JPH11231159A - Manufacture of optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide manufacturing method which can easily embed an upper clad even when the ratio of the height of a core and the distance between cores is large and manufacture a high-precision optical waveguide. SOLUTION: This manufacturing method for the optical waveguide in which cores and a clad layer surrounding the core are formed on a substrate includes a process for forming the lower clad layer 12 on the substrate 11, a process for forming a core groove 12a in the lower clad layer, a process for embedding a core material 14 in the core groove, a process for removing the core material projecting from the core groove, and a process for forming the upper clad layer 16 over the entire surface of the lower clad and core material. Even when the distance between the cores is smaller than the height of the cores, the core material is embedded in the core groove and neither the core material nor the clad layer needs to be formed between the cores where it is difficult to embed the core material, so the cores can easily be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical waveguide, and more particularly to a method for manufacturing a silica-based optical waveguide.

[0002]

2. Description of the Related Art A conventional method for manufacturing a silica-based waveguide is described in "N.
TT R & D Vol. 43, NO. 11, 1994,
Sections 101 to 108 ". In the following, FIG.
A conventional method for manufacturing a silica-based optical waveguide will be described with reference to FIG.

[0003] First, silicon oxide glass fine particles (having a particle diameter of 0,1) obtained by heating and hydrolyzing the same gaseous raw material as the optical fiber (main component: silicon tetrachloride) in an oxyhydrogen flame using an oxyhydrogen torch 37. (1 μm or less) is sprayed and deposited on the silicon substrate 31. At this time, by changing the composition (GeO dopant concentration) of the silicon oxide glass particles, the SiO ₂ particles 3
2 ′ is deposited on the entire upper surface of the SiO ₂ fine particles 32 ′.
Deposit iO ₂ -GeO ₂ fine particles 33 ′ (FIG. 5A)
See).

Then, the silicon oxide glass fine particle film is heated at a high temperature of 1250 ° C. or more in an electric furnace to form a transparent silicon oxide glass film covering the upper surface of the silicon substrate 31. As described above, by changing the composition of the silicon oxide glass fine particles (GeO dopant concentration), an optical waveguide film having a two-layer structure of the lower clad layer 32 and the core layer 33 is obtained (see FIG. 5B).

Next, after a predetermined pattern is transferred to the core layer 33 by a photomask 38, a reactive ion etching (RIE) method is used.
Unnecessary portions of the core layer 33 are removed by ing) to form a ridge-shaped core 35 having a line width of 4 to 10 μm and a height of 4 to 10 μm (see FIG. 5C). Finally, the SiO ₂ fine particles 36 ′ are coated by a flame deposition method (FHD: Frame Hydrolysis Depo) so as to cover the core 35.
(see FIG. 5D), and furthermore, the upper clad layer 36 is made transparent.
A buried SiO ₂ —GeO ₂ single mode optical waveguide is completed (see FIG. 5E).

[0006]

When manufacturing an optical waveguide used for a Y-branch circuit, a directional coupler, a Mach-Zehnder interferometer, etc., the minimum distance between a core and another core is 4 μm or less. It is processed as follows. However,
When forming the upper cladding layer, as shown in FIG.
When the distance w between the cores is smaller than the core height h, particularly when the ratio of the core height h to the core distance w exceeds 3: 1 (for example, when the core height h is 8 μm and the core height h is 8 μm, In the case where the distance w between the cores is 2 μm or less, for example, there is a problem that it is not easy to bury the space 36a between the cores with the upper cladding 36.

[0007] In addition, since the refractive index of the core is usually required to be relatively higher than the refractive index of the surrounding cladding, the optical waveguide is doped with impurities for the purpose of controlling the refractive index of the core and the cladding. In the above step, after forming the silicon oxide glass fine particles, it is necessary to heat at a high temperature of 1250 ° C. or more to make the material transparent. There is a problem in that it moves and a desired refractive index distribution cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the conventional method of manufacturing an optical waveguide, and an object of the present invention is to provide a case where the ratio between the height of the core and the distance between the cores is large. Can also easily bury the upper cladding,
An object of the present invention is to provide a new and improved optical waveguide manufacturing method capable of manufacturing a highly accurate optical waveguide.

