JPH09236719A - Production of optical waveguide using siloxane polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an optical waveguide having a refractive index close to that of silica and to enable fine control of refractive index by forming an optical waveguide including a metal-contg. siloxane polymer film by thermal polymn. of a metallic alkoxide added soln. for forming a siloxane polymer film on a substrate. SOLUTION: A metallic alkoxide added soln. for forming a siloxane polymer film is thermally polymerized on a substrate 1 to form an optical waveguide including a metal-contg. siloxane polymer film. That is, the siloxane polymer soln. is applied on the substrate 1 and heated to form a cladding layer 2 made of the siloxane polymer film. Since the metallic alkoxide is added to the siloxane polymer as a material of the optical waveguide, mixing in an arbitrary mixing ratio is facilitated, the refractive index of the waveguide can be arbitrarily set in accordance with the amt. of the alkoxide added and fine control of refractive index is enabled even in the production of a single-mode optical waveguide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides OE on a single substrate.
IC (photoelectric integrated circuit), optical waveguide, LS for OEIC control
The present invention relates to a method for manufacturing an optical waveguide suitable for a photo-electron mixed substrate on which I / LC and a high-frequency electric circuit are mixed, and particularly to a method for manufacturing an optical waveguide using a siloxane-based polymer.

[0002]

2. Description of the Related Art Due to the demand for high-speed information processing in optical communication systems and computers, it has become necessary to use light for signal transmission between integrated circuit chips, between boards on which they are mounted, or between boards on which a plurality of circuit boards are integrated. Has been studied,
Even when light is used for signal transmission, the processing of transmitted signals is performed by electronic components, and thus such optical information processing requires signal conversion between optical signals and electric signals.

In such a conversion region of an optical signal and an electric signal, an optical transmission line composed of an optical fiber or an optical waveguide and an optoelectronic conversion element such as a laser diode / photodiode are used and used in a circuit for performing optical information processing. Is an optoelectronic integrated circuit (OEIC) which is a combination of a transmission line for such light or a photoelectric conversion element, and a photoelectric element and an electronic circuit, or an optical integrated circuit (optical IC) for processing information only by light waves, control of electronic elements, and electrical LSI (large-scale integrated circuit) for processing signals, IC (integrated circuit), high-frequency electric circuit for driving electronic parts at high speed, and the like are mixed.

Hitherto, as a photoelectric conversion device, a module assembled from individual optical components and electronic components has been used. In addition, as the light source system, a gas laser was used for the light source and an optical system combining prisms, lenses, and mirrors was used, but in recent years, reduction optical systems combining laser diodes and photodiodes, optical fibers, rod lenses, etc. Is used. At present, toward further commercialization of optical information processing circuit boards, toward the practical application of an optoelectronic mixed board in which OEICs, optical waveguides, OEIC control LSIs, high frequency electric circuits, etc. are mixed on one board. Research and development is in progress.

According to such an optoelectronic mixed substrate, low power consumption, high speed, high reliability, mass productivity improvement, simplification of assembly, and improvement of stability after assembly can be achieved by high-density integration. However, to realize an optoelectronic mixed board, on a ceramic board,
Alternatively, a technique for forming an optical waveguide on a substrate on which a thin film circuit is formed by laminating on a ceramic electric circuit substrate is required.

For this optical waveguide, precise refractive index control is required for single-mode optical transmission,
In forming the optical waveguide, it is particularly necessary to process the core and control the refractive index of the core and the clad. For example, in the case of a silica-based single mode waveguide, typical specifications are that the core size is 7 μm × 7 μm, and the difference between the refractive index of the core and the refractive index of the clad is about 0.25%.

As a method of forming an optical waveguide, a method of forming an optical thin film having an appropriate thickness and then performing pattern processing to form a core portion is generally used. As a method of forming the optical thin film, a CVD method or a flame volume method is used. Methods, vacuum deposition method, sputtering method, SOG (Spin On Glass) method and the like are known. Among them, the SOG method is attracting attention because it is low in cost and can form a thin film at a relatively low temperature in a short time.

On the other hand, there has been proposed an optoelectronic mixed substrate using fluorinated polyimide as an optical waveguide material.

