JP2008034587A - Method of manufacturing semiconductor laser, semiconductor device, and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the method of manufacturing a semiconductor laser in which the end of a resonator can be used as a current non-injection region by easily etching and removing the p-side electrode of a portion near at least one end surface of the resonator, and the roughness of an etching surface at the time of dry-etching is not produced. <P>SOLUTION: A metal laminated film whose bottom layer comprises a Pd film 16 and whose top layer comprises a Pt film 17 is formed in the shape of a stripe on a GaN semiconductor layer 12 which forms a laser structure. A ridge stripe 18 is formed by carrying out the dry-etching of the GaN semiconductor layer 12 using the metal laminated film as an etching mask. On this occasion, the Pt film 17 is made to be virtually removed at an etching completion time point. Then, a portion other than a portion for use as a p-side electrode of the Pd film 16 and the remaining Pt film 17 is removed by carrying out wet-etching using aqua regia. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor laser, a method for manufacturing a semiconductor element, and a method for manufacturing an element. For example, the present invention is suitable for use in manufacturing a semiconductor laser using a nitride III-V compound semiconductor.

When a semiconductor laser using a nitride III-V compound semiconductor such as GaN has a ridge stripe structure, a p-side electrode is formed on the nitride III-V compound semiconductor layer forming the laser structure. A method of forming a ridge stripe in a self-aligned manner with respect to the p-side electrode by dry-etching the underlying nitride III-V compound semiconductor layer by a reactive ion etching (RIE) method using the p-side electrode as an etching mask There is.
On the other hand, in a semiconductor laser using a nitride III-V compound semiconductor, the p-side electrode in the vicinity of the resonator end face is removed to make the resonator end a current non-injection region. A technique for preventing Catastrophic Optical Damage (COD) is known (for example, see Patent Document 1).
JP 2002-43692 A

However, according to the study by the present inventors, a Pd / Pt film in which the lower layer is a palladium (Pd) film and the upper layer is a platinum (Pt) film is used as the p-side electrode, and dry etching is performed using the p-side electrode as an etching mask. Thus, when the ridge stripe is formed, it is difficult to remove the p-side electrode in the vicinity of the resonator end face. That is, the thickness of the lower Pd film of the p-side electrode is, for example, about 50 nm and the thickness of the upper Pt film is, for example, about 100 nm, but the etching rate of the Pt film by the RIE method is, for example, about 0.01 μm / min. Since the etching rate of the nitride III-V compound semiconductor layer is, for example, about 0.13 μm / min, if the etching depth for forming the ridge stripe is, for example, about 0.5 μm, the dry etching is completed. Even at the time, the Pt film remains at least about 50 nm thick. For this reason, even if an attempt is made to partially remove the p-side electrode by wet etching using aqua regia after dry etching, the etching rate of the Pt film by aqua regia is extremely slow, so this method is practically used. It is difficult.
On the other hand, if a Pd film single layer is used instead of the Pd / Pt film as the p-side electrode, the p-side electrode can be easily and partially etched away by wet etching using aqua regia after dry etching. In this case, however, palladium sputtered during dry etching randomly adheres to the etched surface of the nitride-based III-V compound semiconductor layer, and as a result, the etched surface becomes difficult to continue the subsequent process. In practice, this method is also difficult to use because it becomes rough.

