JP2001074958A - Resin optical waveguide having flattened layer, its production and optical parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of an optical waveguide in which the upper face of the upper clad can be easily flattened although the optical waveguide is made of a resin. SOLUTION: The optical waveguide consists of a substrate 14, a lower clad layer 15, a core layer 16 disposed on part of the lower clad layer 15, upper clad layer 20 covering the core layer 16 and a flattening layer 24 covering the upper face of the upper clad layer 20. The upper clad layer 20 and the flattening layer 24 consist of a resin. The resin constituting the flattening layer 24 has a lower glass transition temperature than the resin constituting the upper clad layer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical waveguide,
In particular, the present invention relates to an optical waveguide whose cladding and core are 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 polymer materials 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 from a polymer material, the film formation 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. For example, Japanese Patent Application Laid-Open No. 9-40774
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a method for manufacturing an optical waveguide using polyimide.

In the method of manufacturing an optical waveguide described in the above publication, first, a polyamic acid solution is spin-coated on a substrate such as silicon and heated and dried and cured to form a polyimide film. This is used as a lower cladding layer. Next, a polyimide film having a higher refractive index than the lower clad is formed by the same procedure, and this is used as a core layer. A predetermined mask is formed on the core layer with a resist, and processed into a desired core shape by reactive ion etching (RIE) or the like. Next, on this core, a polyamic acid solution was further spin-coated, heated and dried, and then further heated and cured to obtain a polyimide film having a lower refractive index than the core,
This is used as the upper cladding layer.

[0006]

In the case where the optical waveguide is formed of a polymer material as in the above-mentioned method of manufacturing an optical waveguide made of polyimide, the procedure involves spin coating of a material solution, drying and heat curing. In this drying step, the solvent of the spin-coated material solution evaporates, so that the coating film of the material solution shrinks at a substantially constant rate in the thickness direction. The rate of reduction is approximately equal to the concentration of the solvent in the material solution. For this reason, the upper clad layer is formed on the patterned core layer even when the upper surface of the film is flat when the material solution film is spin-coated, and thus, after drying, it has the shape of the lower core layer. Along with the upper surface of the convex shape. In a polymer material used for an ordinary optical waveguide, a convex shape at the time of drying is almost maintained even at the time of curing, and the upper surface of the upper cladding layer has a convex shape in the shape of the core. If the upper surface of the upper clad layer has a convex shape as described above, when forming a wiring pattern of an electric circuit or the like on the upper clad layer, uniform film formation cannot be performed.
There is a risk of disconnection in the wiring. Also, when an optical waveguide is further laminated on the upper cladding layer, there is a problem that the shape of the upper optical waveguide becomes convex.

Further, if the thickness of the upper cladding layer can be made very large, the step of the convex shape formed on the upper surface of the upper cladding layer can be reduced. There is a limit, and since the thickness is necessarily reduced by drying, the thickness cannot be increased to a certain extent. Also, by repeating the steps of spin coating, drying and curing, the upper cladding layer has a multilayer structure,
Although it is possible to increase the thickness, the process is complicated by the amount of repetition of the process, and the manufacturing efficiency deteriorates. Further, even when the thickness is very large, the reduction occurs during drying in the same manner, so that the convex shape cannot be completely eliminated to make the surface flat.

The upper surface of the upper clad layer may be polished to make the upper surface flat, but the thickness of the upper clad layer is not so large (about 10 to 20 μm). Is difficult to control the polishing amount. In addition, since a polishing step is separately required, there is a problem that the process is complicated.

An object of the present invention is to provide a structure of an optical waveguide in which the upper surface of an upper clad can be easily flattened while being an optical waveguide made of resin.

[0010]

In order to achieve the above object, according to the present invention, the following optical waveguide is provided. That is, a substrate, a lower cladding layer disposed on the substrate, a core layer partially disposed on the lower cladding layer, an upper cladding layer covering the core layer, and covering an upper surface of the upper cladding layer. A flattening layer, wherein the upper cladding layer and the flattening layer are made of a resin, and a resin forming the flattening layer has a lower glass transition temperature than a resin forming the upper cladding layer. Is an optical waveguide.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical waveguide according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 4 (o), the optical waveguide of the present embodiment includes a lower cladding layer 15 on a silicon wafer substrate 14, and a core layer 16 patterned on the lower cladding layer 15. Are located. The core layer 16 is covered with the upper cladding layer 20, and the flattening layer 24 is arranged so as to fill the convex shape on the upper surface of the upper cladding layer 20. The upper surface of the flattening layer 24 is almost flat with almost no convex shape.

