JPH1123876A - Parts for optical communication and formation of optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation in optical characteristics by repeating respective stages of applying a packing material, etching only the packing material and clad layer and again forming the clad layer to a layer at which the occurrence of overhanging in groove parts is averted until the groove parts are packed with the clad layer. SOLUTION: A resin material 13 as the packing material having approximately equal characteristics to etching to those of the film constituting the clad layer 9 in such a manner that the groove parts 8 are embedded and that the surface of a substrate 5 is made flat over the entire part. The resin material 13 and the clad layer 9 are partly etched by a dry etching method, such as plasma. etching, reactive etching or ECR plasma. etching. The residues of the resin material 13 are removed by dry etching. Next, the clad layer 9 is deposited to the extent of not overhanging at the groove parts 8 again by a CVD process or PVD process. This process is repeated in such a manner until the groove parts 8 are packed by the clad layer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication component such as an optical splitter, an optical coupler, an optical demultiplexer, an optical multiplexer and the like, and more particularly, to a method for forming an optical waveguide on a substrate and its method. The present invention relates to an optical communication component having an optical waveguide formed by the method.

[0002]

2. Description of the Related Art Hitherto, optical communication parts such as optical splitters, optical couplers, optical demultiplexers, optical multiplexers and the like have been used in which an optical waveguide is formed on a substrate. This is formed by forming an optical waveguide in a predetermined pattern using, for example, quartz glass or silicon as a substrate. This optical waveguide is generally composed of a buffer layer, a core layer, and a clad layer, and is formed by a flame deposition method (FHD method), a chemical vapor deposition method (CVD).
Method, a physical vapor deposition method (PVD method), and a combination thereof, and a glass SiO ₂ film is deposited and patterned to form a glass SiO ₂ film (for example, Japanese Patent Publication No. 3-7560).
No. 6).

[0003]

SUMMARY OF THE INVENTION Among the above deposition methods, F
The HD method is advantageous for forming a thick film glass because the deposition rate is high, but for forming a buffer layer, a core layer, and a cladding layer, after depositing glass fine particles, the HD method may be used to form the glass layer.
Since a step of vitrifying transparently at a high temperature of 00 ° C. is necessary, the doping element for adjusting the refractive index is diffused by the high temperature treatment, and the glass of the buffer layer, the core layer, and the cladding layer flows. There's a problem. Therefore, low-temperature deposition (5
(Less than 00 ° C.) CVD method (plasma CVD method, normal pressure CVD method, low pressure CVD method, etc.) and PVD method
Sputtering, etc.) and their combination have been proposed.

However, although this low-temperature film forming method does not have the above-mentioned problem, it has been considered that it is technically difficult to embed a rectangular cross-sectional shape having a narrow pitch and a deep groove due to poor step coverage.

For example, the cross-sectional shape of the optical waveguide chip constituting the optical branching device 1 for connecting the V-groove substrate 2 and the optical fiber array 3 as shown in FIG. It looks like Fig.2. That is, for example, both the width and the height are 8 μm on the substrate 5 with the buffer layer 6 interposed therebetween.
A plurality of cores (layers) 7a and 7b having a rectangular cross section are formed,
A deep groove 8 having a width of about 3 μm is defined therebetween. The periphery (including the groove 8) of each core 7 is made of SiO.
_The clad layer 9 made of _two films covers the clad layer 9.

Here, if the grooves 8 are not filled with the cladding layer 9, that is, if the grooves 8 have so-called voids (voids), the function of the cladding layer deteriorates and the characteristics of the branching device deteriorate. In the conventional CVD method, PVD method, and a combination thereof, the step coverage is poor, and the overhang 9a is generated at the opening of the deep groove 8, and the void 9b is easily generated (FIG. 3).

In the same manner as described above, even when an optical coupler, an optical demultiplexer, an optical multiplexer, or the like has a core with a narrow pitch, good light is required unless the groove between the cores is completely filled with a cladding layer. No characteristics can be obtained.

The present invention has been made in view of the above-mentioned problems of the prior art, and a main object of the present invention is to provide an optical communication component in which an optical waveguide is formed in a predetermined pattern on a substrate. An object of the present invention is to prevent optical characteristics from deteriorating due to generation of voids even when optical waveguides are arranged at a narrow pitch.

