Condensing structure for optical element, method for manufacturing same, and optical element

Abstract

A condensing structure (12) for an optical element in the present invention is formed on a surface of a semiconductor substrate (11) of an optical element (10), and includes: a spherical lens (121) that is convex in a direction perpendicular to the surface of the semiconductor substrate; and a seating portion (122) disposed at the periphery of the lens. The spacing between the lens (121) and the seating portion (122) is 50% or more of the height of the seating portion (122). In addition, the seating portion may be higher than the lens.　As a result, the present invention provides a condensing structure for an optical element, said structure having a lens that has excellent condensing efficiency.

Description

Light condensing structure for optical element, method for manufacturing the same, and optical element

[0001] The present invention relates to a light condensing structure for an optical element having an optical device, a method for manufacturing the same, and an optical element, which condense input light onto the optical device.

[0002] In a communication photodiode (PD), a small element is used to reduce the element capacitance and improve the operation band. However, in a surface-type photodiode, the light receiving area decreases due to miniaturization, and the coupling efficiency with incident light decreases. Therefore, in order to improve the optical coupling efficiency to a small PD, a lens is formed monolithically on a semiconductor substrate on which the PD is formed, and incident light is condensed onto the PD. Thereby, the condensing efficiency to the PD can be improved.

[0003] As shown in FIG. 8, this lens 421 is formed by forming a columnar structure (circular mesa structure) 4210 in a circular pattern by first etching and sphericalizing it by wet etching in the second etching (for example, Patent Document 1).

[0004] Japanese Patent Laid-Open No. 07-030082

[0005] In the lens formed on the above-described optical element, in order to form a lens having a large lens diameter, it is necessary to expand the columnar structure (circular mesa structure). However, when the lens is formed by wet etching in accordance with the positions of adjacent PDs within the wafer surface, the etching applied to the adjacent columnar structures to form adjacent lenses interferes with each other.

[0006] As a result, etching does not proceed normally in the formation of each lens, and as shown in FIG. 9, the shape of the lens 521 is deformed. For example, the lens 521 has an asymmetric spherical shape or a distorted shape. Or, the shape of the lens becomes non-uniform within the wafer surface.

[0007] As a result, the condensing efficiency of the lens to the PD decreases, and the problem has been that the performance of the light receiving element deteriorates.

[0008] As described above, because lenses cannot be formed at high density to prevent etching interference between lenses, the pitch of photodiodes (PDs) is limited, and the number of PDs that can be formed on the wafer decreases, which is a problem.

[0009] To solve the problems described above, the light-gathering structure for an optical element according to the present invention is a light-gathering structure for an optical element formed on the surface of a semiconductor substrate of an optical element, comprising a spherical lens that is convex in a direction perpendicular to the surface of the semiconductor substrate, and a base portion arranged around the lens, wherein the distance between the lens and the base portion is 50% or more of the height of the base portion.

[0010] Furthermore, the present invention relates to a method for manufacturing a light-gathering structure for an optical element, wherein the optical element has an optical device on one side of a semiconductor substrate, and the other side of the semiconductor substrate has a lens and a base portion disposed around the lens, comprising the steps of etching the other side to form a columnar structure and a base portion disposed around the columnar structure, and performing wet etching on the other side on which the columnar structure and the base portion are formed to process the columnar structure into a lens, wherein the distance between the columnar structure and the base portion is 50% or more of the height of the base portion.

[0011] Furthermore, the present invention relates to a method for manufacturing a light-gathering structure for an optical element, wherein the optical element has an optical device on one side of a semiconductor substrate, and the other side of the semiconductor substrate has a lens and a base portion disposed around the lens, comprising the steps of etching the other side to form a columnar structure and a base portion disposed around the columnar structure, and performing wet etching on the other side on which the columnar structure and the base portion are formed to process the columnar structure into a lens, wherein in the wet etching, the etching rate is low on the facet surface of inverse mesa etching on one crystal orientation plane of the semiconductor substrate, and the etching rate is low on the facet surface of forward mesa etching on the other crystal orientation plane perpendicular to the one crystal orientation plane, and the columnar structure has a shape in which, when viewed from above, the length in the direction parallel to the one crystal orientation plane is greater than the length in the direction parallel to the other crystal orientation plane.

