JPH06172533A - Polymer for forming optical waveguide and production of polysiloxane-based optical waveguide - Google Patents

Abstract

PURPOSE:To improve the sectional shape and processing efficiency of an optical waveguide by forming a specific copolymer layer on a lower clad layer formed on a substrate, insolubilizing the copolymer layer, and removing unnecessary parts from the copolymer layer to form a core layer. CONSTITUTION:A lower clad layer is formed by applying a polysiloxane for cladding to a substrate. A core layer is formed by applying, to the lower clad layer, a (co)polymer having repeating units of formula I or II wherein R1, R2, and R3 are each an optionally deuterated or halogenated alkyl group represented by Cn2+1 wherein Y is H, deuterium, or halogen; and n is 5 or lower, an optionally deuterated or halogenated phenyl group represented by C6Y5; R4 is an optionally deuterated or halogenated phenylene group represented by C6Y4; Z is H or deuterium; and m is 100 or lower, irradiating it with far ultraviolet rays or electron beams to insolubilize it, and removing unnecessary parts from it. Then, on the core layer is formed an upper clad layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polysiloxane optical component which can be used as a waveguide for an optical integrated circuit and a method for producing the same.

[0002]

2. Description of the Related Art Inorganic materials such as quartz glass and multi-component glass, which are characterized by low optical transmission loss and wide transmission band, are widely used as the base material of optical parts or optical fibers. Recently, plastic-based materials have been developed and are attracting attention as optical waveguide materials with good performance because they are superior in processability and price compared to inorganic materials. For example, a flat plate-type optical waveguide having a core-clad structure in which a plastic having excellent transparency such as polymethylmethacrylate (PMMA) or polystyrene is used as a core and a plastic having a refractive index lower than that of the core component is used as a clad component is manufactured. [JP-A-3-188402]. However, these conventional plastic optical waveguides have a problem that the waveguide loss and heat resistance do not reach that of inorganic materials. In other words, regarding the problem of waveguide loss, the transmission of light in the waveguide is performed by totally reflecting the light incident on one end of the waveguide along the length direction. The degree to which light is attenuated by absorption or scattering of light is greater in plastic than in inorganic materials. Particularly, since the wavelength of light used for communication is in the range of 650 nm to 1600 nm, it is necessary to reduce the loss of the plastic in this wavelength range.
Regarding the problem of heat resistance, since the glass transition temperature of plastic is generally around 100 ° C., the upper limit of the heat resistant temperature is about 70 ° C., and it is difficult to use the plastic waveguide as a practical one. there were. As a material for solving these problems, polysiloxane having a low loss in the visible to near infrared region and excellent heat resistance can be used (JP-A-3-43423). In order to manufacture a plastic optical waveguide using this material, a low refractive index polysiloxane serving as a clad and a high refractive index polysiloxane serving as a core are required. First, a low-refractive-index polysiloxane layer is formed on a substrate, then a high-refractive-index polysiloxane layer serving as a core is formed thereon, and then this layer is formed by a conventional fine processing technique. Fine processing to the core shape. Specifically, a photosensitive resist layer is further formed on the polysiloxane layer, and the resist pattern formed by exposure / development of the resist is used as a mask for wet etching using an organic solvent, or
The polysiloxane layer is finely processed by dry etching such as reactive ion etching. However,
The fine processing of polysiloxane involves the following difficulties. That is, if the wet etching method is adopted, it is difficult to process the core into a proper rectangular cross-section due to isotropic etching with an organic solvent. Further, even if the anisotropic dry etching method is adopted, there is a drawback that the etching rate is low and it takes a long time to perform fine processing of the core.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and its purpose is
An object of the present invention is to provide a method for efficiently and simply producing a plastic optical waveguide which has a low loss in the near infrared region and is excellent in heat resistance.

[0004]

The present invention will be summarized. The first invention of the present invention relates to a polymer for forming an optical waveguide, which is represented by the following general formula (Formula 1) or (Formula 2):

[0005]

[Chemical 1]

[0006]

[Chemical 2]

[Wherein R ₁ , R ₂ and R ₃ are the same or different, and C _n Y _{2n + 1} (Y is hydrogen, deuterium or halogen, n
Is a positive integer of 5 or less), a deuterated alkyl group, a halogenated alkyl group, or C ₆
A phenyl group represented by Y ₅ (Y is hydrogen, deuterium, or halogen), a deuterated phenyl group, or a halogenated phenyl group; R ₄ is C ₆ Y ₄ (Y is hydrogen, deuterium, or halogen) A phenylene group represented by, a deuterated phenylene group,
Or a halogenated phenylene group, Z is hydrogen or deuterium, m is a positive number less than 100, and Y is all or part of deuterium], or a polymer having a repeating unit represented by: It is characterized by being a copolymer having a repeating unit represented by the general formula (Formula 1) or (Formula 2). A second invention of the present invention relates to a method for manufacturing a polysiloxane optical waveguide, which comprises a step of forming a lower clad layer on a substrate, a step of forming a core portion, and a step of forming an upper clad. In the method for producing a polysiloxane-based optical waveguide to be included, the core portion is formed by a step of insolubilizing a polymer by irradiation with deep ultraviolet rays or an electron beam and a step of removing an unnecessary portion.

