WO2022158001A1

WO2022158001A1 - Optical waveguide and method for producing same

Info

Publication number: WO2022158001A1
Application number: PCT/JP2021/024832
Authority: WO
Inventors: 泰土澤; 達郎開
Original assignee: 日本電信電話株式会社
Priority date: 2021-01-25
Filing date: 2021-06-30
Publication date: 2022-07-28
Also published as: WO2022157958A1; JPWO2022158001A1

Abstract

This method for producing an optical waveguide comprises: a step in which a plasma of an inert gas and deuterium gas is generated; a step in which a silicon target is irradiated with the plasma and sputtering is made to occur; a step in which silicon particles generated by the sputtering are accumulated and an amorphous silicon film containing deuterium is formed; a step in which the amorphous silicon film is machined into an optical waveguide core (13); and a step in which an upper cladding layer (14) is formed so as to cover the optical waveguide core (13).　As a result, this method for producing an optical waveguide makes it possible to provide an optical waveguide using amorphous silicon which exhibits low optical loss and has high stability.

Description

Optical waveguide and its manufacturing method

The present invention relates to an optical waveguide using amorphous silicon and a manufacturing method thereof.

Recent advances in silicon photonics technology have led to the development of waveguide fabrication technology that uses high-refractive-index silicon waveguides to allow light to propagate with low loss even in extremely fine and sharp bends, and is compatible with electronic devices and materials. By integrating optical devices using good silicon waveguides with electronic devices on a silicon substrate, it has become possible to realize compact optoelectronic devices. This optoelectronics convergence technology is gaining importance as a key technology for achieving high speed, miniaturization, low power consumption, and low cost of devices in the field of communication. Furthermore, silicon waveguides are also suitable for optical coupling with light-emitting devices and light-receiving devices made of compound semiconductors with similar refractive indices. Technology development for integration is also progressing.

On the other hand, until now, silicon waveguides have been developed using crystalline silicon on SOI substrates. Although crystalline silicon has the advantage of low optical loss, the use of SOI substrates reduces the degree of freedom in device integration fabrication processes. In addition, the cost of the substrate was high, and there were problems in terms of integration efficiency and cost. It has been shown that a low-loss optical waveguide can be realized by adding hydrogen even to amorphous silicon, which generally has a large optical loss. The possibility of producing an optoelectronic device utilizing the has emerged (see Patent Document 1).

JP 2014-35498 A

However, in hydrogen-containing amorphous silicon, it has become clear that in a high temperature process of 400° C. or higher, Si—H bonds are broken and waveguide loss increases. However, there remains the problem of deterioration in waveguide characteristics and difficulty in application to high-performance optical integrated devices.

The present invention was made to solve this problem, and aims to realize an optical waveguide using amorphous silicon with low optical loss, high heat resistance, and high stability, and a manufacturing method thereof.

In order to solve the above-described problems, the steps of generating a plasma of an inert gas and a deuterium gas, irradiating a silicon target with the plasma to cause sputtering, and removing silicon particles generated by the sputtering are performed. depositing and forming an amorphous silicon film containing deuterium; processing the amorphous silicon film into an optical waveguide core; and forming an upper clad layer so as to cover the optical waveguide core.

Further, the method for manufacturing an optical waveguide according to the present invention includes a first step of irradiating a silicon target with plasma of an inert gas to cause sputtering, depositing silicon particles generated by the sputtering, and forming an amorphous silicon thin film. a third step of irradiating the amorphous silicon thin film with deuterium gas plasma; a step of repeating steps 1 to 3; a step of processing the amorphous silicon thin film having the predetermined thickness into an optical waveguide core; and a step of forming an upper clad layer so as to cover the optical waveguide core. and

Further, an optical waveguide according to the present invention includes, in order, a lower clad layer, an optical waveguide core having amorphous silicon containing deuterium, and an upper clad layer covering the optical waveguide core.

According to the present invention, an optical waveguide using amorphous silicon with low optical loss and high stability and a manufacturing method thereof can be provided.

FIG. 1 is a schematic cross-sectional view showing the configuration of an optical waveguide according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of a film forming apparatus in the optical waveguide manufacturing method according to the first embodiment of the present invention. FIG. 3 is a flowchart of a film forming method in the optical waveguide manufacturing method according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining the method of manufacturing the optical waveguide according to the first embodiment of the present invention. FIG. 5 is a flow chart of a film forming method in the optical waveguide manufacturing method according to the second embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing the structure of an optical waveguide according to a third embodiment of the invention. FIG. 7 is a flow chart of a film forming method in the optical waveguide manufacturing method according to the third embodiment of the present invention.