Therefore, the problem to be solved by the present invention is to dry-etch a nitride-based III-V compound semiconductor layer using a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film as an etching mask. After forming the ridge stripe, the p-side electrode in the vicinity of at least one of the resonator end faces can be easily etched away to make the resonator end a current non-injection region, and the etched surface during dry etching It is an object of the present invention to provide a method for manufacturing a semiconductor laser that does not cause roughening.
More specifically, the problem to be solved by the present invention is to dry a nitride III-V compound semiconductor layer using an etching mask as a metal laminated film in which the lowermost layer is a palladium film and the uppermost layer is a platinum film. It is an object of the present invention to provide a method for manufacturing a semiconductor device in which a metal laminated film at a selected portion can be easily removed after etching and the etching surface is not roughened during dry etching.
More generally, the problem to be solved by the present invention is that the lowermost layer is made of a first metal film such as a palladium film that can be easily wet etched, and the uppermost layer has a dry etching resistance such as a platinum film. Then, after the substrate is dry-etched using the metal laminated film made of the second metal film, which is difficult to perform wet etching, as an etching mask, the metal laminated film in the selected portion can be easily removed by etching, particularly the first metal In the case where the film is a palladium film and the second metal film is a platinum film, there is provided a method for manufacturing an element which does not cause rough etching surfaces during dry etching.

In order to solve the above problem, the first invention is:
A step of forming a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film in a stripe shape on the nitride-based III-V group compound semiconductor layer forming the laser structure;
Forming a ridge stripe by dry-etching the nitride III-V compound semiconductor layer using the metal laminated film as an etching mask, wherein the platinum film is substantially removed at the end of etching; When,
A step of removing the palladium film and the remaining platinum film other than the part used as the p-side electrode by wet etching using aqua regia. is there.

  The thickness of the platinum film of the metal laminated film is selected so that the platinum film is almost removed at the end of etching based on the etching rate of the nitride III-V compound semiconductor layer and the platinum film by dry etching. . Preferably, the platinum film is completely removed at the end of the dry etching. The thickness of the palladium film of the metal laminated film is appropriately selected so that good ohmic contact characteristics can be stably obtained with respect to the underlying nitride III-V compound semiconductor layer. The metal laminated film is not only composed of a two-layer metal film of a lowermost palladium film and an uppermost platinum film, but also one or two layers between the lowermost palladium film and the uppermost platinum film. It may have other metal films as described above. Specifically, for example, a gold film may be provided between a palladium film and a platinum film. In this case, for example, the uppermost platinum film of the metal laminated film is completely removed at the end of the dry etching, and the intermediate gold film is substantially removed. The distance a between the end face of the portion used as the p-side electrode of the palladium film and the remaining platinum film and at least one resonator end face is selected as necessary, but generally 0 <a ≦ 45 μm, Preferably, 3 μm ≦ a ≦ 45 μm, more preferably 5 μm ≦ a ≦ 45 μm, and most preferably 15 μm ≦ a ≦ 45 μm.

Nitride III-V compound semiconductor layer, most _{commonly, Al X B y Ga 1-} xyz In z As u N 1-uv P v ( however, 0 ≦ x ≦ 1,0 ≦ y ≦ 1 , 0 ≦ z ≦ 1,0 ≦ u ≦ 1,0 ≦ v ≦ 1,0 ≦ x + y + z <1,0 ≦ u + v consists <1), more _{specifically, Al X B y Ga 1-} xyz in z N (however, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ x + y + z <1), typically Al _X Ga _1-xz In _z N (where 0 ≦ x ≦ 1, 0 ≦ z ≦ 1).

The second invention is
A step of forming a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film in a predetermined shape on the nitride III-V compound semiconductor layer;
Dry etching the nitride III-V compound semiconductor layer using the metal laminated film as an etching mask, and at this time, the platinum film is almost removed at the end of etching;
And removing the palladium film and the remaining platinum film at a selected portion by wet etching using aqua regia.

In the second invention, the semiconductor element includes a semiconductor light emitting element such as a semiconductor laser and a light emitting diode, a semiconductor light receiving element, a field effect transistor (FET) such as a high electron mobility transistor, and a heterojunction bipolar transistor ( An electronic traveling element such as HBT) is included. The palladium film or the palladium film and the platinum film that are finally left are used as electrodes and wirings of these semiconductor elements.
In the second invention, what has been described in relation to the first invention is valid as long as it is not contrary to the nature thereof.

