JPH0514434B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a light emitting semiconductor device.

[Background technology]

2. Description of the Related Art Light-emitting semiconductor devices are used as light-emitting sources for audio disks, video disks, optical communications, and the like.

Conventionally, for example, as a light-emitting semiconductor device for an audio disk, a semiconductor laser element (chip) was mounted on the inner surface of a copper post fixed to a copper stem, as shown in Nikkei Electronics, September 1, 1981, pages 138-151. A structure is known in which the chip is fixed via a silicon or copper submount, and a metal cap is hermetically attached to the stem to seal the chip and the like. Furthermore, when mounting the chip on the submount, many devices employ a so-called juncture-down structure in which the chip is mounted so that the active layer (optical waveguide) that emits light is located on the submount side. The reason for adopting the juncture-down mounting structure is to efficiently dissipate the heat generated during the operation of the semiconductor laser element through the submount, thereby stabilizing the characteristics of the element. This juncture-down structure is similarly employed in semiconductor laser devices for optical communication, as shown in, for example, Japanese Patent Application Laid-Open No. 50-81771 and Japanese Utility Model Application No. 50-150270.

However, when such a juncture-down structure is adopted, the active layer that emits light (formed several micrometers inward from the chip surface) is placed almost close to the submount, so it does not touch the chip surface. The active layer (optical waveguide) becomes invisible.
In this state, there is a drawback that it is difficult to align the optical axes of the optical fiber and the semiconductor laser element when assembling the semiconductor laser device for optical communication.
Particularly when the optical waveguide is shipped as a stem and the user assembles it into a desired package, it is difficult to align the optical axis with other optical systems if the optical waveguide is not visible.

Therefore, the present applicant has developed a chip mounting structure as shown in FIG. 1 in order to make the optical waveguide visible during assembly without reducing the heat dissipation properties of the chip.

That is, this structure has a so-called juncture-up structure in which the optical waveguide is visible on the top surface of the chip 2 fixed on the submount 1 during optical axis alignment work. However, the distance between the junction (active layer) and the submount is significantly longer than in the junction-down structure (for example, the active layer constituting the optical waveguide is placed at a depth of about 3 μm from the surface of a chip with a thickness of 100 μm). (located at . This SiC
Since it is insulative, it is not possible to conduct the electrodes from the bottom of the chip to the submount and stem as in the conventional case. Therefore, a solder 4 made of Pb-Sn-In is placed on the stem 3.
The submount 1 is fixed, and a chip 2 and a gold piece are respectively attached to the upper surface of the submount 1 (the upper surface has been vapor-deposited with Cr and Au to form a metal layer 5) through a solder material 6 made of Pb-Sn. The lower electrode of the chip 2 can be taken out by adopting a structure in which a metal piece 7 is fixed and a wire 8 is connected to the metal piece 7. Further, a wire 9 is connected to the upper electrode of the chip 2. Incidentally, when assembling the stem into the package, the stem is screwed using the mounting hole 10, and then wire bonding is performed.

This structure has the advantage that the optical waveguide can be seen as a single line on the surface of the chip 2 during optical axis alignment, making it easy and accurate to align the optical axis, but it also has the following drawbacks: This has been made clear by the inventor.

(1) High-speed long-wavelength semiconductor laser devices perform high-speed modulation, but in this case, submount 1 is made of SiC
Since it is an insulator, capacitance occurs, which adversely affects modulation characteristics. For this reason, it is desirable that the submount 1 be as small as possible. However, in the structure in which the chip 2 and the metal piece 6 are placed and fixed on the submount, for example, since the chip 2 and the metal piece 6 are rectangular bodies of about 300 to 400 μm in length and width, at least the submount 1 is only about 1 mm long and 0.5 mm wide, making it impossible to reduce the capacity.