<First embodiment>
An optical waveguide according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.

<Structure of Optical Waveguide>
As shown in FIG. 1, the optical waveguide 10 according to the present embodiment sequentially covers a silicon (Si) substrate 11, a lower clad (SiO ₂ ) layer 12, an optical waveguide core 13, and an optical waveguide core 13. and a cladding layer 14 .

The optical waveguide core 13 is made of amorphous Si containing deuterium, and has a width of about 300 to 500 nm and a thickness of about 200 to 300 nm, for example.

The clad layer 14 is made of SiO ₂ and has a thickness of about 2 to 3 μm, for example.

<Method for manufacturing an optical waveguide>
An apparatus used for film formation of the material of the optical waveguide 10 according to this embodiment will be described.

FIG. 2 shows a cross-sectional view of an example of an ECR sputtering apparatus used as a film forming apparatus in this embodiment. An amorphous Si thin film, which will be the core material of the optical waveguide, is deposited by the ECR sputtering apparatus 100 .

The ECR sputtering apparatus 100 includes, in order, a chamber 101, a plasma generation chamber 102, a vacuum waveguide 106, and a waveguide 108, which are in communication with each other.

The chamber 101 communicates with an evacuation device (not shown), and the inside thereof is evacuated together with the plasma generation chamber 102 by the evacuation device.

The chamber 101 is provided with a sample table 104 on which a substrate 103 on which a film is to be formed is fixed. The sample stage 104 tilts and rotates at a desired angle. The sample table 104 is rotatable by a rotating mechanism (not shown).

In addition, a ring-shaped silicon target 105 is provided so as to surround the opening region in the chamber 101 where the plasma from the plasma generation chamber 102 is introduced. The silicon target 105 is placed in a container 105 a made of an insulator, and the inner surface is exposed inside the chamber 101 .

Also, the plasma generation chamber 102 communicates with a vacuum waveguide 106 , and the vacuum waveguide 106 is connected to a waveguide 108 via a quartz window 107 . Waveguide 108 communicates with a microwave generator (not shown). The microwave generator, the waveguide 108, the quartz window 107, and the vacuum waveguide 106 constitute microwave supply means.

A magnetic coil 110 is also provided around and above the plasma generation chamber 102 . Note that there is also a configuration in which a mode converter is provided in the middle of the waveguide 108 .

Next, a method for forming an amorphous Si film according to the present embodiment using the ECR sputtering apparatus 100 described above will be described with reference to FIG.

First, a silicon substrate 103 having a thermal oxide film of 3 μm formed thereon is placed on a sample table 104 in a chamber 101 . Here, the silicon substrate 103 corresponds to the silicon substrate 11 in the optical waveguide 10 and the thermal oxide film corresponds to the lower clad layer (SiO ₂ ) 12 .

Next, after the chamber 101 and the plasma generation chamber 102 are evacuated, argon gas, which is an inert gas, is introduced into the plasma generation chamber 102 from the inert gas introduction unit 111 .

Further, deuterium is introduced into the chamber 101 through a gas introduction section 112 installed separately from the inert gas introduction section, and the pressure inside the plasma generation chamber 102 is set to about 10-3 Pa, for example.

In this state, after a magnetic field of 875 G was generated in the plasma generation chamber 102 by the magnetic coil 110, microwaves of 2.45 GHz were introduced into the plasma generation chamber 102 through the waveguide 108 and the quartz window 107, An electron cyclotron resonance (ECR) plasma is generated (step 2_11).

The ECR plasma forms a plasma flow in the direction of the sample stage 104 due to the divergent magnetic field from the magnetic coil 110 .

Here, in the ECR sputtering apparatus 100 according to the present embodiment, the microwave power supplied from the microwave generation unit is branched at the waveguide 108, and the plasma generation is performed in the vacuum waveguide 106 above the plasma generation chamber 102. It is coupled from chamber 102 through quartz window 107 . This configuration can prevent scattering particles from the silicon target 105 from adhering to the quartz window 107, and can greatly improve the running time.

In the state in which the plasma is generated in this manner, a high-frequency voltage is applied to the ring-shaped silicon target 105 provided between the plasma generation chamber 102 and the sample table 104, thereby attracting the plasma to the surface of the silicon target 105 and irradiating it. to cause sputtering.

