JPH0447983Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art [Figs. 6 and 7] D. Problem that the invention aims to solve E. Means for solving the problem F. Effect G. Example [Figs. 1 to 7] Figure 5] H Effects of the invention (A Field of industrial application) The present invention involves bonding a laser diode to a part of the surface of a planar semiconductor substrate on which an optical integrated circuit, particularly a monitor photodiode, etc., are formed. The present invention relates to an optical integrated circuit in which an optical fiber and an optical fiber are optically coupled on the surface of a planar semiconductor substrate.

(B. Summary of the invention) This invention aims to reduce the size and integration of an optical integrated circuit in which a laser diode on the surface of a planar semiconductor substrate and an optical fiber are optically coupled, and to increase the optical coupling efficiency at low cost. The optical coupling between the optical fiber and the laser diode on the surface of the planar semiconductor substrate is achieved by fixing the end of the optical fiber on the surface of the planar semiconductor substrate using a fiber holder. The optical coupling efficiency is determined by positioning the optical fiber relative to the laser diode by aligning the alignment mark provided on the fiber holder with the alignment mark provided on the semiconductor substrate. It is designed to increase the

(C Prior Art) [Figures 6 and 7] EO module (Electro-Optical module)
Examples of conventional structures include those shown in FIGS. 6 and 7. The one shown in FIG. 6 is called a connector type, in which a package b in which a light emitting element a is hermetically sealed and an optical fiber c are connected by a receptacle d for optical coupling. e is a glass window formed in the head of package b, f is a converging rod lens, and the light emitted from light emitting element a passes through window e, is focused by converging rod lens f, and then passes through optical fiber c. is incident on the

The one shown in FIG. 7 is called a pigtail type, and in the same figure, g is a stem, and h is a light emitting element that is pellet-bonded onto the center of the stem g via an electrode film (+) i. It emits light in an upward direction. Reference numeral j denotes a cap having a fiber through hole k in its center, into which an optical fiber l is inserted through a metal sleeve m. The metal sleeve m and the cap j are fixed by a resin n, and the metal sleeve m, the optical fiber l, and the cap j are fixed by a resin n, and the tip surface of the optical fiber l is exposed to the light emitting element h. There is.

(Problems to be solved by the invention D) By the way, according to the EO module shown in FIGS. 6 and 7, it is extremely difficult to control the optical coupling efficiency. In other words, the optical coupling efficiency is determined by the constant of the optical system (the lens
NA) and alignment accuracy, and it is necessary to improve alignment accuracy to improve optical coupling efficiency at the assembly stage, but alignment accuracy is determined by the module structure shown in Figures 6 and 7. It is determined approximately by the finishing accuracy of each member that makes up the module, and there is very little room for adjustment to influence alignment accuracy. When a laser diode is used as a light emitting element and the laser beam is guided by an optical fiber, it is usually ±3 to 4 μm.
Sufficient optical coupling efficiency cannot be obtained unless positioning is performed with an accuracy of +/-3 to 4 μm, but it is almost impossible to increase the finishing accuracy of the member to ±3 to 4 μm. Therefore, it is very difficult to sufficiently increase the optical coupling efficiency and there is a problem that it is costly.

Although the modules shown in FIGS. 6 and 7 are not small, only the light emitting elements a, h and the tips of the optical fibers c, l are housed inside. However, when using a laser diode as a light emitting element, a monitoring photodiode and APC (Automatic Power
Control) circuits are required, and if these were to be housed within the module, the EO module would become even larger. This has become a problem and has become a factor that hinders meeting the demand for miniaturization of devices.

The present invention was devised to solve these problems, and is an optical integrated circuit that can be miniaturized and highly integrated, and can perform highly accurate positioning to increase optical coupling efficiency. The purpose is to provide the following.

(E. Means for Solving the Problems) In order to solve the above problems, the optical integrated circuit of the present invention provides optical coupling between the optical fiber and the laser diode on the surface of the planar semiconductor substrate by connecting the end portion of the optical fiber to the laser diode on the surface of the planar semiconductor substrate. This is done on the surface of the planar semiconductor substrate by fixing it on the surface of the planar semiconductor substrate using a fiber holder. Therefore, the optical fiber is characterized in that the position of the optical fiber relative to the laser diode can be determined.

