JP2006237475A - Process for fabricating semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress increase in threshold voltage of a semiconductor laser having a ridge type resonator. <P>SOLUTION: Entire surface layer 106b of a first metal layer composed of nickel (Ni) is deposited by about 10 nm. An inventive anti-oxidation film S is formed on a second metal layer 106c of gold (Au) having a thickness of about 200 nm and located above a p-type contact layer 105b by lift-off method employing photolithography. The anti-oxidation film S is formed of SiO<SB>2</SB>having a thickness of about 70 nm along the flat stripe top surface Σ of a resonator. Stripe width is about 1,500 nm on the flat top surface Σ of the p-type contact layer 105b. Subsequently, density distribution of nickel (Ni) and gold (Au) is inverted by heat treatment to obtain an inverted distribution. Heat treatment is performed in an ordinary pressure treatment atmosphere of nitrogen 98% and oxygen 2% at a treatment temperature of 550°C with a treatment time of 18 min for example. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for manufacturing a semiconductor laser having a ridge-type resonator formed by stacking Group III nitride compound semiconductors, and particularly relates to an electrode stack structure and a manufacturing method.
The present invention is very useful for suppressing increase in threshold voltage of a semiconductor laser and improving electrode reliability.

JP-A-10-56236 JP-A-9-64337 JP, 9-320984, A As a semiconductor laser which formed an electrode from two metal layers of nickel (Ni) and gold (Au), for example, there is one described in patent documents 1 mentioned above.

  The electrode of the light emitting diode is formed from two metal layers of nickel (Ni) and gold (Au), and these two layers are formed by heat treatment at an appropriate temperature of 400 ° C. or higher and 700 ° C. or lower. In the density distribution in the vertical direction of different metal elements, the vertical relationship of each position where the density of each metal element shows the maximum value can be reversed, thereby forming an electrode with excellent ohmic contact. Examples are disclosed in Patent Document 2 and Patent Document 3 described above. Hereinafter, the density distribution of each metal element obtained as a result of such a reversal phenomenon is referred to as a reversal distribution.

FIGS. 3A and 3B illustrate other forms of semiconductor laser electrode formation in the prior art. This semiconductor laser is of a ridge type, and the electrodes formed on the upper surface of the resonator are formed by depositing two layers of Ni and Au or two layers of Co and Au in order from the semiconductor layer side (FIG. 3). A) Further, these two metal layers are obtained by alloying (FIG. 3-B). By mixing oxygen (O ₂ ) into the processing atmosphere in this alloy process, a Ni or Co oxide film appears on the surface of the electrode, and as a reaction, gold (Au) diffuses and moves downward, and the inversion distribution described above. Occurs.
As can be seen from Patent Document 2 and Patent Document 3 described above, this reversal phenomenon, when an element having a low ionization potential is used in the lower layer, a metal that is more easily oxidized appears on the surface of the electrode to generate an oxide. That's what happens.

Further, as can be seen from the above-mentioned Patent Document 2 and Patent Document 3, it is very important to cause such an inversion phenomenon in order to make the electrode make ohmic contact with the semiconductor satisfactorily. The reason is that Ni or Co is strongly bonded to unwanted matter such as dirt adhered to the surface of the semiconductor before the deposition of Ni or Co, and Ni or Co then removes the unwanted matter upward from the interface. In addition, it is possible to obtain a suitable interface cleaning action between the semiconductor and the electrode. As a result, the gold (Au layer) having good ohmic properties that has been vapor-deposited later diffuses and moves downward, and the Some can penetrate deeply from the surface of the semiconductor layer.
That is, by obtaining the inversion distribution as described above, the electrode can be satisfactorily in ohmic contact with the contact portion of the resonator based on these functions.

  However, for example, when a metal oxide layer is formed on the surface of the electrode as shown in FIG. 3B, the resistance of the electrode is increased by these metal oxide layers (eg, Ni oxide layer, Co oxide layer). As a result, there arises a problem that the threshold voltage when the target semiconductor laser is oscillated is increased.

