JPH05190973A - Submount for semiconductor laser - Google Patents

Abstract

PURPOSE:To facilitate the position adjustment thereby enabling the continuous bonding step to be performed by one temperature control by a method wherein the contact surface between Aw and solder layer is accepted only on the bonding side onto a metallic radiator while a barrier layer is provided beneath the solder layer on the bonding side onto a semiconductor chip. CONSTITUTION:A Ti layer 2, a Pt layer 3, and Au layers 4a, 4b are respectively formed on a metallic radiator side reverse to the semiconductor laser chip side of a submount 1. Besides, another Pt layer 6 is laminated to be functioned as a barrier metal on a part or the whole surface of the topmost Au layer 4a on a semiconductor laser chip 8 side to be covered with an AuSn solder layer 7. Furthermore, the Au layer 4a on the semiconductor laser chip side works as the junction region of a metallic wire while the other Au layer 4b on, the metallic radiator side works as a part of the solder layer. At this time, the submount 1 is soldered into the AuSn solder layer 7 on the metallic radiator 9 side so that the submount 1 may be bonded onto the radiator 9 due to the AuSn layer in different composition from that in the initial AuSn layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in controllability of film thickness and composition of solder material, reliability of semiconductor laser, easy position adjustment, and continuous vapor deposition of submount and semiconductor laser and automation of mounting. The present invention relates to a semiconductor laser submount that improves work efficiency including the above.

[0002]

2. Description of the Related Art Recent semiconductor lasers are being put to practical use in the fields of optical information processing and optical communication, and the reliability of the device is an extremely important factor in any field. Such a semiconductor laser is used in a region where the current is several 10 mA to several 100 mA, but since a large amount of heat is generated, a metal radiator is generally used as a heat sink. Further, in order to avoid the stress / distortion caused by the difference in thermal expansion coefficient from affecting the reliability, a material having a thermal expansion coefficient relatively close to that of the semiconductor substrate material is arranged as a submount on the metal radiator. Then, a method of fixing the semiconductor laser chip on it via a solder material is often used. An Au layer is formed on the uppermost layer of the semiconductor laser chip in consideration of ohmic property, adhesive strength and reliability.

It should be noted that the term "adhesion" as used in the present invention does not indicate a technique using a so-called adhesive, but indicates a solid solution state that occurs between a relatively thin metal film and a solder layer or between relatively thin metal films. To do.

An example of the structure of the fixed portion is disclosed in Japanese Patent Laid-Open No. 1-1387.
No. 77 / Ti on both sides of the Si semiconductor substrate
There is a technology consisting of Pt / solder, in which the Ti / Pt layer functions as a barrier metal layer.

Another example is the technique disclosed in Japanese Patent Publication No. 1-40514. That is, both sides of the Si semiconductor substrate are plated with Au, and the Au on the metal radiator side is plated.
Au-Si eutectic solder is formed by increasing the thickness of the layer to 10 to 20 μm, and thermocompression bonding of Au on the semiconductor laser chip side and Au on the submount side is used (Japanese Patent Laid-Open No. 1-40514).
(See the official gazette).

Further, the structure disclosed in Japanese Patent Application Laid-Open No. 2-128486 will be described with reference to the cross-sectional view of FIG. 3. A Ti layer 2, a Pt layer 3, an Au layer 4 and a solder layer 5 are provided on both surfaces of the submount 1. The structure is known.

[0007]

A semiconductor laser chip,
When mounting the submount and metal radiator,
First, the submount is bonded onto the metal radiator, and then the semiconductor laser chip is bonded to the submount. Further, it is necessary to form an Au thin wire on the upper surface of the chip and the surface of the submount in order to pass a current.

In the technique disclosed in Japanese Laid-Open Patent Publication No. 1-138777, the solder layer is exposed on the entire uppermost surface, or the Pt layer is exposed even if the solder layer is partially removed. I can't come.

Further, the technique disclosed in Japanese Patent Application Laid-Open No. 1-40514 has a structure that does not hinder the joining of Au thin wires and allows continuous mounting. However, Au-on the semiconductor laser chip side of the submount is used. The thermocompression bonding of Au cannot be easily moved even if a temperature is applied once it is bonded.
Therefore, it becomes extremely difficult to adjust the position when bonding the semiconductor laser chip.

