JP2001358404A - Semiconductor laser element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laser element which has a stripe structure and is excellent in controllability of mode and optical characteristic, and provide a manufacturing method capable of forming the stripe structure with high precision. SOLUTION: This laser element has a structure having a P-type clad layer and an N-type clad layer which sandwich an active layer. As a resonator, a first protruding part and a second protruding part which is stretched to one end portion of the first protruding part are installed, and resonator surfaces are formed on the end portion of the first protruding part and an external side surface isolated from the first protruding part. By etching a laminated semiconductor layer, the first protruding part is formed, and the second protruding part of wide width is formed in the end portion of the first protruding part. After that, a substrate is divided by a surface almost perpendicular to the stripe direction of the first protruding part, and a reflecting surface of the resonator is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, to a semiconductor device having a stripe-shaped waveguide region by forming a projection on a semiconductor layer on which a nitride semiconductor layer is laminated. The present invention relates to a laser device.

[0002]

2. Description of the Related Art As a semiconductor device mainly using a nitride semiconductor, a blue light emitting diode and a blue laser device are known. In particular, with respect to laser devices, many studies have been made on improving the characteristics of the laser devices for use in various applications.

A laser device using a nitride semiconductor has achieved continuous oscillation for a relatively long time, but there are still many problems for application of the laser device. Above all, in the manufacturing process, a more complicated element structure is required as compared with the light emitting diode, and it is important to improve the precision in the fine processing step. In addition, the structure of a laser device using a nitride semiconductor that is currently generally used is a refractive index waveguide type in which a refractive index difference is provided in a direction perpendicular to the cavity direction. When a heterogeneous substance is used for the substrate, it is difficult to cleave the substrate, so that the substrate is formed by etching.

[0004]

After the nitride semiconductor layer is mainly laminated, fine processing is usually performed by etching to form a resonator. At this time, the semiconductor layer laminated as the resonator has a stripe shape. When a convex portion is formed to form a waveguide region having a refractive index-guided stripe, a convex portion end portion serving as a cavity end surface and a convex portion side surface (stripe) greatly affecting light waveguide. Problem) at the time of micromachining. That is, in the etching, especially in the commonly used dry etching, the processed portion exhibits irregularities by performing fine processing, and the corner becomes round when subjected to fine processing in a complicated shape in a relatively narrow area. And other problems occur.

More specifically, as shown in FIG.
When a relatively narrow stripe structure is formed, fine irregularities are formed on the surface by etching, as schematically shown in an enlarged view (d), and a wavy side surface is formed. You can see that it is. Further, at the end of the convex portion, the corner is rounded, and as shown schematically in the enlarged view (c) of the end, in a place where the corner is concentrated in a narrow area, the figure Etching is performed in the direction shown by the arrow, making it difficult to form a good end face.

In addition, when dry etching a semiconductor layer on which a nitride semiconductor is laminated, a method using Cl ₂ gas by RIE (reactive ion etching) is generally used. However, such dry etching tends to form surface irregularities, and this tendency is particularly pronounced in nitride semiconductors.

In the case where the waveguide region of the laser element has a narrow stripe structure, the influence on the waveguide region particularly at the time of the above-described fine processing increases. That is,
The unevenness on the side surface of the stripe increases the adverse effect on the waveguide region as the stripe width decreases, resulting in deterioration of device characteristics.

Further, regarding the above-described resonator end face,
Similarly, as the stripe width becomes narrower, the flatness of the end face is impaired, and not only is it difficult to obtain a mirror-finished resonator reflection surface, but also the number of defective products due to defective element end faces increases.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a structure in which the reliability of a semiconductor laser device is further improved. An object of the present invention is to realize excellent fine processing for the formation of the stripe-shaped convex side surfaces constituting the device and the element end surfaces serving as the resonator reflection surfaces.

That is, the semiconductor laser device of the present invention comprises:
It has a configuration shown in the following (1) to (4).

(1) A resonator including a structure in which a plurality of layers made of a nitride semiconductor are laminated on a substrate and an active layer is sandwiched between a p-type cladding layer and an n-type cladding layer, and is sandwiched between resonator end faces. A semiconductor laser device having a stripe-shaped waveguide region, wherein the stripe-shaped waveguide region is formed by removing a part of the semiconductor layer; A second convex portion extending to one of the first convex portion end portions, and the resonator reflection surface is formed of the first convex portion end portion and the first convex portion side surface. And an outer side surface spaced apart from the convex portion of the light emitting element. As described above, the semiconductor laser device having a stable transverse mode can be obtained by having the first convex portion and the second convex portion as the resonator. Although the details are unknown, the resonator includes the stripe-shaped waveguide region of the related art and the second convex portion having a wider width in addition to the waveguide region. Change is brought about,
This is considered to be favorably acting on the stability of the transverse mode.

(2) The stripe width of the first projection is:
It is characterized by being 5 μm or less. With this configuration,
In the stripe-shaped waveguide region formed by the first convex portion, good light confinement is enabled, and a laser element with stable transverse mode is obtained. More preferably,
When the thickness is in the range of 1 μm or more and 3 μm or less, a laser device with more stable transverse mode can be obtained.

(3) The distance between the resonator reflection surface provided on the second projection and the first projection is 5 μm or less. With this configuration, the distance between the stripe-shaped waveguide region formed by the first convex portion and the resonator reflecting surface of the second convex portion is set to a distance that does not cause a sharp rise in the oscillation threshold. Will be done. That is, the first
As compared with the case where the waveguide region of the laser element is composed of only the convex portions, the oscillation threshold value tends to increase when the second convex portion is included, but the increase exceeds the distance of 5 μm. This tends to seriously affect device characteristics. More preferably, the length of the second convex portion is set to 1 μm or more and 3 μm or less, so that the second
The element characteristics change due to having the convex portion tends to act favorably.

(4) An electrode is provided in contact with the upper surface of the first projection, and the electrode has a length that does not reach the end of the first projection. With this configuration,
The electrode is not applied to the second convex portion, and the gain in the waveguide region is changed by the second convex portion, which suitably acts on mode control, resulting in a laser device having excellent oscillation characteristics.

The method of manufacturing a semiconductor laser device according to the present invention is a method described in the following (5) to (11).

