KR20050053223A - Inorganic-organic hybrid silica sol-gel solution, optical waveguide and method for manufacturing a optical waveguide using the same - Google Patents

Abstract

An organic-free hybrid silica-based sol-gel solution and a planar optical waveguide and a method of manufacturing the planar optical waveguide are disclosed. The solution of the present invention is at least any one selected from methyltrimethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, phenyltriethoxysilane, phenyltrimethoxysilane and diphenyldiethylhexyloxydiethoxysilane. A precursor consisting of one; Characterized in that a catalyst consisting of hydrochloric acid is included. And a precursor consisting of 3-trimethoxysilylpropyl methacrylate and / or tetraethyl orthosilicate; A catalyst consisting of hydrochloric acid; A photoinitiator consisting of hydroxycyclohexylphenyl ketone; A solvent consisting of isopropyl alcohol; Ultraviolet reaction monomer consisting of methacrylic acid is characterized in that it is included. According to the present invention, the planar optical waveguide manufacturing process can be simplified to reduce the manufacturing cost, and the planar optical waveguide having excellent physical properties that can easily control the refractive index and form a pattern can be manufactured.

Description

Organic-organic hybrid silica sol-gel solution, optical waveguide and method for manufacturing a optical waveguide using the same

The present invention relates to an organic-inorganic hybrid silica-based sol-gel solution and a method of manufacturing a planar optical waveguide and a planar optical waveguide using the same, and in particular, the spin coating method, the optical transfer method, and the wet etching method may be used in the planar optical waveguide manufacturing process. An organic-inorganic hybrid silica-based sol-gel solution, and a planar optical waveguide and a method for manufacturing the planar optical waveguide using the same.

The optical waveguide is composed of a cladding layer and a core layer. The optical waveguide has a function of controlling the traveling direction of the optical signal by limiting the input optical signal into the core layer by using the refractive index difference between the two layers. Although research has been conducted to use polymer as a material to reduce the process cost when manufacturing an optical waveguide, this causes a problem of high transmission loss in the near-infrared region mainly used in optical communication due to infrared vibration absorption loss due to carbon-hydrogen coupling. There is this. In contrast, optical waveguides based on silica-based materials having excellent transmission loss in the near infrared region have already been commercialized.

Generally used optical waveguides are classified into optical fibers and planar optical waveguides. Planar optical waveguide refers to a device that implements an optical fiber structure on a planar substrate by using a fine pattern forming technology used in a semiconductor process, and can provide various functions such as modulation, demodulation, and switching according to the structure of the optical waveguide. . In addition, because of the fine patterning technology, the integration of the device can be improved and the process cost can be reduced through mass production. The fine pattern formation technique applied in the manufacture of such planar optical waveguides is based on a dry etching process.

1 is a schematic diagram illustrating a conventional method for manufacturing a planar optical waveguide through a dry etching process.

Referring to FIG. 1, first, a chemical vapor deposition (CVD) or flame hydrolysis deposition (FHD) method is used to form a lower portion on one surface of a substrate 10 as shown in FIG. The clad layer 20 is formed and the core layer 30 is formed on the lower clad layer 20 as shown in FIG.

Next, as shown in FIG. 1C, a mask layer 40 for forming a pattern on the core layer 30 is formed on the core layer 30, and the photo is spin-coated on the mask layer 40. After applying the resist, a pattern is formed on the photoresist layer 50 by using an optical transfer method and a wet etching process as shown in FIG.

Subsequently, the pattern of the mask layer 40 is formed by a dry etching process as shown in FIG. 1E, and the photoresist layer is removed as shown in FIG. 1F.

Next, a pattern is formed on the core layer 20 by a dry etching process as shown in FIG. 1G, and the mask layer is removed as shown in FIG. 1H.

Subsequently, the upper clad layer 60 is coated on the resultant using chemical vapor deposition or flame hydrolysis deposition as shown in FIG. 1 (i).

As described above, in the case of forming the optical waveguide using the dry etching process, expensive plasma etching equipment is essential and complicated process steps require expensive process costs (time, manpower, cost). In addition, the chemical vapor deposition or hydrolysis deposition method used for coating the cladding layer and the core layer has advantages over other deposition processes in stacking thin films having a thickness of 5 to 15 μm, which are required for the production of planar optical waveguides. Although it has a post-process such as annealing or consolidation at a temperature above 1000 ??

