Optical integrated device and manufacturing method for the same

Abstract

To obtain an optical integrated device that enables high optical coupling efficiency through precise positional control of optical functional elements and optical circuit elements.SOLUTION: An optical integrated device 300 is integrated with an optical functional element 100 and an optical circuit element 200. The optical functional element 100 includes a high-mesa part 16 that partially includes a compound semiconductor substrate 11, has an active layer 12 and a contact layer 13, and has a convex shape and a terrace part 14 that is provided along the high-mesa part 16 and presents a flat surface. The optical circuit element 200 has a lower cladding layer 22, a core layer 23, and an upper cladding layer 25 formed on a semiconductor substrate 21, and is provided with a laminated structure substrate 40 having a first recess 27a and a second recess 27b. The optical functional element 100 and the optical circuit element 200 are flip-chip mounted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to integrated optical devices and methods for manufacturing integrated optical devices. [Background technology]

[0002] In recent years, silicon photonics technology, which integrates optical functional elements on silicon (Si) substrates, has been attracting attention in the field of optical devices such as communications. With silicon photonics technology, mature silicon substrate processing techniques developed in the manufacture of electronic circuits can be applied to manufacturing. In addition, silicon has a higher refractive index than glass, which is commonly used as an optical element, making it possible to confine light in a microscopic area, and so it is hoped that large-scale optically integrated devices that are inexpensive and can be miniaturized will be realized.

[0003] In optical semiconductor devices made of various materials, including not only silicon but also indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), lithium niobate (LiNbO3), and compound semiconductors that contain these materials, the most basic component is the optical waveguide, which can locally confine light in a specific region by making the refractive index higher than the surrounding area and propagate the light to a desired region by forming this specific region in a linear, i.e., stripe, shape. Optical integrated devices made of semiconductors including silicon optical circuit elements can realize large-scale optical integrated devices with various functions by interconnecting each functional block, such as semiconductor lasers, optical receivers, modulators, and optical filters, with the above-mentioned optical waveguides.

[0004] However, there is a major problem with using silicon optical circuit elements as optical semiconductor devices. Silicon is an indirect transition semiconductor, which limits the interaction between electrons and light, making it difficult to realize active functions such as semiconductor lasers and optical amplifiers using silicon alone. Therefore, in order to realize active functions, direct transition semiconductors, such as compound semiconductors such as InP, are essential as constituent materials.

[0005] Therefore, in silicon photonics technology, integration technologies that realize passive and active functions using different materials are being widely studied. Due to the difference in lattice constants between silicon and compound semiconductor materials, monolithic integration on the same substrate using epitaxial crystal growth is difficult. Therefore, at present, a so-called hybrid integration structure is widely used in which an element having an active function made of a compound semiconductor material (hereinafter referred to as an optical functional element) is mounted and integrated on a silicon optical circuit element. In the following explanation, silicon optical circuit elements and optical functional elements may be collectively referred to simply as optical elements.

[0006] Various types of hybrid integrated structures of silicon optical circuit elements and optical functional elements have been proposed. One example of a hybrid integrated structure is a butt coupling method in which a silicon optical circuit element and an optical functional element, each having the optical waveguide extending to its optical end face, are arranged in close proximity so that the cross sections of the optical waveguides on the end faces of the optical elements face each other, thereby introducing light propagating in one optical element into the other optical element through free space.

[0007] Another example of a hybrid integrated structure is a grating coupler type in which light propagating through an optical waveguide formed on a silicon optical circuit element or an optical functional element is reflected in a direction perpendicular to the optical element by a grating, and the light is introduced into the optical waveguide of another optical element via a grating formed on the other optical element arranged opposite the first optical element.

[0008] Furthermore, there is a bonding method in which a silicon optical circuit element and an optical functional element are physically bonded together so that their optical waveguides run parallel to each other in close proximity, thereby introducing light propagating in one optical element into the other optical element by evanescent light.

[0009] However, in the butt coupling method, the cross-sectional size of typical optical waveguides in silicon optical circuit elements and optical functional elements is small, ranging from submicrons to a few microns at most, so if the mounting positions of the silicon optical circuit element and the optical functional element are misaligned even slightly, the light emitted from one optical element cannot be properly guided to the other optical element, resulting in a large loss of optical power.

[0010] In order to reduce the misalignment between the mounting positions of the two, technology has been developed to adjust the relative positions of the optical elements in the in-plane direction with high precision using alignment marks, etc. However, the method using alignment marks does not guarantee precision in the vertical direction of the optical element surface, i.e., in the height direction, and there is a problem that the manufacturing error of each optical element directly affects the optical coupling efficiency.

[0011] The mounting accuracy of the above-mentioned optical elements typically requires submicron-level accuracy in both the in-plane and perpendicular directions, i.e., in the height direction, of the optical elements. In addition, the grating coupler method can expand the size of the light distribution by using a grating, so it is possible to relax the mounting accuracy of the optical elements by about one order of magnitude compared to the butt coupling method. However, the grating coupler method has the disadvantage that the optical coupling loss also varies depending on the polarization and wavelength of the propagating light, because the grating has polarization dependence and wavelength dependence.

[0012] The bonding method requires that optical elements or wafers made of different materials be tightly attached to each other, and requires wafer manufacturing technology and bonding processes that are free of dust and particles, as well as extremely high manufacturing precision.

[0013] In the present disclosure, attention is focused on the butt coupling method, which can be manufactured relatively easily among the above-mentioned methods and can achieve both low polarization dependence and wavelength dependence.

[0014] As a technique for solving the problem of positional accuracy in the vertical direction of the surfaces of the silicon optical circuit element and the optical functional element in the butt coupling method, for example, Patent Document 1 discloses a technique for forming an etching stop layer in the optical functional element between a core layer through which light propagates and a substrate layer, where a chemical reaction different from that in the surroundings occurs, and contacting a surface defined based on this etching stop layer with a surface on the silicon optical circuit element to improve the relative positional accuracy in the vertical direction between the two optical elements, that is, in the height direction. In other words, by forming the etching stop layer in an epitaxial crystal growth process on a compound semiconductor substrate, it becomes possible to control the relative distance between the core layer and the etching stop layer with high precision. This method realizes highly efficient optical coupling between the silicon optical circuit element and the optical functional element. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent No. 6696151 Summary of the Invention [Problem to be solved by the invention]

[0016] Patent Document 1 discloses a manufacturing technique and element structure that utilizes an etching stop layer to improve the relative positional accuracy in the vertical direction, i.e., the height direction, of the element surfaces of a silicon optical circuit element and an optical functional element. However, although the manufacturing technique and element structure described in Patent Document 1 utilize an etching stop layer to achieve high accuracy, there is a problem in that forming an etching stop layer near the core layer (active layer) through which light propagates distorts the propagating optical mode, causing optical loss during propagation or optical coupling between different optical elements.

[0017] In addition, since the etching stop layer is made of a material different from the surroundings, there is a concern that it may hinder the smooth movement of carriers such as electrons and holes. Furthermore, since the energy distribution of the propagating light mode is generally localized more on the semiconductor substrate side having a higher equivalent refractive index, when the etching stop layer is located on the semiconductor substrate side, the effect of the phenomenon in which the propagating light mode is deformed becomes greater.

[0018] To avoid the above problems, the core layer (active layer) and the etching stop layer must be spaced apart by a certain distance, or even if the etching stop layer is located near the core layer (active layer), it must be located on the surface opposite the semiconductor substrate as viewed from the core layer. These problems become more pronounced in the so-called high mesa structure, in which the contact layers above and below the core layer (active layer) are dug to narrow the width of the core layer (active layer) as the optical waveguide structure of the optical functional element. This is because the light and carriers are confined in a narrower region in the optical waveguide structure known as the high mesa structure.

[0019] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical integrated device and a method for manufacturing an optical integrated device that improves the relative positional accuracy in the perpendicular direction, i.e., height direction, between the surfaces of an optical circuit element and an optical functional element, so that excessive light loss can be prevented even when the optical functional element has a high mesa structure. [Means for solving the problem]

[0020] The optical integrated device according to the present disclosure comprises: An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a laminated structure substrate having a lower clad layer, a core layer and an upper clad layer formed on the semiconductor substrate; A first recess provided in the laminated structure substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposite to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the compound semiconductor substrate and the active layer, a height of a top of the convex portion is set at a surface of the core layer on the side of the upper cladding layer, and the surface of the terrace portion and the top of the convex portion are in contact with each other; The active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other.

[0021] A method for manufacturing an optical integrated device according to the present disclosure includes: A method for manufacturing an optical integrated device in which optical functional elements and optical circuit elements are integrated, comprising the steps of: The optical functional element includes: epitaxially growing an active layer and a contact layer on a compound semiconductor substrate; forming a high mesa portion by etching the compound semiconductor substrate, the high mesa portion having at least the active layer and the contact layer, and having a convex shape; forming a terrace portion exposing an outermost layer of the compound semiconductor substrate by wet etching using a mixture of tartaric acid and hydrogen peroxide as an etchant; The method includes the steps of: The optical circuit element includes: forming a first recess and a second recess spaced apart from the first recess in a laminated structure substrate having a lower cladding layer, a core layer, and an upper cladding layer formed on a semiconductor substrate; selectively removing the upper cladding layer at a top of a protrusion formed between the first recess and the second recess to expose the top surface of the core layer; The method includes the steps of: and flip-chip mounting the optical functional element and the optical circuit element while bringing the terrace portion of the optical functional element into contact with the top of the protrusion of the optical circuit element. Effect of the Invention

