JPH08110426A - Method of manufacturing optical waveguide - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing an optical waveguide having excellent optical characteristics, by which an extra glass film for a first cladding layer on a substrate can be uniformly polished and scraped off. [Structure] A bench 23a and a convex portion 23b having the same height as the bench 23a are formed on a substrate 20, and a glass film 24 is formed on the substrate 20 to embed the first clad layer 25 in the groove, The extra glass films 24a, 24b formed on the surface are evenly shaved by polishing to expose the surfaces of the bench 23a and the convex portion 23b. Next, the core waveguide 27 is formed on the first clad layer 25 embedded in the substrate, the second clad layer 29 is formed on the core waveguide 27, and the second clad layer 29 is subjected to fine processing. Bench for mounting semiconductor devices on the board 23
Expose a again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical waveguide, and more particularly to a method for manufacturing an optical waveguide having a bench for mounting semiconductor elements such as a semiconductor light source and a semiconductor photodetector.

[0002]

2. Description of the Related Art When forming an optical integrated circuit on a Si substrate, it is necessary to form an Si bench for mounting a semiconductor optical device such as a semiconductor light source or a semiconductor photodetector and an optical waveguide.

3 (a) to 3 (l) are views showing a conventional example of a method of manufacturing an optical waveguide having a bench for mounting a semiconductor element.

Outer diameter 3 inches, oxide film (SiO ₂ ) on both sides
A resist is applied on a Si substrate 1 having a thickness of 1 mm and having a thickness of 1 μm (FIG. 3A).

After applying a resist, a bench photomask pattern is transferred to the resist by a mask aligner to form a Si bench pattern 2 (FIG. 3).
(B)).

FIG. 4 is a diagram showing the surface of a substrate on which the bench pattern 2 for forming the bench shown in FIG. 3B is formed. The number of optical waveguides to be obtained from one substrate (FIG. 4 has 8 patterns).

Next, the excess oxide film is removed using reactive ion etching (RIE) or hydrofluoric acid, and the Si substrate 1 is etched using the remaining SiO ₂ as a mask. The etchant is an aqueous solution of potassium hydroxide (KOH) having a concentration of 40% by weight and a temperature of 40 ° C., and is etched to a depth of 25 μm to form a first clad layer embedding substrate 3 having a bench 3a composed of a convex mesa portion. Yes (Fig. 3
(C)).

A glass film 4 of SiO _{2 is formed on} the upper surface of the substrate 3 for embedding the first clad layer by 25 μm by an electron beam evaporation method.
m (FIG. 3D).

Excessive SiO ₂ glass film other than the grooves is removed by polishing to expose the surface of the bench 3a, and the remaining glass film is used as the first cladding layer 5 (FIG. 3 (e)).

On the substrate 3 in which the first cladding layer 5 is embedded, a core glass film 6 having a refractive index n ₀ is formed by electron beam evaporation to a thickness of 8 μm (FIG. 3 (f)).

A WSi film of 1 μm is formed on the surface of the core glass film 6 by a magnetron sputtering method.
After applying the resist, the core pattern is transferred with a mask aligner and the core glass film is etched by reactive ion etching to form a core waveguide 7 having a rectangular cross section on the first clad layer 5 extending in the left-right direction in the drawing ( FIG. 3 (g)).

A flame volume method is applied to the core waveguide 7 to form a SiO ₂ —B ₂ O ₃ —P ₂ O ₅ based porous glass film 8 of 300 μm (FIG. 3 (h)).

The substrate was placed in a quartz glass furnace tube in an electric furnace, and was kept in a He gas atmosphere at a temperature of 1330 ° C. for 1 hour to be a transparent vitrification, and a second cladding layer 9 having a thickness of 30 μm was formed. , A quartz glass waveguide (FIG. 3 (i)).

A metal film 10 is formed on the surface of the second cladding layer 9 by the sputtering method (FIG. 3 (j)).

A bench exposure pattern 11 for exposing the surface of the bench 3a is formed by photolithography (FIG. 3 (k)).

Based on this pattern 11, excess silica glass is shaved off by reactive ion etching to form a hole 12 and expose the Si bench 3a (FIG. 3).
(L)).

[0017]

By the way, a SiO ₂ glass having a refractive index n ₀ is formed on a Si substrate which is grooved for embedding the first cladding layer. Excess glass film other than the grooves formed in the Si substrate is ground by polishing to expose the surface of the Si substrate that will be the bench 3a. As shown in FIG. 4, a groove for burying the first cladding layer in the Si substrate is used. Since the Si bench pattern 2 used for processing is not axially symmetric with respect to the center of the Si substrate, it is difficult to grind off the extra glass film formed on the Si substrate uniformly in the plane. As a result,
The thickness of the first clad layer embedded in the Si substrate in the depth direction also varies by ± 5 μm or more in the plane, which significantly deteriorates the optical characteristics of the glass waveguide.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing an optical waveguide having excellent optical characteristics, by which an excessive glass film on a substrate can be uniformly polished and scraped off. is there.

