JP2002071989A - Method for manufacturing optical waveguide device and optical waveguide device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a resin optical waveguide device having a branched part and hardly produces air bubbles in the branched part, and to provide an optical waveguide device. SOLUTION: The method of manufacturing an optical waveguide device has the following processes. The processes are a first process of forming a first resin film on a substrate having a lower clad layer, a second process of patterning the first resin film into a core layer in the form of an optical waveguide, a third process of applying a solution of a second resin material to cover the core layer to form the film of the material solution so that the thickness of the film after dried from the upper face of the lower clad layer is 3.5 to 10 times the thickness of the core layer, and a fourth process of removing the second resin film so that the thickness of the second resin film from the upper face of the lower clad layer is <3.5 times the thickness of the core layer and that the remaining second resin film acts as the upper clad layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical waveguide device and an optical waveguide device obtained by the method, and more particularly to an optical waveguide having an upper clad made of resin.

[0002]

2. Description of the Related Art With the spread of personal computers and the Internet in recent years, the demand for information transmission has rapidly increased. For this reason, it is desired that optical transmission with a high transmission speed be spread to terminal information processing devices such as personal computers. To achieve this, it is necessary to manufacture high-performance optical waveguides for optical interconnection at low cost and in large quantities.

As materials for optical waveguides, inorganic materials such as glass and semiconductor materials and resins are known. When an optical waveguide is manufactured from an inorganic material, a method is used in which an inorganic material film is formed by a film forming apparatus such as a vacuum evaporation apparatus or a sputtering apparatus, and the inorganic film is etched into a desired waveguide shape. . However, the vacuum evaporation apparatus and the sputtering apparatus require large-scale evacuation equipment, and are therefore large and expensive. In addition, since the evacuation step is required, the step becomes complicated. On the other hand, when an optical waveguide is manufactured using a resin, the film forming process can be performed at atmospheric pressure by coating and heating, and thus there is an advantage that the apparatus and the process are simple.

Various resins are known as resins constituting the optical waveguide and the cladding layer. Polyimides having a high glass transition temperature (Tg) and excellent heat resistance are particularly expected. When the optical waveguide and cladding layer are formed of polyimide, long-term reliability can be expected,
It can withstand soldering.

[0005]

As described above, by manufacturing an optical waveguide and a cladding layer with a resin,
Although an optical waveguide can be manufactured by a simple manufacturing process,
In a portion where the distance between two or more optical waveguides is very small, such as a branch portion of a Y-branch optical waveguide, bubbles may be generated at the boundary between the optical waveguide and the upper cladding layer or inside the upper cladding layer. When such bubbles are generated, the propagation efficiency of the optical waveguide is adversely affected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a resin optical waveguide device having a branch portion, which is less likely to generate bubbles at the branch portion, and an optical waveguide device obtained by the method. .

[0007]

In order to achieve the above object, according to the present invention, the following optical waveguide is provided. That is, the first substrate is provided on the substrate having the lower cladding layer.
A first step of forming the first resin film, a second step of patterning the first resin film into a core layer in an optical waveguide shape, and a material solution of a second resin so as to cover the core layer. A third step of forming a film of the material solution so as to have a thickness of 3.5 to 10 times the thickness of the core layer from the upper surface of the lower clad layer after drying, A fourth step of removing the core layer so that the thickness is less than 3.5 times the thickness of the core layer and using the second resin film as an upper clad layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described with reference to the drawings.

The configuration of the optical waveguide device 100 will be described with reference to FIGS. The optical waveguide device 100 includes an optical waveguide laminate 10 on a silicon wafer substrate 1,
The electrode portion 7 is formed in a region where the optical waveguide laminate 10 is not arranged.
Etc. are arranged.

The optical waveguide laminate 10 comprises a lower cladding layer 3 disposed on a silicon wafer substrate 1, a Y-branched ridge type optical waveguide 4 mounted thereon, and an upper cladding layer in which the optical waveguide 4 is embedded. It includes a layer 5 and a protective layer 9.

Lower clad layer 3 and upper clad layer 5
Are all OPI-N10 manufactured by Hitachi Chemical Co., Ltd.
05 (trade name). The thickness of the lower cladding layer 3 is about 6 μm, and the thickness of the upper cladding layer 5 is about 12 μm from the surface of the lower cladding layer 3.
m. The optical waveguide 4 is an OP manufactured by Hitachi Chemical Co., Ltd.
It is made of a polyimide film formed using IN-N3205 (trade name), the thickness is about 6 μm, and the width of the optical waveguide 4 is about 6 μm. The protective layer 9 is a polyimide film formed using PIX-6400 (trade name) manufactured by Hitachi Chemical DuPont Microsystems Co., Ltd. The film thickness is about 5 μm at an end portion away from the optical waveguide 4. . The electrode unit 7 is an electrode for mounting a light emitting element and a light receiving element.

