JP2009015307A - Manufacturing method of optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical waveguide which facilitates visual or optical detection of an alignment mark. <P>SOLUTION: The manufacturing method of an optical waveguide on a substrate 1 includes the steps of: simultaneously forming an under-cladding layer 2 and the alignment mark A from the same material on the substrate 1; forming a photosensitive resin layer 3a for forming a core 3 on the resultant substrate to cover a thin metal film B; and positioning an exposure mask M<SB>2</SB>for forming the core 3 with reference to the thin metal film B detectable through the photosensitive resin layer 3a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an optical waveguide widely used in optical communications, optical information processing, and other general optics.

  An optical waveguide is incorporated in an optical device such as an optical waveguide device, an optical integrated circuit, or an optical wiring board, and is widely used in the fields of optical communication, optical information processing, and other general optics. In an optical waveguide, a core that is a light path is usually formed in a predetermined pattern, and an under cladding layer and an over cladding layer are formed so as to cover the core (see, for example, Patent Document 1). When manufacturing such an optical waveguide, usually, an under cladding layer, a core, and an over cladding layer are laminated in this order on a substrate.

When these under-cladding layer, core and over-cladding layer are formed in a predetermined pattern, a photosensitive resin is usually used as a forming material, and an opening pattern corresponding to the pattern is formed in forming the pattern. An exposure mask is positioned, and exposure is performed with irradiation rays through the exposure mask. And the exposed part is formed in a predetermined pattern through the dissolution removal process of an unexposed part.
JP 2005-173039 A

  The positioning of the exposure mask is usually performed using an optical sensor or the like by forming an alignment mark on the substrate and using the alignment mark as a mark. Recently, studies have been made on an optical waveguide device in which a light emitting element is embedded in an optical waveguide. In such an optical waveguide device, the thickness of the core and the over clad layer tends to be thicker than before. In such a case, when positioning the exposure mask, visual or optical detection of the alignment mark on the substrate becomes difficult, and the positioning accuracy tends to be lowered. In particular, when the alignment mark is formed of the same material as that of the under cladding layer, the alignment mark is transparent, so that it is more difficult to visually or optically detect the alignment mark.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an optical waveguide manufacturing method in which alignment marks can be visually or easily detected.

  In order to achieve the above object, an optical waveguide manufacturing method of the present invention includes a step of forming an undercladding layer and an alignment mark on a substrate with the same material, and a step of forming a metal thin film on the alignment mark. And forming a light-transmitting first photosensitive resin layer so as to cover the undercladding layer and the metal thin film, and positioning the exposure mask using the metal thin film formed on the alignment mark as a mark And a predetermined portion of the first photosensitive resin layer on the undercladding layer is selectively exposed through the exposure mask to form a core by the exposed portion of the first photosensitive resin layer. It is configured to include a process for performing.

  In the present invention, the “alignment mark” means a mark serving as a reference for positioning the exposure mask.

  In the method for producing an optical waveguide of the present invention, a metal thin film is formed on an alignment mark formed on a substrate prior to the formation of a light-transmitting photosensitive resin layer. The alignment mark (metal thin film) can be easily detected through the conductive resin layer. For this reason, positioning of the exposure mask for core formation becomes easy, and the positioning accuracy is improved. As a result, an optical waveguide having excellent core dimensional accuracy can be obtained.

  Further, after the core is formed, a step of forming a light-transmitting second photosensitive resin layer on the substrate so as to cover the undercladding layer, the metal thin film, and the core; and the alignment mark A step of positioning an overcladding layer forming exposure mask using the metal thin film formed thereon as a mark, and an undercladding layer of the second photosensitive resin layer through the overcladding layer forming exposure mask. When the method further includes the step of selectively exposing the predetermined portion above and forming the exposed portion of the second photosensitive resin layer on the over clad layer, it is easy to position the exposure mask for forming the over clad layer. Thus, an optical waveguide excellent in dimensional accuracy of the overcladding layer can be obtained.

  In particular, when the metal thin film is made of silver, the metal thin film is excellent in adhesion to an alignment mark made of a material for forming the under cladding layer. For this reason, in manufacture of an optical waveguide, the metal thin film which consists of silver does not peel off, but the reliability of positioning of an exposure mask improves.

