JPH0141268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor laser device, and more particularly to a method for dividing a semiconductor laser array device on which a mirror surface for optical feedback is formed into individual semiconductor laser devices.

As shown in FIG. 1, a semiconductor laser device is manufactured simply by forming a p-n junction between p- and n-type epitaxial growth layers 13 and 14 on a semiconductor substrate 17 and connecting an electrode 1.
A current is passed perpendicularly to the bonding surfaces from 1 and 12 to the surface 15,
16 as a resonator. Surfaces 15 and 16 are mirror-finished by parallel cleavage. The light travels back and forth between the two surfaces while being reflected by both surfaces, producing laser oscillation, and a portion of the light can be extracted as a laser beam.

Here, as shown in FIG. 2, the method for forming the surface 18 in the conventional laser element is to form a semiconductor laser array element 21 in a bar shape with optical return mirror side surfaces 15 and 16 formed by cleavage. A method of cutting with a razor blade 22 has been used.
However, with this method, the object to be cut is in the form of a bar, which is very small, making it difficult to fix it, and it is difficult to obtain the desired dimensions because it is mainly done manually using a razor blade. Moreover, razor blades are prone to breakage, which often results in very poor cutting shapes. Furthermore, in general, a razor blade is pressed from the p-layer and n-layer side, which are formed on the substrate by epitaxial growth, to cut the p-layer.
The bonding state at the n-junction surface tends to be incomplete, which tends to cause leakage current. This problem is particularly important for InP-based semiconductor lasers because their crystals are soft. For the above-mentioned reasons, the conventional cutting method for semiconductor laser array elements reduces both the appearance yield and the characteristic yield.

On the other hand, if the wafer cutting process that is commonly used in normal semiconductor device manufacturing, that is, scribing with a diamond scriber, is applied to cutting bar-shaped semiconductor laser array elements, it is considered unsuitable because the mirror surface for optical feedback that has been painstakingly created is likely to be damaged. It is being

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for cutting a semiconductor laser device that eliminates the above-mentioned problems.

The method for manufacturing a semiconductor laser device according to the present invention is to form a bar state in which at least an active layer is formed on a semiconductor substrate made of a semiconductor single crystal, a plurality of striped light emitting regions are formed, and a mirror surface for optical feedback is formed. In a conductor laser device, each semiconductor laser device is scribed with a scribe point between the striped light emitting regions in parallel to the stripes and only on the substrate side surface that is at least 10 μm away from the mirror side surface. It is characterized by being divided into two parts. This will be explained in detail below based on examples.

FIG. 3 is a diagram showing a method of cutting a semiconductor laser device according to the present invention, in which the optical return mirror surface 1 is cut by cleaving.
The semiconductor laser array element 21, which is now in the bar state where the rays 5 and 16 are formed, is moved between the striped light emitting region 31 and the adjacent light emitting region 32 from at least the mirror side surfaces 15 and 16 of the substrate side surface 33.
Only a portion 34 separated by 10 μm or more is scribed at a scribe point 35, and 36 is a semiconductor laser element that has been completely cut. Note that 3 in the figure
8 is a crack that has developed due to scribing, and 39 is a mark caused by a scribe point.

The following three points are important in the method of the present invention. Firstly, the scribe point is used to cut, and secondly, the part to be scribed with the scribe point is the substrate side surface 34, and the epitaxial growth layer 13,
The side surface 14 must not be scratched, and third, the portion of the substrate side surface 37 within 10 μm of the mirror side surface must not be scratched.

First, the second important point will be explained using FIG.