(2) Since the chip 2 is sensitive to heat, it cannot be heat-treated at a high temperature, and even during assembly, it cannot be heated to a temperature of about 200° C. or higher, for example.
Therefore, the solder material 4 for attaching the submount 1 to the stem 3, the solder material 5 for attaching the chip 2 and the gold piece 6 to the submount 1 are made of low melting point solder. In addition, this solder is applied to the stem 3 and submount 1 in advance by vapor deposition, and the chip 2 and the gold piece 6 are first fixed to the submount 1, and then this submount 1 is fixed to the stem 3. do. However, when fixing submount 1 to stem 3, this method
Since the solder fixing the chip 2 and the metal piece 6 to the submount 1 also melts, there is a possibility that the position of the chip 2 and the metal piece 6 may easily shift.

(3) As described in (1) above, since the submount 1 is small, measuring 1 mm in length and 0.5 mm in width, it is difficult to mechanically fix the chip 2 and gold piece 6, which are 300 to 400 μm square. In addition, as mentioned in (2) above, when fixing the submount 1 to the stem 3, the tip 2 and the gold piece 6 on the submount 1 are in a state where they are easy to move, so the entire submount 1 is held. It is also difficult to use an automatic machine to fix this to the stem 3, and these connection operations must be done manually, resulting in poor workability.

[Purpose of the invention]

The present invention aims to reduce the submount capacitance in a light emitting semiconductor device in which a semiconductor laser element is fixed to a stem via an insulating submount.

Another object of the present invention is to provide a laser diode device with an optical fiber that enables more reliable communication in an optical communication system.

Another object of the present invention is to provide an optical fiber-equipped laser diode device that is capable of transmitting information over a longer distance than conventional devices with the same output.

Another object of the present invention is to provide a laser diode device with an optical fiber capable of modulating long wavelength communication at high speed.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, the Cu stem and its main surface are small enough to fix only one semiconductor laser element and wire bonding is possible.
A junction-up high-speed long-wavelength semiconductor laser device with a submount made of SiC on which a Cr layer and an Au layer are sequentially formed, electrodes made of a gold-based material on the top and bottom surfaces, and an optical waveguide close to the top electrode. , a single mode fiber, and a monitor fiber, and the submount is Au-
The semiconductor laser element is fixed in a junction-up form via a high-melting-point solder material made of Sn, and a wire is connected to a part of the main surface of the submount adjacent to the side of the semiconductor laser element, A wire is connected to the upper electrode of the semiconductor laser element, and a single mode fiber whose tip relative to the semiconductor laser element has an optical axis alignment accuracy of within ±0.2 to 0.3 μm is fixed to the stem by silver brazing material. Further, the monitor fiber is fixed to the stem so that its tip is brought close to the other optical waveguide of the semiconductor laser element.

Embodiment 1 FIG. 2 is a perspective view showing a semiconductor laser device mounting structure according to an embodiment of the present invention, and FIGS. 3a and 3b are explanatory diagrams similarly showing a manufacturing method of the semiconductor laser device mounting structure.

First semiconductor laser device (light emitting semiconductor device)
The mounting structure will be explained.

As shown in FIG. 2, a high melting point brazing material 4, such as Au-Sn (melting point
A submount (support body) 1 made of SiC (silicon carbide) is fixed at a temperature of 380°C. Further, the submount 1 has a metal layer 5 formed by sequentially depositing Cr and Au to a thickness of several thousand Å to 1 μm over the entire upper surface (principal surface). On top of this is a low melting point brazing material 6, such as solder (Pb-Sn; melting point 180°C).
A semiconductor laser element (chip) 2 having Au-based electrodes on the upper and lower surfaces is fixed thereto. The chip 2 is connected to the optical waveguide 1 as shown by the two-dot chain line in FIG.
1 is fixed in a so-called juncture-up state so that it is located at the top, that is, on the side opposite to the surface in contact with the main surface of the submount.
Further, the stem 3 is provided with two mounting holes 10.

Next, a method of manufacturing such a chip mounting structure will be explained with reference to FIGS. 3a and 3b.
As shown in FIG. 3A, after a stem 3 made of Cu is prepared, a submount 1 made of SiC is prepared, and this submount 1 is held by vacuum suction using a vacuum suction tool 12 and fixed onto the stem 3. Submount 1 has a length of 1mm and a width of 0.5mm, and the top surface (main surface) is
A metal film 5 is formed by sequentially depositing Cr and Au. Furthermore, a high melting point brazing material 4 made of Au--Sn is preliminarily applied to the lower surface. Therefore, this high melting point brazing material 4 was temporarily melted and the submount 1
Position and fix to stem 3.

Next, a chip 2 having length and width of 300 and 400 μm is held by a vacuum suction tool 13, positioned and supplied onto the submount 1. Chip 2 is on the top and bottom respectively.
It has Au-based electrodes. In addition, since a low melting point brazing material (melting point 180°C) 6 made of Pb-Sn has been applied in advance to the surface far from the optical waveguide 11, this low melting point brazing material 6 is temporarily melted to submerge the chip 2. Fix it to mount 1. In addition, submount 1
The upper metal layer 5 is provided over the entire area of the submount 1, and forms a chip attachment part as well as a wire attachment part used for wire attachment, which will be described later. The metal layer 5 and the low melting point solder material 6 are each formed by vapor deposition when the chip 2 is to be formed on a wafer.

Such a chip mounting structure is shipped in this state and assembled into a desired package by the user. Wires 8 and 9 are connected to the metal layer 5 and the upper surface of the chip 2, respectively. Further, the optical axis is aligned using the optical waveguide 11 that appears floating on the chip surface as a guide so that the tip of the optical fiber supported by the package faces the optical waveguide end of the chip 2.

〔effect〕

(1) Since only the chip 2 is mounted on the submount 1 and only the wire 8 is fixed, the submount 1 can be made smaller than the structure shown in FIG. As a result, the capacity of the submount 1 is also reduced, making it possible to modulate long wavelength communication at high speed.

(2) The submount 1 is fixed to the stem 3 using a high melting point brazing material 4, and the tip 2 is fixed to the submount 1.
is fixed using a low melting point iron material 6. Further, the method of fixing the tip 2 is to fix the submount 1 to the stem 3 and then fix the tip 2 to the submount 1. Therefore, the chip 2 is not heated above 200°C, and no thermal deterioration of the chip 2 occurs.

(3) Submount 1 and chip 2 are each 1
Submount bonding and chip bonding can be fixed using a chip bonder commonly used for semiconductor device assembly, and automatic assembly is also possible because there are no other obstacles around the bonding when fixing. Become.

(4) Since the submount 1 is made of SiC, which has high thermal conductivity, it effectively transfers the heat generated in the chip 2 to the stem 3. Therefore, the chip 2 can be fixed to the submount 1 in a junction-up state with the optical waveguide 11 facing upward.
Therefore, the optical waveguide can be observed when aligning the optical axis with the optical fiber, which is a factor that allows the optical axis alignment to be performed accurately and in a short time.

(5) The lower electrode of the chip 2 is taken out through the metal layer 5 and the wire 8 connected to this metal layer 5. Therefore, unlike the structure shown in FIG. 1, there is no need for a gold piece serving as a relay body, and the number of parts can be reduced.

(6) The structure shown in Fig. 1 has a larger heat capacity than the submount 1 of the present invention because the chip 2 and gold piece 7 are fixed to the submount 1 and then the submount 1 is fixed to the stem 3. The submount must be heated, or the submount to which the chips and gold pieces are fixed must be heated, which requires a long heating time. In contrast, in the present invention, when fixing the submount 1 to the stem 3, the submount 1 and the stem 3 are heated, and the tip 2 is heated.
Since the heating of the submount 1 involves heating the chip 2 and the submount 1, the heat capacity becomes small and the heating time can be shortened.

In this embodiment, the metal layer 5 does not cover the entire main surface of the submount 1, but may have a pattern consisting of a chip attachment part, a wire attachment part, and a connecting part connecting these parts.