(Faction) According to the optical integrated circuit of the present invention, the end of the optical fiber is fixed using a fiber holder to the surface of the planar semiconductor substrate on which the monitor photodiode, etc. is formed and the laser diode is bonded. The ends of diodes, laser diodes, and optical fibers can be placed in very narrow spaces. In particular, if an APC circuit is required, its
Since the APC circuit can be formed within a planar semiconductor substrate, there is no need to increase the size of the device.
An APC circuit can also be provided. Therefore, the degree of integration of the device can be made very high.

Further, the positioning of the optical fiber with respect to the laser diode can be performed by positioning the fiber holder fixed to the surface of the planar semiconductor substrate with respect to the planar semiconductor substrate, and the positioning of the fiber holder with respect to the planar semiconductor substrate can be performed by positioning the fiber holder with respect to the planar semiconductor substrate. This can be done by aligning an alignment indicator formed on the surface of the semiconductor substrate and an alignment indicator formed on the surface of the fiber holder. Moreover, the alignment index can be formed with extremely high precision by making full use of lithography technology. Therefore, the positioning between the laser diode and the optical fiber can be performed with extremely high precision, and as a result, the optical coupling efficiency can be made extremely high.

(G Embodiment) [FIGS. 1 to 5] The optical integrated circuit of the present invention will be described in detail below according to the illustrated embodiment.

1 to 3 are for explaining one embodiment of the optical integrated circuit of the present invention, in which FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view, and FIG. 3
It is a cross-sectional view along line -3.

In the drawing, 1 is a planar semiconductor substrate made of silicon Si, 2 is a monitoring photodiode formed on the surface of a partial region of the semiconductor substrate 1, and 3 is a detection result based on the monitoring photodiode 2, which will be described later. Control the laser diode output to maintain a constant value
The APC circuits 4, 4, ... are bonding pads for drawing out electrodes from the APC circuit 3, and one of them, 4a, connects the laser diode to the APC circuit 3.
It is a bonding pad that connects to the 5,5,
... is a wiring film.

A semiconductor region 6 constituting an APC circuit 3 and a monitoring photodiode 2 is selectively formed on the surface of the semiconductor substrate 1. A silicon oxide film 7 and an aluminum wiring film 5 are formed on the surface of the substrate 1, and an insulating film 8 for surface flattening is further formed on the entire surface thereof.

A laser diode 9 is chip-bonded on the semiconductor substrate 1 just in front of the monitor photodiode 2, and emits laser light from the rear end face and the front end face of the laser diode 9. 1
0 is a connecting line connecting the upper electrode of the laser diode 9 and the bonding pad 4a.

11 is an optical fiber that guides the laser beam emitted from the front end face of the laser diode 9, 12 is its core glass, and 13 is a clad glass.

Reference numeral 14 denotes a fiber holder, which is made of, for example, silicon Si, and has a groove 15 with a V-shaped cross section formed approximately in the center of its lower surface so as to bisect the lower surface.
The light incident end of the optical fiber 11 is fitted into the groove 15 and fixed to the fiber holder 14 with an adhesive 16. The fiber holder 14 is fixed to the fiber attachment area 21 of the semiconductor substrate 1 with an adhesive 16. As the adhesive 16, a resin or the like that is cured by UV light is used. The positioning of the fiber holder 14 during fixation, specifically the positioning of the fiber holder 14 relative to the bonding position of the laser diode 9, is as follows:
Alignment marks 17, 17, ... 17' formed in advance on the surface of the semiconductor substrate 1 and alignment marks 1 formed on the upper surface of the fiber holder 14
This is done by adjusting the position of the fiber holder 14 so that the corresponding positions of the fiber holders 8 and 18 are aligned with each other. By this positioning, the light input end face of the optical fiber 11 faces the light output portion of the front end face of the laser diode 9 from which the laser light is emitted. Note that 19, 19, and 19' are alignment indicators used when chip bonding the laser diode 9 onto the semiconductor substrate 1;
The front end surface of the laser diode 9 is located on a straight line connecting the alignment marks 19, 19 when viewed from above, and the front end surface of the laser diode 9 is located on a straight line connecting the alignment marks 17' and 19'.
Bonding is performed after adjusting the position of the laser diode 9 so that the stripe 20 of the laser diode 9 is located on a straight line. Alignment indicators 17, 17, ... 17', 19, on the semiconductor substrate 1
19 and 19' can be made by forming an insulating film at a desired position on the surface of the semiconductor substrate 1 by making full use of photolithography technology, or by selectively removing the insulating film 8 on the surface. is possible,
The position of the alignment index can be defined with very high precision. Also, alignment indicators 18, 18, . . . on the optical fiber 11 made of silicon are provided.
can be made by forming recesses on the silicon surface by photo-etching, or by forming an insulating film such as a silicon nitride film or silicon oxide film on the silicon surface, and forming recesses in the insulating film by photo-etching. , its position can also be defined with high precision. Then, the alignment markers 17, 17, ... 17' and 18, 18, which are positioned with high precision in this way,
By using . 9 can also be aligned with extremely high precision, making it possible to improve the optical coupling efficiency.

