JP2001021746A - Manufacture of optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing an optical waveguide having a glass layer capable of obtaining uniform distribution of concentration of dopant of P and B by adopting a flame accumulation method by bringing a surface temperature of a substrate to a specific value, a flow rate of hydrogen supplied to an oxyhydrogen flame burner to a specific value, and a relative travel speed of the burner and the substrate to a specific value. SOLUTION: A surface temperature of a substrate 1 is properly adjusted within a scope of 500 to 800 deg.C by heating it by a heater arranged in a lower part of a table 10. Glass minute particles are sprayed toward a Si substrate 1 which is one of the substrates together with oxyhydrogen flame from an oxyhydrogen flame burner 11. An amount of hydrogen supplied to the oxyhydrogen flame burner 11 at this time is properly adjusted within a scope of 2 to 8 liters/min. The oxyhydrogen flame burner 11 reciprocates from an outer periphery of the table 10 toward the direction of center. A travel speed of the oxyhydrogen flame burner 11 at this time is adjusted in a scope of 50 to 300 mm/sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical waveguide from a porous glass layer formed by a flame deposition method.

[0002]

2. Description of the Related Art An optical waveguide is used as a component of an optical circuit such as a beam splitter for splitting light into a large number of lights and an optical switch for switching a signal to a desired optical path. Further, a structure in which an optical waveguide and an electric integrated circuit coexist on a single substrate has been developed. For the former optical waveguide, quartz is used as a substrate, and for the latter optical waveguide, the substrate is Si, and an under clad, a core, and an over clad are formed on the substrate.

[0003] In the manufacturing process of an optical waveguide using Si as a substrate, first, a glass layer serving as an under cladding is formed on a substrate, and a core layer is formed thereon. After processing into a waveguide pattern, a glass layer serving as an over cladding is formed. Flame deposition, electron beam evaporation, sputtering, plasma C
The VD method and the like are known. Generally, a flame deposition method is adopted as a method suitable for producing a glass layer having a thickness of several tens of μm.

[0004] The flame deposition method uses an apparatus as shown in FIG.
Oxy-hydrogen flame burner 1 for halides such as Si, B and P
When supplied to 1, SiO2 is hydrolyzed by oxyhydrogen flame₂
And B ₂O₃, P₂O₅Generates oxide glass particles such as
And place it on the surface of the substrate 1 placed on the table 10.
Deposit porous glass particles. Oxyhydrogen flame burner
11 is from the outer periphery of the table 10 toward the center (arrow
Reciprocating movement causes repeated deposition of glass particles.
Then, a porous glass layer is formed. This is an electric furnace
Transparent glass when sintered at a temperature of 1200 to 1400 ° C
A layer is created.

[0005] However, in the glass layer formed by the flame deposition method, the concentrations of the dopants B ₂ O ₃ and P ₂ O _{5 in} the thickness direction are not always uniform. In particular, in the case of a relatively thick glass layer having a thickness of 20 μm or more, the unevenness of the concentration is remarkable.

In order to eliminate such non-uniformity of the dopant concentration, for example, Japanese Patent Application Laid-Open No.
It discloses that a glass layer having a small P concentration distribution in the depth direction of the layer can be obtained by reducing the thickness of a glass layer formed at a time to a certain value or less and repeating deposition and vitrification. However, in order to obtain a glass layer having a thickness necessary for the undercladding or overcladding, many operations of deposition and vitrification must be repeated, which is inefficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and a uniform concentration distribution of P and B dopants can be obtained by employing a flame deposition method. An object of the present invention is to provide a method for efficiently manufacturing an optical waveguide having a glass layer.