[0019]

In order to achieve the above object, the present invention provides a substrate for forming a groove for embedding a first cladding layer and a convex bench for mounting a semiconductor element on the substrate. First having a sufficient thickness to fill a groove thereover
While forming the glass film for the clad layer, the excess glass film formed on the substrate is polished until the bench is exposed, the core glass film is formed on the substrate after this polishing, and the core glass film is subjected to photolithography and A core waveguide is formed on the first clad layer embedded in the groove by reactive ion etching, and a second core is formed on the substrate on which the core waveguide is formed.
In a method of manufacturing an optical waveguide, in which a clad layer is formed and the second clad layer is subjected to microfabrication using photolithography and reactive ion etching to expose the bench, a bench pattern and a bench pattern are formed when the bench is formed. By using a bench photomask in which dummy patterns for polishing are arranged, a convex portion having the same height as the bench is formed on the substrate together with the bench.

In addition to the above structure, the present invention uses a bench photomask pattern in which a polishing dummy pattern is arranged so as to surround the bench mask pattern.

[0021]

According to the above structure, the groove for embedding the first cladding layer and the semiconductor element are mounted by using the bench photomask in which the bench pattern and the polishing dummy pattern are arranged on the substrate. Since the convex bench is formed, the glass film having the same thickness as the glass film in the portion where the bench is formed is formed in the portion corresponding to the polishing dummy pattern. If the substrate on which such a glass film is formed is polished until the bench is exposed, the glass film on the bench pattern and the polishing dummy pattern is polished at the same time. By adjusting the polishing surface based on the polishing condition,
Excessive glass film is scraped off evenly in the plane. When a semiconductor element is mounted on the bench thus formed, excellent optical characteristics can be obtained.

Further, when a bench photomask in which a polishing dummy pattern is arranged so as to surround the bench mask pattern is used, the deviation of the polishing surface can be more easily seen, which makes it easier to correct the glass. Uniform polishing of the film is facilitated.

[0023]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

1 (a) to 1 (l) are views showing an embodiment of a method for manufacturing an optical waveguide according to the present invention, and FIG. 2 is a bench photo for forming the bench shown in FIG. It is a figure which shows a mask pattern.

A resist is applied onto a Si substrate 20 having an outer diameter of 3 inches and a SiO ₂ film of 1 μm formed on both sides and a thickness of 1 mm (FIG. 1A).

The Si bench photomask pattern coated with the resist and the polishing dummy mask pattern are transferred to the resist to form a photomask pattern 21 and a polishing dummy mask pattern 22 (FIG. 1B).

Here, FIG. 2 shows a photomask pattern 2.
It is a figure which shows the surface of the board | substrate which formed 1 and 22, and the dummy mask pattern 22 for polishing as shown in FIG. (The arrangement of the polishing dummy mask pattern 22 is not limited to the substantially square shape, and may be triangular or polygonal).

Excessive oxide film is removed by reactive ion etching or hydrofluoric acid, and the Si substrate 20 is etched using the remaining SiO ₂ as a mask. The etchant is potassium hydroxide (KOH) with a concentration of 40% by weight and a temperature of 40 ° C.
Etching is performed to a depth of 25 μm using
The bench 23a and a plurality of convex portions having the same height as the bench 23a are formed on the i substrate 20, and the first clad layer embedding substrate 23 is formed.
Are formed (FIG. 1C).

A glass film 24 of SiO ₂ is deposited on the first clad layer-embedding substrate 23 by electron beam evaporation to a thickness of 25 μm.
m (FIG. 1D).

Excessive glass films 24a, 24b of SiO ₂ other than the grooves are scraped off by polishing to form the first cladding layer 25 in the grooves (FIG. 1 (e)).

Substrate 2 in which the first cladding layer 25 is embedded
3, a core glass film 26 having a refractive index n ₀ is uniformly formed by electron beam evaporation to a thickness of about 8 μm (FIG. 1).
(F)).

A WSi film of 1 μm is formed on the surface of the core glass film 26 by the magnetron sputtering method. Further, after applying a resist, the core pattern is transferred by a mask aligner, and the core glass film is etched by reactive ion etching to form a core waveguide 27 having a rectangular cross section on the first clad layer 25 and extending left and right in the drawing. (FIG. 1 (g)).

The substrate 23 on which the core waveguide 27 is formed is
It is placed on a heated turntable, and a SiO ₂ —B ₂ O ₃ —P ₂ O ₅ -based porous glass film 28 of 300 μm is formed by the flame deposition method (FIG. 1 (h)).

