JPH08110446A - Light transmission module - Google Patents

Abstract

PURPOSE: To provide a module substrate structure for placing optical elements, such as semiconductor lasers, on a substrate having a waveguide layer in a short time with high accuracy. CONSTITUTION: This module substrate structure is formed to execute optical axis adjustment of the core of the waveguide layer 2 and the active layers of the semiconductor lasers 4 by butting the corner parts 21 of the apertures formed in the waveguide layer 2 of the Si substrate 1 and the corner parts for alignment formed on the semiconductor lasers 4. The module substrate allows the alignment of the semiconductor lasers to the substrate simply by only butting the substrate and, therefore, the alignment is executed in a short time and eventually the low-cost module substrate is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission module, and more particularly to a module substrate structure and an optical element fixing method for positioning and fixing the above optical element on a substrate with high accuracy.

[0002]

2. Description of the Related Art A module substrate is provided with a semiconductor laser, a photodiode, an optical element such as a waveguide including a core and a clad in a waveguide layer, and an electronic circuit element on the substrate. The optical element and the electronic circuit element are hybrid-mounted on the substrate, and the optical elements are optically connected. In order to realize an inexpensive optical transmission module, the module substrate is required to have the following.

(1) High-precision alignment ◆ To minimize the coupling loss between optical elements, for example,
It is necessary to fix the optical elements such as the semiconductor laser and the waveguide, or the photodiode and the waveguide with a positioning accuracy of several μm or less. In particular, when connecting a semiconductor laser and a waveguide, sub-micron accuracy is required because the alignment loss greatly affects the coupling loss.

(2) High-speed alignment ◆ In order to realize a low-cost optical transmission module, it is necessary to fix the optical element on the substrate in a short time while ensuring the alignment accuracy.

As a means for solving the above problem (1),
A method for positioning and fixing a semiconductor laser on a substrate using a solder ball having a diameter of about 50 μm is described in 1993 Spring Conference of the Institute of Electronics, Information and Communication Engineers, page 4-314. In this method, a solder ball is placed between pads of several tens of μm formed on the surface of the semiconductor laser and the surface of the substrate, and the surface tension of the solder ball and the wettability of the solder to the metal pad are used to position the semiconductor laser. It is fixed. In addition, there is a method of performing alignment by aligning a marker formed on the semiconductor laser with a marker on the substrate.
It is described in 1993 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers, page 4-266. In the method of using a marker, the marker of each substrate is detected in the plane where the two substrates are in close contact with each other by an infrared microscope, and the substrate stage is moved and aligned and fixed.

[0006]

A method for positioning and fixing a semiconductor laser on a substrate using a solder ball is as follows.
Since it is aligned using the surface tension of the solder,
The position of the semiconductor laser is determined simply by placing it on the solder ball. That is, the position of the semiconductor laser with respect to the substrate is automatically determined by the pattern of the metal pad formed on the semiconductor laser and the substrate. Therefore, there is an advantage that the semiconductor laser can be positioned and fixed in a short time as compared with the method using the marker, but it also has the following problems.

(1) The distance between the semiconductor laser and the substrate is determined by the volume of the solder ball. Therefore, in order to control the distance between the semiconductor laser and the substrate with an accuracy of ± 1 μm, it is necessary to make the volume of all the solder balls used to fix one semiconductor laser uniform.

(2) Since the solder balls having a diameter of about 50 μm are used, the semiconductor laser placed on the solder balls is higher than the substrate by the height of the solder balls. That is, the substrate under the semiconductor laser must be processed in advance by the height of the solder ball to adjust the height between the semiconductor laser and the waveguide formed on the substrate. As a result of adjusting the height of the substrate, the surface of the substrate becomes uneven, and it becomes difficult to form the metal pad pattern for solder balls and supply the solder balls, which will be performed in the subsequent process. Also,
Since the heat generated by the semiconductor laser diffuses toward the substrate only through the solder balls, the heat dissipation of the semiconductor laser is low and the life of the laser is significantly reduced.

