JP6006158B2 - Manufacturing method of light modulation waveguide - Google Patents

Description

  The present invention relates to a method for manufacturing an optical modulation waveguide having a waveguide structure using a nitride semiconductor.

One of key devices in high-speed optical communication systems and optical information processing systems is an optical modulation waveguide. As the light modulation waveguide, for example, a light modulation waveguide using a dielectric such as LiNbO ₃ (LN) or a light modulation waveguide using a semiconductor is used. Currently, modulators using LiNbO ₃ are widely used.

By the way, the applied voltage for modulation is applied between the signal electrode and the ground electrode, and the distance between the electrodes is about a few tens of μm. However, since the LiNbO ₃ material is not conductive, refraction required for light modulation is required. To obtain a change in rate, a high driving voltage of about 3 to 5 V and an electrode length of about 20 to 40 mm are required. For this reason, the waveguide type modulator using LiNbO ₃ has a problem that power consumption is large and miniaturization of the optical modulation waveguide cannot be realized.

  In order to realize low power consumption and miniaturization in a waveguide type optical modulator, a semiconductor optical modulation waveguide having a nin structure having a GaN-based optical waveguide has been proposed (see Patent Document 1). This light modulation waveguide will be briefly described with reference to the cross-sectional view of FIG. The light modulation waveguide 400 includes an electrode layer 402 made of n-GaN, a lower clad layer 403 made of i-AlGaN, a core layer 404 made of i-GaN, an upper clad layer 405 made of i-AlGaN on a substrate 401. And the electrode layer 406 which consists of n-GaN is laminated | stacked one by one.

  A high mesa waveguide structure including the lower clad layer 403, the core layer 404, the upper clad layer 405, and the electrode layer 406 has n-GaN, i-AlGaN, i-GaN, i-AlGaN, and n-GaN on the substrate 401. Each layer is epitaxially grown and then patterned by a known lithography process and etching process. In addition, after the high mesa structure is formed, the electrode 407 is formed over the electrode layer 402, and the electrode 408 is formed over the electrode layer 406.

In the light modulation waveguide 400 described above, the voltage is applied between the electrode layer 402 and the electrode layer 406 sandwiching the optical waveguide portion having a thickness of about 1 μm where light is confined. Therefore, the LiNbO ₃ modulation guide is used. Compared with a waveguide or the like, it is possible to apply a higher-density electric field to a light guiding region (core layer 404). For this reason, by using the above structure, it is possible to realize a small-sized and low drive voltage optical modulation waveguide having a phase modulation unit length of about 3 mm and a drive voltage of 3 V or less.

JP 2011-186169 A

P. Chen et al., "Enhanced Pockels effect in GaN / AlxGa1.xN superlattice measured by polarization-maintaining fiber Mach-Zehnder interferometer", APPLIED PHYSICS LETTERS, vol.91, 031103, 2007. A. DADGAR et al., "Metalorganic Chemical Vapor Phase Epitaxy of Crack-Free GaN on Si (111) Exceeding 1μm in Thickness", Jpn. J. Appl. Phys., Vol.39, pp.L1183-L1185, 2000.

  By the way, the growth of the nitride semiconductor generally proceeds in the C-axis direction which is the normal direction of the C plane (0001). As the substrate, a nitride semiconductor substrate such as a GaN substrate is also used, but hetero-growth on a substrate that is not a nitride semiconductor, such as a C-plane sapphire substrate, a (0001) plane silicon carbide substrate, or a (111) silicon substrate, for example. It is common to do.

  For this reason, there is a large lattice mismatch or thermal expansion coefficient mismatch between the nitride semiconductor and the substrate. If there is such a mismatch, there is a high possibility that defects such as cracks occur in the grown nitride semiconductor layer when a thick layer structure is grown (see Non-Patent Document 2).

  An optical waveguide requires a waveguide structure having a scale several times larger than the wavelength of light to be guided. When applied for optical communication, the wavelength of light used is 1.3 μm to 1.55 μm. For these reasons, for example, when a GaN-based optical waveguide is applied to optical communication, a nitride semiconductor multilayer structure having a thickness of at least about 2 to 3 μm is formed.

