JP6068085B2 - 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 acrylic resin used in the photoresist is not sufficient in terms of acid resistance, and it has been difficult to use it as a masking agent for solar cell substrate etching. In addition, an ink produced using a low-boiling solvent used in a photoresist is difficult to form a good pattern because the printing stability is not sufficient.

  This invention is made | formed in view of such a subject, The objective exists in provision of the technique which can improve the acid resistance and printing stability 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 includes a novolac resin (A) and a solvent (B) having a boiling point of 190 ° C. or higher, and the content of the solvent (B) with respect to the whole solvent is 70% by mass or more, and It is non-photosensitive.

  According to the etching mask composition of the above aspect, it is possible to improve acid resistance and printing stability when printing on a solar cell substrate.

  The etching mask composition of the above aspect may further comprise a silicon-based, acrylic-based or fluorine-based surfactant (C).

  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 printing stability 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 a novolac resin (A) and a solvent (B) having a boiling point of 190 ° C. or higher.

  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 particular, when the inkjet printing method is used, it is preferable that (A) is prepared so that Mw is 1000 to 3000 as a whole. In addition, it is preferable that 30-70 mass% of novolak resin (A) is contained in the composition for etching masks. When using the inkjet printing method, it is preferable that 10-30 mass% is contained in the composition for etching masks. Further, the novolak resin (A) is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more in the solid content in the etching mask composition.

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

  Specific examples of the solvent (B) 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, Ethylene 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- Methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, dihexyl ether, vinegar 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 (B) described above. However, content of the solvent (B) with respect to the whole solvent is 70 mass% or more, and 90 mass% or more is more preferable.

Examples of solvents other than the solvent (B) (solvents having a boiling point of less than 180 ° C. (B ′)) 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, lactic acid Examples thereof include esters such as butyl and diethyl oxalate. Among these, propylene glycol monomethyl ether acetate, 2-heptanone and butyl acetate are preferable. When the solvent (B ′) is contained, the content of the solvent (B ′) with respect to the whole solvent is 1 to 30% by mass, and more preferably 1 to 20% by mass.

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

  Examples of the fluorine-based surfactant (C) include KL-600 (manufactured by Kyoeisha Chemical Co., Ltd.). As the silicone-based surfactant (C), BYK-310 (manufactured by Big Chem) containing polyester-modified polydimethylsiloxane as a main component, BYK-323 (manufactured by Big Chem) using 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 (C) include BYK-354 (manufactured by Big Chem). Among these, a silicon-based surfactant is preferable, and a polydimethylsiloxane-based surfactant is preferable. 0.001 mass%-1.0 mass% are preferable, and, as for the addition amount of surfactant (C), 0.01 mass%-0.1 mass% are more preferable.

  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. Moreover, by including the solvent (B) having a boiling point of 190 ° C. or higher, drying of the etching mask composition (ink) during printing can be suppressed, and reprintability and ink ejection properties can be improved.

  In addition, since the etching mask composition contains the surfactant (C), when the etching mask composition is printed on the solar cell substrate, 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. 1 (A), a screen printing method and an ink jet printing method using the above-described etching mask composition on a solar cell substrate 10 such as a silicon substrate or a metal substrate such as copper, nickel, or aluminum. The mask pattern 20 is formed using a printing method such as a roll coat printing method, a relief printing method, an intaglio printing method, or an offset printing method. 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.

( Reference Example 1-4 and Comparative Example 1-5)
Table 1 shows the components of the etching mask compositions of Reference Example 1-4 and Comparative Example 1-5. The novolak resin (A) -1 used in the etching mask compositions of Reference Example 1-4 and Comparative Example 1-5 is a novolak resin having a mass average molecular weight of 18000 (m / p = 60/40). Solvent (B) shown in Table 1 was dissolved in this novolak resin (A) -1 to prepare inks comprising the etching mask compositions of Reference Example 1-4 and Comparative Example 1-5.

(Acid resistance evaluation)
Each of the produced inks was printed on a silicon substrate by a screen printing method to form patterns having a width of 500 μm and a width of 1000 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 a 4% hydrofluoric acid aqueous solution or a 69% nitric acid aqueous solution, and the surface state of the pattern was observed with an optical microscope. As a result, for Reference Example 1-4, it was confirmed that there was no change in the film state even when immersed in a 4% hydrofluoric acid aqueous solution for 10 minutes and in a 69% nitric acid aqueous solution for 1 minute. On the other hand, in Comparative Example 1-5, since it was difficult to form a normal pattern due to printing rubbing, the acid resistance evaluation was not achieved.

(Screen printing stability evaluation)
About each ink of the reference example 1-4 mentioned above and the comparative example 1-5, screen printing was implemented continuously and printing stability was confirmed. The results regarding print stability were classified as follows.
○: Good printability when printing 7 shots continuously (no change in print pattern from 1st shot to 7th shot)
Δ: Good printability when printing continuously for 7 shots (surface roughness of the print pattern gradually increases from the first shot, no print rubbing)
X: Printability is poor when printing continuously for 7 shots (print rubbing)
The obtained results are shown in Table 1. From Table 1, it was confirmed that the printing stability was good in Reference Example 1-4 containing the solvent (B) having a boiling point of 190 ° C. or higher. Moreover, it was confirmed that in Comparative Example 5 in which the content of the solvent (B) with respect to the whole solvent was 66.6%, the printing stability was poor. On the other hand, in Reference Example 4 where the content of the solvent (B) with respect to the whole solvent was 70%, it was confirmed that the printing stability was good.

