JP3302649B2 - Manufacturing method of optical waveguide - Google Patents

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 waveguide .

[0002]

2. Description of the Related Art With the development of markets related to optical devices such as optical communication, optical disks, displays, optical sensors, etc., it is required that optical components have both performance and cost. In particular, it itself is for the passive optical components that do not work, have I demand for price reduction Takama.

In particular, optical waveguides and diffraction gratings require very fine and accurate patterns on the surface. In order to form such a pattern, dry etching, which is generally used frequently in a semiconductor process, is used. Hereinafter, a manufacturing process of a single mode optical waveguide for optical communication will be described with reference to the drawings as an example of fine processing by dry etching.

FIG. 8 is a plan view (FIG. 8A) and a cross-sectional view (FIG. 8) of a general quartz-based single mode optical waveguide.
FIG. 9B is a sectional view taken along line AA of FIG. Core 81
Since the refractive index is higher than that of the cladding 82, light satisfying a specific condition is confined in the core pattern and transmitted. An optical circuit can be formed by patterning the core as shown in FIG. In the wavelength band of 1.3 to 1.55 μm, the core generally has a square cross section with a side of about 8 μm.

FIG. 9 is a process chart showing a general method for manufacturing a conventional quartz optical waveguide (for example, Kawachi, Optronics No. 8, 85, 1988 as a reference). In the illustrated process, first, a core film 91 is formed on a quartz substrate 92 also serving as a lower cladding layer by a flame deposition method (FIG. 9A). When a substrate made of a material other than the quartz substrate is used, the lower cladding layer is first formed by a flame deposition method. Next, the core film is patterned into a predetermined pattern by using photolithography and dry etching (FIG. 9B). Further, the upper clad layer 93 is formed by a flame hydrolysis deposition (FIG. 9 (c)). By such a method, a low-loss optical waveguide has been manufactured.

On the other hand, in recent years, resin has been studied as an optical waveguide material. At present, resin materials are inferior to quartz in transmission performance and reliability. However, the resin material is easy to mold, and has excellent transmission performance around a wavelength of 650 to 850 nm. The resin material is a promising optical waveguide material centering on a multimode optical waveguide having a core dimension of the order of tens of μm. As a specific resin material, polymethyl methacrylate (PMM) having excellent transparency is used.
A) is known. Recently, 1.3-
Attempts to reduce absorption in the 1.55 μm wavelength range are also being studied.

In manufacturing an optical waveguide using a resin material, a core layer and a clad layer are mainly formed by spin coating, and dry etching is generally used for patterning of the core layer. The resin material has high productivity because the film deposition time is shorter than that of the quartz material and the annealing temperature is low at about 200 to 300 ° C.

As described above, in the conventional production of an optical waveguide, dry etching is used for patterning the core regardless of the material.

[0009] However, dry etching is a complicated process requiring many facilities. Therefore, considering cost, it is difficult to say that semiconductor devices are suitable for manufacturing passive optical components. Under such circumstances, various methods have been proposed for manufacturing optical components. In particular, molding methods such as press molding and injection molding are promising.

[0010] As a proposal example of press molding, a glass material is exclusively used.
There is a method described in Japanese Patent Publication No. This method is a method of manufacturing an optical waveguide. As shown in FIG. 10, a mold 101 having a predetermined core pattern 102 is pressed at a high temperature against a base material 103 also serving as a lower clad, thereby forming a core pattern. This is a method of forming the groove portions collectively. According to this method, an optical waveguide can be efficiently formed by omitting the photolithography and dry etching steps conventionally used.

A method of manufacturing a diffraction grating by transferring a pattern to a metal reflective film by press molding has also been proposed (JP-A-10-96808).

[0012]

Problems to be Solved by the Invention
Light guide using press molding as described in Japanese Patent Publication No. 0
The method of manufacturing the waveguide is roughly as follows. First,
The substrate (workpiece) is brought into contact with the mold while being softened by heating, cooled while maintaining this state, and separated from the mold in a state where the shape of the substrate is solidified. In this case, as shown in FIG. 11, the protrusions 113 formed on the mold 111 are provided corresponding to the required waveguide pattern.
Is pressed against the resin plate 112 to form an inverted pattern on the resin plate 112.

However, in such a manufacturing method,
In some cases, high pattern accuracy could not be obtained. It is considered that this decrease in pattern accuracy is caused by a difference in thermal expansion coefficient. That is, when the substrate softened by heating is brought into contact with the mold and cooled, thermal stress is generated due to a difference in thermal expansion coefficient between the substrate and the mold. As a result, the accuracy of the pattern transferred to the substrate is reduced, and in some cases, the mold is damaged. Such a problem becomes particularly remarkable when a resin material is used. This is because the resin material has a thermal expansion coefficient that is about one to two orders of magnitude greater than that of a material such as quartz used as a material for the mold.

According to a specific study made by the present inventor, for example, when a pattern as shown in FIG. 11 is transferred to a resin plate by using a mold material such as quartz, the pattern near the center of the resin plate is A pattern having the same shape as the pattern on the transfer surface is formed. However, in the peripheral portion of the resin plate, as the distance from the center increases, the width of the groove increases, and the groove shape is disturbed. This phenomenon is considered to be a result of the resin plate shrinking toward the center thereof because the resin plate shrinks more than the mold.

As described above, the resin material can be formed at a lower temperature compared with, for example, a quartz material and is advantageous in terms of manufacturing cost. There was a problem that it was not possible to transfer accurately.

[0016] The present invention is to solve the aforementioned conventional problems, efficiently, how to transfer a highly accurate fine pattern
And to provide a waveguide path manufacturing method of utilizing.

[0017]

[0018]

[0019]

In order to achieve the above object, a first method for manufacturing an optical waveguide according to the present invention comprises a transfer surface, and a concave-convex pattern radially extended when viewed from the center of the transfer surface. Prepare a mold including, by pressing the transfer surface against the substrate softened by heating, by transferring the reverse pattern of the uneven pattern on the surface of the substrate ,
It is characterized in that a pattern corresponding to the core is formed .

According to another aspect of the present invention, there is provided a method for manufacturing an optical waveguide , comprising: a first linear pattern including a center axis of the transfer surface; and a center of the transfer surface. By preparing a mold including a concavo-convex pattern composed of a second linear pattern radially branched from the first linear pattern as viewed from above, and pressing the transfer surface against a substrate softened by heating, By transferring an inverted pattern of the concavo-convex pattern on the surface of the material, it corresponds to the core
It is characterized by forming a pattern .

[0021] To achieve the above object, the manufacturing method of the third optical waveguide of the present invention, the length of the short direction 5mm
The following is a method for forming a core of an optical waveguide having a transfer surface, traversing the transfer surface along the longitudinal direction of the transfer surface, and being formed so as to be line-symmetric with respect to a central axis along the longitudinal direction. Preparing at least two molds having a concave and convex pattern, transferring the reverse pattern of the concave and convex pattern to the surface of the substrate by pressing the transfer surface of the at least two molds on the substrate softened by heating, The method is characterized in that the base material is divided for each reverse pattern.

According to the first to third methods, the influence of the stress caused by the difference in the coefficient of thermal expansion between the mold and the substrate on the precision of the pattern can be reduced. In the first and second methods, the influence of the stress is reduced by the shape of the pattern formed on the transfer surface. In the third method, the influence of the stress is reduced by using a plurality of dies. In the present invention, the mold used in the first and second methods is at least 2
One prepared, by pressing the transfer surface of the plurality of molds to the substrate softened by heating, by transferring the reverse pattern of the uneven pattern on the surface of the substrate ,
A method for manufacturing an optical waveguide for forming a pattern corresponding to a core is also included.

When a plurality of dies are used, the length of the transfer surface of the dies in the width direction is preferably 5 mm or less. In this case, it is more preferable that the uneven pattern crosses the transfer surface along the longitudinal direction of the transfer surface.

The above method of the present invention is particularly suitable when the difference in the coefficient of thermal expansion between the mold and the substrate is at least 50 × 10 ⁻⁷ / ° C.

In the above method of the present invention, the width of the uneven pattern is preferably 100 μm or less.

In the above method of the present invention, the substrate is preferably an optically transparent thermoplastic resin.
As the thermoplastic resin, any resin selected from polyolefin, polymethyl methacrylate, polycarbonate, norbornene, and acrylic resins is preferable.

[0027]

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 shows an example of a convex pattern 12 formed on a transfer surface 11 of a mold used in the method of the present invention. This mold is made of quartz and has a size of 20 mm × 20 mm. The convex patterns 12 formed on the transfer surface 11 include the central axis of the transfer surface and are formed to be orthogonal to each other.
Book patterns and a total of 8 branches from these two patterns
And a book pattern. Each of the branched patterns is branched in a Y-shape from the pattern including the central axis, and extends radially when viewed from the center of the mold. In addition, the convex pattern 12 has four line symmetry axes on the transfer surface 11.

