JP2001290040A - Method for manufacturing optical waveguide parts and optical waveguide parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing optical waveguide parts by which a part between adjacent cores is embedded without increasing a polarization dependent loss caused by a thermal stress and without generating voids when a clad layer is formed on a substrate and to provide an optical waveguide parts. SOLUTION: In the method for manufacturing the optical waveguide parts and the optical waveguide parts 1 wherein the optical waveguide parts are manufactured by forming cores 4 having a desired shape on the substrate 2 and forming the clad layer 3 coating the cores, the optical waveguide part 1 is manufactured by repeating a process in which overhanging parts Poh of the clad layer 3 formed in the upper part of the cores 4 are removed by etching after the clad layer 3 consisting of silicon oxide coating the cores 4 is formed in a prescribed thickness by a plasma CVD method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical waveguide component and an optical waveguide component.

[0002]

2. Description of the Related Art In an optical waveguide component used in optical communication, a core and a cladding layer are made of a silica-based material, and the refractive index of the core is set to be slightly larger than the refractive index of the cladding layer. The light is reflected at the interface with the substrate and propagated while being confined in the core. A conventional quartz optical waveguide component has a lower clad layer, a core and an upper clad layer covering the core formed on a substrate made of silicon (Si).
When the substrate is quartz, it has a two-layer structure in which a core and a cladding layer covering the core are formed on the substrate.

[0003]

The core and the cladding layers including the upper cladding layer and the lower cladding layer are formed by a flame deposition method, a CVD (chemical vapor deposition) method.
It is formed by a method or a PVD (physical vapor deposition) method. At this time, the cladding layer needs to be formed so as to bury the space between adjacent cores.
It is formed by a flame deposition method or a CVD method having a good embedding property.

However, when the cladding layer is formed by using these methods, the following problems occur. First,
In the flame deposition method, after depositing quartz fine particles on a substrate,
The fine particles are subjected to a heat treatment at 1000 ° C. or more to be melted, and a transparent silicon dioxide film is formed to form an optical waveguide. Therefore, it is relatively easy to embed a plurality of adjacent cores with a cladding layer. However, cracks easily occur in the silicon dioxide film due to thermal stress when the quartz fine particles are melted, and residual stress occurs in the silicon dioxide film due to a difference in thermal expansion coefficient between the substrate and the silicon dioxide film.
There is a problem that the polarization dependence is increased.

[0005] Second, the CVD method can form a transparent cladding layer made of a glass layer directly on a substrate at a low temperature. Therefore, the CVD method does not require heat treatment, and can prevent deterioration of optical characteristics due to thermal stress, which is a problem in the flame deposition method. However, in the CVD method, the formation speed of the cladding layer is different between the core side surface, the upper surface, and the core.
In particular, the formation speed of the clad layer in the upper corner of the core is increased, and the clad layer in the upper part of the core has an overhang shape. As a result, the cladding layer formed by the CVD method has a problem in that voids are generated between adjacent cores as a result of being formed in a state where the space between adjacent cores is not sufficiently buried.

As a countermeasure against such voids, voids are usually removed by forming a cladding layer by adding a dopant and then reflowing at a high temperature. However, also in this case, there arises a problem that birefringence due to thermal stress occurs and polarization-dependent loss increases. The present invention has been made in view of the above points, and does not cause an increase in polarization-dependent loss due to thermal stress when forming a cladding layer on a substrate and between adjacent cores without generating voids. It is an object of the present invention to provide an optical waveguide component manufacturing method and an optical waveguide component that can embed an optical waveguide.

[0007]

In order to achieve the above object, in a method for manufacturing an optical waveguide component according to the present invention, a core having a desired shape is formed on a substrate, and a cladding layer covering the core is formed. In the method of manufacturing an optical waveguide component as a component, a cladding layer made of silicon oxide covering the core is formed to a predetermined thickness by a plasma CVD method, and then an overhang portion of the cladding layer formed on the core is etched. The configuration is such that the step of removing is repeated.

In order to achieve the above object, the optical waveguide component of the present invention is configured to be manufactured by the above manufacturing method.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an optical waveguide component according to the present invention and an optical waveguide component manufactured by the method will be described below in detail with reference to FIGS. As shown in FIG. 1, an optical waveguide component 1 includes a lower clad layer 3a and an upper clad layer 3 on a silicon substrate 2.
b is formed, and the lower cladding layer 3 is formed.
a formed in a desired shape on the upper clad layer 3
b.

Optical waveguide component 1 configured as described above
Is manufactured by the method described below. First, P2O5, B2 was deposited on a silicon substrate 2 by flame deposition.
Silicon dioxide (SiO2) doped with dopants such as O3
Is deposited to a desired thickness (= 20 μm) and then sintered to form a lower cladding layer 3a (see FIG. 2A).

Next, GeO 2,
After depositing silicon dioxide (SiO2) to which a dopant such as P2O5 or B2O3 is added by a flame deposition method, this is sintered and has a slightly higher refractive index than the lower cladding layer 3a.
A core layer 5 having a thickness of about 7 μm is formed (see FIG. 2B). At this time, when quartz is used as the material of the substrate 2, the substrate 2 does not need the lower cladding layer 3a,
Is formed directly on the substrate 2.

As means for forming the lower cladding layer 3a and the core layer 5, in addition to the flame deposition method, a CVD method (normal pressure CVD method, low pressure CVD method, plasma CVD method) or a PVD method (EB (electron beam) evaporation method, sputtering method)
Can be used. Next, the core layer 5 is patterned by photolithography and reactive ion etching to form a plurality of cores 4 having a desired shape with a width of 8 μm (see FIG. 2C). At this time, the plurality of cores 4 are formed such that the ratio of the height / interval at the nearest adjacent portion is 1 or more (height> interval).

