KR20050062257A - Optical transmitter module and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an optical transmission module and a method of manufacturing the same, wherein a monitoring photodiode (MPD) applied to a conventional silicon optical bench type optical transmission module receives only a part of the back light of a light emitting device reflected through a reflector and separately manufactured. By using the ceramic block as a sub-mount to arrange the MPD disposed on the back light path of the light emitting device directly to the back light, the method of receiving the back light directly, the amount of light received is small, the efficiency is low, The direct light receiving method has a fatal problem in that the cost of ceramic sub-mounts to be manufactured separately is high, and precise alignment is difficult due to unevenness of each device due to manufacturing tolerances. In view of the above problems, the present invention forms a vertical structure on a part of the semiconductor substrate, forms a pair of metal electrodes to the side of the vertical structure, and then cuts to form a sub-mount for supporting the MPD and connecting the electrodes. MPD electrodes are connected to each other to extend a pair of electrodes to the MPD electrodes. After bonding it to the silicon optical bench, wire bonding with the external electrode uses the electrode on the side of the vertical structure, thereby greatly improving the alignment of the light emitting source and the MPD because the sub-mount formed by the precise semiconductor process is applied. The light-receiving efficiency can be improved, and the sub-mount can be mass-produced in a batch process through a semiconductor process, which can greatly reduce costs.

Description

Optical transmission module and its manufacturing method {OPTICAL TRANSMITTER MODULE AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission module and a method of manufacturing the same, and more particularly, to a monitoring photo diode (MPD) for detecting a change in output light, in order to align the back light of a light emitting device to a position capable of directly receiving back light of the light emitting device. The present invention relates to an optical transmission module and a method of manufacturing the same, wherein a sub-mount providing an electrode while supporting an electrode is provided through a semiconductor process to increase optical precision and reduce cost.

With the spread of wired and wireless Internet and the spread of various information communication terminals, subscribers' access and use of information are becoming a natural everyday. However, in order to use more information and faster information, it is absolutely necessary to disseminate the optical cable, which is a high-speed communication network that exceeds the limitations of the current high-speed communication network.

Along with the necessity of such a high speed communication network, various researches are being conducted to build an optimal backbone communication network by combining various currently installed network services. In other words, the problem of how to build a high-speed information communication network is to provide various narrow-band services and scattered broadband services at the same time and economically, and to implement various subscriber transmission methods and transmissions for constructing a communication network that can flexibly cope with B-ISDN services. Along with the review of devices, research is being actively conducted.

The conversion from the communication network to the optical communication network using the coaxial cable is progressing mainly with the relay network, but the development is progressing with the aim of expanding to the access network reaching the subscribers.

1 is a conceptual diagram showing a configuration for a general optical communication, as shown in the electrical data to be transmitted is converted into optical information through the optical transmission module 10 through the optical reception module 20 through the optical fiber 15 as a transmission medium Is provided. The optical receiving module 20 restores the received optical information back to electrical data and provides it to the receiving system. The optical transmission module 10 monitors the light output of the driving unit 11 and the light emitting element 12 to control the light emitting element 12 so as to convert an electrical signal applied from the outside into an optical signal, thereby providing uniform light. It consists of a monitoring photodiode (MPD) 13 which ensures the output. The light receiving module 20 includes a photodiode 21 for detecting an optical signal applied through the optical fiber 15 and an amplifier 22 amplifying the output of the photodiode 21 and transmitting the amplified output to a receiving system.

Currently widely used optical communication system is a transmit / receive module mounted in a can-type package (TO-can), and the light source assembled in such a can-type should be combined with the optical fiber 15, thus increasing the manufacturing time for the alignment. This is a factor in the price increase. It is also bulky and easily prone to problems.

Therefore, researches have been actively conducted to enable mass production, miniaturization, and integration of the most essential and expensive optical modules used in the construction of optical networks by applying MEMS (Micro-Electro Mechanialc System) technology.

