JP3031176B2 - Optical fiber guiding structure and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber guide structure, and more particularly to an optical fiber guide structure used for various control systems for industrial use, a wiring system between computer devices, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In order to form an optical circuit by connecting optical circuit elements with each other by an optical fiber, it is necessary to precisely align the core of the optical fiber with the optical axis of the optical circuit element. An optical fiber guide structure is used to facilitate alignment of the optical fiber core with the optical circuit element. For example, at the end of an optical integrated circuit such as an integrated optical switch or an optical coupler, an optical multi-core connector is used to collectively connect a plurality of optical fibers corresponding to a plurality of optical waveguides. . At that time, connection loss occurs at the connection between the optical waveguide and the optical fiber. The connection loss is preferably smaller as the optical axes of the optical waveguide and the optical fiber coincide.
Therefore, there is a demand for an optical multi-core connector capable of accurately setting the fixing position of the optical fiber.

Conventionally, as an optical multi-core connector, there is a connector in which a V-shaped groove is formed in a semiconductor substrate made of silicon (Si), gallium arsenide (GaAs) or the like by an anisotropic etching method. FIG. 10 is a cross-sectional view showing such a V-groove type optical fiber guiding structure 28, in which an optical fiber 29 is fixed along a plurality of V-shaped grooves 27 formed on an upper portion of a substrate 21. use. In addition, a plurality of optical elements such as a light source, a polarizer, and a collimator are arranged on a substrate so as to be aligned on a predetermined optical axis, and a V-groove is similarly formed in order to connect these optical elements with an optical fiber. The formed substrate is used. That is, each optical element can be optically connected by fixing the optical fiber in the V-groove.

In the above-described method of forming the V-shaped groove 27 of the optical fiber guide structure 28, the orientation of the substrate surface is (100).
Silicon oxide (Si)
It is covered with a mask material such as O ₂ ), platinum (Pt), or titanium (Ti), and windows having a predetermined width are opened at predetermined intervals by a photolithography method. Subsequently, an aqueous solution of potassium hydroxide, an aqueous solution of ethylenediamine-pyrocatechol,
Etching is performed in an anisotropic etching solution such as a hydrazine aqueous solution. As a result, a groove 27 having a V-shaped cross section is formed.

[Problems to be solved by the invention]

In such an optical fiber alignment V-groove structure, since the optical fiber 29 is fixed by the two inclined surfaces 27a and 27b of the V-shaped groove 27, the dimensional accuracy of the V-shaped groove 27 is not high and the opening width is not large. Even if there is a variation in 27c, the position of the optical axis 29a of the optical fiber 29 hardly changes in the horizontal direction. However, if the opening width 27c is too wide, the position of the optical axis 29a of the optical fiber 29 is lowered. Conversely, if the opening width 27c is too narrow, the optical axis 29 of the optical fiber 29 is lowered.
The position of “a” rises, and the position of the optical axis 29 a of the optical fiber 29 greatly changes in the vertical direction.

By the way, it is easy to extend the end of the optical waveguide in the horizontal direction, so that the horizontal accuracy of the optical multi-core connector does not cause much problem. However, it is difficult to extend the end of the optical waveguide in the vertical direction, and in the optical multi-core connector, particularly, the positioning accuracy of the optical axis in the vertical direction is required.

Further, with respect to optical elements such as a light source, a polarizer, and a collimator that do not take the shape of an optical waveguide, it is impossible to reduce the influence of the optical axis shift due to the change in the end shape of the optical waveguide as described above. The positioning accuracy of the optical axis in both the horizontal and vertical directions is required.

However, when the V-shaped groove is formed by the anisotropic etching method, the presence of residual stress or crystal defects in the substrate, and the fact that the reaction rate in the etching solution is not constant depending on the location of the substrate. Therefore, it is inevitable that the opening width of the V-shaped groove has a certain degree of variation. As a result, when an optical fiber is used to connect the optical multi-core connector described above or an optical element aligned on a substrate to a predetermined optical axis with an optical fiber, the optical axis positioning accuracy is ± 0.5 μm. Was the limit. Therefore, the conventional optical fiber guide structure has a large connection loss due to the vertical fluctuation of the core position of the optical fiber, and also needs to adjust the optical fiber guide structure to an optimal position where the connection loss is as small as possible. It took a lot of trouble.

The present invention has been made in view of the above-mentioned circumstances, and has excellent dimensional accuracy not only in the horizontal direction but also in the vertical direction with respect to the fixing position of the optical fiber, and has a small connection loss.
It is an object of the present invention to provide an optical fiber guide structure that can be easily aligned and aligned, and a method of manufacturing the same.

[0010]

According to the present invention, there is provided an optical fiber guiding structure comprising a silicon single crystal surface layer (1) on a surface of a substrate having or near a silicon single crystal layer.
11) The same high-concentration p-type diffusion layer and the same silicon oxide layer having a plurality of grooves cut parallel to the plane, and the bottom surfaces of the plurality of grooves are buried under the surface of the substrate. Or the same silicon layer forming the lower layer of the silicon oxide layer.