The optical waveguide 4 shown in FIGS. 1, 2 and 5 is an optical waveguide 4a and an optical waveguide 4 which is obtained by branching the optical waveguide 4a in two directions.
5 shows a Y-branch optical waveguide composed of b and 4c. Optical waveguide 4
The width of a is about 6 μm.

Next, a method of manufacturing the optical waveguide device according to the present embodiment will be described with reference to FIGS. First, the entire upper surface (FIG. 1 (1)) of the Si substrate 1 is
The aforementioned OPI-N1005 is spin-coated to form a material solution film. Thereafter, the solvent is evaporated by heating at 100 ° C. for 30 minutes and then at 200 ° C. for 30 minutes, and then cured by heating at 370 ° C. for 60 minutes to form the lower cladding layer 3 (FIG. 1 (2)).

On the lower cladding layer 3, the above-mentioned OP
A material solution film is formed by spin coating I-N3205. Then, it was dried at 100 ° C. for 30 minutes,
The solvent is evaporated by heating at 0 ° C. for 30 minutes, and then cured by heating at 350 ° C. for 60 minutes to form a polyimide film to be the optical waveguide 4. A resist is spin-coated on the polyimide layer, dried, exposed to a mercury lamp, and developed to form a resist pattern layer. This resist pattern layer is used as a mask for processing the aforementioned polyimide film into the shape of the Y-branch optical waveguide 4 (FIG. 1 (4)). Using the resist pattern layer as a mask, the above-mentioned polyimide layer is reactive ion-etched (O ₂ -R1E) with oxygen to obtain a branched optical waveguide 4 (FIG. 1).
(5)). Thereafter, the resist pattern layer is peeled off (FIG. 1 (6)).

Next, an OPI-based material solution of the second resin is formed so as to cover the optical waveguide 4 and the lower clad layer 3.
N1005 is spin-coated. At this time, a film of the material solution is formed such that the thickness of the material solution from the upper surface of the lower clad layer becomes 3.5 to 10 times the thickness of the core layer after the material solution of the second resin is dried. After drying the material solution of the second resin, the thickness of the core layer is 3.5 to 8 from the upper surface of the lower clad layer.
Preferably, it is twice, more preferably four to six times. If it is less than 3.5 times, the effect of removing bubbles is poor, and if it exceeds 10 times, it takes time in the subsequent step of removing the second resin film in the subsequent step. Then, 30 minutes at 100 ℃ in a dryer,
Next, the material solution film is heated at 200 ° C. for 30 minutes to evaporate the solvent, and heated at 350 ° C. for 60 minutes to form a second resin film of a polyimide film (FIG. 2 (7)).

Further, the second resin film of the polyimide film is removed from the upper surface of the lower clad layer so as to be less than 3.5 times the thickness of the core layer, and the second resin film is used as the upper clad layer 5.

The means for removing the second resin film so as to have a thickness of less than 3.5 times the thickness of the core layer is preferably dry etching. The dry etching includes plasma etching, reactive ion etching, and reactive sputtering. Etching, ion beam etching and the like are mentioned, and reactive ion etching is preferable because anisotropic etching is possible. These are controlled under conditions suitable for the purpose, such as gas composition, pressure, temperature, frequency, and output, as control factors.

The means for removing the second resin film so as to have a thickness of less than 3.5 times the thickness of the core layer may preferably use an abrasive. As the abrasive, colloidal silica, barium carbonate, iron oxide, calcium carbonate, silica, cerium oxide, diamond, or the like is used, and mechanical polishing or mechanochemical polishing is used. Although this method is preferable because the surface is uniformly polished, it is preferable to prevent polishing scratches.

The means for removing the second resin film so as to have a thickness of less than 3.5 times the thickness of the core layer may preferably employ wet etching. Wet etching uses a liquid phase,
This is etching using a chemical reaction. Acids such as hydrogen fluoride, alkali hydroxides, alkalis such as ethylenediamine, oxidizing agents such as potassium permanganate are used, immersion, running water, spray, jet, electrolysis, etc. Control factors include pH, viscosity, temperature, stirring conditions, treatment time, treated area, and the like. In the present invention, since a polyimide resin is used, potassium hydroxide, sodium hydroxide aqueous solution, hydrazine and isopropyl alcohol mixed solution, ethylenediamine and pyrocatechol mixed aqueous solution, and the like can be used after being heated.