Due to the inherent properties of the [100] monocrystalline silicon, anisotropic wet etching has a [100] plane parallel to the wafer surface and a [111] plane exposed through etching to be inclined at 54.74 degrees. By applying the, it is easy to define the V-groove and the optical module parts (light emitting device, photodiode, etc.) where the optical fiber is to be placed. In this way, a semiconductor process is used to define an area in which an optical component is to be placed on a silicon substrate, and then, each component is placed. The electrical connection is performed by using a silicon optical bench (Silicon Optical Bench). SiOB). In the SiOB, alignment of the x, y, and z directions between components is performed through an etching process, and a process of three-dimensionally setting the positions of the components through such an etching process (forming a three-dimensional precision etching structure) and The process of arranging and joining the parts to the formed three-dimensional shape is a key process in manufacturing SiOB.

When the optical module is formed by using the SiOB method, mass production is possible, and the optical fiber can be mounted in the pre-formed V-shaped groove, thereby reducing the alignment cost, and it is also advantageous in speeding up because the light source of the chip state can be used. Do. However, since the sensitivity is sensitive to the external environment, the intensity of light output is changed according to the change of the external environment, thereby increasing the possibility of signal error. Therefore, in order to keep the output of the light emitting source constant, the output of the light emitting source may be adjusted by detecting a change in the light intensity. To this end, an MPD capable of detecting the back light of the light emitting source should be disposed on the back of the light emitting source, and its output should be fed back to the driving circuit of the light emitting source to adjust the current flowing through the light emitting source.

As described above, there are two methods of mounting MPD on SiOB, which is shown in FIGS. 2 and 3, respectively.

FIG. 2 shows grooves in which the reflective metal layer 31 is formed on the rear surface of the light emitting element 12 (opposite to the optical fiber 15), so that the light reflected by the reflective metal layer 31 is reflected to the light receiving portion 13a of the MPD 13. ) To reach.

As shown in the figure, since only a portion of the light provided to the MPD 13 can receive only a portion of the light loss, the sensitivity is lowered and the efficiency is extremely low.

3 is a structure in which the light receiving portion 13a of the MPD 13 is directly positioned on a path of light emitted from the rear of the light emitting device 12 in order to prevent the loss of light as described above. To this end, the sub-mount 40 supporting the MPD 13 is essential. In general, the ceramic block is manufactured separately, and then, the portion A where the MPD 13 is to be positioned and the portion B to be wire bonded are performed. Is connected using a metal film, and the MPD 13 is mounted on the upper portion thereof. The ceramic sub-mount 40 on which the MPD 13 is mounted is bonded to a predetermined position of the SiOB 30 by using an adhesive such as epoxy, and then connected by wire bonding.

Although the structure of the MPD 13 has a good light receiving efficiency, the cost of the sub-mount 40 that must be manufactured separately from the ceramic block is high, and the light receiving efficiency of the MPD 13 is changed when it is aligned with SiOB due to manufacturing variation per ceramic block. This will seriously affect the performance stability or reliability of the device is essential for high speed and high precision optical communication.

As described above, the monitoring photodiode (MPD) applied to the conventional silicon optical bench type optical transmission module receives only a part of the back light of the light emitting element reflected through the reflector and uses a separately manufactured ceramic block as a submount. The MPD disposed above is aligned on the back light path of the light emitting device to directly receive the back light. When the reflected light is used, the amount of light received is low and the efficiency is low. The cost of the mount is high, and precise alignment is difficult due to non-uniformity of each device due to manufacturing tolerances, resulting in a fatal problem of low reliability and stability.

In view of the above problems, the present invention forms a structure perpendicular to a part of a semiconductor substrate, forms a pair of metal electrodes extending from the upper side of the substrate to the side of the vertical structure, and then cuts it into sub-mount sizes. The electrodes formed on the substrate are used for bonding the monitoring photodiode (MPD) or extending the electrodes of the MPD, and the electrodes formed on the side of the vertical structure are attached to the silicon optical bench and then used to connect external signal lines. It is an object of the present invention to provide an optical transmission module and a method for manufacturing the mount, which can be manufactured in large quantities through a precise semiconductor process having a small manufacturing tolerance, thereby increasing the optical alignment of the light emitting device and the monitoring photodiode and reducing the manufacturing cost.