  Moreover, even when the thickness of the photosensitive resin layer formed on the core is 20 μm or more, and even when the thickness of the second photosensitive resin layer formed on the over clad layer is 20 μm or more. The alignment mark (metal thin film) can be detected through each photosensitive resin layer.

  In addition, when embedding the light emitting element in the optical waveguide, the core and the over clad layer are formed thick, but even in such a case, through each photosensitive resin layer formed in the core and the over clad layer, An alignment mark (metal thin film) can be detected.

  As described above, in the present invention, a light-emitting element embedded in an optical waveguide is also included in the range of the optical waveguide.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  1 (a) to (d), FIGS. 2 (a) to (d), FIGS. 3 (a) to (c), and FIGS. 4 (a) to 4 (c) show an optical waveguide manufacturing method according to the present invention. One embodiment is shown. The feature of this embodiment is that when an optical waveguide W [see FIG. 4 (c)] comprising an under cladding layer 2, a core 3, and an over cladding layer 4 is manufactured on a rectangular flat substrate 1, the under cladding is produced. When the layer 2 is formed, alignment marks A made of a material for forming the undercladding layer 2 are formed at the four corners on the substrate 1 (see FIG. 1C), and then a metal thin film B is formed on each alignment mark A. (See FIG. 2 (c)).

That is, by forming the metal thin film B on the alignment mark A, a photosensitive resin layer 3a (see FIG. 3A) formed on the core 3 is formed on the alignment mark A, or on the over clad layer 4. Even if the photosensitive resin layer 4a to be formed (see FIG. 4A) is formed, the alignment mark A (metal thin film B) can be easily detected through the photosensitive resin layers 3a and 4a. The positioning of the exposure mask M ₂ for forming and the positioning of the exposure mask M ₃ for forming the over cladding layer 4 can be facilitated.

  More specifically, the optical waveguide manufacturing method of the present invention is performed as follows, for example.

  First, as shown in FIGS. 1A to 1D, the under cladding layer 2 and the alignment mark A are formed on the substrate 1. That is, first, the substrate 1 (see FIG. 1A) is prepared. The substrate 1 is not particularly limited, and examples of the forming material include glass, quartz, silicon, resin, metal, and the like. The thickness of the substrate 1 is not particularly limited, but is usually set within a range of 20 μm to 5 mm.

  Next, as shown in FIG. 1A, a varnish in which a photosensitive resin as a material for forming the under cladding layer 2 and the alignment mark A is dissolved in a solvent is applied on the substrate 1. The varnish is applied by, for example, a spin coating method, a dipping method, a casting method, an injection method, an ink jet method, or the like. And it is dried by heat processing of 50-120 degreeC x 10-30 minutes. Thereby, the photosensitive resin layer 2a formed in the under clad layer 2 and the alignment mark A is formed. The thickness of the photosensitive resin layer 2a is usually set within a range of 5 to 50 μm.

Next, as shown in FIG. 1B, an exposure mask M _{1 in} which an opening pattern corresponding to the pattern of the under cladding layer 2 and the alignment mark A is formed above the photosensitive resin layer 2a. , it is exposed to irradiation light L ₁ to the photosensitive resin layer 2a via the exposure mask M _1. For example, visible light, ultraviolet light, infrared light, X-rays, α-rays, β-rays, γ-rays or the like are used as the exposure radiation L ₁ . Preferably, ultraviolet rays are used. This is because when ultraviolet rays are used, a large curing rate can be obtained by irradiating large energy, and the irradiation device is also small and inexpensive, and the production cost can be reduced. Examples of the ultraviolet light source, for example, low pressure mercury lamp, high pressure mercury lamp, ultra-high pressure mercury lamp and the like, the dose of ultraviolet radiation is typically, 10 to 10000 mJ / cm ^2, preferably from 50 to 3000 mJ / cm ^2.

  After the exposure, heat treatment is performed to complete the photoreaction. This heat treatment is performed at 80 to 250 ° C., preferably 100 to 200 ° C. for 10 seconds to 2 hours, preferably 5 minutes to 1 hour.

  Subsequently, as shown in FIG. 1 (c), development is performed using a developing solution to dissolve and remove the unexposed portion of the photosensitive resin layer 2a, and the remaining photosensitive resin layer 2a is undercoated. A pattern of the cladding layer 2 and the alignment mark A is formed. The pattern of the alignment mark A is not particularly limited, but is usually formed in a cross shape in plan view (see FIG. 1D). For the development, for example, an immersion method, a spray method, a paddle method, or the like is used. As the developer, for example, an organic solvent, an organic solvent containing an alkaline aqueous solution, or the like is used. Such a developing solution and development conditions are appropriately selected depending on the composition of the photosensitive resin composition.