In this case, the plane orientation of the silicon single crystal layer is (100), the surface of the substrate is on the (100) surface of the substrate, and the cross-sectional shape of the groove is substantially inverted trapezoid. Is preferred.

The plane orientation of the silicon single crystal layer is (110), and the surface of the substrate is (11).
0) on the surface, and the cross-sectional shape of the groove is preferably rectangular.

In the method for manufacturing an optical fiber guide structure according to the present invention, a high-concentration p-type diffusion layer is formed on a silicon single-crystal substrate surface, and the silicon single-crystal substrate is formed on the high-concentration P-type diffusion layer. Non-doped, n-type having the same crystal orientation,
Alternatively, after forming a low-concentration p-type silicon single crystal film to a predetermined thickness and forming a mask layer on the silicon single crystal film, the longitudinal direction of the mask layer portion is (111) of the silicon single crystal substrate. A) removing a part of the groove parallel to the plane, and then removing the silicon single crystal film part whose surface is exposed by removing the mask layer, thereby making the bottom surfaces of the plurality of grooves the same.
Characterized by being formed of a high-concentration p-type diffusion layer .

In this case, it is preferable that the orientation of the silicon single crystal substrate is (100).

It is preferable that the orientation of the silicon single crystal substrate is (110).

Further, in the method for manufacturing an optical fiber guide structure according to the present invention, the two substrate surfaces of a silicon substrate and a silicon single crystal seed substrate are oxidized, and the two substrate surfaces are opposed to each other to be closely adhered.
A heat treatment is performed to form a buried silicon oxide layer, a substrate surface on the silicon single crystal seed substrate side is removed by a predetermined thickness to form a silicon single crystal film, and a silicon single crystal film is formed on the substrate surface on the silicon single crystal seed substrate side. Forming a mask layer on the silicon single crystal film, removing a portion of the mask layer portion into a groove shape whose longitudinal direction is parallel to the (111) plane of the silicon single crystal seed substrate, By removing the silicon single crystal film portion whose surface was exposed by removing the layer , a plurality of
The bottom of the groove is formed of the same buried silicon oxide layer, and
Removes the buried silicon oxide layer further
It is characterized by being formed by a silicon layer forming a lower layer of a silicon layer .

In this case, it is preferable that the orientation of the substrate surface of the silicon substrate is arbitrary, and the orientation of the substrate surface of the silicon single crystal seed substrate is (100).

Preferably, the orientation of the substrate surface of the silicon substrate is arbitrary, and the orientation of the substrate surface of the silicon single crystal seed substrate is (110).

[0019]

First, the orientation of the substrate surface is (100) or (1).
10) A silicon single crystal substrate is prepared,
Highly concentrated on a given surface of the crystal substrate as an etching stop layer
A p-type diffusion layer is formed. Here, high concentration means dopan
10 concentration¹⁸Atom cm ^-3The above concentration is referred to. Limit concentration
The reason for this is that in the etching process
Etching speed compared to undoped silicon
Degree is less than about 1/20, almost no etching
Because it is. To form a high concentration p-type diffusion layer,
Gas or solid containing p-type impurity elements such as
Method, or ion implantation that anneals after ion implantation.
An input method may be used.

Next, a layer to be etched is formed. The layer to be etched is formed by epitaxially growing a non-doped, n-type, or low-concentration p-type silicon single crystal film on the surface of the high-concentration p-type diffusion layer. At this time, the thickness of the layer to be etched is equal to or slightly smaller than the diameter of the optical fiber. This is because it is necessary to partially expose the side surface of the optical fiber from the groove in order to press the side surface of the optical fiber from above and hold the side surface of the optical fiber in contact with the groove bottom surface.

Note that a silicon oxide layer can be used as the etching stop layer. This is because silicon oxide has an etching rate of about 1/500 as compared with non-oxidized silicon and is hardly etched. In this case, first, a silicon support substrate and a silicon single crystal seed substrate are prepared. The silicon support substrate may be either a single crystal substrate or a polycrystalline substrate, and there is no restriction on the crystal orientation. The silicon single crystal seed substrate needs to have a (100) or (110) plane orientation of the substrate surface. Also,
At the time of bonding, each substrate surface is mirror-finished in order to obtain sufficient bonding strength and dimensional accuracy. Next, the surface of the silicon support substrate and the surface of the silicon single crystal seed substrate are oxidized to form a silicon oxide film. The oxidation is performed by an ordinary oxidation method or the like in which oxidation is performed in an oxygen atmosphere. Next, the substrate surfaces of both substrates are brought into contact with each other and bonded at high temperature to be integrated. Adhesion is
Both substrates may be mechanically pressurized, or may simply be overlapped. At this time, the silicon oxide film on the bonding surface fuses to form a buried silicon layer which is an etching stop layer. Further, the silicon single crystal seed substrate side of the bonded substrate is removed until the silicon single crystal layer of the silicon single crystal substrate has a predetermined thickness, and a silicon single crystal film is formed, which is used as a layer to be etched. The removal method is
A normal method such as polishing may be used. Moreover, you may remove by etching or combined use with grinding | polishing.