[0012] According to the present invention, a light-gathering structure for an optical element having a lens with excellent light-gathering efficiency, a method for manufacturing the same, and an optical element can be provided.

[0013] Figure 1A is a schematic top view showing the configuration of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 1B is a schematic cross-sectional view IB-IB' showing the configuration of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 2A is a schematic top view showing an example of the configuration of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 2B is a schematic cross-sectional view IIB-IIB' showing an example of the configuration of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 3 is a flowchart for explaining the manufacturing method of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 4A is a diagram for explaining the operation and effect of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 4B is a diagram for explaining the operation and effect of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 5A is a schematic cross-sectional view showing an example of the configuration of a light-gathering structure according to the second embodiment of the present invention. Figure 5B is a schematic cross-sectional view showing an example of the configuration of a light-gathering structure according to the second embodiment of the present invention. Figure 6A is a diagram for explaining the manufacturing method of a light-gathering structure according to the third embodiment of the present invention. Figure 6B is a diagram illustrating a method for manufacturing a light-gathering structure according to a third embodiment of the present invention. Figure 7 is a diagram illustrating a method for manufacturing a light-gathering structure according to a third embodiment of the present invention. Figure 8 is a diagram illustrating a conventional method for manufacturing a light-gathering structure. Figure 9 is a diagram illustrating a conventional method for manufacturing a light-gathering structure.

[0014] <First Embodiment> The light-gathering structure and optical element according to the first embodiment of the present invention will be described with reference to Figures 1A to 4B.

[0015] <Light-gathering structure for optical element and configuration of optical element> The optical element 10 according to this embodiment is a light-receiving element, and as shown in Figures 1A and 1B, a photodiode (PD) 13 is provided on one side (front side) of the semiconductor substrate 11, and a light-gathering structure 12 is provided on the other side (back side). The light-gathering structure 12 comprises a lens 121 and a base portion 122.

[0016] In the light-receiving element 10, light incident from the back side is focused by the lens 121 and absorbed by the active layer (light-absorbing layer) 132 of the PD 13, generating a photocurrent.

[0017] PD13, as an example, comprises an n-type cladding layer 131, an active layer (light-absorbing layer) 132, a p-type cladding layer 133, and electrodes 134 and 135. PD13 corresponds to the long-wavelength band and is an InP-based semiconductor photodiode. The substrate 11 and cladding layers 131 and 133 are InP. The active layer 132 is, for example, an InGaAs / InGaAs(P) multiple quantum well (MQW).

[0018] PD13 is circular or elliptical when viewed from above, with a diameter of, for example, 10–20 μm.

[0019] The lens 121 is formed by processing the semiconductor substrate 11 (described later). The lens 121 is spherical and convex in a direction perpendicular to the surface of the semiconductor substrate 11. The lens 121 is positioned in accordance with the position of the PD 13 on the surface side, and it is desirable that the center of the PD 13 and the center of the lens 121 are aligned on the same straight line perpendicular to the substrate.

[0020] The diameter of the lens 121 is 100 μm, but may be, for example, 50 to 150 μm. The height of the lens 121 is, for example, 5 to 20 μm. In the photodetector 10, in order to focus the light onto the light absorption layer 132 of the PD 13 via the substrate 11 which has a thickness of 100 μm or more, it is desirable that the height of the lens 121 be 5 μm or more.

[0021] The base portion 122 is positioned around the lens 121. The height of the base portion 122 is, for example, 5 to 20 μm. The width of the base portion 122 is at least 20 μm. The edges of the base portion 122 are rounded by wet etching (described later) or have inclined surfaces.

[0022] The distance between the lens 121 and the base portion 122 is about 10 μm, but may be, for example, 2 to 100 μm. In other words, the width of the groove portion 123 formed between the lens 121 and the base portion 122 is about 10 μm, but may be, for example, 2 to 100 μm.

