JPH03164706A - Production of optical module - Google Patents

Abstract

PURPOSE:To eliminate the need for the alignment of the optical axes of optical elements by piercing a single-crystal silicon substrate with plural through holes by anisotropic etching and irradiating the substrate with UV. CONSTITUTION:The single-crystal silicon substrate 20 is pierced with through holes 22a, 22b and 22c by anisotropic etching, a V-groove 20c is formed on one side, the optical elements 3, 4, 5 and 2 corresponding to the holes 22a-22c and groove 20c are set through an UV curing adhesive, then each hole forming region is irradiated with UV from the UV-transmissive glass substrate 23 side, the groove forming region is irradiated with UV from above the groove 20c, and consequently the elements 3, 4, 5 and 2 are mounted in a module substrate 24. In this case, the module substrate 24 is irradiated with UV from its front to fix the optical fiber 2 by an UV curing adhesive, and the substrate is irradiated with UV from its rear to fix the elements 3 and 4 and permanent magnet 5 except the optical fiber 2 with the adhesive. Consequently, an optical isolator without need for the axes alignment is easily produced without lowering its extinction ration.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing an optical module, the purpose of this invention is to improve productivity and improve optical characteristics by reducing the work of aligning the optical axes of a plurality of optical elements. forming a plurality of penetrating holes having at least a desired shape and size in a single crystal silicon substrate having a surface orientation of by anisotropic etching, and forming a groove of a desired size on one side of the substrate as necessary; A module substrate was constructed by fixing a substrate that transmits ultraviolet rays to one side of the substrate excluding the groove-forming surface, and a corresponding optical element was set in each hole and groove using an ultraviolet curable adhesive. After that, each of the optical elements is mounted on the module substrate by irradiating ultraviolet rays from the side of the substrate that transmits ultraviolet rays in each of the hole forming areas, and by irradiating ultraviolet rays from the top of the groove in the groove forming area. do.

[Industrial application field]

The present invention relates to a method for mounting a plurality of optical elements on the same substrate, and more particularly to a method for manufacturing an optical module that improves productivity and optical characteristics by reducing the work of aligning optical axes between optical elements.

In order to configure an optical module by mounting many types of optical elements on the same substrate, it is necessary to perform optical axis adjustment work to match the optical axes between each optical element. Therefore, it is difficult to expect an improvement in productivity, and furthermore, the optical characteristics deteriorate due to misalignment of each optical element when it is fixed, so a solution to this problem is desired.

[Conventional technology]

FIG. 4 is a diagram for explaining a conventional optical module manufacturing method, and FIG. 5 is a diagram for explaining another manufacturing method.

In the figures, the case where an optical isolator is used as the optical module will be explained.

In FIG. 4, which is a plan view, reference numeral 1 indicates a base made of brass or the like.

Also, an optical fiber 2 equipped with a lens (not shown) at the tip etc.
is held around its end by an optical fiber holder 2a, and 3 in the figure is a polarizer made of crystal or the like, which is held by the polarizer holder 3a.

Furthermore, 4 in the figure is a Faraday rotator in which a bismuth (Bi)-substituted iron garnet film is deposited on a non-magnetic garnet substrate, and is held by a Faraday rotator holder 4a surrounding it. .

Further, the Faraday rotator 4 is provided with a through hole 5a inside.
The permanent magnet 5 that applies a magnetic field is made of samarium cobalt (Sm-Co), for example, and is held by a magnet holder 5b.

Note that 7 indicates a laser diode set on a stage 7a that can move in three dimensions.

Therefore, while passing the laser light emitted from the laser diode 7, for example, the polarizer 3 and the Faraday rotator 4 are first placed at predetermined positions on the base 1, and the optical axes of the polarizer 3 and the Faraday rotator 4 are adjusted. First, the optical fiber 2 is placed on the base 1 so that its end face faces the polarizer 3 side, and the passing light is detected on the other end face side (not shown) of the optical fiber 2. After adjusting the optical axis, place the permanent magnet 5 on the base 1 so as not to interfere with the optical axis, and in that state, attach each optical element and the permanent magnet with a normal thermosetting adhesive such as epoxy resin. The optical isolator 6 is manufactured by adhesively fixing it to the base 1.

In this case, since it is difficult to accurately position each of the above optical elements on the base l, it takes a skilled worker or a long time to adjust the optical axis of the optical isolator each time each optical element is placed on the base l. The drawback is that it takes time.

