JP2007033776A - Manufacturing method of stacked type optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a stacked type optical waveguide, a method capable of reducing uneven thickness as well as improving production efficiency. <P>SOLUTION: The method include: a process of making a first optical waveguide 1 by forming a first core layer 13 on the surface of a first clad layer 12; a process of making a second optical waveguide 2 by forming a second core layer 23 on the surface of a second clad layer 22; and a process of forming a third clad layer 3, by disposing to face each other the surface of the first clad layer 12 of the first optical waveguide 1 and the surface of the second clad layer 22 of the second optical waveguide 2 and, with the first and second core layers 13, 23 placed opposite to each other, by filling a third clad layer 3 forming-material between the first and second clad layers 12, 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a laminated optical waveguide used for various optical components.

  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. Various methods have been proposed for producing an optical waveguide (see FIG. 2 on page 657 of Non-Patent Document 1). For example, a resin material for forming a core layer is applied on an underclad layer and then dried. A method of forming an over clad layer by forming a core layer by forming it into a predetermined pattern, and further applying a resin material for forming an over clad layer so as to include the core layer and then drying. It is done.

In addition, recently, photonic networks that process signals as light have become a reality due to high-speed and large-capacity information communications, and metal cables and wiring between electronic devices and electronic components have become a reality. Is shifting to optical interconnection using optical fibers and optical waveguides. Correspondingly, a highly functional optical component using an optical waveguide has been demanded. As an example, a satellite communication light receiving sensor has been proposed (see FIG. 6 on page 660 of Non-Patent Document 1). This uses a laminated optical waveguide in which optical waveguides are laminated in three stages in the thickness direction, and the fabrication is performed by repeating the conventional optical waveguide fabrication process three times in the thickness direction. .
The Institute of Electronics, Information and Communication Engineers Vol.84 No.9 pp.656-662 September 2001

  However, in the production of the conventional optical waveguide, since the core layer and the clad layer are formed by applying the resin material for forming each layer and then drying, in the production of the laminated optical waveguide, the layer to be molded is formed. As the number increases, the coating and drying steps increase, resulting in poor production efficiency. In addition, when the number of steps of applying the forming resin material increases, the solvent of the forming resin material may damage the base (core layer or cladding layer). In addition, the thickness unevenness due to coating, which can be ignored in one layer, becomes an uneven thickness that cannot be ignored in all layers due to an increase in the number of layers, which may impair the optical function.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a laminated optical waveguide capable of improving production efficiency and reducing thickness unevenness.

  In order to achieve the above object, a method for producing a laminated optical waveguide according to the present invention includes a step of forming a first optical waveguide portion by forming a first core layer on the surface of the first cladding layer, and a surface of the second cladding layer. Forming a second core layer on the first optical waveguide part, and the first cladding layer surface of the first optical waveguide part and the second cladding layer surface of the second optical waveguide part are opposed to each other, A step of forming a third cladding layer by filling a material for forming a third cladding layer between the first cladding layer and the second cladding layer in a state in which the first core layer and the second core layer are opposed to each other; It is configured to have.

  That is, in the manufacturing method of the laminated optical waveguide according to the present invention, first, the first optical waveguide portion in which the first core layer is formed on the surface of the first cladding layer and the second core layer in which the second core layer is formed on the surface of the second cladding layer. In this manufacturing method, an optical waveguide portion is prepared and then laminated through a third cladding layer to obtain a laminated optical waveguide. Therefore, in the present invention, it is not necessary to laminate all the cladding layers and all the core layers in order from the bottom in manufacturing the laminated optical waveguide, and both surfaces of the third cladding layer are formed on the first optical waveguide portion. Positioning is performed between the surface of the first cladding layer and the surface of the first core layer and the surface of the second cladding layer and the surface of the second core layer of the second optical waveguide portion. Therefore, according to the method for producing a laminated optical waveguide of the present invention, the production efficiency can be increased, and the overall thickness unevenness can be reduced.

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

  One embodiment of the method for producing a laminated optical waveguide according to the present invention is a method for obtaining a laminated optical waveguide as shown in FIG. In this laminated optical waveguide, the lower first optical waveguide portion 1 and the upper second optical waveguide portion 2 face each other with the core layers 13 and 23 facing each other, and the third cladding layer 3 and the spacer. 4 are stacked.