With such a convex pattern, even when the transfer surface is pressed against the substrate and cooled together with the substrate, the stress generated in the cross-sectional direction of the groove of the substrate formed by pressing the pattern is extremely limited. It was done. Therefore, even when the difference between the thermal expansion coefficient of the mold and the substrate is large, an accurate fine pattern can be transferred onto the substrate. When a fine pattern is transferred to a substrate using the pattern shown in FIG. 1, optical waveguides can be provided in the vertical and horizontal directions.

Hereinafter, an optical waveguide using the mold shown in FIG.
A specific example of the manufacturing method will be described. The mold was produced by dry-etching quartz. FIG. 2 shows a method for manufacturing a mold. First, a Cr film 22 was formed on a quartz substrate 21 by vapor deposition (FIG. 2A). Next, a photoresist 23 is applied on the Cr film 22 by spin coating,
Baking was performed at 90 ° C. for 30 minutes (FIG. 2B).
The photoresist 23 includes TSMR8 manufactured by Tokyo Ohka Kogyo Co., Ltd.
900 was used. The photoresist 23 was exposed and developed using a photomask having a predetermined pattern (FIG. 2C). After baking, the film was immersed in a Cr etchant for about 5 to 10 minutes to remove the Cr film except for the portion protected by the photoresist. As a result, a configuration was obtained in which a patterned Cr film 24 was formed on a quartz substrate (FIG. 2D).

This Cr functions as a mask during dry etching. Further, the quartz substrate was finely processed by reactive ion etching. CHF ₃ gas was used as an etchant. 8μm depth by etching for about 3 hours
Could be processed up to After the processing, the substrate was taken out and immersed in a Cr etchant to remove the Cr pattern. After washing and drying, the quartz mold 25 was completed (FIG. 2).
(E)).

Next, referring to FIG. 3, an optical waveguide using a mold will be described.
The manufacturing method will be described.

Between the upper mold plate 33 and the lower mold plate 34 of the molding machine, a quartz mold 31 and a resin plate 32 to be processed are provided.
And were placed so that the transfer surface of the quartz mold 31 was in contact with the resin plate 32. At this time, the centers of the quartz mold 31 and the resin plate 32 were matched. In this state, the heater (not shown)
And heat the resin plate 32 to 180 ° C. to soften it,
The quartz mold 31 and the resin plate 32 are combined with the upper and lower mold plates 3 of the molding machine.
3, 34 and pressed. With the convex pattern of the quartz mold 31 biting into the resin plate 32, the temperature was cooled down to about 80 ° C., and the resin plate 32 was taken out. The resin plate 32
ZEONEX (polyolefin resin) manufactured by ZEON CORPORATION was used.

Observation of the surface and cross section of the resin plate taken out using an optical microscope and an electron microscope revealed that the fine pattern groove in which the quartz-type convex pattern was accurately transferred was transferred over the entire resin plate of about 20 mmφ. It was confirmed that it was done.

Subsequently, an epoxy resin having a refractive index higher than that of the above-mentioned material of the resin plate by about 0.3% was buried in the groove of the resin plate, and a flat resin plate made of the above-mentioned Zeonex was bonded from above. . Thus, FIG.
The optical waveguide shown in FIG. This optical waveguide includes an epoxy resin as a core 42 and a Zeonex resin plate as clads 41 and 43. This optical waveguide had sufficient practicality.

The pattern formed on the mold may be a pattern corresponding to a plurality of optical waveguides, and the resin plate on which the pattern is transferred in the same manner as described above may be cut so as to be divided for each pattern. As described above, by manufacturing a resin plate including a plurality of optical waveguides and cutting the resin plate, the optical waveguide can be manufactured more efficiently.

The thermal expansion coefficients of quartz and Zeonex are
^They are respectively 5 × 10 ⁻⁷ / ° C. and 600 × 10 ⁻⁷ / ° C.
However, even when the coefficients of thermal expansion differ by two or more digits, a precise pattern can be accurately transferred over a wide area by using the mold as shown in FIG.

The width of the convex pattern of the mold used above was 8 μm.

