JPH06324226A - Waveguide device and its production - Google Patents

Abstract

PURPOSE:To lessen connection loss by forming specific grooves by dry etching near the connecting surface of a first waveguide part. CONSTITUTION:Only the points 6a, 6b corresponding to connecting surfaces at the time of butt connection are exposed at a desired width and the other surface parts are coated with a resist 7. After the surface over the entire part is subjected to dry etching, the resist 7 is peeled away. Consequently, only the constituting material of the thin-film body existing right under the exposed surfaces 6a, 6b is etched away and the grooves 8 are so formed as to enclose the first waveguide part A to be formed. The grooves 8 are so formed as to have the depth at which the grooves penetrate the entire part of the core layer 4 and further arrive at the point lower than the front surface 2a of a common lower clad 2 existing thereunder. Then, the dry etching surfaces A1, A2 in the first waveguide part A are formed as perpendicular surfaces which are both flat from the surface of the gap layer 6 clown to the desired depth of the common clad 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type device having a butt connection structure and a method for manufacturing the same, and more particularly to a waveguide type device having a small light scattering loss at a connection surface and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Some waveguide type optical devices require a connection between a semiconductor optical amplifier and a waveguide. For example, there is a structure shown in FIG. In this device, a common cladding 2 is formed on the same substrate 1, and a first waveguide portion A having a predetermined layer structure is formed on the common cladding 2.
The second waveguide portions B, B having another layer structure are butt-connected to each other at their connection surfaces A ₁ , A ₂ .

This device is usually manufactured as follows. That is, as shown in FIG. 11, first, a predetermined semiconductor is laminated on the substrate 1 so as to have the same layer structure as that of the first waveguide portion A shown in FIG. A mask 3 made of, for example, SiO _{2 is} formed on the surface corresponding to the plane pattern of the portion A.

Next, the surface 2a of the common lower cladding 2 is exposed by etching away all the portions except the first waveguide portion A using the SiO ₂ film 3 as a mask (FIG. 12). Then, a mask 3 is formed on the exposed surface 2a.
After forming the second waveguide portion having another layer structure using as a growth prevention mask, the mask is removed to manufacture the device having the butt structure shown in FIG.

What is important in the device manufactured in this way is that when the etching shown in FIG.
That is, the connection surfaces A ₁ and A _{2 of the} waveguide portion A are formed as flat vertical surfaces. When the connecting surfaces A ₁ and A ₂ are inclined so that the width becomes narrower as they go upward, when the constituent materials of the second waveguide parts B and B are laminated on the exposed surface 2a of the common lower clad. In addition, the above-mentioned constituent materials are deposited also on the connection surfaces A ₁ and A ₂ , and as a result, the distribution of propagating light is different at that portion, which causes an increase in connection loss.

Further, if the connecting surfaces A ₁ and A ₂ are inclined so that the width becomes wider toward the upper side, the connecting surface is covered with a canopy, so that the first waveguide portion is formed. This is because the problem that the constituent material of the second waveguide portions B, B to be formed is not deposited in the vicinity of the base portion of or is deposited thinner than the other portions, which also causes an increase in connection loss. (Journal of Electronics Materials,
See vol 19, No. 11, 1990).

Further, in the above device, the first waveguide portion A
The relative position at the time of the butt connection between the second waveguide portions B and B depends on the accuracy of the etching depth before forming the second waveguide portions B and B and the flatness of the connection surfaces A ₁ and A ₂ . Stipulated. Conventionally, this etching process is performed only by the wet etching method using a predetermined etchant.
The portion corresponding to the second waveguide portion on the top is removed by etching, or the reactive ion etching method (RIE) or the reactive ion beam etching method (RIB) is used.
A method is employed in which the surface 2a of the common clad 2 is exposed by shallowly etching and removing it to the vicinity of the surface of the common clad 2 by a dry etching method such as E) and then etching the remaining portion by a wet etching method. There is.

[0008]

By the way, if all are performed by the wet etching method, the connection planes A ₁ and A ₂ formed in the portion of the first waveguide portion A have vertical plane orientations in all regions. Therefore, in the butt connection state with the second waveguide portion, the problem that connection is difficult only at a portion where the plane orientation is a vertical plane eventually occurs.

The layer structure of the first waveguide portion is a multilayer structure.
When removing each layer,
It is necessary to select and use a valid etchant
In addition, the horizontal direction of those etchants
Connecting surface A formed when the etching speed is different₁, A
₂Is a vertical plane as a whole, but
Continuation A₁, A₂Then, the edges of each layer are uneven.
Therefore, this connection surface A₁, A ₂Is a flat surface as a whole
There is also the problem of not having it.

On the other hand, in the case of the dry etching method described above, since the selective etching as described above cannot be performed, the wet etching method is used to finally leave the second waveguide portion at the place where the second waveguide portion is to be formed. It is necessary to completely remove the part where it is present. Therefore, there arises a problem that the whole process becomes complicated and that the final wet etching causes the connection surfaces A ₁ and A ₂ of the first waveguide portion A to become surfaces having plane orientation dependence. . Further, when the first waveguide portion A has a multi-layer structure, the edge of each layer may be slightly uneven during the final wet etching.