[0008]

The inventors have studied in detail the tendency of the concentration distribution of dopant in the deposited porous glass layer under various conditions of the flame deposition method. As a result, they have found that if the temperature change on the surface on which the porous glass layer is deposited is large, the concentration distribution in the thickness direction becomes non-uniform, and if it is small, the concentration distribution becomes uniform. If the flow rate of supplying H ₂ , which is a combustion raw material of the oxyhydrogen flame, to the oxyhydrogen flame burner is reduced, the concentration distribution in the thickness direction of the glass layer becomes uniform, but at the same time, the deposition rate is also affected, and It was found that the variation in the thickness of the obtained glass layer and the surface roughness were also affected. Therefore, while keeping the temperature of the substrate high, the flow rate of the supplied H ₂ is reduced to suppress the temperature rise of the substrate due to the oxyhydrogen flame, and the relative movement speed of the oxyhydrogen flame burner to the substrate is increased to increase the oxyhydrogen flame. It has been found that it is necessary to prevent the temperature of the substrate from rising.

Based on this finding, a method for manufacturing an optical waveguide according to the present invention for achieving the above object is shown in FIG. 1 corresponding to an embodiment, in which a substrate 1 and an oxyhydrogen flame burner 1 are provided.
1 are relatively moved, supply the glass material of the main component and the dopant to the oxyhydrogen flame burner 11, and deposit the oxide glass fine particles synthesized by the flame hydrolysis reaction on the surface of the substrate 1. In the method for manufacturing an optical waveguide in which a porous glass layer is formed and a transparent glass layer is obtained by heating and melting the porous glass layer, the surface temperature of the substrate 1 is supplied to the oxyhydrogen flame burner 11 at 500 to 800 ° C. The flow rate of hydrogen is set to 2 to 8 liters / min, and the relative moving speed between the burner 11 and the substrate 1 is set to 50 to 300 mm / sec.

This method of manufacturing an optical waveguide is effective for manufacturing an optical waveguide having a transparent glass layer having a thickness of 20 μm or more.

The component element of the dopant of the glass layer is B
And / or P is effective for manufacturing an optical waveguide.

In this method of manufacturing an optical waveguide, the surface temperature of the substrate, the flow rate of hydrogen, and the relative movement speed between the burner and the substrate are set as described above, so that the temperature of the surface on which the porous glass layer is deposited is reduced during the deposition period. , The concentration of the dopant contained in the glass layer constituting the obtained optical waveguide has a uniform distribution in the thickness direction. Therefore, in the optical waveguide manufactured by the manufacturing method to which the present invention is applied, the refractive index of each layer becomes an expected value, and the propagation characteristics of the optical waveguide can be obtained as designed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail. As shown in FIG. 2, the target optical waveguide obtained by the manufacturing method of the present invention comprises an under clad 2 (20 μm thick), a core 3 (20 μm thick), and an over clad 4 (thickness) on a Si substrate 1. 30μm)
Is formed. Such an optical waveguide is manufactured as follows using a flame deposition method.

First, a glass layer is formed on a Si substrate 1. As shown in FIG. 1, a plurality of Si substrates 1 are mounted on a circular table 10. Heated by a heater arranged at the lower part of the table 10, the surface temperature of the substrate 1 is 500 to
Adjust appropriately within the range of 800 ° C. Glass particles are sprayed together with the oxyhydrogen flame from the oxyhydrogen flame burner 11 toward one of the Si substrates 1. The oxyhydrogen flame burner 11 has H ₂ and O ₂ , which are the raw materials for burning the oxyhydrogen flame,
SiCl ₄ which is a raw material of glass particles, and if necessary
BBr ₃ is supplied by being mixed with O ₂ which is a carrier gas. H ₂ supplied to the oxyhydrogen flame burner 11 at this time
Is appropriately adjusted within the range of 2 to 8 liter / min. While the table 10 rotates slowly, the oxyhydrogen flame burner 11 reciprocates from the outer periphery of the table 10 toward the center (see the arrow) over a width such that the flame sufficiently sweeps the Si substrate 1. The oxyhydrogen flame burner 11 at this time
Is appropriately adjusted within the range of 50 to 300 mm / sec. The exhaust pipe 12 also reciprocates in conjunction with the burner 11.

Supply to the oxyhydrogen flame burner 11 as described above
Glass material SiCl₄, BBr₃Flame with oxyhydrogen flame from
SiO of glass particles by hydrolysis reaction₂, B₂O₃Go
And deposited on the Si substrate 1 to form a porous glass particle layer.
Is formed. On the other hand, the table 10 rotates slowly
Then, glass particles are sequentially deposited on the plurality of Si substrates 1,
A porous glass particle layer is formed. These are 1200
~ 1400 ° C, He and O ₂In an electric furnace with a mixed atmosphere of
When tied, it becomes a transparent glass layer (under clad 2)
You.