[0023] The shape of the base portion 122 can be a circle, ellipse, square, or other polygon when viewed from above. The base portion 122 should be positioned to surround the lens 121.

[0024] As shown in Figures 2A and 2B, the light-receiving element 10 may be configured in which multiple PDs 13 are integrated on the same substrate 11. In this configuration, multiple lenses 121 and multiple base portions 122 are arranged according to the position of each of the multiple PDs 13.

[0025] <Light-gathering structure for optical element and method for manufacturing optical element> The light-gathering structure and method for manufacturing the optical element according to this embodiment will be described with reference to Figure 3. Figure 3 shows a flowchart illustrating the method for manufacturing the light-receiving element 10.

[0026] After covering the multiple PD13 formed on the surface side of the InP substrate with a protective film, the back surface of the substrate (InP) is processed as follows to create the light-gathering structure 12. The multiple PD13 are arranged at predetermined intervals (approximately 100 to 300 μm).

[0027] First, in order to form the cylindrical structure that will serve as the base for the lens 121 and the base portion on the back surface of the InP substrate, resist and SiO ２ The masks are patterned using a lithography process. At this time, the patterning is done so that the cylindrical structure that will become the base of the lens 121 is positioned in accordance with the position of the PD 13 on the surface side (step S1).

[0028] Next, a cylindrical structure and a base are formed by a first etching process using dry etching or wet etching (step S2). The diameter of the cylindrical structure is, for example, about 50 to 150 μm, and the height is, for example, about 5 to 20 μm.

[0029] Next, the mask is removed (step S3).

[0030] Next, the cylindrical structure is processed into a spherical shape by a second etching using wet etching to produce the lens 121 (step S4). For the second etching, hydrochloric acid-based or bromine-based etchants may be used. For example, a mixture of bromine (Br) and methanol may be used. For example, the etching thickness by the second etching is about 10 μm.

[0031] Finally, the photodetectors formed on the InP substrate are separated (cleaved or cut) into individual elements or groups of elements.

[0032] The light-receiving element 10 is manufactured by the above manufacturing method. In the light-receiving element 10, the lens 121 and the base portion 122 are etched in the same way, so their respective heights are approximately the same. Here, "approximately the same" includes being the same and includes a range of manufacturing errors due to etching non-uniformity, etc.

[0033] <Effects and Effects> The effects and effects of the optical element 10 according to this embodiment will be explained with reference to Figures 4A and 4B.

[0034] As shown in Figure 4A, the lens 121 in the light-gathering structure 12 of the optical element 10 is formed by wet etching (second etching) of a columnar structure (for example, a cylindrical structure) 1210. At this time, the base portion 1220 before the second etching is also wet-etched to form the base portion 122.

[0035] Before the second etching, the cylindrical structure 1210 has a diameter D1, and the base portion 1220 has a height h. The base portion 1220 is positioned at a distance w from the cylindrical structure 1210. In other words, the groove portion 1230 formed between the cylindrical structure 1210 and the base portion 1220 has a width w. After the second etching, the lens 121 has a diameter D2.

[0036] Figure 4B shows the relationship between the cross-sectional structure ratio (w / h) in the shape before the second etching and the ratio of the lens diameter D2 to the diameter D1 of the cylindrical structure 1210 (D2 / D1). A higher value of D2 / D1 indicates that the processed lens has a symmetrical spherical shape. In the figure, the solid line shows the experimental results, and the dotted line shows the approximate curve swept based on the experimental results.

[0037] When the cross-sectional structure ratio (w / h) is 50% or more, the lens after the second etching has a symmetrical spherical shape, and D2 / D1 increases with increasing cross-sectional structure ratio. This is because, when the cross-sectional structure ratio is 50% or more, the wet etching (second etching) uniformly immerses the columnar structure, and the wet etching of adjacent cylindrical structures proceeds normally without interfering with each other.

