JP2001235643A - Opto-electric circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-optic circuit substrate which is formed with an organic system optical wavehuide having sufficient strength of tight adhesion on a wiring conductor of the electro-optic circuit substrate. SOLUTION: This electro-optic circuit substrate is constituted by forming the optical waveguide of an organic system having a layer consisting of an organic optical material having a hydroxyl group or alkyl group as a lower clad layer 4 on the electric circuit substrate formed with the wiring conductor 2 atop the same by disposing an intermediate layer 3 consisting of silicon oxide or silicon between the substrate and the wiring conductor 2. The hydroxyl group of the end terminal of the surface of the intermediate layer 3 and the hydroxyl group or alkyl group of the lower clad layer 4 are bonded by dehydration polymerization and dealcohol polymerization and therefore the high strength of tight adhesion may be obtained and the organic optical waveguide may be formed with the high strength of tight adhesion on the wiring conductor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opto-electric circuit board used for an optical communication module and the like.
The present invention relates to an opto-electric circuit board having an optical waveguide formed on an electric circuit board.

[0002]

2. Description of the Related Art Conventionally, an optical communication module or the like has various optical devices mounted on an opto-electric circuit board in which, for example, an electric circuit using a wiring conductor and an optical circuit using an optical waveguide are formed on a silicon substrate. Is used. In addition, there has been proposed an opto-electric circuit board in which an optical waveguide is formed on a ceramic circuit board which has better electrical high-frequency characteristics and mechanical strength than a silicon substrate, and can realize a high electric wiring density by multilayering.

On the other hand, as an optical waveguide, for example, a silica-based optical waveguide in which a three-dimensional clad portion and a core portion are formed using a silica film formed by a flame deposition method on a quartz glass substrate or a silicon substrate, There is an optical waveguide or the like in which a lithium niobate single crystal substrate is used as a clad portion and titanium is thermally diffused on the substrate to form a core portion in a three-dimensional waveguide shape.

However, since a high-temperature heat treatment of about 1000 ° C. or more is required to form these silica-based optical waveguides and the like, they form a base when forming an optical circuit using these optical waveguides on an electric circuit board. The electric circuit board will be damaged.

On the other hand, instead of these conventional silica-based optical waveguides and the like which require high-temperature treatment during fabrication, optical waveguides made of organic optical materials that can be formed at a low temperature are being studied.
Organic optical materials used for this optical waveguide include P
MMA (polymethyl methacrylate), polycarbonate, polyimide, polysiloxane, BCB (benzocyclobutene), fluorine resin, and the like are being studied.

As a method of manufacturing an optical waveguide made of these organic optical materials, a lower cladding layer is formed on a silicon substrate or a glass substrate, and then a core layer having a higher refractive index than the lower cladding layer is formed. Then, the core layer is processed by RIE (reactive ion etching) or the like using a thin film microfabrication technique to form a core portion, and then the upper cladding layer having a lower refractive index than the core portion is covered to form a three-dimensional structure. A method of forming an optical waveguide having a shape has been performed.

[0007]

However, when an optical waveguide made of an organic optical material is to be formed on an electric circuit board such as a ceramic circuit board, the organic optical material for the optical waveguide and the electric wiring of the electric circuit board are required. The lower cladding layer made of an organic optical material for an optical waveguide is used in an electric circuit board in a post-process such as a manufacturing process of an optical waveguide or a subsequent device mounting because of a low adhesion strength with a wiring conductor made of a metal or the like. There has been a problem in that the lower cladding layer is peeled off from the wiring conductor and cracks occur in the lower cladding layer.

The present invention has been devised in view of the above-mentioned problems of the prior art, and has as its object to provide an opto-electric circuit in which an organic optical waveguide is formed with sufficient adhesion strength on a wiring conductor of an electric circuit board. It is to provide a substrate.

[0009]

According to the present invention, there is provided an opto-electric circuit board having an intermediate layer made of silicon oxide or silicon interposed between the wiring conductor and an electric circuit board having a wiring conductor formed on an upper surface thereof. An organic optical waveguide having a layer made of an organic optical material having a hydroxyl group or an alkyl group as a lower cladding layer.

In the above-mentioned structure, the optoelectronic circuit board according to the present invention is characterized in that the organic optical material is a siloxane-based polymer.