[0022] According to the optical integrated device and the method for manufacturing an optical integrated device disclosed herein, the surface of the terrace portion of the optical functional element is formed to be located at a predetermined height with respect to the active layer, and therefore the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled, thereby providing an optical integrated device and a method for manufacturing an optical integrated device with high optical coupling efficiency. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram illustrating a structure of an optical integrated device according to a first embodiment. [Diagram 2] 1 is a top view illustrating a structure of an optical integrated device according to a first embodiment. [Diagram 3] 2 is a schematic cross-sectional view taken along line A in FIG. 1 in the optical integrated device according to the first embodiment. [Figure 4] 2 is a cross-sectional view taken along line A in FIG. 1 in the optical integrated device according to the first embodiment. [Diagram 5] 2 is a cross-sectional view taken along line B in FIG. 1 in the optical integrated device according to the first embodiment. [Figure 6] 2 is a cross-sectional view taken along line C in FIG. 1 in the optical integrated device according to the first embodiment. [Figure 7A] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7B] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7C]2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7D] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7E] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7F] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7G] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 7H] 2A to 2C are cross-sectional views showing a method for manufacturing the optical integrated device according to the first embodiment. [Figure 8] 5 is a diagram showing the relationship between optical coupling efficiency and positional misalignment in the optical integrated device according to the first embodiment. FIG. [Figure 9] 5 is a diagram showing the relationship between optical coupling efficiency and positional misalignment in the optical integrated device according to the first embodiment. FIG. [Figure 10] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a modification of the first embodiment. [Figure 11] 11 is a cross-sectional view taken along line A in FIG. 10 in the optical integrated device according to a modified example of the first embodiment. [Figure 12] 11 is a cross-sectional view taken along line B in FIG. 10 in the optical integrated device according to a modified example of the first embodiment. [Figure 13] FIG. 11 is a schematic diagram illustrating a structure of an optical integrated device according to a second embodiment. [Figure 14] FIG. 11 is a top view illustrating a structure of an optical integrated device according to a second embodiment. [Figure 15] 14 is a schematic cross-sectional view of the optical integrated device according to the second embodiment taken along line A in FIG. 13. [Figure 16] 14 is a cross-sectional view taken along line A in FIG. 13 in the optical integrated device according to the second embodiment. [Figure 17] 14 is a cross-sectional view taken along line B in FIG. 13 in the optical integrated device according to the second embodiment. [Figure 18]14 is a cross-sectional view taken along line C in FIG. 13 in the optical integrated device according to the second embodiment. [Figure 19A] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19B] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19C] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19D] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19E] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19F] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19G] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 19H] 6A to 6C are cross-sectional views showing a method for manufacturing an optical integrated device according to a second embodiment. [Figure 20] FIG. 11 is a top view illustrating a structure of an optical integrated device according to a modification of the second embodiment. [Figure 21] 21 is a cross-sectional view taken along line A in FIG. 20 in the optical integrated device according to a modified example of the second embodiment. [Figure 22] 21 is a cross-sectional view taken along line B in FIG. 20 in the optical integrated device according to a modified example of the second embodiment. [Figure 23] FIG. 11 is a schematic diagram illustrating a structure of an optical integrated device according to a third embodiment. [Figure 24] FIG. 11 is a top view illustrating a structure of an optical integrated device according to a third embodiment. [Diagram 25] 20 is a schematic cross-sectional view taken along line A in FIG. 19 of an optical integrated device according to a third embodiment. [Figure 26] 20 is a cross-sectional view taken along line A in FIG. 19 in the optical integrated device according to the third embodiment. [Figure 27] 20 is a cross-sectional view taken along line B in FIG. 19 in the optical integrated device according to the third embodiment. [Figure 28] 20 is a cross-sectional view taken along line C in FIG. 19 in the optical integrated device according to the third embodiment. [Figure 29A] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29B] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29C] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29D] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29E] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29F] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Figure 29G] 11A to 11C are cross-sectional views showing a method for manufacturing an optical integrated device according to a third embodiment. [Diagram 30] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a modification of the third embodiment. [Diagram 31] 31 is a cross-sectional view taken along line A in FIG. 30 in the optical integrated device according to a modification of the third embodiment. [Diagram 32] 31 is a cross-sectional view taken along line B in FIG. 30 in the optical integrated device according to a modification of the third embodiment. [Diagram 33] FIG. 13 is a schematic diagram illustrating a structure of an optical integrated device according to a fourth embodiment. [Diagram 34] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a fourth embodiment. [Diagram 35] 34 is a schematic cross-sectional view taken along line A in FIG. 33 in the optical integrated device according to the fourth embodiment. FIG. [Diagram 36] 34 is a cross-sectional view taken along line A in FIG. 33 in the optical integrated device according to the fourth embodiment. [Figure 37] 34 is a cross-sectional view taken along line B in FIG. 33 in the optical integrated device according to the fourth embodiment. [Figure 38]34 is a cross-sectional view taken along line C in FIG. 33 in the optical integrated device according to the fourth embodiment. [Figure 39] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a modification of the fourth embodiment. [Diagram 40] 40 is a cross-sectional view taken along line A in FIG. 39 in an optical integrated device according to a modification of the fourth embodiment. [Diagram 41] 40 is a cross-sectional view taken along line B in FIG. 39 in the optical integrated device according to a modification of the fourth embodiment. [Diagram 42] FIG. 13 is a schematic diagram illustrating a structure of an optical integrated device according to a fifth embodiment. [Diagram 43] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a fifth embodiment. [Diagram 44] 43 is a cross-sectional view taken along line A in FIG. 42 in the optical integrated device according to the fifth embodiment. [Diagram 45] 43 is a cross-sectional view taken along line B in FIG. 42 in the optical integrated device according to the fifth embodiment. [Diagram 46] 43 is a cross-sectional view taken along line C in FIG. 42 in the optical integrated device according to the fifth embodiment. [Figure 47] FIG. 13 is a top view illustrating a structure of an optical integrated device according to a modification of the fifth embodiment. [Figure 48] 48 is a cross-sectional view taken along line A in FIG. 47 in an optical integrated device according to a modification of the fifth embodiment. [Figure 49] 48 is a cross-sectional view taken along line B in FIG. 47 in the optical integrated device according to a modification of the fifth embodiment. [Figure 50] FIG. 13 is a cross-sectional view of an optical integrated device according to a sixth embodiment. [Figure 51] FIG. 13 is a cross-sectional view of an optical integrated device according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Embodiment 1 FIG. 1 is a schematic diagram showing the structure of the optical integrated device 300 according to the first embodiment. FIG. 2 is a top view showing the structure of the optical integrated device 300 according to the first embodiment. FIG. 3 is a schematic diagram showing the optical integrated device 300 according to the first embodiment as viewed from a cross section taken along line A in FIG. 1. FIG. 4 is a cross section taken along line A in FIG. 1 of the optical integrated device 300 according to the first embodiment. FIG. 5 is a cross section taken along line B in FIG. 1 of the optical integrated device 300 according to the first embodiment. FIG. 6 is a cross section taken along line C in FIG. 1 of the optical integrated device 300 according to the first embodiment. In FIG. 1 to FIG. 6, the directions of the xyz axes are shown for convenience of explanation. FIG. 6 shows a schematic diagram of the spread 81 of the optical mode propagating through the high mesa portion 16 in the optical functional element 100.

[0025] <Configuration of Optical Integrated Device According to First Embodiment> The optical integrated device 300 comprises an optical functional element 100 and an optical circuit element 200. The optical functional element 100 is made of a compound semiconductor material such as InP. The optical circuit element 200 is made of a semiconductor material such as Si.

[0026] <Configuration of Optical Functional Element in Optical Integrated Device According to First Embodiment> The optical functional element 100 comprises an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11, a high mesa portion 16 which includes the compound semiconductor substrate 11 as a part and has at least the active layer 12 and the contact layer 13 from the compound semiconductor substrate 11 side and has a convex shape, a first electrode formed on the top of the high mesa portion 16, and planar terrace portions 14 which are provided along the high mesa portion 16 and located at a preset height relative to the active layer 12.

[0027] The active layer 12 has a refractive index higher than that of the material constituting the compound semiconductor substrate 11, and has a function of allowing electricity and light to interact with each other, for example, like a multiple quantum well structure. The active layer 12 is formed on the compound semiconductor substrate 11 by epitaxial crystal growth.

[0028] The contact layer 13 is made of a material with a lower refractive index than the active layer 12, and functions as a cladding that confines light in the active layer 12. The contact layer 13 also has the function of making electrical contact with an electrode formed on the surface. The contact layer 13 is formed on the active layer 12 by epitaxial crystal growth.

[0029] The high mesa portion 16 is processed to have a mesa width of submicrons to several microns, and is convex with respect to the surface of the compound semiconductor substrate 11. The high mesa portion 16 includes a portion of the compound semiconductor substrate 11, and has at least an active layer 12 and a contact layer 13 from the compound semiconductor substrate 11 side. The high mesa portion 16 is formed by etching the active layer 12 and contact layer 13, which are formed by epitaxial crystal growth on the compound semiconductor substrate 11, from the surface side of the contact layer 13, to provide a pair of mesa grooves 15. The mesa groove width of each of the pair of mesa grooves 15 is several microns.

[0030] A first electrode 17 made of a metal material having excellent conductivity, such as gold (Au), titanium (Ti), or platinum (Pt), is formed on the top of the high mesa portion 16 so as to enable current to be injected into the contact layer 13 of the high mesa portion 16.

[0031] The terrace portions 14 are provided along the stripe-shaped high mesa portions 16 via the mesa grooves 15. The terrace portions 14 are planar. The surface of the terrace portion 14 is the outermost surface of the compound semiconductor substrate 11. In other words, the height of the surface of the terrace portion 14 coincides with the height of the interface between the compound semiconductor substrate 11 and the active layer 12. The terrace portions 14 are formed by removing the active layer 12 on the compound semiconductor substrate 11 by selective etching or the like.

[0032] Since the terrace portion 14 is configured as described above, the surface of the terrace portion 14 is located at a preset height with respect to the active layer 12. In the case of the optical functional element 100 in the optical integrated device 300 according to the first embodiment, the surface of the terrace portion 14 is located at a position lower than the surface of the active layer 12 on the contact layer 13 side by the layer thickness of the active layer 12. If the layer thickness of the active layer 12 is d AL Then, the surface of the terrace portion 14 is −d AL In the optical functional device 100, the direction from the surface of the compound semiconductor substrate 11 toward the surface of the contact layer 13 is called the height direction. In other words, the direction toward the negative side in the y-axis direction is the height direction. This is also applied to the other embodiments. The above is an overview of each component of the optical functional device 100.

[0033] <Configuration of Optical Circuit Element in Optical Integrated Device According to First Embodiment> The optical circuit element 200 includes a semiconductor substrate 21, a laminated structure substrate 40 having a lower cladding layer 22, a core layer 23, and an upper cladding layer 25 formed on the semiconductor substrate 21, a first recess 27a provided on the laminated structure substrate 40 and having one surface serving as an opening, second recesses 27b provided at a preset distance along both side surfaces having one end in contact with the opening of the first recess 27a, and an optical waveguide section 24 provided in contact with one surface facing the opening of the first recess 27a and including the lower cladding layer 22, the core layer 23, and the upper cladding layer 25. Note that the term "core layer" originally means a layer that guides light, but for convenience of explanation, a thin film layer formed simultaneously with the core layer that guides light will be referred to as the core layer 23 even if it does not have the function of guiding light.

[0034] An example of the semiconductor substrate 21 is a Si substrate. The lower cladding layer 22 and the upper cladding layer 25 formed on the semiconductor substrate 21 have a structure similar to a so-called Buried Oxide layer (BOX layer), and are made of an insulating material such as silicon dioxide (SiO2). An insulating material such as SiO2 has a lower refractive index than the semiconductor substrate 21.

[0035] The core layer 23 is formed between the lower cladding layer 22 and the upper cladding layer 25, and is made of, for example, a thin-film semiconductor layer. The thin-film semiconductor layer constituting the core layer 23 is made of a material having a higher refractive index than the lower cladding layer 22, for example, Si.

[0036] The first recess 27a is provided in the multilayer structure substrate 40, and one of the four side surfaces of the first recess 27a is an opening. The second recess 27b is provided in the multilayer structure substrate 40 at a preset distance along two side surfaces whose one ends contact the opening of the first recess 27a. Note that, although the first recess 27a has a shape in which one side is an opening, the first recess 27a is not limited to a recess with an opening on one side, and may have a shape in which all four sides form side surfaces.

[0037] The optical waveguide section 24 includes a lower cladding layer 22, a core layer 23, and an upper cladding layer 25, and is formed by etching both sides to have a rectangular or convex cross-sectional structure with an optical waveguide width of submicrons to several microns. One end of the optical waveguide section 24 is provided in contact with one surface facing the opening of the first recess 27a. The core layer 23 is sandwiched on both sides between the lower cladding layer 22 and the upper cladding layer 25, which have a refractive index lower than that of the core layer 23, so that light incident from the end face of the core layer 23 becomes guided light that is guided within the core layer 23.

[0038] A protrusion 26 is formed between the first recess 27a and the second recess 27b of the optical circuit element 200. At the top 26a of the protrusion 26, the surface of the core layer 23 is exposed. In other words, the outermost surface of the core layer 23 on the side in contact with the upper cladding layer 25 is exposed. The upper cladding layer 25 is removed in an area equal to or larger than the optical functional element 100, and the outermost surface of the core layer 23 is exposed.

[0039] A second electrode 28 made of a metal material having excellent conductivity is formed on part of the bottom of the first recess 27a. The above is an overview of each component of the optical circuit element 200. In the optical circuit element 200, the direction from the surface of the semiconductor substrate 21 toward the surface of the upper cladding layer 25 is called the height direction. In other words, the direction toward the positive side in the y-axis direction is the height direction. The same applies to other embodiments.

[0040] <Modification of Optical Function Elements and Optical Circuit Elements in an Optical Integrated Device According to the First Embodiment> The optical functional element 100 and the optical circuit element 200 are flip-chip mounted and integrated to form an optical integrated device 300. The mounting form of the optical functional element 100 and the optical circuit element 200 will be described below.