  The present invention has been made to solve the above-described problems, and an object thereof is to suppress an increase in the threshold voltage of a semiconductor laser having a ridge type resonator.

In order to solve the above problems, the following means are effective.
That is, the first means of the present invention is a method of manufacturing a semiconductor laser having a ridge type resonator formed by laminating a group III nitride compound semiconductor, on one entire surface of an element including the upper surface of the resonator. An insulating film forming step of forming an insulating film, and a first removing step of removing the insulating film on the first contact portion on the upper surface of the resonator where the first electrode is formed to expose the first contact portion; A first metal layer laminating step of laminating a first metal layer mainly made of nickel (Ni) or cobalt (Co) on the first contact portion and the insulating film exposed by the first removing step; A second metal layer laminating step for laminating a second metal layer mainly made of gold (Au) on the first metal layer, and an anti-oxidation film for preventing the surface oxidation action of the first electrode are formed on the first contact portion. An antioxidant film forming step for laminating on the second metal layer, and an acid After the formation of the anti-oxidation film, a heat treatment step for heat-treating the element in a treatment atmosphere containing oxygen and an anti-oxidation film removal step for removing the anti-oxidation film from the first electrode are provided.

  However, at least from the viewpoint of productivity, it is desirable to form the first metal layer and the second metal layer from one kind of metal. However, even if these other metal elements are slightly mixed with other metal elements, there is no particular step difference. For example, the main metal element constituting the second metal layer is gold (Au). The first metal layer may be formed from an alloy of nickel (Ni) and cobalt (Co).

Further, in the first removing step for exposing the first contact portion, the insulating film on the first contact portion may be removed by selective etching, and the insulating film on the first contact portion is lifted off. It may be removed using a method.
Further, another process may be interposed between the insulating film forming process and the first removal process. For example, a step of laminating a Ni layer or a Co layer constituting a part of the first metal layer may be interposed therebetween.

The second means of the present invention is the above-mentioned first means, wherein the ratio r (of the stripe width Δ of the resonator in the first contact portion to the film thickness δ of the second metal layer above the first contact portion r ( (≡Δ / δ) is 1 or more and 30 or less.
However, the range of 5 to 15 is better.

The third means of the present invention is to make the thickness of the antioxidant film 30 nm or more and 300 nm or less in the first or second means.
However, more desirably, it is 50 nm or more and 100 nm or less.

According to a fourth means of the present invention, in any one of the first to third means, the film thickness of the first metal layer above the first contact portion is set in the other part of the first metal layer. Lamination is thinner than the film thickness.
For example, a step of laminating a Ni layer or a Co layer constituting a part of the first metal layer over the entire surface of one side of the element including the upper surface of the resonator is interposed between the insulating film forming step and the first removing step. By doing so, the film thickness of the first metal layer above the first contact portion can be made thinner than the film thickness in other parts of the first metal layer.
By the means of the present invention described above, the above-mentioned problems can be effectively or rationally solved.

The effects obtained by the above-described means of the present invention are as follows.
That is, according to the first means of the present invention, even if the above heat treatment is performed, the antioxidant film prevents the contact between oxygen atoms and Ni or Co. The surface oxidation action of the electrode is suppressed. For this reason, a metal oxide layer is not formed immediately below the antioxidant film. Further, in this heat treatment step, nickel (Ni) or cobalt (Co) constituting the first metal layer diffuses to a region in contact with oxygen atoms, that is, a region not covered with the antioxidant film. Oxidized. As a result, an inversion distribution in the first electrode can be reliably obtained.
Therefore, according to the first means of the present invention, it is possible to obtain a good ohmic contact with the resonator (first contact portion) in the first electrode, and to effectively increase the resistance in the surface layer portion of the first electrode. Therefore, an increase in the threshold voltage of the target semiconductor laser can be effectively suppressed.

