JP6045920B2 - Etching mask composition and pattern forming method - Google Patents

Description

  The present invention relates to an etching mask composition used as a masking agent for etching a solar cell substrate.

  In the solar cell manufacturing process, a mask agent is used when a substrate is partially etched. Conventionally, a photoresist has been used in this process, but at present, application of a printing resist is being studied for the purpose of reducing the number of processes. A strong acid such as hydrofluoric acid or nitric acid is used as an etchant for etching the solar cell substrate. For this reason, the characteristics required for the printing type resist are required to be resistant to an etching solution during etching and to be able to form a pattern by a printing method.

JP-A-9-293888

  The conventional printing type resist has room for improvement in that a good pattern is formed by faithfully reproducing the printing design while ensuring sufficient acid resistance. There is also room for improvement in printing stability when continuous printing is performed.

  This invention is made | formed in view of such a subject, The objective exists in provision of the technique which can improve the printability at the time of printing the composition for etching masks on the board | substrate for solar cells.

One embodiment of the present invention is an etching mask composition. The etching mask composition is an etching mask for a non-photosensitive solar cell substrate containing 100 parts by mass of a novolak resin (A), 20 to 100 parts by mass of SiO ₂ particles (B), and a solvent (C). Composition.

  According to the composition for etching mask of the said aspect, the printability at the time of printing on the board | substrate for solar cells can be improved.

In the etching mask composition of the above aspect, the solvent (C) may contain a solvent (C1) having a boiling point of 190 ° C. or higher. The SiO ₂ particles (B) may be hydrophilic. Further, a silicon-based, acrylic-based or fluorine-based surfactant (D) may be further provided.

  Another embodiment of the present invention is a pattern forming method. The pattern forming method includes a step of forming a mask pattern by a printing method on the substrate using the etching mask composition for a solar cell substrate according to any one of the aspects described above, a step of baking the mask pattern, and a substrate. And a step of transferring the mask pattern and a step of removing the mask pattern.

  ADVANTAGE OF THE INVENTION According to this invention, the acid resistance and printability at the time of printing the composition for etching masks on the board | substrate for solar cells can be improved.

1A to 1C are schematic cross-sectional views showing a pattern forming process on a substrate.

  The composition for an etching mask according to the embodiment is non-photosensitive and is suitably used as an etching mask used when a solar cell substrate is partially etched.

The composition for etching masks according to the embodiment includes 100 parts by mass of novolac resin (A), 20 to 100 parts by mass of SiO ₂ particles (B), and a solvent (C). Hereinafter, each component of the composition for etching masks according to the embodiment will be described in detail.

  The novolak resin (A) is a novolak resin obtained by reacting the phenols exemplified below with the aldehydes exemplified below under an acidic catalyst such as hydrochloric acid, sulfuric acid, formic acid, oxalic acid, paratoluenesulfonic acid, etc. Etc.

  Examples of phenols include phenol; cresols such as m-cresol, p-cresol, and o-cresol; xylenols such as 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, and 3,4-xylenol. M-ethylphenol, p-ethylphenol, o-ethylphenol, 2,3,5-trimethylphenol, 2,3,5-triethylphenol, 4-tert-butylphenol, 3-tert-butylphenol, 2-tert Alkylphenols such as butylphenol, 2-tert-butyl-4-methylphenol, 2-tert-butyl-5-methylphenol; p-methoxyphenol, m-methoxyphenol, p-ethoxyphenol, m-ethoxyphenol, p -Propoxyphe And alkoxyphenols such as m-propoxyphenol; isopropenylphenols such as o-isopropenylphenol, p-isopropenylphenol, 2-methyl-4-isopropenylphenol, 2-ethyl-4-isopropenylphenol Arylphenols such as phenylphenol; polyhydroxyphenols such as 4,4′-dihydroxybiphenyl, bisphenol A, resorcinol, hydroquinone, pyrogallol, and the like. These may be used alone or in combination of two or more. Among these phenols, m-cresol and p-cresol are particularly preferable.

  Examples of aldehydes include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, butyraldehyde, trimethylacetaldehyde, acrolein, crotonaldehyde, cyclohexanealdehyde, furfural, furylacrolein, benzaldehyde, terephthalaldehyde, phenylacetaldehyde, α-phenylpropylaldehyde. , Β-phenylpropylaldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, o-chlorobenzaldehyde, m-chlorobenzaldehyde, p-chloro Benzaldehyde, Cinnamon Alde Hydride and the like. These may be used alone or in combination of two or more. Among these aldehydes, formaldehyde is preferable because of its availability.