Embodiment 2 FIG. 4 is a partially cutaway plan view showing a light emitting semiconductor device according to another embodiment of the present invention, that is, a semiconductor device for optical communication (laser diode device with optical fiber), and FIG. FIG. 4 is a sectional view taken along the line V-V, and FIG. 6 is a schematic diagram showing an example in which the optical communication system is incorporated into an optical communication system.

This laser diode device is assembled based on a stem 3 of a rectangular plate. That is, the stem 3 is formed by cutting one side of a rectangular metal plate to form a ring-shaped sealing wall 14 in the center, and by hollowing out the inside of the ring-shaped sealing wall 14 more deeply and forming a pedestal part in the center of the bottom surface. It is made up of 15 shapes. Then, Au-Sn is placed on this pedestal part 15.
A laser diode chip 2 is fixed by a Pb-Sn solder onto a submount 1 made of SiC and having the same structure as in the previous embodiment, which is fixed by a Pb--Sn solder. Furthermore, guide holes 16 and 17 are provided at both ends of the stem 3, respectively, and extend toward the output surface of the chip 2 from which the laser beam is output. A fiber guide 19 having an optical fiber 18 inserted and fixed in the center thereof is fitted into one of the guide holes 16 and fixed to the stem 3 with silver solder 20 . The tip of the optical fiber 18 faces one exit surface of the chip 2, and the laser beam is introduced into the optical fiber 18. At this time, the tip of the optical fiber 18 is fixed to the pedestal part 15 of the stem 3 with a fixing material 21 such as resin or solder, and light is introduced into the optical fiber 18 by tightening, temperature characteristics, vibration, etc. Care has been taken to ensure that the efficiency (optical coupling efficiency) does not fluctuate. In addition,
In the case of a single mode fiber with a core diameter of about 8 μm, the relative optical axis alignment accuracy of the tip of the optical fiber 18 with respect to the chip 2 is required to obtain the desired optical coupling efficiency that can be used. , for example, must be within ±0.2 to 0.2 μm.

On the other hand, a monitor fiber 22 is inserted and fixed into the other guide hole 17. The tip of this monitor fiber 22 faces the other output surface of the chip 2, and is adapted to monitor the light intensity of the laser beam. Further, two leads 23 and 24 are arranged on the stem 3. A wire 9 with one end fixed to the upper electrode of the chip 2 is fixed to the inner end of one lead 23, and a wire 8 with one end fixed to the metal layer of the submount 1 is fixed to the inner end of the other lead 24. ing. In addition, both leads 8,
9 passes through the peripheral wall of the stem 3 and is fixed to the stem 3 via an insulator such as glass. Further, a plate-shaped cap 25 is airtightly attached to the upper surface of the ring-shaped sealing wall 14 by a seam weld, thereby airtightly sealing the chip 2 and the like.

When such a laser diode device 26 is mounted on various types of equipment, it is fixed to a mounting plate with screws using the mounting holes 10 provided at the four corners of the stem 3. For example, in this example, the sixth
As shown in the figure, there is an example of incorporating it into an optical communication system. That is, the laser diode device 26 is fixed on a thermoelectric cooling device 29 fixed on the substrate 28 of the optical communication device 27. Also, this board 28
There are a laser drive circuit 30 that drives and controls the laser diode device 26, a photo sensor 31 that monitors the laser light intensity, and a Peltier control circuit 32 that controls the thermoelectric cooling device 29 so that the chip 2 always operates at a constant temperature. It's built in. Further, the photo sensor 31 is configured to input monitor information of laser light intensity to the laser drive circuit 30.

Such an optical communication device 27 receives an analog signal 34 as a digital signal 35 via a modulator 33, and sends the optical signal to a receiver 36 using the optical fiber 18 as a transmission medium. In the receiver 36, the optical signal is converted into an electrical signal by a photoelectric conversion device 37 such as a silicon photodiode, and the signal is amplified by an amplifier circuit 38. Thereafter, the digital signal 34 is sent to a demodulator 39 to receive communication information as an analog signal 34.

