JPH05210019A - Formation of waveguide - Google Patents

Abstract

PURPOSE:To make a waveguide pattern smooth by reducing thermal damage. CONSTITUTION:A lower clad layer 125 and a core layer are laminated on a silicon substrate 110 and dry etching is carried out according to a specific pattern so that the laminated part is left, thereby forming the waveguide pattern 180. Light 170 from a carbon dioxide laser is converged to locally fuse a roughened part 210. Further, other roughened parts 210 are locally fused by the scanning of the light 170 through a lens 160. The roughened parts which are fused are solidified roundly to become smooth. An upper clad layer 120 is deposited and sintered to embed the waveguide pattern 180.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide which is one of optical components in the field of communication information processing.

[0002]

2. Description of the Related Art As a method for producing a waveguide, there is "Optical No. 1".
Volume 8 No. 12 (1989.12) p.681 ”is generally used. A brief description of this method is as follows. A lower clad layer and a core waveguide layer are laminated on the substrate. Next, the core waveguide layer is etched so as to leave a predetermined pattern to process the waveguide pattern. Then, the upper clad layer is laminated to form a waveguide.

[0003]

In the above-described method for producing a waveguide, the waveguide pattern is processed by etching. At this time, rough portions such as cracks are generated in the waveguide pattern due to fine particles in the air, optical phenomena such as scattering and diffraction, and chemical phenomena such as surface irregularities. Light traveling in the waveguide is scattered by this rough portion, resulting in loss. As a countermeasure against this, there is known a method in which after the waveguide pattern is processed, the entire substrate is heated to make the rough portion of the waveguide pattern circular. However, this method has a problem in that the impurity concentration inside the waveguide pattern is entirely changed and the substrate and the clad layer are distorted due to thermal damage during heating. In addition, when this waveguide is formed inside the optical IC, other integrated elements are also thermally damaged.
As described above, the waveguide is important as a basic technique of the optical IC, but has the above-mentioned problems.

In view of the above-mentioned problems, it is an object of the present invention to provide a waveguide which reduces thermal damage, smoothes the waveguide pattern, and has a small loss.

[0005]

In order to solve the above-mentioned problems, the method for producing a waveguide of the present invention is to provide a predetermined waveguide pattern after laminating a lower clad layer and a core waveguide layer on a substrate, After the light from the light source is melted in the rough portion of the waveguide pattern of the waveguide pattern, a clad layer having a smaller refractive index than the waveguide pattern is further formed on the substrate.

[0006]

In the method of forming a waveguide of the present invention, the condensed light from the light source is condensed on the rough portion of the waveguide pattern, and only the rough portion is melted. This rough part becomes round and solidified. When a clad layer having a smaller refractive index than the waveguide pattern is further formed on the substrate, a waveguide having a smooth waveguide pattern as a core is formed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of the steps of one embodiment of the present invention. The process will be described with reference to this figure.

First, a silicon substrate (Si substrate) 110 is thermally oxidized for a predetermined time to form SiO ₂ to form a lower clad layer 125, and then a flame deposition method (F) is used (FIG. 1A).
S) with a predetermined impurity concentration distribution in HD) and a high refractive index
A core layer 150 of iO ₂ is formed to a thickness of about 10 μm (see FIG. 1).
(B)). Next, a waveguide pattern 180 is formed by dry etching according to a predetermined pattern so as to leave that portion (FIG. 1C). Then, light is incident from the end of the waveguide pattern 180. At this time, if the waveguide pattern 180 has jaggedness, unevenness, cracks, etc., the light is scattered there and is observed from the substrate. The light 170 from the carbon dioxide laser is focused on the rough portion 210 by the lens 160, and the rough portion 210 is partially melted (FIG. 2D). The melted rough portion 210 is rounded and solidified, and becomes smooth.

Next, the light 170 and the lens 160 are scanned and moved to another rough portion observed from the substrate, and that portion is melted. In the rough portion, a portion formed by melting and solidifying once is formed, and a smooth waveguide pattern 180 is formed (FIG. 2E). afterwards,
An upper clad layer 120 of SiO ₂ having a low refractive index doped with fluorine by FHD or CVD is deposited and sintered to fill the waveguide pattern 180 (FIG. 2 (f)).
Then, the ends are polished and exposed.

The waveguide thus formed has a smooth core, and scattering of light traveling in the waveguide is suppressed, resulting in a small loss. Further, after the formation of the waveguide pattern, the roughened portion of the waveguide pattern is irradiated with the light of the gas laser focused and melted, thereby partially melting and smoothing. As a result, the entire substrate is not heated and there is almost no thermal damage. Therefore, the change in the impurity concentration distribution is suppressed, and the initial state is kept good. Further, distortion of the substrate or the clad layer is suppressed. In particular,
When used in an optical IC, it is possible to manufacture a good optical IC with almost no thermal damage to various elements of optical parts (electronic parts in a photoelectric integrated circuit) mounted on the IC. It will be possible.

The present invention is not limited to the above-described embodiment, but can be variously modified.

For example, a carbon dioxide gas laser is used as the light source because the absorption wavelength band is matched, but another light source may be used as long as it can melt the waveguide pattern. Further, SiO ₂ having a predetermined impurity concentration distribution thermal oxidation SiO ₂ core lower clad layer, but the upper cladding was SiO ₂ in the fluorine-doped, or in other combinations if the same index difference. Furthermore, silicon is used for the substrate because it has a high melting point and good thermal conductivity, but the substrate is not limited to this.

[0013]

As described above, according to the method for producing a waveguide of the present invention, the light from the light source is condensed and the rough portion of the waveguide pattern is locally melted to form a round shape. It is possible to suppress the scattering of light traveling in the inside and reduce the loss. Further, since the roughened portion is locally melted, thermal damage can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of the process of the present invention.

FIG. 2 is a schematic view of the process of the present invention.

[Explanation of symbols]

110 ... Si substrate, 120 ... Upper clad layer, 125 ...
Lower cladding layer, 180 ... Waveguide pattern, 190 ... Rough portion.

Claims (1)

[Claims] 1. A lower clad layer is formed on a substrate, and then, a core layer having a refractive index larger than that of the lower clad layer is formed, and then a predetermined waveguide pattern is provided to allow light from a light source to pass through the waveguide pattern. After condensing on the rough portion to melt the rough portion of the waveguide pattern, a clad layer having a refractive index smaller than that of the waveguide pattern is further formed on the substrate. How to make.