Light-condensing structure for optical elements, production method for same, and optical element

Abstract

This light-condensing structure (12) for optical elements is formed on a surface of a semiconductor substrate (11) of an optical element (10), said light-condensing structure comprising: a spherical lens (121) that is convex in a direction perpendicular to the surface of the semiconductor substrate; a base part (122) that is disposed in the periphery of the lens (121); and a recess (124) that is formed in a side wall of the base part in the vicinity of the border between the side wall of the base part and the surface of the semiconductor substrate.　Thus, the present invention can provide a light-condensing structure for optical elements that has a lens with excellent light condensing efficiency.

Description

Light-gathering structure for optical elements, method for manufacturing the same, and optical element

[0001] The present invention relates to a light-gathering structure for an optical element having an optical device, a method for manufacturing the same, and an optical element.

[0002] In photodiodes (PDs) used in optical communications, reducing the element area improves the operating bandwidth. To suppress the decrease in the optical coupling efficiency of the PD and improve optical mounting tolerance, a monolithic lens is fabricated on the back surface of the InP substrate in a configuration where the PD is formed on the surface of the InP substrate.

[0003] In the fabrication of this lens, as shown in Figure 10, first, SiO is placed on an InP substrate. ２ After patterning a mask, the InP is processed into a cylindrical shape 3210 by dry etching or wet etching. Next, the mask is removed and wet etching is performed to process the cylindrical InP into a spherical lens 321 (for example, Patent Document 1).

[0004] In photodiodes, a base portion higher than the height of the lens is formed around the lens to prevent the surface on which the lens is formed from coming into contact with the surrounding area during the mounting process.

[0005] Jaeho Kim, Kyoung Min Kim, Soo-Kun Jeon, Moonjung Kim, Eun-Hyun Park and Young-Se Kwon, "Successively dry-wet etched InP microlens for bell shaped LED," International Conference onIndium Phosphide and Related Materials, 2003., Santa Barbara, CA, USA, 2003, pp. 175-177, doi: 10.1109 / ICIPRM.2003.1205342.

[0006] However, in the PD having the aforementioned lens and base, if multiple PDs are arranged at high density, in other words, if multiple lenses are formed at high density, the shape of each lens becomes non-uniform. As a result, the intensity of light incident on and focused by each PD becomes non-uniform, leading to non-uniform characteristics of the PDs and a decrease in yield.

[0007] For example, when multiple lenses 321 are formed at high density, the spacing between the lenses 321 becomes narrower, and the width of the base portion 322 area placed between the lenses 321 becomes narrower. In this configuration, as shown in Figures 11A and B, the base portion 3220 is side-etched and deformed by etching during lens fabrication (33 in the figure). Alternatively, a part of the base portion may disappear (34 in the figure). As a result, the etching solution penetrates into the area of ​​the adjacent cylindrical structure and interferes with the etching of the adjacent cylindrical structure. In this way, when the structure around the lens changes, the etching rate during lens fabrication changes. As a result, the shape of each lens formed by etching changes, and the shape of each lens becomes non-uniform.

[0008] To solve the problems described above, the light-gathering structure for an optical element according to the present invention is a light-gathering structure 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, a base portion arranged around the lens, and a recess formed in the side wall of the base portion near the edge between the side wall of the base portion and the surface of the semiconductor substrate.

[0009] 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 the 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 and the base portion into the lens and the base portion, respectively, wherein the surface and side walls of the base portion are covered with a protective film.

[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 and the base portion into the lens and the base portion, respectively, wherein the base portion has a groove deeper than the height of the base portion, and the surface of the base portion, the inner wall of the groove and the bottom surface are covered with a protective film.

[0011] 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.

