JP5235155B2 - Fine resin structure and method for manufacturing photoelectric circuit board, fine resin structure and photoelectric circuit board - Google Patents

Description

  The present invention includes a method for producing a fine resin structure for forming a fine resin structure such as an optical waveguide on a substrate, a fine resin structure obtained by the production method, and an optical waveguide that is a fine resin structure. The present invention relates to a photoelectric circuit board.

  In recent years, various sensors and optical devices called MEMS (Micro Electrical-Mechanical System) manufactured by applying semiconductor processing technology, and many types of elements are integrated on one chip called SoC (System on Chip). The use of technology is evolving. As an elemental technology of such MEMS and SoC, a technology for forming a fine three-dimensional structure such as an optical waveguide on the surface of a semiconductor substrate has been studied. However, it is not easy to form a resin-made fine three-dimensional structure on the surface of the semiconductor substrate. As a method for forming a resin-made fine three-dimensional structure on the surface of a semiconductor substrate, a method for forming a fine structure having a thickness on the order of several tens of μm by repeatedly applying a liquid resin material is conventionally known. Yes. Specifically, for example, in Patent Document 1 below, a liquid photocurable resin capable of thick coating is applied on a substrate, planarized using a light transmissive planarizing member, and then transmitted through the light. A method of forming a three-dimensional object by forming a photo-curing resin layer having a predetermined pattern by irradiating only a predetermined region with light through a property flattening member and repeating this operation in the laminating direction is disclosed. As a method for forming a photocurable resin layer having a predetermined pattern, a method of selectively curing by restricting a light irradiation region using a mask is disclosed.

  Patent Document 2 below uses a resin material (trade name “NANO SU-8” manufactured by Micro Chem Co., Ltd.) that is reduced in viscosity by heating in solid at room temperature and photocured by UV irradiation. After the resin layer is formed on the substrate surface with a new resin material, the viscosity of the resin layer is reduced by heating, and the fine mold shape is transferred to the low viscosity resin layer, and then cooled to a temperature at which the resin layer cools and solidifies. A method is disclosed in which after releasing from the mold, photocuring only a predetermined portion by selective UV exposure using a photomask, and then removing an uncured portion by development to obtain a photocured resin structure.

JP 2001-47521 A Japanese Patent Laid-Open No. 2004-200277

  When trying to form a fine resin structure by the above method, there existed the following subjects.

  In complicated MEMS and SoC, micron-order control is required for the height (thickness) and flatness of a fine resin structure. When a liquid resin is applied to the substrate surface using the spin coating method, which is a general application method, the height of the applied surface is increased by forming micron-order irregularities due to spin marks on the applied liquid resin surface. There was a problem of non-uniformity. Specifically, for example, when a liquid resin for forming the core is applied to the substrate surface including the groove for forming the optical waveguide, the thickness of the resin layer is reduced due to the influence of the groove depression or the spin mark. There was a problem of non-uniformity. In such a case, the heights of the cores are different at arbitrary plural locations in the path of the optical waveguide. In particular, in the case where a long optical waveguide or a plurality of optical waveguides are formed on a substrate having a relatively large area, the entire path in the optical waveguide is affected by the unevenness of the height of the coating surface. In other words, the heights of the cores are not uniform, and the heights of the plurality of cores are likely to be non-uniform. Such non-uniform surface height is a factor that increases propagation loss in an optical device such as an optical waveguide.

  As disclosed in Patent Document 1, a liquid photocurable resin is applied onto a substrate, and a predetermined pattern of a photocurable resin layer is formed by irradiating only a predetermined region with light through a light-transmitting flattening member. In such a case, there is a problem that when the light-transmitting planarizing member is removed, the liquid, uncured photocurable resin material scatters and adheres to the surface of the cured resin structure. Moreover, since the uncured liquid photocurable resin is adhered to the removed light transmissive flattening member, it is necessary to clean the light transmissive flattened member every time it is used.

  Further, for example, when a commercially available “NANO SU-8” as disclosed in Patent Document 2 is applied to a groove for an optical waveguide by a general spin coating method, the resin is affected by the presence of the groove. Uniform spread of the film is hindered, and spin marks and irregularities are formed on the coated surface. As a result, a flat coated surface cannot be obtained. In addition, NANO SU-8 is free from various characteristics because it has fixed mechanical properties such as hardness and rigidity, optical properties such as transmittance and refractive index, and tackiness that affects releasability. It was not possible to adjust it. For example, when adjusting the refractive index, a third component is added to increase or decrease the refractive index, but the compatibility between the "NANO SU-8" and the third component is adapted. In order to maintain the original properties (mechanical properties, transparency, etc.), the amount of the third component cannot be increased, and therefore the refractive index cannot be adjusted to a large extent. Further, there has been no method for adjusting these properties even if the mold releasability is changed or the mechanical properties of the structure are low. There is also a disadvantage that it is very expensive.

  In the case of forming a fine resin structure on the surface of a substrate having a stepped surface such as a groove for forming an optical waveguide, for example, the present invention forms a long fine structure or a plurality of fine structures. Even so, an object of the present invention is to provide a manufacturing method in which a fine structure having a uniform height and having various physical property balances adjusted can be obtained.

  A method for producing a fine resin structure according to one aspect of the present invention is a method for producing a fine resin structure for forming a fine resin structure on a substrate having a step such as a groove on the surface, which is at room temperature (25 ° C. ) And a solid epoxy resin (hereinafter sometimes simply referred to as a solid epoxy resin) and a liquid epoxy resin at room temperature (hereinafter sometimes simply referred to as a liquid epoxy resin) at a predetermined ratio, Further, using a photocurable resin composition that is solid at room temperature and melted or softened by heating, obtained by blending a photopolymerization initiator, the following steps (a) to (d): (a) the light on the substrate A resin layer forming step of forming a solid photocurable resin layer by volatilizing and removing the solvent in the varnish after applying the varnish of the curable resin composition, (b) melting or curing the photocurable resin layer Heated to a softening temperature Then, the flat plate is pressed and contacted with the surface of the photocurable resin layer in a state of being parallel to the substrate surface, and cooled to a temperature at which the photocurable resin composition is solidified while maintaining the pressed contact state. A flattening step of forming a primary molded body having a flat surface by separating the flat plate, (c) from the flat surface side of the primary molded body, by selectively exposing a portion excluding a region to be cured, A curing step of selectively curing only the region is performed, and (d) a development step of forming a resin structure by developing and removing the unexposed portion of the primary molded body that has been selectively cured. According to the above manufacturing method, even on the surface of a substrate having a step such as a groove on the surface, an uncured photo-curing resin layer having a high flatness and having a uniform height in the surface ( Hereinafter, it may be referred to as an uncured resin layer). And the fine resin structure of uniform height can be obtained by selectively exposing such an uncured resin layer with high flatness. Moreover, since the thickness of the uncured resin layer can be adjusted by adjusting the pressure applied to the flat plate, the height of the resulting fine resin structure can be adjusted. Furthermore, by using the photocurable resin composition described above, the mechanical properties, the temperature at which the uncured resin layer melts or softens, and tackiness (surface tackiness) when removing the flat plate from the molded body are achieved. It can be adjusted appropriately. As a result, it is possible to obtain a fine resin structure with high flatness in which the occurrence of peeling and cracks is suppressed. As the flat plate, a flat plate with high surface smoothness such as a silicon wafer can be preferably used. The epoxy resin contained in the photocurable resin composition is obtained by blending an epoxy resin having an aromatic ring having a high refractive index and an alicyclic epoxy resin having a low refractive index, and adjusting the blending ratio. The refractive index of the fine resin structure can be easily adjusted. If a bisphenol type epoxy resin is used among the epoxy resins having an aromatic ring, a tougher fine resin structure can be obtained. Moreover, the adhesiveness of the fine resin structure with respect to a board | substrate can be improved by mix | blending 0.1-5 mass% of coupling agents with a photocurable resin composition.