The lower cladding layer 15 and the upper cladding layer 20 are both OPI-N manufactured by Hitachi Chemical Co., Ltd.
It is a polyimide film formed using 1005 (trade name) and has a refractive index of 1.52 to 1.53. The thickness of the lower cladding layer 15 is about 7 μm, and the thickness of the upper cladding layer 20 is about 15 μm. The core layer 16 is a polyimide film formed using OPI-N3205 (trade name) manufactured by Hitachi Chemical Co., Ltd., and has a thickness of about 8 μm. The core layer 16 is also patterned to a width of about 8 μm. The refractive index of the core layer 16 depends on the lower and upper cladding layers 15, 2
About 0.5% larger than 0.

The flattening layer 24 is a polyimide film formed by using PIX-6400 (trade name) manufactured by Hitachi Chemical DuPont Microsystems Co., Ltd.
6 is about 7 μm at an end portion away from 6.

Next, a method of manufacturing the optical waveguide shown in FIG.

First, the silicon wafer substrate 1 shown in FIG.
An extremely thin adhesive layer (not shown) for improving the adhesiveness with the lower cladding layer 15 is formed on the upper surface of the substrate 4. The above-mentioned OPI-N1005 (resin concentration: 15% by weight) is spin-coated thereon to form a material solution film. Thereafter, the solvent is evaporated by heating in a dryer at 100 ° C. for 30 minutes and then at 200 ° C. for 30 minutes, followed by curing by heating at 370 ° C. for 60 minutes to form a polyimide film having a thickness of about 7 μm. Formed. Thereby, the lower cladding layer 15 was formed.

On the lower cladding layer 15, the above-mentioned O
PI-N3205 (resin concentration 15% by weight) is spin-coated to form a material solution film. Then, in a dryer, 100
The solvent was evaporated by heating at 30 ° C. for 30 minutes and then at 200 ° C. for 30 minutes, followed by curing by heating at 350 ° C. for 60 minutes to form a polyimide film having a thickness of about 8 μm. Was formed (FIG. 1B).

Next, as a resist on the core layer 16,
RU-1600P (manufactured by Hitachi Chemical Co., Ltd.) was spin-coated, dried at 100 ° C., and exposed and developed with a mercury lamp to form a resist pattern layer 17 (FIG. 1C). Using this resist pattern layer 17 as a mask, reactive ion etching (O ₂ -R
1E), the core layer 16 was patterned into a desired optical waveguide shape. (FIG. 1 (d)). Thereafter, the resist was stripped (FIG. 1 (e)).

Further, the above-mentioned OPI-N10
05 (resin concentration 25% by weight) was spin-coated to form a material solution film 18 (FIG. 2 (f)). This material solution film 1
Although the upper surface of 8 was flat as shown in FIG. 2 (f), it was heated in a dryer at 100 ° C. for 30 minutes and then at 200 ° C. for 30 minutes to evaporate the solvent to form a precursor film 19. Since the film thickness was reduced at a substantially constant reduction ratio, the upper surface of the precursor film 19 became convex along the shape of the core layer 16 (FIG. 2 (g)). Subsequent to this drying step, the polyamide acid in the precursor film 19 is imidized by heating at 350 ° C. for 60 minutes to be cured, thereby forming an upper clad layer 20 of a polyimide film having a thickness of 15 μm (FIG. 2
(H)). The upper cladding layer 20 substantially maintained the shape of the precursor film 19, and the upper surface was convex along the shape of the core layer 16.

If the upper surface of the upper cladding layer 20 remains convex, there will be a problem in etching the upper cladding layer 20 and the lower cladding layer 15 in the subsequent steps. A flattening layer 24 is formed on the upper surface.

