JPH08292335A - Manufacture of optical waveguide - Google Patents

Abstract

PURPOSE: To improve thermal efficiency, to shorten the number and time for manufacture, to allow patterning with high resolution and to attain the use of a wide range of substrate materials by locally irradiating the parts corresponding to the desired optical waveguide patterns of a material layer formed on a substrate with heat rays. CONSTITUTION: An underclad layer 2 is formed on the quarts substrate 1 and a sol prepd. by mixing silicon alkoxide and germanium alkoxide with water, shrinkage relieving agent, catalyst, thickener, etc., is applied. This sol is dried to cause condensation polymn., by which a gen film 3 is formed. A pair of mask 4 meeting the desired optical waveguide patterns is then put on the gel film 3. The mask 4 is thereafter irradiated with a laser beam 5 to locally irradiate the surface of the dry gel film 3 with the laser beam 5 to the shapes of the patterns of the mask 4. As a result, the gel film 3 is heated to the shapes of the patterns of the mask 4 and is sintered. The pair of gel film 3 after the sintering is developed by a soln. prepd. by mixing alcohol and acid, by which the unnecessary gel film 3 exclusive of the parts sintered by the irradiation with the laser beam 5 is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical component, especially an optical waveguide.

[0002]

2. Description of the Related Art Conventionally, in a waveguide type optical component having an optical demultiplexer-multiplexer, a branch coupler, etc., there are two methods for producing an optical waveguide on a substrate: a deposition method and an ion exchange method. It can be divided into two. One of the deposition methods is a method of depositing a glass film on a substrate made of silicon or the like, which is a flame deposition method (FHD: Flame Hydrolysis Deposision),
-CVD (Chemical Vapor Deposisin), MBE (Molec
ular Beam Epitaxy) Deposition is increased.

When manufacturing an optical waveguide by a deposition method,
For example, the process shown in FIG. 3 is performed. That is, as shown in (a) to (c) of FIG. 3, a glass film having a two-layer structure of a lower clad layer (under clad) b and a core layer (core) c is formed on a substrate (silicon wafer) a. Form a film. The F
When HD is used, fine particles of quartz soot are deposited on a silicon substrate, and this is sintered at high temperature over the entire surface to form a transparent glass, which is used as the core layer c. Then, the core layer c is finely processed to form a waveguide pattern. For example, as shown in FIG. 3D, a mask pattern is transferred by photolithography, and the core layer c is processed into a channel shape by dry etching or the like with the pattern. Then, as shown in FIG. 3E, the core layer c (optical waveguide) processed into the channel shape by the etching is embedded with an upper clad layer (over clad) d. The upper clad layer d can be embedded by the same manufacturing method as the lower clad layer b. As a technique for forming an optical waveguide by using the flame deposition method, there is JP-A-4-344602.

In another ion exchange method, the next step is performed. First, a metal mask having a waveguide pattern is formed on a borosilicate glass substrate. Then, the substrate is dipped in a molten salt containing dopant and the dopant is diffused into the glass substrate on the waveguide pattern by utilizing an ion exchange phenomenon (surface formation of the core layer).

Further, the glass substrate is immersed in a molten salt containing only ions of the same kind as the ions (not the dopant) in the glass, and an electric field is applied to cause the surface core layer (dopant) to migrate inside the glass. (Internal formation of core part),
A high refractive index portion to be an optical waveguide is formed. After removing the mask, the optical waveguide is pushed into the substrate and the surface layer is formed to have a low refractive index.

There is a simple glass manufacturing method called the sol-gel method. In this sol-gel method, liquid raw materials having various chemical compositions such as Si, Al, Zr, Ti, and B, a solution of an organometallic compound, and the like are heated to about 150 ° C. at a temperature of about room temperature to carry out hydrolysis and dehydration condensation reaction. The sol state and gel state are followed by sintering at about 800 ° C. to synthesize a solid glass, ceramic or the like of the product. However, this sol-gel method requires a large number of film-forming speeds, sintering temperatures, and sintering times, and is not currently used for film-forming of glass for a waveguide because of cracks during sintering. . Regarding the sol-gel method, there is JP-A-5-34742.