Next, the surface of the silicon single crystal substrate or the bonded substrate, on which the etching stop layer and the layer to be etched formed by any one of the above methods are laminated, is placed on the silicon single crystal substrate side in ordinary oxygen and water vapor. Forming a mask layer of a silicon oxide film by a thermal oxidation reaction method of overheating at
A laminated body including an etching stop layer, a layer to be etched, and a mask layer (silicon oxide film) is used. The silicon oxide film may be formed by a high-pressure oxidation method using high-pressure oxygen, or a coating method in which a liquid material having a composition containing siloxane is applied by a spinner or the like and then fired.

Next, an opening is provided in the silicon oxide film of the laminate formed by such a method by the following method. That is, for example, HF-HFN ₄ -H is used as a mask with a photoresist having a pattern formed by mask exposure and development.
Etching is performed using a hydrogen fluoride aqueous solution such as ₂ O (hereinafter referred to as “buffered hydrogen fluoride aqueous solution”) or a hydrogen fluoride solution such as HF-HNO ₃ —H ₂ O. Further, this opening may be provided by a dry etching method. At this time, the length direction of the opening provided in the silicon oxide film is made to coincide with the direction parallel to the (111) plane of the silicon single crystal substrate.
The width of the opening provided in the silicon oxide film is equal to or slightly smaller than the groove to be formed. this is,
While the etching in the depth direction of the groove is progressing (11
1) The side surface is slightly etched.
The amount is, for example, 1 μm when digging a groove having a depth of 60 μm.
m. Furthermore, the opening width of the groove to be formed is set so that the optical fiber is in contact with the bottom surface of the groove. Assuming that the inclination angle of the groove side wall is θ, the radius of the optical fiber is r, and the depth of the groove is d, the opening width W of the groove must be at least W = 2 {rtan (θ / 2) + d / tan θ}. If the plate orientation of the layer to be etched is (10
At the time of 0), θ = 54.74 °. Therefore, for example, in order to fit a fiber having a diameter of 125 μm into a groove having a depth of 80 μm, the opening width may be 177.84 μm or more. When the orientation of the layer to be etched is (110), θ
= 90 °. Therefore, for example, in order to fit a fiber having a diameter of 125 μm into the groove, the opening width may be 125 μm or more. Therefore, when a silicon substrate having a plane orientation of (110) is used, the opening width can be suppressed, and more grooves can be provided on a substrate of a fixed length. In addition, in order to make it easy to insert the fiber, the opening width is set to be larger than the above calculated value by 0.1. Although the width may be increased by several μm, the horizontal position of the optical fiber becomes uncertain if the opening width of the guide groove is excessively increased. Therefore, the margin is preferably as small as possible.

As the above-mentioned mask layer, in addition to the silicon oxide layer, a metal film made of platinum, titanium or the like which is not corroded by an anisotropic etching solution of silicon may be used. In this case, a mask layer is formed by an evaporation method or a sputtering method, and a mask opening is formed by a lift-off method.

Next, the silicon single crystal film epitaxially grown or the silicon single crystal film formed by polishing the bonded substrate surface is etched with an anisotropic etching solution. As the anisotropic etchant,
Use potassium hydroxide solution. In addition, an ethylenediamine-pyrocatechol aqueous solution or a hydrazine solution may be used. These anisotropic etching solutions preferentially etch the (100) and (110) planes of the silicon single crystal substrate, and the (111) plane is a groove side surface because the etching speed of the (111) plane is low. Etching proceeds as follows. In this case, the cross-sectional shape of the groove formed by etching becomes an inverted trapezoid when the plane orientation of the layer to be etched is (100), and the plane direction of the layer to be etched is (1).
In the case of 10), it becomes a rectangle. Further, since these anisotropic etching solutions hardly etch the high-concentration p-type diffusion layer or the silicon oxide layer, even if the anisotropic etching solution reaches, the etching does not proceed any further.
Therefore, a substrate having an inverted trapezoidal or rectangular groove in which the depth of the grooves in all rows accurately matches the thickness of the silicon single crystal layer on the etching stop layer can be obtained.

The optical fiber fitted into the groove of the substrate thus formed is held in contact with the bottom of the groove, so that the vertical position of each optical fiber is kept constant. When an optical fiber is fitted into the inverted trapezoidal or rectangular groove substrate and the upper part is fixed with a pressing plate, an optical fiber guiding structure such as an optical multi-core connector is obtained. The holding plate only needs to be capable of fixing the optical fiber, and the holding plate may or may not be attached to the substrate surface using an adhesive or the like.