Furthermore, in the structure disclosed in Japanese Unexamined Patent Publication No. 2-128486, since the solder layers are provided on both surfaces of the submount, it is possible to easily adjust the positions of the submount and the semiconductor laser chip. However, when performing continuous mounts, moving one may move the other. In addition to this, in order to prevent such difficulties, a method of changing the material of the upper and lower solders, that is, the bonding temperature is often used. However, since there is a solder layer on the Au layer, a reaction with Au is likely to occur when the solder is heated, and there is a risk of eroding the area on the submount to which the Au thin wire can be bonded.

The present invention has been made in view of the above circumstances, and in particular, makes it possible to improve work efficiency including continuous bonding of a submount and a semiconductor laser chip and automation of mounting.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] A submount substrate to which a semiconductor laser chip is fixed, a metal heat radiator adhered to the other surface of the submount substrate, and a metal heat radiator side of the submount substrate are stacked in the following order. To form continuously
The i layer, the Pt layer, the Au layer, and the solder layer, the Ti layer, the Pt layer, and the Au layer continuously formed on the semiconductor laser chip side of the submount substrate in the following order, and the Au layer formed on the semiconductor laser chip side. The Pt layer laminated on the layer and the solder layer composed of the same component as the solder layer are characteristic of the semiconductor laser submount according to the present invention.

Another feature is that the thickness of the solder layer formed on the semiconductor laser chip side of the submount substrate is made larger than that of the solder layer on the metal radiator side.

[0014]

Since the solder layers are formed on both sides of the submount, the position adjustment of the semiconductor laser chip and the submount can be easily performed. Further, the semiconductor laser chip side has a solder layer for bonding partially, and since the Pt layer functioning as a barrier layer is installed under the solder layer, the bonding area of the Au thin wire is eroded even during heating for bonding. Will not do.

In addition, many characteristics are that the contact surface between Au and the solder layer is adopted only on the bonding side with the metal radiator, and on the bonding side of the semiconductor chip, the barrier layer is provided under the solder layer. Install. As a result, there is a difference in the bonding time between the upper and lower solder layers, and the problem that the other moves when one is moved while maintaining the ease of position adjustment is overcome. Further, since the solder having the same composition is used on both the upper and lower surfaces, one temperature control is performed, and a continuous bonding process becomes possible.

[0016]

EXAMPLE An example according to the present invention will be described with reference to FIGS. 1 and 2. As the submount 1, aluminum nitride having a good thermal conductivity and a thickness of 400 μm is used. Semiconductor laser chip side of submount 1 (paper submount 1
On the metal radiator side opposite to that of Ti layer 2-100.
0 angstrom, Pt layer 3 to 1000 angstrom, Au layer 4a and Au layer 4b are formed to 5,000 angstrom in this order.

The semiconductor laser chip 8 (see FIG. 2)
The Au layer 4a on the side has a thickness of 2
000 angstrom Pt layer 6 is provided to serve as a barrier metal, where Au having a thickness of ˜5.2 μm is provided.
The Sn solder layer 7 (hereinafter referred to as a solder patterning layer) is covered. The size of the semiconductor laser chip 8 used in this embodiment is approximately 400 × 300 × 100 μm.

The Au layer 4a on the semiconductor laser chip side
Serves as a bonding area for the metal thin wires, but the Au layer 4b on the metal radiator side functions as a part of the solder layer. The formation of the Pt layer 6 on a part or the whole surface of the Au layer 4a on the semiconductor laser chip side is determined by whether or not the semiconductor laser chip is electrically floated. Floating electrically depends on whether a current is passed in the direction of the semiconductor laser chip and the submount, or whether the current is reversed from the middle of the thickness direction and passed.

A semiconductor laser chip 8 as shown in FIGS.
When the Pt layer 6 and the AuSn solder layer 7 are coated on a part of the uppermost Au layer 4a on the side, a component for an electronic circuit including a semiconductor laser is formed on the exposed uppermost part of the Au layer 4a by, for example, a gold wire. Is provided by thermocompression bonding means.

