JP2012015217A - Manufacturing method of optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical semiconductor device which can cause unevenness in a coupling coefficient κ of a diffraction grating at low cost.SOLUTION: The method of manufacturing an optical semiconductor device includes: a first semiconductor layer formation step for forming a first semiconductor layer on a semiconductor substrate; a concave and convex pattern formation step for forming a concave and convex pattern in a laser stripe region 43 in which a waveguide is formed and dummy regions 44 formed on either side of and close to the laser stripe region in a surface of the first semiconductor layer; a second semiconductor layer formation step for forming, by MOCVD, a second semiconductor layer on a concave portion of the first semiconductor layer with the concave and convex pattern formed therein; and a third semiconductor layer formation step for forming a third semiconductor layer on a convex portion of the first semiconductor layer, and on the second semiconductor layer after the second semiconductor layer formation step.

Description

  The present invention relates to a method for manufacturing an optical semiconductor device.

  Currently, a semiconductor laser is used as a light source in optical fiber communication. However, a semiconductor laser used for long-distance transmission is preferably one that oscillates in a single longitudinal mode, such as a distributed feedback (DFB) laser. Has been put to practical use. In general, a distributed feedback laser is provided with a diffraction grating inside, and in order to obtain a high light output, an anti-reflection (AR) film is provided on the light exit surface, and the light exit surface. The opposite surface is coated with a high reflection (HR) film. For this reason, the waveguide of the distributed feedback laser, that is, both ends of the resonator have an asymmetric structure with greatly different reflectivities.

  By the way, when the diffraction grating has a uniform coupling constant κ in the direction of the resonator axis, in a DFB laser having a structure in which an AR film and an HR film are provided at both ends of the resonator, hole burning is performed as the optical output increases. As a result, the light intensity distribution in the resonator axis direction becomes non-uniform. Therefore, a DFB laser having a structure in which the coupling constant κ of the diffraction grating is made nonuniform in order to prevent the light intensity distribution from becoming nonuniform has been reported.

  As described above, the diffraction grating coupling constant κ can be made nonuniform by making the thickness of the diffraction grating nonuniform, by making the composition ratio of the material forming the diffraction grating nonuniform, or by the duty of the diffraction grating. There are methods for making the ratio non-uniform.

  By the way, when manufacturing an optical semiconductor device such as a DFB laser, a metal organic chemical vapor deposition (MOCVD) method is used. In the MOCVD method, by forming a mask layer made of a dielectric on a part of a semiconductor wafer, the in-plane distribution of the film thickness and composition of the crystal growth layer can be changed. This is called a selective MOCVD method. In the selective MOCVD method, by forming a mask layer made of a dielectric material such as silicon oxide on the surface of the semiconductor wafer, a growth material for contributing to crystal growth in the region of the surface of the semiconductor wafer that is originally covered with the mask layer However, the gas phase diffuses around the mask layer. As a result, the film formation rate at the peripheral portion of the mask layer changes and the composition ratio also changes, so that the coupling constant κ of the diffraction grating can be made non-uniform.

  For example, as a method of making the composition ratio of the material forming the diffraction grating non-uniform, a periodic pattern of unevenness for forming the diffraction grating is formed on the surface of the semiconductor substrate or semiconductor layer, and the periodic pattern on the unevenness is formed. Then, a mask layer made of a dielectric is formed. This mask layer is formed on both sides of the laser stripe region serving as a waveguide, and is formed so that the width of the mask layer changes in a direction substantially perpendicular to the light traveling direction. On this, a semiconductor layer made of InGaAsP or the like is formed by the selective MOCVD method described above. As a result, the laser stripe region corresponding to the region where the width of the mask layer is wide may be formed with a composition having a higher refractive index than the laser stripe region corresponding to the region where the width of the mask layer is narrow. it can. Thereby, the coupling coefficient κ of the diffraction grating can be made non-uniform.

Further, as a method of making the thickness of the diffraction grating non-uniform, a SiO ₂ mask having a structure in which the thickness of the semiconductor layer is inclined is formed on the semiconductor wafer, and after the semiconductor layer is formed by MOCVD, This SiO ₂ mask is removed. Thereafter, another SiO ₂ mask for forming the diffraction grating is further formed, and the diffraction grating of the semiconductor layer is formed by dry etching such as RIE. After removing the other SiO ₂ mask, the semiconductor material is removed. There is a way to embed.

