Photosensitive element, method for forming resist pattern, and method for manufacturing wiring board

Abstract

A photosensitive element according to the present disclosure comprises a support and a photosensitive layer formed on the support. The photosensitive layer contains a binder polymer, a photopolymerizable compound, a photopolymerization initiator, and a sensitizer. The photopolymerization initiator contains a hexaarylbiimidazole compound. The content of the sensitizer is 0.019 parts by mass or less with respect to 100 parts by mass of the total amount of the binder polymer and the photopolymerizable compound.

Description

Photosensitive element, method for forming resist pattern, and method for manufacturing wiring board

[0001] The present disclosure relates to a photosensitive element, a method for forming a resist pattern, and a method for manufacturing a wiring board.

[0002] In the field of wiring board manufacturing, photosensitive resin compositions and photosensitive elements comprising a layer formed on a support using the photosensitive resin composition (hereinafter also referred to as a "photosensitive layer") are widely used as resist materials used in etching or plating processes.

[0003] A wiring board is manufactured, for example, by the following procedure. First, a photosensitive layer of a photosensitive element is laminated onto a circuit-forming substrate. Next, a predetermined portion of the photosensitive layer is exposed to light to form a photocured portion. At this time, the support is peeled off before or after exposure. Thereafter, areas of the photosensitive layer other than the photocured portion are removed from the substrate, and a resist pattern, which is a cured product of the photosensitive resin composition, is formed on the substrate. Next, the obtained resist pattern is used as a resist and subjected to an etching process or a plating process to form a conductor pattern on the substrate, and finally the resist is peeled off and removed.

[0004] Known photosensitive resin compositions include, for example, photosensitive resin compositions containing a binder polymer, a photopolymerizable compound, a photopolymerization initiator, and a sensitizer (see Patent Document 1).

[0005] JP 2009-003177 A

[0006] In recent years, there has been a demand for photosensitive resin compositions that can be used in thick film applications (e.g., forming resist patterns with a thickness of 35 μm or more) to form copper pillars that connect IC chips to wiring substrates for semiconductor packages. The thicker the photosensitive layer formed using the photosensitive resin composition, the more difficult it is to uniformly cure the layer to its bottom, and the more likely it is that the bottom of the formed resist pattern will partially peel off and float from the substrate (hereinafter also referred to as the "lifting phenomenon").

[0007] An object of the present disclosure is to provide a photosensitive element capable of forming a thick-film resist pattern with excellent lifting resistance, a method for forming a resist pattern, and a method for manufacturing a wiring board.

[0008] The present disclosure provides the following photosensitive element, method for forming a resist pattern, and method for manufacturing a wiring board. [1] A photosensitive element comprising a support and a photosensitive layer formed on the support, the photosensitive layer containing a binder polymer, a photopolymerizable compound, a photopolymerization initiator, and a sensitizer, the photopolymerization initiator including a hexaarylbiimidazole compound, and the content of the sensitizer being 0.019 parts by mass or less per 100 parts by mass of the binder polymer and the photopolymerizable compound. [2] The photosensitive element according to [1] above, in which the sensitizer includes a benzophenone compound. [3] The photosensitive element according to [1] or [2] above, in which the photopolymerization initiator further includes an N-phenylglycine compound. [4] The photosensitive element according to [3] above, in which the content of the N-phenylglycine compound is 0.010 parts by mass or more per 100 parts by mass of the binder polymer and the photopolymerizable compound. [5] The photosensitive element according to any one of [1] to [4] above, wherein the photosensitive layer further contains a polymerization inhibitor. [6] The photosensitive element according to [5] above, wherein the polymerization inhibitor includes a catechol compound. [7] The photosensitive element according to [6] above, wherein the content of the catechol compound is 0.100 parts by mass or less relative to 100 parts by mass of the total amount of the binder polymer and the photopolymerizable compound. [8] The photosensitive element according to any one of [1] to [7] above, wherein the photosensitive layer has a thickness of 35 μm or more. [9] A method for forming a resist pattern, comprising the steps of forming a photosensitive layer on a substrate using the photosensitive element according to any one of [1] to [8] above, photocuring a portion of the photosensitive layer, and removing an uncured portion of the photosensitive layer.

[10] A method for producing a wiring board, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the method for forming a resist pattern according to [9] above, to form a conductor pattern.

[0009] According to the present disclosure, it is possible to provide a photosensitive element capable of forming a thick-film resist pattern with excellent lifting resistance, a method for forming a resist pattern, and a method for manufacturing a wiring board.

[0010] 2A is a schematic cross-sectional view showing a photosensitive element according to one embodiment, in which (a) of Fig. 2 is a microscopic image of the via pattern obtained in Example 4, (b) of Fig. 2 is a microscopic image of the via pattern obtained in Example 2, and (c) of Fig. 2 is a microscopic image of the via pattern obtained in Comparative Example 1.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended effect of that process is achieved. A numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. The term "layer" encompasses not only a structure that is formed over the entire surface when observed in a plan view, but also a structure that is formed on a portion of the surface. "(Meth)acrylic acid" means at least one of "acrylic acid" and the corresponding "methacrylic acid." The same applies to other similar expressions such as (meth)acrylate.

[0012] As used herein, "EO-modified" means a compound having a (poly)oxyethylene group. "PO-modified" means a compound having a (poly)oxypropylene group. "EO / PO-modified" means a compound having a (poly)oxyethylene group and / or a (poly)oxypropylene group. "(Poly)oxyethylene group" means an oxyethylene group or a polyoxyethylene group in which two or more ethylene groups are linked by ether bonds. "(Poly)oxypropylene group" means an oxypropylene group or a polyoxypropylene group in which two or more propylene groups are linked by ether bonds.

[0013] In this specification, when a composition contains a plurality of substances corresponding to each component, the amount of each component refers to the total amount of the plurality of substances present in the composition, unless otherwise specified. In this specification, the term "solid content" refers to the non-volatile content of the photosensitive resin composition excluding volatile substances. In other words, the term "solid content" refers to components other than the solvent that remain without volatilizing during drying of the photosensitive resin composition, as described below, and includes components that are liquid, syrup-like, or waxy at room temperature (25°C).

[0014] <Photosensitive Element> The photosensitive element according to this embodiment includes a support and a photosensitive layer formed on the support. The photosensitive layer contains (A) a binder polymer (hereinafter also referred to as "component (A)"), (B) a photopolymerizable compound (hereinafter also referred to as "component (B)"), (C) a photopolymerization initiator (hereinafter also referred to as "component (C)"), and (D) a sensitizer (hereinafter also referred to as "component (D)"). The (C) photopolymerization initiator contains a hexaarylbiimidazole compound, and the content of the (D) sensitizer is 0.019 parts by mass or less relative to 100 parts by mass of the total amount of the (A) binder polymer and the (B) photopolymerizable compound. The photosensitive element may further include other layers, such as a protective layer, as necessary.

[0015] (Photosensitive Layer) The photosensitive layer is a layer formed using a photosensitive resin composition containing (A) a binder polymer, (B) a photopolymerizable compound, (C) a photopolymerization initiator, and (D) a sensitizer. Unless otherwise specified in this specification, the solid content of each component (components (A) to (D) and other components) other than volatile substances in the photosensitive layer is the same as the solid content of each component in the photosensitive resin composition that forms the photosensitive layer. Each component will be described below.

[0016] Component (A): The binder polymer photosensitive resin composition contains one or more components (A). Examples of component (A) include acrylic resins, styrene resins, epoxy resins, amide resins, amide-epoxy resins, alkyd resins, and phenolic resins. From the viewpoint of alkaline developability, component (A) may contain an acrylic resin. The acrylic resin is a resin having a structural unit (monomer unit) derived from a (meth)acryloyl group-containing compound.

[0017] The (meth)acryloyl group-containing compound is a compound containing a (meth)acryloyl group. Examples of the (meth)acryloyl group-containing compound include hydroxyalkyl (meth)acrylate, (meth)acrylic acid, (meth)acrylic acid alkyl ester, (meth)acrylic acid aryl ester, (meth)acrylic acid cycloalkyl ester, acrylamide such as diacetone acrylamide, (meth)acrylic acid tetrahydrofurfuryl ester, (meth)acrylic acid dimethylaminoethyl ester, (meth)acrylic acid diethylaminoethyl ester, (meth)acrylic acid glycidyl ester, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, α-bromoacrylic acid, α-chloroacrylic acid, β-furyl (meth)acrylic acid, and β-styryl (meth)acrylic acid.

[0018] The acrylic resin may be, for example, a polymer (a) having at least one unit selected from the group consisting of a hydroxyalkyl (meth)acrylate unit, a (meth)acrylic acid unit, a (meth)acrylic acid alkyl ester unit, and a (meth)acrylic acid aryl ester unit.

[0019] The hydroxyalkyl (meth)acrylate unit is a structural unit derived from a hydroxyalkyl (meth)acrylate. Examples of the hydroxyalkyl (meth)acrylate include hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, and hydroxyhexyl (meth)acrylate. When the alkyl moiety in the hydroxyalkyl (meth)acrylate unit has 3 or more carbon atoms, the hydroxyalkyl (meth)acrylate unit may have a branched structure.

[0020] When the polymer (a) has a hydroxyalkyl (meth)acrylate unit, the content of the hydroxyalkyl (meth)acrylate unit may be 0.5% by mass or more, 0.75% by mass or more, or 1.0% by mass or more, based on the total amount of monomer units constituting the polymer (a), from the viewpoint of dispersibility, and may be 20% by mass or less, 15% by mass or less, or 8% by mass or less, from the viewpoint of water absorbency.

[0021] The (meth)acrylic acid unit is a structural unit derived from (meth)acrylic acid. When the polymer (a) has the (meth)acrylic acid unit, the content of the (meth)acrylic acid unit may be 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more, or may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less, based on the total amount of the monomer units constituting the polymer (a), from the viewpoints of resolution and adhesion.

[0022] The (meth)acrylic acid alkyl ester unit is a structural unit derived from a (meth)acrylic acid alkyl ester. The alkyl group of the (meth)acrylic acid alkyl ester may be, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, or a structural isomer thereof, or may be an alkyl group having 1 to 4 carbon atoms from the viewpoint of releasability.

[0023] When the polymer (a) has (meth)acrylic acid alkyl ester units, the content of the (meth)acrylic acid alkyl ester units may be 1 mass % or more, 2 mass % or more, 3 mass % or more, or 4 mass % or more, based on the total amount of monomer units constituting the polymer (a), from the viewpoint of releasability, and may be 50 mass % or less, 30 mass % or less, 10 mass % or less, 8 mass % or less, or 6 mass % or less, from the viewpoint of resolution and adhesion.

[0024] The (meth)acrylic acid aryl ester unit is a structural unit derived from a (meth)acrylic acid aryl ester. Examples of the (meth)acrylic acid aryl ester include benzyl (meth)acrylate, phenyl (meth)acrylate, and naphthyl (meth)acrylate. When the polymer (a) has a (meth)acrylic acid aryl ester unit, the content of the (meth)acrylic acid aryl ester unit may be 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, or 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less, based on the total amount of the monomer units constituting the polymer (a), from the viewpoint of resolution and adhesion.

[0025] The polymer (a) may further have a structural unit derived from a monomer other than the (meth)acryloyl group-containing compound. The other monomer may be one type or two or more types.

[0026] Examples of other monomers include styrene or styrene derivatives, acrylonitrile, vinyl alcohol ethers such as vinyl n-butyl ether, maleic acid, maleic anhydride, maleic acid monoesters such as monomethyl maleate, monoethyl maleate, and monoisopropyl maleate, fumaric acid, cinnamic acid, α-cyanocinnamic acid, itaconic acid, crotonic acid, and propiolic acid. Examples of styrene derivatives include vinyltoluene and α-methylstyrene.

[0027] When the polymer (a) has a structural unit derived from styrene or a styrene derivative (hereinafter also referred to as a "styrene or styrene derivative unit"), the content of the styrene or styrene derivative unit, based on the total amount of the monomer units constituting the polymer (a), may be 30% by mass or more, 35% by mass or more, or 40% by mass or more from the viewpoint of resolution, and may be 90% by mass or less, 80% by mass or less, 60% by mass or less, or 50% by mass or less from the viewpoint of developability.

[0028] The component (A) may contain a binder polymer other than the polymer (a), or may consist solely of the polymer (a). From the viewpoints of adhesion and resolution, the content of the polymer (a) in the component (A) may be 50 to 100 mass % or 80 to 100 mass % based on the total amount of the component (A).

[0029] The acid value of polymer (a) may be 100 mgKOH / g or more, 120 mgKOH / g or more, 140 mgKOH / g or more, or 150 mgKOH / g or more from the viewpoint of developability, and may be 250 mgKOH / g or less, 240 mgKOH / g or less, or 230 mgKOH / g or less from the viewpoint of adhesion (developer resistance) of the cured product of the photosensitive resin composition. The acid value of polymer (a) can be adjusted by the content of structural units (e.g., (meth)acrylic acid units) constituting polymer (a). When component (A) contains a binder polymer other than polymer (a), the acid value of the other binder polymer may also be within the above range.

[0030] The weight average molecular weight (Mw) of the polymer (a) may be 10,000 or more, 15,000 or more, 20,000 or more, 25,000 or more, 30,000 or more, 35,000 or more, or 40,000 or more from the viewpoint of adhesion (developer resistance) of the cured product of the photosensitive resin composition and ease of forming a thick film resist pattern, and may be 100,000 or less, 80,000 or less, 60,000 or less, or 50,000 or less from the viewpoint of developability. The dispersity (Mw / Mn) of the polymer (a) may be, for example, 1.0 or more or 1.5 or more, and from the viewpoint of adhesion and resolution, may be 3.0 or less or 2.5 or less. When the (A) component contains a binder polymer other than the polymer (a), the Mw of the other binder polymer may also be within the above range.

[0031] The weight average molecular weight and dispersity can be measured, for example, by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene. More specifically, they can be measured under the conditions described in the Examples. For compounds with low molecular weights, if it is difficult to measure the weight average molecular weight using the above-mentioned method, the molecular weight can be measured by another method and the average can be calculated.

[0032] The content of the component (A), based on the total amount of the photosensitive layer, may be 20% by mass or more, 30% by mass or more, or 40% by mass or more from the viewpoint of film formability, and may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 65% by mass or less from the viewpoint of sensitivity and resolution.

[0033] The content of the component (A) in the photosensitive layer may be 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, 45 parts by mass or more, 50 parts by mass or more, or 55 parts by mass or more, from the viewpoint of film formability, relative to 100 parts by mass of the total amount of the component (A) and the component (B); and may be 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less, from the viewpoint of sensitivity and resolution.

[0034] Component (B): Photopolymerizable Compound The photosensitive resin composition contains one or more components (B). The component (B) may be any compound that polymerizes when exposed to light, such as a compound having an ethylenically unsaturated bond. The component (B) may contain a polyfunctional monomer having two or more reactive groups that react with radicals. From the viewpoints of developability, resolution, and releasability after curing, the component (B) may contain a bisphenol A (meth)acrylate compound.

[0035] Examples of bisphenol A type (meth)acrylate compounds include 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane, 2,2-bis(4-((meth)acryloxypolypropoxy)phenyl)propane, 2,2-bis(4-((meth)acryloxypolybutoxy)phenyl)propane, and 2,2-bis(4-((meth)acryloxypolyethoxypolypropoxy)phenyl)propane. From the viewpoints of resolution and strippability, component (B) may contain 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane. As the 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane, a compound having 10 or more oxyethylene groups may be used, or a compound having less than 10 oxyethylene groups may be used, or a compound having 10 or more oxyethylene groups may be used in combination with a compound having less than 10 oxyethylene groups. Examples of 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane include 2,2-bis(4-((meth)acryloxypentaethoxy)phenyl)propane and 2,2-bis(4-((meth)acryloxydiethoxy)phenyl)propane.

[0036] From the viewpoint of resolution and flexibility, component (B) may contain an α,β-unsaturated ester compound obtained by reacting a polyhydric alcohol with an α,β-unsaturated carboxylic acid. Examples of the α,β-unsaturated ester compound include polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and EO-modified polypropylene glycol, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, EO-PO-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and tetramethylolmethane tetra(meth)acrylate.

[0037] From the viewpoint of sensitivity and adhesion, the component (B) may contain a compound having three or more (meth)acryloyl groups. Examples of the compound having three or more (meth)acryloyl groups include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, EO-PO-modified trimethylolpropane tri(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, EO-modified ditrimethylolpropane tetra(meth)acrylate, and EO-modified dipentaerythritol hexa(meth)acrylate.

[0038] The photosensitive resin composition may contain, as component (B), a photopolymerizable compound other than the bisphenol A (meth)acrylate compound and the α,β-unsaturated ester compound.

[0039] Other photopolymerizable compounds include, for example, nonylphenoxy polyethyleneoxy acrylate, phthalic acid compounds, (meth)acrylic acid alkyl esters, and photopolymerizable compounds having at least one cationically polymerizable cyclic ether group in the molecule (such as oxetane compounds).

[0040] Examples of nonylphenoxy polyethyleneoxyacrylates include nonylphenoxytriethyleneoxyacrylate, nonylphenoxytetraethyleneoxyacrylate, nonylphenoxypentaethyleneoxyacrylate, nonylphenoxyhexaethyleneoxyacrylate, nonylphenoxyheptaethyleneoxyacrylate, nonylphenoxyoctaethyleneoxyacrylate, nonylphenoxynonaethyleneoxyacrylate, nonylphenoxydecaethyleneoxyacrylate, and nonylphenoxyundecaethyleneoxyacrylate.

[0041] Examples of phthalic acid compounds include γ-chloro-β-hydroxypropyl-β'-(meth)acryloyloxyethyl-o-phthalate (also known as 3-chloro-2-hydroxypropyl-2-(meth)acryloyloxyethyl phthalate), β-hydroxyethyl-β'-(meth)acryloyloxyethyl-o-phthalate, and β-hydroxypropyl-β'-(meth)acryloyloxyethyl-o-phthalate.

[0042] The content of the (B) component may be 3% by mass or more, 10% by mass or more, or 25% by mass or more, based on the total amount of the photosensitive layer, from the viewpoints of sensitivity and resolution, and may be 70% by mass or less, 60% by mass or less, or 50% by mass or less, from the viewpoint of film formability.

[0043] Component (C): Photopolymerization Initiator The photosensitive resin composition contains a hexaarylbiimidazole compound as component (C). By using the hexaarylbiimidazole compound, the photosensitive resin composition can achieve good resolution and resist pattern formability.

[0044] From the viewpoints of sensitivity, resolution, adhesion, and releasability, the hexaarylbiimidazole compound may be a 2,4,5-triarylimidazole dimer. Examples of 2,4,5-triarylimidazole dimers include 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-bis-(m-methoxyphenyl)imidazole dimer, and 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer. The hexaarylbiimidazole compounds may be used alone or in combination of two or more.

[0045] The content of the hexaarylbiimidazole compound in the photosensitive layer may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 1.5 parts by mass or more, 2.0 parts by mass or more, or 2.5 parts by mass or more, relative to 100 parts by mass of the total amount of the component (A) and the component (B), from the viewpoints of sensitivity and resolution, and may be 10 parts by mass or less, 8 parts by mass or less, 6 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less, from the viewpoints of adhesion, bottom curability, and developability.

[0046] From the viewpoints of sensitivity, resist profile, adhesion, and resolution, the component (C) may further contain an N-phenylglycine compound. Examples of N-phenylglycine compounds include N-phenylglycine, N-methyl-N-phenylglycine, and N-ethyl-N-phenylglycine. From the viewpoints of sensitivity, resist profile, adhesion, and resolution, the N-phenylglycine compound may contain N-phenylglycine.

[0047] When the component (C) contains an N-phenylglycine compound, the content of the N-phenylglycine compound in the photosensitive layer may be 0.010 parts by mass or more, 0.015 parts by mass or more, 0.020 parts by mass or more, 0.025 parts by mass or more, or 0.028 parts by mass or more, and may be 0.150 parts by mass or less, 0.130 parts by mass or less, 0.100 parts by mass or less, 0.090 parts by mass or less, 0.070 parts by mass or less, 0.050 parts by mass or less, 0.040 parts by mass or less, or 0.035 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B).

[0048] The component (C) may further contain a photopolymerization initiator other than the hexaarylbiimidazole compound and the N-phenylglycine compound, as long as the effects of the present disclosure are not impaired.

[0049] The content of the component (C) in the photosensitive layer may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, or 3.0 parts by mass or more, relative to 100 parts by mass of the total amount of the component (A) and the component (B), and may be 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, 6 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less.

[0050] The photosensitive resin composition contains one or more types of component (D). From the viewpoint of achieving better lifting resistance, component (D) may contain a benzophenone compound. Examples of benzophenone compounds include benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 4,4'-dichlorobenzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide. Component (D) may consist solely of a benzophenone compound, or may further contain a sensitizer other than a benzophenone compound, as long as the effects of the present disclosure are not impaired.

[0051] The content of the (D) component in the photosensitive layer is 0.019 parts by mass or less, relative to 100 parts by mass of the total amount of the (A) component and the (B) component. When the content of the (D) component is within this range, uniform curing can be achieved down to the bottom of the resist, and a resist pattern with excellent lifting resistance can be formed. Furthermore, when the content of the (D) component is within this range, a resist pattern with excellent resist shape, adhesion, and resolution can also be formed. From the viewpoint of achieving even better lifting resistance, the content of the (D) component in the photosensitive layer may be 0.018 parts by mass or less, 0.016 parts by mass or less, 0.014 parts by mass or less, 0.012 parts by mass or less, or 0.011 parts by mass or less, relative to 100 parts by mass of the total amount of the (A) component and the (B) component. The lower limit of the content of the component (D) in the photosensitive layer is not particularly limited, but may be 0.001 parts by mass or more, 0.003 parts by mass or more, 0.005 parts by mass or more, or 0.008 parts by mass or more, relative to 100 parts by mass of the total amount of the components (A) and (B).

[0052] The photosensitive resin composition may further contain a polymerization inhibitor (hereinafter also referred to as "component (E)"). Component (E) may contain a catechol compound. Examples of catechol compounds include catechol and alkyl catechols. Examples of alkyl catechols include 2-methyl catechol, 3-methyl catechol, 4-methyl catechol, 2-ethyl catechol, 3-ethyl catechol, 4-ethyl catechol, 2-propyl catechol, 3-propyl catechol, 4-propyl catechol, 2-n-butyl catechol, 3-n-butyl catechol, 4-n-butyl catechol, 2-tert-butyl catechol, 3-tert-butyl catechol, 4-tert-butyl catechol, and 3,5-di-tert-butyl catechol. Component (E) may further contain a polymerization inhibitor other than a catechol compound.

[0053] When the photosensitive resin composition contains the component (E), the content of the component (E) in the photosensitive layer may be 0.001 parts by mass or more, 0.005 parts by mass or more, 0.010 parts by mass or more, 0.012 parts by mass or more, 0.014 parts by mass or more, or 0.015 parts by mass or more, relative to 100 parts by mass of the total amount of the component (A) and the component (B), from the viewpoint of resolution; and may be 0.100 parts by mass or less, 0.080 parts by mass or less, 0.050 parts by mass or less, 0.030 parts by mass or less, 0.020 parts by mass or less, 0.019 parts by mass or less, 0.018 parts by mass or less, or 0.017 parts by mass or less, from the viewpoint of achieving better sensitivity and lifting resistance.

[0054] When the photosensitive resin composition contains an N-phenylglycine compound as the component (C) and a catechol compound as the component (E), the ratio (mass ratio) of the N-phenylglycine compound to the catechol compound in the photosensitive layer may be 1.0 or more, 1.3 or more, 1.5 or more, or 1.8 or more, from the viewpoints of sensitivity and resolution, and may be 5.0 or less, 4.5 or less, 4.0 or less, 3.8 or less, 3.6 or less, 3.0 or less, 2.5 or less, or 2.0 or less.

[0055] The photosensitive resin composition may further contain one or more other components in addition to the components described above. Examples of other components include hydrogen donors (such as bis[4-(dimethylamino)phenyl]methane, bis[4-(diethylamino)phenyl]methane, and leuco crystal violet), tribromophenyl sulfone, thermal color-development inhibitors, plasticizers (such as p-toluenesulfonamide), dyes (such as malachite green), pigments, fillers, antifoaming agents, flame retardants, stabilizers, adhesion promoters, leveling agents, release promoters, antioxidants, fragrances, imaging agents, and thermal crosslinkers. The content of these other components may be 0.005 parts by mass or more, or 0.01 parts by mass or more, or may be 20 parts by mass or less, based on 100 parts by mass of the total amount of component (A) and component (B).

[0056] The photosensitive resin composition may further contain one or more organic solvents to adjust the viscosity, such as methanol, ethanol, acetone, methyl ethyl ketone, cyclopentanone, methyl cellosolve, ethyl cellosolve, toluene, N,N-dimethylformamide, and propylene glycol monomethyl ether.

[0057] The photosensitive resin composition can be used, for example, as a negative photosensitive resin composition. The photosensitive resin composition can be suitably used in the method for forming a resist pattern and the method for manufacturing a wiring board, which will be described later.

[0058] The thickness of the photosensitive layer may be 35 μm or more, 40 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, 160 μm or more, 200 μm or more, 210 μm or more, 220 μm or more, 230 μm or more, or 240 μm or more. The upper limit of the thickness of the photosensitive layer is not particularly limited, but may be 500 μm or less, 400 μm or less, 300 μm or less, or 280 μm or less. The photosensitive element of this embodiment can form a resist pattern with excellent lifting resistance even in an ultra-thick film (for example, a thickness of 200 μm or more). The thickness of the photosensitive layer may be the average value of the thicknesses at 10 locations.

[0059] The content of the residual solvent in the photosensitive layer may be 10 ppm by mass or more, 100 ppm by mass or more, 1000 ppm by mass or more, or 2000 ppm by mass or more, based on the total amount of the photosensitive layer, from the viewpoints of sensitivity and hue stability, and may be 15000 ppm by mass or less, 10000 ppm by mass or less, or 8000 ppm by mass or less, from the viewpoints of appearance and edge fusion resistance.

[0060] (Support) Examples of materials constituting the support include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene-2,6-naphthalate (PEN); and polyolefins such as polypropylene and polyethylene. The support may have a polyester film or a PET film, from the viewpoint of easily suppressing the occurrence of defects in the resist.

[0061] The haze of the support may be 0.01 to 5.0%, 0.01 to 1.5%, 0.01 to 1.0%, or 0.01 to 0.5%. Haze can be measured using a commercially available haze meter (turbidity meter) in accordance with the method specified in JIS K7105. Haze can be measured, for example, using a commercially available turbidity meter such as NDH-5000 (trade name, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0062] The thickness of the support may be 1 μm or more, 5 μm or more, or 10 μm or more from the viewpoint of easily preventing damage to the support when peeling the support from the photosensitive layer, and may be 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of easily and suitably performing exposure when exposing through the support.

[0063] (Protective Layer) The protective layer may be a polymer film having heat resistance and solvent resistance, and for example, a polyolefin film such as a polyethylene film or a polypropylene film can be used. In particular, by using a polyethylene film as the protective layer, it is possible to suppress misalignment of the photosensitive element during winding, and static electricity is unlikely to be generated when the protective layer is peeled off from the photosensitive layer, thereby suppressing damage to the photosensitive layer.

[0064] The thickness of the protective layer may be 1 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more from the viewpoint of easily suppressing damage to the protective layer when the photosensitive layer and the support are laminated onto the substrate while peeling off the protective layer, or may be 100 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less from the viewpoint of easily improving productivity.

[0065] 1 is a schematic cross-sectional view showing a photosensitive element according to one embodiment. As shown in FIG. 1, the photosensitive element 1 includes a support 2, a photosensitive layer 3 provided on the support 2, and a protective layer 4 provided on the side of the photosensitive layer 3 opposite the support 2.

[0066] The photosensitive element 1 can be obtained, for example, as follows. First, a photosensitive layer 3 is formed on a support 2. The photosensitive layer 3 can be formed, for example, by applying a photosensitive resin composition to form a coating layer and drying the coating layer. Next, a protective layer 4 is coated on the surface of the photosensitive layer 3 opposite the support 2.

[0067] The coating layer is formed by a known method such as roll coating, comma coating, gravure coating, air knife coating, die coating, bar coating, etc. The coating layer is dried, for example, at 70 to 150°C for about 5 to 30 minutes.

[0068] In another embodiment, the photosensitive element may further include other layers such as a cushion layer, an adhesive layer, a light absorbing layer, and a gas barrier layer.

[0069] The photosensitive element 1 may be, for example, in the form of a sheet, or in the form of a photosensitive element roll wound around a core. In the photosensitive element roll, the photosensitive element 1 is preferably wound with the support 2 facing outward. The core is formed of, for example, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, or the like. An end separator may be provided on the end face of the photosensitive element roll from the viewpoint of end face protection, or a moisture-proof end face separator may be provided from the viewpoint of edge fusion resistance. The photosensitive element 1 may be wrapped, for example, in a black sheet with low moisture permeability.

[0070] The photosensitive element according to this embodiment can be suitably used in the method for forming a resist pattern and the method for manufacturing a wiring board, which will be described later.

[0071] <Method of Forming Resist Pattern> The method of forming a resist pattern according to this embodiment includes a step of forming a photosensitive layer on a substrate using the photosensitive element (hereinafter also referred to as a "photosensitive layer forming step"), a step of photocuring a portion of the photosensitive layer (hereinafter also referred to as an "exposure step"), and a step of removing an uncured portion of the photosensitive layer (hereinafter also referred to as a "development step"), and may further include other steps as necessary. The resist pattern can also be referred to as a photocured product pattern of the photosensitive resin composition or a relief pattern.

[0072] (Photosensitive Layer Forming Step) In the photosensitive layer forming step, a photosensitive layer is formed on a substrate using a photosensitive element. The substrate is not particularly limited, but typically, a circuit-forming substrate having an insulating layer and a conductor layer formed on the insulating layer, or a die pad (substrate for lead frame) such as an alloy substrate is used.

[0073] For example, the photosensitive layer can be formed on the substrate by removing the protective layer from the photosensitive element and then pressing the photosensitive layer of the photosensitive element onto the substrate while heating, thereby obtaining a laminate having the substrate, photosensitive layer, and support in this order.

[0074] The photosensitive layer forming step may be carried out under reduced pressure from the viewpoint of adhesion and followability. Heating during pressure bonding may be carried out at a temperature of 70 to 130°C, and pressure bonding may be carried out at 0.1 to 1.0 MPa (1 to 10 kgf / cm ２ These conditions can be appropriately selected as needed. Note that if the photosensitive layer of the photosensitive element is heated to 70 to 130°C, it is not necessary to preheat the substrate, but the substrate can be preheated in order to further improve the adhesion and followability.

[0075] In the exposure step, the photosensitive layer may be exposed to actinic rays through the support, or the support may be peeled off and then the photosensitive layer may be exposed to actinic rays. As a result, the exposed area irradiated with actinic rays is photocured to form a photocured area (latent image).

[0076] As the exposure method, a known exposure method can be applied, and examples thereof include a method of irradiating an actinic ray in an imagewise manner through a negative or positive mask pattern called artwork (mask exposure method), an LDI exposure method (direct writing exposure), and a method of irradiating an actinic ray projected from an image of a photomask through a lens in an imagewise manner (projection exposure method).

[0077] The light source for actinic rays is not particularly limited as long as it is a commonly used known light source, and examples thereof include those that effectively emit ultraviolet rays, such as carbon arc lamps, mercury vapor arc lamps, ultra-high pressure mercury lamps, high-pressure mercury lamps, xenon lamps, gas lasers such as argon lasers, solid-state lasers such as YAG lasers, and semiconductor lasers such as gallium nitride blue-violet lasers. Among these, from the viewpoint of improving resolution and alignment in a well-balanced manner, light sources capable of emitting monochromatic i-line light with an exposure wavelength of 365 nm, light sources capable of emitting monochromatic h-line light with an exposure wavelength of 405 nm, or light sources capable of emitting actinic rays with exposure wavelengths that are cross-linked with i, h, and g may be used. Examples of light sources capable of emitting monochromatic i-line light with an exposure wavelength of 365 nm include ultra-high pressure mercury lamps. Examples of light sources capable of emitting monochromatic h-line light with an exposure wavelength of 405 nm include blue-violet laser diodes with a wavelength of 405 nm.

[0078] In the method for forming a resist pattern according to this embodiment, from the viewpoint of adhesion, post-exposure baking (PEB) may be performed after the exposure step and before the development step. The temperature when performing PEB may be 50 to 100° C. Heating may be performed using a heater such as a hot plate, a box dryer, or a heating roll.

[0079] (Developing Step) In the developing step, the uncured portions of the photosensitive layer are removed from the substrate. When the photosensitive layer is exposed through the support, the support and the uncured portions of the photosensitive layer are removed from the substrate. In the developing step, a resist pattern consisting of photocured portions of the photosensitive layer is formed on the substrate. The developing method may be wet development or dry development.

[0080] In the case of wet development, development can be carried out by a known wet development method using a developer suitable for the photosensitive resin composition. Examples of wet development methods include dipping, puddling, high-pressure spraying, brushing, scrubbing, and swinging immersion. These wet development methods may be used alone or in combination of two or more methods.

[0081] The developer is appropriately selected depending on the constitution of the photosensitive resin composition, and may be, for example, an alkaline developer or an organic solvent developer.

[0082] From the viewpoints of safety, stability, and ease of use, an alkaline developer may be used as the developer. The alkaline developer may be an aqueous solution containing a base such as an alkali hydroxide such as lithium, sodium, or potassium hydroxide; an alkali carbonate such as lithium, sodium, potassium, or ammonium carbonate or bicarbonate; an alkali metal phosphate such as potassium phosphate or sodium phosphate; an alkali metal pyrophosphate such as sodium pyrophosphate or potassium pyrophosphate; borax; sodium metasilicate; tetramethylammonium hydroxide; ethanolamine; ethylenediamine; diethylenetriamine; 2-amino-2-hydroxymethyl-1,3-propanediol; 1,3-diamino-2-propanol; or morpholine.

[0083] From the viewpoint of environmental friendliness, an inorganic alkaline developer may be used, such as a dilute solution of 0.1 to 5 mass % sodium carbonate, a dilute solution of 0.1 to 5 mass % potassium carbonate, a dilute solution of 0.1 to 5 mass % sodium hydroxide, or a dilute solution of 0.1 to 5 mass % sodium tetraborate.

[0084] The pH of the alkaline developer used for development may be in the range of 9 to 11, and the temperature of the alkaline developer can be adjusted according to the developability of the photosensitive layer. The alkaline developer may contain, for example, a surfactant, an antifoaming agent, or a small amount of an organic solvent to promote development. Examples of organic solvents used in the alkaline developer include 3-acetone alcohol, acetone, ethyl acetate, an alkoxyethanol having an alkoxy group having 1 to 4 carbon atoms, ethyl alcohol, isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.

[0085] Examples of organic solvents used in the organic solvent developer include 1,1,1-trichloroethane, N-methyl-2-pyrrolidone, N,N-dimethylformamide, cyclohexanone, methyl isobutyl ketone, and γ-butyrolactone. From the viewpoint of preventing ignition, these organic solvents may be used as the organic solvent developer by adding water in a range of 1 to 20% by mass.

[0086] (Other Steps) In the method for forming a resist pattern according to this embodiment, after removing the uncured portion in the development step, heating at 60 to 250° C. or irradiating with 0.2 to 10 J / cm 2 is performed as necessary. ２ The method may further include a step of further hardening the resist pattern by exposing the resist pattern to light at an exposure dose of 1000 nm or more.

[0087] <Method of manufacturing wiring board> The method of manufacturing a wiring board according to this embodiment includes a step of forming a conductor pattern (wiring layer) by etching or plating a substrate on which a resist pattern has been formed by the above-described method of forming a resist pattern, and may also include other steps such as a resist pattern removal step as necessary.

[0088] In the etching process, a resist pattern formed on a substrate having a conductive layer is used as a mask to etch away the conductive layer of the substrate that is not covered with the resist, thereby forming a conductive pattern.

[0089] The etching method is appropriately selected depending on the conductor layer to be removed. Examples of the etching solution include a cupric chloride solution, a ferric chloride solution, an alkaline etching solution, and a hydrogen peroxide-based etching solution. From the viewpoint of a good etch factor, a ferric chloride solution may be used as the etching solution.

[0090] In the plating process, a resist pattern formed on a substrate having a conductor layer is used as a mask to plate copper, solder, etc. on the conductor layer of the substrate that is not covered with the resist. After the plating process, the resist is removed by removing the resist pattern as described below, and the conductor layer that was covered with the resist is then etched to form the conductor pattern.

[0091] The plating method may be electrolytic plating or electroless plating, and examples thereof include copper plating such as copper sulfate plating and copper pyrophosphate plating; solder plating such as high-throw solder plating; nickel plating such as Watts bath (nickel sulfate-nickel chloride) plating and nickel sulfamate plating; and gold plating such as hard gold plating and soft gold plating.

[0092] After the etching or plating process, the resist pattern on the substrate is removed. The resist pattern can be removed, for example, using an inorganic alkaline stripper or an organic alkaline stripper. Examples of inorganic alkaline stripper solutions that can be used include a 1 to 10 mass % aqueous solution of sodium hydroxide and a 1 to 10 mass % aqueous solution of potassium hydroxide. Examples of organic alkaline stripper solutions that can be used include amine-based strippers such as ethanolamine, ethylenediamine, and diethylenetriamine, and tetramethylammonium hydroxide aqueous solutions. From the viewpoint of the strippability of thick-film resist patterns, organic alkaline stripper solutions may also be used.

[0093] Methods for removing the resist pattern include, for example, a dipping method and a spray method, which may be used alone or in combination.

[0094] When the resist pattern is removed after plating, the conductor layer covered with the resist is further etched by etching to form a conductor pattern, thereby manufacturing a desired wiring board. The etching method used in this process is appropriately selected depending on the conductor layer to be removed. For example, the above-mentioned etching solution can be used.

[0095] The method for manufacturing a wiring board according to this embodiment can be applied to the manufacture of not only single-layer wiring boards but also multi-layer wiring boards, and can also be applied to the manufacture of wiring boards having small-diameter through holes.

[0096] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0097] Synthesis of Component (A) 27 parts by mass of methacrylic acid, 5 parts by mass of methyl methacrylate, 45 parts by mass of styrene, and 23 parts by mass of benzyl methacrylate were mixed with 0.9 parts by mass of azobisisobutyronitrile to prepare solution (a). 0.5 parts by mass of azobisisobutyronitrile was dissolved in 50 parts by mass of a mixed solution (x) of acetone / propylene glycol monomethyl ether (mass ratio: 6 / 1) to prepare solution (b). 500 g of mixed solution (x) was placed in a flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen gas inlet tube, and the mixture was stirred while blowing nitrogen gas into the flask and heated to 80°C. Solution (a) was added dropwise to the mixed solution in the flask at a constant dropping rate over 4 hours, followed by stirring at 80°C for 2 hours. Next, the solution (b) was added dropwise to the solution in the flask at a constant rate over 10 minutes, and the solution in the flask was stirred at 80°C for 3 hours. The solution in the flask was then heated to 90°C over 30 minutes and maintained at 90°C for 2 hours. The stirring was then stopped and the solution was cooled to room temperature (25°C), yielding a solution of binder polymer A1. The non-volatile content (solid content) of the binder polymer A1 solution was 48% by mass. The weight-average molecular weight of binder polymer A1 was 40,000.

[0098] The weight average molecular weight was measured by gel permeation chromatography (GPC) and calculated by conversion using a standard polystyrene calibration curve. The GPC conditions are as follows. (GPC conditions) Pump: Hitachi L-6000 type (trade name, manufactured by Hitachi, Ltd.) Column: a total of three columns: Gelpack GL-R420, Gelpack GL-R430, and Gelpack GL-R440 (all manufactured by Resonac Corporation, trade names) Eluent: tetrahydrofuran Measurement temperature: 40°C Flow rate: 2.05 mL / min Detector: Hitachi L-3300 type RI (trade name, manufactured by Hitachi, Ltd.)

[0099] <Preparation of Photosensitive Resin Compositions> Each photosensitive resin composition was prepared by mixing the components shown in Table 1 in the amounts (parts by mass) shown in the table. The amounts (parts by mass) of components other than the solvent shown in Table 1 are the mass of non-volatile components (solid content). Details of each component shown in Table 1 are as follows.

[0100] (Binder polymer) Polymer A1: Binder polymer A1 synthesized above (Photopolymerizable compound) FA-321M: EO-modified bisphenol A dimethacrylate (ethylene oxide adduct of 10 mol on average) (manufactured by Resonac Co., Ltd.) BPE-200: EO-modified bisphenol A dimethacrylate (ethylene oxide adduct of 4 mol on average) (manufactured by Shin-Nakamura Chemical Co., Ltd.) FA-024M: PO / EO-modified dimethacrylate (manufactured by Resonac Co., Ltd., ethylene oxide adduct of 6 mol on average and propylene oxide adduct of 12 mol on average (total value)) (Photopolymerization initiator) B-CIM: 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole (manufactured by Hampford Chemical Co., Ltd.) NPG: N-phenylglycine (Sensitizer) EAB: 4,4'-bis(diethylamino)benzophenone (polymerization inhibitor) TBC: tert-butylcatechol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) LA-7RD: 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (manufactured by Adeka Corporation) (Other components) LCV: Leuco Crystal Violet (manufactured by Yamada Chemical Industry Co., Ltd.) MKG: Malachite Green (manufactured by Osaka Organic Chemical Industry Ltd.) SF-808H: Mixture of carboxybenzotriazole, 5-amino-1H-tetrazole, and methoxypropanol (manufactured by Sanwa Chemical Industry Co., Ltd.) (Solvent) ACS: acetone TLS: toluene MAL: methanol

[0101] <Preparation of Photosensitive Element> A 16 μm thick polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: FB-40) was prepared as a support, and a photosensitive layer having a thickness of 240 μm after drying was formed on the support using a photosensitive resin composition. A polyethylene film (manufactured by Tamapoly Corporation, product name: NF-15) was laminated on this photosensitive layer as a protective layer, thereby obtaining a photosensitive element in which the support, photosensitive layer, and protective layer were laminated in this order.

[0102] <Laminate Preparation> A copper-clad laminate (substrate, manufactured by Resonac Corporation, product name: MCL-E-67) comprising a glass epoxy material and copper foil (thickness: 16 μm) arranged on both sides thereof was pickled, rinsed with water, and then dried in an air stream. The copper-clad laminate was then heated to 80°C, and the protective layer was peeled off. The photosensitive element described above was then laminated onto the copper-clad laminate so that the photosensitive layer was in contact with the copper surface, thereby obtaining a laminate comprising, in order, the copper-clad laminate, the photosensitive layer, and the support. Lamination was performed using a 110°C heat roll at a pressure of 0.4 MPa and a roll speed of 1.0 m / min.

[0103] <Evaluation> (Lifting Resistance) Using a via pattern (via hole pattern) in which the diameter of the round hole opening / the center-to-center pitch of the round holes was x / 2x (x = 30 to 200, unit: μm, 10 μm intervals), the photosensitive layer of the laminate was exposed to light with a projection exposure apparatus (manufactured by Ushio Inc., product name "UX-2240-SM-XJ01") using an ultra-high pressure mercury lamp (365 nm) as a light source, at an exposure amount such that the number of remaining steps on a Hitachi 41-step step tablet was 21.

[0104] After the exposure, the support was peeled off from the laminate to expose the photosensitive layer, and the unexposed areas were removed by spraying a 1% by mass aqueous solution of sodium carbonate at 30° C. for a time twice the minimum developing time. The formed via pattern was observed with an optical microscope.

[0105] FIG. 2(a) is a microscopic image of the via pattern obtained in Example 4, FIG. 2(b) is a microscopic image of the via pattern obtained in Example 2, and FIG. 2(c) is a microscopic image of the via pattern obtained in Comparative Example 1. When lifting occurs, the resist peels off from the substrate along the round hole opening in the via pattern, causing the area around the round hole opening to become black. In contrast, when lifting does not occur, the area around the round hole opening does not become black. The fewer black shadows there are around the round hole opening, the better the lifting resistance. The lifting resistance was evaluated as follows: "A" indicates that almost no black shadows were observed around the round hole opening in the via pattern as shown in FIG. 2(a); "B" indicates that a small amount of black shadow was observed around the round hole opening as shown in FIG. 2(b); and "C" indicates that many black shadows were observed around the round hole opening as shown in FIG. 2(c).

[0106] (Resist Shape) Using a drawing pattern with a line width (L) / space width (S) of 200 / 200 (unit: μm), the photosensitive layer of the laminate was exposed to light using a projection exposure apparatus (manufactured by Ushio Inc., product name "UX-2240-SM-XJ01") with an ultra-high pressure mercury lamp (365 nm) as a light source, at an exposure amount such that the number of remaining steps on a Hitachi 41-step step tablet was 21.

[0107] After exposure, the support was peeled off from the laminate to expose the photosensitive layer, and the unexposed areas were removed by spraying a 1% by mass aqueous sodium carbonate solution at 30°C for twice the minimum development time. After development, the resist pattern was observed at an angle of 60 to 75° to the substrate using a scanning electron microscope (SEM, product name: SU-1500, manufactured by Hitachi High-Technologies Corporation, acceleration voltage: 15.0 kV). The resist shape was evaluated according to the following criteria: S: No irregularities (chipping) were observed on the wall surface of the resist pattern. A: Slight irregularities were observed on the wall surface of the resist pattern. B: Numerous irregularities were observed on the wall surface of the resist pattern, or peeling from the substrate was observed at the bottom of the resist pattern.

[0108] (Adhesion) Using a drawing pattern in which line width (L) / space width (S) is x / x (x=30 to 200, unit: μm, 10 μm intervals), the photosensitive layer of the laminate was exposed to light using a projection exposure apparatus (manufactured by Ushio Inc., product name "UX-2240-SM-XJ01") with an ultra-high pressure mercury lamp (365 nm) as a light source, at an exposure amount such that the number of remaining steps on a Hitachi 41-step step tablet was 21.

[0109] After exposure, the support was peeled off from the laminate to expose the photosensitive layer, and the unexposed areas were removed by spraying a 1% by mass aqueous solution of sodium carbonate at 30°C for twice the minimum development time. After development, the space areas (unexposed areas) were removed without residue, and the line areas (exposed areas) were formed without meandering or chipping. Adhesion was evaluated based on the minimum line width (unit: μm) in the resist pattern. The smaller the numerical value, the better the adhesion.

[0110] (Round hole resolution) Using a via pattern in which the diameter of the round hole opening / the center-to-center pitch of the round holes was x / 2x (x=30 to 200, unit: μm, 10 μm intervals), the photosensitive layer of the laminate was exposed to light with a projection exposure apparatus (manufactured by Ushio Inc., product name "UX-2240-SM-XJ01") using an ultra-high pressure mercury lamp (365 nm) as a light source, at an exposure amount such that the number of remaining steps of a Hitachi 41-step step tablet was 21.

[0111] After exposure, the support was peeled off from the laminate to expose the photosensitive layer, and the unexposed areas were removed by spraying a 1% by mass aqueous solution of sodium carbonate at 30°C for twice the minimum development time. After development, the formed via pattern was observed under an optical microscope, and the round hole resolution was evaluated based on the value of the smallest via pattern diameter among the via patterns arranged in a lattice pattern that were completely removed (opened). The smaller this value, the better the round hole resolution.

[0112] (Sensitivity) After placing a Hitachi 41-step step tablet on the support of the laminate, the photosensitive layer was exposed through the support using a projection exposure apparatus (manufactured by Ushio Inc., product name "UX-2240-SM-XJ01") using an ultra-high pressure mercury lamp (365 nm) as a light source, at an exposure amount such that the number of remaining steps of the Hitachi 41-step step tablet was 21. The exposure amount at this time (unit: mJ / cm ２ The sensitivity was evaluated by the following formula: The lower the exposure amount, the higher the sensitivity.

[0113]

[0114] 1... photosensitive element, 2... support, 3... photosensitive layer, 4... protective layer.

Claims

1. A photosensitive element comprising a support and a photosensitive layer formed on the support, wherein the photosensitive layer contains a binder polymer, a photopolymerizable compound, a photopolymerization initiator, and a sensitizer, wherein the photopolymerization initiator contains a hexaarylbiimidazole compound, and the content of the sensitizer is 0.019 parts by mass or less per 100 parts by mass of the total amount of the binder polymer and the photopolymerizable compound.

2. The photosensitive element of claim 1, wherein the sensitizer comprises a benzophenone compound.

3. The photosensitive element of claim 1, wherein the photoinitiator further comprises an N-phenylglycine compound.

4. The photosensitive element according to claim 3, wherein the content of the N-phenylglycine compound is 0.010 parts by mass or more per 100 parts by mass of the total amount of the binder polymer and the photopolymerizable compound.

5. The photosensitive element of claim 1, wherein the photosensitive layer further contains a polymerization inhibitor.

6. The photosensitive element of claim 5, wherein the polymerization inhibitor comprises a catechol compound.

7. The photosensitive element according to claim 6, wherein the content of the catechol compound is 0.100 parts by mass or less per 100 parts by mass of the total amount of the binder polymer and the photopolymerizable compound.

8. The photosensitive element of claim 1, wherein the photosensitive layer has a thickness of 35 μm or greater.

9. A method for forming a resist pattern, comprising the steps of: forming a photosensitive layer on a substrate using the photosensitive element according to any one of claims 1 to 8; photo-curing a portion of the photosensitive layer; and removing an uncured portion of the photosensitive layer.

10. A method for manufacturing a wiring board, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the method for forming a resist pattern according to claim 9, to form a conductor pattern.

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