JP2001318257A - Method for producing polymeric optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an optical waveguide which includes a step, in which a formed polymer can be released easily so as to easily mass-produce polymeric optical waveguides at a low cost. SOLUTION: In the method for producing a polymeric optical waveguide, a die formed with a sacrificial layer for releasing a polymer from a substrate formed on the substrate with a rugged surface for the core part of the optical waveguide is manufactured and coated with a molten or dissolved polymer for the core, and the polymer is cured under UV or heat and coated with a molten or dissolved polymer for the lower clad. After curing, the die is released by removing the sacrificial layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polymer optical waveguide, and more particularly to a method for manufacturing an optical component such as an optical integrated circuit, an optical interconnection, or an optical multiplexing / demultiplexing.

[0002]

2. Description of the Related Art As an optical component or a base material of an optical fiber, inorganic materials such as quartz glass and multi-component glass having characteristics of small light propagation loss and a wide transmission band are widely used. Recently, a polymer-based material has also been developed, and has been attracting attention as a material for an optical waveguide because it is superior in workability and price as compared with an inorganic material. For example, a flat plate type having a core-cladding structure in which a polymer having excellent transparency such as polymethyl methacrylate (PMMA) or polystyrene is used as a core and a polymer having a lower refractive index than the core material is used as a cladding material. An optical waveguide has been manufactured (Japanese Patent Laid-Open No. 3-188402). On the other hand, Matsuura et al. Have realized a low-loss planar optical waveguide using polyimide which is a transparent polymer having high heat resistance (Japanese Patent Laid-Open No. 2-110500). However, in any of these methods, when forming the core structure on the surface of the cladding layer, formation of a core pattern using a photoresist for each sheet, and subsequent concavo-convex processing such as reactive ion etching are performed. It is necessary, and there were problems in terms of mass productivity and cost reduction. Therefore, mass production is improved by a method in which a mold whose surface is roughened on the core pattern of the waveguide is pressed against the polymer in the molten or solution state, and the polymer is cured as it is and the unevenness is transferred to the polymer surface. Considerations are being made to try. The mold used here is generally manufactured by metal plating. In the field of large-capacity storage such as compact discs, CD-ROMs and optical discs, using a mold made by plating, injection molding is used to form irregularities with a width of about 1 μm and a depth of about 0.1 μm with extremely high surface accuracy. Formed on the surface of a transparent substrate as bit information and guide grooves. Generally, this plating mold is used for a material having a relatively low glass transition temperature, such as polycarbonate, and a mold release material is mixed into a molding raw material so that the plating layer and the polymer are easily separated. In many cases, release processing cannot be performed on transparent polymer resins, and such polymer resins are pressed against a metal plating such as nickel having desired irregularities in a molten state or a solution state, and the polymer resin is left as it is. When cured, it is often difficult to peel off between the mold and the polymer resin.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an optical waveguide using a mold for duplicating a core shape, which is used to mass-produce a low-loss and highly reliable polymer optical waveguide at low cost and simply. To provide. For this purpose, a problem is to remove polymers having various film thicknesses without leaving any foreign matter.

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have solved the above-mentioned problems by immersing a polymer resin applied on a mold in a liquid, removing the sacrificial layer, and peeling the polymer resin from the mold. And completed the present invention.

That is, the present invention provides: (1) a mold in which a sacrificial layer for peeling off a polymer and a substrate is formed on a substrate on which an uneven shape serving as a core of an optical waveguide is formed; After applying a polymer that becomes a core in a state or a solution state, and curing the polymer by ultraviolet light or heat, further apply a polymer that becomes a lower clad in a molten state or a solution state from above, and cure, A method of manufacturing a ridge-type polymer optical waveguide, comprising the step of removing the mold by removing the sacrificial layer thereafter (2) The substrate is a polymer, and the sacrificial layer is etched away. (3) The ridge type polymer optical waveguide according to (1), wherein the sacrificial layer is a silica glass layer, and the sacrificial layer is removed by etching. Optical waveguide The method of production. (4) The method for manufacturing a ridge-type polymer optical waveguide according to (3), wherein the substrate is a silicon wafer, and the sacrificial layer is silica glass obtained by thermally oxidizing the silicon wafer. (5) A method of manufacturing a buried polymer optical waveguide, comprising forming a polymer serving as an upper clad on the ridge-type polymer optical waveguide described in (1) to (4).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The substrate on which the concavo-convex shape serving as the core portion of the optical waveguide is formed can be plated or plasma-coated on a substrate surface of silicon, glass, aluminum, stainless steel, polyimide, or the like, or a substrate surface coated with a polymer on those substrates. The concave and convex shape that becomes the core of the optical waveguide is processed by a method such as etching, chemical etching, or laser ablation.