Further, as a method for making the duty ratio of the diffraction grating non-uniform, when forming a resist pattern for forming a diffraction grating on a semiconductor substrate or semiconductor layer, an electron beam (EB) drawing device or the like is used. The exposure is performed while changing the spot diameter. There is a method of performing etching by RIE (Reactive Ion Etching) or the like using a resist pattern formed by such an EB drawing apparatus, removing the resist pattern, and further forming a semiconductor layer. As a result, a diffraction grating having a non-uniform duty ratio can be formed on the surface of the semiconductor substrate or semiconductor layer.

JP-A-9-64456 JP-A-6-196798 Japanese Patent Laid-Open No. 5-299761

By the way, in the conventional method of making the thickness of the diffraction grating non-uniform, it is extremely difficult to form a resist pattern on the inclined surface, and the number of times of SiO ₂ mask and crystal growth increases, and thus the manufacturing process. In addition, the manufacturing time increases and the manufacturing cost increases.

  In addition, in the conventional method of making the composition ratio of the material forming the diffraction grating non-uniform, changing the composition ratio also changes the lattice constant, which causes distortion and the crystallinity also changes. In some cases, the desired characteristics cannot be obtained.

  Further, in the conventional method of making the duty ratio of the diffraction grating non-uniform, it is necessary to use an electron beam drawing apparatus or the like in order to make the duty ratio of the diffraction grating non-uniform. Since drawing requires a lot of time, the manufacturing cost increases.

  Therefore, there is a demand for a method of manufacturing an optical semiconductor device in which the coupling constant κ of the diffraction grating can be made non-uniform as designed at low cost, and the uniformity of the light intensity distribution is improved.

  According to one aspect of this embodiment, a first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate, and a laser stripe in which a waveguide is formed on the surface of the first semiconductor layer A concave / convex pattern forming step for forming a concave / convex pattern in a dummy region formed close to both sides of the region and the laser stripe region, and a second semiconductor layer in a concave portion of the first semiconductor layer in which the concave / convex pattern is formed After forming the second semiconductor layer by MOCVD, and after forming the second semiconductor layer, a third semiconductor layer is formed on the convex portion of the first semiconductor layer and the second semiconductor layer. A third semiconductor layer forming step, wherein a refractive index of a material forming the second semiconductor layer is a refractive index of a material forming the first semiconductor layer and the third semiconductor layer. Unlike the laser The gap between the lie region and the dummy region is narrower on the other end side where the antireflection film is formed than on the one end side where the reflection film is formed in the waveguide. And

  According to another aspect of the present embodiment, a first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate, and formation of a waveguide on the surface of the first semiconductor layer A step of forming a concavo-convex pattern in a laser stripe region to be formed and a dummy region formed adjacent to both sides of the laser stripe region; A second semiconductor layer forming step of forming the second semiconductor layer by MOCVD; and after the second semiconductor layer forming step, a third semiconductor layer is formed on the convex portion of the first semiconductor layer and the second semiconductor layer. A third semiconductor layer forming step of forming a semiconductor layer, and a refractive index of a material forming the second semiconductor layer is a material forming the first semiconductor layer and the third semiconductor layer Different from the refractive index of In the waveguide, the dummy region is not formed near one end where the reflection film is formed, but the dummy region is formed near the other end where the antireflection film is formed. Is formed.

  According to the disclosed method for manufacturing an optical semiconductor device, the coupling constant κ of the diffraction grating can be made non-uniform at low cost, so that the uniformity of the light intensity distribution can be improved.

The perspective view which shows the structure of the optical semiconductor device manufactured by 1st Embodiment Process drawing (1) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (2) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing of the manufacturing method of the optical semiconductor device in the first embodiment (3) Process drawing (4) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing of the manufacturing method of the optical semiconductor device in the first embodiment (5) Process drawing (6) of the manufacturing method of the optical semiconductor device in 1st Embodiment Structure diagram of dummy region and laser stripe region in the first embodiment Process drawing (7) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (8) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (9) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (10) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (11) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (12) of the manufacturing method of the optical semiconductor device in 1st Embodiment Process drawing (13) of the manufacturing method of the optical semiconductor device in 1st Embodiment Structure diagram of dummy region and laser stripe region in second embodiment Structure diagram of another dummy region and laser stripe region in the second embodiment

  Modes for carrying out the invention will be described below.

[First Embodiment]
A first embodiment will be described. The present embodiment is a method for manufacturing a DFB laser which is an optical semiconductor device.