  After the development, the developer in the remaining photosensitive resin layer 2a formed in the pattern of the under cladding layer 2 and the alignment mark A is removed by heat treatment. This heat treatment is usually performed within a range of 80 to 120 ° C. × 10 to 30 minutes. Thereby, the remaining photosensitive resin layer 2a formed in the pattern of the under clad layer 2 and the alignment mark A is formed on the under clad layer 2 and the alignment mark A, respectively.

  In the present invention, the metal thin film B is formed on the alignment mark A as shown in FIGS. 2A to 2D after the above steps, which is a great feature. That is, as shown in FIG. 2A, the portion excluding the alignment mark A and its periphery is covered with a masking tape T, and in this state, as shown in FIG. A metal thin film B is formed on the alignment mark A by sputtering, plasma method or the like. In this embodiment, the metal thin film B is also formed on the upper surface and side surfaces of the alignment mark A and the peripheral substrate 1 [see FIG. 2 (d)]. Thereafter, the masking tape T is removed as shown in FIG. Examples of the material for forming the metal thin film B include silver, aluminum, nickel, chromium, copper, and the like, and alloy materials containing two or more of these elements. Among these, the alignment mark A and the substrate 1 are formed. Silver is preferable from the viewpoint of excellent adhesion. The thickness of the metal thin film B is not particularly limited, but is preferably in the range of 100 to 500 nm.

  Next, as shown in FIGS. 3A to 3C, the core 3 is formed on the under cladding layer 2. That is, first, as shown in FIG. 3 (a), a light-transmitting light that is to become a core 3 (see FIG. 3 (c)) is formed on the substrate 1 so as to cover the under-cladding layer 2 and the metal thin film B. The first photosensitive resin layer 3a having the property is formed. The formation of the photosensitive resin layer 3a is performed in the same manner as the formation method of the photosensitive resin layer 2a formed on the under cladding layer 2 described with reference to FIG. The thickness is generally set in the range of 5 to 50 μm. The material for forming the core 3 is a material having a higher refractive index than the material for forming the under cladding layer 2 and the over cladding layer 4 described later (see FIG. 4C). The adjustment of the refractive index can be performed, for example, by selecting the type of each forming material of the under cladding layer 2, the core 3, and the over cladding layer 4 and adjusting the composition ratio.

Next, as shown in FIG. 3B, an exposure mask M _{2 in} which an opening pattern corresponding to the pattern of the core 3 [see FIG. 3C] is formed above the photosensitive resin layer 3a. Position it. The positioning of the core 3 forming exposure mask M ₂ is detected through the photosensitive resin layer 3a, takes place as a marker a metal thin film B formed on the alignment mark A. The metal thin film B can be detected through the photosensitive resin layer 3a even if the photosensitive resin layer 3a has a thickness (thickness on the under cladding layer 2) of 20 μm or more. Then, the photosensitive resin layer 3a, via the exposure mask M ₂ (selectively the predetermined portion) was exposed to radiation L _2, a heat treatment is performed. This exposure and heat treatment are performed in the same manner as the formation method of the under cladding layer 2 described in FIG.

  Subsequently, as shown in FIG. 3C, development is performed using a developing solution to dissolve and remove the unexposed portion of the photosensitive resin layer 3a, and the photosensitive layer remaining on the undercladding layer 2 is removed. The conductive resin layer 3 a is formed in the pattern of the core 3. Thereafter, the developer in the remaining photosensitive resin layer 3 a is removed by heat treatment to form the core 3. The development and heat treatment are performed in the same manner as the formation method of the under cladding layer 2 described with reference to FIG.

  Then, an over clad layer 4 is formed on the under clad layer 2 as shown in FIGS. That is, first, as shown in FIG. 4A, the over cladding layer 4 [see FIG. 4C] is formed on the substrate 1 so as to cover the under cladding layer 2, the metal thin film B, and the core 3. A light-transmitting photosensitive resin layer (second photosensitive resin layer) 4a to be formed is formed. The formation of the photosensitive resin layer 4a is performed in the same manner as the method for forming the photosensitive resin layer 2a formed on the under cladding layer 2 described with reference to FIG. Is usually set in the range of 20 to 100 μm.