Still another object of the present invention is to provide a new and improved method of manufacturing an optical waveguide which can prevent loss of the optical waveguide due to high-temperature heat treatment and can increase the yield. It is.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing an optical waveguide in which a core and a cladding layer surrounding the core are formed on a substrate. Forming a lower cladding layer thereon, forming a core groove in the lower cladding layer, embedding the core material in the core groove, removing the core material protruding from the core groove, Forming an upper clad layer over the entire upper surfaces of the clad and core materials. The step of removing the core material may be performed by etching as described in claim 2.

According to this manufacturing method, even if the distance between the cores is smaller than the height of the cores, the place where the core material is embedded is the groove for the core, and the core material or the space between the cores which are difficult to embed. Since there is no need to form a cladding layer, a core can be easily formed. Therefore, a highly accurate optical waveguide can be manufactured, and the loss can be reduced. further,
Since the yield can be increased, the price can be reduced.

[0012] More preferably, the step of removing the core material is performed by polishing. According to such a manufacturing method, since the core material protruding from the core groove can be controlled with high precision, it is possible to further reduce the loss of the manufactured optical waveguide.

[0013] In particular, the present invention provides,
The ratio of the minimum distance between the core grooves to the depth of the core grooves is 1: 3.
The minimum distance between the core grooves is 4 μm or less, and the depth of the core grooves is 4 μm or less.
It is suitably applied when manufacturing an optical waveguide having a thickness of up to 12 μm. According to the manufacturing method of the present invention, the distance between the cores is smaller than the height of the cores, so that even an optical waveguide having a shape which has been difficult in the conventional optical waveguide manufacturing method can be easily manufactured. It is possible.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Preferred embodiments of the method for manufacturing an optical waveguide according to the present invention will be described in detail. In this specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

(First Embodiment) In this embodiment, a silicon substrate 11 is used as a substrate.
An example of a method of manufacturing an optical waveguide manufactured by depositing a quartz film to be the lower clad layer 12, the core material 13, and the upper clad layer 16 on the optical waveguide 1 will be described. For the formation of a quartz film, plasma chemical vapor deposition (hereinafter referred to as “plasma CVD (Chemical Vapor Depos)”
ition) ". ) Method. First, a plasma CVD apparatus 100 for forming a quartz film shown in FIG. 2 will be described as an example of an apparatus used for the plasma CVD method.

A plasma CVD apparatus 100 for forming a quartz film
In the processing chamber 110, a lower electrode 120 for mounting an object to be processed, for example, a silicon substrate 130, is accommodated. Temperature control means is provided inside the lower electrode 120, and the silicon substrate 1 on the lower electrode 120 is provided.
30 is configured to be able to be maintained at a predetermined temperature (for example, a maximum of 500 degrees).

Further, an upper electrode 140 having an ejection hole for supplying a processing gas is provided above the processing chamber 110. A mass flow controller MFC for controlling the flow rate of the processing gas and a processing gas source 170 are sequentially connected to the upper electrode 140, and the upper electrode 140 is connected to the upper electrode 140 via the muffs controller MFC.
A predetermined processing gas, for example, O ₂ , C ₂ F ₆ , N ₂ , tetraethoxysilane (hereinafter, referred to as “TEOS”) or triethoxysilane is introduced into the processing chamber 110 through an ejection port provided at 40. (Hereinafter referred to as “TRIES”) can be introduced at a predetermined flow rate. Further, an exhaust pipe 180 is connected below the processing chamber 110, and the exhaust pipe 180 communicates with an exhaust system 190 including a turbo molecular pump and a rotary pump (not shown) via a butterfly valve BB. The inside of the processing chamber 110 is, for example, 1 ×
The pressure can be reduced to 10 ⁻³ Pa.

The lower electrode 120 is supplied with power from a high frequency power supply 150 that outputs a high frequency power of a predetermined frequency, for example, 13.56 MHz, via a matching unit 160 on the way. . With this configuration, a desired film forming process can be performed on the silicon substrate 130 mounted on the lower electrode 120.

In the following, the above-described plasma CVD apparatus 1
A method of manufacturing an optical waveguide using the 00 will be described with reference to FIG.

(1. Substrate Cleaning Step) First, the silicon substrate 11 is cleaned with a predetermined cleaning apparatus at a temperature of about 85 ° C. in which sulfuric acid and hydrogen peroxide are mixed at about 3: 1 at a temperature of about 5 ° C.
After washing for 1 minute, wash with pure water. Next, about 20% was added using a hydrofluoric acid solution diluted to about 1% with pure water.
After washing for 2 seconds, wash with pure water.

