JP2007288090A - Semiconductor laser device, and its fabrication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device which prevents a dielectric film formed on an emission end face or an opposite end face of the semiconductor laser device from being peeled off, and ensures a high productivity and a method for fabricating the semiconductor laser device. <P>SOLUTION: This semiconductor laser device comprises a semiconductor substrate 1, an active layer formed internally in the semiconductor substrate 1, an electrode formed on two electrode surfaces facing each other on the semiconductor substrate 1 and a dielectric film 5 formed on the emission end face 3 of the semiconductor substrate 1. The electrode surface farther from the active layer on the semiconductor substrate 1 is entirely flat, and a structure for restricting the length of dielectric film 5 to be wrapped around to an electrode side at dielectric film 5 formation is formed on the surface of the electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof.

  In a semiconductor laser device, a dielectric film is usually formed on the light emitting end face and the opposite end face to improve reliability and extend the life. The dielectric film on the light emitting end face is required to have a low reflectance in order to obtain high luminance. On the other hand, the dielectric film on the opposite end surface is required to have a high reflectance so as not to let the laser light escape as much as possible. When the dielectric film is peeled off, desired light emission characteristics cannot be obtained. Therefore, it is important to prevent the dielectric film from being peeled off.

  A conventional method for forming a protective film of a semiconductor laser device will be described with reference to FIG. FIG. 7A is a cross-sectional view schematically showing the arrangement of semiconductor laser bars and spacers 2 in a dielectric film forming step of a conventional semiconductor laser element. The semiconductor laser bar includes a semiconductor substrate 1, an N-side electrode 10 and a P-side electrode 11 formed on the N-side electrode surface 7 and the P-side electrode surface 8 of the semiconductor substrate 1, respectively. FIG. 7A shows a case where the dielectric film 5 is formed on the light emitting end face 3 of the semiconductor substrate 1. A semiconductor laser bar and a spacer 2 shorter than this are arranged on the film-forming jig 6 with the lower ends thereof aligned. For this reason, the semiconductor laser bar protrudes from the spacer 2 and a step is formed. A dielectric film 5 is formed from above the light emitting end face 3 by sputtering, CVD, or the like. Since the dielectric film 5 wraps toward the electrode side by the level difference between the semiconductor laser bar and the spacer 2, it is possible to prevent the dielectric film from peeling off. By removing the semiconductor laser bar and the spacer 2 and rearranging them on the film-forming jig 6, the dielectric film 5 is similarly formed on the opposite end surface 4 of the semiconductor substrate 1. FIG. 7B is a cross-sectional view of the obtained semiconductor element.

  In the case of the conventional method described above, it is necessary to produce the spacer 2. In addition, since the spacers 2 are arranged on the film-forming jig 6, the number of semiconductor laser bars to be mounted is reduced, resulting in poor productivity. A method using a spacer is disclosed in Patent Documents 1 and 2 and the like.

As a method not using a spacer, a method of forming a dielectric film 5 after forming a step on the electrode surface itself of a semiconductor substrate has been proposed (see Patent Document 3). As shown in FIG. 8A, since the dielectric film 5 wraps around the electrode surface by the level difference formed on the N-side electrode surface 7, peeling of the dielectric film can be prevented. In this case, since only the semiconductor laser bar has to be arranged with respect to the film forming jig (not shown), the spacer 2 becomes unnecessary. Since the light emitting portion provided on the light emitting end surface 3 is close to the P side electrode surface 8, a step is formed only on the N side electrode surface 7. FIG. 8B is a cross-sectional view of the obtained semiconductor element.
Japanese Patent Laid-Open No. 11-317565 JP 2001-94194 A JP-A-10-125994

  However, in the case of the semiconductor laser element described in Patent Document 3, the semiconductor substrate 1 shown in FIG. 8 is extremely thin and made of a brittle material such as GaAs, InP, or GaN. There was a problem that stress was concentrated on the portion, and cracking, chipping and the like were likely to occur. In particular, after the dielectric film 5 is formed, cracking, chipping, etc. are likely to occur in the scribing work or breaking work when the semiconductor laser bar is separated into individual chips.

  A semiconductor laser device according to the present invention includes a semiconductor substrate, an active layer formed inside the semiconductor substrate, electrodes formed on two opposing electrode surfaces of the semiconductor substrate, and light emission of the semiconductor substrate. A semiconductor laser device comprising a dielectric film formed on an end surface, wherein an electrode surface far from the active layer of the semiconductor substrate is flat as a whole, and when forming the dielectric film, A structure for limiting the wraparound length of the dielectric film toward the electrode surface is formed on the electrode surface.

  The method of manufacturing a semiconductor laser device according to the present invention includes forming electrodes on both electrode surfaces of a semiconductor substrate having an active layer formed therein, and at least one of the electrodes along a line separating into semiconductor laser bars. A photoresist mask is formed on the electrode so as to be etched in a band shape, the electrode is etched, separated into the semiconductor laser bars, the semiconductor laser bars are arranged, and the light emitting end face or the opposite end face is viewed from above. A dielectric film is formed.

  In another method of manufacturing a semiconductor laser device according to the present invention, electrodes are formed on both electrode surfaces of a semiconductor substrate having an active layer formed therein, and a dielectric film stopper film is formed on at least one of the electrodes. And forming a photoresist mask on the dielectric film stopper film so that dielectric film stoppers are formed on both sides of the line separating each semiconductor laser bar, and etching the dielectric film stopper film, The semiconductor laser bars are separated for each other, and the semiconductor laser bars are arranged to form a dielectric film from the light emitting end face or the opposite end face.

  According to the present invention, it is possible to provide a semiconductor laser element that can prevent peeling of a dielectric film formed on the light emitting end face or the opposite end face of the semiconductor laser element, and is excellent in productivity, and a method for manufacturing the same.

  Embodiments of the present invention will be described below. However, the present invention is not limited to the following embodiment. In addition, in order to clarify the explanation, the following description and drawings are omitted and simplified as appropriate.

Embodiment 1
Embodiment 1 of the present invention will be described below. FIG. 1 is a cross-sectional view schematically showing a state in which semiconductor laser bars are arranged and a dielectric film 5 is formed on the light emitting end face 3 in the dielectric film forming step of the semiconductor laser device according to the first embodiment. . 2A is a plan view of the obtained semiconductor element as viewed from the N-side electrode surface side, and FIG. 2B is a cross-sectional view thereof.

  As shown in FIG. 2, the semiconductor laser bar provided for the semiconductor laser device according to the first embodiment includes a semiconductor substrate 1, a dielectric film 5, an N-side electrode 10, and a P-side electrode 11. The semiconductor laser bar is finally separated and becomes a semiconductor laser element.

  The semiconductor substrate 1 is a main body of the semiconductor laser bar, and generally has an active layer extending from the light emitting end face 3 to the opposite end face 4 for each semiconductor laser element to be finally separated. The efficiency of the semiconductor laser is determined by the structure of this active layer and the surrounding semiconductor layer. As this structure, a homojunction structure, a single heterostructure, a double heterostructure, an embedded heterostructure, and the like can be considered, but the present invention can be applied to any structure. Moreover, although the material which comprises the semiconductor substrate 1 changes with laser wavelengths, this invention is applicable to what kind of material. Examples of the semiconductor layer constituting most of the semiconductor substrate 1 include GaAs, InP, and GaN.

The dielectric film 5 is formed on the light emitting end face 3 and the opposite end face 4. As the dielectric film 5, a metal oxide, a metal nitride or the like can be considered. Examples of the dielectric film 5 include an Al ₂ O ₃ film, a SiO ₂ film, and a Si ₃ N ₄ film. The reflectance required for the dielectric film 5 can be controlled by the material, thickness, multilayering, and the like.

  The N-side electrode 10 is formed on the N-side electrode surface 7 of the semiconductor substrate 1. Here, the N-side electrode 10 is not formed in the vicinity of both ends of the semiconductor substrate 1 on the N-side electrode surface 7 on the light emitting end surface 3 side and the opposite end surface 4 side. That is, the N-side electrode surface 7 is exposed. For this reason, in the step of forming the dielectric film 5, a step for allowing the dielectric film 5 to wrap around is obtained. In addition, if the level | step difference for the dielectric film 5 to wrap around is obtained, the N side electrode surface 7 does not need to be exposed. In other words, it is only necessary to have a step formed by the N-side electrode 10 being thinner than other regions in the vicinity of the light emitting end face and the opposite end face. Further, the step may be formed only on one end face side.

  The dimension from the light emitting end face 3 and the opposite end face 4 where the N-side electrode 10 is not formed, that is, the wraparound length of the dielectric film 5, is preferably 5 μm or more. If the thickness is less than 5 μm, the dielectric film 5 cannot sufficiently wrap around and is easily peeled off. On the other hand, the larger this dimension, the lower the electrical characteristics of the electrode. Therefore, this dimension is preferably 50 μm or less, and more preferably 30 μm or less. Note that this distance need not be constant.

  Further, the thickness of the N-side electrode 10 is preferably 5 μm or more. This is because if the thickness is less than 5 μm, a sufficient step cannot be obtained because the dielectric film 5 wraps around. On the other hand, the thicker the N-side electrode 10, the longer it takes to form the N-side electrode 10. Also, the number of semiconductor substrates 1 mounted on the dielectric film 5 forming jig is reduced. That is, the thicker the N-side electrode 10 is, the lower the productivity is. Therefore, the thickness of the N-side electrode 10 is preferably 50 μm or less, and more preferably 30 μm or less. An example of the N-side electrode 10 is AuGe—Au having a thickness of 10 μm.

  The P-side electrode 11 is formed on the P-side electrode surface 8 of the semiconductor substrate 1. An example of the P-side electrode 10 is Cr—Au having a thickness of 5 μm. In the first embodiment, since the active layer is close to the P-side electrode surface, a step for allowing the dielectric film 5 to wrap around is formed only on the N-side electrode surface 7 side farther from the active layer. However, depending on the positional relationship between the active layer and both electrode surfaces, on the contrary, a step may be formed only on the P-side electrode surface 8 side, and a step on both the N-side electrode surface 7 side and the P-side electrode surface 8 side. May be formed.

  Next, a manufacturing process of a semiconductor laser bar used for the semiconductor laser element according to the first embodiment will be described with reference to FIG. First, as shown in FIG. 3A, an N-side electrode 10 is formed on an N-side electrode surface 7 of a semiconductor substrate 1 on which a basic configuration as a semiconductor laser element is formed, and a P-side is formed on a P-side electrode surface 8. The electrode 11 is formed by a vacuum deposition method, a sputtering method, or the like. Next, as shown in FIG. 3B, a photoresist mask 9 is formed on the N-side electrode 10 so that the N-side electrode 10 is etched in a strip shape along a line separating into semiconductor laser bars. Subsequently, as shown in FIG. 3C, the N-side electrode 10 is etched by dry etching or the like. Thereafter, as shown in FIG. 3D, the photoresist mask 9 is removed. Finally, as shown in FIG. 3E, the semiconductor substrate 1 is separated.

  The semiconductor laser bars obtained by the above steps are arranged as shown in FIG. 1, and a dielectric film 5 is sequentially formed on the light emitting end face 3 and the opposite end face 4 by vacuum deposition, sputtering, CVD, or the like. Finally, the semiconductor laser element is obtained by separating the semiconductor laser bar on which the dielectric film 5 is formed for each chip.

  In the first embodiment, since the N-side electrode 10 is not formed in the vicinity of the light emitting end face 3 and the opposite end face 4 of the semiconductor substrate 1, a step for allowing the dielectric film 5 to go around is obtained. For this reason, peeling of the dielectric film formed on the light emitting end face or the opposite end face of the semiconductor laser element can be prevented. In addition, in the case of the semiconductor laser element described in Patent Document 3, there is a problem that stress is concentrated on the step portion of the semiconductor substrate 1 shown in FIG. In the case of such a semiconductor laser element, since no step is formed in the semiconductor substrate 1 itself, such a problem does not occur. For this reason, the semiconductor laser device according to the first embodiment is also excellent in productivity.

Embodiment 2
The second embodiment of the present invention will be described below. FIG. 4 is a cross-sectional view schematically showing a state in which the semiconductor laser bars are arranged and the dielectric film 5 is formed on the light emitting end face 3 in the dielectric film forming step of the semiconductor laser device according to the second embodiment. . FIG. 5A is a plan view seen from the N-side electrode surface side of the obtained semiconductor element, and FIG. 5B is a cross-sectional view thereof. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The difference from the first embodiment is that the N-side electrode 10 is formed on the entire N-side electrode surface 7 and that a dielectric film stopper 12 is provided on the N-side electrode 10. The dielectric film stopper 12 is not removed even after the dielectric film is formed. That is, it remains on the semiconductor laser element and is integrated.

  The dielectric film stopper 12 is formed on the N-side electrode 10 so as to be separated from the light emitting end surface 3 and the opposite end surface 4 of the semiconductor substrate 1. For this reason, the level | step difference for the dielectric film 5 to wrap around is obtained. The dielectric film stopper 12 may be formed only on one end face side. In the second embodiment, since the active layer is close to the P-side electrode surface, the dielectric film stopper 12 for the dielectric film 5 to wrap around only on the N-side electrode surface 7 side farther from the active layer is formed. Has been. However, depending on the positional relationship between the active layer and both electrode surfaces, on the contrary, the dielectric film stopper 12 may be formed only on the P-side electrode surface 8 side, and the N-side electrode surface 7 side and the P-side electrode surface 8 side. The dielectric film stopper 12 may be formed on both.

  The distance from the light emitting end face 3 or the opposite end face 4 to the adjacent dielectric film stopper 12, that is, the wraparound length of the dielectric film 5, is preferably 5 μm or more. If the thickness is less than 5 μm, the dielectric film 5 cannot sufficiently wrap around and is easily peeled off. On the other hand, the larger this dimension, the lower the electrical characteristics of the electrode. Therefore, this dimension is preferably 50 μm or less, and more preferably 30 μm or less. Note that this distance need not be constant.

  The thickness of the dielectric film stopper 12, that is, the height from the N-side electrode 10 is preferably 5 μm or more. This is because if the thickness is less than 5 μm, a sufficient step cannot be obtained because the dielectric film 5 wraps around. On the other hand, as the dielectric film stopper 12 is thicker, the number of semiconductor substrates 1 mounted on the dielectric film 5 deposition jig is reduced, resulting in poor productivity. Therefore, the thickness of the dielectric film stopper 12 is preferably 50 μm or less, and more preferably 30 μm or less.

  Furthermore, the width of the dielectric film stopper 12 is preferably 5 μm or more from the viewpoint of strength. On the other hand, in order to ensure the electrical characteristics of the N-side electrode 10, it is preferably 30 μm or less. Note that this width need not be constant.

  The dielectric film stopper 12 may be an insulator such as a metal oxide or a metal nitride, but is not limited to an insulator as long as it does not chemically react with the N-side electrode 10. For example, when the N-side electrode 10 is Au, Pt can also be used.

  Next, the manufacturing process of the semiconductor substrate 1 used for the semiconductor laser device according to the second embodiment will be described with reference to FIG. First, as shown in FIG. 6A, the N-side electrode 10 is formed on the N-side electrode surface 7 of the semiconductor substrate 1 on which the basic structure as a semiconductor laser element is formed, and the P-side is formed on the P-side electrode surface 8. The electrode 11 is formed by a vacuum deposition method, a sputtering method, or the like. Next, as shown in FIG. 6B, a stopper film 13 is formed. Further, as shown in FIG. 6C, a photoresist mask 9 is formed on the stopper film 13. Subsequently, as shown in FIG. 6D, the stopper film 13 is etched by dry etching or the like to form the dielectric film stopper 12. Thereafter, as shown in FIG. 6E, the photoresist mask 9 is removed. Finally, as shown in FIG. 6F, the semiconductor laser bars are separated.

  The semiconductor laser bars obtained by the above steps are arranged as shown in FIG. 4, and a dielectric film 5 is sequentially formed on the light emitting end face 3 and the opposite end face 4 by vacuum deposition, sputtering, CVD, or the like. Finally, the semiconductor laser element is obtained by separating the semiconductor laser bar on which the dielectric film 5 is formed for each chip.

  In the second embodiment, since the dielectric film stopper 12 is formed on the N-side electrode 10, a step for allowing the dielectric film 5 to go around is obtained. For this reason, peeling of the dielectric film formed on the light emitting end face or the opposite end face of the semiconductor laser element can be prevented. In addition, in the case of the semiconductor laser element described in Patent Document 3, there is a problem that stress is concentrated on the step portion of the semiconductor substrate 1 shown in FIG. In the case of such a semiconductor laser element, since no step is formed in the semiconductor substrate 1 itself, such a problem does not occur. Further, in the case of the second embodiment, since the entire surface of the N-side electrode surface 7 is covered with the N-side electrode 10, the semiconductor substrate 1 can be protected and cracks, chips, etc. can be prevented. For this reason, the semiconductor laser device according to the second embodiment is also excellent in productivity.

It is sectional drawing which shows typically the arrangement | sequence of the semiconductor laser bar in the dielectric material film formation process of the semiconductor laser element concerning Embodiment 1 of this invention. It is a figure which shows the semiconductor laser element concerning Embodiment 1 of this invention. It is a figure which shows typically the manufacturing process of the semiconductor laser bar | burr used for the semiconductor laser element concerning Embodiment 1 of this invention. It is sectional drawing which shows typically the arrangement | sequence of the semiconductor laser bar in the dielectric material film formation process of the semiconductor laser element concerning Embodiment 2 of this invention. It is a figure which shows the semiconductor laser element concerning Embodiment 2 of this invention. It is a figure which shows typically the manufacturing process of the semiconductor laser bar | burr used for the semiconductor laser element concerning Embodiment 2 of this invention. It is sectional drawing which shows typically the arrangement | sequence of the semiconductor laser bar and spacer in the dielectric film formation process of the conventional semiconductor laser element, and the semiconductor device obtained. 10 is a cross-sectional view schematically showing the arrangement of semiconductor laser bars and the obtained semiconductor element in the dielectric film forming step of the semiconductor laser element described in Patent Document 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Spacer 3 Light emission end surface 4 Opposite end surface 5 Dielectric film 6 Jig for film formation 7 N side electrode surface 8 P side electrode surface 9 Photoresist mask 10 N side electrode 11 P side electrode 12 Dielectric film stopper 13 Stopper Membrane

Claims (12)

A semiconductor substrate;
An active layer formed inside the semiconductor substrate;
Electrodes formed on two opposing electrode surfaces of the semiconductor substrate;
A semiconductor laser device comprising a dielectric film formed on a light emitting end face of the semiconductor substrate,
The electrode surface far from the active layer of the semiconductor substrate is entirely flat,
A semiconductor laser device in which a structure for limiting a wraparound length of the dielectric film toward the electrode surface when the dielectric film is formed is formed on the electrode surface.   The structure is constituted by a step formed in the vicinity of at least one of the light emitting end face or the end face facing the light emitting end face so that the electrode is not formed or is thinner than other regions. 2. The semiconductor laser device according to 1.   The semiconductor laser device according to claim 2, wherein the step is 5 to 50 μm.   2. The structure is configured by a dielectric film stopper formed at a distance from the end face on at least one of a light emitting end face side on the electrode or an end face side facing the light emitting end face side. Semiconductor laser device.   5. The semiconductor laser device according to claim 4, wherein the dielectric film stopper has a thickness of 5 to 50 [mu] m.   6. The semiconductor laser device according to claim 4, wherein the dielectric film stopper has a width of 5 to 30 [mu] m.   The semiconductor laser device according to claim 1, wherein the structure is formed only on an electrode surface far from the active layer.   8. The semiconductor laser device according to claim 1, wherein the structure is formed on both a light emitting end face side on the electrode surface and an end face side facing the light emitting end face side.   The semiconductor laser device according to claim 1, wherein the wraparound length is 5 to 50 μm.   The semiconductor laser device according to claim 1, wherein the wraparound length is constant. Forming electrodes on both electrode surfaces of a semiconductor substrate having an active layer formed therein;
Etching the electrode by forming a photoresist mask on the electrode so that at least one of the electrodes is etched in a strip shape along a line separating the semiconductor laser bars,
Separate for each semiconductor laser bar,
A method of manufacturing a semiconductor laser device, wherein the semiconductor laser bars are arranged to form a dielectric film from a light emitting end face or an opposing end face. Forming electrodes on both electrode surfaces of a semiconductor substrate having an active layer formed therein;
Forming a dielectric film stopper film on at least one of the electrodes;
Etching the dielectric film stopper film by forming a photoresist mask on the dielectric film stopper film so that a dielectric film stopper is formed on both sides of the line separating each semiconductor laser bar,
Separate for each semiconductor laser bar,
A method of manufacturing a semiconductor laser device, wherein the semiconductor laser bars are arranged to form a dielectric film from a light emitting end face or an opposing end face.

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