JPH10160955A - Formation of optical waveguide mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve plane accuracy, to obtain desired consistent accuracy at the time of mass production and to improve productivity by forming an island-shaped region and hinterland region at the ends of optical waveguides and pushing down the island-shaped region to fix the region to the hinterland region or a dielectric substrate. SOLUTION: The optical waveguide 2A is formed on the dielectric substrate 1. The optical waveguide 2A is subjected to FIB processing by a convergent ion beam processing device to form a spacing 2B of a width W1 and spacing 2C of a width W2 at the two points in mid-way of the optical waveguide 2A, by which the island-shaped region 9 and the hinterland region 10 are formed. When an adhesive 11 is dropped to the spacing 2B, the island-shaped region 9 falls down to the hinterland region 10 by surface tension. The island-shaped region 9 does not incline any more where the island-shaped region comes into contact with the hinterland region 10 and simultaneously the island-shaped region 9 is fixed diagonally by the adhesive 11, by which the optical waveguide mirror 9A is formed. The guided light L propagating in the optical waveguides 2A is reflected perpendicular upward by the mirror 9A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an optical waveguide mirror in an optoelectronic integrated circuit required in the fields of optical communication and optical information processing. The present invention relates to a method for forming an optical waveguide mirror that improves productivity by obtaining accuracy.

[0002]

2. Description of the Related Art At present, in optical communication systems and optical disk systems, bulk-type individual components are used as optical components such as microlenses and prisms. There are problems such as being easily affected optically by the environment such as temperature and vibration, and being unable to be miniaturized or mass-produced.

In recent years, research on so-called optoelectronic integrated circuits, in which optical components are thinned and arranged side by side with electronic components on a single substrate, has been actively pursued.

In an optoelectronic integrated circuit, a thin film optical waveguide having a higher refractive index than the surroundings is formed on a substrate in a predetermined pattern, and when the guided light in the optical waveguide is taken out to the surface of the substrate, a predetermined light is introduced into the optical waveguide. Is formed by forming an optical waveguide mirror having an inclination angle of.

[0005] As a conventional method of forming an optical waveguide mirror,
For example, there is one disclosed in JP-A-6-265738.

FIGS. 4A to 4F show a method of forming the optical waveguide mirror. The method of forming the optical waveguide mirror is as follows.
First, as shown in FIG. 4A, an optical waveguide core material 2 made of a fluorinated polyimide material or the like is formed on a dielectric substrate 1 made of a thermally oxidized silicon substrate or the like. Next, as shown in FIG. 4B, an etching mask 3 made of a silicon-based positive photoresist or the like is formed on the optical waveguide core material 2. Thereafter, as shown in FIG. 4C, the size or the density of the opening in the light propagation direction, that is, the optical waveguide pattern partially having the mask pattern 4 in which the amount of light transmission gradually changes. A photomask 6 having a plurality of linear patterns 5 is formed on the etching mask 3. Further, FIG.
As shown in (d), the exposed portion of the etching mask 3 is exposed to light to cause a structural change, and is dissolved by a solvent treatment to form the etching mask 3 into a linear pattern 5.
And an inclined surface 7 proportional to the amount of light transmitted through the mask pattern 4 of the photomask 6 is formed on each of the patterns. Finally, as shown in FIG. 4E, etching is performed by reactive ion etching or the like using oxygen plasma to form an optical waveguide 2A having a pattern corresponding to the pattern of the etching mask 3. At this time, since the etching mask 3 is also etched, an optical waveguide mirror 8 corresponding to the inclined surface 7 of the etching mask 3 is formed on the optical waveguide 2A as shown in FIG.

The optical waveguide mirror 8 manufactured as described above
According to the above, the guided light L propagating through the optical waveguide 2A can be reflected in the direction of the surface of the dielectric substrate 1 (vertically upward in the figure).