  In addition, in the optical waveguide, a difference in refractive index is required between the optical waveguide layer (core) through which light passes and the cladding layer sandwiching the optical waveguide layer. This changes the mixed crystal ratio of the nitride semiconductor mixed crystal. This is realized. For example, the optical waveguide layer and the cladding layer can be formed of AlGaN having different compositions. However, in this case, lattice mismatch occurs according to the difference in composition, and growing a thick layer also increases the possibility of generating dislocations and defects.

  As described above, from the viewpoint of growth, there is a problem in that there is a trade-off that a thick laminated structure must be prepared for use as an optical waveguide, on the other hand, while a thin laminated structure is desired.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to suppress the occurrence of transition and defects in the core of an optical modulation waveguide using a nitride semiconductor. And

The method of manufacturing an optical modulation waveguide according to the present invention includes a step of forming a first core layer made of a nitride semiconductor by epitaxial growth on a first cladding layer, and a nitride semiconductor by epitaxial growth on a second cladding layer. Forming a second core layer, a first core layer formed on the first clad layer, and a second core layer formed on the second clad layer are bonded together to form an integral core After forming, the step of patterning the laminated portion in which the first clad layer, the core, and the second clad layer are laminated to form an optical waveguide extending with a predetermined width and the integral core are formed. Later, the method includes a step of forming a first electrode connected to the first cladding layer, and a step of forming a second electrode connected to the second cladding layer after forming an integral core.

  In the method for manufacturing an optical modulation waveguide, before forming the first core layer, a step of forming a first cladding layer made of a nitride semiconductor on the first substrate by epitaxial growth and a second core layer are formed. Before the second electrode is formed, the second substrate is removed after the step of forming a second cladding layer made of a nitride semiconductor on the second substrate by epitaxial growth and the formation of the integral core. You may make it provide a process.

  In the method for manufacturing an optical modulation waveguide, the step of forming the first contact layer by epitaxial growth on the first substrate before forming the first cladding layer, and the step of forming the second cladding layer before forming the second cladding layer. Forming a second contact layer on the substrate by epitaxial growth, wherein the first cladding layer is formed on the first contact layer, and the second cladding layer is formed on the second contact layer. Also good.

  In the method of manufacturing an optical modulation waveguide, before forming the first core layer, a step of forming a first cladding layer made of a nitride semiconductor on a first substrate having conductivity by epitaxial growth, and a second core Before forming the layer, the step of forming a second cladding layer made of a nitride semiconductor on the second substrate having conductivity by epitaxial growth, and after forming the integral core, the first electrode is connected to the first electrode. There may be provided a step of connecting to the first cladding layer via the substrate and a step of connecting the second electrode to the second cladding layer via the second substrate after forming the integral core. .

  In the method for manufacturing an optical modulation waveguide, the first cladding layer and the second cladding layer may be made of a conductive material.

  As described above, according to the present invention, it is possible to obtain an excellent effect that generation of transitions and defects in the core of the light modulation waveguide using the nitride semiconductor can be suppressed.

FIG. 1A is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1B is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1C is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1D is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1E is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing the optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1F is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing the optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1G is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 1H is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 1 of the present invention. FIG. 2A is a cross-sectional view schematically showing the state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2B is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2C is a cross-sectional view schematically showing the state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2D is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing the optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2E is a cross-sectional view schematically showing the state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2F is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2G is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 2 of the present invention. FIG. 2H is a cross sectional view schematically showing a state of an intermediate step in the method for manufacturing the optical modulation waveguide in Embodiment 2 of the present invention. FIG. 3A is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3B is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3C is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing the optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3D is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3E is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3F is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3G is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 3H is a cross-sectional view schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in Embodiment 3 of the present invention. FIG. 4 is a cross-sectional view showing a configuration of a semiconductor optical modulation waveguide having an nin structure having a GaN-based optical waveguide.

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

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIGS. 1A to 1H. 1A to 1H are cross-sectional views schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in the first embodiment of the present invention.

  First, as shown in FIG. 1A, a first substrate 101 is prepared. Next, as shown in FIG. 1B, on the first substrate 101, first, a first contact layer 102 made of a nitride semiconductor, a first cladding layer 103 made of a nitride semiconductor, and a first core made of a nitride semiconductor. Layer 104 is epitaxially grown sequentially.

