JP2012244011A - Semiconductor light-emitting element, optical module, and method of manufacturing semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element with improved durability and reliability.SOLUTION: A semiconductor light-emitting element comprises: a P-side electrode layer 4 that is stacked with an N-type semiconductor layer 3, an active layer 2, and a P-type semiconductor layer 1 and is composed of a multilayer metal; and an end-face protective film 13 that is formed on a side surface of the stack to prevent optical damage. The end-face protective film 13 has a protective film 5 composed of a material that hardly becomes a diffusion medium, when at least one layer of the P-side electrode layer 4 is a metal thin film that is a diffusant, and a diffusion medium film 6 composed of a material that becomes the diffusion medium and formed on the protective film 5 so as not to contact the metal thin film.

Description

  The present invention relates to a semiconductor light emitting device, an optical module, and a method for manufacturing the semiconductor light emitting device.

  The Internet has spread all over the world, and today it has become an indispensable infrastructure for our economic activities and daily life. Even today, the amount of Internet traffic is increasing explosively, and in Japan, it is increasing at an annual rate of 1.3 times. Along with this, it has become necessary to increase the capacity of routers arranged in the metro network from the trunk network to the subscriber network. In particular, due to the accelerated introduction of the 10 Gb / s trunk optical communication system from the latter half of 1990, a 10 Gb / s transceiver module serving as an optical interface between routers has been awaited. This module has a 1.3 μm band direct modulation laser that operates at 10 Gb / s in a wide temperature range from the viewpoint of short transmission distance, cost and power consumption associated therewith, and single mode fiber with minimal dispersion wavelength. It was considered desirable to install. As a result, due to the research and development of InGaAlAs-based materials that have been developed since the late 1990s, 10 Gb / s direct modulation operation was demonstrated in the 1.3 μm band over a wide temperature range in the early 2000s.

However, particularly in a semiconductor laser containing Al in the active layer, it is easy to cause so-called optical damage in which the end face is destroyed by strong light emitted by itself, and thus ensuring reliability has been a problem. One way to ensure reliability is to form a protective film on the end face. Regarding this end face protective film, Patent Documents 1 to 4 are known so far. These end face protective films are usually formed of multilayer films having different refractive indexes so as to obtain a desired reflection (transmission) rate. For example, Patent Document 1 discloses that Al ₂ O ₃ or the like is used as a low refractive index material and amorphous Si is used as a high refractive index material in a communication wavelength band. By applying the end face protective film as described above, the reliability of the InGaAlAs-based 1.3 μm band direct modulation laser operating at 10 Gb / s is secured, and it has been adopted for a small optical module with low power consumption. This compact optical module is applied to core / edge routers of various companies around the world, and supports the infrastructure of the current advanced information society.

Japanese Patent No. 4699432 Japanese Patent No. 4178022 JP-A-6-204602 JP 2004-327637 A

  Au is usually used for the electrode surface of the semiconductor light emitting element as described above, and is used as a high refractive index material due to the formation error of the electrode metal burr and end face protective film generated during cleavage. Amorphous Si may come into contact with Au forming the electrode, and external heat is applied to such an element, so that Au forming the electrode rapidly diffuses into amorphous Si, thereby protecting the end face. There was a possibility that the reflection (transmission) rate of the film or peeling would occur. Further, diffusion is accelerated by energization of the semiconductor light emitting element and light emitted from the semiconductor light emitting element, and there is a fear that reliability is lowered such as initial deterioration of the element and occurrence of optical damage due to light absorption of self light emission.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor light emitting device with improved durability and reliability.

  The semiconductor light emitting device of the present invention includes an active layer and a semiconductor layer laminated on a semiconductor substrate, an electrode layer made of a multilayer metal, and an end face protective film formed on at least a side surface of the laminated layer to prevent optical damage. The end face protective film comprises at least one of the electrode layers as a metal thin film that is a diffusive material, and is formed of a protective film made of a material that is difficult to serve as a diffusion medium and a material that serves as the diffusion medium, and does not contact the metal thin film Thus, a semiconductor light emitting element comprising: a diffusion medium film formed on the protective film.