The orientation of the silicon single crystal layer epitaxially grown on the substrate is the same as the orientation of the silicon single crystal plate. That is, when the orientation of the silicon single crystal plate is (100), the orientation of the silicon single crystal layer epitaxially grown on the substrate is also (100), and the orientation of the silicon single crystal plate is In the case of (110), the plane orientation of the silicon single crystal layer epitaxially grown on the substrate is also (110).
When the layer to be etched is formed by polishing the bonded substrate surface or the like, it goes without saying that there is no dependency on the orientation of the supporting substrate. When the groove is aligned with the direction parallel to the (111) plane of the substrate, the groove has an inverted trapezoidal or rectangular cross section and good dimensional accuracy, and the other direction deteriorates the dimensional accuracy. When the plane orientation is (100), grooves parallel to the (111) plane can be formed in two directions orthogonal to each other on the substrate plane by the anisotropic etching. When the plane orientation is (110), grooves parallel to the (111) plane may be formed in the two directions crossing each other at an angle of 70.52 ° on the substrate plane by the anisotropic etching. It is possible.

While the etching in the depth direction of the groove is progressing, the (111) side surface is also slightly etched. As a result, the oxide film of the mask layer (mask oxide film) is overhanged by about 1 μm at the upper end of the groove. It remains out of shape. Such a thin oxide film without a support may collide with the side or end surface of the optical fiber when the optical fiber is inserted, and may fall off as a fragment. If the light penetrates and adheres on the axis, the light signal is scattered and attenuated. Therefore, after the anisotropic etching is completed, it is desirable to remove the remaining mask oxide film in the buffered hydrofluoric acid solution. At this time, if the layer to be etched is formed by bonding, the buried oxide film exposed by the formation of the groove is also removed together. However, since the thickness of the buried oxide film is constant with high precision, the surface of the underlying silicon substrate exposed by removing the buried oxide film is also flat with high precision, so that the bottom surface of the groove forms a plane with high precision. This feature of the present invention is not impaired at all. However, in this case, the thickness of the buried oxide film is taken into account when calculating the opening width W of the groove to be formed so that the optical fiber is in contact with the bottom of the groove. That is, assuming that the thickness of the oxide film is a, the calculation is performed by subtracting a from the depth d of the groove. Therefore, the opening width W of the groove may be set to be at least W = 2 {rtan (θ / 2) + (da) / tanθ}.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described more specifically with reference to figures and numerical values. 1 to 9, 1 is a silicon single crystal substrate, 2 is a high concentration p-type diffusion layer, 3 is a silicon epitaxial film, 4 is a mask layer (oxide film), 5 is a photoresist film, 6 is a window, 7 is a window. The groove, 8 is a groove substrate, 11 is a silicon single crystal support substrate, 12 is a silicon single crystal seed substrate, 13 is a silicon oxide layer, 14 is a buried silicon oxide layer, and 15 is a silicon single crystal film. In addition, the size of each part in each drawing is not drawn in proportion to the numerical value related to the size.

First Embodiment A first embodiment of a method for manufacturing an optical fiber guide structure according to the present invention will be described with reference to FIGS. 1 (a) to 1 (g).

The orientation of the silicon single crystal substrate 1 is (100). A high-concentration boron was diffused on the surface of the silicon single crystal substrate 1 to form a high-concentration p-type diffusion layer 2 having a depth of 3 μm and a dopant concentration of 10 ²⁰ atom cm ^{−3 on} the surface [FIG. )reference〕. The dopant concentration was measured by secondary ion mass spectrometry (SIMS). Subsequently, silicon was epitaxially grown on the high-concentration p-type diffusion layer 2 to form a silicon epitaxial film 3 as a silicon single crystal film having a thickness of 80 μm (see FIG. 1B). Further, the surface of the silicon epitaxial film 3 is thermally oxidized to a thickness of 0.1 mm made of silicon oxide.
By forming a mask layer 4 of 5 μm, a multilayer structure was manufactured (see FIG. 1C).

After a photoresist is applied on the mask layer 4, the photoresist film 5 is exposed and developed to a width 177.
Three rows of windows 6 having a length of 30 μm and a length of 30 μm were formed in parallel at intervals of 250 μm (see FIG. 1D). Next, HF: HFN
_4: H ₂ O 1: 15: etched with buffered hydrogen fluoride solution having the composition 5 was removed to form a pattern of the mask layer 4 which is exposed [see FIG. 1 (e)]. Next, anisotropic etching is performed by applying a 50% by weight aqueous solution of potassium hydroxide at a liquid temperature of 60 ° C. for 20 minutes to remove the exposed silicon epitaxial film 3, and to obtain a depth of 80 μm and a width of 1 μm.
An inverted trapezoidal groove substrate 8 was formed in which three rows of inverted trapezoidal grooves 7 having a length of 78 μm and a length of 30 mm were formed in three rows [see FIG. 1 (f)].
The positions of all the bottom surfaces of the three rows of grooves 7 were on a constant plane within a range of variation of ± 0.1 μm. The high-concentration p-type diffusion layer 2 was not removed by etching in an aqueous potassium hydroxide solution. After the completion of the anisotropic etching, the remaining mask oxide film 4 was removed in the buffered hydrogen fluoride aqueous solution. FIG. 1 (g) shows the upper portion of the inverted trapezoidal groove substrate 8 by fitting the optical fiber core wire 9 of the three-core optical cable into each groove 7 and bonding the holding plate 10 to the surface of the groove substrate 8 using an adhesive. Is fixed to show the state of use as an optical fiber guide structure.