[0007]

However, the above-mentioned deposition method has the following problems. Since the optical waveguide is manufactured by three steps including the core layer deposition step, the core layer entire surface sintering step, and the patterning step by lithography, it takes man-hours and time (42 hours for 3 steps). The heat treatment for the entire bulk is inferior to the local heat treatment in terms of thermal efficiency. The resolution limit of core formation is limited by the resolution of lithography and the side etch amount of dry etching.

Further, the above-mentioned ion exchange method has the following problems. Although the core can be manufactured by one process, lithography takes 8 hours or more, and ion diffusion exchange takes 10 hours or more, and it takes tens of hours in total. Since diffusion in solid is used, the resolution limit of core formation is limited by the embedded depth of the core and the resolution of lithography, and it is difficult to obtain high resolution. The substrate is limited to a glass substrate, and a general-purpose silicon substrate cannot be used. In any of the above methods, the heat treatment is performed on the entire bulk, so that the waveguide portion has a thermal history, for example, a warp occurs, which makes it difficult to improve the processing accuracy, or internal stress (residual strain) influences cracking. There are also problems such as occurrence.

The present invention has been made to solve the above-mentioned conventional problems. It improves thermal efficiency, reduces man-hours and time required for manufacturing, and enables patterning with high resolution.
It is an object of the present invention to provide an optical waveguide manufacturing method that enables a wide range of substrate materials to be used and shortens the manufacturing time of the substrate.

[0010]

In order to solve the above-mentioned problems, the invention of claim 1 is a method for producing a substrate-type optical waveguide, in which an optical waveguide material layer before sintering is formed on a substrate. In the material layer, a portion corresponding to a desired optical waveguide pattern is locally irradiated with heat rays, and the portion is heated and sintered by the irradiation of the heat rays to form an optical waveguide. It has a configuration of a waveguide manufacturing method. Further, the invention of claim 2 has a constitution of the method for producing an optical waveguide according to claim 1, characterized in that a quartz substrate is used as a substrate and the optical waveguide material layer is formed by a sol-gel method.

[0011]

According to the invention of claim 1, when a substrate type optical waveguide is manufactured, an optical waveguide material layer before sintering is formed on a substrate and a desired optical waveguide is formed with respect to the formed material layer. The portion corresponding to the pattern is locally irradiated with heat rays, and the portions are heated and sintered by the irradiation of the heat rays to form an optical waveguide. Therefore, the core layer can be formed and patterned in one process by heating and sintering the optical waveguide material layer by local irradiation of heat rays. Further, the energy efficiency is improved as compared with the conventional case where the entire surface is heat-treated by the heat treatment. Further, according to the invention of claim 2, since the quartz substrate is used as the substrate and the optical waveguide material layer is formed by the sol-gel method, the heating portion is locally heated without being heated. Since the material is supplemented from the non-sintered gel-like fluid portion other than the above and sintered, residual strain does not occur, and thus a waveguide made of glass or the like can be produced without cracking or warping.

The film formation of the optical waveguide material layer can be carried out not only by the sol-gel method but also by FHD. Further, the heat ray preferably uses laser light. The laser light has a good convergence of the light flux and can appropriately increase the energy density. Further, if a mask of an optical waveguide pattern is used at the time of irradiating the heat rays, a fine pattern can be formed without increasing the accuracy of focusing the laser light. Various kinds of laser light can be used, but it is preferable to use laser light in the infrared region. This is because heat can be generated intensively. For example, CO ₂ gas laser light (carbon dioxide laser) or the like is used.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1A to 1F are process explanatory diagrams of an optical waveguide manufacturing method according to an embodiment of the present invention. Although this embodiment is an example in which the present invention is applied to the sol-gel method, the FHD or other method can be used for forming the optical waveguide material layer.

