JPH11190811A - Substrate for optical device mounting and its manufacture and optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the substrate for optical device mounting which enables high-precision passive alignment of an optical fiber, an optical waveguide, and a photosemiconductor element without alignment and the optical module using it. SOLUTION: The substrate S for optical device mounting is formed by providing a substrate 1 where an optical waveguide is formed with a mount groove 10 where an optical fiber F is mounted, an optical waveguide W which is optically coupled with the optical fiber F, an electrode pattern 9 where an optical element D emitting or receiving light while coupled optically with the core 4 of the optical waveguide W is mounted, and markers 7 which have top surfaces at a specific distance above the core center axis of the optical waveguide W, and positioning and mounting the optical element D on the markers 7 and electrode pattern 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device mounting substrate used for optical communication and optical information processing and an optical module using the same, and more particularly, to an optical fiber, an optical semiconductor device, and the like.
Optical waveguides can be optically coupled with high precision with an asymmetric core,
In addition, the present invention relates to an optical module capable of supplying an optical module having excellent mass productivity and characteristics.

[0002]

2. Description of the Related Art In recent years, with the advancement of optical communication and optical information processing, passive optical devices in which optical semiconductor elements such as semiconductor lasers and photodiodes (hereinafter simply referred to as optical elements) and optical fibers are mounted without alignment. A technique called alignment has attracted attention. This is because a V-groove formed using anisotropic etching technology such as a silicon substrate with high precision, and an optical element mounting electrode or a positioning marker formed more precisely with respect to this V-groove. This can be achieved by using a mounting substrate that is not suitable.

[0003] On the other hand, with respect to the quartz-based optical waveguide fabrication technology, a flame deposition method (FHD: Flame Hydrolysis Depositio) is used.
n) and monosilane (SiH ₄ ) based atmospheric pressure CVD (Chemic
al Vapor Deposition), plasma CVD, TEOS
(Tetraethoxy Silane)-A technique such as a CVD method has been established, and has been put to practical use in passive devices such as a waveguide type optical splitter and an optical multiplexer / demultiplexer.

[0004] Further, research on a PLC (Planar Lightwave Circuit) platform combined with the above-described passive alignment technology is actively being conducted to reduce the cost of a subscriber optical device. This technology aims at low cost by realizing integration and non-alignment of various optical devices. In particular, non-alignment is considered to be the most important elemental technology for reducing mounting cost.

[0005] In addition, a high-precision patterning technique for a V-groove for mounting an optical fiber and a core portion of the optical waveguide for alignment-free mounting of the optical fiber and the optical waveguide is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-90.
No. 133828. The outline of this technique is to perform patterning of the V-groove pattern and the core portion of the optical waveguide using the same mask to improve the manufacturing accuracy.

Various proposals have been made on high-precision patterning techniques for an optical waveguide and an electrode for mounting an optical semiconductor element or a positioning marker.
There is no report that sufficient positioning accuracy has been obtained yet (for example, see IEICE Technical Report OPE96-9, “WDM optical transceiver module using Si block fiber guide”).

Therefore, even if passive alignment can be performed with high accuracy without alignment between the optical fiber and the optical waveguide, the advantage of using this method is reduced if sufficient accuracy is not obtained for the connection between the optical waveguide and the optical semiconductor element. I do.

[0008] On the other hand, even if a technique capable of high-accuracy passive alignment of an optical waveguide and an optical semiconductor element has been established, the connection between an optical fiber and an optical waveguide must also be highly accurate at the same time unless the technique is capable of high-precision passive alignment. The merit of using the method is reduced.

Accordingly, an object of the present invention is to provide an optical device mounting substrate and an optical module using the same, which are capable of performing passive alignment with high accuracy and without alignment of an optical fiber, an optical waveguide, and an optical semiconductor element. And

[0010]

According to the present invention, there is provided an optical device mounting board according to the present invention, comprising: a mounting groove on which an optical fiber is mounted on a substrate on which an optical waveguide is formed; An optical waveguide optically coupled to the optical fiber, an electrode pattern on which a light emitting or receiving optical element optically coupled to the core of the optical waveguide is mounted, and a predetermined distance upward from a central axis of the core of the optical waveguide. A plurality of markers having upper surfaces at positions are provided, and the optical element is positioned and mounted on the plurality of markers and the electrode pattern.

