JP2003174228A - Method for manufacturing nitride semiconductor laser device and nitride semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a nitride semiconductor laser device capable of improving a yield, and obtaining the nitride semiconductor laser device having good device characteristics. <P>SOLUTION: The method for manufacturing the nitride semiconductor laser device comprises the step of forming the nitride semiconductor device layer having an n-type AlGaN clad layer 5, an NQW active layer 7 and a p-type AlGaN clad layer 11 on a substrate, the step of forming a recess 23 in which at least the p-type AlGaN clad layer 11 and the MQW active layer 7 are removed on a region except the device forming region (protrusion) 30 and forming a device forming region (protrusion) 30 having a different width in a direction perpendicular to the end face of a resonator, and the step of forming a stripe- like ridge 15 on the element forming region (protrusion) 30. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nitride-based semiconductor laser device and a nitride-based semiconductor laser device, and more specifically to a nitride in which a nitride-based semiconductor layer is grown on a substrate. The present invention relates to a method for manufacturing a semiconductor laser diode device and a nitride semiconductor laser device.

[0002]

2. Description of the Related Art In recent years, nitride semiconductor laser devices are expected to be used as a light source for next-generation large-capacity disks,
Its development is being actively conducted.

Conventionally, when forming a nitride-based semiconductor laser device, it is difficult to manufacture a substrate made of a nitride semiconductor (GaN). Therefore, normally, a substrate made of sapphire, SiC, Si or the like is nitrided. The semiconductor layer is grown.

FIG. 18 is a plan view showing a state of a conventional nitride-based semiconductor laser device before a device isolation process. Figure 1
9 is a sectional view taken along the line 250-250 of the conventional nitride-based semiconductor laser device shown in FIG. Also, FIG.
0 is a sectional view taken along the cleavage line 122 of the conventional nitride-based semiconductor laser device shown in FIG.

First, referring to FIGS. 18 to 20, the structure of a conventional nitride-based semiconductor laser device before the device isolation step will be described. In this conventional nitride-based semiconductor laser device, as shown in FIG. 19, on a sapphire substrate 101,
AlGaN buffer layer 102, undoped GaN layer 10
3, n-type GaN contact layer 104, n-type AlGaN cladding layer 105, n-type GaN light guide layer 106, InG
MQW active layer 107 made of aN, undoped AlGa
N cap layer 108, p-type AlGaN optical guide layer 10
9, the p-type GaN light guide layer 110, and the p-type AlGaN cladding layer 111 including the convex portion are formed in this order. A p-type GaN contact layer 112 is formed on the convex portion of the p-type AlGaN cladding layer 111. A convex portion of the p-type AlGaN cladding layer 111,
The p-type GaN contact layer 112 forms a stripe-shaped ridge portion 115. In addition, p-type Al
From GaN cladding layer 111 to n-type GaN contact layer 1
By removing a partial region of 04, n-type GaN
The mesa-etched portion 1 in which the upper surface of the contact layer 104 is exposed
16 are formed. In addition, the n-type GaN contact layer 1 is formed in a region other than the upper surface of the p-type GaN contact layer 112.
A protective film 117 made of a silicon oxide film having an opening is formed on the upper surface of 04. In addition, the p-side electrode 11 is contacted with the upper surface of the p-type GaN contact layer 112.
3 is formed. Then, in the opening of the protective film 117, the n-side electrode 114 is formed so as to come into contact with the upper surface of the n-type GaN contact layer 104.

Next, a manufacturing process of the conventional nitride-based semiconductor laser device shown in FIGS. 18 to 20 will be described.

First, as shown in FIGS. 19 and 20,
On the sapphire substrate 101, a MOCVD method is used.
lGaN buffer layer 102, undoped GaN layer 10
3, Si-doped n-type GaN contact layer 104,
Si-doped n-type AlGaN cladding layer 105, S
i-doped n-type GaN optical guide layer 106, InGa
Multiple quantum wells (MQW; Multiple)
MQW active layer 107 having a Quantum Well structure, undoped AlGaN cap layer 108, Mg
A p-type AlGaN light guide layer 109 doped with Mg, a p-type GaN light guide layer 110 doped with Mg, a p-type AlGaN cladding layer 111 doped with Mg, and a p-type GaN contact layer 112 doped with Mg are sequentially formed. .

After that, the p-type GaN contact layer 112 is formed by using the photolithography technique and the etching technique.
From this, a partial region of the n-type GaN contact layer 104 is etched. Thereby, the n-type GaN contact layer 104
And exposes a partial area of the
To form.

Next, the p-type GaN contact layer 112 is formed by using the photolithography technique and the etching technique.
And a part of the p-type AlGaN cladding layer 111 are etched. Thereby, the ridge portion 115 is formed. After that, a protective film 117 made of a silicon oxide film having an opening on the upper surface of the n-type GaN contact layer 104 is formed in a region other than the upper surface of the p-type GaN contact layer 112.

Next, a p-side electrode 113 is formed so as to contact the p-type GaN contact layer 112. Further, in the opening of the protective film 117, the n-type GaN contact layer 104
The n-side electrode 114 is formed so as to contact the upper surface of the.
As a result, the structure as shown in FIG. 19 is formed on the sapphire substrate 101.

