JPS6259905A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To obtain an optical waveguide by forming an inorg. material mask to a prescribed pattern on a high-polymer layer having a high refractive index, etching the high-polymer layer and superposing a surface clad layer thereon. CONSTITUTION:The prescribed high-polymer material 11 such as PMMA having the high refractive index and the prescribed inorg. material 11 such as SiO2 by a plasma CVD method are superposed on a substrate 1. A photoresists 13 is coated on these materials. UV rays or the like are irradiated via a mask 14 thereto to develop the materials. The inorg. layer 12 is etched by the resist pattern 13' then the high-polymer layer 11 is etched by RIE. The resulted high- polymer layer pattern 11' is coated with a surface clad layer 15. The optical waveguide made of the high-polymer material having the substantial refractive index difference is obtd. with the decreased transmission loss according to the above-mentioned condition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing an optical waveguide. For more details,
Related to optical waveguide manufacturing methods that are advantageous for economicalization, miniaturization, and stabilization of optical components such as optical couplers, optical multiplexers and demultiplexers, which are essential for the diversification and advancement of optical communication systems and optical information processing. It is.

2. Description of the Related Art In optical fiber communication technology and optoelectronics technology, various optical circuit elements are required to form a predetermined optical circuit. Although miniaturized optical elements that are miniaturized conventional optical elements have already been put into practical use, waveguide elements that are smaller and more stable are expected to be put into practical use in the future.
Furthermore, it is presumed that it will be necessary for the production of optical integrated circuits and the like.

Optical waveguides are required to form such optical waveguide circuits, and like optical fibers, these are classified according to the number of modes of light propagating therein, the shape of the refractive index distribution, etc. However, while optical fibers were developed primarily for long-distance optical transmission with low transmission loss, optical waveguides can guide light over short distances and control light through modulation, modification, wavelength conversion, mixing, demodulation, etc. Or provide various conversions such as amplification, pulse waveform shaping, phase shift, optical beam conversion, branching,
It is an optical element useful for performing various types of coupling such as multiplexing and various types of optical information processing.

Optical waveguides, like optical fibers, generally function to confine light within the waveguide in at least two dimensions.

Therefore, in order to confine light within the waveguide, it is necessary to form the waveguide with a material having a higher refractive index than the surrounding environment.

By the way, classically, such optical components were composed of minute optical components such as prisms, and therefore required troublesome operations such as optical axis alignment, and were also difficult to assemble. Therefore,
Various optical waveguides have been proposed in order to avoid these complicated operations by fabricating optical waveguides on a plane.

Conventionally, materials for optical waveguides include semiconductor crystals, dielectric crystals, glass, and polymer materials. Among them, polymer materials are easy to form into thin and thick films, and are relatively easy to refract through photochemical reactions. It is an advantageous material for optical waveguides compared to the above-mentioned materials because it can realize a change in the index.

Conventional methods for manufacturing optical waveguides using polymeric materials involve selectively irradiating a polymeric film containing a low refractive index monomer with ultraviolet rays to selectively polymerize the monomer, thereby changing the refractive index. After forming an optical waveguide, a surface crack layer and a solid layer were formed. That is, to explain this method in more detail based on the attached FIG. 2, a laminate having a structure as shown in FIG. For example, by selectively irradiating ultraviolet rays through a mask 3 (see FIG. 2(b)), monomers in the film 2 are selectively polymerized, and regions with different refractive indexes (A, B) are formed in the film 2. ) (see FIG. 2(C)) to obtain an optical waveguide (A), and then a cladding layer 4 made of a low refractive index material is formed (see FIG. 2(ci)) to obtain an optical waveguide (A) made of a polymeric material. The optical waveguide is completed.

Problems to be Solved by the Invention As mentioned above, optical waveguides useful for waveguide elements, optical integrated circuits, etc. that are expected to be put to practical use in optical fiber communications, optoelectronics, etc., are capable of controlling, converting, coupling, etc. of light. It is an essential optical component for

Various materials have been used for this optical waveguide, but polymer materials such as those explained based on Fig. 2 have been used because they are easy to process, especially to realize changes in refractive index. The use of is attracting attention.

