JP2001108871A - Optical module - Google Patents

Abstract

(57) [Problem] To provide a structure in an optical module that can make the heights of an optical waveguide and an optical element active layer equal without using a complicated structure as described above. SOLUTION: A silicon substrate 1 having a flat surface, an optical waveguide 2 formed on the silicon substrate, an optical element mounting portion 4 formed by removing a clad portion of the optical waveguide on the silicon substrate, and an optical element mounting portion The optical module has an insulating layer (passivation film) 5 formed thereon and an optical element 7 mounted on the optical element mounting section 4 via the insulating layer 5 so as to be optically coupled to the optical waveguide. The thickness of the insulating layer 5 is adjusted so that the center height of the core 2-2 of the optical waveguide and the center of the active layer 7-1 of the optical element match. A transparent resin 8 is interposed between the end face of the optical waveguide and the end face 2-3 of the optical element at the operating light wavelength of the optical element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical circuit component using a planar optical waveguide circuit, and more particularly to an optical module having a structure for facilitating the manufacture of a substrate on which an optical element is mounted.

[0002]

2. Description of the Related Art In a conventional optical module using an optical device mounting substrate in which an optical device mounting portion is formed by removing a clad portion of an optical waveguide formed on a silicon substrate, the height of the optical waveguide and the active layer of the optical device are increased. Silicon substrates with irregularities have been used to match (eg, Hashimoto et al., “L.
D, mounting of monitor PD ”, 1996 IEICE General Conference C-206, p206 (1996)).
FIG. 1 shows a configuration example of an optical module using such a conventional technique. FIG. 6A is a perspective view thereof, and FIG. 6B is a longitudinal sectional view thereof. The optical element mounting portion 4 includes a solder layer (solder film) 6-1 formed on the uneven silicon substrate 1 for fixing the optical element by removing the cladding and the waveguide core portion of the optical waveguide and the electric wiring. 6-2 is formed by deposition. The optical element 7 is mounted on the optical element mounting portion 4 by flip chip bonding, and is hybrid-integrated.

At this time, when the optical axis of the optical waveguide and the optical element 7 are aligned, the in-plane (horizontal, front-back) alignment of the substrate 1 is automatically recognized using the mark 20, and the height direction is determined. From the surface of the optical element 7 (the surface facing the substrate 1), the active layer 7 of the optical element is set so as to be equal in height difference between the surface of the silicon substrate projection 1-1 and the center of the optical waveguide core 2-2.
This is done by adjusting the distance to -1.

Here, the optical waveguide core 2-2 and the cladding 2
In an optical waveguide using a refractive index difference of −1, the electric field of light spreads outside the waveguide core 2-2. The cladding 2-1 (a) needs to have a sufficient thickness. For example, in the case of a silica-based optical waveguide used for communication, the thickness of the under cladding 2-1 (a) is about 20 μm. On the other hand, an optical semiconductor device is required to epitaxially grow the core and clad of an optical waveguide on a substrate.
Deposition of 20 μm is very difficult, and the distance from the substrate surface to the waveguide (active layer) structure is at most about 5 μm even when the waveguide structure is embedded. Therefore, in order to adjust the height, conventionally, a structure has been adopted in which unevenness is provided on the silicon substrate 1 and the optical element 7 is mounted on the convex portion 1-1.

FIG. 7 shows a manufacturing process of such an optical module according to the prior art. First, irregularities are provided on the silicon substrate 1 ((1) in FIG. 7), and the under cladding 2-1 is formed.
(A) is formed ((2) in FIG. 7), and the optical waveguide core 2-2 is formed.
Is formed (FIG. 7 (3)), and the over cladding 2-1 is formed.
(B) is formed ((4) in FIG. 7). Next, the optical element mounting portion 4 is formed by removing the unnecessary cladding and the core (FIG. 7 (5)), and the passivation film 5 is formed on the silicon substrate convex portion 1-1 which is the optical element mounting portion 4. Then, the electric wiring 6-2 and the solder layer 6-1 are formed on the film 5 ((6) in FIG. 7). At this time, it was difficult to manufacture the optical waveguide because the substrate 1 was uneven. Further, the optical waveguide core 2-2
It is necessary to provide a buffer layer 2-4 for adjusting the height of the optical axis (optical element active layer) 7-1 of the optical element 7 ((3) in FIG. 7), and the manufacturing process is complicated.