As a result of intensive studies and research for solving the above-mentioned problems, the present inventors have insolubilized themselves by deep ultraviolet rays or electron beams unlike conventional polysiloxanes which are processed with the help of a resist. However, it has been found that the aforementioned problems can be solved by using a polysiloxane that enables direct processing.

That is, in the present invention, the conventional processing of polysiloxane into an optical waveguide is performed by first forming a photosensitive resist layer and forming a resist mask by exposure and development, and then by a conventional wet etching method using an organic solvent. Since it is performed by using a dry etching method such as or reactive ion etching, not only the processing procedure is complicated, but also the controllability of the waveguide shape and the processing efficiency are extremely low. The core portion is directly formed by using polysiloxane which is insolubilized by the irradiation of. The inventors of the present invention have found that by adopting such a polysiloxane and a processing method, the cross-sectional shape of the waveguide can be appropriately maintained and the processing efficiency can be improved.

The optical waveguide according to the present invention comprises a lower clad formed on a substrate, a core portion formed, an upper clad formed,
It is manufactured through three steps. Hereinafter, the optical waveguide of the present invention and the method for manufacturing the same will be described in more detail step by step.

The substrate for forming the lower clad is not particularly limited as long as it has a smooth surface. For example, silicon wafer, quartz glass, multi-component glass, plastic plate, plastic film, ceramics, metal plate. , Minerals, or a combination of these materials can be used.

The polysiloxane for the clad formed on these is not particularly limited as long as it has a lower refractive index than the polysiloxane to be used in the core portion described below. For example, polyphenylsilsesqui Oxane,
Polydiphenylsiloxane, a copolymer of trichlorophenylsilane and dichlorodiphenylsilane as a monomer, and the like can be used. The clad layer on the substrate can be formed, for example, by spin-coating a solution containing the above-mentioned polysiloxane for clad on the substrate and then drying it, or by immersing the substrate in the solution and then drying it. That is, the method for forming the lower clad layer is not limited in the present invention. The lower clad formed on the substrate may have a single composition or a mixture of a plurality of polysiloxanes. Further, it may be a laminate of a plurality of polysiloxanes.

A core layer is formed on the lower clad formed by the above method. As the polymer for forming an optical waveguide necessary for producing the polysiloxane-based optical waveguide of the present invention, one having a refractive index larger than that of the lower clad described above and insolubilized by irradiation with deep ultraviolet rays or electron beams is used. A polymer having a repeating unit represented by the general formula (Formula 1) or (Formula 2), or represented by the general formula (Formula 1) or (Formula 2) Examples thereof include copolymers of repeating units. Specifically, for example, chloromethylated polyphenylsilsesquioxane, chloromethylated polydiphenylsiloxane, or the like in which a part of hydrogen of the phenyl group is deuterated can be used. When n is 6 or more, the glass transition temperature of the polymer is lowered to cause a problem in heat resistance. Therefore, n is preferably 5 or less. The core layer can be formed by spin coating or immersion in a solution as in the case of the lower clad. Further, the composition of the core layer may be a single composition or a mixture of a plurality of polysiloxanes. The desired portion of the core layer thus formed is irradiated with deep ultraviolet rays or electron beams. In the case of irradiation with deep ultraviolet rays, a mask pattern is formed by stacking a mask on the core layer or by sputtering, and the deep ultraviolet rays are emitted from a mercury lamp or a commercially available exposure device. In the case of electron beam irradiation, an electron beam is directly irradiated onto the core layer in a desired pattern using an electron beam drawing apparatus. Through these steps, the polysiloxane in the portion irradiated with deep ultraviolet rays or electron beams becomes insoluble, and unnecessary polysiloxane other than this portion is dissolved and removed,
A core portion through which light is guided is formed. For dissolving and removing unnecessary polysiloxane, a method of immersing the entire substrate in a solvent, a method of spraying the solvent on the core layer, or the like can be used.

