JP2001281500A - Optical mounting board, its manufacturing method and optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical mounting board and its manufacturing method with which the coupling efficiency of light on the board side is easily improved without applying complicated working treatment to a mounting optical device side and the influence on the characteristics of reflected light in the optical module is suppressed and integration of various optical devices is realized and to provide a highly functional optical module. SOLUTION: In an optical mounting board S1 wherein a plurality of grooves formed by anisotropic etching are provided on the main surface of the board consisting of single crystal material and the optical devices are disposed in these respective grooves, the principal surface of the board is provided with a plurality of groove-formed areas where crystal orientations parallel to the optical axis direction of the optical devices to be disposed are different.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module used for optical transmission such as optical fiber communication and optical interconnection, an optical mounting board used therefor, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, large capacity and multifunctional optical communication systems have been demanded, and accordingly, miniaturization, integration and cost reduction of optical modules have been demanded. In particular, for the purpose of reducing the assembly cost of an optical module, a technique of mounting optical components such as an optical fiber and an optical semiconductor element on the same substrate, a so-called optical hybrid mounting technique, has attracted attention.

According to this technique, V grooves ((111) plane, (111) plane and (1
The optical semiconductor element mounted on the conductor pattern on the same silicon substrate can be assembled without any alignment by simply mounting an optical element such as an optical fiber on the (00) plane). It becomes possible.

[0004] In order to realize such an optical module with higher functions (higher speed and higher integration), a lens is used to increase the coupling efficiency between the optical fiber and the optical semiconductor element or to suppress the reflection between the optical elements. Mounting of a plurality of optical elements, such as optical devices and optical isolators, is required for optical mounting substrates. The optical design at that time is generally designed so that the angle of incidence between the optical elements can be arbitrarily set. For example, to suppress reflection between optical semiconductor elements and optical isolators, the angle should be about 8 °.
When using a filter or the like, the angle is set to about 45 °.

However, when a normally used single crystal silicon substrate having a (100) plane as a main surface is used,
The V-groove formed by anisotropic etching can be formed only in a fixed direction due to the crystal structure. Therefore, it is known that an optical element to be mounted on a mounting substrate is formed obliquely in advance.

FIG. 9 shows an example of an optical receiving module in which an optical fiber and a light receiving element are arranged on a substrate. When the light emitted from the optical fiber 55 is incident on the light receiving element 57 of the surface light receiving type mounted on the chip carrier 56, the surface of the chip carrier 56 is previously set to a predetermined angle (for example, 8 °).
By forming the optical module J at an angle, the influence of light reflected by the optical fiber 55 on the light receiving element 57 is suppressed, and the optical module J
1, stable characteristics can be obtained.
246846).

FIG. 10 shows an example of an optical module having an optical isolator. The optical module J2 uses an optical isolator 60 that is formed by condensing light emitted from an optical fiber 58 by a ball lens 59 and that is obliquely processed at 8 °. In addition, light is transmitted through another ball lens 62. Also in the case of the optical module J2, the return loss of the incident light is suppressed by performing the diagonal processing (Japanese Patent Laid-Open No. 11-7).
No. 2748).

However, it is extremely complicated and difficult to process individual optical elements obliquely in advance as described above, and it is impossible to obtain a high-precision optical element. Therefore, it has been extremely difficult to realize a high-performance optical module.

Therefore, according to the present invention, it is possible to easily improve the light coupling efficiency on the substrate side without performing a complicated processing on the optical element side to be mounted, and furthermore, it has an influence on the characteristics of the reflected light in the optical module. It is an object of the present invention to provide an optical mounting substrate, a method of manufacturing the optical mounting substrate, and a highly functionalized optical module in which various optical elements can be integrated.

[0010]

According to the present invention, in order to achieve the above object, an optical mounting substrate according to the present invention comprises a plurality of grooves formed by anisotropic etching on a main surface of a substrate made of a single crystal material. An optical mounting substrate formed and provided with an optical element in each of the grooves, wherein the main surface of the substrate has different crystal orientations parallel to the optical axis direction of the optical element to be provided in a plurality of regions. It is characterized by being.

In particular, the main surface of the substrate is laminated with a lower groove forming layer and a part of the lower groove forming layer exposed (or an etching resistant layer over the lower groove forming layer). And an upper groove forming layer.

Further, the main surface of the substrate is made of single crystal silicon. In this case, the main surface of the substrate is the (100) plane, and the optical axis direction of the optical element to be provided is parallel to the <110> direction.