  Here, the “side surface of the laminated layer” on which the end face protective film is formed may be an output surface of light that becomes signal light, or may be an output surface of monitor light that is measured for control.

  In the semiconductor light emitting device of the present invention, the diffusion medium film may be formed so as to be in contact with the protective film with an area smaller than the area of the surface on which the protective film is formed.

  In the semiconductor light emitting device of the present invention, the protective film includes a first protective film formed so as to be further stacked on a part of the electrode layer, and a second protective film formed at least on an end face of the stacked layer. And a film.

  In the semiconductor light emitting device of the present invention, a non-diffusible metal layer that is difficult to become the diffusive material may be further laminated on the electrode layer.

  In the semiconductor light emitting device of the present invention, the hardly diffusible metal layer may be any one of Pt, Ni, and Pd.

  Further, in the semiconductor light emitting device of the present invention, the metal thin film that is the diffusive material is any one of Au, Ag, and Cu, and the substance that serves as the diffusion medium is any one of amorphous silicon and silicon, The substance that is difficult to serve as a diffusion medium can be any one of aluminum oxide, titanium oxide, silicon oxide, and tantalum oxide.

  In the semiconductor light emitting device of the present invention, the semiconductor layer can be an InP substrate or a GaAs substrate.

  In the semiconductor light emitting device of the present invention, the active layer may contain Al.

  The optical module of the present invention is an optical module comprising any one of the semiconductor light-emitting elements described above and a light-receiving element that receives light emitted from the semiconductor light-emitting element.

  The method of manufacturing a semiconductor light emitting device according to the present invention includes a lamination process of laminating an electrode layer made of a multilayer metal together with an active layer and a semiconductor layer on a semiconductor substrate, and extends in a light emitting direction as the distance from the electrode layer increases. A mask process in which a mask having a cross-sectional shape is placed over the electrode layer, and after the mask process, at least one layer of the electrode layer is formed as a metal thin film that is a diffusive material on the side surface of the stack. A method of manufacturing a semiconductor light emitting device, comprising: a protective film made of a material that is difficult to be formed; and an end face protective film forming step of forming an end face protective film by sequentially stacking a diffusion medium film made of the material that becomes the diffusion medium It is.

  Here, the “cross-sectional shape extending in the light emitting direction as the distance from the electrode layer increases” may be a surface formed obliquely with respect to the surface of the electrode layer, or may be formed in a step shape. It may be a surface.

  According to the present invention, durability and reliability of a semiconductor light emitting device can be improved.

It is a disassembled perspective view of the optical module carrying the semiconductor light-emitting device based on Example 1 of this invention. It is the schematic of the cross section in the II-II line | wire of FIG. It is sectional drawing of the semiconductor light-emitting device based on Example 1 of this invention. It is a flowchart which shows the manufacturing method of the semiconductor light-emitting device based on Example 1 of this invention. It is a figure for demonstrating the manufacturing method of the semiconductor light-emitting device of FIG. It is sectional drawing of the semiconductor light-emitting device based on Example 2 of this invention. It is a figure for demonstrating the manufacturing method of the semiconductor light-emitting device of FIG. It is sectional drawing of the semiconductor light-emitting device based on Example 3 of this invention. It is sectional drawing of the semiconductor light-emitting device based on Example 4 of this invention.