First, the above-mentioned PIX-6400 (resin concentration: 35.5% by weight) was spin-coated on the upper cladding layer 20 to form a material solution film 21 (FIG. 2 (i)).
The upper surface of the material solution film 21 is formed by spin coating, as shown in FIG.
It was flat as in (i). Then, in a dryer, 100
After heating at 30 ° C. for 30 minutes and then at 200 ° C. for 30 minutes to evaporate the solvent to obtain a precursor film 23, the shape of the precursor film 23 becomes convex along the upper surface of the upper cladding layer 20. (FIG. 3 (j)). However, following this drying process, the polyamide acid in the precursor film 23 was imidized and cured by heating at 350 ° C. for 60 minutes.
As shown in (k), a flattening layer 24 of a 7 μm-thick polyimide film having a substantially flat upper surface was obtained. The surface step of the flattening layer 24 was measured by a contact step meter and found to be 1 μm or less.

The flattened layer 24 having a flat upper surface is obtained for the following reason. Upper cladding layer 2
Both 0 and the planarization layer 24 are polyimide, but have different structural formulas. For this reason, the polyimide of the upper cladding layer 20 formed from OPI-N1005 has a glass transition temperature (Tg) of 325 ° C., while PIX-6400
The glass transition temperature (Tg)
270 ° C., which is lower than that of the upper cladding layer 20. In the manufacturing process of the present embodiment, even when the precursor film 19 of the upper cladding layer 20 is cured into a polyimide film, the planarizing layer 2
Also, when the precursor film 23 of No. 4 is cured into a polyimide film, the heating temperature is the same at 350 ° C. Therefore, the upper cladding layer 20 has a glass transition temperature (T
g) While heated at + 25 ° C., the planarizing layer 24
The polyimide film is also heated to a glass transition temperature (Tg) + 80 ° C. Generally, resins such as polyimide have fluidity at a temperature equal to or higher than the glass transition temperature (Tg), and the fluidity increases as the temperature difference from the glass transition temperature increases. Therefore, when heated to the same 350 ° C., the flattening layer 24 has a higher fluidity and flows more easily than the upper cladding layer 20, and flows from a raised portion to a lower portion, and the upper surface becomes flat. .

The reason why the fluidity of the flattening layer 24 is large is not only the temperature difference between the glass transition temperature (Tg) and the heating temperature, but also the polyimide formed from PIX-6400 and the polyimide formed from OPI-N1005. It is considered that the difference in the chemical constitution between the two also influences.

The flattening layer 24 is made of P, which is a material solution.
The resin concentration of IX-6400 is 35.5%, which is higher than OPI-N1005 (resin concentration 25% by weight) of the material solution of the upper cladding layer 20. For this reason, the degree of reduction when the material solution film 21 of the planarization layer 24 changes to the precursor film 23 due to the drying is the same as the degree of reduction when the material solution film 18 of the upper cladding layer 20 changes to the precursor film 19. Not as great as degree. Therefore, when the precursor film 23 is formed, the step is smaller than the step on the upper surface of the upper clad layer 20. As described above, a material having a concentration of the material solution higher than that of the upper cladding layer 20 is used for the planarizing layer 2.
It is considered that the use of No. 4 is also a factor that can effectively reduce the step of the upper cladding layer 20.

As described above, the optical waveguide of this embodiment is
Since the upper surface is flattened with the flattening layer 24, the lower cladding layer 15 and the lower cladding layer 20 are not affected by the upper cladding layer 20 when patterning as described below.

The patterning step will be described. First,
A silicon oxide film 25 is formed on the planarization layer 24 by a spin-on-glass (SOG) process (FIG. 3 (l)). Next, as a resist film, RU- manufactured by Hitachi Chemical Co., Ltd. was used.
After 1600P was spin-coated and dried at 100 ° C., exposure and development were performed with a mercury lamp to form a resist pattern layer 26 (FIG. 4 (m)). Using the resist pattern layer 26 as a mask, reactive ion etching (F-RIE) was performed with fluorine gas to pattern the silicon oxide film 25 (FIG. 4 (n)). Further, the silicon oxide film 25
Was used as a mask to perform reactive ion etching (O ₂ -RIE) with oxygen to process the planarization layer 24 and the lower and upper cladding layers 20 and 15 into desired shapes. Thereafter, the silicon oxide film 25 was removed (FIG. 4 (o)). Thus, the optical waveguide according to the present embodiment has a flat upper surface (FIG. 4).
(O)) was obtained.