However, in the above method, when forming an optical waveguide by selectively exposing a film containing a low refractive index monomer to ultraviolet rays, the exposed portion, that is, the waveguide portion, becomes colored, resulting in a large transmission loss. There are serious problems such as an increase in refractive index (1 dB/c+n) and an inability to secure a sufficient refractive index difference (approximately 1%).

In addition, since the optical waveguide material is directly exposed and patterned, the standing wave effect causes "sagging" in the cross section of the optical waveguide, as shown in Figure 3, etc., which also contributes to lower transmission loss. ing.

Therefore, it is important to develop a method for manufacturing a new optical waveguide made of polymeric material that can overcome the drawbacks of the conventional method and provide an advantageous optical waveguide, thereby realizing the optical integrated circuits and the like mentioned above. This is of great significance in making these systems compatible with the diversification and advancement of optical communication systems and optical information processing, and this is also the purpose of the present invention. That is, an object of the present invention is to provide a method for manufacturing an optical waveguide made of a polymeric material, which has low transmission loss and has a sufficient refractive index difference or a designed refractive index difference.

Means for Solving the Problems In view of the above-mentioned current state of conventional polymer optical waveguide manufacturing methods, the inventor has conducted various studies and has found that polymerization due to ultraviolet light exposure, which inevitably causes waveguide coloring, has been found. The present invention was completed based on the discovery that it is advantageous to form a polymer optical waveguide using etching technology instead of realizing a refractive index distribution based on a reaction.

That is, in the method for manufacturing an optical waveguide of the present invention, a high refractive index polymer layer is provided on a substrate, an inorganic deposited film is formed on the high refractive index polymer layer, and a photoetching method is applied to the inorganic material film. forming a predetermined pattern, using this as a mask, the polymer layer is selectively etched to obtain an optical waveguide, and after removing the mask pattern of the inorganic material, a surface cladding layer is formed. shall be.

According to another aspect of the present invention, a low refractive index polymeric material layer is applied on a substrate, a thin film of an inorganic material is provided thereon, and a predetermined pattern is formed on the inorganic thin film by photoetching. The low refractive index polymer layer is etched using the inorganic thin film pattern as a mask, and then, after removing the inorganic thin film mask pattern, a high refractive index polymer material is applied, and if necessary, the low refractive index polymer layer is etched. A similar algal molecule optical waveguide can be obtained by removing the high refractive index polymer by etchback and then providing a surface cladding layer.

Substrate materials and cladding layer materials useful for forming optical waveguide structures according to the method of the present invention include low refractive index materials such as silicone resins, vinylidene fluoride polymers such as tetrafluoroethylene vinylidene fluoride,
Benzoin ethyl ether, chloromethylnaphthalene,
In addition to polymeric materials such as hexamethyldioxane and vinyltrimethylsilane, inorganic materials such as glass, semiconductors, and ceramics can be used as examples, and polymeric materials with a high refractive index and low transmission loss can be used as waveguide forming materials. It is advantageous to use polymethyl acrylate (PMMA), epoxy resins, urethane resins and the like.

The method for manufacturing an optical waveguide of the present invention can be carried out, for example, according to a series of steps as shown in FIG. 1 attached.

That is, first, as shown in FIG. 1(a), 5 to 1
The first polymer material #Jll (either high refractive index or low refractive index may be used) is applied to a thickness in the range of 0.00 μm, and then an inorganic material layer 12 is applied in a thickness of 0.1 to 0.0 μm according to FIG. 1(b). .5μ
Deposits of about 1.0 m. This inorganic substance, for example 5i02.513
N4, Ti, etc. need to be deposited at a low temperature that does not deteriorate the polymer material layer 11, and for this purpose, it is preferable to use, for example, a plasma CVD method, an electron cyclotron resonance vapor deposition method, or the like.

Next, a photoresist 13 is applied on the inorganic material layer 12, and the resist is patterned 13' according to a photolithography technique (see FIGS. 1C and 1D). This photoresist 13 is selected from one that is resistant to etching of the underlying inorganic material layer 12.
From various known resists! It can be appropriately selected depending on the etching method of the material layer. As a method of patterning this resist, mask 1 is used as shown in FIG. 1(C).
It is also possible to perform irradiation with ultraviolet rays, electron beams, X-rays, etc. through a 02 plasma, followed by development and post-baking treatment, or direct patterning by a dry process such as ashing using 02 plasma.