  The blending ratio of the solid epoxy resin and the liquid epoxy resin in the photocurable resin composition is preferably in the range of 65/35 to 90/10 by mass ratio. In such a range, the tackiness of the uncured resin layer can be sufficiently suppressed. As a result, when removing the flat plate or the contact-type mask, it is possible to sufficiently suppress the removal failure.

  Moreover, in the said photocurable resin composition, a photoinitiator is a cationic polymerization initiator and this cationic polymerization initiator is 0.1-1 mass part with respect to 100 mass parts of all the epoxy resins. It is preferable. By blending the cationic polymerization initiator, it is possible to suppress the inhibition of curing due to oxygen and to suppress the volume shrinkage that occurs during resin curing.

  Moreover, it is preferable that the said photocurable resin composition contains 0.01-1 mass% of light absorbers which absorb the light exposed at the said process (c). When the photocurable resin composition is applied to the stepped portion of the substrate and exposed, the exposure light is diffusely reflected at the stepped portion, so that the light may reach the portion that should not be cured and may be cured. . In such a case, when a light absorber is blended in the photocurable resin composition, the curability of the portion to be cured is not hindered, and a small amount of light in the portion that should not be cured. Only curing can be suppressed.

  As a solvent used when preparing the varnish containing the said photocurable resin composition, it is preferable to contain the solvent whose boiling point is 120 degreeC or more like propylene glycol monomethyl ether acetate, for example. Since such a solvent does not volatilize at room temperature, a change in viscosity of the varnish can be suppressed. Therefore, variation in the coating amount due to the volatilization of the solvent at the time of coating at room temperature can be suppressed, and the required amount of resin can be applied accurately. Moreover, the storage stability of the varnish is also improved.

  The varnish preferably has a viscosity at room temperature of 100 to 500 mPa · s. In such a case, the varnish can be satisfactorily applied to the substrate surface at room temperature, and precise control of the application amount is facilitated.

  Moreover, it is preferable that the said photocurable resin composition contains 1-10 mass% of phenoxy resins. By mix | blending a phenoxy resin in such a range, a softness | flexibility can be provided to the resin structure obtained without impairing developability. Thereby, crack resistance can be improved. Also, the adhesion of the resin structure to the substrate can be enhanced. Further, since the tackiness of the uncured resin layer is reduced, the phenomenon that the uncured resin layer sticks to a flat plate or a contact-type mask can be suppressed.

  A method for manufacturing a photoelectric circuit board according to one aspect of the present invention uses a silicon substrate having a groove for forming an optical waveguide having a silicon oxide film formed on a surface thereof; an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature Use a photocurable resin composition for a core having a predetermined refractive index that is solid at room temperature and melted or softened by heating, which is obtained by mixing at a predetermined ratio and further by adding a photopolymerization initiator; Steps (e) to (e): (a1) After coating the core photocurable resin composition varnish so as to cover the groove for forming the optical waveguide on the surface of the silicon substrate, the solvent in the varnish is volatilized and removed. A resin layer forming step of forming a solid core photocurable resin layer by heating, (b1) the core photocurable resin heated to a temperature at which the core photocurable resin layer is melted or softened On the surface of the layer The plate is pressed into contact with the surface of the silicon substrate in parallel, cooled to a temperature at which the photocurable resin composition for the core solidifies while maintaining the pressed contact state, and flattened by separating the plate. A planarization step of forming an uncured core resin layer having a surface; (c1) masking and exposing a region excluding the region where the core is formed from the flat surface side of the uncured core resin layer; A curing step for selectively curing only, (d1) a development step for developing and removing the unexposed portion of the selectively cured uncured core resin layer, and (e) a refractive index lower than the refractive index of the core. A clad forming step of forming a clad by covering the core with a resin having a ratio. In a silicon substrate having a groove for forming an optical waveguide having a silicon oxide film formed on the surface, the silicon oxide film can be used as a lower cladding in the optical waveguide. Therefore, since the step of forming the lower clad with resin can be omitted, after applying the photocurable resin composition for forming the core on the surface of the silicon substrate having the groove for forming the optical waveguide, and flattening the upper surface, By selectively exposing only the core forming portion, it is possible to easily form a core having excellent height accuracy. Therefore, according to the said manufacturing method, the photoelectric circuit board which has an optical waveguide excellent in height accuracy can be produced easily.

  As the step (e), the epoxy resin that is solid at room temperature and the epoxy resin that is liquid at room temperature are blended at a predetermined ratio, and further melted or softened by heating obtained by blending a photopolymerization initiator. Using a solid photocurable resin composition for cladding having a refractive index lower than that of the core; steps (a2) to (d2) below: (a2) covering the core on the silicon substrate surface A resin layer forming step of forming a solid photocurable resin layer for clad by volatilizing and removing the solvent in the varnish after applying the varnish of the photocurable resin composition for clad as described above, (b2) With the clad photocurable resin layer heated to a temperature at which the clad photocurable resin layer is melted or softened, the flat plate is pressed and brought into contact with the surface of the clad photocurable resin layer while being parallel to the substrate surface. (C2) a flattening step of forming an uncured clad resin layer having a flat surface by cooling the clad photocurable resin composition to a temperature at which the clad photocurable resin composition is solidified while maintaining the contact state, and separating the flat plate; ) A curing step of selectively curing only the region by masking a portion excluding the region where the cladding is formed from the flat surface side of the uncured cladding resin layer, and (d2) selectively cured uncured It is preferable to perform a development step of forming a clad by developing and removing an unexposed portion of the clad resin layer. According to such a method, it is possible to form a highly accurate clad in which thickness and surface flatness are controlled.