(2. Lower Cladding Layer Forming Step) Next, the lower cladding layer 12
Is deposited. The lower cladding layer 12 in the present embodiment not only serves as the lower portion of the core 15 but also serves as a cladding on the side wall portion of the core 15 as will be described later, but is referred to as a “lower cladding layer” for convenience.

Processing chamber 110 of plasma CVD apparatus 100
The cleaned silicon substrate 11 is placed on the lower electrode 120 inside. The silicon substrate 11 is heated until the temperature reaches about 400 ° C. The inside of the processing chamber 110 is evacuated by a rotary pump (not shown) until the pressure becomes about 1 Pa. Next, the pressure is reduced to about 1 × 1 by a turbo molecular pump (not shown).
The inside of the processing chamber 110 is evacuated until the pressure becomes 0 ⁻³ Pa. TRI
ES or TEOS about 12sccm, oxygen about 400
Sccm and C ₂ F ₆ are introduced into the processing chamber 110 from the upper electrode at the respective flow rates of about 10 sccm. TRIES or TEOS is vaporized at a temperature of about 80 ° C. in advance.

[0023] Incidentally, C ₂ F _6, since the clad formation on the non-doped core, is doped for the purpose of about 0.3% less the refractive index of the cladding than the refractive index of the core. Also,
C ₂ F ₆ is also used for cleaning the processing chamber 110 for removing a film deposited in the processing chamber 110 other than on the silicon substrate 11. Oxygen is also used for cleaning fluorine-containing organic substances generated in the processing chamber 110.

The pressure in the processing chamber 110 is maintained at about 30 Pa, and a high frequency of about 13.56 MHz is applied to the upper electrode 140.
And a lower electrode 120 at a power density of about 1.6 W / cm ² . Plasma is generated in the processing chamber 110, and a quartz film serving as the lower cladding layer 12 having a thickness of about 33 μm and a refractive index of about 1.452 is deposited on the silicon substrate 11 in about 4 hours and 36 minutes (FIG. 1B). See). After film formation, application of high frequency power is stopped.

(3. Core Groove Forming Step) Next, using a mask (not shown) on which the pattern of the optical waveguide is formed, the core groove 12a is formed by an exposure method generally used widely.
Is formed on the silicon substrate 11. First, a resist is applied on the silicon substrate 11 by spin coating to a thickness of about 1 μm. next,
After holding the silicon substrate 11 coated with the resist in a thermostat at a temperature of about 90 ° C. for about 10 minutes, the mask and the silicon substrate 11 are set on a reduction projection exposure machine using i-line. Next, the resist on the silicon substrate 11 is irradiated with i-line at a predetermined exposure amount. Next, the resist pattern 13 of the optical waveguide is formed on the silicon substrate 11 by holding the substrate in a thermostat at a temperature of about 80 ° C. for about 10 minutes after the development.
(See (C)).

As shown in FIG. 3, the resist pattern 13 has no resist on the individual core portions, the resist exists on the cladding portions, and the resist also exists between the cores. This is different from the conventional photomask 38 shown in FIG.

Next, the lower cladding layer 12 is processed. Generally used RIE (Reactive I
A silicon substrate 1 on which a resist pattern 13 of an optical waveguide is formed in a processing chamber 110 of an on-etching apparatus.
1 is set. After the inside of the processing chamber 110 is evacuated to a pressure of about 1 Pa by a rotary pump (not shown), the pressure is evacuated to a pressure of about 1 × 10 ⁻³ Pa by a turbo molecular pump (not shown). Next, CHF3 is put into the processing chamber 110 for about 100 hours.
Introduce at a flow rate of sccm. The pressure in the processing chamber 110 is maintained at about 2 Pa, and a high frequency of about 13.56 MHz is applied at a power density of about 1 W / cm ² . The core groove 12a is etched using the resist as a mask. After about 40 minutes, the high-frequency discharge and the introduction of CHF ₃ are stopped, and the processing chamber 110 is evacuated to a pressure of about 1 × 10 ⁻³ Pa using a rotary pump (not shown) and a turbo molecular pump (not shown) in this order. After evacuation, nitrogen is introduced into the processing chamber 110 to make it atmospheric pressure, and then the silicon substrate 11 is taken out. The resist is stripped off by a widely used oxygen plasma asher method followed by washing with a solution of sulfuric acid and hydrogen peroxide mixed at a temperature of about 85 ° C. in a ratio of about 3: 1. Subsequently, the substrate is washed with pure water. By the above process, the height h is about 8μ.
m and a width w of about 8 μm and a minimum groove w between the core grooves 12a of about 1 μm is formed.
(D), see FIG. 4).