Further, according to the second means of the present invention, nickel (Ni) or cobalt (Co) constituting the first metal layer is likely to have an oxidizing action such as the periphery outside in the horizontal direction of the antioxidant film. When diffusing into a region, the diffusion path becomes shorter and a wide diffusion path is secured, so that the time required for the diffusion process can be shortened and the diffusion action can be obtained sufficiently and reliably. it can.
Therefore, according to the second means of the present invention, the above heat treatment step can be carried out efficiently and reliably.

  However, the value of the ratio r (≡Δ / δ) is more preferably in the range of 5-15. If this value is too large, the above-mentioned diffusion path becomes unnecessarily long, or a wide diffusion path cannot be secured. If this value is too small, the necessary resonator stripe width cannot be secured sufficiently, or the second metal layer must be laminated much thicker than necessary, which is undesirable in either case.

  In addition, according to the third means of the present invention, the portion above the first contact portion of the first electrode and the heat treatment atmosphere can be well separated so as not to contact each other in the heat treatment step. It is possible to reliably prevent oxidation due to heat treatment of the metal. However, the film thickness of the antioxidant film is more preferably 50 nm or more and 100 nm or less. If this thickness is too thin, it may not be possible to obtain a sufficient antioxidant effect depending on the material. On the other hand, if this thickness is too thick, it takes more time than necessary to stack and remove the antioxidant film, which is undesirable in either case.

According to the fourth means of the present invention, the amount of atoms (Ni or Co) constituting the first metal layer in the lower region of the antioxidant film is not covered by the antioxidant film (hereinafter referred to as the other region). This region is referred to as a peripheral region), and is relatively smaller than the amount of Ni or Co in the region, so that the region (Ni or Co) constituting the first metal layer is formed in the region below the antioxidant film. Is completed relatively earlier than the diffusion in the vertical direction of atoms (Ni or Co) constituting the first metal layer in the peripheral region. Therefore, when the diffusion of Ni or Co in the lower region of the antioxidant film into the peripheral region is completed, atoms (Ni or Co) constituting the first metal layer still remain on the insulating film in the peripheral region. It will be in the state.
Therefore, the metal layer that is in direct contact with the insulating film is not an Au layer, but a Ni layer or a Co layer that has good adhesion to the insulating film, thereby ensuring good adhesion between the insulating film and the first electrode.
Therefore, according to the fourth means of the present invention, the first electrode can be reliably fixed to the resonator.

  In addition, as for the film thickness at the time of laminating | stacking said 1st metal layer in this invention, the range of 5-10 nm is desirable. If this thickness is too thick, it takes too much time for the atoms (Ni or Co) constituting the first metal layer to diffuse on the first contact portion and be oxidized near the exposed surface of the first electrode. It is not desirable. On the other hand, if the thickness is too thin, the above-described interface cleaning action in the first contact portion tends to be insufficient, which is not desirable.

The antioxidant film is preferably formed of an insulating film having heat resistance against the heat treatment. In addition to silicon dioxide (SiO ₂ ), these materials include, for example, alumina (Al ₂ O ₃ ), zinc oxide (ZnO), beryllia (BeO), silicon nitride (Si _x N _y ), aluminum nitride ( AlN), boron nitride (BN), or the like can be used. If these materials are used, it is possible to surely prevent an undesirable chemical or physical interaction between the antioxidant film and the first electrode in the heat treatment step. Removal processing and the like can be easily performed.
In addition, an appropriate temperature range in the heat treatment process is about 500 ° C to 600 ° C.

  Further, it is desirable that the film thickness δ of the second metal layer above the first contact portion is laminated to be larger than the film thickness of the second metal layer on the side wall surface extending in the stripe direction of the ridge forming the resonator. . For example, the deposition is performed by making the inclination angle of the side wall extending in the stripe direction of the ridge portion forming the resonator steep and flying gold (Au) in a direction substantially perpendicular to the entire surface of one side of the element including the upper surface of the resonator. Then, the film thickness δ of the second metal layer above the first contact portion can be laminated thicker than the film thickness of the second metal layer on the side wall surface of the ridge portion. According to this method, the above-mentioned film thickness δ becomes relatively large, and a wide diffusion path is ensured immediately below the antioxidant film of the atoms (Ni or Co) constituting the first metal layer. Since the first metal layer on the side wall surface is relatively close to the processing atmosphere, the oxidizing action of the first metal layer in that portion starts relatively early. By this action, the diffusion of atoms (Ni or Co) constituting the first metal layer from the first contact portion to the peripheral region efficiently progresses, so that the productivity of the semiconductor laser is improved.

Hereinafter, the present invention will be described based on specific examples.
However, the embodiments of the present invention are not limited to the following examples.

FIG. 1 shows a cross-sectional view of a semiconductor laser 10 according to the first embodiment. This semiconductor laser is a ridge type, and its p-electrode 106 (first electrode) was obtained by alloying a metal layer laminated by vapor deposition. This semiconductor laser 10 is a semiconductor chip 100 having the following structure, which is fixed upside down on a submount 13 with solder 11 as shown in FIG. is there.
In other words, the semiconductor chip 100 includes a buffer layer 102, an n-type semiconductor layer 103, an active layer 104, a p-type cladding layer 105a, and a p-type cladding layer 105a formed on a crystal growth surface of a sapphire substrate 101 by crystal growth of a group III nitride compound semiconductor. A p-type contact layer 105b is sequentially stacked, and then a ridge or the like is formed by etching, and then an n-electrode 107, an insulating film 110, and a p-electrode 106 are sequentially formed in this order.

Hereinafter, the structure of the semiconductor chip 100 will be described in detail by returning the vertical relationship in the stacked structure of the semiconductor layers to the original state (reverse to FIG. 1), that is, returning to the vertical relationship at the time of crystal growth. A buffer layer 102 made of aluminum nitride (AlN) is stacked on the sapphire substrate 101. Further thereon, a high carrier concentration n ⁺ layer 103a made of silicon (Si) -doped GaN, an intermediate layer 103b made of non-doped In _0.03 Ga _0.97 N, an n-type cladding layer 103c made of AlGaN, and an n-type layer made of GaN. An n-type semiconductor layer 103 composed of a total of four layers is formed in the order of the type light guide layer 103d.

Further thereon, an active layer 104 having a multiple quantum well (MQW) structure found in a known edge-emitting laser diode is formed.
Immediately above the active layer 104 is a p-type light guide layer 108 made of magnesium (Mg) -doped GaN and a p-type clad layer 105a made of p-type Al _0.12 Ga _0.88 N. P-type contact layers 105b made of p-type Al _0.05 Ga _0.95 N are sequentially stacked.

The high carrier concentration n ⁺ layer 103a of the n-type semiconductor layer 103 is exposed by etching from the upper side (p-type semiconductor layer side) in parallel with the resonance direction of the resonator (ridge). By this etching, a flat ridge (resonator portion) standing substantially perpendicular to the substrate is formed. A negative electrode 107 made of vanadium and aluminum (V / Al) is formed by vapor deposition on the exposed portion of the high carrier concentration n ⁺ layer 103a of the n-type semiconductor layer 103. In addition, on both sides of the resonator, insulating walls 110 made of SiO ₂ having a refractive index of about 1.5 are formed by CVD. The insulating wall 110 is formed in close contact over substantially the entire resonator side wall.

The semiconductor chip 100 having the above structure is fixed to the submount 13 by a junction down system in which the electrode forming portion is mounted downward (FIG. 1). The submount 13 includes a copper substrate 14, an electrical insulating member 15, and lead electrodes 16 </ b> A and 16 </ b> B. ing. Lead electrodes 16A and 16B made of gold (Au) are laminated on the upper surface of the insulating member 15 at two left and right positions in the drawing. The n electrode 107 and the p electrode 106 are fixed to the lead electrodes 16A and 16B, respectively, using a solder 11 made of gold (Au) or Au / Sn having excellent thermal conductivity.
Reference numeral w denotes a power supply wire, and these wires w are also connected to the corresponding lead electrodes 16A and 16B, respectively.