Further, on the upper surface of the upper cladding layer 5, a PI
X-6400 is spin-coated and dried in a dryer at 100 ° C. for 30 minutes.
After heating at 200 ° C. for 30 minutes to evaporate the solvent, and subsequently heating at 350 ° C. for 60 minutes, a protective layer 9 of a 5 μm thick polyimide film having a substantially flat upper surface is obtained.

Next, the laminated film of the protective layer 9, the upper clad layer 5, the optical waveguide 4, and the lower clad layer 3 is cut in the thickness direction by dicing to form a protective layer formed in the region of the electrode portion. 9 to the lower cladding layer 3 are peeled off from the substrate 1 and removed. Thereby, the optical waveguide laminate 10 becomes a part of the shape shown in FIG. 2, and in the region of the electrode portion 7 on the substrate 1, the electrode portion 7 and the Si substrate 1 are exposed.

A metal alloy layer having a desired shape may be formed on the exposed electrode. Thereafter, the wafer-shaped substrate 1 is cut out by dicing, and the side surface is polished to complete the optical waveguide device 100.

The branch portion of the optical waveguide 4 of the optical waveguide device 100 manufactured by such a manufacturing method is observed with a microscope, and it is determined whether or not bubbles are contained in the gap between the optical waveguide 4b and the optical waveguide 4c (see FIG. 5). Was inspected. At this time, after drying the material solution of the second resin so as to cover the core layer, the thickness of the film was changed from the upper surface of the lower clad layer based on the thickness of the core layer. As a result, as shown in FIG. 4, the non-bubble optical waveguide device has a non-defective bubble rate (a large number of optical waveguides are formed on one wafer substrate, and bubbles are generated in the Y branch portion therein). The percentage varies with the percentage of the optical waveguide not formed) and the thickness of the second resin film formed on the upper surface of the lower clad layer. The thicker the thickness, the better the result. When the thickness of the second resin film is 3.5 to 10 times, more preferably 4 to 6 times the thickness of the core layer, it is possible to manufacture an optical waveguide free from bubbles of about 60% or more. it can.

As shown in FIG. 5, the bubble 51 mainly occurs in a portion from the root 52 of the branch portion to about 50 μm ahead, and the gap between the optical waveguide 4b and the optical waveguide 4c is It is presumed that the dead end at the root 52 caused the material solution of the upper cladding layer 5 not to sufficiently enter and the embedding became incomplete.

Further, the optical waveguide device of the present embodiment has a high Tg and excellent heat resistance because all layers from the lower cladding layer 3 to the protective layer 9 are formed of polyimide. Therefore, the optical waveguide device of the present embodiment can maintain the propagation characteristics even at a high temperature. Further, since polyimide can withstand a high-temperature process such as soldering, it is possible to solder another optical waveguide device, an electric circuit element, or a light emitting / receiving element on the optical waveguide device.

In the above-described embodiment, the layers from the lower cladding layer 3 to the protective layer 9 are formed by a polyimide film.
It can also be formed of an inorganic material such as O ₂ . When the protective layer 9 is formed as an inorganic film, the protective layer 9 is formed by CVD.
It can be formed by a known film formation method such as a deposition method or a vapor deposition method. Also, it can be formed by a solution coating method like SOG.

(Embodiment 2) Next, a method of manufacturing an optical waveguide device according to a second embodiment of the present invention will be described. In the second embodiment, bubbles are reduced by improving the wettability when applying the material solution of the upper cladding layer 5.

The configuration of the optical waveguide device manufactured in this embodiment is the same as that of the optical waveguide device 100 of the first embodiment.
Since the same configuration and the same material are used, the description of the configuration is omitted. A method for manufacturing the optical waveguide device according to the present embodiment will be described. 1 (1) to 1 (6), the optical waveguide 4 is formed on the substrate 1 in the same manner as in the first embodiment.
To form

Next, in the present embodiment, before the step of forming the upper cladding layer 5, a process for improving the wettability of the upper cladding layer 5 with respect to the material solution is performed on the upper surface of the lower cladding layer 3 and the light guide. This is performed on the side surface and the upper surface of the wave path 4. This process is a process of applying a solvent used for a material solution of the upper cladding layer 5 or a solvent for lowering the surface tension to the upper surface including the upper surface of the lower cladding layer 3 and the side surfaces of the optical waveguide 4. Here, N, N-dimethylacetamide as a solvent used for the material solution of the upper cladding layer 5 is applied. The application method is spin coating,
A dip method (immersion in a solvent), a Wheeler method (spray of a solvent), or the like can be used. Also, instead of coating,
By disposing the substrate 1 in a container filled with the solvent vapor, a method of attaching the solvent vapor to the surface of the substrate 1 to be processed can be used. In addition, in order to fill the vapor in the container, a method of reducing the pressure in the container or heating the solvent can be used, if necessary, in consideration of the vapor pressure of the solvent.