Next, a core 3 is formed on the under clad 2. The plurality of Si substrates 1 on which the under cladding 2 is formed as described above are returned on the circular table 10. The surface temperature of the substrate 1 is adjusted to be the same as the previous setting.
The oxyhydrogen flame burner 11 is supplied with a combustion raw material, glass fine particle raw material SiCl ₄ and, if necessary, POCl ₃ together with a carrier gas O ₂ . Then, the fine glass particles SiO ₂ and P ₂ O ₅ are sprayed and deposited on the under clad 2 by the flame hydrolysis reaction. At this time, the flow rate of H ₂ and the moving speed of the oxyhydrogen flame burner 11 are appropriately adjusted within the above ranges. The table 10 is rotated, and the glass fine particles are deposited on the under clad 2 formed on the plurality of Si substrates 1 to form a porous glass fine particle layer. When these are sintered, a glass layer to be a transparent core 3 is obtained. The core 3 is formed from the glass layer by a conventional lithography.

Further, an over cladding 4 is formed so as to cover the core 3 on the under cladding 2. This procedure is the same as the procedure for forming the undercladding 2, and the same raw material to be supplied to the oxyhydrogen flame burner 11 and the raw material for glass particles are the same, so that the same glass layer is formed. The surface temperature of the substrate 1, the flow rate of H _2, the moving speed of the oxyhydrogen flame burner 11 is adjusted to the same as that of the under-cladding 2. Thus, the Si substrate 1 shown in FIG. 2 is manufactured.

According to the preferred embodiment, Si
An embodiment in which a glass layer is formed on a substrate will be described below.

(Embodiment 1) A circular table 1 having a diameter of 80 cm.
On the outer periphery of No. 0, nine Si substrates having a diameter of 10 cm and a thickness of 1 mm were mounted. The distance from the substrate 1 to the crater of the burner 11 is 2
0 cm, the angle of inclination of the burner with respect to the normal direction of the substrate 1 was 70 °, and the distance between the burner and the exhaust pipe was 6.6 mm.
8 liters / mi of H ₂ as a raw material for combustion in the burner 11
n, O ₂ at 6 liter / min, seal Ar at 1 liter / min, glass material as SiCl ₄ at 43 cc / min, Bbr ₃
20 cc / min, POCl ₃ at 20 cc / min and carrier gas O
Supplied with ₂ . The temperature of the substrate 1 was heated to about 500 ° C. by a heater provided below the table 10.
The burner 11 was reciprocated at a stroke width of 16 cm at 10 mm / min while rotating the table 10 on which the substrate 1 was mounted at 2 rpm. During the reciprocation, the distance between the substrate and the crater, the inclination angle of the burner was 70 °, and the distance between the burner and the exhaust pipe was kept constant. Ignition burner 11, SiO ₂ , B
Glass particles of ₂ O ₃ and P ₂ O ₅ were deposited for about 90 minutes. The Si substrate 1 on which the porous glass particle layer is formed is placed in an electric furnace at 1350 ° C. for 2 hours in which He is flowing at 2.5 L / min and O ₂ is flowing at 0.3 L / min. The sintering process was performed while holding. The thickness of the layer vitrified by this treatment was about 20 μm.

The Si substrate 1 on which the glass layer 2 is formed is cut into 1 cm × 1 cm and polished obliquely at an angle of about 1 ° as shown in FIG. It was measured with an electron beam microanalyzer (EPMA). As a result, as shown in FIG. 4, the minimum density with respect to the maximum density was 80%. The other dopant, B, has a low EPMA measurement sensitivity, and is therefore subject to scanning Auger electron spectroscopy (AES).
py). As a result, as shown in FIG. 5, the concentration distribution of B was uniform.