Accordingly, a manufacturing method based on a relatively inexpensive sol-gel process has been proposed as an alternative for manufacturing planar optical waveguides. The sol-gel process is a process of forming an oxide through the hydrolysis and condensation reaction of metal alkoxide precursors that are uniformly mixed in the solution phase. Since a silica film may be formed from the solution phase, a simple process such as spin coating or dip coating is performed. Thin films can be laminated. In addition, since the precursor is laminated in a state in which the composition is controlled for controlling the physical properties of the laminated film, there is an advantage of having excellent physical property control ability.

On the other hand, there is a problem in that a crack of the film due to capillary stress occurs when forming a thick film having a thickness of 5 to 15 μm, and a high temperature process is also required for removing the organic matter remaining in the laminated film and densifying the film.

In order to overcome the problems of the sol-gel process, an organic-inorganic hybrid silica-based sol-gel process has been proposed. In the conventional sol-gel process, a metal alkoxide is used as a precursor, but in the organic-free hybrid silica-based sol-gel process, a metal alkoxide in which some functional groups are substituted with an organic material is added, thereby applying flexibility of the organic material to the laminated film. There is an effect of suppressing the occurrence of cracking due to capillary stress, so that thick film formation is facilitated. Also, 250 ?? Since a dense film is formed at the following low temperature, not only a high temperature heat treatment is required, but also the added organic material can form a crosslink by ultraviolet irradiation, so that the solubility of the hybrid silica is changed according to the ultraviolet irradiated area, and thus the negative type. There is an advantage that the photosensitive pattern can be implemented.

Accordingly, an object of the present invention is to provide a solution capable of an organic-inorganic hybrid silica-based sol-gel process.

In addition, another object of the present invention is to provide a planar optical waveguide using a solution capable of an organic-inorganic hybrid silica-based sol-gel process and a method of manufacturing the same.

An organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention for achieving the above technical problem is: methyltrimethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, phenyltriethoxysilane, phenyl A precursor consisting of at least one selected from trimethoxysilane and diphenyldiethylhexyloxydiethoxysilane; Characterized in that a catalyst consisting of hydrochloric acid is included.

An organic-inorganic hybrid silica-based sol-gel solution according to another embodiment of the present invention for achieving the above technical problem comprises: a precursor consisting of 3-trimethoxysilylpropyl methacrylate and / or tetraethyl orthosilicate; A catalyst consisting of hydrochloric acid; A photoinitiator consisting of hydroxycyclohexylphenyl ketone; A solvent consisting of isopropyl alcohol; Ultraviolet reaction monomer consisting of methacrylic acid is characterized in that it is included.

In accordance with another aspect of the present invention, a planar optical waveguide includes:

The cladding layer consists of at least one selected from methyltrimethoxysilane, methyltriethoxysilane, tetraethylorthosilicate, phenyltriethoxysilane, phenyltrimethoxysilane and diphenyldiethylhexyloxydiethoxysilane. Precursors; It is formed of a first organic-free hybrid silica-based sol-gel solution containing a catalyst consisting of hydrochloric acid,

The core layer comprises: a precursor consisting of 3-trimethoxysilylpropylmethacrylate and / or tetraethylorthosilicate; A catalyst consisting of hydrochloric acid; A photoinitiator consisting of hydroxycyclohexylphenyl ketone; A solvent consisting of isopropyl alcohol; It is characterized in that it is formed of a second organic-inorganic hybrid silica-based sol-gel solution containing an ultraviolet reaction monomer consisting of methacrylic acid.

The method of manufacturing the planar optical waveguide includes: forming a lower clad layer by applying the first organic-free hybrid silica-based sol-gel solution on a substrate; Applying a second organic-inorganic hybrid silica-based sol-gel solution on the lower clad layer to form a core layer, and removing a predetermined region of the core layer to expose a predetermined region of the lower clad layer; And applying the first organic-free hybrid silica-based sol-gel solution on the resultant to form an upper clad layer.

At this time, the lower clad layer, the core layer and the upper clad layer is preferably applied by spin coating, respectively.