By this sputtering, particles of the target material (silicon) fly out from the surface of the silicon target 105 and reach the substrate 103 together with the plasma emitted from the plasma generation chamber 102 .

The deuterium gas activated by the plasma also reaches the substrate 103 together with the particles. As a result, amorphous Si containing deuterium is deposited on the substrate 103, and an amorphous Si film is formed on the thermal oxide film of the substrate 103 (step 2_12).

Here, the film thickness to be deposited can be controlled by checking the deposition rate in advance and controlling the sputtering time. For example, the sputtering is stopped when the film thickness of the amorphous Si to be deposited reaches 200 nm (step 2_13). As a result, an amorphous Si film with a thickness of 200 nm is formed on the thermal oxide film with a thickness of 3 μm. After that, the introduction of the gas is stopped, and the substrate is taken out from the chamber after a predetermined time has passed.

Next, a method for manufacturing an optical waveguide using the amorphous Si film described above will be described with reference to FIG.

First, an oxide film (SiO ₂ ) 12 is formed on a silicon substrate 11 (step 1).

Next, an amorphous Si thin film 13_1 is formed on the oxide film (SiO ₂ ) 12 by the film forming method described above (step 2).

Next, a mask pattern 15 of SiO ₂ is formed on the amorphous Si thin film 13_1 by a normal lithographic technique (step 3).

For example, first, a silicon oxide film is formed on an amorphous Si thin film by plasma CVD. Subsequently, a resist mask pattern is formed on the silicon oxide film by lithography.

Next, the silicon oxide film is selectively etched by dry etching using a mixed gas of _SF6 _gas and a gas containing carbon and fluorine such as _C2F6 . Subsequently, the remaining resist pattern is removed by, for example, ashing with ozone. As a result, a mask pattern 15 made of a silicon oxide film having a rectangular cross section is formed.

Next, by dry etching using a gas containing carbon and fluorine such as CF ₄ gas, a mask pattern 15 made of a silicon oxide film is used to hide the amorphous Si thin film 13_1, thereby forming an optical waveguide made of amorphous silicon having a rectangular cross section. A core 13 is formed (step 4).

Finally, an upper clad layer 14 made of silicon oxide is formed by plasma CVD to cover the optical waveguide core 13 (step 5). At this time, the SiO ₂ mask pattern 15 may or may not be removed before forming the upper clad layer 14 . If not removed, the remaining SiO ₂ mask pattern 15 forms the upper cladding layer together with the overlying upper cladding layer 14 .

Here, if hydrogen is contained in the upper clad layer 14, OH groups are formed in the film, causing light loss due to light absorption. Therefore, in the plasma CVD method used to form the upper clad layer 14, it is desirable to use a deuterated (deuterium-containing) gas as a material gas for film formation.

As a result, the upper cladding layer 14 has silicon oxide containing deuterium. Here, the upper cladding layer 14 may be entirely made of silicon oxide (SiO ₂ ) containing deuterium, or may partially contain silicon oxide (SiO ₂ ) containing hydrogen.

Also, if the ECR plasma CVD method is used as the plasma CVD method, a high-quality film can be formed at a low temperature of 200° C. or less, so the film can be formed without damaging the optical waveguide core made of amorphous Si during film formation.

The reason for using amorphous Si containing deuterium for the core is explained below. Since amorphous Si has a large optical loss due to light absorption by dangling bonds, it is difficult to practically use amorphous Si for waveguide cores.

Here, by including hydrogen in amorphous Si and terminating dangling bonds with hydrogen, light absorption can be suppressed and light loss can be reduced. However, when hydrogen-terminated amorphous Si is heated or irradiated with strong light, the hydrogen-terminated hydrogen atoms are removed by external energy, increasing light absorption.

On the other hand, by including deuterium in amorphous Si and terminating dangling bonds with deuterium, light absorption can be suppressed and light loss can be reduced. In this case, since deuterium has a stronger bond with the dangling bonds of amorphous Si than hydrogen, the deuterium-terminated dangling bonds are maintained even when external energy is input. As a result, optical loss does not increase.

Thus, an optical waveguide that does not lose light due to temperature rise in the optical integrated device manufacturing process can be realized by using amorphous Si containing deuterium for the core.

As described above, according to the optical waveguide and the manufacturing method thereof according to the present embodiment, an optical waveguide with high heat resistance, stability, and low loss is realized by using amorphous Si containing deuterium as the optical waveguide core. can. Furthermore, this optical waveguide can be applied to an optical integrated device, and high performance of the optical integrated device can be realized.

