JP3146735B2 - Stack laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to obtain a high output laser beam by stacking semiconductor lasers, and is particularly used as a high output semiconductor laser constituting a laser radar system for distance measurement. is there.

[0002]

2. Description of the Related Art In recent years, a system has been studied which measures the distance between vehicles by using a semiconductor laser and keeps the distance between the vehicles constant, or issues an alarm when the vehicle is too close to a preceding vehicle. In such a system, it is inevitable to detect an object 100 m away, and in order to satisfy such specifications, a laser output of 40 to 80 W is required by a pulse drive in a semiconductor laser. . In general, a single-chip semiconductor laser currently commercially available can obtain an output of only about 10 to 20 W at a maximum in practical use. Therefore, a number of the above-described elements are stacked in the vertical direction, joined with a brazing metal, and formed into a stack. Thus, the light output is increased. Here, in the joining of the elements, Au / S
n, Au / Si, or an alloy composed of Sn / Pn, etc. is heated and melted while pressing the element at a predetermined temperature.
By cooling it, it is made eutectic and joined.

[0003]

However, the distance between the junction of each element and the light emitting section for emitting laser light is about 5 μm.
When the brazing material is joined by applying temperature, the molten brazing material, when protruding from the joining surface, flows as it is onto the light emitting surface of the element located at the lower stage, obscuring the laser emitting part, There is a problem that the output is reduced.

[0004] On the other hand, it is conceivable to join at a temperature lower than the temperature at which the brazing material melts and flows out. In this case, however, the joining strength between the elements is weak, and in a vibrating environment such as an automobile, etc. At the time of use, there is a problem that each element is peeled off at the joint, and the reliability of the stacked laser becomes low.

Accordingly, an object of the present invention is to provide a stacked laser in which the light emitting surface is not contaminated by the brazing material.

[0006]

In order to solve the above-mentioned problems, a stacked laser according to the first aspect of the present invention comprises: a pedestal; a first laser element mounted on the pedestal; The first laser element and the light emitting surface are in the same direction, and the brazing metal is placed on the first laser element such that the light emitting surface is located behind the light emitting surface of the first laser element. And a second laser element installed via the second laser element.

According to a second aspect of the present invention, there is provided a stacked laser, comprising: a pedestal; a first laser element mounted on the pedestal;
The laser device and the light emitting surface are arranged in the same direction, and are installed on the first laser device via a brazing metal which is provided on the back electrode and has both ends shorter than the back electrode and shorter than the cavity length. And a second laser element.

A stacked laser according to a third aspect of the present invention provides a first laser element having a pedestal, a first laser element provided on the pedestal, and having a brazing metal protrusion preventing member provided on an upper surface of the element on the light emitting surface side; The laser device and the light emitting surface are in the same direction,
A second laser element provided on the first laser element via a brazing metal.

[0009]

According to the first aspect of the present invention, the second laser element is bonded to the first laser element so that its light emitting surface is behind the light emitting surface of the first laser element. Therefore, when joining the first laser element and the second laser element by melting the brazing metal, the molten brazing metal is melted by the first laser element and the second laser element. Even if it overflows from the junction surface with the first laser, it flows to the upper surface of the first laser and is held there, so that the molten brazing metal does not overflow to the light emitting surface of the first laser element.

According to the second aspect of the present invention, both ends of the brazing metal joined to the back electrode of the second laser element are shorter than the cavity length of the second laser element. Since the brazing material is shortened, when the brazing metal is melted and the first laser element and the second laser element are joined, the molten brazing metal flows so as to spread to both shortened ends. The molten brazing metal does not overflow to the light emitting surface of the first laser element.