In the first embodiment, the orientation of the silicon single crystal substrate must be (100). Thereby, the plane orientation of the silicon epitaxial film is also (1)
00), a groove substrate having an inverted trapezoidal cross section is formed by anisotropic etching. Also, when the longitudinal direction of the groove is made to coincide with the direction parallel to the (111) plane of the substrate, a groove having an inverted trapezoidal cross section and good dimensional accuracy can be obtained. become worse.

Second Embodiment A second embodiment of the method for manufacturing an optical fiber guide structure according to the present invention will be described with reference to FIGS. 2 (a) to 2 (g) and FIG.

The orientation of the substrate surface of the silicon single crystal supporting substrate 11 is (100), while the orientation of the substrate surface of the silicon single crystal seed substrate 12 is (100). Silicon single crystal support substrate 11 and silicon single crystal seed substrate 1
2 was placed in an oxygen atmosphere with the two substrate surfaces facing each other, and heat-treated at a temperature of 1100 ° C. for 20 minutes to form a silicon oxide layer 13 having a thickness of 0.25 μm on both substrate surfaces [FIG. a)]. Subsequently, in a state where the above-mentioned heat treatment oxygen atmosphere and the temperature are maintained, the opposing substrate surfaces are brought into contact with each other, and then the heat treatment is continued for 10 minutes, whereby the silicon single crystal support substrate 11 and the silicon single crystal seed substrate No. 12 was firmly adhered. At this time, the silicon oxide layer 13 on the substrate surface was fused at the contact portion, and became a buried silicon oxide layer 14 (see FIG. 2B).

Next, the silicon single crystal seed substrate 12 was polished to expose a silicon single crystal layer having a thickness of 80 μm to form a silicon single crystal film 15 (see FIG. 2C). Subsequently, the surface of the silicon single crystal film 15 is thermally oxidized to form a 0.5 μm thick silicon oxide mask layer 4.
A multilayer structure was manufactured. Subsequently, a photoresist is applied on the silicon oxide mask layer 4 and exposed and developed to form a photoresist film 5 having a width of 177 μm and a length of 30 m.
m windows 6 were formed in parallel at intervals of 250 μm (see FIG. 2D). Next, the exposed portion of the mask layer 4 is removed in the same manner as in the first embodiment (see FIG. 2E), and the silicon single crystal film 15 is exposed in the same manner as in the first embodiment. 80μm depth, width 1
An inverted trapezoidal groove substrate 8 having three rows of inverted trapezoidal grooves 7 having a length of 25 μm and a length of 30 mm was manufactured [see FIG. 2 (f)]. The positions of all the bottom surfaces of the three rows of grooves 7 are ± 0.1 μm.
It was on a constant plane within the range of variation of m. The buried silicon oxide layer 14 was not removed by etching in an aqueous potassium hydroxide solution. After the completion of the anisotropic etching, the remaining mask oxide film 4 and silicon oxide layer 13 were removed in the buffered hydrogen fluoride aqueous solution. At this time, the buried silicon oxide layer 14 exposed at the bottom of the groove was also removed. FIG. 2G shows that the optical fiber core wire 9 of the three-core optical cable is fitted into each groove 7 of the substantially inverted trapezoidal groove substrate 8, and the holding plate 10 is bonded to the surface of the groove substrate 8 using an adhesive. Shows the state of use as an optical fiber guide structure with the upper part fixed.

Also in the second embodiment, when the longitudinal direction of the groove is made to coincide with the direction parallel to the (111) plane of the silicon single crystal seed substrate 12, the groove has a substantially inverted trapezoidal cross section and good dimensional accuracy. Is obtained, but in other directions, the dimensional accuracy deteriorates.

A substantially inverted trapezoidal groove substrate 8 according to the second embodiment.
Was cut into a width of 5 mm × a length of 25 mm, and optical fibers 9 were arranged in each groove 7 and fixed thereon with a holding plate 10 to obtain an optical multi-core connector (see FIG. 3). Then, the optical axis was aligned with the optical integrated circuit substrate 17 having the optical waveguide 16 at intervals of 250 μm. While monitoring the transmitted light intensity,
Just by aligning the optical axes of the two outer optical fibers 9a and 9b, the optical axes of the other optical fibers 9c were also aligned. Optical waveguide 1
The joint loss due to the connection between the optical fiber 6 and the optical fiber 9 was all 0.5 dB or less, which was less than half of the conventional product.

Third Embodiment FIGS. 4 (a) to 4 (g) and FIGS. 5 (a) to 5 (a) to 5 (c) show a third embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.
This will be described with reference to FIG.