The present invention solves the above-mentioned problems in manufacturing a conventional waveguide type device having a butt connection structure,
An object of the present invention is to provide a waveguide type device having a connection surface which is a vertical surface and a flat surface and has a small connection loss, and a manufacturing method thereof.

[0012]

In order to achieve the above-mentioned object, in the present invention, the first waveguide portion and the second waveguide portion are butted and connected to each other at their connecting surfaces on the same substrate. In the waveguide type device, a waveguide type device is provided in which the second waveguide portion is present in a position deeper than other portions in the vicinity of the connection surface, and the same substrate is also provided. And manufacturing a waveguide type device by butt-connecting a first waveguide part having a predetermined layer structure and a second waveguide part having a different layer structure having a common lower clad at their connection surfaces. Then, a thin film body having the same layer structure as that of the first waveguide portion is formed on the surface of the substrate, and then a mask is patterned on the surface of the thin film body while exposing only the portion where the connection surface is to be formed. , The common lower layer from the exposed surface by a dry etching method. A groove having a depth reaching a position lower than the surface of the pad is formed, a wet etchant resistant material is filled in the groove, and then a thin film body other than the first waveguide is formed by a wet etching method. The surface of the common lower cladding is exposed by etching, the filling material is removed from the groove, the second waveguide is formed on the exposed surface of the common lower cladding, and then the mask is removed. A method of manufacturing a waveguide device is provided.

[0013]

In the present invention, a groove is formed near the connection surface of the first waveguide portion to be formed by the dry etching method down to the position below the surface of the common lower cladding. Therefore, the dry etching surface (connection surface) formed at this point is a vertical and flat surface.

By filling the groove with a wet etchant-resistant filling material, the dry etching surface has the entire area from the entire surface to a position below the surface of the common lower cladding. Covered with filler material. Therefore, even when the entire portion where the second waveguide portion is to be formed is removed by wet etching, the dry etching surface is not etched due to the protective effect of the filling material. Therefore, if the filling material is removed, dry etching is performed. The surface is exposed as a vertical and flat surface that is the same as that formed by the dry etching method.

Therefore, when the second waveguide portion is formed,
Since the butt connection state is maintained vertical, the connection loss in the obtained device is reduced.

[0016]

【Example】

Example 1 As shown in FIG. 1, a compound semiconductor such as n-InP is formed on a substrate 1 made of, for example, an n-InP single crystal by applying a film forming method such as a CVD method or a MOCVD method. Then, the common lower cladding 2 is formed.

On the common lower cladding 2, i-InG is formed.
By stacking aAsP, the confinement layers 4a and 4b having a bandgap wavelength of 1.05 μm and a thickness of 0.22 μm, and a bandgap wavelength of 1.3 μm sandwiched therebetween are 0.16 μm in thickness.
A core layer 4 having a three-layer structure composed of a core 4c of μm is formed, and a 2.5 μm-thick upper clad 5 made of p-InP and a thickness of 0.2 μm made of p-InGaAs are further formed thereon
The cap layer 6 is sequentially formed to obtain a thin film body having a layer structure of the first waveguide portion A to be formed. And the first to be formed
A growth preventing mask 3 made of, for example, SiO ₂ is patterned on the surface of the waveguide portion A.

Then, as shown in FIG. 2, only the portions 6a, 6a corresponding to the connection surface at the time of butt connection are exposed with a desired width (for example, about 2 μm), and the other surface portion is covered with the resist 7. To do. Then, for example, R on the whole surface
Resist 7 after dry etching such as IE
Peel off.

As a result, as shown in FIG. 3, the exposed surface 6
By etching away only the constituent material of the thin film body located immediately below a and 6a, a groove 8 having a width of about 2 μm is formed so as to surround the first waveguide portion A to be formed. At this time, the depth of the groove 8 is formed so as to penetrate the entire core layer 4 and reach a portion below the surface 2a of the common lower cladding 2 located below the core layer 4. For example, it is etched about 0.5 μm deeper than the surface 2a of the common lower cladding.

Therefore, the dry-etched surfaces A ₁ and A ₂ of the first waveguide portion A (which become the butt connection surfaces with the second waveguide portion) are located at the desired depth of the common clad 2 from the surface of the cap layer 6. All of them are formed as flat vertical surfaces. Then, as shown in FIG. 4, a wet etchant resistant material 9 such as polyimide is filled in the formed groove 8. The dry-etched surfaces A ₁ and A ₂ in the first waveguide portion A are covered with the filled material 9.

After that, wet etching is performed using a predetermined wet etchant. As a result, as shown in FIG. 5, except for the first waveguide portion A and the filling material 9,
The thin film bodies of all semiconductor materials are removed by etching to expose the surface 2a of the common lower cladding 2. At this time, since the surface of the first waveguide portion A is covered with the etching protection film 3 and the dry etching surfaces A ₁ and A ₂ are covered with the filling materials 9 and 9, they are not etched.