  More specifically, the first optical waveguide unit 1 includes a first substrate 11, a first cladding layer 12 formed on the surface of the first substrate 11, and a desired pattern on the surface of the first cladding layer 12. The first core layer 13 is formed on the first core layer 13. Similarly, the second optical waveguide section 2 has a second substrate 21, a second cladding layer 22 formed on the surface of the second substrate 21, and a desired pattern on the surface of the second cladding layer 22. The second core layer 23 is formed on the second core layer 23. The third cladding layer 3 is formed so as to include the first core layer 13 and the second core layer 23 facing each other. The spacer 4 is in contact with the left and right ends of the surface of the first cladding layer 12 and the left and right ends of the surface of the second cladding layer 22, and is not in contact with the first core layer 13 and the second core layer 23. (In FIG. 1, three pieces are arranged at one end of each side).

  Such a laminated optical waveguide can be manufactured as follows.

  First, the first substrate 11 and the second substrate 21, the first cladding layer 12 and the second cladding layer 22, the first core layer 13 and the second core layer 23, and the third cladding layer 3. Prepare the forming material.

  That is, the material for forming the first substrate 11 and the second substrate 21 is not particularly limited, and examples thereof include soda glass, synthetic quartz, silicon wafer, silicon wafer with silicon dioxide, and polyimide resin. In addition, the formation material of the 1st board | substrate 11 and the formation material of the 2nd board | substrate 21 may be the same, and may differ.

  Examples of the material for forming the first cladding layer 12 and the second cladding layer 22 include a polyimide resin precursor containing a coupling agent. This polyimide resin precursor is obtained by reacting tetracarboxylic dianhydride and diamine, and a material containing a coupling agent is used as a forming material. The material for forming the first cladding layer 12 and the material for forming the second cladding layer 22 may be the same or different.

  Examples of the material for forming the first core layer 13 and the second core layer 23 include a photosensitive polyimide resin precursor containing a photosensitive agent and the like. And the said photosensitive polyimide resin precursor is obtained by mix | blending additives, such as a photosensitive agent, with the polyimide resin precursor obtained by making the tetracarboxylic dianhydride and diamine mentioned above react. .

  Examples of the material for forming the third cladding layer 3 include an ultraviolet curable resin. This ultraviolet curable resin can be obtained by blending a photocuring initiator into an epoxy resin or polyamic acid.

  The first core layer 13 has a higher refractive index than the first clad layer 12 and the third clad layer 3 and the second core layer 23 has the second clad layer 22 and the third clad because of the relationship constituting the optical waveguide portion. The refractive index needs to be higher than that of the layer 3. For example, the adjustment of the refractive index can be performed by selecting a combination of the tetracarboxylic dianhydride and the diamine or forming the first core layer 13 and the second core layer 23. It can be carried out by blending an additive such as a photosensitizer with the material. Specifically, the relationship between the refractive index of the first core layer 13 and the refractive indexes of the first cladding layer 12 and the third cladding layer 3, and the refractive index of the second core layer 23, the second cladding layer 22 and the third cladding layer 3. The relationship with the refractive index of the clad layer 3, that is, the relative refractive index difference Δ [relative refractive index difference Δ = (n core-n clad) / n core: n = refractive index] is usually 0.2 to It may be in the range of 1.0%.

  Then, using the first substrate 11 and the second substrate 21 prepared in this manner and various forming materials, first, the first optical waveguide portion 1 and the second optical waveguide portion 2 are formed by a conventionally known manufacturing method. Make it.

  That is, as shown in FIG. 2, a polyimide resin precursor solution (polyamic acid solution), which is a material for forming the first cladding layer 12, is formed on the surface of the first substrate 11 so that the thickness after drying is preferably 1 to 1. The resin layer made of the polyimide resin precursor composition is formed by applying the film to 30 μm, particularly preferably 5 to 15 μm, and drying. As the coating method, a general film forming method such as a spin coating method or a casting method can be used. Subsequently, the first clad layer 12 made of polyimide resin is formed on the surface of the first substrate 11 by heating in an inert atmosphere to complete the removal of the residual solvent in the resin layer and the imidization of the polyimide resin precursor. Form. Similarly, the second cladding layer 22 is formed on the surface of the second substrate 21.

As shown in FIG. 3, a photosensitive polyimide resin precursor that is a material for forming the first core layer 13 made of a material having a higher refractive index than the first cladding layer 12 is formed on the surface of the first cladding layer 12. The body solution (photosensitive polyamic acid varnish) is applied so that the film thickness after drying is preferably 2 to 30 μm, particularly preferably 6 to 10 μm, and the photosensitive polyimide resin precursor that becomes the first core layer 13 by initial drying. The body layer 13a is formed. Next, a photomask M is placed on the photosensitive polyimide resin precursor layer 13a so that a desired pattern is obtained, and ultraviolet rays L are irradiated from above. Sufficient resolution is possible with an exposure dose of 5 to 50 mJ / cm ² when irradiated with the ultraviolet ray L. Thereafter, in order to complete the photoreaction, post-exposure heat treatment called Post Exposure Bake (PEB) is performed, and development is performed using a developer (wet process method). And in order to imidize the desired pattern obtained by image development, normal heat processing is performed. The heating temperature at this time is generally 300 to 400 ° C., and the solvent is removed and the curing reaction (curing) is performed in a vacuum or a nitrogen atmosphere.

  By imidizing in this way, as shown in FIG. 4, the first core layer 13 that forms a polyimide resin pattern is formed. In this way, the first optical waveguide portion 1 can be manufactured. Similarly, the second optical waveguide portion 2 can be manufactured by forming the second core layer 23 on the surface of the second cladding layer 22.

  The developer used for the development is not particularly limited, and for example, an alkaline alcohol aqueous solution is used. More specifically, a mixed aqueous solution of tetramethylammonium hydroxide and ethanol is preferably used from the viewpoint that the resolution is good and the development speed is easily controlled. The proportion of tetramethylammonium hydroxide in the mixed aqueous solution is preferably set in the range of 2 to 10% by weight, and the proportion of ethanol is preferably set in the range of 40 to 50% by weight.

  Then, as shown in FIG. 5, the surface of the first cladding layer 12 of the first optical waveguide section 1 and the surface of the second cladding layer 22 of the second optical waveguide section 2 are opposed to each other, and both core layers of both cladding layers are Make them confront. In order to maintain this facing state, the spacer 4 is disposed between the surface of the first cladding layer 12 and the surface of the second cladding layer 22 so as not to contact both core layers. In addition, the distance between the surface of the first cladding layer 12 and the surface of the second cladding layer 22 is preferably set to 5 to 90 μm, particularly preferably 17 to 35 μm.

  The material for forming the spacer 4 is not particularly limited, but is preferably the same type of resin (epoxy resin or the like) as the third cladding layer 3.

  Next, as shown in FIG. 6, an ultraviolet curable resin, which is a material for forming the third cladding layer 3, is filled between the first cladding layer 12 and the second cladding layer 22. The filling method is not particularly limited, but the edge portions of the first cladding layer 12 and the second cladding layer 22 are placed on the edge of the ultraviolet curable resin with the first cladding layer 12 and the second cladding layer 22 facing each other. And a method of filling by soaking in a capillarity and a method of injecting the ultraviolet curable resin with an injector. Thereafter, the ultraviolet curable resin is cured by irradiating with ultraviolet rays, and the third cladding layer 3 is formed. In this way, the laminated optical waveguide shown in FIG. 1 can be produced.

  In addition, the manufacturing method of the laminated optical waveguide of this invention is not limited to the said embodiment, Others may be sufficient. For example, in the above embodiment, both the core layers 13 and 23 are formed in parallel, but as shown in FIG. 7, they may be formed so as to intersect in plan view. Moreover, as shown in FIG. 8, you may form both core layers 13 and 23 offset. Furthermore, as shown in FIG. 9, both core layers 13 and 23 may be formed so as to be positioned in the lateral direction of each other. Further, in the above embodiment, the core layers 13 and 23 are formed one by one in each of the optical waveguide sections 1 and 2, but two core layers 13 and 23 may be formed as shown in FIG. Also, three or more may be formed (not shown).

  Furthermore, as long as each forming material can be configured as an optical waveguide, materials other than the above embodiment may be used. In the above-described embodiment, the clad layers 12 and 22 are formed by applying the material for forming the clad layers 12 and 22 to the surfaces of the substrates 11 and 21 and then drying them. However, the substrates 11 and 21 are used. Alternatively, a resin film such as a polyimide resin film or an epoxy resin film may be used as the cladding layers 12 and 22.