(Embodiment 2) H ₂ to be supplied to the burner 11
Was set to 6 liter / min, and the glass layer having a thickness of about 20 μm was obtained under the same conditions as in Example 1 except that the deposition time of the glass particles was set to 120 min. The concentration distribution of P in the thickness direction of the glass layer was measured by EPMA in the same procedure as in Example 1. As a result, as shown in FIG.
The concentration distribution of P was uniform.

(Comparative Example) Example 1 was repeated except that the temperature of the substrate 1 was heated to about 300 ° C., H ₂ supplied to the burner 11 was set to 4 liter / min, and the deposition time of the glass particles was set to 80 min. Under the same conditions, a glass layer having a thickness of about 20 μm was obtained. The concentration distribution of P in the thickness direction of the glass layer was measured in the same procedure as in Example 1. As a result, as shown in FIG. 7, the minimum value of P in the thickness direction of the glass layer is about 50% of the maximum value. Similarly, the concentration distribution of B was measured by AES in the same manner as in Example 1. As a result, as shown in FIG. 8, the minimum value of the concentration of B in the thickness direction of the glass layer is about 50% or less of the maximum value.

In the optical waveguide, an under clad,
In each layer of the core and the over cladding, it was examined how much the concentration distribution of the dopant in the thickness direction should be uniform. Therefore, the glass layer having a thickness of 20 μm formed on the Si substrate in Example 1 was thinned by polishing, and it was examined whether or not the refractive index was uniform. As a result, when the ratio of the minimum concentration to the maximum concentration of the dopant shown in FIG. 4 was 80% or more, the dependency of the refractive index on the layer thickness was not observed.

[0024]

As described in detail above, the method for manufacturing an optical waveguide to which the present invention is applied employs the flame deposition method, and the temperature of the surface on which the porous glass layer is deposited becomes substantially constant throughout the deposition period. Therefore, in the glass layer forming the obtained optical waveguide, the concentration of the contained dopant has a uniform distribution in the thickness direction. Therefore, in the optical waveguide manufactured by the method of the present invention, the refractive index of each layer becomes an expected value, and the propagation characteristics of the optical waveguide can be obtained as designed.

[Brief description of the drawings]

FIG. 1 is a view showing a process in the course of a method of manufacturing an optical waveguide to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a structure of an optical waveguide manufactured by a method to which the present invention is applied.

FIG. 3 is a diagram illustrating a sample of performance measurement.

FIG. 4 is a view showing an EPMA distribution of a dopant in a glass layer manufactured by a method to which the present invention is applied.

FIG. 5 is a diagram showing an AES concentration of a dopant in a glass layer manufactured by a method to which the present invention is applied.

FIG. 6 is a view showing an EPMA distribution of a dopant in a glass layer manufactured by a method to which the present invention is applied.

FIG. 7 is a view showing an EPMA distribution of a dopant in a glass layer manufactured by a method excluding the present invention.

FIG. 8 is a graph showing the AES concentration of a dopant in a glass layer manufactured by a method excluding the present invention.

[Explanation of symbols]

1 is a substrate, 2 is an under clad, 3 is a core, 4 is an over clad, 10 is a table, 11 is an oxyhydrogen flame burner, and 12 is an exhaust pipe.

Continuation of the front page (72) Inventor Shinji Makikawa 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Research Laboratory F-term (reference) 2H047 PA05 PA14 PA24 QA04 TA42 TA44 4G014 AH12 AH15 AH19 AH21 AH23

Claims (3)

[Claims] 1. An oxide-hydrogen flame burner in which a substrate and an oxyhydrogen flame burner are relatively moved, and a glass material of a main component and a dopant is supplied to the oxyhydrogen flame burner, and oxide glass fine particles synthesized by a flame hydrolysis reaction are provided. Is deposited on the surface of the substrate to form a porous glass layer, and the porous glass layer is heated and melted to obtain a transparent glass layer.
℃, the flow rate of hydrogen supplied to the oxyhydrogen flame burner is 2 to
8 liter / min, relative movement speed between burner and substrate 5
A method for forming an optical waveguide, which is performed at 0 to 300 mm / sec. 2. The transparent glass layer has a thickness of 20 μm.
2. The method for forming an optical waveguide according to claim 1, wherein: 3. The method according to claim 1, wherein the component element of the dopant is B and / or P.