JPS635310A - Production of optical connecting circuit - Google Patents

Abstract

PURPOSE:To permit the formation of an optical fiber fixing groove with good accuracy even on a stepped substrate by forming the groove for fixing the optical fiber to the position where the central axis of an optical waveguide and the central axis of the optical fiber align to each other. CONSTITUTION:The worked substrate 1 is immersed into a vessel 9 contg. a KOH etching soln. 8 and a laser beam 11 emitted from an Ar laser 10 is projected through a reflecting mirror 12 and a condenser lens 13 at a spot of smallest 3mum to the substrate 1. The spot diameter can be adjusted and the beam can be set to a desired start position by using an observation optical system 14 and changing the focal position. The vessel 9 is fixed onto a precision moving table 15. The optical waveguide having a desired shape and pattern and the V groove 7 for fixing the optical fiber are formed by controlling the extent of the movement of the table 15 and the output of the Ar laser 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical connection circuit used in optical integrated circuits and the like, and particularly to an optical connection circuit between an optical fiber and an optical waveguide on a silicon substrate.

[Conventional technology]

With the development of optical communications, various optical circuits are being developed in which optical functional elements such as semiconductor lasers and optical switches are assembled and stacked on a substrate in a hybrid circuit, and these elements are connected by all-optical waveguides. There is a demand for optical connection circuits between these optical circuits and optical fibers, or between optical circuits and optical fiber arrays, and in particular, optical connection circuits with high precision and high productivity.

Many methods have been proposed for such optical connection circuits, one of which is the silicon/(1
00) An optical waveguide 6 is formed on the substrate 1, and a groove 7 of a desired size is made of silicon (
100) An optical fiber 18 is formed on the substrate 1, and an optical fiber 18 is formed in this V-groove 7.
A method is known in which alignment is performed by inserting.

Conventionally, this V-groove for fixing optical fibers has been formed using photolithography technology after forming an optical waveguide.

1. Pattern it as a mask and use anisotropic etching of silicon with an etching solution such as KOH to
1> Formed with exposed crystal planes. However, when a resist pattern with grooves is fabricated using photolithography technology, there is a step between the optical waveguide and the silicon (100) cover plate by the thickness of the optical waveguide. This level difference is more than 10 μm for single mode optical waveguide and 80 μm for multimode optical waveguide.
It will be about m. Therefore, there are disadvantages that a good resist pattern cannot be obtained because the photoresist cannot be applied uniformly, and a gap occurs between the photomask and the photoresist, which deteriorates the resolution of the pattern.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional manufacturing method for optical connection circuits, there is a step between the optical uniform wave path and the silicon (100) substrate, which makes it difficult to obtain a good resist pattern and deteriorates the processing accuracy of the V-groove. Problems such as an increase in loss in the connected circuit and variations in loss occur. Furthermore, since photolithography technology is used, many pretreatment steps such as photomask production and resist patterning are required.

[Means for Solving the Problems] The method for manufacturing an optical connection circuit of the present invention includes a thermally reactive etching liquid bath in which a silicon substrate on which an optical waveguide is formed is immersed, and a laser beam that irradiates the silicon substrate with a laser beam. It has a beam irradiation means and a moving means for moving the irradiation position of the laser beam on the silicon substrate, and fixes the optical fiber at a position where the central axis of the optical waveguide and the central axis of the optical fiber coincide. This is realized by forming a groove.

[Effect]

A silicon substrate is immersed in a thermally reactive etching solution, such as a KOH solution, and a focused laser beam is irradiated to partially heat the silicon substrate, thereby inducing a local etching reaction.

Hereinafter, this etching method will be referred to as laser unstretched etching. According to the above laser unstooth etching, even a substrate with a step on the surface can be processed with high precision by adjusting the focal position of the beam.

Furthermore, it is possible to process not only the 710-meter process on a Noricon substrate, but also the 4-wave optical layer on a silicon substrate at the same time. Furthermore, since the etching method does not use a mask, the process can be significantly shortened and the pattern can be changed much more easily.

〔Example〕

Hereinafter, a method for manufacturing an optical connection circuit according to the present invention will be explained with reference to the drawings.

FIG. 1 is a process diagram showing a first embodiment of the present invention. In this embodiment, not only the groove for fixing the optical fiber but also the optical wave path is formed at the same time. In the process shown in FIG. 3(a), a buffer 7 layer 2, an optical waveguide layer 3,
After forming the cladding layer 4, a method such as reactive ion etching is used to expose the silicon surface of the portion where the optical fiber fixing groove will be formed, and at the same time form the waveguide end face.

Next, in the step shown in FIG. 6(b), the substrate 1 is immersed in a KOH etching solution, irradiated with a laser beam, and heated locally to locally induce an etching reaction (described later). . Etching is performed linearly by moving the laser beam irradiation position.