[0041] The optical functional element 100 is joined to the optical circuit element 200 in an upside-down orientation with the compound semiconductor substrate 11 on top. That is, the optical functional element 100 and the optical circuit element 200 are flip-chip mounted. In the flip-chip mounting, the optical functional element 100 is positioned so that the center of the high mesa portion 16 of the optical functional element 100 and the center of the first recess 27a of the optical circuit element 200 coincide with each other.

[0042] The terrace portion 14 of the optical functional element 100 is in contact with the top portion 26a of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 200.

[0043] In addition, the top of the high mesa portion 16 is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16 and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and a conductive adhesive.

[0044] When the optical functional element 100 and the optical circuit element 200 are flip-chip mounted and integrated as described above, the active layer 12 of the high mesa portion 16 on the optical functional element 100 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 200 side are optically coupled. This will be described in detail later.

[0045] 3 and 4, the light propagation direction 80 is indicated by an arrow when the optical functional element 100 is a light-emitting device such as a semiconductor laser or a semiconductor optical amplifier (SOA). The arrow indicating the light propagation direction 80 in Fig. 3 and Fig. 4 is reversed when the optical functional element 100 is a light-receiving device, such as a photodiode (PD), but since the light-receiving device can be treated in the same way as a light-emitting device in the first embodiment, no distinction is made between the two here. Fig. 6 shows a schematic spread 81 of an optical mode propagating through the high mesa portion 16 in the optical functional element 100.

[0046] <Method of Manufacturing Optical Functional Element in Optical Integrated Device According to First Embodiment> A method for manufacturing the optical functional element in the optical integrated device 300 according to the first embodiment will be described below with reference to FIGS. 7A to 7H.

[0047] First, as shown in Fig. 7A, an active layer 12 made of Indium Gallium Arsenide Phosphide (InGaAsP) having a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or an active layer 12 made of Aluminum Gallium Indium Arsenide (AlGaInAs) having a composition ratio corresponding to a similar peak wavelength, and a contact layer 13 are epitaxially grown in sequence on a compound semiconductor substrate 11 made of InP. Examples of epitaxial crystal growth methods include Metal Organic Chemical Vapor Deposition (MOCVD) and Molecular Beam Epitaxy (MBE). The contact layer 13 is made of InP doped to be n-type or p-type.

[0048] After the epitaxial crystal growth, as shown in FIG. 7B, in order to protect the high mesa portion 16 and the non-terrace portion, i.e., the portions other than the terrace portion 14, a mask 51 made of an insulating film such as SiO2 is formed by photolithography and etching techniques.

[0049] 7C, the contact layer 13 in the portion not covered by the mask 51 is removed by dry etching 52 with high verticality. After etching, the outermost layer of the active layer 12 is exposed in the portion not covered by the mask 51.

[0050] 7D, the active layer 12 in the portion not covered by the mask 51 is selectively etched and removed by wet etching using, for example, a mixed solution 53 of tartaric acid and hydrogen peroxide as an etchant. In the portion not covered by the mask 51, the outermost layer of the compound semiconductor substrate 11 is exposed.

[0051] 7E, a mask 54 made of an insulating film such as SiO2 is formed to cover the portion covered by the mask 51 and the terrace portion 14. The mask 54 has an opening in a portion where the mesa groove 15 is to be formed.

[0052] After the formation of mask 54, as shown in FIG. 7F, dry etching 55 with high verticality is again used to remove a portion of compound semiconductor substrate 11 not covered by mask 54 to form mesa groove 15, thereby completing high mesa portion 16 with a convex shape.

[0053] Next, as shown in FIG. 7G, the mask 51 and the mask 54 are removed by dry etching or wet etching.

[0054] Finally, as shown in Fig. 7H, a first electrode 17 is formed on the top of the high mesa portion 16. Examples of the metal material constituting the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam deposition. Through the above manufacturing steps, the optical functional device 100 is completed.

[0055] <Method of Manufacturing Optical Circuit Element in Optical Integrated Device According to First Embodiment> The optical circuit element 200 is manufactured by a known manufacturing method that employs silicon processing technology, and therefore the details of the manufacturing method for the optical circuit element 200 are omitted.

[0056] <Method of Manufacturing Optical Integrated Device According to First Embodiment> The optical functional element 100 and the optical circuit element 200 are flip-chip mounted by arranging the optical functional element 100 upside down so that the compound semiconductor substrate 11 of the optical functional element 100 is on top and so that the center of the high mesa portion 16 of the optical functional element 100 coincides with the center of the first recess 27a of the optical circuit element 200.

[0057] In the optical functional element 100 and the optical circuit element 200, the terrace portion 14 of the optical functional element 100 is in contact with the top portion 26a of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 200. Meanwhile, the first electrode 17 formed on the top portion of the high mesa portion 16 and the second electrode 28 formed on the bottom portion of the first recess 27a are electrically and mechanically joined to each other by the joining member 30. Through the above manufacturing steps, an optical integrated device 300 in which the optical functional element 100 and the optical circuit element 200 are flip-chip mounted is completed.

[0058] By going through each of the manufacturing processes for the optical functional element 100 described above, and utilizing selective etching between the constituent material of the active layer 12 and the constituent material other than the active layer 12, it is possible to control the relative positional deviation in the height direction between the optical functional element 100 and the optical circuit element 200 with high precision without using a so-called etching stop layer.

[0059] On the other hand, when the above-mentioned height control method is used, the position of the terrace portion 14 is limited to the interface between the active layer 12 and the compound semiconductor substrate 11. Therefore, in the first embodiment, in the optical circuit element 200, the upper cladding layer 25 of the top 26a of the protrusion 26, which is the region on which the optical functional element 100 is mounted, is selectively removed, thereby setting the distance in the height direction between the active layer 12 of the high mesa portion 16 of the optical functional element 100 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200 to be approximately equal to an accuracy of submicrons or less.

[0060] <Operation and Features of the Optical Integrated Device According to the First Embodiment> The operation and features of the optical integrated device 300 according to the first embodiment will be described below. In Figure 8, 1 / e 2 An optical functional device 100 having a half-angle far field pattern (FFP) of 20 degrees and emitting light with a wavelength of 1.55 μm from an active layer 12 in a high mesa portion 16; 2 FIG. 1 shows the results of calculating the relationship between the relative positional deviation in the x and y directions and the optical coupling efficiency when optical circuit element 200, in which light with a half angle FFP of 15 degrees is output from core layer 23 of optical waveguide section 24, is directly opposed to one another with a distance of 5 μm in the z direction shown in FIG.

[0061] Assuming that the target value of the coupling efficiency is -2 dB (= 63%), when the misalignment in the y direction is 1.0 μm, the misalignment in the x direction that is allowed to achieve the target value is approximately ±0.3 μm or less, which is a very strict value.

[0062] On the other hand, if the y-direction deviation can be controlled with high precision to within 0.5 μm, the x-direction deviation that is allowed to achieve the target value is within approximately ±1.0 μm, which is a reasonable value even when manufacturing variations are taken into account.

[0063] Figure 9 shows the 1 / e 2 An optical functional device 100 in which light having a half angle FFP of 20 degrees is emitted from an active layer 12 in a high mesa portion 16; 2FIG. 1 shows the results of calculating the relative positional shifts in the y and z directions and the optical coupling efficiency when an optical circuit element 200, in which light with a half angle of FFP of 15 degrees is emitted from a core layer 23 of an optical waveguide section 24, is faced directly with an x-direction shift of 0 μm as shown in FIG.

[0064] As in the case of Figure 8, when the y-direction misalignment is 1.0 μm, the x-direction misalignment allowable to achieve the target value is strict at approximately 6 μm or less. On the other hand, when the y-direction misalignment can be controlled with high precision to 0.5 μm, the z-direction misalignment allowable to achieve the target value is 10 μm or less, which is a more than ample value even when manufacturing variations are taken into account.

[0065] In addition, in Figure 8, when the y-direction shift is 2.5 μm or more, the maximum value of the optical coupling efficiency is other than z = 0 μm. This shows that when the relative position shift in the vertical direction to the light propagation becomes too large, more optical power can be guided to the core layer 23 of the optical waveguide section 24 of the optical circuit element 200 by placing the optical functional element 100 at a position slightly away where the light is diffused, than when the optical axis direction shift is 0.

[0066] From the above calculation results, it can be seen that in order to obtain high optical coupling efficiency between the optical functional element 100 and the optical circuit element 200, the relative positional deviation in the height direction between the optical functional element 100 and the optical circuit element 200 should be 1 μm or less, more preferably about 0.5 μm, and the relative positional deviation in the optical axis direction should be 6 μm or less.

[0067] In the optical integrated device 300 according to the first embodiment, the terrace portion 14 located just below the active layer 12 of the optical functional element 100 and the top 26a of the protrusion 26 located just above the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200 are in contact with each other by flip-chip mounting, so that the relative positional deviation in the height direction between the terrace portion 14 and the top 26a does not exceed the relative positional deviation in the height direction between the active layer 12 of the optical functional element 100 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200. Generally, the relative positional deviation in the height direction between the optical functional element 100 and the optical circuit element 200 is about 0.5 μm, so that the target value of the optical coupling efficiency is ensured by employing the optical integrated device 300 according to the first embodiment.

[0068] On the other hand, with regard to the relative positional deviation in the axial direction, i.e., the y direction, the requirement that the relative positional deviation be 6 μm or less can be easily achieved by forming alignment marks, for example in the shape of a cross, on each of the optical functional element 100 and the optical circuit element 200, and aligning them while observing their respective relative positions using a camera or the like.

[0069] The shape, material, and positional relationship of the optical integrated device 300 do not need to be limited to the configuration of the first embodiment. For example, the optical functional element 100 may be a light receiving device such as a photodiode (PD) instead of a light emitting device such as a semiconductor laser or SOA. In the case of a light receiving device, the same can be considered if the direction of light input and output is reversed.

[0070] Alternatively, the device may be an optical integrated device in which both light incident on the optical functional element 100 from the optical circuit element 200 and light emitted from the optical functional element 100 to the optical circuit element 200 are mixed, such as an MZ (Mach-Zehnder) modulator or an EA (Electro-Absorption) modulator.

[0071] In addition to InP, the compound semiconductor material may be GaAs-based material or GaN-based material, or may be various combinations of these materials, such as mixed crystals. The optical circuit element 200 has been described as an example of a configuration in which a lower cladding layer 22 made of SiO2, a core layer 23 made of a Si thin film, and an upper cladding layer 25 made of SiO2 are formed on a Si substrate. However, the core layer 23 may be formed using a silicon nitride film (SiN) or a silicon oxynitride film (SiON), or a non-silicon material such as lithium niobate (LiNbO3) may be used. When SiN or SiON is used as the core layer 23, there is a drawback that the refractive index is lower than that of Si, so that the device size becomes large, but there is an advantage that a low-loss optical integrated device can be realized because the optical loss of the propagating light is smaller than that of Si.

[0072] When SiN or SiON is used as the core layer 23, the mode distribution of the propagating light is broadened compared to a core layer 23 made of a Si thin film, which has the advantage of easing the tolerance of the optical coupling efficiency for relative positional misalignment between the optical functional element 100 and the optical circuit element 200.

[0073] When LiNbO3 is used as the core layer 23, since LiNbO3 is a ferroelectric material with a high E / O coefficient, the refractive index can be changed by applying an electric field to LiNbO3, and it becomes possible to provide the optical circuit element 200 with functions such as an MZ modulator. In addition, by utilizing the refractive index change of LiNbO3, it becomes possible to adjust the optical mode distribution of the propagating light, for example, and actively correct the optical coupling efficiency in response to the relative positional deviation between the optical functional element 100 and the optical circuit element 200.

[0074] <Advantages of the First Embodiment> As described above, according to the optical integrated device and the manufacturing method for an optical integrated device of the first embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the compound semiconductor substrate, and therefore the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled, thereby providing an optical integrated device and a manufacturing method for an optical integrated device with high optical coupling efficiency.