The pattern formed on the transfer surface of the mold is not limited to the pattern shown in FIG. 1, but may be, for example, a pattern 52 as shown in FIG. This convex pattern 52
It extends radially from the center of the transfer surface 51. The transfer surface 51 has four line symmetry axes. The convex pattern 52 includes four linear patterns including the center axis of the transfer surface and crossing the transfer surface.

As shown in FIGS. 1 and 5, the pattern formed on the transfer surface is preferably constituted by a linear pattern extending radially from near the center of the transfer surface. In addition, it preferably has, for example, at least four axis of line symmetry. Preferably, a branch pattern is provided which branches radially from a linear pattern including the central axis as viewed from the center of the transfer surface.

As described above, it is preferable to form a pattern on the transfer surface so as to reduce the generation of stress due to the difference in the coefficient of thermal expansion between the mold and the substrate.

FIG. 6 shows another embodiment of the method for manufacturing an optical waveguide according to the present invention. In this form, using multiple types,
The pattern is transferred to the resin plate 61. In the example shown in FIG. 6, four dies 62, 63, 64, 65 are arranged between the upper die plate 66 and the lower die plate 67 together with the resin plate 61. Patterns can be formed on these molds by the method described in the first embodiment.

FIG. 7 shows an example of a pattern formed on the transfer surface of each mold. These convex patterns 71, 72, 7
Each of Nos. 3 and 74 has a linear pattern that vertically crosses the transfer surface in the longitudinal direction of the transfer surface. Each of these patterns is line-symmetric with respect to a central axis along the longitudinal direction of the transfer surface. The length of the transfer surface in the width direction is 5 mm or less.

Using a mold having such a pattern, the pattern was transferred to the resin plate 61 in the same manner as in the first embodiment. At this time, the intervals between the dies 61, 62, 63, 64 were 0.5 mm or more.

When the surface and cross section of the resin plate taken out were observed using an optical microscope and an electron microscope, the fine pattern groove in which the quartz-type convex pattern was accurately transferred was transferred over the entire resin plate of about 20 mmφ. It was confirmed that it was done.

Subsequently, an epoxy resin having a refractive index higher than that of the material of the resin plate by about 0.3% was buried in the groove of the resin plate, and a flat resin plate made of Zeonex was bonded from above. . Thereafter, the resin plate was cut so as to correspond to the patterns of the above-mentioned respective types. Thus, four optical waveguides were produced. This optical waveguide is
Epoxy resin was used as the core, and Zeonex resin plate was used as the clad, which provided sufficient practicality.

According to the above method, by using a plurality of molds, the contact area between each mold and the substrate, particularly the width of the transfer surface in the direction crossing the pattern is limited. Therefore, the stress caused by the difference in the coefficient of thermal expansion between the mold and the substrate is also limited.

Further, according to the above method, a plurality of patterns can be transferred to the substrate by one molding, so that the patterns can be transferred efficiently.

The number of molds used above is not particularly limited as long as it is two or more. Further, the pattern is not limited to the form shown in FIG.

[0050]

In the above embodiment, a mold having a convex pattern is used. However, the pattern may be a concave pattern or a pattern having both irregularities.
Similar effects can be obtained.

Also, when examining various materials,
The method of the present invention was particularly effective when the difference in the coefficient of thermal expansion between the mold and the substrate was 50 × 10 ⁻⁷ / ° C. or more, and the width of the pattern was 100 μm or less.

The material of the mold is not limited to quartz, but may be any material having no problem in heat resistance and strength, and various metal materials and various ceramic materials can be used. A cemented carbide or diamond may be used.

The material of the substrate is not particularly limited, but is particularly effective for a thermoplastic resin having a relatively large thermal expansion coefficient such as a polyolefin resin. Examples of the thermoplastic resin other than the polyolefin-based resin include polymethyl methacrylate-based, polycarbonate-based, acrylic-based, and norbornene-based resins. Further, if a protective coating is applied to the mold, a fine pattern can be transferred to a glass material.

[0055]

As described above, according to the present invention,
Efficiently, by transferring a highly accurate fine pattern, the optical waveguide
It is possible to produce the road. In particular, the present invention enables fine and accurate pattern transfer over a wide area even for a resin material whose large thermal expansion coefficient has been a problem as a material for an optical component. Thus, according to the present invention, it is possible to efficiently manufacture the optical waveguide path.

[Brief description of the drawings]

FIG. 1 is a plan view of a transfer surface of a mold for illustrating an example of a pattern formed on the mold used in the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of a mold used in the present invention.