According to the third aspect of the present invention, since the brazing metal protrusion preventing member is provided on the upper surface of the first laser device on the light emitting surface side, the first laser device and the second laser device are provided. When joining the laser element with the brazing metal by melting the brazing metal, the molten brazing metal does not overflow onto the light emitting surface of the first laser element.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 show a first embodiment, which is a so-called three-stack laser in which semiconductor laser elements 11, 12, and 13 are sequentially stacked on a copper heat sink 2 having a gold-plated surface. Things.
FIG. 1 shows that the stack laser is used for emitting light 11 a, 12 a, 13.
FIG. 2A is a view seen from obliquely forward, and FIG. 2 is a view seen from the lateral direction of the light emitting surface. Here, the upper electrodes 113, 123, and 133 of the respective semiconductor laser elements are formed by forming a thin film composed of Cr / Au by a vacuum evaporation method and then performing a heat treatment at about 360 ° C. to form an ohmic contact. The lower electrode (not shown) of the semiconductor laser is obtained by forming a thin film composed of AuGe / Ni / Au by the same method as described above and then performing a heat treatment to obtain an ohmic contact. On the lower electrode of the semiconductor laser, brazing materials 112, 122, 132 for joining the respective elements are provided.
Are formed by a vacuum evaporation method. This brazing material is composed of Sn and A
u, each having a thickness of 800 nm and 2
00 nm.

Next, the manufacturing process of the above-mentioned stacked laser will be briefly described. The first-stage semiconductor laser element 11 is welded to the copper heat sink 2 with a die bonder at a temperature of 440 ° C. while applying a load to the element, and is joined to the heat sink 2. Next, the second-stage semiconductor laser element 12 is arranged, in the same manner as described above, such that the light-emitting surface 12a is located 20 μm behind the light-emitting surface 11a of the first-stage semiconductor laser element 11, The semiconductor laser device 11 is bonded on the upper electrode 113. Finally, the third-stage element 13 is joined to the electrode 123 on the second-stage semiconductor laser element 12 as described above. At this time, similarly to the above, the light emission surface 1 of the third-stage semiconductor laser 13
3a is a distance 2 from the light emitting surface of the second-stage semiconductor laser 12.
It is arranged behind by 0 μm. In the joining with the die bonder device, three elements may be heated and joined at a time while applying a load. Finally, the Au wire 3 is formed on the upper electrode 133 on the third-stage semiconductor laser device 13 by a wire bonder.

The dimensions of the semiconductor laser elements 11, 12, and 13 manufactured as described above are the stripe width (light emission width).
400 μm, cavity length (length a in FIG. 2) 600 μm
Same as m.

With this structure, the light emitting portions 111 and 121 of the semiconductor laser elements 11 and 12 are not covered by the brazing filler metal 122 or 132. This is because the brazing material that has been melted and extruded to the front is held on the upper electrodes 223 and 113 of the lower elements 12 and 11 protruding from the upper elements 13 and 12 as shown in FIG. Because it is. By adopting such a configuration, it is possible to obtain an optical output just three times as large as that of a one-chip device without lowering the luminous efficiency of the three-stack laser.

FIGS. 3 and 4 show a second embodiment, which is another example of a three-stack laser joined by the same method as the stack laser shown in FIGS. 1 and 2. FIG.
This is achieved by bonding a semiconductor laser 21 having the longest cavity length among the three semiconductor laser devices on the heat sink 2 and successively reducing the cavity length of the devices, that is, the cavity length of each device. a, b,
The semiconductor lasers 22 and 23 are joined so that c becomes a>b> c, and the light emitting surface for emitting laser light is located on the rear side as the upper element. Then, the wire 3 is bonded onto the upper electrode 233 of the semiconductor laser 23 to form a three-stack laser.

In this configuration, since the length of the upper element and the like is reduced and the element is mounted in a pyramid shape, the molten brazing material is extruded to the front and the back when the elements are joined. As described above, the light-emitting portions 211 and 221 are held on the upper electrodes 213 and 223, and do not obscure the light-emitting portions 211 and 221. In addition, 231 in FIGS.
Represents a light emitting unit.

In this embodiment, the joining method of the semiconductor laser device is not particularly limited to a pyramid shape, as long as the front end face portion having the laser light emitting portion is located closer to the rear of the upper device.

FIG. 5 and FIG. 6 show a third embodiment, which is an example of a stacked laser joined by the same method as described above. The stack laser of this example is a semiconductor laser device 1
The length d in the cavity length direction of the formation region of the brazing material 124 made of Sn / Au formed on the second back electrode is smaller than the cavity length e.