Hereinafter, the detailed structure and the preparation procedure of the p-electrode 106 will be described with reference to FIGS. 2A to F illustrate an example of a procedure for forming the p-electrode 106 of the semiconductor laser 10 in FIG. As shown in FIG. 2A, the p-type cladding layer 105a and the p-type contact layer 105b are etched by reactive dry etching to form a ridge having a height of about 400 nm, and then the insulating film 110 made of SiO ₂ is formed by CVD. Further, nickel (Ni) is vapor-deposited on the insulating film 110 to a thickness of about 100 nm, so that a part of the first metal layer (: lower part of the region excluding the upper part of the resonator) The border layer 106a is formed. Thereafter, the edge layer 106a is referred to as an edge layer because the part located at the upper part of the resonator is removed and only the parts around both sides of the resonator are left.

  In this way, by laminating the insulating film 110 over the entire surface of one side of the semiconductor chip 100, the laminated area of the first electrode 106 can be expanded, thereby increasing the vapor deposition area of the first electrode 106. As a result, the first electrode 106 is difficult to peel off. In addition, since the resonator is covered with the metal layer constituting the first electrode 106 with the insulating film 110 interposed therebetween, the heat radiation effect from the resonator is also increased. Furthermore, if the refractive index of the insulating film 110 is appropriately selected, the optical confinement effect of the resonator is also improved.

After the first metal layer border layer 106a is stacked, each part of the insulating film 110 and the first metal layer border layer 106a located above the flat top surface Σ of the contact portion of the resonator is wet-etched or dry-etched. It is removed by etching (FIG. 2-B). The etching procedure may be as follows.
(A) A photoresist is uniformly applied to the junction side.
(B) Next, a window is opened in a target etching target region (contact portion of the resonator) on the photoresist by photolithography.
(C) Next, wet etching or dry etching is performed on the junction side with a gas containing chlorine. As a result, the photoresist becomes a resist mask, and the portion exposed from the window is selectively etched. At this time, in order to surely remove the insulating film 110 from the flat top surface Σ, the p-type is formed so that the flat top surface Σ of FIG. 2-B is slightly lower than the flat top surface Σ of FIG. The upper surface of the contact layer 105b may be slightly shaved.
(D) Finally, the photoresist is removed.

After obtaining the state shown in FIG. 2B by the etching process described above, an entire surface layer 106b of a first metal layer made of nickel (Ni) is deposited on the junction side to a thickness of about 10 nm. As a result, the entire surface layer 106b of the first metal layer made of the same kind of metal (Ni) and the border layer 106a are integrated, and as a result, a series of one Ni layer is formed. This integrated Ni layer corresponds to the first metal layer of the present invention. At this time, at the interface between the first metal layer (the composite of the border layer 106a and the entire surface layer 106b) and the p-type contact layer 105b, nickel (Ni) constituting the first metal layer is converted into the p-type contact layer 105b. It strongly binds to unnecessary objects such as dirt on the surface.
Thereafter, a second metal layer 106c made of gold (Au) is deposited to a thickness of about 200 nm by vapor deposition (FIG. 2-C).

Next, as shown in FIG. 2-D, the antioxidant film S of the present invention is sputtered on the second metal layer 106c located above the p-type contact layer 105b according to the lift-off method using photolithography. Formed by. The antioxidant film S is formed of SiO ₂ having a thickness of about 70 nm, and is formed along the stripe-shaped flat top surface Σ of the resonator. The stripe width on the flat top surface Σ of the p-type contact layer 105b is about 1500 nm.

Thereafter, the semiconductor chip 100 was heat-treated under the following conditions.
(1) Temperature of processing atmosphere: 550 ° C
(2) Pressure of treatment atmosphere: normal pressure (3) Volume ratio of treatment atmosphere: Nitrogen (N ₂ ) 98%, Oxygen (O ₂ ) 2%
(4) Heat treatment time: 25 minutes

  By this heat treatment, an inversion distribution of the metal elements (Ni and Au) constituting the first electrode is obtained as shown in FIG. FIG. 2-E shows the p-electrode after the reversal of the density distribution of the metal element of the first electrode composed of the entire surface layer 106b, the border layer 106a, and the second metal layer 106c constituting the first metal layer is completed. A cross-sectional view of 106 is shown.