  Examples 1 to 4 of the present invention will be described below. In the following description of Examples 1 to 4 and the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  1 is an exploded perspective view of an optical module 100 on which a semiconductor light emitting element 26 according to Example 1 of the present invention is mounted, and FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. As shown in FIGS. 1 and 2, the optical module 100 includes a stem 22, three lead pins 23 attached to the stem 22 and serving as electrical terminals of the optical module 100, and a mount attached to the stem 22. Part 24, submount part 25 and semiconductor light emitting element 26 attached so as to be stacked from mount part 24, light receiving element 27 attached to stem 22 and receiving monitor light 29 from semiconductor light emitting element 26, and mount A cap 21 attached to the stem 22 so as to cover the portion 24, the submount portion 25, the semiconductor light emitting element 26 and the light receiving element 27, and a non-attached portion attached to the cap 21 so that the emitted light 7 is transmitted substantially through the center. Electrical signals are transmitted from the spherical lens 20 and the lead pin 23 to the semiconductor light emitting element 26 and the light receiving element 27. It is provided with a lead wire 28, a.

  The electrical signal transmitted to the semiconductor light emitting element 26 via the lead pin 23 and the lead wire 28 is converted into an optical signal by the semiconductor light emitting element 26 and transmitted to the outside as the emitted light 7. On the other hand, the monitor light 29 is converted into an electric signal or the like by the light receiving element 27 and transmits information such as the state of the semiconductor light emitting element 26 to the outside via the lead pin 23 and the lead wire 28.

  FIG. 3 is a cross-sectional view of the semiconductor light emitting device 26, in which the active layer 2 is formed on the N-type semiconductor layer 3, the P-type semiconductor layer 1 is formed on the active layer 2, and the P-type On the semiconductor layer 1, a multilayer P-side electrode layer 4 having at least a surface made of an easily diffusible metal is formed. Further, at least one end face of the semiconductor light emitting element 26 has a protective film 5 in which the easily diffusible metal of the P-side electrode layer 4 does not become a diffusive material at least from the end face side, and then the P-side electrode so that the reflectance is approximately 0%. An end face protective film 13 composed of at least two layers is formed in the order of the diffusion medium film 6 serving as a diffusion medium of the easily diffusible metal of the layer 4, and the emitted light 7 is emitted by energizing the semiconductor light emitting element 26. . In this figure, the N-side electrode formed on the N-type semiconductor layer 3 is omitted. The protective film 5 is formed so as to cover the end face side of the easily diffusible metal of the P-side electrode layer 4 and substantially uniformly with respect to the end face, and the diffusion medium film 6 is substantially uniform with respect to the end face. It is formed so that the area is smaller than that of the inner side. That is, the diffusion medium film 6 is formed so as to be in contact with the protective film 5 with an area smaller than the area of the surface on which the protective film 5 is formed. By forming in this way, even if formation errors such as accidental electrode burr at the time of cleavage and film thickness of the end face protective film 13 occur, the easily diffusible metal of the P-side electrode layer 4 becomes the diffusion medium film 6. As a result, heat is applied during assembly to prevent the diffusible metal of the P-side electrode layer 4 from diffusing into the diffusion medium film 6, and the end face protective film 13 is peeled off, initial failure, operation Sometimes it prevents sudden failures.

  FIG. 4 shows a method for manufacturing the semiconductor light emitting device 26. As shown in this figure, first, in the film forming process of step S11, the above-described active layer 2, P-type semiconductor layer 1, and P-side electrode layer 4 are sequentially stacked on an N-type semiconductor substrate (wafer). An N-side electrode is formed on the opposite side of the substrate. Next, in the cleavage step of step S12, the substrate is cleaved to form a bar-shaped object in which the semiconductor light emitting elements 26 are arranged in a line. The state of the cross section of one semiconductor light emitting element 26 in the rod-like object at this time is shown in step S21 in FIG. In FIG. 5, the N-side electrode is not shown. Subsequently, in step S13, the mask 10 for end face coating is attached to the end face of the laminated surface of the rod-shaped object and corresponding to the exit face of the emitted light 7 and the monitor light 29. Step S22 in FIG. 5 shows a state when the mask 10 is attached. As shown in this figure, the mask 10 is attached so as to sandwich a rod-shaped object between both the P-side electrode side and the N-side electrode side. The mask 10 attached to the P-side electrode side has a cross-sectional shape that extends in the light emission direction as the distance from the electrode layer increases. In the present embodiment, the mask 10 has an oblique surface only on the outgoing light side surface on the P-side electrode layer 4 side, but the surface on the monitor light side emits the monitor light. The mask 10 on the N-side electrode side may have such an oblique surface.