In addition, to fix each optical element, we use a thermosetting adhesive that is heated at 65 to 70°C for 3 hours, so the difference in thermal expansion coefficient between the base and each optical element will cause the temperature to rise. The extinction ratio (the ratio of the optical output Ps when an optical signal is received and the optical output Pb when no optical signal is received) when the optical elements are returned to room temperature after adhesion, Ps/Pb: ext
For example, experimental results have confirmed that the extinction ratio decreases by 7 dB from 40 dB to 33 dB.

FIG. 5 shows a method of manufacturing an optical isolator that takes such drawbacks into account.

Generally, when chemical etching is performed on a single crystal silicon plate, there are planes with a high etching speed in the specific direction of the crystal orientation, and as a result, sharp and precise rectangular or figure 7 holes or grooves are formed. It is well known that this phenomenon is generally referred to as anisotropic etching.

In FIG. 5, 1 and 1 in steps (1) and (2) represent a plan view, and 2 and 3 represent corresponding side views, respectively.

In steps (1) ■ and ■, the board IO is etched.
Is the plane orientation of a (110), orientation flat plane (hereinafter simply referred to as orientation flat plane) 10b (11
1) A single crystal silicon plate with a thickness of 330 μm was cut out.

Therefore, after performing masking processing corresponding to the respective positions and sizes so that each optical element and permanent magnet explained in FIG. When anisotropic etching is performed, the wall surface in the direction perpendicular to the optical axis (direction a in the figure), that is, the crystal orientation (l l l), is almost perpendicular to the etching surface lea.

The wall surface in the direction parallel to the optical axis is the etched surface 10a.
A slope is formed at a predetermined angle θ (#35.3°) with respect to the surface.

Therefore, if the etching time is set to about 6 hours, for example, the area corresponding to the optical fiber 2 in FIG.
109°) and a depth d of approximately 200 μm, the V-groove 2b is
In addition, in the area corresponding to the polarizer 3 and the Faraday rotator 4, the plane perpendicular to the optical axis is almost perpendicular, and both sides parallel to the optical axis have a depth d where the slope is at the angle θ (=35.3°). (approximately 200 .mu.m) recesses 3b and 4b, and similar recesses 5c are formed in areas corresponding to the permanent magnets 5, thereby obtaining a module substrate 11.

Next, after applying the adhesive described in FIG. 4 to each of the recesses and grooves, (2) attach the optical fiber 2 shown in FIG.

After positioning the Faraday rotator 4 in the concave hole 4b as a guide in the optical axis direction so that each predetermined end face is in contact with the wall surface of the crystal orientation (111) perpendicular to the optical axis, as shown in FIG. By positioning the permanent magnet 5 having the through hole 5a in the recessed hole 5c and heating it at 65 to 70°C for about 3 hours,
As shown in the side sectional view shown in step (3), it is possible to obtain an optical isolator 12 in which optical elements and permanent magnets are mounted.

Especially in this case, each of the above-mentioned concave holes 3b, 4b, 5c
Since the V-groove 2a is formed with extremely high precision, there is no need to adjust the optical axis between the optical elements, and the laser diode 7 explained in FIG. This allows the isolator 12 to function efficiently.

However, since a thermosetting adhesive similar to that shown in Fig. 4 is used to fix each optical element, the above-mentioned distortion of the optical element and reduction in extinction ratio cannot be avoided; For example, it has been confirmed that the power level decreases by 3 dB from 40 dB to 37 dB.

[Invention or problem to be solved]

In conventional optical module manufacturing methods, when each optical element is individually fixed to a base, there is a problem in that adjusting the optical axis takes a lot of man-hours and the extinction ratio decreases significantly.

In addition, when fixing each optical element corresponding to the hindlimb concave hole and groove formed by anisotropic etching on a single crystal silicon substrate, the optical axis adjustment work becomes unnecessary or the extinction ratio decreases. There was a problem that there was no way to suppress it.

[Means to solve the problem]

The above problem can be solved by forming a plurality of penetrating holes having at least the required shape and size in a single crystal silicon substrate having a predetermined surface orientation by anisotropic etching, and if necessary, forming holes of the required size on one side of the substrate. A module board is constructed by fixing a substrate that transmits ultraviolet rays to one side of the substrate excluding the groove-forming surface, and attaching corresponding optical elements to each of the above grooves using an ultraviolet curable adhesive. After setting the optical elements through the module substrate, ultraviolet rays are irradiated from the side of the substrate that transmits ultraviolet rays in each of the hole forming areas, and ultraviolet rays are irradiated from the top of the groove in the groove forming area, so that each of the optical elements is attached to the module substrate. The problem is solved by a method for manufacturing an optical module that is mounted on a PC.

[For production]

If the thermosetting adhesive is replaced with an ultraviolet curable adhesive, a heating step during adhesion becomes unnecessary, thereby eliminating distortion of the optical element and suppressing a decrease in extinction ratio.

On the other hand, in the conventional method of constructing an optical isolator, the base or substrate made of brass or silicon is opaque, and because it is made of a Faraday rotator or a material that absorbs ultraviolet rays, the back side or surface of the base or substrate is It is impossible to use UV-curable adhesives due to UV irradiation from the side.

Therefore, in the present invention, after mechanically processing a groove for fixing an optical fiber to a single-crystal silicon substrate, the substrate is penetrated by anisotropic etching at positions corresponding to optical elements and permanent magnets excluding the optical fiber. Precise holes are formed, and a transparent substrate that transmits ultraviolet rays is attached to the back side of the V-groove forming surface to form a module substrate.

In this case, the optical fiber is fixed by irradiating ultraviolet rays from the front side of the module board, and the optical element and the permanent magnet, excluding the optical fiber, are bonded and fixed by irradiating ultraviolet rays from the back side with an ultraviolet curable adhesive. can do.

Therefore, an optical isolator that does not require optical axis alignment can be easily manufactured without reducing the extinction ratio.

〔Example〕

FIG. 1 is a process diagram showing the method for manufacturing an optical module according to the present invention, and similarly to FIG. 5, it shows the case of an optical isolator.

Further, FIG. 2 is a diagram showing the case where the present invention is applied to a magneto-optical switch, and FIG. 3 is a diagram showing the case where the present invention is applied to an optical head.

In FIG. 1, steps (B) and subsequent steps are shown as cross-sectional views of a perspective view of step (A) taken along a center line a-a' perpendicular to the orientation flat surface.

In step (A) of FIG. 1, the etched surface 20a of the silicon substrate 20 has a (110
), a V-groove 20C similar to that shown in FIG. 5 is formed by, for example, a cutting saw in a direction perpendicular to the orientation flat surface 20b of a single crystal silicon plate cut out so as to have an orientation flat surface 20b (111). In this case, the V-groove 20c can be precisely machined on the order of microns.

Note that A indicated by a broken line on the etched surface 2Oa indicates the area where the polarizer 3 is mounted in FIG. 5, B indicates the area where the Faraday rotator 4 is mounted, and C indicates the area where the permanent magnet 5 is mounted. each represents.

Therefore, a SiO□ film with a thickness of, for example, 0.5 μm is formed on the etched surface 2Oa by a known thermal oxidation method, and then a photoresist is applied and a mask is formed so that the above regions A, B, and C are arranged. After exposure and development, etching was performed at room temperature for 4 minutes in a solution containing 5 ammonium fluoride and 1 liter of hydrofluoric acid, resulting in the areas A, B,
A 5in2 film 21 with only the portion C removed can be formed on the silicon substrate 20.

(B) represents this state.

Next, with the remaining SiO
30 μm) After etching, the above SiO□ film 2
1 is removed, the above areas A, B, and C are removed as shown in (C).
It is possible to obtain a silicon substrate 22 with holes 22a, 22b, and 22c penetrating only the portions .

At this point, the V-groove 20c formed in (A) is exposed on the surface.

Furthermore, an ultraviolet curable adhesive is applied to the back side of the V-groove 20c forming surface of the silicon substrate 22, and the glass substrate 23 is brought into close contact with the glass substrate 23 having a thickness of about 500 μm, and ultraviolet rays are irradiated from the glass substrate 23 side. The module board 24 shown in (D) can be obtained by bonding and fixing.

In this case, the above companies 22a, 22b, 22c are the fifth
As explained in the figure, it is extremely sharp and formed with high precision.

Therefore, after applying the above-mentioned ultraviolet curable adhesive to the groove 20c of the module board 24 and setting the optical fiber 2 similar to that shown in FIG. 2 can be fixed to the substrate 24.

Further, by applying the same adhesive to each company's 22a, 22b, and 22c, the polarizer 3 shown in FIG.
The optical isolator 25 shown in (E) can be easily manufactured by setting the optical isolator 25 on the substrate 24 in the same manner as shown in FIG. can.

In particular, in this case, not only is it unnecessary to align the optical axes between each optical element, but there is no heating process for bonding each optical element, so no distortion occurs in the optical element, and furthermore, it is possible to suppress a decrease in extinction ratio. can.

Experimental results show that the extinction ratio is, for example, 41 dB to 40 dB.
It has been confirmed that the reduction in ldB to dB is sufficient.

In FIG. 2(a), 26 represents a module board formed by the same method as in FIG.

This module substrate 26 consists of a single-crystal silicon substrate 27 with a thickness of 330 μm and a glass substrate 23 with a thickness of 500 μm. In particular, the surface of the silicon substrate 27 has a crystal orientation (110), and its -side 27a has a crystal orientation. Direction (111)
It becomes. Therefore, after mechanically forming two V-grooves 27b at predetermined positions on each side in a direction perpendicular to the above-mentioned side 27a, concave holes 28a for fixing the two polarizing prism groups 28 are formed at predetermined positions across the V-grooves 27b. and the two polarizing prisms 2
8, a concave hole 29a for fixing an optical element 29 integrated with a Faraday rotator and a λ/2 plate is formed by anisotropic etching.

Next, after applying an ultraviolet curing adhesive to the valley grooves and each concave hole of the module board 26, optical fibers 30 are attached to the four V-grooves 27b, and polarizing prism groups are attached to the two concave holes 28a. 28, and the optical element 2 is placed in the concave hole 29a.
After setting the optical fibers 9 so as to face each predetermined direction, the optical fibers 30 are connected from the top surface of the substrate 26, and the optical fibers 30 are
The required magneto-optic switch 31 can be obtained by irradiating each optical element except 0 with ultraviolet rays from the bottom surface of the substrate 26.

In FIG. 3(a), 36 is also a module substrate formed by the same method.

This module substrate 36 consists of a single-crystal silicon substrate 37 with a thickness of 330 μm and a glass substrate 23 with a thickness of 500 μm, and the crystal orientation is (110) on the surface as in the case of FIG. is (111). Therefore, by using the method shown in FIG.
A polarizing prism and λ/ between a and the two optical lenses 38
A concave hole 39a for fixing an optical element 39 in which four plates are integrated.
It is constructed by forming.

Next, after applying an ultraviolet curable adhesive to each of the concave holes of the module substrate 36, the optical lenses 38 are placed in the two concave holes 38a, and the optical element 39 is placed in the concave hole 39a so that they face each predetermined direction. By setting and further irradiating ultraviolet rays from the lower surface of the substrate 36, the required optical head 40 shown in (b) can be obtained.

Note that 41 shown by broken lines represents a light source, 42 represents an optical disk, and 43 represents a photodetector, and by arranging these devices as shown, the optical head 40 can function as a head.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a method for manufacturing an optical module that improves productivity and optical characteristics by reducing the work of aligning optical axes between a plurality of optical elements.

[Brief explanation of the drawing]

Figure 1 is a process diagram showing the method for manufacturing an optical module according to the present invention, Figure 2 is a diagram showing the case where it is applied to a magneto-optical switch, Figure 3 is a diagram showing the case where it is applied to an optical head, and Figure 4. 5 is a diagram illustrating a conventional optical module manufacturing method, and FIG. 5 is a diagram illustrating another manufacturing method. In the figure, 2.30 is an optical fiber, 3 is a polarizer, 4 is a Faraday rotator, 5 is a permanent magnet, 20 and 22 are silicon substrates, 20a is an etched surface, 2
0b is an orientation flat surface, 20c, 27b are V grooves, 21 is a Sin, film, 22a to 22c are holes, 23 is a glass substrate, 24, 26.36 are module substrates, 25 is an optical isolator, 27, 37 are silicon substrates, 27a and 37a are sides, 28 is a polarizing prism group, 28a and 29a are concave holes, 29 and 39 are optical elements, 31 is a magneto-optic switch, -
4 38 is an optical lens, 38a, 39a are concave holes, 4
0 represents an optical head, 41 a light source, 42 an optical disk, and 43 a photodetector, respectively. This invention IJJ5 Old Mora Ale's 3-step process map (α) (b) The 3rd process chart of the IJJ5 old Mora Ale, which uses ff ki literally and i...nochi. i to \2.7 Toyo 2, Kojitsu hL 7' Niji bow stand 2
111 η of 1111F and 16

Claims (1)

[Claims] A single crystal silicon substrate (20) having a predetermined plane orientation,
A plurality of through holes (22a, 22b, 22c) having at least the required shape and size are formed by anisotropic etching, and if necessary, a groove (20c) of the required size is formed on one side of the hole, A module substrate (24) is constructed by fixing a substrate (23) that transmits ultraviolet rays to one side of the substrate excluding the groove forming surface, and the holes (22a, 22b, 22c) and grooves (20c)
), after setting the corresponding optical elements (3, 4, 5, 2) via an ultraviolet curable adhesive, in each hole forming region, ultraviolet rays are irradiated from the substrate side that transmits ultraviolet rays,
Further, in the groove forming region, each of the optical elements (3, 4, 5, 2) is mounted on the module substrate (24) by irradiating ultraviolet rays from above the groove. .