The present invention for achieving the above object, the optical fiber and the light emitting element and the silicon optical bench structure consisting of an electrode for electrical connection between the elements; A monitoring photodiode disposed on a path of back light of the light emitting element; A portion of the silicon substrate has a structure perpendicular to the front surface of the substrate and a pair of electrodes extending from the front surface of the substrate to the side of the structure, wherein one of the electrodes is bonded to the monitoring photodiode and the adjacent electrode is the monitoring. And a monitoring photodiode sub-mount, which is connected by photodiode and wire bonding, and has wire bonding connections for external connection to extension portions of the electrodes formed on the side of the vertical structure.

In addition, the present invention comprises the steps of vertically removing a portion of the silicon substrate to form a vertical structure having a side perpendicular to the top of the substrate; Forming an insulating layer on the front surface of the structure, and forming a plurality of electrodes extending from the top of the silicon substrate to the side of the vertical structure and spaced apart from each other; Forming a soldering layer on an electrode on a substrate to be bonded to the monitoring photodiode among the formed electrodes, and cutting the structure to form a monitoring photodiode submount having a stepped side structure in which a pair of electrodes extends; It is characterized by.

Arranging a monitoring photodiode on a solder layer on the formed monitoring photodiode sub-mount and then performing heat treatment to bond the wires to each other and to wire-bond the adjacent electrode with another electrode of the monitoring photodiode; Placing and adhering the sub-mount to which the monitoring photodiode is bonded to the silicon photobench structure such that the light-receiving portion of the monitoring photodiode is positioned on a light emitting element back light path of the silicon lightbench structure to which the light emitting element is bonded; And connecting the external electrodes to the external electrodes by wire bonding using portions formed on side surfaces of the vertical structure among the electrodes on the sub-mount as wire bonding pads.

DETAILED DESCRIPTION OF THE EMBODIMENTS Embodiments of the present invention implemented as described above will be described in detail with reference to the accompanying drawings.

4A to 4F are cross-sectional views illustrating a manufacturing process of a sub-mount of a monitoring photodiode (MPD) applied to an embodiment of the present invention. As shown in FIG. By manufacturing, it is possible to mass-produce submounts of the same standard.

First, as shown in FIG. 4A, a portion of the silicon substrate 50 is vertically etched to form a vertical structure. In the present exemplary embodiment, a photoresist pattern, a silicon oxide film or a nitride film pattern, a metal mask, or the like is applied to the substrate 50 and then vertically etched to a desired depth by a deep reactive ion etching method. The same vertical structure can be formed.

Next, as shown in FIG. 4B, an insulating layer 51 for insulation is formed on the front and rear surfaces of the formed structure. The insulating film may deposit AlN, ZnO, or BeO having a large heat transfer coefficient by sputtering or vapor deposition, and a silicon oxide film or a nitride film which is generally used may be used. The use of materials with large heat transfer coefficients can easily dissipate the heat generated when the monitoring photodiode is subsequently placed.

Next, as shown in FIG. 4C, an electrode layer 52 is formed on the formed structure by a lift-off method or a metal etching process, wherein the electrode layer 52 is formed from the top of the substrate. An electrode pattern is formed so as to extend to the side surface of the at least one pair of electrode layers 52 per sub-mount to connect with the electrodes of the MPD.

Next, as shown in FIG. 4D, a solder layer 53 is formed on the upper portion of the substrate of the electrode layer 52 to which the MPD is to be bonded. This can be formed by the lift off method.

Next, as shown in FIG. 4E, the formed structure is cut in sub-mount units using the dicing blade 60 so that at least one side of the formed vertical structure is positioned and extends to the side of the vertical structure. It has a pair of electrode layer 52 is made.