[0012] 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 3A 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 3B is a schematic cross-sectional view IIII-IIII' showing an example of the configuration of a light-gathering structure and optical element according to the first embodiment of the present invention. Figure 4A is a schematic cross-sectional view for explaining the manufacturing method of the light-gathering structure according to the first embodiment of the present invention. Figure 4B is a schematic cross-sectional view for explaining the manufacturing method of the light-gathering structure according to the first embodiment of the present invention. Figure 4C is a schematic cross-sectional view for explaining the manufacturing method of the light-gathering structure according to the first embodiment of the present invention. Figure 4D is a schematic cross-sectional view for explaining the manufacturing method of the light-gathering structure according to the first embodiment of the present invention. Figure 4E is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to the first embodiment of the present invention. Figure 4F is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to the first embodiment of the present invention. Figure 5A is a schematic top view showing the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 5B is a schematic VB-VB' cross-sectional diagram showing the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 6A is a schematic top view showing an example of the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 6B is a schematic VIB-VIB' cross-sectional diagram showing an example of the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 7A is a schematic top view showing an example of the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 7B is a schematic VIII-VIIII' cross-sectional diagram showing an example of the configuration of a light-gathering structure and optical element according to the second embodiment of the present invention. Figure 8A is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to the second embodiment of the present invention. Figure 8B is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to the second embodiment of the present invention.Figure 8C is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to a second embodiment of the present invention. Figure 8D is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to a second embodiment of the present invention. Figure 8E is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to a second embodiment of the present invention. Figure 8F is a schematic cross-sectional diagram illustrating a method for manufacturing a light-gathering structure according to a second embodiment of the present invention. Figure 9A is a diagram illustrating the effect of an optical element according to a second embodiment of the present invention. Figure 9B is a diagram illustrating the effect of an optical element according to a second embodiment of the present invention. Figure 10 is a diagram illustrating a conventional method for manufacturing a light-gathering structure. Figure 11A is a schematic top view illustrating a conventional method for manufacturing a light-gathering structure. Figure 11B is a schematic XIB-XIB' cross-sectional diagram illustrating a conventional method for manufacturing a light-gathering structure.

[0013] <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 4F.

[0014] <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.

[0015] 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) of the PD 13, generating a photocurrent.

[0016] 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).

[0017] PD13 is circular when viewed from above, and its diameter is, for example, 10 to 20 μm.

[0018] 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 11.

[0019] The diameter of lens 121 is, for example, about 100 μm, but may be 50 to 150 μm. The height of lens 121 is, for example, about 10 μm, but may be 5 to 20 μm.

[0020] The base portion 122 is positioned around the lens 121. The height of the base portion 122 is, for example, about 10 μm, but may be 5 to 20 μm. The minimum width of the base portion 122 (for example, the width along the line connecting the centers of adjacent PDs 13) is, for example, 10 to 100 μm.

[0021] The distance between the lens 121 and the base portion 122, that is, the width of the groove portion 123 between the lens 121 and the base portion 122, is, for example, 10 to 100 μm.

[0022] The base portion 122 has a recess 124 on its side wall, near the edge between the side wall of the base portion 122 and the surface of the semiconductor substrate 11, as shown in the inset in Figure 1B. The recess 124 is formed by wet etching during the formation of the lens 121 (described later), and for example, its height (direction perpendicular to the substrate surface) h is about 10 μm, and its depth (direction parallel to the substrate surface) d is about 10 μm.

[0023] The height of the base portion 122 is preferably greater than the height of the lens 121. In order to focus the light onto the light-absorbing layer of the PD 13 via the substrate 11 which has a thickness of 100 μm or more in the light-receiving element 10, the height of the lens 121 must be 5 μm or more. Therefore, it is preferable that the height of the base portion 122 be 5 μm or more.

[0024] 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.

[0025] The protective film 125 used in the manufacturing process of the optical element (described later) may be left on the surface and side walls of the base portion 122. In this case, the base portion 122 is provided with the protective film 125 on its surface and side walls, as shown in Figures 2A and 2B. The protective film 125 is SiO ２ The thickness of the protective film 125 is, for example, about 0.1 to 1 μm. The protective film 125 may also be made of other dielectrics such as SiN or metals.

[0026] As shown in Figures 3A and 3B, 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.

[0027] <Light-gathering structure for optical element and method for manufacturing optical element> The method for manufacturing the light-gathering structure 12 and optical element 10 according to this embodiment will be described with reference to Figures 4A to 4F.

[0028] After covering the multiple PDs (not shown) formed on the surface side of the substrate 11 with a protective film, the back surface of the substrate (InP) 11 is processed as follows to produce the lens 121 and the base portion 122. The multiple PDs are arranged at predetermined intervals (for example, about 100 to 500 μm).

[0029] First, on the back surface of the InP substrate 11, 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 form the base of the lens is positioned according to the position of the PD on the surface.

[0030] Next, a cylindrical structure 1210, which will serve as the base of the lens, and a base portion 1220, which will serve as the base of the pedestal, are formed by a first etching process using dry etching or wet etching. The diameter of the cylindrical structure 1210 is, for example, about 100 μm, but may be 30 to 200 μm. The height between the cylindrical structure 1210 and the base portion 1220 is, for example, about 10 μm, but may be 5 to 20 μm. The distance between the cylindrical structure 1210 and the base portion 1220 is, for example, about 10 to 100 μm.

[0031] Next, the mask is removed. As described above, a columnar structure 1210 and a pedestal base 1220 are formed on the back surface of the substrate (InP) 11 (FIG. 4A).