FIG. 3 is a process drawing showing an example of the manufacturing method of the present invention by a cross section.

FIG. 4 is a cross-sectional perspective view showing an example of an optical waveguide formed by the method shown in FIG.

FIG. 5 is a plan view of a transfer surface of a mold for illustrating an example of a pattern formed on the mold used in the present invention.

FIG. 6 is a process drawing showing a cross section of another example of the manufacturing method of the present invention.

FIG. 7 is a plan view of a transfer surface of a mold for illustrating an example of a pattern formed on the mold used in the present invention.

8A and 8B are a plan view and a cross-sectional view of a general silica-based single mode optical waveguide.

FIG. 9 is a process chart for illustrating a conventional method for manufacturing a general optical waveguide.

FIG. 10 is a cross-sectional view illustrating a method of manufacturing an optical waveguide by conventional press molding.

FIG. 11 is an example of a conventional pattern used in a method of manufacturing an optical waveguide by press molding.

[Explanation of symbols]

 11, 21 Quartz substrate 12, 52, 71 to 74 Convex pattern 22 Cr film 23 Photoresist 25, 31, 61 to 64 Quartz mold 32, 61 Resin plate 33, 66 Upper mold plate 34, 67 Lower mold plate 41, 43 Clad 42 core

Continuation of front page (56) References JP-A-9-11328 (JP, A) JP-A-9-114406 (JP, A) JP-A-56-159127 (JP, A) JP-A-8-160239 (JP , A) JP-A-61-19327 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 59/00-59/02 G02B 5/18 G02B 5/30 G02B 6/13 B29C 43/00 B29C 33/00

Claims (11)

(57) [Claims] 1. A mold having a transfer surface and including a pattern of concavo-convex extending radially when viewed from the center of the transfer surface is prepared, and the transfer surface is pressed against a base material softened by heating, whereby By transferring the reverse pattern of the concavo-convex pattern on the surface, a pattern corresponding to the core is formed.
A method for manufacturing an optical waveguide , comprising: 2. A first linear pattern including a transfer surface and including a central axis of the transfer surface, and a second linear pattern radially branched from the first linear pattern when viewed from the center of the transfer surface. Prepare a mold including a concavo-convex pattern composed of a pattern, press the transfer surface against a substrate softened by heating, and transfer a reverse pattern of the concavo-convex pattern to the surface of the base material, thereby corresponding to the core. Form a pattern
A method for manufacturing an optical waveguide . 3. A process according to claim 1 or 2, wherein at least two to prepare a mold for use in the process according to, by pressing the transfer surface of the at least two mold base was softened by heating, the substrate By transferring an inverted pattern of the concavo-convex pattern on the surface of the
A method of manufacturing an optical waveguide , comprising forming a pattern . 4. The method of manufacturing an optical waveguide according to claim 3, wherein the length of the transfer surface of the mold in the lateral direction is 5 mm or less. 5. The optical waveguide according to claim 4, wherein the concave / convex pattern crosses the transfer surface along a longitudinal direction of the transfer surface .
Construction method. 6. The difference in thermal expansion coefficient between the mold and the substrate is 50 × 1.
The light guide according to any one of claims 1 to 5, which has a temperature of ^0-7 / C or more.
Waveguide manufacturing method. 7. The method for manufacturing an optical waveguide according to claim 1, wherein the width of the uneven pattern is 100 μm or less. 8. The method for producing an optical waveguide according to claim 1, wherein the substrate is an optically transparent thermoplastic resin. 9. The method of manufacturing an optical waveguide according to claim 8, wherein the thermoplastic resin is any resin selected from polyolefin, polymethyl methacrylate, polycarbonate, norbornene, and acrylic resins. 10. divides the substrate into each of the reverse pattern of the plurality of inverting patterns after transferring claims 1-9 Neu
A method for manufacturing an optical waveguide according to any of the above. 11. A transfer surface having a length of 5 mm or less in a transverse direction, traversing the transfer surface along a longitudinal direction of the transfer surface, and being line-symmetric about a central axis along the longitudinal direction. Preparing at least two molds with a concavo-convex pattern for forming a core of an optical waveguide formed as described above,
By pressing the transfer surface of the at least two molds onto a substrate softened by heating to transfer a reverse pattern of the concavo-convex pattern to the surface of the substrate, dividing the substrate for each reverse pattern. Of manufacturing an optical waveguide.