  Returning to FIG. 4, in the end surface coating step of step S14, the protective film 5 and the diffusion medium film 6 are sequentially formed (step S23 of FIG. 5). Thereafter, by removing the mask 10, the diffusion medium film 6 is formed on the inner side of the protective film 5 with a smaller area as shown in Step S <b> 24 of FIG. 5, thereby easily diffusing metal of the P-side electrode layer 4. An end face protective film 13 having a shape that does not touch is formed. Finally, in the dicing process of step S15 in FIG. 4, the rod-shaped object is cut to form the semiconductor light emitting element 26.

  By forming the protective film 5 as described above, the protective film 5 is formed so as to cover the end face side of the easily diffusible metal of the P-side electrode layer 4 and to be substantially uniform with respect to the end face. Due to the special shape, it is formed so as to be substantially uniform with respect to the end surface, smaller in area than the protective film 5 and inside. The end surface protective film 13 is also formed on the surface of the P-side electrode side of the easily diffusible metal on the end surface side of the P-side electrode layer 4.

  The active layer 2 is made of InGaAlAs-based material or InGaAsP-based material, and the P-type semiconductor layer 1 or N-type semiconductor layer 3 is made of InP material or GaAs material, but is not limited thereto. Examples of the protective film 5 include, but are not limited to, aluminum oxide, titanium oxide, silicon oxide, and tantalum oxide. Examples of the diffusion medium film 6 include amorphous silicon and silicon, but are not limited thereto. Further, examples of the easily diffusible electrode material used for the P-side electrode layer 4 include, but are not limited to, Au, Ag, and Cu.

  FIG. 6 is a cross-sectional view of a semiconductor light emitting device 36 according to Example 2 of the present invention. An active layer 2 is formed on the N-type semiconductor layer 3, a P-type semiconductor layer 1 is formed on the active layer 2, and at least the surface of the P-type semiconductor layer 1 is a diffusible metal. A multi-layered P-side electrode layer 4 is formed, and a first protective film 11 is formed on the easily diffusible metal of the P-side electrode layer 4 in the vicinity of the end face of the semiconductor light emitting element. Further, at least one end face of the semiconductor light emitting element has a second protective film 8 in which the diffusible metal of the P-side electrode layer 4 does not become a diffusive material at least from the end face side, so that the reflectance is approximately 0%, and then the P side. An end face protective film 13 composed of at least two layers is formed in the order of the diffusion medium film 6 serving as a diffusion medium of the easily diffusible metal of the electrode layer 4, and the emitted light 7 is emitted by energization of the semiconductor light emitting element 36. Is done. The second protective film 8 is formed substantially uniformly with respect to the end face, the diffusion medium film 6 is formed so as to be substantially uniform with respect to the end face, and the first protective film 11 and the second protective film 8 are formed. It is formed so as to be in contact with the first protective film 11 and the second protective film 8 with an area smaller than the surface area.

  The first protective film 11 is formed by the following method. An active layer 2, a P-type semiconductor layer 1, and a P-side electrode layer 4 are sequentially formed on a substrate (wafer) of the N-type semiconductor layer 3 by a known semiconductor process. Next, as shown in FIG. 7, the first protective film 11 is formed on the surface of the P-side electrode layer 4 on which the easily diffusible metal is formed. Next, etching is performed by a normal photolithography process or the like so that the first protective film 11 remains only in a specific portion of the easily diffusible metal of the P-side electrode layer 4. In this state, the approximate center position 12 of the first protective film 11 is cleaved. By forming in this way, accidental burr of the electrode at the time of cleavage is suppressed, and even if a formation error such as the film thickness of the end face protective film 13 occurs, the diffusible metal of the P-side electrode layer 4 The diffusion medium film 6 is not in contact, and as a result, heat is applied during assembly or the like to prevent the diffusible metal of the P-side electrode layer 4 from diffusing into the diffusion medium film 6, and the end face protective film 13 is peeled off. No initial failure or sudden failure during operation.