(DFB laser)
First, a DFB laser manufactured by the method for manufacturing an optical semiconductor device in the present embodiment will be described with reference to FIG. This DFB laser has an n-GaAs substrate 11, an n-GaAs buffer layer 12, an n-AlGaAs cladding layer 13, a quantum dot active layer 14, a diffraction grating layer 15, a p-InGaP cladding layer 16, and a p-GaAs contact layer. 17 is laminated. In the diffraction grating layer 15, a p-InGaP layer 19 having a refractive index of 3.14 is formed in a lattice shape in a p-GaAs layer 18 having a refractive index of 3.4. Specifically, in the p-InGaP layer 19, a lattice formed in a stripe shape so as to extend in a direction substantially perpendicular to the waveguide direction indicated by the arrow A is arranged along the waveguide direction indicated by the arrow A. It is formed as follows. In the present embodiment, the waveguide direction indicated by arrow A is formed to be the [110] direction. The p-InGaP cladding layer 16 and the p-GaAs contact layer 17 have a ridge portion 21 having a ridge structure. The SiO ₂ film 22 is formed on the side surface of the ridge portion 21 and the surface of the diffraction grating layer 15. Is formed. Further, a p-side electrode 23 is formed on the upper surface of the p-GaAs contact layer 17, a side surface and a surface of the SiO ₂ film 22, and an n-side electrode 24 is formed on the back surface of the n-GaAs substrate 11. . In the diffraction grating layer 15, the p-InGaP layer 19 that forms the diffraction grating layer 15 is formed so that the film thickness decreases from one surface 31 toward the other surface 32. An HR film having a high reflectance is formed on one surface 31 of the DFB laser, and an AR film serving as an antireflection film is formed on the other surface 32. The light is emitted from the other surface 32 on which is formed.

(Manufacturing method of optical semiconductor device)
Next, a method for manufacturing the optical semiconductor device in the present embodiment will be described with reference to FIG. 2 to 7 and 9 to 15, (a) is a cross-sectional view along the waveguide direction of a DFB laser manufactured by the method of manufacturing an optical semiconductor device in the present embodiment, that is, ( It is sectional drawing in a 1-10 (plane). FIG. 12B is a cross-sectional view in the direction perpendicular to the waveguide direction, that is, a cross-sectional view in the (1 1 0) plane, and FIGS. 12B to 15B are laser stripes. It is an enlarged view of a section in a field.

First, as shown in FIG. 2, by MBE (Molecular Beam Epitaxy), an n-GaAs buffer layer 12, an n-AlGaAs cladding layer 13, a quantum dot active layer on an (0 0 1) plane n-GaAs substrate 11 are used. Layer 14 and p-GaAs layer 18a are sequentially formed. At this time, the n-GaAs buffer layer 12 is formed with a thickness of about 300 nm, and a layer made of n-Al _0.3 Ga _0.7 As is formed as the n-AlGaAs cladding layer 13 with a thickness of about 500 nm. The quantum dot active layer 14 forms, for example, a wetting layer and a quantum dot structure (not shown) by forming several molecular layers of i-InGaAs on the i-GaAs layer, and further, an i-GaAs layer is formed thereon. Are formed by laminating layers each having a structure in which is formed. In the present embodiment, the quantum dot active layer 14 is formed by laminating about 10 quantum dots composed of an i-GaAs layer and i-InGaAs, and emits light in the 1.3 μm band. is there. On this quantum dot active layer 14, the p-GaAs layer 18a used as a 1st semiconductor layer is formed.

Next, as shown in FIG. 3, an SiO ₂ film (silicon oxide film) 41, which is a dielectric film, is formed on the p-GaAs layer 18a. The SiO ₂ film 41 is formed by a CVD (Chemical Vapor Deposition) method.

Next, as shown in FIG. 4, an SiO ₂ mask 41a to be a silicon oxide pattern is formed. Specifically, a photoresist is applied on the SiO ₂ film 41, and exposure and development are performed by an exposure apparatus, thereby forming a resist pattern (not shown) in a region where the SiO ₂ mask 41a is formed. This resist pattern is a striped resist pattern having a fine period formed by interference exposure using an exposure apparatus. In the interference exposure, exposure is performed by an exposure apparatus using a mask or the like in which a phase shifter is formed in a striped pattern, whereby a striped resist pattern having a fine period can be formed. The striped resist pattern to be formed has a stripe extending in a direction perpendicular to the [110] direction, which is the waveguide direction, so that the direction in which the stripes are arranged is the light emitting direction. It is formed so as to be arranged along the direction. Thereafter, the SiO ₂ film 41 in the region where the resist pattern is not formed is removed by RIE or the like, and the resist pattern is removed to form a SiO ₂ mask 41a on the p-GaAs layer 18a. FIG. 4B is a sectional view in a region where the SiO ₂ mask 41a is not formed.

Next, as shown in FIG. 5, a resist pattern 42 is formed on the p-GaAs layer 18a and the SiO ₂ mask 41a. As will be described later, the resist pattern 42 has openings in a laser stripe region 43 and a dummy region 44 where a waveguide is formed. Specifically, the resist pattern 42 is formed by applying a photoresist on the entire surface of the p-GaAs layer 18a and the SiO ₂ mask 41a, and performing exposure and development with an exposure apparatus.

Next, as shown in FIG. 6, in the region where the SiO ₂ mask 41a and the resist pattern 42 are not formed, the surface of the p-GaAs layer 18a is dry-etched by RIE or the like to thereby form the p-GaAs layer 18a. An uneven pattern is formed on the surface of the substrate. Specifically, dry etching is performed so that a concavo-convex pattern is formed in the laser stripe region 43 and the dummy region 44, which are regions where the resist pattern 42 is not formed. That is, the uneven pattern on the surface of the p-GaAs layer 18a is formed by etching the p-GaAs layer 18a in a region where the resist pattern 42 is not formed and where the SiO ₂ mask 41a is not formed. To do. A depth B of the formed uneven pattern is, for example, about 30 μm.

Next, as shown in FIG. 7, the SiO ₂ mask 41a and the resist pattern 42 are removed. As a result, on the surface of the p-GaAs layer 18a, an uneven pattern is formed in the laser stripe region 43 and the dummy region 44, and an uneven pattern is not formed in the region other than the laser stripe region 43 and the dummy region 44. . The figure which looked at the thing of this state from the upper surface is shown in FIG. In FIG. 8, the cross-sectional view taken along the broken line 8A-8B corresponds to FIG. 7A, and the cross-sectional view taken along the broken line 8C-8D corresponds to FIG. 7B. is there. As shown in the figure, in the concavo-convex pattern, the distance between the laser stripe region 43 formed linearly at substantially the same width in the central portion and the laser stripe region 43 on both sides of the laser stripe region 43 gradually changes. Thus, two dummy regions 44 are formed. That is, the dummy region 44 is a laser beam from the one side 31a serving as the one surface 31 toward the other side 32a serving as the other surface 32 (from the one side 31a toward the other side 32a). The gap between the stripe region 43 and the dummy region 44 is formed so as to be gradually narrowed.

  Therefore, the distance between the laser stripe region 43 and the dummy region 44 is narrower on the other side 32a than on the one side 31a. Note that the distance C between the laser stripe region 43 and the dummy region 44 on one side 31a, that is, the maximum distance between the laser stripe region 43 and the dummy region 44 is preferably 150 μm or less. When the interval C exceeds 150 μm, the p-InGaP layer 19 formed in the concavo-convex pattern in the laser stripe region 43 is formed with the same thickness without depending on the interval C, as will be described later. Because it ends up. In the present embodiment, the distance between the laser stripe region 43 and the dummy region 44 is gradually narrowed from one side 31a toward the other side 32a. Thus, the dummy region 44 may be formed to have a large width. By forming in such a shape, it is considered that the change in the film thickness of the p-InGaP layer 19 formed in the uneven pattern in the laser stripe region 43 can be made more remarkable.

Next, as shown in FIG. 9, a p-InGaP layer 19 to be a second semiconductor layer is formed. Specifically, by supplying a raw material for forming the p-InGaP layer 19 by MOCVD, the p-InGaP layer 19 is formed in the concave portion of the concavo-convex pattern in the laser stripe region 43. The concavo-convex pattern is also formed in the dummy region 44, and more of the raw material for forming the p-InGaP layer 19 flows in the dummy region 44 near the laser stripe region 43. Therefore, in the portion where the distance between the laser stripe region 43 and the dummy region 44 is narrow, the thickness of the p-InGaP layer 19 formed in the concave portion of the concavo-convex pattern of the laser stripe region 43 is thin. In the present embodiment, the dummy region 44 is formed so that the distance between the laser stripe region 43 and the dummy region 44 becomes gradually narrower from the one side 31a toward the other side 32a. For this reason, the thickness of the p-InGaP layer 19 formed in the concave portion of the concave / convex pattern of the laser stripe region 43 is formed so as to be gradually reduced corresponding to this interval. At this time, the p-InGaP layer 19 formed in the concave portion of the concave / convex pattern is formed to have a thickness of about 20 nm in the vicinity of the one side 31a and about 10 nm in the vicinity of the other side 32a. When a p-InGaP layer is formed on the surface of the concavo-convex pattern by MOCVD, first, the p-InGaP layer 19 is formed only in the concave portion of the concavo-convex pattern, and the p-InGaP layer is hardly formed on the convex portion. Not formed. For this reason, if the thickness of the p-InGaP layer 19 is thinner than the depth B of the concavo-convex pattern, the p-InGaP layer is not formed on the convex portion of the concavo-convex pattern. When the p-InGaP layer 19 is formed by MOCVD, TMI (Trimethylindium) and TEG (Triethylgallium) are used as Group III materials, PH ₃ is used as Group V materials, p Impurity elements that become molds are mixed. The substrate temperature when forming the p-InGaP layer 19 is 500 ° C. to 650 ° C., for example, about 600 ° C.

Next, as shown in FIG. 10, a p-GaAs layer 18b to be a third semiconductor layer is stacked and formed. The p-GaAs layer 18b is formed by MOCVD using TEG as a group III source material, AsH ₃ as a group V source material, and a p-type impurity element mixed therein. The substrate temperature when forming the p-GaAs layer 18b is 500 ° C. to 650 ° C., for example, about 600 ° C. The p-GaAs layer 18b formed by MOCVD can planarize the surface of the p-GaAs layer 18b by forming a sufficient film thickness even if the underlying layer has an uneven shape. For this reason, the surface of the formed p-GaAs layer 18b is flat. The p-GaAs layer 18b formed on the p-GaAs layer 18a and the p-InGaP layer 19 forms the p-GaAs layer 18 together with the p-GaAs layer 18a, and further, the p-GaAs layer. A diffraction grating layer 15 is formed by 18 and the p-InGaP layer 19.

  Next, as shown in FIG. 11, a p-InGaP cladding layer 16 and a p-GaAs contact layer 17 are stacked on the p-GaAs layer 18b.

Next, as shown in FIG. 12, an SiO ₂ mask 45 is formed on the p-GaAs contact layer 17. Specifically, a SiO ₂ film is formed on the p-GaAs contact layer 17 by CVD, a photoresist is applied on the SiO ₂ film, and exposure and development are performed by an exposure apparatus, thereby forming a resist pattern (not shown). Form. Thereafter, by using this resist pattern as a mask, dry etching such as RIE is performed to remove the SiO ₂ film in the opening region of the resist pattern. Thereafter, the resist pattern is removed to form the SiO ₂ mask 45. As described above, FIG. 12B and FIGS. 13B to 15B described later are enlarged views of the cross section in the laser stripe region.

Next, as shown in FIG. 13, the p-InGaP cladding layer 16 and the p-GaAs contact layer 17 in the region where the SiO ₂ mask 45 is not formed are removed, and the ridge portion 21 having a ridge structure is formed. Specifically, the ridge portion 21 is formed by removing the p-InGaP cladding layer 16 and the p-GaAs contact layer 17 by performing dry etching such as RIE or wet etching.

Next, as shown in FIG. 14, the SiO ₂ mask 45 is removed, and an SiO ₂ film 22 is formed on the upper surface of the ridge portion 21 so that all or part of the p-GaAs contact layer 17 is exposed. Specifically, after the SiO ₂ mask 45 is removed, a SiO ₂ film is formed on the entire surface including the upper surface and side surfaces of the ridge portion 21 by CVD, a photoresist is applied thereon, and exposure and development by an exposure apparatus are performed. Do. Thus, a resist pattern having an opening is formed on the upper surface of the ridge portion 21, and the SiO ₂ film formed in the opening of the resist pattern is removed by RIE or the like, whereby all or one of the p-GaAs contact layers 17 is formed. The SiO ₂ film 22 is formed so that the part is exposed.

Next, as shown in FIG. 15, the p-side electrode 23 is formed on the side where the SiO ₂ film 22 is formed, and the n-side electrode 24 is formed on the back surface of the n-GaAs substrate 11. On the side where the SiO ₂ film 22 is formed, the p-GaAs contact layer 17 is exposed on the upper surface of the ridge portion 21, and is thus connected to the p-side electrode 23 in this region.

  As described above, the DFB laser is manufactured by the method for manufacturing the optical semiconductor device in the present embodiment described above. In the present embodiment, the p-InGaP layer 19 formed periodically in the diffraction grating layer 15 is transferred from one side 31a to the other side 32a without increasing the number of crystal growths of layers such as GaAs and InGaP. On the other hand, the film thickness can be reduced. Therefore, since the diffraction grating layer 15 having a non-uniform coupling constant κ can be formed in a short time with few steps, a DFB laser can be manufactured at low cost.

In the above description, the case where the p-GaAs layer 18a and the p-GaAs layer 18b are formed of the same material has been described. However, instead of the p-GaAs layer 18b, a p-AlGaAs layer having a wider band gap than GaAs. May be formed. At this time, in order to form a p-AlGaAs layer, TMA (Trimethylaluminum) and TEG are used as Group III materials, AsH ₃ is used as Group V materials, and a p-type impurity element is mixed. . The substrate temperature for forming the p-AlGaAs layer is 500 ° C. to 650 ° C., for example, about 600 ° C. The p-AlGaAs layer thus formed is a layer made of p-Al _0.2 Ga _0.8 As and has a refractive index of 3.32.

Further, in the above, after forming a concavo-convex pattern on the surface of the p-GaAs layer 18a as shown in FIG. 6, the SiO ₂ mask 41a and the resist pattern 42 are removed, and as shown in FIG. The method for forming the InGaP layer 19 has been described. However, as shown in FIG. 6, after forming a concavo-convex pattern on the surface of the p-GaAs layer 18a, only the resist pattern 42 is removed (resist pattern removal step), and the SiO ₂ mask 41a is formed. Alternatively, a method of forming the p-InGaP layer 19 may be used. At this time, after the p-InGaP layer 19 is formed, the SiO ₂ mask 41a is removed (dielectric pattern removing step), and a p-GaAs layer 18b as a third semiconductor layer is formed. In this formation method, the p-InGaP layer 19 is more reliably formed only in the concave portion of the concavo-convex pattern formed on the surface of the p-GaAs layer 18a without depending on the film formation method, film formation conditions, and the like. be able to.

[Second Embodiment]
Next, a second embodiment will be described. This embodiment is a method of manufacturing an optical semiconductor device in which the shape of the dummy region is different from that of the first embodiment.

  This embodiment will be described with reference to FIG. In this embodiment, the laser stripe region 143 is the same as the laser stripe region 43 in the first embodiment, but the dummy region 144 is not formed on one side 131a, and the other It is the structure currently formed in the side 132a. For example, as shown in FIG. 16, the dummy region 144 may be formed in a rectangular shape, as long as the thickness of the p-InGaP layer in the diffraction grating portion can be made nonuniform in the laser stripe region 143. Any shape is acceptable. By forming the dummy region 144 on the other side 132a, the p-InGaP layer can be formed thicker on one side 131a and thinner on the other side 132a in the formed diffraction grating layer. be able to. As a result, the coupling constant κ can be made nonuniform in the diffraction grating layer. Note that the one side 131a and the other side 132a in the present embodiment correspond to the one side 31a and the other side 32a in the first embodiment.

  The dummy area may be plural. For example, as shown in FIG. 17, two types of dummy areas 154 and 155 may be provided. In this case, a dummy region 154 is formed adjacent to one side 131a, and a dummy region 155 is formed adjacent to the other side 132a. The dummy region 154 is formed so that the distance between the laser stripe region 143 and the dummy region 155 increases from the other side 132a toward the one side 131a. Further, the dummy region 155 is formed in a rectangular shape with the laser stripe region 143 and the dummy region 155 having substantially the same interval. Note that the number of dummy regions formed is not limited to two dummy regions 154 and 155 shown in FIG. 17, and may be two or more. In addition, as shown in FIG. 16, even when the dummy region is formed on the other side 132a, two or more dummy regions may be formed on both sides of the laser stripe region 143.

  The manufacturing method of the optical semiconductor device in the present embodiment is the same as that in the first embodiment except that the dummy region 144 or the dummy regions 154 and 155 are formed in a shape different from that in the first embodiment. It is.

  Although the embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes can be made within the scope described in the claims.

In addition to the above description, the following additional notes are disclosed.
(Appendix 1)
A first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate;
A concavo-convex pattern forming step of forming a concavo-convex pattern in a laser stripe region where a waveguide is formed and a dummy region formed adjacent to both sides of the laser stripe region on the surface of the first semiconductor layer;
A second semiconductor layer forming step of forming a second semiconductor layer by MOCVD in a recess of the first semiconductor layer having the concavo-convex pattern formed thereon;
After the second semiconductor layer forming step, a third semiconductor layer forming step of forming a third semiconductor layer on the convex portions of the first semiconductor layer and the second semiconductor layer;
And the refractive index of the material forming the second semiconductor layer is different from the refractive index of the material forming the first semiconductor layer and the third semiconductor layer,
The distance between the laser stripe region and the dummy region is narrower on the other end side where the antireflection film is formed than on the one end side where the reflection film is formed in the waveguide. A method of manufacturing an optical semiconductor device characterized by the above.
(Appendix 2)
2. The method of manufacturing an optical semiconductor device according to appendix 1, wherein two or more dummy regions are formed on each side of the laser stripe region.
(Appendix 3)
In the dummy region adjacent to one end portion of the waveguide, the distance between the dummy region and the laser stripe region is from the one end side toward the other end side. The manufacturing method of an optical semiconductor device according to appendix 1 or 2, wherein the interval is gradually narrowed.
(Appendix 4)
A first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate;
A concavo-convex pattern forming step of forming a concavo-convex pattern in a laser stripe region where a waveguide is formed and a dummy region formed adjacent to both sides of the laser stripe region on the surface of the first semiconductor layer;
A second semiconductor layer forming step of forming a second semiconductor layer by MOCVD in a recess of the first semiconductor layer having the concavo-convex pattern formed thereon;
After the second semiconductor layer forming step, a third semiconductor layer forming step of forming a third semiconductor layer on the convex portions of the first semiconductor layer and the second semiconductor layer;
And the refractive index of the material forming the second semiconductor layer is different from the refractive index of the material forming the first semiconductor layer and the third semiconductor layer,
In the waveguide, the dummy region is not formed near one end where the reflection film is formed, but the dummy region is formed near the other end where the antireflection film is formed. A method for manufacturing an optical semiconductor device.
(Appendix 5)
5. The method of manufacturing an optical semiconductor device according to appendix 4, wherein two or more dummy regions are formed on each side of the laser stripe region.
(Appendix 6)
6. The optical semiconductor device according to any one of appendices 1 to 5, wherein, in the second semiconductor layer forming step, the second semiconductor layer is formed thinner than a step of the concavo-convex pattern. Production method.
(Appendix 7)
7. The method of manufacturing an optical semiconductor device according to any one of appendices 1 to 6, wherein the third semiconductor forming step forms the third semiconductor layer by CVD.
(Appendix 8)
The uneven pattern forming step includes
On the first semiconductor layer, a dielectric pattern forming step of forming a dielectric pattern made of a dielectric in a portion corresponding to the convex portion of the concave and convex pattern;
Forming a resist pattern having an opening in the laser stripe region and the dummy region; and
An etching step of etching the first semiconductor layer in a region where the dielectric pattern and the resist pattern are not formed;
The method for manufacturing an optical semiconductor device according to any one of appendices 1 to 7, further comprising:
(Appendix 9)
The method of manufacturing an optical semiconductor device according to appendix 8, wherein the dielectric is silicon oxide.
(Appendix 10)
After the concavo-convex pattern forming step, having a pattern removal step of removing the resist pattern and the dielectric pattern,
10. The method of manufacturing an optical semiconductor device according to appendix 8 or 9, wherein the second semiconductor layer forming step is performed after the pattern removing step.
(Appendix 11)
After the concave / convex pattern forming step, a resist pattern removing step for removing the resist pattern,
A dielectric pattern removing step of performing the second semiconductor layer forming step after the resist pattern removing step, and removing the dielectric pattern after the second semiconductor layer forming step;
10. The method of manufacturing an optical semiconductor device according to appendix 8 or 9, wherein the third semiconductor layer forming step is performed after the dielectric pattern removing step.
(Appendix 12)
The dielectric pattern forming step includes
A silicon oxide film forming step of forming a silicon oxide film on the first semiconductor layer;
Applying a photoresist on the silicon oxide film, exposing by interference exposure, and developing to form a resist pattern by interference exposure; and
Removing the silicon oxide film in a region where a resist pattern is not formed by the interference exposure by etching; and
The method for manufacturing an optical semiconductor device according to any one of appendices 8 to 11, wherein:
(Appendix 13)
13. The method of manufacturing an optical semiconductor device according to any one of appendices 1 to 12, wherein an interval between the laser stripe region and the dummy region is 150 μm or less.
(Appendix 14)
14. The method of manufacturing an optical semiconductor device according to any one of appendices 1 to 13, wherein the first semiconductor layer and the third semiconductor layer are formed of the same material.
(Appendix 15)
Appendix 14 characterized in that the first semiconductor layer and the third semiconductor layer are made of a material containing GaAs, and the second semiconductor layer is made of a material containing InGaP. The manufacturing method of the optical semiconductor device of description.
(Appendix 16)
The first semiconductor layer is made of a material containing GaAs, the second semiconductor layer is made of a material containing InGaP, and the third semiconductor layer is made of a material containing AlGaAs. 14. The method of manufacturing an optical semiconductor device according to any one of appendices 1 to 13, wherein the optical semiconductor device is manufactured.
(Appendix 17)
17. The method of manufacturing an optical semiconductor device according to any one of appendices 1 to 16, wherein the first semiconductor layer is formed on an active layer formed on the semiconductor substrate.