According to the opto-electric circuit board of the present invention, an organic optical material having a hydroxyl group or an alkyl group is provided on the wiring conductor of the electric circuit board with an intermediate layer made of silicon oxide or silicon interposed therebetween. Since an organic optical waveguide having a lower cladding layer was formed, an intermediate layer made of silicon oxide or silicon was formed on a wiring conductor by, for example, a sputtering method, an electron beam evaporation method, an ion beam evaporation method, or a laser ablation film formation method.・ By being formed by a well-known method such as a CVD method, chemical bonding is performed by forming an intermediate layer on the wiring conductor surface in a highly active state, and film forming material particles on the wiring conductor surface Has sufficient adhesion strength to the wiring conductor by obtaining the physical anchor effect by the implantation of A hydroxy group or alkyl group in the lower cladding layer of the path is strongly bonded by dehydration polymerization or dealcoholization polymerization, and an optoelectronic circuit with an organic optical waveguide formed with sufficient adhesion strength on a wiring conductor made of metal etc. A substrate can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an opto-electric circuit board according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an example of an embodiment of an optical waveguide according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate, and 2 denotes wiring conductors formed on the upper surface of the substrate 1, and these constitute an electric circuit substrate. Reference numeral 3 denotes an intermediate layer, 4 denotes a lower cladding layer made of an organic optical material for an optical waveguide, 5 denotes a core portion of the optical waveguide, and 6 denotes an upper cladding layer of the optical waveguide.

The substrate 1 is a substrate for forming an electric circuit substrate by forming an electric circuit and an optical circuit. Various substrates used as substrates for handling optical signals, such as an optical integrated circuit substrate and a photoelectric mixed substrate, For example, a silicon substrate, an alumina substrate, a glass ceramic substrate, a multilayer ceramic electric circuit substrate, a ceramic electric circuit substrate on which a thin film multilayer electric circuit is formed, a plastic electric wiring substrate, and the like can be used.

The wiring conductor 2 forms a predetermined electric circuit on the surface or inside of the substrate 1 to form an electric circuit board, and includes Au, Pt, Al, Cu, W, Ti, Mo,
What is necessary is just to form using a well-known conductor material for electric wirings, such as Cr and Ni. The wiring conductor 2 is formed using a thin film processing technique such as photolithography after forming a conductor layer using, for example, a sputtering method, an electron beam evaporation method, an ion beam evaporation method, a laser ablation film formation method, a CVD method, or the like. What is necessary is just to process it into a desired wiring pattern. Also, a desired wiring pattern may be formed by utilizing a well-known metallizing technique for a ceramic substrate by screen printing or the like.

The intermediate layer 3 is a layer formed of silicon oxide or silicon and formed on at least the surface of the wiring conductor 2 on the upper surface of the substrate 1. As a method for forming the intermediate layer 3, a sputtering method, an electron beam evaporation method, an ion beam evaporation method, a laser ablation film formation method, a CVD method, or the like can be used. Among them, the sputtering method and the ion beam evaporation method are preferable because the adhesion effect between the intermediate layer 3 and the wiring conductor 2 is increased by the anchor effect because the effect of implanting the film forming material particles on the surface of the wiring conductor 2 is large. .

The reason why silicon oxide or silicon is used as the intermediate layer 3 in the present invention is that the adhesion strength between the intermediate layer 3 and the lower cladding layer 4 formed thereon can be sufficiently increased. The reason is that the surface of the intermediate layer 3 made of silicon oxide or silicon can be terminated with a hydroxyl group, and the lower clad layer 4 made of an organic optical material contains a hydroxyl group or an alkyl group. This is because a hydroxyl group on the surface and a hydroxyl group or an alkyl group of the lower cladding layer 4 are strongly bonded by dehydration polymerization or dealcoholization polymerization, and a large adhesion strength is obtained between the two layers.

Even if the lower cladding layer 4 made of an organic optical material does not contain a hydroxyl group or an alkyl group, if the underlying layer is silicon oxide or silicon, a well-known silane coupling material is used. Thereby, a hydroxyl group or an alkyl group bonded to the intermediate layer 3 and the organic functional group having a large adhesion strength to the lower clad layer 4 can be provided between the intermediate layer 3 and a large adhesion strength. be able to. As such a silane coupling material, glycidoxypropyltrimethoxysilane, hexamethoxydimethylsilazane, methacryloxypropyltrimethoxysilane, trimethoxysilylpropylethylenediamine, or the like can be used.

