JP3752363B2 - Optical module, method for manufacturing the same, and apparatus for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical module used for converting an optical signal and an electrical signal.
[0002]
[Prior art]
In recent years, an optical module in which a light emitting element and an optical fiber are fixed on a silicon substrate has been developed.
[0003]
As shown in FIG. 1, a V-shaped groove 11 for placing an optical fiber 22 is formed on a silicon substrate 10, and an optical element 20 such as a laser diode is formed on the extended line of the groove. The optical fiber 22 is mounted and fixed in the groove 11. Further, an electrode 12 for energizing the optical element 20 is provided on the substrate 10, and this electrode is joined to a lead wire (not shown) and the whole is resin-molded or sealed in a package. A module is configured. An electrical signal introduced from the outside can be converted into an optical signal by the optical element 20 and led out to the outside by the optical fiber 22.
[0004]
If such an optical module is prepared by accurately aligning the groove 11 and the optical element 20 in advance, when the optical module is assembled, it is only necessary to place the optical fiber 22 in the groove 11. There is no need to align the two while the optical element 20 emits light and is monitored by the optical fiber 22. Such a technique is called passive alignment, and an optical module can be easily manufactured.
[0005]
In addition, in order to accurately align and mount the optical element 20 on the substrate 10, the alignment marker 13 is formed on the substrate 10, and the optical element 20 is mounted in accordance with this. Yes.
[0006]
Specifically, as shown in FIG. 5, the substrate 10 is placed on a jig 40 that also serves as a heating device, and the optical element 20 can be moved on the substrate 10 with a distance d of about 10 cm. The held stage 44 is arranged. Between the two, a mirror 41 tilted at 45 ° and a position adjusting device comprising an image device 42 such as two CCD cameras arranged coaxially on both sides are interposed.
[0007]
In this state, the position of the alignment marker 13 on the substrate 10 is detected by one image device 42 via the mirror 41, while the position of the alignment marker 21 formed on the optical element 20 is detected via the mirror 41. The image is detected by the other image device 42, the two images are overlapped, and the stage 44 is moved in the XY direction so that both the alignment markers 13 and 21 coincide.
[0008]
Then, in a state where both the alignment markers 13 and 21 coincide with each other, the position adjusting device composed of the mirror 41 and the image device 42 is removed, and the stage 44 is lowered, so that the optical element 20 is brought to a predetermined position on the substrate 10. Can be installed.
[0009]
[Problems to be solved by the invention]
However, in the manufacturing method of the optical module as shown in FIG. 5 described above, since there is a distance d of about 10 cm between the optical element 20 and the substrate 10, a positional shift occurs when the stage 44 is lowered, and the optical element 20. There is a problem that it cannot be mounted on the alignment marker 13 accurately. For example, if the lowering direction of the stage 44 is inclined by 0.01 ° with respect to the vertical direction, the position of the optical element 20 on the substrate 10 is shifted by about 20 μm.
[0010]
Therefore, the optical module thus obtained has a problem that the coupling efficiency is lowered due to the misalignment between the optical element 20 and the optical fiber 22 placed in the groove 11.
[0011]
[Means for Solving the Problems]
In view of the above problems, the present invention provides an optical module in which an optical fiber is mounted in a groove formed on a substrate, and the optical element is mounted on the substrate that is an extension of the groove. Forming an alignment marker made of a material that transmits light having a wavelength longer than the transmission wavelength of the substrate, and the alignment marker is a concave or convex step of 1000 mm or more by anisotropic etching, and The back surface of the substrate is a mirror surface having a surface roughness (Ra) of 0.5 μm or less.
Further, in the optical module manufacturing method, the mask for forming the groove and the mask for forming the alignment marker are shared, and a material that transmits light having a wavelength longer than the transmission wavelength of the substrate is used. From the step of aligning and mounting the optical element while detecting the optical element from the back side of the substrate through the substrate using the imaging device after forming the alignment marker at the position where the optical element is mounted. It is characterized by becoming.