  Examples of the first protective film 11 include, but are not limited to, aluminum oxide, titanium oxide, silicon oxide, and tantalum oxide.

  FIG. 8 is a cross-sectional view of a semiconductor light emitting device 46 according to Example 3 of the present invention. An active layer 2 is formed on an N-type semiconductor layer 3, and a P-type semiconductor layer 1 is formed on the active layer 2. A multi-layer P-side electrode layer 4 having at least a surface made of a diffusible metal is formed on the P-type semiconductor layer 1, and the entire P-side electrode layer 4 on the diffusible metal is formed. Alternatively, a hardly diffusible metal layer 9 whose surface is made of a hardly diffusible metal is formed in part. Further, at least one end face of the semiconductor light-emitting element 46 has a protective film 5 in which the easily diffusible metal of the P-side electrode layer 4 does not become a diffusive material at least from the end face side, and then the P-side electrode so that the reflectance is approximately 0%. The end face protective film 13 composed of at least two layers is formed almost uniformly with respect to the end face in the order of the diffusion medium film 6 serving as the diffusion medium of the easily diffusible metal of the layer 4. Outgoing light 7 is emitted. By forming in this way, even if formation errors such as accidental electrode burr at the time of cleavage and film thickness of the end face protective film 13 occur, the easily diffusible metal of the P-side electrode layer 4 becomes the diffusion medium film 6. As a result, heat is applied during assembly to prevent the diffusible metal of the P-side electrode layer 4 from diffusing into the diffusion medium film 6, and the end face protective film 13 is peeled off, initial failure, operation Sometimes sudden failures no longer occur. The present embodiment is merely an example for explaining the present invention, and the present invention is not limited to this example.

  For example, Pt, Ni, and Pd are preferably used as the hardly diffusible electrode material for forming the hardly diffusible metal layer 9, but are not limited thereto.

  FIG. 9 is a cross-sectional view of a semiconductor light emitting device 56 according to Example 4 of the present invention. The active layer 2 is formed on the N-type semiconductor layer 3, and the P-type semiconductor layer 1 is formed on the active layer 2. On the P-type semiconductor layer 1, a multilayer P-side electrode layer 4 having at least a surface made of an easily diffusible metal is formed. Further, at least one end face of the semiconductor light emitting element has a protective film 5 in which the diffusible metal of the P-side electrode layer 4 does not become a diffusive material at least from the end face side, and then the P-side electrode layer so that the reflectance is approximately 0%. The end face protective film 13 composed of at least two layers is formed in the order of the diffusion medium film 6 serving as a diffusion medium of the 4 easily diffusible metal, and the emitted light 7 is emitted by energization of the semiconductor light emitting element 56.

  The protective film 5 is formed substantially uniformly with respect to the end face, the diffusion medium film 6 is substantially uniform with respect to the end face, has a sufficiently smaller area than the protective film 5 and is located inside, and emits semiconductor light. It is formed so as to be larger than the near-field image of the light emitted from the element. That is, the diffusion medium film 6 is formed so as to be in contact with the protective film 5 with an area smaller than the area of the surface on which the protective film 5 is formed. By forming in this way, even if formation errors such as accidental electrode burr at the time of cleavage and film thickness of the end face protective film 13 occur, the easily diffusible metal of the P-side electrode layer 4 becomes the diffusion medium film 6. As a result, heat is applied during assembly to prevent the diffusible metal of the P-side electrode layer 4 from diffusing into the diffusion medium film 6, and the end face protective film 13 is peeled off, initial failure, operation Sometimes sudden failures no longer occur.