According to the method of manufacturing an optical mounting substrate of the present invention, a first single-crystal substrate and a second single-crystal substrate having the same principal plane as the first single-crystal substrate are interposed between the first single-crystal substrate and the second single-crystal substrate. A step of joining the main surfaces with a set angle shifted with an etching-resistant layer interposed therebetween, a step of forming a groove in the first single-crystal substrate by anisotropic etching, Removing a part of the etching-resistant layer to expose the second single-crystal substrate; and forming a groove by anisotropic etching on an exposed surface of the second single-crystal substrate. It is characterized by.

In the optical module of the present invention, an optical fiber is disposed in a groove formed in the upper groove forming layer, and a surface emitting or surface receiving type optical semiconductor device is disposed in the groove formed in the lower groove forming layer. Is provided. Further, it is preferable that an optical fiber is provided in a groove formed in the lower groove forming layer, and an edge-emitting or edge-receiving optical semiconductor device is provided in the groove formed in the upper groove forming layer. Features.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an optical mounting board S1 according to the present invention. According to the present invention, a plurality of V-shaped cross-sectional grooves formed by anisotropic etching are formed on a main surface of a substrate made of a single crystal material, and an optical element is disposed in each of these grooves. The main surface of the substrate is different in a plurality of regions having different crystal orientations parallel to the optical axis direction of the optical element to be provided.

That is, the main surface of the optical mounting substrate S1 is, for example, a (100) plane, which is made of single-crystal silicon which can be anisotropically etched, and has a first silicon layer (upper groove forming layer).
1 is a second silicon layer having a (100) plane as a main surface, similarly to the first silicon layer 1, via an insulating layer 2 made of silicon oxide, silicon nitride, or the like, which is an etching resistant layer for anisotropic etching. (Second groove forming layer) 3. The bonding in this case is performed by applying heat or a load, using an adhesive, or the like.

Here, the <110> of the first silicon layer 1
Direction (crystal orientation parallel to the optical axis of the optical element to be disposed) 4
On the other hand, the <110> direction 5 of the second silicon layer 3 is different from the set angle (approximately 8 °). As a result, the first direction formed by anisotropic etching of single crystal silicon The groove 6 of the silicon layer 1 and the groove 7 (length direction) of the second silicon layer 3 are formed at different angles θ.

As described above, since the two silicon layers 1 and 3 bonded via the insulating layer 2 have different crystal orientation <110> directions 4 and 5, the grooves formed in the respective layers are not formed. Since the angle θ is different, the optical mounting substrate has a groove having a different angle θ.

With such a configuration, not only is the advantage of the optical mounting substrate that the assembly is completed only by mounting the optical element in the groove, but also grooves having different inclinations are formed on the same substrate. It is possible to arbitrarily change the angle between the optical elements mounted thereon,
As a result, the degree of freedom in designing an optical module using the optical mounting substrate is increased.

The presence of the insulating layer 2 depends on the optical mounting substrate S1.
When exposing the main surface of the second silicon layer 3 during the manufacture of
By using the insulating layer 2 as a stopper layer when removing the first silicon layer 1, the thickness of the second silicon layer 3 from the substrate surface can be maintained. Can be. Here, when there is no insulating layer 2, in the step of removing the first silicon layer 1,
Since the second silicon layer 3 is removed and the thickness from the substrate surface changes, the height is reduced by the change in thickness when forming the groove, and the characteristics as an optical module are sufficiently satisfied. I can't let it.

Further, the existence of the insulating layer 2 can be achieved by forming electric wiring on the insulating layer 2 in a region not shown in FIG. 1 without forming a thick insulating layer on a substrate separately. It is possible to provide an optical mounting substrate having excellent characteristics.

As shown in FIG. 2, the optical mounting substrate S1 and the optical module M1 according to the present invention have an optical fiber 9 in a groove 8 formed in the first silicon layer 1 and a second silicon layer 3 in the groove 8.
A chip carrier 12 (optical semiconductor device) having a surface-emitting or surface-receiving optical semiconductor element 11 mounted in a groove 10 formed therein is positioned and mounted according to the shape of the groove 10.

Thus, an optical mounting board and a transmitting optical module or a receiving optical module that achieve desired optical coupling can be obtained. That is, it is possible to minimize the influence of the reflected light at the optical fiber end face on the optical semiconductor element, and to stabilize the optical module.