In this embodiment, the fiber holder 14 is made of silicon Si having a light-shielding property.
It covers the APC circuit 3. Therefore,
Light from the monitor photodiode leaks
The fiber holder 14 can prevent the fiber from returning into the APC circuit 3 . To explain this point in detail, there are several PN junctions in the APC circuit 3, and among them, the PN junction that receives a voltage in the opposite direction may operate as a photodiode when it receives light. Therefore, when the laser light from the laser diode 9 is incident on the PN junction, there is a possibility that the laser light will be photoelectrically converted and enter the APC circuit 3 in the form of an electrical signal. This is not desirable, so the laser light from laser diode 9 is
It is desirable to prevent the fibers from entering the APC circuit 3, but if the fiber holder 14 is made of a non-transparent material such as silicon and the fiber holder 14 covers the APC circuit 3, then The fiber holder 14 can play the role of preventing the laser light from the laser diode 9 from leaking to the APC circuit 3.
In addition, when the fiber holder 14 is made to play the role of light shielding in this way, silicon is used as its material.
It is also possible to use not only Si but also ceramic or the like.

In the above embodiment, the fiber holder 14 also plays the role of shielding light between the laser diode 9 and the APC circuit 3, but this role is also played by a film formed on the surface of the semiconductor substrate 1, such as a film for planarization. It goes without saying that the insulating film 8 may be responsible for this. In such a case, a transparent material can be used as the fiber holder 14. In this way, the fiber holder 14
If it is decided to use a transparent material as the fiber mounting area 21 of the semiconductor substrate 1, alignment indicators 17, 17, ... 17' can be formed in the fiber attachment area 21 of the semiconductor substrate 1, and the alignment indicators 17, 17, ... 17,1
7,...Fiber holder 1 when looking at 17' from above
Alignment index 18,1 formed on the surface of 4
It can be provided at a position where it can overlap with 8, . Therefore, more accurate alignment can be achieved. This is because, according to the illustrated embodiment, an opaque fiber holder 14 is used, so that the alignment marks 17, 1 on the semiconductor substrate position are
7, . . . 17' must all be provided in areas protruding from the fiber attachment area 21, and when alignment is performed, the alignment indicators 17, 1 can be seen from above using a microscope.
7, . . . 17' and the alignment indicators 18, 18, . I had no choice but to adopt. Therefore, it can be said that there is some room for alignment errors to occur. However, when a transparent material is used as the fiber holder 14, the alignment indicators 17, 17, . . . , 17' overlap with the alignment indicators 18, 18, . The alignment indicators 17, 17, . . .
17' and the alignment marks 18, 18, . . . completely overlap each other and appear as one mark, an alignment method may be adopted in which alignment is deemed to have been achieved. Therefore, very highly accurate alignment with almost no errors can be achieved.

FIG. 3 shows a modification 14a of the fiber holder for the optical integrated circuit of the present invention. The fiber holder 14a is not a V-shaped groove but a groove 1 having a rectangular cross section.
The fiber holder 14 differs from the fiber holder 14 of the embodiment shown in FIGS. 1 to 3 in that it has the fiber holder 5a, but is otherwise the same. While the V-shaped groove 15 of the fiber holder 14 can be formed by anisotropic etching, the groove 15a of the fiber holder 14a having a rectangular cross section can also be formed by anisotropic etching. It can also be formed by half-cutting using a saw.

