JPH0353203A - Production of flash type optical waveguide element made of organic crystal body - Google Patents

Abstract

PURPOSE:To provide an element which hardly receives mechanical external forces by constituting the element by a stage for producing the ridge type optical waveguides made of an org. crystal body, a stage for forming a layer consisting of a material having the refractive index lower than the refractive index of the org. crystal body and a stage for removing a resist and the layer consisting of the material having the refractive index lower than the refractive index of the org. crystal body on the resist. CONSTITUTION:The ridge type optical waveguides made of the org. crystal body are produced by applying a resist 3 sensitive to light to electron beams on the thin-film org. crystal body 2 formed on a substrate 1, exposing and developing the resist to a desired fine pattern, then etching the thin-film org. crystal body 2. The layer 4 consisting of the material having the refractive index lower than the refractive index of the org. crystal body 2 is formed by vapor deposition or sputtering on the optical waveguides made of the org. crystal body and the substrate in such a manner that the this layer is formed to the same film thickness as the film thickness of the org. crystal body 2. The resist 3 on the optical waveguides made of the org. crystal body and the layer 4 consisting of the material having the refractive index lower than the refractive index of the org. crystal body on the resist are then removed. Consequently, the element is substantially kept free from the mechanical external forces. and the scattering loss of the light is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a buried optical waveguide element made of a functional organic crystal, which is attracting attention mainly in the optoelectronic technology field. In particular, optical information processing, optical communication, optical measurement and
It is usefully used as an organic nonlinear optical crystal guiding waveguide device suitably used in technical fields such as control.

[Prior Art] In recent years, the development of functional organic materials such as nonlinear optical materials, organic conductors, and organic photochromic materials has been remarkable, and they are expected to play an active role in future optoelectronic technology. Such functional organic materials are often used in the form of crystals. In order to utilize such crystals in the optoelectronic technology field, patterning to control the flow of electrons and the propagation direction of light, that is, the method of manufacturing a leading waveguide, is an important technique.

2. Description of the Related Art Optical waveguides made of inorganic crystals such as semiconductors are conventionally known, and processing methods used in integrated circuit processing and the like are known as methods for manufacturing them.

However, it has not been possible to apply this method to organic crystals. This is because the various conditions in the semiconductor microfabrication process, especially the etching conditions, are harsher than the heat resistance and chemical resistance of the organic crystal, resulting in deterioration and alteration of the organic crystal.

In addition, there are two basic configurations of three-dimensional optical waveguides made of inorganic crystals: (1) buried type (Figure 6) and (2) ridge type (Figure 7). In the figure, 1 indicates the substrate and 2 indicates the optical waveguide.) In the ridge-type optical waveguide, the waveguide layer protrudes from the substrate, so it has a structure that is susceptible to external mechanical force.

Therefore, when trying to apply it to a leading waveguide of an organic crystal, molecular crystals such as organic crystals generally have lower mechanical strength than inorganic materials and are considered to be difficult to use.

On the other hand, embedded optical waveguides can protect organic crystal optical waveguides with low mechanical strength, and because the waveguide surface is flat, it is possible to protect electro-optic devices using second-order nonlinear optical materials, for example. It is believed that control electrodes and the like can be easily formed.

Furthermore, in order to fabricate a buried waveguide using an inorganic material, a thermal diffusion method using metal ions having a high refractive index is usually used. However, such methods cannot be applied to organic crystals.

[Problems to be Solved by the Invention] The present invention provides an optical waveguide element made of an organic crystal, and furthermore,
It is an object of the present invention to provide a method for manufacturing a buried organic crystal optical waveguide element, which is less susceptible to mechanical external forces than a ridge-type waveguide, and which also facilitates the manufacture of electrodes after the waveguide has been manufactured.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure.

``A method for manufacturing an embedded organic crystal guiding waveguide, which is characterized by comprising the steps A, C, and C below.