[0009]

According to the present invention, there is provided a method for forming an optical waveguide having a buffer layer, a core layer, and a clad layer on a substrate in a predetermined pattern. A first step of forming a buffer layer on the substrate, a second step of forming a core layer having the predetermined pattern on the buffer layer and having an etching protection film on the surface, A third step of forming a film forming a cladding layer on the substrate to a thickness that does not cause overhang in the groove between the layers, and filling the groove and forming the cladding layer so that the substrate surface becomes entirely flat. A fourth step of applying a filler material having substantially the same etching characteristics as the film to be formed, and exposing the film forming the clad layer deposited on the bottom of the groove or depositing the film on the side wall of the groove. A fifth step of etching only the filler and the film forming the cladding layer until the film forming the lad layer is substantially removed, and after removing the remaining filler, the film forming the cladding layer is removed again. A sixth step of forming the groove to a thickness that does not cause overhang in the groove, and repeating the fourth to sixth steps until the groove is filled with a film forming the cladding layer. This is achieved by providing a method for forming an optical waveguide of a communication component. In particular, the etching in the fifth step is preferably performed by dry etching, and the side wall of the film forming the cladding layer in the groove is preferably inclined so as to gradually narrow from the opening toward the bottom.

[0010]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The optical branching device 1 as an optical communication component to be manufactured is the same as that shown in FIGS. 1 and 2, and a description thereof will be omitted.

FIGS. 4 to 6 show a procedure for forming an optical waveguide.
First, a substrate 5 made of silicon or quartz glass (FIG. 4)
(A)) A buffer layer 6 and a core layer 7 made of SiO ₂ are formed thereon by a CVD method, a PVD method, or a combination thereof (FIG. 4B). Next, CV is applied on the core layer 7.
The etching protection film 10 is formed by the D method or the PVD method (FIG. 4C). The material of the protective film 10 may be a metal or a semi-metal having a sufficient selectivity with SiO ₂ in dry etching.

A photoresist 11 is applied on the protective film 10 (FIG. 4D), and a mask 12 of an optical waveguide pattern to be formed is disposed thereon (FIG. 4E). After exposure (FIG. 4E), development is performed to obtain desired resist patterns 11a and 11b (FIG. 4F). Using the resist patterns 11a and 11b as masks, the protective film 10 is dry-etched (FIG. 5A), and the resist patterns 11a and 11b are removed to obtain the same protective film patterns 10a and 10b (FIG. 5B )). Subsequently, the core layer 7 is dry-etched using the protective film patterns 10a and 10b as masks to form core patterns 7a and 7b (FIG. 5C).

Next, a cladding layer 9 is formed by a CVD method or a PVD method. At this time, the adjacent cores 7
The SiO ₂ film forming the cladding layer 9 is not overhanged in the groove 8 between the holes a and 7b. The SiO ₂ film is deposited so as to leave a gap of, for example, about 1 μm to 1.5 μm, depending on the film formation method and the film formation conditions. FIG. 5D). Then, a resin material 13 as a filler having substantially the same etching characteristics as the film forming the clad layer 9 is applied so as to fill the grooves 8 and flatten the entire surface of the substrate 5 (FIG. 5).
(E)). As the resin material 13, an epoxy resin, a silicone resin, a polyimide resin, or the like is preferably used.

Next, the resin material 13 and a part of the clad layer 9 are etched by a dry etching method such as plasma etching, reactive etching, and ECR plasma etching (FIG. 5F). At this time, the resin material 13 and the cladding layer 9 are removed until the film forming the cladding layer 9 deposited on the bottom of the groove 8 is exposed or the film forming the cladding layer deposited on the side wall of the groove 8 is substantially partially removed. Only diagonally etch. Then, as shown in FIG.
Side wall portions 9c and 9 of the film forming the cladding layer deposited in the groove portion 8
d inclines so that it gradually narrows from the opening of the groove 8 toward the bottom. That is, overhang is less likely to occur during the next film formation described later. Further, since the groove 8 is filled with the resin material 13, there is no fear that the bottom is etched and the groove becomes deep. Residue of the resin material 13 is removed by dry etching.

Next, the cladding layer 9 is deposited again by the CVD method or the PVD method so that the cladding layer 9 does not overhang in the groove 8 as described above (FIG. 6A). The resin material 13 is applied so as to be entirely flat (FIG. 6B), and the resin material 13 and a part of the clad layer 9 are dry-etched as described above (FIG. 6).
(C)).

When the groove 8 is sufficiently filled with the cladding layer 9, the protective film patterns 10a and 10b are removed by dry etching, and the residue of the resin material 13 is also removed by dry etching (FIG. 6D). .

Finally, the cladding layer 9 is formed by CVD or P
It is formed thick by the VD method, and the core patterns 7a and 7b are embedded.

