JP4153442B2 - Manufacturing method of optical module - Google Patents

Description

The present invention relates to a method of manufacturing an optical module.

  An optical module is known as a device used for optical connection between light emitted from a light emitting element such as a semiconductor laser or a surface emitting laser and an optical transmission medium such as an optical fiber (for example, see Patent Document 1).

  FIG. 13 is a diagram illustrating a configuration of a typical optical module 1. The optical module 1 has a microlens array 3 in which a plurality of microlenses 3a are arranged on one surface 2a of a lens array substrate 2, and is an opposite surface opposite to the surface on which the microlens array 3 is formed. A recess 5 for inserting and fixing the optical fiber 4 is formed on the other surface 2 b side, and the optical fiber 4 is fixed to the recess 5. Light 6 emitted from a light source (not shown) is collected by each microlens 3 a of the microlens array 3 and enters the optical fiber 4 fixed in the recess 5. Alternatively, the light emitted from the optical fiber 4 is emitted from the lens array substrate 2 as light 6 collimated by the microlens 3a.

  FIG. 14 is a diagram for explaining a conventional method of manufacturing an optical module. A conventional method for manufacturing a typical optical module 1 will be described with reference to FIG. 14A, a sol-gel layer 7 is formed by applying a sol-gel material on the other surface 2b of the lens array substrate 2 on which the microlens array 3 is formed on one surface 2a. In the step shown in FIG. 14B, the mold 8 on which the inverted pattern of the recess 5 for inserting and fixing the optical fiber is pressed against the sol-gel layer 7, and the inverted pattern of the recess 5 is transferred to the sol-gel layer 7. . In the step shown in FIG. 14C, the mold 8 is peeled from the sol-gel layer 7, the lens array substrate 2 having the sol-gel layer 7 in which the recess 5 is formed is baked, the sol-gel layer 7 is cured, and the light The optical module 1 in which the recess 5 for inserting and fixing the fiber 4 is formed is manufactured.

  However, the manufacturing method of the optical module 1 disclosed in Patent Document 1 has the following problems. The optical fiber 4 is formed of a core and a cladding layer covering the periphery of the core, and light is transmitted through the core. In the optical module 1, it is necessary to collect the light emitted from the light emitting element and make it incident on the core portion. However, since the diameter of the core portion is as small as several μm, the microlens array 3 and the optical fiber 4 have a high height. Accurate positioning (hereinafter referred to as alignment) is required.

  In the manufacturing method disclosed in Patent Document 1, the recess 5 for fixing the optical fiber 4 is formed by molding the sol-gel layer 7 using the molding die 8, but the method for aligning the microlens array 3 and the molding die 8. There is no disclosure about. Therefore, when it shape | molds simply based on the manufacturing method disclosed by patent document 1, a position shift will arise in the microlens array 3 and the recessed part 5, and there exists a problem of causing the fall of light transmission efficiency.

  Patent Document 1 also discloses that an ultraviolet curable resin is used instead of the sol-gel material as a member for forming the recess 5. When an ultraviolet curable resin is used instead of the sol-gel material, the reversal pattern of the recess 5 is transferred to the ultraviolet curable resin by the mold 8 and the ultraviolet curable resin is cured, and then the mold 8 is peeled from the lens array substrate 2. There is a process. In recent years, there has been a demand for miniaturization of optical modules, and as means for realizing miniaturization, the diameter of the optical fiber, the diameter and shortening of the microlens constituting the optical module, and the thinning of the lens array substrate are reduced. Has been tried.

  However, in the manufacturing method disclosed in Patent Document 1, there is a step of peeling the mold 8 from the lens array substrate 2 after curing the ultraviolet curable resin, and in this peeling step, stress is applied to the lens array substrate 2. Therefore, when the lens array substrate 2 is thinned, there is a problem that the lens array substrate 2 cannot withstand the stress and is damaged, and the thinning of the lens array substrate 2 is hindered.

  Moreover, since the process of forming the microlens array 3 on the lens array substrate 2 and the process of forming the recess in the sol-gel layer 7 or the ultraviolet curable resin layer are performed in separate processes, many processes are required for production. There is also the problem of reducing production efficiency.

JP 2002-350674 A

The present invention has been made in view of the above problems, and its purpose is to manufacture an optical module excellent in alignment accuracy between a microlens array and a recess into which an optical fiber is inserted and fixed in a small number of manufacturing steps. It is to provide a manufacturing method that can be used.