Further, Japanese Patent Laid-Open No. 5-66301 proposes a siloxane-based polymer and an optical material using the same as a material for an optical waveguide. The refractive index can be easily controlled by combining a silicon element with other elements. It is disclosed that this can be done. According to this, the silicon element in the siloxane-based polymer is partially replaced by a tetravalent element other than silicon or a trivalent element other than rare earth, and the refractive index is changed with respect to the unsubstituted polymer. As a method of substitution, a desired siloxane-based polymer is obtained by hydrolyzing / polymerizing a silane chloride and a chloride or alcoholate of an element to be substituted such as Al.

[0010]

SUMMARY OF THE INVENTION However, SOG
The sol-gel method using alkoxysilane as a starting material, which is one of the methods, produces a nearly perfect inorganic silica, but since volume shrinkage during film deposition is large and cracks are likely to occur, a film with a thickness of several μm or more is used. Because it ’s difficult to get
Since the silica-based single-mode optical waveguide needs to have a thickness of at least 15 μm for both the core portion and the clad portion, there is a problem that it is difficult to apply it to the production of the optical waveguide. Further, there is a problem that the obtained film has a large internal stress, which causes birefringence.

On the other hand, besides silica materials, organic materials such as polyimide and PMMA (polymethylmethacrylate) / polycarbonate are often used because they are easy to form a film and are low in cost. Since the material of the system has a larger refractive index than the material of the silica system, there is a problem that the transmission loss and the loss at the connection portion with the optical fiber are large. In addition, except for polyimide, there are problems such as high hygroscopicity, low heat resistance, and low glass transition point.

On the other hand, when fluorinated polyimide is used as the material for the optical waveguide, the refractive index of fluorinated polyimide is 1.53.
Since it is about the same and the difference from the refractive index of silica is 1.44,
There is a problem that Fresnel reflection loss becomes large when connecting with a silica optical fiber. In addition, since the optical transmission is multimode, there is a problem that it is difficult to connect with a silica single mode optical fiber.

Further, the proposal of Japanese Patent Laid-Open No. 5-66301 also has a problem that it is difficult to control the reaction because the highly reactive materials are mixed as raw materials.
Therefore, there is a problem that a high level of technical skill and expensive equipment are required to produce a stable mixture at an arbitrary mixing ratio.

Further, in general, in order to form the core of the optical waveguide, the film surface of the optical waveguide must be smooth, and the surface roughness (Ra) is at least 1 of the used light source wavelength.
/ 10 or less is desirable for low propagation loss, and when manufacturing an optical waveguide, it is necessary to set the internal refractive index to an arbitrary value, especially for manufacturing a single mode optical waveguide. Need to control the refractive index
When forming an optical waveguide on a thin film circuit board, it must have excellent flatness after film formation regardless of the irregularities and surface roughness of the underlying substrate surface, and that it must have adhesion to the underlying substrate.
When it is formed on an optoelectronic mixed substrate, it is required to have heat resistance when mounting an optical device such as a laser diode or a photodiode or an electronic device such as an LSI by soldering. There has been a demand for a method of manufacturing an optical waveguide that can be easily controlled with a simple facility and can be manufactured with simple equipment.

The present invention has been devised in view of the above problems of the prior art, and its object is to have a refractive index close to that of silica and to control the refractive index stably and easily. The surface roughness after film formation is small regardless of the unevenness and surface roughness of the base substrate, the flatness is excellent, the adhesion to the base substrate is excellent, and the heat resistance for solder mounting is sufficient. Another object of the present invention is to provide a manufacturing method capable of producing an optical waveguide made of a siloxane-based polymer, which is suitable for application to an optoelectronic mixed substrate, with simple equipment in a short time at low cost.

[0016]

A method of manufacturing an optical waveguide using a siloxane-based polymer according to the present invention is a method for producing a metal-containing siloxane-based polymer by thermally polymerizing a solution for forming a siloxane-based polymer film containing a metal alkoxide on a substrate. It is characterized in that an optical waveguide made of a film is formed.

