JPH08166520A - Dielectric optical waveguide and its production - Google Patents

Abstract

PURPOSE: To provide a dielectric optical waveguide which can be easily produced and has high transmission efficiency. CONSTITUTION: A recessed groove 5 or projection ridge 6 having a mesa structure is formed in a semiconductor substrate 1. A first clad layer 2, optical waveguide layer 3, and second clad layer 4 are successively formed in one film forming process on the surface of the substrate 1 where the mesa structure is formed. When light is made incident on the end face of the part 3B of the optical waveguide layer corresponding to the bottom of the groove 5 or the part 3C of the optical waveguide layer corresponding to the top of the ridge 6, the light is confined and transmitted in the area 3B or 3C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric optical waveguide which can be used in various electronic optical devices and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional method for manufacturing a dielectric optical waveguide. Conventionally, as shown in FIG. 3A, TEOS-plasma-CV is formed on the upper surface of a semiconductor substrate 1 such as silicon.
The first clad layer 2 made of a dielectric layer such as SiO ₂ is formed by the D method or the like, and on the upper surface of the first clad layer 2,
An optical waveguide layer 3 made of a similar dielectric layer such as SiO ₂ having a refractive index higher than that of the first cladding layer 2 is deposited. In order to form the optical waveguide layer 3, for example, (O ₂ / TE) is selected from the film forming conditions for forming the first cladding layer 2.
Increase the supply ratio of OS) (increasing the flow rate of O ₂ )
By doing so, it is possible to continuously perform in the same chamber.

With the optical waveguide layer 3 formed, the optical waveguide layer 3 is once taken out of the film forming apparatus and is etched to form the optical waveguide layer 3 in a line shape as shown in FIG. 3B to form an optical waveguide line 3A. After forming the optical waveguide line 3A, it is returned to the film forming apparatus again, and the second cladding layer 4 having the same refractive index as the first cladding layer 2 is deposited and formed on the first cladding layer 2 and the optical waveguide line 3A. Obtain a dielectric optical waveguide.

[0004]

Conventionally, after forming the first cladding layer 2 and the optical waveguide layer 3, the semiconductor substrate 1 is once taken out from the film forming apparatus, and after the etching step, the film forming step is not performed again. Don't Therefore, there is a disadvantage that the manufacturing process is complicated. Further, conventionally, since the step of etching the optical waveguide layer 3, that is, the dielectric layer in a line shape is included as shown in FIG. 3B, the accuracy of this etching is affected by the accuracy of the mask formation and is therefore poor. Therefore, unevenness is formed on the side portion (etched surface) of the optical waveguide line 3A. When unevenness exists on the side portion of the optical waveguide line 3A, light is scattered on the uneven surface, which causes a drawback that the transmission efficiency deteriorates.

[0005]

According to the manufacturing method of the present invention, a line-shaped ridge or groove having a mesa structure is formed on the surface of a semiconductor substrate, and a first clad layer is formed on the surface on which the line is formed. Subsequently, a dielectric optical waveguide is manufactured by a step of forming an optical waveguide layer having a refractive index larger than that of the first cladding layer and having a thin film thickness, and depositing a second cladding layer on the optical waveguide layer. It is characterized by doing.

A feature of the manufacturing method according to the present invention is that an etching step for forming a linear convex line or a concave groove with a mesa structure in a semiconductor substrate is performed once, and a series of film forming steps is performed after the etching step. Since the first clad layer, the optical waveguide layer and the second clad layer are adhered and formed, the film forming step can be completed only once. Therefore, there is an advantage that the manufacturing time is shortened and the manufacturing is easy.

Further, according to the dielectric optical waveguide of the present invention, the optical waveguide layer 3 is thin, and the optical waveguide layer 3 is adhered to the top side portion of the mesa-shaped convex stripe or the bottom surface portion of the concave groove by bending. Light is confined in the optical waveguide layer to form an optical waveguide. Since the side part of this optical waveguide is regulated and formed on the surface formed by selectively etching the semiconductor substrate,
A smooth surface without irregularities is formed. As a result, an optical waveguide with high transmission efficiency can be obtained.