The present invention corresponds to a microlens that forms a microlens array on the other surface side, which is the opposite surface opposite to one surface of the transparent substrate, with the microlens array formed on one surface side of the transparent substrate. In the method of manufacturing an optical module in which a recess for inserting an optical fiber is formed,
Forming a negative photosensitive layer on one surface of the transparent substrate;
Forming a positive photosensitive layer on the other surface of the transparent substrate;
A step of disposing a light-shielding mask on the side of any one of the negative photosensitive layer and the positive photosensitive layer and spaced from the photosensitive layer;
A process of exposing the positive photosensitive layer or the negative photosensitive layer by irradiating the negative photosensitive layer or the positive photosensitive layer with light through the transparent substrate through the light passage opening of the light shielding mask. When,
Developing a negative photosensitive layer to form a microlens array;
And a step of developing a positive photosensitive layer to form a recess.

In the present invention, after the step of developing the positive photosensitive layer to form the recess,
The method includes a step of heat-treating the positive photosensitive layer in which the recess is formed.

In the present invention, after the step of developing the positive photosensitive layer to form the recess,
The method includes a step of etching the other surface of the transparent substrate including the positive photosensitive layer in which the recess is formed to form the recess in the transparent substrate.

The present invention also includes a step of developing a negative photosensitive layer to form a microlens array,
The method includes a step of forming a microlens array on a transparent substrate by etching one surface of a transparent substrate having a negative photosensitive layer on which a microlens array is formed.

In the present invention, after the step of developing the negative photosensitive layer to form the microlens array, one side of the transparent substrate having the negative photosensitive layer on which the microlens array is formed is etched to form a microlens array on the transparent substrate. Forming a lens array;
After the step of developing the positive photosensitive layer to form the recess, etching the other surface of the transparent substrate having the positive photosensitive layer with the recess formed to form the recess in the transparent substrate. It is characterized by including.

  In the present invention, the developer used in the step of developing the positive photosensitive layer to form the recess and the step of developing the negative photosensitive layer to form the microlens array is an alkaline developer. It is characterized by.

  According to the present invention, a negative photosensitive layer is formed on one surface side of a transparent substrate, a positive photosensitive layer is formed on the other surface side of the transparent substrate, and a light-shielding mask is separated on one of the photosensitive layer sides. The negative photosensitive layer and the positive photosensitive layer are simultaneously irradiated with light through a light-shielding mask for exposure, and then the negative photosensitive layer is developed to form a microlens array. To develop a recess. As described above, since the recess for inserting and fixing the microlens array and the optical fiber can be simultaneously exposed using one light-shielding mask, the microlens and the recesses constituting the microlens array can be formed. Can be formed with high precision alignment. Moreover, a process saving can be realized. Further, in the step of forming the microlens array and the recess and the subsequent steps, stress is not applied to the transparent substrate such as peeling the member from the transparent substrate, so the transparent substrate is thinned and the optical module is thinned. It becomes possible.

  According to the invention, the step of developing the positive photosensitive layer and forming the recess includes the step of heat-treating the positive photosensitive layer in which the recess is formed. By this heat treatment, the corner of the member that forms the recess is formed to have a curvature, so that a recess having a wide opening is formed, and insertion into the recess of the optical fiber is easy. The tact time of manufacturing can be shortened.

  According to the invention, after the step of developing the positive photosensitive layer to form the recess, the other surface of the transparent substrate including the positive photosensitive layer having the recess is etched to form a recess in the transparent substrate. Forming a point. As a result, it is possible to form a recess that is aligned with high precision on the other surface of the transparent substrate with respect to the microlens array formed on the one surface side of the transparent substrate. This improves the soundness of the portion where the optical fiber is inserted and fixed.

  According to the invention, after the step of developing the negative photosensitive layer to form the microlens array, one surface of the transparent substrate including the negative photosensitive layer on which the microlens array is formed is etched to form the transparent substrate. Includes a step of forming a microlens array. As a result, the microlens array can be formed on one surface of the transparent substrate, so that the displacement of the microlens array due to environmental temperature changes can be reduced.

  In addition, according to the present invention, both steps of forming a microlens array on one surface by etching on a transparent substrate and forming a recess on the other surface are included. The soundness of the portion where the fiber is inserted and fixed can be further improved, and the positional deviation of the microlens array due to the environmental temperature change can be reduced.

  According to the invention, both the positive photosensitive layer and the negative photosensitive layer are developed with an alkaline developer. As a result, the positive photosensitive layer and the negative photosensitive layer can be developed in the same process using the same developer, so that the manufacturing process can be reduced and the developer cost can be reduced.

  FIG. 1 is a diagram for explaining a photosensitive layer exposure method relating to the method for producing an optical module of the present invention, and FIG. 2 is a diagram showing a profile of the photosensitive layer after developing the photosensitive layer exposed by the method shown in FIG. It is. An ultraviolet curable resin, which is a photosensitive material, is applied on one surface 10 a of the transparent substrate 10 to form a first ultraviolet curable resin layer 11. On the other surface 10 b facing the one surface 10 a of the transparent substrate 10. When the ultraviolet curable resin is applied to form the second ultraviolet curable resin layer 12 and exposed by irradiating the ultraviolet rays 15 through the openings 14 of the light shielding mask 13 disposed away from the first ultraviolet curable resin layer 11, The present inventors have found a phenomenon that the profiles of the first and second ultraviolet curable resin layers 11 and 12 after development are formed into curved surfaces such as the line 16 in FIG. The present invention is based on the above findings.

FIG. 3 is a diagram for explaining an optical module 20 and a method for manufacturing the optical module 20 according to an embodiment of the present invention. With reference to FIG. 3, the optical module 20 of this invention and the method of manufacturing the optical module 20 are demonstrated. 3A, the negative photosensitive layer 22 is formed on one surface 21a of the transparent substrate 21, and the other surface 21b that is the opposite surface facing the one surface 21a of the transparent substrate 21 is formed. Then, the positive photosensitive layer 23 is formed. For forming the negative photosensitive layer 22 and the positive photosensitive layer 23 on each surface of the transparent substrate 21, a known film forming method such as a coating method is used. When a coating method is used, a spin coating method or a dipping method is appropriately selected.

  Examples of the material used for the transparent substrate 21 include a glass material such as quartz or borosilicate. Examples of the positive photosensitive material constituting the positive photosensitive layer 23 include a positive resist (manufactured by Clariant Japan Co., Ltd .: AZ series). As the negative photosensitive material constituting the negative photosensitive layer 22, either an ultraviolet curable resin or a visible light curable resin can be used, and it is desirable to use a material having a high light transmittance upon exposure. For example, urethane Examples thereof include acrylic monomers such as acrylate, epoxy acrylate, polyester acrylate, and polyether acrylate, and mixed compositions obtained by mixing a photoinitiator with an epoxy monomer.

  In this embodiment, since the ultraviolet curable resin is used as the negative photosensitive material, the negative photosensitive layer 22 is hereinafter referred to as the ultraviolet curable resin layer 22.

  In the step of FIG. 3B, a light shielding mask 24 is disposed on the ultraviolet curable resin layer 22 side so as to be separated from the ultraviolet curable resin layer 22, and the ultraviolet curable resin layer 22 and the positive photosensitive layer 23 are disposed with respect to the light shielding mask 24. A light source 25 is disposed on the opposite side of the transparent substrate 21 having the light source. In the light shielding mask 24, a light passage opening 26 is formed in advance so as to allow the light emitted from the light source 25 to pass through, corresponding to the arrangement of the recesses into which the microlens array and the optical fiber are to be inserted and fixed. . In the present embodiment, since the negative photosensitive layer is the ultraviolet curable resin layer 22, a material that can emit ultraviolet rays is selected as the light source 25.

  3C, the light emitted from the light source 25 is irradiated and exposed to the ultraviolet curable resin layer 22 and the positive photosensitive layer 23 through the light passage opening 26 of the light shielding mask 24. At this time, the light emitted from the light source 25 passes through the ultraviolet curable resin layer 22 and the transparent substrate 21 and is also irradiated to the positive photosensitive layer 23. As a result, the ultraviolet curable resin layer 22 and the positive photosensitive layer 23 corresponding to the light passage opening 26 of the light shielding mask 24 are exposed simultaneously.

  In the step of FIG. 3D, a microlens array 27 is formed by developing the ultraviolet curable resin layer 22 and removing the unexposed portion, and developing the positive photosensitive layer 23 and removing the exposed portion. A recess 28 is formed.

The negative photosensitive material containing the ultraviolet curable resin is desirably developable with an alkaline developer. By using a material that can be developed with an alkaline developer, the positive photosensitive layer 23 and the negative photosensitive layer 22 can be developed in the same process using the same developer. It is possible to reduce the amount and the developer cost can be reduced. Examples of the alkaline developer include tetramethylammonium hydroxide (TMAH) -based organic alkali developer and inorganic alkali developer such as KOH / NaOH / Na ₂ CO ₃ .

  As described above, the microlens array 27 is formed on the one surface 21a side of the transparent substrate 21, and the other surface 21b side of the transparent substrate 21 corresponds to the microlens 27a constituting the microlens array 27. The optical module 20 in which the recess 28 for inserting the optical fiber is formed is manufactured.

  As described above, in the optical module 20, the micro lens array 27 and the recess 28 for inserting and fixing the optical fiber are formed by simultaneously exposing using the single light shielding mask 24. The microlens 27a and the recess 28 constituting the member 27 are formed with high precision alignment.

  FIG. 4 is a diagram illustrating a state in which the optical fiber 29 is inserted and fixed in the recess 28 of the optical module 20. An adhesive such as an ultraviolet curable resin is applied to the portion of the optical module 20 that faces the recess 28 of the positive photosensitive layer 23, and an optical fiber 29 is inserted into the recess 28 and fixed. The thickness of the transparent substrate 21 in the optical module 20 is set so that the end face 30 of the optical fiber 29 inserted and fixed in the recess 28 matches the focal position of each microlens 27 a constituting the microlens array 27. Here, the optical module 29 is included in the optical module in a broad sense, including a device configured by inserting and fixing the optical fiber 29 in the recess 28 of the optical module 20.

  In the optical module 20 manufactured as described above, since the microlens array 27 and the recess 28 are aligned with high accuracy, the light 31 can be accurately collected with respect to the core of the optical fiber 29. It becomes possible to increase the light transmission efficiency.

  Moreover, since the formation of the recess 28 for inserting and fixing the microlens array 27 and the optical fiber 29 is performed by simultaneous exposure using one light shielding mask 24, it is possible to realize a process saving. Further, in the step of forming the microlens array 27 and the recess 28 and the subsequent steps, no stress is applied to the transparent substrate 21 such as peeling the member from the transparent substrate 21. This can contribute to making the module 20 thinner.

  FIG. 5 is a diagram showing a configuration of an optical module 40 according to the second embodiment of the present invention, and FIG. 6 is a diagram showing a state in which an optical fiber 29 is inserted and fixed in the optical module 40 shown in FIG. The optical module 40 of this embodiment is similar to the optical module 20 of the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  It should be noted in the optical module 40 that the positive photosensitive layer 42 in which the recess 41 is formed is formed so that the corner 43 of the portion facing the recess 41 has a curvature. The positive photosensitive layer 42 in which the corner 43 facing the recess 41 has a curvature is formed after the step of developing the positive photosensitive layer 42 to form the recess 41. This is realized by adopting a process of heat-treating the positive photosensitive layer 42. By heating the positive photosensitive layer 42 in which the recess 41 is formed, a portion of the corner 43 facing the recess 41 is softened to form a so-called sagging and have a curvature.

  In such an optical module 40 in which the recess 41 having the wide opening is formed, the optical fiber 29 can be easily inserted into the recess 41, so that the manufacturing tact time is shortened.

FIG. 7 is a view for explaining an optical module 50 and a method for manufacturing the optical module 50 according to the third embodiment of the present invention. FIG. 8 shows a recess 51 of the optical module 50 manufactured by the method shown in FIG. It is a figure which shows the state in which the optical fiber 29 was inserted and fixed. The optical module 50 and the manufacturing method thereof according to the present embodiment are similar to the optical module 20 and the manufacturing method thereof according to the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

A method for manufacturing the optical module 50 will be described with reference to FIG. In the process of FIG. 7A, first, as in the first embodiment, an ultraviolet curable resin layer 22 and a positive photosensitive layer 23 are formed on each surface of the transparent substrate 21, and simultaneously through a light shielding mask. After the exposure, the microlens array 27 and the recess 28 are formed by developing with an alkaline developer. Next, etching is performed from the side where the recess 28 is formed in the positive photosensitive layer 23. This etching is performed by, for example, reactive ion etching (abbreviated as RIE) or inductively coupled plasma (
It can be realized by a dry etching method such as Inductively Coupled Plasma (abbreviation ICP).

  In the step of FIG. 7B, etching is continued from the side where the recess 28 is formed in the positive photosensitive layer 23. As a result, the positive photosensitive layer 23 and the transparent substrate 21 constituting the bottom of the recess 28 are etched at substantially the same speed, so that the shape of the recess 28 formed in the positive photosensitive layer 23 is obtained. As the thickness is reduced, a recess 51 starts to be formed in the transparent substrate 21.

  In the step of FIG. 7C, the etching is terminated when the positive photosensitive layer 23 is removed by etching. In this manner, the optical module 50 in which the recess 51 having the same shape as the recess 28 formed in the positive photosensitive layer 23 is formed in the transparent substrate 21 is manufactured.

  By forming the recess 51 in the transparent substrate 21, the portion where the recess 51 is formed is constituted by the transparent substrate 21 itself, so that the strength can be improved. Therefore, the soundness of the portion where the optical fiber 29 is inserted and fixed can be further improved.

  Note that, after the recess 28 is formed in the positive photosensitive layer 23 on the other surface side of the transparent substrate 21 and before the etching is started, the positive photosensitive layer 23 is subjected to a heat treatment to form the recess 28. You may make it the corner of the part which faces to have a curvature. Accordingly, the recess 51 formed in the transparent substrate 21 by the subsequent etching can also be formed so that the corner of the portion facing the recess 51 has a curvature. Therefore, the optical module 40 according to the second embodiment. The same effect can be achieved.

FIG. 9 is a diagram for explaining an optical module 55 and a method for manufacturing the optical module 55 according to a fourth embodiment of the present invention. FIG. 10 shows a recess 28 of the optical module 55 manufactured by the method shown in FIG. It is a figure which shows the state in which the optical fiber 29 was inserted and fixed. The optical module 55 and the manufacturing method thereof according to the present embodiment are similar to the optical module 20 and the manufacturing method thereof according to the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  A method for manufacturing the optical module 55 will be described with reference to FIG. In the step of FIG. 9A, first, similarly to the first embodiment, the ultraviolet curable resin layer 22 and the positive photosensitive layer 23 are formed on the respective surfaces of the transparent substrate 21, and simultaneously through a light shielding mask. After the exposure, the microlens array 27 and the recess 28 are formed by developing with an alkaline developer. Next, etching is performed from the side where the microlens array 27 is formed on the ultraviolet curable resin layer 22.

  In the step of FIG. 9B, etching is continued from the side where the microlens array 27 is formed on the ultraviolet curable resin layer 22. As a result, the microlens array 27 made of an ultraviolet curable resin and the transparent substrate 21 around the base of the microlens array 27 are etched at substantially the same speed, so that the microlens 27a constituting the microlens array 27 is formed. As the shape is reduced, the microlens 56a, that is, the microlens array 56 starts to be formed on the transparent substrate 21.

  In the step of FIG. 9C, the etching is finished when the microlens array 27 made of the ultraviolet curable resin is etched away. In this manner, the optical module 55 in which the microlens array 56 having the same shape as the microlens array 27 made of ultraviolet curable resin is formed on the transparent substrate 21 is manufactured.

  By forming the microlens array 56 on the transparent substrate 21, since the transparent substrate 21 and the microlens array 56 are made of the same material and have the same linear expansion coefficient, the displacement of the microlens array due to environmental temperature changes is reduced. It becomes possible to do.

  FIG. 11 is a diagram showing a configuration of an optical module 60 according to a fifth embodiment of the present invention. FIG. 12 shows a state in which the optical fiber 29 is inserted and fixed in the recess 51 of the optical module 60 shown in FIG. FIG. The optical module 60 of the present embodiment is similar to the optical modules 50 and 55 of the third and fourth embodiments, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  The optical module 60 is manufactured by using both a manufacturing method for forming the recess 51 on the other surface of the transparent substrate 21 and a manufacturing method for forming the microlens array 56 on one surface of the transparent substrate 21 by etching. The microlens array 56 and the recess 51 are formed in the transparent substrate 21. In such an optical module 60, both of the effects that the optical modules 40 and 50 according to the third and fourth embodiments respectively express.

  As shown in FIGS. 8, 10 and 12, even when the microlens array 56 and / or the recess 51 are formed on the transparent substrate 21, the thickness of the transparent substrate 21 is the same as that of the microlens 56a or the microlens 27a. It is set so that the end face 30 of the optical fiber 29 is disposed at the focal position. Such a setting can be realized as follows. The initial thickness of the transparent substrate 21 is set in advance larger than the focal length of the microlens 56a or the microlens 27a by the thinning due to the etching, and after the etching, the optical fiber 29 is placed at the focal position of the microlens 56a or the microlens 27a. What is necessary is just to set so that the end surface 30 may correspond.

  As described above, in the embodiment of the present invention, the light-shielding mask 24 is spaced apart and disposed above the surface of the transparent substrate 21 on which the negative photosensitive layer 22 is applied. Without being limited thereto, the exposure may be carried out by being spaced apart above the positive photosensitive layer 23 side.

It is a figure explaining the exposure method of the photosensitive layer regarding the manufacturing method of the optical module of this invention. It is a figure which shows the profile of the photosensitive layer after developing the photosensitive layer exposed by the method shown in FIG. It is a figure explaining the manufacturing method of the optical module 20 and the optical module 20 which are one Embodiment of this invention. FIG. 3 is a diagram showing a state in which an optical fiber 29 is inserted and fixed in a recess 28 of the optical module 20. It is a figure which shows the structure of the optical module 40 which is the 2nd Embodiment of this invention. It is a figure which shows the state which inserted and fixed the optical fiber 29 to the optical module 40 shown in FIG. It is a figure explaining the manufacturing method of the optical module 50 and the optical module 50 which are 3rd Embodiment of this invention. It is a figure which shows the state by which the optical fiber 29 was inserted and fixed to the recess 51 of the optical module 50 manufactured by the method shown in FIG. It is a figure explaining the manufacturing method of the optical module 55 and the optical module 55 which are the 4th Embodiment of this invention. It is a figure which shows the state by which the optical fiber 29 was inserted and fixed to the recess 28 of the optical module 55 manufactured by the method shown in FIG. It is a figure which shows the structure of the optical module 60 which is 5th Embodiment of this invention. It is a figure which shows the state by which the optical fiber 29 was inserted and fixed to the recess 51 of the optical module 60 shown in FIG. 1 is a diagram illustrating a configuration of a typical optical module 1. FIG. It is a figure explaining the manufacturing method of the conventional optical module.

Explanation of symbols

20, 40, 50, 55, 60 Optical module 21 Transparent substrate 22 Negative photosensitive layer 23, 42 Positive photosensitive layer 24 Light shielding mask 25 Light source 27, 56 Micro lens array 28, 41, 51 Recess 29 Optical fiber

Claims (6)

A microlens array is formed on one surface side of the transparent substrate, and light is applied to the other surface side, which is the opposite surface opposite to one surface of the transparent substrate, so as to correspond to the microlenses constituting the microlens array. In the method of manufacturing an optical module in which a recess for inserting a fiber is formed,
Forming a negative photosensitive layer on one surface of the transparent substrate;
Forming a positive photosensitive layer on the other surface of the transparent substrate;
A step of disposing a light-shielding mask on the side of any one of the negative photosensitive layer and the positive photosensitive layer and spaced from the photosensitive layer;
A process of exposing the positive photosensitive layer or the negative photosensitive layer by irradiating the negative photosensitive layer or the positive photosensitive layer with light through the transparent substrate through the light passage opening of the light shielding mask. When,
Developing a negative photosensitive layer to form a microlens array;
And a step of developing a positive photosensitive layer to form a recess. After the step of developing the positive photosensitive layer to form the recess,
2. The method of manufacturing an optical module according to claim 1, further comprising a step of heat-treating the positive photosensitive layer in which the recess is formed. After the step of developing the positive photosensitive layer to form the recess,
2. The method of manufacturing an optical module according to claim 1, further comprising a step of forming a recess in the transparent substrate by etching the other surface of the transparent substrate including the positive photosensitive layer in which the recess is formed. After the step of developing the negative photosensitive layer to form the microlens array,
2. The method of manufacturing an optical module according to claim 1, comprising a step of etching one surface of a transparent substrate having a negative photosensitive layer on which a microlens array is formed to form a microlens array on the transparent substrate. . After the step of developing the negative photosensitive layer to form the microlens array, one surface of the transparent substrate having the negative photosensitive layer on which the microlens array is formed is etched to form the microlens array on the transparent substrate. Process,
After the step of developing the positive photosensitive layer to form the recess, etching the other surface of the transparent substrate having the positive photosensitive layer with the recess formed to form the recess in the transparent substrate. The method of manufacturing an optical module according to claim 1, comprising:   The developer used in the step of developing the positive photosensitive layer to form the recess and the step of developing the negative photosensitive layer to form the microlens array is an alkaline developer. Item 6. The method for manufacturing an optical module according to any one of Items 1 to 5.

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