  As described above, in the semiconductor light emitting device of the present invention, durability and reliability can be further improved.

  In the above-described embodiment, an N-type substrate is used for each semiconductor light emitting element, but the same applies to the case where a P-type substrate or an insulating substrate is used. Further, even when an easily diffusible metal is used for the N-side electrode, durability and reliability can be further improved by the same method. Moreover, although the end surface protective film 13 is described as two layers in the drawing, it may be formed of two or more layers.

  1 P-type semiconductor layer, 2 active layer, 3 N-type semiconductor layer, 4 P-side electrode layer, 5 protective film, 6 diffusion medium film, 7 outgoing light, 8 second protective film, 9 hardly diffusible metal layer, 10 mask 11 First protective film, 13 End face protective film, 20 Aspheric lens, 21 Cap, 22 Stem, 23 Lead pin, 24 Mount part, 25 Submount part, 26 Semiconductor light emitting element, 27 Light receiving element, 28 Lead wire, 29 Monitor Light, 36 Semiconductor light emitting device, 46 Semiconductor light emitting device, 56 Semiconductor light emitting device, 100 Optical module.

Claims (10)

An electrode layer made of a multi-layer metal, laminated with an active layer and a semiconductor layer on a semiconductor substrate;
An end face protective film formed on at least the side surface of the laminate and preventing optical damage,
The end face protective film is
A protective film made of a material that is difficult to serve as a diffusion medium, with at least one of the electrode layers being a metal thin film that is a diffusive material,
A semiconductor light emitting device comprising a diffusion medium film made of a substance that serves as the diffusion medium and formed on the protective film so as not to contact the metal thin film. The semiconductor light emitting device according to claim 1,
The diffusion medium film is formed so as to be in contact with the protective film with an area smaller than the area of the surface on which the protective film is formed. The semiconductor light-emitting device according to claim 1 or 2,
The protective film is
A first protective film formed to be further laminated on a part of the electrode layer;
A second protective film formed on at least the end face of the stack;
A semiconductor light-emitting element comprising: The semiconductor light-emitting device according to claim 1,
A semiconductor light-emitting element, wherein a non-diffusible metal layer that is difficult to become a diffusive material is further laminated on the electrode layer. The semiconductor light emitting device according to claim 4,
The semiconductor light emitting element, wherein the hardly diffusible metal layer is any one of Pt, Ni, and Pd. A semiconductor light emitting device according to any one of claims 1 to 5,
The metal thin film that is the diffusive material is one of Au, Ag, and Cu,
The substance serving as the diffusion medium is either amorphous silicon or silicon,
The semiconductor light emitting element characterized in that the substance that is difficult to serve as a diffusion medium is any one of aluminum oxide, titanium oxide, silicon oxide, and tantalum oxide.   7. The semiconductor light emitting device according to claim 1, wherein the semiconductor layer is an InP substrate or a GaAs substrate. 8.   8. The semiconductor light emitting device according to claim 1, wherein the active layer contains Al. 9. A semiconductor light emitting device according to any one of claims 1 to 8,
A light receiving element that receives light emitted from the semiconductor light emitting element. A lamination step of laminating an electrode layer made of a multilayer metal together with an active layer and a semiconductor layer on a semiconductor substrate;
A mask process in which a mask having a cross-sectional shape extending in the light emission direction as the distance from the electrode layer increases is placed on the electrode layer; and
After the masking process, at least one layer of the electrode layer is formed as a diffusive metal thin film on the side surface of the laminate, and a protective film made of a substance that is difficult to become a diffusion medium, and a diffusion medium film made of the substance that becomes the diffusion medium And a step of forming an end face protective film by sequentially stacking the end face protective films.

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