According to the method of manufacturing an optical waveguide of the present invention, by adding a metal alkoxide to a relatively stable siloxane polymer as a material of the optical waveguide, mixing at an arbitrary mixing ratio becomes easy, and at the same time, Since it is possible to set the value of the refractive index of the optical waveguide composed of the metal-containing siloxane-based polymer film obtained by thermal polymerization to any value by the addition amount of the metal alkoxide, it is possible to make fine adjustments in the production of the single mode optical waveguide. The refractive index can be controlled. Further, since the internal stress of the film obtained by the small volume shrinkage due to the thermal process at the time of film formation is small, cracks do not occur even at a film thickness of 15 μm or more and do not cause birefringence. Further, since a siloxane-based polymer having a refractive index substantially equal to that of silica is used, an optical waveguide having a high coupling coefficient with a silica-based optical fiber can be obtained. as a result,
By using the optical waveguide manufacturing method of the present invention,
The G method makes it possible to form a film in a short time at low cost and at a relatively low temperature, and obtain an optical waveguide capable of highly efficient connection with a silica single mode optical fiber.

Further, since the liquid is applied on the substrate as a manufacturing method, the applied liquid surface is flat regardless of the state of the substrate surface as the base, and the volume shrinkage upon thermosetting is small, which is excellent. An optical waveguide having flatness can be obtained.

Further, the optical waveguide according to the present invention has excellent heat resistance (thermal stability) because it has a siloxane bond (-Si-O-Si-) as a skeleton.

Further, the present inventor has also found that when a metal alkoxide containing erbium (Er) is used as the metal alkoxide, there is an effect that a guided light amplification effect can be obtained together with finely controlled refractive index.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The siloxane-based polymer film-forming solution used in the method for producing an optical waveguide of the present invention includes, for example, a siloxane-based polymer having a phenyl group or a methyl group at the terminal group or an alkyl such as butyl group or propyl group. Group, aryl group such as phenyl group / tolyl group, siloxane polymer having functional group partially substituted with fluorine, hydroxyl group, etc. as terminal group, and propylene glycol monomethyl ether or 3 methoxy 3 methyl 1 butanol ethylene glycol Although a mixed solution with monobutyl ether etc. is used,
Above all, it is preferable to use a mixed solution of a siloxane polymer having a phenyl group or a methyl group as an end group and propylene glycol monomethyl ether.

The metal alkoxide added to the siloxane-based polymer film forming solution is, for example, tetra-n.
-Butoxy titanium, tetramethoxy titanium, tetrapropoxy titanium, tetramethoxy germanium, tetraethoxy germanium, tetrapropoxy germanium
There are tetrabutoxygermanium and trimethoxyerbium. Among them, in the alcohol of the same metal species, C
The use of an alcoholate having a large number of (carbon) is preferable because the chemical stability is superior to that having a small number of C and gelation is less likely to occur during mixing and mixing can be easily performed.

By thus adding the metal alkoxide to the siloxane-based polymer film-forming solution, the metal-containing siloxane-based polymer film is formed by a more stable reaction than the method of directly reacting a monomer as previously proposed. Since the metal alkoxide can be added to and mixed with the siloxane-based polymer film-forming solution at an arbitrary ratio, the refractive index of the optical waveguide can be precisely controlled.

Further, the metal-containing siloxane-based polymer film obtained by the present invention has a structure consisting of a portion in which a metal alkoxide is mixed as a metal oxide as it is and a portion which is chemically incorporated in the polymer. The structure of the film according to the method disclosed in Japanese Patent Application Laid-Open No. 5-66301 is different from the structure in which the metal is partially replaced with the Si atom of the siloxane-based polymer. Therefore, it is easier to control the refractive index.

The amount of the metal alkoxide added is
It is desirable to measure the refractive index of the polymer film with respect to the addition amount of the metal alkoxide in advance with respect to the siloxane-based polymer film forming solution obtained by combining the respective raw materials, and set the desired addition amount based on the refractive index.

The addition method and conditions are, for example, to dilute the alcoholate with a sufficient amount of alcohol and mix it with the siloxane-based polymer film forming solution while refluxing. The alcohol used at this time should be the same as the alcohol alkoxy.