  In the above embodiment, when forming the core layers 13 and 23, a photosensitive resin material is used as a forming material, and a desired pattern is formed by ultraviolet irradiation. However, the present invention is not limited to this. For example, a non-photosensitive resin material or the like may be used as a forming material, and a desired pattern may be formed by dry etching.

  In the above embodiment, the spacer 4 is disposed between the first optical waveguide portion 1 and the second optical waveguide portion 2. However, the spacer 4 is disposed if both the core layers 13 and 23 can be held in opposition. It does not have to be installed.

  The laminated optical waveguide manufactured in this way is used for high-performance optical components. Examples of optical components include optical switches, wavelength tunable optical filters, optical sensors, optical splitters, optical multiplexers, optical multiplexers / demultiplexers, optical amplifiers, wavelength converters, wavelength dividers, optical splitters, directional couplers. Etc. And according to the kind of the optical component, the number of core layers 13 and 23, an opposing state, a pattern, etc. are set suitably.

  Next, examples will be described together with comparative examples.

[Polyamic acid solution: forming material of the first cladding layer and the second cladding layer]
In a 500 ml separable flask equipped with a stirrer, 26.66 g (0.06 mol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) as the acid dianhydride As a diamine, 18.54 g (0.058 mol) of 2,2′-bis (trifluoromethyl) benzidine (BTFB) as a diamine and 182.85 g (2 of N, N-dimethylacetamide (DMAc) as an organic solvent Then, the mixture was reacted at room temperature (25 ° C.) for 10 hours to obtain a polyamic acid solution (polyimide resin precursor solution).

[Photosensitive Polyamic Acid Solution: Material for Forming First Core Layer and Second Core Layer]
1% -ethyl-3,5-dimethoxycarbonyl-4- (2-nitrophenyl) -1,4-dihydropyridine is added to the polyamic acid solution as a photosensitizer at 2% by weight based on the solid content of the polyamic acid solution. Further, as a dissolution preparation agent, a polyethylene glycol dimethyl ether having a weight average molecular weight of 500 is blended so as to be 30% by weight with respect to the solid content of the polyamic acid solution, thereby obtaining a photosensitive polyimide acid solution (photosensitive polyimide). Resin precursor solution) was obtained.

[Ultraviolet curable resin: forming material of the third cladding layer]
An ultraviolet curable resin was obtained by blending an epoxy resin, diacrylate, and a photocuring initiator.

[Production of first optical waveguide part]
The polyamic acid solution was applied to the surface of a quartz substrate (thickness: 525 μm) by spin coating, and dried at 90 ° C. to form a resin film made of a polyimide resin precursor composition. Thereafter, the removal of the residual solvent in the resin film and the imidization of the polyimide resin precursor are completed by heating at 385 ° C. under vacuum, and a first cladding layer (refractive index) having a thickness of 15 μm is formed on the surface of the quartz substrate. 1.51) was formed.

And the photosensitive polyimide resin precursor layer which consists of a photosensitive polyimide resin precursor composition by apply | coating the said photosensitive polyamic-acid solution to the surface of the said 1st clad layer by a spin coat method, and drying at 90 degreeC. Formed. Next, a predetermined photomask (line width 6 μm × length 50 mm) was placed on the photosensitive polyimide resin precursor layer, and exposure was performed by ultraviolet irradiation at 30 mJ / cm ² from above. Further, post-exposure heating was performed at 170 ° C. for 10 minutes. Next, an aqueous solution containing 2 to 10% tetramethylammonium hydroxide and 40 to 50% ethanol is used as a developer, developed at 35 ° C. to dissolve unexposed portions, and then washed with water to obtain a negative image. A pattern having Then, imidation of the photosensitive polyimide resin precursor was completed by heating at 330 ° C. under vacuum, and a first core layer (refractive index 1.52) having a predetermined pattern was formed. The size of the cross section of the formed core layer was 6 μm wide × 6 μm high. Thus, the first optical waveguide part was obtained.

[Production of second optical waveguide part]
A second optical waveguide portion was obtained in the same manner as the first optical waveguide portion manufacturing method.

