JP2001183539A - Organic optical waveguide, optical module, and optical integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of an optical waveguide which has a large thermal expansion coefficient difference between the insulating film and substrate 1 forming the organic optical waveguide. SOLUTION: A resin 9 is brought into contact with the substrate, a lower clad 2, a core 3, and an upper clad 4, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic optical waveguide, an optical module having the organic optical waveguide, and an optical integrated circuit having the organic optical waveguide.

[0002]

2. Description of the Related Art In recent years, research has been conducted on optical waveguides and optical modules using the same, and miniaturization and cost reduction of optical components have been promoted. Among the optical waveguides, the organic optical waveguide is easy to manufacture, has excellent mass productivity, and can be expected to reduce the cost.
As conventional techniques of an organic optical waveguide and an optical module using the same, JP-A-4-9807 and JP-A-9-21
9020, JP-A-11-133254, W
For example, Japanese Patent Application Laid-Open No. 098137445 is known.

FIG. 2 shows the structure of a conventional organic optical waveguide described in the above-mentioned WO 09137445. In this organic optical waveguide, first, an adhesive layer 10 for improving the adhesion between an insulating film constituting the organic optical waveguide and the silicon substrate 1 is applied on a silicon substrate 1, and then a polyimide precursor to be a lower clad 2 is formed. A body (polyamic acid) is applied, imidized by baking to form a lower clad 2, a polyimide precursor to be the core 3 is applied and baked thereon, and the core 3 is formed by photolithography and dry etching. Furthermore, upper cladding 4
The upper clad 4 is formed by applying and baking a polyimide precursor to be used. here,
A polyimide precursor is selected so that the refractive index of the core 3 is higher than the refractive indexes of the lower cladding 2 and the upper cladding 4.

[0004]

By the way, it can be expected that the cost of the organic optical waveguide can be reduced, but the peeling of the polyimide film at the end face of the organic optical waveguide is one of the causes of the deterioration of the organic optical waveguide. Was.

FIG. 3 is a diagram showing the result of measuring the correlation between the peeling width of the polyimide film and the loss at the end face of the optical waveguide having the structure shown in FIG. In this measurement, the input and output end faces of the organic optical waveguide to which the accelerated deterioration test at a temperature of 121 ° C. and a humidity of 100% was applied for 500 hours were cut by 2 mm each, and the light loss before cutting and the light loss after cutting were cut. By taking the difference, the loss at the end face of the optical waveguide is obtained. In the organic optical waveguide shown in FIG. 2 as a conventional example, an adhesive layer 10 is provided between the substrate 1 and the lower clad 2 to improve the adhesiveness between the substrate 1 and the polyimide film. Insufficient, film peeling occurs. FIG. 3 shows that the loss at the end face of the optical waveguide increases as the film peeling proceeds.

This film peeling occurs because the coefficient of thermal expansion of the polyimide film is larger than the coefficient of thermal expansion of the silicon substrate 1. When manufacturing an organic optical waveguide using polyimide,
Baking for imidization is performed. In the process of returning from the baking temperature to room temperature, a tensile stress due to a difference in thermal expansion coefficient acts on the silicon substrate 1 from the polyimide film. The pulling stress due to such a difference in thermal expansion coefficient is a main factor for causing the polyimide film to peel off.

The tensile stress is proportional to the product of the difference between the coefficient of thermal expansion between the polyimide film and the silicon substrate 1 and the thickness of the polyimide film. Since the thermal expansion coefficients of the polyimide film and the silicon substrate 1 are 4.0 × 10 ⁻⁵ (/ ° C.) and 3.0 × 10 ⁻⁶ (/ ° C.), the difference is about 2.5
× 10 ⁻⁵ (/ ° C.). The thickness of the polyimide film in the organic optical waveguide tested in FIG. 3 is 25 μm.
Further, the optical waveguide shown in FIG.
A structure is provided in which an adhesive layer 10 is provided between the first and second layers to prevent film peeling. Therefore, even if the adhesive layer 10 is provided between the substrate 1 and the lower clad 2, the difference in thermal expansion coefficient is 2.5 × 1
0 ^-5 (/ ° C.) and the thickness of the polyimide film is 25
Above μm, the film peeling shown in FIG. 3 occurs and the loss increases.

FIG. 3 shows an organic optical waveguide in which an adhesive layer 10 is provided between a polyimide film and a substrate 1. However, if there is no adhesive layer 10 between the substrate 1 and the lower clad 2, thermal expansion will occur. When the coefficient difference reaches 2.5 × 10 ⁻⁵ (/ ° C.), when the thickness of the polyimide film is 10 μm or more, film peeling occurs, and loss increases.

When the optical waveguide is designed to propagate only a single mode, the thickness of the polyimide constituting the optical waveguide is about 10 μm. However, when the optical waveguide is designed to propagate the multimode, the core 3 Area is 4 times, 16
Therefore, the heights of the lower cladding 2 and the upper cladding 3 are also doubled and quadrupled. That is, when the optical waveguide is designed to propagate the multi-mode, the thickness of the polyimide becomes twice or four times.

The tensile stress is proportional to the product of the difference between the coefficients of thermal expansion and the thickness of the polyimide film. Therefore, when the thickness of the polyimide film is twice as large as 20 μm, the difference in the coefficient of thermal expansion is 1.50. At 2 × 10 ⁻⁵ (/ ° C.), film peeling occurs to the extent shown in FIG. 3 and loss increases. Further, when the thickness of the polyimide film is 40 μm, which is four times as large, the film exfoliation of the degree shown in FIG. 3 occurs at a thermal expansion coefficient difference of 0.6 × 10 ⁻⁵ (/ ° C.), which is a quarter. Loss increases.

The peeling of the film at the end face of the optical waveguide is as follows.
The product of the thermal expansion coefficient difference between the insulating film forming the organic optical waveguide and the substrate 1 and the insulating film forming the organic optical waveguide are not limited to the organic optical waveguide manufactured using the polyimide film. Occurs when the value is reached. FIG. 3 shows an organic optical waveguide in which one adhesive layer 10 is provided between the polyimide film and the substrate 1. However, even when the adhesive layer 10 has a multilayer structure, film peeling occurs.

An object of the present invention is to prevent the above-described peeling of the polyimide film at the end face of the optical waveguide in order to improve the reliability of the organic optical waveguide.

[0013]

By sealing the end face of the organic optical waveguide with a resin, the resin adheres the insulating film forming the optical waveguide to the substrate 1, thereby preventing film peeling. In particular, as shown in FIG.
When the temperature reaches 0 ^-5 (/ ° C.) and the film thickness of the organic optical waveguide is 10 μm or more, film peeling occurs and loss increases.

Based on this, the present invention solves the above problem by adopting the following structure of an organic optical waveguide. That is, the organic optical waveguide is formed by laminating the lower clad, the core, and the upper clad on the substrate in order from the bottom, and the thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is equal to that of the substrate. The coefficient of thermal expansion is larger than 2.5 × 10 ⁻⁵ (/ ° C.), the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 10 μm or more. An organic optical waveguide having a structure in contact with a substrate, a lower clad, a core, and an upper clad.

On the other hand, the tensile stress which causes film peeling is proportional to the product of the difference between the coefficient of thermal expansion between the polyimide film and the silicon substrate 1 and the thickness of the polyimide film. For this reason, if the thickness of the film constituting the organic optical waveguide is large, even if the difference in thermal expansion coefficient is small, film peeling occurs, and loss increases.

For example, when the thickness of the film constituting the organic optical waveguide is 20 μm or more, the difference in thermal expansion coefficient is 1.2 × 10
^{At -5} (/ ° C.), film peeling occurs, and when the film thickness is 40 μm or more, film peeling occurs at a thermal expansion coefficient difference of 0.6 × 10 ^-5 (/ ° C.). Also in these cases, film peeling can be prevented by adopting a structure in which the resin is in contact with the insulating film forming the optical waveguide and the substrate 1.

An intermediate layer such as an adhesive layer 10 or a second lower clad 2 may be provided between the substrate 1 and the lower clad 2 of the organic optical waveguide. Even in the case where the intermediate layer is provided, film peeling can be prevented by adopting a structure in which the resin is in contact with the insulating film forming the optical waveguide, the substrate 1, and the intermediate layer. When a plurality of intermediate layers are provided, film peeling can be prevented by adopting a structure in which the resin is in contact with the insulating film forming the optical waveguide, the substrate 1, and the plurality of intermediate layers.

On the other hand, when an optical module is manufactured by mounting an organic optical waveguide, a resin 9 used for sealing the optical module can be used. The sealing resin enters the end face of the organic optical waveguide. By doing so, the sealing resin 9 adheres the polyimide film to the substrate, and film peeling can be prevented.

Specifically, the problem can be solved by adopting the following optical module structure. That is, in the optical module mounted with an organic optical waveguide and sealed with a resin, the organic optical waveguide is formed by sequentially laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom, The thermal expansion coefficient of the insulating film forming the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 × 10 ⁻⁵ (/ ° C.) or more. An optical module having a structure in which the thickness of an insulating film constituting a clad is 10 μm or more, and a resin used for resin sealing enters an end face of an organic optical waveguide and contacts all of a substrate, a lower clad, a core, and an upper clad.

When the resin 9 used for sealing the optical module is used, the thickness of the insulating film constituting the organic optical waveguide is 2.
If it is four times or four times, the film separation occurs when the difference in thermal expansion coefficient between the substrate 1 and the insulating film is 1/2 or 1/4. Also in this case, film peeling can be prevented by adopting a structure in which the sealing resin is in contact with the substrate 1 and the insulating film constituting the optical waveguide. Further, even when the adhesive layer 10 is provided between the substrate 1 and the lower clad 2 of the organic optical waveguide, a structure in which the sealing resin contacts the substrate 1, the intermediate layer, and the insulating film forming the optical waveguide. By doing so, film peeling can be prevented.

Since the polyimide film has a large thermal expansion coefficient, the present invention is particularly effective when an organic optical waveguide is formed using this polyimide film.

Although the case where the optical module is sealed with a resin has been described above, the present invention is also effective when the optical integrated circuit is sealed with a resin. Therefore, not only optical modules but also optical integrated circuits are included in the present invention.

[0023]

(Embodiment 1) Hereinafter, an embodiment in which the present invention is applied to an organic optical waveguide will be described with reference to FIG. FIG. 4A is a cross-sectional view showing a state where the lower clad 2 is formed. A polyimide precursor (polyamic acid) is applied onto a silicon substrate 1 by spin coating. The thickness is 5 μm. This is baked at 350 ° C. to imidize the polyamic acid. By imidization, infrared absorption due to vibration of the CH group in the polymer is reduced, and the loss of an optical waveguide having a wavelength of 1.4 ± 0.5 μm is reduced.

FIG. 4B is a view in which the core 3 is formed.
A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm. At this time, a polyimide precursor is selected so that the refractive index of the core 3 is larger than the refractive index of the lower clad 2. Then, an extra portion is removed by photolithography and dry etching to form a core 3.

FIG. 4C is a diagram in which the upper clad 4 is formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm on the upper part of the core 3.
m. At this time, a polyimide precursor is selected such that the refractive index of the upper clad 4 is the same as the refractive index of the lower clad 2. When the upper clad 4 is completed, the thickness of the polyimide film is 15 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 is 2.5 × 10 ⁻⁵ (/ ° C.).

FIG. 4D is a view in which a silicon resin 9 is adhered to the end face of the optical waveguide. The silicon resin 9 penetrates into the end face of the optical waveguide and adheres to the polyimide film and the substrate 1.
By doing so, peeling of the polyimide film can be prevented.
That is, it is possible to prevent the organic optical waveguide from being deteriorated due to the peeling of the film and to improve the reliability.

FIG. 1A is a schematic perspective view of the optical waveguide manufactured as described above. Also, FIG.
3A is a cross-sectional view of an end face portion indicated by a circle.

FIG. 5 is a diagram showing the effect of the present invention. It can be seen that film adhesion can be prevented by bonding the resin 9 to the polyimide film and the substrate 1.

(Embodiment 2) Next, an embodiment in which an intermediate layer is provided between the silicon substrate 1 and the lower clad 2 will be described with reference to FIG. In this embodiment, the intermediate layer is an adhesive layer 1 for improving the adhesion between the polyimide film and the substrate 1.
0.

FIG. 6A shows an adhesive layer 1 as a first intermediate layer.
It is the figure which formed 0. An adhesive layer 10 is applied on a silicon substrate 1 by spin coating. The film thickness is 0.1μ
m.

FIG. 6B is a view in which the lower clad 2 is formed. A polyimide precursor (polyamic acid) is applied on the structure of FIG. 6A by spin coating. The thickness is 5 μm. This is baked at 350 ° C. to imidize the polyamic acid. By imidization, infrared absorption due to vibration of the CH group in the polymer is reduced, and the loss of an optical waveguide having a wavelength of 1.4 ± 0.5 μm is reduced.

FIG. 6C is a view in which the core 3 is formed.
A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm. At this time, a polyimide precursor is selected so that the refractive index of the core 3 is larger than the refractive index of the lower clad 2. Then, an extra portion is removed by photolithography and dry etching to form a core 3.

FIG. 6D is a view in which the upper clad 4 is formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm on the upper part of the core 3.
m. At this time, a polyimide precursor is selected so that the refractive index of the upper clad 4 is the same as the refractive index of the lower clad 2. When the upper clad 4 is completed, the thickness of the polyimide film is 15 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 is 2.5 × 10 ⁻⁵ (/ ° C.).

FIG. 6E is a view in which a silicon resin 9 is adhered to the end face of the optical waveguide. The silicon resin 9 penetrates into the end face of the optical waveguide and adheres to the polyimide film and the substrate 1.
By doing so, peeling of the polyimide film can be prevented.
That is, it is possible to prevent the organic optical waveguide from being deteriorated due to the peeling of the film and to improve the reliability.

FIG. 7 is a diagram showing the effect of the present invention. Although the adhesiveness with the polyimide film was improved by providing the adhesive layer 10, it was insufficient and film peeling occurred. On the other hand, when the resin 9 is bonded to the polyimide film and the substrate 1, it can be seen that the film peeling can be prevented.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG. In this embodiment, an intermediate layer is provided between the silicon substrate 1 and the lower clad 2, as in the second embodiment. However, the intermediate layer is the second lower cladding layer 2. The second lower cladding layer 2 is provided for improving light confinement in the optical waveguide.

FIG. 8A is a view in which the second lower cladding layer 2 has been formed. A polyimide precursor (polyamic acid) is applied onto a silicon substrate 1 by spin coating. The thickness is 3 μm. This is baked at 350 ° C. to imidize the polyamic acid. By imidization, infrared absorption due to vibration of the CH group in the polymer is reduced, and the loss of an optical waveguide having a wavelength of 1.4 ± 0.5 μm is reduced.

FIG. 8B is a view showing the lower clad 2 formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm.

FIG. 8C is a view in which the core 3 is formed.
A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm. At this time, a polyimide precursor is selected so that the refractive index of the core 3 is larger than the refractive index of the lower clad 2. Then, an extra portion is removed by photolithography and dry etching to form a core 3.

FIG. 8D is a view showing the upper clad 4 formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm on the upper part of the core 3.
m. At this time, a polyimide precursor is selected so that the refractive index of the upper clad 4 is the same as the refractive index of the lower clad 2. When the fabrication of the upper clad 4 is completed, the polyimide film thickness is 18 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 is 2.5 × 10 ⁻⁵ (/ ° C.), so that film peeling occurs.

FIG. 8E is a view in which the silicon resin 9 is adhered to the end face of the optical waveguide. The silicon resin 9 penetrates into the end face of the optical waveguide and adheres to the polyimide film and the substrate 1.
By doing so, peeling of the polyimide film can be prevented.
That is, it is possible to prevent the organic optical waveguide from being deteriorated due to the peeling of the film and to improve the reliability. In the case of this embodiment as well, the effect shown in FIG. 5 can be obtained.

(Embodiment 4) A fourth embodiment will be described with reference to FIG. This embodiment is an example in which first and second intermediate layers are provided between a silicon substrate 1 and a lower clad 2. In this embodiment, the first and second intermediate layers are respectively
Adhesive layer 1 for improving adhesion between polyimide film and substrate 1
0 and a second lower cladding 2 for improving confinement of light in the optical waveguide.

FIG. 9A is a view in which the adhesive layer 10 is formed. An adhesive layer 10 is applied on a silicon substrate 1 by spin coating. The thickness is 0.1 μm.

FIG. 9B is a view in which the second lower cladding layer 2 has been formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 3 μm.

FIG. 9C is a view in which the lower clad 2 is formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm.

FIG. 9D is a view showing the core 3 formed.
A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm. At this time, a polyimide precursor is selected so that the refractive index of the core 3 is larger than the refractive index of the lower clad 2. Then, an extra portion is removed by photolithography and dry etching to form a core 3.

FIG. 9E is a view showing the formation of the upper clad 4. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm on the upper part of the core 3.
m. At this time, a polyimide precursor is selected so that the refractive index of the upper clad 4 is the same as the refractive index of the lower clad 2. When the fabrication of the upper clad 4 is completed, the polyimide film thickness is 18 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 is 2.5 × 10 ⁻⁵ (/ ° C.), so that film peeling occurs.

FIG. 9F is a view in which a silicon resin 9 is adhered to the end face of the optical waveguide. The silicon resin 9 penetrates into the end face of the optical waveguide and adheres to the polyimide film and the substrate 1.
By doing so, peeling of the polyimide film can be prevented.
That is, it is possible to prevent the organic optical waveguide from being deteriorated due to the peeling of the film and to improve the reliability. Also in the case of this embodiment, the effect shown in FIG. 7 can be obtained.

(Embodiment 5) Embodiment 5 will be described with reference to FIG. This embodiment is an embodiment in which the substrate 1 has a two-layer structure composed of a SiO ₂ film and silicon. When the substrate 1 has a two-layer structure, light confinement of the optical waveguide can be improved.

FIG. 10A is a view in which the lower clad 2 is formed. A polyimide precursor (polyamic acid) is applied by spin coating on a substrate 1 having a two-layer structure of silicon and a SiO ₂ film. The thickness is 5 μm. This is baked at 350 ° C. to imidize the polyamic acid. By imidation, infrared absorption due to vibration of the CH group in the polymer is reduced, and the wavelength is 1.4 ± 0.1.
Optical waveguide loss of 5 μm is reduced.

FIG. 10B is a view in which the core 3 is formed. A polyimide precursor is applied and baked on the structure of FIG. The thickness is 5 μm. At this time, core 3
Is selected so that the refractive index is higher than the refractive index of the lower cladding 2. Excess portions are removed by photolithography and dry etching, and the core 3 is removed.
To form

FIG. 10C is a view in which the upper clad 4 is formed. A polyimide precursor is applied and baked on the structure of FIG. The film thickness is 5 μm on the upper part of the core 3. At this time, a polyimide precursor is selected so that the refractive index of the upper clad 4 is the same as the refractive index of the lower clad 2. When the upper clad 4 is completed, the thickness of the polyimide film is 15 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 is 2.5 × 10 ⁻⁵ (/ ° C.).

FIG. 10D is a view in which a silicon resin 9 is adhered to the end face of the optical waveguide. The silicon resin 9 penetrates into the end face of the optical waveguide and adheres to the polyimide film and the substrate 1 having a two-layer structure. By doing so, peeling of the polyimide film can be prevented. That is, it is possible to prevent the organic optical waveguide from being deteriorated due to the peeling of the film and to improve the reliability. In the case of this embodiment as well, the effect shown in FIG. 5 can be obtained.

(Embodiment 6) The following is an embodiment in which the present invention is applied to an optical module. Hereinafter, an embodiment will be described with reference to FIG.

