formed from a synthetic resin film, substrate, or the like by a heating embossing method using the original plate 21a as a mold.
[0056]
The embossing mold 27 does not necessarily need to be constituted by the stamper 25 and the glass plate 26, and may be constituted by the stamper 25 alone without the glass plate 26. In this case, it is preferable to increase the thickness of the stamper 25 so that the stamper 25 can be easily separated from the replication mold 24 and the stamper 25 can maintain a desired strength. Further, when used in the heating embossing method, it is preferable that the pressed surface of the stamper 25 be a smooth surface so that a uniform pressure can be applied to the entire embossing mold 27.
[0057]
The masking removal step is not always necessary, and is omitted if the replication mold 24 can be peeled off from the original plate 21a without any trouble by, for example, applying a release agent made of a fluororesin or the like to the surface of the original plate 21a. May be.
[0058]
The coating film 22 is not limited to being formed of a silicon oxide film, but may be formed of, for example, a nitride film.
The diameter of the core 13 is not limited to 100 μm, but may be changed to a desired size by changing the width of the masking pattern 22a of the original plate 21a and the etching conditions when performing the anisotropic wet etching method. You may.
[0059]
The clad lid 14 may be formed of any synthetic resin as long as the synthetic resin has a lower refractive index than the synthetic resin used for the core 13 and has a refractive index similar to that of the clad base 11. For example, the clad base 11 may be formed of a thermoplastic synthetic resin, and the clad lid 14 may be formed of an ultraviolet curable resin. Alternatively, the clad lid 14 may be formed of a thermosetting resin such as polyimide. The clad lid 14 does not necessarily have to have the same form as the clad base 11 made of a film, a substrate, or the like. The coating may be applied to the surface of the clad base 11 and cured by a method such as a coating method.
[0060]
Further, technical ideas that can be grasped from the embodiment will be described below.
(1) The masking method according to any one of claims 1 to 5, further comprising a masking removing step for removing a coating film remaining from a surface of the manufactured original sheet, between the original sheet manufacturing step and the duplication step. A method for producing a polymer optical waveguide. With this configuration, it is possible to prevent the coating film and the replica mold from being firmly joined.
[0061]
(2) A polymer optical waveguide manufactured by the manufacturing method according to any one of claims 1 to 5, which is made of a transparent synthetic resin, and has a concave core pattern formed on its surface. A clad base, a core made of a transparent synthetic resin having a higher refractive index than the synthetic resin, a core formed in the core pattern of the clad base, and a synthetic resin having a lower refractive index than the synthetic resin forming the core. And a clad lid formed so as to cover an exposed portion of the core on the surface of the clad base, and a core diameter of 3 to 1000 μm. With this configuration, a polymer optical waveguide having a large core diameter can be obtained at low cost.
[0062]
(3) The polymer photoconductor according to (2), wherein the inner surface of the core pattern in the clad base has an arithmetic average roughness (Ra) specified in JIS B0601-1994 of less than 0.1 μm. Wave path. With this configuration, irregular reflection of light waves in the core can be suppressed, and the resulting polymer optical waveguide can be of high quality.
[0063]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
According to the first aspect of the present invention, the embossing mold can be easily manufactured at low cost in a short time.
[0064]
According to the second aspect, in addition to the effects of the first aspect, the core pattern of the original plate can be formed with precise dimensional accuracy.
According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, a resist pattern can be formed easily and quickly, and the manufacturing time of the embossing mold is further reduced. Can be achieved.
[0065]
According to the invention described in claim 4, in addition to the effects of the invention described in any one of claims 1 to 3, the masking pattern is formed with precise dimensional accuracy without affecting the silicon substrate. Can be.
[0066]
According to the invention set forth in claim 5, in addition to the effects of the invention set forth in any one of claims 1 to 4, workability during the production of the embossing mold can be improved.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view showing a clad base in a state where a core is formed in a core pattern, and FIG. 1B is a cross-sectional view showing a polymer optical waveguide according to an embodiment.
2A is a cross-sectional view showing a state in which a coating film and a resist film are formed on a surface of a silicon substrate, and FIG. 2B is a cross-sectional view showing a state in which a resist pattern is formed on the surface of the coating film; .
FIG. 3A is a cross-sectional view showing a state in which a masking pattern is formed by etching a coating film, and FIG. 3B is a cross-sectional view showing a state in which a silicon substrate is etched to form an original plate.
FIG. 4A is a cross-sectional view showing a state in which a masking pattern has been removed from the surface of an original plate, and FIG. 4B is a cross-sectional view showing a state in which a duplicate mold has been formed on the surface of the original plate.
FIG. 5A is a cross-sectional view showing a state in which an embossing mold is formed on the surface of a duplicate mold, and FIG. 5B shows a state in which another form of embossing mold is formed on the surface of the duplicate mold. Sectional view.
6A is a cross-sectional view showing a state in which a clad base is formed using an embossing mold, and FIG. 6B is a cross-sectional view showing the formed clad base.
[Explanation of symbols]
11: clad base, 12: core pattern provided on clad base, 13: core, 14: clad lid, 21: silicon substrate, 21a: original plate, 21b: first core pattern provided on original plate, 22: coated Covering film, 22a: masking pattern, 23: resist film, 23a: resist pattern, 24: copy mold, 25a: third core pattern provided on the embossing mold, 27: embossing mold.