In this embodiment, an example in which the optical waveguide core is made of amorphous Si containing deuterium is shown, but the optical waveguide core may partially contain amorphous Si or Si (crystal) that does not contain deuterium. The optical waveguide core may have amorphous Si containing deuterium.

<Second Embodiment>
The configuration of the optical waveguide according to this embodiment is substantially the same as that of the first embodiment, but the manufacturing method is different.

<Method for manufacturing an optical waveguide>
Another method for forming an amorphous Si film in the method for manufacturing an optical waveguide according to this embodiment will be described with reference to FIG.

First, in the ECR sputtering apparatus 100 , a silicon substrate 103 having a thermal oxide film of 3 μm formed thereon is placed on a sample table 104 in a chamber 101 . Here, the silicon substrate 103 corresponds to the silicon substrate 11 in the optical waveguide, and the thermal oxide film corresponds to the lower clad layer (SiO ₂ ) 12 .

At this time, in order to prevent the substrate 103 from being irradiated with plasma, a shutter is installed directly above the sample table 104 and the shutter is closed (a state in which the plasma is blocked).

Next, after the chamber 101 and the plasma generation chamber 102 are evacuated, argon gas, which is an inert gas, is introduced from the inert gas introduction part 111 . For example, argon gas is introduced at a flow rate of 20 sccm, and the pressure inside the plasma generation chamber 102 is set to about 10 ⁻³ Pa.

Next, generate electron cyclotron resonance (ECR) plasma by generating a magnetic field and introducing microwaves (step 2_31).

Next, by applying a high-frequency voltage to a ring-shaped silicon target 105 provided between the plasma generation chamber 102 and the sample table 104, plasma is attracted to the surface of the silicon target 105 to cause sputtering. This state is maintained for a predetermined time until the plasma stabilizes.

Next, the shutter is opened to irradiate the substrate 103 with plasma to start forming an amorphous Si film on the substrate 103 (step 2_32). For example, this state is maintained for 25 seconds to form an amorphous Si thin film with a thickness of about 2 nm. Here, the film thickness of the amorphous Si thin film is desirably 1 nm or more and 3 nm or less.

Next, stop the introduction of microwaves, stop plasma generation, and close the shutter.

Next, after evacuating the argon gas, deuterium is introduced from the gas introduction part 112, the inside of the plasma generation chamber 102 is set to a predetermined pressure, and plasma is generated (step 2_33). For example, deuterium is introduced at a flow rate of 20 sccm, and plasma is generated at a pressure of about 10 ^-3 Pa.

Next, after the plasma state is stabilized, the shutter is opened to irradiate the amorphous Si thin film on the substrate surface with deuterium plasma for a predetermined time, for example, about 1 minute (step 2_34). As a result, the amorphous Si thin film becomes a film containing deuterium. Here, the deuterium plasma irradiation time is preferably about 1 minute or more and about 10 minutes or less.

Here, deuterium may be contained in the entire amorphous Si thin film or may be contained in part of the amorphous Si thin film by irradiation with deuterium plasma. It may be contained to such an extent that the effect of deuterium such as improvement of heat resistance is exhibited.

Next, after closing the shutter and stopping plasma generation, deuterium gas is exhausted.

Next, it is determined whether the amorphous Si film containing deuterium formed on the substrate has a predetermined thickness, for example, 200 nm thickness (step 2_35). Repeat 2_34.

Finally, when the film thickness of the amorphous Si reaches a predetermined thickness, the microwave and magnetic field are stopped, plasma generation is stopped, and film formation is stopped (steps 2_35 and 2_36). After that, the introduction of the gas is stopped, the gas in the gas generation chamber is exhausted, and the substrate is taken out from the chamber after a predetermined time has passed.

The optical waveguide according to the present embodiment is manufactured in the same steps as in the first embodiment using the amorphous Si film formed in the steps from step 2_31 to step 2_36 described above.

In this way, after the amorphous Si thin film is formed on the lower clad layer, the deuterium plasma is irradiated so that the amorphous Si thin film contains the deuterium plasma. Amorphous Si containing can be formed.

As described above, according to the optical waveguide and the method for manufacturing the same according to the present embodiment, the stability of the optical waveguide core is made of amorphous Si containing deuterium, which has excellent adhesion to the lower clad layer and the substrate, and has low loss. It is possible to realize an optical waveguide with a high Furthermore, this optical waveguide can be applied to an optical integrated device, and high performance of the optical integrated device can be realized.