Furthermore, as shown in FIG. 1(e), the photoresist pattern 13'' formed in step (d) is masked and
The inorganic material layer 12 is etched. Any known method can be used as this etching method, and wet etching or dry etching may be used.

Next, as shown in FIG. 1(f), the polymer layer 11 is etched using the patterned inorganic material layer 12" as a mask. This etching is particularly performed by ion etching using 02 gas or reactive ion etching. After the etching of the polymer layer 11 is completed, the remaining inorganic material layer 12' is removed by an appropriate means such as wet etching (see FIG. 1 (powder)), and finally the surface cladding layer 15 is etched. Deposition or application (generally 1-10 μm
) to complete the optical component.

On the other hand, according to the second aspect of the method of the present invention, since the first polymer layer is a low refractive index polymer layer, as shown in FIG.
After etching the first polymer layer according to the method and removing the inorganic thin film pattern, applying a second polymer material, i.e., a high refractive index polymer material, within the etching groove for forming an optical waveguide,
The second polymer material layer on the first polymer material layer 11 is removed by etching back.

This etchback is performed by reactive ion etching or ion etching, similar to the etching of the first polymer material layer. Next, a surface cladding layer of a low refractive index polymer material is provided to obtain an optical waveguide product having a structure as shown in FIG. 2 (6). Here, the first polymer layer and the surface cladding layer may be made of the same polymer material.

The problems with manufacturing polymer optical waveguides according to the conventional method are, firstly, that the material for forming the optical waveguide is directly exposed to ultraviolet light, and as a result, it is exposed to high temperatures. As a result, the resulting optical waveguide is colored, and "sagging" occurs at the interface with the adjacent low-refractive-index polymer layer due to the standing wave effect, resulting in a significant increase in optical transmission loss. In particular, and secondly, it is not possible to provide a sufficient refractive index difference between the optical waveguide and its surrounding environment. Furthermore, since the selection of polymeric materials is limited, the refractive index difference that can be realized is also limited.

Therefore, in the present invention, the drawbacks of the above-mentioned conventional methods are almost completely solved by applying etching technology to form the optical waveguide and using a polymeric material with low transmission loss as the material for forming the optical waveguide.

That is, the first problem is that by forming the optical waveguide or, in the second embodiment, forming the groove for the optical waveguide, by a specific dry etching method, the polymer layer for the optical waveguide is exposed to ultraviolet rays. This makes it possible to completely avoid the occurrence of defects such as coloring, and to avoid the occurrence of droop at the interface between the optical waveguide and its surrounding environment. Regarding this interface, as shown in the attached FIG. 3, when an optical waveguide is formed by etching according to the method of the present invention, it is formed with an extremely steep profile as shown in FIG. According to the law, the same figure (
As shown in b), a sag 21 is seen in the cross section, which causes an increase in transmission loss.

Furthermore, in the method of the present invention, since the polymer materials for the core part and the cladding part can be selected independently, the refractive index difference between them can be freely designed, and a sufficient refractive index difference can be provided. be able to.

From the above, according to the method of the present invention, optical waveguides with low transmission loss and high refractive index difference can be advantageously manufactured, and as a result, optical communication systems and optical information processing can be diversified and advanced. It becomes possible to do so.

EXAMPLES Hereinafter, the method of the present invention will be explained in more detail based on examples, and the effects thereof will be demonstrated.

However, the scope of the present invention is not limited in any way by the following examples.

Example 1 Glass was used as a substrate, and PM was deposited on it with a thickness of 50 μm.
MA was applied. Next, 5102 was deposited to a thickness of 0.2 μm using the plasma CVD method, and a photoresist (AZ13
50J Nijiplay Co., Ltd.) was applied, exposed to ultraviolet light through a mask, and developed to form a resist pattern. Using this resist pattern as a mask, S+02Fi is etched by plasma etching to form the resist opening S.
The i02 layer was removed. Remove this resist pattern,
PMMA other than the optical waveguide portion was removed by reactive ion etching using 02 gas using the SiO2 pattern as a mask.
layer removed. The SiO2 pattern was removed using a hydrofluoric acid-based etching solution, and then a hexamethyldioxane cladding layer was formed to a thickness of 10 μm by plasma CVD so that the remaining PMMA layer was completely covered. An optical waveguide component according to the present invention was manufactured.

Similarly, optical waveguides were fabricated using epoxy resin and urethane resin with low transmission loss.