The plane direction of the substrate surface of the silicon single crystal substrate 1 is (110). A high-concentration boron was diffused on the surface of the silicon single crystal substrate 1 to form a high-concentration p-type diffusion layer 2 having a depth of 3 μm and a dopant concentration of 10 ²⁰ atom cm ^{−3 on} the surface [FIG. )reference〕. The dopant concentration was measured by secondary ion mass spectrometry (SIMS). Subsequently, silicon was epitaxially grown on the high-concentration p-type diffusion layer 2, and a silicon epitaxial film 3 as a silicon single crystal film having a thickness of 80 μm was laminated [FIG.
(See (b)). Further, the surface of the silicon epitaxial film 3 is thermally oxidized to a thickness of 0.5 of silicon oxide.
A multilayer structure was manufactured by forming a mask layer 4 having a thickness of μm (see FIG. 4C).

After a photoresist is applied on the mask layer 4, the photoresist film 5 is exposed and developed to a width 124.
Three rows of windows 6 having a length of 30 μm and a length of 30 μm were formed in parallel at intervals of 250 μm (see FIG. 4D). Next, HF: HFN
_4: H ₂ O 1: 15: etched with buffered hydrogen fluoride solution having the composition 5 was removed to form a pattern of the mask layer 4 which is exposed [see FIG. 4 (e)]. Next, anisotropic etching is performed by applying a 50% by weight aqueous solution of potassium hydroxide at a liquid temperature of 60 ° C. for 20 minutes to remove the exposed silicon epitaxial film 3, and to obtain a depth of 80 μm and a width of 1 μm.
A rectangular groove substrate 8 in which three rows of rectangular grooves 7 having a length of 25.2 μm and a length of 30 mm were formed in parallel was manufactured (see FIG. 4F). The positions of all the bottom surfaces of the three rows of grooves 7 are ± 0.1 μm.
It was on a constant plane within the range of variation of m. The high-concentration p-type diffusion layer 2 was not removed by etching in an aqueous potassium hydroxide solution. After the completion of the anisotropic etching, the remaining mask oxide film 4 was removed in the buffered hydrogen fluoride aqueous solution. FIG. 4G shows an optical fiber core wire 9 of a three-core optical cable in each groove 7 of the rectangular groove substrate 8.
And fixing the upper portion by, for example, bonding the holding plate 10 to the surface of the groove substrate 8 using an adhesive,
It shows a use state as an optical fiber guide structure.

FIG. 5 shows an example in which an optical fiber guide structure is manufactured in the same manner as in the above embodiment. In the present embodiment, the manufacturing process proceeded under the same conditions as in the above embodiment until a photoresist was applied on the mask layer 4 except that the mask layer 4 was formed only on the surface of the silicon epitaxial film 3. [See FIG. 5 (a)] Then, the photoresist film 5 is exposed to light and developed to form a width of 123 μm and a length of 30 mm.
5 rows were formed in parallel at intervals of 250 μm [FIG.
(See (b)). Next, in the same manner as in the above embodiment, the exposed portion of the mask layer 4 is removed (see FIG. 5C).
Further, the exposed portion of the silicon single crystal film 15 is removed in the same manner as in the above embodiment to obtain a depth of 80 μm and a width of 125 μm.
A rectangular groove substrate 8 having five rows of rectangular grooves 7 having a length of 30 mm and a length of 30 mm was manufactured [see FIG. 5 (d)]. 5 grooves 7
Were located on a constant plane within a variation of ± 0.1 μm. The high concentration p-type diffusion layer 2
Was not removed by etching in an aqueous potassium hydroxide solution. FIG. 5E shows an optical fiber core wire 9 of a five-core optical cable inserted into each groove 7 of the rectangular groove substrate 8, and the holding plate 10 is adhered to the surface of the groove substrate 8 by using an adhesive or the like. FIG. 3 shows a state of use as an optical fiber guide structure when fixed.

In the third embodiment, the orientation of the silicon single crystal substrate must be (110). Thereby, the plane orientation of the silicon epitaxial film is also (11)
0), and a groove substrate having a rectangular cross section is formed by anisotropic etching. Also, the longitudinal direction of the groove is aligned with (11) of the substrate.
1) A groove having a rectangular cross-section and a high dimensional accuracy can be obtained if it is made coincident with a direction parallel to the plane, but dimensional accuracy is deteriorated in any other direction.

Fourth Embodiment FIGS. 6A to 6G and FIGS. 7A to 7C show a fourth embodiment of the method for manufacturing an optical fiber guiding structure according to the present invention.
(G) and FIG.