(4. Core Material Embedding Step) Next, using a plasma CVD apparatus 100, a quartz film serving as the core material 14 is deposited so as to fill the core groove 12a provided in the lower cladding layer 12. Processing chamber 1 of plasma CVD apparatus 100
A silicon substrate 11 is placed on the lower electrode 10. The silicon substrate 11 is heated until the temperature reaches about 400 ° C. The inside of the processing chamber 110 is evacuated to a pressure of about 1 Pa by a rotary pump (not shown). Subsequently, the gas is exhausted to a pressure of about 1 × 10 ⁻³ Pa by a turbo molecular pump MBP (not shown).

About 12 scc of TRIES or TEOS
m and oxygen are introduced into the processing chamber 110 from the upper electrode 140 at a flow rate of about 400 sccm, respectively. TRIES or TEOS is vaporized at a temperature of about 80 ° C. in advance. The pressure in the processing chamber 110 is maintained at about 30 Pa, and a high frequency of about 13.56 MHz is applied between the upper electrode 140 and the lower electrode 120 at a power density of about 1.6 W / cm ² . Plasma is generated in the processing chamber 110 for about 1 hour 10 hours.
The quartz film serving as the core material 13 having a refractive index of 1.456 is buried in the core groove 12a provided in the lower cladding layer 12 (see FIG. 1E). The high-frequency discharge and introduction of gas are stopped, and a rotary pump (not shown) and a turbo molecular pump (not shown) are used in this order, and the pressure in the processing chamber 110 is about 1 × 1
Evacuate to 0 ^-3 Pa. After evacuation, nitrogen is introduced into the processing chamber 110 to make it atmospheric pressure, and then the silicon substrate 11 is taken out.

(5. Core Material Removal Step) Next, the core material 14 protruding from the core groove 12a of the lower cladding layer 12 is removed by etching. R widely used in general
A silicon substrate 11 in which a core material 14 is embedded in a groove of a lower clad layer 12 is placed in a processing chamber of an IE apparatus. The pressure inside the processing chamber is about 1 Pa by a rotary pump (not shown)
After evacuating to a pressure of about 1 × 10 ⁻³ Pa using a turbo molecular pump (not shown). Next, CHF ₃
Is introduced into the processing chamber at a flow rate of about 100 sccm. The pressure in the processing chamber is maintained at about 2 Pa, and the frequency is about 13.56 M
A high frequency of 1 Hz is applied at a power density of about 1 W / cm ² .
After about 10 minutes, the portion of the core material 14 protruding from the upper surface of the lower clad 12 is etched and removed to form the core 15 (see FIG. 1F). The high-frequency discharge and the introduction of CHF ₃ are stopped, and the processing chamber is evacuated to a pressure of about 1 × 10 ⁻³ Pa using a rotary pump (not shown) and a turbo molecular pump (not shown) in this order. After evacuation, nitrogen is introduced into the processing chamber to atmospheric pressure, and then the silicon substrate 1
Take 1 out.

(6. Upper Cladding Layer Forming Step) Next, a quartz film serving as the upper cladding layer 16 is deposited using the plasma CVD apparatus 100. A silicon substrate 11 having a core 15 formed therein is placed in a processing chamber 110 of a plasma CVD apparatus 100.
Is installed. The silicon substrate 11 is heated until the temperature reaches about 400 ° C. The inside of the processing chamber 110 is evacuated to a pressure of about 1 Pa by a rotary pump (not shown). Then,
A pressure of about 1 × 10 ^-3 Pa by a turbo molecular pump (not shown)
Exhaust until About 12 sc of TRIES or TEOS
cm, oxygen about 400 sccm, C ₂ F ₆ about 10 sccc
m, and is introduced into the processing chamber 110 from the upper electrode at each flow rate. TRIES or TEOS is vaporized at a temperature of about 80 ° C. in advance.

The pressure in the processing chamber 110 is maintained at about 30 Pa, and a high frequency of about 13.56 MHz is applied between the upper and lower electrodes at a power density of about 1.6 W / cm ² . Processing room 1
A plasma is generated in the substrate 10, and a quartz film serving as the upper cladding layer 16 having a thickness of about 20 μm and a refractive index of about 1.452 is deposited on the core in about 3 hours and 28 minutes (see FIG. 1 (G)). . After deposition, stop applying high frequency. Next, TEOS
Alternatively, stop the introduction of TRIES, C ₂ F ₆ and oxygen, and use a rotary pump (not shown) and a turbo molecular pump in order,
The inside of the processing chamber 110 is evacuated to a pressure of about 1 × 10 ⁻³ Pa.
After evacuation, nitrogen is introduced into the processing chamber 110 to make it atmospheric pressure, and then the silicon substrate 11 is taken out.