[0008]

However, according to the conventional method of forming an optical waveguide mirror, in order to expose an etching mask such that the amount of exposure gradually changes, ultraviolet light having a uniform illuminance distribution is illuminated. Although it is necessary to pass through a mask pattern finer than the resolution of the optical system, it is difficult to design such a mask pattern, and the amount of data of the pattern is enormous, which is not realistic. Therefore, there is a problem that it is difficult to expose the etching mask such that the exposure amount changes gradually. Further, since the etching rate of the etching mask and the etching rate of the core material of the optical waveguide are not exactly the same, there is a problem that it is difficult to transfer the inclined surface of the etching mask to the optical waveguide. By optimizing the process conditions such as reactive ion etching, the etching rate is somewhat 1: 1.
However, it is difficult to make the ratio 1: 1 accurately over the entire substrate due to variations in the manufacturing conditions of the etching mask and the optical waveguide core material. Such a problem on exposure and a problem on etching tend to cause a curved surface on the inclined surface functioning as a mirror, and the accuracy in mass production is apt to vary, which causes a decrease in productivity.

Therefore, an object of the present invention is to provide a method of forming an optical waveguide mirror which can improve the productivity by improving the planar accuracy and obtaining a desired constant accuracy in mass production. is there.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in order to improve the flatness and to obtain a desired constant accuracy in mass production to improve productivity.
In the method of forming an optical waveguide mirror for forming an optical waveguide mirror that reflects the guided light of the optical waveguide at the end of the optical waveguide formed on the dielectric substrate, a processing method capable of performing a highly straight cutting process in the vertical direction. Forming a first gap at the end of the optical waveguide and a second gap located behind the first gap to form an island region and a back region, and the island region leans against the back region. It is an object of the present invention to provide a method of forming an optical waveguide mirror in which an island region is tilted in such a manner and the island region is fixed to a back region or a dielectric substrate.

In the formation of the island region and the back region, the widths of the first and second gaps are set so that the aspect ratio determined by the relationship between the width and height of the island region becomes a predetermined value. It is preferred to do so.

The formation of the island region and the back region is preferably performed by electron beam processing or ion beam processing.

The formation of the island region and the back region is preferably performed by forming an etching mask on the optical waveguide and thereafter performing etching by a dry etching method.

In the formation of the island region and the back region, the ratio of the thickness of the optical waveguide to the width of the second gap is determined.

(Equation 2) It is preferable to perform so that

The above-mentioned island-like region is lowered by the surface tension of the adhesive dropped into the second gap, and the above-mentioned island-like region and the back region or the dielectric substrate is fixed by the adhesive. Is preferred.

Hereinafter, a method for forming an optical waveguide mirror according to the present invention will be described in detail with reference to the accompanying drawings.

[0017]

1 (a) to 1 (c) show a method for forming an optical waveguide mirror according to a first embodiment of the present invention. First, an optical waveguide core material is formed on a dielectric substrate, and the optical waveguide core material is formed into a plurality of linear patterns.
As shown in (a), an optical waveguide (core) 2A having a predetermined thickness d is formed on the dielectric substrate 1. Next, as shown in FIG. 1 (b), the optical waveguide is formed by a processing method capable of performing notch processing with high linearity in the vertical direction, for example, electron beam processing, ion beam processing, or dry etching processing by photolithography. Width w _{1 at} two places in the middle of 2A
By forming a gap 2B and gap 2C width w _2,
Island region 9 having a width w ₃ and a vertical side wall surface with high flatness
And the back region 10 is formed. Finally, as shown in FIG. 1 (c), the island region 9 is tilted so as to lean on the back region 10, and the island region 9 is fixed to the back region 10 to form an optical waveguide mirror 9A.

Here, the width w ₃ of the island region 9 is set so as to increase the aspect ratio of the island region 9, that is, the ratio d / w ₃ to the film thickness d of the optical waveguide 2A. The width w ₂ of the gap 2B is set according to the inclination angle of the optical waveguide mirror 9A determined by consideration of the thickness d of the optical waveguide 2A. Usually, the inclination angle of the optical waveguide mirror 9A is set to 45 degrees so as to reflect light vertically upward.
The ratio of the film thickness d of A to the width w ₂ of the gap 2B is

(Equation 3) Is set to be

The optical waveguide mirror 9 manufactured as described above
According to A, the guided light L propagating through the optical waveguide 2A is
The light can be reflected in a predetermined direction (vertically upward in the figure) on the opposite side to the dielectric substrate 1.