11 n-GaAs substrate 12 n-GaAs buffer layer 13 n-AlGaAs cladding layer 14 quantum dot active layer 15 diffraction grating layer 16 p-AlGaAs cladding layer 17 p-GaAs contact layer 18 p-GaAs layer 18a p-GaAs layer 18b p -GaAs layer 19 p-InGaP layer 21 Ridge portion 22 SiO ₂ film 23 p-side electrode 24 n-side electrode 31 One surface (surface on which a high reflection (HR) film is formed)
32 The other surface (surface on which an antireflection (AR) film is formed)
41 SiO ₂ film 41a SiO ₂ mask 42 resist pattern 43 laser stripe region 44 dummy region 45 SiO ₂ mask

Claims (7)

A first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate;
A concavo-convex pattern forming step of forming a concavo-convex pattern in a laser stripe region where a waveguide is formed and a dummy region formed adjacent to both sides of the laser stripe region on the surface of the first semiconductor layer;
A second semiconductor layer forming step of forming a second semiconductor layer by MOCVD in a recess of the first semiconductor layer having the concavo-convex pattern formed thereon;
After the second semiconductor layer forming step, a third semiconductor layer forming step of forming a third semiconductor layer on the convex portions of the first semiconductor layer and the second semiconductor layer;
And the refractive index of the material forming the second semiconductor layer is different from the refractive index of the material forming the first semiconductor layer and the third semiconductor layer,
The distance between the laser stripe region and the dummy region is narrower on the other end side where the antireflection film is formed than on the one end side where the reflection film is formed in the waveguide. A method of manufacturing an optical semiconductor device characterized by the above.   2. The method of manufacturing an optical semiconductor device according to claim 1, wherein two or more dummy regions are formed on both sides of the laser stripe region.   In the dummy region adjacent to one end portion of the waveguide, the distance between the dummy region and the laser stripe region is from the one end side toward the other end side. The method for manufacturing an optical semiconductor device according to claim 1, wherein the interval is gradually narrowed. A first semiconductor layer forming step of forming a first semiconductor layer on a semiconductor substrate;
A concavo-convex pattern forming step of forming a concavo-convex pattern in a laser stripe region where a waveguide is formed and a dummy region formed adjacent to both sides of the laser stripe region on the surface of the first semiconductor layer;
A second semiconductor layer forming step of forming a second semiconductor layer by MOCVD in a recess of the first semiconductor layer having the concavo-convex pattern formed thereon;
After the second semiconductor layer forming step, a third semiconductor layer forming step of forming a third semiconductor layer on the convex portions of the first semiconductor layer and the second semiconductor layer;
And the refractive index of the material forming the second semiconductor layer is different from the refractive index of the material forming the first semiconductor layer and the third semiconductor layer,
In the waveguide, the dummy region is not formed near one end where the reflection film is formed, but the dummy region is formed near the other end where the antireflection film is formed. A method for manufacturing an optical semiconductor device.   5. The optical semiconductor device according to claim 1, wherein, in the second semiconductor layer forming step, the second semiconductor layer is formed thinner than a step of the concavo-convex pattern. Manufacturing method. The uneven pattern forming step includes
On the first semiconductor layer, a dielectric pattern forming step of forming a dielectric pattern made of a dielectric in a portion corresponding to the convex portion of the concave-convex pattern;
Forming a resist pattern having an opening in the laser stripe region and the dummy region; and
An etching step of etching the first semiconductor layer in a region where the dielectric pattern and the resist pattern are not formed;
The method of manufacturing an optical semiconductor device according to claim 1, wherein: After the concavo-convex pattern forming step, having a pattern removal step of removing the resist pattern and the dielectric pattern,
The method of manufacturing an optical semiconductor device according to claim 6, wherein the second semiconductor layer forming step is performed after the pattern removing step.

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