  Next, as shown in FIG. 1C, a second substrate 121 is prepared. Next, as shown in FIG. 1D, on the second substrate 121, a second contact layer 122 made of a nitride semiconductor, a second cladding layer 123 made of a nitride semiconductor, and a second core layer 124 made of a nitride semiconductor. Are epitaxially grown sequentially.

For example, the first substrate 101 and the second substrate 121 may be made of sapphire (corundum) whose main surface has a C-plane orientation. The first contact layer 102 and the second contact layer 122 may be made of GaN doped with silicon at about 5 × 10 ¹⁸ cm ⁻³ , and the layer thickness may be about 2000 nm. The first cladding layer 103 and the second cladding layer 123 may be made of AlGaN doped with silicon at about 5 × 10 ¹⁸ cm ⁻³ .

Here, each cladding layer may be composed of two layers, and the layer on the core layer side may be in a state in which the composition changes. For example, the contact layer side is made of Al _0.15 Ga _0.85 N doped with silicon at about 5 × 10 ¹⁸ cm ⁻³ and has a layer thickness of about 400 nm, and the core layer side has 5 × 10 ¹⁸ cm ^−3. A composition gradient layer made of AlGaN doped with silicon and having a thickness of about 50 nm may be used. In the composition gradient layer, the Al composition may be changed from 15% to 10%. By using the composition gradient layer, the difference in Al composition between the core layer and the clad layer composed of Al _0.15 Ga _0.85 N and having a thickness of about 400 nm can be filled.

  The first core layer 104 and the second core layer 124 may have, for example, a multiple quantum well structure including an AlN layer and a GaN layer. For example, each core layer may have a multiple quantum well structure in which 15 pairs of AlN layers having a thickness of 2 nm and GaN layers having a thickness of 18 nm are alternately stacked.

  Further, each layer described above may be formed by epitaxial growth by a well-known metal organic chemical vapor deposition (MOCVD) method or molecular beam epitaxy (MBE) method.

  Next, as shown in FIG. 1E, the first core layer 104 and the second core layer 124 are bonded together. By this bonding, the core 140 in which the first core layer 104 and the second core layer 124 are integrated is formed. Here, the first core layer 104 and the second core layer 124 may be half the thickness of the desired core 140 thickness. The total thickness of the first core layer 104 and the second core layer 124 only needs to be the desired thickness of the core 140. Thus, since the first core layer 104 and the second core layer 124 do not need to be formed thick, it is possible to suppress the generation of dislocations and defects due to the occurrence of lattice mismatch depending on the difference in composition.

  For example, the first core layer 104 and the second core layer 124 may be bonded by direct bonding such as surface activated bonding (SAB) or atomic diffusion bonding (ADB). Alternatively, the first core layer 104 and the second core layer 124 may be bonded together by indirect bonding using a UV resin, an adhesive, or a low melting point glass. However, in this indirect joining, since the joining surface where the material different from the core exists is located at the center of the core 140, the direct joining is more preferable. However, when a material that does not affect the optical waveguide is used as an adhesive or the like sandwiched between the bonding surfaces, indirect bonding may be used.

  After forming the integral core 140 as described above, the second substrate 121 is removed, and one surface of the second contact layer 122 is exposed as shown in FIG. 1F. A second cladding layer 123 is formed on the other surface of the second contact layer 122. For example, the second substrate 121 may be removed by a chemical mechanical polishing method or the like.

  Next, a laminated portion composed of the first cladding layer 103, the core 140 (the first core layer 104, the second core layer 124), the second cladding layer 123, and the second contact layer 122 is formed by a well-known lithography technique and Patterning is performed by etching art to form a mesa structure that becomes an optical waveguide extending with a predetermined width, as shown in FIG. 1G. This optical waveguide extends from the front side to the back side in FIG. 1G. Accordingly, FIGS. 1A to 1H show cross sections perpendicular to the direction in which light is guided when optical waveguides are used.

  Next, as shown in FIG. 1H, a first electrode 105 and a second electrode 106 for applying electric field modulation are formed. In the first embodiment, the first electrode 105 is formed on the surface of the first contact layer 102 exposed by forming the mesa structure. The second electrode 106 is formed on one surface of the second contact layer 122. In this case, the first electrode 105 is connected to the first cladding layer 103 via the first contact layer 102, and the second electrode 106 is connected to the second cladding layer 123 via the second contact layer 122.

  According to the first embodiment described above, since the core 140 is obtained by bonding the first core layer 104 and the second core layer 124, it is necessary to form each layer thickly. Therefore, it is possible to suppress the occurrence of dislocations and defects due to the occurrence of lattice mismatch according to the difference in composition.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIGS. 2A to 2H. 2A to 2H are cross-sectional views schematically showing a state of an intermediate step in the method for manufacturing an optical modulation waveguide in the second embodiment of the present invention.

  First, as shown in FIG. 2A, a first substrate 201 having conductivity is prepared. Next, as shown in FIG. 2B, on the first substrate 201, a first cladding layer 202 made of a nitride semiconductor and a first core layer 203 made of a nitride semiconductor are sequentially epitaxially grown.

  Next, as shown in FIG. 2C, a second substrate 221 having conductivity is prepared. Next, as shown in FIG. 2D, a second cladding layer 222 made of a nitride semiconductor and a second core layer 223 made of a nitride semiconductor are sequentially epitaxially grown on the second substrate 221.

  For example, the first substrate 201 and the second substrate 221 may be made of, for example, silicon having a low resistance (typically a resistivity of less than 0.1 Ω · cm). The first cladding layer 202 and the second cladding layer 222 may be made of undoped AlN.

  Here, each cladding layer may be composed of two layers, and the layer on the core layer side may be in a state in which the composition changes. For example, the substrate side may be made of undoped AlN and have a layer thickness of about 400 nm, and the core layer side may be a composition gradient layer made of undoped AlGaN with a layer thickness of 100 nm. In the composition gradient layer, the Al composition may be changed from 30% to 0%. By using the composition gradient layer, the difference in Al composition between the core layer and the clad layer composed of undoped AlN and having a thickness of about 400 nm can be filled.

  The first core layer 203 and the second core layer 223 may have a multiple quantum well structure including, for example, an AlN layer and a GaN layer. For example, each core layer may have a multiple quantum well structure in which 15 pairs of AlN layers having a thickness of 2 nm and GaN layers having a thickness of 18 nm are alternately stacked.

  Each layer described above may be formed by epitaxial growth by a well-known metal organic chemical vapor deposition method or molecular beam epitaxy method.

  Next, as shown in FIG. 2E, the first core layer 203 and the second core layer 223 are bonded together. By this bonding, the core 230 in which the first core layer 203 and the second core layer 223 are integrated is formed. Here, the first core layer 203 and the second core layer 223 may be half the thickness of the desired core 230 thickness. The total thickness of the first core layer 203 and the second core layer 223 only needs to be the desired thickness of the core 230. Thus, since the first core layer 203 and the second core layer 223 do not need to be formed thick, it is possible to suppress the occurrence of dislocations and defects due to the occurrence of lattice mismatch depending on the difference in composition.

  For example, the first core layer 203 and the second core layer 223 may be bonded together by direct bonding such as surface activated bonding or atomic diffusion bonding. Alternatively, the first core layer 203 and the second core layer 223 may be bonded together by indirect bonding using UV resin, adhesive, or low melting point glass. However, in this indirect joining, since the joining surface where the material different from the core exists is located at the center of the core 230, the direct joining is more preferable. However, when a material that does not affect the optical waveguide is used as an adhesive or the like sandwiched between the bonding surfaces, indirect bonding may be used.

  After the integrated core 230 is formed as described above, the second substrate 221 is thinned as shown in FIG. 2H. Next, as shown in FIG. 2G, the first electrode 205 is formed on the back surface side of the first substrate 201. Further, a second electrode 206 having a predetermined shape is formed on the back surface side of the thinned second substrate 221. The surface of the second substrate 221 where the second cladding layer 222 is formed is the front surface, and the opposite surface is the back surface. In this case, the first electrode 205 is connected to the first cladding layer 202 via the first substrate 201, and the second electrode 206 is connected to the second cladding layer 222 via the second substrate 221. Here, the shape (particularly the width) of the second electrode 206 in plan view is set to the width in plan view of a mesa structure that becomes a waveguide to be described later.