The orientation of the substrate surface of the silicon single crystal support substrate 11 is (100), while the orientation of the substrate surface of the silicon single crystal seed substrate 12 is (110). Silicon single crystal support substrate 11 and silicon single crystal seed substrate 1
2 was placed in an oxygen atmosphere with the two substrate surfaces facing each other, and heat-treated at a temperature of 1100 ° C. for 20 minutes to form a silicon oxide layer 13 having a thickness of 0.25 μm on both substrate surfaces [FIG.
(A)]. Subsequently, in the above-described heat treatment oxygen atmosphere,
By bringing the opposing substrate surfaces into contact with each other and continuing the heat treatment for 10 minutes thereafter, the silicon single crystal supporting substrate 11 and the silicon single crystal seed substrate 12 were firmly bonded.
At this time, the silicon oxide layer 13 on the surface of the substrate was fused at the contact portion to form a buried silicon oxide layer 14 (see FIG. 6B).

Next, the silicon single crystal seed substrate 12 was polished to expose a silicon single crystal layer having a thickness of 80 μm, thereby forming a silicon single crystal film 15 (see FIG. 6C). Subsequently, the surface of the silicon single crystal film 15 is thermally oxidized to form a 0.5 μm thick silicon oxide mask layer 4.
A multilayer structure was manufactured. Subsequently, a photoresist is applied on the silicon oxide mask layer 4 and exposed and developed to form a photoresist film 5 having a width of 124 μm and a length of 30 m.
M windows 6 were formed in parallel at intervals of 250 μm (see FIG. 6D). Next, similarly to the third embodiment, the exposed portions of the mask layer 4 are removed (see FIG. 6E).
Further, the exposed portion of the silicon single crystal film 15 is removed in the same manner as in the third embodiment to obtain a depth of 80 μm and a width of 12 μm.
A rectangular groove substrate 8 in which three rectangular grooves 7 each having a length of 5.2 μm and a length of 30 mm were formed in parallel (see FIG. 6F).
The positions of all the bottom surfaces of the three rows of grooves 7 were on a constant plane within a range of variation of ± 0.1 μm. The buried silicon oxide layer 14 was not removed by etching in an aqueous potassium hydroxide solution. After the completion of the anisotropic etching, the remaining mask oxide film 4 and silicon oxide layer 13 were removed in the buffered hydrogen fluoride aqueous solution. At this time, the buried silicon oxide layer 14 exposed at the bottom of the groove was also removed. FIG. 6G shows an optical fiber core wire 9 of a three-core optical cable inserted into each groove 7 of the rectangular grooved substrate 8, and a pressing plate 10 is adhered to the surface of the grooved substrate 8 by using an adhesive. FIG. 3 shows a state of use as an optical fiber guide structure when fixed.

FIG. 7 shows an example in which an optical fiber guide structure is manufactured in the same manner as in the above embodiment. In this embodiment, after the manufacturing process is advanced under the same conditions as in the above embodiment until a photoresist is applied on the mask layer 4, the photoresist film 5 is exposed and developed to a width of 123 μm and a length of 30 mm. The windows 6 were formed in three rows in parallel at intervals of 250 μm (see FIGS. 7A, 7B, 7C, and 7D).
Next, as in the above embodiment, the exposed portion of the mask layer 4 is removed (see FIG. 7E), and the silicon single crystal film 15 is exposed as in the above embodiment. Remove the part, depth 80μm, width 125μm, length 30m
A rectangular groove substrate 8 in which three rows of m rectangular grooves 7 were formed in parallel was manufactured (see FIG. 7F). The positions of all the bottom surfaces of the three rows of grooves 7 were on a constant plane within a range of variation of ± 0.1 μm. The buried silicon oxide layer 14 was not removed by etching in an aqueous potassium hydroxide solution. FIG. 7 (g) shows an upper portion of the rectangular grooved substrate 8 in which the optical fiber core wire 9 of the three-core optical cable is fitted into each groove 7 and the holding plate 10 is adhered to the surface of the grooved substrate 8 using an adhesive. Is fixed to show the state of use as an optical fiber guide structure.

Also in the fourth embodiment, when the longitudinal direction of the groove is made to coincide with the direction parallel to the (111) plane of the silicon single crystal seed substrate 12, a groove having a rectangular cross section and good dimensional accuracy is obtained. However, if the direction is other than the above, the dimensional accuracy deteriorates.

The rectangular groove substrate 8 according to the fourth embodiment is
The optical fiber 9 was cut into each of the grooves 7 and fixed with a pressing plate 10 from above to obtain an optical multi-core connector (see FIG. 8). Then, the optical axis was aligned with the optical integrated circuit substrate 17 having the optical waveguide 16 at intervals of 250 μm. While monitoring the transmitted light intensity, only the optical axes of the two outer optical fibers 9a and 9b were aligned, and the optical axes of the other optical fibers 9c were also aligned. The joint loss due to the connection between the optical waveguide 16 and the optical fiber 9 was 0.5 dB or less in all cases, which was less than half the value of the conventional product.

Fifth Embodiment A fifth embodiment of the optical fiber guide structure according to the present invention is shown in FIG. The fifth embodiment is an example in which a plurality of rectangular grooved substrates 8 are laminated, a plurality of rows of optical fibers 9 are laminated, and a holding plate 10 is mounted on the upper rectangular grooved substrate 8.