[0038] On the other hand, when the cross-sectional structure ratio is less than 50%, the lens after the second etching does not have a symmetrical spherical shape, and the ratio of the lens diameter to the diameter of the columnar structure cannot be measured. This is due to the fact that the etching solution is not uniformly introduced into the groove between the columnar structure and the pedestal, and a symmetrical spherical lens is not formed. For example, when the volume of the groove is small and the etching solution interferes with the etching of the adjacent cylindrical shape beyond the pedestal, a symmetrical spherical lens is not formed.

[0039] From the above, by setting the cross-sectional structure ratio to 50% or more, a symmetrical spherical lens can be formed.

[0040] Further, in the light receiving element 10, the distance (width) between the lens 121 formed by the second etching and the pedestal 122 is 50% or more of the height of the pedestal 122.

[0041] According to the present embodiment, a lens having a large diameter and a symmetrical spherical shape can be formed for the optical element. Also, in the optical element, a large number of symmetrical spherical lenses can be manufactured collectively, and the uniformity of the shape of each lens can be improved.

[0042] Thereby, in the optical element, the light condensing efficiency on the optical device by the lens can be improved, and the performance of the optical element can be improved.

[0043] <Second Embodiment> The light condensing structure and the optical element according to the second embodiment of the present invention will be described with reference to FIGS. 5A and 5B.

[0044] <Configuration of the Light Condensing Structure and the Optical Element for the Optical Element> The optical element 20 according to the present embodiment is a light receiving element, and includes a photodiode (PD) on one surface (front surface) side of the semiconductor substrate, and a light condensing structure on the other surface (back surface) side. The light condensing structure includes a lens and a pedestal. In the light condensing structure, the height of the pedestal is higher than the height of the lens.

[0045] <Optical Element Condensing Structure and Method for Manufacturing Optical Element> In the method for manufacturing an optical element according to this embodiment, the height of the pedestal portion 2220 before the second etching (wet etching) is higher than the height of the columnar structure 2210. For example, it is desirable that the height of the columnar structure 2210 is 5 to 20 μm, and the height of the pedestal portion 2220 is about 0.5 to 5 μm higher than the height of the columnar structure. Other configurations and steps are the same as those in the first embodiment.

[0046] As a configuration example of the pedestal portion 2220 before the second etching (wet etching), as shown in FIG. 5A, a protective film (for example, SiO ２ ) 2221 may be provided on the surface of the semiconductor (for example, InP) of the pedestal portion 2220. The thickness of the protective film 2221 is, for example, about 500 nm. The protective film 2221 may be a dielectric such as SiN or a metal in addition to SiO ２ .

[0047] In this configuration, in the manufacturing process in the first embodiment, the mask of the pedestal portion used in the first etching may be left as it is without being removed and used as the protective film 2221.

[0048] Alternatively, as a configuration example of the pedestal portion 2220, as shown in FIG. 5B, the height of the pedestal portion 2220 made of a semiconductor (for example, InP) may be made higher than the height of the columnar structure 2210 made of a semiconductor (for example, InP).

[0049] In this configuration, in the manufacturing process in the first embodiment, after etching the peripheral region including the lens region without removing the mask of the pedestal portion after the first etching, the mask of the pedestal portion may be removed to produce it.

[0050] In the condensing structure manufactured by the above manufacturing method, the height of the pedestal portion is higher than the height of the lens. For example, the lens height is 5 to 20 μm, and the height of the pedestal portion is about 0.5 to 5 μm higher than the height of the lens. Other configurations are the same as those in the first embodiment. Also, when manufacturing the condensing structure using the protective film 2221, the condensing structure may include the protective film 2221.

[0051] <Effect> In the formation of the lens described above, a lower columnar structure allows for easier processing from the columnar shape to a spherical shape using wet etching (second etching).

[0052] However, in the lens formation in the first embodiment, when a low columnar structure is formed in the first etching, the base portion is also formed low at the same time. As a result, during the second etching, the etching solution penetrates beyond the base portion into the adjacent lens region, affecting the etching of the adjacent lens. This prevents the formation of a symmetrical spherical lens, resulting in an uneven lens shape across the wafer surface.