On the other hand, Au provided on the semiconductor laser chip side
An AuSn solder layer 7 having a thickness of 4 μm, for example, is formed on the layer 4b to be thinner than that on the semiconductor laser chip side. That is, the solidification time determined by the total amount of solder will be different if the difference between the two layers is about 1.2 μm, which is advantageous in the assembly process.

In the assembling process, first, the submount 1 in which the above layers are stacked is placed on the metal heat sink 9 shown in FIG. 2 on the metal heat sink side (hereinafter, the metal heat sink side is the lower side, and the semiconductor laser chip side is the lower side). It is soldered to the AuSn solder layer 7 (described as the upper side), but the support base for fixing the metal radiator plate 9 is preheated to about 300 ° C. At this time, the AnSn solder layer 7 and the Au4b layer become an AuSn layer having a different composition from the initial composition after a certain time of reaction with each other, and firmly bond the submount 1 and the metal heat sink 9 to each other. AnSn of FIG.
The solder layer 7 reveals the state after the reaction, and Au
The 4b layer was omitted. Note that the soldering time is about 1 minute as a guide, and the upper AuSn following this soldering process
It is enough time for the alignment required for soldering.

Next, for example, on an arrow-string type support (not shown) communicating with a pressure reducing mechanism attached to a so-called mounter,
The held semiconductor laser chip 8 is brought close to the molten AnSn solder layer 7 installed on the submount 1 by the operation of the mounter as much as possible, and furthermore, the outer surface of the submount 1 is positioned as a reference and then the two are contacted and soldered. I do. In addition, it cools by spraying nitrogen gas.

At this time, since the AuSn solder layer 7 on the metal heat dissipation plate side and the metal heat dissipation plate 9 are fixed by soldering, the subsequent soldering proceeds extremely easily. Since such a soldering process proceeds extremely smoothly, it takes a short time, and since it is possible to perform continuous bonding in a process controlled by one temperature, it is possible to shorten the process.

When the AuSn solder 7 layer on the upper side is melted, the presence of the Pt layer 6 as the barrier layer does not react with the Au 4a layer and maintains the property as a solder, which is suitable for thermocompression bonding of fine gold wires. The state can be maintained.

Although AlN is used as the material of the sub-mout 1 in this embodiment, a material having good thermal conductivity such as SiC, diamond, or Si can be used, and a reaction with a solder material such as SiC is relatively likely to occur. The same effect can be obtained by making the AuSn solder 7 on the upper side thicker than that on the lower side for the one in which the reaction proceeds beyond the Pt layers 3 and 6 when left for a long time.

Further, as the solder, materials such as AuGe, AuSi &) and InPb which easily react with Au can be sufficiently applied.

[0027]

As described above, according to the present invention, the position adjustment is easy and the thermocompression bonding area of the Au thin wire is ensured, and the submount-metal radiator plate and submount-semiconductor laser chip are controlled by one temperature control. Since the continuous adhesion between the two is possible, the process can be shortened.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a semiconductor laser submount according to the present invention.

FIG. 2 is a sectional view of a main part after a semiconductor laser chip is bonded to a submount according to the present invention.

FIG. 3 is a sectional view of a conventional semiconductor laser chip submount.

[Explanation of symbols]

 1: Submount, 2: Ti layer, 3, 6: Pt layer, 4a, 4b: Au layer, 7: AuSn solder layer, 8: Semiconductor laser chip, 9: Metal heat sink.

Claims (3)

[Claims] 1. A submount substrate to which a semiconductor laser chip is bonded, a metal heat radiator to be bonded to the other surface of the submount substrate, and a metal heat radiator side of the submount substrate, which are successively stacked in the following order. Ti layer, Pt layer to be formed,
An Au layer and a solder layer, and a Ti layer continuously formed on the semiconductor laser chip side of the submount substrate in the following order:
A submount for a semiconductor laser, comprising a Pt layer and an Au layer, a Pt layer laminated on the Au layer formed on the semiconductor laser chip side, and a solder layer composed of the same components as the solder layer. 2. A submount for a semiconductor laser, wherein the thickness of the solder layer formed on the semiconductor laser chip side of the submount substrate is larger than that of the solder layer on the metal radiator side. 3. A semiconductor laser sub, comprising a Pt layer laminated on a part of an Au layer formed on the semiconductor laser chip side of the submount substrate and a solder layer made of the same component as the solder layer. mount