  The novolac resin (A) may be composed of one kind of novolac resin or may be composed of two or more kinds of novolac resins. When the novolak resin (A) is composed of two or more types of novolak resins, the Mw of each novolak resin is not particularly limited, but the novolak resin (A) as a whole is prepared so that the Mw is 1000 to 100,000. preferable. In addition, it is preferable that 20-80 mass% is contained in novolak resin (A) in components (solid content) other than the solvent (C) in the composition for etching masks, and 60-80 mass% is more preferable.

  A characteristic common to the novolak resin (A) described above is excellent acid resistance.

The content of SiO ₂ particles (B), relative to the novolak resin (A) 100 parts by mass of a 20 to 100 parts by weight. When the content of the SiO ₂ particles (B) is less than 20 parts by mass with respect to 100 parts by mass of the novolak resin (A), it becomes difficult to obtain sufficient printability. On the other hand, when the content of the SiO ₂ particles (B) is more than 100 parts by mass with respect to 100 parts by mass of the novolak resin (A), it becomes difficult to ensure sufficient acid resistance. The average particle diameter of the SiO ₂ particles (B) is preferably 7 nm to 30 nm. When the average particle diameter of the SiO ₂ particles (B) is smaller than 7 nm, the particles are likely to aggregate. On the other hand, if the average particle diameter of the SiO ₂ particles (B) is larger than 30 nm, the viscosity increase and thixotropy are reduced. The SiO ₂ particles (B) are preferably hydrophilic. “Hydrophilic” as used herein means having a hydroxyl group (OH group) on the particle surface. Since the SiO ₂ particles (B) are hydrophilic, the printing accuracy can be increased.

  The content of the solvent (C) is preferably 30 to 70% by mass based on the entire composition for etching mask.

  The solvent (C) preferably contains a solvent (C1) having a boiling point of 190 ° C. or higher. Specific examples of the solvent (C1) include ethylene glycol, hexylene glycol, propylene glycol diacetate, 1,3-butylene glycol diacetate, diethylene glycol, dipropylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether. , Diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate Diethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monophenyl ether acetate, dipropylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, glycerin, benzyl alcohol, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3 -Methoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxy Pentyl acetate, 4-methyl-4-methoxypentyl acetate, dihexyl ether, Benzyl, ethyl benzoate, diethyl maleate, .gamma.-butyrolactone, etc. terpineol and the like. These may be used alone or in combination of two or more.

  The composition for etching mask according to the embodiment may contain a solvent other than the solvent (C1) described above. However, content of the solvent (C1) with respect to the whole solvent is 70 mass% or more, and 90 mass% or more is more preferable.

  Solvents other than the solvent (C1) (solvent (C2) having a boiling point of less than 190 ° C.) include ketones such as cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, 2-heptanone; ethylene glycol, propylene glycol, etc. Polyhydric alcohols; derivatives of polyhydric alcohols such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), dipropylene glycol dimethyl ether, propylene glycol propyl ether; other butyl acetate, ethyl acetoacetate, butyl lactate And esters such as diethyl oxalate. Among these, propylene glycol monomethyl ether acetate, 2-heptanone and butyl acetate are preferable.

  The etching mask composition according to the embodiment may further include a silicon-based, acrylic-based or fluorine-based surfactant (D).

  As the silicone-based surfactant (D), BYK-310 (manufactured by Big Chem.) Containing polyester-modified polydimethylsiloxane as a main component, BYK-323 (manufactured by Big Chem.) Containing aralkyl-modified polymethylalkylsiloxane as a main component. , BYK-SILCLEAN 3720 (manufactured by Big Chemi), whose main component is polyether-modified hydroxyl group-containing polydimethylsiloxane, and KF-353 (manufactured by Shin-Etsu Chemical Co., Ltd.), whose main component is polyether-modified methylpolysiloxane. . Examples of the acrylic surfactant (D) include BYK-354 (manufactured by Big Chem). Examples of the fluorine-based surfactant (D) include KL-600 (manufactured by Kyoeisha Chemical Co., Ltd.). Among these, a silicon-based surfactant is preferable, and a polydimethylsiloxane-based surfactant is preferable. The addition amount of the surfactant (D) is preferably 0.001% by mass to 1.0% by mass, and more preferably 0.01% by mass to 0.1% by mass, based on the entire composition for the etching mask.

As mentioned above, the composition for etching masks described above improves the resistance to an etching solution in a state where it is formed as a mask on a solar cell substrate by printing by containing a novolak resin (A) having excellent acid resistance as a resin component. be able to. Further, with respect to the novolak resin (A) 100 parts by mass of, SiO ₂ particles (B) by containing 20 to 100 parts by weight, it is possible to improve the printability. In addition, by containing a solvent (C), in particular, a solvent (C1) having a boiling point of 190 ° C. or higher, the etching mask composition (ink) is prevented from drying during printing, and reprintability (printing stability). And ink ejection properties can be improved.

  Moreover, when the composition for etching mask contains surfactant (D), when the composition for etching mask is printed on the substrate for solar cells, it is actually printed with respect to the set print pattern width. It is possible to suppress the increase in the width of the pattern, that is, the occurrence of printing bleeding.

(Pattern formation method)
As shown in FIG. 1A, a solar cell in which a silicon substrate, a metal substrate such as copper, nickel, aluminum, or the like, or an oxide film such as SiO ₂ or a nitride film such as SiN is deposited on the silicon substrate. A mask pattern using the above-described etching mask composition on the substrate 10 using a printing method such as a screen printing method, an ink jet printing method, a roll coat printing method, a letterpress printing method, an intaglio printing method, or an offset printing method. 20 is formed. In addition, you may pre-process a board | substrate as needed before forming the mask pattern 20. FIG. Examples of the pretreatment include a step of forming a liquid-repellent layer, for example, a step described in JP-A-2009-253145. Subsequently, the mask pattern 20 is heated to bake the mask pattern 20. The heating conditions are appropriately set depending on the composition of the etching mask composition, the film thickness of the mask pattern 20, and the like, and are, for example, 200 ° C. and 3 minutes.

  Subsequently, as shown in FIG. 1B, the solar cell substrate exposed at the opening of the mask pattern 20 is selectively removed using an etching solution such as a mixed acid of hydrofluoric acid and nitric acid, and the mask pattern 20 is removed. The solar cell substrate in the opening (exposed portion) is etched to transfer the mask pattern.

  Subsequently, as shown in FIG. 1C, the mask pattern 20 is removed after the etching process. Examples of the removing method include a method of immersing in an aqueous alkali solution, an organic solvent, a commercially available stripping solution, etc. for about 5 to 10 minutes at room temperature for peeling. Examples of the alkaline aqueous solution include a sodium hydroxide aqueous solution and a tetramethylammonium hydroxide (TMAH) aqueous solution. Examples of the organic solvent include propylene glycol monomethyl ether acetate (PGMEA) and dimethyl sulfoxide (DMSO). As a commercially available stripper, organic solvent-based peeler 105 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or the like can be used. As a result, a pattern in which convex portions corresponding to the mask pattern 20 are transferred onto the solar cell substrate 10 can be obtained. In addition, an electrode, a diffused layer, etc. are mentioned as a function of the convex part formed in the board | substrate for solar cells.

  Through the above steps, a convex portion having a predetermined pattern can be formed on the solar cell substrate. Since the etching mask composition described above is excellent in acid resistance and pattern formation accuracy, a desired pattern can be accurately formed on the solar cell substrate. In addition, since the pattern is formed on the solar cell substrate by a printing method without passing through a complicated process such as a photolithography method, the manufacturing process of the solar cell is simplified, and consequently the manufacturing cost of the solar cell is reduced. be able to.

  Examples of the present invention will be described below. However, these examples are merely examples for suitably explaining the present invention, and do not limit the present invention.

表２中、フィラー２とフィラー３は比重が異なる。フィラー３の方が比重が大きいため取り扱いが容易である。

(Example 1-11 and Comparative Example 1-12)
Table 1 shows the components of the etching mask compositions of Example 1-11 and Comparative Example 1-12. The novolak resin 1 and the novolak resin 2 used in the etching mask compositions of Example 1-11 and Comparative Example 1-12 have a mass average molecular weight of 12000 (m / p = 60/40) and a mass average molecular weight of 2100 ( m / p = 36/64) novolak resin. Table 2 shows the details of the fillers used in Examples 1-11 and Comparative Examples 5-12. Table 3 shows details of the surfactants used in Examples 1, 2, 4-11, and Comparative Example 3-12.
By using combinations of the components shown in Table 1, inks comprising the etching mask compositions of Example 1-11 and Comparative Example 1-12 were produced.

In Table 2, filler 2 and filler 3 have different specific gravity. Since the specific gravity of the filler 3 is larger, handling is easier.

(Screen printability evaluation)
Each of the produced inks was printed on a silicon substrate by a screen printing method to form three patterns of 100 μm width, 150 μm width, and 200 μm width as print design widths. The formed pattern was dried on a hot plate at 200 ° C. for 3 minutes. The finished line width of the obtained pattern was measured to confirm the printability. The results regarding printability were classified as follows. The results obtained for printability are shown in Table 4.
◎ (good): printing blur of all patterns is 20 μm or less ○ (possible): two patterns having printing bleeding of 20 μm or less × (defect): one or 0 pattern having printing bleeding of 20 μm or less
Note that the printing blur is calculated by the following equation.
Printing blur = Finished line width-Print design width

(Thixotropic evaluation)
Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE550 viscometer), the viscosity curve of each ink was measured, and the viscosity index was calculated based on the following formula.
Viscosity index = viscosity at 1 rpm / viscosity at 15 rpm The obtained viscosity index was classified as follows, and thixotropy was evaluated. The results obtained for thixotropic properties are shown in Table 4.
◎ (Good): Viscosity index of 3.0 or more ○ (possible): Viscosity index of 2.0 or more and less than 3.0 x (Poor): Viscosity index of less than 2.0

As shown in Table 4, each ink of Comparative Example 1-12 was poor in both printability and thixotropy. On the other hand, it was confirmed that each of the inks of Example 1-11, Reference Example 12-14 has a printability and thixotropy characteristics of ◯ (possible) or more. In particular, when Example 2 and Example 3 were compared, it was confirmed that the printability was further improved by adding a surfactant. When Example 1 and Example 6 were compared, it was confirmed that printability and thixotropy improved more as the particle size of the filler was smaller. When Example 1 and Example 7 were compared, it was confirmed that printability and thixotropy were further improved due to the hydrophilicity of the filler.

表５より、沸点（平均沸点を含む）が１９０℃以上の溶剤を含む場合に印刷安定性が良好となることが確認された。実施例１、８−１０は１ショット目から７ショット目まで印刷パターンに印刷擦れはなく、特に、実施例１、８、９は１ショット目から７ショット目まで印刷パターン表面の平滑性も高いままであることが確認できた。 (Screen printing stability evaluation)
For each of the inks of Examples 1, 8-10 and Reference Examples 12-14, screen printing was continuously performed for 7 shots, and the printing stability was confirmed. Table 5 shows the number of shots that could be printed without printing rubbing as a result of printing stability. In Examples 9 and 10, the boiling point of the solvent is the average boiling point obtained from the boiling point and mixing ratio of the two types of solvents.

From Table 5, it was confirmed that the printing stability is good when a solvent having a boiling point (including an average boiling point) of 190 ° C. or higher is contained. In Examples 1 and 8-10, there is no print rubbing on the printed pattern from the first shot to the seventh shot. In particular, in Examples 1, 8, and 9, the surface of the printed pattern is highly smooth from the first shot to the seventh shot. It was confirmed that there was so far.

(Acid resistance evaluation)
Each ink of Example 1-11 was printed on a silicon substrate by a screen printing method to form patterns having a width of 100 μm and a width of 200 μm. The formed pattern was dried on a hot plate at 200 ° C. for 3 minutes. In order to confirm the acid resistance of the formed pattern, it was immersed in 5% hydrofluoric acid aqueous solution (condition 1) or 10% sulfuric acid aqueous solution (condition 2), and the surface state of the pattern was observed with an optical microscope. As a result, it was confirmed that in each of the inks of Example 1-11, there was no change in the film state in both conditions 1 and 2, and no pattern peeling or cracking occurred.

10 Substrate for solar cell, 20 Mask pattern

Claims (4)

100 parts by weight of novolac resin (A),
20 to 100 parts by mass of SiO ₂ particles (B),
Solvent (C),
Only including,
The solvent (C) is a non-photosensitive composition for an etching mask for a solar cell substrate , containing 70% by mass or more of a solvent (C1) having a boiling point of 190 ° C. or higher . The etching mask composition according to claim 1 , wherein the SiO ₂ particles (B) are hydrophilic. Silicon, the mask composition according to claim 1 or 2 further comprising an acrylic or fluorine-based surfactant (D). A step of forming a mask pattern on the substrate by a printing method using the composition for etching mask of a substrate for solar cells according to any one of claims 1 to 3 ,
A step of baking the mask pattern;
Etching the substrate and transferring the mask pattern;
A pattern forming method including a step of removing the mask pattern.

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