Next, as shown in FIG. 4B, an exposure mask M ₃ in which an opening pattern corresponding to the pattern of the overcladding layer 4 [see FIG. 4C] is formed above the photosensitive resin layer 4a. Positioning. The positioning of the exposure mask M ₃ for forming the over cladding layer 4 is performed using the metal thin film B formed on the alignment mark A detected through the photosensitive resin layer 4a as a mark. The metal thin film B can be detected through the photosensitive resin layer 4a even if the thickness of the photosensitive resin layer 4a (the thickness on the under cladding layer 2) is 20 μm or more. Then, the photosensitive resin layer 4a, via the exposure mask M ₃ (selectively the predetermined portion) was exposed to radiation L _3, a heat treatment is performed. This exposure and heat treatment are performed in the same manner as the formation method of the under cladding layer 2 described in FIG.

  Subsequently, as shown in FIG. 4C, development is performed using a developing solution to dissolve and remove the unexposed portion of the photosensitive resin layer 4a, and the photosensitive material remaining on the under cladding layer 2 is removed. The conductive resin layer 4 a is formed in the pattern of the over clad layer 4. Thereafter, the developer in the remaining photosensitive resin layer 4 a is removed by heat treatment to form the over clad layer 4. The development and heat treatment are performed in the same manner as the formation method of the under cladding layer 2 described with reference to FIG.

  In this way, the optical waveguide W composed of the under cladding layer 2, the core 3, and the over cladding layer 4 can be manufactured on the substrate 1. And the said optical waveguide W is peeled from the board | substrate 1 as needed.

  In the above embodiment, the over clad layer 4 is formed. However, the over clad layer 4 is not essential, and the optical waveguide may be formed without forming the over clad layer 4 in some cases.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to the examples.

[Formation material of under clad layer and over clad layer]
35 parts by weight of bisphenoxyethanol fluorenediglycidyl ether (component A), 40 parts by weight of (3 ′, 4′-epoxycyclohexane) methyl 3 ′, 4′-epoxycyclohexyl-carboxylate (component B), alicyclic epoxy resin (Delcel Chemical Co., Celoxide 2021P) (Component C) 25 parts by weight, 4,4-bis [di (β-hydroxyethoxy) phenylsulfinio] phenyl sulfide-bis-hexafluoroantimonate 50% propionate carbonate solution (Photoacid generator: Component D) By mixing 1 part by weight, a material for forming an under cladding layer and an over cladding layer was prepared.

[Core forming material]
Component A: 70 parts by weight, 1,3,3-tris {4- [2- (3-oxetanyl)] butoxyphenyl} butane: 30 parts by weight, Component D: 0.5 parts by weight of ethyl lactate 28 parts by weight The core forming material was prepared by dissolving in part.

[Production of optical waveguide]
First, the under clad layer forming material was applied on a glass substrate (thickness: 1.0 mm) by a spin coating method, followed by drying at 100 ° C. for 15 minutes to form a photosensitive resin layer. Next, exposure was performed by irradiation with ultraviolet rays of 2000 mJ / cm ² through a synthetic quartz-based exposure mask in which an opening pattern having the same shape as the pattern of the undercladding layer and alignment mark to be formed, and then 150 ° C. × 60 Heat treatment was performed for a minute. Next, by developing with an aqueous γ-butyrolactone solution, the unexposed portion was dissolved and removed, and then heat treatment was performed at 100 ° C. for 15 minutes to form an under cladding layer and an alignment mark (both thicknesses). 25 μm).

  Next, the portion excluding the alignment mark and the periphery thereof is covered with a masking tape, and in that state, a silver thin film (thickness 150 nm) is formed on the upper and side surfaces of the alignment mark and the surrounding glass substrate by vacuum deposition. Formed. Thereafter, the masking tape was removed.

Next, the core forming material is applied on a glass substrate so as to cover the under-cladding layer and the metal thin film by a spin coating method, followed by a drying process at 100 ° C. for 15 minutes. A photosensitive resin layer having a thickness of 24 μm on the under cladding layer was formed. Next, using the silver thin film visually observed through the photosensitive resin layer as a mark, a synthetic quartz-based exposure mask having an opening pattern having the same shape as the core pattern was positioned above the photosensitive resin layer. Then, from above, exposure by ultraviolet irradiation of 4000 mJ / cm ² was performed by a contact exposure method, followed by heat treatment at 120 ° C. for 15 minutes. Next, development was performed using a γ-butyrolactone aqueous solution to dissolve and remove unexposed portions, and then a heat treatment was performed at 120 ° C. for 30 minutes to form a core.