[0053] On the other hand, in this embodiment, the raised base portion suppresses the penetration of etching solution into adjacent lens regions, thereby suppressing etching interference between adjacent lenses. As a result, a symmetrical spherical lens is formed, and the lens shape becomes uniform across the wafer surface.

[0054] Furthermore, in a configuration where metal is used for the protective film of the base, the metal of the protective film and the metal part of the element can be heat-fused together when mounting the element to the base.

[0055] According to this embodiment, a lens with a larger diameter than the optical element can be formed in a symmetrical spherical shape. Furthermore, a large number of symmetrical spherical lenses can be manufactured simultaneously in the optical element, further improving the uniformity of the shape of each lens.

[0056] This allows for further improvement in the light-gathering efficiency of the lens on the optical device, thereby further enhancing the performance of the optical element.

[0057] <Third Embodiment> A light-gathering structure for an optical element and an optical element according to a third embodiment of the present invention will be described with reference to Figures 6A to 7.

[0058] <Light-gathering structure for optical element and method for manufacturing optical element> In the method for manufacturing the optical element 30 according to this embodiment, the columnar structure before the second etching has an elliptical columnar structure. The other configurations and steps are the same as in the first embodiment.

[0059] In the first embodiment, depending on the wet etching conditions used in the second etching, the curved shape of the lens may depend on the crystal orientation due to etching anisotropy. In this case, since the lens shape is not a symmetrical spherical shape, the efficiency of focusing the light incident on the lens onto the photodiode decreases, thus reducing the performance of the photodetector.

[0060] In this embodiment, considering the anisotropy of the second etching, a cylindrical structure is formed in the first etching. This makes it possible to fabricate a lens with a symmetrical spherical shape whose curved surface shape does not depend on the crystal orientation. Details are described below.

[0061] When wet etching exhibits etching anisotropy, for example, when wet etching is performed on a semiconductor having a mask 3 on its surface, an inverse mesa structure 1 as shown in Figure 6A is formed on one of the crystal orientation planes (the plane parallel to the x-direction in the figure). In this etching (hereinafter referred to as "inverse mesa etching"), the etching rate is low on the crystal planes (facet planes) 4 on the side of the inverse mesa.

[0062] Furthermore, a forward mesa structure 2, as shown in Figure 6B, is formed on the other crystal orientation plane (the plane parallel to the y-direction in the figure). In this etching process (hereinafter referred to as "forward mesa etching"), etching is low on the crystal planes (facet planes) 5 on the side of the forward mesa.

[0063] Here, the angle between the bottom surface of the substrate and the outer surface of the facet is called the "facet angle" θ. In the inverse mesa structure 1, the facet angle θ is acute, and in the forward mesa structure 2, the facet angle θ is obtuse.

[0064] In this embodiment, when forming a lens using this etching method, since there is no mask on the semiconductor surface, etching proceeds from the surface at a low etching rate on the crystal plane (facet plane) 4 on the reverse mesa side of one crystal orientation plane. As a result, depending on the etching conditions, the shape caused by the facet plane 4 due to reverse mesa etching may remain on the outer circumference of the lens. In addition, in reverse mesa etching, etching proceeds near the bottom surface of the mesa structure, so the diameter in the x-direction of the lens after etching decreases.

[0065] On the other crystal orientation plane, etching proceeds from the surface at a low etching rate on the crystal planes (facet planes) 5 on the forward mesa side. As a result, depending on the etching conditions, shapes caused by the facet planes 5 due to forward mesa etching may remain on the outer circumference of the lens. Also, in forward mesa etching, there is little etching near the bottom surface of the mesa structure, so the diameter in the y direction of the lens after etching is longer than the diameter in the x direction.

[0066] Thus, when a lens is formed using the wet etching method described above, the length of the columnar structure in the direction parallel to one crystal orientation plane (x-direction) is reduced compared to the length in the direction parallel to the other crystal orientation plane (y-direction). As a result, when this wet etching is applied to a cylindrical structure, lenses are formed with different diameters, curved shapes, and radii of curvature depending on the crystal orientation.