The thickness of the intermediate layer 3 is not problematic in principle as long as silicon oxide or silicon has several molecular layers or several atomic layers, but the surface of the wiring conductor 2 generally has a rough surface For example, when an alumina substrate or an aluminum nitride substrate is used as the substrate 1, the surface of the wiring conductor 2 has a surface roughness of 10 nm or more. 10nm to get
It is preferable that the thickness be not less than the above.

On the other hand, when silicon oxide or silicon is formed by a sputtering method, an electron beam evaporation method, an ion beam evaporation method, a laser ablation film formation method, a CVD method, or the like,
Usually, the film stress is 100 MPa or more. When the thickness of the layer is large, there is a problem that the substrate is largely warped by the film stress, the layer is peeled off from the substrate surface, and cracks are generated. On the other hand, the thickness of the intermediate layer 3 is 50
When the thickness is 0 nm or less, the film stress can be suppressed to about the same level as that of the lower cladding layer 4 made of an organic optical material.
Such a problem does not occur.

The optical waveguide formed on the upper surface of the substrate 1 including the surface of the wiring conductor 2 with at least the intermediate layer 3 interposed between the substrate and the wiring conductor 2 is composed of a cladding portion 4 comprising a lower cladding layer 4 and an upper cladding layer 6. 6 is an optical waveguide having a three-dimensional waveguide shape in which a core portion 5 is formed. As the forming material, an optical waveguide made of an organic optical material made of, for example, polyimide, fluorinated polyimide, siloxane-based polymer, PMMA, or olefin-based resin and having a hydroxyl group or an alkyl group as a terminal group is used.

As a method of manufacturing the optical waveguide, first, the lower cladding layer 4 is formed. For this, an organic solvent solution of an organic optical material such as polyimide, fluorinated polyimide, siloxane-based polymer, PMMA, or olefin-based resin is applied to the intermediate layer 3.
Is formed on the substrate 1 on which is formed a predetermined thickness by a spin coating method or the like and heat-treated.

The core part 5 has a polyimide / fluorinated polyimide / siloxane-based polymer / PMM on the lower cladding layer 4.
A. An organic solvent solution of an organic optical material such as an olefin resin is applied to the substrate 1 on which the lower cladding layer 4 is formed to a predetermined thickness by, for example, a spin coating method or the like, and a layer is formed by heat treatment. It may be formed in a predetermined shape by using a known thin film microfabrication technique such as RIE or RIE. Here, the core portion 5 is made of a material having a higher refractive index than the lower cladding layer 4.

After forming the core portion 5, the upper cladding layer 6 is formed by applying an organic solvent solution of an organic optical material such as polyimide, fluorinated polyimide, siloxane-based polymer, PMMA, or olefin-based resin to the lower cladding layer 4 and the core portion. 5 is formed on the substrate 1 on which the layer 5 is formed by applying a predetermined thickness by, for example, a spin coating method or the like, and performing a heat treatment.

Here, the height, width and refractive index of the core portion 5, the thickness and refractive index of the lower cladding layer 4, and the thickness and refractive index of the upper cladding layer 6 can be set to desired values using a well-known optical waveguide theory. What is necessary is just to design by specification.

As described above, an optical waveguide having a buried three-dimensional waveguide shape is manufactured.

In the photoelectric circuit substrate of the present invention, when a siloxane-based polymer is used as an organic optical material for forming the lower cladding layer 4, for example, an organic solvent of the siloxane-based polymer is applied to the substrate 1 by spin coating or the like. After the application, the lower cladding layer 4 can be formed by a low-temperature heat treatment at about 100 ° C. to 300 ° C., and a metal-containing siloxane-based polymer can be easily mixed with a metal alkoxide to control the refractive index. Since the optical waveguide can be manufactured, and the desired refractive index can be accurately controlled, the optical waveguide can be easily manufactured. Further, since the shrinkage during the formation of the layer is small, the surface of the layer formed on the surface of the substrate 1 is excellent in flatness and smoothness, and the substrate 1 or the wiring conductor 2 having a large surface roughness as the substrate 1 Even when an undulating electric circuit board is used, an optical waveguide can be manufactured with high accuracy on it.

Since the siloxane-based polymer has a siloxane bond, an optical waveguide having excellent thermal stability can be formed. Furthermore, it is easy to make a hydroxyl group or an alkyl group a terminal group, and when a film serving as the lower cladding layer 4 is formed on the intermediate layer 3, dehydration polymerization or dealcoholization polymerization with the hydroxyl group on the surface of the intermediate layer 3 is performed. Thereby, a large adhesion strength with the intermediate layer 3 is obtained.