In the manufacturing apparatus of the above Symbol light module consists stage holding the jig for mounting a substrate, and an image device arranged on the lower side of the jig, an optical device arranged on the upper side of the jig, the image While the optical element is detected over the substrate by the apparatus, the optical element is moved on the stage and mounted at a predetermined position on the substrate.
[0012]
That is, the present invention uses a material that transmits light having a wavelength longer than the transmission wavelength of the substrate as the alignment marker on the substrate side. An optical element can be detected. Therefore, when the alignment marker is detected by the image device, the alignment is performed in a state where the substrate and the optical element are brought close to each other by detecting from the back side of the substrate, not between the substrate and the optical element as in the conventional example. This can be performed, and the positional deviation when the optical element is subsequently lowered can be reduced.
[0013]
According to another aspect of the present invention, there is provided an optical module in which an optical fiber is placed in a groove formed on a substrate, and the optical element is mounted on a substrate that is an extension of the groove. In addition, an alignment marker made of a material that transmits light having a wavelength longer than the transmission wavelength of the substrate is formed, and the back surface of the substrate is a mirror surface.
[0014]
That is, an optical module in which optical elements are aligned with high accuracy by the manufacturing method described above is characterized. The reason why the back surface of the substrate 10 is a mirror surface is to facilitate detection from the back surface side.
[0015]
The present invention also provides an optical module manufacturing apparatus in which an optical fiber is placed in a groove formed on a substrate, and an optical element is mounted on the substrate that is an extension line of the groove. And a stage for holding the optical element disposed on the upper side of the jig, while detecting the optical element over the substrate by the image apparatus, The optical element is moved on a stage and mounted at a predetermined position on the substrate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
As shown in FIG. 1, in the optical module of the present invention, a V-shaped groove 11 for placing an optical fiber 22 is formed on a substrate 10 made of silicon or the like, and a laser diode is formed on an extension line of the groove. The optical element 20 is mounted, and the optical fiber 22 is placed and fixed in the groove 11. Further, an electrode 12 for energizing the optical element 20 is provided on the substrate 10, and this electrode is joined to a lead wire (not shown) and the whole is resin-molded or sealed in a package. A module is configured. An electrical signal introduced from the outside can be converted into an optical signal by the optical element 20 and led out to the outside by the optical fiber 22.
[0018]
If such an optical module is prepared by accurately aligning the groove 11 and the optical element 20 in advance, when the optical module is assembled, it is only necessary to place the optical fiber 22 in the groove 11. There is no need to align the two while the optical element 20 emits light and is monitored by the optical fiber 22. Such a technique is called passive alignment, and an optical module can be easily manufactured.
[0019]
The substrate 10 is generally formed of silicon. By controlling the crystal orientation, the V-shaped groove 11 can be easily formed using anisotropic etching. . However, the material of the substrate 10 is not limited to silicon, and glass, ceramics, or the like can be used.
[0020]
Further, in order to accurately position and mount the optical element 20 on the substrate 10, the alignment marker 13 is formed on the substrate 10, and the optical element 20 is mounted in accordance with this.
[0021]
The alignment marker 13 is provided in a predetermined shape at a predetermined position on the substrate 10 and is optically detected, and is formed of a material that transmits light having a wavelength longer than the transmission wavelength of the substrate 10. Yes. In other words, any light that passes through the substrate 10 must be transmitted through the alignment marker 13. Therefore, as will be described in detail later, when the optical element 20 is mounted, the optical element 20 can be detected through the substrate 10 from the back surface 15 side.
[0022]
Specifically, when the substrate 10 is formed of silicon, the transmission wavelength is about 1.2 μm, and therefore, SiO ₂ , Si ₃ N ₄ or the like is used as a material that transmits light having a wavelength of 1.2 μm or more. . Then, for example, as shown in FIG. 2, a film 14 made of the above material is formed on the surface of the substrate 10, and a part having a different film thickness is formed in a part thereof, which is used as an alignment marker 13. At this time, since the path length of the light is different in the stepped portion of the film 4, interference occurs, and this portion can be detected optically and can act as the alignment marker 13.