Then, as shown in FIG. 4F, a pair of electrode layers 52 extending from the front to the side may be obtained, and one of the individual unit submounts having the solder layer 53 formed thereon may be obtained.

FIG. 5 is a perspective view showing a state in which the MPD 13 is bonded to the formed MPD sub-mount, and as shown in FIG. 5, the MPD 13 is attached to one of the pair of electrode layers 52 formed on the substrate 50. The upper portion of the substrate of the remaining electrode layer 52 is electrically connected to the MPD 13 through wire bonding. Thus, the pair of electrode layers 52 become electrodes capable of driving the MPD 13. In the above embodiment, the vertical structure is formed only at the portion where the electrode layer 52 is formed, but may be formed entirely with respect to the entire surface of one side of the substrate.

As described above, the sub-mount in which the MPD 13 is bonded is attached to the silicon optical bench, so that the light receiving portion of the MPD 13 is directly positioned in the back light path of the previously formed optical element.

Since the electrode capable of driving the MPD is extended to the pair of electrode layers 52, the sub-mounts are bonded to each other, and the external electrodes can be wire-bonded using the electrode layers 52 formed on the side of the vertical structure of the submount. have.

6A to 6F illustrate a sub-mount manufacturing process applied to another embodiment of the present invention, and only the process of forming a vertical structure on the silicon substrate 50 as shown in FIGS. 4A to 4F Different.

As shown, FIG. 6A shows a half-cut process in which only a part of the substrate is cut using the dicing blade 65 used to cut the substrate. This makes it possible to quickly and simply form a vertical structure on the substrate, in which case the vertical structure is elongated with respect to the front surface of the substrate.

Since the types of the dicing blades 65 vary, an appropriate type may be applied according to the width of the vertical structure to be formed, and the side of the vertical structure partially cut using the actual dicing blade is uniform. The cut side of the vertical structure is such that it can be used as a reflective layer without any treatment. Therefore, there is no problem in carrying out the metal processing on the side of the vertical structure.

Thereafter, the process of FIGS. 6B to 6F is the same as the process of FIGS. 4A to 4F described above.

FIG. 7 is a perspective view illustrating a state in which the MPD 13 is bonded to the MPD sub-mount formed through the process of FIGS. 6A to 6F, and a vertical structure formed on the side surface is formed on one side of the substrate as shown in FIG. It can be seen. The MPD 13 is bonded to one of the pair of electrode layers 52 formed on the substrate 50, and the upper part of the substrate of the remaining electrode layers 52 is electrically connected to the MPD 13 through wire bonding. . Subsequently, the sub-mount to which the MPD 13 is bonded is attached to the silicon optical bench as described above, and the external electrode is connected by wire bonding using the electrode layer 52 formed on the side of the vertical structure of the sub-mount.

As described above, when the MPD sub-mount is formed through the semiconductor process, the manufacturing standard of each sub-mount can be unified by the precise semiconductor process and the manufacturing tolerance can be greatly reduced, so that the sub-mount is compared with the ceramic sub-mount manufactured separately. The standard deviation between them can be greatly reduced. This greatly contributes to the improvement of alignment between the light emitting source and the MPD, thereby increasing the light receiving efficiency. In addition, the embodiment of the present invention through the semiconductor process can produce a large number of sub-mounts at a time, so that the yield is high and the manufacturing cost is greatly reduced.

As described above, the optical transmission module of the present invention and a method of manufacturing the same have a structure perpendicular to a part of a semiconductor substrate, form a pair of metal electrodes to the side of the vertical structure, and then cut the sub-mount for MPD support and electrode connection. And a pair of electrodes extending to the MPD electrodes by connecting MPD electrodes to the electrodes, respectively. After bonding it to the silicon optical bench and wire bonding with the external electrode by using the electrode on the side of the vertical structure, by applying a sub-mount formed by a precise semiconductor process, the specification of the sub-mount can be unified, so It greatly contributes to improving the alignment of the MPD, thereby increasing the light receiving efficiency, and can greatly reduce the cost by mass-producing the sub-mount in a batch process through the semiconductor process.