B. Coat a resist 1 sensitive to light or electron beams on the thin film organic crystal formed on the substrate, expose and develop the resist into a desired fine pattern, and then apply the thin film organic crystal. This process involves etching to create a ridge-shaped organic crystal guiding waveguide.

B. On the organic crystal optical waveguide and substrate obtained in step (a), a layer made of a substance having a lower refractive index than the organic crystal is vapor-deposited so that the thickness of the layer is the same as that of the organic crystal. Or a process of forming by sputtering.

C. A step of removing the resist on the organic crystal guided waveguide obtained in step (b) and a layer made of a substance having a lower refractive index than the organic crystal on the resist.

A method for manufacturing a buried guiding waveguide of the present invention will be described below with reference to the drawings. A ridge-type organic crystal optical waveguide having the cross section shown in FIG. 1 can be manufactured by the above step A. In FIG. 1, reference numeral 1 indicates a substrate 2 that is an organic crystal, and reference numeral 3 indicates a resist. Subsequently, the structure having the cross section shown in FIG. 2 is formed by the step (b) above. Finally, by the step shown in C above, a desired embedded type guiding waveguide element having the cross section shown in FIG. 3 can be manufactured.

In the present invention, organic nonlinear optical materials, organic conductors, organic photochromic compounds, and the like are particularly preferably used as organic crystals. As an organic nonlinear optical material, practically, the second-order nonlinear optical constant χ■ is I
0"esu or more, or a third-order nonlinear optical constant χ0 of IXIO-"esu or more is desirable. Specific compounds include 2-methyl-4-nitroaniline, metanitroaniline, N-(4- nitrophenyl)-
(L) Monoprolinol, 2-(N,N-dimethylamino)-5-nitroacetanilide, 4°-nitrobenzylidene-3-acetamin-4-methoxyaniline, 2-
(N-prolinol)-5-nitropyridine, (-)
Second-order nonlinear optical materials such as 2-((1-methylbenzylamino)-5-nitropyridine, and third-order nonlinear optical materials such as boridiacetylene and charge transfer complexes are well known. Also, as organic conductors, , charge transfer complexes such as tetrathiafulvalene-tetracyanoquinodimethane complex, bisethylene dithiotetrathiafulvalene-halogen complex, and phthalocyanines, etc. are well known.

Furthermore, as organic photochromic compounds, spiropyran compounds, spirooxazine compounds, azo compounds, fulgide compounds, indigo compounds, and the like are well known based on their basic molecular structures.

In addition to these, there are also substances used as scintillators and phosphors such as anthracene, pyrene, perylene, ferrocene, etc., but if they are organic crystals whose functions can be utilized by microfabrication, these It is not limited to the materials.

Resists sensitive to light or electron beams related to the present invention include various positive and negative resists commonly used in semiconductor microfabrication processes, as well as photopolymerization reaction, photocrosslinking reaction, and photosolubilization. Various photosensitive polymer materials or electrosensitive polymer materials based on reactions, photodegradation reactions, etc. can be used. Regarding these, see "Recording Materials and Photosensitive Resins" (Gakkai Publishing Center, 1979), "
Known examples are described in detail in "Photosensitive Polymer" (Kodansha, 1977), and can be applied to the present invention.

In the present invention, as for the method of etching the organic crystal, if the etching method used in normal semiconductor microfabrication processes is used as is, the etching conditions will be harsher than the heat resistance and chemical resistance of the organic crystal. Since this may cause deterioration and alteration of the organic crystal, it is preferable to carry out, for example, the following method.

■Wet etching method: A protective layer is provided on the organic crystal or on the organic crystal, a photoresist is applied on top of it, the resist is exposed to light, and after development, only the organic crystal is removed without dissolving the resist. A method of etching organic crystals using a solvent that dissolves them.

■Dry etching method: A protective layer is provided on the organic crystal or on the organic crystal, a photoresist is applied on top of it, and after exposure and development, a reactive ion etching device (
A method of etching an organic crystal using an RIE device. During etching using an RIE device, halogenated hydrocarbon or a mixed gas of halogenated carbon and oxygen is used as the plasma generating gas, and the voltage is I W /
ct or less and further cooling the electrode on the side on which the organic crystal is placed is preferable because deterioration and alteration of the organic crystal during etching can be prevented.