In the method of positioning and fixing the semiconductor laser on the substrate by using the marker, since the semiconductor laser and the substrate are bonded through the solder layer of several μm, the processing of the substrate as described in the above solder ball is performed. Therefore, the substrate and the semiconductor laser can be easily processed until the bonding. Also,
Since the entire semiconductor laser is fixed on the substrate, heat generation in the semiconductor laser section does not matter. However, it is difficult to position the semiconductor laser in a short time because the active alignment method using the marker detection is used for positioning the semiconductor laser. Therefore, there is an inconvenience that the cost of the module substrate itself becomes high.

An object of the present invention is to provide a module structure and an optical element fixing method capable of accurately positioning and fixing an optical element in a short time.

[0011]

The above object is to provide a semiconductor laser that emits light on a substrate, a photodiode that receives light and converts it into an electric signal, and an optical element that guides the light from the semiconductor laser and the light to the photodiode. In an optical transmission module comprising a semiconductor laser and a photodiode and a waveguide layer for optically coupling an optical element, an opening is provided in the waveguide layer, and the corners of the semiconductor laser and the photodiode are provided at the corners of the opening. It is achieved by fitting and fastening together.

In the above optical transmission module, a convex shape for mounting the semiconductor laser and the photodiode may be formed on the substrate, and a plurality of openings are provided, and the semiconductor laser or the semiconductor laser is provided at the corner of each opening. You may fix a photodiode.

Further, the above object is to provide either a semiconductor laser that emits light on a substrate or a photodiode that receives light and converts it into an electric signal, an optical element that guides light from the semiconductor laser or light to the photodiode, a semiconductor laser or In an optical transmission module including a waveguide layer for optically coupling a photodiode and an optical element, an opening is provided in the waveguide layer, and a corner of a semiconductor laser or a photodiode is fixed to a corner of the opening for fixation. It is achieved by
In this optical transmission module, a convex shape for mounting a semiconductor laser or a photodiode may be formed on the substrate.

Further, the above object is to provide a semiconductor laser that emits light on a substrate, a photodiode that receives the light and converts it into an electric signal, an optical element that guides the light from the semiconductor laser and the light to the photodiode, the semiconductor laser and the photodiode. In a method of manufacturing an optical transmission module comprising a waveguide layer that optically couples an optical element with an optical element, positioning is performed by pressing a corner portion of a semiconductor laser and a photodiode against a corner portion of an opening formed in the waveguide layer. After that, it is achieved by fixing the semiconductor laser and the photodiode. In the above method of manufacturing the optical transmission module, the semiconductor laser and the photodiode may be joined to the convex portion provided on the substrate.

[0015]

In the above module substrate, the corner of the opening formed in the waveguide layer on the substrate and the alignment corner formed on the semiconductor laser are abutted and positioned, and the semiconductor laser is directly placed on the substrate. Place and fix. For this reason, in the present module substrate structure, the semiconductor laser is mounted directly on the substrate, so that the height of the semiconductor laser with respect to the substrate can be made more accurate than when a solder ball is used. Further, the heat generated by the semiconductor laser also diffuses from the entire surface of the semiconductor laser to the substrate, so that heat generation due to laser oscillation does not pose a problem. Further, in this module substrate structure, the module substrate can be easily manufactured because there is no need to mount the solder balls and there is no need to deeply process the substrate.

The present module substrate structure has a semiconductor laser or photodiode, and a semiconductor laser and a photodiode positioned with respect to a waveguide formed on the substrate only by abutting the semiconductor laser and the photodiode on the corners of the opening in the waveguide layer. Since they can be aligned with each other, positioning can be performed in a shorter time than in the active alignment method that performs marker detection, and as a result, a low-priced module substrate can be obtained.