[0075] A variation of the first embodiment. Fig. 10 is a top view showing the structure of an optical integrated device 301 according to a modification of the first embodiment, Fig. 11 is a cross-sectional view of the optical integrated device 301 according to the modification of the first embodiment taken along line A in Fig. 10, and Fig. 12 is a cross-sectional view of the optical integrated device 301 according to the modification of the first embodiment taken along line B in Fig. 10. For convenience of explanation, xyz axis directions are shown in Fig. 10 to Fig. 12.

[0076] The optical integrated device 301 according to the modification of the first embodiment differs from the optical integrated device 300 according to the first embodiment in that, in the optical integrated device 300, one of the four side surfaces of the first recess 27a provided in the optical circuit element 200 forms an opening, whereas in the optical integrated device 301 according to the modification of the first embodiment, none of the four side surfaces of the first recess 27c provided in the optical circuit element 201 has an opening. That is, in a configuration in which the optical functional element 101 and the optical circuit element 201 are flip-chip mounted, the high mesa portion 16 of the optical functional element 101 fits into the first recess 27c and is surrounded by the side surfaces of the first recess 27c.

[0077] In the optical integrated device 301 according to the modified example of the first embodiment, in addition to the propagation direction 80 of the light emitted from the high mesa portion 16 of the optical functional element 101 toward the optical waveguide portion 24 of the optical circuit element 201, the light emitted from the other end face of the high mesa portion 16 is also guided within the optical circuit element 201 and becomes available for use, thereby achieving even higher functionality of the optical integrated device 301.

[0078] <Effects of the Modification of the First Embodiment> As described above, in the optical integrated device according to the modified example of the first embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the compound semiconductor substrate. This not only enables precise control of the relative positional deviation in the height direction between the optical functional element and the optical circuit element, but also makes it possible to utilize the light emitted from the other end face of the high mesa portion of the optical functional element, thereby achieving an even higher level of functionality for the optical integrated device.

[0079] Embodiment 2 FIG. 13 is a schematic diagram showing the structure of the optical integrated device 310 according to the second embodiment. FIG. 14 is a top view showing the structure of the optical integrated device 300 according to the first embodiment. FIG. 15 is a schematic diagram showing the cross section of the optical integrated device 310 according to the second embodiment taken along line A in FIG. 13. FIG. 16 is a cross section of the optical integrated device 310 according to the second embodiment taken along line A in FIG. 13. FIG. 17 is a cross section of the optical integrated device 310 according to the second embodiment taken along line B in FIG. 13. FIG. 18 is a cross section of the optical integrated device 310 according to the second embodiment taken along line C in FIG. 13. In FIG. 13 to FIG. 18, the directions of the xyz axes are shown for convenience of explanation. FIG. 18 shows a schematic diagram of the spread 81 of the optical mode propagating through the high mesa portion 16 in the optical functional element 110.

[0080] <Configuration of Optical Integrated Device According to Second Embodiment> The optical integrated device 310 is made up of an optical functional element 110 and an optical circuit element 210. The optical functional element 110 is made up of a compound semiconductor material such as InP. The optical circuit element 210 is made up of a semiconductor material such as Si.

[0081] <Configuration of Optical Functional Element in Optical Integrated Device According to Second Embodiment> The optical functional element 110 includes an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11, a high mesa portion 16 that includes the compound semiconductor substrate 11 as a part thereof and has at least the active layer 12 and the contact layer 13 from the compound semiconductor substrate 11 side and is convex, a first electrode 17 formed on the top of the high mesa portion 16, and planar terrace portions 14a provided along the high mesa portion 16 and positioned at a preset height relative to the active layer 12. In the following description, only the parts that are structurally different from the optical functional element 100 of the optical integrated device 300 according to the first embodiment will be described.

[0082] The terrace portions 14a are provided along the high mesa portions 16 via the mesa grooves 15. The terrace portions 14a are planar. The surface of the terrace portion 14a is the outermost surface of the active layer 12. In other words, the height of the surface of the terrace portion 14a coincides with the height of the interface between the active layer 12 and the contact layer 13. The terrace portions 14a are formed by removing the contact layer 13 on the active layer 12 by selective etching or the like.

[0083] Since the terrace portion 14a is configured as described above, the surface of the terrace portion 14a is located at a preset height with respect to the active layer 12. In the case of the optical functional element 110 in the optical integrated device 310 according to the second embodiment, the surface of the terrace portion 14a is located at the same height as the surface of the active layer 12 on the contact layer 13 side. In other words, with the surface of the active layer 12 on the contact layer 13 side as the reference, the surface of the terrace portion 14 is located at a height of zero. The above is an overview of the characteristic parts of each component of the optical functional device 110.

[0084] <Configuration of Optical Circuit Element in Optical Integrated Device According to Second Embodiment> The optical circuit element 210 according to the second embodiment has basically the same configuration as the optical circuit element 200 according to the first embodiment, but there are some differences in the configuration. Therefore, only the differences will be described below.

[0085] At the top 26b of the convex portion 26 formed between the first concave portion 27a and the second concave portion 27b of the optical circuit element 210, the lower cladding layer 22 is exposed. That is, the outermost surface of the side where the lower cladding layer 22 contacts the core layer 23 is exposed. The upper cladding layer 25 and the core layer 23 are removed in an area equal to or larger than the optical functional element 110, and the outermost surface of the lower cladding layer 22 is exposed. In this respect, it differs from the optical circuit element 200 of the first embodiment in which the core layer 23 is exposed at the top 26b of the convex portion 26. The above are characteristic parts of the configuration of the optical circuit element 210.

[0086] <Modification of Optical Function Elements and Optical Circuit Elements in an Optical Integrated Device According to the Second Embodiment> The optical functional element 110 and the optical circuit element 210 are flip-chip mounted and integrated to form an optical integrated device 310. The mounting form of the optical functional element 110 and the optical circuit element 210 will be described below.

[0087] The optical functional element 110 is joined to the optical circuit element 210 in an upside-down orientation with the compound semiconductor substrate 11 on top. That is, the optical functional element 110 and the optical circuit element 210 are flip-chip mounted. In the flip-chip mounting, the optical functional element 110 is positioned so that the center of the high mesa portion 16 of the optical functional element 110 and the center of the first recess 27a of the optical circuit element 210 coincide with each other.

[0088] The terrace portion 14 a of the optical functional element 110 is in contact with the top portion 26 b of the protrusion 26 formed between the first recess 27 a and the second recess 27 b of the optical circuit element 210 .

[0089] In addition, the top of the high mesa portion 16 is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16 and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and a conductive adhesive.

[0090] As described above, when the optical functional element 110 and the optical circuit element 210 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16 on the optical functional element 110 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 210 side are optically coupled.

[0091] <Method of Manufacturing Optical Functional Element in Optical Integrated Device According to Second Embodiment> A method for manufacturing the optical functional element 110 in the optical integrated device 310 according to the second embodiment will be described below with reference to FIGS. 19A to 19H.

[0092] First, as shown in Fig. 19A, an active layer 12 having a multiple quantum well structure made of InGaAsP with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more or AlGaInAs with a composition ratio corresponding to a similar peak wavelength, and a contact layer 13 are epitaxially grown in sequence on a compound semiconductor substrate 11 made of, for example, InP. Examples of the epitaxial crystal growth method include MOCVD and MBE. The contact layer 13 is made of, for example, InP doped to n-type or p-type.

[0093] After the epitaxial crystal growth, as shown in FIG. 19B, in order to protect the high mesa portion 16 and the non-terrace portion, i.e., the portions other than the terrace portion 14a, a mask 51 made of an insulating film such as SiO2 is formed by photolithography and etching techniques.

[0094] As shown in FIG. 19C, the contact layer 13 in the portion not covered by the mask 51 is removed by dry etching 52 with high verticality, leaving a small thickness.

[0095] 19D, the contact layer 13 in the portion not covered by the mask 51 is selectively etched and removed by wet etching using a mixed solution 53 of hydrochloric acid and phosphoric acid as an etchant, for example. After the etching, the outermost layer of the active layer 12 is exposed in the portion not covered by the mask 51.

[0096] 19E, a mask 54 made of an insulating film such as SiO2 is formed so as to cover the portion covered by the mask 51 and the terrace portion 14a. The mask 54 has an opening in a portion where the mesa groove 15 is to be formed.

[0097] After the formation of the mask 54, as shown in FIG. 19F, dry etching 55 with high verticality is again used to remove a portion of the active layer 12 and the compound semiconductor substrate 11 that is not covered by the mask 54, thereby forming a mesa groove 15, thereby completing a convex high mesa portion 16.

[0098] Next, as shown in FIG. 19G, the masks 51 and 54 are removed by dry etching or wet etching.

[0099] 19H, a first electrode 17 is formed on the top of the high mesa portion 16. Examples of the metal material constituting the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam deposition. Through the above manufacturing steps, the optical functional device 110 is completed.

[0100] <Method of Manufacturing Optical Integrated Device According to Second Embodiment> The optical functional element 110 and the optical circuit element 210 are flip-chip mounted by arranging the optical functional element 110 upside down so that the compound semiconductor substrate 11 of the optical functional element 110 is on top and so that the center of the high mesa portion 16 of the optical functional element 110 coincides with the center of the first recess 27a of the optical circuit element 210.

[0101] In the optical functional element 110 and the optical circuit element 210, the terrace portion 14a of the optical functional element 110 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 210. Meanwhile, the first electrode 17 formed on the top portion of the high mesa portion 16 and the second electrode 28 formed on the bottom portion of the first recess 27a are electrically and mechanically joined to each other by the joining member 30. Through the above manufacturing steps, the optical integrated device 310 is completed, in which the optical functional element 110 and the optical circuit element 210 are flip-chip mounted together.

[0102] By going through each of the manufacturing processes for the optical functional element 110 described above, and utilizing selective etching between the constituent material of the active layer 12 and the constituent material other than the active layer 12, it is possible to control the relative positional deviation in the height direction between the optical functional element 110 and the optical circuit element 210 with high precision without using a so-called etching stop layer.

[0103] On the other hand, when the above-mentioned height control method is used, the position of the terrace portion 14a is limited to the interface between the active layer 12 and the contact layer 13. Therefore, in the second embodiment, in the optical circuit element 210, the upper cladding layer 25 and the core layer 23 of the top 26b of the protrusion 26, which is the region on which the optical functional element 110 is mounted, are selectively removed, so that the distance in the height direction between the active layer 12 of the high mesa portion 16 of the optical functional element 110 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 210 is made to be approximately equal to an accuracy of submicrons or less.

[0104] <Operation and Features of the Optical Integrated Device According to the Second Embodiment> By applying such a structure to the optical functional element 110, the terrace portion 14a located just above the active layer 12 of the optical functional element 110 and the top 26b of the convex portion 26 located just below the optical waveguide portion 24 of the optical circuit element 210 are in contact by flip-chip mounting, so that structurally, the relative positional deviation in the height direction between the optical functional element 110 and the optical circuit element 210 does not exceed the relative positional deviation in the height direction between the active layer 12 of the optical functional element 110 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 210.

[0105] Generally, the relative positional deviation in the height direction between the optical functional element 110 and the optical circuit element 210 is about 0.5 μm. Therefore, by using the element structure of embodiment 2, the relative positional deviation in the height direction between the optical functional element 110 and the optical circuit element 210 is 1 μm or less, which satisfies the requirement of about 0.5 μm, thereby ensuring the realization of high optical coupling efficiency.

[0106] In the optical integrated device 310 according to the second embodiment, similarly to the first embodiment, by devising an element structure and a manufacturing method, it is possible to realize high mounting accuracy in the height direction of the optical functional element 110 and the optical circuit element 210 without using an etching stop layer, and it is possible to avoid the problem of optical loss during propagation or optical coupling between different optical elements due to deformation of the propagating light mode caused by different refractive index regions, which becomes a problem when an etching stop layer is provided.

[0107] <Advantages of the second embodiment> As described above, according to the optical integrated device and the manufacturing method for an optical integrated device of the second embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the active layer, and therefore the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled, thereby providing an optical integrated device and a manufacturing method for an optical integrated device with high optical coupling efficiency.

[0108] A variation of the second embodiment. Fig. 20 is a top view showing a structure of an optical integrated device 311 according to a modification of the second embodiment, Fig. 21 is a cross-sectional view of the optical integrated device 311 according to the modification of the second embodiment taken along line A in Fig. 20, and Fig. 22 is a cross-sectional view of the optical integrated device 311 according to the modification of the second embodiment taken along line B in Fig. 20. For convenience of explanation, the directions of the x, y and z axes are shown in Figs. 20 to 22.

[0109] The optical integrated device 311 according to the modification of the second embodiment differs from the optical integrated device 310 according to the second embodiment in that, in the optical integrated device 310, one of the four side surfaces of the first recess 27a provided in the optical circuit element 210 forms an opening, whereas in the optical integrated device 311 according to the modification of the second embodiment, none of the four side surfaces of the first recess 27c provided in the optical circuit element 211 has an opening. That is, in a configuration in which the optical functional element 111 and the optical circuit element 211 are flip-chip mounted, the high mesa portion 16 of the optical functional element 111 fits into the first recess 27c and is surrounded by the side surfaces of the first recess 27c.

[0110] In the optical integrated device 311 according to the modified example of the second embodiment, in addition to the propagation direction 80 of the light emitted from the high mesa portion 16 of the optical functional element 111 toward the optical waveguide portion 24 of the optical circuit element 211, the light emitted from the other end face of the high mesa portion 16 is also guided within the optical circuit element 211 and becomes available for use, thereby achieving even higher functionality of the optical integrated device 311.

[0111] <Effects of the Modification of the Second Embodiment> As described above, in the optical integrated device according to the modified example of the second embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the active layer. This allows precise control of the relative positional deviation in the height direction between the optical functional element and the optical circuit element. This not only provides the effect of obtaining an optical integrated device with high optical coupling efficiency, but also makes it possible to utilize the light emitted from the other end face of the high mesa portion of the optical functional element, thereby achieving even higher functionality of the optical integrated device.

[0112] Embodiment 3 FIG. 23 is a schematic diagram showing the structure of the optical integrated device 320 according to the third embodiment. FIG. 24 is a top view showing the structure of the optical integrated device 320 according to the third embodiment. FIG. 25 is a schematic diagram showing the optical integrated device 320 according to the third embodiment as viewed from a cross section taken along line A in FIG. 23. FIG. 26 is a cross section taken along line A in FIG. 23 of the optical integrated device 320 according to the third embodiment. FIG. 27 is a cross section taken along line B in FIG. 23 of the optical integrated device 320 according to the third embodiment. FIG. 28 is a cross section taken along line C in FIG. 23 of the optical integrated device 320 according to the third embodiment. In FIG. 23 to FIG. 28, the directions of the xyz axes are shown for convenience of explanation. FIG. 28 shows a schematic diagram of the spread 81 of the optical mode propagating through the high mesa portion 16 in the optical functional element 120.

[0113] <Configuration of Optical Integrated Device According to Third Embodiment> The optical integrated device 320 is composed of an optical functional element 120 and an optical circuit element 220. The optical functional element 120 is made of a compound semiconductor material such as InP. The optical circuit element 220 is made of a semiconductor material such as Si.

[0114] <Configuration of Optical Functional Element in Optical Integrated Device According to Third Embodiment> The optical functional element 120 includes an active layer 12, an etching stop layer 18, and a contact layer 13 formed on a compound semiconductor substrate 11, a high mesa portion 16a that includes the compound semiconductor substrate 11 as a part and has at least the active layer 12, the etching stop layer 18, and the contact layer 13 from the compound semiconductor substrate 11 side and has a convex shape, a first electrode 17 formed on the top of the high mesa portion 16a, and planar terrace portions 14b that are provided along the high mesa portion 16a and are located at a preset height relative to the active layer 12.

[0115] The etching stop layer 18 has a property of exhibiting a different reactivity from the contact layer 13 described below in a specific etching process. The optical functional element 120 of the third embodiment is characterized in that the etching stop layer 18 is provided between the active layer 12 in the high mesa portion 16a and the contact layer 13. In the following description, only the parts that are structurally different from the optical functional element 100 of the optical integrated device 300 according to the first embodiment will be described.

[0116] The terrace portions 14b are provided along the high mesa portions 16a via the mesa grooves 15. The terrace portions 14b are planar. The surface of the terrace portions 14b is the outermost surface of the etching stop layer 18. In other words, the height of the surface of the terrace portions 14b coincides with the height of the interface between the etching stop layer 18 and the contact layer 13. The terrace portions 14b are formed by removing the contact layer 13 on the etching stop layer 18 by selective etching or the like.

[0117] Since the terrace portion 14b is configured as described above, the surface of the terrace portion 14b is located at a preset height with respect to the active layer 12. In the case of the optical functional element 120 in the optical integrated device 320 according to the third embodiment, the surface of the terrace portion 14b is located at the same height as the surface of the etching stop layer 18 on the contact layer 13 side. If the layer thickness of the etching stop layer 18 is d ESL Then, with respect to the surface of the active layer 12 on the etching stop layer 18 side, the surface of the terrace portion 14b is +d ESL It will be located at the height of The above is an overview of the characteristic parts of each component of the optical functional element 120.

[0118] <Configuration of Optical Circuit Element in Optical Integrated Device According to Third Embodiment> The optical circuit element 220 according to the third embodiment has the same configuration as the optical circuit element 210 according to the second embodiment. That is, the lower cladding layer 22 is exposed at the top 26b of the convex portion 26 formed between the first concave portion 27a and the second concave portion 27b of the optical circuit element 220. That is, the outermost surface of the lower cladding layer 22 on the side where the lower cladding layer 22 contacts the core layer 23 is exposed. The upper cladding layer 25 and the core layer 23 are removed in an area equal to or larger than the optical functional element 120, and the outermost surface of the lower cladding layer 22 is exposed.

[0119] <Modification of Optical Function Elements and Optical Circuit Elements in an Optical Integrated Device According to the Third Embodiment> The optical functional element 120 and the optical circuit element 220 are flip-chip mounted and integrated to form an optical integrated device 320. The mounting form of the optical functional element 120 and the optical circuit element 220 will be described below.

[0120] The optical functional element 120 is joined to the optical circuit element 220 in an upside-down orientation with the compound semiconductor substrate 11 on top. That is, the optical functional element 120 and the optical circuit element 220 are flip-chip mounted. In the flip-chip mounting, the optical functional element 120 is positioned so that the center of the high mesa portion 16a of the optical functional element 120 and the center of the first recess 27a of the optical circuit element 220 coincide with each other.

[0121] The terrace portion 14b of the optical functional element 120 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 220.

[0122] In addition, the top of the high mesa portion 16a is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16a and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and a conductive adhesive.

[0123] As described above, when the optical functional element 120 and the optical circuit element 220 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16a on the optical functional element 120 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 220 side are optically coupled.

[0124] <Method of Manufacturing Optical Functional Element in Optical Integrated Device According to Third Embodiment> A method for manufacturing an optical functional element in an optical integrated device 320 according to the third embodiment will be described below with reference to FIGS. 29A to 29H.

[0125] First, as shown in Fig. 29A, an MQW active layer 12 made of InGaAsP with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more or AlGaInAs with a composition ratio corresponding to a similar peak wavelength, an etching stop layer 18 made of AlInAs with a layer thickness of 0.1 μm or less, and a contact layer 13 are epitaxially grown in this order on a compound semiconductor substrate 11 made of InP, for example. Examples of epitaxial crystal growth methods include MOCVD and MBE. The contact layer 13 is made of InP doped to n-type or p-type, for example.

[0126] After the epitaxial crystal growth, as shown in FIG. 29B, in order to protect the high mesa portion 16a and the non-terrace portion, i.e., the portions other than the terrace portion 14b, a mask 51 made of an insulating film such as SiO2 is formed by photolithography and etching techniques.

[0127] After the mask 51 is formed, as shown in FIG. 29C, a highly vertical dry etching 52 is used to selectively remove the contact layer 13 in the portion not covered by the mask 51 by reactive ion etching. After etching, the outermost layer of the etching stop layer 18 is exposed in the portion not covered by the mask 51. Methane gas, for example, is suitable as an etching gas used in the dry etching 52. However, the etching gas is not limited to methane gas.

[0128] 29D, a mask 54 made of an insulating film such as SiO2 is formed so as to cover the portion covered by the mask 51 and the terrace portion 14b. The mask 54 has an opening in a portion where the mesa groove 15 is to be formed.

[0129] After the formation of the mask 54, as shown in FIG. 29E, dry etching 55 with high verticality is again used to remove a portion of the etching stop layer 18, the active layer 12, and the compound semiconductor substrate 11 that are not covered by the mask 54, thereby forming a mesa groove 15, thereby completing a convex high mesa portion 16a.

[0130] Next, as shown in FIG. 29F, the mask 51 and the mask 54 are removed by dry etching or wet etching.

[0131] Finally, as shown in Fig. 29G, a first electrode 17 is formed on the top of the high mesa portion 16a. Examples of the metal material constituting the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam evaporation. Through the above manufacturing steps, the optical functional element 120 is completed.

[0132] <Method of Manufacturing Optical Circuit Element in Optical Integrated Device According to Third Embodiment> The optical circuit element 220 is manufactured by a known manufacturing method that uses silicon processing technology, and therefore the details of the manufacturing method for the optical circuit element 220 are omitted.

[0133] <Method of Manufacturing Optical Integrated Device According to Third Embodiment> The optical functional element 120 is oriented upside down with the compound semiconductor substrate 11 of the optical functional element 120 facing upward, and the center of the high mesa portion 16a of the optical functional element 120 is aligned with the center of the first recess 27a of the optical circuit element 220, and then bonded to the optical circuit element 220.

[0134] In the optical functional element 120 and the optical circuit element 220, the terrace portion 14b of the optical functional element 120 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 220. Meanwhile, the first electrode 17 formed on the top portion of the high mesa portion 16a and the second electrode 28 formed on the bottom portion of the first recess 27a are electrically and mechanically joined to each other by the joining member 30. Through the above manufacturing steps, an optical integrated device 320 is completed in which the optical functional element 120 and the optical circuit element 220 are flip-chip mounted together.

[0135] <Operation and Features of the Optical Integrated Device According to the Third Embodiment> By going through each of the manufacturing processes for the optical functional element 120 described above, and in particular by utilizing selective etching by methane gas between AlInAs, which is the material of the etching stop layer 18, and InP, which is the material of the contact layer 13, it is possible to control the relative positional deviation in the height direction between the optical functional element 120 and the optical circuit element 220 with high precision.

[0136] On the other hand, when the above-mentioned height control method is used, the position of the terrace portion 14b is limited to the interface between the etching stop layer 18 and the contact layer 13. Therefore, in the third embodiment, in the optical circuit element 220, the upper cladding layer 25 and the core layer 23 of the top 26b of the protrusion 26, which is the region on which the optical functional element 120 is mounted, are selectively removed, so that the distance in the height direction between the active layer 12 of the high mesa portion 16a of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220 is made to be approximately equal to an accuracy of submicrons or less.

[0137] By applying such a structure to the optical functional element 120, the terrace portion 14b located at a height just above the active layer 12 of the optical functional element 120 and the top 26b of the convex portion 26 located at a height just below the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220 are in contact by flip-chip mounting, so that structurally, the relative positional deviation in the height direction between the optical functional element 120 and the optical circuit element 220 does not exceed the relative positional deviation in the height direction between the active layer 12 of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220.

[0138] In the optical functional element 120 of the third embodiment, the thickness of the etching stop layer 18 is set to 0.1 μm or less, and therefore the relative positional deviation in the height direction between the optical functional element 120 and the optical circuit element 220 is 1 μm or less, which satisfies approximately 0.5 μm, thereby ensuring the realization of high optical coupling efficiency.