Generally, when a semiconductor crystal is scribed with a scribe point, the damage layer is said to be several to tens of micrometers deep. When this damaged layer reaches the pn junction surface, it becomes a cause of leakage current at the pn junction surface. Now, if we consider this problem with respect to semiconductor laser devices, the depth of the p-n junction of semiconductor laser devices is usually about several μm from the epitaxial growth surface, and generally the p-n junction exists over the entire wafer surface. do. Therefore, when scribing with a scribe point from the epitaxial growth surface side as shown in FIG. This causes a significant decrease in the characteristic yield and reliability of the semiconductor laser device. On the other hand, when the substrate side surface is scribed and cut with a scribe point as shown in Figure 4b, the depth of the damaged layer is several to tens of μm, whereas the original thickness of the substrate is generally about 100 μm. The damaged layer 44 does not reach far to the pn junction surface 41. Therefore, no leakage current occurs during this cutting process.
Furthermore, since the damaged layer does not reach the pn junction surface, there is less disturbance in the cutting state of the pn junction than in the method shown in FIG. 4a, and reliability is high. As explained above, by scribing the substrate side surface with a scribe point, the characteristic yield of semiconductor laser devices can be improved.
It was found that improvement in reliability can be expected.

The effects of the present invention will be explained below while comparing with conventional methods. FIG. 5 shows typical external appearances of semiconductor laser devices cut by the conventional method and the method of the present invention. The main conditions are as follows.

Material InP Surface orientation (100) Side orientation (011) and (011) Distance between both mirror surfaces 300 μm Crystal thickness 40 to 140 μm Scribing point scribing direction <011> Figure 5 a shows the conventional An example of the appearance of a semiconductor laser device produced by the method is shown. The cuts were made using a sharp razor blade. Cut surface 51
The cracks are extremely irregular, and the cut portions often have protruding portions 52 with minute cracks. In particular, the thicker the crystal, the more likely irregular cracks and protrusions will occur.

FIG. 5b shows an example of the external appearance of a semiconductor laser device cut by uniformly scribing and cutting the entire substrate side surface with a scribe point. No irregular cracks or protrusions are observed. However, at the stage of scribing with a scribe point, a large notch 55 is formed on the mirror side surfaces 15 and 16.
occurs. This kind of chipping is 10μm from the mirror side.
This occurs with a high probability when scribing the surface of the board with a scribe point within
Almost no occurrence occurred when the substrate side surface was scratched at a distance of 10 μm or more. In a semiconductor device such as a semiconductor laser, which operates with the side surface as a functional part, chipping of the side surface is fatal. 53 in the diagram
is a mark made with a scribe point over the entire area between both sides 15 and 16 of the substrate side surface 33.

FIG. 5c shows an example of the appearance of a semiconductor laser device manufactured by the method according to the present invention. With the method of the present invention, irregular cracks and protrusions that occur in the conventional method and chips on the side surface that occur in the method shown in FIG. 5B do not occur. In order to prevent the chipped portion 55 on the side surface that occurs with the method shown in Fig. 5b, from both sides.
It is important to use a scribe point to scribe only on the inside by 10 μm or more.

As can be seen from the above examples, in order to obtain a semiconductor laser device that does not have defects in appearance as shown in FIG. 5c in the cutting process, it is necessary to
It was found that it is important to limit the scribe point to only the inner part of 10 μm or more.
In other words, this is nothing but the first and third important points mentioned above.

The above method can be applied to other crystalline materials such as GaAs in exactly the same way.

In addition, in order to be practically effective, the above-mentioned characteristic yield and appearance yield must be good, as well as workability and
Mass productivity, including reproducibility and ease of automation, becomes a major issue. Therefore, among these mass productivity factors, we will discuss the ease of automatic processing in particular. First, there are two problems when considering automatic processing. That is,
There are two issues: how to fix the semiconductor laser array element to be cut, and whether the method of creating scratches that leads to cutting can be easily automated.

First, let us consider the method of fixing the semiconductor laser array element. The size of semiconductor laser array elements is extremely small compared to conventional wafers. Therefore, when an adhesive tape used in a normal wafer cutting process is used, the adhesive strength increases in proportion to the contact area, so the adhesive strength between the semiconductor laser array element and the adhesive tape is very weak. Therefore, it is conceivable that the semiconductor laser array element moves during cutting. In the conventional method shown in FIG. 2, in particular, if the razor blade 22 contacts the semiconductor laser array element 21 with even a slight inclination, the semiconductor laser array element 21 often moves. However, in the method of cutting the semiconductor array element 21 using the scribe point 35 shown in FIG. It did not occur. In the method of the present invention, the area to be scribed with the scribe point 35 is a part 39 of the substrate side surface.
There is no need for the scribe point 35 to come into contact with the mirror side surfaces 15, 16, and it is quite possible to cut without contact.
Therefore, it can be said that fixing the semiconductor laser array element is much easier than with conventional methods.