In this manner, the optical fiber fixing V-groove 7 is formed by laser assisted etching, but the (111) plane and (111) plane of the silicon are exposed due to the etching anisotropy of the KOH etching solution with respect to silicon.

The narrow grooves 5a and 5b are also formed by this laser-assisted etching, and the portion sandwiched between the narrow grooves 5a and 5b becomes the optical waveguide 6.

FIG. 2 is an explanatory diagram showing an apparatus for forming optical waveguides and V-grooves for fixing optical fibers by laser-assisted etching. In the figure, a substrate 1 processed up to the step shown in FIG. 1(a) is immersed in a container 9 containing a KOH etching solution 8. As shown in FIG. The laser beam 11 emitted from the Ar laser 10 passes through a reflecting mirror 12 and a focusing lens 13 and is irradiated onto the substrate 1 with a minimum spot diameter of 3 μm. Furthermore, by changing the focal position using the observation optical system 14, the spot diameter can be adjusted and the beam can be set at a desired starting position.

The container 9 is fixed on a precision moving table 15, and by controlling the amount of movement of this precision moving table 15 and the output of the Ar laser 1o, an optical waveguide with a desired shape and pattern and a V-groove 7 for optical fiber identification are formed. can be formed.

In the step of FIG. 1(b), the buffer layer 2 is made of thermally oxidized Si.
The optical waveguide layer 3 is a glass thin film with a refractive index of about 1.5 (film thickness 2.2 μm) formed by sputtering.
m), the cladding layer 4 is sputtered 8i0. (film thickness 1.0μ
m), the output of the Ar laser 10 is set to IW%, the movement speed of the precision moving table 15 is about 100 to 500 μm/see,
A good optical waveguide pattern can be obtained by setting the spot diameter to several μm. Further, when creating the V-groove 7 for fixing the fiber, the output is 3 W, the moving speed is 25 to 100 μm/g, and the spot diameter is several μm.

However, since the above-mentioned etching conditions depend on the film thickness and etching resistance of the film, it is necessary to adjust the etching conditions in accordance with the desired dimensions.

FIG. 3 is a process diagram showing a second embodiment of the present invention. In this embodiment, the optical fiber fixing groove is formed by mirror laser assisted etching.

After forming a buffer layer 2, an optical waveguide layer 3, and a cladding layer 4 on a silicon (too) substrate in the process shown in FIG. At the same time, the optical waveguide 6 is formed at the same time as exposing the silicon surface of the portion to be formed.

Next, in the step of FIG.

FIG. 4 is a perspective view showing a third embodiment of the present invention. In the figure, by using a silicon (111) substrate 16 as the substrate, a rectangular groove 17 is used as an optical fiber fixing groove.
form.

In the above embodiments, an Ar laser was used as the laser light source, but the invention is not limited to this; other lasers in a wavelength range that can pass through the etching solution and heat the silicon substrate, such as a YAG laser, may be used. You can also do it. It is also possible to perform etching while moving the laser beam instead of moving the substrate using a precision moving table.

〔Effect of the invention〕

As explained above, according to the method of manufacturing an optical connection circuit of the present invention, it is possible to form optical fiber fixing grooves with high precision even on a substrate with steps.

Furthermore, the process for producing optical connection circuits can be significantly shortened.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(a) and ('b) are perspective views showing the steps of the first embodiment of the present invention, and FIG. 2 is an explanation of the method of forming an optical fiber fixing groove of the present invention. 3(a) and (b) are perspective views showing the steps of the second embodiment of the present invention, FIG. 4 is a perspective view showing the third embodiment of the present invention, and FIG. 5(a) ) and (b
) are a perspective view and a sectional view showing the connection between an optical waveguide and an optical fiber. 1... Silicon (100) substrate, 2゛°°°“
°Buffer layer, 3... Optical waveguide layer, 4...
- Cladding layer, 5a. 5b... Thin groove, 6... Optical waveguide, 7.
...V groove for fixing optical fiber, 8...KOH
Etching liquid, 9. Container for etching liquid, 10
...Ar laser, 11 ... Laser beam, 12 ... ° ... Reflection mirror, 13 ... Focusing lens, 14 ... Observation optical system, 15...
...Precision moving table, 16...Silicon (111)
Substrate, 17... Square groove for fixing optical fiber, 18...
...Optical fiber, 19...Optical fiber core. '-1 3 1. -Itun Figure 1 (required) Figure 2-~14 Figure 13 (of) Figure 4

Claims (1)

[Scope of Claims] A thermally reactive etching liquid bath in which a silicon substrate on which an optical waveguide is formed is immersed, a laser beam irradiation means for irradiating the silicon substrate with a laser beam, and irradiation of the laser beam on the silicon substrate. a moving means for moving the optical fiber, and forming a groove for fixing the optical fiber at a position where the central axis of the optical waveguide and the central axis of the optical fiber coincide. .