Method for manufacturing nitride semiconductor laser device and nitride semiconductor laser device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

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, a method for manufacturing a nitride-based semiconductor laser device in which a nitride-based semiconductor layer is grown on a substrate. And nitride-based semiconductor laser devices.

【0002】

[Conventional technology]

In recent years, nitride-based semiconductor laser devices are expected to be used as light sources for next-generation large-capacity optical discs, and their development is being actively carried out.

【0003】

Conventionally, when forming a nitride semiconductor laser device, it is difficult to manufacture a substrate made of a nitride semiconductor (GaN). Therefore, usually, a nitride semiconductor layer is formed on a substrate made of sapphire, SiC, Si, or the like. Is growing.

【0004】

FIG. 18 is a plan view showing the state of the conventional nitride-based semiconductor laser device before the element separation step. FIG. 19 is a cross-sectional view taken along the line 250-250 of the conventional nitride-based semiconductor laser device shown in FIG. Further, FIG. 20 is a cross-sectional view taken along the cleavage line 122 of the conventional nitride-based semiconductor laser device shown in FIG.

【0005】

First, with reference to FIGS. 18 to 20, the structure of the conventional nitride-based semiconductor laser device before the element separation step will be described. In this conventional nitride-based semiconductor laser device, as shown in FIG. 19, an AlGaN buffer layer 102, an undoped GaN layer 103, an n-type GaN contact layer 104, an n-type AlGaN clad layer 105, and an n-type are placed on a sapphire substrate 101. The GaN optical guide layer 106, the MQW active layer 107 made of InGaN, the undoped AlGaN cap layer 108, the p-type AlGaN optical guide layer 109, the p-type GaN optical guide layer 110, and the p-type AlGaN clad layer 111 including the convex portion It is formed in this order. A p-type GaN contact layer 112 is formed on the convex portion of the p-type AlGaN clad layer 111. The convex portion of the p-type AlGaN clad layer 111 and the p-type GaN contact layer 112 form a striped ridge portion 115. Further, by removing a part of the n-type GaN contact layer 104 from the p-type AlGaN clad layer 111, a mesa-etched portion 116 in which the upper surface of the n-type GaN contact layer 104 is exposed is formed. Further, 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. Further, the p-side electrode 113 is formed so as to come into contact with the upper surface of the p-type GaN contact layer 112. Then, the n-side electrode 114 is formed in the opening of the protective film 117 so as to come into contact with the upper surface of the n-type GaN contact layer 104.

【0006】

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

【0007】

First, as shown in FIGS. 19 and 20, the AlGaN buffer layer 102, the undoped GaN layer 103, the Si-doped n-type GaN contact layer 104, and the Si-doped n were used on the sapphire substrate 101 by the MOCVD method. Type AlGaN clad layer 105, Si-doped n-type GaN optical guide layer 106, MQW active layer 107 with multiple quantum well (MQW) structure composed of InGaN, undoped AlGaN cap layer 108, Mg-doped p The type AlGaN optical guide layer 109, the Mg-doped p-type GaN optical guide layer 110, the Mg-doped p-type AlGaN clad layer 111, and the Mg-doped p-type GaN contact layer 112 are sequentially formed.

【0008】

Then, a part of the region of the p-type GaN contact layer 112 to the n-type GaN contact layer 104 is etched using the photolithography technique and the etching technique. As a result, a part of the n-type GaN contact layer 104 is exposed and the mesa-etched portion 116 is formed.

【0009】

Next, the p-type GaN contact layer 112 and a part of the p-type AlGaN clad layer 111 are etched by using a photolithography technique and an etching technique. As a result, 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.

【0010】

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

【0011】

Finally, the back surface of the sapphire substrate 101 is polished to bring the sapphire substrate 101 to a predetermined thickness. Then, the cleavage is formed at the cleavage line 122 shown in FIG. 18 to form the resonator end face of the nitride-based semiconductor laser device, and the elements are separated by dicing at the dicing line 121. In this way, the conventional nitride-based semiconductor laser device has been formed.