[0006]

As described above, in a conventional optical module using an optical element mounting substrate in which an optical element mounting portion of an optical waveguide formed on a silicon substrate is formed, the silicon substrate is provided with irregularities. Since the structure in which the optical element is mounted on the convex portion is adopted, there is a problem to be solved in that the manufacturing process is complicated.

An object of the present invention is to provide an optical module,
It is an object of the present invention to provide a structure capable of making the heights of an optical waveguide and an optical element active layer coincide with each other without using a complicated structure as described above.

[0008]

In order to achieve the above object, an optical module according to the first aspect of the present invention comprises a silicon substrate having a flat surface, an optical waveguide formed on the silicon substrate, and an optical module formed on the silicon substrate. An optical element mounting portion formed by removing the clad portion of the optical waveguide, an insulating layer formed on the optical element mounting portion, and the insulating layer through the insulating layer so as to be optically coupled to the optical waveguide. And an optical element mounted on the optical element mounting portion.

Here, the thickness of the insulating layer may be adjusted so that the height of the core of the optical waveguide coincides with the height of the center of the active layer of the optical element.

[0010] The insulating layer may be continuously integrated with an over cladding that covers a core of the optical waveguide from above.

[0011] The optical waveguide may be characterized in that the insulating layer further covers an over clad that covers the core of the optical waveguide from above.

[0012] Further, the invention is characterized in that the insulating layer is formed of an organic material.

Further, a transparent resin is interposed between the end face of the optical waveguide and the end face of the optical element at the operating light wavelength of the optical element.

[Operation] In the present invention, by adjusting the thickness of the insulating layer (passivation film of the embodiment) with the above configuration, the cladding portion of the optical waveguide formed on the silicon substrate is removed, and the optical element mounting portion is removed. The height of the core of the optical waveguide and the height of the active layer of the optical element can be adjusted without processing the silicon substrate into irregularities with respect to the formed optical element mounting substrate. Further, by using the insulating layer as the over cladding, an electric field confinement structure can be easily manufactured. Further, by using an organic material for the insulating layer, the production is further simplified. In addition, by interposing a transparent resin at the operating light wavelength of the optical element between the end face of the optical waveguide and the end face of the optical element, the light goes straight and the light emitted from the core of the optical waveguide is activated by the optical element. It can be surely incident on the layer.

[0015]

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

[First Embodiment] FIG. 1A shows the premise of the present invention, and FIG. 1B shows the structure of an optical module according to a first embodiment of the present invention.

Conventionally, as shown in FIG. 6 described above, a silicon substrate 1 having unevenness is used for adjusting the optical axis of the active layer 7-1 of the optical element 7 and the core 2-2 of the optical waveguide. Was.

On the other hand, in the present embodiment, a quartz optical waveguide is formed on a flat silicon substrate 1 as described below. As a result, not only the labor required for processing the unevenness can be saved, but also in the subsequent steps, since there is no step, the production yield is improved, and the production process is facilitated.

In this embodiment, the optical waveguide core 2-
2, the difference in refractive index from the cladding part 2-1 is about 0.4
%, And a core 2-2 having a cross section of 7 μm × 7 μm was used. The spread of the electric field at this time is I / e ^{2 of the} peak intensity.
Is about 9 μm, the distance between the optical waveguide core 2-2 and the silicon substrate 1 needs to be wider than this distance so that the bottom of the light intensity profile does not overlap the silicon substrate 1. is there. According to the study in the present embodiment, in order to suppress the total loss including the propagation loss of the waveguide to a loss of about 0.2 dB / cm, about 15 μm is required.
The center of the core had to be separated from the substrate by about m. At this time, as shown in FIG. 1A, the distance from the surface of the chip of the optical element 7 on which the optical element 7 is mounted to the active layer 7-1 is about 7 μm, which is 8 μm or more with respect to the above 15 μm. There was a difference.

Therefore, in the present embodiment, as shown in FIG. 1B, as the passivation film 5 as an insulating layer,
A quartz glass having a thickness of about 5 μm is deposited, and a further 3 μm
Was deposited. Thereby, the height of the optical waveguide core 2-2 and the height of the active layer 7-1 of the optical element 7 completely match.