As described above, in the first embodiment, the island-like region 9 and the back region 10 having a high flatness of the side wall surface are formed in the optical waveguide 2A by a processing method capable of performing a cutting process with high straightness in the vertical direction. Since the optical waveguide mirror 9A is formed by tilting the island-shaped region 9 to the back region 10, the planar accuracy of the optical waveguide mirror 9A can be improved, and a desired constant accuracy can be obtained during mass production.

[0021]

Embodiment 1 Hereinafter, a first embodiment of a method for manufacturing an optical waveguide mirror according to the present invention will be described with reference to FIG.

First, polyimide or PMMA (methyl methacrylate polymer) is applied on a Si wafer having an oxide film formed on the surface or a dielectric substrate formed of a glass substrate (Corning 7059) by a spin coating method and baked. The optical waveguide core material has a thickness d of 10 μm. In this embodiment, a fluorinated polyimide (manufactured by Hitachi Chemical) having high light transmittance and excellent heat resistance is used. Then, the optical waveguide is formed by forming the optical waveguide core material into a plurality of linear patterns using a normal photolithography method. FIG. 2A shows one of them.
2 shows a cross section of the book in the light propagation direction, in which an optical waveguide 2 </ b> A is formed on a dielectric substrate 1.

Next, a focused ion beam (hereinafter simply referred to as FI
Formed by B hereinafter) processing unit, subjected to FIB processing to the optical waveguide 2A, as shown in FIG. 2 (b), a gap 2C gap 2B and the width w ₂ of width w ₁ in the middle two positions of the optical waveguide 2A By doing so, the island-shaped region 9 and the back region 10 are formed.
The FIB processing has good beam straightness and the processed surface has very good flatness, so that the side wall surface of the island-shaped region 9 is a good mirror surface. The width w1 of the gap 2B is ₁ μm,
The width w ₂ of C was 7 [mu] m, a width w ₃ of the island region 9 and 2 [mu] m. In the present embodiment, FIB processing is used, but a side wall having high flatness can be obtained by electron beam processing.

Thereafter, a photocurable adhesive is applied to the tip of a needle (not shown). Then, as shown in FIG. 2C, the adhesive 11 is dropped into the gap 2B. The adhesive 11 may be dropped with a micro dispenser. When the adhesive 11 is dropped into the gap 2B in this manner, the island region 9 falls down to the back region 10 due to surface tension. When the island region 9 comes into contact with the back region 10, the island region 9 is no longer tilted. At the same time, the island region 9 is fixed obliquely by the adhesive 11, and as shown in FIG. Is formed. In this embodiment, since the thickness d of the optical waveguide 2A is 10 μm and the width w _{3 of the} gap 2C is 7 μm,
The island region 9 has a 45 degree inclination. Therefore, the optical waveguide 2
The guided light L that has propagated through A is reflected vertically upward by the optical waveguide mirror 9A.

[0025]

Embodiment 2 Hereinafter, a second embodiment of the method for forming an optical waveguide mirror according to the present invention will be described with reference to FIG.

First, polyimide or PMMA (methyl methacrylate polymer) is applied on a Si wafer having an oxide film formed on its surface or a dielectric substrate made of a glass substrate (coming 7059) by a spin coating method and baked. Thus, an optical waveguide core material having a film thickness d of 10 μm is formed (FIG. 3A). In this embodiment, a fluorinated polyimide (manufactured by Hitachi Chemical) having high light transmittance and excellent heat resistance is used.

Next, as shown in FIG. 3B, a plurality of linear optical waveguides 2 are formed by ordinary photolithography.
A and a photoresist pattern 12 corresponding to an island-shaped region 9 and a back region 10 described later are formed as an etching mask. Then, as shown in FIG. 3 (c), reactive ion etching (RIE) gap 2C gap 2B and the width w ₂ of width w ₁ by anisotropic dry etching in the middle two positions of the optical waveguide 2A, such as By forming, the island-shaped region 9 and the back region 10 are formed. Anisotropic dry etching by RIE or the like can perform processing with high straightness in the vertical direction, and the processed surface has very good flatness, so that the side wall surface of the island-shaped region 9 becomes a good mirror surface. The width w _{1 of the} gap 2B is set to 1 μm.
m, 7 [mu] m width w ₂ of the gap 2C, the width w ₃ of the island region 9 was 2 [mu] m. In this embodiment, a photoresist is used as an etching mask. However, a metal such as Al may be deposited and patterned to form an etching mask.