This Si substrate was placed in a quartz glass furnace tube in an electric furnace and heated at 1330 ° C. in a He gas atmosphere.
By virtue of holding for 1 hour at the temperature of
The second clad layer 29 is formed with a thickness of 30 μm to form a silica glass waveguide. In this example, the width and height of the core waveguide are both 8 μm, and the relative refractive index difference Δ between the core, the first cladding, and the second cladding is 0.3% (FIG. 1 (i)).

Next, in order to expose the Si bench 23a for mounting a semiconductor element (not shown) on the Si substrate, the silica glass portion other than the optical waveguide portion on the Si substrate is removed. First, a metal film 30 is formed on the surface of the second cladding layer 29 by a sputtering method (FIG. 1).
(J)).

Si bench 23 is formed by photolithography.
A pattern 31 for exposing the surface of a is formed (FIG. 1 (k)).

Based on this pattern 31, excess silica glass is scraped off by reactive ion etching to form a hole 32 and expose the Si bench 23a (FIG. 1 (l)).

The substrate is diced to finally obtain an optical waveguide chip.

Next, the operation of the embodiment will be described.

Since a groove for embedding the first cladding layer 25 is formed on the substrate 20 using a bench photomask in which the bench pattern 21 and the polishing dummy pattern 22 are arranged, the bench 23a is formed. The glass film 24b having the same thickness as that of the glass film 24a of the part can be formed on the convex portion 23b corresponding to the polishing dummy pattern 22. When the substrate 23 having such glass films 24a and 24b formed thereon is polished, the bench 23a and the convex portion 23b have the same height, and the glass films 24a and 24b formed thereon have the same thickness. Because
When the glass films 24a and 24b are uniformly polished, and if they are not uniformly polished, it is easy to know whether or not the glass films 24a and 24b are uniformly polished because a part of the convex portion 23b is exposed first. By adjusting the polishing surface based on the polishing condition, the excess glass film 24 can be uniformly coated in the surface.
a and 24b are scraped off. When a semiconductor element is mounted on the bench 23a thus formed, excellent optical characteristics can be obtained.

As described above, according to the present embodiment, the bench photomask pattern in which the bench pattern and the polishing dummy pattern are arranged is used before the groove processing for embedding the first cladding layer is performed on the substrate. By forming the bench pattern and the polishing dummy pattern on the substrate, the excess glass film on the substrate can be scraped off uniformly, and an optical waveguide having excellent optical characteristics can be manufactured.

In this embodiment, a Si substrate is used as the substrate and the quartz glass waveguide is used as the waveguide. However, the present invention is not limited to this.

[0043]

In summary, according to the present invention, the following excellent effects are exhibited.

By forming the bench and the convex portion having the same height as the bench on the substrate, the excess glass film for the first cladding layer can be evenly scraped off, so that an optical waveguide having excellent optical characteristics can be manufactured. can do.

[Brief description of drawings]

1A to 1L are views showing an embodiment of a method for manufacturing an optical waveguide of the present invention.

FIG. 2 is a diagram showing the surface of the substrate shown in FIG.

3 (a) to 3 (l) are diagrams showing a conventional example of a method of manufacturing an optical waveguide having a bench for mounting a semiconductor element.

FIG. 4 is a diagram showing a substrate surface shown in FIG. 3 (b).

[Explanation of symbols]

20 Substrate (Si Substrate) 21 Bench Pattern (Photomask Pattern) 22 Polishing Dummy (Mask) Pattern (Photomask Pattern) 23 First Cladding Layer Embedded Substrate (Substrate) 23a Bench 23b Convex Section 25 First Cladding Layer 29 Second clad layer

Front page continuation (72) Inventor Tatsuo Teraoka 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd.

Claims (2)

[Claims] 1. A groove for embedding a first clad layer and a convex bench for mounting a semiconductor element are formed on a substrate, and the groove has a thickness sufficient to embed the groove on the substrate. A glass film for the first cladding layer is formed, and an extra glass film formed on the substrate is polished until the bench is exposed, and a core glass film is formed on the substrate after the polishing. The first trench embedded in the groove by photolithography and reactive ion etching.
A core waveguide is formed on the clad layer, a second clad layer is formed on the substrate on which the core waveguide is formed, and the second clad layer is subjected to microfabrication by photolithography and reactive ion etching. In the method of manufacturing an optical waveguide in which the bench is exposed by performing the process, when forming the bench, a bench photomask on which a bench pattern and a polishing dummy pattern are arranged is used and the same height as the bench is formed on the substrate. A method for manufacturing an optical waveguide, characterized in that the convex portion of the ridge is formed together with the bench. 2. The method of manufacturing an optical waveguide according to claim 1, wherein a bench photomask in which the polishing dummy pattern is arranged so as to surround the bench mask pattern is used.