【0012】

[Problems to be Solved by the Invention]

However, in the above-mentioned method of crystal-grow each layer 102 to 112 made of a nitride semiconductor on the conventional sapphire substrate 101, each layer 101 to 112 made of a nitride semiconductor is usually grown at a high temperature. In this case, when the substrate temperature is lowered to room temperature after the nitride semiconductor layer is formed on the sapphire substrate 101 at a high temperature, it is caused by the difference in the coefficient of thermal expansion between the sapphire substrate 101 and the nitride semiconductor layer. Internal stress is generated between the sapphire substrate 101 and the nitride semiconductor layer. Therefore, there is an inconvenience that a large warp occurs in the entire substrate. In such a state where a large warp occurs, the lithography process at the time of element formation, the resonator manufacturing process (opening process), the element separation process, etc. cannot be performed satisfactorily, and as a result, the nitride-based semiconductor laser element becomes There is a problem that the yield and the element characteristics are lowered.

【0013】

Therefore, conventionally, in order to satisfactorily form the resonator end face of a nitride semiconductor laser device by cleavage, a split groove having a depth that does not reach the active layer is formed on the surface of the nitride semiconductor after the element is formed. At the same time, a method has been proposed in which a split groove is formed on the opposite sapphire substrate side, and the cleavage is opened by using the split groove as a trigger at the time of cleavage. These are disclosed in, for example, Japanese Patent Application Laid-Open No. 8-222807.

【0014】

However, even in the method of cleaving the nitride-based semiconductor laser element triggered by the split groove, the coefficient of thermal expansion of the sapphire substrate and the nitride-based semiconductor layer is the same as in the conventional structures shown in FIGS. Since it is difficult to relax the internal stress generated due to the difference, it is difficult to reduce the warp of the entire substrate. Therefore, it is difficult to obtain a good resonator end face.

【0015】

The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to reduce the warp of the substrate to improve the yield and to have good element characteristics. It is an object of the present invention to provide a method for manufacturing a nitride semiconductor laser device capable of forming a physical semiconductor laser device.

【0016】

Another object of the present invention is to obtain a good resonator end face by cleavage in the above-mentioned method for manufacturing a nitride semiconductor laser device.

【0017】

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

【0018】

[Means for solving problems]

The method for manufacturing a nitride semiconductor laser device according to the first aspect of the present invention is to: on a substrate, a first conductive type first clad layer, an active layer on the active layer, and a second conductive type first on the substrate. A step of forming a nitride semiconductor device layer including a two-clad layer and a recess in a region other than the device forming region from which at least the second clad layer and the active layer have been removed are formed, and resonance occurs in the device forming region. It includes a step of forming convex portions having different widths in a direction perpendicular to the end surface of the instrument and a step of forming a striped ridge portion in the element forming region.

【0019】

In the method for manufacturing a nitride semiconductor laser device according to the first aspect, as described above, a substrate is formed by forming a recess in a region other than the device forming region from which at least the second clad layer and the active layer have been removed. Since the stress generated due to the difference in the coefficient of thermal expansion between the nitride-based semiconductor device layer and the nitride semiconductor device layer can be relaxed, the warpage of the substrate can be effectively reduced. As a result, the lithography process, the resonator manufacturing process, the element separation process, and the like at the time of element formation can be performed in a state where the warp of the substrate is reduced, so that the yield can be improved and the element characteristics are good. A nitride-based semiconductor laser device can be formed. Further, by forming 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 cleaving is small, the cleaving can be performed satisfactorily. As a result, a good resonator end face can be obtained.

【0020】

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

【0021】

In the above method for manufacturing a nitride semiconductor laser device, preferably, the step of forming the concave portion includes a step of forming the concave portion so as to surround the periphery of the portion other than the vicinity of the resonator end face of the convex portion. With this configuration, the stress generated due to the difference in the coefficient of thermal expansion between the substrate and the nitride semiconductor device layer can be further relaxed, so that the warpage of the substrate can be reduced more effectively. ..

【0022】

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

【0023】

The nitride-based semiconductor laser device according to the second aspect of the present invention has a first conductive type first clad layer formed on a substrate, an active layer formed on the first clad layer, and an active layer on the active layer. In the formed second conductive type second clad layer, the striped ridge portion, the recess formed in the region other than the element forming region, and at least the second clad layer and the active layer are removed, and the element forming region. It is formed and includes protrusions having different widths in a direction perpendicular to the resonator end face.

【0024】

In the nitride-based semiconductor laser device according to the second aspect, as described above, the substrate and the nitride are formed by forming recesses from which at least the second clad layer and the active layer have been removed in a region other than the element formation region. Since the stress generated due to the difference in the coefficient of thermal expansion from the system semiconductor element layer can be relaxed, the warp of the substrate can be effectively reduced. As a result, the lithography process, the resonator manufacturing process, the element separation process, and the like at the time of element formation can be performed in a state where the warp of the substrate is reduced, so that the yield can be improved and the element characteristics are good. A nitride-based semiconductor laser device can be formed. Further, by forming 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 cleaving is small, the cleaving can be performed satisfactorily. As a result, a good resonator end face can be obtained.

【0025】

In the nitride-based semiconductor laser device according to the second aspect, the width of the convex portion in the vicinity of the resonator end face is preferably smaller than that of the other portion of the convex portion. With this configuration, the area of the portion to be cleaved at the time of cleaving when forming the resonator end face is reduced, so that the cleaving can be performed satisfactorily. As a result, a good resonator end face can be obtained.

【0026】

In the method for manufacturing a nitride semiconductor laser device according to the first aspect, the width of the convex portion in the vicinity of the resonator end face may be 5 times or more and 7 times or less the width of the ridge portion. With this configuration, cleavage can be performed satisfactorily.

【0027】

Further, in the method for manufacturing a nitride semiconductor laser device according to the first aspect, the maximum width of the convex portion may be smaller than the width of the substrate.

【0028】

Further, in the method for manufacturing a nitride semiconductor laser device according to the first aspect, a step of forming a resonator end face by cleavage may be further provided.

【0029】

Further, in the method for manufacturing a nitride semiconductor laser device according to the first aspect, a step of sequentially forming a first conductive type first clad layer, an active layer, and a second conductive type second clad layer on a substrate. Prior to this, a step of forming a low defect layer on the substrate may be further provided.

【0030】

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

【0031】

Further, in the nitride semiconductor laser device according to the second aspect, the width of the convex portion in the vicinity of the resonator end face may be 5 times or more and 7 times or less the width of the ridge portion. With this configuration, cleavage can be easily performed.

【0032】

Further, in the nitride semiconductor laser device according to the second aspect, the maximum width of the convex portion may be smaller than the width of the substrate.

【0033】

Further, in the nitride semiconductor laser device according to the second aspect, the concave portion may be formed so as to surround the periphery of the portion other than the vicinity of the resonator end face of the convex portion. With this configuration, the stress generated due to the difference in the coefficient of thermal expansion between the substrate and the nitride semiconductor device layer can be further relaxed, so that the warpage of the substrate can be reduced more effectively. ..

【0034】

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

【0035】

Further, in the nitride semiconductor laser device according to the second aspect, the resonator end face may be formed by cleavage.

【0036】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

【0037】

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

【0038】

First, with reference to FIGS. 1 to 3, the structure of the nitride semiconductor laser device according to the first embodiment before the element separation step will be described. In this first embodiment, as shown in FIG. 2, an AlGaN buffer layer 2, an undoped GaN layer 3, an n-type GaN contact layer 4, an n-type AlGaN clad layer 5, and an n-type GaN optical guide layer are placed on the sapphire substrate 1. 6. MQW active layer 7 made of InGaN, undoped AlGaN cap layer 8, p-type AlGaN optical guide layer 9, p-type GaN optical guide layer 10, and p-type AlGaN clad layer 11 including convex portions are formed in this order. Has been done. A p-type GaN contact layer 12 is formed on the convex portion of the p-type AlGaN clad layer 11. The convex portion of the p-type AlGaN clad layer 11 and the p-type GaN contact layer 12 form a striped ridge portion 15.

【0039】

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

【0040】

The n-type AlGaN clad layer 5 is an example of the "first clad layer" of the present invention, and the MQW active layer 7 is an example of the "active layer" of the present invention. The p-type AlGaN clad layer 11 is an example of the "second clad layer" of the present invention.

【0041】

Here, in the nitride-based semiconductor laser device of the first embodiment, as shown in FIGS. 1 to 3, the concave portion 23 surrounds the element forming region (convex portion) 30 including the ridge portion 15 and the mesa-etched portion 16. It is formed. The recess 23 is formed so that the surface of the sapphire substrate 1 is exposed. That is, in the recess 23, each layer 2 to 12 made of the nitride semiconductor is completely removed. Further, the concave portion 23 is formed so as to enter one of the resonator end face portions 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.

【0042】

Specifically, one resonator end face portion 30b is formed so as to have a width of about 10 μm in a range of about 100 μm in the stripe direction from the resonator end face. 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 so as to have a width of about 200 μm.

【0043】

In the nitride-based semiconductor laser device of the first embodiment, as described above, the sapphire substrate 1 and the nitride are formed by forming the recess 23 that reaches the sapphire substrate 1 so as to surround the element forming region (convex portion) 30. The stress generated due to the difference in the coefficient of thermal expansion from each layer 2 to 12 made of a system semiconductor can be relaxed. Thereby, the warp of the substrate can be effectively reduced. As a result, in the manufacturing process described later, the lithography process and the element separation process (opening process) at the time of element formation can be performed in a state where the warp of the sapphire substrate 1 is reduced, so that the end face of the resonator and the element characteristics are good. It becomes possible to form a nitride-based semiconductor laser device having the above.

【0044】

Further, by forming the recess 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 cleavage portion can be reduced at the time of cleavage, which is better. Cleavage can be performed. As a result, it is possible to obtain a better resonator end face.

【0045】

4 to 7 are cross-sectional views for explaining the manufacturing process of the nitride semiconductor laser device according to the first embodiment shown in FIGS. 1 to 3. Hereinafter, the manufacturing process of the nitride-based semiconductor laser device of the first embodiment will be described with reference to FIGS. 1 to 7. Here, the manufacturing process in the cross section shown in FIG. 2 (cross section along the line 100-100 in FIG. 1) will be described.

【0046】

First, as shown in FIG. 4, using the MOCVD method, an AlGaN buffer layer 2, an undoped GaN layer 3, a Si-doped n-type GaN contact layer 4, and a Si-doped n-type AlGaN clad are placed on the sapphire substrate 1. Layer 5, Si-doped n-type GaN optical guide layer 6, MQW active layer 7 made of InGaN, undoped AlGaN cap layer 8, Mg-doped p-type AlGaN optical guide layer 9, Mg-doped p-type GaN optical guide A layer 10, a p-type AlGaN clad layer 11 doped with Mg, and a p-type GaN contact layer 12 doped with Mg are sequentially formed.

【0047】

Next, in the manufacturing process of the first embodiment, as shown in FIGS. 1 and 5, the element forming region (convex portion) 30 of the nitride semiconductor laser device and one of them are used by using the photolithography technique and the etching technique. By etching the region other than the resonator end face portion 30b of the above, the recess 23 is formed so that the sapphire substrate 1 is exposed. Etching at the time of forming the concave portion 23 leaves a width of about 10 μm in the range of about 100 μm from the resonator end face in the stripe direction in one resonator end face portion 30b (see FIG. 1), and also leaves an element forming region (convex portion). The other part of 30 should be left with a width of about 200 μm.

【0048】

Then, as shown in FIG. 6, one of the n-type GaN contact layers 4 is etched by etching a part of the n-type GaN contact layer 4 from the p-type GaN contact layer 12 using the photolithography technique and the etching technique. Exposing the area. As a result, the mesa-etched portion 16 is formed.

【0049】

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

【0050】

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

【0051】

(Second Embodiment) FIG. 8 is a plan view showing a state before the element separation step of the nitride semiconductor laser device according to the second embodiment of the present invention. Further, FIG. 9 is a cross-sectional view taken along the lines 150-150 of the nitride semiconductor laser device according to the second embodiment shown in FIG. Further, FIG. 10 is a cross-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. In this second embodiment, unlike the first embodiment described above, the width of both resonator end face portions of the element forming region (convex portion) is smaller than the width of the other portion of the element forming region (convex portion). An example of this case will be described.

【0052】

First, with reference to FIGS. 8 to 10, the structure of the nitride-based semiconductor laser device according to the second embodiment before the element separation step will be described. In this second embodiment, as shown in FIG. 9, an AlGaN buffer layer 32, an undoped GaN layer 33, an n-type GaN contact layer 34, an n-type AlGaN clad layer 35, and an n-type GaN optical guide layer are placed on the sapphire substrate 31. 36, MQW active layer 37 made of InGaN, undoped AlGaN cap layer 38, p-type AlGaN optical guide layer 39, p-type GaN optical guide layer 40, and p-type AlGaN clad layer 41 including convex portions are formed in this order. Has been done. A p-type GaN contact layer 42 is formed on the convex portion of the p-type AlGaN clad layer 41. The convex portion of the p-type AlGaN clad layer 41 and the p-type GaN contact layer 42 form a striped ridge portion 45.

【0053】

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

【0054】

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

【0055】

Here, in the nitride-based semiconductor laser device of the second embodiment, as shown in FIGS. 8 to 10, the concave portion 53 surrounds the element forming region (convex portion) 60 including the ridge portion 45 and the mesa-etched portion 46. It is formed. The recess 53 is formed so that the surface of the sapphire substrate 31 is exposed. That is, in the recess 53, each layer 32 to 42 made of the nitride semiconductor is completely removed. Further, unlike the first embodiment, the concave portion 53 is formed so as to enter both the resonator end face portions 60a and 60b of the element forming region (convex portion) 60. 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.

【0056】

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

【0057】

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

【0058】

Further, in the second embodiment, unlike the first embodiment described above, the recess 53 is formed so that the widths of both resonator end face portions 60a and 60b are smaller than the widths of the other portions, so that the recess 53 is formed at the time of cleavage. Since the area of the cleavage portion can be reduced, better cleavage can be performed in both resonator end face portions 60a and 60b. As a result, it is possible to obtain a better resonator end face.

【0059】

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. 8 to 10. Hereinafter, the manufacturing process of the nitride-based semiconductor laser device of the second embodiment will be described with reference to FIGS. 8 to 14. Here, the manufacturing process in the cross section shown in FIG. 9 (cross section along the lines 150 to 150 in FIG. 8) will be described.

【0060】

First, as shown in FIG. 11, using the MOCVD method, an AlGaN buffer layer 32, an undoped GaN layer 33, a Si-doped n-type GaN contact layer 34, and a Si-doped n-type AlGaN cladding are placed on the sapphire substrate 31. Layer 35, Si-doped n-type GaN optical guide layer 36, MQW active layer 37 made of InGaN, undoped AlGaN cap layer 38, Mg-doped p-type AlGaN optical guide layer 39, Mg-doped p-type GaN optical guide A layer 40, a p-type AlGaN clad layer 41 doped with Mg, and a p-type GaN contact layer 42 doped with Mg are sequentially formed.

【0061】

Next, in the manufacturing process of the second embodiment, as shown in FIGS. 8 and 12, the element forming region (convex portion) 60 and both of the nitride-based semiconductor laser device are used by using the photolithography technique and the etching technique. By etching the regions other than the resonator end face portions 60a and 60b, the recess 53 is formed so that the sapphire substrate 31 is exposed. Etching at the time of forming the recess 53 leaves a width of about 15 μm in the range of about 50 μm from each resonator end face in the stripe direction in both resonator end face portions 60a and 60b (see FIG. 8), and also leaves an element formation region (see FIG. 8). Convex part) The other part of 60 should be left with a width of about 170 μm.

【0062】

Then, as shown in FIG. 13, one of the n-type GaN contact layers 34 is etched by etching a part of the n-type GaN contact layer 34 from the p-type GaN contact layer 42 using the photolithography technique and the etching technique. Exposing the area. As a result, the mesa-etched portion 46 is formed.

【0063】

Next, the p-type GaN contact layer 42 and a part of the p-type AlGaN clad layer 41 are etched using the photolithography technique and the etching technique. As a result, the striped ridge portion 45 as shown in FIG. 9 is formed. After that, a protective film 57 made of a silicon oxide film having an opening on the upper surface of the n-type GaN contact layer 34 is formed in a region other than the upper surface of the p-type GaN contact layer 42. 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 within the opening of the protective film 57. By doing so, a nitride-based semiconductor laser device before the element separation step as shown in FIG. 9 is formed.

【0064】

Finally, after polishing the back surface of the sapphire substrate 31 to a predetermined thickness, dicing is performed along the dicing line 51 and cleavage is performed along the cleavage lines 52a and 52b. 2 The nitride-based semiconductor laser device according to the embodiment is completed.

【0065】

(Third Embodiment) FIG. 15 is a plan view showing a state before the element separation step of the nitride semiconductor laser device according to the third embodiment of the present invention. Further, FIG. 16 is a cross-sectional view taken along the line 200-200 of the nitride semiconductor laser device according to the third embodiment shown in FIG. Further, FIG. 17 is a cross-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 first embodiment described above, an example in which each layer 4 to 12 is formed on a low-defect nitride-based semiconductor layer formed by using selective lateral growth will be described. The other structures of the third embodiment are the same as those of the first embodiment.

【0066】

First, with reference to FIGS. 15 to 17, the structure of the nitride-based semiconductor laser device according to the third embodiment before the element separation step will be described. In this third embodiment, as shown in FIG. 16, the AlGaN buffer layer 61 is formed on the sapphire substrate 1.

【0067】

Here, in the third embodiment, unlike the first embodiment described above, a base layer (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. There is. Further, on the base layer 62, a mask layer 63 made of a silicon nitride film (SiN film) having a thickness of about 10 nm to about 1000 nm is formed in a stripe shape at intervals of about 7 μm. Then, a low defect layer (undoped GaN layer) 64 made of undoped GaN having a thickness of about 5 μm to about 10 μm is formed on the base layer 62 and the mask layer 63.

【0068】

Further, as in the first embodiment, on the low defect layer 64, an n-type GaN contact layer 4, an n-type AlGaN clad layer 5, an n-type GaN optical guide layer 6, an MQW active layer 7 composed of InGaN, and an undoped AlGaN cap A layer 8, a p-type AlGaN optical guide layer 9, a p-type GaN optical guide layer 10, and a p-type AlGaN clad layer 11 including a 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 clad layer 11. The convex portion of the p-type AlGaN clad layer 11 and the p-type GaN contact layer 12 form a striped ridge portion 15.

【0069】

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

【0070】

Here, in the nitride-based semiconductor laser device of the third embodiment, as shown in FIGS. 15 to 17, the element forming region (convex portion) 30 including the ridge portion 15 and the mesa-etched portion 16 is similar to the first embodiment. A recess 23 is formed so as to surround the. The recess 23 is formed so that the surface of the sapphire substrate 1 is exposed. That is, in the recess 23, the layers 4 to 12 and 61 to 64 made of the nitride semiconductor are completely removed. Further, the concave portion 23 is formed so as to enter one of the resonator end face portions 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.

【0071】

Specifically, one resonator end face portion 30b is formed so as to have a width of about 10 μm in a range of about 100 μm in the stripe direction from the resonator end face. 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 so as to have a width of about 200 μm.

【0072】

The nitride-based semiconductor laser device of the third embodiment is similar to the first embodiment by forming a recess 23 reaching the sapphire substrate 1 so as to surround the element forming region (convex portion) 30 as described above. The stress generated due to the difference in the coefficient of thermal expansion between the sapphire substrate 1 and the layers 4 to 12 and 61 to 64 made of the 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 lithography process and the element separation process (opening process) at the time of element formation can be performed in a state where the warp of the sapphire substrate 1 is reduced, so that the end face of the resonator and the element characteristics are good. It becomes possible to form a nitride-based semiconductor laser device having the above. In particular, in the nitride-based semiconductor laser device of the third embodiment, as described above, the formation of the low defect layer 64 on the substrate increases the thickness of the entire growth layer, so that a large internal stress is generated. As a result, a larger warp of the substrate is generated, so that the effect of reducing the warp of the substrate due to the recess 23 is great. Further, by growing each layer 4 to 12 made of a nitride semiconductor on the low defect layer 64, each layer 4 to 12 made of a nitride semiconductor having better crystallinity can be formed. As a result, it becomes possible to obtain a nitride-based semiconductor laser device having even better device characteristics.

【0073】

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

【0074】

First, as shown in FIG. 16, the AlGaN buffer layer 61 is formed on the sapphire substrate 1 by using the MOCVD method. Then, 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. On the base layer 62, a mask layer 63 made of a silicon nitride film (SiN) having a thickness of about 10 nm to about 1000 nm is formed in a stripe shape at intervals 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, a low defect layer (undoped GaN layer) 64 made of undoped GaN is selected on the underlying layer 62 exposed by the openings of the mask layer 63 and the mask layer 63. Lateral growth technology. Is formed using.

【0075】

After that, by using the same manufacturing process as in the first embodiment, the nitride-based semiconductor laser device before the element separation step according to the third embodiment shown in FIG. 16 is formed.

【0076】

It should be noted that the embodiments disclosed this time are examples in all respects and should not be considered to be restrictive. The scope of the present invention is shown by the scope of claims, not the description of the above-described embodiment, and further includes all effects within the meaning and scope equivalent to the scope of claims.

【0077】

For example, in the above embodiment, the recess that reaches 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.

【0078】

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

【0079】

Further, in the third embodiment, the mask layer made of a silicon nitride film is formed, but the present invention is not limited to this, and a mask layer made of another material may be used.

【0080】

Further, in the third embodiment, after the base layer is formed on the substrate, a low defect layer made of a nitride semiconductor layer using the selective lateral growth technique is formed on the base layer. Is not limited to this, and a low defect layer using the selective lateral growth technique may be formed directly on the substrate without forming the base layer.

【0081】

Alternatively, in the third embodiment, the selective lateral growth technique is used in the step of forming the low defect layer, but the PENDEO method or the lateral growth technique for growing the low defect layer on the grooved substrate is used. You may.

【0082】

Further, in the third embodiment, the mask layer is formed so that the stripe direction of the mask layer is parallel to the stripe direction of the ridge portion of the nitride-based semiconductor laser element, but the present invention is not limited to this. The stripe direction of the ridge portion and the stripe direction of the ridge portion do not have to be parallel. 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.

【0083】

Further, in the above-mentioned third embodiment, the striped mask layer is formed at a predetermined interval, but the present invention is not limited to this, and the shape of the mask layer may be another shape. 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 shape such as a circle, a hexagon, or a triangle.

【0084】

[Effect of the invention]

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 element characteristics can be obtained. In addition, a good resonator end face can be obtained by cleavage.

[Simple explanation of drawings]

[Figure 1]

It is a top view which showed the state before the element separation process of the nitride-based semiconductor laser element by 1st Embodiment of this invention.

[Figure 2]

FIG. 5 is a cross-sectional view taken along line 100-100 of the nitride semiconductor laser device according to the first embodiment shown in FIG.

[Fig. 3]

FIG. 5 is a cross-sectional view taken along the cleavage line 22b of the nitride semiconductor laser device according to the first embodiment shown in FIG.

[Fig. 4]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment of this invention.

[Fig. 5]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment of this invention.

[Fig. 6]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment of this invention.

[Fig. 7]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment of this invention.

[Fig. 8]

It is a top view which showed the state before the element separation process of the nitride-based semiconductor laser element by the 2nd Embodiment of this invention.

[Fig. 9]

FIG. 5 is a cross-sectional view taken along the line 150-150 of the nitride semiconductor laser device according to the second embodiment shown in FIG.

[Fig. 10]

FIG. 5 is a cross-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]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 2nd Embodiment of this invention.

[Fig. 12]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 2nd Embodiment of this invention.

[Fig. 13]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 2nd Embodiment of this invention.

[Fig. 14]

It is sectional drawing for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 2nd Embodiment of this invention.

[Fig. 15]

It is a top view which showed the state before the element separation process of the nitride-based semiconductor laser element by the 3rd Embodiment of this invention.

[Fig. 16]

FIG. 5 is a cross-sectional view taken along the line 200-200 of the nitride semiconductor laser device according to the third embodiment shown in FIG.

[Fig. 17]

FIG. 5 is a cross-sectional view taken along the cleavage line 82b of the nitride semiconductor laser device according to the second embodiment shown in FIG.

[Fig. 18]

It is a top view which showed the state before the element separation process of the conventional nitride-based semiconductor laser element.

[Fig. 19]

FIG. 8 is a cross-sectional view taken along the line 250-250 of the conventional nitride-based semiconductor laser device shown in FIG.

[Fig. 20]

FIG. 8 is a cross-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 (1st clad layer) 7, 37 MQW active layer (active layer) 11, 41 p type AlGaN clad layer (second clad layer) 15, 45 Ridge