Hereinafter, a method for manufacturing a mold in which the surface of a polyimide film of a substrate is processed to have irregularities will be described. A polyamic acid solution, which is a precursor of polyimide, is applied on the substrate 0 by a method such as spin coating, and is heated and imidized to obtain a polyimide layer 1 on the substrate. As the solvent used for the polyamic acid solution, N-methyl-2-pyrrolidone,
N, N-dimethylacetamide, methylsulfoxide,
A polar organic solvent such as dimethylformamide is used. Next, a mask layer 2 for forming an optical circuit pattern is formed thereon. As the mask, a metal such as aluminum or titanium, silicon oxide, spin-on-glass (SOG), a silicon-containing resist, photosensitive polyimide, or the like can be used. After forming the mask layer, perform photoresist coating, pre-baking, exposure, development, after-baking,
A patterned resist layer 3 is obtained. Next, portions of the mask layer that are not protected by the resist layer are removed by reactive ion etching, an etchant, or the like to form a desired waveguide pattern. When a silicon-containing resist or photosensitive polyimide is used as the mask layer 2, it is not necessary to use a photoresist.

Next, after only the exposed portion of the polyimide is etched to a predetermined depth by reactive ion etching, the remaining mask layer 2 is removed by reactive ion etching or using a stripping solution. Sacrificial layer 4 on top
Aluminum, copper, or the like is formed by a vapor deposition method, a sputtering method, a plating method, or the like. In this way, a desired mold is obtained. When a silica glass layer is used as a sacrificial layer on a substrate having irregularities, a silica glass layer is formed on the substrate having irregularities by about 10 nm by a vapor deposition method, a sputtering method, or the like.
It is formed thick. In this way, a desired mold is obtained.

A method for forming a sacrifice layer of a silica glass layer by thermal oxidation on a silicon wafer whose surface is unevenly processed will be described. Using a plasma etching technique or a chemical etching technique which has matured a silicon wafer as a semiconductor LSI technique, irregularities corresponding to the core pattern are formed. The silicon wafer is thermally oxidized to form silica glass. In this way, a desired mold for producing a polymer optical waveguide can be produced. Next, using the thus obtained mold for producing a polymer optical waveguide,
An optical waveguide manufacturing method will be described. Here, a description will be given by taking as an example the production of a polyimide optical waveguide using a polyamic acid solution which is a precursor of polyimide.However, the production is performed using a resin solution of an optical material other than the polyamic acid solution as an optical waveguide material. Of course, it is possible. In FIG. 2, an example of a process for manufacturing an optical waveguide using a mold is shown as a process diagram. 2, reference numeral 11 denotes a mold, 12 denotes a core layer, 13 denotes a lower cladding layer, and 14 denotes an upper cladding layer. First, a first polyamic acid solution is applied on the obtained polymer optical waveguide mold 11 by a method such as spin coating, and is heated and imidized to form a polyimide core layer in a concave portion of the mold. Embed 12 Next, the lower clad layer 13 is formed by applying a second polyamic acid solution thereon by spin coating or the like, and heating and imidizing the second polyamic acid solution. Next, the polymer is peeled from the mold by immersing the mold in a liquid and removing the sacrificial layer. Thus, a ridge type polymer optical waveguide can be manufactured.

A second polyamic acid solution, which is a polyimide precursor to be the upper clad layer 14, is applied thereon by spin coating or the like, with the surface that was in contact with the mold facing up. Is heated and imidized. In this manner, a buried polymer optical waveguide can be manufactured using the polymer optical waveguide mold.

[0011]

EXAMPLES The present invention will be described in more detail with reference to several examples. It is apparent that an unlimited number of polymer optical waveguides of the present invention can be obtained by using solutions of various polymers having different molecular structures. Therefore, the present invention is not limited to only these examples.