[0032] Next, SiO ２ 141 is formed (laminated) on the entire back surface of the InP substrate 11 by CVD, sputtering, evaporation, or the like. At this time, a dense SiO ２ film is formed including the side walls of the pedestal base 1220 (FIG. 4B).

[0033] Next, a resist mask 142 is formed on the SiO ２ film in accordance with the position of the pedestal base 1220 (FIG. 4C). Subsequently, the protective film on and around the columnar structure 1210 is removed using dry etching (FIG. 4D). As a result, a protective film 125 is formed on the surface and side walls of the pedestal base 1220.

[0034] Next, the columnar structure 1210 is processed into a spherical shape to produce a lens 121 by a second etching using wet etching (FIG. 4E). For the second etching, a hydrochloric acid-based or bromine-based etchant 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.

[0035] At this time, since the etching of the bottom surface between the lens 121 and the pedestal base 1220 proceeds during the second etching, the lower part of the protective film is exposed on the side walls of the pedestal base 1220. As a result, side etching of the exposed portion of the side wall of the pedestal base 1220 proceeds to form a recess 124 (inserted view in FIG. 4E). The shape (etching depth, etc.) of the recess 124 formed on the side wall by side etching depends on the surface orientation depending on the etching conditions. In this way, the pedestal base 1220 is processed to form a pedestal portion 122.

[0036] Next, the protective film 125 on the surface and side walls of the pedestal portion 122 is removed (FIG. 4F). Here, the protective film 125 on the surface and side walls of the pedestal portion 122 may be left without being removed.

[0037] Finally, the light receiving elements formed on the InP substrate 11 are divided (cleaved or cut, etc.) for each single element or for each plurality of elements.

[0038] According to this embodiment, side etching of the pedestal portion is suppressed during etching for lens fabrication, and the in-plane uniformity of the etching rate is improved. Therefore, a lens with a highly symmetric shape can be formed. Further, in the light receiving element, when a plurality of lenses are fabricated collectively, the uniformity of the shape of each lens can be improved.

[0039] As a result, 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.

[0040] <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 to 9B.

[0041] <Configuration of Optical Element> The optical element 20 according to this embodiment is a light receiving element, and as shown in FIGS. 5A and B, a photodiode (PD) 13 is provided on one surface (front surface) side of the semiconductor substrate 11, and a light condensing structure 22 is provided on the other surface (back surface) side. The light condensing structure 22 includes a lens 221 and a pedestal portion 222.

[0042] The configurations of the PD 13 and the lens 221 are the same as those in the first embodiment.

[0043] A groove 224 is provided around the side wall of the pedestal portion 222 on the surface of the semiconductor substrate 11. For example, the groove 224 is an annular shape concentric with the center of the lens 221 in a top view. The width of the groove 224 is 2 to 10 μm, and the depth is about 10 μm to 100 μm.

[0044] On the surface of the pedestal portion 222, and on the bottom surface and the inner surface of the groove 224, as shown in FIGS. 6A and B, the protective film 225 used in the manufacturing process of the optical element (described later) may be left. In this case, the protective film 225 is provided on the surface of the pedestal portion 222, and on the bottom surface and the inner surface of the groove 224. The protective film 225 is SiO ２ and the thickness of the protective film 225 is, for example, about 0.1 to 1 μm. The protective film 225 may be other dielectrics such as SiN or metal.

[0045] In the light-gathering structure 22, as shown in Figures 7A and 7B, an outer wall portion 226 made of semiconductor (InP) may be provided on the outer circumference of the groove 224. The width of the outer wall portion 226 is, for example, about 5 μm. This configuration is formed when InP is not completely removed and remains during the side etching of InP from the outer circumference of the base portion 222 in the optical element manufacturing process (described later). In other words, in this configuration, the groove 224 is provided perpendicular to the surface of the base portion 222. The groove 224 is an annular shape concentric with the center of the lens 221 when viewed from above. The width of the groove 224 is, for example, 2 to 10 μm. The depth of the groove 224 is, for example, 20 μm to several hundred μm.

[0046] In this configuration, the protective film 225 used in the manufacturing process of the optical element (described later) may be left in place, and the protective film 225 may be provided on the surface of the base portion 222 and on the bottom and inner surfaces of the groove 224. The shape of the protective film 225 is the same as the shape of the protective film 225 shown in Figures 6A and 6B.

[0047] In the base portion 222, the configuration other than that described above is the same as in the first embodiment.

[0048] <Manufacturing Method for Light-Concentrating Structure and Optical Element> The manufacturing method for the light-concentrating structure 22 and the optical element 20 according to this embodiment will be described with reference to Figures 8A to 8F.

[0049] After covering the multiple PDs (not shown) formed on the surface side of the substrate 11 with a protective film, the back surface of the substrate (InP) 11 is processed as follows to produce the lens 221 and the base portion 222. The multiple PDs are arranged at predetermined intervals (for example, about 100 to 500 μm).

[0050] First, to form grooves in the base portion on the back surface of the InP substrate 11, resist and SiO ２ Masks such as these are patterned using a lithography process.

[0051] Next, grooves are formed in the base portion by dry etching with high verticality. The width of the grooves is, for example, 2 to 10 μm. The depth of the grooves is, for example, 20 μm to several hundred μm. Subsequently, the mask is removed to form grooves 224 in the base portion (Figure 8A).

[0052] Next, SiO is formed (stacked) on the entire back surface of the substrate 11 including the inner surface and the bottom surface of the groove 224 by CVD, sputtering, evaporation, etc. ２ Next, by lithography and etching, SiO is left in the peripheral region 2220 of the columnar structure 2210 serving as the base of the lens, the pedestal portion 222, and the groove 224, and SiO masks 24 and 225 are formed (Fig. 8B). ２ ２

[0053] Next, by the first etching, a columnar structure 2210 serving as the base of the lens and a pedestal portion 222 are formed (Fig. 8C). At this time, it is desirable that the groove portion 2230 to be etched is shallower than the groove 224 of the pedestal portion. In other words, it is desirable that the bottom surface of the groove 224 is disposed at a position deeper than the bottom surface of the columnar structure 2210. The groove 224 is formed, for example, at a position about 10 μm from its outer periphery in the peripheral region 2220 of the pedestal portion having a width of 40 μm.

[0054] Subsequently, the SiO mask 24 of the columnar structure 2210 is removed, and the SiO mask in the peripheral region 2220 of the pedestal portion 222 and the groove 224 is left as a protective film 225 (Fig. 8D). ２ ２

[0055] Next, the lens 221 is fabricated by the second etching (wet etching) (Fig. 8E).

[0056] Here, when forming the lens 221, the InP outside the groove 224 of the pedestal portion 222 may be completely removed by the second etching (wet etching). That is, the surface outside the protective film 225 on the inner wall of the groove 224 may be exposed. Or, the InP outside the groove 224 of the pedestal portion 222 may remain without being completely removed.

[0057] Next, the surface of the pedestal portion 222 and the protective film 225 of the groove 224 are removed (Fig. 8F). Here, the surface of the pedestal portion 222 and the protective film 225 of the groove 224 may be left without being removed.

[0058] Finally, the light receiving elements formed on the InP substrate 11 are divided (cleaved or cut, etc.) for each single element or each plurality of elements.

[0059] In this embodiment, an example was shown in which the lens and base are formed after the groove of the base is formed. However, as described below, the groove of the base may be formed after the lens and base are formed.

[0060] First, similar to the first embodiment, a cylindrical structure and a base are formed on the back surface of the substrate (InP) (Figure 4A). Next, SiO is applied to the entire back surface of the InP substrate. ２ The film is then formed (layered) (Figure 4B).

[0061] Next, a resist pattern for the grooves to be formed on the base is created. Then, the grooves on the base are formed by dry etching. Subsequently, the grooves on the base are formed by removing the mask.

[0062] Next, SiO is applied to the entire back surface. ２ Forms a film, SiO ２ A resist pattern is formed on the surface of the film, including the grooves of the base portion, and after dry etching, the resist pattern is removed. This leaves SiO on the surface of the base portion and the inner surface of the grooves. ２ A protective film is formed (Figure 8D). SiO ２ The protective film may be formed by a lift-off process.

[0063] Hereinafter, similar to the second embodiment, wet etching may be performed to fabricate the lens, and each element may be separated (cleaved or cut, etc.) to manufacture the light-gathering structure 22 and the optical element 20.

[0064] <Effects> The effects of the light-gathering structure 22 and the optical element 20 according to this embodiment will be explained with reference to Figures 9A and 9B.

[0065] In the first embodiment, as shown in Figure 9A, during the second etching, etching of the bottom surface of the groove 1230 between the cylindrical structure 1210 and the base 1220 progresses, exposing the lower part of the protective film 125 on the side wall of the base 122. As a result, side etching progresses on the exposed portion of the side wall of the base 122, forming a recess 124 below the protective film 125 (black arrow in the figure). If the base collapses or is damaged due to this side etching, the etching solution penetrates into the area of ​​the adjacent cylindrical structure 2210, interfering with the etching of the adjacent cylindrical structure 2210. As a result, the etching rate cannot be completely uniform in the plane, and the symmetry of the lens shape decreases. Furthermore, in a photodetector, when multiple lenses are manufactured at once, the uniformity of the shape of each lens decreases.

[0066] According to this embodiment, as shown in Figure 9B, the protective film 225 of the groove 224 of the base portion can stop side etching (white arrow in the figure), so that no recess is formed below the protective film 225. As a result, the base portion 222 can be maintained stably. Therefore, the in-plane uniformity of the etching rate can be further improved, and lenses with a more symmetrical shape can be formed. In addition, when manufacturing multiple lenses at once in a photodetector, the uniformity of the shape of each lens can be further improved.

[0067] This improves the light-gathering efficiency of the lens on the optical device in the optical element, thereby improving the performance of the optical element.

[0068] In this embodiment, a protective film is formed on the side walls and bottom surface of the groove, but not on the side walls of the base. However, a protective film may be formed on the side walls of the base. This further reduces the effects of side etching. Therefore, the in-plane uniformity of the etching rate can be further improved, and lenses with a more symmetrical shape can be formed. In addition, when manufacturing multiple lenses at once in a photodetector, the uniformity of the shape of each lens can be further improved.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 can be implemented within the technical concept of the present invention by those with ordinary skill in the art.

[0073] Some or all of the embodiments described above, or examples thereof, may also be described as follows, but are not limited to these.

[0074] (Note 1) A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of an optical element, comprising: a spherical lens convex in a direction perpendicular to the surface of the semiconductor substrate; a base portion arranged around the lens; and a recess formed in the side wall of the base portion near the edge between the side wall of the base portion and the surface of the semiconductor substrate.

[0075] (Note 2) A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of an optical element, comprising a spherical lens convex outward from the optical element, a base portion disposed around the lens, and a groove formed on the surface of the semiconductor substrate around the side wall of the base portion.

[0076] (Note 3) The light-gathering structure for an optical element as described in Note 2, wherein the outer circumference of the groove is provided with an outer wall made of the semiconductor.

[0077] (Note 4) 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.

[0078] (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 wet etching the other side on which the columnar structure and the base portion are formed to process the columnar structure and the base portion, respectively, into the lens and the base portion, wherein the surface and side walls of the base portion are covered with a protective film.

[0079] (Note 6) 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 and the base portion, respectively, into the lens and the base portion, wherein the base portion has a groove deeper than the height of the base portion, and the surface of the base portion, the inner wall of the groove and the bottom surface are covered with a protective film.

[0080] (Note 7) The light-gathering structure described in Note 1, wherein the surface and side walls of the base portion are covered with a protective film.

[0081] (Note 8) The light-gathering structure according to Note 2, wherein the surface of the base portion, the side wall of the base portion, the inner wall of the groove, and the bottom surface of the groove are covered with a protective film.

[0082] (Note 9) The light-gathering structure according to Note 3, wherein the surface of the base portion, the side wall of the base portion, the inner wall of the groove, the bottom surface of the groove, the inner wall of the outer wall portion, and the surface of the outer wall portion are covered with a protective film.

[0083] This invention can be applied to optical communication devices and optical communication systems.

[0084] 12 Light-gathering structure 121 Lens 122 Base 124 Recess

Claims

1. A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of an optical element, comprising: a spherical lens convex in a direction perpendicular to the surface of the semiconductor substrate; a base portion disposed around the lens; and a recess formed in the side wall of the base portion near the edge between the side wall of the base portion and the surface of the semiconductor substrate.

2. A light-gathering structure for an optical element, formed on the surface of a semiconductor substrate of an optical element, comprising: a spherical lens convex outward from the optical element; a base portion disposed around the lens; and a groove formed on the surface of the semiconductor substrate around the side wall of the base portion.

3. The optical element focusing structure according to claim 2, wherein the outer circumference of the groove is provided with an outer wall portion made of the semiconductor.

4. 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.

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, 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 and the base portion, respectively, into the lens and the base portion, wherein the surface and side walls of the base portion are covered with a protective film.

6. A method for manufacturing a light-gathering structure for an optical element, wherein the optical element has an optical device on one side of the 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 wet etching the other side on which the columnar structure and the base portion are formed to process the columnar structure and the base portion, respectively, into the lens and the base portion, wherein the base portion has a groove deeper than the height of the base portion, and the surface of the base portion, the inner wall of the groove and the bottom surface are covered with a protective film.

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