FIG. 3 shows an optical mounting board S2 and an optical module M2 according to the present invention. The optical fiber 14 is positioned in the groove 13 formed in the second silicon layer 3, and the edge emitting or edge receiving type optical semiconductor device 16 is positioned in the groove 15 formed in the first silicon layer 1 by the groove 15. By being mounted and mounted, an optical mounting board and a transmitting optical module or a receiving optical module that realize desired optical coupling can be obtained.

With such a configuration, the same effects as those of the optical mounting board S1 and the optical module M1 shown in FIG. 2 can be obtained. Also, by precisely controlling the width and depth of the groove 15 by anisotropic etching, the mounting can be performed simply and accurately simply by fitting the optical semiconductor device 16 into the groove.

Furthermore, if the depth is made equal to the thickness of the first silicon layer 1, it is not necessary to consider the etching control in the depth direction of the groove 15 when forming by the anisotropic etching. Thus, the optical mounting substrate can be manufactured more easily.

FIG. 4 shows an embodiment of the optical module M3 in which the optical isolator 22 and the like are mounted on the optical mounting board S3 according to the present invention. A set of grooves 1 formed in the first silicon layer 1
7 and 18 have a structure in which a groove 19 formed in the second silicon layer 3 is sandwiched from both sides, and two grooves 17 and 1 are provided.
The optical fibers 20 and 21 are mounted on the groove 8, and the optical isolator 22 is positioned on the groove 19 with the groove 19.

With this configuration, it is possible to incorporate the optical isolator into the optical module without performing unnecessary slant processing.

FIG. 5 shows an optical module M4 in which the optical isolator 32 and the like are mounted on the optical mounting board S4 according to the present invention.
A pair of grooves 23 and 24 formed in the first silicon layer 1 and a pair of grooves 25 and 26 formed in the second silicon layer 3
And optical fibers 28 and 29 in grooves 23 and 24, ball lenses 30 and 31 in grooves 25 and 26, and an optical isolator 32 in groove 27.
, And are positioned and mounted.

According to such a configuration, the same effect as that of the optical module M3 in FIG. 4 can be obtained, and an optical module having more excellent coupling efficiency can be obtained by using a ball lens.

The inclination .theta. Of the groove formed in the second silicon layer 3 with respect to the groove formed in the first silicon layer 1 in FIGS. It is common to set in a range.

FIG. 6 shows an embodiment in which the wavelength filter 38 and the like are mounted on the optical mounting substrate S5 according to the present invention.

Light emitting element 3 mounted on first silicon layer 1 while being electrically insulated from second silicon layer 3
3 and a light receiving element 34 are mounted, and light emitted from the light emitting element 33 is collected by a ball lens 36 mounted in a groove 35 formed on the second silicon layer 3,
By transmitting the light through a filter 38 mounted in a groove 37 formed in the silicon layer 3, the light is coupled to an optical fiber 40 mounted in a groove 39 formed in the first silicon layer 1. Further, the light incident from the optical fiber 40 is reflected by the filter 38 mounted on the groove 37, so that the light is condensed by the ball lens 42 mounted on the groove 41 formed on the second silicon layer 3, and the light is received. Optically coupled to element 34.

Here, in FIG. 6, the arrangement of the light emitting element 33 and the light receiving element 34 is switched so that the light emitted from the light emitting element 33 is formed in the groove 41 formed on the second silicon layer 3.
The light is condensed by a ball lens 42 mounted on the second silicon layer 3, and further reflected by a filter 38 mounted on a groove 37 formed on the second silicon layer 3 to form a groove 39 formed on the first silicon layer 1. You may make it couple | bond with the optical fiber 40 mounted. The light incident from the optical fiber 40 passes through the filter 38 mounted on the groove 37, and is condensed by the ball lens 36 mounted on the groove 35 formed on the second silicon substrate. 34
May be optically coupled.

With the configuration shown in FIG. 6,
Since the optical semiconductor devices (33, 34) and the optical fiber 40 to be optically coupled and the ball lenses 36, 42 and the filter 38, which are optical elements larger than these optical elements, can be mounted on separate silicon layers, It is not necessary to prepare grooves for securing the optical path on the substrate side in advance, and it is possible to design to suppress the influence of the reflected light from the optical element. It is possible to provide a functional optical module.

In FIG. 6, the angle θ of the groove formed in the second silicon layer with respect to the groove formed in the first silicon layer is set to about 45 °.