Further, the method of manufacturing an optical device mounting substrate according to the present invention comprises the steps of:
An optical waveguide optically coupled to the optical fiber, an electrode pattern on which a light emitting or receiving optical element optically coupled to the core of the optical waveguide is mounted, and a position separated by a predetermined distance from a central axis of the core of the optical waveguide. Forming a lower cladding layer of the optical waveguide on one main surface of the substrate, comprising: a step of forming a lower cladding layer of the optical waveguide on one principal surface of the substrate; Forming a high-refractive-index layer having a higher refractive index than the lower cladding layer in the upper predetermined region, forming an opening pattern for forming the mounting groove on the high-refractive-index layer, and forming a core of the optical waveguide; Forming a mask pattern having a core pattern and a marker pattern for forming the marker, and using the mask pattern to form the optical waveguide and an electrode pattern on which the optical element is mounted. Characterized in that it comprises a step of forming the marker, and the mounting groove, respectively.

An optical module according to the present invention comprises an optical fiber and an optical element which are optically coupled to the optical waveguide on a substrate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an optical module according to the present invention will be described in detail with reference to the drawings. First, as shown in FIGS. 1 and 2 (a), a substrate 1 made of silicon single crystal or the like is prepared, and as shown in FIG. 2 (b), a lower clad layer 3 having a thickness of, for example, about 30 μm is formed by a flame deposition method or various other methods. CV
It is formed by the D method or the like.

Next, as shown in FIG. 2C, a core layer 4 which is a high refractive index layer having a higher refractive index than the lower clad layer 3 is formed on the lower clad layer 3. In this case, phosphorus (P), boron (B), fluorine (F), germanium (Ge), or the like is added to silica (SiO ₂ ) to lower the refractive index of the lower cladding layer 3, and to add a method of using a SiO ₂ of, using conventional SiO ₂ in the lower cladding layer 3, P to the core layer 4, Ge, aluminum (Al), titanium (Ti), tantalum (Ta), arsenic (as) or erbium A method of adding one or more materials selected from (Er) to SiO ₂ to increase the refractive index of the core layer 4 is considered.

Next, FIGS. 3 and 4 (a), FIG. 5 (a),
As shown in FIGS. 6A and 7A, a V-groove forming groove for forming a V-groove which is a mounting groove of an optical fiber having an opening 6a on the core layer 4 with the surface of the core layer exposed. Pattern 6
A core part forming pattern 5 for forming a core part of an optical waveguide, an electrode pattern (not shown) for mounting an optical element such as an optical semiconductor element, and / or a reference for positioning and arranging the optical element. Patterning is performed using one photomask (self-aligned mask) provided with a pattern for forming a plurality of positioning markers 7 used as points.

In this case, the material of the mask patterns 5, 6, and 7 formed on the core layer 4 may be amorphous silicon or RIE dry mask for forming a core (waveguide core) described later. It is necessary to use a material having good etching resistance such as tungsten silicide (WSi).

Next, by using the mask patterns 5, 6, and 7, the layers other than the core layer 4 in the waveguide core portion are removed by dry etching, and the layers shown in FIGS. 4 (b), 5 (b) and 5 (b) are removed. 6
As shown in (b) and FIG. 7 (b), after only the core portion forming pattern 5 on the core layer 4 is removed by etching from the mask pattern, FIGS. 4 (c), 5 (c) and 6 (C),
As shown in FIG. 7C, the upper cladding layer 8 is formed.

Here, since it is necessary to form the upper cladding layer 8 with the mask patterns 6 and 7 remaining on the substrate 1, the method of forming the upper cladding layer 8 may affect the remaining mask patterns. It is desirable to use a low-temperature film forming process that does not affect the film formation. For example, TEOS-CV
When a film forming method such as the method D is used, the film can be formed at a low temperature of about 350 to 400 ° C. and at a very high speed, and thus is suitable for this method. In order to reduce the waveguide loss, 8
Although heat treatment at about 00 ° C. needs to be performed, the influence on the metal film is extremely small since the film is formed, and no major problem occurs.