  Next, a part of the first substrate 201, the first cladding layer 202, the core 230 (the first core layer 203 and the second core layer 223), the second cladding layer 222, and the second substrate 221 are formed in the thickness direction. The laminated portion is patterned by a well-known lithography technique and etching art to form a mesa structure that becomes an optical waveguide extending with a predetermined width as shown in FIG. 2H. This optical waveguide extends from the front to the back of the sheet of FIG. 2G. Therefore, FIGS. 2A to 2H show a cross section perpendicular to the direction in which light is guided in the case of an optical waveguide.

  Also in the second embodiment described above, the core 230 is obtained by bonding the first core layer 203 and the second core layer 223. Therefore, it is not necessary to form each layer thickly. Therefore, it is possible to suppress the occurrence of dislocations and defects due to the occurrence of lattice mismatch depending on the difference in composition.

[Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. 3A to 3H. 3A to 3H are cross-sectional views schematically showing a state of an intermediate process in the method for manufacturing an optical modulation waveguide according to Embodiment 3 of the present invention.

  First, as shown in FIG. 3A, a first substrate 301 having conductivity is prepared. Next, as shown in FIG. 3B, a first core layer 302 made of a nitride semiconductor is epitaxially grown on the first substrate 301. Next, as shown in FIG. 3C, a second substrate 321 having conductivity is prepared. Next, as shown in FIG. 3D, the second core layer 322 is epitaxially grown on the second substrate 321. In the third embodiment, the first substrate 301 becomes the first cladding layer, and the second substrate 321 becomes the second cladding layer.

For example, the first substrate 301 and the second substrate 321 may be formed of, for example, a β-Ga ₂ O ₃ substrate having a low resistance (typically a resistivity of less than 0.1 Ω · cm). The first core layer 302 and the second core layer 322 may have a multiple quantum well structure including, for example, an AlN layer and a GaN layer. For example, each core layer may have a multiple quantum well structure in which 15 pairs of AlN layers having a thickness of 2 nm and GaN layers having a thickness of 18 nm are alternately stacked.

  Each layer described above may be formed by epitaxial growth by a well-known metal organic chemical vapor deposition method or molecular beam epitaxy method. Note that a GaN layer doped with silicon may be formed as a buffer layer between the first core layer 302 and the first substrate 301. In other words, after forming a GaN layer doped with silicon on the first substrate 301, the first core layer 302 having the above-described configuration may be formed. Similarly, a GaN layer doped with silicon may be formed as a buffer layer between the second core layer 322 and the second substrate 321.

  Next, as shown in FIG. 3E, the first core layer 302 and the second core layer 322 are bonded together. By this bonding, a core 330 in which the first core layer 302 and the second core layer 322 are integrated is formed. Here, the first core layer 302 and the second core layer 322 may be half the thickness of the desired core 330 layer thickness. The total thickness of the first core layer 302 and the second core layer 322 only needs to be the desired thickness of the core 330. Thus, since the first core layer 302 and the second core layer 322 do not need to be formed thick, it is possible to suppress the occurrence of dislocations and defects due to the occurrence of lattice mismatch according to the difference in composition.

  For example, the first core layer 302 and the second core layer 322 may be bonded together by direct bonding such as surface activated bonding or atomic diffusion bonding. Alternatively, the first core layer 302 and the second core layer 322 may be bonded together by indirect bonding using UV resin, adhesive, or low melting point glass. However, in this indirect joining, since the joining surface where the material different from the core exists is located at the center of the core 330, the direct joining is more preferable. However, when a material that does not affect the optical waveguide is used as an adhesive or the like sandwiched between the bonding surfaces, indirect bonding may be used.

  After the integrated core 330 is formed as described above, the second substrate 321 is thinned as shown in FIG. 3H. Next, as shown in FIG. 3G, a first electrode 305 is formed on the back side of the first substrate 301. Further, the second electrode 306 having a predetermined shape in plan view is formed on the back surface side of the thinned second substrate 321. The surface of the second substrate 321 where the second core layer 322 is formed is the front surface, and the opposite surface is the back surface. In this case, the first electrode 305 is directly connected to the first substrate 301 that is the first cladding layer, and the second electrode 306 is directly connected to the second substrate 321 that is the second cladding layer. Here, the shape (width) of the second electrode 306 in plan view is set to be the shape (width) of plan view of a mesa structure to be an optical waveguide described later.