This siloxane-based polymer film forming solution is applied by a coating method such as a spin coating method, a dip coating method, or a roller coating method, to a copper polyimide substrate, a Si substrate, a ceramic substrate, a multilayer ceramic electric circuit substrate, a thin film multilayer circuit substrate, or the like. After coating on a substrate such as a Si circuit substrate, heat treatment is carried out, for example, in an oven or a hot plate to thermally polymerize, whereby a crosslinking reaction of siloxane bonds proceeds and a silica-based siloxane-based polymer film is obtained.

Here, the heat treatment temperature for thermal polymerization is about 270 ° C., and the decomposition temperature (typical value) of polyimide generally used as an insulating layer of a thin film circuit board for forming an optical waveguide according to the present invention. Is sufficiently lower than about 450 ° C.), it is possible to form an optical waveguide without damaging a base substrate such as a thin film circuit substrate by heat treatment.

As a base substrate for forming an optical waveguide, as described above, a copper polyimide substrate, a Si substrate, a ceramic substrate, a multilayer ceramic electric circuit substrate, a thin film multilayer circuit substrate, or S
Although there are i-circuit boards and the like, the surface condition forming the optical waveguide is such that the unevenness and surface roughness are optically smooth and flat, and the unevenness and surface roughness due to the underlying wiring are not negligible. However, since the shrinkage during thermosetting is small, the flatness when the siloxane-based polymer film forming solution is applied is maintained, so that an optical waveguide having excellent flatness can be formed regardless of them.

For this, for example, a line pattern having a height of 4 μm and a width and pitch of 20 to 60 μm is formed on the substrate, and the siloxane-based polymer film according to the present invention is formed on the line pattern to obtain a flattening effect. As a result, when the siloxane-based polymer film having a thickness of 4 μm was formed, the unevenness of the film surface was 0.15 μm or less, and when the siloxane-based polymer film having a thickness of 8 μm was formed, the unevenness of the film surface was formed. Height is
It was confirmed that the thickness was 0.07 μm or less and that there was a good improvement (flattening) effect.

Further, when a siloxane polymer film according to the present invention having a thickness of 4 μm was formed on an alumina substrate having a surface roughness of Ra = 0.23 μm and the surface roughness of the film surface was measured, Ra = 0.026. It was confirmed that the film had a thickness of μm and had a good surface smoothing effect together with an excellent flattening effect.

From these, it was found that by using the siloxane polymer film obtained by the manufacturing method of the present invention, an optical waveguide having excellent flatness can be obtained regardless of the state of the substrate surface.

Moreover, according to the result confirmed experimentally by the inventor of the present invention, since the adhesiveness with the underlying substrate is sufficient for processing for lamination, it is possible to obtain an optical fiber with excellent adhesiveness with the underlying substrate. A waveguide is obtained.

[0034]

EXAMPLES Specific examples of the method for manufacturing an optical waveguide of the present invention will be described below.

[Example 1: Formation of siloxane-based polymer film and its characteristics] As a siloxane-based polymer, a siloxane polymer having a phenyl group and a methyl group as terminal groups was used, and this was mixed with propylene glycol monomethyl ether at 40 wt%. A siloxane-based polymer solution for forming a silica-based film was prepared.

This solution was treated with Si having a surface roughness Ra = 3 nm.
1,500 rpm / 15 by spin coating on wafer substrate
After coating under the condition of rotating for 2 seconds, heat treatment was carried out in a batch type oven in an atmosphere of 85 ° C / 30 minutes + 270 ° C / 30 minutes, and thermal polymerization was performed to obtain a siloxane-based polymer film having a thickness of 4 µm. .

When the refractive index of this film was measured by using a refractive index measuring device using a prism coupler, a wavelength of 63
It was 1.451 for light of 2.8 nm and 1.441 for light of wavelength 1550 nm.

When the radius of curvature of the warp of the substrate after the film formation was measured to measure the internal stress of the film, it was 20 MPa.
Tensile stress of SiO by sputtering method
₂ Compressive stress of 160 MPa and sol-
It was found that the tensile stress of the SiO ₂ film by the gel method was extremely small as compared with the tensile stress of 100 MPa.

When the film structure was examined by NMR (nuclear magnetic resonance), it was found to have a structure represented by the following chemical formula 1.