Further, in the removing of the predetermined region of the core layer, it is preferable to form a pattern using an optical transfer method and to remove the same by a wet etching process.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a schematic view showing a cross-linked silica network structure in an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention, and FIGS. 3A and 3B are organic-inorganic hybrids according to an embodiment of the present invention. 4A to 4D illustrate a method of manufacturing a planar optical waveguide using silica-based sol-gel solutions, and FIG. 4A illustrates a clad layer formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention. Figure 4b is a graph of the change in refractive index according to the concentration of the precursor at a wavelength of 1550nm, Figure 4b is a SEM photograph of the cladding layer formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention 5A is a SEM photograph of a core layer formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention, and FIG. 5B is in accordance with FIG. 5A. And a picture when forming a pattern by a wet etching process eocheung taken by an optical microscope, Figure 5c is a SEM photo photographed the case of forming a pattern of the core layer according to Figure 5a by a wet etching process.

The organic-inorganic hybrid silica-based sol-gel solution according to the present invention is classified into a solution used for forming a clad layer and a solution used for forming a core layer.

The solution used to form the cladding layer (hereinafter referred to as the first organic-inorganic hybrid silica-based sol-gel solution) includes methyltrimethoxysilane (hereinafter referred to as MTMS) and methyltriethoxy. Silane (methyltriethoxysilane, hereinafter referred to as MTES), tetraethylorthosilicate (hereinafter referred to as TEOS), phenyltriethoxysilane (hereinafter referred to as PhTEOS), phenyltrimethoxysilane At least one selected from the group consisting of PhTMOS) and diphenyldiethylhexyloxydiethoxysilane (hereinafter referred to as DPS) is used as a precursor, and 0.1 N hydrochloric acid promotes hydrolysis and condensation reactions. It is used as a catalyst to make.

Hydrolysis and condensation reactions are the basic reactions in the sol-gel process. Hydrolysis converts the alkoxy groups (OR) present in the precursors into silanol groups (OH) as shown in Formula 1 below. The Si-O-Si bonds are finally connected to form a silica network.

Among the aforementioned precursors, PhTEOS, PhTMOS, and DPS include a phenyl group represented by Formula 2 below.

Referring to Chemical Formula 2, the phenyl group is a functional group having a ??-bonded orbital and has a large electronic polarizability because the electron cloud of the orbital is easily deformed when an external electric field is applied. This acts as an element which raises the refractive index of a material when light is irradiated to the material containing a phenyl group. Therefore, when the cladding layer is formed using the first organic-inorganic hybrid silica-based sol-gel solution according to the present invention, the core layer and the clad required for the optical waveguide are controlled by controlling the concentration of PhTEOS, PhTMOS or DPS. There is a property that can control the difference in refractive index of the layer.

Next, a solution (hereinafter referred to as a second organic-inorganic hybrid silica-based sol-gel solution) used for forming the core layer will be described.

In the second organic-inorganic hybrid silica-based sol-gel solution, 3-trimethoxysilylpropyl methacrylate (hereinafter referred to as MAPTMS) and TEOS are used as precursors, and hydrolysis thereof 0.01 N hydrochloric acid is used as a catalyst to promote the condensation reaction, and hydroxycyclohexylphenylketone (hereinafter referred to as HCPK) is added as a photoinitiator for inducing crosslinking by ultraviolet rays. In addition, isopropyl alcohol (hereinafter referred to as IPA) is used as a common solvent for homogeneous mixing of the above substances, and methacrylic acid (hereinafter referred to as MMA) is a UV reactive monomer. Is added.

Hydrolysis and condensation reactions form silica meshes based on MAPTMS and TEOS precursors as in the first organic-free hybrid silica-based sol-gel solution described above. The methacrylate group present in the silica network containing MAPTMS induces crosslinking by ultraviolet light. In addition, crosslinking is induced by ultraviolet rays because MMA, which is present independently without participating in hydrolysis and condensation reactions, also contains methacrylate groups. The crosslinking reaction induced by these ultraviolet rays is shown in Chemical Formula 3 below.