[0017]

Embodiments of the present invention will be described with reference to the drawings. ◆
FIG. 1 is a perspective view of an optical transmission module in which a semiconductor laser and a photodiode are hybrid-mounted on the surface of a substrate using the butting method. The optical transmission module includes an optical waveguide layer 2 formed on a substrate 1, a semiconductor laser 4, a semiconductor laser driving circuit 6, a photodiode 5, a photodiode circuit 7, a waveguide in a waveguide layer, and an optical waveguide. At least one optical fiber 8 to be connected and a cap 3 for individually enclosing the semiconductor laser 4 and the photodiode 5 are provided. The optical element and the electronic circuit element are hybrid-mounted on the substrate, and the optical elements are optically connected. The waveguide layer 2 having an opening is formed on the substrate, and the semiconductor laser 4 and the photodiode 5 have an opening 60 in the waveguide layer 2.
Placed on. The alignment between the core in the waveguide 2 and the active layer of the semiconductor laser 4 is performed by abutting the semiconductor laser 4 and the photodiode 5 on the corners of the opening 60 formed in the waveguide layer 2. The optical fiber 8 is positioned and fixed by the groove formed on the substrate 1. When the waveguide layer is formed up to the end face of the substrate, the optical fiber can be fixed to the end face of the substrate 1. The semiconductor laser 4 and the photodiode 5 are inserted into the individual independent openings 60 in order to prevent crosstalk between signals of the semiconductor laser and the photodiode.

The abutting structure of the semiconductor laser portion will be described with reference to FIGS. It should be noted that although the drawings after FIG. 2 only show the case where the semiconductor laser is mounted on the substrate, the photodiode can be mounted on the substrate as in the case of the semiconductor laser.

FIG. 2 shows a semiconductor laser mounting portion of a module substrate in which the semiconductor laser 4 is mounted on the substrate by the butting method. The figure shows only the laser mounting portion of the optical transmission module. The semiconductor laser mounting portion includes a Si substrate 1, a waveguide layer 2, a semiconductor laser 4, and a Si cap 3. A boss portion (projection shape) 9 is formed on the Si substrate for adjusting the height of an active layer for oscillating a laser formed in a semiconductor laser and a core for guiding light formed in a waveguide layer. There is. By changing the height of the boss portion 9, the height of the active layer of the laser with respect to the substrate (correctly, the waveguide) is adjusted.

Further, the semiconductor laser 4 is aligned in the plane by pressing the corner of the semiconductor laser 4 against one corner of the opening 60 formed in the waveguide layer. Since the corners of the semiconductor laser 4 and the openings formed in the waveguide layer 2 are formed by the dry etching apparatus used in the semiconductor fine processing technology, the corners of the semiconductor laser 4 serving as a reference for alignment are The opening in the waveguide layer 2 can be formed with submicron processing accuracy.

Further, the positions of the corners formed in the semiconductor laser and the positions of the openings in the waveguide layer are patterned with submicron positional accuracy with respect to the active layer of the semiconductor laser and the core of the waveguide, respectively. . Therefore, the active layer of the semiconductor laser and the waveguide core on the substrate can be positioned with sub-micron accuracy.

The positional relationship between the parts shown in FIG. 2 will be described with reference to FIGS. 3 to 7. It should be noted that the dimensions shown in FIGS. 3 to 7 are examples, and each dimension differs depending on the size of the semiconductor laser 4 and the size of the waveguide structure.

FIG. 3 is a perspective view of the module substrate of the semiconductor laser portion excluding the cap shown in FIG. 3 is shown in FIG.
4 is a sectional view taken along line A-A of the module substrate shown in FIG. 6, FIG. 6 is a sectional view taken along line BB of the module shown in FIG.
6 is an enlarged sectional view of the region C of FIG.

FIG. 4 shows a structure in which the semiconductor laser 4 is pressed against an opening formed in a part of the waveguide layer 2 and positioned by using the positioning end 19 of the semiconductor laser. The semiconductor laser alignment end 19 is processed based on the shape of the active layer 13 of the semiconductor laser 4 (a stripe pattern forming an optical resonator).

In FIG. 6, using the boss portion 9 on the Si substrate,
The active layer 13 of the semiconductor laser 4 and the core 11 in the waveguide layer 2
It is shown that the heights of and are being adjusted. The laser is also pressed against the end face of the waveguide layer 2 in the laser emission direction.