<Third Embodiment>
An optical waveguide according to a third embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG. The optical waveguide 20 and its manufacturing method according to the present embodiment are substantially the same as those of the first embodiment, but differ in the configuration of the optical waveguide core.

<Structure of Optical Waveguide>
As shown in FIG. 6, the optical waveguide 20 according to the present embodiment includes, in order, a Si (silicon) substrate 21, a _SiO2 layer (lower clad layer) 22, an optical waveguide core 23, and an optical waveguide core 23. and an overlying upper cladding layer 24 . The optical waveguide core 23 is made of amorphous Si, and has a width of approximately 300 to 500 nm and a thickness of approximately 200 to 300 nm, for example. The cladding layer 24 is made of SiO ₂ and has a thickness of, for example, about 2 to 3 μm.

The optical waveguide core 23 sequentially comprises a lower core 231 in contact with the SiO ₂ layer 22 and an upper core 232 . The lower core 231 does not contain deuterium D, and the upper core 232 contains deuterium D. Thus, by having the lower core 231 that does not contain deuterium D between the lower clad layer 22 and the upper core 232, the adhesion of the optical waveguide core 23 to the lower clad layer 22 is improved. Amorphous Si containing high deuterium can be formed on the lower cladding layer 22 .

Here, the upper core 232 is made thicker than the lower core 231 so that light is guided through the upper core 232 mainly containing deuterium. The thicknesses of the lower core 231 and the upper core 232 can be controlled by adjusting the time to start introducing deuterium and the sputtering time in the manufacturing method described later.

<Method for manufacturing an optical waveguide>
A method of forming an amorphous Si film according to this embodiment will be described with reference to FIG.

In the ECR sputtering apparatus 100, a silicon substrate 103 having a thermal oxide film of 3 μm formed thereon is placed on a sample table 104 in a chamber 101. As shown in FIG. Here, the silicon substrate 103 corresponds to the silicon substrate 21 in the optical waveguide 20 and the thermal oxide film corresponds to the lower clad layer (SiO ₂ ) 22 .

Next, after evacuating the chamber 101 and the plasma generation chamber 102, argon gas, which is an inert gas, is introduced from the inert gas introduction unit 111 at a flow rate of 20 sccm, and the pressure in the plasma generation chamber 102 is set to about 10 to 3 Pa. do.

Next, generate electron cyclotron resonance (ECR) plasma by generating a magnetic field and introducing microwaves (step 2_21).

Next, by applying a high-frequency voltage to a ring-shaped silicon target 105 provided between the plasma generation chamber 102 and the sample table 104, plasma is attracted to the surface of the silicon target 105 to cause sputtering. This state is maintained for a predetermined time, eg, 2 minutes, until the plasma stabilizes.

Next, the shutter is opened to irradiate the substrate 103 with plasma, the film formation of amorphous Si on the substrate 103 is started, and the film formation of amorphous Si on the substrate 103 is started for a predetermined time, for example, about two minutes equivalent) is maintained (step 2_221). As a result, an amorphous Si film containing no deuterium (another amorphous Si film) is formed.

Next, deuterium is introduced from the gas introduction part 112 at a flow rate of 5 sccm and maintained for a predetermined time, for example, about 15 minutes (step 2_222). Then close the shutter. As a result, amorphous Si containing deuterium is continuously formed on the 10 nm-thick amorphous Si to a total thickness of 200 nm.

Finally, the microwave and magnetic field are stopped to stop plasma generation (step 2_23). After that, the introduction of the gas is stopped, and the substrate is taken out from the chamber after a predetermined time has passed.

In this embodiment, an example of introducing deuterium after introducing argon gas was shown, but if argon and deuterium are introduced at the same time, the thickness of the lower core 231 becomes zero.

The optical waveguide according to the present embodiment is manufactured in the same steps as in the first embodiment using the amorphous Si film formed in the steps 2_21 to 2_23 described above.

In this embodiment, an example in which the upper core of the optical waveguide core is made of amorphous Si containing deuterium is shown, but the upper core may partially contain amorphous Si or Si (crystal) that does not contain deuterium. The upper core may have amorphous Si containing deuterium.