  According to the present invention, a fine resin structure having a uniform height can be formed on the surface of a substrate having a step such as a groove on the surface.

FIG. 1 is an explanatory view illustrating a photoelectric circuit substrate having an optical waveguide obtained by the manufacturing method of one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view for explaining a process of manufacturing an optical waveguide, which is an embodiment of the manufacturing method of the present invention. FIG. 3 is a schematic cross-sectional view for explaining a process of manufacturing the core portion of the optical waveguide in Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 4 is a schematic cross-sectional view for explaining a process of manufacturing the clad portion of the optical waveguide in Examples 4 to 8 and Comparative Examples 4 to 6.

  First, the photocurable resin composition used in the present invention will be described.

  The photocurable resin composition used in the present invention contains a solid epoxy resin and a liquid epoxy resin in a predetermined ratio, further contains a photopolymerization initiator, and is solid at room temperature that is melted or softened by heating. It is a photocurable resin composition.

  Such a photocurable resin composition can be obtained by dissolving a solid epoxy resin and a liquid epoxy resin in a solvent at a predetermined blending ratio, and further drying a varnish obtained by adding a photopolymerization initiator.

  Epoxy resins may be liquid or solid at room temperature depending on the type and molecular weight (repeating unit). In the present invention, an epoxy resin that is liquid at room temperature and an epoxy resin that is solid at room temperature are blended in a solvent at a predetermined blending ratio, thereby adjusting the melting or softening temperature, the surface tackiness after drying, and the like. be able to. Specifically, the blending ratio of the liquid epoxy resin can be increased to reduce the viscosity of the varnish, or the fluidity during heating can be increased. In addition, the blending ratio of the solid epoxy resin can be increased to reduce tackiness, or to improve the mold release property and increase work efficiency.

  The type of epoxy resin that is solid or liquid at normal temperature is not particularly limited as long as it is solid or liquid at normal temperature. In addition, the number of epoxy groups of each epoxy resin is not particularly limited as long as it is 2 or more per molecule.

  The mixing ratio of the liquid epoxy resin and the solid epoxy resin is appropriately adjusted according to the purpose and the type of the epoxy resin to be combined. Specifically, for example, solid epoxy resin / liquid epoxy resin = 90/10 to 65/35 A range of (mass ratio) is preferable.

  Specific examples of the solid or liquid epoxy resin are solid or liquid, for example, bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; phenol novolac type epoxy resin Novolak type epoxy resins such as cresol novolac type epoxy resin and bisphenol A novolak type epoxy resin; epoxy resins having aromatic rings such as naphthalene skeleton type epoxy resin, and alicyclic epoxy resins such as hydrogenated bisphenol type epoxy resin Can be mentioned.

  Moreover, when manufacturing the fine resin structure used for an optical use, the transparent photocurable resin composition formed by mix | blending a transparent solid epoxy resin and a transparent liquid epoxy resin is used. Among such combinations, for example, a combination of a bisphenol-type epoxy resin having a high refractive index by having an aromatic ring and an alicyclic epoxy resin having a relatively low refractive index can be obtained by adjusting the blending ratio. This is preferable because the refractive index can be freely adjusted. For example, in the formation of an optical waveguide, the ratio of bisphenol-type epoxy resin having a high refractive index is increased for forming the core part, and the ratio of alicyclic epoxy resin having a low refractive index is increased for forming the cladding part. preferable.

The photopolymerization initiator blended in the photocurable resin composition is a polymerization initiator for causing ring-opening self-polymerization of the epoxy group of the epoxy resin by light irradiation. Specific examples thereof include aryldiazonium salts having, for example, PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , SbCl ₆ ²⁻ , BF ₄ ⁻ , SnCl ₆ ⁻ , FeCl ₄ ⁻ , BiCl ₅ ^{2− and the} like as anions. In addition, as anions, PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , SbF ₆ ⁻ , SbCl ₆ ²⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , FSO ₃ ⁻ , F ₂ PO ₂ ⁻ , Diaryl iodonium salts having B (C ₆ F ₅ ) ₄ ⁻ , triarylsulfonium salts, triarylselenonium salts, and dialkylphenacyl having PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ^{− and the} like as anions Sulfonium salt, dialkyl-4-hydroxylphenylsulfonium salt, and α-hydroxymethylbenzoy Sulfonate esters, N-hydroxyimide sulfonate, sulfonate esters such as α-sulfonyloxyketone and β-sulfonyloxyketone, iron allene compounds, silanol-aluminum complexes, o-nitrobenzyl-triphenyl ether, etc. It is done. In addition, as commercial products, trade names “Adekaoptomer SP-170” and “Adekaoptomer SP-150” manufactured by Adeka Corporation, and product names “CPI-101A” and “CPI-200K” manufactured by San Apro Corporation are also preferable. Used.

  In the photocurable resin composition used in the present invention, as a component other than the above, various additives such as an exposure light absorber, a coupling agent, a flow modifier, and the like within a range not impairing the object of the present invention. A lubricant, a colorant and the like can be added as necessary.

  As the exposure light absorber, an absorber (such as an ultraviolet absorber) having a high absorption rate with respect to the wavelength of exposure light (such as ultraviolet rays) used for photocuring is preferable. As an ultraviolet absorber, an epoxy resin having a carbon conjugated double bond having a high absorptance with respect to an exposure light wavelength (eg, 365 nm) (an epoxy resin having a naphthalene skeleton, an epoxy resin having a biphenyl skeleton, a phenol novolac epoxy) Resin, a cresol novolac type epoxy resin, an oxetane resin having an aromatic ring, etc.) and various other known UV absorbers and various UV-absorbing sensitizers. As the commercially available product, for example, trade name “Adekaoptomer SP-100” manufactured by Adeka Company and the like can be mentioned.

  Specific examples of the ultraviolet absorber include, for example, a benzophenone ultraviolet absorber, an acetophenone ultraviolet absorber, an acenaphthene ultraviolet absorber, a 2-acenaphthone ultraviolet absorber, a benzotriazole ultraviolet absorber, and a phenyltriazine ultraviolet absorber. Perylene ultraviolet absorbers, anthracene ultraviolet absorbers, acridine ultraviolet absorbers such as acridine orange, phenothiazine ultraviolet absorbers, 2,4-diethylthioxanthone, and salicylic acid ultraviolet absorbers. Moreover, as the commercial item, the brand name "TINUVIN329" (benzotriazole type ultraviolet absorber) by the Ciba Japan company etc. are mentioned, for example.

  In particular, the photocurable resin composition preferably contains 0.01 to 1% by mass of a light absorber that absorbs light to be exposed. When the photocurable resin composition is applied to the stepped portion of the substrate and exposed, the exposure light is diffusely reflected at the stepped portion, so that the light may reach the portion that should not be cured and may be cured. . In such a case, when a light absorber is blended in the photocurable resin composition, the curability of the portion to be cured, which is exposed to strong light, is not hindered, and a small amount of the portion that should not be cured. Only curing by light can be suppressed. If the blending ratio of the light absorber is too high, the exposure light may reduce the deep curability of the portion that should be cured, and if it is too small, the effect of inhibiting the curing of the portion that should not be cured is ineffective. There is a tendency to become sufficient.

  It is preferable that a coupling agent such as a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent is further added to the photocurable resin composition. By blending the coupling agent, the adhesion between the substrate surface and the resin structure is improved. Specific examples of such a coupling agent include, for example, trade name “KBM-403” (silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd. As a compounding ratio of a coupling agent, it is preferable that it is about 0.1-5 mass% in the photocurable resin composition whole quantity.

  It is preferable that a phenoxy resin is further added to the photocurable resin composition. The phenoxy resin is a polyhydroxy ether having an epoxy group in a molecule synthesized from, for example, a bisphenol type epoxy resin and epichlorohydrin, and is a thermoplastic resin that can be cross-linked by a hydroxyl group in the molecule. When an appropriate amount of phenoxy resin is blended in the photocurable resin composition, it is preferable from the viewpoint of improving the releasability from a flat plate or a contact-type photomask by reducing tackiness. Further, the brittleness of the cured resin is reduced, so that the crack resistance is improved, and further, the adhesion of the resulting fine resin structure to the substrate can be improved.

  The molecular weight of the phenoxy resin is preferably in the range of about 40,000 to 100,000, more preferably about 50,000 to 80,000 in terms of weight average molecular weight (Mw). Specific examples of such a phenoxy resin include, for example, a trade name “Epicoat 1256” manufactured by Japan Epoxy Resin Co., Ltd. (Mw approximately 50,000 for bisphenol A type), and a trade name “Phenotote YP-50” manufactured by Tohto Kasei Co., Ltd. (A bisphenol A type having an Mw of about 70,000).

  The blending ratio of the phenoxy resin is preferably 1 to 10% by mass in the photocurable resin composition. When the blending ratio of the phenoxy resin is too high, the fluidity at the time of flattening the resin composition is lowered, resulting in insufficient flattening, or after-curing to increase the crosslinking density after exposure. In addition, the cured product tends to undergo thermal deformation. Furthermore, there is a tendency to reduce the pattern accuracy during development.

  The photocurable resin composition is obtained by dissolving and mixing a solid epoxy resin, a liquid epoxy resin, a photopolymerization initiator, and an exposure light absorber, a phenoxy resin, a coupling agent, and the like used as necessary in a solvent. The obtained resin varnish is dried and the solvent is removed by volatilization.

  As the solvent for forming the resin varnish, a solvent capable of dissolving a solid epoxy resin, a liquid epoxy resin, a photopolymerization initiator, and a phenoxy resin blended as required is preferably used. Examples of such a solvent include methyl ethyl ketone (MEK), cyclohexanone, propylene glycol monomethyl ether acetate (PGMEA) and the like. These may be used alone or in combination of two or more.

  In addition, when apply | coating a resin varnish on a board | substrate, a solvent volatilizes during application | coating and the viscosity of a varnish may change. In such a case, the amount of varnish dripping varies, and the thickness of the formed fine resin structure becomes non-uniform. Therefore, it is preferable to use a solvent having a high boiling point and hardly volatilizing at room temperature. As specific examples of such a solvent, for example, cyclohexanone (boiling point: 156 ° C.) and PGMEA (boiling point: 146 ° C.) are particularly preferable.

  The mixing ratio of the photocurable resin component and the solvent in the varnish is not particularly limited, and is not particularly limited as long as it can be adjusted to a viscosity (for example, 100 to 500 mPa · s) suitable for application on the substrate in the varnish state. Specifically, in consideration of volume reduction during solvent volatilization, it is preferable to adjust the mixing ratio so that a desired viscosity is obtained before and after the mass ratio of 1: 1.

  Next, as a specific example of the resin structure formed on the substrate having a step on the surface using the varnish prepared as described above, the light is applied to the substrate surface having a groove for forming an optical waveguide. A method of forming a waveguide will be described with reference to the drawings.

  FIG. 1A is a plan view of a photoelectric circuit substrate 1 having an optical waveguide 4 obtained by the manufacturing method of the present embodiment, and FIG. 1B is a cross-sectional view taken along the line BB in FIG. FIG.1 (c) is CC sectional view taken on the line of Fig.1 (a).

  1A to 1C, reference numeral 2 denotes a silicon substrate, and a groove 3 in which an optical waveguide 4 is formed is formed in the silicon substrate 2. 4a is a core part which comprises the optical waveguide 4, and 4b is a clad part which comprises the optical waveguide. A silicon oxide film 5 is formed on the surface of the silicon substrate 2. A 45 ° mirror 6 is formed at the end of the groove 3.

  An electrical circuit (not shown) is formed on the surface of the silicon substrate 2 (more precisely, on the silicon oxide film 5 formed over the entire surface). In addition, the 45 ° mirror portion 6 is formed with a reflective film for increasing the light reflectance. The reflective film is formed by vapor deposition of gold or aluminum. Note that a reflective film may not be formed depending on the wavelength of light used.

  In this photoelectric circuit substrate 1, the light propagating through the optical waveguide 4 as shown by the broken line arrow in FIG. As shown in FIG. 1 (b), light incident on a photoelectric conversion element (not shown) mounted on the surface or light emitted from the photoelectric conversion element (not shown) is converted by the 45 ° mirror section 6 into an optical axis by 90 °. ) Is propagated through the optical waveguide 4 in the direction opposite to the broken-line arrow.

  The manufacturing process of such a photoelectric circuit board 1 will be described with reference to schematic cross-sectional views shown in FIGS.

  First, as shown in FIG. 2A, a silicon substrate 2 on which a groove 3 and a silicon oxide film 5 are formed is prepared. In the formation of the optical waveguide of this embodiment, the silicon oxide film 5 having a refractive index lower than that of the core 4a serves as the lower cladding of the optical waveguide. Therefore, it is possible to omit a separate step of forming the lower clad with the resin material.

  The groove 3 formed in the silicon substrate 2 is formed by anisotropically etching the silicon substrate with, for example, a potassium hydroxide aqueous solution added with alcohol or a tetramethylammonium hydroxide (TMAH) aqueous solution added with a surfactant. Is done. Although not shown in FIGS. 2A to 2H, a 45 ° mirror portion 6 as shown in FIG. 1B is formed at the end of the groove 3 in the direction of paper penetration.