The boss portion 9 provided on the Si substrate 1 is formed by etching the Si substrate 1. In this embodiment, it is formed by anisotropic etching using an aqueous solution of potassium hydroxide. The height of the boss portion 9 is controlled by the etching amount of the Si substrate 1. Since the etching amount of the Si substrate 1 can be controlled with submicron accuracy, the height of the boss portion 9 can also be processed with high accuracy as shown in FIGS. Further, in this embodiment, the semiconductor laser 4 is mounted on the Si boss portion 9 with the junction down (the active layer 13 is on the lower side).

From the above, in this embodiment, the position of the active layer 13 of the semiconductor laser 4 can be positioned with respect to the etched Si substrate surface with submicron height accuracy.

FIG. 8 shows a plan view of the module substrate shown in FIG. 3 as seen from above. 9 and 10 are enlarged views of the area E of FIG. FIG. 9 shows the shape of the opening of the waveguide layer before mounting the semiconductor laser 4 on the substrate.
Reference numeral 0 indicates a state after mounting the semiconductor laser 4.
As shown in FIG. 9, two recessed shapes 15 and 15 ′ are formed in the opening formed in a part of the waveguide layer 2.
One is formed at the corner of the opening and the other is formed at the end of the core 11 of the waveguide. The recess 15 at the corner of the opening is formed to prevent the corner of the laser chip 4 from hitting the corner of the opening when the semiconductor laser 4 is mounted. By providing the recess 15 at the corner of the opening, the semiconductor laser 4 contacts the opening on two surfaces and is positioned. The recess 15 ′ at the end of the core 11 of the waveguide is for preventing the end face of the active layer 13 formed in the semiconductor laser from coming into contact with the opening and breaking when the semiconductor laser 4 is mounted. .

FIG. 11 shows details of the cap 3, the semiconductor laser 4, and the waveguide substrate 14, which are the main components of the semiconductor laser module section. Each component is described below. The waveguide substrate 14 is based on the Si substrate 1,
Si boss portion 9 for adjusting the height of the semiconductor laser 4 and the waveguide, solder layer 18 for semiconductor laser bonding, waveguide layer 2, corner portion 21 of the opening 60 for aligning the semiconductor laser 4 and the waveguide, semiconductor A feedthrough electrode 20 for the laser 4 is formed. In addition to the active layer, the semiconductor laser 4 has an L-shaped end portion 1 for aligning the semiconductor laser with the waveguide.
9. A semiconductor laser bonding solder layer 18 is added. On the cap 3, a cap groove 16 and a bonding solder layer 17 for bonding the cap to the substrate are formed.

The processing process of each component will be described below with reference to FIGS. 12 to 17. ◆ Fig. 12 shows the process of processing the cap. In addition, each figure showed the cross-sectional view of the cap.

(A) Formation of cap structure (FIG. 12)
(A)) An etching mask 22 was formed on the Si substrate 1 by photolithography. 40% based on etching mask 22
Groove 1 by etching Si in an aqueous solution of potassium hydroxide
6 was formed. The Si substrate 1 has a plane orientation of (100). A silicon oxide film was used for the etching mask 22. For the etching, anisotropic etching having different etching rates depending on the crystal axis of Si was used. The depth of the groove 16 is preferably determined based on the size of the optical element such as the semiconductor laser 4 mounted on the substrate.

(B) Removal of etching mask (FIG. 12)
(B)) The etching mask 22 used in the above (a) is removed. In this example, the silicon oxide film as the etching mask was removed using a mixed solution of hydrofluoric acid and ammonium fluoride.

(C) Formation of solder layer for cap bonding (FIG. 12 (c)) A solder layer 17 for bonding the cap 3 and the waveguide substrate 14 is formed on the terrace portion of the cap. In this embodiment, the solder metal 17 is formed using a metal mask. A vacuum evaporation method with high directivity was used for forming the solder metal 17. It is also possible to form a film by a sputtering method. It is also possible to form the solder metal film 17 only on the terrace portion by photolithography using a photoresist.