In this embodiment, an example in which the lower core of the optical waveguide core is made of amorphous Si that does not contain deuterium is shown, but the lower core may also contain amorphous Si or Si (crystal) that partially contains deuterium. The lower core may have amorphous Si that does not contain deuterium, and the region in contact with the lower clad is desirably amorphous Si that does not contain deuterium.

In this embodiment, deuterium gas is introduced into the state of sputtering by plasma of argon gas, and an example of continuously forming an amorphous Si film containing deuterium from an amorphous Si film containing no deuterium is shown. However, it is not limited to this. After stopping the deposition of the amorphous Si film containing no deuterium after sputtering with argon plasma, the amorphous Si film containing deuterium may be deposited with plasma of argon gas and deuterium gas.

In this embodiment, an example in which the upper core is formed by the method of forming the amorphous Si film in the first embodiment is shown, but the present invention is not limited to this. The upper core may be formed by the method of forming an amorphous Si film in the second embodiment.

Although silicon oxide (SiO ₂ ) is used for the upper clad layer and the lower clad layer in the embodiment of the present invention, SiN _x (silicon nitride) or SiN _x O _y may be used. Any dielectric material may be used as long as it has a dielectric constant lower than that of amorphous Si, which is the optical waveguide core, and can confine guided light in the optical waveguide core.

Although argon gas is used as an inert gas in the embodiment of the present invention, a rare gas such as xenon or krypton may be used.

Although an example using a silicon substrate has been shown in the embodiment of the present invention, the present invention is not limited to this. Other materials may be used for the substrate. A glass substrate such as quartz may be used. In this case, since the substrate becomes the lower clad layer, it is not necessary to form the lower clad layer made of SiO2 or the like on the substrate.

In the embodiment of the present invention, an example in which a Si substrate having an oxide film on its surface as a lower clad layer is installed in a film forming apparatus has been shown, but the present invention is not limited to this, and a substrate (for example, a Si substrate) is installed in a film forming apparatus. Then, a lower clad layer may be formed on the substrate by a film forming apparatus.

In the embodiment of the present invention, the shutter is used in the film forming apparatus in the second and third embodiments, but of course the shutter may be used in the film forming apparatus in the first embodiment.

In the embodiment of the present invention, an example of the structure, dimensions, materials, etc. of each component is shown in the structure of the optical waveguide, the manufacturing method, etc., but the present invention is not limited to this. Any material may be used as long as it exhibits the function of the optical waveguide and produces an effect.

The present invention can be applied to silicon photonics devices and can be applied to devices for optical communication systems.

10 Optical waveguide 11 Silicon substrate 12 Lower clad layer 13 Optical waveguide core 14 Upper clad layer

Claims

generating a plasma of inert gas and deuterium gas;
irradiating a silicon target with the plasma to cause sputtering;
depositing the silicon particles generated by the sputtering to form an amorphous silicon film containing deuterium;
processing the amorphous silicon film into an optical waveguide core;
and forming an upper clad layer so as to cover the optical waveguide core.
A first step of irradiating a silicon target with plasma of an inert gas to cause sputtering;
a second step of depositing the silicon particles generated by the sputtering to form an amorphous silicon thin film;
a third step of irradiating the amorphous silicon thin film with deuterium gas plasma;
repeating the first step to the third step until the total thickness of the amorphous silicon thin film reaches a predetermined thickness;
a step of processing the amorphous silicon thin film having the predetermined thickness into an optical waveguide core;
and forming an upper clad layer so as to cover the optical waveguide core.
Before the optical waveguide manufacturing method according to claim 1 or claim 2,
A step of irradiating a silicon target with plasma of an inert gas to cause sputtering;
and depositing the silicon particles generated by the sputtering on the lower clad layer to form another amorphous silicon film.
The method for manufacturing an optical waveguide according to any one of claims 1 to 3, wherein the upper clad layer is formed by a CVD method using ECR plasma.
The method for manufacturing an optical waveguide according to any one of claims 1 to 4, wherein the upper clad layer is silicon oxide formed using a gas containing deuterium.
in turn a lower cladding layer;
an optical waveguide core having amorphous silicon containing deuterium;
and an upper clad layer covering the optical waveguide core.
a top layer in which the optical waveguide core comprises amorphous silicon containing deuterium;
consisting of a lower layer having amorphous silicon that does not contain deuterium;
7. The optical waveguide according to claim 6, wherein the optical waveguide is in contact with the lower clad layer through the lower layer.
The optical waveguide according to claim 6 or 7, wherein the upper clad layer comprises silicon oxide containing deuterium.