[0067] In this embodiment, the structure formed by the first etching is set considering etching anisotropy. For example, the structure formed by the first etching is a columnar structure 3210 having an elliptical shape in a top view, where the diameter in the direction parallel to one crystal orientation plane (x direction) is longer than the diameter in the direction parallel to the other crystal orientation plane (y direction), as shown in Figure 7.

[0068] When a second etching (wet etching) is applied to this elliptical columnar structure 3210, the etching proceeds from the surface of the columnar structure. At this time, the etching rate of the facets of the reverse mesa etching is slow on the x-direction side of the columnar structure, and the etching rate of the facets of the forward mesa etching is slow on the y-direction side. In addition, at the bottom surface of the elliptical columnar structure, the reverse mesa etching in the x-direction proceeds faster than the forward mesa etching in the y-direction.

[0069] As a result, the base of the elliptical cylindrical structure is etched to the same length in both the x and y directions. Furthermore, the cross-sectional shape of the elliptical cylindrical structure is etched to the same shape and radius of curvature in both the x and y directions. This makes it possible to fabricate a symmetrical spherical lens in the light-receiving element 30.

[0070] In the wet etching process described above, the side walls of the base portion 3220 are also etched in a forward mesa / reverse mesa manner. The shape of the base portion may be adjusted by increasing or decreasing the dimensions in the x and y directions to match the shape of the columnar structure.

[0071] The lens and base produced in this embodiment may have a shape on a part of the outer circumference resulting from a faceted surface created by forward mesa etching or reverse mesa etching.

[0072] According to this embodiment, a lens with a larger diameter than the optical element can be formed in a symmetrical spherical shape. Furthermore, a large number of symmetrical spherical lenses can be manufactured simultaneously in the optical element, further improving the uniformity of the shape of each lens.

[0073] This allows for further improvement in the light-gathering efficiency of the lens on the optical device, thereby further enhancing the performance of the optical element.

[0074] In the embodiments of the present invention, an example is shown in which the columnar structure formed by the first etching is circular or elliptical in shape when viewed from above, but it may also be polygonal. Furthermore, this columnar structure includes not only cylindrical or elliptical columnar shapes, but also mesa shapes in which the cross-section perpendicular to the substrate is trapezoidal.

[0075] In the embodiments of the present invention, an example using a long-wavelength PD is shown, but PDs corresponding to other wavelength bands may also be used. Furthermore, an example using an InP substrate is shown, but other semiconductor substrates such as GaAs may also be used. Also, an example showing an optical element equipped with a PD is shown, but other optical devices such as LDs and LEDs may also be included, and the optical element is not limited to a photodetector but may also be other optical elements such as light-emitting elements.

[0076] In the embodiments of the present invention, examples of the structure, dimensions, materials, etc. of each component in the light-gathering structure for optical elements and the configuration and manufacturing method of optical elements are shown, but the invention is not limited to these examples. Any structure that performs the function of the light-gathering structure for optical elements and optical elements and produces the desired effect is acceptable.

[0077] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations are possible within the technical concept of the present invention by those with ordinary skill in the art. For example, the third embodiment may be combined with the second embodiment.

[0078] Some or all of the embodiments described above, or examples thereof, may also be described as follows, but are not limited to these.

[0079] (Note 1) A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of the optical element, comprising a spherical lens convex in a direction perpendicular to the surface of the semiconductor substrate, and a base portion arranged around the lens, wherein the distance between the lens and the base portion is 50% or more of the height of the base portion.

[0080] (Note 2) The light-gathering structure for an optical element as described in Note 1, wherein the base portion is higher than the lens.

[0081] (Note 3) An optical element comprising a light-gathering structure for an optical element as described in Note 1 or Note 2, the semiconductor substrate, and a semiconductor device disposed on the side of the semiconductor substrate opposite to the light-gathering structure.