Then, a material for forming the over clad layer is applied onto the glass substrate so as to cover the under clad layer, the metal thin film, and the core by a spin coat method, followed by a drying process at 100 ° C. for 15 minutes. A second photosensitive resin layer having a light property (thickness of 35 μm on the under cladding layer) was formed. Next, synthetic quartz in which an opening pattern having the same shape as the pattern of the overcladding layer is formed above the second photosensitive resin layer using the silver thin film visually observed through the second photosensitive resin layer as a mark. The system exposure mask was positioned. Then, from above, exposure by ultraviolet irradiation of 2000 mJ / cm ² was performed by a contact exposure method, followed by heat treatment at 150 ° C. for 60 minutes. Next, development was performed using a γ-butyrolactone aqueous solution to dissolve and remove the unexposed portion, and then heat treatment was performed at 100 ° C. for 15 minutes to form an overcladding layer.

  Thus, an optical waveguide in which an under cladding layer, a core, and an over cladding layer were laminated in this order on a glass substrate could be manufactured.

[Comparative Example 1]
In Example 1 above, the thickness of the photosensitive resin layer formed on the core and the thickness of the second photosensitive resin layer formed on the overcladding layer are all formed without forming a silver thin film on the alignment mark or the like. The optical waveguide was manufactured with a thickness of 20 μm. Other than that, it was the same as in Example 1 above.

  As a result, in Comparative Example 1, it was difficult to visually check the alignment mark. For this reason, the positioning of the exposure mask for forming the core and the positioning of the exposure mask for forming the overclad layer required more time than in Example 1.

(A)-(c) is explanatory drawing which shows typically the formation method of the under clad layer and alignment mark in one Embodiment of the manufacturing method of the optical waveguide of this invention, (d) is the said alignment mark. It is the expanded top view. (A)-(c) is explanatory drawing which shows typically the formation method of the metal thin film on the alignment mark in one Embodiment of the manufacturing method of the said optical waveguide, (d) is the metal on the said alignment mark. It is the top view which expanded the thin film part. (A)-(c) is explanatory drawing which shows typically the formation method of the core in one Embodiment of the manufacturing method of the said optical waveguide. (A)-(c) is explanatory drawing which shows typically the formation method of the over clad layer in one embodiment of the manufacturing method of the said optical waveguide.

Explanation of symbols

1 Substrate 2 Underclad layer 3 Core 3a Photosensitive resin layer A Alignment mark B Metal thin film M ₂ Exposure mask

Claims (6)

  A step of forming an undercladding layer and an alignment mark on the substrate with the same material, a step of forming a metal thin film on the alignment mark, and a light-transmitting property so as to cover the undercladding layer and the metal thin film A step of forming a first photosensitive resin layer comprising: a step of positioning an exposure mask using the metal thin film formed on the alignment mark as a mark, and the first photosensitive resin through the exposure mask. A method of manufacturing an optical waveguide, comprising: a step of selectively exposing a predetermined portion on an under cladding layer of the layer to form a core by the exposed portion of the first photosensitive resin layer.   After the core is formed, a step of forming a light-transmitting second photosensitive resin layer on the substrate so as to cover the undercladding layer, the metal thin film, and the core; and on the alignment mark A step of positioning an exposure mask for forming an overcladding layer using the formed metal thin film as a mark, and an overcladding layer on the undercladding layer of the second photosensitive resin layer through the exposure mask for forming the overcladding layer The method for manufacturing an optical waveguide according to claim 1, further comprising: selectively exposing a predetermined portion and forming an exposed portion of the second photosensitive resin layer on the over clad layer.   The method of manufacturing an optical waveguide according to claim 1, wherein the metal thin film is made of silver.   The method for manufacturing an optical waveguide according to claim 1, wherein the first photosensitive resin layer has a thickness of 20 μm or more.   The thickness of the 2nd photosensitive resin layer is 20 micrometers or more, The manufacturing method of the optical waveguide as described in any one of Claims 1-4.   The manufacturing method of the optical waveguide as described in any one of Claims 1-5 which embeds a light emitting element in an optical waveguide.

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