Next, FIG. 4 (d), FIG. 5 (d), FIG.
(D), as shown in FIG. 7 (d), only the optical waveguide portion is covered by using the same mask pattern as described above, and the upper cladding layer 8, the V-groove forming pattern 6, and the optical semiconductor element mounting are covered. Electrode pattern forming part or marker 7
And dry etching the lower cladding layer to the substrate surface using a known technique. Thereafter, as shown in FIG. 4 (e), FIG. 5 (e), FIG. 6 (e), and FIG.
/ Au or Ti / Pt / Au electrode pattern (and solder pattern (not shown) for mounting) is formed, the surface of the substrate including the electrodes and the waveguide is covered with a protective film, and KOH solution or EDP (Ethylene Diamine) is used. 4 (f), FIG. 5 (f), FIG. 6 (f), FIG.
As shown in (f), the V-groove portion is anisotropically etched to form a V-groove 10 as a mounting groove, and thereafter, a fiber stopper groove 11 is also formed by dicing. Thus, the optical device mounting substrate S as shown in FIG. 8 can be manufactured. Further, as shown in FIG. 9, an optical module M in which an optical fiber F and an optical element D such as a semiconductor laser or a photodiode are mounted on the optical device mounting substrate S can be provided. The device will be positioned on the substrate with high precision.

FIGS. 10 and 11 show the positional relationship between the optical fiber and the optical element on the optical device mounting substrate S. FIG. V
The position of the core 13 of the optical fiber F when mounted on the groove 10 and the position of the optical element D on the positioning marker pattern 7 of the optical element D
The thickness of each film-forming layer such as a cladding layer and the V-groove width are calculated in advance based on the position of the active layer 14 at the time of mounting and the distance d between the marker mounting surface of the optical element D and the active layer 14. If the pattern is determined and designed, high-precision positioning in both the height direction and the horizontal direction can be easily realized. In this case, the electrical connection is preferably made of a material that can increase the height of the solder bump 12 or the like.

Next, another embodiment will be described with reference to the drawings. First, as shown in FIGS. 12 and 13 (a), a substrate 1 of silicon single crystal or the like is prepared, and anisotropic etching using an alkaline etching solution such as an aqueous solution of potassium hydroxide is performed on the substrate 1 to a depth of about 1 mm. After the recess 2 having a thickness of about 5 μm is formed, a lower cladding layer 3 having a thickness of about 30 μm is formed by a flame deposition method or various CVD methods as shown in FIG.

Next, in order to form a height reference plane for mounting an optical element described later on the substrate 1, the surface of the substrate 1 is flattened by polishing, etching, or the like. Expose the part.

Further, as shown in FIG. 13C, a core layer 4 having a larger refractive index than the lower clad layer 3 is formed on the lower clad layer 3. In this case, the refractive index of the lower cladding layer 3 is reduced by adding P, B, F, Ge, and the like to SiO ₂ , as in the above-described embodiment.
Using the method of using a conventional SiO _2, a conventional SiO ₂ in the lower cladding layer 3, P to the core layer 4, Ge, Al,
A method of increasing the refractive index of the core layer 4 by adding at least one material selected from Ti, Ta, As, Er or the like to SiO ₂ may be considered.

Then, in the same manner as in the above embodiment (FIGS. 3, 4 (a) to (f), FIGS. 5 (a) to (f), FIG.
(Refer to (a) to (f) and FIGS. 7 (a) to (f)), the optical device mounting substrate and the optical module can be completed.

Here, the positional relationship between the optical fiber and the optical element on the optical device mounting board S is shown in FIGS. Core 1 of optical fiber F when mounted on V-groove 10
3, the position of the active layer 14 when the optical element D is mounted on the positioning marker pattern 7 of the optical element D, and the distance d between the marker mounting surface of the optical element D and the active layer 14,
If the thickness of each film forming layer such as the cladding layer and the V-groove width are obtained in advance by calculation and the pattern design of the self-alignment mask is performed, highly accurate positioning in both the height direction and the horizontal direction can be easily realized. . In this case, the electrical connection can be made using a multilayer solder such as Au / Sn or the like, and the height accuracy of the marker is not required. This also makes it possible to effectively utilize the heat radiation effect of the substrate (silicon substrate).

In the above embodiment, the case of a straight waveguide has been described. However, an optical branching coupler, an optical multiplexer / demultiplexer, or the like may be used, and the optical element also corresponds to such a branched waveguide. For this purpose, a plurality of light receiving elements and / or light emitting elements may be positioned and mounted, and can be appropriately modified and implemented without departing from the gist of the present invention.

[0027]

According to the present invention, the mounting groove pattern, the pattern for forming the core of the optical waveguide circuit, and the electrode pattern or positioning marker pattern for mounting the optical semiconductor element with high precision are formed using the same mask. By being formed, the precision of each pattern and the displacement accuracy are improved, and an excellent optical device mounting substrate capable of performing high-precision positioning in the direction perpendicular to the optical axis and the substrate and in the horizontal direction. Can be provided.