[0082] (Note 4) A method for manufacturing a light-gathering structure for an optical element, in which an optical device is provided on one side of a semiconductor substrate, wherein the other side of the semiconductor substrate is provided with a lens and a base portion disposed around the lens, comprising the steps of: etching the other side to form a columnar structure and a base portion disposed around the columnar structure; and wet etching the other side on which the columnar structure and the base portion are formed to process the columnar structure into a lens, wherein the distance between the columnar structure and the base portion is 50% or more of the height of the base portion.

[0083] (Note 5) A method for manufacturing a light-gathering structure for an optical element, in which an optical device is provided on one side of a semiconductor substrate, wherein the other side of the semiconductor substrate is provided with a lens and a base portion disposed around the lens, comprising the steps of: etching the other side to form a columnar structure and a base portion disposed around the columnar structure; and performing wet etching on the other side on which the columnar structure and the base portion are formed to process the columnar structure into the lens, wherein in the wet etching, the etching rate is low on the facet surface of inverse mesa etching on one crystal orientation plane of the semiconductor substrate, and the etching rate is low on the facet surface of forward mesa etching on the other crystal orientation plane perpendicular to the one crystal orientation plane, and the columnar structure has a shape in which, when viewed from above, the length in the direction parallel to the one crystal orientation plane is greater than the length in the direction parallel to the other crystal orientation plane.

[0084] (Note 6) The light-gathering structure for an optical element as described in Note 2, wherein the base portion is provided with a protective film on the side opposite to the side facing the semiconductor substrate.

[0085] (Note 7) The light-gathering structure for an optical element according to Notes 1 to 3 and 6, wherein the distance between the lens and the base portion is five times or less the height of the base portion.

[0086] (Note 8) The method for manufacturing a light-gathering structure for an optical element according to Notes 4 and 5, wherein the base portion is higher than the lens.

[0087] (Note 9) The method for manufacturing a light-gathering structure for an optical element according to Note 5, wherein the distance between the columnar structure and the base portion is 50% or more of the height of the base portion.

[0088] This invention can be applied to optical communication devices and optical communication systems.

[0089] 12. Light-gathering structure 121. Lens 122. Base

Claims

1. A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of the optical element, comprising: a spherical lens convex in a direction perpendicular to the surface of the semiconductor substrate; and a base portion arranged around the lens, wherein the distance between the lens and the base portion is 50% or more of the height of the base portion.

2. The light-gathering structure for an optical element according to claim 1, wherein the base portion is higher than the lens.

3. An optical element comprising: a light-gathering structure for an optical element according to claim 1 or claim 2; a semiconductor substrate; and a semiconductor device disposed on the semiconductor substrate on the side opposite to the light-gathering structure for an optical element.

4. A method for manufacturing a light-gathering structure for an optical element, in which an optical device is provided on one side of a semiconductor substrate, the optical element comprising a lens and a base portion disposed around the lens on the other side of the semiconductor substrate, comprising the steps of: etching the other side to form a columnar structure and a base portion disposed around the columnar structure; and wet etching the other side on which the columnar structure and the base portion are formed to process the columnar structure into a lens, wherein the distance between the columnar structure and the base portion is 50% or more of the height of the base portion.

5. A method for manufacturing a light-gathering structure for an optical element, wherein the optical device is provided on one side of the semiconductor substrate, and the other side of the semiconductor substrate comprises a lens and a base portion disposed around the lens, comprising the steps of: etching the other side to form a columnar structure and a base portion disposed around the columnar structure; and performing wet etching on the other side on which the columnar structure and the base portion are formed to process the columnar structure into a lens, wherein in the wet etching, the etching rate is low on the facet surface of inverse mesa etching on one crystal orientation plane of the semiconductor substrate, and the etching rate is low on the facet surface of forward mesa etching on the other crystal orientation plane perpendicular to the one crystal orientation plane, and the columnar structure has a shape in which, when viewed from above, the length in the direction parallel to the one crystal orientation plane is greater than the length in the direction parallel to the other crystal orientation plane.

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