(5) A semiconductor layer having a structure in which an active layer is sandwiched between a p-type clad layer and an n-type clad layer is laminated on a substrate,
A method for manufacturing a laser device having a stripe-shaped waveguide region in a first projection formed by removing a part of the semiconductor layer by etching, wherein a layer made of a nitride semiconductor is formed on the substrate. After stacking, etching is performed to form a first convex portion of the stripe shape by etching and a second convex portion wider than the stripe width of the first convex portion at at least one end of the first convex portion. And a substrate dividing step of, after the etching step, dividing the substrate on a surface substantially perpendicular to the stripe direction of the first convex portion on the first convex portion to form a resonator reflection surface. It is characterized by becoming. According to this manufacturing method, in forming a stripe-shaped protrusion which has conventionally been a problem, the second protrusion is formed to extend to the end of the first protrusion, thereby forming a first structure having a fine structure. To prevent damage to the end of the projection, a waveguide region can be obtained with high accuracy, and a good element end surface can be obtained by the substrate dividing step. Also, in the case where the second convex portion is formed only on one of the end portions, even if the other first convex portion end portion is damaged by etching, the damaged portion is eliminated by the substrate dividing step. Thus, a resonator reflection surface can be formed. That is, the laser device according to this manufacturing method is one in which a resonator having a favorable reflection surface is formed on the device end face by etching on the second convex portion, and on the end portion of the first convex portion formed by the substrate dividing step. Becomes

(6) In the etching step, the first semiconductor layer exposed by removing a part of the stacked semiconductor layers is removed.
Forming the first and second projections on the surface of the semiconductor layer, etching deeper than the first surface, and separating the first projections in the semiconductor layer to form an electrode. It is characterized by providing a surface. According to this manufacturing method, the first convex portion formed on the first surface can maintain a favorable stripe shape, end portion, and side surface without being damaged even in the subsequent etching for the electrode formation surface, A laser device having an excellent waveguide region can be obtained, and the first convex portion is finely processed with high precision. Therefore, a laser device having excellent device reliability and having small device variations can be obtained.

(7) In the etching step, the first
An outer side surface substantially perpendicular to the stripe direction of the convex portion and separated from the first convex portion is formed as the second convex portion to serve as a resonator reflection surface. According to this manufacturing method, it is not necessary to form the end of the first convex portion having a fine structure, which has conventionally been a problem, by etching, and the side surface of the second convex portion wider than the first convex portion (external side surface) By forming the etched end face in (1), a good cavity reflection surface is formed. This is because, when the etching end face is buried in the conventional fine stripe-shaped projection, severe damage is observed on the end face,
Although a good resonator reflecting surface could not be formed, this can be avoided by forming an etching end face on the second projection. This makes it possible to use the etched end surface having higher productivity than the substrate division surface also for a laser element having a fine stripe-shaped projection.

(8) In the etching step, a substantially rectangular opening is provided so that the first opening sandwiched by the opening is formed.
Is formed. According to this manufacturing method, the first convex portion and the second convex portion can be formed without forming a complicated mask pattern in the etching step.
Since the first convex portion is formed between the second convex portions at both ends, the stripe shape is finely processed with high precision.

(9) In the etching step, the first
And a third convex portion extending from the second convex portion while being separated from the second convex portion.

(10) In the etching step, at least a first convex portion and a plurality of second convex portions having a stripe width wider than the first convex portion are provided on the first surface by etching. After forming the stripe-shaped protrusions, etching is performed so as to divide the stripe-shaped protrusions, and the outer side surface is formed as a second protrusion. According to this manufacturing method, since the second convex portion is formed simultaneously with the formation of the first convex portion, the first convex portion having a smaller width can be formed without damaging the microstructure particularly at the end portion. By forming a cavity reflection surface on the second convex portion, the method can be used to manufacture a laser element having excellent productivity.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Semiconductor Laser Device) As a semiconductor laser device of the present invention, specifically, as shown in FIGS. 5 to 7, a plurality of layers made of a nitride semiconductor are stacked on a substrate 10; The active layer 16 is formed on the laminate by a p-type cladding layer and n-type cladding layer.
Having a structure sandwiched between (14, 15) and the mold cladding layer,
The resonator has a stripe-shaped waveguide region as shown in the figure. As shown in the figure, the resonator on the substrate has a first convex portion 1 forming a stripe-shaped waveguide region and a second convex portion 2 extending to the first convex portion 1. In addition, the structure is such that the cavity reflection surface is provided on the end of the first convex portion and the side surface of the second convex portion (external side surface 5). That is, as a resonator on a substrate, in addition to the first protrusion 1 forming a stripe-shaped waveguide region as in a conventional semiconductor laser device, a second protrusion 2 provided with a resonator reflection surface is provided. It has. At this time, the other cavity reflection surface is provided at the end (end surface) of the first convex portion.

Further, in the present invention, the nitride _{semiconductor, Al x Ga y In 1-} xy (0 ≦ x ≦ 1,0 ≦ y ≦ 1,
0 ≦ x + y ≦ 1), and the semiconductor laser device of the present invention is obtained by laminating a layer made of the nitride semiconductor on a substrate. Preferably, as a laminated structure formed on the substrate, an active layer is formed by a p-type clad layer made of a p-type nitride semiconductor and an n-type clad layer made of an n-type nitride semiconductor as in the examples described later. It is preferable that the active layer has a layer made of a nitride semiconductor containing In. This is because a resonator having such a laminated structure and including the above-described first convex portion and second convex portion has a stripe-shaped convex portion as a resonator as shown in a comparative example described later. Compared to just
Good oscillation characteristics are obtained, and particularly, the oscillation threshold value is reduced due to the improvement of the light reflectance at the second convex portion, and the stability in single mode oscillation tends to be improved.

Here, in the present specification, the length of the first convex portion is the length of the first convex portion in the stripe shape in the stripe direction (longitudinal direction) as seen in FIG. The width of the first protrusion is a length in a direction perpendicular to the stripe direction. Similarly, the length of the second protrusion is the length of the first protrusion in the stripe direction, and the width of the second protrusion is the width of the second protrusion in the stripe direction. The length in the vertical direction. (Resonator) In the semiconductor laser device of the present invention, as a resonator on a substrate, a semiconductor laminated as described above is subjected to fine processing by etching or the like, and the first and second convex portions are formed. Have For example, as shown in FIGS. 5 to 7, the resonator structure may be a ridge structure formed by removing a part of the semiconductor layer by etching and remaining first and second protrusions. , A first protrusion, a second protrusion, and the like may be formed and then regrown and embedded. At this time, confinement of light and mode control are performed mainly by the waveguide region in the form of a stripe formed by the first convex portion as the resonator.

More specifically, as described in the following embodiments, in the semiconductor laser device of the present invention, a waveguide of a refractive index guide type is formed by the first convex portion, and the waveguide is formed in the second convex portion. The structure is such that the resonator reflection surface is provided at the end of the first projection, and the other resonator reflection surface is provided. (First convex portion) In the semiconductor laser device of the present invention, the first convex portion has the first convex portion and the second convex portion as resonators. It is provided with a shorter stripe length, and as described above, a stripe-shaped waveguide region is mainly formed by the first convex portion.

In the laser device of the present invention, the first
Is preferably less than 5 μm, more preferably in the range of 1 μm or more and 3 μm or less. The reason for this is that if it is within the above range, a refractive index guided laser device that realizes stable oscillation in the single transverse mode as described above will be obtained. In this case, an electrode is formed on the upper surface of the first convex portion as shown in FIGS. 5 to 7. At this time, the electrode is preferably provided only on the first convex portion. . This is because the electrode is formed only on the first convex portion forming the stripe-shaped waveguide region, that is, excluding the upper portion of the second convex portion, so that the electrode is formed on the gain region of the second convex portion. A change is generated, and this tends to enable efficient light oscillation in the waveguide region by the first convex portion, resulting in a laser element having excellent oscillation characteristics. For this reason, it is preferable that the electrode be provided with a length that does not reach the end of the first protrusion, that is, shorter than the length of the first protrusion. In addition, even if the end of the first protrusion is not provided with the second protrusion, the length of the electrode does not reach the end. This is preferable because peeling of the electrode can be prevented.

Further, in the laser device of the present invention, of the cavity reflection surfaces provided on the outer side surface of the first convex portion and the second convex portion, the first convex portion end is formed by the laser light. It is preferable to be on the emission side. This is because, as described later, the light is guided at a width wider than the width of the first convex portion at the second convex portion, so that the optical characteristics such as the aspect ratio of the laser light are reduced. Since it deteriorates and it is structurally difficult to control it, variations in the characteristics between elements also increase. For this reason, by setting the cavity reflection surface provided at the end of the first convex portion on the laser light emission side, good light confinement and mode control in the striped optical waveguide by the first convex portion are achieved. , Light can be emitted with high efficiency. (Second Projection) In the semiconductor laser device of the present invention, the length of the second projection is preferably 5 μm or less. This is because when the length of the second convex portion 2 exceeds 5 μm, the oscillation characteristics of the laser element tend to sharply decrease. This is because the waveguide is changed and the mode stability tends to be increased by providing the resonator reflection surface on the second convex portion 2, but the adverse effect due to the presence of the second convex portion also occurs. In particular, a decrease in the slope efficiency in the current-light output characteristics is observed, and the slope efficiency is particularly remarkable when it exceeds 5 μm. More preferably, 1 μm or more and 3 μm
By providing the second convex portion with a length in the following range, it is possible to improve the mode stability by having the second convex portion as a resonator while suppressing the above-described decrease in element characteristics. Tend to be obtained.

In the laser device of the present invention, the second
2 to 9 are provided so as to extend to the end of the first protrusion, and the first protrusion end and the second protrusion side surface (resonator reflection surface (A surface separated from the outer side surface). Further, when the second convex portion is provided at both ends of the first convex portion, the above-described change in the waveguide region becomes large, and the loss becomes large. In this case, since the cavity reflection surface provided on the second convex portion serves as the emission surface, the shape of the laser beam is deteriorated, and the dispersion of elements tends to increase, which is not preferable. (Third Projection) In addition to the first projection and the second projection constituting the above-described resonator, the semiconductor laser device of the present invention further comprises:
A third protrusion may be provided so as to surround the outer periphery of the resonator. The third convex portion is separated from the first convex portion when forming the first convex portion or the second convex portion, as will be described in a method of manufacturing a semiconductor laser element described later, and the third convex portion is formed. The first and second projections are formed so as to extend to the two projections, and do not function as a resonator in driving the laser element, unlike the first and second projections that constitute the resonator. That is, light is hardly guided since it is separated from the first convex portion which is a stripe-shaped waveguide region. In addition, the semiconductor laser device of the present invention is separated from the upper surface of the first projection and the first projection,
In the case of a structure having an electrode on the surface of the semiconductor layer (electrode formation surface) at a position apart from the third convex portion as viewed from the convex portion, there is a tendency that leakage current is prevented and the reliability of the element is improved.
preferable. (Method of Manufacturing Semiconductor Laser Element) Next, a method of manufacturing the semiconductor laser element of the present invention will be described in detail below.

A layer made of a nitride semiconductor is laminated on a substrate, and a first convex portion and a second convex portion are formed by etching the laminated semiconductor layer as a resonator. It forms a reflective surface. Hereinafter, each step will be described in order.

In the manufacturing method of the present invention, when forming the first projection, the second projection is formed at the end.

First, as a semiconductor to be laminated on a substrate,
As shown in Examples, a nitride semiconductor represented by the above composition formula is mainly used. Specifically, a laminate formed on the substrate has at least a structure in which an active layer is sandwiched between a p-type clad layer and an n-type clad layer, and preferably, as described above, And a p-type cladding layer made of n-type nitride semiconductor
It has a structure sandwiching an active layer having a nitride semiconductor containing n. (Etching step) In the manufacturing method of the present invention, the term “etching step” refers to a step in which a semiconductor layer on a substrate is subjected to fine processing by etching after laminating each layer to form a first projection and a second projection forming a resonator. This is a step of forming a part. In this etching step, in order to solve the above-described problem at the time of the conventional etching, a first convex portion mainly forming a stripe-shaped waveguide region and a second convex portion extending therefrom are formed. However, various methods can be used as the embodiments. Hereinafter, a specific example will be described.

Specifically, as the etching step, FIG.
As shown in the schematic cross-sectional view of FIG.
After laminating, a film 12 serving as a mask at the time of etching is formed on the surface of the semiconductor layer 11, and a photoresist film 20 having a desired pattern is further formed (FIG. 1A). 12 (FIG. 1B), and the first convex portion 1 sandwiched between the openings 6 by the mask 12 is provided on the semiconductor layer 11 (FIG. 1C). Next, a protective film 13 for providing an electrode on the first convex portion 1 is provided on the surface, and the mask 1 is provided so that the protective film 13 is provided inside the opening 6.
Unnecessary protective film 13 is removed by lift-off method using 2 (FIG. 1 (d)), and electrode forming surface 4 is exposed at a position separated from the bottom surface (first surface) of opening 6 to form a first electrode. Electrodes 40 and 41 are provided on the upper surface of the convex portion and the electrode forming surface 4, respectively (FIG. 1E). Finally, a portion of the semiconductor layer 11 is removed by etching until the substrate surface 7 is exposed so as to provide a plurality of element regions on the substrate 10 (FIG. 1F). This is through a substrate dividing step of dividing into regions and forming a resonator reflection surface.

As various embodiments in this etching step, as shown in a schematic perspective view of FIG. 2, first, an opening 6 sandwiching the first convex portion 1 is provided in the semiconductor layer 11 by etching, and then, As shown in FIGS. 2B to 2D,
A resonator structure is formed, and the substrate is cut along a cutting plane AA to form a first substrate.
A resonator reflection surface is formed on the convex portion 1 of the substrate. In FIG. 2B,
The semiconductor layer 1 at a position separated from the first projection 1 and the opening 6
1 is partially removed to expose the electrode forming surface 4, and as shown in the figure, the second convex portion 2 extending to the first convex portion 1 is bridged between the second convex portions 2. Convex portion 3 formed as follows
Thus, the first projection 1 is formed so as to surround the periphery. In FIG. 2C, the first projection 1 is formed in the same manner as in FIG. 2B except that a part of the opening 6 is removed in the stripe width direction. In FIG. 2D, it is formed in the same manner as in FIG. 2C except that one second convex portion 2 is removed.

In this way, as shown in FIG. 2A, first, the first convex portion 1 is formed, and then, as shown in FIGS. 2B to 2D, the second convex portion 2 and the first convex portion 1 are formed. By forming the outer side surface 5 including the resonator reflection surface, the shape defect / partial defect near the end and the surface unevenness on the side surface of the stripe, which have conventionally been problems in the formation of the stripe-shaped protrusion, can be effectively prevented. Thus, a good resonator can be formed.

Further, as another embodiment, as shown in a schematic perspective view in FIG. 3, a part of the semiconductor layer 11 is removed by etching to form the first convex portion 1 and the first convex portion. A stripe-shaped protrusion having a second protrusion 2 having a wider stripe width than the part 1 is formed (FIG. 3A).
Subsequently, as shown in FIG. 3B, a part of the semiconductor layer 11 at a position separated from the stripe-shaped protrusion is removed to expose the electrode forming surface 4, and then the hatched portion in the figure is removed. 22 and then etching until the substrate surface is exposed,
An external side surface including a resonator reflection surface may be formed on the convex portion 2 of the semiconductor device. Further, after forming the stripe-shaped convex portion, the semiconductor is etched by masking the hatched portion 21 in FIG. A part of the layer 11 is removed to form the outer side surface 5 of the second projection 2 and the electrode formation surface 4 as shown in FIG. According to these methods, a good resonator structure can be formed as in the above-described method.

As still another embodiment, as shown in FIG. 4, an opening 6 sandwiching the first projection 1 is provided by etching, and the opening 6 and the second projection 6 are arranged in the stripe direction of the first projection 1. And the convex portions 2 are alternately provided, and in a direction perpendicular to the stripe, there is a mode in which the opening 6 is provided so as to sandwich the first convex portion 1 and the third convex portion is further provided outside the opening 6. In this embodiment, the outer side surface is not formed on the second convex portion 2, and the mask region is changed to 22, 2 in the drawing by etching in the next stage.
An end face serving as a resonator reflection surface is provided on the second convex portion as 2 ′.

Here, in this specification, what is described as an electrode forming surface is used for forming an electrode.
When a pair of positive and negative electrodes are provided on the same surface side of the substrate, it is preferable that element chips can be efficiently formed on a wafer without leakage current or the like. The surface is etched deeper than the surface (first surface) on which the first protrusion is formed, and is exposed at a position closer to the substrate than the first surface. The exposed surface is formed at a position separated from the first protrusion, and when the third protrusion is formed, the first surface (opening) is sandwiched between the first protrusions. And a third on the outside
Are formed, and an electrode formation surface is formed further outside. Such an electrode forming surface may be a surface on which no electrode is provided in the case where an electrode is provided on the upper surface of the first convex portion and the substrate, and the electrode is disposed to face the substrate. The surface is the same as the surface on which the electrodes are formed, except that the surface is not provided. (First convex portion) In the manufacturing method of the present invention, the first convex portion is formed in a stripe shape, and the second convex portion is formed on at least one end portion.
Are formed on the end surfaces of the convex portions. As shown in FIG. 2A, the first convex portion may be formed so as to be sandwiched between substantially rectangular openings 6 to form the first convex portion 1. As shown in ()), a stripe-shaped protrusion having a plurality of first protrusions 1 and a plurality of second protrusions having a wider stripe width than the first protrusion 1 may be formed on the opening bottom surface 6 '. Here, if the stripe width of the first projection is relatively narrow, the end of the stripe is destroyed by etching. Therefore, the formation of the first projection in the manufacturing method of the present invention is performed at both ends. Is formed so as to be protected by a second protrusion wider than the stripe width of the first protrusion. When the width of the first protrusion is 5 μm or less, the first protrusion having a good stripe shape can be obtained by providing the second protrusion.
Further, when the thickness is in the range of 1 μm or more and 3 μm or less, conventionally, it seriously affects the end of the above-mentioned stripe-shaped projection, and the first projection of the stripe width in this range. By forming the second convex portion at the end at the time of forming by etching, it is possible to prevent the end portion of the stripe-shaped convex portion from being destroyed.

Specifically, conventionally, when a stripe-shaped convex portion is formed, as shown in FIGS. 11B, 11C, and 11E, the end portion has a higher priority by etching. As a result, the convex portion 30 was rounded at the end, and a concave portion 32 was formed on the end surface due to the extra removal of the semiconductor layer 11, so that a flat end surface could not be formed. However, in the manufacturing method of the present invention, by forming the second protrusion having a stripe width wider than the first protrusion, the end of the first protrusion is protected from damage due to etching. Further, by forming the side surface (outer side surface) of the second convex portion after forming the first convex portion, it is possible to form an end surface having good flatness to be a resonator reflection surface. This is because, in the etching step, the manufacturing method of the present invention first forms the first convex portion, and thus, compared to the case where a mask is provided in a state where the semiconductor layer is uneven as shown in FIG. Another object of the present invention is to maximize the accuracy of an etching mask and realize an excellent etching accuracy.

Here, methods for etching the nitride semiconductor include wet etching and dry etching, and dry etching is preferably used to form a smooth surface. Dry etching includes, for example, devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and ion beam etching. It can be formed by etching a nitride semiconductor. (Second convex portion) In the manufacturing method of the present invention, the second convex portion formed by the etching step is formed to extend to the first convex portion, and specifically, the first convex portion end. It is formed at the time of forming the first convex portion or after that. The second convex portion is formed wider than the first convex portion, that is, the first convex portion is formed.
The second convex portion is spread outward at the convex portion end. At this time, it is preferable that the joining portion of the first convex portion and the second convex portion is joined at a substantially right angle in view of the shape of the etching mask. Even if the second convex portion is slightly rounded, an external side surface is formed on the second convex portion at a position separated from the first convex portion by an etching process, and the external side surface becomes a resonator reflection surface. Element end face. The outer side surface serving as the resonator reflection surface is preferably formed by etching after forming the first projection. This is because forming at a stage different from that of the first projection does not result in fine processing of a complicated shape as compared with the case of forming the first projection at the same time. By forming the outer side surface by etching on the second convex portion, a flat etched end surface can be obtained, and this can be used as a resonator reflection surface.

Here, as for the size of the second protrusion after forming the outer side surface, if the width of the first protrusion is 5 μm or less, damage at the time of fine processing by etching becomes large. By setting the width of the second convex portion to preferably 5 μm or more, the occurrence of damage due to etching on the external side surface serving as the cavity reflection surface is suppressed, and more preferably 10 μm.
By setting m or more, an external side surface with good flatness can be obtained. In this case, rather than considering only the second convex portion, considering the accuracy of the mask pattern at the time of etching,
It is important to consider the difference in the stripe width between the first convex portion and the second convex portion. If the difference is large, it is easy to form a mask pattern in manufacturing, and the yield is improved. For example, when the opening 6 as shown in FIG. 2 is formed, the difference between the stripe widths corresponds to the width of the opening 6, so that a large difference means that the width of the opening can be widened. This makes it possible to form a mask pattern with high accuracy, and allows an etching process to be performed with high yield. Specifically, the difference between the stripe widths of the first protrusion and the second protrusion is at least 2 μm.
By setting it to m or more, it is possible to manufacture a joint portion between the first convex portion and the second convex portion and the formation of the outer side surface with a high yield in the etching step, to suppress element variation, and more preferably to 10
When the thickness is not less than μm, the first and second protrusions can be formed in which the bonding portion and the outer side surface are formed with high precision and the occurrence of roundness, surface irregularities, and the like is suppressed to a low level. More preferably,
By setting the thickness to 50 μm or more, an etching end surface having excellent flatness is formed at a position facing the outer side surface of the second convex portion, particularly, a joint portion with the first convex portion which is a region functioning as a cavity reflecting surface. You. (Third convex part) In the manufacturing method of the present invention, the third convex part formed by the etching step is formed to extend to the second convex part, and specifically, the first convex part. The second and third convex portions surrounding the opening are formed by providing an opening sandwiching the. Specifically, as shown in FIG.
After the projection 1 and the opening 6 are provided (FIG. 2A), a mask is applied to cover the size, and the non-mask region is removed by etching, as shown in FIG. 2D. A third convex portion that is separated from the first convex portion is formed. At this time, by making the mask width (the width of the first convex portion in the direction perpendicular to the stripe direction) narrower than that, FIGS.
As shown in (1), a form in which the third convex portion is not formed can be adopted. (First Surface) In the present invention, the first surface is provided with a first convex portion constituting a resonator, and when an opening is formed, it serves as a bottom surface of the opening. Here, the substantially rectangular opening may be substantially square. (Division of Substrate) In the manufacturing method of the present invention, the first convex portion,
After the etching step of forming the second projection, a substrate dividing step of dividing the substrate is provided. This substrate dividing step
More specifically, the division is performed at the division position AA in FIGS. 2B to 2D.
Outer side surface 5 of the second convex portion 2 provided at the end of the convex portion 1
Is divided at a position separated by a resonator length from. As a result, a division surface is formed on the first projection at the division position AA, which is used as a resonator reflection surface, the other resonator reflection surface is used as the outer side surface 5, and the first projection 1 serves as a resonator. And a laser element having the second convex portion 2 are obtained.

There are other forms of the substrate dividing step.
For example, as shown in FIG. 9, by setting a substantially central portion of the first convex portion 1 formed in the etching process as the substrate dividing position AA, the divided surface to be formed is divided by the dividing process as shown in FIG. 9.
In each of the block-shaped element regions arranged on the substrate, two laser elements and a division surface thereof are formed. In this mode, the division through one element region can form a division surface at each end of the first convex portion of the laser element, and while the resonance surface is formed efficiently, the division surface is vulnerable to shock at the time of division. There is a tendency that many surface irregularities are observed.

In the substrate dividing step of the present invention, there is no particular limitation, and the substrate can be divided by a conventionally known method. Specifically, the substrate may be divided using a scriber, a dicer, or the like. When it is difficult to divide by only means, means such as breaking by mechanically applying an external force such as braking may be used, and these may be combined and appropriately selected according to the properties of the substrate.
At this time, in order to assist the division, the substrate may be thinned in advance by means of polishing or the like, or other grooves may be formed so that the same effect as substantially reducing the thickness of the substrate may be obtained. . These methods divide the substrate by appropriately selecting or combining them according to the substrate material, thickness, and the like.

Conventionally, when a substrate that is difficult to cleave, such as a sapphire substrate, is used as a nitride semiconductor substrate, as shown in FIG.
The cleavage is affected by the cleavage of the semiconductor layer 11 on the substrate 11, and the divided surface 33 having severe irregularities on the surface is formed. This is because it is difficult to cleave the sapphire substrate at the cleavage plane when the substrate is divided based on the cleavage plane of the semiconductor layer having the nitride semiconductor (which substantially corresponds to the cleavage plane of GaN). The cleavage plane of the semiconductor layer cannot be taken out from the side close to 10 to a certain thickness of the semiconductor layer 11. Thus, the substrate 10
Back surface (surface facing the main surface on which semiconductor layer 11 is provided)
When the substrate is divided by the above-described means, the surface 33 having irregularities is initially cracked from the side close to the substrate 10 irrespective of the cleavage plane of the semiconductor layer 11, and the cleavage plane is first cracked to a certain thickness. It is said that it is divided
The substrate is divided in the process. Therefore, when a heterogeneous substrate made of a material different from that of the nitride semiconductor and not well matched to the cleavage properties of the semiconductor layer having the nitride semiconductor, that is, a heterogeneous substrate that is difficult to cleave is used, This is a division step.

[0044]

[Embodiment 1] FIG. 10 is a schematic sectional view showing the structure of a laser device according to an embodiment of the present invention, and shows a laminated structure cut along a plane perpendicular to a stripe-shaped projection. It is shown. Hereinafter, the first embodiment will be described with reference to FIG.

As the substrate 101, a sapphire substrate having a (0001) C plane as a main surface was used. At this time, the orientation flat surface was the A surface. As a substrate on which a nitride semiconductor is grown, in addition to sapphire (main surfaces are C-plane, R-plane, and A-plane), Si
C, ZnO, spinel (MgAl ₂ O ₄ ), GaAs, S
For growing a nitride semiconductor such as iC (including 6H, 4H, and 3C), a different substrate made of a material different from the nitride semiconductor, which is conventionally known, can be used. Also,
It may be directly laminated on a substrate made of a nitride semiconductor such as GaN.

First, the substrate 1 made of sapphire was
Set in a VPE reaction vessel, set the temperature to 500 ° C,
Trimethyl gallium (TMG), ammonia (NH ₃ )
And a buffer layer (not shown) made of GaN
It is grown to a thickness of 0 ° (angstrom).

Underlayer 102: After growing the buffer layer, the temperature is raised to 1050 ° C., and an underlayer 102 made of undoped GaN is grown to a thickness of 4 μm using TMG and ammonia. This layer acts as a substrate in the growth of each layer forming the element structure. Thus, on a heterogeneous substrate,
When a nitride semiconductor element structure is formed, a low-temperature growth buffer layer and a base layer serving as a nitride semiconductor substrate may be formed.

Next, the following layers are sequentially laminated as an element structure.

N-side contact layer 103: 4 μm thick, S
GaN anti-crack layer 104 doped with 3 × 10 ¹⁸ / cm ³ i: 0.15 μm thick In _0.06 G
a _0.94 N (may be omitted) n-side cladding layer 105: superlattice structure having a total thickness of 1.2 μm undoped Al _0.16 Ga _0.84 N having a thickness of 25 °, and a film thickness of 2
5 °, and GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si are alternately stacked.

N-side light guide layer 106: undoped GaN active layer 107 having a thickness of 0.2 μm: multiple quantum well structure having a total thickness of 380 °; barrier layer (B) made of Si doped In _0.05 Ga _0.95 N having a thickness of 100 °; Undoped In _0.2 Ga 0.8 N with a thickness of 40 °
And a well layer (W) made of these are laminated in the order of (B)-(W)-(B)-(W)-(B).

P-side cap layer 108: thickness 300 ° M
g × 1 × 10 ²⁰ / cm ³ doped p-type Al _0.3 Ga _0.7 N p-side light guide layer 109: 0.1 μm thick, 1 × 1 Mg
0 ¹⁸ / cm ³ -doped p-type GaN p-side cladding layer 110: superlattice structure with a total thickness of 0.6 μm Undoped Al _0.16 Ga _0.84 N with a thickness of 25 ° and 1 × 10 ²⁰ / cm of Mg with a thickness of 25 ° ^3- doped p-type GaN
And are alternately stacked.

P-side contact layer 111: thickness 150 °,
Mg 2 × 10²⁰/cm^ThreeDoped p-type GaN After forming the device structure,
Semiconductor layer taken out of the substrate and laminated as an etching process
Then, a first projection and a second projection are formed. This etching
In the process, the wafer is set in a PVD apparatus as shown in FIG.
And put SiO _TwoMask 12 made of semiconductor layer 11
Formed on the surface and masked by photolithography
12 are formed in a predetermined pattern (FIG. 1A,
(B)) The first striped stripe is formed by etching.
An opening 6 sandwiching the convex portion 1 is provided (FIG. 1C). this
At this time, the stripe width of the first protrusion 1 is 1.8 μm.
You.

Subsequently, the wafer is transferred to a PVD apparatus, and FIG.
As shown in (d), an insulating film 13 made of Zr oxide (mainly ZrO ₂ ) is formed on almost the entire surface of the wafer, the wafer is immersed in hydrofluoric acid, and the mask 6 is removed by a lift-off method. An insulating film 13 is formed on the inner surface. When an electrode is formed on the upper surface of the first convex portion 1, the insulating film 13 is p-type.
This is to insulate n from each other, and in addition, it is possible to achieve good stability of the transverse mode in the stripe-shaped waveguide region formed by the first convex portion 1. As shown in FIG. 1F, after the insulating film 13 is formed on the inner surface of the opening 6, the insulating film 13 is etched deeper than the bottom surface of the opening 6 at a position separated from the first convex portion 1, and the n-side in the semiconductor layer is etched. Exposing the contact layer. At this time, as shown in FIGS. 2B and 8A, a second convex portion 2 is provided at both ends of the first convex portion 1, and a third convex portion is provided between the second convex portions 2. 3 to form a second
And the width of the third protrusion 3 was 5 μm, and the width of the opening (in the stripe width direction of the first protrusion) was 50 μm. 2B and 8A by exposing the surface 4 of the n-side contact layer.
As shown in (2), the outer side surface 5 is also formed on the second convex portion 2 so as to be separated from the first convex portion 1 and substantially perpendicular to the stripe direction. This surface 4 (electrode formation surface) has an n-electrode 4
1 is formed, and p is formed on the upper surface of the first convex portion 1 via the insulating film 13.
An electrode 40 is formed (FIG. 1E). At this time, the p-electrode is formed so as to have a width of 100 μm, a length of several μm to several tens μm shorter than the first convex part, and not to cover the end of the first convex part. This is because, in the subsequent substrate dividing step, by forming the electrodes on the first convex portions with a length that does not extend to the dividing position, the electrodes can be protected from the impact at the time of division, and the electrodes can be prevented from being chipped or peeled off. This is because the electrode can be manufactured well, and is not limited to the above-described length of the electrode, and in consideration of this, it is preferable to form the electrode shorter than the first protrusion.

As described above, after the etching step, the dielectric multilayer film 1 made of SiO ₂ and TiO _{2 is formed} on almost the entire surface of the wafer.
13, the multilayer film 113 is provided with openings for exposing a part of the surface of the p-electrode and the n-electrode, and extraction electrodes 111 and 112 electrically connected to the electrodes are formed as shown in FIG. Formed. Thereby, the etching end surface side (the outer side surface of the second convex portion) serving as the resonator reflection surface
In addition, each extraction electrode is formed with a length shorter than the resonator length, and is set to a length that does not reach the division position in the subsequent substrate division process, so that each extraction electrode is chipped by the impact at the time of division. It is preferable because peeling can be avoided. As shown in FIG. 10, the extraction electrode 112 electrically connected to the electrode above the first convex portion is formed continuously up to the upper portion of the opening adjacent to the first convex portion, so that Wire bonding is preferable.

Finally, the semiconductor layer 11 is separated into blocks by etching at a depth where the substrate 10 is exposed, and the semiconductor layer 11 is arranged so as to obtain one laser element from each block (FIG. 1F). , FIG. 8 (b)). As described above, after the etching step, the process proceeds to a substrate dividing step of dividing the wafer, but before that, in order to ensure the substrate division,
The substrate may be thinned by a method such as polishing. Here, the sapphire substrate was polished to a thickness of about 70 μm. As described above, even when the substrate is difficult to be cleaved by thinning the substrate before the substrate dividing step, the accuracy of the substrate division can be increased, and good substrate division can be performed.

Next, as a substrate dividing step, the wafer is divided by the following method to obtain a laser device. 2 (b), 8
As shown in (b), the block-like semiconductor layer is
Divide by the A division plane. Specifically, a groove is provided on the back surface of the substrate 10 (the main surface on which the semiconductor layer is not formed) by a scriber so as to be the divided surface AA, and the substrate is braked.
Divide by plane AA. As a result, a cut surface is provided at the end of the first convex portion 1, and this is used as a resonator reflection surface. At this time, the length of the resonator, that is, the length from the end of the first protrusion to the outer side surface of the second protrusion is preferably 300 to 500 μm, and the electrode on the first protrusion is preferably 40 is formed shorter than the dividing position AA. The plane AA substantially coincides with the orientation flat plane (sapphire A plane) of the sapphire substrate, substantially coincides with the M plane that is the cleavage plane of gallium nitride in the semiconductor layer, and this gallium nitride M plane is included in the divided plane. By being extracted to the element structure of the semiconductor layer, a good resonator reflection surface is obtained. As shown in FIG. 8C, the substrate is further divided along the division planes BB and CC into the substrate divided into a bar shape to obtain a laser element.

When a heat sink was attached to the obtained laser element and laser oscillation was attempted at room temperature, continuous oscillation was confirmed at a wavelength of 405 nm at a threshold current density of 2.5 kA / cm ² , a threshold voltage of 5 V, and 10,000 hours at room temperature. This shows the above life.

[Embodiment 2] In the etching step, after the opening 6 sandwiching the first projection 1 is formed (see FIG. 2).
(A)), in the stripe width direction of the first convex portion 1,
As shown in FIG. 2C, a mask is provided with a width not forming the third protrusion, and the first protrusion is formed on the first surface 6 and the second protrusion is formed on both ends thereof, as shown in FIG. Form a convex part.
Except for this, a laser device is obtained in the same manner as in the first embodiment (FIG. 7). Since the third convex portion is not provided, the danger such as generation of a leak current is increased in the formation of the insulating film formed in the opening and the electrodes formed therethrough, as compared with the first embodiment. Although the manufacturing yield tends to decrease slightly, the characteristics of the obtained laser device are almost the same, and the laser device has good characteristics.

[Embodiment 3] After the opening 6 is formed in the etching step, as shown in FIG. 2D, the first projection 1 and one of its ends are formed on the first surface 6. A laser device is obtained in the same manner as in the first embodiment except that only the second end is formed. At this time, in the substrate dividing step, in forming the element end surface, the dividing position AA in the drawing is a position farther from the end of the first convex portion 1 as compared with the first and second embodiments. this is,
At the end where the second convex portion 2 is not formed, the length of the first convex portion 1 is reduced to avoid damage due to etching.
The length is made longer than in the first and second embodiments, and the first projection 1 is divided at a position apart from the end of the first projection 1 on the side where the second projection 2 is not provided. Although the characteristics of the obtained laser element tend to be worse than those of Examples 1 and 2, the laser element has better characteristics than the conventional laser element.

Example 4 In the etching step, the first convex portion 1 was formed twice as long as the stripe length of the first convex portion of the obtained laser element, as shown in FIG. A plurality of block-shaped regions provided with a first convex portion 1, a second convex portion 2, and a third convex portion 3 on a surface 4 exposing an n-side contact layer; In the dividing step, as shown in FIG. 9B, the substrate is divided at a position where the stripe length of the first convex portion 1 becomes almost half as the substrate dividing position AA. Other manufacturing conditions are the same as those of the first embodiment, and a laser device schematically shown in FIG. 5 is obtained.

The obtained laser device is formed at the division position AA as compared with the first embodiment, and the divided surfaces facing each other are the cavity reflection surfaces of different laser devices, so that the number of chips per wafer is larger. Become. However, different from the first embodiment, since the impact at the time of dividing the substrate is applied to each of the block-shaped element regions joined at the dividing surfaces, the shape becomes weak against the impact, and a good dividing surface cannot be obtained. In this case, the laser device chip obtained from the block-shaped device region becomes defective, and as a result, the non-defective rate per wafer tends to be lower than that in the first embodiment. In addition, the characteristics of the laser element having a good division surface exhibit oscillation characteristics substantially equal to those of the first embodiment.

[Embodiment 5] In the etching step, as shown in FIG. 3A, a stripe-shaped projection is formed on the first surface 6 'by etching, and this projection is
Convex portion 1 and second convex portion 2 having a wider stripe width
And at least a plurality of first protrusions 1 sandwiched between the second protrusions 2 are formed. Subsequently, as shown by a hatched area 21 in the figure, a region 21 composed of the first convex portion 1 and a part of the second convex portion 2 sandwiching the first convex portion 1 is masked and a non-mask region is etched. Then, as shown in FIG. 3C, the n-side contact layer surface 4 is exposed,
The outer side surface 5 is formed on the convex portion 2 of FIG. Others are described in Example 1.
A laser device is obtained in the same manner as described above. At this time, the length of the second protrusion 2 in the stripe width direction of the first protrusion 1 is:
It is formed to be longer than the width (1.8 μm) of the first projection 1 and shorter than 200 μm in width of the first surface 6 ′ when the surface 4 is exposed. In this case, the width is 150 μm.

In the obtained laser device, since the second convex portions are formed with sufficient width and length at both ends of the first convex portions, good stripe-shaped convex portions (the first convex portions) are formed. (Protrusions) can be formed, and have characteristics similar to those of the first and second embodiments.

[Embodiment 6] In the etching step, as shown in FIG.
After forming on the first surface 6 ′ a projection having a plurality of projections and a plurality of second projections 2, a stripe shape wider than the projections and substantially parallel to the stripe direction of the first projections 1 is formed. Is formed, and a portion of the semiconductor layer 11 in the non-mask region is removed by etching, thereby exposing the surface 4 of the n-side contact layer. As in the first embodiment, the first surface 6 ′ is formed.
And the above-mentioned side surface insulating film for the convex portion is formed (not shown). At this time, the stripe width of the first convex portion 1 is 2 μm, the stripe width of the second convex portion is 150 μm, and the stripe width of the first surface formed on the n-side contact layer surface 4 (first
Of the convex portion 1 in the direction perpendicular to the stripe direction)
Is set to 200 μm, as in the case of the fifth embodiment.
Unlike this, a first surface 4 wider than the second convex portion 2 is formed.

Subsequently, the p-electrode is first interposed via the insulating film.
And an n-electrode is formed on the surface 4 in the hatched area 22. At this time, as in the first embodiment, the p-electrode is formed with a length that does not reach the second protrusions 2 provided at both ends of the first protrusion 1, and the n-electrode is also formed in the same manner as in the first embodiment. Are formed in parallel with the stripe direction of the first convex portion 1. Next, the semiconductor layer in the unmasked region is removed by masking the hatched region 22 in the figure and etching to a depth where the surface of the substrate 10 is exposed.

After the above etching step, a laser element chip is obtained in the same manner as in the first embodiment. As in the case of the fifth embodiment, a good laser element can be manufactured from the obtained laser element, and the laser element has excellent characteristics as in the first embodiment.

[Embodiment 7] In the etching step, after the opening is formed by etching in the same manner as in Embodiment 1, as shown in FIG. 4, the opening provided with the first projection 1 substantially at the center is provided. A mask having a stripe shape is formed with a width covering the portion, and a non-mask region is etched to a depth at which the n-side contact layer is exposed to remove a part of the semiconductor layer. Get. At this time, the stripe-shaped mask is provided with a stripe width such that the width of the opening is 80 μm and the width of the third projection is 5 μm. As a subsequent etching step, a mask is provided in the hatched area 22 'in the figure, and the unmasked area is etched to a depth at which the substrate 10 is exposed, and a block-like semiconductor is formed on the surface of the substrate 10 as shown in FIG. A layer region is arranged, and external side surfaces serving as resonator reflection surfaces are formed on second convex portions 2 provided at both ends of the first convex portion 1. Finally, n and p electrodes are respectively provided on the exposed surfaces of the n-side contact layer and the p-side contact layer, and as a substrate dividing step, the wafer is cut at a cutting position AA in the drawing to form the first convex portion 1. A laser device is obtained by forming a cavity reflection surface at one end.

The obtained laser device is a laser device having excellent characteristics as in the first embodiment. In the manufacture of the laser device, similarly, a laser device having a good resonance surface and a stripe side surface with high accuracy is also used. can get.

[Embodiment 8] A laser device is obtained in the same manner as in Embodiment 7, except that the mask for exposing the surface of the substrate 10 is a hatched area 22 in FIG. At this time, as shown in the figure, one of the second protrusions 2 provided at both ends of the first protrusion 1 is etched by a length reaching the next adjacent first protrusion 1. A mask is formed. The obtained laser device has a larger distance between the first protrusions than in the seventh embodiment, and therefore is more resistant to the impact at the time of dividing the substrate, and tends to have less irregularities on the resonance surface due to the division. A good resonance surface is formed.

[Embodiment 9] The first protrusion has a width of 2.5 μm.
Other than that, a laser device is obtained in the same manner as in the first embodiment.

The laser device obtained is almost as good as that of the first embodiment, and the lateral mode control is good although the control of the transverse mode tends to be slightly inferior to that of the first embodiment. Further, when the width of the first convex portion is increased to 3 μm or 5 μm, the controllability of the transverse mode tends to be clearly deteriorated, and it tends to be difficult to obtain a laser element having a good laser beam spot shape.

[Embodiment 10] A laser device is manufactured in the same manner as in Embodiment 1, except that the width of the second convex portion is set to 2 µm. The obtained laser device shows almost the same device characteristics as in Example 1. Further, when the width of the convex portion is increased to 2.5 μm or 3 μm, the control of the transverse mode tends to be inferior. -Field pattern deteriorates. Further, when it is larger than 3 μm, it becomes difficult to obtain a good laser beam.

[Embodiment 11] In the etching step,
The bottom of the opening has a thickness of 0.1 μm for the n-side cladding layer.
A laser device is obtained in the same manner as in Example 1, except that the etching is performed to a depth of m. As shown in FIG. 6, the obtained laser element includes the active layer 16 in the first projection,
The present embodiment realizes better confinement of the transverse mode than the first embodiment.

[Comparative Example 1] In the same manner as in Example 1, after the respective layers are laminated on the substrate, as an etching step, a stripe-shaped convex portion for forming a waveguide region is formed as follows.

After transferring the wafer to the PVD apparatus, the SiO ₂
Was etched by photolithography at a depth such that the n-side contact layer was exposed. At this time, as shown in FIG. 11A, a stripe-shaped protrusion having a width of about 50 μm is formed on the exposed surface of the n-side contact layer, and a stripe serving as a waveguide region is formed on the protrusion. First, as shown in FIG. 11A, a mask 12 made of SiO ₂ is provided on almost the entire surface of the wafer, and a photoresist film 20 is formed on the mask 12 by a photolithography technique in a stripe-shaped pattern. Provided above. Subsequently, the mask 12 in a region where the photoresist film 20 is not provided is removed by RIE using SiCl ₄ gas, and a stripe-shaped mask 12 having a width of about 2 μm is formed on the convex portion. Is etched to expose the p-side cladding layer surface, and FIG.
As shown in (b), a stripe-shaped projection (ridge stripe) is formed on the surface. At this time, the etching depth is a position where the thickness of the p-side cladding layer becomes 0.1 μm.

Observation of the obtained ridge stripe 30 revealed that both ends of the ridge stripe were damaged by etching, and as shown schematically in FIG.
It had a rounded shape. In addition, FIG.
As shown in (e), the end surface tends to be greatly damaged in a region (hatched region 32 in the figure) from the active layer to the stripe-shaped convex portion 30, and is indicated by a white arrow in the figure. It is thought that erosion has occurred in the water. When such an end face is used as the cavity reflection surface, laser oscillation becomes difficult. Furthermore, as shown in FIG. 11D, some of the projections 30 had irregularities on the side surfaces.

After the ridge stripe 30 is formed,
The wafer is transferred to the VD device and _TwoAbove the mask 12
Over the exposed surface of the ridge stripe formed from
And Zr (mainly ZrO_Two)
μm thick, the wafer is immersed in hydrofluoric acid,_Two
Is removed by a lift-off method. Then, implement
Exposed p-side contact layer and n-side contact as in Example 1.
P and n electrodes are formed on the surface of the
The wafer is divided at the cutting position CC shown in
An end face serving as a resonator reflection surface was formed on the ip 30.

Among the obtained laser devices, there is a laser device in which the etched end face which is the resonator reflection surface of the ridge stripe has damage as shown in FIG. 11, and the device characteristics are as described in Example 1. In comparison, the controllability in the transverse mode was inferior, and the threshold current tended to increase.

[0079]

According to the present invention, even in a laser device structure in which a stripe-shaped waveguide region is provided with a stripe-shaped protrusion, the mode controllability is superior to that of a conventional laser device. In addition, a laser element having excellent laser light optical characteristics can be obtained. Furthermore, in its manufacture,
It is possible to improve the damage to the side surface and the end portion of the convex portion, which has conventionally been a problem, and to accurately manufacture a waveguide region that functions well as a waveguide.

[0080]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a manufacturing method of the present invention.

FIG. 2 is a schematic view illustrating a laser device of the present invention.

FIG. 3 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating a manufacturing method of the present invention.

FIG. 9 is a schematic diagram illustrating a manufacturing method of the present invention.

FIG. 10 is a cross-sectional view illustrating an element structure according to an embodiment of the present invention.

FIG. 11 is a schematic view illustrating a conventional laser element.

FIG. 12 is a schematic diagram illustrating a conventional laser element.

[Explanation of symbols]

 1 First convex part 2 Second convex part 3 Third convex part 4 Electrode forming surface 5 Resonator end surface 6 · Opening bottom surface · First surface 7 ··· Substrate surface 8 ··· Divided surface (resonator end surface) 10 ··· Substrate 11 ··· Semiconductor layer 12 ··· Mask 13 ··· ..Insulating films 14, 15... Cladding layer 16... Active layer 20... Photoresist film 21... Mask region 22... Mask region 40. .... n electrode

Claims (10)

[Claims] 1. A semiconductor laser having a structure in which a plurality of layers made of a nitride semiconductor are stacked on a substrate, and has a structure in which an active layer is sandwiched between a p-type clad layer and an n-type clad layer, and has a stripe-shaped waveguide region. An element, wherein the stripe-shaped waveguide region has a stripe-shaped first protrusion, and a second protrusion extending to one end of the first protrusion; A semiconductor laser device, wherein a cavity reflection surface is provided on an end portion of the first convex portion and an outer side surface of the second convex portion side surface which is separated from the first convex portion. 2. The method according to claim 1, wherein the stripe width of the first projection is 5 μm.
2. The semiconductor laser device according to claim 1, wherein: 3. The semiconductor laser device according to claim 2, wherein a distance between the cavity reflection surface provided on the second convex portion and the first convex portion is 5 μm or less. . 4. An electrode is provided in contact with an upper surface of said first convex portion, and said electrode has a length not reaching an end of said first convex portion. 3. The semiconductor laser device according to 3. 5. A semiconductor layer having a structure in which an active layer is sandwiched between a p-type clad layer and an n-type clad layer on a substrate, and a first layer formed by removing a part of the semiconductor layer by etching. A method of manufacturing a laser device having a stripe-shaped waveguide region in a convex portion, wherein a layer made of a nitride semiconductor is laminated on the substrate, and then the first convex portion in the stripe shape is etched by etching. An etching step of forming a second projection wider than the stripe width of the first projection on at least one end of the first projection; and, after the etching step, a first projection on the first projection. A substrate dividing step of dividing a substrate on a surface substantially perpendicular to a stripe direction of the convex portion to form a cavity reflection surface. 6. In the etching step, after forming the first convex portion and the second convex portion on the first surface exposed by removing a part of the laminated semiconductor layer, 6. The method of manufacturing a semiconductor laser device according to claim 5, wherein an etching surface is provided deeper than the first surface, and an electrode formation surface is provided in the semiconductor layer so as to be separated from the first protrusion. 7. In the etching step, an outer side surface substantially perpendicular to a stripe direction of the first convex portion and separated from the first convex portion is formed in the second convex portion to form a resonator reflection surface. 7. The method for manufacturing a semiconductor laser device according to claim 5, wherein: 8. The semiconductor laser device according to claim 5, wherein, in the etching step, a first convex portion sandwiched between the openings is formed by providing a substantially rectangular opening. Production method. 9. The semiconductor according to claim 5, wherein in the etching step, a third convex portion is formed so as to be spaced from the first convex portion and extend to the second convex portion. Laser element. 10. A stripe having a plurality of at least a first convex portion and a second convex portion having a wider stripe width than the first convex portion on the first surface by etching in the etching step. 10. The semiconductor according to claim 5, wherein after forming the convex portion having a shape, etching is performed so as to divide the convex portion having a stripe shape, and the outer side surface is formed as a second convex portion. Laser element manufacturing method.