That is, when ultraviolet light is irradiated, the C = C bond of the methacrylate group is transferred to the C-C bond. This links the silica network and reduces solubility in certain solvents, as shown in FIG. Therefore, in the case of forming the core layer using the second organic-inorganic hybrid silica-based sol-gel solution, selective irradiation of ultraviolet rays through optical transfer and a wet etching process using a specific solvent may be used.

3A and 3B, a method of manufacturing a planar optical waveguide using the first and second organic-inorganic hybrid silica-based sol-gel solutions described above will be described.

First, the planar substrate 100 is prepared (S10), and the first organic-inorganic hybrid silica-based sol-gel solution is applied onto the substrate by using a spin coating method. The lower clad layer 200 is formed by heat treatment at the following temperature (S20).

Next, a second organic-inorganic hybrid silica-based sol-gel solution is coated on the lower clad layer 200 by using spin coating to form a core layer 300 (S30).

Next, an optical transfer method for irradiating ultraviolet rays to a predetermined region of the core layer 300 is performed to cause partial crosslinking (S40).

Subsequently, the core layer 300 induces a difference in solubility between the ultraviolet-irradiated and non-irradiated regions and forms a pattern by dissolving the non-irradiated ultraviolet rays with a specific solvent (S50). Then, the patterned core layer is formed into a dense silica film. Heat treatment at the following temperature is carried out.

Subsequently, the first organic-inorganic hybrid silica-based sol-gel solution was applied onto the resultant up to the above-mentioned step by spin coating, The upper cladding layer 400 is formed by heat treatment at the following temperature (S60).

Hereinafter, embodiments using the above-described first and second organic-free hybrid silica-based sol-gel solutions will be described. However, the embodiments to be described later are described by way of example and are not necessarily limited thereto, and the scope of the present invention is not limited thereto.

Example 1

TEOS: MTES: PhTMOS = 40: (60-x): After mixing the precursors in a molar ratio of x, 0.1 N hydrochloric acid was added to the mixed precursor in a molar ratio of 1: 1.5, whereby the first organic-free hybrid Silica-based sol-gel solution was prepared. At this time, the molar ratio of PhTMOS is set to 7, 9, 10, 22, 25, 28, 30% to control the refractive index of the cladding layer to be formed using the prepared first organic-inorganic hybrid silica-based sol-gel solution. Each changed. Then, the mixture was stirred for 5 hours at room temperature and nitrogen atmosphere for homogeneous mixing of the prepared solution, and exposed to a general atmosphere for further reaction. The solution having undergone the above-described process was applied on a silicon substrate by spin coating and heat-treated at 150 ° C. for 1 hour to form a clad layer.

Referring to FIG. 4A, when the clad layer is formed using the first organic-inorganic hybrid silica-based sol-gel solution, the refractive index of the clad layer may be changed only by changing the molar ratio of PhTMOS. It can be seen that the control is easy.

Referring to FIG. 4B, it can be seen that a dense clad layer without cracks having a thickness of 7 μm is formed.

Example 2

0.01N hydrochloric acid was mixed in MAPTMS at a molar ratio of 1: 0.75, followed by stirring for 30 minutes, and a solution was prepared by adding TEOS, MMA, and IPA. At this time, TEOS was added in a molar ratio of MAPTMS: TEOS = 8: 2, MMA was added in a molar ratio of TEOS: MMA = 4: 1, and IPA was added in a volume ratio of TEOS: IPA = 1: 1.2.5. . After the solution was stirred for 1 hour, distilled water was added to a molar ratio of 1.5 times with respect to the mixed precursor, followed by stirring for 30 minutes. Then, HCPK was added so as to have a molar ratio of 0.02 times the mixed precursor to prepare a second organic-inorganic hybrid silica-based sol-gel solution. The solution thus prepared was further stirred for 21 hours at room temperature and nitrogen atmosphere. The solution having undergone the above-described process was applied onto a silicon substrate by spin coating and dried at 110 ° to form a core layer. Referring to FIG. 5A, it can be seen that a dense core layer without cracks having a thickness of 9 μm was formed. Subsequently, an ultraviolet lamp of 25 mJ / cm ² was irradiated to the core layer by using an ultraviolet lamp irradiated with a wavelength of 350 nm or more, and then a region in which no ultraviolet ray was irradiated was dissolved using IPA to form a pattern on the core layer. After pattern formation, heat treatment was performed at 150 ° C. for 1 hour for densification of the film. 5B and 5C, it can be seen that the pattern formation of the core layer was easily performed. The refractive index of the formed core layer was 1.4733 at a wavelength of 1550 nm.

