JP4964027B2 - Nitride semiconductor laser device fabrication method - Google Patents

Description

  The present invention relates to a method for manufacturing a nitride semiconductor laser device, and more particularly to a method for manufacturing a nitride semiconductor laser device manufactured by stacking a nitride semiconductor on a nitride semiconductor substrate.

  Nitride-based semiconductors (eg, AlN, GaN, InN, AlGaN, InGaN, etc.), which are so-called III-V semiconductors composed of Group III elements and Group V elements, emit blue or blue-violet light from their band structures. Expected to be used as a light-emitting element, it has already been used for light-emitting diodes and laser elements.

  In addition, since a high-quality nitride-based semiconductor substrate has not been obtained so far, a nitride-based semiconductor element has been manufactured using a heterogeneous substrate such as a sapphire substrate. However, sapphire substrates, in particular, have a thermal conductivity at room temperature that is only a fraction of that of nitride semiconductor substrates, making it difficult to dissipate heat generated from nitride semiconductor devices through the substrate. there were. Therefore, there has been a problem that the lifetime of the nitride-based semiconductor element is extremely shortened by the generated heat.

In response to this problem, high-quality gallium nitride substrates can be obtained in recent years, and nitride-based semiconductor elements with excellent heat dissipation can be obtained by manufacturing semiconductor elements using these substrates. Can now. (See Patent Document 1 and Patent Document 2).
JP 2002-33282 A JP 2001-102307 A

  However, even when a substrate manufactured by the methods of Patent Document 1 and Patent Document 2 is used, it is difficult to obtain a sufficient life due to another problem. In particular, in the case of fabricating a laser element by electrically connecting and fixing a nitride-based semiconductor laser chip with solder, the interface between the chip and the solder may not be good, resulting in poor electrical characteristics. Therefore, there is a problem of shortening the life.

  Specifically, as shown in the graph showing the relationship between the energization time and the drive voltage deviation of the nitride-based semiconductor laser device in FIG. 12, when the interface between the chip and the solder is not good, the drive is performed as the energization time elapses. The voltage will increase significantly. Therefore, the amount of heat generation increases with an increase in drive voltage, and the lifetime of the nitride-based semiconductor laser device is shortened.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a nitride-based semiconductor laser device that manufactures a nitride-based semiconductor laser device having a long device lifetime by suppressing an increase in drive voltage with respect to the energization time during continuous oscillation. And

In order to achieve the above object, a method for producing a nitride-based semiconductor laser device according to the present invention includes forming a plurality of device structures on a first main surface of a substrate and opposite the first main surface of the substrate. Forming the electrode covering the second main surface of the first step of obtaining a wafer, and after the first step, irradiating a part of the electrode formed in the first step with laser light, A second step of scattering the portion and a third step of dividing the wafer after the second step. The second step is to irradiate a laser beam while avoiding a portion directly below the portion where the element structure of the electrode is formed, and to form a groove portion by scattering the electrode. And the depth of the groove is substantially equal to the thickness of the electrode.

  With this configuration, the portion immediately below the laminated structure of the electrodes is not scattered by the laser light irradiation, and only a small portion of the electrodes around the chip are scattered. Therefore, increase in contact resistance due to chipping of the electrode can be reduced.

  With this configuration, the groove portion does not have a depth that reaches the deep portion of the substrate, so that the strength of the wafer can be sufficient. Therefore, when the wafer is cleaved or divided, the wafer can be prevented from cracking in an unintended direction. In addition, if a large amount of substrate material is scattered and adheres to the electrode, the interface between the solder for fixing the chip and the chip electrode may be defective. Therefore, the interface between the solder and the chip electrode can be kept good.