Next, we will consider whether the method of creating scratches that leads to cutting is easy to automate. With conventional methods, razor blades are prone to breakage and require frequent replacement of razor blades. This means that even if the cutting process itself is automated, if the razor blade replacement work remains manual, the effectiveness of automation will be halved, implying the necessity of automating the razor blade replacement work. However, automation of razor blade replacement work is not necessarily easy considering the complexity of the work itself.

On the other hand, regarding the method of scribing with a scribe point of the present invention, a scriber is already available as conventional equipment, and it is sufficient to add a function to control the scribing distance to the conventional scriber.
Technology to control such distances is not at all difficult today, as pulse motors and control computers have developed. Therefore, it is not at all difficult to create a scriber that can control the scribing distance as described above.

As described above, the method of the present invention is easier to automate than conventional methods, and once automation is implemented, workability and reproducibility are expected to be dramatically improved, leading to a dramatic increase in mass productivity. We can expect this to increase significantly.

As described above, according to the present invention, it is possible to cut a semiconductor laser array element into individual semiconductor laser elements without degrading the characteristics or damaging the appearance. Furthermore, automation is not at all difficult and mass productivity can be greatly expected.
As described above, the method of the present invention is extremely advantageous for mass-producing semiconductor laser devices.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic structure of a semiconductor laser device. 2 and 3 show the process of cutting a semiconductor laser array element to produce a semiconductor laser element, with FIG. 2 showing the conventional method and FIG. 3 showing the method of the present invention. FIG. 4 is a diagram for explaining the importance of scribing with a scribe point from the surface side of the substrate in the present invention.
FIG. 4A is a diagram showing a semiconductor laser device cut by scribing the epitaxial growth layer side surface with a scribe point, and FIG. 4B is a diagram showing a semiconductor laser device cut by the method of the present invention. Furthermore, FIG. 5 is a diagram showing the typical appearance of a semiconductor laser device manufactured by the method of the present invention and a method for explaining the advantages of the conventional method and the present invention, and FIG. FIGS. 5b and 5c show the appearance of a semiconductor laser device manufactured by the method of the present invention. 11, 12... electrode, 13, 14... p and n
type epitaxial growth layer, 15, 16... (for optical return mirror surface) side surface, 17... semiconductor substrate, 18...
Side surface, 21... Semiconductor laser array element, 22...
...Razor blade, 31, 32...Striped light emitting region, 33...Substrate side surface, 34...Substrate side surface at least 10 μm or more inside from the mirror side surface, 3
5...Scribe point, 36...Semiconductor laser element whose cutting has been completed by the method of the present invention, 37...
Substrate side surface within 10 μm near the side surface for mirror surface, 38...
...The crack that is progressing due to the marking, 39...
...Injury marks from the scribe point, 41...p
-n junction surface, 42, 44...Damage layer due to scribe point, 43...Leakage current, 51...
...Cut surface created by conventional method, 52... Protruding part, 53... Trace of scratching with scribe point,
54...Cut plane created with scribe point,
55...Crack on the side surface for mirror surface.

Claims (1)

[Claims] 1. In a bar-shaped semiconductor laser array element in which at least an active layer is formed on a semiconductor substrate made of a semiconductor single crystal, a plurality of striped light emitting regions are formed, and a mirror surface for optical feedback is formed, the striped light emitting regions and light emitting parallel to the stripe and at least from the mirror side.
A method for manufacturing a semiconductor laser device, characterized in that only the surface of the substrate side separated by 10 μm or more is scribed with a scribe point to divide it into each semiconductor laser device.