As described above, in the present embodiment, an optical waveguide having a flat upper surface can be obtained by disposing the planarization layer 24 on the upper clad layer 20 on the upper surface. Therefore, even when an optical waveguide is further formed on the optical waveguide or a wiring pattern is formed, the upper optical waveguide can be satisfactorily formed, and there is no possibility that the wiring pattern may be disconnected. In the above-described embodiment, the upper clad layer 20 and the lower clad layer 15 are formed as shown in FIGS.
Although the case of patterning by the process of FIG. 4 (o) has been described, the upper cladding layer 20 and the lower cladding layer 15 are not patterned, and the core layer 1 is formed as shown in FIG. 7 (a).
6 may be used as a flat plate having a flat upper surface.

The optical waveguide of FIG. 4 (o) and the optical waveguide of FIG. 7 (a) of this embodiment can be used as optical components for optical interconnection for connecting between an optical module and an optical fiber. is there. Further, by making the pattern shape of the core layer 16 of the optical waveguide of the present embodiment a predetermined shape, it is possible to configure an optical component such as an optical path conversion element, an optical path branching element, and a directional coupler.

In the method of manufacturing an optical waveguide according to the present embodiment, all of the lower cladding layer 15, the core layer 16, the upper cladding layer 20, and the planarizing layer 24 are formed by simple spin coating, drying and curing. Since the film can be formed at atmospheric pressure in the process, it is suitable as a method for manufacturing a large amount of optical waveguides at low cost. In the configuration of this optical waveguide, the planarizing layer 24
Has almost no effect on the propagation of light in the core layer 24, so that the material can be selected without considering the refractive index and the like.

Further, the optical waveguide of the present embodiment has a structure in which the planarization layer 24 for planarization is disposed separately from the upper cladding layer 20, so that the upper surface can be formed only by disposing the thin planarization layer 24. Can be flattened. Therefore, in order to reduce the step of the convex shape on the upper surface of the upper cladding layer 20, the upper cladding layer 20 and the thin planarization layer 2 are thinner than when the thickness of the upper cladding layer 20 is increased.
4 can achieve flattening. This facilitates the formation of the upper cladding layer 20 and the planarization layer 24,
Since the upper cladding layer 20 does not need to have a multilayer structure or the like in order to increase the thickness, the purpose of flattening can be effectively achieved by a simple process.

As a material of the upper cladding layer 20 of the optical waveguide, in order to reduce the refractive index and the propagation loss,
Polyimide containing fluorine is often used like the above-mentioned OPI-N1005. However, the polyimide containing fluorine has a property that the solvent resistance is not so high and the adhesion to other materials is low. For this reason, if the upper clad layer 20 is exposed to the outside as it is, corrosion resistance is deteriorated, and even if an optical component or the like is to be adhered on the upper clad layer 20, it is difficult to adhere. In this embodiment, the flattening layer 24 is used in FIG.
Since the upper cladding layer 20 can be covered as described above, the corrosion resistance and adhesion of the optical waveguide can be improved by using a material having a low fluorine content or a material not containing fluorine as the planarizing layer 24. The effect is also obtained. The upper cladding layer 20 and the planarizing layer 2
4 is the same polyimide, so that the adhesiveness is good.

When the upper and lower clad layers 20 and 15 are used as a flat optical waveguide without being etched as shown in FIG. 7A, the width of the core layer 16 is very small at several μm. It is not easy to visually check the presence or absence of the core layer 16 from the upper surface or the end surface or with a microscope. However, in the optical waveguide of the present embodiment, FIG.
The position of the core can be confirmed from the upper surface as shown in FIG. This is because the planarization layer 24 has a shape that embeds the convex shape of the upper surface of the upper cladding layer 20, so that the thickness of the planarization layer 24 is reduced in the upper portion 71 of the core layer 16, This is because the resin forming the layer 24 is a colored material having a lower visible light transmittance than the resin forming the upper and lower cladding layers 20 and 15. Therefore, when the upper and lower cladding layers 20 and 15 are irradiated with illumination light, more illumination light is transmitted from the thin portion 71 of the flattening layer 24 to the upper surface, and the thin portion 71 can be observed as a bright line. Moreover, since the width of the thin portion 71 is wider than the width of the core layer 16, the shape of the core layer 16 can be easily confirmed even when the width of the core layer 16 is narrow.