As described above, according to the first embodiment, even if the height and the width of the cores 15 are 8 μm and the distance between the cores 15 is 1 μm, as shown in FIG. Since the embedding location is the core groove 12a, the ratio between the height h and the width s of the embedding groove is 1: 1. On the other hand, according to the conventional manufacturing method, as shown in FIG.
When the ratio of the distance w between the core and the core is as large as 8: 1, the upper cladding cannot be easily buried. Further, when the distance w between the cores is 1 μm or less, the embedding becomes more difficult according to the conventional method. However, according to the manufacturing method according to the present embodiment, the distance w between the cores w
The height h is 8 μm and the width s is 8 μm.
m, and the ratio is 1: 1 so that the distance w between the cores is 1 μm.
m, the core material 14 can be easily embedded. Therefore, it is possible to easily manufacture an optical waveguide capable of reducing the loss and the cost as compared with the conventional method of manufacturing an optical waveguide in which an upper clad is formed between cores.
Furthermore, it is possible to prevent the loss of the optical waveguide due to the high-temperature heat treatment, and to increase the yield.

(Second Embodiment) A method for manufacturing an optical waveguide according to a second embodiment is described in 5. The core material removing step is an improvement of the optical waveguide manufacturing method according to the first embodiment. Below, 1. 1. substrate cleaning process;
2. lower cladding layer forming step; 3. groove forming step for core;
5. core material embedding step, and Since the upper clad layer forming step is the same as that of the first embodiment, the description thereof will be omitted. The core material removing step will be described.

(5. Core Material Removal Step) As in the first embodiment, the core material 14 protruding from the core groove 12a of the lower cladding layer 12 is removed. The core material 14 is removed by a mechanical polishing device. A chemical mechanical polishing apparatus is an apparatus that polishes a polishing cloth by placing an abrasive containing a component that chemically erodes the material to be polished and bringing the polishing material into contact with the polishing cloth and rotating. , CMP (ChemicalMech)
analytic Polishing).

The silicon substrate 11 in which the core material 14 is embedded in the core groove 12a of the lower clad 12 is placed on the substrate chuck of the above-described generally used chemical mechanical polishing apparatus 100. The surface of the silicon substrate 11 is pressed against an abrasive cloth in which an abrasive flows in a pressurized state. As the silicon substrate 11 rotates on the polishing cloth, the surface of the silicon substrate 11 is polished. The polishing rate is about 0.
At 2 μm / min, the thickness uniformity after polishing is about 1%.
After about 10 minutes, the portion of the core material 14 protruding from the upper surface of the lower clad 12 is polished and removed, thereby removing the core 1.
5 is formed (see FIG. 1F). After polishing, cleaning is performed to remove the abrasive from the surface of the silicon substrate 11. At this time, if a brush is used together, the effect of removing the abrasive is increased. After the cleaning, the silicon substrate 11 is taken out by spin drying or spraying dry nitrogen onto the surface of the silicon substrate 11 to remove moisture on the surface.

As described above, according to the second embodiment,
As in the first embodiment, as shown in FIG. 4, the groove to be embedded has a height h of 8 μm and a width s regardless of the distance w between the cores.
Is 8 μm, and the ratio is 1: 1.
Even when the core material is 1 μm or less,
4 can be embedded. Therefore, it is possible to easily manufacture an optical waveguide capable of reducing the loss and the cost as compared with the conventional method of manufacturing an optical waveguide in which an upper clad is formed between cores. Furthermore, it is possible to prevent the loss of the optical waveguide due to the high-temperature heat treatment, and to increase the yield.

Further, since the core material 14 protruding from the lower clad is removed by chemical polishing, the core material 14 is ± 0.1 μm.
The film thickness can be controlled with the following accuracy, and the upper surface of the core becomes flat. Therefore, it is possible to further reduce the loss of the manufactured optical waveguide.

Although the preferred embodiment of the method for manufacturing an optical waveguide according to the present invention has been described with reference to the accompanying drawings, the present invention is not limited to this example. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those modifications naturally fall within the technical scope of the present invention. It is understood to belong.