Here, as shown in FIG. 2A, the film 5 deposited as passivation is formed on the end face 2-3 of the optical waveguide.
And the thickness thereof is not uniform, so that light may be refracted and the optical axis 10 may be shifted. In order to solve this problem, in the present embodiment, as shown in FIG. 2B, a transparent resin 8 is injected into a gap between the optical element 7 and the optical waveguide end face 2-3. The injection of the resin 8 allows the waveguide end face 2
Quartz glass film (passivation film) adhered to -3
Since the refractive index mismatch at the interface between the surface of the optical waveguide and the transparent resin 8 is eliminated, the light emitted from the optical waveguide core 2-2 travels substantially straight and enters the active layer 7-1 of the optical element 7. The resin 8 used here is a transparent silicone resin having a refractive index of 1.43 which is extremely close to the refractive index of quartz glass of 1.44. The resin 8 also has an effect of sealing the optical element 7.

As described above, by adjusting the thickness of the passivation film 5, which is an insulating layer, the optical waveguide 2 and the optical element 7 can be aligned in the height direction without using a silicon substrate having irregularities. Becomes Further, by injecting the transparent resin 8 into the gap between the optical element 7 and the optical waveguide 2, the quartz glass film 5 adhered to the optical waveguide end face 2-3 without interrupting the optical coupling between the optical waveguide 2 and the optical element 7. The effect of the non-uniformity of the film thickness can be substantially eliminated.

[Second Embodiment] FIG. 3 shows a manufacturing process of an optical module according to a second embodiment of the present invention. The optical waveguide is a quartz-based optical waveguide formed on the silicon substrate 1 as in the first embodiment.

First, on a silicon substrate 1 having a flat surface,
After forming the under cladding 2-1 (a) and the optical waveguide core 2-2 ((1) in FIG. 3), the under cladding 2-1 (a) and the core portion 2-2 of the optical element mounting portion 4 are etched. And removed ((2) in FIG. 3). Here, the structures of the under cladding 2-1 (a) and the optical waveguide core 2-2 are the same as in the first embodiment. Therefore, the height of the center of the optical waveguide core 2-2 from the silicon substrate 1 is about 15
μm.

In this state, a quartz glass film 5 having a thickness of about 5 μm is deposited ((3) in FIG. 3),
The electric wiring / solder layer 6 was deposited ((4) in FIG. 3). Here, the deposited 5 μm quartz glass film 5 used had a refractive index about 0.4% lower than the core portion so as to function as the over cladding 2-1 (b). Thereby, the quartz glass film 5 has a function of an over cladding and a function of a passivation film.

An optical element 7 similar to that of the first embodiment was mounted thereon, and a 10 μm thick transparent silicone resin 8 was applied later ((5) in FIG. 3). Here, a transparent resin 8 having the same refractive index as the quartz glass film 5 was used so as not to distort the distribution shape of the electric field. Further, by making the transparent resin 8 have a lower refractive index than the quartz glass film 5, it is also possible to tightly confine light. Thus, the step of forming the optical waveguide over-cladding and the step of forming the passivation film can be performed by a single deposition step, and the manufacturing step is extremely simplified.

Further, the transparent resin 8 not only functions as the second over clad 2-1 (b) of the waveguide, but also
It also has a function of suppressing refraction on the end face of the optical waveguide smoothed in the manufacturing process.

As described above, when the present invention is used, the passivation film and the optical waveguide clad can be manufactured at once without using a silicon substrate having irregularities, and the manufacturing process is extremely simplified.

Although a quartz glass film is used as the passivation film 5 in this embodiment, an organic material such as silicone and polyimide may be used. When a resin is used as the passivation film 5, the passivation film 5 may be applied by spin coating or the like, and can be manufactured extremely easily.

[Third Embodiment] FIG. 4 shows a manufacturing process of an optical module according to a third embodiment of the present invention. The optical waveguide is a quartz-based optical waveguide formed on the silicon substrate 1 as in the first embodiment.

First, an under clad 2-1 (a), an optical waveguide core 2-2 and an over clad 2-1 (b) are formed on a flat silicon substrate 1 (FIG. 4 (1)). Then, the clad and core portions of the optical element mounting portion 4 are etched and removed ((2) in FIG. 4). Here, the structures of the under cladding 2-1 (a) and the optical waveguide core 2-2 are the same as in the first embodiment. Therefore, the height of the center of the optical waveguide core 2-2 from the silicon substrate 1 is about 1
5 μm. In this example, since the time required for etching the optical waveguide is shortened, the over cladding 2-1 (b)
Was 5 μm, which is thinner than normal 20 μm.

In this state, a quartz glass film 5 having a thickness of about 4 μm is deposited ((3) in FIG. 4).
The electric wiring / solder layer 6 was deposited ((4) in FIG. 4). The same optical element 7 as in the first embodiment is mounted on this, and
A transparent silicone resin 8 having a thickness of 0 μm was applied ((5) in FIG. 4). Here, the deposited 4 μm quartz glass film 5 had a refractive index of about 0.2% lower than that of the over clad 2-1 (b). Thereby, this quartz glass film 5
Has the function of the second over cladding and the function of the passivation film.

In the function of the second overcladding of the quartz glass film 5, the quartz glass film 5 is formed by the optical waveguide core 2-2.
Since the refractive index is lower than that of the first over cladding surrounding the first over cladding, the distribution of light leaked from the first over cladding to the second over cladding as shown in FIG. Decays more rapidly than in the cladding. Therefore, the first
The overcladding 2-1 (b) is a relatively thin overcladding as described above, but the electric field does not reach the surface of the second overcladding of the quartz glass film 5 and the electric power is applied to the second overcladding. Even if the wiring 6-2 is formed, the characteristics of the optical waveguide hardly change. As described above, reducing the thickness of the first over cladding 2-1 (b) can shorten the etching process in the manufacturing process of the optical element mounting substrate of the present embodiment, reduce the level difference in the substrate, and reduce the optical module. There are two advantages that the fabrication of the semiconductor device becomes easy.

As described above, according to the present invention, processing can be performed by using a glass film having the function of the second over cladding and the function of the passivation film without using a silicon substrate having irregularities. Can be simplified.

[Fourth Embodiment] In a fourth embodiment of the present invention, a quartz glass optical waveguide is formed on a silicon substrate in the same manner as in the above-described third embodiment of the present invention, and then an optical element is formed. The core and the clad were removed to provide the mounting part. Then, instead of depositing a quartz glass film as a passivation film, a silicone resin (refractive index: 1.43) is applied by spin coating to form a passivation film, and then the same silicone resin is injected to seal an optical element or the like. Then, an optical module of the present invention was produced.

As described above, according to the present invention, it becomes easier to manufacture an optical waveguide substrate having an optical element mounting portion.

[Fifth Embodiment] FIG. 5 shows a sectional structure of an optical module according to a fifth embodiment of the present invention.

First, a quartz glass optical waveguide 2 is formed on a silicon substrate 1 in the same manner as in the third embodiment of the present invention.
After preparing -1 (a), 2-2 and 2-1 (b), the core 2-2 and the cladding 2 are provided to provide the optical element mounting portion (4).
-1 (b) was removed.

Thereafter, instead of depositing a quartz glass film as a passivation film, a photosensitive silicone resin 9 (refractive index: 1.43) is applied by spin coating.
The portion of the resin 9 adhering to the waveguide end face 2-3 of the optical waveguide was exposed through a mask and removed by development, and the other resin portion 9 was left as a passivation film.

Thereafter, in the same process as in the third embodiment, a transparent silicone resin 8 (refractive index: 1.43) having a lower refractive index than that of the cladding portion 2-1 is injected to thereby form the optical element 7 and the like. Was sealed to produce an optical module of the present invention.

As described above, when the present invention is used, it is easy to manufacture an optical waveguide substrate having an optical element mounting portion.
Furthermore, it is possible to prevent the passivation film from adhering to the end face of the waveguide due to the good workability of the resin.

[Sixth Embodiment] Even when a photosensitive polyimide resin (refractive index: 1.6) is used instead of the photosensitive silicone resin 9 in the fifth embodiment of the present invention, the light of the present invention is similarly obtained. It is possible to make modules. However, in this case, since the refractive index of the polyimide resin is high, the thickness of the upper clad of the quartz glass waveguide is set to 15 to 20 μm in consideration of the loss.

As described above, according to the present invention, it is easy to manufacture an optical waveguide substrate having an optical element mounting portion.
Furthermore, it is possible to prevent the passivation film from adhering to the end face of the waveguide due to the good workability of the resin. here,
Since polyimide resin has high heat resistance, it is extremely effective for an optical module that requires a manufacturing process with a severe heat history such as soldering.

As the passivation film in the fifth and sixth embodiments, a photosensitive benzocyclobutene resin, an epoxy resin or the like can be used. The optical module of the present invention can be manufactured even when a benzocyclobutene resin, an epoxy resin, a silicone resin, or a polyimide resin is used as the film of the fourth embodiment.

[0045]

As described above, according to the present invention,
In an optical module in which an optical element mounting part is provided on an optical waveguide substrate and an optical element is hybrid-integrated in the optical element mounting part, a silicon substrate having a flat surface is used, and an alignment between the optical element and the optical waveguide in a height direction is performed by an insulating layer. Since the film thickness is adjusted by adjusting the film thickness, the manufacturing process can be remarkably simplified.

Further, according to the present invention, the optical waveguide can be manufactured more easily by providing the insulating layer with a function as the cladding of the optical waveguide.

According to the present invention, the manufacturing process can be further simplified by manufacturing the insulating layer from an organic material.

Light According to the present invention, a transparent resin is interposed between the end face of the waveguide and the end face of the optical element at the operating light wavelength of the optical element, so that light can travel straight, and The light emitted from the core can reliably enter the active layer of the optical element.

Therefore, the structure of the optical module of the present invention is as follows.
This is extremely effective in realizing a low-cost optical module.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining the basic concept of the present invention. FIG. 1A is a cross-sectional view showing a positional relationship of an optical axis when a simple flat silicon substrate is used as a premise of the present invention, and FIG. FIG. 3 is a cross-sectional view illustrating a structure of an optical module using a passivation film as an insulating layer.

FIGS. 2A and 2B are diagrams showing a structure of the optical module according to the first embodiment of the present invention, in which FIG. 2A is a cross-sectional view showing a shift of an optical axis on a substrate on which a passivation film is merely deposited, and FIG. It is sectional drawing which shows the linearity of an optical axis at the time of interposing resin.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of an optical module according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of an optical module according to a third embodiment of the present invention.

FIG. 5 is a sectional view of an optical module according to a fifth embodiment of the present invention.

FIG. 6 is a view showing a structural example of a conventional optical module;
(A) is a perspective view of an optical element mounting part, and (b) is a cross-sectional view of the optical element mounting part.

FIG. 7 is a cross-sectional view showing a manufacturing process of an optical waveguide substrate having an optical element mounting portion used in a conventional optical module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 1-1 Silicon substrate convex part 1-2 Silicon substrate concave part 2 Optical waveguide 2-1 Cladding 2-1 (a) Under cladding 2-1 (b) Over cladding 2-2 Optical waveguide core 2-3 Optical waveguide End face 2-4 Buffer (height adjustment) layer 4 Optical element mounting part 5 Passivation film (quartz glass film) 6 Electric wiring / solder layer 6-1 Solder layer (solder film) 6-2 Electric wiring 7 Optical element 7-1 Optical element active layer 8 Transparent resin 9 Photosensitive resin 10 Optical axis 20 Alignment mark

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mikitaka Itan 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoji Omori 2-chome, Otemachi, Chiyoda-ku, Tokyo No. 1 Nippon Telegraph and Telephone Corporation (72) Inventor Akio Sugita 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Kuniharu Kato Otemachi, Chiyoda-ku, Tokyo No.3-1, Nippon Telegraph and Telephone Co., Ltd. (72) Inventor Akira Tomaru 2-3-1, Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Telegraph and Telephone Co., Ltd. 2H037 BA02 CA34 DA03 DA06 DA11 DA18 2H047 KA03 KA15 MA07 QA02 QA05 TA43

Claims (6)

[Claims] A silicon substrate having a flat surface; an optical waveguide formed on the silicon substrate; an optical element mounting portion formed on the silicon substrate by removing a clad portion of the optical waveguide; An optical module comprising: an insulating layer formed on a mounting portion; and an optical element mounted on the optical element mounting portion via the insulating layer so as to be optically coupled to the optical waveguide. 2. The optical module according to claim 1, wherein the thickness of the insulating layer is adjusted so that the height of the center of the core of the optical waveguide and the center of the active layer of the optical element coincide with each other. . 3. The optical module according to claim 2, wherein the insulating layer is continuously integrated with an over clad that covers a core of the optical waveguide from above. 4. The optical module according to claim 2, wherein the insulating layer further covers an over clad that covers the core of the optical waveguide from above. 5. The optical module according to claim 2, wherein the insulating layer is formed of an organic material. 6. The optical device according to claim 1, wherein a transparent resin is interposed between an end face of the optical waveguide and an end face of the optical element at an operating light wavelength of the optical element. An optical module according to item 1.