  Next, a well-known lithography technique and etching are performed on a laminated portion including a part of the first substrate 301, the core 330 (the first core layer 302, the second core layer 322), and the second substrate 321 in the thickness direction. Patterned by fine art, as shown in FIG. 3H, a mesa structure is formed which becomes an optical waveguide extending with a predetermined width. This optical waveguide extends from the front side to the back side in FIG. 3G. Therefore, FIGS. 3A to 3H show cross sections perpendicular to the direction in which light is guided when the optical waveguide is used.

  Also in Embodiment 3 described above, since the core 330 is obtained by bonding the first core layer 302 and the second core layer 322, it is not necessary to form each layer thickly. Therefore, it is possible to suppress the occurrence of dislocations and defects due to the occurrence of lattice mismatch depending on the difference in composition.

  In the third embodiment, since the layer thickness of the entire laminated structure is thin, the substrate bonding process is smoothly advanced without using the composition gradient layer used in the configurations of the first and second embodiments. A degree of flatness can be secured. In the case where the flatness is deteriorated due to the structure of the core or the like, a composition gradient layer may be used.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, even if it is other than the materials described in the above-described embodiments, if the requirements of the substrate, the relationship between the refractive index as the cladding layer and the core, etc. are in the range having the relationship required as an optical waveguide, It goes without saying that the effects of the present invention can be obtained with other materials and structures.

  DESCRIPTION OF SYMBOLS 101 ... 1st board | substrate, 102 ... 1st contact layer, 103 ... 1st clad layer, 104 ... 1st core layer, 105 ... 1st electrode, 106 ... 2nd electrode, 121 ... 2nd board | substrate, 122 ... 2nd contact Layer, 123 ... second cladding layer, 124 ... second core layer, 140 ... core.

Claims (5)

Forming a first core layer made of a nitride semiconductor by epitaxial growth on the first cladding layer;
Forming a second core layer made of a nitride semiconductor by epitaxial growth on the second cladding layer;
Said first core layer formed on the first cladding layer, after forming the core and integrally bonded to said formed on the second cladding layer and the second core layer, wherein Patterning a laminated portion in which the first clad layer, the core, and the second clad layer are laminated to form an optical waveguide extending with a predetermined width ; and
Forming a first electrode connected to the first cladding layer after forming the integral core;
And forming a second electrode connected to the second cladding layer after forming the integrated core. A method for manufacturing an optical modulation waveguide, comprising: In the manufacturing method of the light modulation waveguide of Claim 1,
Forming the first cladding layer made of a nitride semiconductor on the first substrate by epitaxial growth before forming the first core layer;
Forming the second cladding layer made of a nitride semiconductor on the second substrate by epitaxial growth before forming the second core layer;
And a step of removing the second substrate after forming the integrated core and before forming the second electrode. In the manufacturing method of the light modulation waveguide of Claim 2,
Forming a first contact layer by epitaxial growth on the first substrate before forming the first cladding layer;
Forming a second contact layer by epitaxial growth on the second substrate before forming the second cladding layer, and
The first cladding layer is formed on the first contact layer;
The method of manufacturing an optical modulation waveguide, wherein the second cladding layer is formed on the second contact layer. In the manufacturing method of the light modulation waveguide of Claim 1,
Before forming the first core layer, forming the first cladding layer made of a nitride semiconductor on the first substrate having conductivity by epitaxial growth;
Forming the second cladding layer made of a nitride semiconductor on the second substrate having conductivity by epitaxial growth before forming the second core layer;
Connecting the first electrode to the first cladding layer via the first substrate after forming the integral core; and
And a step of connecting the second electrode to the second clad layer through the second substrate after forming the integrated core. In the manufacturing method of the light modulation waveguide of Claim 1,
The method of manufacturing an optical modulation waveguide, wherein the first cladding layer and the second cladding layer are made of a conductive material.

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