Example 1 Pyromellitic dianhydride (P) was deposited on a 4-inch silicon substrate.
A solution of MDA) and 4,4′-oxydianiline (ODA) in a polyamic acid at 15 wt% N, N-dimethylacetamide (DMAc) was heated and spin-coated so that the film thickness became 30 μm. The polyimide film was formed by heat imidization. A silicon-containing resist layer having a thickness of 1.5 μm was applied thereon, and then prebaked at about 90 ° C. Next, contact exposure was performed using a photomask in which 40 linear optical waveguide patterns having a line width of 6 μm and a length of 10 cm were drawn at intervals of 100 μm, and then the exposed portions of the photoresist were developed and removed using a developing solution. Thereafter, post baking was performed at 90 ° C. Using the patterned resist layer as a mask, the polyimide film was etched to a depth of 6 μm from the film surface by oxygen reactive ion etching. Next, the resist layer remaining on the polyimide was removed with a stripper. Aluminum having a thickness of 50 nm was vacuum-deposited thereon as a sacrificial layer. By observing the surface irregularities by SEM, a groove having a width of 6 μm and a depth of 6 μm was confirmed, and a mold having a desired shape could be produced.

Next, 2,2-bis (3,4) to be a core layer
-Dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 15 wt% of polyamic acid of ODA
The DMAc solution was applied to the concave portions of the mold by spin coating or the like, and embedded by heat imidization. Furthermore, a 15 wt% DMAc solution of 6FDA and 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl (TFDB), which is to be a cladding layer, in DMAc is printed thereon to a thickness of 0.1 mm after heating. This was applied by a method, and this was heated and imidized. Thereafter, the polyimide laminated film was peeled from the mold by immersing in a 10% hydrochloric acid aqueous solution. Finally, a 15 wt% DMAc solution of polyamic acid of 6FDA and TFDB serving as an upper cladding layer is applied by a method such as spin coating with the surface that has been in contact with the mold facing up, and is heated and imidized. In this way,
A buried optical waveguide was produced.

Comparative Example 1 A photoresist was applied on a glass substrate to a thickness of 0.1 μm, exposed to a laser beam, developed, and nickel-plated on the uneven surface obtained by development to form a plating layer. By peeling, the irregularities were transferred to nickel plating to produce a mold. Next, a polyamic acid solution of 6FDA and ODA was coated on the concave portion of the mold, imidized by heating, and embedded. Further, from above, a polyamic acid solution of 6FDA and TFDB was spin-coated to a thickness of 0.1 mm and imidized by heating. At that time, the coated polyimide film could not be peeled from the mold.

EXAMPLE 2 A 15 wt% DMAc solution of polyamic acid of PMDA and ODA was heated on a 4-inch silicon substrate to a thickness of 30 μm.
Was applied by a spin coating method. This is 7
2 hours at 0 ° C, 1 hour at 160 ° C, 30 minutes at 250 ° C,
Heat treatment was performed at 350 ° C. for 1 hour to form a polyimide film. A silicon-containing resist layer having a thickness of 1.5 μm was applied thereon, and then prebaked at about 90 ° C. Next, a linear optical waveguide pattern having a line width of 6 μm and a length of 10 cm
After contact exposure was performed using a 40 photomask drawn at 0 μm intervals, the exposed portion of the photoresist was developed and removed using a developing solution. Thereafter, post baking was performed at 90 ° C. Using the patterned resist layer as a mask, the polyimide film was etched to a depth of 6 μm from the film surface by oxygen reactive ion etching. Next, the resist layer remaining on the polyimide was removed with a stripper.
A 10-nm-thick silica glass was deposited thereon by electron beam evaporation. Observing the surface irregularities by SEM,
Formation of a groove having a width of 6 μm and a depth of 6 μm was confirmed, and a mold having a desired shape could be produced.