[0139] In the optical integrated device 320 according to the third embodiment, as compared with the optical integrated devices 300 and 310 according to the first and second embodiments, the introduction of the etching stop layer 18 has the disadvantage of causing optical loss during optical propagation or optical coupling between different optical elements due to the influence of deformation of the propagating optical mode caused by the different refractive index regions of the etching stop layer 18. However, by selecting a material with high selectivity by etching, it is possible to significantly suppress manufacturing errors in the manufacturing process of the optical integrated device.

[0140] <Advantages of the Third Embodiment> As described above, according to the optical integrated device and the manufacturing method for an optical integrated device of the third embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and therefore the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled, thereby providing an optical integrated device and a manufacturing method for an optical integrated device with high optical coupling efficiency.

[0141] A variation of the third embodiment. Fig. 30 is a top view showing a structure of an optical integrated device 321 according to a modification of the embodiment 3, Fig. 31 is a cross-sectional view of the optical integrated device 321 according to the modification of the embodiment 3 taken along line A in Fig. 30, and Fig. 32 is a cross-sectional view of the optical integrated device 321 according to the modification of the embodiment 3 taken along line B in Fig. 30. For convenience of explanation, the directions of the x, y and z axes are shown in Figs. 30 to 32.

[0142] The optical integrated device 321 according to the modification of the third embodiment differs from the optical integrated device 320 according to the third embodiment in that, in the optical integrated device 320, one of the four side surfaces of the first recess 27a provided in the optical circuit element 220 forms an opening, whereas in the optical integrated device 321 according to the modification of the third embodiment, none of the four side surfaces of the first recess 27c provided in the optical circuit element 221 has an opening. That is, in a configuration in which the optical functional element 121 and the optical circuit element 221 are flip-chip mounted, the high mesa portion 16a of the optical functional element 121 fits into the first recess 27c and is surrounded by the side surfaces of the first recess 27c.

[0143] In the optical integrated device 321 according to the modified example of the third embodiment, in addition to the propagation direction 80 of the light emitted from the high mesa portion 16 a of the optical functional element 121 toward the optical waveguide portion 24 of the optical circuit element 221, the light emitted from the other end face of the high mesa portion 16 a is also guided within the optical circuit element 221 and becomes available for use, thereby achieving even higher functionality of the optical integrated device 321.

[0144] <Effects of the Modification of the Third Embodiment> As described above, in the optical integrated device according to the modified example of the third embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer. Therefore, the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled. This not only provides the effect of obtaining an optical integrated device with high optical coupling efficiency, but also makes it possible to utilize the light emitted from the other end face of the high mesa portion of the optical functional element, thereby achieving an even higher level of functionality in the optical integrated device.

[0145] Embodiment 4 FIG. 33 is a schematic diagram showing the structure of an optical integrated device 330 according to the fourth embodiment. FIG. 34 is a top view showing the structure of an optical integrated device 300 according to the first embodiment, FIG. 35 is a schematic diagram showing a cross section of the optical integrated device 330 according to the fourth embodiment taken along line A in FIG. 33, FIG. 36 is a cross section of the optical integrated device 330 according to the fourth embodiment taken along line A in FIG. 33, FIG. 37 is a cross section of the optical integrated device 330 according to the fourth embodiment taken along line B in FIG. 33, and FIG. 38 is a cross section of the optical integrated device 330 according to the fourth embodiment taken along line C in FIG. 33. In FIG. 33 to FIG. 38, the directions of the xyz axes are shown for convenience of explanation. FIG. 38 shows a schematic diagram of the spread 81 of an optical mode propagating through the high mesa portion 16b in the optical functional element 130.

[0146] <Configuration of Optical Integrated Device According to Fourth Embodiment> The optical integrated device 330 is made up of an optical functional element 130 and an optical circuit element 230. The optical functional element 130 is made up of a compound semiconductor material such as InP. The optical circuit element 230 is made up of a semiconductor material such as Si.

[0147] <Configuration of Optical Functional Element in Optical Integrated Device According to Fourth Embodiment> The optical functional element 130 includes an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11, a high mesa portion 16b that includes the compound semiconductor substrate 11 as a part thereof and has, from the compound semiconductor substrate 11 side, at least the active layer 12, a first contact layer 13a, an etching stop layer 18, and a second contact layer 13b, and is convex, a first electrode 17 formed on the top of the high mesa portion 16b, and planar terrace portions 14c that are provided along the high mesa portion 16b and are positioned at a preset height relative to the active layer 12.

[0148] The first contact layer 13a and the second contact layer 13b are made of the same compound semiconductor material, InP. The etching stop layer 18 is formed on the first contact layer 13a and is made of a compound semiconductor material, such as AlInAs, that exhibits a different reactivity from the second contact layer 13b in a specific etching process. In the following description, only the structural differences between the optical integrated device 300 according to the first embodiment and the optical functional element 100 will be described.

[0149] The terrace portions 14c are provided along the high mesa portion 16b via the mesa grooves 15. The terrace portions 14c are planar. The surface of the terrace portion 14c is the outermost surface of the etching stop layer 18. That is, the height of the surface of the terrace portion 14c coincides with the height of the interface between the etching stop layer 18 and the second contact layer 13b. The terrace portions 14c are formed by removing the second contact layer 13b on the etching stop layer 18 by selective etching or the like.

[0150] Since the terrace portion 14c is configured as described above, the surface of the terrace portion 14c is located at a preset height with respect to the active layer 12. In the case of the optical functional element 130 in the optical integrated device 330 according to the fourth embodiment, the surface of the terrace portion 14c is located at the same height as the surface of the etching stop layer 18 on the second contact layer 13b side. When the layer thickness of the first contact layer 13a is d CN1 , the thickness of the etching stop layer 18 is d ESLThen, with the surface of the active layer 12 on the first contact layer 13a side as a reference, the surface of the terrace portion 14c is d CN1 +d ESL It will be located at the height of The above is an overview of the characteristic parts of each component of the optical functional device 130.

[0151] <Configuration of Optical Circuit Element in Optical Integrated Device According to Fourth Embodiment> The semiconductor substrate 21 is exposed at the top 26c of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 230 according to the fourth embodiment. That is, the interface where the semiconductor substrate 21 contacts the lower cladding layer 22 is exposed. The lower cladding layer 22, the core layer 23, and the upper cladding layer 25 are removed in an area equal to or larger than the optical functional element 130, and the semiconductor substrate 21 is exposed.

[0152] <Modification of Optical Function Elements and Optical Circuit Elements in an Optical Integrated Device According to the Fourth Embodiment> The optical functional element 130 and the optical circuit element 230 are flip-chip mounted and integrated to form an optical integrated device 330. The mounting form of the optical functional element 130 and the optical circuit element 230 will be described below.

[0153] The optical functional element 130 is joined to the optical circuit element 230 in an upside-down orientation with the compound semiconductor substrate 11 on top. That is, the optical functional element 130 and the optical circuit element 230 are flip-chip mounted. In the flip-chip mounting, the optical functional element 130 is positioned so that the center of the high mesa portion 16b of the optical functional element 130 and the center of the first recess 27a of the optical circuit element 230 coincide with each other.

[0154] The terrace portion 14c of the optical functional element 130 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 230.

[0155] In addition, the top of the high mesa portion 16b is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16b and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and a conductive adhesive.

[0156] As described above, when the optical functional element 130 and the optical circuit element 230 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16b on the optical functional element 130 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 230 side are optically coupled.

[0157] 35 and 36, the arrow indicates the light propagation direction 80 when the optical functional element 130 is a light emitting device such as a semiconductor laser or an SOA. Also, Fig. 38 shows a schematic view of the spread 81 of the optical mode propagating through the high mesa portion 16b in the optical functional element 130.

[0158] <Operation and Features of the Optical Integrated Device According to the Fourth Embodiment> By going through each manufacturing process of the optical functional element 130, and in particular by utilizing selective etching by methane gas between AlInAs, which is the material of the etching stop layer 18, and InP, which is the material of the second contact layer 13b, it is possible to control the relative positional deviation in the height direction between the optical functional element 130 and the optical circuit element 230 with high precision.

[0159] On the other hand, when the above-mentioned height direction control method is used, the position of the surface of the terrace portion 14c is limited to the interface between the etching stop layer 18 and the second contact layer 13b. Therefore, in the fourth embodiment, the thickness of the first contact layer 13a of the optical functional element 130 is set to be the same as the thickness of the lower cladding layer 22 of the optical circuit element 230, and further, in the optical circuit element 230, the lower cladding layer 22, the core layer 23 and the upper cladding layer 25 of the top 26c of the protrusion 26, which is the region on which the optical functional element 130 is mounted, are selectively removed, so that the height direction distance between the active layer 12 of the high mesa portion 16b of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 230 is made to be approximately the same with an accuracy of submicrons or less.

[0160] By applying such a structure to the optical functional element 130 and the optical circuit element 230, the terrace portion 14c located just above the etching stop layer 18 of the optical functional element 130 and the top 26c of the convex portion 26 located just below the lower cladding layer 22 of the optical circuit element 230 are in contact by flip-chip mounting, so that structurally, the relative positional deviation in the height direction between the optical functional element 130 and the optical circuit element 230 does not exceed the sum of the layer thicknesses of the active layer 12, etching stop layer 18, and first contact layer 13a of the optical functional element 130, and the sum of the layer thicknesses of the lower cladding layer 22 and core layer 23 of the optical circuit element 230.

[0161] In the optical functional device 130 of the fourth embodiment, the thickness of the etching stop layer 18 is set to 0.1 μm or less, and the first contact layer 13a can have its thickness variation suppressed to about ±0.1 μm by highly accurate thickness control during epitaxial crystal growth. Also, the thickness variation of the lower cladding layer 22 of the optical circuit device 230 can be suppressed to within a range of about ±0.1 μm, assuming a typical BOX layer thickness of several μm used in SOI substrates and a thickness tolerance of ±5%.

[0162] Based on the above numerical values ​​relating to the variations in layer thickness, the relative position in the height direction between the optical functional element 130 and the optical circuit element 230 is 1 μm or less, which satisfies approximately 0.5 μm, thereby ensuring the realization of high optical coupling efficiency.

[0163] In the optical integrated device 330 of the fourth embodiment, in comparison with the first to third embodiments, the accuracy of the relative positions in the height direction between the optical functional element 130 and the optical circuit element 230 is increased by the variation in the layer thickness of the first contact layer 13a and the lower cladding layer 22. This may be a disadvantage in terms of the accuracy of alignment in the height direction. However, since it is possible to space the active layer 12 of the high mesa portion 16b, which guides light, away from the etching stop layer 18 by the layer thickness of the first contact layer 13a, it is possible to avoid the problem of optical loss occurring during light propagation or optical coupling between different optical elements due to the influence of deformation of the propagating light mode caused by the different refractive index regions of the etching stop layer 18.

[0164] <Advantages of the Fourth Embodiment> As described above, according to the optical integrated device and the manufacturing method for an optical integrated device of the fourth embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the active layer and the etching stop layer are separated from each other. Therefore, it is possible to precisely control the relative positional deviation in the height direction between the optical functional element and the optical circuit element, and it is possible to reduce the effect of the etching stop layer on the propagating light. As a result, it is possible to obtain an optical integrated device and a manufacturing method for an optical integrated device with high optical coupling efficiency.

[0165] A variation of the fourth embodiment. Fig. 39 is a top view showing the structure of an optical integrated device 331 according to a modification of the fourth embodiment, Fig. 40 is a cross-sectional view of the optical integrated device 331 according to the modification of the fourth embodiment taken along line A in Fig. 39, and Fig. 41 is a cross-sectional view of the optical integrated device 331 according to the modification of the fourth embodiment taken along line B in Fig. 39. For convenience of explanation, the directions of the x, y and z axes are shown in Figs. 39 to 41.