In the embodiment, when manufacturing an optical waveguide, a synthetic quartz substrate 1 shown in FIG. 1 (a) is prepared. Next, as shown in FIG. 1B, an underclad layer 2 is formed on the quartz substrate 1, and as shown in FIG. 1C, a silicon alkoxide and a germanium alkoxide are formed on the underclad layer 2. Is coated with a sol in which water, a shrinkage easing agent, a catalyst, a thickener, etc. are applied, and the sol
The gel film 3 is obtained by drying and polycondensing at a temperature of about 0 ° C.
As the raw material of the sol-gel, in addition to the above, those added with metal alkoxides such as tetramethoxysilane, tetraethoxysilane, tetrapropylsilane, tetrabutylsilane, etc., water, and a shrinkage-relieving agent, a catalyst, and a thickener may also be used. You can

Then, as shown in FIG. 1D, a mask 4 is formed on the gel film 3 in accordance with a desired optical waveguide pattern.
Cover. Then, as shown in FIG. 1E, the laser beam 5 is irradiated onto the mask 4 to locally irradiate the dry gel film 3 in the pattern of the mask 4 with the laser beam 5. As a result, the gel film 3 is heated into the shape of the max 4 pattern and is sintered (vitrified). The laser light 5 is preferably laser light in the infrared region,
A CO ₂ gas (carbon dioxide) laser is preferably used.
As a result, heat can be intensively generated. In addition, during the sintering, the light amount (energy amount) of the laser light 5 can be controlled by feeding back the reflected light amount or the transmitted light amount of the laser light 5. For example, when the gel film 3 is sintered and vitrified, the laser light 5 is no longer absorbed and is transmitted, and this is detected. Thus, if feedback control is performed, the shortest sintering time can be obtained, and the time required for the process can be reduced. When a CO ₂ gas laser is used as the laser beam 5, glass is used as a mask, and when a YAG laser is used, a metal is used as a mask. In case of excimer laser,
A metal may be used or glass may be used.

Next, the gel film 3 after sintering is treated with alcohol,
As shown in FIG. 1 (e), the unnecessary gel film 3 other than the portion 6 (the core layer which becomes the optical waveguide by vitrification) is developed by developing with an acid-prepared solution. Remove. In the case of the example, it is sufficient to locally irradiate the laser beam in order to produce the sintered portion 6 to be the optical waveguide, and therefore, heating and sintering can be performed with low power and in a short time. For this reason, the thermal efficiency has been remarkably improved. That is, as in the conventional method, in order to heat and sinter the material layer formed by FHD as a whole, heating and sintering (2000 w × 10
However, in the example, heating and sintering could be performed with a small amount of power and in a short time (for example, 500 w × 1 hour). In addition, the sol-gel method, which could not be used for producing an optical waveguide in the conventional method, could be effectively used.

Further, in the manufacturing method of the embodiment, the gel film 3 made of alkoxide can be manufactured in 0.5 hours, and the core layer forming and patterning such as patterning and sintering are performed at the same time. It took about time. On the other hand, when the core layer is formed by FHD by the conventional technique, it is 3
It takes 1.5 hours to deposit the core layer, 10 hours to sinter, and 10 hours to lithographically.
It took time. Moreover, when the ion exchange method is used, two steps and several tens hours are required. Therefore, in the example, it is understood that the number of steps can be reduced and the time can be greatly shortened. Further, in the conventional method, as described above, since heating was performed with a large amount of power for a long time, there was a problem that the substrate was warped, but in the example, a small amount of local heating for a short time was required. Therefore, the occurrence of warpage was eliminated and the processing accuracy was improved. Also,
Internal stress (residual strain) was also reduced, and the occurrence of cracks in the waveguide chip was eliminated. That is, the gel film 3 by the sol-gel method
Since the material is locally heated, the material is supplemented from the unsintered gel-like fluid portion other than the heated portion during sintering, and sintering does not occur, so that residual strain does not occur, and therefore, cracks do not occur and glass is used. The following waveguide can be manufactured.
Further, since the pattern formation does not include the etching process and the diffusion process, the resolution is equal to the resolution of lithography and a high resolution (1 micron rule) can be obtained.

Then, general methods (FHD, CVD,
As shown in FIG. 1F, an over cladding layer 7 is formed by a sputter ring or sol-gel method so as to cover the sintered portion 6. The over-cladding layer 7 and the under-cladding layer 2 have different refractive indexes from the sintered portion 6, and form an optical waveguide. Through the above steps, an optical waveguide is manufactured on the quartz substrate 1.