In the method for manufacturing a nitride semiconductor laser element, the laser light may be Nd-YAG laser light.
In the method for manufacturing a nitride semiconductor laser element, the substrate includes a first region in which dislocations are locally concentrated, and a second region having a dislocation density smaller than the second region, In the first step, the element structure is formed avoiding the first region of the substrate, and in the second step, a portion formed on the first region of the electrode is irradiated with a laser beam. It does n’t matter what you do

  According to the method for producing a nitride-based semiconductor laser device of the present invention, it is possible to change the film quality of the electrode by irradiating the electrode with laser light. As a result, it is possible to prevent the solder for electrically connecting and fixing the chip from penetrating into the electrode of the chip, and the interface between the solder and the electrode becomes good. Therefore, an increase in drive voltage with respect to the energization time during continuous oscillation is suppressed, and the device life of the nitride-based semiconductor laser device to be manufactured can be extended.

  Hereinafter, a method for producing a nitride-based semiconductor laser device according to the present invention will be described with reference to FIGS. First, a series of methods for manufacturing a nitride-based semiconductor laser device will be described with reference to FIGS. 1 to 5, and then an embodiment of the present invention will be described with reference to FIGS. 6 to 11.

<< Method for Fabricating Nitride Semiconductor Laser Device >>
<Wafer fabrication method>
First, an example of a wafer manufacturing method will be described with reference to the schematic views of the wafer in FIGS. FIG. 1A is a schematic plan view of a wafer, and FIG. 1B is a schematic cross-sectional view showing the AA cross section of FIG. 1A and 1B also show the crystal orientation of the substrate, and the crystal orientation of the substrate is also shown in the following figures.

  According to the wafer manufacturing method of this example, by laminating various layers on the substrate 2, the current path portion (ridge portion 10) as shown in FIGS. 1A and 1B becomes <1-100> of the substrate. A wafer 1 having a configuration in which a plurality of wafers are aligned so as to be substantially parallel to the direction is manufactured. Here, the pad electrode 12 is aligned in a direction along the ridge portion 10 and in a direction substantially perpendicular to the ridge portion 10. Further, one pad electrode 12 has one element structure, and a plurality of chips can be obtained by dividing the wafer 1 into pad electrodes 12 as will be described later.

  Next, an example of a wafer manufacturing method will be described with reference to FIGS. 2 is a schematic cross-sectional view showing the same cross section as FIG. 1, and FIG. 3 is a schematic cross-sectional view of the active layer.

  As shown in FIG. 2 (a), first, an n-type cladding layer 3 made of n-type AlGaN is formed on the {0001} plane of an n-type GaN substrate 2 having a thickness of about 100 μm. An active layer 4 is formed on the mold cladding layer 3. At this time, as shown in FIG. 3, the active layer 4 includes a plurality of well layers 4a made of undoped InGaN having a thickness of about 3.2 nm and barrier layers 4b made of undoped InGaN having a thickness of about 20 nm. A multiple quantum well structure is formed by stacking. In the example of FIG. 3, a case where three well layers 4a and four barrier layers 4b are stacked is shown.

  Further, an optical guide layer 5 made of undoped InGaN having a thickness of about 50 nm is formed on the active layer 4 having the multiple quantum well structure, and a thickness of about 5 nm made of undoped AlGaN is formed on the optical guide layer 5. A 20 nm cap layer 6 is formed. FIG. 2A shows a state in which the cap layer 6 is laminated on the substrate 2.

Then, a p-type cladding layer 7 made of p-type AlGaN and having a thickness of about 400 nm is formed on the cap layer 6 shown in FIG. Then, a contact layer 7 made of undoped InGaN and having a thickness of about 3 nm is formed on the p-type cladding layer 7. Then, a p-side ohmic electrode 9 composed of a Pt layer having a thickness of about 1 nm and a Pd layer having a thickness of about 10 nm is formed on the contact layer 7, and a thickness of about 240 nm is formed on the p-side ohmic electrode 9. The SiO ₂ layer 14 is formed. In this way, each layer is formed to obtain a structure as shown in FIG.

Next, in order to form the ridge portion 10, the stacked structure shown in FIG. At this time, a striped photoresist (not shown) having a width of about 1.5 μm and extending in the <1-100> direction of the substrate is formed in a portion where the ridge portion 10 is to be formed. Then, etching by the RIE method is performed using a CF ₄ gas. Then, only the SiO ₂ layer 14 and the ohmic electrode 9 of the part forming the photoresist remains, the SiO ₂ layer 14 and the ohmic electrode 9 of the portion not forming a photoresist is removed.

Further, the photoresist is removed here, and etching is performed by the RIE method using a chlorine-based gas such as Cl ₂ or SiCl ₄ . At this time, the contact layer 8 and the p-type cladding layer 7 where the SiO ₂ layer 14 is not present are etched using the SiO ₂ layer 14 as a mask. Then, when the p-type cladding layer 7 remains in a state where about 80 nm remains, the etching is stopped and the SiO ₂ layer 14 is removed. Then, as shown in FIG. 2C, a part of the p-type cladding layer 7 protrudes, and a ridge part in which the contact layer 8 and the ohmic electrode 9 are sequentially formed on the protruding part of the p-type cladding layer 7. A structure with 10 is obtained.

Next, a SiO ₂ layer having a thickness of 200 nm is formed on the structure shown in FIG. 2C, and a photoresist is formed on the SiO ₂ layer formed in a portion other than the ridge portion 10. Then, etching by RIE using CF ₄ gas is performed, and the SiO ₂ layer formed on the ridge portion 10 is removed to form the current blocking layer 11 made of the SiO ₂ layer. Then, a structure as shown in FIG. 2D is obtained, and thereafter, a pad electrode 12 made of Au and having a thickness of 3 μm is continuously formed so as to cover the ridge portion 10 surrounded by the current blocking layer 11. A plurality of ridges 10 are formed.

  Further, an n-side electrode 13 is formed on the surface opposite to the surface of the substrate 2 on which the above-described laminated structure is formed. Then, after the n-side electrode 13 is formed, a part of the n-side electrode 13 is irradiated with laser light to scatter the electrode material. The method of irradiating the n-side electrode 13 with laser light and the effects obtained thereby will be described in detail in the examples described later. Then, a wafer as shown in FIG. 1B can be obtained by the manufacturing method described above.

In the wafer manufacturing method described above, the MOCVD (Metal Organic Chemical Deposition) method may be used for forming each nitride-based semiconductor layer, or the MBE (Molecular Beam Epitaxy) method or the HVPE (Hydride Vapor Papor) method. (Epitaxial) method and other methods may be used. In addition, a formation method such as sputtering or vapor deposition may be used for forming the electrode, and as the vapor deposition, electron beam vapor deposition may be used, or resistance heating vapor deposition may be used. In addition, a method such as PECVD (Plasma Enhanced Chemical Vapor Deposition) or sputtering may be used for forming the SiO ₂ layer.

  In FIG. 1A, the wafer 1 is shown as a square shape for simplicity, but a laminated structure is formed on a substantially circular substrate including an orientation flat surface and a notch for confirming the crystal orientation. However, a wafer may be produced.

  In this example of the wafer manufacturing method, a laminated structure is formed on the {0001} plane of the substrate. However, it may be formed on the {11-20} plane or the {1-100} plane of the substrate. I do not care. Further, when the surface of the substrate 2 forming the laminated structure is changed in this way, the direction in which the ridge portion 10 is formed and the cleavage direction are appropriately changed. Further, the above-described wafer manufacturing method is an example, and any other manufacturing method may be used to manufacture the wafer. For example, the shape of the laminated structure formed on the pad electrode 12 or the substrate 2 may be different from the shape shown in FIGS.

<Wafer cutting>
Next, the obtained wafer 1 is cleaved and divided to obtain chips, and an example of a method for manufacturing a nitride-based semiconductor laser device using the chips will be described with reference to FIGS. FIG. 4 is a schematic plan view showing the bar and the chip, and shows the same plane as that of FIG. 1A of the bar and the chip. FIG. 5 is a schematic perspective view of a nitride semiconductor laser element. Hereinafter, a case where a wafer obtained by an example of the above-described wafer manufacturing method is used will be described.

  First, as shown in FIG. 4A, the wafer 1 is cleaved along the <11-20> direction of the substrate 2 to obtain the bar 15. The bar 15 obtained at this time has two end faces ({1-100} face) obtained by cleaving as resonator end faces, and the element structures are aligned in a line in the <11-20> direction.

Then, the resonator end faces of the obtained bar 15, for example, may be subjected to a coating consisting of SiO ₂ and _TiO 2, _Al 2 _{O 3.} Further, the coating formed on one of the end faces is made up of a large number of layers of about 10 layers, and the reflectance is increased, and the coating formed on either of the end faces is made up of a small number of layers of about one layer. The reflectance may be lowered.

  Further, as shown in FIG. 4B, the chip 16 is obtained by dividing the obtained bar 15 along the <1-100> direction. At this time, one chip 16 includes one element structure, and a nitride-based semiconductor laser element 20 as shown in FIG.

  In the above-described cleavage from the wafer 1 to the bar 15 and the division from the bar 15 to the chip 16, grooves along the respective cleavage direction and division direction are formed in the wafer 1 or the bar 15, and along the grooves. Cleavage and division may be performed. The groove may be a solid line or a broken line. Further, grooves may be formed on the surface of the wafer 1 or the bar 15 where the pad electrode 12 or the current blocking layer 11 is formed, or the groove may be formed on the surface of the n-side electrode 13 formed. It doesn't matter.

<Mount chip>
As shown in FIG. 5, the nitride-based semiconductor laser device 20 includes a submount 23 in which the chip 16 is electrically connected and fixed (mounted) by solder, a heat sink 22 connected to the submount 23, and a heat sink 22 A stem 21 connected to a certain surface, pins 24a and 24b passing through a surface of the stem 21 connected to the heat sink 22 and a surface opposite to the certain surface and insulated from the stem 21, and one pin 24a And a wire 25 b that electrically connects the pad electrode 12 of the chip 16 and a wire 26 b that electrically connects the other pin 24 b and the submount 23.

  Further, although not shown for easy understanding of the configuration of the nitride-based semiconductor laser device 20, it is connected to the surface with the stem 21 to which the heat sink 22 is connected, the chip 16, the submount 23, the heat sink 22, The cap 24 which seals the part which protrudes from the surface with the stem 21 of the pins 24a and 24b, and the wires 25a and 25b.

  Then, current is supplied to the chip 16 through the two pins 24 a and 24 b to oscillate, and laser light is emitted from the chip 16. At this time, the cap is provided with a window made of a material transparent to the emitted laser beam, and the laser beam is emitted through the window.

  Note that the configuration of the nitride-based semiconductor laser device 20 shown in FIG. 5 is an example, and the configuration of the heat sink 22, the submount 23, the pins 24a and 24b, the wires 25a and 25b, and the cap is another configuration. It doesn't matter.

<< Example >>
The series of methods for manufacturing the nitride-based semiconductor laser device according to the present invention has been described above. In the following, the method for irradiating the n-side electrode in the above-described wafer manufacturing method with reference to FIGS. Detailed description.

<First embodiment>
First, a first embodiment of a method for irradiating an n-side electrode with laser light according to the present invention will be described with reference to FIG. 6A and 6B are plan views showing a surface opposite to the wafer surface shown in the plan view of FIG. Further, since the ridge portion 10 and the pad electrode 12 that were visible on the front surface in the plan view of FIG. 1A are on the back side of the wafer in FIG. 6, they are indicated by broken lines in this figure.

  When the n-side electrode 13 is formed by the method for forming the n-side electrode 13 in this embodiment, first, as shown in FIG. 6A, the entire surface opposite to the surface on which the laminated structure of the substrate 2 is formed is formed. An n-side electrode 13 is formed.

  Next, as shown in FIG. 6B, a part of the n-side electrode 13 formed on the substrate 2 is irradiated with laser light, so that the irradiated portion of the n-side electrode 13 is scattered. The output of the laser light at this time is preferably such that only the n-side electrode 13 is scattered without damaging the deep part of the substrate. In the present embodiment, the case where the laser beam is irradiated in the <1-100> direction, which is a direction substantially parallel to the ridge portion 10, is shown at a substantially intermediate position between the adjacent ridge portions 10. In addition, the n-side electrode 13 in the portion irradiated with the laser light is scattered to form a groove portion, and in FIG. 6B, the substrate 2 serving as a base is exposed from the groove portion. It is assumed that no groove is formed by irradiation.

  Thus, by irradiating the laser beam, a part of the material of the n-side electrode 13 is scattered on the surface of the n-side electrode 13 and heat is applied to the n-side electrode 13 and the substrate 2. Therefore, the film quality of the n-side electrode 13 changes, and it is possible to prevent the solder used when mounting a chip obtained by cleaving and dividing the wafer 1 from penetrating into the n-side electrode 13.

  Therefore, using the chip obtained by cleaving and dividing the wafer 1 in which a part of the n-side electrode 13 is irradiated with the laser light as described above, a nitride-based semiconductor laser device is manufactured as described above and continuously oscillated. In this case, as shown in the graph of the relationship between the energization time and the drive voltage deviation in FIG.

  In particular, the effect is remarkable as compared with the conventional example. In FIG. 12 showing the conventional example, the drive voltage increases by about 0.1 when energized for 20 hours, but in this embodiment, as shown in FIG. 7, the drive voltage is 0.01 to 0 even when energized for 20 hours. Only grows to about .02. Therefore, by applying the manufacturing method in this embodiment, it is possible to suppress an increase in driving voltage and an increase in the amount of heat generation, and it is possible to extend the life of the nitride-based semiconductor laser device.

  Further, by irradiating the laser beam in this way, it is possible to prevent the wafer 1 from being easily cracked by forming a deep groove reaching the deep part of the substrate 2, and when the wafer 1 is cleaved and divided. In addition, the wafer 1 can be prevented from cracking in an unintended direction.

  Moreover, since the board | substrate 2 is not damaged deeply with a laser beam, it can prevent that the material of the board | substrate 2 scatters in large quantities. For this reason, it is possible to prevent the interface failure between the solder and the n-side electrode 13 that occurs when the chip is mounted due to the material of the substrate 2 being scattered in large quantities and adhering to the n-side electrode 13. The rise of the drive voltage with respect to the energization time is suppressed, and the device life of the manufactured nitride-based semiconductor laser device can be extended.

  In addition, as a laser device used for scattering a part of the n-side electrode 13, any solid laser such as an Nd-YAG (Neodymium doped Yttrium Aluminum Garnet) laser, a gas laser such as a carbon dioxide gas laser or an ArF excimer laser, etc. Such a laser device may be used. Further, laser light irradiation may be performed in an air atmosphere. However, it is desirable that the laser light output by these laser devices be suppressed to such an extent that the substrate is not damaged deeply.

  In this embodiment, the electrode is irradiated with the laser beam to the extent that the substrate is exposed. However, if the amount of scattering of the electrode and the heat applied are sufficient, it is not always necessary to expose the substrate. Therefore, the laser light output may be adjusted and irradiated so that the depth does not penetrate the electrode.

  Further, if the wafer 1 has a mark such as an orientation flat surface, the position where the laser beam is irradiated may be specified by the distance from the mark. Further, such a mark may be formed on the substrate in advance.

<Second embodiment>
Next, a second embodiment of the method of irradiating the n-side electrode with laser light according to the present invention will be described with reference to FIG. FIG. 8 corresponds to FIG. 6B shown for the first embodiment, and is a plan view of the wafer shown on the same side as the side shown for FIG. 6B. Also in this figure, as in FIG. 6B, the ridge portion 10 and the pad electrode 12 are indicated by broken lines.

  The method of irradiating the n-side electrode with the laser beam in this example is the same as that of the first example. As shown in FIG. 6A, after forming the n-side electrode 13 on the substrate, the laser beam is emitted. A part of the n-side electrode 13 is scattered by irradiation. Since the only difference is the position of the n-side electrode 13 that is scattered by the laser beam irradiation, the description of the same components as in the first embodiment is omitted.

  In the method of irradiating the n-side electrode 13 with the laser beam in this embodiment, after forming the n-side electrode 13 on the substrate, the laser beam is irradiated in a direction substantially parallel to the ridge portion 10 as shown in FIG. At this time, the direction and output of the laser beam and the laser beam output are the same as those in the first embodiment, but in the second embodiment, the distance between the positions irradiated with the laser beam is higher than that in the first embodiment. Is getting wider.

  Specifically, in the first embodiment, laser light is irradiated between all the ridge portions 10, but in this embodiment, every other ridge portion is irradiated with laser light. Therefore, the irradiated portion of the laser beam is about half that of the first embodiment.

  Even when the laser beam is irradiated in this way, similarly to the first embodiment, the n-side electrode 13 can be scattered and heated by irradiation, and the characteristics shown in the graph of FIG. 7 can be obtained. it can. For this reason, it is possible to suppress an increase in driving voltage during continuous oscillation, and it is possible to extend the life of the nitride semiconductor laser element.

  Further, it becomes possible to prevent the wafer 1a from being easily cracked by forming a deep groove reaching the deep part of the substrate 2, and the wafer 1a is cracked in an unintended direction when the wafer 1a is cleaved and divided. Can be prevented.

  Moreover, since the board | substrate 2 is not damaged deeply with a laser beam, it can prevent that the material of the board | substrate 2 scatters in large quantities. Therefore, it is possible to prevent the interface failure between the solder and the n-side electrode 13 that occurs when the chip is mounted due to the material of the substrate 2 being scattered in large quantities and adhering to the n-side electrode 13.

  As in the first embodiment, the position of the n-side electrode 13 that irradiates the laser beam may be specified by the distance from the predetermined mark on the wafer 1a, and any type of laser device may be used. It doesn't matter if you do. Further, laser light irradiation may be performed in an air atmosphere.

<Third embodiment>
Next, a third embodiment of the method of irradiating the n-side electrode with laser light according to the present invention will be described with reference to FIGS. 9 (a) to 9 (d) correspond to FIG. 6 (b) shown for the first embodiment and FIG. 8 shown for the second embodiment, and are shown in FIG. 6 (b) and FIG. It is the top view of the wafer shown about the surface on the same side as the surface which was covered. Also in this figure, the ridge portion 10 and the pad electrode 12 are indicated by broken lines as in FIG. 6B and FIG.

  The irradiation method and output of the laser beam to the n-side electrode in this example are the same as those in the first and second examples, and the n-side electrode 13 is formed on the substrate as shown in FIG. Later, a part of the n-side electrode 13 is scattered by irradiating with laser light. Since the only difference is the position of the n-side electrode 13 that is scattered by the laser light irradiation, the description of the same components as those in the first and second embodiments is omitted.

  In the first embodiment and the second embodiment, the laser beam is irradiated in the <1-100> direction, which is a direction substantially parallel to the ridge portion 10, but in this embodiment, not only this direction, In addition, the laser beam is also irradiated in the <11-20> direction substantially perpendicular to the ridge portion 10.

  For example, as shown in FIGS. 9A and 9B, when the laser beam is irradiated along the <11-20> direction, the laser beam may be irradiated between all the pad electrodes 12. Absent. At this time, as shown in FIG. 9A, when irradiating the laser beam along the <1-100> direction, the same interval as in the first embodiment may be used. As shown, the same interval as in the second embodiment may be used.

  Further, as shown in FIGS. 9C and 9D, the interval when irradiating the laser beam along the <11-20> direction is made wider than that shown in FIGS. 9A and 9B. It doesn't matter. FIGS. 9C and 9D show laser beams irradiated along the <11-20> direction every other pad electrode 12. Further, in FIG. 9C, the interval at which the laser beam is irradiated along the <1-100> direction is the same as that in the second embodiment. Further, in FIG. 9D, the interval at which the laser beam is irradiated along the <1-100> direction is the same as that in the first embodiment.

  Even when the laser beam is irradiated in this way, similarly to the first and second embodiments, the n-side electrode 13 can be scattered and heated by irradiation, and the characteristics shown in the graph of FIG. Obtainable. For this reason, it is possible to suppress an increase in driving voltage during continuous oscillation, and it is possible to extend the life of the nitride semiconductor laser element.

  Further, it is possible to prevent the wafers 1b to 1e from being easily cracked by forming a deep groove reaching the deep part of the substrate 2, and the wafers 1b to 1e are intended when the wafers 1b to 1e are cleaved and divided. It is possible to prevent cracking in the direction that does not.

  Moreover, since the board | substrate 2 is not damaged deeply with a laser beam, it can prevent that the material of the board | substrate 2 scatters in large quantities. Therefore, a large amount of the material of the substrate 2 scatters and adheres to the n-side electrode 13, thereby preventing the interface failure between the solder and the n-side electrode 13 that occurs when the chip is mounted.

  Moreover, it is possible to disperse many materials of the n-side electrode 13 and apply heat. Furthermore, since the laser beam is irradiated so as to surround the periphery of the chip, the material of the n-side electrode 13 can be scattered substantially uniformly over the entire surface of the n-side electrode 13 to apply heat.

  As in the first and second embodiments, the position of the n-side electrode 13 that irradiates the laser light may be specified by the distance from the predetermined mark on the wafers 1b to 1e, and any type. The laser device may be used. Further, laser light irradiation may be performed in an air atmosphere.

  Further, in all cases shown in the first to third embodiments, the laser light is irradiated to the portion along the line to be cleaved and divided, so that the portion where the n-side electrode 13 is scattered is the end of the chip. It becomes a small part of. Therefore, the increase in contact resistance due to the lack of the n-side electrode when the chip is mounted is extremely small. Further, in the above-described example, the laser beam is irradiated until the substrate 2 is exposed. However, the laser beam may be irradiated so that the n-side electrode 13 remains partially. Absent.

<Other examples>
In addition, as shown in FIG. 10, the present invention provides a gallium nitride substrate 2a including a stripe core 2b in which dislocations are concentrated and another region 2c in which dislocations are reduced by concentrating the dislocations in the stripe core 2b. An embodiment in which this substrate is used will be described below. The stripe cores 2b have a stripe shape extending in the <1-100> direction and are aligned at approximately equal intervals in the <11-20> direction.

  An example of a wafer in which the above-described laminated structure is formed on the substrate 2a will be described with reference to FIG. FIG. 11 corresponds to FIG. 1B, and is a cross-sectional view of a wafer manufactured using a substrate provided with a stripe core. Since the laminated structure and the n-side electrode are the same as those shown in FIG. 1B, the same reference numerals are given and detailed description thereof is omitted.

  The wafer 1f is formed so as to avoid the portion directly above the stripe core 2b and to form dislocations from the stripe core 2b to the ridge portion 10. Further, when a chip is manufactured by dividing the bar obtained by cleaving the wafer 1f, the chip is divided along the stripe core 2b. In this example, since the two ridges 10 are provided between the stripe cores 2b, the two ridges 10, that is, the middle part of the stripe core 2b is also divided when obtaining a chip from the bar. .

  In the example shown in FIG. 11, the n-side electrode 13 formed on the stripe core 2b is irradiated with laser light to be scattered. Note that the output of the laser light irradiated at this time is desirably large enough not to deeply damage the substrate 2a, as in the first to third embodiments, and the n-side electrode 13 as shown in FIG. It is more desirable if it is a size that can only scatter.

  Further, as shown in the third embodiment, the laser beam may be irradiated along the direction substantially perpendicular to the stripe core 2b, that is, the <11-20> direction. In this case, FIG. ) And a portion where the n-side electrode 13 is scattered is formed as in the wafers 1b and 1c shown in FIG. 9C.

  Even when the laser beam is irradiated in this manner, the n-side electrode 13 can be scattered and heated as in the first to third embodiments, as shown in the graph of FIG. Characteristics can be obtained. For this reason, it is possible to suppress an increase in driving voltage during continuous oscillation, and it is possible to extend the life of the nitride semiconductor laser element.

  Further, since the region on the stripe core 2b of the substrate 2a has poor adhesion to the n-side electrode 13, when the wafer 1f is cleaved, the n-side electrode 13 provided in the region on the stripe core 2b is used as a starting point. The electrode may peel off. Therefore, as shown in FIG. 11, the n-side electrode 13 on the stripe core 2a is scattered in advance, so that the occurrence of electrode peeling can be suppressed.

  Further, it is possible to prevent the wafer 1f from being easily cracked by forming a deep groove reaching the deep part of the substrate 2a, and the wafer 1f is cracked in an unintended direction when the wafer 1f is cleaved and divided. Can be prevented.

  Further, since the substrate 2a is not deeply damaged by the laser beam, it is possible to prevent the material of the substrate 2a from being scattered in large quantities. Therefore, a large amount of the material of the substrate 2a scatters and adheres to the n-side electrode 13, so that it is possible to prevent the interface failure between the solder and the n-side electrode 13 that occurs when the chip is mounted.

  Note that the stripe core 2b and the other region 2c have different crystallinity and can be visually recognized with an electron microscope or an optical microscope. Further, since it can be visually recognized from the formation of the n-side electrode 13, the portion to be irradiated with the laser light may be specified by visual recognition.

  Similarly to the first to third embodiments described above, the position of the n-side electrode 13 that irradiates the laser beam may be specified by the distance from the predetermined mark on the wafers 1b to 1e. Various types of laser devices may be used. Further, laser light irradiation may be performed in an air atmosphere.

  The present invention relates to a method for manufacturing a nitride-based semiconductor laser device, and is particularly suitable when applied to a method for manufacturing a semiconductor laser device manufactured by stacking a nitride-based semiconductor on a nitride-based semiconductor substrate. is there.

These are a schematic plan view and a cross-sectional view showing an example of a wafer. These are typical sectional drawings which show an example of the manufacturing method of a wafer. These are the typical sectional views shown about the active layer. FIG. 3 is a schematic plan view showing an example of a bar and a chip. FIG. 3 is a schematic perspective view showing an example of a nitride-based semiconductor laser device. These are the typical top views of the wafer which show the irradiation method of the laser beam to the n side electrode in 1st Example. These are graphs showing the relationship between the energization time and drive voltage deviation of the nitride-based semiconductor laser device obtained by the manufacturing method according to the present invention. These are the typical top views of the wafer which show the irradiation method of the laser beam to the n side electrode in 2nd Example. These are the typical top views of a wafer which show the irradiation method of the laser beam to the n side electrode in 3rd Example. These are the typical top views of the board | substrate in another Example. These are typical sectional drawings of the wafer in other examples. These are the graphs which show the relationship between the energization time of the conventional nitride semiconductor laser element, and a drive voltage deviation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 2, 2a Substrate 2b Stripe core 2c Other area 3 N-type cladding layer 4 Active layer 4a Well layer 4b Barrier layer 5 Optical guide layer 6 Cap layer 7 P-type cladding layer 8 Contact layer 9 P-side ohmic electrode 10 Ridge part 11 current blocking layer 12 pad electrode 13 n-side electrode 14 SiO ₂ layer 15 bar 16 chip

Claims (3)

A first step of obtaining a wafer by forming a plurality of element structures on a first main surface of a substrate and forming an electrode covering a second main surface opposite to the first main surface of the substrate;
After the first step, a second step in which a part of the electrode is scattered by irradiating a part of the electrode formed in the first step with laser light;
A third step of dividing the wafer after the second step;
Bei example,
The second step is
The portion of the electrode that is directly below the portion where the element structure is formed is irradiated with laser light, and the groove is formed by scattering the electrode. The depth of the groove Is substantially equal to the thickness of the electrode . 2. The method for manufacturing a nitride-based semiconductor laser device according to claim 1 , wherein the laser beam is an Nd-YAG laser beam . The substrate includes a first region in which dislocations are locally concentrated, and a second region having a lower dislocation density than the second region,
The first step is to form the element structure while avoiding the first region of the substrate,
3. The nitride semiconductor laser element according to claim 1, wherein the second step irradiates a portion of the electrode formed on the first region with a laser beam. 4. Manufacturing method.

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