FIG. 13 shows a processing process of the semiconductor laser 4. ◆ (a) Formation of semiconductor laser on substrate (FIG. 13A) ◆ A light emitting device is formed on a compound semiconductor substrate 51, for example, an InP substrate. The active layer 13 portion in the figure is a light emitting portion.

(B) Formation of L-shaped end portion 19 for aligning the semiconductor laser 4 and the waveguide (FIG. 13B) ◆ A dry etching mask is formed on the substrate on which a plurality of semiconductor lasers are formed. It is formed by lithography. The substrate is etched by about 30 μm with a reactive ion etching device based on the mask pattern to form an L-shaped end portion 19 for aligning the semiconductor laser and the waveguide. The etching amount is the thickness of the waveguide layer 2 and the Si boss portion 9
It is desirable to be determined from the height, the position of the active layer 18 in the semiconductor laser, and the like. That is, the substrate is etched by the depth required for positioning and fixing.

(C) Formation of solder layer 18 for bonding (see FIG. 13)
(C)) ◆ The semiconductor laser bonding solder layer 18 is formed on the substrate.
For solder formation, the above-mentioned "formation of solder layer for cap bonding"
The metal film 18 was formed on the substrate by the same method as described above. That is, a metal mask or photoresist was used for patterning the solder layer, and either vacuum vapor deposition or sputtering was used for film formation.

(D) Chip formation (FIG. 13 (d)) ◆ The chip-shaped semiconductor laser 4 is formed by cleaving and dicing the substrate 51. The substrate 51 is separated by a part of the etching hole formed in (b). Since the portion 19 for aligning the semiconductor laser and the waveguide is the end face of the opening formed by dry etching, the processing accuracy of dicing does not contribute to the alignment of the chip-shaped semiconductor laser.

14 and 15, the waveguide layer 2 is formed on the substrate 1.
The processing process of the waveguide substrate 14 in which is formed is shown. FIG.
4 is a structural perspective view of each processing step of the waveguide substrate 14, and FIG. 15 is a sectional display portion CC, DD, E- of each of FIGS. 14A, 14B, and 14C. The sectional view of the E part was shown. The method of manufacturing the waveguide substrate 14 will be described below.

(A) Formation of height adjusting boss between semiconductor laser 4 and waveguide (FIG. 14 (a)) ◆ Boss 9 for matching the height of the active layer of the semiconductor laser with the height of the core of the waveguide. Are formed on the Si substrate 1. ◆ Si substrate 1 based on mask 22 formed by photolithography
Is etched to form the Si boss portion 9. Si substrate 1
The surface orientation was (100). A silicon oxide film was used as an etching mask and a 40% potassium hydroxide aqueous solution was used as an etching solution. For the etching, anisotropic etching having different etching rates depending on the crystal axis of Si was used.

(B) Preparation of feedthrough electrode 20 (FIG. 14B) ◆ Feedthrough electrode 20 is formed on Si substrate 1 as a means for supplying power to semiconductor laser 4. Although platinum is used as the electrode material in this embodiment, it is desirable to appropriately select the electrode material in consideration of matching with the subsequent process. In addition to the role of supplying power to the semiconductor laser, the feed-through electrode 20 pattern also has a role of protecting a part of the Si substrate during dry etching which is one of the subsequent steps. Further, in order to keep the surface of the waveguide layer 2 formed on the feed-through electrode in a later step flat even in a portion not actually used for the feed-through electrode 20, the electrode pattern 24 is formed.
Are formed.

(C) Formation of opening for aligning the waveguide 10 and the semiconductor laser 4 (FIG. 14 (c)) ◆ Opening for aligning the waveguide 10 and the semiconductor laser on the substrate The corner 21 is formed in a part of the waveguide layer 2. The method of manufacturing the waveguide layer 2 will be described below.