The third invention is
On the substrate, a metal laminated film made of a first metal film having a lowermost layer that is easy to wet-etch and a second metal film having a dry-etching resistance that is difficult to wet-etch in a predetermined shape. Forming, and
Dry etching the substrate using the metal laminated film as an etching mask, wherein the second metal film of the metal laminated film is substantially removed at the time of completion of etching;
And a step of removing the first metal film and the remaining second metal film in a selected portion by wet etching.

  The first metal film that is the lowest layer of the metal laminated film and that is easy to wet etch is, for example, a palladium film that can be easily wet etched at a practical etching rate using aqua regia. The second metal film that is dry etching resistant and difficult to wet etch, which is the uppermost layer, has an etching rate that is low enough to serve as an etching mask when dry etching is performed by, for example, the RIE method. Even if it is used, it is a platinum film that is difficult to wet-etch at a practical etching rate.

  The thickness of the second metal film is selected based on the etching rate of the substrate and the second metal film by dry etching so that the second metal film is almost removed at the end of etching. Preferably, the second metal film is completely removed at the end of the dry etching. The metal laminated film is not only composed of a two-layer metal film of a lowermost first metal film and an uppermost second metal film, but also a lowermost first metal film and an uppermost second metal film. Another metal film having one layer or two or more layers may be provided between the two metal films. Specifically, for example, a third metal film that is difficult to perform wet etching is provided between the first metal film and the second metal film, and at the end of etching by dry etching, The second metal film may be completely removed, and the intermediate third metal film may be substantially removed.

The substrate may be a substrate on which a layer for forming an element structure is formed or the substrate itself. In addition to semiconductor elements (semiconductor light emitting elements, semiconductor light receiving elements, electron transit elements, etc.), these elements include piezoelectric elements, pyroelectric elements, optical elements (second harmonic generation elements using nonlinear optical crystals, etc.), dielectrics Various devices such as an element (including a ferroelectric element) and a superconducting element may be used. In addition to the nitride III-V compound semiconductor, the material for the substrate or the element structure may be a wurtzit structure, more generally another semiconductor having a hexagonal crystal structure. For example, it may be ZnO, α-ZnS, α-CdS, α-CdSe, etc., and may be various semiconductors having other crystal structures. Furthermore, piezoelectric elements, pyroelectric elements, optical elements, Various materials such as oxides can be used for dielectric elements, superconducting elements, and the like.
In the third invention, what has been described in relation to the first and second inventions is valid as long as it is not contrary to the nature thereof.

In the first and second inventions configured as described above, the platinum film that cannot be easily removed by wet etching using aqua regia is substantially removed by dry etching to form a ridge stripe. Therefore, the palladium film and the remaining platinum film can be easily removed by wet etching using aqua regia after that. In addition, during dry etching, the metal laminate film always has a platinum film as the outermost surface, and the palladium film surface is not exposed, and the platinum film is completely removed and the palladium film surface is exposed. However, since it is only exposed for the first time at the end of etching, there is no problem of roughness of the etched surface of the nitride III-V compound semiconductor layer during dry etching.
In the third invention, the second metal film, which cannot be easily removed by wet etching, is almost removed when the substrate is dry-etched. The metal film and the remaining second metal film can be easily removed by etching.