Here, FIGS. 4A to 5C show the first and second steps, FIG. 5D shows the third step, FIG. 5E shows the fourth step, and FIG. (F) is a fifth step, and FIG. 6 (a) is a sixth step. The steps from the fourth step to the sixth step are repeated until the groove 8 is sufficiently filled with the cladding layer 9. In the above description, FIG. 6B shows the second fourth step, FIG. 6C shows the second fifth step, and FIG.
The sixth process was repeated only once (total 2
Degree) and repeating the process three times or more while adjusting the thickness of the clad layer at the time of film formation according to the width and depth of the groove or the step coverage of the film forming apparatus. Is better filled in the cladding layer.

[0019]

As is apparent from the above description, according to the optical communication component and the method for forming the optical waveguide of the present invention, the substrate is etched in a predetermined pattern via the buffer layer and on the surface. First and second steps of forming a core layer having a film, a third step of forming a clad layer to a thickness that does not cause an overhang in a groove between mutually adjacent cores, and filling the groove and substrate surface A fourth step of applying the filler such that the cladding is deposited on the bottom of the groove or until the cladding deposited on the sidewall of the groove is partially removed. And a fifth step of etching only the clad layer, and a sixth step of forming the clad layer again to a thickness that does not cause overhang in the groove after removing the remaining filler, Steps 4 to 6 are repeated until the grooves are filled with the cladding layer, thereby preventing voids from being generated in the grooves and deteriorating the optical characteristics even if the optical waveguides are arranged at a narrow pitch. Since this does not occur, not only the reliability of the optical communication component is improved, but also the pattern can be made denser and the component can be reduced in size. Also, in the etching in the fifth step, the overhang at the time of film formation can be more effectively prevented by inclining the cladding layer side wall of the groove so as to gradually narrow from the opening toward the bottom. This makes it difficult to prevent the occurrence of voids.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state of connection between an optical branching device as an optical communication component, a V-groove substrate, and an optical fiber array.

FIG. 2 is an enlarged sectional view taken along line II of FIG. 1;

FIG. 3 is a view similar to FIG. 2, showing a problem of a conventional optical communication component.

4 (a) to (f) together with FIGS. 5 (a) to 5 (f) and FIGS. 6 (a) to 6 (e) explain the procedure for forming an optical waveguide to which the present invention is applied. FIG.

FIGS. 5 (a) to 5 (f) together with FIGS. 4 (a) to 4 (f) and FIGS. 6 (a) to 6 (e) explain the procedure for forming an optical waveguide to which the present invention is applied. FIG.

6 (a) to 6 (e) together with FIGS. 4 (a) to 4 (f) and FIGS. 5 (a) to 5 (f) explain a procedure for forming an optical waveguide to which the present invention is applied. FIG.

FIG. 7 is an enlarged view of FIG.

[Explanation of symbols]

 Reference Signs List 1 optical branching device 2 V groove substrate 3 optical fiber array 5 substrate 6 buffer layer 7 core layer 7a, 7b core (pattern) 8 groove portion 9 cladding layer 9a overhang 9b void 9c, 9d side wall portion 10 etching protective film 10a, 10b protection Film pattern 11 Photoresist 11a, 11b Resist pattern 12 Mask 13 Resin material

Claims (4)

[Claims] 1. A method for forming an optical waveguide having a buffer layer, a core layer, and a cladding layer on a substrate in a predetermined pattern, comprising: a first step of forming a buffer layer on the substrate; A second step of forming a core layer having the predetermined pattern on the surface of the buffer layer and having an etching protection film on a surface thereof; and forming a core layer having a thickness that does not cause overhang in a groove between the adjacent core layers. A third step of forming a film forming a cladding layer, and a step of applying a filler having substantially the same etching characteristics as the film forming the cladding layer so as to fill the groove and flatten the entire substrate surface. Step 4 and until the film forming the clad layer deposited on the bottom of the groove is exposed or the film forming the clad layer deposited on the side wall of the groove is substantially removed. A fifth step of etching only the filler and the film forming the cladding layer; and removing the remaining filler, and forming the film forming the cladding layer again to a thickness that does not cause overhang in the groove. 6. A method of forming an optical waveguide for an optical communication component, comprising: repeating steps 4 to 6 until the groove is filled with a film forming the cladding layer. 2. The etching in the fifth step is performed by dry etching, and a sidewall of the film forming the cladding layer in the groove is inclined so as to gradually narrow from an opening to a bottom. The method for forming an optical waveguide of an optical communication component according to claim 1, wherein: 3. The method for forming an optical waveguide of an optical communication component according to claim 1, wherein the filler is made of a resin material. 4. An optical communication component having an optical waveguide formed by the method according to claim 1. Description: