JPH1070335A - Manufacture of semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To divide a laser chip into individual chips without giving damage to the laser chip by a method wherein linear or broken line-shaped grooves are all formed in a substrate consisting of a semiconductor crystal by etching or the like in the directions vertical and parallel to striped luminous regions and the semiconductor crystal is cleaved along these grooves. SOLUTION: Etching grooves 111 and 112 are respectively formed in a substrate 102 from the rear of the substrate 102 in the directions vertical and parallel to striped electrodes 101. The grooves in the direction vertical to the electrodes 101 are formed in such a way that the width between the grooves is equal to a resonator length and the grooves in the direction parallel to the electrodes 101 are formed in such a way that the positions of the grooves are positioned in roughly the center between the electrodes 101, which are adjacent to each other. As the grooves in the direction vertical to the electrodes 101 are formed from the rear of the substrate 102 and the thickness of an epitaxial layer is about 10μm or thinner compared with that of 100 to 200μm or thereabouts of the substrate 102, the grooves 111, which are used as guide grooves for cleavage, can be bored fully deep. Thereby, a semiconductor crystal can be easily cleaved and the yield of the manufacture of a semiconductor laser can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser, and a method for forming a good resonator.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view for explaining a conventional method for manufacturing a semiconductor laser. FIG. 3A is a view of the substrate before cleavage as viewed from the back surface, and FIG. 3B shows individual laser chips after cleavage. Thus, a semiconductor laser that continuously oscillates at room temperature usually has some kind of stripe structure. This is because the entire region of the semiconductor crystal does not contribute to laser oscillation, but only the stripe portion contributes to reduce the operating current.

FIG. 3B shows an electrode stripe structure which is a kind of stripe structure. Reference numeral 301 denotes a (p-type) stripe electrode. 302 denotes a semiconductor substrate;
Each layer shown as 3 is called an active layer or a cladding layer,
Such a multilayer structure is adopted because the laser oscillates at a low threshold current. The stripe-shaped light emitting region 304 in the active layer contributes to actual oscillation. 305 is n
Type electrode.

With such a structure, the current flowing through the pn junction of the laser can be limited only to the region below the stripe electrode 301, and the laser oscillation region can be limited to this stripe region. In order to divide the laser chip into individual laser chips, as shown in FIG. 3A, several etching grooves 311 having a width equal to the laser cavity length are formed on the back surface of the substrate in a direction perpendicular to the direction of the stripe electrode 301. Then, a force is applied by applying a blade to this groove, and the groove is first divided by cleavage into several bar-shaped crystals including several laser chips. Thereafter, in a direction parallel to the stripe electrodes, a blade is applied to a position approximately at the center between the stripe electrodes to apply a force to divide the laser chips into individual laser chips.

[0005]

Although such a conventional method is effective for a semiconductor having a cubic crystal structure, it has been found that epitaxial growth on a C-plane of a hexagonal crystal such as SiC is difficult. When the crystal is divided into individual laser chips, it is difficult to cleave the crystal in two directions perpendicular to each other. For this reason, in the conventional method as described above, even if it can be successfully cleaved into a bar-shaped crystal including several laser chips, it is difficult to cleave in a direction perpendicular to the direction of the bar because it is divided into individual chips. It is difficult to expect high yield.

The present invention solves such a conventional problem,
An object of the present invention is to provide a method for dividing a laser chip into individual laser chips at a high yield without damaging the laser chip.

[0007]

In order to solve this problem, according to the present invention, a straight or broken groove is formed by etching or the like in both directions perpendicular and parallel to a stripe-shaped light emitting region in a semiconductor crystal. Then, a method for manufacturing a semiconductor laser with a high yield is provided by cleaving the semiconductor crystal along the groove. Further, a method for manufacturing a semiconductor laser with a higher yield is provided by thinning the substrate side of a semiconductor crystal by polishing before forming a groove.

[0008]

Embodiments of the present invention will be described below.

(Embodiment 1) FIG. 1 shows a first embodiment of a method for manufacturing a semiconductor laser using a hexagonal substrate according to the present invention. FIG. 1A is a simplified view of the substrate before cleavage from the back surface, and FIG. 1B shows individual laser chips after cleavage. FIG. 3C shows the crystal axis of the hexagonal crystal on the C plane. FIG. 1 (b)
The substrate 102 is 6H-SiC having a hexagonal structure, and n-GaN, n-AlGaN, In
A layer 103 of GaN, p-AlGaN, p-GaN or the like is sequentially formed by epitaxial growth, and a stripe-shaped p-type electrode 101 is formed thereon. 1
05 denotes an n-type electrode. The crystal face 121 is made of SiC (1
The (-100) plane and the crystal plane 122 also indicate the (11-20) plane.

In order to divide the laser chip into such individual laser chips, etching grooves 111 and 112 are formed on the substrate before cleavage in a direction perpendicular to and parallel to the stripe electrode 101 from the back surface of the substrate as shown in FIG. Formed. The grooves in the vertical direction are formed so that the width between the grooves is equal to the length of the resonator, and the grooves in the parallel direction are formed so that their positions are approximately in the middle between adjacent stripe electrodes. When the vertical groove 111 reaches the light-emitting region 104, this portion is damaged, cannot play a sufficient role as a mirror surface for an optical resonator, and cannot cause laser oscillation. The groove is formed from the back surface and the substrate 1
Since the thickness of the epitaxial layer is 10 μm or less as compared with 100 to 200 μm, the etching groove 111 serving as a cleavage guide groove can be dug sufficiently deep, and the cleavage can be facilitated.

Similarly, an etching groove 112 having a sufficient depth is formed in a direction parallel to the stripe electrode. Then, first, a blade is applied in a direction perpendicular to the stripe electrode to apply a force to cleave, and then similarly, a blade is applied in a direction parallel to the stripe electrode to apply a force to cleave. The direction perpendicular to the stripe electrode is the (1-100) plane, and the direction parallel thereto is the (11-2) plane.
0) The plane is cut out.

As shown in FIG. 1C, in a hexagonal crystal, cleavage in the direction perpendicular to the C plane is the easiest cleavage (1
In the (-100) plane, there are two directions relatively easily cleaved indicated by 132 and 133 in the drawing other than the desired cleavage direction 131 at an arbitrary point in the periodic structure of the crystal. Therefore, it is much more difficult to obtain a one-way cleavage plane over the width of several laser chips without a groove serving as a guide as compared with a cubic crystal. The (11-20) plane is (1-10)
Since cleavage is more difficult than in the 0) plane, it is more difficult to obtain a one-way cleavage plane over the width of the laser chip without a groove serving as a guide.

[0013] Since SiC is a very hard crystal, it is difficult to cleave without a guide groove from the viewpoint of hardness. FIG. 3C shows how the substrate is divided when the hexagonal substrate is cleaved without guide grooves. In the figure, the direction 341 is <1-1.
00> direction and direction 342 are <11-20> directions,
Indicates the desired cleavage direction. As described above, the substrate is divided in a direction shifted from the cleavage direction at a much higher probability than in the case of the cubic crystal.

However, according to the present invention, the etching grooves 11
The grooves 1 and 112 serve as cleavage guide grooves, so that the cleavage into individual laser chips can be successfully performed at a much higher probability than in the conventional method, and the production yield of the semiconductor laser can be greatly improved. FIG. 1D shows a state of cleavage of the hexagonal substrate according to the present invention.

As described above, it becomes possible to cleave the substrates in directions perpendicular to each other with a much higher probability than in FIG. It is clear that the effect of the present invention is not limited to the semiconductor laser having the hexagonal crystal structure as described above, but as described in the present embodiment, the hexagonal crystal structure described in claim 2 is used. A particularly remarkable effect is exhibited in a semiconductor crystal epitaxially grown on the C-plane of a crystal substrate.

(Embodiment 2) FIG. 2 is similar to (Embodiment 1) in that an etching groove is formed by the method according to claim 3 and a substrate of a semiconductor crystal and individual parts after cleavage are formed. 3 shows a laser chip. As shown in FIG. 2 (a), in the direction perpendicular to the stripe electrode, avoid the lower part of the stripe electrode, and form a dotted etching groove 2 from the back surface of the substrate.
11 are formed, and a continuous etching groove 212 is formed substantially at the center of the adjacent stripe electrodes in the parallel direction.

According to this method, since the etching groove 211 does not exist below the light emitting region 204 as shown in FIG. 2B, the direction of the etching groove is cleaved as shown in FIG. The step 106 caused by slight deviation from the direction is less likely to occur in the light emitting region 204, and a method of manufacturing a semiconductor laser with improved yield can be provided. In the present embodiment, a semiconductor laser having a stripe-shaped electrode has been described as an example, but the effect of the present invention is not limited to this, and it is apparent that the present invention can be applied to a semiconductor laser having another stripe structure. The present invention can be applied to a structure in which the width of the light emitting region is sufficiently smaller than the width of the laser chip.

(Embodiment 3) In the present invention, a remarkable effect can be obtained as the distance between the bottom of the guide groove and the surface of the semiconductor epitaxial growth layer described in Embodiments 1 and 2 becomes shorter. In order to realize this, the thickness of the substrate itself may be reduced by polishing the back surface side of the substrate before the formation of the guide groove, or the guide groove may be formed deep to several tens μm or more. .

For polishing the substrate, a hard substrate such as SiC can be polished to a desired thickness by using diamond abrasive grains or the like. By thus reducing the thickness of the substrate to about 150 μm or less before forming the cleavage guide groove, the cleavage of the semiconductor laser chip can be successfully performed with a higher probability.

The guide groove having a depth of several tens of μm or more can be formed by wet or dry etching using a guide groove etching mask as long as the material is easily etched. Further, a deep groove can be formed even by using a hard material such as SiC or sapphire by making full use of a laser processing technique. Further, if the specific resistance of the sample substrate is equal to or less than a certain reference value, electric discharge machining by spark discharge is also possible. By forming the guide groove deeper in this manner, cleavage in directions perpendicular to each other is more easily performed, and the effects of the present invention described in the first and second embodiments can be made more remarkable.

[0021]

As described above, according to the present invention, in a semiconductor laser having a stripe-shaped light emitting region, a groove is formed by etching or the like in a direction perpendicular and parallel to the stripe from the substrate side, and the semiconductor is formed along the groove. By cleaving the crystal, the production yield of the semiconductor laser can be improved.

[Brief description of the drawings]

FIG. 1 shows a semiconductor substrate, a laser chip, and a direction of a crystal axis according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a semiconductor substrate and a laser chip according to a second embodiment of the present invention.

FIG. 3 is a view showing a semiconductor substrate and a laser chip in a conventional semiconductor laser manufacturing method.

[Explanation of symbols]

101, 201, 301 Stripe electrodes 102, 202, 302 Semiconductor substrates 104, 204, 304 Light-emitting regions 105, 205, 305 N-type electrodes 106, 306 Steps 111, 112, 211, 212, 311 due to cleavage Etching grooves 131, 132, 133 direction of crystal axis

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiko Ishibashi 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 72) Inventor Yoshiaki Hasegawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] In a semiconductor laser having a stripe-shaped light emitting region in a semiconductor crystal, a groove is formed in a direction perpendicular and parallel to the stripe from the substrate side of the semiconductor crystal, and the semiconductor crystal is cleaved along the groove. A method of manufacturing a semiconductor laser. 2. The method according to claim 1, wherein the semiconductor crystal is epitaxially grown on a (0001) plane, that is, a C plane of a hexagonal substrate. 3. The method of manufacturing a semiconductor laser according to claim 1, wherein said groove is formed in a dashed shape in at least one direction. 4. The method according to claim 1, wherein the groove is formed by etching. 5. The method according to claim 1, wherein said groove is formed by laser processing. 6. The method for manufacturing a semiconductor laser according to claim 1, wherein said groove is formed by electric discharge machining. 7. The method according to claim 1, further comprising a step of polishing the substrate side of the semiconductor crystal to reduce the thickness of the substrate before forming the groove. The manufacturing method of the semiconductor laser according to the above.