When the optical waveguide is observed from the end face, the boundary between the colored flattening layer 24 and the upper cladding layer 20 is clearly visible. Can be. Therefore, if the core layer 16 is present in the vicinity of the convex portion 71, it can be observed with a microscope or the like, and the boundary of the core layer 16 can be easily confirmed.

As described above, if the position of the core layer 16 can be confirmed visually or from a top surface or an end surface with a microscope, the user of the optical waveguide can use the positioning mark when coupling the optical fiber and the optical waveguide. This is very effective.

In the above-described embodiment, since the upper surface of the cladding layer 20 is covered with the flattening layer 24 having a flat upper surface, the width of the core layer 16 can be accurately detected from the upper surface by microscopic observation or the like. Is possible. This is because, when the planarization layer 24 is not provided, the illumination light is refracted by the interface between the clad layer 20 having a convex upper surface and air, so that the upper surface of the clad layer 20 becomes a lens and the optical waveguide 1
The width of No. 6 could not be measured accurately. However, by arranging the flattening layer 24, the interface with air becomes flat, and the illumination light does not refract. Further, the difference in the refractive index between the upper cladding layer 20 and the planarization layer 24 is substantially smaller than the difference in the refractive index between the upper cladding layer 20 and the air, and thus has little effect. For this reason, the width of the core layer 16 can be detected with a microscope from the upper surface, and it can be easily detected whether or not the core layer 16 of the optical waveguide falls within an allowable range at the time of shipment. However, it is necessary to use light having a wavelength that is hardly absorbed by the planarizing layer 24 and the upper cladding layer 20 as illumination light for microscopic observation. When a material having high visible light transmittance is used as the material of the planarizing layer 24 and the upper cladding layer 20, it can be observed with visible light. When the upper clad layer 20 and the planarizing layer 24 have the same refractive index, the width of the core layer 16 can be detected more accurately.

Although the upper surface of the flattening layer 24 may not be completely flat depending on the manufacturing conditions as shown in FIG. 6, the flattening layer 24 having the shape shown in FIG. By setting the ratio higher than that of the upper cladding layer 20, the upper portion 61 of the core layer 16 can have the function of a concave lens. By providing the function of the concave lens in this manner, when the core 16 is observed from above the flattening layer 24, the refraction of light at the loose convex portion on the upper surface of the flattening layer 24 is canceled by the action of the concave lens. Therefore, even if the upper surface of the planarization layer 24 is not completely flat, the width of the core layer 16 can be accurately detected from the upper surface by microscopic observation or the like.

The curing temperature of the polyimide film when forming the upper cladding layer 20 without using the flattening layer 24 is as follows.
By raising the temperature higher than the glass transition temperature (Tg), the fluidity of the upper cladding layer 20 may be increased, and the upper surface itself of the upper cladding layer 20 may be flattened. However, when the material constituting the upper cladding layer 20 has a high Tg (for example, 325 ° C. described above), it is necessary to heat to a high temperature of about 400 ° C. in order to obtain sufficient fluidity, and the polyimide may be decomposed. There is. Considering the temperature resistance of the optical waveguide, a material having a high glass transition temperature (Tg) is more preferable as the material of the cladding layer. Therefore, a material having a low Tg is selected as the material of the upper cladding layer 20. Is difficult. In addition, since it is necessary to select a material whose optical properties such as the refractive index can form the optical waveguide in relation to the core layer 16, it is necessary to select a material having a low glass transition temperature (Tg) when selecting the material. Is not easy. Therefore, the configuration of the present embodiment in which the planarization layer 24 is provided separately from the upper clad layer 20 is highly effective not only in that the heat resistance of the optical waveguide is not deteriorated, but also in that the material can be easily selected.