First, the clad 12 in the waveguide layer is formed on the substrate on which the feedthrough electrode 20 is formed (FIG. 15).
(C-1)). By forming the clad 12, the boss portion 9
Planarize the substrate having. Next, the core 11 is formed on the clad 12, and the core 11 is patterned using the mask pattern 22 of tungsten silicide (WSi) (FIG. 15C-2). A reactive ion beam etching apparatus, which is one of dry etching apparatuses, was used for patterning the core 11. Finally, the core 11 is embedded using the clad 12 having a thickness of several tens of μm to form the waveguide layer 2 (FIG. 15C-3). In this example, any one of vacuum vapor deposition, sputtering, and flame deposition was used for forming the cladding, and vacuum vapor deposition or sputtering was used for forming the core.

A method of forming the alignment opening corner portion 21 in the waveguide layer 2 will be described. ◆ A metal mask pattern 22 for dry etching is formed on the waveguide layer 2.
The mask pattern 22 is aligned with submicron accuracy with respect to the position of the core pattern 11 in the waveguide layer. The waveguide layer portion is etched based on the metal mask pattern 22 to manufacture the opening corner portion 21 (FIG. 15C.
-4)). At this time, the feed-through electrode portion formed on the Si substrate serves as an etching stop layer.

Next, the solder layer 18 for semiconductor laser bonding is formed on the boss portion 9. The manufacturing method is the same as the method described in "Formation of solder layer for cap joining" described above, and the solder layer 18 is formed on the boss portion 9 (FIG. 15).
(C-5)). That is, a metal mask or photoresist was used for patterning, and either vacuum vapor deposition or sputtering was used for film formation. The solder layer 18 also plays a role of electrically connecting the semiconductor laser 4 and the feedthrough electrode 20.

In the above method (a) of manufacturing the waveguide substrate,
A boss portion was formed on the Si substrate by the Si etching method. 16 and 17 show another method of forming a boss portion on a Si substrate. In FIG. 16, the boss portion is formed by using the plating film.

A boss forming metal pattern 24 is formed on the substrate 1.
Is created by photolithography. Then, a metal film is grown only on the metal pattern 24 by plating to form the boss portion 25. In the method shown in FIG. 16, since the boss portion on which the semiconductor laser is mounted is formed of a metal having a thermal conductivity higher than that of Si, the heat generated by the semiconductor laser on the boss portion is efficiently diffused to the substrate. Therefore, there is an advantage that a high output semiconductor laser can be used. FIG.
Also in the method shown in FIG. 6, the height of the boss portion can be manufactured with submicron accuracy by controlling the plating film formation time.

In FIG. 17, the boss portion is formed by combining the Si etching technique and the etching stop technique. In this method, an SOI (silicon on insulator) substrate 1 in which a silicon oxide film 27 is sandwiched between Si substrates is used. Etching mask pattern 2 on the upper Si 26
Form 2 The upper Si 26 is etched based on the mask pattern 22 to form the Si boss portion 9. In the case of this method, since the etching rate of the embedded silicon oxide film 27 is much slower than that of Si, the etching stops at the silicon oxide film layer. That is, the height of the boss portion corresponds to the thickness of Si on the upper side.

In the method described with reference to FIG. 14A, since the height of the boss is controlled only by the etching time, there is a problem that the etching amount (height of the boss) varies depending on the manufacture. In the method shown in FIG. 17, Si
Etching is an etching stop layer (silicon oxide film)
Since it ends uniquely when reaching, it is possible to manufacture a boss portion having a uniform height with good reproducibility.
It is desirable that the height of the boss portion 9 is determined from the size of the semiconductor laser 4 mounted on the substrate and the size of the optical element such as the optical waveguide.

18 and 19, the cap 3, the semiconductor laser 4, and the waveguide substrate 14 manufactured in FIGS. 12 to 17 are manufactured.
The procedure for assembling is shown. FIG. 18 is a perspective view of each component of the module substrate, and FIG. 19 is FIG.
The cross-sectional display portions FF, GG, H shown in (b) and (c)
A sectional view corresponding to -H is shown. 18 (a) and 1
9 (a) shows a waveguide substrate 14 which is a base for assembly. The semiconductor laser 4 manufactured by the method of FIG. 13 is pressed onto the boss portion 9 of the waveguide substrate 14 manufactured by the method of FIGS. 14 and 15, and the corner portion 21 of the opening formed in the waveguide layer 2 is pressed. After aligning with the
(B), FIG. 19 (b)).

The electrical connection between the outside and the semiconductor laser 4 is
Feedthrough electrode 20 via solder layer 18 at the boss
And a portion connected from the back surface of the semiconductor laser 4 to the other feedthrough electrode 20. When fixing the semiconductor laser 4 on the boss 9, the laser 4 is positioned by being pressed against the corner 21 of the opening of the waveguide. Finally, the cap 3 having the solder layer formed thereon is bonded onto the waveguide substrate 14 to hermetically seal the semiconductor laser 4 portion (FIGS. 18C and 19).
(C)).

In the above manufacturing method, the semiconductor laser 4 and the outside
The contact between the semiconductor laser and the boss feed-through electrode by semiconductor laser bonding and the contact between the semiconductor laser and the feed-through electrode by the gold wire 29 have been used for electrical connection with. FIG. 20 shows a module structure in which the electrical connection part by the gold wire 29 is improved. In the embodiment shown in FIG. 20, the metal layer formed in the cap is used as the electrode wiring from the back surface of the semiconductor laser. That is, in the embodiment shown in FIG. 20, the cap 3 is joined to the waveguide surface on the substrate and the semiconductor laser back surface to hermetically seal the semiconductor laser and perform electrode wiring. This method has an advantage that it is simpler than the method using a gold wire because the cap joining also serves as an electrical contact. 21 shows an external view of the module shown in FIG. 20, and FIG. 22 shows a perspective view of each component.

[0052]

According to the module substrate of the present invention, the corners for alignment formed on the semiconductor laser are abutted and fixed to the corners of the opening formed in the waveguide layer on the Si substrate. That is, in this module substrate structure, since the semiconductor laser is mounted directly on the substrate, the height of the semiconductor laser with respect to the substrate can be made more accurate than when solder balls are used. Further, the heat generated by the semiconductor laser also diffuses from the entire surface of the semiconductor laser to the substrate, so that heat generation due to laser oscillation does not pose a problem. Furthermore, in this module substrate structure, the module substrate can be easily manufactured because the troublesomeness of placing the solder balls and the deep processing of the substrate are not required.

In this module substrate, the position of the semiconductor laser can be aligned with the substrate just by abutting it, so that the positioning can be performed in a short time, and as a result, a low-cost module substrate can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing an entire module substrate in which a semiconductor laser and a photodiode are mounted on a substrate surface having a waveguide by a butting method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a semiconductor laser mounting portion of a module substrate in which a semiconductor laser is mounted on a substrate according to an embodiment of the present invention.

FIG. 3 is a perspective view of the module substrate for explaining the positional relationship of each part in the module substrate of the semiconductor laser portion of FIG.

FIG. 4 is a cross-sectional view taken along the line AA of FIG.

5 is an enlarged cross-sectional view of a region C of FIG.

6 is a cross-sectional view taken along the line BB in FIG.

7 is an enlarged sectional view of a region D of FIG.

8 is a plan view of the module substrate of FIG.

9 is an enlarged view of a region E of FIG. 8 before mounting a semiconductor laser.

10 is an enlarged view of a region E of FIG. 8 after mounting the semiconductor laser.

FIG. 11 is a perspective view illustrating a combination relationship of main components of a module substrate of a semiconductor laser portion according to an embodiment of the present invention.

12 is a cross-sectional view showing a processing process of the module substrate cap of FIG.

FIG. 13 is a cross-sectional view showing a processing process of the semiconductor laser for module substrate of FIG. 11.

14 is a perspective view showing a processing process of the waveguide substrate for module substrate of FIG. 11. FIG.

FIG. 15 is a cross-sectional view showing a processing process of the module substrate waveguide substrate corresponding to FIG. 14;

16 is a cross-sectional view showing a part of another processing process of the waveguide substrate for module substrate of FIG.