In this manner, the island region 9 and the back region 10
Is formed, the photoresist pattern 12 is removed as shown in FIG.

Thereafter, a photocurable adhesive is applied to the tip of a needle (not shown). Then, as shown in FIG. 3E, the adhesive 11 is dropped into the gap 2B. The adhesive 11 may be dropped with a micro dispenser. When the adhesive 11 is dropped into the gap 2B in this manner, the island region 9 falls down to the back region 10 due to surface tension. When the island-shaped region 9 comes into contact with the back region 10, the island-shaped region 9 is no longer tilted. At the same time, the island-shaped region 9 is fixed obliquely by the adhesive 11, and as shown in FIG. Is formed. In this embodiment, since the thickness d of the optical waveguide 2A is 10 μm and the width w _{3 of the} gap 2C is 7 μm,
The island region 9 has a 45 degree inclination. Therefore, the optical waveguide 2
The guided light L that has propagated through A is reflected vertically upward by the optical waveguide mirror 9A.

[0030]

As described above, according to the method for forming the optical waveguide mirror of the present invention, the island-like region and the back region are formed at the end of the optical waveguide by a processing method capable of performing a notch processing with high linearity in the vertical direction. It is formed and fixed to the back region or the dielectric substrate by tilting the island region, so that the planar accuracy is improved and the desired constant accuracy is obtained at the time of mass production, thereby improving the productivity. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method for forming an optical waveguide mirror according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a method for forming the optical waveguide mirror according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a method for forming an optical waveguide mirror according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional method for forming an optical waveguide mirror.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 dielectric substrate 2 optical waveguide core material 2A optical waveguide 2B, 2C gap 3 etching mask 4 photomask 5 linear pattern 6 mask pattern 7 inclined surface 8 optical waveguide mirror 9 island region 9A optical waveguide mirror 10 back region 11 adhesive 12 Photoresist pattern L guided light w _{1 to} w ₃ width d film thickness

Claims (6)

[Claims] 1. A method of forming an optical waveguide mirror for forming an optical waveguide mirror for reflecting guided light of an optical waveguide at an end of the optical waveguide formed on a dielectric substrate, wherein the optical waveguide mirror has high linearity in a vertical direction. A first gap formed at an end of the optical waveguide by a processing method capable of performing notch processing;
Forming an island-shaped region and a back region by forming a second gap located behind the gap, and tilting the island region so that the island region leans against the back region, A method of forming an optical waveguide mirror, comprising fixing an area to the rear area or the dielectric substrate. 2. The method according to claim 1, wherein the island region and the back region are formed by:
2. The method for forming an optical waveguide mirror according to claim 1, wherein the width of the first and second gaps is set such that an aspect ratio determined by the relationship between the width and height of the island region is a predetermined value. . 3. The formation of the island region and the back region,
2. The method for forming an optical waveguide mirror according to claim 1, wherein the method is performed by electron beam processing or ion beam processing. 4. The formation of the island region and the back region,
2. The method for forming an optical waveguide mirror according to claim 1, wherein the etching is performed by forming an etching mask on the optical waveguide and thereafter performing etching by a dry etching method. 5. The formation of the island region and the back region,
The ratio of the thickness of the optical waveguide to the width of the second gap is given by: 2. The method for forming an optical waveguide mirror according to claim 1, wherein 6. The tilting of the island-shaped region is performed by surface tension of an adhesive dropped into the second gap, and the fixing of the island-shaped region and the back region or the fixing of the dielectric substrate is performed by 2. The method for forming an optical waveguide mirror according to claim 1, wherein the method is performed with an adhesive.