Then, filling with oxygen plasma, for example
Material 9, 9 is removed. As a result, as shown in FIG.
To the connection surface A of the first waveguide portion A₁, A₂Is a dry etch
Exposed in the same condition as when it was pressed. And finally, S
iO₂Using film 3 as a growth-prevention mask
For example, i-InGaAsP is laminated on the exposed surface 2a of the battery 2.
And the bandgap wavelength is 1.15 μm and the thickness is 0.6 μm.
Of the core layer 10 of p-InP
2.5 μm thick upper clad 11, p-InGaA
Then, a cap layer 12 made of s and having a thickness of 0.2 μm is sequentially formed.
After forming the second waveguide parts B, B by ₂Membrane 3
Remove it to form the desired butt-connection structure device.
It

In this connection structure, since the connection surfaces A ₁ and A ₂ of the first waveguide portion A are the dry etching surfaces as they are, they are flat vertical surfaces. Therefore, since the plane orientations of the core layer 4 of the first waveguide portion A and the core layer 10 of the second waveguide portion B are matched, the connection loss is reduced. Example 2 In the configuration shown in FIG. 7 of Example 1, the same substrate 1 is an n-InP substrate, and the common lower cladding 2 is an n-In substrate.
P, i-InGaAsP as the core layer 4, p-InP as the upper cladding 5, and p-InGa as the cap layer 6.
The first waveguide portion A is formed by using As, and the second waveguide portion B is formed.
Is a core layer 10 made of Fe-doped InGaAsP, an upper cladding 11 made of Fe-doped InP, and a cap layer 12
Of Fe-doped InGaAs.

A plan view of the resulting device is shown in FIG.
In this device, as shown in FIG. 9, the first waveguide portion A
X so that the connecting surface between the second waveguide portion B and the second waveguide portion B becomes a reflecting surface.
A V-shaped waveguide C was formed and an electrode was loaded therein. The resulting device acted as a switch.

[0025]

As is apparent from the above description, in the waveguide type device of the present invention, the butt connection surface between the first waveguide portion and the second waveguide portion is a flat vertical surface. , Connection loss is reduced. This means that during the etching process performed when forming the first waveguide portion, dry etching is performed up to a position below the surface of the common lower cladding, and a wet etchant resistant material is filled in the dry etching, and the next wet etching is performed. This is the effect brought about by protecting the dry etching surface.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state where the same layer structure as a first waveguide portion is formed on a substrate in a method of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a resist is formed.

FIG. 3 is a cross-sectional view showing a state where a groove is formed by a dry etching method.

FIG. 4 is a cross-sectional view showing a state where a groove is filled with a wet etchant resistant material.

FIG. 5 is a cross-sectional view showing a state after a wet etching process.

FIG. 6 is a cross-sectional view showing a state where a wet etchant resistant material is removed.

FIG. 7 is a sectional view showing a waveguide type device of the present invention.

FIG. 8 is a plan view showing another example device of the present invention.

9 is a plan view showing a state in which an X-shaped waveguide is formed in the device shown in FIG.

FIG. 10 is a cross-sectional view showing a conventional waveguide type device having a butt connection structure.

FIG. 11 is a cross-sectional view showing a state in which the same layer structure as the first waveguide portion is formed on the substrate.

FIG. 12 is a cross-sectional view showing a state after an etching process in manufacturing a conventional device.

[Explanation of symbols]

1 same substrate 2 common lower clad 2a surface of common lower clad 2 mask 4 core layer of first waveguide part A 5 upper clad of first waveguide part 6 cap layer of first waveguide part 6a first conductor Surface of the portion where the connection surface of the waveguide portion A is to be formed 7 Resist 8 Groove 9 Wet etchant resistant material 10 Core layer of the second waveguide portion 11 Upper clad of the second waveguide portion 12 Second waveguide portion B cap layer A 1st waveguide section A ₁ , A ₂ Connection surface (dry etching surface) of 1st waveguide section A 2nd waveguide section C X-shaped waveguide

Claims (3)

[Claims] 1. A waveguide type device in which a first waveguide portion and a second waveguide portion are butt-connected on a same substrate by mutual connection surfaces, and in the vicinity of the connection surface, other parts A waveguide type device, wherein the second waveguide portion is present at a deepest position. 2. A first waveguide portion having a predetermined layer structure and a second waveguide portion having a different layer structure having a common lower cladding and a second waveguide portion having a different layer structure are abutted and connected to each other on the same substrate and guided. When manufacturing a waveguide device, a thin film body having the same layer structure as that of the first waveguide portion is formed on the surface of the substrate, and then only the portion where the connection surface is to be formed is exposed on the surface of the thin film body. Patterning the mask in this state, forming a groove having a depth from the exposed surface to a position lower than the surface of the common lower cladding by dry etching, and forming a wet etchant resistant material in the groove. After filling, the thin film body other than the first waveguide is etched away by a wet etching method to expose the surface of the common lower cladding, and then the filling material is removed from the groove, and then the common lower cladding. Exposure table A method for manufacturing a waveguide type device, characterized in that the mask is removed after forming a second waveguide portion on the surface. 3. The method of manufacturing a waveguide type device according to claim 2, wherein at least the second waveguide is formed by a CVD method or a MOCVD method.