In this way, an optical waveguide with excellent properties that can be put to practical use with a transmission loss of 0.1 to 0.3 dB/cm was obtained with a refractive index change Δn (0△n≦5%).

Effects of the Invention As explained in detail above, the method of the present invention can achieve various effects as shown below, and provides a practical optical waveguide with low transmission loss and large refractive index change. be able to.

(i) Since the optical waveguide is made of a polymer material with low transmission loss, high performance can be achieved.

(11) Since the polymer material layer constituting the optical waveguide is etched by ion etching or the like, an optical waveguide with a steep profile can be obtained.

In other words, the cross section is vertical as shown in Figure 3 (a), and the sag due to the standing wave effect (see Figure 3, etc.), which is conventional, is eliminated, and as a result, the transmission loss at the core-clad interface is greatly reduced. It can be reduced.

<1ii) Since the polymer materials for the core portion and the cladding portion can be selected independently, the refractive index difference between them can be freely designed.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(a) are diagrams schematically showing a series of steps for explaining the method for forming an optical waveguide of the present invention, and FIGS. 3(a) and 3(a) are diagrams showing a series of steps similar to FIG. 1 for explaining the method for forming a polymer waveguide, and FIGS. FIG. 2 is a cross-sectional view schematically showing the state of the core-clad interface. (Main reference numbers) 1...Substrate, 2...Low refractive index monomer-containing film, 3.14.
...Mask, 4...Surface cladding, 11.11'...First polymer material layer, 12.12".
...Inorganic material layer, 13, 13'... Resist, 15... Surface cladding layer (second polymer material layer), 20... Optical waveguide, 21... Who

Claims (10)

[Claims] (1) Coat a high refractive index polymer material on a substrate, provide an inorganic material layer thereon, form a predetermined pattern on the inorganic material layer by photo-etching, and use the resulting pattern as a mask to make the polymer material A method for manufacturing a polymer optical waveguide, comprising etching a material layer to obtain an optical waveguide, and providing a surface cladding layer after removing the mask pattern. (2) The method for manufacturing a polymer optical waveguide according to claim 1, wherein the etching of the polymer material layer is performed by reactive ion etching or ion etching. (3) The polymer optical waveguide according to claim 1 or 2, wherein the polymer material is one selected from the group consisting of polymethyl methacrylate, epoxy resin, and urethane resin. manufacturing method. (4) The surface cladding layer is one type selected from the group consisting of silicone resin, vinylidene fluoride polymer, styrene polymer, acrylic acid polymer, vinyl acetal polymer, acrylonitrile polymer, butadiene polymer, and polyester. A method for manufacturing a polymer optical waveguide according to any one of claims 1 to 3, characterized in that: (5) Claims 1 to 4, characterized in that the inorganic material is SiO_2, Si_3N_4, or Ti.
A method for manufacturing a polymer optical waveguide according to any one of Items 1 to 9. (6) Coat a polymer material with a low refractive index on a substrate, provide a thin film of an inorganic material on it, form this into a predetermined pattern by photo-etching, and use the pattern as a mask to etch the polymer layer. to form an optical waveguide groove,
After removing the mask pattern of the inorganic material, a high refractive index polymer material layer is provided, and if necessary, after removing the high refractive index polymer on the low refractive index polymer layer by etchback, a surface cladding layer is provided. A method for manufacturing a polymer optical waveguide characterized by: (7) The etching of the low refractive index polymer layer and the etching back of the high refractive index polymer are carried out by reactive ion etching or ion etching. Method for manufacturing molecular optical waveguide. (8) The group in which the low refractive index polymer and surface cladding layer are silicone resins, vinylidene fluoride polymers, styrene polymers, acrylic acid polymers, vinyl acetal polymers, acrylonitrile polymers, butadiene polymers, and polyesters. 1 selected from
A method for manufacturing a polymer optical waveguide according to claim 6 or 7, which is a seed. (9) The polymer light guide according to any one of claims 6 to 8, wherein the high refractive index polymer is selected from the group consisting of polymethyl methacrylate, epoxy resin, and urethane resin. Method of manufacturing wave channels. (10) Claims 6 to 6, wherein the inorganic material is SiO_2, Si_3N_4 or Ti.
9. The method for manufacturing a polymer optical waveguide according to any one of Item 9.