The polysiloxane for the upper clad formed on these is not particularly limited as long as it has a lower refractive index than the polysiloxane used for the above-mentioned core portion, but the same one as the lower layer is used. desirable. The upper clad layer is formed, for example, by spin-coating a solution containing the above polysiloxane on a substrate and then drying it, or by immersing the substrate in the solution and then drying it. Etc. can be formed by the same method as when forming the lower clad. That is, the method for forming the upper clad layer is not limited in the present invention. The upper clad formed may have a single composition, a mixture of a plurality of polysiloxanes, or a laminate of a plurality of polysiloxanes.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 An optical waveguide was manufactured using chloromethylated poly-heavy-phenyl silsesquioxane (chloromethylation rate: 10%) as a core component and poly-heavy-phenyl silsesquioxane as a lower layer and an upper clad component. The above-mentioned two kinds of polymers were used as a methyl isobutyl ketone solution. First, the clad component polymer was applied on a silicon substrate to a thickness of about 20 μm. heating·
After the drying treatment, the core component polymer was applied on the lower clad layer to a thickness of about 8 μm. After superimposing a photomask having a pattern of 8 μm on it and insolubilizing it by irradiating with deep ultraviolet rays, spraying methyl isobutyl ketone removes the core component in the part which was not insolubilized, and the core part polymer was extended. Height 50 mm, width 8 μm, height 8
It was processed into a linear rectangular pattern of μm. A clad component was applied on this to obtain a waveguide. When the loss of the waveguide was calculated by inputting light having a wavelength of 1300 nm from one end of the waveguide and measuring the amount of light emitted from the other end, the waveguide loss was 0.3 dB / cm or less. Also, -20 ° C to 15
No increase in waveguide loss was observed after 10 heat cycle tests at 0 ° C.

Examples 2 to 4 Optical waveguides were manufactured on a silicon wafer under various conditions in the same manner as in Example 1. In any case, the core material was a material obtained by chlormethylating a part of the aromatic ring in the clad material. The manufacturing conditions are summarized in Tables 1 and 2.

[0018]

[Table 1] Table 1 ──────────────────────────────────── Example number Clad material Chloromethylation rate ──────────────────────────────────── 1 Deuterated polyphenylsilsesquioxane 10 % 2 Deuterated polydiphenylsilsesquioxane 22% 3 Copolymer obtained from deuterated trichlorophenylsilane and deuterated dichlorodiphenylsilane 17% 4 Deuterated polymethylphenylsilsesquioxane 31% ── ───────────────────────────────────

[0019]

[Table 2] Table 2 ──────────────────────────────────── Example number Solvent insolubilization method Core Development method of ───────────────────────────────────── 1 Methyl isobutyl ketone Far UV irradiation Spraying solvent 2 Methyl isobutyl ketone Far-UV irradiation Solvent spray 3 Methyl isobutyl ketone Far-UV irradiation Solvent spray 4 Methyl ethyl ketone electron beam irradiation Immersed in solvent ──────────────────────── ─────────────

Using the manufactured optical waveguides, the waveguide loss and heat resistance were evaluated in the same manner as in Example 1, and it was confirmed that all the optical waveguides had extremely low waveguide loss and high heat resistance. It was

[0021]

As described above, the polysiloxane-based optical waveguide according to the present invention has extremely excellent optical transmission characteristics in the visible to near-infrared region as compared with the conventional plastic optical waveguide, and at the high temperature for a long time. Even if exposed, the performance is not significantly reduced. Therefore, there is an advantage that it can be stably used as an optical integrated circuit component in the near infrared region or as an optical signal transmission medium for a distance of several 100 m using a near infrared light source. Moreover, since the direct waveguide processing procedure by insolubilizing only a desired portion is used in the manufacturing process, the manufacturing process can be simplified, and
The controllability of the waveguide shape can be improved. That is, by the manufacturing method of these polymeric materials and optical waveguide,
There is an advantage that an optical signal transmission system such as a local area network having excellent economical efficiency can be configured.

Claims (2)

[Claims] 1. The following general formula (Formula 1) or (Formula 2): [Chemical 2] [In the formula, R ₁ , R ₂ and R ₃ are the same or different and are C _n Y
_{2n + 1} (Y is hydrogen, deuterium, or halogen, n is a positive integer of 5 or less), a deuterated alkyl group, a halogenated alkyl group, or C ₆ Y ₅ (Y
Is a hydrogen, deuterium, or halogen) phenyl group, a deuterated phenyl group, or a halogenated phenyl group,
R ₄ is a phenylene group represented by C ₆ Y ₄ (Y is hydrogen, deuterium, or halogen), a deuterated phenylene group, or a halogenated phenylene group, Z is hydrogen or deuterium, and m is a positive number less than 100. And Y is a polymer having a repeating unit represented by all or a part thereof] or a repeating unit represented by the general formula (Formula 1) or (Formula 2). A polymer for forming an optical waveguide, which is a copolymer. 2. A method of manufacturing a polysiloxane-based optical waveguide comprising the steps of forming a lower clad layer on a substrate, forming a core portion, and forming an upper clad, wherein the formation of the core portion comprises: A method for producing a polysiloxane-based optical waveguide, which comprises performing a step of insolubilizing a polymer by irradiation with far ultraviolet rays or an electron beam and a step of removing an unnecessary portion.