Further, as a comparative example, in the same manner as in the above-described manufacturing method, up to the upper cladding layer 20 shown in FIG. 2H, and without forming the upper planarizing layer 24, the same as in the above-described embodiment. A silicon oxide film 25 is formed by SOG (FIG. 5)
(L ′)), forming a resist pattern 26 (FIG. 5)
(M ′)) and pattern the silicon oxide film 25 (FIG. 5).
(N ')), when etching by RIE was performed,
As shown in FIG. 5 (o ′), the etching was performed up to the core layer 16 and the core layer 16 disappeared. This is because the silicon oxide film 25 cannot be formed thick by the method of forming the silicon oxide film 25 by SOG, so that the convex portion of the upper clad layer 20 cannot be covered, and the upper clad of the convex portion is exposed.

On the other hand, in the optical waveguide of the present embodiment, since the flattening layer 24 is arranged as described above,
The silicon oxide film 25 that can be used as a mask is
G can be formed. Therefore, there is no need to use a vapor deposition method or a sputtering method to form the silicon oxide film 25, and there is an advantage that the silicon oxide film 25 can be easily formed by SOG.

In the above embodiment, FIG.
Although the silicon oxide film 25 is removed in the step, since the silicon oxide film 25 does not affect the propagation of light, it can be left as it is.

In the above-described embodiment, the heating temperature for curing the upper cladding layer 20 and the flattening layer 24
Although the heating temperature for curing is the same, it is not necessary that the heating temperature be the same.
The heating temperature can be determined in consideration of the fluidity of the resin during heating.

In the above-described embodiment, the core layer 16, the upper and lower clad layers 15, 20 and the planarization layer 24 are formed of polyimide films having different structures as described above. Materials that can be used for the optical waveguide are not limited to the above-described materials. The fluidity of the flattening layer 24 at the time of heat curing is different from that of the upper cladding layer 2.
Any material may be used as long as the material has a fluidity of 0 during heat curing.
For example, the upper clad 20 is formed of polyimide,
A resin having a lower Tg than polyimide (for example, polyimide, polymethyl methacrylate, polycarbonate, polystyrene, styrene copolymer, styrene / acrylonitrile copolymer, vinyl chloride, epoxy resin, polyolefin, polyether, polyester, Polyurethane, silicone resin, polyamide, an acrylic resin including an alicyclic acrylic resin, an olefin resin including an alicyclic olefin resin) and the like.
Further, the upper clad 20 is formed of polycarbonate or epoxy resin, and the flattening layer 24 is formed of a resin having a lower Tg than those (eg, polymethyl methacrylate, polystyrene, styrene copolymer, styrene / acrylonitrile copolymer, vinyl chloride). Etc.

[0043]

As described above, according to the present invention,
It is possible to provide an optical waveguide structure that can easily make the upper surface of the upper clad flat even though it is a resin optical waveguide.

[Brief description of the drawings]

FIGS. 1A to 1E are cross-sectional views showing steps of manufacturing an optical waveguide according to an embodiment of the present invention.

FIGS. 2F to 2I are cross-sectional views showing steps of manufacturing an optical waveguide according to one embodiment of the present invention.

FIGS. 3 (j) to (l) are cross-sectional views showing steps of manufacturing an optical waveguide according to an embodiment of the present invention.

FIGS. 4 (m) to (n) are cross-sectional views showing steps of manufacturing an optical waveguide according to an embodiment of the present invention, and (o) are cross-sectional views of the optical waveguide according to an embodiment of the present invention.

FIGS. 5A to 5C are cross-sectional views illustrating a manufacturing process of an optical waveguide of a comparative example.

FIG. 6 is an explanatory view showing a concave lens action portion 61 when the upper surface of the flattening layer 24 is not completely flat in the optical waveguide according to one embodiment of the present invention.

7A and 7B are a cross-sectional view and a top view, respectively, showing the shape of an optical waveguide without processing the upper and lower claddings 20 and 15 according to the embodiment of the present invention.