Finally, the back surface of the sapphire substrate 101 is polished so that the sapphire substrate 101 has a predetermined thickness. Then, by cleaving along the cleavage line 122 shown in FIG. 18, an end face of the cavity of the nitride-based semiconductor laser device is formed, and by dicing along the dicing line 121, element isolation is performed. Thus, the conventional nitride-based semiconductor laser device is formed.

[0012]

However, in the above-described method of crystal-growing each layer 102-112 made of a nitride-based semiconductor on the sapphire substrate 101, each layer 101-112 made of a nitride-based semiconductor is usually formed by crystal growth. , Grown at high temperature. In this case, when the nitride-based semiconductor layer is formed on the sapphire substrate 101 at a high temperature and then the substrate temperature is lowered to room temperature, it is caused by a difference in thermal expansion coefficient between the sapphire substrate 101 and the nitride-based semiconductor layer. Internal stress is generated between the sapphire substrate 101 and the nitride-based semiconductor layer. Therefore, there is an inconvenience that a large warp occurs on the entire substrate. In such a state in which a large warp occurs, the lithography process, the resonator manufacturing process (cleavage process), the device isolation process, and the like during device formation cannot be performed well, and as a result, the nitride-based semiconductor laser device There is a problem that the yield and the device characteristics are deteriorated.

Therefore, conventionally, in order to satisfactorily form the cavity end face of a nitride-based semiconductor laser device by using cleavage, a split groove having a depth that does not reach the active layer is formed on the surface of the nitride-based semiconductor after device formation. It has been proposed to form a split groove on the side of the sapphire substrate that faces the substrate and to perform cleavage at the time of cleavage by using the split groove as a trigger. They are,
For example, it is disclosed in JP-A-8-222807.

However, also in the method of cleaving the nitride-based semiconductor laser device triggered by the split groove, as in the conventional structure shown in FIGS. 18 to 20, the heat of the sapphire substrate and the nitride-based semiconductor layer is removed. Since it is difficult to relieve the internal stress that occurs due to the difference in expansion coefficient, it is difficult to reduce the warpage of the entire substrate. Therefore, it is difficult to obtain a good resonator end face.

The present invention has been made to solve the above problems, and one object of the present invention is to:
It is an object of the present invention to provide a method for manufacturing a nitride-based semiconductor laser device capable of forming a nitride-based semiconductor laser device having good device characteristics while improving yield by reducing the warp of the substrate.

Another object of the present invention is to obtain a good cavity facet by cleavage in the above method for manufacturing a nitride semiconductor laser device.

Still another object of the present invention is to provide a nitride-based semiconductor laser device capable of improving yield and obtaining good device characteristics.

[0018]

According to a first aspect of the present invention, there is provided a method for manufacturing a nitride-based semiconductor laser device, comprising: a first conductivity type first clad layer; an active layer formed on the first clad layer; A step of forming a nitride-based semiconductor device layer including a second conductivity type second clad layer thereon, and forming a recess in which at least the second clad layer and the active layer are removed in a region other than the device formation region. In addition, the method further includes a step of forming convex portions having different widths in a direction perpendicular to the cavity end face in the element forming region, and a step of forming a stripe-shaped ridge portion in the element forming region.

In the method for manufacturing a nitride-based semiconductor laser device according to the first aspect of the present invention, as described above, the recess in which at least the second cladding layer and the active layer are removed is formed in the region other than the device forming region. Thus, the stress generated due to the difference in thermal expansion coefficient between the substrate and the nitride-based semiconductor element layer can be relieved, so that the warp of the substrate can be effectively reduced. As a result, it is possible to perform a lithographic step, a resonator manufacturing step, an element isolation step, and the like during element formation while reducing the warp of the substrate, so that it is possible to improve the yield and to have good element characteristics. It is possible to form a nitride-based semiconductor laser device. Further, by forming the convex portions having different widths in the direction perpendicular to the resonator end face, for example, if the width of the resonator end face is made smaller than the width of other portions, the resonator end face is formed. Since the area of the portion to be cleaved at the time of cleavage is small, the cleavage can be performed well. As a result, a good resonator end face can be obtained.

In the method for manufacturing a nitride-based semiconductor laser device according to the first aspect, preferably, the width of the convex portion in the vicinity of the cavity end face is smaller than that of the other portion of the convex portion. According to this structure, the area of the cleaved portion at the time of cleaving when forming the resonator end face is small, so that the cleaving can be favorably performed. As a result, a good resonator end face can be obtained.

In the above-described method for manufacturing a nitride-based semiconductor laser device, preferably, the step of forming the concave portion includes the step of forming the concave portion so as to surround the periphery of the convex portion other than the vicinity of the cavity end face. According to this structure, the stress generated due to the difference in the coefficient of thermal expansion between the substrate and the nitride-based semiconductor element layer can be more relaxed, so that the warp of the substrate can be more effectively reduced. .

In the above method of manufacturing a nitride semiconductor laser device, preferably, the step of forming the recess includes the step of forming the recess so that the substrate is exposed. According to this structure, the nitride-based semiconductor element layer in the recess is completely removed, so that the stress generated between the substrate and the nitride-based semiconductor element layer can be further relaxed.

A nitride-based semiconductor laser device according to a second aspect of the present invention is a first-conductivity-type first laser device formed on a substrate.
A clad layer, an active layer formed on the first clad layer, a second clad layer of the second conductivity type formed on the active layer, a striped ridge portion, and a region other than the element formation region And at least the second clad layer and the active layer are removed, and a convex portion formed in the element formation region and having a different width in the direction perpendicular to the cavity facets.

In the nitride-based semiconductor laser device according to the second aspect, as described above, by forming the recess in which at least the second cladding layer and the active layer are removed in the region other than the device forming region, the substrate Since the stress generated due to the difference in thermal expansion coefficient between the nitride-based semiconductor element layer and the nitride-based semiconductor element layer can be relaxed, the warp of the substrate can be effectively reduced. As a result, in a state where the warp of the substrate is reduced, a lithography process and a resonator manufacturing process at the time of element formation,
Since the element isolation process and the like can be performed, the yield can be improved, and a nitride-based semiconductor laser element having good element characteristics can be formed. Further, by forming the convex portions having different widths in the direction perpendicular to the cavity end face, for example,
If the width of the resonator end face is made smaller than the width of the other part, the area of the part to be cleaved at the time of cleavage when forming the resonator end face becomes smaller, and thus the cleavage can be favorably performed. As a result, a good resonator end face can be obtained.

In the nitride-based semiconductor laser device according to the second aspect, preferably, the width of the convex portion near the cavity end face is smaller than that of the other portion of the convex portion. According to this structure, the area of the cleaved portion at the time of cleaving when forming the resonator end face is small, so that the cleaving can be favorably performed. As a result, a good resonator end face can be obtained.

In the method for manufacturing a nitride-based semiconductor laser device according to the first aspect, the width of the convex portion near the cavity facet may be 5 times or more and 7 times or less the width of the ridge portion.
According to this structure, the cleavage can be satisfactorily performed.

In the method for manufacturing a nitride-based semiconductor laser device according to the first aspect, the maximum width of the protrusion may be smaller than the width of the substrate.

The method for manufacturing a nitride-based semiconductor laser device according to the first aspect may further include the step of forming the cavity facet by cleavage.

In the method for manufacturing a nitride-based semiconductor laser device according to the first aspect, a first conductivity type first clad layer, an active layer, and a second conductivity type second clad layer are sequentially formed on a substrate. Prior to the forming step, a step of forming a low defect layer on the substrate may be further provided.

The step of forming the low defect layer may include a step of forming the first nitride semiconductor layer by selective lateral growth.

In the nitride semiconductor laser device according to the second aspect, the width of the convex portion near the cavity end face is
It may be 5 to 7 times the width of the ridge portion. With this configuration, the cleavage can be easily performed.

In the nitride semiconductor laser device according to the second aspect, the maximum width of the protrusion may be smaller than the width of the substrate.

In the nitride-based semiconductor laser device according to the second aspect, the recess may be formed so as to surround the periphery of the projection other than the vicinity of the cavity end face. According to this structure, the stress generated due to the difference in the coefficient of thermal expansion between the substrate and the nitride-based semiconductor element layer can be more relaxed, so that the warp of the substrate can be more effectively reduced. .

In the nitride semiconductor laser device according to the second aspect, the recess may be formed so that the substrate is exposed. According to this structure, the nitride-based semiconductor element layer in the recess is completely removed, so that the stress generated between the substrate and the nitride-based semiconductor element layer can be further relaxed.

In the nitride semiconductor laser device according to the second aspect, the cavity end face may be formed by cleavage.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a plan view showing a state before a device isolation process of a nitride semiconductor laser device according to a first embodiment of the present invention. 2 is a sectional view taken along the line 100-100 of the nitride-based semiconductor laser device according to the first embodiment shown in FIG. Also, FIG.
FIG. 3 is a sectional view taken along the cleavage line 22b of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

First, the structure of the nitride-based semiconductor laser device according to the first embodiment before the device isolation step will be described with reference to FIGS. In the first embodiment, as shown in FIG. 2, on an sapphire substrate 1, an AlGaN buffer layer 2, an undoped GaN layer 3, an n-type GaN contact layer 4, an n-type AlGaN cladding layer 5, and an n-type GaN light guide layer. 6, MQW active layer 7 made of InGaN, undoped AlGaN cap layer 8, p-type AlGaN light guide layer 9, p-type GaN light guide layer 10, and p-type AlGaN cladding layer 11 including a convex portion are formed in this order. Has been done. On the convex portion of the p-type AlGaN cladding layer 11,
A p-type GaN contact layer 12 is formed. This p
Of the stripe-shaped ridge portion 1 by the convex portion of the AlGaN cladding layer 11 and the p-type GaN contact layer 12.
5 are configured.

Further, by removing a partial region of the n-type GaN contact layer 4 from the p-type AlGaN cladding layer 11, a mesa-etched portion 16 in which the upper surface of the n-type GaN contact layer 4 is exposed is formed. In addition, p-type Ga
A protective film 17 made of a silicon oxide film having an opening is formed on the upper surface of the n-type GaN contact layer 4 in a region other than the upper surface of the N contact layer 12. In addition, p-type Ga
A p-side electrode 13 is formed so as to contact the upper surface of the N contact layer 12. Then, in the opening of the protective film 17, the n-side electrode 14 is formed so as to come into contact with the upper surface of the n-type GaN contact layer 4.

The n-type AlGaN cladding layer 5 is an example of the "first cladding layer" in the present invention, and the MQW active layer 7 is an example of the "active layer" in the present invention. Also, p-type A
The lGaN cladding layer 11 is an example of the “second cladding layer” in the present invention.

Here, in the nitride-based semiconductor laser device of the first embodiment, as shown in FIGS.
And element formation region (projection) 3 including the mesa-etched portion 16
A recess 23 is formed so as to surround 0. The recess 23 is formed so that the surface of the sapphire substrate 1 is exposed. That is, in the recess 23, the layers 2 to 12 made of the nitride-based semiconductor are completely removed. Also,
The concave portion 23 is formed so as to enter the one resonator end face portion 30b of the element forming region (convex portion) 30. Therefore, the width of one resonator end face portion 30b of the element forming region (convex portion) 30 is smaller than the width of the other portion of the element forming region (convex portion) 30. The width of the other resonator end face portion 30a of the element forming region (convex portion) 30 is the same as the width of the other portion of the element forming region (convex portion) 30.

Specifically, one resonator end face portion 30b
In the above, it is formed so as to have a width of about 10 μm in the range of about 100 μm from the resonator end face in the stripe direction. The width of the resonator end face portion 30b is preferably about 5 to about 7 times the width of the ridge portion 15. Further, the other portion of the element forming region (convex portion) 30 is formed to have a width of about 200 μm.

In the nitride-based semiconductor laser device of the first embodiment, as described above, by forming the recess 23 reaching the sapphire substrate 1 so as to surround the device forming region (projection) 30, the sapphire substrate 1 and The stress generated due to the difference in thermal expansion coefficient between each of the layers 2 to 12 made of a nitride semiconductor can be relaxed. Thereby, the warp of the substrate can be effectively reduced. As a result, in the manufacturing process described later, the lithographic step and the element separating step (cleaving step) at the time of forming the element can be performed with the warpage of the sapphire substrate 1 reduced.
It is possible to form a nitride-based semiconductor laser device having good cavity facets and device characteristics.

Further, by forming the concave portion 23 so that the width of one resonator end face portion 30b is smaller than the width of the other portion, the area of the cleaved portion can be reduced at the time of cleavage. Better cleavage can be performed. As a result, it becomes possible to obtain a better resonator end face.

FIGS. 4 to 7 are sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIGS. The manufacturing process of the nitride-based semiconductor laser device of the first embodiment will be described below with reference to FIGS. Here, the manufacturing process in the cross section shown in FIG. 2 (cross section taken along the line 100-100 in FIG. 1) will be described.

First, as shown in FIG. 4, the AlGaN buffer layer 2, the undoped GaN layer 3, and the Si-doped n-type Ga are formed on the sapphire substrate 1 by the MOCVD method.
N contact layer 4, Si-doped n-type AlGaN cladding layer 5, Si-doped n-type GaN optical guide layer 6, InGaN MQW active layer 7, undoped A
lGaN cap layer 8, Mg-doped p-type AlGa
N light guide layer 9, Mg-doped p-type GaN light guide layer 10, Mg-doped p-type AlGaN cladding layer 1
1 and the p-type GaN contact layer 12 doped with Mg are sequentially formed.

Next, in the manufacturing process of the first embodiment, as shown in FIGS. 1 and 5, the element formation region (convex portion) of the nitride-based semiconductor laser device is formed by using the photolithography technique and the etching technique. The recess 23 is formed so that the sapphire substrate 1 is exposed by etching a region other than 30 and one resonator end face portion 30b. The etching at the time of forming the recess 23 is such that, in one resonator end face portion 30b (see FIG. 1), a width of about 10 μm is left in the range of about 100 μm from the resonator end face in the stripe direction, and an element forming region (convex portion) is formed. In the other portion of 30, the width of about 200 μm is left.

After that, as shown in FIG. 6, p-type GaN is formed by using the photolithography technique and the etching technique.
By etching a partial region of the n-type GaN contact layer 4 from the contact layer 12, a partial region of the n-type GaN contact layer 4 is exposed. As a result, the mesa-etched portion 16 is formed.

Next, by using the photolithography technique and the etching technique, the p-type GaN contact layer 12 and the
A part of the p-type AlGaN cladding layer 11 is etched. As a result, the stripe-shaped ridge portion 15 as shown in FIG. 2 is formed. After that, the n-type GaN contact layer 4 is formed on a region other than the upper surface of the p-type GaN contact layer 12.
A protective film 17 made of a silicon oxide film having an opening is formed on the upper surface of the. Then, the p-type GaN contact layer 1
The p-side electrode 13 is formed so as to be in contact with 2, and
By forming the n-side electrode 14 in the opening of the protective film 17 so as to be in contact with the surface of the n-type GaN contact layer 4, the nitride semiconductor laser before the element isolation step as shown in FIG. The element is formed.

Finally, after polishing the back surface of the sapphire substrate 1 by a predetermined thickness, dicing is performed along the dicing line 21 and cleavage is performed along the cleavage lines 22a and 22b, as shown in FIG. The nitride semiconductor laser device according to the first embodiment is completed.

(Second Embodiment) FIG. 8 is a plan view showing a state of a nitride semiconductor laser device according to a second embodiment of the present invention before a device isolation process. 9 is a sectional view taken along the line 150-150 of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. In addition, FIG.
FIG. 9 A sectional view taken along the cleavage lines 52 a and 52 b of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. 8. In the second embodiment, unlike the above-described first embodiment, the width of both resonator end face portions of the element formation region (convex portion) is smaller than the width of the other portion of the element formation region (convex portion). An example of such a case will be described.

First, the structure of the nitride-based semiconductor laser device according to the second embodiment before the device isolation step will be described with reference to FIGS. In this second embodiment, FIG.
As shown in FIG. 3, on the sapphire substrate 31, an AlGaN buffer layer 32, an undoped GaN layer 33, an n-type GaN contact layer 34, an n-type AlGaN cladding layer 35, an n-type GaN light guide layer 36, and an MQW active layer 37 made of InGaN. , Undoped AlGaN cap layer 38, p-type A
lGaN light guide layer 39, p-type GaN light guide layer 40,
Also, the p-type AlGaN cladding layer 41 including the convex portion is formed in this order. A p-type GaN contact layer 42 is formed on the convex portion of the p-type AlGaN cladding layer 41. The convex portion of the p-type AlGaN cladding layer 41 and the p-type GaN contact layer 42 form a striped ridge portion 45.

Further, by removing a partial region of the n-type GaN contact layer 34 from the p-type AlGaN cladding layer 41, a mesa-etched portion 46 in which the upper surface of the n-type GaN contact layer 34 is exposed is formed. In addition, in the region other than the upper surface of the p-type GaN contact layer 34, n-type Ga is formed.
A protective film 57 made of a silicon oxide film having an opening is formed on the upper surface of the N contact layer 34. Also, p
A p-side electrode 43 is formed so as to contact the type GaN contact layer 42. Then, in the opening of the protective film 57, the n-side electrode 44 is formed so as to come into contact with the upper surface of the n-type GaN contact layer 34.

The n-type AlGaN cladding layer 35 is
The MQW active layer 37 is an example of the "first clad layer" in the present invention, and the MQW active layer 37 is an example of the "active layer" in the present invention. Also, p
The type AlGaN cladding layer 41 is an example of the “second cladding layer” in the present invention.

Here, in the nitride-based semiconductor laser device of the second embodiment, as shown in FIGS.
5 and the element formation region including the mesa-etched portion 46 (convex portion)
A recess 53 is formed so as to surround 60. The recess 53 is formed so that the surface of the sapphire substrate 31 is exposed. That is, in the recess 53, the layers 32 to 42 made of the nitride-based semiconductor are completely removed.
Further, unlike the first embodiment, the concave portion 53 has both the resonator end face portions 60a and 6 of the element forming region (convex portion) 60.
It is formed so as to enter 0b. Therefore, the widths of both resonator end face portions 60a and 60b of the element forming region (convex portion) 60 are smaller than the widths of the other portions of the element forming region (convex portion) 60.

Specifically, both resonator end face portions 60a are
And 60b are formed so as to have a width of about 15 μm in the range of about 50 μm from the resonator end face in the stripe direction. The width of the resonator end face portions 60a and 60b is preferably about 5 times to about 7 times the width of the ridge portion 45. The other part of the element forming region (convex portion) 60 is formed to have a width of about 170 μm.

In the nitride-based semiconductor laser device of the second embodiment, as described above, the recess 53 reaching the sapphire substrate 31 is formed so as to surround the device forming region (projection) 60, so that the sapphire substrate 31 and The stress generated due to the difference in the coefficient of thermal expansion from each of the layers 32 to 41 made of the nitride-based semiconductor can be relaxed. Thereby, the warp of the substrate can be effectively reduced. In particular,
In the second embodiment, since the recess 53 is formed so as to enter both the resonator end face portions 60a and 60b, the effect of reducing the warpage is greater than that in the first embodiment. As a result, in the manufacturing process to be described later, the lithography step and the element separating step (cleaving step) at the time of forming the element can be performed in a state where the warp of the sapphire substrate 31 is further reduced. It is possible to form a nitride-based semiconductor laser device having characteristics.

Further, in the second embodiment, unlike the above-described first embodiment, both resonator end face portions 60a and 6a are formed.
The width of 0b is smaller than the width of other parts, so that the recess 5
By forming 3, the area of the cleaved portion can be reduced at the time of cleaving, so that better cleaving can be performed in both resonator end face portions 60a and 60b. As a result, it becomes possible to obtain a better resonator end face.

11 to 14 are cross-sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIGS. The manufacturing process of the nitride-based semiconductor laser device of the second embodiment will be described below with reference to FIGS. The manufacturing process in the section shown in FIG. 9 (the section taken along the line 150-150 in FIG. 8) will be described here.

First, as shown in FIG. 11, the AlGaN buffer layer 32, the undoped GaN layer 33, the Si-doped n-type GaN contact layer 34, and the Si-doped n are formed on the sapphire substrate 31 by MOCVD. Type A
lGaN clad layer 35, n-type GaN doped with Si
Optical guide layer 36, MQW active layer 3 made of InGaN
7, undoped AlGaN cap layer 38, Mg-doped p-type AlGaN light guide layer 39, Mg-doped p-type GaN light guide layer 40, Mg-doped p-type A
lGaN clad layer 41 and Mg-doped p
The type GaN contact layer 42 is sequentially formed.

Next, in the manufacturing process of the second embodiment, as shown in FIGS. 8 and 12, the element forming region (convex portion) of the nitride semiconductor laser element is formed by using the photolithography technique and the etching technique. The recess 53 is formed so that the sapphire substrate 31 is exposed by etching a region other than 60 and both resonator end face portions 60a and 60b. The etching at the time of forming the recess 53 is performed in both the resonator end face portions 60a and 60b (see FIG. 8) by about 5 in the stripe direction from each resonator end face.
A width of about 15 μm is left in the range of 0 μm, and a width of about 170 μm is left in the other part of the element forming region (convex portion) 60.

Then, as shown in FIG. 13, a p-type Ga layer is formed by using a photolithography technique and an etching technique.
By etching a partial region of the n-type GaN contact layer 34 from the N contact layer 42, a partial region of the n-type GaN contact layer 34 is exposed. As a result, the mesa-etched portion 46 is formed.

Next, the p-type GaN contact layer 42 and the p-type GaN contact layer 42 are formed by using the photolithography technique and the etching technique.
A part of the p-type AlGaN cladding layer 41 is etched. As a result, the stripe-shaped ridge portion 45 as shown in FIG. 9 is formed. After that, the n-type GaN contact layer 3 is formed in a region other than the upper surface of the p-type GaN contact layer 42.
A protective film 57 made of a silicon oxide film having an opening is formed on the upper surface of 4. Then, the p-side electrode 43 is formed so as to be in contact with the p-type GaN contact layer 42, and the n-side electrode 44 is formed so as to be in contact with the surface of the n-type GaN contact layer 42 in the opening of the protective film 57. By doing so, the nitride-based semiconductor laser device before the device isolation step as shown in FIG. 9 is formed.

Finally, after polishing the back surface of the sapphire substrate 31 by a predetermined thickness, dicing is performed along the dicing line 51 and cleavage is performed along the cleavage lines 52a and 52b, as shown in FIG. Second
The nitride-based semiconductor laser device according to the embodiment is completed.

(Third Embodiment) FIG. 15 shows a third embodiment of the present invention.
FIG. 3 is a plan view showing a state before a device isolation process of the nitride-based semiconductor laser device according to the embodiment. 16 is a sectional view taken along the line 200-200 of the nitride-based semiconductor laser device according to the third embodiment shown in FIG. Also,
FIG. 17 is a sectional view taken along the cleavage line 82b of the nitride-based semiconductor laser device according to the third embodiment shown in FIG. In the third embodiment, unlike the above-described first embodiment, an example will be described in which each of the layers 4 to 12 is formed on the low-defect nitride-based semiconductor layer formed by selective lateral growth. The other structure of the third embodiment is similar to that of the first embodiment.

First, the structure of the nitride-based semiconductor laser device according to the third embodiment before the device isolation process will be described with reference to FIGS. In the third embodiment, as shown in FIG. 16, AlGaN is formed on the sapphire substrate 1.
The buffer layer 61 is formed.

Here, in the third embodiment, the above-mentioned first
Unlike the embodiment, an underlayer (undoped GaN layer) 62 made of undoped GaN having a thickness of about 2 μm to about 3 μm is formed on the AlGaN buffer layer 61. Further, on the base layer 62, about 10 nm to about 10 nm
A mask layer 63 made of a silicon nitride film (SiN film) having a thickness of 00 nm is formed in a stripe shape with an interval of about 7 μm. Then, on the underlying layer 62 and the mask layer 63, a low defect layer (undoped Ga) made of undoped GaN having a thickness of about 5 μm to about 10 μm.
N layer) 64 is formed.

Further, as in the first embodiment, the low defect layer 64 is formed.
An n-type GaN contact layer 4, an n-type AlGaN cladding layer 5, an n-type GaN light guide layer 6, an MQW active layer 7 made of InGaN, an undoped AlGaN cap layer 8, a p-type AlGaN light guide layer 9, and a p-type are provided on the upper side. The GaN light guide layer 10 and the p-type AlGaN cladding layer 11 including the convex portion are formed in this order. A p-type GaN contact layer 12 is formed on the convex portion of the p-type AlGaN cladding layer 11. The convex portion of the p-type AlGaN cladding layer 11 and the p-type GaN contact layer 12 form a striped ridge portion 15.