As described above, since both ends are shorter than the back electrode of the element so that the brazing metal is shorter than the cavity length of the element, when joining the semiconductor laser elements,
As shown in FIG. 6B, the molten brazing metal spreads to the end of the upper electrode even after the element is joined, and does not overflow into the light emitting surface 11a having the laser light emitting portion 111.

FIG. 7 shows a fourth embodiment.
This is because the light emitting surfaces 31a and 32 having the laser light emitting portions 311 and 321 of the semiconductor lasers 31 and 32 as the lower element.
brazing metal protruding suppressing portions 3 on the joint surface on the a side
1B, 32B, the semiconductor laser 31,
This represents a three-stack laser consisting of 32 and 33. The upper semiconductor lasers 32, 33 are joined by the brazing metal protruding suppressing portions 31B, 32B as shown in FIG.

With this configuration, when the elements are joined to each other, the molten brazing metal 322, 332 becomes a light emitting surface 31a having laser emitting portions 311, 321 by the brazing metal protrusion preventing portions 31B, 32B. , 32a does not overflow.

Although the embodiment of the present invention has been described in detail with reference to the example of two stacks and three stacks, the present invention is not limited to the above, and can be applied to any stack laser for joining each element.

According to this method, since the light emitting portion is not covered by the molten brazing material, the light output of the stack laser is not reduced by the brazing material. Moreover, since the brazing material does not cover the light emitting portion, the brazing material can be melted at a high temperature and the elements can be joined, thereby increasing the joining strength. Therefore, a reliable stack laser can be manufactured at a high yield rate.

[0025]

According to the present invention, since the brazing metal does not obscure the light emitting surface of the first laser element, the problem of a decrease in light output due to the adhesion of the brazing metal as a stacked laser is completely solved. it can. Moreover, with this configuration, the brazing metal does not obscure the light exit surface, so that the temperature of the brazing metal can be sufficiently increased and the joining can be performed at the eutectic temperature. Therefore, it is possible to join in a state where the brazing metal is completely melt-alloyed, and it is possible to supply a stacked laser having high joining strength and extremely high reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view of a three-stack laser in which light emitting surfaces of respective semiconductor elements are sequentially shifted and joined.

FIG. 2 is a side view of the three-stack laser of FIG.

FIG. 3 is a perspective view of a three-stack laser in which an upper element joins an element having a shorter cavity length than a lower element.

FIG. 4 is a side view of the three-stack laser of FIG. 4;

FIG. 5 is an explanatory diagram showing a joining process of a two-stack laser in which a brazing metal is shorter than a cavity length of a semiconductor laser.

FIG. 6 is a side view of the two-stack laser shown in FIG. 5;

FIG. 7 is a side view of a three-stack laser in which a stopper is provided above a light emitting unit.

[Description of Signs] 2 Copper heat sink 3 Gold wire 11 First-stage semiconductor laser 12 Second-stage semiconductor laser 13 Third-stage semiconductor laser 111 Light-emitting portion of semiconductor laser 121 Light-emitting portion of semiconductor laser 131 Light-emitting portion of semiconductor laser 112 Brazing material Metal 122 brazing metal 132 brazing metal 113 upper electrode 123 upper electrode 133 upper electrode 11a light emitting surface 12a light emitting surface 13a light emitting surface

Continuation of the front page (72) Inventor Yoshiki Ueno 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-1-231380 (JP, A) JP-A-1-259587 (JP) JP-A-4-186689 (JP, A) JP-A-2-137389 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (3)

(57) [Claims] 1. A base, a first laser element mounted on the base, and a light emitting surface on the first laser element, wherein a light emitting surface of the first laser element and the light emitting surface are in the same direction. A second laser element installed via a brazing metal so as to be installed behind the light emitting surface of the first laser element. 2. A pedestal, a first laser element mounted on the pedestal, and a light emitting surface in the same direction as the first laser element, the light emitting surface being set on the back electrode, and both ends of the back electrode being located on both ends. And a second laser element disposed on the first laser element via a brazing filler metal shorter than the cavity length. 3. A first laser element provided on the pedestal, provided on the pedestal, and provided with a brazing metal protrusion preventing member on the upper surface of the element on the light emitting surface side; and a first laser element and the light emitting surface. In the same direction, the second laser installed on the first laser element via brazing metal
A stacked laser comprising: a laser element according to claim 1;