In this heat treatment step, nickel (Ni) forming the nickel layer in FIG. 2-D (the upper surface of the entire surface layer 106b and the border layer 106a) acts as follows with oxygen (O ₂ ) in the heat treatment atmosphere. Thus, a metal oxide layer (Ni oxide layer 106d) is formed on the surface of the p-electrode 106.

  For example, in a region that is not covered with the antioxidant film S, first, a region in which nickel (Ni) of the entire surface layer 106b constituting the first metal layer can come into contact with oxygen atoms contained in the heat treatment atmosphere, That is, it is thermally diffused upward and is oxidized there to form the Ni oxide layer 106d. Thereafter, when these reactions (thermal diffusion and oxidation) further progress and the entire surface layer 106b in the region not covered with the antioxidant film S is thermally diffused upward, it is not covered with the antioxidant film S. In the region, the nickel (Ni) constituting the border layer 106a under the entire surface layer 106b is thermally diffused up to the region that can come into contact with the oxygen atoms contained in the heat treatment atmosphere, that is, the oxidation. Then, the Ni oxide layer 106d is enlarged.

On the other hand, in the region immediately below the antioxidant film S, the nickel (Ni) of the entire surface layer 106b constituting the first metal layer on the first contact portion can be in contact with oxygen atoms contained in the heat treatment atmosphere, That is, thermal diffusion is performed to a place not covered with the antioxidant film S, where it is oxidized to form the oxidized Ni layer 106d.
At this time, unnecessary matter strongly bonded to Ni at the interface Σ (FIG. 2D) on the first contact portion of the p-type contact layer 105b is taken away together with Ni, so that the interface on the first contact portion is thereby removed. In Σ, an interface cleaning action is obtained.

  However, as can be seen from Patent Document 2 and Patent Document 3 described above, this inversion phenomenon is caused by the density distribution of each metal element in the depth direction based on the movement (thermal diffusion) of each metal element (Ni, Au). The peak positions are interchanged with each other, and the stacking order of the metal layers is not completely replaced with a layer unit. Therefore, in practice, the boundary surfaces between the metal layers are not clearly formed after the heat treatment.

Finally, as shown in FIG. 2F, the antioxidant film S made of SiO ₂ is removed by wet etching.
At least a part of the edge layer 106a of the first metal layer in FIG. 2E remains on the insulating film 110 even after the heat treatment step, and becomes a part in close contact with the insulating film 110, but constitutes the remaining part. The Ni layer corresponds to the adhesion layer 106a ′ in FIG. That is, the adhesion layer 106a 'is formed of a Ni layer in which a part of the edge layer 106a of the first metal layer made of nickel (Ni) remains in its original position without being diffused even after heat treatment. The ohmic contact layer 106c ′ is an Au layer formed by rearranging the second metal layer 106c (FIG. 2-D) made of gold (Au) by diffusing and moving downward by heat treatment. A part of the Au element penetrates deeply downward from the upper surface (first contact portion of the resonator) of the p-type contact layer 105b subjected to the interface cleaning action by this heat treatment. For this reason, the p-type contact layer 105b and the p-electrode 106 show good ohmic contact.

  Therefore, by such a structure of the p-electrode 106 and the preparation procedure, a good ohmic contact between the p-electrode and the semiconductor on the ridge (first contact portion of the resonator), and the first electrode near the first contact portion. The effect of reducing the resistance of the surface layer portion can be secured at the same time. Therefore, the threshold voltage of the semiconductor laser having the first electrode manufactured in this way can be made lower than that of the conventional one.

  In addition, since the adhesion layer 106a ′ made of Ni is strongly adhered to the insulating film 110, the p-electrode 106 made of the adhesion layer 106a ′, the ohmic contact layer 106c ′, and the Ni oxide layer 106d is separated from the resonator. The first contact portion of the resonator can be securely fixed without being peeled off.