1 is a conceptual diagram showing a configuration for a general optical communication.

2 is a cross-sectional view of a general optical transmission module.

3 is a cross-sectional view of a conventional improved optical transmission module.

Figures 4a to 4f is a cross-sectional view showing a manufacturing process of the monitoring photodiode sub-mount applied to the optical transmission module of an embodiment of the present invention.

5 is a perspective view illustrating a state in which a monitoring photodiode is bonded to a sub-mount manufactured by the process of FIGS. 4A to 4F.

6a to 6f is a cross-sectional view showing a manufacturing process of the monitoring photodiode sub-mount applied to the optical transmission module of another embodiment of the present invention.

FIG. 7 is a perspective view illustrating a state in which a monitoring photodiode is bonded to a submount manufactured through the process of FIGS. 6A to 6F.

* Description of the symbols for the main parts of the drawings *

10: optical transmission module 12: light emitting unit

13: monitoring photodiode (MPD) 15: optical fiber

20: light receiving module 30: silicon light bench

50: substrate 51: insulating layer

52: electrode layer 53: solder layer

60: dicing blade 65: dicing blade

Claims (7)

A silicon optical bench structure configured with an optical fiber and an electrode for electrical connection between the light emitting element and the elements; A monitoring photodiode disposed on a path of back light of the light emitting element; A portion of the silicon substrate has a structure perpendicular to the front surface of the substrate and a pair of electrodes extending from the front surface of the substrate to the side of the structure, wherein one of the electrodes is bonded with a monitoring photodiode, and the adjacent electrode is the monitoring photo. And a monitoring photodiode sub-mount, wired with a diode and wire-bonded for external connection to extension portions of the electrodes formed on the side of the vertical structure. The optical transmission module according to claim 1, wherein the vertical structure of the monitoring photodiode sub-mount is a stepped structure in which only the side portions of the substrate of the portion where the electrode is formed are removed to the same depth. The optical transmission module according to claim 1, wherein the vertical structure of the monitoring photodiode sub-mount is a stepped structure in which one front surface of the substrate is removed to the same depth. Vertically removing a portion of the silicon substrate to form a vertical structure having a side perpendicular to the top of the substrate; Forming an insulating layer on the front surface of the structure, and forming a plurality of electrodes extending from the top of the silicon substrate to the side of the vertical structure and spaced apart from each other; Forming a soldering layer on an electrode on a substrate to be bonded to the monitoring photodiode among the formed electrodes, and cutting the structure to form a monitoring photodiode submount having a stepped side structure in which a pair of electrodes extends; Optical transmission module manufacturing method characterized in that. The method of claim 4, further comprising: arranging a monitoring photodiode on a solder layer on the formed monitoring photodiode sub-mount and then heat-treating the same, and wire bonding an adjacent electrode to another electrode of the monitoring photodiode; Placing and adhering the sub-mount to which the monitoring photodiode is bonded to the silicon photobench structure such that the light-receiving portion of the monitoring photodiode is positioned on a light emitting element back light path of the silicon lightbench structure to which the light emitting element is bonded; And connecting the external electrodes to the external electrodes by wire bonding using portions formed on the side surfaces of the vertical structure among the electrodes on the sub-mount as wire bonding pads. The method of claim 4, wherein the removing of the silicon substrate vertically to form a vertical structure having a side surface perpendicular to the upper portion of the substrate comprises forming a mask pattern on the silicon substrate, and then dry etching a portion of the substrate. Optical transmission module manufacturing method comprising the step of forming. The method of claim 4, wherein the vertical removal of the portion of the silicon substrate to form a vertical structure having a side perpendicular to the upper portion of the substrate is performed by half-cutting a portion of the substrate using a blade having a suitable shape. Optical transmission module manufacturing method comprising the step of forming.