JP2021015296A - Photosensitive element, method for forming resist pattern, and method for manufacturing printed wiring board - Google Patents

Abstract

To provide a photosensitive element capable of suppressing the occurrence of resist loss.SOLUTION: A photosensitive element 1 includes a support film 10 and a photosensitive layer 20 arranged on the support film 10. The photosensitive layer 20 contains a binder polymer, a photopolymerizable compound having an ethylenically unsaturated bond, and a photoinitiator. The number of defects having a diameter of 2 μm or more on a main surface 12 on the photosensitive layer 20 side of the support film 10 is 30 or less per 2 mm2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a photosensitive element, a method for forming a resist pattern using the photosensitive element, and a method for manufacturing a printed wiring board.

Conventionally, in the field of manufacturing printed wiring boards and the field of precision processing of metals, resist materials used for etching, plating, etc. include a support film, a layer made of a photosensitive resin composition (hereinafter referred to as "photosensitive layer"), and , Photosensitive elements composed of protective films are widely used.

The printed wiring board is manufactured, for example, as follows. First, the protective film of the photosensitive element is peeled off from the photosensitive layer, and then the photosensitive layer is laminated on the conductive film of the substrate. Next, after pattern exposure is applied to the photosensitive layer, the unexposed portion is removed with a developing solution to form a resist pattern. Then, a printed wiring board is formed by patterning the conductive film based on this resist pattern.

As the support film used for the photosensitive element, a support film having a specified haze value, a support film having a limited lubricant particle size, or the like may be used (see, for example, Patent Documents 1 and 2 below).

Japanese Unexamined Patent Publication No. 2001-13681 Japanese Unexamined Patent Publication No. 2014-74764

With the recent increase in the resolution of circuit formation, the resolution required for the photosensitive element and the exposure apparatus used for the circuit formation has increased, and the resist defect (for example, resist) derived from the lubricant of the support film of the photosensitive element or its aggregate has increased. The increase in defects such as chips) has become a problem.

For example, when a highly transparent conventional support film having a sufficiently small haze value or lubricant particle size is used, a high resolution photosensitive resin composition or a high resolution exposure machine (for example, a projection exposure machine and a direct drawing exposure machine) ) May increase the loss of resist significantly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photosensitive element capable of suppressing the occurrence of resist deficiency. Another object of the present invention is to provide a method for forming a resist pattern and a method for manufacturing a printed wiring board using the photosensitive element.

Regarding the defect of the resist in the conventional photosensitive element, the defect on the surface of the support film in contact with the photosensitive layer (for example, particles such as lubricant and the unevenness caused by the particle) is the main factor causing the defect of the resist. It was found in the examination of the present inventor. However, it is very difficult in manufacturing to reduce particles such as lubricant in order to reduce the loss of resist derived from the support film, and there is a limit to the existing improvement method for reducing the size and number of particles such as lubricant. ..

On the other hand, the present inventor has investigated in detail the influence and cause of the defect of the support film on the resist. First, in order to investigate the influence of the particles in contact with the photosensitive layer, the influence of the surface of the support film in contact with the photosensitive layer on the occurrence of pattern defects was investigated using a support film coated with a lubricant on both sides. As a result, the present inventor has found the following findings. That is, it was clarified that the defect of the surface of the support film that does not contact the photosensitive layer (the surface opposite to the surface of the support film that contacts the photosensitive layer) has a small effect on the defect of the resist. On the other hand, it has been found that the resist defects can be significantly improved by smoothing the support film by reducing the number of defects on the surface in contact with the photosensitive layer.

The photosensitive element according to the present invention is a photosensitive element including a support film and a photosensitive layer arranged on the support film, and the photosensitive layer has a binder polymer and an ethylenically unsaturated bond. The number of defects having a diameter of 2 μm or more on the surface of the support film on the photosensitive layer side, which contains a polymerizable compound and a photopolymerization initiator, is 30 or less per 2 mm ² .

In the photosensitive element according to the present invention, the number of defects on the surface of the support film on the photosensitive layer side is reduced. As a result, the smoothness of the surface of the support film on the photosensitive layer side is improved, so that the occurrence of resist defects can be suppressed. Further, according to the photosensitive element according to the present invention, it is possible to suppress the occurrence of resist defects even when a high-resolution exposure machine is used, and good resist formability can be obtained.

In the photosensitive element according to the present invention, the support film has a polyester film, a resin layer, and a lubricant layer, the resin layer is arranged between the photosensitive layer and the polyester film, and the lubricant layer is polyester. It may be arranged on the side opposite to the resin layer in the film. The thickness of the support film is preferably 1 to 200 μm.

The haze value of the support film is preferably 0.01 to 1.0%.

The method for forming a resist pattern according to the present invention includes a laminating step of laminating the photosensitive layer of the above-mentioned photosensitive element on a substrate, and an exposure step of irradiating a predetermined portion of the photosensitive layer with active light to form a photocurable portion. A development step of removing a region other than the photocurable portion of the photosensitive layer is provided.

In the method for manufacturing a printed wiring board according to the present invention, a step of applying at least one selected from the group consisting of etching treatment and plating treatment to a substrate having a resist pattern formed by the above-mentioned resist pattern forming method is performed. Be prepared.

According to the present invention, it is possible to provide a photosensitive element capable of suppressing the occurrence of resist deficiency. Further, according to the present invention, it is possible to provide a method for forming a resist pattern and a method for manufacturing a printed wiring board using the photosensitive element. According to the present invention, even when a high-resolution exposure machine is used, it is possible to suppress the occurrence of resist defects, and good resist formability can be obtained.

It is a schematic cross-sectional view which shows one Embodiment of the photosensitive element of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as necessary. The dimensional ratios in the drawings are not limited to the ratios shown.

As used herein, the term "(meth) acrylate" means at least one of "acrylate" and its corresponding "methacrylate". The same applies to other similar expressions such as "(meth) acrylic".

<Photosensitive element>
FIG. 1 is a schematic cross-sectional view showing a photosensitive element according to the present embodiment. The photosensitive element 1 shown in FIG. 1 includes a support film 10 and a photosensitive layer (layer of a photosensitive resin composition) 20. The photosensitive layer 20 is provided on the first main surface 12 of the support film 10 and is in contact with the first main surface 12. The support film 10 has a second main surface 14 on the side opposite to the first main surface 12. Here, the first main surface 12 refers to the surface of the support film 10 on the photosensitive layer 20 side, and the second main surface 14 refers to the surface of the support film 10 opposite to the photosensitive layer 20. Say that.

Conventionally, when light scattering occurs due to a lubricant or a foreign substance contained in a support film in an exposure process, a defect occurs in the resist after development. In particular, when a high-resolution exposure machine is used, the influence of light scattering is large, and the resist after development tends to be damaged. When a photosensitive element having such a support film is used for manufacturing a printed wiring board, it contributes to the occurrence of open defects during etching or short-circuit defects during plating, resulting in a manufacturing yield of printed wiring boards. Tends to decline.

In the conventional support film, it is said that the haze value is preferably 0.01 to 1.0% from the viewpoint of obtaining high transparency for the purpose of reducing the defect of the resist. However, conventionally, for example, if the lubricant layer of the support film is present on the photosensitive layer side and a dent having a depth of 2 μm or more is formed in the photosensitive layer, resist deficiency is likely to occur, and a high-resolution exposure machine is used. If this is the case, resist loss is particularly likely to occur.

On the other hand, in the photosensitive element according to the present embodiment, the number of defects having a diameter of 2 μm or more on the surface (first main surface 12) of the support film 10 on the photosensitive layer 20 side is 30 or less per 2 mm ² . As a result, it is possible to suppress the formation of a dent having a depth of 2 μm or more in the photosensitive layer 20, and it is possible to suppress the occurrence of resist defect.

(Support film)
The support film 10 has, for example, a base material layer (polyester film or the like), a resin layer, and a lubricant layer (a layer containing a lubricant). The resin layer is arranged between the photosensitive layer 20 and the base material layer, and is located on the first main surface 12 side. The resin layer may contain particles (for example, fine particles), or may be a lubricant layer (layer containing a lubricant). The first main surface 12 of the support film 10 is preferably smooth. The lubricant layer is arranged on the side opposite to the resin layer in the base material layer, and is located on the side of the second main surface 14.

The thickness of the resin layer (lubricant layer, etc.) is preferably 0.05 to 5.0 μm from the viewpoint of easily maintaining the mechanical strength. The resin layer (lubricant layer or the like) can be formed by using a known method such as a roll coater, a flow coater, a spray coater, a curtain flow coater, a dip coater, or a slit die coater.

The number of defects having a diameter of 2 μm or more on the first main surface 12 on the photosensitive layer 20 side of the support film 10 is 30 or less per 2 mm ² from the viewpoint of suppressing the occurrence of resist defects. From the viewpoint of further suppressing the occurrence of resist defects, the number of defects is preferably 20 or less, and more preferably 10 or less per 2 mm ² . The defect diameter is, for example, the maximum diameter of the defect. The measurement area having an area of 2 mm ² is, for example, an area of 18 mm × 0.11 mm. The number of defects is, for example, an average value of a plurality of measured values. The average value can be obtained as an average value of five measured values obtained by measuring the number of defects in any five regions on the surface (first main surface 12) of the support film 10 on the photosensitive layer 20 side. it can. The number of defects can be measured using a polarizing microscope or an optical interference measurement method.

The diameter of defects (for example, particles such as lubricant) contained in the first main surface 12 of the support film 10 is preferably 2 μm or less. Even if a large number of defects having a diameter of less than 2 μm are contained in the support film 10, the effect on light scattering is not large. The reason is that when the photosensitive layer is irradiated with light in the exposure process, the photocuring reaction of the photosensitive layer is not only in the light-irradiated portion but also in the lateral direction (for example, light) in which light is not directly irradiated. It also progresses in the direction perpendicular to the irradiation direction). Therefore, when the diameter is small, the photo-curing reaction directly under the defect proceeds sufficiently, but as the diameter increases, the photo-curing reaction directly under the defect does not proceed sufficiently, so that minute resist defects occur. Conceivable.

Here, the defect of the support film 10 is a defect derived from a component constituting the support film 10. Factors that form defects include, for example, a gel-like polymer; a monomer that is a raw material; a catalyst used during production; and if necessary, inorganic or organic fine particles that are contained in agglomerate during the production of the support film 10. Object: Swelling due to the lubricant and the adhesive generated when the lubricant layer is applied onto the support film 10; particles (lubricant or the like) having a diameter of 2 μm or more contained in the support film 10 can be mentioned. Examples of the particles having a diameter of 2 μm or more contained in the support film 10 include particles protruding from the first main surface 12 of the support film 10, particles existing inside the surface of the support film 10. The number of defects can be adjusted by selectively using particles having a small particle size, particles having excellent dispersibility, and the like. Here, the average particle size of the particles can be obtained as the median diameter (d50) of the particle size distribution measured using a laser diffraction / scattering type microtrack particle size distribution meter or the like.

The support film (base material layer, etc.) can be used without particular limitation. Examples of the support film include polyesters such as polyethylene terephthalate (hereinafter referred to as "PET"), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN); and polyolefins such as polypropylene and polyethylene. Be done. The support film may be a single layer or a multilayer.

The haze value of the support film is preferably 0.01 to 1.0%, more preferably 0.01 to 0.85%, and even more preferably 0.01 to 0.7%. , 0.01-0.55% is particularly preferable. When the haze value is 0.01% or more, the support film itself tends to be easily manufactured. When the haze value is 1.0% or less, it tends to be easy to suppress the decrease in sensitivity and resolution. Here, the "haze value" means the degree of cloudiness. As the haze value, a value measured using a commercially available turbidity meter (turbidity meter) in accordance with the method specified in JIS K 7105 can be used. The haze value can be measured with a commercially available turbidity meter such as NDH-5000 (manufactured by Nippon Denshoku Industries Co., Ltd., trade name).

The thickness of the support film is preferably 1 to 200 μm, more preferably 5 to 200 μm, further preferably 11 to 100 μm, particularly preferably 12 to 50 μm, and 15 to 40 μm. It is highly preferable to have it. When the thickness is 1 μm or more, it tends to be easy to prevent the support film from being torn when the support film is peeled from the photosensitive element. When the thickness is 200 μm or less, the cost tends to be excellent.

As the support film, a commercially available general industrial film that can be used as a support film for the photosensitive element may be obtained and appropriately processed and used. Examples of the support film include the PET film "QS-series" (manufactured by Toray Industries, Inc., development name).

(Photosensitive layer)
The photosensitive layer 20 is a layer made of a photosensitive resin composition. The photosensitive resin composition constituting the photosensitive layer 20 contains, for example, (A) a binder polymer, (B) a photopolymerizable compound having an ethylenically unsaturated bond, and (C) a photopolymerization initiator. .. Hereinafter, each component will be described in detail.

[(A) Binder polymer]
As the binder polymer as the component (A), the binder polymer used in the conventional photosensitive resin composition can be used without particular limitation. Examples of the binder polymer include acrylic resin, styrene resin, epoxy resin, amide resin, amide epoxy resin, alkyd resin, and phenol resin. Among these, acrylic resin is preferable from the viewpoint of excellent alkali developability. The binder polymer may be used alone or in combination of two or more.

The binder polymer can be produced by radically polymerizing a polymerizable monomer. Polymerizable monomers include (meth) acrylic acid, styrene, alkyl (meth) acrylate (methyl (meth) acrylate, etc.), benzyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth). ) Examples include glycidyl acrylate and maleic acid.

The binder polymer preferably has a carboxyl group in the molecule from the viewpoint of excellent alkali developability. The binder polymer having a carboxyl group can be produced by radically polymerizing a polymerizable monomer having a carboxyl group, and the polymerizable monomer having a carboxyl group and other polymerizable monomers are used. , May be radically polymerized. As the polymerizable monomer having a carboxyl group, (meth) acrylic acid is preferable. As the binder polymer, a binder polymer having a structural unit derived from (meth) acrylic acid and a structural unit derived from (meth) acrylic acid alkyl ester is preferable.

The acid value of the binder polymer may be 80 to 250 mgKOH / g, 90 to 240 mgKOH / g, 100 to 230 mgKOH / g, or 100 to 200 mgKOH / g from the viewpoint of easily improving the adhesion and resolution. The acid value of the binder polymer can be adjusted by the content of the structural units constituting the binder polymer (for example, the structural unit derived from (meth) acrylic acid).

The weight average molecular weight (Mw) of the binder polymer may be 1000 to 100,000, 2000 to 80,000, or 2500 to 60000 from the viewpoint of easily improving the mechanical strength and resolution of the film. The weight average molecular weight can be measured, for example, by gel permeation chromatography (GPC) using a standard polystyrene calibration curve. More specifically, the measurement can be performed under the conditions described in the examples.

The content of the binder polymer is preferably 40 to 90 parts by mass, and more preferably 50 to 80 parts by mass with respect to 100 parts by mass of the total amount of the components (A) and (B). When the content is 40 parts by mass or more, it tends to be suppressed that the photocured product becomes brittle. When the content is 90 parts by mass or less, sufficient resolution and light sensitivity tend to be easily obtained.

[(B) Photopolymerizable compound having an ethylenically unsaturated bond]
The component (B) (photopolymerizable compound having an ethylenically unsaturated bond) preferably contains a compound having 4 to 40 oxyalkylene units (alkylene glycol units) having 2 to 6 carbon atoms in the molecule. When the component (B) contains such a compound, the compatibility with the component (A) can be improved.

Examples of the oxyalkylene unit having 2 to 6 carbon atoms include an oxyethylene unit, an oxypropylene unit, an oxyisopropylene unit, an oxybutylene unit, an oxypentylene unit, an oxyhexylene unit, and the like. As the alkylene unit, at least one selected from the group consisting of oxyethylene units and oxyisopropylene units is preferable from the viewpoint of improving resolution and plating resistance.

Further, among the photopolymerizable compounds, from the viewpoint that the effect of the present invention tends to be obtained more reliably, from the group consisting of bisphenol A-based (meth) acrylate compounds and polyalkylene glycol di (meth) acrylates. At least one selected is particularly preferably used.

As the bisphenol A-based (meth) acrylate compound, a compound represented by the following general formula (I) is preferable.

In the general formula (I), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, and are preferably a methyl group. X ¹ and X ² each independently represent an alkylene group having 2 to 6 carbon atoms. p and q satisfy p + q = 1 to 40. The value of p + q is preferably 2 to 40, more preferably 4 to 40, further preferably 5 to 30, particularly preferably 8 to 20, and 8 to 16. Is extremely preferable, and 8 to 12 is very preferable. In addition, p and q indicate the number of structural units of a structural unit. Therefore, a single molecule shows an integer value, and an aggregate of a plurality of types of molecules shows a rational number which is an average value. Hereinafter, the same applies to the number of constituent units of the constituent units.

When the value of p + q is 1 or more, the decrease in compatibility with the component (A) is suppressed, and it tends to be easy to suppress peeling when the photosensitive element is laminated on the circuit forming substrate. When the value of p + q is 40 or less, the increase in hydrophilicity is suppressed, the resist image is less likely to peel off during development, and the plating resistance to solder plating or the like is lowered, but tends to be suppressed. In any case, the decrease in the resolution of the photosensitive element tends to be suppressed.

Examples of the alkylene group having 2 to 6 carbon atoms include an ethylene group, a propylene group, an isopropylene group, a butylene group, a pentylene group and a hexylene group. Among these, at least one selected from the group consisting of an ethylene group and an isopropylene group is preferable from the viewpoint of improving resolution and plating resistance.

Examples of the compound represented by the general formula (I) include 2,2-bis (4-((meth) acryloxipolyethoxy) phenyl) propane and 2,2-bis (4-((meth) acryloxipoly) phenyl). Propoxy) phenyl) propane, 2,2-bis (4-((meth) acryloxipolybutoxy) phenyl) propane, 2,2-bis (4-((meth) acryloxipolyethoxypolypropoxy) phenyl) propane, etc. Examples thereof include bisphenol A-based (meth) acrylate compounds.

As 2,2-bis (4-((meth) acryloxipolyethoxy) phenyl) propane, 2,2-bis (4-((meth) acryloxidiethoxy) phenyl) propane, 2,2-bis ( Examples thereof include 4-((meth) acryloxipentaethoxy) phenyl) propane and 2,2-bis (4- (methacryloxypentadecaethoxy) phenyl) propane. Of these, 2,2-bis (4- (methacryloxypentaethoxy) phenyl) propane is commercially available as FA-321M (trade name, manufactured by Hitachi Kasei Co., Ltd.). 2,2-Bis (4- (methacryloxypentadecaethoxy) phenyl) propane is commercially available as BPE-1300 (trade name, manufactured by Shin Nakamura Chemical Industry Co., Ltd.). 2,2-Bis (4-((meth) acryloxidiethoxy) phenyl) propane is commercially available as BPE-200 (trade name, manufactured by Shin Nakamura Chemical Industry Co., Ltd.). These can be used individually by 1 type or in combination of 2 or more types.

Examples of the polyalkylene glycol di (meth) acrylate include a compound represented by the following general formula (II), a compound represented by the following general formula (III), and a compound represented by the following general formula (IV). Can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

In the general formula (II), R ³ and R ⁴ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, EO represents an oxyethylene unit, PO represents an oxypropylene unit, and m ¹ , m ² and n ¹ satisfy m ¹ + m ² + n ¹ = 4 to 40.

In the general formula (III), R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, EO represents an oxyethylene unit, PO represents an oxypropylene unit, and m ³ . n ² and n ³ satisfy m ³ + n ² + n ³ = 4 to 40.

In the general formula (IV), ^{R 7} and ^{R 8} each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, EO represents an oxyethylene unit, PO represents an oxypropylene unit, ^{m 4} and n ⁴ satisfies m ⁴ + n ⁴ = 4 to 40.

Examples of the alkyl group having 1 to 3 carbon atoms in the general formulas (II), (III) and (IV) include a methyl group, an ethyl group, an n-propyl group and an isopropyl group, and a methyl group is preferable. The total number of structural units of the oxyethylene group (m ¹ + m ² , m ³ and m ⁴ ) in the general formulas (II), (III) and (IV) is preferably 1 to 30 independently, and 1 to 1 It is more preferably 10, further preferably 4 to 9, and particularly preferably 5 to 8. When the total number of the structural units is 30 or less, sufficient tent reliability and resist shape tend to be easily obtained.

The total number of constituent units of the oxypropylene group (n ¹ , n ² + n ³ , and n ⁴ ) in the general formulas (II), (III), and (IV) is preferably 1 to 30 independently. It is more preferably 5 to 20, further preferably 8 to 16, and particularly preferably 10 to 14. When the total number of the structural units is 30 or less, sufficient resolution is likely to be obtained, and sludge generation tends to be suppressed.

Specific examples of the compound represented by formula (II), for example, ^{R 3} and ^{R 4} is a methyl ^{group, m 1 + m 2 = 4} ( average ^value), and n ¹ = 1 ² (average value) vinyl Examples thereof include a compound (manufactured by Hitachi Kasei Co., Ltd., trade name: FA-023M).

Specific examples of the compound represented by the general formula (III) include vinyl compounds in which R ⁵ and R ⁶ are methyl groups, m ³ = 6 (mean value), and n ² + n ³ = 12 (mean value). (Manufactured by Hitachi Kasei Co., Ltd., trade name: FA-024M).

As a specific example of the compound represented by the general formula (IV), for example, a vinyl compound in which R ⁷ and R ⁸ are hydrogen atoms, m ⁴ = 1 (mean value), and n ⁴ = 9 (mean value) (new). Nakamura Chemical Industry Co., Ltd., trade name: NK ester HEMA-9P) can be mentioned.

As the component (B), in addition to the compounds represented by the above general formulas (I) to (IV), (meth) acrylate compounds having a skeleton derived from dipentaerythritol and the like can be used. The (meth) acrylate compound having a skeleton derived from dipentaerythritol means an esterified product of dipentaerythritol and (meth) acrylic acid, and the esterified product is a compound modified with an alkyleneoxy group. Is also defined as containing. The number of ester bonds in one molecule is 6, but compounds having 1 to 5 ester bonds may be mixed. This compound is commercially available as DPH-12E (trade name, manufactured by Shin Nakamura Chemical Industry Co., Ltd.).

As the component (B), one type can be used alone or two or more types can be used in combination.

The content of the component (B) is preferably 10 to 60 parts by mass and more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the total amount of the component (A) and the component (B). When the content is 10 parts by mass or more, sufficient resolution and light sensitivity tend to be easily obtained. When the content is 60 parts by mass or less, it tends to be suppressed that the photocured product becomes brittle.

[(C) Photopolymerization Initiator]
Examples of the component (C) (photopolymerization initiator) include N, N, N'such as benzophenyl; N, N, N', N'-tetramethyl-4,4'-diaminobenzophenone (also known as Michler ketone). , N'-tetraalkyl-4,4'-diaminobenzophenone; 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, 2-methyl-1- [4- (methylthio) phenyl ] -2-Aromatic ketones such as morpholino-1-propanone; quinone compounds such as alkylanthraquinone; benzoin ether compounds such as benzoin alkyl ethers; benzoin compounds such as benzoin and alkylbenzoins; benzyl derivatives such as benzyl dimethyl ketal; 2- (O-Chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5 2,4, such as −diphenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-diphenylimidazole dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer, etc. 5-Triarylimidazole dimer; aclysine derivatives such as 9-phenylaclydin, 1,7-bis (9,9'-acridinyl) heptane; N-phenylglycine; N-phenylglycine derivative; coumarin compounds; 1- Pyrazoline compounds such as phenyl-3- (4-methoxystyryl) -5- (4-methoxyphenyl) pyrazoline; catechol compounds such as 4-t-butylcatechol may be mentioned. Among these, 2,4,5-triarylimidazole dimer is preferable from the viewpoint of improving adhesion and sensitivity. As the component (C), one type can be used alone or two or more types can be used in combination.

The content of the component (C) is preferably 0.1 to 20 parts by mass and 0.2 to 10 parts by mass with respect to 100 parts by mass of the total amount of the components (A) and (B). Is more preferable, and 0.5 to 5 parts by mass is further preferable. When the content is 0.1 part by mass or more, sufficient light sensitivity tends to be easily obtained. When the content is 20 parts by mass or less, the increase in light absorption on the surface of the photosensitive resin composition during exposure is suppressed, and the internal photocuring tends to be sufficiently suppressed. is there.

[Other ingredients]
The photosensitive resin composition contains, if necessary, a photopolymerizable compound (oxetan compound, etc.) having at least one cationically polymerizable cyclic ether group in the molecule, a cationic polymerization initiator, a dye (malakite green, etc.), and light. Color formers (tribromophenyl sulfone, leuco crystal violet, etc.), thermal color inhibitor, plasticizers (p-toluenesulfonamide, etc.), pigments, fillers, defoaming agents, flame retardants, stabilizers, adhesion imparting agents, It may contain additives such as leveling agents, peeling accelerators, antioxidants, fragrances, imaging agents and thermal cross-linking agents. These can be used individually by 1 type or in combination of 2 or more types. The content of these additives may be 0.01 to 20 parts by mass, respectively, with respect to 100 parts by mass of the total amount of the components (A) and (B).

The photosensitive resin composition is dissolved in a solvent such as methanol, ethanol, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N, N-dimethylformamide and propylene glycol monomethyl ether, or a mixed solvent thereof, if necessary. It can be prepared as a solution having a solid content of about 30 to 60% by mass.

The photosensitive layer 20 in the photosensitive element 1 can be formed by applying the above-mentioned photosensitive resin composition on the support film 10 and then removing the solvent. Here, as the coating method, for example, known methods such as roll coating, comma coating, gravure coating, air knife coating, die coating, and bar coating can be adopted. Further, the solvent can be removed by, for example, treating at 70 to 150 ° C. for about 5 to 30 minutes. The amount of the residual organic solvent in the photosensitive layer 20 is preferably 2% by mass or less from the viewpoint of preventing the diffusion of the organic solvent in a later step.

The photosensitive element 1 may be provided with a protective film (not shown) on the side of the photosensitive layer 20 opposite to the support film 10. As the protective film, it is preferable to use a film in which the adhesive force between the photosensitive layer 20 and the protective film is smaller than the adhesive force between the photosensitive layer 20 and the support film 10. As the protective film, it is preferable to use a low fish eye film. Examples of the protective film include an inert polyolefin film (polyethylene, polypropylene, etc.). As the protective film, a polyethylene film is preferable from the viewpoint of excellent peelability from the photosensitive layer 20. The thickness of the protective film varies depending on the application, but is preferably about 1 to 100 μm.

In addition to the support film 10, the photosensitive layer 20, and the protective film, the photosensitive element 1 may further include an intermediate layer such as a cushion layer, an adhesive layer, a light absorption layer, and a gas barrier layer, or a protective layer.

The photosensitive element 1 may be stored as it is, for example, or may be stored in a state where a protective film is laminated on the photosensitive layer 20 and wound around a cylindrical winding core. At this time, it is preferable that the support film 10 is wound in a roll shape so as to be the outermost layer.

<Method of forming resist pattern>
The method for forming the resist pattern according to the present embodiment includes a laminating step of laminating the photosensitive layer 20 of the photosensitive element 1 on a substrate and an exposure of irradiating a predetermined portion of the photosensitive layer 20 with active light to form a photocurable portion. It includes a step and a developing step of removing a region other than the photocurable portion of the photosensitive layer 20.

In the laminating step, for example, the photosensitive layer of the photosensitive element and the supporting film are laminated on the substrate in this order. In the laminating step, as a method of laminating the photosensitive layer 20 on the substrate, for example, when a protective film is present on the photosensitive layer 20, after removing the protective film, the photosensitive layer 20 is placed at 70 to 130 ° C. Examples thereof include a method of laminating by crimping the substrate with a pressure of about 0.1 to 1 MPa while heating to a certain degree. In the laminating step, laminating is also possible under reduced pressure. The surface of the substrate on which the photosensitive layer 20 is laminated is usually a metal surface, but is not particularly limited. Further, in order to further improve the stackability, the substrate may be preheat-treated.

Next, a photomask having a negative or positive mask pattern is aligned with the second main surface 14 of the support film 10 and brought into close contact with the photosensitive layer 20 that has been laminated in the laminating step.

Next, in the exposure step, for example, a predetermined portion of the photosensitive layer 20 is irradiated with active light through the support film 10 to form a photocurable portion in the photosensitive layer 20. The exposure step is performed, for example, by irradiating the photosensitive layer 20 with active rays in an image shape through the support film 10 to form a photocurable portion on the photosensitive layer 20. As the light source of the active light, a known light source (for example, a light source that effectively emits ultraviolet rays, visible light, etc., such as a carbon arc lamp, a mercury vapor arc lamp, a high-pressure mercury lamp, and a xenon lamp) is used. A laser direct drawing exposure method can also be used.

After the exposure step, the photomask is peeled off from the support film 10. Next, the support film 10 is peeled off from the photosensitive layer 20.

Next, in the developing step, a region other than the photocurable portion in the photosensitive layer is removed. In the developing step, for example, the unexposed portion (unlightened portion) of the photosensitive layer 20 is removed by wet development with a developing solution such as an alkaline aqueous solution, an aqueous developer, or an organic solvent, or dry development to develop a resist pattern. Can be manufactured.

Examples of the alkaline aqueous solution include a 0.1 to 5% by mass sodium carbonate solution, a 0.1 to 5% by mass potassium carbonate solution, and a 0.1 to 5% by mass sodium hydroxide solution. The pH of the alkaline aqueous solution is preferably in the range of 9-11. The temperature of the alkaline aqueous solution is adjusted according to the developability of the photosensitive layer 20. Further, the alkaline aqueous solution may contain a surface active agent, an antifoaming agent, an organic solvent and the like. Examples of the developing method include a dip method, a spray method, brushing and slapping.

Further, as a treatment after the developing step, the resist pattern may be further cured by heating at about 60 to 250 ° C. or exposing at about 0.2 to 10 J / cm ² , if necessary.

By the above method, a resist pattern can be formed on the conductor layer on which the wiring pattern is formed. The resist pattern can be used as a solder resist that prevents solder from adhering to unnecessary portions on the conductor layer when joining mounting components.

Further, the resist pattern obtained by the above-mentioned forming method is used for forming a cured resin having excellent physical characteristics (tensile strength, elongation, etc.) and satisfying electrolytic corrosion resistance on a rigid substrate. It may be used as a permanent mask (solder resist) formed on a rigid base material. Specifically, the resist pattern is useful when used as a solder resist for a printed wiring board including a rigid substrate or a solder resist for a semiconductor package substrate including a rigid substrate.

<Manufacturing method of printed wiring board>
In the method for manufacturing a printed wiring board according to the present embodiment, at least one selected from the group consisting of etching treatment and plating treatment is applied to a substrate having a resist pattern formed by the method for forming a resist pattern. Be prepared. Here, the etching or plating of the substrate can be performed by etching or plating the surface of the substrate by a known method using the developed resist pattern as a mask.

As the etching solution used for etching, for example, a cupric chloride solution, a ferric chloride solution, and an alkaline etching solution can be used. Examples of the plating include copper plating, solder plating, nickel plating, and gold plating.

After etching or plating, the resist pattern can be peeled off with, for example, a stronger alkaline aqueous solution than the alkaline aqueous solution used for development. As the strongly alkaline aqueous solution, for example, a 1 to 10 mass% sodium hydroxide aqueous solution and a 1 to 10 mass% potassium hydroxide aqueous solution are used. Further, examples of the peeling method include a dipping method and a spraying method. The printed wiring board on which the resist pattern is formed may be a multilayer printed wiring board or may have a small-diameter through hole.

When plating is performed on a substrate provided with an insulating layer and a conductor layer formed on the insulating layer, it is necessary to remove the conductor layer other than the resist pattern. As a method of removing this, for example, a method of lightly etching after peeling off the resist pattern; the wiring portion is masked with solder by peeling off the resist pattern after performing solder plating or the like after the plating, and then with solder. Examples thereof include a method of treating only the unmasked portion of the conductor layer with an etching solution capable of etching.

<Manufacturing method of semiconductor package substrate>
The photosensitive element according to the present embodiment can also be used for a semiconductor package substrate including a rigid substrate and an insulating film arranged on the rigid substrate. In this case, the photocurable portion of the photosensitive layer may be used as an insulating film. When the photocurable portion of the photosensitive layer is used as a solder resist for a semiconductor package, for example, after the development in the resist pattern forming method described above is completed, ultraviolet rays are irradiated by a high-pressure mercury lamp for the purpose of improving solder heat resistance, chemical resistance, etc. Alternatively, heating is preferable. When irradiating with ultraviolet rays, the irradiation amount can be adjusted as needed, and for example, irradiation can be performed with an irradiation amount of about 0.2 to 10 J / cm ² . When the resist pattern is heated, it is preferable that the resist pattern is heated in the range of about 100 to 170 ° C. for about 15 to 90 minutes. Further, it is also possible to carry out ultraviolet irradiation and heating at the same time, and it is also possible to carry out either one and then the other. When irradiating with ultraviolet rays and heating at the same time, it is more preferable to heat at 60 to 150 ° C. from the viewpoint of effectively imparting solder heat resistance, chemical resistance and the like.

This solder resist also serves as a protective film for wiring after soldering to the substrate, and has excellent physical characteristics (tensile strength, elongation, etc.) and thermal shock resistance, so it is effective as a permanent mask for semiconductor packages. is there.

A semiconductor package substrate having such a resist pattern is subsequently mounted on an electronic device such as a personal computer after mounting a semiconductor element or the like (for example, wire bonding and solder connection).

According to the photosensitive element, the resist pattern forming method, the printed wiring board, and the semiconductor package substrate manufacturing method according to the present embodiment, in the photosensitive element provided with the supporting film, the surface of the supporting film on the photosensitive layer side (first). Since the number of defects on the main surface 12) is reduced, the defects of the resist can be sufficiently reduced. In particular, when a high-resolution exposure machine is used, the defect of the resist can be reduced.

By the way, the depth of focus (focal range) of the exposure machine for forming a fine circuit is, for example, ± 40 μm when obtaining a resolution of 4 μm, and ± 10 μm when obtaining a resolution of 2 μm or less. In this way, when a fine circuit (high resolution) is obtained, the depth of focus becomes narrow. Here, if the lubricant layer (for example, the lubricant layer arranged on the second main surface 14 side of FIG. 1) is arranged at a position outside the range of the depth of focus, defects tend to be reduced. Further, when a surface in contact with the photosensitive layer (for example, the first main surface 12 in FIG. 1) is included within the range of the depth of focus, the surface is preferably smooth.

Although the present invention has been described in detail above based on the embodiment, the present invention is not limited to the embodiment. The present invention can be modified in various ways without departing from the gist thereof.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Synthesis of binder polymer>
The binder polymer having the composition shown in Table 1 was synthesized according to the following synthesis example.

To a flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas introduction tube, 420 g of a mixture of toluene and methyl cellosolve having a mass ratio of 6: 4 was added, and then the mixture was stirred while blowing nitrogen gas. , Heated to 80 ° C. Further, a solution (hereinafter referred to as “solution a”) in which the predetermined materials shown in Table 1 are mixed as a copolymerization monomer is prepared, and the above-mentioned formulation heated to 80 ° C. (toluene: methylcellosolve = mass ratio 6: Solution a was added dropwise to 4) over 4 hours. Then, the dropping funnel was washed with 40 g of a mixture of toluene and methyl cellosolve having a mass ratio of 6: 4 and added to the flask. Then, it was kept warm for 2 hours with stirring at 80 ° C. Further, a solution prepared by dissolving 1.0 g of azobisisobutyronitrile in 40 g of a mixture of methyl cellosolve and toluene having a mass ratio of 6: 4 was added dropwise into the flask over 30 minutes. The dropping funnel was washed with 120 g of a mixture of toluene and methyl cellosolve having a mass ratio of 6: 4 and added to solution a. The solution after dropping was kept warm at 80 ° C. for 3 hours with stirring, and then heated to 90 ° C. over 30 minutes. After keeping warm at 90 ° C. for 2 hours, it was cooled to obtain a binder polymer solution as a component (A). Toluene was added to this binder polymer solution to adjust the non-volatile component concentration (solid content concentration) to 40% by mass. The weight average molecular weight of the binder polymer was measured. The weight average molecular weight was measured by a gel permeation chromatography (GPC) method and calculated by converting using a standard polystyrene calibration curve. The conditions of GPC are shown below. The acid value was measured according to the following measurement procedure. Table 1 shows the measurement results of the weight average molecular weight and the acid value.

[GPC conditions]
Pump: Hitachi L-6000 type [manufactured by Hitachi, Ltd.]
Column: Gelpack GL-R420 + Gelpack GL-R430 + Gelpack GL-R440 (3 in total) [above, manufactured by Hitachi Kasei Co., Ltd., product name]
Eluent: tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 2.05 mL / min Detector: Hitachi L-3300 type RI [Hitachi, Ltd., product name]

[Measurement method of acid value]
After weighing the synthesized binder polymer solution into an Erlenmeyer flask, a mixed solvent (mass ratio: toluene / methanol = 70/30) was added to dissolve the binder polymer. Next, a phenolphthalein solution was added as an indicator, and then titrated with a 0.1N potassium hydroxide alcohol solution to measure the acid value.

<Preparation of solution of photosensitive resin composition>
A solution of the photosensitive resin composition was prepared by blending each component shown in Table 2 below.

<Manufacturing of photosensitive element>
As the support film for the photosensitive element, the support film shown in Table 3 (“film name” in Table 3) was prepared. The details of each support film are as follows.

QS series: A biaxially oriented film having a three-layer structure having a PET film and lubricant layers (resin layers containing particles) arranged on both sides of the PET film. The number of lubricants contained in one lubricant layer is extremely smaller than that of the other lubricant layer; FB-40 manufactured by Toray Industries, Inc .: PET film and lubricant layers (resins containing particles) arranged on both sides of the PET film. A biaxially oriented film having a three-layer structure having a layer (average particle size of contained particles: 1 μm or less); A-1517 manufactured by Toray Industries, Inc .: a PET film and a first arranged on one side of the PET film. It has a lubricant layer (resin layer containing particles) and a second lubricant layer (resin layer containing particles. Average particle size of contained particles: 2 μm or more) arranged on the other surface of the PET film. Biaxially oriented film with a two-layer structure; A-4100 manufactured by Toyo Spinning Co., Ltd .: A PET film, a first lubricant layer (resin layer containing particles) arranged on one surface of the PET film, and the PET film. A biaxially oriented film having a two-layer structure having a second lubricant layer (resin layer containing particles. Average particle size of contained particles: 2 μm or more) arranged on the other surface of the film; G2H: manufactured by Toyo Spinning Co., Ltd. Biaxially oriented PET film with a single layer structure containing particles (average particle size: 2 μm or more); manufactured by Teijin DuPont Film Co., Ltd.

Table 3 shows the results of measuring the thickness of the support film, the number of defects having a diameter of 2 μm or more on the surface of the support film, the transmittance, and the haze value. The number of defects was measured by using optical interference to measure the number of defects (aggregate particles, etc.) having a diameter of 2 μm or more existing in a region of 2 mm ² (18 mm × 0.11 mm). As the measuring machine, the trade name "Hybrid Confocal Microscope" manufactured by Lasertec Co., Ltd. was used. The number of measurements (n number) at that time was set to 5, and the average value was calculated. The surface on which the photosensitive layer is formed (the first main surface 12 in FIG. 1; “the surface on the photosensitive layer side” in Table 3) and the surface opposite to the surface on which the photosensitive layer is formed (in FIG. 1). The number of defects on the second main surface 14. “The surface opposite to the photosensitive layer” in Table 3) was measured. The transmittance and the haze value were measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

Next, the solution of the photosensitive resin composition was applied onto each support film so as to have a uniform thickness, and then dried in a hot air convection dryer at 100 ° C. for 2 minutes to remove the solvent. When A-1517 or A-4100 is used as the support film, a photosensitive layer is formed on the second lubricant layer (resin layer containing particles. Average particle size of contained particles: 2 μm or more). After drying, the photosensitive layer was coated with a protective film made of polyethylene (manufactured by Tamapoli Co., Ltd., trade name "NF-15A", thickness: 28 μm) to obtain a photosensitive element. The thickness of the photosensitive layer after drying was 10 μm.

<Preparation of laminate>
Acid on the copper surface of a double-sided copper-clad laminate (manufactured by Hitachi Kasei Co., Ltd., trade name "MLC-E-679", 125 mm x 200 mm square), which is a glass epoxy material in which copper foil (thickness: 35 μm) is laminated on both sides. After washing and washing with water, it was dried by air flow. After heating the obtained copper-clad laminate to 80 ° C., the photosensitive element was laminated so that the photosensitive layer was in contact with the copper surface while peeling off the protective film. As a result, a laminate in which the copper-clad laminate, the photosensitive layer, and the support film were laminated in this order was obtained. Lamination was performed using a heat roll at 110 ° C. at a crimping pressure of 0.4 MPa and a roll speed of 1.5 m / min.

<Evaluation>
(Measurement of minimum development time)
The photosensitive layer of the test piece (laminated body) was exposed at 250 mJ / cm ² using a projection exposure machine (UX-7 series, manufactured by Ushio, Inc.) equipped with a high-pressure mercury lamp, and then the support film was peeled off. Next, the photosensitive layer was spray-developed, and the time during which the unexposed portion was completely removed was measured and obtained as the minimum development time. The measurement results are shown in Table 3.

(Measurement of light sensitivity)
A 41-step step tablet was placed as a negative on the support film of the test piece (laminated body). Then, using a projection exposure machine (UX-7 series, manufactured by Ushio, Inc.) equipped with a high-pressure mercury lamp, the irradiation amount is adjusted in order to obtain a predetermined irradiation energy amount at which the number of resist curing stages after development is nine. While exposing the photosensitive layer.

Next, the support film was peeled off, and a 1% by mass sodium carbonate aqueous solution at 30 ° C. was spray-developed for twice the minimum development time, and the unexposed portion was removed for development. Then, it was confirmed that the number of steps of the photocurable film step tablet formed on the copper-clad laminate was 9 steps, and the irradiation energy amount (exposure amount, mJ / cm ² ) in the exposure was obtained. The measurement results are shown in Table 3. The smaller the value of the irradiation energy amount, the higher the light sensitivity.

(Measurement of adhesion and resolution)
In order to check the adhesion and resolution, a photo tool with a 41-step step tablet and a glass chrome type with a wiring pattern with a line width / space width of 2/6 to 20/90 (unit: μm) as a negative for adhesion evaluation. Photo tool, a glass chrome type photo tool with a wiring pattern with a line width / space width of 2/2 to 20/20 (unit: μm) as a negative for resolution evaluation, and a projection exposure machine (UX) with a high-pressure mercury lamp. Using a -7 series (manufactured by Ushio Denki Co., Ltd.), the photosensitive layer of the laminate was exposed with an irradiation energy amount such that the number of remaining steps after development of the 41-step step tablet was 9. Next, the support film was peeled off, and a 1% by mass sodium carbonate aqueous solution was spray-developed at 30 ° C. for twice the minimum development time, and the unexposed portion was removed for development. Here, the adhesion and the resolution were evaluated by the smallest value (unit: μm) of the space width between the line widths in which the unexposed portion could be removed cleanly by the developing process. The smaller the numerical value, the better the evaluation of adhesion and resolution. The results are shown in Table 3.

(Evaluation of resist deficiency)
Using a scanning electron microscope SU-1500 (manufactured by Hitachi, Ltd.), the resist line of the substrate used in the measurement of adhesion and resolution was observed, and the number of resist defects per 2 mm ² was evaluated. The results are shown in Table 3.

When exposure was performed with a high-resolution projection exposure machine at a low number of curing stages so that ST = 9/41, no resist deficiency was confirmed in Examples 1 to 3, whereas in Comparative Examples 1 to 4, the resist was not defective. A defect in the resist, which is thought to be derived from the lubricant of the support film, was confirmed.

The particle size of the lubricant of the support film used in Comparative Example 1 is smaller than the particle size of the lubricant contained in Comparative Examples 2 to 4, but at the interface between the photosensitive layer and the support film (the surface of the support film on the photosensitive layer side). , Since there are many defects derived from lubricants and the like, it is considered that the defects block the exposed light beam and cause resist defects. In Comparative Examples 2 and 3, since the number of lubricants present at the interface between the photosensitive layer and the support film (the surface of the support film on the photosensitive layer side) is large, the aggregates block the exposed light rays and cause resist defects. Conceivable.

According to the present invention, it is possible to provide a photosensitive element capable of suppressing the occurrence of resist deficiency. Further, according to the present invention, it is possible to provide a method for forming a resist pattern and a method for manufacturing a printed wiring board using the photosensitive element.

1 ... Photosensitive element, 10 ... Support film, 12 ... First main surface (surface on the photosensitive layer side of the support film), 14 ... Second main surface (surface opposite to the photosensitive layer of the support film), 20 ... Photosensitive layer (layer of photosensitive resin composition).

Claims (1)

A photosensitive element comprising a support film and a photosensitive layer arranged on the support film.
The photosensitive layer contains a binder polymer, a photopolymerizable compound having an ethylenically unsaturated bond, and a photopolymerization initiator.
A photosensitive element in which the number of defects having a diameter of 2 μm or more on the surface of the support film on the photosensitive layer side is 30 or less per 2 mm ² .

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