According to the first aspect of the present invention, a ridge stripe is formed by dry etching a nitride III-V compound semiconductor layer using a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film as an etching mask. After that, the p-side electrode in the vicinity of at least one of the resonator end faces can be easily etched away to make the resonator end portion a current non-injection region, and the etched surface becomes rough during dry etching. Absent.
According to the second invention, after the nitride-based III-V compound semiconductor layer is dry-etched using the metal laminated film whose bottom layer is made of a palladium film and the top layer is a platinum film as an etching mask, the selected portion The metal laminated film can be easily removed by etching, and the etched surface is not roughened during dry etching.
According to the third invention, the lowermost layer is made of the first metal film such as a palladium film that is easy to wet etch, the uppermost layer has a dry etching resistance such as a platinum film, and the second etching is difficult. After dry etching a substrate such as a nitride-based III-V compound semiconductor layer using a metal laminated film made of a metal film as an etching mask, the metal laminated film at a selected portion can be easily removed by etching. When the first metal film is a palladium film and the second metal film is a platinum film, the etching surface does not become rough during dry etching.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are denoted by the same reference numerals.
1 to 18 show a method of manufacturing a GaN semiconductor laser according to the first embodiment of the invention. This GaN-based semiconductor laser has a ridge stripe structure, and removes the p-side electrode in the vicinity of the resonator end face to make both ends of the resonator have current non-injection regions.
In the first embodiment, first, as shown in FIG. 1A, a GaN-based semiconductor layer 12 that forms a laser structure is grown on an n-type GaN substrate 11, and an insulating film 13 is formed on the GaN-based semiconductor layer 12. Then, a resist 14 is coated on the insulating film 13. For example, a SiO ₂ film can be used as the insulating film 13, but is not limited thereto. Next, the resist 14 is exposed using a photomask 15 on which a mask pattern having a predetermined shape is formed.

As a specific example of the GaN-based semiconductor layer 12 that forms the laser structure, an example of a GaN-based semiconductor laser having an SCH (Separate Confinement Heterostructure) structure is given. In order from the lower layer, an n-type AlGaN cladding layer and an n-type GaN optical waveguide layer , the active layer of undoped _{Ga 1-x in x N /} Ga 1-y in y N multiquantum well structure, undoped InGaN deterioration preventive layer, p-type AlGaN cap layer, p-type GaN optical guide layer, p-type AlGaN cladding layer And a p-type GaN contact layer.

Next, as shown in FIG. 1B, the opening 14a is formed by developing the resist 14 selectively exposed as described above. The planar shape of the opening 14a has a stripe shape corresponding to the shape of a ridge stripe to be formed later. A large number of the openings 14a are actually formed in parallel with each other at a predetermined pitch, but only one is shown here.
Next, as shown in FIG. 1C, the opening 13a is formed by etching the insulating film 13 using the resist 14 as an etching mask. For example, when a SiO ₂ film is used as the insulating film 13, wet etching is performed using a hydrofluoric acid-based etchant, but the present invention is not limited to this.

  Next, as shown in FIG. 2A, a Pd film 16 and a Pt film 17 are sequentially formed from the direction perpendicular to the surface of the n-type GaN substrate 11 by, for example, a vacuum deposition method while leaving the resist 14 left. . Here, the thickness of the Pt film 17 is very thin because the Pt film 17 is almost removed by etching at the end of dry etching by RIE performed to form a ridge stripe later, for example, a thickness of 5 nm or less or 3 nm or less. Let it be the thickness that remains. Specifically, for example, the Pd film 16 has a thickness of 150 nm and the Pt film 17 has a thickness of 30 nm, but the present invention is not limited to this.

Next, the resist 14 is removed together with the Pd film 16 and the Pt film 17 formed thereon (lift-off). Thus, as shown in FIG. 2B, stripe-shaped Pd film 16 and Pt film 17 extending in one direction are formed. The widths of the stripe-shaped Pd film 16 and Pt film 17 are, for example, 10 to 12 μm, but are not limited thereto.
Next, as shown in FIG. 2C, the insulating film 13 is removed by etching. For example, when a SiO ₂ film is used as the insulating film 13, wet etching is performed using a hydrofluoric acid-based etchant, but the present invention is not limited to this. FIG. 3 shows a perspective view of this state. FIG. 4 shows a plan view of this state over a wider region of the n-type GaN substrate 11. FIG. 4 shows an example of the shape and size of one chip area, but the present invention is not limited to this.