[0166] The optical integrated device 331 according to the modification of the fourth embodiment differs from the optical integrated device 330 according to the fourth embodiment in that, in the optical integrated device 330, one of the four side surfaces of the first recess 27a provided in the optical circuit element 230 forms an opening, whereas in the optical integrated device 331 according to the modification of the fourth embodiment, none of the four side surfaces of the first recess 27c provided in the optical circuit element 231 has an opening. That is, in a configuration in which the optical functional element 131 and the optical circuit element 231 are flip-chip mounted, the high mesa portion 16b of the optical functional element 131 fits into the first recess 27c and is surrounded by the side surfaces of the first recess 27c.

[0167] In the optical integrated device 331 according to the modified example of the fourth embodiment, in addition to the propagation direction 80 of the light emitted from the high mesa portion 16 b of the optical functional element 131 toward the optical waveguide portion 24 of the optical circuit element 231, the light emitted from the other end face of the high mesa portion 16 b is also guided within the optical circuit element 231 and becomes available for use, thereby achieving even higher functionality of the optical integrated device 331.

[0168] <Effects of the Modification of the Fourth Embodiment> As described above, in the optical integrated device according to the modified example of the fourth embodiment, the surface of the terrace portion of the optical functional element is the outermost surface of the etching stop layer, and the active layer and the etching stop layer are spaced apart. Therefore, the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled, and the effect of the etching stop layer on the propagating light can be reduced. As a result, in addition to the effect of obtaining an optical integrated device with high optical coupling efficiency, it is also possible to utilize the light emitted from the other end face of the high mesa portion of the optical functional element, thereby achieving even higher functionality of the optical integrated device.

[0169] Embodiment 5. Fig. 42 is a schematic diagram showing the structure of an optical integrated device 340 according to the fifth embodiment. The optical integrated device 340 according to the fifth embodiment is composed of an optical functional element 140 and an optical circuit element 240. Fig. 43 is a top view showing the structure of the optical integrated device 340 according to the fifth embodiment, Fig. 44 is a cross-sectional view of the optical integrated device 340 according to the fifth embodiment taken along line A in Fig. 42, Fig. 45 is a cross-sectional view of the optical integrated device 340 according to the fifth embodiment taken along line B in Fig. 42, and Fig. 46 is a cross-sectional view of the optical integrated device 340 according to the fifth embodiment taken along line C in Fig. 42.

[0170] <Configuration of Optical Functional Element in Optical Integrated Device According to Fifth Embodiment> As shown in the cross-sectional views of Figures 44, 45, and 46, the optical integrated device 340 of embodiment 5 is characterized in that there is no first contact layer 13a between the etching stop layer 18a and the active layer 12 in the optical functional element 140, and instead the layer thickness of the etching stop layer 18a is made thicker by the same layer thickness as the first contact layer 13a.

[0171] In the optical integrated device 340 according to the fifth embodiment, the number of layers in the high mesa portion 16c in the optical functional element 140 is reduced by one, i.e., the first contact layer 13a is reduced, and therefore the optical integrated device 340 is easier to fabricate than the optical integrated device 340 according to the fourth embodiment. In addition, by making the thickness of the etching stop layer 18a sufficiently thick, the etching stop layer 18a itself functions as a cladding layer, and the boundary surface between the etching stop layer 18a and the first contact layer 13a, which have different refractive indices, does not exist in the mode distribution of the propagating light, so that it is possible to suppress deformation of the propagating light mode to a small extent, and therefore it is possible to avoid the problem of optical loss occurring during optical coupling between optical elements.

[0172] <Advantages of the Fifth Embodiment> As described above, according to the optical integrated device and the manufacturing method of the optical integrated device of the fifth embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the layer thickness control is performed by the etching stop layer. Therefore, the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled. This not only provides the effect of obtaining an optical integrated device with high optical coupling efficiency, but also provides the effect of easily manufacturing such an optical integrated device.

[0173] A variation of the fifth embodiment. Fig. 47 is a top view showing the structure of an optical integrated device 341 according to a modification of the fifth embodiment, Fig. 48 is a cross-sectional view of the optical integrated device 341 according to the modification of the fifth embodiment taken along line A in Fig. 47, and Fig. 49 is a cross-sectional view of the optical integrated device 341 according to the modification of the fifth embodiment taken along line B in Fig. 47. For convenience of explanation, the directions of the x, y and z axes are shown in Figs. 47 to 49.

[0174] The optical integrated device 341 according to the modification of the fifth embodiment differs from the optical integrated device 340 according to the fifth embodiment in that, in the optical integrated device 340, one of the four side surfaces of the first recess 27a provided in the optical circuit element 240 forms an opening, whereas in the optical integrated device 341 according to the modification of the fifth embodiment, none of the four side surfaces of the first recess 27c provided in the optical circuit element 241 has an opening. That is, in a configuration in which the optical functional element 141 and the optical circuit element 241 are flip-chip mounted, the high mesa portion 16c of the optical functional element 141 fits into the first recess 27c and is surrounded by the side surfaces of the first recess 27c.

[0175] In the optical integrated device 341 according to the modified example of the fifth embodiment, in addition to the propagation direction 80 of the light emitted from the high mesa portion 16 c of the optical functional element 141 toward the optical waveguide portion 24 of the optical circuit element 241, the light emitted from the other end face of the high mesa portion 16 c is also guided within the optical circuit element 241 and becomes available for use, thereby achieving even higher functionality of the optical integrated device 341.

[0176] <Effects of the Modification of the Fifth Embodiment> As described above, in the optical integrated device according to the modified example of the fifth embodiment, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the layer thickness control is performed by the etching stop layer. Therefore, the relative positional deviation in the height direction between the optical functional element and the optical circuit element can be precisely controlled. This not only provides the effect of obtaining an optical integrated device with high optical coupling efficiency, but also makes it possible to utilize the light emitted from the other end face of the high mesa portion of the optical functional element, thereby achieving even higher functionality of the optical integrated device.

[0177] Embodiment 6 <Configuration and Features of Optical Functional Element in Optical Integrated Device According to Sixth Embodiment> The sixth embodiment is a modification of the third and fourth embodiments. FIG. 50 is a cross-sectional view of an optical integrated device 350 according to the sixth embodiment. The optical integrated device 350 according to the sixth embodiment is composed of an optical functional element 150 and an optical circuit element 250. The optical integrated device 350 according to the sixth embodiment is characterized in that the etching stop layer is composed of a laminated structure composed of at least two layers of AlInAs having different compositions. As a laminated structure of the etching stop layer, for example, an etching stop layer composed of a layer having an Al(0.48)In(0.52)As composition that is lattice-matched with the InP substrate and a layer having a higher Al content than the above, for example, an Al(0.7)In(0.3)As composition, can be mentioned.

[0178] A specific example of an etching stop layer consisting of two layers is a configuration in which the first etching stop layer 18b on the side close to the active layer 12 is a layer having an Al(0.48)In(0.52)As composition, and the second etching stop layer 18c on the side away from the active layer 12 is a layer having an Al(0.7)In(0.3)As composition.

[0179] The optical integrated device 350 according to the sixth embodiment includes a layer made of an AlInAs composition that does not meet the lattice matching conditions with the InP substrate, and therefore distortion may occur in the crystal, which may cause problems with the crystal quality, reliability, etc. However, if the laminate structure of the etching stop layer is made up of layers with a composition that contains a lot of aluminum (Al), the oxidation phenomenon of Al becomes more pronounced in dry etching with methane gas, and the etching selectivity with InP can be increased, which is expected to improve the function as an etching stop layer.

[0180] Furthermore, since the refractive index decreases in a layer containing a large amount of Al, the first etching stop layer 18b on the side close to the active layer 12 has a large refractive index, and the second etching stop layer 18c on the side away from the active layer 12 has a small refractive index. Since the two layers form a core layer and cladding layer relationship in the optical waveguide, it is possible to minimize deformation of the propagating light mode, and it is possible to avoid the problem of optical loss occurring during optical coupling between optical elements.

[0181] <Advantages of the Sixth Embodiment> As described above, according to the optical integrated device and the manufacturing method of the optical integrated device of the sixth embodiment, the etching stop layer has a laminated structure. This makes it possible to precisely control the relative positional deviation in the height direction between the optical function element and the optical circuit element. This not only provides an optical integrated device with high optical coupling efficiency, but also provides the advantage of making it easy to manufacture such an optical integrated device.

[0182] Embodiment 7 The seventh embodiment is a modification of the first to sixth embodiments. FIG. 51 is a cross-sectional view of an optical integrated device 360 ​​according to the seventh embodiment. The optical integrated device 360 ​​according to the seventh embodiment includes an optical functional element 160 and an optical circuit element 260. In the optical integrated device 360 ​​according to the seventh embodiment, the tip of the core layer 23 of the optical waveguide portion 24 formed in the optical circuit element 260 has a tapered shape that is continuously narrowed in the x direction toward the front facing the optical functional element 160, and further has a rectangular xy cross-sectional shape in which the upper cladding layer 25 and the lower cladding layer 22 are integrated from the tip portion of the optical waveguide portion 24 and the layer thickness in the x direction is the sum of the layer thicknesses of the upper cladding layer 25 and the lower cladding layer 22. Also, the second optical waveguide portion 29 is formed with the cladding layer material as the core and air as the cladding material.

[0183] In the optical integrated device 360 ​​according to the seventh embodiment, the second optical waveguide portion 29 having a smaller refractive index is formed at the tip portion of the optical waveguide portion 24 of the optical circuit element 260, thereby expanding the mode diameter of optical propagation and functioning as a so-called spot size converter (SSC). By applying the spot size converter structure, it is possible to relax the optical coupling efficiency tolerance for the mounting position deviation between the optical functional element 160 and the optical circuit element 260.

[0184] In the above explanation, a structure in which the SSC is provided on the optical circuit element 260 has been given as an example, but the SSC may be provided not only on the optical circuit element 260 side but also on the optical function element 160 side. The structure of the SSC does not need to be limited to the example of the seventh embodiment, and for example, SiN or SiON material may be used in addition to SiO2. Also, it is possible to simply provide a tapered shape at the tip of the core layer 23 of the optical waveguide portion 24 without forming the second optical waveguide portion 29.

[0185] <Advantages of the Seventh Embodiment> As described above, according to the optical integrated device of the seventh embodiment, the SSC is provided on the optical function element side or the optical circuit element side, so that it is possible to relax the optical coupling efficiency tolerance against misalignment of the mounting position, thereby achieving an optical integrated device with high optical coupling efficiency.

[0186] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations.