FIG. 17 is a cross-sectional view showing a part of another processing process of the waveguide substrate for module substrate of FIG. 11.

18 is a perspective view showing an assembling procedure of the module board of FIG. 11. FIG.

FIG. 19 is a sectional view showing an assembling procedure of the module board corresponding to FIG. 18;

FIG. 20 is a sectional view showing a module substrate according to another embodiment of the present invention.

FIG. 21 is a perspective view showing the module substrate of the embodiment of FIG.

22 is a perspective view illustrating a combination relationship of main components of the module board of the embodiment of FIG. 20. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Waveguide layer, 3 ... Cap, 4 ... Semiconductor laser, 5 ... Photodiode, 6 ... Semiconductor laser drive circuit, 7 ... Photodiode drive circuit, 8 ... Optical fiber,
9 ... Boss portion, 10 ... Waveguide, 11 ... Core, 12 ... Clad, 13 ... Active layer, 14 ... Waveguide substrate, 15 ... Recess, 1
6 ... cap groove, 17 ... cap joining solder layer,
Reference numeral 18 ... Solder layer for joining semiconductor laser, 19 ... End portion for alignment between semiconductor laser and waveguide, 20 ... Electrode for feedthrough, 21 ... Corner portion for alignment opening between semiconductor laser and waveguide, 22 ... Mask, 24 ... Metal pattern, 2
5 ... Plating layer, 26 ... Si, 27 ... SiO2, 28 ... Electrode pad, 29 ... Gold wire.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naoto Uezuka 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Hitachi Cable Company, Ltd., Optro System Research Center (72) Inventor Hiroaki Okano Hitachi City, Hidaka, Ibaraki Prefecture 5-1-1, Machi, Hitachi Cable, Ltd., Optro System Laboratory (72) Inventor, Tatsuo Teraoka 5-1-1, Hidakacho, Hitachi City, Ibaraki Hitachi Cable, Ltd., Optro System Laboratory

Claims (7)

[Claims] 1. A semiconductor laser that emits light onto a substrate, a photodiode that receives the light and converts it into an electric signal, an optical element that guides the light from the semiconductor laser and the light to the photodiode, and the semiconductor laser and the photodiode. In an optical transmission module comprising a waveguide layer for optically coupling an element with each other, an opening is provided in the waveguide layer, and corners of the semiconductor laser and photodiode are aligned and fixed to corners of the opening. An optical transmission module characterized by: 2. The optical transmission module according to claim 1, wherein a convex shape for mounting a semiconductor laser and a photodiode is formed on the substrate. 3. The optical transmission module according to claim 1, wherein a plurality of the openings are provided, and a semiconductor laser or a photodiode is fixed to a corner of each opening. 4. A semiconductor laser which emits light on a substrate or a photodiode which receives light and converts it into an electric signal,
In an optical transmission module comprising an optical element that guides light from the semiconductor laser or light to a photodiode, and a waveguide layer that optically couples the semiconductor laser or photodiode and the optical element, in the waveguide layer. An optical transmission module, characterized in that an opening is provided, and a corner of a semiconductor laser or a photodiode is aligned and fixed to a corner of the opening. 5. The optical transmission module according to claim 4, wherein a convex shape for mounting a semiconductor laser or a photodiode is formed on the substrate. 6. A semiconductor laser that emits light on a substrate, a photodiode that receives the light and converts it into an electric signal, an optical element that guides the light from the semiconductor laser and the light to the photodiode, and the semiconductor laser and the photodiode. In a method of manufacturing an optical transmission module comprising a waveguide layer optically coupling an element, positioning is performed by pressing the corners of the semiconductor laser and the photodiode against the corners of the opening formed in the waveguide layer. After that, the method for manufacturing an optical transmission module is characterized in that the semiconductor laser and the photodiode are fixed. 7. The method of manufacturing an optical transmission module according to claim 6, wherein the semiconductor laser and the photodiode are joined to a convex portion provided on a substrate.