  Next, as shown in FIG. 5, the GaN-based semiconductor layer 12 is dry-etched to a predetermined depth by RIE using, for example, a chlorine-based etching gas, using the stripe-shaped Pd film 16 and the Pt film 17 as an etching mask. A ridge stripe 18 is formed. At this time, as described above, the thickness of the Pt film 17 is extremely thin when the Pt film 17 is almost removed by etching at the end of the dry etching, for example, a thickness that remains by 5 nm or less or 3 nm or less. Therefore, the Pd film 16 is always covered with the Pt film 17 during dry etching. For this reason, there is no possibility that the etching surface will be roughened due to the surface of the Pd film 16 being sputtered and adhering to Pd during dry etching, which hinders the execution of subsequent processes and adversely affects the reliability of the laser. There is no fear. The etching rate by this RIE method is, for example, 0.01 μm / min for the Pt film 16 and 0.13 μm / min for the GaN-based semiconductor layer 12. The height of the ridge stripe 18 is, for example, 0.4 to 0.5 μm, but is not limited thereto. FIG. 6 shows a perspective view of this state. For example, when the GaN-based semiconductor layer 12 has the configuration as in the above specific example, the ridge stripe 18 is formed to a depth in the middle of the p-type AlGaN cladding layer. The finally left stripe-shaped Pd film 16 and Pt film 17 constitute a p-side electrode.

Next, as shown in FIG. 7A, a resist 19 is coated on the entire surface of the GaN-based semiconductor layer 12 including the portions of the Pd film 16 and the Pt film 17, and then a photomask 20 on which a mask pattern having a predetermined shape is formed. Then, the resist 19 is exposed.
Next, as shown in FIG. 7B, the resist 19 thus selectively exposed is developed to form an opening 19a. FIG. 8 shows a plan view of this state over a wider area of the n-type GaN substrate 11. FIG. 7B corresponds to a cross-sectional view taken along line BB in FIG. The planar shape of the opening 19a has a total width 2a on each side a in the resonator length direction around the resonator end face formation position, and a total width 2b on each side b around the center line of the ridge stripe 18. Having a rectangular shape.

  Next, as shown in FIG. 7C, wet etching is performed using aqua regia using this resist 19 as an etching mask, so that the Pt film 17 and the Pd film 16 remaining extremely thin are removed by etching. Here, the etching rate of the Pt film 17 by aqua regia is extremely small compared to the Pd film 16, but since the Pt film 17 is extremely thin, the Pt film 17 can be removed by etching in a short time. The film 16 can be removed by etching at a sufficient etching rate. The etching rate of the Pd film 16 by aqua regia is, for example, about 50 nm / min. Thus, the Pd film 16 and the Pt film 17 inside the opening 19a of the resist 19 can be completely removed by etching.

Next, as shown in FIGS. 9A and 9B, the resist 19 is removed. FIG. 10 shows a perspective view of this state. FIG. 11 shows a plan view of this state over a wider region of the n-type GaN substrate 11. Here, FIG. 9A is a cross-sectional view taken along line AA in FIG. 11, and FIG. 9B is a cross-sectional view taken along line BB in FIG.
Next, as shown in FIG. 12A, an insulating film 20 is formed on the entire surface of the GaN-based semiconductor layer 12 including the Pd film 16 and the Pt film 17 by vacuum deposition or the like. For example, a SiO ₂ film can be used as the insulating film 13, but is not limited thereto. The thickness of the insulating film 13 is, for example, 200 nm, but is not limited to this.
Next, as shown in FIG. 12B, after a resist 21 is coated on the insulating film 20, the resist 21 is exposed using a photomask 22 on which a mask pattern having a predetermined shape is formed. The thickness of the resist 21 is, for example, 0.8 μm, but is not limited to this.
Next, as shown in FIG. 12C, the resist 21 thus selectively exposed is developed to form an opening 21 a above the ridge stripe 18.

Next, as shown in FIG. 13A, the resist 21 and the insulating film 20 are etched back by, for example, the RIE method, so that the insulating film 20 above the ridge stripe 18 is removed by etching to expose the Pt film 17.
Next, as shown in FIG. 13B, the resist 21 is removed.
Next, as shown in FIG. 13C, after the resist 23 is coated on the insulating film 20 and the Pt film 17, the surface of the resist 23 is cured by treating with chlorobenzene to form a hardened layer 24. The total thickness of the resist 23 and the cured layer 24 of chlorobenzene is, for example, 3.0 μm, but is not limited thereto. Next, the resist 23 and the hardened layer 24 are exposed using a photomask 25 in which a mask pattern having a shape corresponding to the isolation electrode is formed.

Next, as shown in FIG. 14A, the resist 23 and the hardened layer 24 thus exposed are developed to form an opening 26 having a predetermined shape. At this time, the hardened layer 24 has a bowl-like shape protruding into the opening 26.
Next, as shown in FIG. 14B, with the resist 23 and the hardened layer 24 left, the Ti film, the Pt film, and the like are formed by, for example, vacuum deposition from a direction perpendicular to the surface of the n-type GaN substrate 11. A Ni film is sequentially formed to form a Ti / Pt / Ni film 27. In the Ti / Pt / Ni film 27, for example, the thickness of the lowermost Ti film is 10 nm, the thickness of the Pt film is 100 nm, and the thickness of the uppermost Ni film is 100 nm, but is not limited thereto. It is not a thing.
Next, the resist 23 and the hardened layer 24 are removed together with the Ti / Pt / Ni film 27 formed thereon (lift-off). At this time, since the hardened layer 24 has a bowl shape protruding into the opening 26, the lift-off can be easily performed. Thus, as shown in FIG. 14C, the isolation electrode 28 made of the Ti / Pt / Ni film 27 is formed.

Next, as shown in FIG. 15A, a resist 29 is coated on the entire surface so as to cover the isolation electrode 28, and then the surface of the resist 29 is cured by treatment with chlorobenzene to form a hardened layer 30. The total thickness of the resist 29 and the cured layer 30 of chlorobenzene is, for example, 3.0 μm, but is not limited thereto. Next, the resist 29 and the hardened layer 30 are exposed using a photomask 31 on which a mask pattern having a shape corresponding to the pad electrode is formed.
Next, as shown in FIG. 15B, the resist 29 and the hardened layer 30 thus exposed are developed to form openings 32 having a predetermined shape. At this time, the hardened layer 30 has a bowl-like shape protruding into the opening 32.
Next, as shown in FIG. 15C, with the resist 29 and the hardened layer 30 left, for example, a Ti film, a Pt film, and A Ti / Pt / Au film 33 is formed by sequentially forming an Au film. In the Ti / Pt / Au film 33, for example, the thickness of the lowermost Ti film is 10 nm, the thickness of the Pt film is 100 nm, and the thickness of the uppermost Au film is 300 nm, but is not limited thereto. It is not a thing.

Next, the resist 29 and the hardened layer 30 are removed together with the Ti / Pt / Au film 33 formed thereon (lift-off). At this time, since the hardened layer 30 has a bowl shape protruding into the opening 32, the lift-off can be easily performed. Thus, as shown in FIG. 16, the pad electrode 34 made of the Ti / Pt / Au film 33 is formed.
Next, the n-side electrode 35 is formed on the back surface of the n-type GaN substrate 11 in each chip region, for example, by a lift-off method.
Next, a laser bar is formed by, for example, cleaving the n-type GaN substrate 11 on which the laser structure is formed as described above to form both resonator end faces. Next, after end face coating is applied to the end faces of these resonators, the laser bar is cleaved or the like to form a chip.
Thus, the target GaN-based semiconductor laser is manufactured.
The GaN-based semiconductor laser thus chipped is shown in FIGS. Here, FIG. 17 is a perspective view, FIG. 18A is a sectional view taken along line AA in FIG. 17, FIG. 18B is a sectional view taken along line BB in FIG. 17, and FIG. Sectional drawing along line -C is shown. In this GaN-based semiconductor laser, the p-side electrode composed of the Pd film 16 and the Pt film 17 is not formed in the part of the width a in the cavity length direction from both resonator end faces, and this part becomes a current non-injection region. ing.