Claims (5)

Forming a resist pattern on the surface of the silicon substrate by masking the surface with a coating film, and then forming a resist pattern on the surface of the silicon film with a resist film;
A masking pattern forming step of etching a coating film other than the resist pattern and forming a masking pattern by the coating film on the surface of the silicon substrate;
An original plate manufacturing process of manufacturing an original plate having a core pattern formed of convex portions on the surface by etching the surface of the silicon substrate on which the masking pattern is formed by an anisotropic wet etching method,
After molding the core pattern of the original plate on the surface of the duplication mold, using this duplicate mold, a duplication step of duplicating the core pattern composed of the same protrusions as the core pattern of the original plate on the surface of the embossing mold,
By a heating embossing method using the same embossing mold, after forming a clad base having a concave core pattern formed on the surface, a core is formed in the concave portion, and thereafter, the exposed portion of the core is covered. Forming a clad lid on the surface of the clad base as described above. In the original plate manufacturing process, the anisotropic wet etching method is performed by immersing a silicon substrate having a masking pattern formed on its surface in an etching solution, and a strong alkaline solution having a pH of 12 or more is used as the etching solution. The method for manufacturing a polymer optical waveguide according to claim 1, wherein In the resist pattern forming step, a positive or negative photoresist is applied to the surface of the coating film to form a resist film, and the resist film is irradiated with active energy rays to expose the positive or negative photoresist. After drawing the resist pattern and developing, the resist pattern is removed by removing the exposed portion of the resist film in the case of a positive photoresist or the unexposed portion of the resist film in the case of a negative photoresist. The method for producing a polymer optical waveguide according to claim 1, wherein the polymer optical waveguide is formed. The silicon oxide film formed by oxidizing the surface of a silicon substrate, wherein the silicon oxide film is etched using dilute hydrofluoric acid or buffered hydrofluoric acid in the masking pattern forming step. Item 4. The method for producing a polymer optical waveguide according to any one of Items 3. In the replication step, a liquid silicone rubber is applied to the surface of the original plate, and the silicone rubber is cured and peeled from the surface of the original plate, thereby forming a core pattern composed of the convex portions of the original plate and a core pattern composed of the corresponding concave portions. After forming the replica having the surface, the concave portion of the replica is filled with a liquid active energy ray-curable resin, and the active energy ray-curable resin is cured by irradiating the active energy ray, and then the replica mold is The polymer optical waveguide according to any one of claims 1 to 4, wherein an embossing mold made of the active energy ray-curable resin is formed by peeling off the cured active energy ray-curable resin from the surface. Method.

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