[0051]

As described above, according to the present invention, it is possible to provide an optical fiber guide structure which is excellent in dimensional accuracy in the vertical direction, has small connection loss, and is easy to align and align. .

[Brief description of the drawings]

1 (a) to 1 (g) are schematic explanatory views showing a first embodiment of a method for manufacturing an optical fiber guide structure according to the present invention.

FIGS. 2A to 2G are schematic explanatory views showing a second embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.

FIG. 3 is an explanatory view of an optical axis alignment test of an optical fiber guide structure according to the present invention in a second embodiment.

4 (a) to 4 (g) are schematic explanatory views showing a third embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.

FIGS. 5A to 5E are schematic explanatory views showing a modification of the third embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.

6 (a) to 6 (g) are schematic explanatory views showing a fourth embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.

FIGS. 7A to 7G are schematic explanatory views showing a modification of the fourth embodiment of the method for manufacturing an optical fiber guide structure according to the present invention.

FIG. 8 is an explanatory view of an optical axis alignment test of an optical fiber guide structure according to the present invention in a fourth embodiment.

FIG. 9 is an explanatory view showing a fifth embodiment of the optical fiber guiding structure according to the present invention.

FIG. 10 is an explanatory view of a conventional V-groove type optical fiber guiding structure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon single crystal substrate 2 high concentration p-type diffusion layer 3 epitaxial film 4 mask layer (oxide film) 5 photoresist film 6 window 7 groove 8, 21 groove substrate 9 optical fiber (core wire) 10 holding plate 11 silicon single crystal support substrate 12 silicon single crystal seed substrate 13 silicon oxide layer 14 buried silicon oxide layer 15 silicon single crystal film 16 optical waveguide 17 optical integrated circuit substrate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 6/00 G02B 6/30 G02B 6/36 H01L 29/84

Claims (9)

(57) [Claims] 1. The method according to claim 1, wherein the surface of the substrate having the silicon single crystal layer on or near the surface thereof has a (1) thickness of the silicon single crystal surface layer.
11) The same high-concentration p-type diffusion layer and the same silicon oxide layer having a plurality of grooves cut parallel to the plane, and the bottom surfaces of the plurality of grooves are buried under the surface of the substrate. Or the same silicon layer forming a lower layer of the silicon oxide layer. 2. The method according to claim 1, wherein the plane orientation of the silicon single crystal layer is (1).
00), and the surface of the substrate is the (100) of the substrate.
The optical fiber guide structure according to claim 1, wherein the groove is substantially inverted trapezoidal on a surface. 3. The silicon single crystal layer has a plane orientation of (1).
10), and the surface of the substrate is the (110) of the substrate.
The optical fiber guiding structure according to claim 1, wherein the groove is formed on a surface, and a cross-sectional shape of the groove is rectangular. 4. A high-concentration p-type diffusion layer is formed on the surface of a silicon single crystal substrate, and a non-doped, n-type,
Alternatively, after forming a low-concentration p-type silicon single crystal film to a predetermined thickness and forming a mask layer on the silicon single crystal film, the longitudinal direction of the mask layer portion is (111) of the silicon single crystal substrate. A) removing a part of the groove parallel to the plane, and then removing the silicon single crystal film part whose surface is exposed by removing the mask layer, thereby making the bottom surfaces of the plurality of grooves the same.
A method for manufacturing an optical fiber guiding structure formed of a high concentration p-type diffusion layer . 5. The method for manufacturing an optical fiber guide structure according to claim 2, wherein the plane orientation of the substrate surface of the silicon single crystal substrate is (100). 6. The method for manufacturing an optical fiber guide structure according to claim 2, wherein the plane orientation of the substrate surface of the silicon single crystal substrate is (110). 7. Oxidizing both substrate surfaces of a silicon substrate and a silicon single crystal seed substrate, bringing the two substrate surfaces into contact with each other,
A heat treatment is performed to form a buried silicon oxide layer, a substrate surface on the silicon single crystal seed substrate side is removed by a predetermined thickness to form a silicon single crystal film, and a silicon single crystal film is formed on the substrate surface on the silicon single crystal seed substrate side. Forming a mask layer on the silicon single crystal film, removing a portion of the mask layer portion into a groove shape whose longitudinal direction is parallel to the (111) plane of the silicon single crystal seed substrate, By removing the silicon single crystal film portion whose surface was exposed by removing the layer , a plurality of
The bottom of the groove is formed of the same buried silicon oxide layer, and
Removes the buried silicon oxide layer further
A method for manufacturing an optical fiber guiding structure formed of a silicon layer forming a lower layer of a silicon layer . 8. The silicon wafer according to claim 3, wherein the silicon substrate has an arbitrary plane orientation, and the silicon single crystal seed substrate has a plane orientation of (100). A method for manufacturing an optical fiber guide structure. 9. The silicon substrate according to claim 3, wherein the substrate orientation of the substrate surface of the silicon substrate is arbitrary, and the substrate orientation of the substrate surface of the silicon single crystal seed substrate is (110). A method for manufacturing an optical fiber guide structure.