(Example 5-11)
Table 2 shows the components of the etching mask composition of Example 5-11. Each of Examples 5-11 contains a surfactant (C). Table 3 shows the details of the surfactant (C) used in Examples 5-11.

(Screen bleeding evaluation)
According to the pattern formation conditions described in “Evaluation of acid resistance”, patterns having a width of 500 μm and a width of 1000 μm were formed on a silicon substrate using the inks of Reference Example 1 and Example 5-11, and printing bleeding was evaluated. Evaluations regarding print bleeding were classified as follows.
Δ: The difference | A−B | between the width A of the actually formed pattern and the set width B is 300 μm or more. ○: The difference between the width A of the actually formed pattern and the set width B | A −B | is 60 μm or more and 300 μm or less ◎: Table 4 shows the results obtained when the difference | A−B | between the width A of the actually formed pattern and the set width B was less than 60 μm. From the evaluation results of printing bleeding shown in Table 4, the effect of suppressing printing bleeding was confirmed in any ink of Reference Example 1 and Example 5-11. In particular, Example 9-11 (content of surfactant (C): 0.1, 0.01, 0) using BYK-SILCLEAN 3720 (polyether-modified hydroxyl group-containing polydimethylsiloxane) as the surfactant (C) (0.001% by mass), it was confirmed that printing bleeding was remarkably suppressed.

(Examples 12-14, Comparative Example 6)
Table 5 shows the components of the etching mask compositions of Examples 12-14 and Comparative Example 6. Each example includes a surfactant (C). In Table 5, (A) -2 is a novolak resin having a mass average molecular weight of 2150 and (m / p = 60/40), and KF-353 is manufactured by Shin-Etsu Chemical Co., Ltd., silicon-based, main component: poly Ether-modified methylpolysiloxane, a surfactant having a nonvolatile content of 100 wt%.

(Evaluation of inkjet printability)
An etching mask composition of each example was applied to a pre-treated substrate having a texture surface with a width of 4 μm and a height of 4 μm by an inkjet printer (product name “MID-500C”, manufactured by Musashi Engineering Co., Ltd.) under the following conditions. The solution was discharged and baked at 200 ° C. for 3 minutes. A pattern and a film thickness were observed when three or five times of overcoating were performed. In either case, a line pattern of about 30 μm could be formed, and it was confirmed that the printability was good.
<Discharge conditions>
Printing frequency (frequency): 3000 Hz
Printing stage temperature: 80 ° C
Print design: 1 pixel x 1 line Print head: KM512M (14 pl)

(Acid resistance evaluation)
About the produced said pattern, it immersed in 4% hydrofluoric acid aqueous solution or 69% nitric acid aqueous solution, and observed the surface state of the pattern with the optical microscope. As a result, it was confirmed that none of the film states changed.

(Evaluation of inkjet injection stability)
An etching mask composition of each example was applied to a pre-treated substrate having a texture surface with a width of 4 μm and a height of 4 μm by an inkjet printer (product name “MID-500C”, manufactured by Musashi Engineering Co., Ltd.) under the following conditions. The solution was discharged and baked at 200 ° C. for 3 minutes. After the first discharge, the discharge was performed again after an interval of 1 minute and 5 minutes, and evaluation was performed according to the following criteria. The results obtained are shown in Table 6.
○: When a pattern according to the print design is obtained ×: When a pattern according to the print design is not obtained <Discharge conditions>
Printing frequency (frequency): 4255Hz
Printing stage temperature: 80 ° C
Print design: 1 pixel x 512 lines Print head: KM512M (14 pl)

From the above results, it was confirmed that the etching mask compositions of Examples 12 to 14 according to the present invention have good printability by inkjet in addition to acid resistance. In Example 13, although a solid content concentration was lower than that of Comparative Example 6, a printed film having a thickness equal to or greater than that was formed.

Claims (3)

Novolac resin (A),
A solvent (B) having a boiling point of 190 ° C. or higher;
A silicon-based, acrylic-based or fluorine-based surfactant (C);
The including, non-photosensitive, a etching mask composition of the substrate for a solar cell,
The etching mask composition may include a solvent (B ′) having a boiling point of less than 180 ° C. When the etching mask composition includes a solvent (B ′), the solvent (B) and the solvent (B ′) ) The content of the solvent (B) with respect to the total is 70% by mass or more,
The solvent (B) and the solvent (B ′) are compositions for an etching mask for a solar cell substrate, which dissolves the novolac resin (A).   The solvent (B) is 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 mono Butyl 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 Recall 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 acetate Ethyl benzoate, diethyl maleate, .gamma.-butyrolactone, terpineol, and the mask composition according to claim 1, characterized in that it is selected from the group consisting of two or more thereof. A step of forming a mask pattern on a substrate by a printing method using the composition for an etching mask of a substrate for solar cells according to claim 1 or 2,
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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