Next, a 15 wt% DMAc solution of polyamic acid of 6FDA and ODA to be a core layer was applied to a mold recess by spin coating or the like, and embedded by heating to imidization. Furthermore, a polyamide acid 15 wt% DMAc of 6FDA and TFDB to be a cladding layer thereon
After heating, the solution was applied by a printing method so as to have a thickness of 0.7 mm, and this was heated and imidized. Thereafter, the polyimide laminated film was peeled from the mold by dipping in a 2% hydrofluoric acid aqueous solution. Finally, a 15 wt% DMAc solution of polyamic acid of 6FDA and TFDB serving as an upper cladding layer is applied by a method such as spin coating with the surface that has been in contact with the mold facing up, and is heated and imidized. Thus, a buried optical waveguide was manufactured.

Comparative Example 2 A photoresist was applied on a glass substrate so as to have a thickness of 0.1 μm, exposed to a laser beam, developed, and nickel-plated on an uneven surface obtained by development. By peeling, the irregularities were transferred to nickel plating to produce a mold. Next, a polyamic acid solution of 6FDA and ODA was coated on the concave portion of the mold, imidized by heating, and embedded. Further, a polyamic acid solution of 6FDA and TFDB was spin-coated thereon to a thickness of 0.7 mm and imidized by heating. At that time, the coated polyimide film could not be peeled from the mold.

Example 3 A 4-inch silicon wafer having a 6 μm wide ridge and a 6 μm high ridge formed by plasma etching was thermally oxidized to form silica glass with a thickness of 10 nm, thereby preparing a mold for a polymer optical waveguide. Next, 6FDA and O serving as a core layer
A 15 wt% DMAc solution of DA polyamic acid was applied to the mold recesses by spin coating or the like, and embedded by heating to imidization. Furthermore, about 15 wt.% Of polyamic acid of 6FDA and TFDB to be a cladding layer thereon.
After heating, a% DMAc solution was applied by a printing method so as to have a thickness of 0.2 mm, and this was heated and imidized. Thereafter, the polyimide laminated film was peeled from the mold by dipping in a 2% hydrofluoric acid aqueous solution. 6FDA and TFDB to be the upper clad layer with the surface that was the contact surface with the mold last
A 15 wt% DMAc solution of polyamic acid is applied by a method such as spin coating, and this is heated and imidized. Thus, a buried optical waveguide was manufactured.

Comparative Example 3 A photoresist was applied on a glass substrate so as to have a thickness of 0.1 μm, exposed to a laser beam, developed, and nickel-plated on an uneven surface obtained by development. By peeling, the irregularities were transferred to nickel plating to produce a mold. Next, a polyamic acid solution of 6FDA and ODA was coated on the concave portion of the mold, imidized by heating, and embedded. Further, a polyamic acid solution of 6FDA and TFDB was spin-coated thereon to a thickness of 0.2 mm and imidized by heating. At that time, the coated polyimide film could not be peeled from the mold.

[0020]

According to the method for producing a polymer optical waveguide of the present invention, a mold and a polymer film can be easily separated from each other, and polymer optical waveguides having various thicknesses can be mass-produced.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an example of a process for producing a polymer mold.

FIG. 2 is a process chart showing an example of a process for producing an optical waveguide using a mold.

[Explanation of symbols]

0: substrate, 1: polyimide layer, 2: mask layer, 3: resist layer, 4: sacrificial layer 11: mold, 12: core layer, 13: lower cladding layer, 1
4: Upper cladding layer

Claims (5)

[Claims] 1. A mold in which a sacrificial layer for separating a polymer and a substrate is formed on a substrate having an uneven shape serving as a core portion of an optical waveguide, and a core in a molten state or a solution state is formed. After applying the polymer to be cured, the polymer is cured by ultraviolet light or heat, and then a polymer to be a lower clad in a molten state or a solution state is further applied and cured, and then the sacrificial layer is removed. A method for manufacturing a ridge-type polymer optical waveguide, comprising a step of removing a mold by the method. 2. The method according to claim 1, wherein the substrate is a polymer, and the sacrificial layer is removed by etching. 3. The method according to claim 1, wherein the sacrificial layer is a silica glass layer, and the sacrificial layer is removed by etching. 4. The method according to claim 3, wherein the substrate is a silicon wafer, and the sacrificial layer is a silica glass obtained by thermally oxidizing the silicon wafer. 5. A method for manufacturing a buried polymer optical waveguide, comprising forming a polymer serving as an upper clad on the ridge-type polymer optical waveguide according to claim 1.