FIGS. 7 and 8 are schematic plan views and cross-sectional views illustrating a method of manufacturing an optical mounting substrate according to the present invention. First, FIG.
As shown in FIGS. 7A and 7B, a first silicon substrate (first single crystal substrate) 43 having a (100) plane as a main surface where a V-groove can be formed most suitably and quickly, and FIG. (C), (d)
As shown in (1), a second silicon substrate (second single crystal substrate) 44 also having a (100) plane as a main surface is bonded via an insulating layer 47 formed on one or both sides. At this time, the <110> direction 45 of the first silicon substrate 43 and the <110> direction 46 of the second silicon substrate 44 are set at a desired angle θ and bonded. The bonding at this time is performed by applying heat or a load, interposing an adhesive at the bonding interface, or the like.

Next, the first silicon substrate 43 is adjusted to a desired thickness by polishing it from the surface opposite to the bonding surface with the second silicon substrate 44, and the first silicon substrate 43 has the (100) plane orientation. 7 (e), (f), (g),
As shown in (h), a substrate 52 in which a first silicon layer 48 and a second silicon layer 50 having different <110> directions are joined by an insulating layer 47 is manufactured.

Then, as shown in FIGS. 8 (a1) and 8 (a2), after the grooves formed on the first silicon layer are formed with the groove forming mask pattern 53, as shown in FIGS. 8 (b1) and 8 (b2). As shown, a groove 49 is formed on the first silicon layer by anisotropic etching using an alkaline aqueous solution such as a KOH aqueous solution or a TMAH aqueous solution.

Next, as shown in FIGS. 8C1 and 8C2, after removing the first groove forming mask pattern 53, a step of exposing the second silicon layer 50 is performed.
1) and (d2), the groove forming mask pattern 5
After the formation of the groove 4, a groove 51 is formed in the second silicon layer 50 in the same manner as the groove 49, and as shown in FIGS. 8 (e1) and 8 (e2), the second groove forming mask pattern 54 is removed. By doing so, an optical mounting substrate is manufactured.

In this step, by preparing the substrate 52 first, since the subsequent groove forming process can be handled as a wafer process, there is an advantage that the manufacturing is very easy. Further, the existence of the insulating layer 47 can be used as a stopper layer for exposing the second silicon layer 50 as described above, and the second silicon layer 50
The thickness from the substrate surface can be maintained, and the groove 51 with high accuracy can be formed.

Although the embodiment has been described by taking single-crystal silicon as an example of the single-crystal material of the substrate, the present invention is not limited to this. A body can be used, and other configurations can be appropriately modified and implemented without departing from the gist of the present invention.

[0044]

As described above, according to the optical mounting substrate of the present invention, when an optical module is realized by mounting various optical elements on the same substrate, the optical elements are required to have an angle adjustment in advance. Optical mounting substrate with grooves with different angles to increase the light coupling efficiency on the substrate side and enable integration of various optical elements without the need for contrivance, that is, processing such as oblique processing of the incident surface is required. , Thereby providing a highly functionalized optical module.

According to the optical module of the present invention, the influence of reflection on the optical element can be suppressed as much as possible, and the width and depth of the groove are precisely controlled, and the optical element is fitted into the groove. Accurate mounting can be realized. Furthermore, by making the depth of the groove equal to the thickness of the upper groove forming layer, it is not necessary to consider the control of etching in the depth direction of the groove when forming by anisotropic etching, and the accuracy can be reduced. Good groove formation can be realized more easily.

According to the method for manufacturing an optical mounting substrate of the present invention,
Since the groove manufacturing process can be treated as a wafer process, the manufacturing is very easy, and the stopper when the etching resistant layer removes the upper groove forming layer when exposing the lower groove forming layer due to the presence of the etching resistant layer. Since the layer functions as a layer, and the thickness from the surface of the lower groove forming layer can be maintained, accurate groove processing can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram for schematically explaining an embodiment of an optical mounting board according to the present invention, wherein (a) is a perspective view and (b) is a plan view.

FIGS. 2A and 2B are diagrams schematically illustrating an embodiment of an optical mounting board and an optical module according to the present invention, wherein FIG. 2A is a perspective view and FIG. 2B is a plan view.

3A and 3B are diagrams schematically illustrating an embodiment of an optical mounting board and an optical module according to the present invention, wherein FIG. 3A is a perspective view and FIG. 3B is a plan view.

FIGS. 4A and 4B are diagrams schematically illustrating an embodiment of an optical mounting board and an optical module according to the present invention, wherein FIG. 4A is a perspective view and FIG. 4B is a plan view.