  In the manufacture of the photoelectric circuit substrate 1, a resin varnish containing a photocurable resin composition for the core is prepared, and the resin varnish is applied to the grooves 3 formed in the silicon substrate 2. As described above, a dispenser or the like is used for applying the resin varnish.

  Next, the applied resin varnish is heated in a temperature range in which the photopolymerization initiator and other additives in the resin composition are not deactivated, and the solvent is evaporated and dried, as shown in FIG. Thus, the uncured resin layer 8 made of a solid photocurable resin composition is formed in the groove 3.

  Subsequently, as shown in FIG. 2B, after the uncured resin layer 8 is heated and melted, the lower surface is pressed from above with a predetermined pressing pressure with a flat plate 7 whose surface is smoothly adjusted to the micron order, and constant. By maintaining the time, the uncured resin layer 8 is flattened while being adjusted to a desired thickness. At this time, the flat plate 7 is supported by the press so as to maintain a parallel state with the surface of the silicon substrate 2. Thereafter, the resin is re-solidified by cooling to room temperature while maintaining the press pressure constant. Then, by separating the flat plate 7, as shown in FIG. 2C, an uncured resin layer 8a having a flattened surface is obtained.

  As the flatness of the surface of the flat plate, the surface roughness (Ra) is preferably 1 μm or less, and more preferably 0.1 μm or less.

  Further, the material of the flat plate is not particularly limited, such as a metal, an inorganic material, or a resin, but it is preferable to use a silicon wafer because it is particularly excellent in surface smoothness. The surface of the flat plate is preferably treated with a release agent. Specific examples of the release agent include fluorine-based resins such as trade name “Cytop” manufactured by Asahi Glass Co., Ltd. and trade name “Novec” manufactured by Sumitomo 3M.

  In this manufacturing method, the upper surface of the uncured resin layer 8a can be flattened by such a flattening process. And by this process, the height of the core 4a obtained by a subsequent process can be made uniform in the whole path | route of an optical waveguide.

  Next, as shown in FIG. 2D, the flattened uncured resin layer 8a is masked with a photomask 9, and ultraviolet rays (UV) are exposed from the openings 9a of the mask 9, thereby opening the mask openings. The portion corresponding to 9a is selectively photocured. By this selective exposure, the outline of the core 4a is defined. In order to ensure the curing, for example, a heat curing process called PEB (Post Exposure Bake) in which heat treatment is performed at about 150 ° C. for about 15 minutes may be performed.

  Thereafter, as shown in FIG. 2 (e), the resin layer after the selective curing treatment is developed, and the uncured resin in the unexposed portion is washed and removed, thereby being a fine resin structure composed only of a cured resin. An optical waveguide core 4a is formed. The cross-sectional shape of the core 4a is a fine one having a height of about 20 to 80 μm and a width of about 20 to 80 μm, for example.

  For the development, for example, various solvent-based developers and the like that remove unexposed uncured portions by a treatment such as ultrasonic treatment by immersing in a solution containing a surfactant can be used without any particular limitation.

  The core 4a thus formed is then covered with a clad 4b.

  For the formation of the clad 4b, a method similar to the method for forming the core 4a described above is used except that a photocurable resin composition having a refractive index and the like adjusted for the clad is used.

  First, as shown in FIG. 2 (f), a resin varnish prepared for cladding is applied to the groove 3 of the silicon substrate 2 on which the core 4a is formed, and the solvent is evaporated and dried to thereby remove the core in the groove 3 An uncured resin layer 10 made of a photocurable resin composition is formed so as to cover 4a.

  Next, as shown in FIG. 2 (g), after the uncured resin layer 10 is heated and melted, the flat plate 7 supported by the press so as to be in parallel with the silicon substrate 2 is subjected to a predetermined press pressure from above. The uncured resin layer 10 is spread to a desired thickness by pressing and holding for a certain time. Thereafter, the resin is solidified by cooling to room temperature while maintaining the pressing pressure constant, and then the flat plate is separated, thereby uncured for the flattened clad as shown in FIG. The resin layer 10a is obtained.

  Next, as shown in FIG. 2I, the flattened uncured resin layer 10a is masked with a photomask 11, and ultraviolet rays are exposed from the openings 11a of the photomask 11, thereby corresponding to the openings 11a. The portion to be selectively photocured. You may heat cure as needed.

  Then, the resin layer after the selective curing treatment is developed and the uncured resin in the unexposed portion is washed and removed, thereby forming the optical waveguide cladding 10b as a resin structure as shown in FIG. 2 (j). . By this development process, the clad 10b is formed only in the region where the optical waveguide 4 of the silicon substrate 2 is formed, and the uncured resin remaining in the other regions is removed.

  Through the steps described above, the photoelectric circuit substrate 1 having the optical waveguide 4 as shown in FIG. 1 is obtained. The core 4a constituting the optical waveguide 4 formed on the photoelectric circuit substrate 1 thus obtained is flat on the order of microns in the entire path of the optical waveguide 4. Therefore, the propagation loss is smaller than that of an optical waveguide having an unflattened core. Further, since the silicon oxide film formed on the silicon substrate surface can be used as the lower clad, the formation of the lower clad can be omitted. Therefore, the production cost can be reduced.

  In addition, as one embodiment of the present invention, the production of an optical waveguide as a fine structure has been described in detail. However, the production method of the present invention is not limited to the production of an optical waveguide, and a resin structure having a certain thickness on a substrate surface with a step. It can be used for various purposes to form a body. Even in the case where a plurality of fine structures are individually formed in a plurality of grooves formed on a surface having a relatively large area, the above-described planarization process can achieve a uniform height in all the fine structures. Can be added.

  Specific examples of the fine resin structure include, besides an optical waveguide, a fine flow path such as a biochip, a polymer spring structure, an optical lens using binary optics, a diffraction grating, and the like.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited at all by the Example.

  First, the raw materials used in this example are summarized below.

(Solid epoxy resin)
-Alicyclic epoxy resin: Trade name “EHPE3150” manufactured by Daicel Chemical Industries, Ltd.
・ Bisphenol A type epoxy resin: Product name “JER1006FS” manufactured by Japan Epoxy Resin Co., Ltd.
・ Hydrogenated bisphenol A type epoxy resin: trade name “YX8040” manufactured by Japan Epoxy Resin Co., Ltd.
(Liquid epoxy resin)
Alicyclic epoxy resin: trade name “Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.
・ Bisphenol A type epoxy resin: Product name “EPICLON 850-S” manufactured by DIC Corporation
・ Hydrogenated bisphenol A epoxy resin: trade name “YX8000” manufactured by Japan Epoxy Resin Co., Ltd.
(Phenoxy resin)
・ Methyl ethyl ketone dissolved product of phenoxy resin: Trade name “Phenotote YP-50EK35” manufactured by Tohto Kasei Co., Ltd.
(Photopolymerization initiator)
Triarylsulfonium salt-based cationic polymerization initiator: trade name “Adekaoptomer SP-170” manufactured by Adeka Company
(UV absorber)
UV sensitizer: trade name “ADEKA OPTMER SP-100” manufactured by ADEKA
(Coupling agent)
Silane coupling agent: trade name “KBM-403” manufactured by Shin-Etsu Chemical Co., Ltd.
(solvent)
-Propylene glycol monomethyl ether acetate (PGMEA): General reagent-Methyl ethyl ketone (MEK): General reagent Moreover, the preparation method of the silicon substrate in which the silicon oxide film which has a groove | channel was formed is demonstrated below.
(Preparation method of silicon substrate having a silicon oxide film having grooves)
An anisotropic etching process is performed on a silicon substrate having a diameter of 1 inch having a patterned opening and a silicon oxide film having a thickness of 1 μm, whereby a depth of 40 μm, a groove bottom width of 60 μm, a groove opening width of 140 μm, 1000 grooves having a length of 5 mm and a side surface angle of 45 ° were formed. The anisotropic etching was performed by the following method. First, an etchant in which 0.5 L of isopropyl alcohol was mixed with 4 L of a 40 mass% potassium hydroxide aqueous solution was prepared. Then, the silicon substrate was immersed in an etchant heated to 80 ° C. for 1 hour, and then the oxide film mask was dissolved with hydrofluoric acid.

  Next, the silicon substrate with the groove formed was placed in a thermal oxidation furnace and heated in an oxygen atmosphere to form a 2 μm thick silicon oxide film on the entire surface. Then, the silicon substrate on which the silicon oxide film was formed was surface-treated in oxygen plasma.

[Examples 1-3 and Comparative Examples 1-3: Evaluation of Core]
Examples 1-3 and Comparative Examples 1-3 prepare each photocurable resin composition according to the compounding composition of Table 1, and it explains in detail below using the obtained photocurable resin composition. A core was formed. Then, the characteristics of the core alone were evaluated without forming a clad. The evaluation methods in Examples 1 to 3 and Comparative Examples 1 to 3 will be described with reference to FIG.

  First, a resin varnish of a photocurable resin composition was prepared according to the composition shown in Table 1. To prepare the resin varnish, first weigh out the solvent at room temperature, then add a predetermined amount of solid epoxy resin, liquid epoxy resin, and phenoxy resin in this order, and stir and mix while heating to 50 ° C in a sealed container. And dissolved. And after cooling to normal temperature, the predetermined amount photoinitiator, the ultraviolet absorber (ultraviolet sensitizer), and the coupling agent were added, and it stirred and mixed at 50 degreeC in the airtight container.

  And the resin varnish of the photocurable resin composition 8 prepared in each groove | channel of the silicon substrate 2 in which the groove | channel 3 was formed was dripped with the dispenser. In addition, the dripping amount dripped the varnish more than twice the groove volume with respect to each groove | channel. And the photocurable resin layer 8 was formed by drying a resin varnish by heating on 130 degreeC and the conditions for 60 minutes using a hotplate (FIG. 3 (a)).

  Next, the silicon substrate 2 on which the photocurable resin layer 8 was formed was sucked and held on the lower stage of the press device. Then, a silicon wafer flat plate 7 having a surface roughness Ra of 1 nm or less that was subjected to the mold release process was adsorbed to the upper stage of the press apparatus. Then, the upper stage and the lower stage were heated to about 130 ° C. to melt the photocurable resin layer, and flattened by pressurizing with a flat plate 7 at a pressure of 0.6 to 0.7 MPa for 3 minutes (FIG. 3). (B)). And after cooling to room temperature (25 degreeC), the upper and lower stages were opened. And the flat plate 7 was peeled from the silicon substrate 2 with which the photocurable resin layer was formed (FIG.3 (c)).

Next, the photocurable resin layer was selectively photocured by ultraviolet patterning using the photomask 9 having the core pattern opening 9a (FIG. 3D). For the exposure, ultraviolet light using a high-pressure mercury lamp as a light source (with a wavelength of 365 nm selected by a filter) was used, and exposure was performed at an irradiation amount of 1000 mJ / cm ² . And in order to accelerate | stimulate hardening and to further improve the adhesiveness of a photocurable resin layer and a silicon substrate, the baking process for 15 minutes was performed at 120 degreeC.

  Then, after cooling to room temperature, the silicon substrate is immersed in a surfactant solution (trade name “Pine Alpha ST-100SX” manufactured by Arakawa Chemical Co., Ltd.) heated to about 55 ° C. and ultrasonically cleaned. The uncured portion of the photocurable resin layer was removed (FIG. 3 (e)). The silicon substrate was further washed with pure water and then heated at 150 ° C. for 15 minutes to remove moisture. In this way, the core 4a of the optical waveguide was formed.

The following evaluation tests were performed in each process in the manufacturing process.
(Observation of the state of the photocurable resin composition at room temperature (25 ° C.))
The state of the photocurable resin composition obtained by drying and removing the solvent in the prepared resin varnish was observed to determine whether it was solid or liquid.

(Tackiness of photocurable resin composition)
The surface of the photocurable resin layer was touched with a finger and judged according to the following criteria. The tackiness is an index of releasability and also an index for indirectly grasping the temperature (solidification point) at which the resin liquefied by heating is re-solidified.
A: When a finger is pressed against the surface of the photocurable resin layer, there is no stickiness and no fingerprint is attached.
○: When a finger is pressed against the surface of the photocurable resin layer, a trace of a fingerprint is slightly attached.
Δ: A finger is pressed against the surface of the photocurable resin layer, and when it is released, it feels sticky but there is no separation of the resin.
X: When the finger was pressed against the surface of the photocurable resin layer, fingerprint marks remained clearly and the resin adhered to the finger.

(Flatness)
The height variation of the core surface formed from the silicon substrate surface was measured. In addition, the measurement of height was performed at 10 random places and judged according to the following criteria. In addition, KLA-Tencor's contact type step gauge Alphastep AS-500 was used for the measurement.
(Double-circle): The range of the dispersion | variation in the height of the core surface of ten places was less than 2 micrometers.
A: The range of variations in the height of the core surface at 10 locations was in the range of 2 to 3 μm.
(Triangle | delta): The range of the dispersion | variation in the height of the core surface of ten places was the range of 3-5 micrometers.
X: The range of variation in height of the core surface at 10 locations was more than 5 μm.

(Crack resistance / adhesion)
The silicon substrate on which the core of the optical waveguide was formed was cut with a dicing saw so as to cross the optical waveguide, and the cut surface was observed and judged according to the following criteria.
A: No cracks were observed in the core, and no separation of the optical waveguide from the silicon substrate was observed.
○: Slight cracks or peeling was observed in the core.
Δ: Cracks or peeling was observed in about half of the cores.
X: Cracks and peeling were observed in almost all the cores.

(Flowability)
When the silicon wafer (flat plate) was peeled from the silicon substrate, the thickness of the photocurable resin composition overflowing from the groove 3 to the surface outside the groove 3 of the silicon substrate was measured and evaluated according to the following criteria.
A: The thickness was less than 6 μm.
A: The thickness was 6 to 10 μm.
X: The thickness was more than 10 μm.

(Core developability)
The cured state of the cured product after the development processing of the core was determined according to the following criteria.
(Double-circle): Only the selective exposure area | region did not collapse at all, the core formation part was hardened as planned, and the unexposed part was removed correctly.
○: A part of the corner of the core was slightly rounded.
(Triangle | delta): The extra burr | flash and the unnecessary hardening part were formed from the outline of the core.
X: Reflection of selective curing was not seen.

  The results are shown in Table 1.

  From the results of Table 1, in the cores formed using the photocurable resin compositions for cores of Examples 1 to 3, there is little variation in the height of the core surface, and adhesion, flowability, and developability. The balance was also excellent. On the other hand, when the core was formed using the photocurable resin composition of Comparative Example 1 that did not contain a liquid epoxy resin, almost all the cores were cracked and peeled. Further, in Comparative Examples 2 and 3 in which a phenoxy resin capable of imparting flexibility to the cured product was added in order to eliminate the occurrence of cracks and peeling in Comparative Example 1, the resin viscosity was rapidly increased by the blending of the phenoxy resin. Thus, even if the flattening step was performed, the flattening could not be sufficiently performed.

[Examples 4 to 8 and Comparative Examples 4 to 6: Evaluation of cladding]
Examples 4-8 and Comparative Examples 4-6 prepare each photocurable resin composition according to the compounding composition of Table 2, and it explains in detail below using the obtained photocurable resin composition. A clad was formed. The characteristics of the clad alone were evaluated without forming the core. The evaluation methods in Examples 4 to 8 and Comparative Examples 4 to 6 will be described with reference to FIG.

  First, a resin varnish of a photocurable resin composition was prepared according to the composition shown in Table 2. The resin varnish was prepared in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3.

  And the resin varnish of the photocurable resin composition was dripped at each groove | channel of the silicon substrate 2 in which the groove | channel 3 was formed with the dispenser. In addition, the dripping amount dripped the varnish more than twice the groove volume with respect to each groove | channel. And the photocurable resin layer 10 was formed by drying a resin varnish by heating on 130 degreeC and the conditions for 60 minutes using a hotplate (FIG. 4 (a)).

  Next, the silicon substrate 2 on which the photocurable resin layer 10 was formed was sucked and held on the lower stage of the press apparatus. Then, a silicon wafer (flat plate) 7 having a surface roughness Ra of 1 nm or less that was subjected to the mold release process was adsorbed on the upper stage of the press apparatus. Then, the upper stage and the lower stage are heated to about 130 ° C. to melt the photocurable resin layer, and flattened by applying pressure to the silicon wafer 7 at a pressure of 0.6 to 0.7 MPa for 3 minutes (FIG. 4 (b)). And after cooling to room temperature (25 degreeC), the upper and lower stages were opened. Then, the silicon wafer 7 was peeled from the silicon substrate 2 on which the photocurable resin layer was formed (FIG. 4C).

Next, the photocurable resin layer was selectively photocured by ultraviolet patterning using the photomask 11 having the opening 11a of the clad pattern (FIG. 4D). For the exposure, ultraviolet light using a high-pressure mercury lamp as a light source (with a wavelength of 365 nm selected by a filter) was used, and exposure was performed at an irradiation amount of 1500 mJ / cm ² . And in order to accelerate | stimulate hardening and to further improve the adhesiveness of a photocurable resin layer and a silicon substrate, the baking process for 15 minutes was performed at 120 degreeC.

  Then, after cooling to room temperature, the silicon substrate is immersed in a surfactant solution (trade name “Pine Alpha ST-100SX” manufactured by Arakawa Chemical Co., Ltd.) heated to about 55 ° C. and ultrasonically cleaned. The uncured portion of the photocurable resin layer was removed (FIG. 4 (e)). The silicon substrate was further washed with pure water and then heated at 150 ° C. for 15 minutes to remove moisture. Thus, the clad 10b of the optical waveguide was formed.

  And the characteristic of the photocurable resin composition was evaluated by the method similar to Examples 1-3 and Comparative Examples 1-3. The formed clad 10b was evaluated as follows.

(Flatness)
The variation in the height of the clad surface formed from the silicon substrate surface was measured. In addition, the measurement of height was performed at 10 random places and judged according to the following criteria. In addition, KLA-Tencor's contact type step gauge Alphastep AS-500 was used for the measurement.
(Double-circle): The range of the dispersion | variation in the height of the clad surface of ten places was less than 2 micrometers.
A: The range of variation in height of the clad surface at 10 locations was in the range of 2 to 3 μm.
(Triangle | delta): The range of the dispersion | variation in the height of the clad surface of ten places was the range of 3-5 micrometers.
X: The range of variation in height of the clad surface at 10 locations was more than 5 μm.

(Crack resistance / adhesion)
The silicon substrate on which the clad of the optical waveguide was formed was cut with a dicing saw so as to cross the optical waveguide, and the cut surface was observed and judged according to the following criteria.
A: No cracks were observed in the cladding, and no optical waveguide was peeled off from the silicon substrate.
○: Slight cracks or peeling was observed in the cladding.
Δ: Cracks or peeling was observed in about half of the clad.
X: Cracks and peeling were observed in almost all clads.

(Flowability)
When the silicon wafer was peeled from the silicon substrate, the thickness of the photocurable resin composition overflowing from the groove to the surface outside the groove of the silicon substrate was measured and evaluated according to the following criteria.
A: The thickness was less than 6 μm.
A: The thickness was 6 to 10 μm.
X: The thickness was more than 10 μm.

(Clad developability)
The cured state of the cured product after the development processing of the clad was determined according to the following criteria.
(Double-circle): Only the selective exposure area | region did not collapse at all, but the clad formation part was hardened as planned, and the unexposed part was removed correctly.
○: A part of the corner of the clad was slightly rounded.
(Triangle | delta): The extra burr | flash and the unnecessary hardening part were formed from the outline of the clad.
X: Reflection of selective curing was not seen.

  The results are shown in Table 2.

  From the results shown in Table 2, in the clads formed using the photocurable resin compositions for clads of Examples 4 to 8, there is little variation in the height of the clad surface, and adhesion, flowability, and developability. The balance was also excellent. On the other hand, when a clad was formed using the photocurable resin composition of Comparative Example 4 that did not contain a liquid epoxy resin, cracks and peeling were observed in almost all of the clad. Moreover, in Comparative Examples 5 and 6 in which a phenoxy resin capable of imparting flexibility to the cured product was added in order to eliminate the occurrence of cracks and peeling in Comparative Example 4, the resin viscosity was rapidly increased by blending the phenoxy resin. Thus, even if the flattening step was performed, the flattening could not be sufficiently performed. Moreover, in the developability evaluation of Comparative Examples 4 to 6, the developability of all clads deteriorated due to unnecessary curing by the reflected exposure light from the groove inclined surface.

  From the above results, the photocurable resin compositions of Examples 1 to 3 were used as the core material, and the photocurable resin compositions of Examples 4 to 8 were used as the cladding material, and the above-described silicon having a groove On the silicon substrate on which the oxide film is formed, the core and the clad are formed in the groove in this order by the process shown in FIG. 2, the core width is 40 μm, the core height is 45 μm, and both ends are 45 ° silicon surfaces (mirrors). When manufacturing optical waveguides terminated with a low loss with excellent flatness, adhesion, flowability, and developability in a process that has good dropping properties with a dispenser and good peeling properties with a flat plate during flattening The optical waveguide was successfully manufactured.

DESCRIPTION OF SYMBOLS 1 Optoelectronic circuit board 2 Silicon substrate 3 Groove 4 Optical waveguide 4a Core 4b Clad 5 Silicon oxide film 6 Mirror part 8, 10 Uncured resin layers 8a, 10a Flattened uncured resin layers 9, 11 Mask 9a, 11a Mask opening Part

Claims (11)

A method for producing a fine resin structure for forming a fine resin structure on a substrate having a step on the surface,
A solid photocuring resin composition at room temperature that melts or softens by heating, which is obtained by blending epoxy resin that is solid at normal temperature and epoxy resin that is liquid at normal temperature in a predetermined ratio, and further by adding a photopolymerization initiator. Using objects;
The following steps (a) to (d):
(A) a resin layer forming step of forming a solid photocurable resin layer by volatilizing and removing the solvent in the varnish after coating the varnish of the photocurable resin composition on the substrate surface;
(B) In a state where the photocurable resin layer is heated to a temperature at which the photocurable resin layer is melted or softened, the flat plate is brought into press contact with the surface of the photocurable resin layer while being parallel to the substrate surface. Cooling to a temperature at which the photocurable resin composition is solidified while being held, and a flattening step of forming a primary molded body having a flat surface by separating the flat plate,
(C) From the flat surface side of the primary molded body, a curing step of selectively curing only the region by masking and exposing a portion excluding the region to be cured;
(D) a developing step of forming a resin structure by developing and removing an unexposed portion of the selectively cured primary molded body;
A method for producing a fine resin structure, comprising:   The method for producing a fine resin structure according to claim 1, wherein the flat plate is a silicon wafer.   The method for producing a fine resin structure according to claim 1 or 2, wherein a blending ratio of the epoxy resin that is solid at normal temperature and the epoxy resin that is liquid at normal temperature is in a range of 90/10 to 65/35 by mass ratio. .   The photopolymerization initiator is a cationic polymerization initiator, and the cationic polymerization initiator is contained in an amount of 0.1 to 1 part by mass with respect to 100 parts by mass of the total epoxy resin. The manufacturing method of the fine resin structure of description.   The fine resin according to any one of claims 1 to 4, wherein the photocurable resin composition contains 0.01 to 1% by mass of a light absorber that absorbs light exposed in the step (c). Manufacturing method of structure.   The method for producing a fine resin structure according to any one of claims 1 to 5, wherein the varnish contains at least one or more solvents having a boiling point of 120 ° C or higher.   The manufacturing method of the fine resin structure of any one of Claims 1-6 in which the said photocurable resin composition contains 1-10 mass% of phenoxy resins further. A method of manufacturing a photoelectric circuit board having an optical waveguide,
Using a silicon substrate having a groove for forming an optical waveguide having a silicon oxide film formed on the surface;
Mixing epoxy resin that is solid at normal temperature and epoxy resin that is liquid at normal temperature in a predetermined ratio, and melting or softening by heating obtained by adding a photopolymerization initiator, it has a predetermined refractive index that is solid at normal temperature Using a photocurable resin composition for a core having;
The following steps (a1) to (e):
(A1) After applying the varnish of the core photocurable resin composition so as to cover the optical waveguide forming groove, the solvent in the varnish is volatilized and removed to form a solid core photocurable resin layer. A resin layer forming step to be formed;
(B1) In a state in which the core photocurable resin layer is heated to a temperature at which the core photocurable resin layer is melted or softened, a flat plate is brought into pressure contact with the surface of the core photocurable resin layer while being kept parallel to the silicon substrate surface. And a flattening step of forming an uncured core resin layer having a flat surface by cooling to a temperature at which the core photocurable resin composition is solidified while maintaining a pressed contact state, and separating the flat plate.
(C1) a curing step of selectively curing only the region by masking and exposing a portion excluding the region where the core is formed from the flat surface side of the uncured core resin layer;
(D1) Development step of forming a core by developing and removing the unexposed portion of the selectively cured uncured core resin layer,
(E) a clad forming step of forming a clad by coating the core with a resin having a refractive index lower than that of the core;
A method for manufacturing a photoelectric circuit board, comprising: The step (e)
Refractive index of the core, which is solid at room temperature, melted or softened by heating, obtained by blending epoxy resin that is solid at room temperature and epoxy resin that is liquid at room temperature at a predetermined ratio, and further incorporating a photopolymerization initiator A photocurable resin composition for cladding having a lower refractive index than the above;
The following steps (a2) to (d2):
(A2) A resin layer for forming a solid photocurable resin layer for clad by applying a varnish of the photocurable resin composition for clad so as to cover the core and then removing the solvent in the varnish by volatilization and removal. Forming process,
(B2) In a state where the photocurable resin layer for cladding is heated to a temperature at which the clad photocurable resin layer is melted or softened, a flat plate is pressed and brought into contact with the surface of the photocurable resin layer for clad while being parallel to the substrate surface. And a flattening step of forming an uncured clad resin layer having a flat surface by cooling to a temperature at which the photocurable resin composition for clad is solidified while maintaining a pressed contact state, and separating the flat plate.
(C2) a curing step of selectively curing only the region by masking and exposing a portion excluding the region where the cladding is formed from the flat surface side of the uncured cladding resin layer;
(D2) a developing step of forming a clad by developing and removing an unexposed portion of the selectively cured uncured clad resin layer;
The method for producing a photoelectric circuit board according to claim 8, wherein:   A fine resin structure obtained by the production method according to claim 1.   A photoelectric circuit board obtained by the manufacturing method according to claim 8.

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