A layer made of a substance having a lower refractive index than the organic crystal, which is formed on the optical waveguide on which the resist is mounted, is formed by vapor deposition or sputtering so that the film thickness is the same as that of the organic crystal.

As the component, any substance can be used as long as it has a lower refractive index than the organic crystal. For example, SiO2, ¥20
Examples include inorganic oxides such as No. 3, inorganic halides such as MgF, and polymers such as polyethylene and polypropylene. In particular, inorganic oxides are preferably used because the film thickness can be easily controlled by vapor deposition or sputtering. Further, examples of the vapor deposition method include electron beam evaporation, resistance heating, etc., and examples of the sputtering method include DC sputtering, AC sputtering, etc.

After forming the above-mentioned low refractive index layer on the resist, the resist and the low refractive index layer formed thereon can be removed by plasma ashing for negative resists, and by using a resist solution for positive resists. is possible. Therefore, among organic crystals, it is preferable to process materials that are expected to undergo thermal deterioration under plasma using a positive resist.

Further, the embedded organic crystal guided waveguide of the present invention has a fifth
It is also possible to provide a control electrode as shown in the figure and use it as an electro-optical element. In FIG. 5, 5 indicates an electrode.

[Examples] The present invention will be described below using specific examples, but the content of the present invention is not limited to the following examples.

Example 1 A powder of 2-methyl-4-nitroaniline was sandwiched between two glass plates and melted at a high temperature of 140°C, and then gradually cooled from one end of the glass plate to crystallize it.

Furthermore, one glass plate was peeled off and a film with a thickness of 0 was applied on the glass plate.
．． A 7 μm 2-methyl-4-nitroaniline crystal thin film was obtained. On the 2-methyl-4-nitroaniline crystal thin film,
After forming a 0.2 μm thick aluminum thin film as a protective layer to prevent the thin film from deteriorating due to the positive resist solution, a quinone diazide positive resist was applied, and then ultraviolet light was passed through a photomask with a desired pattern drawn on it. was irradiated. Furthermore, the areas exposed to ultraviolet rays were dissolved and removed using a developer exclusively used for positive type resists. At this time, the aluminum thin film was also removed at the same time. Next, etching was performed using a solution of cyclohexane/dichloroethane = 1/1 (volume ratio), and the desired pattern was drawn on the 2-
A crystal thin film of methyl-4-nitroaniline could be obtained. Furthermore, this sample was coated with SiO
After depositing 2-methyl to a thickness of 0.7 μm, the entire surface was exposed to ultraviolet rays, and the remaining resist, 8 1 0 2 on the resist, and aluminum of the protective layer were removed using a developer exclusively for positive resists. A buried optical waveguide of -4-nitroaniline could be fabricated.

Example 2 After dissolving 4′-nitropenzylidene-3-acetamin-4-methoxyaniline in dimethylformamide,
The solution is sandwiched between two glass plates, and the solvent is gradually evaporated from the gap between the glass plates to a thickness of approximately 0.5 μm.
4'-Nitropenzylidene-3-acetamino-4-
A thin film single crystal of methoxyaniline was obtained. After peeling off one glass plate, a quinonediazide-based positive resist was applied to the upper surface of the thin film crystal using a spinner. After obtaining a desired resist pattern in the same manner as in Example 1, etching was performed using a reactive ion etching apparatus. Etching conditions are CF4/02 (volume ratio) = 90
/10, chamber vacuum level 0.07 5 forr,
When the interelectrode voltage was 0.63 W/cd and the cooling temperature of one electrode was 25°C, the resist was only slightly etched, and the thin film of 4"-2-2trobenzylidene-3-acetamin-4-methoxyaniline It was possible to form a fine pattern of crystals.Furthermore, after applying a Si02 layer of 065 μm to this sample by sputtering, the entire surface was exposed to ultraviolet rays, and the remaining portion was removed using a developer exclusively used for positive resists. Resist and Si02 on resist
By removing the layer, a buried optical waveguide of 4°-nitropenzylidene-3-acetamin-4-methoxyaniline could be obtained. Next, aluminum was patterned as shown in FIG. 4 to form electrodes, and a branching interference type optical modulator could be manufactured. FIG. 4 is a drawing of the obtained optical waveguide viewed from the surface where the organic crystal is formed.