Thereafter, an upper cladding layer 3b made of silicon dioxide (SiO 2) covering the plurality of cores 4 is formed by a plasma CVD method as follows. Here, an outline of a plasma CVD apparatus (hereinafter, referred to as “PCVD apparatus”) used for forming the upper cladding layer 3b will be described with reference to FIG. In the PCVD apparatus 10, a substrate holding table 11a and a shower plate 11b are arranged opposite to each other in a chamber 11, and a heater wire 11c is wired near the shower plate 11b. The substrate holder 11a and the shower plate 11b form a parallel plate type lower electrode and upper electrode, respectively, and a high frequency voltage is applied to the substrate holder 11a from a high frequency power supply 13 via a matching box 12. The chamber 11 is provided with the first pipe 1
4 is connected to a process gas tank 15. As shown in FIG. 3, the first pipe 14 is provided with an oxygen gas (O
2) and a second pipe 16 for introducing argon gas (Ar) is connected, and a heater 14a, a vaporizer 14b, and a controller 14c for controlling the flow rate of the process gas are provided. In the chamber 11, a pump 17 which is a combination of a mechanical booster pump and a rotary pump is arranged on the discharge side of the process gas. here,
As a process gas, silane (Si
H4) or tetraethoxysilane (TEOS)
NO2, O2, H2 as reaction gas added to the raw material gas
Use a gas such as

Therefore, when the upper cladding layer 3b is formed by the PCVD apparatus 10, first, the process gas (TEOS) supplied from the tank 15 by the first pipe 14 is vaporized at 110 ° C. by the vaporizer 14b, 12 at 14a
While heating to 0 ° C., about 20 cm of oxygen is supplied from the second pipe 16.
^It was supplied at a rate of ³ / min and introduced into the chamber 11. Then, the output of the high-frequency power supply 13 was set to 100 W, and the substrate 2 on which the core 4 was formed as shown in FIG. 2C was formed while being heated to 200 ° C. on the substrate holding table 11a.

At this time, when the thickness of the silicon dioxide (SiO 2) deposited on the core 4 becomes about 2 μm, the thickness at the upper corner of the core 4 becomes about 2.5 μm. For this reason, as shown in FIG. 4A, an overhang portion Poh that protrudes in both sides in the width direction of the core 4 is formed in the formed upper cladding layer 3b made of silicon dioxide (SiO2). You. Therefore, the film formation is temporarily stopped with the formation of the overhang portion Poh as a guide. The film thickness when the film formation is temporarily stopped is not limited to the above thickness (= about 2 μm). However,
If the silicon dioxide (SiO2) film becomes excessively thick, this film is connected to the film deposited on the adjacent core 4, so that the overhang portion Poh cannot be removed in the next etching step. For this reason, it is desirable that the film formation be temporarily stopped before the overhang portion Poh is formed.

Next, supply of the process gas (TEOS) and oxygen is stopped, argon gas is newly introduced into the chamber 11 from the second pipe 16 at about 50 cm ³ / min, and the output of the high frequency power supply 13 is reduced to 400 W. Etching was performed by setting. At this time, by making the etching time twice as long as the film forming time, as shown in FIG.
Of the core 4 can be removed.
Did not scrape the upper corner. However, as shown, the upper cladding layer 3 between the cores 4 is etched by etching.
A groove T is formed in b, and the groove T is backfilled as described later. Here, the gas used for etching is not limited to the above-mentioned argon gas, and for example, gases such as helium (He), oxygen (O2), and nitrogen (N2) can be used.

Next, a silicon dioxide (SiO 2) film was formed again by the PCVD method on the etched silicon dioxide (SiO 2) film. At this time, when the overhang portion Poh shown in FIG. 4A is formed on the silicon dioxide (SiO2) film, etching is performed again to remove this portion as shown in FIG. 4B. As described above, by alternately repeating the film formation and the removal of the overhang portion Poh by etching, the concave groove T shown in FIG.
Are backfilled as shown in FIG. Finally, as shown in FIG. 1, the optical waveguide component 1 in which the upper portions of the plurality of cores 4 are slightly raised but have no trace of the concave groove T is manufactured.

In the manufactured optical waveguide component 1, no void was generated even in a portion where the interval between the plurality of cores 4 was narrow. In addition, during the formation of the upper cladding layer 3b by the PCVD method, the temperature of the
Because it was kept at 0 ° C, a lower temperature than the conventional film forming method,
An increase in polarization dependent loss caused by thermal stress can also be prevented.

[0019]

According to the first and second aspects of the present invention, when the cladding layer is formed on the substrate, the polarization dependent loss caused by the thermal stress does not increase and the adjacent layers do not generate voids. It is possible to provide a method of manufacturing an optical waveguide component capable of embedding between cores and an optical waveguide component.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an optical waveguide component of the present invention.

FIG. 2 is a process chart showing a process of forming a lower cladding layer and a plurality of cores on the optical waveguide component of FIG.

FIG. 3 is a schematic configuration diagram of a PCVD apparatus used for forming an upper cladding layer.

FIG. 4 is a process diagram showing a film forming process of an upper clad layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical waveguide component 2 Substrate 3 Cladding layer 3a Lower cladding layer 3b Upper cladding layer 4 Core

Claims (2)

[Claims] 1. A method for manufacturing an optical waveguide component, wherein a core having a desired shape is formed on a substrate, and a cladding layer covering the core is formed to form an optical waveguide component. A method for manufacturing an optical waveguide component, comprising: forming a predetermined thickness by a plasma CVD method; and repeating a process of removing an overhang portion of the cladding layer formed on the core by etching. 2. An optical waveguide component manufactured by the manufacturing method according to claim 1.