5A and 5B are diagrams schematically illustrating an embodiment of an optical mounting board and an optical module according to the present invention, wherein FIG. 5A is a perspective view and FIG. 5B is a plan view.

6A and 6B are diagrams for schematically explaining an embodiment of an optical mounting board and an optical module according to the present invention, wherein FIG. 6A is a perspective view and FIG. 6B is a plan view.

FIGS. 7A and 7B are diagrams schematically illustrating an embodiment of a method for manufacturing an optical mounting board according to the present invention, wherein FIG.
(B) is a plan view of (a), (c) is a cross-sectional view, (d) is a plan view of (c), (e) is a cross-sectional view, (f) is a plan view of (e), (g) Is a sectional view, and (h) is a plan view of (g).

8A and 8B are diagrams for schematically explaining an embodiment of a method for manufacturing an optical mounting board according to the present invention, wherein FIG. 8A is an end view, FIG. 8A is a plan view of FIG. 8A, and FIG. Is an end view,
(B2) is a plan view of (b1), (c1) is an end view, (c)
2) is a plan view of (c1), (d1) is an end view, (d2)
Is a plan view of (d1), (e1) is an end view, and (e2) is a plan view of (e1).

FIG. 9 is a plan view schematically illustrating an example of a conventional optical module.

FIG. 10 is a plan view schematically illustrating an example of an optical module equipped with a conventional optical isolator.

[Explanation of symbols]

1: first silicon layer (upper groove forming layer) 2: insulating layer (etching-resistant layer) 3: second silicon layer (lower groove forming layer) 4: <110> orientation of first silicon layer 5: first <110> orientation of the silicon layer of No. 6, 8, 15, 17, 18, 23, 24, 39, 49:
Grooves 7, 10, 13, 19, 25, 26, 27, 35, 3 formed in first silicon layer
7, 41, 51: grooves formed in the second silicon layer 9, 14, 20, 21, 28, 29, 40: optical fiber 11: surface-emitting or surface-receiving optical semiconductor element 12: chip carrier 16 : Edge-emitting or edge-receiving optical semiconductor element 22, 32: Optical isolator 30, 31, 36, 42: Ball lens 38... Filter 43: First silicon substrate (first single crystal substrate) 44: Second silicon substrate (second single crystal substrate) 52: Substrate 53: First groove forming mask pattern 54: Second groove forming mask pattern S1 to S5: Optical mounting substrate M1 to M5: Optical module

Claims (7)

[Claims] An optical mounting substrate comprising: a plurality of grooves formed by anisotropic etching on a main surface of a substrate made of a single crystal material; and an optical element disposed in each of the grooves. An optical mounting substrate, wherein a main surface of the substrate includes a plurality of groove forming regions having different crystal orientations parallel to an optical axis direction of an optical element to be provided. 2. The method according to claim 1, wherein the plurality of groove forming regions include a lower groove forming layer and an upper groove forming layer laminated with a part of the lower groove forming layer exposed. The optical mounting substrate according to claim 1. 3. The optical mounting substrate according to claim 1, wherein a main surface of the substrate is made of single crystal silicon. 4. The optical mounting according to claim 3, wherein the main surface of the substrate is a (100) plane, and an optical axis direction of an optical element to be disposed is parallel to a <110> direction. substrate. 5. A method for manufacturing an optical mounting substrate, wherein a plurality of grooves are formed in two bonded single-crystal substrates, and an optical element is provided in each of the grooves. The first
Bonding a single crystal substrate and a second single crystal substrate having the same plane orientation as a main surface thereof with an etching-resistant layer interposed therebetween with the main surfaces shifted from each other at a set angle; Forming a groove in the single crystal substrate by anisotropic etching,
Removing the first single-crystal substrate and part of the etching-resistant layer to expose the second single-crystal substrate; and forming a groove in the exposed surface of the second single-crystal substrate by anisotropic etching. Forming an optical mounting substrate. 6. The optical mounting board according to claim 2, wherein an optical fiber is provided in a groove formed in said upper groove forming layer, and an optical fiber is provided in said groove formed in said lower groove forming layer. An optical module comprising a surface-emitting or surface-receiving optical semiconductor device to be connected. 7. The optical mounting board according to claim 2, wherein an optical fiber is provided in a groove formed in the lower groove forming layer, and an optical fiber is provided in the groove formed in the upper groove forming layer. An optical module comprising an edge-emitting or edge-receiving optical semiconductor device to be connected.