[Explanation of symbols]

14 silicon wafer substrate, 15 lower clad layer, 16 core layer, 17 resist pattern layer, 18 material solution film, 19 precursor film, 20
... upper clad layer, 21 ... material solution film, 23
..Precursor film, 24: planarization layer, 25: silicon oxide film, 26: resist pattern layer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Honda 48 Wadai, Tsukuba-shi, Ibaraki Pref. Within the Research Laboratory of Hitachi Chemical Co., Ltd. F-term (reference) in Yamazaki Works of Industrial Co., Ltd. 2H047 KA04 PA02 PA21 PA24 QA05 QA07 TA00

Claims (9)

[Claims] A substrate, a lower cladding layer disposed on the substrate, a core layer partially disposed on the lower cladding layer, an upper cladding layer covering the core layer, and an upper cladding layer. A flattening layer covering the upper surface, wherein the upper clad layer and the flattening layer are made of resin,
The resin constituting the flattening layer has a lower glass transition temperature than the resin constituting the upper cladding layer. 2. A substrate, comprising: a lower cladding layer disposed on the substrate; a core layer disposed on a part of the lower cladding layer; an upper cladding layer covering the core layer; A flattening layer covering the upper surface, wherein the upper clad layer and the flattening layer are made of resin,
An optical waveguide, wherein the resin forming the planarization layer has higher fluidity during heating than the resin forming the upper cladding layer. 3. A substrate, a lower cladding layer disposed on the substrate, a core layer disposed on a part of the lower cladding layer, and the core layer and the lower portion along a shape of the core layer. An upper cladding layer covering the cladding layer, and a flattening layer for burying a convex shape along the core on the upper surface of the upper cladding layer and flattening the flattening layer is disposed on the upper surface of the upper cladding layer. An optical waveguide characterized by the above. 4. The optical waveguide according to claim 1, wherein the upper cladding layer and the planarizing layer are made of polyimides having different compositions. 5. An optical component using the optical waveguide according to claim 1, 2 or 3. 6. A first step of forming a lower clad layer on a substrate and forming a core layer on a part of the lower clad layer, and applying a first resin material solution on the core layer. A second step of forming a resin-made upper clad layer by heating and curing to a predetermined first temperature after drying, and a second resin material on the upper clad layer. A third step of forming a resin-made flattening layer by applying the solution, drying, and then heating and curing to a predetermined second temperature to form a resin-made flattening layer. The difference between the second temperature and the glass transition temperature of the second resin is larger than the difference between the first temperature and the glass transition temperature of the first resin in the second step. , Wherein the first and second temperatures are determined. . 7. A first step of forming a lower cladding layer on a substrate and forming a core layer on a part of the lower cladding layer, and applying a first resin material solution on the core layer. Then, after drying, a second step of forming a resin upper clad layer by heating and curing to a predetermined temperature, and applying a second resin material solution on the upper clad layer After drying, the resin is heated to the predetermined temperature and cured to form a resin-made flattening layer.
And a step of using a resin having a lower glass transition temperature than the first resin as the second resin. 8. A first step of forming a lower clad layer on a substrate and forming a core layer on a part of the lower clad layer, and applying a first resin material solution on the core layer. A second step of forming a resin-made upper clad layer by heating and curing to a predetermined first temperature after drying, and a second resin material on the upper clad layer. A third step of forming a resin-made flattening layer by applying a solution, drying, and then heating and curing to a predetermined second temperature to form a resin-made flattening layer. An optical waveguide manufacturing method, wherein a resin having a higher fluidity at the second temperature than a fluidity of the first resin at the first temperature is used. 9. A first step of forming a lower clad layer on a substrate and forming a core layer on a part of the lower clad layer; and disposing a first resin material on the core layer with a solvent. A second step of forming a resin upper clad layer by applying a solution dissolved in the above, drying and then curing by heating to a predetermined temperature, on the upper clad layer, Applying a solution in which the resin material is dissolved in a solvent, drying, and then heating and curing the resin to a predetermined temperature to form a resin flattening layer. The method of manufacturing an optical waveguide, wherein a solid content concentration of the second resin material in the solution is higher than a solid content concentration of the first resin material in the solution.