For example, in the above embodiment, an example in which a silicon substrate is used as the substrate has been described.
The present invention is not limited to this. The present invention is applicable even when a glass substrate is used as the substrate.

Further, in the above embodiment, an example in which a parallel plate type plasma enhanced chemical vapor deposition apparatus is used for forming the cladding layer has been described, but the present invention is not limited to this. Similarly, the present invention is applicable if an apparatus capable of forming a clad layer is used. Similarly, the RIE device used in the core material removing step is not limited to this.

Further, in the core embedding step in the first embodiment, the deposition is divided into a plurality of times, and between each deposition, reflow at 900 ° C. for 30 minutes in a nitrogen atmosphere or anisotropic etching of the deposited film. May be performed.

Furthermore, in the first embodiment, an example in which etching is performed using only a resist has been described, but the present invention is not limited to such an example. The present invention is applicable to a multilayer resist structure in which a film of amorphous silicon, tungsten silicide, aluminum, chromium, or the like is formed under a resist and the core is etched using the film as a mask.

[0044]

As described above, according to the present invention,
When the height and width of the cores are 8 μm and the distance between the cores is 1 μm, since the place where the quartz film is embedded is the core groove, the ratio of the width to the height of the embedded groove is 1. On the other hand, according to the conventional manufacturing method, the ratio between the distance and the height between the cores in which the quartz film is embedded is as large as 8 and cannot be easily embedded. Also,
When the distance between the cores is 1 μm or less, embedding becomes more difficult according to the conventional method. However, according to the present invention, since the groove to be embedded has a height of 8 μm, a width of 8 μm and a ratio of 1 without depending on the distance between the cores, the distance between the cores of 1 μm or less can be easily achieved. . further,
The loss of the optical waveguide due to the high-temperature heat treatment can be prevented, and the yield can be increased.

Further, according to the third aspect of the present invention,
Since the core material protruding from the lower clad is removed by chemical polishing, the film thickness can be controlled with an accuracy of ± 0.1 μm or less, and the upper surface of the core becomes flat. Therefore, it is possible to realize low-loss and low-cost optical transmission as compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is a process chart of a method for manufacturing an optical waveguide according to the present invention, and FIG. 1 (A) shows a silicon substrate;
1B shows a state in which a lower clad layer is formed, FIG. 1C shows a state in which a resist pattern is formed, and FIG. 1D shows a state in which a core groove is formed. 1 (E) shows a state where the core material is embedded, FIG. 1 (F) shows a state where the core material is removed, and FIG. 1 (G) shows a state where the upper cladding layer is formed. FIG.

FIG. 2 is a block diagram schematically illustrating a plasma enhanced chemical vapor deposition apparatus.

3A and 3B are explanatory views showing a state in which a resist pattern is formed, FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view.

FIG. 4 is an explanatory view showing a state in which a core groove is formed.

FIG. 5 is a process chart of a conventional method for manufacturing an optical waveguide. FIG. 5A shows a state in which a lower clad and a core layer are deposited on a silicon substrate, and FIG. 5C shows a state in which a core is formed, FIG. 5D shows a state in which an upper clad is formed, and FIG. FIG.

FIG. 6 is an explanatory view showing a state in which a resist pattern is formed in a conventional optical waveguide manufacturing process.
6A is a plan view, and FIG. 6B is a cross-sectional view.

FIG. 7 is an explanatory view showing a state in which a core is formed in a conventional optical waveguide manufacturing process.

[Explanation of symbols]

 Reference Signs List 11 silicon substrate 12 lower cladding layer 13 resist pattern 14 core material 15 core 16 upper cladding layer

Claims (5)

[Claims] 1. A method of manufacturing an optical waveguide in which a core and a clad layer surrounding the core are formed on a substrate, comprising: forming a lower clad layer on the substrate; and forming a core groove in the lower clad layer. Forming a core material in the core groove, removing the core material protruding from the core groove, and forming an upper clad layer on the entire upper surface of the lower clad and the core material. A method of manufacturing an optical waveguide. 2. The method according to claim 1, wherein the step of removing the core material is performed by etching. 3. The method according to claim 1, wherein the step of removing the core material is performed by polishing. 4. The method according to claim 1, wherein a ratio of a minimum interval between the core grooves to a depth of the core grooves is 1: 3 or more. Manufacturing method of optical waveguide. 5. The method according to claim 4, wherein a minimum interval between the core grooves is 4 μm or less, and a depth of the core grooves is 4 to 12 μm.