[0040]

Embedded image

In the chemical formula 1, R is --CH ₃ or-
C ₆ H ₅ and Si is contained in this siloxane-based polymer film.
It contained 35.5 wt%, CH ₃ 18.0 wt% and C ₆ H ₅ 16.2 wt%.

Further, when the water absorption of this film was measured, the water absorption was a very small value of 1% or less because it had a siloxane bond as the skeleton, and the moisture resistance was 2a.
The results showed that there was no change in appearance or adhesion under the conditions of tm, 120 ° C., 100% RH, and 100 hours.

The surface roughness of this siloxane-based polymer film was measured and found to be Ra = 4 nm, which was a sufficiently small value as the roughness of the core wall surface of the optical waveguide.

Furthermore, the thermal stability of this film was evaluated by thermogravimetric measurement and FT-IR (Fourier transform infrared absorption spectroscopy). It was also found that even when used as an optical waveguide, it can withstand the soldering temperature when mounting a chip element.

Then, this siloxane-based polymer film was formed on a polyimide film, and 1 mm × 1 formed on this film.
Cu wire is soldered to a Cu / Mo dot pattern of mm, and the load is measured by pulling vertically upward with a load cell to measure the load when those films are peeled off at the interface to obtain the adhesion strength of the interface. On average, 2.2
A value of kgf / mm ² was obtained, and it was also confirmed that the adhesiveness was sufficient to form an optical waveguide on a polyimide substrate.

From the above, it was confirmed that the siloxane polymer is suitable as the material for the optical waveguide of the photoelectron mixed substrate.

[Example 2: Formation of Ti-containing siloxane-based polymer film] Tetra-n-butoxytitanium (Ti (O-C ₄ H
₉ ) ₄ ) A mixed solution of 1.91 g and 5 ml of n-butanol,
5 g of the siloxane polymer solution of [Example 1] (solid content 1.50)
g) was mixed and stirred to obtain a transparent siloxane-based polymer film forming solution. This solution was spin-coated on a 4-inch Si wafer at 200 rpm / 2 seconds + 1500 rpm.
/ 10 seconds, then heat-treated in a batch oven in the air at 85 ° C / 30 minutes + 300 ° C / 30 minutes to thermally polymerize, and a thickness of Ti-containing siloxane-based polymer A 1.6 μm transparent coating was obtained.

The refractive index of this metal-containing siloxane-based polymer film was measured with a refractive index measuring device using a prism coupler, and was found to be 1.51 for light with a wavelength of 632.8 nm.
It was 14.

When the radius of curvature of the warp of the film-formed substrate was measured to measure the internal stress of the film, it was 20M.
It was a tensile stress of Pa and was found to be extremely small.

Further, when the surface roughness of this film was measured in the same manner as in [Example 1], it was found that Ra = 2 nm, which was a sufficiently small value as the roughness of the core wall surface of the optical waveguide.

Furthermore, the thermal stability of this film is shown in [Example 1].
When evaluated in the same manner as above, it was found that it has a thermal stability of 400 ° C. or higher and can withstand a soldering temperature when mounting a chip element when it is used in an optical waveguide of a mixed optoelectronic substrate.

Then, the metal-containing siloxane polymer film was formed on the polyimide film, and the adhesion strength at the interface between these films was measured in the same manner as in [Example 1].
A value of 2 kgf / mm ² was obtained, and it was also confirmed that the adhesiveness was sufficient to form an optical waveguide on a polyimide substrate.

From the above, it was confirmed that the metal-containing siloxane polymer according to the present invention is suitable as a material for an optical waveguide of a photoelectron mixed substrate.

[Example 3: Formation of Ti-containing siloxane-based polymer film] A mixed solution of 4.78 g of tetra-n-butoxytitanium and 5 ml of butanol, and 5 g of siloxane-based polymer solution of [Example 1] (solid content 1.50 g) Were mixed and stirred to obtain a transparent siloxane-based polymer film forming solution. This solution was spin-coated on a 4-inch Si wafer at 200 rpm.
/ 2 seconds + 1500 rpm / 10 seconds, then apply in a batch type oven in the air at 85 ℃ / 30 minutes + 300 ℃
/ 30 minutes heat treatment to heat-polymerize
A 0.96 μm thick transparent coating consisting of the siloxane-based polymer was obtained.