Example 3 As an organic crystal to be microfabricated, copper phthalocyanine was deposited on a potassium chloride substrate by vacuum evaporation,
Thickness 0. A 3 μm thin film crystal was used. A cyclized rubber-based negative photoresist was coated on this copper capped cyanine crystal thin film, and ultraviolet rays were irradiated onto it through a photomask with a desired pattern drawn thereon. Furthermore, the areas that were not exposed to ultraviolet rays were dissolved and removed using a developer exclusively used for negative photoresists. This material was placed in an etching chamber and reactive ion etching was performed (etching conditions: CF4/02 (volume ratio) = 50/5G
, chamber vacuum level 0.11orr, interelectrode voltage 0. (95 W/car, electrode cooling (25° C.)) As a result, it was possible to form a fine pattern of copper phthalocyanine. Furthermore, after forming a Y2O3 layer of 0.3 μm on this sample by electron beam evaporation, the resist and the Y203 layer on the resist were removed using a negative resist remover to create a copper cap cyanine crystal embedded guide waveguide. did it.

[Effects of the Invention] According to the manufacturing method of the present invention, it is possible to provide a buried waveguide element having a feature that light scattering loss can be reduced. Furthermore, it can be used for various purposes such as easy production of control electrodes.

4. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross-sectional view of an optical waveguide element at a stage where a ridge-type organic crystal guiding waveguide and a resist are formed in the manufacturing method of the present invention.

FIG. 2 shows a cross-sectional view of the guiding waveguide element at a stage in which a layer made of a substance with a low refractive index is provided on the ridge-type organic crystal optical waveguide and the photoresist in the manufacturing method of the present invention.

FIG. 3 shows a cross-sectional view of the embedded organic crystal guided waveguide device of the present invention.

FIG. 4 is a drawing of the organic crystal optical waveguide device obtained in Example 2, viewed from the side having the waveguide.

FIG. 5 shows the branching interference type optical modulator obtained in Example 2.
It is a drawing seen from the surface side having a waveguide.

FIG. 6 is a drawing showing a conventional buried optical waveguide element.

FIG. 7 is a drawing showing a conventional ridge type optical waveguide element.

1 is a substrate, 2 is an organic crystal, 3 is a resist, 4 is a substance having a lower refractive index than the organic crystal, 5 is an electrode, and 6 is a leading waveguide.

Patent applicant: Toray Co., Ltd. 1 figure No. 2 figure Third figure No. ≠ figure Fifth figure

Claims (2)

[Claims] (1) A method for manufacturing a buried organic crystal optical waveguide device, which is characterized by comprising the following steps (a), (b), and (c). B. A resist sensitive to light or electron beams is applied onto the thin organic crystalline film formed on the substrate, the resist is exposed and developed into a desired fine pattern, and then the thin organic crystalline film is etched. process to fabricate a ridge-type organic crystal optical waveguide. B. On the organic crystal optical waveguide and substrate obtained in step A, a layer made of a substance having a lower refractive index than the organic crystal is formed so that its thickness is the same as that of the organic crystal. A process of forming by vapor deposition or sputtering. C. A step of removing the resist on the organic crystal optical waveguide obtained in step B and the layer made of a substance having a lower refractive index than the organic crystal on the resist. (2) The method for manufacturing a buried organic crystal optical waveguide element according to claim (1), wherein the organic crystal is a crystal having optical nonlinearity.