While the optical waveguide 4 and the lower clad layer 3 coated with the solvent or treated with the solvent vapor are kept wet with the solvent, the OPI-
N1005 is spin-coated. As a result, the material solution of the upper cladding layer 5 covers the optical waveguide 4 and spreads to all corners of the lower cladding layer 3. Therefore, the OPI is provided up to the gap between the optical waveguide 4b and the optical waveguide 4c at the branch portion of the optical waveguide 4.
-N1005 can be embedded. In addition, since the wettability is high, bubbles are hardly entrained. Thereafter, the solvent of the material solution film is evaporated by heating at 100 ° C. for 30 minutes and then at 200 ° C. for 30 minutes, and heated at 350 ° C. for 60 minutes to form the upper clad layer 5 of the polyimide film ( FIG. 1 (7)).

Subsequent steps complete the optical waveguide device in the same manner as in the manufacturing method of the first embodiment.

In the present embodiment, the material solution of the upper cladding layer 5 is applied after the treatment for improving the wettability of the upper surfaces of the lower cladding layer 3 and the optical waveguide 4 is performed.
Embedding failure is less likely to occur at the branch portion of the branched optical waveguide 4, and bubbles are less likely to be involved when the material solution spreads. Thereby, generation of bubbles in the upper cladding layer 5 can be reduced.

In the above-described wettability improving step, the material solution of the upper cladding layer 5 is applied with the above-mentioned solvent while the upper surfaces of the optical waveguide 4 and the lower cladding layer 3 are wet. After the solvent is once dried, a step of applying the material solution of the upper clad layer 5 may be performed. Even when dried, wettability was improved according to experiments performed by the inventors. This is because once wet with the solvent,
It is presumed that some change occurred in the surface layer of the polyimide film constituting the optical waveguide 4 and the lower cladding layer 3.

Also in the method of manufacturing the optical waveguide device of the present embodiment, since the bubbles at the branch portion of the optical waveguide 4 can be reduced, the Y-branch type optical waveguide device 100 having excellent optical characteristics can be easily formed by a resin film. Can be manufactured.

The solvent used in the treatment for improving the wettability or the solvent for lowering the surface tension is not limited to the above-mentioned solvents, and other solvents and solvents can be used. For example, N-methylpyrrolidone can be used.

Table 1 shows the results obtained in the second embodiment of the present invention. After drying the material solution of the second resin so as to cover the core layer, the thickness of the core layer is set to 3.9 times from the upper surface of the lower cladding layer, and N, N-dimethylacetamide is spin-coated before covering the core layer. The treatment was performed for the case where the sample was filled with steam, the case where the sample was allowed to stand still, and the case where the sample was filled with steam and the pressure was reduced.

[0037]

[Table 1]

As shown in Table 1, when treated, the generation of bubbles is reduced. After forming the core layer of the optical waveguide in FIG. 3 and drying the material solution of the second resin so as to cover this core layer, the thickness of the core layer becomes 2 to 3.4 times the thickness of the core layer from the upper surface of the lower clad layer. In the conventional method of forming a film of the material solution described above, after drying the material solution of the second resin so as to cover the core layer, the thickness becomes 3.5 to 10 times the thickness of the core layer from the upper surface of the lower clad layer. The method of the present invention for forming a film of the material solution is shown in FIG. In the present invention, since the upper clad layer is formed thick and is removed from the upper surface of the lower clad layer so as to be less than 3.5 times the thickness of the core layer.
The upper surface of the upper cladding layer becomes smoother. In the case of RIE, there was a difference in height of 3 to 4 μm between the upper surface and the end of the core layer in the conventional method, but in the present invention, the difference was 1/3 to 1 μm or less. For this reason, the surface of the protective layer and the upper clad layer is smooth, which is advantageous when the structure is further multilayered, and has the effect of reducing the thickness of the protective layer. Therefore, in the present invention, it is preferable that the difference between the maximum value and the minimum value of the height from the lower surface of the lower clad layer to the upper surface of the upper clad layer is 30% or less of the core layer thickness.

The cladding layer covering the core layer of the optical waveguide exhibits sufficient propagation efficiency if it is about twice the thickness of the core layer. Therefore, the second resin film is formed to have a thickness of 2 to less than 3.5 times the thickness of the core layer. It is preferable to remove them.