  FIGS. 19 to 21 show the results of a maximum output measurement experiment performed by changing the width a of the current non-injection region from the cavity end face to 15 μm, 30 μm, and 45 μm, respectively, in this GaN semiconductor laser. For comparison, FIG. 22 also shows the result of a maximum output measurement experiment of a GaN-based semiconductor laser in which no current non-injection region is provided. However, in any GaN-based semiconductor laser, the ridge stripe 18 has a width (stripe width) of 12 μm and a resonator length of 1.4 mm. The measurement was performed at 25 ° C. As shown in FIG. 22, in the GaN-based semiconductor laser not provided with the current non-injection region, the optical output is rapidly reduced when the injection current is 2000 mA or more, as shown in FIGS. Even if the width a of the current non-injection region is 15 μm, 30 μm, or 45 μm, the light output is prevented from abruptly decreasing up to at least 2500 mA.

  FIG. 23 shows the results of an aging test when the width a of the current non-injection region from the cavity end face is 30 μm in this GaN-based semiconductor laser. For comparison, FIG. 24 shows the results of an aging test of a GaN-based semiconductor laser in which no current non-injection region is provided. However, in any GaN-based semiconductor laser, the ridge stripe 18 has a width (stripe width) of 12 μm and a resonator length of 1.4 mm. The measurement was performed at 25 ° C. As shown in FIG. 24, in a GaN-based semiconductor laser not provided with a current non-injection region, end face deterioration occurs due to COD even after aging for about 70 hours, whereas the light output decreases rapidly. As shown in FIG. 5, the GaN-based semiconductor laser having a current non-injection region width a of 30 μm has a very good aging characteristic with very little decrease in light output even when the aging time is about 300 hours.

  As described above, according to the first embodiment, the ridge stripe 18 is formed on the p-side electrode formed of the stripe-shaped Pd film 16 and the Pt film 17, and both resonator end faces are formed. It is possible to easily manufacture a GaN-based semiconductor laser in which the p-side electrode in the vicinity is removed and both ends of the resonator are used as current non-injection regions. This GaN-based semiconductor laser can effectively prevent COD at the end face of the resonator due to the current non-injection region at both ends of the resonator, and can extend the life and improve the reliability. .

Next explained is a GaN semiconductor laser manufacturing method according to the second embodiment of the invention.
In the second embodiment, the process proceeds in the same manner as in the first embodiment, and as shown in FIGS. 2C, 3 and 4, stripe-shaped Pd films 16 and Pt are formed on the n-type GaN substrate 11. A film 17 is formed.
Next, using the stripe-shaped Pd film 16 and the Pt film 17 as an etching mask, the GaN-based semiconductor layer 12 is dry-etched to a predetermined depth by, for example, RIE using a chlorine-based etching gas to form a ridge stripe 18. . At this time, unlike the first embodiment, the Pt film 17 is completely etched away at the end of the dry etching so that the surface of the Pd film 16 is exposed. This state is shown in FIG. FIG. 26 shows a perspective view of this state.
Thereafter, the process proceeds in the same manner as in the first embodiment, and the target GaN-based semiconductor laser is manufactured as shown in FIG. Here, FIGS. 27A, B, and C correspond to FIGS. 18A, B, and C, respectively.
According to the second embodiment, the same advantages as those of the first embodiment can be obtained.

As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible.
For example, the numerical values, structures, substrates, raw materials, processes, and the like given in the above-described embodiments are merely examples, and different numerical values, structures, substrates, raw materials, processes, and the like may be used as necessary.
Specifically, for example, in the above-described first and second embodiments, the case where the present invention is applied to the manufacture of a GaN semiconductor laser having an SCH structure has been described. The present invention can also be applied to the manufacture of a GaN-based semiconductor laser having a Heterostructure structure.

It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a perspective view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a perspective view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a perspective view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a perspective view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 1st Embodiment of this invention. It is a basic diagram which shows the measurement result of the maximum output characteristic when the width | variety of the current non-injection area | region of the GaN-type semiconductor laser manufactured by 1st Embodiment of this invention is 15 micrometers. It is a basic diagram which shows the measurement result of the maximum output characteristic when the width | variety of the current non-injection area | region of the GaN-type semiconductor laser manufactured by 1st Embodiment of this invention is 30 micrometers. It is a basic diagram which shows the measurement result of the maximum output characteristic when the width | variety of the current non-injection area | region of the GaN-type semiconductor laser manufactured by 1st Embodiment of this invention is 45 micrometers. It is a basic diagram which shows the measurement result of the maximum output characteristic of the GaN-type semiconductor laser of a comparative example with the GaN-type semiconductor laser manufactured by 1st Embodiment of this invention. It is an approximate line figure showing a measurement result of an aging characteristic of a GaN system semiconductor laser manufactured by a 1st embodiment of this invention. It is a basic diagram which shows the measurement result of the aging characteristic of the GaN-type semiconductor laser of a comparative example with the GaN-type semiconductor laser manufactured by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 2nd Embodiment of this invention. It is a perspective view for demonstrating the manufacturing method of the GaN-type semiconductor laser by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the GaN-type semiconductor laser by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... n-type GaN substrate, 12 ... GaN-type semiconductor layer, 13, 20 ... Insulating film, 14, 19, 21, 23, 29 ... Resist, 15, 20, 22, 25, 31 ... Photomask, 16 ... Pd film 17 ... Pt film, 18 ... ridge stripe, 24, 30 ... hardened layer, 28 ... isolation electrode, 34 ... pad electrode, 35 ... n-side electrode

Claims (7)

A step of forming a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film in a stripe shape on the nitride-based III-V group compound semiconductor layer forming the laser structure;
Forming a ridge stripe by dry-etching the nitride III-V compound semiconductor layer using the metal laminated film as an etching mask, wherein the platinum film is substantially removed at the end of etching; When,
A step of removing a portion of the palladium film and the remaining platinum film other than a portion used as a p-side electrode by wet etching using aqua regia.   2. The method of manufacturing a semiconductor laser according to claim 1, wherein the platinum film is completely removed at the end of the etching.   2. A gold film is provided between the palladium film and the platinum film, and the platinum film is completely removed at the end of the etching, so that the gold film is substantially removed. The manufacturing method of the semiconductor laser of description.   The distance a between the end face of the portion used as the p-side electrode of the palladium film and the remaining platinum film and at least one resonator end face is 0 <a ≦ 45 μm. Semiconductor laser manufacturing method. A step of forming a metal laminated film having a lowermost layer made of a palladium film and an uppermost layer made of a platinum film in a predetermined shape on the nitride III-V compound semiconductor layer;
Dry etching the nitride III-V compound semiconductor layer using the metal laminated film as an etching mask, and at this time, the platinum film is almost removed at the end of etching;
And a step of removing the palladium film and the remaining platinum film at a selected portion by wet etching using aqua regia. On the substrate, a metal laminated film made of a first metal film having a lowermost layer that is easy to wet-etch and a second metal film having a dry-etching resistance that is difficult to wet-etch in a predetermined shape. Forming, and
Dry etching the substrate using the metal laminate film as an etching mask, wherein the second metal film is substantially removed at the end of etching;
And a step of removing the first metal film and the remaining second metal film of the selected portion by wet etching. A method for manufacturing an element, comprising: A third metal film that is difficult to wet-etch between the first metal film and the second metal film, and the second metal film is completely removed at the end of the etching; 7. The method of manufacturing an element according to claim 6, wherein the metal film of 3 is substantially removed.

Images