〔effect〕

(1) The chip 2 is fixed to the stem 3 via the submount 1 in the juncture-up state. Therefore, when aligning the optical axis with the optical fiber 18, the optical axis can be aligned using the optical waveguide 11 visible on the chip surface as a guide, resulting in high efficiency and high accuracy of the optical axis alignment operation. Therefore,
More reliable communication is possible in optical communication systems.

(2) For the reason mentioned in (1) above, since the light absorption efficiency of the optical fiber can be improved, information can be transmitted farther than before with the same output (increasing the length of the transmission path).

(3) Since only the chip 2 is fixed on the submount 1, the submount 1 can be made smaller. As a result, the capacity can be reduced and long wavelength communication can be modulated at high speed.

(4) The chip 2 is fixed to the submount 1, which is fixed to the stem 3 via a high melting point brazing material, via a low melting point brazing material. For this reason, chip 2 is 200 yen when assembled.
Since the chip is not exposed to high heat exceeding ℃, there is no thermal deterioration of the chip.

(5) As noted in (4), submount 1 is placed on stem 3, chip 2 is placed on submount 1, and so on.
By assembling the parts one by one, automatic assembly becomes possible.

Although the invention made by the present inventor has been specifically explained based on the examples above, the present invention is not limited to the above examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

[Application field]

The above explanation has mainly been about the case where the invention made by the present inventor is applied to optical communication technology, which is the background field of application, but it is not limited thereto. It can be applied to mounting techniques for chips each having an electrode.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a semiconductor laser device mounting structure already developed by the applicant, FIG. 2 is a perspective view showing a semiconductor laser device mounting structure according to an embodiment of the present invention, and FIGS. 3a and 3b are the same. An explanatory diagram showing a method of manufacturing a semiconductor laser element mounting structure, FIG. 4 is a partially cutaway plan view of a semiconductor device for optical communication according to another embodiment, and FIG. 5 is taken along V-V in FIG. 4.
A cross-sectional view taken along the line, FIG. 6, is a schematic diagram showing an example of incorporating the same into an optical communication system. DESCRIPTION OF SYMBOLS 1... Submount, 2... Semiconductor laser element (chip), 3... Stem, 4... Solder material, 5...
...metal layer, 6...brazing material, 7...gold piece, 8,9...
Wire, 10...Mounting hole, 11...Optical waveguide, 1
2, 13... Vacuum adsorption tool, 14... Ring-shaped sealing wall, 15... Pedestal portion, 16, 17... Guide hole, 18... Optical fiber, 19... Fiber guide, 20... Silver solder, 21...Fixing material, 22...
...Monitor fiber, 23, 24...Lead,
25...Cap, 26...Laser diode device, 27...Optical communication device, 28...Substrate, 29
... Thermoelectric cooling device, 30 ... Laser drive circuit,
31... Photo sensor, 32... Peltier control circuit, 33... Modulator, 34... Analog signal,
35...Digital signal, 36...Receiver, 37...
...Photoelectric equipment, 38...Amplification circuit, 39...Demodulator.

Claims (1)

[Claims] 1 The Cu stem and its main surface are small enough to fix only one semiconductor laser element and wire bonding is possible, and the main surface has a Cr layer,
A submount made of SiC on which Au layers are sequentially formed, and electrodes made of gold-based material are formed on the top and bottom surfaces.
It has a junction-up high-speed long-wavelength semiconductor laser device with an optical waveguide close to the upper electrode, a single mode fiber, and a monitor fiber, and the submount is mounted through a high melting point brazing material made of Au-Sn. The semiconductor laser device is fixed in a juncture-up configuration, and a wire is connected to a part of the main surface of the submount near the side of the semiconductor laser device, and a wire is connected to the upper electrode of the semiconductor laser device. is connected to the semiconductor laser element, and a single mode fiber whose tip has a relative optical axis alignment accuracy of within ±0.2 to 0.3 μm is fixed to the stem by silver brazing material, and the monitor fiber is fixed to the stem by silver solder. 1. A laser diode device with an optical fiber, characterized in that the laser diode device is fixed such that its tip is brought close to the other optical waveguide of the semiconductor laser element.