FIG. 11A is a view showing the mounting portion 7 of the photodetector 5 formed. The polyimide film is removed from the structure of FIG. 4C by photolithography and dry etching to form the mounting portion 7.

FIG. 11B is a diagram in which the fiber block 8 is mounted on the input side of the organic optical waveguide. Separation of the polyimide film at the end face of the optical waveguide on the input side can be prevented because the fiber block 8 suppresses the end face of the input side from above.

FIG. 11C is a diagram in which the photodetector 5 is mounted on the output side of the organic optical waveguide.

FIG. 11D is a view in which the resin 9 is sealed to protect the optical module. Silicon gel is generally used as the sealing resin 9. At this time, sealing is performed so that the resin 9 covers the output side of the organic optical waveguide and the photodetector 5. By doing so, the resin 9 enters the output side end face of the polymer optical waveguide, and comes into contact with each of the substrate 1, the lower clad 2, the core 3, and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the output side end face can be prevented. That is, deterioration of the optical module due to film peeling can be prevented, and reliability can be improved. In Example 6, the thickness of the polyimide film was 15 μm, and the difference in thermal expansion coefficient between the polyimide film and the substrate 1 was 2.5 × 10 ⁻⁵ (/ ° C.). However, the effect shown in FIG. 5 is obtained also in the case of the present embodiment by bonding the resin 9 to the substrate 1 and the polyimide film.

(Embodiment 7) Embodiment 7 will be described with reference to FIG. This embodiment is an embodiment in which the present invention is applied to an optical module, in which a fiber 11 is fixed directly to an input side of an optical waveguide with a resin 9. By doing so, the resin 9 covers the input side end face of the optical waveguide, so that the film separation on the input side end face can be prevented.

FIG. 12A is a view showing the mounting portion 7 of the photodetector 5 formed. The polyimide film is removed by photolithography and dry etching from the structure shown in FIG.

FIG. 12B is a diagram in which the fiber 11 is fixed with the resin 9 on the input side of the organic optical waveguide. When the polyimide film is peeled off at the input side end face of the optical waveguide, the resin 9 enters the input side end face of the polymer optical waveguide and comes into contact with the substrate 1, the lower clad 2, the core 3 and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the input side end face can be prevented.

FIG. 12C is a diagram in which the photodetector 5 is mounted on the output side of the organic optical waveguide.

FIG. 12D is a view in which the resin 9 is sealed to protect the optical module. Silicon gel is generally used as the sealing resin 9. At this time, sealing is performed so that the resin 9 covers the output side of the polymer optical waveguide and the photodetector 5. By doing so, the resin 9 enters the output side end face of the polymer optical waveguide, and comes into contact with each of the substrate 1, the lower clad 2, the core 3, and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the output side end face can be prevented. That is, deterioration of the optical module due to film peeling can be prevented, and reliability can be improved. In Example 7, the polyimide film thickness was 15 μm, and the thermal expansion coefficient difference between the polyimide film and the substrate 1 was 2.5 × 10 ⁻⁵ (/ ° C.). However, the effect shown in FIG. 5 is obtained also in the case of the present embodiment by bonding the resin 9 to the substrate 1 and the polyimide film.

(Eighth Embodiment) An eighth embodiment will be described with reference to FIG. This embodiment is an embodiment in which the present invention is applied to an optical module, in which an intermediate layer is provided between a silicon substrate 1 and a lower clad 2. In this embodiment, the intermediate layer is an adhesive layer 10 for improving the adhesiveness between the polyimide film and the substrate 1.

FIG. 13A is a view in which the mounting section 7 of the photodetector 5 is formed. The polyimide film is removed by photolithography and dry etching from the structure shown in FIG.

FIG. 13B is a diagram in which the fiber block 8 is mounted on the input side of the organic optical waveguide. Separation of the polyimide film at the end face of the optical waveguide on the input side can be prevented because the fiber block 8 suppresses the end face of the input side from above.

FIG. 13C is a diagram in which the photodetector 5 is mounted on the output side of the organic optical waveguide.

FIG. 13D is a view in which the resin 9 is sealed to protect the optical module. Silicon gel is generally used as the sealing resin 9. At this time, sealing is performed so that the resin 9 covers the output side of the polymer optical waveguide and the photodetector 5. By doing so, the resin 9 enters the output side end face of the polymer optical waveguide, and comes into contact with each of the substrate 1, the lower clad 2, the core 3, and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the output side end face can be prevented. That is, the deterioration of the optical module due to the peeling of the film can be prevented and the reliability can be improved. In Example 10, the polyimide film thickness was 15 μm, and the thermal expansion coefficient difference between the polyimide film and the substrate 1 was 2.5 × 10 ⁻⁵ (/ ° C.). However, in the case of this embodiment, the effect shown in FIG. 7 is obtained by bonding the resin 9 to the substrate 1 and the polyimide film.

(Embodiment 9) Embodiment 9 will be described with reference to FIG. This embodiment is an embodiment in which the present invention is applied to an optical module, in which an intermediate layer is provided between a silicon substrate 1 and a lower clad 2, and a fiber 11 is directly connected to a resin 9 on the input side of an optical waveguide. It is fixed with. In this embodiment, the intermediate layer is composed of the polyimide film and the substrate 1.
And an adhesive layer 10 for improving adhesiveness with the adhesive. Further, since the resin 9 covers the input end face of the optical waveguide by fixing the fiber 11 directly to the input side of the optical waveguide with the resin 9, it is possible to prevent the input end face from peeling off.

FIG. 14A is a view in which the mounting section 7 of the photodetector 5 is formed. The polyimide film is removed by photolithography and dry etching from the structure shown in FIG.

FIG. 14B is a diagram in which the fiber 11 is fixed with the resin 9 on the input side of the organic optical waveguide. When the polyimide film is peeled off at the input side end face of the optical waveguide, the resin 9 enters the input side end face of the polymer optical waveguide and comes into contact with the substrate 1, the lower clad 2, the core 3 and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the input side end face can be prevented.

FIG. 14C is a view in which the photodetector 5 is mounted on the output side of the organic optical waveguide.

FIG. 14D is a view in which the resin 9 is sealed to protect the optical module. Silicon gel is generally used as the sealing resin 9. At this time, sealing is performed so that the resin 9 covers the output side of the polymer optical waveguide and the photodetector 5. By doing so, the resin 9 enters the output side end face of the polymer optical waveguide, and comes into contact with each of the substrate 1, the lower clad 2, the core 3, and the upper clad 4. Then, the polyimide film constituting the optical waveguide and the substrate 1 are bonded to each other, and peeling of the polyimide film on the output side end face can be prevented. That is, the deterioration of the optical module due to the peeling of the film can be prevented and the reliability can be improved. In Example 11, the polyimide film thickness was 15 μm, and the thermal expansion coefficient difference between the polyimide film and the substrate 1 was 2.5 × 10 ⁻⁵ (/ ° C.). However, in the case of this embodiment, the effect shown in FIG. 7 is obtained by bonding the resin 9 to the substrate 1 and the polyimide film.

(Embodiment 10) In this embodiment, a laser diode is inserted in place of the photodetector 5 in the structure shown in FIG. 11 of Embodiment 6 of the present invention.
Similarly to this embodiment, it is possible to insert a laser diode instead of the photodetector 5 in the seventh to ninth embodiments.

[0075]

According to the present invention, since the resin 9 in contact with the end face of the organic optical waveguide bonds the organic optical waveguide to the substrate 1, peeling of the insulating film forming the organic optical waveguide is prevented. Therefore, the reliability of the organic optical waveguide and the optical module equipped with the organic optical waveguide can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view and a partially enlarged cross section showing an example of an organic optical waveguide structure according to the present invention.

FIG. 2 is a schematic perspective view showing an example of a conventional organic optical waveguide structure.

FIG. 3 is a measurement diagram showing a correlation between a separation width of a polyimide film and a loss at an end face of an optical waveguide.

FIG. 4 is a sectional view showing a manufacturing process of the optical waveguide according to the first embodiment of the present invention.

FIG. 5 is a measurement diagram showing the results of an accelerated deterioration test in Example 1 of the present invention and a conventional example.

FIG. 6 is a sectional view showing a manufacturing process of the optical waveguide according to the second embodiment of the present invention.

FIG. 7 is a measurement diagram showing the results of an accelerated deterioration test in Example 2 of the present invention and a conventional example.

FIG. 8 is a sectional view showing a manufacturing process of the optical waveguide according to the third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a manufacturing process of the optical waveguide according to the fourth embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a manufacturing process of the optical waveguide according to the fifth embodiment of the present invention.

FIG. 11 is a sectional view showing a manufacturing process of the optical waveguide according to the sixth embodiment of the present invention.

FIG. 12 is a sectional view showing a manufacturing process of the optical waveguide according to the seventh embodiment of the present invention.

FIG. 13 is a sectional view showing a manufacturing process of the optical waveguide according to the eighth embodiment of the present invention.

FIG. 14 is a sectional view showing a manufacturing process of the optical waveguide according to the ninth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Lower clad, 3 ... Core, 4 ... Upper clad, 5 ... Photodetector, 7 ... Mounting part, 8 ... Fiber block, 9 ... Resin, 10 ... Adhesive layer, 11 ... Optical fiber.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takamitsu Nagara 5-22-1, Josuihonmachi, Kodaira-shi, Tokyo Inside Hitachi Super LSI Systems Co., Ltd. (72) Inventor Mari Mari Koizumi Tokyo 1-280, Higashi-Koigakubo, Kokubunji-shi, Hitachi, Ltd. Central Research Laboratory, Ltd. (72) Inventor Akira Kuwahara 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 2H047 KA04 KA15 MA05 MA07 PA02 PA21 PA24 PA28 QA05 QA07 TA00

Claims (27)

[Claims] An organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom, and thermal expansion of an insulating film constituting the lower clad, the core, and the upper clad. The coefficient is larger than the coefficient of thermal expansion of the substrate, the difference is not less than 2.5 × 10 ⁻⁵ (/ ° C.), and the thickness of the insulating film constituting the lower clad, the core and the upper clad is not less than 10 μm. An organic optical waveguide characterized in that the organic optical waveguide has a structure in which the resin contacts all of the substrate, the lower clad, the core, and the upper clad. 2. The organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom, and the thermal expansion of an insulating film constituting the lower clad, the core, and the upper clad. The coefficient is larger than the coefficient of thermal expansion of the substrate, the difference is 1.2 × 10 ⁻⁵ (/ ° C.) or more, and the thickness of the insulating film forming the lower clad, the core, and the upper clad is 20 μm or more. An organic optical waveguide characterized in that the organic optical waveguide has a structure in which the resin contacts all of the substrate, the lower clad, the core, and the upper clad. 3. The organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom, and thermal expansion of an insulating film forming the lower clad, the core, and the upper clad. The coefficient is larger than the coefficient of thermal expansion of the substrate, the difference is 0.6 × 10 ⁻⁵ (/ ° C.) or more, and the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 40 μm or more. An organic optical waveguide characterized in that the organic optical waveguide has a structure in which the resin contacts all of the substrate, the lower clad, the core, and the upper clad. 4. The organic optical waveguide is formed by laminating an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom, and an insulating film constituting the lower clad, the core, and the upper clad. Has a coefficient of thermal expansion larger than that of the substrate, the difference is not less than 2.5 × 10 ⁻⁵ (/ ° C.), and the thickness of the insulating film constituting the lower clad, the core and the upper clad is 10 μm. The organic optical waveguide as described above, further comprising a structure in which the resin is in contact with all of the substrate, the intermediate layer, the lower clad, the core, and the upper clad. 5. The organic optical waveguide is formed by laminating an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom, and an insulating film forming the lower clad, the core, and the upper clad. Has a coefficient of thermal expansion larger than that of the substrate, the difference is not less than 1.2 × 10 ⁻⁵ (/ ° C.), and the thickness of the insulating film constituting the lower clad, the core and the upper clad is 20 μm. The organic optical waveguide as described above, further comprising a structure in which the resin is in contact with all of the substrate, the intermediate layer, the lower clad, the core, and the upper clad. 6. The organic optical waveguide is formed by laminating an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom, and an insulating film constituting the lower clad, the core, and the upper clad. Has a coefficient of thermal expansion larger than that of the substrate, the difference is 0.6 × 10 ⁻⁵ (/ ° C.) or more, and the thickness of the insulating film forming the lower clad, the core, and the upper clad is 40 μm. The organic optical waveguide as described above, further comprising a structure in which the resin is in contact with all of the substrate, the intermediate layer, the lower clad, the core, and the upper clad. 7. An organic optical waveguide is formed by laminating a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad on a substrate in this order from the bottom. The thermal expansion coefficient of the insulating film constituting the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 × 10 ⁻⁵ (/ ° C.) or more. The thickness of the constituent insulating film is 10
An organic optical waveguide having a thickness of at least μm and having a structure in which a resin contacts all of a substrate, a lower clad, a core, and an upper clad. 8. An organic optical waveguide comprising: a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad laminated on a substrate in this order from the bottom; The thermal expansion coefficient of the insulating film constituting the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is at least 1.2 × 10 ⁻⁵ (/ ° C.). The thickness of the constituent insulating film is 20
An organic optical waveguide having a thickness of at least μm and having a structure in which a resin is in contact with a substrate, a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad. 9. An organic optical waveguide comprising: a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad laminated on a substrate in order from the bottom; The thermal expansion coefficient of the insulating film constituting the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 0.6 × 10 ⁻⁵ (/ ° C.) or more. The thickness of the constituent insulating film is 40
An organic optical waveguide having a thickness of at least μm and having a structure in which a resin is in contact with a substrate, a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad. 10. An organic optical waveguide formed by laminating a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 × 10 ⁻⁵ (/ ° C.) or more. , The core and the upper cladding have an insulating film thickness of 10 μm or more, and the resin is formed of a substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core and an upper clad. An organic optical waveguide having a structure in contact with all. 11. An organic optical waveguide formed by laminating a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 1.2 × 10 ⁻⁵ (/ ° C.) or more. , The core and the upper clad have an insulating film thickness of 20 μm or more, and the resin is formed of a substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core and an upper clad. An organic optical waveguide having a structure in contact with all. 12. An organic optical waveguide formed by laminating a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 0.6 × 10 ⁻⁵ (/ ° C.) or more. , The core and the upper cladding have an insulating film thickness of 40 μm or more, and the resin is formed of a substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer, a lower clad, a core and an upper clad. An organic optical waveguide having a structure in contact with all. 13. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom. And the lower cladding,
The thermal expansion coefficient of the insulating film constituting the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 × 10 ^−5.
(/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core and the upper clad is 10 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide, and An optical module having a structure in contact with all of a core, a core, and an upper clad. 14. An optical module mounted with an organic optical waveguide and sealed with a resin, wherein the organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 1.2 × 10
^-5 (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 20 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide, and An optical module having a structure in contact with all of a lower clad, a core, and an upper clad. 15. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide is formed by laminating a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 0.6 × 10
^-5 (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 40 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide, and An optical module having a structure in contact with all of a lower clad, a core, and an upper clad. 16. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide is formed by stacking an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 ×
10 ^-5 (/ ° C.) or more, furthermore, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 10 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide. An optical module having a structure in contact with all of an intermediate layer, a lower clad, a core, and an upper clad. 17. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide is formed by stacking an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 1.2 ×
10 ⁻⁵ (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 20 μm or more, and the resin used for resin encapsulation enters the end face of the organic optical waveguide. An optical module having a structure in contact with all of an intermediate layer, a lower clad, a core, and an upper clad. 18. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide is formed by laminating an intermediate layer, a lower clad, a core, and an upper clad on a substrate in order from the bottom. The lower cladding, the core, the thermal expansion coefficient of the insulating film constituting the upper cladding is larger than the thermal expansion coefficient of the substrate, the difference is 0.6 ×
10 ^-5 (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core and the upper clad is 40 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide and An optical module having a structure in contact with all of an intermediate layer, a lower clad, a core, and an upper clad. 19. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide comprises a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad in this order from the bottom. Each of them is formed by laminating on the substrate, and the thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 2.5 × 10 ^−5. (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 10 μm or more, and the resin used for resin sealing enters the end face of the organic optical waveguide, and
An optical module having a structure in contact with all of the intermediate layer, the second intermediate layer, the lower clad, the core, and the upper clad. 20. In an optical module having an organic optical waveguide mounted thereon and sealed with a resin, the organic optical waveguide includes a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad in order from the bottom. Each is formed by laminating on a substrate, and the thermal expansion coefficient of the insulating film constituting the lower clad, the core and the upper clad is larger than the thermal expansion coefficient of the substrate, and the difference is 1.2 × 10 ^−5. (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 20 μm or more, and furthermore, the resin used for resin sealing enters the end face of the organic optical waveguide, and the substrate,
An optical module having a structure in contact with all of the intermediate layer, the second intermediate layer, the lower clad, the core, and the upper clad. 21. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide comprises a first intermediate layer, a second intermediate layer, a lower clad, a core, and an upper clad in order from the bottom. Each is formed by laminating on a substrate, and the thermal expansion coefficients of the insulating films constituting the lower cladding, the core, and the upper cladding are larger than the thermal expansion coefficient of the substrate, and the difference is 0.6 × 10 ^−5. (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core, and the upper clad is 40 μm or more, and further, the resin used for resin sealing enters the end face of the organic optical waveguide, and the substrate,
An optical module having a structure in contact with all of the intermediate layer, the second intermediate layer, the lower clad, the core, and the upper clad. 22. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide comprises a first intermediate layer, a second intermediate layer, a third intermediate layer, and a lower cladding in order from the bottom. , A core, and an upper clad are laminated on a substrate, respectively. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate. 0.5 × 10 ⁻⁵ (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core and the upper clad is 10 μm or more, and the resin used for resin sealing is the end face of the organic optical waveguide. A penetrating substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer,
An optical module having a structure in contact with all of a lower clad, a core, and an upper clad. 23. In an optical module having an organic optical waveguide mounted thereon and sealed with a resin, the organic optical waveguide is formed of a first intermediate layer, a second intermediate layer, a third intermediate layer, and a lower cladding in order from the bottom. , A core, and an upper clad are laminated on the substrate, respectively, and the thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate. 2 × 10 ⁻⁵ (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core and the upper clad is 20 μm or more, and the resin used for resin sealing is the end face of the organic optical waveguide. A penetrating substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer,
An optical module having a structure in contact with all of a lower clad, a core, and an upper clad. 24. An optical module having an organic optical waveguide mounted thereon and sealed with a resin, wherein the organic optical waveguide comprises a first intermediate layer, a second intermediate layer, a third intermediate layer, and a lower cladding in order from the bottom. , A core, and an upper clad are laminated on a substrate, respectively. The thermal expansion coefficient of the insulating film constituting the lower clad, the core, and the upper clad is larger than the thermal expansion coefficient of the substrate. 0.6 × 10 ⁻⁵ (/ ° C.) or more, the thickness of the insulating film constituting the lower clad, the core and the upper clad is 40 μm or more, and the resin used for resin sealing is the end face of the organic optical waveguide. A penetrating substrate, a first intermediate layer, a second intermediate layer, a third intermediate layer,
An optical module having a structure in contact with all of a lower clad, a core, and an upper clad. 25. The organic optical waveguide according to claim 1, wherein the insulating film constituting the lower clad, the core, and the upper clad is made of polyimide. 26. The optical module according to claim 13, wherein an insulating film forming a lower clad, a core, and an upper clad of the organic optical waveguide is made of polyimide. 27. An optical integrated circuit comprising the organic optical waveguide according to any one of claims 1 to 12.