Further, in the above-described embodiment, the configuration and the manufacturing method for reducing the bubbles at the branch portion of the Y-branch type optical waveguide have been described, but the configuration and the manufacturing method are not limited to the Y-branch. The present invention can be applied when manufacturing a fine structure portion of an optical waveguide having a fine structure. For example, when a resin is used to manufacture an optical waveguide branched into three or more, a directional coupler having a portion where two or more optical waveguides come close to each other at a minute interval, an optical switch in which two or more optical waveguides cross, or the like. Can be applied.

[0041]

As described above, according to the present invention,
It is possible to provide a resin optical waveguide having a branch portion, wherein the resin optical waveguide hardly generates bubbles at the branch portion.

[Brief description of the drawings]

FIGS. 1 (1) to 1 (9) are cross-sectional views schematically showing steps of manufacturing an optical waveguide device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing an optical waveguide device obtained by a method of manufacturing an optical waveguide device according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a method (b) for manufacturing an optical waveguide device of the present invention in comparison with a conventional method (a).

FIG. 4 is a graph showing a non-defective rate of bubbles when a material solution of a second resin is formed by changing the thickness of a core layer from the upper surface of a lower clad layer after drying.

FIG. 5 is an enlarged top view showing a shape of a branch portion of the optical waveguide 4 of the optical waveguide device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 3 ... Lower cladding layer 4 ... Optical waveguide 5 ... Upper cladding layer 6 ... Mask 7 ... Electrode part 9 ... Protective layer 10 ... Optical waveguide lamination Body 51: Bubbles 52: Root of branch 100: Optical waveguide device

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masatoshi Yamaguchi 48 Wadai, Tsukuba, Ibaraki Prefecture Within Hitachi Chemical Co., Ltd. In-house (72) Inventor Hiroshi Masuda 48 Wadai, Tsukuba, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. 2H047 KA04 PA01 PA21 PA24 PA28 TA00

Claims (14)

[Claims] 1. A method according to claim 1, further comprising the steps of:
A first step of forming a resin film, a second step of patterning the first resin film into a core layer in an optical waveguide shape, and a material solution of a second resin so as to cover the core layer. After the drying, the thickness of the core layer from the upper surface of the lower cladding layer to 3.
A third step of forming a film of the material solution so as to have a thickness of 5 to 10 times, and removing the second resin film from the upper surface of the lower clad layer so as to be less than 3.5 times the thickness of the core layer And a fourth step of using the second resin film as an upper cladding layer. 2. The optical waveguide device according to claim 1, further comprising a step of attaching a solvent for improving wettability to the upper surfaces of the core layer and the lower clad layer between the second step and the third step. Manufacturing method. 3. The method for manufacturing an optical waveguide device according to claim 2, wherein the solvent includes a solvent contained in the second resin film. 4. The method of manufacturing an optical waveguide device according to claim 2, wherein the solvent is applied to the upper surface to attach the solvent, or the upper surface is exposed to vapor of the solvent. A method for manufacturing an optical waveguide device, comprising using: 5. The method for manufacturing an optical waveguide device according to claim 2, wherein the solvent is attached to the upper surface,
A method of manufacturing an optical waveguide device, wherein the third step is performed without drying. 6. The method of manufacturing an optical waveguide device according to claim 1, wherein the means for removing the second resin film so as to have a thickness less than 3.5 times the thickness of the core layer uses dry etching. 7. The method for manufacturing an optical waveguide device according to claim 6, wherein the dry etching is reactive ion etching. 8. The method of manufacturing an optical waveguide device according to claim 1, wherein the means for removing the second resin film so as to have a thickness less than 3.5 times the thickness of the core layer uses an abrasive. 9. The method according to claim 1, wherein the means for removing the second resin film so as to have a thickness of less than 3.5 times the thickness of the core layer uses wet etching. 10. The method according to claim 1, wherein the second resin film has a thickness of 2 to 2 core layers.
2. The method of manufacturing an optical waveguide device according to claim 1, wherein the removal is performed so as to be less than 3.5 times. 11. The method according to claim 1, further comprising a fifth step of forming a protective layer on the upper surface of the upper clad layer after the fourth step. 12. An optical waveguide device obtained by the method of manufacturing an optical waveguide device according to claim 1. 13. The optical waveguide device according to claim 12, wherein the difference between the maximum value and the minimum value of the height from the lower surface of the lower cladding layer to the upper surface of the upper cladding layer is 30% or less of the core layer thickness. 14. The optical waveguide device according to claim 12, wherein the second resin film is a fluorinated polyimide resin.