The siloxane-based polymer used for the cladding portions 4 and 6 and the core portion 5 of such an optical waveguide may be basically a resin having a siloxane bond included in the polymer skeleton, for example, polyphenylsilyl. Sesquioxane, polydiphenylsilsesquioxane, polymethylphenylsilsesquioxane, and the like can be used.

[0030]

Next, a specific example of the photoelectric circuit board of the present invention will be described.

<Example 1> First, 3 of Ti / Pt / Au
An intermediate layer 3 made of a silicon oxide layer having a thickness of 10 nm was formed by a sputtering method on the entire surface of a substrate 1 made of aluminum nitride on which a wiring conductor 2 having an outermost surface having a layer structure made of Au was formed. Next, a step index type optical waveguide was formed in which the cladding parts 4 and 6 were composed of a siloxane-based polymer and the core part 5 was composed of a titanium-containing siloxane-based polymer. At this time, the refractive index of the core part 5 and the clad part were 1.444 and 1.440, respectively, the width of the core part 5 was 8 μm,
The height is 8 μm, and the upper cladding layer 6
Was 4 μm in thickness. The thickness of the lower cladding layer 4 between the substrate 1 and the core 5 was 12 μm.

At this time, no peeling or cracking of the optical waveguide layer was observed during the fabrication. Also, in the chip separation by dicing after the formation of the optical waveguide, peeling of the optical waveguide layer was not observed. Further, no problem was found in the waveguide characteristics of the optical waveguide.

<Example 2> For comparison with the present invention, Ti
A step index type optical waveguide having a cladding portion made of a siloxane-based polymer and a core portion made of a titanium-containing siloxane-based polymer is formed on an aluminum nitride substrate having a three-layer structure of / Pt / Au on which a wiring conductor made of Au is formed. Formed. At this time, as in Example 1, the refractive indices of the core portion and the cladding portion were 1.444 and 1.440, respectively, the width of the core portion was 8 μm, the height was 8 μm, and the thickness of the upper cladding layer above the core portion was 4 μm. The thickness of the lower cladding layer between the substrate and the core was 12 μm.

In the case of this embodiment in which no intermediate layer is formed,
During fabrication, peeling and cracking of the optical waveguide layer were observed in the portion of the wiring conductor.

As described above, according to the present invention, it was confirmed that an opto-electric circuit board having an organic optical waveguide formed with sufficient adhesion strength on the wiring conductor of the electric circuit board could be provided.

It should be noted that the present invention is not limited to the above-described embodiments, and that various changes and improvements can be made without departing from the scope of the present invention.

[0037]

As described above, according to the opto-electric circuit board of the present invention, the intermediate layer made of silicon oxide or silicon is provided between the wiring conductor and the electric circuit board having the wiring conductor formed on the upper surface. Since the organic optical waveguide having the lower clad layer made of the organic optical material having a hydroxyl group or an alkyl group was formed therebetween, an intermediate layer made of silicon oxide or silicon was formed on the wiring conductor by, for example, a sputtering method. And the formation of an intermediate layer on the surface of the wiring conductor in a highly active state by forming it by well-known methods such as electron beam evaporation, ion beam evaporation, laser ablation film formation, and CVD. It has sufficient adhesion strength to the wiring conductor by performing a strong coupling and obtaining a physical anchor effect by driving the film-forming material particles into the wiring conductor surface. Rutotomoni, a hydroxyl group or alkyl group of the lower cladding layer of the hydroxyl group and the optical waveguide of the surface termination of the intermediate layer is firmly bonded by dehydration polymerization or dealcoholization polymerization. As a result, it was possible to obtain an opto-electric circuit board having an organic optical waveguide formed on a wiring conductor made of metal or the like with sufficient adhesion strength.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a photoelectric circuit substrate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Wiring conductor 3 ... Intermediate layer 4 ... Lower cladding layer (cladding part) of optical waveguide 5 ... Core part of optical waveguide 6 ... Upper cladding layer of optical waveguide (Cladding)

Claims (2)

[Claims] 1. An organic optical material having a hydroxyl group or an alkyl group, wherein an intermediate layer made of silicon oxide or silicon is interposed between the wiring conductor and an electric circuit board having a wiring conductor formed on an upper surface thereof. An opto-electric circuit board, comprising: an optical waveguide having a layer formed as a lower cladding layer. 2. The optoelectronic circuit board according to claim 1, wherein the organic optical material is a siloxane polymer.