[0008]

1 shows the structure of a dielectric optical waveguide according to the present invention. The structure will be described below together with the manufacturing method. For example, linearly formed ridges or grooves having a mesa structure are formed on one surface of the semiconductor substrate 1 such as silicon. In the example shown in FIG. 1, the case where the concave groove 5 is formed is shown. For the etching of the semiconductor substrate 1, for example, selective etching in which the etching proceeds in the direction in which the <111> plane of the semiconductor is exposed is used.

After forming the concave groove 5, the semiconductor substrate 1 is inserted into the chamber of the film forming apparatus, and a thick film of SiO ₂ to be the first cladding layer 2 is formed by, for example, TEOS-plasma-CVD, and subsequently. The optical waveguide layer 3 is formed. The film formation of the optical waveguide layer 3 is performed with a large (O ₂ / TEOS) ratio (O ₂ / TEOS).
By increasing the number of ₂ ) and changing the film forming conditions, the optical waveguide layer 3 having a refractive index higher than that of the first cladding layer 2 can be formed. The film thickness of the optical waveguide layer 3 is, for example, about 1/10 of the film thickness of the first cladding layer 2, for example, 1 μm.
Form to about m.

After the time when it is predicted that the film thickness of the optical waveguide layer 3 has reached the desired film thickness, the film forming conditions are returned to the film forming conditions of the first cladding layer 2 and the second cladding layer 4 is formed. . The film forming process is terminated when a time period during which the film thickness of the second cladding layer 4 is predicted to reach a desired film thickness has elapsed. According to the dielectric optical waveguide manufactured by the above-described manufacturing method, when light is incident on the end face of the optical waveguide layer 3B in the concave groove 5, the light is confined in the optical waveguide layer 3B in the concave groove 5. Being propagated. In other words, the optical waveguide layer 3 is thin, and the optical waveguide layer 3 is defined by etching upward on both sides of the bottom surface of the groove 5.
Since the light is bent at an angle of 5 °, the light is confined in the optical waveguide layer 3B in the groove 5 by this bending and propagates in a low loss state.

In the above description, the case where the concave groove 5 is formed in the semiconductor substrate 1 has been described. However, as shown in FIG. 2, a convex line 6 having a mesa structure (trapezoid) is formed, and the first line is formed along the convex line. Even if the clad layer 2, the optical waveguide layer 3 and the second clad layer 4 are formed, dielectric light propagating while being confined in the optical waveguide layer 3C corresponding to the top surface portion of the ridge 6 in the same manner as described above. A waveguide can be obtained.

[0012]

As described above, according to the manufacturing method of the present invention, the first clad layer 2 and the optical waveguide layer 3 are formed in one film-forming step after the concave groove 5 is formed by etching.
And the second cladding layer 4 can be continuously formed. Therefore, the number of manufacturing steps can be reduced and the manufacturing time can be shortened. Therefore, the dielectric optical waveguide can be easily manufactured in a short time.

Further, the optical waveguide layers 3B and 3 which become the optical waveguides.
Since the side surface of C is defined by the surface formed by etching the semiconductor, the surface is formed as a smooth surface. Therefore, light is transmitted without being scattered, so that an optical waveguide with low loss can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a modified example of the present invention.

FIG. 3 is a cross-sectional view for explaining a conventional technique.

[Explanation of symbols]

 1 Semiconductor Substrate 2 First Cladding Layer 3 Optical Waveguide Layer 4 Second Cladding Layer 5 Recessed Groove 6 Relief Line

Claims (2)

[Claims] 1. A. First Embodiment A ridge or groove having a mesa structure formed on a semiconductor substrate; B. A first clad layer deposited on the surface where the ridges or grooves are formed; An optical waveguide formed on the upper surface of the first cladding layer and having a refractive index higher than that of the first cladding layer; The optical waveguide is formed on the surface on which the first waveguide is formed,
A dielectric optical waveguide comprising a second cladding layer having a refractive index equivalent to that of the cladding layer. 2. A step of forming a first clad layer on the surface where the convex or concave groove is formed after the step of forming the convex or concave groove of the mesa structure on the semiconductor substrate by etching, the first clad layer A step of forming an optical waveguide layer having a refractive index larger than that of the first cladding layer on the optical waveguide layer, and a step of forming a second cladding layer having the same refractive index as the first cladding layer on the optical waveguide layer. A method of manufacturing a dielectric optical waveguide according to claim 1, wherein the dielectric optical waveguide is manufactured by performing the steps continuously and performing one etching step and one film forming step.