JPS6249998B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor laser device.

In recent years, optical communications have improved in reliability and are rapidly moving toward practical application. Therefore, a stable, large-scale supply of optical devices such as semiconductor lasers has become necessary. One of the biggest problems in the mass production of semiconductor lasers is the method of dividing them into chips.

Conventionally, when dividing a semiconductor laser into chips, the following method was used. In other words, diffusion
The metallized wafer is cut into a thin strip with a width of 200 to 300μ using a sharp object such as the tip of a safety razor.
The method used was to cleave the material into 50 m bars, which were then further divided into individual chips using a safety razor or the like. This method requires great skill and is not suitable for mass production because the shape of the chips obtained is not uniform. On the other hand, if the active layer is cut across when dividing into chips, cracks may occur in the active layer. Chips with cracks in this manner often undergo sudden deterioration during operation, impairing the reliability of semiconductor laser devices. Furthermore, when cleavage is performed to include ohmic metals, the cleavage line may easily bend due to distortion of the alloy, which causes a drop in yield when dividing into chips.

An object of the present invention is to provide a method for manufacturing a semiconductor laser element that has high reliability and can be stably produced without requiring special skills.

According to the present invention, on one main surface of a semiconductor substrate,
preparing a wafer by forming a plurality of epitaxial layers including an active layer and then depositing an ohmic metal layer on top of the epitaxial layers; a first groove, and a plurality of second grooves that are perpendicular to the first groove and have a missing part in the center sandwiched by the first groove, and are parallel to each other at predetermined intervals. forming a mask on the ohmic metal layer of the wafer; forming grooves deeper than the active layer using the mask, corresponding to the first groove and the second groove, respectively; There is obtained a method for manufacturing a semiconductor laser device, comprising the step of cleaving the wafer along a groove corresponding to the groove.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a semiconductor laser chip for explaining one embodiment of the present invention.

First, as is generally done, a G _a A _s substrate 1 having a (100) plane as the main surface is
A wafer is prepared by sequentially epitaxially growing Al _x G _a1-x A _s layer 2, Al _y G _a1-y A _s layer 3, Al _x G _a1-x A _s layer 4, and Ga _{A s} layer 5. .

Next, G is removed from the surface of the G _a A _s layer 5 of this wafer.
_A predetermined impurity having a conductivity type different from that of the a _As layer 5 is selectively diffused to form a plurality of striped impurity diffusion layers 6 extending in the (110) direction and parallel to each other.
Next, an ohmic metal layer 7 is formed by vacuum evaporation or the like. A photoresist film is deposited and then selectively removed to form a first groove 10 parallel to the impurity diffusion layer 6 and a second groove 9 perpendicular thereto, forming part of a lattice as shown in FIG. A mask is formed that has a groove pattern that is missing. Here, the portion 8 where the lattice is partially missing must match the impurity diffusion layer 6 formed by the selective diffusion described above. Using a mask made of a photoresist film having such a pattern, the ohmic metal layer 7 is removed by a technique such as etching or ion milling.
At this time, the ohmic metal 7 on the impurity diffusion layer 6 remains without being removed. Next, the portion of the crystal from which the ohmic metal 7 has been removed is etched to create lattice-like grooves (the first grooves 1 of the photoresist film described above) in the crystal.
0, a groove corresponding to the second groove 9) is formed. This groove extends from the fourth layer G _a A _s layer 5 of the crystal to the third layer G a
Formed to a depth that penetrates the Al _x G _a1-x A _s layer and the second Al _y G _a1-y A _s layer 3 to reach the first Al _x G _a1-x A _s layer 2. . At this time, the crystal in the impurity diffusion layer 6 remains without being etched. After forming the lattice-like grooves in this manner, the grooves 9 are cleaved along approximately the center of the grooves 9 to form cleavage bars. When the cleavage bar is formed in this manner, patterned grooves are dug at regular intervals, so variations in characteristics due to the length of the active region are reduced, and a semiconductor laser with uniform characteristics can be obtained. After a passivation film or the like is applied to this cleavage bar to suppress end face deterioration, it is cut out along another groove 10 to form individual chips. The semiconductor laser obtained here has a constant shape with uniform length and width. Furthermore, since the peripheral portion of the device other than the emitting portion 12 of the laser beam 11 is etched through the active layer 3, cracks that occur due to pelletization and rapid deterioration during operation are no longer caused.

Although the above description concerns the surface of the semiconductor laser chip on the active region side, removing the ohmic metal on the substrate 1 side at the periphery of the device chip is also an effective means for pelletizing with good reproducibility. Ohmic metal formation on the substrate side is performed after processing on the active region side is completed and the total thickness of the wafer is reduced to about 70 to 100 μm. FIG. 3 shows a grid pattern 13 formed by photoresist on the ohmic metal on the substrate side. This lattice pattern is formed by matching the position of the pattern on the active region side with the lattice. When ohmic metal is etched into this grid pattern 13, the ohmic metal at the same position facing the etching grooves 9 and 10 on the active region side is removed. In this way, by removing the metal from the parts to be separated when dividing into chips, the reproducibility when dividing into chips is improved and the yield is improved.

In this example, the depth of the groove dug into the crystal was set to penetrate through the active layer and reach the middle of the first layer, but the same effect can be obtained even if it penetrates deeper through the epitaxial layer and reaches the substrate. is clear.

As described above, the semiconductor laser can be divided into chips by digging a groove in the crystal on the active region side that passes through the active layer, and if necessary, removing the ohmic metal on the substrate side in a lattice pattern in line with the groove. Easy and reproducible. Moreover, the obtained chips have a constant shape, which is very convenient for the subsequent assembly process. On the other hand, since the active layer is not split across the chip when it is divided into chips, there is no occurrence of cracks that affect the active region, and reliability is improved.

On the other hand, I _{o Ga,} which is known as a long wavelength light emitting element,
The A _s P/I _o P system element is AlG _a A _s /G _a A _s in the example.
It is clear that the effects of the present invention are more pronounced because the elements are more susceptible to scratches than other elements.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a semiconductor laser chip for explaining one embodiment of the present invention, FIG. 2 is a plan view showing a groove pattern for removing ohmic metal on the active region side and digging an etching groove, and FIG. 3 1 is a plan view of a groove pattern for removing ohmic metal from the substrate side. 1...Substrate, 2...First layer Al _x G _a1-x A _s layer, 3... Second layer
Layer Al _y G _a1-y A _s layer, 4...Third layer Al _x G _a1-x A _s layer, 5...
4th layer _{Ga As} layer, 6... Impurity selective diffusion layer, 7... Ohmic metal on active region side, 11... Laser light,
DESCRIPTION OF SYMBOLS 12... Laser light emitting part, 8... Partially missing part of the lattice pattern to prevent the laser light emitting part from being etched, 9... Discrete second groove perpendicular to the active region, 10... Active region continuous first grooves parallel to 13...continuous lattice patterns orthogonal to each other;

Claims (1)

[Claims] 1. Preparing a wafer by forming a plurality of epitaxial layers including an active layer on one main surface of a semiconductor substrate and then depositing an ohmic metal layer on the top layer of the epitaxial layers; a plurality of first grooves that are parallel to each other with a predetermined interval; and a plurality of first grooves that are perpendicular to the first groove and have a missing part in the center sandwiched between the first grooves, and are parallel to each other and have a predetermined interval. forming a mask having a plurality of second grooves on the ohmic metal layer of the wafer; and using the mask to form the first grooves deeper than the active layer.
and a step of forming grooves corresponding to the second groove, respectively, and cleaving the wafer along the groove corresponding to the second groove. Production method.