[0023]
In addition, although the concave thing was shown as the alignment marker 13 in FIG. 2, it can also be made into convex shape conversely. Moreover, if the level | step difference of the uneven | corrugated | grooved part which comprises the alignment marker 13 is 1000 mm or more, it can fully identify.
[0024]
Further, in order to form the alignment marker 13 on the substrate 10, a mask may be provided on the substrate 10 and coated with SiO ₂ , Si ₃ N ₄ or the like. Further, if the mask for forming the groove 11 and the mask for forming the alignment marker 13 in the anisotropic etching for forming the groove 11 are made common, the groove 11 and the alignment marker 13 can be aligned with high accuracy. can do.
[0025]
Next, a method for aligning the optical element 20 on the substrate 10 thus obtained will be described.
[0026]
As shown in FIG. 3, in order to place and heat the substrate 10, a jig 30 having a through hole 31 in the center is prepared. An image device 32 having a lens is disposed below the through-hole 31 of the jig 30, and a stage 33 for holding the optical element 20 is disposed above.
[0027]
Then, the substrate 10 on which the alignment marker 13 as described above is formed at a predetermined position on the surface is placed on the jig 30 so that the alignment marker 13 is on the through hole 31. On the other hand, the optical element 20 provided with the alignment marker 21 is similarly held on the stage 33. The stage 33 is movable in the horizontal (XY) direction and the vertical (Z) direction, and is brought close to each other so that the distance d between the substrate 10 and the optical element 20 is 1 to 5 μm. Deploy.
[0028]
In this state, the image device 32 emits light having a wavelength that transmits the substrate 10 and detects the reflected light. Therefore, the alignment marker 21 of the optical element 20 can be detected through the substrate 10, and the alignment marker 13 on the substrate 10 side can also be detected by light interference as described above. Therefore, the image device 32 can simultaneously detect both the alignment marker 13 on the substrate 10 and the alignment marker 21 on the optical element 20 side.
[0029]
Therefore, as shown in the monitor screen of the image device 32 in FIG. 4, the stage 33 is moved in the XY direction so that the alignment marker 13 on the substrate 10 side and the alignment marker 21 on the optical element 20 side coincide. .
[0030]
If the stage 33 is lowered and the optical element 20 is placed on the substrate 10 and heated by the jig 30 and bonded by soldering or the like, the optical element 20 can be mounted.
[0031]
According to such a method, it is possible to make the distance d between the substrate 10 and the optical element 20 as small as about 1 to 5 μm in advance by detecting with the image device 32 from the back side of the substrate 10, and X− After the alignment in the Y direction, the amount of positional deviation when lowered is extremely small.
[0032]
When the optical element 20 is mounted by the above-described method of the present invention, first, after roughly adjusting the alignment of the optical element 20 by the conventional method shown in FIG. It is more preferable to finely adjust the 20 alignment.
[0033]
Further, in order for the image device 15 to detect well, it is preferable that the back surface 15 of the substrate 10 be a mirror surface. Here, the mirror surface specifically means that the surface roughness (Ra) is 0.5 μm or less, and is obtained by polishing with abrasive grains of 4000 or less, preferably 12000 or less.
[0034]
In the above embodiment, the optical element 20 is not limited to a light emitting element such as a laser diode, but a light receiving element such as a photodiode can also be used. Alternatively, a plurality of optical elements 20 can be mounted on the substrate 10, and elements such as a thermistor and various circuits can be mounted in addition to the optical elements 20.
[0035]
Furthermore, the cross section of the groove 11 is not limited to the V shape, and may be a square shape or a curved surface, and can be mechanically processed.
[0036]
Moreover, the planar view shapes of the alignment markers 13 and 21 can be various, such as a cross shape as shown in FIG. Further, the alignment can be performed by using the edge or the outer side of the optical element 20 itself without forming the alignment marker 21 on the optical element 20 side.
[0037]
【Example】
As an example of the present invention, an alignment marker 13 having a width of 20 μm was formed on a substrate 10 made of silicon having a size of 2 × 4 × 0.8 mm by a film 14 of Si ₃ N ₄ . On the other hand, a laser diode having dimensions of 0.35 × 0.55 × 0.1 μm was used as the optical element 20, and an alignment marker 21 having a width of 20 μm was formed on this surface.