Further, a part of the n-type GaN contact layer 4 is removed from the p-type AlGaN cladding layer 11 to form a mesa-etched portion 16 in which the upper surface of the n-type GaN contact layer 4 is exposed. In addition, p-type Ga
A protective film 17 made of a silicon oxide film having an opening is formed on the upper surface of the n-type GaN contact layer 4 in a region other than the upper surface of the N contact layer 12. In addition, p-type Ga
A p-side electrode 13 is formed so as to contact the upper surface of the N contact layer 12. Then, in the opening of the protective film 17, the n-side electrode 14 is formed so as to come into contact with the upper surface of the n-type GaN contact layer 4.

Here, in the nitride-based semiconductor laser device of the third embodiment, as in the first embodiment, as shown in FIGS. 15 to 17, a device formation region including a ridge portion 15 and a mesa etch portion 16 (convex) is formed. Part) 30 so as to surround 30
Are formed. The recess 23 is formed on the sapphire substrate 1
Is formed so that its surface is exposed. That is, in the recess 23, each of the layers 4 to 12 and 61 made of the nitride-based semiconductor is formed.
~ 64 has been completely removed. In addition, the concave portion 23 is one resonator end face portion 30 b of the element forming region (convex portion) 30.
It is formed to enter. Therefore, the width of one resonator end face portion 30b of the element forming region (convex portion) 30 is smaller than the width of the other portion of the element forming region (convex portion) 30. The width of the other resonator end face portion 30a of the element forming region (convex portion) 30 is determined by the element forming region (convex portion) 3
It is the same as the width of the other part of 0.

Specifically, one resonator end face portion 30b is provided.
In the above, it is formed so as to have a width of about 10 μm in the range of about 100 μm from the resonator end face in the stripe direction. The width of the resonator end face portion 30b is preferably about 5 to about 7 times the width of the ridge portion 15. Further, the other portion of the element forming region (convex portion) 30 is formed to have a width of about 200 μm.

In the nitride-based semiconductor laser device of the third embodiment, as described above, the recess 23 reaching the sapphire substrate 1 is formed so as to surround the device forming region (projection) 30. Similar to sapphire substrate 1
And layers 4 to 12 and 61 to 64 made of nitride semiconductor
The stress generated due to the difference in the coefficient of thermal expansion between and can be relaxed. Thereby, the warp of the substrate can be effectively reduced. As a result, in the manufacturing process to be described later, it is possible to perform a lithography step during element formation, an element separation step (cleavage step), etc., with the warp of the sapphire substrate 1 reduced, and thus, a good resonator end face and element characteristics can be obtained. It is possible to form a nitride-based semiconductor laser device having Particularly, in the nitride-based semiconductor laser device of the third embodiment, as described above, by forming the low-defect layer 64 on the substrate, the thickness of the entire growth layer becomes large, so that large internal stress occurs. As a result, a larger warp of the substrate occurs, so that the effect of reducing the warp of the substrate due to the recess 23 is great. Further, by growing the layers 4 to 12 made of a nitride semiconductor on the low defect layer 64, the layers 4 to 12 made of a nitride semiconductor having better crystallinity can be formed. As a result, it is possible to obtain a nitride-based semiconductor laser device having better device characteristics.

Next, with reference to FIGS. 15 to 17, the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment will be described. The manufacturing process in the cross section shown in FIG. 16 (cross section taken along line 200-200 in FIG. 15) will be described here.

First, as shown in FIG. 16, the AlGaN buffer layer 61 is formed on the sapphire substrate 1 by using the MOCVD method. Then, the AlGaN buffer layer 61
On top, undoped G having a thickness of about 2 μm to about 3 μm
A base layer (undoped GaN layer) 62 made of aN is formed. On this base layer 62, about 10 nm to about 1000 n
A mask layer 63 made of a silicon nitride film (SiN) having a thickness of m is formed in a stripe shape with an interval of about 7 μm. The opening of the mask layer 63 is preferably formed so as to be parallel to the [11-20] direction or the [1-100] direction of the sapphire substrate 1. Then, using the mask layer 63 as a selective growth mask, the mask layer 63 and the base layer 62 exposed by the openings of the mask layer 63.
A low-defect layer (undoped GaN layer) 64 made of undoped GaN is formed thereon by using the selective lateral growth technique.

Thereafter, by using the same manufacturing process as that of the first embodiment, the nitride semiconductor laser device before the device isolation step according to the third embodiment shown in FIG. 16 is formed.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and further includes meanings equivalent to the scope of the claims and all effects within the scope.

For example, in the above embodiment, the recess reaching the surface of the sapphire substrate is formed, but the present invention is not limited to this, and the recess may be formed by removing at least the active layer. . By doing so, the warp of the substrate can be reduced.

Although the sapphire substrate is used as the substrate in the above embodiment, the present invention is not limited to this, and SiC is used.
Substrate, Si substrate, GaAs substrate, GaP substrate, ZrB ₂
A substrate, a ZnO substrate, a spinel substrate, or the like may be used. In particular, the effect is great in the case of a substrate such as Si having a large difference in thermal expansion coefficient from GaN. Further, a low dislocation substrate having a low defect layer formed by using a selective lateral growth technique on these substrates may be used. Also,
A GaN substrate may be used. When the nitride-based semiconductor layer is formed on the GaN substrate, the warp is reduced, but it is not completely eliminated. Therefore, the present invention is also effective in this case.

Although the mask layer made of the silicon nitride film is formed in the third embodiment, the present invention is not limited to this, and mask layers made of other materials may be used.

Further, in the third embodiment described above, after forming the underlayer on the substrate, the low defect layer made of the nitride-based semiconductor layer using the selective lateral overgrowth technique is formed on the underlayer. The present invention is not limited to this, and the low defect layer using the selective lateral overgrowth technique may be directly formed on the substrate without forming the underlayer.

Alternatively, in the third embodiment, the selective lateral overgrowth technique is used in the step of forming the low defect layer, but the PENDEO method or the lateral overgrowth for growing the low defect layer on the substrate in which the groove is formed. Technology may be used.

In the third embodiment, the stripe direction of the mask layer and the stripe direction of the ridge portion of the nitride semiconductor laser device are formed so as to be parallel to each other.
The present invention is not limited to this, and the stripe direction of the mask layer may not be parallel to the stripe direction of the ridge portion. For example, the mask layer may be formed so that the stripe direction of the mask layer and the stripe direction of the ridge portion are orthogonal to each other.

Further, in the third embodiment, the stripe-shaped mask layers are formed at a predetermined interval, but the present invention is not limited to this, and the mask layers may have other shapes. . For example, a mask layer having a shape such as a circle, a hexagon, or a triangle may be formed. Further, the same effect can be obtained by forming a mask layer having a plurality of openings having a circular shape, a hexagonal shape, a triangular shape, or the like.

[0084]

As described above, according to the present invention, since the warp of the substrate can be reduced, the yield can be improved and a nitride semiconductor laser device having good device characteristics can be obtained. be able to. Also, a good resonator end face can be obtained by cleavage.

[Brief description of drawings]

FIG. 1 is a plan view showing a state before a device isolation process of a nitride semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line 100-100 of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

3 is a sectional view taken along the cleavage line 22b of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 4 is a sectional view illustrating the manufacturing process for the nitride-based semiconductor laser device according to the first embodiment of the present invention.

FIG. 5 is a sectional view illustrating the manufacturing process for the nitride-based semiconductor laser device according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment of the present invention.

FIG. 8 is a plan view showing a state before a device isolation process of a nitride semiconductor laser device according to a second embodiment of the present invention.

9 is a sectional view taken along the line 150-150 of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 10 is a sectional view taken along the cleavage lines 52a and 52b of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 11 is a cross-sectional view illustrating the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment of the present invention.

FIG. 12 is a sectional view illustrating the manufacturing process for the nitride-based semiconductor laser device according to the second embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment of the present invention.

FIG. 15 is a plan view showing a state before a device isolation process of a nitride semiconductor laser device according to a third embodiment of the present invention.

16 is a sectional view taken along the line 200-200 of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

17 is a sectional view taken along the cleavage line 82b of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 18 is a plan view showing a state before a device isolation step of a conventional nitride-based semiconductor laser device.

19 is a sectional view taken along the line 250-250 of the conventional nitride-based semiconductor laser device shown in FIG.

20 is a sectional view taken along the cleavage line 122 of the conventional nitride-based semiconductor laser device shown in FIG.

[Explanation of symbols]

5, 35 n-type AlGaN clad layer (first clad layer) 7, 37 MQW active layer (active layer) 11, 41 p-type AlGaN clad layer (second clad layer) 15, 45 Ridge part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiko Matsushita             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F term (reference) 5F073 AA11 AA74 AA81 CA07 DA32                       EA29

Claims (6)

[Claims] 1. A step of sequentially forming a first clad layer of a first conductivity type, an active layer, and a second clad layer of a second conductivity type on a substrate, and at least the second clad layer in a region other than an element formation region. A step of forming a concave portion from which the clad layer and the active layer are removed, and forming a convex portion having a different width in a direction perpendicular to the cavity end face in the element forming region, and the element forming region, And a step of forming a stripe-shaped ridge portion. 2. The method for manufacturing a nitride-based semiconductor laser device according to claim 1, wherein the width of the convex portion in the vicinity of the cavity end face is smaller than that of the other portion of the convex portion. 3. The nitride-based semiconductor according to claim 1, wherein the step of forming the recess includes a step of forming the recess so as to surround a portion of the protrusion other than the vicinity of the resonator end face. Laser element manufacturing method. 4. The step of forming the recess includes the step of forming the recess so that the substrate is exposed.
4. The method for manufacturing a nitride-based semiconductor laser device according to any one of 3 above. 5. A first conductivity type first clad layer formed on a substrate, an active layer formed on the first clad layer, and a second conductivity type second clad layer formed on the active layer. 2 clad layer, stripe-shaped ridge portion, a concave portion formed in a region other than the element formation region, in which at least the second cladding layer and the active layer are removed, and a cavity facet formed in the element formation region And a convex portion having a different width in a direction perpendicular to the nitride semiconductor laser element. 6. The nitride semiconductor laser device according to claim 5, wherein the width of the convex portion near the cavity end face is smaller than the width of the other portion of the convex portion.