As described above, when the planar optical waveguide is manufactured using the organic-inorganic hybrid silica-based sol-gel solution of the present invention, the core layer and the clad layer required for the optical waveguide production are controlled by adjusting the concentration of the precursor forming the clad layer. The refractive index difference can be controlled, the pattern can be formed on the core layer by optical transfer method, and a predetermined region of the core layer can be removed by a wet etching process, and the spin coating method can be used to form the clad layer and the core layer. It can be applied.

Therefore, the planar optical waveguide manufacturing process can be simplified to reduce the manufacturing cost, and the planar optical waveguide having excellent physical properties that can easily control refractive index and form a pattern can be manufactured.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

1 is a schematic view for explaining a planar optical waveguide manufacturing method through a conventional dry etching process;

Figure 2 is a schematic diagram showing the cross-linked silica network structure in the organic-free hybrid silica-based sol-gel solution according to an embodiment of the present invention;

3A and 3B are views for explaining a method of manufacturing a planar optical waveguide using organic-organic hybrid silica-based sol-gel solutions according to an embodiment of the present invention;

Figure 4a is a graph measuring the change in refractive index according to the concentration of the precursor when the cladding layer is formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention at a wavelength of 1550nm;

Figure 4b is a SEM photograph of the cladding layer formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention;

5A is a SEM photograph of a core layer formed using an organic-inorganic hybrid silica-based sol-gel solution according to an embodiment of the present invention;

FIG. 5B is a photograph taken with an optical microscope of a case in which the core layer of FIG. 5A is patterned by a wet etching process; FIG. And

FIG. 5C is a SEM photograph of a case in which the core layer of FIG. 5A is patterned by a wet etching process. FIG.

Claims (6)

A precursor consisting of at least one selected from methyltrimethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, phenyltriethoxysilane, phenyltrimethoxysilane and diphenyldiethylhexyloxydiethoxysilane; An organic-inorganic hybrid silica-based sol-gel solution comprising a catalyst consisting of hydrochloric acid. A precursor consisting of 3-trimethoxysilylpropylmethacrylate and / or tetraethylorthosilicate; A catalyst consisting of hydrochloric acid; A photoinitiator consisting of hydroxycyclohexylphenyl ketone; A solvent consisting of isopropyl alcohol; An organic-inorganic hybrid silica-based sol-gel solution, characterized in that it comprises an ultraviolet reaction monomer consisting of methacrylic acid. The cladding layer consists of at least one selected from methyltrimethoxysilane, methyltriethoxysilane, tetraethylorthosilicate, phenyltriethoxysilane, phenyltrimethoxysilane and diphenyldiethylhexyloxydiethoxysilane. Precursors; It is formed of a first organic-free hybrid silica-based sol-gel solution containing a catalyst consisting of hydrochloric acid, The core layer comprises: a precursor consisting of 3-trimethoxysilylpropylmethacrylate and / or tetraethylorthosilicate; A catalyst consisting of hydrochloric acid; A photoinitiator consisting of hydroxycyclohexylphenyl ketone; A solvent consisting of isopropyl alcohol; A planar optical waveguide comprising a second organic-inorganic hybrid silica-based sol-gel solution containing an ultraviolet reaction monomer composed of methacrylic acid. The method of manufacturing a planar optical waveguide according to claim 3 is: Applying the first organic-free hybrid silica-based sol-gel solution on a substrate to form a lower clad layer; Applying a second organic-inorganic hybrid silica-based sol-gel solution on the lower clad layer to form a core layer, and removing a predetermined region of the core layer to expose a predetermined region of the lower clad layer; And applying the first organic-inorganic hybrid silica-based sol-gel solution on the resultant to form an upper cladding layer. The method of manufacturing a planar optical waveguide according to claim 4, wherein the lower clad layer, the core layer, and the upper clad layer are respectively coated by spin coating. The method of claim 4, wherein the removing of the predetermined region of the core layer is performed by using an optical transfer method to form a pattern and by a wet etching process.