Although the material layer is formed by the sol-gel method in the above embodiment, the material layer 9 may be formed by FHD on the substrate 8 made of silicon as in the other embodiment of FIG. In the case of this FHD, the flame gas contains O ₂ , H ₂ ,
A material layer 9 of SiO ₂ powder is deposited on the substrate 8 with a composition of SiCl ₄ , GeCl ₄ , POCl ₃ , BBr ₃ , and Ar. Then, patterning, sintering and the like may be simultaneously performed in the same steps as those in (d) to (f) of FIG.

[0020]

As described above, according to the present invention, the time required for core formation was conventionally 3 steps and 24 hours, but in the present invention, it can be greatly reduced to 2 steps and 3 hours. The number of manufacturing processes and manufacturing time can be greatly reduced. Moreover, since the local heating and sintering are performed, the amount of energy required for core formation can be significantly reduced. For example, in order to sinter the material layer formed by FHD by the conventional method as a whole, heating and sintering with high power for a long time (for example, 2000 w × 10
However, in the present invention, heating and sintering can be performed with low power and in a short time (for example, 500 w × 1 hour). Moreover, since the heating is performed locally, the amount of energy input is greatly reduced, and the temperature rise of the substrate can be suppressed to a small level. Therefore, the warp that occurs during heating is reduced, and the processing accuracy is improved. For example, when the chip length is 30 mm, the conventional method has a warp of 100 μm / 30 mm, but when the present invention is carried out, the warp is 0 μm / 30 mm, and the outer shape accuracy is improved from 10 μm to 5 μm, which is 1/2. Was done. Furthermore, since the substrate does not have to be exposed to a high temperature and the temperature rise is small, the internal stress can be greatly reduced. When the material layer was formed by FHD, the internal stress was 25.3 kg / mm ² in the conventional method, but when the present invention was carried out, the internal stress was reduced to 0 kg / mm ² . Also,
Since the temperature rise of the substrate is small, the selection range of the substrate material used is increased. That is, since it was necessary to sinter at 1300 ° C. in the conventional method, chemically at 1300 ° C.,
A thermally stable material was required, but in the method of the present invention,
Only the surface irradiated with heat rays is locally heated, and the temperature does not rise so much.

Further, in the present invention, since the material layer can be formed on various substrates by various methods including the sol-gel method, the material and composition of the core and the clad can be selected. In addition, if the sol-gel method is used for producing the material layer,
Since the composition of the sol-gel can be adjusted to broaden the absorption wavelength range of heat rays and increase the heat ray absorption efficiency, the setting of heat treatment conditions can be controlled considerably freely. Further, since the pattern formation does not include an etching process and a diffusion process, the resolution only depends on the resolution of lithography, and thus a high resolution pattern (1 micron rule) can be obtained.

[Brief description of drawings]

FIG. 1A to FIG. 1F are explanatory diagrams of respective steps of an optical waveguide manufacturing method according to an example of the present invention.

FIG. 2 is an explanatory diagram of another embodiment of the present invention.

3 (a) to 3 (e) are explanatory diagrams of respective steps of a conventional optical waveguide manufacturing method.

[Explanation of symbols]

 1 Quartz Substrate 2 Underclad Layer 3 Gel Film (Corresponding to Material Layer) 4 Mask 5 Laser Light 6 Sintered Part Irradiated with Laser Light (Core Layer) 7 Overclad Layer 8 Substrate 9 Material Layer

Claims (2)

[Claims] 1. A method for producing a substrate type optical waveguide, wherein an optical waveguide material layer before sintering is formed on a substrate, and a portion corresponding to a desired optical waveguide pattern is formed on the formed material layer. A method for producing an optical waveguide, comprising locally irradiating a heat ray, and heating and sintering the portion by the irradiation of the heat ray to form an optical waveguide. 2. The method for producing an optical waveguide according to claim 1, wherein a quartz substrate is used as the substrate, and the optical waveguide material layer is formed by a sol-gel method.