[0038]
Using the substrate 10 and the optical element 20, as a comparative example, first, using the apparatus shown in FIG. 5, the distance d between the substrate 10 and the optical element 20 is adjusted to 10 cm, and the optical element 20 is lowered as it is. Mounted on the substrate 10.
[0039]
On the other hand, in the embodiment of the present invention, the apparatus shown in FIG. 3 is used, and after coarse adjustment is first performed by the same method as in the prior art, the optical element 20 is lowered until the distance d between the optical element 20 and the substrate 10 becomes 5 μm. It was. In this state, as shown in FIG. 3, the image device 32 detects from the back surface 15 side, and after further fine adjustment, the optical element 20 is lowered and mounted on the substrate 10.
[0040]
In any case, the descending direction of the stage 33 was inclined by about 0.01 ° with respect to the vertical direction. Therefore, in the comparative example, the final position of the optical element 20 is shifted by about 20 μm from the predetermined position, whereas in the embodiment of the present invention, the shift amount from the predetermined position is 0.014 μm, and the position is extremely high accuracy. It was confirmed that they could be combined.
[0041]
【The invention's effect】
As described above, according to the present invention, in an optical module manufacturing method in which an optical fiber is placed in a groove formed on a substrate and an optical element is mounted on the substrate that is an extension of the groove, Using a material that transmits light having a wavelength longer than the transmission wavelength, an alignment marker is formed at a position on the substrate where the optical element is mounted, and then light is transmitted through the substrate from the back side of the substrate using the imaging device. Detecting the optical element from the back side of the substrate by manufacturing the optical module from the process of aligning and mounting the optical element while detecting the element, and aligning the substrate and the optical element in a close state This can be done, and the positional deviation when the optical element is lowered thereafter can be reduced. As a result, the position accuracy of the optical element can be extremely increased by a simple process, and an optical module with high coupling efficiency can be provided.
[Brief description of the drawings]
FIGS. 1A and 1B are perspective views showing an optical module of the present invention.
FIG. 2 is a cross-sectional view of an alignment marker portion of a substrate constituting the optical module of the present invention.
FIG. 3 is a cross-sectional view for explaining an optical module manufacturing method of the present invention.
FIG. 4 is a diagram showing a monitor screen of the image device in the method for manufacturing an optical module of the present invention.
FIG. 5 is a cross-sectional view for explaining a conventional method of manufacturing an optical module.
[Explanation of symbols]
10: Substrate 11: Groove 12: Electrode 13: Positioning marker 14: Film 15: Back surface 20: Optical element 21: Positioning marker 22: Optical fiber 30: Jig 31: Through hole 32: Image device 33: Stage

Claims (3)

In an optical module in which an optical fiber is placed in a groove formed on a substrate and an optical element is mounted on the substrate that is an extension of the groove, the transmission wavelength of the substrate is placed at the position where the optical element is mounted on the substrate. An alignment marker made of a material that transmits light having a longer wavelength is formed. The alignment marker is a concave or convex step of 1000 mm or more by anisotropic etching, and the back surface of the substrate is roughened (Ra ) Is a mirror surface having a thickness of 0.5 μm or less. 2. The method of manufacturing an optical module according to claim 1, wherein a mask for forming the groove and a mask for forming the alignment marker are shared, and a material that transmits light having a wavelength longer than the transmission wavelength of the substrate is used. Then, after forming an alignment marker at the position where the optical element is mounted on the substrate, the optical element is aligned while detecting the optical element from the back side of the substrate through the substrate using the image device. An optical module comprising a mounting process. The optical module manufacturing apparatus according to claim 1, comprising: a jig for placing a substrate; an image device disposed on a lower side of the jig; and a stage for holding an optical element disposed on the upper side of the jig; An apparatus for manufacturing an optical module, wherein an optical element is moved by a stage and mounted at a predetermined position on a substrate while detecting the optical element through the substrate by the image device.

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