[Production of laminated optical waveguide]
Then, the first clad layer surface of the first optical waveguide portion and the second clad layer surface of the second optical waveguide portion are opposed to each other with an epoxy resin spacer (distance between the surfaces of both clad layers is 22 μm). Both core layers were opposed so that the core layer and the second core layer intersected at an angle of 0.8 degrees in plan view (see FIG. 7). In this state, the edge portions of the first clad layer and the second clad layer are immersed in the ultraviolet curable resin and sucked up by capillary action so that the ultraviolet ray is interposed between the first clad layer and the second clad layer. Filled with curable resin. Thereafter, the ultraviolet curable resin was cured by irradiating ultraviolet rays (30 mJ / cm ² ) from the second substrate side of the second optical waveguide portion, thereby forming a third cladding layer (refractive index 1.51). In this way, a laminated optical waveguide was obtained.

  This laminated optical waveguide functions as an optical branching device (optical separation device) because the first core layer and the second core layer intersect at a predetermined angle (0.8 degrees) in plan view. . It was also confirmed that when light having a wavelength of 1.55 μm was guided to the first core layer by the cutback method, part of the light was separated and propagated to the second core layer.

[Comparative example]
In the above embodiment, after the first optical waveguide portion is fabricated, the third cladding layer, the second core layer, and the second cladding layer are formed in this order as follows, and the second cladding layer is formed on the second cladding layer. A laminated optical waveguide was manufactured by bonding two substrates. Each forming material was the same as in Example 1 above.

That is, the ultraviolet curable resin is applied to the surfaces of the first cladding layer and the first core layer of the first optical waveguide portion by a spin coating method, and then irradiated with ultraviolet rays (30 mJ / cm ² ). The curable resin was cured to form a third cladding layer. Next, the surface of the third cladding layer was etched to form a pattern groove of the second core layer. Then, after pouring the photosensitive polyamic acid solution into the pattern groove, drying, exposure, heating, development, and imidization by heating are performed in this order in the same manner as in the above-described example to form the second core layer. did. Next, after the polyamic acid solution is applied to the surfaces of the third cladding layer and the second core layer by a spin coat method, imidation by drying and heating is performed in this order in the same manner as in the above examples. A second cladding layer was formed. Then, the second substrate was bonded onto the second cladding layer using an adhesive. In this way, a laminated optical waveguide was obtained.

[Comparison between Examples and Comparative Examples]
Comparing the production method of the above example and the production method of the comparative example, the production time of the laminated optical waveguide was shorter in the example. From this, it can be seen that the production methods of the examples are excellent in production efficiency. Further, when each laminated optical waveguide is cut so as to cross the first core layer and the second core layer, and the cut surface is observed with a microscope, which laminated optical waveguide is obtained by the manufacturing method of the example, In contrast, the layered optical waveguide obtained by the manufacturing method of the comparative example had almost no thickness unevenness, but in the order in which the layers were formed (the order of the third cladding layer, the second core layer, and the second cladding layer). ) The thickness unevenness was large.

It is a perspective view which shows an example of the laminated optical waveguide obtained by the manufacturing method of the laminated optical waveguide of this invention. It is explanatory drawing which shows the manufacturing method of the said laminated | stacked optical waveguide. It is explanatory drawing which shows the manufacturing method of the said laminated | stacked optical waveguide. It is explanatory drawing which shows the manufacturing method of the said laminated | stacked optical waveguide. It is explanatory drawing which shows the manufacturing method of the said laminated | stacked optical waveguide. It is explanatory drawing which shows the manufacturing method of the said laminated | stacked optical waveguide. It is a top view which shows the 2nd example of the said laminated | stacked optical waveguide. It is sectional drawing which shows the 3rd example of the said laminated optical waveguide. It is sectional drawing which shows the 4th example of the said laminated optical waveguide. It is sectional drawing which shows the 5th example of the said laminated | stacked optical waveguide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st optical waveguide part 2 2nd optical waveguide part 3 3rd clad layer 12 1st clad layer 13 1st core layer 22 2nd clad layer 23 2nd core layer

Claims (1)

  Forming a first optical waveguide portion by forming a first core layer on the surface of the first cladding layer, and forming a second optical waveguide portion by forming a second core layer on the surface of the second cladding layer. And the first clad layer surface of the first optical waveguide portion and the second clad layer surface of the second optical waveguide portion are opposed to each other, and the first core layer and the second core layer are opposed to each other, And a step of forming a third cladding layer by filling a material for forming a third cladding layer between the first cladding layer and the second cladding layer.

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