JP2010169918A - Optical element array and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element array in which an anti-reflection film of predetermined film thickness is securely formed on the surface of the optical face by a simple method, and to provide a method for manufacturing the optical element array. <P>SOLUTION: The plurality of optical faces 3 are formed on at least the one side of a substrate 2 made of a semiconductor material. The substrate 2 with the optical faces 3 formed on the one side thereof is thermally oxidized or thermally oxynitrogenized, thereby forming an oxidized or oxynitrogenized film 4 on both sides of the substrate 2. When the refractive index is represented by n, the film thickness is represented by d, and the wavelength of light to be transmitted is represented by λ, the oxidized or oxynitrogenized film 4 is formed to satisfy the relation expressed by nd=λ/4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate and a manufacturing method thereof, and more particularly to an optical element array in which an antireflection film is formed on the surface of the substrate and a manufacturing method thereof.

  Conventionally, an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate is known. An optical surface having a lens surface, for example, is used as a lens array optically coupled to an optical fiber array in an optical communication device.

  The substrate constituting the optical element array is made of a semiconductor material having infrared light transparency, for example, silicon. A resist is applied to the substrate, and the shape of the optical surface is formed by photolithography and heat treatment. An optical surface is formed on the substrate by performing RIE (reactive ion etching). As an optical element array formed by such a manufacturing method, for example, there is one described in Patent Document 1.

JP 2006-293396 A

  In the optical element array, an antireflection film may be formed on the optical surface in order to suppress reflection of transmitted light. In this case, the antireflection film is formed on the surface of the substrate by a technique such as vapor deposition or sputtering. Thus, in order to perform vapor deposition and sputtering, a large-scale apparatus is required, which has been a factor in increasing manufacturing costs. In addition, when a film is formed on the surface of an optical surface composed of a concave or convex surface such as a lens by vapor deposition or sputtering, the film thickness is reduced on a surface inclined with respect to the direction of vapor deposition or sputtering. There was a problem that the film thickness could not be obtained.

  The present invention has been made in view of the above-described problems, and provides an optical element array capable of reliably forming an antireflection film having a predetermined thickness on the surface of an optical surface by a simple method and a method for manufacturing the same. Objective.

In order to solve the above problems, an optical element array according to the present invention is an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate.
The substrate having the optical surface is made of an infrared light transmissive material, and both surfaces of the substrate are covered with an oxide film or an oxynitride film.

  In the optical element array according to the present invention, the substrate having the optical surface is formed of a semiconductor material.

Furthermore, the method for manufacturing an optical element array according to the present invention is a method for manufacturing an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate.
An oxide film or an oxynitride film is formed on both surfaces of the substrate by forming the plurality of optical surfaces on at least one surface of a substrate made of a semiconductor material, and subjecting the substrate on which the optical surfaces are formed to thermal oxidation or thermal oxynitridation treatment. It is configured to form.

  Furthermore, in the method of manufacturing an optical element array according to the present invention, the oxide film or oxynitride film of the substrate has a refractive index of n, a film thickness of d, and a wavelength of transmitted light λ, nd = λ / 4 is formed so as to satisfy the relationship of 4.

  According to the optical element array of the present invention, the substrate having an optical surface is made of a material having infrared light transparency, and both surfaces of the substrate are covered with an oxide film or an oxynitride film, thereby oxidizing or oxynitriding. Thus, the antireflection film can be easily formed on the surface of the substrate and the film thickness can be made uniform.

  Further, according to the optical element array of the present invention, the substrate having the optical surface is formed of a semiconductor material, so that an optical element array in which an antireflection film is easily formed can be manufactured using a semiconductor manufacturing process. it can.

  Furthermore, according to the method for manufacturing an optical element array according to the present invention, a plurality of optical surfaces are formed on at least one surface of a substrate made of a semiconductor material, and the substrate on which the optical surfaces are formed is subjected to thermal oxidation or thermal oxynitridation treatment. Thus, by forming an oxide film or an oxynitride film on both surfaces of the substrate, an antireflection film can be easily formed on the surface of the substrate by oxidation or oxynitridation, and the film thickness can be made uniform.

  Furthermore, according to the method for manufacturing an optical element array according to the present invention, the oxide film or oxynitride film of the substrate has a refractive index of n, a film thickness of d, and a wavelength of transmitted light λ, nd = λ By forming so as to satisfy the relationship of / 4, the transmittance of light of a predetermined wavelength can be increased by adjusting the film thickness.

It is sectional drawing of the optical element array in this embodiment. It is a graph showing the relationship of the transmittance | permeability of the light of 1550 nm wavelength with respect to the refractive index of an antireflection film. It is a graph of the transmittance | permeability characteristic of the antireflection film with respect to the wavelength of light. It is sectional drawing showing the manufacturing process of the optical element array.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a cross-sectional view of the optical element array in the present embodiment. As shown in this figure, the optical element array 1 of the present embodiment has a plurality of optical surfaces 3 formed on one surface of a flat substrate 2.

  The optical surface 3 formed on the substrate 2 is a convex lens surface made of a spherical surface, and the optical element array 1 of this embodiment is configured as a lens array in which a plurality of lens surfaces are arranged. The lens array is used, for example, in an optical communication device so as to be optically coupled to an optical fiber array in which a plurality of optical fibers are arranged.

  The substrate 2 having the optical surface 3 is made of a material having infrared light transmission property that transmits infrared light, and is specifically formed of silicon (Si) as a semiconductor material. As the material of the substrate 2, other semiconductor materials may be used. For example, germanium may be employed. The light transmitted through the optical element array 1 of the present embodiment has a wavelength of 1550 nm.

  An antireflection film 4 is formed on the surface of the substrate 2 including the optical surface 3. The antireflection film 4 is made of silicon oxynitride (SiO. X. N. y.) And is formed on both surfaces of the substrate 2. The antireflection film 4 can prevent light incident on the optical surface 3 from being reflected.

  The refractive index of silicon constituting the substrate 2 is about 3.48, while the silicon oxynitride constituting the antireflection film 4 changes in refractive index depending on the nitrogen content. When nitrogen is not included, that is, in silicon oxide (SiO2), the refractive index is about 1.47, and the refractive index increases as the nitrogen content increases.

  FIG. 2 is a graph showing the relationship between the refractive index of the antireflection film 4 and the transmittance of light having a wavelength of 1550 nm when silicon (refractive index: about 3.48) is used for the substrate 2. As shown in this figure, when the antireflective film 4 is about 1.47, which is the refractive index when silicon oxide is used, the light transmittance is about 90%. If the nitrogen content is higher than that and the refractive index is increased, the light transmittance is increased. When the refractive index is about 1.84, the light transmittance is almost 100%. As the refractive index increases further, the light transmittance decreases. Therefore, when silicon (refractive index of about 3.48) is used for the substrate 2, the optimal refractive index of the antireflection film 4 is about 1.84. This is because the light transmittance is maximized when the refractive index n of the antireflection film 4 satisfies the half power of the refractive index of the substrate.

  FIG. 3 shows a graph of the transmittance characteristics of the antireflection film 4 with respect to the wavelength of light. This figure shows a plurality of cases where the refractive index of the antireflection film 4 is different. As described above, the antireflection film 4 is premised on the transmission of light of 1550 nm. When the refractive index is n, the film thickness is d, and the wavelength of the transmitted light is λ, the relationship of nd = λ / 4 is established. It is formed to satisfy. Thus, as shown in FIG. 3, the transmittance is highest when the wavelength of light is 1550 nm. At any wavelength, the light transmittance is the highest when the refractive index is about 1.84. Here, the light with a wavelength of 1000 to 2000 nm is infrared light (infrared light).

  Next, the manufacturing process of the optical element array 1 in this embodiment will be described. FIG. 4 is a cross-sectional view showing the manufacturing process of the optical element array 1. As shown in FIG. 4A, first, a plate-like substrate 2 made of silicon is prepared, and a resist 10 is applied on one surface thereof by a spin coater or spraying. When the resist 10 is applied to the substrate 2, pre-baking is performed in order to increase the adhesive force between the substrate 2 and the resist 10.

  Subsequently, as shown in FIG. 4B, a photomask 11 having a pattern in which circles are arranged two-dimensionally is disposed so as to face the surface of the substrate 2 coated with the resist 10, and exposure is performed. Do. Then, by exposing the exposed substrate 2 to a developer and removing the excess portion of the resist, as shown in FIG. 4C, a pattern in which the columnar resists 10 are two-dimensionally arranged is formed on the substrate. 2 is formed on one side.

  Next, the resist 10 is heated and reflowed to change the shape of the resist 10 to a spherical shape as shown in FIG. If the resist 10 has a spherical shape, the resist 10 is removed by reactive ion etching, and the shape of the resist 10 is transferred to the surface of the substrate 2, and a plurality of optical elements are applied to the surface of the substrate 2 as shown in FIG. Surface 3 is formed.

  After the optical surface 3 is formed on the substrate 2, the substrate 2 is accommodated in a heating furnace and heated to 1000 to 1200 ° C. in an atmosphere of oxygen and nitrogen. As a result, the entire surface of the substrate 2 including the optical surface 3 is thermally oxynitrided, and an antireflection film 4 made of an oxynitride film is formed as shown in FIG. Here, the ratio of oxygen and nitrogen in the heating furnace is set so that the refractive index of the antireflection film 4 formed as described above is about 1.84. Next, as shown in FIG. 4G, when the substrate 2 is cut to a desired size, the antireflection film 4 is formed on both the surface of the substrate 2 on which the optical surface 3 is formed and the opposite surface. The optical element array 1 shown in FIG. 1 can be formed.

  Thus, the substrate 2 on which the optical surface 3 is formed is thermally oxynitrided, and the oxynitride film is formed on both surfaces of the substrate 2, thereby easily forming the antireflection film 4 having a uniform thickness on the optical surface 3. can do. Further, by forming the antireflection film 4 on both surfaces of the substrate 2, it is possible to suppress warping of the substrate 2 due to film stress generated when the antireflection film 4 is formed only on the surface on the optical surface 3 side. .

  Here, the oxynitride film is formed so that the refractive index is 1.84 so that the transmittance of the antireflection film 4 at 1550 nm is the optimum value. However, when the required level of transmittance is not so high. The antireflection film 4 may be formed more simply as an oxide film.

  Although the embodiment of the present invention has been described above, the application of the present invention is not limited to this embodiment, and can be applied in various ways within the scope of its technical idea. For example, although the optical surface 3 is configured as a convex lens in the present embodiment, the optical surface 3 may be another optical functional surface such as a concave lens, a Fresnel lens, or a diffraction grating. In the present embodiment, the optical surface 3 is formed only on one surface side of the substrate 2, but may be formed on both surfaces.

DESCRIPTION OF SYMBOLS 1 Optical element array 2 Board | substrate 3 Optical surface 4 Antireflection film 10 Resist 11 Photomask

Claims (4)

In an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate,
An optical element array, wherein the substrate having the optical surface is made of an infrared light transmissive material, and both surfaces of the substrate are covered with an oxide film or an oxynitride film.   2. The optical element array according to claim 1, wherein the substrate having the optical surface is made of a semiconductor material. In the method of manufacturing an optical element array in which a plurality of optical surfaces are formed on at least one surface of a flat substrate,
An oxide film or an oxynitride film is formed on both surfaces of the substrate by forming the plurality of optical surfaces on at least one surface of a substrate made of a semiconductor material, and subjecting the substrate on which the optical surfaces are formed to thermal oxidation or thermal oxynitridation treatment. A method of manufacturing an optical element array, comprising: forming an optical element array.   The oxide film or oxynitride film of the substrate is formed so as to satisfy a relationship of nd = λ / 4, where n is a refractive index, d is a film thickness, and λ is a wavelength of transmitted light. The manufacturing method of the optical element array of Claim 3.

Images