The refractive index of this metal-containing siloxane-based polymer film was measured with a refractive index measuring device using a prism coupler, and was found to be 1.59 with respect to light having a wavelength of 632.8 nm.
It was 49.

The internal stress of this film is a tensile stress of 20 MPa, the water absorption is a very small value of 1% or less, and the surface roughness of the film is Ra = 2 nm and the roughness of the core wall surface of the optical waveguide. Was a sufficiently small value.

Further, this film was also excellent in thermal stability and adhesion strength at the interface with the polyimide film, similar to those in [Example 1] and [Example 2].

From the above, it was confirmed that the metal-containing siloxane polymer according to the present invention is suitable as a material for an optical waveguide of a photoelectron mixed substrate.

[Example 4: Ti Content and Refractive Index in Ti-Containing Siloxane Polymer Film] Similar to [Example 2] and [Example 3], the addition amount of tetra-n-butoxytitanium was changed to a siloxane polymer. A film forming solution was prepared to form several Ti-containing siloxane-based polymer films, and the refractive index of each film was measured.

As a result, the relationship between the weight ratio of tetra-n-butoxytitanium to the solid content of the siloxane-based polymer solution and the refractive index of the obtained film is as shown in the diagram of FIG. It was confirmed that there is. The lower horizontal axis in the figure tetra -n- butoxytitanium _{(Ti (O-C 4 H} 9) 4)
And the solid content of the siloxane-based polymer solution, x, and the upper horizontal axis corresponds to Ti and Si (silicon).
And the vertical axis represents the refractive index n of the Ti-containing siloxane-based polymer film obtained from the film forming solution. The circles and dotted lines in the figure indicate the wavelength of 632.8.
The measured value of the refractive index with respect to the light of nm and its characteristic curve are shown, and the solid line shows the measured value of the refractive index with respect to the light of wavelength 1550 nm and its characteristic curve.

From the results shown in FIG. 1, it can be seen that there is a linear relationship between the weight ratio x of tetra-n-butoxytitanium and the solid content of the siloxane polymer solution and the refractive index n of the film. According to the result of this example, the relationship between x and n is 632.8
For light of nm, n = 0.04436 x + 1.451, wavelength 15
It was found that for light of 50 nm, n = 0.04406 x +1.439.

[Example 5: Structure of siloxane-based polymer film of Ti-containing] For examining the structure of the siloxane-based polymer film obtained in [Example 2] to [Example 4], for forming the siloxane-based polymer film of [Example 3] FT-IR measurement was performed using the solution.
As a result, absorption due to the -Si-O-Ti- bond was confirmed. It was also confirmed that the heat treatment increased the absorption. This is silanol and tetra-n-
The dealcoholization polymerization between butoxy titanium and -S
It is believed that i-O-Ti-bonds are formed.

Further, the structure of the Ti-containing siloxane-based polymer film of [Example 3] was investigated by NMR. As a result, this film had a structure represented by the above chemical formula 1 (where R is —CH _3).
Or -C ₆ is H _5, the molar ratio of CH ₃ / C ₆ H ₅ is a siloxane-based polymer film of EXAMPLE 3 was 5.7)
And a structure represented by the following chemical formula 2.

[0064]

Embedded image

The siloxane-based polymer film disclosed in Japanese Patent Laid-Open No. 5-66301 starts from the synthesis of a monomer and has a structure in which elements other than Si, such as Al and Ti, are incorporated in the molecule. On the other hand, since the siloxane-based polymer film according to the present invention mixes a metal alkoxide with a siloxane polymer, a part of the metal is taken in the polymer, but the other is not taken in and mixed in the polymer as a single metal oxide. There is a structural difference in that it seems to be.

Example 6 Formation of Optical Waveguide According to the manufacturing process shown in FIG. 2, a solution for forming a siloxane-based polymer film to which a metal alkoxide is added is thermally polymerized on a substrate to form an optical waveguide including a metal-containing siloxane-based polymer film. Was formed.
2A to 2D are cross-sectional views showing an example of such a manufacturing process.