In the embodiments shown in FIGS. 1 to 3, the optical fiber 11 has a light incident end face cut perpendicular to the axis and is not provided with a lens. but,
In order to improve the optical coupling efficiency, it goes without saying that an optical fiber 11a having a spherical tip and a spherical portion 12a having a lens function as shown in FIG. 5 may be used.

Alternatively, an optical fiber without a spherical portion at the tip may be used, and a focusing rod lens may be provided on the tip side of the optical fiber to increase the optical coupling efficiency.

As described above, the present invention can be implemented in various ways, and many variations are possible.

(H Effect of the invention) As described above, in the optical integrated circuit of the present invention, a laser diode is bonded to a part of the surface of a planar semiconductor substrate on which a photodiode for monitoring etc. is formed, and the laser diode on the surface of the semiconductor substrate is An alignment mark is formed near or inside a fiber mounting area provided on the light emitting surface side of the diode, and an alignment mark is formed in the fiber mounting area so that the end of the optical fiber corresponds to the alignment mark. The fiber holder is fitted into the fiber holding groove of a fiber holder which is formed and has a fiber holding groove on the back surface, and in this state, the fiber holder is positioned so that the corresponding positions of the alignment indicators of the semiconductor substrate and the fiber holder are aligned with each other. and is fixed to the fabric mounting area of the semiconductor substrate on the back surface.

Therefore, according to the optical integrated circuit of the present invention, a fiber holder is used to directly fix the monitor photodiode and the laser diode to the surface of the planar semiconductor substrate on which the monitor photodiode and the like are formed and the laser diode is bonded. , the end of the optical fiber can be placed in a very narrow space. In particular, if an APC circuit is required, its
Since the APC circuit can be formed within a planar semiconductor substrate, there is no need to increase the size of the device.
An APC circuit can be provided. Therefore, the degree of integration of the device can be made very high.

Further, the positioning of the optical fiber with respect to the laser diode can be performed by positioning the fiber holder fixed to the surface of the planar semiconductor substrate with respect to the planar semiconductor substrate, and the positioning of the fiber holder with respect to the planar semiconductor substrate can be performed by positioning the fiber holder with respect to the planar semiconductor substrate. This can be done by aligning the alignment marks formed on the surface of the semiconductor substrate and the alignment marks formed on the surface of the fiber holder.Moreover, the alignment marks are made with extremely high precision using lithography technology. Can be formed with precision. Therefore, the positioning between the laser diode and the optical fiber can be performed with extremely high precision, and as a result, the optical coupling efficiency can be made extremely high.

[Brief explanation of the drawing]

1 to 3 are for explaining one embodiment of the optical integrated circuit of the present invention, in which FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view, and FIG. −
4 is a sectional view showing a modified example of the fiber holder of the optical integrated circuit of the present invention, FIG. 5 is a sectional view showing another example of the optical fiber, and FIG. 6 is a sectional view showing another example of the optical fiber.
FIG. 7 is a perspective view of an EO module as a conventional example, and FIG. 7 is a sectional view of an EO module as a second conventional example. Explanation of symbols, 1... Planar semiconductor substrate, 2...
...Monitor photodiode, 9...Laser diode, 11, 11a...Optical fiber, 14,
14a... Fiber holder, 15, 15a... Fiber holding groove, 17, 18... Positioning index,
21...Fiber attachment area.

Claims (1)

[Claim for Utility Model Registration] A laser diode is bonded to a part of the surface of a planar semiconductor substrate on which a photodiode for monitoring, etc. is formed, and a fiber is attached to the surface of the semiconductor substrate on the light emitting surface side of the laser diode. An alignment indicator is formed near or inside the region, and the end of the optical fiber is attached to the fiber holder of a fiber holder, which has an alignment indicator corresponding to the alignment indicator and a fiber holding groove formed on the back surface. The fiber holder is fitted into the holding groove, and the fiber holder is fixed to the fiber mounting area of the semiconductor substrate from the back side by positioning the semiconductor substrate and the fiber holder so that corresponding alignment indicators of the fiber holder are aligned with each other. An optical integrated circuit characterized by: