JP3982795B2 - Optical waveguide forming material and optical waveguide - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an optical waveguide forming material and an optical waveguide using the material.
[0002]
[Prior art]
With the rapid spread of the Internet and the like, there is an urgent need to develop a communication infrastructure for transmitting information at high speed and in large quantities. Specifically, a shift from metal wiring such as copper to optical interconnection using an optical waveguide is being promoted. Conventionally, such an optical waveguide has been manufactured using an inorganic glass material such as quartz glass. However, since the manufacturing requires heat treatment at a high temperature, such a circuit is formed directly on the substrate. It was extremely difficult.
[0003]
In recent years, materials using a polymer material such as polymethyl methacrylate (PMMA) have been proposed as materials for optical waveguides that do not require high-temperature treatment. By using a polymer material, there is an advantage that not only the above-described heat treatment at high temperature is unnecessary, but also processing such as enlargement of area and film formation is easy.
[0004]
[Problems to be solved by the invention]
Usually, the optical waveguide is composed of a lower clad layer having a refractive index and high refractive index core layer. As a method for obtaining such a refractive index difference using a polymer material, for example, a method using a polymer material in which the copolymerization ratio of monomers is changed, a method using a different polymer material, and the like are known. . However, when an optical waveguide is formed by such a method, two or more kinds of polymer materials having different compositions (refractive indexes) must be prepared, and each polymer material is applied in the manufacturing process. -It had to be hardened and the manufacturing process was complicated. Furthermore, although a (meth) acrylic acid ester-based polymer material such as PMMA is excellent in optical characteristics, it generally has a drawback of low heat resistance.
[0005]
[Means for Solving the Problems]
The present inventors have advanced research to solve the above problems and put it to practical use as a chemically amplified photoresist that is a material for patterning by utilizing the difference in solubility in a solvent generated between an unexposed part and an exposed part. Focusing on the fact that a material composed of a certain kind of poly (meth) acrylate and photoacid generator changes its composition by exposure, the structure and composition change of this poly (meth) acrylate As a result of various investigations on the difference in refractive index and heat resistance, the present invention was completed.
[0006]
That is, the present invention relates to an optical waveguide forming material for forming an optical waveguide using a portion not irradiated with light as a core layer and a portion irradiated with light as a cladding layer, and an alcohol having an alicyclic skeleton and (meth) An optical waveguide forming material comprising a polymer containing a monomer unit based on an ester with acrylic acid, and a photoacid generator.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0008]
In the present invention, a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid is used as an optical waveguide forming material.
[0009]
By using a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid, visible light or near infrared light used for signal transmission in an optical waveguide Therefore, the resulting optical waveguide has high heat resistance.
[0010]
A polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid has an ester portion formed by an acid generated by irradiating light to a photoacid generator described later. Cleavage to poly (meth) acrylic acid and ester cleavage product. The ester cleavage product is an alcohol having an alicyclic skeleton or a derivative thereof. The mixture of poly (meth) acrylic acid and ester cleavage product resulting from the cleavage of this ester is compared to a polymer containing monomer units based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid. since the refractive index becomes lower, and a portion not irradiated with light (unexposed portion), a core layer having a high refractive index, the light irradiated portion (exposed portion) and a clad layer having a relatively low refractive index An optical waveguide having an arbitrary pattern can be formed by irradiating light using a photomask or the like.
[0011]
The alcohol having an alicyclic skeleton is not particularly limited and may be any known compound, specifically, cyclohexanol, 1-methylhexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4- Alcohol having a monocyclic alicyclic skeleton such as methylcyclohexol; bornyl alcohol, 1-norbornyl alcohol , 2-norbornyl alcohol, 1-adamantanol, 2-adamantanol, 2-methyl-2- Examples thereof include alcohols having a polycyclic alicyclic skeleton such as adamantanol and 2-ethyl-2-adamantanol.
[0012]
Specific examples of the monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid include cyclohexyl (meth) acrylate, 1-methylcyclohexyl (meth) acrylate, (meth Based on ester of (meth) acrylic acid with alcohol having monocyclic alicyclic skeleton such as 2-methylcyclohexyl acrylate, 3-methylcyclohexyl (meth) acrylate, 4-methylcyclohexyl (meth) acrylate Monomer unit; bornyl (meth) acrylate, 1-norbornyl (meth) acrylate, 2-norbornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-adamantyl (meth) acrylate, (meth ) 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl (meth) acrylate Monomer unit or the like based on esters of alcohol and (meth) acrylic acid having a polycyclic alicyclic skeleton can be given the like.
[0013]
The polymer in the present invention may be a polymer composed of only one of the above monomer units, or may include a plurality of different monomer units.
[0014]
Furthermore, the polymer in the present invention is not limited to the effects of the present invention, but in addition to the monomer unit based on the ester of the alcohol having the alicyclic skeleton and (meth) acrylic acid, other single amount It may include a body unit.
[0015]
Although it does not restrict | limit especially as such other monomer units, A transparent thing is preferable in an ultraviolet-near infrared region, Specifically, (meth) methyl acrylate, (meth) ethyl acrylate And monomer units obtained from propyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile, vinyl acetate and the like.
[0016]
The polymer in the present invention is not particularly limited as long as it contains a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid in the polymer, and any monomer unit. In the polymer, alcohol having a cycloaliphatic skeleton and (meth) acrylic acid may be combined with each other in terms of excellent heat resistance and a large difference in refractive index obtained after light irradiation. The monomer unit based on the ester and the other monomer units are preferably in a molar ratio of 1: 0 to 1: 100, more preferably 1: 0 to 1:10.
[0017]
Further, the alicyclic skeleton in monomer unit based on esters of alcohol and (meth) acrylic acid having an alicyclic skeleton, it is an alicyclic skeleton of polycyclic core layer, clad layer together It is particularly preferable in that it has excellent heat resistance, has a large stability of the ester cleavage product, and also has a large difference in refractive index, resulting in an optical waveguide having excellent physical properties. Most preferably, the alicyclic skeleton of the ring is an adamantane skeleton.
[0018]
In addition, it is not necessary to weigh and mix various monomers when producing a polymer, and a polymer having a constant refractive index can always be obtained without taking special care. The polymer unit is preferably a polymer having a substantially single monomer unit, and any one of the monomer units based on the ester of (meth) acrylic acid with an alcohol having a polycyclic alicyclic skeleton. A polymer consisting of only one is most preferred.
[0019]
The degree of polymerization of the polymer is preferably 100 to 200,000, and preferably 1,000 to 50,000, from the viewpoint of heat resistance and moldability.
[0020]
The production method of the polymer is not particularly limited, and may be produced by any known method. Generally, however, the monomer (alicyclic skeleton) corresponding to each monomer unit is used. It is obtained by blending an appropriate amount of a radical polymerization initiator with respect to an ester of (meth) acrylic acid having alcohol and polymerizing by heating, light irradiation or the like.
[0021]
The second component of the optical waveguide forming material of the present invention is a photoacid generator. In addition, a photo-acid generator is defined as what generate | occur | produces an acid, for example, a bond is cleaved by irradiating light.
[0022]
As described above, light is irradiated to a part of a material for forming an optical waveguide containing a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid, and a photoacid generator. Then, an acid is generated in the exposed portion, and the ester is cleaved by the acid to produce poly (meth) acrylic acid and an ester cleavage product. At the same time, the refractive index is lowered as compared with an unexposed portion made of a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid. As a result, it is possible to obtain an optical waveguide and an unexposed portion high refractive index layer (core layer), and the exposed portion low refractive index layer (clad layer). In this case, by adjusting the amount of light irradiation, the amount of photoacid generator added, etc., all the esters are not cleaved, and the poly (meth) acrylic acid to be produced has an ester side chain with an alcohol moiety having an alicyclic skeleton. It is also possible to adjust the refractive index according to the purpose. Incidentally, it is preferable that the refractive index difference between the core layer and the clad layer is 0.01 or more in the optical waveguide, and more preferably 0.03 or more.
[0023]
Specifically, for example, when a homopolymer of 2-methyl-2-adamantyl methacrylate is used as the polymer in the present invention, the ester is cleaved by light irradiation, and poly (meth) acrylic acid and methylene adamantane (ester cleavage). Product). When the ester cleavage proceeds almost completely, the refractive index before light irradiation is about 1.54, the refractive index after light irradiation is about 1.49 (value at 589.3 nm), and the refractive index is about 0.05. Create a rate difference.
[0024]
As described above, the photoacid generator is not particularly limited as long as it is a compound that generates acid when irradiated with light, and any known compound can be used without any limitation, but it is mainly used for signal transmission in an optical waveguide. It is preferably a compound that is transparent (insensitive) to visible light or near infrared light, that is, a compound that generates an acid by ultraviolet light. Specifically, an aryldiazonium salt, a diaryliodonium salt, Tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate of onium salts such as triarylsulfonium salt and triarylphosphonium salt; 2-nitrobenzyl ester of sulfonic acid, iminosulfonate, 1-oxo-2- Diazonaphthoquinone-4-sulfonate derivative, N-hydroxy Bromide = sulfonate, tri (methanesulfonyloxy) benzene derivatives; carboxylic acid o- nitrobenzyl ester, 1-oxo-2-diazonaphthoquinone-5-arylsulfonate; and triaryl phosphate ester derivative is exemplified. These photoacid generators may be used alone or in combination of a plurality of types.
[0025]
The blending ratio of the photoacid generator to the polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid is not particularly limited, but sufficient ester cleavage is performed. In order to make it easy to control the difference in refractive index, it is preferable that it is large. On the other hand, in order to reduce light loss due to scattering in the obtained optical waveguide, it is preferable that it is small. It is preferable to set it as 0.1-15 weight part with respect to 100 weight part of polymers.
[0026]
In addition, the optical waveguide forming material in the present invention includes, if necessary, a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid, and a photoacid generator. In addition, other polymers, stabilizers and the like may be blended within a range not impairing the effects of the present invention.
[0027]
Next, an example of a specific method for manufacturing an optical waveguide using the optical waveguide forming material of the present invention will be described with reference to FIG.
[0028]
First, a polymer containing monomer units based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid is dissolved in an organic solvent such as chloroform, and a predetermined amount of a photoacid generator is added to uniformly Make a solution. The polymer concentration at this time may be appropriately selected according to the film thickness to be obtained and the degree of polymerization of the polymer, and generally may be about 1 to 50% by weight. Subsequently, the solution is applied onto the substrate 2 on which the optical waveguide is to be formed by spin coating, dip coating, or the like, and the organic solvent is volatilized and distilled off to obtain the thin film 1 (a in FIG. 1). Next, ultraviolet light is irradiated through a photomask 3 having a mask hole of a predetermined pattern (b in FIG. 1). Thereby, a high refractive index layer (core layer; 4) comprising an unexposed portion (consisting of a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid); exposed portion (poly (meth) consisting of acrylic acid and ester cleavage product) consisting of a low refractive index layer (clad layer; 5) and can be obtained, an optical waveguide is obtained in accordance with the pattern of the photomask (C in FIG. 1).
[0029]
The optical waveguide thus obtained can be further coated with various polymers as required.
[0030]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0031]
Example 1 10 parts by weight of polymethyl 2-methyl-2-adamantyl methacrylate and 0.1 part by weight of hexafluoroantimonate of a photoacid generator 4-phenylthiophenyldiphenylsulfonium were dissolved in 90 parts by weight of chloroform. After spin coating this on a glass substrate, chloroform was distilled off by vacuum drying at room temperature to obtain a thin film. Using a photomask engraved with an optical waveguide pattern having a width of 4 to 20 μm, ultraviolet rays having a wavelength of 313 nm and an illuminance of 200 mW / cm ² were irradiated.
[0032]
The refractive index of the obtained optical waveguide, wavelength 589.3 nm, the results measured at 20 ° C., the refractive index of the core layer (unexposed portion) 1.537, the refractive index of the clad layer (exposed portion) is 1. 491.
[0033]
Further, it was clear that this optical waveguide was excellent in heat resistance without being softened or melted at 100 ° C.
[0034]
Example 2
10 parts by weight of 1-methylcyclohexyl polymethacrylate and 0.1 part by weight of hexafluoroantimonate of a photoacid generator 4-phenylthiophenyldiphenylsulfonium were dissolved in 90 parts by weight of chloroform. After spin coating this on a glass substrate, chloroform was distilled off by vacuum drying at room temperature to obtain a thin film. Using a photomask engraved with an optical waveguide pattern having a width of 4 to 20 μm, ultraviolet rays having a wavelength of 313 nm and an illuminance of 200 mW / cm ² were irradiated.
[0035]
The refractive index of the obtained optical waveguide, wavelength 589.3 nm, the results measured at 20 ° C., the refractive index of the core layer (unexposed portion) 1.511, the refractive index of the clad layer (exposed portion) is 1. 491, which produced a refractive index difference of 0.02 at that wavelength. The softening temperature of this optical waveguide was about 90 ° C.
[0036]
Comparative Example 1
10 parts by weight of polyethyl methacrylate and 0.1 part by weight of hexafluoroantimonate of photoacid generator 4-phenylthiophenyldiphenylsulfonium were dissolved in 90 parts by weight of chloroform. After spin coating this on a glass substrate, chloroform was distilled off by vacuum drying at room temperature to obtain a thin film. Using a photomask engraved with an optical waveguide pattern having a width of 4 to 20 μm, ultraviolet rays having a wavelength of 313 nm and an illuminance of 200 mW / cm ² were irradiated.
[0037]
The refractive index of the obtained optical waveguide, wavelength 589.3 nm, the results measured at 20 ° C., the refractive index of the core layer (unexposed portion) 1.489, the refractive index of the clad layer (exposed portion) is 1. It was 491, and a sufficient refractive index difference was not obtained at this wavelength. In this case, the optical waveguide was softened when heated to 80 ° C.
[0038]
【The invention's effect】
According to the present invention, a high refractive index (core) layer and a low refractive index (clad) layer, it is possible to easily produce by contrast film made of a material of the same composition is irradiated with light, Further, an excellent optical waveguide can be formed by a highly accurate method of light irradiation using a photomask. Furthermore, the obtained optical waveguide is excellent in heat resistance, and it is also possible to adjust the refractive index by appropriately selecting a combination of monomer units of the polymer to be used, light irradiation conditions, and the like.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a process of forming an optical waveguide from a thin film made of the optical waveguide forming material of the present invention.
[Explanation of symbols]
1. A film comprising a polymer containing a monomer unit based on an ester of an alcohol having an alicyclic skeleton and (meth) acrylic acid, and a photoacid generator.
2. Substrate 3. Photomask4. 4. Core (high refractive index) layer Clad (low refractive index) layer

Claims (4)

An optical waveguide forming material for forming an optical waveguide with a portion not irradiated with light as a core layer and a portion irradiated with light as a cladding layer, and an ester of alcohol having an alicyclic skeleton and (meth) acrylic acid An optical waveguide forming material comprising: a polymer containing a monomer unit based thereon; and a photoacid generator. The material for forming an optical waveguide according to claim 1, wherein the alicyclic skeleton is an adamantane skeleton. An optical waveguide using the optical waveguide forming material according to claim 1 or 2. A semiconductor device formed with the optical waveguide according to claim 3 .