In FIG. 2A, 1 is a substrate such as a thin film circuit substrate, and a Si wafer was used in this example. No. 2 is a clad layer made of a siloxane-based polymer film, which is formed by applying the siloxane-based polymer solution of [Example 1] on the substrate 1 and performing heat treatment under the conditions of 85 ° C / 30 minutes + 270 ° C / 30 minutes. Is. The clad layer 2 has a thickness of 5 μm and a wavelength of 1550.
The refractive index with respect to the light of nm was 1.4405.

3 is tetra-n on the clad layer 2.
A metal (Ti) -containing siloxane-based polymer film formed in the same manner as in [Example 2] using a metal-containing siloxane-based polymer film-forming solution prepared with a butoxytitanium / siloxane-based polymer solid content weight ratio of 0.082. Is a core layer. This core layer 3 has a thickness of 7 μm and a wavelength of 1550n.
The refractive index for the light of m was 1.4437.

Reference numeral 4 denotes a metal layer 4 formed on the core layer 3 by a sputtering method and serving as a mask when processing the core layer 3, and an Al layer having a thickness of 0.5 μm was used. Further, 5 is a line width of 1 to 15 which is a pattern of the core layer 3 formed on the metal layer 4 by a photolithography method.
It is a resist pattern of μm.

Next, H ₃ PO ₄ , CH ₃ COOH and HN
The Al layer 4 was etched with a mixed solution of O ₃ to obtain an Al pattern 6 to which the resist pattern 5 was transferred, as shown in FIG.

Next, after removing the resist pattern 5,
The core layer 3 was patterned by RIE (reactive ion etching). Here, the RIE conditions were an O ₂ flow rate of 60 sccm, a reaction pressure of 5 Pa, and an RF output of 600 W. As a result, as shown in FIG. 2C, the core 7 having the sidewalls substantially vertical was formed.

Then, the Al pattern 6 is removed, and the pattern shown in FIG.
As shown in (d), the second cladding layer 8 was formed in the same manner as the cladding layer 2. The thickness of this second cladding layer 8 is 15 μm, and the refractive index for light with a wavelength of 1550 nm is
It was 1.451.

From the above, the core height is 7 μm and the wavelength is 1550.
The refractive index of the core is 1.4437 for the light of
An embedded optical waveguide having a refractive index of the cladding portion for light of 1550 nm of 1.4405 was manufactured.

Optical waveguides having various core widths were prepared in the same manner as described above, and a near-field image (NFP) of emitted light was observed by entering light having a wavelength of 1550 nm.
It has been confirmed that the optical waveguide having a thickness of μm or less functions particularly preferably in the single mode. Also, when the propagation loss was measured by the cutback method, both were 0.5
It was a small value of dB / cm.

From the above, it was confirmed that the optical waveguide made of the metal-containing siloxane-based polymer film manufactured by the manufacturing method of the present invention has excellent characteristics.

[Example 7: Fabrication of Photoelectron Mixed Substrate] [Example 6]
An optical waveguide made of a metal (Ti) -containing siloxane-based polymer film was produced on a copper-polyimide thin-film multilayer circuit board by the same process as described above.

In the production of this optical waveguide, first, the siloxane polymer solution of [Example 6] was applied on a copper polyimide thin film multilayer circuit board, and heat treatment was performed at 85 ° C./30 minutes + 270 ° C./30 minutes, A clad layer 2 (having a refractive index of 1.4405 for light having a wavelength of 1550 nm) made of a siloxane-based polymer film having a thickness of 5 μm was formed.

Next, on the clad layer 2, tetra-n
-Butoxy titanium / siloxane polymer solid weight ratio = 0.
Using the siloxane-based polymer film-forming solution prepared as 082, a core layer 3 (refractive index 1.4437 for light having a wavelength of 1550 nm) made of a metal (Ti) -containing siloxane-based polymer film having a thickness of 7 μm was formed.

Next, on the core layer 3, a 0.5 μm thick A film was formed.
The metal layer 4 consisting of 1 layer is formed by the sputtering method, and the resist pattern 5 having a line width of 1 to 15 μm is further formed.
Was formed by a photolithography technique.

After that, H ₃ PO ₄ , CH ₃ COOH and H
The Al layer 4 was etched by a mixed solution with NO ₃ to obtain an Al pattern 6 to which the resist pattern 5 was transferred, and after removing the resist pattern 5, RIE (conditions: O ₂ flow rate 60 sccm, reaction pressure 5 Pa, RF output) The core layer 3 was patterned by 600 W) to form the core 7 whose sidewalls were almost vertical.

Then, the Al pattern 6 is removed, and the second cladding layer 8 having a thickness of 8 μm is formed in the same manner as the cladding layer 2.
(Refractive index 1.451 for light of wavelength 1550 nm) is formed, core height is 7 μm, refractive index of core for light of wavelength 1550 nm is 1.4437, and refractive index of clad for light of wavelength 1550 nm is 1.4405. An embedded optical waveguide was prepared.

FIG. 3 is a perspective view showing an example of an optoelectronic mixed substrate on which an optical waveguide is formed using the siloxane polymer film according to the present invention manufactured as described above.

In the optoelectronic mixed board 10 of FIG. 3, 11 is a multilayer circuit board made of ceramic or copper polyimide thin film, 12 is an optical fiber for inputting / outputting an optical signal to / from the outside, and 13 is an optical fiber 12 which is a multilayer circuit board. A coupler for connecting to 11, and 14 are optical waveguides using the siloxane-based polymer film according to the present invention, which are formed as described above, for example. Through this optical waveguide 14, the optical signal from the optical fiber 12 is input to the OEIC 15, or the optical signal from the OEIC 15 is output to the optical fiber 12. Further, 16 is a GaAs IC for controlling the OEIC 15, 17
Is an MPU for arithmetic processing, and these and the OEIC 15 are mounted on the multilayer circuit board 11 and are connected by the electric transmission line 18 and the circuit wiring in the multilayer circuit board 11.

By using the optoelectronic mixed substrate 10 as described above, it is possible to stably transmit a low-loss optical signal through the single-mode optical waveguide 14 whose refractive index is precisely controlled, and to integrate the circuit at a high density. It was possible to realize low power, high speed, and highly reliable optical information processing using optical and electrical signals.

The present invention is not limited to the above-described embodiments, and various modifications and improvements may be added without departing from the gist of the present invention.

[0086]

According to the method of manufacturing an optical waveguide using a siloxane-based polymer of the present invention, a solution containing a metal alkoxide for forming a siloxane-based polymer film is thermally polymerized on a substrate to form a metal-containing siloxane-based polymer film. By forming the optical waveguide having the above, it was possible to form an optical waveguide having a refractive index close to that of silica and to control the refractive index stably and easily and finely.

Further, according to the method for producing an optical waveguide using the siloxane-based polymer of the present invention, the surface roughness after film formation is small and the flatness is excellent regardless of the unevenness and surface roughness of the surface of the underlying substrate, To produce an optical waveguide made of siloxane-based polymer, which has excellent adhesion to the base substrate and has sufficient heat resistance for solder mounting, and which is suitable for application to a mixed optoelectronic substrate, with simple equipment in a short time and at low cost. I was able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a weight ratio of tetra-n-butoxytitanium and a solid content of a siloxane polymer solution in a metal-containing siloxane polymer film according to the present invention and a refractive index of the film.

2A to 2D are cross-sectional views showing an example of a manufacturing process of an optical waveguide including a metal-containing siloxane-based polymer film according to the present invention.

FIG. 3 is a perspective view showing an example of an optoelectronic mixed substrate in which an optical waveguide using a siloxane-based polymer film according to the present invention is formed.

[Explanation of symbols]

 1 ... Substrate 2 ... Clad layer 3 ... Core layer 4 ... Metal layer 5 ... Resist pattern 6 ... Al pattern 7 ...・ ・ ・ Core 8 ・ ・ ・ Second clad layer 10 ・ ・ ・ Opto-electronic mixed board 11 ・ ・ ・ Multi-layer circuit board 14 ・ ・ ・ Optical waveguide 15 ・ ・ ・ ・ ・ OEIC Integrated circuit)

Claims (1)

[Claims] 1. An optical waveguide using a siloxane-based polymer, wherein a solution for forming a siloxane-based polymer film containing a metal alkoxide is thermally polymerized on a substrate to form an optical waveguide comprising a metal-containing siloxane-based polymer film. Waveguide manufacturing method.