[0187] Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment. [Explanation of symbols]

[0188] REFERENCE SIGNS LIST 11 compound semiconductor substrate, 12 active layer, 13 contact layer, 13a first contact layer, 13b second contact layer, 14, 14a, 14b, 14c terrace portion, 15 mesa groove, 16, 16a, 16b, 16c high mesa portion, 17 first electrode, 18, 18a etching stop layer, 18b first etching stop layer, 18c second etching stop layer, 21 semiconductor substrate, 22 lower cladding layer, 23 core layer, 24 optical waveguide portion, 25 upper cladding layer, 26 convex portion, 26a, 26b, 26c top portion, 27a, 27c first recess, 27b second recess, 28 second electrode, 29 second optical waveguide portion, 30 bonding member, 40 laminated structure substrate, 51, 54 mask, 52, 55 Dry etching, 53 Mixture, 80 Direction of light propagation, 81 Spread of optical modes, 100, 101, 110, 111, 120, 121, 130, 131, 140, 141, 150, 160 Optical functional elements, 200, 201, 210, 211, 220, 221, 230, 231, 240, 241, 250, 260 Optical circuit elements, 300, 301, 310, 311, 320, 321, 330, 331, 340, 341, 350, 360 Optical integrated devices

Claims

1. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the compound semiconductor substrate and the active layer, a height of a top of the convex portion is set at a surface of the core layer on the side of the upper cladding layer, and the surface of the terrace portion and the top of the convex portion are in contact with each other; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

2. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the active layer and the contact layer, a height of a top of the convex portion is set at a surface of the core layer on the side of the lower cladding layer, and the surface of the terrace portion and the top of the convex portion are in contact with each other; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

3. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having, from the compound semiconductor substrate side, at least an active layer and a contact layer, and an etching stop layer provided between the active layer and the contact layer, and having a convex shape; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the etching stop layer and the contact layer, a height of a top of the convex portion is set at a surface of the lower cladding layer on the side of the core layer, and the surface of the terrace portion and the top of the convex portion are in contact with each other; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

4. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer, a first contact layer, an etching stop layer, and a second contact layer from the compound semiconductor substrate side, the high mesa portion being convex; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the etching stop layer and the second contact layer, a height of a top of the convex portion is set at an interface between the semiconductor substrate and the lower cladding layer, the etching stop layer and the lower cladding layer have the same layer thickness, the surface of the terrace portion and the top of the convex portion are in contact with each other, an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

5. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having, from the compound semiconductor substrate side, at least an active layer, a contact layer, and an etching stop layer provided between the active layer and the contact layer, and having a convex shape; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set at an interface between the etching stop layer and the contact layer, a height of a top of the convex portion is set at an interface between the semiconductor substrate and the lower cladding layer, a thickness of the etching stop layer is set to be the same as a thickness of the lower cladding layer, the surface of the terrace portion and the top of the convex portion are in contact with each other, an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

6. An optical integrated device in which optical functional elements and optical circuit elements are integrated, The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having, from the compound semiconductor substrate side, at least an active layer, a first contact layer, a first etching stop layer, a second etching stop layer, and a second contact layer, the high mesa portion being convex; a terrace portion provided along the high mesa portion and having a planar shape, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along a side surface of the first recess and spaced apart from the side surface; a protrusion formed between the first recess and the second recess; an optical waveguide portion provided in contact with a side surface of the first recess portion different from the side surface and a side surface opposed to the side surface, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; a height of a surface of the terrace portion is set to an interface between the second etching stop layer and the second contact layer, a height of a top of the convex portion is set to an interface between the semiconductor substrate and the lower cladding layer, and the surface of the terrace portion and the top of the convex portion are in contact with each other; the first etching stop layer and the second etching stop layer are made of different compound semiconductor materials, the refractive index of the first etching stop layer is higher than the refractive index of the second etching stop layer, and the etching selectivity of the second etching stop layer is higher than the etching selectivity of the first etching stop layer; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled to each other;

7. 4. The optical integrated device according to claim 3, wherein the etching stop layer has a thickness of 0.1 [mu]m or less.

8. 5. The optical integrated device according to claim 4, wherein the etching stop layer has a thickness of 0.1 [mu]m or less.

9. 7. The optical integrated device according to claim 6, wherein the first etching stop layer is made of AlInAs, the second etching stop layer is made of AlInAs having a higher Al composition ratio than the first etching stop layer, and the second contact layer is made of InP.

10. 10. The optical integrated device according to claim 1, wherein the compound semiconductor substrate is made of InP, the active layer is made of a multiple quantum well structure composed of InGaAsP having a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or AlGaInAs having a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, and the contact layer is made of InP.

11. 10. The optical integrated device according to claim 1, wherein either one of a tip of the high mesa portion on the optical waveguide portion side and a tip of the optical waveguide portion on the high mesa portion side has a spot size converter structure.

12. 10. The optical integrated device according to claim 1, wherein a first electrode formed on a top of the high mesa portion and a second electrode formed on a bottom of the first recess are mechanically and electrically joined via a conductive joining member.

13. 10. The optical integrated device according to claim 1, wherein a distance between the active layer of the high mesa portion and a core layer of the optical waveguide portion is 6 [mu]m or less.

14. A method for manufacturing an optical integrated device in which optical functional elements and optical circuit elements are integrated, comprising the steps of: The optical functional element includes: epitaxially growing an active layer and a contact layer on a compound semiconductor substrate; forming a high mesa portion by etching the compound semiconductor substrate, the high mesa portion having at least the active layer and the contact layer, and having a convex shape; forming a terrace portion exposing an outermost surface of the compound semiconductor substrate by wet etching using a mixture of tartaric acid and hydrogen peroxide as an etchant; The method includes the steps of: The optical circuit element includes: forming a first recess and a second recess spaced apart from the first recess in a semiconductor substrate having a lower cladding layer, a core layer, and an upper cladding layer formed thereon; selectively removing the upper cladding layer at a top of a protrusion formed between the first recess and the second recess to expose the top surface of the core layer; The method includes the steps of: a step of flip-chip mounting the optical functional element and the optical circuit element while bringing the terrace portion of the optical functional element into contact with the top of the protrusion of the optical circuit element; A method for manufacturing an optical integrated device comprising the steps of:

15. A method for manufacturing an optical integrated device in which optical functional elements and optical circuit elements are integrated, comprising the steps of: The optical functional element includes: epitaxially growing an active layer, an etching stop layer having a thickness of 0.1 μm or less, and a contact layer on a compound semiconductor substrate in this order; forming a high mesa portion by etching, the high mesa portion including at least the active layer, the etching stop layer, and the contact layer, the high mesa portion having a convex shape, the high mesa portion including the compound semiconductor substrate as a part thereof; forming a terrace portion by dry etching using methane gas as an etching gas, whereby an outermost layer of the etching stop layer is exposed; The method includes the steps of: The optical circuit element includes: forming a first recess and a second recess spaced apart from the first recess in a semiconductor substrate having a lower cladding layer, a core layer, and an upper cladding layer formed thereon; selectively removing the upper cladding layer and the core layer at a top of a protrusion formed between the first recess and the second recess to expose the top surface of the lower cladding layer; The method includes the steps of: a step of flip-chip mounting the optical functional element and the optical circuit element while bringing the terrace portion of the optical functional element into contact with the top of the protrusion of the optical circuit element; A method for manufacturing an optical integrated device comprising the steps of:

16. An optical integrated device integrating optical functional elements and optical circuit elements, comprising: The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion having a planar shape provided along the high mesa portion and positioned at a predetermined height with respect to the active layer, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along two opposing side surfaces of the first recess at a predetermined distance from the side surfaces; an optical waveguide portion provided in contact with a side surface different from the two side surfaces of the first recess, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; the terrace portion of the optical functional element is in contact with a top portion of a protrusion formed between the first recess and the second recess of the optical circuit element, the top surface of the core layer being exposed; a high mesa portion of the optical functional element is disposed so as to coincide with a center of the first recess of the optical circuit element; a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess at a position opposite to the first electrode are mechanically and electrically joined by a joining member; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less;

17. An optical integrated device integrating optical functional elements and optical circuit elements, comprising: The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion having a planar shape provided along the high mesa portion and positioned at a predetermined height with respect to the active layer, The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along two opposing side surfaces of the first recess at a predetermined distance from the side surfaces; an optical waveguide portion provided in contact with a side surface different from the two side surfaces of the first recess, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; the terrace portion of the optical functional element is in contact with a top portion of a protrusion formed between the first recess and the second recess of the optical circuit element, the top surface of the semiconductor substrate being exposed; a high mesa portion of the optical functional element is disposed so as to coincide with a center of the first recess of the optical circuit element; a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess at a position opposite to the first electrode are mechanically and electrically joined by a joining member; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less;

18. An optical integrated device integrating optical functional elements and optical circuit elements, comprising: The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having at least an active layer and a contact layer from the compound semiconductor substrate side, and having a convex shape; a terrace portion provided along each of the high mesa portions, the terrace portion being flat and positioned at a predetermined height relative to the active layer, the terrace portion having a surface that is the outermost surface of the compound semiconductor substrate or the outermost surface of the active layer; The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along two opposing side surfaces of the first recess at a predetermined distance from the side surfaces; an optical waveguide portion provided in contact with a side surface different from the two side surfaces of the first recess, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; the terrace portion of the optical functional element is in contact with a top of a convex portion formed between the first concave portion and the second concave portion of the optical circuit element; a high mesa portion of the optical functional element is disposed so as to coincide with a center of the first recess of the optical circuit element; a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess at a position opposite to the first electrode are mechanically and electrically joined by a joining member; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less;

19. An optical integrated device integrating optical functional elements and optical circuit elements, comprising: The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having, from the compound semiconductor substrate side, at least an active layer and a contact layer, and an etching stop layer provided between the active layer and the contact layer, and having a convex shape; a terrace portion provided along each of the high mesa portions, the terrace portion being flat and positioned at a predetermined height with respect to the active layer, the terrace portion having a surface that is the outermost surface of the etching stop layer; The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along two opposing side surfaces of the first recess at a predetermined distance from the side surfaces; an optical waveguide portion provided in contact with a side surface different from the two side surfaces of the first recess, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; the terrace portion of the optical functional element is in contact with a top of a convex portion formed between the first concave portion and the second concave portion of the optical circuit element; a high mesa portion of the optical functional element is disposed so as to coincide with a center of the first recess of the optical circuit element; a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess at a position opposite to the first electrode are mechanically and electrically joined by a joining member; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less;

20. An optical integrated device integrating optical functional elements and optical circuit elements, comprising: The optical functional element includes: A compound semiconductor substrate; a high mesa portion including the compound semiconductor substrate as a part thereof, the high mesa portion having, in order from the compound semiconductor substrate side, at least an active layer, a first contact layer, a first etching stop layer made of AlInAs, a second etching stop layer made of AlInAs having an Al composition ratio larger than that of the first etching stop layer, and a second contact layer, the high mesa portion having a convex shape; a terrace portion provided along each of the high mesa portions, the terrace portion being flat and positioned at a predetermined height with respect to the active layer, the terrace portion having a surface that is an outermost surface of the second etching stop layer; The optical circuit element includes: A semiconductor substrate; a lower cladding layer, a core layer and an upper cladding layer formed on the semiconductor substrate; a first recess provided in the semiconductor substrate; a second recess provided along two opposing side surfaces of the first recess at a predetermined distance from the side surfaces; an optical waveguide portion provided in contact with a side surface different from the two side surfaces of the first recess, the optical waveguide portion including the lower cladding layer, the core layer, and the upper cladding layer; the terrace portion of the optical functional element is in contact with a top of a convex portion formed between the first concave portion and the second concave portion of the optical circuit element; a high mesa portion of the optical functional element is disposed so as to coincide with a center of the first recess of the optical circuit element; a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess at a position opposite to the first electrode are mechanically and electrically joined by a joining member; an optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less;

21. An optical integrated device described in any one of claims 16 to 20, characterized in that either the tip of the high mesa portion on the optical waveguide portion side or the tip of the optical waveguide portion on the high mesa portion side has a spot size converter structure.

22. An optical integrated device as described in any one of claims 16 to 20, characterized in that a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess are mechanically and electrically joined via a conductive joining member.

23. The optical integrated device described in claim 20, characterized in that the first etching stop layer and the second etching stop layer are made of different compound semiconductor materials, the refractive index of the first etching stop layer is higher than the refractive index of the second etching stop layer, and the etching selectivity of the second etching stop layer is greater than the etching selectivity of the first etching stop layer.

24. An optical integrated device as described in any one of claims 16 to 20, characterized in that the compound semiconductor substrate is made of InP, the active layer is made of a multiple quantum well structure composed of InGaAsP with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or AlGaInAs with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, and the contact layer is made of InP.

25. An optical integrated device as described in any one of claims 18 to 20, characterized in that the top of a convex portion formed between the first recess and the second recess of the optical circuit element exposes the outermost surface of the core layer.

26. An optical integrated device as described in any one of claims 18 to 20, characterized in that the top of a convex portion formed between the first recess and the second recess of the optical circuit element exposes the outermost surface of the lower cladding layer.

27. ​​An optical integrated device as described in any one of claims 18 to 20, characterized in that the top of a convex portion formed between the first recess and the second recess of the optical circuit element exposes the outermost surface of the semiconductor substrate.

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