[Other variations]
The embodiment of the present invention is not limited to the above-described embodiment, and other modifications as exemplified below may be made. Even with such modifications and applications, the effects of the present invention can be obtained based on the functions of the present invention.

For example, in Example 1 described above, the first metal layer (106a, 106b) has a two-layer structure through a plurality of laminating processes. However, in general, the first metal layer has only one deposition process (lamination process). May be laminated. Even in such a configuration, with respect to the threshold voltage of the semiconductor laser, it is possible to obtain substantially the same operation and effect as in the first embodiment.
In the first embodiment, the first metal layer (106a, 106b) is formed from nickel (Ni). However, the first metal layer may be formed from cobalt (Co). Also in this case, substantially the same operation and effect as in the first embodiment can be obtained.

In the first embodiment, the first electrode formed on the ridge is a p-electrode. However, the first electrode formed on the first contact portion on the upper surface of the resonator may be an n-electrode. . In the case where the semiconductor forming the semiconductor layer that provides the upper surface of the resonator is n-type, such a configuration can also be adopted.
The first electrode formed on the top of the ridge (first contact portion) may be supplied with power by wire bonding.
In the first embodiment, the ridge type edge emitting semiconductor laser is exemplified. However, the present invention can be similarly applied to a surface emitting semiconductor laser.

Sectional view of the semiconductor laser 10 of the first embodiment. Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of p electrode of semiconductor laser 10 Sectional drawing which illustrates the preparation procedure of the p electrode of the conventional semiconductor laser Sectional drawing which illustrates the preparation procedure of the p electrode of the conventional semiconductor laser

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Semiconductor laser 100: Semiconductor chip 101: Sapphire substrate 102: Buffer layer 103: N-type semiconductor layer 104: Active layer 105a: P-type clad layer 105b: P-type contact layer 106: P electrode 106a: Edge of 1st metal layer Layer 106a ′: Adhesion layer 106b: Full surface layer of first metal layer (becomes a metal oxide layer)
106c: Second metal layer (becomes ohmic contact layer)
106c ': Ohmic contact layer 106d: Ni oxide layer (corresponding to metal oxide layer)
107: n-electrode 110: insulating film 11: solder 13: submount 14: copper substrate 15: insulating member 16B: lead electrode w: wire

Claims (4)

In a method of manufacturing a semiconductor laser having a ridge type resonator formed by stacking group III nitride compound semiconductors,
An insulating film forming step of forming an insulating film on the entire surface of one side of the element including the upper surface of the resonator;
A first removing step of exposing the first contact part by removing the insulating film on the first contact part on the upper surface of the resonator on which the first electrode is formed;
A first metal layer laminating step of laminating a first metal layer mainly made of nickel (Ni) or cobalt (Co) on the first contact portion and the insulating film exposed by the first removing step. When,
A second metal layer laminating step of laminating a second metal layer mainly made of gold (Au) on the first metal layer;
An anti-oxidation film forming step of laminating an anti-oxidation film for preventing surface oxidation of the first electrode on the second metal layer on the first contact portion;
A heat treatment step of heat-treating the element in a treatment atmosphere containing oxygen after the formation of the antioxidant film;
A method for manufacturing a semiconductor laser, comprising: an antioxidant film removing step of removing the antioxidant film from the first electrode. The ratio r (≡Δ / δ) of the stripe width Δ of the resonator in the first contact portion to the film thickness δ of the second metal layer above the first contact portion is:
2. The method of manufacturing a semiconductor laser according to claim 1, wherein the method is 1 or more and 30 or less. The film thickness of the antioxidant film is
3. The method of manufacturing a semiconductor laser according to claim 1, wherein the semiconductor laser has a thickness of 30 nm to 300 nm. The thickness of the said 1st metal layer above the said 1st contact part is laminated | stacked thinner than the film thickness in the other part of the said 1st metal layer, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. A method for producing a semiconductor laser according to the item.