This greatly simplifies the mounting process, which previously required a long time, and enables highly accurate positioning, so that excessive loss during mounting can be suppressed.
An optical module (hybrid optical integrated module) with low cost and low loss can be provided.

Further, the optical waveguide circuit can be formed by a low-temperature process, and the warpage and unnecessary residual stress of the substrate due to the difference in thermal expansion coefficient between the substrate material and the waveguide forming material are eliminated. A highly accurate positional relationship is maintained, and adverse effects on various characteristics such as PDL (polarization dependent loss) of the optical waveguide circuit can be avoided as much as possible.

[Brief description of the drawings]

FIG. 1 is a plan view of a substrate for explaining an embodiment according to the present invention.

FIGS. 2 (a) to 2 (c) are cross-sectional views taken along line XX in FIG. 1 for explaining manufacturing steps of one embodiment according to the present invention.

FIG. 3 is a plan view of a substrate for explaining an embodiment according to the present invention.

4 (a) to 4 (d) are cross-sectional views taken along line AA in FIG. 3 for explaining manufacturing steps of one embodiment according to the present invention.

5 (a) to 5 (d) are cross-sectional views taken along the line BB in FIG. 3 for explaining manufacturing steps of one embodiment according to the present invention.

6 (a) to 6 (d) are cross-sectional views taken along the line CC in FIG. 3 for explaining manufacturing steps of one embodiment according to the present invention.

7 (a) to 7 (d) are cross-sectional views taken along the line DD in FIG. 3 for explaining manufacturing steps of one embodiment according to the present invention.

FIG. 8 is a perspective view for explaining an embodiment of an optical device mounting substrate according to the present invention.

FIG. 9 is a perspective view illustrating an embodiment of the optical module according to the present invention.

FIG. 10 is a cross-sectional view showing a positional relationship between a core and a core layer of an optical fiber in one embodiment of the optical module according to the present invention.

FIG. 11 is a cross-sectional view showing a positional relationship between a photoactive layer of an optical element and a marker in one embodiment of the optical module according to the present invention.

FIG. 12 is a plan view of a substrate for explaining another embodiment according to the present invention.

FIGS. 13 (a) to 13 (c) each illustrate a manufacturing process according to another embodiment of the present invention.
FIG. 4 is a sectional view taken along line -Y.

FIG. 14 is a cross-sectional view illustrating a positional relationship between an optical fiber core and a core layer in another embodiment of the optical module according to the present invention.

FIG. 15 is a sectional view showing a positional relationship between a marker and a photoactive layer of an optical element in another embodiment of the optical module according to the present invention.

[Explanation of symbols]

 1: substrate 2: concave portion 3: lower cladding layer 4: core layer 5, 6, 7: mask pattern 8: upper cladding layer 9: electrode pattern 10: mounting groove (V groove) D: optical element F: optical fiber W: Optical waveguide S: Optical device mounting substrate M: Optical module

Claims (3)

[Claims] 1. A substrate on which an optical waveguide is formed, a mounting groove on which an optical fiber is mounted, an optical waveguide optically coupled to the optical fiber, and light emission or light reception optically coupled to a core of the optical waveguide. An electrode pattern on which an optical element is mounted; and a plurality of markers having an upper surface at positions spaced apart from the core axis of the optical waveguide by a predetermined distance, and the optical element is provided on the plurality of markers and the electrode pattern. A substrate for mounting an optical device, wherein the substrate is positioned and mounted. 2. A mounting groove on which an optical fiber is mounted, an optical waveguide optically coupled to the optical fiber, and an optical element for emitting or receiving light, which is optically coupled to a core of the optical waveguide, is mounted on the substrate. An optical device mounting substrate manufacturing method comprising: an electrode pattern; and an optical element positioning marker formed at a predetermined distance from a core center axis of the optical waveguide. Forming a lower cladding layer of the optical waveguide, and forming a high refractive index layer having a higher refractive index than the lower cladding layer in a predetermined region on the lower cladding layer,
Forming an opening pattern for forming the mounting groove on the high refractive index layer, a core pattern for forming a core of the optical waveguide, and a mask pattern having a marker pattern for forming the marker; and Forming the optical waveguide, the electrode pattern on which the optical element is mounted, the marker, and the mounting groove, respectively, using the mask pattern. 3. An optical module comprising: an optical fiber optically coupled to the optical waveguide; and an optical element disposed on the substrate according to claim 1.